Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/02—Non-macromolecular additives
  • C09J11/06—Non-macromolecular additives organic
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/08—Macromolecular additives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]

Definitions

• Embodiments of the present invention relate to adhesive compositions and adhesive sheets.
• a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is used in a wide range of fields for labeling or adhesive purposes because of its ease of handling.
• a thinner pressure-sensitive adhesive layer of an adhesive sheet in various applications.
• the adhesive force of the adhesive sheet generally decreases as the thickness of the adhesive layer decreases. Therefore, there is a strong demand for the development of a pressure-sensitive adhesive sheet having high adhesive strength even under thin film conditions.
• Patent Document 1 discloses a pressure-sensitive adhesive sheet comprising a thin pressure-sensitive adhesive film containing a certain amount of a monomer having a carboxyl group and having a predetermined weight-average molecular weight and gel fraction.
• Patent Document 2 discloses a thin-film pressure-sensitive adhesive sheet using a pressure-sensitive adhesive containing an acrylic copolymer containing n-butyl (meth)acrylate and a synthetic hydrocarbon-based tackifying resin.
• An embodiment of the present invention is a pressure-sensitive adhesive that exhibits high adhesive strength to both high-polarity adherends and low-polarity adherends, even if it is a thin film, and is also excellent in holding power and curved surface adhesion. and provide adhesive sheets.
• the copolymer (A) includes an alkyl (meth)acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, and a (meth)acrylate (a2) having no reactive functional group and having an aliphatic cyclic structure.
• the (meth)acrylate (a3) having a carboxyl group includes (meth)acrylate (a3-1) represented by general formula (1) and (meth)acrylate (a3-2) represented by general formula (2).
• a pressure-sensitive adhesive composition comprising at least one of (In the formula, R 1 is a hydrogen atom or a methyl group, m is an integer of 2 to 10, and n is an integer of 1 to 5.) (In the formula, R 2 is a hydrogen atom or a methyl group, R 3 is a divalent hydrocarbon group, and p is an integer of 1 to 5.) [2] The pressure-sensitive adhesive composition according to [1] above, wherein the (meth)acrylate (a3) contains a (meth)acrylate (a3-2) represented by the general formula (2). [3] The adhesive composition according to [1] or [2] above, wherein the copolymer (A) has an acid value in the range of 0.1 to 24.0 mgKOH/g.
• tackifying resin contains at least one selected from the group consisting of a rosin-based tackifying resin, a synthetic hydrocarbon-based tackifying resin, and a terpene-phenol-based tackifying resin.
• the pressure-sensitive adhesive composition according to any one of [5].
• Adhesive sheets can be provided.
• the disclosure of the present application relates to the subject matter described in Japanese Patent Application No. 2021-107190 filed on June 29, 2022, and the entire disclosure content thereof is incorporated herein by reference.
• (Meth)acrylic acid includes acrylic acid and methacrylic acid.
• (Meth)acrylates include acrylates and methacrylates.
• a monomer is a monomer having an ethylenically unsaturated double bond.
• the adherend refers to the other party to which the pressure-sensitive adhesive sheet is attached.
• the various components described herein may be used singly or in combination of two or more.
• the adhesive composition that is one embodiment of the present invention contains a copolymer (A) and a curing agent (B).
• the copolymer (A) includes an alkyl (meth)acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, and a (meth)acrylate (a2) having no reactive functional group and having an aliphatic cyclic structure. ) and a monomer mixture containing a (meth)acrylate (a3) having a carboxyl group.
• the (meth)acrylate (a3) having a carboxyl group includes (meth)acrylate (a3-1) represented by general formula (1) and (meth)acrylate (a3-2) represented by general formula (2).
• R 1 is a hydrogen atom or a methyl group
• m is an integer of 2 to 10
• n is an integer of 1 to 5.
• R 2 is a hydrogen atom or a methyl group
• R 3 is a divalent hydrocarbon group
• p is an integer of 1 to 5.
• the polarity of the copolymer is lowered to Adhesion can be improved, and at the same time, compatibility with low-polarity tackifying resins can be improved.
