Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]

Definitions

• the present invention relates to an adhesive composition and a method for producing an adhesive layer using the same.
• the present invention relates to an adhesive composition that reduces the burden on the environment.
• the solids concentration of the adhesive composition is adjusted using an organic solvent from the viewpoint of coatability.
• Toluene is one example of the organic solvents mentioned above, and is a cause of sick house syndrome and is of concern as an indoor pollutant.
• Patent Document 1 discloses an adhesive composition that does not contain toluene and uses at least one organic solvent selected from the group consisting of ethyl acetate, acetone, methyl ethyl ketone, and methyl isobutyl ketone as the solvent.
• Patent documents 2 to 4 disclose adhesive compositions that use alcohol-based organic solvents.
• Ketone-based solvents and ester-based solvents are widely used as organic solvents to replace toluene, due to their ease of availability.
• alternative materials are desired not only for toluene, but also for ketone-based solvents and ester-based solvents.
• the present invention therefore aims to provide an adhesive composition that reduces the burden on the environment. It also aims to provide a method for producing an adhesive layer using the above adhesive composition.
• a pressure-sensitive adhesive composition comprising a (meth)acrylic polymer and an organic solvent
• the organic solvent includes an alcohol-based organic solvent, A pressure-sensitive adhesive composition having a solid content concentration of 50 mass % or more.
• Aspect 2 2.
• Aspect 3 The alcohol-based organic solvent contains methanol, A pressure-sensitive adhesive composition according to aspect 1 or 2, wherein the content of the methanol in the organic solvent is 80 mass % or more.
• Aspect 4 The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the solid content concentration is 60 to 90 mass%.
• Aspect 5 The pressure-sensitive adhesive composition according to any one of claims 1 to 4, having a turbidity of 25 or less.
• Aspect 6 The pressure-sensitive adhesive composition according to any one of Aspects 1 to 5, wherein the (meth)acrylic polymer has a molecular weight distribution (Mw/Mn) of 4.0 or less.
• Aspect 7 The pressure-sensitive adhesive composition according to any one of Aspects 1 to 6, wherein the (meth)acrylic polymer is a polymer of monomer components containing 60 to 99.5% by mass of a (meth)acrylic acid alkyl ester having an alkyl group of 4 to 18 carbon atoms and 0.01 to 10% by mass of a crosslinkable functional group-containing monomer.
• Aspect 8 The pressure-sensitive adhesive composition according to aspect 7, wherein 60 mass% or more of the (meth)acrylic acid alkyl esters having an alkyl group of 4 to 18 carbon atoms are (meth)acrylic acid alkyl esters having a biomass-derived carbon content of 70% or more.
• Aspect 9 A step of applying the pressure-sensitive adhesive composition according to any one of aspects 1 to 8 to a substrate to form a layer made of the pressure-sensitive adhesive composition; and A step of drying the layer made of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer, The method for producing a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a haze of less than 5% when the thickness is 25 ⁇ m.
• the organic solvent in the pressure-sensitive adhesive composition includes methanol,
• the method for producing a pressure-sensitive adhesive layer comprises determining the degree of dryness based on a change in turbidity of the layer made of the pressure-sensitive adhesive composition.
• the pressure-sensitive adhesive composition according to the present embodiment contains a (meth)acrylic polymer and an organic solvent, and the organic solvent includes an alcohol-based organic solvent.
• the pressure-sensitive adhesive composition has a solid content of 50 mass % or more. In this specification, mass % and weight %, and parts by mass and parts by weight have the same meaning.
• the adhesive composition according to this embodiment contains an alcohol-based organic solvent as the organic solvent, which reduces the burden on the environment compared to the use of conventional organic solvents such as ester-based solvents, ketone-based solvents, and toluene.
• the burden on the environment is further reduced.
• the organic solvent in the present embodiment includes an alcohol-based organic solvent.
• the alcohol-based organic solvent can reduce the burden on the environment compared to conventional organic solvents such as ester-based solvents, ketone-based solvents, toluene, etc. Furthermore, compared to other organic solvents, the alcohol-based organic solvent can obtain a pressure-sensitive adhesive composition with a viscosity suitable for coating by using a small amount of the alcohol-based organic solvent.
• the content of the alcohol-based organic solvent in the organic solvent is, for example, 50 to 100% by mass.
• the content is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.
• the content of the alcohol-based organic solvent is also preferable that it is 100% by mass, i.e., the organic solvent consists only of the alcohol-based organic solvent.
