阅读说明：本技术 一种热收缩膜共聚物的生产工艺 (Production process of heat shrinkable film copolymer ) 是由 张跃胜 柴青立 龚磊 刘雄 曹文 景辽宁 陈文兴 包建娜 于 2021-08-23 设计创作，主要内容包括：本发明涉及高分子材料领域内的一种热收缩膜共聚物的生产工艺,其以芳香族二元酸、脂肪族二元醇为原料制备而得的酯化物,与相对数均分子量1000-5000g/mol的聚乳酸低聚物反应得到含聚乳酸链段的共聚物。本发明工艺中涉及到的聚乳酸低聚物是由聚乳酸合成过程中副产粗丙交酯制备得到,同时利用该工艺生产的共聚物可应用于热收缩膜领域,具有良好的可降解性能。(The invention relates to a production process of a copolymer of a heat shrinkable film in the field of high polymer materials, which takes aromatic dibasic acid and aliphatic dihydric alcohol as raw materials to prepare an esterified substance, and the esterified substance reacts with a polylactic acid oligomer with the relative number average molecular weight of 1000-5000g/mol to obtain the copolymer containing a polylactic acid chain segment. The polylactic acid oligomer involved in the process is prepared from crude lactide byproduct in the polylactic acid synthesis process, and the copolymer produced by the process can be applied to the field of heat shrinkable films and has good degradability.)

1. The production process of the heat shrinkable film copolymer is characterized by comprising the following steps:

(1): adding a catalyst into a mixture of aromatic dibasic acid and aliphatic diol, reacting for 2-5h at the temperature of 240-260 ℃ and under the pressure of 0.15-0.20Mpa to obtain a primary esterified substance, and continuously reacting for 1-3h at the temperature of 250-270 ℃ to obtain a secondary esterified substance;

(2): adding a polylactic acid oligomer with the relative number average molecular weight of 1000-5000g/mol and a chain extender into the secondary esterified product, uniformly stirring, reacting for 1-3h under the conditions of 225-250 ℃ and 8-10Kpa to obtain a prepolymer A, continuously reacting for 1-3h under the conditions of 230-250 ℃ and 0.5-3Kpa to obtain a prepolymer B, and reacting for 0.5-1h under the conditions of 240-260 ℃ and 0.1-0.3Kpa to obtain a copolymer containing a lactic acid segment.

2. The process for producing a heat shrinkable film copolymer according to claim 1, wherein the aromatic dibasic acid is at least one of terephthalic acid and isophthalic acid.

3. The production process of the heat shrinkable film copolymer as claimed in claim 2, wherein the aromatic dibasic acid is a mixture of terephthalic acid and isophthalic acid, and the mixing molar ratio of the two is (90-95): (5-10).

4. The production process of the heat shrinkable film copolymer as claimed in claim 1, wherein the aliphatic diol is a mixture of ethylene glycol and neopentyl glycol, and the mixing molar ratio of the ethylene glycol to the neopentyl glycol is (70-80): (20-30).

5. The production process of the heat shrinkable film copolymer according to claim 1, wherein the molar ratio of the aromatic dibasic acid to the aliphatic diol is 1: (1.05-1.3).

6. The process for producing a heat shrinkable film copolymer as claimed in claim 1, wherein the melting point of the secondary ester is 120-220 ℃.

7. The production process of the heat shrinkable film copolymer as claimed in claim 1, wherein the catalyst is one or more selected from ethylene glycol antimony, antimony trioxide, tetrabutyl titanate, stannous octoate and zinc acetate, and the amount of the catalyst is 0.03-0.5% of the molar amount of the dibasic acid.

8. The production process of the heat shrinkable film copolymer as claimed in claim 1, wherein the polylactic acid oligomer is prepared from crude lactide which is a byproduct in the polylactic acid synthesis process, the crude lactide contains 80-98% of lactide, the lactic acid content is 2-20%, and the lactide is a mixture of L-lactide, D-lactide and meso-lactide in any proportion.

9. The production process of the heat shrinkable film copolymer of any one of claims 1 to 8, wherein the weight ratio of the polylactic acid oligomer to the secondary esterified substance is (30-60): (40-70).

10. The process for producing a heat shrinkable film copolymer according to any one of claims 1 to 8, wherein the chain extender is one selected from the group consisting of toluene diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate, and is used in an amount of 0.5 to 4% by weight based on the total weight of the polylactic acid oligomer and the secondary esterified product.

Technical Field

The invention relates to the field of high polymer materials, in particular to a production process of a heat shrinkable film copolymer.

