Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
1996-07-11
2002-05-14
Moore, Margaret G. (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C528S015000, C528S031000, C528S032000, C008SDIG001, C008S115600
Reexamination Certificate
active
06387451
ABSTRACT:
This invention is concerned with curable coating compositions which adhere well to a variety of substrates.
Coating compositions are known which cure by a hydrosily-lation reaction without producing undesirable by-products. However, the said coating compositions do not adhere well to certain substrates, for example, synthetic textiles.
Priming a substrate with a primer composition prior to applying a curable coating composition is an effective solution. Primers are adequate to provide strong adhesion between a cured coating composition and a substrate. However, this solution suffers from the disadvantage that the coating process requires at least two steps, one step of which involves waiting for the applied primer composition to dry.
Self-adhering coating compositions are known which cure by a hydrosilylation reaction. They contain additives which aid adhesion to a variety of substrates, obviating the need for application of a primer composition prior to coating.
One example of a self-adhering coating composition is described in U.S. Pat. No. 4,087,585 wherein a coating composition curable by a hydrosilylation reaction is disclosed which comprises an adhesion promoting additive consisting essentially of a polyorganosiloxane containing a silicon bonded hydroxyl group, a silicon-bonded vinyl group and an epoxy silane.
U.S. Pat. No. 4,754,013 discloses a self-adhering coating composition curable by a hydrosilylation reaction which comprises an adhesion promoting additive consisting essentially of at least one hydroxyl terminated polydiorganosiloxane, at least one silane containing at least three alkoxy groups per molecule and a titanium compound as a catalyst.
The prior art compositions cited above will cure to form elastomeric materials which adhere well to inorganic substrates such as metal or glass and plastic materials in the case of U.S. Pat. No. 4,754,013 and inorganic substrates such as metals or glass in the case of U.S. Pat. No. 4,087,585, however, the onset of adhesion of these compositions to substrates is rather slow.
EP 596,534 discloses a curable polyorganosiloxane composition which exhibits initial adhesion to various substrates comprising a certain polyorganosiloxane composition which can be cured by addition reaction and a certain amount of an organosilicon compound comprising 1 to 20 mole % siloxane units with the general formula R
4
e
R
5
1−e
SiO
3/2
; 20 to 80 mole % siloxane units with the general formula R
4
f
R
5
g
R
6
h
SiO
2/2
, and 20 to 80 mole % units with the general formula R
4
i
R
5
j
R
6
k
SiO
1/2
, wherein R
4
represents an alkenyl group, R
5
is a group selected from alkyl groups, alkoxyalkyl groups and epoxy-containing organic groups with the proviso that at least one of the preceding siloxane units in a molecule contains an epoxy-containing organic group as R
5
; R
6
represents an alkoxy group having 1 to 4 carbon atoms, e, f, h and i are 0 or 1, g is an integer with a value of 0 to 2, f+g+h is 2, j is an integer with a value of 0 to 3, k is an integer with a value of 0 to 2, i+j+k is 3, with the proviso that R
4
comprises at least 2 mole % of the total silicon-bonded organic groups in the organosilicon compound and R
6
comprises at least 5 mole % of the total silicon-bonded organic groups in the organosilicon compound. However, the use of such complex polyorganosiloxane compounds in the curable composition is not desirable, as these materials are difficult and expensive to make. In addition, it is taught in EP 596,534 that to achieve the required initial adhesion, the compositions need to be cured for one hour in a hot air circulation oven at 150° C. There is a desire to reduce the time required to achieve initial adhesion of curable organopolysiloxane compositions preferably without the need to use complex materials.
It is an important criterion in the industrial manufacture of certain coated substrates, for example textiles, that the coating process and subsequent adhesive bond between substrate and cured coating is achieved as rapidly as possible to meet ever increasing demands on manufacturing output. There is a need therefore to provide a curable coating composition which may be coated easily onto a suitable substrate and which is able to cure rapidly and achieve adhesion to the suitable substrate quicker than heretofore possible without adversely affecting the physical properties of the cured material.
We have now found that we can provide curable coating compositions which may easily be coated onto a suitable substrate and cure thereon with concomitant rapid onset of adhesion by using certain compounds as adhesion promoting additives.
Therefore, in a first embodiment of this invention, there is provided a curable coating composition comprising (A) a composition curable by a hydrosilylation reaction, (B) an inhibitor of said hydrosilylation reaction, (C) a silicone resin and (D) an adhesion promoting additive comprising (i) an organosilicon compound having epoxy and alkoxy functionalities, (ii) an organotitanium compound (iii) an alkenyl functional silanol-terminated polyorganosiloxane and (iv) a metal chelate compound.
In a second embodiment of the invention, there is provided a curable coating composition comprising (i) a composition curable by a hydrosilylation reaction, (ii) an inhibitor of said hydrosilylation reaction, (iii) an adhesion promoting additive which is a reaction product of an epoxy-substituted alkoxysilane and an alkenyl-functional silanol-terminated organopolysiloxane and (iv) a metal chelate compound.
Curable coating compositions according to the invention are possessed of numerous advantages. Such coating compositions are able to cure and at the same time rapidly develop an adhesive bond to a variety of substrates, in particular certain synthetic textiles, for example polyesters, and polyamides, e.g. nylon 66. Thereafter the cured coating compositions exhibit good resistance to washing and the adhesive bond to a suitable substrate is still acceptable after numerous wash cycles in hot aqueous detergent solutions. Component (A) of the first embodiment of the curable coating composition according to the invention is a composition curable by a hydrosilylation reaction. Operative compositions are those well known in the art which comprise a polyorganosiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogensiloxane having at least three silicon-bonded hydrogen atoms per molecule and a noble metal catalyst. Organopolysiloxanes having at least two silicon-bonded alkenyl groups per molecule are well known in the art and may vary from viscous materials to freely flowing liquids. It is preferred that at least some, preferably most of the organopolysiloxanes having silicon-bonded alkenyl groups have a viscosity of not greater than 100 Pa.s at 25° C., more preferably 20 to 60 Pa.s at 25° C. They may be homopolymers, copolymers or mixtures thereof which comprise units of the general formula R
a
R′
b
SiO
[4−a+b)]/2
wherein R is a monovalent hydrocarbon group, R′ is a monovalent unsaturated hydrocarbon group, a is 0, 1, 2 or 3 and b is 0 or 1 provided that a+b is not greater than 3. The organohydrogensiloxanes of component (A) contain curing agents for the hydrosilylation reaction and are well known in the art. They may vary from viscous materials to freely flowing liquids. Preferred materials have a viscosity of not greater than 500 Mpa.s at 25° C., more preferably 5 to 55 Mpa.s at 25° C.
They may be homopolymers, copolymers or mixtures thereof which comprise units of the general formula R
a
H
b
SiO
[4−(a+b]/2
wherein R, a and b are as hereinabove defined.
The component (A) also comprises a noble metal catalyst for the reaction of the aforementioned alkenyl substituted polyorganosiloxane with the organohydrogensiloxane. The noble metal catalyst may be a rhodium or platinum containing material. Platinum catalysts are preferred and may take any of the known forms, ranging from platinum deposited onto carriers
Collins Alan
Peeters Antoon
Cesare James L. De
Dow Corning Limited
McKellar Robert L.
Moore Margaret G.
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