JP2023005131A - Adhesive composition and adhesive sheet - Google Patents

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

An embodiment of the present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same.

Various resin-based compositions are known as adhesive compositions, and among them, acrylic adhesive compositions are widely used. Acrylic pressure-sensitive adhesive compositions are used in various applications because their adhesive properties such as adhesive strength, tackiness, and holding power can be easily adjusted depending on the monomer composition. Furthermore, in recent years, in addition to adhesive properties such as adhesive strength, tack, and holding power, there is a demand for higher functionality such as transparency of coating films.

Adhesive labels and adhesive tapes are sometimes discarded underground. In this case, adhesive labels composed of typical acrylic adhesive compositions are mainly made of petroleum-derived raw materials, and the rate of decomposition by microorganisms is extremely slow. It remains inside and can even cause destruction of the subterranean ecosystem. Therefore, in recent years, the use of biodegradable raw materials has begun to be recommended.

Further, as a method of disposal into the ground, there is a method in which an adhesive label or adhesive tape is left attached to the container, or a method in which the adhesive label or adhesive tape is removed from the container after use. In this case, adhesive strength or removability to the extent that it is attached to a container and does not come off is required. In particular, with regard to removability, it is required that adhesive residue does not occur even when exposed to harsher environments while maintaining appropriate adhesive strength.

In Patent Document 1, one or more alkyl acrylates having an alkyl group having 1 to 14 carbon atoms containing 20% by mass or more of n-octyl acrylate and a functional monomer copolymerizable as a main component are used together in a solvent. An acrylic solvent-based pressure-sensitive adhesive obtained by polymerization is disclosed.

In Prior Document 2, an acrylic acid alkyl ester having an alkyl group having 2 to 12 carbon atoms, a nitrogen-containing vinyl monomer and a caprolactone-modified (meth)acrylic acid ester are copolymerized, and a polymerizable unsaturated carboxylic acid is substantially An acrylic pressure-sensitive adhesive composition is disclosed that contains an acrylic copolymer resin that does not contain a polyisocyanate compound and a polyisocyanate compound as a cross-linking agent.

JP-A-10-067974 JP-A-5-163480

However, in Patent Documents 1 and 2, although adhesive properties are exhibited, biodegradability is not sufficient. In particular, in Patent Document 2, caprolactone, which is a biodegradable raw material, is used. As described in paragraph [0010], it is difficult to improve biodegradability while maintaining adhesive properties. In addition, fluidity is lowered due to gel matter during production and aggregates contained in the pressure-sensitive adhesive composition, and it is difficult to suppress the generation of foreign matter on the film during coating.
As described above, the conventional pressure-sensitive adhesive composition cannot satisfy the pressure-sensitive adhesive property and biodegradability, and further satisfies the suppression of the generation of foreign matter derived from gels and aggregates in the pressure-sensitive adhesive composition. .

Therefore, the present invention provides a pressure-sensitive adhesive composition that is excellent in biodegradability, suppresses the formation of gels and aggregates, and has excellent fluidity. , removability, and excellent transparency of the coating film can be provided.

In order to solve the above problems, the inventors have conducted extensive studies and completed the present invention. That is, embodiments of the present invention relate to: However, the present invention includes various embodiments without being limited to the embodiments described below.

《ただし、Ｒ１、Ｒ３、およびＲ４はそれぞれ独立に、水素原子、または１～９個の炭素原子を有するアルキル基であり、Ｒ２は２～８個の炭素原子を有するアルキレン基であり、ｍは３～１０の整数、ｎは１～１３の整数を表わす》 That is, the present invention contains 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. One, it relates to an adhesive composition.

<<where 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, and m is An integer of 3 to 10, n represents an integer of 1 to 13>>

The present invention also relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

According to the present invention, a pressure-sensitive adhesive composition having excellent fluidity in which the formation of gels and aggregates is suppressed even if the degree of biodegradability is high, and the pressure-sensitive adhesive composition using the pressure-sensitive adhesive composition, removability, removability, It is also possible to provide a pressure-sensitive adhesive sheet having excellent coating film transparency.

Terms are defined prior to describing the present invention.
In this specification, a numerical range specified using "to" means to include the numerical values described before and after "to" as a range of lower and upper values.
In the present specification, the terms "(meth)acrylic acid" and "(meth)acrylate" are assumed to represent "acrylic acid or methacrylic acid" and "acrylate or methacrylate", respectively, unless otherwise specified. do.
As used herein, the term "polymer" means having structural units derived from monomers and including homopolymers and copolymers.

In this specification, the monomer (ax) represented by the general formula (I), the monomer having a carboxyl group or an active methylene group (ay), and the other monomer (az) are each referred to as a monomer. They are sometimes abbreviated as monomer (ax), monomer (ay), and monomer (az).

Embodiments of the present invention will be described in detail below, but the following description is an example (representative example) of embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist.
In addition, unless otherwise noted, the various components described in this specification may be independently used singly or in combination of two or more.

