MXPA06007764A - Orientated acrylate adhesive materials, method for the production and use thereof - Google Patents

Abstract

The invention relates to an orientated adhesive material and to a method for the production thereof. The adhesive material comprises a UV cross-linked polymer based on acrylate, which consists of at least 50%by mass of at least one acrylic monomer according to general formula (I), wherein R1 represents hydrogen (H) or a methyl group (CH3) and R2 represents hydrogen (H) or an unbranched or branched, saturated C1 - C30- hydrocarbon radical which is substituted, optionally, by a functional group. The adhesive material in the form of a film which is applied as a melt (hot-melt) has a preferred direction, said direction being characterised in the free film by a back shrinkage of at least 3%in relation to an initial expansion of the film in the preferred direction. Orientation is produced after polymerisation by a suitable coating method and subsequently frozen by UV cross-linking. The adhesive material has excellent properties as an adhesive layer on single or double-sided adhesive strips.

Description

ORIENTED ACRYLIC ADHESIVE MATERIALS, METHOD FOR THE PRODUCTION AND USE OF THEM DESCRIPTION OF THE INVENTION The invention relates to oriented polyacrylate pressure sensitive adhesives (PSA), to their preparation and to their use for adhesive tapes. As a result of cost pressures and environmental structures always increased there is now a tendency to prepare ASP with little, if any, solvent. This objective can be more easily realized by means of the thermoimpregnation technology. An additional advantage of this technology is the acceleration of production and the concomitant cost reduction, since the hot-melt lines can laminate adhesives much more quickly to carriers or release paper. The heat-impregnation technology, however, improves the increasingly demanding requirements of adhesives. For high-grade industrial applications, particular reference is made to polyacrylates, due to their stability to atmospheric alteration and transparency. To prepare acrylate adhesive substances, conventionally, the acrylate monomers are polymerized in solution and the solvent is then removed in an extruder in a concentration operation. In addition to the stability disadvantages of Ref. 173163 atmospheric alteration and transparency, however, acrylate ASPs are also required to meet the stringent requirements in terms of shear strength. This requirement is met by polyacrylates of high molecular weight and high polarity with subsequent efficient crosslinking. One of the factors which represents a significant part as far as the properties of ASP are related is the orientation of the macromolecules. During the preparation, additional processing or subsequent (mechanical) stress of the polymers or polymer compositions there may be high degrees of orientation of the macromolecules in preferential directions within the polymer assembly as a whole. The orientation can lead to particular properties in the corresponding polymers. Some examples of properties which can be influenced by the degree of orientation include the strength and rigidity of the polymers and plastics produced thereof, thermal conductivity, thermal stability and also anisotropy with respect to gas and liquid permeability. In addition, however, oriented polymers may exhibit anisotropic stress / strength characteristics. An important property dependent on the orientation of the monomer units is the refraction of light (expressed by way of the corresponding refractive index n and / or delay d). The measurement of the refraction of light is therefore used as a method to determine the orientation of polymers, particularly in ASP. Another method to determine the orientation is to measure the shrinkage in the free film. The retention of partial orientation in ASP of conventional partially crystalline natural rubber is described in US 5,866,249. The anisotropic adhesive properties allow for the definition of novel ASP applications. In DE 100 34 069, in contrast, an operation is described for preparing oriented acrylate ASPs by means of electron irradiation (HE irradiation). DE 100 52 955, furthermore, describes the use of such oriented acrylate ASPs prepared by the process in accordance with DE 100 34 069. Electron beam crosslinking provides advantages from the point of view of process technology. Therefore, for example, certain states can be "frozen" by means of crosslinking. The irradiation of electrons is not without its disadvantages, nevertheless. For example, the electron beams penetrate not only the acrylate ASP but also the backing material and thus tend to damage the ASP tape. Generally speaking, the quality of crosslinking is equally limited when compared to other crosslinking mechanisms, since as a result of high energy some decomposition of the polymer is also observed. In addition, the cost and complexity of the device for HE irradiation are very high. Therefore, there is a need for a process to prepare ASPs oriented by another crosslinking method which prevents polymer degradation. Therefore, an object of the invention is to provide an oriented acrylate ASP which does not have the aforementioned disadvantages of the prior art. In particular, the acrylate ASP must be preparable by a process which can be performed without greater cost or complexity of the apparatus, and the unwanted polymer degradation of the ASP and / or backup material should be avoided. This object is achieved, surprisingly and in an unpredictable manner for the skilled person, by means of a pressure sensitive adhesive as described in the main claim and by its preparation according to claim 15. The main claim accordingly provides a permanently oriented pressure sensitive adhesive which is obtainable by free radical addition polymerization, comprising an acrylate-based UV crosslinked polymer which 1) is synthesized in a mass fraction of at least 50% from less an acrylic monomer according to the general formula (I) (I) in which Rx is hydrogen (H) or a methyl group (CH3) and R2 is hydrogen (H) or a hydrocarbon radical of Cx to C30 saturated, branched or unbranched, which may be optionally substituted by one or more functional groups, and 2) is composed in a mass fraction from 0.05% to 1% of a UV-crosslinked photoinitiator, which may have been reticulated according to Norrish type I or type II, the pressure sensitive adhesive, in the form of a film applied as a melt (adhesive substance), which has a preferential direction which is characterized in the film free by a retraction of at least 3% in relation to an original stretch of the film in the preferential direction. In a further highly preferred version the ASP has a refractive index measured in the preferential direction, nDM, which is greater than a refractive index measured in a direction perpendicular to the preferential direction, nrc, the difference? N = nDM - nD is at minus 1 »10 ~ 6. This anisotropy based on the orientation can be measured in a simple manner in accordance with Test B. The orientation of the ASP is permanently maintained: the term "permanent" means a period of at least 30 days, in particular at least 3 months, preferably at least 1 year, within which an original contraction of the material is reduced to no more than 20%, in particular no more than 10%, advantageously based on the initial value. The properties of the desired material are favored by an average polymer molecular mass which must be at least 200,000 g / mol. The monomers used for the polymerization are chosen so that the resulting polymers can be used as ASPs at room temperature or higher temperatures, particularly so that the resulting polymers possess ASP properties in accordance with the "Handbook of Pressure Sensitive Adhesive Technology" of Donatas Satas (van Nostrand, New York, 1989). To obtain a preferred polymer vitreous transition temperature TG, ie Tg = 10 ° C, in accordance with the above observations, the monomers are most preferably selected in such a form, and the quantitative composition of the monomer mixture is advantageously chosen in such a manner. Thus, the desired TG for the polymer is obtained in accordance with the equation of Fox (El) (cited, TG Fox, Bull. Am. Phys. Soc. 1 (1956) 123).

