JPS5952658B2 - Manufacturing method of high polymerization degree polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly polymerized polyester suitable for producing various molded products such as high-strength fibers, films, and hollow containers.

BACKGROUND OF THE INVENTION Polyesters, particularly polyesters mainly composed of ethylene terephthalate repeating units, have been widely used as fibers, films, and molded products such as hollow containers because of their many excellent properties.

Polyester, which is used for processing and forming fibers for industrial materials such as belts and tire cords, and films and hollow containers used for packaging and filling foods and cosmetics, is especially sensitive to its processing properties during melting and the ultra-high quality of products. The degree of polymerization of the polyester itself must be sufficiently high in order to meet required performance such as strength and hygiene (low polymer and acetaldehyde content). As a method for obtaining high polymerization degree polyester,
There is a melt polymerization method at a temperature above the melting point of polyester and a solid phase polymerization method at a temperature below the melting point, but in the former case, a thermal decomposition reaction occurs at the same time as the polymerization reaction, so only colored, low-quality polymers can be obtained.

Therefore, especially when it is desired to obtain a polyester with a high degree of polymerization, a solid phase polymerization method is employed. In the solid phase polymerization method, as is already well known, pellets of a polyester prepolymer with a low degree of polymerization obtained by the melt polymerization method or its pulverized product are heated under reduced pressure or under a stream of inert gas to determine the melting point of the polyester prepolymer. The polycondensation reaction is advanced by heating at the following temperature.

Factors that are generally known to affect the reaction rate of solid-state polymerization are the chemical properties and crystallinity of the prepolymer, the shape and size of chips or crushed materials, polycondensation temperature, degree of vacuum or inert gas. For example, in the case of polyethylene terephthalate, a prepolymer with few diethylene glycol units in the polymer main chain and a relatively high terminal carboxyl concentration is used, the particle size is made as fine as possible, and the particle size is made as close to the melting point as possible. Polymerization at high temperature and under high vacuum increases the solid state polymerization rate. The shape of polyester chips used for fibers, films, and various molding processes is usually a prismatic or cylindrical shape with a length of about 1 to 5 mm. The surface layer of the chip, where glycol and/or water, which is a reaction product of solid phase polymerization, easily diffuses has a higher polymerization rate than the center part, and a polymer having a wide distribution of degree of polymerization is produced inside and outside the polymer chip.

Furthermore, not only the degree of polymerization distribution within the chip particles themselves, but also the powder and small fragments of chips present in the raw prepolymer during cutting, the contact between chips during solid phase polymerization, and the contact between chips and the walls of the polymerization equipment, Powders and small pieces smaller than a normal chip shape, such as small notched pieces produced by friction, etc., are simultaneously solid-phase polymerized, so that these powders and small pieces have an abnormally higher degree of polymerization than the chips. Polymers obtained by solid-state polymerization contain chips with a wide distribution of polymerization degree and small particles with an abnormally high degree of polymerization, so when melt-molding these solid-state polymerized polyesters, extremely large causing a decrease in intrinsic viscosity,
This may lead to fluctuations in melt viscosity.

A more fatal drawback is that small particles with an abnormally higher degree of polymerization than the average degree of polymerization of the chip and the surface layer of the chip are unevenly or incompletely melted during melting, resulting in avatar-like mottling and abnormalities on the surface of the molded product. It can appear as a fluid pattern. Particularly in the case of melt extrusion molded products such as films and hollow containers made by diretor five-prong molding, such avatar or crater-shaped spots are likely to occur, which is a serious problem. In view of the current situation, the inventors of the present invention have conducted repeated research on a method for producing a polyester with a high degree of polymerization that does not have a wide distribution of degree of polymerization, and as a result, they have arrived at the present invention.

That is, the present invention provides a method for producing a polyester with a higher degree of polymerization by solid phase polymerization using a polyester obtained by melt polycondensation of dimethyl ester of an aromatic dicarboxylic acid and glycol through transesterification reaction as a prepolymer. As the prepolymer to be used, the methyl ester end group concentration exceeds 5 (equivalent/106 g polymer) and 15 (
equivalent weight/106g polymer), and the sum of methyl ester end groups and carboxyl end groups is less than 25(equivalent/1
It is characterized in that a prepolymer having a weight of more than 0.6 g polymer (equivalent weight/10 g polymer) and less than 50 (equivalent weight/10 g polymer) is used. When using the method of the present invention, by using a prepolymer having a specific amount of specific terminal groups, the distribution of the degree of polymerization in the inner and outer layers of the chip is narrow, and the distribution of the degree of polymerization is narrow due to the size of the chip particle size 4. It has the characteristic that polyester can be easily obtained. Therefore, melting during molding is easy and uniform, which prevents a decrease in the intrinsic viscosity of the polymer, provides stable melt viscosity, and prevents avatar-like or flow patterns from forming on the surface of the molded product. Excellent effects can be achieved. The amount of methyl ester end groups contained in the prepolymer to be subjected to the solid phase polymerization of the present invention exceeds 5 (equivalent/106 g polymer) and 15 (equivalent/106 g polymer).
106g polymer), and the sum of methyl ester end groups and carboxyl end groups is less than 25 (equivalent/1
06g polymer) and less than 50 (equivalent/106g polymer).

