Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-24
2001-08-07
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C362S507000, C525S074000, C525S083000
Reexamination Certificate
active
06270615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a lamp employed for vehicle use such as headlamp, turn signal lamp, or stop-lamp, in which a lamp lens is joined to a lamp body made of synthetic resin.
2. Description of the Related Art
As a method of joining a lamp lens to a lamp body consisting of synthetic resin, the method of fixing these two together by using a adhesive could be employed. However, in view of environmental problems, the so-called hot plate melt-bonding method, in which the lamp body, typically consisting of a thermoplastic resin such as ABS resin, is melted by pressing a hot plate onto it and the molten part is then press-fixed onto a lamp lens consisting of methyl methacrylate resin etc. is becoming more widely adopted since, unlike the method in which fixing is effected using adhesive, it employs no solvent at all. However, with such a hot plate melt-bonding method, there was sometimes the problem that, on separating the hot plate after using the hot plate to melt the thermoplastic resin constituting the lamp body made of ABS resin or the like, the molten resin gets drawn out in the form of a thread (hereinbelow this is referred to as “thread drawing”) which adheres to the surface of the molding of the lamp lens or lamp body, adversely affecting its appearance. As a method of improving the situation regarding thread drawing in this hot plate melt-bonding method, for example Early Japanese Patent Publication H. 9-12902 proposes the method of adding a fluorine resin such as polytetrafluoroethylene to the thermoplastic resin such as polycarbonate or ABS resin. However, with this method, the cost of the vehicle lamp that is manufactured is increased and also, since the external slipperiness of fluorine resins is high, if the added amount is large, when the resin is extruded from the extrusion molding machine in extrusion manufacture of the pellets for molding, so-called surging occurs, adversely affecting productivity. Furthermore, secondary processing may be adversely affected in that there may be poor adhesion of the evaporated film or coating when vacuum evaporation is performed onto the inner surface of the molded lamp body or its outer surface is coated.
SUMMARY OF THE INVENTION
With the foregoing in view, when manufacturing a vehicle lamp by joining a lamp body to a lamp lens using the hot plate melt-bonding method, it is an object of the present invention to improve the situation regarding thread drawing of the resin used to constitute the lamp body without either increasing manufacturing costs or impairing secondary processing capability.
As a result of meticulous study aimed at achieving this object, the inventors arrived at the present invention by discovering that thread drawing when manufacturing a vehicle lamp by joining a lamp body and lamp lens by the hot plate melt-bonding method could be greatly improved with a resin composition obtained by blending a graft copolymer containing specific constituents with a vinyl copolymer.
Specifically, according to the present invention, when manufacturing a vehicle lamp by melting a lamp body comprising thermoplastic resin by pressing onto it a heated hot plate, then joining the lamp body and a lamp lens by press-fixing the melted part onto the lamp lens, as the lamp body there is employed a lamp body molded by a resin composition (C) as chief constituent whereof a total of 100 weight parts consist of 80~5 weight parts of the graft copolymer (A) specified below and 20~95 weight parts of the vinyl copolymer (B) specified below:
(A) graft copolymer obtained by graft polymerization of 80~5 weight parts of a mixture of monomers with 20~95 weight parts of rubber-like polymer; said monomer mixture comprising 99.9~60 weight % of one or two or more vinyl compounds selected from vinyl cyanide compounds, aromatic vinyl compounds and alkyl (meth)acrylate compounds, 0~30 weight % of another copolymerizable vinyl compound, and 0.1~40 weight % of an &agr;,&bgr;-unsaturated acid glycidyl ester compound;
(B) vinyl copolymer obtained by reacting 10~40 weight % of a vinyl cyanide compound with 60~90 weight % of an aromatic vinyl compound and 0~30 weight % of another copolymerizable vinyl compound.
What is particularly important in the present invention is the graft copolymer (A) in the resin composition used for molding the lamp body. Specifically, the graft copolymer (A) that is employed in the present invention is a graft copolymer obtained by, in graft polymerization of 80~5 weight parts of a mixture of monomers with 20~95 weight parts of rubber-like polymer, reacting, as necessary constituent, 0.1~40 weight parts, preferably 0.5~30 weight parts, and even more preferably 5~20 weight parts, of &agr;,&bgr;-unsaturated acid glycidyl ester compound, with 99.9~60 weight % of one or two or more vinyl compounds selected from vinyl cyanide compounds, aromatic vinyl compounds, or alkyl(meth)acrylate compounds, more preferably 99.9~60 weight % of vinyl compounds comprising 0~40 weight % of vinyl cyanide compounds, 60~90 weight % of aromatic vinyl compounds, or 0~30 weight % of alkyl(meth)acrylate compounds, and 0~30 weight t of other copolymerizable vinyl compounds.
In this graft copolymer (A) it is undesirable that the rubber-like polymer should be less than 20 weight parts since this lowers the impact strength of the lamp body or that it should exceed 95 weight parts since this results in extremely poor fluidity of the resin. Furthermore it is undesirable that the amount of &agr;,&bgr;-unsaturated acid glycidyl ester compound in the monomer mixture that is graft-polymerized with the rubber-like polymer should be less than 0.1 weight %, since a sufficient improvement effect in respect of thread drawing when the lamp lens is joined by the hot plate melt-bonding method is then not obtained, or that it should exceed 40 weight %, since this results in reduced fluidity of the resin when the lamp body is molded and reduced impact resistance of the molded lamp body.
There is no particular restriction on the rubber-like polymer employed in the graft copolymer (A) and examples that may be given include: diene rubbers such as polybutadiene rubber, styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), or butyl acrylate—butadiene rubber; acrylic rubbers such as butyl acrylate rubber, butadiene—butyl acrylate rubber, acrylic acid 2—ethylhexyl butylacrylate rubber, methacrylic acid—ethylhexyl butylacrylate rubber, stearyl acrylate—butylacrylate rubber, dimethyl siloxane butylacrylate rubber, or silicone/butylacrylate composite rubber; polyolefin rubber polymers such as ethylene—propylene rubber or ethylene—propylene diene rubber; or silicone rubber polymers such as polymethyl siloxane rubber; these may be used alone or in a combination of two or more. Preferably the mean grain size of these rubber polymers is 0.05~1 &mgr;m, and even more preferably 0.07~0.4 &mgr;m. Rubber-like polymers manufactured by the coagulation dilation method using an acidic group-containing latex could also be employed.
Examples of glycidyl ester compounds of &agr;,&bgr;-unsaturated acids that undergo graft polymerization with the rubber-like polymer include glycidyl acrylate, glycidyl methacrylate, and glycidyl ethacrylate; one or two or more of these may be employed.
As the (vinyl cyanide compound) used in graft copolymer (A) and vinyl copolymer (B), (acrylonitrile or methacrylonitrile may be mentioned as examples; as the aromatic vinyl compound, styrene, &agr;-methylstyrene, p-methylstyrene, p-isopropylstyrene, chlorostyrene, or bromostyrene may be mentioned as examples. Also, as the alkyl (meth)acrylate compound, methyl (meth)acrylate, ethyl (meth)acrylate, or butyl (meth) acrylate may be mentioned as examples. Furthermore, as the other copolymerizable vinyl compound, acrylic acid, methacrylic acid, maleimide compounds such as for example N-phenyl maleimide, vinyl acetic acid, or ethyl vinyl ether may be mentioned as examples. These may be used alone or as a combination of two or more.
Hashimoto Yoshihiko
Nishimoto Kenji
Armstrong Westerman Hattori McLeland & Naughton LLP
Gallagher John J.
Kaneka Corporation
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