WO2018108387A1 - Method for producing an adhesive bond between an adhesive compound layer and an lse substrate surface - Google Patents

Abstract

The invention relates to a method for producing an adhesive bond between an adhesive compound layer containing: a) 40-70 wt%, in relation to the total weight of the adhesive compound, of at least one poly(meth)acrylate; b) 15-50 wt%, in relation to the total weight of the adhesive compound, of at least one synthetic rubber; and c) at least one tackifier compatible with the poly(meth)acrylate(s), and an LSE substrate surface. In the method, a surface of the adhesive compound layer is plasma-treated, and the plasma-treated surface is adhesively bonded to the LSE substrate surface.

Description

 description

Method for producing an adhesive bond between an adhesive layer and an LSE substrate surface

The invention relates to a method for producing an adhesive bond between a pressure-sensitive adhesive and an LSE substrate surface.

In many areas of technology, adhesive tapes are increasingly being used to join components. Especially in the case of adhesions on surfaces of automobiles, the difficulty resulting from the nonpolar nature of automotive component surfaces arises. The non-polar surfaces are hydrophobic to create a particularly strong dirt and water repellent effect. However, this also has the disadvantage that adhesives usually adhere poorly to them. High bond strengths due to polar substrates, for example on polyethylene or polypropylene surfaces are often not or only very difficult to implement.

Basically, the bonding together of surfaces by means of adhesives has the problem of applying them permanently and firmly to the surface of the substrate. This requires a particularly high adhesion of the PSA to the surface. Adhesion is usually referred to as the physical effect which brings about the cohesion of two phases brought into contact at their interface on the basis of intermolecular interactions occurring there. Adhesion thus determines the adhesion of the adhesive to the substrate surface, which can be determined as tack ("tack") and as bond strength. [Um Um] In order to influence the adhesion of an adhesive selectively, plasticizers and / or tackifying resins ( so-called "tackifiers") added. A simple definition of adhesion may be "the interaction energy per unit area" [in mN / m], which is not measurable due to experimental constraints such as ignorance of the true contact surfaces, and often surface energy (OFE) with "polar" and " This simplified model has been widely used in practice, often measuring the energy and its components by measuring the static contact angles of different test liquids, and assigning polar and non-polar components to the surface tensions of these liquids The test surface is used to determine the polar and non-polar parts of the surface energy of the test surface, which can be done according to the OWKR model, for example.An industrial standard alternative method is the determination by means of test inks according to DIN ISO 8296.

In the context of such discussions, the terms "polar" and "high energy" are often equated, as are the terms "nonpolar" and "low energy". Behind this is the realization that polar dipole forces are comparatively strong compared to so-called "disperse" or "nonpolar" interactions, which are built up without the involvement of permanent molecular dipoles. The basis of this model of interfacial energy and interfacial interactions is the notion that polar components interact only with polar and nonpolar with only non-polar ones.

However, a surface may also have small or medium polar parts of the surface energy without the surface energy being "high." A guideline may be that, as soon as the polar fraction of the OFE is greater than 3 mN / m, the surface is in the sense of this Invention is to be referred to as "polar". This roughly corresponds to the practical lower detection limit.

Basically, there are no hard limits for terms such as high and low energy. For the purpose of the discussion, the limit is set at 38 mN / m and 38 dyn / cm (at room temperature, respectively). This is a value above which, for example, the printability of a surface is usually sufficient. For comparison, one can consider the surface tension (= surface energy) of pure water; this is around 72 mN / m (including temperature-dependent). Especially on low-energy substrates such as PE, PP or EPDM, but also on many paints there are great problems in achieving satisfactory adhesion, both when using PSAs and other adhesives or coatings.

The physical pretreatment of substrates (for example, by flame, corona, plasma) to improve bonding strengths is common especially in liquid reactive adhesives. An object of the physical pretreatment can also be a cleaning of the substrate, for example of oils, or roughening to increase the effective area.

In a physical pretreatment one usually speaks of an "activation" of the surface, which usually implies an unspecific interaction in contrast to, for example, a chemical reaction according to the key-lock principle Activation usually implies an improvement of wettability, printability or anchoring of a coating ,

For self-adhesive tapes, it is common to apply a primer to the substrate. However, this is often an error-prone, time-consuming, manual step.

The success in improving the adhesion of PSAs by physical pretreatment of the substrate (flame, corona, plasma) is not universal, since nonpolar adhesives such as synthetic rubber typically do not benefit.

A corona treatment is defined as a surface treatment with filamentary discharges generated by high alternating voltage between two electrodes, the discrete discharge channels meeting the surface to be treated, see also Wagner et al., Vacuum, 71 (2003), pages 417-436 Further qualification is to be assumed as process gas ambient air.

Almost always, the substrate is placed or passed in the discharge space between an electrode and a counter electrode, which is defined as a "direct" physical treatment, and web-shaped substrates are typically passed between an electrode and a grounded roller. In particular, in industrial applications, the term "corona" is usually understood to mean a "dielectric barrier discharge" (DBD). At least one of the electrodes consists of a dielectric, ie an insulator, or is coated or coated with such a dielectric. The substrate can also act as a dielectric in this case.

The treatment intensity of a corona treatment is given as "dose" in [Wmin / m ² ], with the dose D = P / b ^* v, with P = electrical power [W], b = electrode width [m], and v = web speed [ m / min].

Almost always, the substrate is placed or passed in the discharge space between an electrode and a counterelectrode, which is defined as a "direct" physical treatment, and web-shaped substrates are typically passed between an electrode and a grounded roller, sometimes called the "blown-out corona This is not comparable to an atmospheric pressure plasma because very irregular discharge filaments are "blown out" together with a process gas and no stable, well-defined, efficient treatment is possible.

From FR 2 443 753 a device for surface treatment by means of a corona discharge is known. In this case, the two electrodes are arranged on the same side of the surface to be treated of the object, wherein the first electrodes are formed from a plurality of points, along which a curved arrangement of a second electrode is provided. Between the two electrodes an alternating voltage of a few kV with a frequency of 10 kHz is applied. The corona discharge along the field lines influences the passing surface and leads to a polarization of the surface, whereby the adhesion properties of a pressure-sensitive adhesive on the surface treated by the corona effect are improved.

A disadvantage of the device, however, is that the surface treatment is difficult to control by the corona effect. To allow a more uniform intensive corona treatment of materials of various types, shape and thickness is to completely avoid the corona effect on the surface of the material to be treated by a double-pin electrode is selected according to EP 0497996 B1, with a separate channel for each pin electrode Pressurization is present. Between the two tips of the electrodes, a corona discharge is created, which ionizes the gas stream flowing through the channels and converts it into a plasma. This plasma then passes to the surface to be treated, where it in particular performs a surface oxidation, which improves the wettability of the surface. The type of physical treatment is referred to here as indirect, because the treatment is not performed at the place of production of the electrical discharge. The treatment of the surface takes place at or near atmospheric pressure, but the pressure in the electrical discharge space or gas channel may be increased. By plasma is meant here an atmospheric pressure plasma, which is an electrically activated homogeneous reactive gas which is not in thermal equilibrium, with a pressure close to the ambient pressure in the effective range. In general, the pressure is 0.5 bar more than the ambient pressure. The electrical discharges and ionization processes in the electric field activate the gas and generate highly excited states in the gas constituents. The gas used and the gas mixture are called process gas. In principle, gaseous substances such as siloxane, acrylic acids or solvents or other constituents can also be added to the process gas. Components of the atmospheric pressure plasma can be highly excited atomic states, highly excited molecular states, ions, electrons, unchanged constituents of the process gas. The atmospheric pressure plasma is not generated in a vacuum but usually in an air environment. This means that if the process gas itself is not already air, the outflowing plasma contains at least components of the surrounding air.

