Layer structure for winding an adhesive tape into a reel, reel and method for producing a reel

Abstract

A layered structure for winding an adhesive tape into a spool, comprising: - an adhesive tape (1) comprising at least one outer pressure-sensitive adhesive layer (PSA-A, 3); - a release liner (RL, 2) resting on the outer pressure-sensitive adhesive layer (PSA-A, 3); and - an interliner (IL, 4) resting on the side of the adhesive tape (1) opposite the outer pressure-sensitive adhesive layer (PSA-A, 3), the side (6) of which interliner is provided with an adhesive finish; characterized in that all layers of the layered structure are flush and the interliner (IL, 4) is not firmly bonded to the adhesive tape.

Description

[0001] The invention lies in the technical field of adhesive tapes, which are widely used for the temporary or permanent bonding of a wide variety of substrates. More specifically, the invention relates to a layered structure comprising an adhesive tape and two liners, allowing the adhesive tape to be easily wound into a spool.

[0002] For the large-scale or automated use and processing of adhesive tapes, for example in the automotive industry, preference is often given to an adhesive tape that is available in virtually endless lengths. Accordingly, the adhesive tape is conveniently delivered from the adhesive tape manufacturer to the user in a type of container that can accommodate extremely long lengths of adhesive tape. With the most common type of container, the so-called pan-cake, which is produced by winding the adhesive tape around a core without axial feed, so that the resulting roll has the same width as the adhesive tape, longer lengths and narrower tape widths cannot generally be achieved. Alternatively, the "spool" type of container, sometimes also called a "level wound spool" or simply "spool", has been available for decades.Spooling involves winding with an axial feed rate that is usually uniform across the spool width and whose orientation reverses at the designated spool edges, i.e., at the transition to the next layer of turns. For terminology related to spooling technology, please refer to the electronic textbook entitled "Technical Information on the Principles of Spooling" by Neal Rothwell, published online since July 1, 2001, by Double R Controls LTD, England.

[0003] The starting material for adhesive tape production is usually a very wide roll, e.g., 200 to 600 mm (master roll), from which several individual strips are produced using a cutting unit in the width required for the intended use of the adhesive tape. The spooling process therefore typically consists of the following steps: a) Unwinding the parent roll; b) producing a plurality of substantially parallel individual strips (“ribbons”) of the required width; c) Winding the individual ribbons on a corresponding number of winding stations to form cross-wound bobbins.

[0004] The adhesive tapes to be wound up are usually covered on one side with a release liner and, if necessary, also with a so-called interliner on the remaining side, which offers additional protection during winding and subsequent storage on a spool. In the case of single-sided adhesive tapes with no or low side edge tack, the interliner is, if required, conveniently laminated to the unwound adhesive tape in front of the cutting unit in the same width. The adhesive tape, which is covered with liner on both sides, is then cut. This then forms a layered structure with flush layers and can be wound up on a spool. Typical adhesive tapes with no or low side edge tack are, for example, those consisting of a PE foam core and a pressure-sensitive adhesive layer on each of the two main sides of the cross-section of the PE foam. The two secondary sides of the adhesive tape cross-section represent the side edges.The foamed PE has no adhesive or tack, so the side edges of the adhesive tape cannot or hardly stick together.

[0005] Typical adhesive tapes with higher side edge tack are, for example, foamed pressure-sensitive adhesives (single-layer foam adhesive tapes) or multi-layer foam adhesive tapes with a foamed acrylate-based core and additional pressure-sensitive adhesive layers.

[0006] For adhesive tapes with pronounced side edge tack, the interliner must usually be wider than the adhesive tape and therefore protrudes on at least one side, usually on both sides. This overhang prevents the side edges of the adhesive tape wound onto the spool from sticking together, a process also known as "blocking". However, the overhang also means that the interliner cannot be laminated before cutting, but must only be cut to the target width afterwards and applied separately to each tape. This represents a significant logistical and technical overhead, requiring additional stations on the spooler and reducing the spooling speed. Due to the more complex and slower process, spooling adhesive tapes with side edge tack is significantly more expensive than those without.

[0007] There is no shortage of attempts in the state of the art to find optimized solutions, especially for adhesive tapes with pronounced side edge stickiness.

[0008] EP 3 216 838 A1 describes a composite system comprising - an adhesive tape (A) comprising a pressure-sensitive adhesive layer and a heat-activatable adhesive layer; - a release liner lying on the pressure-sensitive adhesive layer of the adhesive tape (A); and - an adhesive tape (B) comprising a carrier layer, a release layer on one side of the carrier layer, and a pressure-sensitive adhesive layer on the side of the carrier layer opposite the release layer; wherein the pressure-sensitive adhesive layer of the adhesive tape (B) is in direct contact with the heat-activatable adhesive layer of the adhesive tape (A), and the adhesive tape (B) has an adhesive strength of maximum 5 N / cm to the heat-activatable adhesive layer of the adhesive tape (A), determined according to EN 1939:2003. The sticky side of the interliner (adhesive tape (B)) is oriented toward the heat-seal layer of the adhesive tape (A) in order to generate adhesion between the interliner and the adhesive tape. The interliner is described as being wider than the adhesive tape.

[0009] EP 2 746 356 A1 discloses a roll of acrylic foam tape comprising an acrylic foam tape, which in turn comprises an acrylic foam with opposing first and second major surfaces. The first major surface comprises a pressure-sensitive adhesive protected by a first liner; the second major surface comprises a heat-activatable adhesive. The acrylic foam tape is wound in helical turns around a core to form a cheese, a second liner is disposed on the heat-activatable adhesive and extends over at least one edge of the second major surface. The acrylic foam is thermally cross-linked.

[0010] DE 10 2017 223 768 A1 describes a splittable liner suitable for covering an adhesive tape; a double-sided adhesive tape covered with this liner; and a reel with such an adhesive tape wound thereon. The liner is intended to extend beyond at least one of the two edges of the actual adhesive tape. This design is intended to reduce the tendency for wrinkling during winding and unwinding of a thick, preferably foamed adhesive tape and to stabilize the reel.

[0011] EP 1 035 185 A2 relates to a multi-layer, cross-wound spool of carrierless, double-sided pressure-sensitive adhesive transfer tape. The spool consists of a pressure-sensitive layer of an adhesive film, the layers of which are wound onto a spool body with a removable liner and an additional intermediate layer, forming a spool. The intermediate liner has a weak pressure-sensitive adhesive at least on the reverse side and is wider than the adhesive tape.

[0012] EP 2 039 506 A1 describes a release liner made of a single-layer or laminated film comprising a release layer having an adhesive strength (23 °C) on an acrylate substrate of 0.02 to 0.5 N / 20 mm. Also described is an adhesive tape in which such a release liner adheres to one of its pressure-sensitive adhesive surfaces, the width of the release liner being greater than that of the pressure-sensitive adhesive surface.

[0013] WO 2017 / 205444 A1 discloses a double-sided adhesive tape used for applications such as attaching front glass for mobile devices. A core layer of the double-sided adhesive tape is produced by adding an acrylic elastomer, which is free of carbon-carbon double bonds and simultaneously readily miscible with an acrylic resin, to one or more acrylic monomers and curing, which can improve the impact resistance of the finished double-sided adhesive tape. A double-sided adhesive tape is disclosed, which consists of a foamed acrylic rubber layer, a substrate film layer based, for example, on polyester, arranged thereon, and poly(meth)acrylate adhesive layers arranged on the respective free sides of these two layers. The adhesive tape may additionally contain a release liner.

