Tackifier and adhesive composition

Abstract

To provide a tackifier that exhibits superior heat resistance, and an adhesive composition comprising the tackifier.SOLUTION: This tackifier comprises structural units derived from a styrene-based monomer and structural units derived from a polyfunctional aromatic compound, and has a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) in terms of standard polystyrene of 1.80 or more and 5.50 or less as measured by gel permeation chromatography (GPC).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a tackifier and an adhesive composition. [Background technology]

[0002] BACKGROUND ART It has been known to blend a tackifier into a pressure-sensitive adhesive composition in order to improve the adhesive strength.

[0003] As such a tackifier, for example, a homopolymer of isopropenyl toluene has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 52-78289 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, pressure-sensitive adhesive compositions are required to have heat resistance depending on the application and purpose.

[0006] The present invention provides a tackifier having excellent heat resistance, and a pressure-sensitive adhesive composition containing the tackifier. [Means for solving the problem]

[0007] The present invention [1] is a tackifier that contains structural units derived from a styrene-based monomer and structural units derived from a polyfunctional aromatic compound, and has a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) in terms of standard polystyrene measured by gel permeation chromatography (GPC) of 1.80 or more and 5.50 or less.

[0008] The present invention [2] includes the tackifier according to the above [1], which has a z-average molecular weight of 6,000 or less.

[0009] The present invention [3] includes the tackifier according to the above [1] or [2], in which the content of the structural units derived from the polyfunctional aromatic compound is 10 mol % or more and 25 mol % or less relative to the total amount of the structural units derived from the styrene-based monomer and the structural units derived from the polyfunctional aromatic compound.

[0010] The present invention [4] includes the tackifier according to any one of the above [1] to [3], in which the structural unit derived from a styrene-based monomer is a structural unit derived from isopropenyl toluene.

[0011] The present invention [5] includes the tackifier according to any one of the above [1] to [4], in which the structural unit derived from the polyfunctional aromatic compound is a structural unit derived from divinylbenzene.

[0012] The present invention [6] includes a pressure-sensitive adhesive composition comprising the tackifier according to any one of the above [1] to [5], a (meth)acrylic resin, and a crosslinking agent. [Effects of the Invention]

[0013] The tackifier of the present invention has a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) of 1.80 or more and 5.50 or less, and therefore has excellent heat resistance.

[0014] The pressure-sensitive adhesive composition of the present invention contains the tackifier of the present invention, and therefore has excellent heat resistance. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows gel permeation chromatograms of the tackifiers of Production Example 1, Production Comparative Example 1, and Production Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1. Tackifier The tackifier contains structural units derived from a styrene-based monomer and structural units derived from a polyfunctional aromatic compound. Such a tackifier is a polymer of a first polymerization component containing a styrene-based monomer and a polyfunctional aromatic compound.

[0017] The first polymerization component contains, as essential components, a styrene-based monomer and a polyfunctional aromatic compound.

[0018] <Styrene-based monomers> Examples of styrene-based monomers include styrene, α-alkyl-substituted styrene, nuclear-alkyl-substituted styrene, and isopropenyl toluene.

[0019] Examples of α-alkyl substituted styrenes include α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-n-butylstyrene, α-isobutylstyrene, α-t-butylstyrene, α-n-pentylstyrene, α-2-methylbutylstyrene, and α-3-methylbutyl-2-styrene.

[0020] Examples of the nuclear alkyl-substituted styrenes include methylstyrenes (e.g., o-methylstyrene, m-methylstyrene, p-methylstyrene), ethylstyrenes (e.g., o-ethylstyrene, m-ethylstyrene, p-ethylstyrene), propylstyrenes (e.g., o-propylstyrene, m-propylstyrene, p-propylstyrene), and butylstyrenes (e.g., o-butylstyrene, m-n-butylstyrene, p-n-butylstyrene, o-isobutylstyrene, m-isobutylstyrene, p-isobutylstyrene, ot-butylstyrene, mt-butylstyrene, and pt-butylstyrene).

[0021] As the styrene-based monomer, isopropenyl toluene is preferable from the viewpoint of reliably adjusting the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) described below to fall within a predetermined range.

[0022] The styrene-based monomers can be used alone or in combination of two or more kinds.