In a corona discharge as defined above, filamentary discharge channels with accelerated electrons and ions form due to the applied high voltage. In particular, the light electrons hit the surface at high speed with energies sufficient to break most of the molecular bonds. The reactivity of the resulting reactive gas components is usually a minor effect. The broken bond sites then react with constituents of the air or process gas. A decisive effect is the Formation of short-chain degradation products by electron bombardment. For higher intensity treatments, significant material removal also occurs.

The reaction of a plasma with the surface of the substrate increases the plasma constituents directly "built-in." Alternatively, an excited state or an open binding site and radicals can be generated on the surface, which then continue to react secondarily, for example with atmospheric oxygen from the ambient air Like noble gases, no chemical bonding of the process gas atoms or molecules to the substrate is to be expected, where activation of the substrate takes place exclusively via secondary reactions.

The essential difference is that during the plasma treatment there is no direct action of discrete discharge channels on the surface. The effect is therefore homogeneous and gentle, especially on reactive gas components instead. In an indirect plasma treatment, free electrons may be present, but not accelerated, because the treatment takes place outside the generating electric field.

The plasma treatment is thus less destructive and more homogeneous than a corona treatment, since no discrete discharge channels strike the surface. There are fewer short-chain degradation products of the treated material, which can form a layer with a negative influence on the surface. That's why you can often do better

Wettability after plasma treatment over corona treatment is achieved with longer duration of the effect.

The lower chain degradation and homogeneous treatment by using a

Plasma treatment contribute significantly to the robustness and effectiveness of the learned

Procedure at.

The plasma apparatus of EP 0 497996 B1 has quite high gas flows in the range of 36 m ³ per hour, at 40 cm electrode width per gap. The high flow rates result in a short residence time of the activated components on the surface of the substrate. Furthermore, only those components of the plasma reach the substrate, which are correspondingly durable and can be moved by a gas flow. For example, electrons can not be moved by a stream of gas, so they do not matter. A disadvantage of the above-mentioned plasma treatment, however, is the fact that the plasma impinging on the substrate surface has high temperatures of at least 120 ° C. in the most favorable case. Frequently, however, the resulting plasma has high temperatures of some 100 ° C. The known plasma guns lead to a high thermal input into the substrate surface. The high temperatures can cause damage to the substrate surface, resulting in addition to the activating unwanted by-products known as LMWOM Low-Molecular-Weight-Oxidized Materials. This highly oxidized and water-soluble polymer scrap, which is no longer covalently bonded to the substrate, leads to a low resistance to humid climates.

In addition to the high-temperature plasma treatment, it is also possible to pretreat the substrate surfaces in a low-temperature plasma treatment. Thus, it is possible to treat the substrate surface of a substrate prior to bonding with a low-temperature plasma treatment and thereby to increase an adhesive force between the substrate surface and the adhesive surface of an adhesive.

For example, a low temperature discharge configuration is understood to mean a configuration that generally generates low temperature plasma. In this case, a process gas in an electric field, which is generated for example by a piezoelectric element, and thereby excited to the plasma. A plasma discharge space is the space in which the plasma is excited. The plasma exits from an exit from the plasma discharge space.

A low-temperature plasma is understood here to mean a plasma which has a temperature when it strikes the surface of at most 70 ° C., preferably at most 60 ° C., more preferably at most 50 ° C. Due to the low temperature, the surfaces are less damaged, and in particular there are no unwanted by-products, the so-called LMWOMs (Low-Molecular-Weight-Oxidized Materials). These LMWOMs lead to a reduction in the adhesive force of the adhesive on the substrate surface, in particular in moist, warm ambient conditions. The low temperature of the plasma also has the advantage that a plasma nozzle of the plasma generator can be moved over the treatment surface at a very small distance of less than 2 mm and this distance can be maintained constant, regardless of the properties of the surface. In particular, the substrate surface can thereby be activated at the same distance from the plasma nozzle as the adhesive surface, which leads to a significant acceleration of the process. Previously, when using high-temperature plasma nozzles, the distance of the plasma jet exit from the surface of the substrate had to be adapted to each material. This is done according to the prior art in that the treatment distance is increased or decreased to the material surface. However, this is associated with an increased expenditure of time and a complication of the activation process.

The low-temperature plasma is conveniently generated by a plasma nozzle based on a piezoelectric effect. In this case, a process gas is guided past a piezoelectric material in a plasma discharge space. The piezoelectric material is vibrated as a primary region via two electrodes by a low-voltage AC voltage. The vibrations are transmitted to the further secondary region of the piezoelectric material. Due to the opposite polarization directions of the multilayer piezoceramic electric fields are generated. The resulting potential differences allow the generation of plasmas with low temperatures of at most 70 ° C, preferably 60 ° C, more preferably at most 50 ° C. Low heat generation can only occur through the mechanical work in the piezoceramic. In common plasma nozzles with arc-like discharges, this can not be achieved because the discharge temperature is above 900 ° C for excitation of the process gas.

The substrate surfaces used according to the invention are LSE substrate surfaces such as Apo1.2 or HighSolid. LSE stands for Low Surface Energy.

The LSE surfaces are low-energy, ie non-polar surfaces in contrast to high-energy, ie polar surfaces. In general, adhesive adheres better to high-energy surfaces. According to the invention, however, an adhesive bond to low-energy surfaces is produced. low-energy However, surfaces have the advantage that dirt, water etc. are less liable to them. They are therefore well suited as paints, in particular car paints.

The wettability of a surface is described by the surface energy. In this case, a drop of water is applied to the surface, and the contact angle of the water drop is measured. Measuring methods are known according to DIN 53364 or ASTM D 2578-84. By LSE substrate surfaces are here understood substrate surfaces whose contact angle is at an approximate level of non-polar polymers such as polypropylene or polypropylene.

The problem with the known plasma treatment of the substrate surfaces is the fact that this is relatively complicated, since the entire component whose surface, even if it only needs to be partially pretreated, must be moved and fed to an exact processing.

It is therefore an object of the present invention to produce a method for producing an adhesive bond between a pressure-sensitive adhesive and an LSE substrate surface, which causes a significant increase in adhesive strength and yet is easily applicable.

The object is achieved by an initially mentioned method with the features of claim 1.

It has surprisingly been found that the bond strengths between an adhesive layer and the surface of an LSE substrate can be significantly increased if the surface of the adhesive layer is plasma-treated, preferably exclusively the surface of the adhesive layer is plasma-treated. Of course, a plasma treatment of an adhesive layer is much easier to handle than the plasma treatment of the substrate surface, since the adhesive layer can usually be provided on a carrier substrate or by layers of rolled-up adhesive tape separated by a liner.

It has been found that for certain layers of adhesive, the adhesion between the adhesive layer and the LSE substrate surface can be increased if the surface of the adhesive layer is plasma-treated. The adhesive layer contains a) 40-70 wt .-% based on the total weight of the PSA of at least one poly (meth) acrylate, b) 15 to 50 wt .-% based on the total weight of the PSA of at least one synthetic rubber and c) at least one with the poly (meth) acrylates compatible tackifier. First, such a PSA already shows a very good bond strength both at room temperature and at minus 30 ° C and at plus 70 ° C.

A "pressure-sensitive adhesive" is understood to mean, in accordance with the general understanding of the person skilled in the art, a viscoelastic adhesive whose set dry film is permanently tacky at room temperature and remains tacky and can be adhered to a variety of substrates by applying light contact pressure.