In this equation n represents the serial number of the monomers used, wn denotes the mass fraction of the respective monomer n (in% by weight) and Tg, n denotes the respective vitreous transition temperature of the homopolymer of the respective monomer n in K. It is particularly preferably contemplated that for at least one acrylic monomer a compound according to the general formula I is chosen in which the radical Rx is hydrogen (H) or CH3 and the radical R2 is hydrogen (H) or a radical selected from the group consisting of group of saturated C4 to C14 hydrocarbon radicals, branched or unbranched, especially C4 to C9 hydrocarbon radicals, and R2 can be replaced by one or more polar and / or functional groups. In a highly preferred version, the monomers used include acrylic or methacrylic esters, the specific non-limiting examples are methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate. , n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, and also the branched isomers of these , the examples are isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate and isooctyl methacrylate. Additional classes of the compound which may be employed include monofunctional acrylates and / or methacrylates of the formula (I) in which R2 comprises a substituted or unsubstituted, bridged or unbridged cycloalkyl group composed of at least 6 carbon atoms. Examples of suitable substituents include Ci to Cs alkyl radicals and halide or cyanide groups. Specific examples of such monomers are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantyl acrylate. In a further version monomers are used which carry functional and / or polar groups such as carboxyl, sulfonic acid, phosphonic acid, hydroxyl, lactam and lactone, N-substituted amide, N-substituted amino, carbamate, epoxy, thiol, ether groups. , alkoxy and cyano or the like. According to a further advantageous embodiment of the invention, at least one acrylic monomer of the formula (I) is polymerized with at least one additional comonomer which can also carry one or more of the functional and / or polar groups mentioned above. Moderate basic comonomers are, for example, N, N-dialkyl-substituted amides. Examples in this regard include in particular N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N-tert-butylacrylamide, N-vinylpyrrolidone, N-vinyl lactam, dimethylaminoethyl acrylate, dimethylamino-yl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, N-methylolacrylamide, N-methylol-methacrylamide, N- (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide and N-isopropylacrylamide. Additional preferred examples are hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic anhydride, itaconic acid, glycidyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl acrylate. , 2-butoxyethyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinylacetic acid, tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid, and dimethylacrylic acid, this list is not conclusive. In a further highly preferred embodiment the comonomers used include vinyl esters, vinyl ethers, vinyl halides, vinylidene halides and vinyl compounds with aromatic rings and heterocycles in the o-position. At this point, mention may also be made not only of certain examples: vinyl acetate, vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

In a further preferred embodiment, the comonomers having a high static vitreous transition temperature are added to the monomers described. Suitable components include vinyl aromatic compounds, such as styrene, in this case the aromatic nuclei may preferably be composed of C4 to C18 and may also contain heteroatoms. Particularly preferred examples are 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenylmethacrylate, t-butylphenyl acrylate, methacrylate t-butylphenyl, 4-biphenylyl acrylate, 4-biphenylyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate and also mixtures of these monomers, this listing is not conclusive. The pressure sensitive adhesive oriented according to the present invention can be prepared by a process which comprises the following steps: (a) polymerizing at least one acrylic monomer according to the general formula (I), wherein Ri. is hydrogen (H) or a methyl group (CH3) and R2 is hydrogen (H) or a saturated, branched or unbranched Cx to C30 hydrocarbon radical which is optionally substituted by a functional group, (b) ) coating the acrylic polymer of the melt to form a film, in the course of which an orientation occurs in the pressure sensitive adhesive, and (c) crosslinking the film by means of UV radiation. In this context it is possible to use all the monomers described above, to which additional comonomers, also mentioned above, can be added where appropriate. Preferably the polymerization takes place in the presence of one of the aforementioned crosslinkers. Poly (meth) acrylate ASPs are advantageously prepared by conducting conventional free radical addition polymerizations. For polymerizations which proceed in accordance with a free radical mechanism it is preferred to use initiator systems which additionally contain additional free radical initiators for polymerization, particularly thermally decomposed free radical forming peroxo or azo initiators. In principle, however, all familiar familiar initiators are suitable to the expert person for acrylates. The production of centered C radicals is described in Houben eyl, Methoden der Organischen Chemie, Vol. E 19a, p. 60-147. These methods are preferentially employed analogously. Examples of free radical sources are peroxides, hydroperoxides and azo compounds; a number of non-exclusive examples of typical free radical initiators that may be mentioned at this point include potassium peroxodisulfate, dedibenzoyl peroxide, eumenohydroperoxide, cyclohexanone peroxide, di-t-butylperoxide, azodiisobutyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate and benzpinacol. In a highly preferred version the free radical initiator used as 1,1'-azobis (cyclohexanecarbonitrile) (Vazo 88 ^ from DuPont) or azodiisobuityronitrile (AIBN). In addition, in a highly preferred embodiment, photoinitiators containing a copolymerizable double bond are used. Suitable photoinitiators include Norrish photoinitiators I and II. Examples are benzoin acrylate and an acrylated benzophenone from UCB (Ebecryl P 36®). This enumeration is not complete. In principle it is possible to use any of the photoinitiators known to the skilled person that are capable of crosslinking the polymer via a free radical mechanism under UV irradiation. A summary of the possible photoinitiators which can be used and which can be functionalized with a double bond is given in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. For additional details it is possible to refer to Carroy et al. in "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints", Oldring (Ed.), 1994, SITA, London. The average molecular weights Mw of the ASPs formed in the course of free radical polymerization are most preferably chosen to be in a range from 200,000 to 4,000,000 g / mol; specifically for further use as hot-melt ASPs, ASPs are prepared having average molecular weights Mw from 600,000 to 800,000 g / mol. The average molecular weight is determined by size-exclusion chromatography (GPC) or matrix-assisted laser ionization / desorption mass spectrometry (MALDI-EM). The polymerization can be carried out in volume, in the presence of one or more organic solvents, in the presence of water, or in mixtures of organic solvents and water. The object is to minimize the amount of solvent used. Suitable organic solvents are pure alkanes (e.g., hexane, heptane, octane, isooctane), aromatic hydrocarbons (e.g., benzene, toluene, xylene), esters (e.g., ethyl acetate, propyl, butyl or hexyl), hydrocarbons halogenated (e.g., chlorobenzene), or alkanols (e.g., methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether), and ethers (e.g., diethyl ether, dibutyl ether) or mixtures thereof. A water-miscible or hydrophilic co-solvent can be added to the aqueous polymerization reactions to ensure that during the monomer conversion the reaction mixture is in the form of a homogeneous phase. The cosolvents which can be used advantageously for the present invention are selected from the following group, consisting of aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkylpyrrolidones, polyethylene glycols, polypropylene glycols, amides, carboxylic acids and salts thereof, esters, organic sulfides, sulfoxide, sulfones, alcohol derivatives, hydroxy ether derivatives, amino alcohols, ketones and the like, and also derivatives and mixtures thereof. The polymerization time is between 4 and 72 hours, depending on the conversion and temperature. The higher the reaction temperature can be chosen, ie the higher the thermal stability of the reaction mixture, the shorter the reaction time that can be chosen. For initiators which undergo thermal decomposition, the introduction of heat is essential to initiate the polymerization. For thermally decomposed primers the polymerization can be initiated by heating from 50 to 160 ° C, depending on the type of initiator. Another advantageous preparation process for polyacrylate ASPs is anionic polymerization. In this case it is preferred to use inert solvents as the reaction medium, such as aliphatic and cycloaliphatic hydrocarbons, for example, or in their place aromatic hydrocarbons. In this case the existing polymer is generally represented by the structure PL (A) -Me, in which Me is a metal of group I, such as lithium, sodium or potassium, and PL (A) is an increasing polymer block of monomers A. The molar mass of the polymer to be prepared is controlled by the ratio of initiator concentration to monomer concentration. Examples of suitable polymerization initiators include n-propyl-lithium, n-butyl-lithium, sec-butyl-lithium, 2-naphthyl-lithium, cyclohexyl-lithium, and octyl-lithium, with this list not making an integrity claim. In addition, initiators based on samarium complexes are known for the polymerization of acrylates (Macromolecules, 1995, 28, 7886) and can be used at this point. In addition, it is also possible to use difunctional initiators, such as 1,1,4-tetraphenyl-1,4-dithiobutane or 1,1,1-tetraphenyl-1, -dithioisobutane. The co-initiators can also be used. Suitable co-initiators include lithium halides, alkali metal alkoxides or alkylaluminum compounds. In a very preferred version the ligands and co-initiators are chosen so that the acrylate monomers, such as n-butyl acrylate and 2-ethylhexyl acrylate, for example can be directly polymerized and do not need to be generated in the polymer by a transesterification with the corresponding alcohol. To prepare polyacrylate ASPs having a narrow molecular weight distribution, controlled radical polymerization methods are also suitable. For the polymerization it is then preferred to use a control reagent of the general formula: (D (p) in which R and R1 are independently selected from each other or are identical and are selected from the group including the following radicals: - C 1 to C 8 branched or unbranched alkyl radicals; C 3 alkenyl radicals eradicate C3 to C18 alkynyl radicals, Cx to C8 alkoxy radicals, C3 alkynyl radicals to Ci8, C3 to Ci8 alkenyl radicals, Cx to C8 alkyl radicals substituted by at least one OH group or an atom. of halogen or a silyl ether; - heteroalkyl radicals of C2 to C? 8 having at least one oxygen atom and / or a group NR * in the carbon chain, R * represents any radical (especially organic); C 3 to C 8 alkynyl radicals, C 3 to C alkenyl radicals, C x to C 8 alkyl radicals substituted by at least one ester group, amine group, carbonate group, cyano group, isocyanate group and / or epoxide group and / or by sulfur; - C3 to C2 cycloalkyl radicals; - C6 to C18 aryl or benzyl radicals; The control reagents of type (I) are preferably composed of the following additionally restricted compounds, with the following list serving only as examples of the respective groups of compounds does not claim integrity: - The halogen atoms in the present they are preferably F, Cl, Br or I, more preferably Cl and Br. As alkyl, alkenyl, and alkynyl radicals in the various substituents, both straight and branched chains are suitably suitable.

