JP3620170B2 - Method for producing polylactic acid copolymer and polylactic acid copolymer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a biodegradable plastic having improved transparency, flexibility, impact resistance and the like.
[0002]
[Prior art]
In recent years, from the viewpoint of protecting the natural environment, biodegradable polymers that can be decomposed in the natural environment and molded products thereof have been demanded, and research on natural degradable resins such as aliphatic polyesters has been actively conducted. In particular, a lactic acid-based polymer has a sufficiently high melting point of 170 to 180 ° C. and is excellent in transparency, and thus is highly expected as a packaging material. However, polylactic acid has a drawback that it is inferior in impact resistance and brittle due to its rigid molecular structure, and improvement of these lactic acid polymers is desired.
[0003]
Regarding the improvement of lactic acid-based polymers, for example, JP-A-7-173266 describes a copolymer of polylactic acid and other aliphatic polyesters and a method for producing the same. As the production method, lactide and an aliphatic dicarboxylic acid component composed of various constituent ratios and / or a polyester polymer composed of an aromatic dicarboxylic acid and a diol component are reacted in the presence of a ring-opening polymerization catalyst. As the reaction mechanism, it is considered that lactide ring-opening addition polymerization to the terminal OH group of the polyester forms an A-B-A type block copolymer, and further the ester exchange reaction between the polymers proceeds. ing. Furthermore, it is said that a lactic acid copolymer polyester containing no homopolymer can be obtained by sufficiently carrying out this transesterification reaction. Moreover, it is described that the polymer obtained by this method is excellent in transparency and flexibility.
[0004]
However, in the method described in JP-A-7-173266, block copolymerization and transesterification are difficult to control, and the polylactic acid segment size and the polyester polymer segment size in the resulting copolymer cannot be guaranteed, and are not manufactured. The physical properties of the polymer are not stable. That is, block copolymerization is a technique that is often used to improve impact resistance, but if the polymer segment is split by random transesterification, the effect of adding a modifier cannot be exhibited.
[0005]
Further, in copolymerization with a high molecular weight aliphatic polyester, it is difficult to obtain a copolymer having excellent transparency and flexibility because of the high crystallinity of the aliphatic polyester itself. On the other hand, in the copolymerization with a low molecular weight aliphatic polyester, the OH group concentration acting as a reaction initiator becomes high, so it is difficult to obtain a high molecular weight copolymer that can withstand post-processing.
[0006]
That is, in practice, polymers that can be copolymerized as a modifier to obtain transparency and flexibility are greatly limited, and it is very important to control the size of each component segment in the copolymer.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a biodegradable lactic acid copolymer having sufficient high molecular weight and excellent impact resistance, transparency and flexibility by controlling the segment size of various polymers. It is in.
[0008]
[Means for Solving the Problems]
In order to solve such problems, the present inventors have intensively studied, and as a result, one or more ring-opening polymerization catalysts and one or more kinds of carbamic acid are obtained by urethane-crosslinking polyurethanes of lactide and polyols having various constituent ratios. Flexible and transparent lactic acid copolymer having better internal plastic effect by ring-opening copolymerization and ester and / or ester amide exchange reaction in the presence of ester exchange and / or ester amide exchange catalyst for ester I found that a coalescence could be produced.
[0009]
That is, the present invention relates to transesterification of lactide (A) 50 to 99% by weight and polyurethane (B) 1 to 50% by weight with respect to one or more ring-opening polymerization catalysts (C) and one or more carbamates. Alternatively, it is a method for producing a lactic acid copolymer in which ring-opening copolymerization and ester and / or ester amide exchange reaction are carried out in the presence of an ester amide exchange catalyst (C ′).
[0010]
Moreover, this invention is a manufacturing method of the above-mentioned lactic acid-type copolymer whose weight average molecular weights of a polyurethane (B) are 10,000-500,000. Furthermore, the present invention provides a method for producing the above-mentioned lactic acid-based copolymer containing 0.1 to 10% by weight of nitrogen in the polyurethane (B) molecule, and the above-mentioned lactic acid-based copolymer wherein the polyurethane (B) is a polyester polyurethane. A method for producing a coalescence, a method for producing the above-mentioned lactic acid copolymer having a lower melting point or softening point of polyurethane (B), which is 200 ° C. or lower, and the ring-opening polymerization catalyst (C) are a tin compound and a titanium compound. A method for producing a certain lactic acid-based copolymer, a ring-opening polymerization catalyst (C), and a transesterification and / or ester amide-exchange catalyst (C ′) for a carbamate, wherein the lactic acid-based copolymer is tin octylate. A method for producing a polymer, a method for producing a lactic acid copolymer described above having a melting point of 150 ° C. or higher, and a lactic acid copolymer produced by the production method.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the lactide, polyurethane, and catalyst used in the present invention will be described in order.
