DE102015115717B4 - Asymmetric adhesive film with a force decoupling function and use - Google Patents

Abstract

Double-sided adhesive film for force decoupling between two joining partners, having a first adhesive layer, a carrier layer and a second adhesive layer different from the first adhesive layer, the second adhesive layer having a reactive adhesive mass which produces a structural bond on elastomers, and the first adhesive layer is a removable pressure-sensitive adhesive layer .

Description

The present invention relates to an asymmetrical double-sided adhesive film with a force-decoupling function.

State of the art

Asymmetric adhesive films (and in particular adhesive tapes) are generally understood to mean adhesive films and tapes with a double-sided adhesive finish, the adhesive present on one side of the film/tape being different from that on the other side. Such asymmetric adhesive films and tapes are used in particular where a single adhesive system is unable to satisfactorily bond two surfaces of different nature.

Asymmetrically structured adhesive tapes are known from practice and also from the patent literature. So describes already EP 0 284 564 B1 a multi-layer, heat-curable adhesive film based on epoxy resins and dicyandiamide as curing agent, containing a tacky, curable layer and a dry, curable layer for bonding construction parts, in particular made of metal, optionally with a nonwoven carrier material between these two layers. DE 10 2008 054 031 A1 claims an adhesive multilayer composite in which two identical or different aqueous polymer dispersions are applied to each side of a carrier material. The purpose of such an adhesive tape is to achieve a certain thickness of the composite to level out uneven surfaces, especially in masonry.

goal of EP 0 019 451 B1 was to decouple work processes from one another to the extent that the multilayer adhesive system according to the invention made it possible to apply pressure-activatable adhesive layers to two different layers that were to be glued together and then to join the layers attached to the two objects together and thereby the pressure-activatable to form composite adhesive material. A middle detachment layer is provided as an aid here, for example, which is introduced between the first and second adhesive layers, each of which can be activated by pressure, and is releasably attached thereto. After this middle release layer has been removed, pressure is then applied to create a permanent connection between the objects.

An asymmetrical adhesive film is the subject of EP 0 397 177 A2 , comprising a substrate with an adhesive layer on both sides, the adhesive layers being chemically and/or geometrically and/or physically asymmetrical, in particular for bonding multilayer semiconductor systems.

EP 0 688 845 A1 describes a double-sided adhesive tape having a moisture-curing adhesive on one side of the backing and a pressure-sensitive adhesive on the other side of the backing for bonding surfaces that would not be satisfactorily bonded with a single system.

U.S. 2009/0 317 610 A1 finally claims a system of 2 or more adhesives of different types and/or properties applied directly to one another, optionally with the aid of a primer, for example again for the bonding of surfaces that cannot be bonded or only insufficiently bonded with a single adhesive or also where larger gaps are filled and bridged where a thick film of adhesive made from just one single adhesive could possibly melt under pressure due to its thickness and thus be squeezed out of the adhesive joint. Such an undesirable adhesive behavior could be avoided, for example, by combining adhesives with different rheological properties.

Structural bonding or structural bonding is understood below to mean such connections in which the adhesive and the surfaces to be bonded are connected to one another after curing of the adhesive in such a way that they form a homogeneous structure, so that when this structure changes as a result of, for example, tensile or impact movements So the adhesive connection is no longer necessarily the point at which these movements attack and weaken or possibly even break the bond. Structural adhesives are typically liquid adhesives, but these adhesives are increasingly found in tape form, which has significant advantages over liquid form. Such structural connections are created, for example, by mixing and then reacting different components (as with 2-component epoxy systems) or under certain climatic conditions (minimum temperature or humidity), which cause the adhesive to harden and its structural connection to the surface to be bonded.

Structural adhesives in tape form are available both as hybrid adhesive systems, ie consisting of an adhesive based on two different polymer bases causing a structural adhesive bond, and as an adhesive based on a single polymer basic structure exists. The latter is discussed, for example, in the form of a band in DE 10 2010 013 145 A1 , relating to a heat-activatable, latently reactive adhesive based on a polyurethane dispersion or based on an epoxy-functional acrylate as in WO 2014 / 044 242 A1 described. An adhesive tape based on several different polymers that causes a structural connection is used, for example, in WO 2013 / 144 776 A1 claimed, namely the combination of a specific cyanoacrylate with an ethyl vinyl acetate as a film-forming copolymer and the use of this adhesive system in a single-sided or double-sided adhesive system.

