Primer composition for producing an adhesive bond

Abstract

A primer composition for producing an adhesive bond, containing (a) at least one thermoplastic polyurethane and (b) at least one organosilane selected from the group consisting of trialkoxysilylalkylsuccinic anhydrides, trialkoxyphenylsilanes, (3‑mercaptopropyl)trialkoxysilanes, (3‑aminopropyl)alkoxysilanes, 3‑(2‑aminoethylamino)propyltrialkoxysilanes, vinyltrialkoxysilanes and (3‑glycidyloxypropyl)trialkoxysilanes.

Description

[0001] tesa Societas Europaea Norderstedt

[0002] Description

[0003] Primer composition for creating an adhesive bond

[0004] The present invention relates to a primer composition for producing an adhesive bond, a method for producing an adhesive bond, and a bonded composite obtainable by the method, as well as the use of the bonded composite.

[0005] Primer compositions for the production of adhesive bonds, in particular by means of adhesive films, are known to those skilled in the art.

[0006] The present invention is based on the objective of providing a primer composition for producing an adhesive bond which, compared to the prior art, achieves a further improvement in bond strength and also an improvement in chemical resistance. Furthermore, the bond strength should remain at a very good level even after storage under humid and warm conditions.

[0007] The problem is solved according to the invention by a primer composition as described in claim 1. Advantageous embodiments of the primer composition are described in the dependent claims. Furthermore, the solution according to the invention includes a method for producing an adhesive bond and a bonded composite obtainable by the method. Another object of the invention is the use of the bonded composite in the automotive industry and / or the electronics industry.

[0008] Accordingly, the present invention relates to a primer composition for producing an adhesive bond comprising at least the following components: (a) at least one thermoplastic polyurethane; and

[0009] (b) at least one organosilane selected from the group consisting of trialkoxysilylalkyl succinic anhydrides, trialkoxyphenylsilanes, (3-

[0010] Mercaptopropyl)trialkoxysilanes, (3-Aminopropyl)alkoxysilanes, 3-(2-Aminoethylamino)propyltrialkoxysilanes, Vinyltrialkoxysilanes, and (3-Glycidyloxypropyl)trialkoxysilanes.

[0011] The term "primer" is known to those skilled in the art in connection with adhesive bonds. In the sense of the invention, the term "primer" means in particular a base coat applied to a substrate which is able (either on a chemical or physical basis) to interact with two material layers and enable their adhesion.

[0012] A primer is generally considered a formulated product (usually containing more than one component) that is applied from the liquid phase using a specific method (immersion, brushing, spraying, etc.). According to this definition, the primer should not only enable adhesion but also form a uniform primer layer on the substrate surface by adjusting its viscosity, wetting properties, drying rate, and other characteristics.

[0013] Within the scope of the present invention, the composition of the primer is considered and described in particular with regard to its components and thus the “primer composition”.

[0014] Because the primer composition according to the invention contains the combination of (a) at least one thermoplastic polyurethane and (b) at least one organosilane selected from the group consisting of trialkoxysilylalkyl succinic anhydrides, trialkoxyphenylsilanes, (3-mercaptopropyl)trialkoxysilanes, (3-aminopropyl)alkoxysilanes, 3-(2-aminoethylamino)propyltrialkoxysilanes, vinyltrialkoxysilanes, and (3-glycidyloxypropyl)trialkoxysilanes, a bonded composite of at least one substrate and an adhesive film using the primer composition surprisingly exhibits improved bond strengths between the substrate and the adhesive film, even after storage under humid-warm conditions and after contact with chemicals, and thus simultaneously improved chemical resistance.

[0015] The primer composition according to the invention thus enables the production of a stronger adhesive bond.

[0016] All descriptions apply to the primer composition according to the invention, the method according to the invention, the bonded composite according to the invention, and the use of the layered body.

[0017] The invention also encompasses all features that are the subject matter of any dependent claims. Furthermore, the invention encompasses combinations of individual features with one another, including combinations of different preferred features. Thus, for example, the invention encompasses the combination of a first feature designated as "preferred" with a second feature designated as "particularly preferred." This also includes features designated as "embodiments" of varying preferred features.

[0018] The thermoplastic polyurethane (a) according to the invention preferably has no free isocyanate groups. The content of free isocyanate groups is determined, in particular, by IR spectroscopy. Polyurethanes with free isocyanate groups, especially those obtained as polyurethanes with terminal isocyanate groups due to an excess of di- and / or poly-isocyanates during the production of the polyurethane, are moisture-curing and thus cure upon contact with atmospheric moisture.

[0019] The thermoplastic polyurethane (a) contained in the invention is preferably hydroxy-terminated and thus preferably has terminal OH groups. Such a polyurethane is non-moisture-curing and therefore does not react with atmospheric moisture. It is therefore particularly well suited for the production of the primer composition according to the invention.

[0020] According to preferred embodiments, the polyurethane is the chemical reaction product of a1) at least one diol and / or polyol, and a2) at least one di- and / or poly-isocyanate, wherein in the reaction an excess of a1) diols and / or polyols is preferably selected over the a2) di- and / or poly-isocyanates.

[0021] In principle, all known aliphatic or aromatic di- or multi-hydroxyl-functionalized substances are eligible as diols / polyols, in particular all polyester diols / polyols, including all polycaprolactone diols / polyols, all polyester carbonate diols / polyols, all polyether diols / polyols, and all polybutadiene diols / polyols, as well as substances derived from or derivatives of these substances. Furthermore, so-called chain extenders and / or crosslinkers are also eligible, which here are understood to be di- or multi-hydroxyl-functionalized substances that are not poly compounds.

[0022] Polyester diols / polyols usable according to the invention are polyesters with terminally bonded hydroxyl groups. Polyester diols have two terminally bonded hydroxyl groups and are therefore difunctional. The number of terminally bonded hydroxyl groups in polyester polyols is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyester polyols are understood to be those with more than two hydroxyl groups per molecule. Polyester diols / polyols usable according to the invention are generally obtained by polycondensation from diols / polyols and di- / polycarboxylic acids, or, in the case of polycaprolactone polyols, by ring-opening polymerization from μ-caprolactone and a di- or polyfunctional starter molecule.

[0023] Polyester carbonate diols are doubly hydroxyl-functionalized polyesters whose molecular chain also contains at least one carbonic acid ester group. They can be obtained, for example, by the poly-reaction of a diol, a dicarboxylic acid, and dimethyl carbonate (DMC) or diphenyl carbonate (DPC). The number of terminally bonded hydroxyl groups in polyester carbonate polyols is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyester carbonate polyols are defined as those with more than two hydroxyl groups per molecule.

[0024] Polyether diols (Z-polyols) usable according to the invention are polyethers with terminally bonded hydroxyl groups. Polyether diols have two terminally bonded hydroxyl groups and are therefore difunctional. The number of terminally bonded hydroxyl groups in polyether polyols is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyether polyols are understood to be those with more than two hydroxyl groups per molecule. Polyether diols (Z-polyols) usable according to the invention are primarily produced from ethylene oxide, propylene oxide, or tetrahydrofuran by ring-opening polymerization or copolymerization using a starter molecule that determines the functionality.

[0025] Polybutadiene diols are doubly hydroxyl-functionalized polybutadienes produced from butadiene via an anionic polymerization process. Well-known commercial products include, for example, the KrasolO types from Cray Valley. Polybutadiene polyols can contain two or more hydroxyl groups per molecule. In this document, polybutadiene polyols are defined as those with more than two hydroxyl groups per molecule. They are produced from butadiene via a radical polymerization process. Well-known commercial products include, for example, the Poly bd® types from Cray Valley.

[0026] Examples of chain extenders are 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, propylene glycol, dipropylene glycol, 1,4-cyclohexanediethanol or 2-eth-1,3-hexanediol.