The lactide (A) used in the present invention is a compound obtained by cyclic dimerization of lactic acid, and consists of two L-lactides composed of L-lactic acid, D-lactide composed of D-lactic acid, L-lactic acid and D-lactic acid. There are three types of lactide, meso-lactide.
[0012]
A copolymer containing only L-lactide or D-lactide crystallizes to obtain a high melting point. The lactic acid-based copolymer of the present invention can obtain more favorable characteristics by combining these three types of lactide.
[0013]
In the present invention, in order to obtain a high melting point, the lactide preferably contains L-lactide in an amount of 75% or more in the total lactide, and in order to obtain a higher melting point, the lactide contains 90% or more in the total lactide. preferable.
[0014]
The polyurethane (B) used in the present invention means a polymer containing at least two urethane bonds in the molecule. When considering the reaction with lactide, the polyurethane (B) to be used preferably has a melting point or a softening point which is lower than 200 ° C., particularly preferably 80 to 170 ° C. Here, the melting point referred to in the present invention is a value measured using a scanning differential calorimeter (DSC), and the softening point conforms to JIS K-2531.
[0015]
In general, polyurethane is a common name for a polymer containing a urethane bond (—NHCOO—) in a molecule. This is not obtained by polymerization of monomers, but is usually obtained by reaction of polyisocyanate with a compound having active hydrogen such as a hydroxyl group, for example, polyol. At this time, polyurethanes having various characteristics can be obtained depending on the components and molecular weight of the polyol used as a raw material. The polyurethane (B) preferably contains 0.1 to 10% by weight of nitrogen in the molecule. If the amount is 0.1% by weight or less, the modification effect due to the modification is small. On the other hand, if the amount is 10% by weight or more, the number of reactive sites is too large, resulting in a highly random copolymer and lowering thermal properties.
[0016]
Although it does not specifically limit as a polyol component in a polyurethane (B), Specifically, a polyester polyol, polyether polyol, a polycarbonate polyol, etc. are mention | raise | lifted.
In particular, polyester polyols are generally obtained by polycondensation of polyfunctional carboxylic acids and polyfunctional hydroxy compounds, but polycondensation of hydroxycarboxylic acids, polymerization of cyclic esters (lactones), polyaddition of epoxides to polycarboxylic acid anhydrides. It can also be obtained by a reaction between an acid chloride and an alkali salt of a hydroxy compound, a transesterification reaction or the like.
[0017]
Furthermore, the dicarboxylic acid component in the polyester polyol is not particularly limited, and examples thereof include adipic acid, orthophthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, and sebacic acid. The diol component in the polyester polyol is not particularly limited as long as it is a diol, but ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,5-pentanediol, cyclohexanedimethanol and the like can be mentioned.
[0018]
In the urethane foam, a polyester polyol having a slight branch is usually used. Branching is obtained by the use of branching agents such as polycarboxylic acids or polyhydric alcohols.
[0019]
The polyurethane (B) used in the present invention is a polymer containing at least two or more urethane bonds in a molecule, in which a desired amount of isocyanate is added to these various polyols as raw materials and crosslinked. There is no restriction | limiting in particular in the kind of isocyanate used for bridge | crosslinking of a polyol, A commercially available thing is used as it is, for example, 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, And mixtures thereof, diphenylmethane diisocyanate, 1,6-naphthalene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and the like. Furthermore, polyisocyanates can also be used, thereby allowing branching in the molecule. The molecular weight of the raw material polyol used at this time and the molecular weight (degree of polymerization) of the polyurethane (B) cross-linked with isocyanate greatly influence the transparency, flexibility, and molecular weight of the lactic acid copolymer produced thereafter. The weight average molecular weight of the polyurethane (B) is preferably 10,000 to 500,000. If it is 10,000 or less, the terminal OH concentration of polyurethane becomes high and a high molecular weight copolymer cannot be obtained, and if it is 500,000 or more, it is difficult to carry out a uniform reaction due to high viscosity.
