FI80637B - Process for coating plate-like products with a thermoplastic polymer - Google Patents

Abstract

The invention relates to a process for coating plate-like products 1 with thermoplastic polymer, in which process molten thermoplastic polymer is extruded from the die gap 12 of an extrusion die 20 to a film, which is pressed firmly to the surface of the plate-shaped product 1 by means of a press roller 5 or press belt. The plate-shaped product 1 is in the longitudinal direction an essentially rigid plate which advances in a single plane. The die gap of the extrusion die 20 is at an adjustable distance from the surface of the product 1 to be coated and from the place at which the coating web 4 formed by the extruded molten thermoplastic polymer meets the surface of the product 1 to be coated, thereby allowing oxidation of the thermoplastic polymer before it is pressed firmly to the surface of the plate-shaped product 1. <IMAGE>

Description

80637 1 Method for coating a sheet-like product with a thermoplastic polymer Förfarande för beläggning av skivformiga produkter med en en thermoplastisk polymer 5

The invention relates to a method for coating sheet-like products with a thermoplastic polymer by extrusion.

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Extrusion coating is a well-known technique for coating track-like products such as paper, board and plastic film. However, equipment used in the extrusion coating of such products cannot be used to coat rigid sheet-like products because they are designed to function only for coating relatively thin and flexible products, usually in roll form.

Equipment 20 using extrusion technology has also been designed to coat rigid products. For example, U.S. Patent 3,544,669 discloses an extrusion coating of a rigid, circular cross-section product in which a hot melt adhesive layer is added from the first extrusion nozzle and a plastic coating is added from the second annular nozzle. In this method, the extrusion nozzle 25 is formed by a channel that opens onto the surface of the product to be coated. Thus, in the device described in the patent, the product to be self-coated forms part of the surfaces delimiting the extrusion die orifice.

The coating equipment described has many serious drawbacks.

30 First, the coating device is limited to products of a certain size and shape. Second, the material to be extruded cannot be subjected to adhesion-enhancing treatments such as oxidation, which, for example, when coated with polyolefins, is necessary to achieve sufficient adhesion without separate adhesion layers. Thirdly, in the apparatus according to the patent, it is not possible to carry out the lamination coating by attaching additional layers to the product.

U.S. Pat. No. 4,80637 1 discloses an apparatus for joining a thermoplastic plastic layer to a rigid sheet product by an extrusion method such that molten plastic is extruded to the surface of the product from an extrusion die. Also in the extrusion apparatus according to this patent, the nozzle opening of the extrusion nozzle opens to the surface of the product and the product itself thus forms part of the surfaces defining the extrusion nozzle opening. This patent has the same disadvantages as the apparatus of U.S. Patent 3,544,669, i.e., oxidation of the extrudable melt to improve adhesion and incorporation of additional layers into the Ίq product is impossible.

The present invention relates to a method and an apparatus for coating rigid sheet-like products by extrusion with a thermoplastic which does not have the disadvantages described above.

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A method of coating sheet-like products with a thermoplastic polymer according to the invention, wherein the molten thermoplastic polymer is extruded from a nozzle slot of an extrusion nozzle into a film which is melted the nozzle gap is at an adjustable distance from the surface of the product to be coated and from the point where the coating web formed by the extruded molten thermoplastic polymer meets the surface of the product to be coated, allowing the thermoplastic polymer to be oxidized before being pressed onto the sheet product.

The method according to the invention achieves many of the advantages described below. Since the distance of the nozzle gap of the extrusion nozzle from the surface of the product to be coated and from the point of contact of the extruded polymer and the product can be adjusted, the method allows sheet products of different thicknesses to be coated in the same device. At the same time, the oxidizing effect which occurs in the air gap between the nozzle gap of the extrusion nozzle and the point of contact between the coating and the surface of the product can be adjusted. The effect of oxidation can be further enhanced by introducing 3 80637 l of oxidizing agent, for example air or ozone, into said air gap or melt membrane. In addition, in the method according to the invention, it is very easy to add one or more layers of some other coating material to the product to be coated, which is introduced in the form of a web to the pressing point 5. In the method according to the invention, it is also very easy to form coatings which are patterned or contain additives which affect the appearance or surface properties of the coating surface. In addition, the invention allows the use of several different types of plastics simultaneously. In this case, several extruders can be used, which feed the molten plastic into the same nozzle.

The molten plastics coalesce either in the nozzle or shortly thereafter and penetrate the nozzle opening as a layered product.

The method according to the invention can be applied to the coating of all rigid Ί5 sheet-like products with thermoplastic polymers. Such products include e.g. molded plywood, hardboard, fibreboard, gypsum board, particle board, parquet, boards and board panels, metal sheets and insulation boards. The thicknesses of the sheet products are freely selectable, since the method according to the invention does not place any restrictions on the thickness of the product to be coated.

Likewise, in the process according to the invention, the thermoplastic polymer or polymers to be extruded are freely selectable, provided that the plastics in question are suitable for extrusion.

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In addition to coating sheet-like products, the method according to the invention is very well suited for the production of laminate products, in which case the extruded synthetic polymer is used as an air layer between the sheet product and a thinner laminate surface. The laminate web 30 is then guided, for example, from a roll to pass under a press roll which presses the extruded synthetic polymer onto the surface of the sheet product. At the same time, the laminate layer is pressed into the sheet product and adhered to it by means of a synthetic polymer layer. Of course, it is possible to add separate layers of adhesive between the laminate layers. Examples of such product applications are parquet / foam, sheet / foam, sheet / foil (aluminum, polyethylene, polypropylene, polyamide), sheet / fabric, sheet / paper, 4 80637 J sheet / tile, sheet / veneer, sheet / insulation, sheet / plate, plate / cell structure, etc.