[0014] DE 10 2008 031 356 A1 discloses a double-sided adhesive tape for bonding electronic components, comprising two outer layers of adhesive, a carrier layer made of a foamed polymer material, a carrier layer laminated to the foamed carrier layer in the form of a film made of a polymer material, characterized in that the foam carrier layer has a thickness of not more than 400 µm and the film carrier layer has a thickness of not more than 40 µm.

[0015] DE 10 2015 112 206 A1 discloses an assembly tape for the printing industry. The adhesive tape comprises a foam layer, a reinforcing carrier layer arranged on the foam layer, and a first adhesive layer arranged on the carrier layer. The carrier layer has a tensile force of at least 1 N at 1% elongation in the longitudinal direction and, at the same time, a tear propagation resistance of more than 0.2 N in the longitudinal and / or transverse direction. An adhesive tape is disclosed, composed of a first adhesive layer covered with a cover layer, a carrier layer reinforced with PET fibers, a polyacrylate foam layer, and a second adhesive layer, wherein an adhesion promoter layer can be provided between the layers. Furthermore, it is disclosed that the adhesive tape can be wound into a roll.

[0016] US 2010 / 0 119 803 A1 discloses a roll of pressure-sensitive adhesive tape comprising a spool and a double-sided pressure-sensitive adhesive tape spirally wound around it. Helically winding double-sided adhesive tapes with a release liner onto a spool is described as advantageous for increasing the wound adhesive tape length for a given spool core dimension.

[0017] Other double-sided pressure-sensitive adhesive tapes are described, for example, in DE 103 14 898 A1, DE 103 47 024 A1, US 2014 / 0 213 716 A1 and EP 2 695 925 A1.

[0018] The object of the invention was to provide a structure with which an adhesive tape can be wound into a reel in a simple manner and with little equipment expenditure. A first and general object of the invention, with which this object is achieved, is a layer structure for winding an adhesive tape into a reel, which - an adhesive tape (1) comprising at least one outer pressure-sensitive adhesive layer (PSA-A, 3); - a release liner (RL, 2) applied to the outer pressure-sensitive adhesive layer (PSA-A, 3); and - an interliner (IL, 4) resting on the side of the adhesive tape (1) opposite the outer pressure-sensitive adhesive layer (PSA-A, 3), at least the side of which facing away from the adhesive tape is provided with an adhesive; and which is characterized in that all layers of the layer structure are flush and the interliner (IL, 4) is not firmly bonded to the adhesive tape. Such a structure enables, on the one hand, a stable position of the individual sections or layers of the adhesive tape provided with the liners on the spool even under external or internal loads and, on the other hand, can be produced in such a way that the interliner (IL, 4) can be laminated to the adhesive tape unwound from the parent roll during the production of the parent roll or in the spooler, and thus before cutting.This eliminates the need to separately laminate the interliner, cut to the target width, onto each individual adhesive tape cut to the target width. Instead, the layer structure can be provided with the master roll, cut to the target width, and then immediately wound onto a spool. In addition, the pressure-sensitive adhesive fixation of the sections or layers allows for the production of a dimensionally stable spool even at low winding tensions, allowing the adhesive tape to be wound very gently and without crushing, preventing sticking between sections despite the lack of interliner width.

[0019] An adhesive tape is commonly understood as a strip-like structure with a pressure-sensitive adhesive finish, which may or may not have a carrier material. The adhesive tape with the layered structure according to the invention comprises at least one outer pressure-sensitive adhesive layer. Furthermore, the structure of the adhesive tape is fundamentally arbitrary. The adhesive tape can comprise one or more carrier materials or carrier layers, which can consist of all common materials, in particular films or foams. The adhesive tape can also comprise any functional layers, e.g., barrier layers.

[0020] The expression “comprises at least one outer layer of pressure-sensitive adhesive” also includes an adhesive tape that consists of only a single layer of pressure-sensitive adhesive (transfer adhesive tape).

[0021] In accordance with the object of the invention, the layer structure according to the invention and thus also the adhesive tape can preferably be wound up into a spool, ie the adhesive tape is preferably correspondingly deformable and sufficiently dimensionally stable so that when the individual layers are wound over one another, the layers do not squeeze out or slip in such a way that the character of an adhesive tape is lost.

[0022] For the purposes of the invention, a pressure-sensitive adhesive is understood, as is common parlance, to be a substance that is permanently tacky and adhesive, at least at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and remains adhered there, whereby the pressure to be applied and the duration of this pressure are not defined in more detail. In general, however, depending on the exact type of pressure-sensitive adhesive and the substrate, the temperature, and the humidity, the application of short-term, minimal pressure, which does not go beyond a light touch for a brief moment, is sufficient to achieve the adhesion effect; in other cases, a longer exposure period of higher pressure may be necessary.

[0023] Pressure-sensitive adhesives have special, characteristic viscoelastic properties that lead to their permanent tack and adhesive strength. They are characterized by the fact that, when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The respective proportions of both processes are in a specific relationship to each other, depending on the precise composition, structure, and degree of crosslinking of the pressure-sensitive adhesive, as well as the speed and duration of the deformation and the temperature.

[0024] The viscous flow component is necessary to achieve adhesion. Only the viscous components, often caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high pressure-sensitive adhesion (also referred to as tack or surface stickiness) and thus often to high adhesion. Highly cross-linked systems, crystalline, or glass-like polymers, are generally not or at least only slightly pressure-sensitive due to the lack of flowable components.

[0025] The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transfer of forces acting on an adhesive bond. They ensure that an adhesive bond can sufficiently withstand continuous loading, for example, in the form of permanent shear stress, over an extended period of time.

[0026] For a more precise description and quantification of the degree of elastic and viscous components as well as the relationship between the components, the storage modulus (G') and loss modulus (G"), which can be determined using Dynamic Mechanical Analysis (DMA), are used. G' is a measure of the elastic component, G'' a measure of the viscous component of a material. Both parameters depend on the deformation frequency and the temperature.

[0027] These parameters can be determined using a rheometer. The material under test is subjected to sinusoidal oscillating shear stress, for example, in a plate-on-plate arrangement. Shear stress-controlled devices measure the deformation as a function of time and the temporal offset of this deformation relative to the application of the shear stress. This temporal offset is referred to as the phase angle δ.

[0028] The storage modulus G' is defined as follows: G' = (τ / γ) · cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G'' is: G'' = (τ / γ) · sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector).

[0029] A mass is considered to be a pressure-sensitive adhesive and is defined as such in the sense of the invention in particular if at 23 °C in the deformation frequency range of 10 0 up to 10 1 rad / sec both G' and G'' are at least partly in the range of 10 3 up to 10 7 Pa. “Partially” means that at least a section of the G' or G'' curve lies within the window defined by the deformation frequency range of 10 0 up to and including 10 1 rad / sec (abscissa) and the range of G' and G'' values ​​from 10 3 up to and including 10 7 Pa (ordinate) is spanned.

