WO2003076539A1

WO2003076539A1 - Method for producing flat moulded parts

Info

Publication number: WO2003076539A1
Application number: PCT/EP2003/002142
Authority: WO
Inventors: Robert Magunia; Norbert Schmitz
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2002-03-11
Filing date: 2003-03-03
Publication date: 2003-09-18
Also published as: DE10210477A1; AU2003214087A1

Abstract

The invention relates to a method for bonding flat moulded parts, according to which an aqueous adhesive dispersion is applied to at least one contact surface of the moulded parts that are to be bonded. Said aqueous adhesive dispersion is then dried carefully with the aid of electromagnetic radiation. Substantial portions of the radiation, which produce heat, lie in the near infra-red wavelength range. Coated (sheet-shaped) moulded parts of this type can be stored temporarily and the adhesive layer can be subsequently activated in such a way that the moulded parts can be optionally joined together by compression. Said method is suitable for producing moulded parts used in vehicle manufacturing, in particular door side sections, roof liners, body columns, rear parcel shelves, dashboards and similar functional elements used in vehicle manufacturing.

Description

"Process for the production of flat molded parts"

The invention relates to a method for producing flat molded parts and functional elements for vehicle interiors produced by this method.

A multitude of functional elements, such as e.g. Door side parts, headlining or roof stiffeners, parcel shelves, dashboards, instrument panels, for use, which are made up of essentially flat molded parts. These molded parts usually consist of a carrier material that is coated with one or more decorative layers. A large number of plastics are used as carrier materials, examples being acrylonitrile-styrene-butadiene (ABS), polypropylene, polyethylene, polystyrene, in particular as foamed polystyrene (EPS), and plastic alloys such as ABS-polycarbonate alloys. Furthermore, fiber composites based on textile fabrics made of hemp, sisal, flax, glass fibers, as well as wood-based materials such as wood flour or wood chips or paper bound with reactive resins such as epoxy resins, phenolic resins, SMC (sheet molding compounds) are used as carrier materials. Foamed backing materials made of polyurethanes or epoxy resins are also used, which may also be glass fiber reinforced. Metals are also used as carrier materials, for example for the A, B or C pillars. Steel sheets, aluminum sheets, magnesium sheets or sheets made of Mg-Al alloys may be mentioned here as examples. These molded carrier parts are laminated with flat materials in foil or textile form. Woven fabrics, knitted fabrics, nonwoven fabrics, gauze or the like are used as textile fabrics. The textiles can also be used, for example, in the form of carpets (with or without a back coating with a foam). Furthermore, the textile structures or foils can consist of a large number of plastics, examples being polyethylene, polypropylene, ABS, polyvinyl chloride (PVC), acrylonitrile-styrene-acrylate (ASA), thermoplastic urethanes (TPU) or thermoplastic olefins (TPO).

For the areas of the automotive industry, these functional elements for the vehicle interior are typically manufactured or assembled by automotive suppliers. For this purpose, the molded carrier part must be permanently and age-resistant connected to the decorative surface layer, usually this is done under Use of adhesives. Mostly, thermoplastic adhesives in the form of hot melt adhesives or dispersions are applied with the aid of rollers, nozzles or spraying devices to the interface of the carrier material or the decorative cover layer to be bonded or to both. Hot melt adhesives must be applied at temperatures between 150 to 250 ° C. The adhesives are often applied to the sheet-like preliminary products before the final assembly, so that they have to be reactivated after the assembly and before the parts are joined. Temperatures from 150 ° C to over 250 ° C are necessary. With this application of adhesive to the decorative layer materials, the web-shaped decorative material is often deformed, delaminated, burned or destroyed. In the subsequent reactivation of the adhesives during the joining process, surface temperatures above 120 ° C. are also necessary in order to achieve an adequate bond between the layers. This high energy demand often leads to tension in the composite material and sometimes to the destruction of the molded parts, at least on their surface. This has led to the fact that these functional inner parts are often produced in complex processes.

