JP7310135B2 - Adhesive sheet for vinyl chloride film containing plasticizer and acrylic adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet for forming a pressure-sensitive adhesive layer used in a vinyl chloride film containing a plasticizer, and an acrylic pressure-sensitive adhesive.

Adhesive sheets including an adhesive layer such as stickers and labels are used in a wide range of fields because they can be easily attached to an object (adherend), and are excellent in durability, transparency, etc. Therefore, acrylic adhesives are generally used.
However, when an acrylic pressure-sensitive adhesive sheet formed using such an acrylic pressure-sensitive adhesive is used as a label on a vinyl chloride film (hereinafter sometimes referred to as a PVC film) as an adherend, There is a problem that the plasticizer in the adhesive sheet migrates to the surface of the adhesive layer of the adhesive sheet, resulting in a decrease in adhesive strength, and the adhesive sheet cannot follow the shrinkage of the PVC film during heating and is easily peeled off.

As a method for solving such problems, for example, in Patent Document 1, 35 to 85% by mass of methyl (meth)acrylate units and 10 of 2-ethylhexyl acrylate units are added to a polyvinyl chloride base film. ~60% by mass, 0.5 to 10% by mass of monomer units having a carboxyl group, and 0.01 to 5% by mass of monomer units having a hydroxyl group (meth)acrylic acid ester copolymer 100 A pressure-sensitive adhesive sheet containing parts by weight, 0.1 to 7 parts by weight of an isocyanate curing agent, and 0 to 0.25 parts by weight of an epoxy curing agent is disclosed.

Further, Patent Document 2 includes a (meth)acrylic acid alkyl ester monomer having an alkyl group having 4 carbon atoms, a (meth)acrylic acid alkyl ester monomer having an alkyl group having 1 to 2 carbon atoms, and a carboxyl group-containing monomer. Frequency 1 Hz, 70° C. of the pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive comprising an acrylic resin that is a copolymer of a monomer mixture and at least one curing agent selected from an isocyanate curing agent, an epoxy compound and a metal chelate. A pressure-sensitive adhesive for polyvinyl chloride having a storage modulus of 0.05 to 1 MPa is disclosed.

Although there are attempts to solve this problem by presuming that the plasticizer will migrate, the pressure-sensitive adhesive layer is made hard in advance. There was a problem that the layer could not follow.

WO2013/080979 JP 2018-127509 A

The problem to be solved by the present invention is to provide a pressure-sensitive adhesive sheet having good plasticizer resistance, PVC film deformation followability, and workability, and an acrylic pressure-sensitive adhesive forming the pressure-sensitive adhesive sheet. .

The present inventors have made intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by the plasticizer-containing pressure-sensitive adhesive sheet for vinyl chloride film shown below, and have completed the present invention.

That is, a pressure-sensitive adhesive sheet for a plasticizer-containing vinyl chloride film having a pressure-sensitive adhesive layer (X) containing an acrylic resin (A) and a curing agent (B), wherein the frequency of the pressure-sensitive adhesive layer (X) is 1 Hz, 70 ° C. The pressure-sensitive adhesive layer (X) is attached to a vinyl chloride film having a thickness of 400 μm, which has a shear storage elastic modulus of less than 0.05 MPa and contains 36% by mass of a plasticizer, and after heating at 70° C. for 5 days, Furthermore, the plasticizer migration amount from the vinyl chloride film to the adhesive layer (X) after 5 days in a 25 ° C.-50% RH environment is 20 parts by mass or more with respect to 100 parts by mass of the adhesive layer (X). The present invention relates to a pressure-sensitive adhesive sheet for a plasticizer-containing vinyl chloride film.

Further, according to the present invention, the acrylic resin (A) is an acrylic copolymer obtained by copolymerizing a monomer mixture, wherein 0.0% of the monomer (a2) having a hydroxyl group is contained in 100% by mass of the monomer mixture. It relates to the plasticizer-containing pressure-sensitive adhesive sheet for vinyl chloride film containing 01 to 1% by mass.

Further, in the present invention, the curing agent (B) contains an isocyanate curing agent, and the content of the curing agent (B) is 0.01 to 0 with respect to 100 parts by mass of the acrylic resin (A). .6 parts by mass of the pressure-sensitive adhesive sheet for a plasticizer-containing vinyl chloride film.

The present invention also relates to the plasticizer-containing pressure-sensitive adhesive sheet for a vinyl chloride film, wherein the acrylic resin (A) has a weight average molecular weight of 600,000 to 1,500,000.

The present invention also relates to the plasticizer-containing pressure-sensitive adhesive sheet for a vinyl chloride film, wherein the monomer mixture contains a (meth)acrylic acid alkyl ester having an alkyl group of 8 to 12 carbon atoms.

Further, the present invention provides the plasticizer-containing vinyl chloride film, wherein the content of (meth)acrylic acid alkyl ester having an alkyl group with 8 to 12 carbon atoms in 100% by mass of the monomer mixture is 60 to 84% by mass. Regarding the adhesive sheet.

The present invention also relates to the plasticizer-containing pressure-sensitive adhesive sheet for a vinyl chloride film, wherein the monomer mixture contains a (meth)acrylic acid acrylic ester or vinyl ester having a glass transition temperature Tg of 0° C. or higher.

Further, the present invention provides the plasticizer-containing vinyl chloride film containing 15 to 35% by mass of a (meth)acrylic acid acrylic ester or a vinyl monomer having a glass transition temperature Tg of 0 ° C. or higher in 100% by mass of the monomer mixture. Regarding the adhesive sheet.

The present invention also relates to an acrylic pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer (X) of the plasticizer-containing pressure-sensitive adhesive sheet for vinyl chloride film according to any one of claims 1 to 8.

ADVANTAGE OF THE INVENTION By this invention, the acrylic pressure sensitive adhesive for forming the adhesive sheet which has favorable plasticizer resistance, vinyl chloride film deformation|transformation followability, and processability, and this adhesive sheet can now be provided.

Terms are defined before describing the present invention in detail. First, sheet, film and tape are synonymous. (Meth)acrylic acid means acrylic acid and methacrylic acid. By monomer is meant an ethylenically unsaturated double bond-containing monomer. The adherend refers to the other party to which the pressure-sensitive adhesive sheet is attached. In addition, "parts" and "%" represent "mass parts" and "mass%", respectively, unless otherwise specified.

