EP1372926A1

EP1372926A1 - Composite moulded parts comprising a film coating and method for producing the same

Info

Publication number: EP1372926A1
Application number: EP02752880A
Authority: EP
Inventors: Achim Grefenstein; Rainer Klenz
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2001-03-16
Filing date: 2002-03-13
Publication date: 2004-01-02
Also published as: DE10113273A1; WO2002074515A1

Abstract

The invention relates to a method for producing composite moulded parts, whereby a) a single or multilayered film is introduced into a tool, b) said film being or to be thermoformed, c) the film is rear-injected or rear-pressed according to an injection moulding method or a pressing method, with a fused plastic material containing a pore-forming foaming agent and a fibrous material, and d) the composite moulded part is removed from the tool.

Description

Composite molded parts with a film coating and process for their production

description

The present invention relates to methods for producing composite molded parts with a film coating, the composite molded parts obtainable in this way and their use as internal or external body components, as components for shipbuilding and aircraft construction or as components for household or electrical appliances.

Composite molded parts made of a plastic molding compound provided with a film are known to the person skilled in the art. Instead of laminating or gluing plastic components with a film, nowadays there is an increasing trend in industrial applications to inject, press or foam the films directly in the molding tool with the plastic molding compound (A. Grefenstein, "Film injection molding instead of painting, new technology for Karos series components made of plastic "in metal surface, 10/99, 53rd year, Carl Hanser Verlag, Munich, 1999). In this way, the desired composite molded part can be obtained in one work step without the need for further process steps.

For example, DE-A 19928774 describes a process in which multilayer films are injection-molded with thermoplastic materials using the injection molding process. The use of multilayer films makes it possible to provide the components with a decor and, if appropriate, also a protective layer, so that subsequent painting is not necessary. Composite molded parts are obtained which are characterized by good rigidity and high tensile strength, and e.g. as components for the body shop. However, these mostly large-area components have a relatively high dead weight, which makes them appear disadvantageous in certain cases, in particular for body roof components. In addition, such components can show a different mechanical load behavior depending on the direction. The same applies to the thermal linear expansion - a parameter that is particularly critical in automotive engineering - which is usually reproduced as a CTE value (Coefficient of Thermal Elongation according to DIN 53752).

In particular in the case of fiber-reinforced injection-molded components, as well as in the case of fiber-reinforced molded or back-molded composite parts, a distortion of the entire component can sometimes be determined, which leads to the complete uselessness of the Component (see also Technical Information 05/99, BASF AG), for example if high fitting accuracy is required, such as in body or housing component construction.

EP-A 995 667 discloses composite molded parts back-foamed with polyurethane and a process for their production. Foamed composite molded parts, however, have a property profile that is not suitable for all component applications. In particular, it would be desirable to achieve better film adhesion and thus a higher heat resistance of the component and material recycling of the overall composite. In contrast to the back-injection process, lower pressures, which are generally in the range from 3 to 10 bar, occur in the foaming tool. However, these are usually not sufficient to iron out surface defects after thermoforming the film. In addition, adhesion problems between the film and the foam layer can often not be avoided without special additional measures such as flame treatment of the film or the use of adhesives (see also EP-A 995 667).

The process for producing composite molded parts according to DE-A 1 942 494, in which e.g. thermoformed a PVC film in the injection molding tool and then back-injected with a plastic molding compound containing a blowing agent, depends on an adhesion promoter or a welding aid in order to obtain sufficient adhesion between the film and the back-injection material.

From WO 99/63019 it is known that components made of thermoplastic elastomers with a particularly fine-pored structure can be produced, for example, by using carbon dioxide or nitrogen in supercritical form as a blowing agent. Composite molded parts and their manufacture are not mentioned, however.

The object of the present invention was therefore to make composite molded parts available which are distinguished by a uniform / isotropic thermal and mechanical property profile, can be produced in a simple manner, in particular also in the context of series production, and conventional components with regard to rigidity and fracture behavior are superior. Furthermore, composite molded parts should be obtained which, in their film-side appearance, meet all requirements for a so-called Class-A surface. Accordingly, composite molded parts have been found which are obtained by a) inserting a single-layer or multilayer film into a tool, b) which may or may not be deep-drawn or thermoformed, c) this film in the injection molding or pressing process with a melt-shaped one Injection molding or injection molding of plastic material, the plastic material containing a pore-forming blowing agent and fiber materials, and d) removing the composite molded part from the tool.

Both single-layer and two-layer or multilayer films are suitable as films. Preference is given to two-layer or multilayer films, i.e. resorted to composite layer films.

