Adhesive composition and adhesive sheet

Abstract

To provide: an adhesive composition which has excellent biodegradability, reduced formation of gels and aggregates, and excellent flowability; and an adhesive sheet employing the adhesive composition excellent in adhesion properties, removability and coating transparency.SOLUTION: The adhesive composition contains an acrylic polymer (A) and an organic solvent (B). The acrylic polymer (A) is a polymer of a monomer mixture containing 30 mass% or more of a monomer (ax) represented by general formula (I), and has a weight-average molecular weight of 400,000 to 1,500,000.SELECTED DRAWING: None

Description

Technical Field

[0001] Embodiments of the present invention relate to an adhesive composition and an adhesive sheet using the same.

Background Art

[0002] Various resin-based compositions are known as adhesive compositions, and among them, acrylic-based adhesive compositions are widely used. Acrylic-based adhesive compositions are used in various applications because the adjustment of adhesive properties such as adhesive force, tack, and holding power is easy depending on the monomer composition. Furthermore, in recent years, in addition to adhesive properties such as adhesive force, tack, and holding power, high functionality such as transparency of the coating film has also been required.

[0003] By the way, adhesive labels and adhesive tapes may be discarded in the soil. In this case, an adhesive label composed of a typical acrylic-based adhesive composition mainly uses petroleum-derived raw materials, and since the decomposition rate by microorganisms is extremely slow, the adhesive composition remains in the soil semi-permanently, and furthermore, it may cause damage to the ecosystem in the soil. Therefore, in recent years, the use of biodegradable raw materials has begun to be recommended.

[0004] In addition, as a method of disposing in the soil, there is a method in which an adhesive label or an adhesive tape remains attached to a container or is peeled off from the container after use and then processed. In this case, an adhesive force such that the adhesive label or adhesive tape does not peel off from the container or re-peelability is required. In particular, for re-peelability, it is required that no adhesive residue occurs even when exposed to a more severe environment while maintaining an appropriate adhesive force.

[0005] Patent Document 1 discloses an acrylic solvent-based adhesive obtained by copolymerizing in a solvent, with a functional monomer copolymerizable with one or more alkyl acrylates having an alkyl group having 1 to 14 carbon atoms and containing 20% by mass or more of n-octyl acrylate as main components.

[0006] In Prior Art Document 2, there is disclosed an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer resin obtained by copolymerizing an alkyl acrylate having an alkyl group with 2 to 12 carbon atoms, a nitrogen-containing vinyl monomer, and a caprolactone-modified (meth)acrylate, and substantially free of a polymerizable unsaturated carboxylic acid, and a polyisocyanate compound as a crosslinking agent.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in Patent Document 1 and Patent Document 2, although the adhesive properties are exhibited, the biodegradability is not sufficient. In particular, in Patent Document 2, although caprolactone, a biodegradable raw material, is used, it is described that when the caprolactone-modified (meth)acrylate exceeds 2% by mass in the acrylic copolymer resin, gelation of the adhesive solution occurs and the practicality deteriorates (as described in paragraph

[0010] ), and it is difficult to increase the biodegradability while maintaining the adhesive properties. In addition to this, the fluidity is reduced due to gels during production and aggregates contained in the pressure-sensitive adhesive composition, and it is difficult to suppress the generation of foreign substances on the film during coating. Thus, conventional pressure-sensitive adhesive compositions cannot satisfy both the adhesive properties and the biodegradability, and further cannot sufficiently satisfy the suppression of the generation of foreign substances derived from gels and aggregates in the pressure-sensitive adhesive composition.

[0009] Therefore, the present invention provides a pressure-sensitive adhesive composition having excellent biodegradability, suppressed formation of gels and aggregates, and excellent fluidity, and further, by using the pressure-sensitive adhesive composition, it is possible to provide a pressure-sensitive adhesive sheet excellent in adhesive properties, re-peelability, and transparency of the coating film.

Means for Solving the Problems

[0010] The present inventor has conducted intensive studies to solve the above problems and completed the present invention. That is, embodiments of the present invention relate to the following. However, the present invention is not limited to the embodiments described below and includes various embodiments.

[0011] That is, the present invention includes an acrylic polymer (A) and an organic solvent (B), The acrylic polymer (A) is a polymer of a monomer mixture containing 30% by mass or more of a monomer (ax) represented by the following general formula (I), and has a weight average molecular weight of 400,000 to 1,500,000, and relates to an adhesive composition.

Chemical formula

[0012] Further, the present invention relates to an adhesive sheet having an adhesive layer formed from the above adhesive composition relates to.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an adhesive composition having excellent fluidity in which the formation of gels and aggregates is suppressed even when the biodegradability is high, and an adhesive sheet having excellent adhesive properties, re-peelability, and transparency of the coating film using the adhesive composition.

Embodiments for Carrying Out the Invention

[0014] Define terms before describing the present invention. In this specification, a numerical range specified using "~" means that the numerical values described before and after "~" are included as the range of the lower limit value and the upper limit value. In this specification, when "acrylic acid (methacrylic acid)" or "acrylate (methacrylate)" is mentioned, unless otherwise specified, they represent "acrylic acid or methacrylic acid" and "acrylate or methacrylate", respectively. In this specification, the term "polymer" means having a structural unit derived from a monomer and including a homopolymer and a copolymer.

[0015] In this specification, the monomer (ax) represented by the general formula (I), the monomer (ay) having a carboxyl group or an active methylene group, and the other monomer (az) may be abbreviated as monomer (ax), monomer (ay), and monomer (az), respectively.

[0016] The embodiments of the present invention will be described in detail below. However, the following description is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist thereof. Each of the various components described in this specification may be used independently alone or in combination of two or more thereof unless otherwise noted.

[0017] ≪Adhesive Composition≫ The adhesive composition of the present invention contains an acrylic polymer (A) and an organic solvent (B) as essential components, and optionally contains a curing agent (C), a tackifier resin (D), or other optional components. By containing the acrylic polymer (A) and the organic solvent (B), an adhesive composition excellent in biodegradability and having suppressed formation of gels and aggregates and excellent fluidity can be obtained. Thereby, for example, even when the biodegradability percentage is 30% or more, an adhesive composition excellent in fluidity can be obtained, and the adhesive properties, re-peelability, and transparency of the obtained adhesive sheet can also be excellent.

[0018] <Acrylic Polymer (A)> The acrylic polymer (A) is a polymer having a weight average molecular weight of 400,000 to 1,500,000 obtained by polymerizing a monomer mixture containing at least monomer (ax), and contains 30% by mass or more of (ax) in 100% by mass of the monomer mixture. Note that the acrylic polymer (A) may be a polymer of a monomer using 100% by mass of monomer (ax). The monomer mixture preferably further contains monomer (ay), and the content of monomer (ay) is preferably 10% by mass or less in 100% by mass of the monomer mixture. Thereby, the cohesive force of the adhesive layer can be further improved. Further, the monomers constituting the polymer may further contain other monomer (az), which is a monomer other than monomer (ax) and monomer (ay).

