MXPA96004958A - Block copolymers in the form of star, easily degradab - Google Patents

Abstract

Star block copolymers containing blocks of polycaprolactone and polylactide of limited molecular weight are easily degradable, hard polymers. Such copolymers, which are non-crystalline and having glass transition temperatures near or below room temperature, are useful in many packaging and other applications.

Description

BLOCK COPOLYMERS IN STAR FORM, EASILY DEGRADABLE FIELD OF THE INVENTION Presently hydrogenated and biodegradable star block copolymers of caprolactone and lactide are described herein. Despite the relatively low molecular weight, the copolymers are hard, elastomer-like materials. 10 TECHNICAL BACKGROUND Polymers, particularly thermoplastics, are theoretically recyclable, but frequently do not recycle due to the cost of collecting, sorting and purifying recycled plastics. Therefore, most plastics and other polymers, such as elastomers, are disposed of with other waste, such as in solid waste landfills in urban areas. depressions of the land, where these are very chemically stable, and decompose in a minimal way. One way to reduce the amount of stable polymers in urban sprays and the like is to produce polymers that are degradable, such as by hydrolysis, biodegradation or the like. REF: 23158 It is known that under the appropriate conditions, polylactide is biodegradable, and polymers containing this repeat unit have been considered desirable for this reason. However, in most polylactide polymers are plastics, that is, their vitreous transition temperature (Tg) is below room temperature, and these can be crystalline. Polymers that contain repeated units of lactide but still have properties similar to those. elastomers would also be desirable. U.S. Patent No. 5,210,108 describes a foam made of a star-shaped polymer containing repeated units of lactide. The foams produced are rigid, not elastomeric. D. W. Grijpma et al., Makromol, Chem.

Rapid Commun. , vol. . 155-161 (1992) report the synthesis of star block copolymers having blocks of polylactide and trimethylene carbonate or a mixture of trimethylene carbonate and another block of lactone. These copolymers have a Tg of polylactide of 50-55 ° C BRIEF DESCRIPTION OF THE INVENTION This invention relates to a block copolymer in the form of a star, consisting essentially of a core, 3 to about 20 inner arms of polycaprolactone which are bonded to the core and outer arms of polylactide which are bonded to the inner arms, and with the proviso that: the polylactide is at least 50% by weight of the copolymer; the polycaprolatone is about 10% to about 50% by weight of the copolymer; polycaprolactone and polylactide do not crystallize in the fusion process; and polylactide has a glass transition temperature of less than 35 ° C.

