A silicone rubber-based hardening composition includes a linear organopolysiloxane having a vinyl group (A), an organohydrogen polysiloxane (B), and a silica filler (C) of which surface is treated with a silane coupling agent having a trimethylsilyl group. The linear organopolysiloxane having a vinyl group (A) includes a first linear organopolysiloxane having a vinyl group (A1), and a second linear organopolysiloxane having a vinyl group (A2).

The method for producing a surface-modified base material according to the present invention includes a step of bringing a base material having a polar group present on a surface thereof into contact with a hydrosilane compound having a molecular structure A and having a SiH group composed of a silicon atom of the molecular structure A and a hydrogen atom bonded to the silicon atom in the presence of a borane catalyst so as to allow a dehydrocondensation reaction to take place between the base material and the compound, thereby forming the base material surface-modified with the molecular structure A. This production method is capable of surface-modifying a base material at a lower temperature in a shorter time than conventional methods and allows a wide variety of options for the form, type, and application of the base material, the mode of the modification reaction, and the type of the molecular structure with which the base material is surface-modified.

The present invention relates to a composition comprising a) a stable aqueous dispersion of inorganic pigment particles hydrophobically modified with covalently bonded polysiloxane or silyl groups; and b) a polymeric anionic dispersant; wherein the hydrophobically modified inorganic pigment particles have an average particle size in the range of from 200 nm to 10 m, and the solids content of the hydrophobically modified inorganic pigment particles is from 10 to 80 weight percent, based on the weight of inorganic pigment particles and water. The composition of the present invention provides a way to improve water resistance in coatings formulations.

The invention relates to copolymers comprising a chain of siloxane repeat units of at least two different types, a first type of siloxane repeat unit comprising at least one OH group on the silicon atom of the siloxane repeat unit and a second type of repeat unit comprising at least one pendant chain on the silicon atom of said repeat unit, this pendant chain consisting of a polymer chain comprising a chain of repeat units carrying at least one group of formula PO.sub.3R.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 independently represent a hydrogen atom, an alkyl group or a cation.

The present application provides a preparation method for a thermally expandable microsphere containing hydrophilic organic-modified colloidal silicon dioxide. In the preparation method, hydrophilic organic-modified colloidal silicon dioxide is mixed with a mixture of a monomer material capable of polymerizing to form a thermoplastic polymer shell and at least one foaming agent to form an emulsion, and the emulsion is polymerized to form the thermally expandable microsphere. Surface-modified colloidal silicon dioxide with hydrophilic organic group in the present application has good salt tolerance stability, can be stabilized in brine and is beneficial to the preparation of the thermally expandable microsphere; and the prepared microsphere has a narrow particle size distribution, can be easily dispersed in water and an organic system, and has good wettability. The application also relates to a thermally expandable microsphere and use thereof.

A filler for electronic material according to the present invention has a silica particle material produced by a dry method, wherein D50 is 0.2 m or greater and 7.0 m or less. Further, in the filler for electronic material according to the present invention, (BET specific surface area)/(theoretical specific surface area calculated from D50) is 0.85 or greater and 1.2 or less (requirement 1), and/or D10/D50 is 0.55 or greater and 0.75 or less (requirement 2). When at least one of the requirements 1 and 2 is satisfied, electric characteristics such as a Df value are improved. Here, the BET specific surface area is a value measured by using nitrogen, and D50 is a 50 mass % cumulative diameter, i.e., a median diameter, and means a particle diameter at 50 mass % when the masses of particles are sequentially integrated from smaller particle diameters. Similarly, D10 is a 10 mass % cumulative diameter.

The problem to be solved by the present invention is to provide colloidal silica for metal polishing that is capable of achieving a high polishing rate. This problem can be achieved by a colloidal silica for metal polishing, comprising a silica particle having a surface on which a functional group having at least one carboxyl group is immobilized by covalent bonding.

The flake-like substrate has an average particle size of 0.1 to 11 m and an average thickness of 0.1 to 1.0 m and has a particle size distribution in which D9935 m, D10045 m, 3<D90/D10, and (D90D99D100)/D503200 are satisfied, where D10 is a particle size at which a cumulative volume fraction from a smaller-particle side reaches 10%, D50 is a particle size at which the cumulative volume fraction from the smaller-particle side reaches 50%, D90 is a particle size at which the cumulative volume fraction from the smaller-particle side reaches 90%, D99 is a particle size at which the cumulative volume fraction from the smaller-particle side reaches 99%, and D100 is a particle size at which the cumulative volume fraction from the smaller-particle side reaches 100%.

A silica sol uses a carboxylic acid ester as a dispersion medium and a method for produces the same. The silica sol contains, as dispersoids, silica particles in which an alkoxy group represented by SiOR.sup.1 is present on or near surfaces of silane-treated silica particles, a solvent containing a carboxylic acid ester having an R.sup.2COOR.sup.1 structure as a dispersion medium, and an amine. The dispersoids are silica particles in which at least two types of alkoxy groups represented by SiOR.sup.0 and SiOR.sup.1 are present and which have a molar ratio (SiOR.sup.1)/(SiOR.sup.0) of 0.002 to 50. SiOR.sup.0 is SiOCH.sub.3 or SiOC.sub.2H.sub.5. The silica particles have an average particle diameter of 5 to 200 nm determined by a dynamic light scattering method.

The present invention provides a thermally conductive filler having a high filling property into a resin. The present invention includes a thermally conductive filler containing a first surface-treated powder and a second surface-treated powder having a different degree of hydrophobicity from that of the first surface-treated powder. In particular, when in the thermally conductive filler, a particle diameter D50 with a cumulative volume of 50% is 0.1 to 2 m and the amount of coarse particles of 5 m or more is controlled to be small, a heat dissipation material composition filled with the thermally conductive filler exhibits extremely excellent characteristics that it is possible to reliably fill narrow gaps.