[0023] <Polyfunctional aromatic compounds> A polyfunctional aromatic compound is an aromatic compound having two or more vinyl groups. Examples of polyfunctional aromatic compounds include divinyl aromatic compounds. Examples of divinyl aromatic compounds include divinylbenzene (e.g., o-divinylbenzene, m-divinylbenzene, p-divinylbenzene), diisopropenylbenzene (e.g., 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene), divinylnaphthalene (e.g., 1,3-divinylnaphthalene, 1,8-divinylnaphthalene, 1,4-divinylnaphthalene, 1,5-divinylnaphthalene, 2,3-divinylnaphthalene, 2,7-divinyl naphthalene, 2,6-divinylnaphthalene), divinylbiphenyls (e.g., 4,4'-divinylbiphenyl, 4,3'-divinylbiphenyl, 4,2'-divinylbiphenyl, 3,2'-divinylbiphenyl, 3,3'-divinylbiphenyl, 2,2'-divinylbiphenyl, 2,4-divinylbiphenyl), 1,2-divinyl-3,4-dimethylbenzene, 1,3-divinyl-4,5,8-tributylnaphthalene, and 2,2'-divinyl-4-ethyl-4'-propylbiphenyl.

[0024] As the polyfunctional aromatic compound, divinylbenzene is preferred from the viewpoint of reliably adjusting the molecular weight dispersity (z-average molecular weight / weight average molecular weight) described below within a predetermined range. As the polyfunctional aromatic compound, p-divinylbenzene is more preferred.

[0025] The polyfunctional aromatic compounds can be used alone or in combination of two or more kinds.

[0026] <Other ingredients> The first polymeric component may optionally contain other components, such as indene and unsaturated aliphatic hydrocarbons.

[0027] The unsaturated aliphatic hydrocarbon is a component copolymerizable with a styrene-based monomer, a polyfunctional aromatic compound, and indene, and examples thereof include C4 fractions and C5 fractions.

[0028] C4 fractions are obtained by petroleum refining and / or cracking, and generally have a boiling point range of −15° C. to 45° C. under atmospheric pressure, including, for example, unsaturated aliphatic hydrocarbons having 4 carbon atoms and no conjugated double bonds, and unsaturated aliphatic hydrocarbons having 4 carbon atoms and containing conjugated double bonds.

[0029] Examples of unsaturated aliphatic hydrocarbons having 4 carbon atoms and no conjugated double bond include 1-butene, isobutene, and 2-butene.

[0030] An example of an unsaturated aliphatic hydrocarbon having 4 carbon atoms and containing a conjugated double bond is 1,3-butadiene.

[0031] C5 fractions are obtained by petroleum refining and / or cracking, and generally have a boiling point range of −15° C. to 45° C. under atmospheric pressure, including, for example, unsaturated aliphatic hydrocarbons having 5 carbon atoms and no conjugated double bonds, and unsaturated aliphatic hydrocarbons having 5 carbon atoms and no conjugated double bonds.

[0032] Examples of unsaturated aliphatic hydrocarbons having 5 carbon atoms and no conjugated double bond include 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, and 2-pentene.

[0033] Examples of unsaturated aliphatic hydrocarbons having 5 carbon atoms and containing a conjugated double bond include isoprene, 1,3-pentadiene, and cyclopentadiene.

[0034] The other components can be used alone or in combination of two or more.

[0035] The first polymerization component preferably does not contain any other components and is composed of a styrene-based monomer and a polyfunctional aromatic compound, i.e., the tackifier is preferably a copolymer composed of a styrene-based monomer and a polyfunctional aromatic compound.

[0036] In addition, all or part of the components constituting the first polymeric component may be derived from fossil fuels or biomass.

[0037] Fossil fuels include oil, coal, natural gas, shale gas, or combinations thereof. Biomass is any renewable natural raw material and its residues, such as from plants or animals, including fungi, yeast, algae, and bacteria.

[0038] <Production of tackifier> The tackifier is obtained by polymerizing a first polymerization component in the presence of a Friedel-Crafts catalyst.

[0039] Friedel-Crafts catalysts include, for example, phenol complexes (eg, boron trifluoride phenolate complexes).

