Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-08-07
2003-08-12
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S020000, C528S033000, C528S034000, C525S474000, C525S477000, C556S450000, C556S459000, C556S463000, C556S465000, C556S466000, C556S467000, C428S447000
Reexamination Certificate
active
06605683
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing a solution of a silicone oligomer and a film of an organopolysiloxane formed from the solution. More particularly, the present invention relates to a process for producing a solution of a silicone oligomer which exhibits excellent storage stability in high concentrations and contains small or no amounts of acid or base components by hydrolyzing and polycondensing an alkoxysilane in the presence of a self-catalyst and a film of an organopolysiloxane which is formed from the above solution and has excellent physical properties.
BACKGROUND ART
Bulk materials, coating films and self-sustained films having excellent chemical durability such as weatherability, resistance against water and other chemicals and excellent mechanical properties such as hardness etc. are necessary, and preparation of silicone oligomers from organoalkoxysilanes has been actively studied for those purposes. However, since organoalkoxysilanes are insoluble in water which must be used in hydrolysis, organoalkoxysilanes are dissolved in hydrophilic organic solvents such as alcohols etc. to prepare a homogeneous solution and hydrolysis is conducted using the prepared homogeneous solution (The Science of the Sol-Gel Process, by SUMIO SAKKA, published by AGUNE SHOHU Co., Ltd.). It is also proposed that water be added slowly so that a rapid reaction does not take place.
To improve mechanical properties of films of organopolysiloxanes, various processes for forming a composite with silica sol or alumina sol have been proposed. For example, in Japanese Patent Application Laid-Open No. Showa 63(1988)-117074, a coating composition containing a polycondensate of organotrialkoxysilane, colloidal silica, water and a hydrophilic organic solvent is proposed as a coating composition for forming a film having a high hardness and other excellent physical properties on the surface of metals, ceramics and glasses. In Japanese Patent Application Laid-Open No. Showa 63(1988)-137972, a coating composition containing a polycondensate of organotrialkoxysilane, colloidal silica, water, a hydrophilic organic solvent and a heterocyclic compound having 2 or 3 nitrogen atoms or an aluminum alkoxide is proposed. In Japanese Patent Application Laid-Open No. Showa 63(1988)-168470, a coating composition containing a polycondensate of organotrialkoxysilane, colloidal silica, water, a hydrophilic organic solvent and a surfactant having fluorine is proposed. However, these coating compositions have small solid contents.
In Japanese Patent Application Laid-Open No. Showa 62(1987)-289279, as a process for forming a transparent coating film having excellent hardness, heat resistance, resistance against water and corrosion resistance on the surface of metals, cements, glasses, ceramics, plastics, papers and fibers, a method comprising coating a substrate with a composition containing (a) a product of hydrolysis or partial condensation of organotrialkoxysilane, (b) colloidal silica dispersed in a lower aliphatic alcohol and (c) ethylene glycol or a derivative thereof and heating the coated substrate is proposed. However, also in this method, the composition has a small solid content.
As the catalyst for preparing silicone oligomers, in general, an inorganic acid or an organic acid is used. In Japanese Patent Application Laid-Open No. Heisei 8(1996)-165114, the present inventors proposed a process comprising reacting a methyltrialkoxysilane with water in the presence of a metal chelate compound which is soluble in the methyltrialkoxysilane and aging the obtained reaction product to form a gel as the process for easily producing a transparent bulk material of silica gel which has excellent mechanical properties, chemical durability and heat stability and is useful for the host material being doped with an optically functional organic compounds. In this process, it is preferable that pH immediately after preparation of the reaction solution is adjusted to 1 to 7. However, when the product is used as a coating fluid in a condition such that a great amount of an acid is left remaining in the solution, there is the possibility that, in the case of some types of the substrate, the substrate reacts with the acid and a problem arises with respect to the adhesive strength at the interface of the coating film and the substrate. Moreover, a solution of a high concentration tends to gel, since the acid in the coating fluid gradually promotes the reaction. To overcome these problems, it is necessary that a great amount of an organic solvent be used to suppress the formation of a gel. In Japanese Patent Application Laid-Open No. Heisei 10(1998)-298289, as the process for producing with stability a siloxane polymer having an intermediate degree of condensation which is advantageously used for producing sheets, bulk materials and coating materials having heat resistance, an electrically insulating property and excellent transparency, a process comprising hydrolyzing and condensing alkoxysilane in the presence of an acid catalyst and then removing the acid catalyst with an anion exchange resin containing no water is proposed. However, this process has a problem in that the process is complicated.
Therefore, a process for producing a silicone oligomer efficiently without adding an inorganic acid or an organic acid and producing a coating fluid exhibiting excellent storage stability has been desired.
The present invention has an object to provide a process for producing a solution of a silicone oligomer which exhibits excellent storage stability in high concentrations and contains small or no amounts of acid or base components by hydrolyzing and polycondensing an alkoxysilane and a film of an organopolysiloxane which is formed from the above solution and has excellent physical properties.
DISCLOSURE OF THE INVENTION
As the result of extensive studies by the present inventors to achieve the above object, it was found that a solution comprising a silicone oligomer which exhibited excellent storage stability in high concentrations could be obtained by adding to an alkoxysilane, as the self-catalyst, a solution comprising a silicon compound soluble in hydrophilic organic solvents which was obtained by hydrolyzing and polycondensing an alkoxysilane and hydrolyzing and polycondensing the alkoxysilane. The present invention has been completed based on this knowledge.
The present invention provides:
(1) A process for producing a solution of a silicone oligomer which comprises:
adding to an alkoxysilane, as a self-catalyst, a solution comprising a silicon compound which is soluble in hydrophilic organic solvents and has an average structural unit represented by R
1
n
SiO
x/2
(OH)
y
(OR
2
)
z
, wherein R
1
represents an alkyl group having 1 to 3 carbon atoms, vinyl group or phenyl group, a plurality of R
1
may represent a same group or different groups, R
2
represents an alkyl group having 1 to 3 carbon atoms, a plurality of R
2
may represent a same group or different groups and n, x, y and z represent numbers satisfying relations: 0≦n<3, 0<x<4, y>0, z≧0 and y+z=4−n−x,
and hydrolyzing and polycondensing the alkoxysilane;
(2) A process for producing a solution of a silicone oligomer described in (1), wherein a metal chelate compound is added as a catalyst;
(3) A process for producing a solution of a silicone oligomer described in (1), wherein the silicone oligomer comprised in the solution of a silicone oligomer has an average structural unit represented by R
3
a
SiO
b/2
(OH)
c
(OR
4
)
d
, wherein R
3
represents an alkyl group having 1 to 3 carbon atoms, vinyl group or phenyl group, a plurality of R
3
may represent a same group or different groups, R
4
represents an alkyl group having 1 to 3 carbon atoms, a plurality of R
4
may represent a same group or different groups and a, b, c and d represent numbers satisfying relations: 0.8≦a≦1.7, 2<b<3.2, c>0, d>0 and c+d=4−a−b;
(4) A process for producing a solution of a sil
Dawson Robert
Nihon Yamamura Glass Co., LTD
Robertson Jeffrey B.
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