SK9094A3 - Method of production of polyester produced by this method and its use - 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

Process for producing polyester, polyester produced by this process and its use

Technical field

The present invention relates to a process for the manufacture of a polyester or copolyester from polyethylene terephthalate units by polycondensation using a mixed catalyst comprising a plurality of components, wherein at least one component is a lithium or germanium salt, a polyester produced by the process and its use.

BACKGROUND OF THE INVENTION

The production of polyester is known. Usually an acid component, such as terephthalic acid or a methyl ester thereof, and a glycol component, such as ethylene glycol, are used which are directly cross-esterified or re-esterified in the first stage and are carried out in the second production stage after 1condensation a. Catalysts are required for this polycondensation reaction, from which a combination of manganese with antimony has proven to be very suitable for the process starting from dimethyl terephthalate.

Antimony-containing polyesters are harmful for environmental reasons. Difficulties are particularly apparent in two areas. The removal of antimony-containing wastes from the recycling of crude glycol (distillation sludge) is increasingly costly, making the overall production of polyester more economical. In addition, antimony-containing waste waters are produced in the dyeing of polyester fabrics, since the antimony is not fixed firmly on the fiber. The reason for the increased difficulty is the justified concern that antimony might be included in a group of substances with a proven risk of causing cancer.

Due to stricter legislation in numerous industrialized countries, the removal of antimony considered toxic is increasingly acute. Therefore, several solutions have been proposed for methods of making an antimony-free polyester.

For example, R. Gutmann in the work published in the journal Text. Practice. Int., 44 (1) p.29 / 30, 33, 1989, suggests the use of titanium, germanium or aluminum glycolate instead of antimony glycolate. The defined glycolates are produced. The production of glycolates in a separate production stage in constant pure quality is very expensive. The time and place of addition of the polycondensation catalyst is not mentioned in the work.

The use of mixed catalysts consisting of two or more components in the polycondensation of polyesters is known. Thus, EP-A-0425215 describes a process in which a catalyst of Mn / Li / Co / Sb is used in polycondensation. At the same time, lithium in conjunction with antimony should slightly accelerate after 1condensation.

French patent FR-A-2 570 077 discloses the use of lithium germanate as a catalyst for polycondensation. The specification does not contain any exemplary embodiment to show the concentrations and mode of action. The sodium germanite mentioned in the examples is brought to a soluble state by means of an alkali metal oxide or an alkali metal carbonate by a known reaction with germanium oxide, the Na: Ge ratio being about 0.5: 1. The sodium germanite serves to accelerate polycondensation in the reaction mixture, not completely inhibited by phosphate compounds.

SUMMARY OF THE INVENTION It is an object of the invention to economically manufacture antimony-free polyester without reducing the known quality of the polyester.

SUMMARY OF THE INVENTION

The invention solves the problem by adding 10-75 ppm Li and 15-80 ppm Ge to the reaction mixture initially after the 1condensation phase.

It has been found to be advantageous to add 10 to 70 ppm Li, in particular 35 to 45 ppm Li, preferably 30 to 40 ppm Li, and at the same time 15 to 80 ppm Ge, in particular 15 to 40 ppm Ge before the polycondensation, preferably immediately before after 1condensation, in the form of a glycol solution.

The addition of less than 10 ppm Li is disadvantageous because the polycondensation time is too prolonged; addition of more than 75 ppm results in a drastic reduction in the degree of whiteness of the polymer.

The Li: Ge molar ratio ranging from about 12: 1 to 1: 1 has proven to be particularly suitable in a 1condensation catalyst.

The polyester produced should contain less than 50 ppm Li, preferably 20 to 45 pp, Li as well as 20 to 50 ppm Ge.

The invention is further illustrated by the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Example of polycondensation:

transesterification

Weigh into the autoclave 10.0 kg of dimethyl terephthalate (DMT), 6.1 kg of ethylene glycol (EG) and 3.4 of manganese acetate (from Mnaca.HeO) (90 ppm Mn based on DMT) (DMT: EG = 1: 1.9). The transesterification catalyst was completely blocked at 235 ° C by adding 1.9 g (56 ppm P) of 70% phosphoric acid to terminate the transesterification reaction. During the glycol phase, in which excess glycol is distilled off, 5 g of titanium dioxide (0.05%, Hombitan-LWS, a brand product of Sachtleben, Germany) and 7.5 g of Iroganox 1010 ( 0.075%, a brand product of CIBA-GEIGY AG Switzerland) as a suspension in ethylene glycol. The glycol phase is terminated at 245 ° C.

