Tetrahalosilane blends for treating silica

The present invention relates to a method for producing a modified silica filler in which silica is contacted with a blend or mixture of diorganodihalosilane and tetrahalosilane in a weight ratio of 1: 0.1 to 1: 2, respectively.

For example, as described in US Pat. No. 6,051,672 (April 18, 2000), which was assigned to the same assignee as the present invention, this is an improvement in the method of modifying silica fillers. The 672 patent contains the general formula (1) containing tetrahalosilane in a broad sense, but the (i) 672 patent does not disclose a specific tetrahalosilane compound, and the (ii) 672 patent No specific mixture or blend of tetrahalosilane compound and diorganodihalosilane compound is described, which is more effective than any other blend, and (iii) 672 patents are new and unexpected. It does not teach any particular proportion of these silane compounds needed to achieve the results of, i.e., to allow more siloxanes to be deposited on silica relative to improved hydrophobicity.

Further, it is common in the art that the treatment agent used to impart hydrophobicity to the surface must contain an organic or hydrocarbon group characteristic of fats such as alkyl groups, oils, and waxes. Well recognized. However, silicon tetrachloride SiCl₄Since tetrahalosilanes such as these do not contain organic or hydrocarbon groups in their molecules, it was almost unexpected that tetrahalosilanes have this functional usefulness.