Examples of alkyl radicals containing from 1 to 18 carbon atoms are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t- octyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, hexadecyl, and octadecyl. Examples of alkenyl radicals having from 3 to 18 carbon atoms are propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2, 4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl, and oleyl. Examples of alkynyl having from 3 to 18 carbon atoms are propynyl, 2-butynyl, 3-butynyl, n-2-octynyl, and n-2-octadecynyl. - Examples of hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl, and hydroxyhexyl. - A suitable C2-C18 heteroalkyl radical having at least one oxygen atom in the carbon chain is, for example, -CH2-CH2-0-CH2-CH3. Examples of C3-C12 cycloalkyl radicals include cyclopropyl, cyclopentyl, cyclohexyl, and trimethylcyclohexyl. Examples of C6-C18 aryl radicals include phenyl, naphthyl, benzyl, 4-tert-butylbenzyl or additionally substituted phenyl, such as ethyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene. In addition, compounds of the following types can also be used as control reagents (ni) (iv) where R2 can likewise be chosen independently of R and R1 from the group mentioned above for these radicals. In the case of the conventional "RAFT" process, polymerization is usually carried out only at low conversions (WO 98/01478 Al) to obtain very narrow molecular weight distributions. As a result of the low conversions, however, these polymers can not be used as ASPs and in particular not as hot-melt ASPs, since the high friction of the residual monomers adversely affects the technical properties of the adhesive; the residual monomers could contaminate the recirculated solvent in the concentration operation and the corresponding self-adhesive tapes could exhibit very high gas purification behavior. To avoid this disadvantage of low conversions, in a particularly preferred process the polymerization is initiated a number of times. As an additional controlled radical polymerization method it is possible to perform controlled polymerizations with nitroxide. In an advantageous process, the radical stabilization is carried out using nitroxides of type (Va) or (Vb): (Va) (Vb) where R3, R4, R5, R6, R7, R8, R9 and R10 independently of one another denote the following compounds or atoms: halides, such as chlorine, bromine or iodine, - linear, branched, cyclic hydrocarbons and heterocyclics having from 1 to 20 carbon atoms, which may be saturated, unsaturated or aromatic, esters -COOR11, alkoxides -OR12 and / or phosphonates PO (OR13) 2, where R11, R12 and R13 represent radicals of the second group . Compounds of types (Va) or (Vb) can also be attached to polymer chains of any type (mainly in the sense that at least one of the radicals mentioned above constitutes such a polymer chain). More preference is given to controlled regulators, for the polymerization of compounds, of the following type: 2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PROXYL), 3-carba-oil-PROXYL, 2, 2-dimethyl-4, 5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-hydroxylimin-PROXYL, 3-aminomethyl-PROXYL, 3-methoxy-PROXYL, 3-t-butyl-PROXYL, 3,4-di-t-butyl-PROXYL 2 , 2, 6, 6-tetramethyl-1-piperidinyloxyl (TEMPO), 4-benzoyloxy-TEMPO, 4-methoxy-TEMPO, 4-chloro-TEMPO, 4-hydroxy-TEMPO, 4-oxo-TEMPO, 4-amino- TEMPO, 2,2,6,6-tetraethyl-1-piperidinyloxy, 2,2, 6-trimethyl-6-ethyl-1-piperidinyloxy N-tere-butyl-l-phenyl-2-methylpropyl nitroxide N-tert-Nitroxide -butyl 1- (2-naphthyl) -2-methylpropyl-N-tert-butyl-l-diethylphosphono-2, 2-dimethylpropyl nitroxide N- (1-phenyl-2-methylpropyl) 1-diethylphosphono-1-methylethyl nitroxide di-t-butyl nitroxide diphenyl nitroxide or t-butyl t-amyl nitroxide US 4,581,429 A describes a polymerization process of controlled growth radical ual uses as its initiator a compound of the formula R'R "N-0-Y, in which Y denotes a species of free radicals which is capable of polymerizing unsaturated monomers. In general, however, the reactions have low conversion rates. A particular problem is the polymerization of acrylates, which takes place only with molar masses and very low yields. WO 98/13392 Al discloses open chain alkoxyamine compounds which have a symmetric substitution configuration. EP 735 52 Al describes a process for preparing thermoplastic elastomers having narrow molar mass distributions. WO 96/24620 A1 discloses a polymerization process in which very specific radical compounds, such as phosphorus-containing nitroxides based on imidazolidine, are used. WO 98/44008 A1 discloses specific nitroxyls based on morpholines, piperazinones and piperazindiones. DE 199 49 352 A1 discloses heterocyclic alkoxyamines as regulators in controlled growth radical polymerizations. The corresponding additional developments of the corresponding alkoxyamines or free nitroxides improve the efficiency for the preparation of polyacrylates (Hawker, contribution to the National Meeting of the American Chemical Society, Spring 1997, Husemann, contribution to the IUPAC World Polymer Meeting 1998, Gold Coast). As an additional controlled polymerization method, atom transfer radical polymerization (ATRP) can advantageously be used to synthesize the polyacrylate ASPs, in this case it is preferably used, as initiator, of monofunctional or difunctional secondary or tertiary halides and, for extracting the halide (s) from complexes of Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au (EP 0 824 111 Al; EP 826 698 Al; 824-110 Al; EP 841 346 Al; EP 850 957 Al). The various possibilities of ATRP are further described in US 5,945,491 A, US 5,854,364 A, and US 5,789,487 A. For further development, the resins can be blended to the polyacrylate ASPs. As tackifying resins for addition it is possible without exception to use any of the tackifying resins which are already known and are described in the literature. As representative, mention can be made of pinene resins, indene resins, and rosins, their disproportionated, hydrogenated, polymerized, esterified salts and derivatives, the aliphatic and aromatic hydrocarbon resins, terpene resins and terpene phenolic resins, and also C5, C9 hydrocarbon resins, and others. Any of the desired combinations of these and other resins can be used to adjust the properties of the resulting adhesive in accordance with that desired. In general it is possible to use any resin which is compatible (soluble) with the corresponding polyacrylate; in particular, reference can be made to all aliphatic, aromatic and alkylaromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional hydrocarbon resins, and natural resins. Explicit reference is made to the representation of the state of the art in the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, 1989). In addition, it is also optionally possible to add plasticizers, fillers (for example, fibers, carbon black, zinc oxide, titanium dioxide, chalk, solid and hollow glass beads, microbeads made of other materials, silica, silicates), nucleators, blowing agents, mixing agents and / or aging inhibitors, in the form for example of primary and secondary antioxidants or in the form of light stabilizers. Additionally, crosslinkers and crosslinkers can be mixed. Examples of crosslinking agents suitable for UV crosslinking include difunctional or polyfunctional acrylates and methacrylates. For cross-linking with UV light, the UV-absorbing photoinitiators are advantageously added to the polyacrylate ASPs. Useful photoinitiators which are very good to use include benzoin ethers, such as methyl ether benzoin and isopropyl ether benzoin, for example, substituted acetophenones, such as 2,2-diethoxyacetophenone. (available as Irgacure 651® from Ciba Geigy®), 2, 2-dimethoxy-2-phenyl-1-phenylethanone, dimethoxy-hydroxyacetophenone, substituted ketole, such as 2-methoxy-2-hydroxypropiophenone, for example, aromatic sulfonyl, such as 2-naphthylsulfonyl chloride, for example, and photoactive oximes, such as 2- (o-ethoxycarbonyl) oxime of 1-phenyl-1,2-propanedione, for example. The photoinitiators mentioned above and others which may be used, including those of the Norrish I or Norrish II type, may contain the following radicals: benzophenone, acetophenone, benzyl, benzoin, hydroxyalkylphenone, phenyl cyclohexyl ketone, anthraquinone, trimethylbenzoylphosphine oxide, methylthiophenyl morpholinyl ketone, amino ketone, azobenzoin, thioxanthone, hexaarylbisimidazole, triazine, or fluorenone, it is possible for each of these radicals to be further substituted by one or more halogen atoms and / or one or more alkyloxy groups and / or one or more amino groups or hydroxyl groups. A general representative view is given by Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. For further details, it is possible to consult Carroy et al. in "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints", Oldring (Ed.), 1994, SITA, London. To produce oriented ASPs, the polymers described above are preferably coated as hot-melt systems. For the production process it may therefore be necessary to remove the solvent from the ASP. In principle it is possible at this point to use any of the techniques known to the skilled person. A highly preferred technique is that of concentration using a single screw extruder or two screws. The two-screw extruder can be operated co-rotationally or counter-rotatively. The solvent or water is preferably distilled off via two or more vacuum stages. In addition, the counter-heating is carried out depending on the distillation temperature of the solvent. The residual solvent fractions are preferably < 1%, more preferably < 0.5% and very preferably < 0.2%. The thermoimpregnation is further processed from the melt. In a preferred process, the orientation within the ASP is produced by the coating process. For coating as a thermoimpreg, and therefore also for orientation, it is possible to employ a variety of coating techniques. In one embodiment the polyacrylate ASPs are coated by a roller coating process, and the orientation is produced by stretching. Several techniques of coating with rollers are described in the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York, 1989). In another version the orientation is achieved by coating through a fusion die. A distinction can be made at this point between the process with contact and the process without contact. The