Background

Polylactic acid is an environment-friendly biodegradable material, the main production process of the polylactic acid is a lactide ring-opening polymerization method, and during the synthesis process of the polylactic acid, especially during the purification process of the lactide, some byproducts containing the lactide, called 'crude lactide', can be generated. The "crude lactide" contains by-products such as D-lactide and meso-lactide, and if the "crude lactide" is returned to the production system again, the optical purity and chemical purity of L-lactide are reduced, but if the "crude lactide" is directly discarded, the production cost is increased, and the energy and raw materials are greatly wasted.

Polyethylene terephthalate (PET) is a very important thermoplastic material and is widely used in the fields of films, fibers and the like. Publication No. CN112876704A discloses a synthesis process of a heat shrinkable film, which introduces isophthalic acid, diethylene glycol, etc. into polyethylene terephthalate to prepare a heat shrinkable film polyester with good performance, but it belongs to a traditional petroleum-based material, and is difficult to degrade after being discarded, which may cause environmental pollution.

Disclosure of Invention

In order to solve the problem of recycling crude lactide and endow the heat shrinkable film with good degradability, the invention provides a production process of a heat shrinkable film copolymer.

In order to achieve the above object, the present invention adopts the following scheme: the production process of the heat shrinkable film copolymer is characterized by comprising the following steps:

(1): adding a catalyst into a mixture of aromatic dibasic acid and aliphatic diol, reacting for 2-5h at the temperature of 240-260 ℃ and under the pressure of 0.15-0.20Mpa to obtain a primary esterified substance, and continuously reacting for 1-3h at the temperature of 250-270 ℃ to obtain a secondary esterified substance;

(2): adding a polylactic acid oligomer with the relative number average molecular weight of 1000-5000g/mol and a chain extender into the secondary esterified product, uniformly stirring, reacting for 1-3h under the conditions of 225-250 ℃ and 8-10Kpa to obtain a prepolymer A, continuously reacting for 1-3h under the conditions of 230-250 ℃ and 0.5-3Kpa to obtain a prepolymer B, and reacting for 0.5-1h under the conditions of 240-260 ℃ and 0.1-0.3Kpa to obtain a copolymer containing a lactic acid segment.

Preferably, the aromatic dibasic acid is at least one selected from terephthalic acid and isophthalic acid, more preferably, a mixture of terephthalic acid and isophthalic acid, and the mixing molar ratio of the two is (90-95): (5-10).

Preferably, the aliphatic diol is a mixture of Ethylene Glycol (EG) and neopentyl glycol (NPG) in a mixing molar ratio of (70-80): (20-30).

Preferably, the molar ratio of the aromatic dibasic acid to the aliphatic diol is 1: (1.05-1.3).

Preferably, the melting point of the secondary ester is 120-220 ℃.

Preferably, the catalyst is selected from one or more of ethylene glycol antimony, antimony trioxide, tetrabutyl titanate, stannous octoate and zinc acetate, and the using amount of the catalyst is 0.03-0.5% of the molar amount of the dibasic acid.

Preferably, the polylactic acid oligomer is prepared from crude lactide, wherein the lactide content of the crude lactide is 80-98%, the lactic acid content of the crude lactide is 2-20%, and the lactide is a mixture of L-lactide, D-lactide and meso-lactide in any proportion.

Preferably, the weight ratio of the polylactic acid oligomer to the secondary esterified substance is (30-60): (40-70).

Preferably, the chain extender is selected from one of toluene diisocyanate, hexamethylene diisocyanate and diphenylmethane diisocyanate, and the amount of the chain extender is 0.5-4% of the total weight of the polylactic acid oligomer and the secondary esterified substance.

Compared with the prior art, the production process of the heat shrinkable film copolymer provided by the invention introduces the excellent biodegradability of polylactic acid on the basis of keeping the high shrinkability of the modified polyethylene terephthalate. Through the selection of the process parameters, the product has good thermal shrinkage rate and is suitable for being used as a material of a thermal shrinkage film.

Detailed Description

Embodiments of the invention are further described below by way of examples, and the scope of the invention is not limited to only these examples, which are given by way of illustration only. The invention is not limited to the embodiments described herein, but is capable of numerous modifications and variations within the spirit and scope of the invention.

The test method of the invention comprises the following steps: the intrinsic viscosity is tested according to the national standard GB/T14190-2017 fiber grade Polyester (PET) chip test method; the degradation performance test is to place the copolymer material in a proteinase K buffer solution, and calculate the weight loss rate after degradation for 28 days at constant temperature.

