EP4731723A1 - Adhesive system including a curable adhesive film and a solid activator composition and related kit and method - Google Patents

Abstract

An adhesive system includes a tape and a solid activator composition. The tape includes a curable adhesive film including a film of a polymer, unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, and a transition metal cation. The solid activator composition includes an oxidizing agent and is not a free-standing film. A kit including the tape and the solid activator composition in the form of a crayon or paste is also described. A method of bonding a first substrate includes rubbing or spreading a solid activator composition onto the first substrate and then applying the tape. A crayon including an oxidizing agent and an acrylic polymer including a crystalline monomeric unit having from 16 to 50 carbon atoms and at least one other monomeric unit is also described.

Description

ADHESIVE SYSTEM INCLUDING A CURABLE ADHESIVE FILM AND A SOLID

ACTIVATOR COMPOSITION AND RELATED KIT AND METHOD

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Application No. 63/522,680, filed June 22, 2023, the disclosure of which is incorporated by reference in its entirety herein.

BACKGROUND

U.S. Pat. Appl. Nos. 2020/0362204, 2021/0102095, and 2021/0102097, each to Ranade et al., each describe an adhesive system including a curable adhesive free-standing film comprising a blend of a) a first film-forming polymer or oligomer, b) a first species comprising first unsaturated free-radically polymerizable groups, which may be a) or a species other than a), and c) a first transition metal cation. The curable adhesive free-standing film may be a pressure sensitive adhesive. The curable adhesive freestanding film may be used with a primer that is liquid at normal temperature and pressure and includes an oxidizing agent. The curable adhesive free-standing film may also include d) a reducing agent with no oxidizing agent and may be used in combination with a second curable adhesive free-standing film comprising a blend of: e) a second film-forming polymer or oligomer; f) a second species comprising second unsaturated free-radically polymerizable groups, which may be e) or may be a species other than e); and g) an oxidizing agent. Methods of bonding using such a curable adhesive free-standing film are also described.

In unrelated art, U.S. Pat. Nos. 5,604,268 (Randen et al.) and 11,267,997 (June et al.) disclose glue crayons and friction-activated adhesive formulations and application devices, respectively. U.S. Pat. No. 6,852,193 (Kneafsey et al.) discloses a composition in the form of a stick that includes an anaerobically polymerizable compound.

SUMMARY

In one aspect, the present disclosure provides an adhesive system that includes a tape and a solid activator composition. The tape includes a curable adhesive film including a film of a polymer, unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, and a transition metal cation. The solid activator composition includes an oxidizing agent and is not a free-standing film.

In another aspect, the present disclosure provides a kit that includes a tape and a solid activator composition. The tape includes a curable adhesive film including a film of a polymer, unsaturated free- radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, and a transition metal cation. The solid activator composition is in the form of a crayon or paste and includes an oxidizing agent.

In another aspect, the present disclosure provides a method of bonding a first substrate. The method includes applying a solid activator composition onto a surface of the first substrate and contacting the solid activator composition with a first surface of a tape. The solid activator composition includes an oxidizing agent and is applied by at least one of rubbing or spreading. The tape includes a curable adhesive film including a film of a polymer, unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, and a transition metal cation.

In another aspect, the present disclosure provides a crayon including an acrylic polymer and an oxidizing agent. The acrylic polymer includes a crystalline monomeric unit having from 16 to 50 carbon atoms and at least one other monomeric unit.

The term "polymer" refers to a molecule having a structure which includes the multiple repetition of units derived, actually or conceptually, from one or more monomers. The term “monomer” refers to a molecule of low relative molecular mass that can combine with others to form a polymer. The term “polymer” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction. The term “polymer” includes random, block, graft, and star polymers. The term “polymer” encompasses oligomers.

A “monomer unit” of a polymer or oligomer is a segment of a polymer or oligomer derived from a single monomer.

The terms "cure" and “curable” refer to joining polymer chains together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network polymer. Therefore, in this disclosure, the terms “cured” and “crosslinked” may be used interchangeably. A cured or crosslinked polymer is generally characterized by insolubility but may be swellable in the presence of an appropriate solvent. The term “crosslinked” includes partially crosslinked.

Oxygen permeable refers to having an oxygen permeability of a least 4000 centimeters cubed (cm³)*micrometer (pm)/meter squared (m²)*day*atmosphere (atm) (4000 cm³*pm/m²*day*atm) at 23°C to 25 °C without a specified relative humidity percentage.

The term adjacent, as used throughout the description, refers to two superimposed layers within the tape or constructions including the tape, activator, and one or more substrates, which are arranged directly next to each other, i.e., which are abutting each other and are typically in direct contact with each other.

The term "film-forming” means capable of forming a continuous and coherent film, which in some embodiments may result from one or more of solidification, curing, drying, or solvent removal of a melt, solution, or suspension.

The term “solid” means materials that are substantially self-supporting at room temperature (i.e., 20°C to 25 °C) such that if left at rest they will retain their shape without deforming or flowing. The term “free-standing film” means a film that is solid at normal temperature and pressure and has mechanical integrity independent of contact with any supporting material (which excludes, inter alia, liquids, surface coatings dried or cured in situ such as paints or primers, and surface coatings without independent mechanical integrity).

The term “hot melt processable” in the context of one of the polymer-containing layers or films described herein means the polymer-containing composition includes little or no conventional solvent (which is various embodiments may be less than 5 weight percent, less than 3 weight percent, less than 1 weight percent, less than 0.5 weight percent, less than 0. 1 weight percent, or less than 0.01 weight percent of conventional solvent), which may be hot melt processed under conventional conditions, where hot melt processes include hot melt blending and extruding.

The term “(meth)acrylate” includes, separately and collectively, methacrylate and acrylate.

The term “normal temperature and pressure” or “NTP” means a temperature of 20°C (293.15 K, 68°F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa).

The term “pendant” in the context of functional groups of a polymer or oligomer are functional groups that do not form a part of the backbone of the polymer or oligomer and are not terminal groups of the polymer.

The term “structural adhesive” means an adhesive that binds by irreversible cure.

“Pressure sensitive adhesives” (PSAs) are well known to those of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and typically, (4) sufficient cohesive strength to be cleanly removable from the adherend. PSAs are tacky and have the ability to adhere without activation by any energy source such as light, heat, or a chemical reaction. Materials that have been found to function well as PSAs are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power. One method useful for identifying pressure sensitive adhesives is the Dahlquist criterion. This criterion defines a pressure sensitive adhesive as an adhesive having a creep compliance of greater than 3 x 10’⁶ cm²/dyne as described in Handbook of Pressure Sensitive Adhesive Technology, Donatas Satas (Ed.), 2nd Edition, p. 172, Van Nostrand Reinhold, New York, NY, 1989. Alternatively, since modulus is, to a first approximation, the inverse of creep compliance, pressure sensitive adhesives may be defined as adhesives having a storage modulus of less than about 3 x 10⁵ N/m².

The term “glass transition temperature” or “Tg” refers to the temperature at which a material changes from a glassy state to a rubbery state. In this context, the term “glassy” means that the material is hard and brittle (and therefore relatively easy to break) while the term “rubbery” means that the material is elastic and flexible. For polymeric materials, the Tg is the critical temperature that separates their glassy and rubbery behaviors. If a polymeric material is at a temperature below its Tg, large-scale molecular motion is severely restricted because the material is essentially frozen. On the other hand, if the polymeric material is at a temperature above its Tg, molecular motion on the scale of its repeat unit takes place, allowing it to be soft or rubbery. Any reference herein to the Tg of a monomer refers to the Tg of a homopolymer formed from that monomer. The glass transition temperature of a polymeric material is often determined using methods such as Dynamic Mechanical Analysis (“DMA”) or Differential Scanning Calorimetry (e.g., Modulated Differential Scanning Calorimetry). Alternatively, the glass transition of a polymeric material can be calculated using the Fox Equation if the amount and Tg of each monomer used to form the polymeric material are known.

The term “alkyl” refers to a monovalent group which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof, and typically has 1 to 32 carbon atoms. Unless otherwise indicated, the alkyl group contains 1 to 25, 1 to 20, 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, 2-ethylhexyl, 2-octyl and 2-propylheptyl.

The term “aryl” refers to a monovalent group that is aromatic and, optionally, carbocyclic. The aryl has at least one aromatic ring. Any additional rings can be unsaturated, partially saturated, saturated, or aromatic. Optionally, the aromatic ring can have one or more additional carbocyclic rings that are fused to the aromatic ring. Unless otherwise indicated, the aryl groups typically contain from 6 to 30 carbon atoms. In some embodiments, the aryl groups contain 6 to 20, 6 to 18, 6 to 16, 6 to 12, or 6 to 10 carbon atoms. Examples of an aryl group include phenyl, naphthyl, biphenyl, phenanthryl, and anthracyl.

The term “aralkyl” refers to a monovalent group that is an alkyl substituted with an aryl group (e.g., as in a benzyl group). The term “alkaryl” refers to a monovalent group that is an aryl substituted with an alkyl group (e.g., as in a tolyl group). In some embodiments, for both groups, the alkyl portion has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms and an aryl portion has 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.

The term “alkylene” refers to a divalent group that is a radical of an alkane and includes groups that are linear, branched, cyclic, bicyclic, or a combination thereof. Unless otherwise indicated, the alkylene group typically has 1 to 30 carbon atoms. In some embodiments, the alkylene group has 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. Examples of “alkylene” groups include methylene, ethylene, propylene, 1,4-butylene, 1,4-cyclohexylene, and 1,4- cyclohexyldimethylene .

The term “arylene” refers to a divalent group that is aromatic and, optionally, carbocyclic. The arylene has at least one aromatic ring. Optionally, the aromatic ring can have one or more additional carbocyclic rings that are fused to the aromatic ring. Any additional rings can be unsaturated, partially saturated, or saturated. In some embodiments, the arylene group has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one aromatic ring. For example, the arylene group can be phenylene. Unless otherwise specified, arylene groups have 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms. The term “aralkylene” refers to a divalent group that is an alkylene group substituted with an aryl group or an alkylene group attached to an arylene group. The term “alkarylene” refers to a divalent group that is an arylene group substituted with an alkyl group or an arylene group attached to an alkylene group. In some embodiments, for both groups, the alkyl or alkylene portion has from 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. In some embodiments, for both groups, the aryl or arylene portion has from 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.

As used herein, the term “or” is generally employed in its usual sense including “and/or” unless the content clearly dictates otherwise. As used herein, the term “and/or” is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B).

As used herein, the term “room temperature” refers to a temperature in the range of 20°C to 25°C.

Herein, the term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims. Such terms will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements. By “consisting of’ is meant including, and limited to, whatever follows the phrase “consisting of.” Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present. By “consisting essentially of’ is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase “consisting essentially of’ indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they materially affect the activity or action of the listed elements. Any of the elements or combinations of elements that are recited in this specification in open-ended language (e.g., comprise and derivatives thereof), are considered to additionally be recited in closed-ended language (e.g., consisting of and derivatives thereof) and in partially closed-ended language (e.g., consisting essentially of, and derivatives thereof).

In this application, terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terms “a,” “an,” and “the” are used interchangeably with the term “at least one.” The phrases “at least one of’ and “comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

Also herein, all numbers are assumed to be modified by the term “about” and in certain embodiments, by the term “exactly.” As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Herein, “up to” a number (e.g., up to 50) includes the number (e.g., 50). Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.) and any sub-ranges (e.g., 1 to 5 includes 1 to 4, 1 to 3, 2 to 4, etc.).

The term “in the range” or “within a range” (and similar statements) includes the endpoints of the stated range.

Reference throughout this specification to “some embodiments,” means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list. Thus, the scope of the present disclosure should not be limited to the specific illustrative structures described herein, but rather extends at least to the structures described by the language of the claims, and the equivalents of those structures. Any of the elements that are positively recited in this specification as alternatives may be explicitly included in the claims or excluded from the claims, in any combination as desired. Although various theories and possible mechanisms may have been discussed herein, in no event should such discussions serve to limit the claimable subject matter. The drawings are not to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of one embodiment of a tape useful in the adhesive system of the present disclosure.

FIG. 2 is a cross section of another embodiment of a tape useful in the adhesive system of the present disclosure.

FIG. 3 is a cross section of one embodiment of a construction using a tape of the type shown in FIG. 2, solid activator compositions, and first and second substrates.

FIG. 4 is a cross section of one embodiment of a double-sided tape with only one curable adhesive film layer, useful in the adhesive system of the present disclosure.

FIG. 5 is a cross section of one embodiment of a double-sided multi-layer tape with a barrier film support layer, useful in the adhesive system of the present disclosure. FIG. 6 is a cross section of another embodiment of a construction using a tape of the type shown in FIG. 2, a solid activator composition, and first and second substrates.

FIG. 7 is a cross section of an embodiment of the adhesive system of the present disclosure covered with an oxygen-permeable liner.

FIG. 8 is a cross section of another embodiment of the adhesive system of the present disclosure covered with an oxygen-permeable liner.

FIG. 9 depicts an embodiment of a method for bonding two substrates using an embodiment of the adhesive system of the present disclosure.

FIG. 10 depicts another embodiment of a method for bonding two substrates using an embodiment of the adhesive system of the present disclosure.

FIG. 11 depicts yet another embodiment of a method for bonding two substrates using another embodiment of the adhesive system of the present disclosure.

FIG. 12 is a side (part-sectional) elevational view of a container for holding the solid activator composition.

FIG. 13 is a top view of a carrier which forms part of the container of FIG. 12.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The adhesive system of the present disclosure includes a tape. The tape comprises a curable adhesive film includes a film of a polymer, unsaturated free-radically polymerizable groups, and a transition metal cation. The unsaturated free-radically polymerizable groups, which may be bonded to the polymer (i.e., a component of the polymer) or may be in a species other than the polymer. In some embodiments, the curable adhesive film also includes a redox accelerator. The unsaturated free-radically polymerizable groups serve to crosslink the curable adhesive film.

In some embodiments, the curable adhesive film is a first layer of a multilayer curable adhesive film, wherein the multilayer curable adhesive film further comprises a support layer. In some embodiments, the support layer is a foam support layer, in some embodiments, a curable foam support layer. In some embodiments, the multilayer curable adhesive film is a double-sided tape with one curable adhesive film adjacent each major surface of a curable foam support layer (i.e., a second curable adhesive film is adjacent the surface opposite the first curable adhesive film). Thus, in this embodiment, a first curable adhesive film is adjacent to a first major surface of a curable foam support layer, and a second curable adhesive film is adjacent to a second major surface of the curable foam support layer.

As shown in FIG. 1 (not to scale), an embodiment of tape 110 includes a curable adhesive film 140 (having two major surfaces 142 and 144) adjacent to a support layer 150 (having two major surfaces 152 and 154). In some embodiments, the support layer 150 is a foam. In some embodiments, the support layer 150 is curable. As shown in FIG. 2, an embodiment of a multilayer curable adhesive fdm 210 includes a first curable adhesive film 240 (having two major surfaces 242 and 244), and a second curable adhesive film 260 (having two major surfaces 262 and 264), each of which are adjacent to opposite surfaces of a support layer 250 (having two major surfaces 252 and 254). More specifically, the first major surfaces 242 and 262 form the outer adhesive surfaces of multilayer curable adhesive film 210; the second major surface 244 of the first adhesive film 240 is adjacent the first major surface 252 of the support layer 250; and the second major surface 264 of the second adhesive film 260 is adjacent the second major surface 254 of the support layer 250. In some embodiments, the support layer 250 is a foam. In some embodiments, the support layer 250 is curable.

The second layer is a second curable adhesive film comprising a second film of a second polymer, second unsaturated free-radically polymerizable groups, which may be which may be bonded to the second polymer or in a second species other than the second polymer, and a second transition metal cation. The components of the first and second curable adhesive films may be the same or different. In some embodiments, the second unsaturated free-radically polymerizable groups are bonded to the second polymer. In some embodiments, the second unsaturated free-radically polymerizable groups are in a second species other than the second polymer, and the second polymer does not comprise unsaturated free-radically polymerizable groups.

In some embodiments of FIG. 2, the first curable adhesive film 240 is borne on a first major surface 252 of the support layer 250, and the second curable adhesive film 260 is borne on a second major surface 254 of the support layer 250. That is, the layers are typically made in one step, such as occurs in a coating or coextrusion process. In some embodiments of FIG. 2, the first curable adhesive film 240 is directly bound to a first major surface 252 of the support layer 250 and the second curable adhesive film 260 is directly bound to a second major surface 254 of the support layer 250. That is, the layers are typically made in two or more steps, such as occurs in a lamination process. Such procedures are well- known in the preparation of tapes. However the multilayer curable adhesive film is made, a major surface 244 of the curable adhesive film 240 is adjacent to a major surface 252 of the curable foam support layer 250.

