A METHOD OF MANUFACTURING RELIEF PATTERNED SHEET-LIKE PRODUCTS

PROCEDE DE PRODUCTION DE PRODUITS EN PLAQUE A MOTIF EN RELIEF

English Abstract

Sheet-like products comprising a fibrous material, such as sawdust, wood
chippings or wood powder, and a thermoplastic glue can be provided with a
relief pattern by compression moulding the products in a pressure-cell press.

French Abstract

Produits en plaque constitués d'un matériau fibreux tel que de la sciure de bois, des copeaux de bois ou de la poudre de bois et d'une résine thermoplastique. Ces produits, qui peuvent comporter un motif en relief, sont obtenus par moulage sous pression dans une presse à cellule de compression.

Claims

Claims
1. A method of producing relief-patterned products, characterized by compressionmoulding in a pressure-cell press a product produced from a mixture of fibrous
material and thermoplastic glue.
2. A method according to Claim 1, characterized in that the product is a sheet-like
product.
3. A method according to Claim 1 or 2, characterized in that the fibrous material is a
wood-fibre based material, such as sawdust, wood powder or wood chips.
4. A method according to any one of the preceding Claims, characterized in that the
thermoplastic glue is EVA, ethylene-acrylate-copolymer, PVAC or olefin glue.
5. A method according to any one of the preceding Claims, characterized by heating
the sheet-like product to a temperature of 40-60°C, preferably 45-60°C, prior to the
actual pressing process.
6. A method according to any one of the preceding Claims, characterized by raising
the temperature of the pattern forming tool in the pressing process.
7. A method according to Claim 6, characterized by maintaining said temperature in
the range of 30-160°C, preferably 50-100°C.
8. A method according to any one of the preceding Claims, characterized by
maintaining the press pressure above 800 bars, preferably above 1000 bars.

Description

CA 02245946 l998-08-ll
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A Method Of Manufacturin~ Relief Patterned Sheet-Like Products
The present invention relates to m~nllf;lc*-rin~ relief patterned sheet-like products.
Examples of such sheet-like products are doors, cupboard doors, patterned woodenpanels, and so on. The products are produced from materials that have thermoplastic
properties, preferably materials that contain wood-fibre based material.
Relief patterned sheet-like products, such as kitchen cupboard doors, patterned panels,
doors, etc., are in great ~lem~nd Such products are typically produced from a wooden
sheet into which the pattern is cut. ~ltPrn~1ively, pre-shaped wooden blanks or
preforms can be fastened onto one surface of the sheet. It is also known to combine
these two techniques.
The work involved in providing sheet-like products with a relief pattern, which is done
m~nu~lly to a large extent, is expensive, time consuming and requires a high degree of
expertise. Co~equently, there is a need of less complicated and cheaper methods of
producing relief patterned sheet-like products.
When compression moulding particle boardj for instance, in a mould that has steep
transitions between raised and sunken parts, a poor result is obtained due to the ease in
which the board cracks. The board may even break in some cases.
WO 82/03595 teaches an ~pal~Lus and a method for producing patterned wood-fibre
board which is intended mainly for use as a sound-in~ tin~ wall coveTing. According
to this method, a wet wood-fibre pulp is formed with the aid of a patterned roll and
then dried. When pr~c~in~. this known method, the board is patterned in the stage of
its manufacture. C~onseqllPntly, it is necessa~y to make large investments and to apply a
complicated process when wishing to use this technique.
EP 0 489 994 describes a door that is provided with one or layers of relief-patterned
thermoplastic material. In this case, the actual wood has not been forrned or shaped