[0027] Examples of crosslinking agents are glycerin, trimethylolpropane, or 1,2,4-butanetriol.

[0028] According to particularly advantageous embodiments of the invention, the a1 ) is at least one diol and / or polyol selected from the group consisting of polyester diols, polyester polyols, polyester carbonate diols and polyester carbonate polyols, wherein polyester diols and / or polyester carbonate diols are again particularly preferred.

[0029] a2) Di- and / or poly-isocyanates that can be used according to the invention are all known aliphatic and / or aromatic di-isocyanates and / or poly-isocyanates. Di-isocyanates have two isocyanate groups per molecule and are therefore difunctional. Poly-isocyanates have two or more isocyanate groups per molecule. In this document, poly-isocyanates are understood to be those with more than two isocyanate groups per molecule.Examples of suitable di- and / or poly-isocyanates are 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (isophorone diisocyanate, I PDI), hexane-1,6-diisocyanate (hexamethylene diisocyanate, HDI), dicyclohexylmethane-4,4'-diisocyanate (H12MDI), toluene diisocyanate, diphenylmethane-4,4'-diisocyanate (4,4' MDI) and / or m-tetramethylxylene diisocyanate (TMXDI), mixtures of the aforementioned isocyanates or chemically derived isocyanates, for example dimerized, trimerized or polymerized types containing, for example, urea, uretdione or isocyanurate groups.

[0030] Difunctional starting materials, i.e. diols and diisocyanates, are particularly preferred.

[0031] According to advantageous embodiments, diisocyanate a2) diphenylmethane-4,4'-diisocyanate (4,4' MDI) and / or hexane-1,6-diisocyanate (hexamethylene diisocyanate, HDI) is used, wherein diphenylmethane-4,4'-diisocyanate (4,4' MDI) is particularly preferred.

[0032] According to advantageous embodiments, a polyester polyurethane is used as the thermoplastic polyurethane a). For this purpose, a reaction product of a diol with a carboxylic acid, in particular a dicarboxylic acid, is preferably obtained as the macrodiol component. For example, 1,6-hexanediol is used as the diol a1) and adipic acid as the dicarboxylic acid.

[0033] To accelerate the reaction of the diols / polyols with the di- / poly-isocyanates, one or more catalysts known to those skilled in the art, such as tertiary amines, bismuth or organotin compounds, to name just a few, can be used. Catalysts containing bismuth and carbon can be used very advantageously, preferably a bismuth carboxylate or a bismuth carboxylate derivative, in particular bismuth trisneodecanoate, CAS No.: 34364-26-6. The catalyst concentration is adjusted to the diols / polyols and di- / poly-isocyanates used. Generally, it is between 0.01 wt% and 0.5 wt% of the polyurethane to be produced.

[0034] The thermoplastic polyurethane (a) contained according to the invention is preferably a semicrystalline thermoplastic polyurethane. This particularly well solves the problem underlying the invention.

[0035] The thermoplastic polyurethane (a) contained according to the invention preferably has a storage modulus G', determined by DMA, of more than 1 MPa. Particularly preferably, the storage modulus G' is more than 5 MPa, again more preferably more than 15 MPa, particularly up to 100 MPa, and most preferably up to 50 MPa.

[0036] The storage modulus G' is determined using dynamic mechanical analysis (DMA) in accordance with DIN EN ISO 6721:2019-09. The measurement is performed with a TA HR20 (TA instrument) rheometer. Approximately 0.1 g of the granular material is placed on the round, lower plunger of the rheometer. The plunger temperature is raised above the melting point of the material under investigation, thus melting it. The molten material is then flattened with a flat metal plunger. This process is repeated three to four times until a layer thickness of approximately 1 mm is achieved. The upper plunger is then brought into contact with the polymer film. Any material that has oozed out of the joint is removed.

[0037] The furnace doors surrounding the parallel plates and shafts of the rheometer are closed, and the temperature is raised to 100 °C and held for 5 minutes to relieve any residual stresses. The axial force is then set to 0 to maintain contact between the material and the plates. The temperature was initially set to -50 °C and then increased from -50 °C to 200 °C at a rate of 5 °C / min, while the parallel plates oscillated at a frequency of 1 Hz with an initial strain amplitude of 0.15%. The strain was increased by 50% of the current value as soon as the measured torque fell below 1 g-cm, with a maximum allowable strain amplitude of 10%.

[0038] A suitable thermoplastic polyester polyurethane is available, for example, under the trade name Laricol 1460 from Coim. Another suitable thermoplastic polyester polyurethane is available under the trade name I ROSTIC® S-6558-06 from Huntsman.

[0039] According to preferred embodiments, the primer composition according to the invention contains at least one solvent, in particular at least one organic solvent. The solvent primarily serves the purpose of dissolving the thermoplastic polyurethane used. Thus, according to preferred embodiments, the primer composition according to the invention contains at least one solvent, in particular at least one organic solvent, wherein the thermoplastic polyurethane is soluble in the solvent. According to preferred embodiments, in the process for producing the adhesive bond, i.e., when applying the primer composition to at least one surface of a substrate and / or adhesive film to be bonded, the primer composition according to the invention contains at least one solvent, in particular at least one organic solvent. The solvent primarily serves the purpose of dissolving the thermoplastic polyurethane used.According to preferred embodiments, the primer composition according to the invention thus contains at least one solvent, in particular at least one organic solvent, in the process for producing the adhesive bond, i.e., when applying the primer composition to at least one surface of a substrate to be bonded and / or adhesive film, wherein the thermoplastic polyurethane is soluble in the solvent.

[0040] Preferably, and by way of example, the organic solvent is an anhydrous mixture of 80 wt% ethyl acetate and 20 wt% methyl ethyl ketone (MEK), or 100% methyl ethyl ketone, or acetone. However, the invention is not limited to these examples. It is understood that other solvents in which the thermoplastic polyurethane is soluble are also suitable. Therefore, the organic solvent is selected from the group of solvents in which the thermoplastic polyurethane is soluble. Preferably, the organic solvent is selected from the group consisting of toluene, acetone, ethyl acetate, methyl ethyl ketone, methoxypropanol, methylcyclohexane, xylene, cyclohexane, heptane, and mixtures thereof, as well as mixtures of C1 to C4 alkyl alcohols and toluene, acetone, ethyl acetate, methyl ethyl ketone, methoxypropanol, methylcyclohexane, xylene, cyclohexane, and heptane.The organic solvent is particularly preferred if selected from the group consisting of pure acetone, pure methyl ethyl ketone, and an 80:20 mixture of ethyl acetate and methyl ethyl ketone. Furthermore, the organic solvent is preferably anhydrous, i.e., it has a water content of at most 2%, determined, for example, according to Karl Fischer.

[0041] The solvent evaporates, especially after the primer is applied, so that the primer or the applied primer layer dries.

[0042] Within the scope of the present invention, the undried primer composition is considered on the one hand, and the dried primer composition resulting from the evaporation of solvent, in particular from the applied primer layer, on the other.

[0043] According to advantageous embodiments of the invention, the primer composition before drying contains 2 to 10 wt.%, preferably 3 to 8 wt.%, particularly preferably 3 to 5 wt.%, based on the total weight of the undried primer composition, of the at least one thermoplastic polyurethane (a).

[0044] Preferably, the dried primer composition contains 70 to 90 wt.%, particularly preferably 70 to 85 wt.%, most preferably 75 to 85 wt.%, of the at least one thermoplastic polyurethane (a), in each case based on the total weight of the dried primer composition.

[0045] In the event that two or more different thermoplastic polyurethanes are included as component (a), the quantities stated refer to the total quantity of thermoplastic polyurethane.

[0046] The aforementioned quantities result in particularly advantageous properties, especially a particularly high bond strength of the adhesive joint produced with the primer composition.

