CA2091185A1 - Packaging thermoplastics from lactic acid - Google Patents

Abstract

A first general embodiment includes environmentally biodegradable compositions of poly(lactic acid) intimately plasticized with derivatives of oligomers of lactic acid, and mixtures such as lactic acid. A second general embodiment includes biodegradable polymer comprising polymerized lactic acid where the number of repeating lactic acid units n is an integer between 450 and 10,000 and the alpha carbon is a mixture of L- and D-configurations with a preponderance of either D- or L-units. A third general embodiment includes an environmentally degradable composition of blends of a physical mixture of poly(lactic acid), and a polymer selected from the group consisting of poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof. A fourth general embodiment includes an environmentally degradable composition that comprises blends of a physical mixture of a poly(lactic acid), comprising about 1 to 99 weight percent of the composition, and an elastomeric blend compatible polymer.

Description

WC 0~l3 -1- PCT/~:S91/063~
~: .~ v ` ~ ., PACXAGING T~ERMOPLASTICS FROM L~CTIC ACID

The present application is derived from and claims priority of the following four U.S~ applications:
the application entitled BIODEGRADA3LE PACKAGING
THERMOPLASTICS FROM POLYLACTIC ACID having Serial No.
07/579,005, filed September 6, 1990; the application entitiad BIODEGRADABLE REPLACEMENT OF CRYSTs~L POLYSTYRENE
having Serial No~ 07/579,46S, filed September 6, 1990; the application entitled BLENDS OF POLYLACTIC ACID having S~rial No. 07/579,000, filQd Septamber 6, 1990; and the appli~ation entitled DEG2ADABLE INPACT MODIFIED POLYLACTIC
ACID having Serial No. 07/579,460, filed September 6, 1990; all of the above applications having Battelle Memorial Institute as assignee.

lS FIELD OF THE INVENTION
A first major embodiment of the present invention relates to plasticized biodegradable polymers of L-lactide, D-lactide, D,L-lactide and mixtures thereof suitable for packaging applications conventionally served by nondegradable plastics (e~g. polyethylene~. This embodiment further relates to a method for producing pliable films and other packaging items from such polymers and to the unique produc' thereoC. The invention has utility in producing a product that has the physical characterist~cs of the usual Cilm for~ing ?lastics, yet is biodegradable.
The second major embodiment of this invention discloses a material and process of preparing it which is an offset, t~at is a replacement for crystal polystyrene, 3~ sometimes known as orientable polystyrene or oPS. The m2terial is an offset '_r c-ystal polystyrene but is composed of a polyester capable of degrading in the environment ove~ apr~xim2~ely one ye2-s time. The material is ~ polyest~ om-~ised c' poly~e ized lact~c - _ci~, p-ep2~ed C_O~ ei_her ~-'2C~ ,d ^- _-lactic -c~d, and D,L~lactic acid. The ratio of the two polymerized monomer units, the process treatment and in some cases certain adjuvants, determine the precise physical properties required for the exacting requirements of a crystal polystyrene offset. Thus, at approximately a ratio of 90/10, L-lactic/D,L-lactic acid, the polymerized lactic acid (PLA) is a well behaved thermoplastic that is clear, colorlQss~ and very stiff. ~s suc~ it is very suit~bl~ for preparing films, foams, and other thermoformed items of disposable or one-way plastic.
Having served its purpose as a pacXaging plastic, the poly(lactic acid) slowly environmentally biodegrades to innocuous products when left in the anviron~ent. This harmless disappearance can help alleviate the mounting problems of plastic pollution in the environment.
A third major embodiment of the invention relates to the blending of conventional thermoplastics with poly(lactic acid). This provides nove`, environmentally degradable thermoplastics. The environmentally degradable thermoplastics are useful in a wide variety of applications.
A fourth major embodiment of the invention relates to the blending of compatible elastomers with polylactides. This provides impact-resistant modified poly(lactic acids) that are us~ful in a wide variety of applications including those where impact-modified polystyrene would be used.

BACKGROUND OF T~ INVENTION
The_e is a need fo_ an envi_onmentall~
3~ biodegradable pack2sin~ thermoplastic 25 2n answer to the tremendous 2~0un.s o~ ~isc2rce~ plastic packasing m2terials. '~.a. ~las~ic sales in lq~ we_e ~3.7 billio~
pounds ~f w~i_h 2.7 billion pounds were listed 25 plastics in p2c~agins. A significant amount of 'his 12s~_c i5 __s____ei ni ~2co~es ?l~s.ic ?ollu_2n_ _hc, is 2 ~ _n _ne 12nisc2pe ~n-` ~re_. =o m~rin~

~'C ~ 91iO6~'-; -3-Mortality estimates range as high as 1-2 million seabirds and 100,000 marine mammals per year.
A further problem with the disposal of plastic packaging is the concern for dwindling landfill space. It has been estimated that most major cities will have used up available land~ills for solid waste disposal by the early 1990'5~ Plastics comprise approximately 3 percent by weight and 6 percent of the volume of solid waste.
One ot~er disadvantage o~ conventional plastics is that they are ultimately derived fro~ petroleum, which leavQs plastics dependent on the uncertainties of foreign crude oil imports. A better fe~dstock would be one that derives ~rom renewable, domestic resources.
However, there are good reasons for the use of packaging plastics. They provide appealing aesthetic qualities in the form of attractive packages which can be quickly fabricated and filled with specified units of products. The packages maintain cleanliness, storage stability, and desirable qualities suc~ as transparency for inspection of contents~ These packages are known for their low cost of production and chemical stability. This stability, however leads to very lony li e of plastic, so that when its one time use is completed, discarded pac~ages remain on, and in, the environment for

2~ incalculably long times.
The polymers and copolymers o~ lactic acid have been ~nown for some time as unique materials since they are biodegr~dzble, biocomp2tible and thermoplastic. These polymers are well behaved thercoplastics, and are 100

3~ percent bioàegradable in an animal body via hydrolysis over a time pe-iod of sever2i mor.ths to a year. In a wet envi-onment they begin ~:~ show de~-~d2_ion a~ter several e!~s ~ isc~~e~ -'s ~-e ~:~e~ leC_ ~
.n t~e soil o- seaw2ter. ~he dêgr2d2'io~ products 2re _ la_~ic ~c d, c~ 3n dio~i~e a~d ~ate- all o' whic~ -re h~ 'ess~

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It will be appreciated by those skilled in the art that duplicating the properties of one thermoplastic with another is not predictable. Thus, with crystal polystyrene, there are exacting requirements for satisfac-tory performance of the polystyrene, which has beendeveloped over many years to meet man~facturing and end-use specifications of crystal polystyrene grades~
In practice, lactic acid is converted to its cyclic dimer, lactide, which becomes ~he monomer for polymeri~ation. Lactic acid is potentially available from inexpensive feedstocks such as cornstarch or corn syrup, by fermentation, or from petrochemical feedstocks such as ethylene. Lactide monomer is conveniently converted to resin by a catalyzed, melt polymerization, a general t5 process well-known to plastics producers. By performin~
the polymerization from an intermediate monomer, versatility in the resin composition is permitted.
Molecular weight can be easily controlled. Compositions can be varied to introduce specific properties.
Homopolymers and copolymers of various cyclic esters such as glycolide, lactide, and the lactones have been disclosed in numerous patents and scientific publications. Early patents disclosed processes for pol~erizing lactic acid, lactide, or both, but did not 25 achieve high molecular weight polymers with good physical properties, and the polymer products were frequently tacky, sticky materials. See, for example, U.S. Patents 1,995,970; 2,362,511; 2,683,136; and 3,565,869. The Lowa patent, U.S. Patent 2,668,162, teaches the use of pure 30 glycolide and lactide to 2chieve hi~.h molecula- weisht ?olymers a~d copol~e_s of lactide. Copolymeri~ation of l~c,ide and glycoli~e im?ar_ed _~ hness ?~d im~-o~e~
~ st~ s~ _s ~ e h-~?-!~~
me-s. E~?hasis ~2s ?l2cec cn o~ien~2ble, c~ld-c-a~able :8 ~i~e_C. ~ilms ^~e cescri~ed ?S self-su??G--i~, or s'iff, ~ -~ C?2~`~C ~e ?~ -s -~-e~e ~
m~ g an-~ s~iff. '-J._`. ~ a~e-;~ ~ _65.^6~ dis_los_s .he ~V~ '(~13 PCT/~S91/063~

typical attitude to the presence of monomer in polyglycolide-the removal of the monomer from the product.
In U.S. 2,396,994, Filachione et al disclose a process for producing poly(lactic acids) of low molecular weights from lactic acid in the presence of a strong mineral acid cataly6t. In U.S. 2,438,208, Filachione et al disclose a continuous process for preparing poly(lactic acid) with an acidic esCeri'iCatiOn cacalysc. In U.S. 4,683,288, Tanaka ~t al disclose the polymeri~ation or copolymeri2ation of lactic and/or glycolic acid wit~ a catalyst of acid clay, activated clay~ The average molecular weight of the polymer is at least S,000 and preferably 5,000-30,000. In U.S. 4,789,726, Hutchinson discloses a process for production of polylactides or poly (lactide-co-qlycolide) of specified low-mediu~ molecular weight, by controlled hydrolysis of a higher molecular weight polyester.
Similar disclosures in the patent and other literature developed the processes of polymerization and copolymerization of lactide to produce very strong, 20 crystalline, orientable, stiff polymers ~hich were fabricated into fibers and prosthetic devices that were biodegradable and biocompatible, sometimes called absorbable. The pol~ers slowly disappeared by hydrolysis. See, for example, U.S. Patents 2,703,316;
2,75&,987; 3,297,033; 3,463,158; 3,498,957; 3,531,561;
3,620,218; 3,636,956; 3,?36,646; 3,797,499; 3,839,297;
3,982,543; ~,2~3, /75; ~,~3S,253; 4,~56,~46; 4,621,638;
European ~a~e-.~ Appli_at_on Er 014639O, International ~pplica~ion WO 86/00533, 2nd West German 3~ Offenlequn~ssch-irt ~E ^118127 (1971). U.S. pacents 4,5~a,9ol an~ 4,550,44^ __ m~_n- _eaches ~ h molecul~-~ - r~_e-~`s s~ c, ;~' G ' --es;~_~a~' 2 t~.r~ ?12~_`` _ -~-~e~ ~ , __e ~ r~ ~ C

~ c ~ c ~ ^es ^.~ c_- --_~
. _ _ ~_ . . _ . . ^ c ~ _ _ _ _ _ . . . _ _ _ _ _ . . _ _ ~ ~ _ _ _ v _ c ~ _ ~ .

O9'/~ 3 i'CT/~S~

nerve repair. R.G. Sinclair et al in, Preparation and Evaluation of Glycolic and Lactic Acid-3ased for Implant Devices Used in Nanagement of Maxillofacial Trauma, I;
AD748410, National Technical Information Service, prepares and evaluats polymers and copolymers of L-lactide and glycolide, the polymers were light brown in the casa of the polyglycolide with increasing color i~ the case of the polymers incorporating more lactide, i~ a second series of polymers the homopolymer of lactide was a snow white crystalline solid.
Other patents teach thc use of t~ese poly~ers as stiff surgical elements for biomedical fasteners, screws, nails, pins, and bone plates. See, for example, U.S.
Patents 3,739,773; 4,060,089; and 4,279,249~
lS Controlled releasQ devices, usiny mixtures of bioactive substances with the polymers and copolymers of lactide and/or glycolide, have been disclosed~ See, for example, U~S. Patents 3,773,919; 3,887,699; 4,273,920;
4,419,340; 4,471,077; 4,578,384; in 4,728,721, Yamamoto et al disclose t~e treatment of biodegradable high molecular weiyht polymers with water or a mixture of water and water soluble organic solvents so as to remove unreacted mono~er or monomers and polymers of low polymerization deyree.
Poly(lactic acid) and copolymers of lactic and glycolic acid of 2,000 to 50,000 molecular waight are prepared by direct condensation for use as an excipient for microcapsules; R.G. Sinclair, in ~nvi-onmental Science &
~echnology, (10), ~5 ~157 )- R.G. Sinclai_, P_oceedincs. 5t~. Tnternational S~posium on Controlled Release of Bioactive ~.~terials, ~.12 ~n~i ~.2, University cf ~~on ~-ess, '9 ~ T~ese _?~li_Ptions of l_c__~e pol~e-s cn- -^p^l~er_ ~e_~ai-e~ ~0~ -! O~ clssy p.~ysi_zl --c?e~~ies --- o_viou- use _n ~e~opl~stlc _ 2 C ~ `. 5 _ _ `_ _ _ 2 _ S ` ~ c ~ C _ i _ ?^'~ -C~ 2- ~ e ~?~ ~ -io~e~-cc`~

~O~'/0~l~ PCT~S91/063~-Util. Conf., p. 211, June 11-12, 1987, discusses some of the advantases of lactides as homopolymers and as copolymers with glycolide and caprolactones.
Some mention has been disclosad in the prior art for use of lactide copolymers for packaging applications.
Thus, in the aforementioned patent to Lowe, clear, self-supporting films are noted of a copolymer of lactide and glycolide. In U.S. Patent 2,703,316 lactide polymers are described as film formers, which are tou~h and orientable.
"Wrapping tissue" was disclosed that was tough, fle~ible, and strong, or pliable. However, to obtain pliability the polylactide must bQ wet with volat~le solvent, otherwise, ~ti~f and brittle polymers were o~tai~ed. This is an example of the prior art which teaches special modifications of lactide polymers to obtain pliability.
U.S. Patent 2,758,987 discloses homopolymers of either L-or D,L-lactide which are described as melt-pressable into clear, strong, orientable films. The properties of the poly(L-lactide) are given as: tensile strength, 29,000 psi; percent elongation, 23 percent; and tensile modulus, 710,000 psi. The poly(D,L-lactide) properties were:
26,000 psi tensile strength; 48 percent elongation; and a tensile modulus of 260,000 psi. Copolymers of L- and D,L-lactide, that is copolymers of L- and D,L-lactic acid, are disclosed only for a 50/50 ~y weiqht ~ixt~re. Only tack point properties are given (Example 3). It was claimed that one anti?odal (optically acti~e, e.s., L-lac~ide) monomer s~ecies is --e~e--ed ~o- the ca~e'o~men~ c~ his~
s-_encth~ Th~s, i.. ~J~5~ 2 tan~ ',021,309, lac'~des are ~o c~ol~eri7ed wit~ delta ~alerolac~one and ca~rolactone to `cc~~ ?~ 5 c~ o~ .i'e, s~~ e~ ~l`dC~ 5~~_~ sol`_ _O?O1~T2- co-~?csi~ c~
.~ ~ _ ~ ~ _ _ _ ~ . ~ _ _ ~ ~ _ ; _ _ ~ . = . ~ _ _ _ _ _ = _ _ ~ _ _ _ _ _ ~ ~; _ _ _ . . _ _ . . _ ~, -di-~_h~ e~ -h~d-~:y?~ -c _ _ r.
r . _ _ _ ., ~09,~ 't~i~`à~!J~3' _, _ ~ 3 preparation of elasto~ers and foams. This patent excludes lactides and uses compositions based on 7- to 9-membered r`ng lactones, such as epsilon caprolactone, to obtain the desired intermediates. No tensile strength, modulus, or percent elongation data are given. U.S. Patent ~,297,033 teachcs the use of glycolide and glycolide-lactide copolymers to prepare opaque materials, oriQntable into ~ibers suitable for sutures. It is stated that "plasticizers interfere with crystallinity, but arc useful for sponge and films"~ Obvious in these disclosures is that the lactide polymers and copolymers are stiff unless plasticized. This is true also of U.S. Patent 3,736,646, where lactide-glycolide copolymers are softened by the use of solvents such as methylene chloride, xylene, or toluene. In U.S. Patent 3,797,499 copolymers of ~-lactide and D,L-lactide are cited as possessing greater flexi-bility in drawn fibers for absorbable sutures. These fibers have strengths greater than 50,000 psi with elongation percentages of approximately ~0 percent. In column 5, line 1, Schneider teaches against enhanced properties in the range provided in the present invention.
Plasticizers such as glyceryl triacetate, ethyl benzoate and diethyl phthalate are used. Moduli are about one million psi. These are still quite stiff compositions compared to most flexible pac~aging compositions, reflecting their use for sutures. U.S. Paten~ 3,844,987 discloses the use of ~raf' and blends OL biodegradable poly~ers wf-h natu-a_lv occur~ing biodegradable products, such 2S cellulosic materi21s, so~a bean ~owder, rice hulls, anc _rewe-'s yaas~ - a~.icles _` ~anufactu=e SUCh _~ 2 c~n~ai.e- ~o hc~ a me_~u.~ ~o germin_te and ~ro~
~e~ ea~ e _~ 'ea ~c ~ -e _-e ~.-_ 2~^ ~ '' _ t - ^ . ~ U _ _; _ ~ , ^ r ~ ~

C ` ~ C ` _ ~ r~ r--s _.~ T ~ r ~e ~-c~-----~ - ~----^ - ~ --! ^ - `' r' ~ ~ ' ~ ~ ` ~ `~ ~ i " ,_ ~- C _ i ~ _ ~ _ r~ ~ r `~ ~ i ~)~ _ S _ nr ~ 0~0~l~ ~'cr/~ 63'7 . ;.J i ~ ~

suture materials. These disclosures teac~ the use of highly crystalline materials, which are oriented by drawing and annealing to obtain tensile strengths and moduli, typically, greater than 50,000 psi and 1,000,000 psi, respectively. Although ~ormability is mentioned into a variety of s~aped articles, physical propertiQs of unoriQnted ~xtrudates and moldings are not mentioned. For Qxampls, U.S. Patent 3,636,956 toaches t~e preparation of a copolymer ~avin~ 85/15, 90/10, 92.5~7~5, or a 95/5 1~ weig~t ratio o~ L-lactide/D,L-lactide; drawn, oriented f ibers are cited; other plasti~izers suc~ as glyceryl tria~etate, and dibutyl pt~alate are taught; however, i~
is preferred in this disclosure to use pure L-lactide monomer for greater crystallinity and drawn fiber ~5 strength; and finally, the advantages of the present invention (e~g~, an intimate dispersion of lactic acid-based plasticizers that provides unique physical properties) are not obtained~
U.S. Patent 4,620,999 discloses a biodegradable, disposable bag composition comprised of pol~.~ers of 3-hydroxybutyrate and 3-hydroxybutyrate/3-hydroxyvalerate copolymer. Lactic acid, by comparison, is 2-hydroxy propionic acid. U~S~ Patent 3,982,543 teaches the use of volatile solvents as plasticizers wit~ lactide copolymers 25 to obtain pliabilitv. U.S. ~atents 4,045,418 and 4,057,537 rely on copolymeri2ation of caprolactone with lactides, eit~er ~-lactide, or D,~-lactide, to obtain pli2~ y. '~. S . ~aten~ ~,0~2,9&& teac~es t~.e use cc poly (p-~iox2none) ~o o~tain i~proved l:nct tving ~nd l~not 30 security for absor~a~le s~t~res. '~.S. ?atents 4,307,763 znd 4,~-6,6g5 ~isclose ~e use cf lac~i~e z~d clvcolide ?~i~2~-s ~ Ers ~.~ ~E ^ --~~
_ ;~

_ _ i -_r~ atEri-l~ ~.s ~ -e~
= ~ r _ ~ _ _ . --= _ _ ~ . _ C C . ~ _ _ _ i c _ _ _ _ _ _ _ O _ ~_ c i.. e_ ~09'/~ 10- PCT/~S91/n63'-,~S, lactide polymers only by plasticizers which are fugitive, volatile solvents, or other comonomer materials.
Copolymers of L-lactide and D,L-lactide are known from the prior art, but citations note that pliability is not an intrinsic physical property. The homopolymers of L-lactide and D,L-lactide, as wQll as the 75/25, 50/50, and 25/75, weight ratio, of L-/D,~-lactide copolymers are exa-mpled in U.S~ Patent ~,951,828. The copol-ymers have softenir.g points of 110-135 C. No other physical property data are given relating to sti~'rness and ~lexibility. The 95J5, 92.5/7~5, 90/10, and 85/15, wei~ht ratio, of L-lactide/D,L-lactide copolymers aro cited in U.S. Patents 3,636,956 and 3,797,499~ They are evaluated as filaments from drawn fibers and have tensile strengths in excess of 50,000 psi, moduli of about one million, and percent elongations of approximately 20 percent. Plasticizers, the same as in U.S. Pa~ent 3,636,956, above, were used to impart pliability. A snow-white, obviously crystalline polymer, is cited in Offenlegungsschrift 2118127 for a 90/10, L-lactide/D,L-lactide copolymer. No physical properties were siven for this copolymer. The paten.
teaches the use of surgical elements.
Canadian Patent 808,731 cites the copolymers of L- and D,L-lactide where a divalent ~etal of Group II is ~5 part of the structure. The 90/10, L-/D,L-lactide copalymer (Example 2~ and the L-lactide homopolymer were àescri'~ed as "suitable ~or films and fibers". The 90/10 copol-ymer is des_ribed as 2 sno~-white copoly~er and the homo?Ql~er of T~-lac-ide c--n ~e ~olded t3 'ransp2rent ~0 _ilms. (~r,e more c-ystal~ine polymer sho~ld be 'he s~ e, _~ r.i~e ~ .eri~ c~ ~s ~e ~ c ~'he _~e.~ ~is_'oses `'_he ~_-~ th-_ ~.e ~.ove' ~ l_c=ic.s _ ~ s ~
-he c-tclis~ i-. _'-_ ~c-m __ ~ '~~~_e is belie-~e~ _o be cr :-e -~.`I__C-`_~ C-S ~hic:~ -~

~O 9_/0~13 PCT/~S91/Ofi3'-i _ J
met~ods". No physical property data are given on the strength and flexibility of the films.
Canadian Patent 863,673 discloses compositions of L-lactide and D,L-lactide copolymers in the ratios of

5 g7/3, 95/5, 92.5/7.5, 90/10, and 85/15 ratios of L-/D,L-lactide, respectively. These were all characterized as drawn filaments for surgical applications. Tensile strength, approximately 100,000 psi, was ~igh, elongation was approximately 20 percent and plasti~izers were mentioned to achieve pliability. D,~-lactide compositions of less than 15 weig~t percent are claimed.
Canadian Patent 923,245 discloses the copolymers of L- and D,L-lactide (Exa~ple 15). The 90/10 copoly~er is described as a snow white polylactide. The 1~ polylactides prepared by the methods of the patent are stated to have utility in the manufacture of fil~s or fibers prepared by conventional thermoplastic resin fabricating methods.
U.S. Patent 4,719,246 teaches the use of simple blending of poly L-and poly (D-lactide), referred to as poly (S-lactide~ and poly (R-lactide~. The examples are all physical mixtures. The special properties of the ~interlocking" stem from racemic compound formation (cf.
"Stereochemistry of Carbon Compounds", E. L. Eliel, 2~ ~cGraw-Hill, 19~2, p. ~5). ~acemic com?ounds consist o~
interlocked enantiomers, that is, the D and L forms (or R
and S) a_e bonded to eac~ c~er by ?olar rorces~ This can cause a lowe~ n~, o_ ~aising, of t~e c-ystalline melting ~oin_s, de?endin on ~`net~e~ -~e D _o D (or L to L) fo-cQs ~0 r~P less, o_ ~~eater, ~h,_.. -~e D to L forces. Requi_ed o~
-e- ~ c ~ ?~ s ~o ~ t~.e e ^ec~
~t--QC. `~ `-. ?_-~ . ~ 2 ~c) ,--_ _ . _ ~ ~ . , _ _ : _ _ ~ ~ ~ _ _ . . _ _ _ _ _ _ _ = _ _ ,, , 0~]3 -1-- PCT/~`S91/n63~-art of racemic compounds has a long history that goes back to classical chemistry.
Okuzumi et al, U.S. 4,137,921, in Example 4, teaches a 90/10 random copolymer of L-lactide and D,L-lactide, however, the advantages of the present inventionare not obtained. Hutchinson, U.S. 4,789,?26, teaches a process for t~e manufacture of polyestQrs~ particularly polylactides of low ~olecular weigh~, by for~ing high molecular weight material and t~en degradin~ it to lower weight products of controlled polydispersity, however, monomers are removed in the process.
U.S. Patents 3,736,646; 3,~13,919; 3,887,699;
4,~73,920; ~,471,077; and 4,578,384 teach the use of lactide polymers and copolymers as sustained-drug release ~5 matrices that are biodegradable and biocompatible. Again, physical properties of the polymers from ordinary thermoforming methods such as film extrusion or molding are not mentioned.
Additional related art includes: Low molecular weight poly D,L-lactide has been recently added to high molecular weight D,L-lactide along with a drug such as caffeine, salicylic acid, or quinidine, see R. Bodmeier et al, International J. of Pharm. 51, pp. 1-8, (1989).
Chabot et al in polymerizing L-lactide and racemic D,L-lactide for medical applications removed residual monomer~nd ? ower oligomers, see Polymer, Vol. 24, pp. 53-59, tl983). A.S. C~wl~ and Chang produced four differant ~olecular ~eight 3,L-la~tide poly~ers ~-u_ re~o~ed monomer f~ o dec~~d~tion s~eies, see B_omct., ~e~ e~
30 Ar~. Q-S-- 13(-`.~, ?~- 13-162, (1985-85). Xleine 2nd 'leine ~o-~ec_ _e~e~_' 'e; -esi~'u~l monc-e-, -o'y(lc~
__ic~ _ -e~e~~ 7~ eY2`~

;`c~. _~, .-. _~-'~, ':'-5~ ' c`~o r~ es : _ ~ _ _ _ _ _ ,~ ~ ~, _ ,~ _: _ _ ~ _ ~ _ _ ; , _ _ ~_ ~ ~--, ~ _ _ -- ~ _ ~ = ~ _ ~ _ _, _ ~ rc~ t~ _c~ ?~ ~ Scl~c_ ;`~`

~0 9_/0~1~ PC~/~:S91/n63'-~ 5~
molecular weight polylactides with elimin~tion of residual monomer, see Makromol. Chem., Suppl~ 5, pp~ 30-41, (1981)~
M. Vert, in Macromol~ Chem.,Macromol~ S~p. 6, pp.l09-122, (1986), discloses similar poly(~-/D,L-lactide) 5 polylactides, see Table 6, p. 118. In E 3~1,065 ~1989) poly D r L-lactid~ is prepared as an implant material ~or drug delivery as t~e ~aterial de~rades, the material contains drugs, low molecular weig~t polylactide, and other additives; EP 314,245 (1989) teaches 8 polylactide having a low amount of residual monom~_, thQ polymer is prepared by polymerization of meso D,L-lactide or other monomers; West German Offenlegungsschri f t DE 3,820,299 (1988) teaches the polymerization of meso D,L-lactice with lactides, however, the advantages of the present invention are not obtained; and West German Offenlesungsschrift DE
3,820,299 (1988) teaches the polymerization of meso D,L-lactide with lactides; however, the advantages of the present invention are not obtained.
Of particular interest, U.S. patent 4,719,246 teaches the blending of homopolymers of L-lactide, D-lactide, polymers or mixtures thereof; and copolymers of L-lactide or D-lactide with at least one nonlactide comonomer. The blending is intended to produce compositions having interacting segments of poly(L-lactide) and poly(D-lactide)~
U.S. 3,636,956 teaches an interweaving of fibers th~t is not blenciny or me'~ blending of a composition to ~_ke ~ physic21 mi~tu-e~ J.S. ?a_en_ ~,719,'~6 teaches the blen_ing f ~.o~o?ol~e_s cf L-lac'ide, ~-lactide, ~olymers 5f mi~._u-es thereo_; an~ co?olyme-s or L-lac~ice o~ 3-7actide ~ h __ 'e_s~ one non'ac_ide c-monome~. The _``~?~ , `S `~ '`t- -~ e c~?os~
_ ~ ~ _ _ _ _ _ ~ .... _ ~ ~ _ _ . ~ ~ _ ~ . _ _ ~ _ _ _ _ ~ _ _ ~ _ _ _ _ _ _, _ ~ . _ , _ _, ~ _ 1-_ ~_--). c ~ _s-'~e~ -ec -_~ec.____ ~ ~_,~____ _ _ _~____ _,__ _ _ _~__ ~

`jO~/0~13 PCT/~S9l/063'-iY--synthetic replacements of biological tissues and orqans in reconstructive surgery. PCT publication ~o 8~/00419 to Barrows reveals a bone spacer comprising a blend or mixture of a nonabsorbable polymer and a bioabsorbable S polvmer, polylactic acid is one of th~ preferred biodegradable polymers but plasticizers are not revealed therein. PCT publication WO 84/00~03 to Goyolews~i et al su~3gests blends of polyesters and polyurethanes for preparing surgical filam~nts. Cohn et al, in Biodegradable PEO/~LA Block Copolymers, Journal o~ Biomed.
Mater. Res., Vol. 22, p. ~93, 1988, reveals a physical mixture of poly(ethylene oxide) and poly~lactic acid).
Nowhere in the prior art is it disclosed t~t lactic acid or lactide polymers can ~e the source of lS pliable, highly extensible compositions by the use of lactide monomers, or lactic acid, or oligomers of lactic acid, or derivatives of oliqomers of lactic acid, or oligomers of lactide as the plasticizer~ None of the prior compositions are suitable for well-defined packaging needs.

8RIEF DESCRI~TION O~ T~E INVENTIO~
A. The general teaching of the portion of the invention providing for flexible materials is that poly~lactic acids) derived fro~ lactic acid (homopolymers or copolymers of L-lactic acid or D-lactic acid) or lactides (ho~o?oly~e_s o co~olv~ers of L-lac'ide, D-lac~ide, ~eso D,~-lac~ide, c~ r~ce~ic D,~ c~`da) th~t e ~e~ e~ S~ 2~ ?'~s_~c~_e- s~-~~s '_c~ic a^id, l~c_ide, oligo~e-s o~ 12c_i_ acid, ol~o~^_s ~ -iv2.~ e~`~
~c~ -~o~s ~ ^c _:~er~ .c~-e ~ v ~

`~ r_2.~_`_~ s~ _e-~ le ?-câ _i^-~ ~ . _ . ~ ; :: _ _ _ _ _ _ _ _ _ _ _ _ _ .. _ _ ~ ~ _ . ~ ~ _ _ . . ~ . _ ~: . _ _ }: c j . ~ .
= _ _ _~ _ . . = _ . _ _ _ _ _ _ _ . _ _ _ _ c _ _ _ _ _ . ~ _ _ _ . . _ ~,. ~ _ = _ -~ O9'/0~13 ~'CT/~S91/n63-'-polymer. Since both lactic acid and lactide can achieve the same repeating unit, the general term poly(lactic acid) as used herein refers to polymers having the repeating unit of formula I without any limitation as to S how the polymer was made (e.g. from lactides, lactic acid, or oligomers), and without refersnce to the degree of polymerization or levsl of plasticization.
In general, a first e~bodiment of the invention for flexible materials provides for an environmentally biodeqradable composition useful as a replacement ~or thermoplastic poly~er compositions comprising a poly~lactic acid) and a plasti~izer selected from the groups below, wherein the pl~stici~er is intimately dispers~d within the polymer~ The poly(lactic acid) lS polymer has the repeating units of the formula, ~3 1l ~ I ~n wherein n is the number of repeating units and n is an integer equal to at least about 150. ~referably the unoriented composition has the physical properties of:
150 < n < 20,000, a tensile strength of about 300 to about 25 20,000 psi, an elongation to failure of about 50 to about 1,000 percent, and a tangent modulus of about 20,000 to about 250,000 3si. The intimate dispersior. of the plasticizer c~n yiel~ a substantially transparent composition, al_b.ou5~ transpare-._y m2y no~ be obtained ~o with cert~in processes, 2S when the composition is fo2med.
_~ c ~ e~a~ _..e ~ -osi~ _c.~
-epl~ce~er.t 'or ?olyethylene when the ur.oriented c^~a-s 'ion h~s _ensi;C s~~en -h c- ~àou_ ~,:30 -o cbo~_~

_ _~ 3~-_er._. ~., ~ ~_.~ o__ __ ~ ~
~a~ C~ _r`, ~r~ err~.~

_ ~ ~, r ~ r ~ ~=~ r ~

U`09~ ~l3 l'~/L~9l/(~3'~

;~ ~. v . _ ~, _, elongation to failure of about 100 to about 600 percent, a tangent modulus of about 165,000 to about 225,000, and a melting point of about 150 to about 190 F.
A further embodiment of the invention provides a process for producing an environmentally biodegradable composition useful as a replacement for thermoplastic polymer compositions having thQ staps: (a) polymeri2ing a lactide monomer selected from the group consisting of D-lactide, L-lactide, ~eso D,L-lactide, racemic D,L-lactide, and mixtures thereof, in t~e presence of a suitable catalys~; (b) controlling the polymer~zation to allow the reaction to be stopped prior to complete polymeri2ation;
(c) ~onitoring the level of remaining monomer; (d) stopping the polymeri~ation prior to complete reaction so that unreactQd monomer in a predetermined amount is trapped in association with the polymer; and (e) treating the polymer and unreacted monomer to obtain an intimately plasticized composition~ The polymerization reaction is preferably stopped at a monomer level up to about 40 weight percent. If desired additional plasticizer may be incorporated into the composition prior to, during, or after the treating step, wherein the plasticizer is selected from the group of plasticizers discussed below.
The sum of remaining monomer and additional plasticizer is preferably below about 40 weight percent and is most prefarably between about 7 0 and about 40 weight percent for a pliable composition.
.~ vet f~_the~ embo~iment includes a ?_ocoss fo-_-o~ucin~ ~ plas_i_i-e~ ~ol~e- of ?o~y('~__ic acid) ~ t ~0 com?-ises mi~in~! he~~in~t 2ni mel_in~ one or more lac~i~e ~_~o~e-~ ~nd ~ _a ~~ e~ .e ~ .e 5~~ ?~ ?~ -e~c~i^.~;
. _ _ _ __ _ _ _ _ . _ . _ ~ _ _ ~ ~ _ ~ ~ ~ . . _ _ . .. ~
_ ~ . _ _ . . _ _ _ _ _ -- _ _ _ . . _ _ _ _ _ _ _ _ ~ _ _ ~ _ _ _ . _ _ _ _ ~ _ . _ . .
e~ p~

?^-`~ c~ a cesc~

09'/0~13 PCT~'S91/063', ~ 3 ~ ~

plasticizers may be added to obtain the desired properties.
A yet further embodiment includes a process for the preparation of a biodegradable blown film through the inclusion of the below listed plasticizers in poly(lactic acid) to achieve desired properties followed by extrusion o~ the plasticized poly ( lactic acid) as a blown film.
Plasticizers useful with the invention include lactic acid, lactide, oligo~ers of lactic acid, oligomers of lactide, and mixtures thereof. The preferred oligomers of lactic acid, and oligomers of lactide are defined by the formula:
IH3 ll HO ~--C - C~~~ m H II

where m is an integer: 2 < m < 75. ~referably m is an integer: 2 < m < lO.
Further plasticizers useful in the invention include oligomeric derivatives of lactic acid, selected from the group defined by the formula:

R'O ~~~C~~~ q R III

where R = H, 21kyl, aryl, alkylaryl or acetyl, and R is saturated, 33 whe_e R' = H, 2l~ -yl, a'`~;yl:-yl cr a-e_yl, Gn~ R' is sat~rated, S ~ < 5; an~ u_es ~he~ecC ~~e_e_ably c is a~

;C ~e~~.._ ?~-~e..~ ?~ e -`~_~ic~ s ___.. s ___c_.~.__s __ _______, ~ ___~ .e _ _ ______ :__ _ ~ ~ _ c _ _ _ ~ c _ _ ~ _ s ~ . . ::
_: . :: _ . .. _ _ . _ : _ .: _ _ _ : _ _ _ _ _ _ ~ _ _ _ . _ . _ _ _ . . .

