Packaged pressure-sensitive adhesive

Abstract

The packaged adhesive composition comprises a thermoplastic packaging material and a pressure-sensitive adhesive composition contained within the packaging material. The pressure-sensitive adhesive composition is a thermal insulating polymerization composition prepared from a reaction mixture of alkyl (meth)acrylate monomers, reinforcing monomers, photocrosslinkable monomers, and at least one initiator. The packaged adhesive composition is hot-melt processable to form a pressure-sensitive adhesive layer. The hot-melt processed packaged adhesive composition has a higher 180° peel strength and higher shear retention strength than the same hot-melt processed adhesive that is not packaged.

Description

Summary of the Invention

[0001] This specification discloses a packaged pressure-sensitive adhesive, an article prepared using the packaged pressure-sensitive adhesive, and a method of forming an adhesive article.

[0002] In some embodiments, the packaged adhesive composition includes a package material that includes a thermoplastic polymer and a pressure-sensitive adhesive composition housed within the package material. The pressure-sensitive adhesive composition includes a thermally insulating polymerization composition prepared from a reaction mixture that includes at least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, at least one reinforcing monomer selected from an acid-functional monomer, a base-functional monomer, or a macromonomer, at least one photocrosslinkable monomer, and at least one initiator. The packaged adhesive composition is hot-melt processable to form a pressure-sensitive adhesive layer. The hot-melt processed packaged adhesive composition has a higher 180° peel strength and a higher shear holding strength than the same hot-melt processed adhesive that is not packaged.

[0003] Also disclosed is an adhesive article. In some embodiments, the adhesive article includes a substrate having a first major surface and a second major surface, and a pressure-sensitive adhesive layer disposed on at least a portion of the first major surface of the substrate. The pressure-sensitive adhesive layer includes the above-described hot-melt coated packaged pressure-sensitive adhesive. The pressure-sensitive adhesive layer includes thermoplastic particles that are residues of the package material.

[0004] A method of preparing an adhesive article includes providing a substrate having a first major surface and a second major surface, and hot-melt coating a packaged pressure-sensitive adhesive composition onto at least a portion of the first major surface of the substrate to form a pressure-sensitive adhesive layer. The packaged pressure-sensitive adhesive composition is as described above. The method further includes exposing the adhesive layer to actinic radiation to crosslink the adhesive layer.

Mode for Carrying Out the Invention

[0005] Adhesives have been used for a variety of marking, retention, protection, sealing, and masking purposes. Pressure-sensitive adhesives, one type of adhesive, are particularly useful in many applications. The use of adhesives, especially pressure-sensitive adhesives, is increasing in fields such as the medical, electronics, and optics industries. Often, pressure-sensitive adhesives are used to form adhesive articles. A wide range of adhesive articles are possible. Adhesive articles include simple articles such as tapes and films, as well as more complex articles including devices. An article comprises a substrate having a first main surface and a second main surface, and a pressure-sensitive adhesive layer disposed on at least a portion of the first main surface of the substrate. The substrate may be a polymer film, tape backing, or the surface of a device.

[0006] Many types of pressure-sensitive adhesives have been prepared to address the needs of a wide range of articles. These pressure-sensitive adhesives are often supplied as solutions or solvent-based mixtures, and often contain large amounts of solvent. During coating or distribution, the solvent needs to be removed to form an adhesive layer. Often, the solvent is removed by using high-temperature treatments, such as heating in an oven. Such solvent removal processes can add cost to the formed articles because they require additional steps for solvent removal. Not only do these processes involve additional steps, but because solvents are volatile and generally flammable, these processes often require special care, precautions, and equipment. Furthermore, transporting adhesive solutions incurs additional costs due to the added weight of the solvent and may require special transport precautions due to the presence of the solvent. Environmental concerns are also an issue with solvent-based adhesives, as solvent release into the environment is likely to occur even with the use of solvent regeneration equipment.

[0007] Therefore, 100% solid adhesive systems were developed. Among these 100% solid systems are hot-melt adhesives, including pressure-sensitive adhesives that can be hot-melted. When solvent processing was replaced by hot-melt processing, difficulties arose. It is often difficult to reproduce the properties of solvent-delivered adhesive layers in a hot-melt delivery system.

[0008] Furthermore, since 100% solid pressure-sensitive adhesives are tacky polymer compositions, handling these compositions, especially on a large scale, can be problematic. A wide range of techniques have been developed to address these handling issues. One such technique is the preparation of (meth)acrylate-based pressure-sensitive adhesive polymers or compositions within thermoplastic polymer packages, as described, for example, in PCT International Publication 97 / 23945. These packages can then be handled without contact with the tacky polymer composition. The entire package can then be hot-melted and coated, for example, in an extruder or similar mixing apparatus, to form a pressure-sensitive adhesive layer. This layer contains not only the pressure-sensitive adhesive polymer or composition but also residues from the pouch material. These particulate residues can be problematic in some applications, such as optical applications. Furthermore, there are limitations on the polymers that can be prepared within the packages.

[0009] Other solvent-free methods have been developed, such as the bulk adiabatic polymerization process for ethylenically unsaturated monomers described in U.S. Patent No. 5,986,011. These bulk polymerized (meth)acrylate polymers differ from those prepared by solvent polymerization methods because they are not produced in a solvent. Generally, these bulk polymers have lower molecular weights than solvent-polymerized adhesive polymers. While these polymers possess desirable properties, their relatively low molecular weight and adhesive nature make them very difficult and costly to handle and process for forming adhesive articles.

[0010] This specification discloses an adhesive composition which is a pressure-sensitive adhesive contained within a thermoplastic package. The pressure-sensitive adhesive polymer is not prepared within the package, but rather prepared by bulk polymerization technology and placed within the package. Since the polymer is prefabricated, substantially any size package can be used, with at least one dimension ranging from 2 centimeters (less than 1 inch) to 25 centimeters (10 inches). Furthermore, the package can have a wide range of shapes.