• a (meth)acrylate having a carboxyl group represented by general formula (1) or general formula (2) cohesion and flexibility can be imparted to the pressure-sensitive adhesive layer.
• the copolymer (A) includes an alkyl (meth)acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, and a (meth)acrylate (a2) having no reactive functional group and having an aliphatic cyclic structure. , and a (meth)acrylate (a3) having a carboxyl group, and optionally a (meth)acrylate (a4) having a hydroxyl group and other monomers as optional monomers, obtained by polymerizing a monomer mixture It is a copolymer.
• the acid value of the copolymer (A) is preferably 0.1-24.0 mgKOH/g, more preferably 0.2-20.0 mgKOH/g.
• the acid value of the copolymer (A) is 0.1 to 24.0 mgKOH/g, the cohesive force and flexibility of the adhesive layer can be imparted in a well-balanced manner, and the adhesive force, holding force, and curved surface It becomes easier to achieve both adhesiveness.
• (Meth)acrylate (a1) is an alkyl (meth)acrylate having an alkyl group having 4 to 12 carbon atoms.
• (Meth)acrylate (a1) is preferably 60% by mass or more, more preferably 70% by mass or more in 100% by mass of the monomer mixture based on the total mass of the monomer mixture (100% by mass). you can On the other hand, the content may be preferably 99% by mass or less, more preferably 98% by mass or less, still more preferably 95% by mass or less, and even more preferably 92% by mass or less.
• the content of (meth)acrylate (a1) is preferably 60 to 99% by mass, more preferably 70 to 98% by mass, based on 100% by mass of the monomer mixture.
• (meth)acrylate (a1) is an alkyl group having 4 to 7 carbon atoms ( It preferably contains a meth)acrylate (a-1) and an alkyl (meth)acrylate (a-2) having an alkyl group with 8 to 12 carbon atoms.
• alkyl (meth)acrylate (a-1) having an alkyl group having 4 to 7 carbon atoms examples include n-butyl (meth)acrylate, isobutyl (meth)acrylate, and n-hexyl (meth)acrylate. .
• n-butyl (meth)acrylate is preferred from the viewpoint of achieving both adhesive strength and holding power.
• alkyl (meth)acrylate (a-2) having an alkyl group having 8 to 12 carbon atoms examples include 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl ( meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate and the like.
• 2-ethylhexyl (meth)acrylate is preferred from the viewpoint of achieving both adhesive strength and holding power.
• (Meth)acrylate (a2) is a (meth)acrylate having no reactive functional group and having an alicyclic structure.
• (Meth)acrylate (a2) is preferably used in a content of 1 to 20% by mass based on 100% by mass of the monomer mixture. The above content is more preferably 2 to 15% by mass.
• (Meth)acrylate (a2) is characterized by not having a reactive functional group other than an acryloyl group.
• reactive functional groups include carboxyl groups, hydroxyl groups, amino groups, and epoxy groups.
• Aliphatic cyclic structures include, for example, a cyclohexyl group, a dicyclopentenyl group, a dicyclopentanyl group, and an isobornyl group. From the viewpoint of improving adhesive strength to low-polar adherends and compatibility with tackifying resins, it is preferable to have a dicyclopentenyl group, a dicyclopentanyl group, or an isobornyl group as the aliphatic cyclic structure.
• (Meth)acrylates (a2) include, for example, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.
• dicyclopentenyl (meth)acrylate and dicyclopentanyl having a three-dimensional aliphatic cyclic structure from the viewpoint of improving the adhesive strength to low-polar adherends and compatibility with tackifying resins (Meth)acrylates and isobornyl (meth)acrylates are preferred, and isobornyl (meth)acrylates are more preferred.
• [(meth)acrylate (a3)] is a (meth)acrylate having a carboxyl group, and (meth)acrylate (a3-1) represented by general formula (1) and general formula (2) (meth) ) contains at least one of acrylates (a3-2). Among them, it is more preferable to contain (meth)acrylate (a3-2) represented by formula (2) from the viewpoint of obtaining adhesive strength to both high-polarity adherends and low-polarity adherends.
