Composite adhesives comprising polymeric nanoparticles

Abstract

A composite adhesive composition is described herein. The composition comprises: a plurality of polymeric nanoparticles dispersed in a (meth) acrylate-based matrix; and the (meth) acrylate-based matrix is derived from C1 to C12 (meth) acrylate monomers and (meth) acrylate macromonomers. In some embodiments, these composite adhesives exhibit good impact resistance and good dynamic shear resistance. In one embodiment, an ionic liquid is added to the composite adhesive to achieve electrical exfoliation.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an impact resistant adhesive comprising a (meth)acrylate-based matrix having a plurality of polymeric nanoparticles dispersed therein. SUMMARY

[0002] In electronic devices, particularly mobile electronic devices (e.g., handheld or wearable electronic devices), pressure sensitive adhesives (PSAs) are commonly used to bond cover glass (or lenses) to underlying display modules, to bond touch sensors to cover glass and displays, or to bond lower components of displays to housings. For these applications, often referred to as electronic device bonding or e-bonding, the PSA should have a strong enough adhesive strength to properly maintain good adhesion to the components not only when the mobile electronic device is operating under normal conditions, but also when they are deformed (e.g., bent, folded, flexed) by external forces, subjected to traumatic forces (e.g., the mobile electronic device is dropped onto a hard surface), or subjected to extreme environmental conditions (e.g., high temperature conditions and / or high humidity conditions). Regarding deformation, the components of the electronic device can deform when a user is sitting in a chair while the electronic device is in their pocket or their hip is pressing down on the electronic device. Under such conditions, the pressure sensitive adhesive should have an adhesion strength sufficient to maintain, for example, adhesion to the cover glass (sometimes referred to as anti-wrinkling). Regarding traumatic forces, the pressure sensitive adhesive should have a strong enough drop or impact resistance so that it maintains adhesion of the components even when a large instantaneous impact is applied to the mobile electronic device upon dropping of the mobile electronic device.

[0003] In view of the electronics industry trend towards device simplification (i.e., combining layers and / or layer functions) and reducing the bonding area and overall device thickness (and, in addition, requiring enhanced mechanical durability), there is an increasing need for tapes that have good adhesion to device substrates, good impact / drop resistance, and sufficient shear resistance. There is a need for adhesives that achieve this balance of properties.

[0004] In one aspect, a composition is disclosed. The composition comprises: (i) a plurality of polymeric nanoparticles, wherein the polymeric nanoparticles comprise an interior region and a shell, the interior region comprises a polymer having a glass transition temperature below room temperature, and the shell comprises a polymer having a glass transition temperature of at least 50 °C; and (ii) a polymerizable matrix comprising: (a) a (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide), a poly(tetrahydrofuran) group, or a combination thereof; (b) a Ci to C 12one or more (meth)acrylate monomers; (c) a crosslinker; and (d) 0 to at most 7 weight percent of a hydroxyl-containing (meth)acrylate monomer.

[0005] In another aspect, a composition is described. The composition comprises: (i) a plurality of polymeric nanoparticles, wherein the polymeric nanoparticles comprise an interior region and a shell, the interior region comprises a polymer having a glass transition temperature below room temperature, and the shell comprises a polymer having a glass transition temperature of at least 50°C; and (ii) a matrix derived from: (a) a (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide), a poly(tetrahydrofuran) group, or a combination thereof; (b) a Ci to C 12 one or more (meth)acrylate monomers; (c) a crosslinker; and (d) 0 to at most 7 weight percent of a hydroxyl-containing (meth)acrylate monomer.

[0006] In another aspect, an adhesive article is described. The adhesive article comprises a hybrid adhesive composition derived from one of the above compositions, wherein the hybrid adhesive composition is disposed on a substrate.

[0007] In yet another embodiment, a method of making an adhesive article is described. The method comprises: (i) obtaining a polymerizable matrix, the polymerizable matrix comprising: (a) a (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide), a poly(tetrahydrofuran) group, or a combination thereof; (b) a Ci to C 12 one or more (meth)acrylate monomers; (c) a crosslinker; and (d) 0 to at most 7 weight percent of a hydroxyl-containing (meth)acrylate monomer; and (ii) adding a plurality of polymeric nanoparticles to the polymerizable matrix to form a composition.

[0008] In yet another embodiment, a method of making an adhesive article is described. The method comprises: (i) obtaining a polymerizable matrix, the polymerizable matrix comprising: (a) a (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide), a poly(tetrahydrofuran) group, or a combination thereof; (b) C1 to C 12 one or more of a (meth)acrylate monomer; (c) a crosslinker; and (d) 0 to at most 7 weight percent of a hydroxyl-containing (meth)acrylate monomer; and (ii) at least partially polymerizing the polymerizable matrix to form an at least partially polymerized composition, and (iii) adding a plurality of polymer nanoparticles, wherein the polymer nanoparticles comprise an interior region comprising a polymer having a glass transition temperature below room temperature and an outer shell comprising a polymer having a glass transition temperature of at least 50 °C.

[0009] The above summary is not intended to describe each embodiment. Additional details of one or more embodiments of the application are set forth in the following detailed description and claims. Other features, objects, and advantages will be apparent from this summary and the claims. BRIEF DESCRIPTION OF DRAWINGS

[0010] Embodiments of the disclosure are illustrated by way of example in the accompanying drawings, which are schematic and not drawn to scale, and in which:

[0011] Figure 1 is a schematic cross-sectional view of a multi-layer adhesive article including a composite adhesive layer according to one embodiment of the disclosure; and

[0012] Figure 2 is a schematic cross-sectional view of a composite adhesive layer according to one embodiment of the disclosure.

[0013] Figure 3A is a top view of a test sample for a random free fall test, Figure 3B is a side view schematic of the test sample.

[0014] Figure 4 is a schematic cross-sectional view of a multi-layer adhesive article including a composite adhesive layer according to one embodiment of the disclosure.

[0015] Figure 5 is a schematic cross-sectional view of a multi-layer adhesive article including a composite adhesive layer according to one embodiment of the disclosure. DETAILED DESCRIPTION

[0016] As used herein, the term

[0017] "one", "a", and "the" are used interchangeably and refer to one or more; and

[0018] "and / or" is used to indicate one or both stated cases can occur, for example, A and / or B includes (A and B) and (A or B); "crosslinking" refers to the joining of two preformed polymer chains using a chemical bond or chemical group in order to increase the modulus of the material; and "(meth)acrylate" refers to a compound containing an acrylate (CH2=CHCOOR) or methacrylate (CH2=CCH3COOR) structure or a combination thereof.

[0019] As used herein, the term "macromonomer" refers to a monomer having a polymerizable group. Macromonomers are a subset of the term "monomer".

[0020] The term "monomeric unit" refers to the reaction product of a polymerizable component (i.e., a monomer (including a macromonomer)) within a (meth)acrylate copolymer. For example, a monomeric unit of acrylic acid is

[0021] wherein the asterisk ( ) indicates a point of attachment to another group, such as another monomeric unit or end group in a (meth)acrylate copolymer.

[0022] The term "(meth)acrylate macromonomer" refers to a monomer having a single (meth)acryloyloxy group (i.e., a group having the formula CH2=CR-(CO)-O-, wherein R is hydrogen or methyl) plus a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide) group, or a poly(tetrahydrofuran) group.

[0023] The term "poly(ethylene oxide) group" refers to a group containing at least 3 ethylene oxide (- (C2H4O)-) groups, and the term "poly(propylene oxide) group" refers to a group containing at least 3 propylene oxide (- (C3H6O)-) groups.

[0024] The term "poly(ethylene oxide-co-propylene oxide) group" contains at least 3 groups, including at least one ethylene oxide group and at least one propylene oxide group. Poly(ethylene oxide-co-propylene oxide) groups are copolymer groups.

[0025] The term "poly(tetrahydrofuran)(meth)acrylate macromonomer" refers to a monomer having a single (meth)acryloyloxy group (i.e., a group of the formula CH2=CR-(CO)-O-, where R is hydrogen or methyl) plus a poly(tetrahydrofuran) group containing at least three -(C4H8O)- groups. The term "poly(tetrahydrofuran)" can be used interchangeably with the terms "poly(tetramethylene oxide)" and "poly(tetramethylene glycol)".

[0026] Also herein, ranges expressed by endpoints include all numbers subsumed within that range (e.g., 1 to 10 includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10).

[0027] Also herein, the expression "at least" followed by a number includes that number and all greater numbers (e.g., "at least 1" includes at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0028] The adhesive of the present disclosure is a composite material comprising a plurality of polymeric nanoparticles dispersed in a (meth)acrylate-based matrix.

[0029] Polymer nanoparticles

[0030] The particles of the present disclosure are polymers comprising at least two different polymer regions (an interior polymer region and a shell). The interior of the particle comprises a polymer having a glass transition temperature (Tg) below room temperature, while the shell of the particle comprises a polymer having a high Tg. While not wishing to be bound by theory, it is believed that the low Tg polymer interior is able to absorb impact forces, while the harder shell enables the particle to be well dispersed in the matrix. The Tg of the particle can be determined, for example, by using differential scanning calorimetry (DSC). If the particle is composed of individual polymers, a peak should appear in the analysis of each individual polymer as long as the amount of the polymer in the matrix is sufficient (e.g., greater than 10 wt% or even 5 wt%).

[0031] The polymeric particles of the present disclosure are nanostructured, meaning that the largest dimension (e.g., diameter) is less than 900 nanometers, 800 nanometers, 750 nanometers, 500 nanometers, 400 nanometers, 350 nanometers, or even 300 nanometers (nm). In one embodiment, the average particle size of the particles is at least 20 nm, 50 nm, 100 nm, 150 nm, or even 170 nm and at most 500 nm, 400 nm, 350 nm, 300 nm, 250 nm, or even 200 nm. Particle size can be measured using techniques known in the art, such as using a particle size analyzer (such as a Malvern Zetasizer) using calibration standards or a microscope (such as a scanning electron microscope). In one embodiment, the average size of the interior polymeric region is at least 10 nm, 20 nm, or even 50 nm and at most 75 nm, 100 nm, 200 nm, 300 nm, 400 nm, or even 500 nm. The size of the interior polymeric region can be measured using techniques known in the art, such as transmission electron microscopy.

[0032] In one embodiment, the polymer of the shell of the polymeric particles has a Tg of at least 50 °C, 60 °C, 70 °C, 80 °C, 100 °C, 120 °C, or even 150 °C; and no more than 300 °C, 250 °C, 200 °C, or even 175 °C. In one embodiment, the shell comprises poly(methyl methacrylate) or poly(glycidyl methacrylate).