Examples of suitable film-forming polymers useful for the polymer film in the curable adhesive film include (meth)acrylate polymers; aromatic or aliphatic polyurethanes (e.g., including those polyurethanes made with aliphatic or aromatic diols, polyamides, saturated and unsaturated polyesters, such as polybutylene terephthalate, polyethylene terephthalate, polyglycolic acid, polylactic acid, polyphydroxy butyrate, polycaprolactone, and combinations containing maleic acid repeating units); polyethers (e.g., such as polyacetal and its copolymers, polyphenylene oxide, polyetherketone, polyetheretherketone); natural and synthetic rubbers (e.g., polyisoprene, polychloroprene, nitrile rubber, butadiene-based rubbers); alkyds; phenolic resins (e.g., novolacs and resoles); amino resins (e.g., ureaformaldehyde resins, melamine-formaldehyde resins, and melamine-urea copolymer resins); and epoxies (e.g., those made from Bisphenol A or adducts using telechelic amino resins capped with oxirane functional groups). In some embodiments, the fdm -forming polymer or oligomer is a (meth)acrylate functional polymer, such as that made by adding (meth)acrylate end groups to polyester, polyurethane, polybutadiene, or polyether polymers. Various combinations of any of these film-forming polymers may be useful in the curable adhesive film in the article of the present disclosure.

In some embodiments, the film-forming polymer of the curable adhesive film is a (meth)acrylate polymer. In some embodiments, the curable adhesive films are pressure sensitive adhesives before cure upon contact with the solid activator described herein. As such, they are capable of maintaining substrates in position before cure, for example, under shop or factory conditions, without clamps or other supports. In some embodiments in which the curable adhesive film is a (meth)acrylate polymer and/or a pressure sensitive adhesive, the (meth)acrylate polymer comprises linear or branched alkyl (meth)acrylate ester monomer units selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n- propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, iso-pentyl (meth)acrylate, n-hexyl (meth)acrylate, iso-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, octyl (meth)acrylate, iso-octyl (meth)acrylate, 2-octyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, stearyl (meth)acrylate, isobomyl (meth)acrylate, benzyl (meth)acrylate, nonyl (meth)acrylate, isophoryl (meth)acrylate, and any combinations or mixtures thereof. In some embodiments, the (meth)acrylate polymer includes monomer units of at least one of 2-methylbutyl acrylate, isooctyl acrylate, lauryl acrylate, 4-methyl-2 -pentyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, isodecyl acrylate, isodecyl methacrylate, or isononyl acrylate.

Suitable monomer units further include mixtures of at least two or at least three structural isomers of a secondary alkyl (meth)acrylate of Formula I: wherein R¹ and R² are each independently a Ci to C30 saturated linear alkyl group; the sum of the number of carbons in R¹ and R² is 7 to 31; and R³ is H or CH3. The sum of the number of carbons in R¹ and R² can be, in some embodiments, 7 to 27, 7 to 25, 7 to 21, 7 to 17, 7 to 11, 7, 11 to 27, 11 to 25, 11 to 21, 11 to 17, or 11. Methods for making and using such monomers and monomer mixtures are described in U.S. Pat. No. 9,102,774 (Clapper et al.). In some embodiments, the alkyl (meth)acrylate ester monomer units may be copolymerized with one or more monoethylenically unsaturated monomers that have polar groups such as acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, N-substituted acrylamides (for example, N,N-dimethyl acrylamide), acrylonitrile, methacrylonitrile, hydroxyalkyl acrylates, cyanoethyl acrylate, N-vinylpyrrolidone, N-vinylcaprolactam, and maleic anhydride. In some embodiments, these polar copolymerizable monomers are used in amounts of less than 20% by weight and/or at least 6%, at least 8%, or at least 10%, based on the total weight of the monomer units. In some embodiments, the (meth)acrylate polymer comprises at least 6% by weight acrylic acid, at least 8% by weight, or at least 10% by weight acrylic acid, each based on the total weight of the monomers in the (meth)acrylate polymer. In some embodiments, the (meth)acrylate polymer includes from 0.1 weight percent to 12 weight percent of (meth)acrylic acid monomer units, based on the weight of the (meth)acrylate polymer. The (meth)acrylate polymer may also include small amounts of other useful copolymerizable monoethylenically unsaturated monomers such as alkyl vinyl ethers, vinylidene chloride, styrene, and vinyltoluene.

In some embodiments, the alkyl (meth)acrylate ester monomer units may be copolymerized with a crosslinking agent, such as 1,6-hexanediol diacrylate or with a photoactive triazine crosslinking agent such as taught in U.S. Pat. No. 4,330,590 (Vesley) and U.S. Pat. No. 4,329,384 (Vesley et al). Filmforming polymers can also be crosslinked with a heat-activatable crosslinking agent such as a lower- alkoxylated amino formaldehyde condensate having CM alkyl groups, for example, hexamethoxymethyl melamine or tetramethoxymethyl urea or tetrabutoxymethyl urea. Crosslinking the film-forming polymer may also be achieved by irradiating the composition with electron beam (or “e-beam”) radiation, gamma radiation, or x-ray radiation. This crosslinking occurs in the preparation of the film of the polymer, which occurs before reaction of unsaturated free -radically polymerizable groups in the curable adhesive film.

In some embodiments, the (meth)acrylate polymer has a Tg of no greater than 0°C. In some embodiments, the (meth)acrylate polymer has a Tg of -70°C to 0°C, -70°C to -10°C, -60°C to -10°C, -60°C to -20°C, -60°C to -30°C, -55°C to -35°C, or -50°C to -40°C.

In some embodiments, the curable adhesive film is a pressure sensitive adhesive including a first (meth)acrylate copolymer comprising from 0.1 weight percent to 12 weight percent of (meth)acrylic acid monomer units, based on the weight of the first (meth)acrylate copolymer; and a second (meth)acrylate copolymer comprising from 15 weight percent to 40 weight percent of (meth)acrylic acid monomer units, based on the weight of the second (meth)acrylate copolymer. The first (meth)acrylate copolymer and/or the second (meth)acrylate copolymer can comprise, as main monomer units, any of those described above. In some embodiments, the first (meth)acrylate copolymer and/or the second (meth)acrylate copolymer comprise, as main monomer units, linear or branched alkyl (meth)acrylate ester monomer units selected from the group consisting of 2-ethylhexyl (meth)acrylate, 2-propylheptyl (meth)acrylate, iso-octyl (meth)acrylate, and any combinations or mixtures thereof. In some embodiments, the first (meth)acrylate copolymer has a Tg of no greater than 0°C and the second (meth)acrylate copolymer has a Tg of greater than 0°C. In some embodiments, the second (meth)acrylate copolymer has a Tg of no greater than 100°C, no greater than 80°C, no greater than 60°C, no greater than 50°C, no greater than 45 °C, or even no greater than 40°C. In some embodiments, the first (meth)acrylate copolymer has a Tg of -70°C to 0°C, -70°C to -10°C, -60°C to -10°C, -60°C to -20°C, -60°C to -30°C, -55°C to -35°C, or -50°C to -40°C. In some embodiments, the second (meth)acrylate copolymer has a Tg of 2°C to I00°C, 2°C to 80°C, 2°C to 60°C, 2°C to 50°C, 2°C to 45°C, 5°C to 45°C, 5°C to 40°C, 5°C to 35°C, or I0°C to 30°C. In some embodiments, the curable adhesive film comprises from 65 to 99 weight percent, from 70 to 95 weight percent, from 75 to 95 weight percent, from 75 to 90 weight percent, or from 75 to 85 weight percent, of the first (meth)acrylate copolymer, and wherein the weight percentages are based on the total weight of the curable adhesive film composition. In some embodiments, the curable adhesive film in the article of the present disclosure comprises from 1 to 35 weight percent, from 1 to 30 weight percent, from 2 to 25 weight percent, from 3 to 25 weight percent, from 3 to 20 weight percent, from 4 to 20 weight percent, or even from 4 to 15 weight percent, of the second (meth)acrylate copolymer, and wherein the weight percentages are based on the total weight of the curable adhesive film composition. In some embodiments, these pressure sensitive adhesive compositions are described in U.S. Pat. Appl. Pub. No. 2021/0102099 (Unverhau et al.).

The polymer in the film of a polymer can be prepared by any suitable polymerization method. Suitable polymerization methods include, but are not limited to, photopolymerization, thermal polymerization, or ionizing radiation polymerization. These methods can be carried out in solution, emulsion, or bulk without solvent. Bulk polymerization methods are described in U.S. Pat. No. 5,804,610 (Hamer et al.). Optionally, photopolymerizable monomers may be partially polymerized to a viscosity of from 1000 cps to 40,000 cps to facilitate coating. Alternatively, partial polymerization can be effected by heat. If desired, viscosity can also be adjusted by mixing monomers with a thixotropic agent such as fumed silica.

Photopolymerization can take place in an inert atmosphere such as under a blanket of nitrogen or argon gas. Alternatively, an inert environment can be achieved by temporarily covering the photopolymerizable coating with a plastic film transparent to ultraviolet radiation and irradiating the coating through the film. If the polymerizable coating is not covered during photopolymerization, the permissible oxygen content of the inert atmosphere can be increased by mixing into the photopolymerizable composition an oxidizable tin compound such as disclosed in U.S. Pat. No. 4,303,485 (Uevens), which can enable relatively thicker coatings to be polymerized in air.

The curable adhesive film useful in the article of the present disclosure includes unsaturated free- radically polymerizable groups, which may be bonded to the polymer (i.e., a reactive polymer comprising unsaturated free-radically polymerizable groups) or in a species other than the polymer. Unsaturated free- radically polymerizable groups include ethylenically unsaturated groups (e.g., vinyl-containing groups such as (meth)acrylate groups). In some embodiments, the unsaturated free -radically polymerizable groups are part of a crosslinker (i.e., crosslinkable species) distinct from the polymer making up the polymer fdm. Such crosslinkers include two or more or three or more unsaturated free -radically polymerizable groups. In some embodiments, the crosslinker is a crosslinking monomer. In some embodiments, the crosslinker is an oligomer.

Examples of suitable crosslinkers include trimethylolpropane triacrylate (TMPTA), ethoxy trimethylolpropane triacrylate, propoxy glycerol triacrylate, pentaerythritol triacrylate, bistrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, ethoxy pentaerythritol tetraacrylate, trimethylolpropane trimethacrylate, ethoxy pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, glycerol diacrylate, glycerol triacrylate, ethylene glycol dimethacrylate, 1,3 -propanediol dimethacrylate, 1,2,4-butanetriol trimethacrylate, hexane diol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, and combinations thereof. Further examples of crosslinkers include other multifunctional polyol esters. For example, acrylic acid or methacrylic acid esters of a variety of polyols in which at least two hydroxy groups are esterified can be used as crosslinkers.

The curable adhesive film useful in the article of the present disclosure additionally comprises a transition metal cation. Examples of suitable transition metal cations include molybdenum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or zinc. In some embodiments, the transition metal cation is a copper cation, such as Cu(II), such as may be found in copper(II) acetate monohydrate and copper (II) naphthenate. In some embodiments, the transition metal cation is an iron cation, such as Fe(II) or Fe(III), such as may be found in Black 11 (FesCE or FeO FezCE), Red 102 (FezCE), or Yellow 42 (FezCE FEO).

Useful transition metal complexes are described in U.S. Pat. No. 11,370,940 (Townsend et al.), and have the general formula: [ML_p]ⁿ⁺A“, wherein M represents a transition metal capable of participating in a redox cycle with an oxidizing agent and a reducing agent. Useful transition metals, M, may include the catalytically active valent states of Cu, Fe, Ru, Cr, Mo, Pd, Ni, Pt, Mn, Rh, Re, Co, V, Au, Nb, and Ag. In some embodiments, the transition metal cation is a low valent transition metal including Cu(II), Fe(II), Ru(II), and Co(II). Other valent states of these metals may be used, and the active low valent state may be generated in situ.

In complexes of the formula [ML_p]ⁿ⁺A“, L represents a ligand. The ligand, L, may be used to solubilize the transition metal salts in a suitable solvent and adjust the redox potential of the transition metal for appropriate reactivity and selectivity. The ligands can direct the transition metal complex to undergo a desired one-electron transfer process, rather than a two-electron process such as oxidative addition/reductive elimination. The ligands may further enhance the stability of the complexes in the presence of different monomers and solvents or at different temperatures. Acidic monomers and monomers that strongly complex transition metals may still be efficiently polymerized by appropriate selection of ligands. Useful ligands include those having one or more nitrogen, oxygen, phosphorus, and/or sulfur atoms which can coordinate to the transition metal through a sigma-bond, ligands containing two or more carbon atoms which can coordinate to the transition metal through a pi-bond, etc.

Such ligands may be monodentate or polydentate compounds, in some embodiments, containing up to about carbon atoms and up to 10 heteroatoms selected from aluminum, boron, nitrogen, sulfur, non- peroxidic oxygen, phosphorus, arsenic, selenium, antimony, and tellurium, where upon addition to the metal atom, following loss of zero, one, or two hydrogens, the polydentate compounds can form with the metal, Mⁿ⁺, a 4-, 5-, or 6-membered saturated or unsaturated ring. Examples of suitable monodentate ligands are carbon monoxide; alcohols such as ethanol, butanol, and phenol; pyridine, nitrosonium (i.e., NO⁺); compounds of Group 15 elements such as ammonia, phosphine, trimethylamine, trimethylphosphine, tributylphosphine, triphenylamine, triphenylphosphine, triphenylarsine, or tributyl phosphite; nitriles such as acetonitrile or benzonitrile; isonitriles such as phenylisonitrile or butylisonitrile; carbene groups such as ethoxymethylcarbene or dithiomethoxy carbene; alkylidenes such as methylidene or ethylidene.

Examples of suitable polydentate compounds include dipyridyl, l,2-bis(diphenyl- phosphino)ethane; l,2-bis(diphenylarsino)ethane, bis(diphenylphosphino)methane, polyamines (e.g., ethylenediamine, propylenediamine, tetramethylethylenediamine, hexamethyl tris-aminoethylamine, diethylenetriamine, 1,3 -diisocyanopropane, and hydridotripyrazolylborate), hydroxycarboxylic acids (e.g., glycolic acid, lactic acid, and salicylic acid), polyhydric phenols such as catechol and 2,2’- dihydroxybiphenyl, hydroxyamines (e.g., ethanolamine, propanolamine, and 2-aminophenol); dithiocarbamates such as diethyldithiocarbamate and dibenzyldithiocarbamate, xanthates such as ethyl xanthate and phenyl xanthate, dithiolenes such as bis(perfluoromethyl)-l,2-dithiolene, aminocarboxylic acids (e.g., alanine, glycine, and o-aminobenzoic acid); dicarboxylic diamines as oxalamide and biuret, diketones such as 2,4-pentanedione, hydroxyketones such as 2-hydroxyacetophenone, a-hydroxy oximes such as salicylaldoxime, ketoximes such as benzil oxime, 1,10-phenanthroline, porphyrins, cryptands and crown ethers such as 18-crown-6 ether, and glyoximes such as dimethylglyoxime.

Other suitable ligands that can coordinate to the transition metal through a sigma bond are the inorganic groups (e.g., F“, OH“, CE, Br“, F, and hydride) and organic groups (e.g., CN“, SCN“, acetoxy, formyloxy, and benzoyloxy). The ligand can also be a unit of a polymer, for example, the amino group in poly(ethylenimine), the phosphino group in poly(4-vinylphenyldiphenylphosphine), the carboxylic acid group in poly(acrylic acid), and the isonitrile group in poly(4-vinylphenylisonitrile).

