Catalyst for polyester production, process for producing polyester using the catalyst, polyester obtained by the process, and uses of the polyester

Abstract

The present invention provides a catalyst for polyester production capable of producing a polyester with high catalytic activity, a process for producing a polyester using the catalyst and a polyester produced thereby. The catalyst comprises a solid titanium compound obtained by dehydro-drying a hydrolyzate obtained by hydrolysis of a titanium halide and which has a molar ratio (OH / Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4. In the process, the polyester is obtained by polycondensing an aromatic dicarboxylic acid, or an ester-forming derivative thereof, and an aliphatic diol, or ester-forming derivative thereof, in the presence of the catalyst. The resulting polyester has excellent transparency and tint, a titanium content of 1 to 100 ppm, a magnesium content of 1 to 200 ppm and a magnesium to titanium weight ratio of not less than 0.01.

Description

[0001]This application is a divisional of application Ser. No. 09 / 470,664, filed Dec. 22, 1999, now U.S. Pat. No. 6,346, 070.FIELD OF THE INVENTION[0002]The present invention relates to a catalyst for polyester production, a process for producing a polyester using the catalyst, a polyester obtained by the process and uses of the polyester.BACKGROUND OF THE INVENTION[0003]Because of their excellent mechanical strength, heat resistance, transparency and gas barrier properties, polyesters such as polyethylene terephthalate are favorably used as not only materials of containers of various beverages such as juice, soft drinks and carbonated beverages but also materials of films, sheets and fibers.[0004]The polyesters can be generally produced using, as starting materials, dicarboxylic acids such as aromatic dicarboxylic acids and diols such as aliphatic diols. In more detail, a dicarboxylic acid and a diol are first subjected to esterification reaction to form a low condensate (low molec...

AI Technical Summary

Benefits of technology

[0709]The catalyst for polyester production according to the invention can produce a polyester with higher catalytic activity as compared with a germanium compound or an antimony compound which has been heretofore used as a polycondensation catalyst. According to the invention, a polyester having more excellent transparency and tint and lower acetaldehyde content can be obtained as compared with the case of using an antimony compound as a polycondensation catalyst.

[0710]The catalyst for polyester production according to the invention, which comprises the solid titanium compound (I-a) and / or the titanium-containing solid compound (I-b), and if necessary, the co-catalyst component (II), can produce a polyester with higher catalytic activity as compared with a germanium compound or an antimony compound which has been heretofore used as a polycondensation catalyst. Further, when this catalyst is used, a polyester having more excellent transparency and tint and lower acetaldehyde content can be obtained as compared with the case of using an antimony compound as a polycondensation catalyst. Furthermore, a polyester, e.g., polyethylene terephthalate, obtained by the use of the catalyst of the invention and a molded product formed therefrom have excellent transparency and tint and have a low acetaldehyde content.

[0711]The catalyst for polyester production according to the invention, which comprises the solid titanium compound (I-c) and the co-catalyst component (II) or comprises the titanium-containing solid compound (I-d) and if necessary the co-catalyst component (II), can produce a polyester with higher catalytic activity as compared with a germanium compound or an antimony compound which has been heretofore used as a polycondensation catalyst. Further, when this catalyst is used, a polyester having more excellent transparency and tint and lower acetaldehyde content can be obtained as compared with the case of using an antimony compound as a polycondensation catalyst.

[0712]The catalyst for polyester production according to the invention, which comprises the solid titanium compound (I-e), the solid titanium compound (I-f), the titanium-containing solid compound (I-g) or the titanium-containing solid compound (I-h), and if necessary, the co-catalyst component (II), can produce a polyester with higher catalyst activity as compared with a germanium compound or an antimony compound which has been heretofore used as a polycondensation catalyst. Further, when this catalyst is used, a polyester having more excellent transparency and tint and lower acetaldehyde constant can be obtained as compared with the case of using an antimony compound as a polycondensation catalyst.

[0713]The catalyst for polyester production according to the invention, which comprises the solid titanium compound (I-i) and if necessary the co-catalyst component (II), can produce a polyester with higher catalytic activity as compared with a germanium compound or an antimony compound which has been heretofore used as a polycondensation catalyst. Further, when this catalyst is used, a polyester having more excellent transparency and tint and lower acetaldehyde content can be obtained as compared with the case of using an antimony compound as a polycondensation catalyst.

[0714]The catalyst for polyester production according to the invention, which comprises a slurry obtained by heating a mixture of (A-1) the hydrolyzate (I-j) or the hydrolyzate (I-k), (B) the basic compound and (C) the aliphatic diol, can produce a polyester having a desired intrinsic viscosity for a short period of time.

Problems solved by technology

However, the polyester produced by the use of the antimony compound as a polycondensation catalyst is inferior to the polyester produced by the use of a germanium compound as a polycondensation catalyst in the transparency and the heat resistance.

On the other hand, the germanium compound is considerably expensive, so that the production cost of polyester becomes high.

However, when the conventional titanium compounds are used as the polycondensation catalysts, their activity is inferior to that of the antimony compound or the germanium compounds.

In addition, the resulting polyester has a problem of being markedly colored yellow, and hence they have not been put into practical use yet.

In the industrial production of polyesters using these titanium compounds as the polycondensation catalysts, further, there is a problem of corrosion caused by elution of chlorine content in case of catalysts containing a large amount of chlorine, such as titanium tetrachloride and partial hydrolyzate of titanium tetrachloride.

Therefore, catalysts having low chlorine content are sometimes desired.

As for the molded product obtained from the conventional polyester such as conventional polyethylene terephthalate, however, the content of acetaldehyde is increased during the molding and the acetaldehyde remains in the resulting molded product, so that flavor or scent of the contents filled in the molded product is sometimes considerably deteriorated

However, the increase of the acetaldehyde content in the polyethylene terephthalate obtained by these processes cannot be lowered down below a certain level.

In this method, however, the phosphoric acid functions as an aced catalyst to perform hydrolysis, and as a result, decrease of the intrinsic viscosity is accelerated during the melt molding.

The stain of the mold causes surface roughening or whitening of the resulting blow molded article.

In the production of a blow molded article using the conventional polyester, the stain of the mold must be frequently removed, and this results in conspicuous lowering of productivity of the blow molded article.

In addition, the polyester obtained by the use of the antimony compound or the germanium compound as a polycondensation catalyst sometimes has low melt flowability and is insufficient in the moldability.

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