WO~ PCT/~S~1/063~7 t ~ ~

This composition allows many of the desirable ch~racter-istics of nonàegradable polymers, e.g. polyethylene, such as pliability, transparency, and toughness. In addition, the presence of plasticizer facilitates ~elt processing, prevents discoloration, and enhances t~e degradation rate of the compositions in contact with the environment.
The intimately plasticized composition should be processed into a final product in a manner adapted to retain the plasticizer as an intimate dispersion in the poly~7er. The treat~ents to obtain an inti~ate dispersion includ~ ) quenching the composition at a rate adapted to retain the plasticizer as an intimate dispersion; (2) melt processing and quenching the composition at a rate adapted to retain the plasticizer as an intimate disper-sion; and (3) processing the composition into a finalproduct in a manner adapted to maintain the plasticizer as an intimate dispersion.
The composition may comprise from about 2 to about 60 weight percent plasticizer. When a lactide is selected, the composition preferably comprises from about 10 to about 40 weight percent lactide plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mix-tures thereof.
If desired, the plasticizer can ~e selected from the group of lactides consisting of D-lactide, L-lactide, ~eso D,L-'ec~iCe. racemic 3,L-12ctice and 2ixt~res thereor so _ha~ ~ le2st 2rt c~ .he lac'id- Dlas.icize is s~e-coc~emica~ y di__e-on~ C-cm the ~cnome~ a~sed to pre~are the ol~e~. ~imi'a-l~y the mlas.icizer m~y comprise ~ e-s o- '^c~i~e~ ^- c'igQmers ^ lactic , _ _ ~ ~ _ ~ ~ _ ~ _ ^ _ ~ _ _ _ _ _ _ _ _ . ~ _ _ - . ., _ . _ _ ~ ~ . .
_ _ . . _ _ _ . _ .. . _ _ _ . . _ ~ _ _ _ _ _ _ _ _ _ _ _ . . _ _ ., _ _ ~ ~ _ _ _ _ _ _ _ _ ~. ) _ ~0g'~lt PCT/~`S91/063~-sroup consisting of oligomers of lactic acid, oligomers oflactide, and mixtures thereof; and melt blending with the blend a second plasticizer selected from the group consisting of lactic acid, L-lactide, D-lacti~e, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof. If desired, a first plasticizer defined by the formula III
may be used alone or in a~mixture with an oligomer of for~ula II. This procedure allows the blending of the first plasticizer at a first te~perature and the blending of the second plasticizer at a second temparature lower than the first temperature.
B. In general, a first embodiment of the invention for replacement of c~ystal polystyrene provides for an environmentally decomposable polymeric composition suitable for use as a substitute for crystal polystyrene.
The composition comprises a poly(lactic acid), where the repeating unit is an L- or D-enantiomer and there is a preponderance of either enantiomer, having intimately dispersed therein a plasticizer, as described below, wherein the unoriented composition has the ohysical properties of a tensile strength of at least 5,000 psi, a tangent modulus of at least 200,000 psi, and is colorless.
The composition can be adjusted to be form stable above about 70 C.
A further embodiment of the invention provides ~or a substitute for crystal polystyrene comprising a __pol~er o~ ~h_ -~r~u't T ~herA n ~ an inte~e- between about ~50 and abou_ lo,o~ here ~e ~_?eating un _ is an ~0 an2ntiomer; end he~in ~n~i~ct~el~ dispe-sei t~erein 2~ a~ G~ t~ - ?e--r~

_ ~ _ _ _ ~ . ~ = ~ ~ _ ~ ~ _ ~ ~ ~ _ _ _ _ ~ _ _ _ ~_ _ ~ . _ _ . ~ _ _ ~=_~-_~. ;_ ~_ _e^~ ~ ~5 ~_~ -.- e r~ o_ . ~ ` s 5 _ _ _ ~2r ~ !2 V . ~ ~
and most preferably between about 2.5/97~5 and 7.5/92.5, or between about 32.5/7.5 and s~s/2~
A yet further e~bodiment of the invention provides a composition comprising a physical mixture of:
(a) a first poly(lactic acid) having a preponderance of either D- or L- enantiomers; (b) a second poly~lactic acid) selected from the group consisting of poly~D-lactic acid) or a poly(~-la~tic acid), wherein t~e wei~ht percent ratio of the first poly(lactic acid~ to the second poly(lactic acid) is between about 1~99 and 9g/1; and ~c) greater than about C.l wei~ht parecent of plasticizer as described below, wherein the plasticizer is intimately dispersed within the poly(lactic acid); and the unoriented composition ~as a tensile strength of at least S,000 psi ~S and a tangent modulus of at least 200,000 psi, is form stable above 70 C, and is substantially colorless.
Preferred ratios of the first and second polylactic acids are between about 98/2 to about 75/25, and most preferably between about 85~15 and about 95/5. The first poly(lactic acid) may be defined by formula I, where n is an integer between about 450 and about 10,000; and the second poly(lactic acid) by the ~ormula:

t--C---C~ p IV

where p is an inte~e- between about 450 and about 10,000;
?nn rhe ur.o=ien.ed co~pcsi__o~ hzs the ph~-sicc~ prope=,ies ~0 of a tensile s~-en~th o^ z~ least 5,000 psi, a tangen~.

co~posi~_cn _^ ~his embo~i~en_ m~ `e crien~e_ n-~n-e~'~e- ~ s_~ e-s -- ~ -- -- .. ~ _ - . -_ _ ~_ ~ . ~ _ _ _ _ ~ ~_ _ ~ _ ~ . _ ~ ~ _ _ ~ _ _ _ _: _ _ . : , _ _ _ : ~
~ . e~ce~s ~ 3 -s~. c __~ n~
_ ~ ~ _ ~ ~ ~ ~ ~ ~ ~ _ ~, -- -- ~ _, _ _ _ = _,, ~ _ ~-- , _ _ ~_ _ _ _: _ _ ~ _ _ _ ::

~;09",'0~l3 -21- rCTi~S91/n~3'-temperatures above 70 C. The product can be biaxially oriented.
A yet further embodiment of the invention provides ~or an oriented and annealed environmentally decomposable film or sheet product suitable for use as a substitute for oriented crystal polystyrenQ film or sheet comprising: a film or sheet of a copolymer of the formula I: where n is betwaen a~out 450 and about 10,000; where thn repeating unit is an L- or D-enantiomer, and there is a pr~ponderance of either enantiomer; the product having intimately dispersed therein t~e residue of a plasticizer, as described below; the oriented and annealQd product having the physical properties of: a `ensile strength in excess of 7,500, a ~angent modulus in excess of 350,000, and dimensional heat stability at temperatures above about ,0 C~ The product may be biaxially oriented~ Other embodiments of the product may contain the other plasticizers discussed below~
A further embodiment provides for an oriented and annealed environmentally decomposable film or sheet product suitable for use as a substitute for oriented crystal polystyrene film or sheet comprising: a physical mixture of between about 0~09 and about 99 weight percent of a poly~lactic acid) of the formula I: where n is an ~`5 integer between about ~50 and abou_ 1~,000 and having a preponderance of either the D- or the L-enantiomers;
~etweer. ~b~ c~ ~d ~o~~ 0~0~ e~ ._ ?e-~ett.~ of~ ?~
poly~lactic 2ciii~ of ~he ~ormula I~ nere p is 2n t, ~ r~--'i2~ ~t-t~ ;t;~1, r ~ ?
~ repe2~n~ us~_ is 2 D- o- cn L-e~ t.e-; below 2 ~ _St,`_`_r~~ ~ S t~a;.--~ t~}-;`. ~ is?2-~e `
_ _ ~ _ ~ ~ _ r ~_ ~ _ ~- . _ _ _ _ _ _ ~ ~ _ . . _: _ . . _ -- _ ~. _ _ ~: _ ~I S _ O . . _ _ _, ~ . 2 _ ~
. ~ _. _ _ ~: _ _ _ _ . _: _ . ~ _ _ _ _ . . _ _ _ _ _ . _ _ . . _ _ _ .

~O97/~l3 PCT/~S91/~63'--~2-A further embodiment provides for an environmen-tally decomposable polymeric foam composition comprising a copolymer of the formula I: where n is an integer between about 450 and about 10,000, where the repeating unit is an L-or D-enantiomer and there is a prepondarance of either enantiomer; having intimately dispersed therein a plasticizer discussed belaw and wherein thQ composition is ~orc stable above 70 C.
A yet further embodiment o~ the invention provides for an environmentally decomposable polylactide product suitable 2S a substituta for crystal polystyrene comprising: a poly(lactic acid~; and a plastici~er, as discussed below, intimately dispersed in the poly(lactic acid), wherein the poly(lactic acid) has a number averaoe 15 molecular weight, M~, between about 50,000 and 400,000, a tensile strength of at leas~ about 7500 psi and a tangent modulus of at least 350,000, form stability above 70 C, and is substantially clear and colorless after processing into a product.
Plasticizers contemplated for the compositions and processes in the present invention include: (a) lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof; where oligomers of lactic acid and o!igomers o~ l~ctide defined by the formula II: where m is an integer: 2 ~ m < 75; and ~à) one o. more ce ivatives o n olicome- o- lac-i- acia defined by the formula III: where R = n, al~yi, aryl, ,0 al~yl, aryl, a'}:yl2-yl c_ ace~yl, and ~' is saturateà;

_ ., ~. 2 --~ e ~21~e~ i3.~

_ -` _--` _ ~ i ~ ~ _ ~ '` _ _ _ _ _ ~ _. ,. 2 5 i t _ _ . . _ ~ S i . .
. ::: _ _ _ _ . ~ _ _ _ _ ~ _ . . _ _~ _ 5 _ _ _ ~ ~ _ ~

~0 9't()~lt 1'Cr/~`S~I/nh3`'-3 _ . ` ` ~c3 first plasticizer selected from the group consisting of an oligomer of lactide, or an oligomer of lactic acid; and a second plasticizer selected from t~e group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and ~ixtures th~reo~; and (b) a first plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula III: where R - H, alkyl, aryl, al~ylaryl or acetyl, and R is saturated; where R' - H, alXyl, aryl, alkylaryl or acetyl, and R' is saturated; where R and ~' cannot both be ~; and where q is an integer: 2 ~ q ~ 75;
and a second plasticizer selected from the ~roup consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.
The amount of plasticizer present must be above about 0.1 weight percent. The upper limit is defined by the amount of plasticizer that will give the physical properties for crystal polystyrene as defined herein. A
preferred amount of plasticizer is between about 0.1 weight percent and about 10 weight percent. The plasticizer may be added for example in an amount (1) effective to provide substantial transparency, (2) effective to prevent degradation during processing, and (3) effective to prevent discoloration during processing.
The plasticizer ~2y be added ~y methods known in the art for blending (e.g. ~ill blending) to obtain an intimate dispersion.
u_.he~ e2bo_imen, ~-o~ides fc- ~ ~roc_ss ~ ~e -~ ~n e~ r~c~ c3r~?0s `3 `-`1~ cr sheet ~orming poly-~eric composiu ~n comprisins~
c_~cl~,~e~~ r~ 2~. ble~ c ~.o~e- s~ , ,hc _o-_~ -or.s ~ `_2, n,-`-1~
.~ _ _ _ . _, _ _ _ _ _ _ _ _ _ _ _ ~-- _, _ _ _ _ _ _ _~ = ~ _ ~ ~ _ _ .~ . _ _ _ _ , t~ onc~e~s __ 2 ~
c~ " _ _ _ ~ _ _ S ; _ _ ~ . _ _ _ _ ~ _ . _ 2 ~ _ . _ _ C _ _: _ . _ _ _ . . _ J
~ o-~^-; ,~r.-i~c.~ .e ?cl~ -tic~ c~

~0 ~'~0~1~ PC r/~ssl/nfi3~, ~ 3 intimately dispersed plasticizer as discussed herein, the unoriented composition having a tensile strength of at least 5,000 psi and a tangent modulus of at least 200,000 psi; and treating the co~position to maintain the plasticizer as an intimate dispersion within the polymer whereby a substantially colorless composition is obtained.
If desired additional plasticizer may be added after the poymerization reaction is ter~inate~ The composition may also be rendered transparent as described below.
10The process preferably selects the ty~e and amount o~ monomer to provide a ratio of L-enantiomer to D-enantiomer of b~tween about 1/99 and 99/1. More preferably, the monomer is selected to obtain a ratio of L-enantiomer to D-enantiomer of between about 2.5~97.5 and 157.5/92.5 or between about 92.5/7.5 and 97.5/2.5. The proce~s most prefera`oly uses ~he selected monomers in the molten blend comprising between about 85 and 9S weight percent D-lactide or L-lactide, and between about 5 and 15 weight percent meso D,L-lactide or racemic D,L-lactide.
~0The polymeric composition may advantageously be extruded into a film or sheet and physically treated by orientation and~or annealing to provide a polymeric film or sheet having a tensile strength of at least ~,500 psi and a tangent modulus of at least 350,000 psi. An ~S additional treatment comprises ~iaxiallv orienting and heat treating the polymeric co2position.
The _reatment ~2V c~prise adding nucle~ting agen~s, adding ~-lac~i_e ~_ L-lac~ice h~opo'~er ~
`~i2~ e~ c-. C~ Q_ ~C~ S C_~ ~e _C exc'u~ed by pe-_o~in~ ,he ?oly~erizatiQn in ~n inert .~o~phe~e and a_ ~e~c~ion _en?e~a_u~es ~el~ c.
dwesi--~ .e ~~e_.~nt __e- -_-prises ~-.nea~ ~he `-~ w-~?_ _ ` ~
er~ c .~.cw- ~ _c ~s ~_~ine_.

r_c~ si_~ co.~?-i~ e~s W09~/0~3 ~ )632 ~_ ;; r~ r ._ i J `J
polymers selected from the group consisting of a poly(ethylene terephtbalate), a polymer or copolymer o~
styrene, ethylene, propylene, vinyl cbloride, vinyl acetate, alkyl methacrylate, al~yl acrylate, and physical mixtures thereof; and one or more plasticizers discussed below.
The poly(lactic acid) present in the blends may be represented by the formula I: where n is an integer between 75 and 10,000~
Plastici2ers use~ul with the invention include D-lactic acid, L-lac~ic acid, racemic D,L-lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers o~ lactide, And mixtures thereof. The oligomers of lactic acid and oligomers of lactide are defined by formula II: where m is an integer: 2 < m ~ 75~ Preferably m is an integer:
2 < m < 10. These limits correspond to number average molecular weights below about 5,400 and below about 720, respectively.
Further plasticizers useful in tbe invention include oligomeric derivatives of lactic acid, selected from the group defined by formula III: wbere R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated;
where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated; wbere R and R' cannot both be H, where q is an integer: 2 ~ q ~ 75; and mixtures tbereo~. Preferably q is an integer: 2 ~ q ~ 10~
Tbe p`2s ici~e~s may ~e ~re52n- in ~nv a~ount tba_ -rovides t~.e desi-e~ cbaracteristics. ?o- e~ample, ~" ~brr VriO'IC t~'?eS 0~ las~ici2ers discusse~ be_ein and in tbe otbe- gene-~i e-~oc me.~ts p-o~i~e c-: (2) mo~-~
~ e cs.~.?_~ `a~ o~ e'_ ~ ` ca_~?~Qn._C;

. . _ ( C ~ C _ . ~ _ _ _~ 1 _ . . _ ~ _ _ ~. _ _ ~ _ _ ._ _~ . -- -- -- . . -- -- --. -- _ _ .
~ ? `-^i~ s=1~ - _s --eser.^ ~-.
~~ ~ c ~ c ~ v~._~. _ ~, ;-~ ~ ` _ - _ _, ~ e _ ~. . c_ c C= ~ ~

~13 PCT~S91/063'--2~-J :J

lower amounts. The compositions allow many o~ the desirable characteristics of pure nondegradable polymers.
In addition, the presence of plasticizer facilitates melt processinq, prevents discoloration, and enhances the degradation rate of the compositions in contact with the environment. The intimately plasticized composition should be processed into a final product in a ~anner adapted to retain the plastici2er as an intimate dispersion in the polymer for certain properties. These can include: (1) quenching the co~position at a rate adaptQd to ret~in the plasticizer as an intimate dispersion; (2) melt processing and quenching the composition at a rate adapted to retain the plastici~er as an intimate dispersion; and (3) processing the compoeition into a final product in a manner adapted to maintain the plasticizer as an intimate dispersion. The plastici2ers are preferably at least intimately dispersed within the polylactic acid if not in the coblended polymer.
Particularly advantageous is the sequential incorporation of plas,icizer into poly(lactic acid) and the other polymer by melt blending wit~ them a first plasticizer selected rrom the group consisting of oligomers o~ lactic acid,- oligomers of lactide, and ~ixtures thereof; and melt blending with the blend a second plasticize~ selec.ed ^~om ~he grou? consis~ing o~
lactic acid, L-lactide, D-lactide, meso D,L-lactide, acemic D,L-12__ida, and m`~U-QS ~he~e~. Ir desi_~d, a rirst plasticizer de^ined by ~he ~or~ul2 II- m2y be used ~ ~ ThiS ?rOCadU_ ~11Q~S the blending Q ^` _he -irs~
_ 1 C 5 _ _ C _ _ ~ _ ~ _ _ _ _ _ = = _ ~ .. ~ ~ _ _ ~ ~_ ~ _ _ . . _ _ . ~ _ _ . _ ~ . _ _ . . _ C ~ . . _ 5 _ _ . ~ ~ ~ ~ _ _ _ _ _ _ _ _ ~ ~ ~ _ _ _ ~ . ~ _ ~ _ . ~ ~ ~ _ _ ~ _ ~ _ _ _ _ _ _ . .. .. _ . ~

_ _ ~ _ _ _ ~ _ _ _ _ ~. _ _ . _ . . ~. = ~ . _ . . : _ . . . ~; _ _ ~ ~ , _ _ ~,09~ 'CT~Sql/n63~-~ ~ J ' ~ ~ j resistance to the blended composition. Such an elastomer may be, for example, a Hytrel~: a segmented polyester which is a block copolymer of hard crystalline segments of poly(butylene terephthalate) and soft long chain segments of poly(ether glycol). one example is known by the trade name as Hytrel~ 4056 (DuPont) segmented polyester~
In addition to the above there are disclosed blends including on~ or more plastici2ers. T~e blends are useful with the above materials, as well as with others as further discussed ~erein.
The poly(lactic acid) present in the blends may be represented by formula I: where n is an integer between 75 and 10,000.
Plasticizers useful with the invention include D-lactic acid, L-lactic acid, racemic D,L-lactic acid, D-lactide, L-lactide, meso D,L-!actide, racemic D,L-lac~ide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof. The oligomers of lactic acid and cligomers o~ lactide are defined by formula II: where m is an integer: 2 < m < 75. These limits correspond to number average molecular weights below about 5,400 and below about 720, respectively.
Further plasticizers useful in the invention include oligomaric derivatives of lactic acid, selected rom th~ ou? defined hv r_rmul~ III: where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated;
whe-e R' = ~ a`~ 1, ai~c~'ar~l c- acc~~;~ and R' is saturateà; ~he_e R an- R' c~nnot b- h be H; ~here is n ~3 The ? astici~ars .~y be ~resan_ i.... any ?~our _`._- -~_t~ e _ec~ 5-`'-~ _c, _ _ _ = ; _ _ -- -- _ -- _ ~ ` _ _ _,~; , __ ,, _ _ ~ ,, _~ _ _ _ , _, . _:
~ e c-_~?_~ ic.............. _ =:~e ~ ?~
_ ~ _ _ ~ _ _ _ ~ _ _ _ _ _ _ _ _ _ _ . ~ ~ _ :. . _ _ _ _ _ . . ~ _ _ _ _ _ :~ ~ ~ = -- _ ~: _ = _ _ . ._ ~ ~ _ _ ~ _ = ,, _ _ _ , _ ~ -- _ _ _ ' ~ ~ _ , .

~O9~/t~13 PCT/~s9l/o63~-_~s_ moisture. For pliability, plasticizer is present in higher amounts while other characteristics are enhanced by lower amounts. The compositions allow many of the desirable characteristics of pure nondegradable polymers.
In addition, t~e presence of plastici2er ~acilitates melt processing, prevents discoloration, and enhances the degradation rate of the compositions in contact with the environment. The intimately plasticized composition should be processed into a ~inal product in a manner adapted to retain the plasticizer as an intimate di~persion in ~he pol~lactic aci~ and~or its coblended polymer for certain properties. These steps can include:
~1) quenching the composition at a rate adapted to retain the plasticizer as an intimate dispersion; (2) melt processing and quenching the composition at a rate adapted to retain the plasticizer as an intimate dispersion; and (3) processing the composition into a final product in a manner adapted to maintain the plasticizer as an intimate d~sperslon.
Particularly advantageous is the sequential incorporation of plasticizer into poly(lactic acid) and the other poly~er by melt blending with them, a first plasticizer selected from the group consisting of oliqomers o~ lactic acid, oligomers of lactide, and mi~tures thereo^; and melt blending with the blend a second plas~ici~er selected r`ro~ the group consisting of lacti_ acid, L-la~--ide, 3-lactide, meso D,'-lactide, `-~C2~`_ D.L-la-=ide, and ~i~_u~es the~eo~. T~ desi_ed, a ci_st plas~ici e- d~ ed by the fo~ ula T~T mav ~e ~sed alone or in a_mi~:_m-e ~i_n ~n oiigo~er c_ rc~ula ,1.
~his p-ccec~a~e ~ilo~ he ~lendi?.v oî .he firs.

?e-~

~09'/0~13 -23- PCT/~S91/Q63~, w ~ v B~IEF DESC~I~TION O~ ~H~ FIGURES
Fiyure 1 is a graph showing the relationship between percent lactide (abscis~a X) in the composition as plasticizer and tensile strength measured in PSI (ordinate Y)~
Figure 2 is a graph showin~ the relationship between weight percent lactide (abscissa X) in the composition as plastici2er and elastic ~odulus measured in 1000 PSI tordinate Y)~
Figure 3 is a graph showing the relationship b~tween percent oligomer (a~scissa X) in the composition as plasticizer and tensile strength measured in PSI
(ordinate Y) where curve A is ~or a 90/10 copolymer and curve B is for a 92.5/7.5 copolymer.
Figure 4 is a graph showing the relationship between percent oligomer (abscissa X) in the composition as plasticizer and the elastic modulus measured in 1000 PSI (ordinate Y) where curve A is for a 90/10 copolymer and curve B is for a 92.5/7.5 copolymer.
Figure 5 is a graph showing a DSC plot of a control composition prepared by the teachings of the present invention. Temperature is measured in C (abscissa X); heat flow is measured in m~ (ordinate Y). curve A
represents a first scan of the ~aterial and curve B the 2~ second scan.
FigurP 6 is 2 yraph sho~ing a DSC plot of the c^m?os_ti~n Oc ~am?le S~ Temperature is ~e2sur2d i~ C
~absciss2 X); hea~ f' 5~' lS ~e~sured in mW ~o_dinate i).

3~ s_ar..

?-si~ ?~ c ~e~

res~ s-_~ e-~l -.^ c~

_ _ _ _ _ _ _ _ _ _ ~ . ~ _ _ _ _ _ _ . ~ _ _ _ _ _, _ _ . . ~ _ . ~

~'0 9'/()~13 ~ 9~ n~

copoltlmer of Example 5B. Temperature is measured in C
(abscissa X); heat flow is measured in mW ~ordinate Y).
Curve A is unquenched copolymer; curve ~ is quenched copolymer.
Figure 9 illustrates the DSC plot o~ t',s material of Example 5B after remaining at 70 C ~ox 100 minutes.
Temperature is ~easured in C' (abscissa X); heat flow is measured in mW (ordinate Y). Curve A is unquenched copol~mer; curve B is quenched copolymer~
Figure 10 illust-ates the DSC plot o~ the ~aterial of Exa~ple 5B after anne~ling in 185 F overnight~
Temperature is measured in C (abscissa X); heat flow is measurQd in m~ (ordinate Y). Curve A is unquenched copolymer.
Fi~ure 11 illustrates the DSC plot of the material of Ex2mple SB that has been blended with 5 percent calcium lactate. Temperature is measured in C
tabscissa X); heat flow is measured in mW (ordinate Y).
Curve A is unquenched copol,vmer; curve B is quenched copoly~er.
Figure 12 co~pares the melt viscosity (poise) in thousands (ordinate Y) versus shear rate characteristics (l/sec) in thousands (abscissa X) of polystyrene (curve A) at C and the lactide polymer prepared as in Example 8B
(curve B) at ~60 C.
Figure 13 illustrates a DSC ?lo~ for ,he co~ ,~er c~ am?le ~ 'em?er2tu_e ~s me2sured '~ C
(~sciss~ `~3; h ~a_ fl o~i ~s teas.~-ed in m~ (ordin2~e ~
-~t~-~ et ~ s ~: t~ en_~ct~' -G?ol~,~e-~ c~ e ~ ~` s ~uP t~c~ed ~ O c--_~ o l t,~t t Fi~u-e '` il`us~-ates ~ DS~ or t~e ;-_-C-~2 `'`~ ^?;'~ `_ `5 ~t-c~ r` C-?~ '- C-~ _ _ ., _ ~. _ . . _ . . _ _ . . _ ._ _ _ _' _, .~ _ _ . _ _ _ ~ _ _ _ _ _ . ~ ~ . ~. _ ~ . _ _ ~. _ _ _ _ .
5 ~ __s c. tt~t~ .e ~ e~ c -~-?-- -- ` ~ ~~~ c ~ ?~ ~r-1 -t --09'/0~ 31- PCT/~S91/Ofi'.' ~ ' .. ~. 3 and a homopoly~er of L-lactide. Temperature is measured in c (abscissa x)i heat flow is measured in mW (ordinate Y). Curve A is the unquenched blend of copolymer and homopolymer; curve B is the quenched blend of copolymer and homopolymer.
Figure 16 illustrates a plot of the glass transition temperature of 90/10, L-/D,L-lactide copolymers versus residual lactide monomer. Abscissa X is lactide measured in wt.~; ordinate Y is T~ measured in C.
Figure 17 illustrates a DSC plo~ o~ 90j~0, L-/D,L-lactide copoly~er blended wit~ S weight percent polystyrene. Te~perature is measured in C (abscissa X);
heat flow is measured in mW (ordinate Y). Curve A is the first heating; cur~e B is the second heating.

DET~ILED DESC~IPTION OF

A~__First General Embodiment The environmentally biodegradable compositions disclosed herein are completely degradable to environmentally acceptable and compatible materials. The intermediate products of the degradation: lactic acid and short chain oligomers of lactide or lactic acid are widely distributed naturally occurring substances that are easily ~etaboli-2d by 2 ~ide variety o organis2s. ~hei~ natural end degradation products are carbon dioxide and water.
~c..~_m?12~oc e~u~valen~s o~ _~ese. com?osit~o~s s~ch as those .hat _c..~ai~ or amounts o_ o_her ma~eri~ls, ^i'l~-s. _~ rs -~ e'~
enviro~.-e~.t_lly ~eg:~a~le ~v ~ro?e- cho c_ c- mal e~izls.
e _-~?cs~ c-.s ~ r.;i~ n~â`~ e~
_ _ _ _ _ ~ _ c ~

~ .~ic-.al .~ _e __c--~e ~ ej _~^_ l _ _ A, wos~/~t3 PCT/~S9l/n632 _37_ ~ J

more slowly degrading residue will remain. T~is residue will have a higher surface area than the bulk product and an expected faster degradation rate.
T~e general applic~tion of the invention results S in the first and general embodi~ent of the invention. T~e homopolymers of D-lactide, L-lactide, D,L-lactide as well as copolymers of D-lactide, L-lactide; D-lactide, D,L-lactide; L-lactide, D,L-lactide; and D-lactide, L-lactide, and D,L-lactide all produce ~aterials useful in the invention when plasticized by lactide monomers, lactic acid, oligomers of lactide, oligomers of lactic acid, deriYatives of oligomeric lactide and mixtures thereof that are intimately dispersed in t~e polymer. A plasti-cizer may be produced by stopping t~e reaction before polymerization is completed. Optionally additional plasticizer consisting of lactide monomers (D-lactide, L-lactide, D,L-lactide, or mixtures thereof), lactic acid, oligomers lactide or oligomers of lactic acid or its derivatives including all L-, D-, and DL- configurations, and mixtures thereof can be added to the formed polymer.
While aspects of the invention can be applied to various polylactides in general, one preferred polymer is defined by the formula:

l ll whe-e n is _~ 2 r` e~_ee o poly~e~i~~ n (number c-repeatin~ units), pl2sticized with a pl2sticizer derived ~ r.~e~-s ~sc_ __ p_oduce t:~e po'~e~ T~e m~~e l~._im~tely _~e pl2stlc-~er ~`s ~t2~ te~ wi ~ .2 ?~1~.C- ~ b~_e_ c_e ~,c _ . ~ _ _ _ _ = _ _ _ ~ _ _ _ _ ~ , _ ~ _ = _ = _ ~ . _ _-- = ~ ~ _ .

~ . _ c~ ~e~, c~ n~m_r -~-_1___~__ ___~=____~_ __~ __ _____ ~_ ~... ._si__c_ ~.~____ _ _ _ _ _ _ _ . _ : _ . _ ~ _ . ~ _ . ~ ; ~: _ _ _ _ . _ _ s _ _ _ _ . : _ = _ _ ,~ rcr/~sql/o polymerization. The preferred oligomers of lactic acid, and oligomers of lactide including all L-, D-, D~-configurations and mixtures thereof, both random and block confi~urations, useful for a plasticizer are de.ined by the formula:
l 3 1 H0 ~ r~
H
where ~ is an inte~er: 2 < m < 75~ Preferably m is an in~eger: 2 c ~ ~ lO~
The oligomers of lactic acid and its derivatives including all L-, D-, D~- configurations and mixtures thereof, both random and block configurations, useful for a plasticizer are defined by the formula III:
CH3 o R'O _ q R III
H
where R = H, alkyl, aryl, al~ylaryl or acetyl, and R is saturated, and where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, where q is an integer: 2 < q < 75; and ~ixtures thereof.
?referzDly a is ^-n in~ege~: 2 ~ q < o.
The plasticisers added to the ~olymer osi.io~ a _0'13~ .s:
(a) They zct as ?las~lcize-s inl~odu-ing __-posit_or.s no~ _ound i-. ~?~'y~er-5~

;lscosi~y ~ r _~.e ?o~vr.ers a~ e_s _:.e _ . _ = _ _ _ ~ , . _ _ . _ _ _ _ _ _ _ ~ _ .

WO '~'/0~ 1 ~ I S~ 63', --3~--. .L ~J ~t (c) The plasticizers prevent heat build up and consequent discoloration and molecular weight decrease during extrusion forming of poly(lactic acid).
(d) The plasticizers add impact resistance to the compositions not found in the polymer ~lone.
In addition, the plasticizers may act as compatibilizers for melt-blends of polylactides and other de~radable and nondegradable poly~ers. That is, molten mixtures of two dif~erent polymers can more intimately associate and mix into well-dispersed blends in t~e presence of the plasticizers. The plasticizers may also improve performance in solution blendinq.
The subscripts n, m, and q above refer to the average number of mers (the repeating unit) of the polymer or oligomer. Number average molecular weight M~ as used herein is related to the mers by multiplying n, m, or q by the molecular weight of the individual mer, for poly(lactic acid) this number is 72. The nu~ber o~ ~ers present in a polymer is also called the degree of polymerization. The reader is referred to the following texts where this subject is discussed further ~olymer C~emistry an Introduction, 2nd Edition, R. Seymour et al, ~5 Marcel DekXe_, Inc., 1988 cnd Tnt-oduction to Polymer Chemi~trv, R. Seymour, McGraw-Hill, New York, 1971.
The pro?o__~ons ~ lactice, D-lac~ide, and ~rT_ la~_id- in _he pol~o_ C_ e not c_~ al to c~ n~
'-s~i-s; ho~ . t~ io-C ~ D.~-~ctide may ~-_ry ca_~ai~ pe__~es as ~~r~er discussed ~elo~ c_=e o~ ~-lcc~ -l_c~ cc~ide ~O9'/~13 rCT/~`S91!063'-D-lactide is a dilactone, or cyclic dimer, of D-lactic acid. Similarly, L-lactide is a cyclic dimer of L-lactic acid. Meso D,L-lactide is a cyclic di~er of D- and L-lactic acid. Racemic D,L-lactide comprises a mixture of D-lactide and L-lactide. Nhen used alone herein, the term "D,L-lactide" is intended ~o include meso D,L-lactide or racemic D,L-lactide.
one of the methods raported in t~e literature for preparing a lactide is to de~ydrate lactic acid under high vacuum. The product is distillQ~ at a hiqh temperature and low pressure, Lactides and t~ei- preparation are discussed by W. ~. Carothers, G. L. Dorough and M. J.
Johnson (J. Am. Chem. Soc. 54, 7~t-762 ~1932]); ~. Gay-~ussac and J. Pelouse (Ann. 7, 43 ~1833~; C. A. ~ischoff 1 and P. Walden (Chem. Ber. 26, 263 ~1903~; Ann. 279, 171 tl984~); and Heinrich Byk (Cer. Pat. 2~7,826 ~1912~);
through Chem. A~str. 8, 554, 2034 ~1914]).
The optically active acids can be prepared by direct fermentation of almost any nontoxic carbohydrate product, by-product or waste, utilizing numerous strains of the bacterial genus ~actobacillus, e.g~ L2ctobacil~s delbrueckii, L. salivarius, ~. casei, etc. The optically active acids can also be obtained by the resolution o~ the racemic mixture through the zinc ammonium salt, or the ~5 sal' witb alX21cids, such ~s mo ?hine~ L-lac'ide is a white powder having a molecular weight o~ 144. I_ an im-~r~ e~ ~ y-~2i~b~ p~~ ie e-~?l~ve~ ~
~ccorc2nce with ~ha present invention, it is p_-efa-able ~o v ~ alli~_t~n ~ r~
~3 i_cbu~yl l~et^n.e. ~he sno~ hi~a c ys-~ls ^~ `-lzctice r~ at cc-~~ s usa~ ~E-a`` n ~ha s~ol _ dsno~as ~`e-~ C^~ e?'-_~e ~ c- e`

_ ~. c_: _ e__ ~_ _~.,;~____i: = ~ __ ~- e W(>s7/n~l~ PCT/~S91/063'7 ., . ~ i 3 ~
lactonitrile (acetaldehyde cyanohydrin~ or by direct fermentation of almost any nontoxic carbohydrate product, by-product or waste, utili2ing numerous strains of the bacterial genus Lactobacillus. D,L-lactide is a whlte powder having a molecular weight of 144. If an i~pure, commercially-available product is employed in accordance with the present invention, I prefer to purify it by recrystalli~ation from anhydrous me~yl isobutyl ketone.
One such commercially available product co~prising a mushy sémisolid melting at 90-130 C was recrystallized from methyl isobutyl ketone and decolori2ed using charcoal.
After three suc~ recrystallizations, the product was t~mble-dried in vacuo under a nitrogen bleed ~or 8 t~ 24 hours at room temperature. The snow white crystals thus obtained comprise a D,L-lactide mixture melting fro~ 115-128 C.
In preparing the compositions in accordance with the invention, it is preferred to carry out the reaction in the liquid phase in a closed, evacuated vessel in the presence of a tin ester of a carboxylic acid containing up to 18 carbon atoms. The c~mpositions, however, can also be prepared at atmospheric p-essure with the polymerization system blanketed by an inert gas such as, for example, nitrogen. If polymerization is conducted in ~5 'he oresence of oxygen or 2ir, some discolor2tion occurs with a resulting decrease in mole~ular weisht and tensile s,_2ns~h. 'he p~ocess c_n `~e c~rried out 2t ~e~?eratures ~here the ?o'~e_i_ ~ic~ is s`~ssish in i_s la-e_ ~es ~ is_~s ~ ~ _ _0 mel_. ~re er-ed te~?er2~ures ~ his ?ur?cse Fr_ ~ene-~lly ~etwee-. _he meltin~ ?ci..-~ 2~ pure ~ c_i~e _~
~ure ~ lac~i__, ~~ ~^~;ee.~ ~ _c `_, ^ ihi' t _-. ?._ ~i~V

~=E5e..~ el~ 3~ ^ ^ r ~~
_ _ _. ~ _ _ .
_ _ __ __ _ .
~ c-~-.. = `__~ c~r ~ t~

UIO9~ 3 PCT/~S91/063~-eutectic mixture, which melts t~ a mobile fluid that is an intimate solution of one, two, or three monomers.
2. The ~luid melt is polymerized by catalyst to form an increasingly viscous solution and eventually unrQact~d ~onomer is trappQd in association with the polymer as a solution, rather than as a distinct heterogeneous phase. The monomer no longer can react since the reaction is extremely di~fusion controlled and cannot efficiently contact the low concentration of active end-groups of the poly~er.
3. The polymeri2ation ceases or slows considerably so that at room temperature the blend of monomer and polymer are a solid solution that imparts plasticization, clarity, and flexibility to the composition.
4. The catalyst deactivates so that subsequent melt-fabrication does not reinitiate the polymerization.
5. The plasticized composition is quite stable since the residual monomer is very high .a ~oilin5, e.g., l~ctide has a `aoiling point of 142 C at 8 torr, and is tightly ~sso__~e~ s~ h i.s o?en-ch_in t~ut~ e~-polylacti~e.

