Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-09-28
2003-11-11
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S107000, C526S279000, C526S319000, C526S320000, C526S326000, C526S328000, C526S329700, C528S038000, C528S035000, C524S424000
Reexamination Certificate
active
06646048
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a primer composition. More particularly, the present invention relates to a primer composition that is excellent in storage stability so that it can retain excellent adhesion from the time after the coating of a primer until the coating of a sealant and that is excellent also in weatherability and that it can be advantageously used on glass or silicon hard coat, particularly when using a sealant for fixing glass of automobiles.
BACKGROUND ART
Usually, for bonding window glasses of an automobile, excellent initial adhesion, high bonding strength and bonding durability are required under various conditions such as low temperatures, high temperatures and high humidities. Furthermore, after the bonding of window glasses, the periphery of the window glass of an automobile directly contacts the open air and exposed to sunlight, so that it is very important that the bonding is excellent in weatherability (including weatherability to light, that is, resistance to light).
Sealants useful for bonding nonporous substrates such as glass typically include urethane base sealants. However, where a glass substrate is bonded to a metal using such a urethane base sealant (when a window glass is incorporated in the manufacture of automobiles and so forth), the repeated shear strength of the bonded substrate may sometimes fail to reach the desired safety guideline or structural guideline. Accordingly, in most car body assembly works, coating of a primer prior to the coating of a sealant is generally adopted in the case where the front glass and rear window are bonded to the body.
As such a primer, there has heretofore been used those primers that comprise a binder component (film-forming component) such as polyester polyurethane or acrylic resin and a silane coupling agent, polyisocyanate, carbon black or the like blended therein.
When urethane resin such as polyester polyurethane is used as the binder component, the quality is at high levels but there has been a problem that the weatherability and cost are ill-balanced. In particular, when a certain time elapsed after coating the primer, the isocyanate groups in the urethane resin react with the moisture in the open air so that the activity of the primer surface is deteriorated. As a result, the urethane resin has to be coated again in order to obtain a sufficient adhesion, thus causing the problem of poor workability.
The isocyanate based glass primer as described above caused another problem that it gives only insufficient adhesion to the resin glass with a silicone hard coat, and so forth.
To improve these problems, JP 10-060365 A discloses an example in which instead of the urethane based film forming component, a combination usage, a silicate oligomer component and an acrylic based resin component obtained by copolymerization of an acrylate monomer with a hydroxyl group- or alkoxysilyl group-containing acrylate monomer in a predetermined ratio in the co-presence of a silicate oligomer.
Also, JP 10-060216 A discloses an example in which an acrylic copolymer having a hydroxyl group, an alkoxysilyl group-containing acrylic copolymer having an epoxy group and a hydroxyl group, a curing catalyst and a hydrolyzable silicone compound are blended.
However, although the acrylic based film forming component improves the storage stability and weatherability, it gives rise to poor adhesion as compared with the primer that uses the isocyanate component.
Accordingly, there has been demanded a primer composition that is excellent in both storage stability and weatherability, has high retention of adhesion after the coating of the primer so that its workability can be improved, and ensures sufficient adhesion to resin glass with a silicone hard coat.
Therefore, an object of the present invention is to provide a primer composition that is excellent in storage stability, can retain excellent adhesion without losing the effect during the time from the coating of the primer to the coating of the sealant, and further has excellent weatherability. In particular, an object of the present invention is to provide a primer composition that can be advantageously used for glass or silicone hard coat of glass fixing sealant in an automobile.
DISCLOSURE OF THE INVENTION
According to the present invention, there is provided a primer composition characterized by comprising:
(A) 100 parts by weight of a reactive acrylic resin comprising a main chain composed of a copolymer of a methacrylate with an alkyl group having 1 or 2 carbon atoms and a methacrylate with an alkyl group having 4 to 10 carbon atoms in a weight ratio of 9:1 to 3:7 and a side chain having a group with a hydroxyl group and at least one aromatic ring at a ratio of 0.1 to 30% based on the degree of polymerization of the main chain;
(B) 100 to 500 parts by weight of a silane compound obtained by reaction of 2 to 3 moles in total of dialkoxyepoxysilane and trialkoxyepoxysilane per mole of an aminosilane having two amino groups, with the molar ratio of the above-mentioned dialkoxyepoxysilane to the trialkoxyepoxysilane being 3:7 to 9:1;
(C) 10 to 300 parts by weight of an epoxy resin of bisphenol A type having an epoxy equivalent of 1,000 to 2,000 g/eq.; and
(D) 100 to 500 parts by weight of carbon black.
Further, according to the present invention, there is provided a primer composition, characterized in that the reactive acrylic resin (A) further contains in the side chain thereof 10% or less, based on the degree of polymerization of the main chain, of a group having an alkoxysilyl group.
Still further, according to the present invention, there is provided a primer composition, characterized in that in said reactive acrylic resin (A), the main chain thereof comprises a copolymer composed of methyl methacrylate and butyl methacrylate.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the primer composition of the present invention will be described in detail. First, the components that constitute the primer composition of the present invention are illustrated.
(A) Reactive Acrylic Resin
The reactive acrylic resin used in the present invention is a reactive acrylic resin comprising a main chain composed of a copolymer of a methacrylate with an alkyl group having 1 or 2 carbon atoms and a methacrylate with an alkyl group having 4 to 10 carbon atoms in a weight ratio of 9:1 to 3:7 and a side chain having a group with a hydroxyl group and at least one aromatic ring.
In the main chain of the above-mentioned reactive acrylic resin, the methacrylate with an alkyl group having 1 or 2 carbon atoms includes methyl methacrylate and ethyl methacrylate and so forth, with methyl methacrylate being particularly preferred.
On the other hand, the methacrylate with an alkyl group having 4 to 10 carbon atoms includes n-butyl methacrylate (butyl methacrylate), isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate and so forth, with n-butyl methacrylate and isobutyl methacrylate being preferred since these are inexpensive.
The methacrylate with an alkyl group having 1 or 2 carbon atoms and the methacrylate with an alkyl group having 4 to 10 carbon atoms may be selected from among the above exemplified compounds, and may be used singly or two or more of them may be used in combination.
In the present invention, the above-mentioned two types of methacrylates are used as the monomers that constitute the main chain of the reactive acrylic resin. Use of monomers with alkyl groups with large carbon atom numbers gives high adhesion of the acrylic resin to an adherend, which can contribute to the improvement of adhesion. However, use of the monomers with large carbon atom numbers alone is not desirable since it leads to a decrease in flowability of the acrylic resin and conversely results in a deteriorated adhesion of the acrylic resin to an adherend. Accordingly, in the present invention it is attempted to adjust the balance between them by using in combination a monomer with a smaller carbon atom number and a monomer wit
Ishikawa Kazunori
Matsuda Hideyuki
Miyata Akihiro
Dawson Robert
The Yokohama Rubber Co. Ltd.
Zimmer Marc S.
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