Also known are double-sided adhesive tapes in which there is a pressure-sensitive adhesive on one side and a structurally connecting adhesive on the other side, as described, for example, in WO 2012 / 152 713 A1 , in which the structurally connecting adhesive is a thermoplastic.

From the WO 2013/174 430 A1 a crosslinkable adhesive film applied to a release liner or carrier is known, which has at least one specific cyanoacrylate monomer and at least one film-forming (co)polymer.

From the EP 0 688 845 A1 an asymmetrical, double-sided adhesive tape is known which has a moisture-crosslinking adhesive based on dextrin or polyvinyl alcohol on one side and an acrylate-based pressure-sensitive adhesive on the other side.

From the DE 199 40 340 A1 a method is known for producing structural adhesive connections of parts to be joined, in which the parts to be joined are held in a predetermined position while the adhesive is curing and a film made of heat-sealable construction adhesive with a pressure-sensitive adhesive coating on both sides is inserted into the bonded joint, with the parts to be joined being bonded by pressing against the Pressure-sensitive adhesive film is fixed to one another in a specified position and the construction adhesive is cured by the action of heat.

Presentation of the invention

Proceeding from the known prior art, it is an object of the present invention to provide an improved adhesive film that enables an improved adhesive connection between two surfaces and, in particular, has a structure that is tailored to the special features of the surfaces to be connected. In particular in cases where one of the surfaces is subjected to lifting, pressure, pushing, turning or pulling processes, the present invention is intended to solve the problem of bringing about a permanently reliable adhesive connection.

This object is achieved by a double-sided adhesive film having the features of claim 1. Claim 9 describes a use according to the invention of the double-sided adhesive film. Advantageous developments result from the dependent claims.

character list

• 1 eine Verklebung zwischen einem Profil und einem Untergrund mit einem herkömmlichen Haftklebstoff;
• 2 eine Verklebung zwischen einem Profil und einem Untergrund mit einer erfindungsgemäßen Klebefolie; und
• 3 den schematischen Aufbau einer bevorzugten Ausführungsform der erfindungsgemäßen Klebefolie.

The invention and preferred embodiments are explained in more detail by the following description, also with reference to the figures. show:

• 1 a bond between a profile and a substrate with a conventional pressure-sensitive adhesive;
• 2 a bond between a profile and a substrate with an adhesive film according to the invention; and
• 3 the schematic structure of a preferred embodiment of the adhesive film according to the invention.

In the description of the figures, elements that are the same, similar or have the same effect are provided with identical reference symbols in the different figures, and a repeated description of these elements is sometimes omitted in order to avoid redundancies.

Detailed Description of the Invention

In a first aspect, the present invention relates to an asymmetrical double-sided adhesive film, preferably in the form of an adhesive tape or a stamped part, with a backing layer. The present invention understands double-sided adhesive film as adhesive tapes, adhesive strips, and diecuts/diecut parts with a carrier layer and an adhesive layer on each side of the carrier layer. The adhesive film has a first adhesive layer (for example a pressure-sensitive adhesive or a reactive adhesive) on one side of the backing layer, and on the other side it has an adhesive layer that is different from the first adhesive layer and has a reactive adhesive composition. "Different from the first adhesive layer" means that the composition of the adhesive of the second adhesive layer is different from the composition of the adhesive of the first adhesive layer, and not that only parameters that are independent of the composition of the adhesive layers, such as the thickness of the adhesive layers, are different.

The backing layer and the second adhesive layer preferably act together as a force decoupling layer, as described below. The reactive adhesive composition of the second adhesive layer likewise preferably cures when the adhesive film is used, ie after the second adhesive layer has been bonded to an object, and produces a structural bond to the object. The reactive adhesive layer can harden as a result of a chemical reaction and/or under certain climatic conditions (temperature and/or humidity).

The reactive adhesive mass of the second adhesive layer creates a structural bond with elastomers. Elastomers are understood to mean, for example, natural rubber (NR), polybutadiene (BR), polyisoprene (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber (EPM, EPDM), butyl rubber (IIR), chloroprene rubber (CR), silicone rubber, thermoplastic elastomers (TPE), polyolefin rubbers (from Röthemeyer, Sommer; gummi technology, Munich 2013).

