CA2025424A1 - Composition containing a polymer of unsaturated hydrocarbon and a starch derivative - Google Patents

Abstract

COMPOSITION CONTAINING A POLYMER OF UNSATURATED
HYDROCARBON AND A STARCH DERIVATIVE
Abstract of the Invention The invention herein is a composition comprising a polymer of an unsaturated hydrocarbon, a starch derivative and a compatibilizing agent, where the starch derivative is a C1-4 alkyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25 and the compatibilizing agent is selected from the group consisting of a vinyl copolymer, an acryl copolymer, and one or more esters of C1-4 alcohols and C6-20 organic acids.

Description

COMPOSITION CONTAINING A POI,YMER OF UNSATUR~TED
HYDROCARBON AND A STARCH DERIVATIVE
Background of the Invention Field of the Invention The invention herein is a composition containing a polymer of an unsaturated hydrocarbon and a starch derivative such that the composition has improved biodegradability.
In the past there have been research attempts to develop biodegxadable material. The reason for this research activity is that polymers of unsaturated hydrocarbons, such as polyethylene, polypropylene and polystyrene, poses little biodegradable properties.
The use of biodegradable material is advantageous since the majority of the product will degrade so that there will be less ~aste in processing and/or environmental pollution.
One such development in the field is the incorporation of an artificial resin of gelatinized or ungelatinized starch or derivatives thereof. The starch or starch derivative functions as a filler therein. According to US Patent No. 4,016,117, blown films of polyethylene with a predried starch and small amounts of ethyl oleate and oleic acid were manufactured in this manner. However, more than 15 percent of these films became paper-like.
In another US Patent No. 4,021,388, pretreated starch is used, and one can obtain with 8 percent pretreated starch a film with better properties than those obtained in the '117 Patent. The '338 Patent states that one may use a maximum of 50 percent starch derivative. Additionally, according to US
Patent No. 4,125,495, a pretreated starch is used as a filler in polyvinyl chloride composition that contains up to 50 percent of plasticizers and a typical stabilizing agent. The content of the pretreated starch ::

~ 2 --here is 51 weight percent. According to this patent, the critical limit would here amount to 60 weight percent, at which the material becomes porous, because the amount of polymer is not su~Eficient to fill the interstices between the starch grains. A11 of these patents thus mentioned are in the name of Coloroll Limited, and this company, on the basis of these, patents now produces a polyethy:Lene bag which contains 7 to 10 percent starch.
Another proposal for the use of starch as a filler occurred in _d Enq. Chem. Prod._Res. Dev., 16 (4), 305-3-08 (1977) and in Ind. Enq. Chem.~ Prod. Res.
Dev., 19 (4), 592-595 (1980). According to the first mentioned article, a flexible film is prepared from a composition of a water-dispersible copolymer of ethylene and acrylic acid (EAA) and a starchy material.
The starchy product is unmodified starch, but one may also use amylase or amylospectine component or also modified starch products, such as partially depolymerized starches and starch derivatives.
The proposal in Ind. Enq. Chem.. Prod. ResO
Dev. also discloses the preferred use of starch materials that have been gelatinized. The starch grains should be sufficiently swollen and broken in order to form a smooth, viscous, aqueous dispersion.
Preferably, essential amino acids (EAA) are used as a wat~r-dispersible copolymer obtained from a mixture of 20 weight percent acrylic acid and 80 weight percent ethylene. In the second article mentioned above, in Ind. Enq. Chem. Prod. Res. Dev., further experiments were completed with an extrusion-blowing technique, wherein the EAA could also be partially replaced with low pressure polyethylene. With air-dried corn-starch (11 percent m~isture), it was reported that clear, flexible and uniform films in the case of mixtures contained 40 percent of starch and no more than about . 12. ~0 ~12: 42 PM >kFITCH, EVE~ T. hL. PrJ~

