JP7253533B2 - Adhesive tape - Google Patents

Description

The present disclosure relates to adhesive tapes.

In recent years, due to growing environmental awareness, there is a demand for reducing the amount of volatile organic compounds (VOC) generated from industrial materials. Such demands are particularly conspicuous in the automobile industry, and strict VOC amount control is imposed mainly on manufacturers having bases in Asia. Therefore, it is necessary to suppress the amount of VOCs in adhesive tapes used in automobile manufacturing.

JP 2008-285554 A Japanese Patent No. 5142446

However, with conventional pressure-sensitive adhesive tapes, it has been difficult to reduce the amount of VOCs while satisfying the performance required for industrial applications. Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive tape that achieves both excellent pressure-sensitive adhesive performance and reduced VOC content.

Aspects of the present invention are, for example, as follows.
[1] Using a test piece having an adhesive layer containing an adhesive composition, the thickness of the adhesive layer being 30 μm or more, and the area of the adhesive layer being 100 mm × 100 mm, and a 5 L sampling bag A pressure-sensitive adhesive tape having a total volatile organic compound (TVOC) concentration of 20000 μg/m ³ or less calculated using the test piece and the sampling bag, and an alcohol concentration of 2500 μg/m ³ or less calculated using the test piece and the sampling bag.
[2] The pressure-sensitive adhesive tape according to [1], wherein the pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture containing a nitrogen atom-containing monomer.
[3] The pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture, and the content of (meth)acrylic acid in the monomer mixture containing the nitrogen atom-containing monomer is The adhesive tape according to [2], which is 2.5% by mass or less with respect to the total mass of.
[4] The pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture, and the monomer mixture containing the nitrogen atom-containing monomer is substantially free of (meth)acrylic acid. The adhesive tape according to [2].
[5] The pressure-sensitive adhesive tape according to any one of [1] to [4], wherein the isoparaffin concentration calculated using the test piece and the sampling bag is 5000 μg/m ³ or less.
[6] The adhesive composition contains a polymer obtained by copolymerizing a monomer mixture,
The pressure-sensitive adhesive tape according to any one of [1] to [5], wherein the isoparaffin content in the initiator used for the copolymerization is 0.03% by mass or less with respect to the total solid content of the pressure-sensitive adhesive composition. .
[7] The adhesive composition contains a polymer obtained by copolymerizing a monomer mixture,
The pressure-sensitive adhesive tape according to any one of [1] to [6], wherein the initiator used for the copolymerization substantially does not contain isoparaffin.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive tape which can be compatible with the outstanding adhesive performance and the reduction of the amount of VOC can be provided.

A pressure-sensitive adhesive tape according to one aspect of the present invention will be described below.

In this specification, the term "polymer" is used to include homopolymers and copolymers, and the term "polymerization" is used to include homopolymerization and copolymerization. In addition, the compound represented by formula (i) (where i is the formula number) is also simply referred to as "compound (i)". Further, in this specification, (meth)acrylic means acrylic or methacrylic, (meth)acrylate means acrylate or methacrylate, and (meth)acrylo means acrylo or methacrylo.

[Adhesive composition]
A pressure-sensitive adhesive tape according to one aspect of the present invention includes a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive composition. This adhesive composition usually contains a polymer obtained by copolymerizing a monomer mixture. The adhesive composition is typically an acrylic adhesive composition.

[polymer]
The above polymer may be synthesized by a normal radical polymerization method, or may be synthesized by a living radical polymerization method. The weight average molecular weight (Mw) of this polymer measured by gel permeation chromatography (GPC) is, for example, 50,000 to 3,000,000, preferably 50,000 to 2,500,000. , more preferably 50,000 to 2,000,000. The molecular weight distribution (Mw/Mn) of this polymer measured by the GPC method is, for example, 30.0 or less, preferably 25.0 or less, more preferably 20.0 or less.

This polymer is, for example, a (meth)acrylic polymer. This polymer may be a random polymer or a block polymer. This polymer may be, for example, a (meth)acrylic random polymer or a (meth)acrylic block polymer.