In a preferred embodiment, the reactive adhesive of the second adhesive layer has at least one cyanoacrylate, preferably a solid cyanoacrylate, particularly preferably phenylethyl cyanoacrylate. The cyanoacrylate monomers react by polymerisation during bonding and thus form a structural connection. In addition to the cyanoacrylate monomers, the adhesive may, as is known from the prior art, also contain one or more film formers, preferably at least one ethylene vinyl acetate copolymer (EVA copolymer). For this purpose, the adhesive may contain suitable stabilizers in order to prevent premature polymerization, as is known from the prior art. The handling and coating of the reactive adhesive mass of the second adhesive layer is preferably carried out from solvent, for example from an approximately 50% solution in ethyl acetate.

Depending on the intended application of the adhesive film, the reactive adhesive composition can also contain other additives known from the prior art, such as plasticizers, defoamers, fillers, accelerators, resins, hardeners, etc.

The carrier layer preferably has a film, a textile (for example a woven fabric or fleece) and/or a foamed material. Polyester, polycarbonate, polylactide or particularly preferably polymethyl methacrylate (PMMA), for example, can be used as the material for the film, in addition to other plastics.

The first adhesive layer of the adhesive film according to the invention is a redetachable pressure-sensitive adhesive layer which has a pressure-sensitive adhesive based on acrylate, rubber, silicone, polyurethane and/or mixtures thereof. In an embodiment not according to the invention, the first adhesive layer can also be a reactive adhesive layer which has a second reactive adhesive which (in terms of composition) differs from the reactive adhesive of the second adhesive layer described above, and when the adhesive film is used, i.e. after Adhering this first adhesive layer to an object, curing and creating a structural bond to the object.

The advantage of a pressure-sensitive adhesive layer as the first adhesive layer is that the adhesive film (and with it the object bonded to the adhesive tape by means of the reactive second adhesive layer) can be removed again from the substrate to which the adhesive film was stuck by means of the pressure-sensitive adhesive layer. This is particularly advantageous if the object has to be replaced due to wear or if the object is to be repositioned/moved on the ground. For example, such a double-sided adhesive film according to the invention can be used to attach rubber seals, e.g. on windows and doors or also on household appliances (so-called white goods), decorative strips, e.g. in the automotive sector, rubber printing plates and cloths on printing cylinders, creasing matrices, punching tools or Stamping tool parts, table tennis bat rubbers, tool handles, door stoppers, etc. can be used.

Surprisingly, it has been found that the use, not yet described, of a structural reactive adhesive system in at least one adhesive layer together with another different adhesive in a second layer in an asymmetric, carrier-based, double-sided adhesive material in the form of an adhesive film, an adhesive tape, an adhesive strip or an adhesive die-cut is not only ideally suited to permanently and structurally connecting different and otherwise unsatisfactorily bondable surfaces, but that such a system forms a force decoupling layer in addition to this bonding at the same time during lifting, pressing, pushing, rotating or pulling processes, in which it would be expected by their nature that a permanent and under the influence of such lifting, pressing, pushing, turning or pulling processes over a longer period of time or after numerous repetitions still present adhesion g is hardly possible. Such processes are, for example, punching or printing processes.

In the physical sense, force refers to an effect on a mass that causes a change in movement. The force is a directed, ie vector quantity. If a force acts on a fixed body, it can cause its deformation, if it acts on a moving body, it can accelerate it. Forces have various causes, after which they can be named, for example, such as frictional force, impact force, tensile force, centrifugal force or weight. If a deformation under the influence of a force is proportional to the acting force and the body returns to its original state after the force has been applied, this is referred to as an elastic change in shape. The restoring force of the body is responsible for this return to the original state. In the present context, force decoupling is understood to mean that the force acting on a body is permanently present to the extent required for an intended application, but the effects of this force action are modified to such an extent that undesirable behaviors of the body on which the force is acting do not occur. For example, numerous repetitions of a force acting on an elastic body often have the effect that its restoring force is negatively affected with the number of repetitions and the body then no longer completely returns to its original state in proportion to the number of repetitions of the force action, which is the case, for example, in processes in which a return to baseline, which is necessary to maintain the body's full ability to function, has adverse effects. Another example is when the repeated application of force eventually causes an undesirable displacement of the body on which the force is applied. In both cases, this can affect elastic sealing systems, for example, which ultimately no longer develop their full restoring force with the number of force effects or change their position under the pressure of the repeated force effects and in both cases become leaky as a result.

