JPS6134449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester. More specifically, the present invention relates to a method for producing a polyester containing 1,4-butanediol as the main diol component, which has excellent color tone. Polyesters containing 1,4-butanediol as the main diol component, especially poly 1,4-butylene terephthalate, exhibit excellent physical properties and are known to be useful as materials for various molded products, and their uses are increasingly expanding. It's coming. However, as its uses have expanded, the properties required of polyester have also become more diverse, and improvements in properties have become increasingly necessary. For example, polyester often requires further improvement in terms of color tone, and techniques for improving it are becoming more important. When a titanium compound is used as a catalyst for polybutylene terephthalate, the polymer is also colored, and color tone improvement is required. Conventionally, a method of adding a phosphorus compound during or after polyester production has been known as a method for improving the color tone of polyethylene terephthalate. Although this color tone improvement method can also be applied to polyesters containing 1,4-butanediol as the main diol component, the color tone of the resulting polyesters cannot necessarily be said to be sufficient. Focusing on this point, the present inventor has conducted various studies on a method for producing polyester with excellent color tone using a titanium compound as a catalyst. As a result, the present inventor has found that when a specific metal compound is used, 1,4-butanediol, which has excellent color tone, can be used as the main diol component. The present invention was achieved based on the discovery that a polyester having the following properties can be obtained. That is, the present invention provides a method for producing polyester by reacting at least one difunctional carboxylic acid or its ester-forming derivative with a diol mainly consisting of 1,4-butanediol or its ester-forming derivative. A titanium compound is used as a titanium compound, and at any stage until the reaction is completed, at least one weak acid salt of a metal selected from the group consisting of Li, Na, K, and Zn is added to the system in a color-improving proportion. This is a characteristic method for producing polyester. The polyester referred to in the present invention is a polyester whose main diol component is 1,4-butanediol, and is mainly intended for polyester whose acid component is terephthalic acid, but some or all of the terephthalic acid component is difunctional carboxylic acids such as isophthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid,
4,4'-diphenyl dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 3,3'-dimethyl-
Aromatic dicarboxylic acids such as 4,4'-diphenyl dicarboxylic acid and diphenoquinethanedicarboxylic acid; aliphatic and alicyclic acids such as adibic acid, sebacic acid, azelaic acid, dodecanedioic acid, hexahydroterephthalic acid, etc. Dicarboxylic acid; may be a homopolymer or copolymer substituted with one or more oxy acids such as β-hydroxyethoxybenzoic acid, ε-oxycaproic acid, etc.; , 4-butanediol, such as trimethylene glycol, hexamethylene glycol, decamethylene glycol, 2,2-bis(β-hydroxyethoxyphenyl)propane, bis(β-hydroxyethoxyphenyl)sulfon, neopentyl glycol It may also be a copolymer substituted with one or more of the following. Further, polyfunctional compounds having trifunctional or higher functionality such as trimesic acid, trimethylolpropane, pentaerythritol, etc., and/or monofunctional compounds such as 0-benzoylbenzoic acid, 4-diphenylsulfone monocarboxylic acid, etc., or functional compounds thereof The polymer may be copolymerized with one or more derivatives to the extent that the polymer is substantially linear. Such polyester can be manufactured by a normal polyester manufacturing method. For example, at least one difunctional carboxylic acid or its ester-forming derivative (e.g., lower alkyl ester such as dimethyl ester, aryl ester such as phenyl ester, etc.) and 1,4-butanediol or its ester-forming derivative (e.g. (lower fatty acid ester such as acetate ester, etc.) in the presence or absence of a catalyst at 110 to 250°C, preferably 110 to 230°C.
The resulting reaction product is subjected to an esterification or transesterification reaction in the presence of a polycondensation catalyst in an inert gas atmosphere or under vacuum at a temperature of 220°C to 280°C, preferably 260°C, more preferably 260°C. can be produced by melt polycondensation reaction at temperatures up to 250°C to form polyester. In the method of the present invention, at least one weak acid salt of a metal selected from the group consisting of Li, Na, K, and Zn is added to the reaction system at any stage before the end of the polycondensation reaction during the production of the polyester. do. Specific examples of weak metal salts include lithium acetate, potassium acetate, sodium acetate, zinc acetate, lithium carbonate, lithium propionate, lithium oxalate, lithium benzoate, lithium caproate, lithium phthalate, potassium tartrate, Sodium bicarbonate, zinc carbonate, potassium carbonate, sodium bitartrate, zinc phthalate, potassium bicarbonate,
Examples include sodium carbonate, zinc stearate, potassium diphthalate, potassium carbonate, sodium, zinc salicylate, sodium formate, lithium citrate, and lithium stearate. these are,
They may be used alone or in combination of two or more. Among these, lithium compounds and zinc compounds are particularly preferred because they have good solubility in polymers. The amount of such a metal compound added may be an amount that improves color tone, but the total amount is usually 0.005 to 0.05 per total acid component.
0.5 mol%, and even 0.01 to 0.3 mol%, especially
It is preferably 0.05 to 0.2 mol%. The addition time may be at any stage until the polycondensation reaction is completed, but the degree of polymerization from the time of charging the raw materials is expressed as the solution viscosity measured at a concentration of 1.2 g/dl in orthochlorophenol at 35°C. In this case, the polycondensation reaction stage until the solution viscosity reaches 0.2 is preferable, and it is particularly preferable to add it before entering the vacuum polycondensation reaction stage. The addition may be done once or in several parts. A titanium catalyst is usually preferably used in the polycondensation reaction. As a titanium catalyst, for example, the formula XmTi(OR)l, (ME)nTiF ₆ , (Ti)P(OOCR')q [However, in the formula, 6), Me is a metal atom or NH ₄ , R' is alkyl, aryl, cycloalkyl, aralkyl (carbon number: 6 to 12) that may contain a carboxyl group, m and l are 0 or a positive integer (however, l or Any one of m is a positive integer),
n, p and q are positive integers. ] Examples include compounds represented by the following, and more specifically, tetramethyl titanate, tetrabutyl titanate, titanium tetrachloride, lithium salts, potassium salts, magnesium salts of titanate fluoride, titanium oxalate,
Examples include titanium trimellitate, titanium acetate, titanium pyromellitate, and the like. Furthermore, these hydrolysates or derivatives can also be used. Such titanium catalysts are also useful as catalysts for esterification or transesterification reactions. The amount of these catalysts used is usually based on the total acid content.
It is used in an amount of 0.005 to 1 mol%. The polyester produced by the method of the present invention includes glass fibers, carbon fibers, other reinforcing agents, fillers, flame retardants, flame retardant aids, antioxidants, light stabilizers, fluorescent brighteners, and pigments. If necessary, one or more of the following may be added. According to the method of the present invention, a polyester containing 1,4-butanediol as the main diol component and having excellent color tone can be easily obtained. EXAMPLES The present invention will be explained in more detail with reference to Examples below. In the examples, parts are parts by weight, and [η] is 35% at a concentration of 1.2 g/dl in orthochlorophenol.
Intrinsic viscosity measured at °C. Example 1 50 parts of dimethyl terephthalate, 32.5 parts of 1,4-butanediol, 0.031 part of tetra(n-butyl) titanate, and 0.013 parts of lithium acetate dihydrate were charged into a transesterification reactor, and the temperature was raised to 180°C. The reaction was allowed to proceed for 120 minutes while separating the distilled methanol. Next, the reactant was transferred to a polycondensation reaction tank, and the temperature was increased from 180°C to 245°C over 45 minutes.
The degree of vacuum was gradually increased to approximately 0.5 mm/Hg. After continuing the reaction in this state for an additional 120 minutes, the polymer was taken out of the system and made into chips. The η value of the chip taken out was 1.121, and the color tone had an L value of 86.9 and a b value of 0.4. The polymer color tone was measured using a CM-20 color difference meter manufactured by Nippon Color Machine Co., Ltd. Examples 2 to 4 The same procedure as in Example 1 was conducted except that the metal compounds shown in Table 1 were used instead of lithium acetate dihydrate. [η] and color tone of the obtained polyester are shown in Table 1.