orientation of the PSA at this point can be produced, on the one hand, within the coating die, by virtue of the design of the die, or after the exit of the die, by a drawing operation. The orientation is freely adjustable. The stretching ratio can be controlled, for example, by the width of the die opening. Stretching occurs each time the layer thickness of the ASP film in the backing material to be coated is less than the width of the die opening. In another preferred process, orientation is achieved by extrusion coating. Extrusion coating is preferably done using an extrusion die. The extrusion dies used can originate from one of the following three categories: T dies, fishtail dies, and hanging dies. Individual types differ in the design of their flow channel. Through the shape of the extrusion die it is also possible to produce an orientation inside the hot-melt ASP. Additionally, at this point, in analogy with the melt-die coating, it is also possible to obtain an orientation after the exit of the die, by stretching the ASP-tape film. To produce oriented acrylate ASPs, it is particularly preferred to perform the coating on a backing using a hanging die, specifically in such a way that a polymer layer is formed in the backing by means of a die movement relative to the backing. The time which elapses between the coating and crosslinking - the relaxation time, as it is called, is preferably short. In a preferred process, the crosslinking is performed less than 60 minutes after the coating; in another preferred pss, after less than 3 minutes. In a very preferred pss, in an on-line pss, the crosslinking takes place in less than 5 seconds after the coating. In a preferred version, the coating is made directly on a backing material. Suitable backing materials include, in principle, all materials known to the skilled person, such as BOPP, PET, PVC or non-woven, foam or release papers (glassine, HDPE or LDPE). The best orientation effects are obtained by deposition on a cold surface. Therefore the backing material during the coating should be cooled directly by means of a roller. The roller can be cooled by a liquid film / contact film from the outside or inside, or by a refrigerant gas. The refrigerant gas can also be used to cool the ASP leaving the coating die. In a preferred version the roller is moistened with a contact means, which is then located between the roller and the backing material. Preferred embodiments for the implementation of such a technique are described later. For this pss it is possible to use both a melting die and an extrusion die. In a very preferred version the roller is cooled to room temperature, in an extremely preferred version at a temperature below 10 ° C. The roller must rotate during this. In an additional version of this preparation pss, in addition, the roller is used for the cross-linking of the oriented ASP. UV crosslinking is carried out by brief irradiation with ultraviolet radiation in a wavelength range from 200 to 400 nm, depending on the UV photoinitiator used, especially using high or medium pressure mercury lamps with an output of 80 to 240 W / cm. The intensity of irradiation is adapted to the respective quantum yield of the UV photoinitiator, the degree of crosslinking that originates, and to adjust the degree of orientation. An additional option is to crosslink the polyacrylate ASP further with electron beams. The typical irradiation equipment which can be used includes linear cathode systems, scanning systems, and segmented cathode systems, where electron beam accelerators are related. A detailed description of the state of the art, and the most important pss parameters, can be found in Skelhorne, Electron Beam Pssing, in Chemistry and Technology of UV and EB formulation for Coatings, Inks and Paints, Vol. 1, 1991, SITA , London. Typical acceleration voltages are located in the range between 50 kV and 500 kV, preferably between 80 kV and 300 kV. The dispersion doses used vary between 5 to 150 kGy, in particular between 20 and 100 kGy. In a further preferred preparation pss, the oriented ASP is coated on a roller provided with a contact means. As a result of the contact medium it is possible to carry out the very rapid cooling of the ASP. As the contacting means, a material can also be used which has the ability to cause contact between the PSA and the roll surface, especially a material which fills the cavities between the backing material and the roll surface (e.g. on the surface of the roller, bubbles). To implement this technology, a rotating chill roll is coated with a contact means. In a preferred version the contact means chosen is a liquid, such as water, for example. Examples of suitable additives for water as the contact medium include alkyl alcohols such as ethanol, propanol, butanol, and hexanol, without wishing to be restricted in the alcohol section as a result of these examples. Also particularly advantageous are long-chain alcohols, polyglycols, ketones, amines, carboxylates, sulfonates., and similar. Many of these compounds decrease surface tension or raise conductivity. A decrease in surface tension can also be achieved by adding small amounts of nonionic and / or anionic and / or cationic surfactants to the contact medium. The simplest way to achieve this is by using commercial washing compositions or soap solutions, preferably at a concentration of a few g / 1 in water as the contact medium. Particularly suitable compounds are special surfactants which can be used even at low concentrations. Examples thereof include sulfonium surfactants (eg, β-di- (hydroxyalkyl) sulfonium salt), and also, for example, ammonium salts of ethoxylated nonylphenylsulfonic acid or block copolymers, especially diblock. At this point, reference can be made in particular to the state of the art under "surfactants" in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Relay, Wiley-VCH, Weinheim 2000. As a means of contact it is possible to use the aforementioned liquids previously, even without the addition of water, in each case alone or in combination with another. To improve the properties of the contact medium (for example, to increase the shear strength, reduce the transfer of surfactants or the like to the surface of the liner, and consequently possibilities for improved cleaning of the final product), salts, gels, and additives which increase the similar viscosity can also be advantageously added to the contact medium and / or to the adjuvants used. In addition, the roller can be microscopically smooth or it can have a surface with a low level of structuring. It has been found appropriate that the roller has a surface structure, especially a corrugated surface. This allows the wetting by the contact means to be improved. The process proceeds particularly with good effect if the roller is of controllable temperature, preferably in a range from -30 to 200 ° C, with particular preference from 5 ° C to 25 ° C. The contact means is preferably applied to the roller, although it is also possible to perform application without contact, by spraying, for example. To prevent corrosion, the roller is commonly coated with a protective coating. This coating is preferably selected so that it is effectively wetted by the contact medium. In general, the surface is conductive. It may also be more favorable, however, to coat it with one or more coatings of insulating or semi-conducting material. Where a liquid is used as the contact medium, an existing method is to rotate a second roller, which advantageously has a wettable or absorbent surface, through a bath containing the contact medium, the roller then becomes moistened or impregnated with the contact means and applies a film of this contact means by contact with the roller. The ASP oriented on the cooling roller provided with the contacting means is preferably immediately reticulated, then transferred onto the backing material. The characterization of the orientation within the acrylate ASPs is dependent on the coating process. The orientation can be controlled, for example, by the temperature of the die and coating temperature and also by the molecular weight of the polyacrylate ASP. The degree of orientation is freely adjustable through the opening width of the die. The thicker the ASP film expressed from the coating die, the greater the degree to which the adhesive can be stretched to a relatively thin ASP film in the backing material. This stretching operation can be freely adjusted not only by the freely adjustable die width but also by the mesh speed of the backed backing material. The intensity of UV irradiation, moreover, it also serves as an adjuster parameter for the degree of orientation. By raising the UV dose it is possible to reduce the degree of orientation. The intensity of irradiation therefore serves to vary the degree of crosslinking, to vary the technical adhesive properties, and to control the anisotropy. The orientation of the adhesive can be measured with a polarimeter, by infrared dichroism, or by using X-ray diffusion. It is known that the orientation in the acrylate ASPs in the non-crosslinked state is retained only for a few days. During rest or storage, the system relaxes and loses its preferential direction. As a result of crosslinking after coating, this effect can be suppressed significantly. The relaxation of the oriented polymer chains converges towards zero, and the oriented ASPs can be stored for a very long period of time without loss of their preferential direction. In addition to measuring the orientation by determination of? N (see Test B), the measurement of retraction in the free film (see Test D) is equally suitable for determining the orientation and anisotropic properties of the ASP. In addition to the processes described, orientation may also occur after coating. In this case, then, a stretchable backing material is preferably employed, with the ASP being stretched at the same time as the elongation. In this case it is also possible to use acrylate ASPs conventionally coated with solution or water. In a preferred version, then, this stretched ASP is in turn reticulated with UV radiation. The invention further provides the use of such pressure sensitive adhesives oriented for ASP tapes coated on one side or double side. The process of the invention is described later in the modeling examples.