Useful ligands containing two or more carbon atoms that can coordinate to the transition metal through a pi-bond are provided by any monomeric or polymeric compound having an accessible unsaturated group, e.g., an ethylenic group, acetylenic group, or aromatic group which has accessible pi- electrons regardless of the total molecular weight of the compound. Examples of pi-bond ligands include the linear and cyclic ethylenic and acetylenic compounds having less than 100 carbon atoms (when monomeric), in some embodiments, having less than 60 carbon atoms, and from zero to 10 heteroatoms selected from nitrogen, sulfur, non-peroxidic oxygen, phosphorous, arsenic, selenium, boron, aluminum, antimony, tellurium, silicon, germanium, and tin. Specific examples of such pi-bond ligands include ethylene, acetylene, propylene, methylacetylene, a-butene, 2-butene, diacetylene, butadiene, 1,2- dimethylacetylene, cyclobutene, pentene, cyclopentene, hexene, cyclohexene, 1,3 -cyclohexadiene, cyclopentadiene, 1,4-cyclohexadiene, cycloheptene, 1-octene, 4-octene, 3,4-dimethyl-3-hexene, 1-decene; r|³-allyl, r|³-pentenyl, norbomadiene, r|⁵-cyclohexadienyl, cycloheptatriene, and cyclooctatetraene. Further suitable pi-bond ligands include substituted and unsubstituted carbocyclic and heterocyclic aromatic ligands having up to 25 rings and up to 100 carbon atoms and up to 10 hetero atoms selected from nitrogen, sulfur, non-peroxidic oxygen, phosphorus, arsenic, selenium, boron, aluminum, antimony, tellurium, silicon, germanium, and tin. Specific examples of such pi-bond ligands include r|⁵- cyclopentadienyl, benzene, mesitylene, toluene, xylene, tetramethylbenzene, hexamethylbenzene, fluorene, naphthalene, anthracene, chrysene, pyrene, p⁷-cycloheptatrienyl, triphenylmethane, paracyclophane, 1,4-diphenylbutane, p⁵-pyrrolo, r -thiophcnc. r -furan. pyridine, y-picoline, quinaldine, benzopyran, thiochrome, benzoxazine, indole, acridine, carbazole, triphenylene, silabenzene, arsabenzene, stibabenzene, 2,4,6-triphenylphosphabenzene, q⁵-selenophene, dibenzostannepine, r|⁵- tellurophene, phenothiazine, selenanthrene, phenoxaphosphine, phenarsazine, phenatellurazine, r|⁵- methylcyclopentadienyl, q⁵-pentamethylcyclopentadienyl, and 1 -phenylborabenzene.

In some embodiments, ligands include unsubstituted and substituted pyridines and bipyridines, tertiary amines, including polydentate amines such as N,N,N’,N’-tetramethylethylenediamine and tris(N,N-dimethylamino-ethyl)amine, acetonitrile, phosphites (e.g., (CfLOFP). 1,10-phenanthroline, porphyrin, cryptands and crown ethers (e.g., 18-crown-6 ether). In some embodiments, the ligand is a polydentate amine, bipyridine, or a phosphite. Ligands and ligand-metal complexes useful in the initiator systems of the present disclosure are described in Matyjaszewski and Xia, Chemical Reviews, 2001, vol. 101, pp. 2921-2990.

In complexes of the formula [ML_p]ⁿ⁺A“, A“ represents an anion. Examples of useful anions, A” include halide (e.g., chloride, bromide, fluoride), alkoxy groups having from 1 to 6 carbon atoms (i.e., Ci-Cg alkoxy), nitrate, sulfate, phosphate, biphosphate, hexafluorophosphate, triflate, methanesulfonate, arenesulfonate, cyanide, alkanecarboxylates (e.g., acetate), and arenecarboxylates (e.g., benzenecarboxylate). In complexes of the formula [ML_p]ⁿ⁺A“, n represents the formal charge on the transition metal having a whole number value of 1 to 7, in some embodiments, 1 to 3, and p is the number of ligands on the transition metal having a number value of 1 to 9, in some embodiments, 1 or 2.

In some embodiments, the curable adhesive fdm additionally includes a redox accelerator, such as a quaternary ammonium salt, amine hydrochloride, sodium chloride, or a phosphonium salt. Suitable quaternary ammonium salts may be represented by formula (R⁷)4N+ X-, wherein each R⁷ is independently alkyl, aryl, or a combination thereof, any of which may be substituted or unsubstituted, and X is Cl, Br, F, SbF, BF, or PF. Examples of suitable quaternary ammonium salts include dimethyl benzyl aniline chloride (DMBAC) and benzyltriethylammonium chloride. Suitable phosphonium salts may be represented by formula (R⁸)4?+ X-, wherein each R⁸ is independently alkyl, aryl, or a combination thereof, any of which may be substituted or unsubstituted, and X is Cl, Br, F, SbF, BF, or PF. In some embodiments, each R⁸ is independently phenyl or C1-C5 alkyl. Examples of suitable phosphonium salts include allyltriphenylphosphonium bromide (ATPB), 2-(ethoxycarbonyl)ethyl-triphenylphosphonium bromide, 1 -ethoxy carbonylethyl triphenylphosphonium bromide, 4-ethoxycarbonylbutyl triphenylphosphonium bromide, carbethoxymethyl triphenylphosphonium bromide, and methyltriphenylphosphonium bromide. Various combinations of redox accelerators may be used if desired. In some embodiments, the redox accelerator is used in an amount of at least 0.25 weight percent, and typically up to 4 weight percent, based on the total weight of the curable adhesive fdm.

While this disclosure is not to be bound by any theory or proposed mechanism, it is believed that the oxidizing agent in the curable adhesive film oxidizes the transition metal cation (e.g., Cu(I) to Cu(II)) forming radicals that initiate crosslinking of the crosslinkable species (typically catalytically) thereby forming a crosslinked network. It is believed that the redox accelerator, when present, serves as a reducing agent of the initially provided Cu(II) cation to Cu(I).

The curable adhesive film useful in the article of the present disclosure is typically a room temperature solid and also a free-standing film as defined herein, regardless of any support layer that may be present. The curable adhesive film may be made using conventional techniques such as solution coating onto a web. In some embodiments, including the embodiments illustrated herein, the curable adhesive film is made from an adhesive film that is hot melt processable and is made in a hot melt process. Hot melt processing, such as hot melt blending or hot melt extrusion, may be accomplished by any suitable means, including those disclosed in U.S. Pat. Appl. Pub. No. 2013/0184394 (Satrijo et al.). In some embodiments, adhesive films that may be hot melt processable comprise a blend of a reactive polymer comprising unsaturated free-radically polymerizable groups, which are typically pendant groups, and a transition metal cation. In some embodiments, adhesive films that may be hot melt processed comprise a blend of a film-forming polymer or oligomer, a reactive species comprising unsaturated free- radically polymerizable groups, and a transition metal cation. In some of these embodiments, the adhesive film further includes a redox accelerator (e.g., a quaternary ammonium salt). The adhesive film made by hot melt processing can then be applied directly adjacent an activator on a substrate or release liner to provide the adhesive system of the present disclosure.

The curable or cured adhesive film in the article of the present disclosure may be of any suitable thickness. In some embodiments, the thickness is at least 20 micrometers, at least 25 micrometers, at least 50 micrometers, at least 100 micrometers, at least 200 micrometers, at least 250 micrometers, at least 300 micrometers, or at least 350 micrometers. In some embodiments, the thickness is not more than 2000 micrometers, not more than 1000 micrometers, or not more than 500 micrometers. The curable adhesive film can be cured when comes into contact with the solid activator composition disclosed here, which includes an oxidizing agent. Typically, the oxidizing agent of the activator migrates into the curable adhesive films thereby initiating cure of the curable adhesive film or films, typically, in the absence of oxygen.

In some embodiments, the curable adhesive film is a first layer of a multilayer curable adhesive film, wherein the multilayer curable adhesive film further comprises a support layer. In some embodiments, the support layer is a foam support layer, in some embodiments, a curable foam support layer. In some embodiments, the curable support layer includes a base polymer. The base polymer may be the same or different than the film -forming polymer useful for the film of the polymer in the curable adhesive film and may be any of those described above for the curable adhesive film. The base polymer of the curable foam support layer may be the same as the polymer in the curable adhesive film, which may or may not include unsaturated free -radically polymerizable groups. The base polymer can also be made and processed by any of the processes described above for the curable adhesive film.

In some embodiments, the base polymer of the support layer, which may be a foam support layer or a curable foam support layer, is a silicone polymer. Acrylate and silicone foams are useful due to their ultraviolet light stability, conformability, and ability to distribute stress. Suitable silicone polymers can include an MQ resin containing a resinous core and nonresinous polyorganosiloxane group terminated with a silicon-bonded hydroxyl group, a treated MQ resin, and a polydiorganosiloxane terminated with a condensation reactable group. Such compositions may be used for structural glazing applications, as described in U.S. Pat. No. 8,298,367 (Beger et al.).

In some embodiments, the support layer, which in some embodiments, is a foam support layer or a curable foam support layer, includes a crosslinker mixed therein. If the base polymer of the curable foam support layer does not include unsaturated free -radically polymerizable groups, in some embodiments, such groups may be provided by a distinct species within the curable foam support layer, or they may be provided by a species that migrates into the curable foam support layer. Examples of suitable crosslinkers include those described above for the curable adhesive films.

Thus, in some embodiments, the curable foam support layer includes a base polymer that is receptive to receiving a crosslinker that is migratable into the curable foam support layer. In some embodiments, the crosslinker migrates from the curable adhesive film into the curable foam support layer. Thus, in these embodiments, the crosslinker of the curable foam support layer is the same as the species comprising unsaturated free-radically polymerizable groups of the curable adhesive film. The same crosslinker may also be separately loaded into the curable adhesive film and the curable foam support layer. The crosslinker of the curable foam support layer may, in other embodiments, be different than the species comprising unsaturated free-radically polymerizable groups of the curable adhesive film.

The crosslinker that is included within the curable foam support layer and/or migrates into the curable foam support layer, and that is included within the curable adhesive film, is activated when the curable adhesive film contacts the solid activator composition, typically when oxygen is excluded from the curable adhesive film or multilayer curable adhesive film, to start the redox cycle, thereby initiating crosslinking. This crosslinking of the crosslinker results in curing of both the curable adhesive film and the curable foam support layer. It is believed that an interpenetrating crosslinked network is formed in the bulk of the adhesive layers wherein the first network is that formed from the crosslinker(s) and the second network is that from the film -forming polymer(s). This crosslinked network is formed across the boundary between the various layers of the multilayer curable adhesive film (e.g., across the boundary between a cured adhesive film and a cured foam support layer), which is evidenced by cohesive failure, for example, splitting the foam support layer.

In some embodiments, the curable foam support layer includes a transition metal cation as described for the curable adhesive film. In some embodiments, the curable foam support layer also includes a redox accelerator as described for the curable adhesive film.

The foam support layer, in some embodiments, the curable foam support layer of the multilayer curable adhesive film useful in some embodiments of the present disclosure may be a closed cell foam, an open cell foam, a syntactic foam, a non-syntactic foam, or a combination thereof. Such foams can be made using chemical foaming agents, physical foaming agents, and mechanical foaming processes, for example. In some embodiments, the curable foam support layer includes a foaming agent and the same components as the curable adhesive film. In some embodiments, the foaming agent comprises at least one of expandable microspheres, hollow glass bubbles, or gas (e.g., nitrogen) bubbles, which are optionally surfactant stabilized. For example, a foam can be made from froth formed from physical agitation and stabilized with surfactant, such as a silicone or a fluorochemical known to be useful for foaming organic liquids that have low surface tension (e.g., those described in U.S. Pat. No. 4,415,615 (Esmay et al.)).

In some embodiments, the foam is a syntactic foam containing hollow microspheres, for example, hollow ceramic (e.g., glass) microspheres. Useful hollow glass microspheres include those having a density of less than 0.4 gram per milliliter (g/mE) and having a diameter of from 5 to 200 micrometers. The microspheres may be clear, coated, stained, or a combination thereof. Useful hollow glass microspheres include those available under the trade designation “3 M GEAS S BUBBLES K37” from 3M Co., St Paul, MN). The microspheres typically comprise from 5 to 65 volume percent of the foam composition. Examples of useful acrylic foams thus made are disclosed in U.S. Pat. No. 4,415,615 (Esmay et al.) and U.S. Pat. No. 6,103,152 (Gehlsen et al.).

In some embodiments, foams are formed by blending expanded polymeric microspheres into a polymerizable composition. In some embodiments, foams are formed by blending expandable polymeric microspheres into a composition and expanding the microspheres. An expandable polymeric microsphere includes a polymer shell and a core material in the form of a gas, liquid, or combination thereof. Upon heating to a temperature at or below the melt or flow temperature of the polymeric shell, the polymer shell expands to form the microsphere. Suitable core materials include propane, butane, pentane, isobutane, neopentane, isopentane, and combinations thereof. The thermoplastic resin used for the polymer microsphere shell can influence the mechanical properties of the foam, and the properties of the foam may be adjusted by the choice of microsphere, or by using mixtures of different types of microspheres. Examples of commercially available expandable microspheres include those available under the trade designation “EXPANCEL” (e.g., under the trade designation “EXPANCEL 551 DE”) from Akzo Nobel Pulp, Duluth, GA, and Performance Chemicals AB, Sundsvall, Sweden. Methods of making foams containing expandable polymeric microspheres and particulars of these microspheres are described in U.S. Pat. No. 6,103,152 (Gehlsen et al.).

Foams may also be prepared by forming gas voids in a composition using a variety of mechanisms including, for example, mechanical mechanisms, chemical mechanisms, and combinations thereof. Useful mechanical foaming mechanisms include, for example, agitating (for example, shaking, stirring, or whipping the composition, and combinations thereof), injecting gas into the composition (for example, inserting a nozzle beneath the surface of the composition and blowing gas into the composition), and combinations thereof. Methods of making the foams with voids formed via a foaming agent are described in U.S. Pat. No. 6,586,483 (Kolb et al.).

In some embodiments, the curable support foam layers have a foam density of from 320 kilograms per cubic meter (kg/m³) to 1041 kg/m³, from 400 kg/m³ to 880 kg/m³, or from 561 kg/m³ to 800 kg/m³.

In some embodiments, the curable foam support layer further includes a polymer modulus modifier to provide a desirable modulus. In some embodiments, the polymer modulus modifier comprises a polymer having a Tg of no greater than 100°C, no greater than 90°C, no greater than 80°C, no greater than 70°C, no greater than 60°C, no greater than 50°C, or no greater than 40°C. In some embodiments, the polymer modulus modifier comprises a polyvinyl acetal resin, particularly polyvinyl butyral (PVB). In some embodiments, the polymer modulus modifier comprises a high acid polymer. It is believed the polymer modulus modifier increases the modulus of the foam and/or toughens the system against an applied force.

In some embodiments, the polyvinyl acetal resin includes polymerized units having the formula: where Ri is hydrogen or an alkyl group having 1 to 7 carbon atoms (C1-C7). Polyvinyl acetal resins may be obtained, for example, by reacting polyvinyl alcohol with aldehyde, as known in the art. Polyvinyl alcohol resins are not limited by the production method. For example, those produced by saponifying polyvinyl acetate, for example, with alkali, acid, or ammonia water can be used. Polyvinyl alcohol resins may be either completely saponified or partially saponified. In some embodiments, the polyvinyl alcohol resin has a saponification degree of 80 mol % or more. Polyvinyl alcohol resins may be used singly or in combination of two or more.

Examples of suitable aldehydes used in the production of the polyvinyl acetal resin include formaldehyde (including paraformaldehyde), acetaldehyde (including para-acetaldehyde), propionaldehyde, butyraldehyde, n-octylaldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2- ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde, 2- methylbenzaldehyde, 3 -methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m- hydroxybenzaldehyde, phenylacetaldehyde, and beta-phenylpropionaldehyde. These aldehydes may be used singly or in combination of two or more.

In some embodiments, the alkyl residue of aldehyde includes 1 to 7 carbon atoms. In other embodiments, the alkyl reside of the aldhehyde includes 3 to 7 carbon atoms such as in the case of butylaldehyde, hexylaldehyde, and n-octylaldehyde. Of these butyraldehyde, also known as butanal, is most commonly utilized. Polyvinyl butyral (“PVB”) resin is commercially available from Kuraray under the trade designation MOWITAL and Solutia under the trade designation BUTVAR.

In some embodiments, the polyvinyl acetal (e.g., butyral) resin has a Tg ranging from 60°C to 80°C, or 60°C to 75°C. In some embodiments, the Tg of the polyvinyl acetal (e.g., butyral) resin is at least 65°C, or at least 70°C. When other aldehydes, such as n-octyl aldehyde, are used in the preparation of the polyvinyl acetal resin, the Tg may be less than 65°C, or even less than 60°C. The Tg of the polyvinyl acetal resin is typically at least 35°C, at least 40°C, or at least 45°C. When the polyvinyl acetal resin has a Tg of less than 60°C, higher concentrations of high Tg monomers may be employed in comparison to those utilizing polyvinyl butyral resin. When other aldehydes, such as acetaldehyde, are used in the preparation of the polyvinyl acetal resin, the Tg may be greater than 75 °C, or greater than 80°C. When the polyvinyl acetal resin has a Tg of greater than 70°C, higher concentrations of low Tg monomers may be employed in comparison to those utilizing polyvinyl acetal butyral resin.

The polyvinyl acetal (e.g., PVB) resin typically has a weight average molecular weight (Mw) of at least 10,000 g/mole, 15,000 g/mole or 30,000; and no greater than 100,000 g/mole, 80,000 g/mole or 60,000 g/mole.