[0047] According to the invention, the primer composition (b) contains at least one organosilane selected from the group consisting of trialkoxysilylalkyl succinic anhydrides,

[0048] Trialkoxyphenylsilanes,

[0049] (3-Mercaptopropyl)trialkoxysilanes,

[0050] (3-Aminopropyl)alkoxysilanes,

[0051] 3-(2-Aminoethylamino)propyltrialkoxysilanes,

[0052] Vinyltrialkoxysilanes, and (3-Glycidyloxypropyl)trialkoxysilanes.

[0053] In general, organosilane is a compound of the type R-Si(R) known to those skilled in the art. 1 R 2 R 3 ), where R represents an organic residue which may contain heteroatoms and R1 , R 2 and R 3 The remaining groups attached to the silicon atom are preferably selected from alkoxy and alkyl groups. The R groups 1 , R 2 and R 3 They can be the same or different, independently of each other. R is particularly preferred. 1 , R 2 and R 3 Alkoxy groups, and in turn preferably selected from methoxy and ethoxy groups.

[0054] According to particularly advantageous embodiments of the invention, the organosilane (b) is selected from the group consisting of trialkoxysilylalkyl succinic anhydrides,

[0055] Trialkoxyphenylsilanes,

[0056] (3-Mercaptopropyl)trialkoxysilanes,

[0057] Vinyltrialkoxysilanes, and

[0058] (3-Glycidyloxypropyl)trialkoxysilanes.

[0059] (3-Glycidyloxypropyl)trialkoxysilane is preferred as (3-Glycidyloxypropyl)triethoxysilane and / or (3-Glycidyloxypropyl)triethoxysilane.

[0060] Particularly preferred is the organosilane (b) comprising at least one trialkoxysilylalkyl succinic anhydride in the primer composition.

[0061] Surprisingly, this results in improved chemical resistance and very good bond strengths before and after storage under humid and warm conditions.

[0062] Preferably, the alkyl group of the trialkoxysilylalkyl succinic anhydride is a linear alkylene group with 1 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. A propylene group is particularly preferred. Thus, the silane is preferably a trialkoxysilylpropyl succinic anhydride.

[0063] Preferably, the trialkoxy groups within a molecule are identical. Preferably, the alkoxyl groups of the trialkoxysilylalkyl succinic anhydride are selected from methoxy and ethoxy groups.

[0064] According to particularly advantageous embodiments of the invention, the primer contains (3-triethoxysilylpropyl) succinic anhydride as trialkoxysilylalkyl succinic anhydride and thus as organosilane (b).

[0065] According to advantageous embodiments of the invention, the amount of organosilanes (b) contained in the undried primer composition is 0.5 to 5.0 wt.%, preferably 0.5 to 3.0 wt.%, particularly preferably 0.5 to 1.5 wt.%, based on the total weight of the undried primer composition.

[0066] According to advantageous embodiments of the invention, the amount of organosilanes (b) contained in the dried primer composition is 10 to 30 wt.%, preferably 15 to 30 wt.%, particularly preferably 15 to 25 wt.%, based on the total weight of the dried primer composition.

[0067] According to advantageous embodiments of the invention, the ratio of the total amount of thermoplastic polyurethane (a) to the total amount of organosilanes (b), in particular (3-triethoxysilylpropyl) succinic anhydride, is from 3:1 to 5:1, particularly preferably 3.5:1 to 4.5:1, most preferably 3.75:1 to 4.25:1, in particular 4:1.

[0068] Organic solvents and water are not included in this ratio.

[0069] A particularly preferred dried primer composition contains, based on the total weight of the dried primer composition:

[0070] (a) 75 to 85 wt.% of at least one thermoplastic polyurethane,

[0071] (b) 15 to 25 wt.% of at least one organosilane selected from the group consisting of trialkoxysilylalkyl succinic anhydrides, trialkoxyphenylsilanes, (3-mercaptopropyl)trialkoxysilanes, (3-aminopropyl)alkoxysilanes, 3-(2-aminoethylamino)propyltrialkoxysilanes, vinyltrialkoxysilanes, and (3-glycidyloxypropyl)trialkoxysilanes.

[0072] Preferably, the sum of the amounts of components (a) and (b) is 98 to 100 wt.%, particularly 100 wt.%. If the sum is less than 100 wt.%, it contains, in particular, amounts of solvent that have not yet evaporated or have not yet evaporated. The primer composition according to the invention is prepared, in particular, by combining and mixing the aforementioned components (a) and (b). The thermoplastic polyurethane and the organosilane are combined as separate substances. In particular, they are not reacted with each other, so that, in particular, no silane-functionalized polyurethane is used in the preparation of the primer composition according to the invention.

[0073] The components are mixed together, in particular in at least one organic solvent.

[0074] In the context of the present invention, the term "solvent" refers to solvents other than water, in particular organic solvents.

[0075] The primer composition according to the invention is adjusted, in particular and preferably, by adding organic solvent to a desired solids content, especially with regard to a desired viscosity, so that it is adapted to the respective conditions during application for the production of the adhesive bond.

[0076] According to preferred embodiments, the total amount of organic solvents is 85 to 98 wt.%, preferably 93 to 98 wt.%, in particular and for example 95 wt.%, based on the total weight of the undried primer composition.

[0077] Applying the primer composition according to the invention to a surface, for example to a substrate, in particular a component, and / or an adhesive compound, thus particularly and preferably results in an initially undried primer layer with a certain layer thickness.

[0078] Before adding another layer to this primer layer, the primer layer is dried as already described, in particular and preferably, resulting in a dried primer layer with a correspondingly reduced layer thickness.

[0079] The primer composition according to the invention is preferably used for bonding at least one substrate to at least one adhesive film. According to preferred embodiments, the primer composition according to the invention is used for bonding a substrate to an adhesive film. According to further preferred embodiments, the primer composition according to the invention is used for bonding two substrates to each other by means of an adhesive film.

[0080] Another object of the present invention is a layered body comprising a first substrate A, a primer layer on the substrate A, wherein the primer layer is based on a primer composition according to the invention, which is applied in particular from a liquid phase, and an adhesive film which is connected to the first substrate A via the primer layer.

[0081] The primer composition is preferably applied to the substrate A and / or to the adhesive film.

[0082] According to preferred embodiments, the layered body according to the invention comprises at least one further substrate B, which is arranged on the side of the adhesive film opposite the substrate A. Further preferred embodiments will become apparent from the description below of the method according to the invention for producing an adhesive bond between a first substrate A and a second substrate B by means of an adhesive film.

[0083] A further object of the present invention is a method for producing an adhesive bond between a first substrate A and a second substrate B by means of an adhesive film, wherein a surface of the first substrate A is brought into contact with a first surface of the adhesive film, and wherein a surface of the second substrate B is brought into contact with the second surface of the adhesive film, wherein at least the surface of the first substrate A that is brought into contact with the adhesive film is treated with the primer composition according to the invention before being brought into contact, and / or at least the first surface of the adhesive film that is brought into contact with the first substrate A is treated with the primer composition according to the invention before being brought into contact.According to preferred embodiments of the invention, the surface of the second substrate B, which is brought into contact with the adhesive film, is also treated with the primer composition according to the invention before contact and / or the second surface of the adhesive film, which is brought into contact with the second substrate B, is treated with the primer composition according to the invention before contact.

[0084] It was found in particular that the problem of the invention is solved especially well in the bonding of substrates with inorganic surfaces whose contact surfaces are primed. Priming of the contact surface means priming the corresponding substrate surface, the corresponding adhesive film surface, or both surfaces.

[0085] When two substrates are bonded together, it is advantageous to prime at least the contact surface formed by the inorganic surface and the adhesive film. If the surfaces of both substrates are inorganic, it is advantageous according to the invention to prime at least one of the contact surfaces – substrate surface, adhesive film surface, or substrate and adhesive film surface – preferably both contact surfaces are primed.

