JP2008285521A - Biodegradable resin composition and biodegradable film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable resin composition and a biodegradable film having improved biodegradability and being friendly to the environment and also being appealing from the view point of economy, by improving the biodegradability of an aliphatic polyester, improving steam barrier property of the biodegradable film, and actively utilizing an aliphatic polycarbonate prepared from carbon dioxide. <P>SOLUTION: The biodegradable resin composition comprises a combination of 5-99 mass% of an aliphatic polyester (A) and 95-1 mass% of an aliphatic polycarbonate (B) prepared by alternating copolymerization of carbon dioxide and an epoxide. The biodegradable film is prepared by forming the composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biodegradable resin composition and a biodegradable film. More specifically, the present invention relates to a biodegradable resin composition having improved biodegradability and moldability, and a biodegradable film having improved water vapor barrier properties and mechanical properties.

Biodegradable resins are known to decompose relatively easily without producing harmful substances in water or soil. For this reason, it is attracting worldwide attention from the viewpoint of environmental conservation such as the problem of waste disposal. Among these, the aliphatic polyester resin may have physical properties close to that of polyethylene, and the film obtained by molding the resin may be used for films such as agricultural materials, civil engineering materials, vegetation materials, and packaging materials. It is expected (see, for example, Patent Documents 1 and 2).
However, the conventional biodegradable film is essentially a film that easily permeates water vapor because its chemical structure has an ester bond and is polar.
In some cases, this characteristic has the advantage that the contents do not get steamed as a characteristic required for non-woven fabrics, etc., but when it is made into a container, the liquid of the content permeates and decreases. When used as a film, there were problems such as drying of the soil.
On the other hand, another major problem in the global environment is the emission of carbon dioxide. Energy consumption has increased remarkably due to the development of industry, transportation, etc., and the amount of carbon dioxide emitted has increased, leading to the destruction of the global environment due to the greenhouse effect. Efforts to reduce emissions are being made in each country based on the Kyoto Protocol, but there are limits to just reducing emissions. Therefore, the development of polymers using carbon dioxide as a raw material has attracted attention as carbon neutral. As one method of carbon neutral, research on polylactic acid using lactic acid which is a plant-derived raw material as a raw material has been actively conducted. Furthermore, aliphatic polycarbonate is directly listed as a polymer using carbon dioxide as a raw material. This is a copolymer having a highly advanced alternating structure using carbon dioxide gas and an epoxy compound as raw materials. Since this polymer has an ester bond in the main chain, it can be photodegraded and is also a completely biodegradable plastic. Such a high molecular weight copolymer film has good transparency and has an excellent function of not allowing oxygen gas and water vapor to permeate. A wide range of applications are expected in areas such as pharmaceuticals and food packaging materials.
In fact, as shown in Non-Patent Documents 1 to 8 or Patent Document 3, research and development relating to polymerization is being vigorously conducted. However, in a practical sense, techniques such as a foam insulation (Patent Document 4), a polymer solid electrolyte (Patent Document 5), and a polymer dispersion (Patent Document 6) have been disclosed. There is no disclosure of technology. This is because, in order to make a molded article such as a film, since the glass transition temperature is generally low and the crystallinity is also low, there are problems in moldability and physical properties such as blocking between pellets and blocking of the formed film. is there.

Japanese Patent Laid-Open No. 5-271377 Japanese Patent Laid-Open No. 6-170941 JP 2004-263168 A Japanese Patent No. 2746069 Japanese Patent No. 3384174 Japanese Patent No. 3197353 Macromolecules: 24,5305,1991 Macromolecules: 30,3147,1997 20 J.Polym.Sci .: PartA: Polym.Chem.37,1863,1999 Macromolecules: 28,7577,1995 Macromolecules: 32,2137,1999 Journal of American Chemical Society: 1998,120,4690 Journal of American Chemical Society: 1999,121,107 Journal of American Chemical Society: 1998,120,11018