The polyacetal resin is typically a random copolymer; however, block copolymers and tapered block copolymers may provide similar benefits as random copolymers. Examples of polyvinyl acetal resins are described in U.S. Pat. Appl. Pub. No. 2021/0102100 (Xia et al.).

In some embodiments, if used, the polyvinyl acetal resin is used in an amount of at least 5 weight percent, at least 7 weight percent, or at least 10 weight percent, based on total weight of the curable foam support layer composition. If used, the polyvinyl acetal resin is used in an amount of up to 25 weight percent, up to 20 weight percent, or up to 15 weight percent, based on total weight of the curable foam support layer composition. In some embodiments, the polymer modulus modifier comprises a high acid polymer. High acid in this context means there is an acrylate polymer that has higher amounts of acrylic acid in it than in a conventional pressure sensitive adhesive, such as 90: 10 isooctyl acrylate: acrylic acid. This makes the polymer “stiffer” (i.e., with a higher modulus).

In some embodiments, the high acid polymer is the second (meth)acrylate copolymer comprising from 15 weight percent to 40 weight percent of (meth)acrylic acid monomer units, based on the weight of the second (meth)acrylate copolymer, described above for some embodiments of the curable adhesive film. In some embodiments, the high acid polymer has a Tg of 2°C to 100°C, 2°C to 80°C, 2°C to 60°C, 2°C to 50°C, 2°C to 45°C, 5°C to 45°C, 5°C to 40°C, 5°C to 35°C, or I0°C to 30°C. The high acid polymer is believed to provide outstanding mechanical properties, due in particular to the relatively high concentration of (meth)acrylic acid monomer units.

In some embodiments, if used, the high acid polymer is used in an amount of at least 1 weight percent, at least 2 weight percent, at least 3 weight percent, or at least 4 weight percent, based on the total weight of the curable foam support layer. If used, the high acid polymer is used in an amount of up to 35 weight percent, up to 30 weight percent, up to 25 weight percent, up to 20 weight percent, or up to 15 weight percent, based on the total weight of the curable foam support layer.

The curable foam support layer and curable adhesive films may contain one or more optional additives. Such additives can include fillers, antioxidants, viscosity modifiers, pigments (inorganic or organic), tackifying resins, fibers, flame retardants, antistatic and slip agents, thermally conductive particles, electrically conductive particles, continuous microfibers, filaments, and mixtures thereof. Various additives may be used in amounts typical for adhesive tapes.

Besides the hollow microspheres described above, useful fillers include glass beads, metal oxide particles, silica particles (e.g., fumed silica), carbonates, metal oxides, silicates (e.g., talc, asbestos, clays, mica), sulfates (e.g., barium sulfate), metals in powder form (e.g., aluminum, zinc and iron), silicon dioxide, and aluminum trihydrate. In some embodiments, the solid or hollow filler particles comprise a polymer, glass, ceramic, or metal oxide material. Combinations of two or more fillers may be used if desired. In some embodiments, the filler comprises fumed silica.

Examples of useful organic pigments include halogenated copper phthalocyanines, aniline blacks, anthraquinone blacks, benzimidazolones, azo condensations, arylamides, diarylides, disazo condensations, isoindolinones, isoindolines, quinophthalones, anthrapyrimidines, flavanthrones, pyrazolone oranges, perinone oranges, beta-naphthols, BON arylamides, quinacridones, perylenes, anthraquinones, dibromanthrones, pyranthrones, diketopyrrolo-pyrrole pigments (DPP), dioxazine violets, copper and copper-free phthalocyanines, and indanthrones. Examples of useful inorganic pigments include titanium dioxide, zinc oxide, zinc sulphide, lithopone, antimony oxide, barium sulfate, carbon black, graphite, black iron oxide, black micaceous iron oxide, brown iron oxides, metal complex browns, lead chromate, cadmium yellow, yellow oxides, bismuth vanadate, lead chromate, lead molybdate, cadmium red, red iron oxide, Prussian blue, ultramarine, cobalt blue, chrome green (Brunswick green), chromium oxide, hydrated chromium oxide, organic metal complexes, and laked dye pigments.

The polymer used to make the curable foam support layer may be initially coated onto and polymerized against a flexible backing sheet (for example, a release liner) that has a low-adhesion surface from which the polymerized layer is readily removable. If the opposite face of the backing sheet also has a low adhesion surface, the backing sheet with its polymerized layer may be wound up in roll form for storage prior to assembly of the finished adhesive article.

The curable or cured foam support layers in the article of the present disclosure may be of any suitable thickness. In some embodiments, the thickness is at least 20 micrometers, at least 25 micrometers, at least 50 micrometers, at least 100 micrometers, at least 200 micrometers, at least 250 micrometers, at least 300 micrometers, or at least 350 micrometers. In some embodiments, the thickness is not more than 2000 micrometers, not more than 1000 micrometers, or not more than 500 micrometers.

Multilayer curable adhesive films in the tape useful in the adhesive system of the present disclosure may include two or more curable adhesive films having components that are the same or different (i.e., they are independently selected). Multilayer curable adhesive films may include two or more curable foam support layers having components that are the same or different (i.e., they are independently selected). In some embodiments, the multilayer curable adhesive film further comprises a second curable adhesive layer comprising a second film of a second independently selected polymer, second independently selected unsaturated free-radically polymerizable groups, which may be bonded to the second independently selected polymer or in a second species other than the second independently selected polymer, and a second independently selected transition metal cation. In some embodiments, the second curable adhesive layer is adjacent to a surface of the foam support layer opposite the first layer.

The adhesive system of the present disclosure includes a solid activator composition comprising an oxidizing agent. The solid activator composition is solid at normal temperature and pressure. The solid activator composition is useful as an activator for the tape. In some embodiments, the solid activator composition is not a free-standing film. In other words, a film of the solid activator composition lacks mechanical integrity independent of contact with any supporting material (e.g., a release liner or substrate to be bonded). When the solid activator composition is not a free-standing film, the solid activator composition can retain its shape; however, an intact film of the solid activator composition cannot be removed from a supporting material on which it is deposited. The solid activator composition can be in the form of a crayon or paste.

In the method of bonding a first substrate according to the present disclosure, the solid activator composition is applied to the substrate, and the solid activator composition is then contacted with a curable adhesive film on a first surface of the tape as described above in any of its embodiments. With reference to FIG. 3 (not to scale), in one embodiment, construction 300 includes tape 310 and substrates 320 and 330. As shown in FIG. 3, a solid activator composition 370 is applied to first substrate 320, and a solid activator composition 380 is applied to second substrate 330. The solid activator compositions 370 and 380 may be the same or different. A double-sided tape 310, according to one embodiment of the present disclosure, that includes curable adhesive films 340 and 360 adjacent to a support layer 350 is applied to solid activator 370 and 380 on substrates 320 and 330 such that the curable adhesive films 340 and 360 are in contact with the solid activator composition 370 and 380, respectively. In some embodiments, the assembly is held by external forces, e.g., a clamp, until the curable adhesive films become cured; however, in other embodiments the tackiness of the tape alone holds the assembly until cure. The tape cures to form cured structural adhesive layers from curable adhesive films 340 and 360, which are adjacent to solid activator compositions 370 and 380. In some embodiments, the support layer 350 is also cured. In some embodiments, the support layer 350 is a foam support layer.

Applying the solid activator composition 370 and 380 to the substrate or substrates 320 and 330 may be carried out by at least one of rubbing or spreading. For example, a crayon comprising the solid activator composition can be rubbed on substrates 320 and 330. In another example, solid activator composition in the form of a paste can be spread on substrates 320 and 330 using any suitable implement. Solid activator composition 370 and 380 may be cured or not cured in the final construction, which, in the embodiment illustrated in FIG. 3, includes two substrates bonded together by a double-sided tape using structural adhesive bonds. In some embodiments, the solid activator composition does not include unsaturated free-radically polymerizable groups. In some embodiments, the solid activator composition is not curable as applied and is not cured in the final bonded construction.

The first and second substrates in the methods of the present disclosure, as described above and below in any of their embodiments, may be composed of any suitable material. Suitable substrate materials include metals (e.g., aluminum, titanium, stainless steel, and steel), polymeric materials (e.g., polyolefins, polyethylenes, polypropylenes, polystyrenes, poly(meth)acrylates, polyurethanes, natural or synthetic rubbers, and polydienes), natural materials (e.g., wood and stone) or derivatives thereof (e.g., composite board and concrete), glass material, and ceramic materials. If two substrates are bonded together in the articles and processes of the present disclosure, the two substrates are independently selected.

In some embodiments, at least one of the surfaces of the first substrate or the surface of the second substrate comprises at least one of metal, glass, a polymer, paper, a painted surface, a nonwoven or woven fabric, wood, foam, or a composite. The material of the surface of the first and second substrate may be found throughout the substrate, or the surface may include a different material from the bulk of the substrate. In some embodiments, the surface of the first substrate and/or second substrate comprises at least one of metal (e.g., steel, stainless steel, or aluminum), glass (e.g., which may be coated with indium tin oxide, for example,), a polymer (e.g., a plastic, rubber, thermoplastic elastomer, or thermoset), paper, a painted surface, or a composite. A composite material may be made from any two or more constituent materials with different physical or chemical properties. When the constituents are combined to make a composite, a material having characteristics different from the individual components is typically achieved. Some examples of useful composites include fiber-reinforced polymers (e.g., carbon fiber reinforced epoxies and glass-reinforced plastic); metal matrix compositions; and ceramic matrix composites. The surface of at least one of the first or second substrates may include polymers such as polyolefins (e.g., polypropylene, polyethylene, high density polyethylene, blends of polypropylene), polyamide 6 (PA6), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), PC/ABS blends, polyvinyl chloride (PVC), polyamide (PA), polyurethane (PUR), thermoplastic elastomers (TPE), polyoxymethylene (POM), polystyrene, polyester (e.g., polyethylene terephthalate), poly(methyl) methacrylate (PMMA), and combinations thereof. The surface of at least one of the first or second substrate may also include a metal coating on such polymers. In some embodiments, at least one of the first or second substrate comprises a transparent material such as glass or a polymer (e.g., acrylic or polycarbonate).

In some embodiments, a tape useful in the adhesive system of the present disclosure also includes one or more barrier film support layers (having two major surfaces), one or more conventional adhesive layers (having two major surfaces) that include an adhesive that is not curable upon contact with the solid activator, and/or a tape backing material or release liners commonly used in multilayer tapes. For example, a double-sided tape of the present disclosure may include only one curable adhesive film and, in some embodiments, a curable foam support layer, and may include a secondary adhesive layer that is not curable upon contact with the solid activator composition.

As shown in FIG. 4 (not to scale), tape 410 includes a curable adhesive film 440, and a secondary adhesive layer 460, which may be any of a variety of conventional adhesives (e.g., pressure sensitive adhesives) that are not curable upon contact with the solid activator composition, each of which are adjacent to opposite surfaces of support layer 450. Examples of conventional adhesives include pressure sensitive adhesives that are tacky and bond instantly when pressure is applied, thermoplastic adhesives that bond with applied heat and pressure and can be reversible with heat, and thermosetting adhesives that bond when subjected to heat and pressure for a predetermined period of time so as to cause some irreversible chemical reaction to occur. In some embodiments secondary adhesive layer 460 is a conventional pressure sensitive adhesive, which achieves lower adhesion strength than the curable adhesive film 440 applied to an activator on a substrate.

One or more barrier film support layers (i.e., barrier layers) may be used in the tape of the adhesive system of the present disclosure to provide a barrier, for example, to migration of the oxidizing agent and/or crosslinkable species, for example. For example, a tape of the type described in FIG. 1 can further include a barrier film support layer adjacent the major surface of the support layer opposite that of the curable adhesive film, such that a 3-layer tape including curable adhesive/support layer/barrier is formed. In another example, a tape of the type described in FIG. 2 can further include a barrier film support layer disposed between the support layer and one of the curable adhesive fdms. In this embodiment, a first curable adhesive film is adjacent a support layer, which is adjacent a barrier film support layer, which is adjacent a second curable adhesive film, such that a 4-layer tape including curable adhesive/support layer/barrier/curable adhesive is formed. In some embodiments, the support layer is a foam. In some embodiments, the support layer is curable. In some embodiments, the first curable adhesive film is adjacent the curable foam support layer, the barrier film support layer is adjacent a surface of the curable foam support layer opposite the first curable adhesive film, and the second curable adhesive film is adjacent a surface of the barrier film support layer opposite the curable foam support layer.

In another example, a multilayer tape can be prepared from two tapes of the type described in FIG. 1 with a barrier film support layer disposed between the support layers of the two tapes, such that a 5 -layer tape including curable adhesive film/support layer/barrier/support layer/curable adhesive film is formed. In some embodiments, the support layer is a foam. In some embodiments, the support layer is curable.

In yet another example, a multilayer tape can be prepared from two double-sided tapes of the type shown in FIG. 2 with a barrier film support layer disposed between the two tapes, such that a 7-layer tape including curable adhesive film/support layer/curable adhesive film/barrier/curable adhesive film/support layer/curable adhesive film is formed. That is, in such an embodiment, a first curable adhesive film, a first support layer, a second curable adhesive film, a barrier film support layer, a third curable adhesive film, a second support layer, and a fourth curable adhesive film are sequentially stacked. In some embodiments, the support layer is a foam. In some embodiments, the support layer is curable.

More specifically, as shown in FIG. 5 (not to scale), the tape 510 includes a first curable adhesive film 540, and a second curable adhesive film 560, each of which are adjacent to the opposite major surfaces of a first support layer 550. The tape 510 also includes a third curable adhesive film 540’, and a fourth curable adhesive film 560’, each of which are adjacent to the opposite major surfaces of a second support layer 550’. The curable adhesive film 560 has a surface 562 that is adjacent a first surface 592 of barrier film support layer 590, and the curable adhesive film 560’ has a surface 562’ that is adjacent a second surface 594 of barrier film support layer 590. Barrier film support layer 590 prevents migration of crosslinkable species and/or oxidizing agent across it. Thus, different curing mechanisms and curable components can be used on either side of the barrier layer (i.e., within layers 540/550/560 as compared to layers 54075507560’). In some embodiments of the method of the present disclosure, the tape 510 including barrier layer 590, a solid activator composition is used when bonding tape 510 to a first substrate, for example, through third curable adhesive film 540’. The layers 54075507560’ cure to form cured structural adhesive layers while barrier 590 may prevent curing of layers 540/550/560. Another, independently selected, solid activator composition may be used to bond tape 510 to a second substrate through first curable adhesive film 540. The layers 540/550/560 may then cure to form structural adhesive layers. In this embodiment, n is possible to apply the tape to a substrate at a first time or location and bond it to an activated second substrate at a later time or different location, providing flexibility in making bonded articles using the adhesive system of the present disclosure.

In some embodiments of the method of making a bonded article according to the present disclosure, such as the embodiment illustrated in FIG. 6, a double-sided tape 610, according to some embodiments of the present disclosure, that includes curable adhesive films 640 and 660 adjacent to a single support layer 650 is applied to second substrate 630 such that curable adhesive film 660 is in contact with second substrate 630. In some embodiments, the support layer is a foam. In some embodiments, the support is curable. A solid activator composition 670 in the adhesive system of the present disclosure is applied to first substrate 620. After applying the tape and the solid activator composition to their respective substrates and waiting for any desirable independently selected length of time, the solid activator 670 and the curable adhesive film 640 of the double-sided tape 610 are brought into contact. Once the solid activator 670 and the curable adhesive film 640 are brought into contact, curing begins and continues through foam support layer 650 and curable adhesive film 660. The tape cures to form cured structural adhesive layers from curable adhesive films 640 and 660 and cured foam support layer 650. In some embodiments, the assembly is held by external forces, e.g., a clamp, until the curable adhesive films become cured; however, in other embodiments, the tackiness of the tape alone holds the assembly until cure. Solid activator composition 670 may be cured or uncured in the final cured construction 600, which include two substrates bonded together by a double-sided tape including structural adhesive bonds. The solid activator composition can be applied using any of the methods described above in connection with the embodiment of FIG. 3.

In some embodiments of the adhesive system and method of the present disclosure, the tape may be attached to a substrate at the point of manufacture and bonded at a different time and/or place. In some embodiments, the tape may be attached to a first substrate at the point of manufacture, and the tape may optionally be covered with a conventional release liner for any period of time before bonding it to an activated second substrate. The solid activator composition may be applied to a second substrate at a second point of manufacture, and the first substrate having the tape thereon and the activated second substrate may be bonded at the second point of manufacture or even at a third time and/or place. Thus, it is possible to apply the tape to a substrate at a first time or location and bond it to an activated second substrate at a later time or different location, providing flexibility in making bonded articles using the adhesive system of the present disclosure.