Mode examples Test methods The following test methods have been used to evaluate the technical adhesive properties of the prepared ASPs. 180 ° Adhesion Strength Test (Test A) A strip, 20 mm wide, of an acrylate pressure sensitive adhesive coated on a polyester or siliconized release paper was applied to steel plates. Depending on the direction and stretched, the longitudinal or transverse specimens were attached to the steel plate. The ASP strip was pressed onto the substrate twice using a 2 kg weight. The adhesive tape was then immediately removed from the substrate at an angle of 180 ° and at 30 mm / min. The steel plates were washed twice with acetone and once with isopropanol. The results were reported in N / cm and averaged over three measurements. All measurements were conducted at room temperature under controlled climate conditions.

Measurement of birefringence (Test B) Version 1 Two crossed polaroid filters were placed in the sample beam of a Uvikon 910 spectrophotometer. The oriented acrylates were fixed between two notches. The trajectory length of the oriented sample was determined from preliminary experiments by means of thickness gauges. The sample thus prepared was placed in the measuring beam of the spectrophotometer with its direction of orientation deviated in each case by 45 ° from the optical axes of the two polaroid filters. The transmission, T, was then monitored for extra time by means of a resolved time measurement. The transmission data were then used to determine the birefringence according to the following relationship: T = sin2 (p x R), in which R is the delay and T is the transmission, defined as T = It / I0. With the delay R according to the following equation R = -An,? in which d is the sample thickness, this finally provides, the birefringence? n: n - with I = intensity T = transmission? = wavelength? n = birefringence R = delay.

