Aqueous adhesive for bonding especially metallic surfaces

Abstract

The invention especially relates to an adhesive system (3) comprising an aqueous polymer dispersion, preferably in the form of an epoxy resin dispersion, with hotmelt polymer particles (4) present therein. The hotmelt polymer particles are preferably highly polymeric and particularly preferably comprise reactive end groups, especially NH2 end groups. The adhesive system (3) more preferably comprises polyisocyanate for reaction with these reactive end groups. The invention more preferably relates to an apparatus comprising a metal sheet (2) and a homogeneous dispersion adhesive layer (2) composed of the adhesive system (3) applied thereto. The hotmelt polymer particles (4) may be larger than an adhesive layer (5) composed of the, especially dried, aqueous polymer dispersion, with the result that they protrude above the adhesive layer (5). As a result, the apparatus may be particularly readily rolled up without a risk of sticking within the coil. The invention finally preferably relates to a process for producing at least one apparatus, especially for producing a plurality of apparatuses, wherein the adhesive system (3) is applied to the metal sheet (2) and the apparatus(es) are dried.

Description

[0001] Aqueous adhesive for bonding especially metallic surfaces

[0002] The invention relates to an adhesive system, a device comprising a sheet and a dispersion adhesive layer made of such an adhesive system, and a method for producing at least one such device.

[0003] It is known from EP 0 671 451 B1 to coat adhesive on metal sheets, to press several of these coated sheets together and thereby to bond them.

[0004] The problem is that these sheets are rolled up, meaning that several layers of sheet adhesive are already in contact on one roll. The individual layers in these rolls should not be bonded together.

[0005] It is therefore an object of the invention to provide an adhesive system that, on the one hand, enables significantly better bonding than the prior art, but, on the other hand, does not cause bonding between layers of a rolled sheet metal. It is also an object of the invention to provide a device with such an adhesive system and a method for producing at least one such device.

[0006] This object is achieved by an adhesive system according to claim 1, a device according to claim 14 and a method according to claim 15. The dependent claims represent preferred embodiments.

[0007] The adhesive is particularly suitable for bonding metallic surfaces. For this purpose, it is coated onto metal strips using the collating process and dried, allowing it to be reactivated and bonded at a later time using heat and pressure.

[0008] Adhesive technology has also proven itself in recent years for the production of metal composites or metal packages.

[0009] In addition to creating a strong, full-surface and permanent bond, when bonding surfaces, especially when bonding the surfaces of metallic parts, it is of primary importance that a bonding layer of adhesive is created in the adhesive joint between the surfaces, the material properties of which correspond as closely as possible to the material properties of the composite material over a wide temperature range during use.

[0010] This objective can only be achieved unsatisfactorily with the known adhesive systems.

[0011] The electrical industry has been using bonded laminated cores made of magnetizable silicon-containing steel sheets for decades. These cores are used primarily in electric motor construction as form-fitting composite cores for rotors and stators. Experts are aware that form-fitting bonding offers advantages over mechanical joining methods.

[0012] Previous adhesive systems, which are applied to metal surfaces by roller coating (coil coating), are physically dried above the minimum film-forming temperature of the dispersions they contain and below the deblocking temperatures of the crosslinking resins or the reactive but blocked groups contained in the dispersion. They are then temporarily stored and further processed. These are then punched out into sheet metal discs or laser cut and stacked into sheet stacks. These sheet stacks are then compressed and heated using clamping tools or presses. The bonding parameters are typically 1–3 N / mm². 2Pressure and temperatures between 170°C and 230°C, with a bonding time of 30 minutes to several hours depending on the size of the component and the reactivity of the adhesive. Due to this lengthy bonding process and the application method used, the adhesives used here are also referred to as self-bonding systems.

