WO2008150227A1 - An electrochemically weakable adhesive and a laminate structure - Google Patents

An electrochemically weakable adhesive and a laminate structure Download PDF

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Publication number
WO2008150227A1
WO2008150227A1 PCT/SE2008/050654 SE2008050654W WO2008150227A1 WO 2008150227 A1 WO2008150227 A1 WO 2008150227A1 SE 2008050654 W SE2008050654 W SE 2008050654W WO 2008150227 A1 WO2008150227 A1 WO 2008150227A1
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WO
WIPO (PCT)
Prior art keywords
adhesive composition
particles
composition according
adhesive
electrically weakable
Prior art date
Application number
PCT/SE2008/050654
Other languages
French (fr)
Inventor
Petronella Norberg
Tommi Remonen
Xin Wang
Mats Sandberg
Original Assignee
Stora Enso Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Stora Enso Ab filed Critical Stora Enso Ab
Publication of WO2008150227A1 publication Critical patent/WO2008150227A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/04—Non-macromolecular additives inorganic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/48—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
    • B29C65/4855—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by their physical properties, e.g. being electrically-conductive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/76—Making non-permanent or releasable joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0003—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular electrical or magnetic properties, e.g. piezoelectric
    • B29K2995/0005—Conductive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2009/00—Layered products
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
    • C08K3/017—Antistatic agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/24—Acids; Salts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3442—Heterocyclic compounds having nitrogen in the ring having two nitrogen atoms in the ring
    • C08K5/3445—Five-membered rings
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/50—Additional features of adhesives in the form of films or foils characterized by process specific features
    • C09J2301/502—Additional features of adhesives in the form of films or foils characterized by process specific features process for debonding adherents

Definitions

  • the present invention relates to an electrochemically weakable adhesive and a laminate structure comprising said electrochemically weakable adhesive.
  • US 6,620,308 B2 discloses a material for use in the airplane industry.
  • the composition disclosed in US 6,620,308 B2 is developed for use as coatings and adhesives and is capable of releasing when subjected to a voltage current.
  • the composition has a matrix functionality and an electrolyte functionality, wherein the electrolyte functionality is provided by a block copolymer or a graft copolymer.
  • the matrix functionality provides an adhesive bond to a substrate, and the electrolyte functionality provides sufficient ionic conductivity to the composition to support a faradic reaction at an interface with an electrically conductive surface in contact with the composition, whereby the adhesive bond is weakened at the interface.
  • the composition may be a phase-separated composition having first regions of substantially matrix functionality and second regions of substantially electrolyte functionality.
  • US 6,620,308 further relates to a bonded structure comprising two electrically conductive surfaces and the electrochemically disbondable composition.
  • the electroche ⁇ u cally disbondable composition disclosed in US 6,620,308 is suitable for use m various industrial applications.
  • the voltage required to break the adhesive bonds m the composition disclosed in US 6,620,308 is qu] te high and the releasing time, i.e. the time needed to supply voltage to the adhesive for the adhesive bonds to be broken, is long. This limits its field of applications and makes it unsuitable for use m, e.g., packaging or distribution of products .
  • WO20070115675 provides a package adapted to be opened by the application of a voltage.
  • the package comprises an electrically weakable adhesive incorporated in its opening.
  • the adhesive bonds are weakened or broken whereby the package can be opened.
  • the electrically weakable adhesives previously known in the art such as the one described m US 6,620,308, are developed for industrial use and not particularly suitable for use in packages in contact with a consumer.
  • Another object of the invention is to provide an electrically weakable adhesive suitable for a wide field of applications and which adhesive enables a wide range of materials of the conductive surface to which the adhesive is bound.
  • Yet another object of the invention is to provide an electrically weakable adhesive suitable for use an packaging- and or distribution of products, e.g. m the opening of a package.
