DE948919C - Process for the production of improved butyl rubber vulcanizates - Google Patents

Description

This invention relates to the substantial improvements in the properties of butyl rubber vulcanizates which are filled with precipitated hydrous silicon dioxide, precipitated hydrous calcium silicate or kaolin. It is based on the discovery that the physical properties of butyl rubber vulcamsates which are filled with precipitated hydrous silicon dioxide, precipitated hydrous calcium silicate or kaolin are significantly improved by using a filler which is combined with io-undecenyl-trichlorosilane the formula CH ₂ = (CH ₂ ) ₉ Si Cl _{3 was} implemented. This unsaturated trichlorosilane is unique in improving the reinforcing properties of these fillers. It is particularly outstanding in its effect on increasing the modulus and reducing the hysteresis of the resulting materials. In terms of improving the hysteresis, it is superior to the cycloalkenylhalosilanes such as cyclohexenyltrichlorosilane and the cycloalkenylalkylhalosilanes such as β- (3-cyclohexenyl) ethyltrichlorosilane.

The reduction of the hysteresis of butyl rubber vulcanizates is unusual due to the treatment of the filler with io-undecenyl-trichlorosilane large and makes it possible for the rubber manufacturer

Manufacture butyl rubber vulcanizates with are filled with the above fillers and have a remarkably low hysteresis.

A precipitated water-containing silicon dioxide, a precipitated water-containing calcium silicate or a kaolin can be used as filler. The particle size of the fillers should not be larger than ίο μ .

The fillers effective according to the invention absorb under normal atmospheric conditions Water and are generally obtained with an absorbed film of water. Generally will According to the application, fillers whose water of hydration is not less than 0.02 g per 100 square meters of the preferred Surface area is.

Fillers which have been produced or dried at high temperatures (260 ° ^C. or more) are not favorably influenced in their reinforcing properties by the treatment according to the invention. Such a filler has been e.g. Manufactured according to U.S. Patent 2,535,036.

The essential feature of the fillers according to the invention is the content of hydroxyl groups which are chemically bonded to the filler material. In water-based silicon dioxide and calcium silicate, the OH groups are bonded to the silicon atoms, and in kaolin the OH groups are bonded to the aluminum atoms. For an exhaustive discussion of this, see Pauling, "The Nature of the Chemical Bond"? Cornell University Press, 1940. Good results have been obtained with finely divided hydrous silica (about 200 Angstrom units in diameter) which has a surface area of 150 square meters per gram and has a degree of hydration corresponding to 0.073 g moisture per 100 square meters of surface. Fine-grain hydrous silicon dioxide (about 250 angstrom units in diameter), which was prepared by removing water from an aqueous dispersion of hydrous silicon dioxide and which has a surface area of 125 square meters per g and a degree of hydration of 0.046 g moisture per 100 square meters, has also been used with good success Surface has. Good results have also been obtained with a filler which is a precipitated hydrous calcium silicate having a particle size of approximately 300 Angstrom units in diameter and containing 13 to 19 percent by weight of water. Clays of the type commonly used as a reinforcing filler for rubber have also been used with good success. An example of this is a kaolin which has plate-like particles with a wide spread in width, on average approximately 5000 angstrom units, and a degree of hydration of 14.1 weight percent water. All of these fillers respond well to the treatment according to the invention and have an average particle size of not more than 10 μ and a degree of hydration of not less than 0.02 g of moisture per 100 square meters of surface area.

The amount of io-undecenyl-trichlorosilane, according to the invention for treatment of the filler applied can vary widely; in general an amount corresponding to 5 to 15% of the weight of the filler is used.

A method of the process according to the invention for the production of butyl rubber vulcanizates to carry out, is that a filler is used that with the io-undecenyl-trichlorosilane before it is mixed with the butyl rubber. In order to pretreat the To carry out the filler, both the solution method and the vapor phase method are used. In the solution method, the filler to be treated is in a low-boiling hydrocarbon Slurried, the undecenyl-trichlorosilane added to this slurry, the mixture heated to reflux and continued heating to reflux until substantially all of the silane has reacted with the filler. The amount of liquid vehicle that is required to form a smooth-flowing slurry differs depending on the filler. The fillers with a larger particle size do not occupy as much space as those with a smaller particle size and accordingly require less liquid. Almost four to seven times as much liquid fillers (by weight) are commonly used for the fillers described herein. Any inert, highly volatile solvent for the silane can be used. It aromatic hydrocarbons can be used as solvents, e.g. B. benzene can be used, but its Costs prohibit this when working on a technical scale. The use of paraffin-carbon hydrocarbons, like petroleum ether, is preferred because these hydrocarbons in relation to the silane and the hydrogen chloride given off during the treatment are inert and at the same time good Form solvents for the silane and are readily available at low cost.