A "poly (meth) acrylate" is understood as meaning a polymer whose monomer base consists of at least 60% by weight of acrylic acid, methacrylic acid, acrylic acid esters and / or methacrylic acid esters, acrylic esters and / or methacrylates being at least partly, preferably at least 50% by weight. In particular, a "poly (meth) acrylate" is understood as meaning a polymer which can be obtained by free-radical polymerization of acrylic and / or methacrylic monomers and optionally other copolymerizable monomers.

According to the invention, the poly (meth) acrylate or poly (meth) acrylates to 40 to 70 wt .-%, based on the total weight of the PSA included. The pressure-sensitive adhesive of the invention preferably contains from 45 to 60% by weight, based on the total weight of the PSA, of at least one poly (meth) acrylate.

The glass transition temperature of the poly (meth) acrylates which can be used according to the invention is preferably <0 ° C., more preferably between -20 and -50 ° C. The glass transition temperature of polymers or of polymer blocks in block copolymers is determined in the context of this invention by means of dynamic scanning calorimetry (DSC). For this purpose, approx. 5 mg of an untreated polymer sample are weighed into an aluminum pan (volume 25 μΙ_) and closed with a perforated lid. For measurement, a DSC 204 F1 from Netzsch is used. It is worked for the purpose of inertization under nitrogen. The sample is first cooled to -150 ° C, then heated at a heating rate of 10 K / min to +150 ° C and again on - Cooled to 150 ° C. The subsequent second heating curve is driven again at 10 K / min and recorded the change in heat capacity. Glass transitions are recognized as steps in the thermogram. The glass transition temperature is obtained as follows (see FIG. 1):

 The linear area of the trace before and after the step is increased in the direction of increasing (range before the stage) or decreasing (range after stage) temperatures. In the area of the step, a regression line 5 parallel to the ordinate is laid so that it intersects the two extension lines, so that two surfaces 3 and 4 (between the one extension line, the equalization line and the measurement curve) of the same content arise. The intersection of the thus positioned regression line with the trace gives the glass transition temperature. The poly (meth) acrylates of the PSA of the invention are preferably obtainable by at least partial incorporation of functional monomers which are preferably crosslinkable with epoxide groups. Particular preference is given to monomers having acid groups (especially carboxylic acid, sulfonic acid or phosphonic acid groups) and / or hydroxyl groups and / or acid anhydride groups and / or epoxide groups and / or amine groups; particular preference is given to monomers containing carboxylic acid groups. It is particularly advantageous if the polyacrylate comprises copolymerized acrylic acid and / or methacrylic acid. All of these groups have a crosslinking ability with epoxide groups, whereby the polyacrylate is advantageously accessible to thermal crosslinking with incorporated epoxides.

Other monomers which can be used as comonomers for the poly (meth) acrylates, in addition to acrylic acid and / or methacrylic acid esters having up to 30 carbon atoms per molecule, for example vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl aromatic with up to 20 C atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 C atoms, aliphatic hydrocarbons having 2 to 8 C atoms and having one or two double bonds or mixtures of these monomers. The properties of the relevant poly (meth) acrylate can be influenced in particular by varying the glass transition temperature of the polymer by different weight proportions of the individual monomers. The poly (meth) acrylate (s) of the invention may preferably be attributed to the following monomer composition:

a) acrylic acid esters and / or methacrylic acid esters of the following formula

CH ₂ = C (R ') (COOR ") where R ¹ = H or CH ₃ and R" is an alkyl radical having 4 to 14 C atoms,

b) olefinically unsaturated monomers having functional groups of the type already defined for reactivity with preferred epoxy groups, c) optionally further acrylates and / or methacrylates and / or olefinically unsaturated monomers which are copolymerizable with component (a).

The proportions of the respective components (a), (b), and (c) are preferably selected such that the polymerization product has a glass transition temperature of <0 ° C, more preferably between -20 and -50 ° C (DSC). It is particularly advantageous, the monomers of component (a) in a proportion of 45 to 99 wt .-%, the monomers of component (b) in a proportion of 1 to 15 wt .-% and the monomers of component (c) in a proportion of 0 to 40% by weight (the data are based on the monomer mixture for the "base polymer", that is to say without additives of any additives to the finished polymer, such as resins, etc.) The monomers of component (a) are especially plasticizing and / or nonpolar monomers, preferably monomers (a) used are acrylic and methacrylic acid esters having alkyl groups consisting of 4 to 14 C atoms, particularly preferably 4 to 9 C atoms, examples of such monomers being n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate and their branched isomers such as isobutyl acrylate, isooctyl acrylate , Isooctylmetha crylate, 2-ethylhexyl acrylate or 2-ethylhexyl methacrylate. The monomers of component (b) are, in particular, olefinically unsaturated monomers having functional groups, in particular having functional groups capable of undergoing reaction with epoxide groups. For component (b), preference is given to using monomers having functional groups which are selected from the group comprising: hydroxyl, carboxy, sulfonic or phosphonic acid groups, acid anhydrides, epoxides, amines.

Particularly preferred examples of monomers of component (b) are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, hydroxyethyl acrylate, in particular 2-hydroxyethyl acrylate, hydroxypropyl acrylate, in particular 3 Hydroxypropyl acrylate, hydroxybutyl acrylate, in particular 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, in particular 6-hydroxyhexyl acrylate, hydroxyethyl methacrylate, in particular 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, in particular 3-

Hydroxypropyl methacrylate, hydroxybutyl methacrylate, especially 4-

Hydroxybutyl methacrylate, hydroxyhexyl methacrylate, especially 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate. In principle, all vinylically functionalized compounds which are copolymerizable with component (a) and / or component (b) can be used as component (c). The monomers of component (c) can serve to adjust the properties of the resulting PSA. Exemplary monomers of component (c) are:

Methylacrylate, ethylacrylate, propylacrylate, methylmethacrylate, ethylmethacrylate, benzylacrylate, benzylmethacrylate, sec-butylacrylate, ie f-butylacrylate, phenylacrylate, phenylmethacrylate, isobornylacrylate, isobornylmethacrylate, ie / f-butylphenylacrylate, tert-butylaphenylmethacrylate, dodecylmethacrylate, isodecylacrylate, laurylacrylate, n-undecylacrylate , Stearyl acrylate, tridecyl acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyl adamantyl acrylate, 4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, 4 Biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, Dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, 3-methoxyacrylic acid methyl ester, 3-methoxybutyl acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate,

Butyl diglycol methacrylate, ethylene glycol acrylate, ethylene glycol monomethyl acrylate, methoxy polyethylene glycol methacrylate 350, methoxy polyethylene glycol methacrylate 500, propylene glycol monomethacrylate, butoxy diethylene glycol methacrylate, ethoxy triethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,3,3-hexafluoroisopropyl acrylate, 1, 1, 1, 3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3, 3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7, 7,8,8,8-pentadecafluorooctyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, Λ / - (1 -

Methylundecyl) acrylamide, / V- (n-butoxymethyl) acrylamide, / V- (butoxymethyl) methacrylamide, / V- (ethoxymethyl) acrylamide, / V- (n-octadecyl) acrylamide, furthermore Λ /, / V-dialkyl-substituted Amides such as Λ /, / V-dimethylacrylamide, Λ /, / V-dimethylmethacrylamide, N-benzylacrylamide, / V-isopropylacrylamide, / V-ie / f-butylacrylamide, / V-ie f-octylacrylamide, N-methylolacrylamide, / V-methylolmethacrylamide, acrylonitrile, methacrylonitrile, vinyl ethers, such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether, vinyl esters, such as vinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride, vinylidene halides, vinylpyridine, 4-vinylpyridine, / V-vinylphthalimide, / V-vinyllactam, / V- Vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3,4-dimethoxystyrene. Macromonomers such as 2-polystyrene ethyl methacrylate (weight-average molecular weight Mw, as determined by GPC, from 4000 to 13000 g / mol), poly (methyl methacrylate) ethyl methacrylate (Mw from 2000 to 8000 g / mol).