3~ te~pe-et~-P bet~een the ~elting poi..t o. _he T-lactide ~nd 20G C cn_ ~ c~ s ~ 5~ e n^~ ~r ~ C~C`~ n_-e~cin~
e~ e -~ a5 ' a ~~ c e~.~~

~0~"~l3 ~cr/ls4l/n~3~/

. v ~
are obtained by heating a mixture of L-lactide and D,L-lactide at a temperature between about 110 C and 160 C.
The catalysts employed in accordance with the invention are tin salts and esters o~ c~rboxylic acids containing up to 18 carbon atoms. Examp~es of such acids are formic, acetic, propionic, butyric, valeric, caproic, caprylic, pelargonic, capric, lauric, myri~tic, palmitic, stearic and benzoic acids. G~od results have been obtained wieh stannous acetate and stannous caprylate.
1~ The catalyst is used in nor~al ca~alytic amounts.
In aenaral, a c~talyst concentration in the ~ange o~ about 0.001 to about 2 percent by weight, based on the total weight of the L-lactide and D,L-laceide is sui_able. A
catalyst concentration in the range of ~bout 0.01 to about 1 ~ percent by weight is preferred. Good results were o~ained when the catalyst concentration is in the range of about 0.02 to about 0.5 percent by weight. The exact amount of catalyst in any particular case depends to a large extent upon the catalyst employed and the operating variables including time and temperature. The exact conditions can be easily determined by those skilled in the art.
The reaction time of the polymeri-ation step, per se, is governed by the other reaction variables including ~5 the rezc~ion te~perature, t~e particular c~talyst, the amount o~ cat~lyst and whe~her a liquid vehicle is em?10Yed. ThP ~eactior. ti~e c~n vary ^~om 2 -~atte_ ^_ s ~ e_~od ~ _s, c~ ys, ~'2p~?.~ t~
~2_ ~ a_ ^ C~ r~s .~ e ?'~ .e-o_ the mi~tu~-e e~ manome-s is cont`nued ur..il he ~esire~
le~el ~ e-~ s ~ ec_e~ e~
~.~xi2at~ e~G_=i-.e- ~ si~ as~
~ _ . . _ _. _ _ _ . .^~ _ _ _ _ _ _ i _ ~. . ~ _ ~ . _ . _ . _ . . . _ _ _ _ _ ~. ~

~i~ec~ -c=- ?~- E c: ~ ~. ` 5 .
_ ~ _ . ~ _ _ . _ _ _ _ _ _ _ _ _ _ . . . ~ ~ _ _ . . _ _ _ ~ . _ _ _ . ~ ~ _ C _ _ _ _ _ . . . _ _ ~o s~/n~l rcr!~s4l~0fi3~-. ~ ~
, attained the conversion of monomer to polymer that is desired to achieve the desired plasticization. In the preferred embodiment of the invention, approximately 2 to 30 percent lactide is left unreacted, depending on the degree of plasticization to be achieved.
In general it is preferred to conduct the polymerization in the absence of impurities which contain active hydrogen since t~e presence of suc~ i~pu~ities tends to deact_~ate t~e catalyst and~or increase the lQ rea~tion time~ It is also preferred to conduct t~e polymerization under subst~ntially a~ydrous conditions.
The copolymers of the invention can be prepared by bulk poly~erization, suspension polymeri~ation or solution polyneri2ation. The poly~eri2ation can be carried out in the presence of an inert normally-liquid organic vehicle such as, for exa~.ple, aromatic hydrocarbons, e.g., benzene, toluene, xylene, ethylbenzene and the like; oxygenated organic compounds such as anisole, the dimethyl and diethyl esters of ethylene qlycol; normally-liquid saturated hydrocarbons including open chain, cyclic and alkyl-substituted cyclic saturated hydrocarbons such as hexane, heptane, cyclohexane, alkylcyclohexanes, decahydronaphthalene and the li~e.
The polymerization process can be conducted in a _5 ~ __h, semi-c_~.t~nuous, cr con_~.uous manr.e~
preparing the lactide mono~eric reactants and catalyst for sl~s~ent ~ io~ y ~-r. ~_ 2d~i~ r.
or~er accorGing ~o ~nown ~oly~eri2ation ~echnicues. Thus, 3~ re2c~an~s. ~he_e2_`_e-, t;~e cr-~lys~-con-2inin ,oao~e_ ~ 3e ~ c- ~~ e_. _-~ G
_ ~ _~ ~ ~_ _ _ _ ; ~ _ ~_ ~ ~_ ~ ~ _ _ _ ~_ ~ A _ _ _ A = _ _ = _ _ --~ _ _ _, _ ~ _. _ _ ~ .

--r~ ~ _ , _ _ _ _ _ _ _ _ _ ~ _ ~ _ = _ ~ ~ _ _ _ _ _ _ _ _ _ A = _ _~ _ S
~ = ` ^ ' _ " 3 G

~o~Jo~,l3 rcT'~nl/n6~'~
--~o--;~ `.; .' .1 :,`', be added to the catalyst, catalyst solution or catalyst suspension. Still further, the catalyst and the monomeric reactants can be added to a reaction vessel simultane-ously. The reaction vessel can be equipped with a conventional heat exchanger and/or a mixing device. The reaction vessel can be any equipment normally employed in the art of making poly~ers. One suitable vessel, for example, is a st~inless steel vessel.
The environ~entally biodegradable compositions produced in accordance with the present invention depQnding upon the L-lactide, D-lactide, meco D,L-lactide ratios, ~ind utility in articles of manufacture, such as ~ilms, fibers, moldings and laminates, which are prepared by conventional fabricating methods. These articles of manufacture are contemplated for nonmedical uses i.e.
outside the body whe~e they can substitute for the common environmentally nondegradable plastics.
Filaments, for example, are formed by melt-extruding the copolymer through a spinneret. Films are formed by casting solutions of the biodegradable compositions and then -emo~ing the solvent, by pressing solid biodegradable compositions in a hydraulic press having heated platens, or by extrusion through a die, including Blown Film techniques.
a-io~s ~ech~nisues i.._ludi-.g me'_ blenQi~c, slow cooling, and rapid cooling (quenc~ing) can be employed in ~r2p~r~g ~._3duc-s ~ s -~ ?~ s a~
copolymers or the invention.

'~ tem~e-2tu-e is --o?-e~ -aDi_l ; ~ --ever.t e~:'e~.sive -~s~ .2 ?ol~.~e_. ~ s=~
~ _ ~ ,_ ~ _ _ ~ -- ; ' _; _ ~ ~, . _ ~ .~ _ _ ~ _ , _,, _ _ .. ~ _ . . _ _ is ~ ~ e =~ ss--~ si=~ ?~

. ~ _ i ~ ~ ~. `` ` ---- -- ` -- ` _ _ _ i C 2 S . . _ _ _ _ _ _ _ _ `_ _ -- -- ;l -- -- ` -- --~09'/0~13 -41- PCT/~`S91/Ofi3'-;t' ~'2~

does not have the ti~e required and remains largely amorphous. The time required to quench depends on the thickness of the sample, its molecular weight, melt viscosity, composition, and its Tg, where it is frozen-in as a glassy state. Note that melt viscosity and Tg axe lowered by plasticization and favor quenc~inq. Thin ~ilms obviously cool very quickly bocause of their high sur~ace-to-volume ratio while ~olded items cool ~ore slowly with their greater thicknesses and ti~e spent ~n a warm ~nold ba~ore removal~ Regular structures such as poly ~L-lactide) order more easily and crystalli~e more quickly than more random structures such as a copolymer.
With the polylactides the melting points are approximately 150-190 C depending on the L-lactide content and, therefore, the regularity of stru~ture. The Tg of all the polylactides, including various L and D,L
homopolymers and copolymers is 60 C. The Tg decreases when residual lactide is intimately dispersed with the polymer. Q~lenching to an amorphous state reqmires that the polymer or copolymer in an amorphous melt is rapidly _ooled fro~ its molten state to a te~pe-ature below its Tg. Failure to do so allows spherulitic crys~allinity to develop, that is, crystalline domains of submicron to micron size. The latter scatters lisht and the polymer s?~ci~e?~s ~co.~ o~ue~ ~ose _-ys_~lli?~-~ Co~s hGve i~proved stability to heat distor~ion. This spherulitic c_vst~ll n~=v is o-_~n cal'ed sho-~ _~ or~el-long rance ~isorder since the c ys~alli.es are ser ~-ted by a~o-?ho~s ,0 crosslini~s ~o -.ain~ain di.e..sional s~2~ y abo~e the T

_ _ _ ~ _ _ ~ ~ _ ~ ~ ~ ~ _ ~ _; _ _ _ _ _ _: _ _ _ _ . _ _ t~oi~ . _.e ?~ _e~c~ - lc.:
_ _ _ ~ _ _ . . _ = _ _ _ .~ . _ _ = _ _ ~ _ . . _ _ _ _ . _ _ ~ _ . . _ _ . ~. _ . i _~ _ _ _ . ~ -- -- --.. ~ ~ ~ _ _ __ _ _ ~ . ~ _ _ , ~ _ _ _ ; _ _ _ _ ~ ~ _ ~ . _ _. . _ _ _ , ~ _ _ _ ~ _ _ _ . _ _ . . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~ _ _ ~ _ _ _ _ _ _ _ _ _ _ ~ ~ _ _ ~'0 9~ .2- r~ '5(~1/()63~-different order, called long-range order, short range disorder. Transparency and resistance to heat distortion are favored.
A detailed discussion can be found in textbooks, for example, "Structural Polymer Properties", by Robert J.
Samuels, Wiley Publications, NY, NY 197~
Contemplated equivalents of th~ compositions of the invention aro those that contain minor amounts of other materials. ~he copol~ers produced in accordance with the present invention can be modified, if d~sired, by the addition of a cross~ ~ing agent, other plasticizers, a coloring agent, a filler and the lika, or minor amounts of other lac'one monomers such as glycolide or caprolactone.
Cross-linXiny can be effected by compounding the compositions with free-radical initiators such as cumene hydroperoxide and then molding at elevated ~-emperatures.
This can improve heat-and solvent-resistance. Curing can also be effected by compounding the copolymers with multifunctional compounds such as polyhydric alcohols and molding, or thermoforming under heat and vacuum. Graft-extruder reactions to effect curing of the polyesters is an obvious method of cross-lin~ing and chain-extending the copolymers.
In -reparin~ -oldin~s, a ~il'er _an ~e incorporated in the compositions prior to curing. A
~iller has _~.e ^unc~i_-. o~ rmodifyinv _he --o?er~ies ef a moldins, in_`udir.~ hardness, s,-en~~h, vempera-ure ? ~ _e ___ _.1~.
.o -o~de-, ?owde_ed calcium c~r~ona~e, si'i-a, ~aolini~e ~ _ s _ _ _ _ ~ 'i_ 5~ ~e~ es~~_`_. ~ ?er~j ~ ~ _ _ _ _ _ _, _ _ _ _ _ _ _ ~ S ~ _ . . _ ._ _ _ _ C _ _ _ _ _ . ~ _ ~

~o ~/n~~ s~l/06,~--~3-.~, .; v _ _ v ~

The compositions prepared according to the present invention can be used in producing reinforced laminates according to Xnown procedures~ In general, laminates are made from a fibrous mat or by assembling a multiplicity of sheets of material to form a matrix which is consoli~ated into a unitary structure by ~lowing molten precuxsor or composition through the fibrou material and curing it while in a mold or hydraulic press to form t~e polymQr. Fibers which are used in forming the matrix i~clud~ natural and synthetic fibers s~ch as cal~ulose darived from woo~, cotton, linen, hemp, an~ the li~e, glass, nylon, cellulose acetate and tha lika~
The compositions of the first ~eneral embodiment and their preparation are further illustrated by the following specific examples.

~xam~le 1 80/20. ~-lactide/race~ic D.L-lactide 160 grams of L-lactide and 40 grams of racemic D,L-lactide, both of high purity (Purac, Inc., triply recrystalli~ed~, were charged into a 500 ml, round-bottom flask and purged with dry nitrogen overnight. 10 ml of stannous octoate is dissolved in 60 ml of anhydrous toluene, and 10 ml of the solvent is distilled to a Dean-s~~ e~ -o ^-'-ec~ c-yness or this cata'vs~ solu-ion ~v azeotropic distillation. From the 10 ml of stannous octoate in _~ ml o- _r~ ~oluene a 0~2 ml ~or~ion ic removad with 2 syringe ~n~ injec~ec i:_o the ic_-iies in a si~in~e needle conne_ __n ~hat enters ~ eao_io. l~s];
~~ _`-_s~h ~ ~ se-=~ .=s -~__ 2 `~`P-^- ~ _`_~`'~1_ ~ _ ~ _ .
_ _ _ ~ . _ _ ~ ~ ~ _ i ,~ ~_ _ _ _ _~ _ _ ~ _ _ r~ ;_ _ ~ _ ~; ~ _ ~ _ _ _ ~
_ _ _ ~ ~ _ _ _ _ _ _ ~_ .. . _ _ _ _ _ _ _ _~ _ _ _ . . _ ~ _ ~ . = ~ _ _~ _ . ~ ~ _ _ ~ . _ _ _ = _ _. .
_ . ~ _ _ _ ~ _ _ .. ... ~ _ _ . ~ _ ~
~ _, a . ~ _ 2 _ _--. ~ ' _ ^ = ` _ 2 5 `-~ _ 1 _ c:. . . _ _ ~ -- .. i ~ G "

_ _ _ _ ~ _ _ _ _ _ ~ ~ _ _ ~ ~ ~ ~ ~ _ _ _ _ _ ~ . _; _ _ . ~ . _ . . _ _ _ _ _ . . ~ . . ~

~0 '~/n~13 rcr/~ssl/ofi3~--~4-the colorless, transparent products are removed from the heating bath, cooled, the flask broken, and shocked with liquid nitrogen to remove glass from the product. The copolymer was molded in a heated hydraulic press.
Compression molding to 5- to 10-mil t~ick films was possible at 20,000 lb pressure, at 170 C, in a time period of 2 minutes. The films were evaluated for their tensile properties on a Instron tester, and ~he results are listed in Table 1. Samples 1/8-inc~ thic~ were also molded for impact strencth testing. A ther~ogravimetric analysis of t~e product was performed, noting the weig~t loss upon heating the sample to 150 C in ~ minutes and holding the temperature at 150 C for 60 minutes. The weight loss of the sample was 19.5 percent and nearly complete in 60 minutes. T~e weight loss is attributed to loss of lactide ~onomer. Results of differential scanning calorimetry reveal that the composition has an endothèrm beginning about 110 C, becoming more pronounced as t~e temperature increases to 200 C. No melting point was observed.
2~ Specimens were annealed at 185 F overnight and reexamined.
They remained transparent, colorless and pliabls. Samples of the copolymer could be remolded 6 times without any discoloration or obvious loss of strength. Thin ~ilms were clear, transparent, colorless, and quite flexible, _5 de~pite t~e ~e-e2ted ...ol~_ng.

~09_/0~13 PCT/~S~l/063 : -4~-~ _.

TABLE 1. PROP~RTIES OF COPOLYMERS(a~ OF L-LACTIDE AN~
D,L-LACTIDE WHtEN PLASTICI~ED BY LACTIDE

Example 1 2 3 .. ..
Film thickness, mil 8 8 10 Tensile strength, 1000 psi, ASTM 3.9 1.~ 7.9 ~longation, perce~t 280 S06 3.S
100 percQnt ~odulus, 1~00 psi 0~
200 percent ~odulus, 1000 psi 1.~0 -~ --Tangent modulus, 1000 psi36.6 -- 289 I20d impact strength, ft-lb/0~3 -- C.4 Mw~ 1000's 540 281 341 Mb, lOOO's 270 11897.5 Residual lactide~C), percent19.5 27.~ 2.7 (a) 80/20, weight ratio, of L-/racemic D,L-lactide tb~ l/8-inch, notched samples By isothermal thermogravimetric analysis weight loss at 150 C

Exa~ple 2 In a 3-liter, round-bottom flas~ was charged 1.84 Kg of L-lactide, 0.46 Kg of racemic D,L-lactide and 2.3 ml of the stannous octoate solution, similar to Example 1.
T~e mi~ture was purged with a-yon ~r 3 hours, t;nen healec isothe-ma~ in a '25 C o~l b th. ~he -i~t~re melts, was ed th.~~ou~h~ ~ s-.~i~liny, ^-n_ rc-~s a ho~ogen~ous, '~ar.s?a_ent, co~c~less ='~ic ~hos~ viscosi_y in--eases su~stan~ialiy a~`tDr seve_~l ho~rs. A~te_ ~ ~.ours ,he fi~sl; was remo~ad f-o~ the heating ~at!l, cooled, and the 3C gl2ss r2~c~ed -_m ~he _'ear, t-ans?c-en_, solid produc_.
~ c ~
~ d -o ~ - s._ll__ si~e in ~ g-inde- ~i.h d_v _ ~. _ ~ . . _ _ _ _ . . _ ~ _ . _ . ~ _ .~ _ _ _ _ _ _ _ _ _ . . ~ c _ . . _ _ '` C~ r ~C~ ce`~e~c~ ~S~ C~U~ -ie~ o~er~icr,t -_ ~~__.~_ ___~_~__~_~ ~_.__e___ .~ _2____ __.~

'0 9~/0~13 PCl~S91/Ofi3~-~ 3 prepared as described in Example 1 and the films were examined for their tensile properties and weight loss by thermogravimetric analysis as shown in Table 1.

ExamDle 3 In a 250-ml, round bottom flas~ was plac~d 79.98 g of L-lactide, 20.04 ~ of racemic D,L-lactide~ and 0.20 ml of stannous octoate solu'io~, simil2x to Example 1.
Tho flas~ was swept ~y nit~o~an through inlets and outlets and heated in a 125 C oil bath. The mixture melted to a colorless and ~luid liquid ~hat ~was thoroughly mixed by swirling th~ flask. After 2 hours, the oil ~ath temperature was increased to 1~7 C, and after 14 ~.ours total heating time, the te~perature was decreased to 131 C. Total heating time was 18 hours. The product is transparent, colorless, and glassy. It was evaluated, similar to the preceding examples and the results are recorded in Table 1.
Examples 1 to 3 reveal the effect of reaction temperature on the properties of the copolymers as occasioned by the resulting csmposition.

Exam~le 4 Films of the copolymers o Examples 1 and 3 were immersed in wa_er ~- ce~e_al m~nths~ r.~_r 3 weeks, the copolymer of Example 1 became hazy while that of Example 3 2~ ~emained clear c- a~__~;im~_aly ~ m_n_hs~ a_te~ 3 cr.th~
the ~ilm of Example 3 became no~icaably ha2y a~ the fil~

in cor.t~c~ ~i_h the "- f _~ar.?le 1 tastas acidic ~hiie that c' ~ m?le 3 is -_S~2l 25~

~ _ 2 _ _. ~ _ S _~ . ~_ . .; _ _ _ ~ ... ~. . _ . _ _.

i-. ;'~e __~ ;~ ,r ~ 5~ ?-~?~ s _~.e -~?~ 2- 2~r- _~ `` C~`` .~ C~: `lC.~^-f`ll ~

~097/0~13 ~CT/~S9~/063'-? ,. ,i ! ~ ~

tangent modulus compare favorably with polyethylene compositions used, for example, in plastic trash bags, general film wrap, plastic shopping bags, sandwich wrap, six pack yo~es and the like. The shape Q f the stress-strain curves are approximately the same ~or both thecopolymer and that for a linear low density polyethylene composition co~monly used in trash bag compositions. A
comparison o~ properties are s~own in Ta~e 2~

TABLE ~. COMP~RISON OF POLYET~YLENE TO POLYLACTIC ACID

Property NA 272 LLDPE~ Lac~ide Tensile strength, 2.18 2.9 ~.9 1000 psi, ASTM
Standard C
Elongation, S 261 500 280 15 Tangent modulus, 5~.9 51.0 36.6 1000 psi 100~ modulus, 1000 1.77 -- 0.74 psi 200% modulus 1.82 -- 1.20 20 HDT~d), 264 psi, F 95 99 122 ~ v . ~, ._ _. _ __ . . _ _ .
(a) Linear low-density polyethylene, 5-10 mil, 2-in./min., our experiments.
~b~ Lir.e~- lo~-àensity -ol~ce=~ en2, da~- ~~c~ c~p~t_~
file.
(C~ Copolyme~ cf L-lactide/racemic D,L-12ctide, ~x2mple 1 d ) ~.e2~ deL~ec-~ 3n te~?-`-~`~-e-r~ e_2 ~ c~e~ -_o-~ '~ c~ e~s~ o . ~ c~~~
~ashio.... This is illus~ rx2~m?1es 1 2nd . T.
t i _ ~ 3 . . _ .~ ._ _ _ S ~. _ C~ ~ C _ ` ~i r c C~ '~ 2 _; ~ 2 ~ ^ r~ i f _ ~ _ r~

WO~2/(~13 i~r,~i~31io~
-~8-~ 3 The compounding can be accomplished by blending the molten polymer with lactide monomer in conventional processing equipment such as a mill roll or a twin screw compounder. The normally stiff, glassy, lactide polymers are flexibilized by the lactide and remain transparent, colorless, and very nearly odorless. The lactide i5 not very fugitive, requiring heating, and a nitrogen sweep, typically, 170-200 C for 20-60 minutes to remove the lactide in a gravimetric analysis. Neither is the lactide visible in films under an optical microsco~e~ The lactide d~mains are sub~ic~on in size. T~is lexibili~ing of the poly tlactic acid) suggests its use as a environmentally biodegradable replacement for polyolefin, disposable, pac~aging films.

ExamDles 5-16 A series of experiments were performed in which copolymers of L- and racemic D,L-lactide were prepared, melt blended with variable amounts of lactide, and the physical properties of the blends evaluated as a function of the lactide composition. Monomer lactide content was assayed by a pre~iously developed isothermal, thermogravimetric analysis. The lac.ide contents were measured before and after compounding and molding into films.
It ~-as observed t~a, open ~all, ? -oll, milling tended to volatilize the lactide at temperatures required ~or .~.e ver~ hig~, ~olecula- weig~.t lactide copolymers.
~ese 10SSQS COU~ d be ~inimi2ed by masterbatc~ing o- by using lo~e~ mo_acui_r ~e_g~ ida __~ai}~--s ~_..`e ~
3~ lo~er a~ta~._2.t mixin~ tem~e~~_ures~. ~ bette- ~i~:ir.~ ano ~le.~in~ me~.o_ ~_s 2 -onve~.ri n-~ in s_re~ e~t~ude~, in T~bie ~.

_ _ _ C i ;~, _ _ 5 ~ ~ _ ~ i c ;~ _ ~ C ~ i ~ c _ ~ ~, ~` ' ` _~&I~ ~S. ` ~ _ C ` ~ ~'e '_S ~ 3 _ _ eJ_~~:

0~13 PCT/~S~I/Ofi3'-- v ~ 3 a flexible film, whereby the oligomers or their derivatives are added first, allowing the lactide to be mixed in the melt later at lower temperature. By adding oligomers first the melt viscosity decreases very significantly, allowing the temperature to be lowered, and the lactide can then be mixad in at a lower temperature without significant volatilization. This is demonstrated in Example 16~.

~m~
A 90/10, LID,~-lactide copolymer prepared by methods previously described, and analyzed by gel permeation c~.romatography to have a weight-average molecular weight of 480,000, a number average molecular weight o~ 208,000, was banded, that is, melted and ~ixed on an open 2-ro~l mill preheated to 350 F. The copolymer will not melt and band well on the mill below 350 F. To 25 grams of this melted copolymer was added 10 grams of oligomeric lactic acid of a degrse of polymerization of 2.34. After all of the oligomeric lactic acid mixed in, the temperature was dropped to 300 F, where the mixing was still quite good. With the roll temperature at 300 F, 10 grams of L-lactide was added slowly and mixed. The mix was stripped from the roll and pressed into a thin film in a press at 30~ he ~ ~il thic~ film was colorless, transparent and very flexible. ~ithout the lactide the resulting fi'~ ~oul~ have been s iff~ Withou~ firs~
ad~ing the olisomeric l~ctic acid the lac ide could no voia.ili~atior,~
c~~ c-.~ '~ e -' ca~` ci~e-sir~ s_ ;~-~
s _ . ~ _ ~__-.sparen~. ~r._e ~e~y f~in_ (?le2s~nc~ o_i~ o lGc=ice _s ~e~c=ab` _n~ is_2_..7C-lG t~s7~e " - ` cC=i~2 ~'CS
`~ 12s ~ r~?~s t;~re _ _ _ _ _ _ S _ _ _ _ ~ _ _ _ _ _ _ ~ -- -- ~----~-- -- ! --~-- _ _ . . ) _ ~ _ 1 C ~ e_ ~`O97,(~i3 ~'CTi~S91/~

without shattering or tearing. They stiffen somewhat when placed in a cooler (5 C, 40 F), but remain flexible and creasible without breaking. These films noticeably soften in the hand, indicating a glass transition temperature S below 37 C. When the lactide content is less than 20 percent, the ~ilms will have a rattle typical of a polyolefin film. At greater lactide contents the films have the drape and '`warm'` feel o~ a plasticized poly(vinyl chloride) (P~C). In fact, the co~positions of the invention are ~lso a replacement fo~ plas~icized P~C in ~any applications.
As shown in Table 3, the elastic moduli (initial tangent moduli) can be relatively high, similar to a linear low density polyethylene (LLDPE~. This is an indication of potential form stability. Lower moduli and tensile strengths are similar to low density polyethylene (LDPE). Physical properties, as a function of lactide content, were plotted as shown in Figures 1 and 2.
Referring to Table 3, at approximately 17-20 percent lactide content, the tensile proparties are similar to polyethylenes used in trash bags and shopping bags.
At lower lactide contents, the blends have a similarity to polypropylene. Some data can be compared in Table 3. Table 4 defines the conventional plastics used in the comparisons.

WO ~t/O~tl3 -51- PCr/l~S91/0632~

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~ 4--~ 3 Table 3 reveals some data for lactide and polylactide mixtures. The results do not differ remarkably from similar compositions of Examples 1 and 2, prepared by other means. However, those s~illed in the art will recognize that the precise physical properties will vary somewhat depending on the intimacy of the mixture, the tensile testing conditions, and the fabrication tec~nique for preparing the films.
Comparisons from Table 3 reveal that the lactide-poly~er mi~tures have a ~road rang~ of controllable compositions t~at mimic many conventional, nondegradabl~ plastic ~ypes.

Example 17 An oli~omeric poly~lactic acid) (OPL~) t"~as pre~pared for mixing with polylactides as follows. An 88 percent solution of L-lactic acid (956 g~ was charged to a 3-nec~ flas~ ~1 liter) fitted with a mech nical s~irrer and a pot thermometer. The reaction mixture was concentrated under a nitrogen purge at 150-190 ~ at 200 mm ~g for 1 hour until the theoretical water of dilution was removed. No catalyst was used except for lac~ic acid and its oligomers. This temperature and vacuum were maintained and distillation continued for 2 hours until 73 percent of the theoretical water of dehydration was removed.
'~ T~ -es~ e~ ho-~-s. ~ 5 time the reaction was stopped. The water samples and the ?~ oli~
ecid, 26.2 g, W25 found in ~he waler dis~ . The p~t en ~_cj: _i-__1_5 ;;i_h s~_nd2_d '.. ~S~ e d2_~ c-a a_~r~ ~l-a ~ e ~ _`_ ?-'~ C -~

,-he~e ~ s ~ Q5 ~ h~ c~ r~:a~

-~5-TABLE 5. CH~URACTERIZATION OF OPLA OE EXAMPLE 1 .. .. . .. .... . .. ... . . . .
Total Percent Titratable Titratable Expre~sed Degrea of Dehydrated, Acid, Ester, as Lactic Polymeri-Theoretical percent percent Acid zation _ percent S8 34.4 ~2~4 116~ 3.4 ~m~
T~e procedure of ~ample 17 was repeated except the distillation was conducted more slowly. After 8 ~ours o~ heating during whi_~ t~e temperature was slowly advanced from 63 to 175 C at 200 mm Hg, a sample of the pot was titrated to reveal 62.2 percent o~ theoretical water removal. Titration revealed a deg-ee of polymerization of 4.3. The molecular weight of the oligomeric polytlactic acid) was further advanced over 2 hours by heating at 179 C and using a vacuum pump. The oligomeric poly(lactic acid~ was no longer soluble in 0.lN
NaO~, was water whi,e, and would cold f low . This material is a second example of an oligomeric poly(lactic ~cid) preparation with somewhat higher degree o` polymerization as compared to Example 1. It was mixed with polylactide i.. E~am?les 22 ~nd 2-~ T_ is es_imated '~ ` the dec~ee of polymerization was about 6-10.

_xam~le ' 5 ol~ '2~ ~.e~ e-~ si-.~ o.

_ ~ ~ _ _ _ _. _ _ _ _ ~_ _ ~ ~ ~ . _. .~ _ _ ~. ~, _ _ _ _ _ ~ _ _ ~ _ _ _ _ _ _ ~ ~ _ ~ _ _ _ _ .. _ _ ~!--?;i~ ~cc F-c~c~ .e __?o~ s ~r _= ~ ` e~

? ~

average molecular weight (Mw) of 182,000 and a number-average molecular weight (Mn) of 83,000. Residual lactide monomer by thermogravimetric analysis was 1.7 weight percent. This blend was mixed with the oligomeric s poly(lactic acid) of Example 17 to provide material for Example 20. The tensile properties are listed in Table 6.

~.i~Q
The polymer o~ Example 19 was melt blended with the oli~omeric polytlactic acid) o~ Example 17 on an open, 2-roll, mill fo~ 20 minUtQS at 325 F. The mix was compression molded into films and tested as shown i~ Table

6~ The gel permeation chromatography molecular weights were smooth, monomodal distributions (~wi~n = 2. 6) with Y~
= 192,000 and Mn = 73.000.

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Exam~le 21-25 The copoly~er of ~xample 19 was melt blended with 20 percent of the L-PLA described in Example 19. The blend is listed as Example 21 in Table 6, where its analyses and tensile properties are listed. Example 21 was, in turn, melt blended with various a~ounts of the oligomeric poly(lactic acid) of Exampla 18 and these were tested as befcre and listed in Table 6, Examples 22 to 2~.
mable 7 lists the gel permeation chromatography molecular wei~hts of ~hese composition~. The tensile strengths and ~oduli are compared to the weight percentages of oligomeric poly(lactic acid~ in Fi~ures 3 and ~ ~Lower Curves).

~'O C'"O~I~ PCT/~S91/063~-~t~ m~ ~
U~ ~ ~o ~C ~ ~o~ s ~ ~ S~ ~ 3 t., ~t~ s~ U~
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- t~! ~ 3 ri ixi--~ E E ~i - r~ ` o ~ x ~ ~
C ~ ~ ~: _ Exam~les 26-30 A second series o~ copolymers was ~lended with the oligomeric poly(lactic acid). ~ 9~.5/7.5, L-/racemic D, ~-lactide copolymer was prepared by methods similar to Examples 19 and 21. This is E~ample 2~ of Tables 8 and 9.
It was melt blended with the oligomeric poly(lactic acid) of Example 18 on an open, 2-roll mill at 325 F for approximately 20 minutes. The blends were compression molded into 3-5 mil thicX films and their tensile properties and gel permeation c~romatography molecular weights measured. The properties are recorded in Tables 8 and 9, and plotted in Figures 3 and 4. The second SeriQs of blends revealed significantly higher values for the tensile properties although the molecular weights were lower. This may be due to lower residual lactide monomer and/or the change in high poly~er composition. All of the oligomeric poly(lactic acid) polylactide blends could be easily molded into tac~ free, transparen~ ~ilms~

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6_ TABLE 9. MOLECULAR WEIGHTS OF 9.25/7.5, L-/RACEMIC D,L-LACTIDE COPOLYMERS

.. . . _ _ ..

