Aqueous binder composition for organic fibers, organic fiber aggregate, and pressure-sensitive adhesive sheet

Abstract

To provide an aqueous binder composition for organic fibers that enables the formation of an organic fiber aggregate exhibiting superior tensile characteristics and having superior adhesion to hot-melt adhesives.SOLUTION: An aqueous binder composition for organic fibers comprises a (meth)acrylic polymer and a tackifier (excluding the (meth)acrylic polymer). The (meth)acrylic polymer has a glass transition point of 10°C or lower. The content of the tackifier is 0.1 to 50 pts.mass relative to 100 pts.mass of the (meth)acrylic polymer .SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous binder composition for organic fibers, an organic fiber aggregate, and an adhesive sheet.

Background Art

[0002] In organic fiber products such as nonwoven fabrics and paper making, a binder resin for bonding organic fibers is used to enhance the mechanical strength of the organic fiber products. Further, as the binder resin in these organic fiber products, various techniques using (meth)acrylic polymers have been conventionally proposed (see, for example, Patent Document 1 and Patent Document 2).

[0003] Patent Document 1 discloses that in an aqueous composition for nonwoven fabrics containing an acrylic binder and an emulsion of a release agent having a melting point of 50°C or higher, as the acrylic binder, a polymer having a glass transition temperature of -50°C or higher and 20°C or lower and containing an epoxy group and a carboxylic acid group in a predetermined ratio is used. Further, Patent Document 2 discloses that when an acrylic resin dispersion for papermaking is obtained by emulsion-polymerizing a monomer mixture containing an acrylic monomer in the presence of a surfactant, a carboxylate-type anionic surfactant is used as the surfactant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] A base material in which fibers formed from organic fibers are adhered to each other with a binder resin (hereinafter also referred to as an "organic fiber aggregate") may be used as an adhesive tape by applying an adhesive or transferring an adhesive sheet. In recent years, from the viewpoints of environmental aspects and workability, a hot-melt adhesive may be used as a material for forming an adhesive layer provided on the surface of an organic fiber aggregate. However, as a result of investigations by the present inventor, it has been found that an organic fiber aggregate obtained by attaching a (meth)acrylic polymer as a binder resin to a fibrous base material formed from organic fibers has insufficient adhesion to a hot-melt adhesive. Considering the practicality of the organic fiber aggregate and the adhesive sheet using the same, it is required to improve the adhesion of the organic fiber aggregate to a hot-melt adhesive while maintaining good tensile properties of the organic fiber aggregate.

[0006] The present invention has been made in view of the above circumstances, and a main object thereof is to provide an aqueous binder composition for organic fibers capable of obtaining an organic fiber aggregate that exhibits good tensile physical properties and excellent adhesion to a hot-melt adhesive.

Means for Solving the Problems

[0007] The present inventor has found that the above problems can be solved by an aqueous binder composition obtained by containing a specific component together with a (meth)acrylic polymer as a binder resin. Specifically, the following means are provided according to the present invention.

[0008] 〔1〕 An aqueous binder composition for organic fibers, which contains a (meth)acrylic polymer and a tackifier (excluding the (meth)acrylic polymer), wherein the glass transition point of the (meth)acrylic polymer is 10°C or lower, and the content of the tackifier with respect to 100 parts by mass of the (meth)acrylic polymer is 0.1 to 50 parts by mass. 〔2〕 The aqueous binder composition for organic fibers according to 〔1〕, which is for non-woven fabric or papermaking. 〔3〕An aqueous binder composition for organic fibers according to 〔1〕or 〔2〕, having a surface tension of 35 mN / m or less. 〔4〕An aqueous binder composition for organic fibers according to any one of 〔1〕to 〔3〕, wherein the (meth)acrylic polymer contains a structural unit derived from an ethylenically unsaturated monomer having a nitrile group. 〔5〕An aqueous binder composition for organic fibers according to any one of 〔1〕to 〔4〕, wherein the (meth)acrylic polymer contains a structural unit derived from an ethylenically unsaturated monomer having a carboxyl group. 〔6〕An aqueous binder composition for organic fibers according to any one of 〔1〕to 〔5〕, wherein the (meth)acrylic polymer contains a structural unit derived from N - alkoxyalkyl (meth)acrylamide in an amount of 0.1% by mass or more and 2.5% by mass or less based on the total structural units constituting the (meth)acrylic polymer. 〔7〕An aqueous binder composition for organic fibers according to any one of 〔1〕to 〔6〕, wherein the tackifier contains a rosin ester. 〔8〕An organic fiber aggregate in which organic fibers are adhered to each other with the aqueous binder composition for organic fibers according to any one of 〔1〕to 〔7〕. 〔9〕An adhesive sheet comprising an organic fiber layer formed from the organic fiber aggregate of 〔8〕and an adhesive layer formed from a hot - melt type adhesive.

Advantages of the Invention

[0009] According to the aqueous binder composition for organic fibers of the present invention, an organic fiber aggregate having good tensile physical properties (particularly, tensile strength and tensile elongation) and excellent adhesion to a hot - melt type adhesive can be obtained.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. In this specification, “(meth)acrylic” means acrylic and / or methacrylic. “(meth)acrylo” means acrylo and / or methacrylo.