• (Meth)acrylate (a3) is preferably used in a content of 0.1 to 10% by mass based on 100% by mass of the monomer mixture.
• the above content is more preferably 0.2 to 8% by mass.
• Metalacrylate (a3-1) is a (meth)acrylate represented by general formula (1).
• R 1 is a hydrogen atom or a methyl group
• m is an integer of 2 to 10
• n is an integer of 1 to 5.
• m represents an integer of 2-10.
• m is an integer of 2 to 10 from the viewpoint of coexistence of adhesive strength, holding power and curved surface adhesiveness.
• m is preferably an integer of 2-8, more preferably an integer of 3-5.
• n represents an integer of 1-5.
• n may be an integer of 1 to 5, preferably an integer of 2 to 4, from the viewpoint of compatibility between adhesive strength, holding power, and curved surface adhesiveness.
• (Meth)acrylate (a3-1) may be one produced by a conventional method, or one appropriately selected from commercially available monomers.
• (Meth)acrylates (a3-1) include, for example, ⁇ -hydroxyethyl acrylate and ⁇ -carboxypolycaprolactone mono(meth)acrylate. These monomers are commercially available, for example, under the trade names of " ⁇ -CEA” (manufactured by Daicel Ornex) and "Aronix M-5300" (manufactured by Toagosei Co., Ltd.), and these commercial products can be used.
• ((meth) acrylate (a3-2)) (Meth)acrylate (a3-2) is a (meth)acrylate represented by general formula (2).
• R 2 is a hydrogen atom or a methyl group
• R 3 is a divalent hydrocarbon group
• p is an integer of 1 to 5.
• p represents an integer of 1-5.
• p may be an integer of 1 to 5, preferably an integer of 1 to 3, from the viewpoint of compatibility between adhesive strength, holding power, and curved surface adhesiveness.
• R3 represents a divalent hydrocarbon group.
• hydrocarbon groups include saturated aliphatic hydrocarbon groups such as alkylene groups, saturated alicyclic hydrocarbon groups such as cycloalkylene groups, aromatic hydrocarbon groups such as phenylene groups, unsaturated aliphatic hydrocarbon groups, or Examples include unsaturated alicyclic hydrocarbon groups.
• R 3 is preferably a saturated aliphatic hydrocarbon group from the viewpoint of improving adhesion by imparting flexibility.
• R 3 is more preferably an alkylene group, more preferably an alkylene group having 1 to 4 carbon atoms.
• (Meth)acrylate (a3-2) may be one produced by a conventional method, or one appropriately selected from commercially available monomers.
• Examples of (meth)acrylates (a3-2) include 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl fumarate, and 2-(meth)acryloyloxyethyl phthalate. .
• These monomers are, for example, "light ester HO-MS”, “HOA-MS (N)”, “light acrylate HOA-HH (N)” and “HOA-MPL (N)” (manufactured by Kyoeisha Chemical Co., Ltd.). It is marketed as a brand name, and these commercial products can be used.
• (Meth)acrylate (a3) in addition to (meth)acrylate (a3-1) and (meth)acrylate (a3-2), (meth)acrylate (a3-3) having a carboxyl group other than these ) may be further contained.
• Other (meth)acrylates (a3-3) having a carboxyl group include, for example, (meth)acrylic acid.
• (Meth) acrylate (a3-1) and (meth) acrylate (a3-2) are the main chain of the acrylic polymer compared to (meth) acrylates having short carboxyl groups in side chains such as acrylic acid and the carboxyl group are far apart. Therefore, excellent adhesion to a highly polar adherend can be obtained without being disturbed by the large alicyclic structure derived from the (meth)acrylate (a2). In addition, since the side chain is not too long, it is possible to suppress interference with the adhesion of the (meth)acrylate (a2)-derived aliphatic cyclic structure to the low-polar adherend.