[0013] This patented new adhesive is characterized by its suspension form. This consists of a dispersion adhesive as the carrier liquid and a cohesive polymer with a relatively high or preferably high degree of polymerization. The carrier liquid consists of dispersions such as epoxy resin dispersions, polyvinyl acetate dispersions, polybutadiene dispersions, polyacrylate dispersions, rubber dispersions, EPDM dispersions, or copolymer dispersions of the types mentioned. These can be contained individually or in blends, or present as a copolymer in a dispersion. These dispersion binders contain reactive end groups on the polymer and can be equipped with adhesion-promoting functional comonomers.The reactive groups in the polymer are usually hydroxyl groups, which react with blocked polyisocyanates after the isocyanate's deblocking temperature is exceeded during the bonding process to form a higher-polymer thermoset or thermosetting polymer. In recent years, silanes have also been successfully used as crosslinkers and adhesion promoters to the substrate as copolymers in dispersions. The crosslinking rate can be accelerated by catalysts.

[0014] Epoxy dispersions exhibit excellent adhesion to metals as well as very good chemical and heat resistance. They can be combined with other dispersion binders, for example, to improve these properties in terms of elasticity and reactivity.

[0015] The disadvantage of previous dispersion systems is that after application and drying to the metal substrate, they must be reactivated under temperature and pressure, which means they must be melted and reacted completely. The melt viscosity and reactivity must be adjusted so that no adhesive oozes out at the bond line. Dispersion adhesives typically have a relatively low glass transition point (Tg), which is due to the nature of the monomer composition and the amorphous structure of the polymer in the dispersion. However, the amorphous structure of the dispersion allows the dispersion to liquefy during the heating process when painting the metal surface and to form a continuous paint film, which in this state is capable of wetting the metal substrate and simultaneously creating a homogeneous mixture of all paint components.After cooling, a physically dried polymer film forms that adheres firmly to the metal surface. This polymer film is then melted and cured in a second downstream pressing process under heat and pressure. Only during the second heating process in the pressing tool is the adhesive's crosslinking mechanism activated by deliberately exceeding the blocking point of the crosslinking component.

[0016] The blocking resistance of the polymer layer resulting from the coating process is determined by the filmed polymer mixture that is then formed, which represents the sum of the glass transition temperatures of all individual components. In this state, this polymer film is only physically dried, and the deblocking temperature of the crosslinker it contains has not yet been exceeded. The glass transition points in this physically dried polymer layer are usually just above room temperature. This state of the adhesive layer on the metal rolls (cols) or sheets can then lead to adhesion and the beginning of physical film formation of the contacting adhesive films at elevated temperatures in summer or on tool surfaces. This can go so far that the adhesive, through further physical film formation, already in this state creates bonds that can no longer be removed without damage during further processing.

[0017] At room temperature or temperatures arising during the processing, surfaces can become so soft and elastic and their tribological properties and associated sliding properties of the metal parts coated with the adhesive can change so negatively that they cannot be punched out and processed into sheet packages before the actual bonding.

[0018] Due to the molecular weights and amorphous structure of the polymers used in the dispersions, they exhibit very low melt viscosities when bonded under pressure and temperature and, in this state, cannot transmit adhesive forces. The strength of the polymer only increases after a time delay when the polymer layer begins to crosslink. This crosslinking in the mold leads to a polymer network with a further increase in molecular weight. However, this often results in networks that have only a slightly higher melting point and glass transition point than the original dispersion binders. These generally have a softening point of approximately 90° to 110°C after curing and lose their strength when heated above the glass transition temperature. This property corresponds more to the structure of a thermoset than to that of a thermoset.

[0019] However, electronic components such as motors or transformers are used at continuous temperatures of 150°C to 180°C. Commercially available bonding varnish systems are therefore only capable of transferring very low adhesive forces at these operating temperatures, which are approximately 20 to 30% of the adhesive strength at room temperature.

[0020] Since conventional bonding varnishes tend to crosslink to a thermoset and cannot form a thermosetting network, especially with shorter bonding and cycle times, the components are held in place by a tool under pressure during the bonding and cooling period to prevent relative movement. After the crosslinking process, a high-polymer adhesive has developed that contains thermoset components but still has a low glass transition temperature below the intended continuous use temperature.

