JP5263471B2 - Biodegradable elastomer and method for producing the same - Google Patents

Description

  The present invention relates to a biodegradable elastomer containing polylactic acid and polycaprolactone structures in the main chain, and a method for producing the same.

  Various copolymer polymers and modified polymers containing lactic acid have been disclosed in order to obtain biodegradable polymers that cover the fragile mechanical properties of polylactic acid and have mechanical properties and moldability that can withstand practical use. As an example, modified polymer polylactic acid modified by urethanization or alkylesterification is disclosed (for example, see Patent Document 1).

  Also, a biodegradable polyester having an average molecular weight of 80000 or more obtained by copolymerizing 99.5 to 85% by weight of an L-lactic acid and / or D-lactic acid component and 0.5 to 15% by weight of an aliphatic polyester. Copolymers are disclosed (see, for example, Patent Document 2).

  Further, an ethylene-vinyl acetate copolymer having a biodegradability of 10 to 99% by weight comprising an oxyacid polymer or copolymer and an ethylene content of 20 to 60% by mole of a vinyl acetate component having a saponification degree of 90% by weight or more. A copolymer comprising 99 to 1% by weight of a polymer saponified product is disclosed (for example, see Patent Document 3).

Further, a method for producing a copolymerized polylactic acid is disclosed in which a reaction product of an aromatic dicarboxylic acid and an aliphatic diol is reacted with lactic acid to produce a copolymerized polylactic acid (see, for example, Patent Document 4).

  Further, the polylactic acid segment (A) is a block copolymer obtained by bonding the aromatic polyester segment (B) and the polyalkylene ether segment (C) to each other, and the weight ratio (A / B + C) is 99. A polylactic acid copolymer characterized by a ratio of 1 to 50/50 is disclosed (see, for example, Patent Document 5).

  Also disclosed are a resin composition comprising polylactic acid and an epoxidized diene block copolymer, and a biodegradable resin composition comprising polylactic acid, an epoxidized diene block copolymer and polycaprolactone (for example, And Patent Document 6).

  Furthermore, in the polymerization of polylactic acid or lactic acid copolymer, it is disclosed that polyvinyl alcohol is mixed and reacted in the polymerization system during the polymerization reaction (for example, see Patent Document 7).

  However, these copolymer polymers are not intended to have a tensile stress at 100% elongation (hereinafter referred to as 100% tensile stress) of 5 MPa or less, which falls within the category of low-modulus elastomers.

  Further, by having a first block made of polylactic acid having hydroxyl groups at both ends and a second block made of a polymer having higher mobility than the polylactic acid, the mechanical properties can be obtained without impairing biodegradability. A novel multi-block copolymer having a more improved random block arrangement has been disclosed (see, for example, Patent Document 8). This multi-block copolymer is disclosed as one of the examples in which polycaprolactone is used as the second block, hexamethylene diisocyanate is used as the chain extender, and the elastic modulus is 1.2 MPa. However, this multi-block copolymer uses polylactic acid having a hydroxyl group at both ends as a raw material for the polylactic acid component, and there is a secondary process for obtaining this raw material and the availability in the market such as lactone. The process of obtaining polylactic acid that requires relatively difficult and expensive starting materials and has hydroxyl groups at both ends is complicated. Furthermore, since chain extension is performed in an organic solvent (dichloromethane), a process and operation for handling the solvent are required, and production takes time. In particular, since a solvent may cause environmental pollution at the time of leakage or disposal, a process that does not use a solvent is desired.

On the other hand, PLA-PCL-PLA (triblock body) was synthesized by reacting lactide on both sides of a polycaprolactone diol having a molecular weight of 2000, and (PLA: polylactic acid (including lactic acid oligomer), PCL: polycaprolactone). It is disclosed that a body is linked with HDI (hexamethylene diisocyanate) to extend a chain to obtain a biodegradable polymer (for example, see Non-Patent Document 1). The modulus of the polymer obtained in Non-Patent Document 1 is 40 MPa or more, and it is not a low elastic modulus elastomer having a 100% tensile stress of 5 MPa or less. Furthermore, in this method as well, since the chain extension reaction of the triblock body is carried out in a solvent (dioxane), a process and operation for handling the solvent are required, and the production takes time.
JP-A-5-214230 JP-A-7-300520 JP 7-316367 A JP-A-8-302003 Japanese Patent Laid-Open No. 9-100345 JP 2000-219803 A JP 2004-43727 A JP 2006-183042 A D. Cohn, et. al. Biomaterial 26, 2297 (2005) Designing biogradable multiblock PCL / PLA thermoplastic elastomers.

