JPS6323924A - Solid-state polymerization into polyester - Google Patents

Abstract

PURPOSE:To obtain a polyester of a high degree of polymerization easily within a short time, by heating low-viscosity fine particulate prepolymer based on ethylene terephthalate and subjecting the particulate prepolymer to solid-state polymerization in a partially fused state by a specified two-stage polymerization process. CONSTITUTION:A fine particulate prepolymer based on ethylene terephthalate and having an intrinsic viscosity of 0.1-0.32 and a particle diameter of about 100-500mum is prepared. This prepolymer is subjected to solid-state polymerization in a state in which the particles partially fused with each other at a polymerization temperature of 200-260 deg.C. The polymer is cooled to below 200 deg.C and kept in this state for 30min-3hr during the course of the progress of polymerization, for example, by supplying an inert gas into the polymerization apparatus. Next, the solid-state polymerization is continued by heating. In this way, the formation of ethylene glycol in the polymer particles can be prevented, and a polyester of a high degree of polymerization and an intrinsic viscosity >=about 1.7 can be obtained within a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a solid phase polymerization method for obtaining a polyester with a high degree of polymerization and a low acetaldehyde content in a relatively short time.

(Prior Art) Polyesters mainly composed of polyethylene terephthalate or ethylene phthalate are widely produced in large quantities as fibers, films, and molded products such as bottle containers. In particular, polyester obtained by solid phase polymerization has a low acetaldehyde content and can have a relatively high degree of polymerization, and has rapidly attracted attention in recent years as a container material for carbonated drinks such as beer and cola. It is a material that exists.

(Problems to be Solved by the Invention) Such high polymerization degree polyesters have conventionally been produced by first producing polyester pellets with a relatively low degree of polymerization by melt polycondensation, and after preliminary crystallization, the polyester pellets are produced under reduced pressure or through an inert gas flow. Polyester pellets made by solid phase polymerization under
The fusion between the pellets that occurs during pre-crystallization or solid phase polymerization inhibits increasing the degree of polymerization. In order to avoid such inconveniences, conventionally various considerations have been made regarding equipment and conditions. In particular, in order to avoid such inconveniences, the polymerization temperature is kept low at 240C or less, so that the rate of increase in the degree of polymerization is also small, and the initial polymer with an intrinsic viscosity of 0.68 used as a starting material is reduced to an intrinsic viscosity of 1. 2
It takes at least ten hours of polymerization time to form a polymer. Therefore, although high polymers having an intrinsic viscosity of 1.7 or more are expected as functional materials, they have not been substantially obtained.

(Means for Solving the Problems) In view of these circumstances, the present inventors have intensively studied a method for obtaining a polyester with a low acetaldehyde content and a high degree of polymerization and an intrinsic viscosity of 1.7 or more. The present invention was completed based on the discovery that the object could be achieved by using a polymerization method.

In order to obtain a high degree of polymerization polyester by solid phase polymerization of an initial polymer mainly composed of ethylene terephthalate according to the present invention,
Intrinsic viscosity is 0.10-0.32, particle size approximately 100-50
The initial polymer in the form of fine particles of 0 μm was heated at a polymerization temperature of 20
It is characterized in that the polymers are partially fused to each other and polymerized in a tentative state at a temperature of 0 to 260C, and that the polymers are once cooled to a temperature of less than 200C during the process of advancing the polymerization. A solid phase polymerization method for polyester. When the intrinsic viscosity of the initial polymer used in carrying out the present invention is smaller than 0.10, the rate of increase in degree of polymerization (value obtained by dividing the value of increase in degree of polymerization by the time required) is extremely low, and the intrinsic viscosity is 1. It takes too much time to obtain a polymer with a molecular weight of 7 or more, and the melting point is low, so it easily fuses and is difficult to handle, making it impractical.In addition, the particle size of the initial polymer has a large effect on the polycondensation reaction efficiency in a solid-state polymerization system. In order to increase the particle size, the particle size is preferably 100 to 500μ, and as a fine particle initial polymer, the intrinsic viscosity is preferably 0.10 to 0.32, preferably 0.14 to 0.25, and the particle size is approximately 100 to 5.
00 μm, preferably 200 to 400 μm.

When the polymerization temperature is less than 200C, the rate of increase in the degree of polymerization becomes small, and it is substantially difficult to obtain a high polymer having an intrinsic viscosity of 1.7 or more. On the other hand, if the polymerization temperature exceeds 260C, the content of acetaldehyde in the obtained polyester will not increase, but the fusion of fine particles will occur rapidly during the polymerization process, resulting in voids in the fine particle packed bed in the polymerization apparatus. This decreases the specific surface area of the fine particle packed bed, significantly impairing the diffusivity of ethylene glycol, and significantly decreasing the rate of increase in the degree of polymerization, making it substantially difficult to obtain a polymer with an intrinsic viscosity of 1.7 or higher. Become. Therefore, in the process of polymerization, it is necessary for the fine particulate polymer to have a porous structure in which individual fine particles adjacent to each other are partially fused on the surface, and the polymerization temperature is 200°C. ~26
0 C, preferably 210 to 250 C.