After 1condensation i

Before the vacuum phase proper after the 1-condensation phase, 3.35 g (35 ppm Li) of lithium acetate (from Liac2.2 H2O) and 0.6 g (30 pp, Ge) of germanium or sodium are heated and dissolved in the glycol. and the resulting solution is pumped into the autoclave at 245 ° C. After reaching the desired viscosity (viscosity index 74.0, measured in a mixture of o-dichlorobenzene with phenol 50/50 w / w), the melt is extruded from the autoclave and granulated.

The granulated polymer is dried in a double-cone dryer and crystallized as follows:

At a vacuum of about 8 kPa, the resulting 8 to 10 kg of polymer are heated at 90 ° C for 1 hour and then at 115 ° C for an additional hour. Heating is then continued until a final temperature of 170 ° C is reached. After two hours, the vacuum is reduced from 8 kPa to about 100 Pa. After a further 13 hours the polymer is cooled and filled into bottles which are sealed airtight.

Melting

The dried and crystallized polymers are spun into dtex 55F24 fibers as described below:

spinneret: 24/0 (capillaries), 23 / 4D (capillary diameter) extruder temperature: 280/288 / 290 ° C (zone 1/2/3) melt temperature: spinning titer: 2 9 3 ° C (measured) 187 dtex

bobbin speed: 1250 m / min

The fibers are then reduced in a laboratory elongation apparatus in a single stage to a residual loading of 28 + 2%. In this case, the fiber is passed through a heating surface of 200 ° C. The temperature of the galette 1 is 85 ° C. The recovery galley is cold. Mining takes place at a towing speed of 100 m / min. The digestion ratio is approximately 3.3.

The results of the tests with polycondensation and fibers prepared from the obtained polymers are shown in Table 1.

Table 1

Ex. no. catalyst Polymer condensation CIE-Lab fiber color difference. Mn ppm P ppm Li ppm Ge ppm temp. max. 'c bag. min. viskind. DEG% I CEG aol / t DL Will give db ref. have got, 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

As a reference material for all comparative measurements, a laboratory polymer was used, which was produced only with germanium as the after-condensation catalyst. In order to proceed sufficiently quickly after 1 -condensation and to proceed quickly, 25 ppm of manganese from the transesterification had to remain free at 1condensation i. A disadvantage here is that the fiber is yellowed too much during its production.

In Examples 1 to 7, manganese was completely blocked with phosphorous acid (molar ratio Mn: P = 1: 1 to 1: 1.2, preferably 1: 1.11. However, in order to achieve the desired time after 1condensation, it would have to be added either more germanium or a cocatalyst would have to be used.

Surprisingly, it has been shown that lithium, added in the form of lithium acetate, together with germanium exhibits very considerable activity in the polycondensation phase.

In the preliminary experiments, all the vacuum phases at a constant concentration of germanium (75 ppm) were clearly operating for the usual time after a condensation of 230 to 240 min.

It can be seen from Examples 1 to 7 that lithium acetate as a co-catalyst together with germanium is very suitable for polycondensation. By adding lithium, the polycondensation time could be shortened so much that it was also possible to reduce the required amount of germanium. The germanium content could be reduced by more than half. This method is particularly advantageous for producing glossy polyester products.

Both the combination of many lithium and low germanium (examples 1 and 2), as well as the combination with almost equal amounts of lithium and germanium (example 7) exhibit favorable polycondensation times. The disadvantage of Examples 1 and 2 is that the color is too strong in the yellow area on the fiber (high Db value). the fiber of Example 7 is both lighter (positive DL) and more neutral in color (lower Da and Db).

(An additional antimony-free glossy catalyst formulation for shiny polyethylene terephthalate was found.)

Industrial usability

The process according to the invention is suitable for the economical production of antimony-free polyesters without reducing the known quality of the polyester. The polyester produced by the process of the invention can be used to produce bottles, films, films, fibers, fibers and shaped bodies.

Claims (3)

PATENT CLAIMS A process for producing a polyester or copolyester of at least 85% by weight, polyethylene terephthalate units after 1-condensation using a mixed catalyst comprising a plurality of components, wherein at least one component is a lithium salt or a germanium salt, characterized in that the reaction mixture is initially 10-75 ppm Li and 15-80 ppm Ge. The polyester produced by the process of claim 1, characterized in that it has a Li content of from 10 to 50 ppm and a Ge content of from 20 to 50 ppm and a diethylene glycol content of less than 1% w / w. Use of a polyester produced by the process of claim 1 for the manufacture of bottles, films, films, fibers, fibers and shaped bodies.