[0011] 《Aqueous Binder Composition for Organic Fibers》 The aqueous binder composition for organic fibers of the present invention (hereinafter, also simply referred to as "aqueous binder composition") is a sizing agent for adhering and bundling organic fibers. For example, it is used as a binder for adhering fibers to each other by attaching the aqueous binder composition to each fiber of a fibrous substrate formed of organic fibers. The aqueous binder composition of the present invention contains a (meth)acrylic polymer and a tackifier (excluding the (meth)acrylic polymer).

[0012] <Organic fiber> The organic fiber may be a fiber mainly composed of an organic material, and the raw material is not particularly limited. Examples of the organic fiber include natural fiber pulp such as wood pulp (pulp derived from woods such as eucalyptus, acacia, pine, cedar, cypress, mulberry, mitsumata, and ganpi), non-wood pulp (linter pulp, bamboo pulp, kenaf pulp, bagasse pulp, palm pulp, etc.); natural fibers such as cotton, hemp, wool, and silk; synthetic fiber pulp such as vinylon synthetic pulp, rayon synthetic pulp, and polyolefin synthetic pulp; synthetic fibers such as polyester, polyamide, nylon, vinylon, and acrylic fiber; regenerated fibers such as rayon, cupra, and tencel; and semi-synthetic fibers such as acetate, triacetate, and promix. According to the aqueous binder composition of the present invention, while maintaining the flexibility and texture of the fibrous substrate formed of organic fibers, it can enter the gaps between the fibers to bind the fibers together and impart excellent tensile properties (particularly, tensile strength and tensile elongation) to the fibrous substrate. Such an aqueous binder composition of the present invention is particularly suitable as a binder composition for non-woven fabric or paper-making for bundling the fibers of the non-woven fabric or paper.

[0013] Next, the (meth)acrylic polymer and tackifier contained in the aqueous binder composition of the present invention, and any components (hereinafter, also referred to as "other components") optionally blended will be described in detail.

[0014] <(Meth)acrylic polymer> (Glass transition point) The (meth)acrylic polymer contained in the aqueous binder composition has a glass transition point (Tg) of 10°C or lower. If the glass transition point of the (meth)acrylic polymer is higher than 10°C, when organic fibers are adhered to each other with the aqueous binder composition to form an organic fiber aggregate, sufficient adhesion to the hot melt type adhesive cannot be ensured. For this reason, when a hot melt type adhesive is applied to the organic fiber aggregate to form an adhesive sheet, peeling may easily occur between the organic fiber aggregate and the hot melt type adhesive.

[0015] From the viewpoint of obtaining an organic fiber aggregate having excellent adhesion to the hot melt type adhesive, the glass transition point of the (meth)acrylic polymer is preferably 5°C or lower, more preferably 0°C or lower, still more preferably -5°C or lower, even more preferably -10°C or lower, yet even more preferably -20°C or lower, and still even more preferably -30°C or lower. The lower limit of the glass transition point of the (meth)acrylic polymer is not particularly limited, but in terms of obtaining a fiber aggregate having better tensile strength and elongation at break and even better adhesion to the hot melt type adhesive, -80°C or higher is preferred. The glass transition point of the (meth)acrylic polymer is more preferably -70°C or higher, still more preferably -65°C or higher, even more preferably -60°C or higher, and yet even more preferably -55°C or higher.

[0016] In this specification, the method for calculating the glass transition point of the (meth)acrylic polymer is as follows: according to the following mathematical formula (1). 1 / Tg=(Wa / Tga)+(Wb / Tgb)+(Wc / Tgc)+… (1) Here, in the above mathematical formula (1), Tg is the glass transition point of the (meth)acrylic polymer (unit: K), Tga, Tgb, Tgc, etc. are the glass transition points of the homopolymers of the respective monomers a, b, c, etc. (unit: K), and Wa, Wb, Wc, etc. represent the mass fractions of the respective monomers a, b, c, etc. in the copolymer. Also, the glass transition points of the homopolymers of the respective monomers are referred to the values described in "POLYMER HANDBOOK 4th Edition" (published by John Wiley & Sons, Inc.).

[0017] (Monomer) (Meth)acrylic polymers may be polymers mainly composed of structural units derived from (meth)acrylic compounds, and the monomers constituting the polymers are not particularly limited. As the monomers constituting the (meth)acrylic polymer, various ethylenically unsaturated monomers including (meth)acrylic compounds can be applied. Examples of the ethylenically unsaturated monomers constituting the (meth)acrylic polymer include (meth)acrylic acid esters, carboxyl group-containing unsaturated compounds, unsaturated acid anhydrides, (meth)acrylic acid hydroxyalkyl esters, amide group-containing unsaturated compounds, nitrile group-containing unsaturated compounds, sulfonic acid group-containing unsaturated compounds, esters of (meth)acrylic acid containing a polyalkylene oxide skeleton, aromatic vinyl compounds, and the like.

[0018] As specific examples of these, compounds in which a hydrogen atom in the carboxyl group of (meth)acrylic acid is replaced by a hydrocarbon group having 1 to 18 carbon atoms can be mentioned as (meth)acrylic acid esters. Further specific examples of (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and octadecyl (meth)acrylate; aliphatic cyclic esters of (meth)acrylic acid such as cyclohexyl (meth)acrylate and methylcyclohexyl (meth)acrylate; aromatic esters of (meth)acrylic acid such as phenyl (meth)acrylate and benzyl (meth)acrylate. From the viewpoints of polymerizability and availability, etc., compounds in which the hydrocarbon group in the ester moiety has 1 to 12 carbon atoms are more preferable as (meth)acrylic acid esters, and it is more preferable to contain compounds having 4 to 12 carbon atoms in terms of sufficiently lowering the glass transition point of the (meth)acrylic polymer.

