WO2008020036A1

WO2008020036A1 - Method for fastening a component on a joining partner to be enameled

Info

Publication number: WO2008020036A1
Application number: PCT/EP2007/058449
Authority: WO
Inventors: Klaus KEITE-TELGENBÜSCHER; Hans Karl Engeldinger; Anja Staiger
Original assignee: Tesa Ag
Priority date: 2006-08-17
Filing date: 2007-08-15
Publication date: 2008-02-21
Also published as: DE102006038624A1; DE112007001739A5

Abstract

Method for fastening of a component on a joining partner (3) to be enameled, wherein a section of a heat activated adhesive film (1) is heated, so that the adhesive film does not reach a complete cross-linked state, the component (2) being fastened with the section of the not completely cross-linked heat activated adhesive film on the joining partner, the joining partner being enameled together with the fastened component thereon, the enameled joining partner being dried with the fastened component thereon in a thermal drying, wherein the thermal energy leads to a complete cross-linking of the heat activated adhesive film, so that the component is permanently fastened on the joining partner.

Description

description

Method for fixing a component on a joining partner to be painted

The invention relates to a method for fixing a component on a joining partner to be painted.

On bodywork of automobiles, many parts are now firmly attached by means of a permanent adhesive. This applies to bolts or similar parts, which themselves serve again later, more components, especially plastic parts can be attached to them.

It is particularly known, for example, to glue such bolts by means of a two-component liquid adhesive (structural bonding). This requires a complex mixture and metering of the liquid systems during cultivation. The complicated processing (such as mixing, maintain pot life, frequent contamination) is disadvantageous to these systems, even if they have prevailed for lack of alternatives, for example in the Scheibenverklebung. In addition, the final layer thickness is difficult to set exactly. Bolt or nut designs with a plate-shaped foot to increase the adhesive surface are also known.

From FR 2 542 829 A an adhesive connection is known, in which this is achieved by a double-sided effective pressure-sensitive adhesive tape, the outwardly facing

Adhesive surface is first covered by a thin film and only after removing the

Slide becomes effective. Apart from the fact that the previous removal of the protective film is perceived as cumbersome, the adhesive connection experience does not reach the required holding force for a permanent connection between the protective strip and the body surface. There is also a risk that the protective film during the Transport is damaged and then stick the parts together. This type of adhesive attachment has apparently not proven in the automotive industry and is therefore hardly used. Similar fastening elements coated with pressure-sensitive adhesives are known from DE 87 12 151 U1.

From US 4,250,596 A a glued fastener is known in which the adhesive surface is equipped with a curable hot melt adhesive, which is reactivated by means of heat to produce a permanent adhesive bond. The known thermosetting adhesive has the property of softening at the temperature at which the final coating of the paint applied to the body is cured, and it solidifies when the applied paint coat cools. However, this means that the fasteners must be kept as long on the body panel during the adhesive until the cooled adhesive has entered a strong adhesive bond. Since the curing of the adhesive in a r baking temperature of 180 ⁰ C usually takes about 30 minutes, the holding means must remain in operation during this time.

Also known from EP 0 741 842 B1 are fastening elements which are equipped with a layer of a hardenable reactive hot-melt adhesive by means of injection molding. Similar fasteners having a component-sintered reactive polyurethane adhesive layer are sold under the Techbond brand by Raybond (Saint-Louis, France). The adhesive application is very high here with about 900 microns thick, resulting in the squeezing of the adhesive from the adhesive joint under the pressure of the binding process. Moreover, disadvantageous in both of the aforementioned fasteners of the great effort for injection molding or sintering (in particular the equipment and tool costs), which must be driven to produce the adhesive layers. The alternatively proposed in EP 0 741 842 B1 immersion of the fasteners to be coated in a bath of molten adhesive leads to less accurate application rates and due to the adhesive flow uneven adhesive surfaces.

The problem with fixing with an adhesive is that the bodies are painted. The bolts, for example, can therefore no longer be glued to the paint after the painting because it does not provide a good primer. On the other Side would be a corresponding treatment of the body after painting, for example, a partial removal of the paint, too expensive.

The bonding process must therefore be done before the painting process. This poses the problem that the adhesive used on the one hand survives the processes taking place during the painting and on the other hand during the

Lackens used media, for example, the solvents, is insensitive.

In particular, the adhesive must not give any components in the respective baths, because this entails contamination of the paint baths, which in turn led to a very undesirable premature replacement of the same for obvious reasons.

Furthermore, it is necessary that the adhesive has a sufficient initial tack, so that the desired component is immediately fixed to the substrate at least so far that the bond withstands mechanical stress until, if necessary, the adhesive reaches its final bond strength in subsequent process steps.

A disadvantage of the aforementioned solutions of the prior art is that the adhesive must first have largely reached its final bond strength in order to withstand the painting process. For crosslinking systems this means waiting for longer curing times before painting can begin.

The sequence of an industrial series painting of automobile bodies is as follows. Figure 1 provides a visual overview. After assembly, the body is cleaned of adhering contaminants such as fats, oils and dirt particles in a multi-stage degreasing and rinsing zone. During degreasing alkaline cleaners and possibly additional surfactants are usually used. The subsequent rinsing takes place with water.

Following the cleaning process, the phosphating takes place, nowadays usually a zinc phosphating.