No. OPLA M~
26 0 63124 2281.95 27 2Q 60108 1891.81 2~ 30 4880 1251~66 5~96 1511.65 5692 1~6~
~ Gel permeation chromatography ~GPC) molocular weights as re~errQd to monodisp~rse polystyrene standards Examples 31 and 32 Film specimens with, and without ~l~sticizer were exposed to seawater at Daytona, Florida from Narch through May. The pH of the water varied from ?~3 to 7.6 and the salinity from 33.2 to 38.~ ppt. The water gradually warmed in the test from 15 to 27 C. The specimens were cut into strips and tensile tested before, and after, periodic intervals in the seawater. The results are shown in Table 10. All of the samples showed whitening and physical degradation, which became progressive with time.
Without plasticizer the samples showed whitening and degradation after six weeks in t~e seawater. The oligomeric poly(lactic acid) polylactide blend degraded ~2st~, -evealing clear eviden-e c_ degradation 2 ~ter ^
~;e_ks. T~e in^~po_~ti~n o~ ~ ?e-ce-._ lactide ?rovo]~ed immediate whi~ening ~n- o~vious de -ada_i~n ~~~er one ;;ee~;
of e~:Dosl~re.

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Exam~le 33 Examples 33 to 51 teach the use of incorporating lactide in conjunction with quenching to obtain pliability and transparency. Alternatively, the polymers can be annealed to improve stability ayainst heat distortion.
Poly L-(lactide) was prepared by methods previously described. Thus 300 g of triply recrystallizad and thoroughly dried L-lactide was loaded into a clean, flame-d_ied, argon-cooled, 500 ~1 round-~ottom flas~. The ~las~ was fitted with a ru~ber septum and inle' and outlet syringe needles that admitted a continuous argon purge.
Stannous octoate solution was prepared by dissolving 20 g in 110 ml of toluene, previously dried over molecular sieves, then distilling 10 ml toluene in order to azeotropically dry the solution. The ~inal concentration was 0.2 g/ml stannous octoate in toluene. A 0.3 ml quantity was injected through the septum onto the L-lactide. The flask and its contents were placed in a 150 C oil bath, and when melted, swirled vigorously to o~tain a homogeneous mix. The argon purge continued and a thermocouple was ~itted through the septum into the uelt.
The melt was 143 C. The temperature of the oil bath was advanced to 200 C and heating and lig~t purge continued for 20 hours. The temperature O r the melt advances to 170-174 C in the first two hours Or heating. The final tempe_atu-e ~'25 170 C. ~ter ~0 hou-s o~ he2._in~ the flask was cooled in air to room temperature and the solid O- ~s t---s?~
Pol~er ~;~s recover~c by sho_;~ing _he ~las~ ~lth ~;cs _~__~ ,_2vi~ s~
r~le_-~l2_ ~ s ~ g~ ~r~e-~~ 2~ _ 2 ~ ` ~ S
,~ -oin` ando~he_ms ~i_h pe^}~s c_ ^?-ro~:im_~el~ ~ c~ ?
~ el ?e~ 2~~ --c~ c.~- :

~o 9'.'~ Pc r/~ssl /n h ~ 3 ' Residual monomer by thermogravimetric analysis was 2.3 percent, (Example 33, Table 11.) The experiment ~hows that L-lactide can be polymeri2ed above, or near, its melting point and the products remain transparent and more S amorphous.

~L
By methods similar to Example 33, 104.0 g of L-lactide was polymerized using 0~10 ml o~ stannous octoate catalyst solution. However, the reac_ion temperatures were 155-1~5 C for 72 hours~ The polymer ~No. 3~ of Table 11) slowly crystallizes upon ~orming and is a white opaque solid at reaction or room temperature. Since the sample was smaller than the preceding experiment the polymer cooled more quickly, but it did still not quench to a transparent solid. In co~parison to Example 33, the lower reaction temperature per~its the poly(L-lac~ide) to crystallize and become opaque, thus an intimate dispersion of plasticizer does not form.
The temperature is slowly advanced in many of these experiments to accommodate the poly~erization exotherm. The reaction temperature must reach at least 170-175 degrees before there is substantial monomer-to-polymer conversion, otherwise the poly(L-lactide) cr~stallizes and is difficu't to remelt.
In Examples 36-~2 the polymerization of L-lactide was ~eceated v~_y n- the conc~tions to obtain ?olv(L-lac~i_es) wi~h ~ -r-.._ resi~ual l_c~ide _a.._e-.ls and c-~stallini~ .e es~s a~e sho~n ~n ~ble 1' where i` is seen -h ~ ?l~a~ ,nc touchness ~ere obt~ined ~a only ;;hen ~he -~odu__ ~.as ~een c~len^h.2d .--ar. _he melt, is t~c.~pcrcn_ _ -~c~ _e~er~ e~

~ ved ~ e ~.c~~?^'i~-- ~~
?c!~..e-i~ed i-. _~e ~e:t, 2-.d _~ .c~e~ .he ~.anc~e~-e~-e~ -le- ' c~
-e?.~-o~ 2~ c t ~ e~

.~iJ.~_ ~ _ properties. ~hen t~e poly(L-lactide) crystallizes during polymerization because the polymeri-ation temperature is well below the polymer's melting point, the residual monomer is no longer effective as a plasticizer. I~ the S polymer crystallizes upon cooling to room temperature, it also loses its plasticization. Annealing at elevated temperatures will restore crystallinity to amorphous samples.

~O 9'/0~13 f'CT/~ S91/Oh32, TABLE 11. POLYMERIZATION OF L-LACTIDE
... . . .... - ! ~ r Eo Amount Temp ~ours Appearance Monomer Si~e 33 0.02 156-201(~ 20 clear 2~30 300 150-174P~ transparont, hard, glassy 34 0.02 155-165~7~ cryutallinQ, -- 104 opaque, hard, brlttlQ
0~005 120-200~') 2~crystallina, -- 100 111-200~ opaqu~, hard, brittle 36 0.02 135-145(') 22crystallinQ(~, 1.1 500 1~5-152~b) opaque, hard, brittlQ
37 0.02 117-lS52~ ~rystalline,1.74 100 120-175~b~) opaquQ, hard, brlttle 38 0.02 15~-170(~ 3e~ystalline,2.1~ 2,000 opaque, hard, br~ttle 39 0.02 145(~)15 cry~talline,3.6 25 137-144~) opaque, hard, brittlu 0.0553 190l~ 0.3 clear, 10.1 25 160-215 pliable, tough, transparent 41 0.05S3 198-193~ 0.29olaa:, 22.9 25 147-200P) transparent, pliable except ~t edge of polymeri-ate 42 0.02 l4s~l)2~75 crystalline~,52.5 25 150-133P) opaque, hard, brlt le Oil bath ~e~perzture ?ol~ a~~_-2 ~d~ ^e~, a-~ r~,o~
ran~?-~:ent a~ -ea_tior. te~?e:2:u:e; --ystall:^es e?on ~ooli~

~ ? ~ r _ ?.'' ~. :~ C~ "-- ' C 2 1 ~ -` c: _ I e~ C ~ e~ `` ~ r c t i O

_o?ol~ e_ P2si~ cucn_.~es ~~ c~ ns~c^.~nt soli-. Tne easily. The 100 percent L-lactide polymer quenches with difficulty fro~ thick sections of the polymer to a transparent material. Some comparisons are shown by Examples 43-47 of Table 12. Thinner cross sections, i.e., films of the L-lactide polymer can be plasticized and quenched to pliable and transparent materials. The 80~20 copolymer quenches very easily to a transparent solid.
The latter has only a trace of crystallinity as seen by di~ferential scanning calorimetry.

TAB~E 1~ T~NSPARENC~' OF ~ACTIDE P~LYMERS

~ . . ~A . _ No Ratlo TemD;, _ _vercent 43 95/5 145-160 67 SO385,000 2.64 44 100 135-152 22 O32~,000 1.1 45 90/10 150-157 4S TS21,000 ~.95 46 90/10 150-170 48 T27&,000 1.37 47 80/20 135-175(C~ 23 T -- - -(~ Melt temperature (polymerization temperature) (b~ opaqueness/transparency ~O/T) after air-cooling Or polymerizates; opaque (O); slightly opaque (So);
transparent (T) (C~ Slow-cooled for 1 hour All D,L-lactide is racemic.
All of the lactide poly~ers thermororm easily, _-Dd ~y 2 ~a~ e~te~ ~._il sc~_, t:~en 5~ r. ~ _t~ e~ he ~z~te-~ c~ th~e mcld e_sil~m :-lo;ia~e~ a poly(L-12c_i~e) ~ec~es ,~-ti~ 2n~ . c~e 9-~5, !' 0, _~.d ~C~ ?-_~.e~ ~le_~ _~,-`
~ ~ _ _ . ~ _ _ _ _ ~ . ~ _ _ . . _ _ _ . . ~ _ _ ~ _ . ~ . _ _ . ~ . ~ _ .

r~la C
~ ?--~ c~ r~?l~ ~3 ~'GS
~^ . -- i, ~ _ ~ . ~_ ~ ~ -` ~ _,, ,--_ -- ' -- ` _ _ _ ,_~ ~ _ ~, = _ ~ _ = _ _ _ _ W09'/0~13 PCT/~S9l/06327 ~ 3 (190 C), then compression molded at 375 C for 2 minutes, then air-quenched to room temperature in approximately 30 seconds. Both 7-and 20-mil thick films were prepared.
Both were clear and transparent without trace of haze or opacity. Residual monomer in the film was 0.79 percent.
The films are very stiff.

Exa~m~ 1 e 4 9 The experiment was repeated except th~t the milling was con~inued for 10 ~inutes instead o~ S ~inutes.
The films were analyzed by thermogravi~etric analysis again and found to have 0.38 percent lactide. The films were clear, transparent, and stiff.

Exa~le 50 The ~ill-rolled polymer ~2s also compression 15 molded into a 1/4 x 1/2 x 1 inch plaque. This plaque required 5-10 minutes to cool in the press by turning on the cooling water to the press. The plaque was white, opaque, and crystalline except for the extreme edges, which were transparent.
The above Examples 48-50 teach the quenching of films of poly L-lactide to maintain transparency. When cooled more slowly, they crystallize and lose their transparency.
As D,L-lactide is introduced as a comonomer, quenchinq can be reDlaced by ordinary cooling to retain transparency~ Spher~ c-ystallinity c~n be intr~duced into these films bv anne21ing and the 100 percent L-lactide pol~er is the faslest to crystallize. ~here t.ansparency is not required the higher L-lactide polymers can be annealed to greatly improve thei~ resistance to ~hermal disto~~ion. Convers21y, whe_e ~_anspa~ency is re~uired, such as in a polystyrene offset, great care must be taken ~o avoid _his ~y~e ~f opa~ue crvs'allinity.

~0~7/~ ?l/n(.,7-Exam~le S1 The poly(L-lactide) film samples were annealed on a hot plate at 240 F (115 C). The film turned hazy in approximately 1 minute and completely cloudy in approximately 2 minutes. By way of comparison, a 90/10, L/D,L-lactide copolymer film required 10 minutes to turn hazy, 15 minutes to become completely cloudy. When suspended by one end hori~ontally in an oven and advancinq the temperature slowly, the annealed poly~L-lactide) sample remained straig~t until a te~perature of 295 F tl46 C) was obtained~ The film then bent over. The annealed 90/10 copolymer bent over at a temperature of 185 F (8~
C). The results show that the amount of crystallinity of polylactides can increase thei~ form-stabili~y at elevated temperatures to a temperature that is well above their Tg.

Examp~es 52-5S
The following examples illustrate the beneficial effects of addinq lactide during compounding. The examples show that without lactide as modifier, the lactide polymer degrades during compounding. With the addition of lactide both discoloration and molecular weight decrease are prevented or substantially reduced during compounding.
Thus, in Example 52, a 90/10, L-/D,L-lactide 2S copolymer prepcred as describe~ ~y previous methods using 0.02 pph SnC12 2H20 catalyst was ground and extruded into pellets Crom a ~in sc 2W co~pounde-, adding 5 weigh_ percent lactide. The melt zone temperatu~e o~ the e~-uce- rose ~ .S0 s, t~e p~l~e- disc310~e , _n~ _he .0 weig~t average moiecul2r weigh` (~, by gel permeat_on c~romatogr2phy) decre2sed b~ ~pproxim~_e!y ~0 ?e-cen~.
T~.e ~esu'.s ir.__~_~e7 -.-__ insu~ ien_ _a_~i_- ~cs -dde~
_or this ~ery his~ pol~ci_. The -es_l_s ~-e sho~n a q7~ble 13. ~7~e ?ellets f-om ~his com?ounding ~ere o~.?o_.7.~ c~ 7~ eic:~_ ?~

WO92/0~13 PCT~`S91/0632-the results were much better: further discoloration did not occur, molecular weight decreased sliyhtly, or within experimental error, and a pliable composition was obtained.

5 TABLE 13. EFFECT OF LACTIDE AS MODIFIER
DURING COMPOUNDlNG

Ex. Before Compoundin~ Lactide~b~
No. Color ~ ta) weight percent 52 Light yellow 513 2.15 ~.78 1053 Light ~ellow 278 1.80 1.37 Ex. ~fter Compounding Lactide~) No. Color Mw~ JM (~) weight percent 52 Dark yellow 322 2.05 5.56(C) 53 Yellow 184 1.90 2.26 1554 Dark yellow 307 2.00 14.4( colorless(Q~ 324 1.99 14.6 ta) GPC x 10 (b) By thermogravimetric analysis, at 200 C
(~) Five weight percent lactide added during compounding.
(d) Further 10 weight percent lactide added during compound.
(e) Thin film To ascertain that the ~econd compounding and extrusion were facilitated due to the lactide modifier and not the decreased molecular weight, anothe- compounding (Example 53~ was per~ormed starting with 2 similar-Mw copolymer of _0/10, L-/D,L-lactide. In this case, no lactide was added bac~ in during the compounding. The melt zone temperature was 382 F, the copolymer was i~ discolored, ~n_ the M~ decreased ~v approxim2tely 6~
percent. In addition, approxim2tely 5 percent more torque was required o compound the mix of MW 278, 000 2S co~p2red ~o the one of ~ Or 322,000 ~ith added 'ac'iàe.

~o 97/0~l3 PCr/~S91/063',

7 2--After compounding twice with lactide, Example 54 was analy~ed by thermogravimetric analysis and found to have a lactide content of 14.4 percent~ The material of Example 54 was converted to a blown film by means of a Haake-Brabender extruder in Example 55. Thin films of this composition are colorless, highly tr~nsparant, and very pliable and extensible as described balow in Examples 60 - 64. The Mw by gQl parmeation chromatography was 324,000 ~cf. Mw ~ 307,000 before compounding and extrusion). The Tg of this plasticized material is 42 C
and diffQrQntial scanning cslorimQtry reveals a very small amount of ~rystallinity melting at approximately 138 C.
~he amount of lactide present is 14.6 percent as estimated by thermogravimetric analysis.

15 Exam~les 56 and 57 The compounded polylactides, Example 52 and 53, were mixed together in the twin-screw compounder with extra lactide to raise the lactide level to approximately 20 percent. The compounding temperature was 347 F 1175 C), much reduced from the previous 375 to 385 F. The compounding proceeded smoothly without further discoloration.
The above results clearly show the beneficial effects of added lactide as modifier. The required torque to compound the compositions, the discoloration, and the working temperature are decreased when adding lactide.
Further evidence of plasticization is seen in the lowered Tg and the pliability of the compositions. In addition, molecular weisht decreases are avoided and stable compositions are obtained. It will be obvious to those skilled in the art that the amount of lactide empioyed depends on m2ny factors, in^ludin~ .he desi_ed amount of plastici2ation sousht, the type of compounder tha~ is used, and the ~olecular weish~ of the polylactides.

W092/~13 PCT/US91/0632 ~ 73-.~`3~
ExamPles 58 and 59 Examples 58 and 59 illustrate blown film extrusion of polylactides. These pliable films mimic polyolefins. The plasticized compounds of Examples 56 and 57 were adjusted to approximately 20 percent lactide in the twin-ccrew extruder. They were converted to blown films using a HaaXe-Brabender Qxtruder. This consists of a 3/4-inch extruder with a blown-film die and take-up device. The blown-film was achie~ed using a 12.7 mm outside diameter orifice and a pin to establish an extrusion gap of 0.48~ mm. An extrudate temperature of 187 C was maintained. A stable bubble was blown at this temperature with the inflation air at ~ oz/in.2 gauge pressure. Cooling air was blown against the exterior of lS the bubble at 18 pci. Since the final average film thickness was 0.158 mm ~6.2 mil), the blow-up ratio was 3:1. When the extruder gap was reduced from 0.483 to 0.254 mm, or the temperature raised, the polymer quenched readily to a crystalline, cloudy extrudate that would not expand. The larger orifice die produced an extrudate that was thicker and more viscous, cooled more slowly, and expanded in a consistent manner. The extruded film exhibited some elastic memory when stretched. The film also was resistant to tear and puncture and was very difficult to break by stretching. The blown film had an average elastic modulus of 117,000 psi, an averaqe tensile strength of ,73S psi, and an average elongation to break of 370 percent. This modulus is slightly higher than that of linear low density polyethylene, but the strength and elongation to break are comparable. The Elmerdorf Tear Strength (AST~ 1922) was 424 g in the cross machine direction ar.d 18~ g in the machine direction. The Tg of the material ~2s ~6 C, ~r~ by gel permeation chromatography was 229,000, ~he residual lactide by thermogravimetric analysis ~-as 19.7 percent, znd the differential scanning calorimetry c~rves showed a we2k endotherm cen~ered at 2pproximately :,_ C.

C~l/nf) Exam~les 60-64 These examples illustrate plasticiza'ion with oligomeric esters of poly(lactic acid). Copolymers of 90/10, L-/D,L-lactide were melt blended with added lactide, esters of oligomeric/lactic acid, and mixtures thereof~ They were characterized by tensile and thermal properties.
In Example 60, a control copolymer of 90/10, L-/D,L-lactide was assayed by thermogravimetric analysis to be 6.74 percent lactide. This was mixe~ with 30 percent by weight oliqomeric polymethyllactate ~Mella) in Example 61, which was prepared by heating 2,500 g of ~S)-mathyllactate in an autoclave at 210 C for 3 hours, then collecting the Mella which fractionally distilled at 81 to 85 C/1.25 torr. The mixture was melt blended on an open 2-roll mill at approximately 350 F. The blend was compression molded in a press at approximately 350 F into clear, pliable films. The tensile properties, before and after, adding the Mella are recorded in Table 1~. The glass transition temperature (Tg) was reduced by the Mella plasticizer.
For Example 62, the 90/10, L-/D,L-lactide copolymer was melt blended with added L-lactide in a twin screw extruder to adjust the L-lactide content to 20 percent by weight. The blend was further mixed with oligomeric polvethyllac ate (Ella) (Example 63) znd Mella (Example 64). The properties of the~e blends are also -~cc_-e~

~O 9_J0~ j'31 /()OJ_ .

J

TABLE 14. CHU~RACT ~ ISTICS OF POLY ~ CTIDESIa~ PII~STICIZED
WITH OLIGOMERIC ESTERS OF L~C~I~ ACID

. . . _ ... .. .... _ Elastlc ~raak Strain Ex Plastici~er ~oduluD Strength Break, T~ m( . . . _ . _ _ _ 5 60 6.74~(~ L-l~ctlde 370,000 6,903 ~ 51 141 61 6.7~ -lactlde15~,0002,012 100 301~1 ~nd 10~ ~clla(') 62 20~ E-lactida101,0002,~3~ 2~S -- --63 20~ L-la~tidQ and~,31~ ~,S~l ~39 -- --3~ Ella~n 6~ 20~ ~-lacCidQ and3,620 ~9S 83 -- --30~ M~lla~') (^~ 90/10, L-/racemic D,~-lactlde ~opolymer ~las~ ~ransltion temp4raturQ
(') ~Qlting point t~ Analyzed by thermoqravLmQtri~ ~nalysi~
I') Methyllactate oligomer (~ Ethyllactaee oligomer Examples 65-81 Comparative Examples 65 to 81 were selected from the patent literature that presented conditions most likely to result in materials of the present invention.
The materials produced in these patents were not completely characterized, thus experiments were needed to allow a more complete characterization of the examples and provide meaningful comparisons th~t WouiQ damonslrate that the materials of the present invention a-e indeed novel.
With regard to the present invention, co~Dositions were sought that had residual lactide or lactic acid contents ~~ a~o~ iS-- ?e_c~ _n -^~
~2y have ~he lac~ic- c- lz__ic aciQ inti~2telv dis~ersed ;i_hi~. the ~ ~e-~ ~h2 -2sUl ts ~all i~-o o~vious ~ei5h~s, ~:~,, less _hz-. I3,~03 d_ n-~ have _~.e p~ ici ?-~?e.~i~s _~ e~ e ?-es~ zc_ s '~~ .es2 1~ .?.~s~ c~
~e .,n~`~_ _- =^ 5-~

~v ~'"~ rT~'7!~(~f~-v.~
It is known from the teachings herein that lactic acid, lactide, or oligomers of lactide or lactic acid, or derivatives of lactic acid must be, present to provide plasticization and some pliability~ The lactide must be present in amounts greater than about 10 weight percent while the oligomers of lactic acid, oligomers of lactide and the derivatives of lactic acid must generally be present above about 40 percent to provide obvious plasticization and pliability to polylactides. ~owever, any amount of plas'ici~er as tausht herein when added to the composition will change properties and can be used to obtain specialty ormulated compositions. Thus, if ~ ide is intimately dispersed and effectively mixed as plasticizer, the mix of lactide and polylac`ide is completely transparent. The heterogeneous domain size of the lactide is small enough, generally less than one micron, so that it will no longer scatter light, i.e., it is intimately dispersed. Conversely, white opaque samples are always hard ~ecause they have crystallized under the test conditions. Crystallization squee2es the lactide out of the polymer mass, resulting in hard stiff compositions that are a gross mixture of monomer and polymer. This is also obvious from differential scanning calorimetry (DCS).
Monomeric lactide that has segregated reveals itself with a separate melting point at 95 to 100 C, whereas well-plas'ici~ed 52. ?les C'7 not show 2 ~is~inct mon3mer meltin~
point.
One ve-; _____~a.._ r7_n_ ~5 ~h-_ _he ci.ed patents frequently specify L-lactide homopolyme- ("100 i~c~i~e easily c~ys~ es -ecause 3_ i-s hish ~el_ln ?~in A_ `~ c~--ic.. ~c-~?e--~ s~ '~e ~ ?~l~e-_ _ . ~ ~ _ _ _ ., _ _ . . _ _ ~ _ _ _ _ _ _, ~ _ _ _, _ _ _ , _ ., _, _ , _ .
c~?~ .io~ _~ `7~5 ~ ..e ~5 -eRc~ion ~e~?e~ctu~e- ~~e L-ls__i^e ?oi~e-i~es so _ _ _ _ . _ ~ = . . _ _ _ _ _ . ~ _ _ _ _ _ _ _ _ _ , _ .

~0~ ~13 ~ 9ll)6 -~7 -t~ ?~ ~, polymerization with substantial monomer left in the product.
Inspecting the results listed in Table 15A and 15B reveals that the comparative examples obtain either products with low residual lactide or else the polymerizations did not work or worked so poorly that greater than 40 percent lactide was left at the end of the specified polymerizations. Thus, Examples 65, 66 (vQry similar also to the work of Schneider), 67, 69, 73, 74, and 75 obtain low residual lactide. The Examples ~0, 71, 72, 7~, 77, and 78 examples did not work well as written in the patent examples. The best known laboratory techniques were added to the procedures, described in the footnotes, on these examples, from a historical standpoint (monomer purity, for example) in an effort to make the procedures work, with indifferent success. In no exanples were pliable products found. Either glassy, or hard, crystalline, opaque products were obtained. It should be noted that only those examples using tin compounds as catalysts appear to be acceptable for many oackaging applications.
It appeared particularly that the Tunc met~ods would provide the materials of the present invention. To ascertain this, it was necessary to do the listed experiments on the teachings o Tunc in laborious detail as shown in ExAmples 7g oo 81. Figure 5 is a differential scanning calorimetry of one of the polylactides of the p-esent invention~ ~here is no detecsable ~elting point fo- residual 12ctide mono~er in the vicinity of 95 to 100 nly `~e ?~'y~ ce~ c` ;~s 2~se~ .e-~ .e~-~ 2-.' ~ ' 5 ~
S~O'~ 12, ~ _e-~
~ ; ~ . _ _ . . = _ . ~ _ . . _ _ _ _ _ _ . i ~. _: .:

~r~c=~~c _~ s~`s -c~c`~ e~._ _~ c~i _c~_~e ~-- o~e c~ __e~â ~ _.. ? ~ c~~
_ _ _ _ _ _ ~ . ~ _ _ _ _ _ _ _ . . . ~ _ . . _ _ _ _ _ _ _. _ _ _ _ .. _ . . _ _ ._ _ _ _ _ _ _ _ _ i. ~, V.

shown in Figure 6, where a very distinct monomer melting point is seen. This corresponds to segregated lactide with a melting point within its own heterogeneous domain.
Whereas this polymer is white, opaque, very hard and S stiff, the composition of the present invention preparation is clear, transparent, and very pliable.
A similar result was obtained repeating the teachings of Tunc in Example 81. This analyzed as 32.2 percent lactide and revealed a monomer melting point (Figure 7)~ The material was very white, crystalline, and hard. The results are reviewed in Table 15A and 15B.

0 ~7/()~13 i~tT~i'3l/o6 TABLE 15A. RELATED ART POLYMERIZATION5 OF LACTIDE
CONDITIONS

p Lactide Catalyst Polymeri~ati Eox. Patent Eaxt. ~onomer -~ ~ ~-( 8 ~ Type pph TQCP' Hours 2,7S8,987 1 L- PbO 0.30 150 42 66 2,758,987 3 50/50 PbO 3.00 150 89 L-~D,L
67 3,982,543 3 L- PbO 0.30 150 31 68 DD 14548 2 L- SnO(~) 0 009 193 3 69 4,137,921 4 90/10 Sn~Oct~2, 0.055; 180 0.33 L-/0, L GA/ 190 0.33 dioxanQ~) 210 0.33 Ga 755,447 4 D,L 2nO~') 0.02 150 24 71 GB 755,447 2 D,L powdQirt~ 0.02 140 25.5 72 GB 755,447 6 D,L 2n 0.02 140 2 Carbon- 150 3 i~te Hy-droxide(C) 73 CA 932,382 1 D,L Tetraphe- 0.02 165 20 nyl Tin 74 CA 923,245 1,7 ~ L- Et,Zn 0.167 105- 2

8 110 DE 946,664 2 D,L(" ZnC12 0.25 140 48 76 DE 1 L- Sn 0.00S7 205- 0.5 1,112,293 - Stuarate as Sn 210 77 2,951,828 1 L-;0 SnCl~ 0.30 160 5 sua~en-8 ion~) 78 3,268,487 2 D,' T_ifi(2- 0.88 80 24 a~vl)a-~ina~
108,~_5 ?o!y-~19S~
~,5i3,~
~,53ci,9 :
e;.~
e~ ~,539,981, ?^1~- _- B~.~3_o)~ 3~33`2~ e j~ c ~,55Q,C~ ~t-2--~ct~ l -e~_?e ~ cn~ro~ c~ir~ 5~,c ?P~ c c - ~o -Included was glycolic acld as chain transfer agent.
(~) In8Oluble In~oluble after 24 hours plu~ additional 1.5 hou-~ with 700 ~1 88 p~rcent lactic acid and 100 /~1 H20.
~') In toluene; product colorlens and ~ery viscous.
( In minaral spirit~, Stoddard ~ol~ent No. R-66.
Agglomerated ~ In dioxane containing 0.517 pph ~OH; no polymeri:a~ion.

~V092/1)~13 r~ `S91/~)63'-~ 3 TABLE 15B. RELATED ART POLYMERIZATIONS OF
LACTID~ RESULTS

RQsidualGPC x loJ
Eo MonomQr,M~ ~ M~/N~ App~arance 0 254~54 7171.79 Ll~ht yellow, cryntalline, opaqu~
66 0 97187 3221.94 L~ght yellow~
transparQnt 67 0.85 95195 3~52.06 Partially opaquc cry~tallinQ, partlal tran~parent 68 l7~s~a) 5 7 91.47 Whlta, crystalllnQ, 7.1S 7~77 8 101.25 opaquQ
69 4.6 116218 3561.88 Li~ht yollow, transpar~nt 0 70 47.7 -- -- -- -- White, crystalline (mOnOr~Qr~, opaquo 71 65.3 -- -- -- -- White, crystalline (monomer)~ opaque 72 79.6 -- -- -- -- Whlte, crystalline (monomQr~ opaque 73 1.4 116214 3401.84 YQ11OW~ transparent 74 1.9 80150 2351.87 OrangQ, crystalline, opaque 5.4(~ 164377 6572.3 Hard, colorlQss 2.5; 1.9~1307527808 1.72 76 43.3 30 35 411.17 Hard, crystalline, opaque 77 8.6; 9.6219343S041.57 Hard, crystalline, opaque 78 100 -- -- -- -- All crystalline monomer 79 5,0 :~ 2-`~5 :.SS ',;hite, c_vstallir.e, oDaque film~ 14 26 351.82 Some tran~pArency rt edae~
?0 80 ~0.^~;' Greaec- ch~c. 1,w03,COO h'hiee, c-y~_all_.le, o .~

~ ate~ r~ e, c_~ e, o_a ~e Sc.. ~r_c .. c._c_ ~ ir~
~cmovc c_Lvcn~.
~`~ s~ e ~e;:~ c~ . C ~ --u~ r~ -2 re~^~2;~ c~l~ r~._.
r~ n5?- r~r. ~ rr` ~
'~' unc o~ir.~ `-.1 ?~cen_, ~ c~ _u~ 5~

t~C ~

~:J ~ 1 ~ 3 The above examples establish that an all-lactic acid composition can be a pliable thermo?lastic useful for flexible, plastic packaging films and containers. By way of comparison, nonplasticized homopoly (L-lactide) is a highly crystalline polymer with a tensile strength of about 7000 psi with an elongation cf l percent and an initial modulus of 500,000 psi. It is very brittle, opaque, and crazes easily. It is not a well behaved thermoplastic, nor is it transparent. Poly tracemic D,L-lactide) is an amorphous, glassy, poly~er with a glasstransition temperature of approximately 50 C, a tensile strength of about 6300 psi, an elongation of approximately 12 percent, and an initial modulus of l~,000 psi. It is also very brittle although transparent. In stark contrast, a copolyner of L-lactide/race~ic D,L-lactide that is plasticized with lactide monomer is remarkably different. For exa~ple, tha plasticized pol~ers can have a tensile strength of approximately 3900 psi, an elongation of 431 percent, and an initial modulus of 2056,000 psi. The plasticized polymer is clear and colorless, and the blend must be heated to above lO0 c to remove th~ ?lasticizer.
Allhough theory would predict a more amorphous structure as a result of plasticization, what is 25~rprising is the pliable, transparent, stable com-positions th2_ car ~-ise! c~n~, sec~ lv, _he nea-ly e~act Eit of properties needed for certain packaging applications, such 25 po;ye~hylene. ~his irve.-~i^n C0225 at a time when there is 2 need for such ini~ial properties sinc2 i_ CO~_ ld ~11 evic~e -lzs~ic -~ . p__~le~-.
~_ wi;l ~e -??~re-._ -o ~ se ski``~d _: =he er_ ~ _ . _ _ _ ~ _ _ ~ . _ _ ~ _ . _ ~ _ _ _; _ _; _ _ ~ . .
?~~ _s c_~_ c~ - r----------_--~ ~~~~~~
-_ `c-~ t:-ie ~ i ?~ ?e~~ies ~ G
2r;'i_ o.. r~ __~c-.__ ~;~

~,J0~l3 p~ 91/()6J

The amount of plasticizer in the polymer depends on the compositional characteristics desired. If lac~ide is used as plasticizer the ranye is preferably 10 to 40 weight percent whereas if only oligomers of lactide or lactic acid are used the range may be from 10 to 60 weight percent. Surprisingly, oligomer may be added at up to ~0 weiqht percent without substantially affecting the tensile strength or modulus. See Fi~ures 3 and 4. Addition of 30 to 60 weight percent oligomers produces significant plastici~ation and attenuation o~ physical propertieC.
This adds grQat economy to the composition since oligomeric lactic acid is chcaper than the high molecular weight polylactide. Oligomer may be prepared from lactic acid or any lactide. It is important to note that the oligomer of lactic acid normally contains significant amounts of lactic acid unless removed. This is an important consideration in tailoriny compositions having specific properties. Those skilled in the art and knowing the teachings of this invention will be able to select reaction conditions to obtain appropriate chain len~ths for the polymer, and the proportions of polymer and plasticizer so as to obtain fabricated compositions having physical properties similar to commonly used packaging thermoplastics and yet degrade comparatively rapidly. For ~5 example, higher amounts of plasticizer result in polymers having increased flexi~ility and increasingly tough physical p~operties, however, an increasing degradation -a.e will also be obt2ined. F~-th2~, shorte- chai~
lengths ~o- the pol~er will -equire less plastici~e- to 3~ obtain the same p_c?e~~ies as ~ e_ ieng'hs.
?~e-e~-`y ~ n~e~s is -_ ~ e _ e 5 5 _ _ ~ , ~" ~ ~ ~. ~ ~ ~ - O C 2 C 5 ' .~ - _ _ _ ~, r ---- -- -- ~ c~
_ ~2~e_c_~_~e ~ ~el2i~~ e ~`~
e -, ~2-~e_~ _~3~e 1~? ~. _-_iC-~j C~ ~ 1 ~ C~ `~ 2-~ 2d~ er polymerization the retention of monomer during processing is of course not as critical.
The unoriented compositions of the invention should have a tensile strength of 300 to 20,000 psi, an 5 elongation to failure of 50 to 1,000 percent and a tangent modulus of 20,000 to 250,000 psi. Preferably for a polyolsfin replacement the compositions have a tensile strength of at least 3000 psi, an elongation to failure of at least 250 percent, and a tangent modulus of at least 50,000 psi.
A composition for the replacement of polyathylene is adjusted so that the unoriented composition ~as a tsnsilQ strength of about t ,200 to about 4,000 psi, an alongation to failure of about 100 to a~out 800 percent, and a tangent modulus of about 20,000 to about 75,000 psi, while a composition for the replacement polypropylene, is adjusted so that the unoriented composition has a tensile strength of about 4,500 to about 10,000 psi, an elongation to failure of about 100 to about 600 percent, a tanqent modulus of about 165,000 to about 225,000, and a melting point of about 150 to about 190 F.
The homopolymers and copolymers of the present invention are insoluble in water but upon constant contact with water are slowly degradable. However, degradation is fast when compared to polyolefin compositions that are -eplaced ~y -he inver._io... ~hus, Ih-ow3nay c~e_~s m_~e from the polymers are environmentallv attractive in that ~hey slowly de~rade ~o na-niess s~s~nces. ~ ojec~s made from polymers of the invention are incinera~ed, they . ~
The c_~r-si~ie~.s he-ein _-e ~se__' _~-_e?i_cene-._ __ ?o'yci~_irl -snp_si_i~..s ane p2--`~ c`^~ y ^~ t~,e ~o;-e li s~, the ~ethod is `_CE~ -C- =e?lace~e.~ -~
~ __ s~ ` ce~c~-, c`i~

~0 Y'/U~13 ~ i91/~)63', V ` ~
from mixtures of the monomers in the listed group and physical mixtures of the polymers and copolymers of the above group are likewise replaceable. Those skilled in the art will recognize that minor amounts of lactide and lactic acid can be replaced by contemplated equivalents such as glycolide, glycolic acid, and caprolactone.