[0033] In one embodiment, the Tg of the interior polymer of the polymeric particle is less than 25°C, 23°C, 20°C, 15°C, 10°C, 5°C, 0°C, -10°C, -20°C, -25°C, or even -40°C and more than -120°C, -90°C, -80°C, -75°C, or even -50°C. Exemplary polymers that can be used in the interior of the polymeric particle include isoprene homopolymers or butadiene homopolymers, (meth)acrylic acid homopolymers or copolymers derived from (meth)acrylate monomers having 1 to 18 carbons, preferably 4 to 18, or even more preferably 4 to 12 or even 4 to 8 carbon atoms, isoprene-butadiene copolymers, copolymers of isoprene with up to 98 wt% of a vinyl monomer, and copolymers of butadiene with up to 98 wt% of a vinyl monomer. The vinyl monomer can be styrene, alkylstyrene, acrylonitrile, alkyl (meth)acrylate, or butadiene or isoprene, as long as the polymer results in the requisite low Tg interior portion. Multi-functional monomers can be used during polymerization of the interior polymer or grafted onto the interior polymer to introduce sites for partial or complete crosslinking of the polymer. Such multi-functional (e.g., di- or tri-functional) monomers include poly(meth)acrylates of polyols, such as butanediol di(meth)acrylate and trimethylolpropane trimethacrylate; divinylbenzene; trivinylbenzene; and triallyl cyanurate; the addition of these functional groups can result in crosslinking of the shell into a polymeric matrix. Other monomers for polymer crosslinking include unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, anhydrides of unsaturated carboxylic acids and unsaturated epoxides, maleic anhydride, (meth)acrylic acid, and glycidyl methacrylate. Crosslinking can also be carried out by using the inherent reactivity of monomers, such as diene monomers.

[0034] In one embodiment, the reactive functional groups present on the exterior of the nanoparticle, such as hydroxyl, glycidyl, or acid groups, can be functionalized, for example, by reaction with alkyl acetoacetoxy groups, such as t-butyl acetoacetoxy groups.

[0035] In one embodiment, the nanoparticle is a core-shell particle comprising a lower Tg polymer core that is encapsulated by a higher Tg polymer shell.

[0036] Exemplary shells of the present disclosure comprise a styrene homopolymer, an alkylstyrene homopolymer, or a methyl methacrylate homopolymer, or a copolymer comprising at least 70 wt% of one of the aforementioned monomers and at least one comonomer, another alkyl (meth)acrylate, vinyl acetate, and / or acrylonitrile. The shell can be functionalized as known in the art by grafting or by incorporation of unsaturated functional monomers (such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids, and anhydrides of unsaturated epoxides) during polymerization as comonomers. For example, maleic anhydride, glycidyl (meth)acrylate, hydroxyethyl methacrylate, and alkyl (meth)acrylamides can be used. In one embodiment, the core-shell particles comprise a polystyrene shell and / or a copolymer with a poly(methyl methacrylate) (PMMA) shell. The shell can also contain imide functional groups by copolymerization with maleimides or by chemical modification of PMMA with primary amines. Advantageously, the molar concentration of imide functional groups is 30% to 60% (relative to the entire shell).

[0037] In one embodiment, the core-shell particles comprise a poly(methyl methacrylate) shell and a poly(butadiene-co-styrene) inner portion or core.

[0038] In one embodiment, the core-shell particles comprise more than one shell. There are also core-shell copolymers with two shells, one made of polystyrene and the other on the outside made of PMMA.

[0039] In one embodiment, the outermost shell in contact with the (meth)acrylic resin comprises a polymer with a Tg greater than 25°C or even 50°C.

[0040] In one embodiment, the core-shell ratio is in the weight range between 10 / 90 and 90 / 10, 40 / 60 and 90 / 10, 60 / 40 and 90 / 10, or even 70 / 30 and 85 / 15.

[0041] Core-shell particles comprising an elastomeric core can be manufactured using techniques known in the art. See, for example, EP 2 465882 B1 (Navarro et al.). Such particles are also commercially available under the trade names “CLEAST STRENGTH XT100” and “W300” from Arkema, Cedex, France; “KANE ACE M731” and “KANE ACE B-564” from Kaneka Corp., Belgium; and “PARALOID EXL-2691J” from Dow Chemical Co., Midland, MI.

[0042] In the present disclosure, a plurality of polymeric nanoparticles are dispersed in a (meth)acrylate-based matrix to form a composite adhesive.

[0043] (Meth)acrylate-based matrix

[0044] The matrix of the adhesive of the present disclosure is a (meth)acrylate-based matrix derived from a (meth)acrylate macromonomer and a second (meth)acrylate monomer.

[0045] The (meth)acrylate macromonomer included in the polymerizable component used to form the (meth)acrylate-based matrix has a (meth)acryloyloxy group plus (i) a poly(ethylene oxide) group, (ii) a poly(propylene oxide) group, (iii) a poly(ethylene oxide-co-propylene oxide) group, the latter three can also be referred to as poly(ethylene glycol), poly(propylene glycol), or poly(ethylene glycol-co-propylene glycol) groups, respectively, (iv) a poly(tetrahydrofuran) group, or (v) a combination thereof. If the macromonomer includes a poly(ethylene oxide) group, it can be referred to as a poly(ethylene oxide) (meth)acrylate. If the macromonomer includes a poly(propylene oxide) group, it can be referred to as a poly(propylene oxide) (meth)acrylate. If the macromonomer includes a poly(ethylene oxide-co-propylene oxide) group, it can be referred to as a poly(ethylene oxide-co-propylene oxide) (meth)acrylate, which is a copolymer. If the macromonomer includes a poly(tetrahydrofuran) group, it can be referred to as a poly(tetrahydrofuran) (meth)acrylate.

[0046] The (meth)acrylate macromonomer typically has a number average molecular weight in the range of 350 to 10,000 Daltons. For example, the (meth)acrylate macromonomer has a number average molecular weight of no more than 10,000 Daltons, 8000 Daltons, 6000 Daltons, 4000 Daltons, 2000 Daltons, 1000 Daltons, 800 Daltons, 650 Daltons, or even 500 Daltons. The number average molecular weight can be determined by gel permeation chromatography using techniques known in the art.

[0047] The (meth)acrylate macromonomer typically has a Tg of no more than -10°C (as measured using a homopolymer of the macromonomer). For example, the glass transition temperature can be no more than -10°C, -20°C, -30°C, or even -40°C. In one embodiment, the Tg is below -70°C or even -80°C. This low Tg of the macromonomer imparts conformability and flexibility to the (meth)acrylate copolymer and adhesive composition.

[0048] Examples of such commercially available (meth)acrylate macromonomers include poly(ethylene glycol)methyl ether acrylates such as those having a reported number average molecular weight (Mn) of 480 Daltons (available from Sigma-Aldrich) and poly(propylene glycol) acrylates such as those having a reported number average molecular weight of 475 Daltons (available from Sigma-Aldrich). Other suitable macromonomers are available from Geo Specialty Chemicals, Ambler, PA under the trade designation BISOMER, such as BISOMER PPA6 (a poly(propylene glycol) acrylate with a reported number average molecular weight of 420 Daltons), BISOMER PEM63P HD (a mixture of poly(ethylene glycol)methacrylate and poly(propylene glycol) with a reported number average molecular weight of 524 Daltons), BISOMER PPM5 LI (a poly(propylene glycol)methacrylate with a reported number average molecular weight of 376 Daltons), BISOMER PEM6 LD (a poly(ethylene glycol)methacrylate with a reported number average molecular weight of 350 Daltons), BISOMER MPEG350MA (a methoxypoly(ethylene glycol)methacrylate with a reported number average molecular weight of 430 Daltons), and BISOMER MPEG550MA (a methoxypoly(ethylene glycol)methacrylate with a reported number average molecular weight of 628 Daltons). Other suitable macromonomers are available from Miwon Specialty Chemical Company, Gyeonggi-do, Korea under the trade designation MIRAMER, such as MIRAMER M193MPEG600MA (a methoxypoly(ethylene glycol)methacrylate with a reported number average molecular weight of 668 Daltons), MIRAMER M164 (a nonylphenol poly(ethylene glycol) acrylate with a reported number average molecular weight of 450 Daltons), MIRAMER M1602 (a nonylphenol poly(ethylene glycol) acrylate with a reported number average molecular weight of 390 Daltons), and MIRAMER M166 (a nonylphenol poly(ethylene glycol) acrylate with a reported number average molecular weight of 626 Daltons). Other suitable macromonomers are available from Sans Esters Corporation, New York, NY, such as MPEG-A400 (a methoxypoly(ethylene glycol) acrylate with a reported number average molecular weight of 400 Daltons) and MPEG-A550 (a methoxypoly(ethylene glycol) acrylate with a reported number average molecular weight of 550 Daltons).Various combinations of such macromonomers can be used, if desired.

[0049] The macromonomer having a poly(tetrahydrofuran) group can be prepared, for example, by polymerizing tetrahydrofuran using a cationic polymerization reaction. More specifically, the polymerization reaction can be carried out at room temperature (e.g., 20 °C to 25 °C) using a triflate as an initiator to form an intermediate (A), where n is equal to the number of -CH2CH2CH2CH2O- groups. Intermediate (A) is then reacted with hydroxybutyl acrylate in the presence of N,N-diisopropylethylamine to form a poly(tetrahydrofuran) (meth)acrylate macromonomer. The weight average molecular weight of the poly(tetrahydrofuran) (meth)acrylate macromonomer is typically in the range of 350 to 10,000 Daltons, which can be determined using known methods such as gel permeation chromatography with polystyrene as a standard. If the molecular weight is too high, the macromonomer can not be miscible with other components in the polymerizable composition and / or can crystallize before, during, or after polymerization of the matrix. In many embodiments, the weight average molecular weight of the poly(tetrahydrofuran) (meth)acrylate macromonomer is at least 500 Daltons, 600 Daltons, 800 Daltons, 1,000 Daltons, 2,000 Daltons, or even 3,000 Daltons, and at most 10,000 Daltons, 8,000 Daltons, 6,000 Daltons, 5,000 Daltons, or even 3,000 Daltons.

[0050] The second (meth)acrylate monomer in the polymerizable matrix is a Ci to C 12 (meth)acrylate monomer. Useful Ci to C 12The (meth)acrylate monomers include at least one monomer selected from the group consisting of monofunctional (meth)acrylates of linear, branched, and / or cyclic non-tertiary alkyl alcohols having alkyl groups comprising at least 1, 2, 3, 4, 5, 6, 7, or even 8 carbon atoms; and at most 10, 11, or even 12 carbon atoms. In one embodiment, the (meth)acrylate monomers comprise from 1 to 12 carbon atoms. Exemplary second (meth)acrylate monomers include: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methylbutyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, 2-propylheptyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, nonyl acrylate, isophoryl (meth)acrylate, dodecyl (meth)acrylate, and any combination or mixture thereof.