[0011] The packaged adhesive can be conveniently transported, handled, and dispensed, for example, into a hot-melt processing machine. When the pressure-sensitive adhesive is hot-melt coated, it forms an adhesive layer containing thermoplastic polymer particles dispersed therein. The thermoplastic polymer particles are the residue of the packaging material after hot-melt processing. Surprisingly, it has been found that the pressure-sensitive adhesive layer containing thermoplastic polymer particles exhibits increased 180° peel adhesion and shear retention compared to the same pressure-sensitive adhesive layer without thermoplastic polymer particles. Therefore, the adhesive composition of this disclosure not only offers convenient transport, handling, and dispensing, but also possesses improved adhesive properties.

[0012] Previous disclosures of adhesives, PCT International Publication 97 / 23577 and PCT International Publication 97 / 18166, teach a wide range of pressure-sensitive adhesive blends with thermoplastic polymers, showing that these blends have improved adhesive properties compared to pressure-sensitive adhesives without thermoplastic polymers. Typically, the thermoplastic polymer in these blends is at least 5% by weight of the adhesive layer, and is often quite high, so it is surprising that the low levels of thermoplastic material in current adhesive layers, often less than 3% by weight, can improve adhesive properties. While not bound by theory, polymers formed by bulk thermal insulation polymerization techniques are considerably different from the conventional pressure-sensitive adhesives disclosed in PCT International Publication 97 / 23577 and PCT International Publication 97 / 18166, and therefore the effect of thermoplastic particles is also likely to be different. In addition, typically, current pressure-sensitive adhesive layers are crosslinked after hot-melt coating, which can also affect the behavior of the final pressure-sensitive adhesive layer.

[0013] As used herein, the term “adhesive” refers to a polymer composition useful for bonding two adherends together. An example of an adhesive is a pressure-sensitive adhesive.

[0014] It is well known to those skilled in the art that pressure-sensitive adhesive compositions have the following properties: (1) strong and permanent tackiness, (2) adhesion under pressure less than finger pressure, (3) sufficient ability to be retained on a substrate, and (4) sufficient cohesive force to be easily removed from the substrate. Materials found to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit the viscoelastic properties necessary to provide a desirable balance of tackiness, peel adhesion, and shear retention. Achieving the right balance of properties is not an easy process.

[0015] The term "(meth)acrylate" refers to an ester of an alcohol of monomeric acrylic acid or methacrylic acid. Acrylates and methacrylate monomers or oligomers are collectively referred to as "(meth)acrylate" in this specification. A material referred to as "(meth)acrylate-based" is a material that contains one or more (meth)acrylates as its main component.

[0016] As used herein, the term "siloxane-containing" refers to a polymer containing siloxane units. The terms silicone or siloxane are used interchangeably and refer to units having dialkyl or diarylsiloxane (-SiR2O-) repeating units.

[0017] The terms "room temperature" and "ambient temperature" are used interchangeably to refer to temperatures in the range of 20°C to 25°C.

[0018] The terms "Tg" and "glass transition temperature" are used interchangeably. When measured, the Tg value is determined by differential scanning calorimetry (DSC) at a scanning rate of 10°C / min unless otherwise specified. Typically, the Tg value of copolymers is not measured, but is calculated using the well-known Fox equation, using the homopolymer Tg value provided by the monomer supplier, as understood by those skilled in the art.

[0019] As used herein when referring to two layers, the term “adjacent” means that the two layers are in close proximity to each other without an open space interposed between them. They may be in direct contact with each other (e.g., stacked together), or there may be an intervening layer.

[0020] The terms “polymer” and “macromolecule” are used herein in accordance with their general usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. As used herein, the term “macromolecule” is used to describe groups bonded to monomers having multiple repeating units. The term “polymer” is used to describe materials formed from polymerization reactions, resulting in the material being produced.

[0021] The term "alkyl" refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. Alkyls can be linear, branched, cyclic, or a combination thereof, and typically have 1 to 20 carbon atoms. In some embodiments, alkyls contain 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyls include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

[0022] The term "aryl" refers to a monovalent group that is aromatic and has a carbocyclic structure. An aryl group may have one to five rings bonded to or fused to an aromatic ring. Other ring structures may be aromatic, non-aromatic, or a combination thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perilenyl, and fluorenyl.

[0023] The terms "free radical polymerizability" and "ethylenically unsaturated" are used interchangeably and refer to reactive groups containing carbon-carbon double bonds that can be polymerized via the free radical polymerization mechanism.

[0024] As defined herein, "substantially adiabatic" means that the total absolute value of any energy exchanged with the batch during the course of the reaction is less than about 15% of the total energy released due to the corresponding amount of polymerization reaction that occurred during the time that the polymerization took place. Substantially adiabatic reactions are exemplified, for example, in U.S. Patent No. 5,986,011 (Ellis).

[0025] Disclosed herein is a packaged adhesive composition comprising a packaging material comprising a thermoplastic polymer and a pressure-sensitive adhesive composition contained within the packaging material. The pressure-sensitive adhesive composition comprises an adiabatic polymerization composition prepared from a reaction mixture comprising at least one alkyl (meth)acrylate monomer having an alkyl group having 4 to 20 carbon atoms, at least one reinforcing monomer selected from an acid-functional monomer, a base-functional monomer, or a macromonomer, at least one photocrosslinkable monomer, and at least one thermal initiator.

[0026] The packaged adhesive composition is hot melt processable to form a pressure-sensitive adhesive layer, and the hot melt processed packaged adhesive composition has a higher 180° peel strength and a higher shear holding strength than the same hot melt processed adhesive that is not packaged. The 180° peel strength and shear holding strength are fundamental properties of the pressure-sensitive adhesive, and the techniques for measuring these values are described in detail in the Examples section.

[0027] The packaged adhesive composition comprises a packaging material that forms a package containing the pressure-sensitive adhesive. The method of preparing the packaged adhesive composition is similar to that described in U.S. Patent No. 6,294,249 (Hamer et al.). However, Hamer et al. packaged a pre-adhesive composition, i.e., a composition that is later polymerized to form a pressure-sensitive adhesive, whereas in the present disclosure, a pre-made pressure-sensitive adhesive composition is packaged. Since the pre-made pressure-sensitive adhesive has a relatively low viscosity, packages can be formed using the same techniques used with the polymerizable pre-adhesive composition.