[0019] The weight average molecular weight of the acrylic polymer (A) is 400,000 to 1,500,000, preferably 600,000 to 1,000,000, and more preferably 700,000 to 900,000. When the weight average molecular weight is 400,000 or more, the cohesive force of the adhesive layer increases and the adhesive force is further improved. When the weight average molecular weight is 1,500,000 or less, the formation of gel-like substances and aggregated parts is suppressed, and the fluidity of the adhesive composition is easily improved.

[0020] [Monomer (ax)] Monomer (ax) is a monomer represented by the following general formula (I). [Chemical formula] (However, R1, R3, and R4 are each independently a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, R2 is an alkylene group having 1 to 8 carbon atoms, m represents an integer of 3 to 10, and n represents an integer of 1 to 13.)

[0021] The monomer (ax) represented by the general formula (I) can be synthesized, for example, by the synthesis method disclosed in JP-A-57-185236.

[0022] In the general formula (I), R1 is a hydrogen atom or an alkyl group containing 1 to 9 carbon atoms. For example, in the case of an acrylate ester, R1 is a hydrogen atom, and in the case of a methacrylate ester, R1 is a methyl group.

[0023] In the general formula (I), R2 is an alkylene group having 1 to 8 carbon atoms. When a (meth)acrylic acid alkyl ester having a hydroxyl group is used as a raw material, for example, when 2-hydroxyethyl (meth)acrylate is used, R2 is an ethylene group. When 4-hydroxybutyl (meth)acrylate is used, R2 is an n-butylene group. When 8-hydroxyoctyl (meth)acrylate is used, R2 is an n-octylene group. When produced using a (meth)acrylic acid alkyl ester having a hydroxyl group as a raw material, for example, when 2-hydroxyethyl (meth)acrylate is used, R2 is an ethylene group. When 4-hydroxybutyl (meth)acrylate is used, R2 is an n-butylene group. When 8-hydroxyoctyl (meth)acrylate is used, R2 is an n-octylene group.

[0024] In the general formula (I), R3 and R4 are each independently a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. When a lactone is used as a raw material for production, these depend on the structure of the lactone used. For example, when γ-butyrolactone, σ-valerolactone, and ε-caprolactone are used as raw materials, R3 and R4 are both hydrogen atoms. When β-methyl-δ-valerolactone is used, R3 and R4 are a methyl group and a hydrogen atom. When 3-ethyl-caprolactone is used, R3 and R4 are an ethyl group and a hydrogen atom.

[0025] In the general formula (I), m is an integer from 3 to 8, which also depends on the structure of the raw material lactone. For example, in the case of γ-butyrolactone, m = 3 [general formula (II)], in the case of σ-valerolactone, m = 4, in the case of ε-caprolactone, m = 5 [general formula (III)], and in the case of cyclooctanone lactone, m = 7.

[0026]

Chemical formula

Chemical formula

[0027] Among these, since raw materials such as γ-butyrolactone, σ-valerolactone, and ε-caprolactone show biodegradability, it is preferable to use the monomer (ax) using these raw materials.

[0028] When synthesized using a raw material of a (meth)acrylic acid alkyl ester having a hydroxyl group and a lactone, in the general formulas (I) to (III), n is the number of moles of the added lactone. For example, when 5 moles of lactone are added to 1 mole of a (meth)acrylic acid alkyl ester having a hydroxyl group using a raw material of a (meth)acrylic acid alkyl ester having a hydroxyl group and a lactone, n = 5.

[0029] The monomer (ax) according to the present invention is preferably a polycaprolactone-modified hydroxyalkyl acrylate or methacrylate obtained by ring-opening polymerization of ε-caprolactone or γ-butyrolactone with a (meth)acrylic acid ester having a hydroxyl group.

[0030] In the general formulas (I) to (III), n is an integer of 1 to 13, preferably 3 to 10. When n is 10 or less, it is preferable because the acrylic polymer (A) does not have crystallinity and the adhesive properties such as tack are enhanced. In addition, when n is 3 or more, it is preferable because the degree of biodegradability is enhanced.

[0031] Examples of commercially available products of the monomer (ax) represented by the general formula (I) include PLACCEL FM-1, PLACCEL FM-2, PLACCEL FM-3, PLACCEL FM-4, PLACCEL FM-5, PLACCEL FA-1, PLACCEL FA-2, PLACCEL FA-3, PLACCEL FA-5, etc. manufactured by Daicel Corporation.

[0032] In 100% by mass of the monomer mixture constituting the acrylic polymer (A), the monomer (ax) is 30% by mass or more, preferably 60% by mass or more and 100% by mass or less, and more preferably 60% by mass or more and 99.9% by mass or less. When within the above range, it becomes easier to balance the tackiness and other adhesive properties and the degree of biodegradability.

[0033] [Monomer (ay)] The monomer (ay) is a monomer having a carboxyl group or an active methylene group. For example, the monomer (ay-1) having a carboxyl group described later and the monomer (ay-2) having an active methylene group can be mentioned. The carboxyl group or the active methylene group has hydrogen bonding properties, and by including these, the cohesive force of the adhesive layer can be further improved. When the monomer (ay) is included in the acrylic polymer (A), the holding power can be improved, and when combined with a curing agent described later, it is preferable because the holding power can be further increased.

[0034] Examples of the monomer (ay-1) having a carboxyl group include (meth)acrylic acid, phthalic acid mono-hydroxyethyl acrylate, p-carboxybenzyl acrylate, ethylene oxide-modified (number of EO addition moles: 2 to 18) phthalic acid acrylate, phthalic acid mono-hydroxypropyl acrylate, succinic acid mono-hydroxyethyl acrylate, β-carboxyethyl acrylate, 2-(4-benzoyl-3-hydroxyphenoxy)ethyl acrylate, maleic acid, monoethyl maleic acid, itaconic acid, citraconic acid, and fumaric acid. Among these, (meth)acrylic acid is preferable because it can enhance the holding power.

[0035] Examples of the monomer (ay-2) having an active methylene group include 2-ethoxymalonyl oxyethyl (meth) acrylate, 2-acetoxyacetoxyethyl (meth) acrylate, N-(2-acetacetylaminoethyl) acrylamide, 2-(N-acetacetylaminoethyl) (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N-(2-cyanoacetoxyethyl) acrylamide, N-(2-propionylacetoxybutyl) acrylamide, N-4-(acetoxyacetoxymethyl) benzyl acrylamide, N-(2-acetacetamideethyl) acrylamide, N-(2-acetacetamideethyl) methacrylamide, and the like. Among these, 2-acetoxyacetoxyethyl (meth) acrylate is preferred because it can enhance the holding power.