In the present case, force decoupling means that the force is applied to the full extent necessary to achieve the desired effect on a body, but negative changes in the state of the body due to the repeated use of this force do not occur or a significant higher number of force actions is possible than with conventional systems until negative and undesired effects of this force action become noticeable - in other words: The desired error-free functioning of a system under repeated action of a force occurring at regular or irregular intervals is maintained significantly longer than this is the case with conventionally known systems.

The reason for the force-decoupling effect of the system according to the invention in the present case lies in the interaction of the two sides equipped with adhesive and the carrier material of the adhesive system, such as an adhesive tape, an adhesive strip or a stamped part.

Using the example of 1 and 2 is to explain the effect of the force decoupling according to the invention compared to a conventional adhesive bond. 1 shows the bonding of a profile (2) to a substrate (1) using a simple pressure-sensitive adhesive layer (3) which is suitable for bonding the materials of the profile and substrate to one another. For example, the profile (2) can be a door seal made of an elastomer and the base (1) can be a door frame made of wood. When the door is now closed, it presses against the profile (2) and exerts a force F on the profile (2) in the direction of the arrow ( 1 , to the right). This causes the profile (2) to be compressed in the direction of force F and the profile (2) to expand in the plane perpendicular to force F. The pressure-sensitive adhesive (3) cannot fully accommodate the expansion of the profile (2). follow, which leads to a load on the pressure-sensitive adhesive connection between the pressure-sensitive adhesive layer (3) and the substrate (1). If such a load occurs with a large number of repetitions and/or over a longer period of time, the pressure-sensitive adhesive layer (3) and the substrate (1) or profile (2) or both will break. The bond is released and the profile begins to float. In 1 the pressure-sensitive adhesive connection is produced by means of a transfer adhesive layer, ie without the use of a carrier material. However, experience has shown that a backing-based pressure-sensitive adhesive film also shows these negative consequences after repeated use several times and/or after prolonged use, regardless of the type or thickness of the material.

A bond between profile (2) and substrate (1) with an adhesive film according to the invention is in 2 shown. The adhesive film according to the invention has a carrier layer (11) and, on one side, a first adhesive layer (12) which is suitable for effecting an adhesive connection between the carrier layer (11) and the substrate (1) which is sufficiently strong for the intended purpose , and on the other side a second, reactive adhesive layer (10), which leads to a structural adhesion of the carrier layer (11) to the profile (2). The structural bonding results in a reinforcement of the profile (e.g. an elastomer profile), so that when a force F is applied in the direction of the arrow ( 2 , right) - for example, as above, a door that presses against a door seal when closed - cannot spread out at the point of adhesion in the plane perpendicular to the force F. As a result, the bond between the carrier layer (11) and the substrate (1), ie the first adhesive layer (12), is not stressed and remains stable even under repeated and/or prolonged stress.

In particular, if a pressure-sensitive adhesive is used as the first adhesive layer, such a force decoupling is advantageous, since in this case unnecessary stress on the pressure-sensitive adhesive connection is avoided and the pressure-sensitive adhesive material can therefore be selected, for example, so that after age-related embrittlement of the profile or even if the profile is to be offset, the pressure-sensitive adhesive material can be removed from the substrate again, preferably without leaving any residue.

In principle, adhesive systems that can be used here on one side of the carrier as reactive, structural adhesive systems can be both systems based on a single polymer backbone and hybrid systems, i.e. mixtures of different polymer backbones. It is advantageous here if these systems are in a solid, band-like form. Although the use of liquid adhesive systems is also conceivable from a variety of applications, the disadvantages associated with it, such as possible application inaccuracy and impurity and the impossibility of being able to clearly decouple the actual bonding process from the adhesive application process in terms of time and space, speak for themselves to streamline the manufacturing process for a fixed, tape form of application.