  In view of the above-mentioned problems of the prior art, the object of the present invention is to improve the biodegradability of aliphatic polyester and the water vapor barrier property of a film formed from the polyester, or to improve the moldability of aliphatic polycarbonate. A biodegradable resin composition and a biodegradable film that can be used as an improvement measure for global environmental problems by blocking the blocking of films obtained from polycarbonate and actively utilizing carbon dioxide-based polymers. It is to provide.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problem can be solved by a resin composition comprising an aliphatic polyester and a specific aliphatic polycarbonate, and the present invention has been completed. It came to do.
That is, the present invention includes the following:
(1) Biodegradability comprising a combination of aliphatic polyester (A) 5 to 99% by mass and aliphatic polycarbonate (B) 95 to 1% by mass obtained by alternating copolymerization of carbon dioxide and epoxide Resin composition,
(2) The biodegradable resin composition according to (1), wherein the biodegradation rate ratio is 0.1 to 0.6 in the case of (A) alone,
(3) The biodegradable resin composition according to the above (1) or (2), wherein the epoxide is propylene oxide,
(4) The biodegradability according to any one of the above (1) to (3), wherein the (B) substantially does not contain an amount of catalyst sufficient to further polymerize or depolymerize itself and the (A). Resin composition,
(5) In the above (1) to (4), (A) is an aliphatic polyester obtained by copolymerization of an aliphatic polycarboxylic acid and an aliphatic polyol, and having a weight average molecular weight of 30,000 to 300,000. Any one of the biodegradable resin compositions,
(6) The above (A) is obtained by further coupling a prepolymer having a weight average molecular weight of 30,000 to 50,000 obtained by copolymerization of an aliphatic polycarboxylic acid and an aliphatic polyol with a polyisocyanate. The biodegradable resin composition according to any one of (1) to (5), which is an aliphatic polyester having a weight average molecular weight of 100,000 to 300,000,
(7) The above (A) is polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, polybutylene adipate terephthalate, poly-3-hydroxybutyrate, poly-3-hydroxybutyrate-3-hydroxyvalerate copolymer Any one of (1) to (6) selected from a polymer, a poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer, polylactic acid, polycaprolactone, and a copolymer thereof. Biodegradable resin composition,
(8) The biodegradable resin composition according to any one of the above (1) to (7), which is obtained by dry blending the (A) and the (B).
(9) A biodegradable film formed by molding the biodegradable resin composition according to any one of (1) to (8) above, and (10) a water vapor barrier property (conforming to JIS Z0208) is (A ) The biodegradable film according to (9), which is 1.2 to 20.0 times the film obtained from a single resin.

  According to the present invention, the biodegradation rate of an aliphatic polyester is moderately reduced, the water vapor barrier property when it is formed into a film is improved, or the moldability of an aliphatic polycarbonate is improved, and carbon dioxide is used as a raw material. The biodegradable resin composition which is one of the measures for improving the global environmental problems by being actively used as a polymer, and suitable for compost bags, agricultural films and packaging materials, etc. A biodegradable film is provided.

The present invention will be specifically described below.
The aliphatic polyester of one resin component (A) in the biodegradable resin composition of the present invention is not particularly limited, but may be any one that itself has biodegradability and is thermoplastic in view of moldability. Preferably there is.
They may be resins belonging to any of chemically synthesized resins, microbial resins, natural product utilizing resins and the like. For example, polybutylene succinate, polybutylene succinate-adipate, aliphatic polyester obtained by polycondensation of polyol and polycarboxylic acid such as polyethylene succinate, intermolecular of oxycarboxylic acid such as polycaprolactone and polylactic acid Polymers and copolymers, polylactic acid-polyglycolic acid copolymer, poly-3-hydroxybutyrate, poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer, polyhydroxybutyrate-valerate copolymer Etc. These may be used alone or in combination of two or more.
Among them, when considering film moldability and physical properties, the aliphatic polyester is obtained by copolymerization of an aliphatic polycarboxylic acid and an aliphatic polyol, has a melting point of 50 to 180 ° C., and has a weight average molecular weight (hereinafter referred to as Mw). Is preferably 30,000 or more from the viewpoint of obtaining a good molded product, and more preferably about 100,000 to 300,000 from the viewpoint of obtaining a good molded product. An aliphatic polyester having a weight average molecular weight of this degree can be obtained in a single stage using special equipment under special conditions, but the weight average is obtained by polycondensation of an aliphatic polyol and an aliphatic polycarboxylic acid. A prepolymer having a molecular weight of about 30,000 to 50,000 is produced and then coupled by a polyisocyanate, and it is particularly preferable from the viewpoint of economy to use such an aliphatic polyester.
Examples of the aliphatic polyol include glycols (diols) such as ethylene glycol, 1,4-butane polyol, 1,6-hexanediol, decamethylene glycol, and neopentyl glycol. Examples of the aliphatic polycarboxylic acid include dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid, and anhydrides thereof.
Further, as other components, a small amount of trifunctional or tetrafunctional polyol, polycarboxylic acid or oxycarboxylic acid may be added and copolymerized.
Moreover, the aromatic polyol or the aromatic polycarboxylic acid component may be included in the range which does not impair biodegradability.