[0019] In the (meth)acrylic polymer, the proportion of the structural unit derived from the (meth)acrylic acid ester is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, even more preferably 60% by mass or more, yet even more preferably 70% by mass or more, still even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total amount of the structural units constituting the (meth)acrylic polymer. By setting the structural unit derived from the (meth)acrylic acid ester within the above range in the (meth)acrylic polymer, a polymer excellent in strength and transparency can be obtained.

[0020] In addition, among the (meth)acrylic acid esters that constitute the (meth)acrylic polymer, the proportion of the (meth)acrylic acid ester having a hydrocarbon group with 4 to 12 carbon atoms in the ester moiety is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, even more preferably 60% by mass or more, yet even more preferably 70% by mass or more, and still even more preferably 80% by mass or more, based on the total amount of the (meth)acrylic acid esters that constitute the (meth)acrylic polymer.

[0021] The carboxyl group-containing unsaturated compound may be any ethylenically unsaturated monomer having a carboxyl group. Examples of the carboxyl group-containing unsaturated compound include unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, itaconic acid, and fumaric acid. Among these, (meth)acrylic acid is preferred in terms of polymerizability and ease of handling.

[0022] The (meth)acrylic polymer preferably contains a structural unit derived from a carboxyl group-containing unsaturated compound. By the (meth)acrylic polymer containing a structural unit derived from a carboxyl group-containing unsaturated compound, it is preferable in terms of being able to stably disperse the (meth)acrylic polymer in a particulate state in an aqueous medium, and in terms of being able to enhance the adhesion to a hot melt type adhesive in an organic fiber aggregate obtained using the aqueous binder composition. From the viewpoint of obtaining a stable aqueous dispersion of particles and further enhancing the adhesion to a hot melt type adhesive, the proportion of the structural unit derived from the carboxyl group-containing unsaturated compound is preferably 0.1 to 10% by mass, more preferably 0.5 to 10% by mass, still more preferably 0.5 to 5.0% by mass, and even more preferably 0.5 to 2.5% by mass, based on the total amount of the structural units that constitute the (meth)acrylic polymer. The carboxyl group-containing unsaturated compound that constitutes the (meth)acrylic polymer is particularly preferably (meth)acrylic acid.

[0023] Examples of the (meth)acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the unsaturated acid anhydride include maleic anhydride and itaconic anhydride.

[0024] Examples of the amide group-containing unsaturated compound include (meth)acrylamide, N-methylol (meth)acrylamide, and N-alkoxyalkyl (meth)acrylamide. Examples of the N-alkoxyalkyl (meth)acrylamide include N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-isobutoxymethyl (meth)acrylamide.

[0025] (Meta)acrylic polymers preferably contain structural units derived from N - alkoxyalkyl (meth)acrylamide. When the (meta)acrylic polymer contains structural units derived from N - alkoxyalkyl (meth)acrylamide, in the organic fiber aggregate formed by attaching the aqueous binder composition to the fibrous substrate, the balance between the adhesion to the hot - melt adhesive and the tensile strength can be maintained better. From the viewpoint of making the adhesion to the hot - melt adhesive and the tensile strength more excellent, the (meta)acrylic polymer preferably contains 0.1 to 5.0% by mass of the structural units derived from N - alkoxyalkyl acrylamide based on the total amount of the structural units constituting the (meta)acrylic polymer. The proportion of the structural units derived from N - alkoxyalkyl (meth)acrylamide is more preferably 0.1 to 2.5% by mass, still more preferably 0.1 to 2.0% by mass, and even more preferably 0.2 to 2.0% by mass based on the total amount of the structural units constituting the (meta)acrylic polymer. Among N - alkoxyalkyl (meth)acrylamides, N - methoxymethylacrylamide is particularly preferred.

[0026] The nitrile - group - containing unsaturated compound may be any ethylenically unsaturated monomer having a nitrile group. Examples of the nitrile - group - containing unsaturated compound include acrylonitrile, methacrylonitrile, α - ethylacrylonitrile, α - isopropylacrylonitrile, and the like.

[0027] (Meta)acrylic polymers preferably contain structural units derived from nitrile group-containing unsaturated compounds. When the (meta)acrylic polymer contains structural units derived from nitrile group-containing unsaturated compounds, the balance between the adhesive strength and the tensile strength of the (meta)acrylic polymer (and thus the organic fiber aggregate formed by attaching the aqueous binder composition to the fibrous substrate) can be maintained better. From the above viewpoints, the proportion of the structural units derived from nitrile group-containing unsaturated compounds is preferably 1.0 to 10% by mass, more preferably 1 to 8.0% by mass, still more preferably 1.0 to 7.0% by mass, even more preferably 1.0 to 5.0% by mass, and still even more preferably 1.5 to 5.0% by mass, based on the total amount of the structural units constituting the (meta)acrylic polymer. Among the nitrile group-containing unsaturated compounds constituting the (meta)acrylic polymer, acrylonitrile is particularly preferred.

[0028] Examples of the sulfonic acid group-containing unsaturated compounds include (meth)acryloxybenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, sulfoethyl acrylate, allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, p-styrenesulfonic acid, and the like.