  • an electrically weakable adhesive composition possessing adhesive properties to provide an adhesive bond and possessing ion conductive properties to enable a weakening of said adhesive bond at the application of a voltage across the adhesive composition, wherein said composition further comprises particles and/or fibres enabling the formation of co-continuous networks of ion conducting channels m the composition .
  • the composition may comprise conductive- and/or non- conductive particles, preferably of nano and/or micro size.
  • the adhesive composition can comprise fibers, preferably of nano and/or micro size.
  • electrochemically weakable adhesive is an adhesive that possesses adhesive properties as well as ion conductive properties, which adhesive forms adhesive bonds to an electrically conductive surface in contact with said composition and wh.ch bonds are weakened or broken at the application of a voltage to said adhesive.
  • the adhesive thus possesses sufficient ion conductive properties to enable an electrochemical reaction, e.g. a faradic reaction, to occur at the adhesive bonds.
  • the adhesive bond is broken by the electrochemical reaction.
  • the adhesive is an electrochemically breakable adhesive.
  • the particles and/or the fibers enable the formation of nano-sized co-continuous networks in the adhesive, with ion conducting channels, without the need of further additives.
  • the formation of ion conducting channels in the adhesive facilitates the electrochemical reaction at the adhesive bonds and, thus, enables weakening of the adhesive bonds at lower voltages and at shorter releasing times.
  • the particles as such may, but need not, be conductive. Furthermore, the addition of particles improves the viscous properties of the adhesive.
  • the addition of particles may also be used to make the composition more brittle, thereby facilitating the release once initial breaking points are established by the electrochemical reaction.
  • the size of the particles is below 10 ⁇ m, more preferably below 5 ⁇ m or below 2 ⁇ m and most preferably below 1 ⁇ m.
  • the particle size is within the range of 1 nm to 10 ⁇ m, or within the range of 10 nm to 10 ⁇ m and even more preferably within the range of 100 nm to 10 ⁇ m.
  • the size of the particles can also be within the range of 10 nm to 5 ⁇ m .
  • the particle size is smaller than the distance between the surfaces to which the adhesive is bound .
  • the particles are added to the composition in an amount of at least 1 % by weight of the composition, preferably within the range of 1% ⁇ 25%.
  • Rod-like particles are preferably added within range of l%-10% by weight of the total composition, while spherical or essentially spherical particles are preferably added within the range of 10%-25%, most preferably within the range of 15%-20% by weight of the total composition.
  • the fibers are added to the composition in an amount of at least II, more preferably within the range of l%-10% and most preferably within the range of 2%-5%.
  • the particles and/or fibers can be added to the adhesive composition at an amount at or below the percolation threshold.
  • the particles can consist of, e.g., metal oxides, glass, such as quart glass or silicate glass, glass- ceramics, silicates, such as alkali silicates, zeolites such as ammonium zeolites or a mixture of any of the above.
  • the particles can, e.g., consist or comprise silicon dioxide.
  • the particles could also be of ceramics materials, such as gypsum ceramics e.g. silicate ceramics materials.
  • the particles are of oxide ceramics.
  • Oxide ceramics are nonporous fired fine ceramics consisting mainly of single phase metal oxides with high melting points.
  • the particular oxide ceramics suitable include, but are not limited to; aluminum oxide, zirconium(IV) oxide, beryllium oxide, uranium oxide, thorium oxide, magnesium oxide and titanium oxide or mixtures thereof .
  • the particles are carbides, e.g. metal carbides such as silicon carbide or silicon carbide ceramics, boron carbide or boron carbide ceramics.
  • the particles are of clay, e.g. bentonite.
  • the fibers can be naturally fibers such as cellulose fibers or synthetic fibers such as glass fibers or carbon fibers .
  • the particles and/or fibres are conducting, most preferably ion conducting particles and/or fibres.
  • the electrically weakable adhesive according to the invention is suitable for use in packaging and/or distribution of products.
  • the adhesive may, e.g., be used in the opening of a package.
