阅读说明：本技术 一种聚乳酸基共聚物及其制备方法 (Polylactic acid-based copolymer and preparation method thereof ) 是由 张宝 王天昶 边新超 冯立栋 陈学思 于 2021-11-11 设计创作，主要内容包括：本发明提供了一种聚乳酸基共聚物的制备方法,包括：将双端羧基聚乳酸与双端羧基聚酯混合,再采用环氧大豆油熔融扩链,得到聚乳酸基共聚物。与现有技术相比,本发明中的环氧大豆油作为共聚物链段,直接起到扩链剂的作用,避免了毒性较大的二异氰酸酯的使用；共聚物柔韧性好,力学性能高；共聚物熔体强度高,解决了聚乳酸加工性能差的问题；共聚物的合成解决了环氧大豆油易迁移和渗透的问题,提高了改性聚乳酸的稳定性；本发明工艺技术简单,制备成本低,共聚物具有良好的生物降解性。(The invention provides a preparation method of a polylactic acid-based copolymer, which comprises the following steps: mixing the double-end carboxyl polylactic acid and the double-end carboxyl polyester, and then adopting epoxy soybean oil to melt and extend a chain to obtain the polylactic acid-based copolymer. Compared with the prior art, the epoxidized soybean oil in the invention is used as a copolymer chain segment and directly plays a role of a chain extender, so that the use of diisocyanate with higher toxicity is avoided; the copolymer has good flexibility and high mechanical property; the copolymer has high melt strength, and solves the problem of poor processability of polylactic acid; the synthesis of the copolymer solves the problems of easy migration and permeation of epoxidized soybean oil, and improves the stability of the modified polylactic acid; the invention has simple process technology, low preparation cost and good biodegradability of the copolymer.)

1. A polylactic acid-based copolymer having the structure of formula I:

in the formula I, the compound is shown in the specification,is composed of

x＝30～200，m＝10～200，n＝0～100，p＝1～20，q＝1～20；

R is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected from alkylene, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl;

represents a copolymer repeat unit structure having the structure of formula II:

in the formula II, x is 30-200, m is 10-200, n is 0-100, r is 1-20, and s is 1-20;

r is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected from alkylene, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl.

2. The polylactic acid-based copolymer according to claim 1, wherein M in formula I and formula II is independently selected from- (CH)₂)_z-, z is 2 to 10; or;

3. a method for preparing a polylactic acid-based copolymer, comprising:

carrying out a first reaction on polylactic acid and succinic anhydride to obtain carboxyl-terminated polylactic acid;

carrying out a second reaction on the polyester and succinic anhydride to obtain double-end carboxyl polyester;

and carrying out chain extension reaction on the epoxidized soybean oil, the carboxyl-terminated polylactic acid and the carboxyl-terminated polyester to obtain the polylactic acid-based copolymer.

4. The method according to claim 3, wherein the preparation method of the polylactic acid comprises:

carrying out polycondensation reaction on lactic acid to obtain polylactic acid; or;

and (3) carrying out ring-opening polymerization on the diol and the lactide to obtain the dihydroxy polylactic acid.

5. The method according to claim 3, wherein the polyester is selected from one or more of aliphatic copolyester and aliphatic-aromatic copolyester.

6. The method according to claim 3, wherein the temperature of the first reaction is 120 to 200 ℃; the time is 3-30 hours.

7. The method according to claim 3, wherein the temperature of the second reaction is 130 to 180 ℃; the time is 1-10 hours.

8. The method according to claim 3, wherein the temperature of the chain extension reaction is 150-220 ℃; the time is 1-15 hours.

9. The method according to claim 3, wherein the polyester has a number average molecular weight of 5000 to 50000 and a melting point of 100 to 150 ℃.

10. The method according to claim 3, wherein the mass ratio of succinic anhydride to polylactic acid is (1-3): 1;

the mass ratio of the polyester to the succinic anhydride is 1: (0.5 to 3);

the ratio of the mass of the epoxidized soybean oil to the total mass of the double-end carboxyl lactic acid and the double-end carboxyl polyester is (1-20): (80-99);

the mass ratio of the double-end carboxyl lactic acid to the double-end carboxyl polyester is (1-9): (9-1).

Technical Field

The invention belongs to the field of high polymer materials, and particularly relates to a polylactic acid-based copolymer and a preparation method thereof, and more particularly relates to a polylactic acid-based polyester-epoxidized soybean oil copolymer and a preparation method thereof.

Background

With the increasing severity of environmental pollution, people put forward higher requirements on plastic packages, and the plastic packages are required to have no pollution to the environment while the use performance of materials is met. Polylactic acid (PLA) is a degradable green high polymer material based on biomass resources, is non-toxic and non-irritant, has the advantages of good biocompatibility, bioabsorbability and the like, but contains a large number of ester bonds, is poor in hydrophilicity, reduces the compatibility of the PLA with other substances, and is high in brittleness and poor in impact resistance, so that the wide use of the PLA is limited.

In view of the above-mentioned disadvantages of polylactic acid, many researchers have conducted extensive studies on modification of polylactic acid in recent years. Epoxidized soybean oil is a better modifier of polylactic acid, but the epoxidized soybean oil has a small molecular weight, so that the processing of the material is not facilitated, and the material performance is unstable due to the migration of small molecules after the epoxidized soybean oil is used, so that the application of the epoxidized soybean oil modified polylactic acid in the field of packaging is limited. Therefore, how to improve the flexibility and the melt strength of the polylactic acid and reduce the preparation cost of the product by a simple and effective method has very important social and economic values.

Disclosure of Invention

In view of the above, the present invention aims to provide a polylactic acid-based copolymer and a preparation method thereof, the polylactic acid-based copolymer prepared by the method provided by the present invention has the advantages of high molecular weight, high melt strength, good flexibility, low toxicity, simplicity, effectiveness and contribution to industrial production.