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W 097/28937 2 PCT/SE97/~0137
and there is used a pre-formed sheet of another material. Different areas of the surface
are produced from different m~t~-ris~l with this technique. Furthermore, the technique is
not suitable for producing sheet-like products that are patterned with sunken surfaces.
EP 0 574 953 teaches a method of producing relief-patterned wood-composite sheets,
wherein the sheets may be formed with va~ious different patterns at the same time. The
press time is relatively long (about 5 min.), which results in relatively high
m~nllf~cturing costs. Furthermore, the patterned sheets have a relatively small surface
size (20 x 20 inches).
There is thus a need of ~ltern~1;ve methods for pro~ cin~ relief-patterned sheet-like
products with which the aforesaid problems are resolved and which enable sheets
having a surface area of at least 1.5--2m2 to be pressed.
Summary of the Invention
It has now been found that a relief-p~ttPrned sheet-like product of good quality can be
produced quickly and simply by compression-moulding a sheet-like pre-form that
includes a mixture of fibrous m~teri~l and thermoplastic glue in a press of the pressure
cell type.
The invention will now be described in more detail with reference to the
accompanying drawing, in which
Figure 1 illustrates an example of a board pattern that can be produced by the inventive
method; and
Figure 2 is a cross-sectional view of the patterned board shown in Figure 2.
i

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Detailed Description of the Invention
By using a pressure-cell type press, it is possible to achieve effects that cannot be
achieved with a conventional piston-type press. In a pressure-cell press, pressure is
transferred by an elastic membrane. The blank is therewith pressed in many directions
~iml-lt~neously, which enables the blank to be shaped quickly and readily in
accordance with the shape of an underlying moulding tool. This enables the
compression moulded product to be provided with very complicated p~ttPrn~ Suitable
blanks can also be pressed at very high pressures, about 800 bars and preferably in
excess of 1000 bars, therewith achieving very short press times, e.g. press times below
two minlltes, preferably below one mimlte
SE-C-452 436 describes a pressure-cell type plant which is well-suited for use in
conjunction with the method for producing relief-patterned sheet-like products in
accordance with the invention. This press is designed for the m~mlf~ lre of not-readily shaped sheet-metal elP.me.nt~ A hard shaping tool is placed in the bottom of a
tray and the blank or preform to be pressed is placed on top of the tool. The tray is
pushed into the press and the blank then pressed against the shaping tool by means of
an elastic membrane, for instance an hydraulically operated membrane.
If a sheet of fibrous material, for instance particle board, that contains no thermoplastic
~lue is compression moulded at high pressure with the aid of a pressure-cell press and
a hard shaping tool, the sheet will buckle or collapse. Because thermoplastic glue is a
cold flowing glue, these problems do not occur as readily when compression moulding
a sheet of fibrous material that includes such glue. The pressing properties of such a
sheet can also be enhanced by heating the sheet. The person skilled in this art will be
able to establish appropriate press temperatures for different glue sorts~ with the aid of
simple tests.

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According to the invention, the shapability of the fibrous sheet can be further
enhanced, by heating the sheet to a temperature of 40-70~C, preferably to 45-60~C,
prior to pressing. The sheet may be heated conveniently in a microwave oven.
The fibrous m~te.risll is preferably a wood-fibre based material, such as sawdust, wood
chippings or wood powder, and so on. Suitable thermoplastic glues are polymer glues,
for instance EVA (ethylene-vinyl acetate-copolymer), ethylene-acrylate-copolymer,
and PVAC (polyvinyl acetate) and other olefin glues, etc. The aforesaid sheet, or
board, co~ i o~; fibrous material and thermoplastic glue is produced by methods
known in the manufacture of particle board, board sheets, etc.
The invention will now be described with reference to the following Example. TheExample is given by way of illustration only and is not intended to limit the scope of
the invention.
Example
A particle board whose glue component comprised the thermoplastic polymer EVA
was first heated to a temperature of 60~C in a microwave oven and then pressed in a
pressure-cell press obtained from ABB, Vasteras, Sweden. The particle board was
pressed on a ~h~ping tool of the desired pattern. The tool was heated to 80~C and the
board then pressed for one minute at a pressure of 1000 bars. A particle board having a
pronounced relief pattern was obtained.