<<Adhesive composition>>
The pressure-sensitive adhesive composition of the present invention contains an acrylic polymer (A) and an organic solvent (B) as essential components, and optionally a curing agent (C), a tackifying resin (D), or other optional components. .
By containing the acrylic polymer (A) and the organic solvent (B), it is possible to obtain a pressure-sensitive adhesive composition that is excellent in biodegradability, suppresses the formation of gels and aggregates, and has excellent fluidity. .
As a result, for example, even if the biodegradability percentage is 30% or more, it is possible to make a pressure-sensitive adhesive composition excellent in fluidity, and the pressure-sensitive adhesive sheet obtained has adhesive properties, removability, and a coating film. The transparency of the film can also be made excellent.

<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 the monomer (ax), and in 100% by mass of the monomer mixture, ( ax) in an amount of 30% by mass or more. Incidentally, the acrylic polymer (A) may be a monomer polymer using 100% by mass of the monomer (ax).
The monomer mixture preferably further contains a monomer (ay), and the content of the monomer (ay) is preferably 10% by mass or less in 100% by mass of the monomer mixture. Thereby, the cohesive force of the pressure-sensitive adhesive layer can be further improved. Moreover, the monomers constituting the polymer may further contain other monomers (az) which are monomers other than the monomers (ax) and the monomers (ay).

The acrylic polymer (A) has a weight average molecular weight of 400,000 to 1,500,000, preferably 600,000 to 1,000,000, more preferably 700,000 to 900,000.
When the weight-average molecular weight is 400,000 or more, the cohesive strength of the pressure-sensitive adhesive layer increases, and the pressure-sensitive adhesive strength is further improved. When the weight-average molecular weight is 1,500,000 or less, the formation of gels and aggregates is suppressed, and the fluidity of the pressure-sensitive adhesive composition tends to be improved.

《ただし、Ｒ１、Ｒ３、およびＲ４はそれぞれ独立に、水素原子、または１～９個の炭素原子を有するアルキル基であり、Ｒ２は１～８個の炭素原子を有するアルキレン基であり、ｍは３～１０の整数、ｎは１～１３の整数を表わす》 [monomer (ax)]
A monomer (ax) is a monomer represented by the following general formula (I).

<<where 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, and m is An integer of 3 to 10, n represents an integer of 1 to 13>>

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

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

In 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 starting material, for example, when 2-hydroxyethyl (meth)acrylate is used, R2 becomes an ethylene group. When 4-hydroxybutyl (meth)acrylate is used, R2 becomes an n-butylene group. When 8-hydroxyoctyl (meth)acrylate is used, R2 becomes an n-octylene group.

R3 and R4 in general formula (I) are each independently a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. When produced using lactone as a raw material, these depend on the structure of the lactone used. For example, when γ-butyrolactone, σ-valerolactone and ε-caprolactone are used as starting materials, R3 and R4 are all hydrogen atoms. When β-methyl-δ-valerolactone is used, R3 and R4 are methyl groups and hydrogen atoms. When 3-ethyl-caprolactone is used, R3 and R4 become ethyl groups and hydrogen atoms.

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

《ただし、Ｒ１は、水素原子、または１～９個の炭素原子を有するアルキル基である。ｎは１～１３整数を表わす》

<<where R1 is a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. n represents an integer from 1 to 13>>

Among these, γ-butyrolactone, σ-valerolactone, and ε-caprolactone raw materials are biodegradable, and monomers (ax) using these raw materials are preferably used.

In the case of synthesis using a (meth)acrylic acid alkyl ester having a hydroxyl group and a lactone raw material, in the general formulas (I) to (III), n is the number of moles of the added lactone. ) When 5 mol of lactone is added to 1 mol of (meth)acrylic acid alkyl ester having a hydroxyl group using raw materials of alkyl acrylate and lactone, n=5.

The monomer (ax) according to the present invention is a polycaprolactone-modified hydroxyalkyl acrylic acid ester or methacrylic acid ester obtained by ring-opening polymerization of ε-caprolactone or γ-butyrolactone on a (meth)acrylic acid ester having a hydroxyl group. Preferably.

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

Commercial products of the monomer (ax) represented by the general formula (I) include, for example, PLACCEL FM-1, PLACCEL FM-2, PLACCEL FM-3, PLACCEL FM-4, PLACCEL FM-5 manufactured by Daicel Corporation, PLACCEL FA-1, PLACCEL FA-2, PLACCEL FA-3, PLACCEL FA-5 and the like.

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 60% by mass or more and 99% by mass. 0.9% by mass or less is more preferable. When it is within the above range, it becomes easy to achieve both adhesive properties such as tackiness and biodegradability.

[monomer (ay)]
The monomer (ay) is a monomer having a carboxyl group or an active methylene group. For example, a monomer having a carboxyl group (ay-1) and a monomer having an active methylene group (ay- 2).
A carboxyl group or an active methylene group has hydrogen bonding properties, and the cohesive force of the pressure-sensitive adhesive layer can be further improved by including them. When the acrylic polymer (A) contains the monomer (ay), the holding power can be improved. It is preferable because it can further increase power.

Examples of the monomer (ay-1) having a carboxyl group include (meth)acrylic acid, phthalic acid monohydroxyethyl acrylate, p-carboxybenzyl acrylate, ethylene oxide-modified (EO addition mole number: 2 18) Phthalate acrylate, phthalate monohydroxypropyl acrylate, succinate monohydroxyethyl acrylate, β-carboxyethyl acrylate, 2-(4-benzoyl-3-hydroxyphenoxy)ethyl acrylate, Maleic acid, monoethyl maleic acid, itaconic acid, citraconic acid, fumaric acid, and the like. Among these, (meth)acrylic acid is preferable because it can enhance the holding power.