[0040] The blending ratio of the Friedel-Crafts catalyst is, for example, 0.01 to 1 part by mass with respect to 100 parts by mass of the first polymer component.

[0041] As for the polymerization conditions, the polymerization temperature is, for example, −50° C. to 50° C., preferably −30° C. to 30° C., and more preferably −10° C. to 10° C. The polymerization time is, for example, 10 minutes to 10 hours.

[0042] The reaction is carried out in the presence of a solvent or without a solvent, and is preferably carried out in the presence of a solvent.

[0043] Examples of the solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, and alkyl esters. Preferably, the solvent is an aromatic hydrocarbon. Examples of the aromatic hydrocarbon include toluene and xylene. Preferably, the aromatic hydrocarbon is toluene.

[0044] The solvents can be used alone or in combination of two or more kinds.

[0045] This gives a tackifier (a tackifier solution).

[0046] The tackifier solution has a solids concentration of, for example, 5% by mass to 70% by mass, or preferably 10% by mass to 60% by mass.

[0047] In such a tackifier, the content of the structural units derived from a styrene-based monomer is, for example, 75 mol% to 90 mol%, preferably 76 mol% to 85 mol%, and more preferably 78 mol% to 80 mol%, based on the total amount of the structural units derived from a styrene-based monomer and the structural units derived from a polyfunctional aromatic compound.

[0048] Specifically, the content of the structural units derived from styrene-based monomers relative to the total amount of the structural units derived from styrene-based monomers and the structural units derived from polyfunctional aromatic compounds is, from the viewpoint of heat resistance, for example, 75 mol% or more, preferably 76 mol% or more, more preferably 78 mol% or more, and from the viewpoint of heat resistance, 90 mol% or less, preferably 85 mol% or less, more preferably 80 mol% or less.

[0049] Furthermore, the content of structural units derived from styrene-based monomers relative to the tackifier is, from the viewpoint of heat resistance, for example, 75 mol% to 90 mol%, preferably 76 mol% to 85 mol%, and more preferably 78 mol% to 80 mol%.

[0050] The content of the structural units derived from the polyfunctional aromatic compound is, for example, 10 mol % to 25 mol %, preferably 15 mol % to 24 mol %, and more preferably 20 mol % to 22 mol %, based on the total amount of the structural units derived from the styrene-based monomer and the structural units derived from the polyfunctional aromatic compound.

[0051] Specifically, the content of the structural units derived from the polyfunctional aromatic compound is, from the viewpoint of heat resistance, for example, 10 mol% or more, preferably 15 mol% or more, more preferably 20 mol% or more, based on the total amount of the structural units derived from the styrene-based monomer and the structural units derived from the polyfunctional aromatic compound, and from the viewpoint of heat resistance, for example, 25 mol% or less, preferably 24 mol% or less, more preferably 22 mol% or less.

[0052] Furthermore, the content of the structural unit derived from the polyfunctional aromatic compound relative to the tackifier is, from the viewpoint of heat resistance, for example, 10 mol % to 25 mol %, preferably 15 mol % to 24 mol %, and more preferably 20 mol % to 22 mol %.

[0053] The content of structural units derived from other components is, for example, 20 mol % or less, preferably 10 mol % or less, more preferably 1 mol % or less, and even more preferably 0 mol % relative to the tackifier.

[0054] The ratio of the above constituent units is as follows: 13 It can be measured by C-NMR spectroscopy.

[0055] The molecular weight dispersity (z-average molecular weight / weight-average molecular weight) of the tackifier, measured by gel permeation chromatography (GPC) and converted into standard polystyrene, is 1.80 to 5.50, preferably 2.30 to 4.00, more preferably 2.80 to 3.50, and even more preferably 3.00 to 3.20.

[0056] Specifically, the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is 1.80 or more, preferably 2.30 or more, more preferably 2.80 or more, even more preferably 3.00 or more, and 5.50 or less, preferably 4.00 or less, more preferably 3.50 or less, even more preferably 3.20 or less.

[0057] When the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is equal to or higher than the lower limit, the heat resistance is improved.

[0058] On the other hand, if the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is less than the lower limit, the heat resistance decreases.

[0059] Furthermore, when the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is equal to or less than the upper limit, the heat resistance is improved.