• bioalcohol as the alcohol-based organic solvent is more preferable from the viewpoint of reducing the burden on the environment.
• bioalcohol include biomethanol and bioethanol, which can be produced by conventional methods.
• biomethanol may be obtained by oxidizing methane derived from biomass.
• the alcohol-based organic solvent is not particularly limited, but for example, alcohols having 1 to 6 carbon atoms or 1 to 4 carbon atoms are more preferable. Among these, methanol, ethanol, and isopropyl alcohol are more preferable, and methanol is particularly preferable from the viewpoint of volatility and viscosity adjustment. Only one type of alcohol-based organic solvent may be used, or two or more types may be used in combination.
• the methanol content in the organic solvent is, for example, 50 to 100% by mass.
• the content is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.
• the methanol content There is no particular upper limit to the methanol content, and it is also preferable for it to be 100% by mass, i.e., the organic solvent consists only of methanol.
• the methanol content may be 70% by mass or less or 50% by mass or less.
• organic solvents that are conventionally used to adjust the coatability of adhesive compositions can be used.
• the solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethan
• the content of organic solvents other than the above-mentioned alcohol-based organic solvents is preferably as low as possible, and is preferably 30% by mass or less or 10% by mass or less of the total organic solvents.
• the (meth)acrylic polymer refers to at least one of an acrylic polymer and a methacrylic polymer.
• the weight average molecular weight (Mw) of the (meth)acrylic polymer is preferably 30,000 to 2,000,000 from the viewpoint of the coatability of the adhesive composition and imparting heat resistance to the resulting adhesive layer.
• the weight average molecular weight may be 30,000 or more, 50,000 or more, 80,000 or more, 100,000 or more, 120,000 or more, or 150,000 or more.
• the weight average molecular weight may also be 2,000,000 or less, 1,500,000 or less, 1,000,000 or less, 500,000 or less, 300,000 or less, 200,000 or less, or 150,000 or less.
• the molecular weight distribution (Mw/Mn) of the (meth)acrylic polymer is preferably, for example, 1.5 to 4.0. From the viewpoint of proper formation of a crosslinked structure during preparation of the adhesive layer and stabilizing the physical properties of the resulting adhesive sheet, the molecular weight distribution is preferably 4.0 or less, and more preferably 3.0 or less. This molecular weight distribution (Mw/Mn) may be 1.5 or more, 2.0 or more, or 2.5 or more.
• alcohol used as the solvent, an adhesive composition with excellent coatability can be obtained even if the molecular weight distribution is within the above range.
• the weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic polymer are measured by the method described in the Examples.
• the monomer components constituting the (meth)acrylic polymer are not particularly limited, but preferably contain, for example, an alkyl (meth)acrylate ester having an alkyl group with 4 to 18 carbon atoms. It is more preferable to contain a crosslinkable functional group-containing monomer in addition to the alkyl (meth)acrylate ester having an alkyl group with 4 to 18 carbon atoms. This allows the adhesive layer obtained from the adhesive composition to exhibit good heat resistance and adhesive properties. If desired, the composition may contain a monomer other than the alkyl (meth)acrylate ester having an alkyl group with 4 to 18 carbon atoms and the crosslinkable functional group-containing monomer.
• the (meth)acrylic acid alkyl ester preferably has an alkyl group having 4 to 18 carbon atoms, more preferably 4 to 8.
• the number of carbon atoms is preferably 4 or more, and is preferably 18 or less, more preferably 8 or less.
• Examples of (meth)acrylic acid alkyl esters having an alkyl group with 4 to 18 carbon atoms include n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, nonyl (meth)acrylate, iso-nonyl (meth)acrylate, decyl (meth)acrylate, iso-decyl (meth)acrylate, undeca(meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, iso-octadecyl (meth)acryl
• the ratio of (meth)acrylic acid alkyl esters having an alkyl group with 4 to 18 carbon atoms in the monomer components constituting the (meth)acrylic polymer is preferably 60 to 99.5% by mass.
• the above ratio is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.
• the above ratio is preferably 99.5% by mass or less, more preferably 99% by mass or less, and even more preferably 95% by mass or less.
• the (meth)acrylic acid alkyl ester having an alkyl group with 4 to 18 carbon atoms preferably contains a raw material with a high biomass content, for example, a (meth)acrylic acid alkyl ester with a biomass-derived carbon content of 70% or more.