[0029] Examples of the (meth)acrylate ester containing a polyalkylene oxide skeleton include mono(meth)acrylate esters of polyalkylene glycol (the number of alkylene glycol units is 2 or more) such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol mono(meth)acrylate, polyethylene glycol polybutylene glycol mono(meth)acrylate, polypropylene glycol polybutylene glycol mono(meth)acrylate, and polyethylene glycol polypropylene glycol polybutylene glycol mono(meth)acrylate; and mono(meth)acrylate esters of alkoxypolyalkylene glycol such as methoxypolyethylene glycol mono(meth)acrylate, methoxypolypropylene glycol mono(meth)acrylate, methoxypolybutylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, ethoxypolypropylene glycol mono(meth)acrylate, and ethoxypolybutylene glycol mono(meth)acrylate.

[0030] Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, β-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylxylene, and vinylnaphthalene.

[0031] Examples of the monomer constituting the (meth)acrylic polymer include, in addition to the above, vinyl ester monomers such as vinyl acetate and vinyl propionate; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, and vinyl phenyl ether; N-vinylpyrrolidone; and vinylpyridine.

[0032] (Meth)acrylic polymers may be crosslinked if necessary. The method for introducing a crosslinked structure into the (meth)acrylic polymer is not particularly limited. Examples of the method for introducing a crosslinked structure into the (meth)acrylic polymer include, for example, a method by reaction of a polymer having reactive functional groups such as a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group, and a carbonyl group with a crosslinking agent. Also, a method of copolymerizing a crosslinkable monomer having two or more vinyl groups in one molecule; a method of copolymerizing a monomer having a self-crosslinkable functional group, etc. can also introduce a crosslinked structure into the (meth)acrylic polymer. Here, examples of the crosslinkable monomer include methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, etc. Examples of the monomer having a self-crosslinkable functional group include a monomer containing a methylol group and a monomer containing a hydrolyzable silyl group, etc.

[0033] The crosslinking agent may be a compound having a functional group (i.e., a crosslinkable functional group) capable of reacting with the reactive functional group introduced into the (meth)acrylic polymer, and is not particularly limited. Specific examples of the crosslinking agent include, for example, one or more selected from crosslinking agents such as epoxy-based, isocyanate-based, hydrazide-based, carbodiimide-based, oxazoline-based, and metal crosslinking-based crosslinking agents can be used. The amount of the crosslinking agent used can be appropriately adjusted depending on the intended use and performance. For example, it can be 0.05 to 10 parts by mass, and may be 0.1 to 5.0 parts by mass, based on 100 parts by mass of the (meth)acrylic polymer.

[0034] In the (meth)acrylic polymer, the content of the structural unit derived from the (meth)acrylic compound is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, yet more preferably 85% by mass or more, and still even more preferably 90% by mass or more, based on all the structural units constituting the (meth)acrylic polymer. When the structural unit derived from the (meth)acrylic compound in the (meth)acrylic polymer is within the above range, it is preferable in that a polymer excellent in strength and transparency can be obtained. The (meth)acrylic compound constituting the (meth)acrylic polymer may be only one kind or two or more kinds. The (meth)acrylic compound refers to a compound having a (meth)acryloyl group and includes a compound having a (meth)acrylamide group (for example, (meth)acrylamide, etc.).

[0035] Particularly preferred monomers that can be introduced into the (meth)acrylic polymer include n-butyl acrylate and 2-ethylhexyl acrylate. In the (meth)acrylic polymer, the proportion of the structural unit derived from either or both of n-butyl acrylate and 2-ethylhexyl acrylate is preferably 35% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, even more preferably 70% by mass or more, yet more preferably 80% by mass or more, and still even more preferably 90% by mass or more, based on the total amount of the structural units constituting the (meth)acrylic polymer, in that the adhesion between the organic fiber aggregate formed using the aqueous binder composition and the hot melt type adhesive can be made better.

[0036] Further, the (meth)acrylic polymer preferably has a structural unit derived from acrylonitrile in an amount of 1.0 to 10% by mass based on the total amount of the structural units constituting the (meth)acrylic polymer. When the (meth)acrylic polymer has a structural unit derived from acrylonitrile within the above range, the balance between the adhesive strength and the tensile strength of the (meth)acrylic polymer can be maintained well. From the above viewpoints, the proportion of the structural unit derived from acrylonitrile is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and still more preferably 5.0% by mass or less based on the total amount of the structural units constituting the (meth)acrylic polymer.

[0037] The (meth)acrylic polymer preferably contains a structural unit derived from (meth)acrylic acid in an amount of 0.1 to 10% by mass based on the total amount of the structural units constituting the (meth)acrylic polymer. When the (meth)acrylic polymer has a structural unit derived from (meth)acrylic acid within the above range, the (meth)acrylic polymer can be stably dispersed in an aqueous medium in the form of particles. From the viewpoint of obtaining a stable aqueous dispersion of particles, the proportion of the structural unit derived from (meth)acrylic acid is more preferably 0.5 to 10% by mass, still more preferably 0.5 to 5.0% by mass, and even more preferably 0.5 to 2.5% by mass based on the total amount of the structural units constituting the (meth)acrylic polymer.

[0038] Further, the (meth)acrylic polymer preferably contains a structural unit derived from N-alkoxymethylacrylamide in an amount of 0.1 to 5.0% by mass based on the total amount of the structural units constituting the (meth)acrylic polymer. When the proportion of the structural unit derived from N-alkoxymethylacrylamide is within the above range, the balance between the adhesion between the organic fiber aggregate and the hot-melt type adhesive and the tensile strength of the organic fiber aggregate can be maintained better. Among them, N-methoxymethylacrylamide is particularly preferred. The proportion of the structural unit derived from N-alkoxymethylacrylamide is more preferably 0.1 to 2.0% by mass, and still more preferably 0.2 to 2.0% by mass based on the total amount of the structural units constituting the (meth)acrylic polymer.