DETAILS OF THE INVENTION The present copolymer is a block copolymer in the form of a star containing blocks of polycaprolastone and polylactide. The copolymers also contain a core, which is often the "starting point" for the copolymer. The core is originally a multifunctional material, which usually contains the same number of functional groups as arms, which the star-shaped copolymer is proposed to have. For the functional group in this example is given to understand a group that either by itself, or by a reaction of the group, forms a site for the initiation of a copolymer chain (an arm of the star). In this case, it will initiate the polymerization of caprolactone. Suitable functional groups for the core include hydroxyl, amino and sufhydryl. These can be used in normal ways to initiate the polymerization of caprolactone. For example, a catalyst such as stannous octoate can be used. Such polymerizations are described in European Patent Application No. 117,538, which is why it is included by reference. The polymerization can be made pure (without solvent) or with a solvent present. Polycaprolactone is formed in the present from epsilon-caprolastone, which is the monomer. The polycaprolactone forms an "inner arm" of the copolymer herein. An inner arm is the polymer that binds or binds to the nucleus. Since the Tg of the polycaprolactone is really low (below 0o) this property does not generally affect the rigidity of the product of the invention. However, polycaprolactone is partially crystallized if the molecular weight is sufficiently high. Therefore, the molecular weight of the polycaprolactone blocks must be low enough so that such crystallization does not take place in the fusion process. A useful molecular weight range for the inner arm of polycaprolactone is a number average molecular weight of about 800 to about 40,000. It is preferred if the polycaprolactone is about 10% to about 40% by weight of the copolymer, is more preferred if it is from about r- * 15% to about 30%, and especially preferred if it is about 18% to about 22% by weight of the copolymer. When the caprolactone is polymerized, the final group is normally a hydroxyl group, which can be used to help initiate the polymerization of the " lactide. Therefore, the block of lactide polymer becomes bound (attached) to the end of the block of j "polycaprolactone, and therein it is called the outer arm. Lactide in the form D, L or meso, or any combination thereof, can be used to form the polylactide block. The lactide homopolymer is semicrystalline and has a Tg of about 55-6 ° C. Therefore, the polylactide block should be small enough (low in molecular weight) so that the Tg is 35 ° C or less, preferably 30 ° C or less. A useful range, typical of the polylactide block sizes is from about 1,000 to about 12,000 in number average molecular weight, but this will vary somewhat with the size of the polycaprolactone block. It is preferred that the number average molecular weight of each polylactide block be about 3,000 or more. It is also preferred if the polylactide is at least 70% by weight of the copolymer. The polylactide block is formed by the polymerization of the lactide itself. This polymerization is carried out in a number of ways, but is usually done with a catalyst. The stannous octoate is a useful catalyst, but the preferred catalysts are rare earth metal compounds, selected, such as those described in U.S. Patent Nos. 5,028,667 and 4,292,859, which, therefore, are both included by reference . The catalysts described in the above patent are especially preferred. These polymerizations are carried out pure or with a solvent present, but pure polymerizations (without solvent present) are preferred. The polymerization temperatures are not critical, and a convenient range is 0 ° C to about 200 ° C. The polymerization of caprolactone and lactide can be done in sequential steps in the same reactor, or the polycaprolactone star-shaped polymer (attached to the core) can be isolated and then mixed with the lactide to be polymerized to form the final copolymer . Star block copolymers of the present have 3 to 20 arms, preferably 3 to 10 arms, more preferably 3 to 6 arms, and most preferably 4 arms. The copolymers described herein are relatively hard elastomer-like materials that are suitable for many uses. Among these uses are the packaging of liquid food, such as milk bags, juice bags, coatings for coated paperboard for refrigerated liquids, and paper for wrapping processed meat; packaging of dry food such as the outer wrapper for boxed meals, as a part of the multilayer packaging film, and as the coating on coated paperboard for frozen foods; coating for coated cardboard for fast food, such as glasses for refreshment; other consumer products such as non-woven absorbent materials for diapers, flexible, soft back sheets for diapers, overwrap of film for toilet products and personal care products; agricultural products such as manure and straw film; medical products such as bandages for flexible wounds and surgical implants of the low module; as a hardening additive for other polymers, such as polymers used for schemes or mounds by blowing compressed air and a modifier for the polymer to be spun into fibers to improve elongation and toughness; and other uses such as adhesives, overwraps of films for animal feed supplements and artificial snow. The copolymer described herein is particularly useful in these applications due to its biodegradability, rigidity, resistance to tearing and softness to the touch. The copolymers herein should not be crystalline, that is, they should not have a melting transition of more than 3 J / g when tested by Differential Scan calorimetry (see test for later Tg) in the fusion processing. The sample for such a test is prepared by injecting some of the copolymer in question into a 3.2 mm thick plate, with the molding temperature being about 10 ° C, and the copolymer having a melting temperature. (leaving the cylinder or barrel with screw of approximately 150 ° C. The molecular weight measurements in the present are made by Gel Permeation Chromatography using polystyrene standards.The average molecular weight of an outer arm of polylactide is weight average molecular weight in number of the copolymer records of the weight fraction of the polylactide in the copolymer divided by the nominal number of arms in the copolymer Similarly, the average molecular weight of the inner arm of polycaprolactone is the average molecular weight in number of the copolymer records of the weight fraction of polycaprolactone in the copolymer divided by the nominal number of arms in the copolymer The vitreous transition temperature (Tg) of the copolymer (particularly the polylactide blocks) is measured by the following procedure. About 0.5 g of copolymer is dissolved in 5 mL of methylene chloride and the resulting solution is added dropwise to 50 mL of rapidly stirred methanol (this is done to remove any free lactide in the copolymer, which acts as a plasticizing substance). -Joard). The precipitated fluff is collected by filtration and / or decantation and dried in vacuo at room temperature. 300 MHz-H-NMR is used to verify that residual lactide does not remain in the co-limero. Differential Scanning Calorimetry (DSC) is performed using a Ta Instruments 2100 analyzer, with a sample of 5-10 mg in a sealed, covered, normal aluminum container. The heating rate is 10 ° C / min. The Tg is taken as the midpoint of the transition step. It is preferred if the Tg of the polylactide in the copolymer is 30 ° C or less. In the following examples, Mn is the number average molecular weight and Mw is the weight average molecular weight.

