HU212446B - Method of producing polyester - Google Patents

Abstract

The invention concerns a method of producing, without using antimony, a polyester from poly(ethylene terephthalate) units. Following esterification, a mixed catalyst consisting of 10 to 75 ppm of lithium and 15 to 80 ppm of germanium is used for polycondensation. The antimony-free polyester thus obtained is suitable for use in the manufacture of bottles, sheeting, film, fibre, filaments and moulded articles.

Description

FIELD OF THE INVENTION The present invention relates to a process for preparing polyester or copolyester for polyethylene terephthalate units by the polycondensation of polyethylene terephthalate units for the manufacture of bottles, films, films, fibers, fibers and bodies, one component being a lithium salt or a germanium salt.

The preparation of polyesters is known. In general, an acid component, such as terephthalic acid or methyl ester, and a glycol component, such as ethylene glycol, are directly esterified in the first step. is transesterified, and in a second step is subjected to polycondensation. This requires catalysts; In the case of dimethyl terephthalate, the combination of manganese and antimony proved to be very suitable.

Antimony-containing polyesters are undesirable for environmental reasons, especially in two areas. On the one hand, the cost of final storage of antimony-containing waste (the bottom of the distillation) from recycled glycol increases the cost-effectiveness of the whole polyester production, and on the other hand, the dyeing of polyester fabrics results in antimony-free wastewater. Against the backdrop of rising barriers, there is a legitimate fear that antimony will be classified as a carcinogen in the near future.

Stringent legislation in many advanced industrialized countries is making it increasingly difficult to eliminate toxic antimony, and many solutions have been developed to produce antimony-free polyester.

R. Gutmann, for example, [Text. Prax. Int. 44 (1), 29/30, 33 (1989)] suggests the use of Ti, Ge or Al glycolate instead of antimony glycolate. However, this requires the production of defined glycols. Producing high quality, high purity glycols in a single step is quite expensive. The article does not disclose the time and place of addition of the polycondensation catalyst.

In the polycondensation of polyesters, mixed catalysts containing two or more components are also used. EP-A-0 425 215. describes a condensation using an Mn / Li / Co / Sb catalyst. The combination of lithium and antimony is described to moderately accelerate polycondensation.

No. 5,570,077 to Fr-A. In French Patent No. 5,123, the use of lithium germanate as a polycondensation catalyst is mentioned. However, there is no exemplary embodiment showing the concentration and effect. The sodium germanate used is made from germanium dioxide via an alkali metal oxide or carbonate at a Na: Ge ratio of about 0.5: 1. It serves to accelerate the polycondensation of a reaction mixture partially inhibited by sodium germanate phosphate compounds.

SUMMARY OF THE INVENTION It is an object of the present invention to economically produce an antimony-free polyester without degrading the quality of the polyester.

According to the present invention, this object is solved by adding 10-75 ppm of lithium and 15-80 ppm of germanium in the form of their salts to the reaction mixture at the start of the polycondensation.

It has been found particularly advantageous to add 10-70 ppm, most preferably 35-45 ppm, most preferably 30-40 ppm lithium and at the same time 15-80 ppm, particularly preferably 15-40 ppm germanium, to the melt immediately before polycondensation in the form of a glycol solution.

Addition of lithium less than ppm results in too long a polycondensation time, while addition of more than 75 ppm results in a loss of whiteness of the polymer.

It has been found particularly advantageous to have a molar ratio of Li to Ge of from 12: 1 to 1: 1. The polyester produced has a Li content of less than 50 ppm, preferably between 20 and 45 ppm, and a Ge content of 20 to 50 ppm.

The invention is further illustrated by the following examples.

An example of polycondensation

transesterification

10.0 kg of dimethyl terephthalate (DMT) into an autoclave,

6.1 kg of ethylene glycol (EG) and 3.4 g (90 ppm, based on DMT) of manganese acetate (ex MnAcjX1H10) were measured (MMT: EG = 1: 1.9). The transesterification catalyst is completely inactivated by the addition of 1.9 g (56 ppm P) of 70% phosphoric acid at 235 ° C to stop the transesterification reaction. The excess glycol was distilled off, while at 240 ° C 5.0 g of titanium dioxide (0.05% w / w, Hombitan-LWS, manufactured by Sachtleben, Germany) and 7.5 g of Irganox 1010 (0.075% w / w) were added. (Ciba-Geigy AG, Switzerland) is added as a suspension in ethylene glycol. At 245 'C, glycol distillation is complete.

polycondensation

Before the actual polycondensation under vacuum, 3.35 g (35 ppm Li) lithium acetate (ex LiAc ₂ x 2H ₂ O) and 0.6 g (30 ppm) sodium germanate were dissolved in glycol with heating and the solution was heated to 245 ° C. pumped to the autoclave at mass temperature. After the desired viscosity (viscosity index of 74.0, measured in a 50:50 mixture of o-dichlorobenzene and phenol), the melt is removed from the autoclave and granulated.

