Compositions comprising particles and two liquid phases and related methods

Abstract

A curable composition includes from 25% to 70% by volume of particles, from 25% to 74.8% by volume of a primary liquid phase, and from 0.15% to 20% by volume of a secondary liquid phase, based on the total volume of the curable composition. The primary liquid phase includes a first monomer containing at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer wherein the alkyl group is linear or branched and has at least five carbon atoms. The secondary liquid phase and the primary liquid phase form a separated phase after mixing in a temperature range of-20 DEG C to 30 DEG C, and the particles are insoluble in the primary liquid phase and the secondary liquid phase in a temperature range of-20 DEG C to 30 DEG C. A pressure sensitive adhesive precursor capillary suspension, a pressure sensitive adhesive made from the capillary suspension, and a method for preparing the pressure sensitive adhesive are also described.

Description

BACKGROUND OF THE INVENTION

[0001] Adhesives have been used for a variety of marking, fixing, protecting, sealing, and masking applications. Pressure-sensitive adhesives can be used in many applications. Pressure-sensitive adhesives (PSAs) are well known to those of ordinary skill in the art and have certain properties including: (1) strong and permanent tack, (2) the ability to adhere under no more than finger pressure, (3) sufficient ability to remain adhered to an adherend, and (4) sufficient cohesive strength. As the use of pressure-sensitive adhesives has increased significantly in recent years, the performance requirements have become increasingly demanding. Materials that have been found to work well as pressure-sensitive adhesives are polymers that are designed and formulated to exhibit the desired viscoelasticity such that the tack, peel adhesion, and shear strength are balanced as desired. The most commonly used polymers for pressure-sensitive adhesives are various (meth)acrylate-based polymers, natural rubbers, synthetic rubbers, and silicones.

[0002] U.S. Patent Application Publication Nos. 2016 / 0083628 (Heimink et al.) and 2011 / 0129661 (Tsubaki et al.) describe pressure-sensitive adhesives containing hollow glass microspheres. SUMMARY OF THE INVENTION

[0003] The present disclosure provides a curable composition that can be used, for example, as a pressure-sensitive adhesive precursor. The curable composition can become a pressure-sensitive adhesive after curing. Generally, and advantageously, the curable composition has little flow, which allows the curable composition to be dispensed in a desired shape and retain that shape upon curing and for a desired time before curing. Thus, the curable composition enables great flexibility in the shape of the pressure-sensitive adhesive and the bonded articles constructed from the pressure-sensitive adhesive.

[0004] In one aspect, the present disclosure provides a curable composition comprising: particles in an amount of 25 volume % to 70 volume % based on the total volume of the curable composition; a primary liquid phase in an amount of 25 volume % to 74.8 volume % based on the total volume of the curable composition; and a secondary liquid phase in an amount of 0.15 volume % to 20 volume % based on the total volume of the curable composition. The primary liquid phase comprises a first monomer that contains at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer, wherein the alkyl is straight-chain or branched and has at least five carbon atoms. The secondary liquid phase and the primary liquid phase form a separated phase after mixing in a temperature range of -20 °C to 30 °C, and the particles are insoluble in the primary liquid phase and the secondary liquid phase in a temperature range of -20 °C to 30 °C. In some embodiments, the curable composition is a capillary suspension.

[0005] On the other hand, the present disclosure provides a pressure-sensitive adhesive precursor capillary suspension. This can also be understood as a pressure-sensitive adhesive precursor composition in the form of a capillary suspension and a capillary suspension comprising the pressure-sensitive adhesive precursor composition.

[0006] On the other hand, the present disclosure provides a pressure-sensitive adhesive made from a capillary suspension.

[0007] On the other hand, the present disclosure provides a method for preparing a pressure-sensitive adhesive. The method includes curing a curable composition to prepare the pressure-sensitive adhesive.

[0008] In the present application, terms such as "a", "an", and "the" are not intended to refer only to a single entity, but include general categories that can be used to illustrate specific examples. The terms "a", "an", "the", and "said" can be used interchangeably with the term "at least one". The phrases "at least one of... " and "comprising at least one of... " followed by a list refer to any one of the items in the list and any combination of two or more items in the list. Unless otherwise indicated, all numerical ranges include their end values and non-integer values between the end values (e.g., 1 to 5, including 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

[0009] As used herein, the terms "primary liquid phase" and "secondary liquid phase" describe the respective phases in their liquid form. This means that the description of their properties refers to temperatures above their melting points. For example, the description that a particle is insoluble in the primary liquid phase "at temperatures of 30 °C and below" defines a temperature range above the melting point of the primary liquid phase and 30 °C. Thus, the description that a particle is insoluble in the secondary liquid phase "at temperatures of 30 °C and below" defines a temperature range above the melting point of the secondary liquid phase and 30 °C. Therefore, the description that the primary liquid phase and the secondary liquid phase form a separate phase when mixed "at temperatures of 30 °C and below" defines a temperature range above the melting points of both the primary liquid phase and the secondary liquid phase and 30 °C.

[0010] The terms "first" and "second" are used in the present disclosure only in their relative sense. It should be understood that these terms are used only for convenience in describing one or more of the embodiments unless otherwise specified.

[0011] The term "acrylic" refers to acrylic and methacrylic polymers, oligomers, and monomers.

[0012] The term "(meth)acrylate" with respect to a monomer, oligomer, or polymer means a vinyl-functional alkyl ester formed as a reaction product of an alcohol with acrylic acid or methacrylic acid. "(meth)acrylate" includes methacrylates and acrylates individually and collectively.

[0013] Unless otherwise indicated, the term "alkyl group" and the prefix "alk-" include both straight-chain and branched-chain groups having up to 30 carbon atoms (in some embodiments, up to 20, 15, 12, 10, 8, 7, 6, or 5 carbon atoms). The term "alkyl" refers to a monovalent group that is a saturated hydrocarbon. It is understood that hydrocarbons include only carbon-carbon and carbon-hydrogen bonds.

[0014] "Alkylene" is the polyvalent (e.g., divalent or trivalent) form of the "alkyl" group as defined above.

[0015] "Arylalkylene" refers to the "alkylene" moiety to which an aryl group is attached.

[0016] As used herein, "aryl" and "arylene" include carbocyclic aromatic rings or ring systems, e.g., having 1, 2, or 3 rings and optionally containing at least one heteroatom (e.g., O, S, or N) in the ring, which rings are optionally substituted with up to five substituents including one or more alkyl groups having up to 4 carbon atoms (e.g., methyl or ethyl), alkoxy groups having up to 4 carbon atoms, halogen (i.e., fluorine, chlorine, bromine, or iodine), hydroxyl, or nitro groups, examples of which include phenyl, naphthyl, biphenyl, fluorenyl, and furyl, thienyl, pyridyl, quinolinyl, isoquinolinyl, indolyl, isoindolyl, triazolyl, pyrrolyl, tetrazolyl, imidazolyl, pyrazolyl, oxazolyl, and thiazolyl.

[0017] The term "polymer" refers to a molecule having a structure that includes multiple repeating units that are actually or conceptually derived from one or more monomers. The term "monomer" refers to a low molecular weight molecule that can combine with other molecules to form a polymer. The term "polymer" includes homopolymers and copolymers and homopolymers or copolymers that can form in miscible blends, e.g., by coextrusion or by reaction. The term "polymer" includes random polymers, block polymers, graft polymers, and star polymers. The term "polymer" includes oligomers.

[0018] A "monomer unit" of a polymer or oligomer is a segment of the polymer or oligomer that is derived from a single monomer.

[0019] The term "crosslinking" refers to joining polymer chains together via covalent chemical bonds (usually by crosslinking molecules or groups) to form a network polymer. Crosslinked polymers are generally characterized by insolubility but can be swellable in the presence of a suitable solvent. The term "crosslinking" includes partial crosslinking.

[0020] The terms "curable," "curing," and "cured" refer to forming polymer chains from one or more monomers.

[0021] The term "ceramic" refers to glass, crystalline ceramics, glass ceramics, and combinations thereof.

[0022] 3D printing (also known as "additive manufacturing") refers to a method of forming a three-dimensional object by sequentially depositing materials (usually by generating successive layers of material) within a defined area. The object is typically fabricated under computer control from a 3D model or other electronic data source by an additive printing device (commonly referred to as a 3D printer).

[0023] The foregoing summary of the disclosure is not intended to describe every disclosed embodiment or every implementation of the disclosure. The following description more specifically illustrates exemplary embodiments. Accordingly, it should be understood that the drawings and the following description are for illustrative purposes only and should not be construed as unduly limiting the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosure can be more fully understood in connection with the following detailed description of various embodiments of the disclosure with reference to the accompanying drawings, in which:

[0025] Figure 1 is a photograph of Example 4 after dispensing; and

[0026] Figure 2 is a photograph of Example 4 after dispensing and curing. DETAILED DESCRIPTION

[0027] The curable composition of the present disclosure (which can be a capillary suspension) comprises particles in an amount of 25 volume % (vol%) to 70 volume % based on the total volume of the curable composition, a primary liquid phase in an amount of 25 volume % to 74.8 volume % based on the total volume of the curable composition, and a secondary liquid phase in an amount of 0.15 volume % to 20 volume % based on the total volume of the curable composition. It should be understood that the total volume % of the curable composition cannot be higher than 100%. Thus, when the curable composition comprises more than 55 volume % of particles, it must comprise less than 20 volume % of the secondary liquid phase. In some embodiments, the curable composition comprises particles in an amount of 25 volume % to 65 volume %, 25 volume % to 60 volume %, 35 volume % to 60 volume %, or 35 volume % to 55 volume % based on the total volume of the curable composition. In some embodiments, the curable composition comprises a primary liquid phase in an amount of 30 volume % to 74.8 volume %, 35 volume % to 74.8 volume %, 40 volume % to 70 volume %, or 38 volume % to 65 volume % based on the total volume of the curable composition. In some embodiments, the curable composition comprises a secondary liquid phase in an amount of 0.2 volume % to 20 volume %, 0.5 volume % to 20 volume %, 0.4 volume % to 10 volume %, 0.4 volume % to 5 volume %, or 0.4 volume % to 2 volume % based on the total volume of the composition. In some embodiments, the curable composition comprises particles in an amount of 35 volume % to 60 volume % based on the total volume of the composition; a primary liquid phase in an amount of 38 volume % to 64.6 volume % based on the total volume of the composition; and a secondary liquid phase in an amount of 0.4 volume % to 2 volume % based on the total volume of the composition. In some embodiments, the particles, the primary liquid phase, and the secondary liquid phase account for at least 90 volume %, 95 volume %, 96 volume %, 97 volume %, 98 volume %, or 99 volume % and at most 100 volume % of the composition.

[0028] In some embodiments, the particles are hollow particles (e.g., hollow ceramic microspheres or hollow polymer microspheres), and are present in an amount of 5 weight % (wt%) to 30 weight %, 10 weight % to 25 weight %, or 10 weight % to 20 weight % based on the total weight of the curable composition, the primary liquid phase is present in an amount of 45 weight % to 94.5 weight %, 50 weight % to 89.5 weight %, or 60 weight % to 85 weight %, and the secondary liquid phase is present in an amount of 0.5 weight % to 35 weight %, 0.5 weight % to 20 weight %, or 0.5 weight % to 5 weight %. The hollow particles generally have a density less than that of the primary and secondary liquid phases.

[0029] A variety of particles can be used in the curable compositions of the present disclosure, and the curable compositions can be capillary suspensions. Examples of suitable particles include inorganic filler particles, hollow particles, porous particles, ceramic particles, hollow ceramic particles, polymer particles, hollow polymer particles, surface-modified particles, metal particles, hollow metal particles, carbon nanotubes, polymer composite particles, coated particles, coated hollow particles, and combinations thereof. Suitable particles can have various particle sizes, particle shapes, particle size distributions, and particle aspect ratios. The particles can have regular or irregular shapes and can be generally spherical, rod-shaped, or plate-shaped. Suitable inorganic fillers include metal oxides, metal carbides, metal nitrides, metal carbides, and metal phosphates. Suitable ceramics include barium titanate, alumina, boron nitride, zirconia, silicon nitride, and silicon carbide. Suitable polymer particles include polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene, perfluoroalkoxy alkane, fluorinated elastomer, perfluoroelastomer, polyethylene, polypropylene, polyamide 12, polyamide 11, polyetheretherketone, polyetherketone, and polyetherketone. Suitable metal particles include silver, iron, steel, copper, nickel, and titanium.

