Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1990-11-15
1992-05-19
Kight, III., John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528308, 5283085, C08G 6378
Patent
active
051150859
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of polyester and alkyd resins formed from bifunctional and/or polyfunctional carboxylic acids and/or carboxylic anhydrides and/or carboxylic acid esters and from bifunctional and/or polyfunctional alcohols, in which the reaction is carried out with the application of pressure in stirred kettle reactors which are operated discontinuously and equipped with rectifying columns.
Saturated and unsaturated polyesters and alkyds are used, in particular, in crosslinking systems in the paint resin sector and for the preparation of thermosetting resins. They are preferably prepared in discontinuously operated stirred kettle reactors which can be employed for all-purpose use. These stirred kettle reactors are usually equipped with a device for removing water from the system, comprising a vapor pipe, a condenser and a separation vessel (cf. Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Volume A1, Alkyds, Verlag Chemie, Weinheim 1985, pages 415-416).
For carrying out condensation reactions--particularly on a large scale--this reactor set-up has a number of disadvantages:
Owing to losses in feedstock, which are difficult to monitor, the use of a simple vapor pipe without fractionating action as a vapor outlet from the reactor results in displacements in the stoichiometric composition and hence in variations in the quality of the product. In order to improve the manner in which the reaction is carried out rectifying columns have been suggested as a replacement for the simple vapor pipe.
From the aspect of mass transfer the unmodified stirred kettle reactor has a very unfavorable geometry. A decisive factor for the performance of the reactor is the speed at which the component liberated in the course of the polyester condensation (water and alcohol), hereinafter also described as the condensation component, is removed from the polyester melt and the reactor. As the size of the reactor increases there is a diminishment in the specific mass transfer area, which is a co-determining factor in this regard.
In order to improve the transport of the condensation component from the reactor an entraining agent which is not miscible with the condensation component, such as, for example, xylene or toluene, is frequently employed. The state of the art is to pour this entraining agent onto the surface of the resin melt (Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Volume A1, page 415).
In order to assist the expulsion of the condensation component from the polyester melt - above all as the viscosity of the melt increases towards the end of the condensation reaction--it is also possible to pass a stream of inert gas (nitrogen, carbon dioxide or argon) through or over the melt, with vigorous stirring (cf. Kunststoff--Handbuch ("Manual of Plastics"), Volume VIII, Polyesters, Hanser Verlag, Munich 1973, pages 266-269). For economic reasons, however, this process is only suitable in exceptional cases.
The esterification of terephthalic acid with glycols under pressure and at an elevated temperature is described in French Patent Specification 1,140,847. Apart from the description of the known esterification reaction, accelerated at an elevated temperature, and the suppression of the formation of byproducts (tetrahydrofuran from 1,4butanediol), the patent specification does not supply any teaching to solve the present problem of the discontinuous preparation of polyesters in stirred kettle reactors, in particular any reference to the use of an entraining agent.
The use of pressure, in order to reduce the production of undesired byproducts, is known from the transesterification of dimethyl terephthalate (cf., for example, German Offenlegungsschrift 2,365,934). Thus, for example, the transesterification of dimethyl terephthalate with ethylene glycol under pressure using a reaction column is suggested in Austrian Patent Specification 242,122, with the aim of reducing the undesired formation of diethylene glycol. German Auslegeschrift 1,130,433 describes
REFERENCES:
patent: 3039980 (1962-06-01), Mallison
Chem. Abstracts, vol. 81, No. 6, 12; Aug. 1974 (Columbus, Ohio) (Kanelafuchi Spinning Co. Ltd-Abstract #26194).
Chem. Abstracts, vol.98, No. 20, 16 May 1982 (Columbus, Ohio, U.S.), Abstract #161746.sub.m YCS, A, 203350 (Leser F. et al); Oct. 15, 1982.
International Polymer Science & Term (Rapra), vol. 12, No. 4 1985 (Shawbury, Shrewbury, GB) F. Leser: "Equipment".
Dangschat Manfred
Diefenbach Horst
Laser Theo
Sadlowski Jurgen
Schmitt Deiter
Acquah Sam A.
BASF Lacke+Farben Aktiengesellschaft[DE/DE] Max-
Kight, III. John
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