JPH01259027A - Production of polyester - Google Patents

Abstract

PURPOSE:To obtain a colorless polyester at a high reaction rate, by reacting an aromatic dicarboxylic acid with tetramethylene glycol using an organotitanium compound, etc., as an esterification catalyst and niobic acid as a polycondensation catalyst. CONSTITUTION:In producing a polyester consisting of an aromatic dicarboxylic acid (pref. terephthalic acid) as the main acid component and a tetramethylene glycol (pref. 1,4-butanediol) as the main glycol component, an organotitanium compound (pref. titanic acid alcohol ester) and/or an organotin compound (pref. monoalkyltin oxide) is used as an esterification catalyst and niobic acid obtained by heat treatment of a hydrous niobium compound at 80-400 deg.C is used as a polycondensation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a polyester whose main components are aromatic dicarboxylic acid and tetramethylene glycol.

(Prior art) Generally, polytetramethylene terephthalate is produced by direct polymerization of terephthalic acid and 1,4-butanediol, using dimethyl terephthalate and 1,4-butanediol as raw materials, and using a transesterification method. As in the case of , the first step is the esterification reaction of terephthalic acid and 1,4-butanediol to obtain bis(4-hydroxybutyl) terephthalate and its low polymer, and this is further polycondensed. It consists of a second stage reaction.

In such a production method, if a reaction catalyst is not used in either the first step esterification reaction or the second step polycondensation reaction, the reaction will be significantly delayed, and the esterification reaction may not be completed in the first step. Yes, and does not proceed beyond a certain viscosity in the second stage. That is, in order to effectively promote these reactions, it is known to add a catalyst such as an organic titanium compound or an organic tin compound to -a.

(Problem to be solved by the invention! 1) However, when a method using an organic titanium catalyst was examined in detail, it was found that it has the drawback of being deteriorated by moisture in the reaction system. That is, although the catalyst exhibits a reaction promoting effect in both the first and second stages, it is decomposed by the water produced as a by-product in the first stage esterification reaction, and loses its effectiveness as a catalyst. As a result, the second stage polycondensation reaction is significantly delayed. If the amount of catalyst used is increased to compensate for this, the resulting polymer will become opaque due to the precipitation of its decomposition products, making it difficult to use for general fibers, films, etc.
It was found that the commercial value of products such as molded products was impaired.

Furthermore, when an organotin compound is used, it exhibits a reaction accelerating effect in both the first and second stages, but the resulting polymer is colored, which also impairs the commercial value of the product and reduces the amount of catalyst used. It was found that the polycondensation reaction, especially in the second stage, was significantly delayed.

As a result of intensive research, the present inventors discovered that a specific niobium compound significantly accelerates the second-stage polycondensation reaction.
Alternatively, the present invention was achieved by discovering that the amount of organic tin compounds used can be reduced and a polymer that can be used as a high-quality product can be obtained.

(Means for Solving the Problems) That is, the method of the present invention uses an organic titanium compound and an organic tin compound as an esterification catalyst when producing a polyester containing an aromatic dicarboxylic acid as the main acid component and tetramethylene glycol as the main glycol component. At least one compound selected from the group consisting of compounds and a hydrated niobium compound as a polycondensation catalyst are used at 80°C to 400°C.
It is characterized by using niobic acid that has been heat-treated in the temperature range of °C.

The structure of the present invention will be explained in detail below along with its operation.

As the organic titanium compound applied to the method of the present invention, Ti
(OR) a (where R is an alkyl group or an aryl group) or transesterified products thereof, specifically, for example, tetramethyl titanate, tetrabutyl titanate, tetraisopropyl titanate, ethylene glycol titanate, tetrabutylene glycol titanate, tetra(2
(ethylhexyl) titanate, tetraoctyl titanate, tetrastearyl titanate, tetrabenzoic acid titanate, transesterified products thereof, and the like. At least one type of these can be used, and several types can be used in combination as necessary.

Further, as the organic tin compound, the following general formula, X is used.

(However, R is an alkyl group, an aryl group,
a is a monovalent group including an alkyl group, an aryl group, an allyloxy group, a cyclohexyl group, a hydroxy group, or a halogen group, and X is a sulfur or oxygen atom).