《Adhesive sheet for vinyl chloride film containing plasticizer》
The pressure-sensitive adhesive sheet of the present invention is used for attaching the plasticizer-containing vinyl chloride film and the pressure-sensitive adhesive layer (X). Alternatively, the adherend may be a vinyl chloride film containing a plasticizer.
When the substrate is a plasticizer-containing vinyl chloride film, the shear storage modulus and the amount of plasticizer migration of the pressure-sensitive adhesive layer (X) are measured under the same conditions using a substrate that is not a plasticizer-containing vinyl chloride film. (Composition of adhesive layer, film thickness, etc.) can be determined using an adhesive sheet having an adhesive layer formed thereon.
The pressure-sensitive adhesive layer (X) of the pressure-sensitive adhesive sheet for a plasticizer-containing vinyl chloride film of the present invention contains an acrylic resin (A) and a curing agent (B), and the frequency of the pressure-sensitive adhesive layer (X) is 1 Hz at 70°C. The adhesive layer (X) is attached to a vinyl chloride film having a thickness of 400 μm, which has a shear storage modulus of less than 0.05 MPa and contains 36% by mass of a plasticizer, and after heating at 70 ° C. for 5 days, further The amount of plasticizer transferred from the vinyl chloride film to the adhesive layer (X) after 5 days in a 25° C.-50% RH environment is 20 parts by mass or more with respect to 100 parts by mass of the adhesive layer (X). .

The pressure-sensitive adhesive sheet of the present invention preferably has a substrate in addition to the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive sheet of the present invention. As another aspect, a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a core material, or a cast pressure-sensitive adhesive sheet having only a pressure-sensitive adhesive layer without a base material and a core material is also preferable. The pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive onto a substrate and drying it. Alternatively, it can be formed by coating a release sheet with an adhesive, drying it to form an adhesive layer, and then laminating a substrate.

When applying the pressure-sensitive adhesive, the viscosity can be adjusted by adding the solvent described in the solution polymerization.

When the adherend is a vinyl chloride film containing a plasticizer, the base material of the pressure-sensitive adhesive sheet may be, in addition to the vinyl chloride film, for example, cellophane, other plastics, rubber, foam, fabric, rubberized cloth, resin-impregnated cloth, glass. , and wood etc. can be used. The shape of the base material can be selected from a plate shape and a film shape, but the film shape is preferable because it is easy to handle. A single substrate or a laminate of two or more substrates can be used.

<Vinyl chloride film>
A vinyl chloride film used as an adherend is formed by polymerizing a vinyl chloride monomer and then softening and stabilizing the resin with an additive such as a plasticizer to form a film. Excellent durability, weather resistance, chemical resistance, transparency and workability can be achieved by adjusting the polymerization conditions and additives. Since it can be manufactured at a very low cost, it is widely used not only for industrial materials, construction materials, and automobile materials, but also for general consumer goods used by consumers.
A preferred amount of the plasticizer contained in the vinyl chloride film is 5% by mass to 55% by mass in the vinyl chloride film.
The thickness of the vinyl chloride film can be appropriately selected depending on the application and is not particularly limited, but is preferably about 25 μm to 2000 mm.

[Plasticizer]
As the plasticizer contained in the vinyl chloride film, one having excellent compatibility with the vinyl chloride resin, exhibiting the necessary flexibility with a small addition amount, and having low volatility is used. In addition to these basic functions, plasticizers are selected according to the properties required for each application. For example, adipate esters for food wrap films, phthalate esters for medical applications, and citrate esters for baby toys are typical. Used.
The pressure-sensitive adhesive sheet for vinyl chloride films of the present invention can be suitably used for general vinyl chloride films that are developed for various purposes by controlling the amount of migration of the plasticizer contained in the vinyl chloride film to the adhesive layer. is.

The other plastics include, for example, polyolefins such as polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; norbornene, polyarylate, polyacryl, polyphenylene sulfide, polystyrene, polyamide, polyimide, and the like.

<Adhesive layer>
The adhesive layer contains an acrylic resin (A) and a curing agent (B), and can be formed using an acrylic adhesive containing the acrylic resin (A) and the curing agent (B).
In the present invention, the pressure-sensitive adhesive layer has a shear storage modulus of less than 0.05 MPa at a frequency of 1 Hz and 70°C. Furthermore, a 400 μm thick vinyl chloride film containing 36% of a plasticizer is attached with an adhesive layer, heated at 70 ° C. for 5 days, and further from the vinyl chloride film after 5 days in a 25 ° C.-50% RH environment. The amount of plasticizer migrated to the adhesive layer is 20 parts by mass or more with respect to 100 parts by mass of the adhesive layer.
By having such an adhesive layer, it is possible to have good plasticizer resistance, vinyl chloride film deformation followability, and workability.

The method of applying the adhesive is not particularly limited, and examples thereof include Meyer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, and spin coater. be done. It is preferable to carry out a drying process during coating. The drying apparatus is not particularly limited, and examples thereof include hot air dryers, infrared heaters, decompression methods, and the like. The drying temperature is usually about 60 to 140°C.

The thickness of the adhesive layer is preferably 1-300 μm, more preferably 5-100 μm. When the thickness is in the range of 1 to 300 μm, the adhesive physical properties can be adjusted to an appropriate range.

[Amount of plasticizer migration]
The pressure-sensitive adhesive sheet of the present invention is obtained by attaching the pressure-sensitive adhesive layer (X) of the pressure-sensitive adhesive sheet to a vinyl chloride film (100% by weight) containing 36% by weight of a plasticizer and having a thickness of 400 μm. After heating for 5 days, the amount of plasticizer transferred from the vinyl chloride film to the adhesive layer (X) after 5 days in a 25 ° C.-50% RH environment was 20 parts per 100 parts by mass of the adhesive layer (X). Part by mass or more.

The plasticizer migration amount is measured by using a calibration curve prepared by adding the same plasticizer as the plasticizer contained in the vinyl chloride film to the adhesive layer (X), and measuring the amount of plasticizer in the adhesive layer. can be obtained by That is, the pressure-sensitive adhesive layer (X) of the pressure-sensitive adhesive sheet was attached to a 400 μm thick vinyl chloride film containing 36% by mass of a plasticizer in a vinyl chloride film (100% by mass), heated at 70°C for 5 days, and then further heated at 25°C. It can be determined by measuring the amount of plasticizer in the adhesive layer (X') of the adhesive layer (X') after 5 days in an environment of -50% RH.