The invention provides a polylactic acid-based copolymer, which has a structure shown in a formula I:

in the formula I, the compound is shown in the specification,is composed of

x＝30～200，m＝10～200，n＝0～100，p＝1～20，q＝1～20；

R is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected fromHydrocarbyl radical, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl;

represents a copolymer repeat unit structure having the structure of formula II:

in the formula II, x is 30-200, m is 10-200, n is 0-100, r is 1-20, and s is 1-20;

r is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected from alkylene, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl.

Preferably, M in formula I and formula II is independently selected from- (CH)₂)_z-, z is 2 to 10; or;

the invention provides a preparation method of a polylactic acid-based copolymer, which comprises the following steps:

carrying out a first reaction on polylactic acid and succinic anhydride to obtain carboxyl-terminated polylactic acid;

carrying out a second reaction on the polyester and succinic anhydride to obtain double-end carboxyl polyester;

and carrying out chain extension reaction on the epoxidized soybean oil, the carboxyl-terminated polylactic acid and the carboxyl-terminated polyester to obtain the polylactic acid-based copolymer.

Preferably, the preparation method of the polylactic acid comprises the following steps:

carrying out polycondensation reaction on lactic acid to obtain polylactic acid; or;

and (3) carrying out ring-opening polymerization on the diol and the lactide to obtain the dihydroxy polylactic acid.

Preferably, the polyester is selected from one or more of aliphatic copolyester and aliphatic-aromatic copolyester.

Preferably, the temperature of the first reaction is 120-200 ℃; the time is 3-30 hours.

Preferably, the temperature of the second reaction is 130-180 ℃; the time is 1-10 hours.

Preferably, the temperature of the chain extension reaction is 150-220 ℃; the time is 1-15 hours.

Preferably, the number average molecular weight of the polyester is 5000-50000, and the melting point is 100-150 ℃.

Preferably, the mass ratio of the succinic anhydride to the polylactic acid is (1-3): 1;

the mass ratio of the polyester to the succinic anhydride is 1: (0.5 to 3);

the ratio of the mass of the epoxidized soybean oil to the total mass of the double-end carboxyl lactic acid and the double-end carboxyl polyester is (1-20): (80-99);

the mass ratio of the double-end carboxyl lactic acid to the double-end carboxyl polyester is (1-9): (9-1).

Compared with the prior art, the method has the advantages that polylactic acid reacts with succinic anhydride to obtain carboxyl-terminated polylactic acid; polyester and succinic anhydride are adopted to react to obtain double-end carboxyl polyester; then the double-end carboxyl group polylactic acid and the double-end carboxyl group polyester are subjected to chain extension reaction with the epoxy soybean oil to obtain the polylactic acid group polyester-epoxy soybean oil copolymer. The polylactic acid-based copolymer provided by the invention is composed of epoxidized soybean oil, polylactic acid and a polyester chain segment, the problem of poor compatibility of the epoxidized soybean oil and the polylactic acid is solved, the prepared epoxidized soybean oil copolymer solves the problems of migration and permeation of the epoxidized soybean oil in polylactic acid resin caused by a conventional blending method, and the introduction of the polyester improves the flexibility of the copolymer and solves the problem of hard and brittle polylactic acid; the preparation method provided by the invention adopts the epoxy group of the biomass to replace isocyanate as a chain extender for reaction, so that the toxicity of a reaction monomer is greatly reduced, and meanwhile, the synthesis method provided by the invention avoids the use of a solvent in the synthesis process, has the advantages of low toxicity, simplicity, high efficiency, low cost and good controllability, and is beneficial to industrial production. The modified components used in the invention are all degradable substances and have good biodegradability. In addition, the invention can synthesize and prepare products by a one-pot method, so that the process is simplified, and the cost is greatly reduced.

The invention tests the mechanical property of the prepared polylactic acid-based copolymer, and the specific process is as follows:

the polylactic acid-based copolymer of 70mm × 4mm × 1mm was placed on a tensile tester to perform tensile property test at a tensile rate of 20mm/min and a test temperature of 23 ℃, and the elongation at break of the polylactic acid-based copolymer was recorded. The test result shows that: the breaking elongation of the polylactic acid-based copolymer provided by the invention is up to 550%.

Drawings

FIG. 1 shows the nuclear magnetic spectrum of the poly (lactic acid-poly (butylene adipate-co-butylene terephthalate) -epoxidized soybean oil copolymer prepared in example 1 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other examples, which may be modified or appreciated by those of ordinary skill in the art based on the examples given herein, are intended to be within the scope of the present invention. It should be understood that the embodiments of the present invention are only for illustrating the technical effects of the present invention, and are not intended to limit the scope of the present invention. In the examples, the methods used were all conventional methods unless otherwise specified.

The invention provides a polylactic acid-based copolymer, which has a structure shown in a formula I:

in the formula I, the compound is shown in the specification,is composed of

x＝30～200，m＝10～200，n＝0～100，p＝1～20，q＝1～20；

R is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected from alkylene, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl;

represents a copolymer repeat unit structure having the structure of formula II:

in the formula II, x is 30-200, m is 10-200, n is 0-100, r is 1-20, and s is 1-20;

r is selected from alkylene- (CH)₂)_z-，z＝2～10；

T is selected from alkylene, - (CH)₂)_v-，v＝1～8；

M is selected from alkylene or aryl.

In the invention, x in the formula I and the formula II is independently preferably 50-150, more preferably 80-120, and most preferably 100; m is independently preferably 50-150, more preferably 80-120, and most preferably 100; n is preferably 10 to 90 independently, more preferably 20 to 80 independently, more preferably 30 to 60 independently, and most preferably 40 to 50 independently.

In the invention, p in the formula I is preferably 5-15, more preferably 8-12, and most preferably 10; q is preferably 5 to 15, more preferably 8 to 12, and most preferably 10.

In the invention, z in R in the formula I and the formula II is preferably 5-8 independently, and more preferably 6-7 independently; v in T is independently preferably 2 to 6, more preferably 3 to 5, and most preferably 4.