GENERAL ANALYTICAL DETAILS The molecular weights were measured using dimensional exclusion chromatography (SEC, GPC) in THF solvent at 25 ° C using polystyrene calibration standards. Residual lactide monomer and total caprolactone contents are measured using 300 MHz H-NMR. The physical properties are measured using a Laboratory Mycrosystems tester in a full scale load range of 9.1 kg and a crosshead speed of 5.1 cm per minute. The values reported are the average of at least five determinations. The film samples (0.025-0.050 mm thick) were prepared by compression molding at 150 to 180 ° C and a pressure of 6.9 to 34-5 MPa depending on the flow characteristics of the individual polymer sample.

EXAMPLE 1 Synthesis of 14% Star Block Polylactide 4-Arm Caprolactone Seven grams of polycaprolactone tetrol (Lot # 17360-10 from Union Carbide, Mn 7240) were charged under argon, 41.3 g of L-Lactide and 1.7 g of K, L-Lactide p to a carefully dried Helicone C2V mixer.

(Atlantic Research Corp.), held at 164 ° C. After 10 minutes of agitation, 0.657 L of a 0.45 M solution (140 Solvent 66/3 of Unocal, later referred to as AMSCO 140) of the catalyst La (2, 2,6,6-tetramethyl-heptan) were added by syringe. -3, 5-dione-to) .bis (ethoxyethyl ether). After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water. The conversion of lactide to the caprolactone content by the rmn-H was 92.4 and 1%? respectively, and the Tg was 27 ° C. Mn was 40,000 and Mw / Mn was 1.4. Resistance to tension,% elongation and modulus (later referred to as TEM) was 103 MPa, 137%, 448 MPa, respectively, as measured in compression foxhole film.

EXAMPLE 2 Synthesis of 10% Polylactide of Star Block with 3 Arms of Caprolactone Five grams of polycaprolactone triol (Lot # 16874-95 from Union Carbide, Mn .5260) 43.2 g of L-Lactide and 1.8 g of D, L-Lactide were charged to a carefully dried Helicone C2V mixer (Atlantic Research Corp.). ), held at 164 ° C. After 10 minutes of agitation, 0.687 mL of a 0.45 M solution (AMSCO 140) of the catalyst La (,, 6,6-tetramethyl-heptan-3,5-dione-to-bis (ethoxyethyl ether) was added by syringe. After 15 minutes, the pale yellow, viscous, molten polymer was drained and rapidly quenched in water, The Tg was 19 ° C. Mn was 39,000 and Mw / Mn was 1.6, TEM = 3.5 MPa, 210%, 82.7 MPa.

EXAMPLE 3 Synthesis of 20% Star-Shaped Polylactide with 3 Caprolactone Arms Ten grams of polycaprolactone triol (Lot # 16874-95 from Union Carbide, Mn 5260) 38.4 g of L-Lactide and 1.6 g of D, L-Lactide R to a carefully dried Helicone C2V mixer were charged under argon.

(Atlantic Research Corp.), maintained at 167 ° C. After 10 minutes of agitation, 0.615 mL of a 0.45 M solution (AMSCO 140) of the La catalyst (2.2, 6.6-) was added via syringe. tetramethyl-heptan-3, 5-dione-to) .-, .bis (ethoxyethyl ether) After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water, The Tg was 20 ° C. it was 63,000 and Mw / Mn was 1.2, TEM = 3.5 MPa, 123%, 110 MPa.