There are no particular restrictions on the types of monomers that can be contained in the monomer mixture. As such a monomer, (meth)acrylic acid ester is mainly used, but other functional group-containing monomers and copolymerizable monomers can also be used.

《(Meth)acrylic acid ester》
Examples of (meth)acrylic acid esters include alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono (meth)acrylates, and alicyclic or aromatic group-containing (meth)acrylates. . However, functional group-containing (meth)acrylates such as hydroxyl group-containing (meth)acrylates and carboxyl group-containing (meth)acrylates are excluded from (meth)acrylic acid esters.

The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate is preferably 1-20. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl ( meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, Decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, n-stearyl (meth)acrylate, iso-stearyl (meth)acrylate, dodecyl (meth)acrylate.

Alkoxyalkyl (meth)acrylates include, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl ( meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate.

Examples of alkoxypolyalkylene glycol mono(meth)acrylates include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, Methoxytriethylene glycol mono(meth)acrylate is mentioned.

Examples of alicyclic group- or aromatic group-containing (meth)acrylates include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, and phenoxyethyl (meth)acrylate. be done.

(Meth)acrylic acid esters may be used singly or in combination of two or more. The total amount of (meth)acrylic acid ester used is, for example, 70 to 99.9% by mass, preferably 80 to 99.5% by mass, more preferably 85 to 98.95% by mass, based on the total mass of all raw material monomers. %.

<<Functional Group-Containing Monomer>>
Functional group-containing monomers other than (meth)acrylic acid include, for example, hydroxyl group-containing monomers, acid group-containing monomers, and nitrogen atom-containing monomers. The acid group includes, for example, a carboxy group, an acid anhydride group, a phosphate group, and a sulfate group. Nitrogen atom-containing monomers contain nitrogen atoms in the form of amino groups or amide bonds, for example.

Examples of hydroxyl-containing monomers include hydroxyl-containing (meth)acrylates, specifically 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate and other hydroxyalkyl (meth)acrylates. The number of carbon atoms in the alkyl group in the hydroxyalkyl (meth)acrylate is generally 2-8, preferably 2-6.

Carboxy group-containing monomers include, for example, β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, ω-carboxypolycaprolactone mono(meth)acrylate. , acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid. Acid anhydride group-containing monomers include, for example, maleic anhydride. Phosphate group-containing monomers include (meth)acrylic monomers having phosphoric acid groups in side chains, and sulfate group-containing monomers include (meth)acrylic monomers having sulfate groups in side chains.

Nitrogen atom-containing monomers include, for example, amino group-containing monomers and amide bond-containing monomers. Here, the term "amino group" is used as a concept including not only primary amino groups but also secondary and tertiary amino groups. The amino group is preferably a tertiary amino group, and the tertiary amino group may be a cyclic amino group. Also, the amide bond may be part of a lactam structure.

When the amino group-containing monomer contains a secondary or tertiary amino group, the nitrogen atom of the amino group is preferably modified with an alkyl group. Examples of the alkyl group include those having 1 to 6 carbon atoms, and specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl groups, and tert-butyl groups.

The amino group-containing monomer is more preferably an aminoalkyl (meth)acrylic acid ester. Preferred aspects of the amino group in the aminoalkyl (meth)acrylate are the same as above. Further, the alkyl group in the aminoalkyl group includes, for example, those having 1 to 6 carbon atoms, and specifically, methyl group, ethyl group, n-propyl group, iso-propyl group and n-butyl group. , sec-butyl, iso-butyl, and tert-butyl groups. Aminoalkyl groups include, for example, tert-butylaminoethyl, dimethylaminoethyl, and diethylaminoethyl groups.

Specific examples of amino group-containing monomers include tert-butylaminoethyl methacrylate (TBAEMA), dimethylaminoethyl methacrylate (DMAEMA; DM), diethylaminoethyl methacrylate (DEAEMA), and dimethylaminoethyl acrylate. (DMAEA).

Amide bond-containing monomers are preferably (meth)acrylamide derivatives or lactams with vinyl groups.

The (meth)acrylamide derivative is, for example, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, or diacetoneacrylamide. Examples of the alkyl group include those having 1 to 6 carbon atoms, and specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl groups, and tert-butyl groups.