[0060] On the other hand, if the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) exceeds the upper limit, the heat resistance decreases.

[0061] The molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is adjusted to fall within the above range by adjusting the blending recipe of each component and the polymerization conditions.

[0062] The z-average molecular weight, calculated as standard polystyrene, measured by gel permeation chromatography (GPC) is, from the viewpoint of heat resistance, for example, 6000 or less, preferably 5500 or less, more preferably 5300 or less, and from the viewpoint of heat resistance, for example, 2000 or more, preferably 3000 or more, more preferably 4000 or more, even more preferably 5000 or more.

[0063] The weight average molecular weight, calculated as standard polystyrene, measured by gel permeation chromatography (GPC) is, from the viewpoint of heat resistance, for example, 1000 to 5000, preferably 1200 to 4000, more preferably 1400 to 3000, and still more preferably 1600 to 2000.

[0064] The number average molecular weight, calculated as standard polystyrene, measured by gel permeation chromatography (GPC) is, for example, 650 to 800, or preferably 660 to 700, from the viewpoint of heat resistance.

[0065] From the viewpoint of heat resistance, the molecular weight dispersity (weight average molecular weight / number average molecular weight) is 1.60 to 6.00, preferably 1.80 to 5.00, more preferably 2.00 to 4.00, still more preferably 2.20 to 3.00, and particularly preferably 2.30 to 2.50.

[0066] The molecular weight dispersity (z-average molecular weight / weight average molecular weight), z-average molecular weight, weight average molecular weight, number average molecular weight, and molecular weight dispersity (weight average molecular weight / number average molecular weight) are obtained by dissolving the tackifier in tetrahydrofuran and measuring the soluble content in standard polystyrene terms using gel permeation chromatography (GPC). The measurement conditions for gel permeation chromatography are described in detail in the examples below.

[0067] 2. Adhesive composition The adhesive composition contains a tackifier, a (meth)acrylic resin, and a crosslinking agent.

[0068] <Tackifier> The tackifier imparts tackiness and heat resistance.

[0069] The tackifiers can be used alone or in combination of two or more kinds.

[0070] The content of the tackifier is, for example, 2 to 40 parts by mass, preferably 10 to 30 parts by mass, and more preferably 15 to 25 parts by mass, relative to 100 parts by mass of the total amount of the tackifier and the (meth)acrylic resin.

[0071] The content of the tackifier relative to the adhesive composition is, for example, 2 to 40% by mass, preferably 10 to 30% by mass, and more preferably 15 to 25% by mass.

[0072] <(Meth)acrylic resin> The (meth)acrylic resin can be obtained, for example, as a polymer of a second polymerization component containing a (meth)acrylic acid alkyl ester, where (meth)acrylic refers to acrylic and / or methacrylic.

[0073] Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters having an alkyl moiety with 1 to 12 carbon atoms. Examples of (meth)acrylic acid alkyl esters having an alkyl moiety with 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate.

[0074] Preferred examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate and alkyl acrylate esters having 2 to 8 carbon atoms. More preferred examples of the (meth)acrylic acid alkyl ester include butyl (meth)acrylate. Even more preferred examples of the (meth)acrylic acid alkyl ester include butyl acrylate.

[0075] The (meth)acrylic acid alkyl esters can be used alone or in combination of two or more kinds.

[0076] The blending ratio of the (meth)acrylic acid alkyl ester relative to 100 parts by mass of the second polymer component is, for example, 60 parts by mass to 100 parts by mass, preferably 70 parts by mass to 99.9 parts by mass, more preferably 80 parts by mass to 99.9 parts by mass, and even more preferably 90 parts by mass to 99.9 parts by mass.

[0077] The second polymerization component may also contain a copolymerizable monomer that is copolymerizable with the (meth)acrylic acid alkyl ester.

[0078] Examples of copolymerizable monomers include functional group-containing vinyl monomers, vinyl esters, aromatic vinyl monomers, N-substituted unsaturated carboxylic acid amides, heterocyclic vinyl compounds, vinylidene halide compounds, α-olefins, and dienes.

