EP2222468A1

EP2222468A1 - Method for coating a transparent molded article

Info

Publication number: EP2222468A1
Application number: EP08863229A
Authority: EP
Inventors: Lars Koppelmann; Roland Streng; Markus Salzmann; Joachim Strauch; Peter Kitzel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2007-12-19
Filing date: 2008-12-18
Publication date: 2010-09-01
Also published as: WO2009077596A1

Abstract

The invention relates to a method for coating a transparent molded article, characterized by a) arranging and securing the molded article in a die, the plastic film being applied between the wall of the die and the molded article, b) evacuating the air from the chamber between the plastic film and the molded article, c) heating the plastic film, d) using ambient air to relieve a second chamber between the plastic film and the wall of the die to atmospheric pressure, and e) thereby pressing the plastic film onto the molded article and while maintaining a vacuum during this pressing step. The invention also relates to coated molded articles, to facade, privacy protection and paneling elements that are for the first time obtainable by this method.

Description

Process for coating a transparent molding

description

The invention relates to a method for coating a transparent molded part, characterized in that

a) the molded part is arranged and fixed in a capsule, the plastic film being mounted between the capsule wall and the molded part, b) the air in the chamber is evacuated between the plastic film and the molded part, c) the plastic film is heated, d ) a second chamber between the plastic film and the capsule wall with ambient air is released to atmospheric pressure and e) the plastic film is thereby pressed onto the molded part and during this pressing process, a vacuum is maintained.

Furthermore, the invention relates to coated moldings, facade, visual protection and clothing elements, which are accessible for the first time with this method and the use of the moldings.

So far, only lavish laminating techniques were available for coating transparent moldings. Transparent moldings which have a structured surface could not be produced with this coating technique. For example, to produce visual protection elements, the transparent molded part had to be etched, vapor-deposited or sand-blasted using sophisticated technology, or the structured molded part had to be manufactured entirely from expensive, pigmented frosted glass.

The shape, color and surface of molded parts can hardly be changed at all, if at all. Straight look and features such as feel and weather resistance of the moldings often leave something to be desired.

Object of the present invention was therefore to find a method that allows a subsequent surface design of the transparent moldings.

Surprisingly, it has now been found that the method mentioned in the introduction is outstandingly suitable for carrying out a subsequent surface design for molded parts.

A similar process for coating doors is already out

WO 01/032400 known. However, WO 01/032400 can not be seen if and on which way transparent moldings can be coated with this method.

The method described in WO 01/032400 is expressly incorporated herein 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, whereby the plastic film is preferably heated to 120 to 180 ⁰ C prior to pressing - blistering, cracking of the film or

White fracture of the film at the edges can thus be avoided;

• Separate chambers between the molding and film (chamber A), as well as between the film and the capsule wall (chamber B) - advantageously, the chambers A and B are applied simultaneously or preferably successively with a vacuum. As a rule, a vacuum of less than 50 or preferably less than 30 mbar is set. This prevents buckling of the film or premature contact of the film with the molded part. By releasing the vacuum in chamber B to atmospheric pressure, the film is pressed onto the molded part while the vacuum in chamber A is still maintained; • Simultaneous coating of the molded part with foil on opposite sides - this is most easily achieved by anchoring the molded part in a frame made of wood, metal or plastic and centered in the center of the coating chamber by a holder at the head ends of the frame. Below the molding, another film is introduced, whereby a third chamber C is formed between this film and the lower capsule wall. Then, as already described above, all three chambers are subjected to a vacuum and the molded part is coated on both sides after the films have been heated by opening the chambers A and C.

Coating of the plastic film or preferably of the molded part with an adhesive which allows the permanent adhesion of the film to the molded part.

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.

Surprisingly, the method according to the invention is suitable for coating transparent molded parts - in particular with a structured surface - which hitherto were not accessible to a coating with plastic film.

Particularly preferred are transparent moldings which have a textured surface with elevations of 2 to 15 mm. These elevations may be as regular or irregular three-dimensional structure on either or preferably one Be attached side of the molding. In other words, particularly preferred molded parts have a smooth underside and a three-dimensionally structured upper side. When backlighting these moldings show an interesting room depth effect. The moldings generally have a total layer thickness of 2 to 100 mm and can be up to several meters long.

The molded parts to be coated are transparent or at least translucent. Even after the coating, the moldings are usually transparent or at least translucent. The transparent shaped parts are preferably a flat, transparent, structured plate. In particular, the transparent molded part is a glass or plastic glass plate, each having a smooth and a structured surface.

The moldings to be coated are preferably made of glass or plastic glass. Plastic glasses are understood to be transparent materials such as polycarbonate, PMMA, SAN, AMSAN, etc. The best known representative is Plexiglas.

In order to avoid deformations of the molded part during the coating process, the molded part may be clamped in a temporary frame during the entire process. If the frame is to remain in the finished coated molding, it is sprayed before coating with a corresponding adhesive, which is then activated in the coating process by the heat of the film. If the frame is to be removed after the coating, no adhesive is applied and the film is cut along the frame, preferably with a blade.

