Adhesive tape for strapping applications

Abstract

The aim of the invention is to provide an adhesive tape for strapping applications which meets the usual requirement profile for a strapping tape and has a carrier which consists of a material that is advantageous in terms of sustainability. This is achieved using an adhesive tape for strapping applications, comprising a pressure-sensitive adhesive layer and an impregnated paper layer. The invention further relates to the use of impregnated paper as a carrier material in the construction of an adhesive tape for strapping applications.

Description

[0001] Adhesive tape for strapping applications

[0002] The invention relates to the technical field of adhesive tapes, as they are used in many areas of technology for temporarily or permanently bonding a wide variety of substrates or for securing device parts, among other purposes. More specifically, the invention relates to an adhesive tape for strapping applications that has an impregnated paper layer.

[0003] The term "strapping" refers to any measure that can be implemented using adhesive tapes and is aimed at temporarily bundling individual elements or objects into transportable packages, as well as temporarily securing movable parts of equipment. The adhesive tapes described here are therefore suitable for bundling objects, for example, pipes, profiles, or stacked boxes. Furthermore, these adhesive tapes are suitable for securing movable parts on equipment, such as white appliances, such as refrigerators and freezers or air conditioners; red appliances, such as (gas) stoves; and / or electrical appliances, such as printers. These measures are often used to facilitate or secure transport, but are also used for other purposes.

[0004] In technical terms, a distinction is often made between the fixing of moving parts of the device

[0005] - Appliance, i.e. the fixing of moving parts of refrigerators and freezers as well as other household appliances such as gas stoves and others; and

[0006] Office automation, i.e. the fixing of moving parts of office equipment such as printers, copiers, etc.

[0007] Other examples of strapping applications include the temporary fixing of larger components, for example the fixing of car windshields after insertion into the frame until the typically used liquid adhesive has cured, in order to prevent slipping during the curing process; the so-called end tabbing (end layer bonding) of metal coils; the temporary sealing of containers; and generally the bonding of surfaces with the requirement of residue-free removability even at low temperatures.

[0008] In particular, strapping applications include any measures that can be implemented using adhesive tapes to assemble and secure objects for transport. Adhesive tapes intended exclusively for conveying information, such as attaching warning labels and the like, are excluded.

[0009] As is clear from the above, strapping tapes are generally intended for temporary applications. This implies their removability from the respective bonded substrates after application. It is obvious that the adhesive tapes should be removable from the substrate as residue-free as possible. The residue-free removability – also referred to as redetachability – of an adhesive tape from different substrates depends largely on the required peel forces, which develop after different periods of time when removing the adhesive tape from the respective substrates. Ideally, the peel force increases only slightly or even not at all compared to the initial peel force, since increasing peel force increases the risk of either the adhesive tape backing tearing or adhesive residue remaining on the substrate. If the peel forces are too high, the adhesive tape backing can fail and tear and / or split.Further consequences of excessive peel forces can include cohesive splitting of the adhesive or interlaminar failure of the adhesive, resulting in detachment from the backing. In all of these cases, unwanted residues of the adhesive tape remain on the substrate, either in the form of parts of the adhesive tape itself or parts of the adhesive.

[0010] There is therefore a continuing need for strapping tapes that can be used universally on all relevant substrates. Suitable substrates include the plastics ABS, PS, PP, PE, PC, POM, PVC, HIPS, and GPPS, steel, various metals, as well as solvent-based, water-based, and powder-applied paints and other solvent-free paints such as UV-curing paints. The adhesive tapes must adhere securely to these substrates with sufficiently high bond strengths of generally at least 2.5 N / cm, yet be removable without leaving residue or damage, even after extended storage at various temperatures ranging from -20°C to +60°C and / or after UV irradiation.

[0011] Strapping tapes are known in various forms in the state of the art.

[0012] WO 2018 / 154106 A1 describes, against the background of strapping applications, an adhesive tape having a carrier made of a film to which an adhesive is applied on at least one side, wherein the film is a monoaxially oriented film which consists of at least 95% by weight of a propylene polymer composition with different phases.

[0013] WO 2022 / 112372 A1 - also against the background of strapping applications - relates to an adhesive tape having a carrier made of a film to which an adhesive is applied on at least one side, wherein the film is a monoaxially stretched film in the longitudinal direction which contains at least 90 wt.% polyester polymers.