Such band-shaped applications can be permanent, i.e. the application period ideally covers the entire life cycle of an application or a product in which the application was processed, or it can also be limited in time, for example where parts of the application or the product wear out during use and must be replaced at certain intervals in order to maintain full functionality. Essential characteristics for products or applications in which systems according to the invention are used are, on the one hand, the need for a completely satisfactory adhesive strength for the respective application and, on the other hand, the decoupling of a force acting on the product or acting in the application to the extent that that the adhesion is not adversely affected or only to a significantly lesser extent than is the case with previously known systems.

Durable applications within the meaning of the present invention include many types of seals that are repeatedly subjected to a certain force acting on them, for example in doors or windows or in machines with repeated lifting, pushing, pushing, rotating or pulling processes, where the complete tightness of the system is also important. In such cases, double-sided adhesive systems according to the invention that are not according to the invention can expediently be used, in which there are different reactive, structurally bonding adhesives on the two sides.

Parts of a product or application that are subject to regular or permanent exposure to force and therefore have a limited time due to signs of wear and tear in their correct functioning and must therefore be renewed again and again are, for example, automated stamp imprints at exactly the same place in a manufacturing process or stamping or embossing processes , where it depends on the permanently perfect accuracy of the punching or embossing in one plane. Equally suitable here are applications in which, as a result of a certain amount of wear and tear on a part involved in the respective application, it is important to replace this part as quickly and easily as possible. Such processes always include a basic device, unchanged in use and durable, which performs lifting, pushing, pulling, rotating or compressing processes and a part placed on this device, which is either subject to a certain wear and therefore residue-free at certain intervals has to be removed and replaced with a new part of the same type, or it should be exchangeable for a different part quickly and easily for a new application and thus in a certain way also be replaceable and repositionable at the same time.

3 shows schematically a section through a preferred embodiment of an adhesive film according to the invention. The adhesive film shown has a carrier layer (11) which can consist, for example, of a film, a textile (eg woven fabric or fleece) or a foamed material. The thickness of the carrier layer can be between about 5 μm and about 500 μm. A PMMA film with a thickness of about 90 μm is particularly preferably used as the carrier layer.

On one side of the backing layer (11), the adhesive film has an adhesive layer (10) with a reactive adhesive based on a cyanoacrylate, in particular a solid cyanoacrylate. For example, the reactive adhesive comprises phenylethyl cyanoacrylate, in particular in a mixture with an EVA copolymer. In a preferred embodiment, the reactive adhesive consists of 50% phenylethyl cyanoacrylate, 49.5% Levamelt 900 (an EVA copolymer available from Lanxess AG, Leverkusen, Germany) and 0.5% stabilizer.

On the other side of the backing layer (11), the adhesive film has an adhesive layer (12) with a pressure-sensitive adhesive. With its properties (viscoelasticity, adhesion to the substrate, cohesion, repositionability, residue-free detachment, long-term behavior), the PSA can be adapted to the planned use of the adhesive film. In a preferred embodiment, the PSA consists of a rubber solvent-based adhesive, particularly preferably based on styrene block copolymers. The construction and adaptation of a PSA are known to those skilled in the art (Donata Satas: Handbook of Pressure-Sensitive Adhesive Technology, June 1982). Formulations of rubber-solvent pressure-sensitive adhesives are described, for example, in Müller, Rath: Formulation of adhesives and sealants, Hanover 2004, from page 225, in particular solvent-based adhesives based on styrene block copolymers, from page 230.

At least one of the adhesive layers is covered with a cover layer (13) (also called release liner or liner), for example to prevent the pressure-sensitive adhesive layer from adhering to an undesired location or premature curing of the reactive adhesive layer. However, it is also entirely possible to use two identical or different liners in order to cover both adhesive layers. The cover layer (13) is siliconized, for example, and is compatible with the adhesive(s) covering the cover layer. In this context, “compatible” means that the covering layer can be easily detached from the respective adhesive layer in the application state, i.e., for example in the case of a covering layer for a reactive adhesive layer, before the reactive adhesive has cured, and that the covering layer does not induce premature curing of the reactive adhesive. In a preferred embodiment, the cover layer consists of graded siliconized PET film. "Graduated" means that the release values (i.e. the force required to detach the cover layer from the respective adhesive layer) can be different on both sides, depending on the respective adhesive system.