Suitable monolayer are for example amides of mixtures of poly- and polyethylene ionomers such as ethene / methacrylic acid co- polymers containing, for example, sodium, zinc and / or lithium counter ions (eg under the trademark Surlyn ^® from. DuPont), or formed from copolyesters , However, all other common single-layer films such as PVC, ABS, ASA polyester or polycarbonate films can also be used.

Composite layer films composed of, in this order, at least one substrate layer (1), optionally at least one intermediate or decorative layer (2), and at least one transparent cover layer (3) are particularly suitable.

The substrate layer (1) usually contains thermoplastic polymers such as ASA polymers, ABS polymers, polycarbonates, polyesters such as polyethylene terephthalate or polybutylene terephthalate, polyamides, polyetherimides, polyether ketones, polyphenylene sulfides, polyphenylene ethers or mixtures of these polymers. ASA polymers are preferably used for the substrate layer. In addition, preference is given to using blends of ASA and / or ABS polymers with polycarbonates or polybutylene terephthalate.

ASA polymers are generally understood to mean impact-modified styrene / acrylonitrile polymers in which graft copolymers of vinylaromatic compounds, in particular styrene, and vinyl cyanides, in particular acrylonitrile, on polyalkylacrylate rubbers are present in a copolymer matrix of, in particular, styrene and acrylonitrile. Commercially ASA polymers such as are available under the name Luran ^® S (BASF AG). Suitable polycarbonates are known per se. Particularly preferred polycarbonates are those based on bisphenol A or bisphenol A together with up to 80 mol% of further aromatic dihydroxy compounds. Are commercially available, for example 5, the polycarbonates Makrolon ^® (Bayer AG) and Lexan ^® (GE Plastics BV). There are also copolycarbonates based on bisphenol A and, for example, bis- (3,5-dimethyl-4-hydroxyphenyl) sulfone or 1,1-di- (4-hydroxyphenyl) -3,3,5-trimethyl-cyclohexyl, which are characterized by a high heat resistance, in question.

10 The latter copolycarbonate is commercially available under the trade name Apec ^® HT (Bayer AG). The polycarbonates can be used both as regrind and in granular form. As a component of the mixture, in particular in an ASA substrate layer, polycarbonates are usually present in amounts of 0 to

15 60% by weight, preferably 20 to 50% by weight, based on the total molding composition. The addition of polycarbonates leads, among other things, to higher thermal stability and improved crack resistance of the composite layer films.

20 Instead of ASA polymers or their blends with polycarbonates or in addition to these, the substrate layer (1) can also be composed of ABS polymers (these include impact-modified styrene / acrylonitrile polymers in which graft copolymers of Styrene and

25 acrylonitrile on polybutadiene in a copolymer of styrene and acrylonitrile are present) acrylates, mixtures of poly (meth) acrylates and SAN polymers with polyacrylate rubbers are impact modifier such as Terlux ^® (BASF AG), polycarbonates, polyesters, such as polybutylene terephthalate ( PBT)

30 (e.g. Ultradur ^® , BASF AG) or polyethylene terephthalate (PET), polyamides (Ultramid ^® , BASF AG), polyetherimides (PEI), polyether ketones (PEK), polyphenylene sulfides (PPS), polyphenylene ethers or blends of these polymers. The aforementioned polymer materials are generally known and can be found, for example, in H.

35 Dominingha s, The plastics and their properties, VDI-Verlag, Düsseldorf (1992).

In a preferred embodiment, the substrate layer (1) is made of ASA polymers, mixtures of ASA polymers and polymers.

40 carbonates, formed from ABS polymers, polycarbonates, polybutylene terephthalate, polyethylene terephthalate, polyamides or blends from ASA polymers and polybutylene terephthalate. The substrate layer (1) particularly preferably contains a molding composition made of ASA polymers or mixtures of ASA polymers and polymers.

45 carbonates. It can also consist essentially or completely of these polymers. The layer thickness of the substrate layer (1) is preferably 100 to 2000 μm, in particular 150 to 1500 μm and particularly preferably 200 to 1000 μm.

The substrate layer (1) may also contain, as additives, those compounds which are typical and customary for the (co) polymers described and their mixtures. Examples of additives which may be mentioned are: dyes, pigments, effect colorants, antistatic agents, antioxidants, stabilizers for improving the thermostability, for increasing the stability to light or for increasing the resistance to hydrolysis or chemicals, and in particular lubricants and / or lubricants for the production of moldings or molded parts are appropriate.