[0036] When using the monomer (ay), it is preferably contained in an amount of 10% by mass or less in 100% by mass of the monomer mixture constituting the acrylic polymer (A). More preferably, it is 0.01 to 10% by mass, and even more preferably 0.1 to 6% by mass. When within the above range, the holding power becomes better and it is easier to balance the adhesive properties. Also, it can suppress the formation of gels and aggregates during production, and is preferred because the fluidity of the adhesive composition is improved.

[0037] [Monomer (az)] The acrylic polymer (A) may contain other monomers (az) other than the monomer (ax) and the monomer (ay). The other monomers (az) are used to impart various functions to the polymer and to adjust the adhesive properties. Examples of the other monomers (az) include (meth) acrylic acid alkyl esters, (meth) acrylic acid alkyl esters having a hydroxyl group, (meth) acrylic acid alkyl esters having an epoxy group, (meth) acrylic acid esters having an alkyleneoxy group, (meth) acrylic acid alkyl esters having an amino group, (meth) acrylic acid alkyl esters having an amide group, (meth) acrylic acid alkyl esters having an aromatic ring, vinyl monomers, and the like. Among these, (meth)acrylic acid alkyl esters are preferred because they can improve the adhesive properties.

[0038] (Meth)acrylic acid alkyl esters include for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, isobornyl (meth)acrylate, and eicosyl (meth)acrylate. The structure of the alkyl chain may have any of a linear structure, a branched structure, and a cyclic structure.

[0039] (Meth)acrylic acid alkyl esters having a hydroxyl group include for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate, glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and 1,4-cyclohexanedimethanol mono(meth)acrylate, and hydroxyethyl acrylamide.

[0040] (Meth)acrylic acid esters having an epoxy group include For example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate, etc. can be mentioned.

[0041] The (meth)acrylate ester having an alkyleneoxy group is For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth)acrylate ester, ethoxypolyethylene glycol (meth)acrylate ester, methoxypolypropylene glycol (meth)acrylate ester, ethoxypolypropylene glycol (meth)acrylate ester, phenoxypolyethylene glycol (meth)acrylate ester, and phenoxypolypropylene glycol (meth)acrylate ester, etc. can be mentioned.

[0042] The alkyl (meth)acrylate ester having an amino group is For example, monoalkylamino esters of (meth)acrylic acid such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate can be mentioned.

[0043] The monomer containing an amide bond is For example, (meth)acrylamides such as (meth)acrylamide, N-methylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetoneacrylamide, N-(hydroxymethyl)acrylamide, and N-(butoxymethyl)acrylamide; heterocyclic ring-containing compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine; N-vinylformamide, N-vinylacetamide, and N-vinyl-N-methylacetamide, etc. can be mentioned.

[0044] Alkyl (meth)acrylate having an aromatic ring, For example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, biphenyl (meth)acrylate, etc. can be mentioned.

[0045] The vinyl monomer is, For example, vinyl acetate, acrylonitrile, styrene, α-methylstyrene, etc. can be mentioned.

[0046] In 100% by mass of the monomer mixture constituting the acrylic polymer (A), the monomer (az) is preferably 70% by mass or less, and more preferably 0 to 40% by mass. When it is within this range, the adhesion characteristics are easily adjusted.

[0047] <Organic solvent (B)> The organic solvent (B) contained in the pressure-sensitive adhesive composition is used as a synthesis solvent during the production of the acrylic polymer (A), a dilution solvent after production, an adjustment solvent during the production of the pressure-sensitive adhesive composition, etc. In addition, the organic solvent (B) during the production of the acrylic polymer (A) is referred to as an organic solvent (b). By using the organic solvent (B), it is excellent in compatibility, and polymerization reaction control, extraction, washing, and coating by viscosity adjustment become easy, which is preferable. Further, in order to obtain a pressure-sensitive adhesive layer removed during drying, an organic solvent having a boiling point of 60°C to 160°C is preferable. Examples of the organic solvent (B) include ester solvents, ketone solvents, hydrocarbon solvents, alcohol solvents, etc.

[0048] As the ester solvent, For example, methyl acetate, ethyl acetate, etc., As the ketone solvent, For example, acetone, methyl ethyl ketone, cyclohexanone, etc., As the hydrocarbon solvent, For example, toluene, xylene, etc., As the alcohol solvent, For example, primary alcohols such as methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, and n-octanol, 3,3-dimethyl-1-butanol, benzyl alcohol; secondary alcohols such as isopropanol, 2-butanol, 3-pentanol, 3-methyl-2-butanol, 4-methyl-2-pentanol, 4-heptanol, 1-phenyl-2-propanol, 2-octanol, cyclohexanol, 4-methylcyclohexanol, 3-isopropylcyclohexanol, 4-phenylcyclohexanol, 1-phenyl-1-ethanol, 1-(4-isopropylphenyl)-1-ethanol, 1-phenyl-1-propanol, diphenylcarbinol; tertiary alcohols such as tert-butyl alcohol, tert-pentyl alcohol, 3-methyl-3-pentanol, 2,3-dimethyl-2-pentanol, 4-phenyl-2-methyl-2-hexanol, 1-phenyl-2-methyl-2-propanol, 1-methylcyclohexanol, 4-ethyl-1-methylcyclohexanol, 2-phenyl-2-propanol, 1,1-diphenyl-1-ethanol, 2-phenyl-2-butanol, 2-(4-isopropylphenyl)-2-propanol; polyhydric alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,3-butanediol, 1,2-butanediol, 1,2-pentanediol, 2,4-pentanediol, glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,5-pentanetriol, etc. may be mentioned.

[0049] Among the organic solvents (B), in order to improve the storage stability of the pressure-sensitive adhesive composition, it is preferable to contain an ester-based solvent, a ketone-based solvent or an alcohol-based solvent, more preferably to contain a ketone-based solvent or an alcohol-based solvent, and even more preferably an alcohol-based solvent. Among the primary alcohols, secondary alcohols and tertiary alcohols which are alcohol-based solvents, primary alcohols are more preferable.

[0050] The ester solvent, ketone solvent or alcohol solvent is preferably contained in an amount of 40% by mass or more, more preferably 60% by mass or more and 100% by mass or less in 100% by mass of the organic solvent (B). When the content of the ester solvent, ketone solvent or alcohol solvent is 40% by mass or more, the storage stability of the pressure-sensitive adhesive composition can be further improved.

[0051] The pressure-sensitive adhesive composition of the present invention preferably contains a primary alcohol in terms of storage stability. The organic solvent used in combination with the primary alcohol is preferably an ester solvent or a ketone solvent, or an alcohol other than the primary alcohol in terms of improved compatibility, and more preferably a ketone solvent.