In the present invention, M in the formula I and the formula II is independently preferably- (CH)₂)_z-, z is 2 to 10; or

The invention provides a preparation method of a polylactic acid-based copolymer, which comprises the following steps:

carrying out a first reaction on polylactic acid and succinic anhydride to obtain carboxyl-terminated polylactic acid;

carrying out a second reaction on the polyester and succinic anhydride to obtain double-end carboxyl polyester;

and carrying out chain extension reaction on the epoxidized soybean oil, the carboxyl-terminated polylactic acid and the carboxyl-terminated polyester to obtain the polylactic acid-based copolymer.

In the invention, the number average molecular weight of the polylactic acid is preferably 5000-40000, more preferably 10000-30000, and most preferably 20000; the melting point is preferably 140 to 180 ℃, more preferably 150 to 170 ℃, and most preferably 160 ℃.

In the present invention, the method for preparing polylactic acid preferably comprises:

and carrying out polycondensation reaction on the lactic acid to obtain the polylactic acid.

In the present invention, the lactic acid is preferably one or more of levolactic acid and dextrolactic acid.

In the present invention, the polycondensation reaction is preferably carried out under the action of a catalyst; the catalyst is preferably selected from one or more of tetrabutyl titanate, zinc oxide, zinc chloride, aluminum oxide, iron oxide, tin oxide, titanium oxide, stannous chloride, isopropyl titanate, stannous octoate, zinc acetate and p-toluene sulfonic acid.

In the present invention, the mass ratio of the catalyst to the lactic acid is preferably (0.0002-0.01): 1, more preferably (0.0005-0.008): 1, more preferably (0.001-0.006): 1, more preferably (0.002-0.005): 1, and most preferably (0.003-0.004): 1.

In the invention, the temperature of the polycondensation reaction is preferably 130-200 ℃, more preferably 140-190 ℃, more preferably 150-180 ℃, and most preferably 160-170 ℃; the time is preferably 3 to 20 hours, more preferably 5 to 15 hours, more preferably 8 to 12 hours, and most preferably 10 hours.

In the present invention, the preparation method of polylactic acid preferably comprises:

and (3) carrying out ring-opening polymerization on the diol and the lactide to obtain the dihydroxy polylactic acid.

In the present invention, the diol is preferably HO- (CH)₂)_kPreferably, k is 2 to 10, and k is 3 to 8, more preferably 4 to 6, and most preferably 5.

In the present invention, the lactide is preferably selected from one or more of levorotatory lactide, dextrorotatory lactide and racemic lactide.

In the present invention, the ring-opening polymerization is preferably carried out under the action of a catalyst; the catalyst is preferably selected from one or more of tetrabutyl titanate, zinc oxide, zinc chloride, aluminum oxide, iron oxide, tin oxide, titanium oxide, stannous chloride, isopropyl titanate, stannous octoate, zinc acetate and p-toluene sulfonic acid.

In the present invention, the molar ratio of the diol to the lactide is preferably 1: (40-300), more preferably 1: (60-200), most preferably 1: (80-100).

In the present invention, the mass ratio of the catalyst to the lactide is preferably (0.0005-0.01): 1, more preferably (0.001-0.006): 1, more preferably (0.002-0.005): 1, and most preferably (0.003-0.004): 1.

In the invention, the ring-opening polymerization temperature is preferably 110-180 ℃, more preferably 130-160 ℃, and most preferably 140 ℃; the time is preferably 3 to 24 hours, more preferably 6 to 12 hours, and most preferably 9 hours.

In the invention, the ratio of the amounts of the succinic anhydride and the polylactic acid is preferably (1-3) to 1, more preferably (1.5-2.5): 1, most preferably 2: 1; the mass ratio of the succinic anhydride to the polylactic acid prepared by the polycondensation reaction is preferably (1-2) to 1, and more preferably 1.5 to 1; the ratio of the succinic anhydride to the polylactic acid prepared by ring-opening polymerization is preferably (1.5-3): 1, more preferably (1.8-2.5): 1, and most preferably 2: 1.

In the invention, the temperature of the first reaction is preferably 130-180 ℃, more preferably 140-170 ℃, and most preferably 150-160 ℃; the time is preferably 1 to 10 hours, more preferably 3 to 8 hours, more preferably 4 to 6 hours, and most preferably 5 hours.

In the present invention, the number average molecular weight of the double-terminal carboxyl polylactic acid is preferably 5000 to 40000, more preferably 10000 to 30000, and most preferably 20000.

In the present invention, the polyester is preferably selected from one or more of aliphatic copolyester and aliphatic-aromatic copolyester; the number average molecular weight of the polyester is preferably 5000-50000, more preferably 10000-40000, and most preferably 20000-30000; the melting point is preferably 100 to 150 ℃, more preferably 110 to 140 ℃, and most preferably 120 to 130 ℃.

In the invention, the aliphatic copolyester is preferably one or more selected from polyethylene glycol succinate, polybutylene succinate, polyhexamethylene succinate, polyethylene glycol adipate, polybutylene adipate, polyhexamethylene adipate, polyethylene glycol sebacate, polybutylene sebacate, polyhexamethylene sebacate and polyhydroxyalkanoate.

In the invention, the number average molecular weight of the aliphatic copolyester is preferably 5000-50000, more preferably 10000-40000, and most preferably 20000-30000; the melting point is preferably 100 to 150 ℃, more preferably 110 to 140 ℃, and most preferably 120 to 130 ℃.

In the present invention, the aliphatic-aromatic copolyester is preferably one or more selected from the group consisting of polyethylene succinate/terephthalate, polybutylene succinate/terephthalate, polyhexamethylene succinate/terephthalate, polyethylene adipate/terephthalate, polyhexamethylene sebacate/terephthalate, polybutylene sebacate/terephthalate, and polyhexamethylene sebacate/terephthalate.

In the invention, the number average molecular weight of the aliphatic-aromatic copolyester is preferably 5000-50000, more preferably 10000-40000, and most preferably 20000-30000; the melting point is preferably 100 to 150 ℃, more preferably 110 to 140 ℃, and most preferably 120 to 130 ℃.

The source of the polyester is not particularly limited in the present invention, and the polyester can be prepared by a polyester preparation method well known to those skilled in the art.