[0021] The adhesive formulation described here is based on the principle of combining two polymers that are physically mixed and formulated into an adhesive formulation. These combination hotmelt adhesives (KLS systems) contain, in addition to the dispersion, fine-particle hotmelt polymer particles, which improve the bonding properties to such an extent that holding times during bonding are significantly reduced, bond strength is significantly increased, and fast cycle times in the pressing tool are enabled.

[0022] These hot-melt polymer particles are known in the adhesives industry as heat-seal adhesives and are also extruded and processed in the melt from nozzles or gravure rollers. Another form of hot-melt adhesive is ultrafine powder. These can be applied by powder scattering or as a paste dot coating. The textile industry has been a major application area for decades.

[0023] The adhesive formulation described here utilizes this group of hot melt adhesives in the finely divided form of the polymer particles, which are incorporated into the coating. Furthermore, the significantly higher melt viscosity of the hot melt adhesive in the form of hot melt polymer particles is utilized compared to dispersions.

[0024] This adhesive is a suspension composed of an aqueous dispersion or a mixture of several dispersions and high-molecular-weight hot-melt adhesive particles. These hot-melt adhesive particles are usually present as a crystalline or semi-crystalline high polymer. The dispersion, on the other hand, is amorphous and serves as a carrier fluid for the hot-melt particles in the suspension.

[0025] The polymers in the dispersion and the hot-melt adhesive particles are present in the liquid adhesive in very different particle sizes. The particle size of the dispersion ranges from 15 nm to 5 pm, preferably from 50 nm to 200 nm. Due to the relatively low minimum film formation temperature (MFT) during the painting and baking process, these dispersion particles are capable of liquefying and forming a film, thereby wetting both the metal surface and the hot-melt polymer contained therein, and incorporating them into the adhesive film.

[0026] The minimum film formation temperature (MFT) of a dispersion describes the minimum temperature that must be reached after the evaporation of water and co-solvent for the dispersion particles to physically fuse and thus physically bond to form a polymer film. After the water has evaporated during the drying process, the dispersion particles inevitably come into contact with one another. This is referred to as the white point because the dispersion particles are still finely divided and, depending on their particle size, create a white or opaque color of the dispersion film through light refraction. Due to the co-solvents still present in them, the dispersion particles are very soft and amorphous in structure and begin to physically flow as the temperature increases further. The co-solvents have largely evaporated by the end of the drying process, but a small amount usually remains in the film and acts as an external plasticizer in the adhesive film.These residual co-solvents are also referred to as volatile organic components (VOCs), which describe the fact that these organic molecules often only escape from the polymer layer and evaporate after a certain time delay. The remaining VOC content lowers the glass transition point during this time and, among other things, causes additional stickiness on the surface of the adhesive film.

[0027] The hotmelt polymer particles are suspended in a grain size of 5 μm to a maximum of 63 μm, preferably 5 μm to 20 μm, and have a melting point of 110°C to 260°C, preferably 170°C. This means that the melting point of the hotmelt polymer particles is well above the minimum film formation temperature (MFT) of the dispersions. Therefore, they are not completely melted during the drying of the adhesive film and are therefore separately distributed within it. These hotmelt adhesive particles are only completely softened during the second heating process in the pressing tool during bonding when their glass transition point is exceeded, and only then are they completely melted and liquefied when their melting point is reached. Their viscosity in the molten state is determined by the melt viscosity of the hotmelt adhesive polymer and can be varied and adapted to the application depending on the type of hotmelt adhesive.

[0028] The mechanical properties of the bond, including its adhesive strength and elasticity, can be controlled by the properties inherent in the hot-melt polymer, such as its glass transition point, melting point, crystallinity, and internal tensile and flexural strength. This can have a particularly positive effect on vibration behavior and noise generation at different temperatures.