Specific examples of amide bond-containing monomers include N,N-dimethylacrylamide (DMAA), N,N-diethylacrylamide (DEAA), N-isopropylacrylamide (NIPAM), diacetoneacrylamide (DAAM), N-acryloylmorpholine ( ACMO), N-vinyl-2-pyrrolidone (NVP), N-vinyl-caprolactam (NVC), and N-(2-hydroxyethyl)acrylamide (HEAA).

One type of functional group-containing monomer can be used alone, or two or more types can be used. The total amount of functional group-containing monomers other than (meth)acrylic acid used is preferably 0 to 15% by mass, more preferably 0.05 to 10% by mass, based on the total mass of all raw material monomers. be.

Among the functional group-containing monomers, the total amount of the amino group-containing polymer is, for example, 0 to 10% by mass, preferably 0.5 to 8% by mass, more preferably 0, based on the total mass of all raw material monomers. 7 to 7% by mass, more preferably 0.8 to 6% by mass.

Among the functional group-containing monomers, the total amount of the amide bond-containing polymer is, for example, 0 to 4.5% by mass, preferably 1 to 4% by mass, more preferably 1 to 4.5% by mass, based on the total mass of all raw material monomers. .5 to 3.5% by mass, more preferably 2 to 3% by mass.

In addition, it is preferable that the monomer mixture for producing the above polymer does not substantially contain (meth)acrylic acid. The amount of (meth)acrylic acid used is, for example, 2.5% by mass or less, preferably 2% by mass or less, more preferably 1% by mass or less, relative to the total mass of all raw material monomers. By adopting such a configuration, it becomes possible to further reduce the amount of VOCs (especially the amount of alcohol), which will be described later.

<<Copolymerizable Monomer>>
Examples of copolymerizable monomers include alkylstyrenes such as styrene, methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene and octylstyrene, fluorostyrene, chlorostyrene, bromostyrene, dibromo Styrenic monomers such as styrene, iodostyrene, nitrostyrene, acetylstyrene and methoxystyrene, and vinyl acetate. The copolymerizable monomers may be used singly or in combination of two or more.

[Other ingredients]
The pressure-sensitive adhesive composition contains, as other components, a tackifying resin, a cross-linking agent, a silane coupling agent, an antistatic agent, an organic solvent, an antioxidant, a light stabilizer, a metal corrosion inhibitor, a plasticizer, a cross-linking accelerator, It may further contain nanoparticles and the like.

<Tackifying resin>
The pressure-sensitive adhesive composition may contain a tackifying resin. By using a tackifying resin in addition to the above polymer as a component constituting the pressure-sensitive adhesive composition, for example, it can be applied to olefin-based adherends such as polyethylene and polypropylene, which are generally difficult-to-adhere adherends for acrylic pressure-sensitive adhesives. Good adhesiveness (adhesiveness) can also be exhibited. Moreover, the constant-load peeling resistance of the pressure-sensitive adhesive layer to be obtained can be improved.

As the tackifying resin, it is preferable to use a rosin ester resin, and in particular, a polymerized rosin ester resin may be used in combination. As the tackifying resin, for example, a terpene-based tackifying resin or a hydrocarbon-based petroleum resin may be used.

The tackifying resin may be used singly or in combination of two or more. The total content of the tackifying resin in the adhesive composition is, for example, 1 to 40 parts by mass, preferably 5 to 35 parts by mass, and more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the polymer.

<Crosslinking agent>
Examples of cross-linking agents include isocyanate-based compounds, epoxy-based compounds, metal chelate-based compounds, and the like.

As the isocyanate compound, an isocyanate compound having two or more isocyanate groups in one molecule is usually used. Examples of isocyanate compounds include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl Aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate can be mentioned. Alicyclic diisocyanates include alicyclic compounds having 7 to 30 carbon atoms such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Diisocyanates can be mentioned. Examples of aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenylether diisocyanate, diphenylmethane diisocyanate and diphenylpropane diisocyanate.