[0014] The Chinese utility model CN ​​213172172 U describes a bundling adhesive tape which has an adhesive tape core comprising a release layer, an adhesive layer which is firmly bonded to the upper end of the adhesive tape core, a first thickening layer which is firmly bonded to the lower end of the adhesive layer, a base material layer which is firmly bonded to the lower end of the first thickening layer, a second thickening layer which is firmly bonded to the lower end of the base material layer, and an anti-scratch layer which is bonded to the lower end of the second thickening layer.

[0015] WO 2021 / 142097 A1 describes a container comprising a reinforcing element attached to a portion of the container, which in turn comprises a continuous paper strip, to the first or second side of which a layer of an adhesive composition is applied, which secures the reinforcing element to the container. A specific requirement for strapping tapes is high tear resistance. This refers to the resistance that an adhesive tape already provided with a small tear offers to the tendency for further tearing starting from the existing tear. Smaller tears, which then act as a nucleation point for further tearing, occur, for example, when the adhesive tape must be applied over edges.In order to enable the adhesive tape to continue to function in the sense of holding containers together or securing moving parts of equipment, it is important that the adhesive tape does not simply continue to tear, but rather offers the strongest possible resistance to this tendency, which is referred to in the specialist world as tear resistance.

[0016] In addition to the existing requirements profile for adhesive tapes for strapping applications, sustainability aspects are also increasingly coming into focus. This requires that at least individual components of the adhesive tapes be made of materials that are comparatively less problematic in this regard.

[0017] It was an object of the invention to provide an adhesive tape suitable for strapping applications, in particular for transport securing, which meets the usual requirement profile for a strapping tape and has a carrier made of a material that is advantageous from a sustainability perspective.

[0018] It was a further object of the invention to provide such an adhesive tape which in particular offers high tear resistance.

[0019] A complementary task was to equip the adhesive tape with high strength in the z-direction. Accordingly, the adhesive tape also had to exhibit high splitting strength or breaking force in the z-direction.

[0020] A further additional object of the invention was to provide an adhesive tape that combines the properties already mentioned with the highest possible tensile strength.

[0021] The inventors have now found that the above problems can be solved with an adhesive tape provided with an impregnated paper layer.

[0022] The above objects are accordingly achieved by the subject matter of the invention as defined in the claims. Preferred embodiments according to the invention emerge from the subclaims and the following statements. Those embodiments which are referred to as preferred below are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to as particularly preferred below are therefore very particularly preferred. Likewise preferred are embodiments in which a feature of an embodiment referred to as preferred to any extent is combined with one or more further features of other embodiments which are referred to as preferred to any extent. Features of preferred uses emerge from the features of preferred adhesive tapes.

[0023] To the extent that both specific amounts or proportions of an element and preferred embodiments of the element are disclosed below, the specific amounts or proportions of the preferably configured elements are also disclosed. Furthermore, it is disclosed that, with the corresponding specific total amounts or total proportions of the elements, at least some of the elements can be preferably configured, and in particular, that preferably configured elements can in turn be present in the specific amounts or proportions within the specific total amounts or total proportions.

[0024] A first and general object of the invention is an adhesive tape for strapping applications, which comprises a pressure-sensitive adhesive layer and an impregnated paper layer.

[0025] In this way, it has been possible to provide an adhesive tape suitable for strapping applications, which has a central component based on a renewable raw material and, on the other hand, combines high tear resistance with good strength in the z-direction.

[0026] The term adhesive tape is clear to those skilled in the art in the field of adhesive technology. In the context of the present invention, the term tape refers to all thin, flat structures, i.e. structures with a predominant extension in two dimensions, in particular tapes with an extended length and limited width as well as corresponding tape sections and also die-cut parts and labels. The adhesive tape can be in the form of a roll, i.e. wound on itself in the form of an Archimedean spiral, or in the form of a cross-wound spool. In this case, it can be lined on the adhesive side with a release material such as, for example, siliconized paper or siliconized film. Adhesive tapes according to the invention preferably have running lengths of 25 to 100 m in the form of conventional adhesive tape rolls or of 1,000 to 30,000 m in the form of spools.

[0027] A pressure-sensitive adhesive (PSA) is, in accordance with expert understanding, an adhesive that possesses pressure-sensitive adhesive properties, i.e., the ability to form a permanent bond with a substrate even under relatively light pressure. Pressure-sensitive adhesives are generally permanently tacky even at room temperature; they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even under light pressure. Furthermore, the pressure-sensitive adhesives used for strapping tapes can usually be removed from the substrate after use, leaving essentially no residue.