[0086] "Bringing into contact" refers to bringing the aforementioned elements into contact with each other, for example:

[0087] "at least the surface of the first substrate A, which is brought into contact with the adhesive film, is treated with the primer composition according to the invention before being brought into contact" to be read as

[0088] "at least the surface of the first substrate A, which is brought into contact with the adhesive film, is treated with the primer composition according to the invention before the surface of the first substrate A is brought into contact with the adhesive film".

[0089] The term “treated with the primer composition according to the invention” is understood in particular to mean that the primer is applied to the respective surface.

[0090] The primer is applied manually (e.g., by brushing or spraying) or mechanically (e.g., by coating or printing). If the primer contains solvents and / or water, it is subsequently dried. The primer layer preferably has a thickness of 0.05 µm to 50 µm after drying, particularly 0.05 µm to 10 µm, and most preferably 0.5 to 5 µm, and more particularly 0.7 to 1.8 µm.

[0091] Preferably, the primer is applied using a printer, a dispensing nozzle, a squeegee, a brush or a suitable stick.

[0092] According to advantageous embodiments, the primer is applied using a guided dispensing nozzle, e.g., the “EV series automated dispensing systems” from Nordson EFD.

[0093] According to further advantageous embodiments, the primer is applied using a printer.

[0094] Preferably, the primer is applied to the substrate and / or the adhesive film in a closed surface (full area).

[0095] The thickness of the primer layer is determined using laser optics (CLSM (Convocal Laser Microscope, Keyence).

[0096] The thickness of the adhesive tape is determined using a thickness gauge in a manner known to those skilled in the art.

[0097] The adhesive film of all objects and embodiments of the invention can in principle be any type of adhesive film in which a primer has the effect described above.

[0098] This can be a reactive, a latently reactive, or an immediately adhesive film.

[0099] A "reactive adhesive film" is understood to be an adhesive film that achieves its adhesive effect by having the chemical reaction intensified after appropriate activation due to Arrhenius kinetics.

[0100] For example, it could be a heat-activated reactive adhesive film, in which a targeted application of heat accelerates a chemical reaction that occurs very slowly at room temperature.

[0101] Through the chemical reaction, the adhesive mass chemically bonds, resulting in a higher internal strength of the adhesive joint. In contrast, a "latent reactive" adhesive film is a reactive adhesive film in which the chemical reaction is only enabled by activation, for example, by heat. Latent reactive systems are therefore stable at room temperature, as the corresponding chemical reaction does not occur, or is largely absent, at low temperatures.

[0102] According to particularly advantageous embodiments of the invention, the adhesive film is a latent reactive adhesive film or a self-adhesive film.

[0103] According to particularly advantageous embodiments of the invention, the adhesive film is a latent reactive adhesive film.

[0104] Particularly preferably, the latent reactive adhesive film comprises at least one latent reactive adhesive film layer comprising a thermoplastic component having a melting temperature T(melt) of 35 °C < T(melt) < 120 °C, preferably < 90 °C, and containing functional groups that can react with isocyanate, and an isocyanate-containing component that is dispersed particulately into the thermoplastic component and is blocked, microencapsulated, or substantially deactivated in the region of the particle surface, wherein the particles have a start-up temperature T(start-up) of 40 °C < T(start-up) < 125 °C and wherein T(start-up) > T(melt).

[0105] The thermoplastic component is preferably at least a thermoplastic polyurethane, in particular a thermoplastic polyester polyurethane.

[0106] The thermoplastic polyurethane is preferably a semi-crystalline thermoplastic polyurethane.

[0107] For the purposes of this description, T(melt) is the melting temperature of the thermoplastic component and T(start) is the temperature at which the isocyanate groups of the particles dispersed in the thermoplastic component are enabled to react with the functional groups of the thermoplastic polyurethane (e.g., because they disperse in the matrix with the thermoplastic polyurethane). In the case of blocked isocyanate groups, T(start) is associated with the unblocking temperature; in the case of microencapsulation, with the release of isocyanate from the microcapsules (e.g., by melting the microcapsule shell); and in the case of isocyanates deactivated in the region of the surface of the isocyanate particles, with the melting of the isocyanate particles. For the purposes of this invention, all blocked, microencapsulated, orIn the area of ​​the particle surface, deactivated isocyanate-containing systems are conceivable that meet the specifications for T(Anspring). The thermoplastic polyurethanes and the isocyanate-containing component are preferably dispersible in or already dispersed in aqueous media.

[0108] Latent reactive adhesive films, also according to e.g. DE 10 2021 200 580 A1, which are produced from solution, can be used advantageously in the sense of this invention.

[0109] Melting temperatures are determined using differential scanning calorimetry (DDK, DSC) according to DIN EN ISO 11357-3 : 2018-7.

[0110] The onset temperature (T(Anspring)) is also determined using differential scanning calorimetry (DDK, DSC). The exothermic signal in the thermogram of the first heating curve at a heating rate of 10 K / min, corresponding to the reaction of the isocyanate groups, is evaluated. The onset temperature of this signal is used as T(Anspring).

[0111] The heating of the latent-reactive adhesive film to a temperature that is at least equal to or higher than the activation temperature T(activation) is preferably carried out with respect to a pre-composite created from substrate A and the adhesive film, or from a pre-composite created from substrate A, the adhesive film, and substrate B. For this purpose, the corresponding substrate and adhesive film surfaces are brought into contact as described above. Optionally, the contact surface of substrate A with the adhesive film surface and / or the contact surfaces of substrate B with the adhesive film surface can also be pre-fixed, for example by heat lamination (in the case of heat lamination on both sides, carried out simultaneously or sequentially), heat input into one or both contact surfaces (in the latter case, simultaneously or not simultaneously), or the like.Any heat applied for pre-fixation should be so far below the activation temperature of the latent adhesive film that the final bonding – caused by the reaction of the isocyanate with the functional groups of the thermoplastic component – ​​does not yet begin (is initiated).

[0112] In particular and preferably, at least the surface of the first substrate A, which is brought into contact with a first surface of the latent reactive adhesive film, is formed entirely or partially, in particular at least predominantly, from an inorganic material.

[0113] The surface of the second substrate to be bonded is also preferably entirely or partially – and in particular predominantly – inorganic. In this case, it is especially preferred if both contact surfaces are primed.

[0114] The latent reactive adhesive films contain a thermoplastic component with a melting point, T(melt), and functional groups capable of reacting with isocyanate, as well as an isocyanate-containing component that is dispersed in the thermoplastic component in particulate form, particularly as fine particles, and is blocked, microencapsulated, or substantially deactivated in the particle surface area. "Fine particles" here means with a particle size distribution dso < 50 pm, preferably < 15 pm.

[0115] Latent reactive adhesive films are preferably based on so-called 1K latent reactive polyurethane, obtained from aqueous polyurethane dispersion, preferably Dispercoll® U® from Covestro AG; the isocyanate-containing component is one that is essentially deactivated in the area of ​​the particle surface.

[0116] The particles have an activation temperature, T(activation), for which T(melting) < T(activation). T(melting) is between 35 °C and 120 °C, preferably between 35 °C and 90 °C, and particularly preferably between 40 °C and 60 °C. T(activation) is between 40 °C and 125 °C, preferably at most 100 °C, and most preferably at most 90 °C. A lower limit of 50 °C is preferred, and 60 °C is particularly preferred. The latent reactive adhesive films are not tacky at room temperature, thus ensuring good (re)positionability before thermal initiation and the development of the bond strength.