In the invention, the ratio of the amount of the polyester to the amount of the succinic anhydride is preferably 1 (0.5-3), more preferably 1 (1-2.5), and most preferably 1: 2.

In the invention, the temperature of the second reaction is preferably 130-180 ℃, more preferably 140-170 ℃, and most preferably 150-160 ℃; the time is preferably 1 to 10 hours, more preferably 3 to 8 hours, more preferably 4 to 6 hours, and most preferably 5 hours.

In the present invention, the number average molecular weight of the carboxyl group-both terminal polyester is preferably 5000 to 50000, more preferably 10000 to 40000, and most preferably 20000 to 30000.

In the invention, the epoxy value of the epoxidized soybean oil is preferably 4 to 6.8%, more preferably 5 to 6.6%, and most preferably 6%.

In the invention, the ratio of the mass of the epoxidized soybean oil to the total mass of the carboxyl-terminated lactic acid and the carboxyl-terminated polyester is preferably (1-20): 80-99, more preferably (5-15): 85-95), more preferably (8-12): 88-92, and most preferably 10: 90.

In the invention, the mass ratio of the double-end carboxyl lactic acid to the double-end carboxyl polyester is preferably (1-9): (1-9), more preferably (2-8): (2-8), more preferably (3-6): (3 to 6), most preferably (4 to 5) and (4 to 5).

In the invention, the temperature of the chain extension reaction is preferably 120-200 ℃, more preferably 150-180 ℃, and most preferably 160-170 ℃; the time is preferably 1 to 15 hours, more preferably 5 to 10 hours, and most preferably 6 to 8 hours.

Compared with the prior art, the method has the advantages that polylactic acid reacts with succinic anhydride to obtain carboxyl-terminated polylactic acid; polyester and succinic anhydride are adopted to react to obtain double-end carboxyl polyester; then the double-end carboxyl group polylactic acid and the double-end carboxyl group polyester are subjected to chain extension reaction with the epoxy soybean oil to obtain the polylactic acid group polyester-epoxy soybean oil copolymer. The copolymer prepared by the invention is composed of epoxidized soybean oil, polylactic acid and a polyester chain segment, so that the problem of poor compatibility of the epoxidized soybean oil and the polylactic acid is solved, the copolymer of the epoxidized soybean oil is prepared, the migration and permeation phenomena caused by the epoxidized soybean oil in polylactic acid resin are solved, the flexibility of the copolymer is improved by the introduction of the polyester, and the problem of hard and brittle polylactic acid is solved; the method provided by the invention adopts the epoxy group of the biomass to replace isocyanate as a chain extender for reaction, so that the toxicity of a reaction monomer is greatly reduced, and meanwhile, the synthesis method provided by the invention avoids the use of a solvent in the synthesis process, has the advantages of low toxicity, simplicity, high efficiency, low cost and good controllability, and is beneficial to industrial production. The modified components used in the invention are all degradable substances and have good biodegradability. In addition, the invention can adopt a one-pot method to synthesize the polylactic acid-based copolyester, thereby simplifying the process and greatly reducing the cost.

Example 1

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 140 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 1g of stannous chloride when the water does not flow out, heating to 180 ℃, and continuing to perform a pressure reduction reaction for 25 hours; 3g succinic anhydride is added into the system, and discharging is carried out after 2h, thus obtaining the double-end carboxyl polylactic acid with the number average molecular weight of 9000.

570g terephthalic acid, 670g adipic acid, 1500g butanediol and 4g tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 190 ℃ until no liquid is distilled off, the temperature is raised to 240 ℃ and the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 6 hours, the poly (butylene adipate-co-butylene terephthalate) copolymer with the number average molecular weight of 1.5 ten thousand is obtained.

300g of the poly (butylene adipate-co-butylene terephthalate) copolymer and 4g of succinic anhydride are added into a 500mL three-neck flask, the flask is heated to 170 ℃, reactants are stirred, and discharging is carried out after 2h, so that the poly (butylene adipate-co-butylene terephthalate) with double carboxyl groups is obtained.

100g of the above-mentioned double-end carboxyl polylactic acid, 200g of the above-mentioned double-end carboxyl poly (butylene adipate-co-terephthalate) and 25g of epoxidized soybean oil were added to a 500mL three-necked flask, the flask was heated to 180 ℃ and the reactants were stirred, and after 1 hour, the polylactic acid-poly (butylene adipate-co-terephthalate) -epoxidized soybean oil copolymer having a number average molecular weight of 7.6 ten thousand was obtained.

The high molecular weight polylactic acid-poly (butylene adipate-co-butylene terephthalate) copolymer in example 1 is subjected to nuclear magnetic testing, and the detection results are shown in fig. 1, (1) chemical shifts of the structural units of poly (butylene adipate-co-butylene terephthalate), (2) chemical shifts of the structural units of polylactic acid, and (3) chemical shifts of epoxidized soybean oil, wherein the chemical shifts appearing on a nuclear magnetic spectrum correspond to the chemical shifts of the components in the copolymer, and the molecular weight is greatly increased, which indicates that the three components do undergo a chain extension reaction.

The structural formula of the polylactic acid-poly (butylene adipate-co-butylene terephthalate) -epoxidized soybean oil copolymer prepared in the embodiment 1 of the present invention is:

according to the method of the technical scheme, the mechanical property of the product prepared in the embodiment 1 is tested, and the polylactic acid is correspondingly tested; the test results are: the elongation at break of the polylactic acid resin prepared in the embodiment 1 of the present invention is 510%, which is much larger than that of pure polylactic acid (4.2%).

Example 2

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 140 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 2g of tin oxide when the water does not flow out, heating to 180 ℃, and continuing to perform a reduced pressure reaction for 20 hours; 4g succinic anhydride is added into the system, and discharging is carried out after 2h, so that the double-end carboxyl polylactic acid with the number average molecular weight of 8000 is obtained.

570g terephthalic acid, 670g adipic acid, 1000g ethylene glycol and 5g tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 180 ℃ until no liquid is distilled off in the reaction, the temperature is raised to 240 ℃, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 5 hours, the poly (ethylene adipate-co-ethylene terephthalate) copolymer with the number average molecular weight of 1.3 ten thousand is obtained.