• the content of (meth)acrylic acid alkyl esters having an alkyl group with 4 to 18 carbon atoms and having a biomass-derived carbon content of 70% or more is preferably, for example, 60 to 100% by mass, relative to (meth)acrylic acid alkyl esters having an alkyl group with 4 to 18 carbon atoms.
• the content is preferably 60% by mass or more, more preferably 80% by mass or more, and may be 100% by mass, i.e., all of the (meth)acrylic acid alkyl esters having an alkyl group with 4 to 18 carbon atoms have a biomass-derived carbon content of 70% or more.
• n-octyl acrylate NOAA: biomass-derived carbon content of 72%; manufactured by Osaka Organic Chemical Industry Co., Ltd.
• dodecyl acrylate LA: biomass-derived carbon content of 80%; manufactured by Osaka Organic Chemical Industry Co., Ltd.
• stearyl acrylate STA: biomass-derived carbon content of 85%; manufactured by Osaka Organic Chemical Industry Co., Ltd.
• n-dodecyl methacrylate Light Ester L: biomass-derived carbon content of 75%; manufactured by Kyoeisha Chemical Industry Co., Ltd.
• n-stearyl methacrylate Light Ester S: biomass-derived carbon content of 81%; manufactured by Kyoeisha Chemical Industry Co., Ltd.
• n-dodecyl acrylate Light
• the biomass-derived carbon content of (meth)acrylic acid alkyl esters can be the value in the seller's catalog. If the seller's catalog value is unknown or if the material is not obtained from a seller but is obtained by synthesis or other means, the value measured using a method conforming to ASTM D6866-20 can be used.
• the crosslinkable functional group-containing monomer is preferably a monomer having at least one of a hydroxy group and a carboxy group as a crosslinkable functional group, and more preferably at least one monomer selected from a hydroxy group-containing monomer and a carboxy group-containing monomer.
• the ratio of the crosslinkable functional group-containing monomer to the monomer components constituting the (meth)acrylic polymer is, for example, 0.1 to 30% by mass.
• the ratio may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 10% by mass or more, or 15% by mass or more, or 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.
• hydroxyl group-containing monomers that are crosslinkable functional group-containing monomers include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, chloro-2-hydroxypropyl acrylate, diethylene glycol mono(meth)acrylate, and allyl alcohol.
• 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.
• the hydroxyl group-containing monomers may be used alone or in combination of two or more.
• the content of the hydroxyl group-containing monomer is, for example, 0.1 to 30% by mass.
• the content may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 10% by mass or more, or 15% by mass or more, or 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.
• Carboxy group-containing monomers that are crosslinkable functional group-containing monomers include, for example, (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 3-carboxypropyl (meth)acrylate, 4-carboxybutyl (meth)acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid, and maleic anhydride. Of these, (meth)acrylic acid is preferred.
• the carboxy group-containing monomers may be used alone or in combination of two or more.
• the content of the carboxyl group-containing monomer is, for example, 0.1 to 30% by mass.
• the content may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 10% by mass or more, or 15% by mass or more, or 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.
• examples of monomer components that become (meth)acrylic polymers include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 3 carbon atoms, alicyclic hydrocarbon group-containing (meth)acrylates, nitrogen atom-containing monomers, alkoxyalkyl (meth)acrylates, epoxy group-containing (meth)acrylates, acetoacetyl group-containing (meth)acrylates, aromatic ring-containing monomers, methacryloxypropyl methoxysilane, vinyl acetate, vinyl chloride, (meth)acrylonitrile, etc.
• Examples of (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and iso-propyl (meth)acrylate.
• Examples of (meth)acrylates containing alicyclic hydrocarbon groups include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.
• Nitrogen atom-containing monomers include monomers having at least one of the functional groups of an amide group and an amino group, and specific examples include amide group-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, acryloylmorpholine, N-vinylacetamide, diacetone(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, vinylpyrrolidone, methylol(meth)acrylamide, and methoxyethyl(meth)acrylamide; and amino group-containing monomers such as N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and aminoethyl(meth)acryl
• alkoxyalkyl (meth)acrylates examples include methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.
• epoxy group-containing (meth)acrylates examples include glycidyl (meth)acrylate.
• acetoacetyl group-containing (meth)acrylates examples include acetoacetoxyethyl (meth)acrylate.
• Aromatic ring-containing monomers include benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, styrene, methylstyrene, vinyltoluene, etc.
• the ratio of the other monomers to the total monomer components is preferably 0.1 to 30% by mass, and more preferably 0.2 to 25% by mass.