[0029] In addition to the material properties of the hot-melt adhesive polymer used, the thermosetting and thermoplastic properties of the cured adhesive layer can be varied by adjusting the mixing ratio of dispersion to hot-melt polymer. The formulation also contains the stoichiometrically required proportion of crosslinker groups, corresponding to the reactive groups present in the dispersion and the hot-melt polymer. This ratio can be used to vary the crosslinking density of the cured adhesive.

[0030] The specific melting point of the hot-melt polymer particle can be selected so that it lies well above the deblocking point of the hardener, but its recrystallization point is selected high enough that further reaction of the dispersion-hardener mixture can continue after partial cooling until solidification. For hot-melt adhesives, the expert refers to the temperature range between the melting point and recrystallization point of the polymer used as the open time of the hot-melt adhesive, which can be used for specific technical purposes. Thus, once the temperature has fallen below the recrystallization point and the hot-melt adhesive polymer contained in the adhesive has solidified, the pressing or holding tool can be opened. The adhesive can then be further crosslinked without pressure and with further temperature control below this temperature.

[0031] By adding hot-melt polymer particles, a targeted surface roughness is created that improves blocking resistance and further processing in the punching tool. Conventional slip, hardness, and abrasion measurements, such as pendulum hardness or Buchholz hardness, as well as Taber Abraser measurements, show that the addition of hot-melt polymer particles that protrude within and above the coating layer results in a significantly higher glass transition temperature and thus higher hardness, as well as better abrasion resistance and sliding properties than the surrounding adhesive layer. This significantly improves storage stability and further processability before final bonding. By varying the ratio of the adhesive layer thickness to the particle size of the hot-melt polymer particles used, the extent to which the particles protrude from the surface and create a raised area in the adhesive film can be adjusted. See Figures 1 and 2.This creates a visually visible structure and significantly reduces the gloss level of the adhesive film and can then be determined, for example, using a gloss meter or Wave Scan as well as Altek Mobility Tester.

[0032] The size of the hotmelt polymer particles relative to the thickness of the adhesive layer (made from an aqueous polymer dispersion) can be selected depending on the glass transition temperature (Tg). In particular, at a high glass transition temperature, the size of the hotmelt polymer particles can be selected so small that they do not protrude beyond the thickness of the adhesive layer, and at a low glass transition temperature, they can be selected so large that they protrude beyond the thickness of the adhesive layer.

[0033] The embedded hotmelt polymer particles are capable of spontaneously combining in the melt and creating a bond when the adhesive layer is subsequently heated and pressed against the next identical layer or another suitable adhesion promoter layer after the melting point has been exceeded by liquefaction and the formation of a viscous melt.

[0034] The hot-melt adhesive particles primarily function to create cohesive forces in the adhesive layer and possess viscoelastic properties. The cross-linking adhesive dispersion embeds the hot-melt polymer particles and can be incorporated into the polymer film via terminal reactive groups in the hot-melt polymer. The adhesive layer, consisting of a reactive dispersion, cures with a time delay to form the thermoset and primarily performs the task of transferring adhesive forces to the metal substrate and the embedded hot-melt polymer particles.

[0035] Since hotmelt adhesives can have different melting points as well as different melt viscosities due to appropriate co-polymerization, by selecting these in combination with the reactivity of the adhesive, it can be adjusted so that it does not leak out when the sheet stack is bonded to the edge of the respective layer.

[0036] Additionally, mechanically acting spacers in the form of thermosetting polyacrylate spheres or hollow glass microspheres can be included in the adhesive. These then mechanically reduce the compression of the adhesive layer to a minimum gap, thus preventing the adhesive from seeping out of the edges and additionally adjusting the relative parallelism of the layers in the sheet stacks. This is of particular interest for very thin steel sheets under 0.3 mm, as the ratio of steel sheet to adhesive layers shifts significantly, meaning the flatness of the sheet stack is heavily influenced by the adhesive.