[Table] Example 5 A polymer was produced in exactly the same manner as in Example 1, except that 0.04 part of titanium trimellitate was used instead of tetra(n-butyl) titanate. The chip quality of the obtained polymer was as follows.

[Table] Comparative Example 1 Example 1 except that lithium acetate dihydrate was not used
The quality of the polymer obtained in the same manner as above was as follows.

[Table] Comparative Example 2 A polymer obtained in the same manner as in Example 1 except that lithium acetate dihydrate was not used and 0.04 part of titanium trimellitate was used instead of tetra(n-butyl) titanate as a catalyst. The quality was as follows.

[Table] Examples 6 to 11 The same procedure as in Example 1 was conducted except that the metal compounds shown in Table 2 were used instead of lithium acetate dihydrate. [η] and color tone of the obtained polyester are shown in Table 2.

【table】

[Table] Comparative Example 3 In Example 1, 0.013% of lithium acetate dihydrate
Chips were produced in the same manner as in Example 1, except that 0.00065 parts (0.002% by weight of 1,4-butanediol) was added instead of 1 part. The chip's η is 1.136, and the color tone is the L value.
It was 83.6, and the b value was 3.7.

Claims (1)

[Claims] 1. When producing polyester by reacting at least one difunctional carboxylic acid or its ester-forming derivative with a diol mainly consisting of 1,4-butadiol or its ester-forming derivative, a titanium compound is used as a catalyst. At any stage until the reaction is completed, Li, Na,
A method for producing polyester, which comprises adding at least one weak acid salt of a metal selected from the group consisting of K and Zn in a color tone improving proportion.