B. Second General EmbQdiment The environmentally degradable compositions disclosed herein are co~pletely degradable to environmentally acceptable and compatible materials. The intermediate products of the degradation: lactic acid is a widely distributed naturally occurring substance that is easily metabolized by a wide variety of org~nisms. Its natural end degradation products are carbon dioxide and water. Contemplated equivalents of these compositions such as those that contain minor amounts of other materials, fillers, or extenders can also be completely environmentally degradable by proper choice of materials.
The compositions herein provide environmentally acceptable materials because their physical deterioration and degradation is much more rapid and complete than the conventional nondegradable plastics that they replace.
Further, since all or a ma~or portion of the composition will be poly(lactic acid), and/or a lactic acid derived ~5 lactide or oligomer, no residue or only a small portion of more slowly degrading residue will remain. This residue will have 2 higher sur~ace are2 than ~he bulk product and n e~pected faster de~radction rate. Since both !actic ~ n~ c_~ _c~ e s~ o?_ ~3 general ter~ ?olytl~ cic~ ~s ~sed herein -efers -~?31~e-s h_vi-. =he -e~e-~in unit -f f5~1~ 2 T withou~
: . . _ _ _.: _ ~. _ _ ., _ , : : ~ ^ ~ _ ~ -- -- -- . _ _ _ _ _ e~ -l;~~~ r - ~ ~ - ~ - ~ .; - ~ ,, . _ _ _ _ _ _ ~ _ r _ _ _ _ _ _ _ _ _ ~ _ _ _ _ _ _ _ .~ _ _ _ ~ ~ . . _ . _ _ ~ ~ _ ~.
_ _ . ~ . ~ . _ _ _ _ _ ~ . _ _ _ _ _ _ _ _ _ _ ~ ~ _ . ~ ~ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ ; l~s_ic~ c~_^.~.

~ ~:J i ~ 3 ~

The preferred composition of the present invention comprises polymerized lactic acid units with for~ula I: wherein n is an integer with a value between about 450 and about 10,000 and the alpha carbon is a random mixture of D and L (or R and S) with a preponderance of one of the pure enantiomers when plasticized by lactic acid, lactide monomers, oligomers of lactide, oligomers of lactic acid, derivatives of oligomeric lactide and various mixtures thereof. A
plasticizer may be produced by stopping the r_action beforQ polymeri2ation is completed. Optionally additional plastici2er consisting of lactide monomers (D-lactide, L-lactide, D,L-lactide, or mixtures thereof), lac~ic acid, oligomers lactide or oligomers of lactic acid or its derivatives including all L-, D-, and DL- configurations, and mixtures thereof can be added to the formed polymer.
The more intimately the plasticizer is inteqrated within the polymer the better are its characteristics. In fact very intimate dispersion and integration is needed to obtain the advantages of the invention as further discussed below. If desired, additional monomer or oligomer plasticizer can be added to any residual monomer or oligomer remaining in the composition after polymerization. The oligomers of lactic acid and oligomers of lactide defined by formula II: where m is an integer: 2 < - _ .5 (i-_luding ,all L-, ~-, 3L-configurations and mixtures thereof, both random and block confiaurations, user~l fo- a pias,ici-e-). '~he derivatives of oligo~eric lactic acid (including all L-, 2nd ~lo~i; c-n~isu-~ ions, useful _o_ 2 ?lcs~`ci_e~) _~e ~2~ e `o~ lI: wh~e ~ = ;-. ,_~!;~`l -~1, ~ ~ "~ ,~
_ _ _ _ _ _ _ , ~ e~e ~~ --n~ ?~ r.~

W09'/0~l3 PCr/~'~91/063 -87- ;_~ v ~

and where q i5 an integer: 2 < q ~ 75, however, the preferable rangè is: 2 < m < 10. The plasticizers added to the polymer compositions have the following functions:
ta) They act as plastici2ers introducing s pliability and flexibility into the polymer compositions not found in polymer-only composition~
~b) Addition of these plastici2ers to the polytlactic acid) reduces the melt viscosity of the polymers and lowers the temperature, pressure, and shear rate required to melt form the compositions.
(c) The plasticizers prevent heat build up and consequent discoloration and molecular weight decrease during extrusion forming of poly(lactic acid).
(d) The plasticizers add impact resistance to the compositions not found in the polymer alone.
In addition, the plasticizers may act as compatibilizers for melt-blends of polylactides and other degradable and nondegradable polymers. That is, molten mixtures of two different polymers can more intimately associate and mix into well dispersed blends in the presence of the plasticizers. The plasticizers ma~v also improve perform~nce in solution blending.
The su~sc~ipts n, m, p, and ~ above refer to the averase nu~ber o ~e_s ~he -epeating un,_) of _he pol~er ~_ cl~ e ~`e~ ,ei-h_ ~ ~s use~
e~o~ is ~elc~ Q ~e~_ ~t ~ r., ,~ ~, c.
~y _~e ~^le~ v`~ 2~
Ci~ _5 .~_~__ _S . ~ '' n_ ~_ ~ ~__c ?- ~ 2~ c- i~ rer~

~ t~ __ s~ ?^ ~ ?.. ce~ t -r~ 9l /n~
--8~--Marcel Dekker, Inc., 1988 and Introduction to PolYmer Chemistry, R. Seymour, McGraw-Hill, New YorX, 1971.
When n is low, the poly(lactic acid), is easily processable, but is considerably weaker than when n is larger. When n is quite large, e~g., ~000 or greater, the poly(lactic acid) is quite strong but difficult to injection mold. Preferably n is approxim~tely 500 to 3000 for the best balance of melt-processability and end-use physical properties. The amount and type of monomer is selected to obtain L-/D ratios from lactic ~cid or their cyclic dimer, lactide, as further discussed below. Both lactic acid and lactide achieve the repeating poly(lactic acid) unit, shown above, but lactide is pre~erred since it more easily obtains the higher molecular weights necessary for good physical properties. Since lactide has two aipha carbons which are assymetric, there are three types of lactide, viz., D,D- (or D-); L, L- (cr L-); and meso D,L-lactide.
D-lactide is a dilactide, or cyclic dimer, of D-lactic acid. Similarly, L-lactide is a cyclic dimer of L-lactic acid. Meso D,L-lactide is a cyclic dimer of D- and L-lactic acid. Racemic D,L-lactide comprises a 50/50 mixture of D-, and L-lactide. When used alone herein, the term '`D,L-lactide" is intended to include meso D,L-lactide 2S or racemic D,L lactide. The term intimately dispersed as used he~ein means t`ee mat-rial is homogeneously and intimately mixed with the polymer.
e -ol~y'~ -_ic 2cid) an~ poiv(~-lacti^ 2c~d!
~ave poor processi~ c~a-2c~Pris~ics, easiiy c-~ze and ~c~ _ ~.^_ -s ~~- c_ ~~ le ~ .e 1~ e c~ 2e_s ~ n^~ _- 3 -~ ~ c~ -.~c~_.
~ , _ _ r ~ ~

~ _ ~ c ~ ~ ~ _ ~ _ e _ ~ _ _ i ~ r ~ 0 1 ! ~ _ ~ J ~

_ ~ ., _ _; . ~ _ _: ~_ ;~ ~, _ . .~; _ _ _ ~ . _ -- ~-- _ ~ _ _ _ _ ~ . ._ ~ _ ; _ _ .. ~ _ .. _ _ _ .. .. _ ~ _ ~ . ~ _ ~ _ _ .. _ _ .. _ . _ _ .. _ _ _ _ _ .. _ _ _ .

~13 rCT/~`S91/Ofi3'--~3-difficult to thermoform without crazing and easily becomes opaque at room temperature. Also, at ratios above ss/5 the material becomes bimorphic and difficult to extrude because of different crystalline forms that affect the processing conditions. Further, above ratios of 95/5 the material must be processed too close to its decomposition point to obtain reasonable viscosities without color formation. At lower ratios than 85/lS, the lactide copolymers exhibit lower moduli than the predominantly L
or D copol~mers. Further, at ratios below 8S~15 it is dif~icult to obtain a required crystallinity in a reasonable time period. In between these limits the copolymers are quenched from the melt in typical manufacturing/processing equipment of plastics technology to achieve films and moldings which are clear, colorless, and extremely rigid. Their properties as formed, above, are closely matched to those properties of a crystal polystyrene. However, a wider range of L-/D-enantiomeric ratio may be useful for special applications.
Another advantage of this invention is that the all-lactic acid copolymer can utilize inexpensive feedstocks. Corn syrup via starch and corn can be fermented to either L- or racemic D,L-lactic acid, ~5 depending on the microo-qanism. Racemic D,L-lactic acid is cheaply ob~ainable via ethylene whi_h can be oxidized to acetaldehYde r which is reacted with hydro~en c~vanide to m lac~onit~-ile, whi_h is hvd.-olized t3 racemi_ 3,~-'ac=ic ac,_. _actide i~ s_m-`~ ab~ained by dictil~ cn -~ of la-ti_ ecid~ ~`o ca~n~e --^ _he ste~eocna~strv cf the ~s~c~e~ _à_-. c^^~__s ~ _c_~
~ -`e ~ ^ci~ c~s~~lla~ _en~__i^-. r~ v-s~

i~ _is_~ c- :~-ei.~ e-~ 2 ~ e .~ 3_ ;~as__ i~e-` ~ e~ u~ c-~.

~1~'0 O~ ~t t p(-r/11~S91/Ofi3 --~0--product; the only difference being that it rotates light in a different direction.
The copolymers of the present invention are preferably formed by heating the mixture of monomers to form a homogeneous melt and adding a catalyst to cause the lactides to undergo a ring-opening polymerization. The polymerization is preferably carried out in an inert, anhydrous, atmosphere, such as nitrogen or ar~on, or in a vacuum. Suitable catalysts include divalent metal oxides and organo-metallic compounds such as stannous octo~te, zinc acetate, cadmium acetata, aluminum acetate or butanoat~, tin chloride, tin benzoate, and antimony oxide.
Stannous octoate is the preferr~d catalyst because of its high solubility in the monomers, ease of preparation in ~5 anhydrous form, and low toxicity. The amount o~ catalyst required can vary from approximately 0.02 to 2 percent by weight, based on ~lonomers and is preferably about 0.2 percent. The molecular weight and melt viscosities of the copolymers are controllable by the amount of catalyst and/or chain-transfer agents such as glycolic acid. The reaction temperature of the polymerization is between approximately 100 to 200 C. The least color formation occurs below 140 C and the rate of polymerization is best above 135 C. Since racemic D,L-lactide melts at 127 C it is best for conversion of monomer to polymer to polymerize at a temperat~~e above 127 C.
Where a su~stantially clear and transparent co~osition is re~uired, as ~ith crystal polvstyrene ~îf se _s, _~e co?o`~e_s of ~.is in~er._ion _re ~ol~eri-e~
-Q C~ ._el~ ints, ~re cene_-21ly in t~e ~5 ~ ~50 c r_n~e. The mol-_~
~c~i~e c^?~ c -~s'~ ~T~ e- ~` ~.
~--c~s c~ c ~ c~ ?~ ~~ S~_e` `~ ~
_ . . _ _ _ _ ~ _ _ ~ . .: _~ _ _ _ _ ~ . _ ., _ _ .: _ ~ _ _ _ _: ~ _ _ ~ _: _ _ . ~ . .
~ ~ I o . o_ ~ __ , cc~

~ _ _ ~ ~ _ ~ _ . _ _ ~ _ . . _ _ _ _ . . _ _ ~ . _ . . . _ ~ /U~13 PCT/~S91~1~63_ 31 ~ :

cooling the fabricated item. Thereafter, the copolymers remain transparent unless heated for several hours above their glass transition temperature, Tg, and below the melting point, Tm. Slow cooling of thermoformed sheets, slabs, films, and molded items can induce spherulite crystallinity in the copolymers which qains improvemant in the heat stability of the fabricated item, but causes some loss of transparency. Nucleating agents such as sodium benzoate, calcium lactate, and the like, can also induce rapid and qubstantial crystallinity. ~ modest amount of drawing of the copolymer, between its Tq and Tm, induces oriQntation of the polymer molecules and can substantially improve physical properties without loss of transparency.
Blending of different types of lactide polymer or copolymer can substantially change the physical properties. As an e~ample, the mel_-blending of the high-melting L-lactide polymer with a lower melting lactide copolymer can provide a transparent material which has a sufficient amount and type of crystallinity to remain substantially transparent. ~hose skilled in the art will recognize that transparency in molded films, great stiffness, elevated heat distortion temperature, thermo-processability, and environmental biodegradability are a rare combination of properties. Thus, the polymers can be ~5 ~lended, as well 25 nucleated, oriented, and controlled bv molecular weight to provide a great deal of latitude in the processabili~v and final p-oDerties in the final _ompounce~` ~hc-_crl~s_i_.

ydr^_~-e ~2cl; :0 12c-ic 2c` o ` n _he presence o~ mois.u~e.
~-n the presence cf ____en_ ci_ ~.d humidi~ _..e h~_olvci~

`_ol~ `s ~_^c-=~ r~ s ___e `e3--.-`i.- _n _h- ^ -~^si i^- -olecul_- ~ eirhts . ' ~ -n4~1~ PC-r/~'~i91/l)fi377 the particular, aqueous environment the copolymers are placed in. Microorganisms can further reduce the lactic acid to carbon dio~ide and water. ~s an approximate measure, the copolymers have a shelf life of several months, but disappear within about a year when thoroughly WQt.
The followiny examples are merely illustrative of the present invention. In Example~ lB to 7B, a co~position series was prepared and evaluated. It was discovered, in contrast to the prior art, that there are distinct di~f~rences in the processing be~avior and physical properties of the L-lactide/D,L-lactide copolymers.

XamDle lB
In a dry, ~00 ml, round-bottom flask was charged 160 g of ~-la tide (Purac, Inc., "t iple-star" grade) and 40 g of racemic D,L-lactide (Purac, Inc., "triple star"
grade). This mixture was heated for approximately 1 hour at 123-129 C under a stopper with a continuous nitrogen purge throug~ a stopper inlet and outlet. The monomers form a clear melt, which is mixed thoroughly by swirling the melt. Catalyst solution was prepared and dried by azeotropic distillation, that is, 10 ml of stannous octoate (Polysciences, Inc.) was dissolved in 60 ml of toluene; 10 21 of tol~uene, with trace water, was distilled to a Dean-Star~ trap that was vented via a drying tube. A
0~20 ~1 auantitv O r the stannous octoate solution was pipetted in.o ~he mel` ar.d ~2d ~ho_ough'y~. Th- n_tro3en s~ ? ~-.'ir.~es ~ s ~r.~ sir. ~ 5 ^~0 ~e~ the ne~_ 3 ho_~s. .-eati-.3 _on~inues ,_t ' ,-;27 C fo--0-24 hou~s. ~:e ~ u-e w,_c _llo~e~ to c~ol _~ -o-~
_ ~ . ~ _ _ _ ~ ~ _ _ ~ ~ _ _ ~ . ~ _ _ _ _ . ~ . . _ _ _ _ _~ . _ _ _ . . _ _ _ _ . _ _ _ _ ~ . . _ ~ . _ . ~ _ _ _ . _ _ _ _ . ~ _ _ _ _ _ _ . _ ~ _ _ _ _ ~ ~ ~ _ _ ~ e~ f~~ ?~l~e- -i' --?~
- -_e-- ~ c~ S~ s e-;--~ Ir=~~ `.- _ sC~ es--~V04'/n~l~ ~'C~/~S9l~063', in a heated hydraulic press for later tensile testing.
Slabs, 1/~ inch thick were molded for impact testing by notched Izod, ASTM, D256 and heat deflection temperature, ASTM, D648. Glass transition temperature (Tg) and melting point (Tm, center of the endotherm) were evaluated by differential scanning calorimetry (DSC).

~m~les 2~-73 The procedures of Example lB were repeated except that the ratio of L- and racemic D,L-lactide were changed as shown in Table lB with the test results. The pure L-lactide polymer, Example 7B, would not always mold well at 170 - 200 C since it frequently crazed badly on cooling in the mold. Frequently, on cooling, it opacified. Figures lS-18 illustrate DSC plots from material of Example 53 as further discussed below.

V

u~ o a~ D In ~ 'd I ~ I I I ~

P. c a ~ `O ~,~ ~
~1 O ¢~ ~ N N ) c oa~ '~ C O

t~ ~n ~ ~ I _ I~ ~ C ~ O ~ m c ~

c~ C ~ h Ln ct~ ~ tO C
m . .
~ c~ u~ ~ In ~ O ~ ~ n I ~
O O tO O J~ ~

E~ o c: o ~ m, a~ I I I m I ~ O h O R

¦ ~ _ Ei~-~
3~ ~ u _ o ~ C ~ cl _ u c ~ ~ c I r~ o _~
X O ~ o r~
_ _ _ 09_~0~1~ ~'CT/~S91/~632 _9,_ ~ `

Exam~le 8B
Similar to Examples 4B and 5B, a 90/10 weight ratio copolymer of L-lactide/racemic D,L-lactide was prepared. Into a dry, nitrogen-swept, 2-liter flask was placed 1045~8 g L-lactide and 116.4 g of racemic D,L-lactide. A 1.O ml quantity of anhydrous stannous octoate (0.2 ml per ml of toluene) solution was added. The flas~
was swept with nitrogen overnight, t~en heated in a 141 C
oil bath until the monomers are melted and well mixad, and 10 the heating decreased slowly to 125 C and continued for 72 hours. The poly~er slowly whitens on cooling. After removing the glass, the cloudy, colorless, glassy copoly-mer was evaluated. Gel permeation chromatography obtains a weight-average molecular weight (Mw) of 522,000, and a 15 nu~ber-average molecular weight (Mn) of 149,000, A DSC o r the lactide polymer reveals a strong Tm at 145 C, see Figure 13. The lactide polymer was melted, quenched, and examined again by DSC to reveal no crystal-lization or melting points. However, a Tg appears at approximately 50-55 C. The results show the polymer can be crystalline or amorphous, depending on its heat history.

Examples 9B-12B
The composition series was extended, using the 2S procedures of Example lB except other L- and racemic D,L-actide ratios were used and heating was 2 hours 125 C, 14 s 125-1~. C, 'hen 2 ~.o~rs 14--'2' c. T~.e ~esul_s arr i~ ~.` i ;3 TABLE 2B. TENSILE AND MODULUS PROPERTIES OF L-LACTIDE
AND D,L-LACTIDE COPOLYMERS

,.. ... .. . . .. ~
Composition, Weight Rat o, L-Lactide/ 70/30 60/40 20/80 0/100 (Racemic) Example No. 9B 10B llB 12B
Color/Transparency Colorless/
Clear -~ ~~ -~
Film Thickness, Mil ~-9 4-6 4-5 ;-~
Tensile Strength(~), 1000 ~si, ASTN
D63g(i~ 6.9 6.7 S.8 5.6 Elongation, S 3.2 3.0 2.7 2.8 Tangent Modulus, 1000 psi 287 293 275 278 (a) Films were pulled at a ~aw separation of 0.2"/min. and chart speed of 5"/min.

The results of the above examples reveal that only certain compositions have the required properties for a crystal polystyrene offset. The main requirements for a crystal polystyrene-like material are clarity and celor-lessness, tensile strength greater than 7000 psi, tangent modulus (a measure of stiffnèss) ~reater than 400,000 psi and well-behaved thermoplasticity. Table 3B lists some side-by-side comparisons of a crystal polystyrene (OPS) and a ~7.5 weight percent L-lactide and 12.5 weish.
pe-can~ rG~~emic D,B-lac_ide randor~ co?ol~e~

~>C~ 9l/~1637 ~_ , ;, ,_ ~ J _:

TABLE 3B. PHYSICAL PROPERTY COMPARISONS

Property acid),Polystyrene Impact strength, notched Izod, ft-lb/in. 0.4 0 4 Ultimate tensile strength, psi 8300 7400 Elongation, % 6.0 ~.o Elastic modulus, psi 694,000450,000 Deflection temperature, F
under load, 264 psi (a) 200 Specific gravity 1.25 1.05 Rockwell hardness (b~ M7~
Vicat softening point, F ~c~ 225 Melt flow rate, D1238(G) 1.7 g~l0 min.(e) 40-46(d)1.6 g/10 min. ~f) (~ Depends on heat history (b~ Shore D = 97 (C~ DSC, Tm = 125 C (257 F~ at 10 degree/min.
(d) Flow rate decreases at lower temperature (e~ Listed by manufacturer (f ~ By our experiment Exam~le 13B
The copolymer of Example 2B was molded and remolded several times to determine if color would develop in the films and .he molecular weights remained hish.
~5 ~is dete~mines ~ the ce201~G- can ~e -ecycled, an ~mpo--2n_ coneide 2tion o- m~nl~_2ctu_in~ cticos. The _esul_s of ~ab_e ~3 sho~ ~h2~ ~he co?ol~e- _eri~a r.eG
c~?le-el~ .s~ .~ 2~ SS 2^~ e- -~:?e~te~
n~ _e~ e ~ o _~?ol~
~. ~ ~ _ _ ._ ~ _ _ _ _ . ~ _ _ _ _ _ _ _ _ ~ _ _ _ ~ ~ _ _ _ ~ ~. ~ . _ --'~8-- ~ ~.
`t . . ~

TABLE 4B. EFFECT OF MOLDING ON LACTIDE COPOLYMER

No. History Appearance 10MW0~s 1O00~S ~w/Mn Example Not Completely 928 218 --5 2B(a~ molded, transparent directly and from colorless poly~eri-zation Exa~ le Ex. 2B Completely 301 135 2.22 13Bt ~ after transparent molding~b~ and colorless Exam~lQ Ex. 2B Completely 137 56.7 2.42 13B~ ) after transparent molding 6 and times ~b~ colorless .. . , .. . .... . , . , ~ . . . .
~ 85/15, ~-lacti~ ./racemic D,L-lactide copolymer (b) Compression molding at 167 C ~333 F) fo. 7 minutes to 5-mil film Exam~les 14B-18B
The copolymers c~ Examples 2B, 33 and 6B were compression molded into f ilms of approximately 20 to 30-mil thickness and were placed in a heated Instron tester where the films were drawn 5 times their length at 83 C at a rate of 0.5 inch per minùte. The f ilms were cooled quickly upon removal from the Instron, and found to be approximately 5-mil in thic~ness~ T~ey were clear and c^lorless. Tensile properties were evaluated and are ~is~ed ia T2blQ 53~ Tihen d-=~. S to 10 ~i~es _heir len~ e fi'ms ~c-~ ev~`dC-co cf -r~s_al fo -.ation b~A~
vir_ue o_ h~ze Gevelop~en- c?~ SO~' les- o_ `__c?S~ ~-es~
~~ T;~e -esu'~s ce-^ns_~__e _~~_ ve-i 'hi?. f '` l~s C_?.
^. -~ _Cn-~ _c.Sc~~
_. _ ~ _ _ _ _ _ ` _ _ ~ _ _ _ _ _ _, ` ` _ _ ---- ` -- -` ` ~ . _ . _ _ _ ~ _ _ _ _ = _ _ _ _ _ _ C~ . . _ _ _ C~ ;~ _ _ _ _ _~ _ _ _ _ _ _ ~ _ ~_ _ _ J _; ~
~ ~ _ .. _ _ _ ~ .

)~l3 ~'CT/~S9l/063 ~ 3 TABLE 5B. PROPERTIES OF L-LACTIDE/RACEMIC D,L-LACTIDE
COPOLYMERS AFTER ORIENTATION~ a ) .... _ _ Composition, Weight Ratio, L-Lactide/ 85/1585t-5 85/15 8~5/12.5 95/5 D, L-Lactide (Racemic~ _ Example Number 14a 15E7 16B 17B 18B
Film thickness, mil S.S 5~0 6.5 5.0 4.0 T~nsile strength, 1000 psi 14.0 1~.7 lS.O 13.0 1~.0 Elongation, S31.5 15.4 30.0 23.8 37.4 Tangent modulus, 1000 psi -- 564 41g 432 513 _. ___.. _ _ __,~",~., . .. . . ,_,_ --. ~ . ,~_._ (~) 5X oriented at 83 C using a draw down speed of 0.5 in./min. on Ins~.on Exam~le 19B
Films of the copolymers of lactide of Table lB
were immersed in water for several months interval. The copolymers remained clear for approximately 2 months;
after 3 months a slight haziness developed. Upon setting on the shelf in humid air and with frequent handling, the films remain virtually unchanged for approximately 1 year ~lthouch Ins'_on d~a ~ill sho~ a slo~ decrease in the strength and elongation after several months. In a l_n~_il`, _he ~u_i-` i'_s dis~ æ- i- 5 m2..~hs '- 2 years, de~enning on _he moisru-e, 7~ em~2er~_e, c1~

~ ~ " ,~ _ ~he i2c__-e c~ ~.e~ ~ ~am~ie -7 (c~en_~e-, --n-ress70n-m2i~e-` _` `` ' n ;`'-S e.~ ` -e-` -y ~`- _ns` -_un-' ;;`~ ``' ~i~ i r~.~' ~o~ !n~

polymer of Example 5B was annealed in a 185 F oven for 16 hours. The sample turned hazy and the DSC of the sample, see Figure 10 revealed a pronounced increase in the crystallinity. The sample showed a 264 psi heat deflection temperature (~DT) of 90 to 95 C. A similar sample without annealing ex~ibited a he~t deflection temperature of 50 to 55 C, which corresponds to its Tg.

Exam~le 21~
Calcium lacta~a, 5 weight percent, was blended on a heat~d mill ~oll wit~ the lactide copolymer of Example 53 at 170 C or app.o~imately 5 minutes. The blend ~s stripped off the roll as a sheet and examined. It was stiff, strong, and hazy. Optical microscopy at ~2X
reveals heterogeneous domains in the size range of from a few microns to 30 microns. DS~ reveals a substantial increase in crystallinity in the vicini'y of 145 c, see Fiyure 11, which remain on quenching and reheating. The results, above, comparing Examples 8B, 20B, and 21B, show that nucleating agents are more prompt and efficient in inducing crystallinity in lactide copolymers. Nucleating agents such as salts of carboxylic acids may ~e used, salts of lactic acid are preferred.

Exam~le 22B
T~, 2 500~ -r.ec`;, ~o~ancl ~o~;om -las~, equip~ed ~ith a mechanical stirrer and a nitrogen i:._et and outlet, 12ctide (botn Boehrin~er ~nd Ingelheim, _aGe s)~ ~e er: s~eC? =~ e `_~ -s _-~_ ~o.: ~ ^~

. ~
~ . s ~ _ _ _ _ . . _ ~ _ . ~ _ _:, ; , _ _ . , _ ~ , ~ _ ,= _ =,, _ ;
~ 5 ~ e.~?_-~ s ci~ -se~

_ _ _ ~ . _ ~ _ _ _ _ _ c _ . . _ _ ~ _ _ . _ _ _ _ . . _ _ _ _ _ . .

WO~2/~W13 --101-- . ~

lactides allowed to polymerize at 141 C over 3 days time.
The highly swollen, polystyrene floats to the top after turning off the stirrer. The lower, polylactide phase was cooled and examined by DSC. The sample has a low Tg, approximately ~5 C, and is otherwise lacking in apparent temperature transitions. Compression-molded films are clear, colorless, and very pliable. These results indicate that the polystyrene thoroughly interrupts crystallinity formation.

10 E~am~le ~3B
ThQ lactide copolymer of Example 8B was mill-roll blended with 20 weight percent of the homopolymer of L-lactide produced in Example 7B. A sample of the homopolymer was analyzed by DSC, see Figure 14. The lS blended sample was examined by DSC and ~ound to have a Tg of 59-6~ C and strong Tm's at 150 and 166 C, see Figure 15. Films were clear to slightly hazy, ~epending on their cooling rate after pressing. Quenched samples easily crystallize on heating to approximately 80-~0 C. As a result the heat deflection temperature of the blend is now quite high. The blend becomes hazy at 80-90 C but does not deflect with heat as does the unblended 90/10 copolymer. Tensile data as shown in Table 6B were obtained on unoriented, compression-molded films and compared to si~ilarly obtained data for polystyrene.

a~ )l TABLE 6B. COMPARISON OF BLEND OF POLYLACTIDE OF
~ EXAMPLE 23B WITH CRYSTAL POLYSTYRENE

_ _ Example Crystal 23B a ~ POlyStyrene ( a, b) Film thickness, mil 8 14 Tensile strength, ASTM 7.7 6.0 S D882, 1000's psi Elongation, %, to 6.5 ~.2 yield Tangent modulus, 323 267 1000's psi (a) Thin ~ilms, unoriented, compre5sion-molded specimens t~ Melt Index 1.7 This example illustrates that melt blending is an excellent way to improve the properties of the copolymer so that advantageous properties similar to polystyrene are realized. The higher the amount of homopolymer based on L-lactide (or D-lactide) blended with the polymer the higher will be the heat deflection temperature, however, haziness will also increase. Thus addition of homopolymer may be combined with other methods of increasing polystyrene like properties while still retaining clari.y.
As a further example, orienting films produced from the polymer increases the tensile properties. At eisht to ten times ~he d_aw `he ?hvsic~il p-operties are still increasing but the material becomes hazy. The ~S eeqree of orien~a~io~ hus neeid to be cor.~rcll^d ~nd combined with the othe_ prope-ty changing methods ~o _~2m~i~s 2~
~ _ c _ ~ _ _ _ _ _ ;. _ _ . . c , . ~ c = _ _ . ~ _ _ c i~
de~.-nst z._~g .h~_ molei~~'ar ~ei-.._s __n ~c _o..=-ollc~
~s.,.~ ~_cn~Ce~ ~_..~s ~ ^ _s '~ esult--\~ o s~n~ l ~ P(~ S9 1 /063~ î

relationship exists between the amount of transfer agent and the reciprocal of the weight average molecular weight.
Preferred chain transfer agents are lactic acid or glycolic acid.

5 TABLE 7B. MOLECULAR WEIGHT CONTROL
USING CHAIN TRANSFER AGENTS

_ _ _ Example PPH of~tb~Mw~) /M
No~ CTA rl ~w n -24B 0.2213,S00107,300 8~0 10 25B 0~4512,80066,700 5.2 ~6B 0~90 7,30029,900 4~1 27B 1~80 4,70013,900 2~9 .. .. ... ..
~a) Parts of glycolic acid chain transfer agent (CTA) pe~ ~undred parts of lactide 15 in polymerization recipe~
(b~ Gel permeation chromatography in tetrahydrofuran solvent, 23 C, with 106, 105, 104, and 103 anhstrom columns, number average, Mn. and weight average, Mw, molecular weights are calculated compared to monodisperse polystyrene standards.
Exam~le 28B
A 4~0-mil, compression-molded film of the lactide copolymer of E~ample ~B was evaluated as a barrier ;-il~ by ASTM methods~ The results are shown in Table 8B. The lac~ide copcl~er is 2 much be,ter bar-ie- to c2rbon dioxide 2nd oxv~en t~ar. is polvst~rene. 3y compa~ison to s~ o-~_r ~ c-~ -_`-s, ~ ?~ a ~C cn 2de~u~.e 3a~~ie_ _ilr r^c- man~ ?2c~2~ins a??lic~ions.

~O ~n~ r~r/~ sl/~637--iO4-TABLE 8B. EXAMPLE 28B PERMEABILITY TO GASES( a ) ...._ . . -- -Vinylidi~neOLaotidP C~ystal~) Poly(uthylQne Chlor'de-UnitsExP plQ 2B Polystyrene terepht~al~te) Chlorlde .
e~/100 ln.2/
24-hr. /atmo8.
Co2 32.1 900 15-25 3~8-~
~ l9~g 3S0 6-8 0~8-6~9 (') AST~ D1434-75, Exampl~ 25 wa~ a 4~3-m~ omprQ~ion-moldtad film~
Valu~ ~rom Modern Pl~tics ncyclop~di~

10 ~sm~2~
SheQts, 1/8-inch thick of the lactide copolymers o~ Examples lB-6B were immersed overnight in a mixture of petroleum ether and methylene chloride, At ratios of 70/30 to 60/40, petroleum ether/methylene chloride, the copolymers would foam when placed in boiling water.
Irregular, but well expanded, foams would form~
Thus, compatible chemical or physical blowing ` agents may advantageously be used with other processing steps to produce foamed materials. ~hese materials are useful where foamed styrene is typically used (e.g. eating utensils, packaging, building materials and the like).
For example, a foaming agent can be added prior to extrusion or injection molding.

Example 30 ^5 ~ c~m?2rison W25 m2àe of the melt visccsities o~
a ,ommerci21, cryst~l ?olvstyrene tT~re 201, U.untsman ~n2 mel. in~e~:, AS~ 23~ t~-!, c~` _he ?ol~styrene ~2s 1. b c~o rin~ 2. ~33 C usi-.~ ~he S-n~5-;1 -` ~ '2ich ~ he e~ s~ s ,.~ -e~ 3 ~ v~ e ~s t~ r~-2 -`e~ e~ ?--~ c-~iC^cs~~ies W5S `___2' ne~ c~se~~ing ~ne 2e_= ~iscosi_ies ~!0 9'/()~113 PCI`/~S91/063~
~;05--J i ' 8`3 of the two polymers in an Instron Capillary Viscometer.
The comparative results are shown in Figure 12. The shear rates normally encountered during extrusion and injection moldin~ are approximately 100 to 1000 reciprocal seconds.
Inspection of the data of Fiqure 12 shows that the melt viscosity of the lactide polymer at 160 C is very similar to that of the polystyrene at 200 C~
The above results illustrate that lactide polymers can be ~elt-processed, at lower tempera~ures than polystyrene, by very similar methods.