[0052] The primary alcohol is preferably contained in an amount of 40% by mass or more, more preferably 60 to 97% by mass in 100% by mass of the organic solvent (B). When the content of the primary alcohol solvent is 40% by mass or more, the storage stability of the pressure-sensitive adhesive composition is further improved, and when it is 97% by mass or less, the compatibility is improved and the appearance of the coating film and others can be improved, which is preferable.

[0053] [Method for producing the acrylic polymer (A)] The acrylic polymer (A) can be synthesized by polymerizing a monomer mixture. The polymerization can be carried out by known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., but solution polymerization is preferable. As the solvent used in solution polymerization, the organic solvents described in the description of the organic solvent (B) can be used, and the monomer concentration can be produced at 10 to 70% by mass. The polymerization temperature is preferably a boiling point reaction of 60 to 120°C. The polymerization time is preferably about 5 to 12 hours.

[0054] The production of the acrylic polymer (A) is preferably carried out by polymerizing a monomer mixture containing 30% by mass or more of the monomer (ax) and, if necessary, 10% by mass or less of the monomer (ay) in an organic solvent (b) to obtain a polymer having a weight average molecular weight of 400,000 to 1,500,000.

[0055] In the production of the acrylic polymer (A), the organic solvent (b), which is a polymerization solvent used in solution polymerization, can be used alone or in combination of two or more, and is preferably an organic solvent containing a ketone solvent or an alcohol solvent, and more preferably an alcohol solvent. Among primary alcohols, secondary alcohols, and tertiary alcohols, the primary alcohol is preferred as the alcohol solvent.

[0056] When producing the acrylic polymer (A), by using an organic solvent (b) containing 40% by mass or more of a primary alcohol in 100% by mass of the organic solvent (b) during polymerization, the formation of gels and aggregates during production can be suppressed, and the fluidity of the pressure-sensitive adhesive composition can be made more excellent, which is preferable. More preferably, it is 60% by mass to 97% by mass. At this time, as the diluting solvent, an ester solvent, a ketone solvent, or an alcohol solvent is preferably used.

[0057] After producing the acrylic polymer (A), it may be appropriately diluted with an organic solvent (B). The diluting solvent is preferably an ester solvent, a ketone solvent, or an alcohol solvent.

[0058] The primary alcohol is preferably used during the production of the acrylic polymer (A). As another embodiment, a ketone solvent or an alcohol solvent other than the primary alcohol can also be used as the polymerization solvent. In this case, it is preferable to use a primary alcohol as the diluting solvent after production, and it is preferable to dilute so that the organic solvent (B) contained in the pressure-sensitive adhesive composition contains 40% by mass or more of the primary alcohol. More preferably, it is 60 to 97% by mass.

[0059] The polymerization initiator used for polymerization is preferably a thermal radical polymerization initiator. Peroxides and azo compounds are common as thermal radical polymerization initiators.

[0060] Peroxides include, for example, dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-di(t-butylperoxy)hexyne-3; peroxy esters such as t-butyl peroxybenzoate, t-butyl peroxyacetate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide; peroxyketals such as 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate; hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide; diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide; peroxydicarbonates such as bis(t-butylcyclohexyl) peroxydicarbonate, etc.

[0061] Azo compounds include, for example, 2,2'-azobisbutyronitriles such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN), 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobisvaleronitriles such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobispropionitriles such as 2,2'-azobis(2-hydroxymethylpropionitrile); Examples include 1,1'-azobis-1-alkanenitriles such as 1,1'-azobis(cyclohexane-1-carbonitrile). In addition, azo compounds having a carboxyl group or a hydroxyl group include, for example, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-azobis(N-(carboxyethyl)-2-methylpropionamidine) tetrahydrate, and the like.

[0062] It is preferable to use 0.001 to 10 parts by mass, more preferably 0.01 to 2 parts by mass of the thermal radical polymerization initiator with respect to 100 parts by mass of the monomer mixture.

[0063] <Hardener (C)> The hardener (C) reacts with the hydroxyl group of the acrylic polymer (A) or the carboxyl group when the monomer (ay) is included as the monomer mixture. It is preferable to use the hardener (C) in combination with the acrylic polymer (A) because the holding power can be further enhanced. When using the hardener (C), the content of the hardener (C) is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). When the content is 0.05 parts by mass or more, the holding power and the re-peelability are improved, and when it is 20 parts by mass or less, it is preferable because it is easier to balance the adhesive properties such as tack.

[0064] Examples of the hardener (C) include isocyanate compounds, aziridine compounds, epoxy compounds, metal chelates, or carbodiimide compounds. Among these, being an isocyanate compound, an aziridine compound, an epoxy compound, or a metal chelate compound is preferable in terms of the re-peelability of the adhesive composition, and isocyanate compounds and aziridine compounds are more preferable.

[0065] The isocyanate compound is an isocyanate having two or more isocyanate groups. The isocyanate compound is preferably, for example, an isocyanate monomer such as an aromatic polyisocyanate, an aliphatic polyisocyanate, an araliphatic polyisocyanate, an alicyclic polyisocyanate, and their biuret bodies, nurate bodies, and adduct bodies.

[0066] Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4''-triphenylmethane triisocyanate, and the like.

[0067] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (alias: HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and the like.

[0068] Examples of the araliphatic polyisocyanate include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.

[0069] Aliphatic polyisocyanates include, for example, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, and the like.

[0070] The burette body is a self-condensate having a burette bond formed by self-condensation of isocyanate monomers. Examples of the burette body include the burette body of hexamethylene diisocyanate.

[0071] The nurate body is a trimer of isocyanate monomers. Examples include trimers of hexamethylene diisocyanate, trimers of isophorone diisocyanate, trimers of tolylene diisocyanate, and the like.

[0072] The adduct body is a polyfunctional isocyanate compound formed by the reaction of an isocyanate monomer with a polyfunctional low-molecular-weight active hydrogen-containing compound. Examples of the adduct body include compounds obtained by reacting trimethylolpropane with hexamethylene diisocyanate, compounds obtained by reacting trimethylolpropane with tolylene diisocyanate, compounds obtained by reacting trimethylolpropane with xylylene diisocyanate, compounds obtained by reacting trimethylolpropane with isophorone diisocyanate, compounds obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate, and the like.

[0073] From the perspective of forming a sufficient cross-linked structure, a trifunctional isocyanate compound is preferred as the isocyanate compound. More preferably, the isocyanate compound is an adduct obtained by reacting an isocyanate monomer with a trifunctional low-molecular-weight active hydrogen-containing compound, or a nurate. Preferred isocyanate compounds include trimethylolpropane adducts of hexamethylene diisocyanate, nurate of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, nurate of tolylene diisocyanate, trimethylolpropane adducts of isophorone diisocyanate, and nurate of isophorone diisocyanate. More preferred are trimethylolpropane adducts of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, and trimethylolpropane adducts of isophorone diisocyanate.