Examples of isocyanate compounds having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, and 4,4′,4″-triphenylmethane triisocyanate. , a trimer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a biuret or isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate, a reaction product of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (for example, tolylene diisocyanate trimolecular adduct of isocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (eg, trimolecular adduct of hexamethylene diisocyanate), polyether polyisocyanate, and polyester polyisocyanate.

As the epoxy-based compound, for example, an epoxy compound having two or more epoxy groups in one molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N' -tetraglycidyl-m-xylylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mN,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyl toluidine, N,N-diglycidylaniline;

As metal chelate compounds, for example, polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium are coordinated with alkoxides, acetylacetone, ethyl acetoacetate, and the like. compound. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethylacetoacetate/diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

The cross-linking agent is in the range of 0.01 to 10 parts by weight, preferably 0.01 to 8 parts by weight, and more preferably 0.01 to 5 parts by weight, per 100 parts by weight in total with the polymer. Including the cross-linking agent in this range provides a balance between the various cohesive physical properties required.

<Silane coupling agent>
The silane coupling agent can strongly adhere the pressure-sensitive adhesive layer to an adherend such as a glass substrate, and prevent peeling of the pressure-sensitive adhesive layer in a high humidity and heat environment.

Silane coupling agents include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, silane coupling agents containing polymerizable unsaturated groups such as methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3- epoxy group-containing silane cups such as glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; Ringing agent; amino group-containing silanes such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane Coupling agent: Halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane can be mentioned.

Among these, an epoxy group-containing silane coupling agent is preferable in terms of stress relaxation and the like. In the composition of the present invention, the content of the silane coupling agent is usually 1 part by mass or less, preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.05 part by mass, per 100 parts by mass of the polymer. 5 parts by mass. When the content is within the above range, peeling of the adhesive layer in a high-humidity and heat environment and bleeding of the silane coupling agent in a high-temperature environment tend to be prevented.

<Antistatic agent>
Antistatic agents include, for example, surfactants, ionic compounds, and conductive polymers.

Examples of surfactants include quaternary ammonium salts, quaternary amide quaternary ammonium salts, pyridium salts, cationic surfactants having cationic groups such as primary to tertiary amino groups; sulfonate groups, sulfate esters Anionic surfactants having anionic groups such as bases and phosphate ester bases; , sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, alkyldiethanolamides and other nonionic surfactants. be done.

In addition, reactive emulsifiers having a polymerizable group can also be used as surfactants, and polymeric surfactants obtained by increasing the molecular weight of monomer components containing the above surfactants or reactive emulsifiers can also be used.

Conductive polymers include, for example, polythiophene, polyaniline, polypyrrole and derivatives thereof.

In the pressure-sensitive adhesive composition, the content of the antistatic agent is usually 3 parts by mass or less, preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2.5 parts by mass, relative to 100 parts by mass of the polymer. part by mass.

<Organic solvent>
The pressure-sensitive adhesive composition does not necessarily contain a solvent, but may contain an organic solvent in order to adjust its coatability. In the pressure-sensitive adhesive composition, the content of the organic solvent is usually 30-90% by mass, preferably 30-85% by mass. In this specification, the term “solid content” refers to all components excluding the above organic solvent among the components contained in the pressure-sensitive adhesive composition, and the term “solid content concentration” refers to 100% by mass of the pressure-sensitive adhesive composition. It refers to the ratio of the solid content.

〔Adhesive tape〕
The pressure-sensitive adhesive tape according to the present invention includes, for example, a double-sided pressure-sensitive adhesive sheet having only a pressure-sensitive adhesive layer formed on a release-treated cover film (hereinafter also referred to as a separator), a substrate, and a A double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer (in this case, the substrate is also referred to as a core material), a single-sided pressure-sensitive adhesive sheet having a substrate and the pressure-sensitive adhesive layer formed on one side of the substrate, and adhesives thereof It includes a pressure-sensitive adhesive sheet in which a release-treated cover film is attached to the surface of the pressure-sensitive adhesive layer of the sheet that is not in contact with the substrate.