[0030] The adhesive tape with the layered structure according to the invention can comprise one or two outer pressure-sensitive adhesive layers, i.e. it can consist of just a single pressure-sensitive adhesive layer and thus be in the form of a so-called transfer adhesive tape, or it can have a pressure-sensitive adhesive layer on only one or both sides of a carrier material and thus be designed as a single- or double-sided adhesive tape. It is also possible for the carrier material itself to be pressure-sensitively adhesive, so that an adhesive tape provided with an additional pressure-sensitive adhesive layer on only one side can also be designed to be double-sided adhesive. In addition, the adhesive tape can also have one or more internal pressure-sensitive adhesive layers which serve to bond other layers present in the structure of the adhesive tape to one another.

[0031] The design of the outer pressure-sensitive adhesive layer (PSA-A) and any additional outer pressure-sensitive adhesive layer present is also fundamentally arbitrary, provided that it does not conflict with the purpose of the invention.

[0032] In one embodiment, the adhesive tape comprises a foam layer. A “foam layer” or “foamed layer” is understood to be a layer that comprises a matrix material and a plurality of cavities, such that the density of the foam is reduced to a technically usable extent compared to the density of the pure matrix material. In particular, a foam in adhesive tapes is a continuous polymer matrix filled with air / gas bubbles without their own shell or with their own shell - e.g. with expanded polymer microballoons and / or hollow glass spheres - such that the resulting foam has a density of e.g. 100 to 900 g / L. Foamed layers often give adhesive tapes particularly advantageous properties, e.g. higher adhesive strengths on uneven substrates and the ability to absorb shocks as well as to compensate for different thermally induced expansions and gap tolerances.On the other hand, adhesive tapes with foam layers are particularly susceptible to the phenomenon of side edge stickiness, so that the advantages of the layer structure according to the invention with regard to the production of wound adhesive tape are particularly evident here.

[0033] The matrix material of the foam layer preferably comprises at least one poly(meth)acrylate, at least one synthetic rubber, natural rubber, and / or a mixture of two or more of these polymers; particularly preferably, the matrix material comprises at least one poly(meth)acrylate and / or at least one synthetic rubber.

[0034] A "poly(meth)acrylate" is understood to mean a polymer obtainable by radical polymerization of acrylic and / or methacrylic monomers and, optionally, other copolymerizable monomers. In particular, a "poly(meth)acrylate" is understood to mean a polymer whose monomer base consists of at least 50 wt.% acrylic acid, methacrylic acid, acrylic esters, and / or methacrylic esters, with acrylic esters and / or methacrylic esters being present at least proportionally, preferably at least 30 wt.%, based on the total monomer base of the polymer in question.

[0035] In one embodiment, the foam layer contains poly(meth)acrylate in a total amount of 40 to 70 wt. %, preferably in a total amount of 45 to 60 wt. %, based in each case on the total weight of the foam layer. In another embodiment, the foam layer contains poly(meth)acrylate in a total amount of at least 90 wt. %, preferably at least 95 wt. %, based in each case on the total weight of the foam layer. A (single) poly(meth)acrylate or multiple poly(meth)acrylates may be present. In particular, the foam layer is based on poly(meth)acrylate.

[0036] The glass transition temperature of the poly(meth)acrylate of the foam layer is preferably < 0 °C, more preferably between -20 and -50 °C. The glass transition temperature of polymers or polymer blocks in block copolymers is determined according to the invention by means of dynamic scanning calorimetry (DSC), with glass transitions being detected as steps in the thermogram.

[0037] In one embodiment, the poly(meth)acrylate of the foam layer contains at least one partially polymerized, functional monomer that is preferably reactive with epoxy groups to form a covalent bond. The partially polymerized, functional monomer that is particularly preferably reactive with epoxy groups to form a covalent bond particularly preferably contains at least one functional group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxy groups, and amino groups; in particular, it contains at least one carboxylic acid group. Most preferably, the poly(meth)acrylate contains partially polymerized acrylic acid and / or methacrylic acid. All of the aforementioned groups exhibit reactivity with epoxy groups, whereby the poly(meth)acrylate is advantageously amenable to thermal crosslinking with incorporated epoxides.

[0038] In a further embodiment, the poly(meth)acrylate of the foam layer contains at least one partially polymerized monomer with at least one functional group that can initiate or support subsequent radiation-chemical crosslinking, in particular by UV radiation. Preferably, the poly(meth)acrylate of the foam layer contains partially polymerized benzoin acrylate or at least one partially polymerized acrylate-functionalized benzophenone derivative.

[0039] Crosslinking of the poly(meth)acrylate with electron beams is also possible in principle.

[0040] The poly(meth)acrylate of the foam layer can preferably be traced back to the following monomer composition: a) at least one acrylic acid ester and / or methacrylic acid ester of the following formula (1) CH2=C(R I )(COOR II ) (1), where R I = H or CH3 and R IIis an alkyl radical having 4 to 18 C atoms; b) at least one olefinically unsaturated monomer having at least one functional group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxy groups and amino groups; c) optionally further acrylic acid esters and / or methacrylic acid esters and / or olefinically unsaturated monomers which are copolymerizable with component (a).

[0041] It is particularly advantageous to select 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 wt.%, whereby the data refer to the monomer mixture for the base polymer without addition of any additives such as resins, etc.

[0042] The monomers of component a) are generally plasticizing, relatively non-polar monomers. R'' in monomers a) is particularly preferably an alkyl radical having 4 to 10 carbon atoms or 2-propylheptyl acrylate or 2-propylheptyl methacrylate. The monomers of formula (1) are in particular selected from the group consisting of 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, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-propylheptyl acrylate and 2-propylheptyl methacrylate.

[0043] The monomers of component b) are particularly preferably selected from the group consisting of 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, in particular 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, in particular 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate.

[0044] Examples of monomers of component c) are: Methylacrylat, Ethylacrylat, Propylacrylat, Methylmethacrylat, Ethylmethacrylat, Benzylacrylat, Benzylmethacrylat, sec-Butylacrylat, tert-Butylacrylat, Phenylacrylat, Phenylmethacrylat, Isobornylacrylat, Isobornylmethacrylat, tert-Butylphenylacrylat, tert-Butylaphenylmethacrylat, Dodecylmethacrylat, Isodecylacrylat, Laurylacrylat, n-Undecylacrylat, Stearylacrylat, Tridecylacrylat, Behenylacrylat, Cyclohexylmethacrylat, Cyclopentylmethacrylat, Phenoxyethylacrlylat, Phenoxyethylmethacrylat, 2-Butoxyethylmethacrylat, 2-Butoxyethylacrylat, 3,3,5-Trimethylcyclohexylacrylat, 3,5-Dimethyladamantylacrylat, 4-Cumylphenylmethacrylat, Cyanoethylacrylat, Cyanoethylmethacrylat, 4-Biphenylacrylat, 4-Biphenylmethacrylat, 2-Naphthylacrylat, 2-Naphthylmethacrylat, Tetrahydrofufurylacrylat, Diethylaminoethylacrylat, Diethylaminoethylmethacrylat, Dimethylaminoethylacrylat, Dimethylaminoethylmethacrylat, 3-Methoxyacrylsäuremethylester, 3-Methoxybutylacrylat, 2-Phenoxyethylmethacrylat,Butyldiglykolmethacrylat, Ethylenglycolacrylat, Ethylenglycolmonomethylacrylat, Methoxypolyethylenglykolmethacrylat 350, Methoxypolyethylenglykolmethacrylat 500, Propylenglycolmonomethacrylat, Butoxydiethylenglykolmethacrylat, Ethoxytriethylenglykolmethacrylat, Octafluoropentylacrylat, Octafluoropentylmethacrylat, 2,2,2-Trifluorethylmethacrylat, 1,1,1,3,3,3-Hexafluoroisopropylacrylat, 1,1,1,3,3,3-Hexafluoroisopropylmethacrylat, 2,2,3,3,3-Pentafluoropropylmethacrylat, 2,2,3,4,4,4-Hexafluorobutylmethacrylat, 2,2,3,3,4,4,4-Heptafluorobutylacrylat, 2,2,3,3,4,4,4-Heptafluorobutylmethacrylat, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctylmethacrylat, Dimethylaminopropylacrylamid, Dimethylaminopropylmethacrylamid, N-(1-Methylundecyl)acrylamid, N-(n-Butoxymethyl)acrylamid, N-(Butoxymethyl)methacrylamid, N-(Ethoxymethyl)acrylamid, N-(n-Octadecyl)acrylamid; N,N-Dialkyl-substituierte Amide wie beispielsweise N,N-Dimethylacrylamid und N,N-Dimethylmethacrylamid; N-Benzylacrylamid,N-isopropylacrylamide, N-tert-butylacrylamide, N-tert-octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylonitrile, methacrylonitrile; vinyl ethers such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether; vinyl esters such as vinyl acetate; vinyl halides, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-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, determined by GPC, from 4000 to 13000 g / mol), poly(methyl methacrylate) ethyl methacrylate (Mw from 2000 to 8000 g / mol).