E~3~æ~ L-~4~.
Small, test polymerizations of purified (recrystallized and dried) mesolactide ~meso D,L-lactide~
were carried out as the homopolymer and the copolymer.
i5 The molecular weights were evaluated by GPC and compared to analogues of D,L-lactide. The results are presented in Table 9B. The polymers were melt pressed into films and their physical properties evaluated and compared as shown in Table 10B. Within experimental differences of sheet thickness and molecular weight, the copolymers are similar within experimental error. The homopolymer of mesolactide is somewhat weaker.

TABLE qB. GPC MOLECULAR WEIGHT COMP~RISONS OF MESO-AN~
RAC_~'IC L~CT-~)E POL~`~lE~S ~ COPOL~;~SE~a Example C~mpoci~ion ~es. G?C x.~0 ~I~/M~

(a) ;~ ._pT !. __ `'7 - ~ 7 3.~c } ~ S ~ ~ ~ 5 4 ~) ?~c~ __r-;; 9';~ lOi~- ~CT/Us~l/n~

3 ~3 1~ oo~ !

3 s ~ ,, ~
~^t Ic~

a a s ~ ; V ~ ~ ; I
C E ~ U ~ O
C r~ O ~J O ~ O (~ ¦¦ E

0 9 ' / 0 ~ ¦ ~i I C'T / ~ S 9 1 /1) fi 3 _ V ~
ExamPles 3SB-478 These examples illustrate the pre~erred copolymer ratio of the L/D,L polylactide copolymer series (racemic D,L-lactide was used throughout these examples). of particular interest were the 80/20, 90/10, 95/5, and 100/0 ratios. Each of these copolymers is a material having different properties. Table llB contains data on the thermal properties of these unoriented copolymers. The ~lass transition temperature, Tg, varies with the amount of intimately dispersed residual lactide monomer~ A
t~ical relationship is shown in Figure 16 where the residual lactide was measured by TGA and the Tg was estimated by DSC. To a close approximation, the Tg ~ollows this relationship for all o~ the L-/D,L-lactide copolymer ratios. The 80/20 copolymer typically is an amorphous material with a glass transition temperature of 56 C. This copolymer has limited commercial use since its heat distortion temperature will be on the order of 45-50 C, which is considered too low for many packaging applications which require a rigid polymer used in applications up to 70 C.
The other copolymers have the same or only slightly higher glass transition temperatures, but can be crYstallized to improve their thermal st~bility. The rate 2S o~ crystallization inc-eases as the D,L content decreases znd the molecular weight decreases. F-om the point o~
view cf ther.mal prope~ties alone the lOo percent pcly(L-lac~ide) ~ol~e- is ~os, desirable. ~:owever, when othe~
t~__s___s s~ _~s~ ~ 2 ~
~i~, ex~~uded sh~pes, t~e ca?~ v to -`o so 2t lowe-_cm?eratU~cS `n``~h ess ;is_~si,y _nd _-lcr ~ G- icn, -ic~ -e~c~~ ~ r~ ~~};e~ t~
_ë ~_~-__``~__ ___~` ` _~ / ~_ ' _ _ _ `_ ~ - _`__'=.i--`:
_is_~ss~

TABLE llB. SUMMARY OF THERMAL PROPERTIES
OF LACTIDE COPOLYMERS

.
Ex~ Copolymer Transltion Tempe~atgre No. Ratio C C

36B 90/10 55 lS0 37B 95/5 59 16~

The mechanical properties of sheet extruded from each of these copolymers also differs somewhat, depending on copolymer ratio~ Table 12B summarizes data that has been obtained on as-extruded and 3x biaxially oriented sheet. The biaxially oriented sheet can be either amorphous or semi-crystalline through crystal growth during annealing. The annealed sheet has been found to be thermally stable up to the annealing temperature, approximately 110 C.
Since the 80/20 copolymer does not crystallize upon annealing, it will always be subject to thermal distortion when heated above its glass transition temperature. Orientation does increase its room temperature ~ech~ni~-al pro?ar~ies tc ~eri~ hi~h 'e~els, howevex~
The 90/10 copol~T~er sho~s an increase i~ rost ~5 properties ~rom ~oth annealing and orientation. The app-c~,:im~tel~ the sare as `hat c~ the ~0~0 c_?ol~e-.
~he ~~ ~`la~le da.a on ~he ~achanic_l ~ro?e_~ies th~ ~---e ~ c~ ;_0 _~~3'~ J`~--~ e, c- e.~ ?le, ~:~?12 and 5~ e mechanical pro?er,ies c- .he ~ c_ie-.,e~

~'09'~n~~ S91/063~, f ~ j iJ

80l20 copolymer or the 90/10 copolymer. Howevexl they can be considered acceptable for most applications~ The reason for the drop in mechanical properties has been attribut ~ to numerous micro defects found in the oriented sheet. The cause of those defects has never been identified; however, the material is known to craze easily upon crystallizing.
For comparison Boehrin~er Ingelheim poly~L-la~tide~, Resomer L21~, a pol~er with a Mw ~f 800,000 is sho~m as Exa~ples 38B and 47B. The tensile stren~th of this polymer is not very differQnt from that of the copolymers examined, but its tangent modulus is considerably higher; however, the values used in the tables were as published values not from the tests used to 1~ evaluate the other exa~ples~

TABLE 12B. SUMMARY OF MECHANICAL PROPERTIES
OF LACTIDE COPOLYMERS

Tnn~ile Tangent Elonga-No Copatioer Morphology Process Strength ~odulus tion 39B 80/20 A E7,500 30S,000 5.7 408 80/20 A 0-3x12,200 427,00018.2 41B 90/10 A E8,000 lS0,000 5.0 C23 90/10 C ~8,500 188,000 4.6 43B 90/10 A 0-3x11,700 494,000~1.2 44B 90~10 C 0-3x10.2Q0 401,00020.7 ~5~ 95/5 .~ 0-'x9,~Q0 ^t3,0005S~5 ~53 _/5 ~ 0-_~i6,S00 2~5,0006P.C
A / ,r~ ` O3; O r ~Y - r OO~i 30 ~ OOO __ ir~lOl~E
_ = C-ts_~lli^~
r " --, f; _ _ _~ _; _ ~ ,_ _ _ _ ; _ _ `-- -- `` -- _ _ -- ~ j_ _ _ ~ _ _ = `_ _ _ _ _ _ _ = ~_ _~___ c_ ~ r~ -J`-~ eci_~

~; "~ - r~ n~

h. ~.` <.~ .. 1 ~; j hiyher melting point than the copolymers, the 100/0 polymer has to be processed at higher temperatures than the other two materials. With a Mw of approximately 200,000 pure poly(L-lactide) has to be heated to 200 C in order to have a zero shear melt viscosity below 100,000 poise. By way of contrast, the 95/5 copolymer and 90/10 copolymers having Mw's of 200,000 have ze~o shear viscosity of 100,000 poise at 175 C and 160 C, respectively.

~a~es 48B-56B
Processing aids ~plasticizers) are necessary in prQventing color during extrusion and compounding. The pure poly(lactic acid~ can be substantially heated by the work put into it by a high-shear zone of a twin-screw extruder. An extruder set at 350 F, will work on a high molecular weight poly(lactic acid), with no processing aid, to cause its internal temperature to rise to 390 F, or higher, causing browning of the extrudate. For a high shear extruder this can be prevented using approximately 5 percent lactide incorporated into the polymer. I~ is presently believed that the processing aid acts as a lubricant to prevent discoloration. Other processing aids such as calcium lactate, sodium stearate, and sodium benzoate also are effective. ~ome illustrative results ~5 ~-e shown in Table 13~i. To those s~illed in the a_t it will be obvious that the e~act amount of processing aid ~`11 dapend or. he ~lecu~2~ weish~s _ r ' he poly(l -tlc acid) and the 2mount of she2r mi~in~ imposed.

he~_-c~r2c~ c~ r ~~.e ~ e 3~.~ 1 ~ ~, ~ 2_~_ _ _~ __o__ssi.._ ___ ~l~s~i_i~ ;, _ _ _ _ _ _ _ _ ~ ~ _ _ _ _ _ _ _ ; _ _ _ _ i _ _ _ _ . _ . . ~ .~. . i ss~ c~ lc~ _= _c .~e_ tha~ o~her p-o_essir~ ai_s su_h _s s~-iium ~en~o_te an~
__l^ium l^_~^=e o__^i-. ~~l_~'-r- -a-~c_~=es w:~en use-` i:

~o ~"~ cr; -~91i~)6,~, ,~. i; v ~ `J

TABLE 13B. USE OF PROCESSING AIDS

Co- Processing Aid zOne(b) Compositlon Type Wt S Temp, Extrudate 483 95/5 Lactide 15~5 391 Colorless 49B 90/10 Lactide 15.0 381 Colorless 50B 90/10 Lactide 12~ 385 Colorless 51B92.5/7.5 Lactide 8.1 3~4 Colorless 52B 90/lC Lactidc ~,5(C) ~81 Colorless 53B 90/10 Lactid~ 4.6 390 Sliqhtly brown 5~3 90J10 Lactide 3.~ 40~ Brown 55B 90/10 Sodium 2.0 3~8 Colorless benzoate 56B 90/10 Calcium 2.0 384 Colorless lactate (~ Monomer ratio, L-/racemic D,L-lactide (b) Temperature at high-shear zone in twin-screw extruder Exam~le 57B
Examples 57B to 753 teach the incorporation of lactide in conjunction with quenching to obtain pliability and transparency. Alternatively, the polymers can be annealed to i-?rove stability against heat distorti3n.
Poly(L-lactide) was prepared by methods previously des~ ed~ T~u~ ~00 ~ o~ triply recrystallized and _horoughly d_ied ~-l=c_ide was loaded into a clean, ~ -c-~e~ A, 5~ u~ o_~ h-f! as~: was r` ~~e_ wi-h _ ~``~` ~~~ sep~ 2-~d inl_t 2n_ c~tle s _in~e nee_!es ~2- ~dm` _ ~ csntinuous a-_~n ?u~rJe .. ct~r.~s ~-_^--~e ~ ; 'D C ~ _ e? _-r~ C `

sieves, ~ s~ "_c.~e __eo--c?ic~ e c~ i.. a~ 3n ? -~ c ` ~ ~ C_=`- ~ ~e ~-?-~-~- _~.-~ ~^~e _-~l -- v ~

lactide. The flask and its contents were placed in a lS0 C oil bath, and when melted, swirled vigorously to obtain a homogeneous mix. The argon pur~e continued a~d a thermocouple was fitted through the septum into the melt.
The melt was 143 C. The temperature of the oil bath was advanced to 200 C and heating and l~ght purge continued for 20 hours. The temperature of the melt advances to 170-174 C in the first two hours of heating. The f~nal tQmperature was 170 C. Afte 20 hours o~ heating the ~las3~ was cooled in 2i- to roo~ temperature and the solid polymer was transparent~
Poli~er was reco~ered by shoc~ing the flask with dry ic~ to free it from the glass. The residual monomer was analyzed by thermogravimetric analysis and the molecular weights by gel permeation chromatography.
Differential scanning calorimetry reveals a glass ~ransition temperature ~9) at 53 degrees and two melting point endother~s with peaks at approximately 170 and 190 C. The gel permeation chromatography molecular weights:
20 Mn = 129,000; MW = 26i,000; Mz = 462,000; 3~W/Mn = 2~08.
~esidual monomer by thermogravimetric analysis was 2.3 percent, (Example 57B, Table 14B.) The experiment shows that L-lactide can be polymerized above, or near, its melting point and the products remain transparent and more amorphous.

Example 58B
ay ~_~ s~ E~ " 0~ O ~ _c L-l~ctide ~as p~l~eri~ed usin~ 0.,0 ~1 o~ stann~us C_to2~e _ _ _: ~ _ _ _ ~ . . _ _ _ _ _ ~ ~ ~ ~ _ ~ _ _ ~ . _ ~ i . _ ~: . _ ~. _ _ _ ~ _ _ . .: ~ _ _ _ _ _ _ . _ _ c_C 15~ ``~S. -h_ -~ ?1~ 5c- G, ~_~_e ~ 5~~~-` ~~ -c- ~?-~ ~=i.._ G ~ ~ _ S ; "~ ` ~ r e~ cn~ ?3~ e- c ~led ~ c ~ic3~
= _ _ _ _ _ ~ ~ _ -- --r _ _ _ _ . _ . ~ ?
_~ _ ~ I _ ~ _ _ = _ ~ ~ ~ _ _ -- ^ - ~ ~ ; ~ , _ _ ;_ _ _ _ _ _ _ _, _ _ _ = ., _ --113-- ` :` ~

poly(L-lactide) to crystallize and become opaque, thus an intimate dispersion of plasticizer does not form.
The temperature is slowly advanced in many of these experiments to accommodate the polymerization exotherm. The reaction temperature must reach at least 170-175 degrees prior to a substantial monomer-to-polymer conversion, otherwise the poly(L-lactide) crystallizes and is difficult to remelt~
In Examples 60B-66~ the polymeri2ation of L-lactid~ was repeated varying the conditions to obtainpoly~L-lactides) with di~rerent residual lactide contents and crystallinities. The results are shown in Table llB, where it is seen that pliability and toughness were obtained only when the product has been quenched from the melt, is transparent at room temperature, and contained approximately 10 percent or more residual lac'ide. It is believed that the L-lactide homopolymer must be pol~erized in t~e melt, and quenched from the monomer-polymer melt temperatures, to a transparent material as ~o evidence of its homogeneous and intimately plasticized properties. When the poly(L-lactide) crystallizes during polymerization because the polymerization temperature is well below the polymer's melting point, the res`'ual monomer is no longer effective as a plasticizer. I the polymer crystallizes upon cooling to room temperature, it also loses its pl2sticization. Annealing at elevated .emperatures will -estore crystallini'y to amorphous s2m?1es~

9'"`''!~ T'(~/l`~C91/()fi~'-.

TABLE 14B. POLY~ERIZATION OF L-I~CTIDE

. . . _ . . _ _ No o~h Temp ~i~e Appuaranc~onomer Size 578 0.02156-201(') 20 cl~ar 2.30 300 150-174 transparent, hard ~ glaB By 58B 0.02155-165~') 72orystalllne, -- 104 opaque, hard, brlttln S9B 0.005120-2C0('~ 2~cry~tall~ne, -- 100 111-200 opaquQ, hard, brittle 60B 0.02135-145~') 22ory~tallin~ 1 S00 135-152~) opaquQ, hard, brittlQ
61B 0~02117-185(') 24cry~talllne, 1.74 100 120-175~') opaque, hard, brittle 62B 0.02160-170(l) 8crystallinQ, 2~18 2,000 opaque, hard, brittle 63B 0.02145(d lScrystalline, 3.6 25 li/-144 opaque, hard, brittl~
64B 0.0553~90(') 0.3 clQar, 10.1 25 160-215~) pliable, touqh, transparent 6SB 0~0553188-193(~) 0.23 clear, 22~9 2S
147-200 transparent, pliable except at edqe of polymari ate 55~ 0~02145(~) 2~7;crystalline(~,52~5 25 150-ii3`~` opaque, ha_ , brittle "' Oil b~th tem~era-ure io " Polym~r melt t~m~er2tu e :) -hi~ polymer -ry~talli-ed a- 160-169 a~ the tem?er.~-ure wa~
paren~ ~ e~?~-a_~_es ~:?_r~ n~

~V09~ 3 1~CT/~S91!~)6~'-This transparency and intimacy of association between polymer and monomer is also affected by the ratio of L/D,L-lactide. At approximately 95/5 ratio the copolymer easily quenches to a transparent solid. The 90/10 ratio, L/D,L-lactide copolymer quench2s quite easily. The 100 percent L-lactide polymer quenches with difficulty from thick sections of the polymer to a transparent material. Some comparisons are shown by Examples 67E3-71B o~ Table 15B. T~inner cross sections, 0 i.Q~ I films of the L-lactide polymer can be plasticized and qu~nched to pliable and t.ansparent materials~ T~e 80/20 copolymer quenches very easily to a transparent solid~ The latter has only a trace of crystallinity as seen by differential sranning calorimetry.

TA.3LE 15B. TRANSPARENCY OF LACTIDE POLYMERS

. .
~x L/D,L- c(ai ~Oumrs O/T(b) GPC Mw Monomer, 67B ss/s 145-160 67 SO385,000 2.64 68B 100 135-152 22 O322,000 1.1 69B 90/10 150-157 45 T821,000 4.95 70B 90/10 150-170 48 T278,000 1.37 71B 80~20 '35-175lC) 23 T -- --a) Melt temperatu~e (polvmeri~ation temper2ture) b! Cpaquen2ss/~~_..sp_~ency tGJ~` a~te- air~ lin~ ~f pcly~er~-~tes; o?aq~e ~); sligh~ly opaque ~SO);
tr~ns~arent ~

ed _5`~ c~~ e ~ol~. t~e~ 1_ \~ o ~ n ~ PC r~ /n~3~-. . ;~
~ J
90/10, and 80/20 copolymers are quite clear and transparent throughout their thermoforms.

ExamDle 7~B
The poly(L-lactide) from Example 57B was melted and mixed on an open 2-roll mill for 5 minutes at 375 F
~190 C), then compression mold~d at 375 C for 2 minutes, then air~quenched to room temperature in approximately 30 seconds. Both 7-and 20-mil thick films were prepared.
Both were clear ~nd transparent without trace of ha~e or opacity. Rasidual monomer in the film was 0.79 percent~
The films are very stiff.

Ex~m~le 73~
The experiment was repeated except that the milling was continued for 10 minutes instead of 5 minutes.
The films were analyzed by thermogravimetric analysis again and found to have 0.38 percent lactide. The films were clear, transparent, and stiff.

Exam~le 74B
The mill-rolled polymer was also compression molded into a 1/4 x 1/2 x 1 inch plaque. This plaque required 5-10 minutes to cool in the press by turning on the cooling water to the press. The plaque was white, op2oue, 2nd crystalline .e~cept for `he extreme edges, which were transparent.
~5 ~he a~^ve ~æmples 7~B-743 te~ch the quenching Or ~ilms of poiy(~-12~ e~ -o main~ain _ransparenci. ~ihen er~
~e~ s `~5C_ :~e~~~. in-~c_~~s `~ --^?~ ?'~ e~ c~:~en~
_: = _ _ _: _ _ _: _ . _ _ . _ _ _ _, . _ . _ ~ _ = _ ~ _ _ _ _ _ _ _ . ~ ~
3 ~ s i s _ s i ~ p ~ o ~ ~- s s ~ ~ c ` ` i _ i ?. ~ ~ _ 5 _ ) ' 2C_^-~.,~ ` '`.- . ;`~'`~-~ ='`~i' is r`c~ e e~e-~

\~09~ 3 I'~ 9l/()6~
.

some time to allow the molecules to order themselves into extensive crystalline lattices. ~his is callad annealing.
When cooled rapidly from an amorphous melt, the polyme-does not have the time required and remains largely amorphous. The time required to quench depends on the thickness of the sample, its molecular weight, melt viscosity, composition, and its T~, where it is frozen-in as a glassy state. Note that melt viscosity and Tg are lowered by plasticization and favor quenchin~. Thin films ~0 obviouslv cool very quic~ly because o~ their high surface-to-volun ratio while molde~ items cool more slowly with th~ir greater thic~nesses and time spent in a warm mold before removal. Regular structures such as poly(L-lactide) order more easily and crystallize more quickly than more random structures such as a copolymer.
With the polylacti~es the melting points are approximately 150-190 C depending on the L-lactide content and, therefore, the regularity of structure. The Tg of all the polylactides, including various L and D,L
homopolymers and copolymers is 60 C. The Tg decreases when residual lactide is intimately dispersed with the polymer. Quenching to an amorphous state requires that the polymer or copolymer in an amorphous ~elt is rapidly cooled from its molten state to a temperature below its Tg. Failure to do so allows spherulitic crystallinity to develop, that is, crystalline domains of su~micron tO
micron size. The lat~er scatters liyht and the. polymer s~eci~ens be~^me o?a~e~ Thcse c.ystalline ~c~2s ha~e im?rovQd stcbili_v ~ heat distortion. This spherulitic -~a c_ys~allini~- is _~en ~ sh__= ~an~e _~~e--~^n_ ~iso~de- si-.~c _~.e ~ s ~-~ se?~ e~ _v ~
ecicns~ evc_, ~e ^_ys~e''i~_es ect ~s pse~aco C i _ ~_ _ _ _ _ . . ~ _~ _ i ~ ~ = _ ~ ~: _ _ _ _ . . _ = _ ~ C _ ~ ~ . = _ _ _ _ _ ~ ~
~~ s_~ e -~~,_ci..e~ C~
.~.C~ C`15 ~l~ e~ ~bc~ e _ts T3 b~lt belo~i i's ~l'i~3 er .~o~ec~ -- _è ~=_c__~c~ __ G~

n~ pcr/~ ~9l/nfi some long range ordering, then "heat set" to permit the ordering to complete, that is, given some time to anneal.
The amorphous polymer is thereby crystallized into a different order, called long-range order, short range disorder. Transparency and resistance to heat distortion are favored.
A detailed discussion can be found in textboo~s, for example, "Structural Polymer Properties", by Robert J.
Samuels, Wiley Publica~ions, NY, NY 1974.
As D,L-lactide is introduced as a comonomer, auenching can be replaced by ordinary cooling to retain transparency. Spherulitic crystallinity can be introduced into these films by annealing and the 100 percent L-lactide poly~er is the fastest to crystallize. Where transparency is not required the higher L-lactide polymers can be annealed to greatly improve their resistance to thermal distortion. Conversely, where transparency is required, such as in a crystal polystyrene offset, great care must be taken to avoid this ty~e of opaque crystallinity.

Exam~le 75B
The poly(L-lactide) film samples were annealed on a hot plate at 240 F (115 C). The film turned hazy in approximately 1 minute and completely cloudy in ap~ro~im2tely 2 ~inutes~ By way ol co~pe~ison, a 90/10, L/D,L-lactide copolymer film required 10 minutes to turn _ , _ .i..u_es A _ _ C ~ C _ O U _ ~. en suspended by one end hc-i~ontally in an o~en ~n~ ad~-anciny .0 s~ lD _ema_ne~ s~-~is~.~ u..~ _e-?2~3;u_~ o ~
~\ r'~~ _~_2~.e~ h.en e~ e-. ~ne -~
e _ ., _ _ _. ,,~_ .__, _ __ ._ _ _ _ _ , _ _ ~ . .~ . . _ _ _~ _ _ _ ~ ~ ~ _ ~ _ ~ ~ _ _ _ . _ _ .~ _ ~ ~ _ _ _ _ _ _ _ _~ _ _ _. . ~ _ _ _ _ _ acl y l~c~ i ces c_n i-cre2se l!~.e_r -o-~-s._b_ 1 ity a= e ` ~vc,~^-? A~ ~ ~ ~ - ~ ~ r--c ~ ~ ~--^ ` h _ = - ~ 2 '~ ` c 3 ~ ~ 2 ~

!'C~ )o3'~

~ ~ 3 Ex~mples 76B-79B
The ollowing examples illustrate the beneficial effects of adding lactide during compounding. The examples show that without lactide as modifier, the lactide polymer degrades during compounding. With the addit~ ~ of lactide both discolorat.ion and molecular weight decrease are prevented or substantially reduced duriny compounding.
Thus, in Example 76B, a 90/10, L-/D,L-lactide copolymer prepared as described by previous methods using 0.02 pph SnC12~21i2O catalyst ~a~ ground and axtruded into pellets from a twin screw compounder, adding ~ weight percent lactide~ The melt zone temperature of the extruder rose to 390 F, the polymer discolored, and the weight average molecular weight (Mw, by gel permeation chromatography) decreased by approximately 40 percent~
The results indicated that insufficient lactide was added for this very high Mw copolymer~ The results are shown in Table 16B~ The pellets from this compounding were ~0 recompounded adding 2 further 10 weight percent lactide (Example 78B)~ The melt zone temperature was 375 F, and the results were much better: further discoloration did not occur, molecular weight decreased slightly, or within experimental error, and a pliable composition was obtained~

~T 'T `,~ !/nfi~--. ~ Ji TABLE 16B. EFFECT OF LACTIDE AS MODIFIER
DURING COMPOUNDING

Ex. Before Compoundinq Lactide~b~
No. Color M~ M~./Mn(a~ weight percent 76B Light yellow 513 2.15 0.78 77B Li~ht vellow 278 1.80 1.37 Ex. After Compoundin~ Lactide (b~
No. Color M~ta) ~ /M ~a) weisht percent .6B ~ark yellow 322 2.05 5.56(C) 77B Yellow 184 1.90 2.26 78B Dark yellow 307 2.00 14.4t 79B Colorlesst~ 324 1.99 14.6 (a~ GPC x 10 3 (b~ By thermogravimetric analysis, at 200 C
(~ Five weisht percent lactide added during compoundin~.
(d) Further 10 weight percent lactide added during compound.
(e~ Thin film To ascertain that the second compounding and extrusion were facilitated due to the lactide modifier and not the decreased molecular weight, another compounding (Example 77B) was performed starting with a similar-Mw copolymer of 90/10, L-/D,L-lactide. In this case, no 'actide was added bac~ in durinc t~e co~?oundins. The melt zone temperature W2S 382 F, the copo!ymer was ~is~ 2~ .e ~ e--2~C~e~ tel~ 5~
percent. In ad~ition, ap?ro~:imat21y 5 pe~ccnl mo_e to~~ue c _ c . . c _ .

_ ~ _ _ _ ~.. ~ _ ~. _ _ _ ~ . ~ . _ ~. _ _ _ . ~ . _ _ ~. . _ . _ _ . .

WO9~/0~13 PCT/~S91/()632 very pliable and extensible as described below in Examples 60B-64B. The Mw by gel permeation chromatography was 324,000 (cf. Mw = 307,000 before compounding and extrusion). The Tg of this plasticized material is 42 C
and differential scanning calorimetry reveals a very small amount of crystallinity melting at approximately 138 C.
The amount o~ lactide present is 14.6 percent as estimated by thermogravimetric analysis.

~amles ~OB and 8~
~he compounded polylactides, E~ampla 7~B and 77B, wer~ mixed together in the twin-screw compounder wit~
extra lactide to raise the lactide level to approximately 20 percent. The compounding temperature was 347 F tl75 ~), much reduced from the previous 375 to 385 F. The compounding proceeded s~oothly without f urther discoloration.
The above results clearly show the beneficial effects of added lactide as modifier. The required torque to compound the compositions, the discoloration, and the working temperature are decreased when adding lactide.
Further evidence of plasticization is seen in the lowered Tg and the pliability of the compositions. In addition, molecular weight decreases are avoided and stable compositions are obtained. It will be obvious to those sXilled in the art that the amount of lactide employed àepends on many factors, includinc the desired amount of ~lsticiza~icn ~ou~h`, _he s~3e cf _-m?ol~nder ~hat is ~~.~ _~,r ~ e~ _ c_ _~.~ ?31~1~cti~es.

` `'?.~ C ~
~ esa e~:-m?le- illus=-_~_ ?l-s_~ atio~ ti--_: _ _ _ .~ _ _ _ _ _ _ _ _ ~ . _ ~ _ _ ~ _ _ _ _ ~ _ _ _ _ _, . _ _ ~. _: ... _ ~ _ _ :.
-i~Jia, ~-!r~2~ -e ~e _ ^~ `2_ ~_=.; G
____~c2 ! ~ - - ~ _ C C _ _ ~ _ n~
__e_ro r~he!r .~e_n -~aracte-ir~ tensile an~ thermal ,.7;~ 4l /nf.~~

i~

In Example 82B, a control copolymer of 90/10, L-/racemic D,L-lactide was assayed by thermogravimetric analysis to be 6.74 percent lactide. This was mixed with percent by weight oligomeric poly(methyl lactate) (Mella) in Example 83B, which was prepared by heating 2,500 g of (S)-methyl lactate in an autoclav~ at 210 C for 3 hours, then collecting the Mella which ~ractionally distilled at 81 to 85 Cl1.25 torr~ The mixt~re was melt blended on an open 2-roll mi~l at approximately 7~50 F.
0 T~e blend was co~pression molded in a press a~
ap~roximately 350 F into clear, pliable films~ The tensilQ properties, before and after, adding the Mella are recorded ie Table 17B. The glass transition temperature tTg) was reduced by the Mella plasticizer.
For Example 84B, the 90/10, L-/racemic D,L-lactide copoly~er was melt blended with added L-lactide in a twin screw extruder ~o adjus~ the L-lactide content to 20 percent by weight. The blend was further mixed with oligomeric poly(ethyl la~tate) (Ella~ (Example 85B~ and Mella (Example 86B). T~e properties of these blends are also recorded in Table 17B.

PCT/~ S9 1 /ûfi3', , ~ ~ J ` l '~
T~BLE 17B. C~ARACTFRISTICS OF POLYLACTIDES(a) PLASTICI2ED
WITH OLIGOMERIC ESTERS OF LACTIC ACID

~la~tlc Brcak Strain Ex Pla~tici2er ~odulu~ psi Break, T~) T~(C) _ 82B6.7~ L-lactide 370,000 6,903 2 Sl 1~1 83B6~74~ L-lactidQ lS~,000 2,012 100 30 1~1 and 309 ~ella~
8~B20~ L-lactide 101,000 2.637 2~
SSB20~ L-la_t~d~ and 7,~1~ 2,561 ,39 -- --30~ Ella~
86B20~ ~-lactid~ and 3,620 495 83 -- --30~ Mella~') 0 (-! 90/lO, L-/racemic D,L-la~tide copolymer Gla~s transition temperature (') ~elt~ng point (~ Ana:i2ed by thermosravimetric analysis ~ Methyllactate oligomer (n Ethyllactate olisomQr Exam~les 87B-92B
These examples illustrate the injection molding of polylactide copolymers and the process for increasing their heat distortion temperature.
90/lO L-/racemic D,L-lactide copolymer (about 1.3 weight percent residual monomer~ was injection molded on a New Britain injec'ion molding m3chine having 75 tons of clamping capacity and a maximum shot si2e of 6 ounces.
Standard ASTM D-638 tensile bars were molded during these '~ _rials. The ~.oldiny _o..di~ivns we_e væ ied ove~ a ang2 ` o~ A ~e~ e-i~e ieculc~ we`~ ~ e~ , r^~ ~as suc~ess_~ olded to _s ~e~ o`~se-~ ~he ~olà `_e- iliin~, ~_= _ri~_ 1- e~,e_~icn, ;c ;a~iC_ _ ~ e ~ ~ ; ~ _ _ _ _ _ _ ~ _ . . . ~. _ ~ _ _ _ _ _ ~ -~;'0 9','~ r~ n~

Calcium lactate, at a 1 weight percent concentration, was compounded into the polymer before injection molding. This was done to provide nucleation sites to increase the rate of crystallization.
Crystallization in the injection molded parts was desirable to increase the heat distortion temperature of the polymer.
For example, molded parts of the nucleated 90/10 copolymer, were annealed bet~sen metal plates at about 110 C for times betwaen about 30 seconds and about 4 minutes.
Aftar exa~ining L-he DSC cu-ves of the annealed parts for the presence and degree of crystallinity, it was foun~
t~at annealing times between about 1 and 2 minutes were required to develop full crystallization when the polymer is in contact with solid walls at 110 C. Mechanical properties of injection molded samples are shown in Table l~B. This table shows that annealing does affect the heat distortion temperature, but does not strongly influence the strength, modulus, or elongation to break. The heat distortion temperatures listed in this table were obtained under a load of 264 psi. If a 66 psi condition had been used to deter~ine ~eat distortion temperatures, the increase observed fo. the annealed sample would have been even greater.

TABLE lSB. MEC.U~NICAL ~O~-RTTES or INJECTION

.
~xa~ple ~ St-en t~, ~.o~ulu~, ~lon~a~ion, .~T, .o~s~ ce~ C
S,a :nje~t.--n 5c~0 ::~0,000 c ~6 ~ D. " ~ ! C--'` i ^ ~
~nne~le~
_ ~ _ _al-iur~ lac-2~e-nucle-~_i pol~er ;-s ir,~e~
e~ ir.~c~ = c~ cn~ 1 in-_ _ ~ _ _ _ _ _ ~ _ ~. . _ . ~ _ _ ~ ~ . _ _ _ . . . _ = i ~ . ~ _ _ ~oo~0~ 3 PCI/~S91/063~-insl~fficient to develop full crystallinity in the sample.
The mold heating system was improved t~ provide in mold annealing at temperatures higher t~an 8S C, most preferably between about 110 and about 135 C.
Samples were also injection molded using a melt blend of the 90/10 L-/racemic D,L-lactide copolymer and about 5 to about 20 weight percent poly~L-lactide) as nucleating agent. The results are shown in Table l9B.
The injection molded specimens were well fo~med with excellent strengt~s, stiffness, and impact resistance.
T~e heat distortion temperatures shown in Table 19~ c~n be improved by annealinq.