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40 perc~l3nt o~ thcl low ~r~u~R poly~hylene~ In ~hl~
techni~aus app~n~ly ~he oarboxy groupl3 o~ the ESAA
promote th~ ~ter~ p~r~ability o~ the ~o~npo~ltlon and pos;~lbly al~o ~ondlng ~w~an the carboxy gr~u~ o:E the 5 EA~ zlnd th~ nydroxy group~ Q~ ~ho ~tarc;h occure, but no commer~$~1 usel Df thi~ re~ars~h hi~s b~com~ known~
Anot:~r t~hnlque 1~ th-3 u~ o~ g~t polyme~ o~ starc~ ln ~r~ lal ~4sin~. ~h~ prinalple oï thi~ hcd i~ ~h~t a ~re~ radical i~ ~o~med on the 10 bac:~cbo~0 o~ the ~t~rch, wh~r~:eter thllt; le. re~cte~ with ~ polyr~riza~lR ~finyli~ or aaryllc: ~nom~r~ Initi~tion c~n take pl~3 ch~ ally~ or l:~y rældi~tion. Severe~l monomsr~ hav~ b~en tri~dl u~1~g thl~ method, ~e~ YÇ1 ~9~ Suppl. n~ 5-6~g ~1977) 15 and E?Q~ cl~, 17 ~5) 311~ 316 (1~77) .
Accordia~ to t~iR t~chniqu~, ~ynthetio pol~mer~ c~an be ~b~a~necl having a varying gla~s tran~iition tempera~ure [~g). The obtained ~raft ~opolymer~: wer~ extru~ed without thQ addition o~
20 thsrmoplastic:~ ho~cspolymer, and in thi~ way, contihuous, poly~ac~:haride-~ille~ pla~tics were obt;~ined which were deg~adable. ~ith poly~tryen~ and methylmet~c:rylate, hard and ~rittle p~oduct~ were obtain~d, and w~th methy- and bu~ylacrylat~, t~e pro~uot~ were more flexibl~ ~n~ leather-like~ In the ~e~hyl acryla~e ~eri~s, it appeare~ that bettet r~sults wer~ obtained wlth yelatini~ed s~arch th~ wi h ~arch in the form of grni~s. Addlt$onally, ~cording to Starke, 21, 47 ~1~6~ the ac~ta~e, propion~te and ~tyra~e esters of graft oopol~mer~ oP st~rah with ~hyl acryla~e and ~t~r~h wlth butyl acrylate are also thermopla~tic ma~erlal~ whi~h c~n ~a~ily be ~haped.
In u~ing the gr~ing technique, i~ is not possi~le to obtain flexible f~lm material~ ~uch a~
35 th~se mad~ fr~m polyethyl~ne, polypropylene and pol~
~lnyl chlorlde. Howerer, one does obtain a moldable ~, .

2 ~1 2 ~

plastic, but only when exclusively untreated or gelatinized starch are used.
Another technique is proposed, which encompasses incorporating a polysaccharide, i.e.
pullulan and resin. Pullulan is a high molecular weight polymer-containing unit of maltriose, a glucose-trimer where the glucose molecules have been bonded to each other in a repeating way through a ~-1,6 bond.
Pullulan is a white powder which is easily soluble in water and can be recovered as a sticky substance ~rom a culture broth of a strain of the incomplete microorganism Pullaria.
Pullulan not only is water-soluble, but it is also not toxic and is edible. Furthermore, even during burning, Pullulan does not emit noxious gas, and is spontaneously decomposed by micro-organisms, even if it is dumped as waste in the unmodified state.
Furthermore, a thin pullulan film is impermeable to oxygen and consequently can protect pharmaceuticals or food products against oxidation. Compositions of pullulan and thermoplastic r~sins have been disclosed in U.S. Patents 3,976,605, 3,992,496 and 4,045,388.
The decomposition temperature of the pullulan resin is the temperature at which th~ resin during gradual heating starts to give off heat as a result of oxidative decomposition and starts to show a clear weight loss. This temperature is 250C to ~60C.
It appears that, by etherification or esterification of pullulan, products may be obtained having decomposition temperatures varying from 170C to 300C. Thus, pullenan per se is a promising material, but the high production costs thereof ~orm an obstacle for its practical use, particularly for using it in cheap packaging materials. Etheri~ication or esterification may further improve the properties of the pullulan, but thereby the material becomes still .
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more expensive.
Therefore, until now it had been highly desirable to find a simple and economical method of producing biodegradable products.
Summary of the Invention The invention herein is a composition comprising a polymer of an unsaturated hydrocarbon, a starch derivative and a compatibilizing agent, where the starch derivative is a C14 alXyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25 and the compatibilizing agent is selected from the group consisting of a vinyl copolymer, an acryl copolymer, and one or more esters of C14 alcohols and C620 organic acids-The composition preferably contains a plasticizer when the compatible-making agent is a vinyl copolymer, an acryl copolymer or mixtures thereof. The plasticizer is of the carboxylic acid type and it is preferably oleic acid.
When the compatible-making agent is a vlnyl or acryl copolymer, it is either a copolymer of ethylene and vinyl acetate or a copolymer of ethylene and acrylic acid. When the compatible-making agent is one or more esters of C14 alcohols and ~6-20 organic acids, such as carboxylic acids, the esters are methyl or ethyl esters.
This composition can be used in a variety of applications. Typically, the composition can be used to make articles that were, prior to the invention herein, made with polyethylene, polypropylene and poly vinyl chloride.
Detailed Description It has now been found that, with a simple and cheaply prepared starch derivative, it is possible to obtain a composition which is degradable to a considerable degree and which, in view of its price and : , . . ' , ' ' ' .

