DE1014533B - Process for the preparation of a colloidal solution of silica - Google Patents

Description

Process for the preparation of a colloidal solution of silica The invention relates to the production of colloidal silica solutions which, Applied to the appropriate fabrics, prevent static electricity in synthetic resins such as acrylic, polystyrene and vinyl resins, and synthetic ones Fibers such as nylon, vinylon and acetate can arise. Static electricity is has been used in the field of paint technology and for collecting dust, but on the other hand is the presence of static electricity in the field of explosives manufacture, High pressure equipment, undesirable and in operating rooms of hospitals, etc. can cause loss of life and property in an instant.

Static electricity can also be caused by friction between fibers and Apparatus parts arise when spinning synthetic fibers and results in poorer ones Quality, production downtimes and noticeable impairment of the appearance of the product, because synthetic resins such as especially methacrylic acid resins, vinyl chloride resins and Polystyrene resins, can absorb such strong electrical charges that they are in the Strongly attract air-dispersed dust. In addition, if the one from such a Resin-made item is carelessly wiped with a dry cloth remove the adhering dust, not only damage the smooth surface, but also stronger static electricity due to friction between the dry Cloth and the resin surface are produced, thereby increasing the adhesive strength of the dust is further increased.

As is known, the antistatic effect is the one previously used Staticizer excellent right after use, but disappears by washing.

According to the present invention, a colloidal solution of silica, which is suitable as a degassing agent, prepared by adding a mixture of Alkyl acetate with a monohydric aliphatic alcohol in the presence of water under Addition of a silicon halide is implemented, the system being 4 to 7 percent by volume Contains water.

The alkyl acetate used in the present case can be methyl acetate, Be ethyl acetate, butyl acetate, or any other alkyl acetate. The first described three types of acetate are widely used because of their accessibility. The quality the product obtained with each of the three acetates is excellent.

The alcohol used can be a monohydric aliphatic alcohol such as methyl alcohol, ethyl alcohol or allyl alcohol. The effect of aromatic alcohols. on the product is not favorable. Of the alcohols mentioned, ethyl alcohol is preferably used. The alcohol used is mixed with the acetate in a weight ratio of about 1: 1. In the present invention, a silicon halide of the general formula SiX4 is used, where X = Cl, Br or J and can be the same or different, e.g. B. Si Cl, Si Br4, Si J4, Si Cl, Br2, Si Cl, Br, Si Cl Br, or Si C13 J. Here, Si C1 gives the best results.

The presence of water in the reaction system of the present invention is absolutely necessary. If an anhydrous alcohol is to be used, the 4 to 7 percent by volume of water was added to the mixed solution. When someone uses alcohol containing water, no water needs to be added. Because a silicon halide generally reacts with air humidity and therefore smokes, it is advisable to when the reaction is carried out in an atmosphere of low humidity will. The reaction in which a silicon halide is added; runs so stormy that the halide is added dropwise while stirring the mixture of the alcohol and alkyl acetate should be added. The reaction is carried out at room temperature.

The colloidal solution of silicic acid that is obtained during the conversion, is thin when fresh and is best for further use in this form suitable. When the colloidal solution of silica several days after its preparation If left standing, the colloidal particles grow and often white ones are formed Excretions when the solution gels and is applied to an article. Before the solution gels completely, it is mixed with the alcohol used in the reaction or with a solution of said alcohol and alkyl acetate in a ratio of preferably 1: 1. Once the solution is so diluted, it will not gel further even if left standing. the Silica solution prepared according to the method can be used in any way, e.g. B. by To brush, Dipping, or spraying, on products to be applied, the first two being Species are preferred. The products can be made of glass, synthetic resins or be synthetic fibers. If the solution is to be applied to fibers, the fibers are in a mixture of the colloidal silica solution with an 0l or dipped in the dilute silica solution.

When the colloidal silica solution on a film of such substances is applied, this has a surface resistance in the order of magnitude of 101 ° r .. 1011 ohms at a relative humidity of 60 ° / o and one Temperature of 20 °. This resistance is also not reduced when the film is washed.

Example 1 When 500 parts of ethyl acetate and 550 parts of ethyl alcohol, which contains 10% water, with 40 parts of silicon tetrachloride with slow stirring are reacted, a stable colloidal solution of silica is obtained.

Example 2 When 500 parts of methyl acetate and 600 parts of methyl alcohol, which contains 10 ° / Q water, with 40 parts of silicon tetrabromide with slow stirring reacted and left to stand for 2 to 5 days after cooling, becomes a stable obtained colloidal solution of silica.

Example 3 If 500 parts of ethyl acetate and 550 parts of C2 05 O H containing 10% water are reacted with 40 parts of Si C14 with slow stirring and left to stand for 3 to 4 days, a stable colloidal solution of silica is obtained. When well washed and dried glass and synthetic resins, e.g. B. methyl methacrylic acid resin, cellulose acetate and vinyl chloride, are immersed in this solution, the excess of the adhering solvent is removed and then dried, a very simple, stable, solid silica film is formed thereon. It was dried at room temperature for 10 hours and at 50 to 60 ° for 2 hours.

When a silica film on the surfaces of optical glass and optical resins are to be applied which are free of reflections to the greatest possible extent must, in order to increase the light transmission and the protection of the surface, the thickness of the film is adjusted with the help of a special device in which Centrifugal force is applied. The same effect can be achieved using methyl alcohol or allyl alcohol can be used in place of ethyl alcohol. It was also found that that methyl or butyl acetate can be used in place of ethyl acetate.

When the strength of the silica film due to the concentration of the solution To be adjusted, the solution is diluted with a mixture containing alcohol and ethyl acetate in a ratio of 1: 1.

Example 4 When 60 to 100 parts of ethyl acetate and 110 parts of anhydrous Ethyl alcohol and 10 parts of water with 8 parts of silicon tetrachloride under slow Stirring is implemented, becomes a colloidal solution of silica with antistatic Properties preserved. Example 5 100 parts of ethyl acetate, 110 parts of anhydrous Alcohol and 5 to 15 parts of water are slowly mixed with 8 parts of silicon tetrachloride added and stirred well so that the hydrogen chloride gas can escape. Here creates an antistatic, colloidal solution of silica.

Such solutions are also obtained when using another alcohol of the formula R - O H, such as methyl alcohol, propyl alcohol or butyl alcohol, instead of ethyl alcohol.

Claims (4)

PATENT CLAIMS: 1. Process for the preparation of a colloidal solution of silica, characterized ,, that a silicon halide of the general Formula SiX4, in which X can be either Cl, Br or I, in the presence of water with stirring to a mixture of alkyl acetate and a monovalent aliphatic Alcohol is given in a weight ratio of about 1: 1, the system being 4 to Contains 7 percent by volume water. 2. The method according to claim 1, characterized in that that the alkyl acetate is ethyl acetate. 3. The method according to claim 1, characterized in that that the alcohol is ethyl alcohol. 4. The method according to claim 1, characterized in that the silicon halide is S'C14. Documents considered: German Patent No. 679,418; U.S. Patent Nos. 2,269,059, 2,408,654, 2408656.