[0030] The particles can be, for example, conductive particles, thermally conductive particles, electrically insulating particles, thermally insulating particles, lightweight particles, flame retardant particles, toughening particles, water-absorbing particles, water-repellent particles, piezoelectric particles, magnetic particles, dielectric particles, and any combination thereof. These properties can be provided by the particles themselves or by coatings on particles of different compositions. For example, non-conductive particles can be coated with a conductive coating and / or a thermally conductive coating. Suitable conductive particles include metal particles and carbon black particles. Suitable thermally conductive particles include boron nitride particles, graphite particles, alumina particles, zinc oxide particles, aluminum nitride particles, silver particles, and ceramic microspheres. Suitable electrically insulating particles include boron nitride particles, talc particles, and particles coated with amorphous silica. Suitable thermally insulating particles include hollow ceramic microspheres (e.g., glass bubbles). Suitable flame retardant particles include aluminum trihydrate, magnesium hydroxide, dolomite, and hydromagnesite. Suitable water-absorbing particles include sodium polyacrylate, polyacrylamide copolymer, ethylene maleic anhydride, and polyvinyl alcohol. Suitable water-repellent particles include any of the above fluoropolymers. Suitable piezoelectric particles include polyvinylidene fluoride, polyamide, polyvinylidene chloride, lead zirconate titanate, lead titanate, quartz, potassium niobate, and barium titanate. Suitable magnetic particles include iron, nickel, cobalt, and neodymium iron boron. Suitable dielectric particles include polyvinylidene fluoride, polyethylene, polytetrafluoroethylene, ceramics, steatite, alumina, mica, inflated particles, barium titanate, titanium oxide, strontium titanate, and zirconium oxide. Any of these particles can be hollow or solid. In some embodiments, the particles include at least one of ceramic microspheres, polymer microspheres, metal particles, conductive particles, or thermally conductive particles, any of which can be hollow or solid. In some embodiments, the particles are not conductive. In some embodiments, the particles are not thermally conductive. The particles are available from a variety of commercial sources. For example, alumina particles can be obtained under the trade name "BAK" from Bestry Perfomance Materials, Shagnhai, China.

[0031] Hollow particles can be used, for example, for lightweighting. Examples of suitable hollow particles include hollow ceramic microspheres (i.e., glass bubbles), hollow inorganic beads, hollow inorganic particles or nanoparticles, hollow silica particles or nanoparticles, hollow carbide particles (e.g., silicon carbide particles, boron carbide particles), hollow nitride particles (e.g., carbon nitride particles, aluminum nitride particles, silicon nitride particles, boron nitride particles), hollow polymer particles, hollow aluminum balloons, and combinations thereof. In some embodiments, the particles include at least one of hollow ceramic microspheres or hollow polymer particles. In some embodiments, the particles include hollow glass microspheres.

[0032] Available hollow glass microspheres include those sold by 3M Company under the trade name "3M Glass Bubbles" (e.g., grades K1, K15, S15, S22, K20, K25, S32, K37, S38, S38HS, S38XHS, K46, A16 / 500, A20 / 1000, D32 / 4500, H50 / 10000, S60, S60HS, and iM30K); glass bubbles sold by Potters Industries, Valley Forge, PA (a subsidiary of PQ Corporation) under the trade names "Q-Cel Hollow Spheres" (e.g., grades 30, 6014, 6019, 6028, 6036, 6042, 6048, 5019, 5023, and 5028) and "Sphericel Hollow Glass Spheres" (e.g., grades 110P8 and 60P18); and hollow glass particles sold by Silbrico Corp., Hodgkins, IL under the trade name "SIL-CELL" (e.g., grades SIL 35 / 34, SIL-32, SIL-42, and SIL-43). Available hollow ceramic microspheres also include aluminosilicate microspheres (i.e., coal balls) extracted from fly ash collected from coal-fired power plants. Available coal balls include those sold by Sphere One, Inc., Chattanooga, TN under the trade name "EXTENDOSPHERES Hollow Spheres" (e.g., grades XOL-200, XOL-150, SG, MG, CG, TG, HA, SLG, SL-150, 300 / 600, 350, and FM-1); and those sold by 3M Company under the trade name "3M Hollow Ceramic Microspheres" (e.g., grades G-3125, G-3150, and G-3500). Available hollow ceramic microspheres also include perlite microspheres, such as those available from, for example, Silbrico Corporation, Hodgkins, IL.Available hollow polymer particles include elastomeric particles that are available, for example, under the trade name "EXPANCEL" from Akzo Nobel, Amsterdam, The Netherlands.

[0033] Available hollow ceramic microspheres (e.g., glass bubbles) have an average true density in the range of 0.1 g / cm 3 to 1.2 g / cm 3 , 0.1 g / cm 3 to 1.0 g / cm 3 , 0.1 g / cm 3 to 0.8 g / cm 3 , 0.1 g / cm 3 to 0.5 g / cm 3 or, in some embodiments, 0.1 g / cm 3 to 0.3 g / cm 3 The term "average true density" is the quotient obtained by dividing the mass of a glass bubble sample by the true volume of the glass bubbles of that mass measured by a gas pycnometer. "True volume" is the total volume of the aggregate of glass bubbles, not the bulk volume. For the purposes of the present disclosure, the average true density is measured using a pycnometer in accordance with ASTM D2840-69, "Average True Particle Density of Hollow Microspheres". The pycnometer is available, for example, under the trade name "Accupyc 1330 Pycnometer" from Micromeritics, Norcross, Georgia, USA. The measurement accuracy of the average true density is typically 0.001 g / cc. Thus, each of the density values given above can be ± one percent.

[0034] The median particle size of the particles useful in practicing the present disclosure can be, for example, in the range of 0.1 micrometers (μm) to 250 μm (in some embodiments, 5 μm to 250 μm, 5 μm to 150 μm, 10 μm to 120 μm, 20 μm to 100 μm, or 50 μm to 100 μm). The particles can have a multimodal (e.g., bimodal or trimodal) particle size distribution (e.g., to improve packing efficiency), as described, for example, in U.S. Patent Application Publication No. 2002 / 0106501A1 (Debe). As used herein, the term particle size represents the maximum dimension of the particle and is considered equivalent to the diameter and height of the microsphere. For the purposes of the present disclosure, the volume median particle size (D50) is determined by laser diffraction of the glass bubbles dispersed in degassed deionized water. A laser diffraction particle size analyzer can be purchased, for example, from Micromeritics under the trade name "SATURN DIGISIZER". When the curable composition is a capillary suspension, it may be useful for the particle size of the particles to be greater than the droplet size of the secondary liquid phase in the capillary suspension. The droplet size can be determined by optical microscopy.

[0035] It may be useful, for example, for at least a first portion of the conductive filler to have a median (i.e., D50) particle size in the range of 20 micrometers to 100 micrometers or 50 micrometers to 90 micrometers of at least 20 micrometers. Additionally, at least a second portion of the conductive filler can have a median particle size in the range of 5 micrometers to 20 micrometers or 5 micrometers to 15 micrometers. It may also be useful for a third portion of the conductive filler to have a median particle size of up to 5 micrometers, in some embodiments, in the range of 0.1 micrometers to 5 micrometers, 0.5 micrometers to 5 micrometers, or 0.5 micrometers to 2.5 micrometers. Inclusion of a conductive filler having a plurality of particle size distributions may be useful for achieving a high loading amount of the conductive filler in the composition.

[0036] The particles described above in any of their embodiments can be surface-modified or coated. Suitable coated particles include those having a metal coating or a metal oxide coating. Inorganic particles can be surface-modified to have organic groups on the surface. The organic groups can be polymerizable groups (e.g., amino-alkyl or (meth)acrylate groups) or nonpolar groups (e.g., alkyl groups). The organic groups can be formed on the surface of the inorganic particles by covalent bonds, in some embodiments by siloxane bonds, in a manner such that the inorganic particles are reacted with a silane containing at least one hydrolyzable functional group and at least one non-hydrolyzable functional group. Suitable silanes of this type include, for example, alkoxysilanes represented by the following formula:

[0037] (R 4 O) m -Si-(R 5 ) 4-m

[0038] wherein each R 4 is independently an alkyl group having from 1 to 6 (in some embodiments, 1 to 4 or 1 to 2) carbon atoms. m is from 1 to 3 (in some embodiments, 2 or 3 or 3); and each R 5 is independently an alkyl having from 1 to 30 carbon atoms (in some embodiments, 1 to 25, 4 to 22, 4 to 18 or 8 to 18 carbon atoms). Hydrophobic coatings can also be applied to the particles using emulsions, suspensions or solutions of hydrocarbon waxes, polyethylene waxes, fluorinated hydrocarbon waxes, siloxanes or combinations thereof.

[0039] Available methods of treating the particles with a compound of formula (R 4 O) m -Si-(R 5 ) 4-m include combining the compound with the particles in a medium comprising water. Hydrolysis of the hydrolyzable groups in the compound of formula (R 4 O) m -Si-(R 5 ) 4-m typically produces silanol groups which participate in condensation reactions to form siloxanes and / or participate in bonding interactions with silanol groups on silica-containing fillers. Hydrolysis can occur, for example, in the presence of water, optionally in the presence of an acid or a base. The water necessary for hydrolysis is typically added to a composition comprising the compound of (R 4 O) m -Si-(R 5 ) 4-m and the particles, but in some cases, water can be adsorbed onto the surface of the filler or can be present in the atmosphere to which the filler is exposed (e.g., an atmosphere having a relative humidity of at least 10%, 20%, 30%, 40% or even at least 50%). In some embodiments, it is useful to surface treat the particle surface at elevated temperature for about 1 to 24 hours under acidic or basic conditions. The particles can then be separated from the liquid phase and dried. Additional methods for preparing hollow non-porous particles having a hydrophobic coating or surface modification are described, for example, in U.S. Patent Application Publication No. 2016 / 0083628 (Heimink et al.).

[0040] The main liquid phase in the curable composition (which can be a capillary suspension) of the present disclosure comprises a first monomer comprising at least one of n-butyl acrylate, an alkyl acrylate monomer or an alkyl methacrylate monomer, wherein the alkyl is straight-chain or branched and has at least five carbon atoms. Examples of suitable (meth)acrylate alkyl esters include those represented by formula I:

[0041] CH2=C(R')COOR (I)

[0042] In Formula I, R is straight-chain or branched-chain and has 4 to 32 carbon atoms. In some embodiments, the alkyl group contains 4 to 25, 6 to 20, 6 to 18, 6 to 16, 6 to 12, or 8 to 12 carbon atoms. Examples of the alkyl group include n-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, 2-ethylhexyl, 2-octyl, and 2-propylheptyl. In Formula I, R' is hydrogen or methyl, and in some embodiments is hydrogen.

[0043] In some embodiments, the first monomer comprises at least one of the following: n-butyl acrylate, hexyl acrylate, heptyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate, isodecyl acrylate, n-dodecyl acrylate, myristyl acrylate, isomyristyl acrylate, n-tridecyl acrylate, n-tetradecyl acrylate, stearyl acrylate, isostearyl acrylate, 17-methyl-1-heptadecyl acrylate, 2-methylbutyl acrylate, 4-methyl-2-pentyl acrylate, and the methacrylate of any of the foregoing acrylates other than n-butyl acrylate. In some embodiments, the first monomer comprises at least one of the following: isooctyl acrylate, 2-ethylhexyl acrylate, 2-propylheptyl acrylate, 2-octyl acrylate, the methacrylate of the foregoing acrylates, or n-butyl acrylate. In some embodiments, the first monomer comprises at least one of the following: isooctyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, or 2-propylheptyl acrylate. 2-Octyl can be prepared by conventional techniques and / or can be derived from biomaterials, which means that at least a part (e.g., at least 50% by weight) of its chemical structure is from biomaterials. In some embodiments, the first monomer comprises at least one of isooctyl acrylate or 2-ethylhexyl acrylate.

[0044] Suitable first monomers also include a mixture of at least two or at least three structural isomers of the secondary alkyl (meth)acrylate of Formula II:

[0045]

[0046] wherein R 1 and R 2 are each independently a C1 to C 30 saturated linear alkyl group; the sum of the number of carbon atoms in R 1 and R 2 is 7 to 31, and R 3 is H or CH3. In some embodiments, R 1 and R 2The total carbon number therein can be 7 to 27, 7 to 25, 7 to 21, 7 to 17, 7 to 11, 7, 11 to 27, 11 to 25, 11 to 21, 11 to 17, 7, or 11. Methods for making and using such monomers and monomer mixtures are described in U.S. Patent No. 9,102,774 (Clapper et al.). A mixture of monomers of one or more of Formula I, Formula II, or a combination of Formula I and II can be used for the first monomer. In some embodiments, at least one of the alkyl acrylate monomers or alkyl methacrylate monomers comprises at least one acrylate (as opposed to methacrylate).

[0047] The acrylic polymer materials contained in known pressure-sensitive adhesives are often prepared from one or more nonpolar (meth)acrylate monomers (e.g., any of the aforementioned first monomers) having a relatively low glass transition temperature (Tg) (i.e., the Tg of the monomer as measured for the homopolymer prepared from the monomer) plus various optional monomers. The terms "glass transition temperature" and "Tg" are used interchangeably and refer to the glass transition temperature of the material or mixture.

