Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-06-05
2004-04-06
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C525S100000
Reexamination Certificate
active
06716946
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to acrylic silicone coatings.
2. Prior Art
Acrylic silicone coatings prepared by the solution polymerization of a silicon macromer having a double bond on one end of the molecule with an acrylic monomer are already known as materials which form high-lubricity coats when applied to a substrate. To enhance the strength and heat resistance of the applied coat, it is common practice to introduce a hydroxyl group onto the molecule by using a compound such as hydroxyethyl methacrylate as part of the acrylic monomer and to use an isocyanate to crosslink the resulting copolymer. However, environmental concerns in recent years have created a strong desire for safe crosslinking systems that can be used in place of isocyanate crosslinking.
The practice of copolymerizing a compound having both a hydrolyzable silyl group and a double bond with an acrylic monomer, then subjecting the resulting copolymer to silane crosslinking is also familiar to the art. Yet, when silane crosslinking is carried out on a silicone macromer-containing copolymer, coats formed from the resulting coating have improved heat resistance, but lack toughness. Moreover, although such coats have a good adhesion to inorganic substrates, their adhesion to organic substrates is inadequate. For these reasons, applied coats of a quality comparable to that of the above-described isocyanate-crosslinked copolymer coats have not previously been achieved.
A desire has thus been felt for the development of acrylic silicone coatings which provide coats having a lubricity, heat resistance, adhesion and toughness comparable with those of isocyanate-crosslinked copolymer coats.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide acrylic silicone coatings which are capable of forming coats endowed with excellent lubricity, heat resistance, weatherability, pigment dispersibility, adhesion and toughness.
We have arrived at a useful copolymer by copolymerizing (1) a silicone macromer having a double bond at one end of the molecule, (2) an unsaturated monomer having on the molecule both a carboxyl or acid anhydride group and a double bond, (3) an unsaturated silane monomer having on the molecule both a hydrolyzable silyl group and a double bond, (4) an unsaturated monomer having on the molecule both an amide, imide, carbamate or urea group and a double bond and, optionally, (5) another copolymerizable unsaturated monomer. We have discovered in particular that adhesion to the substrate is improved by copolymerizing a carboxyl group-bearing monomer and that, when a monomer containing on the molecule both an amide, imide, carbamate or urea group and a double bond is copolymerized, the coat obtained after silane crosslinking is tough and is of a quality comparable to that of isocyanate-crosslinked copolymer coats.
Accordingly, the invention provides a coating composition comprising (A) a copolymer prepared by copolymerizing above constituents (1) to (4) and optional constituent (5), in combination with (B) a crosslinking catalyst.
DETAILED DESCRIPTION OF THE INVENTION
As noted above, a primary component of the inventive coating is a copolymer (resin) prepared by copolymerizing (1) a silicone macromer having a double bond at one end of the molecule, (2) an unsaturated monomer having on the molecule both a carboxyl or acid anhydride group and a double bond, (3) an unsaturated silane monomer having on the molecule both a hydrolyzable silyl group and a double bond, (4) an unsaturated monomer having on the molecule both an amide, imide, carbamate or urea group and a double bond and, optionally, (5) another copolymerizable unsaturated monomer.
Constituent (1) used in preparing the copolymer is a silicone macromer which has a double bond at one end of the molecule and preferably has the following structural formula.
In the formula, R
1
is a monovalent hydrocarbon group of 1 to 8 carbons, such as an alkyl (e.g., methyl) or aryl (e.g., phenyl). Methyl is especially preferred. Like R
1
, R
2
is also a monovalent hydrocarbon group of 1 to 8 carbons, although an alkyl group of 1 to 6 carbons is preferred. X is an organic group having an aliphatic unsaturated double bond, examples of which include acryloxypropyl, methacryloxypropyl and styryl groups. The letter n is a number from 3 to 300, and preferably from 20 to 200. If the letter n is too small, the coat obtained by applying the coating to a substrate has inadequate lubricity; on the other hand, if n is too large, the coat has diminished strength.
Such silicone macromers which include as a functional group a methacryl or methacryloylpropyl group and are thus suitable for use as constituent (1) are commercially sold and readily available.
Constituent (2) is an unsaturated monomer having on the molecule both a carboxyl or acid anhydride group and an aliphatic double bond. Illustrative examples include methacrylic acid, acrylic acid, (meth)acryloyloxyethylphthalic acid, (meth)acryloyloxyethylsuccinic acid, alkyl esters of maleic acid, alkyl esters of fumaric acid, maleic anhydride and fumaric anhydride. Of these, methacrylic acid is especially preferred for achieving good heat resistance because polymers thereof have the highest glass transition point.
Constituent (3) is an unsaturated silane monomer having on the molecule both a hydrolyzable silyl group and an aliphatic double bond. Preferred examples include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, (meth)acryloxypropyltrimethoxysilane, (meth)acryloxypropyltriethoxysilane, (meth)acryloxypropylmethyldimethoxysilane, (meth)acryloxypropylmethyldiethoxysilane, styryltrimethoxysilane, styryltriethoxysilane, styrylmethyldimethoxysilane and styrylmethyldiethoxysilane.
Constituent (4) an unsaturated monomer having on the molecule both an amide, imide, carbamate or urea group and an aliphatic double bond. Illustrative examples include methyl (meth)acrylamide, ethyl (meth)acrylamide, propyl (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, dipropyl (meth)acrylamide, N-(meth)acryloyloxyethyl-phthalimide, N-(meth)acryloyloxyethyl-succinimide, N-(meth)acryloyloxyethyl-hexahydrophthalimide, the reaction products of isocyanate ethyl methacrylate with a lower alcohol or phenol, and the reaction products of isocyanate ethyl methacrylate with an aliphatic or aromatic amine. A monomer having on the molecule both an imide group and an aliphatic double bond is especially preferred.
Optional constituent (5) may be any radical polymerizable monomer that is copolymerizable with above constituents (1) to (4). Suitable examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate and styrene.
The silicone macromer serving as constituent (1) is used to confer the applied coat with lubricity. It is used in an amount of preferably 5 to 50 parts by weight, and most preferably 10 to 30 parts by weight, per 100 parts by weight of the resin (copolymer) solids. At less than 5 parts by weight, the coat may have insufficient lubricity, whereas at more than 50 parts by weight, the coat strength may decline to an unacceptable level.
The unsaturated monomer having on the molecule both a carboxyl or acid anhydride group and a double bond that serves as constituent (2) is used to impart the resin with adhesive properties. In addition, it also has a pigment dispersibility enhancing effect. This unsaturated monomer is used in an amount of preferably 2 to 30 parts by weight, and most preferably 5 to 15 parts by weight, per 100 parts by weight of the resin solids. At less than 2 parts by weight, adhesion by the resin to substrates tends to be inadequate. On the other hand, at more than 30 parts by weight, phase separation with the silicone macromer tends to arise during polymerization. Methacrylic acid in particu
Ichinohe Shoji
Miyadai Shinji
Birch & Stewart Kolasch & Birch, LLP
Moore Margaret G.
Shin-Etsu Chemical Co. , Ltd.
LandOfFree
Coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3235225