KR940009418B1 - Process for preparation of polyester with biodegradation - Google Patents

Abstract

The biodegradable polyester copolymer having tensile strength of 100-350 kg/cm2 and elongation of 250-500 % is prepared by: (A) polymerizing an aromatic polyester with 80-110 DP at 230-270 deg.C by an ester exchange reaction; (B) copolymerization aromatic (I) and aliphatic (II) polyester that has a composition ratio of 50(I):50(II) - 90:10.

Description

Method for producing a biodegradable polyester

The present invention relates to a method for producing a biodegradable polymer using the exchange reaction of the ester. More specifically, the present invention relates to a method for producing a biodegradable polyester having a tensile strength of 100-350 kg / cm 2 and an elongation of 250-500%.

In general, aliphatic polyester is biodegradable, but its use is limited because of its low melting point and poor physical properties such as heat resistance and mechanical strength, whereas aromatic polyester is known to have good physical properties but no biodegradability. Recently, environmental pollution is a serious problem, and various problems are removed, especially as artificial polymers, which are not easily decomposed in the ecosystem, accumulate in the ecosystem and thus damage the aesthetics. In order to solve these problems, attempts have recently been made to produce polymers that can be rapidly decomposed in an ecosystem by mixing polyethylene and starch, and various biodegradable polymers are actually used. As part of this attempt, the situation is now widely used in various fields. As part of this attempt, the synthesis of biodegradable polymers using polyesters, which are currently used in many ways, has been studied. As an example, when aromatic polyester is heated and melted, aliphatic polyester is added together with a catalyst and reacted while stirring to form a typical transesterification reaction to form a biodegradable random copolymer. Has been said to depend on the content of aromatic polyesters. ["Journal of applied polymer science" Vol. 26, (1981), p. 441-448]. However, when the random copolymer is prepared in this way, thermal decomposition of polyester occurs, so that it is difficult to obtain desired polymerization degree and physical properties, and when the content of aromatic polyesters is increased to obtain physical properties, the biodegradability is encountered.

It is an object of the present invention to provide a method for producing a biodegradable polyester random copolymer having a controlled polymerization degree of aromatic polyesters without increasing the content of aromatic polyesters in order to improve physical properties.

Polygon composition in the present invention is characterized in that the polymerization degree of the aromatic polyester in 50-90 parts by weight of aromatic polyester and 10-50 parts by weight of aliphatic polyester is about 50-150. Preferred degrees of polymerization of the aromatic polyester include about 80-110 degrees.

When explaining the present invention in detail, the first polymerized aromatic polyester is polymerized from the monomer to reach the desired degree of polymerization without melting the polymerized polyester and causing transesterification, and then aliphatic polyester is rapidly melted to stir in the presence of a catalyst. It is characterized by obtaining a biodegradable polyester polymer having a random distribution of aliphatic and aromatics by transesterification.

More specifically, butylene terephthalate, ethylene terephthalate, and the like used in the preparation of aromatic polyesters have a desired degree of polymerization in the presence of ethylene glycol and a catalyst generally used for ester polymerization in a weight-to-volume ratio of 2: 7-7: 1. The reaction is carried out until the reaction is carried out, and a suitable amount of biodegradable aliphatic polyester such as polycaprolactone is added to cause a transesterification reaction to obtain a copolymer in which aliphatic and aromatic are randomly distributed.

The polymer produced by the present invention shows similar physical properties even when the content of the aromatic polyester is low compared to the conventional method described above, and when the content ratio is similar, the degradability and physical properties are excellent.

The preparation of monomers and aliphatic polyesters used in the present invention is already known.

It is also a known fact to prepare aromatic polyesters from monomers. As a condition for preparing a polymer having better physical properties, the polymerization temperature of the aromatic polyester is suitably 200-300 ° C., preferably 230-270 ° C., and the polymerization time is 1-3 hours, preferably 1.5-2.5. Time is right. The stirring speed is 40-50 rpm, and after the addition of the aliphatic polyester, it is possible to obtain a better physical polymer by lowering the reaction temperature to 190-220 ° C.

Zinc acetate anhydride is suitable as a catalyst for the transesterification reaction, and the reaction time is 0.5-1.5 hours, preferably 50-90 minutes.