[0028] In some embodiments, two lengths of thermoplastic film are heat sealed together across the bottom and at each of the side edges on a liquid molding - filling - sealing machine to form an open - end package. A pressure - sensitive adhesive composition is pumped through a hose to fill the package, and then the package is heat sealed across the top to completely enclose the pressure - sensitive adhesive composition.

[0029] Generally, a molding - filling - sealing machine includes an impulse sealer for forming top and bottom seals across the package. Such a sealer has one or two sets of jaws that hold and close the package before sealing. Then, a sealing wire is heated to perform the seal, and the seal is cooled before the jaws are released. The seal temperature is generally higher than the softening point and lower than the melting point of the film used to form the package.

[0030] Alternatively, a single length of film can be folded lengthwise, one edge sealed, filled with the pressure - sensitive adhesive composition, and sealed. In another embodiment, a single length of film can be pulled through a forming collar, sealed to form a tube, filled with the pressure - sensitive adhesive composition, and sealed. Another embodiment can be implemented on a commercially available liquid molding - filling - sealing machine. A source for such a machine is the Packaging Machinery Division of Eagle. It is contemplated that the seal can be achieved in any of several different configurations along the length of the film and to form multiple pouches along the length of the film. For example, in addition to sealing the side edges, a seal can be formed along the center of the length of the film to form an intersecting seal to form two filled packages. The packages can be left attached to each other by the intersecting seal and / or vertical seals, or can be cut into individual packages or strands of packages.

[0031] The packaging material is generally a thermoplastic material that melts at or below the processing temperature of the pressure-sensitive adhesive composition (in other words, the temperature at which the pressure-sensitive adhesive composition flows). The packaging material generally has a melting point of 200°C or less, or 170°C or less. In some embodiments, the melting point is in the range of 90°C to 150°C. The packaging material may also be a flexible thermoplastic polymer film. Flexible thermoplastic polymer films are prepared from thermoplastic materials. Suitable thermoplastic materials include polyethylene and ethylene copolymers such as ethylene / polyolefin copolymers, and ethylene / vinyl copolymers such as ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA), ethylene acrylic acid (EAA), EAA ionomer, and polypropylene, as well as other thermoplastic materials such as acrylic, polyphenylene ether, polyphenylene sulfide, acrylonitrile-butadiene-styrene copolymer (ABS), polyurethane, and others known to those skilled in the art. Blends of thermoplastic materials can also be used. Particularly suitable thermoplastic materials are polyethylene and EVA.

[0032] Flexible thermoplastic films have a thickness ranging from 0.01 mm to 0.25 mm. The thickness is typically in the range of 0.025 mm to 0.127 mm to obtain a film that is thin enough to be quickly heat-sealed and minimize the amount of film material used, while also having good strength during processing.

[0033] The amount of packaging material depends on the type of material and the desired final properties. The amount of packaging material present in the adhesive layer is typically in the range of 2% to 15% by weight, more typically 3% to 5% by weight. In some particularly preferred embodiments, the amount of packaging material present in the adhesive layer is less than 3% by weight.

[0034] The packaged adhesive composition also includes a thermally polymerized pressure-sensitive adhesive composition. The thermally polymerized pressure-sensitive adhesive is a (meth)acrylate polymer polymerized by a method similar to that described in U.S. Patent No. 5,986,011.

[0035] In some embodiments, the polymerization method includes providing a first reaction mixture, deoxygenating the first reaction mixture, heating the first reaction mixture to a temperature above the activation temperature of the thermal initiator in the first reaction mixture, polymerizing the first reaction mixture under essentially adiabatic conditions to obtain a mixture that is at least partially polymerized, cooling the mixture that is at least partially polymerized, adding an additional thermal initiator and a chain transfer agent to the partially polymerized mixture to form a second reaction mixture, deoxygenating the second reaction mixture, heating the second reaction mixture to a temperature above the activation temperature of the additional thermal initiator, and polymerizing the second reaction mixture under essentially adiabatic conditions to form a polymer.

[0036] The first reaction mixture comprises at least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, at least one reinforcing monomer, at least one photocrosslinkable monomer, and at least one thermal initiator.

[0037] A wide range of alkyl (meth)acrylate monomers are preferred. Alkyl (meth)acrylate monomers are of formula I: CH2=CR 1 -(CO)-OR 2 Equation I [In the formula, R 1 is either an H atom or a methyl group; -(CO)- is a carbonyl group C=O, R 2 [It is an alkyl group having 4 to 20 carbon atoms.] This is explained by:

[0038] Suitable examples of alkyl (meth)acrylates include n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isoamyl (meth)acrylate, 2-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, isobornyl (meth)acrylate), This includes adamantyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isotridecyl (meth)acrylate, isostearyl (meth)acrylate, octadecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, heptadecanyl (meth)acrylate, branched alkyl (meth)acrylates which are (meth)acrylic acid esters of Guerbet alcohols having 12 or more carbon atoms as described in PCT International Publication No. 2011 / 119363 (Clapper et al.), and combinations thereof.

[0039] In some embodiments, the alkyl (meth)acrylate comprises the alkyl (meth)acrylate of formula I, where R 2 These are alkyl groups having 8 to 16 carbon atoms. Examples include 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isobornyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, branched alkyl (meth)acrylates which are (meth)acrylic acid esters of Guerbet alcohols having 12 or more carbon atoms, as described in PCT International Publication No. 2011 / 119363 (Clapper et al.), and combinations thereof.

[0040] The first reaction mixture also contains at least one strengthening monomer. A broad range of strengthening monomers, typically acid-functional monomers, basic-functional monomers, or macromonomers, are preferred.

[0041] Examples of acid-functional monomers include ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, and ethylenically unsaturated phosphoric acids, as well as mixtures thereof. Examples of such compounds include, but are not limited to, those selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, β-carboxyethyl acrylate, sulfoethyl methacrylate, and mixtures thereof.