• (meth)acrylate (a3) based on the total mass of (meth)acrylate (a3) (100% by mass), other carboxyl groups other than (meth)acrylate (a3-1) and (meth)acrylate (a3-2)
• the content of (meth)acrylate (a3-3) may be 43% by mass or less.
• (meth)acrylate (a3) includes (meth)acrylate (a3-1) and (meth)acrylate (a3-2), and (meth)acrylate (a3-3) having a carboxyl group. and the content of (meth)acrylate (a3-3) in 100% by mass of (meth)acrylate (a3) may be greater than 0.1% by mass and 43% by mass or less.
• (meth)acrylate (a3) contains only (meth)acrylate (a3-1) and (meth)acrylate (a3-2), and (meth)acrylate (a3) having a carboxyl group -3) is not included. That is, the content of (meth)acrylate (a3-3) may be 0% by mass.
• the content of the (meth)acrylate (a3) component other than (meth)acrylate (a3-1) and (meth)acrylate (a3-2) is preferably as low as possible.
• the content of the above components is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total 100% by mass of the (meth)acrylate (a3), and 20% by mass. % or less.
• the above content may be 0% by mass. When the above content is adjusted to 40% by mass or less, excellent adhesion to both highly polar adherends and low polar adherends can be easily obtained, which is preferable.
• [(meth)acrylate (a4)] is a (meth)acrylate having a hydroxyl group.
• the monomer mixture may further contain a (meth)acrylate (a4) having a hydroxyl group.
• Inclusion of a (meth)acrylate (a4) having a hydroxyl group is preferable because cohesive force can be easily expressed and excellent holding power and curved surface adhesiveness can be easily obtained.
• the (meth)acrylate (a4) having a hydroxyl group is preferably used in a content of 0.05 to 3% by mass based on 100% by mass of the monomer mixture. More preferably, the content is 0.1 to 2% by mass.
• the hydroxyl group-containing (meth)acrylate (a4) is used at a content of 0.05 to 3% by mass, the cohesive strength of the pressure-sensitive adhesive layer is improved, making it easier to improve the holding power and adhesion to curved surfaces.
• (Meth)acrylates (a4) having a hydroxyl group include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, Hydroxyalkyl (meth)acrylates such as acid 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate, and polyethylene glycol mono (meth)acrylates, polypropylene glycol mono(meth)acrylates, and glycol mono(meth)acrylates such as 1,4-cyclohexanedimethanol mono(meth)acrylate, and the like.
• 2-hydroxyethyl (meth)acrylate is preferred.
• Other monomers include an alkyl (meth)acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, a (meth)acrylate (a2) having an aliphatic cyclic structure without a reactive functional group, and a carboxyl group. and (meth)acrylates other than (a3) having a hydroxyl group (meth)acrylate (a4) and monomers other than (meth)acrylates.
• Other monomers can be used as long as they do not impair the adhesive strength, holding power, and curved surface adhesiveness of the adhesive. Specific examples thereof include alkyl (meth)acrylates having an alkyl group other than (meth)acrylate (a1). Other specific examples include monomers having an amide bond, monomers having an epoxy group, monomers having an amino group, monomers having an aromatic ring, monomers having an alkoxy(poly)alkylene oxide, and other vinyl monomers.
• Alkyl (meth)acrylate monomers other than the (meth)acrylate (a1) include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-octadecyl ( meth)acrylate, and isooctadecyl (meth)acrylate, and the like.
• the content thereof is preferably 0.1 to 20% by mass in 100% by mass of the monomer mixture.
• Monomers having an amide bond include, for example, (meth)acrylamide, N-methylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropyl(meth)acrylamide, (Meth)acrylamide compounds such as diacetoneacrylamide and N-(butoxymethyl)acrylamide, and heterocyclic ring-containing compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine.
• Examples of monomers having an epoxy group include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and the like.
• Monomers having an amino group are, for example, monoalkylamino (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate. ) acrylates and the like.
• a monomer having an amide bond, a monomer having an epoxy group, and a monomer having an amino group are used, their content is preferably 0.1 to 1% by mass in 100% by mass of the monomer mixture.