[0079] Examples of functional group-containing vinyl monomers include carboxy group-containing vinyl monomers, hydroxy group-containing vinyl monomers, amino group-containing vinyl monomers, glycidyl group-containing vinyl monomers, cyano group-containing vinyl monomers, sulfonic acid group-containing vinyl monomers and salts thereof, acetoacetoxy group-containing vinyl monomers, phosphoric acid group-containing compounds, and amide group-containing vinyl monomers.

[0080] Examples of carboxy group-containing vinyl monomers include (meth)acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, and crotonic acid.

[0081] Examples of hydroxyl group-containing vinyl monomers include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0082] Examples of amino group-containing vinyl monomers include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethylamino)ethyl (meth)acrylate.

[0083] An example of the glycidyl group-containing vinyl monomer is glycidyl (meth)acrylate.

[0084] An example of the cyano group-containing vinyl monomer is (meth)acrylonitrile.

[0085] Examples of sulfonic acid group-containing vinyl monomers include allyl sulfonic acid and methallyl sulfonic acid. Examples of salts thereof include alkali metal salts (e.g., sodium salts and potassium salts) of the sulfonic acid group-containing vinyl monomers, such as ammonium salts. Specific examples include sodium allyl sulfonate, sodium methallyl sulfonate, and ammonium methallyl sulfonate.

[0086] Examples of the acetoacetoxy group-containing vinyl monomer include acetoacetoxyethyl (meth)acrylate.

[0087] An example of the phosphate group-containing compound is 2-methacryloyloxyethyl acid phosphate.

[0088] An example of the amide group-containing vinyl monomer is (meth)acrylamide.

[0089] Examples of vinyl esters include vinyl acetate and vinyl propionate.

[0090] Aromatic vinyl monomers include, for example, styrene, α-methylstyrene, and divinylbenzene.

[0091] An example of the N-substituted unsaturated carboxylic acid amide is N-methylol (meth)acrylamide.

[0092] An example of the heterocyclic vinyl compound is vinylpyrrolidone.

[0093] Examples of vinylidene halide compounds include vinylidene chloride and vinylidene fluoride.

[0094] Examples of the α-olefins include ethylene and propylene.

[0095] An example of the dienes is butadiene.

[0096] Further, the copolymerizable monomer may be a crosslinkable vinyl monomer.

[0097] Examples of crosslinkable vinyl monomers include compounds containing two or more vinyl groups, such as methylenebis(meth)acrylamide, divinylbenzene, and polyethylene glycol chain-containing di(meth)acrylate.

[0098] The copolymerizable monomers can be used alone or in combination of two or more kinds.

[0099] The blending ratio of the copolymerizable monomer is, for example, 0 to 40 parts by mass, preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the second polymerization component.

[0100] The polymerization method for the second polymerization component is not particularly limited, and a known polymerization method may be used.

[0101] As a method for polymerizing the second polymerization component, the second polymerization component is preferably radically polymerized in a solvent (e.g., ethyl acetate). In this method, for example, the second polymerization component and a polymerization initiator are blended in a solvent and polymerized in the solvent.

[0102] The polymerization initiator is not particularly limited, and examples of the polymerization initiator include persulfates, organic peroxides, and azo compounds.

[0103] The blending ratio of the polymerization initiator is appropriately set depending on the purpose and application.

[0104] The polymerization initiators can be used alone or in combination of two or more kinds.

[0105] In the polymerization, a molecular weight modifier may be added as needed.

[0106] Examples of molecular weight regulators include mercaptans, allyl compounds, and low-molecular-weight halogen compounds. Examples of mercaptans include t-dodecyl mercaptan and n-dodecyl mercaptan. Examples of allyl compounds include allyl sulfonic acid, methallyl sulfonic acid, and sodium salts thereof.

[0107] The blending ratio of the molecular weight modifier is appropriately set depending on the purpose and application.

[0108] The molecular weight regulator can be used alone or in combination of two or more kinds.

[0109] The polymerization conditions are, under normal pressure, a polymerization temperature of, for example, 30° C. to 150° C., or preferably 50° C. to 120° C. The polymerization time is, for example, 1 hour to 30 hours, or preferably 2 hours to 20 hours.

[0110] This gives a (meth)acrylic resin (a (meth)acrylic resin solution).

[0111] The (meth)acrylic resin has a glass transition temperature of, for example, -30°C to 20°C, or preferably -20°C to 0°C.