Examples of the monomer (ay-2) having an active methylene group include 2-ethoxymalonyloxyethyl (meth)acrylate, 2-acetoacetoxyethyl (meth)acrylate, and N-(2-acetoacetylaminoethyl)acrylamide. , 2-(N-acetoacetylaminoethyl) (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N- 4-(acetoacetoxymethyl)benzylacrylamide, N-(2-acetoacetamidoethyl)acrylamide, N-(2-acetoacetamidoethyl)methacrylamide and the like. Among these, 2-acetoacetoxyethyl (meth)acrylate is preferred because it can increase the holding power.

When the monomer (ay) is used, it is preferable that the monomer (ay) is contained in an amount of 10% by mass or less in 100% by mass of the monomer mixture constituting the acrylic polymer (A). 0.01 to 10% by mass is more preferable, and 0.1 to 6% by mass is even more preferable. When it is within the above range, the holding power becomes better and the adhesive properties are likely to be compatible. In addition, it is preferable because the formation of gels and aggregates during production can be suppressed, and the fluidity of the pressure-sensitive adhesive composition is improved.

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

(Meth) acrylic acid alkyl ester
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 structure of a linear structure, a branched structure, and a cyclic structure.

A (meth)acrylic acid alkyl ester having a hydroxyl group is
For example, 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, hydroxyalkyl (meth)acrylate such as 8-hydroxyoctyl (meth)acrylate, and polyethylene glycol mono(meth)acrylic acid esters, polypropylene glycol mono(meth)acrylic acid esters, glycol mono(meth)acrylic acid esters such as 1,4-cyclohexanedimethanol mono(meth)acrylic acid esters, and hydroxyethyl acrylamide.

A (meth)acrylic acid ester having an epoxy group is
Examples include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate and the like. .

(Meth) acrylic acid ester having an alkyleneoxy group,
For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate, methoxypolypropylene glycol (meth)acryl acid esters, ethoxypolypropylene glycol (meth)acrylic acid esters, phenoxypolyethyleneglycol (meth)acrylic acid esters, phenoxypolypropyleneglycol (meth)acrylic acid esters, and the like.

A (meth)acrylic acid alkyl ester having an amino group is
For example, monoalkyl (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate Amino esters include

The amide bond-containing monomer is
For example, (meth)acrylamide, N-methylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetoneacrylamide, N-( (meth)acrylamides such as 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.

(meth)acrylic acid alkyl ester having an aromatic ring,
Examples include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, and biphenyl (meth)acrylate. mentioned.

Vinyl monomers are
Examples include vinyl acetate, acrylonitrile, styrene, α-methylstyrene and the like.

The content of the monomer (az) in 100% by mass of the monomer mixture constituting the acrylic polymer (A) is preferably 70% by mass or less, more preferably 0 to 40% by mass. Within this range, it becomes easier to adjust the adhesive properties.

<Organic solvent (B)>
The organic solvent (B) contained in the pressure-sensitive adhesive composition is used as a synthetic solvent during production of the acrylic polymer (A), a diluting solvent after production, an adjustment solvent during production of the pressure-sensitive adhesive composition, or the like.
The organic solvent (B) used in producing the acrylic polymer (A) is referred to as the organic solvent (b).
It is preferable to use the organic solvent (B) because it has excellent compatibility and facilitates control of the polymerization reaction, removal, washing, and coating by adjusting the viscosity. Also, an organic solvent having a boiling point of 60° C. to 160° C. is preferable in order to obtain a pressure-sensitive adhesive layer that is removed during drying.
Examples of the organic solvent (B) include ester-based solvents, ketone-based solvents, hydrocarbon-based solvents, and alcohol-based solvents.

As an ester solvent,
For example, methyl acetate, ethyl acetate, etc.
As a ketone solvent,
For example, acetone, methyl ethyl ketone, cyclohexanone, etc.
As a hydrocarbon solvent,
For example, toluene, xylene, etc.
As an alcohol solvent,
primary alcohols such as, for example, methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, and n-octanol, 3,3-dimethyl-1-butanol, benzyl alcohol;
isopropanol, 2-butanol, 3-pentanol, 3-methyl-2-butanol, 4-methyl-2-pentanol, 4-heptanol, 1-phenyl-2-propanol, 2-octanol, cyclohexanol, 4-methyl Cyclohexanol, 3-isopropylcyclohexanol, 4-phenylcyclohexanol, 1-phenyl-1-ethanol, 1-(4-isopropylphenyl)-1-ethanol, 1-phenyl-1-propanol, diphenylcarbinol, etc. secondary alcohol;
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 - tertiary alcohols such as isopropylphenyl)-2-propanol;
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 and other polyhydric alcohols.

Among the organic solvents (B), since the storage stability of the pressure-sensitive adhesive composition is improved, it is preferable to contain an ester solvent, a ketone solvent or an alcohol solvent, and it is possible to contain a ketone solvent or an alcohol solvent. More preferred, alcoholic solvents are even more preferred.
Primary alcohols are more preferred among primary alcohols, secondary alcohols and tertiary alcohols that are alcohol solvents.

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-based solvent, ketone-based solvent, or alcohol-based solvent is 40% by mass or more, the storage stability of the pressure-sensitive adhesive composition can be further improved.