[0045] Monomers of component c) can also advantageously be selected to contain functional groups that support subsequent radiation-chemical crosslinking (e.g., by electron beams, UV). Suitable copolymerizable photoinitiators include benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers that support crosslinking by electron irradiation include tetrahydrofurfuryl acrylate, N-tert-butylacrylamide, and allyl acrylate.

[0046] The poly(meth)acrylates are preferably produced by conventional radical polymerizations or controlled radical polymerizations. The poly(meth)acrylates can be produced by copolymerization of the monomers using conventional polymerization initiators and, if appropriate, regulators. Polymerization takes place at conventional temperatures in bulk, in emulsion, for example, in water or liquid hydrocarbons, or in solution.

[0047] The poly(meth)acrylates are preferably prepared by copolymerizing the monomers in solvents, particularly preferably in solvents having a boiling range of 50 to 150 °C, in particular of 60 to 120 °C, using 0.01 to 5 wt.%, in particular 0.1 to 2 wt.%, in each case based on the total weight of the monomers, of polymerization initiators.

[0048] In principle, all conventional initiators are suitable. Examples of radical sources include peroxides, hydroperoxides, and azo compounds, for example, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, and benzpinacol. Preferred radical initiators are 2,2'-azobis(2-methylbutyronitrile) (Vazo® 67™ from DuPont) or 2,2'-azobis(2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN; Vazo® 64™ from DuPont).

[0049] Preferred solvents for the preparation of the poly(meth)acrylates are alcohols such as methanol, ethanol, n- and isopropanol, n- and isobutanol, especially isopropanol and / or isobutanol; hydrocarbons such as toluene and especially gasolines with a boiling range of 60 to 120°C; ketones, especially acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, and mixtures of the aforementioned solvents. Particularly preferred solvents are mixtures containing isopropanol in amounts of 2 to 15 wt.%, especially 3 to 10 wt.%, based in each case on the solvent mixture used.

[0050] Poly(meth)acrylates can also be produced solvent-free. For example, the monomers can be prepolymerized under the influence of heat or UV radiation to a syrupy consistency. The resulting syrup, which contains both monomers and polymer, can then be mixed with other components and subsequently formed into a sheet. The final polymerization and, if necessary, crosslinking take place shortly after forming by further heat treatment or UV irradiation of the resulting sheet. The other components with which the syrup is mixed can include foaming agents, e.g., hollow polymer microspheres or hollow glass spheres; the foam is then obtained directly with the final polymerization.

[0051] In another variant of the process for producing the foam layer, the poly(meth)acrylates are then concentrated after polymerization, and further processing of the poly(meth)acrylates is carried out essentially solvent-free. The polymer concentration can be carried out in the absence of crosslinking and accelerator substances. However, it is also possible to add one of these compound classes to the polymer prior to concentration, so that the concentration then takes place in the presence of these substances.

[0052] After the concentration step, the polymers can be transferred to a compounder, where they are blended with other components, especially the foaming agents. If necessary, the concentration and compounding can also take place in the same reactor.

[0053] The weight-average molecular weights M wThe molecular weights of the polyacrylates are preferably in a range from 20,000 to 2,000,000 g / mol; very preferably in a range from 100,000 to 1,500,000 g / mol, and extremely preferably in a range from 150,000 to 1,000,000 g / mol. For this purpose, 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 adjust the desired average molecular weight. The number-average molecular weights M n and the weight-average molecular weight M w in this document refer to the known determination by gel permeation chromatography (GPC).

[0054] The poly(meth)acrylate of the foam layer preferably has a polydispersity PD < 4 and thus a relatively narrow molecular weight distribution. Foams based on this material exhibit particularly good shear strength after crosslinking despite a relatively low molecular weight. Furthermore, the lower polydispersity enables easier melt processing, as the flow viscosity is lower than that of a more broadly distributed poly(meth)acrylate while maintaining largely the same application properties. Narrowly distributed poly(meth)acrylates can be advantageously produced by anionic polymerization or by controlled radical polymerization methods, the latter being particularly suitable. Corresponding poly(meth)acrylates can also be produced via N-oxyls.Furthermore, atom transfer radical polymerization (ATRP) can be advantageously used for the synthesis of narrowly distributed poly(meth)acrylates, with monofunctional or difunctional secondary or tertiary halides preferably being used as initiators and Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag, or Au complexes being used for the abstraction of the halides. RAFT polymerization is also suitable.

[0055] In one embodiment, the poly(meth)acrylates are crosslinked by linking reactions—in particular in the sense of addition or substitution reactions—of the functional groups contained therein with thermal crosslinkers. All thermal crosslinkers can be used which - ensure a sufficiently long processing time so that gelling does not occur during the processing process, especially the extrusion process, - as well as rapid post-crosslinking of the polymer to the desired degree of crosslinking at temperatures lower than the processing temperature, especially at room temperature.

[0056] Thermal crosslinkers are preferably used at 0.1 to 5 wt.%, in particular at 0.2 to 1 wt.%, based on the total amount of the polymer to be crosslinked.

[0057] Crosslinking via complexing agents, also known as chelates, is also possible. A preferred complexing agent, for example, is aluminum acetylacetonate.

[0058] Preferably, the poly(meth)acrylate of the foam layer is crosslinked using an epoxy or one or more substances containing epoxy groups. The epoxy-containing substances are, in particular, multifunctional epoxides, i.e., those with at least two epoxy groups; accordingly, the overall result is an indirect linkage of the building blocks of the poly(meth)acrylates bearing the functional groups. The epoxy-containing substances can be both aromatic and aliphatic compounds.

[0059] The poly(meth)acrylates are particularly preferably crosslinked using a crosslinker-accelerator system ("crosslinking system") in order to obtain better control over the processing time, the crosslinking kinetics, and the degree of crosslinking. The crosslinker-accelerator system preferably comprises at least one substance containing epoxy groups as a crosslinker and at least one substance that accelerates the crosslinking reaction at a temperature below the melting temperature of the polymer to be crosslinked as an accelerator.

