EP2227392A1

EP2227392A1 - Method for coating both sides of a molded article from a wood-derived or gypsum-derived material

Info

Publication number: EP2227392A1
Application number: EP08862036A
Authority: EP
Inventors: Lars Koppelmann; Roland Streng; Joachim Strauch; Markus Salzmann; Peter Kitzel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2007-12-19
Filing date: 2008-12-18
Publication date: 2010-09-15
Also published as: WO2009077597A1

Abstract

The invention relates to a method for method for coating both sides of a molded article from a wood-derived or gypsum-derived material with a plastic film, characterized by a) arranging at a distance and securing the molded article in a die between the plastic films to be applied, thereby forming three chambers A, B and C, chamber A between the two plastic films, the molded article being positioned in the middle between the two films, and two chambers (B and C) between the plastic film and the wall of the die, b) evacuating the air from chambers A, B and C, c) heating the films, d) using ambient air to relieve chambers B and C to atmospheric pressure, and e) thereby pressing the films onto opposite surfaces of the molded article and while maintaining a vacuum between the films.

Description

Process for double-sided coating of a wood-based or gypsum material molding

description

The invention relates to a method for coating both sides of a wood-based material or gypsum material molding with a plastic film, characterized in that

a) the molded part is arranged and fixed in a capsule between the plastic films to be applied at a distance ratio, so that 3 chambers A,

B and C are formed: chamber A between the two plastic films, in the middle of which the molded part is positioned and two chambers (B and C) each between plastic film and capsule wall, b) the air from the chambers A, B and C evacuated c) the films are heated, d) the chambers B and C are vented to atmospheric pressure with outside air, and e) the films are thereby pressed onto opposite surfaces of the molded article while maintaining a vacuum between the films in chamber A.

For subsequent surface treatment of wood-based or gypsum material moldings, only one-sided coating processes have hitherto been described in the prior art. If a multi-sided coating is desired, the process must be repeated several times. A complete sheathing of wood-based or gypsum material moldings can be done only cumbersome with the literature known methods.

Shape and surface can be subsequently only lavishly changed in wood-based or gypsum material moldings. This is especially true in the case of molded parts which have a structured three-dimensional surface. Straight look and features - such as feel or easy care - the wood material or gypsum material moldings often leave much to be desired.

Object of the present invention was therefore to find a method that allows a simple and subsequent surface design of wood-based or gypsum material moldings.

Surprisingly, it has now been found that the method mentioned at the beginning is outstandingly suitable for carrying out a subsequent surface design in the case of wood-based or gypsum-metal molded parts. A comparable method for coating doors is already known from WO 01/032400. However, WO 01/032400 does not disclose whether and in a soft way wood-based or gypsum material moldings can be coated with this method.

The method described in WO 01/032400 is hereby incorporated by reference. In particular, reference is made explicitly to the following process and device features of WO 01/032400, which are used individually or preferably in combination:

• Infrared heating, which heats the plastic film prior to pressing, preferably above the softening point. Blistering, tearing of the film or whitening of the film at the edges is thus avoided;

• Separate chambers between wood-based material or gypsum material molding and foil (chamber A), as well as between foil and capsule wall (chamber B). Advantageously, the chambers A and B are simultaneously or preferably successively subjected to a vacuum. As a result, buckling of the film, or premature contact of the film with the wood-based or gypsum material molding is prevented. By releasing the vacuum in chamber B to atmospheric pressure, the film is pressed onto the wood-based material or gypsum material molding, while the vacuum in chamber A is still maintained;

Simultaneous coating of the wood material or gypsum material molding with foil on opposite sides - for example, this can be achieved by the wood material or gypsum material molding anchored in a frame made of wood, metal or plastic and centered in the middle of the coating chamber by a bracket to the head ends of the Frame is held. Below the fiber cement or concrete molding a further film is introduced, whereby a third chamber C between this film and the lower capsule wall is formed. Then, as already described above, all three chambers are subjected to a vacuum and the wood-based material or gypsum material molded part is coated on both sides in accordance with heating of the film by opening the chambers A and C.

Coating of the plastic film or preferably of the wood material or gypsum material molding with an adhesive that allows the permanent adhesion of the film on the wood material or gypsum material molding.

The adhesive can be based either on an aqueous, VOC-free PU base, or on a sprayable (PU) hotmelt, which is applied with a special application gun. The inventive method for two-sided coating of a wood material or gypsum material molding with a plastic film is characterized in that

a) placing and fixing the molded article in a capsule between films at a distance ratio; b) evacuating the air from the capsule; and c) pressing the films onto opposite surfaces of the molded article while maintaining a vacuum between the films.

The inventive method is surprisingly suitable for two- or multi-sided coating of wood-based or gypsum material moldings, which were previously accessible to a coating with plastic film only in several steps.

Under wooden materials are in particular plywood or plywood (this include

Veneer plywood, plywood, resin molded wood, molded plywood, composite plywood and cross laminated timber), composite panels (these are multi-layer composites with, for example, high strength cover layers and light center layers), wood chipboard materials (such as chipboard or chipboard) or wood fiber materials (such as porous fiberboard, bitumen Fiber board, MDF or HDF.