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properties, is also suitable as a packaging film.
The invention herein is a composition comprising a polymer of an unsaturated hydrocarbon, a starch derivative and a compatibilizing agent, where the starch derivative is a C14 alkyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25 and the compatibilizing agent is selected from the group consisting of a vinyl copolymer, an acryl copolymer, and one or more esters of C14 alcohols and C620 organic acids.
The starch is esterified to decrystallize the starch grains and to disrupt the hydrogen bonds between the starch molecules, whereby the rigid structure vanishes. By ~Ising elevated temperatures and friction forces, the esterified starch qrains can be easily disintegrated. The disintegrated material, when combined with the plasticizers, already has the per se possibility to form plastic films. Furthermore, in combination with the polymer of unsaturated hydrocarbon, the starch ether does not function as the primary filler, but forms a copolymer with the hydrocarbon.
The unsaturated hydrocarbons used herein are polyolefins, such as polyethylene, both high pressure and low pressure polyethylene, and polypropylene, as well as polystryene and copolymers of these unsaturated hydrocarbons.
As stated previously, the degree of substitution for the starch, for the present purposes, should be at least 0.25. Preferably, the degree of substitution for the starch is higher- suitably at about 0.4 to about 1. On the other hand, a starch that has a substitution that is too high is disadvantageous for the degradability, and for this reason, the degree of substitution for the starch is preferably not higher than 2.

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Hydroxypropyl ethers are prefsrably used and can be obtained by condensation of staxch with propylene oxide. These product:s are already known and available. The hydroxypropyl ether is prepared in accordance with the general principles of condensation of compounds having an active hydrogen~ ie. a hydroxy group with alkylene oxides. Basic or acid catalysis can be used, but basic is preferred for starch derivatives. More specifically, the basic cakalyst one can use simply and cheaply is sodium hydroxide. Of course, substitution at several of the hydroxyl groups on the starch can occur and also the introduction of the hydroxypropyl group may further react with the molecules of the propylene oxide. It is well known that, in such condensation reactions with basic, catalyst usually a static distribution is established.
The hydroxypropylation of starch has been described in more detail in "Modified Starches: Properties and Uses", Editor O.B. Wurzburg, M.S., CRC Press, Inc., chapter 6, by J.V. Tuschoff., which is incorporated herein by reference.
The compatible making agent can be selected from the group consisting of a vinyl copolymer, an acryl copolymer, and one or more esters of C14 alcohols and C620 organic acids. The vinyl and acryl copolymers are units of an olefin that may contain hydrophilic groups. More specifically, the vinyl and acryl copolymers are copolymers of ethylene and vinyl acetate, EVA polymers, and copolymers of ethylene and acrylic acid and EAA polymers.
The esters of Cl4 alcohols and C620 organic acids are preferred, because the esters can be used in smaller amounts than the vinyl and acryl copolymers.
Furthermore, if the asters are used as the compatible-making agent, plasticizers or lubricating agents arenot necessary for superior results. It is speculated 2 ~