[0020]
Moreover, since the polyurethane (B) has a branch, a copolymer having a large Mw / Mn value, which is a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), can be easily obtained. It is known that this generally has good film formability.
[0021]
Examples of the ring-opening polymerization catalyst (C) used in the present invention include metals such as tin, zinc, lead, titanium, bismuth, zirconium, germanium and derivatives thereof, which are generally known as ring-opening polymerization catalysts for cyclic esters. Of these derivatives, metal compounds, carboxylates, carbonates, oxides, and halides are particularly preferable. Specific examples include tin chloride, tin octylate, zinc chloride, zinc acetate, lead oxide, lead carbonate, titanium chloride, alkoxytitanium, germanium oxide, zirconium oxide and the like. Acid tin is preferred.
[0022]
The transesterification and / or ester amide exchange catalyst (C ′) for the carbamic acid ester used in the present invention may be a metal compound generally used for the polymerization reaction of isocyanate or the reaction of isocyanate with an active hydrogen-containing compound, particularly tin. Compounds are preferred. Furthermore, in order to obtain more excellent transparency and flexibility, tin octylate is particularly preferable.
[0023]
The addition amount of the ring-opening polymerization catalyst (C) is preferably 0.0001 to 0.3 parts by weight with respect to the weight of the lactide (A). The amount of the ester exchange and / or ester amide exchange catalyst (C ′) relative to the carbamate is preferably 0.0001 to 0.3 parts by weight relative to the weight of the polyurethane (B). Furthermore, the total amount of the ester exchange and / or ester amide exchange catalyst (C ′) relative to the ring-opening polymerization catalyst (C) and the carbamate is 0 with respect to the total weight of the lactide (A) and the polyurethane (B). 0002-0.6% by weight is preferred. Depending on the addition amount ratio of the transesterification and / or transesterification catalyst (C ′) to the ring-opening polymerization catalyst (C) and the carbamate, the rate of ring-opening polymerization of lactide (A), lactide (A) and polyurethane (B The rate of transesterification and / or ester amide exchange with respect to the carbamic acid ester of) is controlled, whereby a lactic acid copolymer excellent in transparency and impact resistance as compared with conventional copolymers can be obtained. In addition, the total amount of the ester exchange and / or ester amide exchange catalyst (C ′) relative to the ring-opening polymerization catalyst (C) and the carbamate ester varies depending on the production method, but the thermal stability of the resulting lactic acid copolymer is increased. When considered, 0.1% by weight or less is preferable.
[0024]
Next, a manufacturing method is demonstrated in order.
The mixture of lactide (A) and polyurethane (B) is heated and melted, and the ring-opening polymerization catalyst (C) and the ester exchange and / or ester amide exchange catalyst (C ′) for the carbamate are added. When the reaction temperature is equal to or higher than the melting point of lactide, the reaction system can be made uniform and a high polymerization rate can be obtained. In particular, for the equilibrium of the reaction, a temperature of the melting point of lactide of about 100 ° C. or higher and 180 ° C. or lower is desirable, and the coloration of the copolymer and the decrease in molecular weight accompanying the decomposition reaction can be reduced.
[0025]
That is, it is preferable to react after melting the lactide (A) and further dissolving and mixing the polyurethane (B) to be copolymerized in the lactide (A). In order to prevent decomposition and coloring of the copolymer, the reaction is preferably performed in a dry inert gas atmosphere. In particular, a nitrogen or argon gas atmosphere or a bubbling state is good. Furthermore, the polyurethane (B) as a raw material for suppressing the hydrolysis reaction needs to be sufficiently vacuum-dried in order to remove moisture.
[0026]
The polymerization reaction includes a reaction in which lactide undergoes ring-opening addition polymerization in a block form to the terminal OH group of the polyurethane used for copolymerization, and an ABA type block copolymer is formed. Transesterification and / or ester amide exchange reaction for a certain polylactic acid and a carbamate ester in polyurethane proceed in parallel, and a ring-opening polymerization catalyst (C) and a transesterification and / or ester amide exchange catalyst for a carbamate ester The relationship between the two reaction rates is determined by the addition amount ratio of (C ′). Thereby, a lactic acid copolymer having various physical properties from a copolymer having a strong block property to a copolymer having a strong random property can be freely obtained. In particular, with an appropriate addition amount ratio, it is possible to obtain a lactic acid-based copolymer having high thermal characteristics comparable to that of a block copolymer and excellent transparency and flexibility comparable to that of a random copolymer.