Substrates include, for example, polyester films such as polyethylene terephthalate (PET), plastic films such as polycarbonate, polyethylene, polypropylene, polyolefin films such as ethylene-vinyl acetate copolymer, woven fabrics and non-woven fabrics. Plastic films, woven fabrics, and non-woven fabrics may be those in which various additives are blended or those in which a plurality of layers are laminated. Although the thickness of the substrate is not particularly limited, it is usually 1 to 2000 μm, especially 3 to 500 μm, especially 10 to 100 μm.

Cover films include, for example, polyester films such as polyethylene terephthalate (PET) optionally surface-release-treated, and plastic films such as polycarbonate, polyethylene, polypropylene, and polyolefin films such as ethylene-vinyl acetate copolymers. Moreover, as the plastic film, a film in which various additives are blended, a film in which a plurality of layers are laminated, or the like can be used.

As a method for applying the pressure-sensitive adhesive composition, known methods such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating may be used to obtain a predetermined thickness. A method of coating and drying can be used, and a pressure-sensitive adhesive layer can be formed in this way.
The pressure-sensitive adhesive layer has a thickness of 30 µm or more, preferably 40 µm or more, and more preferably 50 µm or more, formed in a single coating step. Moreover, the thickness of the pressure-sensitive adhesive layer formed in a single coating step is 30 μm or more, but for example, a plurality of such layers may be laminated. In particular, when the pressure-sensitive adhesive layer is formed of multiple layers, the total thickness of the pressure-sensitive adhesive layer is usually 60 μm or more. Although the upper limit of the total thickness of the adhesive layer is not particularly limited, it is usually 1000 μm or less. When the pressure-sensitive adhesive layer is formed of multiple layers, a base material may be provided between the pressure-sensitive adhesive layers, or a plurality of pressure-sensitive adhesive layers may be directly laminated without providing a base material.

[Total VOC concentration]
The pressure-sensitive adhesive tape according to the present invention has a total volatile organic compound (TVOC) concentration of 10000 μg/m ³ or less calculated using a test piece having an area of the pressure-sensitive adhesive layer of 100 mm × 100 mm and a 5 L sampling bag. . In this specification, a Tedlar (registered trademark) bag (manufactured by GL Sciences: model: AA-5) is used as a sampling bag.

The inventors have found that conventional pressure-sensitive adhesive tapes cannot achieve the VOC concentration described above. As a result of intensive studies, the inventors have found that isoparaffin and alcohol have a great influence on the VOC concentration. Furthermore, the present inventors can adjust the composition of the polymer, the type of initiator used when synthesizing the polymer, the remaining amount of the initiator in the adhesive composition, and the drying conditions of the adhesive layer. It was found that the above VOC concentration can be achieved while ensuring the necessary physical properties.

First, as the initiator, it is preferable to use a diluent containing as little isoparaffin as possible. That is, it is preferable to use an initiator having a decomposition temperature so high that a diluent is unnecessary. Specifically, the isoparaffin content in the initiator is preferably 0.03% by mass or less, more preferably 0.02% by mass or less, relative to the total solid content of the adhesive composition. , 0.01% by mass or less. It is also particularly preferred that the initiator is substantially free of isoparaffins. Here, the term "isoparaffin" means a chain saturated hydrocarbon having about 20 or more carbon atoms and having a side chain.

Next, it is preferable to reduce the residual amount of the initiator in the pressure-sensitive adhesive composition as much as possible. For this purpose, it is preferable, for example, to reduce the amount of initiator used, to use an initiator with a low decomposition temperature, or to raise the final polymerization temperature.

Examples of the above-mentioned initiators having a relatively high decomposition temperature include PBND100 [manufactured by NOF Corporation; t-butylperoxyneodecanoate], V601 [manufactured by Wako Pure Chemical Industries; (2,2′-Azobis (isobutyronitrile)], V-65 [Wako Pure Chemical Industries; (2,2′-Azobis (2,4-dimeyhylvaleronitrile)], V-59 [Wako Pure Chemical Industries, Ltd. (2,2'-Azobis (2-methylbutyronitrile)], and Perroyl L [manufactured by NOF; is of course possible.

Drying conditions for the adhesive layer also affect the total VOC concentration. The total VOC concentration can be reduced by drying the adhesive layer at a high temperature for a long time. When using a polymer containing (meth)acrylic acid, as in the system according to the present invention, the contribution of alcohol in the VOC is relatively large, so adjustment of drying conditions is particularly important.