Example 1

The molar ratio of the aromatic dibasic acid to the aliphatic dihydric alcohol is 1: 1.3 preparing slurry, adding a catalyst with the molar weight of the aromatic dibasic acid of 0.5 percent, reacting for 3 hours at the temperature of 250 ℃ and 255 ℃ and under the pressure of 0.18-0.20Mpa to obtain a primary esterified substance, and continuously reacting for 3 hours at the temperature of 260 ℃ and 265 ℃ and under the pressure of 0.11-0.14Mpa to obtain a secondary esterified substance; adding polylactic acid oligomer with the relative number average molecular weight of 1000g/mol and toluene diisocyanate into the secondary esterified substance, wherein the amount of the toluene diisocyanate is 2 percent of the total weight of the polylactic acid oligomer and the secondary esterified substance; after stirring uniformly, reacting at 230-235 ℃ and 9-10Kpa for 3h to obtain prepolymer A, reacting at 235-240 ℃ and 0.5-0.7Kpa for 2h to obtain prepolymer B, and reacting at 250-255 ℃ and 0.1-0.2Kpa for 0.5h to obtain the copolymer containing polylactic acid segment.

Table 1 shows the properties of polyester heat shrinkable films synthesized from different raw materials

As can be seen from Table 1, the copolymer containing polylactic acid segments obtained by the above technical scheme has good thermal shrinkage rate and good degradation performance.

In the above steps, corresponding parameters are selected in a wider range, the catalyst can be one or more of ethylene glycol antimony, antimony trioxide, tetrabutyl titanate, stannous octoate and zinc acetate, and the using amount of the catalyst is 0.03-0.5% of the molar weight of the dibasic acid; when the primary esterification is carried out at the temperature of 240 ℃ and 260 ℃ and under the condition of 0.15-0.20Mpa for 2-5 h; the secondary esterification is carried out for 1 to 3 hours at the temperature of 250 ℃ and 270 ℃ and under the pressure of 0.11 to 0.14 Mpa; the relative number average molecular weight of the polylactic acid oligomer is 1000-5000 g/mol; the chain extender is one of toluene diisocyanate, hexamethylene diisocyanate and diphenylmethane diisocyanate, and the using amount of the chain extender is 0.5-4% of the total weight of the polylactic acid oligomer and the secondary esterified substance. After the secondary esterified substance, the polylactic acid oligomer and the chain extender are uniformly stirred, the mixture is reacted for 1 to 3 hours under the conditions of 225-250 ℃ and 8 to 10Kpa to obtain a prepolymer A, the prepolymer A is continuously reacted for 1 to 3 hours under the conditions of 230-250 ℃ and 0.5 to 3Kpa to obtain a prepolymer B, and the prepolymer B is reacted for 0.5 to 1 hour under the conditions of 240-260 ℃ and 0.1 to 0.3Kpa to obtain the copolymer containing the lactic acid chain segment. The copolymer still has the degradation performance basically the same as that of the copolymer in the table 1, and the longitudinal heat shrinkage rate of the copolymer at 90 ℃ is 30-60%, so that the material requirement of a heat shrinkable film can be met. Through a comparison test, after the secondary esterified substance, the polylactic acid oligomer and the chain extender are uniformly stirred, other conditions are not changed, the reaction temperature is only changed, when the reaction temperature is increased to exceed the upper limit value of 10-30 ℃, the polylactic acid is easy to pyrolyze, so that the copolymerization rate of the polylactic acid is reduced, and when the reaction temperature is lower than the lower limit value of 10-30 ℃, the reaction is incomplete, and the thermal shrinkage rate of a product is obviously reduced.

Example 2

Preparing terephthalic acid, isophthalic acid, ethylene glycol and neopentyl glycol into slurry, wherein the molar ratio of the terephthalic acid to the isophthalic acid in the slurry is 95: 5, the molar ratio of ethylene glycol to neopentyl glycol is 75: 25 and tetrabutyl titanate with the molar ratio of 0.2 percent of the total mole of the dibasic acid, forming an esterified product through primary esterification and secondary esterification, and then carrying out primary prepolymerization, secondary prepolymerization and final polymerization on the esterified product and a polylactic acid oligomer with the weight accounting for 50 percent to obtain the copolymer containing the polylactic acid chain segment under the action of a chain extender, namely diphenylmethane diisocyanate.

Table 2 shows the various parameters and properties of the copolymerization

。

Embodiment 3

The crude lactide is dehydrated for 2 to 20 hours at the temperature of 130 ℃ and 180 ℃ and under the pressure of 0.6 to 6Kpa to obtain polylactic acid oligomer, and the polylactic acid oligomer and the esterified product of the modified polyethylene glycol terephthalate are copolymerized to synthesize the copolymer containing the polylactic acid chain segment under the action of the chain extender.

Table 3 shows the synthesis of copolymers containing polylactic acid segments and the properties of the copolymers under different "crude lactide" conditions

。

As can be seen from tables 2 and 3, the obtained product has an intrinsic viscosity of 0.6 to 0.9 dl/g and can be used for the production of films.