[0039] (Method for producing (meth)acrylic polymer) (Meth)acrylic polymers can be obtained by polymerizing one or more monomers according to known polymerization methods. There are no particular restrictions on the polymerization method. For example, they can be obtained in the form of an aqueous resin emulsion by a polymerization method using an aqueous medium such as emulsion polymerization, microemulsion polymerization, and miniemulsion polymerization. Alternatively, they may be produced by performing solvent removal and neutral phase inversion after solution polymerization.

[0040] When producing a (meth)acrylic polymer by emulsion polymerization, an emulsifier may be used to emulsify and stabilize the monomers and the resulting polymer particles.

[0041] As the emulsifier to be used, known emulsifiers used in emulsion polymerization can be appropriately used. Examples of emulsifiers include various emulsifiers such as anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, and zwitterionic emulsifiers.

[0042] Examples of anionic emulsifiers include dialkyl sulfosuccinates, alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene alkyl diphenyl ether sulfates, polyoxyethylene alkyl ether sulfates, alkyl diphenyl ether disulfonates, polyoxyethylene polycyclic phenyl ether sulfates, polyoxyalkylene disulfonates, and polymeric emulsifiers.

[0043] Examples of nonionic emulsifiers include polyoxyethylene higher alcohol ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl diphenyl ethers, polyoxyethylene - polyoxypropylene block copolymers, acetylene diol - based emulsifiers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher fatty acid esters, polyoxyethylene higher fatty acid esters, glycerin higher fatty acid esters, polycarboxylic acid - based polymeric emulsifiers, and polyvinyl alcohol.

[0044] Examples of cationic emulsifiers include alkyl (amido) betaine and alkyldimethylamine oxide. Examples of special emulsifiers include fluorine-based emulsifiers and silicone-based emulsifiers. When producing a (meth)acrylic polymer, one type of emulsifier may be used alone, or two or more types may be used in combination.

[0045] The amount of emulsifier used is selected according to the type of emulsifier and polymerization conditions, etc., but is usually 0.05 to 20 parts by mass per 100 parts by mass of the monomer. The amount of emulsifier used is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 10 parts by mass per 100 parts by mass of the monomer. By setting the amount of emulsifier used to an appropriate amount, it is possible to ensure stability during production and suppress the generation of aggregates, and at the same time, it is possible to suppress a decrease in water resistance and a decrease in performance such as adhesive strength due to the emulsifier in the binder absorbing moisture and water.

[0046] Known methods can be adopted for the method of emulsifying the monomer. Specifically, after mixing each monomer and emulsifier, etc. in an aqueous medium, an emulsion is obtained by stirring and mixing under normal pressure or pressure.

[0047] Examples of the equipment for performing stirring and mixing include various mixers such as a homomixer, a colloid mill, various emulsifiers such as a high-pressure emulsifier and a high-pressure discharge type emulsifier.

[0048] As the polymerization initiator, known radical polymerization initiators such as peroxides and azo compounds can be used. The radical polymerization initiator may be used alone, or two or more types may be used in combination. Also, polymerization can be carried out by a redox polymerization initiation system using a peroxide and a reducing agent in combination.

[0049] Examples of peroxides include hydrogen peroxide; inorganic peroxides such as persulfates (sodium persulfate, ammonium persulfate, potassium persulfate, etc.); hydroperoxides (cumene hydroperoxide, paramethane hydroperoxide, tert-butyl hydroperoxide, etc.), dialkyl peroxides (tert-butyl cumyl peroxide, dicumyl peroxide, etc.), diacyl peroxides, peroxy esters (tert-butyl peroxylaurate, tert-butyl peroxybenzoate, etc.), benzoyl peroxide, lauroyl peroxide, peracetic acid, and organic peroxides such as succinic peroxide; and the like.

[0050] Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); and the like.

[0051] Examples of reducing agents used when polymerizing with a redox polymerization initiator system include, for example, ascorbic acid, sodium ascorbate, sodium erythorbate, tartaric acid, citric acid, metal salts of formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite, and ferric chloride; and the like.

[0052] The amount of the radical polymerization initiator used is selected according to the type of the radical polymerization initiator, the polymerization conditions, etc., but is usually 0.01 to 10 parts by mass with respect to 100 parts by mass of the monomer.

[0053] In emulsion polymerization, a chain transfer agent may be added. Specific examples of the chain transfer agent include mercapto group-containing compounds (ethanethiol, butanethiol, dodecanethiol, benzenethiol, toluenethiol, α-toluenethiol, phenethyl mercaptan, mercaptoethanol, 3-mercaptopropanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, α-mercaptoisobutyric acid, methyl mercaptopropionate, ethyl mercaptopropionate, thioacetic acid, thiomalic acid, thiosalicylic acid, octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, tert-tetradecyl mercaptan, etc.).

[0054] When a chain transfer agent is used in polymerization, the amount of the chain transfer agent used is usually 0.01 to 1.0 parts by mass based on 100 parts by mass of all monomers. By adding 0.01 part by mass or more of the chain transfer agent, it is possible to improve the adhesion of the (meth)acrylic polymer to the hot melt type adhesive. Further, by setting the amount of the chain transfer agent used to 1.0 part by mass or less, the tensile strength of the organic fiber aggregate obtained using the aqueous binder composition can be further increased.

