Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2000-11-09
2003-11-25
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S413000, C428S418000, C428S423100, C428S458000, C180S089100, C180S193000, C180S325000, C180S330000, C180S331000
Reexamination Certificate
active
06652960
ABSTRACT:
The present invention relates to a plastic-coated metal plate prepared by sticking a plastic film at least on one face of a metal plate via a coating film of a thermosetting adhesive comprising an amine-added epoxy resin and a polyisocyanate compound, which is excellent in a corrosion resistance, an adhesive property and a finishing property and which is particularly useful for forming a car body.
A laminating technique for elevating a durability and a dressing property by coating a plastic film or a coating film on a surface of a base material such as a steel plate via an adhesive has so far been put to practical use in various fields, and the adhesives used for this technique is always required to be improved. The reason therefor is that an intrinsic function of an adhesive is to adhere a film and a coating film on a base material face but in addition thereto, functions to prevent rusts from being produced under corrosive environment and inhibit lift and blister on film and coating film faces from being caused are very important as well.
A lot of trials to add rust preventive pigments to adhesives have been proposed as solving means therefor (for example, Japanese Patent Application Laid-Open No. 61456/1980, Japanese Patent Application Laid-Open No. 58859/1981, Japanese Patent Application Laid-Open No. 171949/1983, Japanese Patent Application Laid-Open No. 14941/1984 and Japanese Patent Application Laid-Open No. 14943/1984).
Addition of a rust preventive pigment to an adhesive elevates the corrosion resistance but provides the defects that the adhesive property with a film is reduced and it becomes difficult to well balance the corrosion resistance with the adhesive property. Accordingly, the poor adhesive property is sometimes brought about, and peeling and lifting on a film face and a blistering phenomenon by blister are caused during use over a long period of time. Further, involved are the problems that since a temperature of about 190° C. or higher is required as a hot pressing condition of a laminate film in conventional techniques, the facilities become large-scaled, and energy consumption becomes excessive and that a residual stress of an adhesive grows large and peeling in an adhesion interface is liable to proceed with the passage of time.
In order to avoid these problems, proposed is a method in which an undercoating material containing a specific resin component containing a rust preventive pigment is coated on a base material face and then an adhesive containing no rust preventive pigment is coated thereon, followed by heating and pressing the film (for example, Japanese Patent Application Laid-Open No. 64125/1994). Involved in this method, however, are the defects that the number of the steps is increased and that a rust preventive pigment contained in an undercoating film is liable to bring about a reduction in finish appearance such as flatness.
On the other hand, a coating step of a shell plate part of a car is carried out by molding, working and assembling a metal plate, immersing it in a cationically electrodepositable coating material bath and applying an electric current to form undercoating films on both front and back sides and end face parts thereof and then coating an intermediate coating material and a top coating material primarily on the outer face parts. In recent years, however, step saving, energy cutting and a reduction in CO
2
in a coating line are strongly required, and in addition thereto, performances such as a throwing property of an electrodepositable coating material toward an end face part and a chipping resistance and a corrosion resistance of a combined coating film are requested to be further improved.
Intensive researches repeated by the present inventors in order to solve such problems as described above in conventional techniques have resulted in finding that a mixture comprising an amine-added epoxy resin (A) and a polyisocyanate compound (B) is used as an adhesive to stick a plastic film on a metal face via a coating film of this adhesive, whereby obtained is a plastic-coated metal plate which is excellent in an adhesive property and a corrosion resistance and which is useful for a car body, and they have come to complete the present invention.
Thus, the present invention provides a plastic-coated metal plate prepared by adhering a plastic film at least to one face of a metal plate via a thermosetting adhesive comprising an amine-added epoxy resin (A) and a polyisocyanate compound (B).
The plastic-coated metal plate of the present invention shall be explained below in further details.
Amine-added Epoxy Resin (A)
The amine-added epoxy resin (A) which is one component of the thermosetting adhesive used in the present invention is a polyester-modified epoxy resin, preferably polyester-modified epoxy resin (A′) obtained by reacting a poly addition reaction product of a hydroxyl group-containing epoxy resin having an epoxy equivalent of 200 to 400 (a) with a cyclic ester (b), a polyphenol compound (c) and an amino group-containing compound (d) in order of mention.
The hydroxyl group-containing epoxy resin (a) is a resin having both hydroxyl group and epoxy group in a molecule, and to be specific, it is preferably a resin having a hydroxyl group, preferably a secondary hydroxyl group of at least 0.5 group, preferably 0.8 to less than 2 groups per molecule on an average and an epoxy group of 2 or more groups, preferably 2 groups on an average. The hydroxyl group-containing epoxy resin (a) has preferably an epoxy equivalent falling in a range of 200 to 400, particularly 230 to 350 and a number average molecular weight falling in a range of about 400 to about 1000, particularly about 450 to about 700.
Polyglycidyl ethers of polyphenol such as bisphenol are included in such hydroxyl group-containing epoxy resin (a). Representative examples of such epoxy resin include glycidyl ethers of polyphenol such as bis(4-hydroxyphenyl)-2,2-propane, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)methane, 4,4′-dihydroxydiphenylsulfone, phenol novolak and cresol novolak, and polymers thereof. Further, these epoxy resins (a) may be modified with, for example, polyetherpolyol, polyesterpolyol, polyamideamine, polycarboxylic acid and polyisocyanate compounds each having a softening point falling in a range of −30 to 50° C., particularly −20 to 40° C.
Included in the cyclic ester (b) is a lactone compound represented by the following formula:
wherein R represents a hydrogen atom or methyl, and n is 3 to 6. To be specific, included are &dgr;-valerolactone, &egr;-caprolactone, &zgr;-enalactone, &eegr;-caprylolactone, &ggr;-valerolactone, &dgr;-caprolactone, &egr;-enalactone and &zgr;-caprylolactone.
The cyclic ester (b) is addition-reacted with the hydroxyl group-containing epoxy resin (a) described above to produce the poly addition reaction product (c).
This poly addition reaction can be carried out by conventionally known methods. It can be carried out, for example, by heating both components (a) and (b) at a temperature of about 100 to about 250° C., preferably about 140 to about 220° C. for about one to about 15 hours in the presence of a catalyst, wherein used as the catalyst are, for example, titanium compounds such as tetrabutoxytitanium and tetrapropoxytitanium; organic tin compounds such as tin octylate, dibutyltin oxide and dibutyltin laurate; and inorganic metal compounds such as stannous chloride. A use amount of the above catalyst falls suitably in a range of usually 0.5 to 1000 ppm based on the total weight of both components.
It is assumed that the addition reaction of both components described above is carried out by allowing the cyclic ester (b) to be opened and reacted with a secondary hydroxyl group contained in the epoxy resin (a). It is considered that as a result thereof, a side chain with a large plasticizing capacity having a primary hydroxyl group having an excellent reactivity is introduced into the poly addition reaction product, so that an adhesive-coating film formed is improved in a corrosion r
Hiraki Tadayoshi
Tominaga Akira
Watanabe Tadashi
Yawata Takeshi
Kansai Paint Co. Ltd.
Kiliman Leszek
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