Phosphating is understood to mean the production of a sparingly soluble metal phosphate layer on the metallic base body, the substrate. Although the result is corrosion protection, this process is always associated with corrosion. By chemical processes, the acid phosphating solution becomes a necessary pickling reaction is triggered, which not only dissolves the top (almost not measurably small) metal layers, but also at the same time breaks off the last impurities. During phosphating, the steel component is either immersed in a metal phosphate bath or sprayed in a chamber with metal phosphate solution. This forms on the surface of about 1 to 30 microns thin, firmly bonded to the base metal metal phosphate layer. These may be iron, manganese or zinc phosphate layers. The metal phosphate layer serves as a primer for a paint coating and prevents sub-rusting of the paint layer. Further fields of application are phosphating for the cold forming of steel in combination with lubricants, corrosion protection in combination with corrosion inhibitors such as oils and the reduction of manganese phosphating.

In order to produce as many small crystals as possible during the formation of the layer, the body is pre-rinsed in an activating solution. The polymeric titanium phosphates contained therein act as nucleation nuclei for the subsequent zinc phosphating. Since the highest demands are placed on corrosion resistance, zinc phosphating is preferred over iron phosphating. The zinc phosphating baths are acidified (pH 3) and usually contain manganese, nickel and zinc phosphates as layer-forming substances as well as various additives for better process control and suppression of gas bubble formation in the pickling reaction. In the case of zinc phosphating, the reaction of the phosphating solution with the base material forms a firmly adhering fine-crystalline zinc phosphate layer. The resulting sludge from reaction products must be removed from the process. After phosphating, a multiple rinse with demineralized water and a post-passivation, in which the interstices are sealed within the phosphate layer. Post-passivation baths based on organic polymers or zirconium salts are available here. The only a few thousandths of a millimeter thick phosphate layer forms an ideal primer for the paint.

Subsequently, the electrocoating takes place.

The electrophoretic painting (electrocoating) is a dipping process in which the coating is effected by the action of an electric field (50 to 400 V). The body to be painted, the electric current conducting body is introduced as an anode or cathode in the dye bath, in practice, the pool wall acts as a second Electrode. The deposited amount of paint is directly proportional to the amount of electricity supplied. The electrophoretic coating is used especially for priming. There are no spray losses, and the resulting coatings are very even in hard to reach places. For non-conductive substrates, such as plastics, glass, ceramics, etc., it is used to coat the electrostatic charge of the paint particles (so-called electrostatic coating). All electrodeposition paints are water-soluble (suspensions of binders and pigments in demineralised water) with only low concentrations of organic solvents (about 3%). Thus, neither fire protection nor special occupational safety measures are necessary when operating KTL systems

As already mentioned, cathodic dip coating is preferred in the automotive industry. The KTL bath consists of about 80% water, 19% are binders and pigments, only about 1 to 2% are organic solvents. The pH is slightly acidic and is about 6 to 6.5. The deposition mechanism is divided into several stages: The water-insoluble synthetic resin becomes dispersible in water only in combination with an organic acid. In the area of the negatively charged workpiece (cathode), an alkaline boundary layer formation (pH 11 to 13) occurs due to the evolution of hydrogen. Due to the increased OH concentration on the workpiece surface, the paint dissolved in the water coagulates and deposits on the component in the form of a fine lacquer layer. In order to prevent sedimentation and to exclude the formation of dead spaces, the bath in the tank at an average flow rate of about 0.2 m / s is moved, based on the tank contents, the bath is circulated 4 to 6 times per hour. With a paint consumption of 2 to 3 kg / body and a non-negligible water evaporation at bath temperatures around 30 ⁰ C, a constant control of the bath composition is required. The organic acids released at the anode are separated by a dialysis system and thus the pH of the bath is kept stable. This is followed by a multi-stage rinsing zone with ultrafiltrate from the paint recovery or demineralized water. The paint is baked at about 180 ⁰ C, the layer thickness is 20 to 30 microns. Depending on the process variant, an additional second lacquer layer is applied as a filling layer. Only now does the actual painting with the coloring topcoat, as well as the clearcoat. When the following is the solvent-free paint, this means aqueous paints, powder coatings or powder slurries.

Powder coating is a coating process in which a usually electrically conductive material is coated with powder coatings. The powder is sprayed electrostatically or tribostatically on the substrate to be coated and then baked. In advance, the workpiece is to be degreased well and, if necessary, treated with corrosion protection. Today, the baking temperatures, depending on the application, vary widely. Typical baking conditions are between 140 and 200 ^° C. Various binders are used today, but typical are powder coatings based on, for example, polyurethane, epoxy or polyester resins.

Alternatively, the powder may also be applied by vortex sintering. In this case, a heated workpiece is immersed briefly in a fluidized by means of compressed air powder made of plastic. The surface-adherent powder melts due to the heat of the workpiece and coats the surface with a continuous plastic layer.

Powder clearcoats are known, for example, from DE 42 22 194 A.

Powder slurry coatings are powder coatings in the form of aqueous dispersions. Such slurries are described for example in US 4,268,542 A, DE 195 18 392 A, DE 196 13 547 A and DE 198 14 471 A.

It is therefore an object of the invention to provide a method characterized by short joining times for fixing a component to a joining partner to be painted, wherein on the one hand it is to be avoided that the adhesive used or the adhesive film used should be removed by the painting and necessary methods. and after treatment processes and media are impaired in their function and on the other hand, the adhesive used or the adhesive film used adversely affect the painting process or the media involved.

