Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-02-02
2004-01-13
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S038000, C526S279000, C106S287110
Reexamination Certificate
active
06677047
ABSTRACT:
This invention relates to coating compositions for forming mar and weather-resistant protective coatings on plastic substrates, typically polycarbonate resin substrates, a method for the surface protection of plastic substrates using the coating compositions, and coated articles having coatings thereof.
BACKGROUND OF THE INVENTION
As glazing substitutes, shatterproof or highly shatter resistant transparent materials have been widely utilized for these decades. For example, plastic substrates, especially polycarbonate resins have superior transparency, impact resistance and heat resistance and are currently used as structural members instead of glass in a variety of applications including building and vehicle windows and instrument covers.
The polycarbonate resins, however, are inferior to glass in surface properties such as mar resistance and weather resistance. It is desired to improve the surface properties of polycarbonate resin parts. Nowadays, polycarbonate resin parts for use as vehicle windows and acoustic barrier walls along highways are required to withstand more than 10 years of weathering.
Known means for improving the weather resistance of polycarbonate resin parts include the lamination of a weather resistant acrylic resin film on the surface of a polycarbonate resin substrate and the formation of a ultraviolet absorber-containing resin layer on the resin surface, for example, by co-extrusion.
For improving the mar resistance of polycarbonate resin parts, it is known to coat thermosetting resins such as polyorganosiloxanes and melamine resins and to coat photo-curable resins such as polyfunctional acrylic resins.
As to the manufacture of transparent articles having both weather resistance and mar resistance, JP-A 56-92059 and JP-A 1-149878 disclose ultraviolet-absorbing transparent substrates having a primer layer loaded with a large amount of UV absorber added and a protective coating of colloidal silica-containing polysiloxane paint overlying the primer layer.
However, several problems arise with this approach. The addition of a large amount of UV absorber can adversely affect the adhesion to the substrate. During heat curing step, the UV absorber can volatilize off. On outdoor use over a long period of time, the UV absorber will gradually bleed out, causing whitening. From the mar resistance standpoint, it is impossible to add a large amount of UV absorber to the protective coating of colloidal silica-containing polysiloxane.
From these considerations, it was also attempted to fix a UV absorber by silyl modification. For example, JP-A 57-21476 discloses alkylcarbamyl addition products of alkoxysilyl or alkanoylsilyl. Also U.S. Pat. Nos. 4,316,033 and 4,349,602 disclose silyl addition products obtained by reacting benzotriazole compounds with halogenated allyl compounds in the presence of bases. These methods, however, involve complex steps and are uneconomical.
Further, in JP-A 9-286912, the reaction product of a (meth)acrylic acid derivative of benzotriazole with an amino group-containing silane compound is added to a room temperature curable composition for the purpose of imparting weather resistance. In Japanese Patent Nos. 2,885,669, 2,885,671, and 2,885,672, a silyl-modified UV absorber in the form of a reaction product resulting from addition reaction between a benzotriazole containing a polymerizable vinyl group and a silane or silicone compound containing a Si—H group is used in cosmetic compositions as the sunscreen agent.
These silyl-modified UV absorbers are advantageous in that because of the inclusion of alkoxysilyl groups which undergo condensation reaction during the heat curing step, the absorbers are fixed within the coating during the heat curing step so that the absorbers might not bleed out. Heretofore, coating compositions having such silyl-modified UV absorbers added thereto and capable of forming mar and weather-resistant coatings have not been proposed.
It is also known from JP-A 6-299132, 7-90184 and 10-25434 that a copolymer of a benzotriazole based UV absorbing vinyl monomer or a benzophenone based UV absorbing vinyl monomer with another vinyl monomer copolymerizable therewith is used in tackifier compositions, light and chemical-resistant synthetic resins, and powder paint resins for the purpose of improving weather resistance. However, the use of such UV absorbing copolymers in a primer or undercoat layer is unknown. Undesirably, the use of such UV absorbing copolymers adversely affects the adhesion to the substrate and to the protective coating of colloidal silica-containing polysiloxane paint to be applied on the primer layer.
Moreover, it is known from JP-A 8-151415 that a mixture of a benzotriazole based UV absorbing vinyl monomer or a benzophenone based UV absorbing vinyl monomer and another vinyl monomer copolymerizable therewith is used in coating compositions which are effective for forming protective coatings on surfaces of synthetic resins. Since these protective coatings are based on vinyl polymers, their mar resistance is limited.
SUMMARY OF THE INVENTION
An object of the invention is to provide a coating composition and method for forming a protective coating having improved mar and weather resistance. Another object is to provide a coated article having a mar and weather-resistant coating.
The inventors have found that the reaction product of a benzotriazole compound having a polymerizable vinyl group and a hydroxyl group with a silane compound and/or a (partial) hydrolyzate thereof and preferably the reaction product of a compound of the general formula (A) with an amino group-containing organoxysilane of the general formula (B) and/or a (partial) hydrolyzate thereof becomes an effective component in a coating composition.
Herein R
1
and R
2
each are hydrogen, a halogen atom or alkyl group of 1 to 10 carbon atoms, R
3
is a substituted or unsubstituted divalent hydrocarbon group of 1 to 18 carbon atoms, R
4
is hydrogen or an alkyl group of 1 to 4 carbon atoms, n is an integer of 0 to 2, and m is an integer of 1 to 3.
(R
5
HN—R
6
)
p
—SiR
7
q
(OR
8
)
4−p−q
(B)
Herein R
5
is hydrogen or an alkyl group of 1 to 15 carbon atoms, R
6
is a divalent hydrocarbon group of 1 to 15 carbon atoms or an amino group-containing divalent hydrocarbon group of 1 to 15 carbon atoms, R
7
is an alkyl group or aryl group of 1 to 10 carbon atoms, R
8
is hydrogen or a monovalent organic group of 1 to 10 carbon atoms, p is equal to 1 or 2, q is equal to 0 or 1, and p+q is equal to 1 or 2.
Studying a coating composition for improving the mar and weather resistance of molded parts of thermoplastic resins such as polycarbonate, the inventors have discovered that a silyl-modified benzotriazole compound is so compatible with other components in the coating composition due to the effect of silyl groups that the silyl-modified benzotriazole compound may be added in larger amounts, as compared with unmodified benzotriazole compounds. The silyl-modified benzotriazole compound, even when added in large amounts, does not exacerbate the adhesion to the substrate or to the primer layer.
It has been found that outstanding weather resistance is established because the UV absorber can be loaded in large amounts and does not bleed out due to the fixation effect of silyl groups.
Also the inventors have found that the above-described problems can be overcome by a primer coating composition using an organic copolymer comprising (A) a benzotriazole base UV absorbing vinyl monomer, (B) a vinyl monomer containing an alkoxysilyl group, and (C) another monomer copolymerizable therewith, the vinyl monomer containing an alkoxysilyl group accounting for 0.1 to 50% by weight of the copolymer. Preferably an acrylic monomer having a cyclic hindered amine base photo-stabilizing group is used as the other monomer (C) in an amount of 0.1 to 10% by weight of the copolymer. The primer coating composition may further contain, per 100 parts by weight of the organic copolymer, 0.1 to 50 parts by weight a compound containing a nitrogen atom and a
Higuchi Koichi
Kato Yoshifumi
Komori Takashi
Kudo Muneo
Matsumura Kazuyuki
Birch & Stewart Kolasch & Birch, LLP
Moore Margaret G.
Shin-Etsu Chemical Co. , Ltd.
LandOfFree
Coating composition, coating method, and coated article 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 composition, coating method, and coated article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating composition, coating method, and coated article will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3212388