[0028] Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be viewed as an extremely viscous liquid with an elastic component. It therefore exhibits characteristic viscoelastic properties that lead to the permanent inherent tack and pressure-sensitive adhesive strength described above. It is assumed that, upon mechanical deformation, pressure-sensitive adhesives undergo both viscous flow processes and the build-up of elastic restoring forces. The viscous flow component serves to achieve adhesion, while the elastic restoring forces component is particularly necessary to achieve cohesion. The relationships between rheology and pressure-sensitive tack are known in the art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology," Third Edition, (1999), pages 153 to 203.To characterise the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G") are usually used, which can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189323 A1. In the context of the present invention, an adhesive is preferably understood to be pressure-sensitive and thus a pressure-sensitive adhesive if, at a temperature of 23°C in the deformation frequency range from 10° to 10. 1 rad / sec G' and G“ each at least partly in the range of 10 3 up to 10 7 Pa lie.

[0029] The pressure-sensitive adhesive layer of an adhesive tape according to the invention can, in principle, comprise all known pressure-sensitive adhesive systems. The pressure-sensitive adhesive layer of an adhesive tape according to the invention preferably comprises one or more polymers selected from the group consisting of natural rubbers, synthetic rubbers, silicones, and poly(meth)acrylates. More preferably, the pressure-sensitive adhesive layer of an adhesive tape according to the invention comprises one or more polymers selected from the group consisting of natural rubbers and synthetic rubbers, as well as blends thereof. In the case of a blend, the weight fraction of the total synthetic rubbers is preferably at most as high as the weight fraction of the total natural rubbers in the blend. Rubber pressure-sensitive adhesives exhibit a good combination of adhesive strength, tack, and cohesion, as well as balanced adhesive behavior on virtually all relevant substrates, and are thus very well suited for adhesive tapes according to the invention.These adhesive systems are generally known to those skilled in the art; details can be found in standard works on adhesive tapes such as the “Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas.

[0030] The synthetic rubbers are preferably selected from the group consisting of randomly copolymerized styrene-butadiene rubbers (SBR), butadiene rubbers (BR), synthetic polyisoprenes (IR), butyl rubbers (HR), halogenated butyl rubbers (XIIR), acrylate rubbers (ACM), ethylene-vinyl acetate copolymers (EVA), polyurethanes and blends of these synthetic rubbers.

[0031] The pressure-sensitive adhesive layer of an adhesive tape according to the invention preferably comprises one or more natural rubbers. The natural rubber(s) can in principle consist of any available grade, such as crepe, RSS, ADS, TSR, or CV grades; the skilled person can make a selection depending on the required purity and viscosity level. The pressure-sensitive adhesive layer can be produced in any manner known to the skilled person, for example, from an aqueous dispersion, solvent-based, from the melt, or from a latex. The latex used is preferably an aqueous dispersion of an untreated natural rubber.

[0032] Particularly preferably, the pressure-sensitive adhesive layer of an adhesive tape according to the invention comprises one or more natural rubbers and is produced from the melt. In particular, the pressure-sensitive adhesive layer of an adhesive tape according to the invention comprises one or more natural rubbers and is produced by extrusion. Very particularly preferably, the shaping into the layer takes place by means of a calender. The application weight of the pressure-sensitive adhesive layer comprising one or more natural rubbers is preferably 20 to 80 g / m 2 , more preferably 40 to 60 g / m 2The polymer(s) of a pressure-sensitive adhesive according to the invention are preferably crosslinked, more preferably thermally, by irradiation with UV light or by means of electron beams. Crosslinking is particularly advantageous for the redetachability of the adhesive tape after application. If thermal crosslinking occurs, this is preferably done via one or more thermal crosslinkers selected from the group consisting of accelerated sulfur or sulfur donor systems; isocyanate systems; reactive melamine, formaldehyde and (optionally halogenated) phenol-formaldehyde resins as well as reactive phenol resin and diisocyanate crosslinking systems with the corresponding activators, in particular maleimides, allyl esters such as triallyl cyanurate and polyfunctional esters of acrylic and methacrylic acid; and epoxidized polyester and acrylate resins.These crosslinkers are preferably activated at temperatures of 50 °C and above, especially at temperatures of 100 °C to 160 °C, and most preferably at temperatures of 110 °C to 140 °C. Alternatively or additionally, the thermal excitation of the crosslinkers can also be achieved by IR radiation or high-energy alternating fields.

[0033] Particularly preferably, the pressure-sensitive adhesive layer or the polymer(s) of a pressure-sensitive adhesive layer according to the invention are crosslinked by means of electron beams.

[0034] The pressure-sensitive adhesive layer of an adhesive tape according to the invention may comprise one or more additives selected from the group consisting of tackifiers (resins), plasticizers, fillers, pigments, UV absorbers, light stabilizers, age inhibitors, crosslinking agents, crosslinking promoters and elastomers.