Here, the total VOC concentration calculated using the test piece and the sampling bag is preferably 15,000 μg/m ³ or less, more preferably 12,000 μg/m ³ or less, and 10,000 μg/m ³ or less. It is even more preferable to have In addition, the isoparaffin concentration calculated using the test piece and the sampling bag is preferably 5000 μg/m ³ or less, more preferably 4000 μg/m ³ or less, and 3000 μg/m ³ or less. is more preferred. The alcohol concentration calculated using the test piece and the sampling bag is preferably 2000 μg/m ³ or less, more preferably 1500 μg/m ³ or less, and 1000 μg/m ³ or less. is more preferred.
<Example>

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following descriptions of Examples and the like, "parts" means "parts by mass" unless otherwise specified.

[Synthesis of polymer]
[Synthesis Examples 1 to 8]
A reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet was charged with n-butyl acrylate (BA), 2-hydroxyethyl acrylate (2HEA), acrylic acid (AA), dimethylaminoethyl methacrylate ( DM), N-isopropylacrylamide (NIPAM), hydroxyethyl acrylate (HEA), and vinyl acetate (VAc) in the proportions shown in Table 1, 100 parts of ethyl acetate was charged, and the temperature was raised to 80° C. while introducing nitrogen gas. Then, an initiator was added in the ratio shown in Table 1, and a polymerization reaction was carried out at 80° C. for 6 hours under a nitrogen gas atmosphere. After completion of the reaction, the polymer solution was diluted with ethyl acetate to prepare a polymer solution having a solid concentration of 50% by mass. PBND100, PBND, PHPV, PBPV, and PL355 are initiators manufactured by NOF, and V601 is an initiator manufactured by Wako Pure Chemical Industries.

The polymers obtained in Synthesis Examples 1 to 8 were mixed with a tackifying resin, a cross-linking agent and the like as necessary to obtain a pressure-sensitive adhesive composition. Table 2 below shows the composition, the remaining amount of the initiator, and the amount of isoparaffin (IP) in the initiator. Here, the IP content and the residual amount of the initiator in Table 2 represent the amounts relative to the total solid content of the pressure-sensitive adhesive composition. In Reference Example 2 and Example 3, PCJ (polymerized rosin ester resin, manufactured by Harima Kasei Co., Ltd.) was used as the tackifying resin.

Each pressure-sensitive adhesive composition thus obtained was applied to a light release film and dried to form a pressure-sensitive adhesive layer having a thickness of 55 μm. The pressure-sensitive adhesive layer was transferred to one surface of a PET film (Lumirror: manufactured by Toray Industries, Inc.) having a thickness of 25 μm. The procedure for forming a pressure-sensitive adhesive layer having a thickness of 55 μm was performed again, and the pressure-sensitive adhesive layer was transferred to the other side of the previous PET film. That is, the pressure-sensitive adhesive tape has a structure of (adhesive layer/PET film (substrate)/adhesive layer), and the total thickness of the pressure-sensitive adhesive layer is 110 μm, and the total thickness of the pressure-sensitive adhesive tape is 135 μm.

[Total VOC concentration]
The above adhesive tape was cut out in an area of 100 mm × 100 mm, and a 5 L Tedlar (registered trademark) bag (manufactured by GL Sciences: model; AA-5) was used to store total VOC, ethyl acetate, toluene, alcohol, and isoparaffin (IP ) was measured. Here, each detected amount is a value obtained by converting the area of the peak corresponding to each target substance analyzed in the gas chromatograph into toluene. The total VOC is a value obtained by converting the sum of gas chromatographic detection peak areas detected in the range from n-hexane to n-hexadecane into the toluene detection peak area. Further, the isoparaffin concentration is a value obtained by converting the total sum of the detection peak group areas corresponding to the paraffin-derived parts into the toluene detection peak area. Those results are shown together in Table 2.