As the polycondensation type aliphatic polyester, there are commercially available products, for example, “Bionore” series manufactured by Showa Polymer Co., Ltd. is well known.
Examples of commercially available products of polycaprolactone include “Cell Green PH” series manufactured by Daicel Chemical Industries, Ltd. and “Tone” series manufactured by Union Carbide. Examples of commercially available polylactic acid include the “U'z” series manufactured by Toyota Motor Corporation, the “Lacia” series manufactured by Mitsui Chemicals, Inc., and the “Nature Works” series manufactured by Cargill Dow.

An aliphatic polycarbonate obtained by alternating copolymerization of carbon dioxide and epoxide of the other component (B) in the biodegradable resin composition of the present invention, wherein -O-R-O-CO- (wherein R is There is no particular limitation as long as it has a repeating unit represented by a substituted or unsubstituted linear, branched or cyclic alkylene group, preferably having a total carbon number of 2 to 35).
The aliphatic polycarbonate of component (B) is usually produced by alternating copolymerization of carbon dioxide and epoxide in the presence of a polymerization catalyst at a temperature of -30 to 220 ° C. As a polymerization catalyst, a mixture of an organic zinc compound and a compound having a divalent or higher active hydrogen (for example, a binary catalyst of dimethyl zinc, diethyl zinc or the like and water), or an alcohol or a chelate with the binary catalyst. Three-way catalyst with compound added (for example, yttrium trichloroacetate-glycerin-diethylzinc), zinc alkoxide, alkyllithium, and a mixture of these with water, metal oxide-supported organozinc compound, zinc acetate, zinc hydroxide A reaction mixture of bismuth and aliphatic dicarboxylic acid, or a metal oxide-supported zinc halide, organoaluminum compound such as trimethylaluminum, triethylaluminum, or triisobutylaluminum, and a water binary catalyst, and an alcohol or chelate compound added thereto Ternary catalyst, aluminum trialkoxide Dialkylaluminum alkoxides, dialkylaluminum hydrides, alkylaluminum dialkoxide, methylaluminoxane, organic aluminum sulfate, alkyl magnesium, and mixtures thereof with water, the organic having other reducing ability, inorganic compounds, and the like. Among the above, it is preferable to use a ternary catalyst containing a zinc compound such as yttrium trichloroacetate-glycerin-diethylzinc from the viewpoint of enhancing the alternating copolymerization property.
The polymerization catalyst is preferably 0.0001 to 10 equivalents, more preferably 0.002 to 2 equivalents, relative to the number of moles of epoxide.
The polymerization catalyst used is preferably removed (deashing treatment). By removing the catalyst, further polymerization and depolymerization of the component (A) and the component (B) are prevented, and the biodegradable resin composition of the present invention and The stability of the quality of the biodegradable film obtained therefrom can be ensured. The removal of the catalyst is usually performed by adding a poor solvent of component (B) such as methanol to the component (B), usually 2 to 10 times, preferably about 3 to 8 times the mass, and washing. .
In the present invention, “substantially free of an amount of catalyst sufficient for further polymerization or depolymerization” means an amount in which the catalyst remaining in the component (B) does not substantially exhibit a catalytic action. This means that it is 100 ppm (mass basis) or less.