  • a first and a second portion of a package, which portions form the opening of the package, might be provided with at least one conductive surface and the electrically weakable adhesive of the invention.
  • a voltage is applied across the adhesive whereby bonds in the adhesive is weakened and/or broken whereby the package can be opened.
  • the invention further relates to a laminate structure comprising a first and a second electrically conducting surface and a layer of an electrically weakable adhesive composition arranged between said surfaces , which electrically weakable adhesive composition comprises conductive- or non-conductive particles, preferably of nano and/or micro size.
  • electrically weakable adhesive composition comprises conductive- or non-conductive particles, preferably of nano and/or micro size.
  • the electrically conducting surfaces are arranged at a distance from each other and the electrically weakable adhesive composition partly bridges said distance.
  • the electrically weakable adhesive composition can bridge the whole distance between the conducting surfaces. Alternatively, the distance is bridged by the electrically weakable adhesive composition and a second layer formed of an electrically conductive adhesive.
  • the thickness of the layer of the electrically weakable adhesive composition can be, e.g., 10-500 ⁇ m, such as within the range of 100-200 ⁇ m or within the range of 200 - 500 ⁇ m. Thinner layers, e.g. within the range of 10 - 200, are advantageous since the material consumption is decreased. However, thicker layers, e.g. within the range of 200 - 500 ⁇ m, can enable resealing of the laminate due to its sticky properties.
  • the high ion conductive properties of the adhesive according to the invention make it possible to have thick layers of the adhesive on the conductive surfaces and still obtain the weakening of the adhesive bonds at the application of a voltage.
  • the conducting surfaces of the laminate can be of any conducting material, e.g. metals.
  • the conducting surfaces comprise carbon, e.g. graphite.
  • the conducting surfaces are of conducting polymers. Carbon based materials, e.g. graphite, and conducting polymers can be easily printed on a non conducting surface and are therefore particularly suitable for use as conducting surfaces m packaging and distribution of products.
  • the use of the adhesive composition according to the invention facilitates the use of printed conducting surfaces .
  • the invention further relates to a method of dclaminating, i.e. disbondmg, the laminate described above by applying a voltage across the electrochemica] Iy weakable adhesive .
  • the electrochemical] y weakable adhesive of the invention is composed of a composition possessing adhesive properties to provide an adhesive bond to an electrically conducting surface and sufficient ion conductive properties to enable a weakening of said bond, wherein said composition comprises at least one ionic compound in an effective amount to give said ion conductive properties and wherein said composition further comprises particles and/or fibres of micro and/or nano size.
  • the adhesive properties provide sufficient adhesive bonds to bind surfaces to one another mechanically or chemically.
  • the adhesive properties may be provided by polymers, polymer resins or fibres that possess adhesive properties.
  • the adhesive properties of the adhesive composition can be provided by at least one polymer, including, but not limited to, a polymer selected from the group consisting of epoxies, acrylics, polyesters, urethanes, polyamides, vinyls and phenolics.
  • the polymer should be present m an amount of at least 10%, preferably in an amount of at least 25 % by weight of the total adhesive composition.
  • the el ectrochemically weakable adhesive can, e.g., be an electrochemically weakable hot-melt adhesive, an electrochemically weakable contact adhesive, an electrochemically weakable pressure sensitive adhesive or an electrochemically weakable thermoset adhesive.
  • the conductive properties provide the ion conductivity necessary to support a faradic reaction, i.e. an electrochemical reaction an whj ch a material is oxidized or reduced, or some other chemical/physical reaction.
  • the materials are preferably chosen and designed such that the reaction occurs at the interface between one or both of the electrically conducting surfaces and the bonding layer.
  • the bonding layer may be designed such that the reaction will occur within the e] ectr ⁇ caliy weakable adhesive. This may, e.g., be accomplished by providing islands of a material with electrolyte functionality within the matrix material.
  • the electrolyte functionality may be provided by adding a salt to the material or by modifying the polymer so that it includes ion-coordinating moieties.
