DE1054232B - Process for the production of foams - Google Patents

Description

Process for the production of foams It is known, aqueous Solutions of curable reaction products from aminoplasts or phenoplasts Compounds and aldehydes. so-called precondensation products, the hardening agents for these precondensates may contain, with inert gases, in particular with air, to foam and the resulting synthetic resin foam at room temperature or to harden and dry at elevated temperature. The curable synthetic resin foam can with particular advantage on bodies or surfaces to be isolated, e.g. B. on masonry or pipelines, are applied and hardened there. Here, however, occurs Shrinkage of the foam. This can cause the foam to crack and become detach from the ground.

It is also known to use aqueous solutions of urea-formaldehyde precondensates to foamed men that contain low molecular weight alcohols such as glycol or glycerine. The disadvantage here, however, is that these additives very strongly attract moisture and hold, so that an undesirably high moisture level in the foams obtained is maintained.

Finally, in the French patent specification 1091086, the addition from tetravalent and polyhydric alcohols to foam-forming masses made of curable Aminoplasts known. Here, an indifferent, low-boiling point is first emulsified and organic liquid insoluble in water with the aid of an emulsifying agent in the aqueous solution of a urea-formaldehyde resin. After that, the im received Organic liquid containing synthetic resin foam by warming or lowering it. the pressure is converted into the gaseous state.

Finally, the synthetic resin foam, the 10 to 350/0 polyethylene glycol, is hardened contains, at temperatures above the boiling point of the organic used Liquid. In this patent it is stated that, in contrast to polyethylene glycol numerous other compounds, for example sorbitol, are or even ineffective worsen the mechanical properties of the foams. By polyethylene glycol the hardening of the synthetic resin foam is slowed down. The resin foam needed at room temperature for about a month to dry.

The density of the foams obtained is z. B. 26.5 kg / m3. They have preferred structural directions, so that their mechanical properties are much worse in one direction than in another. For the production This process is far too cumbersome for insulation in construction.

It has now been found that it is very elastic and when drying and curing low shrinkage foams from curable reaction products made of aminoplasts or phenoplast-forming compounds and aldehydes by foaming their aqueous ones Solutions by incorporating inert gases at normal temperature below Addition of wetting agents and optionally hardening agents for the hardenable reaction products and hardening and drying of the synthetic resin foam obtained, if before, during or alcohols with four or more hydroxyl groups are added after foaming.

Suitable alcohols with at least four hydroxyl groups are, for. B. the erythrites, pentites and especially hexites. A suitable pentitol is e.g. B. the arabite. As Hexit, for. B. sorbitol can be used. Generally applies about 5 to 20 ovo of the tetravalent and polyhydric alcohols, based on the precondensation p roduct. It is particularly advantageous to add about 5 to 15e / o of these alcohols.

The foams are produced in the usual way. So you can the solutions of the hardenable precondensates in stirred tanks with wetting agents and optionally mix with hardeners for the precondensation products. Since the tetravalent and polyhydric alcohols are very easily soluble in water, you can they can be added to the solutions of the curable precondensates without difficulty.

The solutions of the aminoplasts containing wetting agents can be advantageous be foamed with the help of air or other inert gases. This can take place in stationary or mobile foaming apparatus. In the latter case can the maintainable synthetic resin foam, for example in construction trips Attach in place as an insulating material.

The synthetic resin foam leaving the foaming device is molded and then dried at ordinary or elevated temperature. The new, Foam compounds containing tetravalent and polyhydric alcohols from curable precondensation products do not dry slower than the known resins. In contrast, the new foam masses shrink ze drying is much slower than the known ones.

This balances out internal tensions, so leave the hardened ones Products do not tear and do not detach from the substrate. Besides, the extent is shrinkage is greatly reduced. The slight smell of formaldehyde, which in general Foam made with formaldehyde adheres, is caused by the use tetravalent and polyvalent alcohols practically eliminated.

The parts mentioned in the examples are weight parts.

Example 1 In 1250 parts of a 400 / above aqueous solution, however 50 parts of sorbitol are dissolved in the condensation product of urea and xormaldehyde. This solution is made with the addition of 10 parts of sodium dibutylaphthalenesulfonate, 7.5 parts of 50% strength dhosphoric acid and 670 parts of water in a stirring apparatus foamed and then immediately formed into 3 blocks. After about an hour you can the retained blocks are removed from the mold.

The shrinkage of these moldings is only a small percentage and takes place very slowly over the course of several weeks. On the other hand are the received. Molded body within completely dried in a few days. You get a practically odorless foam, which does not contain any cracks.

Example 2 99 parts of a 500% aqueous solution of a conventional one Curable phenolic resin prepared in this way is mixed with 4 parts of sorbitol, 2 parts of the sodium salt of the dioctylsulfosuccinic acid ester and 1.5 parts of oxalic acid mixed. This mixture is foamed in a mold by introducing air.

A molded body made of porous phenolic resin is obtained. The waning at.m hardening and drying of the porous mass. is only slight.

Claims (1)

PATENT CLAIM: Process for the production of foams from curable Reaction products of aminoplasts or compounds forming phenoplasts and Aldehydes by foaming the aqueous solutions of these reaction products Incorporation of inert gases at normal temperature with the addition of wetting agents and optionally hardeners for the hardenable reaction products and hardeners and drying the synthetic resin mold obtained, characterized in that before, added during or after foaming alcohols with four or more hydroxyl groups will. Documents considered: German Patent No. 901 471; French Patent No. 1,091,086; U.S. Patent No. 2,443,368.