KR100349595B1 - Process for producing biodegradable copolyester - Google Patents

Abstract

The present invention relates to a novel biodegradable terpolymer having improved impact strength and, more particularly, to a process for producing a novel biodegradable terpolymer having improved impact strength, After the esterification reaction, the catalyst is added and condensation is carried out under high temperature and high vacuum, or an ester reaction of an aliphatic dicarboxylic acid and an aliphatic divalent alcohol is carried out, and then a polybutylene terephthalate-polytetramethylene ether glycol copolymer is added together with a catalyst The polymer is polymerized under high temperature and high vacuum so that the aliphatic ester unit contains 60 to 92 mol% of the terpolymer, 3 to 15 mol% of the aromatic ester unit and 5 to 25 mol% of the tetramethylene ether unit, To a method for producing a copolymer polyster.

Description

Process for producing biodegradable copolyester

The present invention relates to a novel biodegradable terpolymer having improved impact strength and, more particularly, to a process for producing a novel biodegradable terpolymer having improved impact strength, After the ester reaction, the catalyst is added and condensation is carried out under high temperature and high vacuum, or an ester reaction of an aliphatic dicarboxylic acid and an aliphatic dicarboxylic acid is carried out, and then a polybutylene terephthalate-polytetramethylene ester glycol copolymer is added together with a catalyst The present invention relates to a method for producing biodegradable copolyester by intensive polymerization under high temperature and high vacuum conditions.

Recently, as the problem of environmental pollution caused by waste plastics becomes serious, researches on biodegradable polymers have been actively conducted worldwide. As a result, commercialization of biodegradable polymers such as starch-based polymers, cellulose acetate, polyhydroxybutyrate, polylactide, polycaprolactone, and polybutylene succinate has been commercialized. Among them, a biodegradable polymer produced by condensation polymerization of a dihydric alcohol and a dicarboxylic acid, such as polybutylene succinate, is excellent not only in physical properties and processability but also in mass production, and is expected to be the most promising biodegradable polymer Is expected to be. Japanese Patent Application Laid-Open Nos. 4-189822 and 59-213724 disclose a process for producing a pure aliphatic polyester by reacting an aliphatic dicarboxylic acid with a dihydric alcohol. U.S. Patent Nos. 5374259 and 5391644 disclose a process for producing an aliphatic polyester A method of using a diisocyanate to increase the molecular weight is disclosed.

Generally, aliphatic polyesters have biodegradability, but have low melting point, low mechanical and thermal resistance, while aromatic polyesters have good physical properties but no biodegradability. Studies have been made on the production of a random copolymer having biodegradability by causing a typical transesterification reaction by stirring the aromatic polyester and the aliphatic polyester together with the catalyst by utilizing these characteristics (JP-A-2-11013, U. S. Patent No. 42447678, U.S. Patent No. 5292783). On the other hand, Patent Application No. 90-22052 discloses a method for producing a biodegradable polyester copolymer in which the degree of polymerization of an aromatic polyester is controlled instead of increasing the content of aromatic polyester in order to improve the physical properties of the aliphatic polyester. 027071 discloses a process for copolymerizing aliphatic divalent alcohols and aromatic divalent alcohols with aliphatic divalent carboxylic acids and aromatic divalent carboxylic acids. Generally, the biodegradability is reduced as the aromatic content increases. However, as in the case of the random copolymer, it is known that when the length of the aromatic block is short, the aliphatic polyester portion is decomposed first and then the residual aromatic portion is relatively low molecular weight. .

However, despite these research efforts, the production cost of the biodegradable polymer is higher than that of the general-purpose resin, so that the use range of the biodegradable polymer is limited to the special purpose. As part of efforts to lower production costs, research into the blend of cheap starch and biodegradable polymerizers has been actively conducted, and the production of starch and biodegradable polymer blends is also high worldwide and is of great industrial value. However, since starch is mostly insoluble, it is not compatible with biodegradable polymeric materials, and as a result, the interfacial adhesion between the polymeric materials is deteriorated, which degrades mechanical properties and processability.

