DE1138928B - Process for the production of multilayer molded articles - Google Patents

Description

INTERNAT. KL. C 08 g

GERMAN

PATENT OFFICE

116985 IVd / 39b

REGISTRATION DATE: SEPTEMBER 17, 1959

NOTICE
THE REGISTRATION
ANDOUTPUTE
EDITORIAL: OCTOBER 31, 1962

The invention relates to a method for producing multilayer molded articles Joining layers of glass fabric and asbestos.

Various binders have been used and described for the production of multilayer moldings so were the organopolysiloxanes. These can be cured without the aid of a curing accelerator, but require in in such a case longer heating times at higher temperatures. Various hardeners are also used but of which even the best have drawbacks.

As a hardener for organopolysiloxanes with a low ratio of organic groups too Silicon atoms, for example from 1.0: 1 to 1.3: 1, has been used in the manufacture of multilayered glass fabric and articles molded therefrom already used triethanolamine. Although one made from organopolysiloxanes, the triethanolamine as a hardener, can satisfactorily produce multilayer bodies, the required amount is triethanolamine often unduly large. This can cause excessive discoloration of the multilayer Subject lead, and also the mixture of siloxane and triethanolamine has a very limited Shelf life.

As a hardener for organopolysiloxanes, especially those in which the ratio of organic Groups to silicon atoms in the order of 1.3: 1 to 1.8: 1 and which are mainly for Surface coatings and electrically insulating paints are used, zinc-2-ethyl caprylate is also used been. Such mixtures have excellent storage stability and heat resistance of the hardened material is often improved by the zinc residue. The zinc caprylate as However, mixtures containing curing agents are normally used in the manufacture of multilayer fabrics or multi-layer objects, as they are excessive when cured under pressure flow. It has been proposed to use mixtures of triethanolamine and metallic soaps, for example Zinc stearate, to be used as a catalyst for siloxanes. However, such mixtures only work very weakly catalytic and are therefore no better than triethanolamine or zinc caprylate alone.

Various other hardeners have also been used, for example lead and tin salts of certain carboxylic acids and certain quaternary ammonium salts such as choline 2-ethyl caproate or choline bicarbonate. These, too, are not entirely satisfactory and in many cases have different methods of production
of multilayer moldings

Applicant:
Imperial Chemical Industries Limited, London

Representative: Dr.-Ing. H. Fincke,

Berlin-Lichterfeäde, Drakestr. 51,

Dipl.-Ing. H. Bohr and Dipl.-Ing. S. Staeger,

Munich 5, patent attorneys

Claimed priority:

Great Britain 22 September 1958

and July 10, 1959 (No. 30 175)

Ernest Arthur Mason, Kilwinning, Ayrshire,

and James Joseph Gallagher,

Saltcoats, Ayrshire (UK),

have been named as inventors

Disadvantages, for example insufficient shelf life, brittleness of the cured product, in addition, they flow when hardening.

The invention now relates to a method for producing multilayer molded articles Curing - in the heat and under pressure - of any number of glass fabric or Layers of asbestos coated with a curable organopolysiloxane with 1.0 to 1.8 organic groups per Silicon atom and a mixture of a metal salt of a carboxylic acid and an amine as a catalyst have been coated or impregnated. The method according to the invention is characterized in that that the catalyst mixture used is 0.01 to 5.0 percent by weight, based on the organopolysiloxane a complex of zinc 2-ethylcaprylate and triethanolamine is used. The in the invention The layers used can be any of those used to make multilayer Objects commonly used layers. Particularly suitable layers are Glass fabric, asbestos paper and woven and knitted fabrics based on synthetic fibers with a softening point above about 150 ° C.

209 679/342

The organopolysiloxanes that can be used contain from 1.0 to 1.8 organic groups per silicon atom. Preferably those having from 1.0 to 1.4 organic groups per silicon atom are used. The organic groups can be alkyl, aryl or unsaturated groups.