[0055] The emulsion polymerization is usually carried out in a reaction system heated in an aqueous medium while stirring and reflux cooling. Here, the addition method of raw material components such as the emulsion and the polymerization initiator may be any of a batch addition method, a continuous addition method, and a split addition method. In the case of the continuous addition method, the supply rate may be constant or variable. Also, in the case of the split addition method, the addition interval of the raw material components may be constant or variable.

[0056] As the aqueous medium, only water may be used, or a mixed liquid composed of water and a water-soluble organic solvent (alcohol, ketone, ether, dimethyl sulfoxide, dimethylformamide, etc.) may be used. When a mixed liquid of water and a water-soluble organic solvent is used as the aqueous medium, the water content is usually 30% by mass or more based on the total amount of the aqueous medium.

[0057] The polymerization temperature of the monomer is appropriately selected according to the type of monomer and the type of radical polymerization initiator, etc., but is usually 40 to 95 °C.

[0058] (Volume average particle diameter) The volume average particle diameter of the (meth)acrylic polymer contained in the aqueous binder composition is not particularly limited, but preferably falls within the range of 50 to 1,000 nm. More preferably, the volume average particle diameter of the (meth)acrylic polymer falls within the range of 50 to 700 nm, and still more preferably within the range of 100 to 700 nm. In this specification, the volume average particle diameter of the (meth)acrylic polymer is a value measured by a particle size analyzer using the dynamic light scattering method. The volume average particle diameter of the (meth)acrylic polymer can be adjusted by increasing or decreasing the addition amount of the surfactant in the polymerization process.

[0059] <Adhesion promoter> Examples of the adhesion promoter include rosin-based resins such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene-based resins mainly composed of terpene phenol resin, α-pinene, β-pinene, or limonene; (hydrogenated) petroleum resins such as C5 petroleum resin, C9 petroleum resin, C5 / C9 petroleum resin, and dicyclopentadiene resin; coumarone-indene resin; hydrogenated aromatic copolymer; styrene-based resin; phenolic resin; xylene-based resin, etc. In terms of being able to make the adhesion between the organic fiber aggregate obtained using the aqueous binder composition and the hot melt adhesive more excellent, among these, rosin-based resin, terpene-based resin, or (hydrogenated) petroleum resin is preferable as the adhesion promoter, rosin-based resin is more preferable, and rosin ester is particularly preferable.

[0060] Examples of rosin esters include natural and modified rosin esters such as unmodified rosin esters, disproportionated rosin esters, polymerized rosin esters, and hydrogenated rosin esters. Examples of commercially available rosin esters include, for example, under the trade names, the Ester Gum series, Pencil series, and Super Ester series manufactured by Arakawa Chemical Industries; the SYLVALITE series and SYLVARES series manufactured by Arizona Chemical; the PICCOLYTE series manufactured by PINOVA; the YS Resin PX series manufactured by Yasuhara Chemical, etc.

[0061] The content of the tackifier is 0.1 to 50 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer contained in the aqueous binder composition. When the content of the tackifier is less than 0.1 part by mass or exceeds 50 parts by mass, the adhesion of the organic fiber aggregate obtained using the aqueous binder composition to the hot-melt type adhesive is not sufficient. From the viewpoint of obtaining an organic fiber aggregate having excellent adhesion to the hot-melt type adhesive, the content of the tackifier is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 part by mass or more, and even more preferably 2.0 part by mass or more with respect to 100 parts by mass of the (meth)acrylic polymer. Also, the content of the tackifier is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic polymer. Note that, as the tackifier, one kind may be used alone, or two or more kinds may be used in combination.

[0062] <Other components> The aqueous binder composition of the present invention may further contain, if desired, other components different from the above-described (meth)acrylic polymer and tackifier. Examples of other components include surfactants, crosslinking agents, defoaming agents, preservatives, hydrophilic (wetting) agents such as polyethylene glycol, thickeners, pH adjusters, film-forming aids such as water-soluble alcohols, antistatic agents, and the like. Note that, as other components, one kind may be used alone, or two or more kinds may be used in combination. In addition, the content of other components can be appropriately set within a range that does not impair the effects of the present invention.

[0063] The aqueous binder composition can be prepared by blending the above-described (meth)acrylic polymer, tackifier, and optionally other components, and preferably stirring. The treatment for mixing each component can be performed, for example, at a temperature within the range of 0 to 100°C. Further, when mixing each component, it may be performed under normal pressure, but it may also be performed under pressure or reduced pressure.

[0064] <Surface Tension of Aqueous Binder Composition> The aqueous binder composition preferably has a surface tension of 35 mN / m or less. When the surface tension of the aqueous binder composition is 35 mN / m or less, when obtaining an organic fiber aggregate in which organic fibers are aggregated by a binder by impregnating the fibrous substrate with the aqueous binder composition, the aqueous binder composition easily penetrates to the inside of the fibrous substrate. Thereby, an organic fiber aggregate exhibiting excellent tensile strength can be obtained. From the viewpoint of obtaining an organic fiber aggregate having a higher tensile strength, the surface tension of the aqueous binder composition is more preferably 32 mN / m or less, and even more preferably 30 mN / m or less. Note that, in order to lower the surface tension of the aqueous binder composition and adjust it to be within the above range, for example, it can be achieved by adding a surfactant. Examples of the surfactant used when adjusting the surface tension of the aqueous binder composition include those exemplified as emulsifiers that may be used in the polymerization in the description of the method for producing the (meth)acrylic polymer.