In some embodiments of the method of the present disclosure, the method includes applying a tape as described above in any of its embodiments to a first substrate, applying a solid acti vator composition as described above in any of its embodiments to a second substrate, and contacting the tape on the first substrate and the activator on the second substrate to bond the first and second substrates. In some embodiments, applying the tape is carried out at least 1, 3, or 5 days or at least 1, 2, 3, 4, 5, or 6 weeks before contactfog the tape on the first substrate and the activator on the second substrate. In some embodiments, the tape is covered with a release liner, in some embodiments, for any of the times described above, and the release liner is removed before contacting the tape on the first substrate and the activator on the second substrate.

In some embodiments of the adhesive system and method of the present disclosure, the article 700 shown in FIG. 7 may be useful. The article 700 includes a curable adhesive film 740 and an oxygen- permeable liner 725 on at least one side of the curable adhesive film. The curable adhesive film 740 comprises a film of a polymer, unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, a transition metal cation, and an oxidizing agent. The embodiment illustrated in FIG. 7 also includes a first substrate 720. The illustrated embodiment may be made by a process including applying solid activator composition 730 to the substrate 720, wherein the activator comprises the oxidizing agent, applying an adhesive film directly adjacent the solid activator composition 730 on the substrate 720, and joining the adhesive film with the oxygen-permeable liner. The adhesive film comprises the film of the polymer, the unsaturated free-radically polymerizable groups, and the transition metal cation. Typically, the oxidizing agent of the solid activator composition 730 migrates into the adhesive film. However, curing of the curable adhesive film is inhibited by oxygen. Therefore, while the oxygen-permeable liner is in place, the curable adhesive film does not cure for a period of several days or several weeks. In some embodiments, the process of making the illustrated embodiment includes forming the adhesive film on the oxygen-permeable liner and applying an adhesive film directly adjacent the activator while the adhesive film is in contact with the oxygen-permeable liner.

In some embodiments of the adhesive system and method of the present disclosure, the article 800 shown in FIG. 8 may be useful. The article 800 includes a curable adhesive film 840 and an oxygen- permeable liner 825 on at least one side of the curable adhesive film. The curable adhesive film 840 comprises a film of a polymer, unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer, a transition metal cation, and an oxidizing agent. In the embodiment illustrated in FIG. 8, the oxygen-permeable liner 825 comprises ridges 827 on at least one surface 826. The height of the ridges may be in a range from 4 micrometers (pm) to 200 pm, from 8 pm to 100 pm, or from 10 pm to 30 pm. In these embodiments, the ridges can be considered microstructures. The ridges may be in regular patterns or may appear randomly spaced and may have a variety of cross-sectional shapes. The curable adhesive film 840 includes channels 843 corresponding to the ridges 827 in surface 846. Such channels are capable of aiding in the escape of air during the later application of the surface 846 to a substrate. The channels, and methods of their production, may be as taught in U.S. Pat. No. 6,655,281 (Jordan et al.).

The embodiment illustrated in FIG. 8 also includes a release liner 815. The illustrated embodiment may be made by applying a solid activator composition 830 to the release liner 815, wherein the solid activator composition comprises the oxidizing agent. The adhesive film including the film of the polymer, the unsaturated free -radically polymerizable groups, and the transition metal cation, conveniently formed on the oxygen-permeable liner including ridges, can then be applied directly adjacent the activator 830 on the release liner. Typically, the oxidizing agent of the activator 230 migrates into the adhesive fdm; however, curing of the curable adhesive fdm is inhibited by oxygen. Therefore, while the oxygen-permeable liner is in place, the curable adhesive fdm does not cure for a period of several days or several weeks. Although not shown in the embodiment illustrated in FIG. 8, air bleed channels 843 may also be formed in the opposing surface of the adhesive fdm, which may help to improve contact when it is applied to the solid activator composition.

FIG. 9 illustrates another embodiment of the method of bonding a first substrate according to the present disclosure. The method comprises bonding first and second substrates using an article 900 such as article 700 shown in FIG. 7. The process illustrated in FIG. 9 includes removing oxygen-permeable liner 925 to expose curable adhesive fdm 940. Although not illustrated in FIG. 9, curable adhesive fdm 940 may also be the first layer of a multilayer curable adhesive fdm 110, 210 as shown in FIGS. 1 or 2. After removing oxygen-permeable liner 925, the process includes bonding second substrate 980 to curable adhesive film 940. In some embodiments, the bonded article is held by external forces, e.g., a clamp, until the curable adhesive fdm becomes cured; however, in other embodiments tackiness of the curable adhesive fdm alone holds the assembly until the curable adhesive fdm becomes cured. Once cured, the curable adhesive fdm 940 provides a structural adhesive layer.

In some embodiments of the process for making bonded article 905, the process further comprises applying an optional solid activator composition 935 to the second substrate 980 before bonding second substrate 980 to curable adhesive fdm 940. Optional solid activator composition 935 comprises a second oxidizing agent, wherein the second oxidizing agent is the same or different from the oxidizing agent in the first solid activator 930. Typically, the oxidizing agent of the activator composition 935 migrates into the curable adhesive fdm 940 to participate in curing the curable adhesive fdm 940 to form a structural adhesive layer. After curing, bonded article 905 includes first and second substrates 920, 980 bonded together with a structural adhesive made from first solid activator composition 930, curable adhesive film 940, and optional solid activator 935.

FIG. 10 illustrates another embodiment of the method of bonding a first substrate according to the present disclosure. The method comprises bonding first and second substrates using two independently selected articles 1000, 1000a such as article 700 shown in FIG. 7. The process illustrated in FIG. 10 includes removing oxygen-permeable liner 1025 from two articles 1000, 1000a to expose curable adhesive film 1040 on both articles 1000 and 1000a. The two articles 1000, 1000a may be the same or different from each other, including first and second substrates 1020, 1080, which may be the same or different from each other, curable adhesive films 1040, which may be the same or different from each other, and oxygen-permeable liners 1025, which may be the same or different from each other. Although not illustrated in FIG. 10, one or more of the curable adhesive films 1040 may also be the first layer of a multilayer curable adhesive film 110, 210 as shown in FIGS. 1 and 2. As shown in FIG. 10, the curable adhesive films 1040 are positioned to contact each other once the oxygen-permeable films are removed and then bonded together. In some embodiments, the bonded article is held by external forces, e.g., a clamp, until the curable adhesive film becomes cured; however, in other embodiments tackiness of the curable adhesive film alone holds the assembly until the curable adhesive film becomes cured. Once cured, the curable adhesive film 1040 provides a structural adhesive layer.

FIG. 11 illustrates another embodiment of the method of bonding a first substrate according to the present disclosure. The method includes making a bonded article 1105 including two substrates using an embodiment of the article similar to that shown in FIG. 8 except that no ridges 827 or channels 843 are shown in FIG. 11. Although not illustrated in FIG. 11, curable adhesive film 840 may also be the first layer of a multilayer curable adhesive film 110, 210 as shown in FIGS. 1 and 2. The process illustrated in FIG. 11 includes removing the release liner 1115 to provide a first adhesive surface 1148, removing the oxygen-permeable liner 1125 to provide a second adhesive surface 1146, bonding the first adhesive surface 1148 to a first substrate 1120, and bonding the second adhesive surface 1146 to a second substrate 1180. Removing oxygen-permeable liner 1125 and release liner 1115 may be carried out simultaneously or sequentially in any order. Likewise, bonding first adhesive surface 1148 to a first substrate 1120 and bonding second adhesive surface 1146 to a second substrate 1180 can be carried out simultaneously or sequentially in any order. Bonding first adhesive surface 1148 to a first substrate 1120 can be carried out before removing the oxygen-permeable liner 1125, or bonding second adhesive surface 1146 to a second substrate 1180 can be carried out before removing release liner 1115. In some embodiments, the bonded article is held by external forces, e.g., a clamp, until the curable adhesive film becomes cured; however, in other embodiments, tackiness of the curable adhesive film alone holds the assembly until the curable adhesive film becomes cured. Once cured, the curable adhesive film 1140 provides a structural adhesive layer.

In some embodiments of the process for making bonded article 1105, the process further comprises applying solid activator composition 1135 to at least one of first substrate 1120 or second substrate 1180 before bonding first and second adhesive surfaces 1148, 1146 to first and second substrates 1120, 1180, respectively. In some embodiments, solid activator composition 1135 is applied to only one of the first substrate 1120 or the second substrate 1180. In some embodiments, solid activator composition 1135 is applied to both the first substrate 1120 and the second substrate 1180. Optional solid activator composition 1135 comprises a second oxidizing agent, wherein the second oxidizing agent is the same or different from the oxidizing agent in the first solid activator composition 1130. The solid activators composition 1135 and their components applied to first substrate 1120 and second substrate 1180 may be the same or different. Typically, the oxidizing agent of the solid activator 1135 migrates into the curable adhesive film 1140 to participate in curing the curable adhesive film 1140 to form a structural adhesive layer. The embodiment illustrated in FIG. 11 does not include ridges on the oxygen-permeable liner 1125 or the release liner 1115. In other embodiments, one or both of oxygen-permeable liner 1125 or release liner 1115 has ridges on a surface that contacts curable adhesive fdm 1140 to provide channels in the curable adhesive film. Returning to FIG. 8, when a curable adhesive film has channels 843 in one surface 846 and not the other, the surface without channels may be placed on a first substrate 820 and the second substrate 880 may then be brought into contact with the surface 846 including channels. This approach may be useful, for example, when two stiff substrates are to be joined, since it allows air bleed and adaptability to uneven surfaces despite the inflexibility of the substrates.

Any oxygen-permeable liner that allows sufficient oxygen to pass through to inhibit the curing of the unsaturated free-radically polymerizable groups may be useful in the articles and processes of the present disclosure. Suitable materials for a liner include paper, polyvinyl chloride (PVC), polylactic acid (PLA), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polystyrene (PS), and polyolefins (e.g., polypropylene, high density polyethylene (HDPE), low density polyethylene (LDPE), biaxially oriented polypropylene (BOPP)). In some embodiments, the oxygen-permeable liner comprises at least one of paper or a polyolefin. The oxygen-permeable liner may have a low-adhesion surface provided, for example, by a silicone, a fluoropolymer, a carbamate, an acrylic, a urethane, or a polyolefin. Examples of useful release agents that may, in some embodiments, be coated on the oxygen-permeable liner include silicone copolymers (e.g., silicone acrylates, silicone polyurethanes, and silicone polyureas), fluorosilicones, perfluoropolyethers, polyethylene, polypropylene, low-density polyethylene), and combinations thereof. In some embodiments, the oxygen-permeable liner is poly coated kraft paper (i.e., paper coated with polyethylene), which may or may not be silicone-coated.

In some embodiments, the curable adhesive film is stable at room temperature for at least two weeks. In some embodiments, applying the curable adhesive film covered with an oxygen-permeable liner is carried out at least 1, 3, or 5 days or at least 1, 2, 3, or 4 weeks before removing the oxygen- permeable liner and bonding the curable adhesive film to the second substrate. Thus, it is possible to apply the curable adhesive film to a substrate at a first time or location and bond it to a second substrate at a later time or different location, providing flexibility in making bonded articles using the articles and processes of the present disclosure.

While it is possible that a curable adhesive film containing no oxidizing agent may be attached to a first substrate at the point of manufacture, and an activator including an oxidizing agent may be applied to a second substrate and at a second point of manufacture, and the first substrate and the activated second substrate may be bonded at the second point of manufacture or even at a third time and/or place, the methods illustrated in FIGS. 7 to 11 provide even greater flexibility, since it is possible that second substrate may not even need to be activated to achieve adequate bonding. Moreover, allowing more time for the oxidizing agent to migrate throughout the curable adhesive film while it is covered with an oxygen-permeable liner may provide stronger structural adhesive bonds more quickly once the oxygen- permeable liner is removed and the curable adhesive film is bonded to the second substrate.

While U.S. Pat. Appl. Nos. 2020/0362204, 2021/0102095, and 2021/0102097, each to Ranade et al., describe an adhesive system as described above in a construction that includes a release liner, the purpose of the release liner is to exclude oxygen. The release liner is said to preferably be left in place until cure is complete. The ability of the oxygen-permeable liner in the article of the present disclosure to provide two or more weeks of stability of the curable adhesive film, which includes the unsaturated free- radically polymerizable groups, the transition metal cation, and the oxidizing agent, is quite unexpected. Herein, when it is said that the curable adhesive film is stable at room temperature for at least two weeks, it means that the dynamic shear adhesion on aluminum, measured as described in the Examples below, does not fall to lower than 90% of the initial adhesion value, measured on the day the curable adhesive film is applied to the activator.

The release liner, as described above in connection with FIGS. 8 and 11, may be an oxygen- permeable liner as describe above in any of its embodiments. However, the release liner need not be oxygen-permeable and can include other materials, for example, ethylene vinyl acetate, polyurethanes, cellulose acetate, polyvinylidene fluoride, and polyesters such as polyethylene terephthalate. The release liner may be coated with a layer of a release agent such as a silicone, a fluoropolymer, a carbamate, an acrylic, or a polyolefin, including any of those described above in connection with the oxygen-permeable liner. Coatings may be present on both sides of a release liner, and these liners may be the same or different. Suitable release liners include commercially available liners that have a silicone release coating on polyethylene terephthalate film. The release liner can have ridges on its surface as described above in any of their embodiments in connection with the oxygen-permeable liner.

In some embodiments of the method of the present disclosure, including the methods described above in any of their embodiments, rubbing or spreading of the solid activator composition onto at least one of the surface of the first substrate or the surface of the second substrate comprises rubbing or spreading the solid activator composition onto intermittent portions of the first substrate or the second substrate while not applying the solid activator composition to other portions of the first substrate or the second substrate. In embodiments in which the solid activator composition is a crayon, it is easy to apply the solid activator composition in any desired pattern. Upon contact with the solid activator composition, the curable adhesive film begins to cure, forming structural adhesive domains; however, the present investigators have found that this cure demonstrates limited propagation in the plane of the adhesive film. Thus, cured structural adhesive domains are formed adjacent to the solid activator composition while uncured pressure sensitive adhesive domains can remain over the portions of the first substrate to which the solid activator composition was not applied. The structural adhesive domains may constitute 1% to 99%, 1% to 75%, 1% to 50%, 1% to 25%, 75% to 99%, 50% to 99%, 25% to 99% or any desired portion of the adhesive film with the remainder of the adhesive film being pressure sensitive adhesive domains. Any suitable patern of structural adhesive domains may be used, such as straight, curved, angled or broken lines; square, rectangular, triangular, hexagonal, or other polygonal grids; or random or ordered spots which may be circular, elliptical, polygonal, or other shapes. Patern features may have any desired width and/or pitch dimensions. In various embodiments, the structural adhesive domains may be continuous or discontinuous and the pressure sensitive adhesive domains may be continuous or discontinuous. In some embodiments, the structural adhesive domains are discontinuous and surrounded by a continuous pressure sensitive adhesive domain, e.g., an arrangement of distinct posts of structural domain separated by a continuous pressure sensitive adhesive domain. In some embodiments, discontinuous pressure sensitive adhesive domains are surrounded by a continuous structural adhesive domain.

The solid activator composition useful in the adhesive system and method of the present disclosure comprises an oxidizing agent. The solid activator is solid at normal temperature and pressure. In some embodiments, the solid activator is not a free-standing fdm. The solid activator can be in the form of a crayon or paste. Any suitable oxidizing agent may be used in the adhesive system, method, or crayon of the present disclosure. Suitable oxidizing agents include organic peroxides and hydroperoxides, inorganic peroxides, and persulfates.