[0117] Particularly preferred is a melting temperature (T(melt)) < starting temperature (T(start)), as this reliably prevents unwanted initiation of the crosslinking reaction during the production of the web-like latent-reactive adhesive film. Preferably, the thermoplastic component is a compound functionalized with OH and / or NH₂ groups. Most preferably, the thermoplastic component is at least one semicrystalline polyester polyurethane.

[0118] The latent reactive adhesive film preferably contains an anionic, high-molecular-weight polyurethane dispersion as a thermoplastic component, which has a melting temperature (in dried form) T(melt) of 35°C < T(melt) < 120°C, preferably < 90°C, in particular 40°C < T(melt) < 60°C, and contains functional groups that can react with isocyanate, for example in the form of commercially available products from the Dispercoll® U family mentioned above; such as Dispercoll® U53, Dispercoll® U54, Dispercoll® U56, Dispercoll® U 8755, Dispercoll® U XP 2815, Dispercoll® VP KA 8758, Dispercoll® U XP 2682, Dispercoll® U 2824 XP, Dispercoll® U XP 2701, Dispercoll® U XP 2702, Dispercoll® U XP 2710 and / or Dispercoll® BL XP 2578 (Dispercoll® is a registered trademark of Covestro AG).

[0119] The latent reactive adhesive film preferably contains toluene diisocyanate compounds (TDI compounds), such as Dispercoll® BL XP 2514 (TDI dimer) and / or Aqualink U (dispersion of blocked TDI dimer) and / or isophorone diisocyanates (IPDI), such as Aqualink D (dispersion of blocked IPDI trimer), as an isocyanate-containing component. This component is present in particulate form, particularly as fine particles, dispersed within the thermoplastic component and is blocked, microencapsulated, or substantially deactivated at the particle surface. The diisocyanates are used, for example, in the form of aqueous suspensions of the respective latent reactive solid isocyanate. Aqualink is offered by Aquaspersions. The aforementioned diisocyanate products can be used as a crosslinking component, particularly in combination with anionic, high-molecular-weight polyurethane dispersions as the thermoplastic component (such as the Dispercoll® U products mentioned above).Other isocyanates, including monomeric and oligomeric compounds as well as polyisocyanates, can be used.

[0120] The latent reactive adhesive film may also contain other formulation components. These include thickeners, wetting agents, defoamers, fillers (e.g., thermally conductive ones), pigments (including agents for coloring, whiteness adjustment, and / or blackening), catalysts, stabilizers, antioxidants, light stabilizers, and other polymers for adjusting specific adhesive properties. Specific adhesive properties can be adjusted, for example, by adding aqueous dispersions of amorphous polymers (e.g., polyether urethanes or polyacrylates) and / or by adding aqueous resin dispersions (especially those based on rosin esters) or liquid resins.

[0121] According to further particularly advantageous embodiments of the invention, the adhesive film is a self-adhesive film.

[0122] The adhesive film comprises at least one outer surface, which is the surface of an adhesive compound.

[0123] In this context, an adhesive compound is understood, as is generally understood, to be a substance that is permanently sticky and adhesive, particularly at room temperature. A characteristic of an adhesive compound is that it can be applied to a substrate by applying pressure and adheres there, although the required pressure and its duration are not precisely defined. In some cases, depending on the specific type of adhesive compound, the temperature, humidity, and the substrate, the application of minimal, short-term pressure, not exceeding a light touch for a brief moment, is sufficient to achieve the desired adhesion effect; in other cases, a longer duration of high pressure may be necessary.

[0124] Pressure-sensitive adhesives possess special, characteristic viscoelastic properties that result in their permanent tackiness and bonding strength. A defining characteristic is that when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The relative proportions of these two processes depend on the precise composition, structure, and degree of cross-linking of the pressure-sensitive adhesive, as well as the rate and duration of deformation and the temperature.

[0125] The proportion of viscous flow is necessary to achieve adhesion. Only the viscous components, caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high tack (also known as surface tack) and thus often also to high adhesive strength. Highly cross-linked systems, crystalline or glassy polymers, are generally not tacky or at least only slightly tacky due to a lack of flowable components.

[0126] The elastic restoring forces are necessary to achieve cohesion. They are generated, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transmission of forces acting on an adhesive bond. This allows an adhesive bond to withstand a sustained load, such as continuous shear stress, to a sufficient degree over an extended period.

[0127] To more precisely describe and quantify the degree of elastic and viscous components, as well as their ratio, the storage modulus (G') and loss modulus (G"), which can be determined using Dynamic Mechanical Analysis (DMA, according to DIN EN ISO 6721:2019-09), can be used. G' is a measure of the elastic component, and G'' is a measure of the viscous component of a material. Both quantities depend on the deformation frequency and the temperature.

[0128] The properties can be determined using a rheometer. The material under investigation is subjected, for example, to a sinusoidally oscillating shear stress in a plate-plate arrangement. In shear-stress controlled devices, the deformation is measured as a function of time, along with the time lag of this deformation relative to the application of the shear stress. This time lag is called the phase angle θ.

[0129] The memory module G' is defined as follows:

[0130] G' = (T / Y) • cos(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector).

[0131] The definition of the loss modulus G" is:

[0132] G" = (T / Y) *sin(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector).

[0133] A material is generally considered to be adhesive and is defined as adhesive within the meaning of the invention if, at room temperature, here by definition at 23°C, in the deformation frequency range of 10° to 10 1 rad / sec G' at least partly in the range of 10 3 up to 10 7Pa lies within this range, and if G" also lies at least partially within this range. "Partially" means that at least a section of the G' curve lies within the window defined by the deformation frequency range from 10° inclusive to 10° inclusive. 1 rad / sec (abscissa) and the range of G' values ​​including 10 3 up to and including 10 7 Pa (ordinate) is spanned. The same applies to G".

[0134] Preferably, the adhesive compound exhibits in the deformation frequency range of 10° to 10 1 rad / sec at 23 °C a storage module G' and a loss module G" in the range of 10 3 up to 10 7 Pa, determined according to DIN EN ISO 6721 : 2019-09.

[0135] To achieve viscoelastic properties, the monomers on which the polymers underlying the pressure-sensitive adhesive are based, as well as any other components of the adhesive, are selected such that the adhesive has a glass transition temperature (according to DIN EN ISO 11357-2: 2020-08) below the application temperature (i.e., typically below room temperature (23 °C)). By using suitable cohesion-enhancing measures, such as crosslinking reactions (formation of bridge-forming links between the macromolecules), the temperature range in which a polymer exhibits pressure-sensitive properties can be increased and / or shifted. The application range of the pressure-sensitive adhesive can thus be optimized by adjusting the balance between flowability and cohesion.

[0136] In particular, the adhesive compound has a glass transition temperature of < 23 °C, determined according to DIN EN ISO 1 1357-2 : 2020-08.

[0137] Unlike pressure-sensitive adhesives, hot melt adhesives, e.g. based on polyamides, polyurethanes or modified polyethylenes, typically do not exhibit tackiness at room temperature (23 °C), although this may also be the case in hot melt adhesive compositions.

[0138] Particularly preferably, the adhesive film has at least one outer adhesive layer containing at least one poly(meth)acrylate or at least one nitrile rubber. According to preferred embodiments of the invention, the adhesive film has at least one outer adhesive layer containing at least one poly(meth)acrylate.

[0139] According to preferred embodiments of the invention, the adhesive film has at least one outer adhesive layer which contains at least one poly(meth)acrylate and, as matrix-forming polymers, one or more poly(meth)acrylates to 90 to 100 wt.%, in particular to 100 wt.%.

[0140] According to preferred embodiments of the invention, the adhesive film has at least one outer adhesive layer comprising at least a first phase i.) comprising at least one poly(meth)acrylate and at least a second phase ii.) comprising at least one vinyl aromatic block copolymer.