[0060] In one embodiment, the foam layer or the matrix material of the foam layer contains at least one synthetic rubber.

[0061] The foam layer can contain synthetic rubber in a total amount of 15 to 50 wt. %, more preferably in a total amount of 20 to 40 wt. %, based in each case on the total weight of the foam layer. In particular, the foam layer then also contains at least one poly(meth)acrylate. In this case, the synthetic rubber is preferably dispersed in the poly(meth)acrylate in the foam layer. Accordingly, poly(meth)acrylate and synthetic rubber are preferably homogeneous phases. In this embodiment, the foam layer preferably contains 40-70 wt. % of at least one poly(meth)acrylate and 15-50 wt. % of at least one synthetic rubber, based in each case on the total weight of the foam layer.

[0062] However, the foam layer can also be based on synthetic rubber and then contains at least 90 wt.% synthetic rubber, preferably at least 95 wt.% synthetic rubber, based in each case on the total weight of the foam layer. One or more synthetic rubbers can be contained in the foam layer.

[0063] Preferably, the synthetic rubber of the foam layer is a block copolymer with a structure AB, ABA, (AB) n , (AWAY) n X or (ABA) n X, where - the blocks A independently represent a polymer formed by polymerization of at least one vinyl aromatic compound; - the blocks B independently represent a polymer formed by polymerisation of conjugated dienes having 4 to 18 carbon atoms and / or isobutylene, or a partially or fully hydrogenated derivative of such a polymer; - X is the residue of a coupling reagent or initiator and - n stands for an integer ≥ 2.

[0064] In particular, if several are present, all synthetic rubbers in the foam layer are block copolymers with a structure as described above. The foam layer can therefore also contain mixtures of various block copolymers with the above structure.

[0065] The preferred synthetic rubbers, which are also referred to as vinyl aromatic block copolymers, thus comprise one or more rubber-like blocks B (soft blocks) and one or more glassy blocks A (hard blocks). The synthetic rubber is particularly preferably a block copolymer having a structure AB, ABA, (AB)3X, or (AB)4X, where A, B, and X have the above meanings. Very particularly preferably, all synthetic rubbers of the foam layer are block copolymers having a structure AB, ABA, (AB)3X, or (AB)4X, where A, B, and X have the above meanings. In particular, the synthetic rubber of the foam layer is a mixture of block copolymers having a structure AB, ABA, (AB)3X, or (AB)4X, which preferably contains at least diblock copolymers AB and / or triblock copolymers ABA.

[0066] Block A is, in particular, a glassy block with a preferred glass transition temperature (Tg, DSC) that is above room temperature. The Tg of the glassy block is particularly preferably at least 40°C, in particular at least 60°C, very particularly preferably at least 80°C, and extremely preferably at least 100°C. The proportion of vinylaromatic blocks A in the total block copolymers is preferably 10 to 40% by weight, particularly preferably 20 to 33% by weight. Vinylaromatics for constructing block A preferably include styrene and α-methylstyrene. Block A can thus be present as a homopolymer or copolymer. Block A is particularly preferably a polystyrene.

[0067] Block B is, in particular, a rubber-like block or soft block with 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.

[0068] Preferred conjugated dienes as monomers for soft block B are selected in particular from the group consisting of butadiene, isoprene, ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene, dimethylbutadiene, and the farnesene isomers, as well as any desired mixtures of these monomers. Block B can also be present as a homopolymer or as a copolymer.

[0069] Particularly preferably, the conjugated dienes used as monomers for soft block B are selected from butadiene and isoprene. For example, 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, polybutylenebutadiene; or a polymer made from a mixture of butadiene and isoprene. Block B is most preferably a polybutadiene.

[0070] The foaming of the matrix material of the foam layer can, in principle, be carried out in any known manner, for example, with expandable or pre-expanded microballoons; with other hollow microspheres such as hollow polymer spheres, hollow glass spheres, or hollow ceramic spheres; with solid spheres such as solid polymer spheres, solid glass spheres, solid ceramic spheres, or solid carbon spheres; chemically by substances that react with gas release; or physically by introducing a propellant or propellant gas. The foam layer preferably contains at least partially expanded microballoons or hollow glass spheres.

[0071] "Microballoons" are elastic, and thus expandable in their ground state, hollow microspheres with a thermoplastic polymer shell. These spheres are filled with low-boiling liquids or liquefied gas. Polyacrylonitrile, PVDC, PVC, or polyacrylates are particularly used as shell materials. Low-boiling liquids, such as isobutane or isopentane, are particularly common, and are enclosed in the polymer shell as liquefied gas under pressure.

[0072] When exposed to external influences, particularly heat, the outer polymer shell softens. At the same time, the liquid propellant gas contained within the shell transforms into a gaseous state. The microballoons expand irreversibly and expand three-dimensionally. The expansion is complete when the internal and external pressures equalize. Since the polymer shell remains intact, a closed-cell foam is created.

[0073] A variety of microballoon types are commercially available, differing primarily in their size (6 to 45 µm diameter in the unexpanded state) and the starting temperatures required for expansion (75 to 220 °C). Unexpanded microballoon types are also available as aqueous dispersions with a solids or microballoon content of approximately 40 to 45 wt.%, and also as polymer-bound microballoons (masterbatches), for example, in ethylene-vinyl acetate with a microballoon concentration of approximately 65 wt.%. Both the microballoon dispersions and the masterbatches, like the unexpanded microballoons, are suitable for foaming the foam layer matrix material.

[0074] The foamed layer can also be created using so-called pre-expanded microballoons. In this group, the expansion takes place before mixing into the polymer matrix. The foam layer preferably contains at least partially expanded microballoons, regardless of the manufacturing method and the initial shape of the microballoons used.

[0075] The term "at least partially expanded microballoons" is understood to mean that the microballoons are expanded at least to the extent that this results in a reduction in the density of the matrix material to a technically reasonable extent compared to the same layer with the unexpanded microballoons. This means that the microballoons do not necessarily have to be fully expanded. Preferably, the "at least partially expanded microballoons" are each expanded to at least twice their maximum dimension in the unexpanded state.

[0076] The term "at least partially expanded" refers to the state of expansion of the individual microballoons and is not intended to imply that only a portion of the microballoons in question must be partially expanded. Therefore, if "at least partially expanded microballoons" are included in the carrier layer, this means that all of these "at least partially expanded microballoons" are at least partially expanded in the above sense, and unexpanded microballoons are not included in the "at least partially expanded microballoons."

[0077] The foam layer preferably contains silica, particularly preferably precipitated silica surface-modified with dimethyldichlorosilane. This is advantageous because it allows the thermal shear strength of the foam layer to be adjusted, and in particular increased. Silicas are also excellent for use in transparent layers. Silica is preferably present in the foam layer in quantities of up to 15% by weight, based on the total amount of all polymers contained in the foam layer.

[0078] Other components of the foam layer can be conventional additives, for example plasticizers, anti-aging agents, fillers and / or flame retardants and the like.

[0079] The compressive strength at 25% indentation depth (DIN EN ISO 3386-2 (2010), 25 x 25 mm, preload 4 kPa, indentation speed 30 mm / min, 1st cycle) of the foam layer is preferably more than 10 N / cm 2 , particularly preferably more than 15 N / cm 2, especially more than 30 N / cm 2 .