Suitable organic peroxides include hydroperoxides, di-peroxides, ketone peroxides, diacyl peroxides, dialkyl peroxides, peroxyketals, peroxyesters, and peroxydicarbonates. Suitable organic hydroperoxides include those represented by formula R-O-O-H with R being linear alkyl (e.g., C1-C20 linear alkyls), branched alkyl (e.g., C3-C20 branched alkyls), cycloalkyl (e.g., C6-C12 cycloalkyls), alkaryl (e.g., C7-C20 alkaryls), aralkyls (e.g., C7-C20 aralkyls), and aryls (e.g., C6-C12 aryls). Examples of suitable organic hydroperoxides include t-butyl hydroperoxide, t-amyl hydroperoxide, p-diisopropylbenzene hydroperoxide, cumene hydroperoxide, pinane hydroperoxide, p-methane hydroperoxide, and 1,1, 3, 3- tetramethylbutyl hydroperoxide. Suitable organic peroxides include di-peroxides represented by formula R¹-O-O-R²-O-O-R³, with R¹ and R³ being independently selected from H, linear alkyls (e.g., Ci-Cg linear alkyls), branched alkyls (e.g., Ci-Cg branched alkyls), cycloalkyls (e.g., C5-C10 cycloalkyls), alkaryls (e.g., C7-C12 alkaryls), aralkyls (e.g., C7-C20 aralkyls), or aryls (e.g., Cg-Cio aryls), and R² being selected from linear or branched alkylene (e.g., Ci-Cg linear or branched alkylene). Suitable ketone peroxides include methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, methyl cyclohexanone peroxide, and cyclohexanone peroxide. Suitable peroxyesters include alpha-cumylperoxyneodecanoate, t-butyl peroxypivarate, t-butyl peroxyneodecanoate, 2,2,4-trimethylpentylperoxy-2-ethyl hexanoate, t- amylperoxy-2 -ethyl hexanoate, t-butylperoxy-2-ethyl hexanoate, di-t- butylperoxy isophthalate, di-t-butyl peroxy hexahydroterephthalate, t-butylperoxy-3,3,5- trimethylhexanoate, t-butylperoxy acetate, t- butylperoxy benzoate, and t- butylperoxymaleic acid. Suitable peroxydicarbonates include di-3-methoxy peroxidicarbonate, di-2-ethylhexyl peroxy-dicarbonate, bis(4-t- butylcyclohexyl)peroxidicarbonate, diisopropyl-l-peroxydicarbonate, di-n-propyl peroxidicarbonate, di-2-ethoxyethyl-peroxidicarbonate, and diallyl peroxidicarbonate. Suitable diacyl peroxides include acetyl peroxide, benzoyl peroxide, decanoyl peroxide, 3,3,5-trimethylhexanoyl peroxide, 2,4-dichlorobenzoyl peroxide, and lauroylperoxide. Suitable dialkyl peroxides include di-t-butyl peroxide, dicumylperoxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5- di(t-butylperpoxy)hexane, l,3-bis(t-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(t- butylperoxy) -3 -hexane. Suitable peroxyketals include l,l-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, l,l-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, and 4,4- bis(t-butylperoxy)valeric acid-n-butylester. Other suitable organic peroxides may additionally include t- butyl peroxy ethylhexyl carbonate, t-butyl peroxy trimethylhexanoate, t-butyl peroxy ethylhexanoate, t- amyl peroxy ethylhexanoate, t-octyl peroxy ethylhexanoate, t-amyl peroxy ethylhexyl carbonate, t-butyl peroxy isopropyl carbonate, t-butyl peroxyneodecanoate, and t-butyl peroxyisobutyrate.

The solid activator composition useful in the adhesive system and method of the present disclosure can include a variety of polymeric compositions. For examples, the solid composition can contain starch derivatives, condensation products of an aldehyde and/or ketone with a polyol (e.g., the reaction product of sorbitol and benzaldehyde), or plasticized rubbers (e.g., natural or synthetic rubbers).

In some embodiments, the solid activator composition useful in the adhesive system, method, or crayon of the present disclosure comprises an acrylic polymer comprising a crystalline monomeric unit with a pendent alkyl chain having 16 to 50 carbon atoms and at least one other monomeric unit. Useful crystalline monomer units include those from monomers in which a homopolymer thereof has a melting temperature in a range from 45 °C to 68 °C. The crystalline monomeric unit can be made from a vinyl, acrylate, or methacrylate monomer. In some embodiments, the pendent alkyl chain has 16 to 40, 16 to 30, 16 to 22, or 18 to 22 carbon atoms. Generally, these are straight-chain alkyl groups to promote crystallinity. Useful acrylate monomers for producing the crystalline monomer units include octadecyl acrylate, behenyl acrylate, tricontyl acrylate, tetracontyl acrylate, and pentacontyl acrylate, which have pendent alkyl chains having 18, 18 to 22, 26 to 34, 36 to 44, and 46 to 54 carbon atoms, respectively.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is a waxy monomeric unit with a pendent alkyl chain having 14 to 50 carbon atoms. Useful crystalline monomer units include those from monomers in which a homopolymer thereof has a melting temperature in a range from 25 °C to 44 °C. The crystalline monomeric unit can be made from a vinyl, acrylate, or methacrylate monomer. In some embodiments, the pendent alkyl chain has 14 to 40, 14 to 30, 14 to 22, or 16 to 22 carbon atoms. Useful monomer may have some branching and may be methacrylates, which can be useful for disrupting crystallinity. Useful methacrylate monomers for producing the waxy monomer units include octadecyl methacrylate (i.e., stearyl methacrylate), behenyl methacrylate.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is a monomer unit from a monomer that when homopolymerized provides a noncrystalline polymer. In some embodiments, the monomer units arise from a high Tg monomer. As used herein, the term “high Tg monomer” refers to a monomer that has a Tg greater than 30 °C, greater than 40 °C, or greater than 50 °C when homopolymerized (i.e., a homopolymer formed from the monomer has a Tg greater than 30 °C, greater than 40 °C, or greater than 50 °C). Some suitable high Tg monomers have a single (meth)acryloyl group such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl (meth)acrylate, cyclohexyl methacrylate, isobomyl (meth)acrylate, stearyl (meth)acrylate, phenyl acrylate, benzyl methacrylate, 3,3,5 trimethylcyclohexyl (meth)acrylate, 2-phenoxyethyl methacrylate, N- octyl (meth)acrylamide, and mixtures thereof. Other suitable high Tg monomers have a single vinyl group that is not a (meth)acryloyl group such as, for example, various vinyl ethers (e.g., vinyl methyl ether), vinyl esters (e.g., vinyl acetate and vinyl propionate), styrene, substituted styrene (e.g., a-methyl styrene), vinyl halide, and mixtures thereof.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is a non-crystalline low Tg monomer. As used herein, the term “low Tg monomer” refers to a monomer having a Tg no greater than 20°C when homopolymerized (i.e., a homopolymer formed from the low Tg monomer has a Tg no greater than 20°C). Suitable low Tg monomers are often selected from an alkyl (meth)acrylates, heteroalkyl (meth)acrylates, aryl substituted alkyl acrylate, and aryloxy substituted alkyl acrylates. Examples of low Tg alkyl (meth)acrylate monomers often are non- tertiary alkyl acrylates but can be alkyl methacrylates having a linear alkyl group with at least 4 carbon atoms. Examples of alkyl (meth)acrylates include n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, sec-butyl acrylate, n-pentyl acrylate, 2-methylbutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2- octyl acrylate, isooctyl acrylate, isononyl acrylate, isoamyl acrylate, n-decyl acrylate, isodecyl acrylate, n- decyl methacrylate, lauryl acrylate, isotridecyl acrylate, n-octadecyl acrylate, isostearyl acrylate, and n- dodecyl methacrylate. Isomers and mixture of isomers of these monomers can be used. Examples of low-Tg heteroalkyl (meth)acrylate monomers often have at least 3 carbon atoms, at least 4 carbon atoms, or at least 6 carbon atoms and can have up to 30 or more carbon atoms, up to 20 carbon atoms, up to 18 carbon atoms, up to 16 carbon atoms, up to 12 carbon atoms, or up to 10 carbon atoms. Specific examples of heteroalkyl (meth)acrylates include 2-ethoxyethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2 -methoxyethyl (meth)acrylate, and tetrahydrofurfiiryl (meth)acrylate. Examples of low-Tg aryl substituted alkyl acrylates or aryloxy substituted alkyl acrylates include 2-biphenylhexyl acrylate, benzyl acrylate, 2-phenoxyethyl acrylate, and 2-phenylethyl acrylate.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is derived from at least one of isooctyl acrylate, 2-ethyl hexyl acrylate, 2-octyl acrylate, n-octyl acrylate, n-butyl acrylate, scc-butyl acrylate, ethyl acrylate, diethyleneglycol methyl ether acrylate, triethyleneglycol methyl ether acrylate, allyl glycidyl ether, ethyl vinyl ether, 2-ethyl hexyl vinyl ether, hydroxyl ethyl acrylate, dodecyl methacrylate, dodecyl vinyl ether, polydimethylsiloxyl and amorphous polyether (meth)acrylates.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is an acrylic monomer unit comprising a carboxylic acid group. Examples of suitable acrylic monomers comprising a carboxylic acid group to provide these monomer units include methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, ethacrylic acid, crotonic acid, citraconic acid, cinnamic acid, beta-carboxy ethyl acrylate, and ^-methacryloyl oxyethyl hydrogen succinate. In some embodiments, the acrylic monomer units comprising a carboxylic acid group are acrylic acid monomer units or methacrylic acid monomer units, in some embodiments, acrylic acid monomer units.

In some embodiments, the at least one other monomeric unit in the acrylic polymer of the solid activator composition is a macromer monomeric unit. Suitable macromers are prepared from the corresponding prepolymers of, for example, octadecyl acrylate (ODA), behenyl acrylate (BeA) and mixtures of tetradecyl acrylate (TDA), tetradecyl methacrylate (TDMA), hexadecyl acrylate (HD A), hexadecyl methacrylate (HDMA), ODA, octadecyl methacrylate (ODMA), eicosyl acrylate (ECA), eicosyl methacrylate (ECMA), and behenyl methacrylate (BeMA). In some embodimens, the final macromer melting temperatures (T_m) is within the range of from about 35 °C to about 120 °C, about 35 °C to about 70 °C, or about 45 °C to about 60 °C. The macromers are incorporated into the semicrystalline polymers via standard polymerization techniques for the glue crayon polymers described herein. Preparing a macromer can be carried out by polymerizing any of the monomers mentioned above in the presence of a functional chain-transfer agent, for example, 2-mercaptoethanol. Hydroxy-terminated telechelic polymers can then be functionalized by reaction with acryloyl chloride, methacryloyl chloride, 2'-isocyanatoethyl methacrylate, 3-isopropenyl-alpha, or alpha-dimethylbenzyl isocyanate(IPDMBI), for example, as described in U.S. Pat. No. 5,604,268 (Randen et al.).

In some embodiments, the acrylic polymer useful in the solid activator composition comprises from about 5 to about 96, or from about 5 to about 60, parts by weight per 100 parts by weight of acrylic polymer of at least one crystalline monomer having an alkyl carbon length of at least 16, typically not more than 50, carbon atoms; from about 4 to about 70, or from about 12 to about 59, parts by weight per 100 parts by weight of acrylic polymer of at least one non-crystalline monomer having a homopolymer Tg below about 80°C; from 0 to about 70 parts by weight per 100 parts by weight of acrylic polymer of at least one waxy monomer having an average pendant alkyl carbon length of at least 14, typically not more than 50, carbon atoms ; from 0 to about 10, or from about 0.5 to about 3, parts by weight per 100 parts by weight of acrylic polymer of at least one monomer having acid or base functionality; and from 0 to about 40, or from 0 to about 30, parts by weight per 100 parts by weight of acrylic polymer of at least one macromer unit having a melting temperature from about 35°C to about 120°C. The crystalline monomer component and non-crystalline monomer component can be selected such that when combined the non-crystalline component disrupts the crystallinity of the resultant adhesive polymer composition to an extent that the resultant composition will exhibit a melting temperature (Tm) of not more than 60 °C, 50 °C, or 40 °C as measured by Differential Scanning Calorimetry using the method described in U.S. Pat. No. 11,267,997 (June et al.). In some embodiments, the composition will exhibit a major Tm in the range of about 25 °C to about 35 °C.

In some embodiments, the acrylic polymer useful in the solid activator composition comprises monomeric units of octadecyl acrylate, octadecyl methacrylate, a macromer octadecyl acrylate, acrylic acid, and at least one of isooctyl acrylate (homopolymer, T_g about -54°C), butyl methacrylate (homopolymer, T_g about 20°C), or benzyl methacrylate (homopolymer, T_g about 54°C). Acrylic polymers can conveniently be made by any of the methods described above for making acrylic polymers.

In some embodiments, tackifiers may be present in the solid activator composition useful in the adhesive system, method, or crayon of the present disclosure. In some embodiments, the tackifier comprises at least one of a polyterpene (e.g., those based on a-pinene, P-pinene, or limonene), a terpene phenolic tackifier, a rosin acid, a rosin ester, an aliphatic hydrocarbon resin (e.g., those based on cis- or trans-piperylene, isoprene, 2-methyl-but-2-ene, cyclopentadiene, dicyclopentadiene, or combinations thereof), an aromatic resin (e.g. those based on styrene, a-methyl styrene, methyl indene, indene, coumarone, or combinations thereof), or a mixed aliphatic-aromatic hydrocarbon resin. The aromatic hydrocarbon resins may be C9-type petroleum resins obtained by copolymerizing a C9 fraction produced by thermal decomposition of petroleum naphtha, and aliphatic hydrocarbon resins may be C5-type petroleum resins obtained by copolymerizing a C5 fraction produced by thermal decomposition of petroleum naphtha. Mixed aliphatic/aromatic resins may be C5/C9-type petroleum resins obtained by polymerizing a combination of a C5 fraction and C9 fraction produced by thermal decomposition of petroleum naphtha. Any of these tackifier may be hydrogenated (e.g., partially or completely). The term rosin, as employed herein, includes natural rosin, refined or unrefined (refined rosin will usually contain, by weight, about 90% of rosin acids and about 10% of inert material), such as natural wood rosin, natural gum rosin, and tall oil rosin; modified rosin, refined or unrefined, such as disproportionated rosin, hydrogenated rosin, and polymerized rosin; and the pure or substantially pure acids, of which rosin is comprised, alone or in admixture. In some embodiments, the rosin includes the rosin acid C19H29COOH, in some embodiments, at least one of abietic acid, neoabietic acid, palustric acid, levopimaric acid, pimaric acid, or an isopimaric acid. In some embodiments, the rosin comprises dehydro- or hydrogenated rosin acids, for example, dehydroabietic acid, dihydroabietic acid, and tetrahydroabietic acid. The tackifier can also include a metal rosinate (sometimes referred to in the art as a metal resinate). The metal rosinate can be metal salt (e.g., zinc, calcium, or magnesium) of any of the rosins described above. In some embodiments, the solid activator composition comprises 0 to about 50, or from about 5 to about 40, parts by weight per 100 parts by weight of the solid activator composition of at least one tackifier. Crystalline additives with varying functionality such as acids, diacids, alcohols, diols, and waxes based on linear hydrocarbons can be added to the solid activator composition useful in the adhesive system, method, or crayon of the present disclosure. Crystalline additives can be selected so that they are melt miscible with the acrylic polymers described above (i.e., will form a transparent single phase system when molten). Upon cooling, such additives can partially or completely crystallize and form finely dispersed phases in the polymer. Crystalline additives can provide improved storage stability (i.e., resistance to creep and flow) to the polymers up to the melting point of the crystalline additives. In some embodiments, about 3 to about 50 wt. % may be included in the solid activator composition. The additives have an n-alkyl chain length of at least 20 carbons and may have a melting point of at least about 50°C or at least about 70°C. Examples of suitable crystalline additives include stearic acid, zinc stearate, calcium stearate, stearyl alcohol, behenyl alcohol, behenic acid, C-30 alcohol, or a C-50 alcohol. In some embodiments, the solid activator composition comprises 0 to about 50, 3 to 50, or 0 to about 30, parts by weight per 100 parts by weight of solid activator composition of at least one crystalline additive.

In some embodiments, the solid activator composition comprises from 0 to about 30, or about 1 to about 10, parts by weight of oil per 100 parts by weight of solid activator composition. Examples of useful oils include olive oil, glycerin, mineral oil, low molecular weight polyethylene oxide, and low molecular weight polypropylene oxide.

In some embodiments, the solid activator composition comprises from 0 to about 50, or from about 10 to about 40, parts by weight of surfactant per 100 parts by weight of solid activator composition. Examples of useful surfactants include anionic, non-ionic, and cationic surfactants such as stearic acid, block copolymers of ethylene oxide, propylene oxide, and blends thereof; C12 to C50 alcohol ethoxylates, alkylphenol ethoxylates, ethoxylated fatty acid esters, fatty acids, and ethoxylated fatty acids. Examples of commercially available surfactants suitable for practicing the present disclosure include those obtained under the trade designations “UNITHOX” 420, 450, 480, 490, 550, 720, and 750 (from Baker Hughes), “TERGITOL” 15-S-3 and 15-S-20 (from Dow Chemical), “PLURONIC” F38, F87, F68, F98, F127, and P85 (from BASF), and “TETRONIC” 904, 908, 1107, 1304 (from BASF).

Fillers such as calcium carbonate, silica, bentonite clays, glass spheres and bubbles, and wood flour can be included in the solid activator composition. Dyes, pigments, and anti-oxidants can also be included. In some embodiments, the solid activator composition useful in the adhesive system, method, and crayon of the present disclosure comprises 0 to about 50 parts by weight per 100 parts by weight of solid activator composition of at least one filler.