In the present invention, during the polymerization process, the polymerization temperature of the fine particles is lowered to 200C or less, held under reduced pressure for 50 minutes or more and about 5 hours, and then polymerized at a specified polymerization temperature. The rate of increase in the degree of polymerization of the obtained polyester can be significantly increased, and a polymer having an intrinsic viscosity of 1.7 or more can be obtained relatively easily compared to conventional methods.

Since the intrinsic viscosity of the initial polymer used in carrying out the present invention is as low as 0.10 to 0.32, ethylene glycol is intensely generated from the fine particles at the initial stage of polymerization, and the average concentration of ethylene glycol within the fine particles is low. The rate of increase in the degree of polymerization decreases markedly, but if the polymerization temperature is lowered under reduced pressure during the reaction at this point, the generation of ethylene glycol is suppressed, and the average concentration of ethylene glycol in the fine particles is reduced. Therefore, the rate of increase in the degree of polymerization can be significantly improved.

Methods for heating the particulate initial polymer to the above polymerization temperature include a conductive heat transfer method using a heating medium, a heater, etc. under reduced pressure, a thermal transfer method using infrared rays, a dielectric or induction heating method using high frequency, or any of these methods. A method that combines the two may also be used.

To lower the temperature of the particulate polymer, the jacket may be water-cooled or air-cooled under reduced pressure, or the vacuum may be broken by -degrees, forced cooling is performed using an inert gas, etc., and the material is returned to vacuum. .

The initial polymer mainly composed of ethylene terephthalate used in the present invention is mainly a polyester obtained by reacting terephthalic acid or its ester-forming derivative with ethylene glycol or its ester-forming derivative. In addition to both components, a copolymer of other dicarboxylic acid and/or diol components in a proportion of 20 mol % or less of the total components may also be used. Examples of dicarboxylic acids that can be copolymerized include isophthalic acid, ortho-7thalic acid, diphenyl ether a, a'-dicarboxylic acid, naphthalene dicarboxylic acid, hexahydroterephthalic acid, adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, and cyclohexanedicarboxylic acid. Acid, aromatic, aliphatic or alicyclic dicarboxylic acids such as 5-sodium sulfoisoheptacuric acid, and ester-forming derivatives of these dicarboxylic acids are used. or,
Diol components that can be copolymerized include aliphatic or alicyclic glycols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, and cyclohexane dimetatool, hydroquinone, resorcinol, 2,2
-bis(3-hydroxyphenyl)propane, 2,2-
Examples include aromatic diols such as bis(4-hydroxyethoxyphenyl)propane. Also, as an oxyacid, P
-Citapolyester copolymerized with -oxybenzoic acid, P-oxyethoxybenzoic acid, or an ester-forming derivative thereof can also be used.

(Examples and Comparative Examples) Next, the present invention will be specifically explained using Examples and Comparative Examples. The intrinsic viscosity of polyester is the value measured at 25C using an equal weight mixed solvent of phenol/tetrachloroethane, and the acetaldehyde content in polyester is 16
．． The value (unit: ppm) was determined by a gas chromatography quantitative method after water extraction with Oc for 2 hours.

Example 1 After preparing an initial polymer of ethylene terephthalate with a particle size of about 250 μm and an intrinsic viscosity of 0.18 and charging it into a reactor, the temperature of the initial polymer was adjusted to 150 C and the pressure to 0.5 Torr.
Preliminary drying was performed for 3 hours under reduced pressure. Next, the temperature of the reactor was raised to bring the temperature of the initial polymer to 250C, and the pressure to O, +
After performing solid phase polymerization under reduced pressure of 0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000. I
The temperature of the polymer was cooled to 1500°C under reduced pressure of Torr, held for 1 hour, and then raised to 25QC and further cooled to 60°C.
Time-isophase polymerization was performed. The results are shown in Table-1.

Comparative Example 1 An ethylene terephthalate initial polymer having a particle size of about 250 μm and an intrinsic viscosity of 0.18 was prepared and pre-dried in the same manner as in Example 1. Next, the temperature of the reactor was raised, and the temperature of the initial polymerized product was set at 230C, and solid phase polymerization was carried out for 6 hours under reduced pressure of 0 and I Torr.The results are shown in Table 1. Table -
As is clear from 1, in the comparative example where no decompression operation was performed, 8
The intrinsic viscosity of the polyester obtained after time polymerization is significantly lower than that of the polyester obtained in Example 1.

Claims (3)

[Claims] (1) When obtaining a high polymerization degree polyester by solid phase polymerization of an initial polymer mainly composed of ethylene terephthalate, the intrinsic viscosity is 0.10 to 0.32, and the particle size is approximately 100 to 500μ.
The initial polymerized product in the form of fine particles of m is heated at a polymerization temperature of 200 to 2
The polymers are polymerized at 60°C in a state where they are partially fused to each other, and in the process of advancing the polymerization, the polymers are once heated to 200°C.
A method for the solid state polymerization of polyester, characterized by cooling to a temperature below (2) Cooling time during the process of polymerization: 30 minutes to 3
The solid phase polymerization method according to claim 1, wherein the solid phase polymerization method is performed for a certain period of time. (3) The solid phase polymerization method according to claim 1, characterized in that the method of cooling the polymerized product during the process of polymerization is performed by introducing an inert gas into the polymerization apparatus.