[0048] In some embodiments of the curable compositions (which may be capillary suspensions) of the present disclosure, the main liquid phase further comprises a second monomer. In some embodiments, the second monomer comprises a polar functional group and a polymerizable carbon-carbon double bond. Examples of polar functional groups include carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, ketones, amides, amines, alcohols, ethers, and combinations thereof. The polymerizable group may be a (meth)acryloyl group or an ethylenic group that is not a (meth)acryloyl group (i.e., a CH2═CH2-group). In some embodiments, the second monomer is a (meth)acrylate having a polar functional group. Examples of suitable monomers having a polar functional group include acrylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, oleic acid, (meth)acrylic acid-β-carboxyethyl ester) and their salts, sulfonic acids (e.g., 2-sulfoethyl methacrylate, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid) and their salts, phosphonic acids (e.g., vinylphosphonic acid) and their salts, acrylamides (e.g., acrylamide, methacrylamide, N-ethylacrylamide, N-hydroxyethylacrylamide, 3-hydroxypropylacrylamide, N-isopropylacrylamide, N-tert-octylacrylamide, N-octylacrylamide, N-tert-butylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dipropylacrylamide, N,N-dibutylacrylamide, N-ethyl-N-dihydroxyethylacrylamide, and methacrylamides of the foregoing acrylamides), hydroxy- or amino-substituted acrylates (e.g., 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, 8-hydroxyoctyl acrylate, 10-hydroxydecyl acrylate, 12-hydroxylauryl acrylate, methyl (4-hydroxymethylcyclohexyl)acrylate, ethoxylated hydroxyethyl methacrylate, such as monomers commercially available under the trade names CD570, CD571, CD572 from Sartomer, dimethylaminoethyl acrylate, tert-butylaminoethyl acrylate, aminoethyl acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate, and methacrylates of the foregoing acrylates), N-vinyl-2-pyrrolidone, N-vinylcaprolactam, (meth)acrylonitrile ethyl cyanoacrylate, acrylonitrile, maleic anhydride, and combinations thereof. Salts of any suitable acidic group may be used. In many embodiments, the cation of the salt is an alkali metal ion (e.g., sodium, potassium, or lithium ion), an alkaline earth metal ion (e.g., calcium, magnesium, or strontium ion), an ammonium ion, or an ammonium ion substituted with one or more alkyl or aryl groups. Still other suitable polar second monomers having an ethylenic unsaturation comprise those having a single ethylenic unsaturation and an ether group (i.e., a group comprising at least one alkylene-oxy-alkylene of the formula –R–O–R–, where each R is an alkylene having 1 to 4 carbon atoms).Examples of monomers containing an ether group include, but are not limited to, alkoxylated (meth)acrylic acid alkyl esters such as cabester acrylate, 2-methoxyethyl acrylate, and 2-ethoxyethyl acrylate; and poly(alkylene oxide) acrylates such as poly(ethylene oxide) acrylate and poly(propylene oxide) acrylate having end groups such as a hydroxyl group and an alkoxy group. In some embodiments, the second monomer contains a heterocyclic group. Examples of suitable second monomers containing an alicyclic group include tetrahydrofurfuryl (meth)acrylate, N-vinyl-2-pyrrolidone, and N-vinylcaprolactam. A variety of monomers having polar functional groups can be used, for example, to increase the adhesion of the resulting pressure-sensitive adhesive to a substrate or a backing layer, enhance the cohesive strength of the resulting pressure-sensitive adhesive, or both.

[0049] Combinations of any of the above polar monomers can be useful. A variety of suitable amounts of polar monomers can be used to prepare the pressure-sensitive adhesive. In some embodiments, the polar monomer is present in an amount of up to 15 wt% based on the total weight of the polymerizable monomers. In some embodiments, the polar monomer is present in an amount of at least 0.1 wt%, at least 0.5 wt%, at least 1 wt%, or at least 2 wt%, or even at least 3 wt% based on the total weight of the polymerizable monomers. Thus, in some embodiments, the polar monomer is present in an amount in the range of 0.1 wt% to 15 wt%, 0.5 wt% to 15 wt%, 1.0 wt% to 10 wt%, 2.0 wt% to 8.0 wt%, 2.5 wt% to 6.0 wt%, or 3.0 wt% to 6.0 wt% based on the total weight of the polymerizable monomers. In some embodiments, the amount of the polar monomer is up to 10 wt% or up to 5 wt%. For example, based on the total weight of the polymerizable monomers, the polar monomer can be present in an amount in the range of 0.5 wt% to 10 wt%, 1 wt% to 10 wt%, 0 wt% to 5 wt%, 0.5 wt% to 5 wt%, or 1 wt% to 5 wt%.

[0050] In some embodiments, the second monomer comprises a second nonpolar monomer having a polymerizable carbon-carbon double bond. In some embodiments, the second monomer comprises an alkyl group having fewer than four or at most four carbon atoms. Suitable second monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl methacrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, vinyl acetate, vinyl pivalate, vinyl propionate, and vinyl valerate. In some embodiments, the second monomer comprises an aromatic group. Examples of suitable second monomers comprising an aromatic group include phenyl (meth)acrylate, benzyl (meth)acrylate, 2-biphenylhexyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, vinyl benzoate, vinyl 4-tert-butylbenzoate, styrene and its derivatives, such as alkyl-substituted styrenes and other substituted styrenes (e.g., α-methylstyrene, 4-tert-butoxystyrene, 4-(tert-butyl)styrene, 4-chloromethylstyrene, chloromethylstyrene, 3-chlorostyrene, 2-(diethylamino)ethylstyrene, 2-methylstyrene, 4-methylstyrene, and 4-nitrostyrene), and combinations thereof. In some embodiments, the second monomer comprises a cycloalkyl group. Examples of suitable second monomers comprising a cycloalkyl group include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, isophorone (meth)acrylate, cyclohexyl (meth)acrylate, and any combination or mixture thereof. In some embodiments, the second monomer comprises at least one of isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, isophorone (meth)acrylate, and combinations thereof. In some embodiments, the second monomer comprises isobornyl (meth)acrylate, and in some embodiments comprises isobornyl acrylate.

[0051] In some embodiments, when formed into a homopolymer (i.e., a polymer prepared using a single polymerizable material), the second monomer (e.g., the second nonpolar monomer) has a relatively high Tg. When formed into a homopolymer, these monomers generally have a glass transition temperature (Tg) of at least 20 °C, or at least 25 °C, or at least 30 °C, or at least 40 °C, or even at least 50 °C. Such second monomers can be useful for adjusting the Tg of the polymerizable material and / or for providing enhanced adhesion strength in the resulting pressure-sensitive adhesive.

[0052] In some embodiments, the second monomer comprises a polymerizable carbon-carbon double bond and at least one of the following: a polar functional group, an alicyclic group, a heterocyclic group, an aromatic group, or an alkyl group having fewer than four carbon atoms. It should be understood that any combination of the above second monomers can be used. For clarity, a combination of two or more second monomers may hereinafter be referred to as the second monomer and additional monomers, where the additional monomers can be any of the above second monomers.

[0053] In some embodiments of the curable composition, which can be a capillary suspension, the first monomer is present in the main liquid phase in an amount of at least 50% by weight, based on the total weight of the main liquid phase. In some embodiments, the main liquid phase comprises from 50% to 99.5% by weight or from 60% to 90% by weight of the first monomer and from 0.5% to 50% by weight, from 1.0% to 50% by weight, from 3.0% to 40% by weight, from 5.0% to 35% by weight, or from 10% to 30% by weight of one or more of the above-described second monomers, based on the total weight of the main liquid phase. Generally, the first monomer is used in an amount of from 75% to 100% by weight, based on the total weight of the monomers used to prepare the acrylic polymer, and one or more of the second monomers as described above are used in an amount of from 0% to 25% by weight, based on the total weight of the monomers used to prepare the acrylic polymer. In some embodiments, the first monomer is used in an amount of at least 80% by weight, 85% by weight, 90% by weight, 92% by weight, 95% by weight, 97% by weight, 98% by weight, or 99% by weight, based on the total weight of the monomers, and one or more of the second monomers are used in an amount of at most 20% by weight, 15% by weight, 10% by weight, 8% by weight, 5% by weight, 3% by weight, 2% by weight, or 1% by weight, based on the total weight of the monomers.

[0054] In some embodiments of the curable composition of the present disclosure, which can be a capillary suspension, the main liquid phase further comprises a crosslinking monomer having at least two polymerizable carbon-carbon double bonds. The crosslinking monomer can be used, for example, to increase the cohesive strength and tensile strength of the resulting pressure-sensitive adhesive. Suitable crosslinking monomers can have more than 2, for example, at least 3 or 4 polymerizable carbon-carbon double bonds (in some embodiments, (meth)acryloyl groups). Crosslinking agents having multiple (meth)acryloyl groups include di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, and penta(meth)acrylates. Mixtures of crosslinking monomers can also be used.

[0055] Examples of suitable crosslinking monomers having two acryloyl groups include: ethylene glycol diacrylate, 1,3-propanediol diacrylate, 1,9-nonanediol diacrylate, 1,12-dodecanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, butanediol diacrylate, bisphenol A diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polyethylene / polypropylene copolymer diacrylate, polybutadiene diacrylate, neopentyl glycol hydroxypivalate modified caprolactone diacrylate, and dimethacrylate of any of the foregoing diacrylates, and combinations thereof. Examples of crosslinking monomers having three or four (meth)acryloyl groups include: trimethylolpropane triacrylate (e.g., commercially available under the trade name TMPTA-N from Cytec Industries, Inc., Smyrna, GA and under the trade name SR-351 from Sartomer Company, Exton, PA), pentaerythritol triacrylate (e.g., commercially available under the trade name SR-444 from Sartomer Company), tris(2-hydroxyethyl isocyanurate) triacrylate (commercially available under the trade name SR-368 from Sartomer Company), a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (e.g., commercially available under the trade names PETIA (where the ratio of tetraacrylate to triacrylate is approximately 1:1) and PETA-K (where the ratio of tetraacrylate to triacrylate is approximately 3:1) from Cytec Industries), pentaerythritol tetraacrylate (e.g., commercially available under the trade name SR-295 from Sartomer Company), di-trimethylolpropane tetraacrylate (e.g., commercially available under the trade name SR-355 from Sartomer Company), and ethoxylated pentaerythritol tetraacrylate (e.g., commercially available under the trade name SR-494 from Sartomer Company). Suitable examples having five (meth)acryloyl groups include dipentaerythritol pentaacrylate (e.g., commercially available under the trade name SR-399 from Sartomer Company). The methacrylates of the foregoing acrylates and combinations thereof are also useful.

[0056] Further suitable polyfunctional crosslinking monomers include polyfunctional acrylate oligomers containing two or more acrylate groups. The polyfunctional acrylate oligomers can be urethane acrylate oligomers, epoxy acrylate oligomers, polyester acrylates, polyether acrylates, polypropylene acrylate acrylates, methacrylate esters of any of the foregoing acrylates, or combinations thereof. Examples of such crosslinkers include poly(alkylene oxide) having at least two acryloyl groups (e.g., polyethylene glycol diacrylate commercially available from Sartomer Company, such as SR210, SR252, and SR603) and poly(urethane) having at least two (meth)acryloyl groups (e.g., polyurethane diacrylate obtained from Sartomer Company, such as CN9018). When present, the crosslinking monomer is present in the main liquid phase in an amount of no more than 5 wt%, 4 wt%, 3 wt%, or 2 wt% based on the total weight of the main liquid phase. In some embodiments, the crosslinking monomer is present in an amount of 0.002 parts to 2 parts per hundred parts of the first monomer and the second monomer (e.g., about 0.01 parts to about 0.5 parts or about 0.05 parts to 0.15 parts per hundred parts of the first monomer and the second monomer).

[0057] Other types of crosslinking agents can be used, in addition to those having at least two polymerizable carbon-carbon double bonds. The crosslinking agent can have multiple groups that react with functional groups on the second monomer such as acidic groups. For example, monomers having multiple aziridinyl groups that react with carboxyl groups can be used. For example, the crosslinking agent can be a bisamide crosslinking agent as described in U.S. Patent No. 6,777,079 (Zhou et al.). In other crosslinking methods, heat crosslinking agents can be used, optionally in combination with suitable accelerators and retarders. Suitable heat crosslinking agents for use herein include isocyanates, more specifically trimeric isocyanates and / or sterically hindered isocyanates without blocking agents, and epoxy compounds such as epoxy-amine crosslinking agent systems. Advantageous crosslinking agent systems and methods are described, for example, in DE202009013255 U1 published on March 18, 2010, U.S. Patent Nos. 5,877,261 (Harder et al.), 7,910,163 (Zollner et al.), 7,935,383 (Zollner et al.), 8,449,962 (Prenzel et al.), 8,802,777 (Zollner et al.), 10,457,791 (Czerwonatis et al.), 9,505,959 (Grattner et al.), and 9,896,605 (Zollner et al.) and in the description of U.S. Patent Application Publication No. 2011 / 0274843 (Grittner et al.). Suitable accelerator and retarder systems are described, for example, in U.S. Patent No. 9,200,129 (Czerwonatis et al.). If present, the crosslinking agent can be used in any suitable amount. In many aspects, the crosslinking agent is present in an amount of up to 5 wt%, 4 wt%, 3 wt%, or 2 wt% based on the total weight of the main liquid phase. In some embodiments, the crosslinking agent is present in an amount in the range of 0 wt% to 5 wt%, 0.01 wt% to 5 wt%, 0.05 wt% to 5 wt%, 0 wt% to 3 wt%, 0.01 wt% to 3 wt%, 0.05 wt% to 3 wt%, 0 wt% to 1 wt%, 0.01 wt% to 1 wt%, or 0.05 wt% to 1 wt% based on the total weight of the main liquid phase.

[0058] Crosslinking can also be achieved in pressure-sensitive adhesives using high-energy electromagnetic radiation such as γ or electron beam radiation.

[0059] In some embodiments, the curable composition (which can be a capillary suspension) further comprises a free radical initiator. The initiator for free radical polymerization is typically added to the main liquid phase. The polymerization initiator can be a thermal initiator, a photoinitiator, or both. Any suitable thermal initiator or photoinitiator known for free radical polymerization reactions can be used. Based on the total weight of the first monomer and optionally the second monomer and the crosslinking monomer, the initiator is typically present in an amount in the range of 0.01 wt% to 5 wt%, in the range of 0.01 wt% to 2 wt%, in the range of 0.01 wt% to 1 wt%, or in the range of 0.01 wt% to 0.5 wt%.