[0080] The foam preferably has a high compressive strength according to the above, so that the foam largely retains its shape and dimensions even under continuous load. This advantageously prevents lateral squeezing even under unplanned higher loads on the reel. This behavior is also advantageous if the installation distance between adjacent sections of the layered structure according to the invention wound on the reel is sufficiently large. On the other hand, this distance should not be so large that the tape tilts on the reel when the winding direction changes or penetrates into grooves and thus deforms.

[0081] The foam layer can be an internal layer in the adhesive tape structure, meaning it can be provided with a pressure-sensitive adhesive on one or both sides. In one embodiment, the foam layer itself has pressure-sensitive adhesive properties; preferably, the foam layer is the outer pressure-sensitive adhesive layer (PSA-A) of the adhesive tape of the layer structure according to the invention.

[0082] The layer structure according to the invention comprises a release liner (RL) lying on the outer pressure-sensitive adhesive layer (PSA-A).

[0083] Adhesive tapes coated with adhesives on one or both sides are usually wound into a roll or spool at the end of the manufacturing process, as already explained. To prevent the adhesives from coming into contact with each other in the case of double-sided adhesive tapes, or to ensure easier unwinding in the case of single-sided adhesive tapes, the adhesive is covered with a release liner (also known as a release material) before the tape is wound. Such release liners are known to those skilled in the art as release liners. In addition to covering single- or double-sided adhesive tapes, liners are also used to cover labels.

[0084] The release liners also ensure that the adhesive is not contaminated before application. In addition, release liners can be adjusted by the type and composition of the release materials so that the tape can be unrolled with the desired force (light or heavy). For adhesive tapes coated with adhesive on both sides, the release liners also ensure that the correct side of the adhesive is exposed first during unrolling.

[0085] A liner or release liner is not a component of an adhesive tape or label, but merely an aid in their production, storage, or further processing. Furthermore, unlike an adhesive tape carrier, a liner is not permanently bonded to an adhesive layer.

[0086] Release liners are industrially used paper or film backings coated with an abhesive coating compound (also known as a dehesive or anti-adhesive compound) to reduce the tendency of adhering products to adhere to these surfaces (separating function). In general, and accordingly also for release liners (RL), a variety of different substances can be used as abhesive coating compounds, also known as release coatings: waxes, fluorinated or partially fluorinated compounds, and in particular silicones, as well as various copolymers containing silicone components. In recent years, silicones have become widely accepted as release materials in the field of adhesive tape applications due to their good processability, low costs, and broad property profile. Liners with polyolefin release layers have also attracted interest.

[0087] The release layer of the release liner (RL) is preferably based on a crosslinkable silicone system. These crosslinkable silicone systems include mixtures of crosslinking catalysts or initiators and so-called thermally curable, condensation- or addition-crosslinking polysiloxanes, or radiation-induced crosslinking polysiloxanes. The silicone release layer (SR1) is preferably based on a radiation- (UV or electron beam), condensation-, or addition-crosslinking system, particularly preferably an addition-crosslinking system.

[0088] The silicone release layer of the release liner (RL) can be traced back to solvent-containing and / or solvent-free systems, preferably it can be traced back to a solvent-free system.

[0089] Silicone-based release agents based on addition curing can usually be cured by hydrosilylation. The formulations used to manufacture these release agents typically include the following components: - a linear or branched polydiorganosiloxane containing alkenyl groups, - a polyorganohydrogensiloxane crosslinking agent and - a hydrosilylation catalyst.

[0090] Platinum or platinum compounds, such as the Karstedt catalyst (a Pt(0) complex), have proven particularly effective catalysts for addition-curing silicone systems (hydrosilylation catalysts). More specifically, such addition-curing release coatings can include the following components: a) a linear or branched dimethylpolysiloxane consisting of approximately 80 to 200 dimethylpolysiloxane units and terminated at the chain ends with vinyldimethylsiloxy units. Typical examples include solvent-free, addition-curing silicone oils with terminal vinyl groups; b) a linear or branched crosslinker, which either has only methylhydrogensiloxy units in the chain (homopolymer crosslinker) or is composed of methylhydrogensiloxy and dimethylsiloxy units (copolymer crosslinker), with the chain ends saturated with either trimethylsiloxy or dimethylhydrogensiloxy groups. Typical representatives of this product class are, for example, hydrogenpolysiloxanes with a high content of reactive Si-H; c) a silicone MQ resin which, in addition to the commonly used trimethylsiloxy units, also has vinyldimethylsiloxy units as the M unit; d) a silicone-soluble platinum catalyst such as a platinum divinyltetramethyldisiloxane complex, commonly referred to as Karstedt complex.

[0091] Silicone-containing systems for the production of release coatings can be purchased commercially, for example from Dow Corning, Wacker or Momentive.

[0092] Typically, a silicone release system is applied in an uncured state and subsequently cross-linked.

[0093] Of the silicones mentioned, addition-curing silicones are the most economically important. However, an undesirable property of these systems is their sensitivity to catalyst poisons, such as heavy metal, sulfur, and nitrogen compounds (see "Chemical Engineering, Processes and Products" by R. Dittmeyer et al., Volume 5, 5th edition, Wiley-VCH, Weinheim, Germany, 2005, Chapter 6-5.3.2, page 1142). Electron donors can generally be considered platinum poisons (A. Colas, Silicone Chemistry Overview, Technical Paper, Dow Corning). Accordingly, phosphorus compounds such as phosphines and phosphites are also considered platinum poisons. The presence of catalyst poisons leads to the crosslinking reaction between the various components of a silicone release agent no longer taking place, or only taking place to a limited extent.Therefore, in the production of anti-adhesive silicone coatings, the presence of catalyst poisons, especially platinum poisons, is generally strictly avoided.

[0094] Special versions of the silicone systems include polysiloxane block copolymers, for example, with a urea block, or release systems made of fluorosilicones, which are used particularly in adhesive tapes with silicone adhesives. Furthermore, photoactive catalysts, so-called photoinitiators, can be used in combination with UV-curable, cationically crosslinking siloxanes based on epoxy and / or vinyl ethers, or with UV-curable, radically crosslinking siloxanes such as acrylate-modified siloxanes. The use of electron-beam-curable silicone acrylates is also possible. Photopolymerizable organopolysiloxane compositions can also be used. Examples include compositions that are crosslinked by the reaction between organopolysiloxanes containing hydrocarbon radicals substituted with (meth)acrylate groups and directly bonded to silicon atoms, in the presence of a photosensitizer.Also usable are compositions in which the crosslinking reaction between organopolysiloxanes containing mercapto-substituted hydrocarbon radicals directly bonded to silicon atoms and organopolysiloxanes containing vinyl groups directly bonded to silicon atoms occurs in the presence of a photosensitizer. When using organopolysiloxane compositions containing epoxy-substituted hydrocarbon radicals directly bonded to silicon atoms, the crosslinking reaction is induced by the release of a catalytic amount of acid obtained by photodecomposition of added onium salt catalysts. Other organopolysiloxane compositions curable by a cationic mechanism are materials containing, for example, propenyloxysiloxane end groups.

[0095] Depending on the intended use, the silicone systems may also contain other additives, such as stabilizers or flow aids.