that when the composition is subjected to a shaping process where heat is liberated, the ~ster undergoes a reaction, possibly saponification, whereby the resulting free acid functions as a lubricator. This is just a theoretical explanation, and the invention is independent of such an explanation.
In this respect, the methyl and ethyl esters are preferred, because the alcohols liberated therefrom by heating or saponification are more volatile than the propanols and butanols. The acid moiety of the ester can be derived from each of the C620 carboxylic acids, i.e., oleic acid, caproic acid, behenic acid and mixtures thereof. The acid moiety can also be derived from carboxylic acids having an intermediate number of carbon atoms, and furthermore, both naturally occurring acids having even number of carbon atoms and the synthetic acids having odd number of carbon atoms, as well as mixtures of such acids, can be used.
Additionally, these acids may be saturated or unsaturated. Esters of oleic acid are preferred, particularly methyl and ethyl oleat~.
In the composition described above, the amount of components may vary. The composition contains about 20 to about 80 weight percent polymer of unsaturated hydrocarbon, about 30 to about 70 weight percent starch derivative, and about ll to about 19 weight percent compatible-making agent, if the agent is a vinyl or acryl copolymer and can also further contain a plasticizer if so desired in an amount greater than zero to about 8 weight percent. If the composition contains as the compatible-making agent esters of C14 alcohols and C620 organic acids, then the composition contains about 20 to about 79 weight percent polymer of unsaturated hydrocarbon, about 20 to about 70 weight percent of starch derivative and about 1 to about lO
weight percent of the ester. The higher the ester , : -' ~
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value within the prescribed ranye, the higher the starch value to obtain the mors preferred results. By increasing the amount of starch derivative and ester used in the composition, the tensile strength of the resulting product decreases somewhat. However, because of the concern and d~sire to have biodegradable products, for instance in packaging materials, for which flexibility is also more important then tensile strength, this decraase in tensile strength is completely acceptable~
It is also ~dvantageous for the composition to also contain a plasticizer of the carboxylic acid type for the hydrocarbon polymer if the compatible-making agent is a vinyl or acryl copolymer. Examples of such plasticizers include stearic acid, oleic acid and di-oleic acid. If a plasticizer is used, it is used in an amount generally no greater than 8 weight percent of the total composition. Furthermore, the amount of plasticizer is preferably related to the amount of compatible-making agent, with the ratio between the plasticizer and the compatible-making agent being about 2:1 to about 4:1, and ratios in-between these ranges. The plasticizer functions to make the starch derivative more hydrophilic and helps protect the composition against discolorization.
~ he composition can be made by simply admixing all the components at a temperature above the melting point of the hydrocarbon polymer employed and subjPcting the admixture to a shaping treatment, i.e., extrusion or pressing.
The following Examples are for illustrative purposes only and are not meant to limit the scope of the invention herein.

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09. 12. 90 ~2: 42 PM ~kFITCH, EVEN, ET. AL. PO~

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An ~lmixtur~ w~ m~de og 30 p~l~tB by weight o~ hlgh prelc~ure polye~hyl~ne, 5~ p~rt~ ~y ~lght o~
5 cond~n~atlon p~odu~t ~ g~ h ~nd propyl~n~ oxidl3 having a dlagr~ oi~ ti~lltiG31 0~ O. 5, 15 E)ZlrtlEI by wi~i~h~ o~ ~YA. aop~ r ~na 5 pArts by wal~ht o~
o~lc aoi~ . The a~ xtur~3 wa~ he~at~d ~t 1~ ln an extru~r ~d 0xtrud~ to ~o~ a ~r~ula~ n~ ~he lO gr~n1~1ate wa~ ~ur~hor p~roae~ed. ~:o tr~n~luc~nt ~ilm~
'rhe~e fllm~ d ~ n~ rangth to ~ d ~15 paa)ca~in~ ~lm~, ~nd du~ to éhe pre~enco o~ the ~arc;h derlvative, th~ w~re ~oio~eg~adable ~n ~ mu~h b~ter de~re~ th~ h~a u~ual polyethyler~ ~llma~
15 ~m~le ~
Admlxture~ w~ pr~par~d ~ ~n ~x~mpl~ I wl~h low pre~su~ poly~t;hylone ~DP~), and l~neAr low pressur~ pc~ly~hyle~ (L~DPE~ 3ç~p~tlv~1y, ~nd wi~h the u ~ of EAA a~ oompa~ e-m~klhg c:opolymer, and the ~o obtairled admixturR~ w~re pre~d to sh~t~, and ~om~
ph~sical proper~ were m~ured. The compo~i'cion~ of the mixt.ure~ and the~e reE~ults are as ~ollows A B ~ l ~ I
I.~P:~ 30 __ __ 3 0 LLDPE -- 3 o 5 0 E~A 15 15 15 S~ari~ a~ld S 5 5 3S Hydroxypropyl ~tarch 50 5~ 30 Elongati,on ~t l:~re~k 9s 0 57 ~300 Tensils ~treng~h N/mm2 14 . 4lS 17 ~ ~
Dens~y kg~m3 954 _~_ 2J ~3 ~J ~j fi~

~Qa ~ o~po~ on ~:: o~ E3c~ple II W~~ proc~e~ d t~
form a ~llm WhiC:h hACl t.h~ ~ollowing p~operti~s:
E~n~ lo~ A~; b2~3a)~ 35~
T~n~ ns~th, 2~ 18 . 9 ~lou~ Tran;~pilr~n~e, v~ browr ~en~al a~pear~n-;:e +~