The plasticizer migration amount is a value obtained using the same plasticizer as the plasticizer such as adipate, phthalate, or citric acid ester contained in the vinyl chloride film. By controlling, good plasticizer resistance and vinyl chloride film deformation followability can be expressed.

The plasticizer migration amount is 20 parts by mass or more, preferably 25 parts by mass or more, more preferably 30 parts by mass or more. The upper limit is 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less. Within this range, the plasticizer resistance and the vinyl chloride film deformation followability can be improved.

With conventional PSA sheets, the plasticizer that is discharged from the vinyl chloride film but not migrated accumulates at the interface between the PSA layer and the adherend, reducing the actual contact area of the PSA layer with the adherend. As a result, the adhesive strength is reduced, and the adhesive layer cannot follow the shrinkage of the vinyl chloride film. In contrast, the pressure-sensitive adhesive sheet of the present invention is designed to suppress performance deterioration due to the plasticizer entering the interface between the vinyl chloride film and the pressure-sensitive adhesive layer, and the inside of the pressure-sensitive adhesive layer. It has become possible to produce a pressure-sensitive adhesive sheet having a vinyl chloride film deformation followability and workability.
That is, as has been studied in the past, if the plasticizer derived from the vinyl chloride film is not absorbed and is completely repelled, the plasticizer will accumulate at the interface between the vinyl chloride film and the adhesive layer, The interaction between the layers is lost and the adhesion is greatly degraded. Conversely, when all the plasticizer is absorbed, the cohesive strength of the adhesive layer itself is lost, and the adhesive strength deteriorates due to the loss of elasticity. Therefore, by controlling the storage modulus, cross-linking density, and weight average molecular weight, it is possible to maintain an appropriate absorption amount of the plasticizer and balance the adhesive force before and after the heating test.

[Shear storage modulus]
The pressure-sensitive adhesive layer (X) has a shear storage modulus of less than 0.05 MPa at a frequency of 1 Hz and 70°C. When the shear storage modulus of the pressure-sensitive adhesive layer (X) is within this range, a vinyl chloride film can be used as the base material or the adherend, and excellent heat resistance can be obtained. Under conditions where the vinyl chloride film shrinks (for example, heating in a microwave oven), it is possible to follow the deformation of the vinyl chloride film without peeling off the adhesive layer. On the other hand, when the shear storage modulus is 0.05 MPa or more, the pressure-sensitive adhesive layer becomes too hard and cannot cope with the deformation of the substrate or the adherend.

The preferred range of shear storage modulus at a frequency of 1 Hz and 70° C. has a lower limit of 0.005 MPa or higher, more preferably 0.008 MPa or higher, and still more preferably 0.015 MPa or higher. Also, the upper limit is less than 0.045 MPa, more preferably less than 0.040 MPa. By setting the shear storage elastic modulus within the above range, both workability and vinyl chloride film deformation followability can be achieved.

The shear storage modulus of the adhesive layer (X) is measured, for example, by stacking the adhesive layers to form an adhesive layer with a thickness of 1 mm, and using a dynamic viscoelasticity measuring device manufactured by TA Instruments Japan. DYNAMIC ANALYZER RDA III".

《Acrylic adhesive》
The acrylic pressure-sensitive adhesive of the present invention contains an acrylic resin (A) and a curing agent (B).

<Acrylic resin (A)>
The acrylic resin (A) is a copolymer such as (meth)acrylic acid ester, and can also be used in combination with other vinyl esters or the like.
Monomers that can be used include (meth)acrylic acid alkyl esters (a1), hydroxyl group-containing monomers (a2), carboxyl group-containing monomers (a3), amide bond-containing monomers, epoxy group-containing monomers, and amino group-containing monomers. is a copolymer obtained by copolymerizing a monomer mixture containing a monomer having

It is preferable to use the monomer (a2) having a hydroxyl group, because the pressure-sensitive adhesive layer can have excellent cohesion.
In addition, (meth)acrylic acid acrylic esters having an alkyl group of 8 to 12 carbon atoms are preferable because they can be made more excellent in adhesive strength, tackiness, and vinyl chloride film deformation followability.
In 100% by mass of the monomer mixture, the content of the monomer having an alkyl group with 8 to 12 carbon atoms is preferably 50 to 89% by mass, more preferably 55 to 84% by mass, and even more preferably 60 to 84% by mass. . When the content is 50 to 89% by mass, the adhesive strength and the PVC film deformation followability are excellently imparted.

In addition, by using a (meth)acrylic acid alkyl ester having a glass transition temperature Tg of 0° C. or higher or a vinyl ester having a glass transition temperature Tg of 0° C. or higher, cohesive force is imparted to the acrylic resin (A), Even the pressure-sensitive adhesive layer that has absorbed the plasticizer derived from the vinyl chloride film can retain its cohesive force. On the other hand, it also has the function of suppressing the outflow of the plasticizer from the vinyl chloride film due to its workability.
Incidentally, (meth)acrylic acid alkyl esters having a glass transition temperature Tg of 0° C. or higher exclude (meth)acrylic acid acrylic esters having alkyl groups of 8 to 12 carbon atoms.

The content of the (meth)acrylic acid alkyl ester having a glass transition temperature Tg of 0°C or higher or the vinyl ester having a glass transition temperature Tg of 0°C or higher is 10 to 40 parts by weight in 100 parts by weight of the monomer mixture. preferably 15 to 40 parts by mass, and even more preferably 15 to 35 parts by mass. Use of 10 to 40 parts by mass facilitates the development of vinyl chloride film deformation followability and workability. In addition, when using these together, preferable content points out a total amount.

(Meth)acrylic acid acrylic esters having a glass transition temperature Tg of 0° C. or higher include, for example, methyl acrylate (Tg: 10° C.), methyl methacrylate (105° C.), ethyl methacrylate (Tg: 10° C.), and propyl methacrylate. (Tg: 35°C), and butyl methacrylate (Tg: 20°C). Examples of vinyl esters having a glass transition temperature Tg of 0° C. or higher include vinyl acetate (Tg: 32° C.). Among these, methyl acrylate is preferred. These can also be used in combination.