[0141] The vinyl aromatic block copolymer(s) is in particular and preferably a polyvinyl aromatic polydiene block copolymer, for example a styrene-butadiene-styrene block copolymer (SBS) or a styrene-isoprene-styrene block copolymer (SIS), in particular a styrene-isoprene-styrene block copolymer (SIS).

[0142] According to preferred embodiments of the invention, the adhesive film has at least one outer adhesive layer containing at least one nitrile rubber.

[0143] According to preferred embodiments of the invention, the adhesive film has at least one outer adhesive layer containing at least two different nitrile rubbers.

[0144] Preferably, the outer adhesive layer contains at least a first nitrile rubber N1 with an acrylonitrile content of at least 14 wt.% and at most 22 wt.% and at least a second nitrile rubber N2 with an acrylonitrile content of at least 25 wt.% and at most 32 wt.%.

[0145] Furthermore, the outer adhesive layer preferably contains, based on the total weight of the adhesive layer, 40.0 wt.% to 62.0 wt.%, preferably 40.0 wt.% to 55.0 wt.%, at least one adhesive resin, in particular and preferably in combination with at least one nitrile rubber, preferably the aforementioned at least two nitrile rubbers N1 and N2.

[0146] The at least one adhesive resin is preferably selected from the group consisting of adhesive resins with aromatic structural elements, in particular based on C9 monomer streams, and polymers of pure C8 or C9 aromatics, aliphatically modified aromatic hydrocarbon resins, so-called C9 / C5 resins.

[0147] Furthermore, the outer adhesive layer preferably contains at least one filler, preferably polyurethane-based fillers, such as in particular so-called polyurethane beads, preferably in combination with at least one nitrile rubber, preferably the aforementioned at least two nitrile rubbers N1 and N2.

[0148] According to preferred embodiments, the described

[0149] Foamed adhesive layers, preferably using expanded microspheres.

[0150] According to preferred embodiments, the described

[0151] Adhesive layers colored by means of a pigment or dye, for example colored black.

[0152] Another object of the present invention is a bonded composite obtainable by a method according to the invention.

[0153] The invention therefore also relates to a composite of at least one substrate A and an adhesive film, in particular of two substrates A and B and an adhesive film, as is obtainable by the inventive method and in particular according to the embodiments given within the scope of the present invention relating to the method or to the composite itself.

[0154] Preferably, the bonded adhesive film has a layer thickness of 2 pm to 2000 pm.

[0155] Preferably, the layer thickness in the case of a latent reactive adhesive film is between at least 10 pm and at most 500 pm, particularly preferably between at least 20 pm and at most 250 pm.

[0156] Preferably, the layer thickness in the case of a self-adhesive film is between at least 10 pm and at most 500 pm, particularly preferably between at least 20 pm and at most 250 pm.

[0157] The terms “adhesive film” and “adhesive tape” are used synonymously within the scope of the present invention.

[0158] For the purposes of this invention, the general term "adhesive tape" includes all planar structures whose dimensions in two spatial directions (x-direction and y-direction; length and width) are significantly greater than in the third spatial direction (z-direction; thickness), such as films or film sections, tapes with extended length and limited width, tape sections, die-cut pieces, labels and the like.

[0159] The adhesive tape can be supplied in fixed lengths, such as by the meter, or as continuous material on rolls (Archimedean spiral), i.e., disc-shaped adhesive tape rolls, which are referred to in technical terms as "pancakes".

[0160] Alternatively, the adhesive tape can be wound onto a core, similar to a textile yarn, whose length is significantly greater than the width of the tape. By superimposing a rotational movement of the core and an axial movement of the core or the tape guide element, the tape initially forms a first, radially innermost layer of helical turns. At the end of the first layer and the transition to the second layer, the orientation of the axial movement is inverted while the rotational movement remains unchanged. At the end of the second layer and the transition to the third layer, the orientation of the axial movement is inverted again, thus reverting to the original orientation, while the rotational movement remains unchanged. The pitch angle remains constant between each of these orientation reversal points. In this way, numerous layers of turns can be formed, with each turn intersecting the others (cross-wound coils).

[0161] According to preferred embodiments, an “adhesive tape” comprises a carrier material which is provided on one or both sides with an (adhesive) compound and may optionally have further, intermediate layers.

[0162] In particular, the term "adhesive tape" as used in the present invention also includes so-called "transfer adhesive tapes," that is, adhesive tape without a backing. In a transfer adhesive tape, the adhesive is applied between flexible liners prior to application. These liners are provided with a release layer and / or have anti-adhesive properties. For application, one liner is typically removed first, the adhesive is applied, and then the second liner is removed. The adhesive can thus be used directly to bond two surfaces. Such backingless transfer adhesive tapes are particularly preferred according to the invention. With such a backingless transfer adhesive tape, especially one with a high-pressure adhesive, very precise bonding in terms of positioning and application is possible.The adhesive tape can be produced either in the form of a roll, i.e., wound around itself in the form of an Archimedean spiral, or with the adhesive side covered with separating materials such as siliconized paper or siliconized film.

[0163] A non-linting material such as a plastic film or a well-glued, long-fiber paper is preferably suitable as a separating material.

[0164] Substrate A

[0165] For window and display applications in electronic and mobile devices, glass is increasingly used as substrate A. This can be made from materials such as mineral glass, quartz glass, or sapphire glass. Various modifications allow for the targeted manipulation of the optical and physical properties of the glass. For decorative purposes, for example, smoked or tinted glass is used. Surface coatings or lacquers, which can be applied by spraying or vapor deposition, also allow for targeted control of the optical appearance. Anti-reflective coatings, scratch-resistant coatings, and other functional surface coatings are also common. In its simplest form, glass exists as flat glass, but it can also be cast into three-dimensional windows or components.

[0166] Other materials to be bonded to substrate A can be metallic or have a metallic surface. Such metallic components can generally be made from all common metals and metal alloys. Preferred metals include aluminum, stainless steel, steel, magnesium, zinc, nickel, brass, copper, titanium, ferrous metals, and austenitic alloys. Additives and alloys of all kinds are also common. Furthermore, the components can be multi-layered and made of different metals. Surface modifications are frequently applied to the metal components for aesthetic reasons and to improve surface properties and quality. For example, brushed aluminum and stainless steel components are commonly used. In addition to chromating, coatings with, for example, gold or silver are used for passivation.The metal parts can take on a wide variety of shapes and sizes and can be flat or three-dimensional. Furthermore, their functions can vary greatly, ranging from decorative elements to stiffening beams, frame components, covers, etc. Anodizing is common for aluminum and magnesium, often combined with coloring processes. The resulting surface to be bonded then has a ceramic-like appearance.

[0167] Materials for substrate A can also be non-inorganic, i.e., organic materials such as plastics, which are inorganically (hydrophilically) modified on the surface bonded or to be bonded with the latent reactive adhesive film. If the substrate A material is a plastic, then the plastic parts for consumer electronics components or other mobile devices are preferably based on plastics that can be processed by injection molding. This group includes, for example, ABS, PC, ABS / PC blends, PMMA, polyamides, glass fiber reinforced polyamides, polyvinyl chloride, polyvinyl fluoride, cellulose acetate, cycloolefin copolymers, liquid crystal polymers (LCP), polylactide, polyetherketones, polyetherimide, polyethersulfone, polymethacrylmethylimide, polymethylpentene, polyphenyl ether, polyphenylene sulfide, polyphthalamide, polyurethanes, polyvinyl acetate, styrene acrylonitrile copolymers, polyacrylates, etc.Polymethacrylates, polyoxymethylene, acrylates, styrene-acrylonitrile copolymers, polyethylene, polystyrene, polypropylene, or polyesters (e.g., PBT, PET). This list is not exhaustive. Preferably, the plastics used are polycarbonate, polyamide, PMMA, or ABS. In these cases, the surface modification consists of a coating with an inorganic (hydrophilic) material such as metal or ceramic (especially oxides or layers produced by sol / gel processes). Surface coatings applied by physical vapor deposition (PVD) or chemical vapor deposition (CVD) are common examples of such surface modifications.