  An object of the present invention is to provide a biodegradable elastomer having a high elongation and a low elastic modulus having a 100% tensile stress of 5 MPa or less regardless of a complicated process.

The gist of the present invention is an elastomer, which is a polylactic acid (PLA) unit-polycaprolactone (PCL) unit-polylactic acid (PLA) unit structure triblock polymer and polylactic acid randomly via diisocyanate. The molecular weight of the PCL unit is 550 or more and less than 3000 , the molar ratio of the lactic acid monomer unit to the caprolactone monomer unit in the elastomer is 5: 3 to 1: 3, and the elongation at break is 500%. As described above, it is a biodegradable elastomer having a 100% tensile stress of 0.1 to 5 MPa.

  The diisocyanate can be hexamethylene diisocyanate.

In addition, the gist of the present invention is that
Preparing a heated object comprising a mixture of polycaprolactone diol and polylactic acid;
Heating the object to be heated at a temperature at which polylactic acid is partially depolymerized;
It is a method for producing a biodegradable elastomer, comprising the step of adding diisocyanate to the heated article to be heated and heating it to maintain the molten state to cause chain expansion.

  In the method for producing a biodegradable elastomer, a molar ratio of a lactic acid monomer unit in polylactic acid to a caprolactone monomer unit in polycaprolactone diol in the mixture may be 5: 3 to 1: 3.

  In the method for producing the biodegradable elastomer, the polylactic acid may have a molecular weight of 10,000 to 300,000.

  In the chain extending step, approximately equimolar amounts of the diisocyanate may be added to the polycaprolactone diol.

  In the method for producing the biodegradable elastomer, the diisocyanate may be hexamethylene diisocyanate.

  Furthermore, the gist of the present invention resides in an elastomer composition containing the biodegradable elastomer and a plasticizer.

  According to the present invention, a biodegradable elastomer having a low elastic modulus with a 100% tensile stress of 5 MPa or less and a breaking elongation of 500% or more is provided.

  According to the present invention, there is provided a method for producing a biodegradable elastomer containing polylactic acid and polycaprolactone as constituent elements without using a complicated process and without using a solvent.

An embodiment of the present invention will be described. The biodegradable elastomer of the present invention is
Preparing a heated object comprising a mixture of polycaprolactone diol and polylactic acid;
A heating step of heating the object to be heated at a temperature at which polylactic acid is partially depolymerized;
It is produced by a production method comprising the step of adding diisocyanate to the heated article to be heated and heating it to keep it in a molten state for chain expansion.

  The biodegradable elastomer of the present invention obtained by such a production method is a high elongation elastomer having a breaking elongation of 500% or more and a 100% tensile stress of 0.1 to 5 MPa, which is soft.

  In the heating step, polylactic acid is partially depolymerized to lower the degree of polymerization, and polylactic acid molecules are bonded to both ends of polycaprolactone diol to form PLA-PCL-PLA (PLA: polylactic acid (unit)). , PCL: polycaprolactone (unit)) polymer (hereinafter referred to as triblock polymer (TBP)) is produced. The heating temperature of the article to be heated in the heating step may be a temperature at which polylactic acid is depolymerized, and is preferably 180 to 200 ° C. The heating is preferably performed until a uniform and transparent melt is obtained by heating and stirring. In the article to be heated after heating, TBP and PLA having a lowered degree of polymerization are mixed. In this state, the molecular weight distribution of the melt is a statistically ordered distribution according to the statistical law of reaction. In the middle of reaching this state, the molecular weight distribution of polylactic acid, the molecular weight distribution of polycaprolactone diol depolymerized and reduced in polymerization degree, and the molecular weight distribution of the polymer product overlap to form a non-uniform molecular weight distribution. . Therefore, it is desirable to carry out the heating until it is determined that a statistically uniform distribution is obtained by measuring the molecular weight of the melt by GPC.