[0042] Examples of basic functional monomers include acrylamides, N,N-dialkyl-substituted acrylamides, N-vinyl lactams, and N,N-dialkylaminoalkyl acrylates, as well as mixtures thereof. Exemplary examples include, but are not limited to, those selected from the group consisting of N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate, NVP (N-vinylpyrrolidone), and mixtures thereof.

[0043] Macromers are high molecular weight monomers. An example of a macromonomer is a macromeric (meth)acrylate. Examples of macromeric (meth)acrylates include (meth)acrylate-terminated styrene oligomers and (meth)acrylate-terminated polyethers, which are described, for example, in PCT International Publication 84 / 03837 and European Patent Application 140941. A methacrylate-terminated polydimethylsiloxane macromer is described in U.S. Patent No. 4,693,935 (Mazurek).

[0044] Particularly preferred reinforcing monomers include acrylic acid, NVP (N-vinylpyrrolidone), siloxane-containing macromers, or styrene-containing macromers.

[0045] The first reaction mixture further comprises at least one photocrosslinking agent. The photocrosslinking agent has free radical polymerizable groups for copolymerization with the above monomers and also contains photosensitive groups. When exposed to light of the appropriate wavelength, typically high-intensity ultraviolet (UV) radiation, the photosensitive groups can form free radicals, thereby forming crosslinks in the polymer.

[0046] Suitable photocrosslinking agents include monoethylene unsaturated aromatic ketone comonomers that do not contain ortho-aromatic hydroxyl groups, such as those described in U.S. Patent No. 4,737,559 (Kellen et al.). Specific examples include para-acrylooxybenzophenone (ABP), para-acryloxyethoxybenzophenone, para-N-(methylacrylooxyethyl)-carbamoylethoxybenzophenone, para-acrylooxyacetophenone, ortho-acrylamidoacetophenone, and acrylic anthraquinone. Particularly preferred are ABP para-acrylooxybenzophenone and AeBP acrylooxyethylbenzophenone.

[0047] The first reaction mixture also comprises at least one thermal initiator. Suitable thermal initiators include various azo compounds, such as those traded as VAZO from EIDuPont de Nemours Co. (Wilmington, DE, USA), including VAZO 67, which is 2,2'-azobis(2-methylbutanenitrile); VAZO 64, which is 2,2'-azobis(isobutyronitrile); VAZO 52, which is 2,2'-azobis(2,4-dimethylpentanenitrile); and VAZO 88, which is 1,1'-azobis(cyclohexanecarbonitride); as well as benzoyl peroxide, cyclohexane peroxide, lauroyl peroxide, di-tert-amyl peroxide, tert-butylperoxybenzoate, dicumyl peroxide, and LUPEROX from Atofina Chemical, Inc. (Philadelphia, PA), such as LUPEROX, which is traded as 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Examples include various peroxides, such as those commercially available as LUPEROX 130 (which is 2,5-dimethyl-2,5-di-(tert-butylperoxy)-3-hexine); various hydroperoxides, such as tert-amyl hydroperoxide and tert-butyl hydroperoxide; and mixtures thereof.

[0048] The first and second reaction mixtures may also contain additional optional components, provided that none of the components interfere with the reaction or subsequent curing of the polymer. In particular, the second reaction mixture may further contain a chain transfer agent to control the molecular weight of the resulting (meth)acrylate copolymer. Examples of useful chain transfer agents include, but are not limited to, carbon tetrabromide, alcohols (e.g., ethanol and isopropanol), mercaptans or thiols (e.g., lauryl mercaptan, butyl mercaptan, tert-dodecyl mercaptan, ethanethiol, isooctyl thioglycolate, 2-ethylhexyl thioglycolate, 2-ethylhexyl mercaptopropionate, ethylene glycol bisthioglycolate), and mixtures thereof.

[0049] As described above, the packaged adhesive composition includes an insulating polymerization reaction mixture contained within the package. The package can have a wide variety of shapes and sizes. In some embodiments, where the package also serves as a reaction vessel for polymerization of the reaction mixture, it may be more convenient to have a larger package than is typically preferred. In some embodiments, the package may be relatively small, and in other embodiments, the package may be relatively large. Since the package can have various shapes, the size of a three-dimensional package can be described by at least one dimension. This dimension may be length, width, or depth. In some embodiments, at least one dimension of the package is between 2 centimeters (less than 1 inch) and 25 centimeters (about 10 inches).

[0050] Adhesive articles are also disclosed herein. In some embodiments, an adhesive article comprises a substrate having a first main surface and a second main surface, and a pressure-sensitive adhesive layer disposed on at least a portion of the first main surface of the substrate. The pressure-sensitive adhesive layer comprises a hot-melt coated pressure-sensitive adhesive and thermoplastic particles dispersed in the pressure-sensitive adhesive. The pressure-sensitive adhesive comprises an insulating polymerization composition prepared from a reaction mixture comprising at least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, at least one reinforcing monomer selected from acid-functional monomers, basic-functional monomers, or macromonomers, at least one photocrosslinkable monomer, and at least one thermal initiator. The adhesive article has a higher 180° peel strength and higher shear retention strength than the same adhesive article having the same pressure-sensitive adhesive composition without thermoplastic particles.

[0051] Typically, the pressure-sensitive adhesive layer contains a low concentration of thermoplastic particles. In some embodiments, the thermoplastic particles constitute 3% to 5% by weight of the pressure-sensitive adhesive layer. In some embodiments, the thermoplastic particles constitute less than 3% by weight of the pressure-sensitive adhesive layer.

[0052] Thermoplastic particles include polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene acrylate ionomer, polypropylene, acrylic polymers, polyphenylene ether, polyphenylene sulfide, acrylonitrile-butadiene-styrene copolymer, polyurethane, and mixtures and blends thereof.

[0053] The heat-insulating polymerization reaction mixture that forms the pressure-sensitive adhesive layer is the pressure-sensitive adhesive composition in the package described above. The thermoplastic particles are residual particles resulting from the hot-melt processing of the packaged adhesive composition, and this packaged adhesive composition comprises a package material containing a thermoplastic polymer and a heat-insulating polymerization pressure-sensitive adhesive composition contained within the package material.

