Process for the production of plastics containing amide groups

Details Process for the production of plastics containing amide groups Process for the production of plastics containing amide groups

1994-07-29

1996-06-18

Seidleck, James J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

528199, 528203, 528205, 528 60, 528 61, 528 64, 528 75, 528 80, 528 83, 521 90, 521 94, 521 97, C08G 6400

Patent

active

055278760

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a process for the production of thermoplastics or thermosets containing amide groups by catalytic reaction of carboxylic acids and polyfunctional isocyanates with formation of CO.sub.2, to the plastics obtainable by this process and to their use.
2. Discussion of Related Art
It is generally known that carboxy groups give off carbon dioxide when reacted with isocyanates and can thus contribute towards the blowing reaction in PUR plastics.
Thus, O. Bayer (see "Angewandte Chemie" 59, 1947, pages 257-288) describes on page 267 a foam of a) a polyester of a dicarboxylic acid and a trihydric alcohol containing both free hydroxyl groups and also carboxyl groups with b) a diisocyanate. 50 to 300 kg/m.sup.3 foams were obtained (trade name MOLTOPREN). In the case of the aromatic isocyanates used on an industrial scale, this NCO/COOH reaction is very complicated and is unsuitable for industrial-scale blowing reactions, i.e. for obtaining relatively low densities. In addition, the polyurethanes obtained in this way are often strongly colored.
An improvement was achieved by using formic acid as blowing agent, as described in DE 32 23 567. According to this document, polyurethane foams are produced from carboxylic acids, polyols, diisocyanates, tertiary amines and water. Formic acid is used as the carboxylic acid (see Examples). It is not absolutely essential to use water as blowing agent (see page 6, lines 11 to 27). In addition to organometallic compounds, the catalysts mentioned also include tertiary amines, such as dimethyl benzyl amine, tetramethyl ethylene diamine, triethylene diamine, hexamethylene tetramine and dimethyl cyclohexyl amine. The temperatures at which the reaction takes place are not specifically mentioned.
The disadvantage of this process lies in the evolution of CO (inflammable, toxic) in addition to CO.sub.2 as blowing gas. As in the case of water-blown foams, the formic acid has to be added to the polyol/isocyanate mixture immediately before foaming. In addition, polar formic acid--in exactly the same way as water--is incompatible with most other PUR raw materials.
DE 30 41 589 describes mixed carboxylic acid/carbamic acid anhydrides as blowing agents for the production of foam plastics. They are obtained from aliphatic and/or cycloaliphatic isocyanates by reaction with weak mono- or polycarboxylic acids. The anhydrides must have a melting point of more than 40.degree. C. The evolution of CO.sub.2 requires temperatures of more than 100.degree. C. although in some cases the elimination of CO.sub.2 actually begins at around 60.degree. to 70.degree. C. No catalysts are required for the actual blowing reaction. However, it is possible to use catalysts, for example organometallic compounds, Mannich bases and also tertiary amines, for example n-methyl morpholine, 1,2-diazabicyclo-(2,2,2)-octane, bis-(dimethylaminoalkyl)-piperazine and 1,2-dimethyl imidazole, organometallic compounds (for example organotin compounds) being preferred. Semirigid to rigid PUR foams having a density of at least 128 kg/m.sup.3 are obtained. Apart from the high starting temperature, which makes the blowing agent extremely difficult to use, and the high density of the foams, the process in question is attended by the following disadvantages (see DE 38 40 817, page 2):
"The mixed anhydrides on the one hand should be stable in storage at temperatures of up to about 60.degree. C., even in solution, and on the other hand should develop their blowing effect at temperatures as low as about 80.degree. C. with elimination of carbon dioxide. Accordingly, there are very narrow limits to the temperature at which the carbon dioxide is eliminated. Only aliphatic isocyanates can be used for the production of the mixed anhydrides. By contrast, the aromatic polyisocyanates typically used as polyisocyanate component are unsuitable for the production of the special blowing agents.
To carry out the process, the mixed anhydrides first have to be prepared in a separat

REFERENCES:
patent: 3557027 (1971-01-01), Marsh et al.
patent: 3620987 (1971-11-01), McLaughlin et al.
patent: 4016144 (1977-04-01), Tilley
patent: 4528334 (1985-07-01), Knopf et al.
"Angewandte Chemie" 59, 1947, pp. 257-288.
PUR World Congress, Sep. 1991, pp. 686 to 690.
H. Beyer, Lehrbuch der organischen Chemie, 18th Edition, p. 613.
H. R. Christen, Grundlagen der org. Chemie, 4th Edition 1977, pp. 378 et seq.

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