DE1065608B - Process for the production of high molecular weight polyethylene glycol terephthalic acid ester - Google Patents

Description

According to the known method, high molecular weight polyethylene glycol terephthalic acid ester is prepared in principle in such a way that low molecular weight polyethylene glycol terephthalic acid ester (precondensate), as it is, for. As obtained during the reaction of dimethyl terephthalate with ethylene glycol or the reaction of terephthalic acid with Äthylenglykolcarbonat first weiterkonderisiert in the presence of catalysts under vacuum with stirring by heating to temperatures above 260 ⁰ C with the elimination of ethylene glycol to high molecular weight products. Although in various patents temperatures up to about 300 ⁰ C mentioned as coming for the further condensation of the low molecular weight Polyäthylenglykolterephthalsäureesters to high molecular weight products (high condensation phase) in question, described but in no case applied as effectively. This is consistent with the prior art underlying experience that during the heating of polyethylene glycol terephthalate according to the previously practiced procedures about 285 to 29o ⁰ C addition degradation processes (eg. As color, degree of condensation), the quality of the polycondensate substantially affect (W . Griehl, "Research and Textile Technology," /, 4 [1954], p. 381). Typical for all previously known methods for converting low molecular Polyäthylenglykolterephthalsäureester in a high molecular weight condensation product are relatively long condensation times of typically more than 2 hours at the stage of polycondensation by heating the melt in the vacuum to temperatures between 260 and about 29o ⁰ C.

It has now been found that it is possible to produce high-molecular condensation products of excellent quality from low-molecular-weight polyethylene glycol terephthalates in much shorter condensation times and thus in a very economical way that does not damage the quality of the condensation products if a melt of low-molecular-weight polyethylene glycol terephthalates, e.g. B. those with a viscosity number Ζη according to Staudinger (see H. Staudinger, Kolloidchemie, 3rd edition [1950], p. 210) less than 0.03, measured at 25 ° C in phenol-tetrachlorethylene (60:40), in the presence of suitable catalysts in a 1 to 18 cm layer thickness with stirring for no longer than about 20 minutes from 240 to 290 ° C in a vacuum increasing from initially about 20 mm Hg to about 0.5 mm Hg and the temperature in about further 10 minutes to a height between 300 and about 320 ⁰ C and does not hold longer than up to about a further 14 minutes in this temperature range; a viscosity number of the condensate of over 0.06 is achieved.

The main feature of the process (high-temperature short-term process) is that exactly from one another-

for the production of high molecular weight
Polyethylene glycol terephthalic acid ester

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brünmgstr. 45

Dr. Ludwig Orthner, Frankfurt / M.-South,

Dr. Rudolf Reuber, Frankfurt / M.-Eschersheim,

and Dr. Max Grossmann, Frankfurt / M.,

have been named as inventors

coordinated interaction of several connections, namely

1. the application of a defined layer thickness between 1 and 18 cm of the material to be condensed Good in cooperation with

2. high temperatures in the range 300 to 320 ⁰ C and

3. a duration of the final condensation of not more than 20 minutes.

It is already known from German patents 901 592 and 918 778, based on diamines and dicarboxylic acids, resulting in polyamides by polycondensation within thin layers is carried out, as well as differently structured polycondensation products by draining the Further condensation could be produced within thin layers. These known methods of Condensation management in thin layers, whereby thin layers are generally only understood in technology whose layer thicknesses are at most a few millimeters, usually even much less, as from the Process of thin-film evaporation is known, but cannot be applied to the further condensation of transferred from low molecular weight polyethylene glycol terephthalates existing precondensates. This here The resulting high molecular weight polycondensation product is namely due to a very unfavorable flow behavior characterized. On the basis of this fact it can

909 628/429

Claims (1)