<p> The present invention relates to a method for producing a modified silica filler in which silica is contacted with a blend or mixture of organosilicon compounds. In particular, the present invention relates to improvements in the treatment of silica with blends or mixtures of diorganodihalosilanes and tetrahalosilanes, each with a weight ratio of 1: 0.1 to 1: 2.</p><p> The weight ratio is preferably 1: 0.3 to 1: 1 and most preferably 1: 0.5. Similarly, the blend or mixture is preferably dialkyldichlorosilane and tetrahalosilanes such as silicon tetrachloride, silicon tetrabromide and silicon tetraiodide, preferably dimethyldichlorosilane and silicon tetrachloride. Most preferred. In some further embodiments, the blend or mixture can also include compositions containing (i) dimethyldichlorosilane, (ii) silicon tetrachloride, and (iii) mercaptopropyltriethoxysilane.</p><p> These and other features of the invention will become apparent in light of the detailed description.</p><p> [Description] The silica used in the production of the modified silica filler according to the present invention is used in the preparation of polymer compositions such as rubber (particularly, rubber compositions used for improving the mechanical properties of tire rubber in the production of vehicle tires). Is a type of colloidal silica or precipitated silica. Such silicas are described in detail in 672 patents and US Pat. No. 5,908,660 (June 1, 1999), which are referenced and incorporated herein by reference.</p><p> Mineral fillers such as silica, which have a small particle size and a large surface area, can increase the tensile strength of rubber compounds and are therefore useful as reinforcing materials for rubber, especially the mineral surface of the filler is hydrophobic. Useful when converted to low energy surfaces. Typically, this is done with methylchlorosilane, which liberates hydrochloric acid by reacting with surface water on the surface of the mineral or water present in the reaction (ie, hydrolysis and condensation of silanol). A very thin film of methylpolysiloxane with a low critical surface tension that is not moistened by water is simultaneously deposited. A very simple display is: Si-Cl + H₂O SiOH + HCl Si-O-Si</p><p> One of several other reasons why it may be desirable to impart hydrophobicity to the silica surface is thereby in organic systems such as defoamers, as well as in the processing of foods, dairy products and vegetables. The silica surface is easily dispersible. In other applications, fully hydrophobic silica particles can be retained at the oil-water interface. The surfaces of oxide minerals modified with a single layer of organic functional silane to make the surface hydrophobic make them against oil recovery, ore suspension, pigment dispersion, and metal surface modification. Make it useful. These water repellent, low energy surfaces are useful in water resistant treatments for masonry, insulation, chromatographic filling, and in non-caking fire extinguishers. Ceramic insulators treated in this way can maintain high electrical resistance under wet conditions. Brick, mortar, sandstone, and concrete are protected from spalling, cracking, and efflorescence by forming an insoluble, water-resistant methylpolysiloxane film on the surface.</p><p> When the silicone rubber is reinforced with untreated silica, a reaction can be carried out to make the mixture tough and nervy, which allows the mixture to be prepared unless processing is performed immediately after preparation of the mixture. Further processing becomes difficult. By treating the silica surface with a material capable of reacting with the hydroxyl groups present on the silica surface, reactions known as structuring and crepe aging can be prevented. While many methods have been devised for treating silica as a powder and water dispersant to prevent structuring and crepe aging, the present invention is also useful for strengthening silicone rubber treated silica. Provides a simplified means for manufacturing.</p><p> The silica treatment agent according to the present invention is a blend of organodichlorosilane and tetrahalosilanes such as silicon tetrachloride, silicon tetrabromide and silicon tetraiodide. Organodichlorosilanes can contain alkyl groups, cycloalkyl groups, araalkyl (arylalkyl) groups, alkalil (alkylaryl) groups, aryl groups, and certain substituted groups that are not reactive with the silica surface. it can.</p><p> Some specific examples of alkyl groups are methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, octadecyl and nonadecylic. Some specific examples of cycloalkyl groups are cyclobutyl and cyclohexyl. Some specific examples of araalkyl (arylalkyl) groups are benzyl, phenylethyl and 2-phenylpropyl. Some specific examples of alkaline (alkylaryl) groups are tolyl and mesityl. Some specific examples of aryl groups are phenyl, xenyl, naphthyl and anthracyl. Some specific examples of substituted groups that are not reactive with the silica surface include alkyl halide groups and chloromethyl, dichloromethyl, trichloromethyl, 3-chloropropyl, chlorocyclohexyl, chlorophenyl and dichloroxenyl and the like. Aryl group; an alkyl group containing an alkoxy group (radical) such as methoxy, ethoxy, butoxy and pentoxy; an alkyl group containing a sulfide (-S-), disulfide or polysulfide group; and a cyano (-CN) group. It is an alkyl group containing.</p><p> Representative examples of some organodichlorosilanes and tetrahalosilanes that can be used according to the present invention are silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, n-butylmethyldichlorosilane, t-butylmethyldichlorosilane, t-Butylphenyldichlorosilane, cyclohexylmethyldichlorosilane, n-decylmethyldichlorosilane, di-n-butyldichlorosilane, di-t-butyldichlorosilane, dicyclohexyldichlorosilane, dicyclopentyldichlorosilane, diethyldichlorosilane, di- n-hexyldichlorosilane, dimesityldichlorosilane, dimethyldichlorosilane, di-n-octyldichlorosilane, di-phenyldichlorosilane, di- (p-tolyl) dichlorosilane, docosylmethyldichlorosilane, dodecylmethyldichlorosilane , Ethylmethyldichlorosilane, n-heptylmethyldichlorosilane, hexylmethyldichlorosilane, n-octylmethyldichlorosilane, phenylethyldichlorosilane, phenylmethyldichlorosilane and p-tolylmethyldichlorosilane.</p><p> A general method for producing the modified silica filler according to the present invention is described below in Example A, wherein the modified silica filler is described, for example, in 660, 672 and US Pat. No. 6,384,125 (May 2002). It can be manufactured by any known and accepted technique as described in detail in issue 7). Although these patents describe general methods, they do not describe the features of the invention, namely the use of specific mixtures or blends of diorganodihalosilanes and tetrahalosilane compounds in specific ratios.</p><p> When used in rubber compositions for the manufacture of vehicle tires, carbon black, various oils, plasticizers, accelerators, antioxidants, heat stabilizers, light stabilizers, zone stabilizers, bulking agents and color pigments. Other conventional additives, including other fillers such as, can be used with the modified silica filler.</p>

The following examples are shown to illustrate the present invention in more detail. The silica slurry used in the examples contains 6.5% by weight of silica and is a commercial product of PPG Industries, Inc. (Pittsburgh, PA). Neutralization was performed by using a standard solution containing 25 wt% sodium hydroxide, which was prepared by dissolving 1000 grams of sodium hydroxide pellets in 3000 ml of deionized water.