The composite layer films can furthermore have an intermediate layer (2) made of thermoplastic and / or thermosetting plastics, optionally with further additives. The intermediate layer (2) is also used as an ink carrier or decorative layer. Suitable thermoplastics are e.g. the polyalkyl and / or aryl esters of (meth) acrylic acid, also in impact-modified form, poly (meth) acrylamides or poly (meth) acrylonitrile, also called acrylic resins, furthermore ABS polymers, styrene / acrylonitrile polymers (SAN) , Polycarbonates, polyester, for example Polyethylene or polybutylene terephthalate, polyamides, especially amorphous polyamide, e.g. Polyamide 12, polyether sulfones, thermoplastic polyurethanes, polysulfones, polyvinyl chloride or ASA polymers. Blends of the above (co) polymers are also suitable, e.g. Mixtures of ASA polymers and polycarbonates, as described above for the substrate layer (1). Also thermoplastic polyurethanes, especially weather-resistant aliphatic polyurethanes, e.g. the commercial product Elastollan (from Elastogran, Lemförde) (see also Kunststoff-Handbuch, Polyurethane, Volume 7, 2nd edition, Carl Hanser Verlag, Munich, 1983, pages 31 to 39) can be considered as film materials. Acrylic resins, polycarbonates and / or styrene (co) polymers are preferably used.

The intermediate layer is preferably composed of impact-resistant polymethyl methacrylate (PMMA), polycarbonates or the ASA polymers described above for the substrate layer (1) or their blends with polycarbonates.

Suitable impact-modified poly (meth) acrylates are described, for example, by M. Stickler, T. Rhein in üllmann's encyclopedia of industrial chemistry Vol. A21, pages 473-486, VCH Publishers Weinheim, 1992, and H. Domininghaus, Plastics and their properties, VDI-Verlag Dusseldorf, 1992. poly methyl methacrylates are known in the art, however, and for example, under the trademarks Lucryl® ^® (BASF AG) and Plexiglas ^® (Röh GmbH ) available.

The intermediate layer (2) can have effect colorants as a decorative layer. These are, for example, dyes, effect colorants, metal flakes or pigments. Organic or inorganic compounds are suitable as dyes or pigments. Colored, white and black pigments (color pigments) and liquid crystal pigments may be mentioned as organic pigments. Also suitable as inorganic pigments are color pigments and luster pigments and the inorganic pigments usually used as fillers.

In a further embodiment, the substrate layer (1) - alone or together with an intermediate layer (2) which may be present - has the aforementioned effect colorants.

The layer thickness of the decorative layer (2) is generally in the range from 10 to 1000, preferably from 50 to 500 and particularly preferably from 100 to 400 μm.

The cover layer (3) is usually translucent, preferably transparent. It is composed of poly (meth) acrylate polymers, impact-resistant poly (meth) acrylate, in particular impact-resistant polymethyl methacrylate, fluorine (co) polymers such as polyvinylidene fluoride (PVDF), ABS polymers, polycarbonates, polyethylene terephthalate, amorphous polyamide, Polyether sulfones, polysulfones or SAN copolymers or mixtures thereof. In particular, the cover layer contains polymethyl methacrylate, impact-resistant polymethyl methacrylate or polycarbonates, preferably poly-methyl methacrylate, impact-resistant polymethyl methacrylate, PVDF or mixtures thereof. The polymers or their mixtures are generally chosen so that they lead to a transparent cover layer.

In a further embodiment, the cover layer is based on a radiation-curable composition which contains ionic and, in particular, radical-curable functional groups. The free-radically radiation-curable cover layer preferably contains i) polymers with ethylenically unsaturated groups or ii) mixtures of these polymers with ethylenically unsaturated low molecular weight compounds or iii) mixtures of thermoplastic polymers without ethylenically unsaturated groups with ethylenically unsaturated compounds.

As ethylenically unsaturated groups in polymer i) e.g. maleic acid, fumaric acid, maleic anhydride or (meth) acrylic acid residues can be used. Suitable polymers i) can be based on polyesters, polyethers, polycarbonates, polyepoxides or polyurethanes.

Examples of ethylenically unsaturated low-molecular compounds are alkyl (meth) acrylates such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate or 2-ethylhexyl acrylate, vinyl aromatics such as vinyl toluene or styrene, vinyl esters such as vinyl stearate or vinyl acetate, vinyl ethers such as vinyl methyl ether, acrylonitrile or methacrylonitrile in question.

Suitable saturated thermoplastic polymers e.g. Polymethyl methacrylate, impact-resistant polymethyl methacrylate, polystyrene, impact-resistant polystyrene (HIPS), polycarbonate or polyurethane.

The radiation-curable composition may contain photo-initiators, leveling agents or stabilizers, e.g. UV absorber and radical scavenger included.

The top layer is radiation-hardened with high-energy radiation, e.g. UV light or electron radiation, possibly at elevated temperatures.

For further details regarding the composition of the radiation-curable cover layer and its production, reference is hereby expressly made to WO 0063015.