A reflux time of 3 hours is usually sufficient for the filler to react with the io-undecenyl-trichlorosilane essentially to be completed. Unreacted chlorine groups can be hydrolyzed with water or can remain as they do not affect vulcanization to any significant extent.

When the reaction of the filler with the silane is essentially complete, the filler becomes separated from the liquid by filtration or centrifugation, then the residual solvent evaporated, usually by moderate heating. If desired, the detached Filler are washed, e.g. B. with the same solvent that was used as the carrier during the reaction was used before heating to remove residual solvent.

With the vapor phase method for the pre-treatment of the filler, the filler is simply put into an iac Filled into the tube and air saturated with io-undecenyl-trichlorosilane passed through the tube, whereby unreacted silane and hydrogen chloride are collected from the outflowing gas.

The i »5 treated with the io-undecenyl-trichlorosilane Fillers for butil rubber are new material

compositions, but no patent protection is claimed for them in the context of the present invention. They can be kept for an unlimited period of time and can easily be used like other commercially available ones Products are transported.

Instead of the filler with the io-Undecenyltrichlorsüan pretreatment, the treatment of the filler can also be done "in situ", i. H. by bringing them together of the undecenyl trichlorosilane directly with the ίο butyl rubber and the filler on the usual Rubber mixing mills or in the usual rubber mixers. The improvement the physical properties of the resulting vulcanizate is just as great as if that iS filler with the io-undecenyl-trichlorosilane in the type described above has been pretreated.

When the "in situ" method of treatment is applied the mixture of butyl rubber, filler and io-undecenyl-trichlorosilane works best subjected to hot mastication at 120 to 205 °, until the reaction between the filler and the undecenyl-trichlorosilane has ended. These Hot mastication is carried out before the zinc oxide and vulcanizing agent are added to the rubber will. The zinc oxide and the vulcanizing ingredients are then at a relatively low level Temperature, essentially below 120 °, added to the resulting mixture, and the mixture is then vulcanized in the usual way. Since hydrogen chloride is a reaction product of io-undecenyl-trichlorosilane with the fillers, It is important to provide good ventilation during the mixing process. It was also found that it is appropriate to use an alkaline earth carbonate, e.g. B. calcium carbonate or barium carbonate of the mixture made of butyl rubber, filler and io-undecenyl-trichlorosilane add in an amount sufficient to account for all of the hydrogen chloride formed during the reaction of the filler with the silane to neutralize. The use of I part by weight of fine-grain calcium carbonate ι part by weight of the io-undecenyl-trichlorosilane, which was used for the treatment of the filler, is generally sufficient.

An example of the main use of the vulcanizates according to the invention is production of rubber tubes for pneumatic tires. So far, carbon black has been the only filler that has sufficient strength-increasing properties Properties for use in butyl hoses for top quality vehicle tires owns. The invention makes the manufacture of the best quality butyl tubing from materials possible in which the carbon black is completely replaced by white fillers. It has very great advantages if it is possible to replace carbon black with a cheap white filler such as the clays, of which previously they were believed to be inferior to carbon black as rubber fillers.

The following examples illustrate the invention. Unless otherwise specified, the in Physical property data reported to the Examples were obtained at room temperature.

The load at 300% elongation is the measure of the modulus. The permanent elongation was after Break determined after 30 seconds instead of 10 minutes as determined by ASTM (American Society for material testing) is required. The results of the hysteresis were at 138 ° with a torsion hysterometer (see M. Mooney and R. H. Gerke, India Rubber World, 103, 29 [1941]). the Durometer hardness was measured by a Shore A durometer after 5 seconds. All parts are parts by weight.

example 1

A water-containing silicon dioxide commercially available as a filler (diameter about 200 angstroms, Degree of hydration 0.073 / 100 qm surface) is slurried in low-boiling hydrocarbon; then 10 percent by weight io-undecenyl-trichlorosilane, based on the filler, added to the slurry. The mixture is taking 3 hours Heated to reflux, after which the filler is separated by filtration and kept at a moderate temperature dried to remove the residual solvent.