EXAMPLE 4 Synthesis of 20% Star-Block Polylactide with 4 Arms of Caprolactone Ten grams of polyketprolactone tretol (Lot # 17360-10 from Union Carbide, were charged under argon, Mn 7240) 38.4 g of L-Lactide and 1.6 g of D, L-Lactide R to a carefully dried Helicone C2V mixer (Atlantic Research Corp.), held at 161 ° C. After 10 minutes of agitation, 0.615 mL of a 0.45 M solution (AMSCO 140) of the catalyst La (2,2,6,6-tetramethyl-heptan-3,5-dione-to) was added via syringe. .bis (ethoxyethyl ether). After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water. The Tg was 10 ° C. Mn was 36,400 and Mw / Mn was 1.3. TEM = 11.7 MPa, 247%, 330 MPa.

EXAMPLE 5 Vitrea Transition against the Study of Composition Polycaprolactone tetrol (# of arms = 4; Lot # 17360-10 of Union Carbide, Mn 7240) and lactide in varying amounts were charged • to flame-dried Pyrex test tubes in a glove box filled with nitrogen, capped with nitrogen. rubber partitions, and heated in a steam bath to 140 or i66oc. After allowing 5 minutes for the molten monomer mixture to rise to the temperature, the catalyst was added to (2,2-6,6-tetramethylheptane-3,5-dionate). bis (ethoxy-ethylether) by means of a long needle microsyringe with vigorous agitation. When the polymerization was completed, as is evident by the high viscosity, a small sample was removed and quickly cooled in water and dried. The polymers were then dissolved at room temperature in dichloromethane and precipitated with rapid stirring in 5 volumes of methanol in order to remove the residual lactide monomers. The composition and analytical results are as shown below.

Tetrol Catalyst Rxn Mn Tg Sample (g) Lactide% CL 1 (μL) (° C) (GPC) (° C) 1 2.8 7.2 25.6 74 140 36000 25 2 2.6 7.4 24-3 76 140 38100 23 3 2.4 7.6 20.4 78 140 42400 25 4 2.2 7.8 20.5 80 140 46200 28 2.0 8.0 19.7 82 140 45000 30 6 1.8 8.2 16.7 84 140 51500 34 7 1.6 8.4 14.7 86 140 54400 36 1 1% CL =% by weight of caprolactone, by rmn- H EXAMPLE 6 Synthesis of 22% Block Polylactide - Star Shaped 4 Arms of Caprolactone Eleven grams of polycaprolactone tretol were charged under argon (Lot # 17360-10 from Union Carbide, p Mn 7240) 39 g of L-Lactide to a carefully dried Helicone C2V mixer (Atlantic Research Corp.), held at 167 ° C. After 10 minutes of agitation, 0.615 mL of a 0.45 M solution (AMSCO 140) of the catalyst La (2, 2,6,6-tetramethylheptan-3,5-dionate) ^. Bis (ethoxyethyl ether) was added via syringe. . After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water. The Lactide conversion and the caprolactone content by the rmn-H were 95.1, and 22% respectively, and the Tg was 18 ° C. Mn was 34,200 and Mw / Mn was 1.3. TEM = 13.1 MPa, 94%, 351 MPa.

EXAMPLE 7 24% Synthesis of 3-Star Star-Shaped Block Polilactide of Caprolactone 12 grams of polycaprolactone tretol were charged under argon (Lot # 17360-10 from Union Carbide, p Mn 7240) 38 g of L-Lactide to a carefully dried Helicone C2V mixer (Atlantic Research Corp.), held at 163 ° C. After 10 minutes of agitation, 0.615 mL of a 0.45 M solution (AMSCO 140) of the catalyst La (2,2,6,6-tetramethylheptan-3, 5-dionate) .-, .bis (. ethoxyethyl ether). After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water. The Lactide conversion and the caprolactone content by the rmn-H were 92.8, and 25% respectively, and the Tg was 16 ° C. Mn was 32,200 and Mw / Mn was 1.3. TEM = 9.7 MPa, 84%, 214 MPa.