Monomers of component (c) may advantageously also be chosen such that they contain functional groups which promote a subsequent radiation-chemical crosslinking (for example by electron beams, UV). Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers which promote electron beam crosslinking are, for example, tetrahydrofurfuryl acrylate, N-he / f-butylacrylamide and allyl acrylate.

The preparation of the polyacrylates ("polyacrylates" is understood in the context of the invention to be synonymous with "poly (meth) acrylates") can be familiar to the person skilled in the art Processes are carried out, in particular advantageous by conventional free-radical polymerizations or controlled radical polymerizations. The polyacrylates can be prepared by copolymerization of the monomeric components using the usual polymerization initiators and optionally regulators, being polymerized at the usual temperatures in bulk, in emulsion, for example in water or liquid hydrocarbons, or in solution.

Preferably, the polyacrylates are prepared by polymerization of the monomers in solvents, in particular in solvents having a boiling range of 50 to 150 ° C, preferably from 60 to 120 ° C using the usual amounts of polymerization initiators, generally at 0.01 to 5, in particular at 0.1 to 2 wt .-% (based on the total weight of the monomers) are prepared.

In principle, all known to the expert, customary initiators are. Examples of radical sources are peroxides, hydroperoxides and azo compounds, for example dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-i-butyl peroxide, cyclohexylsulfonylacetyl peroxide, diisopropyl percarbonate, ί-butyl peroctoate, benzpinacol. In a very preferred procedure, the free-radical initiator used is 2,2'-azobis (2-methylbutyronitrile) (Vazo® 67 ™ from DuPont) or 2,2'-azobis (2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN Vazo® 64 ™ from DuPont).

Suitable solvents for the preparation of the poly (meth) acrylates are alcohols such as methanol, ethanol, n- and iso-propanol, n- and iso-butanol, preferably isopropanol and / or isobutanol, and hydrocarbons such as toluene and in particular gasoline having a boiling range of 60 up to 120 ° C in question. Further, ketones such as preferably acetone, methyl ethyl ketone, methyl isobutyl ketone and esters such as ethyl acetate and mixtures of solvents of the type mentioned can be used, mixtures containing isopropanol, in particular in amounts of 2 to 15 wt .-%, preferably 3 to 10 wt .-% , based on the solvent mixture used, are preferred.

Preferably, after the preparation (polymerization) of the polyacrylates, a concentration takes place, and the further processing of the polyacrylates takes place essentially solvent-free. The concentration of the polymer can be done in the absence of crosslinker and accelerator substances. But it is also possible, one of these Add compound classes to the polymer before the concentration, so that the concentration then takes place in the presence of this substance (s).

The polymers can be converted into a compounder after the concentration step. Optionally, the concentration and the compounding can also take place in the same reactor.

The weight-average molecular weights Mw of the polyacrylates are preferably in a range of 20,000 to 2,000,000 g / mol, more preferably in a range of 100,000 to 1,500,000 g / mol, most preferably in a range of 150,000 to 1,000,000 g / mol , The data of the average molecular weight Mw and the polydispersity PD in this document refer to the determination by gel permeation chromatography. For this it may be advantageous to carry out the polymerization in the presence of suitable polymerization regulators such as thiols, halogen compounds and / or alcohols in order to set the desired average molecular weight.

The statements of the number-average molar mass Mn and the weight-average molar mass Mw in this document refer to the determination by gel permeation chromatography (GPC). The determination is carried out on 100 μΙ clear filtered sample (sample concentration 4 g / l). The eluent used is tetrahydrofuran with 0.1% by volume of trifluoroacetic acid. The measurement takes place at 25 ° C.

The precolumn is a column type PSS-SDV, 5 μηη, 10 ³ Å, 8.0 mm ^* 50 mm (details here and below, in the order: type, particle size, porosity, internal diameter ^* length; 1 Ä = 10 ^"10 For separation, a combination of the columns of the type PSS-SDV, 5 μm, 10 ³ A and 10 ⁵ A and 10 ⁶ A with 8.0 mm ^* 300 mm in each case is used (columns from Polymer Standards Service; flow rate is 1, 0 ml per minute Calibration is carried out with polyacrylates against PMMA standards (polymethyl methacrylate calibration) and otherwise (resins, elastomers) against PS standards (polystyrene calibration).

The polyacrylates preferably have a K value of 30 to 90, particularly preferably 40 to 70, measured in toluene (1% solution, 21 ° C). The K value according to Fikentscher is a measure of the molecular weight and the viscosity of the polymer. The principle of the method is based on the capillary-viscometric determination of the relative solution viscosity. For this purpose, the test substance is dissolved in toluene by shaking for 30 minutes, so that a 1% solution is obtained. In a Vogel-Ossag viscometer, the flow time is measured at 25 ° C and determined therefrom in relation to the viscosity of the pure solvent, the relative viscosity of the sample solution. The K value can be read from tables according to Fikentscher [PE Hinkamp, Polymer, 1967, 8, 381] (K = 1000 k).

Especially suitable according to the invention are polyacrylates which have a narrow molecular weight distribution (polydispersity PD <4). Despite relatively low molecular weight after crosslinking, these compositions have a particularly good shear strength. In addition, the lower polydispersity allows for easier melt processing, since the flow viscosity is lower compared to a more widely dispersed polyacrylate with largely similar application properties. Narrowly distributed poly (meth) acrylates can be advantageously prepared by anionic polymerization or by controlled radical polymerization, the latter being particularly well suited. Also via / V-Oxyle can be produced corresponding polyacrylates. Furthermore, atom transfer radical polymerization (ATRP) can advantageously be used for the synthesis of narrowly distributed polyacrylates, preference being given to initiating monofunctional or difunctional secondary or tertiary halides and to abstraction of the halide (s) Cu, Ni, Fe -, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au complexes are used.

The monomers for preparing the poly (meth) acrylates preferably contain proportionally functional groups which are suitable for entering into linking reactions with epoxide groups. This advantageously allows thermal crosslinking of the polyacrylates by reaction with epoxides. By linking reactions are meant in particular addition and substitution reactions. Thus, it is preferable to link the building blocks carrying the functional groups with building blocks bearing epoxy groups, in particular in the sense of crosslinking the polymer building blocks carrying the functional groups via crosslinking molecules carrying epoxide groups as bridging bridges. The epoxide group-containing substances are preferably multifunctional epoxides, ie those having at least two epoxide groups; Accordingly, it is preferable in total to an indirect linkage of the blocks carrying the functional groups. The poly (meth) acrylates of the PSA of the invention are preferably crosslinked by linking reactions - in particular in the context of addition or substitution reactions - of functional groups contained in them with thermal crosslinkers. It is possible to use all thermal crosslinkers which ensure both a sufficiently long processing time, so that there is no gelling during the processing process, in particular the extrusion process, as well as a rapid post-crosslinking of the polymer to the desired degree of crosslinking at lower temperatures than Processing temperature, especially at room temperature, lead. For example, a combination of polymers containing carboxyl, amine and / or hydroxyl groups and isocyanates, in particular aliphatic or amine-deactivated trimerized isocyanates, as crosslinkers is possible. Suitable isocyanates are in particular trimerized derivatives of MDI [4,4-methylene di (phenyl isocyanate)], HDI [hexamethylene diisocyanate, 1,6-hexylene diisocyanate] and / or IPDI [isophorone diisocyanate, 5-isocyanato-1-isocyanatomethyl-1, 3, 3-trimethylcyclohexane], for example the types Desmodur® N3600 and XP2410 (in each case BAYER AG: aliphatic polyisocyanates, low-viscosity HDI trimers). Also suitable is the surface-deactivated dispersion of micronized trimerized IPDI BUEJ 339®, now HF9® (BAYER AG).

