DE1520098C - Process for the production of thread and {transforming polyesters - Google Patents

Description

For the production of linear thread and film-forming polyesters, such as polyethylene terephthalate, many catalysts are known, both for the initial transesterification and for the later polycondensation stage.

Among the many catalysts that are known are the separate uses of germanium, Antimony and titanium, as well as compounds of these three metals.

For example, U.S. Patent 2,578,660 describes the use of germanium and Germanium dioxide.

The use of titanium compounds as catalysts for the production of fiber-forming polyesters is in British Patents 775 316, 777 216, 793 111, 851061 and U.S. Patents 2 727 881 and 2 822 348 mentioned. In many cases, these titanium compounds can be used for both the transesterification and polycondensation stages can be used.

From the Belgian patent 543 309 it is known in the polycondensation of bis (<5-hydroxyn-butyl) terephthalate To use germanium dioxide, while at the same time titanium dioxide is present in the mass as a delustering agent.

The subject of German patent 1,216,544 is germanium alkoxide as a polycondensation catalyst to be used for bis (hydroxyalkyl) terephthalate, titanium dioxide also being used as a delustering agent is present.

According to the invention, there is a substantial improvement in terms of the polyester product.

If it has also been shown that the germanium compounds alone polyester with excellent Color or whiteness, they do not give a very high rate of polycondensation. On the other hand, although titanium compounds have a very high reaction rate in the polycondensation stage effect, and reduce the total time of the operation, they lead to formation of polyesters, which are clearly yellow in color.

Surprisingly, it has now been found that when using a germanium compound together a titanium alkoxide avoids this disadvantage of yellowing in the resulting polyester can be, while at the same time there is the advantage that the titanium alkoxide has a high Polycondensation speed is essentially maintained.

In the production of polyethylene terephthalate is generally used as a polycondensation catalyst an antimony compound is used. In terms of the superiority of antimony compounds over Compounds of other metals it is surprising that the combination of a germanium compound shows better results with titanium alkoxide

ίο than the combination of antimony with titanium alkoxide.

The invention now relates to a method for

Production of thread and film-forming polyesters by transesterification of ethylene glycol with an ester the terephthalic acid and polycondensation of the diol terephthalate obtained, at least during the polycondensation stage is a mixture of a titanium and a germanium compound, which is characterized in that a mixture of titanium alkoxide and a catalyst is used Germanium compound used.

Preferably the titanium alkoxides and the germanium compounds should be in the reaction mixture be soluble, and the preferred compounds of these two metals are titanium tetraisopropoxide, titanium tetrabutoxide and germanium tetraethoxide. Optionally, the transesterification in the presence of a additional transesterification catalyst take place and are the preferred transesterification catalysts Calcium compounds, especially the acetate. It is often desirable to use the transesterification catalyst metal to inactivate before polycondensation begins, and a common method of doing this is by additive a phosphorus compound, for example triphenyl phosphite or phosphoric acid.

The following examples illustrate the invention; all parts and percentages relate to that Weight.

In all examples the percentages relate to the weight of the dimethyl terephthalate used and in each case 0.07% calcium acetate was added as a transesterification catalyst. In Comparative Example A and Example 1 120 g of dimethyl terephthalate were used, while g are used in the following experiments 1552 per mole of diester was transesterified in each trial of this diester at 160 to 210 ⁰ C with 2.5 moles of ethylene glycol. After the transesterification was complete, as indicated by no further release of methanol, the titanium (0.02%), germanium (0.035%) or antimony (0.057%) and phosphorus compounds were added to the transesterification reaction mixture in the table below Way added. The polycondensation was then carried out in each case at a temperature of 285 ° C. and a pressure of less than 0.3 mm of mercury until the indicated intrinsic viscosity (size V) was reached. The intrinsic molar viscosity was measured in orthochlorophenol at 1% concentration (1 g polyester in 100 ecm orthochlorobenzene) at 25 ° C.

In the small-scale Comparative Example A and Example 1, the optical densities in solution (OD i. Sol.) Were determined using a 6.5 percent strength by weight solution of the polymer in dichloroacetic acid. The values given are the optical densities using a 1 cm cell at 400 ηψ with pure dichloroacetic acid as the reference substance.

example Ti compound 2. catalytic
connection phosphorus
connection Polycondens
station
operation
(Minutes) Size V. L. G L-G Optical
Poetry
in solution Comparison Ti (OC ₃ H ₇ ) ₄ none T. P. P. 130 0.650 _ , 0.312 example A (0.111%) example 1 Ti (OC ₃ H ₇ ) ₄ Ge (OC ₂ H ₅ ), T. P. P. 141 0.622 - · - - 0.055 (0.111%) Comparison Ti (OC ₄ H ⁹ V none H ₃ PO ₃ 58 0.673 74 38 36 - example B (0.035%) Example 2 Ti (OC ₄ H ₉ ), Ge (OC ₂ HO ₁ T. P. P. 71 0.686 74 16 58 - (0.111%) Comparison none Ge (OC ₂ H ₅ ) ₄ T. P. P. 140 0.734 77 7th 70 - example C (0.136%). Comparison Ti (OC ₃ H ₇ ), none T. P. P. 47 0.684 70 38 32 - example D (0.111%) Comparison Ti (OC ₃ H ₇ ), Antimonic acid T. P. P. 54 0.683 68 36 32 - example E (0.111%) Comparison none Antimonic acid 'T. P. P. 95 0.677 67 9 58 - example F (0.111%)

T. P. P. = triphenyl phosphite.

In the following experiments, wherein during the preparation of the polymer 0.5% titanium dioxide as Matting agent was added, the luminosity (L) and the yellow value (G) of the resulting polyester determined using a »Colormastor«, which is the trade name for the Manufacturers Engineering and Equipment Corporation is a differential colorimeter manufactured by Manufacturers Engineering and Equipment Corporation.

The luminosity is a measure of the amount of reflected incident light and the yellow value a measure which, according to C. I. E. (Conference Internationale d'Eclairage), is based on color coordinates for the separation of the point represented by the color value of the polymer from that of the illuminant standard Point representing "0", with positive values in the direction of a predominant wavelength from 580 to 590 πιμ and negative values in the direction of a predominant wavelength of 470 to 490 ηιμ were measured.

Relatively small deviations from the luminosity and yellowness values for thread and Polyesters produced for film end purposes can be of considerable importance in the decision of the Value of such polyester for commercial purposes, so it is essential, especially for thread end purposes, that such polyesters have high levels of luminosity along with low yellow values.

It has now been found that when the yellowness index is not significantly less than 0 and when used a germanium or antimony compound as a polycondensation catalyst is a useful color criterion by subtracting the yellowness value from that of the luminosity is obtained. The best color will be obtained when the luminous value minus yellow value is at a maximum. But it is for someone to be employed Such a comparison is essential that the polyesters in the examples to be compared under identical conditions, for example in the same plant and in the same apparatus as well as under Use the same transesterification catalyst where a compound other than one can be used Titanium compound is used for this purpose.

Claims (1)

Claim: Process for the production of thread- and film-forming polyesters by transesterification of Ethylene glycol with an ester of terephthalic acid and polycondensation of the diol terephthalate obtained, a mixture of a titanium and a germanium compound being present at least during the polycondensation stage is, characterized in that the catalyst used is a mixture of titanium alkoxide and a germanium compound are used.