Among them, a (meth)acrylic acid ester having an alkyl group with 8 to 12 carbon atoms, a (meth)acrylic acid acrylic ester having a glass transition temperature Tg of 0°C or higher, or a vinyl monomer having a glass transition temperature Tg of 0°C or higher It is preferable because it can express good plasticizer resistance and workability by including.
Incidentally, the glass transition temperature Tg referred to here is determined according to "Polymer Handbook, Fourth Edition", J. Am. Brandrup, E. H. Immergut, andE. A. It refers to the Tg of the homopolymer as described by Grulke (1999).

- (meth)acrylic acid alkyl ester (a1)
(Meth)acrylic acid alkyl esters, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, (meth)acryl isobutyl (meth)acrylate, hexyl (meth)acrylate, oleyl (meth)acrylate, and stearyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, (meth)acrylic isooctyl acid, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylate Examples include tetradecyl acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, lauryl (meth)acrylate, and the like.

Among these, (meth)acrylic acid alkyl esters with an alkyl group of 8 to 12 carbon atoms provide the acrylic resin (A) with basic performance as an adhesive such as adhesion and tackiness, as well as vinyl chloride film deformation followability. It is preferable because it can be given.
Examples of (meth)acrylic acid alkyl esters having an alkyl group of 8 to 12 carbon atoms include octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and nonyl (meth)acrylate. , isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and lauryl (meth)acrylate. Among these, 2-ethylhexyl acrylate and isononyl acrylate are preferred.
These monomers can be used alone or in combination of two or more.

The content of the (meth)acrylic acid alkyl ester is preferably 50 to 89% by mass, more preferably 55 to 84% by mass, based on 100% by mass of the monomer mixture in terms of imparting adhesive strength and deformation followability to vinyl chloride film. is more preferred, and 60 to 84% by mass is even more preferred.

- A monomer having a hydroxyl group (a2)
Monomers having a hydroxyl group include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and polyethylene Glycol mono(meth)acrylates, polypropylene glycol mono(meth)acrylates, 1,4-cyclohexanedimethanol mono(meth)acrylates and other glycol mono(meth)acrylates, caprolactone-modified (meth)acrylics Acid esters, N-hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and the like. Among these, 2-hydroxyethyl (meth)acrylate is preferred.

A monomer having a hydroxyl group can be used for the purpose of cross-linking the acrylic resins (A) via the curing agent (B) in order to impart cohesive force to the pressure-sensitive adhesive layer. The content is preferably 0.01 to 5% by mass, more preferably 0.03 to 2% by mass, still more preferably 0.05 to 1% by mass, based on 100% by mass of the monomer mixture. By setting the content of the hydroxyl group-containing monomer to this level, both adhesive strength and cohesive strength can be achieved at a higher level.

- A monomer having a carboxyl group (a3)
Monomers having a carboxyl group include, for example, (meth)acrylic acid, monohydroxyethyl phthalate acrylate, p-carboxybenzyl acrylate, ethylene oxide-modified (moles of ethylene oxide added: (2 to 18)) phthalate acrylic acid ester, monohydroxyethyl succinate acrylate, β-carboxyethyl acrylate, itaconic acid, etc. Among these, (meth)acrylic acid is preferred.

A monomer having a carboxyl group plays a role not only as a cross-linking point for imparting cohesive strength to the adhesive layer, but also as maintaining adhesive strength after absorption of a plasticizer derived from a vinyl chloride film. The content is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, even more preferably 1 to 5% by mass, based on 100% by mass of the monomer mixture. When it is 0.5 to 10% by mass, the adhesion to the vinyl chloride film is further improved.
A monomer having a carboxyl group is preferable because it can provide better adhesion to a vinyl chloride film.

- Monomers having an amide bond Monomers having an amide bond are, for example, (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl (Meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetone (meth)acrylamide, N-(butoxymethyl)acrylamide and other (meth)acrylamide compounds; N-vinylpyrrolidone, N-vinylcaprolactam, and compounds having a heterocyclic ring such as acryloylmorpholine;

Epoxy Group-Containing Monomer Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

Monomers having an amino group Examples of monomers having an amino group are monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethyl (meth)acrylate. (Meth)acrylic acid monoalkylaminoesters such as aminopropyl and the like.

The monomer having an amide bond, the monomer having an epoxy group, and the monomer having an amino group are preferably included in 0.1 to 1 part by mass each in 100 parts by mass of the monomer mixture.

Aromatic Ring-Containing Monomer Examples of aromatic ring-containing monomers include phenoxyethyl acrylate, benzyl acrylate, phenoxydiethylene glycol (meth)acrylate, and ethylene oxide-modified nonylphenol (meth)acrylate.

The aromatic ring-containing monomer is preferably contained in 0.1 to 10 parts by mass in 100 parts by mass of the monomer mixture.

Alkoxy(poly)alkylene oxide-containing monomer Monomers containing alkoxy(poly)alkylene oxide are, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth)acryl acid esters, ethoxypolyethylene glycol (meth)acrylates, methoxypolypropyleneglycol (meth)acrylates, ethoxypolypropyleneglycol (meth)acrylates, phenoxypolyethyleneglycol (meth)acrylates, and phenoxypolypropyleneglycol (meth)acrylates Examples include acrylic acid esters.

The monomer having alkoxy(poly)alkylene oxide is preferably contained in 0.1 to 10 parts by mass in 100 parts by mass of the monomer mixture.

・Other monomers Other monomers that can be used include styrenes such as styrene and α-methylstyrene, vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether and isobutyl vinyl ether, vinyl acetate, and propion. Examples thereof include vinyl esters such as vinyl acid and vinyl cyanides such as acrylonitrile.

Other monomers are preferably contained in an amount of 0.1 to 10 parts by mass in 100 parts by mass of the monomer mixture.

The acrylic resin (A) can be produced by adding a polymerization initiator to the monomer mixture and appropriately selecting known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. Among these, solution polymerization is preferred because it facilitates adjustment of the weight-average molecular weight of the acrylic resin.

Solvents used in the solution polymerization include, for example, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, and isopropanol. is preferred, and ethyl acetate is more preferred. Solvents can be used alone or in combination of two or more.

