DE1159168B - Process for the production of poly (ethylene glycol terephthalate) - Google Patents

Description

ENTERNAT.KL. C 08 g

GERMAN

PATENT OFFICE

V17301IVd / 39c

REGISTRATION DATE: SEPTEMBER 23, 1959

NOTICE
THE REGISTRATION
ANDOUTPUTE
EDITORIAL: DECEMBER 12, 1963

It is known that in the production of high molecular weight poly (ethylene glycol terephthalate) the two successive reactions of transesterification and polycondensation in general be favored by various catalysts. While in the first development phase of the Polyesters, no care was taken to distinguish precisely between these catalysts Later work in this area led to the realization that a Polycondensation catalyst is partially inactivated in almost all cases before the polycondensation begins. So one went over to the polycondensation catalyst only at a later date Time to add. Inorganic salts or oxides are used as condensation catalysts, of which antimony trioxide is currently the most common. Especially with this in itself right Well-acting catalyst, discoloration of the polyester can occur if the antimony trioxide penetrates Compounds formed or released during the reaction are reduced to metallic antimony will.

The invention now relates to a process for the production of poly (ethylene glycol terephthalate) by Transesterification of dimethyl terephthalate with ethylene glycol in the presence of zinc acetate and polycondensation of the bis-glycol ester of terephthalic acid obtained in the presence of a polycondensation catalyst, which is characterized in that the transesterification and / or the polycondensation is carried out in the presence from 0.01 to 0.1 percent by weight of phthalimide, based on dimethyl terephthalate.

In addition to shortening the polycondensation time, which is normally 4 hours, by 30 to 60 minutes are obtained by using phthalimide as a polycondensation catalyst, polyester, which are characterized by a better color. A deterioration in the physical data of the Polyester does not enter, on the contrary, an increase in the softening temperature is even found.

The details of the process are illustrated in the following examples.

example 1

500 g of dimethyl terephthalate are melted under a nitrogen atmosphere in a flask with 344 ml of ethylene glycol and 0.015 percent by weight of zinc acetate (based on dimethyl terephthalate) while stirring. The temperature is then increased so rapidly that no ester is distilled over with the methanol or glycol which has been split off. (!. Hour method of manufacture
of poly-ethylene glycol terephthalate)

Applicant:

United Glanzstoff-Fabriken AG,
Wuppertal-Elberfeld, Glanzstoff House

Dr. Lothar Riehl, Grebben (RhId.),
has been named as the inventor

160 to 200 ° C; 2nd hour 200 to 235 ° C; 3rd hour 235 to 240 ° C). From the start of the process until the temperature of 240 ° C is reached are a total Three or four hours passed.

0.02 percent by weight of phthalimide, dispersed in as little glycol as possible, and 2.5 g of titanium dioxide (0.5 percent by weight) as a 20% glycol dispersion are then added to the reaction mixture. It reduces the pressure within 60 minutes carefully, avoiding splash applications, to 0.1 mm Hg. Until that time, the internal temperature rises to just 270 ⁰ C. With a gradual increase in temperature to 276 ° C., the vacuum is maintained until the polycondensation end point is reached. This is reached after a total condensation time of 2 ³ Ai to 3 hours. (The total condensation time is calculated from the beginning of evacuation.) The polyester has a solution viscosity } j _{rc [} from 1.64 to 1.65 and a softening temperature of 261 to 262 ° C. The degree of remission is 76 to 78 Vo. It is a measure of the whiteness of the polyester, which is determined by measuring the remission at 460 ηΐμ, based on a corresponding remission measurement on pure white magnesium oxide, which is assumed to be 100%.

Example 2

500 g of dimethyl terephthalate are, as described in Example 1, melted with 344 ml of ethylene glycol and 0.015 percent by weight of zinc acetate and 0.02 percent by weight of phthalimide while stirring. The transesterification and the polycondensation then take place as in Example 1, without the addition of a further catalyst. The total condensation time of 3 ¹ to 3 U V2 hours. The solution

309 768/447

The viscosity η _{Γ0 [of} the polyester obtained is determined to be 1.64, the softening point at 260 to 261 ° C and the degree of remission at 73%.

Comparative experiment

The procedure is as in Example 1, except that 0.02 percent by weight of the known polycondensation catalyst antimony trioxide is used instead of phthalimide. Under these conditions, the Polykondensationsendpunktes 4 to 4 ¹ U hours total condensation time needed to achieve. The solution viscosity η _{η1 of} the polyester is 1.635 to 1.645, the softening point is 260 to 261 ° C and the degree of remission is 70 to 72%.

Nitrogen-containing compounds have been used as catalysts in the manufacture of polyesters made of dimethyl terephthalate and ethylene glycol. These are organic Ammonium bases, especially alkylammonium terephthalate. Although the required amount of catalyst is relatively high, at about 0.5 percent by weight, based on dimethyl terephthalate, are very long Reaction times required for transesterification and polycondensation, for example 2 V2 to 10 hours for the transesterification and 6 to 7 hours for the polycondensation. If you post the polycondensation breaks off a time of 3 hours, so after a time that in the method according to the invention for Achieving a polyester with very good properties is sufficient, so one obtains according to the known Working method a poly (ethylene glycol terephthalate) with a low solution viscosity.

Claims (1)

PATENT CLAIM: Process for the preparation of poly (ethylene glycol terephthalate) by transesterification of dimethyl terephthalate with ethylene glycol in the presence of zinc acetate and polycondensation of the bis-glycol ester obtained in the presence of a polycondensation catalyst, characterized in that the transesterification and / or polycondensation in the presence of 0.01 to 0.1 percent by weight of phthalimide, based on dimethyl terephthalate. Considered publications:
Dutch Patent No. 90 066;
published documents of Belgian patent No. 544 855. © 309 768/447 12.