Gypsum materials are to be understood in particular as gypsum plasterboard, gypsum fiber or gypsum chipboard shaped articles such as, for example, ribbons.

From the company XeIIa drywall systems under the name Fermacell are commercially available. FERMACELL consists of gypsum and paper fibers, which are obtained in a recycling process from paper. These two natural raw materials are mixed and pressed after addition of water - without further binders - under high pressure to stable plates, dried, impregnated with a water-repellent and tailored to the required formats.

The gypsum reacts with water, permeates and envelops the fibers. This results in the high stability and non-combustibility of FERMACELL. Due to the material composition, FERMACELL is a construction, fire protection and damp-proofing board at the same time.

The adhesives used are preferably aqueous polyurethane-based systems, both one-component and two-component systems. As one-component adhesives, PU dispersions come into consideration, for example Jowapur® 150.50 may be mentioned here. Suitable two-component adhesives are combinations of PU dispersions such as, for example, Jowapur® 150.30 with isocyanates such as, for example, Jowat® 195.40. As a rule, however, adhesives based on acrylate or epoxy resin are also suitable for use. The application of the adhesive may be by conventional methods such as brushing, rolling or spraying, with spraying being particularly preferred. A drying time of 20 minutes at room temperature following the adhesive application is sufficient in the systems described.

It is also possible to use hot melt adhesives which are rolled up, lapped, rolled and sprayed. Preferably, polyurethane adhesives are used which crosslink with moisture.

Suitable plastic films are, in particular, polyvinyl chloride, styrene copolymers, polypropylene, polyvinylidene fluoride, thermoplastic polyurethane (TPU) and polymethyl methacrylate (PMMA). Due to their weather resistance, especially polyvinyl chloride and styrene copolymers such as SAN, AMSAN and in particular ASA have proved suitable for outdoor applications. In the case of, for example, the ASA

Copolymer, the film may be modified by 0.5-30% by weight of a thermoplastic elastomer. Typical typical thermoplastic elastomer classes include: TPE-O (olefin-based thermoplastic elastomers, predominantly PP / EPDM), TPE-V (olefin-based cross-linked thermoplastic elastomers, predominantly PP / EPDM), TPE-U (urethane-based thermoplastic elastomers), TPE E (thermoplastic copolyesters) TPE-S (styrene block copolymers such as SBS, SEBS, SEPS, SEEPS, MBS) and TPE-A (thermoplastic copolyamides, eg PEBA). SAN, AMSAN, ASA, TPU or PMMA films are particularly preferably used. Particularly preferred is the use of coextrusion films which have a hard and scratch-resistant cover layer and a softer support layer. For example, a coextrusion film with a hard, scratch-resistant outer layer such as PMMA and a more flexible ASA inner layer is suitable.

Furthermore, it is possible in particular to use the coextruded two-layer films described in WO-A 96/23823 and WO-A 97/46608 for coating wood-based or gypsum-material molded parts. The two-layer films consist of a carrier layer such as polystyrene or HIPS and a primer layer, for example based on elastomeric styrene-butadiene block polymers. As already mentioned above, an additional adhesive can usually be dispensed with in these cases. The coextruded film is pressed onto the fibreboard in such a way that the adhesion promoter layer comes into direct contact with the plate.

The films described in the sections above can be used both in various solid colors and printed surfaces. In addition, the surface can be structured by various embossing rollers during the extrusion of the film. The films used have a thickness between 50 and 750 .mu.m, preferably between 100 and 500 .mu.m and particularly preferably between 200 and 350 .mu.m. They may be prepared from the corresponding granular precursors by the known film production processes, the extrusion process being preferred for cast film production.

To improve adhesive properties, the films may have been corona treated on one or both sides.

The wood-based or plaster-molded parts to be coated generally have a dimension of approximately 100 × 150 cm in size up to a few square meters. The plates can be several meters long.

Due to the coating according to the invention, the wood-based or gypsum-metal molded parts are decisively improved in their load-bearing capacity and resistance to breakage. This is achieved by the complete removal of air between the plate and the film, which can not be done with conventional lamination process. Furthermore, by applying the vacuum, the film is pressed onto the plate, which results in a strong bond between the film and the plate, which can be intensified by the application of an adhesive.

Finally, the plastic film can act as a primer, which allows easy post-treatment such as brushing, printing, for example, with advertising slogans, etc.

Films such as the above-mentioned ASA films can be subsequently changed in color and shape by a suitable post-treatment such as brushing, printing or embossing.

Furthermore, the coated wood-based or gypsum material moldings can be cleaned more easily, for example by washing with soapy water, than the uncoated molded parts.

Due to their ease of care, the coated wood-based or gypsum-molded parts are suitable for interior applications in construction.

In particular, the moldings come as wall or ceiling paneling, partitions, doors, window frames, window sills, baseboards, railings, handrails, balcony clothing, expansion boards, housing of speakers and Hifigeräten etc. in question.