[0060] In some embodiments, the free radical initiator is a thermal initiator. Suitable initiators soluble in the main liquid phase include: various azo compounds such as those commercially available under the trade name VAZO from E.I. DuPont de Nemours Co., including VAZO 67 (which is 2,2'-azobis(2-methylbutyronitrile)), VAZO 64 (which is 2,2'-azobis(isobutyronitrile)), and VAZO 52 (which is 2,2'-azobis(2,4-dimethylvaleronitrile)); and various peroxides such as benzoyl peroxide, cyclohexanone peroxide, lauroyl peroxide, and mixtures thereof.

[0061] Suitable photoinitiators include those available from IGM Resins, Waalwijk, The Netherlands under the trade name OMNIRAD, and include 1-hydroxycyclohexyl phenyl ketone (OMNIRAD 184), 2,2-dimethoxy-1,2-diphenylethan-1-one (OMNIRAD 651), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (OMNIRAD 819), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropan-1-one (OMNIRAD 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one (OMNIRAD 369), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (OMNIRAD 907), and 2-hydroxy-2-methyl-1-phenylpropan-1-one (OMNIRAD 1173), the oligo[2-hydroxy-2-methyl-1-[4-(1-methylethenyl)phenyl]propanone] available from IGM Resins under the trade name ESACURE KIP 150, and the bifunctional α-hydroxy ketones available from IGM Resins under the trade names ESACURE ONE and ESACURE KIP 160 (2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropanoyl)phenoxy]phenyl]-2-methylpropanone). Bifunctional α-hydroxy ketones mean that the photoinitiator includes two α-hydroxy ketone groups. Polyfunctional α-hydroxy ketones mean that the photoinitiator includes two or more α-hydroxy ketone groups. Additional suitable photoinitiators include benzyldimethyl ketal, 2-methyl-2-hydroxyacetophenone, benzoin methyl ether, benzoin isopropyl ether, anisoin methyl ether, aromatic sulfonyl chlorides, photoactive oximes, and combinations thereof.

[0062] Also suitable photoinitiators include monoethylenically unsaturated aromatic ketones. Examples of such photoinitiators include polyfunctional benzophenones (e.g., acryloyloxybenzophenone (ABP), p-acryloyloxyethoxybenzophenone (AEBP), p-N-(acryloyloxyethyl)-carbamoylethoxybenzophenone, 4-acryloyloxy diethoxy-4-chlorobenzophenone) and acetophenones (e.g., p-acryloyloxyacetophenone and o-acrylamidoacetophenone). Still other suitable photoinitiators include triazines such as 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-triazine, the triazine described in U.S. 4,330,590 (Vesley), and 2,4-bis(trichloromethyl)-6-naphthyl-s-triazine and 2,4-bis(trichloromethyl)-6-(4-methoxy)naphthyl-s-triazine described in U.S. 4,329,384 (Vesley).

[0063] In some embodiments of the curable composition (which can be a capillary suspension) of the present disclosure, the main liquid phase further includes a chain transfer agent, which can be used, for example, to control the molecular weight of the resulting acrylic polymer. Examples of chain transfer agents that can be used include carbon tetrabromide, alcohols, thiols such as isooctyl thioglycolate, and mixtures thereof. If used, based on the total weight of the first monomer and optionally the second monomer and the crosslinking monomer, the main liquid phase can include up to 0.5 wt% of the chain transfer agent. For example, based on the total weight of the first monomer and optionally the second monomer and the crosslinking monomer, the main liquid phase can contain 0.01 wt% to 0.5 wt%, 0.05 wt% to 0.5 wt%, or 0.05 wt% to 0.2 wt% of the chain transfer agent.

[0064] In some embodiments of the curable composition (which can be a capillary suspension), the main liquid phase further includes a polymer prepared by partial polymerization of the first monomer. In some embodiments, the polymer is prepared by partial polymerization of the first monomer, one or more second monomers, and / or one or more crosslinking monomers. The curable composition can be a solution of the polymer in the first monomer and optionally the second and / or crosslinking monomers, and can be, for example, about 3% to 15% polymerized. In some embodiments, based on the total weight of the curable composition, the curable composition contains at least 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt% of monomers. In some embodiments, the curable composition is exposed to ultraviolet radiation to provide a solution of the polymer in the first monomer. The solution of the polymer in the first monomer can also be made by partial free radical polymerization using a thermal initiator or other free radical sources as described above. The partial polymerization can be carried out by a variety of conventional free radical polymerization methods, which include solution, bulk (i.e., containing little or no solvent), dispersion, emulsion, and suspension methods. The reaction product of the partial polymerization can be a random or block copolymer.

[0065] Available solventless polymerization methods are disclosed in U.S. Patent No. 4,379,201 (Heilmann et al.). Initially, a portion of the photoinitiator can be used by exposing a mixture of a first monomer and optionally a second and / or crosslinking monomer to UV radiation in an inert environment for a time sufficient to form a coatable base slurry, and then adding additional second monomer and / or crosslinking monomer and the remaining photoinitiator to polymerize the mixture. The monomer can be any of the monomers in any of the amounts described above. This final slurry containing the crosslinker (e.g., which can have a Brookfield viscosity of about 500 centipoise (cps) to about 10,000 cps at 23°C, about 100 cps to about 6,000 cps at 23°C, or about 5,000 cps to about 7,500 cps at 23°C, as measured with a No. 4 LTV spindle at 60 revolutions per minute) can then be combined with additional additives (e.g., optionally a tackifying resin and a plasticizer, particles, and a secondary liquid phase as described below).

[0066] The primary liquid phase can include additional components, particularly nonpolar or polar liquids or solvents. The primary liquid phase can include an organic solvent or can be free or substantially free of an organic solvent. As used herein, the term "substantially free" with respect to an organic solvent means that the organic solvent is present in an amount of less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.2 wt%, or less than 0.1 wt% based on the weight of the primary liquid phase. Examples of organic solvents include methanol, tetrahydrofuran, ethanol, isopropanol, heptane, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, toluene, xylene, ethylene glycol alkyl ethers, and combinations thereof.

[0067] In some embodiments, the curable composition of the present disclosure (which can be a capillary suspension) further includes a tackifying resin. Tackifying resins, as well as plasticizers (i.e., plasticizing agents), are often added to adjust the Tg, adjust the storage modulus, and / or change the tack of the pressure-sensitive adhesive. A variety of tackifying resins commonly included in conventional pressure-sensitive adhesive compositions can be used. Any tackifying resin included in the curable composition is generally selected to be compatible with the primary liquid phase.

[0068] Suitable tackifying resins include rosin resins such as rosin acids and their derivatives (e.g., rosin esters); terpene resins such as polyterpenes (e.g., α-pinene-based resins, β-pinene-based resins, and limonene-based resins) and aromatic modified polyterpene resins (e.g., phenol-modified polyterpene resins); benzofuran-indene resins; and petroleum-based hydrocarbon resins such as C5-based hydrocarbon resins, C9-based hydrocarbon resins, C5 / C9-based hydrocarbon resins, dicyclopentadiene-based resins, and combinations thereof. If desired, the tackifying resin may be partially or fully hydrogenated. In some embodiments, the tackifying resin comprises at least one of a C5-based hydrocarbon resin, a C9-based hydrocarbon resin, or a C5 / C9-based hydrocarbon resin. In some embodiments, the tackifying resin comprises at least one of a hydrogenated terpene resin, a hydrogenated rosin resin, a hydrogenated C5-based hydrocarbon resin, a hydrogenated C9-based hydrocarbon resin, or a hydrogenated C5 / C9-based hydrocarbon resin.

[0069] Rosin ester tackifying resins are reaction products of various rosin acids and alcohols. Suitable rosin esters include methyl esters of rosin acids, triethylene glycol esters of rosin acids, glycerol esters of rosin acids, and pentaerythritol esters of rosin acids. Rosin acids and rosin ester tackifying resins may be commercially available, for example, under the trade names PERMALYN, STAYBELITE, and FORAL from Eastman Chemical Company, and under the trade names NUROZ and NUTAC from Newport Industries. Fully hydrogenated rosin resins may be commercially available, for example, under the trade name FORAL AX-E from Eastman Chemical Company. Partially hydrogenated rosin resins may be commercially available, for example, under the trade name STAYBELITE-E from Eastman Chemical Company.

[0070] Tackifying resins as hydrocarbon resins can be prepared from various petroleum-based raw materials. These raw materials can be aliphatic hydrocarbons (mainly C5 monomers, and there are some other monomers such as a mixture of trans-1,3-pentadiene, cis-1,3-pentadiene, 2-methyl-2-butene, dicyclopentadiene, cyclopentadiene, and cyclopentene), aromatic hydrocarbons (mainly C9 monomers, and there are some other monomers such as a mixture of vinyltoluene, dicyclopentadiene, indene, methylstyrene, styrene, and methylindene), or mixtures thereof. Tackifying resins derived from C5 monomers are called C5-based hydrocarbon resins, while those derived from C9 monomers are called C9-based hydrocarbon resins. Some tackifying resins are derived from a mixture of C5 and C9 monomers, or are blends of C5-based hydrocarbon tackifying resins and C9-based hydrocarbon tackifying resins. These tackifying resins can be called C5 / C9-based hydrocarbon tackifying resins.

[0071] C5-based hydrocarbon tackifying resins are commercially available under the trade names PICCOTAC and EASTOTAC from Eastman Chemical Company, under the trade name WINGTACK from CrayValley, under the trade name NEVTAC LX from Neville Chemical Company, and under the trade name HIKOREZ from Kolon Industries, Inc. C5-based hydrocarbon resins of various degrees of hydrogenation are commercially available under the trade name EASTOTAC from Eastman Chemical.

[0072] C9-based hydrocarbon resins are commercially available under the trade names PICCO, KRISTLEX, PLASTOLYN, PICCOTAC, and ENDEX from Eastman Chemical Company, under the trade name NORSOLENE from CrayValley, under the trade name NOVAREZ from Ruetgers N.V., and under the trade name HIKOTAC from Kolon Industries, Inc. These resins may be partially or fully hydrogenated. Prior to hydrogenation, C9-based hydrocarbon resins typically have about 40% aromatics, as measured by proton nuclear magnetic resonance. Hydrogenated C9-based hydrocarbon resins are commercially available, for example, under the trade names REGALITE and REGALREZ from Eastman Chemical, which are 50% to 100% (e.g., 50%, 70%, 90%, and 100%) hydrogenated. Partially hydrogenated resins typically have some aromatic rings.

[0073] Various C5 / C9-based hydrocarbon tackifying resins are commercially available under the trade name ARKON from Arakawa, under the trade name QUINTONE from Zeon, under the trade name ESCOREZ from Exxon Mobile Chemical, and under the trade names NURES and H-REZ from Newport Industries.

[0074] Any of the tackifying resins can be used in an amount of up to 100 parts relative to 100 parts of the first monomer and optionally the second monomer and additional monomers in the main liquid phase. In some embodiments, the tackifying resin can be used in an amount of up to 50 parts, up to 45 parts, up to 40 parts, up to 35 parts, or up to 30 parts relative to 100 parts of the first monomer and optionally the second monomer and additional monomers. Based on 100 parts of the first monomer and optionally the second monomer and additional monomers, the amount of the tackifier can be, for example, in the range of 3 parts to 50 parts, in the range of 3.5 parts to 45 parts, in the range of 4 parts to 40 parts, in the range of 4.5 parts to 35 parts, in the range of 5 parts to 30 parts, or in the range of 8 to 25 parts.

[0075] In some embodiments, the curable composition of the present disclosure (which can be a capillary suspension) further includes one or more plasticizers. The plasticizer is typically selected to be compatible (i.e., miscible) with the main liquid phase. Examples of suitable plasticizers include: various polyalkylene oxides (e.g., polyethylene oxide or propylene oxide), adipates, formates, phosphates, benzoates, phthalates, sulfonamides, naphthenic oils, and combinations thereof.

