JP2667887B2 - Method for synthesizing high polymerization degree polyester - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for synthesizing a polyester having a high degree of polymerization, and more specifically to a solid phase polymerization method for a polyethylene terephthalate (hereinafter abbreviated as PET) polyester. is there.

(Prior art) PET-based polyester has a very large dependence on the molecular weight of the melt viscosity, and it is difficult to achieve a high degree of polymerization by melt polymerization because it undergoes thermal decomposition at high temperatures. If copolymerization of, for example, a linear dicarboxylic acid is carried out in order to reduce the melt viscosity, various physical properties such as heat stability will be impaired. Therefore, in order to obtain a high polymer having an intrinsic viscosity of 0.9 or more, it is general to carry out melt polymerization to a certain degree of polymerization, then to make a chip (pellet), and then perform solid phase polymerization. At present, it took an extremely long time and a great deal of energy.

(Problems to be Solved by the Invention) Accordingly, the present invention relates to a highly efficient solid-state polyester polymerization method which eliminates the large loss of time and energy.

(Means for Solving the Problems) That is, in the present invention, 1 mol% or more and 20 mol% or less of a compound represented by the following formula (1) in which 80 mol% or more of the structural unit is an ethylene terephthalate residue is copolymerized. A method for synthesizing a polyester having a high degree of polymerization, characterized in that the intrinsic viscosity of the obtained polyester is 0.9 or more by solid phase polymerization.

Here, m and n are integers of 1 or 2. According to the present invention, solid-state polymerization at a lower temperature than that of ordinary PET polyesters is possible by copolymerizing the compound represented by the formula (1). Further, since the polymerization rate at the same temperature is greatly improved, an intrinsic viscosity of 0.9 or more can be realized with high efficiency. Although the melting point is slightly reduced, PET
The secondary transition temperature (glass transition temperature), which is an advantage of the system polyester, can be rather increased.

The copolymerization rate of the compound represented by the above formula (1) in the present invention is 1 mol% or more and 20 mol% (hereinafter abbreviated as mol%) by regarding the compound represented by the above formula (1) as a unit of polyester. ) Is more preferably 1 mol% or more and 8 mol% or less. Of course, depending on the purpose, 8
The range of not less than mol% and not more than 20 mol% can be preferably used.

If the copolymerization rate of the compound represented by the formula (1) is less than 1 mol%, a sufficient polymerization rate cannot be obtained. On the other hand, if it exceeds 20 mol%, the polymerization rate increases but the polymer becomes amorphous. It is undesired because it becomes close and the melting point decreases.

As for the compound represented by the formula (1), m,
n is preferably 1 or 2, and particularly preferably m = n = 1. When m = n = 2, the obtained polyester becomes elastic, which is preferable for some purposes.
As is generally known, when m and n exceed 2, the ether bond is liable to be decomposed by light, which limits the application.

In particular, when an impurity having a phenolic OH group such as m or n is 0, the ability to form an ester bond is significantly reduced, as is generally known. Also in the polymerization step, the polymerization rate will decrease. Therefore, in practicing the present invention, the amount of impurities having m or n = 0 should be limited to 0.2 mol% or less in the compound represented by the formula (1).

80 mol% of the PET polyester used in the present invention
Those in which the above is an ethylene terephthalate residue are preferably used. In addition to the components represented by the above formula (1), aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid and their derivatives, adipic acid and sebacic acid, as long as they do not exceed 20 mol% as modifying components. And a diol such as cyclohexadimethanol and 1,4-butanediol.

Additives such as antioxidants, matting agents, dyestuffs, and polyethylene glycol can also be used.

Furthermore, as a result of intensive investigations by the present inventors regarding the synthesis method and the case where a vacuum is used and a gas is used, the following preferable conditions have been found.

As a result of earnest studies, the present inventors have found that solid phase polymerization can be performed using a gas containing oxygen to increase the degree of polymerization.

That is, using air having a dew point of 0 ° C. or lower, the following formula (2)
Perform the solid-phase polymerization in the above temperature range.

130.0 ≤ T ≤ 200.0 where 1 ≤ β ≤ 10 130.0 ≤ T ≤ 200.0-2.1 (β-10) (2) where 10 ≤ α ≤ 20 α: Copolymerization rate of the compound represented by formula (1) (Mol%) β: Copolymerization rate of the modifier containing the compound represented by the formula (1) (mol%) When a gas containing oxygen is used, oxidative decomposition occurs at a high temperature, so that an inert gas is generated. It is necessary to lower the polymerization temperature than when it is used, and since the modification level also affects it, it is essential to control it within the range shown by the formula (2).

The air in the present invention refers to a gas containing 21% by volume or less of oxygen. In the present invention, the copolyester may be directly subjected to the solid phase polymerization step, or the copolyester may be pre-dried at about 100 ° C. to be crystallized to some extent and then subjected to the solid phase polymerization step.

In practicing the present invention, it is preferable that the chip is substantially stirred or fibrillated during the solid phase polymerization.
Therefore, when vacuum is used, a rotary tumbler type apparatus or the like is used, and when gas is used, a fluidized bed type apparatus or the like is preferably used.

The high polymerization degree polyester synthesized as described above is useful for high-strength fibers for industrial materials and for direct blow.

The intrinsic viscosity referred to in the present invention is defined as 30.0% by using a phenol / tetrachloroethane = 1/1 (weight ratio) mixed solvent as a solvent.
It means the value measured using an Ubbelohde viscometer at ° C. However, there is no substantial difference even when the solvent is orthochlorophenol.

 Hereinafter, an embodiment will be described.

Example 1 and Comparative Examples 1-2 Terephthalic acid (hereinafter abbreviated as TA) and ethylene glycol (hereinafter abbreviated as EG) were used as main raw materials, and a compound represented by the formula (1) with m = n = 1 (however, 0.01 mol% of m or n = 0, 8.7 mol% of m or n = 2, m
= N = 2, 1 mol% mixture) as an auxiliary material, and the addition time is after the end of the esterification reaction.
Polyester containing 0.05% by weight of titanium oxide synthesized by the esterification method (TA method) using 400 ppm of ₂ O ₃ and 2mmφ
X 1.5 mmL chips.

Table 1 shows the results of performing intrinsic polymerization with air using this chip. As a reference example, the results of solid-state polymerization under a nitrogen atmosphere are shown.
The polymerization rates are almost the same, and it can be seen that solid-state polymerization can be performed by specifying the polymerization temperature even in the presence of air.

In Comparative Example 1, since the air having a high dew point was used, the polymer was decomposed and deteriorated.

In Comparative Example 2, since the polymerization temperature was too high, the polymer was oxidatively decomposed, and the polymer turned yellow.

Comparative Example 3 A sodium sulfoisophthalate was copolymerized as a third component,
Despite the total amount of modification being 12.5 mol%, solid-state polymerization was performed under the condition that the formula (2) was not satisfied, so that the polymer yellowed due to oxidative decomposition, Stalemate was seen.

If solid phase polymerization in the presence of air is carried out for 7 hours or longer, yellowing (decomposition) tends to occur, so the solid phase polymerization time should be within 7 hours.

Claims (1)

(57) [Claims] 1. A polyester obtained by copolymerizing 1 mol% or more and 20 mol% or less of a compound represented by the following formula (1) in which 80 mol% or more of the structural unit is an ethylene terephthalate residue as it is or about 100%. After pre-drying at ℃, in the presence of air having a dew point of 0 ℃ or less, solid-state polymerization is carried out in the temperature range defined by the following formula (2), and the intrinsic viscosity is 0.9 or more, and a high degree of polymerization polyester. Synthesis method.