Basically suitable for crosslinking, however, are other isocyanates such as Desmodur VL 50 (polyisocyanates based on MDI, Bayer AG), Basonat F200WD (aliphatic polyisocyanate, BASF AG), Basonat HW100 (water-emulsifiable polyfunctional isocyanate based on HDI, BASF AG), Basonat HA 300 (allophanate-modified polyisocyanate based on isocyanurate, HDI-based, BASF) or Bayhydur VPLS2150 / 1 (hydrophilic modified IPDI, Bayer AG). Preference is given to using thermal crosslinkers at from 0.1 to 5% by weight, in particular from 0.2 to 1% by weight, based on the total amount of the polymer to be crosslinked.

The poly (meth) acrylates of the PSA of the invention are preferably crosslinked by means of epoxide (s) or by means of one or more epoxide group-containing substance (s). The epoxide group-containing substances are in particular multifunctional epoxides, ie those having at least two epoxide groups; Accordingly, there is an overall indirect linkage of the functional groups bearing blocks of poly (meth) acrylates. The epoxide group-containing substances can be both aromatic and aliphatic compounds.

Highly suitable multifunctional epoxides are oligomers of epichlorohydrin, polyether polyhydric alcohols (especially ethylene, propylene and butylene glycols, polyglycols, thiodiglycols, glycerol, pentaerythritol, sorbitol, polyvinyl alcohol, polyallylalcohol and the like), epoxy ethers of polyhydric phenols [especially resorcinol, hydroquinone, bis - (4-hydroxyphenyl) -methane, bis (4-hydroxy-3-methylphenyl) -methane, bis (4-hydroxy-3,5-dibromophenyl) -methane, bis- (4-hydroxy-3,5- difluorophenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) -propane, 2 , 2-bis (4-hydroxy-3-chlorophenyl) -propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) -propane, 2,2-bis (4-hydroxy-3, 5-dichlorophenyl) -propane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) -4'-methylphenylmethane, 1, 1-bis (4-hydroxyphenyl) -2,2,2-trichloroethane, bis (4-hydroxyphenyl) - (4-chlorophenyl) -met han, 1,1-bis (4-hydroxyphenyl) -cyclohexane, bis (4-hydroxyphenyl) -cyclohexylmethane, 4,4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylsulfone] and their hydroxyethyl ethers , Phenol-formaldehyde condensation products, such as phenol alcohols, phenol-aldehyde resins and similar, S- and N-containing epoxides (for example, N, N-diglycidylanillin, N, N'-dimethyldiglycidyl-4,4-diaminodiphenylmethane) and epoxides, which by conventional methods from polyunsaturated carboxylic acids or monounsaturated carboxylic acid residues of unsaturated alcohols, glycidyl esters, polyglycidyl esters which can be obtained by polymerization or copolymerization of glycidyl esters of unsaturated acids or from other acidic compounds (cyanuric acid, diglycidylsulfide, cyclic trimethylenetrisulfone or its derivatives and others) are. Very suitable ethers are, for example, 1,4-butanediol diglycidyl ether, polyglycerol-3-glycidyl ether, cyclohexanedimethanol diglycidyl ether, glycerol triglycidyl ether, neopentylglycol diglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, bisphenol A diglycidyl ether and bisphenol F diglycidyl ether. Particularly preferred for the poly (meth) acrylates as polymers to be crosslinked is the use of a crosslinking accelerator system ("crosslinking system") described, for example, in EP 1 978 069 A1, for better control over both processing time, crosslinking kinetics and degree of crosslinking The crosslinker-accelerator system comprises at least one substance containing epoxide groups as crosslinking agent and at least one substance accelerating at a temperature below the melting temperature of the polymer to be crosslinked for crosslinking reactions by means of compounds containing epoxide groups.As accelerators, particular preference is given according to the invention to amines (formally as In the following formulas, these substituents are represented by "R" and include, in particular, alkyl and / or aryl radicals and / or other organic radicals), in particular those amines which are used mi t the building blocks of the polymers to be crosslinked little or no reaction.

In principle, both primary (NRh), secondary (NR2H) and tertiary amines (NR3) can be selected as accelerators, of course also those which have a plurality of primary and / or secondary and / or tertiary amine groups. However, particularly preferred accelerators are tertiary amines such as triethylamine, triethylenediamine, benzyldimethylamine, dimethylamino-methylphenol, 2,4,6-tris- (N, N-dimethylaminomethyl) -phenol, N, N'-bis (3- (dimethyl-amino ) propyl) urea. Advantageously, multifunctional amines such as diamines, triamines and / or tetramines can also be used as accelerators. For example, diethylenetriamine, triethylenetetramine, trimethylhexamethylenediamine are excellent.

In addition, amino alcohols are preferably used as accelerators. Secondary and / or tertiary amino alcohols are particularly preferably used, wherein in the case of several amine functionalities per molecule, preferably at least one, preferably all amine functionalities are secondary and / or tertiary. Preferred amino alcohol accelerators may be triethanolamine, N, N-bis (2-hydroxypropyl) ethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, 2-aminocyclohexanol, bis (2-hydroxycyclohexyl) methylamine, 2- (diisopropylamino) ethanol, 2- Dibutylamino) ethanol, N-butyldiethanolamine, N-butylethanolamine, 2- [bis (2-hydroxyethyl) amino] -2- (hydroxymethyl) -1, 3-propanediol, 1 - [bis (2-hydroxyethyl) amino] -2- propanol, triisopropanolamine, 2- (dimethylamino) ethanol, 2- (diethylamino) ethanol, 2- (2-dimethylaminoethoxy) ethanol, N, N, N'-trimethyl-N'-hydroxyethyl bisaminoethyl ether, Ν, Ν, Ν'-trimethylaminoethylethanolamine and / or Ν, Ν, Ν'-

Trimethylaminopropylethanolamin be used.

Other suitable accelerators are pyridine, imidazoles (such as 2-methylimidazole) and 1,8-diazabicyclo [5.4.0] undec-7-ene. Cycloaliphatic polyamines can also be used as accelerators. Also suitable are phosphate-based accelerators, such as phosphines and / or phosphonium compounds, for example triphenylphosphine or tetraphenylphosphonium tetraphenylborate.

The PSA of the invention further contains at least one synthetic rubber. According to the invention, the synthetic rubber or synthetic rubbers in the PSA are present at from 15 to 50% by weight, based on the total weight of the PSA. The PSA preferably contains from 20 to 40% by weight, based on the total weight of the PSA, of at least one synthetic rubber.

Preferably, at least one synthetic rubber of the PSA of the invention is a block copolymer having a structure AB, ABA, (AB) _n , (AB) _n X or (ABA) _n X, in which

 - The blocks A independently of one another for a polymer formed by polymerization of at least one vinyl aromatic;

 - the blocks B independently of one another for a polymer formed by polymerization of conjugated dienes having 4 to 18 C atoms and / or isobutylene, or for a partially or fully hydrogenated derivative of such a polymer;

 X for the remainder of a coupling reagent or initiator and

 - n for an integer> 2

stand.

