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EP-4737529-A1 - ADHESIVE COMPOSITION, ADHESIVE TAPE AND THE USE THEREOF, AND METHOD FOR ELECTRICALLY MODIFYING THE ADHESIVE STRENGTH OF THE ADHESIVE TAPE

EP4737529A1EP 4737529 A1EP4737529 A1EP 4737529A1EP-4737529-A1

Abstract

The present invention provides an adhesive composition and an adhesive tape which allow bonding strength recovery and possess excellent reworking function, allowing to use it multiple times without significantly losing its adhesive properties. Furthermore, the invention relates to a method for modifying the adhesive strength of the adhesive tape on demand by controlling the rate of electrochemical stimuli or different DC voltages at different time scales and polarities; and to a use of the adhesive tape for bonding, electroadhesion, rebonding, and debonding in a wide range of applications.

Inventors

  • HASAN, Nazmul

Assignees

  • TESA SE

Dates

Publication Date
20260506
Application Date
20241105

Claims (13)

  1. An adhesive composition, prepared by polymerizing a mixture comprising at least the following components: a) 35 to 70 wt % of acrylate monomer (a1) from the group of (meth)acrylic esters containing at least one oxygen atom; and b) 20 to 40 wt % of acrylate monomer (a2) from the group of (meth)acrylic esters and/or amides containing at least one nitrogen atom; and c) 0.1 wt % to 15 wt % of one or more electro-responsive compounds from the group of polymerizable zwitterionic monomers and/or non-polymerizable zwitterionic compounds, preferably one or more zwitterionic monomers; and d) 0.005 to 10 wt % of at least one initiator; and e) 0 wt % to 20 wt % of one or more ionic liquids; and f) 0.1 wt % to 20 wt % of one or more conducting salts; and g) optionally 1 wt % to 20 wt % by weight of one or more acrylate monomers (a3), wherein the one or more acrylate monomers (a3) are different from acrylate monomers (a1) and (a2); and h) optionally additives, wherein the weight fractions of the components are based on the total weight of the mixture.
  2. The adhesive composition of claim 1, wherein the weight ratio of monomer (a1) to monomer (a2) in the mixture is in a ratio between 80:20 to 50:50, based on the total weight of monomer (a1) and monomer (a2).
  3. An adhesive tape comprising at least layers as follows: (a) a first layer D of adhesive, the layer D of adhesive containing the adhesive composition of any one of claims 1 or 2, wherein the adhesive composition contains one or more ionic liquids; and (b) optionally a carrier layer T, preferably wherein the carrier layer T is electrically conductive; and (c) optionally a second layer C of adhesive, the layer C of adhesive containing the adhesive composition of any one of claims 1 to 2, wherein the adhesive composition contains no ionic liquid.
  4. An adhesive tape comprising at least layers as follows: (a) a layer C of adhesive, the layer C of adhesive containing the adhesive composition of any one of claims 1 to 2, wherein the adhesive composition contains no ionic liquid; and (b) optionally a carrier layer T, preferably wherein the carrier layer T is electrically conductive.
  5. A method for modifying the adhesive strength of the adhesive tape of claim 3, comprising at least steps as follows: a) connecting a direct-current (DC) voltage source to a substrate A, preferably being electrically conductive, and to the carrier layer T, the substrate A being disposed on a first face of the layer D of adhesive having the carrier layer T being disposed on a second face of the layer D of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate A and a positive terminal of the DC voltage source is connected to the carrier layer T, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate A; and/or c) applying a voltage of 5 to 50 V, preferably 5 to 10 V, when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the carrier layer T, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate A; or d) applying a voltage according to step c), followed by applying a voltage according to step b); and optionally followed by applying a voltage according to step c), or followed by repeating the sequence of steps c) and b) in this order at least one time.
  6. A method for modifying the adhesive strength of the adhesive tape of claim 4, comprising at least steps as follows: a) connecting a direct-current (DC) voltage source to a substrate A, preferably being electrically conductive, and to the carrier layer T, the substrate A being disposed on a first face of the layer C of adhesive having carrier layer T being disposed on a second face of the layer C of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate A and a positive terminal of the DC voltage source is connected to the carrier layer T, thereby increasing the adhesive strength in an interface between the layer C of adhesive and the substrate A; and/or c) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the carrier layer T, thereby increasing the adhesive strength in an interface between the layer C of adhesive and the carrier layer T.
  7. A method for modifying the adhesive strength of the adhesive tape of claim 3, only comprising the first layer D of adhesive, the method comprising at least steps as follows: a) connecting a direct-current (DC) voltage source to a substrate A, preferably being electrically conductive, and to a substrate B, preferably being electrically conductive, the substrate A being disposed on a first face of the layer D of adhesive and the substrate B being disposed on a second face of the layer D of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate A and a positive terminal of the DC voltage source is connected to the substrate B, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate A; and/or c) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the substrate B, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate B; and/or d) applying a voltage of 5 to 50 V, preferably 5 to 10 V, when a negative terminal of the DC voltage source is connected to the substrate A and a positive terminal of the DC voltage source is connected to the substrate B, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate B; and/or e) applying a voltage of 5 to 50 V, preferably 5 to 10 V, when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the substrate B, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate A; or f) applying a voltage according to step d), followed by applying a voltage according to step c); and optionally followed by applying a voltage according to step d), or followed by repeating the sequence of steps d) and c) in this order at least one time; or g) applying a voltage according to step e), followed by applying a voltage according to step b); and optionally followed by applying a voltage according to step e), or followed by repeating the sequence of steps e) and b) in this order at least one time.