  In the step of chain extension, TBP and PLA are randomly linked via diisocyanate to give a copolymer. That is, the biodegradable elastomer of the present invention is obtained. In the chain extending step, the sample only needs to be melted and sufficiently stirred, and may be from the melting point of the sample to the decomposition temperature, and is preferably reacted at 60 to 170 ° C. for 2 to 10 hours.

  As described above, in the present invention, a biodegradable elastomer having a high elongation and a low elastic modulus can be obtained by a simple process in which raw materials are sequentially charged into one container and sequentially heated and reacted. Further, the reaction can be performed simply by heating the raw material or the intermediate raw material, and since no solvent is used, there is no need for labor and facilities for collecting the solvent and preventing leakage. Furthermore, there is no problem of environmental pollution caused by solvent leakage or disposal.

  The molar ratio of caprolactone units to lactic acid units in the mixture of polycaprolactone diol and polylactic acid, that is, the molar ratio of lactic acid monomer units to caprolactone monomer units in the elastomer is preferably 5: 3 to 1: 3. It is preferable for obtaining an elastomer having elongation. If this molar ratio is out of this range, an elastomer having a breaking elongation of 500% or more cannot be obtained. Further, when the molar ratio is 5: 3 to 2: 3, a high elongation and soft elastomer having a breaking elongation of 500% or more and a 100% tensile stress of 0.3 to 5 MPa can be stably obtained.

  The molecular weight of polylactic acid in the mixture of polycaprolactone diol and polylactic acid is preferably 50,000 to 400,000. The molecular weight of the polycaprolactone diol in the mixture of polycaprolactone diol and polylactic acid is preferably a molecular weight of 550 or more and less than 3000 in order to obtain an elastomer having high elongation and low elasticity.

  The amount of diisocyanate used in the chain extending step is preferably approximately equimolar to the polycaprolactone diol in the mixture of polycaprolactone diol and polylactic acid.

  The type of diisocyanate used in the present invention is not particularly limited, and conventionally known diisocyanates can be used. For example, methylene bis (isocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, Isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), trimethylene diisocyanate, tetramethylene diisocyanate (BDI), pentamethylene diisocyanate, 3-methylpentamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), 2 , 4,4-trimethylhexamethylene diisocyanate, heptamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,4-cycl Hexane diisocyanate, 2,2′-diethyl ether diisocyanate, diphenylmethane-4,4′-diisocyanate (MDI), o-xylene diisocyanate, m-xylene diisocyanate (MXDI), p-xylene diisocyanate, 1,5-naphthalene diisocyanate, 1 , 5-tetrahydronaphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 3,3′-methyleneditolylene-4,4′-diisocyanate, 4,4′-diphenyl ether diisocyanate, 2,4′-diphenylmethane diisocyanate, 2, , 2'-diphenylmethane diisocyanate, tetrachlorophenylene diisocyanate, norbornane diisocyanate (NBDI), hydrogenated diphenylmethane diisocyanate Socyanate (H12-MDI), hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate (H6-XDI), 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4 ′ -Biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, tetramethylxylylene diisocyanate, 1,2-diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane, 1,2-diisocyanato Cyclopentane, 1,3-diisocyanatocyclopentane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-2,4'-diisocyanate, ethylethylene diisocyanate, 2-heptyl-3 , 4-bis ( -Isocyanatononyl) -1-pentyl-cyclohexane, 1,2-, 1,4- or 1,3-bis (isocyanatomethyl) cyclohexane, 1,2-, 1,4- or 1,3-bis ( 2-isocyanatoeth-1-yl) cyclohexane, 1,2-, 1,4- or 1,3-bis (3-isocyanatoprop-1-yl) cyclohexane, 1,2-, 1,4- or 1, Examples thereof include 3-bis (4-isocyanatobut-1-yl) cyclohexane, lysine diisocyanate (LDI), dimer acid diisocyanate (DDI), tetramethylxylylene diisocyanate (TMXDI), and 1,4-cyclohexyl diisocyanate (CDI). Of these, aliphatic diisocyanates are preferred for obtaining a polymer with high elongation. Examples of the aliphatic diisocyanate include hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. Hexamethylene diisocyanate is more preferable because the chain extension reaction is stable.