300g of the poly (ethylene adipate-co-ethylene terephthalate) and 5g of succinic anhydride are added into a 500mL three-neck flask, the flask is heated to 165 ℃, reactants are stirred, and discharging is carried out after 2h, so that the double-end carboxyl poly (ethylene adipate-co-ethylene terephthalate) is obtained.

100g of the above double-end carboxyl polylactic acid, 100g of the above double-end carboxyl poly (ethylene adipate-co-ethylene terephthalate) and 15g of epoxidized soybean oil were added to a 500mL three-necked flask, the flask was heated to 190 ℃, and the reactants were stirred and discharged after 30min to obtain a polylactic acid-poly (ethylene adipate-co-ethylene terephthalate) -epoxidized soybean oil copolymer having a number average molecular weight of 7.1 ten thousand.

Nuclear magnetic tests are performed on the polylactic acid-poly (ethylene adipate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in example 2, and nuclear magnetic test results show that characteristic chemical shifts of benzene rings in poly (ethylene adipate-co-ethylene terephthalate) appear at 8.1ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components really have chain extension reaction, and the method can successfully prepare the high molecular weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-poly (ethylene adipate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in embodiment 2 of the present invention is:

represents

According to the method of the technical scheme, the product prepared in the embodiment 2 of the invention is tested, and the test result is as follows: the elongation at break of the polylactic acid resin prepared in example 2 was 420%.

Example 3

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 130 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 1g of stannous benzoate when the water does not flow out, heating to 190 ℃, and continuing to perform a pressure reduction reaction for 15 hours; 5g succinic anhydride is added into the system, and discharging is carried out after 1h, so that the double-end carboxyl polylactic acid with the number average molecular weight of 7000 is obtained.

570g terephthalic acid, 670g adipic acid, 2200g hexanediol and 6g tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 200 ℃ until no liquid is distilled off in the reaction, the temperature is raised to 240 ℃, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 5 hours, the poly (hexanediol adipate-co-hexanediol terephthalate) copolymer with the number average molecular weight of 1.4 ten thousand is obtained.

300g of the poly (hexanediol adipate-co-terephthalate) and 6g of succinic anhydride are added into a 500mL three-neck flask, the flask is heated to 160 ℃, reactants are stirred, and discharging is carried out after 10h, so that the double-end carboxyl poly (hexanediol adipate-co-terephthalate) is obtained.

100g of the above-mentioned double-end carboxyl polylactic acid, 50g of the above-mentioned double-end carboxyl poly (hexanediol adipate-co-terephthalate) and 15g of epoxidized soybean oil were added to a 500mL three-necked flask, the flask was heated to 180 ℃ and the reactants were stirred, and after 1 hour, the polylactic acid-poly (hexanediol adipate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer having a number average molecular weight of 6.5 ten thousand was obtained.

Nuclear magnetic detection is carried out on the polylactic acid-poly (hexanediol adipate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer prepared in the example 3, and nuclear magnetic test results show that the characteristic chemical shift of benzene rings in the poly (hexanediol adipate-co-hexanediol terephthalate) appears at 8.1ppm, the characteristic chemical shift of methine in the polylactic acid appears at 5.2ppm, and the characteristic chemical shifts of the epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, and the results show that the three components really have chain extension reaction, so that the method can successfully prepare the high molecular weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-poly (hexanediol adipate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer prepared in example 3 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the embodiment 3 of the invention are tested, and the test result shows that the elongation at break of the polylactic acid resin prepared in the embodiment 3 is 460%.

Example 4

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 0.6g of stannous octoate when the water does not flow out, heating to 180 ℃, and continuing to perform a reduced pressure reaction for 22 hours; 3g succinic anhydride is added into the system, and discharging is carried out after 2 hours to obtain the double-end carboxyl polylactic acid with the number average molecular weight of 1 ten thousand.

570g terephthalic acid, 500g succinic acid, 1600g butanediol and 8g tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 190 ℃ until no liquid is distilled off, the temperature is raised to 240 ℃ when the reaction is carried out, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 6 hours, the poly (butylene succinate-co-butylene terephthalate) copolymer with the number average molecular weight of 1.5 ten thousand is obtained.

Adding 300g of the poly (butylene succinate-co-butylene terephthalate) and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the reactants, and discharging after 12h to obtain the double-end carboxyl poly (butylene succinate-co-butylene terephthalate).

Adding 20g of the double-end carboxyl polylactic acid, 180g of the double-end carboxyl poly (butylene succinate-co-butylene terephthalate) and 15g of epoxidized soybean oil into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, discharging after 1h to obtain the polylactic acid-poly (butylene succinate-co-butylene terephthalate) -epoxidized soybean oil copolymer with the number average molecular weight of 7.8 ten thousand.

Nuclear magnetic detection is carried out on the polylactic acid-poly (butylene succinate-co-butylene terephthalate) -epoxidized soybean oil copolymer prepared in the embodiment 4 of the invention, and nuclear magnetic test results show that characteristic chemical shifts of benzene rings in poly (butylene succinate-co-butylene terephthalate) appear at 8.1ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, and the results show that the three components really have chain extension reaction.

The structural formula of the polylactic acid-poly (butylene succinate-co-butylene terephthalate) -epoxidized soybean oil copolymer prepared in embodiment 4 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the example 4 are tested, and the test result is as follows: the elongation at break of the polylactic acid resin prepared in example 4 was 570%.

Example 5

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 1g of tetrabutyl titanate when the water does not flow out, heating to 170 ℃, and carrying out a reduced pressure reaction for 20 hours; 4g succinic anhydride is added into the system, and discharging is carried out after 2h, so that the double-end carboxyl polylactic acid with the number average molecular weight of 8000 is obtained.