[0168] Substrate B

[0169] The same definitions apply to substrate B as those given for substrate A. However, the surface of substrate B to be bonded with the latent reactive adhesive film can also have a non-inorganic (hydrophilic) character, i.e., be of an organic nature, such as being made of plastic. If the material of substrate B is plastic, then the plastic parts for consumer electronics components or other mobile devices are preferably based on plastics that can be processed by injection molding. This group includes, for example, ABS, PC, ABS / PC blends, PMMA, polyamides, glass fiber reinforced polyamides, polyvinyl chloride, polyvinyl fluoride, cellulose acetate, cycloolefin copolymers, liquid crystal polymers (LCP), polylactide, polyetherketones, polyetherimide, polyethersulfone, polymethacrylmethylimide, polymethylpentene, polyphenyl ether, polyphenylene sulfide, polyphthalamide, polyurethanes, polyvinyl acetate, styrene acrylonitrile copolymers, polyacrylates, etc.Polymethacrylate, polyoxymethylene, acrylates, styrene-acrylonitrile copolymers, polyethylene, polystyrene, polypropylene, or polyester (e.g., PBT, PET). This list is not exhaustive. The components can take on any shape required for the manufacture of a component or housing for consumer electronics. In their simplest form, they are planar. However, three-dimensional components are also quite common. The components can perform a wide variety of functions, such as housings, viewing windows, or stiffening elements. Polycarbonate, polyamide, PMMA, or ABS are very commonly used plastics.

[0170] Components for substrate B, especially plastic parts, can be painted or otherwise coated. Paints used for surface functionalization / modification of plastics include, for example, anti-reflective coatings, anti-fingerprint coatings, anti-scratch coatings, or decorative printing (so-called backprints). Furthermore, the components, especially the plastic components, can also be equipped with (inorganic) layers such as conductive layers. Indium tin oxide is a particularly noteworthy conductive layer. These paints and layers are sometimes thermally sensitive and therefore necessitate the use of adhesives that can be processed at low temperatures.

[0171] The components, whether made of glass, metal, ceramic, or plastic with an inorganic (hydrophilic) surface, can take on any shape required for manufacturing a component or housing for consumer electronics. In their simplest form, they are planar. However, three-dimensional components are also quite common. The components can fulfill a wide variety of functions, such as housings, viewing windows, or stiffening elements.

[0172] Another object of the present invention is the use of the bonded composite or the layered body according to the invention in the automotive industry, in particular in an automobile.

[0173] Another aspect of the present invention is the use of the bonded composite or the layered body according to the invention in the electronics industry, particularly in an electronic device. The invention will be explained in more detail below by means of examples, without thereby limiting its scope.

[0174] Experiments

[0175] Preparation of a latent reactive adhesive film: A latent reactive adhesive film was prepared from 100 parts Dispercoll® U XP 2702, 13 parts Dispercoll® BL XP 2514, and 1.5 parts Borchigel 0625 (see above). The formulation components were mixed as an aqueous dispersion in a beaker with an anchor stirrer at 60 rpm for 15 minutes at room temperature. The solids content was adjusted to 46% by weight by adding demineralized water.

[0176] A coating was applied to both sides of polyethylene-coated and siliconized paper using a squeegee on a laboratory coating table. The resulting rag samples were first aired at room temperature for 30 minutes and then dried in a circulating air drying oven at 45 °C for 20 minutes.

[0177] The samples had a layer thickness of 100 pm.

[0178] Sections of these samples were used as latent reactive adhesive films to create composites for further measurements. Until measurement, the samples were stored at 23 °C and 50% relative humidity.

[0179] HK1: Furthermore, a black, double-sided acrylic transfer adhesive tape foamed with microspheres, with a layer thickness of 200 pm, was provided between two protective liners.

[0180] HK2: Furthermore, a black, double-sided nitrile rubber transfer adhesive tape foamed with microspheres (24 wt.% Nipol® DN401 L, 24 wt.% Perbunan® 2846 as N1 or N2, 47 wt.% aromatic hydrocarbon resin, 4.5 wt.% polyurethane beads; 0.5 wt.% microspheres) with a layer thickness of 200 pm was provided between two protective liners.

[0181] The composition of the primer was varied.

[0182] Examples in accordance with the invention are marked with “E” and comparative examples with “V”.

[0183] E1: The primer consisted of 4 g of thermoplastic polyurethane (Laricol 1460, Coim), 1 g of (3-triethoxysilylpropyl) succinic anhydride (CAS No. 93642-68-3, Geniosil® GF20, Wacker) and 95 g of an anhydrous mixture of 80 wt.% ethyl acetate and 20 wt.% methyl ethyl ketone (MEK);

[0184] V1: No primer was used; V2: The primer consisted of 5 g (3-triethoxysilylpropyl) succinic anhydride and 95 g of an anhydrous mixture of 80 wt% ethyl acetate and 20 wt% methyl ethyl ketone (MEK);

[0185] V3: The primer consisted of 5 g of thermoplastic polyurethane (Laricol 1460, Coim) and 95 g of an anhydrous mixture of 80 wt% ethyl acetate and 20 wt% methyl ethyl ketone (MEK).

[0186] Test specimens were produced from the various adhesive films and primer solutions to determine the respective properties to be investigated.

[0187] Bond strengths

[0188] Test (A) Push-out:

[0189] The push-out test allows statements to be made about the bond strength of a double-sided adhesive product in the direction of the adhesive layer normal.

[0190] For this purpose, a square substrate S1 with external dimensions of 33 mm x 33 mm is provided.

[0191] On one of the surfaces, the respective primer solution (or no primer, V1) is applied along the edges with a width of 5 mm, so that a 5 mm wide frame with primer is created along the outer edges of the square substrate.

[0192] In addition, a frame-shaped, square die-cut of the adhesive film to be examined is provided – produced by die-cutting from the sheet adhesive film using a die-cutting tool: outer dimensions 30 mm x 30 mm; web width 3.0 mm; inner dimensions (window cutout) 27 mm x 27 mm. The total area of ​​the frame-shaped adhesive film to be examined is 170 mm². 2 .

[0193] In addition, a square, frame-shaped substrate S2 is provided: external dimensions 40 mm x 40 mm; internal dimensions (window cutout) 20 mm x 20 mm.

[0194] On one of the surfaces, the respective primer solution (or no primer, V1) is applied along the inner edges of the frame to a width of 5 mm, creating a 5 mm wide frame with primer along the inner edges of the square, frame-shaped substrate.

[0195] The adhesive film is bonded between substrates S1 and S2 in such a way that the inner cutouts of the frame-shaped adhesive film and substrate S2 are centered on top of each other. As a result, the applied primer on the two substrates protrudes in different directions relative to the adhesive film, so that no primed surfaces without adhesive film touch each other in the bonded assembly.

[0196] In the case of examples E1, V1, V2, V3, a laboratory hot press was used to press at a punch temperature of 90 °C and 5 bar for 120 s, thus creating a corresponding heat-activated composite.

[0197] The format of the frame (substrate S2) exceeds the format of substrate S1, so that the composite can be placed on a support table using the protruding areas of the frame (substrate S2).

[0198] Using a punch clamped in a tensile testing machine, the punch is moved continuously forward through the opening in substrate S2, pressing perpendicularly onto substrate S1 and thus exerting a force on the adhesive joint. The punch speed is 10 mm / s. The force at which substrate S1 detaches from the frame (substrate S2) is recorded. This force is related to the punch area, allowing push-out strengths to be expressed in units of N / mm². 2 result.