[0037] The melting point, melt viscosity and reactivity of the adhesive suspension as well as the pressing pressure, pressing temperature and pressing time can be selected so that no adhesive escapes at the cut edge, but the adhesive layer between the sheets is completely closed. This makes it possible to produce media-tight packages in which no liquids or gases can penetrate the laminated cores. This is of particular interest for electric motors, which in the future can be cooled by gases or liquids through internal cooling channels in the laminated core. The melting point and glass transition point of the hot melt adhesives used can be selected so that they lie above the desired long-term temperature strength of e.g. 150° to 180°C. Hot melt polymers based on polyamide 12 and their co-polyamide polymers have a glass transition point or melting point of approximately 180°C.Hot melt adhesives based on polyamide 6 and its co-polyamide polymers can have glass transition points or melting points of approximately 210°C and are referred to as high-temperature hot melt adhesives. Thus, the adhesive described here achieves a significant increase in the adhesive's softening point and thus improved component strength under prevailing temperature loads during continuous operation.

[0038] The combination of low-molecular and more reactive dispersion adhesives with embedded high-molecular hot-melt polymer particles enables faster heating and cooling rates, as the viscous component introduced into the adhesive creates a rapid, cohesive bond. This can shorten cycle times in the production of the laminated cores.

[0039] The final thermosetting curing of the component can alternatively also take place after the recrystallization point of the hotmelt polymer has been undercut, using the operating temperatures of e.g. 180 °C, since the strengths already present in the adhesive layer due to the partial thermoplastic bonding are sufficient for commissioning the component.

[0040] Within the scope of the method according to the invention, the adhesive layer can be applied over a large area. Alternatively, the adhesive layer can be applied in dot form, in particular in paste dot form, preferably using a rotary printing process.

[0041] The invention is particularly characterized by the following aspects:

[0042] 1 . Adhesive for the production of bonded sheet packages made of silicon-containing strip steel which are bonded under heat and pressure.

[0043] 2. Adhesive consisting of a suspension of at least one aqueous polymer dispersion and finely divided high-polymer hotmelt polymer particles.

[0044] 3. Adhesive with an organic co-solvent and VOC content of 0% to 20%.

[0045] 4. The dispersion used has a particle size of 15 nm to 5 pm, preferably 50 nm to 300 nm.

[0046] 5. The hot melt polymer particles have a particle size of 1 pm to 40 pm, preferably 5 pm to 20 pm.

[0047] 6. The glass transition temperature of the high-polymer hotmelt polymer particles is above the minimum film formation temperature (MFT) and the glass transition point (TG) of the dispersion used.

[0048] 7. The mixing ratio in weight percent of the aqueous dispersion to the proportion of hotmelt polymer particles is between 99% dispersion to 1% hotmelt polymer particles to 5% dispersion to 95% hotmelt polymer particles, preferably 90%: 10% to 40%: 60% dispersion to hotmelt polymer particles. The high-polymer hotmelt polymer particles consist of: a. Polyester b. Co-polyester c. Polyamide 6 d. Polyamide 6.6 e. Polyamide 6.11 f. Polyamide 11 g. Polyamide 12 h. Co-polyamide

[0049] I. Ethylene vinyl acetate, EVA j. EVA copolymer The hotmelt polymer particles are manufactured using the following processes: a. cryoscopic grinding with subsequent sieving and classification b. precipitation from solvents c. production as a bead polymer The adhesive can also contain colored or functional pigments and fillers to improve corrosion protection, heat absorption and electrical breakdown resistance. The hotmelt polymer particles can contain reactive end groups in the hotmelt polymer which can react with the reactive groups contained in the dispersion and are thereby crosslinked from the thermoplastic to the duromer or thermoset. The adhesive can also contain thermosetting microspheres made of polyacrylate or mineral glass which are used to adjust the minimum film thickness and additionally align the laminated cores parallel during pressing.Adhesion promoters can also be added to the formulation at a concentration of 0.1% to 5% to improve the adhesive's adhesion to metal oxides or pretreatments on the metal surface. a. Phenoxy resins b. Carboxy resins c. Epoxy resins d. Phosphoric acid ester resins e. Silanes f. Thiols The adhesion groups listed under point 10 can also be present as copolymers in the dispersions or hotmelt polymer particles used. The adhesive is applied to the metal substrate using a co-coating process. 16. The layer thickness during the painting process is 1 μm to 50 μm, preferably 5 μm to 15 μm on metallic materials.