The solution polymerization is preferably carried out by adding about 0.001 to 1 part by mass of a polymerization initiator to 100 parts by mass of the monomer mixture. Generally, the polymerization can be carried out at a temperature of about 50° C. to 90° C. for 4 to 12 hours under nitrogen stream. Moreover, the weight average molecular weight of the acrylic resin can be appropriately adjusted by using a chain transfer agent during the polymerization.

In the present invention, the acrylic resin (A) preferably has a weight average molecular weight (hereinafter also referred to as Mw) of 400,000 to 2,000,000, more preferably 600,000 to 1,500,000, and even more preferably 800,000 to 1,300,000. By setting the Mw in the range of 400,000 to 2,000,000, the adhesive strength after heating can be maintained and the amount of the curing agent described later can be reduced, so that the effect of vinyl chloride film deformation followability can be easily obtained.

As the polymerization initiator, azo compounds, organic peroxides, and the like can be used.

Azo compounds include, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane 1-carbonitrile), 2,2 '-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4 , 4′-azobis(4-cyanovaleric acid), 2,2′-azobis(2-hydroxymethylpropionitrile), and 2,2′-azobis(2-(2-imidazolin-2-yl)propane ) and the like.

Organic peroxides are, for example, benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate , t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.
A polymerization initiator can be used alone or in combination of two or more.

Chain transfer agents are, for example, n-dodecylmercaptan, mercaptoisobutyl alcohol, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, glycidylmercaptan, α-methylstyrene. Dimer, carbon tetrachloride, chloroform, hydroquinone, and the like.
About 0.01 to 1 part by mass of the chain transfer agent can be used with respect to 100 parts by mass of the monomer mixture.

<Curing agent (B)>
As the curing agent (B), known curing agents such as isocyanate curing agents, epoxy curing agents, or metal chelate curing agents can be used. Among these, isocyanate curing agents are preferred from the viewpoint of plasticizer resistance.

Isocyanate curing agents include, for example, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. , and an adduct of a diisocyanate such as polymethylene polyphenyl isocyanate and a polyol compound such as trimethylolpropane, a burette thereof, an isocyanurate thereof, and the diisocyanate, polyether polyol, polyester polyol, acrylic polyol, polybutadiene Compounds having 3 or more isocyanate groups in the molecule, such as polyols and adducts with polyols such as polyisoprene polyol; Diisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate, and allophanate forms of hexamethylene diisocyanate, etc. a compound having one isocyanate group; and the like. Among these, the trimethylolpropane adduct of tolylene diisocyanate is preferable because it suppresses performance deterioration due to plasticizer absorption. In addition, the number of isocyanate groups is the average number.

The isocyanate curing agent preferably contains 0.01 to 1 part by mass, more preferably 0.01 to 0.6 parts by mass, with respect to 100 parts by mass of the acrylic resin (A), and 0.05 0.6 parts by weight is more preferred, and 0.1 to 0.6 parts by weight is particularly preferred. By including 0.01 to 1 part by mass, it is possible to make the PVC film more excellent in deformation followability and workability. An isocyanate curing agent can be used alone or in combination of two or more.

Epoxy curing agents include, for example, bisphenol A-epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl. ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane and the like.

The epoxy curing agent preferably contains 0.01 to 1 part by mass with respect to 100 parts by mass of the acrylic resin (A). When 0.01 to 1 part by mass is included, it becomes easy to balance the cohesive strength and adhesive strength of the pressure-sensitive adhesive layer. Epoxy compounds can be used alone or in combination of two or more.

Metal chelate curing agents include, for example, 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. mentioned.

The metal chelate curing agent preferably contains 0.1 to 5 parts by mass with respect to 100 parts by mass of the acrylic resin (A). When 0.1 to 5 parts by mass is contained, it becomes easy to balance the cohesive strength and adhesive strength of the pressure-sensitive adhesive layer. A metal chelate can be used alone or in combination of two or more.

Curing agents (B) can be used alone or in combination of two or more.

In addition, a tackifying resin may be included within the range in which the problems of the present invention can be solved. For example, rosin resins, terpene resins, alicyclic hydrocarbon resins, aliphatic petroleum resins, aromatic petroleum resins, alkylphenol formaldehyde resins (oily phenolic resins) and the like are preferred. The tackifying resin can be used alone or in combination of two or more. By including a tackifying resin in the adhesive, the adhesive strength to polyvinyl chloride can be more easily improved.

The tackifying resin is preferably blended in an amount of 10 to 30 parts by mass with respect to 100 parts by mass of the acrylic resin (A).

The softening point of the tackifier resin is preferably 80 to 140°C. A softening point of 80 to 140° C. makes it easy to achieve both adhesive strength and cohesive strength.

The pressure-sensitive adhesive of the present invention has various resins, curing catalysts, silane coupling agents, oils, softeners, dyes, pigments, antioxidants, ultraviolet absorbers, and weather-resistant components as optional components within the range where the problems of the present invention can be solved. Agents, fillers, anti-aging agents, anti-static agents, etc. may be added.

The pressure-sensitive adhesive of the present invention is suitable as a pressure-sensitive adhesive for bonding vinyl chloride films, as well as general labels and stickers, adhesive optical films, paints, elastic wall materials, waterproof coating materials, flooring materials, and tackifiers. , adhesives, adhesives for laminated structures, sealing agents, molding materials, coating agents for surface modification, binders (magnetic recording media, ink binders, casting binders, baked brick binders, graft materials, microcapsules, glass fiber sizing, etc.) ), urethane foam (hard, semi-hard, soft), urethane RIM, UV/EB curing resin, high solid paint, thermosetting elastomer, microcellular, fiber processing agent, plasticizer, sound absorbing material, damping material, surfactant agent, gel coat agent, resin for artificial marble, impact resistance agent for artificial marble, resin for ink, film (laminating adhesive, protective film, etc.), resin for laminated glass, reactive diluent, various molding materials, elastic fiber , as a raw material for artificial leather, synthetic leather, etc., and also as various resin additives and their raw materials.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these. In the examples, "part" means "mass part" and "%" means "mass part". In addition, non-volatile matter shall be described except the solvent.

Methods for measuring the weight average molecular weight (Mw) and the degree of dispersion (Mw/Mn) of the acrylic resin are shown below.