TABLE l~B. PROPERTIES OF INJECTION MOLDED
BIODEGRADABLE POLY~ER

_ _ Formulation() Tengile 1~ Strain XDT I~od lS 90/ ~ p8l p8~ ~

89B 95 5 8,245 227,440 7 115 0.34 90B 90 10 8,32S 221,750 7 117 0.34 91B 85 15 8,631 230,150 7 116 0.35 20 92B 80 2C 8,615 228,840 6 117 0.35 (~ 90/10 5 90/10~ L-/racemic D,L-lactid~ copolyme~;
L-PLA = 100 percent L-lactide polymer E~am~les 93B-10~3 ~ o~e: Examples c3~ ,o 'Q~ listed i?. Tables 20AB and 20BB
2-o contain info ~ ation i~entical to Examples 65 to 81 in `~l~s '~5.~ ~n_ __à c~` se;~
~.m~odiment. ~.e ir~o ~ation is re?ea;ed here for con~enience i?. disc~ssing these e~alr,ples in rela.iGn to -r?~eC ~ ere sel~c_-_ '-_~.?~ --__~e t~ 2.._e~ _~n~ ^.s .~
~el~ ~o ~es~}_ i-. r~terials c- ne inventio.. ~he m ~,2_i:~s ^_O~`_~~~` _.. ~hese p__c-.~ ^.o~ c^~^'etel ~`0 9'~ r(~r/~

characterized, thus experiments were needed to allow a more complete characterization of the examples and provide meaningful comparisons that would demonstrate that the materials of the present invention are indeed novel.
With regard to the present invention, compositions were sought that had residual lactide or lactic acid contents of about 0.1 to about 60 weight percent and in addition may have the lactide or lactic acid intimately dispersed within the pol~er. The results fall into obvious categories. Thus, products with num~er-average molecular weights, Mnl less than 32,000 do not have the physical properties required in the present invention. In fact films from these low ~n compositions ware too brittle to be handled for tensile measurements.
lS It is known from the teachings herein that lactic acid, lactide or oligomers of lactide or lactic acid, or derivatives of lactic acid must be present to provide plasticization and the advantages of tha invention. The plasticizer must be present in amounts greater than about 0.10 weight percent up to about 10 weight percent. Thus, if the plasticizer is intimately dispersed and effectively mixed, the composition is substantially transparent. The heterogeneous domain size of the lactic acid, lactide, oligomer, or oligomeric derivative is small enough, generally less than one micron, so that it will no longer sca'ter ligh', i.e., it is intimately dispersed.
Conversely, white opaque samples are always hard because _~ey h~ve c-ys_a'li~es' ~nder the test conditions.
Cryst~llization squee2es the lactide out o. the poiy~e~

-_ss ~ ~u~e Or mon^re- an' ?ol~e . This is 2150 o~ ious `-om ~ e~e~.=i~l sc~nnin~ _~'o~ime~-y (~C) ~5 r, whe-e2s ~e''-?lcs~ici~ed sam?les do no~ sh_~; c _is, nc_ -^~.^me- .eltin- p^i"_ ~O (`':0~13 ~'Cr/l~`S91/Ofi3''-~ ~. V ' ~ `~
One very important point is t~at the cited patents frequently specify L-lactide homopolymer ("100 percent L-" in Tables 20AB and 20BB)~ The homopolymer of L-lactide easily crystallizes because of its high melting point. At lower reaction temperatures, the ~omopolymer can retain appreciable quantities of monomer, but the composition freezes during polymerization~ At higher, ~elt temperatures, t~e L-lactide polymeri~es so quickly that it is very difficult to stop the polymerization with s~lbstantial ~onomer left in th~ product~ This is true to a lessor extent for poly(L-¦ D,L-lactide~ copolymers also.
Inspecting the results listed in Table 20AB and 20BB reveals that th_ comparative examples obtain either products with low residual lactide, or products with residual lactide that is not intimately dispersed as seen by their color, opaqueness, and crystallinities. Thus, Example 94B (very similar also to the work of Schneider), obtained no residual lactide while Example 97B had 4.6 weight percent residual lactide, and both were off colored products. The best known laboratory techniques were added ~o th~ procedures, described in the footnotes, fo- tnese examples, from a historical standpoint (monomer purity, for example) in an effort to make the procedures work, with indifferent success. Either glassy, or hard, ~5 crystalline, o?aque products were obtained. It should be noted that only those exam~les using tin compounds as catalysts a?pear to be acceptable for many packaging applications.
~ e ~ J~S ~- US
_3 -;/~O~cO~ ~n~ 'S ~ "-~ ld ~ 2 ~~e ~.~te-_~'c c~
_es~ ve~ ~
s~ e ~ e~ ?er~` C~ c- =~ e-~ s -c ~ .2 e::~c~ -c-i~c ~ c_c c--e~ ra-~ c ~ s_s ~.o ~- c~

~09~ -. rcT~ ss 1 /nfi J

detectable residual lactide, the composition of the present invention is colorless and contains small amounts of lactide as a processing aid to prevent color formation during melt fabrication.
A colored product was obtained repeating the teachings of Example 97B. The residual monomer analyzed as 4.6 percent lactide. The material was light yellow, presumably due to the high poly~erization temperature which produced color bodies with the lactide polymer~ the dioxane solvent, and ~tannous octoate.

0 9 . 0 ~1 1 3 C 1' / U S 9 1 / O fi 3 _ 7 TABLE 20AB. REI~TED ART POLY~ERIZATIONS OF LACTIDE
CONDITIONS

Ex, Paeent Pat- Monomer Oataly~t zation No. Ex~ ~ D ~ TYPQ pph TomP- Hourc 93B 2,758,987 1 L- PbO Q.30 150 42 ~4B 2,758,987 3 50~50 PbO 3.00 150 S9 L-/D,~
95B 1,982,543 3 ~- PbO 0~30 150 31 96B DD 14548 ' L- SnO(') o~o09 193 3 97B 4,137~921 4 90/10 Sn(Oct~2, 0.0553 180 0.33 L-/D,L G~ 190 0,33 dioxane~ 210 0.33 98B G8 755,447 4 D,L 2nOO 0.02 150 24 99B GB 755,447 2 D,L 2n 0.02 140 25.5 Powder~
100B GB 755,447 6 D,L 2n 0.02 140 2 Carbon- 150 3 ate Hy-droxidet~
101B CA 932,382 1 D,L Tetraphe- 0.02 16S 20 nyl Tin 102B CA 923,245 1,7 Ç L- Et,2n 0.167 105- 2 '03B DE 946,664 2 D,L(~) 2nCl, 0.25 140 48 104B DE 1 L- - Sn 0.0087 205- 0.5 1,112,293 Stearate as Sn 210 1058 2,951,828 1 L-~0 SnCl~ 0~30 160 5 3~ spen-~ion~
106B 3,268,487 2 D,L T~is(2- 0~38 80 ~ 24 chlo~o-ethyl~a-~ine~
'0.3 ~P ~p~ ~. :- 58.IC-_). û~v~ i5 ~_ :~3,S_~ ?_ ~-(1934~; me_ ~
~., 550, .t.,C, 4,5i9,SE:

4, 7 g-/o~ 3 PCI/~'~91/063~7 (') No reaction untll recipe w~s changQd by adding 0.75 pph of 88 percent lactic acid. Product was white, opaque, very hard and brittle- film too brittle to handle.
~ ) Included was glycolic acid as chain transfer agent.
(C~ Insolubls (~ Insoluble after 2~ hours plus addltional 1.5 hour~ with 700 yl 88 percent lactic acid and 100 ~1 H20.
(') In toluene; product colorless and very ~iscous.
(~ In min~ral spirits, Stoddard ool~snt No. R-66

10 (~ AgglomeratQd ~ ) In dloxanQ containing O.S17 pph ~OH; no poly~eri~ation.

s~n~l~ PCr/~S91/~632, --131-- `:
~ ~' ~' . _ _ V J

TABLE 20BB. REII~TED ~ T POL ~ ~ IZATIONS OF
L~CTIDE RESInLTS

E Re8idual GPC x 103 ~ ~ Poly~erizate No Percent ~ M~ ~ Appearance 5 93B 0 254 454 7171~79 ~i~ht yollow, crystallinu, opaque 94B 0 97 187 3221.94 Llght y~llow, tran~pa~ant 9~8 0.35 95 195 3252.05 Partially opaque crystallinQ~ partial transparent 96B 17.5~a) 5 7 9 1.47 Whita, cry8talline, 7.1; 7.7 7 8 10 1.25 opaque 97B 4.6 116 218 3561.88 Light yQllow, transparent 1~ 98B 47.7 ~ Nhite, crystalline (monomer), opaque 99B 65.3 -- -- ---- Nhite, cry8talline (monomer), opaque 100B 79.6 -- -- ---- White, crystalline (monomer), opaque 101B 1.4 116 214 3401.84 Yellow, transparent 1023 1.9 80 1;0 2351.87 Orange, cryqtalline, opaque 15 103B 5.4('~1643776572.3 Hard, colorless 2.5; 1.9U)307527308 1.72 104B 43.3 30 35 411.17 Hard, crystalline, opaque 105B 8.6; 9.6219 343504 1.57 Hard, cryntalline, opaque 1063 100 -- -- -- -- ~11 crystalline monomer 'C,3 '.0 1~ 35 351.38 White, c-ystalline, o?aGuc ~ilm~ 5 `5l.S~ Some tran~parency a~
e-.-es ~0 1'`-5 ~0. ~' 5_ee:e- :hen ',0'`^,000 White, c-ys:al'ine, opacue 13-3 _- ~c~, ~-e~t-- -h._-. `,033,C00 t;hite, c-ys~alline, ~?2J e 3 ~
-emove ~ol~en_.
_~ '~' ~-a~sp2rc.. t, ~ . b~
~ nc obta:ns ;~.1 ?ercen_, ve-y hich molec~ r weicht.

Compositions having n equal to an integer between 450 and 10,000 have a good balance between strength and melt processability and are preferred. If a monomer is selected as a plasticizer a unique composition may be obtained by adding monomer that is stereochemically different from that used to obtain the polylactide in the composition. Similarly, addition of oliqomer stereochemically different from that which may be obtained during polymerization of the polymer gives a unique product. As tau~ht herein the products are colorless in the absence of coloring agents. Colo~ bodies can be e~cluded by performing the polymeriza~ion in an in~rt at~osphorQ and at roaction tempSraturQS preferably at 140 C or below and by appropriate choice of plastici2er in the composition as described above. Durin~ melt processing, a sufficient amount of plasticizer is intimately mixed to ~revent discoloration and degradation o~ molecular weight.
Various combinations of the above treatments can be emplo~ed to obtain the optimum characteristics as those ~o skillPd in the art will appreciate, once knowing the teachings of the invention.
As can be noted in section A. First General E~bodiment above, a higher amount of plasticizer can have significant effect. In the present application, lower amounts of plasticizer are preferred to impart stiffness.
Plasticizer present in an amount of between about 0.1 and about 10 weight percent is prererred. The plasticizer can -emo~e molding strainC~ lubriccte, maintain a lower processing tempera,ure, ~ain~2in a lower ~elt ~iscosi~y, ? '~ 2r~in~ c-.~ ~e~
5ra~a_ion _i_ e ~ ma_ c^-.?2si`ien -^ntains ?'2sti~i~e- in ;_ d~?e~c. _~ ?ol~ c~i.icr~ c- ~-.

__?_ _~ _e__~

_~e..~ r~--s ~he e-'~
~ : _ _ _ .. _ _ _ ~. _ _ _ _ _ _ _ _ _ _, _ _ _ _ _ _ . . _ _ _ ~0Y',U~:13 3 ~) derivatives of lactic acid, may also be ? 1ded. Unique compositions may be obtained by addition of monomer different from those selected for the polymers in the composition or oligomers different from those o~tained during t~e polymerization.
Contemplated equivalents of the compositions of the invention are those that contain minor amounts o~
other materials. The compositions produced in accordance with the present invention can be modified, if desired, by the addition of a cross-lin~ing agent, nucleating agent, ~the~ plastici~ers, a coloring a~ent, a filler and the li~e. Further treatments such as biaxial orientation and heat treatment provide for a useful film that is a replacement for polystyrene.
After treatment there is obtained a biaxially oriented and annealed environmentally decomposable polylactide film or sheet suitable for use as a substitute for bia~ially oriented c~ystal polystyrene film or sheet comprising, a film or sheet of a copolymer of the formula I, where n is between about 450 and about 10,000 prepared from about 85 and 95 weiqht percent D-lactide or L-lactide and between about 5 and about 15 weight percent D,L-lactide, said film having intimately dispersed therein the residue of a modifier selected from the group consisting of lactic acid, D-lactide, L-lactide, D,L-lactide, oligomers of said acid and said lac~ides, and mixtures thereol, said o_iented and annealed film having a tensile streng~h in e~cess of ,.500 a t~ngent modulus in e~cess of ~50,000, a ~ below a~out 60 C and the capacity of ~eing ens'c~ 2 ~ ~ ~c' ;;r~ ~ C; C ` c- - ~
_ .
~he composi~io.s he~ein c~n __ processed ~y mei_ -?~ c ~_ c.~ cc~ CisDosc _ ' ~ c~ 2 ~ r~ -s, se - vi..g _-ay5, 5y_ ince_, ~cidic21 .rays, ~ac~aging _i~ms ~~ 2 --i~ ?~ c-_ c-;

) n~./n~ sl/nfi3~-can have the characteristics of the usual plastics (eg.
polystyrene) and therefore substitute for them yet degrade in the environment. The amount of plasticizer serves not only as a processing aid, but also governs the initial physical properties. In addition, the amount of plasticizer governs the environmental degradation rate.
The compositions are especially useful for articles having only a one time use or a short life span in use before disposal.
Those s~illed in the art ~ill now recogni~e that there are contemplated equivalents for minor amounts of the polymeri2ed lactide and ~onomeric lact~de~ These include glycolide, caprolactone, valerolactone, and other cyclic esters a~ ~ono~ers, and the sa~e andlor open chain aliphatic esters as plasticizers~

C. Third General ~mbodiment The present invention discloses the blending of poly(lactic acid) (PLA) with polystyrene (Ps), polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP)~ ~he invention discloses that poly(lactic acid) is melt compati~le with these conventional thermoplastics and the effect on their physical properties~ Since both lactic acid and lactide can achieve the same repeating unit, the general term ~5 poly(lactic acid) as used herein refers to polvmers having the repeating unit o~ the fo~mula I ~ thout any limitation as to how the ?olymer was made (e.g. from lactides, lactic a~ , or ol~ e~-s), an~ ho~_ re'æ-ence 'o 'he ~e~-ee t`^.`~ 2~e`~ c~ s~ ic~
en-v-iron~en_a 1~ Ge ~a~iable c-m?osi~i~n, c~ ose~ e~~ e -_ l~_s_ ~

_~c_.~

_ ~ _,h,~ - ~ C~ _.__ .~ _e _~:. -: - --~ ?~ c.~ c - ~`en~s ; =~

~V9'i~l~ i'(~il~9]/~)(.3~~
-'35-i L 1~ ~
small domain sizes the physical deterioration will destroy the original formed produc'. The compositions herein provide environmentally acceptable materials because their physical deterioration and degradation is much more rapid than conventional nondegradable plastics. Further, since a significant portion of the composition can be poly(lactic acid), and/or a lactic acid derived lactide or oligomer only a small portion of more slowly degrading ther~oplastic residue will remain (e.g. polystyrene).
This residue will have a high surface area and is e~pect~d to deco~pose ~as~ur t~an a ~ul~ formed ~roduct.
D-lactide is a dilactone, or cyclic dimer, of D-lactic acid. Si~ilarly, L-lactide is a cyclic dimer of L-lactic acid. Meso D,L-lac~ide is a cyclic dimer o~ D- and L-lactic acid. Racemic D,L-lactide comprises a 50/50 mixture of D-, and L-lactide. When used alone herein, the term "D,L-lactide" is intended to include meso D,L-lactide or racemic D,L-lactide. Poly(lactic acid) may be prepared from one or more of the above.

Exam~le lC
Polystyrene was solvent blended with poly(lactic acid~ and solvent cast from CH2C12 to determine optimum compatibility. The solvent cast ~ilms were translucent and apparently "noncheesy". A sample, appears homogeneous 2~ to the naked eye and resists folding and handling without shredding apar_. o~tic2l ~icrosco?y at 310X reveals ~eteroaene.ous dc ains o~ 3 ~ic_-ns cnd less. ~he ~'end is ap~arentlv ve-v com?ati~le. ~t e~hi~its ro chanGe over 2 ~0 d~es its p?.vsic~ ?er~ies s~w evi~er.ce o_ de~rad2ticn.

_ _ _ _ _ _ ~ct`_~ c ` -?/?T ~ 5~/0 ~ . c~n~

~'O ~ r~

Examples 3C-5C
Melt blends were prepared of poly(lactic aci~) with polystyrene. Both a high molecular weight polystyrene (Piccolastic, E-125, Hercules) and a low molecular weight polystyrene (Piccolastic, D-100) were investigated. Also used was a general purpose polystyrsne, (~untsman polystyrene 208), a crystal polystyrene. These were mixed in a Brabender at ~25 F at different ratios with poly(lactic acid).
The polys~yrene/poly(lactic acid~ ratios use~
were lO0~0 for the control, and 9ollO, and 75/25 for the Huntsman 208, ~eneral purpose polystyrene.

~am~le~ 6C-/C
Two types of polyethylene terephthalate were used. (Goodyear's "Clearstuff" and Eastman's XodapaX TN-0148). These were dried overnight at 90 C and melt blended at 52S F in a Brabender with poly(lactic acid) for only a few minutes. The poly(lactic acid) reduced the melt ~iscosity.

Exam31es ~C-16C
The controls and blends for polypropylene, general purpose polystyrene, and polyetllylene terephthalate (Eastman's) from Examples 2C-7C were ground in an Abbey s-inder and compr-ssion molded into approximately 5 mil films. Polypropylene-poly(lactic ~_~d) _~ l~e ~:e-e ~ e~ ` ~b~ 0~ ;; ?Ol~st~Qr.e-poly(lactic acid~ ~12s were o~ained 2t 250-~oo .~;
~ ? ~ t-? - - ? ~ .. . ` ~ 2C ~ ..... s ~ `_. - -?

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~ _ __............. sh.~ _ _ 5 ~ ~ _ _ ~ _ .. . _ .. 2 _ ~ _ _ _ _ _ _ _ _ _ _ _ ~ ~ _ ~ _ ~ ~ ~ _ ._ _ _ _ _ _ _ _ _ ~ ~ _ . . . _ _ . _ _ _ _ _ _ _ ~

91/063'-~ v._ _~iJ

Exam~les 17C-19C
Three samples of 100 percent poly(lactic acid) using poly (D,L-lactic acid) were prepared as above but with film thicknesses of 10-15 mil. Tests were performed as in Examples 20C-27C below except that the second sample was tested after 82 hours of exposure to 50 percent relative humidity at 72 F~

E~am~les 20c-27C
High density polyethylene, HDPE, ~'O~g~0 gj~cc) ~as mel~ blended with poly(lactic acid) in the Brab~nder Plasticorder at 151 C for 10 minutes. Blend ratios of hig~h-density polyethylene/poly~lactic acid) of 1~0/0 for ~he ~ontrols, 90~10, 80/20, and 50fS0 were used. Two samples of eac~ were prepared. The blends were ground in an Abbey grinder and compression molded into 10-15 mil films. The films were tested in an Atlas Weather-O-Meter set for 51 minutes of carbon arc light and 9 minutes of water spray. Temperature was varied from ambient to 140 F. Tensile strengths, elongation to yield tests and classification of the tensile failure were performed for the samples as shown in Table 2c.

Examples 28C-33c Low density polyethylene, LDPE, (0.917 g/cc) was melt blended with poly(lactic acià) in the Brabender Plasticorder at 151 C for 10 2inutes. Blend ratios of low densi ~ ~ol~eth~lene/pol~(12c~ic acid) o_ lOOfO f~- the co~.t~ols 90~10 2nd =Ot50 were used. ~o sam?les of each ~ e c2se ~ 2.~?1~ C~ es-~'_s 2-e ~o;n. ~
_ ~ ?~

wl_h a mec!lnic~' s_i--~ - a-.d ..~. ~_o~,~en _nle~ an~.- cu.' e~, (~ /n ~ '1 ' rc r/~sslt()fi3~--13&-lactide (both Boehringer and Ingelheim, grade S). The contents of the flask were heated to 110 C under a nitrogen sweep to melt the lactides and 20.1 g of polystyrene (Amoco R3, melt index 3.5 gJ10 min.) was added. The polystyrene swelled highly and partially dissolved while stirring overnight and advancing the heat to 185 C. The temperature was decreased to 141 C and 0.2 ml of anhydrouc stannous octoate solution (0.2 mllml of toluene) was added. The stirrer was turned off and the lactides allowed to polymeri~e at 141 C over 3 days time.
The highly swollen, polystyrene floated to the top after turning off the stirrer. The lower, polylactida phase was cooled and examinQd by differential scanning calorimetry (D~C). The sample has 2 lo~ Ts, approximately 35 C, and ~5 is otherwise lac~ing in apparent temperature transitions.
Compression-molded films are clear, colorless, and very pliable. These ~-esults indicate that the polystyrene thorou~hly interrupts crystallinity formation under these conditions.

Example 35c Poly(lactic acid) was mill roll blended with crystal polystyrene. Th_ blend revealed excellent compatibility of polystyrene dispers~d in poly(lactic acid). Thus 5 weight percent of polystyrene was dispersed in a 90/10 ratio of L-lracemic D,L-lactide copolymer in a two roll mill at 170 C. The material became hazy and exhibited considerable crvstallinity by therm~l analysis.
This example demons~r_~es ~he~ under 'hese c~n~ilicns -e?.~ si`~ r~ e~ 5 _r~ i?. ?~ly ~ t~ ~
~0 --ci~`. A t~e me_ ar.al~ysis ^f the ma~erial, see Ficu~re 17, _evea's ~ he ~__e~i~Y emains _~ys_ll~ne even ~!he-~ e~ c~

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n~ e~G~ e ~?'~ C~ n c_~ c~ ~n; ~r~e~

~;V9'/()J~13 I'C~i~j(3l/l)o~~

in the mixture depending on the mixin~ or blending technique used.
Brabender melt-blends of all types exhibited small heterogeneous particle si~es of 10 microns or less.
The tensile strengths were evaluated before, and after, simulated weathering. After 1248 hours (52 days) in the Atlas Weather-O-Meter all of the polypropylene samples were whitened, extremely brittle and were not able to be tQsted~ The polypropylene samples were retested at shorter intervals as shown in Table lC~ ~t approximately 3QO hours of weathering in the Atlas Weather-O-Meter, the samples exhibited significant environmental degradation~
The polystyrene blends with poly(lactic acid) exhibited environmental degradation that was apparent after 300 hours of simulated weathering. The polyethylene terephthalate blends were also visibly environmentally degraded in approximately 300 hours.

~o ~/n~lt Pc~ ssl/n~3~-~ 3 TABLE lC. TENSILE STRENGTH OF FILMS BEFORE, AND AFTER
ACCELE~ATED ~EATHERIN~a~

Tensile Stren~th~b)/% Elongation and Materlal Before After, Hours 310 ~00 _ _ 100/0 PP(C~/PLA 16~S/61~0 585/1~6 4g4/1~7 90/10, PP/PLA 1568/51~0 954/3~2 34~
~5/25, ~P~PL~ 112~ 0~70/l.i 254/1.0 100/0 PS~d~/PLA 3200/2.0 1066Jl.0 --90/10, PS/PLA 2350/2.0 582Jl.0 --75/25, PS/P~A 149~484/1~0 --100/0 PET(e)/PL~ 3036/--3509J3~0 --90/10, PET/PL~ 2147/--1378~3~0 --75J25, PET/PL~ 2743/--2041/3~0 --.
(~ Weather-o-meter, cycle of 102 minutes of sunshine, 18 minutes of rain (b~ o~ 05 in~/min~, on the Instron (C) Hercules polypropylene 825 d) Huntsman 208 ~e) Tennessee Eastman, ~odapa~ ~ 01~8 The poly(lactic acid), high density polyethylene, low density polyethylene, and their blends were evaluated for physical strength, before, and after simulated weathering and the results are shown in Table 2C.

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The poly(lactic acid) and its blends were much more environmentally degradable than the pure low density or high density polyethylene. The high density polyethylene samples degraded substantially without weight loss while the high density polyethylene-poly(lactic acid) blends exhibited weight loss, particularly where micros-copy revealed poly(lactic acid) was exposed at the surface of the films~ The high density polyethylene degraded by exposure to acti~ic light as shown by microscopy~
With all of the samples, increasing the percentage of poly(l~ctio aci~) decreased the tensile strength before, and after, simulated weathering. The incorporation of poly(lactic acid) introduced a faste-de~radation in blends of polypropylene, polystyrene, polyethylene terephthalate, and high and low density polyethylene. Presumably, the actinic liyht as well as hydrolysis of the polyesters degrades the polymer. The small size of the spherical, microhetero~eneous, domains of the blend are undoubtedly poly(lactic acid), which is mostly buriec Therefore, poly(lactic acid) hydrolysis is slow. Faster degradation via hydrolysis can be achieved by controlling the location of the poly(lactic acid).
This, in turn, is related to the rheology of the blend during melt blendin~. The small size of the dispersed, heterogeneous domains indicates good compatibility of the mixed polymers~
In a simulated landfill, where light is excluded, the controls and ~he blends show much slower rates of degradation~ With hydrolysis, alone, the poly(lactic acid) samples slowly ~hiten, while tne biends are cualit2-~ively unchan~ed for the ti~e ?eriod tested~
~ onverseiy, additio-. o~ rino- a~oun~s o nondes__~able =..e~o?_-s=i_s ~ ?ol~ ci_) to ~^--_o~patible b'ends, usiny, _o- e~2~ple, ?olypropylene, ^'~ ?-lys~yrene, ?oly--thy'ene `2re?h'h~12te a..d hish ~n* lo-~;
d2nsity -o!yethyle-.e ~i'! ~e_~-d ~he deg-2d~tion rate o.-~13 ~CT'~S~

the poly(lactic acid). A preferred compositional range is from 80-99 weight percent poly(lactic acid).
A general description of the environmentally degradable composition comprises blends of a physical mixture of poly(lactic acid) (polylactide), and a polymer selected from the group consisting of a poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, al~yl acrylate, and phys~cal mixtures th~reo~. Other possible compositional ~lends are listed below in the discussion of process embodiments of the invention. While the level of plasticizer can vary over wide ranges depending on the amount of poly(lactic acid~
p.esent and the type of coblended polymer, the prefe~red lS amount for a stiff material is generally about 0.1 to about 10 weight per cent.
The blends preferably use a physical mixture of poly(lactic acid) of the formula I: where n is an inteqer between 75 and 10,000; and a polymer selected from the group consisting of polystyrene, polyethylene, poly(ethylene terephthalate), and polypropylene and other compositions further discussed below. The composition of poly(lactic acid) in the composition may vary over wide limits such as about 1/99 to about 99l1. A preferred composition is that where the poly(lactic acid) comprises to 50 weight percent of the composition. Another preferred composition has a poly(lactic acid) content of about 10 to 20 weight percent, and 2nother about 80 to oa.
The ratio will depend on desired characteristics.
~0 The ?ol~ers ~n~ copolymers seleczed f_om the group above, deeme~ z~e Pdded polymer, c2n be used alone or in com~inazion~ The rou? is not restric_ed tO t~ose _` ~2- ~0~'2 ~-~`-.^e oze_~ ?~ ~e- ' ?es ~-e nc_e~ 2S
com?atible ~ilh ?01~('2c-ic aclc). These inclune ~he polymers and copolyme-s ^om?rised from ,he group of ethylene, p~opylene, _yrene, vir!i ~hl^.ice, ;in~l _^~z__--~ h~c-~ e~, c~ r~`-_ ~0~ 3 PCTI~`S91/063' should be understood that the term copolymers as used herein includes polymers made from mixtures of the monomers in the listed group. Physical mixtures of the polymers and copolymers of the above group are likewise useful in the invention.
A first embodiment of the process for producing the composition includes providing a poly~lactic acid~;
selecting a polymer from the group consi~ting of a poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, ~rinyl acetate, al~yl me~hac~ylate, alXyl acrylate, and physical mixtures thereof; and blending the polymers. The blending may be by melt blending on a mill roll or by compounding in an extruder or by other mechanical means. The polytlactic acid) provided preferably has the formula I
and contains plasticizers as discussed herein.
A second embodiment of the process for producing the composition of the invention includes providing a lactide selected from the group consisting of D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof; selecting a polymer from the group consisting of the polymers or copolymers of styrene, ethylene, ethylene terephthalate, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof. The selected lactide and polymer are mixed and heated to melt the lactide and at leas~ partiall~ dissolve the pol~me Finally, the lactide, is at least partially polymerized to obtain a blend of polylactide, unpolymeri-ed lactide ~0 monomer ~nd ~he selec-ed ?ol~me-. The pol~eri-a~ion is ~e e---blv ~on~-olle~ 20nito_in~ the 2moun~ of lGctide em2i-.in_ _n~ s~p-i-.~ _he ?ol~.eri--li^.. e~ the desired ~ le~i--.. .~d-`i__o._` ~~~_~e- m_..cme- ~- olhe-: ~ ?~ ~crL-~~ _- :-c~c ~ c._-s -- l~_~i-e. n- mi~:t_~es the_ec-, ~he-e ~ r ~

'~;0 9'/(~;1 ` rc~r~ ;91/()6'.''-~ v ' 1 ~ 3 an integer: 2 < m < 75, where the oligomers preferably have a number average molecular weight below about 5,400 and most preferably below about 720; as well as one or more derivativas of an oligomer of lactic acid defined by the formula III: where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' ~ H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 < q S 75, can be added to obtain desired characteristics as taught in parts A and B
abov~, Additionally, the various types of plasticizers discussed herein and in the other general embodiments provide for: ~a~ more effective compatibili2ation of the melt blend components; (b) improved processing characteristics during the blending and processing steps;
and Ic) control and regulate the sensitivity and degradation of the polymer by moisture.
It will be obvious to those s~illed in the art that the proportions of poly(lactic acid) and the added polymer can vary widely depending on their mutual solubilities. Solubilities, in turn, vary with the thoroughness of mixing and the mixing temperature. While placing both the poly(lactic acid) and the added polymer into a mutual solvent solution will obtain intimacy, the use of solvent is impractical for many commercial processes. Physical mixing, such as melt blending on a ~ill--cll c- extruder is rore prac` ic21, but must be controlled ~o achieve 2n intimate dispersion, that is, ~o h~ h she~- is ~equired to achieve the desired intimacy rven ~i~h i-._irate ~ ing -`f~eren' ?o~ers ~y not ~e _or~?2ti~1e, ~ c, ~~e~ may s_il' sep~_ate i~._o ,~Q_~_~,_,~5 _ _,= ` __, ~. ~_ e2:-r~?le ! 10 ~ C =` c-_n 5` ~e~ 0_ la~~e~~ ~h is - s~:~ 5 i~ cnee~' ~i~:_ure, cr _ ~l end ~ i _h p^^- prope-~ies. Wha 5 \Vo 9~ ssl/nO~-~ ,t, ~ 8~
compatible with a wide variety of other polymers, including both polar and nonpolar polymers.
The temperature of the melt blending of the poly(lactic acid) with other polymers may be varied to adjust the proportions of the poly(lactic acid) with one, or more, added polymers. At lower temperatures, the solubilities may not be adequate, while too high a te~perature will cause decompos~tion of thQ mixture. A
general temperature range is 100-220 C, and the preferred range is 1~0-180 C. Egually significant is the melt viscositie~ of the differe~ polymer co~ponents~ With in~reasing molecular weight, the viscosities increase sharply. By controllin~ the proportions of the poly(lactic acid) and the added polymer, or polymers, the temperature, the mixing type and time, and the molecular weight, a wide range of mixtures can be obtained. Thus, for example, the poly(lactic acid) can be dispersed into the added polymer, or polymers, or vice versa, and the size and geometry of the dispersed phase varied greatly, ranging from discrete spheres to strands of different diameters or lengths. This results in a wide latitude of physical properties and degradation times in the environment. The weiqht percent ratio of poly(lactic acid) to the selected polymer can be between 99:1 to 1:99.
Where the lactide monomer is used to dissolve the added polymer and the lactide is subsequently polymerized, the temperature of mixing and polymerizing must be balanced between t~e mu.ual solubilities and the re~c~ivity of _he lactide~ her temperatures generally 3~ ~~oduce lower mo'ec~ c- ei:-~ poli-~12c_i_ 2C`C). ~:
~u-~her mbodi~e?.^ ^- ~he i~ ion is ~o mix 2_ one _e~pe-^tu-e c-.~ ?^~e~i^e ~_ 2no' ~e- te~pe-_tu-c -~

_S C~ S~ SS~ 2~ e~
'. r~ C C `~ â ~ C ~ ~ _ ?~ C ~ S S ê _ '~
'c__-c__ion ir.-^ ~se_~_l -_ic' e5 ^ m n'_ cC ~'~e .~'' n~ -~'O 9~/() ' I '' rr/~ /nfi3~-h eating utensils, trays, plate~, drinking cups, single serving trays, syringes, medical trays, packaging films and the like. The compositions are useful in that they can have the characteristics of the usual plastics and therefore substitute for them yet degrade in the environment. The compositions are especially useful for articles having only a one time use or a short life span in use before disposal.

Within the scope of the invention is included thos~ impact modifiers which are elastomaric discrete, intimately bound and t~e polylactic (or polylactide)/i~pact ~odifie ~lend is hydrophobic, nonporous, nonswellable in water, and hydrolyzes at the same rate or slower than the poly(lactic acid) (or polylactide) alone; and melt compatible with poly(lactic acid). By "melt compatible", it is meant all those polymers which can be intimately mixed with poly(lactic acid) as discussed in section c~ Third General Embodiment. The mix would result in a subs~antially homogeneous blend. All of the examples herein exhibit these properties. Since both lactic acid and lactide can achieve the same repeating unit, the general term poly(lactic acid) as used herein refers to polymers having the repeating unit of the formula I without any limitation as to how the polymer was made (e.g. from lactides, lactic acid, c- oligo~ers), ~rd without reference to the degree of polymerization or level of plasticization.
~ e en~iron~e-._~ cegr2da~1e CO~?Osilions _~ ~is_lcse~ herei-. ~re ~~ le_s~ p~ lly deg-~dc?~le~ ~a_ is _~e ?oly' ~-~ic ~^i^`` --~~ion ^f _he ^om?osi=i^~ ;ill ~ _ ~ ~ `~ 3 ~. 5 _ ~ ^ c ?~ _ C ~ `_ ~ ~ _ ~ ` 5 ` _ _ ` ~ ~ ~ ~ r~o-c~i~.
_ ~he '~`~enc~ exc=~ h~
.?~s~_ic-.~ _~e ~ o~r~ - ~ e~,~r _ ~ ~ _ _ _ ~, _ _ ~ _ _ . . _ _ . _ _ _ . . _ ~ . ~ _ _ _ _ _ _ ~ _ _ _ _ _ _ _ _ _ _ _ _ ~ _ _ , .. _ _. _ _ _ WO9~/0~13 PCT/~;Sgl/n6327 --1~ 9--`J u the original formed product. The compositions herein provide environmentally acceptable materials because their physical deterioration and degradation is much more rapid than conventional nondegradable plastics. Further, since a major portion of the composition will be poly(lactic acid), and/or a lactic acid derived lactide or oligomer only a small portion of more slowly degrading elastomer residue will remain ~e.g. segmented polyester~. This residue will have a high surface area and is expected to decompose faster than a bulk formed product~
The exa~ples below ~how the blending of poly(lactic acid) (PLA) with a Hytrel~, a se~mented polyester which is a block copolymer of h2rd crystalline segments of poly~butylene terephthalate) and soft long-chain segments of poly(ether glycol). It is shown thatpoly(lactic acid) is 3elt compatible with this elastomer and the effect on its physical properties.
D-lactide is a dilactide, or cyclic dimer, of D-lactic acid. Similarly, L-lactide is a cyclic dimer of L-lactic acid. Meso D,L-lactide is a cyclic dimer of D- and L-lactic acid. Racemic D,L-lactide comprises a 50J50 mixture of D-, and L-lactide. When used alone herein, the term "D,L-lactide" is intended to include meso D,L-lactide or racemic L ~-lactide. Poly(lactic acid) may be prepared from one or more of the above~

Exam~le lD
A poiylactide copolymer ~ithout Hytre_'Y seqmented ~c'veste~ ~'2S ~ e?2re` ~sir.a the ?ro-edure ~~_m E~m?le 1 o~` sec_icn B~ Second Gene-~' ~mbodi~en~ ~nd tes~ed .o_ T ~ ?zc- ~ _e.~ ~s___s __~ c~ r _ _ C~ .e~ c~?~-~s~ ic ~ e C_c~ G~ne-_' C -;--_c.C _ ' G~ ~_3 u--` ` Z^--iC~ .