Studies have been carried out to induce the chemical bonding of starch and resin using catalysts or coupling agents to improve the compatibility of resin and starch. However, there is a limitation in increasing the compatibility with such a method Therefore, it is essential to use biodegradable polymeric materials as matrix resins with good mechanical strength, elongation and impact strength. Accordingly, the present inventors have conducted studies for developing a copolymer polyester having excellent mechanical strength, elongation and impact strength while maintaining biodegradability.

In this study, the aliphatic dicarboxylic acid and the aromatic dicarboxylic acid and the aliphatic dicarboxylic alcohol were ester - reacted with the polytetramethylene ether glycol having a molecular weight of 1,000 and then the catalyst was added and condensation was carried out under high temperature and high vacuum, The addition amount and the addition timing of the polybutylene terephthalate-polytetramethylene ether glycol copolymer having different contents of tetramethylene ether with the addition of the catalyst after the esterification reaction of the carboxylic acid and the aliphatic divalent alcohol are controlled, It was possible to develop a biodegradable copolymer polyester having various physical properties and processability. On the other hand, in the case of the copolymer comprising only butylene succinate and butylene terephthalate, the elongation was improved as the content of butylene terephthalate was increased, but the melting point was drastically lowered, which slowed the crystallization rate, lowered the tensile strength, It did not improve much. In the case of a copolymer comprising only butylene succinate and tetramethylene ether glycol, there was no problem in lowering the melting point or in the crystallization speed, but the impact strength did not improve effectively. Hereinafter, the present invention will be described in more detail.

The divalent carboxylic acid to be used in the present invention is preferably a dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, , 1,4-naphthalenedicarboxylic acid and the like, and it is particularly effective to use succinic acid and adipic acid together with terephthalic acid. Specific examples of aliphatic divalent alcohols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and the like , Especially ethylene glycol and 1,4-butanediol.

In the present invention, the amount of terephthalic acid and polytetramethylene glycol charged in the early stage of the ester reaction, or the amount of the polybutylene terephthalate-polytetramethylene ether glycol copolymer charged just before the condensation polymerization, It is effective that the aliphatic ester unit is composed of 60 to 92 mol% of the total resin, 3 to 15 mol% of the butylene terephthalate unit and 5 to 25 mol% of the tetramethylene ether unit. When the content of the butylene terephthalate unit and the tetramethylene ether unit in the terpolymer is less than 5 mol%, the melting point of the copolymerized polyester is insufficient for improving the physical properties. When the content is more than 40 mol% It is low and biodegradable.

Examples of the catalyst used in the present invention include tetraisopropyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetramethyl titanate. The amount of the catalyst to be used is in the range of 0.01 to 0.5% by weight based on the dicarboxylic acid desirable. When the amount of the catalyst used is less than 0.01% by weight, the condensation reaction does not progress effectively and a polymer having a sufficient degree of polymerization can not be obtained. On the other hand, when the amount of the catalyst is more than 0.5% by weight, the reaction rate is accelerated but the obtained polymer tends to be colored and pyrolytic not. A catalyst is not required during the ester reaction, and a catalyst is preferably added at the end of the ester reaction so that the deglycol reaction proceeds effectively in the condensation polymerization reaction.

As the stabilizer to be used in the present invention, it is preferable to use a phenolic compound as the primary antioxidant and a sulfur compound as the secondary antioxidant. When the amount is less than 0.04 to 0.8 wt% based on the dicarboxylic acid, the effect as a stabilizer is insufficient And when it is more than 0.8% by weight, the color of the polymer is deteriorated and the mechanical properties are deteriorated. The addition timing may be at the initial or end of the esterification reaction. In the present invention, in addition to the above-mentioned components, ultraviolet absorbers, pigments, fluorescent whitening agents and the like generally used in the production of polyester can be used.

Hereinafter, the present invention will be described specifically by way of examples, but the present invention is not limited to the examples.

