Curable composition

Abstract

The present invention has its object to provide a curable composition having good storage stability even when it contains a hydrolyzable silicon compound and / or an amino group-containing alkoxysilane or amino-substituted alkoxysilane derivative compound. This invention provides a curable composition which comprises (A) a reactive silicon group-containing polyether oligomer and at least one species selected from the following (B) and (C): (B) a hydrolyzable silicon compound having a hydrolyzable group bound to a silicon atom, said hydrolyzable group being more reactive with H2O than the silicon group in the above reactive silicon group-containing polyether oligomer and (C) an amino group-containing alkoxysilane or amino-substituted alkoxysilane derivative compound,

Description

[0001] The present invention relates to a curable composition having good storage stability, which comprises a reactive silicon group-containing polyether oligomer and a hydrolyzable silicon compound having a hydrolyzable group bound to a silicon atom, said hydrolyzable group being more reactive with H.sub.2O than the silicon group in the reactive silicon group-containing polyether oligomer and / or an amino group-containing alkoxysilane or amino-substituted alkoxysilane derivative compound.PRIOR ART[0002] Room temperature curing compositions comprising a reactive silicon group-containing polyether oligomer, one or more of various additives and a silanol condensation catalyst are known in the art and are used as sealants, adhesives and so on.[0003] It is known that when, in using the above oligomer in an one-component type curable composition, a hydrolyzable silicon compound having a hydrolyzable group bound to a silicon atom, said hydrolyzable group being more reactive with H.sub.2O ...

AI Technical Summary

Benefits of technology

[0078] The addition amount of the sulfur compound can be typically selected from the range of 0.1 to 10 times the number of moles of the metal catalyst, 10.sup.-3 to 10.sup.-6 times the number of moles of the alkenyl group, or 0.001 to 10 ppm based on the total weight of the reaction mixture. If the addition amount is too low, the effect of the invention will not necessarily be attained. If the sulfur compound is added in an excessively large amount, there may at times be encountered a reduction in the catalyst activity or an inhibition in the progress of reaction. Therefore, a judicious selection of the amount of sulfur is recommended.

[0079] The hydrosilylation reaction in the production process according to the present invention can be carried out in the absence of a solvent or in the presence of a suitable solvent. As the solvent for this hydrosilylation reaction, hydrocarbons, halogenated hydrocarbons, ethers and esters can be generally used, although specifically the use of hexane, toluene, xylene, methylene chloride, tetrahydrofuran, diethyl ether or ethylene glycol dimethyl ether is preferred. Particularly in the hydrosilylation of a compound of high molecular weight, the use of a solvent is preferred for assuring dissolution or reduction in viscosity. In this connection, the plasticizer for use in the final formulation of a compound of high molecular weight can be utilized as the reaction solvent.

[0080] In the hydrosilylation reaction according to the present invention, the atmosphere within the hydrosilylation reactor may be exclusively composed of an inert gas, such as nitrogen or helium gas, or may contain oxygen. Hydrosilylation reactions are sometimes conducted in the presence of an inert gas, e.g. nitrogen or helium gas, from the standpoint of safety of inflammable gas handling. However, when a hydrosilylation reaction is carried out in an inert gas atmosphere, such as nitrogen or helium gas, the conversion rate may be low depending on the conditions of reaction used.

[0081] In the process according to the present invention, the progress of hydrosilylation reaction can be safely promoted by using oxygen at an amount capable of avoiding explosive mixture-forming concentration level. Thus, the oxygen concentration of the reactor gas phase may for example be 0.5 to 10%.

[0082] Furthermore, in order to inhibit oxidation of the polyether oligomer, reaction solvent and / or plasticizer in the hydrosilylation reaction system by the oxygen present, the hydrosilylation reaction can be conducted in the presence of an antioxidant. As said antioxidant, there can be mentioned phenolic antioxidants having a radical chain-terminating function, such as 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-meth-yl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), tetrakis{methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate}methane-, and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane. As other radical chain terminators, there can be mentioned amine series antioxidants such as phenyl-.beta.-naphthylamine, .alpha.-naphthylamine, N,N'-di-sec-butyl-p-phenylenediamine, phenothiazine, N,N'-diphenyl-p-phenylenediamine, etc. Those antioxidants are by no means exclusive choices, however.

[0083] In accordance with the process of the present invention, there can be obtained a reactive silicon group-containing polyether oligomer in which the average number of reactive silicon groups is not less than 85% of the total number of molecular chain terminals of the oligomer. By using a polyether oligomer with a silylation rate of not less than 85%, a curable composition having physical properties required of a sealant (breaking strength, elongation at break, etc.) as well as very satisfactory bond strength can be obtained.

Problems solved by technology

However, when such amino group-containing alkoxysilane or amino-substituted alkoxysilane derivative compound is admixed with the reactive silicon group-containing polyether oligomer in the presence of water, the amino group functions as a curing catalyst and the condensation reaction proceeds between the silicon groups in the reactive silicon group-containing polyether oligomer, resulting in worsening of the storage stability.

Moreover, the viscosity of the oligomer will become too high to be handled with ease.

If the amount of the catalyst is too small, the hydrosilylation reaction may fail to proceed sufficiently.

If the amount of the catalyst is too excessive, the large catalyst consumption will be reflected in an increased production cost and increased catalyst residues in the product.

If the sulfur compound is added in an excessively large amount, there may at times be encountered a reduction in the catalyst activity or an inhibition in the progress of reaction.

However, when a hydrosilylation reaction is carried out in an inert gas atmosphere, such as nitrogen or helium gas, the conversion rate may be low depending on the conditions of reaction used.

Those antioxidants are by no means exclusive choices, however.

At an amount exceeding 20 parts by weight, adverse influences are produced on the rubber characteristics after curing.

When the amount of the silanol condensation catalyst is too small relative to the reactive silicon group-containing polyether oligomer, the rate of curing will be unfavorably slow and the curing reaction will hardly proceed to a sufficient extent.

When, on the other hand, the amount of the silanol condensation catalyst is excessive relative to the reactive silicon group-containing polyether oligomer, local heat generation or foaming may unfavorably occur in the step of curing, making it difficult to obtain good cured products.