In particular, all synthetic rubbers of the pressure-sensitive adhesive of the invention are block copolymers having a structure as stated above. The PSA of the invention can thus also contain mixtures of various block copolymers having a structure as above. Suitable block copolymers (vinylaromatic block copolymers) thus comprise one or more rubbery blocks B (soft blocks) and one or more glassy blocks A (hard blocks). More preferably, at least one synthetic rubber of the PSA according to the invention is a block copolymer having a structure AB, ABA, (AB) 3X or (AB) ₄ X, where A, B and X are as defined above. Very particularly preferably, all of the synthetic rubber pressure-sensitive adhesive block copolymers of the invention having a structure AB, ABA, (AB) sX or (AB) ₄ X, where the above apply for A, B and X meanings. In particular, the synthetic rubber of the PSA of the invention is a mixture of block copolymers having a structure AB, ABA, (AB) sX or (AB) ₄ X, which preferably comprises at least AB diblock copolymers and / or triblock copolymers ABA.

Block A is generally a vitreous block having a preferred glass transition temperature (Tg, DSC) above room temperature. More preferably, the Tg of the glassy block is at least 40 ° C, especially at least 60 ° C, most preferably at least 80 ° C and most preferably at least 100 ° C. The proportion of vinylaromatic blocks A in the total block copolymers is preferably from 10 to 40% by weight, particularly preferably from 20 to 33% by weight. Vinylaromatics for the construction of the block A preferably comprise styrene, o methylstyrene and / or other styrene derivatives. The block A can thus be present as a homo- or copolymer. More preferably, block A is a polystyrene.

The vinyl aromatic block copolymer further generally has a rubbery block B or soft block having a preferred Tg of less than room temperature. The Tg of the soft block is particularly preferably less than 0 ° C, in particular less than -10 ° C, for example less than -40 ° C and most preferably less than -60 ° C.

Preferred conjugated dienes as monomers for soft block B are in particular selected from the group consisting of butadiene, isoprene, ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene, dimethylbutadiene and the Farnese isomers and any desired mixtures of these monomers. Block B can also be present as a homopolymer or as a copolymer.

The conjugated dienes are particularly preferred as monomers for the soft block B selected from butadiene and isoprene. For example, the soft block B is a polyisoprene, a polybutadiene or a partially or fully hydrogenated derivative of one of these two Polymers such as in particular polybutylene butadiene; or a polymer of a mixture of butadiene and isoprene. Most preferably, the block B is a polybutadiene.

The PSA according to the invention additionally contains at least one tackifier which is compatible with the poly (meth) acrylate (s) and which can also be referred to as an adhesion promoter or adhesive resin. A "tackifier" is understood, according to the general expert understanding, to be an oligomeric or polymeric resin which increases the auto-adhesion (tack, inherent tack) of the PSA in comparison to the otherwise non-tackified, otherwise identical PSA.

A "tackifier compatible with the poly (meth) acrylate" is understood to mean a tackifier which alters the glass transition temperature of the system obtained after thorough mixing of poly (meth) acrylate and tackifier in comparison with the pure poly (meth) acrylate Only one Tg could be assigned to the blend of poly (meth) acrylate and tackifier A tackifier incompatible with the poly (meth) acrylate (s) would be added in the system obtained after thorough mixing of poly (meth) acrylate and tackifier two Tg, one of which would be assigned to the poly (meth) acrylate and the other the resin domains.The determination of the Tg is carried out in this context calorimetrically by means of DSC (differential scanning calorimetry).

The poly (meth) acrylate-compatible resins of the composition of the invention preferably have a DACP of less than 0 ° C, more preferably of at most -20 ° C, and / or preferably a MMAP of less than 40 ° C preferably of at most 20 ° C, on. For determination of DACP and MMAP values, see C. Donker, PSTC Annual Technical Seminar, Proceedings, pp. 149-164, May 2001.

According to the invention, the tackifier compatible with the poly (meth) acrylates is preferably a terpene-phenolic resin or a rosin derivative, more preferably a terpene-phenolic resin. The PSA of the invention may also contain mixtures of several tackifiers. Among the rosin derivatives, rosin esters are preferred.

The pressure-sensitive adhesive of the invention preferably contains from 7 to 25% by weight, based on the total weight of the PSA, of at least one tackifier compatible with the poly (meth) acrylates. Particularly preferred is the with the poly (meth) acrylates compatible tackifiers or are compatible with the poly (meth) acrylates Tackifier to 12 to 20 wt .-%, based on the total weight of the PSA included.

The tackifier (s) compatible with the poly (meth) acrylates is / are also compatible with the synthetic rubber, in particular with its soft block B, or at least partially compatible, the above definition of the term "compatible" correspondingly applying Polymer / resin compatibility depends, inter alia, on the molecular weight of the polymers or resins The compatibility is better when the molecular weight (s) are lower For a given polymer, it may be possible that the low molecular weight components of the resin molecular weight distribution with the polymer but the higher molecular weight is not, which is an example of partial compatibility.

The weight ratio of poly (meth) acrylates to synthetic rubbers in the pressure-sensitive adhesive of the invention is preferably from 1: 1 to 3: 1, in particular from 1.8: 1 to 2.2: 1.

 The weight ratio of tackifiers which are compatible with the poly (meth) acrylates to synthetic rubbers in the pressure-sensitive adhesive of the invention is preferably not more than 2: 1, in particular not more than 1: 1. At least this weight ratio is preferably 1: 4.

According to the invention, the synthetic rubber in the pressure-sensitive adhesive of the invention is dispersed in the poly (meth) acrylate. The synthetic rubber is preferably dispersed in the PSA according to the invention in the poly (meth) acrylate. Accordingly, poly (meth) acrylate and synthetic rubber are preferably in each case homogeneous phases. The poly (meth) acrylates and synthetic rubbers contained in the pressure-sensitive adhesive are preferably chosen so that they are not miscible to homogeneity at 23 ° C. The PSA of the invention is thus at least microscopically and preferably at least at room temperature in at least two-phase morphology. With particular preference, poly (meth) acrylate (s) and synthetic rubber (e) are not homogeneously miscible with one another in a temperature range from 0 ° C. to 50 ° C., in particular from -30 ° C. to 80 ° C., so that the PSA in these Temperature ranges present at least microscopically at least two phases. For the purposes of this specification, components are defined as "not homogeneously miscible with one another", even if the formation of at least two stable phases can be detected physically and / or chemically, at least microscopically, after intensive mixing, one phase being rich in one component and the second The presence of negligible amounts of one component in the other, which does not preclude the formation of multiphase, is considered to be insignificant in this regard small amounts of poly (meth) acrylate components are present in the synthetic rubber phase, provided that they are not essential amounts which influence the phase separation.

The phase separation may in particular be realized in such a way that discrete regions ("domains") which are rich in synthetic rubber - ie essentially formed of synthetic rubber - in a continuous matrix which is rich in poly (meth) acrylate - thus substantially A suitable analysis system for a phase separation is, for example, scanning electron microscopy, but phase separation can also be recognized, for example, by the fact that the different phases have two mutually independent glass transition temperatures in differential scanning calorimetry (DDK, Phase separation is present according to the invention if it can be clearly demonstrated by at least one of the analytical methods.

Within the synthetic rubber-rich domains, the fine structure may also have additional multiphase, where the A blocks form one phase and the B blocks form a second phase.