EXAMPLE 8 20% Synthesis of 4-Arm Star-shaped Block Polylactide from Caprolatone Ten grams of polycaprolactone tretol (Lot # 17360-10 from Union Carbide, p.

Mn 7240) 40 g of L-Lactide to a carefully dried Helicone C2V mixer (Atlantic Research Corp.), held at 167 ° C. After 15 minutes of agitation, 0.615 mL of a 0.45 M solution (AMSCO 140) of the catalyst La (2,2,6,6-tetramethylheptan-3, 5-dionate) ~. Bis (ethoxyethyl ether) was added via syringe. . After 15 minutes, the viscous, pale yellow molten polymer was drained and rapidly cooled in water. The Lactide conversion and the caprolactone content by the rmn-H were 94.8, and 21% respectively, and the Tg was 23 ° C. Mn was 38,300 and Mw / Mn was 1.4. TEM 14-5 MPa, 316%, 503 MPa.

EXAMPLE 9 Synthesis of 20% of Block Polylactide in the Form of a S trellis of 4 Arms of Caprola_tone (Catalyst of Static Octoate) One g of polycaprolactone tetrol (Lot # 1 7360-1 0 of Union Carbide, Mn 7240) and 4 g of L-p Latida were charged to a Pyrex flame-dried test tube in a glove box filled with nitrogen, covered with rubber partitions, and heated in a steam bath at 166 ° C. After allowing 5 minutes for the molten mixture to reach the temperature, 37 microliters of 0.49 M toluene solution of stannous octoate catalyst is added by means of long needle micro-syringe with vigorous stirring. When the polymerization was completed, as was evident from the high viscosity, a small sample was removed and quickly cooled in water and dried. Lactide conversion and caprolactone content by rmn-H were 94 * 3 and 17.8% respectively, and Tg was 25 ° C, Mn was 49,100 and Mw / Mn was 1.2.

Claims (13)

1. A block copolymer in the shape of a star, characterized in that it consists essentially of a core, 3 to about 20 inner arms of polycaprolactone that are bonded to the core, and outer arms of polylactide that are bonded to the inner arms, and with the condition of that: the polylactide is at least 50% by weight of the copolymer; the polycaprolactone is from about 10% to about 50% by weight of the copolymer; polycaprolactone and polylactide do not crystallize in the fusion process; and the polylactide has a glass transition temperature of less than 35 ° C.

2. The star block copolymer according to claim 1, characterized in that the number average molecular weight for each of the inner arms of polycaprolactone is from about 800 to about 4000.

3. The star block copolymer according to claim 1, characterized in that the polycaprolactone is from about 15% to 30% by weight of the star block copolymer.

4. The star block copolymer according to claim 2, characterized in that the polycaprolactone is from about 18% to about 22% by weight of the star block copolymer.

5. The star block copolymer according to claim 1, characterized in that a number average molecular weight for each of the outer arms of polylactide is from about 1,000 to about 12,000.

6. The star block copolymer according to claim 5, characterized in that a number average molecular weight of each of the outer arms of polylactide is about 3,000 or more.

7. The star block copolymer according to claim 1, characterized in that the polylactide is at least 70% by weight of the copolymer.

8. The star block copolymer according to claim 1, characterized in that the star block copolymer has 3 to 10 arms.

9. The star block copolymer according to claim 8, characterized in that the star block copolymer has 3 to 6 arms.

10. The star block copolymer according to claim 9, characterized in that the star block copolymer has 4 arms.

11. The star block copolymer according to claim 4, characterized in that the star block copolymer has 4 arms.

12. The star block copolymer according to claim 1, characterized in that the vitreous transition temperature is 30 ° C or less.

13. The star block copolymer according to claim 11, characterized in that the vitreous transition temperature is 30 ° C or less.