For example, EP 0825066 A2 describes a method for producing a roof reinforcement for vehicles, in which a multi-layer semifinished product is produced from two outer kraftliners and a middle hard foam layer. This is then split in the middle and cut to the dimensions of the roof skin of the vehicle. Then a single Kraftliner with oversize is cut to the dimensions of the roof skin of the vehicle. Finally, the cut of the split semi-finished product and the cut of the individual kraft liner are provided with a fuel layer between the side of the rigid foam layer and the individual kraft liner and are shaped and glued to the final shape in a mold corresponding to the curvature and the roof skin. As an adhesive, it is proposed to use one-component or two-component polyurethane adhesives or pure monomeric polyisocyanate. The pressing time for joining the molded part depends largely on the adhesive system and the amount of adhesive applied. Similarly, EP 09997265 A1 describes the production of a roof reinforcement molding in which a middle foam layer in the form of a foamed plate or a foamed strip material is wetted or impregnated with a hardening and adhesive agent. A cover layer that has an affinity for should then be placed on both sides of the foamed plate or the foamed strip material which has hardness and adhesive. The composite is then pressed in a heated tool, which determines the contour of the molded part. The hardening and adhesive agent is hardened under the influence of heat. An example of the adhesive process is the impregnation of a sheet of flexible polyurethane foam based on polyester with a monomeric diisocyanate as a binder, the impregnated foam is then passed through a first calender, the gap of which is adjustable, thereby regulating the amount of diisocyanate in the foam so that Excess diisocyanate flows back into the drip pan and remains in the process. The impregnated, foamed strip material is subsequently wetted with a catalyst which consists of a mixture of water and amines. This is followed by the calendering of the upper and lower cover layers on the foamed strip material. Heated molding and pressing tools are required for these manufacturing processes.

US 6113837 A describes a method for forming foam-shaped plastic parts with the aid of pressing tools operated at room temperature. For this purpose, it is proposed to pigment a semi-hard thermoformable plastic foam with carbon black and then to heat the preliminary product to the forming temperature with the aid of infrared radiation (IR) and then to insert and reshape it in the cold pressing tool. A joining process for multi-layer functional parts is not disclosed in this document.

It is also known from the prior art to apply aqueous one-component adhesive dispersions to the web material. With conventional coating, the water must be passed from roll to roll over a ventilating section with or without convection ovens. The economically necessary coating speeds of more than 25 m / min and technically required low drying temperatures between 40 and 60 ° C (to protect the temperature-sensitive web material) result in very long drying ovens with a drying distance of more than 20 m or the use of huge amounts of air is required for drying , both are very expensive.

WO 01/07228 discloses a method for vulcanizing a material, in particular rubber or silicone, in which the vulcanization is effected or supported by heating the material to be vulcanized, at least part of the energy required for heating the material being generated by electromagnetic radiation is transmitted from a radiation source to the material whose radiation components are in the near infrared wave range. This document suggests using this method in particular when the material is extruded as a profile strand from an extruder and then transported through a conveyor.

According to the teaching of WO 00/26011, two bodies can be connected along a common interface by heating at least one of the bodies in an interface region extending along the interface and then bringing the bodies together. In this case, at least one of the bodies should have a material region that is not to be heated, in particular a pressure-sensitive adhesive layer, on a side facing away from the interface. The bodies are then to be brought together and the heating of the interface area is to be brought about by irradiation with electromagnetic radiation, with at least essential radiation components causing the heating to be in the near infrared wave range.

In view of this known state of the art, the inventors have set themselves the task of providing a method for connecting flat shaped parts, which makes it possible to quickly and permanently bond even thermally sensitive substrates to one another. In particular, this method of connecting is said to be suitable for producing functional elements for vehicle interiors.

The solution to the problem according to the invention can be found in the patent claims; it essentially consists in a method for connecting flat molded parts in which an aqueous adhesive dispersion is applied to the interface to be connected of at least one of the two molded parts, and then the dispersion is made using electromagnetic radiation dried, at least essential radiation components causing the heating should be in the wavelength range of the near infrared (near IR). The adhesive-coated molded part can then be stored if necessary. Before the molded parts are joined, one or both interfaces of the molded parts to be connected are then thermally activated, and then the molded parts are joined, optionally with pressing.

Alternatively, the thermal activation of the interfaces or the adhesive application can be carried out after the molded parts have been joined with the aid of a heated or heated press unit. stuff done. Thereby, the molded part can be thermoformed simultaneously or subsequently.