[0035] The term “tackifier”, also referred to as “adhesive resin” or “tackifier” or “tackifier resin”, is understood by those skilled in the art to mean a resin-like substance which increases the adhesive strength or stickiness of the pressure-sensitive adhesive compared to the same pressure-sensitive adhesive without tackifier.

[0036] In the context of the invention, tackifiers are particularly selected from the group consisting of hydrogenated and non-hydrogenated hydrocarbon resins, for example, unsaturated Cs or Cs monomers; terpene-phenolic resins; terpene resins from raw materials such as α- or β-pinene and / or δ-limonene; aromatic resins such as coumarone-indene resins or resins from styrene or α-methylstyrene, as well as rosin and its derivatives such as disproportionated, dimerized, or esterified resins, whereby glycols, glycerin, or pentaerythritol can be used. Particularly suitable are age-resistant resins without an olefinic double bond, such as hydrogenated resins.

[0037] The pressure-sensitive adhesive layer of an adhesive tape according to the invention preferably comprises one or more additives selected from the group consisting of

[0038] Plasticizers, in particular plasticizer oils and low-molecular-weight liquid polymers, for example low-molecular-weight polybutenes; primary antioxidants, in particular sterically hindered phenols; secondary antioxidants, in particular phosphites and thiosynergists (thioethers);

[0039] Process stabilizers, especially C radical scavengers;

[0040] Light stabilizers, in particular UV absorbers and sterically hindered amine processing aids;

[0041] wetting additives;

[0042] adhesion promoters;

[0043] Endblock amplifier resins;

[0044] - other polymers, particularly preferably elastomers, in particular those based on pure hydrocarbons such as, for example, unsaturated polydienes such as natural or synthetically produced polyisoprene or polybutadiene; chemically substantially saturated elastomers such as, for example, saturated ethylene-propylene copolymers; α-olefin copolymers; polyisobutylene; butyl rubber; ethylene-propylene rubber and chemically functionalized hydrocarbons such as, for example, halogen-containing, acrylate-containing, allyl- and vinyl ether-containing polyolefins;

[0045] Fillers such as fibers, carbon black, zinc oxide, titanium dioxide, solid microspheres, solid and hollow glass spheres, silica, silicates and chalk.

[0046] Preferred fillers and pigments are selected from the group consisting of fibers, carbon black, zinc oxide, titanium dioxide, solid microspheres, solid and hollow glass spheres, silica, silicates, chalk, calcium carbonate, and zinc carbonate. The pressure-sensitive adhesive layer of an adhesive tape according to the invention particularly preferably comprises chalk in an amount of 1 to 30 wt. %, more preferably 5 to 20 wt. %, in particular 7 to 15 wt. %, based in each case on the total weight of the pressure-sensitive adhesive layer. Preferred age inhibitors are antiozonants, antioxidants, and light stabilizers and are particularly preferably selected from the group consisting of primary antioxidants, in particular sterically hindered phenols; secondary antioxidants, in particular phosphites and thioethers; UV absorbers; and sterically hindered amines.

[0047] Preferred plasticizers are selected from the group consisting of aliphatic, cycloaliphatic and aromatic mineral oils; di- and poly-esters of phthalic acid, trimellitic acid and adipic acid; liquid rubbers, in particular nitrile and polyisoprene rubbers; liquid polymers of butene and isobutene; acrylic acid esters; polyvinyl ethers; liquid and soft resins based on the raw materials for the adhesive resins; wool wax and liquid silicones.

[0048] An adhesive tape according to the invention comprises an impregnated paper layer. The impregnated paper layer can preferably be considered a carrier layer or at least a component of the carrier layer of an adhesive tape according to the invention. According to the inventors' findings, impregnated paper has proven to be a highly suitable material based on a renewable raw material, and, particularly with regard to tear resistance, at least equivalent and in some cases even advantageous compared to conventional film carriers. Therefore, an adhesive tape according to the invention is preferably free of films.