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-based solvent, a ketone-based solvent, or an alcohol other than the primary alcohol, more preferably a ketone-based solvent, in terms of improving compatibility.

The primary alcohol is preferably contained in an amount of 40% by mass or more, more preferably 60 to 97% by mass, based on 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 can be improved. preferred.

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

In the production of the acrylic polymer (A), 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) is added to the organic solvent (b). It is preferable that the polymer be polymerized in the medium and have a weight average molecular weight of 400,000 to 1,500,000.

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. An organic solvent containing a solvent is preferable, and an alcohol solvent is more preferable. Among primary alcohols, secondary alcohols and tertiary alcohols, primary alcohols are preferred as the alcohol solvent.

During the production of 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, a gel product during production It is preferable because it can suppress the formation of agglomerates and can make the fluidity of the pressure-sensitive adhesive composition more excellent. More preferably, it is 60% by mass to 97% by mass.
At this time, it is preferable to use an ester-based solvent, a ketone-based solvent, or an alcohol-based solvent as the diluting solvent.

The acrylic polymer (A) may be appropriately diluted with the organic solvent (B) after production, and the diluting solvent is preferably an ester solvent, a ketone solvent, or an alcohol solvent.

A primary alcohol is preferably used in the production of the acrylic polymer (A), but in another embodiment, a ketone solvent or an alcohol solvent other than the primary alcohol can be used as the polymerization solvent. In this case, it is preferable to use a primary alcohol as a diluting solvent after production, and dilute so that the primary alcohol is included in 40% by mass or more in 100% by mass of the organic solvent (B) contained in the adhesive composition. is preferred. More preferably 60 to 97% mass.

The polymerization initiator used for polymerization is preferably a thermal radical polymerization initiator. Thermal radical polymerization initiators are generally peroxides and azo compounds.

Peroxides are, for example, di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5- dialkyl peroxides such as di(t-butylperoxy)hexyne-3;
peroxyesters such as t-butyl peroxybenzoate, t-butyl peroxyacetate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxy oxides, ketone peroxides such as methylcyclohexanone peroxide;
2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t- peroxyketals such as butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valate;
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;
and peroxydicarbonates such as bis(t-butylcyclohexyl)peroxydicarbonate.

Azo compounds include 2,2'-azobisbutyronitrile such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN) and 2,2'-azobis(2-methylbutyronitrile);
2,2′-azobisvaleronitrile such as 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile);
2,2′-azobispropionitrile such as 2,2′-azobis(2-hydroxymethylpropionitrile);
1,1'-azobis-1-alkanenitrile such as 1,1'-azobis(cyclohexane-1-carbonitrile) and the like.
Further, azo compounds having a carboxyl group or a hydroxyl group include, for example, 4,4'-azibis(4-cyanopentanoic acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2′-azobis(N-(carboxyethyl)-2-methylpropionamidine) tetrahydrate and the like.

The thermal radical polymerization initiator is preferably used in an amount of 0.001 to 10 parts by mass, more preferably 0.01 to 2 parts by mass, per 100 parts by mass of the monomer mixture.

<Curing agent (C)>
The curing agent (C) reacts with the hydroxyl group of the acrylic polymer (A) or the carboxyl group when the monomer mixture contains the monomer (ay).
It is preferable to use the curing agent (C) in combination with the acrylic polymer (A) because the holding power can be further increased.
When using the curing agent (C), the content of the curing agent (C) is preferably 0.05 to 20 parts by mass, and 0.1 to 10 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). more preferred. When the content is 0.05 parts by mass or more, the holding power and the removability are improved, and when the content is 20 parts by mass or less, adhesive properties such as tack can be easily achieved at the same time, which is preferable.

Examples of the curing agent (C) include isocyanate compounds, aziridine compounds, epoxy compounds, metal chelates, carbodiimide compounds, and the like.
Among these, isocyanate compounds, aziridine compounds, epoxy compounds, or metal chelate compounds are preferred from the standpoint of removability of the pressure-sensitive adhesive composition, and isocyanate compounds and aziridine compounds are more preferred.

An isocyanate compound is an isocyanate having two or more isocyanate groups. Isocyanate compounds are preferably isocyanate monomers such as aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates and alicyclic polyisocyanates, and burettes, nurates and adducts thereof.

Aromatic polyisocyanates are, for example, 1,3-phenylene diisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6- tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4 ''-triphenylmethane triisocyanate and the like.

Aliphatic polyisocyanates include, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as 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.

Aroaliphatic polyisocyanates are, for example, 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.

Alicyclic 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 -cyclohexanediisocyanate, methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), 1,4-bis(isocyanatomethyl)cyclohexane and the like.

The burette body is a self-condensed product having a burette bond formed by self-condensation of an isocyanate monomer. The burette body includes, for example, a burette body of hexamethylene diisocyanate.

The nurate compound is a trimer of isocyanate monomers. Examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, a trimer of tolylene diisocyanate, and the like.

The adduct is a bifunctional or higher isocyanate compound obtained by reacting an isocyanate monomer and a bifunctional or higher low-molecular-weight active hydrogen-containing compound. Adducts include, for example, a compound obtained by reacting trimethylolpropane and hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane and tolylene diisocyanate, a compound obtained by reacting trimethylolpropane and xylylene diisocyanate, trimethylol A compound obtained by reacting propane with isophorone diisocyanate, a compound obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate, and the like can be mentioned.

