DE1228062B - Process for curing dimethyl silicones - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C08g

German KL: 39 b -22/10

Number:
File number:
Registration date:
Display day:

1228 062
G41761IVc / 39b October 13, 1964 November 3, 1966

The invention relates to the curing of dimethyl silicones.

Silicones are conventionally made by grinding together a silicone polymer; H. from Dimethyl silicones, with a vulcanizing agent, d. H. a peroxide, such as. B. Benzoyl peroxide, and possibly with an inorganic filler such as silicon dioxide, iron oxide, titanium dioxide or zinc oxide, produced by curing. Curing is generally achieved by mixing the mixture in a hollow mold in the absence of air to about 150 ° C and then at least in air Is heated to about 250 ° C for 4 hours in order to obtain optimal properties. There are also silicone polymers, which can be crosslinked at room temperature, but are usually complete Hardening is necessary for 2 and more weeks.

All conventional chemical crosslinking and curing processes require heating to one of the temperature dependent on the crosslinking agent. This is a great disadvantage and restricts the application of the various crosslinking agents. For example, benzoyl peroxide is required Mixture temperature already dangerous because the mixture can decompose explosively while other peroxides have such a high decomposition temperature that they are no longer economical are useful. Organotin or organo lead compounds or metal carbyl compounds also proposed as a hardener for polysiloxanes, but it is also when these compounds are used required to heat to harden. A hardener has therefore been sought for a long time sought for dimethylsilicones that can bring about crosslinking without heating.

The invention now provides a method for curing dimethyl silicones by means of metal carbyl compounds proposed as a hardener, which is characterized in that the curing performed without the supply of heat and, as metal carbyl compounds, aluminum carbyl compounds the formula

R'— Al —R "'

R "

in which R ', R "and R'", which can be the same or different, each represent a hydrogen or halogen atom, mean an alkyl radical having 1 to 8 carbon atoms, an aralkyl or cycloalkyl radical, at least but one of R ', R "and R'" is an organic radical mentioned above, in amounts of 0.1

Process for curing dimethyl silicones

Applicant:

W. R. Grace & Co., New York, N.Y. (V. St. A.)

Representative:

Dr. rer. nat. J.-D. Mr. v. Uexküll, patent attorney, Hamburg 52, Königgrätzstr. 8th

Named as inventor:

William Randolph Johnson, Jr., Richmond, Va .; Razmic Sarkies Gregorian, Silver Spring, Md .; Frank Xavier Werber, Rockville, Md. (V. St. A.)

Claimed priority:
V. St. v. America October 22, 1963 (318111)

up to 10 percent by weight of the weight of the dimethyl silicone used.

Examples of suitable aluminum carbyles are triethyl aluminum, triisobutyl aluminum, triisohexyl aluminum, Trioctyl aluminum, diethyl aluminum chloride, ethyl aluminum dihydride, diisobutyl aluminum hydride or diethyl aluminum hydride.

Both pure and mixed aluminum carbide can be used to crosslink the silicone. For example, the aluminum carbyl can be used as a complex with a carboxylic acid ester ranging from 2 to 20 Contains carbon atoms and which is saturated or unsaturated in both the acid and the alcohol part can be present. Examples of suitable complex-forming esters are methyl formate, vinyl formate, Octadecyl acetate, ethyl acetate, ethyl propionate, vinyl propionate, vinyl acetate, methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, Methyl methacrylate or vinyl undecanoate. These complexes are made simply by mixing the aluminum carbyl with the monocarboxylic acid ester in a molar ratio of 1: 1, whereupon the obtained complex is added to the dimethyl silicone. The application of mixed (complex) Aluminum alkylene is preferred in some cases because it increases the rate of reaction is humiliated.

The aluminum carbyl can be mixed with the dimethyl silicone in various ways.

609 709/360

Claims (1)