[0049] According to the invention, the paper layer of the adhesive tape is impregnated. This means that the paper of the paper layer is impregnated or saturated with a functional material used as a solution, emulsion, or dispersion, thereby influencing at least one application-related property of the paper layer. The paper layer is preferably impregnated with an organic material, more preferably with an organic polymeric material. The paper layer is particularly preferably impregnated with one or more materials selected from the group consisting of (meth)acrylic acid ester copolymers, where the (meth)acrylic acid ester copolymers may also contain carboxyl groups; styrene-butadiene copolymers, where the styrene-butadiene copolymers may also contain carboxyl groups; acrylonitrile-butadiene copolymers; and styrene-acrylic acid ester copolymers.The impregnating agent in question is preferably used as an aqueous dispersion. The basis weight of the impregnating agent (dry) is preferably 5 g / m. 2 up to 25 g / m 2 , particularly preferably 9 g / m 2 up to 20 g / m 2 The paper layer is preferably impregnated by immersing the paper in the impregnating agent for a certain time, which is in particular < 1 s, and then squeezing it between two rollers to remove excess impregnating agent.

[0050] Preferably, the non-impregnated paper of the paper layer has a mass fraction of inorganic substances, determined as the ignition residue according to the method described herein, of at least 0.60%. As the inventors' investigations show, this proportion of inorganic substances in the paper layer appears to lead to further improved tear resistance and high strengths in the z-direction. Particularly preferably, the non-impregnated paper of the paper layer has a mass fraction of inorganic substances, determined as the ignition residue according to the method described herein, of at least 0.65%, in particular of at least 0.70%.

[0051] Preferably, the non-impregnated paper of the paper layer has an average fiber length, determined by field flow fractionation according to the method described herein, of a maximum of 0.70 mm.

[0052] Preferably, the non-impregnated paper of the paper layer has a proportion of flake-like fine particles with a diameter of <0.2 mm, determined as a percentage of the projected area of ​​measured particles, of at least 10.0%, more preferably of at least 12.0%, in particular of at least 14.0%. According to the inventors' findings, this proportion appears to have a generally positive effect on the strength properties of the paper layer.

[0053] More preferred

[0054] - the non-impregnated paper of the paper layer has a proportion of flake-like fine particles with a diameter of < 0.2 mm, determined as a percentage of the projected area of ​​measured particles, of at least 10.0%, in particular of at least 12.0%, most preferably of at least 14.0%, and

[0055] - the non-impregnated paper of the paper layer has a mass fraction of inorganic substances, determined as the ignition residue according to the method described herein, of at least 0.60%, in particular of at least 0.65%, most preferably of at least 0.70%. Within the scope of the invention, the inventors have succeeded in identifying a series of paper parameters that provide the skilled person with guidance for selecting suitable paper layers to further enhance the performance of adhesive tapes according to the invention.

[0056] Thus, the non-impregnated paper of the paper layer of an adhesive tape according to the invention preferably has a splitting strength, determined according to Scott Bond according to TAPPI T569 om-22 according to the method described herein, of at least 500 J / m 2 , more preferably at least 600 J / m 2 , particularly preferably at least 700 J / m 2 on.

[0057] Preferably, the non-impregnated paper of the paper layer of an adhesive tape according to the invention has a breaking force in the z-direction, determined according to DIN ISO 15754:2010-04 according to the method described therein, of at least 900 kPa, more preferably of at least 1000 kPa, particularly preferably of at least 1050 kPa, in particular of at least 1100 kPa.

[0058] The non-impregnated paper of the paper layer of an adhesive tape according to the invention preferably has a tear resistance in the transverse direction (“cross direction”), determined by the Elmendorf method according to DIN EN ISO 1974:2012-09 in accordance with the method described herein, of at least 1000 mN, more preferably of at least 1500 mN, particularly preferably of at least 2500 mN, in particular of at least 2900 mN. The non-impregnated paper of the paper layer of an adhesive tape according to the invention also preferably has a tear resistance in the machine direction (“machine direction”), determined by the Elmendorf method according to DIN EN ISO 1974:2012-09 in accordance with the method described herein, of at least 1000 mN, more preferably of at least 1500 mN, particularly preferably of at least 1800 mN, in particular of at least 2000 mN.

[0059] Correspondingly, and based on the same method, the non-impregnated paper of the paper layer of an adhesive tape according to the invention preferably has a tear index in the cross direction of at least 18 mNm 2 / g, more preferably at least 20 mNm 2 / g, in particular of at least 21 mNm 2 / g. The non-impregnated paper of the paper layer of an adhesive tape according to the invention also preferably has a tear index in the machine direction of at least 12 mNm 2 / g, more preferably at least 14 mNm 2 / g, in particular of at least 15 mNm 2 / g on.

[0060] In the simplest case, an adhesive tape according to the invention consists of an impregnated paper layer and a pressure-sensitive adhesive layer.

[0061] In general, it may be advantageous if the paper layer on its side to be coated with the pressure-sensitive adhesive layer and / or the pressure-sensitive adhesive layer on its side in contact with the paper layer have been subjected to a corona, plasma and / or flame treatment before the two layers are brought together.