This problem is solved by a method as laid down in the main claim. The subject of the dependent claims are advantageous developments of the method according to the invention. Accordingly, the invention relates to a method for fixing a component on a joining partner to be painted, wherein a portion of a heat-activatable adhesive film is heated so that the adhesive film reaches a not fully crosslinked state,

The component is fixed to the joining partner with the section of the incompletely crosslinked heat-activatable adhesive film,

• the joining partner, together with the component fixed thereon, is painted, • the painted joint partner together with the component fixed thereon is dried in a thermal drying, the thermal energy leading to complete crosslinking of the heat-activatable adhesive film, so that the component is permanently fixed on the joint partner ,

The first fixation of the component with the film section on the joining partner develops at least such a high holding force that the component is held with its own weight in the appropriate position.

This initial, incompletely crosslinked adhesive bond withstands a painting process, such as a CDP process, and does not appreciably affect the painting process or the media used therein. In particular, the useful life of a phosphating or KLT bath is not significantly reduced.

The joining partner is according to a preferred embodiment of metal, more preferably it is a body of a vehicle such as watercraft, land vehicles (trucks, automobiles, etc.), aircraft, spacecraft or combinations thereof, for example, amphibious vehicles.

Advantageously, a further development of the method is in which the adhesive film is heated after fixing on the joining partner, so that it reaches a not fully crosslinked state and fixes the component on the Fügeteil, ie a method for fixing a component on a to be painted Joining partner, where

The component is fixed on the joining partner with a section of a heat-activatable adhesive film, At least the adhesive film is heated so that it reaches an incompletely crosslinked state and fixes the component on the adherend,

The joining partner is painted together with the component fixed thereon,

• The painted joining partner is dried together with the component fixed thereto in a thermal drying, wherein the thermal energy leads to a complete crosslinking of the heat-activated adhesive film, so that the component is permanently fixed on the joining partner.

The adhesive film may have a thickness of up to 500 μm. According to an advantageous embodiment of the invention, this is 10 to 250 microns, especially 50 to 200 microns,

In the following, several advantageous embodiments of the adhesive film will be described without wishing to restrict the invention.

In an advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: i) one or more vinylaromatic block copolymers, the total content of

Vinylaromatic block copolymers on the adhesive is 20% by weight to 75% by weight, preferably 30% by weight to 70% by weight, particularly preferably 40% by weight to 60%

Wt .-%, and ii) one or more adhesive resins having a softening point measured by the ring and ball method (the usual standard method for determining softening methods (according to the test standard ASTM E 28)) of over 120 ⁰ C in a proportion of 25 wt % to 70% by weight.

Preferably, the vinylaromatic block copolymers are styrenic block copolymers, which in turn, in a particularly advantageous embodiment of the invention, are styrene-butadiene or styrene-isoprene block copolymers.

Thermoplastic elastomers, especially those based on block copolymers are known as elastomeric component for adhesives. Especially in the production of pressure-sensitive adhesives they are used. Vinylaromatic block copolymers, preferably styrene block copolymers, have a very high cohesion due to their block structure and the phase separation of the soft and hard phases implied thereby. Besides They also have a high ductility, as they are used in applications

Modulverklebung is necessary.

Styrene block copolymers alone are not tacky and can also be cured by thermal

Activation not be set sticky. Tackiness comes about only through the addition of different low molecular weight resins. It is between two types of

Resins differ. On the one hand, the medium-block compatible resins, the better with the

Soft block are compatible with the Styrolendblöcken, and those that are better or exclusively compatible with the Endblocks.

The bond strength is significantly increased by the use of high-melting resins with softening points above 120 ⁰ C. Be only high melting

Adhesive resins used, the adhesives are often no longer tacky at room temperature.

The bond strengths can be achieved by skillful selection of resins that of the thermoplastic systems. An advantage of the simultaneous use of vinylaromatic block copolymers is the ease of processing both from solution and from the melt. By the clever choice of the right adhesive resins, the

Softening point and, consequently, the implantation temperature of the

Adhesives are adjusted very well.

Preferred adhesives are those based on block copolymers comprising polymer blocks formed by vinylaromatics (A blocks), preferably styrene, and those formed by polymerization of 1,3-dienes (B blocks), preferably butadiene and isoprene, use. Both homo- and copolymer blocks can be used according to the invention. Resulting block copolymers may contain the same or different B blocks, which may be partially, selectively or fully hydrogenated. Block copolymers may have linear A-B-A structure. It is also possible to use block copolymers of radial form as well as star-shaped and linear multiblock copolymers. As further components, A-B diblock copolymers may be present. Block copolymers of vinylaromatics and isobutylene can likewise be used according to the invention. All of the aforementioned polymers may be used alone or in admixture with each other.

Block copolymers having a block polystyrene content of 20 to 30% by weight have proven particularly advantageous.

Instead of the polystyrene blocks and polymer blocks based on other flavoring tenhaltiger homo- and copolymers (preferably Cs to C ₂ aromatics) with glass Transition temperatures of> about 75 ⁰ C are used as for example α-methylstyrene-containing aromatic blocks. Likewise, polymer blocks based on (meth) acrylate homo and d (meth) acrylate copolymers with glass transition temperatures of> 75 ⁰ C can be used. In this case, block copolymers can be used which use as hard blocks exclusively those based on (meth) acrylate polymers as well as those which use both polyaromatic blocks, for example polystyrene blocks, and also poly (meth) acrylate blocks.

