Process for producing epoxyorganosilicon compounds

Details Process for producing epoxyorganosilicon compounds Process for producing epoxyorganosilicon compounds

2000-05-17

2002-04-02

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C524S588000, C524S858000, C524S861000, C528S031000, C528S027000

Reexamination Certificate

active

06365696

ABSTRACT:

BACKGROUND OF THE INVENTION
In the production of silicon compositions, transition metal catalysts have long been known to promote the hydrosilation reaction. In addition to catalyzing the hydrosilation reaction, many transition metals, in the presence of silicon hydrides (Si—H), also promote epoxide ring-opening polymerization of the ethylenically unsaturated epoxide starting material and the epoxysilane or epoxysilicone product of the hydrosilation reaction. This epoxide ring-opening polymerization reaction during production of an epoxysilane or epoxysilicone can lead to gelation, and may result in both the loss of the entire batch and in considerable loss of time to remove the insoluble gelled resin. Additionally, a partial gelation can occur during epoxysilicone synthesis such that reproducible batch-to-batch viscosities of the epoxysilicone product may be difficult to obtain.
In the presence of precious metal hydrosilation catalysts, e.g., chloroplatinic acid, epoxysilicones have been found to gel slowly on storage at room temperature due to the epoxide ring-opening polymerization, thus shortening the shelf life of the epoxysilicone product. This storage problem can be partially alleviated by adding a hydrochloride acceptor to the reaction to sequester HCl present from decomposition of the catalyst, as reported in U.S. Pat. No. 4,083,856 (F. Mendicino).
The prior art has taught that the epoxide ring-opening polymerization side reaction does not occur in the rhodium-catalyzed hydrosilation reaction of an ethylenically unsaturated epoxide and a Si—H. For example, U.S. Pat. No. 5,442,026 (Crivello et al.), U.S. Pat. No. 5,169,962 (Crivello et al.), U.S. Pat. No. 4,804,768 (Quirk et al.) teach that rhodium catalysts such as Wilkinson's catalyst, RhCl
3
hydrate, RhH(CO)(PPh
3
)
3
can be used to produce epoxysilicones. In addition to rhodium catalysts, certain platinum catalyst systems have been reported to selectively catalyze the hydrosilation reaction of ethylenically unsaturated epoxides and a Si—H versus the epoxide ring-opening polymerization side reaction, as disclosed in U.S. Pat. No. 5,583,194 (Crivello et al.) which teaches that quaternary onium hexachloroplatinate salts, e.g., (R
4
M)
2
PtCl
6
, or as disclosed U.S. Pat. No. 5,260,399 (Crivello et al.) transition metal phosphine complexes, e.g., Pt(PPh
3
)
4
, can be used to produce epoxysilicon compositions. However, these catalysts have not achieved commercial acceptance yet.
U.S. Pat. Nos. 5,240,971, 5,227,420, and 5,258,480 (Eckberg et al.) reported the preparation of epoxysilicones using either RhCl
3
[S(n-Bu)
2
]
3
or PtCl
2
(SEt
2
)
2
as the catalyst in the presence of a tertiary amine to control the viscosity during the hydrosilation reaction. However, only a limited number of transition metal catalysts are active in the presence of this stabilizer.
Carboxylic acids have been reported to promote the transition metal catalyzed hydrosilation reaction, as disclosed in JP 11 180,986 (M. Tachhikawa; K. Takei), F. Mendicino; C. Schilling Jr.
Abstract of Papers
, 32
nd
Organosilicon Symposium; 1999; P-68, and in UDC 415,268 (Belyakova et al.). But, carboxylic acid salts have not. Carboxylic acid salts have been reported to prevent acetal formation through the hydroxyl groups of a silicone polyether copolymer as disclosed in U.S. Pat. No. 4,847,398 (K. R. Mehta et al.); however, no utility for epoxides is disclosed.
The literature does mention that alcohols prevent or retard the epoxide ring-opening polymerization reaction (A. K. McMullen; et al.
Abstract of Papers
, 27
th
Organosilicon Symposium, 1994; Abstract P-45; and Crivello et al. Polym. Preps. 1991, 32, 338).