The granulated polymer is dried and crystallized in a two-cone dryer as follows.

About 80x10 ² Pa under a vacuum of 8-10 kg of polymer was heated at 90 ° C and then one hour at 115 ° C for one hour and then heated to 170 '. After two hours, the vacuum was removed for approx. Increase to 100 Pa. After 13 hours, the polymer is filled into bottles and sealed.

melt spinning

The dried and crystallized polymer is woven into dtex 55-24 fibers with the following parameters.

Spinning nozzle: 24/0 (capillaries), 23 / 4D (capillary diameter)

Extruder Temperature: 280/285/290 'C (Zones 1, 2, 3)

Melting temperature: 293 'C (measured)

Spinning Titer: 187 dtex

HU 212 446 B

Winding speed; 1250 m / min.

Fibers on a laboratory stretcher

It is stretched to a residual stretch of 28 ± 2% while the fiber is pulled over a 200 ° C heating plate. The first galet is 85 'C, the last cold. The scraper speed is approx. 100 m / min, with a stretch ratio of about 3.3.

The results of polycondensation and the properties of the fibers obtained are summarized in Table 1 below.

Catalyst polycondensation Level difference of fibers according to CIE camp Castle. Mn ppm PPPM Li ppm Ge ppm Tmax.'C Blind. min VI DEG% COMPANY M / t DL da db Ref. 90 37 - 75 283 210 76.3 1.10 19.2 0.0 0.0 0.0 1 90 56 75 15 283 250 75.6 0.61 16.7 0.8 -0.3 2.0 2 90 56 75 25 283 205 75.1 0.73 15.5 1.2 -0.3 1.4 3 90 56 75 40 282 190 72.8 0.88 14.4 - - - 4 90 56 40 40 280 195 71.1 1.17 18.6 - - - 5 90 56 20 40 281 225 72.2 1.05 19.4 1.2 -0.3 -0.6 6 90 56 30 30 281 250 73.2 0.89 19.5 - - - 7 90 56 35 30 281 222 72.0 0.96 16.4 2.1 -0.3 -0.3

The reference material was a laboratory polymer prepared using only germanium as a polycondensation catalyst. In order for the polycondensation to be sufficiently rapid, half of the transesterification manganese had to remain free to aid in polycondensation. However, the yarn made from it becomes very yellow during production.

1-7. In Examples 1 to 4, the individual is completely blocked with phosphorus (Mn: P molar ratio 1: 1 to 1: 1.2, preferably 1: 1.1). However, in order to achieve the desired polymerization time, more germanium or auxiliary catalysts should be added.

it has surprisingly been found that lithium in the form of lithium acetate, together with germanium, exhibits high activity during polycondensation. In preliminary experiments, with the same concentration of germanium (75 ppm), the vacuum stage was definitely shorter than in commercial practice (230-240 minutes).

1-7. Examples 1 to 5 show that lithium acetate, along with germanium, is a very suitable co-catalyst for polycondensation. Addition of lithium reduced the time needed for condensation to such an extent that even the amount of germanium could be reduced. The germanium content of the products was thus reduced by more than 50%. The process is mainly suitable for the production of shiny polyester products.

Both the "many lithium-shelled germanium" (Examples 1 and 2) and "almost equal amounts of lithium and germanium" (Example 7) results in advantageous polycondensation times. Examples 1 and 2 have the disadvantage that the product turns yellow (high DB value). The product of Example 7 was lighter (positive DL) and more neutral (low Da and Db).

Claims (3)

PATIENT INDIVIDUAL POINTS A process for the production of polyester or copolyester suitable for the manufacture of bottles, films, films, fibers, fibers and molds from at least 85% by weight polyethylene terephthalate units by polycondensation, using a multi-component mixture catalyst, wherein one component is a lithium salt or a germanium salt, characterized by: that, at the beginning of the polycondensation, a mixture of lithium and 10-75 ppm of lithium and 15-80 ppm of germanium are added to the reaction mixture. 2. The method of claim 1, wherein the lithium salt is lithium acetate and the germanium salt is sodium germanate. 3. The method of claim 1, wherein the lithium content of the polyester is adjusted to 10-50 ppm and the germanium content is adjusted to 20-50 ppm.