The epoxide used for the production of the aliphatic polycarbonate of component (B) is preferably a monoepoxide, such as ethylene oxide, propylene oxide, 1-butene oxide, 2-butene oxide, isobutylene oxide, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octene oxide, 1-decene oxide, cyclopentene oxide, cyclohexene oxide, styrene oxide, vinylcyclohexane oxide, 3-phenylpropylene oxide, 3,3,3-trifluoropropylene oxide, 3-naphthylpropylene oxide , 3-phenoxypropylene oxide, 3-naphthoxypropylene oxide, butadiene monooxide, 3-vinyloxypropylene oxide, 3-trimethylsilyloxypro Ethylene glycidyl carbonate, cholesteryl glycidyl carbonate, preferably ethylene oxide, propylene oxide, 1-butene oxide, 2-butene oxide, isobutylene oxide, 1-hexene oxide, 1-octene oxide, 1-decene oxide And cyclohexene oxide. Among these, ethylene oxide and propylene oxide are particularly preferably used from the viewpoint of easy availability.
The above epoxides may be used alone or in combination of two or more. There is no restriction | limiting in particular about a carbon dioxide, The thing of the purity normally marketed can be used.
The aliphatic polycarbonate of component (B) used in the present invention preferably has a weight average molecular weight of 100,000 to 1,000,000, more preferably 150,000, from the viewpoint of mechanical properties and film forming stability. ~ 500,000.

As the blending ratio of the component (A) and the component (B) in the biodegradable resin composition of the present invention, in particular, the moldability when molding the resin composition to produce a biodegradable film is obtained. From the viewpoint of mechanical properties of the biodegradable film, the component (A) is 5 to 99 mass%, preferably 60 to 80 mass%, based on the total amount of the component (A) and the component (B).
By making aliphatic polyester into 5 mass% or more, blocking of a pellet can be prevented and the improvement effect of the moldability at the time of manufacturing a biodegradable film is acquired.
Moreover, the improvement effect of water vapor | steam barrier property is acquired in the biodegradable film formed from the resin composition of this invention by making aliphatic polyester into 99 mass% or less.
In the biodegradable resin composition of the present invention, the water vapor barrier property of the film formed therefrom is preferably 1.2 to 5.0 times the water vapor barrier property of the film formed from the resin of component (A) alone. The biodegradation rate is preferably 0.1 to 0.5 times that of the film formed from the resin of component (A) alone. In the biodegradable resin composition of the present invention, when the component (A) is 60 to 80% by mass and the component (B) is 40 to 20% by mass, the water vapor barrier property and the biodegradation rate ratio in the above ranges are set. You can have it.
In addition, the water vapor barrier property in this invention is the resin composition which consists of a component (A) and a component (B) in the water vapor permeability (water vapor permeability) of the film produced from the resin of the component (A) independent measured based on JISZ0208. It is represented by a numerical value divided by the moisture permeability of a film produced from the product.
In the present invention, as will be described later, a 10 cm square film cut at a depth of about 10 cm from the ground at a specific location is embedded in a nylon mesh for one month, and then the mass loss is measured. The rate of decrease is taken as the biodegradation rate.

  As a method for producing the biodegradable resin composition of the present invention, an extruder used when melt-mixing a thermoplastic resin may be used, but component (A) and component (B) are dry blended. The biodegradable resin composition can also be prepared only by the above.