The number average molecular weight of the aliphatic polyester used is suitably 20,000-50,000, and 25,000-40,000 is especially preferable. After the transesterification reaction is completed, the polymer is discharged into an aqueous solution to coagulate.

Polymer prepared according to the present invention has a tensile strength of 100-350㎏ / ㎠, elongation is 250-500%, tensile strength of the polymer obtained by the conventional method 70-200㎏ / ㎠, elongation 200-370 Physical properties are better than% and biodegradability is better.

Biodegradability of the polymers prepared according to the invention was evaluated at the rate of dissolution by lipase. 100 micromolar phosphate buffer was used as the reaction solution, and the polymer powder was added so that the amount of aliphatic polyester was 20 milligrams. To this was added 0.2 milligrams of lipolytic enzyme of the genus Rizopus, and the total reaction solution volume was 1 ml, followed by stirring at 37 ° C. for 16 hours. After the reaction, the reaction solution was filtered to determine the biodegradation rate by measuring the total amount of water soluble carbon in the filtrate. It was assumed that the amount of water-soluble carbon was produced only in aliphatic polyester.

Biodegradation rate was determined by the following equation.

Biodegradation rate = [total carbon content in aqueous solution / 20 (mg)] × 100

When explaining the present invention by Examples and Comparative Examples.

Example 1

1 kg of butylene terephthalate, 50 ml of ethylene glycol, and 300 mg of anhydrous zinc acetate were added to a small polymerization tube with a capacity of 2 L, and stirred at 50 rpm at a reaction temperature of 250 ° C. for 1.5 hours to give a polymerization degree of 90 and then polycaprolactone. 500 g was added and the reaction proceeded at 40 rpm for 1 hour while the reaction temperature was decreased to 200 ° C. After the reaction, the polymerization liquid was discharged to solidify in water to extract the unreacted monomer. Table 1 shows the physical properties and biodegradability of the prepared polymer.

Using a conventional method, 1.5 kg of polybutylene terephthalate and 500 g of polycaprolactone were added to a small polymerization tube with a capacity of 2 L, 300 mg of zinc anhydride was added thereto, stirred at 250 rpm at 50 ° C. for 1.5 hours, and the reaction temperature was decreased. The reaction was carried out for 1 hour after falling to 200 ° C. After the reaction, the polymer was discharged to coagulate in water. Table 1 shows the physical properties and biodegradability of the prepared polymer.

TABLE 1

Example 2

0.5 kg of ethylene terephthalate, 250 ml of ethylene glycol and 200 mg of zinc acetate were added to a small polymerization tube with a capacity of 2 L, the reaction proceeded for 1 hour while stirring at a reaction temperature of 230 ° C. to a polymerization degree of 100, and then 500 g of polycaprolactone was added. The reaction was proceeded while stirring at 40 rpm for 30 minutes while lowering the temperature to 210 ℃. After the reaction, the polymer was discharged to solidify in water to extract the unreacted monomer. Table 2 shows the physical properties and biodegradability of the prepared polymer.

Comparative Example 2

0.7 kg of polyethylene terephthalate and 500 g of polycaprolactone were added to a small polymerization tube having a capacity of 2 L by using a conventional method, and 200 mg of anhydrous zinc acetate was added thereto, and the reaction was allowed to proceed for 1 hour while stirring the reaction temperature at 50 ° C. at 230 ° C. The reaction proceeded while stirring at 40 rpm for 30 minutes while lowering the temperature to 200 ℃. After the reaction, the polymer was discharged to coagulate in water. Table 2 shows the physical properties and biodegradability of the prepared polymer.

TABLE 2

Claims (2)

In preparing a random copolymer of an aromatic polyester and an aliphatic polyester, the polymer is first polymerized at an polymerization temperature of 230-270 ° C. from an aromatic polyester monomer in the presence of a conventional transesterification catalyst to a polymerization degree of 80-110, and then the reaction is continued. After lowering the temperature to 190-220 ℃, polymerized aromatic polyester: added aliphatic polyester so that the weight ratio of the introduced aliphatic polyester is 50: 50-90: 10 and melted to cause a transesterification reaction Method for producing a polymer. The method of claim 1, wherein the aromatic polyester is obtained by polymerizing ethylene glycol with an aromatic polyester monomer selected from butylene terephthalate or ethylene terephthalate, and the aliphatic polyester is polycaprolactone.