[0051] In one embodiment, the second (meth)acrylate monomer for the matrix is copolymerized with a polar co-copolymerizable monomer. The polar co-copolymerizable monomer can be an acid functional or non-acid functional polar monomer such as acrylic acid, hydroxyethyl acrylate, N-methyl acrylamide, or any monomer having a side chain comprising at least one of the following: an alcohol, a carboxylic acid, an amine, an amide, an imide, a thiol, an ester, a phosphate ester, and combinations thereof. Exemplary polar monomers include: acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, and maleic acid, hydroxyalkyl acrylates, acrylamides and substituted acrylamides such as N,N-dialkylaminoalkyl (meth)acrylates or t-octyl acrylamide, acrylamides and substituted acrylamides, lactams and substituted lactams, beta-carboxyethyl acrylate, N-vinyl-2-pyrrolidone, N-vinyl caprolactam, acrylonitrile, and any combination or mixture thereof.

[0052] The second (meth)acrylate monomer typically comprises at least about 75 wt% of the polymerizable monomer composition used in the matrix when copolymerized with a strongly polar monomer. The (meth)acrylate monomer typically comprises at least about 50 wt% of the polymerizable monomer composition used in the matrix when copolymerized with a moderately polar monomer. Strongly polar monomers include mono-olefinic mono- and di-carboxylic acids, hydroxyalkyl acrylate, cyanoalkyl acrylate, acrylamide or substituted acrylamide, or from moderately polar monomers such as N-vinyl pyrrolidone, acrylonitrile, vinyl chloride or diallyl phthalate. The strongly polar monomer preferably comprises at most about 25 wt%, more preferably at most about 15 wt%, of the polymerizable monomer composition used in the matrix. The moderately polar monomer preferably comprises at most about 30 wt%, more preferably from about 5 wt% to about 30 wt%, of the polymerizable monomer composition used in the matrix.

[0053] Additional monomers can be added to the polymerizable matrix composition to alter the properties of the matrix in the adhesive, such as non-polar monomers. The non-polar monomer can be a non-polar ethylenically unsaturated monomer selected from monomers comprising a hydrocarbon side chain. Examples of suitable non-polar co-monomers include 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, and combinations thereof.

[0054] Crosslinking agents are used to create a three-dimensional polymer network, and to achieve high internal strength of the (meth)acrylate matrix within the adhesive. Useful crosslinking agents include photoinitiating crosslinking agents, which are activated by ultraviolet (UV) light. Useful crosslinking agents include: multifunctional (meth)acrylates, triazines, and combinations thereof. Exemplary crosslinking agents include substituted triazines such as 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-s-triazine, 2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine, and the chromophore-substituted halo-s-triazines disclosed in U.S. Pat. Nos. 4,329,384 and 4,330,590 (Vesley). Other useful crosslinking agents include multifunctional alkyl acrylate monomers such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, 1,2-ethanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,12-dodecanediol diacrylate. Various other crosslinking agents having different molecular weights between the (meth)acrylate functional groups are also useful.

[0055] In the present disclosure, (meth)acrylates such as C1 to C 12The (meth)acrylate) monomers, (meth)acrylate macromonomers, and any optional co-monomers are polymerized to form a (meth)acrylate matrix. The (meth)acrylate matrix should be derived from no more than 7 wt% hydroxyl-containing (meth)acrylate monomers. For example, no more than 7 wt%, 6 wt%, 5 wt%, 4 wt%, 2 wt%, 1 wt%, or even 0.5 wt% or even no hydroxyl-containing (meth)acrylate monomers are used in the polymerization of the (meth)acrylate matrix. Exemplary hydroxyl-containing (meth)acrylate monomers include C1 to C20 alkyl-containing (meth)acrylates having at least one hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. As shown in the Examples section, even the presence of a large amount of hydroxyl-containing (meth)acrylate monomer (e.g., 10 phr or 20 phr) results in poor adhesion and dynamic shear properties of the resulting adhesive composition.

[0056] In one embodiment, the polymer of the matrix is derived from at least 40 wt%, 50 wt%, 60 wt%, 70 wt%, or even 75 wt%, and at most 80 wt%, 85 wt%, 90 wt%, 95 wt%, 97 wt%, or even 99.5 wt% of C1 to C 12 (meth)acrylate monomers. The C1 to C 12 The (meth)acrylate monomers are in relatively high amounts relative to other co-monomers to provide a sufficiently large adhesion at low temperatures (e.g., below room temperature) and / or at high peel rates (e.g., > 12 in / min). It has been found that using a large amount of high chain length (meth)acrylate monomers (e.g., C18) results in a matrix that has too low and too soft a shear modulus to achieve the desired performance properties. Likewise, the higher carbon chain length acrylates do not have sufficient compatibility with the polymer nanoparticles to sufficiently increase the modulus to improve their performance. Since methacrylate monomers (e.g., methyl methacrylate) can increase the Tg and decrease the molecular weight (and thus limit performance) of the copolymer matrix compared to their acrylate counterparts (e.g., methyl acrylate), in one embodiment, the polymerizable matrix (or matrix derived therefrom) comprises less than 10 wt%, 5 wt%, 3 wt%, 2 wt%, 1 wt%, or even 0.5 wt%, or even an undetectable amount of C1 to C 12 methacrylate monomers.

[0057] Optionally, the polymer of the matrix comprises at least 0.5 wt%, 1.0 wt%, 2.5 wt%, 5 wt%, 8 wt%, or even 10 wt%, and at most 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or even 50 wt% of the polar monomer relative to the other monomers present in the (meth)acrylate matrix.

[0058] In one embodiment, the (meth)acrylate matrix contains at least 1 wt%, 1.5 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or even 35 wt% of the (meth)acrylate macromonomer. In one embodiment, the (meth)acrylate matrix contains at most 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt%, 30 wt%, or even 20 wt% of the (meth)acrylate macromonomer. The amount of (meth)acrylate macromonomer is based on the total weight of the polymerizable components (e.g., monomers) in the matrix.

[0059] In one embodiment, the crosslinking agent can be added at a level of at least 0.01 parts, 0.1 parts, 0.5 parts, 1.0 parts, or even 1.5 parts of solids per 100 parts of solids relative to the weight of all polymerizable components used in making the (meth)acrylate matrix, and at most 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 8 parts, or even 10 parts of solids. In another embodiment, an initiator is used that will generate crosslinks in situ by abstracting a hydrogen from the polymer in the matrix, allowing the (meth)acrylate matrix to crosslink. Typically, the crosslinking initiator is used at a concentration of at least 0.01 parts, 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, or even 2 parts of solids per 100 parts of solids relative to the weight of all monomers used in making the (meth)acrylate matrix, and at most 3 parts, 4 parts, 5 parts, 6 parts, 8 parts, or even 10 parts of solids.

[0060] In one embodiment, the polymer in the (meth)acrylate-based matrix has a weight average molecular weight of at least 100,000, 200,000, 300,000, 400,000, 500,000, 750,000, or even 1,000,000 grams / mole, and up to 20,000,000, 25,000,000, or even 30,000,000 grams / mole. The molecular weight of the polymer can be determined by gel permeation chromatography as known in the art. The polymer typically has a molecular weight dispersity, which can be calculated as the weight average molecular weight divided by the number average molecular weight of the polymer. The intrinsic viscosity is related to the molecular weight of the polymer, but also includes other factors such as the concentration of the polymer. In the present disclosure, the intrinsic viscosity of the polymer can be at least 0.4, 0.45, 0.5, 0.6, 0.7, or even 0.8, and up to 0.7, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, or even 2, 3, as measured in ethyl acetate at a concentration of 0.15 grams per deciliter (g / dL).

[0061] The molecular weight of the polymer in the (meth)acrylate-based matrix can be controlled using techniques known in the art. For example, during polymerization, a chain transfer agent can be added to the monomers to control the molecular weight. Useful chain transfer agents include, for example, those selected from carbon tetrabromide, alcohols, thiols, and mixtures thereof. Exemplary chain transfer agents are isooctyl mercaptoacetate and carbon tetrabromide. At least 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, or even 0.4 parts by weight of chain transfer agent can be used, based on 100 parts, relative to the weight of all monomers used to make the (meth)acrylate-based matrix, and up to 0.1, 0.2, 0.3, 0.4, 0.5, or even 0.6 parts by weight of chain transfer agent can be used.

[0062] The (meth)acrylate-based matrix used in the adhesives of the present disclosure can be polymerized by techniques known in the art, including, for example, conventional solventless polymerization techniques. By "substantially solventless" polymerization of monomers, it is meant that less than 5, 2, 1, or even 0.5 weight percent of solvent is used, more preferably no additional solvent is added during polymerization, based on the weight of the monomers. The term "solvent" refers to both water and conventional organic solvents used in the industry that volatilize in the process.

[0063] Composite adhesive

[0064] The process of making the composite adhesives according to at least one embodiment of the present disclosure is described in more detail below.

[0065] The polymerizable matrix comprising (meth)acrylate macromonomer and second (meth)acrylate monomer and optional comonomer can be polymerized by various techniques, with photoinitiated bulk polymerization being preferred. An initiator is preferably added to aid in the polymerization of the monomers. The type of initiator used depends on the polymerization method. In a preferred embodiment, a photoinitiator is used to initiate polymerization. Photoinitiators useful for polymerizing acrylate monomers include benzoin ethers such as benzoin methyl ether or benzoin isopropyl ether; substituted benzoin ethers such as 2-methyl-2-hydroxypropio- phenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; and photoactive oxides such as 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime. One example of a commercially available photoinitiator is "IRGACURE 651" available from Ciba having the formula 2,2-dimethoxy-1,2-diphenylethan-1-one. Generally, the photoinitiator is present in an amount of about 0.005% to 1% by weight based on the weight of the monomers. In another embodiment, a thermal initiator such as, for example, AIBN (azobisisobutyronitrile) and / or peroxides can be used. The polymerization can be carried out in the presence of at least one free radical initiator. Useful free radical UV initiators include, for example, benzophenone.

[0066] In a preferred practice of the present disclosure, the polymer nanoparticles are blended with an acrylic syrup that becomes part of the (meth)acrylate matrix. As used herein, a syrup refers to a mixture that has been thickened to a coatable viscosity (i.e., preferably between about 300 and 10,000 centipoise or higher, depending on the coating method used), including mixtures in which the monomers are partially polymerized to form the syrup, as well as monomer mixtures that have been thickened with fillers such as silica and the like.