[0050] 17. The drying temperature of the metal substrates in the painting process is between 40°C and 300°C, preferably between 110°C and 160°C.

[0051] 18. The drying time in the painting process is 1 second to 10 minutes, preferably 10 seconds to 60 seconds.

[0052] 19. After drying, the adhesive layer can be wound into coils or stacked as sheets or punched parts and is then block-resistant and storage-stable.

[0053] 20. The adhesive-coated metal substrates can be punched or cut and stacked into sheet stacks and then bonded together using temperature and pressure.

[0054] 21. The pressure during bonding in the press tool is 1-50N / mm 2 .

[0055] 22. The bonding time in the press tool is 0.1 seconds to 120 minutes.

[0056] 23. The temperature during bonding in the press tool is 120°C to 350°C.

[0057] 24. The substrates coated with this adhesive can be pressed and bonded with adhesive layer against adhesive layer and can be pressed and bonded with a different coating suitable for the adhesive on the substrate.

[0058] An example recipe and application data are shown below:

[0059] Example recipes:

[0060] Type of raw material Trade name Quantity

[0061] Epoxy resin dispersion 53% in water EPIREZ 3546WH53 76.6%

[0062] Polyamide 12, 10pm, melting point 177°C Orgasol 2001 EXD NAT1 6.6%

[0063] Polyisocyanate, water-dilutable BAYHYDUR BL XP 2706 3.4%

[0064] Defoamer, silicone-free Moussex SF561 0.2% deionized water for viscosity adjustment 13.2%

[0065] Total 100%

[0066] Application data painting:

[0067] Viscosity: approx. 50 seconds DIN 4mm flow viscosity at 20°C

[0068] Substrate: Si steel N270, 0.27mm

[0069] Drying:

[0070] Dwell time 40s

[0071] Metal object temperature 155°C PMT (Peak Metal Temperature) average layer thickness of adhesive layer in painted state approx. 7 pm maximum layer thickness in the area of ​​the embedded PA 12 particles approx. 10 pm

[0072] Type of raw material Trade name Quantity

[0073] Epoxy resin dispersion 53% in water EPIREZ 3546WH53 74.1%

[0074] Polyamide 12, 5pm, melting point 177°C Orgasol 2001 UD NAT1 6.3%

[0075] Polyisocyanate, water-dilutable BAYHYDUR BL XP 2706 3.3%

[0076] Defoamer, silicone-free Moussex SF561 0.2% deionized water for VI 16.1%

[0077] Total 100%

[0078] Application data painting:

[0079] Viscosity: approx. 50 seconds DIN 4mm flow viscosity at 20°C

[0080] Substrate: Si steel N270, 0.27mm

[0081] Drying:

[0082] Dwell time 40s

[0083] Metal object temperature 155°C PMT (Peak Metal Temperature) average layer thickness of adhesive layer in painted state approx. 3 pm maximum layer thickness in the area of ​​the embedded PA 12 particles approx. 5 pm

[0084] Type of raw material Trade name Quantity

[0085] Epoxy resin dispersion 53% in water EPIREZ 3546WH53 74.1%

[0086] Polyamide 12 with reactive -NH2 groups GRILTEX D2662 PO-35 6.3% Melting point 177°C reground to 7pm

[0087] Polyisocyanate, water-dilutable BAYHYDUR BL XP 2706 4.0%

[0088] Defoamer, silicone-free Moussex SF561 0.2% deionized water for VI 15.4%

[0089] Total 100%

[0090] Application data painting:

[0091] Viscosity: approx. 50 seconds DIN 4mm flow viscosity at 20°C

[0092] Substrate: Si steel N270, 0.27mm

[0093] Drying:

[0094] Dwell time 40s

[0095] Metal object temperature 155°C PMT (Peak Metal Temperature) average layer thickness of adhesive layer in painted state approx. 4 pm maximum layer thickness in the area of ​​the embedded PA 12 particles approx. 7 pm

[0096] Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further-described features can be used individually or in combination in any desired manner. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention.