[Measurement of Weight Average Molecular Weight (Mw) and Dispersity (Mw/Mn)]
GPC was used to measure Mw and Mw/Mn. GPC is liquid chromatography for separating and quantifying a substance dissolved in a solvent (THF; tetrahydrofuran) based on the difference in molecular size, and Mw and Mw/Mn were determined in terms of polystyrene.
Device name: Shimadzu Corporation,
LC-GPC system "Prominence"
Column: 4 GMHXL manufactured by Tosoh Corporation and 1 HXL-H manufactured by Tosoh Corporation connected in series Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 ml/min Column temperature: 40°C

Subsequently, abbreviations of materials used in Examples and Comparative Examples are described below.
<(Meth)acrylic acid alkyl ester (a1)>
2EHA: 2-ethylhexyl acrylate (number of carbon atoms in alkyl group; 8, Tg: -70°C)
NA: nonyl acrylate (carbon number of alkyl group; 9, Tg: -58 ° C.)
MA: methyl acrylate (number of carbon atoms in alkyl group; 1, Tg: 10°C)
MMA: methyl methacrylate (number of carbon atoms in alkyl group; 1, Tg: 105°C)
EA: ethyl acrylate (number of carbon atoms in alkyl group; 2, Tg: -24°C)
BA: butyl acrylate (number of carbon atoms in alkyl group; 4, Tg: -54°C)
<Monomer (a2) having a hydroxyl group>
HEA: 2-hydroxyethyl acrylate <monomer (a3) having a carboxyl group>
AA: acrylic acid MAA: methacrylic acid <others>
VAc: vinyl acetate (Tg: 32°C)
<Curing agent (B)>
TDI/TMP: trimethylolpropane adduct of tolylene diisocyanate TETRAD X: N,N,N',N',-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company)

[Synthesis of acrylic resin (A)]
(Synthesis example 1)
In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube (hereinafter simply referred to as the "reaction vessel"), under a nitrogen atmosphere, 90.8 parts of 2-ethylhexyl acrylate, acrylic 8.5 parts of methyl acid, 0.2 parts of hydroxyethyl acrylate, 0.5 parts of acrylic acid, 75 parts of ethyl acetate, 20.0 parts of acetone, and 0.2 parts of benzoyl peroxide (hereinafter referred to as BPO) were charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reactor was cooled and 77 parts of ethyl acetate was added to obtain an acrylic resin (A-1) solution having a weight average molecular weight of 1,160,000.

(Synthesis Examples 2-12, 18-22, 24, 26-28, 30)
The acrylic resins of Synthesis Examples 2 to 12, 18 to 32 (A-2 to 12, 18 to 22, 24,26-28,30) solutions were obtained.

(Synthesis Example 13)
In a reaction vessel under a nitrogen atmosphere, 73.3 parts of 2-ethylhexyl acrylate, 23.5 parts of methyl acrylate, 0.2 parts of hydroxyethyl acrylate, 3.0 parts of acrylic acid, 112.0 parts of ethyl acetate, and benzoyl peroxide were added. 0.2 part of oxide (hereinafter referred to as BPO) was charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reaction vessel was cooled and 35 parts of ethyl acetate was added to obtain an acrylic resin (A-13) solution having a weight average molecular weight of 450,000.

(Synthesis Example 14)
In a reaction vessel under a nitrogen atmosphere, 73.3 parts of 2-ethylhexyl acrylate, 23.5 parts of methyl acrylate, 0.2 parts of hydroxyethyl acrylate, 3.0 parts of acrylic acid, 80.0 parts of ethyl acetate, and benzoyl peroxide were added. 0.2 part of oxide (hereinafter referred to as BPO) was charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reaction vessel was cooled and 66 parts of ethyl acetate was added to obtain an acrylic resin (A-14) solution having a weight average molecular weight of 610,000.

(Synthesis Example 15)
73.3 parts of 2-ethylhexyl acrylate, 23.5 parts of methyl acrylate, 0.2 parts of hydroxyethyl acrylate, 3.0 parts of acrylic acid, 70.0 parts of ethyl acetate, and 10 parts of acetone were placed in a reaction vessel under a nitrogen atmosphere. 0.0 part and 0.2 part of benzoyl peroxide (hereinafter referred to as BPO) were charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reaction vessel was cooled and 66 parts of ethyl acetate was added to obtain an acrylic resin (A-15) solution having a weight average molecular weight of 900,000.

(Synthesis Example 16)
73.3 parts of 2-ethylhexyl acrylate, 23.5 parts of methyl acrylate, 0.2 parts of hydroxyethyl acrylate, 3.0 parts of acrylic acid, 40.0 parts of ethyl acetate, and 40 parts of acetone were placed in a reaction vessel under a nitrogen atmosphere. 0.0 part and 0.2 part of benzoyl peroxide (hereinafter referred to as BPO) were charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reactor was cooled and 66 parts of ethyl acetate was added to obtain an acrylic resin (A-16) solution having a weight average molecular weight of 1,470,000.

(Synthesis Example 17)
73.3 parts of 2-ethylhexyl acrylate, 23.5 parts of methyl acrylate, 0.2 parts of hydroxyethyl acrylate, 3.0 parts of acrylic acid, 25.0 parts of ethyl acetate, and 55 parts of acetone were placed in a reaction vessel under a nitrogen atmosphere. 0.0 part and 0.2 part of benzoyl peroxide (hereinafter referred to as BPO) were charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reactor was cooled and 66 parts of ethyl acetate was added to obtain an acrylic resin (A-17) solution having a weight average molecular weight of 1,800,000.

(Synthesis Example 23)
A solution of acrylic resin (A-23) of Synthesis Example 23 was obtained in the same manner as in Synthesis Example 17 except that the types and blending amounts of the monomers were as described in Table 1.

(Synthesis Examples 25 and 29)
Acrylic resin (A-25, 29) solutions of Synthesis Examples 25 and 29 were obtained in the same manner as in Synthesis Example 16, except that the types and blending amounts of the monomers were as described in Table 1.

(Synthesis Example 31)
A solution of acrylic resin (A-31) of Synthesis Example 31 was obtained in the same manner as in Synthesis Example 15 except that the types and blending amounts of the monomers were as described in Table 1.