The instruments used to process the silica were a 5 liter round bottom reaction flask with a ball joint, a Teflon® shaft agitation paddle assembly, an overhead electric agitation motor, and a flexible heating mantle. Consists of a Type-K thermocouple temperature controller with. A Dean-Stark trap and a water cooler with a sealed glass thermocouple port fully immersed directly in the reaction flask were placed on top of the reaction flask. Seal the third neck of the reaction flask with a ball joint cap or an additive funnel. The treated silica filler and silica filler cake were filtered and washed in a 253 mm Coors Porcelain Büchner funnel containing Whatman filter paper. The funnel was placed on a 4 liter filtration flask. The conductivity of the filtrate obtained from the washing process was measured using a Fisher brand digital conductivity meter. The pH was measured using a Mettler Toledo portable pH / ion meter (model number MP125).

The following procedure used in Example 2 represents a general procedure and was repeated in Examples 1, 3 and 4. The data of Examples 1 to 4 are shown in Table 1.

[Example A-General procedure for Examples 1 to 4] The reaction flask was filled with 2000 g of silica slurry and 165 g of concentrated sulfuric acid. The slurry was heated to a temperature of 70 ° C and then stopped. At this point, a mixture containing 9.10 g of tetrachlorosilane and 25.5 g of dimethyldichlorosilane was added directly to the reaction flask in a fast form over a long leg funnel for about 2-7 minutes. The treated slurry was then cooled to room temperature for 60 minutes with stirring.

A 600 mL solution containing 25 weight percent sodium hydroxide was added to the stirred slurry to adjust the pH to the range 3.4-3.7. The neutralized slurry was transferred to a Buchner funnel and vacuum filtered to remove the aqueous phase. The filter cake was then repeatedly washed with plenty of water until the filtrate showed less than 100 microohms. It was air dried overnight, the filter cake was transferred to a plastic bucket with a lid and spray dried as follows.

The air-dried silica was re-slurried in deionized water to give a slurry containing 20-40 weight percent treated silica. The slurry was mixed until all the solids were broken. The slurry was then pumped into a Niro Atomizer spray dryer at a rate of about 20 ml / min with an inlet temperature of 260 ° C and an outlet temperature of between 120 and 140 ° C. Moved. The dried and treated silica product was recovered and stored in a glass jar.

Elemental analysis of treated silica was performed in an independent test laboratory. Table 1 shows the results of elemental analysis obtained for the treated silica fillers prepared in Examples 1 to 4. In Table 1, MPTES is 3-mercaptopropyltriethoxysilane HS-CH.₂CH₂CH₂-Si (OCH₃)₃DMDCS is dimethyldichlorosilane.

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Comparison of Examples 1 and 2 shows that the percentage loss was reduced from 58% in Example 1 with dichlorosilane alone to 29% in Example 2 with a blend of dichlorosilane and tetrachlorosilane. , It was possible to understand the new unexpected result obtained by the present invention, that is, more siloxane is deposited. Further improvements can be obtained by adding other silanes to the blend, as seen in Example 3. Example 4 shows that other silanes other than tetrahalosilanes in the blend or mixture are not responsible for the improved performance. Comparison of Examples 3 and 4 shows that the rate of addition is not an important factor in improving the deposition of siloxane on the silica surface.

Therefore, the comparison between Example 1 and Example 2 shows a clear improvement. Example 3 shows that the inclusion of other additives has no adverse effect, but in practice adding them to the blend of dichlorosilane and tetrahalosilane is actually in some cases. Can be advantageous.

Other modifications of the compounds, compositions and methods described herein can be made without departing from the essential features of the invention. The embodiments of the present invention specifically exemplified in the present specification are for illustration purposes only and are intended as a limitation to the scope of the present invention except as defined in the appended claims. Absent.