Instead of styrene-butadiene block copolymers and styrene-isoprene block copolymers and their hydrogenation products, including styrene-ethylene / butylene block copolymers and styrene-ethylene / propylene block copolymers, block copolymers and their hydrogenation products which utilize further polydiene-containing elastomer blocks can also be used according to the invention. such as copolymers of several different 1,3-dienes. Furthermore, functionalized block copolymers, such as, for example, maleic anhydride-modified or silane-modified vinylaromatic block copolymers, can be used according to the invention.

As further polymers, those based on pure hydrocarbons, for example unsaturated polydienes such as natural or synthetically produced polyisoprene or

Polybutadiene, chemically substantially saturated elastomers such as saturated ethylene-propylene copolymers, α-olefin copolymers, polyisobutylene, butyl rubber, ethylene-propylene rubber, and chemically functionalized hydrocarbons such as halogen-containing, acrylate-containing or vinyl ether-containing polyolefins are used which up to a share of up to 100 phr in relation to the

Vinyl aromatic block copolymer may be present.

As tackifiers use pressure-sensitive adhesives according to the invention as the main component in particular medium-block compatible resins having a softening point above 120 ⁰ C, measured by the ring and ball method.

Among others, hydrogenated and nonhydrogenated derivatives of rosin, polyterpene resins, preferably based on alpha-pinene, terpene-phenolic resins, non-crosslinking phenolic resins, novolaks, hydrogenated and non-hydrogenated polymers of dicyclopentadiene, hydrogenated and non-hydrogenated polymers of preferably C ₈ - and are particularly suitable Cg aromatics, hydrogenated C ₅ / C ₉ polymers and aromatically modified, selectively hydrogenated dicyclopentadiene derivatives. The aforementioned adhesive resins can be used both alone and in admixture.

Tackifier resins having a softening point below 120 ⁰ C (measured by the ring and ball method) can be used in formulations of the invention in a weight ratio of 50 wt .-%, based on the total content of midblock compatible resins may be present.

In addition, resins that are compatible with the vinyl aromatic blocks of the vinyl aromatic block copolymers can also be used. Preferred here are, inter alia, resins based on pure aromatics such as, for example, alpha-methylstyrene, vinyltoluene or styrene or resins of mixtures of different aromatic monomers. Also usable are coumarone-indene resins, which are obtained from the coal tar. Another class of useful resins are low molecular weight polyphenylene oxides, which are particularly compatible with Styrolendblöcken in styrene block copolymers. Endblock-compatible resins can be present up to a weight fraction of 25% by weight, based on the total adhesive composition.

Other additives which may be used are typically primary antioxidants, such as sterically hindered phenols, secondary antioxidants, such as phosphites or thioethers, process stabilizers, such as C radical scavengers, light stabilizers, such as UV absorbers or hindered amines, antiozonants , Metal deactivators and processing aids, to name but a few.

Plasticizers, such as plasticizer oils or low molecular weight liquid polymers, such as low molecular weight polyisobutylenes having molecular weights <1500 g / mol (number average), or liquid EPDM types are typically used in small amounts of <10 wt .-%. Fillers such as silica, glass (ground or in the form of spheres), aluminas, zinc oxides, calcium carbonates, calcium sulfates, titanium dioxides, carbon blacks and colored pigments, to name a few, may also be used.

Furthermore, the adhesive film can in particular be added to spheres with a metallic, ie conductive coating (for example gold or silver) or metal-containing particles. The particles may be made of pure metal (gold, silver), but may also be made of an alloy which should then contain the metal to a considerable extent to ensure conductivity. If, in the following, the metallized spheres (preferably of glass) are mentioned, the person skilled in the art knows that these mentioned particles must always be read.

In order to prevent excessive deformation of the adhesive film, it may be advantageous to mix spacer particles, in a proportion of 1 to 10 wt .-%. The Spacerpartikel are of particular spherical geometry and consist of a hard material that does not melt at the increased bonding temperature and is difficult or not deformable. The Spacerpartikel can also be conductive, but they should be harder than the metallized particles. Furthermore, they should have a smaller diameter than the conductive particles.

The thickness of the Spacerpartikel corresponds approximately to the desired thickness of the adhesive layer after the pressing or bonding. They thus have a diameter which is slightly smaller than the thickness of the adhesive film. They allow a precise adjustment of this thickness by the bonding process under temperature, pressure and the plane parallelism of the plunger, even if these bonding parameters vary. The spacers mentioned are preferably spherical hard particles such as glass beads. A metal layer on these spheres is possible, but not necessary, because the optionally additionally present soft metallized particles cause sufficient conductivity and thus already a conductive system is present.

In a further advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: i) one or more vinylaromatic block copolymers, wherein the total proportion of vinylaromatic block copolymers in the adhesive is from 20% by weight to 75% by weight, preferably from 30% by weight to 70% by weight, particularly preferably from 40% by weight to 60 Wt .-%, and ii) one or more endblock compatible resins in a proportion of 25 wt .-% to 70 wt .-%.

While in tack adhesion the midblock compatible resins provide tackiness and the endblock compatible resins are used primarily to enhance cohesion and improved thermal stability, in heat activated systems the endblock compatible resins provide tackiness at elevated temperatures resulting in very high bonding performance. The bond strengths can be achieved by skillful selection of resins that of the thermoplastic systems. Advantageous is the ease of processing both from solution and from the melt.