The process according to the invention for coating wood-based or gypsum-material molded parts with a three-dimensionally structured upper part is particularly advantageous. Surface suitable because these moldings were not to be coated with the previous methods of the prior art. The only option so far was to paint these moldings consuming. Examples of molded parts with a three-dimensionally structured surface are cassette doors, doors with ornamental cuts (emblems or ornaments), decorative and design profiles for interior fittings, curved column cladding, slabs with imitated roughing structure. For the designers of furniture and utensils there are now completely new possibilities. Particularly preferred are wood-based or gypsum material boards with at least one three-dimensionally structured surface.

Interesting are the coated moldings for bathroom or kitchen facilities, as they are easy to clean and are exposed to high humidity. If desired, the liquid absorption of the wood-based or gypsum material molding can be almost completely suppressed by the coating with a plastic film.

By special additives, the pest infestation - such as by fungi and mites - which is already already smaller than in uncoated moldings, be further minimized. The coated molded parts can therefore be used, in particular, in allergy-free apartments and in hospitals.

Due to their attractive surface and their high flexibility, the wood-based or gypsum-metal molded parts according to the invention are outstandingly suitable for laminating, for example, cable ducts, roller shutter boxes and curtain hangings. The moldings can be quickly adapted to the given requirements, for example by cutting.

example 1

Two-sided coating, for example, of an MDF with a three-dimensional surface structure with an ASA film

The substrate to be coated on both sides was an MDF board made of TOPAN® Standard, a commercially available MDF board from Glunz AG. The plate was 120 cm long, 80 cm wide and 19 mm high and had various ornamental cuts on one side. In the first step, the adhesive was first applied. The adhesive used was an aqueous two-component system (consisting of binder and hardener) based on polyurethane, which was prepared immediately before application by mixing the two individual components. To obtain a homogeneous mixture, the mixture was stirred at room temperature for at least 3 minutes using a KPG stirrer. Subsequently, the adhesive was applied by means of a spray gun of Type Walther Pilot applied in an amount of about 80 g / m ² on both surfaces and on the 4 edges of the molding. Subsequently, the molding was allowed to dry for 20 minutes at room temperature. In the next step, the MDF board was fixed by a stop at the two head ends (opposite side surfaces) and positioned in the center of the coating capsule. The two plastic films to be applied were in each case mounted between the capsule wall and the molded part. This created 3 chambers in the coating capsule: a chamber between the two plastic films, in the middle of which was positioned the MDF board (chamber A). The two other chambers were located between the plastic film and the capsule wall (chamber B, C). As plastic film 250 microns were strong, white pigmented cast films made from Luran ^® S, the ASA commercially available from BASF Aktiengesellschaft - copolymer used. Subsequently, all three separate chambers (A, B, C) were evacuated simultaneously in the capsule. After reaching a vacuum of 25 mbar, the two plastic films were heated to a temperature of 150 ^° C. by means of IR emitters which were attached to the capsule walls. Upon reaching the temperature, the heating was stopped and chamber B and C were vented with air to atmospheric pressure while maintaining the vacuum in chamber A. The flooding of chambers B and C produced an overpressure, whereby the heated plastic films were pressed onto the adhesive sprayed surfaces and edges of the molding. At the level of the side surfaces, the two plastic films hit one another and at this point a weld forms, which forms a frame around the entire molded part on the side surfaces. This ended the coating process. By heating with the IR emitters during the process, the adhesive on the top and side surfaces of the molded part was also activated, resulting in a very good adhesion between the adhesive and the plastic film after completion of the process. After completion of the coating process, the coated molded part could be removed from the capsule. The overlapping film passing over the weld was manually removed with a sharp blade.

Claims

claims

1. A method for coating on both sides of a wood-based or gypsum material molding with a plastic film, characterized in that

a) the molding is arranged and fixed in a capsule between the plastic films to be applied in a distance ratio, so that 3 chambers A, B and C are formed: chamber A between the two plastic films, in the middle of the molding is positioned and two chambers (B and C) each between plastic film and capsule wall, b) the air is evacuated from the chambers A, B and C, c) the films are heated, d) the chambers B and C are vented to atmospheric pressure with outside air and e ) the films are thereby pressed onto opposite faces of the molding while maintaining a vacuum between the films in chamber A.

2. The method according to claim 1, characterized in that an adhesive is applied to the molding and / or the plastic films prior to step b).

3. The method according to any one of claims 1 and 2, characterized in that the films represent primer films that can be easily treated.

4. The method according to any one of claims 1 to 3, characterized in that the films of polyvinyl chloride, styrene copolymers, polyethylene, polypropylene, polyvinylidene fluoride, thermoplastic polyurethane and / or polymethylmethacrylate exist.

5. The method according to claim 4, characterized in that the films are ASA films.

6. The method according to any one of claims 1 to 5, characterized in that the molded part is a wood fiber board.

7. The method according to any one of claims 1 to 5, characterized in that the molded part is a gypsum chipboard.

8. The method according to any one of claims 1 to 7, characterized in that the molded part is a plate having at least one three-dimensionally structured surface.

9. The method according to any one of claims 1 to 7, characterized in that the molded part is a wall or ceiling panel for interior work.