Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1994-09-02
1996-10-08
Sluby, P. C.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
264104, 264512, 264494, B32B 516, B29C 4516, B29C 3700
Patent
active
055629792
DESCRIPTION:
BRIEF SUMMARY
This is a continuation-in-part of copending International Application No. PCT/GB93/00453 filed on Mar. 4, 1993 and which designated the United States of America.
The invention relates to a method of forming a moulding by dual injection and a moulding formed in accordance with such a method. In particular, but not exclusively, the invention is concerned with the moulding of a vehicle body component in a way which will avoid having to apply a coating of paint to a pre-formed component.
Dual injection moulding is a technique involving injecting a first plastics material into a mould followed by a second plastics material. The injection steps causes the first material to coat the mould surfaces and the second material forms a substrate for the first. The component so formed may harden in the mould prior to removal from the mould.
An example of dual injection moulding is disclosed in GB-A-1,420,948. However any moulding produced by such a method will require subsequent painting outside the mould.
Another example of dual injection moulding is disclosed in GB-A-2 080 187 which describes a method of resin injection moulding (RIM) where a low viscosity liquid resin, for example liquid paint, is injected at low pressure (eg 7 bar) into a mould followed by a higher viscosity liquid resin. The low viscosity liquid resin forms a coating for the higher viscosity resin. Such low viscosity paints take the form of a liquid thermosetting resin having coloured pigments which is injected in its uncured liquid form and subsequently cured. A disadvantage of using a low viscosity liquid resin is that of controlling accurately the spread of the liquid paint to produce a coating of uniform thickness. Therefore such a process is suitable only for the production of primer coats which have to be finished by applying a coat of paint in a conventional manner outside the mould, e.g. by paint spraying.
An increasing number of motor vehicles are now provided with components such as body panels made from plastics materials. For example it has been proposed to form a vehicle body component by initially injecting an unfilled thermoplastics material followed by a glass filled polymer material as a substrate. The unfilled plastics material thereby forms a smooth coating on the substrate ready to receive paint which is subsequently applied by spraying or dipping the cured moulding in a paint facility. We are unaware of any vehicle component being made by such a process which does not subsequently require a finishing paint coating applied outside the mould and the motor industry continues to refine its painting facilities, which in themselves can involve large capital investment and on-going maintenance sums, and present environmental difficulties.
One object of the present invention is to provide an improved method of forming a moulding by dual injection which will render unnecessary the subsequent painting of the moulding or moulded component.
According to one aspect of the invention there is provided a method of forming a moulding by dual injection comprising injecting a plastics coating material into a mould and injecting a plastics substrate material into the mould to cause the coating material to coat a surface of the mould and to produce a moulding having a coating formed by the plastics coating material, characterised by providing the coating material as a powdered or granulated cross-linking plastics paint material and heating the powdered or granulated plastics paint material to a plastic condition for injection into the mould.
The powdered or granulated paint material heated to a plastic condition and applied in that way provides the required paint finish by an in-mould process which dispenses with the need to spray a coating of paint subsequently on to the moulding. Also it has been found that the use of powdered or granulated plastics paint enables a much more controllable flow to be obtained in the mould resulting in a paint coating thickness which is controllable. Thus it is possible with the method of the present invention to obt
REFERENCES:
patent: 4681712 (1987-07-01), Sakakibara et al.
patent: 5059361 (1991-10-01), Da Re
Plastics Engineering, Feb. 1991, pp. 27 to 31.
Plastiques Modernes Et Elastomeres, Dec. 1991, pp. 64 to 66 and English translation.
Plastverarbeiter, vol. 29, No. 2, 1978, pp. 66 to 71 and English translation.
Reasearch Disclosure, No. 32969, Sep. 1991.
Easterlow Ronald A.
Smith Gordon F.
Rover Group Limited
Sluby P. C.
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