The silica treated in this way is then put into a butyl rubber formulation of the following composition incorporated:

Butyl rubber 100.0 ^ ⁰

Zinc oxide 5.0

Stearic acid 1.0

Sulfur 1.5

Accelerator 2.5

Silica 54.0

The batch is vulcanized under pressure at 152.8 ° for 60 minutes. The resulting vulcanizate has the following Physical Properties:

Durometer hardness 60.0

Breaking strength at room temperature, in kg / cm ² I44 »9

Elongation at break at room temperature, in% 58o, o

permanent elongation at break, in ° / ₀ 25.0 ° "

Modulus at 300 ° / ₀ elongation, in

kg / cm ² 57.75

Torsional hysteresis at 138 ⁰ 0.08

Treatment with io-undecenyl-trichlorosilane gives the vulcanizate a remarkably good modulus and extremely low torsional hysteresis. Comparisons with batches of the same type in which the filler was not treated show a durometer hardness of about 67, a breaking strength at room temperature of 126 kg / cm ² , an elongation at break at room temperature of about 750%, a permanent elongation at break of about 50 %, a modulus at 300% elongation of 25.2 kg / cm ² and a torsional hysteresis of around 0.35.

Example 2

A mixture of 100 g of hydrous silica as in Example 1, 700 g of benzene and 10 g of food Undecenyl-trichlorosilane are 6 hours under back

river heated. The suspension is then cooled, the Filtered off silicon dioxide, washed with benzene and air dried.

The treated silica is in a butyl rubber is used, which has the same composition as that of Example i. The emerging Mixture is vulcanized under pressure at 152 for 40 minutes. A control was used treated similarly by untreated silica. The values for the modulus and the torsional hysteresis were as follows:

Modulus

at 300 ° / ₀ elongation

Untreated filler

22.75 kg / cm ²

Treated filler 47.25kg / cm ²

Torsional hysteresis

at 138.0 °

o.34 0.0875

From the above description it can be seen that the method described offers many advantages. The invention can be carried out in a simple and economical manner. The use according to the invention of the fillers treated in this way results in a remarkable

«5 improvement in the properties of the vulcanizates.

The main advantage of the invention is that it is a

great improvement in reinforcing properties of those fillers that have not yet been considered particularly good, strength-increasing fillers for Rubber were considered. The invention enables such an improvement in the reinforcing effect of an poorly reinforcing fillers, such as kaolin, that. the reinforcing effect of soot with the the same particle size is almost reached or even exceeded. It is particularly noteworthy that the Invention the achievement of a greatly increased modulus and, at the same time, a greatly reduced hysteresis enables.

The expression "butyl rubber" means a rubber-like copolymerizate which a larger amount, generally 80 to 99.5 ° / ₀₎ of isobutylene and a minor amount, generally from 20 to 0.5%, butadiene-i, 3 or isoprene contains. The copolymer is unsaturated with an iodine number below 50, has a molecular weight of over 20,000 and can be vulcanized with sulfur to form an elastic product.

Claims (3)

Patent claims: i. Process for the production of butyl rubber mixtures, characterized in that a filler is used, which precipitated water-containing silicon dioxide, precipitated water-containing Calcium silicate or kaolin and which, if necessary only within the butyl rubber mixture, with io-undecenyl-trichlorosilane was treated with evolution of hydrogen chloride, whereupon the mixture as usual is vulcanized. 2. The method according to claim 1, characterized in that that a filler is used in which the treatment with the io-undecenyl-trichlorosilane is carried out in the presence of so much alkaline earth carbonate that all of the hydrogen chloride, which is developed during the reaction of the filler with the silane, is neutralized. 3. The method according to claim 1, characterized in that that the zinc oxide is not added to the mixture until after the filler has reacted is finished with the silane. © 509 697/492 3.56 (609 603 8.56)