[0054] In addition to the pressure-sensitive adhesive and thermoplastic polymer particles, the pressure-sensitive adhesive layer may also contain additional materials. In some embodiments, the pressure-sensitive adhesive layer further comprises at least one additional adhesive composition, the at least one additional adhesive composition comprising a packaged adhesive composition or an unpackaged adhesive composition. Other additional materials may also be included in the pressure-sensitive layer. In some embodiments, the adhesive layer further comprises at least one additive selected from plasticizers, tackifiers, antimicrobial agents, fillers, and fibers.

[0055] The adhesive article also comprises a substrate. A wide range of substrates are preferred. The substrate may be a release liner, a rigid surface, a tape backing, a film, or a sheet. The adhesive composition may be coated on the release liner, coated directly on the substrate, film, or backing, or formed as a separate layer (e.g., coated on the release liner) and then laminated onto the substrate or film. In some embodiments, the adhesive is a transfer tape, i.e., placed between two release liners.

[0056] In some embodiments, it may be desirable to impart a microstructured surface to one or both main surfaces of the adhesive. It may also be desirable to have a microstructured surface on at least one surface of the adhesive to facilitate air expulsion during lamination. If it is desirable to have a microstructured surface on one or both surfaces of the adhesive film, the adhesive coating or film may be placed on a tool or liner containing the microstructure. The liner or tool can then be removed to expose the adhesive film with the microstructured surface. Generally, in optical applications, it is desirable that the microstructure disappears over time to prevent interference with optical properties. In medical applications, it may be desirable that the microstructure remains to provide a pathway for fluid outflow.

[0057] The substrate included in the adhesive article may contain polymer materials, glass materials, ceramic materials, metal-containing materials (e.g., metals or metal oxides), or combinations thereof. The substrate may include multiple material layers, such as a support layer, a primer layer, a hard coat layer, and a decorative design. The substrate may be permanently or temporarily attached to the adhesive film. For example, a release liner may be temporarily attached and then removed to attach the adhesive film to another substrate.

[0058] The substrate can have various functions, such as providing flexibility, rigidity, strength, support, MVTR (water vapor transmission rate) characteristics, or optical properties such as reflectivity, anti-reflective properties, polarization, or transmittance (e.g., selective for different wavelengths). In other words, the substrate can be flexible or rigid, reflective or non-reflective, visually transparent, colored but transmittance, or opaque (e.g., not transmittance), and polarized or non-polarized.

[0059] Typical examples of polymer substrates include those containing polycarbonate, polyester (e.g., polyethylene terephthalate and polyethylene naphthalate), polyurethane, poly(meth)acrylate (e.g., polymethyl methacrylate), polyvinyl alcohol, polyolefin (e.g., polyethylene and polypropylene), polyvinyl chloride, polyimide, cellulose triacetate, and acrylonitrile-butadiene-styrene copolymer.

[0060] In other embodiments, the substrate is a release liner. Any suitable release liner can be used. Examples of suitable liners include paper, e.g., kraft paper, or polymer films, e.g., polyethylene, polypropylene, or polyester. At least one surface of the liner can be treated with a release agent, such as silicone, fluorochemical, or other low surface energy release materials, to provide a release liner. Suitable release liners and methods for treating liners are described, for example, in U.S. Patents 4,472,480, 4,980,443, and 4,736,048. The liner may have microstructures on its surface that are imparted to the adhesive to form a microstructure on the surface of the adhesive film. The liner can then be removed to expose the adhesive film having the microstructured surface.

[0061] Adhesive articles can have a wide range of applications. In some embodiments, the adhesive article is a medical article. Some medical articles are intended to be attached to the skin of mammals. In these embodiments, the adhesive layer adheres to the skin of mammals.

[0062] Also disclosed herein are methods for preparing adhesive articles. In some embodiments, the method for preparing an adhesive article includes providing a substrate having a first main surface and a second main surface, and hot-melt coating a packaged pressure-sensitive adhesive composition onto at least a portion of the first main surface of the substrate to form a pressure-sensitive adhesive layer. The packaged pressure-sensitive adhesive composition includes a package material containing a thermoplastic polymer and a pressure-sensitive adhesive composition contained within the package material. The pressure-sensitive adhesive composition comprises a thermal insulating polymer composition, and the hot-melt coated pressure-sensitive adhesive composition includes thermoplastic particles dispersed within the pressure-sensitive adhesive layer, and has a higher 180° peel strength and higher shear holding strength than the same pressure-sensitive adhesive layer without thermoplastic particles.

[0063] A method for preparing a hot-meltable packaged adhesive composition is described in detail above. The heat-insulating polymerized pressure-sensitive adhesive composition is placed in a thermoplastic package to form a packaged pressure-sensitive adhesive composition. The package has at least one dimension between 2 cm and 25 cm.

[0064] Methods for forming adiabatic polymerization compositions are described in detail above. In some embodiments, a method for forming adiabatic polymerization composition comprises: providing a first reaction mixture comprising an ethylenically unsaturated silicone-containing monomer, at least one additional ethylenically unsaturated monomer, a chain transfer agent, and a thermal initiator; deoxygenating the first reaction mixture; heating the first reaction mixture to a temperature above the activation temperature of the thermal initiator; polymerizing the first reaction mixture under essentially adiabatic conditions to obtain a mixture that is at least partially polymerized; cooling the mixture that is at least partially polymerized; adding an additional thermal initiator and a chain transfer agent to the partially polymerized mixture to form a second reaction mixture; deoxygenating the second reaction mixture; heating the second reaction mixture to a temperature above the activation temperature of the additional thermal initiator; and polymerizing the second reaction mixture under essentially adiabatic conditions to form a polymer.