In a particular embodiment, the process is controlled so that the surface temperature of the molded part during the drying process of the aqueous dispersion does not exceed 50 to 90 ° C., preferably 60 to 70 ° C.

"Near IR radiation" in the sense of this invention is to be understood to mean electromagnetic radiation which directly adjoins the visible light on the long-wave side; this is preferably a wavelength range between 0.7 μm and 1.5 μm , "Near IR" is also called "Near-Infra-Red" in scientific literature. It is known that infrared radiation has the highest energy density and very advantageous properties in this wavelength range. In particular, it has been shown that, in contrast to the longer-wave IR radiation, the near IR radiation can penetrate deeper into the adhesive volume to be heated and not only heats the surface of the adhesive layer. In addition, the near IR radiation can be focused very well with little effort using suitable devices, so that a directed near IR radiation with a high energy content is available which enables very short heating times of the adhesive layer to be activated in the range of a few seconds, without doing so overheating a thermally sensitive substrate. The near IR radiation source preferably has a temperature radiator which can be operated at emission temperatures of 2500 K or higher, preferably at 2900 K or higher. Such radiation sources are preferably halogen lamps. The near IR radiation source is typically designed as an elongated unit which, when web-shaped material dries, covers the entire web width. During the subsequent thermal activation of the adhesive layer with the aid of near IR radiation before or during the joining, the radiators are also adapted to the width of the molded parts to be joined. In both cases, a control unit regulates the energy input and thus the temperature of the adhesive layer to be heated via sensors.

In order to ensure permanent bonding of the substrate parts, in a preferred embodiment an adhesive dispersion is used which contains at least one polyisocyanate which is solid at room temperature and only deactivated on the surface, and at least one polymer which is reactive with isocyanate. The use of such aqueous dispersions for the production of storage-stable, latent reactive layers or powders is disclosed in EP 0922720 A1. A specific method for producing storage-stable coatings is not specified in this document, in the examples it is only proposed to apply the dispersion at room temperature and to remove the water as much as possible by evaporation at room temperature and / or by infiltration into the substrate. Such a drying process is not economical for the production of functional elements for vehicle construction, especially when joining non-porous substrates that do not allow water to seep in.

The disclosure of EP 0922720 A1 with regard to the composition and preparation of aqueous dispersions which contain at least one surface-deactivated polyisocyanate and at least one polymer which is reactive with isocyanate are expressly part of the present invention.

In the method according to the invention for connecting the flat shaped parts, the aqueous adhesive dispersion is first applied to at least one substrate part. In principle, all common application methods can be used for this purpose, for example brush application, spraying, spraying, knife coating, filling, pouring, dipping, extruding, roller application or printing methods. The one-component adhesive dispersion is particularly preferably applied by means of a roller or by spraying. The adhesive is preferably applied exclusively to the sheet-like material of the decorative layer. The drying is then carried out by the nearby IR emitters, the emitters being controlled by suitable sensors and control circuits in such a way that the adhesive layer or the substrate layer of the web-shaped decorative molded part has temperatures between 50 ° C. and 90 ° C., preferably 60 ° C. and 70 ° C does not exceed.

Since the adhesives to be used according to the invention have only a very low sensitivity to moisture, it is possible to wind the coated and dried web material on rolls and to reactivate them with the second molded part at different times and / or locations for the joining process. As a result, the joining of the flat shaped parts can take place at a spatially separate location and in time independently of the application and drying of the adhesive layer on the web material respectively. The dried reactivatable adhesive layer is superficially non-tacky, so such rolled-up webs can be stored for several weeks.

The decorative material coated in this way can therefore be introduced with the further mold carrier part after intermediate storage or immediately in a lamination process. The adhesive film will be activated by suitable control of the nearby IR emitters within a few seconds to temperatures above 100 ° C, without the substrate overheating, so that the material can be gently laminated. The adhesive film reactivated in this way hardens within a few seconds and, after a few seconds (at least 5 to 10 seconds), a completely laminated part with fully reacted adhesive is generally obtained. Neither the molded carrier part nor the decorative material are subjected to high thermal loads, but cycle times for production are still very short.