[0097] Short description of the drawing

[0098] They show:

[0099] Fig. 1 is a schematic side view of a sheet coated with adhesive;

[0100] Fig. 2 is an enlarged schematic side view of the arrangement of Fig. 1; and

[0101] Fig. 3 shows an enlarged section according to the dashed frame of Fig. 2.

[0102] Detailed description of the drawing

[0103] Fig. 1 shows a side view of a sheet metal element 1, here in the form of a steel sheet. The sheet metal element 1 is coated with a dispersion adhesive layer 2.

[0104] Fig. 2 shows a further schematic view of the arrangement from Fig. 1 . From Fig. 2 it can be seen that the dispersion adhesive layer 2 (see Fig. 1 ) is in the form of an adhesive system 3.

[0105] According to Fig. 3, the adhesive system 3 (see Fig. 2) comprises hotmelt polymer particles 4 (schematically represented as black spheres in the drawing) embedded in an adhesive layer 5 made of a polymer dispersion. The hotmelt polymer particles 4 are preferably larger than the thickness of the adhesive layer 5, so that they protrude beyond the adhesive layer by an amount 6.

[0106] Further information can be found in the following list of the points indicated in the drawing.

[0107] At:

[0108] 1 . Steel sheet, especially with a thickness of 0.27 mm

[0109] 2. Dispersion adhesive layer, especially with a thickness of 7pm

[0110] 3. KLS adhesive system, consisting of dispersion and hotmelt particles as a mixture

[0111] 4. Hotmelt polymer particles, in particular with a diameter of 10 pm, which are preferably embedded in a 7 pm adhesive layer and protrude 3 pm from the adhesive layer

[0112] 5. Adhesive layer, in particular with a thickness of 7pm of the KLS adhesive 6. Difference layer thickness adhesive layer to diameter hotmelt polymer particles, in particular of 3pm

[0113] Taking a summary of all the figures of the drawing, the invention relates in particular to an adhesive system 3 with an aqueous polymer dispersion, preferably in the form of an epoxy resin dispersion, with hotmelt polymer particles 4 contained therein. The hotmelt polymer particles are preferably high-polymer and particularly preferably have reactive end groups, in particular NH2 end groups. More preferably, the adhesive system 3 comprises polyisocyanate for reaction with these reactive end groups. The invention further preferably relates to a device with a metal sheet 2 and a homogeneous dispersion adhesive layer 2 made from the adhesive system 3 applied thereto. The hotmelt polymer particles 4 can be larger than an adhesive layer 5 made from the, in particular dried, aqueous polymer dispersion, so that they protrude beyond the adhesive layer 5.This allows the device to be rolled up particularly well without causing sticking within the coil. Finally, the invention preferably relates to a method for producing at least one device, in particular for producing multiple devices, in which the adhesive system 3 is applied to the sheet metal 2 and the device(s) are dried.

Claims

Patent claims 1 . Adhesive system (3) with an aqueous polymer dispersion, wherein the adhesive system (3) contains hotmelt polymer particles (4) in the polymer dispersion.

2. Adhesive system according to claim 1, wherein the polymer dispersion is in the form of an epoxy resin dispersion.

3. Adhesive system according to one of the preceding claims, in which particles of the polymer dispersion have a particle size of 15 nm to 5 pm, preferably of 1 pm to 2 pm, in particular of 50 nm to 300 nm.