  • the salt can, e.g., be selected from the group consisting of alkali metal, alkaline earth and ammonium salts.
  • the salt includes an anion comprising at least one acidic proton, adding proton conducting functionality to the composition, e.g. bisulfite (HSO4 " ) , dihydrogen phosphate (H2PO4 ) , hydrogen phosphate (HPO4 ? ) , bicarbonate (HCO3 ) or boric acid.
  • the salt is present in the adhesive in an amount of at least 10% by weight, preferably in an amount within the range of 10-40% by weight of the composition.
  • the ion conductive properties can further be provided by an ionic liquid.
  • the ionic liquid is preferably present in the composition in an amount of at least 10 %, even more preferably m an amount of at least 20 % by weight of the total composition.
  • the adhesive of the present invention has an ionic conductivity of above 10 "11 S/cm 2 , preferably above 10 "e S/cm 2 , such as above 10 ⁇ 7 S/cm 2 , and most preferably above 10 "5 S/cm ? .
  • An ion conductivity of above ICT 11 S/cm ? enables an electrochemical reaction to occur at the adhesive bonds, whereby the bonds are weakened or broken.
  • An adhesive with an ion conductivity of above 10 ⁇ 9 S/cm 2 such as above 10 ⁇ 7 S/cm 2 , and most preferably above 10 5 S/cm 2 , requires less voltage in order to break or weaken the bonds.
  • the adhesive can comprise further additives, such as hardeners, solvents, plasticizers, etc. not mentioned herein but known in the art.
  • the hot melt adhesive was melted in a steel can in a furnace and the additives were added stirring the composition in a blender machine. Thereafter, the adhesive composition was allowed to solidify. The thereby produced composition was used to glue aluminum foils together.
  • the adhesive composition was melted and applied onto two surfaces of aluminum foil whereupon the two aluminum foils were heated and pressed together. In this way, totally six laminates were prepared.
  • a 25 V potential difference was applied across three of the prepared laminates. All of the laminates delaminated, i.e. disbonded, within 5 minutes at the application of 25 V. A 10 V potential difference was applied across the other three laminates. Two of the laminates were delaminated within 5 minutes at the application of 10V.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

The disclosure relates to an electrically weakable adhesive composition possessing adhesive properties to provide an adhesive bond and possessing ion conductive properties to enable a weakening of said adhesive bond at the application of a voltage across the adhesive composition, wherein said composition further comprises particles and/or fibres enabling the formation of co- continuous networks of ion conducting channels in the composition. The disclosure also relates to a laminate comprising a first and a second electrically conducting surface and a layer of an electrically weakable adhesive composition arranged between said surfaces.

Description

AN ELECTROCHEMICALLY MEAKABLE ADHESIVE AND Λ LAMINATE
STRUCTURE
Field of invention The present invention relates to an electrochemically weakable adhesive and a laminate structure comprising said electrochemically weakable adhesive.
Technical Background It is well known in the art that polymer chains can be broken by the application of a voltage. This is for example discussed in a review article by G. S. Shapoval (Cathodic initiation of reactions of macromolecule formation and degradation, Theoretical and Experimental Chemistry, Volume 30, Number 6, November 1995) .