[0067] The composite compositions of the present disclosure (i.e., comprising polymeric nanoparticles, and either (meth)acrylate monomers or an acrylic syrup for forming a (meth)acrylate matrix) can be irradiated with activating ultraviolet (UV) radiation having an ultraviolet absorbance maximum in the range of 280 nanometers to 425 nanometers to polymerize the monomer components. UV light sources can be of various types. Low intensity light sources, such as black light lamps, typically provide intensities in the range of 0.1 mW / cm2or 0.5 mW / cm2(milliwatts per square centimeter) to 10 mW / cm2, measured according to procedures approved by the National Institute of Standards and Technology, as for example using a UVIMAP UM 365 L-S radiometer manufactured by Electronic Instrumentation & Technology, Inc., Sterling, VA. High intensity light sources typically provide intensities greater than 10 mW / cm2, 15 mW / cm2, or 20 mW / cm2, ranging up to 450 mW / cm2or more. In some embodiments, high intensity light sources provide intensities up to 500 mW / cm2, 600 mW / cm2, 700 mW / cm2, 800 mW / cm2, 900 mW / cm2, or 1000 mW / cm2. The UV light used to polymerize the monomer components can be provided by various light sources, such as light emitting diodes (LEDs), black light lamps, medium pressure mercury lamps, and the like, or combinations thereof. The composite compositions can also be polymerized with higher intensity light sources available from Fusion UV Systems Inc., Gaithersburg, MD. The UV exposure times for polymerization and curing can vary depending on the intensity of the light source used. For example, complete curing with a low intensity light process can be accomplished in exposure times ranging from about 30 seconds to 300 seconds; whereas, complete curing with a high intensity light source can be accomplished in shorter exposure times ranging from about 5 seconds to 20 seconds. Partial curing with a high intensity light source can typically be accomplished in exposure times ranging from about 2 seconds to about 5 seconds or 10 seconds.

[0068] Preferably, the present adhesive is formed by partial polymerization of the monomer components with a free radical initiator known in the art and can be activated by thermal energy or radiation, such as ultraviolet light. In some cases, it can be preferred to add other monomers to the adhesive as well as other photoinitiators and other additives. An effective amount of at least one free radical initiator is added to the (meth)acrylate monomers or adhesive slurry containing the polymer nanoparticles. The mixture is then coated onto a substrate, such as a clear polyester film, which can optionally be coated with a release coating, and then exposed to ultraviolet radiation in a nitrogen rich atmosphere to form the adhesive. Alternatively, oxygen can be excluded by covering the coated adhesive with a second layer of release coated polyester film and then exposed to ultraviolet radiation. Subsequent exposure of the adhesive to a second energy source can be used to crosslink or further cure the adhesive. Such energy sources include heat, electron beam, gamma radiation, and high intensity ultraviolet lamps such as mercury arc lamps.

[0069] In one embodiment, the adhesive of the present disclosure can be prepared by combining the polymer nanoparticles with a pre-polymerized (meth)acrylate matrix containing a crosslinking agent, a free radical initiator, and optional additional components described below, and then coating the mixture onto a flat substrate, such as a polymeric film. In one embodiment, a plurality of polymer nanoparticles can be pre-dispersed in a monomer solution, such as a (meth)acrylate monomer and polymeric dispersant mixture, to aid in the dispersion of the polymer nanoparticles into the polymerizable matrix. The coated mixture can then be exposed to an energy source, such as a UV radiation source, in a low oxygen atmosphere (i.e., less than 1000 parts per million (ppm), and preferably less than 500 ppm) until polymerization is substantially complete (i.e., less than 10% residual monomer, and preferably less than 5%).

[0070] Alternatively, an atmosphere sufficiently free of oxygen can be provided by enclosing the polymerizable composite composition with, for example, a polymeric film. In one embodiment, the film can be placed over the coated adhesive composition prior to polymerization. In another embodiment, the adhesive composition is placed in a receptacle, which can optionally be sealed, and then exposed to energy, such as heat or ultraviolet radiation, to crosslink the adhesive. The adhesive can then be dispensed from the receptacle for use or the receptacle can be taken to a hot melt coater and coated onto a substrate to make a tape or other type of adhesive coated substrate (e.g., a label). In the latter case, the receptacle material should be hot melt coatable with the adhesive in the receptacle and not deleteriously affect the desired final properties of the adhesive.

[0071] The adhesive composition can include additional components to affect the properties and / or characteristics of the composition. Such additives include plasticizers, tackifiers, antistatic agents, colorants, antioxidants, pigments (e.g., carbon black), dyes, fungicides, bactericides, anti-corrosion additives (e.g., benzotriazole derivatives, n-vinylimidazole, thiourea, 2-(dimethylamino)ethyl acrylate, coumaric acid derivatives, or combinations thereof), organic and / or inorganic filler particles, and the like. Such organic fillers include, for example, pre-expanded polymeric microspheres, which can or can not include a coating with a metal salt, such as DUALITE E135-040D or MFL HEPTEN. The use of these additives is well known to those skilled in the art. In one embodiment, the additives are present in an amount such that the solids in the curable adhesive composition (or cured adhesive) comprise at least 65 wt% of the (meth)acrylate-based matrix. Thus, the total amount of additives should be less than 35 wt%, 30 wt%, 25 wt%, 20 wt%, 10 wt%, 5 wt%, or even 1 wt% of the solids. Certain additives can have a lower weight percentage, for example, less than 0.05 wt% or even less than 0.005 wt% of the solids of a pigment can be added. In some embodiments, such as in the case of inorganic fillers, a large amount of inorganic filler can be used (e.g., greater than 60 wt%, 70 wt%, 80 wt%, or even 95 wt% of the solids).

[0072] Exemplary tackifiers include C5 resins, terpene phenolic resins, (poly)terpenes and rosin esters, hydrogenated and non-hydrogenated hydrocarbon resins. When used, the tackifiers can be added at a level of at least 5 parts, 8 parts, 10 parts, or even 12 parts per 100 parts by weight of all of the (meth)acrylate-based matrix, and at most 15 parts, 20 parts, 25 parts, or even 30 parts.

[0073] In one embodiment, the adhesive composition includes an ionic liquid. The presence of an ionic liquid can be used to facilitate the debonding (or peelability) of the adhesive when the article is reprocessed or recycled. Ionic liquids are unique salts that are liquid at temperatures of about 100°C or less, have negligible vapor pressure, and are highly thermally stable. Ionic liquids are composed of a cation and an anion and have a melting point of about 100°C or less (i.e., are liquid at temperatures of about 100°C or less), about 95°C or less, or even about 80°C or less. Certain ionic liquids exist in a molten state even at ambient temperatures because their melting points are below room temperature, and thus they are sometimes also referred to as ambient temperature molten salts. The cation and / or anion of the ionic liquid are relatively large in steric bulk, and typically, one and / or both of these ions are organic ions. Ionic liquids can be synthesized by known methods, for example, by methods such as anion exchange or metathesis methods, or by acid-base or neutralization methods.

[0074] The cation of the ionic liquid of the present disclosure can be a nitrogen-containing cation, a phosphonium ion, a sulfonium ion, and the like, including various delocalized heteroaromatic cations, but is not limited thereto. The nitrogen-containing cation includes ions such as alkylammonium, imidazolium, pyridinium, pyrrolidinium, pyrrolinium, pyrazinium, pyrimidinium, triazolium, triazinium, quinolinium, isoquinolinium, indolium, quinoxalinium, piperidinium, oxazolinium, thiazolinium, morpholinium, piperazinium, and combinations thereof. Examples of the phosphonium ion include phosphonium ions selected from tetraalkylphosphonium, arylphosphonium, alkylarylphosphonium, and combinations thereof. Examples of the sulfonium ion include sulfonium ions selected from alkylsulfonium, arylsulfonium, thiophenium, tetrahydrothiophenium, and combinations thereof. The alkyl group directly bonded to a nitrogen atom, a phosphorus atom, or a sulfur atom can be a linear, branched, or cyclic alkyl group having a carbon number of at least 1, 2, or even 4 and not more than 8, 10, 12, 15, or even 20. The alkyl group can optionally contain heteroatoms such as O and N and S in the chain or at the end of the chain (e.g., terminal -OH group). The aryl group directly bonded to a nitrogen atom, a phosphorus atom, or a sulfur atom can be a monocyclic or condensed cyclic aryl group having a carbon number of at least 5, 6, or even 8 and not more than 12, 15, or even 20. Any part of the structure constituting such a cation can be further substituted with alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, aralkyl groups, arylalkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, carbonyl groups, carboxyl groups, ester groups, acyl groups, amino groups, dialkylamino groups, amide groups, imine groups, imide groups, nitro groups, nitrile groups, sulfide groups, sulfoxide groups, sulfone groups, halogen atoms, and the like, and heteroatoms such as oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms can be included in the main chain or ring constituting the structure of the cation.

[0075] Specific examples of cations include N-ethyl-N'-methylimidazolium, N-methyl-N'-butylimidazolium, N-methyl-N-propylpiperidinium, N,N,N-trimethyl-N-propylammonium, N-methyl-N,N,N-tripropylammonium, N,N,N-trimethyl-N-butylammonium, N,N,N-trimethyl-N-methoxyethylammonium, N-methyl-N,N,N-tris(methoxyethyl)ammonium, N,N-dimethyl-N-butyl-N-methoxyethylammonium, N,N-dimethyl-N,N-dibutylammonium, N-methyl-N,N-dibutyl-N-methoxyethylammonium, N-methyl-N,N,N-tributylammonium, N,N,N-trimethyl-N-hexylammonium, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium, 1 -propyl- tetrahydrothiophenium, 1 -butyl-tetrahydrothiophenium, 1 -pentyl-tetrahydrothiophenium, 1 -hexyl-tetrahydrothiophenium, glycidyltrimethylammonium, N-ethylacryloyl-N,N,N-trimethylammonium, N-ethyl-N-methylmorpholinium, N,N,N-trioctylammonium, N-methyl-N,N,N-trioctylammonium, N,N-dimethyl-N-octyl-N-(2-hydroxyethyl)ammonium, triethylsulfonium, triethylammonium acrylate, dimethylaminoethyl methyl acrylate, or mixtures thereof.

[0076] Anions of the ionic liquids of the present disclosure can be, for example, sulfate (R-OSO3 - ); sulfonate (R-SO3 - ); carboxylate (R-CO2 - ); phosphate ((RO)2P(=O)O - ); borate represented by the formula: BR4 - such as tetrafluoroborate (BF4 - ) and tetraalkylborate; phosphate represented by the formula: PR6 - such as hexafluorophosphate (PF6 - ) and hexaalkylphosphate; amide (R2N - ); sulfonamide; methide (R3C - ); methide, nitrate ion (NO3 - ); nitrite ion (NO2 - ); or halide, such as iodide or chloride. In the above formulas, each R can independently be a hydrogen atom, a halogen atom (fluorine, chlorine, bromine, iodine), a substituted or unsubstituted alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, an aralkyl group, an arylalkyl group, an acyl group, or a sulfonyl group, and the like. Heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms can be included in the main chain or ring of the R group, and some or all of the hydrogen atoms on the carbon atoms of the R group can be substituted with fluorine atoms. In the case where multiple R' are present in the anion, these R' can be the same or different.