• aromatic ring-containing monomers examples include phenoxyethyl acrylate, benzyl acrylate, phenoxydiethylene glycol (meth)acrylate, and ethylene oxide-modified nonylphenol (meth)acrylate.
• a monomer having an aromatic ring When a monomer having an aromatic ring is used, its content is preferably 0.1 to 10% by mass in 100% by mass of the monomer mixture.
• Monomers with alkoxy(poly)alkylene oxides are, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate, methoxypolypropyleneglycol. (Meth)acrylate, ethoxypolypropyleneglycol (meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate, phenoxypolypropyleneglycol (meth)acrylate and the like.
• a monomer having an alkoxy(poly)alkylene oxide When a monomer having an alkoxy(poly)alkylene oxide is used, its content is preferably 0.1 to 10% by mass based on 100% by mass of the monomer mixture.
• vinyl monomers include, but are not limited to, vinyl acetate, acrylonitrile, and the like. When other vinyl monomers are used, their content is preferably 0.1 to 10% by mass in 100% by mass of the monomer mixture.
• the copolymer (A) can be obtained, for example, by adding a polymerization initiator to a monomer mixture and carrying out solution polymerization.
• 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.
• a polymerization initiator it is preferable to add about 0.001 to 1 part by mass of a polymerization initiator to 100 parts by mass of the monomer mixture.
• the polymerization can be carried out at a temperature of about 50° C. to 90° C. for 6 hours to 20 hours under nitrogen stream.
• the weight average molecular weight of the copolymer can be appropriately adjusted by using a chain transfer agent during the polymerization.
• the weight average molecular weight (Mw) of the copolymer (A) is preferably 300,000 to 1,500,000, more preferably 500,000 to 1,300,000, and even more preferably 600,000 to 1,200,000.
• Mw is adjusted in the range of 300,000 to 1,500,000, it becomes easy to achieve compatibility between adhesive strength, holding power, and curved surface adhesiveness.
• the weight average molecular weight described in this specification is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).
• 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, ⁇ -methyl Styrene 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.
• Polymerization initiators are generally azo compounds and organic peroxides.
• 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 include, for example, benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, Carbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionylperoxide, diacetylperoxide and the like.
• the adhesive composition further contains a curing agent (B).
• a curing agent By including a curing agent, cohesive force can be improved, and holding power and curved surface adhesion can be improved to a practical level.
• Curing agents (B) include, for example, isocyanate curing agents, epoxy curing agents, aziridine curing agents, metal chelate curing agents, amine curing agents, and amino resin curing agents. Among these, at least one selected from the group consisting of isocyanate-based curing agents, epoxy-based curing agents, and metal chelate-based curing agents can be used in order to obtain better holding power and curved surface adhesion. preferable.
• Isocyanate-based 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, triphenylmethane triisocyanate.
• 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 diol.
• glycidyl 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.
• Metal chelate-based curing agents are, 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. etc.
• the content of the isocyanate-based curing agent in the curing agent (B) is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the acrylic copolymer.
• the content of the epoxy curing agent is preferably 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the acrylic copolymer.
• the content of the metal chelate curing agent is preferably 0.1 to 2 parts by mass.
• the adhesive composition may further comprise a tackifying resin.
• tackifying resins include rosin-based tackifying resins, synthetic hydrocarbon-based tackifying resins, terpene-based tackifying resins, and terpene-phenol-based tackifying resins. It preferably contains at least one selected from the group consisting of hydrocarbon-based tackifying resins and terpene-phenol-based tackifying resins.
• the adhesive force can be further improved.
• a rosin-based tackifying resin and a synthetic hydrocarbon-based tackifying resin in combination it is easier to achieve both compatibility and adhesive strength to high-polarity adherends and low-polarity adherends. preferred to become
• Rosin-based tackifying resins include rosin esters obtained by esterifying unmodified rosins such as gum rosin, tall oil rosin, and wood rosin with alcohol; Disproportionated rosin esters obtained by further esterifying these modified rosins with alcohol, modified rosin esters such as polymerized rosin esters and hydrogenated rosin esters, and rosin phenol obtained by adding phenol to the unmodified rosin are preferred. Among these, rosin esters and modified rosin esters are preferred because they further improve adhesive strength and transparency. In the rosin ester and the modified rosin ester, some hydroxyl groups of the alcohol used for esterification may remain unreacted.