[0112] The glass transition temperature can be calculated, for example, by the FOX formula.

[0113] The solid content concentration of the (meth)acrylic resin solution is, for example, 5% by mass to 70% by mass, or preferably 10% by mass to 60% by mass.

[0114] The (meth)acrylic resins can be used alone or in combination of two or more kinds.

[0115] The content of the (meth)acrylic resin is, for example, 60 parts by mass to 98 parts by mass, preferably 70 parts by mass to 90 parts by mass, and more preferably 75 parts by mass to 85 parts by mass, relative to 100 parts by mass of the total amount of the tackifier and the (meth)acrylic resin.

[0116] The content of the (meth)acrylic resin relative to the pressure-sensitive adhesive composition is, for example, 60% by mass to 98% by mass, preferably 70% by mass to 90% by mass, and more preferably 75% by mass to 85% by mass.

[0117] <Crosslinking agent> The crosslinking agent improves adhesion.

[0118] Examples of the crosslinking agent include an epoxy compound, an isocyanate compound, an aziridine compound, and a melamine compound.

[0119] Examples of epoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, and resorcinol diglycidyl ether.

[0120] Examples of the isocyanate compound include derivatives of hexamethylene diisocyanate (for example, trimethylolpropane adducts, isocyanurate derivatives) and derivatives of tolylene diisocyanate (for example, trimethylolpropane adducts, isocyanurate derivatives).

[0121] Examples of the aziridine compound include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), N,N'-toluene-2,4-bis(1-aziridinecarboxamide), and trimethylolpropane-tri-β-(2-methylaziridine)propionate.

[0122] An example of the melamine compound is hexamethoxymethylolmelamine.

[0123] As the crosslinking agent, preferably, an isocyanate compound is used.

[0124] The crosslinking agent can be used alone or in combination of two or more kinds.

[0125] The content of the crosslinking agent relative to the pressure-sensitive adhesive composition is, for example, 0.1 to 2.0% by mass, or preferably 0.5 to 1.5% by mass.

[0126] <Additives> The pressure-sensitive adhesive composition may contain additives in an appropriate ratio, as needed, such as antioxidants, ultraviolet absorbers, antistatic agents, silane coupling agents, coatability improvers, leveling agents, antifoaming agents, plasticizers, surfactants, pigments, fillers, antifungal agents, processing aids, and antioxidants.

[0127] The additives can be used alone or in combination of two or more kinds.

[0128] <Preparation of adhesive composition> The adhesive composition can be obtained by blending a tackifier, a (meth)acrylic resin, a crosslinking agent, and additives that are blended as needed.

[0129] The pressure-sensitive adhesive composition can also be diluted with a known solvent. When the polymerization of the tackifier and / or the (meth)acrylic resin is carried out in the presence of a solvent, the solvent can be used as is.

[0130] When the pressure-sensitive adhesive composition is diluted, the solid content concentration is, for example, 5% by mass to 70% by mass, or preferably 10% by mass to 60% by mass.

[0131] <Action and effect> In the pressure-sensitive adhesive composition, the tackifier has a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) of 1.80 or more and 5.50 or less, which results in excellent heat resistance.

[0132] Specifically, the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is an index of the high molecular weight components in a tackifier; when the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is small, the tackifier tends to have fewer high molecular weight components, and when the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is large, the tackifier tends to have more high molecular weight components.

[0133] As described above, the tackifier is produced by polymerizing a styrene-based monomer and a polyfunctional aromatic compound. Specifically, a vinyl group in the styrene-based monomer reacts with a vinyl group in the polyfunctional aromatic compound. On the other hand, since the polyfunctional aromatic compound has two or more vinyl groups, the vinyl groups in the polyfunctional aromatic compound that do not participate in the reaction with the styrene-based monomer may form a crosslinked structure, resulting in the production of high molecular weight components.

[0134] In contrast, the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) of this tackifier is 5.50 or less. Therefore, the generation of high-molecular-weight components having a crosslinked structure is suppressed. Therefore, the tackifier has a predetermined amount of vinyl groups that do not participate in the above reaction.

[0135] Furthermore, this tackifier has a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) of 1.80 or more, which means that the tackifier has a certain number or more of vinyl groups that are not involved in the above reaction.