In some embodiments, the solid activator composition includes a plasticizer. In some embodiments, the plasticizer is of the following formula: (R — X — )_nZ, wherein: each R may be hydrogen, C1-C14 alkyl, aryl, alkaryl, or aralkyl, each optionally interrupted by oxygen, nitrogen, carbonyl, carboxyl, or carbamide; each X may be oxygen, nitrogen, carbonyl, carboxyl, or carbamide; Z may be a hydrogen, C1-C14 alkyl, aryl, alkaryl, aralkyl, C1-C14 alkylene, arylene, alkarylene, aralkylene, each optionally interrupted by oxygen, nitrogen, carbonyl, carboxyl, or carbamide; and n is an integer of 1 to 5. In some embodiments, n is an integer of 1 to 4. In some embodiments, the plasticizer comprises at least one of a benzoic acid ester, a myristic acid ester, a citric acid ester, an acetic acid ester, a succinic acid ester, a glutaric acid ester, an adipic acid ester, or a sebacic acid ester. In some embodiments, the plasticizer comprises at least one of a benzoic acid ester, a myristic acid ester, or a citric acid ester. A citric acid ester may have one, two, three, or four R groups.

In some embodiments, the solid activator composition further comprises a film-forming polymer. The fdm -forming polymer can be any of these described herein for the curable adhesive film. In some embodiments, the film-forming polymer is a reactive polymer comprising unsaturated free-radically polymerizable groups, as described herein for the curable adhesive film. In some embodiments, the filmforming polymer does not comprise unsaturated free-radically polymerizable groups, as described herein for the curable adhesive film.

In some embodiments, the film-forming polymer may include a rubber and/or a (meth)acrylic resin. In some embodiments, the (meth)acrylic resin is a (meth)acrylic polymer made from any of the monomers described above for the curable adhesive film and the curable foam support layer. In some embodiments, the (meth)acrylic polymer is any of those described above for the curable adhesive film and the curable foam support layer.

In some embodiments, the rubber useful in the solid activator composition comprises a block copolymer of a styrene and an alkene. In some embodiments, the rubber comprises a styrene- ethylene/butylene-styrene triblock copolymer. In some embodiments, the rubber comprises a styrene- ethylene/butylene-styrene block copolymer grafted with maleic anhydride. In some embodiments, the rubber comprises at least one of a styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, a styrene-ethylene-butylene-styrene copolymer. Linear and star block copolymers and combinations thereof can be useful. Plasticizers, including any of those described above, can be useful for formulating the rubber into a paste.

In some embodiments, the oxidizing agent is present in the solid activator composition in an amount of at least 0.5 weight percent, at least 1 weight percent, at least 2 weight percent, or at least 4 weight percent, based on the total weight of the solid activator composition. In some embodiments, the oxidizing agent is present in the activator in an amount of up to 20 weight percent, up to 15 weight percent, up to 10 weight percent, or up to 5 weight percent, based on the total weight of the solid activator composition.

In some embodiments, the activator also includes a transition metal cation, which may be one or more of any of those described herein for the curable adhesive film. In some embodiments, the activator further includes a silane (e.g., epoxy silane).

In some embodiments, the solid activator composition may be in the form of a free-standing film. The free-standing film can include any of the rubbers described above, any of the plasticizers or additives described above, and any of the oxidizing agents described above. In some embodiments, the freestanding film also includes an amine-functional (meth)acrylic resin that is a polymerization reaction product of an amine-functional (meth)acryloyl compound (e.g., amine -functional (meth)acrylic acid esters and amides) and a non-amine-vinyl monomer. In some embodiments, the amine -functional (meth)acrylic resin has a calculated glass transition temperature (Tg) greater than or equal to 12°C. In some embodiments, the amine-functional (meth)acrylic resin has a calculated Tg greater than or equal to 20°C. In some embodiments, the amine-functional (meth)acryloyl compound (e.g., amine-functional (meth)acrylic acid esters and amides) include 2-(N,N-dimethylaminoethyl) (meth)acrylate, 2-(N,N- diethylaminoethyl) (meth)acrylate, 2-(t-butylaminoethyl) (meth)acrylate, 2-(N,N-dimethylaminoethyl) (meth)acrylamide, 2- (N,N-diethylaminoethyl) (meth)acrylamide, 2-(t-butylaminoethyl) (meth)acrylamide, and N- (meth)acryloylpiperidine. In some embodiments, the non-amine-vinyl monomer is selected from the group consisting of a (meth)acrylic acid, a (meth)acrylic acid ester, a (meth)acrylamide, a vinyl ester, a styrene, a (meth)acrylonitrile, and mixtures thereof. In some embodiments, the non-amine-vinyl monomer is a (meth)acrylic acid ester of a Cl to C18 alcohol.

The solid activator composition may be applied any suitable thickness. In some embodiments, thickness is at least 1 micrometer, at least 2 micrometers, at least 3 micrometers, at least 4 micrometers, or at least 5 micrometers. In some embodiments, thickness is not more than 20 micrometers, not more than 15 micrometers, or not more than 10 micrometers. In some embodiments, the solid activator composition is applied in an amount of not more than 3 milligrams per square centimeter. If a layer of the solid activator composition is more than 3 milligrams per square centimeter, as shown in the Examples, below, the low cohesion strength of the solid activator layer may lower the strength of the bonding between the tape and the substrate.

In some embodiments, advantageously, the solid activator composition need not include organic solvent. In some embodiments, the solid activator composition comprises less than 5 weight percent, less than 3 weight percent, less than 1 weight percent, less than 0.5 weight percent, less than 0.1 weight percent, or less than 0.01 weight percent of organic solvent.

The present disclosure provides a kit comprising a tape comprising a curable adhesive fdm comprising a film-forming polymer, a species comprising unsaturated free -radically polymerizable groups, which may be the film-forming polymer or a species other than the film-forming polymer, and a transition metal cation and a solid activator composition comprising an oxidizing agent, wherein the solid activator composition is in the form of a crayon or paste. The tape, curable adhesive film, and the solid activator composition can be any of those described above in any of their embodiments.

In some embodiments, the solid activator composition is in the form of a crayon. The crayon can have any suitable shape, such as a cylinder or prism with any desirable cross-sectional shape such as rectangle, triangle, or square. The shape at an end of the crayon can be adjusted, for example, for ease of writing although this is not a requirement. The kit of the present disclosure can include the tape and the crayon. The crayon can be useful with or without a container. In a container, the crayon can also be referred to as a stick. The kit can include the tape and the stick. An embodiment of a container useful for holding a solid activator composition useful in the adhesive system, method, and crayon of the present disclosure is shown in FIG. 12. The container 1 is cylindrical in cross-section having cylindrical side walls 2. On the base of the container is a knurled wheel 3 which forms part of a propulsion mechanism for the solid activator composition 4 in a generally cylindrical shape. The container further comprises a cap 5 which is snap-fit engageable over the top end 6 of the container 1. The top end 6 can be of lesser diameter than the side walls 2 and has a rim 7 which engages in a corresponding recess on the underside of the cap 5 to secure the cap 5 in place.

The knurled wheel 3 is attached to an elongate drive or winding shaft 8 which is centrally located within the housing formed by the side walls of the container. On the winding shaft 8 is located a moveable carrier 9. The carrier 9 is generally cylindrical (from an end view thereof — see for example FIG. 13) and has a short peripheral upstanding wall 10 formed on its base 11. The solid activator composition may be formed with the carrier 9, optionally the shaft 8, and optionally the wheel 3 in place. As best seen from FIG. 13, the carrier 9 has a central threaded aperture 13 in which the threads 16 of the shaft 8 engage. The knurled wheel 3 and the shaft 8 are both mounted for relative rotation to the container body. When the wheel 3 is turned it moves the carrier up or down the shaft 8 thus controlling the relative position of the mass and the container. In the position shown the carrier has travelled part way up the shaft, moving the solid activator composition 4 to a position where it protrudes from the container. The solid activator composition can then be applied by rubbing the mass against a substrate by manual force. Sufficient shearing of the mass takes place to allow it to rub off onto the substrate. To prevent rotation of the carrier 9 with the shaft, elongate ribs 14 are provided on opposing sides of the internal wall of the container. The ribs 14 run from the base of the container to a position proximate to the mouth if the container. The ribs 14 each engage one of corresponding grooves 15 in the carrier 9 thus preventing relative rotation of the container and the carrier and ensuring that the carrier moves upwardly or downwardly when the shaft 8 turns.

The adhesive systems and methods of the present disclosure do not require mixing of liquid components; rather, the solid activator composition is applied to a substrate or release liner, and the activator-coated substrate or release liner is contacted with the curable adhesive film 140, 210, or 240, into which the oxidizing agent from the activator migrates. An oxygen-permeable liner can be kept in place on the curable adhesive film until the curable adhesive film is ready to bond. Upon joining of the substrates to be adhered, thereby excluding oxygen, the curable adhesive film begins to cure, resulting in structural adhesive bonds. In some embodiments of the adhesive systems and methods of the present disclosure, cure can be achieved at normal temperature and pressure, without heat or autoclave. Likewise, in some embodiments of the adhesive systems and methods of the present disclosure, cure can be achieved without UV or other radiation treatment, and cure propagates well to areas inaccessible to radiation cure. In some embodiments of the present adhesive systems and methods, the curable adhesive fdm and the solid activator composition need not be refrigerated or kept in dark storage.

Some embodiments of the present disclosure

In a first embodiment, the present disclosure provides an adhesive system comprising a curable adhesive film comprising a film-forming polymer, unsaturated free-radically polymerizable groups, which may be bonded to the film -forming polymer or in a species other than the polymer, and a transition metal cation and a solid activator composition comprising an oxidizing agent, wherein the solid activator composition is not a free-standing film. In a second embodiment, the present disclosure provides the adhesive system of the first embodiment, wherein the solid activator composition is in the form of a crayon or paste. In a third embodiment, the present disclosure provides the adhesive system of the first or second embodiment, wherein the solid activator composition is present on a substrate in an amount of not more than 3 milligrams per square centimeter. In a fourth embodiment, the present disclosure provides the present disclosure provides a kit comprising a curable adhesive film comprising a film-forming polymer, unsaturated free-radically polymerizable groups, which may be bonded to the film-forming polymer or in a species other than the polymer, and a transition metal cation and a solid activator composition comprising an oxidizing agent, wherein the solid activator composition is in the form of a crayon or paste.

In a fifth embodiment, the present disclosure provides a method for bonding a first article, the method comprising applying a solid activator composition onto a surface of the first substrate, the solid activator composition comprising an oxidizing agent, wherein applying comprises at least one of rubbing or spreading, and contacting the solid activator composition with a first surface of a tape, the tape comprising a curable adhesive film comprising a film-forming polymer, unsaturated free-radically polymerizable groups, which may be bonded to the film-forming polymer or in a species other than the polymer, and a transition metal cation. In a sixth embodiment, the present disclosure provides the method of the fifth embodiment, further comprising bonding a second surface of the tape to a second substrate. In a seventh embodiment, the present disclosure provides the method of the fifth or sixth embodiment, further comprising at least one of rubbing or spreading the solid activator composition onto a surface of a second substrate and contacting the solid activator composition on the second substrate with a second surface of the tape. In an eighth embodiment, the present disclosure provides the method of the fifth embodiment, further comprising bonding a second surface of the tape to an oxygen-permeable liner. In a ninth embodiment, the present disclosure provides the method of the eighth embodiment, wherein contacting the solid activator composition with a first surface of a tape is carried out while the adhesive film is attached to the oxygen-permeable liner. In a tenth embodiment, the present disclosure provides the method of the eighth or ninth embodiment, the process comprising removing the oxygen-permeable liner from the second surface of the tape and bonding a second surface of the tape to a second substrate. In an eleventh embodiment, the present disclosure provides the method of the tenth embodiment, further comprising at least one of rubbing or spreading the solid activator composition onto a surface of a second substrate and contacting the solid activator composition on the second substrate with a second surface of the tape. In a twelfth embodiment, the present disclosure provides the method of any one of the first to eleventh embodiments, wherein the first substrate is a release liner. In a thirteenth embodiment, the present disclosure provides the method of the twelfth embodiment, the method comprising removing the release liner to provide a first adhesive surface and bonding the first adhesive surface to a surface of a substrate. In a fourteenth embodiment, the present disclosure provides the method of the thirteenth embodiment, further comprising applying a solid activator composition to the surface of the substrate, wherein the second solid activator composition comprises a second oxidizing agent, wherein the second solid activator composition is independently selected form the solid activator composition. In a fifteenth embodiment, the present disclosure provides the method of any one of fifth to fourteenth embodiments, wherein the solid activator composition is applied to the surface of the first substrate and/or the surface of the second substrate in an amount of not more than 3 milligrams per square centimeter. In a sixteenth embodiment, the present disclosure provides the method of any one of the fifth to fifteenth embodiments, wherein the at least one of rubbing or spreading the solid activator composition onto at least one of the surface of the first substrate or the surface of the second substrate comprises at least one of rubbing or spreading the solid activator composition onto intermittent portions of the first substrate or the second substrate while not applying the solid activator composition to other portions of the first substrate or the second substrate.

In a seventeenth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to sixteenth embodiments, wherein the curable adhesive film is a first layer of a multilayer curable adhesive film, wherein the multilayer curable adhesive film further comprises a foam support layer. In an eighteenth embodiment, the present disclosure provides the adhesive system, kit, or method of the seventeenth embodiment, wherein the foam support layer is curable. In a nineteenth embodiment, the present disclosure provides the adhesive system, kit, or method of the seventeenth or eighteenth embodiment, wherein the foam support layer comprises at least one of a closed cell foam or a syntactic foam. In a twentieth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to nineteenth embodiments, wherein the foam support layer comprises a base polymer which is the same as the film-forming polymer in the curable adhesive film. In a twenty-first embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to twentieth embodiments, wherein the foam support layer comprises a crosslinker within the foam support layer. In a twenty-second embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-first embodiment, wherein the crosslinker is different from the species comprising unsaturated free-radically polymerizable groups in the curable adhesive film. In a twenty-third embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-first embodiment, wherein the crosslinker is the species comprising unsaturated free -radically polymerizable groups in the curable adhesive film that migrates and/or has migrated (i.e., having migrated) into the curable support layer. In a twenty-fourth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to twenty-first or twenty-third embodiments, wherein the foam support layer comprises a foaming agent and the same components as the curable adhesive film. In a twenty-fifth embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-fourth embodiment, wherein the foaming agent comprises at least one of expandable microspheres, hollow glass bubbles, or gas bubbles optionally stabilized with a surfactant. In a twenty-sixth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to twenty-fifth embodiments, wherein the curable foam support layer further comprises a polymer modulus modifier. In a twenty-seventh embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-sixth embodiment, wherein the polymer modulus modifier comprises a polymer having a Tg of no greater than 100°C, no greater than 90°C, no greater than 80°C, no greater than 70°C, no greater than 60°C, no greater than 50°C, or no greater than 40°C. In a twenty-eighth embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-sixth or twenty-seventh embodiment, wherein the polymer modulus modifier comprises a polyvinyl acetal resin (e.g., polyvinyl butyral). In a twenty-ninth embodiment, the present disclosure provides the adhesive system, kit, or method of the twenty-sixth or twenty-seventh embodiment, wherein the polymer modulus modifier comprises a high acid polymer. In a thirtieth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to twenty-ninth embodiments, wherein the curable foam support layer further comprises a transition metal cation and a quaternary ammonium salt. In a thirty-first embodiment, the present disclosure provides the article of any one of the seventeenth to thirtieth embodiments, wherein the curable foam support layer is hot melt processable. In a thirty-second embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to thirty-first embodiments, wherein the curable adhesive film is borne on a first major surface of the foam support layer. In a thirty-third embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to twenty-first embodiments, wherein the curable adhesive film is directly bound to (e.g., laminated to) a first major surface of the foam support layer.

In a thirty-fourth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the seventeenth to thirty-third embodiments, wherein the multilayer curable adhesive film further comprises a second curable adhesive layer comprising a second film of a second independently selected polymer, second independently selected unsaturated free-radically polymerizable groups, which may be bonded to the second independently selected polymer or in a second species other than the second independently selected polymer, and a second independently selected transition metal cation. In a thirtyfifth embodiment, the present disclosure provides the adhesive system, kit, or method of the thirty-fourth embodiment, wherein the second curable adhesive layer is adjacent to a surface of the foam support layer opposite the first layer. In a thirty-sixth embodiment, the present disclosure provides the adhesive system, kit, or method of the thirty-fifth embodiment, wherein the first layer is borne on a first major surface of the foam support layer and the second curable adhesive layer is borne on a second major surface of the foam support layer. In a thirty-seventh embodiment, the present disclosure provides the adhesive system, kit, or method of the thirty-fifth embodiment, wherein the first layer is directly bound to a first major surface of the foam support layer and the second curable adhesive layer is directly bound to a second major surface of the foam support layer.