The thermal activation of the adhesive layer can take place inline directly when the web material is fed onto the substrate carrier with the help of the near IR radiation, but it is also possible to prefabricate the web material into suitable sections first and then the adhesive layer and possibly also the carrier molding layer in one Activate the scanning process with the near - IR radiation and then join the two parts, whereby a thermal reshaping can optionally take place for the final shaping of the functional part.

In a further embodiment, adhesive-coated decorative layers and molded parts can be pre-assembled in their dimensions, joined to one another and placed in a heated press tool, so that thermal activation and, if appropriate, simultaneous thermal shaping take place in this heated press tool.

The molded parts made according to the invention from the above-mentioned substrates can preferably be used as door side parts, headlining, body pillars, hat racks, dashboards or instrument panels for vehicle construction.

The following examples are intended to provide a more detailed explanation, they are only exemplary in nature and do not cover the breadth of the adhesive method according to the invention. However, the person skilled in the art can easily derive the entire range of applications from the information provided. Example 1 :

Coating, drying, lamination of headliners with a 1-component dispersion using near-infrared radiation.

Materials used: carrier made of PU foam with TPU film and cotton fleece (using the Tramiko process) textile. The Tramiko process is a manufacturing process of composite films from polymer layers and fiber-containing layers, see for example DE 19931323 AI

Process: A 1-component dispersion containing a surface-deactivated polyisocyanate and a dispersed, isocyanate-reactive polymer (dispersion LH 1127/998, from Henkel Do s) was rolled onto the textile using a roller coating system and then rolled onto a textile using a NIR ^® emitter ( Adphos) dried within 2-3 seconds. The PU foam was fed onto the dried adhesive film. Both substrates were lightly pressed and sealed at temperatures around 100 ° C. (can pouring method). Such a method is described, for example, in EP0891854 A2, EP0769358 A2, EP0835734 A1 or EP0829338 A1. The laminate was rolled up and stored temporarily.

In a subsequent process, the laminate was unwound, coated by means of roller or spray dried and rolled up by means of NIR ^® emitters at temperatures around 60-70 ° C and then.

The coated laminate was drawn into a laminating machine. In the first step, rectangular blanks were produced from the roll. These reach a laminating press via a clamping frame. The Tramiko beam was at the bottom of the tool. A spotlight field was inserted between the carrier and the textile blank. The NIR ^® radiators activated the Tramiko to approx. 120 ° C and the laminate to approx. 80 ° C surface temperature within a few seconds. After the emitters were moved out, they were press-laminated. The locking time was about 5-10sec. During this time, the "microcapsule" (deactivated surface) of the solid isocyanate was melted and the isocyanate portion reacted with the dispersion polymer to form a cross-linked adhesive layer. After this reaction, the adhesive layer consequently had a thermoset character and was no longer meltable. After a total of about 24 hours, the bond had completely reacted and had reached its final strength.

Claims

claims

1. Method for connecting flat shaped parts, characterized by the following essential process steps

(a) applying an aqueous adhesive dispersion to the interface to be connected of at least one of the two molded parts to be connected,

(b) drying the aqueous dispersion with the aid of electromagnetic radiation, at least substantial radiation components causing the heating being in the near infrared (near IR) wavelength range,

(c) if necessary, intermediate storage of the adhesive-coated molded part,

(d) thermal activation of one or both interfaces of the molded parts to be connected,

(e) Joining the molded parts, if necessary, by pressing.

2. The method according to claim 1, characterized in that in step (b) the surface temperature of the molded part does not exceed 50 ° C-90 ° C, preferably 60 ° C-70 ° C.

3. The method according to claim 1 or 2, characterized in that the wavelength range of the near IR radiation between visible light (0.7 microns) and 1.5 microns.

4. The method according to at least one of the preceding claims, characterized in that the thermal activation according to step (d) is carried out by near IR radiation.

5. The method according to at least one of claims 1 to 3, characterized in that the thermal activation according to step (d) after the joining of the molded parts according to step (e) is carried out with the aid of a heated pressing tool.

6. The method according to at least one of the preceding claims, characterized in that the adhesive dispersion at least one at room temperature solid only deactivated on the surface and at least one polyisocyanate Contains isocyanate reactive polymer.

7. Use of the molded parts produced according to at least one of the preceding claims as door side parts, headlining, body pillars, hat racks, dashboards or instrument panels in vehicle construction.