• alcohols used for esterification include monofunctional alcohols such as methanol, bifunctional alcohols such as ethylene glycol, trifunctional alcohols such as glycerin, and tetrafunctional alcohols such as pentaerythritol. Considering the compatibility with the acrylic copolymer, tri- or less functional alcohols are preferred.
• Synthetic hydrocarbon-based tackifying resins include, for example, coumarone-based resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum-based resins.
• styrene-based resins are preferable because they have good compatibility with acrylic polymers and can further improve adhesive performance.
• the tackifying resin used in the pressure-sensitive adhesive composition includes a rosin-based tackifying resin and a synthetic hydrocarbon-based resin from the viewpoint of achieving both high-polarity adherend and low-polarity adherend strength.
• Tackifying resins are preferred.
• Synthetic hydrocarbon-based tackifying resins are more preferred.
• the softening point of the tackifying resin is preferably 80°C or higher, more preferably 90°C or higher. Moreover, the upper limit of the softening point is preferably 170°C, more preferably 160°C, and even more preferably 155°C. When the softening point of the tackifier resin is 80 to 170° C., it becomes easy to achieve both high levels of adhesive strength and holding power.
• the softening point is the softening temperature measured according to the dry bulb method specified in JISK5902.
• the tackifying resin is preferably used in a proportion of 10 to 50 parts by mass, more preferably 15 to 40 parts by mass, per 100 parts by mass of the copolymer (A).
• the tackifying resin is used in a proportion of 10 to 50 parts by mass, it is possible to more easily achieve both adhesive strength, cohesive strength, and curved surface adhesiveness.
• the pressure-sensitive adhesive composition can further include a polyolefin.
• the pressure-sensitive adhesive composition contains polyolefin, the adhesive strength to low-polar adherends made of polyolefin can be improved.
• Chlorinated polyolefins include, for example, chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic-modified chlorinated polypropylene, chlorinated polyethylene, and chlorinated ethylene-vinyl acetate copolymer.
• chlorinated polypropylene chlorinated polypropylene, acid-modified chlorinated polypropylene, and acrylic-modified chlorinated polypropylene are preferable from the viewpoint of excellent solubility and high adhesion to polyolefin adherends.
• Chlorinated polypropylene is more preferred.
• the chlorine content in the chlorinated polyolefin is preferably 20% or more and 45% or less, more preferably 28% or more and 45% or less, from the viewpoint that the effect of improving the adhesive strength to low-polar polyolefin adherends is high.
• Non-chlorinated polyolefins include, for example, polyethylene, polypropylene, ⁇ -olefin-propylene copolymer, ethylene-vinyl acetate copolymer, polybutene, maleated polypropylene, maleated polybutene, polybutadiene and its hydrides, polyisoprene and its hydrides, maleated polybutadiene, maleated polyisoprene, polybutadiene polyol and its hydride, polyisoprene polyol and its hydride, process oil and lubricating oils such as liquid paraffin, and the like.
• ⁇ -olefin-polypropylene copolymer, maleated polypropylene, polybutene, and lubricating oil are preferable from the viewpoint of excellent solubility and high adhesion to polyolefin adherends.
• lubricating oil paraffinic lubricating oil, naphthenic lubricating oil and the like are preferable.
• chlorinated polyolefin is preferable from the viewpoint of excellent solubility and high adhesive strength to polyolefin adherends. Among them, chlorinated polypropylene is more preferable.
• the polyolefin is preferably used in a proportion of 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, per 100 parts by mass of the copolymer (A).
• polyolefin is used in a proportion of 0.01 to 10 parts by mass, it is possible to more easily achieve both adhesive strength, cohesive strength, and curved surface adhesion to low-polar adherends.