[0065] Packaged adhesive compositions are hot-melted using a hot-melt mixer to form a pressure-sensitive adhesive layer. Various hot-melt mixing techniques using various hot-melt mixers are suitable for processing packaged pressure-sensitive adhesive compositions. Both batch and continuous mixing devices can be used. Examples of batch methods include using a BRABENDER (e.g., a BRABENDER PREP CENTER commercially available from CWBrabender Instruments, Inc.; South Hackensack, NJ) or a BANBURY internal mixing and roll milling device (e.g., a device available from Farrel Co.; Ansonia, CN). Examples of continuous methods include uniscrew extrusion, twin-screw extrusion, disk extrusion, reciprocating uniscrew extrusion, and pin-barrel uniscrew extrusion. Continuous methods can utilize dispersing elements such as distributing elements, pin mixing elements, static mixing elements, and Maddock and Saxton mixing elements. A single hot-melt mixer or a combination of hot-melt mixers may be used to process the packaged adhesive compositions of this disclosure.

[0066] The product of the hot melt mixture is coated onto a substrate to form an adhesive layer. When using a batch apparatus, the resulting hot melt blend can be removed from the apparatus and placed in a hot melt coater or extruder to coat the substrate. When preparing the hot melt blend using an extruder, the packaged adhesive composition can be directly extruded onto the substrate to form an adhesive layer. After formation, the adhesive layer or film can be solidified by quenching using both direct methods (e.g., chill roll or water batch) and indirect methods (e.g., air or gas impact).

[0067] The pressure-sensitive adhesive layer contains thermoplastic particles, which are residues of the packaging material from the hot-melt coated packaged adhesive composition. In some embodiments, the thermoplastic particles constitute 3% to 5% by weight of the pressure-sensitive adhesive layer. In other embodiments, the thermoplastic particles constitute less than 3% by weight of the pressure-sensitive adhesive layer.

[0068] In some embodiments, it may be desirable to crosslink the pressure-sensitive adhesive layer after its formation. Crosslinking can be carried out by exposing the pressure-sensitive adhesive layer to a chemical beam to activate a photocrosslinking agent copolymerized with other monomers, thereby forming a pressure-sensitive adhesive composition. Typically, the chemical beam is UV light, often high-intensity UV light. [Examples]

[0069] These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. All parts, percentages, ratios, etc., in the examples and the remainder of the specification are in weight unless otherwise specified. The following abbreviations are used: cm = centimeter, mm = millimeter, m = meter, oz = ounce, g = gram, kg = kilogram, ml = milliliter, min = minute, hr = hour, rad = radian, Pa = Pascal, mJ = millijoule, OD = outer diameter, CW = cross-web direction, DW = down-web direction. The terms "weight %", "weight % (% by weight)", and "weight % (wt%)" are used interchangeably.

[0070] [Table 1]

[0071] Test method 180° peel adhesive strength This peel adhesion test is performed using the stainless steel or Fruehauf substrate described in the test, and is similar to the test method described in ASTM D 3330-90.

[0072] The adhesive coating film was cut into 1.27 cm x 15 cm strips. Each strip was then bonded to a clean substrate surface of 10 cm x 20 cm using a 2 kg roller that passed over the strip once. The bonded assemblies were left at room temperature for approximately 1 minute and tested for 180° peel adhesion at a speed of 2.3 m / min (90 inch / min) over a data acquisition time of 5 seconds using an IMASS slip / peel tester (Model 3M90, commercially available from Instrumentors Inc. (Strongsville, OH)). Two samples were tested. The reported peel adhesion values ​​are the average of the peel adhesion values ​​from each of the two samples.

[0073] DMA-Dynamic Mechanical Analysis Rheological data such as G' (storage modulus), G'' (loss modulus), and tanδ (=G'' / G') were measured by dynamic mechanical analysis.

[0074] The rheometer used for these measurements is the TA Instruments AR1500ex, which has a bottom Peltier plate for temperature control and a 20 mm parallel plate fixture above the sample that is vibrated by an electromagnetic drive system.

[0075] Sample preparation: Twelve layers of PSA with a thickness of 2.0 mm were stacked, and then the test specimens were punched out to a diameter of 8 mm to prepare the samples.

[0076] Sample run: Dynamic time sweep at 1 rad / second for a duration of 2 minutes, with a stress of 1000 Pa applied to a Peltier plate at 100°C.

[0077] shear strength This shear strength test is similar to the test method described in ASTM D 3654-88.

[0078] The adhesive coating on the film was cut into 2.5 cm (1 inch) x 15 cm (6 inch) strips. Each strip was then bonded to a stainless steel panel, with a 2.5 cm x 2.5 cm portion of each strip firmly in contact with the panel and one end of the tape free. The panel with the coated strips attached was held in a rack, and tension was applied by applying a 250 gram force as a hanging weight from the free end of the coated strip, so that the panel formed a 178° angle with the free end of the stretched tape. By using an angle 2° smaller than 180° to counteract the peeling force, it was ensured that only shear strength was measured in an attempt to more accurately determine the holding power of the tape being tested. The time required for each tape example to separate from the test panel was recorded as the shear strength. All shear strength failures reported herein (where the adhesive failed in less than 10,000 minutes) were cohesive failures of the adhesive. Each test was completed at 10,000 minutes unless the adhesive failed in a shorter time (as noted).

[0079] MVTR - Water vapor transmission rate The water vapor permeability of the test materials was evaluated using water contact (inverted cup) and vapor contact (upright cup) methods, which are modified versions of the test methods described in ASTM E96.

[0080] Inverted Cup 25 ml of distilled water was placed in a Paddington cup (commercially available from Bio-Med Engineering, LTD, Liversedge, West Yorkshire, UK) with a 3.5 cm opening. A 2.54 cm diameter sample of the test material was then secured to the flange using a sealing ring and screw clamp. The sample was then placed in a circulating oven in reverse and maintained at 37°C and 20% relative humidity. After approximately 4 hours of preliminary adjustment, the initial sample weight was recorded, and the sample was returned to its reversed position in the oven. After 16 to 24 hours, the cup was removed from the oven and weighed again to measure moisture loss. The water vapor transmission rate for each sample was reported in grams per square meter per 24 hours.