The invention will be described with reference to exemplary embodiments. Showing:

1 heat flow / temperature graph to determine the glass transition temperature,

Fig. 2 is a schematic representation of WTR base 12.121, WTR 12.125 and WTR

 13:41

3a shows a SEM image of an untreated WTR3 surface, FIG. 3b shows a SEM image of a plasma-treated WTR3 surface. FIG.

Especially in the automotive sector, coatings are increasingly being used that meet increasingly higher environmental and scratch resistance. The required property of reduced surface contamination is often referred to as "easy to clean." The problem is that the "easy to clean" effect significantly worsens the adhesive properties of the adhesive on the paint. This is above all disadvantageous for the cultivation, in particular the adhesion of attachments such as rear spoilers o. Ä. There is therefore a need to produce a secure bond on "easy to clean" paint surfaces.

Dirt-repellent and scratch-resistant coatings are known, for example, as High Solid and ApO and are available from the manufacturer PPG. Various variants have been studied to stick an adhesive tape to a lacquer layer, wherein both boundary surfaces were treated by a plasma process or only one of the two interfaces or no interface at all.

Two treatment devices with different discharge concepts were used for the plasma treatment of the interfaces.

1. Manufacturer: Plasmatreat, OpenAir Plasma RD 1004

 • Activation of compressed air via an arc-like discharge

• Separation of the floating discharge at the concentrically arranged nozzle outlet (rotating nozzle)

 • Treatment of the surface with activated "after glow"

 • Power: 1 kW

 Treatment distance: 12 mm (for Ap01.2 lacquer and adhesive)

Number of treatments 1 x per surface

 Speed: 5 m / min

 PCT (PulseCycleTime): 100%

 Temperature plasma: 120 - 300 ° C

2. Manufacturer: Reinhausen Plasma, Piezobrush PZ2 (new development) Activation of ambient air via a multi-layered piezo crystal

 Potential-free treatment

 The device can be operated by hand (about 150 g) and is powered by a power adapter

 Optionally, a battery operation is possible

 Power: 18W

Treatment distance: 2 mm for adhesive, 8 mm for Apo1

 Number of treatments 1 x per surface

 Speed: 83 mm / s, corresponding to approx. 5 m / min

 Temperature plasma: <50 ° C

Initially, two different types of paint were used

Used varnish types

 1. High Solid: HS EODCT CLEARCOAT [A-M126489-DD]

 2. Ap01.2: 2 K-APO CLEAR LACQUER / 1 .2 [A-B203512-GH]

 In addition, the paint systems investigated were used in an unaged condition (activation and bonding took place about one week after painting) and an artificially aged condition (annealed at 150 ° C. for 60 minutes).

Used adhesive tape

1. ACX ^plus 7074

 2. WTR3

plasma parameters

Treatment: Plasmatreat OpenAir, generator FG 5001, nozzle RD 1004 Treatment distance: 12 mm

Number of treatments 1 x per substrate

Speed: 5 m / min

PCT (PulseCycleTime): 100%

Four interface treatments were made. Treatment of the interfaces

 1. Reference, both interfaces untreated (indicated in Figure 1 with "W / O")

2. Plasma Activation Adhesive (referred to in Figure 1 as "PSA with Plasma") 3. Plasma Activation Paint (referred to in Figure 1 as "PPG with Plasma")

4. Plasma Activation Paint and Adhesive (referred to in Graphic 1 as "PPG & PSA with Plasma")

Comparative to the above conditions, the adhesion promoters tesa 60150 (universal primer) and tesa 60152 (polyurethane) were used. The adhesive examination was carried out by means of a bond strength measurement at 300 mm / min, with a take-off angle of 90 ° and a wind-up time of 24 hours. The measurement was carried out according to DIN 30646 or FINAT FTM1. In the case of the adhesion promoters, the time to draw was 72 hours.

The non-treated paint panels exhibit at AC) ^ ^lus 7074 bondings with the Type Ap01.2 bond strengths of up to 15 N / cm, and the high solid type to a maximum of 4.5 N / cm. Adhesive breaks (AF) are present at these values according to graph 1. Therefore, a pre-treatment for the predominant applications is inevitable. When using the tesa adhesion promoters 60150 and 60152 on the Ap01.2 a significant improvement in the bond strength is achieved according to graphic 1. Especially with the Adhesion Promoter 60152, the bond strength increases to more than 40 N / cm with a mixed fracture (AF / FS). In the case of the HighSolid coating, however, a negative effect can be seen in both adhesion promoters in that the bond strength even drops to a barely measurable level. Here it must be assumed that the silanization or the primer by the halogenated polymer is not chemically compatible with the paint surface.

A plasma treatment of either the ^ C ^ " ⁵ 7074 interface or the paint surface (PPG) allows only moderate increases in adhesion up to 18 N / cm with 100% adhesion failure (AF) In contrast, AQXPius 7074 _U nd the paint surface for both-sided plasma treatment In both Ap01.2 and HighSolid, cohesive failure (CF) of the ACX ^plus 7074 product at the KK level of 50 N / cm can be achieved. f l>> «! _s , ^> 1>^'>> Ι. Ί ^' S. iid vs ApOl.2

 [N / cm] Peel Adhes | gn test 90 ", 300 mm / min

Graph 1: Adhesion 90 ° from AC) ^ ' ^US 7074 compared to untreated, primed and

plasma-activated interfaces Furthermore, it was (recorded Wide Temperature Range in accordance graphic 3 in the investigation. Here tend to have higher bond strengths are obtained with untreated surfaces, but comparable to the AC) WTR3 are ^ ^lus 7074 values and not adhesive failure (AF) go out. Both PPG lacquers become much more adhesive thanks to a plasma jet treatment and thus show high bond strengths of more than 50 N / cm. In contrast, the double-sided surface treatment can even bring the bond strength to almost 80 N / cm and provoke a cohesive failure of the viscoelastic II / 7R3 building block. Plasma activation of the WTR3 interface also results in a significant increase in bond strength on the HighSolid-Lac. observed from 4.5 N / cm to 31 N / cm. It is even more astonishing that in Ap01.2 a "pure" l / lTR3 plasma activation, as shown in Graph 2, even achieves a cohesive failure, which indicates that the fundamental adhesion, that is, the interaction of the upper molecular surface layer of the WTR3 to the LSE surface., In addition, an additional interfacial pretreatment of the paint is no longer required and therefore offers a significantly simplified processing in an automated application. Since repair coatings are made at higher temperatures, coating plates were 60 min. annealed at 150 ° C. Annealing improves the bondability of WTR3. The bond strength of ACXplus 7074 is only marginally improved. Cohesive failure could again be detected with bilateral pretreatment (see Figure 3). The one-sided pretreatments must, however, be made up because of insufficient sample quantity.

plasma-activated interfaces

Graphic .3: Adhesion 90 ° by ACX ^? '' ³ 7074 and WTR3 compared to untreated,

plasma-activated and aged (paint) interfaces WTR (Wide Temperature Range) adhesives such as ACX ^{? 1} " ¹¹ have the positive property that plasma activation of the adhesive interface can lead to significant increases in tack strength on LSE (Low-Surface-Energy) Coatings described above "easy to clean" surfaces.