• the ratio is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and is preferably 30% by mass or less, and more preferably 25% by mass or less.
• the other monomers described above may be used alone or in combination of two or more types.
• the polymerization method for the (meth)acrylic polymer according to the present embodiment is not particularly limited, and examples thereof include solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Among these, solution polymerization and bulk polymerization are preferred.
• a polymerization solvent and a monomer component are charged into a reaction vessel, and a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas.
• the reaction start temperature is set to usually 40 to 100°C, preferably 50 to 90°C, and the reaction system is maintained at a temperature of usually 50 to 90°C, preferably 60 to 90°C, and the reaction is allowed to proceed for 3 to 20 hours to obtain a (meth)acrylic polymer.
• An alcohol-based organic solvent may be used as a polymerization solvent, or may be added after the end of the reaction to dilute the obtained (meth)acrylic polymer, thereby obtaining a solution containing a (meth)acrylic polymer.
• a chain transfer agent may be added at the time of charging if desired, and the monomer component, polymerization initiator, chain transfer agent, and polymerization solvent may be added as appropriate during the polymerization reaction.
• the monomer components are charged into a reaction vessel, and a polymerization initiator is added as necessary under an inert atmosphere such as nitrogen gas.
• the temperature in the reaction system rises due to the addition of the polymerization initiator, but the polymerization reaction is continued until the temperature in the reaction system drops without cooling.
• a polymerization initiator may also be added to continue the polymerization reaction.
• an alcohol-based organic solvent is added to obtain a solution containing a (meth)acrylic polymer.
• a chain transfer agent may be added when charging if desired, and the monomer components, polymerization initiator, chain transfer agent, and polymerization solvent may be added as appropriate during the polymerization reaction.
• polymerization initiators examples include peroxide-based polymerization initiators and azo-based initiators.
• peroxide polymerization initiators examples include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propionate, Examples include propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di- ⁇ -cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(
• azo initiators examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2 -amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4,4'-azobis(4-
• the polymerization initiator may be used alone or in combination of two or more types.
• the polymerization initiator may also be added multiple times during polymerization.
• the polymerization initiator is usually used in an amount within the range of 0.001 to 5 parts by mass, and preferably 0.005 to 3 parts by mass, per 100 parts by mass of the monomer components that form the (meth)acrylic polymer.
• the amount of polymerization initiator added may be 0.001 parts by mass or more, preferably 0.005 parts by mass or more, and may be 5 parts by mass or less, preferably 3 parts by mass or less.
• Chain transfer agents include 2-mercaptoethanol, thioglycerol, 3-mercaptohexane-1-ol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 4-mercaptobutanoic acid, 6-mercaptohexanoic acid, 11-mercaptoundecanoic acid, 3-mercaptopyruvic acid, 2-mercaptobenzoic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, thiomalic acid, n-dodecyl mercaptan, pentaerythritol tetrakis (3-mercaptopropionate), ⁇ -methylstyrene dimer, and naphthoquinone-based compounds. Chain transfer agents may be used alone or in combination of two or more.
• a chain transfer agent When a chain transfer agent is used, it is usually used in an amount within the range of 0.01 to 5 parts by mass, preferably 0.02 to 3 parts by mass, per 100 parts by mass of the monomer components that form the (meth)acrylic polymer.
• the amount of the chain transfer agent added may be 0.01 parts by mass or more, preferably 0.02 parts by mass or more, and may be 5 parts by mass or less, preferably 3 parts by mass or less.
• Organic solvents that can be used as polymerization solvents include those mentioned above.
• the pressure-sensitive adhesive composition according to the present embodiment may contain a crosslinking agent.
• the crosslinking agent is not particularly limited as long as it can crosslink the (meth)acrylic polymer.
• an isocyanate compound, an epoxy compound, a metal chelate compound, etc. may be used as the crosslinking agent.
• One type of crosslinking agent may be used alone, or two or more types may be used in combination.
• the isocyanate compound for example, an isocyanate compound having 2 or more isocyanate groups in one molecule is usually used.
• the number of isocyanate groups in one molecule is preferably 2 to 8, and more preferably 3 to 6.
• the number of isocyanate groups is preferably 2 or more, and more preferably 3 or more, and is preferably 8 or less, and more preferably 6 or less. If the number of isocyanate groups is within the above range, it is preferable from the viewpoints of the efficiency of the crosslinking reaction between the (meth)acrylic polymer and the isocyanate compound and maintaining the flexibility of the pressure-sensitive adhesive layer.