In addition, the biodegradable resin composition of the present invention includes additives that are usually used in the technical field as desired, for example, antioxidants, heat stabilizers, ultraviolet inhibitors, antistatic agents, flame retardants, crystals. Accelerators, plasticizers and the like may be added as long as the properties of the present invention are not impaired.
Specifically, hindered phenol-based antioxidants such as 2,6-di-t-butyl-p-cresol and 3,5-di-t-butyl-4-hydroxyanisole as antioxidants; As the agent, triphenyl phosphite, trisnonylphenyl phosphite, etc .; As the ultraviolet absorber, pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2 ^, -carboxybenzophenone 2,4,5-trihydroxybutyrophenone, etc .; N, N-bis (hydroxyethyl) alkylamine, alkylamine, alkylarylsulfonate, alkylsulfonate, etc. as antistatic agent; Hexabromocyclododecane, Tris as flame retardant -(2,3-dichloropropyl) phosphate, pentabromofete Nyl allyl ether and the like; Examples of the crystallization accelerator include talc, holon nitrite, polyethylene terephthalate, poly-transcyclohexanedimethanol terephthalate and the like.

Next, the biodegradable film of the present invention formed by molding the biodegradable resin composition will be described.
As the method for producing the biodegradable film of the present invention, for example, as described above, the component (A) and the component (B) are melt mixed at a temperature of about 130 to 230 ° C., preferably about 150 to 200 ° C. with an extruder. Can be produced continuously by connecting the extruder outlet to a known water-cooled or air-cooled inflation molding, T-die type film molding machine without pelletizing or flaking. it can. This is preferable because the thermal history and shear history are reduced, so that the physical properties of the obtained film and the like can be prevented from being lowered.
Alternatively, the biodegradable resin composition may be once pelletized or flaked and then molded using a known water-cooled or air-cooled inflation molding or T-die type film extruder.
Further, the biodegradable resin composition prepared by dry blending as described above may be supplied to an inflation molding machine or the like without being pelletized or flaked to produce a film or the like. This is preferable because the thermal history and shear history are reduced in the same manner as in continuous production, so that the physical properties of the obtained film and the like can be prevented from being lowered.

As described above, the biodegradable resin composition once pelletized or flaked or the dry-degraded biodegradable resin composition is used instead of continuously producing the film following the preparation of the biodegradable resin composition. When manufacturing a film using a product, the set temperature of the inflation molding or T-die type film extrusion molding machine is about 130 to 180 ° C, preferably about 145 to 170 ° C.
The biodegradable film of the present invention may be obtained by further uniaxially or biaxially stretching the film.
Since the biodegradable resin composition of the present invention has improved moldability when it is formed into a biodegradable film, the productivity is improved, and the obtained biodegradable film has a water vapor barrier property. Has been improved, it is suitably used for biodegradable compost bags, agricultural films and packaging materials.

  The present invention will be described in more detail with reference to examples and comparative examples below, but the present invention is not limited to the following examples.

[Examples 1 to 9 and Comparative Examples 1 to 4]
Table 1 shows the types of aliphatic polyester (A) and aliphatic polycarbonate (B), and the respective amounts (% by mass). The raw materials in each example were mixed in a tumbler and melt-kneaded using a 30 mm screw twin screw extruder (L / D is 25) equipped with a vent made by Ikekai Tekko, and the biodegradable resin composition Pellets were obtained. The set temperature is 150 to 180 ° C.
The pellets obtained in each example were dried at a temperature of 70 ° C. for 3 hours with a dehumidifying air circulation dryer, and then a thickness of 30 μm and a folding width of 300 mm (equivalent to a blow-up ratio = 3) using an inflation molding machine manufactured by Yoshii Tekko Co., Ltd. A film was formed. The molding temperature is 165 ° C.