• the pressure-sensitive adhesive composition further contains, as optional components, a flame retardant auxiliary, a heat stabilizer, a weather stabilizer, an anti-aging agent, an ultraviolet absorber, a leveling agent, an antistatic agent, a slip agent, an anti-blocking agent, and an anti-fogging agent. , lubricants, dyes, waxes, emulsions, magnetics, and dielectric property modifiers.
• Adhesive Sheet Another embodiment of the present invention relates to an adhesive sheet provided with an adhesive layer formed from the adhesive composition of the above embodiment.
• the pressure-sensitive adhesive sheet preferably includes a substrate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition (hereinafter sometimes referred to as pressure-sensitive adhesive) of the above-described embodiment.
• 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 substrate and a core material are preferable.
• the pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive onto a substrate and drying it.
• it can be formed by coating a release sheet with a pressure-sensitive adhesive, drying it to form a pressure-sensitive adhesive layer, and then laminating the substrate.
• a peelable sheet is usually adhered to the surface of the pressure-sensitive adhesive layer that does not come into contact with the base material, and the adhesive layer is stored.
• the viscosity can be adjusted by adding the solvent previously described in the solution polymerization.
• the base material is preferably cellophane, plastic, rubber, foam, fabric, rubberized fabric, resin-impregnated fabric, glass, wood, or the like.
• 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.
• the base material one type can be used alone, or a laminate in which two or more types are combined can be used.
• the above plastics include, for example, polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefins, polyolefins such as ethylene-vinyl acetate copolymer, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polycarbonates, polynorbornene, polyarylate, polyacryl, polyphenylene sulfide, polystyrene, polyamide, polyimide, and the like.
• the method of applying the adhesive is not particularly limited. mentioned. It is preferable to carry out a drying process during coating.
• the drying device 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 160°C.
• the thickness of the adhesive layer is preferably 1 to 20 ⁇ m, more preferably 1 to 15 ⁇ m, even more preferably 1 to 10 ⁇ m.
• the pressure-sensitive adhesive composition of the above embodiment can obtain excellent properties in terms of all of adhesive strength, holding power, and curved surface adhesion, even when the thickness is as thin as 1 to 20 ⁇ m.
• the pressure-sensitive adhesive sheet which is one embodiment of the present invention, can be used for various purposes regardless of the adherend.
• the adherend can be a variety of adherends ranging from highly polar to less polar, such as plastics such as polyolefins, glass, cardboard, and metals.
• the weight average molecular weight (Mw) and acid value of the copolymer were measured by the following methods. ⁇ Measurement of weight average molecular weight (Mw)> GPC was used to measure the weight average molecular weight.
• GPC is liquid chromatography for separating and quantifying a substance dissolved in a solvent (THF; tetrahydrofuran) based on the difference in molecular size, and the weight average molecular weight was determined in terms of polystyrene.
• Apparatus name Shimadzu Corporation, LC-GPC system "Prominence" Column: 4 columns of GMHXL manufactured by Tosoh Corporation and 1 column of HXL-H manufactured by Tosoh Corporation were connected in series.
• Mobile phase solvent Tetrahydrofuran Flow rate: 1.0 ml/min Column temperature: 40°C
• Acid value ⁇ (5.61 ⁇ a ⁇ F) / S ⁇ / (non-volatile content / 100)
• S Sample collection amount
• a consumption of 0.1N-alcoholic potassium hydroxide solution
• F Factor of 0.1N-alcoholic potassium hydroxide solution
• reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube (hereinafter simply referred to as "reaction vessel") was charged with 20 parts of 2-ethylhexyl acrylate, n- 70.8 parts of butyl acrylate, 5 parts of isobornyl acrylate, 0.2 parts of 2-hydroxyethyl acrylate, ⁇ -carboxypolycaprolactone monoacrylate (manufactured by Toagosei Co., Ltd., Aronix M-5300) 2 parts, 2-acryloyloxyethyl 2 parts of succinic acid (HOA-MS (N), manufactured by Kyoeisha Chemical Co., Ltd.), 70 parts of ethyl acetate, and 0.015 part of 2,2'-azobisisobutyronitrile were charged respectively.
