Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-06-21
2001-07-03
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S262000, C524S588000, C427S387000, C428S447000, C106S287110, C106S287140
Reexamination Certificate
active
06255373
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a curable silicone resin composition. More specifically, this invention relates to a curable silicone resin composition capable of forming cured coating films with excellent water-repellent properties.
BACKGROUND OF THE INVENTION
Cured coating films with excellent water-repellent properties can be obtained by applying onto a substrate, a curable silicone resin composition (see Japanese Patent Publications Kokai Hei 3-244681, Hei 3-244996, and Hei 4-45181). The curable silicone resin consists of, at least, a silicone resin having a condensation-reactive group such as a silanol group, an oxime group or an alkoxy group bonded to a silicon atom, a fine inorganic powder, and an organic solvent. This composition is applied onto a substrate, and after the organic solvent is evaporated, a cross-linking reaction is caused by heating or due to absorption of moisture. However, coating films produced by curing these curable silicone resin compositions do not possess sufficient water-repellent properties.
Therefore, it is an object of this invention to provide a curable silicone resin composition capable of forming a cured coating film which possesses excellent water-repellent properties.
SUMMARY OF THE INVENTION
This invention relates to a curable silicone resin composition comprising (A)100 parts by weight of a silicone resin having a condensation-reactive group, (B) 1 to 100 parts by weight of a fine inorganic powder, (C) 0.5 to 50 parts by weight of a silazane compound; and (D) an arbitrary amount of an organic solvent.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a curable silicone resin composition comprising
(A) 100 parts by weight of a silicone resin having a condensation-reactive group,
(B) 1 to 100 parts by weight of a fine inorganic powder,
(C) 0.5 to 50 parts by weight of a silazane compound, and
(D) an organic solvent.
Component (A) is a silicone resin that has a condensation-reactive group. A preferred condensation-reactive group is represented by a hydroxyl group, an alkoxy group such as a methoxy group or an ethoxy group, or an oxime group, wherein the aforementioned condensation-reactive group is bonded to a silicon atom. It is recommended that the condensation-reactive group in component (A) is used in an amount of 0.05 to 5 wt. %.
Preferably component (A) comprises a silicone resin which has a condensation-reactive group bonded to a silicon atom and which comprises a siloxane unit represented by the formula RSiO
3/2
and a siloxane unit represented by the formula R
2
SiO
2/2
. Preferably, the silicone resin is expressed by the following average unit formula (RSiO
3/2
)
x
(R
2
SiO
2/2
)
y
(SiO
4/2
)
z
, wherein each R can be the same or different monovalent hydrocarbon groups having 1 to 10 carbon atoms. Examples of these groups are alkyl groups such as methyl, ethyl, or propyl; alkenyl groups such as vinyl, allyl, or butenyl; aryl groups such as phenyl or tolyl; or halogenated alkyl groups such as 3,3,3-trifluoropropyl. In the above formula, x has a value of 0.2 to 0.9, which shows (in mole fraction) the quantity of siloxane units in the molecule having the formula RSiO
3/2
; y has a value of 0.1 to 0.8, which shows (in mole fraction) the quantity of siloxane units in the molecule having the formula R
2
SiO
2/2
; and z has a value of 0 to 0.3, which shows (in mole fraction) the quantity of siloxane units in the molecule having the formula SiO
4/2
; and x+y+z is equal to 1.
Since the quantity of condensation-reactive groups in the aforementioned average unit formula is small, they are not shown in the description above. However, these groups have the following unit formula: XO
1/2
. In this formula, X shows groups with oxygen atoms removed from the aforementioned condensation reactive groups. The unit expressed by formula XO
1/2
shows that the silicone atoms in siloxane units of formula RSiO
3/2
, siloxane units of formula R
2
SiO
2/2
, or siloxane units of formula RSiO
4/2
are connected via oxygen. It is recommended that the units expressed by formula XO
1/2
be used in such a mole quantity that the amount of the condensation-reactive groups (shown as XO) be within the range of 0.05 to 5 wt. %. Examples of such a silicone resin are a methyl silicone resin, a methylphenyl silicone resin, and a methylvinyl silicone resin.
Component (B) is a fine inorganic powder. Component (B) can be a fine silica powder, fine calcium carbonate powder, fine magnesium carbonate powder, fine alumina powder, or fine mica powder. Fine silica and calcium carbonate powders are preferred. The smaller the diameter of grains in component (B), the better are water-repellent properties in the obtained cured coating film. Therefore, it is recommended that the diameter does not exceed 10 &mgr;m. The fine inorganic powder may be surface treated. For example, fine powdered fumed silica may be subjected to hydrophobic treatment with dimethyldichlorosilane or hexamethyldisilazane.
Preferably, component (B) is used in the curable silicone resin composition in an amount of 1 to 100 parts by weight, preferably 1 to 50 parts by weight, and more preferably, 5 to 50 against 100 parts by weight of component (A). If the content of component (B) exceeds the recommended range, the cured coating film obtained will tend to decrease in physical properties. On the other hand, if the content of component (B) is below the recommended range, water-repellent properties of the coating film will be impaired.
Component (C) is a silazane compound. Component (C) significantly improves water-repellent properties in the coating film obtained by curing the curable silicone resin composition of this invention. The silazane compound of component (C) can be represented by a silazane polymer, a cyclic silazane, or a hexaorganodisilazane. Most preferably, component (C) is a hexaorganodisilazane. Examples of hexaorganodisilazanes include hexamethyl disilazane, 1,3-dihexyl-tetramethyl disilazane, 1,3-di-t-butyl-tetramethyl disilazane, 1,3-di-n-butyl-tetramethyl disilazane, and 1,3-diphenyl-tetramethyl disilazane.
Preferably, component (C) is used in the curable silicone resin composition in an amount of 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight, against 100 parts by weight of component (A). If the content of component (C) exceeds the recommended range, the curable silicone resin composition will have a tendency to decrease in curability, and physical properties in the cured coating film will be impaired. On the other hand, if the content of component (C) is below the recommended range, water repellent properties of the coating film will be impaired.
Component (D) is an organic solvent. Component (D) is used for improving workability of the curable silicone resin composition. The organic solvent is exemplified by aromatic hydrocarbons such as toluene or xylene; aliphatic hydrocarbons such as hexane, heptane, or octane; ketones such as acetone or methyl- isobutyl ketone; or mixtures of the above solvents.
In the curable silicone resin composition, component (D) can be used in an arbitrary amount, which is selected with reference to viscosity of the curable silicone resin composition and the thickness of the coating film obtained after curing.
The curable silicone resin composition of the invention must contain at least components (A) through (D). However, they can be combined with other optional components, such as cross-linking agents and cross-linking accelerators.
Examples of the cross-linking agents include alkoxy silanes such as methyltrimethoxy silane, dimethyldimethoxy silane, vinyltrimethoxy silane, phenyltrimethoxy silane, diphenyldimethoxy silane, methyltriethoxy silane, dimethyl diethoxy silane, phenyl triethoxy silane, or diphenyl diethoxy silane or oxime silanes such as methyltris (methylethylketoxime) silane, dimethylbis (methylethylketoxime) silane, phenyltris (methylethylketoxime) silane, vinyltris (methylethylketoxime) silane, or diphenylbis (methylethylketoxime) silane. These cross-linking agents can be used individually
Akamatsu Shoji
Sasaki Motoshi
Dow Corning Toray Silicone Company, Ltd.
Moore Margaret G.
Troy Timothy J.
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