[0074] Examples of epoxy compounds include glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidylaminophenylmethane, etc.

[0075] Examples of aziridine compounds include trimethylolpropane tris[3-(aziridin-1-yl)propionate], N,N'-diphenylmethane-4,4'-bis(1-aziridine carboxylate), tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane, etc.

[0076] As the carbodiimide compound, a high-molecular-weight polycarbodiimide produced by subjecting a diisocyanate compound to a decarboxylation condensation reaction in the presence of a carbodiimidization catalyst is preferred. Among the commercially available products of the high-molecular-weight polycarbodiimide, the Carbodilite series of Nisshinbo Industries, Inc. is preferred. Among them, Carbodilite V-03, 07, and 09 are preferred because of their excellent compatibility with organic solvents.

[0077] Metal chelates are preferably coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, and acetylacetone or ethyl acetoacetate. Examples of metal chelates include aluminum ethylacetoacetate diisopropylate, aluminum trisacetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate, and aluminum alkylacetoacetate diisopropylate.

[0078] <Adhesion - imparting resin (D)> The pressure - sensitive adhesive composition of the present invention can contain an adhesion - imparting resin (D) as long as the problem can be solved. By containing the adhesion - imparting resin (D), the adhesive force of the adhesive layer is further improved, and the appearance of the coating film can be made better, which is preferable. The content of the adhesion - imparting resin (D) is preferably 1 to 30 parts by mass, more preferably 2 to 28 parts by mass, based on 100 parts by mass of the acrylic polymer (A). Within this range, the adhesive force and the appearance of the coating film can be made better.

[0079] Examples of the adhesion - imparting resin include rosin - based resins, terpene - based resins, petroleum - based resins, macroon resins, macroon indene resins, styrene resins, xylene resins, and phenol resins.

[0080] Rosin - based resins are classified as natural resins and are resins obtained from rosin, which has a tricyclic diterpenoid isomer with 20 carbon atoms as the main component. Examples of rosin - based resins include rosin resins such as gum rosin and wood rosin; rosin ester resins obtained by reacting rosin or rosin resins with glycerin, pentaerythritol, etc.; rosin phenol resins obtained by reacting rosin or rosin resins with phenols; and polymerized rosin. Commercially available products may be used as the rosin - based resin. Examples of commercially available products include A - 18, A - 75, A - 100, A - 115, A - 125, D - 125, D - 160 (all rosin ester resins) manufactured by Arakawa Chemical Industries, Ltd.

[0081] Terpene resins are classified as natural resins and are resins mainly composed of terpenes (for example, α-pinene, β-pinene, limonene, etc.) having isoprene as a constituent unit. Specifically, terpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by reacting aromatic compounds such as styrene with terpenes and terpene resins, terpene phenol resins obtained by reacting phenols with terpenes and terpene resins, and hydrogenated products thereof, such as hydrogenated terpene resins, hydrogenated terpene phenol resins, and hydrogenated aromatic modified terpene resins, can be mentioned. Note that terpene resins can be used alone or in combination of two or more. Commercially available products may be used as the terpene resin. Examples of commercially available products include YS Resin PX1000 and YS Resin PX1150 (both are terpene resins) manufactured by Yasuhara Chemical Co., Ltd.

[0082] Petroleum resins mean those obtained by polymerizing a fraction containing unsaturated hydrocarbon monomers by-produced by thermal decomposition of petroleum naphtha such as petroleum naphtha. Specifically, aliphatic (C5-based) petroleum resins, aromatic (C9-based) petroleum resins, hydrogenated petroleum resins, etc. can be mentioned. Note that petroleum resins can be used alone or in combination of two or more. Commercially available products may be used as the petroleum resin. Examples of commercially available products include FTR-6100, FTR-6110, and FTR-6125 manufactured by Mitsui Chemicals, Inc.

[0083] <Optional component> The pressure-sensitive adhesive composition of the present invention may contain other components as necessary. Examples of other components include plasticizers, silane coupling agents, release imparting agents, heat or light stabilizers, ultraviolet absorbers, leveling agents, defoaming agents, antibacterial agents, moisturizing agents, vitamins, pigments, dyes, fragrances, etc. These can be appropriately selected from known ones and used.

[0084] <Method for producing pressure-sensitive adhesive composition> The method for producing the pressure-sensitive adhesive composition is not particularly limited. The pressure-sensitive adhesive composition only needs to contain an acrylic polymer (A) and an organic solvent (B), and further, a curing agent (C), a tackifier resin (D), and optional components can be mixed as needed to obtain it. The acrylic polymer (A) can be obtained by a known polymerization method described in the above-mentioned method for producing the acrylic polymer (A), and the obtained acrylic polymer (A) solution can also be used as the pressure-sensitive adhesive composition. When used as a pressure-sensitive adhesive composition, the acrylic polymer (A) is preferably obtained by solution polymerization in a solution containing an organic solvent (B).

[0085] As the organic solvent (B) contained in the pressure-sensitive adhesive composition, it is preferable to use at least one of a ketone solvent and an alcohol solvent. As the addition method thereof, (1): during the production of the acrylic polymer (A), or (2): during dilution after production, (3): during the adjustment of the pressure-sensitive adhesive composition, the addition methods can be mentioned. It is preferable to add in (1) or (2) in that it can suppress the formation of gels and aggregates during polymer production, and the fluidity and storage stability of the polymer solution are more excellent, and (1) is more preferable.

[0086] When mixing the curing agent (C), the tackifier resin (D), or the optional component into the polymer solution, the curing agent (C) or the tackifier resin (D) may be dissolved in a solvent or dispersed in a dispersion medium in advance and then mixed. When mixing the components to form the pressure-sensitive adhesive composition, all the components may be added and mixed simultaneously, or the addition timing for each component may be appropriately determined in consideration of the properties and reactivity of each component. When mixing with each component to form the pressure-sensitive adhesive composition, stirring may be performed as needed.

[0087] ≪Adhesive Sheet≫ The adhesive sheet according to the present invention includes an adhesive layer formed from the pressure-sensitive adhesive composition or an adhesive layer that is a cured product of the pressure-sensitive adhesive composition. Among them, it is preferable to include a base material and an adhesive layer.