[0096] The layer structure according to the invention further comprises an interliner (IL) lying on the side of the adhesive tape opposite the outer pressure-sensitive adhesive layer (PSA-A), the side of which is provided with an adhesive facing away from the adhesive tape.

[0097] The interliner (IL, 4) preferably comprises a carrier layer (5) containing monoaxially oriented polypropylene (MOPP), a polyester, a polyamide, or paper, or particularly preferably consisting of MOPP, a polyester, a polyamide, or paper. These materials exhibit advantageous rigidity and are thus particularly well-suited to keeping the foam strips dimensionally stable and stably aligned parallel to the winding core. The polyester is particularly preferably polyethylene terephthalate (PET).

[0098] The adhesive side of the interliner (IL), facing away from the adhesive tape, is preferably formed by a pressure-sensitive adhesive, which is generally any type as long as it is suitable for an interliner. A "pressure-sensitive adhesive suitable for an interliner" preferably exhibits good anchoring to the interliner carrier material, which can optionally be supported by pretreating the carrier or the pressure-sensitive adhesive. Furthermore, the adhesive preferably exhibits good cohesion, so that residues are avoided when peeling off the interliner and no "oozing" (squeezing out) occurs under the pressures and temperatures encountered in a reel.

[0099] The pressure-sensitive adhesive is preferably a poly(meth)acrylate- or natural rubber-based pressure-sensitive adhesive. The pressure-sensitive adhesive preferably has an application weight of 1 to 30 g / m 2Their adhesive strength (Afera 5001, Method A, 300 mm / min, 180°, steel) is preferably 0.3 to 5 N / cm, particularly preferably 1 to 4 N / cm. In particular, the adhesive strength (Afera 5001, Method F, 300 mm / min, 90°, outer side of the release liner (RL)) of the pressure-sensitive adhesive to the relevant release liner (RL) in the spool structure is preferably 0.1 to 3 N / cm. These adhesive forces mean that the interliner or the layer structure according to the invention as a whole does not slip during and after winding into a spool, but on the other hand the interliner can be detached from the release liner with normal force. The side of the release liner of interest here, i.e. the side not in contact with the outer pressure-sensitive adhesive layer (PSA-A), is preferably siliconized or a polyethylene (PE) or polypropylene (PP) layer.

[0100] An "adhesive side of the interliner (IL)" is understood to be an outer side, so that the adhesive finish does not refer to an internal layer in the liner structure, but rather faces outward. The interliner (IL) can thus exert an outward-directed adhesive effect on the relevant side. The adhesive finish on the side of the interliner (IL) facing away from the adhesive tape is preferably formed by a poly(meth)acrylate-based pressure-sensitive adhesive, which is based in particular on an aqueous poly(meth)acrylate dispersion.

[0101] The total thickness (DIN EN 1942(2003), 10mm disc, 51 kPa) of the interliner (IL) is preferably 50 to 300 µm, particularly preferably 70 to 150 µm. These ranges have proven particularly advantageous because the tendency of the wound layers of the layered structure to stick together is greatly minimized without compromising the flexibility of the layered structure, e.g., with regard to its ability to negotiate curves.

[0102] The tensile strength (ISO 527-3 (1995-08); Specimen Type 2, Test Speed ​​150 mm / min) of the interliner (IL) is preferably 10 to 150 N / cm, particularly preferably 50 to 110 N / cm.

[0103] The side of the interliner (IL) facing the adhesive tape is either - formed by a release layer, for which everything said about the release layer of the release liner (RL) applies, or - formed by a further pressure-sensitive adhesive layer, to which everything stated above regarding the pressure-sensitive adhesive forming the side of the interliner (IL) facing away from the adhesive tape applies.

[0104] In one embodiment, the adhesive tape of the layer structure according to the invention comprises an outer heat-activatable adhesive layer which directly adjoins the interliner (IL), and the side of the interliner (IL) facing the adhesive tape is formed by a further pressure-sensitive adhesive layer, to which everything stated above regarding the pressure-sensitive adhesive which forms the side of the interliner (IL) facing away from the adhesive tape applies.

[0105] A "heat-activatable adhesive layer" (hereinafter also referred to synonymously as "heat-activatable adhesive") is understood to mean a layer of adhesive that is non-tacky at room temperature and can only develop sufficient adhesion to a substrate upon heating to create an adhesive bond. "Heating" is typically understood to mean exposure to a temperature in the range of approximately 60 to approximately 200°C, according to the invention in particular in the range of 120°C to 200°C.

[0106] The heat-activatable adhesive layer is preferably a polyolefin layer. The polyolefin can be derived from one or more olefin monomers. The material of the heat-activatable adhesive layer is preferably selected from polyethylene, polypropylene, ethylene-propylene copolymers, and mixtures of these polymers. The material of the heat-activatable adhesive layer is particularly preferably polypropylene.

[0107] A further subject of the invention is a coil comprising a coil core (7) and a layer structure according to the invention wound crosswise thereon in several layers, wherein - in the innermost layer, the adhesive side of the interliner (IL, 6) rests directly on the coil core (7) and - in each layer, the adhesive side of the interliner (IL, 6) forms the inner side of the layer structure oriented towards the coil core (7).

[0108] A reel according to the invention is advantageously designed because the interliner (IL, 6) forms a bond with the underlying layer of adhesive tape provided with the release liner (RL). This principle allows adjacent adhesive tape layers to maintain their distance from each other even under internal and external stresses on the reel, such as those that can occur during storage, transport, and use. Furthermore, reduced winding tension can be utilized during winding, allowing the adhesive tape to be wound gently and without crushing.

[0109] A spool according to the invention preferably has a diameter of up to 500 mm, particularly preferably from 200 to 400 mm. The weight of the spool is preferably a maximum of 20 kg, particularly preferably from 5 to 15 kg. The adhesive tape of the layered structure according to the invention preferably has a running length of up to 2,000 m, particularly preferably from 200 to 1,600 m, on the spool. The width of the adhesive tape and thus - since the layers are essentially flush - of the layered structure according to the invention on the spool is preferably 2 to 40 mm, particularly preferably 3 to 20 mm. The thickness of the layered structure according to the invention on the spool is preferably 200 to 3,000 µm, particularly preferably 400 to 1,600 µm, whereby with increasing thickness, correspondingly fewer running meters are possible and narrower dimensions become increasingly difficult to wind.The installation spacing on the coil between adjacent sections of the layered structure according to the invention is preferably more than 0.7 mm, particularly preferably 0.8 to 2 mm. In principle, the installation spacing can be larger in the inner layers of the coil than in the outer layers.

[0110] The layer structure according to the invention is achieved by Fig. 1, which shows an example of a layer structure according to the invention resting on a coil core and illustrating the sequence of the individual layers. Fig. 1 means: 1 adhesive tape 2 release liners (RL) 3 outer pressure-sensitive adhesive layer (PSA-A) of the adhesive tape 4 Interliners (IL) 5 Interliner carriers (IL) 6 Adhesive side of the interliner (IL) facing away from the adhesive tape 7 coil core

[0111] Another object of the invention is a method for producing a coil according to the invention, which - providing a layer structure according to the invention wound into a master roll; - separating the layer structure in such a way that several webs with a smaller web width than the parent roll are obtained from the web forming the parent roll; - providing coil cores (7); and - winding the webs onto a respective spool core (7) in such a way that ◯ several cross-overlapping layers are created; ◯ in the innermost layer, the adhesive side of the interliner (IL) (6) rests directly on the spool core (7); and ◯ in each layer, the adhesive side of the interliner (IL) (6) forms the inner side of the layer structure oriented towards the coil core;comprises.

