Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-06-16
2001-05-22
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S015000, C528S020000, C528S021000, C528S023000, C528S031000, C528S032000, C528S033000
Reexamination Certificate
active
06235861
ABSTRACT:
TECHNICAL FIELD
This invention relates to an organopolysiloxane composition and, more particularly, a heat-curable organopolysiloxane composition of an addition-reaction type which has a good shelf stability around room temperature and is suitable for the one solution type.
BACKGROUND ART
There has been hitherto well-known an addition-curing silicone composition containing as a main component an organopolysiloxane containing an alkenyl group, an organohydrogenpolysiloxane and a platinum catalyst. These compositions can have a higher curing rate and can be cured even in a thicker part as compared with a moisture-curing composition which may be reacted and cured with the moisture in atmosphere, so that it has been applied for the use of potting and the like.
As the catalyst for reacting an organopolysiloxane with an organohydrogenpolysiloxane in the addition-reaction type silicone, there has been usually employed a platinum catalyst as mentioned above. A rapid addition reaction is brought about by admixing the above-mentioned components to form a cured product. Since curing by this addition reaction may be also brought about rapidly by admixing at ambient temperature, there has been usually adopted such a complicated use method wherein the planinum catalyst and the organohydrogenpolysiloxane are packed in separate vessels to form a two-pack solution type and two solutions are admixed when curing of the composition is required. In the two-pack solution type, although it is convenient to apply a mixing coating applicator and the like in admixing two solutions, it is difficult to prevent a mixing chamber or a nozzle from the curing encountered therein, so that the interior of the applicator should be washed whenever applied, which leads to a troublesome handling.
Under these circumstances, it has been presented the problem to be solved by those skilled in the art to obtain an addition-reaction type silicone composition in the one solution type and there has been desired an addition-reaction type silicone composition wherein all components therefor may be stored over a prolonged time in a mixed state and curing may be brought about first when heated. For solving such a problem, there have been proposed many compositions wherein reaction inhibitors are compounded for imparting a shelf stability at room temperature.
As examples of such inhibitors, there are disclosed organic phosphorous compounds in U.S. Pat. No. 3,188,300, benzotriazole compounds in U.S. Pat. No. 3,192,181, sulfoxide compounds in U.S. Pat. No. 3,445,420 and pyridine compounds in U.S. Pat. No. 3,188,299, respectively.
Moreover, Japanese Patent Kokai JP62-20557A discloses the use of monoalkylamine compounds and Japanese Patent Kokai JP3-95267A discloses inhibiting effect by concomitant use of monoalkylamine compounds with acetylenic compounds.
However, all of said reaction inhibitors are extremely difficult to keep compatible curability with stability; in particular, bidentate conformational compounds such as phosphorous compounds or bipyridyl may exhibit a favorable result in stability around room temperature, but they may have a lowered reaction inhibiting effect with lapse of time when coexisted with a platinum catalyst over a prolonged period of time, whereby thickening or gelation would take place. In order to improve a shelf stability over a prolonged period of time, acetylenic compounds have been frequently used, but, if the amount thereof to be added is increased, curability would be lowered.
And further, addition of ethylenediamine as amine-type compounds has presented the problem of an extremely lowered shelf stability though curability could be improved.
In view of the above, there has been proposed in Japanese Patent Kokai JP1-47442A the use of a platinum catalyst coated with a thermoplastic resin, the so-called microcapsule-type platinum catalyst, to attain a shelf stability. The principle of this catalyst resides in that a platinum catalyst is physically coated with a thermoplastic resin and the thermoplastic resin is melted by heating in use to separate the platinum catalyst, whereby the platinum catalyst may effectively act.
According to this method, a shelf stability could be attained, but properties of heat curable resins are still insufficient. In short, a heating temperature or a heating time until an effective action of the platinum catalyst could be achieved may vary depending upon a thickness of a coated film or a polymerization degree in the heat curable resins because of the physical coating. In order to determine exact temperature and time for improving the reproductivity thereof, a considerable precision is required for the manufacturing step of microcapsules. Moreover, since this method uses physical coating, it has the drawback that microcapsules tend to be broken by vigorous stirring or the like during the manufacturing step of silicone compositions.
OBJECT OF INVENTION
It is an object of this invention to provide an addition-reaction type organopolysiloxane composition which does not cause any lowered catalyst effect with lapse of time as observed in a system blending the prior art reaction inhibitor, is excellent in a shelf stability around room temperature and may be rapidly cured by heating.
SUMMARY OF INVENTION
We have made earnest studies to accomplish the above object and, as a result, found out that the above object can be attained by using selected compounds as a reaction inhibitor of a platinum catalyst, upon which this invention has been completed.
More specifically, this invention is directed to an addition-curing type organopolysiloxane composition comprising an organopolysiloxane containing an alkenyl group, an organohydrogenpolysiloxane, a platinum catalyst and a reaction inhibitor, characterized in that said reaction inhibitor is at least one member selected from the group consisting of a thiophene compound, an isocyanide compound, a cyclic thioether compound, a cyclic azoether compound, an imino compound and a polymer of an average molecular weight of 1,000-200,000 which has a plurality of sulfur atom-, nitrogen atom- or phosphorus atom-containing functional groups capable of forming a complex with a platinum atom.
As the organopolysiloxane containing an alkenyl group (Component 1), the organohydrogenpolysiloxane (Compound 2) and the platinum catalyst (Component 3), which may be employed in this invention, there may be appropriately applied those already used and known in the addition-reaction type silicone composition of the prior art.
The component 1, the organopolysiloxane containing an alkenyl group, which may be used in this invention, has an alkenyl group directly attached to a silicon atom and the siloxane skeleton thereof may be either straight or branched, while it may be a mixture of two or more thereof. As the alkenyl group may be mentioned a vinyl group, an allyl group, a 1-butenyl group, a 1-hexenl group, etc. Of these groups, a vinyl group is preferable in view of reactivity or physical properties after curing.
As the substituent attached to a silicon atom other than the alkenyl group may be mentioned an alkyl group such as a methyl group, an ethyl group, a propyl group, a hexyl group or a dodecyl group, a group having an unsaturated bond within the molecule such as a phenyl group or an allyl group, an aralkyl group, a halogen atom, a substituted hydrocarbyl group and the like. The organopolysiloxane may contain a hydroxyl group or an alkoxy group.
The Component 1 may form an addition-reaction type, curable organopolysiloxane-base polymer and it is essential that the alkenyl group is contained at not less than 0.05 mole %, preferably 0.05-0.2 mole %, in all organic groups attached to the silicon atom. And, the polymerization degree or viscosity thereof is not particularly critical, but a viscosity of 10-1000000 centipoises at 25° C. is practically preferred.
The Component 2, the organohydrogenpolysiloxane, is the component which forms a network of a polymer by the addition reaction with the Component 1 to make a cured product in a gummy or gel state and usua
Dawson Robert
Dilworth & Barrese LLP
Robertson Jeffrey B.
Three Bond
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