Compo~itiono we~o ~pr~p~Fed on th~ o~
linear low pr~s~iu~* poly~thylon~ ~T.,L~P~ ompos~tlc:r~
1 cont~in~ ~6 w~gh~ p~rcon~ o~ LLE~P}~, 30 w~lght p~arc~nt o~E hydroxypr~pyl ~tarc:h on ~ w~ight p~rcent o~
ethyl oleate . Compo~ n ~ c:ont~ ~ n~ ~3 w~ight 15 p~ ent o~ PI3:, 40 we~gh~ per~ n~ o~ hydroxyp~opyl æ~roh ~nd 7 w~i~ht p~rcent o~ l3thyl olez~ For ~somp~ra~ e E~urpo~e~ 10~ per~ent S.~PE
~ompo itlon wa te~d. F~lms w~r~ ext;rud~d ~roln nll th~æ~a ~h~ee c:ompo~t~on~ an~ the ~;~n. 11~ ~r~ng~h ~T~3) 2 o and elongation at break ~13B) in th~ machin~ direc:ti~n ~MD) and in the tran~Y~rse ~lrec~ion ~TD) w~r~ m~a~ur~d thereof, The result~; are a~; ~ollow~:
~k~
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est ~ ;~
I ...... r ~ ~ ~ ~ I

~ompo~ition 1 1~ 14 ~80 710 C~ompo~i~ion ~ 10 9 6~0 7g3 100~ ~I.13PE 38 ~6 ~80 ~33 _ . _ ~m~}
A c:ompo ition o~ 4~6 L~DPE, 15~ EAA. 5%
~:te~ric ac:id an~ 40~ hyt~roxy butyl starch wa~ proce~s~d to fo~m a film wh~c:h h~d the :~ollow~n~ properties.

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Elongation at break % 330 Tensile strength, N/mmZ 23 Colour Transparent, ~ery light brown General appearance ++
Example 6 A composition of 50% polystyrene, 15% SMA
(styrene maleic anhydride) 5% stearic acid and 30%
hydroxy propyl starch was processed to form a 1.2 mm thick sheet which had the following properties:
Elongation at break % 2 Tensile strength, N/mm2 21 -,

Claims (17)

1. A composition comprising a polymer of an unsaturated hydrocarbon, starch derivative and a compatibilizing agent, wherein the starch derivative is a C1-4 alkyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25 and the compatibilizing agent is selected from the group consisting of a vinyl copolymer, an acryl copolymer and one or more esters of C1-4 alcohols and C6-20 organic acids.

2. The composition in Claim 1 wherein the starch derivative is a condensation product of starch and propylene oxide.

3. The composition in Claim 2 wherein the starch derivative has a substitution of about 0.4 to about 1Ø

4. The composition in Claim 1 wherein the composition further contains a plasticizer of the carboxylic acid type.

5. The composition of Claim 4 wherein the plasticizer is selected from the group consisting of stearic acid, oleic acid, di-oleic acid and mixtures thereof.

6. The composition of Claim 4 wherein plasticizer and compatible-making agent are used in a ration of about 2:1 to about 4:1 and ratios in-between this range.

7. The composition of Claim 1 wherein the composition comprises about 20 to about 79 weight percent polymer of an unsaturated hydrocarbon, about 20 to about 70 weight percent starch derivative and about 1 to 10 weight percent of a compatible-making agent, when the compatible-making agent is selected from the group consisting of one or more esters of C1-4 alcohols and C6-20 organic acids.

8. The composition of Claim 1 wherein the composition comprises about 20 to about 8 weight percent polymer of unsaturated hydrocarbon, about 30 to about 70 weight percent starch derivative and about 11 to about 19 weight percent compatible-making agent, wherein the compatible-making agent is a vinyl or acryl copolymer.

9. The composition of Claim 8 wherein the composition further contains a plasticizer in the amount greater than zero to about 8 weight percent.

10. The composition of Claim 1 wherein the compatible-making agent is a vinyl or acryl copolymer and is either copolymer of ethylene and vinyl acetate or a copolymer of ethylene and acrylic acid.

11. The composition of Claim 7 wherein the esters are methyl and ethyl esters.

12. The composition of Claim 7 wherein esters are made from C6-20 carboxylic acids.

13. The composition of Claim 12 wherein the carboxylic acid is oleic acid.

14. The composition of Claim 12 wherein the esters are methyl or ethyl oleate.

15. A process for producing articles comprising the composition of Claim 1 wherein the composition is shape-treated with the use of heat.

16. An article made from the process of Claim 15.

17. The article of Claim 16 wherein the article is a packaging material.