[0112] The process according to the invention can advantageously be carried out without the separate lamination of an interliner - which is wider than the adhesive tape - and is therefore significantly more efficient than conventional processes.

[0113] In an alternative process, the webs are wound onto the spool core in such a way that, in the innermost layer, the release liner (RL) resting on the outer layer of the pressure-sensitive adhesive (PSA-A) rests directly on the spool core and, accordingly, forms the inner side of the layer structure facing the spool core in each subsequent layer. Since in this case the adhesive side of the interliner (IL) faces outward in the last layer, the spool would be wrapped with an additional release liner. ExamplesTest MethodsTest Method T1: Optical Evaluation

[0114] The adhesive tapes listed in Table 1, each covered with a release liner on one side and an interliner on the opposite side, were cut from a master roll to the specified width and cross-wound into a spool using the parameters specified in the table. The resulting spools were stored under the following conditions: - 1 month at 23 °C - 1 month at 40 °C - 2 months at 40 °C.

[0115] Subsequently, a visual assessment was carried out according to the following (negative) criteria: 1. Does the coil show any deviations from its original cylindrical shape? 2. Do the coil cores protrude asymmetrically on the left and right? 3. Is the distribution of the wound tape across the reel width inhomogeneous (different distances between adjacent tape sections)? 4. Have the outermost tapes slipped off the edges of the spool / are they no longer in their original position?

[0116] If all questions could be answered with “no”, an “ok” was given in the visual assessment, otherwise a “not ok” was given. Test method T2: Unwinding behavior

[0117] The reels were unwound on an Ehnert AWS18G unwinder without a pressure roller and without using the interliner winder, following the storage procedure described in Method T1; the unwinding speed was 15 m / min.

[0118] The following criteria were evaluated: 5. Did the wound tape unwind smoothly and without force peaks, especially at the points where the tape changes direction? 6. Did the bond hold together (no accidental detachment of the liner)? 7. Did adjacent tape sections always separate cleanly (no sticking of adjacent tape sections), especially in the area of ​​the winding direction change (up to 5 slight, reversible stickings are acceptable, but were then noted in the table)? 8. Were the interliner and release liner congruent on the tape? 9. Did the distance between adjacent band sections show any noticeable deviations? 10. Were the release liners and interliners wrinkle-free? 11. Did the adhesive tape sections retain their curved shape from the reversal points of the winding direction (comparison of two 1 m long strips from the center of the reel and from the reversal point; assessment of parallelism when placed side by side)? 12. Did the interliner remove smoothly and without rattling after unwinding?

[0119] If all questions could be answered with "yes," the unwinding behavior was rated "OK." Otherwise, it was rated "NO." The observed, still acceptable, defects are also listed in Table 1.

[0120] The following adhesive materials were used as interliners (corresponding to Interliner (IL)): Interliner 1 (IL1): tesa adhesive tape ® 64250 (single-sided acrylic adhesive tape with MOPP backing; commercially available; total thickness 80 µm; tensile strength 100 N / cm) Interliner 2 (IL2): tesa adhesive tape ® 4360 (single-sided acrylic adhesive tape with PE backing; commercially available; total thickness 51 µm; tensile strength 13 N / cm) Interliner 3 (IL3): tesa adhesive tape ® 50600 (single-sided silicone adhesive tape with PET backing; commercially available; total thickness 80 µm; tensile strength 50 N / cm)

[0121] The following adhesive tapes were used: Adhesive tape 1: tesa ® ACX plus7805 PV29 (double-sided acrylic foam tape, one side with release liner; commercially available) in a width of 6 mm; compressive strength 46 N / cm 2 Adhesive tape 2: tesa ® ACX plus 77115 PV28 (double-sided acrylic foam tape, one side with release liner; commercially available) in a width of 10 mm; compressive strength 37 N / cm 2 Adhesive tape 3: tesa ® ACX plus 7812 PV29 (double-sided acrylic foam tape, one side with release liner; commercially available) in a width of 4 mm, compressive strength 46 N / cm 2 Adhesive tape 4: tesa ® ACX plus 77811 PV 15 (double-sided acrylic foam tape, one side with release liner, commercially available) in a width of 6 mm; compressive strength 16 N / cm 2 .

[0122] The respective construction was provided as a master roll with adhesive tape and a release liner and interliner applied. The master rolls were unwound and cut using a winder. The resulting layered structures, cut to the target width, were then wound into cross-wound spools using a winder. The respective parameters are listed in Table 1. Table 1: Nr. Adhesive tape no. Interliner No. Installation spacing Winding tension Reel length Optical assessment Unwinding behavior 1 1 1 0.8 mm 190 cN / cm 900 Ifm OK OK 2 3 1 0.8 mm 190 cN / cm 900 Ifm OK OK 3 2 2 1.0 mm 190 cN / cm 500 Ifm OK ok (2 light plucks when changing direction) 4 4 3 0.9 mm 190 cN / cm 700 Ifm OK ok (3 times light plucking on inner winding layers)

Claims

[1] Layer structure for winding an adhesive tape into a reel, comprising - an adhesive tape (1) comprising at least one outer pressure-sensitive adhesive layer (PSA-A, 3); - a release liner (RL, 2) applied to the outer pressure-sensitive adhesive layer (PSA-A, 3); and - an interliner (IL, 4) lying on the side of the adhesive tape (1) opposite the outer pressure-sensitive adhesive layer (PSA-A, 3), the side (6) of which facing away from the adhesive tape is provided with an adhesive; characterized by that all layers of the layer structure are flush and the interliner (IL, 4) is not firmly connected to the adhesive tape. [2] Layer structure according to claim 1, characterized by that the interliner (IL, 4) comprises a carrier layer (5) containing MOPP, a polyester, a polyamide or paper. [3] Layer structure according to one of claims 1 and 2, characterized by that the adhesive tape (1) comprises a foam layer based on poly(meth)acrylate. [4] Layer structure according to one of the preceding claims, characterized by that the side of the interliner (IL, 6) facing away from the adhesive tape (1) is formed by a poly(meth)acrylate- or natural rubber-based pressure-sensitive adhesive. [5] Coil comprising a coil core (7) and a layer structure wound crosswise thereon in several layers according to one of the preceding claims, wherein - in the innermost layer, the adhesive side of the interliner (IL, 6) rests directly on the coil core (7) and - in each layer, the adhesive side of the interliner (IL, 6) forms the inner side of the layer structure oriented towards the coil core (7). [6] A method of manufacturing a coil according to claim 5, comprising - providing a layer structure wound into a master roll according to one of claims 1 to 4; - separating the layer structure in such a way that several webs with a smaller web width than the parent roll are obtained from the web forming the parent roll; - providing coil cores (7); and - winding the webs onto a respective spool core (7) in such a way that ◯ several cross-overlapping layers are created; ◯ in the innermost layer, the adhesive side of the interliner (IL, 6) rests directly on the spool core (7); and ◯ in each layer, the adhesive side of the interliner (IL, 6) forms the inner side of the layer structure oriented towards the coil core (7).

Images