660g of dimethyl terephthalate, 500g of succinic acid, 2200g of hexanediol and 10g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly increased to 180 ℃, when no liquid is distilled off in the reaction, the temperature is increased to 240 ℃, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 5 hours, the poly (hexamethylene succinate-co-hexamethylene terephthalate) copolymer with the number average molecular weight of 1.4 ten thousand is obtained

Adding 300g of the poly (hexanediol succinate-co-hexanediol terephthalate) and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, and discharging after 2 hours to obtain the double-end carboxyl poly (hexanediol succinate-co-hexanediol terephthalate).

50g of the double-end carboxyl polylactic acid, 150g of the double-end carboxyl poly (hexanediol succinate-co-hexanediol terephthalate) and 16g of epoxidized soybean oil are added into a 500mL three-neck flask, the flask is heated to 180 ℃, reactants are stirred, and the mixture is discharged after 5 hours to obtain the polylactic acid-poly (hexanediol succinate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer with the number average molecular weight of 7.2 ten thousand.

Nuclear magnetic detection is carried out on the polylactic acid-poly (hexanediol succinate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer prepared in the embodiment 5, and nuclear magnetic test results show that the characteristic chemical shift of benzene rings in poly (hexanediol succinate-co-hexanediol terephthalate) appears at 8.1ppm, the characteristic chemical shift of methine in polylactic acid appears at 5.2ppm, and the characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, and the results show that the three components really have chain extension reaction.

The structural formula of the polylactic acid-poly (hexanediol succinate-co-hexanediol terephthalate) -epoxidized soybean oil copolymer prepared in example 5 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the example 5 are tested, and the test result is as follows: the elongation at break of the polylactic acid resin prepared in example 5 was 530%.

Example 6

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 3g of titanium oxide when the water does not flow out, heating to 180 ℃, and continuing to perform a reduced pressure reaction for 28 hours; 3g succinic anhydride is added into the system, and discharging is carried out after 2 hours to obtain the double-end carboxyl polylactic acid with the number average molecular weight of 1.1 ten thousand.

660g of dimethyl terephthalate, 500g of succinic acid, 1400g of ethylene glycol and 8g of tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 180 ℃, when no liquid is distilled off in the reaction, the temperature is raised to 240 ℃, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 6 hours, the poly (ethylene succinate-co-ethylene terephthalate) copolymer with the number average molecular weight of 1.5 ten thousand is obtained.

Adding 300g of the poly (ethylene succinate-co-ethylene terephthalate) and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the reactants, and discharging after 5h to obtain the double-end carboxyl poly (ethylene succinate-co-ethylene terephthalate).

Adding 100g of the double-end carboxyl polylactic acid, 100g of the double-end carboxyl poly (ethylene succinate-co-ethylene terephthalate) and 20g of epoxidized soybean oil into a 500mL three-neck flask, heating the flask to 200 ℃, stirring the reactants, discharging after 30min to obtain the polylactic acid-poly (ethylene succinate-co-ethylene terephthalate) -epoxidized soybean oil copolymer with the number average molecular weight of 7.9 ten thousand.

Nuclear magnetic detection is performed on the polylactic acid-poly (ethylene succinate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in example 6, and nuclear magnetic test results show that characteristic chemical shifts of benzene rings in poly (ethylene succinate-co-ethylene terephthalate) appear at 8.1ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components indeed have a chain extension reaction, and the method can successfully prepare the high molecular weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-poly (ethylene succinate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in embodiment 6 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the embodiment 6 of the invention are tested, and the test result is as follows: the elongation at break of the polylactic acid blend resin prepared in example 6 was 420%.

Example 7

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 1.6g of isopropyl titanate when the water does not flow out, heating to 180 ℃, and continuing to perform a reduced pressure reaction for 20 hours; 5g succinic anhydride is added into the system, and discharging is carried out after 2h, thus obtaining the double-end carboxyl polylactic acid with the number average molecular weight of 8000.

660g of dimethyl terephthalate, 1000g of sebacic acid, 1200g of ethylene glycol and 10g of tetrabutyl titanate are sequentially added into a flask, then the temperature is rapidly raised to 180 ℃, when no liquid is distilled off in the reaction, the temperature is raised to 240 ℃, the polycondensation reaction is carried out by vacuumizing, the pressure is 500Pa, and after 6 hours, the poly (ethylene sebacate-co-ethylene terephthalate) copolymer with the number average molecular weight of 1.4 ten thousand is obtained.

300g of the poly (ethylene sebacate-co-ethylene terephthalate) and 6g of succinic anhydride are added into a 500mL three-neck flask, the flask is heated to 160 ℃, the reactants are stirred, and discharging is carried out after 2h, so that the poly (ethylene sebacate-co-ethylene terephthalate) with double carboxyl groups is obtained.

100g of the above double-end carboxyl polylactic acid, 150g of the above double-end carboxyl poly (ethylene sebacate-co-ethylene terephthalate) and 20g of epoxidized soybean oil were added to a 500mL three-necked flask, the flask was heated to 180 ℃ and the reactants were stirred, and after 6 hours, a polylactic acid-poly (ethylene sebacate-co-ethylene terephthalate) -epoxidized soybean oil copolymer having a number average molecular weight of 6.9 ten thousand was obtained.

Nuclear magnetic detection is performed on the polylactic acid-poly (ethylene sebacate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in example 7, and nuclear magnetic test results show that characteristic chemical shifts of benzene rings in poly (ethylene sebacate-co-ethylene terephthalate) appear at 8.1ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components indeed undergo a chain extension reaction.

The structural formula of the polylactic acid-poly (ethylene sebacate-co-ethylene terephthalate) -epoxidized soybean oil copolymer prepared in example 7 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the example 7 are tested, and the test result is as follows: the elongation at break of the polylactic acid resin prepared in example 7 was 450%.

Example 8

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 3g of zinc oxide when the water does not flow out, heating to 190 ℃, and continuing to perform a pressure reduction reaction for 15 hours; 3g succinic anhydride is added into the system, and discharging is carried out after 1h, so that the double-end carboxyl polylactic acid with the number average molecular weight of 1.1 ten thousand is obtained.