In a further advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: i) one or more vinylaromatic block copolymers and ii) at least one reactive resin.

The use of reactive resins enables secure bonding. Heat-reactive resins are particularly preferred.

The reactive resins used are mainly phenolic resins and alkylphenol resins. The use concentration is in an advantageous embodiment at least 5 wt .-% based on the total adhesive. These resins are preferably used in a concentration of 10 to 25 wt .-%. In order to facilitate the crosslinking of the reactive resins significantly, oxides or salts of polyvalent metals are used, preferably magnesium or zinc compounds, used as oxides or salts of long-chain organic acids, for example as stearates. Other salts can be used. To further improve crosslinking at high temperatures, co-catalysts such as bromobutyl rubber or chlorosulfone rubber may be used, to name but a few.

In addition to the reactive resins, the adhesives used may also contain the adhesive resins customary for the compounding of vinylaromatic block copolymers. As suitable resins, for example, certain rosin, hydrocarbon and coumarone resins have been found

In a further advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: a.) A thermoplastic polymer in an amount of at least 30% by weight, b.) One or more tackifying resins in an amount of from 5 to 50% by weight and / or c.) epoxy resins with hardeners, optionally also accelerators, in a proportion of 5 to 40 wt .-%, d.) optionally metallized particles with a proportion of 0.1 to 40 wt .-%, particularly preferably 10 wt %, e.) optionally only difficult or non-deformable spacer particles with a proportion of 1 to 10% by weight, which do not melt at the bonding temperature of the adhesive film.

The elastomer preferably comes from the group of polyolefins, polyesters, polyurethanes or polyamides or may be a modified rubber such as nitrile rubber or polyvinyl butyral, polyvinyl formal, polyvinyl acetate, carboxylated or epoxylated SEBS polymer.

The chemical crosslinking reaction (based on epoxides or phenolic resin condensation) of the resins at elevated temperature achieves high strengths between the adhesive film and the surface to be bonded and achieves high internal strength of the product.

The addition of the reactive resin / hardener systems also leads to a lowering of the softening temperature of the above-mentioned polymers, which is their Processing temperature and speed advantageously lowers. The suitable product is a self-adhesive product at room or slightly elevated temperatures. When the product is heated, it also reduces the viscosity in the short term, allowing the product to wet even rough surfaces.

In a further advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: a) an acid or acid anhydride-modified acrylonitrile-butadiene copolymer and b) an epoxy resin and / or a reactive resin, as already described above, wherein the weight ratio of the two components a / b is greater than 1.5, and wherein no additional non-polymeric hardener is used.

In a further advantageous embodiment, the heat-activatable adhesive film contains at least the following constituents: a) an acrylonitrile-butadiene copolymer having a weight fraction from 40 to 80% by weight, b) a polyvinyl acetal having a weight fraction from 2 to 30% by weight, c) an epoxy resin with a weight fraction of 10 to 50 wt .-% and d) a curing agent, wherein the epoxy groups are chemically crosslinked at high temperatures with the curing agent.

As nitrile rubbers in particular all acrylonitrile-butadiene copolymers can be used with an acrylonitrile content of 15 to 50 wt .-%. Likewise, copolymers of acrylonitrile, butadiene and isoprene can be used. The proportion of 1, 2-linked butadiene is variable. The aforementioned polymers can be hydrogenated to a different degree and fully hydrogenated polymers having a double bond content of less than 1% can be used.

All of these nitrile rubbers are carboxylated to a certain extent; the proportion of the acid groups is preferably from 2 to 15% by weight. Commercially, such systems are available, for example, under the name Nipol 1072 or Nipol NX 775 from Zeon. Hydrogenated carboxylated nitrile rubbers are commercially available under the name Therban XT VP KA 8889 from Lanxess. With polyvinyl acetals, all acetals are meant as polyvinyl derivatives, including polyvinylformal or polyvinyl butyral, with different contents of polyvinyl alcohol, and preferably polyvinyl butyrals obtained from polyvinyl alcohol. The content of polyvinyl alcohol can vary between 5 and 40 wt .-%. Polyvinyl butyrals are preferred because they are much easier to get in solution. Both the nitrile rubbers and the polyvinyl butyrals can be dissolved in short-chain alcohols and ketones, such as ethanol or butanone. Butanone is preferred because the remaining components, especially the epoxy resins can be better dissolved in butanone.

Epoxy resins are usually understood as meaning both monomeric and oligomeric compounds having more than one epoxide group per molecule. These may be reaction products of glycidic esters or epichlorohydrin with bisphenol A or bisphenol F or mixtures of these two. It is also possible to use epoxy novolak resins obtained by reaction of epichlorohydrin with the reaction product of phenols and formaldehyde. Also, monomeric compounds having multiple epoxide end groups used as thinners for epoxy resins are useful. Also elastically modified epoxy resins can be used. Examples of epoxy resins are Araldite ™ 6010, CY-281 ™, ECN ™ 1273, ECN ™ 1280, MY 720, RD-2 from Ciba Geigy, DER ™ 331, 732, 736, DEN ™ 432 from Dow Chemicals, Epon ™ 812, 825, 826, 828, 830 etc. from Shell Chemicals, HPT ™ 1071, 1079 also from Shell Chemicals, Bakelite ™ EPR 161, 166, 172, 191, 194 etc. from Bakelite AG.

Commercial aliphatic epoxy resins are, for example, vinylcyclohexane dioxides such as ERL-4206, 4221, 4201, 4289 or 0400 from Union Carbide Corp.