[0076] The secondary liquid phase in the curable composition (which may be a capillary suspension) of the present disclosure is generally any liquid phase that forms two phases with the primary liquid phase at a temperature of 30 °C or lower. Examples of suitable secondary liquid phases include water, aqueous solutions of acids (e.g., hydrochloric acid), alkyl alcohols (e.g., alkyl alcohols having 1 to 4 carbon atoms), polyols, glycerol, carbonate-based solvents (e.g., propylene carbonate), sulfoxides (e.g., dimethyl sulfoxide), sulfones (e.g., sulfolane), cyclohexene, polar polymerizable liquids (e.g., acrylic acid and methacrylic acid), ionic liquids (e.g., 2-hydroxyethylammonium formate, choline acetate, 1-benzyl-3-methylimidazolium 1,1,2,2-tetrafluoroethanesulfonate, 1-methyl-3-tetradecylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, trihexyltetradecylphosphonium chloride), polymerizable ionic liquids (e.g., 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide, 1-allyl-3-methylimidazolium chloride, 1-vinyl-3-butylimidazolium chloride, N,N,N,N-butyl dimethyl methacryloyloxyethylammonium bis(trifluoromethanesulfonyl)imide), deep eutectic mixtures (e.g., choline chloride / urea, such as choline chloride:urea 1:2, choline chloride:malonic acid 1:1, zinc chloride:acetamide 1:3; choline chloride / glycerol, such as choline chloride:glycerol 1:2, choline chloride lactate 1:2, proline:oxalic acid 3:1; choline chloride / ethylene glycol, such as choline chloride:ethylene glycol 1:2), polymerizable deep eutectic mixtures (e.g., choline / acrylic acid, such as choline chloride:acrylic acid 1:2, 1:4, and 1:6; tetramethylammonium chloride:acrylic acid 1:2, choline chloride:methacrylic acid 1:2, ethylammonium chloride:acrylic acid 1:1).5), wherein the ratios provided above for the eutectic mixtures are molar ratios, a liquid containing a dissolved salt (e.g., an aqueous solution of [2-(acryloyloxy)ethyl]trimethylammonium chloride, an aqueous solution of [2-(methacryloyloxy)ethyl]trimethylammonium chloride, and an aqueous or organic solvent solution of copper sulfate, copper acetate, or potassium permanganate), a non-polar polymerizable liquid (e.g., perfluoropolyether-urethane acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, tridecafluorohexylethyl methacrylate, 1H,1H,2H,2H-perfluorooctyl acrylate, which are commercially available from Solvay, Brussels, Belgium under the trade names FLUOROLINK MD 700 and FLUOROLINK AD 1700), a non-polar liquid (e.g., hydrofluoroethers such as those described in U.S. Patent No. 9,803,110 (Lee et al.), and those commercially available from 3M Company, St. Paul, MN under the trade names NOVEC 7100 Engineered Fluid, NOVEC 7200 Engineered Fluid, NOVEC 7300 Engineered Fluid, and NOVEC 7500 Engineered Fluid; perfluorinated liquids such as those commercially available from 3M Company under the trade names FLUORINERT Electronic Liquid FC-3283 and FLUORINERT Electronic Liquid FC-72), an oil (e.g., silicone oil, organic oil, vegetable oil, mineral oil (such as paraffin oil and petroleum), and naphthenic oil, and combinations thereof). In some embodiments, the secondary liquid phase contains water. In some embodiments, the secondary liquid phase contains at least one of water or a polymerizable compound (e.g., a polar polymerizable liquid or a non-polar polymerizable liquid). In some embodiments, the secondary liquid phase contains at least one of water or an oil).

[0077] Other examples of suitable ionic liquids include salts derived from 1-methylimidazole, namely, 1-alkyl-3-methylimidazolium salts. Examples of suitable imidazolium cations include 1-ethyl-3-methylimidazolium salts (EMIM), 1-butyl-3-methylimidazolium salts (BMIM), 1-octyl-3-methylimidazolium salts (OMIM), 1-decyl-3-methylimidazolium salts (DMIM), 1-dodecyl-3-methylimidazolium salts (docecylMIM), 1-butyl-2,3-dimethylimidazolium (DBMIM), 1,3-bis(N,N-dimethylaminoethyl)-2-methylimidazolium (DAMI), and 1-butyl-2,3-dimethylimidazolium (BMMIM). Examples of suitable anions in the ionic liquid include chloride ions, fluoride ions, tetrafluoroborate (BF4 - ), hexafluorophosphate (PF6 - ), bis(trifluoromethylsulfonyl)imide (NTf2 - ), trifluoromethanesulfonate (OTf - ), dicyanamide (N(CN)2 - ), hydrogen sulfate (HSO4 - ), ethyl sulfate (EtOSO3 - ). Additional examples of suitable ionic liquids include trioctylmethylammonium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazole chloride, and 1-butyl-3-methylimidazole hexafluorophosphate.

[0078] The secondary liquid phase may also contain non-polar or polar liquids or solvents, provided that the primary liquid phase and the secondary liquid phase form a separate phase. Examples of suitable liquids or solvents include alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated organic solvents, ketones, amines, amides, ethers, acids, bases, esters, sulfoxides, sulfones, fats, oils, and combinations thereof, provided that the first liquid phase and the second liquid phase form a separate phase.

[0079] In the curable compositions (which may be capillary suspensions) of the present disclosure, the particles are insoluble in the primary liquid phase and the secondary liquid phase at temperatures of 30 °C and below. Thus, at temperatures above 30 °C, the particles may or may not be soluble in the primary liquid phase and the secondary liquid phase, but in some embodiments, they are insoluble. At temperatures below the melting point of the primary liquid phase, the primary phase is in a solid state and forms a heterogeneous mixture with the particles. At temperatures below the melting point of the secondary liquid phase, the secondary phase is in a solid state and forms a heterogeneous mixture with the particles. The insolubility of the particles in the primary liquid phase and in the secondary liquid phase can be visually determined, for example, by combining the particles with the primary liquid phase and the secondary liquid phase separately and observing whether they dissolve.

[0080] In the curable composition (which may be a capillary suspension) of the present disclosure, the primary liquid phase and the secondary liquid phase form a separated phase when mixed at a temperature of 30 °C or below. Thus, at a temperature above 30 °C, the primary liquid phase and the secondary liquid phase may form a separated phase when mixed, or may form a homogeneous phase. At a temperature below the melting points of both the primary liquid phase and the secondary liquid phase, both phases are in the solid state and form a heterogeneous mixture. In some embodiments, the primary liquid phase is insoluble in the secondary liquid phase at a temperature of 30 °C or below, and the secondary liquid phase is insoluble in the primary liquid phase at a temperature of 30 °C or below. At a temperature above 30 °C, the primary liquid phase may be soluble or insoluble in the secondary liquid phase, but in some embodiments is insoluble, and the secondary liquid phase may be soluble or insoluble in the primary liquid phase, but in some embodiments is insoluble. At a temperature below the melting point of the primary liquid phase, the primary phase is in the solid state and forms a heterogeneous mixture with the secondary phase. At a temperature below the melting point of the secondary liquid phase, the secondary phase is in the solid state and forms a heterogeneous mixture with the primary phase. Whether the primary liquid phase and the secondary liquid phase form a separated phase can be determined visually, for example, by combining the primary liquid phase and the secondary liquid phase and observing whether they form two separated phases.

[0081] In some embodiments, the primary liquid phase is non-polar and the secondary liquid phase is polar. In some embodiments, the primary liquid phase is non-polar and the secondary liquid phase is non-polar.

[0082] In some embodiments, the curable composition (which may be a capillary suspension) of the present disclosure contains (additional) filler materials. The additional filler materials may be dispersed, for example, in the primary liquid phase. Any filler materials commonly known to those skilled in the art can be used in the context of the present disclosure. Examples of suitable filler materials that can be used include: zeolites, clay fillers, glass beads, silica-based fillers, hydrophobic silica-based fillers, hydrophilic silica-based fillers, pyrogenic silica, fibers (especially glass fibers, carbon fibers, graphite fibers, silica fibers, ceramic fibers), electrically and / or thermally conductive particles, nanoparticles (especially silica nanoparticles), and combinations thereof. Other additives may be optionally included in the curable composition to achieve any desired properties. Examples of such additives include pigments, toughening agents, reinforcing agents, flame retardants, antioxidants, and various stabilizers. The amount of the additives added is sufficient to obtain the desired final properties. In some embodiments, based on the total weight of the curable composition, the filler may be present in the curable composition or the primary liquid phase in an amount of at most 10 wt%, 7.5 wt%, 5 wt%, or 2.5 wt%.

[0083] Although in some embodiments, fumed silica is present in the curable composition, fumed silica and other rheological modifiers are not required to achieve the desired flow characteristics of the curable composition. As shown in the following examples, curable compositions comprising a primary liquid phase, a secondary liquid phase, and particles can behave as capillary suspensions even if they do not contain fumed silica and other rheological modifiers.

[0084] The curable composition can be prepared by combining the primary liquid phase, the secondary liquid phase, and the particles in any order using any standard mixing equipment. The method for preparing the curable composition can include combining the particles with a previously combined mixture of the primary liquid phase and the secondary liquid phase. Alternatively, the method for preparing the curable composition can include combining the secondary liquid phase with a previously combined mixture of the primary liquid phase and the particles.

[0085] The curable compositions described herein are liquid / liquid / solid multiphase suspensions. Adding a small amount of the secondary liquid phase (which is immiscible with the primary liquid phase) to a suspension of the particles in the primary liquid phase can result in particle bridging and network formation by capillary attraction. Compared to a two-component solid / liquid suspension, the rheological properties of the liquid / liquid / solid multiphase suspension are significantly altered by an increase in viscosity, for example from a fluid-like to a gel-like state or from a weak gel to a strong gel. In some embodiments, the liquid / liquid / solid multiphase suspension is a capillary suspension. The transition from a two-component solid / liquid suspension to a capillary suspension and the formation of an internal network occur when the wetting effect of the secondary liquid phase on the particles is much better than that of the primary liquid phase (swing state), or when the wetting effect of the secondary liquid phase on the particles is much worse than that of the primary liquid phase (sub-state). The capillary suspension, their chemical properties, formation, and characteristics are discussed in the article "Capillary suspension: Particle networks formed through capillary force" (by E. Koos, Current Opinion in Colloids & Interface Science, 19(2014)575 - 584).

[0086] The network structure of a liquid / liquid / solid multiphase suspension can be affected by the volume fractions of the particles and the secondary liquid phase. In addition to the increased viscosity, other rheological properties are observed for liquid / liquid / solid multiphase suspensions, such as an induced or increased yield stress, which is believed to be due to capillary forces induced by the secondary liquid phase that joins the percolated particle network by bridging the particles. As described in the following examples, in the linear viscoelastic (LVE) region, the applied strain does not disrupt the microstructure of the capillary suspension. The storage modulus G' is stable on a specific plateau. The larger G' is in the LVE region, the stiffer the sample. The larger the LVE region, the more stable the microstructure is to shear. When the yield point is reached, G' decreases. The presence of a capillary suspension is determined by the presence of a flow point detectable by the crossover of G' and G” (elastic modulus) at a specific shear stress τ0 after the LVE region. At τ below τ0, since the superstructure in the system is built by the capillary suspension, the composition exhibits predominantly elastic (G' > G”). At τ above τ0, since the superstructure is decomposed by the force applied during measurement, the composition exhibits predominantly viscous (G' > G”).

[0087] The curable compositions of the present disclosure (which may be capillary suspensions) may be capable of being cured by UV treatment, heat treatment, chemical treatment, visible light treatment, electron beam treatment, reactive gas treatment, or pH change treatment. In some embodiments, the curable composition is UV curable.

[0088] The present disclosure provides a method for preparing a pressure sensitive adhesive (PSA). Those of ordinary skill in the art are familiar with the properties of PSA, which include: (1) strong and persistent adhesiveness, (2) being able to adhere with a pressure not exceeding finger pressure, (3) having the ability to remain on the adherend, and generally, (4) having sufficient cohesive strength to be cleanly removed from the adherend. It has been found that materials that can be well used as PSA are such polymers that are designed and formulated to exhibit the desired viscoelasticity so as to obtain the desired balance of adhesive force, peel adhesion force, and shear holding force. One method for identifying a pressure sensitive adhesive is the Dahlquist criterion. As described in “Handbook of Pressure Sensitive Adhesive Technology”, edited by Donatas Satas, 2nd edition, page 172, published by Van Nostrand Reinhold, New York (NY), 1989, this criterion defines a pressure sensitive adhesive as having a value greater than 3×10 -6 cm 2An adhesive having a creep compliance of / dyne. Alternatively, since the modulus is approximately the reciprocal of the creep compliance, a pressure-sensitive adhesive can be defined as an adhesive having a storage modulus of less than about 3×10 5 N / m 2 . PSAs include these compositions not merely because the compositions are sticky or capable of adhering to a surface.

[0089] Methods for preparing pressure-sensitive adhesives include curing a curable composition to prepare a pressure-sensitive adhesive. In some embodiments, curing includes exposing the curable composition to radiation. In some embodiments, the curable composition is applied to a substrate and then cured in some embodiments with actinic radiation (e.g., visible or UV light), γ (gamma) radiation, electron beam radiation, or by thermal curing. In some embodiments, the curable composition is cured with UV radiation.

[0090] Once the curable composition is applied to the substrate, polymerization and crosslinking, which can be supplementary to the polymerization for partial polymerization as described above, can be carried out in an inert environment (e.g., nitrogen, carbon dioxide, helium, and argon, which do not include oxygen). A sufficiently inert atmosphere can be achieved by covering the curable composition with a liner (e.g., a release liner) such as a silicone-treated PET film. For UV curing, it is desirable that the liner be transparent to UV radiation. In some embodiments, the curable composition can be cured without a liner. Certain commercially available products such as adhesives obtained from 3M Company of St. Paul, Minnesota, under the trade names "3M SCREEN PRINTABLE UV-CURLING ADHESIVE SP7202" and "3M SCREEN PRINTABLE UV-CURLING ADHESIVE 7555" can be cured without a liner and can be used as the main liquid phase.

[0091] In some embodiments, the method for preparing a pressure-sensitive adhesive according to the present disclosure further includes: covering the curable composition with a liner before curing the curable composition, wherein the curable composition maintains its thickness for a longer period of time or under a greater force than a comparative composition, wherein the comparative composition is the same as the curable composition, except that the comparative composition does not include a secondary liquid phase.