590g of succinic acid, 600g of butanediol and 4g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly raised to 170 ℃ until no liquid is distilled off, the temperature is raised to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 5 hours, the poly (butylene succinate) with the number average molecular weight of 1.5 ten thousand is obtained.

Adding 300g of the polybutylene succinate and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the reactants, and discharging after 5 hours to obtain the polybutylene succinate with carboxyl groups at two ends.

Adding 100g of the double-end carboxyl polylactic acid, 200g of the double-end carboxyl polybutylene succinate and 30g of epoxy soybean oil into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the reactants, discharging after 15h to obtain the polylactic acid-polybutylene succinate-epoxy soybean oil copolymer with the number average molecular weight of 7.7 ten thousand.

Nuclear magnetic detection is performed on the polylactic acid-polybutylene succinate-epoxidized soybean oil copolymer prepared in the embodiment 8, and nuclear magnetic test results show that characteristic chemical shifts of methylene in succinic acid in polybutylene succinate appear at 2.6ppm, characteristic chemical shifts of methylene in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components really have chain extension reaction.

The structural formula of the polylactic acid-polybutylene succinate-epoxidized soybean oil copolymer prepared in the embodiment 8 of the invention is as follows:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in the example 8 are tested, and the test result is as follows: the elongation at break of the polylactic acid resin prepared in example 8 was 550%.

Example 9

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 1g of zinc chloride when the water does not flow out, and carrying out a reduced pressure reaction at the temperature for 25 hours; 4g succinic anhydride is added into the system, and discharging is carried out after 2h, so that the double-end carboxyl polylactic acid with the number average molecular weight of 7000 is obtained.

590g of succinic acid, 800g of hexanediol and 3g of tetrabutyl titanate are sequentially added into a flask, the temperature is quickly raised to 170 ℃ until no liquid is distilled off, the temperature is raised to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 6 hours, the poly (hexanediol succinate) is obtained, wherein the number average molecular weight is 1.6 ten thousand.

Adding 300g of the poly (hexamethylene succinate) and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 170 ℃, stirring the reactants, and discharging after 3 hours to obtain the poly (hexamethylene succinate) with carboxyl at two ends.

Adding 150g of the double-end carboxyl polylactic acid, 150g of the double-end carboxyl poly (hexanediol succinate) and 27g of epoxy soybean oil into a 500mL three-neck flask, heating the flask to 170 ℃, stirring the reactants, discharging after 10h to obtain the poly (lactic acid) -poly (hexanediol succinate) -epoxy soybean oil copolymer with the number average molecular weight of 6.7 ten thousand.

Nuclear magnetic detection is performed on the polylactic acid-poly (hexanediol succinate) -epoxidized soybean oil copolymer prepared in example 9, and nuclear magnetic test results show that characteristic chemical shifts of methylene in succinic acid in the poly (hexanediol succinate) appear at 2.6ppm, characteristic chemical shifts of methylene in the polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components indeed undergo a chain extension reaction, and the method can successfully prepare the high molecular weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-poly (hexanediol succinate) -epoxidized soybean oil copolymer prepared in embodiment 9 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in example 9 are tested, and the test results are as follows: the elongation at break of the polylactic acid resin prepared in example 9 was 430%.

Example 10

Adding 300g of lactic acid into a 500mL three-neck flask, heating the flask to 160 ℃, stirring the lactic acid, collecting water generated in the reaction, adding 3g of zinc acetate when the water does not flow out, heating to 180 ℃, and carrying out a reduced pressure reaction for 15 hours; 3g succinic anhydride is added into the system, and discharging is carried out after 2h, thus obtaining the double-end carboxyl polylactic acid with the number average molecular weight of 8000.

730g of adipic acid, 600g of butanediol and 3g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly raised to 170 ℃ until no liquid is distilled off, the temperature is raised to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 5 hours, the poly (butylene adipate) with the number average molecular weight of 1.4 ten thousand is obtained.

Adding 300g of the polybutylene adipate and 6g of succinic anhydride into a 500mL three-neck flask, heating the flask to 170 ℃, stirring the reactants, and discharging after 2 hours to obtain the polybutylene adipate with double carboxyl groups.

Adding 50g of the double-end carboxyl polylactic acid, 150g of the double-end carboxyl polybutylene adipate and 20g of epoxidized soybean oil into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, discharging after 7h to obtain the polylactic acid-polybutylene adipate-epoxidized soybean oil copolymer with the number average molecular weight of 7.1 ten thousand.

Nuclear magnetic detection is carried out on the polylactic acid-polybutylene adipate-epoxidized soybean oil copolymer prepared in the example 10, and nuclear magnetic test results show that characteristic chemical shifts of methylene in adipic acid in the polybutylene adipate appear at 1.7ppm and 2.3ppm, characteristic chemical shifts of methylene in the polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, and the results show that the three components really have chain extension reaction, so that the method can successfully prepare the high-molecular-weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-polybutylene adipate-epoxidized soybean oil copolymer prepared in the embodiment 10 of the invention is as follows:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in example 10 are tested, and the test results are as follows: the elongation at break of the polylactic acid blend resin prepared in example 10 was 505%.

Example 11

Adding 300g of lactide, 1.24g of ethylene glycol and 0.3g of stannous octoate into a 500mL three-neck flask, stirring and heating to 120 ℃; after 24 hours, 5g of succinic anhydride is added into the system, the temperature is raised to 170 ℃, the mixture is discharged after 1.5 hours of mixing, and the double-end carboxyl polylactic acid with the number average molecular weight of 1.4 ten thousand is obtained.

730g of adipic acid, 750g of hexanediol and 5g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly raised to 170 ℃ until no liquid is distilled off, the temperature is raised to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 5 hours, the polyhexamethylene adipate with the number average molecular weight of 1.3 ten thousand is obtained.

Adding 300g of polyhexamethylene adipate and 6g of succinic anhydride into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, and discharging after 3 hours to obtain the double-end carboxyl polyhexamethylene adipate.