[Comparative Example 1]
61.3 g of polycaprolactone diol (manufactured by Daicel Corporation, trade name: PLACEL 205, molecular weight (measured by hydroxyl value) 530) was put into a separable flask and heated for 1 hour with stirring in a nitrogen stream atmosphere to remove moisture. . Next, 38.7 g of polylactic acid (manufactured by Mitsui Chemicals, trade name: Lacia H-100, molecular weight 100000) is added to the polycaprolactone diol, and the temperature is raised to 195 ° C. Stir and heat for about 4-5 hours until complete. Thereafter, the temperature is lowered to 160 ° C. over 1 hour, equimolar amount of hexamethylene diisocyanate is added to polycaprolactone diol, and the mixture is stirred and heated for 4 hours in this state, and the reaction product is taken out from the separable flask to complete the reaction. A degradable polymer was obtained.

  The melting point measured by taking out a part of this stirred and heated product until it became a uniform and transparent liquid was 37 ° C. The number average molecular weight was 1800, and the molecular weight polydispersity (weight average molecular weight / number average molecular weight) was 1.5.

  The resulting biodegradable polymer had a breaking elongation of 100% and a 100% tensile stress of 0.5 MPa.

[Example 1]
A biodegradable elastomer was obtained in the same manner as in Comparative Example 1 except that Daicel Co., Ltd., trade name: PLACEL 208, molecular weight (measured by hydroxyl value) 820 was used as the polycaprolactone diol.

  A melting point of 37 ° C. was measured by taking out a part of the sample which was stirred and heated until it became a uniform and transparent liquid by visual observation. The polydispersity was 1.4.

  The obtained biodegradable elastomer had a breaking elongation of 500% or more and a 100% tensile stress of 0.7 MPa.

[Example 2]
A biodegradable elastomer was obtained in the same manner as in Example 1 except that Daicel's product name: PLACEL 210, molecular weight (measured by hydroxyl value) 980 was used as the polycaprolactone diol.

  A melting point of 44 ° C. was measured by taking out a part of the sample which had been stirred and heated until it became a uniform and transparent liquid by visual observation. The number average molecular weight was 3000, and the molecular weight polydispersity was 1.5.

  The obtained biodegradable elastomer had a breaking elongation of 500% or more and a 100% tensile stress of 1.5 MPa.

[Example 3]
A biodegradable elastomer was obtained in the same manner as in Example 1 except that Daicel Co., Ltd., trade name: PLACEL 220, molecular weight (measured by hydroxyl value) 2000 was used as the polycaprolactone diol.

  The number average molecular weight measured by taking out a part of what was stirred and heated until it became a uniform and transparent liquid by visual observation was 6800, and the molecular weight polydispersity was 1.5.

  The resulting biodegradable elastomer had a breaking elongation of 500% or more and a 100% tensile stress of 4.5 MPa.

[Example 4]
A biodegradable elastomer was obtained in the same manner as in Example 1 except that the amount of polycaprolactone diol was 44.2 g and the amount of polylactic acid was 55.8 g.

  The biodegradable elastomer obtained had a breaking elongation of 500% or more and a 100% tensile stress of 2.9 MPa.

[Example 5]
A biodegradable elastomer was obtained in the same manner as in Example 1, except that the amount of polycaprolactone diol was 55.3 g and the amount of polylactic acid was 45.7 g.

  The resulting biodegradable elastomer had a breaking elongation of 500% or more and a 100% tensile stress of 1.1 MPa.

[Comparative Example 2]
61.3 g of a polycaprolactone diol having a molecular weight of 3000 (manufactured by Daicel, trade name: PLACEL 230) was put into a separable flask and heated for 1 hour with stirring in a nitrogen stream to remove moisture. Next, 38.7 g of polylactic acid (trade name: Lacia H-100, molecular weight 100000, manufactured by Mitsui Chemicals, Inc.) was added to the polycaprolactone diol, the temperature was raised to 195 ° C., and the mixture was stirred and heated. The operation was interrupted without obtaining a triblock polymer.

