Forming moulding with simulated wood grain surface

Details Forming moulding with simulated wood grain surface Forming moulding with simulated wood grain surface

1996-07-15

2000-07-25

Ortiz, Angela

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

264255, 264293, B29C 3342, B29C 5902

Patent

active

060933569

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the production of synthetic resin mouldings having a simulated wood grain surface.
It is known that products such as panels, doors, door frames, window frames, artificial wooden beams, etc., can be produced with a moulded synthetic resin surface to which a simulated wood grain finish has been applied by effecting contact, usually with pressure, between a surface of a fluid body of curable synthetic resin, e.g. polyester resin, and a mould surface designed to impress the simulated wood grain effect on said resin surf ace. The curable resin is then normally maintained in contact with the mould surface until it has been cured to the state where the fine detail of the impressed finish is not lost or significantly undesirably impaired when the moulding is parted from the mould.
The desired surface of the mould may be obtained, for example, by forming the mould against a suitable wooden surface. The effect may be enhanced by causing the wooden surface to swell, e.g. by soaking it, prior to its use as the former.
The wood grain-like finish on the synthetic resin moulding may be further improved by suitable pigmentation of the resin and/or by surface treatment.
While the method is widely used and very good results may be obtained, there is still room for improvement in the quality of finish. Furthermore, the finishes currently obtained normally require at least two further treatments, namely, staining and varnishing, in order to obtain a quality product, and these add significantly to the cost, especially since often more than one staining step is required. Moreover, the product recovered from the mould cannot be sanded because every scratch is highlighted in any subsequent staining treatment.
It has been proposed e.g. in FR-A-2469263 and WO92/18341 to achieve a further improvement in the simulated wood grain effect achieved by this procedure by coating the surface of the mould with a colourant such as a pigment or dye, so that when the curable resin is applied against the surface of the mould, the colourant transfers to the surface of the resin and is retained thereon when the cured resin moulding is subsequently parted from the mould.
To achieve a wood grain effect that simulates as nearly as possible its natural equivalent, it is desirable for the colourant to accumulate in the valleys of the moulding. This means that the colourant must be concentrated on the peaks of the mould from which the moulding is obtained. However, in the method employed in FR-A-2469263, the colourant tends to be concentrated in the valleys of the mould and while WO92/18341 suggests restricting the coating to the higher areas of the mould, the procedures described therein for the purpose, namely application of the colourant with a stiff pad or use of a carbon paper or coloured transfer paper, have serious drawbacks in practice because they do not lend themselves to automation, are labour-intensive, require a skilled labour force and/or require the use of expensive materials.
This problem is solved by the process of the present invention which involves first applying the colourant over the mould surface and thereafter wiping the surface. Contrary to what would be expected from such a procedure, it has been found that this has the effect of concentrating the residual colourant on the peaks of the mould surface. This is particularly surprising in view of the disclosure in WO92/18341 which teaches that wiping a mould surface on which a colourant has been deposited removes the colourant from the high points of the surface.
Not only is the colourant concentrated on the peaks of the mould surface, and thus in the valleys of the resultant moulding, but it has been found that a greater depth of colourant is found on the higher peaks, thus automatically providing a very desirable gradation of colour tone in the valleys of moulding obtained from the moulds, with the deeper valleys having a deeper tone of colour, as in a natural wood product.
The first step of the process involves applying the colourant over the mould surf

REFERENCES:
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patent: 3561103 (1971-02-01), Dent
patent: 3729368 (1973-04-01), Ingham et al.
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patent: 5075059 (1991-12-01), Green
patent: 5565263 (1996-10-01), Ohsumi et al.

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