[0027]
The lactic acid copolymer of the present invention can be prepared in a known reaction vessel, for example, a vertical reaction vessel or a horizontal reaction vessel in which a uniaxial or multiaxial agitator is disposed, and a uniaxial or multiaxial scraping. A horizontal reaction vessel provided with blades, a single- or multi-axis kneader, or a single- or multi-axis extruder may be used alone, or multiple units are connected in series or in parallel. May be used.
[0028]
In the present invention, the lactic acid copolymer produced has good biodegradability and is useful for reducing the amount of waste after use and in the production process. In particular, it is excellent in decomposability in compost and can be decomposed until the external shape is not maintained within several months. As the use of the lactic acid copolymer produced in the present invention, it can be molded into a sheet, a film, etc., and used for packaging materials such as trash bags, plastic bags, paper packs, cases, etc., but is not limited thereto. Not.
[0029]
Further, the lactic acid copolymer of the present invention can be subjected to various modifications by adding secondary additives. Examples of secondary additives include stabilizers, antioxidants, UV absorbers, pigments, colorants, various fillers, electrostatic agents, mold release agents, plasticizers, perfumes, antibacterial agents, nucleating agents, etc. The similar thing is mentioned.
[0030]
In the present invention and the following examples, the weight average molecular weight of the polymer is a polystyrene conversion value by GPC analysis, and the melting point is a measurement value by a scanning differential calorimeter (DSC). The tensile test was measured according to JIS-K7113, and the Izod impact test was measured according to JIS-K7110. Furthermore, the transparency measured haze according to JIS-K7105.
The synthesis of polyurethane and polyester in Examples and Comparative Examples was made with reference to JP-A-4-189822, JP-A-4-189823, and JP-A-6-293826.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
[0032]
(Example 1)
After mixing and esterifying 216 g of 1,4-butanediol and 236 g of succinic acid in a nitrogen gas atmosphere at 210 to 220 ° C. to give an acid value of 7.9, 1.2 g of tetrabutyl titanate was added to the mixture as a catalyst, Finally, the pressure was reduced to 0.6 torr and deglycolization reaction was carried out for about 5 hours to synthesize a polyester polyol having a weight average molecular weight of 32,000. Subsequently, the temperature was lowered to 190 ° C., 4 g of hexamethylene diisocyanate was added and urethane crosslinking was carried out to obtain a polyester polyurethane (PU1) having a weight average molecular weight of 100,000. To 20 parts by weight of the obtained polyester polyurethane (PU1), 80 parts by weight of L-lactide is added and melt-mixed in an inert gas atmosphere, and 0.10 parts by weight of tin octylate as a ring-opening polymerization catalyst is added to the carbamate. 0.14 parts by weight of di-n-butyltin dilaurate was added as a transesterification and / or transesterification catalyst, polymerized at 190 ° C. for 15 minutes while stirring with a twin-screw kneader, extruded through a nozzle with a diameter of 2 mm, and water-cooled. The lactic acid copolymer chip C1 was obtained by cutting.
[0033]
The chip C1 was treated in nitrogen at 120 ° C. and a pressure of 1.5 kg / cm ² for 12 hours to remove unreacted monomer (lactide) to obtain a chip C2. Chip C2 had a weight average molecular weight of 155,000 and a residual monomer (lactide) of 0.1%. As a result of measuring DSC of this lactic acid copolymer, no glass transition temperature was observed, and two melting points of 91 ° C. and 169 ° C. were observed.
[0034]
Furthermore, after the chip C2 was vacuum-dried at 75 ° C. to make it completely dry, a business card large plate (1 mmt), a tensile test piece (No. 2 type test piece), and an Izod impact test piece (No. 2 A test piece) by injection molding. Was molded. The obtained business card large plate was subjected to a haze, tensile and Izod impact test. As a result, the haze was 1%, the tensile elastic modulus was 0.2 GPa, and the Izod impact strength was 60 kJ / m ² or more (no breakage).
