Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-08-03
2004-07-20
Robertson, Jeffrey B. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C528S025000, C528S028000, C528S038000, C528S043000
Reexamination Certificate
active
06765055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an adhesion promoter for a primer and to a primer composition containing such an adhesion promoter. More particularly, the present invention relates to an adhesion promoter that has high adhesion to various adherends and retains that effect when it is stored for a long time and to a primer composition that is excellent in adhesion to various adherends and of which a reduction in adhesion is prevented.
2. Description of the Related Art
Generally, bonding of window glasses of an automobile requires excellent initial adhesion, high adhesion strength and adhesion durability under various conditions of low temperature, high temperature, high humidity and the like. Further, it is very important that after window glasses were bonded, they have excellent weatherability (including weatherability to light, i.e., resistance to light) since the window glasses of an automobile directly contact open air and directly receive sunbeam.
A typical example of sealants useful for bonding nonporous substrates such as glass is a urethane based sealant. However, when bonding a glass substrate to a metal with a urethane based sealant (for example, incorporating window glasses in the production of automobiles), it may sometimes happen that the stack shear strength of bonded substrates will not reach safety target or structure target, so that in most body assembly operations the coating of a sealant is generally preceded by the coating of a primer in bonding a front window glass or rear window glass.
As the primer, a composition containing a binder component such as polyester polyurethane or acrylic resin, have been conventionally used in combination with an adhesion promoter such as silane coupling agent, polyisocyanate, carbon black, catalyst and the like.
As the adhesion promoter, mention may be made of, for example, isocyanate group containing silane compounds obtained by reacting an organic polyisocyanate with an amino silane compound or mercaptosilane compound, disclosed in Japanese Patent Application Laid-open No. Hei 5-222342. According to the teaching of the publication, this compound is obtained by reacting an NCO group of organic polyisocyanate with an amino group or a mercapto group in a ratio of from 1/0.20 to 1/0.95 and the primer composition containing the compound has high initial adhesion and excellent durability.
However, the reaction of the NCO groups of organic polyisocyanate with the mercapto groups of mercaptosilane or amino groups of aminosilane generates thiourethane groups and urea groups. These groups contain activated hydrogen, which is highly reactive with unreacted NCO groups in the molecule of the resulting isocyanate group-containing silane compound. As a result, when it is stored for a long time, the isocyanate group-containing silane compound will have a deteriorated activity and it has been difficult to use it in combination with a catalyst such as an organotin compound or tertiary amine to be added in order to increase the curability thereof.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an adhesion promoter for a primer that has high adhesion to various adherends and retains that effect when it is stored for a long time.
Another object of the present invention is to provide a primer composition that contains such an adhesion promoter and has excellent adhesion and storage stability.
The present inventors have made extensive study with a view to overcoming the problems of the prior art adhesion promoter and primer composition and provide a novel adhesion promoter and primer composition. As a result, they have found that in a reaction between an NCO group of polyisocyanate and an amino group of aminosilane to generate a urea group when preparing a compound usable as an adhesion promoter for a primer, the reactivity of active hydrogen in the resultant urea group is inhibited if the amino group of amino silane has a phenyl group as a substituent, and that the adhesion of the resultant primer composition containing such an adhesion promoter is not deteriorated after prolonged storage. The present invention is based on this discovery.
That is, in a first aspect, the present invention provides an adhesion promoter for a primer, comprising a silane compound that is a reaction product between a polyisocyanate and a silane coupling agent having a secondary amino group the nitrogen atom of which is directly connected to a phenyl group or a derivative thereof, the silane compound having in average at least one NCO group and in average at least one hydrolyzable alkoxysilyl group in the molecule.
Here, the polyisocyanate is preferably an aliphatic or alicyclic polyisocyanate.
In the adhesion promoter for a primer mentioned above, the silane compound is preferably a reaction product having a reaction ratio of NCO/NH=3/1 to 3/2.
In a second aspect, the present invention provides a primer composition comprising the adhesion promoter mentioned above and a film forming resin.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The adhesion promoter for a primer according to the present invention is a reaction product between a polyisocyanate and a silane coupling agent having a secondary amino group the nitrogen atom of which is directly connected to a phenyl group or a derivative thereof. The silane compound has in average one or more NCO group and in average one or more hydrolyzable alkoxysilyl group in the molecule.
In the present invention, the polyisocyanate that can be used is not particularly limited and specific examples thereof include ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (MDI), or compounds with a lysine skeleton, such as lysine diisocyanate and lysine triisocyanate, xylylene diisocyanate (XDI), isophorone diisocyanate, H
6
XDI (hydrogenated XDI), H
12
MDI (hydrogenated MDI), and carbodiimide modified products of these polyisocyanates or isocyanurate modified products thereof. They may be used singly or two or more of them may be used in admixture.
Among these, hexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, xylylene diisocyanate, and H
6
XDI are preferred since they give rise to reaction products that have high tackifying property.
Here, lysine diisocyanate and lysine triisocyanate are compounds represented by the following formulae:
wherein R represents an alkylene group having 1 to 8 carbon atoms that may be branched, preferred examples of which include a methylene group, an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group and the like.
The term aliphatic polyisocyanate as used herein refers to those compounds in which NCO groups are bonded to aliphatic carbon atoms and also includes, for example, a compound such as XDI having a benzene ring.
In the present invention, the silane coupling agent having a secondary amino group to which a phenyl group or its derivative is bonded directly to the nitrogen atom thereof has a compound of the structure shown by the following formula (1).
In the formula (1) above, R
1
, R
2
, and R
3
independently represent a hydrolyzable group or an alkyl group, at least one of which is a hydrolyzable group. The compounds of formula (1) that have two or three hydrolyzable groups bonded to the silyl group are preferred since the silane compound of the present invention of this type has an increased tackifying property. More preferred are those compounds in which all of R
1
, R
2
, and R
3
are hydrolyzable groups. Appropriate selection of R
1
, R
2
, and R
3
can adjust the hydrolysis rate and adhesion development time depending on the purpose. Specific examples of the hydrolyzable group include a hydrogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amido group, an aminooxy group, a mercapto group, an alkenyloxy group and the li
Ishikawa Kazunori
Matsuda Hideyuki
Miyata Akihiro
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Robertson Jeffrey B.
The Yokohama Rubber Co. Ltd.
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