[0062] In a preferred embodiment, however, an adhesive tape according to the invention comprises a primer layer between the impregnated paper layer and the pressure-sensitive adhesive layer. A primer layer offers the possibility of effectively adjusting the surface energy of the paper layer through appropriate selection of the primer; moreover, a primer-mediated bond between the impregnated paper layer and the pressure-sensitive adhesive layer can also be achieved in the sense of a chemical bond if both the paper layer and the pressure-sensitive adhesive layer form chemical bonds to the primer layer.

[0063] The basis weight of the primer layer is preferably 0.1 to 10.0 g / m 2 , more preferably 0.5 to 5.0 g / m 2 , especially 1 to 3 g / m 2 .

[0064] The primer layer is preferably based on a latex, particularly preferably on an aqueous latex. The latex is preferably a natural latex modified with one or more (meth)acrylates, in particular with one or more alkyl methacrylates.

[0065] An adhesive tape according to the invention preferably comprises a release layer on the side of the impregnated paper layer facing away from the pressure-sensitive adhesive layer. This layer is preferably designed to favorably influence the unwinding properties of the adhesive tape wound into an Archimedean spiral or a cross-wound coil. The release layer preferably contains a polymer selected from the group consisting of silicones, fluorinated silicones, polyvinyl stearyl carbamates,

[0066] Polyethyleniminestearylcarbamides, chromium complexes of C14 to C28 fatty acids and stearyl copolymers, poly(meth)acrylates, and / or a surfactant release system based on long-chain alkyl groups, which in particular contains stearyl sulfosuccinates and / or stearyl sulfosuccinamates. Preferred silicones are selected from the group consisting of polyurethane- and / or polyurea-modified silicones, in particular organopolysiloxane / polyurea / polyurethane block copolymers. Silicones modified in this way provide optimized release behavior with optimized aging resistance and universal writable properties and are therefore advantageous.

[0067] An adhesive tape according to the invention preferably comprises a release layer containing a poly(meth)acrylate on the side of the paper layer facing away from the pressure-sensitive adhesive layer.

[0068] More preferably, this release layer is applied to the paper layer as an aqueous dispersion. The release layer and the impregnating agent of the paper layer of an adhesive tape according to the invention can contain one or more poly(meth)acrylates, which may be the same or different. Preferably, the poly(meth)acrylate(s) of the impregnating agent and the release layer are different from one another, particularly with regard to their chemical structure. Both the impregnating agent and the release layer are preferably based on an aqueous poly(meth)acrylate dispersion.

[0069] The release layer preferably comprises a polyacrylate whose underlying monomer composition comprises at least 80 wt.%, more preferably at least 90 wt.%, in particular at least 95 wt.% of an acrylic acid ester with an alcohol component according to the following formula (1)

[0070] -OR 1 -OC(=O)-NR 2 -R 3(1) comprises, wherein

[0071] R 1 for a Ci-C4 alkylene group;

[0072] R 2 represents H or a Ci-C4 alkyl group; and

[0073] R 3 represent a Ci2-C24 alkyl group.

[0074] Particularly preferably, the monomer composition underlying the polyacrylate of the release layer consists of 100% by weight of an acrylic acid ester with an alcohol component according to formula (1).

[0075] An adhesive tape according to the invention can have an antistatic coating, preferably a coating with amine or amide waxes, on the side of the release layer facing away from the paper layer. Such a coating can reduce the static adhesion of the adhesive tape to fingers and objects.

[0076] Another object of the invention is the use of impregnated paper as a carrier material in the construction of an adhesive tape for strapping applications.

[0077] Examples

[0078] Measurement and test methods - paper layer

[0079] Method A - area-related mass (grammage)

[0080] The mass per unit area was determined according to DIN EN ISO 536:2020-05 using a Sartorius analytical balance with an accuracy of 1 / 1000 g. The test area was 100 cm², which is different from the standard. 2 . From 10 individual measurements, an average value in g / m 2 formed.

[0081] Method B - Scott Bond splitting strength

[0082] The Scott Bond splitting strength was determined according to TAPPI T569 om-22 using the IBT Internal Bond Tester from emco Elektronische Mess- und Steuerungstechnik GmbH. Splitting strength defines the average potential energy in J / m 2relative to the sample surface required for sudden cleavage of a multilayer sample perpendicular to the material plane under defined test conditions. The test was conducted under the following conditions:

[0083] Contact time: 6 seconds

[0084] Contact pressure: 1035 kPa

[0085] Adhesive tape: Nitto tape Permacell P-50 / 08

[0086] Measuring range: MB 2 (300 - 1200 J / m 2 ) 5 individual measurements were taken in the machine direction and the cross direction and an overall mean value was calculated from 10 individual values.

