JPH0226645B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an industrially advantageous method for producing polyethylene terephthalate/isophthalate copolyester. Polyethylene terephthalate/isophthalate copolymer polyester has been well known for a long time as a material for fibers, films, etc., but in recent years, in order to improve the transparency of polyethylene terephthalate for molded products such as bottles, it has been Polyethylene terephthalate/isophthalate copolyester, which is copolymerized with approximately 20 mol% of isophthalic acid components, is attracting attention. The method for producing polyethylene terephthalate/isophthalate copolyester is (1)
A method of mixing and reacting three components: a terephthalic acid component, an isophthalic acid component, and ethylene glycol; (2) a method of reacting an oligomer obtained by reacting a terephthalic acid component and ethylene glycol with an isophthalic acid component and ethylene glycol; (3) A method in which an isophthalic acid component is added to an oligomer obtained by reacting a terephthalic acid component with ethylene glycol. The third method is advantageous when copolyesters are produced in parallel with polyethylene terephthalate homopolyesters. As the third method mentioned above, for example,
No. 931241 describes a method of transesterifying dimethyl terephthalate and ethylene glycol and then adding solid isophthalic acid to perform a polycondensation reaction, but the reaction rate was slow under the conditions shown in this patent. However, there was a problem that polycondensation took a long time. In order to produce polyethylene terephthalate, the present inventors used a molten ethylene terephthalate oligomer obtained by continuous direct esterification in large quantities to produce a terephthalic acid component of 80 to 97 mol% and an isophthalic acid component of 20 to 3 mol%. When producing ethylene terephthalate/isophthalate copolyester having an intrinsic viscosity of 0.6 or more from the acid component consisting of ethylene glycol and ethylene glycol, isophthalic acid and ethylene glycol are added to the molten ethylene terephthalate oligomer separately or mixed, and the total acid Regarding the ingredients, ethylene glycol
After adding 1.1 to 2.0 times the amount by mole, maintaining a state of normal pressure or slightly pressurized for a time that satisfies the following formula, and then polycondensing under reduced pressure, the desired amount can be achieved in a relatively short time. It was discovered that a copolymerized polyester having an intrinsic viscosity of can be produced, and the present invention was achieved. 0.015X＋0.796−0.378R≦t≦0.015X +1.066−0.478R However, in the above formula, X is the copolymerization mol% of the isophthalic acid component (3≦X
≦20), R is the molar ratio of ethylene glycol to the total acid components (1.1≦R≦2.0), t is the time to maintain normal pressure or slightly pressurized state after isophthalic acid and ethylene glycol are added (unit: Hrs) It is. The present invention completes polycondensation under reduced pressure in a relatively short time, making it possible to industrially advantageously produce high-quality polyethylene terephthalate/isophthalate copolyester with few side reactions such as thermal decomposition. It is something to do. In carrying out the process of the present invention, the amount of isophthalic acid component copolymerized ranges from 3 to 2 mole percent of the total acid component. That is, if the amount is less than 3 mol %, there is no noticeable difference in the effect of improving the transparency of the molded article compared to the case where no copolymerization is carried out, whereas if it exceeds 20 mol %, the heat resistance of the molded article will be extremely poor. The desired amount of copolymerization is preferably set in the range of 5 to 15 mol %, taking into account transparency and heat resistance. In addition, it is industrially desirable to use as little amount of ethylene glycol as possible, either separately or mixed with isophthalic acid, but it is 1.1% of the total acid component.
It is necessary to choose so that the amount is ~2.0 moles. That is,
When the amount is less than 1.1 mole times, not only does it take a long time to complete the polycondensation, but sometimes a copolymerized polyester having the desired intrinsic viscosity cannot be prepared by polycondensation. Furthermore, if it is used in an amount exceeding 2.0 moles, it not only causes disadvantages in terms of raw materials, but also makes it impossible to achieve the desired effect of shortening the polycondensation time. Usually, it is 1.1-1.2 times the mole amount.
This is most preferable when raw material cost and energy cost are considered together. Furthermore, after adding isophthalic acid and ethylene glycol, after maintaining a state of normal pressure or slightly pressurized at 250°C to 280°C for a time that satisfies the above formula, the same method as in the case of manufacturing polyethylene terephthalate is carried out. Therefore, in the presence of catalysts such as antimony trioxide, germanium dioxide, n-butyl titanate, and additives such as trialkyl phosphate, triphenyl phosphate, phosphoric acid, etc.
By carrying out polycondensation under reduced pressure at 300°C, preferably 270°C to 290°C, the desired copolyester can be prepared in a relatively short time. Isophthalic acid and ethylene glycol can be added separately without any problem, but the most efficient method is to use 1.1 to 4.0 times the molar amount of ethylene glycol to isophthalic acid and add it as a slurry. It is also the most desirable in that it allows for more precise control of the time during which the normal pressure or slightly pressurized state is maintained. The range of t defined by the above formula was determined by keeping X constant, varying R and t to produce a copolyester, and determining the length of the polycondensation time required at that time. be. The time required for polycondensation was defined as the time required to obtain a copolymerized polyester with an intrinsic viscosity of 0.73. Figures 1 to 3 show the relationship between the length and shortness of the polycondensation time required when copolymerized polyesters were produced by varying R and t while keeping X constant;
5.25Hrs or less, × indicates 5.75Hrs or more. In FIGS. 1 to 3, straight line A shows the lower limit of the above formula, and straight line B shows the upper limit. Next, the present invention will be specifically explained by showing examples and reference examples. Example 1 The ethylene terephthalate oligomer (the amount of ethylene glycol component per 1 mole of terephthalic acid component is 1.1 moles) in a molten state in a polycondensation vessel is shown in Table 1.
followed by an ethylene glycol slurry of isophthalic acid (prepared using 1.5 moles of ethylene glycol per mole of isophthalic acid).
After adding 0.245 parts by weight of germanium dioxide and 0.854 parts by weight of triethyl phosphate as catalysts, the mixture was heated at 26°C under slight pressure of 800 mmHg.
0.15mmHg at 280℃ after holding for the time shown in Table 1.
Polycondensation was carried out under reduced pressure to prepare a copolymerized polyester having an intrinsic viscosity of 0.73, and the results shown in Table 1 were obtained.