[0092] For UV curing, depending on the photoinitiator used, the curable composition can be exposed to radiation at any desired wavelength, e.g., any one or more wavelengths in the range of 320 nm to about 350 nm, about 350 nm to about 390 nm, about 350 nm to about 380 nm, or 320 nm to 420 nm. Any suitable light source can be used, including fluorescent UV bulbs, mercury lamps (e.g., low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps), xenon lamps, metal halide lamps, electrodeless lamps, incandescent lamps, LEDs, and lasers. The UV exposure is typically from about 1,000 mJ / cm 2 to about 5,000 mJ / cm 2 . A UV exposure in the range of about 1,000 mJ / cm 2 to about 3,000 mJ / cm 2 can also be useful. For broadband light sources (e.g., fluorescent UV bulbs, mercury lamps, or incandescent lamps), filters can be used to narrow the wavelength range and / or modify the intensity of the light source.

[0093] When using hollow microspheres as the particles, the pressure - sensitive adhesive can have a density of 0.45 g / cm 3 to 1.5 g / cm 3 , 0.45 g / cm 3 to 1.10 g / cm 3 , 0.50 g / cm 3 to 0.95 g / cm 3 , 0.60 g / cm 3 to 0.95 g / cm 3 , or 0.70 g / cm 3 to 0.95 g / cm 3 .

[0094] Volatile organic compound (VOC) reduction regulations are becoming increasingly common in a variety of fields (e.g., in the construction market or in the automotive or electronics industries). Known acrylate - based pressure - sensitive adhesives can contain low - molecular - weight organic residues such as organic solvents and unreacted monomers, polymerization initiator residues, contaminants from raw materials, or degradation products formed during the manufacturing process. Using solvent - free polymerization methods such as those described above and using clean monomers, low - VOC tackifying resins, and relatively high - molecular - weight photoinitiators (e.g., oligo[2 - hydroxy - 2 - methyl - 1 - [4 - (1 - methylvinyl)phenyl]propanone] obtained from Lamberti Resins under the trade name ESACURE KIP150) can be used to reduce the VOC in the pressure - sensitive adhesives prepared as described herein. Using specific scavengers for organic contaminants, as described in WO 01 / 44400 (Yang), is another alternative way to achieve reduced VOC levels.

[0095] In some embodiments, the method for preparing a pressure-sensitive adhesive further comprises dispensing beads of the curable composition onto a substrate. Liquid compositions and even highly filled compositions that do not have two liquid phases can flow easily after dispensing and during curing, resulting in the loss of the shape of the dispensed beads. The curable compositions of the present disclosure flow little, if at all, after dispensing, which is beneficial for forming bond lines and 3D printing with the curable composition.

[0096] Advantageously, standard automated dispensing and 3D printing machines can be used to dispense the curable compositions of the present disclosure. Such machines are manufactured by different manufacturers, such as Atlas Copco IAS GmbH, Bretten, Germany; bdtronic GmbH, Weikersheim, Germany; Duerr AG, Stuttgart, Germany; Nordson Corporation, Westlake, Ohio, USA; ViscoTec Pumpen-u. Dosiertechnik GmbH, am Inn, Germany according to a wide range of specifications and by axiss Achsen-und Dosiersysteme GmbH, Keltern-Dietlingen, Germany, for example, under the trade name "DISPENSEMOVE 700" machine. The curable composition can be dispensed on any of these or similar machines.

[0097] The compositions of the present disclosure can be advantageously used in an extrusion-based layer deposition system to prepare three-dimensional articles. The three-dimensional article can be prepared, for example, from a computer-aided design (CAD) model by extruding the composition in a layer-by-layer manner. The movement of the extrusion head relative to the substrate (onto which the substrate is extruded) is carried out under computer control according to the build data representing the three-dimensional article. The build data is obtained by initially slicing the CAD model of the three-dimensional article into a plurality of horizontal slice layers. Then, for each slice layer, the host computer generates a build path for the deposition of the composition to form the three-dimensional article.

[0098] The composition can be extruded through a nozzle carried by an extrusion head, for example, and deposited in the form of a series of paths of the molten material on a substrate in the x-y plane. The paths can be in the form of continuous beads or in the form of a series of droplets (e.g., as described in U.S. Patent Application 2013 / 0071599 (Kraibühler et al.)). This can provide at least a portion of the first layer of the three-dimensional article. Then, the position of the nozzle relative to the first layer is incremented along the z-axis (perpendicular to the x-y plane), and the process is repeated to form at least a second layer of the composition on at least a portion of the first layer. Changing the position of the nozzle relative to the deposited layer can be carried out, for example, by lowering the substrate on which the layer is deposited. The process can be repeated as many times as needed to form a three-dimensional article similar to a CAD model. Further details can be found, for example, in Turner, B.N. et al. "A review of melt-extrusion additive manufacturing processes: I. Process design and modeling"; Rapid Prototyping Journal 20 / 3 (2014) 192-204 ("A review of melt-extrusion additive manufacturing processes: I. Process design and modeling"; Rapid Prototyping Journal 20 / 3 (2014) 192-204).

[0099] In some embodiments, a (e.g., non-transitory) machine-readable medium is employed in the method of fabricating a three-dimensional article of the present disclosure. Data is typically stored on the machine-readable medium. The data represents a three-dimensional model of the article, which can be accessed by at least one computer processor interfacing with a layer manufacturing device (e.g., a 3D printer, a manufacturing apparatus, etc.). The data is used to cause an additive manufacturing device to produce a three-dimensional article.

[0100] Computer modeling such as computer-aided design (CAD) data can be used to generate data representing the article. Image data representing the design of the three-dimensional article can be exported in STL format or any other suitable computer-processable form into the additive manufacturing device. Scanning methods can also be employed to scan a three-dimensional object to produce data representative of the article. An example of a technique for obtaining data is digital scanning. Any other suitable scanning technique can be used to scan the article, including radiography, laser scanning, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonic imaging. Other possible scanning methods are described in U.S. Patent Application Publication 2007 / 0031791 (Cinader, Jr. et al.). An initial digital data set that can include both the raw data from the scanning operation and data representative of the article derived from the raw data can be processed to segment the article design from any surrounding structure (e.g., the support of the article).

[0101] Typically, a machine-readable medium is provided as part of a computing device. The computing device may have one or more processors, volatile memory (RAM), means for reading the machine-readable medium, and input / output devices such as a display, keyboard, and pointing device. Additionally, the computing device may also include other software, firmware, or a combination thereof, such as an operating system and other application software. The computing device may be, for example, a workstation, laptop computer, personal digital assistant (PDA), server, mainframe, or any other general-purpose or application-specific computing device. The computing device may read executable software instructions from a computer-readable medium such as a hard disk, CD-ROM, or computer memory, or may receive instructions from another source logically connected to the computer, such as another networked computer.

[0102] In some embodiments, a method of preparing a pressure-sensitive adhesive of the present disclosure includes repeatedly dispensing beads of a curable composition and curing the curable composition. In some embodiments, the method is carried out discontinuously. For example, the curable composition is dispensed and shaped, and then the shaped composition is cured to provide an article. In some embodiments, the curable composition is shaped and cured to provide a portion of the pressure-sensitive adhesive, and then these steps are repeated to provide the pressure-sensitive adhesive in its final form. In some embodiments, the curable composition is cured and shaped simultaneously.

[0103] In some embodiments, a method of preparing a pressure-sensitive adhesive of the present disclosure includes retrieving data representing a three-dimensional model of a desired three-dimensional article from a (e.g., non-transitory) machine-readable medium. The method further includes using the data by one or more processors to execute an additive manufacturing (3D printing) application that interfaces with a manufacturing device, and generating a physical object of the three-dimensional article by the manufacturing device. While three-dimensional articles with support structures can generally be prepared, in some embodiments this is not necessary when using the curable compositions of the present disclosure.

[0104] The disadvantages of hot melt extrusion (which is the standard method for fused filament fabrication) and other melt extrusion additive manufacturing processes are that significantly elevated temperatures are required to melt the corresponding polymeric materials used to produce three-dimensional forms. Additionally, in order to maintain a shape as close as possible to the desired printed result, measures must be taken that achieve rapid cooling of the printed product in order to avoid deformation during the cooling process due to inadequately cooled and thus still flowable material. This either limits the choice of possible materials or requires strict control of the cooling process. Since the curable compositions of the present disclosure are able to retain their shape after dispensing, the methods of the present disclosure can eliminate these disadvantages.

[0105] The curable compositions of the present disclosure can also be used, for example, in reduction polymerization 3D printing methods such as stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD). For SLA 3D printing, the build platform can be positioned in a vat of the curable composition. A UV laser can be used to generate a layer by selectively curing the curable composition according to a desired pattern. A top-down printer places the laser source above the vat, and after each layer is cured, the build platform moves down. A bottom-up printer places the light source below the resin vat. The vat has a transparent bottom that allows the light of the laser to pass through. Although three-dimensional articles with support structures can generally be prepared, in some embodiments, this is not necessary when using the curable compositions of the present disclosure.

[0106] The methods of the present disclosure do not require dispensing multiple layers of the curable composition. In some embodiments, a single layer of the curable composition is dispensed. The shaping of the curable composition can also be carried out in other ways, such as casting on a film, 3D printing, molding, extrusion, coating, and preparation. The curable composition can be coated on a substrate using any conventional coating technique appropriately modified according to the specific substrate. For example, the curable composition can be coated on a variety of solid substrates by methods such as roll coating, flow coating, dip coating, spin coating, spray coating, knife coating, and die coating. These various coating methods allow the curable composition to have a variety of thicknesses on the substrate.

[0107] The curable compositions of the present disclosure can be dispensed or coated on a variety of substrates to produce adhesive-coated articles. The substrates can be flexible or inflexible and are formed of a polymeric material, glass or ceramic material, metal, or a combination thereof. Suitable polymeric substrates include polymeric films such as those prepared from: polypropylene, polyethylene, polyvinyl chloride, polyester (polyethylene terephthalate or polyethylene naphthalate), polycarbonate, poly(methyl)methacrylate (PMMA), cellulose acetate, cellulose triacetate, and ethyl cellulose. Examples of other substrates include metals such as stainless steel and aluminum, polymeric materials coated with a metal or metal oxide, and glass coated with a metal or metal oxide. The substrate can be a medium surface energy (MSE) substrate such as polyamide 6 (PA6), acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC) / ABS blend, PC, PVC, polyamide (PA), polyurethane (PUR), thermoplastic elastomer (TPE), polyoxymethylene (POM), polystyrene, poly(methyl methacrylate) (PMMA), a varnish-coated surface, specifically a varnish-coated surface for vehicle-like transportation or a coated surface for industrial applications, and a composite material such as a fiber-reinforced plastic.

[0108] The pressure-sensitive adhesives prepared from the curable compositions and / or methods of the present disclosure can be used in any article conventionally known to use such components, such as labels, tapes, signs, covers, markers, display components, and touch panels. Flexible backing materials with micro-replicated surfaces are also contemplated. The substrate to which the pressure-sensitive adhesive can be applied is selected according to the particular application. For example, the pressure-sensitive adhesive can be applied to sheet products (e.g., decorative graphics and reflective products), labelstock, and tape backings. Additionally, the pressure-sensitive adhesive assembly can be directly applied to other substrates such as metal sheets (e.g., automotive panels) or glass windows so that another substrate or object can be attached to the panel or window. Thus, the pressure-sensitive adhesives of the present disclosure can be used in the motor vehicle manufacturing industry (e.g., for the attachment of exterior trim or for weatherstripping), the construction industry, and the solar panel construction industry.

[0109] The thickness of the curable compositions and the pressure-sensitive adhesives made from the curable compositions and / or methods of the present disclosure can vary within a wide range according to the needs of the intended application. In some embodiments, the thickness of the curable compositions and the resulting pressure-sensitive adhesives is between 25 μm and 6000 μm, between 40 μm and 3000 μm, between 50 μm and 3000 μm, between 75 μm and 2000 μm, or between 75 μm and 1500 μm. In some embodiments where the particles comprise hollow microspheres, the thickness is between 100 μm and 6000 μm, between 200 μm and 4000 μm, between 500 μm and 2000 μm, or between 800 μm and 1500 μm.

[0110] The curable compositions of the present disclosure can be dispensed or coated onto a backing, for example, to prepare pressure-sensitive adhesive tapes (e.g., single-sided or double-sided tapes). Suitable tape backing layers can be made of plastics (e.g., polypropylene (including biaxially oriented polypropylene), vinyl, polyethylene, polyester (such as polyethylene terephthalate)), non-wovens (e.g., paper, cloth, non-woven scrim), metal foils, foams (e.g., acrylic, polyethylene, polyurethane, neoprene), etc. Polymer foams are available from various suppliers such as Voltek, 3M Co., Sekisui (3M Co., Voltek, Sekisui), and other suppliers. For single-sided tapes, the pressure-sensitive adhesive is present on one surface of the backing material, and a suitable release material is applied to the opposite surface of the backing material. Any suitable release material can be used, including silicone, polyolefin, polyurethane, and polyacrylate.

[0111] When the curable composition is cured on a substrate and / or when a pressure-sensitive adhesive is laminated to a substrate, it may be desirable to treat the surface of the substrate to improve adhesion. Such treatments are typically selected based on the nature of the materials in the pressure-sensitive adhesive and the nature of the substrate, and include primers and surface modifications (e.g., corona treatment and surface abrasion).

