Hydrosilylation process and polymers produced by the process

Details Hydrosilylation process and polymers produced by the process Hydrosilylation process and polymers produced by the process

2000-03-03

2001-10-16

Moore, Margaret G. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S023000, C556S479000

Reexamination Certificate

active

06303728

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a hydrosilylation reaction between a silicon hydride compound and a compound having an alkenyl group (carbon-carbon unsaturated bond). More particularly, the invention relates to a method of accelerating the hydrosilylation reaction.
BACKGROUND ART
The reaction by which a silicon hydride compound having an Si-H group is added to an alkenyl group (C-C unsaturated bond) is commonly known as hydrosilylation.
The major problem known in the technical field utilizing this reaction is that, under respective reaction conditions, the rate of hydrosilylation reaction drops or the reaction stops in the course of reaction due to the decrease in the activity of the catalyst used during the reaction, for instance. The decrease in the reaction rate not only leads to a protracted reaction time but also results in an increase in the proportion of side reactions to lower the selectivity for the objective hydrosilylation reaction. The reaction may be accelerated by raising the addition amount of the expensive metal catalyst but the practice results in an increase in the amount of catalyst residues in the reaction product, which is sometimes objectionable for subsequent use of the product (taking the hydrosilylation of a high polymer as an example, the black particles derived from the catalyst can hardly be removed so that the product suffers from blackish opacification).
Various methods are known for accelerating a hydrosilylation reaction. For example, as described by Onopchenko, A. et al. [J. Org. Chem., 52, 4118, 1987 and Lewis, L. N. et al. [J. Am. Chem. Soc., 112, 5998, 1990 or in Japanese Kokai Publication Hei-5-213972 and Japanese Kokai Publication Hei-8-283339, the technology of using oxygen for reactivating a deactivated platinum catalyst is known. With regard to substances effective in accelerating the reaction, the technology using an acetylene alcohol (Japanese Kokai Publication Hei-8-231563), an unsaturated secondary/tertiary alcohol system (Japanese Kokai Publication Hei-8-291181), a tertiary alcohol (Japanese Kokai Publication Hei-8-333373), an unsaturated ketone (Japanese Kokai Publication Hei-8-208838) or an ene-yne unsaturated compound (Japanese Kokai Publication Hei-9-25281) is known.
Furthermore, in the system containing elemental N, P, S, Sn or As, which is known as the hydrosilylation catalyst poison, the use of an organoiron compound and/or an organoaluminum compound (Japanese Kokai Publication Hei-6-179821) is also known.
While the rate of hydrosilylation reaction is dependent on reactant species and reaction conditions, the reaction activity is liable to drop particularly in the case that the concentration of unsaturated groups is low, the case that the viscosity of the reaction mixture is high, the case that an internal olefin which is less active than a terminal olefin is involved in the reaction, or the case that the starting material or the solvent contains a reaction inhibitor substance.
Furthermore, there is the tendency that in a system experiencing a drop in reaction activity, a protracted reaction time causes to increase formation of byproducts. The hydrosilylation reaction introducing a hydrolyzable silyl group, such as methoxysilyl, into a polymer is important. A polymer containing a hydrolyzable silyl group is capable of forming a crosslinked compound of higher molecular weight through intermolecular silanol condensation reaction and such crosslinkable polymers are of great use. If the rate of a hydrosilylation reaction for introducing a hydrolyzable silyl group into a polymer drops, the density of crosslinking sites is decreased so that the strength of the crosslinked polymer is ultimately sacrificed.
The technology is k now n which comprises using an expensive noble metal catalyst or a silicon compound in an large amount to improve the reaction yield but it is not acceptable economically. The hitherto-known technology for accelerating a hydrosilylation reaction is, thus, not impeccable but is of ten incapable of solving the problem to a fully satisfactory extent.
DISCLOSURE OF INVENTION
In view of the above state of the art, the present invention has for its object providing an effective method of accelerating a hydrosilylation reaction.
Sulfur compounds are generally thought to impede the catalyst activity of metals and, in the field of hydrosilylation, too, it has been the common belief that sulfur compounds should be excluded as far as possible. Therefore, it was almost inconceivable from such common knowledge that a hydrosilylation reaction could ever be conducted in the presence of a sulfur compound which is a catalyst poison as well.
After intensive research, the inventors of the present invention found that a hydrosilylation reaction carried out in the presence of a sulfur compound results in an acceleration of the reaction and is, thus, of great industrial benefit. The inventors have accordingly developed the present invention.
The present invention, therefore, is directed to a hydrosilylation reaction method which comprises carrying out the hydrosilylation reaction between a silicon compound (A) of the following general formula (1) and an alkenyl group-containing compound (B) in the presence of a group VIII metal-containing catalyst (C) and a sulfur compound (D);
R
a
X
b
H
c
Si  (1)
(in the formula, R represents an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms or a triorganosiloxy group; when a is not less than 2, the plurality o f R's may be the same or different; X represents a halogen atom, an alkoxyl group, an acyloxyl group or a hydroxyl group; when b is not less than 2, the plurality of X's may be the same or different; a and b each represents an integer of 0 to 3; c represents an integer of 1 to 3; provided, however, that a, b and c are such that a+b+c=4).
The present invention is further directed to a polymer which is prepared by the reaction method.
In the following, the present invention is described in detail.
The silicon compound (A) mentioned above is not particularly restricted but includes, among others, halosilanes such as trichlorosilane, methyldichlorosilane, dimethylchlorosilane, trimethylsiloxydichlorosilane, etc.; alkoxysilanes such as trimethoxysilane, triethoxysilane, dimethoxymethylsilane, methoxydimethylsilane, dimethoxyphenylsilane, 1,3,3,5,5,7,7-heptamethyl-1,1-dimethoxytetrasiloxane, etc.; acyloxysilanes such as methyldiacetoxysilane, trimethylsiloxymethylacetoxysilane, etc.; hydrosilanes containing two or more Si—H bonds per a molecule, such as dimethylsilane, trimethylsiloxymethylsilane, 1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethylcyclotrisiloxane, etc.; and alkenyloxysilanes such as methyldi(isopropenyloxy)silane and so on. Those compounds can be used each alone or in a combination of two or more species.
Among them, methyldichlorosilane, dimethoxymethylsilane, diethoxymethylsilane, trimethoxysilane and triethoxysilane are preferred.
The amount of use of said silicon compound (A) is not particularly restricted but is generally 0.1 to 20 mols per mol of the alkenyl group. The preferred range, from economic points of view, is 0.5 to 3 mols.
The above-mentioned alkenyl group (C-C unsaturated bond)-containing compound (B) is not particularly restricted but includes alpha-olefins such as ethylene, propylene, 1-butene, 1-hexene, etc.; cyclohexene; trans-2-hexene; butadiene, decadiene; allyltrimethylsilane; alkenyl group-containing polymers; among others. Those compounds can be used each alone or in a combination of two or more species.
The backbone chain of the alkenyl group-containing polymer mentioned above is not particularly restricted but includes among others, a hydrocarbon backbone chain, a halogenated hydrocarbon backbone chain, a saturated hydrocarbon backbone chain, a polyether backbone chain, a polyester backbone chain, a polyamide backbone chain and a polyimide backbone chain.
The preferred backbone chain of said alkenyl group-containing polymer, when the polymer has a s

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