  8. A method for modifying the adhesive strength of the adhesive tape of claim 3, comprising at least steps as follows: a) connecting a direct-current (DC) voltage source to the carrier layer T, and to a substrate B, preferably being electrically conductive, the substrate B being disposed on the outer face of the layer D of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate B and a positive terminal of the DC voltage source is connected to the carrier layer T, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate B; and/or c) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a positive terminal of the DC voltage source is connected to the substrate B and a negative terminal of the DC voltage source is connected to the carrier layer T, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the carrier layer T; and/or d) applying a voltage of 5 to 50 V, preferably 5 to 10 V, when a positive terminal of the DC voltage source is connected to the substrate B and a negative terminal of the DC voltage source is connected to the carrier layer T, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate B; or e) applying a voltage according to step d), followed by applying a voltage according to step b).
  9. A method for modifying the adhesive strength of the adhesive tape of claim 3, comprising at least steps as follows: a') connecting a direct-current (DC) voltage source to the carrier layer T, and to a substrate A, preferably being electrically conductive, the substrate A being disposed on the outer face of the layer C of adhesive; and f) connecting the negative terminal of the DC voltage source to the substrate A and a positive terminal of the DC voltage source to the carrier layer T and applying a voltage of 5 to 50 V, thereby increasing the adhesive strength in an interface between the layer C of adhesive and the substrate A; or g) applying a voltage according to step d) of claim 3, and applying a voltage according to step f).
  10. A method for modifying the adhesive strength of the adhesive tape of claim 3, comprising at least steps as follows: a) connecting a direct-current (DC) voltage source to a substrate A, preferably being electrically conductive, and to a substrate B, preferably being electrically conductive, the substrate B being disposed on the outer face of the layer D of adhesive, and the substrate A being disposed on the outer face of the layer C of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate B and a positive terminal of the DC voltage source is connected to the substrate A, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate B; and/or c) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a positive terminal of the DC voltage source is connected to the substrate B and a negative terminal of the DC voltage source is connected to the substrate A, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate B, and also increasing the adhesive strength in an interface between the layer C of adhesive and the substrate A; or d) applying a voltage according to step c), followed by applying a voltage according to step b); and optionally followed by applying a voltage according to step c), or followed by repeating the sequence of steps c) and b) in this order at least one time.
  11. A method for modifying the adhesive strength of the adhesive tape of claim 3, comprising at least steps as follows: b) connecting a direct-current (DC) voltage source to the carrier layer T, and to a substrate A, preferably being electrically conductive, the substrate A being disposed on the outer face of the layer D of adhesive; and b) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a negative terminal of the DC voltage source is connected to the substrate A and a positive terminal of the DC voltage source is connected to the carrier layer T, thereby weakening the adhesive strength in an interface between the layer D of adhesive and the substrate A; and/or c) applying a voltage of 5 to 50 V, preferably 15 to 50 V, when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the carrier layer T, thereby increasing the adhesive strength in an interface between the layer D of adhesive and the substrate A; or d) applying a voltage according to step c), followed by applying a voltage according to step b); and optionally followed by applying a voltage according to step c), or followed by repeating the sequence of steps c) and b) in this order at least one time.
  12. A method for inducing electroadhesion to the adhesive transfer tape of claim 4, only comprising the second layer C of adhesive, the method comprising steps as follows: a) connecting a direct-current (DC) voltage source to a substrate A, preferably being electrically conductive, and to a substrate B, the substrate A being disposed on a first face of the layer C of adhesive and the substrate B not being in contact with a second face of the layer C of adhesive; and b) applying a voltage of preferably 20 to 100 V when a positive terminal of the DC voltage source is connected to the substrate A and a negative terminal of the DC voltage source is connected to the substrate B, thereby inducing electroadhesion in an interface between the layer C of adhesive and the substrate B, when the substrate B is brought closer to the second face of the layer C of adhesive and for as long as voltage is maintained.
  13. A use of the adhesive tape as claimed in any one of claims 3 or 4 for bonding, electroadhesion, rebonding and debonding in: (i) different metal surfaces or substrates coated with conductive materials; (ii) robotics, preferably in the manufacturing of robotic gripping arm; (iii) haptic devices; (iv) debonding applications; (v) sealing applications; (vi) applications where high bonding strength or debonding is needed without application of heat, light or pressure; (vii) sensing applications; (viii) consumer electronics; (ix) electronic packaging; (x) semi-structural bonding applications; (xi) microelectronics; (xii) battery mounting for EVs or cell phones with reusable functions; (xiii) cell phone back cover mounting, (xiv) biomedical applications; (xv) recycling applications (e.g., disassembly and reassembly of products); (xvi) microfabrication (e.g., transfer and positioning of small components); (xvii) environmental and structural adaptability (adaptability to surface conditions or structural changes); (xviii) application in smart wearable electronics (e.g., health monitoring); and (xix) optoelectronics (e.g., bonding camera modules).