US 6,620,308 B2 discloses a material for use in the airplane industry. The composition disclosed in US 6,620,308 B2 is developed for use as coatings and adhesives and is capable of releasing when subjected to a voltage current. The composition has a matrix functionality and an electrolyte functionality, wherein the electrolyte functionality is provided by a block copolymer or a graft copolymer. The matrix functionality provides an adhesive bond to a substrate, and the electrolyte functionality provides sufficient ionic conductivity to the composition to support a faradic reaction at an interface with an electrically conductive surface in contact with the composition, whereby the adhesive bond is weakened at the interface. The composition may be a phase-separated composition having first regions of substantially matrix functionality and second regions of substantially electrolyte functionality. US 6,620,308 further relates to a bonded structure comprising two electrically conductive surfaces and the electrochemically disbondable composition. The electrocheπu cally disbondable composition disclosed in US 6,620,308 is suitable for use m various industrial applications. The voltage required to break the adhesive bonds m the composition disclosed in US 6,620,308 is qu] te high and the releasing time, i.e. the time needed to supply voltage to the adhesive for the adhesive bonds to be broken, is long. This limits its field of applications and makes it unsuitable for use m, e.g., packaging or distribution of products . Another problem with the electrochemically disbondable composition disclosed in US 6,620,308 is that it exhibits inconsistent disbondmg, especially when one or both of the conductive surfaces to which it is bonded to is not a continuously conducting material, e.g. when the surfaces consist of graphite or conducting polymers printed on a nonconducting surface. Moreover, the composition disclosed m US 6,620,308 is complex since it requires several additives m order to provide sufficient ion conductivity and plasticizers to achieve proper viscous properties. WO20070115675 provides a package adapted to be opened by the application of a voltage. The package comprises an electrically weakable adhesive incorporated in its opening. When a voltage is applied across the electrically weakable adhesive, the adhesive bonds are weakened or broken whereby the package can be opened. However, the electrically weakable adhesives previously known in the art, such as the one described m US 6,620,308, are developed for industrial use and not particularly suitable for use in packages in contact with a consumer.
Summary of invention
It is an object of the invention to provide an electrochemically weakable adhesive which only requires low voltages to weaken the bonds and which gives rise to short releasing times.
Another object of the invention is to provide an electrically weakable adhesive suitable for a wide field of applications and which adhesive enables a wide range of materials of the conductive surface to which the adhesive is bound.
Yet another object of the invention is to provide an electrically weakable adhesive suitable for use an packaging- and or distribution of products, e.g. m the opening of a package.
These objects, as well as other advantages, have been achieved in accordance with the invention with an electrically weakable adhesive composition possessing adhesive properties to provide an adhesive bond and possessing ion conductive properties to enable a weakening of said adhesive bond at the application of a voltage across the adhesive composition, wherein said composition further comprises particles and/or fibres enabling the formation of co-continuous networks of ion conducting channels m the composition .
The composition may comprise conductive- and/or non- conductive particles, preferably of nano and/or micro size. Alternatively or additionally, the adhesive composition can comprise fibers, preferably of nano and/or micro size.
The term "electrochemically weakable adhesive" as used herein is an adhesive that possesses adhesive properties as well as ion conductive properties, which adhesive forms adhesive bonds to an electrically conductive surface in contact with said composition and wh.ch bonds are weakened or broken at the application of a voltage to said adhesive. The adhesive thus possesses sufficient ion conductive properties to enable an electrochemical reaction, e.g. a faradic reaction, to occur at the adhesive bonds. Most preferably, the adhesive bond is broken by the electrochemical reaction. Thus, most preferably the adhesive is an electrochemically breakable adhesive.
The particles and/or the fibers enable the formation of nano-sized co-continuous networks in the adhesive, with ion conducting channels, without the need of further additives. The formation of ion conducting channels in the adhesive facilitates the electrochemical reaction at the adhesive bonds and, thus, enables weakening of the adhesive bonds at lower voltages and at shorter releasing times.
The particles as such may, but need not, be conductive. Furthermore, the addition of particles improves the viscous properties of the adhesive.
Furthermore, the addition of particles may also be used to make the composition more brittle, thereby facilitating the release once initial breaking points are established by the electrochemical reaction.
Preferably, the size of the particles is below 10 μm, more preferably below 5 μm or below 2 μm and most preferably below 1 μm. Most preferably, the particle size is within the range of 1 nm to 10 μm, or within the range of 10 nm to 10 μm and even more preferably within the range of 100 nm to 10 μm. The size of the particles can also be within the range of 10 nm to 5 μm . Most preferably, the particle size is smaller than the distance between the surfaces to which the adhesive is bound .
