JP-7855490-B2 - Silicone rubber particles and aqueous dispersions of silicone rubber particles

Inventors

• 井口 良範

Assignees

• 信越化学工業株式会社

Dates

Publication Date

20260508

Application Date

20221028

Claims (3)

1. Silicone rubber particles are spherical, having a volume average particle size of 0.5 to 50 μm, and are the addition reaction product of a curable liquid silicone composition containing the following components (A-1), (A-2), and (A-3). (A-1) A diorganopolysiloxane having two or more alkenyl groups in one molecule, with an alkenyl group content of 0.0025 to 0.034 mol/100g. (A-2) An organopolysiloxane resin containing R 1 3 SiO 1/2 units and SiO 4/2 units, wherein the molar ratio of R 1 3 SiO 1/2 units to SiO 4/2 units is 0.60 to 1.7, and the amount of alkenyl groups is 0.001 mol/100 g or more. ( The above R1 are independently substituted or unsubstituted monovalent hydrocarbon groups having 1 to 30 carbon atoms that do not have an alkenyl group, or alkenyl groups having 2 to 8 carbon atoms, and at least one of the total R1 is an alkenyl group), and (A-3) an organohydrogenpolysiloxane having two or more silicon atom-bonded hydrogen atoms (referred to as SiH groups) in one molecule, with an SiH group content of 0.030 to 1.30 mol/100g. The amount of component (A-2) is 1.0 to 65 parts by mass per 100 parts by mass of the total of components (A-1), (A-2), and (A-3).
2. The silicone rubber particles according to claim 1, wherein the silicone rubber particles consist of silicone rubber having an elongation of 20% or more at break of a dumbbell-shaped test specimen (Type 3) according to the test method specified in JIS K 6251, and a tensile strength of 1.0 MPa or more at break according to the test method specified in JIS K 6251, for a 1 mm thick rubber sheet heat-treated at 150°C for 30 minutes.
3. An aqueous dispersion of silicone rubber particles comprising: (A) 100 parts by mass of silicone rubber particles according to claim 1 or 2; (B) 0.05 to 20 parts by mass of surfactant; and (C) 20 to 2,000 parts by mass of water.

Description

This invention relates to silicone rubber particles with high strength and elongation, and to aqueous dispersions of said silicone rubber particles. Silicone rubber particles are used in applications such as stress relievers for resins, light diffusers for resins, texture enhancers for cosmetics, matting agents, texture enhancers, and lubricity enhancers for paints and coatings. Generally, silicone rubber particles do not contain fillers such as silica, resulting in low rubber strength and limited elongation. In applications such as paints and coatings, the silicone rubber particles may break down under the load of friction applied to the coating. Patent Document 1 proposes high-strength silicone rubber particles containing silica. These are manufactured by mixing silica with a curable liquid silicone composition, dispersing (emulsifying) the mixture in water containing a surfactant, and then curing it. However, this method results in an emulsion with poor stability, and some particles may aggregate. Furthermore, it is difficult to increase the silica content in the particles, making it challenging to produce rubber particles with higher strength. Patent Document 2 proposes silicone rubber particles containing organosiloxane resin, using diorganopolysiloxane having alkenyl groups, organopolysiloxane resin, and organohydrogenpolysiloxane having silicon atom-bonded hydrogen as raw materials. However, the silicone rubber particles described in Patent Document 2 have low rubber strength and elongation. Japanese Unexamined Patent Publication No. 4-168117Japanese Patent Publication No. 2000-204258 This invention has been made in view of the above circumstances, and aims to provide silicone rubber particles and aqueous dispersions of silicone rubber particles that have high strength and elongation, and a low amount of aggregated particles. The present invention will be described in detail below. [Silicone rubber particles] The shape of the silicone rubber particles (A) of the present invention is spherical. In this specification, "spherical" means that the particle shape is not only a perfect sphere, but also a deformed sphere in which the ratio of the longest axis length to the shortest axis length (aspect ratio) is typically in the range of 1.0 to 4.0, preferably 1.0 to 2.0, more preferably 1.0 to 1.6, and even more preferably 1.0 to 1.4. The shape of the particle can be confirmed by observing the particle with an optical microscope, electron microscope, etc. It can also be measured by a particle shape analyzer using dynamic image analysis. The volume-average particle size is 0.5 to 50 μm, preferably 1.0 to 30 μm, and more preferably 2.0 to 20 μm. The volume-average particle size is measured by the Coulter counter method (electrical resistance method). The silicone rubber of the silicone rubber particles (A) is an addition reaction product of a curable liquid silicone composition containing (A-1) a diorganopolysiloxane having two or more alkenyl groups per molecule, (A-2) an organopolysiloxane resin having alkenyl groups, and (A-3) an organohydrogenpolysiloxane having two or more SiH groups per molecule. (A-1) Diorganopolysiloxanes having two or more alkenyl groups in one molecule of component have the following average composition formula (1) R 2 a R 3 b SiO (4-ab)/2 (1) This is shown by the formula. In the formula, R2 is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and not having an alkenyl group, R3 is independently an alkenyl group having 2 to 8 carbon atoms, and a and b are positive numbers satisfying 0 < a < 3, 0 < b ≤ 3, and 0.1 ≤ a + b ≤ 3. One type of diorganopolysiloxane represented by average composition formula (1) may be used alone, or two or more types may be used in combination. R2 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms. R Examples of group 2 include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, henicosyl, docosyl, tricosyl, tetracosyl, and triacontyl groups; aryl groups such as phenyl, tolyl, and naphthyl groups; aralkyl groups such as benzyl and phenethyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; and hydrocarbon groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with atoms such as halogen atoms (fluorine, chlorine, bromine, iodine) and/or substituents such as acryloyloxy, methacryloyloxy, amino, epoxy, glycidoxy, and carboxyl groups. It is preferable that 50 mol% or more of the total R2 consists of methyl groups. R3 can be a vinyl group, an allyl group, a propenyl group, a butenyl group, a pentenyl group, a he