JPH0372653B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preparing a catalyst for producing polyalkylene terephthalate from terephthalic acid or a derivative thereof and alkylene glycol. More specifically, the present invention is a method for producing polyalkylene terephthalate, in which a tetraalkyl titanate catalyst is prepared as an alkylene glycol solution containing 0.05 to 1.0% by weight of water, and the solution is supplied to a reaction zone. As a catalyst for producing polyalkylene terephthalate, the tetraalkyl titanate described in Japanese Patent Publication No. 36-6795 is known as an excellent catalyst, but in general, this catalyst is dissolved in alkylene glycol to form a solution, and terephthalic acid or its derivatives are used. Used for esterification and polycondensation of and glycol. However, in the method using an alkylene glycol solution of the tetraalkyl titanate, 70
If stored at temperatures below ℃, it becomes cloudy, causing problems such as clogging of the preparation line and deterioration of preparation accuracy.Also, there are problems in that the reaction may be significantly delayed, or the reaction may not proceed beyond a certain stage at all. It turns out that there is something. As a result of intensive studies to overcome the deficiencies of the conventional methods, the present inventors prepared a tetraalkyl titanate catalyst as an alkylene glycol solution containing 0.05 to 1.0% by weight of water and supplied it to the reaction zone. We have found that it is particularly effective to do so, and have arrived at the present invention. That is, the gist of the present invention is to prepare a tetraalkyl titanate catalyst used in the production of polyalkylene terephthalate by reacting terephthalic acid or its derivative with an alkylene glycol as a solution of an alkylene glycol that is the same as and/or different from the above-mentioned alkylene glycol. The method is characterized in that the solution contains 0.05 to 1.0% by weight of water based on the total solution. The present invention relates to a method for preparing a catalyst for producing polyalkylene terephthalate. The present invention will now be described in more detail. Terephthalic acid derivatives are compounds that can react with alkylene glycol to produce polyalkylene terephthalate, and are usually dialkyl esters of terephthalic acid such as dimethyl terephthalate. Examples of the tetraalkyl titanate that can be applied to the method of the present invention include tetramethyl titanate, tetrabutyl titanate, tetraisopropyl titanate,
Examples include tetra(2-ethylhexyl) titanate. Further, examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, and the like. The glycol in which the tetraalkyl titanate is dissolved is preferably the same as the glycol that reacts with terephthalic acid or its derivative, but mixtures of two or more glycols can also be used. The method for preparing the catalyst solution varies depending on the type of tetraalkyl titanate and alkylene glycol used and is not limited. For example, a solution of tetrabutyl titanate, a known catalyst in the production of polytetramethylene terephthalate, is prepared by adding tetrabutyl titanate to 100 parts of 1,4-butanediol under stirring at a temperature of 20.1°C or higher.
Prepared by adding 0.1 to 5.0 parts. Water can be added to the catalyst solution at any stage according to the method of the present invention, and the amount added is 0.05 to 1.0% by weight.
The amount is particularly preferably 0.15 to 0.5% by weight.
If the amount of water added is less than 0.05%, the effect will be small, and if it is more than 1.0% by weight, the effect will not change, but the load on the recovery system will increase, which is not preferable. It should be noted that the higher the preparation temperature of the catalyst solution, the better the problem with regard to white turbidity, but in the absence of water, this does not lead to an essential solution. Conditions for producing polyalkylene terephthalate, ie, the amount of catalyst used, polymerization temperature, degree of pressure reduction, etc., are those well known to those skilled in the art. As detailed above, when the tetraalkyl titanate catalyst prepared by the method of the present invention is added to the esterification and polycondensation for producing polyalkylene terephthalate, clouding of the catalyst preparation solution is eliminated.
There was no blockage problem in the preparation line system for the catalyst preparation liquid, and good results were obtained regarding the preparation accuracy.
The reaction time is shortened and high quality polyalkylene terephthalate can be industrially advantageously produced. Next, the method of the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited by the following Examples and Comparative Examples unless the gist thereof is exceeded. In addition, the intrinsic viscosity in this example and comparative example is 30
It was calculated from the value measured at °C using a tetrachloride ethane-phenol solution as a solvent. Example 1 96 g of 1,4-butanediol, 4 g of tetrabutyl titanate, and 0.2 g of water were heated while stirring,
After complete dissolution, stirring was stopped and the mixture was left at 25°C. Even after 2 weeks of standing, no clouding was observed. Example 2 In Example 1, the amount of water added was changed and the reaction was carried out under the same conditions as in Example 1. Table 1 shows the results.
Shown below. Comparative example 1 is an example when no water is added.
listed as.

[Table] Example 3 132 g of dimethyl terephthalate, 74 g of 1,4-butanediol, and 2.6 g of the non-cloudy catalyst solution prepared in Example 1 were charged into a reaction vessel equipped with a purification tower, and the product was produced at 210°C. When the reaction was carried out while distilling methanol, the amount of methanol distilled reached 90% of the theoretical amount of methanol distilled in 2.5 hours. When this reaction product was subjected to condensation polymerization at 245° C. and a pressure of 1 mmHg, a polymer having an intrinsic viscosity of 0.95 was obtained after 3 hours. Comparative Example 2 In Example 3, the cloudy catalyst solution of Comparative Example 1 shown in Table 1 was used in place of the catalyst prepared in Example 1, and the reaction was carried out under the same conditions as in Example 3. Ta. As a result, the time required for the transesterification reaction was 3.5 hours (the reaction was stopped when 90% of the theoretically distilled methanol had been distilled out). The intrinsic viscosity of the polymer after 3 hours of polymerization reaction was 0.80. Example 4 Terephthalic acid 113g, 1,4-butanediol
110 g and 2.6 g of the non-cloudy catalyst solution prepared in Example 1 were charged into a reaction vessel equipped with a purification tower.
When the reaction is carried out at ℃ while distilling the produced water, the amount of water distilled in 2.5 hours is 90% of the theoretical amount of water distilled.
reached. When this reaction product was subjected to condensation polymerization at 245°C and a pressure of 1 mmHg, the intrinsic viscosity was 0.92 after 3 hours.
of polymer was obtained. Comparative Example 3 In Example 4, the cloudy catalyst solution of Comparative Example 1 shown in Table 1 was used instead of the catalyst prepared in Example 1, and the reaction was carried out under the same conditions as in Example 4 except for that. . As a result, the time required for the transesterification reaction is
The distillation time was 2.8 hours (the distillation was stopped when 90% of the theoretical amount of water was distilled out). The intrinsic viscosity of the polymer after 3 hours of polymerization reaction was 0.82.

Claims (1)

[Scope of Claims] 1. A method for preparing a tetraalkyl titanate catalyst used in the production of polyalkylene terephthalate by reacting terephthalic acid or a derivative thereof with an alkylene glycol as a solution of an alkylene glycol that is the same as and/or different from the above alkylene glycol. , A method for preparing a catalyst for producing polyalkylene terephthalate, characterized in that the solution contains 0.05 to 1.0% by weight of water based on the entire solution. 2. The method for preparing a catalyst for producing polyalkylene terephthalate according to claim 1, wherein the alkylene glycol used in the catalyst preparation is the same as the alkylene glycol reacted with terephthalic acid or its derivative. 3. The method for preparing a catalyst for producing polyalkylene terephthalate according to claim 1 or 2, wherein the alkylene glycol is 1,4-butanediol.