[0087] Method C - Breaking force in z-direction

[0088] The tensile strength in the Z direction was determined according to DIN ISO 15754:2010-04 using the universal testing machine lnspekt 20 from Hegewald & Peschke Meß- und Prüftechnik GmbH. The tensile strength in the Z direction indicates the maximum stress in kPa required to split a square specimen perpendicular to the specimen plane. 25.4 mm wide test strips were placed between double-sided adhesive tape (Nitto tape Permacell P-50 / 08) on square test plates (test area: 645 ± 10 mm). 2) at a constant test speed of 66 mm / min for 6 seconds at a contact force of 900 N. The pressed test specimens were then stretched at 66 mm / min until failure, the maximum force was recorded, and the maximum stress was calculated. Ten individual tests were performed, five of which were conducted in each test strip direction. Due to the adhesive tape detaching from the metallic test plates, the average value could only be calculated from five valid individual measurements. In the other individual tests, the paper's splitting strength exceeded the adhesive strength of the adhesive tape.

[0089] Method D - Tear resistance according to Elmendorf

[0090] The tear resistance according to the Elmendorf method was determined in accordance with DIN EN ISO 1974:2012-09 using the L&W Tearing Tester 298 from ABB. The tear resistance according to the Elmendorf method indicates the force, applied suddenly using a pendulum, required to continue the tearing of an incised sample from the plane of the sheet. Four test sheets (height 62 mm, width 50 mm) of the same lateral orientation and grain direction were combined into a test set, and 10 test sets each were tested in the machine direction and the cross direction. An average value, expressed in mN, was calculated from 10 individual values ​​per test direction. The sample was tested with pendulum B.

[0091] Method E - Ignition residue

[0092] The residue on ignition (GR) was determined in accordance with ISO 1762:2019-07. The residue on ignition indicates the percentage mass fraction of inorganic fillers in paper, cardboard, or cellulose-based materials. The sample was pre-ashed, then burned in a muffle furnace at 525 °C until constant mass was reached, and the residue on ignition of the individual layers was determined gravimetrically from a duplicate determination. The calculated mean value is expressed as a percentage.

[0093] Method F - Fiber length measurement

[0094] The fiber morphological analyses of the samples were conducted using a Valmet Field Flow Fractionator. The fractionator's measurement principle is based on field flow fractionation followed by camera- and computer-assisted analysis and evaluation. The suspended fiber sample is injected into the water flow of a 100 m long tube. In the flow field of the fractionation coil, the fiber suspension is physically separated into its individual fractions according to the flow regime in the separation tube and the flow resistance of the individual particles or fibers. Due to the highest flow velocity in the center of the tube, larger particles and fibers are primarily transported there and exit the tube first. Three measurements were performed for each sample, and an average value was calculated.

[0095] The characteristics of the papers used are listed in Table 1. All papers were tested as non-impregnated papers.

[0096] Table 1 : Characteristics of the papers used cd - cross direction md - machine direction Another characteristic of the paper layers used was the so-called Fines A value, which indicates the proportion of flake-like fine particles < 0.2 mm as a percentage of the projected area of ​​the measured particles. The corresponding values ​​are listed in Table 2.

[0097] Table 2: Fines A values ​​of the papers used

[0098] Production of adhesive tapes:

[0099] The substrates, insofar as they were paper substrates, were first drawn through an immersion bath containing the impregnating agent (Europrene® Latice 5583, previously diluted with water to a solids content of 41%) at a speed of 250 m / min; the residence time of the substrate in the immersion bath was < 1 s. The paper substrates impregnated with the impregnating agent were then passed between two squeeze rollers to remove excess impregnating agent; they were subsequently dried at 105 °C in a 20 m² floating jet dryer.

[0100] The pressure-sensitive adhesive used had the following composition:

[0101] Natural rubber 40 wt.%

[0102] Talc 7 wt.%

[0103] Adhesive resin (Quintone® A100) 39 wt.%

[0104] Chalk 11 wt.%

[0105] Zinc oxide 0.5 wt.%

[0106] - Anti-aging agent 2.5 wt.%

[0107] The components were mixed together in a twin-screw extruder, melted, and extruded as such. The extruded pressure-sensitive adhesive was applied to the carriers using a calendering unit with four rollers; the application weight was 50 g / m² in each case. 2 .