[0199] The composite passes the measurement if the push-out strength is above 3 N / mm². 2 The test climate is 23 °C and 50% relative humidity.

[0200] Test (B) Push-out after contact with defined chemicals

[0201] To determine the chemical resistance of the bond, push-out test specimens, constructed as described above, were placed for 72 h in a 65 °C warm bath of a) isopropanol / water (70 / 30, i.e. 70% volume fractions to 30% volume fractions) or b) oleic acid or c) sunscreen.

[0202] After removal, the test specimens were reconditioned at 23 °C and 50% RH for two hours. The bond strength was then measured as described under Push-Out - Initial.

[0203] Test (C) Push-out after humid heat storage:

[0204] The push-out test (C) is performed according to the specifications of test A. However, the assembly to be measured is stored in a climate chamber at 60 °C and 90% relative humidity for 72 hours prior to measurement, using a first variant of the test method. After storage and before measurement, the assemblies are reconditioned for one day at 23 °C and 50% relative humidity. The substrates S1 and S2 in all push-out tests were steel (SUS).

[0205] Adhesive strength

[0206] The determination of the adhesive strength (according to AFERA ​​5001) is carried out as follows.

[0207] A polished steel plate with a thickness of 2 mm or a polybutylene terephthalate (PBT) plate with a thickness of 3 mm is used as a defined bonding surface.

[0208] The primer solution is applied to each surface, and then the adhesive film is applied to it.

[0209] Unless otherwise specified, the adhesive film is cut to a width of 20 mm and a length of approximately 25 cm, one of the liners of the respective adhesive film is removed, and the free area is brought into contact with the surface of the substrate.

[0210] Instead of the upper line, a 50 pm thick etched PET film is used as a reinforcing film.

[0211] Immediately afterwards, a steel roller weighing 4 kg is used to apply pressure five times at a feed rate of 10 m / min, and a winding time of 72 hours is allowed.

[0212] The adhesive film is then peeled off the substrate at a 180° angle using a tensile testing device (Zwick company) at a speed of v = 300 mm / min, and the force required for this is measured at room temperature. The measured value (in N / cm) is calculated as the average of three individual measurements.

[0213] Applying the primer: The respective primer solution was applied evenly to the respective surface of the substrate using a printer.

[0214] The treated substrates were then stored in a circulating air drying oven at 25 °C for 10 minutes to dry the surface and allow the primer to take effect. The primer thickness was 1 µm after drying.

[0215] The bond strengths of the latent reactive adhesive tapes were tested as described using the different primer solutions (E1 , V2, V3) or using no primer (V1 ).

[0216] The results are summarized in Table 1. The adhesive strength of the provided adhesive tapes HK1 and HK2 was tested on steel or PBT as described, using primer solution E1 or without primer V1.

[0217] The results are summarized in Table 2.

[0218] Table 1

[0219] The results in Table 1 show that the bond strengths for the test composites produced according to the invention using primer E1 are at a high level before (Test A) and after contact with the listed chemicals (Test B), namely > 3 N / mm² as required. 2 and in some cases even > 5 N / mm 2 even after contact with the chemicals.

[0220] After storage under humid-warm conditions (Test C), only the inventive example with primer E1 exhibits a high value of more than 10 N / mm². 2 Only in test E1, compared to test A, is there no significant loss of bond strength after storage under humid-warm conditions.

[0221] Since very low bond strengths were observed when using primer V3 (TPU only, without silane) even after storage under warm, humid conditions, tests B were not performed with this primer. The results in Table 2 show that the adhesive strengths for the test composites produced according to the invention are significantly higher when using primer E1 compared to example V1 without primer, with an increase of at least 100% being observed with primer E1 compared to V1.

[0222] Table 2

Claims

Patent claims 1. Primer composition for the production of an adhesive bond, containing at least the following components: (a) at least one thermoplastic polyurethane; and (b) at least one organosilane, characterized in that the organosilane (b) is selected from the group consisting of trialkoxysilylalkyl succinic anhydrides, trialkoxyphenylsilanes, (3-mercaptopropyl)trialkoxysilanes, (3-aminopropyl)alkoxysilanes, 3-(2-aminoethylamino)propyl trialkoxysilanes, vinyl trialkoxysilanes, and (3-glycidyloxypropyl)trialkoxysilanes.

2. Primer composition according to claim 1, characterized in that the organosilane (b) is selected from the group consisting of trialkoxysilylalkyl succinic anhydrides, trialkoxyphenylsilanes, (3-mercaptopropyl)trialkoxysilanes, vinyltrialkoxysilanes, and (3-glycidyloxypropyl)trialkoxysilanes.

3. Primer composition according to claim 1 or claim 2, characterized in that the primer composition contains at least one solvent.

4. Primer composition according to one of the preceding claims, characterized in that the alkyl part of the trialkoxysilylalkyl succinic anhydride is a linear alkylene group with 1 to 10 carbon atoms, preferably 3 to 8 carbon atoms, wherein a propylene group is particularly preferred and / or the alkoxyl groups of the trialkoxysilylalkyl succinic anhydride are selected from methoxy and ethoxy groups.

5. Primer composition according to one of the preceding claims, characterized in that the organosilane (b) is (3-triethoxysilylpropyl)succinic anhydride.

6. Primer composition according to one of the preceding claims, characterized in that the thermoplastic polyurethane (a) has no free isocyanate groups.

7. Primer composition according to one of the preceding claims, characterized in that the thermoplastic polyurethane (a) has a storage modulus G' of more than 1 MPa.

8. Primer composition according to one of the preceding claims, characterized in that the ratio of the total amount of thermoplastic polyurethane (a) to the total amount of organosilanes (b), in particular (3-triethoxysilylpropyl) succinic anhydride, is from 3:1 to 5:1, particularly preferably 3.5:1 to 4.5:1, most preferably 3.75:1 to 4.25:1, in particular 4:

1.

9. Method for producing an adhesive bond between a first substrate A and a second substrate B by means of an adhesive film, wherein a surface of the first substrate A is brought into contact with a first surface of the adhesive film, and wherein a surface of the second substrate B is brought into contact with the second surface of the adhesive film, wherein at least the surface of the first substrate A that is brought into contact with the adhesive film is treated with the primer composition according to one of claims 1 to 8 before being brought into contact, and / or at least the first surface of the adhesive film that is brought into contact with the first substrate A is treated with the primer composition according to one of claims 1 to 8 before being brought into contact.

10. Method according to claim 9, characterized in that the surface of the second substrate B, which is brought into contact with the adhesive film, is also treated with the primer composition according to one of claims 1 to 8 before being brought into contact and / or the second surface of the adhesive film, which is brought into contact with the second substrate B, is treated with the primer composition according to one of claims 1 to 8 before being brought into contact. 1 1. Method according to one of claims 9 or 1 o, characterized in that the adhesive film is a latent reactive adhesive film or a self-adhesive film.

12. Method according to claim 1 1 , wherein characterized in that the latent reactive adhesive film comprises at least one latent reactive adhesive film layer comprising a thermoplastic component having a melting temperature T(melt) of 35 °C < T(melt) < 120 °C, preferably < 90 °C, and containing functional groups that can react with isocyanate, and an isocyanate-containing component that is dispersed particulately into the thermoplastic component and is blocked, microencapsulated, or substantially deactivated in the region of the particle surface, wherein the particles have a start-up temperature T(start-up) of 40 °C < T(start-up) < 125 °C and wherein T(start-up) > T(melt).

13. Method according to claim 12, characterized in that the adhesive film has at least one outer adhesive layer containing at least one poly(meth)acrylate or at least one nitrile rubber.

14. Bonded composite obtainable by a method according to any one of claims 9 to 13.

15. Use of the bonded composite according to claim 145 in the automotive industry, in particular in an automobile, or in the electronics industry, in particular in an electronic device.

Images