The measuring method of each characteristic is shown below.
<MFR>
Based on JIS K7210, the measurement was performed under conditions of a temperature of 190 ° C. and a load of 21.18 MPa.
<Biodegradability (biodegradation rate)>
A film cut to 10cm square is embedded in nylon mesh at a depth of about 10cm from the ground in Showa Polymer Co., Ltd.'s Tatsuno Plant, and embedded for 1 month. Degradation rate. Considering performance required for practical use such as agricultural mulch (If the biodegradation speed is significantly faster than the period of use, problems such as tearing and scattering will occur, and if it is extremely slow, it will remain undecomposed even if it is swallowed. Then, the following four rankings were performed and shown in Table 1. In addition, the biodegradation rate of the film obtained from each resin composition was divided by the biodegradation degree of the film obtained from the resin of the aliphatic polyester (A) alone, and the biodegradation rate ratio is shown in Table 1.
◎: Less than 30 to 60% ○: Less than 10 to 30% Δ: 60 to less than 80% ×: 80% or more or less than 10% <Film formability>
A three-level evaluation was performed as follows.
○: When the bubble is stable and a film with a predetermined size is obtained. Δ: When the bubble is unstable and the film with a predetermined size cannot be adjusted. ×: When the bubble does not stand up or puncture occurs and cannot be formed. <Physical properties of film>
A four-step evaluation was made based on the results measured by the following method.
A: When the tensile strength at break is 20 MPa or more, the tensile elongation at break is 200% or more, the Young's modulus is 250 to 500 MPa, and the impact strength is 2000 Ncm / mm or more. ○: When any one of the above items is not achieved. When the item is not achieved x: When any of the above three items is not achieved Each measurement method is as follows.
-Tensile strength at break: Measured according to JIS Z-1702.
-Tensile elongation at break: measured according to JIS Z-1702.
-Young's modulus: measured according to ASTM D-822.
Impact strength: measured according to JIS P-8134.
The above-mentioned mechanical properties were measured for each film only when the film formability was evaluated as ◯ or Δ and a film was obtained. Mechanical properties other than impact strength were measured in both the vertical direction (film take-up direction, MD) and the horizontal direction (TD).
<Blocking>
About blocking, it evaluated by the following methods with the opening degree of the shape | molded film. The films immediately after film formation were ranked according to the following criteria and are shown in Table 1.
◎: Open with a light touch ○: Ordinarily twist with a finger and open once or twice △: Ordinarily twist with a finger and open 3 to 5 times ×: Strongly twist with a finger 6 or more times Barrier properties>
For the water vapor barrier property, the water vapor permeability (g / m ² · day · atm) was measured according to JIS Z0208 (40 ° C.) using a molded film having a thickness of 30 μm, and the aliphatic polyester (A) alone was used. The water vapor permeability of the film obtained from the resin was divided by the water vapor permeability of the film obtained from that of each resin composition, and the water vapor barrier properties are shown in Table 1. The water vapor permeability was ranked according to the following criteria, and the results are shown in Table 1.
◎: less than ^{50g / m 2 · day · atm} ○: 50~100g / m less than ^{2 · day · atm △: 100~300g} / m 2 · day · atm less than ^{×: 300g / m 2 · day} · atm or more

<Materials used>
(1) Aliphatic polyester (A): Dehydrated condensation type aliphatic polyester manufactured by Showa Polymer Co., Ltd. [Bionole 3001G (melting point: 95 ° C., MFR; 1.2 g / 10 min)]
In Table 1, this aliphatic polyester (A) is indicated as A-1.
(2) Aliphatic polyester (A): Dehydration condensation type aliphatic polyester manufactured by Showa Polymer Co., Ltd. [Bionole 1001G (melting point: 114 ° C., MFR; 1.2 g / 10 min)]
This aliphatic polyester (A) is indicated as A-2 in Table 1.
(3) Aliphatic polyester (A): Polycaprolactone manufactured by Daicel Chemical Industries, Ltd. [Placcel H-7 (melting point: 60 ° C., MFR; 3.5 g / 10 min)]
In Table 1, this aliphatic polyester (A) is indicated as A-3.
(4) Aliphatic polycarbonate (B):
Polypropylene carbonate was synthesized using yttrium trichloroacetate-glycerin-diethyl zinc having a molar ratio of 1:10:20 as a three-way catalyst.
The catalyst was prepared by the following procedure. Glycerin: yttrium trichloroacetate was added to 1,4-dioxane at a molar ratio of 10: 1, and the temperature of the reaction mixture was kept below 25 ° C. in the presence of carbon dioxide, and yttrium trichloroacetate: dihydrocarbyl zinc Three-way catalyst suspension was prepared by adding dihydrocarbyl zinc dropwise at a molar ratio of 1:20 and then aging for 3 hours in an atmosphere of carbon dioxide. The amount of 1,4-dioxane used was an amount corresponding to 40 ml with respect to 0.002 to 0.02 mol of dihydrocarbyl zinc.
Polymerization of polypropylene carbonate was performed as follows.
First, 166 g of propylene oxide was charged into a 500 ml capacity pressure cooker. Then, an effective amount of the aged three-way catalyst is added in an amount of 8% by mass to an effective catalyst amount of 3.0 g, and immediately charged with carbon dioxide to bring the temperature to 65 ° C. The reaction was started. Carbon dioxide consumed during the reaction was replenished, and the copolymerization reaction was carried out for 10 hours while maintaining the pressure in the kettle at 3.5 MPa (absolute pressure) and the temperature at 65 ° C. until the reaction was completed.
Next, 1.5 times (mass ratio) of methanol is added to the reaction product to stop the reaction, and further 5 times (mass ratio) of methanol is added to the reaction product to wash, and after drying, 98.4 g of white polypropylene carbonate was obtained. The catalyst efficiency was 6,500 g of polypropylene carbonate per mole of diethyl zinc. Polypropylene carbonate had a weight average molecular weight of 80,000, a carbon dioxide fixation rate of 40% by mass or more, and an alternating structure content of 95% or more.
This polypropylene carbonate is indicated as B-1 in Table 1.