Furthermore, an adhesive layer made of an adhesion promoter with a layer thickness of generally 5 to 400, in particular 5 to 100 μm, can adjoin the outer surface of the substrate layer. The adhesion promoter serves to establish a firm connection with a selected substrate that comes to lie under the substrate layer (for example by back injection). The adhesive layer is used when the adhesion of this further substrate to the substrate layer is insufficient (for example in the case of polyolefin substrates). Suitable adhesion promoters are known to the person skilled in the art. Examples of suitable adhesion promoters are ethylene-vinyl acetate copolymers for coupling to polyethylene and maleic anhydride-grafted polypropylenes for coupling to polypropylene. In both cases it becomes more common The liability is achieved by introducing polar groups into the non-polar polyolefins.

The adhesive layer films are by adapter or nozzle coextrusion of the components, preferably in a one-step process. Die coextrusion can be found e.g. in EP-A2-0 225 500 explains the adapter coextrusion process in the conference proceedings of the extrusion technology conference "Coextrusion of foils", 8./9. October 1996, VDI-Verlag Düsseldorf, especially in the contribution by Dr. Networks. Furthermore, the composite layer films can be produced by laminating the individual film layers together in a heatable gap. However, a three-layer film can also be produced from a composite layer film from the two layers (2) and (3) by subsequently providing it with a substrate layer (1).

The one-, two-, three- or multi-layer film can be inserted into the mold as such or in a deep-drawn or thermoformed form. It is also possible to carry out the deep-drawing or thermoforming process only in the back injection or back pressing tool. Furthermore, it is possible to cover the surface of the film during the back injection or pressing or also during the deep-drawing or thermoforming process by choosing a suitable tool surface with a decorative structure, e.g. a grain. This surface structuring can of course also be carried out in a separate step.

Suitable plastic materials are all known thermoplastic molding compounds.

Thermoplastic molding compositions based on ASA, ABS or SAN polymers, poly (meth) acrylates, polyether sulfones, polybutylene terephthalate, polycarbonates, polypropylene (PP) or polyethylene (PE) or mixtures thereof are preferably used as plastic materials. Blends of ASA and / or ABS polymers with polycarbonates or polybutylene terephthalate are preferred, in particular blends of ASA polymer with polycarbonates or polybutylene terephthalate and polycarbonate / polybutylene terephthalate mixtures. Amorphous thermoplastics are generally preferred ^'.

The plastic materials mentioned and their mixtures can have other customary auxiliaries and fillers. Such auxiliary substances are, for example, lubricants or mold release agents, waxes,

Effect colorants, for example pigments such as titanium dioxide, or dyes, Flame retardants, antioxidants, stabilizers, e.g. against exposure to light, or antistatic agents.

Carbon black, wood flour, amorphous silica, magnesium carbonate, powdered quartz, mica, mica, benton te, talc, calcium carbonate, glass spheres, feldspar or in particular calcium silicates such as wollastonite and kaolin can also be used as particulate fillers.

The plastic material used for back-molding or back-pressing contains fibers, which in the present context are also to be understood to mean platelet-shaped products, preferably e.g. fiber-reinforced ABS polymer or a fiber-reinforced PBT / ASA mixture. The fibers are generally present in the plastic material in an amount of 3 to 40% by weight, preferably 10 to 30% by weight, particularly preferably 15 to 20% by weight, based on the total weight of the molding composition ,

Examples of fibrous fillers are carbon, aramid, steel or glass fibers, aluminum flakes, cut glass or glass silk rovings. Glass fibers are particularly preferred. Natural fibers such as flax, hemp, jute, sisal, ramie or carnaf can also be used as fibers.

The glass fibers used can be made of E, A or C glass and are preferably equipped with a size and / or an adhesion promoter. Their diameter is generally in the range from 6 to 30, preferably in the range from 10 to 17 μm. Both continuous fibers (rovings) and chopped glass fibers (staples), usually with a length of 1 to 30 mm, preferably with a length of 3 to 15 mm, or short glass fibers with a length of generally 0.2 to 0.4 can be used mm are used. Long glass fibers are used in particular if the plastic material contains or consists of ABS polymer.

Chemical and physical blowing agents come into consideration as pore-forming blowing agents.

Suitable chemical blowing agents are basically those compounds which split off volatile constituents when exposed to heat or a catalyst or when irradiated with high-energy radiation. In most cases the blowing agent decomposition is thermally induced (see also G. Trausch, "Physically and chemically driven thermoplastic foams, limits of processes and applications" in "Foams from the thermoplastic melt", VDI-Verlag, Düsseldorf, 1981, pages 1 to 16) , The blowing agent is usually chosen so that decomposition is preferred after or during the introduction of the melt-shaped plastic material into the mold.