• reaction vessel was charged with 20 parts of 2-ethylhexyl acrylate, n- 70.8
• Copolymers (A-2 to 11, A'-1 to 4) were prepared in the same manner as for copolymer (A-1), except that the types and amounts of monomers were changed as shown in Table 1. got
• reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube (hereinafter simply referred to as "reaction vessel") was charged with 20 parts of 2-ethylhexyl acrylate, n- 70.8 parts of butyl acrylate, 5 parts of isobornyl acrylate, 0.2 parts of 2-hydroxyethyl acrylate, 4 parts of 2-acryloyloxyethyl succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., HOA-MS (N)), 35 parts of ethyl acetate 35 parts of methyl ethyl ketone and 0.015 part of 2,2'-azobisisobutyronitrile were charged.
• the resulting pressure-sensitive adhesive composition was coated on a release sheet (made of polyethylene terephthalate) having a thickness of 38 ⁇ m using a comma coater so that the thickness after drying was 10 ⁇ m, and the composition was heated at 100° C. for 2 minutes. An adhesive layer was formed by drying. Next, a 25 ⁇ m thick substrate (made of polyethylene terephthalate, hereinafter referred to as a PET sheet) is attached to this adhesive layer, and aged for 1 week at a temperature of 23 ° C. and a relative humidity of 50%. A pressure-sensitive adhesive sheet having a structure of "adhesive sheet/adhesive layer/PET sheet" was obtained.
• Examples 2 to 25, Comparative Examples 1 to 4 The adhesive compositions and adhesive sheets of Examples 2 to 25 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the composition and blending amount were changed as shown in Tables 2 and 3. .
• Adhesive Sheet was evaluated by the following methods. Tables 2 and 3 show the results.
• (1) Adhesive strength The obtained adhesive sheet was prepared in a size of 25 mm in width and 100 mm in length. In an atmosphere of 23° C. and a relative humidity of 50%, the peelable sheet was peeled off from the adhesive sheet, and the exposed adhesive layer was attached to a stainless steel (SUS) plate and crimped once with a 2 kg roll. After being left for 24 hours, the adhesive strength was measured in a 180° peel test in which a tensile tester was used to peel off at a speed of 300 mm/min in the direction of 180°, and evaluation was performed based on the following evaluation criteria.
• SUS stainless steel
• Adhesive strength is 12 N or more
• very good B Adhesive strength is 10 N or more and less than 12 N
• good C Adhesive strength is 6 N or more and less than 10 N
• practical D Adhesive strength is less than 6 N
• Impractical Adhesive strength was measured with respect to a polypropylene (PP) plate in the same manner as described above, and evaluation was performed based on the following evaluation criteria.
• Adhesive strength is 12 N or more, very good B: Adhesive strength is 10 N or more and less than 12 N, good C: Adhesive strength is 6 N or more and less than 10 N, practical D: Adhesive strength is less than 6 N, impractical
• the obtained pressure-sensitive adhesive sheet was cut into a size of 25 mm in width and 100 mm in length to obtain a sample. Then, in an atmosphere of 23° C. and a relative humidity of 50%, the release sheet was peeled off from the sample according to JIS Z 0237, and the exposed 25 mm wide and 25 mm long tip portion of the adhesive layer was attached to a polished stainless steel (SUS) plate. After pressing once with a 2 kg roll, a load of 1 kg was applied in an atmosphere of 70° C. and held for 70,000 seconds. The evaluation indicates the number of seconds when the sample dropped from the SUS plate.
• SUS polished stainless steel
• the pressure-sensitive adhesive sheet according to one embodiment of the present invention has excellent adhesion to both a stainless steel plate, which is a high-polarity adherend, and a polypropylene plate, which is a low-polarity adherend. It was confirmed that the strength and curved surface adhesiveness were also excellent. On the other hand, the pressure-sensitive adhesive sheets of the comparative examples were found to be unsatisfactory in any of the evaluation items, indicating that there is a problem in practical use and that they are not practical.

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