• diisocyanate compounds with two isocyanate groups per molecule examples include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates.
• Aliphatic diisocyanates include aliphatic diisocyanates having 4 to 30 carbon atoms, such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate.
• Alicyclic diisocyanates include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate.
• aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.
• isocyanate compounds with three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4''-triphenylmethane triisocyanate.
• examples of isocyanate compounds include multimers, derivatives, and polymers of the above-mentioned isocyanate compounds having two or more isocyanate groups.
• examples of multimers include dimers or trimers, biurets, and isocyanurates.
• examples of derivatives include addition reaction products of polyhydric alcohols and two or more molecules of diisocyanate compounds.
• the polyhydric alcohols in the above derivatives include low molecular weight polyhydric alcohols such as trimethylolpropane, glycerin, pentaerythritol, and other trivalent or higher alcohols.
• low molecular weight polyhydric alcohols such as trimethylolpropane, glycerin, pentaerythritol, and other trivalent or higher alcohols.
• high molecular weight polyhydric alcohols include polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols.
• isocyanate compounds include trimers of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, biuret or isocyanurate forms of hexamethylene diisocyanate or tolylene diisocyanate, reaction products of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (e.g., a trimer of tolylene diisocyanate or xylylene diisocyanate), reaction products of trimethylolpropane and hexamethylene diisocyanate (e.g., a trimer of hexamethylene diisocyanate), polyether polyisocyanate, polyester polyisocyanate, etc.
• trimers of diphenylmethane diisocyanate polymethylene polyphenyl polyisocyanate
• biuret or isocyanurate forms of hexamethylene diisocyanate or tolylene diisocyanate
• xylylene diisocyanate and hexamethylene diisocyanate crosslinking agents are preferred in terms of resistance to yellowing, and tolylene diisocyanate crosslinking agents are preferred in terms of stress relaxation properties.
• xylylene diisocyanate crosslinking agents examples include xylylene diisocyanate and its oligomers, derivatives, and polymers.
• hexamethylene diisocyanate crosslinking agents examples include hexamethylene diisocyanate and its multimers, derivatives, and polymers
• tolylene diisocyanate crosslinking agents examples include tolylene diisocyanate and its multimers, derivatives, and polymers.
• epoxy compounds include compounds having two or more epoxy groups in the molecule. More specific examples include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diamine glycidylaminomethyl), and the like.
• Metal chelate compounds examples include compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium are coordinated with alkoxides, acetylacetone, ethyl acetoacetate, etc. Specific examples include aluminum isopropylate, aluminum secondary butylate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, and aluminum trisacetylacetonate.
• the content of the crosslinking agent in the adhesive composition is usually 0.05 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0.3 to 2.5 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer.
• the content may be 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more, and may be 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 2.5 parts by mass or less.
• the pressure-sensitive adhesive composition according to the present embodiment may contain other additives within a range that does not impair the effects of the present invention.
• additives include, for example, tackifier resins, silane coupling agents, antistatic agents, antioxidants, light stabilizers, metal corrosion inhibitors, plasticizers, crosslinking accelerators, rework agents, etc.
• the other additives may be used alone or in combination of two or more.
• the content of the other additives will vary depending on the type of additive.
• the total content of the other additives is preferably about 0.01 to 10 mass % per 100 parts by mass of the (meth)acrylic polymer.
• the solid content concentration of the pressure-sensitive adhesive composition according to the present embodiment varies depending on the coating conditions of the pressure-sensitive adhesive composition, but is preferably 50 to 90% by mass.
• the solid content concentration is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% by mass or more.
• the solid content concentration is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.
• the solid content concentration can be adjusted by the content of organic solvent.
• the turbidity of the adhesive composition according to this embodiment is preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less.
• the lower the turbidity the more uniformly the (meth)acrylic polymer is dissolved or dispersed in the solvent.
• the turbidity is within the above range.
• the above turbidity refers to the varnish turbidity.
• the viscosity of the pressure-sensitive adhesive composition according to the present embodiment is not particularly limited, but may be 1.0 to 150 Pa ⁇ s at 25° C.
• the viscosity may be 1.0 Pa ⁇ s or more, 3 Pa ⁇ s or more, 5 Pa ⁇ s or more, 10 Pa ⁇ s or more, or 30 Pa ⁇ s or more, and may be 150 Pa ⁇ s or less, 80 Pa ⁇ s or less, 50 Pa ⁇ s or less, 30 Pa ⁇ s or less, 20 Pa ⁇ s or less, or 10 Pa ⁇ s or less.