Exemplary are organic and suitable chemical propellant compounds such as azo compounds such as azodicarbonamide (under the brand LUVOPOR ^®, BASF AG, commercially available), hydrazide sulphonated, eg, p-toluenesulfonic, such as the product Porofor ^® (Bayer AG), or 4, 4-oxybis (benzolsulfohydra- zid), such as the product Genitron ^® (Bayer AG), semicarbazide, such as p-toluenesulfonyl, citric acid and its esters (under the brand hydrocerol® ^® HK, Boehringer Ingelheim, commercially available), peroxo compounds, (eg the brand Luperoxe ^® , Akzo), triazine compounds such as 2, 4, 6-trihydrazino-l, 3, 5-triazine, tetrazole compounds such as 5-phenyltetrazole, tetramine compounds such as dinitrosepentamethylene tetramine or mixtures of the aforementioned compounds and inorganic compounds such as alkali or alkaline earth carbonates or bicarbonates, for example calcium carbonate or sodium carbonate (soda), or mixtures thereof. Any mixtures of organic and inorganic blowing agents can of course also be used. Suitable blowing agents can also be found in H. Saechtling, Kunststoff-Taschenbuch, Carl Hanser Verlag, Munich, 27th ed., 1998, pages 271, 532 and 767 to 768, to which express reference is hereby made. The chemical blowing agents described split off depending on the type of nitrogen, oxygen or carbon dioxide. The decomposition temperatures for these compounds are generally in the range from 90 to 285 ° C.

The chemical blowing agent is usually present in the plastic material before decomposition in amounts of 0.1 to 5% by weight, preferably in amounts of 0.5 to 2% by weight, based on the total weight of the molding composition. The amount of blowing agent is also determined by the type of blowing agent, i.e. according to its capacity to release volatile constituents and the degree of foaming desired for the respective application.

If necessary, nucleating agents can also be added to the blowing agents to improve the homogeneity of the pore formation. Suitable nucleating agents are, for example, finely divided silicates (Si0), organic bromine compounds, metal oxides, for example zinc oxide or magnesium oxide, metal salts, boron nitride and particularly preferably talc, which is also used, for example, in the production of polystyrene foam (brand name Styrodur ^® from BASF AG) (see also K.-D. Kolossow, "Extrusion of foamed semi-finished products with single-screw extruders" in "Handbuch der Kunststoff-

Extrusionstechnik ", Carl Hanser Verlag, Munich, 1986, pages 423 to 465, or plastic manual, polystyrene, volume 4, Becker and Braun, ed., Carl Hanser Verlag, Munich, 1996, pages 588 to 603). Mixtures of the abovementioned nucleating agents can of course also be used.

The higher molecular decomposition products of chemical blowing agents can also act as nucleating agents.

Suitable amounts of nucleating agent are generally in the range from 0.05 to 10% by weight, preferably in the range from 0.1 to 1% by weight, based on the total weight of polymer to be foamed.

The chemical blowing agent can e.g. liquid or in the form of a powder, granulate or pellet together with the plastic material in the plasticizing unit. It is also possible to mix the blowing agent as a masterbatch with the plastic material. The plastic molding composition on which the masterbatch is based is preferably identical to the plastic material for the composite molding, but is at least partially or fully compatible, i.e. it doesn't find a complete one

Phase separation instead (see also plastic manual, Die Kunststoffe, volume 1, Becker and Braun, ed., Carl Hanser Verlag, Munich, 1990, pages 134 and 135). The propellant can be added continuously or in batches, using separate mixers or metering stations or, in the case of liquid propellants, using separate metering pumps.

The processing of the plastic melt containing blowing agent is possible on all commercially available injection molding machines and extruders. Closure nozzles are advantageously used, which prevent the blowing agent from causing the melt to foam even in the metering zone. In order to prevent foaming in the feed area of the plasticizing unit, the temperature in this area is generally chosen to be below the decomposition temperature of the blowing agent, provided that the decomposition is thermally induced. In the compression zone, on the other hand, the melt temperature can already be selected in such a way that volatile constituents are released. However, the decomposition of the blowing agent particularly advantageously only occurs in the mold.

It has proven to be advantageous to work with the highest possible injection speed in the back injection process. It is also advantageous, particularly with a view to components that are as light as possible, to dispense with a holding pressure phase. Physical blowing agents can also be used for the back injection and the back pressing process. Suitable are, for example, ethanol, methyl ether, n-butane, n-pentane, the branched-chain pentane compounds and cyclopentane and the so-called fluorine-chlorinated hydrocarbons such as R 11, R 12, R 12 Bl, R 12 B2, R 13, R 13 Bl, R 14, R 21, R 22, R 23, R 32, R 112, R 133 or R 114 (notation according to DIN 8962). Nitrogen and carbon dioxide, also in supercritical form, are also suitable. Any mixtures of physical blowing agents can also be used. Very good results are achieved with supercritical carbon dioxide.