Preferably, the particles are added to the composition in an amount of at least 1 % by weight of the composition, preferably within the range of 1%~25%. Rod-like particles are preferably added within range of l%-10% by weight of the total composition, while spherical or essentially spherical particles are preferably added within the range of 10%-25%, most preferably within the range of 15%-20% by weight of the total composition. Preferably, the fibers are added to the composition in an amount of at least II, more preferably within the range of l%-10% and most preferably within the range of 2%-5%. The particles and/or fibers can be added to the adhesive composition at an amount at or below the percolation threshold.
The particles can consist of, e.g., metal oxides, glass, such as quart glass or silicate glass, glass- ceramics, silicates, such as alkali silicates, zeolites such as ammonium zeolites or a mixture of any of the above. The particles can, e.g., consist or comprise silicon dioxide.
The particles could also be of ceramics materials, such as gypsum ceramics e.g. silicate ceramics materials.
In one preferred embodiment, the particles are of oxide ceramics. Oxide ceramics are nonporous fired fine ceramics consisting mainly of single phase metal oxides with high melting points. The particular oxide ceramics suitable include, but are not limited to; aluminum oxide, zirconium(IV) oxide, beryllium oxide, uranium oxide, thorium oxide, magnesium oxide and titanium oxide or mixtures thereof .
In another preferred embodiment the particles are carbides, e.g. metal carbides such as silicon carbide or silicon carbide ceramics, boron carbide or boron carbide ceramics.
In another preferred embodiment, the particles are of clay, e.g. bentonite.
The fibers can be naturally fibers such as cellulose fibers or synthetic fibers such as glass fibers or carbon fibers .
In one embodiment of the invention, the particles and/or fibres are conducting, most preferably ion conducting particles and/or fibres. The electrically weakable adhesive according to the invention is suitable for use in packaging and/or distribution of products. The adhesive may, e.g., be used in the opening of a package. A first and a second portion of a package, which portions form the opening of the package, might be provided with at least one conductive surface and the electrically weakable adhesive of the invention. When the package is to be opened, a voltage is applied across the adhesive whereby bonds in the adhesive is weakened and/or broken whereby the package can be opened.
The invention further relates to a laminate structure comprising a first and a second electrically conducting surface and a layer of an electrically weakable adhesive composition arranged between said surfaces , which electrically weakable adhesive composition comprises conductive- or non-conductive particles, preferably of nano and/or micro size. Preferably, the electrically conducting surfaces are arranged at a distance from each other and the electrically weakable adhesive composition partly bridges said distance. The electrically weakable adhesive composition can bridge the whole distance between the conducting surfaces. Alternatively, the distance is bridged by the electrically weakable adhesive composition and a second layer formed of an electrically conductive adhesive. The thickness of the layer of the electrically weakable adhesive composition can be, e.g., 10-500 μm, such as within the range of 100-200 μm or within the range of 200 - 500 μm. Thinner layers, e.g. within the range of 10 - 200, are advantageous since the material consumption is decreased. However, thicker layers, e.g. within the range of 200 - 500 μm, can enable resealing of the laminate due to its sticky properties. The high ion conductive properties of the adhesive according to the invention make it possible to have thick layers of the adhesive on the conductive surfaces and still obtain the weakening of the adhesive bonds at the application of a voltage.
The conducting surfaces of the laminate can be of any conducting material, e.g. metals. In one preferred embodiment, the conducting surfaces comprise carbon, e.g. graphite. Alternatively, the conducting surfaces are of conducting polymers. Carbon based materials, e.g. graphite, and conducting polymers can be easily printed on a non conducting surface and are therefore particularly suitable for use as conducting surfaces m packaging and distribution of products. The use of the adhesive composition according to the invention facilitates the use of printed conducting surfaces .