  From the results shown in Table 1, the biodegradable resin composition of the present invention is superior in film formability compared with the comparative example, and the obtained biodegradable film is mechanical compared with the comparative example. It can be seen that the strength is excellent and the balance between the anti-blocking performance and the water vapor barrier performance is excellent.

  The biodegradable resin composition of the present invention is excellent in film moldability, and the obtained biodegradable film is excellent in the balance between anti-blocking performance and water vapor barrier performance, and is further excellent in mechanical performance, compost bag, It is suitably used as an agricultural film and packaging material.

Claims (10)

  A biodegradable resin composition comprising a combination of aliphatic polyester (A) 5 to 99% by mass and aliphatic polycarbonate (B) 95 to 1% by mass obtained by alternating copolymerization of carbon dioxide and epoxide. .   The biodegradable resin composition according to claim 1, wherein the biodegradation rate ratio is 0.1 to 0.6 in the case of (A) alone.   The biodegradable resin composition according to claim 1 or 2, wherein the epoxide is propylene oxide.   The biodegradable resin composition according to any one of claims 1 to 3, wherein (B) does not substantially contain an amount of a catalyst sufficient to further polymerize or depolymerize itself and (A).   The raw material according to any one of claims 1 to 4, wherein (A) is an aliphatic polyester obtained by copolymerization of an aliphatic polycarboxylic acid and an aliphatic polyol and having a weight average molecular weight of 30,000 to 300,000. Degradable resin composition.   The weight average obtained by further coupling (A) a prepolymer having a weight average molecular weight of 30,000 to 50,000 obtained by copolymerization of an aliphatic polycarboxylic acid and an aliphatic polyol with a polyisocyanate. The biodegradable resin composition according to any one of claims 1 to 5, which is an aliphatic polyester having a molecular weight of 100,000 to 300,000.   (A) is a polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, polybutylene adipate terephthalate, poly-3-hydroxybutyrate, poly-3-hydroxybutyrate-3-hydroxyvalerate copolymer, poly The biodegradable resin according to any one of claims 1 to 6, which is at least one selected from 3-hydroxybutyrate-3-hydroxyhexanoate copolymer, polylactic acid, polycaprolactone, and a copolymer thereof. Composition.   The biodegradable resin composition according to any one of claims 1 to 7, wherein the (A) and the (B) are dry blended.   The biodegradable film formed by shape | molding the biodegradable resin composition in any one of Claims 1-8.   The biodegradable film according to claim 9, wherein the water vapor barrier property (based on JIS Z0208) is 1.2 to 20.0 times that of the film obtained from the resin (A) alone.