WTR: Ac-SBC blend

7074: Ac with Tackifier The sole treatment of the surface of the adhesive material significantly simplifies the treatment of the surface of the coating. The application of chemical primers as well as the physical pretreatment of the paint surface by plasma can be extremely complicated due to the geometry of the component, by size and type of material. By contrast, the plasma treatment of a flat adhesive strip via suitable dispensers or applicators can be implemented simply, reproducibly and efficiently. As an adhesive AC) ^ ^lus adhesive was solidified with the addition of SBC (styrene butadiene copolymer). The SBC phase is present in the WTR blends dispersed in a continuous acrylate matrix. Treatment conditions:

 Reference, both surfaces untreated

 Plasma activation adhesive

 Plasma activation paint

 Plasma activation paint and adhesive

The following tests and materials were used:

test conditions:

 1 . Adhesive force 90 ° after 24 hours

 2. Adhesive force 90 ° after 7 days of moist warm storage (40 ° C./100% relative humidity)

WTR variants with different resins (see structure in Fig.1):

 • WTR 3 standard (terpene phenolic-based resin)

 • WTR 12.121 with lower concentration of terpene phenolic resin

• WTR 12.125 with KW resin • WTR 13.41 with acrylate resin

 The calculated volume ratio SBC: Ac is approximately 1: 2. In the WTR 3 standard, a high proportion of the DT105 resin is in the SBC phase. In the case of the alternative resins (HC resin, liquid acrylate resin), these are exclusively in the SBC or acrylate phase according to FIG. 2. This can be used to detect dependencies of a plasma activation with respect to the type of resin used and preferred domain incorporation (see Figure 4).

Graph 4: KK 90 ° of plasma-treated WTR variants

It can be seen from the results that the untreated and plasma-treated specimens show predominantly an adhesion break. With the WTR3 standard, a maximum of one mixed fraction can be generated. All l / l / TR variants react with one-sided adhesive activation with high adhesive power increases. Except for the resin-reduced variant, all test specimens show a cohesive failure. Mutual treatment of the interfaces shows, as expected, a cohesive cleavage of all 1 / ITR variants. When looking closely at the fracture type and bond strength level of the 1 / lTR one-sided treatment, differences can be detected. The WTR standard shows the highest KK level with a nearly symmetrical (central) carrier break. It can not be deduced from the values that the activation depends on the phase-specific resin inclusion. This is due to non-existent or manufacturable reference samples, in which the Dertophene T105 is exclusively in the acrylate or SBC phase. However, in terms of resin types, it can be seen that acrylate and HC resins do not adversely affect KM interface activation. This is independent of the phase integration. However, tendentially lower bond strengths are achieved here.

In order to obtain a statement of the surface topography for plasma, an SEM examination according to FIG. 3 was carried out by way of example on the WTR3 standard.

In Fign. 3a, 3b show two SEM images: In FIG. 3a, WTR3 is untreated and in FIG. 3b WTR3 is plasma-treated. Plasma pretreated WTR surfaces show significantly different contrasts after Os04 staining in SEM images. The untreated WTR also appears to have a "white coating" on the dark Ac phase, but is no longer visible after treatment.Phazajets can cause monomolecular microfiltration through thermal effects, and at higher magnification these Ac phases even appear by forming a shadow This may well lead to initial assumptions for the reasons of unilateral CM activation, which could be due to anisotropy, but a production-related anisotropic property has not yet been established and directional molecular chains can affect the boundary layer Further analysis via confocal laser microscopy and AFM can provide further information about the lateral surface structure.

The long-term aging resistance of an adhesive bond is significantly influenced by the quality of the adhesive interfaces. Long-term aging resistance is significantly influenced by the quality of the adhesive interfaces. The aim of a plasma treatment is to create suitable reactive centers on the adhesive surface to increase the bond to the substrate and aging phenomena by z. B. mitigate or eliminate humid storage conditions. Neuralgic points here are also the internal interfaces (interphase) of the ACX ^{plus building} blocks, which also have a decisive influence on the internal adhesion between the formulation constituents and thus also on the overall composite with the plasma interface. Here is the well-known ACX ^plus 6812 dehydration. The collapse of a carrier system under humid-warm conditions can not be compensated by a plasma activation. As described above, a plasma does not act in the volume range of an adhesive, but may cause or promote the advancement of a water front into the interface via the plasma-related hydrophilization. The absorbed moisture triggers physical and chemical changes in the interface. In this case, wet-warm weakness could be eliminated or reduced via suitable parameters of Plasmatreat treatment (distance, speed). Among other things, the thermal influence is responsible for further undesired side effects, which are generated on substrate such as adhesive Low Molecular Weight-Oxidized Materials (LMWOM). Accordingly, highly oxidized polymer or oligomer layers are no longer sufficiently connected to the polymers in the volume of adhesive and additionally water-swellable or soluble.

As discussed in the SEM studies, it suggests that the acrylate phase is deepened to the raised SBC phase. If these structures are retained in the bond interface, they offer a preferred propagation of the water fronts into the possible capillaries. "Water Treeings" are known in which the water ramifications considerably weaken the interfaces and thus the bond.

In the plasma laboratory a technology overview for customer and application solutions is developed. For this purpose the new products Plasmabrush PB3 and Piezobrush PZ2 were tested by manufacturer Reinhausen Plasma GmbH. The Plasmabrush is a discharge similar to the Plasmajet OpenAir Plasma. To this end, the results are presented here by the Piezobrush PZ2. Piezobrush PZ2 is a new atmospheric pressure plasma source that works without external process gas. The plasma is ignited by a multilayer piezoelectric element with atmospheric oxygen, so that a high activation efficiency is generated. At the same time, the device makes it possible to work at extremely low plasma temperatures of around 45 ° C. In addition to a mains connection, it can also be equipped with a rechargeable battery as an energy source, thereby offering maximum flexibility. The occupational safety of the operator is ensured by the low voltage input of 12 volts and the cold plasma. The activation efficiency was tested with the WTR standard (see Figure 5).

ated

Graphic 5: KK 90 ° (24 h RT) with Piezobrush PZ2 activated WTR Despite the lowest performance of the Piezobrush PZ2 of approx. 18 W, considerable increases in adhesion can be detected. Exclusive WTR activation and activation of both interfaces results in nearly symmetric cleavage. In direct comparison to the OpenAir plasma nozzle, a slightly lower KK level is achieved. It will be checked if this can be explained by using another WTR batch. After seven days 40 ° C at 100% relative humidity results in a nearly identical result for 24 hours RT storage (see Figure 6). The formed cohesive fractures are oriented close to the surface after moist-warm storage and are comparable to test pieces with chemically primed coating substrates. ted

 Graph 6: KK 90 ° (7d 40 ° C / 100% rel.F) with Piezobrush PZ2 activated WTR From the activation stage, the system is highly efficient.

Claims

claims

Process for producing an adhesive bond between a

A pressure-sensitive adhesive layer comprising: a) 40-70% by weight, based on the total weight of the PSA, of at least one poly (meth) acrylate;

 b) 15-50 wt .-%, based on the total weight of the PSA, at least one synthetic rubber and

 c) at least one tackifier compatible with the poly (meth) acrylate (s) and an LSE substrate surface by

a surface of the pressure-sensitive adhesive layer is plasma-treated and the plasma-treated surface is adhered to the LSE substrate surface.

Method according to claim 1,

characterized in that the pressure-sensitive adhesive layer comprises an acrylate phase in which an SBC phase is dispersed.

Method according to claim 2,

characterized in that the SBC phase and the acrylate phase are dispersed in a volume ratio of 1: 2.

Method according to one of claims 1 to 3,

characterized in that a rosin derivative, more preferably a terpene phenolic resin, is used as the tackifier.

Method according to one of the preceding claims,

characterized in that the PSA surface with a

 Low-energy plasma nozzle is treated.

Method according to claim 5,

characterized in that the plasma striking the PSA surface is brought to a temperature of at most 70 ° C. Method according to one of the preceding claims,

characterized in that the LSE substrate surface is not plasma treated.