~ o 9'~n~1 ~ Pc r/~ ~9 l /n~3~-,~. ~ ., ` ' 1 `~
Exam~le 2D
Into a 3-neck, 250 ml, round-bottom flask is weighed 10.96 g of D,L-lactide, 108.B6 g of L-lactide, and 5.27 g of Hytrel~ 4056 segmented polyester (Du Pont, a thermoplastic elastomer). Hytrel~ 4056 segmented polyester is a polyester elastomer with a Shore D
durometer, low flexural modulus, high melt viscosity, a melt index of 7, a sp~ gr. of 1.17, a m.p. 334 F, a vicat softeninq temperature of 234 F, and an extrusion temperature o~ 340-~00 F. The flas~ is fitted with a mechanical stirrer and a nitrogen inlet and outlet. The contents are heated by means of an oil bat~. T~e Hytrel~
segmented polyester dissolves in the molten lactides at 170 C~ A catalyst solution is prepared by dissolvinq 10 ml of stannous octoate in 60 ml of toluene and distilling 10 ml into the toluene. A 100 microliter portion of the catalyst solution is injected into the solution of lactide and Hytrel~ segmented polyester. The mixture is stirred under nitrogen at 155 C for approximately 64 hours.
The viscosity increases sharply and the mixture turns cloudy. The product is tough and opaque. Films of 8-9 mil thic~ness were compression molded at 155 C and the tensile properties measured, as shown in Table D.
Slabs, 1/8 inch thick, were compression molded and their Izod impact strength measured using a 2 pound pendulum. The ~esults are recorded in Table D where the data are compared to a similar polylactide copolymer of ~x2m~1e lD witho~t ~ytrel~ se~mented pol~ester, and to data fo- so-c~lled meci~m-impact polvstyrene, Exam?le 7D.

e 'D
EC5.~ ~ c_ E-~2c_i-e ~ cemic 3,L-~rel~ se~2en-e~ ?olyes.er. '--_ l_c_i_c co~el j~C~ i S
~ ~ c_~ _~. _~ _ _c?__~=e ~ T - - i _ _ _ _ 0 ~

0~l3 ~CT/~`S91/0637, catalyst. The polymer ,poly(L-lactic acid~, is white, crystalline, and crazes easily when strucX.
An electrically-heated, 2-roll mill is heated to 375 F, then 8.4 g of Hytrel~ segmented polyester and 19.2 g of poly(L-lactic acid) are banded on the roll. To this was added 172.4 of the lactide copoly~er. The mixture blends easily and is removed from the rolls, ~olded, and tested as in Example 2D. The data are recorded in Table D.

E~2~ D
The lactide copolymer of Example 3D~ 80 g, the poly(L-lactic acid) of E~ample 3D, 10 g, and 10 q of Hyt.el~ 4056 ses3ented polyeste- are 2-roll, mill-blended as described previously in Example 3D. The blend was tested as before and the data are recorded in Table D.

Exam~le 5D
100 g of the blend of Example 3D was further blended with 20 ~ of Hytrel~ 4056 segmented polyester.
The mixture easily mixed on the roll and was apparently quite compatible. The physical properties were measured as described previously and recorded in Table D.

Exam~les 6D and 7D
Typical crystal polystyrene and medium-im?act polystyrene we-e tested and used for comparative controls.
The above results clearly indicate .hat polyl2ctides can be impact-modified~ The blends provided signi__c2n~1y ~` ghe~ 0 ` `--~_- 5__en5=:.s ~r_el _r.e c-~ l ?~l~s-~~e~.~ co~ l c~- c !_ C ~ - C-e-~ 21er.t i.~?~ ~~e~ s ---?~-e~ -~ D~ ?-C~

~~ ~ ~ ----~^ _ C=-- ~_~ r--~

moài~ic-~o 9~ rc r/~s1/n63~-Since polylactides have been shown to be blend-compatible with numerous other compounds and thermoplas-tics in section C. Third General ~mbodiment, the process of impact-modifying polylactides is generic to mixtures of polylactides and elastomers that are blend-compatible.
Also, those skilled in the art will recognize that the data of Table D will improve as the blends are injection-molded, as opposed to compression-molded, since the former often induces orientation of the specimens and, consequently, a profound improvement in impact strength~

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The compositions are useful thermoplastics t~at can be melt fabricated by conventional processes suc~ as extrusion and molding.
The blends preferably use a physical mixture of S poly(lactic acid) of the formula I: where n is an integer between 75 and 10,000; and a polymer comprising a segmented polyester~ The poly(lactic acid) content may vary over a wide latitude such as betwaen about 1 and about 99 wei~ht percent. A useful composition is that where the poly(lactic acid) comprises 50 to 99 weight percent of the composition. A preferred composition has a poly(lactic acid) content of ~0 to 80 weight percent, while other useful compositions include about 5 to about 20 weight percent, depending on the final use of the composition.
Two embodiments of the general process for producing the composition include (1) melt blending of poly(lactic acid) with a blend compatible polymer that provides improved impact resistance and is discrete and intimately bound (such as a segmented polyester); and (2) solution blending during poly(lactic acid) polymerization as in Example 2D where Hytrel~ segmented polyester is dissolved in the poly(lactic acid). The poly(lactic acid~
provided preferably has the formula I. If desired, plasticizer in pliable forming amounts may be added to the blend that is selected from the group consisting of lactide monomer, lactic acid oligomer, lactic acid, and mixtures thereof. The oligomers are defined by the ~ormula 1~: where m is an in~_~e~: ~ ~ m < 75, and is rererably ~ ~ m ~ 1~. C~he~ ?l-s`ici-er ~ht m~y be ad~ed .._lude one cr mo~e deri~ati~es c- -n ^ligome_ o` ia_~ic '-~ t~ c_~l-c~e~

--~e~
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and where q is an integer: 2 < q < 75, and is preferably.
Preferably q is an integer: 2 < q < 10.
Addition of plasticizer will provide additional unique physical properties and processing advantages as discussed in sections A, B, and C above.
The plasticizers may be present in any amount that provides the desired characteristics. For example, the various types of plastici~ers discussed herein and in sections A, B, and C above provide for ~a) more effectiv~
compatibilization o~ the melt blend co~ponents so that greater intimacy is achieved; (b~ i~prov~d processing characteristics during the blending and processing steps;
and (c) control and regulate the sensitivity and degradation of tbe polymer by moisture. For pliability, plasticizer is present in hiqher amounts while other characteristics such as stiffness are enhanced by lower amounts. Tbe compositions allow many of the desirable cbaracteristics of pure nondegradable polymers. In addition, the presence of plasticizer facilitates melt processing, prevents discoloration, and enbances the degradation rate of `he ccmpositions in contact with the environment. The intima~ely plasticized composition sbould be processed into a final product in a manner adapted to retain the plasticizer as an intimate dispersion in the polylactic acid and/or its coblended polymer for ce-tain properties. These steps can include:
(1) quencbing the co~position at a rate adapted to retain the plastici^e~ as 2n inti~2te dispersion; (2) melt ~ essin~ ~r.^ ~en^hi~ tbe co~?osition at a r~te ~d2pt-:d _3 t~ retain th ?!zs~ci^e~ zs an in~irm~te cispersion; cn-~

~2~1n~:~ 2~ 2i~ ^c_ cs c~. i-`.~`..

c ~.ic-cs_o?i~ e~:_min2t~0n o the `P.~-t-el~ seGmentec PcT/~9l/n~

dispersed Hytrel~ segmented polyester is present ln small spherical domains a few microns or less in size. These domain sizes can be adjusted by the mixing conditions such as time, speed of mixing, and temperature.
S Therefore, for example, the polymer, or polymers, added to the poly(lactic acid), should be generally of small, heterogeneous domain size, less than 10 microns, and can be submicroscopic, or dissolved, in the poly(lactic acid)~ In addition, this impact modifier ~ust be el2stomeric.
While not wishing to be held to any particular theory, it is believed that the present invention provides a continuous matrix of poly(lactic acid) containing intimately mi~ed microscopic domains of ~ytre~ segmented polyester that act as crack arresters since the latter is a thermoplastic elastomer compatible with poly(lactic acid).
For this purpose, the impact modifier must be elastomeric and intimately bound into the poly(lactic acid) as a discrete heterogeneous phase. The added polymer, the impact modifier, can be a thermoplastic elastomer, or a crosslinXed rubber, to achieve this elastic behavior. Examples are natural rubber and styrene-butadiene copolymers., Further exa~ples of impact modifiers useful in the invention include polyisoprene ~gutta percha), styrene-isoprene-styrene bloc~ copolymers, acrylonitrile-but~diene-sty~ene block copoly~ers, styrene-ethvlene-styrene block copolymers, p~opylere-ethylene-propylene c~ c ~Q?'~D~ s~?-e~e-?-o?~le~e ~lo_!:
c_polyme_s, ~ -es ~her2~ h- lii;e. P21yu~e~h,-re~
~.. ^_ ~_e r~ isr~r-~ ;ell,~~e ~ 2-e-~ ~ _ _ _ ~ s _e__ _~_ ,,,_= a -.s, ~he ~.~te~Gl ~b_`~_le~ ?--~ ~
~:-2s~ _c ;~ Ct~ 2=e~ t~ e- ~ c _.______. ____3~

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It was further apparent that poly(lactic acid) alone degraded faster than the Hytrel~ se~mented polyester/poly(lactic acid~ mixture. T~us Hytrel~
segmented polyester can also be used to retard the degradation rate of polytlactic acid).
A third component can be added which is compati~le with the other components discussed above to achieve improved compatibility. ~us, where the poly(lactic acid) and the impact modifier have poor co~patibility, a third component c~n be added to improve the compatibility. This t~.ird componen~ is usually ad~ed where it is compatible with the other two, individually, and where the other two, poly(lactic acid) and impact modifier are not very compatible. This works bv lS increasing the interfacial bonding between poly(lactic acid) and elastomeric impact modifier. However, what is surprising is the wide latitude of compatibility of poly(lactic acid) with other polymer types, both polar and nonpolar. This can be referred to in section C. ~hird General Embodiment above.
If desired, minor amounts of plasticizer such as glycolide, poly(glycolic acid), caprolactone, and valerolactone may be added.
The compositions herein can be processed by melt fabrication into useful articles of manufacture such as containers, eating utensils, trays, plates, drinking cups, single serving trays, syringes, medical trays, and the like. The com?ositions are especially useful for ~_ticles havin~ oniy a or.e ~ir~e use or a sho~t ll_e sp~n i~ use 3~ ~2fore disrGsal~
~ ~ _ _ _ _ _ _ _ ;~h~ r.~e~ s ~2e~ desc~i~

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Claims (134)

WO 92/04413 -158- PCT/US91/06327We claim:

1. An environmentally biodegradable composition useful as a replacement for thermoplastic polymer compositions comprising:
a. a poly(lactic acid); and b. a plasticizer of one or more oligomeric derivatives of lactic acid, selected from the group defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, where q is an integer: 2 ? q ? 75; and wherein the plasticizer is intimately dispersed within the polymer.

2. The composition of Claim 1, wherein q is an integer: 2 ? q ? 10.

3. The composition of Claim 1, wherein the poly(lactic acid) is a polymer of the formula:

wherein n is the number of repeating units and n is an integer, 150 ? n ? 20,000.

4. The composition of Claim 1, wherein the composition is unoriented and has a tensile strength of about 300 to about 20,000 psi, in elongated to failure of about 50 to about 1,00- percent, and a tangent module at about 20,000 to about 250,000 psi.

5. The composition of Claim 1, therein the composition is unoriented and has a tensile strength of WO ??/04413 PCT/US91/06327 about 1,200 to about 4,000 psi, an elongation to failure of about 100 to about 800 percent, and a tangent modulus of about 20,000 to about 75,000 psi.

6. The composition of Claim 1, wherein the composition is unoriented and has a tensile strength of about 4,500 to about 10,000 psi, an elongation to failure of about 100 to about 600 percent, a tangent modulus of about 165,000 to about 225,000, and a melting point of about 150 to about 190 F.

7. The composition of Claim 1, wherein the polymer is derived from monomers of lactide selected from the group consisting of L-lactide, D-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

8. The composition of Claim 1, wherein the composition comprises from about 2 to about 60 weight percent plasticizer.

9. The composition of Claim 1, comprising additional plasticizer dispersed within the composition that is selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof.

10. A process for producing a biodegradable composition useful as a replacement for thermoplastic polymer compositions comprising:
a. providing a poly(lactic acid); and b. incorporating plasticizer into the poly(lactic acid) selected from one or more derivatives of an oligomer of lactic acid, defined by the formula:
where R = N, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75.

11. The process of Claim 10, whereby q is an integer: 2 ? q ? 10.

12. The process of Claim 10, wherein the plasticizer is added in an amount to obtain a plasticizer content between about 2 to about 60 weight percent.

13. The process of Claim 10, comprising incorporating additional plasticizer selected from the group consisting of lactic acid, L-lactide, D-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof.

14. The process of Claim 12, comprising incorporating the plasticizer in a manner adapted to obtain an intimate dispersion of the plasticizer within the polymer.

15. The process of Claim 14, extruding the plasticized poly(lactic acid) as a blown film.

16. The process of Claim 15, comprising maintaining the intimate dispersion of plasticizer during the extrusion of the blown film.

17. The process of Claim 14, comprising processing the composition into a final product in a manner adapted to retain the plasticizer as an intimate dispersion within the polymer.

18. The process of Claim 14, comprising quenching the composition at a rate adapted to retain the plasticizer ?? an intimate dispersion within the polymer.

19. The process of Claim 10, comprising melt fabricating and quenching the composition at a rate adapted to retain the monomer ?? ?? intimate dispersion within the polymer.

20. The process of Claim 1?, comprising:
providing the poly(lactic acid) in step (a) having the repeating uni??.

wherein n is the number of repeating units and n is an integer, 150 ? n ? 20,000; and plasticizing the poly(lactic acid) to obtain a composition which when unoriented has a tensile strength of about 1,200 to about 4,000 psi, an elongation to failure of about 100 to about 800 percent, and a tangent modulus of about 20,000 to about 75,000 psi.

21. The process of Claim 15, comprising:
providing the poly(lactic acid) in step (a) having the repeating units, wherein n is the number of repeating units and n is an integer, 150 ? n ? 20,000; and plasticizing the poly(lactic acid) to obtain a composition which when unoriented has a tensile strength of about 4,500 to about 10,000 psi, an elongation to failure of about 100 to about 600 percent, a tangent modulus of about 165,000 to about 225,000, and a melting point of about 150 to about 190 F.

22. A process for incorporating plasticizer into poly(lactic acid) to obtain a blended composition comprising:
a. melt blending with a poly(lactic acid), a first plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof at a first temperature;
b. melt blending with the ??ntained blend a second plas cizer selected from the group consisting of lactic acid, L-lactide, D-lactide.
m??? D,L-lactide racemic D,L-lactide, and mixtures thereof, at a second temperature lower than the first temperature; and whereby an intimate dispersion of the plasticizers is obtained.

23. The process of Claim 22, comprising quenching the composition at a rate adapted to retain the plasticizer as an intimate dispersion within the polymer.

24. A process for incorporating plasticizer into poly(lactic acid) to obtain a blended composition comprising:
a. melt blending with a poly(lactic acid), a first plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid, defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, where q is an integer: 2 ? q ? 75, at a first temperature;
and b. melt blending with the obtained blend a second plasticizer selected from the group consisting of lactic acid, L-lactide, D-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, at a second temperature lower than the first temperature; and whereby an intimate dispersion of the plasticizers is obtained.

25. The process of claim 24, wherein ? is an integer: ? ? q ? 1?.

26. The process of Claim 24, comprising quenching the composition at a rate adapted to retain the plasticizer as an intimate dispersion within the polymer.

27. An environmentally decomposable polymeric composition suitable for use as a substitute for crystal polystyrene comprising a poly(lactic acid), where the repeating unit is an L- or D-enantiomer and there is a preponderance of either enantiomer, having intimately dispersed therein greater than about 0.1 weight percent of a plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid, defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75; wherein the unoriented composition has a tensile strength of at least about 5,000 psi, a tangent modulus of at least about 200,000 psi, and is substantially colorless.

28. The composition of Claim 27, wherein the plasticizer comprises:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers of lactic acid and oligomers of lactide have a number average molecular weight below about 5,?00 and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

29. The composition of Claim 27, wherein the composition is form stable above about 70 C.

30. The composition of Claims 27 or 28 wherein the polylactide is defined by the formula:

where n is an integer between about 450 and about 10,000, where the repeating unit is an L-or D-enantiomer and there is a preponderance of either enantiomer.

31. The composition of Claim 30, wherein the ratio of L-enantiomer to D-enantiomer is between about 1/99 and about 99/1.

32. The composition of Claim 30, wherein the ratio of L-enantiomer to D-enantiomer is between about 2.5/97.5 and 7.5/92.5, or between about 92.5/7.5 and 97.5/2.5.

33. The composition of Claim 30, comprising a nucleating agent selected from the group consisting of lactate salts, benzoate salts, poly(L-lactide), poly(D-lactide), and mixtures thereof.

34. The composition of Claim 30, comprising a plasticizer present in an amount effective to provide substantial transparency.

35. The composition of Claim 28, wherein the oligomers of lactic acid, and the oligomers of lactide have a number average molecular weight below about 720.

36. The composition of Claim 30, wherein the plasticizer is present in an amount between about 0.1 and about 10 weight percent.

37. The composition of claim 36, wherein the plasticizer is present in an amount above about 5 weight percent.

38. An environmentally decomposable polymeric composition suitable for use as a substitute for crystal polystyrene comprising a physical mixture of:

a. a first poly(lactic acid) having a preponderance of either D- or L-enantiomers;
b. a second poly(lactic acid) selected from the group consisting of poly(D-lactic acid) or a poly(L-lactic acid), wherein the weight percent ratio of the first poly(lactic acid) to thc second poly(lactic acid) is between about 1/99 and 99/1; and c. greater than about 0.1 weight percent of plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid, defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, wherein the plasticizer is intimately dispersed within the poly(lactic acid)s, and the unoriented composition has a tensile strength of at least 5,000 psi and a tangent modulus of at least 200,000 psi.

39. The composition of Claim 38, wherein the plasticizer comprises:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers of lactic acid and oligomers of lactide have a number average molecular weight below about 5,400; and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

40. The composition of Claim 39, wherein the composition is form stable above about 70 C.

41. The composition of Claim 33, wherein the ratio of the first poly(lactic acid) to the second poly(lactic acid) is between about 98/2 and about 75/25.

42. The composition of Claim 39, wherein:
a. the first poly(lactic acid) is defined by the formula:

where n is an integer between about 450 and about 10,000;
and b. the second poly(lactic acid) is defined by the formula:

where p is an integer between about 450 and about 10,000.

43. The composition of Claim 42, wherein the plasticizer is present in an amount between about 0.1 and about 10 weight percent.

44. The composition of Claim 43, wherein the plasticizer is present in an amount greater than about 5 weight percent.

45. The composition of Claim 42, comprising a nucleating agent selected from the group consisting of lactate salts, benzoate salts, poly(L-lactide, poly(D-lactide, and mixtures thereof.

46. The composition of claim 43, comprising: a film or sheet produced the oriented and annealed product having a tensile strength in excess of 7,500, a tangent modulus in excess of 350,000, and having dimensional heat stability at temperatures above about 70 C.

47. The product of Claim 46, wherein the product is biaxially oriented.

48. The composition of Claim 46, wherein the ratio of the first poly(lactic acid) to the second poly(lactic acid) is between about 98/2 and about 75/25.

49. The composition of Claims 27, 28, 38, 39, 42, or 46 processed into a foam product.

50. The compositions of Claims 27, 28, 38, 39, 42, and 46 processed into a product wherein: the poly(lactic acid)s have a number average molecular weight, Mn, bctween about 50,000 and 400,000; and wherein the product has the physical properties of: a tensile strength of at least about 7500 psi; a tangent modulus of at least 350,000, form stability above about 70 C, and being substantially colorless after processing into a product.

51. A process for the manufacture of an environmentally decomposable film or sheet forming polymeric composition suitable for use as a substitute for crystal polystyrene comprising:
a. providing a poly(lactic acid) having D- and L-enantiomers with a preponderance of either the D-, or L-enantiomer;
b. incorporating plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid, defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, the unoriented composition having a tensile strength of at least 5,000 psi and a tangent modulus of at least 200,000 psi, is substantially colorless, and wherein the plasticizer is intimately blended with the composition.

52. The process of Claim 51, wherein the polylactide has a ratio of L-enantiomer to D-enantiomer of between about 1/99 and 99/1.

53. The process of Claim 51, wherein the polylactide has a ratio of L-enantiomer to D-enantiomer of between about 2.5J/7.5 and 7.5/32.5 or between about 92.5/7.5 and 97.5/2.5.

54. The process of Claim 51, wherein the plasticizer is added in an amount effective to prevent degradation and discoloration of the film or sheet prior to further processing.

55. The process of Claim 51, wherein the plasticizer comprises:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, having a number average molecular weight below about 5,400; and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D, L-lactide, and mixtures thereo.

56. The process of Claim 51 or 55, wherein the polymeric composition is extruded into a film or sheet and physically treated by orientation and/or annealing to provide a polymeric film or sheet having a tensile strength of at least 7,500 psi and a tangent modulus of at least 350,000 psi.

57. The process of claim 51 or 55, whereby the film or sheet is biaxially oriented.

58. The process of Claim 51 or 55, whereby the film or sheet is oriented and heat-set to retain the orientation.

59. The process of Claim 51 or 55, wherein step (a) of providing a poly(lactic acid) comprises:
1. providing a first poly(lactic acid) havinq a preponderance of either D- or L-enantiomers;
2. providing a second poly(lactic acid) selected from the group consisting of poly(D-lactic acid) or a poly(L-lactic acid), wherein the weight percent ratio of the first poly(lactic acid) to the second poly(lactic acid) is between about 1/99 and 99/1.

60. The process of Claim 59, wherein plasticizer is added in an amount between about 0.1 and about 10 weight percent.

61. The process of Claim 59, wherein the step of incorporating plasticizer comprises:
a. incorporating a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers of lactic acid and oligomers of lactide have a number average molecular weight below about 5,400;
and/or b. incorporating a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

62. The process of claim 59, wherein the composition is form stable above about 70 C.

63. The process of claim 59, wherein the ratio of the first poly(lactic acid) to the second poly(lactic acid) is between about 99/2 and about 75/25.

64. The process of claim 59, wherein:

a. the first poly(lactic acid) is defined by the formula:

where n is an integer between about 450 and about 10,000;
and b. the second poly(lactic acid) is defined by the formula:

where p is an integer between about 450 and about 10,000.

65. The process of Claim 55, wherein the plasticizer is sequentially added by melt blending:
a. one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, whereby the blending is at a first temperature; and b. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, whereby the blending is at a secind temperature lower than the first temperature.

66. The process of claim 61, wherein the plasticizer is sequentially added by melt blending:

a. one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, whereby the blending is at a first temperature; and b. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, whereby the blending is at a second temperature lower than the first temperature.

67. The process of Claim 55, wherein the plasticizer is sequentially added by melt blending:
a. a first plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, whereby the blending is at a first temperature;
and b. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, whereby the blending is at a second temperature lower than the first temperature.

68. The process of Claim 61, wherein the plasticizer is sequentially added by melt blending:
a. a first plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, whereby the blending is at a first temperature;
and b. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, whereby the blending is at a second temperature lower than the first temperature.

69. The process of Claim 55, wherein the plasticizer added is selected to control the rate of environmental decomposition.

70. The process of Claim 55, wherein the provided polymer has a polydispersity, Mw/Mn, of between about 1.8 and about 2.6.

71. The process of Claim 55, wherein the polymer has a viscosity of less than about 100,000 poise.

72. The process of Claim 55, wherein the annealing is carried out at a temperature between about 80 C and about 140 C until the film or sheet has form stability above 70 C.

73. An environmentally degradable composition comprising melt blends of a physical mixture of:
a. a poly(lactic acid);
b. a polymer selected from the group consisting of a poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof; and c. plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:
where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, wherein the oligomers have a number average molecular weight below about 5,400; and wherein the plasticizer is intimately dispersed within at least the poly(lactic acid).

74. The composition of Claim 73, wherein q is an integer: 2 ? q ? 10.

75. The composition of Claim 73, wherein one or more poly(lactic acid)s have the structure:

where n is an integer between 75 and 10,000.

76. The composition of Claim 73, wherein the plasticizer comprises:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5,400; and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

77. The composition of claim 76, comprising a plasticizer in an amount effective to provide compatibilization of the melt blend components.

78. The composition of claim 76, comprising a plasticizer present in an amount effective to regulate sensitivity to dgrradation by moisture.

79. The composition of Claim 73, in which the plasticizer is added in an amount between about 0.1 and about 10 weight percent.

80. The composition of Claim 73, comprising between about 1 to about 99 weight percent poly(lactic acid).

81. The composition of Claim 73, comprising between about 5 to 50 weight percent poly(lactic acid).

82. The composition of Claim 73, comprising between about 10 to 20 weight percent poly(lactic acid).

83. The composition of Claim 73, comprising between about 80 to 99 weight percent poly(lactic acid).

84. A process for producing the composition of Claim 73, comprising:
a. providing a poly(lactic acid);
b. selecting a polymer from the group consisting of poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof;
c. providing a plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75; and d. blending the polymers of steps (a) and (b) with the plasticizer of step (c).

85. The process of Claim 84, comprising providing a plasticizer present in an amount effective to provide compatibilization of the melt blend components.

86. The process of Claim 84, comprising providing a plasticizer present in an amount effective to regulate its sensitivity to degradation by moisture.

87. The process of Claim 84, comprising:
a. providing a second plasticizer selected from the group consisting of an oligomer of lactide, or an oliaomer of lactic acid; and/or b. providing a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

88. The process of Claim 87, wherein the oligomers have a number average molecular weight below about 720.

89. The process of Claim 73, wherein q is an integer: 2 ? q ? 10.

90. The process of Claim 84, in which the plasticizer is added in an amount between about 0.1 and about 10 weight percent.

91. The process of Claim 84, whereby the blending is achieved by melt blending.

92. The process of Claim 84, whereby the blending is achieved by mill roll blending.

93. A process for producing an environmentally degradable composition comprising:
a. providing lactride monomer selected from the group consisting of D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide and mixtures thereof;
b. selecting a polymer from the group consisting of a poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof;
c. mixing and heating the lactide selected in (a) and the polymer selected in (b) at conditions adapted to melt the lactide and at least partially dissolve the polymer;
d. polymerizing the lactide in the mixture of step (c) to obtain a blend of polylactide and polymer; and e. adding to the blend after polymerization a plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, whereby the plasticizer is intimately dispersed within at least the poly(lactic acid).

94. The process of Claim 93, comprising the additional step:
f. forming the belnd into a self supporting structure.

95. The process of Claim 93, comprising monitoring the amount of monomer remaining and controlling the polymerization of step (d) to obtain a blend containing residual monomer.

96. The composition obtained from the process of Claim 93.

97. The process of Claim 93, comprising adding a plasticizer in an amount effective to provide compatibilization of the melt blend components.

98. The process of Claim 93, comprising adding a plasticizer in an amount effective to regulate its sensitivity to degradation by moisture.

99. The process of Claim 93, comprising providing a plasticizer selected from the group consisting of an oligomer of lactide, or an oligomer of lactic acid having a number average molecular weight below about 720.

100. The process of Claim 93, wherein q is an integer: 2 ? q ? 10.

101. The process of Claim 93, comprising:
a. providing a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5,400; and/or b. providing a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

102. The process of Claim 100, in which the plasticizer is added in an amount between about 0.1 and about 10 weight percent.

103. The composition obtained from the process of Claim 93.

104. An environmentally degradable composition comprising: blend of a physical mixture of:
a. a poly(lactic acid);
b. an elastomeric blend compatible polymer that provides an improved impact resistant composition, and the elastomeric blend compatible polymer is discrete and intimately bound; and c. a plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75, and wherein the plasticizer is intimately dispersed within at least the poly(lactic acid).

105. The composition of Claim 104, wherein the plasticizer is present in an amount effective to provide desired stiffness.

106. The composition of Claim 104, comprising plasticizer present in an amount to provide more intimate compatibility of the poly(lactic acid) and the elastomeric impact modifier.

107. The composition of Claim 104, wherein the plasticizer comprises:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5,400; and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

108. The composition of claim 107, wherein the oligomers have a number average molecular weight below about 720.

109. The composition of Claim 104, wherein q is an integer: 2 ? q ? 10.

110. The composition of Claim 104, comprising between about 0.1 to about 10 weight percent plasticizer.

111. The composition of Claim 104, comprising between about 1 to about 99 weight percent poly(lactic acid).

112. The composition of Claim 104, wherein the elastomeric blend compatible polymer is selected from the group consisting of polyisoprene (gutta percha), styrene-isoprene-styrene block copolymers, acrylonitrile-butadiene-styrene block copolymers, styrene-ethylene-styrene block copolymers, propylene-ethylene-propylene block copolymers, propylene-isoprene-propylene block copolymers and mixtures thereof.

113. The process of Claim 104, whereby the elastomeric blend compatible polymer is selected from polyurethanes that are not significantly water swellable or water soluble.

114. The composition of Claim 104, wherein the blend compatible polymer is a segmented polymer.

115. The composition of Claim 114, comprising an elastomeric blend compatible polymer selected from the group consisting of a block copolymer of hard crystalline segments of poly(butylene terephthalate) and soft long chain segments of poly(ether glycols), natural rubber, styrene-butadiene copolymers, and mixtures thereof.

116. A process for producing the composition of Claim 104, comprising:
a. providing a poly(lactic acid);
b. providing a plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75;
c. providing an elastomeric blend compatible polymer that provides an improved impact resistant composition, and the elastomeric blend compatible polymer is discrete and intimately bound; and d. blending the polymers of steps (a) and (c) with the plasticizer of step b.

117. The process of Claim 104, comprising:
providing:
a. a second plasticizer selected from the group consisting of oligomers of lactic acid, oligomers of lactide, and mixtures thereof, having a number average molecular weight below about 5,400; and/or b. a third plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

118. The process of Claim 116, providing oligomers having a number average molecular weight below about 720.

119. The process of claim 117, wherein the first plasticizer is incorporated at a first temperature, and the second plasticizer is incorporated at a second temperature lower than the first temperature.

120. The process of Claim 116, wherein:

1. the plasticizer provided in step (b) is blended in step (d) at a first temperature;
and 2. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof, is blended at a second temperature lower than the first temperature.

121. The process of Claim 116, in which the plasticizer is added in an amount between about 0.10 and about 10 weight percent.

122. A process for producing the composition of Claim 104, comprising:
a. mixing one or more lactides selected from the group consisting of D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide and mixtures thereof with an elastomeric blend compatible polymer that provides an improved impact resistant composition;
b. heating and dissolving the blend compatible polymer in the lactide(s) of step (a) to form a solution;
c. polymerizing the lactide(s) in the solution; and d. incorporating plasticizer in the composition, whereby the plasticizer is intimately dispersed within at least the poly(lactic acid) and the plasticizer is selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:
where R = H, alkyl, aryl, alkylaryl, or acetyl and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75.

123. The process of Claim 122, comprising the step of fabricating the composition into useful forms by melt fabrication.

124. The process of Claim 122, comprising selecting a blend compatible polymer that comprises a segmented polyester.

125. The Process of Claim 122, incorporating a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactido, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5,400.

126. A deyradable composition comprising:
blends of a physical mixture of:
a. a poly(lactic acid); and b. an elastomeric blend compatible polymer that provides improved impact resistance to the poly(lactic acid), wherein the polymer is selected from the group consisting of polyisoprene (gutta percha), styrene-isoprene-styrene block copolymers, acrylonitrile-butadiene-styrene block copolymers, styrene-ethylene-styrene block copolymers, propylene-ethylene-propylene block copolymers, propylene-isoprene-propylene block copolymers and mixtures thereof.

127. A process for producing the composition of Claim 126, comprising:
a. providing a poly(lactic acid);
b. selecting a blend compatible polymer that provides improved impact resistance to the poly(lactic acid) from the group consisting of polyisoprene (gutta percha), styrene-isoprene-styrene block copolymers, acrylonitrile-butadiene-styrene block copolymers, styrene-ethylene-styrene block copolymers, propylene-ethylene-propylene block copolymers, propylene-isoprene-propylene block copolymers and mixtures thereof; and c. blending the polymers of steps (a) and (b).

128. A process for producing the composition of Claim 126, comprising:
a. mixing one or more lactides selected from the group consisting of D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide and mixtures thereof with a blend compatible polymer that provides improved impact resistance to the composition, wherein the blend compatible polymer is selected from the group consisting of polyisoprene (gutta percha), styrene-isoprene-styrene block copolymers, acrylonitrile-butadiene-styrene block copolymers, styrene-ethylene-styrene block copolymers, propylene-ethylene-propylene block copolymers, propylene-isoprene-propylene block copolymers and mixtures thereof;
b. heating and dissolving the blend compatible polymer in the lactide(s) of step a to form a solution; and c. polymerizing the lactide(s) in the solution.

129. An environmentally degradeble composition comprising: blends of a physical mixture of:
a. a poly(lactic acid);
b. an elastomeric bland compatible polymer that provides an improved impact resistant composition, selected from the group consisting of polyisoprene (gutta percha), styrene-isoprene-styrene block copolymers, acrylonitrile-butadiene-styrene block copolymers, styrene-ethylene-styrene block copolymers, propylene-ethylene-propylene block copolymers, propylene-isoprene-propylene block copolymers and mixtures thereof; and c. a plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5,400, and wherein the plasticizer is intimately dispersed within at least the poly(lactic acid).

130. The composition of Claim 129, comprising:
a. a first plasticizer selected from the group consisting of one or more derivatives of an oligomer of lactic acid defined by the formula:

where R = H, alkyl, aryl, alkylaryl or acetyl, and R is saturated, where R' = H, alkyl, aryl, alkylaryl or acetyl, and R' is saturated, where R and R' cannot both be H, and where q is an integer: 2 ? q ? 75; and b. a second plasticizer selected from the group consisting of lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, and mixtures thereof.

131. The composition of claim 129, comprising between about 0.1 to about 10 weight percent plasticizer.

132. The composition of claim 129, comprising between about 1 to about 99 weight percent poly(lactic acid).

133. A process for producing the composition of Claim 129, comprising:
a. providing a poly(lactic acid);
b. providing a plasticizer selected from the group consisting of lactic acidl D-lactide, L-lactide, meso D,L-lactide, racemic D,L-lactide, oligomers of lactic acid, oligomers of lactide, and mixtures thereof, wherein the oligomers have a number average molecular weight below about 5400;
c. providing an elastomeric blend compatible polymer that provides an improved impact resistant composition, and the elastomeric blend compatible polymer is discrete and intimately bound; and d. blending the polymers of steps (a) and (c) with the plasticizer of step b.

134. The process of Claim 133, providing oligomers having a number average molecular weight below about 720.