The invention further relates to a method of dclaminating, i.e. disbondmg, the laminate described above by applying a voltage across the electrochemica] Iy weakable adhesive .
Detailed description of the invention The electrochemical] y weakable adhesive of the invention is composed of a composition possessing adhesive properties to provide an adhesive bond to an electrically conducting surface and sufficient ion conductive properties to enable a weakening of said bond, wherein said composition comprises at least one ionic compound in an effective amount to give said ion conductive properties and wherein said composition further comprises particles and/or fibres of micro and/or nano size.
The adhesive properties provide sufficient adhesive bonds to bind surfaces to one another mechanically or chemically. The adhesive properties may be provided by polymers, polymer resins or fibres that possess adhesive properties. The adhesive properties of the adhesive composition can be provided by at least one polymer, including, but not limited to, a polymer selected from the group consisting of epoxies, acrylics, polyesters, urethanes, polyamides, vinyls and phenolics. The polymer should be present m an amount of at least 10%, preferably in an amount of at least 25 % by weight of the total adhesive composition.
The el ectrochemically weakable adhesive can, e.g., be an electrochemically weakable hot-melt adhesive, an electrochemically weakable contact adhesive, an electrochemically weakable pressure sensitive adhesive or an electrochemically weakable thermoset adhesive.
The conductive properties provide the ion conductivity necessary to support a faradic reaction, i.e. an electrochemical reaction an whj ch a material is oxidized or reduced, or some other chemical/physical reaction. The materials are preferably chosen and designed such that the reaction occurs at the interface between one or both of the electrically conducting surfaces and the bonding layer. Alternatively the bonding layer may be designed such that the reaction will occur within the e] ectrα caliy weakable adhesive. This may, e.g., be accomplished by providing islands of a material with electrolyte functionality within the matrix material. The electrolyte functionality may be provided by adding a salt to the material or by modifying the polymer so that it includes ion-coordinating moieties.
The salt can, e.g., be selected from the group consisting of alkali metal, alkaline earth and ammonium salts. Most preferably, the salt includes an anion comprising at least one acidic proton, adding proton conducting functionality to the composition, e.g. bisulfite (HSO4") , dihydrogen phosphate (H2PO4 ) , hydrogen phosphate (HPO4? ) , bicarbonate (HCO3 ) or boric acid. Preferably, the salt is present in the adhesive in an amount of at least 10% by weight, preferably in an amount within the range of 10-40% by weight of the composition. The ion conductive properties can further be provided by an ionic liquid. The ionic liquid is preferably present in the composition in an amount of at least 10 %, even more preferably m an amount of at least 20 % by weight of the total composition.
Preferably, the adhesive of the present invention has an ionic conductivity of above 10"11 S/cm2, preferably above 10"e S/cm2, such as above 10~7 S/cm2, and most preferably above 10"5 S/cm?. An ion conductivity of above ICT11 S/cm? enables an electrochemical reaction to occur at the adhesive bonds, whereby the bonds are weakened or broken. An adhesive with an ion conductivity of above 10~9 S/cm2, such as above 10~7 S/cm2, and most preferably above 105 S/cm2, requires less voltage in order to break or weaken the bonds. The adhesive can comprise further additives, such as hardeners, solvents, plasticizers, etc. not mentioned herein but known in the art.
The invention is described in more details with reference to an example below. It is to be understood that the invention is not limited to the particular process steps and materials disclosed herein.
Example 1
In a trial, l-octyl~3-methylimida2olium chloride (OMJ- Cl) and TiO2 particles, with a particle size of 2-3 μm, was added to a commercially available hot melt adhesive (Thermelt 869, supplied by Limgrossen AB) in an amount of 17,6 % OMI-Cl and 20 % TiO2 by weight of the total adhesive composition. The hot melt adhesive was melted in a steel can in a furnace and the additives were added stirring the composition in a blender machine. Thereafter, the adhesive composition was allowed to solidify. The thereby produced composition was used to glue aluminum foils together. The adhesive composition was melted and applied onto two surfaces of aluminum foil whereupon the two aluminum foils were heated and pressed together. In this way, totally six laminates were prepared.