[0108] The adhesive tape samples were cut into strips 100 mm long and 20 mm wide. The carrier materials used were the impregnated paper carriers No. 1 described above.

[0109] - 5 and an 85 pm thick film of monoaxially oriented polypropylene (MOPP) was used as carrier no. 6.

[0110] All tested adhesive tapes had an adhesive strength of at least 3.5 N / cm on steel (ASTM).

[0111] Test methods for adhesive tapes

[0112] Method H - Shredding

[0113] In this test, the removability of the adhesive tapes from defined substrates is examined under specified storage conditions. The substrates were panels made of

[0114] Polystyrene (PS)

[0115] High Impact Polystyrene (HIPS) is used.

[0116] The panels used as test substrates are cleaned with ethanol and stored at standard conditions for 2 hours to allow the cleaning agent to evaporate. The steel substrate is cleaned with acetone and stored at standard conditions for 1 hour.

[0117] The adhesive tape to be tested is applied to the specified substrate by rolling it back and forth once with a 2 kg steel roller.

[0118] The resulting composite is stored in a heating cabinet at 40 °C for 24 h, reconditioned for 2 h at standard climate and then stored in a climate cabinet at -10 °C for 24 h.

[0119] Immediately afterwards, the adhesive tape is peeled off from the substrate at -10 °C at an angle of 180 ° and a speed of 600 mm / min.

[0120] The adhesive tape is visually inspected for fiber tears, and the substrate is visually inspected for adhesive residues or other surface changes. The percentage of adhesive residues and / or fiber tears across the entire bonded surface is measured.

[0121] Adhesive residues / fiber tear-outs of up to 60% are considered acceptable. Adhesive residues / fiber tear-outs of 40 to 50% are considered satisfactory. Adhesive residues / fiber tear-outs of 20 to <40% are considered good.

[0122] Adhesive residues / fibre tears of < 20% are considered very good.

[0123] Method I - Re-detachability

[0124] This test also examines the removability of the adhesive tapes from defined substrates under specified storage conditions. The substrates used were panels made of

[0125] Polystyrene (PS)

[0126] High Impact Polystyrene (HIPS)

[0127] Polypropylene (PP)

[0128] - Steel (ASTM) is used.

[0129] The plates used as test substrates are cleaned with ethanol and stored for 2 hours at standard climate to allow the cleaning agent to evaporate.

[0130] The adhesive tape to be tested is applied to the specified substrate by rolling it back and forth once with a 2 kg steel roller.

[0131] The resulting composite is stored in a climate chamber at 60 °C / 95 % relative humidity for 1 week and then reconditioned for 24 h at standard climate.

[0132] The adhesive tape is then removed from the substrate at an angle of 180° at a speed of 20 cm / s under standard climate conditions.

[0133] The adhesive tape is visually inspected for fiber tears, and the substrate is visually inspected for adhesive residues or other changes to the surface.

[0134] The percentage of adhesive residues and / or fiber tears on the entire bonded surface is measured.

[0135] Adhesive residues / fibre tears of up to 60% are still considered acceptable.

[0136] Adhesive residues / fiber tear-outs of 40 to 50% are considered satisfactory. Adhesive residues / fiber tear-outs of 20 to < 40% are considered good.

[0137] Adhesive residues / fibre tears of < 20% are considered very good.

[0138] The results of the adhesive tape tests are shown in Table 3. Table 3: Results of the adhesive tape tests

[0139] See - comparative test

Claims

Patent claims 1. Adhesive tape for strapping applications, comprising a pressure-sensitive adhesive layer and an impregnated paper layer.

2. Adhesive tape according to claim 1, characterized in that the adhesive tape is free of films.

3. Adhesive tape according to one of claims 1 and 2, characterized in that the non-impregnated paper layer has a mass fraction of inorganic substances, determined as ignition residue according to the method described herein, of at least 0.60%.

4. Adhesive tape according to one of the preceding claims, characterized in that the non-impregnated paper layer has an average fiber length, determined by field flow fractionation according to the method described herein, of a maximum of 0.70 mm.

5. Adhesive tape according to one of the preceding claims, characterized in that the pressure-sensitive adhesive layer comprises one or more natural rubbers.

6. Adhesive tape according to one of the preceding claims, characterized in that the adhesive tape has a primer layer between the paper layer and the pressure-sensitive adhesive layer.

7. Adhesive tape according to one of the preceding claims, characterized in that the adhesive tape comprises a release layer containing a poly(meth)acrylate on the side of the paper layer facing away from the pressure-sensitive adhesive layer.

8. Use of impregnated paper as a carrier material in the construction of an adhesive tape for strapping applications.

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