[0136] In other words, in this tackifier, the molecular weight dispersity (z-average molecular weight / weight-average molecular weight) is adjusted to 1.80 or more and 5.50 or less, thereby adjusting the proportion of vinyl groups that do not participate in the above reaction to a predetermined level.

[0137] Such vinyl groups form a crosslinked structure upon heating, thereby improving heat resistance.

[0138] The pressure-sensitive adhesive composition of the present invention contains the tackifier of the present invention, and therefore has excellent heat resistance. [Example]

[0139] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, and parameters used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Form for Carrying Out the Invention."

[0140] <Ingredient details> Details of the abbreviations used in each example and comparative example are given below. Arontack: Acrylic resin (second polymer component contains butyl acrylate), manufactured by Toagosei Co., Ltd. IPT: Isopropenyltoluene DVB: p-divinylbenzene Takenate: Isocyanate compound, manufactured by Mitsui Chemicals

[0141] <Production of tackifier> Manufacturing Example 1 A mixture of the first polymerization component and dehydrated and purified toluene (first polymerization component / toluene = 2 / 3 (volume ratio)) and a boron trifluoride phenolate complex (1.7 times the equivalent of phenol) diluted 10 times with dehydrated and purified toluene were continuously fed into the first stage of a 1270 ml capacity autoclave equipped with a stirring blade, and a polymerization reaction was carried out at 5°C. The mass ratio of isopropenyltoluene to divinylbenzene (isopropenyltoluene / divinylbenzene) was 70 / 30, the feed rate of the mixture of the first polymerization component and toluene was 1.0 L / hour, and the feed rate of the diluted catalyst was 71 mL / hour.

[0142] The reaction mixture was transferred to the second autoclave and the polymerization reaction continued at 5°C. When the total residence time in the first and second autoclaves reached 2 hours, the reaction mixture was continuously discharged from the autoclave. When the residence time reached three times the normal residence time, 1 liter of reaction mixture was collected to terminate the polymerization reaction. After the polymerization was completed, a 1N NaOH aqueous solution was added to the collected reaction mixture to deash the catalyst residue. The resulting reaction mixture was washed five times with a large amount of water, and the solvent and unreacted first polymerization component were then removed under reduced pressure using an evaporator. This produced a tackifier.

[0143] Comparative Manufacturing Example 1 A tackifier was produced based on the same procedure as in Production Example 1. However, the compounding recipe was changed based on Table 1, the mass ratio of isopropenyltoluene to divinylbenzene (isopropenyltoluene / divinylbenzene) was 80 / 20, and the supply rate of the diluted catalyst was 71 milliliters / hour.

[0144] Comparative Manufacturing Example 2 A tackifier was produced based on the same procedure as in Production Example 1. However, the compounding recipe was changed based on Table 1, the mass ratio of isopropenyltoluene to divinylbenzene (isopropenyltoluene / divinylbenzene) was set to 70 / 30, and the supply rate of the diluted catalyst was set to 142 milliliters / hour.

[0145] Comparative Manufacturing Example 3 A tackifier was produced based on the same procedure as in Production Example 1. However, the compounding recipe was changed based on Table 1, the ratio of the mixture of the first polymerization component and toluene was changed to first polymerization component / toluene = 1 / 1 (volume ratio), and the supply rate of the diluted catalyst was changed to 105 mL / hour.

[0146] Comparative Manufacturing Example 4 A tackifier was produced based on the same procedure as in Production Example 1. However, the compounding recipe was changed based on Table 1, the ratio of the mixture of the first polymerization component and toluene was changed to first polymerization component / toluene = 1 / 1 (volume ratio), and the supply rate of the diluted catalyst was changed to 53 milliliters / hour.

[0147] <Preparation of adhesive composition> Example 1, Comparative Examples 1 to 4 A (meth)acrylic resin, a tackifier, and a crosslinking agent (isocyanate compound) were blended according to the descriptions in Table 2. In this way, a pressure-sensitive adhesive composition was prepared.