4. Adhesive system according to one of the preceding claims, wherein the hotmelt polymer particles (4) are in the form of high-polymer hotmelt polymer particles, in particular in the form of: a. Polyester b. Co-polyester c. Polyamide i. Polyamide 6 ii. Polyamide 10 ill. Polyamide 11 iv. Polyamide 12 d. Co-polyamide i. Polyamide 4.6 II. Polyamide 6.6 ill. Polyamide 6.9 iv. Polyamide 6.10 v. Polyamide 6.11 vi. Polyamide 6.12 vii. Polyamide 10.10 viii. Polyamide 12.12 e. Ethylene vinyl acetate, EVA f. EVA copolymer 5. Adhesive system according to one of the preceding claims, wherein the hotmelt polymer particles (4) have a particle size of 1 pm to 40 pm, in particular of 4 pm to 12 pm.

6. Adhesive system according to one of the preceding claims, in which the mixing ratio in percent by weight of the polymer dispersion to the proportion of hotmelt polymer particles (4) is between 99% to 1% and 5% to 95%, in particular between 90% to 10% and 60% to 40%.

7. Adhesive system according to one of the preceding claims, wherein the glass transition temperature of the hotmelt polymer particles (4) is above the minimum film-forming temperature and / or the glass transition temperature of the polymer dispersion.

8. Adhesive system according to one of the preceding claims, in which the hotmelt polymer particles (4) are produced by cryoscopic grinding, wet grinding, precipitation from solvents or as a bead polymer.

9. Adhesive system according to one of the preceding claims, in which the hotmelt polymer particles (4) have reactive end groups, in particular NH2 end groups, wherein the adhesive system preferably comprises polyisocyanate, wherein the adhesive system preferably comprises a co-crosslinking component, in particular an amino resin, silane and / or aminoplast resin, wherein the polymer dispersion preferably has further reactive end groups, in particular due to polyisocyanate, in the polymer dispersion, which can react with the reactive end groups of the hotmelt polymer particles (4), so that crosslinking from the thermoplastic to the duromer or duroplast can particularly preferably take place.

10. Adhesive system according to one of the preceding claims, wherein the adhesive system (3) comprises an organic co-solvent, in particular with a VOC content of 0.1% to 20%.

11. Adhesive system according to one of the preceding claims, wherein the adhesive system (3) comprises colored pigments, functional pigments and / or fillers, in particular graphenes, to improve corrosion protection, heat absorption and / or electrical breakdown resistance, these preferably being present in the form of copolymers in the particles of the polymer dispersion and / or the hotmelt polymer particles.

12. Adhesive system according to one of the preceding claims, wherein the adhesive system (3) contains thermosetting microspheres made of polyacrylate or mineral glass in order to achieve a minimum film thickness and parallel alignment of two adhesive surfaces.

13. Adhesive system according to one of the preceding claims, wherein the adhesive system (3) comprises an adhesion promoter in order to improve the adhesion to metal oxides or metal surfaces, wherein the adhesion promoter in particular has a weight fraction of 0.1% to 5%, wherein the adhesion promoter is preferably in the form of a phenoxy resin, a carboxy resin, an epoxy resin, a phosphoric acid ester resin, a silane or a thiol.

14. Device with a metal sheet (1) and a dispersion adhesive layer (2) made of an adhesive system (3) according to one of the preceding claims, wherein the layer thickness of the dispersion adhesive layer (2) is preferably 1 pm to 50 pm, preferably 2 pm to 10 pm.

15. A method for producing at least one device according to claim 14, wherein the adhesive system (3) is applied to the sheet metal (1) over a large area by means of coil coating or in dots, wherein the following process parameters are preferably used: a) a drying temperature after application is 40°C to 300°C, in particular 110°C to 160°C; and / or b) a drying time after application is 1 second to 10 minutes, in particular 10 seconds to 60 seconds.

16. The method according to claim 15, wherein a plurality of devices are stacked, pressed, and thereby bonded, wherein the following process parameters are preferably applied: a) the pressure during bonding is 1 N / mm2 to 50 N / mm2; b) the bonding time is 0.1 seconds to 120 minutes; and / or c) the temperature during bonding is 120°C to 350°C; wherein particularly preferably the bonded devices are punched and / or cut.

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