[0088] Examples of the base material include cellophane, plastic sheets, rubber, foams, fabrics, rubber fabrics, resin-impregnated fabrics, glass plates, wood, etc., and it may be in the form of a plate or a film. Note that "sheet", "film", and "plate" only differ in name and do not distinguish each other. The base material may be a single layer or a laminate having a plurality of layers. Further, the base material may be provided with a functional layer on the adherend surface for imparting various functional properties such as optical functionality such as antireflection, conductivity, antistatic property, and hard coat property. In addition, a peelable base material with its surface peel-treated can also be used as the base material.

[0089] Specific examples of the above plastic sheets include films of polyvinyl alcohol, triacetyl cellulose, polyolefin resins such as polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; films of polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; films of polycarbonate resins, films of polynorbornene resins, films of polyarylate resins, films of acrylic resins, films of polyphenylene sulfide resins, films of polystyrene resins, films of vinyl resins, films of polyamide resins, films of polyimide resins, films of epoxy resins, etc.

[0090] The thickness of the adhesive layer may be appropriately adjusted according to the application, etc., but from the viewpoint of adhesiveness, etc., 0.1 to 300 μm is preferable, 1 to 200 μm is more preferable, and 3 to 150 μm is even more preferable.

[0091] <Manufacturing method of the adhesive sheet> This pressure-sensitive adhesive sheet can be manufactured, for example, by the following methods: (a) a method of forming an adhesive layer by applying an adhesive composition to a base material, drying it if necessary, and then heating it; (b) a method of forming an adhesive layer by applying an adhesive composition to the release-treated surface of a release-treated film, drying it if necessary, laminating a base material on the surface of the adhesive composition, and then heating it, and then removing the release-treated film; (c) a method of forming an adhesive layer by applying an adhesive composition to the release-treated surface of a release-treated film, drying it if necessary, and then heating it, and then laminating a base material on the surface of the adhesive layer and removing the release-treated film. In the method (a) above, a further release-treated film may be laminated on the surface of the formed adhesive layer. Also, in the methods (b) and (c) above, the release-treated film may be removed immediately before using this pressure-sensitive adhesive sheet.

[0092] The method of applying the present adhesive composition on the base material or the release-treated film can be appropriately selected from known methods. Examples of the coating method include a Meyer bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a reverse coater, a spin coater, etc. Also, the drying and curing method of the adhesive composition is not particularly limited, and examples include hot air drying, those using infrared rays or a vacuum method. The heating temperature varies depending on the material, film thickness, organic solvent, etc. of the adhesive composition, but it is usually sufficient to heat up to about 60 to 130°C.

[0093] When applying the adhesive composition, the viscosity can be adjusted with a solvent. As the solvent, those mentioned in the above organic solvent (B) can be used.

Examples

[0094] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" means parts by mass, "%" means mass%, and "RH" means relative humidity. In addition, the compounding amounts of the raw materials (excluding solvents) described in the examples below and the tables are values in terms of non-volatile content. The weight average molecular weight (Mw) of the copolymer was measured by the following method.

[0095] <Measurement of weight average molecular weight (Mw)> The Mw of each polymer was measured under the following conditions. The determination of Mw was carried out by a calibration curve method using polystyrene with a known weight average molecular weight as a standard substance. Apparatus name: LC-GPC system "Prominence" manufactured by Shimadzu Corporation Columns: 4 GMHXL columns manufactured by Tosoh Corporation and 1 HXL-H column manufactured by Tosoh Corporation connected in series Mobile phase solvent: Tetrahydrofuran (THF) Flow rate: 1.0 ml / min Column temperature: 40 °C

[0096] <Raw materials> The raw materials and abbreviations shown in the table are as follows. [Monomer (ax)] Monomers (ax-1) to (ax-7) were synthesized by the synthesis method described in JP-A-57-185236. (ax-1): Monomer obtained by adding 5 moles of γ-butyrolactone to 1 mole of 2-hydroxyethyl methacrylate (in the general formula (II), R1 = methyl group, n = 5) (ax-2): Monomer obtained by adding 1 mole of ε-caprolactone to 1 mole of 2-hydroxyethyl methacrylate (in the general formula (III), R1 = methyl group, n = 1) (ax-3): Monomer obtained by adding 3 moles of ε-caprolactone to 1 mole of 2-hydroxyethyl methacrylate (in the general formula (III), R1 = methyl group, n = 3) (ax-4): Monomer obtained by adding 5 moles of ε-caprolactone to 1 mole of 2-hydroxyethyl methacrylate (in the general formula (III), R1 = methyl group, n = 5) (ax - 5): Monomer obtained by adding 10 moles of ε - caprolactone to 1 mole of 2 - hydroxyethyl methacrylate (in the general formula (III), R1 = methyl group, n = 10) (ax - 6): Monomer obtained by adding 5 moles of ε - caprolactone to 1 mole of 2 - hydroxyethyl acrylate (in the general formula (III), R1 = methyl group, n = 5)

[0097] [Monomer (ay)] (ay - 1): Monomer having a carboxyl group MAA: Methacrylic acid AA: Acrylic acid (ay - 2): Monomer having an active methylene group AAEM: 2 - Acetoacetoxyethyl methacrylate [Monomer (az)] MMA: Methyl methacrylate 2EHA: 2 - Ethylhexyl acrylate (az - 1): Synthesized by the synthesis method shown in JP - A - 57 - 185236. Monomer represented by chemical formula (1), obtained by adding 15 moles of ε - caprolactone to 1 mole of 2 - hydroxyethyl methacrylate

[0098] Chemical formula (1)

Chemical formula

[0099] [Organic solvent (B)] MeOH: Methanol EtOH: Ethanol BuOH: 1 - Butanol MEK: Methyl ethyl ketone IPA: Isopropyl alcohol [Hardener (C)] C - 1: Trimethylolpropane adduct of tolylene diisocyanate C - 2: Trimethylolpropane tris[3 - (aziridin - 1 - yl)propionate] C-3: N, N, N’, N’-Tetraglycidyl-m-xylenediamine C-4: Aluminum tris(acetylacetonate) C-5: V-03 (carbodiimide compound, manufactured by Nisshinbo Chemicals, Inc.) [Adhesion-imparting resin (D)] D-1: A-75 (manufactured by Arakawa Chemical Industries, Ltd., rosin ester resin)

[0100] (Example 1) Into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube (hereinafter also simply referred to as "reaction vessel"), 30 parts of monomer (ax-3), 70 parts of methyl methacrylate (MMA), 15 parts of methanol (MeOH), 105 parts of ethanol (EtOH), 30 parts of methyl ethyl ketone (MEK), and 0.04 part of 2,2'-azobisisobutyronitrile (AIBN) were charged. Then, the air in the reaction vessel was replaced with nitrogen gas. Next, while stirring under a nitrogen atmosphere, it was heated to 80°C to initiate the reaction, and a polymerization reaction was carried out at the reflux temperature for 7 hours. After the reaction was completed, it was cooled to obtain a polymer (A-1) solution with a non-volatile content of 40%. Also, the weight average molecular weight (Mw) of the obtained acrylic polymer (A-1) was 1,000,000. In addition, the solvent content ratio in the polymer solution after production was adjusted to be the same as that during polymer production. That is, in 100% by mass of the organic solvent in the acrylic polymer (A-1) solution, MeOH: 10% by mass, EtOH: 70% by mass, MEK: 20% by mass.