[0077] In some embodiments, it is advantageous to use perfluorinated ions, such as perfluorinated anions, to achieve excellent corrosion resistance and electrical stripability. However, the use of fluorinated ions should be balanced against the environmental impact of the finished product, as some fluorinated chemicals can be limited in use due to environmental concerns. Examples of anions that can be used that contain perfluoroalkyl groups include bis(perfluoroalkylsulfonyl)imides ((RfSO2)2N - ), perfluoroalkylsulfonates (RfSO3 - ), and tris(perfluoroalkylsulfonyl)methylides ((RfSO2)3C - ) (where Rf represents a perfluoroalkyl group). The perfluoroalkyl group can have (for example) at least 1, 2, 3, or even 4 to at most 8, 10, 12, 15, or even 20 carbons. Specific examples of bis(perfluoroalkylsulfonyl)imides include: bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, bis(heptafluoropropylsulfonyl)imide, bis(fluorosulfonyl)imide, and bis(nonafluorobutylsulfonyl)imide. Specific examples of perfluoroalkylsulfonates include: trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropylsulfonate, nonafluorobutylsulfonate. Specific examples of tris(perfluoroalkylsulfonyl)methylides include: tris(trifluoromethylsulfonyl)methide, tris(pentafluoroethylsulfonyl)methide, tris(heptafluoropropylsulfonyl)methide, tris(nonafluorobutylsulfonyl)methide, and combinations thereof. Examples of fluorinated anions that do not contain C-F bonds are hexafluorophosphate and bis(fluorosulfonyl)imide. Ionic liquids that do not contain C-F bonds include BMI PF6, BMI I, DMAEAM FAI, and DMAEAM TCM.

[0078] In some embodiments, the anion of the ionic liquid does not contain any halogen (e.g., fluorine). One such anion is tricyanomethanide. Ionic liquids that do not contain any fluorine include BMI I and DMAEAM TCM.

[0079] For ionic liquids composed of the above cations and anions, 1 -butyl-3 -methylimidazolium bis(trifluoromethylsulfonyl)imide, triethylsulfonium bis(trifluoromethylsulfonyl)imide, 1 -butyl-3 -methylimidazolium hexafluorophosphate, 1 -butyl-3 -methylimidazolium iodide, ethylpyridinium bis(trifluoromethylsulfonyl)imide, trimethylammonium ethyl acrylate bis(trifluoromethylsulfonyl)imide, dimethylaminoethyl acrylate methyl bis(trifluoromethylsulfonyl)imide, dimethylaminoethyl acrylate methyl bis(fluorosulfonyl)imide, dimethylaminoethyl acrylate methyl tricyanomethylate, and tetraalkylammonium with a hydroxyl functional counterion available under the trade designation "FC-5000" from 3M Co., Maplewood, MN, can be advantageously used as the ionic liquid because of their excellent removability during electrostripping due to a decrease in bond strength upon energization.

[0080] If an ionic liquid is used, the ionic liquid in the composite adhesive can be present in at least 0.5 wt%, 1 wt%, 1.5 wt%, or even 2 wt% and at most 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or even 9 wt%. Enough ionic liquid should be added to achieve electrostripping, while too much ionic liquid can adversely affect the physical properties of the composite adhesive, such as shear, peel adhesion, and / or ability to withstand random free fall testing.

[0081] Incorporation of an ionic liquid into the composite adhesive can enable the composite adhesive to be stripped from a substrate. In one embodiment, the composite adhesive contains a small amount of acid or is substantially free of acid. In electrostripping applications, as described below, it can be advantageous to minimize the amount of acid in the composite adhesive to prevent corrosion of the conductive material. In one embodiment, the composite adhesive contains less than 1 wt%, 2 wt%, 3 wt%, 4 wt%, or even 5 wt% of an acidic monomer, such as acrylic acid, or even no detectable amount of an acidic monomer.

[0082] The selection of the ionic liquid for the composite adhesive can affect electrostripping. For example, it can be advantageous to select an ionic liquid with a high electrical conductivity or ionic mobility. Without being limited by theory, it is believed that an increase in ionic liquid mobility in the adhesive facilitates electrostripping. Thus, it can be advantageous for the ionic liquid to be highly soluble in the adhesive matrix (i.e., the ionic liquid does not phase separate from the adhesive matrix). A high mobility and high electrical conductivity of the ionic liquid in the adhesive matrix (e.g., having a conductivity of less than 1 x 10 3A thin film resistance (typically in the order of 1-10 Ohm / square) can help to achieve an electrical peel in thicker adhesives. In some embodiments, the adhesive thickness can be 10 microns, 25 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 150 microns, 200 microns, 250 microns, 300 microns, 400 microns, or even up to 500 microns thick. Alternatively, or in addition, it can be advantageous to select an ionic liquid with a cation or anion that is electrochemically unstable. Without wishing to be bound by theory, it is believed that a cation or anion with a greater electrochemical instability can result in an increased electrical peel response. Thus, it can be advantageous to select a cation consisting of an imidazolium derivative or a pyridinium derivative, as compared to a quaternary ammonium derivative.

[0083] In one embodiment, it can be advantageous to select an ionic liquid that does not contain carbon-fluorine bonds for environmental reasons. Thus, it can be advantageous to select an ionic liquid containing inorganic fluorine (such as a hexafluorophosphate ion or a tetrafluoroborate ion) instead of an ionic liquid containing organic fluorine (such as bis(trifluoromethylsulfonyl)imide).

[0084] In one embodiment, the composite adhesive disclosed herein is not a foam, meaning that the (meth)acrylate-based matrix contains less than 5% by volume of voids, where the voids can be obtained by cells formed from a gas, or due to the incorporation of hollow fillers (such as hollow polymer particles, hollow glass microspheres, or hollow ceramic microspheres).

[0085] The composite adhesives disclosed herein can be advantageously used to make a wide range of tapes and adhesive articles. Many of these tapes and articles include a backing or release liner to support the adhesive layer. As used herein, a backing is a permanent support intended for use in the end use of the adhesive article. On the other hand, a liner is a temporary support that is not intended for use in the end use of the adhesive article, but rather to support and / or protect the adhesive article during manufacture or storage. The liner is removed from the adhesive article prior to the end use of the adhesive article. To facilitate easy removal from the adhesive layer, the liner is typically coated with a release coating that includes a release agent. Such release agents are known in the art and are described, for example, in "Handbook of Pressure Sensitive Adhesive Technology," D. Satas, editor, Van Nostrand Reinhold, New York, N.Y., 1989, pp. 585-600. In one embodiment, the release agent migrates to the surface (on the inner liner or release coating) to provide the proper release properties. Illustrative examples of release agents include urethanes, silicones, and fluorocarbons. Illustrative examples of surface-applied (i.e., topically applied) release agents include: polyvinyl carbamates such as disclosed in U.S. Patent No. 2,532,011 (Dahlquist et al.); reactive silicones; fluorinated polymers; epoxy silicones such as disclosed in U.S. Patent Nos. 4,313,988 (Bany et al.) and 4,482,687 (Kessel et al.); polyorganosiloxane-polyurea block copolymers such as disclosed in European Patent No. 0250248 Bl (Leir et al.), and the like.

[0086] In one embodiment, the adhesive article is a double-sided tape characterized by adhesive disposed on opposite sides of a backing layer. The adhesive on both sides (i.e., a first adhesive layer and a second adhesive layer) can be the same or different. The backing layer can be a film, a nonwoven web, a paper, or a foam, as further described below. The double-sided tape can include one or two release liners that protect the adhesive surface from contact with the backing layer. In one embodiment, the adhesive layer is disposed between two release liners, which can be the same or different. In another embodiment, the adhesive layer is disposed on a backing, and the opposite side of the backing contains a release agent. The adhesive article is wound on itself such that the exposed surface of the adhesive layer (opposite the backing) contacts the release-coated backing forming, for example, a roll of tape. In yet another embodiment, the adhesive is disposed between a backing and a release liner. In some embodiments, the tape and adhesive article do not include a backing, and thus are free-standing adhesive layers. Transfer adhesive tapes are one example of such adhesive articles. Transfer adhesive tapes (also referred to as transfer tapes) have an adhesive layer delivered on one or more release liners. The adhesive layer is free of a backing therein, and thus there is only adhesive once delivered to a target substrate and the liner is removed. Some transfer tapes are multi-layer transfer tapes, which have at least two adhesive layers, which can be the same or different. Transfer tapes are widely used in the printing and papermaking industries to make automatic splicers of paper webs, and by industry and consumers for a variety of bonding, mounting, and matting applications.

[0087] In one embodiment, the composite adhesive composition can be readily coated onto a carrier film to produce an adhesive-coated sheet material that is cured via ultraviolet radiation. Coating techniques known in the art can be used, such as spraying, flood coating, knife coating, Meyer rod coating, gravure coating, and double roll coating. The coating thickness varies depending on a variety of factors, such as the particular application or the coating formulation. Coating thicknesses of at least 10, 20, 25, 30, 40, 50, 60, 75, or even 100 micrometers (pm) and up to 125, 150, 200, 250, 300, or even 500 pm are contemplated. In some embodiments, it can be preferable to have a thicker adhesive layer, for example, with better impact performance. However, thicker adhesives can be more challenging to electrically strip due to more insulating properties.

[0088] The carrier film can be a flexible or inflexible backing material or a release liner. Exemplary materials that can be used as carrier films for the adhesive articles of the present disclosure include, but are not limited to, polyolefins (such as polyethylene, polypropylene (including isotactic polypropylene and high-impact polypropylene), polystyrene), polyesters (including poly(ethylene terephthalate)), polyvinyl chloride, poly(butylenes terephthalate), poly(caprolactam), polyvinyl alcohol, polyurethane, poly(vinylidene fluoride), cellulose and cellulose derivatives (such as cellulose acetate and cellophane), and woven and nonwoven fabrics. Commercially available carrier films include Kraft paper (available from Monadnock Paper, Inc.); spun-bond poly(ethylene) and poly(propylene), such as those available under the trade designation "TYVEK" and "TYPAR" (available from The Chemours Co.); and porous films available from poly(ethylene) and poly(propylene), such as those available under the trade designation "TESLIN" (available from PPG Industries, Inc.) and under the trade designation "CELLGUARD" (available from Hoechst-Celanese). The carrier film delivers the composite adhesive of the present disclosure to the desired substrate. The carrier film can include pigments, markings, lettering, designs, and the like on the surface opposite the composite adhesive, which are then fixedly adhered to the surface of the substrate, or the carrier film can be free of such pigments and / or markings.