3 4 gen. So a solvent can be used, kung added with a syringe, whereupon To make the aluminum carbyl more uniform in the poly- the solution is stirred at high speed mers to distribute. The solvent may have been used. 5 cm ^{3 of} triisohexylaluminum were with a the polymer or the aluminum carbyl or both hypodermic syringe added. Within 5 seconds to solve. The polymer can also be mixed with a solution. The stirrer came to a standstill because the polymer medium can be soaked by swelling, whereupon it immediately hardened and in the mixer the aluminum carbyl came up to the swollen polymers. The hardened product was smooth, gives. On the other hand, the aluminum carbyl can also be tough and rubbery, with or without a solvent directly to the dimethyl. . silicone can be given. For security reasons, io example 4 the aluminum carbyl usually as a solution in a 100 g of the dimethyl used in Example 1 inert hydrocarbon used, the aliphatic silicone and 200 cm ³ n-pentane as a solvent or can be aromatic, d. H. for example xylene, was placed in a mixer. The stirrer Toluene, benzene, heptane, hexane, pentane, cyclohexane were turned on, and 2 cm ^{3 of} triisohexyl aluminum. orNonan. 15 were added. The polymer hardened ocular The mixing and hardening is preferably seen to result in a tough, rubbery product,
atmospheric pressure and at room temperature. . , carried out, but temperatures between 15 are Example 5
and optionally also 100 ° C possible. The choice of 100 g of a dimethyl silicone with a viscosity of the solvent, if one is used, 20 of 450 poise (measured with a Brookfield must of course be made carefully at the upper temperature limit axis no. 6 at 10 rpm) were operated in a mixing pre-pressure. direction given. 200 cm ^{3 of} n-pentane were used as The dimethyl silicones cured according to the invention solvent added, whereupon the mixing device can be covered with a thin rubber sheet like conventional silicone elastomers, be used. Possible uses After turning on the stirrer, 4 cm ^{3 of} a may be mentioned: seals, electrical insulation over- solution of equal parts by volume of triisohexylalu- Cables, vibration dampers, sealants, etc., minium and n-heptane added. The homogenization The dimethyl silicone-aluminum carbyl mixtures were continued for 1 minute, after which it hardened can add other additives that do not work directly with the polymer immediately. A smooth, tough, rubbery one Aluminum compound react, contain, e.g. B. Product was obtained. Plasticizers, lubricants or extenders, organic. or inorganic fillers, stabilizing or the example 6 Flammability-reducing additives, coloring example 5 was repeated with the difference Additives such as dyes or pigments, as well as anti-35 that the triisohexylaluminum by triethylalu- Oxidants and antistatic agents and similar minerals have been replaced. Here, too, a smooth, In the following examples, the invention is intended to obtain tough silicone rubber. are explained in more detail. _. . , _ Example 7 Example _4o Example 4 was made with diisobutylaluminum hydride 75 g of a commercially available dimethyl silicone are repeated in place of triisohexyl aluminum. A A viscous latex form with a viscosity in smooth, tough silicone rubber was obtained.
Range from 8,000 to 15,000 cP at 25 ° C into an oxygen-free flask with a rubber stopper Example 8 given. Example 3 was repeated with the aid of a hypodermic syringe, but the 1 cm ³ triisohexyl aluminum through the rubber stop 5 cm ³ triisohexyl aluminum at 25 ° C with n-butyl fen in the flask. The mixture that immediately acrylate in a molar ratio of 1: 1 before adding to the started to get lumpy, was complexed on a glass silicone. The mixture was 1 minute shell poured. Within 30 seconds the was stirred vigorously and then into a rectangular shape whole mixture poured hard 50 form at room temperature (25 ° C). That was within 15 seconds become. A soft, tough rubbery product of polymer completely hardened to a smooth, has been received. tough, rubbery product. Example 2 ^ ^{e ernn (} proper use of AIu- Minium carbylene for hardening or vulcanizing 30 g of the dimethyl silicone used in Example 1, resulting in crosslinking of the poly-silicone, were poured into an open dish. Using mers to form a smooth, tough silicone rubber, one of which was injected with 1 cm ^{3 of} triisohexylalu-physical properties of the molecular minimum under the surface of this silicone, depending on the weight of the starting polymer. Whenever stirring was started. The mixture, starting from a dimethyl silicone with a low molecular weight, warmed up and hardened within 30 seconds, giving a sponge-like shape to a smooth, tough silicone rubber. Rubber, while the toughness increases with increasing molecular weight of the starting material. 240 g of the dimethyl claim used in Example 1: Silicones were placed in a mixer, 65 methods of curing dimethylsili- which are secured with a thin rubber band using metal carbyl compounds as hardening continuous rubber sheet covered was 30cm ³ n-pentane, characterized in that one Curing was carried out as a solvent through the rubber cover without supplying heat 5 6 and as metal carbyl compounds aluminum carbon atoms, an aralkyl or cycloalkyl carbyl compounds of the formula mean radical, but at least one of the radicals ρ, αϊ j> '»R'j R" and R' "an organic above Remainder is, in amounts from 0.1 to 10 weight 5 percent of the weight of the dimethyl silicone ^R turns,
in which R ', R "and R'", which are the same or different which can be, in each case a hydrogen or pamphlets considered: Halogen atom, an alkyl radical with 1 to 8 carbon atoms. French Patent No. 1,066,163. 609709/360 10.66 © Bundesdruckerei Berlin