Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Process of storage or protection
Reexamination Certificate
2000-12-01
2003-04-29
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Process of storage or protection
C422S001000, C422S033000, C422S067000, C422S120000, C422S255000, C524S497000, C524S588000, C524S847000, C524S863000, C524S783000, C522S042000, C522S080000, C522S099000, C522S145000, C528S034000
Reexamination Certificate
active
06555056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of preserving components which are separately packaged and mixed together to form a curable silicone composition and to a kit of separate packages.
2. Prior Art
Since silicone materials have excellent characteristic properties such as weatherability, electric properties, low compression set, heat resistance and freeze resistance, they have recently been used in a wide variety of fields such as electronic equipment, automobiles, construction, medical treatment and foods. Silicone materials which are cured at normal temperature are used in such materials as heat resistant coatings, adhesives, coating materials, construction sealing materials, dental silicone rubber impression materials, soft relining materials for denture and the like.
3. Problems to be Solved by the Invention
However, the silicone material which is cured at normal temperature tends to gradually take in air from gaps in a container while it is kept and to dissolve the air in a paste or solution. The dissolved air cannot be dissolved in the material at the time of curing with the result that it remains in its cured product as air bubbles. Therefore, the cured product containing air bubbles involves various problems such as a reduction in the strength of the material itself, a roughened surface due to the low chipping resistance of the surface of the material, a reduction in transparency and deterioration in air tightness. The inventors of the present invention have discovered in the course of the long-term research and development of this silicone material that this material has the above problems.
4. Means for Solving the Problems
The present inventors have conducted intensive studies to solve the above problems and have found that a silicone composition which can provide a cured product containing an extremely small number of air bubbles is obtained by keeping separately packaged agents of each components for forming the silicone composition under reduced pressure and that the cured product containing an extremely small number of air bubbles is free from a reduction in strength and deterioration in surface roughness. The present invention has been accomplished based on the findings.
That is, it is an object of the present invention to provide a method of preserving two or more separately packaged agents for forming a curable silicone composition by mixing together the separately packaged agents, wherein the each separately packaged agents are kept under reduced pressure. It is another object of the present invention to provide a kit of two or more separately packaged agents for forming a curable silicone composition by mixing the separately packaged agents, wherein each separately packaged agent is charged into a container and the container is enclosed in a decompressed sealing material.
SUMMARY OF THE INVENTION
Description of the Embodiments
The curable silicone composition in the present invention is a polyorganosiloxane composition which can be cured by mixing two or more separately packaged agents and which comprises (a) a polyorganosiloxane base polymer, (b) a crosslinking agent and (c) a curing catalyst as basic components. This composition may be used after various additives are uniformly dispersed therein as required.
The above components used in the composition, namely, (a) the polyorganosiloxane base polymer (b) crosslinking agent and (c) curing catalyst are suitably selected according to a curing reaction mechanism for obtaining a rubber elastic material or viscoelastic material. As the curing reaction mechanism, there are known (1) curing caused by a condensation reaction and (2) curing caused by an addition reaction, and a preferred combination of the components (a), (b) and (c) is determined by the reaction mechanism.
The basic structure of the polyorganosiloxane as the base polymer which is the component (a) used in the above reaction mechanisms is a polysiloxane having an organic group such as a monovalent substituted or nonsubstituted hydrocarbon group, alkyl group exemplified by methyl, ethyl, propyl, butyl, hexyl and dodecyl, aryl group exemplified by phenyl, non-substituted hydrocarbon group exemplified by aralkyl groups including &bgr;-phenylethyl and &bgr;-phenylpropyl, or substituted hydrocarbon group exemplified by chloromethyl and 3,3,3-trifluoropropyl; or a polysiloxane obtained by modifying part of these molecules according to the type of curing reaction mechanism. Out of these, a polysiloxane having a methyl group as an organic group is preferred because it can be easily synthesized.
The polyorganosiloxane base polymer (a), crosslinking agent (b) and curing catalyst (c) in the above curing reaction mechanisms (1) and (2) will be described in detail hereinafter.
The base polymer as the component (a) in the above condensation reaction (1) is preferably a polyorganosiloxane having the above basic structure and a hydroxyl group at both terminals. Illustrative examples of the polyorganosiloxane are represented by the following formulas.
Illustrative examples of the crosslinking agent as the component (b) in the condensation reaction include alkoxysilanes such as ethyl silicate, propyl silicate, methyl trimethoxysilane, vinyl trimethoxysilane, methyl. triethoxysilane, vinyl triethoxysilane, methyl tris(methoxyethoxy)silane, vinyl tris(methoxyethoxy)silane and methyl tripropenoxysilane; acetoxysilanes such as methyl triacetoxysilane and vinyl triacetoxysilane; oximesilanes such as methyl tri(acetoneoxime)silane, vinyl tri(acetoneoxime)silane, methyl tri(methylethylketoxime)silane and vinyl tri(methylethylketoxime)silane; and partly hydrolyzed products thereof. Further, cyclic siloxanes such as hexamethyl-bis(diethylaminoxy)cyclotetrasiloxane, tetramethyldibutyl-bis(diethylaminoxy)cyclotetrasiloxane, heptamethyl(diethylaminoxy)cyclotetrasiloxane, pentamethyl-tris(diethylaminoxy)cyclotetrasiloxane, hexamethyl-bis(methylethylaminoxy)cyclotetrasiloxane and tetramethyl-bis(diethylaminoxy)-mono (methylethylaminoxy) cyclotetrasiloxane may also be used. Further, the above polyorganosiloxane base polymer may be used alone or in combination of two or more.
The crosslinking agent may have a silane or siloxane structure and the siloxane structure thereof may be linear, branched or cyclic. Further, the above crosslinking agents may be used alone or in combination of two or more.
The amount of the crosslinking agent as the component (b) is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the base polymer as the component (a). When the amount of the crosslinking agent is smaller than 0.1 part by weight, the obtained cured product cannot have sufficient strength and when the amount is larger than 20 parts by weight, the cured product becomes fragile and can hardly be put to practical use.
Illustrative examples of the curing catalyst as the component (c) in the condensation reaction include metal carboxylates such as iron octoate, cobalt octoate, manganese octoate, tin naphthenate, tin caprylate and tin oleate; and organic tin compounds such as dimethyltin dioleate, dimethyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutyl bis (triethoxysiloxy) tin and dioctyltin dilaurate.
The amount of the curing catalyst as the component (c) is preferably 0.01 to 5.0 parts by weight based on 100 parts by weight of the base polymer as the component (a). Below 0.01 part by weight, the curing catalyst does not serve fully as a curing catalyst, curing takes long time, and an interior portion far from the contact surface with air of the composition is not completely cured. Above 5.0 parts by weight, shelf life becomes short. The amount is more preferably 0.1 to 3.0 parts by weight.
The base polymer as the component (a) in the above addition reaction (2) is, for example, a polyorganosiloxane having the above basic structure, preferably a polyorganosiloxane having organic groups bonded to
Hosoi Yasuhiro
Kawaguchi Toshio
Nakagawa Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Chorbaji Monzer R.
Tokuyama Corporation
Warden, Sr. Robert J.
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