[0148] <Evaluation> [Constituent units of each component] The structural units of each component in the polymer of each production example were determined based on the following conditions: 13 The results were obtained by analyzing the C-NMR spectrum, and are shown in Table 1. {conditions} Equipment: Bruker Biospin AVANCEIII cryo-500 nuclear magnetic resonance spectrometer Measurement nucleus: 13C (125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 μsec) Number of points: 64k Measurement range: 250 ppm (-55 to 195 ppm) Repeat time: 5.5 seconds Number of times accumulated: 128 Measurement solvent: orthodichlorobenzene / benzene-d6 (4 / 1 (volume ratio)) Sample concentration: 60 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 1.0 Hz) Chemical shift reference: δδ signal 29.73 ppm

[0149] [Number average molecular weight (Mn), weight average molecular weight (Mw), z-average molecular weight (Mz), Mw / Mn and Mz / Mw] The tackifier of each Example and Comparative Example was dissolved in tetrahydrofuran to prepare a 20 mg / mL tetrahydrofuran solution. This solution was then added to a glass syringe equipped with a 0.2 μm polyvinylidene fluoride filter manufactured by Millipore Corporation, and filtered through the filter. This resulted in the preparation of a sample. In other words, this sample is a tetrahydrofuran-soluble component.

[0150] Next, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) of the obtained sample were measured using gel permeation chromatography (GPC) under the following conditions, and the Mw / Mn and Mz / Mw ratios were calculated. The results are shown in Table 1 and Figure 1. (conditions) Apparatus: GPC HLC-8320 (Tosoh Corporation) Solvent: tetrahydrofuran Columns: TSKgel G7000 x 1 (Tosoh Corporation), TSKgel G4000 x 2 (Tosoh Corporation), TSKgel G2000 x 1 (Tosoh Corporation) Flow rate: 1.0ml / min Column temperature: 40℃ Detector: Differential refractive index detector Injection volume: 50μl

[0151] [exterior] An ethyl acetate / toluene solution of the pressure-sensitive adhesive composition of each Example and Comparative Example was applied to a release-treated PET film so that the film thickness after drying was approximately 25 μm. After drying at 100°C for 10 minutes, a 25 μm PET film was pressed onto the coated surface to produce a pressure-sensitive adhesive sheet. The sheet was left at 50°C for 3 days to allow the pressure-sensitive adhesive composition to be fully crosslinked. The pressure-sensitive adhesive sheet was visually inspected and evaluated according to the following criteria. The results are shown in Table 1. <Judgment criteria> ○:Transparent △: Slightly cloudy ×: Cloudy

[0152] [Heat resistance] The adhesive sheet obtained above was cut to a width of 20 mm and a length of 100 mm. The release-treated PET film was peeled off, and the adhesive layer was pressed against a SUS plate by rolling it back and forth twice with a 2 kg rubber roller so that the adhesive layer had an adhesive area of ​​20 mm x 50 mm. A 20 g load was applied vertically downward to the longitudinal edge of the adhesive sheet attached to the SUS plate, and the sheet was left at a temperature of 180°C for 30 minutes. The distance (mm) that the adhesive layer peeled off and shifted in the longitudinal direction was measured, and if the adhesive layer completely peeled off and fell, it was evaluated as having fallen. The results are shown in Table 1.

[0153] [Table 1]

[0154] [Table 2]

Claims

1. Contains structural units derived from styrene-based monomers and structural units derived from polyfunctional aromatic compounds, A tackifier having a molecular weight dispersity (z-average molecular weight / weight-average molecular weight) in terms of standard polystyrene measured by gel permeation chromatography (GPC) of 1.80 or more and 5.50 or less.

2. 2. The tackifier of claim 1, having a z-average molecular weight of 6,000 or less.

3. 2. The tackifier according to claim 1, wherein the content of the structural units derived from the polyfunctional aromatic compound is 10 mol % or more and 25 mol % or less based on the total amount of the structural units derived from the styrene-based monomer and the structural units derived from the polyfunctional aromatic compound.

4. The tackifier according to claim 1 , wherein the structural unit derived from a styrene-based monomer is a structural unit derived from isopropenyl toluene.

5. The tackifier according to claim 1 , wherein the structural unit derived from the polyfunctional aromatic compound is a structural unit derived from divinylbenzene.

6. The tackifier according to any one of claims 1 to 5, a (meth)acrylic resin; and a crosslinking agent.

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