• the viscosity of the pressure-sensitive adhesive composition in this specification is a value measured using a B-type viscometer.
• the pressure-sensitive adhesive layer according to this embodiment is formed from the pressure-sensitive adhesive composition described above in "Pressure-sensitive adhesive composition.” That is, the process includes a step of applying the pressure-sensitive adhesive composition onto a substrate or a treated surface of a substrate that has been subjected to a release treatment to form a layer made of the pressure-sensitive adhesive composition, and a step of drying the obtained layer made of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.
• the layer made of the adhesive composition is dried, depending on the type of solvent, but is usually dried at 50 to 150°C, preferably 60 to 100°C, for 1 to 10 minutes, preferably 2 to 7 minutes to remove the solvent.
• the coating film thus formed is the adhesive layer.
• the thickness of the adhesive layer after drying is usually 5 to 200 ⁇ m.
• the adhesive composition can be applied by a known method, such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, or gravure coating, followed by coating and drying to a desired thickness.
• the adhesive layer according to this embodiment may be at least partially crosslinked during the manufacturing process by reacting the (meth)acrylic polymer in the adhesive composition with a crosslinking agent.
• a crosslinking agent is contained in the adhesive composition and the resulting adhesive layer is to be further crosslinked, it is preferable to form it under the following conditions.
• the crosslinking reaction is allowed to proceed by aging for usually 3 days or more, preferably 7 to 10 days, under an environment of usually 5 to 60°C, preferably 15 to 40°C, usually 30 to 70% RH, preferably 40 to 70% RH.
• Crosslinking under the above conditions allows efficient formation of a crosslinked structure.
• the thickness of the adhesive layer in this embodiment is preferably 5 to 200 ⁇ m. From the viewpoint of maintaining adhesive performance, the thickness is preferably 5 ⁇ m or more, and more preferably 10 ⁇ m or more. The thickness is preferably 200 ⁇ m or less, and more preferably 100 ⁇ m or less.
• the preferred embodiments of the adhesive composition are the same as those described in the "Adhesive Composition" above.
• the degree of drying in the step of forming the coating film can be determined by visually observing the state of the coating film. This is because the inventors discovered that when methanol is used as the organic solvent, the coating film is cloudy when the pressure-sensitive adhesive composition is applied to the release-treated surface of a substrate or release sheet, but becomes transparent when drying has progressed sufficiently.
• the content of methanol in the organic solvent is preferably 50 to 100 parts by mass.
• the content is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.
• the adhesive layer according to this embodiment preferably has a haze of less than 5%, more preferably less than 3%, and even more preferably 2% or less. There is no particular lower limit to the haze, but it is usually 1% or more.
• the haze of the adhesive layer in this specification is a value measured by the method and conditions described in the examples below.
• the gel fraction of the adhesive layer according to this embodiment is preferably 10 to 95% by mass. From the viewpoints of adhesive strength, cohesive strength and removability, the gel fraction is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, or 50% by mass or less.
• the gel fraction of the adhesive layer in this specification is a value measured by the method and conditions described in the examples below.
• the adhesive layer according to this embodiment can be used in an adhesive sheet.
• the adhesive sheet may be, for example, an adhesive sheet formed only from the adhesive layer according to this embodiment, or may be a double-sided adhesive sheet having a substrate and adhesive layers formed on both sides of the substrate, with the adhesive layer according to this embodiment being used on at least one of the adhesive layers.
• it may be a single-sided adhesive sheet having a substrate and an adhesive layer according to this embodiment formed on one side of the substrate.
• it may be an adhesive sheet in which substrates are disposed on both sides of the adhesive layer according to this embodiment.
• the substrate used in the adhesive sheet of this embodiment is not particularly limited, and may be a plastic substrate, nonwoven fabric, woven fabric, paper, metal, glass, ceramics, foam, etc.
• the thickness of the substrate varies depending on the application, etc., and there are no particular restrictions, but it is usually between 5 and 200 ⁇ m.
• Plastic substrates that can be used as the above substrate include polyethylene terephthalate, polyvinyl chloride, polyolefin, polypropylene, polymethyl methacrylate, polycarbonate, polyphenylene sulfide, polyether ether ketone, polyethylene naphthalate, polyimide, polytetrafluoroethylene, acrylonitrile butadiene styrene copolymer (ABS), etc.