Example 1

The reactants were added to the reaction mixture in an amount of 0.23 mol of terephthalic acid, 0.36 mol of tetramethylene ether glycol and 1.2 mol of 1,4-butanediol per 1 mol of succinic acid, and 0.1% by weight of each of primary and secondary antioxidants , And the ester reaction was carried out over a period of 100 minutes while gradually raising the temperature from room temperature to 200 占 폚. The resulting water was completely drained out of the system through a condenser. Then, the titanate catalyst was added in an amount of 0.2 wt% based on the succinic acid, mixed well for 10 minutes, and slowly decompressed to maintain the vacuum at a level of 1 torr or less And the condensation reaction was carried out for 3 hours. After completion of the reaction, the vacuum was disassembled and the polymer was discharged with nitrogen to obtain a final product. The composition and physical properties of the final polymer were evaluated and summarized in Table 1.

The measured values shown in Table 1 are the physical property data of the compositions prepared in Examples and Comparative Examples using the following test conditions and methods.

* Content of composition: Analysis of the contents of butylene succinate, butylene terephthalate and tetramethylene ether units using 300-MH _Z ¹ H NMR.

* Melt index: measured according to ASTM D-1238 at 130 ° C under a load of 2160 g, the lower the melting index, the higher the degree of polymerization.

Melting point and melting heat: Measured at a heating rate of 10 ° C / min using DSC.

* Tensile stress: measured by ASTM D-638.

* Izod impact strength: measured by ASTM D-126, using 1/4 inch specimen.

* Biodegradability: Plastics resistance by fungi Test for biodegradability by cultivating for 60 days according to ASTM G 21-70, and dividing the degree of fungus cover on the surface of 5 × 5 × 0.3 cm specimens as follows.

Rating 0 One 2 3 4 Fungal growth surface area (%) 0 0-10 10 to 30 30 to 60 60-100

Example 2

Except that 37 mol% of polybutylene terephthalate-polytetramethylene ether glycol copolymer was added immediately before the condensation polymerization instead of the addition of terephthalic acid and tetramethylene ether glycol in the early stage of the ester reaction, The composition and physical properties of the final polymer were evaluated and are summarized in Table 1.

Examples 3 to 5

The amount of terephthalic acid and tetramethylene ether glycol was changed, and condensation polymerization was carried out in the same manner as in Example 1. The composition and physical properties of the resulting polymer were evaluated and summarized in Table 1.

Comparative Example 1

The polymer was condensed in the same manner as in Example 1 except that succinic acid and 1,4-butanediol were used as reactants. The composition and physical properties of the resulting polymer were evaluated and summarized in Table 1.

Comparative Example 2

The polymer was condensed in the same manner as in Example 1 except that tetramethylene ether glycol was not added. The composition and physical properties of the final polymer were evaluated and summarized in Table 1.

Comparative Example 3

Except that terephthalic acid was not added. The composition and physical properties of the final polymer were evaluated and summarized in Table 1.

Comparative Example 4

Polymerization was carried out in the same manner as in Example 2 except that the amount of the polybutylene terephthalate-polytetramethylene ether glycol copolymer was reduced to 4 mol%. The composition and physical properties of the final polymer were evaluated in Table 1.

Physical properties and biodegradability of various copolyester Composition ^a Melt Index (g / 10 min) Melting point (캜) Tensile strength (Kg _f / cm ²⁾ Elongation (%) Impact strength (Kg _f cm / cm) Biodegradability BS (mol%) BT (mol%) BO (mol%) Example 1 62.9 14.5 22.6 2.6 87 130 NB ^b . 53.1 One Example 2 63.4 13.7 22.9 3.6 89 137 N.B. 51.6 One Example 3 65.9 11.0 23.1 3.0 95 156 N.B. 39.9 2 Example 4 75.8 10.8 16.4 4.2 102 210 N.B. 18.9 2 Example 5 90.1 4.5 5.4 3.1 108 284 N.B. 11.7 3 Comparative Example 1 100 0 0 3.5 114 354 300 5.1 4 Comparative Example 2 93.1 6.9 0 3.7 105 263 620 7.8 2 Comparative Example 3 74.1 0 25.9 5.5 110 258 N.B. 9.8 3 Comparative Example 4 96.0 1.6 2.4 3.6 111 312 347 8.6 4

a. BS: Butylene succinate, BT: Butylene terephthalate, BO: Content of the butylene oxide (tetramethylene ether) in the copolymer.

b. N.B. : no break, extension rate over 900%.

