Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-04-09
2004-09-28
Copenheaver, Blaine (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C029S897200, C204S471000, C427S409000, C180S089100, C296S181200, C428S457000
Reexamination Certificate
active
06797098
ABSTRACT:
The present invention relates to a metal plate for car body which is covered with at least two kinds of plastics layers whose rate of elongation is different each other, and further includes a process of forming a car body, which is excellent in chipping resistance, corrosion resistance etc., by using the covered metal plate.
In a car body of a normal or small passenger car etc., the portion constituted mainly with sheet metal without riggings such as engine or chassis is called shell body. Usually the shell body consists of a main body, consisting of underbody, side member, roof, cowl, upper back, lower back etc., and outer cover parts such as hood, front balance, front fender, cowl louver, door, luggage (back door) etc.
Up to the present, in order to form these main body and outer cover parts, a metal plate is cut and shaped in the size and shape of each constituting part and they are assembled into a shell body, which is dipped into a cationic electrodeposition paint bath to form an undercoat coating film by electrodeposition coating on the surface, backside, edge surface portion etc. of the metal plate. Then the outer surface portions are coated with intermediate paint, topcoat paint etc.
Recently, however, in the field of car body coating, operation step saving, energy saving and reduction of CO2 in the coating line are strongly desired. Moreover, further improvement in throwing power of electrodeposition paint to edge surface portion, and chipping resistance, corrosion resistance etc. of the total coating film is required. In order to improve the chipping resistance, there has been proposed to coat a barrier paint to form a viscoelastic coating film between the layers of these coating films. This has, however, disadvantages that the number of coating steps increases and the manufacturing cost increase, too.
The present inventors have repeatedly conducted studies to solve the problems in the coating of a car body as mentioned above. As a result, this time, they found that a metal plate, covered with more than two kinds of plastics layers whose rates of elongation are different, is excellent in chipping resistance, corrosion resistance etc. and the above-mentioned disadvantages can be dissolved by using it for a part or total of the car body and completed the present invention.
Thus, according to the present invention there is provided a plastics-covered metal plate for car body characterized by being made through covering one surface or both surfaces of a metal plate with at least two kinds of plastics layers whose rate of elongation is different each other (hereinafter referred to as the present covered metal plate).
Further, according to the present invention there is provided a process of covering a car body characterized by forming a shell body of a car body by using partly or totally the present covered metal plate and then by electrodeposition coating the portion of the shell body where metal is exposed (hereinafter referred to as the present covering process).
Then, the plastics-covered metal plate for car body and the process of covering a car body of the present invention are described in more detail.
The present covered metal plate can be used mainly as constituting element of a car body of normal and small passenger car, but can be applied also to truck, bus, motorcycle, vehicle with special kind of equipment etc. in the same manner.
As a metal plate to be covered with a plastics layer according to the present invention there can be used those which have been used for a car body until now in the same manner and there can be mentioned specifically, for example, metal plate made of iron, steel, stainless steel aluminium, copper and alloys containing these metals, and further metal plates made by plating their surface with zinc, zinc
ickel, iron etc. They can be used in the shape of coils or cut plates. The thickness of the metal plates is suitably in the range of usually 0.3-2 mm, particularly 0.5-1 mm. It is preferable that the surface of these metal plates is treated suitably by grinding, degreasing, treatment with phosphate etc. in order to improve the adhesivity with a plastics layer, corrosion resistance etc.
The present covered metal plate is made by covering one surface or both surfaces of the metal plate as mentioned above with at least two kinds of plastics layers whose rate of elongation is different each other.
Here the “rate of elongation” of a plastics layer means the value (%) calculated by the formula: {(L−20)/20}×100 wherein L mm is the length of a film strip, which has been made by forming a film of the same material and the same thickness as those of said plastics layer and by cutting out a film strip of 20 mm long and 5 mm wide, at the time of breakage when being drawn at the speed of 20 mm a minute at +20° C. For example, when a film strip of 20 mm long is broken at the time when it is stretched to 30 mm, its rate of elongation is 50%.
The present covered metal plate is obtained, for example, by laminatedly covering a metal plate with a plastics layer (A) whose rate of elongation is relatively smaller and a plastics layer (B) whose rate of elongation is larger. The order of covering with the plastics layers (A) and (B) is not particularly restricted but can be selected optionally according to the application purpose etc. of the present covered metal plate. It is particularly preferable, however, that the plastics layer (B) whose rate of elongation is larger is generally placed at the nearer side to the metal plate and the plastics layer (A) whose rate of elongation is smaller is placed thereon (at the farther side from the metal plate), that is, they are laminated in the order of metal plate/plastics layer (B)/plastics layer (A).
The difference between the rate of elongation of the plastics layer (A) and the rate of elongation of the plastics layer (B) is not strictly limited. It is preferable, however, that the rate of elongation of the plastics layer (B) is larger than that of the plastics layer (A) generally by at least 10%, preferably 50-200% and more preferably 80-150%. The rate of elongation of the plastics layer (A) itself is preferably in the range of generally 1-100%, particularly 5-70% and more particularly 10-50%.
As modes of covering the plastics layers whose rate of elongation is different each other to one surface or both surfaces of a metal plate in the present covered metal plate there are mentioned, for example, the following.
1) A covered metal plate made by covering with 2-layered multilayered plastics layer made by covering with the plastics layer (B) with larger rate of elongation and then the plastics layer (A) with smaller rate of elongation successively from the side of the metal plate.
2) A covered metal plate made by covering with 3-layered multilayered plastics layer made by covering with the plastics layer (A), the plastics layer (B) and the plastics layer (A) successively from the side of the metal plate.
The oxygen permeability of the plastics layer (A) in its single coating film form at 25° C. is preferably less than 10
−11
cm
3
.cm/cm
2
.sec.cmHg, particularly less than 10
−12
cm
3
.cm/cm
2
.sec.cmHg, because the corrosion resistance of the present covered metal plate to be obtained is further improved.
As a plastics material to form the plastics layer having the above-mentioned rate of elongation and occasionally the above-mentioned oxygen permeability there can be used per se known substances and there can be mentioned, for example, thermoplastic resins such as polyolefin resin such as polyethylene, polypropylene etc., polyester resin such as polyethylene terephthalate (PET) etc., polycarbonate resin, epoxy resin, vinyl acetate resin, vinyl chloride resin, fluorine-containing resin, polyvinyl acetal resin, polyvinyl alcohol resin, polyamide resin, polystyrene resin, acrylic resin, polyurethane resin, phenolic resin, polyether resin, cellulose type resin etc. Among them, particularly polyester resin, polyurethane resin and vinyl chloride resin are preferable.
These pla
Hiraki Tadayoshi
Tominaga Akira
Watanabe Tadashi
Yawata Takeshi
Copenheaver Blaine
Haran John T.
Kansai Paint Co. Ltd.
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