Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-09-14
2003-08-12
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S015000, C528S014000, C528S018000, C528S017000, C528S021000, C528S031000, C528S032000
Reexamination Certificate
active
06605360
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a polyorganosiloxane compound characterized by containing in the molecule both a silicone oil chain structure and a silicone resin structure having an alkoxyl group and/or a silanol group, and also relates to a coating composition making use of this compound. More particularly, this invention relates to a novel polyorganosiloxane compound which is compatible with silicone resins, and a coating composition making use of this compound.
2. Description of the Prior Art
Nowadays, silicone resins are widely used in various fields because of their superior properties in respect of water repellency, heat resistance, weatherability, freeze resistance, electrical insulation properties, chemical resistance and safety to the human body.
Among them, silicone resins having a three-dimensional cross-linked structure composed chiefly of SiO
2
units (Q units) and RSiO
1.5
units (T units; R is an organic group such as an alkyl group or a phenyl group) are widely used in coating materials and binders, using their curability. In particular, a liquid substance having an Si—OR group as a cross-linking group is, as disclosed in Japanese Patent No. 2137192, utilized as a chief ingredient of a solvent-free type coating material which is combustible and does not contain any organic solvent harmful to the human body. Also, there is an advantage that this Si—OR group is not required to be heated to cure because of its cross-linking reaction which proceeds by moisture in air and at room temperature and hence any coating materials making use of this substance as a chief ingredient can be applied in situ.
Such a Si—OR type silicone resin has strong points of good curability and high surface hardness because of its three-dimensional cross-linked structure. It, however, affords an insufficient flexibility to cause cracks in coating films in some cases. In order to improve this flexibility, a method has been employed in which diorganosiloxane (R
2
SiO) units (D units) are incorporated when the silicone resin is synthesized. In this case, however, the D units are incorporated in the structure at random, and hence there is a problem that, the D units must be added in a large quantity in order to impart the flexibility, so that the superior curability and surface hardness, the strong points of this silicone resin, may lower.
In addition, the D units are added to the silicone resin in the form of chain structure. Hence, in an attempt to add a silicone oil comprised of chain structure of D units, its addition may cause milkiness or repellency of coating films because of a poor compatibility of the silicone oil with the silicone resin. Thus, it can not be added as what is expected of itself.
A method of adding a silicone oil terminated with TEOS (Si(OEt)
4
) at both terminals of the molecular chain is also proposed (Polymeric Materials Science and Engineering, 1998, Vol.79, 192). In this case, too, its compatibility with silicone resins is not improved, and its addition causes milkiness or repellency of coating films.
It is also possible to improve the flexibility by adding to the silicone resin a resin other than silicone, such as acrylic resin or epoxy resin. However, these resins commonly have weatherability and so forth which are inferior to those of silicone, so that the resultant coating material has low weatherability and so forth.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a polyorganosiloxane compound having a specific structure, which is compatible with silicone resins.
Another object of the present invention is to provide a coating composition which utilizes this polyorganosiloxane compound and can obtain coatings improved in flexibility without lowering the properties inherent in silicone resins, such as curability, surface hardness and weatherability.
In order to achieve the above objects, the present inventors have made extensive studies and have accomplished the present invention.
More specifically, firstly, the present invention provides a polyorganosiloxane compound which contains in the molecule a silicone oil structure and a silicone resin structure having at least one of an alkoxyl group and a silanol group and is compatible with a silicone resin:
The compound is obtained by allowing the following polyorganosiloxane (a1) to react with the following polyorganosiloxane (a2) in the presence of a hydrosilylation catalyst.
(a1) A polyorganosiloxane represented by the average compositional formula (1):
R
1
a
R
2
b
Si(OR
3
)
c
O
(4−a−b−c)/2
(1)
wherein R
1
is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group; R
2
is a group containing an aliphatic unsaturated double bond; R
3
is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage; and a, b and c are numbers that satisfy the following relation: 0≦a<1.5, 0.01≦b≦1, 0.5≦a+b≦1.8, 0.01≦c≦2.5 and 1≦a+b+c≦3; and having at least one aliphatic unsaturated double bond in the molecule.
(a2) A polyorganosiloxane represented by the general formula (2):
wherein R
1
is as defined in respect of the above formula (1), and n is a number of from 0 to 1,000.
Secondly, the present invention provides a coating composition comprising:
(&agr;) from 0.1 part by weight to 100 parts by weight of the polyorganosiloxane compound described above;
(&bgr;) from 99.9 parts by weight to 0 part by weight of a silane compound and/or silicone resin containing an R
3
O—Si group where R
3
is as defined above;
provided that the total of components (&agr;) and (&bgr;) comes to 100 parts by weight; and
(&ggr;) from 0.01 part by weight to 50 parts by weight of a curing catalyst, based on 100 parts by weight of the total of the components (&agr;) and (&bgr;).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described below in detail.
Polyorganosiloxane Compound
The polyorganosiloxane compound of the present invention which contains in the molecule a silicone oil structure (straight-chain siloxane structure) and a silicone resin structure (branched siloxane structure) having at least one of an alkoxyl group and a silanol group and is compatible with a silicone resin (comprised of a branched siloxane structure). This polyorganosiloxane compound may be produced by a process including, but not particularly limited to, the following two processes.
The first process utilizes the reaction of hydrosilylation of Si—H groups to aliphatic unsaturated double bonds, and comprises allowing a polyorganosiloxane (a1) represented by the following average compositional formula (1), with a polyorganosiloxane (a2) represented by the following general formula (2).
R
1
a
R
2
b
Si(OR
3
)
c
O
(4−a−b−c)/2
(1)
wherein R
1
is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group; R
2
is a group containing an aliphatic unsaturated double bond; R
3
is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage; and a, b and c are numbers that satisfy the following relation: 0≦a<1.5, 0.01≦b≦1, 0.5≦a+b≦1.8, 0.01≦c≦2.5 and 1≦a+b+c≦3; and having at least one aliphatic unsaturated double bond in the molecule.
wherein R
1
is as defined in respect of the above formula (1), and n is a number of from 0 to 1,000.
Polyorganosiloxane (a1):
This polyorganosiloxane (a1) is chiefly composed of R
1
SiX
3
and R
2
SiX
3
, and is obtained using as a starting material at least one of SiX
4
, R
1
2
SiX
2
, R
1
3
SiX, R
2
2
SiX
2
and R
2
3
SiX [where R
1
and R
2
are as defined in respect of the formula (1); X represents in the present specification
Itagaki Akinari
Kizaki Hiroaki
Yamaya Masaaki
Moore Margaret G.
Shin-Etsu Chemical Co. , Ltd.
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