Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-08-01
2004-06-22
Peng, Kuo-Liang (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S021000, C556S482000, C556S458000
Reexamination Certificate
active
06753399
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for the preparation of fine globular particles of a silicone resin. More particularly, the invention relates to a method for the preparation of globular particles of a polyorganosilsesquioxane resin having a relatively large average particle diameter.
As is well known, powders of fine globular silicone resin particles are widely employed as an adjuvant material, for example, in plastic resin-based molding compositions to Impart slipperiness, abrasion resistance and light diffusibility to molded articles thereof and to impart anti-blocking surface to resin films, in rubber compositions to impart surface slipperiness and lubricity to rubber articles or coating thereof, in cosmetic or toiletry preparations and waxes to impart spreadability, surface lubricity and water repellency and in detergents as a grindability-imparting additive.
Needless to say, the requirements for the characteristics of the silicone resin particles are different depending on the intended applications of the particles. For example, silicone resin particles used as an additive in plastic resins to impart surface slipperiness and antiblocking nature of the surfaces are required to have a globular or spherical particle configuration with a relatively large average particle diameter.
A great variety of methods are proposed and practiced heretofore for the preparation of fine silicone resin particles having a globular particle configuration including the methods outlined below. Belgian Patent No. 572412 discloses a method in which methyl trichlorosilane is added dropwise into water under agitation to effect hydrolysis condensation reaction of the silane compound. Japanese Patent Kokai No. 6-157759 teaches that an organotrichlorosilane is dissolved in a solution of an alkali hydroxide followed by the addition of an acid to the solution to effect hydrolysis and condensation reaction of the silane compound. These methods, however, are not suitable when silicone resin particles having a globular particle configuration are desired.
A method is proposed in Japanese Patent Kokai No. 6-179751 according to which an organotrichlorosilane is added to an aqueous solution saturated with hydrogen chloride to effect hydrolysis condensation reaction of the silane compound. This method, however, has a disadvantage of low productivity because it is an extremely complicated and time-consuming procedure to completely remove hydrogen chloride from the product of resin particles.
Further, Japanese Patent Publication No. 52-12219 discloses a method in which an organotrialkoxy silane is added to an acidic or alkaline aqueous solution containing an ionic surfactant to effect hydrolysis condensation reaction of the silane compound. Japanese Patent Publication No. 1-14250 proposes a method according to which an organotrialkoxy silane or a partial hydrolysis-condensation product thereof is dispersed and emulsified in an aqueous medium containing non-ionic and cationic surfactants and then subjected to the hydrolysis condensation reaction with addition of an alkaline compound. Japanese Patent Kokai No. 4-359022 proposes a method in which an alkali metal salt of an organosilanol compound is neutralized with an acid in an aqueous solution and subjected to condensation reaction. These methods, however, are not suitable when the silicone resin particles obtained thereby are desired to have a relatively large average particle diameter.
Besides, a proposal is made in Japanese Patent Kokai No. 63-308067, according to which an organotrialkoxy silane or a partial hydrolysis condensation product thereof is gradually added dropwise into an aqueous solution containing a surfactant to effect hydrolysis condensation reaction and the thus obtained aqueous colloidal suspension of the silicone resin particles is spray-dried. The thus obtained particles have a particle diameter of 1 to 100 &mgr;m and are each an agglomerate of primary particles having a particle diameter of 10 to 150 nm. The powder of such agglomerated resin particles has a problem that the agglomerated particles are subject to disintegration when a composition compounded therewith is worked under a high shearing force if not to mention the disadvantage of low productivity of the process including the step of spray drying of an aqueous colloidal suspension of which the solid concentration is usually low.
Japanese Patent Kokai No. 4-33927 proposes a method in which, by using a non-ionic surfactant as the dispersing agent, an organotrialkoxy silane or a partial hydrolysis condensation product thereof is dispersed and suspended in a non-aqueous dispersion medium in the presence of a basic or acidic catalyst to effect hydrolysis condensation reaction. Since the dispersion medium is non-aqueous, this method is economically disadvantageous.
A method is disclosed in Japanese Patent Kokai No. 6-279589, according to which an organopolysiloxane is dissolved in an aqueous solution of an alkali metal hydroxide and the solution is subjected to an ion exchange treatment to remove the anions followed by a condensation reaction in the solution having a pH value of 10 or higher at a temperature of 50° C. or higher. The disadvantage involved in this method is the low productivity of the process because the organopolysiloxane as the starting material must be prepared beforehand by conducting the hydrolysis condensation reaction of a hydrolyzable organosilane compound.
Other methods heretofore proposed include: a method in which a methyl trialkoxy silane is added under agitation to an aqueous solution of an alkali metal hydroxide, ammonia or an amine compound to effect hydrolysis condensation reaction (see Japanese Patent Publication No. 40-16917), a method in which a methyl trialkoxy silane or a partial hydrolysis condensation product thereof is added to an aqueous solution of an alkaline earth metal hydroxide or an alkali metal carbonate to effect the hydrolysis condensation reaction (see Japanese Patent Publication No. 56-39808), a method in which a methyl trialkoxy silane compound or a partial hydrolysis condensation product thereof is subjected to the hydrolysis condensation reaction in an aqueous solution of ammonia or an amine compound followed by heating at 70 to 80° C. to promote the condensation reaction and the reaction product is washed with water and dried followed by disintegration into a powder (see Japanese Patent Publication No. 2-22767), a method in which an organotrialkoxy silane compound is dissolved in an aqueous solution of a carboxylic acid followed by the condensation reaction in an alkaline aqueous solution (see Japanese Patent Kokai No. 3-244636), a method in which an organotrialkoxy silane compound dissolved in an organic solvent is mixed with an acidic aqueous solution to effect hydrolysis followed by the addition of a basic compound to the reaction mixture to effect the condensation reaction (see Japanese Patent Kokai No. 6-65378), a method in which a hydrolyzable organometallic compound is subjected to the hydrolysis condensation reaction in a liquid medium consisting of a hydrolysis catalyst, water, an electrolyte and an organic solvent (see Japanese Patent Kokai No. 6-122516), a method in which an organoalkoxy silane compound is subjected to the hydrolysis condensation reaction in the presence of an aqueous solution containing a non-ionic surfactant and ammonia and/or an amine compound (see Japanese Patent Kokai No. 11-152336) and a method in which an organoalkoxy silane compound is subjected to the hydrolysis condensation reaction in an aqueous solution containing an anionic surfactant and ammonia and/or an amine compound (see Japanese Patent Kokai No. 11-181095).
According to these methods, fine organopolysiloxane particles having a particle diameter suitable for the above mentioned applications can be obtained with a high efficiency. When a still larger particle diameter is desired of the organopolysiloxane particles, for example, from methyl trimethoxysilane as the starting material, particles having
Millen White Zelano & Branigan P.C.
Peng Kuo-Liang
Shin-Etsu Chemical Co. , Ltd.
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