forming high molecular weight product in a thin layer does not flow sufficiently fast enough, so that at higher Temperatures local overheating can occur. According to the invention, however, it succeeds in satisfying the need Flowability on the one hand with the requirement that the can be removed quickly during further condensation to combine ethylene glycol released by precondensates in a technically usable manner, if not more explicitly thin layers are subjected to further condensation, but those whose layer thickness is more than 1 cm but less than about 18 cm. Surprisingly and by no means expected now that in spite of the necessary high temperature - between 300 and 320 ° C - the flowability of the condensation material is controlled by adjusting the layer cover can be that sufficient flow resistance or possibility of mixing with sufficient faster removability of the ethylene glycol released during further condensation can be. A layer thickness of about 18 cm is allowed are not exceeded in the present process, so that the glycol formed during the condensation removes itself from the melt as quickly as is necessary for the feasibility of this high-temperature, short-term condensation process Requirement is. According to the invention, suitable catalysts are for the high-temperature short-term process for production of high molecular weight polyethylene glycol terephthalic acid ester (VZ 0.06) from low molecular weight (VZ <0.030) elements of the I., IL, III., IV. Main group, the I., IL, VL, VIL, VIII. Intermediate group of the periodic table of the elements (see periodic table of the elements with electron arrangement, Georg Westermann Verlag, Braunschweig, 2nd edition, 1957), in the form of their oxides, hydroxides, alcoholates, phenates or salts of organic Acids, especially in the form of soluble in glycol and / or polyethylene glycol terephthalic acid esters Compounds of compounds of the groups mentioned, e.g. B. zinc acetate, antimony acetate, manganese acetate, Cobalt acetate, potassium antimonyl tartrate. In this high-temperature short-term condensation process, catalyzing compounds of the elements of the groups mentioned can be used individually or in combination. In the latter case, several different catalysts can also be combined in such a way that one or more specific catalysts, such as antimony oxide and zinc acetate, are first used in the initial stages of the polycondensation (e.g. initially for the production of diethylene glycol terephthalate or after low molecular weight polyethylene glycol terephthalate, which is formed during the transesterification of terephthalic acid with volatile monohydric alcohols with ethylene glycol or by reacting terephthalic acid with glycol carbonate), and then prior to application of 26O ⁰ C, but especially from 29o ⁰ C, temperatures exceeding further specific catalysts, such as cadmium acetate, manganese acetate, cobalt acetate, in introduces the condensation melt. Substances can be added to the condensation material that affect the melt during the condensation process protect from discoloration, such as triaryl phosphites. The described high-temperature short-term process according to the invention for the production of high molecular weight polyethylene glycol terephthalic acid ester is suitable excellent for the continuous production of high molecular weight polyethylene glycol terephthalic acid ester, e.g. B. in boiler cascades. - In addition to the high molecular weight polyethylene glycol terephthalic acid esters, the process according to the invention can be used also produce high molecular weight polyesters of different compositions in an analogous manner. example 1
5 a) 14.5 kg of dimethyl terephthalate, 11.60 kg of ethylene glycol, 2.90 g of zinc acetate and 2.90 g of Sb ₂ O ₃ were put in a with stirrer, thermometer, gas inlet tube, distillation attachment and descending condenser ίο provided autoclave made of V2A steel at 160 to 256 ⁰ C in a weak nitrogen stream with stirring under normal pressure (about 755 mm Hg) continuously distilling off methanol (560 ml) and subsequent distilling off of 3 l of free glycol converted to a low molecular weight polyethylene glycol terephthalate with a melting range of 117 to 174 ⁰ C and a viscosity number of 0.012 (measured at 25 ° C in phenol-tetrachloroethane 60:40). 2.6 g of triphenyl phosphite, dissolved in 300 g of ethylene glycol, were stirred into the melt. b) 1 kg of the precondensate prepared according to a) were evacuated to 8 mm Hg in a V 4A-3-1 autoclave equipped with a stirrer, thermometer, manometer, exhaust steam nozzle and descending condenser to 200 ^° C. in 10 minutes, and in a further 10 minutes Heated to 240 ° C. for minutes and completely melted (layer thickness of the solidified product 7 cm), whereupon stirring (55 rpm) was started and the vacuum was immediately increased to 0.7 mm Hg. In a further 22 minutes, the temperature of the melt was increased steadily to 304 ^{° C. and held at 304 °} C. for a further 10 minutes. The melt was then cooled to below 270 ° C. in a further 6 minutes. The melt was colorless; Freezing point 261 ° C; Viscosity number 0.076. Example 2 1 kg of precondensate (example a) was melted as in example 1 in 20 minutes at a pressure of 8 mm Hg and brought to 236 ° C. Then, the vacuum was increased to 0.7 mm Hg, the temperature of the melt was heated with stirring in 10 minutes to 265 ° C in another 10 minutes at 297 ⁰ C in another 10 minutes and up to 309 ° C, an additional 6 minutes 309 ⁰ C and then rapidly cooled ^{below 270 0 C.} The melt was colorless; Solidification point 27O ⁰ C; Viscosity number 0.069. Example 3 1 kg solid precondensate (Example a)) autoclave described were melted under 10 mm Hg in 12 minutes and brought to 24O ⁰ C in which b in the example, then the temperature of the melt within 8 was (110 U / min while stirring.) Minutes to 290 ° C. The pressure was then immediately reduced to 0.5 mm Hg and the stirring speed to 55 rpm, the temperature was increased to 312 ^° C. in a further 8 minutes and held at this level for 12 minutes; it was then cooled ^{below 270 ° C. in 7 minutes.} The melt was almost colorless; Freezing point 261 ° C; Viscosity number 0.071. P Λ T! ■: N T Λ N S P RUCH: Process for the preparation of high molecular weight polyethylene glycol terephthalic acid ester from in known Way, e.g. B. by transesterification of dimethyl terephthalate with ethylene glycol in the presence Terephthalic acid diester of glycol or of a low molecular weight produced by catalysts 5 6 Polyethylene glycol terephthalates (precondensate), since the temperature range from 240 to 18 cm characterized in that the pre-condensate 290 ° C in no more than about 20 minutes through at temperatures above about 250 ⁰ C can step with stirring, the temperature then in about 10 Mi- in the presence of catalysts and in vacuo grooves increased to 300 to 320 ⁰ C and the condensate subject to further condensation, 5 sation terminates when a viscosity number of over that one reaches its melt in layer thicknesses of 1 to 0.06. © 909 628/429 9. 59