Specifically, for example, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylenetin oxide, hexacyclohexyldistin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyltin acetate, Includes dibutyltin acetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, monobutyltin hydroxyoxide, and the like. At least one type of these can be used, and several types can be used in combination as necessary.

The niobic acid used in the present invention is soluble in the reaction mixture and is obtained by heat treating a hydrated niobium compound at a temperature in the range of 80°C to 400°C. The hydrated niobium compound is, for example, “
New Edition of Inorganic Chemistry, written by Toshizo Chiya, published by Sangyo Tosho ■, 1932.
It can be obtained by a known method described in 2003, i.e., by melting the niobate with an alkali, extracting it with hot water, adding a strong acid such as sulfuric acid to the aqueous solution to make it acidic, separating the precipitate, and washing it with water. .

The treatment temperature for the hydrated niobium compound is preferably 100 to 300°C within the above temperature range. At temperatures below 80°C, the reaction promoting effect is insufficient, and at temperatures above 400°C, the catalyst becomes difficult to dissolve in the reaction system and the reaction promoting effect becomes insufficient. When heat treating niobic acid, it is preferable to do so in an inert gas atmosphere or under reduced pressure. Although the cause is unknown, niobic acid may become colored and denature in the air.

The niobic acid obtained in this manner does not require any special consideration in its handling, and exhibits high activity without being altered or degraded when exposed to the atmosphere or due to moisture as a by-product of the reaction.

The reason why heat-treated niobic acid exhibits a significantly high reaction promoting effect is not clear, but it is disclosed in Japanese Patent Application Laid-Open No. 60-44039 and [Surface J, Vol. 23 (1985), P3
9-49, such low-temperature-treated niobic acid has a function Ho indicating the acid strength of the solid acid such that Ho≦−5,6 (
A large amount of acid sites with strong acidity (corresponding to the acid strength of 70% 11□S04) were generated, and these are thought to function as reaction active sites for the catalyst. Niobic acid catalyst has the chemical formula NbzOs as an active ingredient through heat treatment.
XH! 0 (however, Q<x<1), but in the present invention, it is uniformly dispersed in the reaction solution,
Since the produced polymer is transparent, it can be explained that the unique structure is preserved even in the polymer, and due to this, it exhibits a reaction promoting effect.

The polycondensation reaction conditions may be normal ones, but the reaction temperature is 20°C.
0-270°C is preferred.

The amount of the catalyst used in the present invention varies depending on the reaction conditions and the combination of catalysts used, but generally titanium, tin, and niobium metals are contained in the final polyester polymer.
Each amount is 0.001 to 0.1% by weight.

Regarding the timing of using the catalyst of the present invention, it is usually preferable to use the esterification catalyst before the esterification reaction and the polycondensation catalyst before the polycondensation reaction, but the latter may be added before the esterification reaction, or the latter can be added before the esterification reaction. A portion thereof may be added before the subsequent polycondensation reaction.

The polyester targeted in the present invention has an aromatic dicarboxylic acid as the main acid component and tetramethylene glycol as the main glycol component. Here"
"Main" means more than 50 mol%. Therefore, it may contain less than 50 mol% of other components.

In the present invention, "aromatic dicarboxylic acid" refers to a compound in which a carboxylic acid is directly bonded to an aromatic group, such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, etc., and terephthalic acid is particularly preferred.

Examples of the third component (less than 50 mol %) that can be copolymerized in the present invention include aromatic dicarboxylic acids other than the main constituent components of the polyester, such as P-βoxyethoxybenzoic acid, diphenylsulfone dicarboxylic acid, and diphenyl ether dicarboxylic acid. , diphenoxyethane dicarboxylic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, dodecane dicarboxylic acid; ring dicarboxylic acids such as hexahydroterephthalic acid, decalin dicarboxylic acid, tetralin dicarboxylic acid, etc. ; Oxy acids such as glycolic acid and P-oxybenzoic acid; Aliphatic diols other than the main constituents of the polyester such as ethylene glycol, trimethylene glycol, propylene glycol, 1,3-butanediol, neopentyl glycol; cyclohexane diol; Examples include alicyclic diols such as metatool and tricyclodecane dimedylol; aromatic diols such as bisphenol A1 bisphenol S, bishydroxyethoxybisphenol A1 and tetrabromobisphenol A, and the like.