[0089] The thickness of the composite adhesive layer is typically at least 10 micrometers, 15 micrometers, 20 micrometers, or even 25 micrometers (1 mil) and at most 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, or even 400 micrometers (16 mils) thick. In some embodiments, the thickness of the composite adhesive layer is no thicker than 100 micrometers, 150 micrometers, or even 200 micrometers and at most 300 micrometers, 500 micrometers, 1000 micrometers, 1500 micrometers, or even 2000 micrometers (80 mils) thick. The adhesive can be coated as a single layer or multiple layers.

[0090] In one embodiment, the composite adhesive of the present disclosure comprises at least 0.1 grams, 0.3 grams, 0.5 grams, 1 gram, 2 grams, 4 grams, 5 grams, or even 10 grams of the plurality of polymeric nanoparticles per 100 grams of the (meth)acrylate-based matrix. In one embodiment, the composite adhesive composition comprises at most 10 grams, 15 grams, 20 grams, 25 grams, 30 grams, 35 grams, or even 40 grams of the plurality of polymeric nanoparticles per 100 grams of the (meth)acrylate-based matrix. In one embodiment, the plurality of polymeric nanoparticles is uniformly dispersed within the matrix, which can be observed visually by a smooth and clear composition free of visible clusters of particles.

[0091] Typically, the polymeric nanoparticles are uniformly dispersed throughout the (meth)acrylate matrix in the adhesive layer, as shown in Figure 1 . Figure 1 A multilayer adhesive article is depicted, which includes optional first and second substrates 12 and 16, which can independently be adherends, liners, or backings. Sandwiched between these two substrates is a composite adhesive layer 14, which comprises a plurality of polymeric nanoparticles 13 dispersed in a (meth)acrylate matrix 15. Alternatively, the polymeric nanoparticles can be concentrated in one or more regions of the composite adhesive layer. For example, as shown in Figure 2 , the plurality of polymeric nanoparticles 23 in the (meth)acrylate matrix 24 are concentrated near one major surface of the composite adhesive layer 24.

[0092] In one embodiment, the composite adhesive composition of the present disclosure is a pressure sensitive adhesive. Pressure sensitive adhesive compositions are well known to those of ordinary skill in the art, and have properties including: (1) tack and stickiness, (2) adhesion under light pressure, (3) ability to hold on to adherends; and (4) sufficient cohesive strength. Materials that are found to work well as pressure sensitive adhesives are polymers that are designed and formulated to exhibit the desired viscoelastic properties, such that tack, peel adhesion, and shear holding power are balanced as desired.

[0093] In one embodiment, the pressure sensitive adhesive composition has a similar viscoelastic window as defined by E. P. Chang, J. Adhesion, Vol. 34, pp. 189-200 (1991) such that the dynamic mechanical properties of the pressure sensitive adhesive composition, as measured by well-known techniques, fall within the following ranges measured at 25°C: G' measured at an angular frequency of 0.01 rad / sec is greater than 1 x 10 3 Pa; and G' measured at an angular frequency of 100 rad / sec is less than 5 x 10 6 Pa.

[0094] The (meth)acrylate matrix, as another component of the adhesive composition, functions to bond between two adherends, can be tacky at room temperature, or can not be tacky initially, but adhesion builds over time.

[0095] In one embodiment, the composite adhesive composition of the present disclosure is a heat-activated film adhesive, in which the film becomes tacky upon heating (i.e., Dahlquist's criterion for tackiness has a shear storage modulus of less than 0.3 MPa at an angular frequency of 1 Hz).

[0096] The present disclosure has determined that a composite material comprising a plurality of particles dispersed within a (meth)acrylate-based matrix results in an adhesive composition that has good impact resistance against tensile impact forces, but also has good resistance to shear deformation. Generally, the addition of a plurality of particles increases the shear storage modulus (G') of the resulting composition. It is postulated that the increase in shear storage modulus is related to the resistance of the adhesive to shear deformation. In other words, the addition of a plurality of polymeric nanoparticles makes the composite adhesive more "stiff." Generally, it is believed that the addition of (meth)acrylate macromers in the compositions of the present disclosure decreases the shear storage modulus and Tg of the resulting composition, resulting in a composite adhesive that has improved resistance to tensile peel, as evidenced by improved performance in the Random Free Fall Test. As shown in the Examples section, when using a "softer" (meth)acrylate resin (i.e., a resin having a shear storage modulus of less than 80 kPa, or even 60 kPa), the addition of a plurality of polymeric nanoparticles increases the shear storage modulus, however, the Random Free Fall Test is affected. Thus, the addition of (meth)acrylate macromers helps to balance the resistance to tensile peel, enabling these softer resins to resist not only tensile impact forces, but also shear deformation.

[0097] In one embodiment, the composite adhesives disclosed herein have a shear storage modulus (G') of at least 100 kPa, 150 kPa, 200 kPa, 300 kPa, or even 400 kPa (kilopascals) at 25°C and 1 Hz.

[0098] In one embodiment, the composite adhesives disclosed herein have a peak stress in a dynamic shear test of at least 0.5 MPa, 0.7 MPa, 0.8 MPa, or even 0.9 MPa; and at most 2.0 MPa, 1.8 MPa, 1.7 MPa, 1.6 MPa, 1.5 MPa, 1.4 MPa, 1.3 MPa, 1.2 MPa, 1.1 MPa, or even 1.0 MPa.

[0099] In one embodiment, the composite adhesives disclosed herein do not fail when assembled and tested as disclosed in the Random Free Fall Test for 50 drops at 1 meter. In yet another embodiment, the composite adhesives disclosed herein do not fail when assembled and tested as disclosed in the Random Free Fall Test for 100 drops at 1 meter. In another embodiment, the composite adhesives disclosed herein do not fail when assembled and tested as disclosed in the Random Free Fall Test for 250 drops at 1 meter.

[0100] In one embodiment, the composite adhesives according to the present disclosure not only have good adhesion to substrates with high surface energy, but also exhibit good adhesion to low surface energy substrates. In one embodiment, the adhesives of the present disclosure have a peel value of greater than 0.4 N / mm, 0.5 N / mm, 0.6 N / mm, or even 0.8 N / mm when laminated and peeled at room temperature when tested according to ASTM D 3330 / D3330M on a stainless steel substrate with an 8 mil (200 microns) adhesive thickness. The peel strength can be adjusted based on the application required, with some applications requiring higher peel strength (e.g., at least 0.5 N / mm, 0.6 N / mm, 0.7 N / mm, or even 0.8 N / mm, and at most 2.5 N / mm, 2.2 N / mm, 2.1 N / mm, or even 2.0 N / mm).

[0101] In one embodiment, the composite adhesives disclosed herein are optically clear. In one embodiment, the difference between the refractive index of the plurality of polymeric nanoparticles and the refractive index of the (meth)acrylate-based matrix is less than 0.2, 0.1, or even 0.05. The refractive index can be determined using techniques known in the art. For example, the Becke line method, in which certified refractive index test liquids are used along with a microscope to determine the refractive index of a material, or the refractive index can be determined by using a refractometer and measuring the bend of the 589 nm wavelength (sodium D line) in air at 25 °C.

[0102] In one embodiment, the composite adhesives disclosed herein comprising ionic liquids can undergo electrically induced adhesive peeling, in which the composite adhesive can be peeled according to need by applying a voltage across the adherend substrates. While not wishing to be bound by theory, it is believed that when a voltage is applied to a composite adhesive comprising ionic liquids, the ionic liquids undergo electrolysis, in which the cations migrate to the cathode side and the anions migrate to the anode side, thereby weakening the adhesive interface. Typically to perform electric peeling, the composite adhesive comprising ionic liquids should be positioned between two conductive surfaces. For example, in one embodiment, Figure 1 both the first substrate 12 and the second substrate 16 in FIG. 1 comprise conductive materials, forming an anode and a cathode, respectively, to perform electric peeling. If the substrates are not conductive or have low electrical conductivity (e.g., have a thin film resistance of at least 1 x 10 3 ohms / square or even 5 x 10 3 ohms / square), then another layer, such as a conductive coating, should be used to enable electric peeling. Such a schematic is shown in FIG. 2. Figure 4The composite adhesive layer 44 is disposed between the first substrate 42 and the second substrate 46. The first conductive layer 41 is positioned between the first substrate 42 and the composite adhesive layer 44, while the second conductive layer 49 is positioned between the second substrate 46 and the composite adhesive layer 44. The first and second conductive layers can be the same material or can be different materials. The conductive layers can be coatings or layers. In yet another embodiment, the conductive layers are disposed within the composite adhesive layer, as shown in Figure 5 For example, in Figure 5 The first conductive layer 51 is positioned between the composite adhesive layer 54a and the composite adhesive layer 54b, while the second conductive layer 59 is positioned opposite the composite adhesive layer 54b.

[0103] To facilitate peeling as desired, the conductive surfaces (e.g., the first conductive layer 41 and the second conductive layer 49) are electrically coupled to or in electrical communication with a power source in a closeable circuit. The power source can be a direct current power source that provides a DC voltage in the range of about 3 V to 250 V, although other variations are contemplated. The amount of voltage applied can also be determined by the amount of time the voltage is applied (e.g., 0.1 minutes or 1 minute to 5 minutes). For example, a higher voltage can be applied for a short period of time. A potential is applied between the two opposing conductive surfaces (e.g., the first conductive layer 41 and the second conductive layer 49) to cause the composite adhesive 44 to peel away from one or both of the conductive surfaces, thereby enabling the first substrate 42 to separate from the second substrate 46. For example, while not wishing to be bound by any particular theory, it is believed that the movement of ions within the composite adhesive can be affected by the potential applied to the composite adhesive. When a sufficient amount of movement is affected, e.g., a sufficient number of ions are present near the conductive surface, the adhesive material's adhesive quality is reduced, thereby enabling the conductive surface and / or the composite adhesive to separate.

[0104] Exemplary conductive materials include: conductive carbon-containing materials or conductive metals. The conductive surfaces can comprise conventional materials such as metals, mixed metals, alloys, metal oxides, and / or composite metal oxides, or the conductive surfaces can comprise conductive polymers. Examples of suitable metals for the conductive layers include Group 1 metals, metals in Groups 4, 5, and 6, and Group 8 to 10 transition metals. Other examples of suitable metals for the conductive layers include stainless steel, Al, Ag, Mg, Ca, Cu, Mg / Ag, LiF / Al, CsF, and / or CsF / Al, and / or alloys thereof.

[0105] In some embodiments, the composite adhesive compositions described herein are suitable for bonding internal or external components of lighting display devices such as displays of liquid crystal displays ("LCDs") and light emitting diodes ("LEDs"), such as cell phones (including smart phones), wearable (e.g., wrist) devices, car navigation systems, global positioning systems, depth finders, computer monitors, laptop and tablet displays, or for bonding objects (e.g., handles, display stands) to the exterior of electronic devices.