[0065] <pH of Aqueous Binder Composition> The pH of the aqueous binder composition is not particularly limited. However, considering that depending on the intended use of the organic fiber aggregate obtained using the aqueous binder composition (specifically, the fibrous substrate with the aqueous binder composition adhering between the organic fibers), it may be preferable to take into account the impact on the human body, the fibrous substrate, etc., the pH of the aqueous binder composition is preferably in the range of 4 to 8. The pH of the aqueous binder composition can be appropriately adjusted using a pH adjuster. For example, when using a polymer having a carboxylic acid group as the (meth)acrylic polymer, a basic compound such as aqueous ammonia or sodium hydroxide can be added to adjust the pH of the aqueous binder composition to the above range.

[0066] 《Organic Fiber Aggregate》 The organic fiber aggregate of the present invention is an aggregate of organic fibers in which the organic fibers are adhered to each other by the above-described aqueous binder composition of the present invention. The organic fiber aggregate of the present invention can be obtained by attaching the aqueous binder composition to a fibrous substrate formed of organic fibers. Examples of the fibrous substrate include woven fabrics, knitted fabrics, non-woven fabrics, and paper making. Among these, non-woven fabrics and paper making are preferable in that the effect of improving the tensile properties (particularly, tensile strength and tensile elongation) of the fibrous substrate is high by impregnating the aqueous binder composition of the present invention between the fibers. That is, the aqueous binder composition of the present invention is suitable as a binder composition for processing non-woven fabrics or paper making that adheres the fibers of non-woven fabrics or paper making to each other.

[0067] The size, shape, thickness, etc. of the fibrous substrate are not particularly limited and can be appropriately selected according to the desired use. The thickness of the fibrous substrate is, for example, about 0.01 to 1 mm.

[0068] The method for attaching the aqueous binder composition to the fibrous substrate is not particularly limited. Examples of the method for attaching the aqueous binder to the fibrous substrate include, for example, a method of immersing the fibrous substrate in the aqueous binder composition; a method of attaching the aqueous binder composition to the fibrous substrate by spraying; a method of coating the fibrous substrate with the aqueous binder composition using various coaters, etc. In terms of facilitating the impregnation of the aqueous binder composition between the organic fibers of the fibrous substrate and enabling the uniform expression of high tensile strength and tensile elongation with respect to the fibrous substrate, it is preferable to immerse the fibrous substrate in the aqueous binder composition or attach the aqueous binder composition to the fibrous substrate by spraying. When attaching the aqueous binder composition to the fibrous substrate by the method of immersing the fibrous substrate in the aqueous binder composition, the immersion time of the fibrous substrate, the temperature during immersion, etc. can be appropriately set. Further, when immersing the fibrous substrate in the aqueous binder composition, it may be carried out under normal pressure, but it may also be carried out under pressure or reduced pressure.

[0069] 《Adhesive Sheet》 The adhesive sheet of the present invention (hereinafter, also simply referred to as "adhesive sheet") includes an organic fiber layer formed by the above-described organic fiber aggregate of the present invention and an adhesive layer formed by a hot-melt adhesive. Since the organic fibers of the adhesive sheet are adhered to each other by the above-described aqueous binder composition of the present invention, the adhesive sheet has good tensile properties of the organic fiber layer and excellent adhesion to the hot-melt adhesive. Therefore, even when a hot-melt adhesive is adopted as the adhesive layer of the adhesive sheet from the viewpoints of workability and environmental aspects, etc., an adhesive sheet excellent in adhesion between the organic fiber layer and the adhesive layer can be obtained.

[0070] The method for manufacturing the pressure-sensitive adhesive sheet is not particularly limited. For example, a method of obtaining a laminate by applying a hot-melt type pressure-sensitive adhesive to the surface of an organic fiber aggregate to which an aqueous binder composition is adhered to a fibrous substrate; a method of obtaining a laminate by transferring an adhesive layer made of a hot-melt type pressure-sensitive adhesive to the surface of an organic fiber aggregate to which an aqueous binder composition is adhered to a fibrous substrate, etc. can be mentioned. The thickness of the adhesive layer can be appropriately selected according to the use and the like, but is, for example, about 0.1 to 2 mm.

[0071] In addition to the organic fiber layer and the adhesive layer described above, the pressure-sensitive adhesive sheet may further include a layer different from the organic fiber layer and the adhesive layer. Examples of such a layer include a release layer for protecting the outer surface of the adhesive layer, a protective layer for protecting the outer surface of the organic fiber layer, a coloring layer, and the like. Also, there is no particular limitation on the shape of the pressure-sensitive adhesive sheet, and it is appropriately set according to the use and the like. The pressure-sensitive adhesive sheet may be, for example, in the form of a single sheet, in the form of a roll, or may be cut into a strip shape.

[0072] The pressure-sensitive adhesive sheet of the present invention can be applied to various uses. Specifically, it can be used as a pressure-sensitive adhesive sheet in various uses such as building materials, stationery, handicraft supplies, toys, daily sundries, household goods, furniture, clothing, sports goods, medical supplies, automotive interior or exterior parts, etc. The pressure-sensitive adhesive sheet of the present invention is particularly excellent in imparting tensile properties to fibrous materials formed by entanglement of fibers, such as non-woven fabrics and paper, because the aqueous binder composition of the present invention is used as a binder for adhering organic fibers to each other. Such a pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet having a non-woven fabric or paper as a base material, and specifically, it can be preferably applied as a curing tape for construction; a masking tape for stationery, decoration, or craft.