The isocyanate compound is preferably a trifunctional isocyanate compound from the viewpoint of forming a sufficient crosslinked structure. The isocyanate compound is more preferably an adduct or a nurate which is a reaction product of an isocyanate monomer and a trifunctional low-molecular-weight active hydrogen-containing compound. Isocyanate compounds include trimethylolpropane adduct of hexamethylene diisocyanate, nurate of hexamethylene diisocyanate, trimethylolpropane adduct of tolylene diisocyanate, nurate of tolylene diisocyanate, trimethylolpropane adduct of isophorone diisocyanate, and isophorone diisocyanate. A nurate compound is preferred, and a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, and a trimethylolpropane adduct of isophorone diisocyanate are more preferred.

Epoxy compounds include, for example, glycerol 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 and the like.

Aziridine compounds include, for example, trimethylolpropane tris[3-(aziridin-1-yl)propionate], N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxysite), tris-2,4,6 -(1-aziridinyl)-1,3,5-triazine, 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane and the like.

The carbodiimide compound is preferably a high-molecular-weight polycarbodiimide produced by a decarboxylation condensation reaction of a diisocyanate compound in the presence of a carbodiimidation catalyst. Carbodilite series manufactured by Nisshinbo Co., Ltd. is preferable as the commercial product of the high-molecular-weight polycarbodiimide. Among them, Carbodilite V-03, 07 and 09 are preferable because of their excellent compatibility with organic solvents.

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

<Tackifying resin (D)>
The pressure-sensitive adhesive composition of the present invention can contain a tackifying resin (D) as long as the problem can be solved. The inclusion of the tackifying resin (D) is preferable because the adhesive strength of the adhesive layer is further improved and the appearance of the coating film can be improved.
The content of the tackifying 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 strength and coating film appearance can be improved.

Examples of tackifying resins include rosin-based resins, terpene-based resins, petroleum-based resins, macron resins, macron-indene resins, styrene resins, xylene resins, and phenol resins.

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

Terpene-based resins are classified as natural resins, and are resins mainly composed of terpenes (eg, α-pinene, β-pinene, limonene, etc.) having isoprene as a structural unit. Specifically, terpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by reacting terpenes or terpene resins with aromatic compounds such as styrene, terpenes and terpene resins with phenols and hydrogenated terpene resins, hydrogenated terpene phenol resins, and hydrogenated aromatic modified terpene resins, which are hydrogenated products thereof. In addition, terpene resin can be used individually by 1 type or in combination of 2 or more types.
A commercially available product may be used as the terpene-based resin. Commercially available products include YS Resin PX1000 and YS Resin PX1150 (both of which are terpene resins) manufactured by Yasuhara Chemical Co., Ltd.

Petroleum-based resin means a product obtained by polymerizing a fraction containing unsaturated hydrocarbon monomers by-produced by thermal decomposition of petroleum naphtha such as petroleum naphtha, specifically aliphatic (C5) petroleum Resins, aromatic (C9) petroleum resins, hydrogenated petroleum resins, and the like can be mentioned. In addition, petroleum-based resin can be used individually by 1 type or in combination of 2 or more types.
A commercially available product may be used as the petroleum-based resin. Commercially available products include FTR-6100, FTR-6110, FTR-6125 manufactured by Mitsui Chemicals, Inc.

<Optional component>
The pressure-sensitive adhesive composition of the present invention may contain other components as necessary. Other ingredients include plasticizers, silane coupling agents, peeling agents, heat or light stabilizers, UV absorbers, leveling agents, antifoaming agents, antibacterial agents, moisturizers, vitamins, pigments, dyes, fragrances, etc. is mentioned. These can be appropriately selected from known ones and used.

<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 if necessary, a curing agent (C), a tackifying resin (D) and optional components are mixed. can be obtained.
The acrylic polymer (A) can be obtained by the known polymerization method described in the method for producing the acrylic polymer (A) above, and the obtained acrylic polymer (A) solution is It can also be used as an adhesive composition.
When used as an adhesive composition, the acrylic polymer (A) is preferably obtained by solution polymerization in a solution containing the organic solvent (B).

At least one of a ketone solvent and an alcohol solvent is preferably used as the organic solvent (B) contained in the pressure-sensitive adhesive composition. A method of adding during production, or (2): during dilution after production, or (3): during adjustment of the pressure-sensitive adhesive composition is exemplified. It is preferable to add in (1) or (2) in that the formation of gels and aggregates during polymer production can be suppressed, and the fluidity and storage stability of the polymer solution are more excellent, and (1) is more preferable. preferable.

When the curing agent (C), the tackifying resin (D), or optional components are mixed with the polymer solution, the curing agent (C) or the tackifying resin (D) is dissolved in a solvent or dispersed in a dispersion medium in advance. Then you can mix.
When mixing the components to form the pressure-sensitive adhesive composition, all the components may be added and mixed at the same time, or the timing of adding each component may be determined appropriately in consideration of the properties and reactivity of each component. may
When mixing with each component to be the adhesive composition, you may stir as needed.

≪Adhesive sheet≫
The pressure-sensitive adhesive sheet according to the present invention includes a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition or a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition. Among them, it is preferable to have a substrate and an adhesive layer.