[0106] Examples

[0107] Advantages and embodiments of this disclosure are further illustrated by the following 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 application. In these examples, all percentages, proportions and ratios are by weight unless otherwise indicated.

[0108] Unless otherwise indicated, all materials are available from, for example, Sigma-Aldrich Chemical Company, Milwaukee, Wisconsin, either commercially or known to those skilled in the art.

[0109] In the following examples, the following abbreviations are used: °C = degrees Celsius, cP = centipoise, g = gram, lb = pound, kg = kilogram, mL = milliliter, mol = mole, min = minute, cm = centimeter, Hz = hertz, J = joule, kDa = kilodalton, L = liter, mm = millimeter, mW = milliwatt, N = Newton, nm = nanometer, Pa = Pascal, rpm = revolutions per minute, ppm = parts per million, and wt = weight.

[0110] Table 1. Materials used to prepare the examples .

[0111]

[0112] Test methods

[0113] Rheological properties and glass transition temperature

[0114] The two pads, RF02N and RF12N, were removed from the transfer tape sample and the composite adhesive was tested on a TA Instruments discovery hybrid rheometer III (DHR-3) (New Castle, DE). The sample was heated from room temperature to 40 °C at a rate of 3 °C / min, then cooled to -50 °C at a rate of 3 °C / min, warmed to 20 °C, then the sample was heated from 20 °C to 140 °C at a rate of 3 °C / min. Data were collected during the second heating cycle at an oscillation frequency of 1 Hz with a strain value (typically 1 to 5%) in the linear viscoelastic regime. The glass transition temperature (at 1 Hz) was determined as the peak of the tan(5) curve from the rheology plot of G’ and G” (y-axis-1) versus temperature (°C) (x-axis) and tan(5) (y-axis-2). The peak in tan(5) (i.e., the highest value) was selected from y-axis-2, and the corresponding temperature on the x-axis was selected as the glass transition temperature. Tan(5) is an abbreviation for the tangent of the phase angle between the stress and strain oscillations in a shear rheology oscillation plot. Samples meeting the rheology property requirements have a shear storage modulus (G’) > 100 kPa at 25 °C.

[0115] Size exclusion chromatography (SEC)

[0116] Molecular weights (both number average molecular weight Mn and weight average molecular weight Mw) and polydispersity were determined using size exclusion chromatography with polystyrene standards. The chromatographic system included an instrument obtained under the trade designation “ACQUITY” (Waters Corporation, Milford, MA), and the following columns arranged in order (downstream): a Styragel Guard column (20 µm, 4.6 mm x 30 mm), a first Styragel HR 5E column (mixed bed, 5 µm, 7.8 mm x 300 mm, 2K - 4M), and a second Styragel HR 5E column (all columns obtained from Waters Corporation). Analysis was performed using THF mobile phase at a flow rate of 1 mL / min.

[0117] Peel adhesion strength testing

[0118] For all peel adhesion testing, the RF02N release liner was removed from the transfer tape sample and the exposed adhesive side of the transfer tape was contacted with the plasma treated side of a 6 inch (15 cm) wide plasma treated polyester film (3M Company, 2 mil (50 pm) biaxially oriented PET film that has had its surface subjected to the plasma treatment conditions described in U.S. Patent 10,134,566 (David et al.)). A 6 inch (15 cm) rubberized hand roller (Polymag Tek, NY) was then placed on the construction and rolled by hand ensuring that there were no trapped air bubbles between the adhesive and the primed polyester film. Peel adhesion was measured at a 180 degree angle. Peel adhesion testing was performed on annealed 18 gauge 304 stainless steel (SS) test panels purchased from Chem. Instruments, Fairfield, OH. The RF12N release liner was removed from the PET backing of the tape and the exposed adhesive side was directly laminated to a 2 inch x 6 inch (5.08 cm x 15.24 cm) stainless steel test panel using a weighted rubberized (4.5 lb, 2.04 kg) hand roller, 3 second rolls, repeated 4 times. Prior to peel testing, the transfer tape, stainless steel test panel, and transfer tape applied to the stainless steel test panel were placed in a temperature and humidity controlled (CTH) room (set at 23 °C, 50% RH (relative humidity)) to condition. The SS test panels were cleaned with methyl ethyl ketone (MEK) before and after testing. Peel testing was performed using a SP-2100 iMass (iMass Inc., Accord, MA USA) at a rate of 12 inches / minute (0.3 m / min). Each sample was peeled from the same substrate at least three times and the average of all three measurements was recorded. Peel adhesion and failure mode were recorded. All samples exhibited adhesive failure (i.e., failure between the adhesive and the SS panel) except for the labeled samples which failed between the adhesive and the polyester film.

[0119] Dynamic shear testing

[0120] For dynamic shear testing, a modified version of ASTM D1002-2019 – Apparent Shear Strength of Metal Specimens Bonded with Single-Overlap Joint Adhesive was used. The adhesive shear was tested between the ends of two overlapping 304 stainless steel (SS) panels (1 inch (2.5 cm) wide × 4 inches (10.1 cm) long × 1 / 16 inch (1.6 mm) thick, with an overlap adhesive bonded area of ​​1 inch (2.5 cm) × 1 inch (2.5 cm)). To prepare the test specimen, a designated transfer tape sample of 1 inch (2.5 cm) × 1 inch (2.5 cm) square was cut out, the RF02N backing was removed, and the exposed adhesive side of the transfer tape was laminated to the end of one of the SS panels at room temperature. The RF12N backing was then removed from the transfer tape bonded to the first SS panel, and the exposed adhesive was bonded to the second SS panel, ensuring an overlap area of ​​1 inch (2.5 cm) × 1 inch (2.5 cm). The bonded laminate was then subjected to a 50-pound (22.7 kg) weight applied to a 1-inch (2.5 cm) × 1-inch (2.5 cm) adhesive bonding area at room temperature for 30 seconds, and the bonded laminate was allowed to remain under pressure at room temperature for at least one day. After the holding time, the adhesive joint was tested by clamping the opposite ends of the stainless steel substrate within a load frame (MTS, Eden Prairie, MN) at a displacement rate of 10 mm / min (vertical clamp speed). The maximum peak value of the stress in the stress-strain curve was used to determine the peak stress of the adhesive sample in the dynamic shear test.

[0121] Random free fall testing

[0122] like Figure 3A (Top view) and Figure 3B As shown in the cross-sectional view, test sample 30 was subjected to a random free-fall test on the Heina Rotary Tester II (Heina, Halikko, Finland). Figure 3AAs shown, two adhesive strips 35 were used to adhere the polycarbonate panel 34 to the test rack 32. The adhesive strips were 2 mm wide. The polycarbonate test rack (purchased from Chem Instruments, Fairfield, OH, USA) had a base that was 6.25 inches (15.8 cm) long x 3.25 inches (8.3 cm) wide x 0.375 inches (9.5 mm) thick. The test rack had a raised portion along each short side edge (approximately 0.25 inches (0.63 cm) high from the base) that was designed to make contact with the tumble tester surface and prevent direct contact with the polycarbonate panel and the tumble tester surface. The polycarbonate panel was 5.125 inches (13 cm) long x 2.875 inches (73 cm) wide x 0.125 inches (3.2 mm) thick. The test sample was prepared as follows: The adhesive transfer tape was cut into 3.25 inch (8.3 cm) long x 2 mm wide strips using a 2 mm wide tape cutter. The RF02N release liner was removed from each strip of transfer tape and the exposed adhesive side was laminated to the test rack such that the adhesive was placed 1 inch (2.5 cm) parallel from each opposing edge of the test rack. The RF12N liner was then removed from each adhesive strip and the polycarbonate panel was laminated to the test rack using the adhered adhesive strips, ensuring that the panel was a fixed distance from each raised portion of the test rack. A 4 kg weight was placed on the length of each adhered strip of tape and a third 4 kg weight was placed on top of the other two weights. The weights were held on the tape for 30 seconds and then the bonded test sample was placed in a CTH chamber for 3 days. The bonded test sample was then placed in a Heina tumble tester and repeated drops from a height of 1 m at a rate of 12 drops per minute. The drops until failure (as indicated by blowout from one or both sides of the polycarbonate panel of the polycarbonate test rack) were counted. The sample was dropped 250 times. A result of 250 means that the sample was subjected to 250 drops.

[0123] Corrosion testing

[0124] To prepare the test samples, a 1 inch (2.5 cm) x 1 inch (2.5 cm) square of the designated transfer tape sample was cut and the RF02N liner was removed and the exposed adhesive side of the transfer tape was laminated to a 2 mil (50 micrometer) thick polyethylene terephthalate (PET) panel at room temperature. The RF12N liner was then removed from the transfer tape bonded to the PET panel and the exposed adhesive was hand rolled down onto a copper foil sheet. The test samples were placed in an oven set at 65 °C and 90% relative humidity (RH). The samples were removed from the oven and evaluated for signs of corrosion (copper foil discoloration) on day 1, day 3, and day 7. The samples were then scored on a scale of 1 to 3, where 1 = no signs of corrosion, 2 = less than or equal to 25% of the copper foil area had corrosion, 3 = greater than 25% of the copper foil area had visible corrosion.

[0125] Electrical peel

[0126] A tensile push-out apparatus was used that included a stainless steel coupon (40 mm x 40 mm x 3 mm) with a circular hole (diameter = 24 mm) in the center and a circular stainless steel spring disk (diameter = 33 mm, thickness 3 mm). The designated transfer tape was die cut into a ring with an outer diameter of 31 mm and an inner diameter of 26 mm. The RF02N liner was removed and the exposed adhesive side of the transfer tape ring was laminated around the circular hole on the stainless steel coupon. The RF12N liner was then removed from the transfer tape bonded to the coupon and the exposed adhesive was bonded to the stainless steel spring disk such that the spring disk overlaid the hole in the coupon. The test sample was weight pressed at 8 kg with a weight for 30 seconds at 23 °C and then removed. The test sample was then preserviced at 23 °C / 50% RH for at least 2 days prior to testing. The power supply (1685B Series, available from B & K Precision, Yorba Linda, CA) was then connected to the push-out apparatus with the positive terminal connected to the spring disk and the negative terminal connected to the coupon. A voltage of 50 volts was applied to the entire coupon and spring disk for 180 seconds unless otherwise noted. Immediately after the 180 seconds of voltage was applied, the electrodes were disconnected from the test sample and the test sample was loaded onto an electromechanical tester (MTS Criterion Model C43, Eden Prairie, MN). The stainless steel coupon was held in place while a 0.75 inch (19 mm) diameter rod from the electromechanical tester was positioned to pass through the circular hole of the stainless steel coupon, contacting the circular stainless steel spring disk. The electromechanical tester was used to push the spring disk off the coupon at a rate of 10 mm / min under ambient conditions. The peak stress required to remove the spring disk from the coupon was recorded in MPa (megaPascal). Test samples without voltage applied were also tested in this manner. The initial push-out peak stress (i.e., when no voltage was applied prior to testing) and the % reduction in push-out peak stress after 3 minutes (or 180 seconds) of 50 volts applied to the entire test sample are reported in Table 11.