The present invention provides a copolymer polyester having excellent mechanical strength, elongation and impact strength while maintaining biodegradability.

Claims (23)

In the production of a biodegradable ternary copolymerizable polyester, a) esterifying an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid with an aliphatic divalent alcohol and a polytetramethyl ether glycol; b) introducing a catalyst into the ester reaction product; And c) polycondensation of the mixture containing the catalyst under high temperature and high vacuum ≪ / RTI > The method according to claim 1, Wherein the aliphatic dicarboxylic acid is selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, saperic acid and sebacic acid. The method according to claim 1, Wherein the aromatic dicarboxylic acid is selected from terephthalic acid, isophthalic acid, 2,6-naphthalenecarboxylic acid and 1,4-naphthalenedicarboxylic acid. The method according to claim 1, Wherein the aliphatic divalent alcohol is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol ≪ / RTI > The method according to claim 1, Wherein the polytetramethylene ether glycol has a molecular weight of 800 to 1200. The method according to claim 1, Wherein the catalyst is selected from tetraisopropyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetramethyl titanate. The method according to claim 6, Wherein the amount of the catalyst to be used is 0.01 to 0.5 wt% with respect to the divalent carboxylic acid. The method according to claim 1, Wherein the degree of vacuum in the condensation polymerization step is less than or equal to 1 torr. The method according to claim 1, wherein the polymerization temperature in the condensation polymerization step is 200 to 300 占 폚. The method according to claim 1, Wherein the phenol compound and the sulfur compound are added as stabilizers in the step of esterification. 11. The method of claim 10, Wherein the amounts of the phenolic compound and the sulfur compound in the stabilizer are 0.04 to 0.8 wt% based on the divalent carboxylic acid, respectively. In the production of a biodegradable ternary copolymerizable polyester, a) a step of ester-reacting an aliphatic dicarboxylic acid and an aliphatic divalent alcohol; b) introducing polybutylene terephthalate-polytetramethylene ether glycol copolymer with the catalyst into the ester reaction product; And c) polycondensation of the mixture containing the catalyst under high temperature and high vacuum ≪ / RTI > 13. The method of claim 12, Wherein the aliphatic dicarboxylic acid is selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, saperic acid and sebacic acid. 13. The method of claim 12, Wherein the tetramethylene ether unit in the polybutylene terephthalate-polytetramethylene ether glycol copolymer is contained in the copolymer in an amount of 50 to 80 mol%. 13. The method of claim 12, Wherein the aliphatic divalent alcohol is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol ≪ / RTI > 13. The method of claim 12, Wherein the catalyst is selected from tetraisopropyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetramethyl titanate. 17. The method of claim 16, Wherein the amount of the catalyst to be used is 0.01 to 0.5 wt% with respect to the divalent carboxylic acid. 13. The method of claim 12, Wherein the degree of vacuum in the condensation polymerization step is less than or equal to 1 torr. 13. The method of claim 12, And the temperature in the condensation polymerization step is 200 to 300 占 폚. The method according to claim 1, Wherein the phenol compound and the sulfur compound are added as stabilizers in the step of esterification. 21. The method of claim 20, Wherein the amounts of the phenolic compound and the sulfur compound in the stabilizer are 0.04 to 0.8 wt% based on the divalent carboxylic acid, respectively. In the biodegradable ternary copolymerizable polyester comprising three components of aliphatic ester, aromatic ester and tetramethylene ether, Wherein the aliphatic ester unit is 60 to 92 mol%, the aromatic ester unit is 3 to 15 mol%, and the tetramethylene ether unit is 5 to 25 mol%. In the blend of biodegradable copolyester and starch, Wherein the aliphatic ester unit is 60 to 92 mol%, the aromatic ester unit is 3 to 15 mol%, the tetramethylene ether unit is 5 to 25 mol%, and the blend of the starch and the biodegradable copolymerizable polyester.