Examples of the base material include cellophane, plastic sheet, rubber, foam, fabric, rubber cloth, resin-impregnated cloth, glass plate, wood, and the like, and may be plate-like or film-like. Note that "sheet", "film" and "plate" are different only in names and are not intended to distinguish one another.
The substrate may be a single layer or a laminate having multiple layers. Moreover, the base material may be provided with a functional layer that imparts various functionalities such as optical functionality such as antireflection properties, electrical conductivity, antistatic properties, and hard coat properties to the adherend surface.
Also, as the base material, a release base material having a release-treated surface can be used.

Specific examples of the plastic sheet include polyvinyl alcohol films, triacetyl cellulose films, films of polyolefin resins such as polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; Polyester resin films such as phthalate, polylactic acid, and polybutylene succinate; polycarbonate resin films, polynorbornene resin films, polyarylate resin films, acrylic resin films, polyphenylene sulfide resin films, polystyrene A resin film, a vinyl resin film, a polyamide resin film, a polyimide resin film, an epoxy resin film, and the like can be used.

The thickness of the pressure-sensitive adhesive layer may be appropriately adjusted depending on the intended use, but is preferably 0.1 to 300 μm, more preferably 1 to 200 μm, and even more preferably 3 to 150 μm from the viewpoint of adhesiveness.

<Method for manufacturing adhesive sheet>
The present pressure-sensitive adhesive sheet can be produced, for example, by (a) a method of applying a pressure-sensitive adhesive composition to a base material, drying if necessary, and then heating to form a pressure-sensitive adhesive layer; (b) a release-treated film After coating the adhesive composition on the release-treated surface of the adhesive composition, drying if necessary, laminating the base material on the surface of the adhesive composition, and then heating to form an adhesive layer, release treatment is performed. (c) A pressure-sensitive adhesive composition is applied to the release-treated surface of the release-treated film, dried if necessary, and then heated to form a pressure-sensitive adhesive layer. It can be produced by laminating a base material on the surface of the agent layer and removing the release-treated film.
In the above method (a), a release-treated film may be further laminated on the surface of the formed pressure-sensitive adhesive layer. In the above methods (a) and (c), the release-treated film may be removed immediately before using the pressure-sensitive adhesive sheet.

The method of applying the pressure-sensitive adhesive composition onto the base material or the release-treated film can be appropriately selected from known methods. Examples of the coating method include Meyer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater and the like.
Moreover, the method for drying and curing the pressure-sensitive adhesive composition is not particularly limited, and examples thereof include those using hot air drying, infrared rays, and a depressurization method. The heating temperature varies depending on the material, film thickness, organic solvent, etc. of the pressure-sensitive adhesive composition.

When applying the pressure-sensitive adhesive composition, the viscosity can be adjusted with a solvent. As the solvent, those exemplified for the organic solvent (B) can be used.

EXAMPLES 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 description below, unless otherwise specified, "parts" means parts by mass, "%" means % by mass, and "RH" means relative humidity.
In addition, the blending amounts of raw materials (excluding solvents) described in the examples and tables described below are values in terms of non-volatile matter.
The weight average molecular weight (Mw) of the copolymer was measured by the following method.

<Measurement of weight average molecular weight (Mw)>
Mw of each polymer was measured under the following conditions. Mw was determined 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
Column: 4 GMHXL manufactured by Tosoh Corporation and 1 HXL-H manufactured by Tosoh Corporation connected in series Mobile phase solvent: Tetrahydrofuran (THF)
Flow rate: 1.0 ml/min Column temperature: 40°C

<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 disclosed in Japanese Patent Application Laid-Open No. 57-185236.
(ax-1): a monomer obtained by adding 5 mol of γ-butyrolactone to 1 mol of 2-hydroxyethyl methacrylate (in general formula (II), R1 = methyl group, n = 5);
(ax-2): a monomer obtained by adding 1 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate (in general formula (III), R1 = methyl group, n = 1);
(ax-3): a monomer obtained by adding 3 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate (in general formula (III), R1 = methyl group, n = 3);
(ax-4): a monomer obtained by adding 5 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate (in general formula (III), R1 = methyl group, n = 5);
(ax-5): a monomer obtained by adding 10 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate (in general formula (III), R1 = methyl group, n = 10);
(ax-6): a monomer obtained by adding 5 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl acrylate (in general formula (III), R1 = methyl group, n = 5);

[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 according to the synthesis method disclosed in JP-A-57-185236. A monomer represented by the chemical formula (1) obtained by adding 15 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate

chemical formula (1)

[Organic solvent (B)]
MeOH: methanol EtOH: ethanol BuOH: 1-butanol MEK: methyl ethyl ketone IPA: isopropyl alcohol [curing agent (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-xylylenediamine C-4: aluminum tris (acetylacetonate)
C-5: V-03 (carbodiimide compound, manufactured by Nisshinbo Chemical Co., Ltd.)
[Tackifying resin (D)]
D-1: A-75 (manufactured by Arakawa Chemical Industries, Ltd., rosin ester resin)