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, to an adhesive tape comprising the adhesive composition, to a method for modifying the adhesive strength of the adhesive tape, and to a use of the adhesive tape for bonding, electroadhesion, rebonding, and debonding in a wide range of applications. BACKGROUND ART Debondable pressure-sensitive adhesive tapes are known. WO 2023/165966 A1 describes a pressure-sensitive adhesive composition comprising at least one base component selected from the group consisting of a polyacrylate pressure-sensitive adhesive and a synthetic rubber pressure-sensitive adhesive, a salt component and a (polymer) electrolyte component which is detached by applying an electrical DC voltage; as well as a pressure-sensitive adhesive tape comprising at least one electrically conductive backing material and at least one layer of the pressure-sensitive adhesive composition. The adhesive tape bonds to conductive substrates upon application of pressure and is debonded when a direct current (DC) voltage is applied and preferably when it is heated simultaneously. However, such pressure-sensitive adhesive tapes suffer from weak initial bonding, for example the pressure-sensitive adhesive tape described in WO 2023/165966 A1 (at 0 V, room temperature) was reported to have an initial peel adhesion of 4.8 N/cm. Such low adhesive strength limits the practical application of such adhesive tapes in applications where higher adhesive strength is required. One of the possible solutions for increasing the adhesive strength of adhesive tapes is to go in the direction of structural adhesive tapes, of which the structural bond may be activated by heating or UV systems. WO 2024/079548 A1 describes a semi-structural or structural adhesive composition that can be debonded upon application of a direct current electric voltage across the adhesive composition. However, after application of a direct current electric voltage of 50 V across the adhesive composition for 3 min, only a reduction in adhesive strength of between 50 % and 69 % could be achieved. WO 2021/115772 A1 describes curable and debondable two-part (2K) adhesive composition comprising: i) a first part comprising: (meth)acrylate monomer; co-polymerizable acid; and an electrolyte; and, ii) a second part comprising: a first curing agent for the monomers of said first part; a second curing agent for the monomers of said first part; and, a solubilizer. However, such an adhesive composition comprises co-polymerizable acid which may result in gas revolution, thereby decreasing the initial adhesion properties of the adhesive composition and thus limiting its reworking function. On top of that, the high weight percentage of co-polymerizable acid components in the adhesive may raise concerns about conductive substrate corrosion under various weather conditions. Other than the disadvantages mentioned above, there are further issues with structural adhesive tapes. For instance, activation by heating may not be viable for heat-sensitive systems, e.g., electric batteries, as a higher temperature between 100 °C and 200 °C is typically needed to initiate and complete the structural bonding process. In some heat activated adhesives, water vapor is produced as a byproduct, which may result in porous bonding structures. Alternatively, UV-activated structural bonding adhesive tapes may provide sufficient adhesive strength. However, there are several disadvantages that come with UV-activated structural bonding adhesive tapes. For instance, UV-C is mostly used to activate the adhesive and the adhesive needs to be cured over several hours or days or even weeks. UV-C is also harmful to the human body. In addition, the electrical debonding of structural bonding adhesive has not been very successful so far. Furthermore, debonding of the structural adhesive tape may compromise its reusability. In particular, structural bonding adhesive tapes do not have reworking function. In other words, once the adhesive tapes are debonded from a substrate, they can no longer be used again. EP 3858932 A1 describes a separation method for an adherend comprising a first voltage application step in order to allow for debonding of the electrolyte-containing adhesive layer from an adherend, a bonding maintenance step of recovering the adhesive force, a second voltage application step, and a separation step of separating the electrolyte-containing adhesive layer and the adherend. However, the peel adhesion for such an adhesive before and after voltage application and recovery within one hour was reported to be in the range of 6 to 8 N/20 mm, which is still low for various applications. Besides that, the adhesive composition described therein contains a commercially available ionic polymer (e.g., SOMAREX 530: anionic polyacrylamide polymer). TECHNICAL PROBLEM In view of the above, there remains a challenge to provide a suitable adhesive composition and adhesive tape that po