Elastified epoxy resins are available from Noveon under the name Hycar.

Epoxy diluents, monomeric compounds having a plurality of epoxide groups are, for example, Bakelite ™ EPD KR, EPD Z8, EPD HD, EPD WF, etc. of Bakelite AG or Polypox ™ R 9, R 12, R 15, R 19, R 20 etc. from UCCP ,

More preferably, the adhesive film contains more than one epoxy resin. In addition to the acid or acid anhydride modified nitrile rubbers already mentioned, other elastomers can also be used. Besides other acid- or acid-anhydride-modified elastomers, it is also possible to use unmodified elastomers, for example polyvinyl alcohol, polyvinyl acetate, styrene block copolymers, polyvinyl formal, polyvinyl butyral or soluble polyesters. It is also possible to use copolymers with maleic anhydride, for example a copolymer of polyvinyl methyl ether and maleic anhydride, for example available under the name Gantrez ™, marketed by ISP.

Due to the chemical crosslinking of the resins with the elastomers, very high strengths are achieved within the adhesive film.

In order to increase the adhesion, the addition of adhesive resins compatible with the elastomer is also possible.

As tackifiers, non-hydrogenated, partially or fully hydrogenated resins based on rosin and rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively or completely hydrogenated hydrocarbon resins based on C ₅ -, C ₅ / Cg or Cg monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene, hydrogenated polymers of preferably pure Cs and Cg aromatics are used. The aforementioned adhesive resins can be used both alone and in admixture.

As further additives can typically be used:

• primary antioxidants, such as sterically hindered phenols

• secondary antioxidants, such as phosphites or thioethers

• Process stabilizers, such as C radical scavengers

• light stabilizers, such as UV absorbers or hindered amines • processing aids

Fillers, such as silica, glass (milled or in the form of spheres), aluminas, zinc oxides, calcium carbonates, titanium dioxides, carbon blacks, metal powders, etc.

• Color pigments and dyes as well as optical brighteners By using plasticizers, the elasticity of the crosslinked adhesive can be increased. As plasticizers, for example low molecular weight polyisoprenes, polybutadienes, polyisobutylenes or polyethylene glycols and polypropylene glycols can be used.

Since the nitrile rubbers used do not have too low a viscosity even at high temperatures, the adhesive does not generally escape from the adhesive joint during bonding and hot pressing. During this process, the epoxy resins crosslink with the elastomers, resulting in a three-dimensional network.

By adding so-called accelerators, the reaction rate can be further increased. Accelerators can be for example: 1. Mono- and Diurons

2. Tertiary amines, such as benzyldimethylamine, dimethylaminomethylphenol, tris (dimethylaminomethyl) phenol

3. Boron trihalide-amine complexes

4. substituted imidazoles 5. triphenylphosphine

For the purposes of this invention, the term "not completely crosslinked" means that the chemical crosslinking potential is not fully utilized during the process of heat curing, so that the adhesive film remains even softer and more elastic than a completely cured film. in which several chemical reactions are possible and of which in the state of "incomplete crosslinking" at least one is not or has not completely expired. The degree of curing can be determined by a so-called DSC analysis, a differential scanning calorimetry abbreviation The DSC analysis method is codified as "ISO 11 357, parts 1 to 5 of 1999".

To determine the degree of cure, a small sample of the adhesive film from the curing process and an uncured control sample are heated while recording the amount of heat required in the form of curves. Existing chemical reaction potential shows an exothermic reaction peak, which can be quantitatively evaluated in relation to the reference peak. In a further advantageous embodiment, the heat-activatable adhesive film used is resistant to the customary cleaning and pretreatment processes, media and conditions used in body construction, in particular to degreasing, activation, phosphating and passivation.

The crosslinkable adhesive film preferably has a characteristic activation temperature of at least 40 ^° C., more preferably of at least 80 ^° C. This prevents possible reactions already during storage or during transport.

On the other hand, the lowest possible activation temperatures are desirable, in particular in order to achieve a sufficient initial strength at short cycle times. Adhesive films are preferred which already at an activation temperature of not more than 130 ⁰ C, more preferably of not more than 1 10 ⁰ C, an initial strength of more than 1 MPa according to DIN EN 1465 (substrate: aluminum plates 100x20x1.6 mm ³ , etched, bond area 20 mm ² , test speed 10 mm / min).

The activation time to achieve the initial strength is preferably less than 1 minute, more preferably less than 30 seconds, most preferably less than 10 seconds.

Preferably, the films are not or only slightly tacky at temperatures below 60 ⁰ C, so that the film can be easily positioned. The bond strength at room temperature according to ASTM D 3330-04 (on polished steel at a take-off speed of 300 mm / min) is preferably less than 3 N / cm, more preferably less than 1 N / cm.

Strengths of more than 8 MPa are particularly advantageously achieved in the tensile shear test according to DIN EN 1465 (substrate: aluminum plates 100 × 20 × 1, 6 mm ³ , etched, bond area 20 mm ² , test speed 10 mm / min) after curing.

The adhesion is in an advantageous embodiment of the adhesive film on oiled sheets. Further preferably, the adhesive sheet reaches a strength of more than 4 MPa in the tensile shear test according to DIN EN 1465 (bond area 20 mm ² , test speed 10 mm / min) on said oiled body panels.

The heating of the adhesive film at the point of adhesion is carried out by any known to the expert form of heat generation and supply, in particular by heat conduction.