The back injection process is preferably carried out in such a way that the chemical blowing agent is either added to the back injection material together with the glass fibers in the metering funnel or is added to the plasticizing unit in a downstream region after the glass fiber has been added. If the glass fibers are only added during the processing of the back injection material, it is recommended to use a twin-screw extruder in combination with a piston injection unit, as described by Wobbe and Zimmet, Plastververarbeitung, 2001 (52), pages 52 to 54.

Physical blowing agents are regularly metered into the melt under pressure, preferably in liquid or supercritical form, for example via a piston pump into the metering zone of the plasticizing unit. When entering the melt into the mold, care must be taken to ensure that there is no premature foaming of the melt along the flow channel, e.g. due to pressure relief in a divergent flow cross-section. This is usually achieved by designing the mold including the sprue distributor system with the usual computer simulation programs (e.g. from Moldflow Corp., Wayland (US)) in a geometrically suitable form.

For the back-pressing process, chemical blowing agents are preferred, most of which only decompose after they have been inserted into the pressing tool. If chemical blowing agents are used that decompose thermally induced, this regularly requires an exact temperature control in the plasticizing unit. This is preferably achieved if, in addition to the use of high-precision temperature control units (the cylinder temperature advantageously only fluctuates in the range of max. +/- 3 ° C.), the residence times of the polymer melt in the plasticizing unit are kept constant. Downtimes should therefore be avoided regularly. A further process variant therefore consists in the use of chemical blowing agents which do not decompose thermally but, for example, under the influence of high-energy radiation, for example UV radiation, and in the process split off, for example, nitrogen. Suitable compounds are, for example, hydrazides and tetrazone

((N (R ₂ ) N = NN (R ₂ ) with R = C _x - to Cio-alkyl, C ₆ - to -C ₄ aryl or benzyl, where R in a tetrazone compound can have different meanings) into question According to the invention, blowing agents are used in concentrations of 0.05 to 5%, based on the polymer weight.This embodiment is particularly suitable for the backpressing process.The UV radiation is advantageously applied after the melt strand has been inserted into the pressing tool, for example immediately before the Press is closed.

In one embodiment of the method according to the invention for the back injection of films with fiber-reinforced plastic material, plastic and fiber material and further additives are combined, melted and mixed in an extruder or an injection molding machine before the injection molding process. In a particularly suitable embodiment, the extruder or the injection molding machine has at least one dispersive, preferably one distributive, mixing element in the zone adjoining the compression zone. All of the plastic material is preferably in molten form behind the compression zone. In the case of extruders, the compression zone is also referred to as the transition zone (see also Saechtling, Kunststoff-Taschenbuch, 27th edition, Carl Hanser Verlag, Munich, 1998, pages 244 to 247).

Possible distributive mixing elements are, for example, diamond or pin or cam mixing parts or those with openings in the thread. Suitable mixed parts can also be found in "Coloring with plastics", published by VDI-Gesellschaft Kunststoff-technik, VDI-Verlag, Düsseldorf, 1975, pages 261 to 265. A separate mixing ring is preferably used as the mixing element, which is arranged freely around the screw between the housing of the extruder or the injection molding machine (also called the stator) and the screw (also called the rotor) and provided with rows of passages extending in the circumferential direction is also called Twente-Mixing-Ring for short. The passages can take regular or irregular geometric shapes, but are generally circular or oval. Furthermore, they can be arranged in a disordered manner or in circumferential circular paths on the mixing ring. Furthermore, the screw, ie the rotor, can have indentations under the mixing ring, both with the passages of the mixing ring can be brought into congruence and can also be arranged offset to these. The circumferential shape of these indentations can correspond to the passages in the mixing ring, but they can also differ in size and shape from these. The indentations usually have the shape of partial cutouts of a sphere or an ellipsoid, that is to say, for example, hemispherical or semi-ellipsoidal indentations, a smooth transition from the rotor surface and indentation being preferred to an abrupt, sharp-edged transition. Particularly suitable embodiments of extruders or injection molding mixing devices containing a separate mixing ring with passages are also described in EP 340 873 B1 and DE 42 36 662 C2, which are hereby expressly included in the present disclosure.