[0035]
(Example 2)
After mixing and esterifying 255 g of 1,4-butanediol, 202 g of succinic acid and 29 g of adipic acid in a nitrogen gas atmosphere at 200 to 210 ° C. to make the acid value 9.1, 1 g of tetrabutyl titanate was used as a catalyst for the mixture. In addition, the reaction was allowed to proceed and finally, the pressure was reduced to 0.7 torr and deglycolization reaction was performed for about 5 hours to synthesize a polyester polyol having a weight average molecular weight of 30,000. Subsequently, the temperature was lowered to 190 ° C., 5 g of hexamethylene diisocyanate was added and urethane crosslinking was carried out to obtain a polyester polyurethane (PU2) having a weight average molecular weight of 95,000. To 30 parts by weight of the obtained polyester polyurethane (PU2), 70 parts by weight of L-lactide is added and melt-mixed in an inert gas atmosphere, and used as a ring-opening polymerization catalyst and a transesterification and / or ester amide exchange catalyst for a carbamate. After adding 0.24 parts by weight of tin octylate and polymerizing at 190 ° C. for 15 minutes while stirring with a twin-screw kneader, the mixture was extruded with a nozzle having a diameter of 2 mm, cooled with water and cut to obtain a lactic acid copolymer chip C3. Obtained.
[0036]
Chip C3 was treated in nitrogen at 120 ° C. under a pressure of 1.5 kg / cm ² for 12 hours to remove unreacted monomer (lactide), thereby obtaining chip C4. Chip C4 had a weight average molecular weight of 140,000 and a residual monomer (lactide) of 0.1%. As a result of measuring DSC of this lactic acid-based copolymer, two glass transition temperatures of 20 ° C., melting points of 85 ° C. and 167 ° C. were observed.
[0037]
Further, after the chip C4 is vacuum dried at 75 ° C. to be in an absolutely dry state, a business card large plate (1 mmt), a tensile test piece (No. 2 type test piece) and an Izod impact test piece (No. 2 A test piece) are formed by injection molding. Was molded. As a result of carrying out the haze, tensile and Izod impact test of the obtained business card large plate, the haze was 1%, the tensile modulus was 0.05 GPa, and the Izod impact strength was 60 kJ / m ² or more (no breakage).
[0038]
(Comparative Example 1)
162 g of 1,4-butanediol and 146 g of dimethyl succinate were mixed in a nitrogen gas atmosphere, 0.03 g of tetrabutyl titanate was added to the mixture as a catalyst, and the ester was stirred until a theoretical amount of methanol was discharged at 200 to 210 ° C. The reaction was allowed to proceed. Subsequently, 0.3 g of tetrabutyl titanate and 0.8 g of dibutyltin oxide were added to 1,4-butanediol as a slurry, mixed at 230 ° C. for 10 minutes, and then heated to 250 ° C. while increasing the pressure. A polycondensation reaction was carried out at 0.3 mmHg for 5 hours to obtain a polyester (PE1) having a weight average molecular weight of 140,000. To 20 parts by weight of the obtained polyester (PE1), 80 parts by weight of L-lactide is added, melted and mixed in an inert gas atmosphere, and 0.24 parts by weight of tin octylate is added as a ring-opening polymerization catalyst. Polymerization was carried out at 190 ° C. for 15 minutes while stirring with a machine, followed by extrusion with a nozzle having a diameter of 2 mm, cooling with water and cutting to obtain a lactic acid copolymer chip C5.
[0039]
Chip C5 was treated in nitrogen at 120 ° C. under a pressure of 1.5 kg / cm ² for 12 hours to remove unreacted monomer (lactide), thereby obtaining chip C6. Chip C6 had a weight average molecular weight of 123,000 and a residual monomer (lactide) of 0.1%. As a result of measuring DSC of this lactic acid-based copolymer, two glass transition temperatures of 50 ° C., melting points of 102 ° C. and 172 ° C. were observed.
[0040]
Further, after the chip C6 was vacuum-dried at 75 ° C. and completely dried, a business card large plate (1 mmt), a tensile test piece (No. 2 type test piece) and an Izod impact test piece (No. 2 A test piece) were formed by injection molding. Was molded. As a result of carrying out the haze, tensile and Izod impact tests of the obtained business card large plate, the haze was 10%, the tensile modulus was 1.7 GPa, and the Izod impact strength was 3 kJ / m ² .