(Synthesis Example 32)
40.0 parts of 2-ethylhexyl acrylate, 54.5 parts of methyl acrylate, 0.5 parts of hydroxyethyl acrylate, 5.0 parts of acrylic acid, 30.0 parts of ethyl acetate, and 70 parts of methyl ethyl ketone were placed in a reaction vessel under a nitrogen atmosphere. 0.0 part and 0.2 part of benzoyl peroxide (hereinafter referred to as BPO) were charged. The mixture was heated while stirring, and after confirming the initiation of the polymerization reaction, the reaction was carried out at the reflux temperature for 2 hours. Next, 0.04 part of BPO was added to the reaction solution and reacted for 2 hours, and further 0.04 part of BPO was added to the reaction solution and the reaction was continued for 4 hours. After that, the reaction vessel was cooled and 66 parts of ethyl acetate was added to obtain an acrylic resin (A-32) solution having a weight average molecular weight of 200,000.

(Example 1)
Per 100 parts of the acrylic resin (A-1) (non-volatile) in the acrylic resin solution obtained in Synthesis Example 1, 0.3 parts of trimethylolpropane adduct of tolylene diisocyanate as an isocyanate curing agent (non-volatile (in terms of minutes), and ethyl acetate was added as a solvent to adjust the non-volatile content to 30% to obtain an acrylic pressure-sensitive adhesive.
The acrylic pressure-sensitive adhesive is coated on a commercially available release sheet (made of polyethylene terephthalate) having a thickness of 38 μm with a comma coater so that the thickness after drying becomes 25 μm, and dried at 100° C. for 2 minutes. to form an adhesive layer. Next, a substrate with a thickness of 50 μm (polyethylene terephthalate substrate (“Lumirror T-60”, manufactured by Toray Industries, Inc.), hereinafter referred to as a PET sheet) is attached to this adhesive layer, and the temperature is 25° C.-50% RH. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (X) having a structure of "releasable sheet/pressure-sensitive adhesive layer/PET sheet" was obtained by aging for 1 week. However, Example 1 is a reference example.

(Examples 2-35, Comparative Examples 1-2)
Acrylic pressure-sensitive adhesives and pressure-sensitive adhesive sheets of Examples 2-35 and Comparative Examples 1-2 were obtained in the same manner as in Example 1 except that the materials were changed according to the formulations in Tables 2 and 3.
However, Examples 2, 10, 11, 16, 21, 23, 25, 28, 29, 30, 34, and 35 are reference examples.

<Measurement of physical properties of pressure-sensitive adhesive layer and evaluation of pressure-sensitive adhesive sheet>
The storage elastic modulus and the amount of plasticizer migration of the pressure-sensitive adhesive layer were measured, and the evaluation of plasticizer resistance, vinyl chloride (PVC) film followability, and workability were performed by the following methods. Table 1 shows the results.

[Shear storage modulus]
Using the obtained pressure-sensitive adhesive, coat a commercially available release sheet having a thickness of 75 μm with a comma coater (registered trademark) so that the thickness after drying becomes 50 μm, and dry at 100° C. for 2 minutes. to form an adhesive layer. Next, another commercially available release sheet (made of polyethylene terephthalate) with a thickness of 38 μm was laminated instead of the base material, and aged at a temperature of 25 ° C.-50% RH for 1 week, and "75 μm release sheet/adhesive layer/ A pressure-sensitive adhesive layer sandwiched between two release sheets having a structure of "38 μm release sheet" was prepared. Then, one of the release sheets was peeled off, and lamination was repeated so that the adhesive layers overlapped to obtain an adhesive layer with a thickness of 1 mm. After removing air bubbles with an autoclave, a cylinder with a diameter of 8 mm was die-cut to prepare a sample for storage modulus measurement. The peelable sheets on both sides were peeled off, and the sample was measured by the torsional shear method under the following conditions.

Measuring device: Dynamic viscoelasticity measuring device “DYNAMIC ANALYZER RDA III” manufactured by TA Instruments Japan
Frequency: 1Hz
Measurement temperature: Measurement was carried out from -50°C to 200°C, and the storage modulus at 70°C was read.
Heating rate: 10°C/min

[Amount of plasticizer migration]
Acrylic resin (53 parts of butyl acrylate, 41 parts of 2-ethylhexyl acrylate, 6 parts of acrylic acid) per 100 parts (non-volatile), 0.4 parts of trimethylolpropane adduct of tolylene diisocyanate as an isocyanate curing agent (in terms of non-volatile content) and a plasticizer (dioctyl phthalate) in predetermined amounts (0, 5, 10, 20, 50 parts) respectively, and ethyl acetate is added as a solvent to adjust the non-volatile content to 30%, An adhesive for polyvinyl chloride was obtained for preparing a calibration curve. The pressure-sensitive adhesive was coated on a commercially available release sheet having a thickness of 38 μm with a comma coater so that the thickness after drying was 25 μm, and dried at 100° C. for 2 minutes to form a pressure-sensitive adhesive layer. . Next, a base material having a thickness of 50 μm is attached to this pressure-sensitive adhesive layer, and the pressure-sensitive adhesive sheet having a configuration of “releasable sheet/adhesive layer/PET sheet” is aged for one week at a temperature of 25° C.-50% RH. got
A plasticizer-containing pressure-sensitive adhesive sheet with a different plasticizer content was cut into a size of 25 mm in width and 100 mm in length. , a calibration curve was created from the obtained low-molecular-weight (plasticizer)-derived peak intensities.
In addition, since the plasticizer does not react with the acrylic resin or curing agent, and the peak obtained by GPC measurement of the eluted portion does not overlap with other components, it can be used as a calibration curve in the above method. Confirmed that there is.

First, the adhesive sheets obtained in Examples and Comparative Examples were cut into pieces having a width of 25 mm and a length of 100 mm. Subsequently, under an atmosphere of 25° C.-50% RH, the adhesive layer (X) exposed by peeling off the release sheet from the cut adhesive sheet was coated with a 400 μm-thick vinyl chloride containing 36% by mass of a plasticizer (dioctyl phthalate). A sample was prepared by attaching it to a film (hereinafter referred to as a PVC film), reciprocating it once with a 2 kg roll, and leaving it for 24 hours after pressure bonding. After heating the prepared sample at 70° C. for 5 days, it is further aged for 5 days in a 25° C.-50% RH environment, and the adhesive sheet (adhesive layer/PET sheet) is peeled off from the PVC film to transfer the plasticizer. A pressure-sensitive adhesive sheet having a layer (X') was obtained. The pressure-sensitive adhesive sheet to which the plasticizer has been migrated is dissolved in THF (1 sheet/20 g THF), and the peak intensity derived from dioctyl phthalate in the pressure-sensitive adhesive layer (X') is obtained by GPC measurement. After heating at 70° C. for 5 days, the amount of plasticizer contained in the adhesive layer (X′) after 5 days in a 25° C.-50% RH environment was determined, and the amount of plasticizer for the adhesive layer (X) was calculated. , the amount of plasticizer migration.