In a thirty-eighth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to thirty-seventh embodiments, wherein the curable adhesive film comprises a hot melt processable adhesive. In a thirty-ninth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to thirty-eighth embodiments, wherein the unsaturated free- radically polymerizable groups are in a species other than the polymer, and wherein the polymer does not comprise unsaturated free-radically polymerizable groups.

In a fortieth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the eighth to thirty-ninth embodiments, wherein the oxygen-permeable liner comprises at least one of paper or a polyolefin. In a forty-first embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the eighth to fortieth embodiments, wherein the oxygen-permeable liner comprises ridges on at least one surface. In a forty-second embodiment, the present disclosure provides the adhesive system, kit, or method of the forty-first embodiment, wherein the curable adhesive film comprises an outer surface bearing channels corresponding to the ridges, wherein the channels are capable of aiding in escape of air during application of the outer surface to a substrate.

In a forty-second embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-first embodiments, wherein the solid activator composition does not include unsaturated free-radically polymerizable groups. In a forty-third embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-second embodiments, wherein the oxidizing agent is an organic peroxide, an organic hydroperoxide, an inorganic peroxide, or a persulfate. In a forty-fourth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-third embodiments, wherein the solid activator composition comprises an acrylic polymer comprising a crystalline monomeric unit having from 16 to 50 carbon atoms. In a forty-fifth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-fourth embodiments, wherein the solid activator composition comprises at least one of a tackifier or inorganic filler. In a forty-sixth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-fourth embodiments, wherein the solid activator composition comprises at least one of a fatty acid, a fatty acid salt, or a fatty acid ester. In a forty-seventh embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to forty-sixth embodiments, wherein the solid activator composition comprises less than 5 weight percent, less than 3 weight percent, less than 1 weight percent, less than 0.5 weight percent, less than 0.1 weight percent, or less than 0.01 weight percent of organic solvent.

In a forty-eighth embodiment, the present disclosure provides a crayon comprising an acrylic polymer comprising a crystalline monomeric unit having from 16 to 50 carbon atoms and at least one other monomeric unit and an oxidizing agent. In a forty-ninth embodiment, the present disclosure provides the crayon of the forty-eighth embodiment, wherein the crayon does not include unsaturated free-radically polymerizable groups. In a fiftieth embodiment, the present disclosure provides the crayon of the forty-eighth or forty-ninth embodiment, wherein the oxidizing agent is an organic peroxide, an organic hydroperoxide, an inorganic peroxide, or a persulfate. In a fifty-first embodiment, the present disclosure provides the crayon of any one of the forty-eighth to fiftieth embodiments, further comprising at least one of a tackifier or inorganic filler. In a fifty-second embodiment, the present disclosure provides the crayon of any one of the forty-eighth to fifty-first embodiments, further comprising at least one of a fatty acid, a fatty acid salt, or a fatty acid ester. In a fifty-third embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the forty-eight to fifty-second embodiments, wherein the solid activator composition comprises less than 5 weight percent, less than 3 weight percent, less than 1 weight percent, less than 0.5 weight percent, less than 0.1 weight percent, or less than 0.01 weight percent of organic solvent. In a fifty-fourth embodiment, the present disclosure provides the adhesive system, kit, or method of any one of the first to fifty-third embodiments, wherein the solid activator composition is in the form of a crayon having a shape of a cylinder, triangular prism, rectangular prism, or square prism.

In a fifty-fifth embodiment, the present disclosure provides the adhesive system of any one of the first to fifty-fourth embodiments, further comprising a release liner to which the tape and solid activator composition are releasably attached. In a fifty-sixth embodiment, the present disclosure provides the adhesive system of any one of the first to fifty-fourth embodiments, further comprising a substrate to which the tape and solid activator composition are attached.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure. Table 1: Materials

PREPARATIONS Preparation of Curable Adhesive Film 1

Curable Adhesive Film 1 was prepared as described in Hotmelt Compounding of PSA Adhesive Tape in U.S. Pat. Appl. Pub. No. 2023/0088278 (Kugel et al.) Preparation of Multilayer Tape of Curable Adhesive Film 2-Curable Foam Support Layer-Curable

Adhesive Film 2

Curable Adhesive Film 2 was made by combining a polymer and a liquid blend. The polymer was prepared as described in Synthesis Example SI of U.S. Pat. Pub. No. 2013/0184394 Al (Satrijo et al.) except that the pre-adhesive composition was as follows: 89.480 weight percent Ml, 9.942 weight percent AA, 0. 149 weight percent Photoinitiator- 1, 0.030 weight percent CuOAc, 0.398 weight percent Antioxidant- 1, and 0.001 weight percent HDDA. The liquid blend was prepared by using a diaphragm pump (Wilden Pump and Engineering, Grand Terrace, CA, USA) to add 132.8 pounds (lb) (60.2 kilograms (kg)) of DTMPTA to a HM-2.5 basketmill (Hockmeyer Equipment Corporation, Elizabeth City, NC, USA) with 9-spindle hub having been preloaded with clean Zirmil 1.5-millimeter (mm) bead media and equipped with a 0.5-mm Tungsten coated screen and HM-2.5 turbo prop. When addition of DTMPTA was complete, 17.2 lb (7.8 kg) of BTEAC was added to the basketmill using a paddle mixer to incorporate. The mixture was milled for 3 hours at 800 revolutions per minute (rpm) with cooling jacket set at 70°F (21°C). Milled material was further diluted by addition of 254.1 lbs (115.3 kg) of DTMPTA for every 45.9 lbs (20.8 kg) of milled material. This diluted material, a liquid blend, was combined at 28.5 weight percent with the polymer described above at 70.74 weight percent and PB1 at 0.76 weight percent and compounded as described in Hotmelt Compounding of PSA Adhesive Tape in U.S. Pat. Appl. Pub. No. 2023/0088278 (Kugel et al.) to create Curable Adhesive Film 2.

A three-layer co-extruded tape was prepared by co-extruding two layers of Curable Adhesive Film 2 onto the opposing sides of a Curable Foam Support Layer. The Curable Foam Support Layer was the same as Curable Adhesive Film 2 except modified with 2 weight percent DENSITY MODIFIER taken from the balance of the polymer content. The total thickness of the tape from the three-layer multi manifold film die was 12 mil (0.30 mm). The three-layer co-extruded tape was cast between a silicone coated casting roll and a silicone coated paper liner entrained by a second chill roll. The chill rolls were cooled with water at a temperature of about 13°C. Once cooled down, the co-extruded tape left the silicone release coated roll thereby adhering to the silicone coated paper liner and was then rolled up in a winding station.

Preparation of Polymer Blend 1

An ODA Macromer was prepared by polymerizing octadecyl acrylate using the method described under “Method” in U.S. Pat. No. 7,968,661 (Ellis et al.). The resulting polymer had a weight average molecular weight of 69,000 grams/mole with a polydispersity index of 1.7 as measured using the test method described below. Polymer Blend 1 was prepared as described in Example 22 of U.S. Pat. No. 11,267,997 (June et al.) except that the formulation ratio of ODA/ODMA/IOA/AA/ODA Macromer was as follows: 16/47/22/0.5/14.5. The method described under “Method” in U.S. Pat. No. 7,968,661 (Ellis et al.) was followed to make the polymer, and the ODA/ODMA/IOA/AA polymer in the ratio of 18.7/54.7/26/0.6 had a weight average molecular weight of 74,000 grams/mole with a polydispersity index of 2.5 as measured using the test method described below.

General Preparation of Solid Activator Compositions

Semi-solid activators were made by mixing Polymer Blend 1 and other materials shown in Table 2, except for TBEC, on a hotplate with occasional stirring at interval of roughly every 5 minutes in 15-mL glass vials. The hot plate temperature to prepare homogenous melts before addition of TBEC varied from 65 °C, for majority of the polymer/additives used, to 90 °C, for mixtures containing the Rubber. Once the homogeneous melts were observed and the temperature of melts was checked lower than 60 °C, TBEC addition was completed. After briefly mixing, Activators 1 to 4 were poured into 0.4-cm (radius of inscribed circle) by 7.0-cm equilateral triangle plastic mold and Activators 5 to 9 remained in the vials before they cooled down to room temperature. Solid activator compositions shown in Table 2, below.

Table 2: Solid Activator Compositions in weight percent

TEST METHODS

Dynamic Shear Adhesion Test

A dynamic overlap shear test was performed at 71 °F (22°C) using an Insight 30EL load frame (MTS, Eden Prairie, MN). Test specimens were prepared for dynamic shear adhesion using aluminum substrates (Joseph T. Ryerson & Son, Inc., Coon Rapids, MN) (1-inch by 4-inch by 0.064-inch (2.5-cm by 10-cm by 1.6-mm)) that were washed with MEK, then 50/50 water/IPA solution, and then three times with acetone, followed by air-drying for at least 2 minutes. After test specimens were prepared according to the Examples, below, they were loaded into the grips and the crosshead was operated at 0. 1 inch (0.25 cm) per minute, loading the specimen to failure. Stress at break was recorded in units of pounds per square inch (psi) using testing methods disclosed in ASTM D 1002. Six specimens were tested for each Example, and the results were averaged and reported. Coat Weight Measurement

Coat weight measurements were used to measure the delivered solid activator composition thickness. The weight of bare clean substrates was recorded in milligrams as Wo. A 1-inch by 2-inch area was masked with tape. After applying the activator, tape was removed, and the weight of activated substrates was recorded in milligrams as Wi. The coat weight is defined as (Wi-Wo)/2, and the unit is mg/inch². Twelve specimens were tested for each Example, and the results were averaged and reported.

Gel Permeation Chromatograhy (GPC) Analysis

Approximately 50 mg of polymeric solids was placed in 10 mL of THF (stabilized with 250 ppm BHT). The samples were mixed at low speed for approximately three hours on a mechanical shaker (obtained under the trade designation E6010.00 from Eberbach Corporation, Belleville, MI) to provide polymer solutions. All polymer solutions were run through a 0.45 micron syringe filter and analyzed by Gel Permeation Chromatography (“GPC”). The GPC consists of a Pump, Columns and a Detector. The Columns and Detector are described below. The Pump was obtained under the trade designation “AGILENT 1100 HPLC” from Agilent Technologies, Santa Clara, CA.

GPC Equipment and Conditions:

Sample: 50 pL Injection at 5 mg/mL Tetrahydrofuran-stabilized

Sample filtered through 0.45 micron membrane

Mobile Phase: Tetrahydrofuran-UV Grade, stabilized (obtained under the trade designation “EMD OMNISOLV” from MilliporeSigma Co., Burlington, MA); or equivalent grade

Flow Rate: 1.0 mL/min

Detector: Refractive Index Detector (obtained under the trade designation “1200 SERIES G1362” from Agilent Technologies, Santa Clara, CA)

Columns: Two of nominal MW range 500-10⁷ Daltons (obtained under the trade designation “PLGEL 10 MICRON MIXED-B” from Agilent Technologies, Santa Clara, CA) and one of nominal MW range 200-400,000 Daltons, (obtained under the trade designation “PLGEL 5 MICRON MIXED-D” from Agilent Technologies). All columns are 7.8 mm x 300 mm. Columns are held at 40 °C.

Standards: Polystyrene, narrow dispersity; ranging 6.035 x 10⁶ - 580 Mp; (third order polynomial fit) obtained under the trade designation “EASICAL PS-1” from Agilent, Santa Clara, CA

Syringe filter type: 0.45 micron PTFE Examples (Ex.) 1 to 11 and Illustrative Examples (I.E.) 1 and 2

Aluminum Substrates for the Dynamic Shear Adhesion Test were activated using two different activation methods. Examples 1 to 3 and Comparative Example 1 were activated by holding the activator as one would use a crayon and simply writing/rubbing on the upper part of individual clean substrate (at least 1-inch by 2-inch coated). Examples 4 to 11 and Comparative Example 2 were activated with the following process. A small amount of the activator (~10-mg) was applied and then spread evenly on the clean substrate (1-inch by 1.5-inch area) using a Kimwipe. The average coat weight by this method was from 2 to 7 mg/inch². After completing substrate activation, adhesion specimens were made by cutting a 1-inch (2.5-cm) wide strip of Curable Adhesive Films 1 and 2 described previously. One liner was removed, and the curable adhesive films were laid across the activated portion of the substrate. A 2-inch (5.1 -cm) firm rubber roller (MARSHALLTOWN, Marshalltown, IA) was rolled onto the construction with firm hand pressure to ensure full contact of the Curable Adhesive Films and Activated Substrates. Pre-bond specimens made in this way were then stored at room temperature (71 °F /22°C) at times indicated in Table 2 (Pre-Bond Storage Time) before bonds were closed with a second substrate. Bonds were formed by removing the top release liner exposing the Curable Adhesive Film and introducing it to a second activated substrate, activated using the same method as the first substrate. The closed bond was then either subjected to applied pressure of about 18 psi inside a pneumatic driven hydraulic press (Fred S. Carver, Inc. Hydraulic Equipment, Menomonee Falls, WI) between two rubber gaskets for 5 seconds or rolling down 15-lbf with a rate of 12 in/min onto overlapped bond area. The bonded article was dwelled at room temperature (71 °F /22°C) as indicated in Table 3 prior to testing using the Dynamic Shear Adhesion Test. The adhesive systems and results are shown in Table 3, below.

Table 3: Examples (EX) 1 to 11 and Illustrative Examples (I.E.) 1 and 2

The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

What is claimed is:

1. An adhesive system comprising: a tape comprising: a curable adhesive film comprising: a film of a polymer; unsaturated free -radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer; and a transition metal cation; and a solid activator composition comprising an oxidizing agent, wherein the solid activator composition is not a free-standing film.

2. A kit comprising: a tape comprising: a curable adhesive film comprising: a film of a polymer; unsaturated free -radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer; and a transition metal cation; and a solid activator composition comprising an oxidizing agent, wherein the solid activator composition is in the form of a crayon or paste.

3. A method of bonding a first substrate, the method comprising: applying a solid activator composition onto a surface of the first substrate, the solid activator composition comprising an oxidizing agent, wherein applying comprises at least one of rubbing or spreading; and contacting the solid activator composition with a first surface of a tape, the tape comprising: a curable adhesive film comprising: a film of a polymer; unsaturated free -radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer; and a transition metal cation.

4. The method of claim 3, wherein the solid activator composition is applied to the surface of the first substrate in an amount of not more than 3 milligrams per square centimeter.

5. The method of claim 3 or 4, further comprising bonding a second surface of the tape to a second substrate.

6. The method of claim 3 or 4, further comprising covering the second surface of the tape with an oxygen-permeable liner.

7. The adhesive system, kit, or method of any one of claims 1 to 6, wherein the solid activator composition does not include unsaturated free -radically polymerizable groups.

8. The adhesive system, kit, or method of any one of claims 1 to 7, wherein the solid activator composition comprises an acrylic polymer comprising a crystalline monomeric unit having from 16 to 50 carbon atoms.

9. The adhesive system, kit, or method of any one of claims 1 to 8, wherein the solid activator composition comprises at least one of a tackifier, inorganic filler, fatty acid, a fatty acid salt, or a fatty acid ester.

10. The adhesive system, kit, or method of any one of claims 1 to 9, wherein the tape further comprises a support layer adjacent the curable adhesive film.

11. The adhesive system, kit, or method of claim 10, wherein the support layer comprises a foam.

12. The adhesive system, kit, or method of claim 11, wherein the foam comprises a crosslinker comprising unsaturated free-radically polymerizable groups.

13. The adhesive system, kit, or method of any one of claims 10 to 12, wherein the curable adhesive film is a first curable adhesive film, wherein the tape further comprises a second curable adhesive film, wherein the second curable adhesive film, independently of the first curable adhesive film, comprises: a film of a polymer; unsaturated free-radically polymerizable groups, which may be bonded to the polymer or in a species other than the polymer; and a transition metal cation; and wherein the second curable adhesive film is adjacent to a surface of the support layer opposite the first curable adhesive film.

14. The adhesive system, kit, or method of any one of claims 1 to 13, wherein the curable adhesive fdm comprises a hot melt processable adhesive.

15. A crayon comprising : an acrylic polymer comprising a crystalline monomeric unit having from 16 to 50 carbon atoms and at least one other monomeric unit; and an oxidizing agent.