More preferably, the amount of methyl ester end groups is more than 6.5 (equivalents/106 g polymer) and less than 13 (equivalents/106 g polymer), and the sum of the methyl ester end groups and carboxyl end groups is 30 (equivalents/106 g polymer). A prepolymer containing end groups ranging from more than 45 (equivalents/106 g polymer) to less than 45 (equivalents/106 g polymer). If the number of methyl ester terminal groups is less than 5 (equivalent/106 g polymer), it becomes impossible to obtain a high polymerization degree polyester with a narrow polymerization degree distribution, which is the object of the present invention. Also 15 (equivalent / 106g
Polymer) or higher, the transesterification reaction in the solid phase is slow, making it difficult to obtain a polyester with a high degree of polymerization.
Furthermore, even if the methyl ester end group amount is in the range of more than 5 (equivalent/106 g polymer) and less than 15 (equivalent/106 g polymer), if the sum with the carboxyl end group amount is 25 (equivalent/106 g polymer) or less, The purpose of the present invention cannot be achieved.

Moreover, if it exceeds 50 (equivalent/106 g polymer), it is not suitable because the thermal stability of the obtained polymer will deteriorate. As a method for adjusting the concentration of methyl ester end groups and carboxyl end groups in the prepolymer, bisglycol esters of aromatic dicarboxylic acids and their low polymers are produced by a transesterification reaction between dimethyl esters of aromatic dicarboxylic acids and glycols. Control by adjusting the raw material composition ratio of dicarboxylic acid dimethyl ester and glycol, catalyst species, catalyst amount, temperature, time, etc. of transesterification reaction in the process, and adjustment of polymerization temperature, time, degree of vacuum, etc. in the melt polycondensation process. can do. The intrinsic viscosity of the prepolymer is usually 0.3 to 0.8, preferably 0.4.
~0.7 is used. The solid phase polymerization method of the present invention can be carried out using a known method, for example, 5 to 5 % from the melting point of polyester.
Polymerization is carried out at temperatures as low as 0° C. under high vacuum or in an inert gas atmosphere. In this case, the shape particle size and specific surface area of the prepolymer are not particularly limited, but if the particle size becomes too large, the solid phase polymerization time becomes long, so it is usually preferable to have about 2 to 20 meshes, more preferably 3 to 20 meshes. It is particularly preferable that the number of meshes is about 15 meshes. By the method of the present invention, a high degree of polymerization polyester having a narrow degree of polymerization distribution and a high intrinsic viscosity (for example, 1.0 or more) can be advantageously produced industrially.

The dimethyl esters of aromatic dicarboxylic acids used in the present invention include terephthalic acid, 2,6-naphthalene dicanolebonic acid, dimethyl ester of 1,2-diphenoxyethane P,P''-dicanolebonic acid, etc. be.

These dimethyl esters may be mixed with 20 mol % or less of other carboxylic acids or lower alkyl esters of carboxylic acids, such as isophthalic acid, adipic acid, sebacic acid, or lower alkyl esters thereof.
As the glycol component, mainly ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexamethylene glycol, and 1,4-citalohexane dimethanol are used. It is also possible to add small amounts of mixtures of these and other glycols. In addition to these difunctional raw materials, polyfunctional compounds such as trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, etc. may be copolymerized in an amount of 1 mol % or less per dicarboxylic acid or glycol component. The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to the Examples.

The method of measuring characteristic values in Examples and Comparative Examples is as follows. (1) Intrinsic viscosity phenol/tetrachloroethane (60/40 weight ratio)
It was measured at 30°C using a mixed solvent.

(2) Amount of methyl ester end groups in prepolymer The prepolymer is completely decomposed with monoethanolamine, and the methyl alcohol produced is quantified by gas chromatography and expressed as the number of equivalents per 106 g of polymer.
(3) Analysis of the amount of carboxyl terminal groups in the prepolymer
ticalChemistry Vol. 26, p. 1614 (
(1954) according to the method of PhOl.