<Plasticizer resistance>
The obtained adhesive sheet was cut into a size of 25 mm in width and 100 mm in length. In an atmosphere of 25° C.-50% RH, the peelable adhesive layer was peeled off from the cut adhesive sheet, and the exposed adhesive layer was attached to a vinyl chloride sheet (hereinafter referred to as a PVC sheet) containing 36% plasticizer (dioctyl phthalate), A sample was prepared by reciprocating once with a 2 kg roll and leaving it for 24 hours after pressure bonding. After affixing to the PVC sheet according to the conditions of <Plasticizer Migration Amount>, the adhesive strength was measured by a 180° peel test in which the sample was peeled off at a rate of 300 mm/min in a 180° direction using a tensile tester (thermal Adhesive strength before aging).
Separately, after attaching the obtained adhesive sheet to the PVC sheet according to the above adhesive strength conditions, leaving it for 5 days at 70 ° C. DRY, the adhesive strength was measured in the same manner as the adhesive strength before heat aging (adhesive strength after heat aging ), and was evaluated based on the following evaluation criteria.

Retention rate = (adhesive strength after heat aging/adhesive strength before heat aging) x 100

A: The retention rate is 90 or more, which is excellent.
◯: The retention rate is 75 or more and less than 90, which is good.
Δ: The retention rate is 50 or more and less than 75, and is practical.
x: The retention rate is less than 50, or the retention rate cannot be calculated due to cohesive failure, and is not practical.

<PVC film deformation followability>
The obtained pressure-sensitive adhesive sheet was prepared in a size of 100 mm in width and 100 mm in length. Next, a vinyl chloride wrap film (Hitachi Wrap, manufactured by Hitachi Chemical Co., Ltd.) is attached to the container in which 100 mL of water is poured, and the adhesive sheet is attached to the center plane of the wrap film, and then heated in a microwave oven at 500 W for 1 minute. bottom. After the container was taken out from the microwave oven, the pressure-sensitive adhesive sheet that had shrunk and deformed due to heating was visually evaluated for floating or peeling from the wrap film. Evaluation criteria are as follows.

⊚: Excellent, no floating or peeling of the adhesive sheet.
Good: Lifting or peeling of the adhesive sheet of less than 0.5 mm is observed at the edge of the adhesive sheet.
Δ: Lifting and peeling of the adhesive sheet of 0.5 mm or more and less than 2 mm are observed at the edge of the adhesive sheet, practically usable.
x: Lifting and peeling of the adhesive sheet of 2 mm or more are observed, not practical.

<Workability>
The obtained pressure-sensitive adhesive sheet was prepared in a size of 100 mm in width and 100 mm in length. Next, the pressure-sensitive adhesive sheet was pressed under conditions of 40° C.-50% RH for 24 hours under conditions of 5 kg/cm ² , and the state in which the pressure-sensitive adhesive layer protruded from the side surface of the pressure-sensitive adhesive sheet was evaluated. Evaluation criteria are as follows.

⊚: Excellent with no protrusion of the adhesive layer.
◯: Protrusion of less than 0.2 mm of the adhesive layer was observed, but there was no problem in practical use.
Δ: Protrusion of the pressure-sensitive adhesive layer of 0.2 mm or more and less than 0.5 mm was observed, but there was no problem in practical use, and it was practicable.
x: Unusable due to protrusion of the adhesive layer of 0.5 mm or more, impractical.

Claims (4)

A pressure-sensitive adhesive sheet for a plasticizer-containing vinyl chloride film having a pressure-sensitive adhesive layer (X) containing an acrylic resin (A) and a curing agent (B),
The acrylic resin (A) is obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester having an alkyl group with 8 to 12 carbon atoms, a monomer (a2) having a hydroxyl group, and a monomer (a3) having a carboxyl group. An acrylic copolymer having a weight average molecular weight of 600,000 to 1,500,000 ,
The (meth)acrylic acid alkyl ester having 8 to 12 carbon atoms in the alkyl group includes 2-ethylhexyl acrylate or isononyl acrylate,
In 100% by mass of the monomer mixture, the content of (meth)acrylic acid alkyl ester having an alkyl group of 8 to 12 carbon atoms is 60 to 84% by mass, and the content of the monomer (a2) having a hydroxyl group is 0.05 to 1 mass%. % and
The curing agent (B) contains an isocyanate curing agent, and the content of the isocyanate curing agent is 0.01 to 0.6 parts by mass with respect to 100 parts by mass of the acrylic resin (A),
The pressure-sensitive adhesive layer (X) has a shear storage modulus of less than 0.05 MPa at a frequency of 1 Hz and 70 ° C., and a vinyl chloride film having a thickness of 400 μm containing 36% by mass of a plasticizer is coated with the pressure-sensitive adhesive layer (X ), after heating at 70 ° C. for 5 days, and after 5 days in a 25 ° C.-environment, the amount of plasticizer transferred from the vinyl chloride film to the adhesive layer was 100 parts by mass of the adhesive layer (X). 20 parts by mass or more of the plasticizer-containing pressure-sensitive adhesive sheet for a vinyl chloride film. The plasticizer-containing pressure-sensitive adhesive sheet for a vinyl chloride film according to claim 1 , wherein the monomer mixture contains a (meth)acrylic acid alkyl ester or vinyl ester having a glass transition temperature Tg of 0°C or higher. The adhesive for a plasticizer-containing vinyl chloride film according to claim 1 , which contains 15 to 35% by mass of a (meth)acrylic acid alkyl ester or a vinyl monomer having a glass transition temperature Tg of 0 ° C. or higher in 100% by mass of the monomer mixture. sheet. An acrylic pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer (X) of the plasticizer-containing pressure-sensitive adhesive sheet for vinyl chloride film according to any one of claims 1 to 3 .