[0081] Upright cup 50 ml of distilled water was placed in a jar with an opening of 2.54 cm. A 3.8 cm diameter sample of the test material was secured to the flange using a sealing ring and screw clamp. The sample was then placed in an upright position in a circulating oven and maintained at 37°C and 20% relative humidity. After approximately 4 hours of preliminary adjustment, the initial sample weight was recorded, and the sample was returned to the upright position in the oven. After 16 to 24 hours, the cup was removed from the oven and weighed again to measure moisture loss. The water vapor transmission rate of each sample was reported in grams per square meter per 24 hours.

[0082] Shrinkage test A 24-hour application shrinkage test was performed on a Fruehauf panel. X-gash test: A 2-inch x 2-inch (5cm x 5cm) sample was applied to a Fruehauf panel, the X-gash was cut into the sample, the sample was left for 24 hours, the gap size was measured in mils and converted to micrometers.

[0083] Examples E1-E2 and Comparative Examples CE1-CE2 The PSA-1 sample was used as is in Comparative Examples CE1 and CE2, while the PSA-1 sample was packaged in EVA film in Examples E1 and E2.

[0084] Measuring the adhesive: Using a pail unloader provided by Graco, PSA-1 adhesive was metered from a 20-liter epoxy-coated metal pail. The platen, hose, pump, and metering elements were all heated to 120°C. The pail unloader used the platen to generate pressure within the adhesive pail. This pressure helped draw the material into a piston pump fixed to the top of the heated platen. The adhesive was then pumped from the piston pump into a 1.5-meter hose connected to a turbine volumetric flow meter. The adhesive was then pumped 150 cm using an automatic pin valve. 3 The amount was measured into a 3-meter hose at a rate of / min. For the packaged samples, the hose was parallel to a heat sealer, model number F900, and supplied to a 9mm OD hose loosely wrapped in an EVA package. At the end of the 9mm hose, the adhesive filled the EVA package. The adhesive in the EVA package was placed in an aluminum tray and cooled.

[0085] Package creation: A 10cm wide EVA film was pulled from the roll without resistance. It was then pulled through a V-shaped slot to create a fold in the film. The folded EVA film was manually guided into a heater on an F900 Sealer. The edges of the film were convection heated to 115°C while being pulled into the nip. The edges of the film were pressed together with a spring-tensioned nip roller. The edges were then cooled to 25°C using pressurized air and conduction from the nip idler.

[0086] Fabrication of adhesive coatings The adhesive was coated onto either backing material-1 or liner-1. For comparative examples CE1 and CE2, PSA-1 was extruded from a twin-screw extruder, and for examples E1 and E2, packaged PSA-1 samples were extruded from a Bonnot extruder into a twin-screw extruder. All extruded samples were coated to a thickness of 2 mil (51 micrometers) through a rod die. The adhesive samples were photocrosslinked at 50 mJ using a UV lamp. The samples were tested for 180° peel adhesion and MVT according to the test method described above. The data are shown in Table 1.

[0087] [Table 2]

[0088] Examples E3-E4 and Comparative Examples CE3-CE6 Adhesive samples (CE1 and E2) coated on liner-1 were laminated onto different backing materials (backing material-2 or backing material-3). For samples CE5 and CE6, the coated adhesive was exposed to an additional dose of UV radiation (80 mJ). The samples were tested for 180° peel adhesion, tanδ (DMA), and shrinkage according to the test method described above. A description of the samples is shown in Table 2, 180° peel adhesion data in Table 3, tanδ data in Table 4, and shrinkage data in Table 5.

[0089] [Table 3]

[0090] [Table 4]

[0091] [Table 5]

[0092] [Table 6]

[0093] Examples E5-E7 and Comparative Example CE7 To test whether the same effect could be achieved with a hot-melt blend of a heat-insulating polymerizing pressure-sensitive adhesive and packaging material pellets, a sample of PSA-1 was hot-melt coated (Comparative Example CE7), and PSA-1 with different levels of packaging pellets was prepared (Examples E5-E7).

[0094] Measuring the adhesive: Using a pail unloader provided by Graco, PSA-1 adhesive was metered from a 20-liter epoxy-coated metal pail. The platen, hose, pump, and metering elements were all heated to 120°C. The pail unloader used the platen to generate pressure within the adhesive pail. This pressure helped draw the material into a piston pump fixed to the top of the heated platen. The adhesive was then pumped from the piston pump into a 1.5-meter hose connected to a turbine volumetric flow meter. The adhesive was then pumped 150 cm using an automatic pin valve. 3 The amount was weighed into a Bonnot extruder via a 3-meter hose at a rate of / min. For examples involving blended packaged pellets, the desired amount of packaged pellets was fed into the same feed port of the Bonnot extruder using a weight feeder.

[0095] Fabrication of adhesive coatings Adhesive was coated onto liner-1. The samples were extruded from a Bonnot extruder into a twin-screw extruder. All extruded samples were coated to a thickness of 1 mil (25 micrometers) through a rod die. The adhesive samples were photocrosslinked using a UV lamp at 50 mJ. The samples were laminated onto backing material-1 and tested for 180° peel adhesion, shear strength, and upright MVT according to the test method described above. The data are shown in Table 6.

[0096] [Table 7]

Claims

1. Packaging material containing thermoplastic polymer, The pressure-sensitive adhesive composition contained within the package material and including, A packaged adhesive composition, The pressure-sensitive adhesive composition At least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, A strengthening monomer selected from acid-functional monomers, basic-functional monomers, or macromonomers, At least one photocrosslinkable monomer, At least one initiator and The composition comprises an insulating polymerization composition prepared from a reaction mixture containing the following: The packaged adhesive composition is hot-meltable to form a pressure-sensitive adhesive layer, and the hot-melt packaged adhesive composition has a higher 180° peel strength and higher shear holding strength than the same hot-melt adhesive that is not packaged. Packaged adhesive composition.

2. The packaged adhesive composition according to claim 1, wherein the package material comprises polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene acrylate ionomer, polypropylene, acrylic polymer, polyphenylene ether, polyphenylene sulfide, acrylonitrile-butadiene-styrene copolymer, polyurethane, and mixtures and blends thereof.