(Example 1)
30 parts of the monomer (ax-3), methyl methacrylate (MMA ) 70 parts, methanol (MeOH) 15 parts, ethanol (EtOH) 105 parts, methyl ethyl ketone (MEK) 30 parts, 2,2'-azobisisobutyronitrile (AIBN) 0.04 parts after charging, reaction vessel The air inside was replaced with nitrogen gas. Then, the mixture was heated to 80° C. with stirring under a nitrogen atmosphere to initiate the reaction, and the polymerization reaction was carried out at the reflux temperature for 7 hours. After completion of the reaction, the mixture was cooled to obtain a polymer (A-1) solution having a non-volatile content of 40%. The weight average molecular weight (Mw) of the obtained acrylic polymer (A-1) was 1,000,000.
The solvent content ratio in the polymer solution after production was adjusted so as to be the same as during polymer production. That is, MeOH: 10% by mass, EtOH: 70% by mass, and MEK: 20% by mass in 100% by mass of the organic solvent in the acrylic polymer (A-1) solution.

(Examples 2 to 14)
Acrylic polymers (A-2 to 14 ) solution was prepared.
The "primary alcohol content [%] during polymerization" in the table is the primary alcohol content in 100% by mass of the organic solvent during polymerization.
In addition, the solvent content ratio in the polymer solution after production was adjusted so as to be the same as during polymer production.

(Example 15)
60 parts of the monomer (ax-3), methyl methacrylate (MMA ) 40 parts, 15 parts of methanol (MeOH), 105 parts of ethanol (EtOH), 30 parts of methyl ethyl ketone (MEK), 2,2′-azobisisobutyronitrile (AIBN) After charging 0.04 parts, the reaction vessel The air inside was replaced with nitrogen gas. Then, the mixture was heated to 80° C. with stirring under a nitrogen atmosphere to initiate the reaction, and the polymerization reaction was carried out at the reflux temperature for 7 hours. After completion of the reaction, the mixture was cooled to obtain a polymer (A-15) solution having a non-volatile content of 40%. The weight average molecular weight (Mw) of the obtained acrylic polymer (A-15) was 900,000.
The solvent content ratio in the polymer solution after production was adjusted so as to be the same as during polymer production. That is, MeOH: 10% by mass, EtOH: 70% by mass, and MEK: 20% by mass in 100% by mass of the organic solvent in the acrylic polymer (A-15) solution.

A solution of acrylic polymer (A-15) was used as adhesive composition 1.

Adhesive composition 1 is applied to a 38 μm thick polyester separator [trade name “Super Stick” SP-PET38, manufactured by Lintec, hereinafter the same] so that the thickness after drying is 50 μm, and hot air oven and dried at 100° C. for 2 minutes to form an adhesive layer. After drying, it was laminated on a polyethylene naphthalate (PEN) film (Teonex, manufactured by Teijin Ltd.) having a thickness of 25 μm, and further cured at 23° C. and 50% RH for 7 days to obtain an adhesive sheet.

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

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

Then, 30 parts of ethanol (EtOH) was added to 100 parts of the resulting polymer (A-17) solution and stirred to prepare a diluted polymer solution.
The resulting polymer solution was used as adhesive composition 3.
The solvent content ratios in the diluted polymer solution were MeOH: 7% by mass, EtOH: 53% by mass, and MEK: 40% by mass in 100% by mass of the organic solvent.

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.

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

On a 38 μm thick polyester separator [trade name “Super Stick” SP-PET38, manufactured by Lintec, the same applies hereinafter], the adhesive composition 4 is applied so that the thickness after drying is 50 μm, and hot air oven and dried at 100° C. for 2 minutes to form an adhesive layer. After drying, it was laminated on a polyethylene naphthalate (PEN) film (Teonex, manufactured by Teijin Ltd.) having a thickness of 25 μm, and further cured at 23° C. and 50% RH for 7 days to obtain an adhesive sheet.

(Examples 19-38)
As shown in Tables 3 and 4, pressure-sensitive adhesive compositions 5 to 5 were prepared in the same manner as in Example 18, except that the acrylic polymer solution, curing agent, and tackifying resin types and blending amounts (parts by mass) were changed. No. 24 was produced to obtain an adhesive sheet.

<Evaluation items and evaluation methods>
Evaluation items and evaluation methods of the resin composition and the adhesive sheet are as follows. Table 5 shows the results.

<<Evaluation of adhesive composition>>
<Biodegradability>
The biodegradability of the adhesive composition was evaluated according to JIS K 6953-1.
(Evaluation criteria)
A: Biodegradability percentage of 70% or more. excellence.
O: Biodegradability percentage of 50% or more and less than 70%. Good.
Δ: Biodegradability percentage of 30% or more and less than 50%. Practical.
×: Less than 30% biodegradability percentage. Not practical.

<Coating liquid fluidity>
The fluidity of the pressure-sensitive adhesive composition was visually evaluated.
(Evaluation criteria)
⊚: Fluid coating liquid without lumps, lumps, or gel matter. excellence.
Good: The coating liquid has fluidity, although there are very few grainy or lumpy gels or agglomerates. Good.
Δ: The coating liquid has fluidity, although there are a few grainy or lumpy gels or agglomerates. Practical.
x: Coating liquid with no fluidity, with gels or aggregates in the form of lumps or lumps. Not practical.