[Comparative Example 3]
A polymer was obtained in the same manner as in Example 1 except that the amount of polycaprolactone diol was 76 g and the amount of polylactic acid was 24 g.

  The resulting biodegradable polymer had a breaking elongation of 320% and a 100% tensile stress of 1.3 MPa.

[Example 6]
Samples obtained by adding 0, 10, 20, and 30 parts of a plasticizer (DAIFATTY-101 (manufactured by Daihachi Chemical Industry Co., Ltd.)) to 6 g (100 parts) of the sample obtained in Example 1 were petri dishes made of Teflon (trade name). The sample was heated at 160 ° C. for 1 hour and stirred with a glass rod to obtain a sample of an elastomer composition, and 100% tensile stress of the obtained sample was 1 MPa, 0.9 MPa, 0.8 MPa, 0.7 MPa and addition of a plasticizer. It changed in proportion to.

The molecular weights in Examples and Comparative Examples were converted to standard polystyrene values by GPC. The measurement was performed using two columns of TSKgelSuperHZ2000 (exclusion limit molecular weight: 1 × 10 ⁴ ) and TSKgelSuperHZ4000 (exclusion limit molecular weight: 4 × 10 ⁵ ) in series with Tosoh's HLC-8220GPC. Chloroform was used as an eluent, and a sample having a temperature of 40 ° C., a flow rate of 0.35 ml / min, and a concentration of 2.5 mg / ml was used.

  The breaking elongation and 100% tensile stress in Examples and Comparative Examples were measured using a TENSILON (ORIENTEC RTL-1350A) with a 100N load cell. The test piece was prepared by placing a resin on a No. 2 1/2 dumbbell piece mold, sandwiching it between two stainless steel plates, and pressing it at 180 ° C. with a hot press machine. When the distance between the gauge lines is 24 mm, the distance between the gauge lines is 24 mm, the distance between the gauge lines is 40%, the distance between the gauge lines is 12 mm, and the tensile speed is 10 mm / min. -12) / 12 * 100 was defined as elongation at break /%.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

Claims (9)

An elastomer, which is a polylactic acid (PLA) unit-polycaprolactone (PCL) unit-polylactic acid (PLA) unit structure triblock polymer and polylactic acid are randomly chain extended via diisocyanate, and the PCL unit Has a molecular weight of 550 or more and less than 3000 , a molar ratio of lactic acid monomer units to caprolactone monomer units in the elastomer of 5: 3 to 1: 3, elongation at break of 500% or more, and 100% tensile stress of 0.1. Biodegradable elastomer that is 1-5 MPa. The biodegradable elastomer according to claim 1, wherein the polylactic acid constituting the PLA unit and the polylactic acid chain-extended with the triblock polymer are polylactic acids excluding polylactic acid having hydroxyl groups at both ends. The biodegradable elastomer according to claim 1 or 2 , wherein the diisocyanate is hexamethylene diisocyanate. Preparing a heated object comprising a mixture of polycaprolactone diol and polylactic acid;
Heating the object to be heated at a temperature at which polylactic acid is partially depolymerized;
A method for producing a biodegradable elastomer, comprising the step of adding diisocyanate to the heated article to be heated and heating it to maintain a molten state for chain expansion. The method for producing a biodegradable elastomer according to claim 4 , wherein a molar ratio of a lactic acid monomer unit in polylactic acid to a caprolactone monomer unit in polycaprolactone diol in the mixture is 5: 3 to 1: 3. The method for producing a biodegradable elastomer according to claim 4 or 5 , wherein the polylactic acid has a molecular weight of 10,000 to 300,000. The method for producing a biodegradable elastomer according to any one of claims 4 to 6 , wherein in the chain-expanding step, approximately the same amount of the diisocyanate as the polycaprolactone diol is added. The method for producing a biodegradable elastomer according to any one of claims 4 to 7 , wherein the diisocyanate is hexamethylene diisocyanate. An elastomer composition comprising the biodegradable elastomer according to any one of claims 1 to 3 and a plasticizer.