Preferably, the film-molded composite molded parts are produced in a multistage process by a) producing the film, in particular the laminated film by means of adapter or nozzle (co) extrusion of the top, substrate and optionally intermediate layer, the entire laminated film either in a one-step process or is produced by laminating the individual layers to one another or by applying a radiation-curable cover layer to a single-layer or multilayer film,

b) optionally thermoforming or deep-drawing the composite layer film in a molding tool and c) back-injecting the composite layer film with the fiber-reinforced plastic material, whereby plastic material and fiber material before the back-injection in an extruder or an injection molding machine, the at least one distributive mixing element in the zone adjoining the compression zone have, combines, melts and mixes and wherein the chemical blowing agent is added together with the glass fibers directly to the plastic material or after the glass fiber addition in a downstream area to the plasticizing unit.

For back pressing, e.g. the source flow method, the preform method or the strand laying method are used. These processes are known to the person skilled in the art and include by Woite et al. in "Plastics in automotive engineering: raw materials, components, systems", VDI-Verlag GmbH, Düsseldorf, 1994, pages 280 to 313.

In the source flow process, the melt is introduced into the horizontal parting plane through a hot runner system in the lower half of the mold when the mold is open. Depending on the size of the in some cases, several injection points, which can also be used in cascade fashion, are possible.

In the strand laying process, a melt-like mass strand is applied from an extruder or an injection unit to the lower half of the tool. The shaping process then takes place with the film attached to the upper tool half by means of embossing.

In the preforming method, the melt-shaped molding compound introduced into the tool is first brought into a cheap mold and then processed with the actual upper tool to form the composite molded part.

The blowing agent is usually mixed with the plastic material in the plasticizing unit in the backpressing process, similarly as already described for the back injection process, and is usually present in the melt cake or strand introduced into the tool in a homogeneously distributed manner.

In the back pressing process of the described methods, the tool temperatures are generally in the range from 20 to 80 ° C. The temperature of the plastic material in the tool depends on its melt temperature and is generally in the range from 200 to 280 ° C.

The pressures generated during the back pressing are generally in the range from 100 to 300 bar.

In a further embodiment, the back compression molding tool as a whole is exposed to pressure in a pressure chamber at least for the period of the melt entry until the tool is completely closed. This process variant is particularly suitable for the source flow process, in which the melt is generally injected into the open pressing tool, which has a gap width of only a few mm. A correspondingly high back pressure in the amount of the vapor pressure of the blowing agent at processing temperature thus prevents the volatile components of the blowing agent from being expelled early.

The composite molded parts obtainable by the process according to the invention are suitable, for. B. as internal or external body parts, as components for ship and aircraft construction or as components for household or electrical appliances. According to the method according to the invention, composite molded parts are obtained which have a less anisotropic mechanical and thermal property profile, ie have very good values regardless of the test direction, in particular with regard to the CTE value, breaking stress, elongation at break, impact strength and rigidity. For example, CTE values in the range from 30 to 60 x 10 " ⁶ 1 / K and elongation at break values in the range from 2 to 3%, preferably 2.5 to 3%, or stiffnesses of 3000 to 6000 MPa, preferably 3500 to 6000 Achieve MPa easily, for example, with ABS polymer as an injection molded plastic material, even under strong ones

The composite molded parts according to the invention show no or almost no distortion of temperature. This also applies to large-area composite molded parts.

Also with semi-crystalline plastic materials such as polypropylene, polyethylene terephthalate or polyamide, which usually do not foam or only undertake specific modifications, for example by branching or by slight crosslinking of the molecular chains to increase the melt viscosity (see also the foamed polypropylene Profax ^® , Himont) composite moldings can be obtained by the process according to the invention, which have all of the abovementioned properties and in particular lead to a weight reduction, are at the same time very stiff, show significantly less or no distortion and have a Class A surface.

A Class A surface in the sense of the invention is to be understood in the following as a film-side component surface which is at least equivalent in terms of the frequency and size of defects, gloss and color fastness and uniformity to conventional high-quality painted metal components as used in automobile construction are.

Examples:

1. In an injection molding machine KM 1500 (Krauss Maffei; screw diameter 115 mm), an ABS polymer (Terluran ^® GP-22, BASF AG) and as a chemical blowing agent 1% by weight, based on the total amount of injection molding compound, of hydroce- rol ^® SK35 (Boehringer Ingelheim KG) dosed gravimetrically. Immediately after the mixture had melted, a glass fiber roving (R43SX6 from OCF) was drawn in from the screw via a housing opening (15% by weight, based on the total weight of the injection molding composition). Downstream, the injection molding machine had shear mixing elements that distributively mixed the glass fibers with the melt. The melt temperature in the injection molding machine was in the range of 260 ° C, but not above it. The melt obtained was injected into a plate tool (1200 × 300 mm) with a side gating behind a coextruded two-layer film made of acrylic-coated Luran ^® S 778TE (top layer: polymethyl methacrylate; substrate layer ASA) applied to a wall of the mold. The mechanical tests described below were carried out on the composite molded parts obtained.