In addition, within the range where the polyester can be considered to be substantially linear,
trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, trimethylolpropane, glycerin,
A polyfunctional compound such as pentaerythritol, a monofunctional compound such as benzoic acid, naphthoic acid, stearyl alcohol, palmitic acid, or a derivative thereof may be added.

Furthermore, like ordinary polyester, heat stabilizers such as phosphorus compounds, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole, hydroxybenzophenone, and cyanoacrylates, titanium oxide, carbon blanks,
There is no problem even if pigments such as cobalt blue, dyes, antistatic agents, etc. are added.

Note that the other reaction conditions may be normal ones, but the molar ratio of terephthalic acid/glycol is in the range of 1.2 to 2.0,
Even better polymers can be obtained if the reaction temperature is in the range of 200 to 270°C.

(Effects of the Invention) As described above, the present invention uses an organic titanium compound and/or an organic tin compound as an esterification catalyst and uses niobic acid as a polycondensation catalyst in a method for producing polytetramethylene terephthalate by direct polymerization reaction. However, according to the method of the present invention, the esterification reaction and the polycondensation reaction are significantly accelerated, and the resulting polymer is free from turbidity, colorless, and has a good hue.

(Examples) Next, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. In the examples, "parts" are parts by weight, and the intrinsic viscosity is 20° using phenol:tetrachloroethane (60:40) as a solvent.
This is the value measured at C.

Example I Companhia Bras.
Metalurgia e Min
5 parts of hydrated niobium compound manufactured by Eracao) with pure water.
After washing twice, the product was heated for 15 hours and used as a polycondensation catalyst.

Terephthalic acid 166 parts, 1,4-butanediol 153 parts
0.08 parts of tetra-n-butyl titanate as an esterification catalyst and 0.12 parts of niobic acid as the polycondensation catalyst.
5 parts were charged into a reactor equipped with a rectification column, and an esterification reaction was carried out at 220''C while distilling off the produced water.

The time required for terephthalic acid to dissolve (esterification reaction time) was 1 hour and 25 minutes, and the content of tetrahydrofuran in 53.9 g of distillate was 12.5 g.

Next, this reaction product was transferred to a polycondensation reactor and heated to 250°C.
The pressure was gradually reduced while increasing the temperature to 1 Torr or less, and the polycondensation reaction was carried out for 2.5 hours. The obtained polymer is colorless, has little turbidity, and has an intrinsic viscosity of 0.8.
It was 1.

Example 2 The procedure was the same as in Example 1 except that 0.05 part of mono-n-butyltin oxide was used instead of tetra-n-butyl titanate. The obtained polymer had less turbidity, good hue, and unique The viscosity was 0.75.

Comparative Example 1 The procedure was the same as in Example 1 except that niobic acid was not used. The resulting polymer was cloudy and had an intrinsic viscosity of 0.68.

Comparative Example 2 The same procedure as Example 2 was carried out except that niobic acid was not used. The obtained polymer was colored yellow and had an intrinsic viscosity of 0.45.

Claims (1)

[Claims] 1. When producing a polyester containing aromatic dicarboxylic acid as the main acid component and tetramethylene glycol as the main glycol component, an esterification catalyst selected from the group consisting of organotitanium compounds and organotin compounds A method for producing a polyester, characterized in that at least one compound is used as a polycondensation catalyst, and niobic acid obtained by heat-treating a hydrated niobium compound at a temperature range of 80°C to 400°C is used as a polycondensation catalyst. 2. The method according to claim 1, wherein the aromatic dicarboxylic acid is terephthalic acid and the tetramethylene glycol is 1,4-butanediol. 3. The method according to claim 1, wherein the organic titanium compound is a titanic acid alcohol ester. 4. The method according to claim 1, wherein the organotin compound is a monoalkyl tin oxide.