Process for the preparation of composite bodies

Details Process for the preparation of composite bodies Process for the preparation of composite bodies

1994-12-01

1995-08-29

Foelak, Morton

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having voids in a component

4283193, 521117, 521125, B32B 326

Patent

active

054458790

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a novel process for the preparation of composite bodies by back-foaming plastics sheets with a reaction mixture which reacts fully to a soft or semi-rigid polyurethane foam and which contains as catalysts certain hydroxycarboxylic acids present in the alkali salt form, and the composite bodies obtained by said process.
Sheet composite bodies prepared by back-foaming a plastics sheet with a reaction mixture which reacts fully to a soft or semi-rigid polyurethane foam are very important industrially, being very widely used, for example, for motor vehicle and aircraft interiors or in the manufacture of upholstered furniture. It is essential for the majority of these fields of application for the foams to exhibit, in addition to good mechanical properties (in particular excellent tear resistance), good heat resistance and a low "fogging" tendency. In particular, the fogging behaviour (tendency towards dissociation of low-volatile compounds which become deposited on cool surfaces such as car windows) displayed by the known back-charge foams is a problem in respect of which an improvement would be worthwhile.
Tertiary amines, which are frequently utilised as catalysts, are an example of components which lead to fogging when used in the reaction mixture which reacts fully to form polyurethane foam. Attempts have therefore already been made to replace these amines with, for example, alkali metal salts of carboxylic acids, such as potassium acetate. However, catalysis alone using such catalysts is associated with the disadvantage of excessive mould removal time or (if catalyst concentration is increased) excessively short initiation times. Admittedly, when organic tin compounds are used an improvement is generally obtained in the fogging behaviour, but problems then arise as regards the constancy of activation of the polyol component over a protracted storage period, because of the presence of the hydrolytically labile organic tin compounds in the water-containing polyol.
U.S. Pat. No. 4,868,043 recommends using as catalysts semi-esters of (i) intramolecular carboxylic acid anhydrides and (ii) long-chain diols, such semi-esters being present in the alkali salt form, but because these compounds are monofunctional in the sense of the isocyanate addition reaction, the inevitable result is chain-breaking reactions, and hence reduced tear resistance in the foam.
It has now surprisingly been found that an optimum solution to the problems which are addressed is obtainable by using the catalysts which are essential to the invention, which are described below in greater detail. The essential point of the process according to the invention which is described in greater detail below comprises using as catalysts reaction products, present in the alkali salt form, of at least trivalent alcohols and intramolecular carboxylic acid anhydrides, wherein the reaction products must exhibit as a statistical average per molecule at least 2 hydroxyl groups and at least 0.5 alkali carboxylate groups. Virtually no chain-breaking reactions occur because at least bifunctional compounds are used. A further advantage of the incorporatable catalysts essential to the invention, in addition to the excellent fogging behaviour which can be achieved, resides in the possibility afforded by the reaction mixtures according to the invention of comparatively long initiation times, while short mould removal times remain unchanged.
The object of the invention is a process for the preparation of composite bodies by back-foaming a plastics sheet constituting the top layer with a reaction mixture which reacts fully to a soft or semi-rigid polyurethane foam, the mixture substantially comprising chemistry, weight of component b), of reaction products, present in the alkali salt form, of (i) at least trivalent alcohols within the molecular weight range 92 to 10,000 and (ii) intramolecular carboxylic acid anhydrides, is used as component d), the said reaction products exhibiting as a statistical average per molecule at least 2 alcoholic

REFERENCES:
patent: 4336341 (1982-06-01), Fujiwara et al.
patent: 4868043 (1989-09-01), Eling et al.

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