2. Procedure as under 1., but first chopped glass with an initial length of 4 mm (Cratec ^® 152A14C from OCF) and the granular plastic material were mixed in a mixing unit (from Maguire) and then together with the chemical blowing agent in the feed hopper of the injection molding machine.

3. Procedure as in 2, but supercritical CO (1% by weight, based on the injection molding compound) was injected into the metering zone of the plasticizing unit as a physical blowing agent via a piston pump.

4. Procedure as 2, however, a glass-fiber reinforced PBT / ASA blend (Ultradur ^® S 4090 G6, BASF AG) was processed at a melt temperature of 270 ° C as a plastic material.

Examples 1 to 4 were repeated, but without using a blowing agent (Examples VI. To V4.).

Tensile and impact bending tests were carried out on all the composite molded parts obtained according to Examples 1 to 4 and IV to 4V. The rigidity, toughness and thermal linear expansion were determined along and across the flow direction of the melt in the composite molding. The quotient of the aforementioned longitudinal and transverse parameters is a measure of the anisotropy of the composite molded parts. The lower this quotient, the lower the anisotropy (ideal value 1).

The results are summarized in the table below: Table:

a) determined according to ISO 527;

b) determined according to DIN 53752;

c) determined according to IS0179 / lfU.

Claims

claims

1. A process for the production of composite molded parts, in which a) a single-layer or multilayer film is placed in a tool, b) which is or is deep-drawn or thermoformed, if appropriate, c) this film is injection-molded or pressed with a melt-shaped plastic material which contains a pore-forming blowing agent and fiber material, back-injected or back-pressed, and d) removing the composite molded part from the tool.

2. A process for the production of composite molded parts according to claim 1, characterized in that the strand laying, preform or source flow process is used as the pressing process.

3. The method according to claims 1 or 2, characterized in that a chemical blowing agent is used.

4. The method according to claims 1 to 3, characterized in that the blowing agent splits off volatile constituents thermally or radiation-induced.

5. The method according to claims 1 to 4, characterized in that the elimination of volatile constituents from the chemical blowing agents takes place completely or almost completely only after the plastic material containing the blowing agent has been introduced into the mold.

6. The method according to any one of claims 1 to 5, characterized in that the monolayer film is formed from copolyesters or from a mixture containing polyamides and polyethylene ionomers.

7. The method according to any one of claims 1 to 5, characterized in that the multilayer film is composed, in this order, at least one substrate layer (1), optionally at least one intermediate or decorative layer (2), and at least one transparent cover layer (3rd ).

8. The method according to claim 7, characterized in that the substrate layer (1) ASA polymers, ABS polymers, polycarbonates, polyesters, polyamides, polyetherimides, polyether ketones, polyphenylene sulfides, polyphenylene ethers or mixtures thereof, the intermediate layer (2) poly ( meth) acrylates, impact-resistant poly (meth) acrylates, poly (meth) acrylamides, poly (meth) acrylonitrile, ASA polymers, ABS polymers, Polycarbonates, polyesters, polyamides, polyether sulfones, poly sulfones, polyvinyl chloride or mixtures thereof, and the top layer (3) poly (meth) acrylates, impact-resistant poly (meth) acrylates, fluorine (co) polymers, ABS polymers, 5 polycarbonates, polyethylene terephthalate , amorphous polyamide, SAN polymers, polyether sulfones, polysulfones or mixtures thereof.

9. The method according to claim 7, characterized in that the top layer consists of a UV-crosslinkable resin.

10. The method according to claims 1 to 9, characterized in that the plastic material is ASA or ABS polymers, SAN polymers, poly (meth) acrylates, polyether sulfones,

15 uses polybutylene terephthalate, thermoplastic polyurethanes, polycarbonates, polypropylene, polyethylene or mixtures thereof.

11. The method according to claims 1 to 10, characterized in that the fiber material used is glass, carbon or natural fibers.

12. The method according to claims 1 to 11, characterized in that azodicarboxylic acid dia- as chemical blowing agent

25 mid, sulfohydrazides, semicarbazides, citric acid and their

Esters, peroxo, triazine, tetrazole, tetrazone or tetramine compounds, alkali or alkaline earth carbonates or bicarbonates, or as physical blowing agents ethanol, dirnehyl ether, n-butane, n- or i-pentane, cyclopentane, chlorofluorocarbons

30 substances, carbon dioxide or nitrogen are used.

13. Composite molded parts obtainable according to one of claims 1 to 12.

35 14. Use of the composite molded parts according to claim 13 as internal or external body components or as components for shipbuilding and aircraft construction or as components for household or electrical appliances.

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