• the surface of the substrate may be pretreated before forming the adhesive layer in order to improve the polarity of the surface, more specifically, the wettability and chemical affinity for the adhesive composition.
• pretreatments include sodium treatment, corona treatment, primer treatment, flame treatment, fluorination, and plasma treatment.
• the substrate may be a substrate that has been subjected to a release treatment.
• the adhesive sheet is an adhesive sheet in which substrates are disposed on both sides of the adhesive layer according to this embodiment
• at least one of the substrates may be a substrate that has been subjected to a release treatment, and the substrate that has been subjected to the release treatment may be removed when the adhesive sheet adheres to the adherend.
• the method for producing the adhesive sheet in this embodiment is not particularly limited, but for example, the adhesive sheet can be produced by laminating a substrate to at least one surface of the adhesive layer obtained by the method described above in "Adhesive Layer" as necessary.
• Example 1-1 A flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 94 parts by mass of n-butyl acrylate (BA), 4 parts by mass of acrylic acid (AA), and 0.05 parts by mass of ⁇ -mercaptopropionic acid (BMPA), and the contents of the flask were heated to 55° C. while introducing nitrogen gas into the flask.
• BA n-butyl acrylate
• AA acrylic acid
• BMPA ⁇ -mercaptopropionic acid
• V-70 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 0.5 parts by mass of BA as a polymerization initiator was charged into the flask under stirring.
• the polymerization reaction was continued without cooling until a drop in the reaction temperature was confirmed. After a drop in the reaction temperature was confirmed, the flask was cooled until the temperature inside reached 55°C, at which point a solution of 0.5 parts by mass of BA, 0.0042 parts by mass of V-70, and 0.033 parts by mass of BMPA was added.
• reaction temperature rose as a result of the above additions, but the polymerization reaction was continued until a drop in the reaction temperature was observed again.
• reaction temperature reached 55°C
• 24.5 parts by mass of methanol and 0.083 parts by mass of t-hexyl peroxypivalate (Perhexyl PV: NOF Corp.) were added and refluxed for 60 minutes, after which a solution of 0.17 parts by mass of Perhexyl PV in 0.5 parts by mass of methanol was added and refluxed for 90 minutes.
• acrylic polymer solution A which was composed of acrylic polymer (1) and methanol and had a solids concentration of 80% by mass.
• Example 1-2 Example 1-3, Comparative Example 1-1> Methanol was further added to the acrylic polymer solution A obtained in Example 1-1 to adjust the solid content concentration to 65 mass%, 55 mass%, and 40 mass%, to obtain adhesive acrylic polymer solution B, acrylic polymer solution C, and acrylic polymer solution D, respectively.
• Example 1-4 An acrylic polymer solution E containing the acrylic polymer (2) and ethanol and having a solids concentration of 80% by mass was obtained in the same manner as in Example 1-1, except that ethanol was used instead of methanol.
• Example 1-7 An acrylic polymer solution I having a solids concentration of 80% by mass and consisting of the acrylic polymer (3) and isopropyl alcohol was obtained in the same manner as in Example 1-1, except that methanol was changed to isopropyl alcohol.
• Example 1-10 An acrylic polymer solution M having a solid content of 55% by mass and consisting of acrylic polymer (4) and methanol was obtained in the same manner as in Example 1-2, except that 94 parts by mass of BA was replaced with n-octyl acrylate (NOAA: manufactured by Osaka Organic Chemical Industry Co., Ltd.) having a biomass-derived carbon content of 72%.
• NOAA n-octyl acrylate
• Example 1-11 An acrylic polymer solution N having a solid content of 55% by mass and consisting of acrylic polymer (5) and methanol was obtained in the same manner as in Example 1-2, except that BA and AA having a biomass-derived carbon content of 100% were used, and further, methanol obtained by oxidizing biomass-derived methane was used as the methanol.
• the AA with a carbon content of 100% derived from biomass was produced according to the method described in JP 2005-213225 A.
• the BA with a carbon content of 100% derived from biomass was produced by reacting butanol obtained by Guerbet condensation of bioethanol with the AA with a carbon content of 100% derived from biomass.
• Reference Example 1 An acrylic polymer solution O containing the acrylic polymer (6) and ethyl acetate and having a solids concentration of 55% by mass was obtained in the same manner as in Example 1-3, except that methanol was changed to ethyl acetate.
• Example 1-12 Methanol and water were further added to the acrylic polymer solution A and methanol obtained in Example 1-1 to obtain an acrylic polymer solution P having a solid content concentration of 55% by mass.