For this purpose, for example, the bolt and / or the body panel are heated before and / or during the bolt with the intervening film and the

Body panel is pressed. The required heat can also be achieved, for example

Use of ultrasound, high-energy radiation, heating elements or introduced by friction.

Preference is given to achieving a sufficient initial strength, the

Pressing force canceled, so that the cycle times are shortened.

A post-curing of the adhesive bond by the thermal drying is advantageously carried out together with the curing of the body paint in the painting oven. As a result, the cycle time during application of the fastening element (bolt) can be shortened, since it is not necessary to wait until the required final strength is reached. It is also particularly advantageous to supply the heat to the fastening element (bolt) and / or the joining partner and / or the adhesive film already during the approach of the bolt and / or the adhesive film to the bonding site in order to further shorten the cycle times.

In an advantageous embodiment of the method, the fastening element and / or the body panel is heated by induction and thus heat is conducted into the adhesive film. Particularly preferred frequencies of 10 to 2000 kHz are used. Corresponding devices are described in DE 196 38 521 A1 and DE 10 2004 012 786 A1.

Preferably, the adhesive film is adapted in its geometry exactly the bonding surface by punching or otherwise shaping.

In a further advantageous embodiment of the method, the adhesive film is applied to the

Surface of the fasteners prelaminated, wherein the lamination temperature is below the crosslinking temperature. This facilitates the placement of the bolt and the adhesive film on the body. The so equipped fasteners offer the great advantage that they are adhesive-free until the use of fasteners and that only by the activation of the prelaminated adhesive film at the place of use, the inherent adhesive force is released, which practically leads to a permanent connection.

Further advantageous is the use of a robot for placing, heating and pressing of the component, in particular a prefabricated with adhesive film fastener.

In the following, the invention will be explained in more detail with reference to several examples, without being limited in any way.

Examples

Example 1 Production of a Heat-Activatable Adhesive Film

A heat-activatable adhesive film of the following composition was produced:

30 wt. Granulated nitrile rubber

19 parts by weight Natural rubber granulated

30 parts by weight Phenol resin

12 parts by weight Alkylphenol resin 6 parts by weight Hexamethylenetetramine (HMTA) 3 parts by weight talc

Procedure in the production

The talc-powdered rubber granules were homogenized in a kneader together with 100 parts by weight of a mixture of equal parts of methyl ethyl ketone and toluene for 10 hours. Subsequently, the resins and the HMTA were added and eingeknetet.

The adhesive thus prepared was spread by means of a doctor blade on a release paper and dried in a convection oven or drying at 90 to 100 ⁰ C to form an adhesive sheet. Example 2: Preparation of an electrodeposition paint

The preparation of the electrodeposition paint used for test purposes can be taken, for example, from the disclosure of US Pat. No. 4,920,162 A.

Example 3:

A process according to the invention was carried out using the heat-activatable adhesive film from Example 1 in the following steps:

1. Application of a portion of the heat-activatable adhesive film between the overlapping surface of two surface-etched aluminum strips of the dimensions

100x20x1.6 mm ³ , with the strips overlapping at their ends by 10 mm, resulting in a bond area of 20 mm ²

2. Heating the joining part assembly by means of a hot press to 180 ⁰ C under a pressure of 0.5 MPa

3. Maintaining the contact pressure and the temperature over a period of 20 s

4. Remove the pressing device and cool the adhesive bond

5. KTL coating with the paint of Example 2 at a voltage of 300 V and a bath temperature of 30 ⁰ C over a period of 15 min

6. Reheating the adhesive bond in an oven without contact pressure to 180 ⁰ C.

7. Maintain the temperature over 30 min

8. cooling the adhesive bond After step 4, the initial strength of the adhesive bond was tested according to DIN EN 1465 (test speed 10 mm / min). It resulted in a value of 2.3 MPa.

After step 5, the strength of the adhesive bond according to DIN EN 1465 (test speed 10 mm / min) was also tested. It resulted in a value of 2.6 MPa.

After step 8, the strength of the adhesive bond according to DIN EN 1465 (test speed 10 mm / min) was also tested. It gave a value of 16.2 MPa.

To test for possible contamination of the cathodic dip bath with extracts of the incompletely crosslinked adhesive film, strips of the film were freed from the release paper, immersed in the magnetic-stirred KTL bath for 15 minutes, then rinsed off and dried again. Gravimetric determination (weighing before and after) demonstrated that no weight loss had occurred. This was confirmed by analysis of the bath composition.

Example 4:

1. Application of a section of the heat-activatable adhesive film between the overlapping surface of two strips ST 37 of dimensions 100 × 20 × 0.8 mm ³ , the strips overlapping at their end by 10 mm, resulting in a bond area of 20 mm ² One of the strips was previously coated with deep-drawing oil Oest Platinol K103 and wiped with a tissue cloth. The second strip had been cleaned with acetone.

Steps 2 to 4 were carried out according to Example 1. 5. The test specimens were then subjected to an automotive finishing process according to Figure 1 including the pretreatment steps of degreasing, activating, phosphating, passivating and cathodic painting and curing (180 ^° C., 20 minutes) by attaching them to a body shell which went through this process ,

After step 4, the initial strength of the adhesive bond was tested according to DIN EN 1465 (test speed 10 mm / min). It gave a value of 1, 9 MPa.