<<Evaluation of Adhesive Sheet>>
<Adhesive properties>
[Adhesive force]
The obtained adhesive sheet was cut into a size of 25 mm in width and 100 mm in length to obtain a sample. Then, in a 23° C.-50% RH atmosphere, the release sheet was peeled off from the sample in accordance with JIS Z 0237, and the exposed adhesive layer was attached to a polished stainless steel (SUS) plate and crimped once with a 2 kg roll. Then, using a tensile tester, the peel strength (N/25 mm) was measured at a peel speed of 300 mm/min and a peel angle of 180° 24 hours after the application.
(Evaluation criteria)
A: The adhesive strength is 5 N/25 mm or more. excellence.
◯: Adhesive strength is 1 N/25 mm or more and less than 5 N/25 mm. Good.
Δ: Adhesive strength of 0.1 N/25 mm or more and less than 1 N/25 mm. Practical.
x: Adhesive strength is less than 0.1 N/25 mm. Not practical.

[Holding power]
The release sheet was peeled off from the resulting pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer with a width of 25 mm and a length of 25 mm was adhered to a polished stainless steel (SUS) plate. A load of 1 kg was applied in the atmosphere and held for 70,000 seconds. The evaluation indicates the number of seconds when the sample dropped from the SUS plate. When the sample did not drop, it indicates the number of millimeters by which the adhesive tip of the pressure-sensitive adhesive layer and the SUS plate was displaced downward due to the load.
(Evaluation criteria)
A: Sample deviation is less than 0.5 mm. excellence.
◯: Sample misalignment is 0.5 mm or more and less than 2 mm. Better.
◯△: The deviation of the sample is 2 mm or more and less than 5 mm. Good.
Δ: The sample did not drop when the displacement was 5 mm or more. Practical.
x: The sample fell. Not practical.

[Ball tack]
The obtained pressure-sensitive adhesive sheet was prepared in a size of 25 mm in width and 250 mm in length. The release sheet was peeled off from the adhesive sheet and fixed to an inclined plate having an inclination angle of 30 degrees with the adhesive surface facing up. A steel ball (1/32 to 32/32 inches) is rolled on the sample with a PET film for the runway pasted on the top, and the runway 10cm and the glue surface 10cm, and the diameter number of the ball that stops near the center of the glue surface Recorded. The measurement was carried out in an atmosphere of 23° C.-50% RH.
(Evaluation criteria)
A: The ball diameter is 16/32 inches or more. excellence.
◯: Ball diameter is 12/32 inch or more and less than 16/32 inch. Better.
△○: The ball diameter is 8/32 inch or more and less than 12/32 inch. Good.
Δ: The ball diameter is 4/32 inch or more and less than 8/32 inch. Practical.
x: Ball diameter is less than 4/32 inch. Not practical.

<Removability>
The resulting pressure-sensitive adhesive sheet was attached to a stainless steel plate (SUS304) with a sample width of 25 mm under an atmosphere of 23° C.-50% RH, followed by pressure bonding with a 2 kg roll according to JIS0237, followed by exposure to 24° C. under an atmosphere of 23° C.-50% RH. After leaving for a period of time, using a tensile tester, the films were peeled off at a peeling speed of 300 mm/min and a peeling angle of 180°, and appearances such as adhesive residue were compared.
(Evaluation criteria)
A: The adhesive sheet could be peeled off without staining the SUS plate. excellence.
◯: The SUS plate was very slightly contaminated. Good.
Δ: The SUS plate was slightly contaminated. Practical.
x: The SUS plate was contaminated. Not practical.

<Appearance of coating film>
The peelable sheet was peeled off from the obtained adhesive sheet and attached to a glass plate, and the state was visually confirmed.
(Evaluation criteria)
O: It was transparent. Good Δ: Slight whitening was observed. Practical.
x: Completely whitened. Usage prohibited

From the results in Table 5, the pressure-sensitive adhesive compositions obtained in Examples have high fluidity of the coating liquid despite high biodegradability, and the pressure-sensitive adhesive sheets obtained have adhesive performance, removability, and Excellent results were obtained in all aspects of coating transparency.

Claims (8)

Containing 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. There is an adhesive composition.

<<where 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, and m is An integer of 3 to 10, n represents an integer of 1 to 13>> The pressure-sensitive 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. The pressure-sensitive adhesive composition according to claim 1, wherein the organic solvent (B) contains a primary alcohol. Further containing a curing agent (C),
The adhesive composition according to any one of claims 1 to 3, wherein the curing agent (C) is at least one selected from the group consisting of isocyanate compounds, aziridine compounds, epoxy compounds, and metal chelate compounds. The adhesive composition according to any one of claims 1 to 4, further comprising a tackifying resin (D). A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5. A method for producing a pressure-sensitive adhesive composition containing an acrylic polymer (A) and an organic solvent (b),
Polymerizing a monomer mixture containing 30% by mass or more of a monomer (ax) represented by the following general formula (I) in an organic solvent (b),
A step of producing an acrylic polymer (A) having a weight average molecular weight of 400,000 to 1,500,000,
A method for producing a pressure-sensitive adhesive composition, wherein the organic solvent (b) contains 40% by mass or more of a primary alcohol.

<<where 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, and m is An integer of 3 to 10, n represents an integer of 1 to 13>> 8. The method for producing a pressure-sensitive adhesive composition according to claim 7, wherein the monomer mixture contains 10% by mass or less of a monomer (ay) having a carboxyl group or an active methylene group.