Version 2 The birefringence was measured with an experimental procedure as analogously described in the Encyclopedia of Polymer Science, John Wiley & Sons, vol. 10, p. 505, 1987 as a circular polariscope. The light emitted by a diode solid-state laser pumped out of wavelength? = 532 nm was first linearly all polarized by a polarization filter and then circularly polarized using a? / 4 plate with? = 532 nm. The laser beam thus polarized was then passed through the oriented acrylate composition. Since the acrylate compositions are highly transparent, the laser beam is able to pass through the virtually unobstructed composition. Where the polymer molecules of the acrylate composition are oriented, this results in a change in the polarizability of the acrylate composition depending on the angle of observation (birefringence). As a result of this effect, the vector E of the circularly polarized laser beam undergoes a rotation about the axis of progression of the laser beam. After the sample was removed, the laser beam thus manipulated was passed through a second plate of? / 4 with? = 532 nm whose optical axis is deflected by 90 ° from the optical axis of the first plate of? / 4. This filter was followed by a second polarization filter whose polarization plane was also rotated 90 ° from that of the first polarization filter. Finally, the intensity of the laser beam was measured using a photosensor, and n was determined as described under version 1.

Determination of the gel fraction (Test C) After careful drying, the solvent-free adhesive samples were joined in a bag made of polyethylene nonwoven (Tyvek mesh). The gel index was determined from the difference in the sample weights before and after extraction with toluene.

Measurement of retraction ^ (Test D) Strips with a width of at least 30 mm and a length of 20 cm were cut parallel to the coating direction of the adhesive substance. To coating weights of 50 g / m2, 8 strips were laminated one to another, to produce comparable layer thicknesses. The specimen obtained in this form was then cut to a width of exactly 20 mm and at each end it was overlapped with strips of paper, with a spacing of 15 cm. The test specimen thus prepared was then suspended vertically at room temperature and the change in length was monitored for extra time until no additional contraction of the sample could be found. The initial length reduced by the final value was then reported, in relation to the initial length, as the retraction, in percent. To measure the orientation after a long time, the coated and oriented pressure sensitive adhesives were stored in the form of samples for a prolonged period and then analyzed.

Gel permeation chromatography CPG (Test E) Average molecular weight Mw and polydispersity PD were determined by gel permeation chromatography. The eluent used was THF containing 0.1% by volume of trifluoroacetic acid. The measurement was made at 25 ° C. The pre-column used was PSS-SDV, 5 μ, 103 Á, DI 8.0 mm x 50 mm. The separation was carried out using the columns PSS-SDV, 5 μ, 103 and also 105 and 106 A each with DI 8.0 mm x 300 mm. The concentration of the sample was 4 g / 1, the flow rate 1.0 ml per minute. The measurement was made against PMMA standards.

Preparation of the samples The preparation processes described below differ essentially in the solvent mixtures used. The polymerization was carried out in particular in a mixture of acetone and isopropanol, with an isopropanol fraction increasing from Example 1 to Example 4.

Example 1 A conventional 10 L reactor for radical polymerizations was charged with 60 g of acrylic acid, 1800 g of 2-ethylhexyl acrylate, 20 g of maleic anhydride, 120 g of N-isopropylacrylamide and 666 g of acetone / isopropanol (98/2). After the nitrogen gas had been passed for 45 minutes with stirring, the reactor was heated to 58 ° C and 0.6 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. The external heating bath was then heated to 70 ° C and the reaction was carried out constantly at this external temperature. After a reaction time of 45 minutes, 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added. After a reaction time of 70 minutes, an additional 0.2 g of Vazo 52® from DuPont in solution in 10 g of acetone were added, and after a reaction time of 85 minutes 0.4 g of DuPont Vazo 52® in solution in 400 g of acetone / isopropanol (98/2). After 1:45 h, 400 g of acetone / isopropanol (98/2) were added. After 12 h, 1.2 g of 2, 2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. After 5, 6 and 7 h, in each case 2 g of dicyclohexyl dioxycarbonate (Perkadox 16® from Akzo Nobel) in solution in each case in 20 g of acetone were added. After a reaction time of 7 h, the mixture was diluted with 600 g of acetone / isopropanol (98/2).

After a reaction time of 24 h, the reaction was terminated by cooling to room temperature. After cooling, 10 g of isopropylthioxanthone (Speedcure ITX® from Rahn) were added and completely dissolved.

Example 2 A conventional 10 L reactor for radical polymerizations was charged with 60 g of acrylic acid, 1800 g of 2-ethylhexyl acrylate, 20 g of maleic anhydride, 120 g of N-isopropylacrylamide and 666 g of acetone / isopropanol ( 97/3). After the nitrogen gas had been passed for 45 minutes with stirring, the reactor was heated to 58 ° C and 0.6 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. The external heating bath was then heated to 70 ° C and the reaction was carried out constantly at this external temperature. After a reaction time of 45 minutes, 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added. After a reaction time of 70 minutes, an additional 0.2 g of Vazo 52® from DuPont in solution in 10 g of acetone were added, and after a reaction time of 85 minutes 0.4 g of DuPont Vazo 52® in solution in 400 g of acetone / isopropanol (97/3). After 1:45 h, 400 g of acetone / isopropanol (97/3) were added. After 12 h, 1.2 g of 2, 2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. After 5, 6 and 7 h, in each case 2 g of dicyclohexyl dioxycarbonate (Perkadox 16® from Akzo Nobel) in solution in each case in 20 g of acetone were added. After a reaction time of 6 h, the mixture was diluted with 600 g of acetone / isopropanol (97/3). After a reaction time of 24 h, the reaction was terminated by cooling to room temperature. After cooling, 10 g of isopropylthioxanthone (Speedcure ITX® from Rahn) were added and completely dissolved.

EXAMPLE 3 A conventional 10 L reactor for radical polymerizations was charged with 60 g of acrylic acid, 1800 g of 2-ethylhexyl acrylate, 20 g of maleic anhydride, 120 g of N-isopropylacrylamide and 666 g of acetone / isopropanol ( 95/5). After the nitrogen gas had been passed for 45 minutes with stirring, the reactor was heated to 58 ° C and 0.6 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. The external heating bath was then heated to 70 ° C and the reaction was carried out constantly at this external temperature. After a reaction time of 45 minutes, 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added. After a reaction time of 70 minutes, an additional 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added, and after a reaction time of 85 minutes 0.4 g of DuPont Vazo 52® in solution in 400 g of acetone / isopropanol (95/5). After 2 h, 1.2 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 400 g of acetone / isopropanol (95/5) were added. After a reaction time of 4 h, the mixture was diluted with 400 g of acetone / isopropanol (95/5). After 5, 6 and 7 h, in each case 2 g of dicyclohexyl dioxycarbonate (Perkadox 16® from Akzo Nobel) in solution in each case in 20 g of acetone were added. After a reaction time of 5:30, 7, and 8:30 h, the mixture was diluted in each case with 400 g of acetone / isopropanol (95/5). After a reaction time of 24 h, the reaction was terminated by cooling to room temperature. After cooling, 10 g of isopropylthioxanthone (Speedcure ITX® from Rahn) were added and completely dissolved.