As shown in Table 2, in Examples 1 to 4, the total VOC content was suppressed to 20000 µg/m ³ or less and the alcohol content was suppressed to 2500 µg/m ³ or less. On the other hand, in Comparative Examples 1 to 3, the total amount of VOC exceeded 20000 μg/m ³ . Here, when comparing Examples 1 to 4 with Comparative Examples 1 to 3, it can be seen that the total VOC amount could be greatly reduced by using an initiator with a low isoparaffin content. Also, when comparing Examples 1 to 4 with Reference Example 1, it can be seen that the amount of alcohol in the VOCVOC was reduced by reducing the content of acrylic acid.

[Adhesive properties]
For Reference Example 2 and Example 3, the adhesive physical properties were also measured. As shown in Table 3 below, the cross-linking agent (curing agent) includes L-45 (manufactured by Soken Chemical; tolylene diisocyanate) and TD-75 (manufactured by Soken Chemical; trimethylolpropane adduct of tolylene diisocyanate). was used.

(Curved surface sticking test)
The obtained adhesive tape was transferred to a 10 mm thick polyether-based urethane foam material to prepare a test tape for a curved surface adhesion test. This test tape was cut into a size of 20 mm×50 mm to obtain a test piece. This test piece was attached to a SUS304 cylinder with a diameter of 50 mm which had been polished with No. 280 waterproof abrasive paper. After standing at 80° C. for 24 hours, the edge portion of the test piece was lifted or peeled off, and the distance was measured.

(Ball tack test)
J. Measured by the Dow method. Specifically, an adhesive tape obtained by removing the PET release film from a test piece cut to a width of 10 cm was attached to an inclined surface with an inclination angle of 30 degrees so that the adhesive layer was exposed. Next, the steel ball was made to run up from the upper side of the inclined surface, and then slid on the adhesive surface (surface of the adhesive layer). At this time, the run-up distance was 10 cm, and the running distance was 10 cm. Also, the temperature was set to 23° C. or 10° C., and the humidity was set to 50% RH or 10% RH. Then, a sliding test was performed while changing the diameter of the steel ball, and the maximum diameter of the steel ball that stopped sliding within the adhesive surface was determined. The diameter of the steel ball used was X/32 inch (where X is an integer within the range of 1 to 32), and the numerical values shown in Table 3 mean the value of X.

As shown in Table 3, the adhesive tape of Example 3 had sufficient adhesive performance. In addition, the pressure-sensitive adhesive tape of Example 3 was superior to the pressure-sensitive adhesive tape of Reference Example 2 in terms of adhesion to curved surfaces at 80°C and ball tack test results at 10°C.

Claims (4)

It is calculated using a test piece having an adhesive layer containing an adhesive composition, the thickness of the adhesive layer being 30 μm or more, and the area of the adhesive layer being 100 mm × 100 mm, and a 5 L sampling bag. The total volatile organic compound (TVOC) concentration is 20000 μg/m ³ or less, and the alcohol concentration calculated using the test piece and the sampling bag is 2500 μg/m ³ or less,
The pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture containing an alkyl (meth)acrylate, a hydroxyl group-containing monomer, and an amino group-containing monomer ,
70 to 98.95 % by mass of the alkyl (meth)acrylate, 0.05 to (0.2/107.2)×100% by mass of the hydroxyl group - containing monomer , the amino Containing 0.5 to 8% by mass of a group-containing monomer ,
The alkyl (meth)acrylate includes methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, and iso-butyl (meth)acrylate. Acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl ( meth) acrylate, one or more selected from undecyl (meth) acrylate ,
The monomer mixture is substantially free of (meth)acrylic acid;
Adhesive tape used in automobile manufacturing. The pressure-sensitive adhesive tape according to claim 1 , wherein the isoparaffin concentration calculated using the test piece and the sampling bag is 5000 µg/m ³ or less. The pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture,
The pressure-sensitive adhesive tape according to claim 1 or 2 , wherein the isoparaffin content in the initiator used for the copolymerization is 0.03% by mass or less relative to the total solid content of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition contains a polymer obtained by copolymerizing a monomer mixture,
4. The pressure-sensitive adhesive tape according to any one of claims 1 to 3 , wherein the initiator used for said copolymerization does not substantially contain isoparaffin.