[0112] In some embodiments, the curable composition of the present disclosure is provided with a release liner on at least one major surface of its major surfaces. As the release liner, any suitable material known to those skilled in the art can be used. For example, a silicone-coated paper or a silicone-coated polymer film material, particularly a silicone-coated PET film or a silicone-coated PE or PE / PP blend film material. In some embodiments, the curable composition of the present disclosure can be dispensed or coated on the release liner. The pressure-sensitive adhesive and / or method made from the curable composition of the present disclosure can be provided in the form of a pressure-sensitive adhesive transfer tape, wherein at least one layer of the pressure-sensitive adhesive is provided on a release liner that is later applied to a permanent substrate.

[0113] Some embodiments of the present disclosure

[0114] In a first embodiment, the present disclosure provides a curable composition comprising, based on the total volume of the curable composition, from 25 vol% to 70 vol% of particles; from 25 vol% to 74.8 vol% of a primary liquid phase, based on the total volume of the curable composition, the primary liquid phase comprising a first monomer comprising at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer, wherein the alkyl is straight or branched and has at least five carbon atoms; and from 0.15 vol% to 20 vol% of a secondary liquid phase, based on the total volume of the curable composition, wherein the secondary liquid phase and the primary liquid phase form a separated phase after mixing in the temperature range of -20 °C to 30 °C, and wherein the particles are insoluble in the primary liquid phase and the secondary liquid phase in the temperature range of -20 °C to 30 °C. In a second embodiment, the present disclosure provides the curable composition according to the first embodiment, the curable composition being a capillary suspension. In a third embodiment, the present disclosure provides a pressure-sensitive adhesive precursor capillary suspension. This may also be written as a pressure-sensitive adhesive precursor composition in the form of a capillary suspension and a capillary suspension comprising the pressure-sensitive adhesive precursor composition. In a fourth embodiment, the present disclosure provides the pressure-sensitive adhesive precursor capillary suspension according to the third embodiment, the pressure-sensitive adhesive precursor capillary suspension comprising, based on the total volume of the capillary suspension, from 25 vol% to 70 vol% of particles; from 25 vol% to 74.8 vol% of a primary liquid phase, based on the total volume of the capillary suspension, the primary liquid phase comprising a first monomer comprising at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer, wherein the alkyl is straight or branched and has at least five carbon atoms; and from 0.15 vol% to 20 vol% of a secondary liquid phase. In a fifth embodiment, the present disclosure provides the curable composition or the pressure-sensitive adhesive precursor composition according to any one of the first to fourth embodiments, the composition comprising, based on the total volume of the composition, from 35 vol% to 60 vol% of particles; from 38 vol% to 64.6 vol% of a primary liquid phase, based on the total volume of the composition, the primary liquid phase comprising a first monomer comprising at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer, wherein the alkyl is straight or branched and has at least five carbon atoms; and from 0.4 vol% to 3 vol% of a secondary liquid phase.

[0115] In a sixth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to fifth embodiments, wherein the first monomer is present in the main liquid phase in an amount of at least 50% by weight based on the total weight of the main liquid phase. In a seventh embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to sixth embodiments, wherein the first monomer comprises at least one of the following: octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-propylheptyl (meth)acrylate, 2-octyl (meth)acrylate, or n-butyl acrylate. In an eighth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to sixth embodiments, wherein the first monomer comprises a mixture of at least two structural isomers of a compound represented by the following formula:

[0116]

[0117] wherein R 1 and R 2 are each independently a C1 to C 30 saturated linear alkyl group; the total number of carbon atoms in R 1 and R 2 is 7 to 31, and R 3is H or CH3. In a ninth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to eighth embodiments, wherein the second monomer comprises a polymerizable carbon-carbon double bond and at least one of the following: a polar functional group, an alicyclic group, a heterocyclic group, an aromatic group, or an alkyl group having less than four carbon atoms. A combination of any of such compounds can be used as the second monomer. In a tenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to ninth embodiments, wherein the second monomer comprises at least one of the following: acrylic acid, methacrylic acid, hydroxyalkyl acrylate, hydroxyalkyl methacrylate, isobornyl acrylate, or isobornyl methacrylate. In an eleventh embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to tenth embodiments, wherein the main liquid phase further comprises a crosslinking monomer having at least two polymerizable carbon-carbon double bonds, and wherein, based on the total weight of the main liquid phase, the crosslinking monomer is present in the main liquid phase in an amount not exceeding 5% by weight. In a twelfth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to eleventh embodiments, wherein the main liquid phase further comprises a polymer prepared by partial polymerization of the first monomer and optionally the second monomer and / or the crosslinking monomer. In a thirteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twelfth embodiments, wherein the main liquid phase further comprises a radical initiator. In a fourteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to the thirteenth embodiment, wherein the radical initiator is a photoinitiator.

[0118] In a fifteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to fourteenth embodiments, wherein the particles comprise at least one of ceramic microspheres, polymer microspheres, metal particles, conductive particles, or thermally conductive particles, and any one of them can be hollow or solid. In a sixteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to fifteenth embodiments, wherein the particles comprise at least one of hollow ceramic microspheres or hollow polymer microspheres. In a seventeenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to the sixteenth embodiment, wherein the particles are non-conductive or non-thermally conductive. In an eighteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to the sixteenth or seventeenth embodiment, wherein, based on the total weight of the curable composition, the particles are present in an amount of 10% to 30% by weight, the main liquid phase is present in an amount of 65% to 89.5% by weight, and the secondary liquid phase is present in an amount of 0.5% to 5% by weight. In a nineteenth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the sixteenth to eighteenth embodiments, wherein the particles comprise hollow ceramic microspheres, and wherein the hollow ceramic microspheres comprise hydrophobic surface groups. In a twentieth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the sixteenth to nineteenth embodiments, wherein the particles comprise hollow glass microspheres. In a twenty-first embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twentieth embodiments, which further comprises pyrogenic silica.

[0119] In a twenty-second embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twenty-first embodiments, wherein the secondary liquid phase comprises at least one of water or oil. In a twenty-third embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twenty-second embodiments, wherein the secondary liquid phase comprises water. In a twenty-fourth embodiment, the present disclosure provides a curable composition or a pressure-sensitive adhesive precursor composition according to the twenty-second or twenty-third embodiment, wherein the water further comprises an acid or a salt.

[0120] In a twenty-fifth embodiment, the present disclosure provides a pressure-sensitive adhesive made from a capillary suspension. In a twenty-sixth embodiment, the present disclosure provides the pressure-sensitive adhesive according to the twenty-fifth embodiment, wherein the capillary suspension is a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twenty-fourth embodiments. In a twenty-seventh embodiment, the present disclosure provides the pressure-sensitive adhesive according to the twenty-fifth or twenty-sixth embodiment, wherein the pressure-sensitive adhesive is prepared by curing a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twenty-fourth embodiments. In a twenty-eighth embodiment, the present disclosure provides a method for preparing a pressure-sensitive adhesive, the method comprising curing a curable composition or a pressure-sensitive adhesive precursor composition according to any one of the first to twenty-fourth embodiments to prepare a pressure-sensitive adhesive. In a twenty-ninth embodiment, the present disclosure provides the pressure-sensitive adhesive or method according to the twenty-seventh or twenty-eighth embodiment, wherein curing comprises exposing the curable composition or the pressure-sensitive adhesive precursor composition to radiation. In a thirtieth embodiment, the present disclosure provides the method according to the twenty-eighth or twenty-ninth embodiment, which further comprises dispensing beads of the curable composition or the pressure-sensitive adhesive precursor composition onto a substrate. In a thirty-first embodiment, the present disclosure provides the method according to any one of the twenty-eighth to thirtieth embodiments, covering the curable composition with a liner before curing the curable composition, wherein the curable composition maintains its thickness for a longer period of time or under a greater force than a comparative composition, wherein the comparative composition is the same as the curable composition, except that the comparative composition does not include a secondary liquid phase.

[0121] Examples

[0122] The present disclosure is further illustrated by the following examples. These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. Unless otherwise specified, all parts, percentages, ratios, etc. in the examples are by weight. Unless otherwise indicated, all other reagents are obtained from or purchased from fine chemical suppliers or can be synthesized by known methods. The following abbreviations are used in this section: hr = hour, min = minute, sec = second, g = gram, kg = kilogram, mm = millimeter, cm = centimeter, °C = degree Celsius, N = Newton, Pa = Pascal, mPa = millipascal, mbar = millibar, rpm = revolutions per minute, W / m·K = watt per meter-kelvin, J / g / K = joule per gram per kelvin, mW / cm 2 = milliwatt per square centimeter RH = relative humidity, RT = room temperature, Hz = hertz, s = standard deviation.

[0123] Table 1 (below) lists the materials used in the examples and their sources.

[0124] Table 1: Material list

[0125]

[0126] Test substrate

[0127] Stainless steel (SS) test plates: (“Edelstahl 1.4301HID” for peel test: 150 mm × 50 mm × 2 mm; for static shear test: 75 mm × 50 mm × 2 mm) obtained from Rocholl GmbH, Eschelbron, Germany. Before testing, the substrates were cleaned successively with methyl ethyl ketone (MEK), n - heptane, a mixture of isopropyl alcohol and distilled water (1:1), and MEK, and dried with paper towels (“3M PANELWIPES PN345672”, purchased from 3M) after each step.

[0128] PMMA (polymethyl methacrylate) test plates: (“Plexiglas XT 20070FF”, 150 mm × 25 mm × 2 mm) obtained from Rocholl GmbH. These test plates were cleaned with a 1:1 mixture of isopropyl alcohol and distilled water and dried with paper towels (“3M PANEL WIPES PN345672”, purchased from 3M) after cleaning.

[0129] Aluminum test plates: (“5005A (AlMg1)” (50 mm × 25 mm × 1 mm)) obtained from Rocholl GmbH. These test plates were cleaned with MEK in an ultrasonic bath (RK 103HSonorex from Bandelin, Berlin, Germany) for 15 min. The lap area of the shear test plates (12.7 mm × 25 mm) was sandblasted with SMG25 (MHG Sandstrahlanlage, Düsseldorf, Germany). Before testing, the test plates were cleaned again with MEK in the same ultrasonic bath for 15 min. After cleaning, the test plates were dried with paper towels (“3M PANEL WIPES PN345672”, purchased from 3M) and left for 10 min to dry.

[0130] Test method

[0131] Lap shear test

[0132] The lap shear strength was determined using a ZWICK / ROELL Z005 tensile tester (purchased from Zwick GmbH&Co.KG, Ulm, Germany) in accordance with ASTM D1002 standard at a crosshead speed of 12.7 mm / min. For test assembly preparation, two aluminum test plates as described above were joined together in a lap joint with a width of 12.7 mm×25 mm using the pressure-sensitive adhesive assembly of the present invention by pressing these lap shear test assemblies with a force of 150 N (+ / -5 N) for 30 sec. Then, prior to testing, the test assemblies were conditioned at RT of 23°C (+ / -2°C) and 50% RH (+ / -5%) for at least 72 hr. The test results were expressed in N. The cited shear value was the average of three lap shear test measurements.

[0133] 90° peel adhesion test

[0134] For the 90° peel adhesion test, the procedure according to test method AFERA 5001 was followed. A pressure-sensitive adhesive film strip with a width of 12.7 mm and a length >175 mm was cut from the sample. For test sample preparation, the liner was first removed from one adhesive side and placed on an aluminum strip with the following dimensions: 22 cm×1.6 cm. Then, after removing the liner, the adhesive-coated side of each PSA strip was placed on a clean test plate with its adhesive side facing down. Next, the test sample was rolled twice in each direction with a standard FINAT test roller (weighing 6.8 kg) at a speed of approximately 10 mm / sec to obtain close contact between the adhesive substance and the surface. After applying the pressure-sensitive adhesive strip to the test plate, the test sample was allowed to stay at RT (23°C + / -2°C, 50% RH + / -5%) for 20 min or 72 hr before testing.

[0135] For the peel test, in the first step, the test sample was clamped in the lower moving jaws of a Zwick tensile tester (model Z005, purchased from Zwick / Roell GmbH). The pressure-sensitive adhesive strip was folded back at an angle of 90°, and its free end was gripped in the upper jaws of the tensile tester in the configuration commonly used for 90° peel measurement. The tensile tester was set to a jaw separation rate of 300 mm / min. The test results were expressed in Newtons per 10 mm (N / 10 mm). The cited peel value was the average of two 90°-peel measurements.

[0136] Static shear force test

[0137] Static shear is a measure of the cohesiveness or internal strength of an adhesive. It is measured in terms of the time (in minutes) required to pull a standard area of adhesive sheet material from the above-mentioned stainless-steel test plate under a constant standard load stress. A strip of pressure-sensitive adhesive film 12.7 mm wide and 25.4 mm long is cut from the sample and the specimen is placed on a clean steel test plate. Then the opposite side of the test sample is placed on an aluminum plate with a hole for fixing a heavy weight using a slight finger pressure. A standard FINAT test roller (weighing 6.8 kg) is rolled twice in each direction at a speed of approximately 5 mm / sec to obtain a tight contact between the pressure-sensitive adhesive substance and the substrate surface (test plate). After applying the pressure-sensitive adhesive film strip (specimen) to the test plate, the test plate is allowed to have a dwell time of 24 hours at RT (23 °C + / - 2 °C, 50% RH + / - 5%) before testing.