EXAMPLE A conventional 10 L reactor for radical polymerizations was charged with 60 g of acrylic acid, 1800 g of 2-ethylhexyl acrylate, 20 g of maleic anhydride, 120 g of N-isopropylacrylamide and 666 g of acetone / isopropanol (93 / 7). After the nitrogen gas had been passed for 45 minutes with stirring, the reactor was heated to 58 ° C and 0.6 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. The external heating bath was then heated to 70 ° C and the reaction was carried out constantly at this external temperature. After a reaction time of 45 minutes, 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added. After a reaction time of 70 minutes, an additional 0.2 g of DuPont Vazo 52® in solution in 10 g of acetone were added, and after a reaction time of 85 minutes 0.4 g of DuPont Vazo 52® in solution in 400 g of acetone / isopropanol (93/7). After 2 h, 1.2 g of 2,2'-azoisobutyronitrile (AIBN) in solution in 20 g of acetone were added. After 2:10 h, the mixture was diluted with 400 g of acetone / isopropanol (93/7). After 5, 6 and 7 h, in each case 2 g of dicyclohexyl dioxycarbonate (Perkadox 16® from Akzo Nobel) in solution in each case in 20 g of acetone were added. In addition, after a reaction time of 5, 7, and 8:30 h, the mixture was diluted in each case with an additional 400 g of acetone / isopropanol (93/7). After a reaction time of 24 h, the reaction was terminated by cooling to room temperature. After cooling, 10 g of isopropylthioxanthone (Speedcure ITX® from Rahn) were added and completely dissolved.

Coating The polymers prepared according to the above examples were freed from the solvent in a vacuum drying cabinet. A vacuum of 10 torr was applied and the products were slowly heated to 100 ° C. The thermoimpregnating ASP was then coated using a Prois fusion die. The coating temperature was 160 ° C. The coating took place at 20 m / min on a Laufenberg siliconised release paper. The die opening width was 200 μm. After the coating operation, the amount of pressure sensitive adhesive in the release paper was 50 g / m2. The coating was performed by applying a pressure of 6 bar to the melting die so that the hot-melt ASP can be pressed through the die.

Crosslinking UV crosslinking was performed, unless otherwise described, at room temperature 15 minutes after coating. UV crosslinking was performed using an Eltosch coating unit. The UV lamp used was a medium pressure mercury lamp with an intensity of 120 W / cm2. The mesh speed was 20 m / min, and the crosslinking was performed with complete radiation. To vary the dose of UV irradiation, the ASP tape was irradiated with a variable number of steps. The UV dose was linearly raised with the number of steps. The doses of Uv were determined using the Power-Puck® from Eltosch. For example, for 2 steps a UV dose of 0.8 J / cm2 was measured, for 4 steps 1.6 J / cm2, for 8 steps 3.1 J / cm2, and for 10 steps 3.8 J / cm2.

Results First of all the molecular weights of the acrylate ASPs polymerized according to Examples 1 to 4 by polymerization of free radicals in different solvent mixtures were investigated by means of gel permeation chromatography in accordance with Test E. The results they are summarized in Table 1.

Table 1: Molecular weights of polymers by Test E After polymerization, the acrylate ASPs of Examples 1-4 were - as described in the 'Coating' section - solvent-free and processed from the melt. The coating was performed through a melting die at 160 ° C, on a release paper which was left at room temperature. All the adhesives were processable by heat impregnation in terms of temperature stability and flow viscosity. After 15 minutes, UV crosslinking was performed with different doses. To determine the anisotropic properties (orientation), first of all the shrinkage in the free film was measured in accordance with Test D. To determine the degree of crosslinking, Test C was conducted, and therefore the gel fraction was determined . The gel fraction indicates the percentage amount of the crosslinked polymer. The results are summarized in Table 2.

Table 2: Table 2 indicates that a large number of oriented ASPs can be prepared by the process of the invention. The degree of orientation can be very different. Accordingly, it is possible to prepare polyacrylates having a retraction of 5% or having a retraction of 57%. In addition, examples 1 and 4 show that by means of the applied UV dose it is possible to control the retraction and therefore also the orientation. From the figures it can be deduced that the shrinkage decreases when the UV dose rises, and at the same time there is an increase in the gel index. This in turn influences the technical adhesive properties, so that by means of the applied UV dose it is possible to control not only the technical adhesive properties but also the degree of orientation. To confirm the influence of the degree of crosslinking on the technical adhesive properties, the adhesion strengths were measured in accordance with Test A. The results are listed in Table 3.

Table 3 RA = resistance to instantaneous adhesion in steel For use as a targeted ASP, retention of orientation is essential. For a number of examples, therefore, retraction was measured in accordance with Test D after storage for one month at room temperature. The figures are described in Table 4.

Table 4: From table 4 it can be deduced that in some cases the shrinkage decreases, but that the percentage changes are very small. All the represented examples still have a retraction even after storage for 30 days, exhibit very little relaxation if any, and continue to have anisotropic properties. The orientation within the acrylate ASPs was also determined by quantifying the birefringence. The refractive index n of a medium is given by the ratio of the speed of light in a vacuum, c0, at the speed of light in the medium in question, c (n = co / c), n being a function of the wavelength of the respective light. As a measure of the orientation of the pressure sensitive adhesive, use is made of the difference? N between the refractive index measured in a preferential direction (direction of stretch, direction of the DM machine), nDM, and the refractive index measured in an address perpendicular to the preferential direction (cross direction, DC), nDC. In other words,? N = nDM - nDC; This figure is obtainable through the measurements described in Test B. All the examples show the orientation of the polymer chains. The n values found are listed in Table 5.

Table 5: The orientation within the acrylic ASPs was therefore found for the samples measured, by the measurement of birefringence. Taking into account the results, it is possible to make new products of pressure sensitive adhesive tape which make use of this described effect. When adhesive joints are made in wiring harnesses in the engine compartment, the temperature differences which occur are in some cases very high. Therefore it is preferred to use acrylate ASP tapes for such applications. In contrast to a conventional commercial acrylate adhesive, an oriented adhesive will shrink on heating, by the measured and described shrinkage, and will thereby form a firm bond of the cables and the insulating nonwoven. The advantages are retained in relation to the oriented natural rubber adhesives, these advantages are, for example, stability at a higher temperature in a large temperature window, and stability to improved aging. The retraction effect can also be used in the case of adhesive joints on convex surfaces. By applying a tape of pressure-sensitive adhesive to a convex surface, with subsequent heating, the ASP tape contracts and thus forms the convexity of the substrate. In this way, the adhesive bond is greatly facilitated and the number of air inclusions between substrate and tape is greatly reduced. The ASP is able to exert its optimum effect. This feature can be further assisted by a oriented carrier material. After application, under heating, both the carrier material and the oriented ASP contract, so that the joints in the convexity are completely free of tension. The pressure sensitive adhesives of the invention also offer a wide range of applications which utilize the advantages of low stretch in the longitudinal direction and the possibility of retraction in an advantageous manner. The property of pre-stretching of pressure sensitive adhesives can also be used to resist the effect. An additional exemplary field of use for such highly oriented acrylate ASPs is that of the removable two-sided adhesive bonds. Different from the products that can be removed conventionally, the oriented ASP is already pre-stretched to several 100%, so that to remove the double sided union the acrylic ASP needs only to be stretched by a little more percentage in the direction of stretch (DM). With particular preference, these products are produced as acrylate adhesive substances with a film thickness of several 100 μm. Straight acrylates are used with particular preference. When compared to conventional systems (multi-layer systems, SIS adhesives), the oriented acrylate strips are transparent, stable towards aging, cheap to manufacture. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (25)