[0101] (Examples 2 to 14) Acrylic polymer (A-2 to 14) solutions were produced in the same manner as in Example 1, except that the types and blending amounts (parts by mass) of the monomers constituting the copolymer were changed as described in Tables 1 and 2. In addition, the "content rate of primary alcohol during polymerization [%]" in the table is the content rate of primary alcohol in 100% by mass of the organic solvent during polymerization. Also, the solvent content ratio in the polymer solution after production was adjusted to be the same as that during polymer production.

[0102] (Example 15) Into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube (hereinafter, also simply referred to as "reaction vessel"), 60 parts of monomer (ax-3), 40 parts of methyl methacrylate (MMA), 15 parts of methanol (MeOH), 105 parts of ethanol (EtOH), 30 parts of methyl ethyl ketone (MEK), and 0.04 part of 2,2'-azobisisobutyronitrile (AIBN) were charged. Then, the air in the reaction vessel was replaced with nitrogen gas. Next, while stirring under a nitrogen atmosphere, it was heated to 80 °C to initiate the reaction, and a polymerization reaction was carried out at the reflux temperature for 7 hours. After the reaction was completed, it was cooled to obtain a polymer (A-15) solution with a non-volatile content of 40%. Also, the weight average molecular weight (Mw) of the obtained acrylic polymer (A-15) was 900,000. In addition, the solvent content ratio in the polymer solution after production was adjusted to be the same as that during polymer production. That is, in 100 mass% of the organic solvent in the acrylic polymer (A-15) solution, MeOH: 10 mass%, EtOH: 70 mass%, MEK: 20 mass%.

[0103] The solution of the acrylic polymer (A-15) was used as the adhesive composition 1.

[0104] The adhesive composition 1 was coated on a polyester separator with a thickness of 38 μm [trade name "Superstek" SP-PET38, manufactured by Lintec Corporation, the same hereinafter] so that the thickness after drying would be 50 μm, and dried in a hot air oven at 100 °C for 2 minutes to form an adhesive layer. After drying, it was laminated to a polyethylene naphthalate (PEN) film with a thickness of 25 μm (Teonex, manufactured by Teijin Limited), and further cured at 23 °C and 50% RH for 7 days to obtain an adhesive sheet.

[0105] (Example 16, Comparative Examples 1 to 3) As shown in Table 3, except that the acrylic polymer solution was changed, adhesive compositions 2, 25 to 27 were produced in the same manner as in Example 15, and adhesive sheets were obtained.

[0106] (Example 17) Into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube (hereinafter, also simply referred to as "reaction vessel"), 60 parts of monomer (ax-4), 20 parts of methacrylic acid (MAA), 20 parts of methyl methacrylate (MMA), 15 parts of methanol (MeOH), 45 parts of ethanol (EtOH), 90 parts of methyl ethyl ketone (MEK), and 0.04 part of 2,2'-azobisisobutyronitrile (AIBN) were charged. Then, the air in the reaction vessel was replaced with nitrogen gas. Next, while stirring under a nitrogen atmosphere, it was heated to 80 °C to initiate the reaction, and a polymerization reaction was carried out at the reflux temperature for 7 hours. After the reaction was completed, it was cooled to obtain a polymer (A-17) solution with a non-volatile content of 40%. Also, the weight average molecular weight (Mw) of the obtained polymer (A-17) was 650,000. In addition, the solvent content ratio in the polymer solution after production was adjusted to be the same as that during polymer production. That is, in 100% by mass of the organic solvent in the acrylic polymer (A-17) solution, MeOH: 10% by mass, EtOH: 30% by mass, and MEK: 60% by mass.

[0107] Next, 30 parts of ethanol (EtOH) was added to 100 parts of the obtained polymer (A-17) solution and stirred to prepare a diluted polymer solution. The obtained polymer solution was used as the pressure-sensitive adhesive composition 3. The solvent content ratio in the diluted polymer solution is MeOH: 7% by mass, EtOH: 53% by mass, and MEK: 40% by mass in 100% by mass of the organic solvent.

[0108] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 15 except that the pressure-sensitive adhesive composition 3 was used.

[0109] (Example 18) 100 parts of acrylic polymer (A-1) and 3 parts of curing agent (C-1) were blended and stirred to obtain a pressure-sensitive adhesive composition 4. In addition, the solvent content ratio of the pressure-sensitive adhesive composition 4 was set to MeOH: 10% by mass, EtOH: 70% by mass, and MEK: 20% by mass in 100% by mass of the organic solvent.

[0110] On a separator made of polyester with a thickness of 38 μm [trade name "Superstek" SP-PET38, manufactured by Lintec Corporation, the same applies hereinafter], the adhesive composition 4 was applied so that the thickness after drying would be 50 μm, and it was dried in a hot air oven at 100 °C for 2 minutes to form an adhesive layer. After drying, it was laminated onto a polyethylene naphthalate (PEN) film with a thickness of 25 μm (Teonex, manufactured by Teijin Limited), and further cured at 23 °C and 50% RH for 7 days to obtain an adhesive sheet.

[0111] (Examples 19 - 38) As shown in Tables 3 and 4, adhesive compositions 5 - 24 were produced in the same manner as in Example 18, except that the types and blending amounts (parts by mass) of the acrylic polymer solution, curing agent, and tackifier resin were changed, and adhesive sheets were obtained.

[0112] <Evaluation Items and Evaluation Methods> The evaluation items and evaluation methods for the resin composition and the adhesive sheet are as follows. The results are shown in Table 5.

[0113] 《Evaluation of Adhesive Composition》 <Degree of Biodegradability> The degree of biodegradability of the adhesive composition was evaluated in accordance with JIS K 6953 - 1. (Evaluation Criteria) ◎: Degree of biodegradability percentage 70% or more. Excellent. 〇: Degree of biodegradability percentage 50% or more and less than 70%. Good. △: Degree of biodegradability percentage 30% or more and less than 50%. Practically acceptable. ×: Degree of biodegradability percentage less than 30%. Not practically acceptable.

[0114] <Coating Liquid Fluidity> The fluidity of the adhesive composition was evaluated visually. (Evaluation Criteria) ◎: Coating liquid without lumps, gel - like substances, or aggregates, and having fluidity. Excellent. 〇: Coating liquid with very few lumps, gel - like substances, or aggregates, and having fluidity. Good. △: There is a small amount of gel-like or aggregated substances in the form of lumps or blobs, but the coating liquid has fluidity. Practically acceptable. ×: There are lumps or blobs of gel-like or aggregated substances and the coating liquid has no fluidity. Practically unacceptable.