A 25 V potential difference was applied across three of the prepared laminates. All of the laminates delaminated, i.e. disbonded, within 5 minutes at the application of 25 V. A 10 V potential difference was applied across the other three laminates. Two of the laminates were delaminated within 5 minutes at the application of 10V.

Claims

Cl a ims
1. An electrically weakable adhesive composition possessing adhesive properties to provide an adhesive bond and possessing ion conductive properties to enable a weakening of said adhesive bond at the application of a voltage across the adhesive composition, wherein said composition further comprises particles and/or fibres enabling the formation of co-continuous networks of ion conducting channels in the composition.
2. The electrically weakable adhesive composition according to claim 1, wherein said particles and fibres are conductive .
3. The electrically weakable adhesive composition according to claim 1, wherein said particles and fibres are non-conductive .
4. The electrically weakable adhesive composition according to any one of claims 1-3, wherein said particles and fibres are ion-conductive.
5. The electrically weakable adhesive composition according to any one of claims 1-4, wherein said particles and/or fibres are of a micro size and/or a nano size.
6. The electrically weakable adhesive composition according to any one of claims 1-5, wherein the adhesive is an electrochemically breakable adhesive.
7. The electrically weakable adhesive composition according to any one of claims 1-6, wherein the particle size is within the range of 1 nm to 10 μm, preferably within the range of IO nm Lo 10 μm, even more preferably within the range of 100 nm to 10 μm.
8. The electrically weakable adhesive composition according to any one of claims 1-7, wherein the size of the particles is below 10 μm, more preferably below 5 μrn, even more preferably below 2 μm and most preferably below 1 μm.
9. The electrically weakable adhesive composition according to any one of claims 1-8, wherein the particles are added to the composition m an amount of at least 1% by weight of the composition, preferably within the range of l%-25%.
10. The electrically weakable adhesive composition according to any one of claims 1-9, wherein rod-like particles are added within range of l%-10% by weight of the total composition.
11. The electrically weakable adhesive composition according to any one of claims 1-10, wherein spherical or essentially spherical particles are added within the range of 10%-25%, most preferably within the range of 15%-20% by weight of the total composition.
12. The electrically weakable adhesive composition according to any one of claims 1-11, wherein fibers are added to the composition m an amount of at least 1%, more preferably within the range of l%-10% and most preferably within the range of 2%-5% by weight of the total composition .
13. The electrically weakable adhesive composition according to any one of claims 1-12, wherein the particles are of oxide ceramics, such as aluminum oxide, zirconium ( TV) oxide, beryllium oxide, uranium oxide, thorium oxide, magnesium oxide and titanium oxide or mixtures thereof.
14. The electrically weakable adhesive composition according to any one of claims 1-12, wherein the particles are carbides, such as silicon carbide or silicon carbide ceramics, boron carbide or boron carbide ceramics.
15. The electrically weakable adhesive composition according to any one of claims 1-13, wherein the particles are of clay, e.g. bentonite.
16. Laminate structure comprising a first and a second electrically conducting surface and a layer of an electrically weakable adhesive composition in accordance with any one of claims 1-16 arranged between said surfaces .
17. Laminate according to claim 16, wherein the electrically conducting surfaces are arranged at a distance from each other and the electrically weakable adhesive composition at least partly bridges said distance.
PCT/SE2008/050654 2007-06-05 2008-06-04 An electrochemically weakable adhesive and a laminate structure WO2008150227A1 (en)

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CN109468086A (en) * 2018-10-26 2019-03-15 遵义春华新材料科技有限公司 A kind of adhesive and preparation method thereof
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JP2020147761A (en) * 2020-06-17 2020-09-17 日東電工株式会社 Adhesive sheet joint separating method
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