CLAIMS Having described the invention as above, the contents of the following claims are claimed as property:

1. Permanently oriented pressure sensitive adhesive comprising an acrylate-based UV crosslinked polymer, characterized in that i.) Is synthesized in a mass fraction of at least 50% from at least one acrylic monomer according to the general formula (I) ) wherein Ra is hydrogen (H) or a methyl group (CH3) and R2 is hydrogen (H) or a saturated, branched or unbranched Cx to C30 hydrocarbon radical, which may be optionally substituted by a functional group, and ii.) is composed in a mass fraction from 0.05% and 1% of a UV-crosslinked photoinitiator, the pressure-sensitive adhesive, in the form of a film applied as a melt (adhesive substance), which has a preferential direction which is characterized in the free film by a retraction of at least 3% in relation to an original stretch of the film in the preferential direction.

2. Pressure sensitive adhesive according to claim 1, characterized by a refractive index measured in a preferential direction, nDM, which is greater than a refractive index measured in a direction perpendicular to the preferential direction, nDC, the difference? n = nDM - nDC is at least 1 »10" 6.

3. Pressure sensitive adhesive according to claim 1 or 2, characterized by an average molecular weight of the acrylate polymer of at least 200000 g / mol.

Pressure sensitive adhesive according to any of the preceding claims, characterized in that the radical R2 of at least one acrylic monomer according to the general formula (I) is selected from the group of hydrocarbon radicals of C4 to Ci4 saturated, branched and not branched, in particular C4 to C9 hydrocarbon radicals

5. Pressure sensitive adhesive according to any of the preceding claims, characterized in that at least u An acrylic monomer according to the general formula (I) is selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylate. of n-pentyl, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate and behenyl acrylate, and also branched isomers thereof, especially isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate and isooctyl methacrylate.

6. Pressure sensitive adhesive according to any of the preceding claims, characterized in that R2 is a substituted or unsubstituted, bridged or unbridged cycloalkyl group and that in particular at least one acrylic monomer of the formula (I) is selected from the group consisting of group consisting of cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantyl acrylate.

7. Pressure sensitive adhesive according to any of the preceding claims, characterized in that the acrylate polymer is synthesized from at least one additional vinyl or acrylic comonomer.

8. Pressure sensitive adhesive according to any of the preceding claims, characterized in that at least one monomer of the formula (I) and / or at least one comonomer carries a functional group selected from the group consisting of carboxyl group, sulfonic acid , phosphonic acid, hydroxyl, lactam and lactone, N-substituted amide, N-substituted amine, carbamate, epoxy, thiol, alkoxy, cyano, ether or halide.

9. Pressure-sensitive adhesive according to any of the preceding claims, characterized in that at least one comonomer is selected from the group of N-alkyl-substituted amides, in particular from the group consisting of N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N-tere-butylacrylamide, N-vinylpyrrolidone, N-vinyl lactam, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, N-methylolacrylamide, N-methylol-methacrylamide, N - (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide and N-isopropylacrylamide.

10. Pressure sensitive adhesive according to any of the preceding claims, characterized in that at least one comonomer is selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride. , itaconic anhydride, itaconic acid, glycidyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinylacetic, tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid, and dimethylacrylic acid.

Pressure sensitive adhesive according to any of the preceding claims, characterized in that at least one comonomer is selected from the group consisting of vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds containing aromatic rings and vinyl compounds containing heterocycles in position a of the group consisting of vinyl acetate, vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

12. Pressure sensitive adhesive according to any of the preceding claims, characterized in that at least one comonomer is selected from the group consisting of vinyl aromatic compounds, in particular having aromatic Ci to C18 nuclei with or without heteroatoms, especially styrene and derivatives of styrene, 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenylmethacrylate, t-butylphenyl acrylate, methacrylate t-butylphenyl, 4-biphenylyl acrylate, 4-biphenylyl methacrylate, 2-naphthyl acrylate and 2-naphthyl methacrylate.

13. Pressure sensitive adhesive according to any of the preceding claims, characterized in that the acrylate polymer is additionally synthesized from at least one crosslinker which is selected in particular from the group consisting of difunctional or polyfunctional acrylates and / or methacrylates, difunctional or polyfunctional isocyanates and difunctional or polyfunctional epoxides.

Pressure-sensitive adhesive according to any of the preceding claims, characterized in that the resins and / or other additives are added to the pressure-sensitive adhesive, especially aging inhibitors, light stabilizers, ozone protectants, fatty acids, plasticizers, nucleators, blowing agents, accelerators and / or fillers.

15. Process for preparing a pressure sensitive adhesive oriented according to any of claims 1 to 14, characterized in that it comprises the steps of (a) polymerizing at least one acrylic monomer according to the general formula (I), wherein R x is hydrogen (H) or a methyl group (CH 3) and R 2 is hydrogen (H) or a saturated, branched or unbranched C to C 30 hydrocarbon radical which is optionally substituted by a functional group, (b) coating the acrylic polymer of the melt to form a film, in the course of which an orientation occurs in the pressure sensitive adhesive, and (c) crosslinking the film by means of UV radiation.

16. Process in accordance with the claim 15, characterized in that the coating takes place via a roller, through a melting die or through an extrusion die.

17. Process according to claim 15 or 16, characterized in that after the coating operation the film is subjected to a stretching operation.

18. Process according to any of claims 15 to 17, characterized in that prior to the coating operation the solvent residues of the polymerization are removed at least partially, in particular in a concentrating extruder.

19. Process according to any of claims 15 to 18, characterized in that the relaxation time which elapses between the coating and crosslinking is as small as possible.

Process according to claim 19, characterized in that the relaxation time reaches no more than 60 minutes, in particular no more than 3 minutes, preferably no more than 5 seconds.

21. Process according to any of claims 15 to 20, characterized in that a degree of orientation of the pressure-sensitive adhesive is controlled by the UV dose, by the coating temperature, the molecular weight of the polymer, the stretching ratio and / or the relaxation time between the coating and crosslinking.

22. Process according to any of claims 15 to 21, characterized in that the cooling is carried out during the coating.

23. Process according to any of claims 15 to 22, characterized in that the polymerization is carried out in the presence of a crosslinker which is selected in particular from the group consisting of difunctional or polyfunctional acrylates and / or methacrylates, difunctional or polyfunctional isocyanates. and difunctional or polyfunctional epoxides. 2 .

Process according to any of claims 15 to 23, characterized in that for the crosslinking the pressure sensitive adhesive comprises a UV initiator.

25. Use of a pressure-sensitive adhesive according to any one of claims 1 to 14 as a one-side or two-side adhesive layer for a single-sided or double-sided pressure-sensitive adhesive tape.