Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-01-25
2001-01-30
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S040500, C264S328700, C264S328800
Reexamination Certificate
active
06180043
ABSTRACT:
The present invention relates to a method of in-mold coating, comprising steps of forming a molded product by molding a synthetic resin molding material in a mold according to an injection molding method, an injection compression molding method or an injection press molding method, and injecting a coating material into the mold to coat a surface of the molded product with the coating material.
Methods of in-mold coating have been utilized in order to improve the quality of a surface of molded products and to shorten a coating process. In particular, with respect to automobiles required to have appearance and quality at a high level, such methods have been widely applied to exterior plates and exterior parts of automobiles.
Such methods have been disclosed in U.S. Pat. No. 4,076,788, U.S. Pat. No. 4,081,578, U.S. Pat. No. 4,331,735, U.S. Pat. No. 4,366,109, U.S. Pat. No. 4,668,460, JP-A-5301251, JP-A-5318527 and JP-A-8142119 for example.
Although these publications refer to a clamping pressure and separation of mold halves with respect to injection of a coating material into between a surface of the mold and a surface of a molded product after having molded a synthetic resin molding material in the mold, the publications pay little attention to the clamping pressure after injection of the coating material, and the clamping pressure has been constant. A thick-walled portion such as a rib and a boss of the molded product is compressed by the clamping pressure after injection of the coating material, that is to say, by a pressure applied to the injected coating material. As a result, the coating material becomes thicker on such a thick-walled portion, and the coating material is cured in such a state. After that, the clamping pressure is released, and the coated molded product is removed out of the mold. The present inventors have found that, at the time of releasing the clamping pressure, the rib or the boss compressed by the coating material is likely to return to its original form by a spring back phenomenon to provide a rise as a defect on appearance. The inventors have verified that such a phenomenon is apt to occur in particular when the clamping pressure after injection of the coating material is high though the phenomenon is also affected by a degree of curing (solidification) or ease in elastic compression of the molded resin material on injection of the coating material.
It is an object of the present invention to provide a method of in-mold coating capable of preventing the rising phenomenon of a thick-walled portion of a molded product (the hump phenomenon) from occurring when a surface of the molded product is coated with a coating material in a mold after having molded a synthetic resin molding material in the mold according to an injection molding method, an injection compression molding method or an injection press molding method, and ensuring that the molded product thus coated has high quality, considering the circumstances stated earlier.
The present invention provides a method of in-mold coating, comprising steps of forming a molded product by applying a clamping pressure to a mold including a fixed mold half and a movable mold half to mold a synthetic resin molding material in the mold according to an injection molding method, an injection compression molding method or an injection press molding method, then reducing the clamping pressure or parting the fixed mold half and the movable mold half; injecting a coating material into between an inner surface of the mold and a surface of the molded product in the mold; and coating the surface of the molded product with the coating material, clamping the mold again; wherein
(1) the coating material is injected in such a state that the molded product has cured or solidified to such an extent that the surface of the molded product can withstand an injection pressure and a flow pressure of the coating material; and
(2) the clamping of the mold after injection of the coating material is carried out under certain multistagewise variable clamping pressures with certain clamping pressure transitional periods of time.
Examples of the synthetic resin molding material used in the present invention are thermosetting synthetic resin material such as SMC (Sheet Molding Compound) and BMC (Bulk Molding Compound) as fiber reinforced plastic containing a thermosetting resin such as unsaturated polyester resin as a matrix, a thermoplastic synthetic resin material such as polyethylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate and modified polyphenylene ether, alloy materials thereof, and the ones having fibers or scale-shaped fillers mixed.
As the coating material used in the present invention, various kinds of known coating materials for in-mold coating can be used. Typical examples of the coating material used in the present invention are ones disclosed in JP-A-5436369, JP-A-54139962, JP-A-5565511, JP-A-57140, JP-A-60212467, JP-A-60221437, JP-A-1229605, JP-A-570712, JP-A-5148375, JP-A-6107750 and JP-A-8113761 for example.
A particularly preferred example is a coating material which comprises a vehicle component comprising 20-70 wt % of an oligomer having at least two (meth)acrylate groups such as urethane acrylate oligomer and epoxy acrylate oligomer, or its resin or an unsaturated polyester resin thereof, and 80-30 wt % of an ethylenic unsaturated monomer copolymerizable therewith such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, 2-ethyl hexyl(meth)acrylate, (meth)acrylic acid, vinyl acetate and styrene; pigment; a polymerization initiator and so on. Two-pack coating materials such as an epoxy resin/polyamine curing system and a polyol resin/polyisocyanate curing system, of which the main agent and the curing agent are mixed immediately prior to injection into a mold, are also applicable.
REFERENCES:
patent: 4082486 (1978-04-01), Cerano et al.
patent: 4668460 (1987-05-01), Ongena
patent: 5034077 (1991-07-01), Pata
patent: 5044309 (1991-09-01), Crumbach et al.
patent: 5174933 (1992-12-01), Toh et al.
patent: 5736090 (1998-04-01), Yamamoto et al.
patent: 5902534 (1999-05-01), Fujishiro et al.
patent: 05318527A (1993-12-01), None
Yamamoto Yoshiaki
Yonemochi Kenji
Dai Nippon Toryo Co., Ltd.
Heitbrink Jill L.
McDowell Suzanne E.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Method of in-mold coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of in-mold coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of in-mold coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2472554