100g of the double-end carboxyl polylactic acid, 200g of the double-end carboxyl polyadipic acid hexanediol ester and 25g of epoxy soybean oil are added into a 500mL three-neck flask, the flask is heated to 180 ℃, reactants are stirred, and discharging is carried out after 2 hours to obtain the polylactic acid-polyadipic acid hexanediol ester-epoxy soybean oil copolymer with the number average molecular weight of 7.9 ten thousand.

Nuclear magnetic detection is performed on the polylactic acid-polyhexamethylene adipate-epoxidized soybean oil copolymer prepared in the example 11, and nuclear magnetic test results show that characteristic chemical shifts of methylene in adipic acid in the polyhexamethylene adipate appear at 1.6ppm and 2.3ppm, characteristic chemical shifts of methylene in the polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components do generate chain extension reaction, so that the method can successfully prepare the high molecular weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-polyhexamethylene adipate-epoxidized soybean oil copolymer prepared in the embodiment 11 of the invention is as follows:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in example 11 are tested, and the test results are as follows: the elongation at break of the polylactic acid resin prepared in example 11 was 530%.

Example 12

Adding 300g of lactide, 1.86g of ethylene glycol and 0.5g of stannous octoate into a 500mL three-neck flask, stirring and heating to 150 ℃; after 20h, 6g succinic anhydride is added into the system, the temperature is raised to 170 ℃, and discharging is carried out after 1h of mixing to obtain the double-end carboxyl polylactic acid with the number average molecular weight of 1 ten thousand.

730g of adipic acid, 350g of ethylene glycol and 5g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly raised to 170 ℃ until no liquid is distilled off, the temperature is raised to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 6 hours, the polyethylene glycol adipate with the number average molecular weight of 1.5 ten thousand is obtained.

And adding 300g of polyethylene glycol adipate and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, and discharging after 2 hours to obtain the double-end carboxyl polyethylene glycol adipate.

Adding 100g of the double-end carboxyl polylactic acid, 100g of the double-end carboxyl polyethylene glycol adipate and 20g of epoxidized soybean oil into a 500mL three-neck flask, heating the flask to 180 ℃, stirring the reactants, discharging after 2 hours to obtain the polylactic acid-polyethylene glycol adipate epoxidized soybean oil copolymer with the number average molecular weight of 6.8 ten thousand.

Nuclear magnetic detection is performed on the polylactic acid-polyethylene glycol adipate epoxidized soybean oil copolymer prepared in example 12, and nuclear magnetic test results show that characteristic chemical shifts of methylene in adipic acid in polyethylene glycol adipate appear at 1.7ppm and 2.3ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components do generate chain extension reaction, so that the method can successfully prepare the high-molecular-weight polylactic acid-polyester copolymer.

The structural formula of the polylactic acid-polyethylene glycol adipate-epoxidized soybean oil copolymer prepared in the embodiment 12 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in example 12 are tested, and the test results are as follows: the elongation at break of the polylactic acid blend resin prepared in example 12 was 410%.

Example 13

300g of lactide, 1.5g of ethylene glycol and 0.15g of stannous octoate are added into a 500mL three-neck flask, stirred and heated to 140 ℃; after 15h, 3g succinic anhydride is added into the system, the temperature is raised to 180 ℃, the mixture is discharged after 1h, and the double-end carboxyl polylactic acid with the number average molecular weight of 1.2 ten thousand is obtained.

1080g of sebacic acid, 650g of butanediol and 5g of tetrabutyl titanate are sequentially added into a flask, the temperature is rapidly increased to 160 ℃, when no liquid is distilled off in the reaction, the temperature is increased to 230 ℃, vacuum pumping is carried out for polycondensation reaction, the pressure is 500Pa, and after 7 hours, the poly-butanediol sebacate is obtained, wherein the number-average molecular weight is 1.4 ten thousand.

Adding 300g of the polysebacic acid butanediol ester and 5g of succinic anhydride into a 500mL three-neck flask, heating the flask to 150 ℃, stirring the reactants, and discharging after 2 hours to obtain the polysebacic acid butanediol ester with double carboxyl groups.

100g of the above-mentioned double-end carboxyl polylactic acid, 200g of the above-mentioned double-end carboxyl polysebacic acid butanediol ester and 22g of epoxy soybean oil are added into a 500mL three-neck flask, then the flask is heated to 180 ℃, and the reactants are stirred, and after 3h discharging is carried out, the polylactic acid-polysebacic acid butanediol ester-epoxy soybean oil copolymer with 7.1 ten thousand of number average molecular weight is obtained.

Nuclear magnetic detection is performed on the polylactic acid-polybutylene sebacate-epoxidized soybean oil copolymer prepared in example 13, and nuclear magnetic test results show that characteristic chemical shifts of methylene in sebacic acid in polybutylene sebacate appear at 2.2ppm, characteristic chemical shifts of methine in polylactic acid appear at 5.2ppm, and characteristic chemical shifts of epoxidized soybean oil appear at 3ppm and 0.9-1.4 ppm, which show that the three components indeed undergo a chain extension reaction.

The structural formula of the polylactic acid-polybutylene sebacate-epoxidized soybean oil copolymer prepared in embodiment 13 of the present invention is:

represents

According to the method of the technical scheme, the mechanical properties of the product prepared in example 13 are tested, and the test results are as follows: the elongation at break of the polylactic acid resin prepared in example 13 was 530%.

According to the embodiment, the invention provides the preparation method of the polylactic acid-epoxidized soybean oil copolymer, and the method provided by the invention mixes the dicarboxyl polylactic acid and the double-end carboxyl polyester, and adopts the epoxidized soybean oil to melt and extend the chain to obtain the polylactic acid-epoxidized soybean oil copolymer. The epoxidized soybean oil is used as a copolymer chain segment and directly plays a role of a chain extender, so that the use of diisocyanate with high toxicity is avoided; the copolymer has good flexibility and high mechanical property; the copolymer has high melt strength, and solves the problem of poor processability of polylactic acid; the synthesis of the copolymer solves the problems of easy migration and permeation of epoxidized soybean oil, and improves the stability of the modified polylactic acid; the invention has simple process technology, low preparation cost and good biodegradability of the copolymer.

While only the preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.