In the method according to the invention, it is also possible to modify the surface of the sheet product to be manufactured. If the surface of the press roll is provided with a suitable groove or embossing pattern, in the pressing step a pattern is formed on the synthetic polymer layer or laminate surface attached to the sheet product. It is also possible to modify the surface of the sheet product to be produced by adding various additives in the form of particles to the surface of the extruded synthetic polymer, whereby the additive particles are compressed on the surface of the sheet product formed by the press roll. In this way, for example, the friction and appearance properties of the sheet product can be modified.

The method according to the invention will now be illustrated with reference to the accompanying figures, in which Figure 1 shows in general an apparatus for carrying out the method according to the invention, Figure 2 shows in more detail to a coated sheet product, and Figure 4 schematically shows an apparatus for providing a surface texture to a coated product according to the invention.

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In the apparatus 100 according to FIG. In preheating, the surface temperature 35 of the product is raised to the temperature required for coating, and the preheating device 3 is, for example, an infrared or electric heating unit. Preheating improves adhesion, but, depending on the product, is not always necessary. After preheating, the product 1 is passed past a coextrusion nozzle 20, from which a path 4 of synthetic molten polymer from the nozzle 20 is added to the material 1 to be coated. The press roll 5 can be cooled, for example, by means of a cooling roll 7.

The coated product is then passed past a cooling unit 8 where the coated product is cooled. In the embodiment according to Figure 1, an additional laminate 9 is further shown, which is passed from a roll - 10 between the coating 4 added to the product 1 and the press roll 5, whereby the laminate 9 adheres to the surface of the product via a synthetic polymer. However, this is only one additional embodiment to which the method according to the invention is in no way limited.

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Figure 2 shows a detail of the apparatus shown in Figure 1. The synthetic polymer from the feed channel 11 of the extrusion nozzle 20 is extruded out of the nozzle slot 12 into a web 4 formed by molten synthetic polymer. Figure 2 shows that the extrusion nozzle 20q and thus the nozzle gap 12 are spaced from the surface of the product 1 and the press roll 5.

Thus, an air gap is formed which allows the molten coating web 4 to be oxidized before the web 4 is pressed onto the surface of the product 1 by means of a pressing roller 5. The position of the extrusion nozzle 20 relative to the surface of the product 1 25 and the press roll 5 can be changed by moving it in the direction of the arrows A and B, whereby the setting of the oxidizing effect can be adjusted. At the same time, it allows products of different thicknesses to be coated in the same equipment. Of course, the press roll 5 and the counter roll 6 are also adjustable according to the size of the product 1 to be coated.

The oxidizing effect of the extruded synthetic polymer web 4 can be enhanced by introducing an oxidizing agent, for example air or ozone, between the nozzle opening 12 and the press roll 5, preferably 35 by means of one or more tubes 17 directly into the molten film.

In the embodiment according to Fig. 3, an additional 6,80637 l of substance particles 14 are sprinkled from the hopper 13 onto a path 4 formed by the synthetic polymer coming from the extrusion nozzle 20. The particles are compressed and adhered to the coating on the surface of the product 1 by the pressure roll 5. In this way, the surface properties of the coating g, such as friction, adhesion, strength and appearance properties, can be easily changed.

In the embodiment according to Fig. 4, protrusions 15 are made on the surface of the pressing roll 5, which in the pressing form grooves 16 corresponding to the surface layer of the product. In this way, the surface properties of the coating can also be varied. Instead of the protrusions 15, it is of course possible to use grooves which, when pressed, produce corresponding protrusions on the surface of the product.

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Claims (6)

7 80637 A method for coating sheet-like products (1) with a thermoplastic polymer, wherein the molten thermoplastic polymer g is extruded from a nozzle slot (12) of an extrusion die (20) into a film pressed onto the surface of the sheet-like product (1) by a press roll (5) or a press belt. 1) being a substantially rigid plate extending in one plane in the longitudinal plane, characterized in that the nozzle-g gap (12) of the extrusion die (20) is at an adjustable distance from the surface of the product (1) to be coated and where the coating web (4) of extruded molten thermoplastic polymer meets the surface of the product (1) to be coated, which allows the thermoplastic polymer to be oxidized before it is pressed onto the surface of the sheet-like product (1). 15 1 Claims Process according to Claim 1, characterized in that the oxidation is carried out by applying oxygen or ozone to the surface of the coating web (4) formed by the molten thermoplastic polymer at a point before the point of intersection of the extruded molten polymer and the sheet-like 2Q product (1). Method according to Claim 1 or 2, characterized in that the sheet-like product (1) is coated with one or more film-like layers (9) which are passed between the coating web (4) formed by the extruded thermoplastic polymer and the press roll (5) or belt. . Method according to Claims 1 to 3, characterized in that the molten coating (4) contains two or more layers 30 extruded in a so-called by coextrusion to the surface of the product. Method according to one of the preceding claims, characterized in that the coating formed by the thermoplastic polymer is provided with an adhesive or abrasive (14) which is applied to the coating web (4) comprising thermoplastic before it is pressed onto the surface of the sheet-like product (1). 8 80637 Method according to one of the preceding claims, characterized in that the press roll (5) is patterned. 5 10 15 20 25 30 35 9 80637