The adhesives used are preferably aqueous polyurethane-based systems. There are both one-component and two-component systems in question. As one-component adhesives, PU dispersions come into consideration, for example Jowapur® 150.50 may be mentioned here. As two-component adhesives combinations of PU dispersions such as Jowapur® 150.30 with isocyanates such as Jowat® 195.40 come into question. As a rule, however, adhesives based on acrylate or epoxy resin are also suitable for use. Likewise, a two-layer film with a primer based on styrene-butadiene-styrene copolymers on the bottom is suitable. When using the adhesive films can be dispensed with the use of an additional adhesive in the rule. The application of the adhesive can be carried out by the conventional methods such as painting, rolling or spraying, wherein the spraying is particularly preferred. A 20 minute drying time at room temperature following application of the adhesive 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. In particular, the weather resistance and the feel of molded parts can be significantly improved by the coating with plastic films.

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, styrene copolymers such as SAN, AMSAN and in particular ASA have proved suitable for outdoor applications in particular. For example, in the case of 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 (styrenic 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. Such films can be used in various plain colors as well as printed surfaces. Furthermore, the surface can be structured by different 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 can be prepared from the corresponding raw materials in granular form by the known processes for film production, 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.

Due to the interesting lighting effects, the coated moldings can be advantageously used in the construction sector and interior design.

In particular, the moldings and plates according to the invention come as ceiling and wall coverings in question. Due to their interesting transparent / translucent behavior, the molded parts can also be designed with backlighting.

Also as clothing elements in the outdoor area, the moldings of the invention are suitable. Particularly suitable here are weather-resistant films such as PVC, ASA and PMMA coated molded parts. With the method according to the invention facade elements can be produced that allow interesting light and space.

Due to the simple surface design, the molded parts continue to be very well suited for trade fair construction. Partitions, room dividers, stage designs can be created very easily in the lightweight construction.

Because of their attractive surface and their high flexibility, the moldings according to the invention are outstandingly suitable for laminating, for example, cable ducts, roller shutter boxes and curtain suspensions. The moldings can be quickly adapted to the given requirements, for example, by cutting, Flexen, etc., and since they are flexible fit into the respective recess. This process is reversible and in many cases does not require additional support.

In a translucent embodiment, the moldings coated according to the invention are suitable as visual protection elements such as, for example, shower cubicles, partitions, toilet and bathroom doors or windows.

In a transparent and translucent embodiment, the molded parts coated according to the invention are of interest for lighting elements such as lampshades, floodlights, reflectors, etc.

example 1

One-sided coating of a transparent molding

As substrate to be coated on one side, an irregularly structured Plexiglas pane was used. The plate was 120 cm long, 80 cm wide and 6 mm high. 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 to the structured surface and to the 4 edges of the molded part by means of a Waisther Pilot spray gun in an amount of about 80 g / m ² . Subsequently, the molding was allowed to dry for 20 minutes at room temperature. In the next step, the Plexiglas plate was placed in the unilaterally adjusted coating system according to claim 1. The plastic film to be applied was mounted between the capsule wall and molding. This created two chambers in the coating capsule: a chamber between the plastic film and the chamber bottom in which the Plexiglas disk was positioned (chamber A). The other chambers were between plastic film and capsule deck (chamber B). As plastic sheeting, 250 microns thick cast film made from natural Luran ^® S, the ASA commercially available from BASF Aktiengesellschaft - copoly- mer used. Subsequently, the two separate chambers (A, B ₁ ) were evacuated simultaneously in the capsule. After reaching a vacuum of 25 mbar, the plastic film was 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 was depressurized with air to atmospheric pressure while maintaining the vacuum in chamber A. Due to the flooding of chamber B, an overpressure was generated, whereby the heated plastic films were pressed onto the surfaces and edges of the molded part sprayed with adhesive. 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 process for coating a transparent molding, characterized in that

a) the molded part is arranged and fastened in a capsule, the plastic film being mounted between the capsule wall and the molded part, b) the air in the chamber is evacuated between the plastic film and the molded part, c) the plastic film is heated, d ) a second chamber between the plastic film and the capsule wall with ambient air is released to atmospheric pressure and e) the plastic film is thereby pressed onto the molded part and during this pressing process, a vacuum is maintained.

2. The method of claim 1 for coating on both sides of a molded part, characterized in that the molding is placed between two plastic films and in steps b) and e) a vacuum is applied and maintained in the bounded by the two films chamber between the two plastic films and the respective capsule wall two more chambers exist, which are relaxed during the step d) to atmospheric pressure to press the films on the opposite sides of the molding.

3. The method according to any one of claims 1 or 2, characterized in that an adhesive is applied to the molded part and / or the plastic films prior to step b).

4. The method according to any one of claims 1 to 3, characterized in that the transparent molding is a glass or plastic glass.

5. The method of claim 4, wherein the glass or plastic glass molding has a smooth surface and a textured surface.

6. The method according to any one of claims 1 to 5, characterized in that the plastic film is a translucent film.

7. The method according to any one of claims 1 to 6, characterized in that the film consists of one or more plastics selected from the group consisting of SAN, AMSAN, ASA, thermoplastic polyurethane and polymethyl methacrylate or a co-extrusion of these materials is and has a layer thickness between 50-500 microns.

8. The method according to any one of claims 1 to 7, characterized in that the films represent primer films, which can be easily treated.

9. One-side coated molding obtainable according to one of the methods of the claims 1 or 3 to 8.

10. Two-sided coated molding obtainable according to one of the methods of claims 2 to 8.

1 1. One-side coated molding obtainable according to claim 5.

12. Facade element according to claim 9 or 10.

13. Screen element according to claim 9 or 10.

14. Garment element according to claim 9 or 10.