[0138] The test plate is placed in a shear-holding device. After a 10-min dwell time at 70 °C, a 500-g load is suspended into the hole of the aluminum test plate. The timer is started. The results are recorded in minutes until failure and are the average of three shear measurements, unless otherwise indicated. A recorded time of "10000+" indicates that the strip does not fail after 10000 minutes when the test is stopped.

[0139] Rheological measurement

[0140] A rheometer HAAKE MARS 40 (ThermoFisher Scientific, Waltham, MA) is used to characterize the uncured formulation. A plate-plate geometry with a plate diameter of 35.0 mm is used. The sample is placed between the plates and equilibrated for up to 20 sec until a stable temperature of 20 °C (±0.2 °C) is reached. The test method "oscillatory amplitude sweep" is used. The parameters for measurement are as follows: shear stress τ = 0.1 Pa - 1000 Pa; frequency f = 1 Hz; number of steps = 41 (logarithmic distribution); repeated 3 times for each step.

[0141] In the linear viscoelastic (LVE) region, the applied strain does not destroy the microstructure of the sample. The storage modulus G' is stable on a specific plateau. The larger the G' in the LVE region, the stiffer the sample. The larger the LVE region, the more stable the microstructure is to shear. When the yield point is reached, G' decreases. The shear stress τ at the end of the LVE region and the average G' in the LVE region are given in Pa.

[0142] The presence of a capillary suspension is determined by the presence of a flow point detectable by the crossing of G' and G'' (elastic moduli) at a specific shear stress τ0 after the LVE region. At τ below τ0, since the superstructure in the system is built by the capillary suspension, the sample exhibits predominantly elastic behavior (G' > G''). At τ above τ0, since the superstructure is decomposed by the force applied during measurement, the sample exhibits predominantly viscous behavior (G' > G''). The shear stress τ at G' = G'' is given in Pa.

[0143] Through-plane thermal conductivity (λ) measurement

[0144] The through-plane thermal conductivity (λ) of the thermally conductive pressure-sensitive adhesive sample is calculated according to the formula λ = a·ρ·cP, where the thermal conductivity (λ) is expressed in (W / m·K), the thermal diffusivity (a) is expressed in (mm 2 / s), the specific heat (cP) is expressed in (J / g / K) and the density (ρ) is expressed in (g / cm 3 ). The parameters (a) and (cP) are determined simultaneously at 25 °C using the flash method with a flash apparatus (Nanoflash LFA 447 purchased from Netzsch, Selb, Germany) according to the test method ASTM E 1461 / DIN EN 821. The test samples have the following dimensions: 10 mm (length) × 10 mm (width) × 1 mm (thickness), and are spray-coated with graphite to make the samples have higher absorption. Each side of the sample (n = 3) is spray-coated 2 times and left to dry for 2 min.

[0145] Examples

[0146] Preparation of precursors :

[0147] In step 1, a polymer precursor is prepared by combining a monomer with a photoinitiator in a glass container. Before initiating UV exposure, the mixture is flushed with nitrogen for 10 minutes and nitrogen is also bubbled into the mixture throughout the time until the polymerization process is stopped by adding air to the mixture. The mixture is continuously stirred with a propeller stirrer (300 rpm), and the reaction is stopped when a viscosity between 2000 mPa and 4500 mPa is reached (measured with a Brookfield viscometer, T = 23 °C, spindle 4, 12 rpm). In step 2, the remaining amount of initiator, HDDA crosslinker and optionally additional monomers are added to the composition. These main liquid phases are homogenized by rolling on a LABINCO LD209750 Rolling Bench jar roller (purchased from LABINCO, Breda, Netherlands) at 35 rpm for 2 hours. The exact amounts of materials used to prepare the main liquid phases are given in Table 2.

[0148] Table 2: Main liquid phase composition in grams

[0149]

[0150] Preparation of Comparative Examples (C1 - C11)

[0151] The compositions of the base formulations C1 - C11 are reported in Tables 3 - 6. Each formulation is prepared by combining all components in a polypropylene mixing cup. The cup is closed with a polypropylene lid, and the mixture is high-shear mixed at 1000 mbar and 1600 rpm at ambient temperature and pressure for 30 seconds using a SPEEDMIXER (purchased from Hauschild DAC 400.2 VAC-P, Hamm, Germany). The final composition is degassed at 50 mbar and 800 rpm for 120 s. Subsequently, the mixture is coated into a film between two transparent silicone-treated release liners using a doctor blade coater (approximately 15 g of formulation per film, 1 mm thick).

[0152] A custom UV curing station is used to irradiate the coated syrup. At 100% lamp intensity, the maximum irradiance of the curing station is 0.2 mW / cm at a wavelength of 360 nm. 2 The syrup is irradiated for 4 minutes at full intensity level using top and bottom mercury lamps. After 15 seconds, the sample is removed from the UV source and irradiation is continued while the film cools (minimum 1 minute waiting time).

[0153] Preparation of Examples 1 to 17 (Ex.1 - Ex.17)

[0154] The compositions of basic formulations 1 to 17 are reported in Table 3 - 5. Each formulation was prepared by combining all components except the secondary phase and additives in a polypropylene mixing cup. The cup was closed with a polypropylene lid and the mixture was high - shear mixed at 1600 rpm under 1000 mbar for 30 s at ambient temperature and pressure using a SPEEDMIXER (purchased from Hauschild DAC 400.2VAC - P). The secondary phase (water or oil) was added and the mixture was mixed again at 1600 rpm under 1000 mbar for 30 s. In the case of using additives, the additives (2 parts of AEROSIL 200 or 4 parts of AEROSIL R972) were added and the mixture was mixed again at 1600 rpm under 1000 mbar for 30 s. The final composition was degassed at 800 rpm under 50 mbar for 120 s. Subsequently, the mixture was coated into a film between two transparent silicone - treated release liners using a doctor blade coater (about 15 g of formulation per film, 1 mm thick). The films were irradiated as described above for C1 - C11.

[0155] In Table 3 below, GB is for the particles. The 90° peel adhesion, static shear, and lap shear of each example and comparative example were tested according to the above - mentioned test methods. The failure mode of all 90° peel adhesion tests was cohesive, except for the tests on stainless steel, where the failure mode was cohesive, except for 2 on stainless steel, which showed cohesive failure. The results are shown in Table 3 below.

[0156] Table 3: Examples 1 to 11, C1 and C2. Quantities are expressed as g / 100g of the main liquid phase (PLP) 。

[0157]

[0158] Note: Gelation was observed by eye within 24 hours. Samples without water can absorb water from the air and the gel over time.

[0159] Table 4: Examples 12 to 15 and C3. Quantities are expressed in g / 100 g PLP.

[0160]

[0161] Table 5: Examples 16 and 17, C4 and C5. Quantities are expressed in g / 100 g PLP.

[0162]

[0163] These samples can be cured without liners; however, for ease of preparation of test samples, all test samples were prepared between two liners.

[0164] Preparation of Examples 18 to 35 (Ex.18 - Ex.35)

[0165] The compositions of the base formulations Ex.18 to 35 are reported in Table 6. Each formulation was prepared by combining two liquids into a polypropylene mixing cup. The cup was closed with a polypropylene lid and the mixture was high-shear mixed at 1000 mbar and 1600 rpm for 30 seconds at ambient temperature and pressure using a SPEEDMIXER (Hauschild DAC 400.2 VAC-P from Hamm, Germany). Immediately after mixing, the filler was added to the suspension and the mixture was mixed at 1000 mbar and 1600 rpm for 60 seconds. The final composition was degassed at 50 mbar and 800 rpm for 120 s. Subsequently, the mixture was analyzed on a rheometer (HAAKE MARS 40 from Thermo Fisher Scientific, Waltham, Massachusetts) and the mixture was coated into a film between two transparent silicone-treated release liners using a doctor blade coater (approx. 15 g formulation per film, 1 mm thick). The film was irradiated as described above for C1-C11.

[0166] Table 6: Examples 18 to 35. Quantities are expressed as g / 100g PLP 。

[0167]

[0168]

[0169] If no LVE value or flow point was given, no LVE region or flow point was detected.

[0170] The comparative and limit examples do show shorter and smaller LVE regions, if they show an LVE region at all. The more minor phase and filler in the sample, the more the LVE region increases. After a certain amount of filler and minor phase, G' is greater than G'' in the LVE region and thus they cross at higher shear. The presence of such a flow point is defined here as a capillary suspension.

[0171] Allocation of Example 4

[0172] Immediately after manufacture, Example 4 was filled into a "EURO" type 310-mL aluminum cylinder (purchased from Alcan Deutschland GmbH, Göttingen, Germany, now Novelis Deutschland GmbH, Göttingen, Germany). The cylinder was sealed with a piston and stored at room temperature for several days. Dispensing was carried out on a "Dispensmove 700" machine (purchased from Axial Dosiertechnik GmbH, Keltern-Dietlingen, Germany). The dispensing was carried out without heating any components, so all components including the material, equipment and substrate were at a constant RT (23 °C). Immediately before dispensing, the tip of the EURO cylinder was manually opened directly, and a standard EURO application nozzle with a circular opening having a diameter of 1 mm was installed. The nozzle was oriented perpendicular to the surface. As the substrate, a sheet of untreated aluminum alloy 5754 AlMg3 (obtained from Rohröl GmbH) with dimensions of 300 mm × 200 mm × 2 mm was used. The dispensing was carried out at a distance of 1 mm from the nozzle to the surface, a nozzle tip speed of 40 mm / s and a volume flow rate of 0.1 mL / s. As Figure 1 shown, beads with a length of approximately 1500 mm were applied to the sheet during an application time of 37 s. Within 10 minutes after dispensing, the beads were covered with a transparent liner and cured into a tape state by applying UV light with the same equipment and settings as described above for C1-C11. Regular slurries will easily flow in the gap between the substrate and the liner, and thus significantly reduce the height / width ratio of the beads, resulting in the loss of the desired bead characteristics. As Figure 2 shown, Example 4 maintained its shape during the curing step.

[0173] Without departing from the spirit and scope of the present disclosure, various modifications and changes can be made to the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, but should be controlled by the limitations mentioned in the following claims and any equivalents thereof. The present disclosure can be implemented in a suitable manner without any element not specifically disclosed in the present disclosure.

Claims

1. A curable composition, the curable composition comprising: Particles in an amount of 25% to 70% by volume based on the total volume of the curable composition; A main liquid phase in an amount of 25% to 74.8% by volume based on the total volume of the curable composition, the main liquid phase comprising a first monomer, the first monomer comprising at least one of n-butyl acrylate, an alkyl acrylate monomer, or an alkyl methacrylate monomer, wherein the alkyl is straight-chain or branched and has at least five carbon atoms; and A secondary liquid phase in an amount of 0.15% to 20% by volume based on the total volume of the curable composition, wherein the secondary liquid phase and the main liquid phase form a separated phase after mixing in a temperature range of -20°C to 30°C, and wherein the particles are insoluble in the main liquid phase and the secondary liquid phase in a temperature range of -20°C to 30°C.

2. The curable composition according to claim 1, wherein the first monomer is present in the main liquid phase in an amount of at least 50% by weight based on the total weight of the main liquid phase.

3. The curable composition according to claim 1 or 2, wherein the first monomer comprises a mixture of at least two structural isomers of a compound represented by the following formula: wherein R 1 and R 2 are each independently a C1 to C 30 saturated linear alkyl group; the sum of the number of carbons in R 1 and R 2 is from 7 to 31, and R 3 is H or CH3.

4. The curable composition according to any one of claims 1 to 3, wherein the main liquid phase further comprises at least one second monomer, wherein each second monomer independently comprises a polymerizable carbon-carbon double bond and at least one of the following: a polar functional group, an alicyclic group, a heterocyclic group, an aromatic group, or an alkyl group having fewer than four carbon atoms.

5. The curable composition according to any one of claims 1 to 4, wherein the main liquid phase further comprises a crosslinking monomer having at least two polymerizable carbon-carbon double bonds, wherein the crosslinking monomer is present in the main liquid phase in an amount of not more than 5% by weight based on the total weight of the main liquid phase.

6. The curable composition according to any one of claims 1 to 5, wherein the main liquid phase further comprises a polymer prepared by partial polymerization of the first monomer.

7. The curable composition according to any one of claims 1 to 6, wherein the main liquid phase further comprises a radical initiator.

8. The curable composition according to any one of claims 1 to 8, wherein the particles comprise at least one of ceramic microspheres, polymer microspheres, metal particles, conductive particles, or heat-conductive particles, and any one of them can be hollow or solid.

9. The curable composition according to any one of claims 1 to 8, wherein the particles comprise at least one of hollow ceramic microspheres or hollow polymer microspheres, and wherein based on the total weight of the curable composition, the particles are present in an amount of 10% to 30% by weight, the main liquid phase is present in an amount of 65% to 89.5% by weight, and the secondary liquid phase is present in an amount of 0.5% to 5% by weight.

10. The curable composition according to any one of claims 1 to 9, the curable composition further comprising pyrogenic silica.

11. The curable composition according to any one of claims 1 to 10, wherein the secondary liquid phase contains water.

12. A method for preparing a pressure-sensitive adhesive, the method comprising: Curing the curable composition according to any one of claims 1 to 11 to prepare the pressure-sensitive adhesive.

13. The method according to claim 12, the method further comprising: Dispensing beads of the curable composition onto a substrate.

14. A capillary suspension comprising a pressure-sensitive adhesive precursor.

15. A pressure-sensitive adhesive made from a capillary suspension.

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