It is apparent that there exists a need in the industry for a method to eliminate epoxide ring-opening polymerization, and olefin isomerization when commonly used hydrosilation catalysts, such chloroplatinic acid, are employed. There is also a need for an efficient yet economical method of producing epoxysilicone monomers and oligomers in the absence of the epoxide ring-opening polymerization reaction, thereby generating epoxysilicon compositions of reproducible batch-to-batch viscosity. There is additionally a need for epoxysilicon compositions that are stable to the epoxide ring-opening polymerization reaction and therefore have increased the shelf life without an additional processing step.
SUMMARY OF INVENTION
The object of this invention is to provide a method for preparing epoxy organosilicon compositions through the platinum metal-catalyzed hydrosilation reaction between an ethylenically unsaturated epoxide and a hydrido organosilicon in the presence of a carboxylic acid salt where the catalyst efficiently promotes the hydrosilation reaction without also promoting either the epoxide ring-opening polymerization reaction of either the ethylenically unsaturated epoxide starting material, the epoxysilicon composition or the isomerization of the ethylenically unsaturated epoxide starting material. Compositions of epoxy organosilicon compounds and the salt of the carboxylic acid are taught as well wherein the salt suppresses the reactivity of the epoxy functionality.
DETAILED DESCRIPTION OF THE INVENTION
According to the process of the invention, the platinum-catalyzed hydrosilation of an ethylenically unsaturated epoxide with either a hydrido silane or hydrido siloxane occurs in the presence of a carboxylic acid salt without epoxide ring-opening polymerization side reaction, allowing for the production of high yields of epoxyorgano silanes or siloxanes. For certain carboxylic acid salts, both epoxide ring-opening polymerization and olefin isomerization are suppressed. This inventive process allows for greater batch-to-batch consistencies without the use of more complex catalyst systems. While the process is useful for both siloxanes and silanes, given that the internal rearrangement of the olefin is more of an issue in the hydrosilation of a silane, the present invention will find greater utility in the hydrosilation of hydrido alkoxysilanes.
These salts are also useful for the suppression of the reactivity of the epoxide after the hydrosilation reaction and thus are useful to extend the shelf life of epoxy organosilicon materials, even if post added after hydrosilation.
Ethylenically unsaturated epoxides for use herein include linear or cycloaliphatic epoxy compounds wherein the unsaturation is terminal (i.e., ±,
2
) which contain from 4 to 50 carbon atoms. The epoxide may be visualized as an ethylenically unsaturated epoxide of the formula:
where R can be a single bond or an alkylene optionally containing alkyl pendant groups; R
1
, R
2
and R
3
can individually be hydrogen, alkyl straight, branched or cyclic, or any two of R
1
, R
2
or R
3
can be alkylene and combined to form a 5 to 12 carbon cyclic ring, optionally containing alkyl pendants; and the number of carbon atoms in R, R
1
, R
2
, and R
3
are such that the total number of carbon atoms in the epoxide is from 4 to 50. Some representative epoxides are: 4vinylcyclohexene monoxide, 1-methyl-4-isopropenyl cyclohexene monoxide, and butadiene monoxide. The preferred epoxide is 4-vinylcyclohexene monoxide.
The hydridosilanes may be alkoxy silanes. The hydrido alkoxysilanes that may be used include the trialkoxysilanes, such as trimethoxysilane, triethoxysilane, tri-n-propoxysilane, and triisopropoxysilane. Trimethoxysilane and triethoxysilane are preferred. Other hydroalkoxysilanes include dialkoxysilanes such as methyldimethoxysilane, methyldiethoxysilane, dimethylmethoxysilane, and dimethylethoxysilane. Hydrosilanes in general can be represented by the formula R
4
n
(OR
4
)
3−n
SiH, wherein R
4
is a branched or linear alkyl group of 1 to 18 carbon atoms, a cyclic alkyl group of four to eight carbon atoms or an aryl, alkaryl, an aralkyl group of six to twelve carbon atoms, optionally containing halogen, oxygen, or nitrogen substituents with the proviso that such substituents do not interfere with either hydrosilation or promotion, and n is an integer sele

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