[0041]
(Comparative Example 2)
162.2 g of 1,4-butanediol, 118.7 g of dimethyl succinate and 36.2 g of dimethyl adipate as acid components were mixed in a nitrogen gas atmosphere, and 0.03 g of tetrabutyl titanate was added as a catalyst to the mixture. The esterification reaction was allowed to proceed at 200-210 ° C. until the theoretical amount of methanol had flowed out. Subsequently, 0.3 g of tetrabutyl titanate and 0.8 g of dibutyltin oxide were added to 1,4-butanediol as a slurry, mixed at 230 ° C. for 10 minutes, and then heated to 250 ° C. while increasing the pressure. A polycondensation reaction was carried out at 0.3 mmHg for 5 hours to obtain a polyester (PE2) having a weight average molecular weight of 147,000. Add 70 parts by weight of L-lactide to 30 parts by weight of the obtained polyester (PE2), melt and mix in an inert gas atmosphere, add 0.24 parts by weight of tin octylate as a ring-opening polymerization catalyst, and biaxially knead Polymerization was carried out at 190 ° C. for 15 minutes while stirring with a machine, followed by extrusion with a nozzle having a diameter of 2 mm, cooling with water and cutting to obtain a lactic acid copolymer C7.
[0042]
Chip C7 was treated in nitrogen at 120 ° C. and a pressure of 1.5 kg / cm 2 for 12 hours to remove unreacted monomer (lactide), thereby obtaining chip C8. Chip C4 had a weight average molecular weight of 100,000 and a residual monomer (lactide) of 0.1%. As a result of measuring DSC of this lactic acid copolymer, two points were observed: a glass transition temperature of 40 ° C., a melting point of 85 ° C., and a temperature of 171 ° C.
[0043]
Further, after the chip C8 was vacuum dried at 75 ° C. to make it completely dry, a business card large plate (1 mmt), a tensile test piece (No. 2 type test piece), and an Izod impact test piece (No. 2 A test piece) by injection molding. Was molded. The obtained business card large plate was subjected to a haze, tensile and Izod impact test. As a result, the haze was 5%, the tensile modulus was 1.1 GPa, and the Izod impact strength was 7 kJ / m 2.
[0044]
From the above examples and comparative examples, the molded products obtained from the chips C2 and C4 of the present invention have a small haze value, a low tensile elastic modulus, a high Izod impact strength, and clearly transparency, flexibility and impact resistance. Is excellent.
[0045]
【The invention's effect】
According to the present invention, it becomes possible to control the segment size of various polymers copolymerized with lactide, and the production of lactic acid-based copolymers with superior transparency and flexibility compared to copolymers with various polymers that do not contain urethane bonds. Is possible.

Claims (8)

Lactide (A) 50-99% by weight and polyurethane (B) 1-50% by weight of one or more ring-opening polymerization catalysts (C) and one or more transesterification and / or ester amide exchange catalysts for one or more carbamates ( A method for producing a lactic acid copolymer, in which ring-opening copolymerization and ester and / or ester amide exchange reaction are carried out in the presence of C ′). The method for producing a lactic acid copolymer according to claim 1, wherein the weight average molecular weight of the polyurethane (B) is 10,000 to 500,000. The method for producing a lactic acid-based copolymer according to claim 1 or 2, wherein the polyurethane (B) contains 0.1 to 10% by weight of nitrogen in the molecule. The method for producing a lactic acid copolymer according to any one of claims 1 to 3, wherein the polyurethane (B) is a polyester polyurethane. The method for producing a lactic acid copolymer according to any one of claims 1 to 4, wherein the polyurethane (B) has a branch. The method for producing a lactic acid copolymer according to any one of claims 1 to 5, wherein the lower melting point or softening point of the polyurethane (B) is 200 ° C or lower. The method for producing a lactic acid copolymer according to any one of claims 1 to 6, wherein the ring-opening polymerization catalyst (C) is a tin compound or a titanium compound. The lactic acid copolymer according to any one of claims 1 to 7, wherein the ring-opening polymerization catalyst (C) and the transesterification and / or ester amide exchange catalyst (C ') for the carbamate are tin octylates. Manufacturing method.