Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
1996-10-02
2001-07-10
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S458000, C556S425000, C556S414000, C556S428000, C549S215000, C528S026000, C528S032000, C528S033000, C528S038000
Reexamination Certificate
active
06258969
ABSTRACT:
The present invention relates to a novel polyalkoxysiloxane, a process for its production, and its applications.
In recent years, siloxane compounds having (SiO)
n
units have been used alone or in combination with an organic component such as an organic polymer for applications to e.g. a hard coat, an exterior wall coating, a material for a sand mold for casting and an adhesive to improve e.g. scuff resistance, stain resistance and adhesiveness. Among them, an attention has been drawn particularly to a polyalkoxysiloxane which is a partially hydrolyzed condensate of an alkoxysilane having alkoxy groups bonded to silicon. As such a polyalkoxysiloxane compound, a polyethoxysiloxane has heretofore been used, which is a low condensate of tetraethoxysilane (TEOS) having ethoxy groups as the alkoxy groups. However, this compound usually has a low reactivity, and also theoretically, there is a limit in the silica-converted concentration. Accordingly, the inorganic properties of the silica component can not adequately be utilized. Also known is a polymethoxysiloxane which is a condensate of tetramethoxysilane (TMOS) having methoxy groups as the alkoxy groups. This compound has a characteristic that as compared with the polyethoxysilane, a liquid product having a higher Si content per unit weight can be obtained. However, there has been a problem such that it is difficult to control the reaction for the preparation of this polymethoxysiloxane, the obtained product is susceptible to a property change or gelation, or the monomer is highly toxic and if remained in the product, it is likely to create a safety problem in the use of the product. Under the circumstances, a polysiloxane oligomer represented by the following chemical formula has been proposed wherein the monomer content is reduced to a level of at most 1% to improve the storage stability and safety (Japanese Unexamined Patent Patent Publication No. 48454/1995):
These conventional polyalkoxysiloxane compounds have such a nature that when the hydrolytic condensation reaction of alkoxy groups is completely proceeded, they finally form inorganic silica as shown in the following reaction formulas.
Hydrolytic
reaction
&IndentingNewLine;
≡
SiOR
+
H
2
O
→
≡
SiOH
+
ROH
Condensation
reaction
≡
SiOH
+
≡
SiOR
→
≡
SiOSi
≡
+
ROH
≡
SiOH
+
≡
SiOH
→
≡
SiOSi
≡
+
H
2
O
Si
(
OR
)
4
+
2
H
2
O
→
SiO
2
+
4
ROH
Generally, the smaller the carbon number of alkoxy groups, the higher the activity, and the quicker the hydrolytic condensation reaction. Accordingly, it is considered that as compared with a polyethoxysiloxane wherein the alkoxy groups are ethoxy groups, a polymethoxysiloxane wherein the alkoxy groups are methoxy groups, is rich in the reactivity, whereby formation of silica as an inorganic substance is quick, and the performance of the properties is remarkable.
Utilizing such a nature of the polymethoxysiloxane, an attempt has been made to use it alone or in combination with an organic component such as an organic polymer for an application to e.g. a hard coat, an external wall coating, a material for a sand mold for casting or an adhesive to improve e.g. scuff resistance, stain resistance or adhesiveness.
Liquid polymethoxysiloxanes so far available all had a Si content as SiO
2
of not higher than 53 wt %. In order to increase the Si content, it is necessary to increase the degree of hydrolysis of the alkoxy groups of the polymethoxysiloxane to obtain a highly condensed product. However, synthesis of a highly condensed product has a problem such that silanol groups are likely to remain, whereby completion of the reaction is difficult, and the reaction gradually proceeds during the storage of the product to form a three dimensional structure, whereby the product tends to be geled. Accordingly, it has been difficult to obtain on an industrial scale a liquid polyalkoxysiloxane having a high silica content and being excellent in the storage stability without change with time.
Further, conventional polymethoxysiloxanes usually have a low flash point which is usually from 30 to 40° C. and thus are designated as dangerous goods in class 4-2. As a polymethoxypolysiloxane having a high flash point, “MKC silicate MS51” manufactured by Mitsubishi Chemical Corporation, is available, but even with this product, the flash point is at a level of 126° C.
In order to solve such problems, it has been desired to develop a liquid polyalkoxysiloxane which is a highly condensed product having the degree of polymerization increased over conventional polyalkoxysiloxanes and which has a high Si content and a high flash point.
Under these circumstances, the present inventors have conducted extensive studies and as a result, have succeeded in obtaining a novel polyalkoxysiloxane which is a highly condensed product having a high degree of polymerization and which has a high Si content and a high flash point and yet is capable of being present stably in a liquid state, as compared with conventional polyalkoxysiloxanes. The present invention has been accomplished on the basis of this discovery.
Namely, the present invention provides:
(1) A polyalkoxysiloxane of the following rational formula:
SiO
a
(OR)
b
(OH)
c
wherein R is a C
1-4
alkyl group, preferably a methyl group or an ethyl group, a=0.86 to 1.30, b=2.18 to 1.30, and c≦0.10;
(2) A polyalkoxysiloxane having a flash point of at least 130° C.;
(3) A polyalkoxysiloxane having a silica-converted concentration of at least 53 wt %;
(4) A polyalkoxysiloxane having a weight average molecular weight of from 600 to 3,000, a molecular weight distribution within ranges of Mw/Mn=1.4 to 2.7 and Mz/Mw=1.5 to 4.0, and a viscosity at 25° C. of from 10 to 1,000 cp;
(5) The polyalkoxysiloxane according to any one of (1) to (4), wherein the content of tetraalkoxysilane monomer is at most 0.5 wt %;
(6) The polyalkoxysiloxane according to any one of (1) to (5), wherein the content of an alcohol is at most 0.5 wt %;
(7) A process for producing the polyalkoxysiloxane according to any one of (1) to (6), which comprises reacting tetraalkoxysilane with from 0.80 to 1.30 mol times thereto of water for hydrolytic condensation under reflux, then distilling off an alcohol formed by the hydrolytic condensation and a solvent for reaction if used, at the boiling point, and then further distilling off components fractionated at from 120 to 200° C.
(8) A silicon-containing composition or the like, which comprises the polyalkoxysiloxane according to any one of (1) to (6) and an organic compound capable of condensing therewith.
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Derwent Publications, 95-126210/199517, JP 7048454, Feb. 21, 1995.
Patent Abstracts of Japan, vol. 95, No. 5, Jun. 30, 1995, JP 07 048454, Feb. 21, 1995.
Endo Hozumi
Kato Hanako
Katsumata Haruo
Sawai Takeshi
Takazawa Akihiro
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Shaver Paul F.
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