3. The aforementioned thermal insulating polymerization composition At least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, At least one reinforced monomer selected from acid-functional monomers, basic-functional monomers, or macromonomers, At least one photocrosslinkable monomer, and At least one thermal initiator, To provide a first reaction signal, including, Deoxygenation of the first reaction mixture, The first reaction mixture is heated to a temperature exceeding the activation temperature of the thermal initiator, The first reaction mixture is polymerized under essentially adiabatic conditions to obtain a mixture that is at least partially polymerized, Cooling the at least partially polymerized mixture, The process involves adding additional thermal initiators and chain transfer agents to the partially polymerized mixture to form a second reaction mixture, Deoxygenating the second reaction mixture, The second reaction mixture is heated to a temperature exceeding the activation temperature of the additional thermal initiator, The second reaction mixture described above is polymerized under essentially adiabatic conditions to form a polymer. Polymerized by a method including, The packaged adhesive composition according to claim 1.

4. The packaged adhesive composition according to claim 1, comprising at least one alkyl (meth)acrylate monomer having an alkyl group containing 8 to 16 carbon atoms, or a mixture of alkyl (meth)acrylates having an alkyl group containing 8 to 16 carbon atoms.

5. The packaged adhesive composition according to claim 1, wherein the at least one reinforcing monomer is selected from AA, NVP, siloxane-containing macromer, or styrene-containing macromer.

6. The packaged adhesive composition according to claim 1, wherein at least one dimension of the package is between 2 centimeters and 25 centimeters.

7. A substrate having a first main surface and a second main surface, A pressure-sensitive adhesive layer disposed on at least a portion of the first main surface of the substrate and Adhesive articles including, The pressure-sensitive adhesive layer comprises a hot-melt coated pressure-sensitive adhesive and thermoplastic particles dispersed in the pressure-sensitive adhesive. The pressure-sensitive adhesive, At least one alkyl (meth)acrylate monomer having an alkyl group containing 4 to 20 carbon atoms, A strengthening monomer selected from acid-functional monomers, basic-functional monomers, or macromonomers, At least one photocrosslinkable monomer, At least one thermal initiator and The adhesive article comprises a thermal insulating polymerization composition prepared from a reaction mixture containing the thermoplastic particles, wherein the adhesive article has a higher 180° peel strength and higher shear holding strength than the same adhesive article having the same pressure-sensitive adhesive composition that does not contain the thermoplastic particles. Adhesive products.

8. The adhesive article according to claim 7, wherein the thermoplastic particles constitute 3% to 5% by weight of the pressure-sensitive adhesive layer.

9. The adhesive article according to claim 7, wherein the thermoplastic particles constitute less than 3% by weight of the pressure-sensitive adhesive layer.

10. The adhesive article according to claim 7, wherein the thermoplastic particles include polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, ethylene acrylic acid, ethylene acrylate ionomer, polypropylene, acrylic polymer, polyphenylene ether, polyphenylene sulfide, acrylonitrile-butadiene-styrene copolymer, polyurethane, and mixtures and blends thereof.

11. The thermoplastic particles are residual particles resulting from the hot-melt processing of the packaged adhesive composition, and the packaged adhesive composition is Packaging material containing thermoplastic polymer, The heat insulating polymerized pressure-sensitive adhesive composition contained within the package material and The adhesive article according to claim 7, including the following:

12. The adhesive article according to claim 7, wherein the pressure-sensitive adhesive layer further comprises at least one additional adhesive composition, the at least one additional adhesive composition comprising a packaged adhesive composition or an unpackaged adhesive composition.

13. The adhesive article according to claim 7, wherein the adhesive layer adheres to the skin of a mammal.

14. The adhesive article according to claim 7, wherein the adhesive layer further comprises at least one additive selected from plasticizers, tackifiers, antimicrobial agents, fillers, and fibers.

15. A method for preparing adhesive articles, To provide a substrate having a first main surface and a second main surface, The packaged pressure-sensitive adhesive composition is hot-melt coated onto at least a portion of the first main surface of the substrate to form a pressure-sensitive adhesive layer. Includes, The packaged pressure-sensitive adhesive composition Packaging material containing thermoplastic polymer, The pressure-sensitive adhesive composition contained within the package material and Includes, The pressure-sensitive adhesive composition comprising an insulating polymerization composition, The hot-melt coated pressure-sensitive adhesive composition contains thermoplastic particles dispersed within the pressure-sensitive adhesive layer and has a higher 180° peel strength and higher shear holding strength than the same pressure-sensitive adhesive layer that does not contain the thermoplastic particles. method.

16. The method according to claim 15, wherein the method for forming the thermal insulating polymerization composition is Ethylene-unsaturated silicone-containing monomers, At least one additional ethylenically unsaturated monomer, Chain transfer agent, and Thermal initiator To provide a first reaction signal including, Deoxygenation of the first reaction mixture, The first reaction mixture is heated to a temperature exceeding the activation temperature of the thermal initiator, The first reaction mixture is polymerized under essentially adiabatic conditions to obtain a mixture that is at least partially polymerized, Cooling the at least partially polymerized mixture, The process involves adding additional thermal initiators and chain transfer agents to the partially polymerized mixture to form a second reaction mixture, Deoxygenating the second reaction mixture, The second reaction mixture is heated to a temperature exceeding the activation temperature of the additional thermal initiator, The second reaction mixture described above is polymerized under essentially adiabatic conditions to form a polymer. Methods that include...

17. The method according to claim 15, wherein the thermoplastic particles constitute 3% to 5% by weight of the pressure-sensitive adhesive layer.

18. The method according to claim 15, wherein the thermoplastic particles constitute less than 3% by weight of the pressure-sensitive adhesive layer.

19. The method according to claim 15, further comprising exposing the adhesive layer to a chemical beam to crosslink the adhesive layer.

20. The method according to claim 15, wherein the packaged pressure-sensitive adhesive composition includes a package, and at least one dimension of the package is between 2 centimeters and 25 centimeters.

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