[0127] Slurry polymer preparation

[0128] The slurries SRP-1 to SRP-3 were synthesized by adding the monomers (as specified in Table 2) together in the appropriate loading weight %, adding IRG 651 (0.02 grams relative to 100 grams of total monomers), and exposing the monomer solution to 0.3 mW / cm2UV-LED irradiation (365 nm) until the mixture had a higher viscosity (about 1,000 cP). The molecular weight in megaDaltons (MDa) as determined by the SEC test method described above, as well as the polydispersity of the resulting slurries, are shown in Table 3.

[0129] Table 2. Monomer compositions used to make slurry polymers in weight percent Added at phr (parts per hundred parts of total amount of other monomers, amount expressed in parts per hundred of resin).

[0130] Synthesis of dimethylaminoethyl acrylate methyl bis(fluorosulfonyl)imide. (DMAEAM FSI)

[0131] DMAEM Cl (125 g of an 80 wt% aqueous solution, 516 mmol of monomer) was added to a round bottom flask equipped with a Teflon-coated stir bar. The solution was then diluted with 100 g of water and Li FSI (100 g, 533 mmol) was slowly added to the solution while stirring. Upon addition of Li FSI, an organic phase formed and separated from the aqueous phase. After 24 hours, the organic phase was separated from the aqueous phase using a separatory funnel. The organic phase was washed with water (3 x 100 mL). The organic phase was dried by rotary evaporation to yield 85.2 g of DMAEMAM FSI.

[0132] Synthesis of dimethylaminoethyl acrylate methyl tricyano-methylate (DMAEAM TCM)

[0133] DMAEM Cl (50 g of an 80 wt% aqueous solution, 206.5 mmol of monomer) was added to a round bottom flask equipped with a Teflon-coated stir bar. The solution was then diluted with 100 g of water and Na TCM (23.4 g, 206.5 mmol) was slowly added to the solution while stirring. After 14 days of stirring, the solution was added to 3.5 L of acetone to precipitate the NaCl. The solution was allowed to sit overnight and then filtered through celite. The acetone was removed via rotary evaporation to yield a yellow liquid. 1 H-NMR (500 MHz; Acetone-d6): δ 6.42 (dd, J = 17.3, 1.3 Hz, 1H), 6.21 (dd, J = 17.3, 10.5 Hz, 1H), 5.97 (dd, J = 10.5, 1.3 Hz, 1H), 4.72 (dq, J= 7.2, 2.5 Hz, 2H), 3.99–3.97 (m, 2H), 3.44 (s, 9H). 13-C NMR (126 MHz; acetone): δ 164.8, 131.7, 127.8, 120.9, 64.9, 58.0, 53.7, 4.8. Nuclear magnetic resonance (NMR) was performed at 500 MHz using acetone-d6 as the solvent. Samples were prepared at a concentration of 10 wt%. For 1-H NMR, the acetone reference was 2.05 ppm. For 13-C NMR, the acetone reference was 29.84 ppm.

[0134] Table 3. Molecular weight data for the resulting slurry polymers from Table 2

[0135] † Molecular weight (M) w If the concentration is greater than 8 million g / mol, the sample is outside the calibration standard. NT = Not tested.

[0136] Examples 1 to 11 (E1-E11) and Comparative Examples 1 to 10 (CE1-CE10)

[0137] Use the components listed in Table 4 to manufacture the curable composition. The specified syrup is used in 100 parts, and the remaining components are added in the amounts listed (e.g., 5 g of PEG-A is added to 100 g of SRP-1 in E1).

[0138] Each curable composition was then applied between two release liner pads (RF12N and RF02N). The samples were then cured under 405 nm UV-LED light with a total dose of 3.1 J / cm², which was measured using a radiometer equipped with a high-power sensor head (purchased under the trade name "POWER PUCK II" from EIT Incorporated, Sterling, VA, USA) to obtain a transfer tape with an 8 mil (200 µm) thick adhesive layer.

[0139]

[0140] Table 5. Rheological properties of adhesive compositions

[0141] Table 6. 180 degree peel adhesion, dynamic shear, and random free fall data for transfer tapes

[0142] NT = Untested

[0143] Table 7. Summary of test results

[0144] NT = Not Tested

[0145] Examples 12 to 21 (E12-E21) and Comparative Examples 11 to 15 (CE11-CE15)

[0146] Curable compositions were made using the components listed in Table 8 to test the corrosion and electrical peel properties of the adhesives. The specified syrup was used at 100 parts, with the remaining components added in the amounts listed (e.g., 5 g of PEG-A was added to 100 g of SRP-1 in E12).

[0147] Each curable composition was then coated between two release liners (RF12N and RF02N). The samples were then cured under 405 nm UV-LED light at a total dose of 3.1 J / cm2, as measured with a radiometer equipped with a high-power sensor head (available under the trade designation “POWER PUCK II” from EIT, Inc., of Sterling, VA), to give a transfer tape with an 8 mil (200 pm) thick adhesive layer.

[0148]

[0149] Table 9. Rheological properties of adhesive compositions

[0150] Table 10. 180 degree peel adhesion, dynamic shear, and random free fall data for transfer tapes

[0151] NT = Not Tested

[0152] Table 11. Electrical peel Voltage held for 5 minutes instead of 3 minutes

[0153] Table 12. Corrosion results

[0154] Table 13. Summary of results Examples 12 to 21 (E12-E21) and Comparative Examples 11 to 15 (CE11-CE15) Table 9. Rheological properties of adhesive compositions Table 10. 180 degree peel adhesion, dynamic shear, and random free fall data for transfer tapes Table 11. Electrical peel Table 12. Corrosion results Table 13. Summary of results Examples 12 to 21 (E12-E21) and Comparative Examples 11 to 15 (CE11-CE15) Table 9. Rheological properties of adhesive compositions Table 10. 180 degree peel adhesion, dynamic shear, and random free fall data for transfer tapes Table 11. Electrical peel Table 12. Corrosion results Table 13. Summary of results

[0155] Predictable modifications and alterations of this application will be apparent to those skilled in the art without departing from the scope and spirit of this application. This application should not be restricted in scope and spirit to the embodiments shown herein for purposes of illustration.

Claims

1. A polymerizable composition comprising: (i) a polymerizable matrix, the polymerizable matrix comprising: (a) A (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide) group, a poly(tetrahydrofuran) group, or a combination thereof; (b)C1 to C 12 One or more of (meth)acrylate monomers; (c) Crosslinking agent; and (d) 0 to a maximum of 7% by weight of hydroxyl-containing (meth)acrylate monomers; (ii) A plurality of polymer nanoparticles, wherein the polymer nanoparticles include an inner region and a shell, the inner region comprising a polymer with a glass transition temperature below room temperature, and the shell comprising a polymer with a glass transition temperature of at least 50°C; and (iii) Ionic liquids.

2. The composition according to claim 1, wherein the plurality of polymer nanoparticles have an average particle size of less than 800 nanometers.

3. The composition according to claim 1, wherein the plurality of polymer nanoparticles are core-shell nanoparticles, optionally, the core-shell nanoparticles comprising a core comprising a polymer of polybutadiene, poly(butadiene-co-styrene), or (meth)acrylic acid.

4. The composition of claim 3, wherein the core-shell nanoparticles comprise a shell containing poly(methyl methacrylate) or methyl methacrylate-butadiene-styrene.

5. The composition of claim 1, wherein the composition comprises at least 0.1% by weight and at most 40% by weight of the plurality of nanoparticles based on the polymerizable matrix.

6. The composition of claim 1, wherein the polymerizable matrix comprises up to 60% by weight of the (meth)acrylate macromonomer.

7. The composition according to claim 1, wherein the ionic liquid comprises at least one of a nitrogen-containing cation, a phosphonium ion, or a sulfonium ion cation.

8. The composition according to claim 1, wherein the ionic liquid comprises at least one of sulfate, sulfonate, carboxylate, phosphate, borate, imide, sulfonamide, imide or halide anion.

9. The composition according to claim 1, wherein the ionic liquid is free of carbon-fluorine bonds, and optionally the ionic liquid is dimethylaminoethyl acrylate methyl bis(trifluoromethanesulfonyl)imide.

10. The composition of claim 1, wherein the ionic liquid is free of fluorine atoms, and optionally the ionic liquid is dimethylaminoethyl acrylate methyltricyanomethylate.

11. A reaction product of at least partially polymerizing a polymerizable composition according to any one of the preceding claims.

12. An adhesive article comprising an adhesive composition derived from a polymerizable composition according to claim 1, wherein the adhesive composition is disposed on a substrate, and optionally, the adhesive composition has a shear storage modulus of at least 100 kPa at 25°C and 1 Hz.

13. The adhesive article of claim 12, wherein the adhesive article is a tape or a label.

14. A method for manufacturing an adhesive article, the method comprising: (i) Obtaining a polymerizable matrix, the polymerizable matrix comprising: (a) A (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide) group, a poly(tetrahydrofuran) group, or a combination thereof; (b)C1 to C 12 One or more of (meth)acrylate monomers; (c) Crosslinking agent; (d) 0 to a maximum of 7% by weight of hydroxyl-containing (meth)acrylate monomers; and (e) Ionic liquids; and (ii) Adding multiple polymer nanoparticles to the polymerizable matrix to form a composition.

15. A method for separating adhesive articles, the method comprising: (I) An adhesive composite material for adhesively adhering between two conductive substrates, wherein the adhesive composite material comprises: (i) Derived from the following matrix: (a) A (meth)acrylate macromonomer, wherein the (meth)acrylate macromonomer comprises a poly(ethylene oxide) group, a poly(propylene oxide) group, a poly(ethylene oxide-co-propylene oxide) group, a poly(tetrahydrofuran) group, or a combination thereof; (b)C1 to C 12 One or more of (meth)acrylate monomers; (c) Crosslinking agent; as well as (d) 0 to a maximum of 7% by weight of hydroxyl-containing (meth)acrylate monomers; (ii) A plurality of polymer nanoparticles, wherein the polymer nanoparticles include an inner region and a shell, the inner region comprising a polymer with a glass transition temperature below room temperature, and the shell comprising a polymer with a glass transition temperature of at least 50°C; and (iii) Ionic liquids; (II) Apply an electric potential between the two conductive substrates; as well as (III) Separate the two conductive substrates after the potential is applied.

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