If the double-sided adhesive film is in the form of a strip and is to be rolled up (e.g. for storage, transport, etc.), it can be provided that only - as in 3 shown - a single cover layer (13) is used, which then covers both adhesive layers (10, 12) in the rolled state of the adhesive tape (not shown). In this case, the cover layer is preferably compatible with both adhesives. If the double-sided adhesive film is in the form of adhesive strips or diecuts, for example, and therefore cannot be stored rolled up or should not be stored rolled up for other reasons, a separate covering layer is used for each of the two adhesive layers.

In a second aspect, the present invention relates to a manufacturing method for a component using an adhesive film according to the invention. On the one hand, the two surfaces to be bonded can be connected to one another in a single bonding process at the same time or at only a short time interval and then at the same place, on the other hand, the bonding process of the two surfaces can be carried out separately from one another both in terms of time and space. For example, an embossing die can already be structurally and thus permanently connected to a corresponding adhesive film before the pressure-sensitive adhesive connection of the embossing die to the embossing device moving this die takes place at a later time and/or at a different location (immediately before use/at the actual place of use). . At least in the event that an asymmetrical adhesive film according to the invention has a pressure-sensitive adhesive layer and a structurally adhesive layer, this temporal and/or spatial decoupling of the two bonding processes is aimed at on the one hand for reasons of flexibility, even in by far the largest number of possible applications, since the curing of the structural Depending on the type of curing mechanism, a connection on one side of the film with a simultaneous pressure-sensitive adhesive connection on the other side could only be achieved with great effort (e.g. at elevated temperatures or by adding moisture).

A third aspect of the present invention relates to the use of a double-sided adhesive film according to the invention. As described above, an adhesive film according to the invention can be used to achieve a force decoupling between two joining partners that are bonded together, e.g. a component, and the substrate bonded to the component (via the adhesive film). At least one of the joining partners is preferably elastic and more preferably consists at least partially of an elastomer.

If a pressure-sensitive adhesive layer is used as the first adhesive layer, the component can be attached to the substrate in a repositionable manner, thereby enabling it to be detached from the substrate and reattached preferably without residue, or at least preferably without residue from the substrate reason to be detachable. However, when using a reactive adhesive layer not according to the invention as the first adhesive layer, the component can also be structurally connected to the substrate.

As far as applicable, all the individual features that are presented in the above description of the invention and in the exemplary embodiments can be combined with one another and/or exchanged without leaving the scope of the invention.

Reference List

1

underground

2

profile

3

pressure-sensitive adhesive layer

10

second adhesive layer (reactive adhesive)

11

backing layer

12

first adhesive layer (pressure-sensitive adhesive)

13

covering layer

Claims (11)

Double-sided adhesive film for force decoupling between two joining partners, having a first adhesive layer, a carrier layer and a second adhesive layer that differs from the first adhesive layer, the second adhesive layer having a reactive adhesive mass which produces a structural bond on elastomers, and the first adhesive layer is a removable pressure-sensitive adhesive layer . Double-sided adhesive film claim 1 , wherein the carrier layer and the second adhesive layer act together as a force decoupling layer. Double-sided adhesive film according to one of the preceding claims, wherein the reactive adhesive mass of the second adhesive layer hardens as a result of a chemical reaction during use of the adhesive tape and produces a structural bond. Double-sided adhesive film according to any one of the preceding claims, wherein the reactive adhesive has at least one cyanoacrylate, preferably a solid cyanoacrylate, particularly preferably phenylethyl cyanoacrylate. Double-sided adhesive film claim 4 , wherein the reactive adhesive also has one or more film formers, preferably at least one ethylene vinyl acetate copolymer. Double-sided adhesive film according to one of the preceding claims, in which the backing layer comprises a film, a textile or a foam. Double-sided adhesive film claim 6 , wherein the film is a polyester, polycarbonate, polymethyl methacrylate or polylactide film. Double-sided adhesive film according to one of the preceding claims, wherein the first adhesive layer is a pressure-sensitive adhesive layer which has a pressure-sensitive adhesive based on acrylate, rubber, silicone, polyurethane or mixtures thereof. Use of a double-sided adhesive film according to one of Claims 1 - 8th for force decoupling between two joining partners. use after claim 9 , wherein at least one of the two joining partners is elastic and preferably at least partially consists of an elastomer. Use after one of claims 9 and 10 , One joining partner being detachably connected to the other joining partner.

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