(4) Gradient degree of polymerization inside the chip A solid-phase polymerized polyester chip was peeled off from the surface in stages using a heated caustic soda aqueous solution, and the degree of polymerization was determined from the weight and intrinsic viscosity of the particles remaining after peeling.

Examples 1 to 3 and Comparative Examples 1 to 8 100 parts of dimethyl terephthalate and 6 parts of ethylene glycol
0 part and 0.028 part of manganese acetate and 0.024 part of germanium dioxide as catalysts in a nitrogen atmosphere, 150~
Methanol produced by heating to 280°C to carry out transesterification was continuously distilled out of the system.

The transesterification reaction time was 100 minutes in Comparative Example 1, 120 minutes in Example 1, 140 minutes in Example 2, and 140 minutes in Example 3.
was carried out for 160 minutes, Comparative Example 2 was carried out for 180 minutes, and Comparative Example 3 was carried out for 190 minutes. After a predetermined reaction time, 0.042 parts of trimethyl phosphate was added to the obtained bishydroxyethyl terephthalate and its low polymer, and after stirring for 10 minutes, the mixture was transferred to a polymerization kettle, and the polymerization system was gradually heated and depressurized. Finally, melt polycondensation was carried out for 200 minutes at 285° C. and 0.5 mmHg. After the polymerization was completed, the inside of the system was returned to normal pressure with nitrogen, and then discharged into water to a size of 3.4 mm x 3.4 mm x 4.0 m.
It was cut into prismatic chips of m. Next, the obtained prepolymer was placed in a rotary solid phase polymerization apparatus at 120°C and 0.5°C.
After drying and preliminary crystallization for 5 hours under 5 mmHg, the temperature was raised to 235°C, and solid phase polymerization was performed under reduced pressure of 0.2 mmHg for 20 hours.

After completion of solid phase polymerization, (a) average intrinsic viscosity of the chip;
Intrinsic viscosity of the part where 500 microns of the surface layer of the chip is removed with a cutter, (c) Only the center of the chip is 1 mm x 1 m.
The intrinsic viscosity of the center layer cut into a size of m x 1 mm and (d) the intrinsic viscosity of the powder generated during solid phase polymerization were measured.

Intrinsic viscosity of prepolymer, methyl ester end group concentration (
equivalent weight/106g polymer), carboxyl end group concentration (
In conjunction with the data of equivalent weight/106g polymer) (a)
The results of the intrinsic viscosity of ~(d) are shown in Table 1.

For prepolymers with fewer methyl ester end groups, there is a difference in intrinsic viscosity between the chip surface layer and the center layer [(x) - (c)]
Difference in intrinsic viscosity between the powder and the chip powder [(d)-(a)]
becomes very large. Examples 4 to 5 and Comparative Example 4 Prepolymer 1 and solid phase polymerization polymer were prepared in exactly the same manner as in the above Examples, except that the transesterification reaction time, melt polycondensation time, and solid phase polymerization time were changed to the conditions shown in Table 2. I got it.

The properties of the prepolymer and the intrinsic viscosity of the solid phase polymerized polymer are shown in Table 1. In addition, the degree of polymerization (intrinsic viscosity) distribution within the chip obtained by the alkaline peeling method of the solid phase polymerized chips of Example 6 and Comparative Example 5 is shown in Figure 1. Indicated.

As is clear from Comparative Example 4, even if the methyl ester end group is within the range of the present invention, if the amount of carboxyl end group is outside the range of the present invention, only a polymer with a wide distribution of polymerization degree can be obtained.

It also has the disadvantage that the polymerization rate decreases. Example 6
, Comparative Example 5 In Example 1, 64 parts of ethylene glycol was added. Instead, prepolymer 1 was produced in the same manner as in Example 1, except that the transesterification reaction time was 140 minutes in Example 6 and 180 minutes in Comparative Example 5.

Claims (1)

[Claims] 1 When producing a polyester with a higher degree of polymerization by solid phase polymerization using a polyester obtained by melt polycondensation of dimethyl ester of aromatic dicarboxylic acid and glycol through transesterification as a prepolymer, methyl is used as a prepolymer to be subjected to solid phase polymerization. Ester end group concentration exceeds 5 (equivalents/10^6 g polymer) and 15 (equivalents/10^6
g polymer), and the sum of methyl ester end groups and carboxyl end groups is more than 25 (equivalent/10^6 g polymer) and less than 50 (equivalent / 10^6 g polymer). A method for producing a high degree of polymerization polyester.