After step 5, the strength of the adhesive bond according to DIN EN 1465 (test speed 10 mm / min) was tested. It resulted in a value of 13.6 MPa.

Example 5:

In order to bond a pin with a disc base (d = 20 mm), the method according to the invention was likewise carried out using the heat-activatable adhesive film from Example 1 in the following steps:

1. Provision according to the bonding surface of prepunched adhesive films on a carrier paper in roll form

2. Preheating a bolt with a disc base to a temperature of 100 ⁰ C.

3. Removal of a stamped product by means of the preheated fastener from the backing paper (due to the tempering of the stamped product adheres to the bolt)

4. further heating of the fastener with adhering adhesive film to 160 ⁰ C.

5. Pressing the fastener with adhering adhesive film to the joining partner

6. Maintaining the contact pressure and the temperature over a period of 20 s

7. Remove the pressing device and cool the adhesive bond

8. reheating the adhesive bond in an oven without contact pressure to 160 ⁰ C. 9. Maintain temperature for 20 min

10. Cooling of the adhesive bond

It was found that components can be prelaminated with the adhesive film in this way.

In an advantageous embodiment of the method, steps 1 to 3 are already carried out by the manufacturer of the fastening elements and the element with the adhesive film is then cooled. The user of the fasteners then performs only the steps 4 to 10.

The invention will be clarified with reference to the following figures, without being intended to be limiting in any way.

FIG. 2 shows, by way of example, four different embodiments of adhesive components.

FIG. 3 shows a fastening element (2) which is adhesively bonded to a joining partner (3) by means of a heat-activatable adhesive film (1).

Claims

claims

A method for fixing a component to a joining partner to be painted, wherein a portion of a heat-activatable adhesive film is heated so that the adhesive film reaches a not fully crosslinked state, the component is fixed to the portion of the incompletely crosslinked heat-activatable adhesive film on the joining partner, the joining partner is painted together with the component fixed thereon, the painted joining partner is dried together with the component fixed thereto in a thermal drying, wherein the thermal energy to a complete

Crosslinking of the heat-activatable adhesive film leads, so that the component is permanently fixed on the joining partner.

2. The method according to claim 1, characterized in that the joining partner consists of metal, preferably a body of a vehicle.

3. The method according to claim 1 or 2, characterized in that the adhesive film is prelaminated onto the surface of the fastener, wherein the lamination temperature is below the start temperature of the crosslinking.

4. The method according to at least one of Ansprüchel to 3, characterized in that the component is fixed with a portion of a heat-activated adhesive film on the joining partner, at least the adhesive film is heated, so that they are not fully crosslinked

State reached and fixed the component on the adherend, the joining partner is painted together with the component fixed thereon.

5. The method according to at least one of the preceding claims, characterized in that the heat-activatable adhesive film is resistant to the usual cleaning, pretreatment, corrosion protection and painting processes, media and conditions used in the bodywork, in particular with respect to the degreasing, the activation , the passivation of the phosphating and / or the anodic and cathodic dip coating.

6. The method according to at least one of the preceding claims, characterized in that the thermal drying is carried out in a subsequent temperaturbeaufschlagten process, in particular together with the curing of the paint in the painting oven.

7. The method according to at least one of the preceding claims, characterized in that the energy for the thermal drying already during the Hinführens of

Bolzens and / or the adhesive film is supplied to the bonding point the fastener and / or the joining partner and / or the adhesive film.

8. The method according to at least one of the preceding claims, characterized in that the activation time to reach the incompletely crosslinked state less than 1 min, more preferably less than 30 s, most preferably less than 10 s.

9. The method according to at least one of the preceding claims, characterized in that the incompletely crosslinked adhesive film does not affect the painting process or the media used therein, in particular not a phosphating or KLT bath.

10. The method according to at least one of the preceding claims, characterized in that the adhesive film has a thickness of 10 to 250 .mu.m, especially 50 to 200 microns.

1 1. The method according to at least one of the preceding claims, characterized in that the crosslinkable adhesive film has a characteristic activation temperature of at least 40 ⁰ C, more preferably of at least 80 ⁰ C.

12. The method according to at least one of the preceding claims, characterized in that the adhesive film has a strength of more than 8 MPa in the tensile shear test according to DIN EN 1465 (substrate: aluminum plates 100x20x1, 6 mm ³ , etched, bonding surface 20 mm ² , test speed 10 mm / min) and / or a strength of more than 4 MPa in the tensile shear test according to DIN EN 1465 (bond area 20 mm ² , test speed 10 mm / min) on oiled body panels achieved.

13. The method according to at least one of the preceding claims, characterized in that the adhesive film at an activation temperature of not more than 130 ⁰ C, more preferably of not more than 110 ⁰ C, an initial strength of more than 1 MPa according to DIN EN 1465 (substrate: Aluminum plates 100x20x1, 6 mm ³ , etched, bonding area 20 mm ² , activation time 20 s, test speed 10 mm / min).

14. The method according to at least one of the preceding claims, characterized in that the adhesive force of the adhesive film at room temperature according to ASTM D 3330-04 (in a

Withdrawal speed of 300 mm / min) is preferably less than 3 N / cm, more preferably less than 1 N / cm.

15. The method according to at least one of the preceding claims, characterized in that the adhesive film is adapted in its geometry exactly the bonding surface by punching or otherwise shaping.

16. The method according to at least one of the preceding claims, characterized in that a robot for placing, heating and pressing of the fastening element and / or the adhesive film is used.