[0115] 《Evaluation of Adhesive Sheet》 <Adhesive Properties> [Adhesive Force] The obtained adhesive sheet was cut into samples with a size of 25 mm in width and 100 mm in length. Then, in an atmosphere of 23°C - 50% RH, in accordance with JIS Z 0237, the release sheet was peeled off from the sample, and the exposed adhesive layer was attached to a polished stainless steel (SUS) plate. After one reciprocating pressure bonding with a 2 kg roll, using a tensile testing machine, 24 hours after bonding, the peel strength (N / 25 mm) was measured under the conditions of a peel rate of 300 mm / min and a peel angle of 180°. (Evaluation Criteria) ◎: The adhesive force is 5 N / 25 mm or more. Excellent. ○: The adhesive force is 1 N / 25 mm or more and less than 5 N / 25 mm. Good. △: The adhesive force is 0.1 N / 25 mm or more and less than 1 N / 25 mm. Practically acceptable. ×: The adhesive force is less than 0.1 N / 25 mm. Practically unacceptable.

[0116] [Retention Force] The release sheet was peeled off from the obtained adhesive sheet, and the tip part with a width of 25 mm and a length of 25 mm of the exposed adhesive layer was attached to a polished stainless steel (SUS) plate. After one reciprocating pressure bonding with a 2 kg roll, a load of 1 kg was applied in an atmosphere of 40°C and held for 70,000 seconds. The evaluation shows the number of seconds when the sample falls from the SUS plate. If the sample does not fall, it shows the number of millimeters by which the adhesive tip between the adhesive layer and the SUS plate has shifted downward due to the load. (Evaluation Criteria) ◎: The displacement of the sample is less than 0.5 mm. Excellent. ○: The displacement of the sample is 0.5 mm or more and less than 2 mm. Better. 〇△: The displacement of the sample is 2 mm or more and less than 5 mm. Good. △: The displacement of the sample is 5 mm or more and it did not fall. Practically acceptable. ×: The sample fell. Practically unacceptable.

[0117] [Ball Tack] The obtained adhesive sheet was prepared to be 25 mm in width and 250 mm in length. The release sheet was peeled off from the adhesive sheet, and the adhesive surface was fixed upward on an inclined plate with an inclination angle of 30 degrees. A PET film for the runway was attached to the upper part, and a steel ball (1 / 32 to 32 / 32 inches) was rolled on a sample with a 10 cm runway and a 10 cm paste surface, and the number of the diameter of the ball that stopped near the center of the paste surface was recorded. The measurement was carried out in an atmosphere of 23°C - 50% RH. (Evaluation Criteria) ◎: The ball diameter is 16 / 32 inches or more. Excellent. ○: The ball diameter is 12 / 32 inches or more and less than 16 / 32 inches. Better. △〇: The ball diameter is 8 / 32 inches or more and less than 12 / 32 inches. Good. △: The ball diameter is 4 / 32 inches or more and less than 8 / 32 inches. Practically acceptable. ×: The ball diameter is less than 4 / 32 inches. Not practically acceptable.

[0118] [Peelability] The obtained adhesive sheet was adhered to a stainless steel plate (SUS304) with a sample width of 25 mm in an atmosphere of 23°C - 50% RH, roll-pressed according to JIS0237 with a 2 Kg roll, left for 24 hours in an atmosphere of 23°C - 50% RH, and then peeled under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180° using a tensile testing machine, and the appearance such as remaining paste was compared. (Evaluation Criteria) ◎: The adhesive sheet could be peeled off without contaminating the SUS plate. Excellent. ○: The SUS plate was slightly contaminated. Good. △: The SUS plate was slightly contaminated. Practically acceptable. ×: The SUS plate was contaminated. Not practically acceptable.

[0119] [Appearance of Coating Film] The release sheet was peeled off from the obtained adhesive sheet and attached to a glass plate, and the state was visually confirmed. (Evaluation Criteria) 〇: It was transparent. Good △ : Slight whitening was observed. Practically applicable. × : Completely whitened. Not usable.

[0120]

Table 1

[0121]

Table 2

[0122]

Table 3

[0123]

Table 4

[0124]

Table 5

[0125] From the results of Table 5, the adhesive composition obtained in the examples had high fluidity of the coating solution despite its high biodegradability, and furthermore, the obtained adhesive sheet showed excellent results in all of the adhesive performance, re-peelability, and transparency of the coating film.

Claims

1. An adhesive composition comprising an acrylic polymer (A) and an organic solvent (B), wherein the acrylic polymer (A) is a polymer of a monomer mixture containing 30% by mass or more of a monomer (ax) represented by the following general formula (I), and has a weight average molecular weight of 400,000 to 1,500,000, the organic solvent (B) contains 40% by mass or more of a primary alcohol in 100% by mass thereof, and the concentration of the acrylic polymer (A) is 10 to 70% by mass. 【Chemical 1】 ≪However, R1, R3, and R4 are each independently a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, R2 is an alkylene group having 2 to 8 carbon atoms, m represents an integer of 3 to 10, and n represents an integer of 1 to 13≫

2. The adhesive composition according to claim 1, wherein the monomer mixture contains 10% by mass or less of a monomer (ay) having a carboxyl group or an active methylene group.

3. Furthermore, it contains a curing agent (C), and the curing agent (C) is at least one selected from the group consisting of an isocyanate compound, an aziridine compound, an epoxy compound, and a metal chelate compound. The adhesive composition according to claim 1 or 2.

4. The adhesive composition according to any one of claims 1 to 3, further comprising a tackifier resin (D).

5. An adhesive sheet having an adhesive layer formed from the adhesive composition according to any one of claims 1 to 4.

6. A method for producing an adhesive composition comprising an acrylic polymer (A) and an organic solvent (b), wherein a monomer mixture containing 30% by mass or more of a monomer (ax) represented by the following general formula (I) is polymerized in an organic solvent (b) at a monomer concentration of 10 to 70% by mass to produce an acrylic polymer (A) having a weight average molecular weight of 400,000 to 1,500,000, and the organic solvent (b) contains 40% by mass or more of a primary alcohol. A method for producing an adhesive composition. ≪However, R1, R3, and R4 are each independently a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, R2 is an alkylene group having 2 to 8 carbon atoms, m represents an integer of 3 to 10, and n represents an integer of 1 to 13≫

7. The method for producing an adhesive composition according to claim 6, wherein the monomer mixture contains 10% by mass or less of a monomer (ay) having a carboxyl group or an active methylene group. ​ 【Chemical 2】 ​ ​ ​

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