• the content ratio of methanol:water in the acrylic polymer solution P was 45:55 (mass ratio).
• Measuring device HLC-8120GPC (manufactured by Tosoh Corporation)
• GPC column configuration The following five columns (all manufactured by Tosoh Corporation) (1) TSK-GEL HXL-H (guard column) (2) TSK-GEL G7000HXL (3) TSK-GEL GMHXL (4) TSK-GEL GMHXL (5)TSK-GEL G2500HXL Sample concentration: diluted with tetrahydrofuran to 1.0 mg/cm 3 Flow rate: 1.0 cm 3 /min Column temperature: 40° C.
• Examples 1-2, 1-3, 1-6, 1-9, and Reference Example 1 above show that even when an alcohol-based organic solvent is used, a polymer solution exhibiting properties equivalent to those obtained when ethyl acetate is used is obtained. Furthermore, Examples 1-1, 1-2, etc. suggest that a pressure-sensitive adhesive composition with no problems in coatability can be obtained even when the solids concentration is high.
• Comparative Examples 1-1 to 1-3 show that when an alcohol-based organic solvent is used, it is preferable to set the solids concentration of the acrylic polymer solution to 50% by mass or more. Specifically, in Comparative Example 1-1, the turbidity was 30, suggesting that the solution was inhomogeneous. Furthermore, in Comparative Examples 1-2 and 1-3, the viscosity of the solution was low, suggesting that it is not suitable for coating, for example, when forming a thick adhesive layer.
• Example of production Example 2-1 50 g of the acrylic polymer solution B obtained in Example 1-2 was collected, and aluminum trisacetylacetone was added to the acrylic polymer solution B in an amount of 0.4 parts by mass relative to 100 parts by mass of the solid content of the acrylic polymer (1) in the acrylic polymer solution B to obtain a pressure-sensitive adhesive composition.
• the obtained pressure-sensitive adhesive composition was applied onto a 25 ⁇ m polyethylene terephthalate (PET) film (Lumirror 25T60: manufactured by Panac) and dried at 90° C. for 3 minutes to form a pressure-sensitive adhesive layer. The above application was adjusted so that the thickness of the pressure-sensitive adhesive layer after drying was 25 ⁇ m.
• PET polyethylene terephthalate
• a release-treated PET film was attached to the surface of the adhesive layer obtained above opposite to the side in contact with the PET film.
• the adhesive was then aged for 3 days in a dry environment at 40°C to obtain an adhesive sheet with an adhesive layer 25 ⁇ m thick.
• Examples 2-2 to 2-11, Reference Example 2 Except for changing the type of acrylic polymer solution and the amount of aluminum trisacetylacetone to the amounts shown in Table 3 or Table 4, the pressure-sensitive adhesive sheets of Examples 2-2 to 2-10 and Reference Example 2 were produced in the same manner as in Example 2-1. In addition, the type of acrylic polymer solution and the amount of aluminum trisacetylacetone were changed to the amounts shown in Table 4, and the adhesive layer was dried at 100°C for 3 minutes. In the same manner as in Example 2-1, the adhesive sheet of Example 2-11 was produced.
• the obtained adhesive sheet was cut into a size of 20 mm x 100 mm to prepare a test piece.
• the peel-treated PET film was peeled off from the test piece, and the exposed adhesive layer was attached to a SUS plate.
• the above attachment was adjusted so that the attachment area was 20 mm x 20 mm.
• a 2 kg roller was rolled back and forth three times to be pressed, and then the test piece was left to stand for 20 minutes at 40 ° C. in a dry environment.
• a load of 1 kg was applied in the shear direction of the test object, and the amount of displacement of the adhesive layer one hour after the start of the load was measured, and the holding power at 40 ° C. was evaluated.
• the holding power at 80°C was also evaluated in the same manner as above, except that the load was applied in a dry environment at 80°C.
• Tables 3 and 4 when a time is listed as "drop,” it means that the test piece could not be held within the test time and fell, and it is the time from the start of the test until the test piece fell.
• the adhesive layer made of the adhesive composition according to this embodiment can achieve the same performance in terms of adhesive strength, cohesive strength, holding power, etc. as when ethyl acetate, a petroleum-based organic solvent that has been used conventionally, is used.
• the coating film which was opaque during the formation of the adhesive layer, becomes transparent as the drying process progresses, and it was discovered that the degree of drying can be determined by the turbidity.

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