【table】

[Table] Reference example 1 Same as No. 2 of Example 1, except that isophthalic acid,
After charging the ethylene glycol slurry, the holding time under slight pressure was set as shown in Table 2 to prepare a copolymerized polyester, and the results shown in Table 2 were obtained.

[Table] The reaction was completed.
Reference Example 2 Using ethylene isophthalate oligomer obtained by esterification reaction at 250°C for 4 hours using 1.5 mol of ethylene glycol per 1 mol of isophthalic acid in place of the isophthalic acid/ethylene glycol slurry, the procedure of Example 1 was carried out. When a copolymerized polyester was prepared in the same manner as No. 2, the time required for polycondensation was 6.25 Hrs, the polymer intrinsic viscosity was 0.73, and the polymer color tone was 6.9. Reference Example 3 Same as No. 3 of Example 1, except that isophthalic acid.
When a copolymerized polyester was prepared by adding 156 parts by weight of isophthalic acid and 29 parts by weight of ethylene glycol instead of the ethylene glycol slurry and selecting the value of R to be 1.04, polycondensation was performed for 6 hours, but the intrinsic viscosity of the polymer was 0.43. The polymer color tone was 6.3. Reference Example 4 A copolymerized polyester having an intrinsic viscosity of 0.73 was prepared in the same manner as Reference Example 3, except that the amount of ethylene glycol added was increased to 616 parts by weight and the value of R was selected to be 2.05, and the time required for polycondensation was 6.25. Hrs and polymer color tone was 6.8. As is clear from a comparison of Examples and Reference Examples, the method of the present invention has a special effect in preparing polyethylene terephthalate/isophthalate copolyester by polycondensation in a relatively short time. It is. In particular, by shortening the polycondensation time, it not only reduces the amount of steam used in the steam ejector to maintain a reduced pressure state, but also improves productivity and reduces the degree of yellow coloring caused by thermal decomposition. At the very least, it becomes possible to prepare high quality ethylene terephthalate/isophthalate copolyester.

[Brief explanation of drawings]

Figures 1 to 3 show the relationship between the length and shortness of the polycondensation time required when copolymerized polyesters were produced by varying R and t while keeping X constant;
5.25Hrs or less, × indicates 5.75Hrs or more. In FIGS. 1 to 3, straight line A shows the lower limit of the above formula, and straight line B shows the upper limit.

Claims (1)

[Claims] 1. A polyethylene terephthalate/isophthalate copolymer polyester having an intrinsic viscosity of 0.6 or more is produced from an acid component consisting of 80 to 97 mol% of a terephthalic acid component and 20 to 3 mol% of an isophthalic acid component and ethylene glycol. For this purpose, isophthalic acid and ethylene glycol are added to the molten ethylene terephthalate oligomer, either separately or in a mixture, so that the amount of ethylene glycol is 1.1% of the total acid component.
A copolymerized polyester characterized by being added in an amount of ~2.0 moles, maintained at normal pressure or slightly pressurized at 250 to 280°C for a time satisfying the following formula, and then polycondensed under reduced pressure. manufacturing method. 0.015X＋0.796−0.378R≦t≦0.015X +1.066−0.478R However, in the above formula, X is the copolymerization mol% of the isophthalic acid component (3≦X
≦20), R is the molar ratio of ethylene glycol to the total acid components (1.1≦R≦2.0), t is the time to maintain normal pressure or slightly pressurized state after isophthalic acid and ethylene glycol are added (unit: Hrs) It is.