The organopolysiloxane is normally in a solvent or prior to its use Solvent mixture dissolved.

The layers can be coated or impregnated by any of the conventional methods. It is usually preferred to dry the layers prior to pressing and heating to make the multilayer article. Such a method is very convenient because the coated and impregnated and dried layers can easily be stored for a considerable period of time before they are used. Drying is normally done by heating to temperatures of about 100 to 150 ^° C. for 1 to 15 minutes. The further advantage of drying the layers prior to pressing is that the possibility of bubble formation due to evaporation of trapped solvent during pressing and heating is reduced.

The pressing of the layers can be carried out at pressures on the order of, for example, 2.1 to 140 at or higher. The curing of the organopolysiloxane is carried out at temperatures of 150 to 300 ° C carried out for 15 to 300 minutes. It is also common practice to mix one »Post-hardening« - by heating to about 250 ° C for a short period of time - to submit.

The cured multilayer moldings show insignificant or no signs of discoloration, have a high flexural strength and a higher dielectric strength than that obtained so far using only an amine as a hardener.

The invention is further illustrated by the following examples. Parts and percentages relate on weight.

example 1

1.35 parts of a 20% solution (in toluene) of a catalyst mixture of 1 part and triethanolamine 1 part of zinc 2-ethyl caprylate was added to 200 parts of a 60% solution (in toluene) of an organopolysiloxane with 1.2 organic groups per silicon atom, in which the organic groups are methyl and Phenyl groups in the ratio 1.4; 1 were added. 15 pieces of desized by heat treatment Electrical grade glass cloth each 0.127 mm thick and containing the solution impregnated and heated to 120 ° C for 3 minutes were layered and 2 hours heated to 175 ° C under a pressure of 70.3 at, after which time the multilayer body let cool under pressure. The multilayer body was then placed in an oven for 3 hours Air circulation heated to 150 ° C, the heating and cooling each during a period of time of 2 hours was carried out. The product obtained had an average strength of

1.59 mm, a polymer content of 38%, a flexural strength of 2040 kg / cm- at 20 ° C, 1480 kg / cm ² at 150 ° C and 1160 kg / cm ² at 250 ° C and an electrical breakdown strength of 650 volts per 0 , 0254 mm.

Example 2

2.16 parts of a 20% solution (in toluene) of a catalyst mixture of 1 part and triethanolamine 1 part of zinc 2-ethyl caprylate was added to 200 parts of a 60% solution (in toluene) of an organopolysiloxane with 1.36 organic groups per silicon atom, in which the organic groups are methyl and Phenyl groups in a ratio of 2.0: 1 were added. A multilayer molded article was prepared using this solution in the same manner as produced in example 1. The multilayer body obtained had an average thickness of

1.60 mm, a resin content of 36%, flexural strengths of 2400 kg / cm ² at 20 ° C, 1760 kg / cm ² at 150 ° C and 562 kg / cm ² at 250 ° C and a dielectric strength of 600 volts per 0, 0254 mm.

Claims (2)

PATENT CLAIMS: 1. Process for the production of multilayer moldings by curing - in the heat and under pressure - of any number of glass fabric or asbestos layers, which are made with a curable organopolysiloxane with 1.0 to 1.8 organic groups per silicon atom and a mixture of a metal salt a carboxylic acid and an amine have been coated or impregnated as a catalyst, characterized in that the catalyst mixture used is 0.01 to 5.0 percent by weight, based on the organopolysiloxane, of a complex of zinc 2-ethyl caprylate and triethanolamine. 2. The method according to claim 1, characterized in that that one of the components zinc-2-ethylcaprylate or triethanolamine, which the Form complex, is present in excess. References considered: British Patent No. 793 594; Hagen, "Glass fiber reinforced plastics", Berlin 1956, pp. 109, 110. When the application was announced, comparative tests were carried out. © 209 679/342 10.