Examples

[0073] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited by these examples. In the following, "parts" and "%" mean "parts by mass" and "mass%" respectively unless otherwise specified.

[0074] The details of each measurement method used in the following examples and comparative examples are as follows. <Measurement of Non-Volatile Content in Aqueous Resin Dispersion and Aqueous Binder Composition> Approximately 1 g of the measurement sample was weighed, and then the residue after drying at 155°C for 30 minutes in a ventilated dryer was measured. Using the weighed value of the measurement sample as a and the measured value of the residue after drying as b, the non-volatile content was calculated from the following formula. Non-volatile content (%) = (b / a) × 100 A weighing bottle was used for the measurement. For other operations, it was in accordance with JIS K 0067-1992 (Test Methods for Loss in Weight and Residue of Chemical Products).

[0075] <Measurement of Viscosity of Aqueous Resin Dispersion and Aqueous Binder Composition> Under the condition of a liquid temperature of 25°C, using a BM-type viscometer, the viscosity after 90 seconds at a rotation speed of 60 rpm was measured.

[0076] <Measurement of Residual Monomer Amount in Aqueous Resin Dispersion> After mixing the aqueous resin dispersion (5 g) and ethanol (10 g), centrifugation was performed, and 2 g of the supernatant was collected. The solution obtained by adding 0.06 g of a 1% aqueous solution of ethylene glycol monomethyl ether acetate as an internal standard to the collected supernatant was measured using gas chromatography.

[0077] <Measurement of Volume Average Particle Diameter of Acrylic Polymer in Aqueous Resin Dispersion> It was measured using a particle size analyzer (manufactured by Microtrac Bell Corporation, UPA EX150).

[0078] <Measurement of Surface Tension of Aqueous Binder Composition> It was performed using an automatic surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., CBVP-Z), and the data 120 seconds after the start of measurement was read.

[0079] 1. Production of (Meth)Acrylic Polymer (Production Example 1) Into a reaction vessel equipped with a stirrer, a reflux condenser, two dropping funnels, a thermometer, and a nitrogen inlet tube, ion-exchanged water (46 parts) and Emal 2F-30 (a surfactant manufactured by Kao Corporation, a 30% solution of sodium lauryl sulfate) (0.04 part) were charged, nitrogen gas was blown in, and while stirring, the internal temperature was adjusted to 70°C. On the other hand, into another container, ion-exchanged water (33 parts), Emal 2F-30 (1.5 parts), n-butyl acrylate (95.9 parts), acrylonitrile (2 parts), methacrylic acid (1.6 parts), and N-methoxymethylacrylamide (0.5 part) were charged, mixed, and emulsified to obtain an emulsion (total 134.5 parts). Of this emulsion, 2.69 parts were charged into the reactor. Ten minutes after charging, a solution prepared by dissolving ammonium persulfate (0.75 part) in ion-exchanged water (5.25 parts) was charged into the reactor. Furthermore, starting from 15 minutes after the addition of the ammonium persulfate solution, the remaining emulsion was added dropwise over time through the dropping funnel. At the same time, a solution prepared by dissolving ammonium persulfate (2.25 parts) in ion-exchanged water (102.38 parts) was added dropwise from another dropping funnel over 5 hours. At the end of the emulsion dropwise addition, the inside of the dropping funnel for the emulsion was washed with ion-exchanged water (37.5 parts), and the washing solution was charged into the reactor. After the completion of the dropwise addition of the aqueous ammonium persulfate solution, stirring was continued for an additional 1 hour while maintaining 70°C. Thereafter, a solution prepared by dissolving t-butyl hydroperoxide (0.75 part) in ion-exchanged water (26.25 parts) and a solution prepared by dissolving sodium erythorbate (0.68 part) in ion-exchanged water (26.25 parts) were charged into the reactor. It was cooled to 60°C, and again, a solution prepared by dissolving t-butyl hydroperoxide (0.75 part) in ion-exchanged water (30 parts) and a solution prepared by dissolving sodium erythorbate (0.68 part) in ion-exchanged water (30 parts) were charged into the reactor. Furthermore, it was cooled to 50°C, and a solution prepared by dissolving t-butyl hydroperoxide (0.75 part) in ion-exchanged water (30 parts) and a solution prepared by dissolving sodium erythorbate (0.68 part) in ion-exchanged water (30 parts) were charged into the reactor. Subsequently, a solution prepared by dissolving Foam Clean W-500E (manufactured by Hakuto Co., Ltd.) (2.78 parts), which is an antifoaming agent, in ion-exchanged water (9 parts) and SN Deformer 260 (manufactured by San Nopco Ltd.) (1.43 parts) were added. Thereby, an aqueous resin dispersion containing the (meth)acrylic polymer A-1 was obtained. The properties of the obtained (meth)acrylic polymer are as shown in Table 1. The glass transition temperature (Tg) of the (meth)acrylic polymer was calculated by the above formula (1).

[0080] (Production Examples 2 to 12) An aqueous resin dispersion containing a (meth)acrylic polymer was obtained in the same manner as in Production Example 1, except that the monomers were changed as shown in Table 1.

[0081]

Table 1

[0082] Details of the compounds used in Table 1 are shown below. · BA: n-Butyl acrylate · HA: 2-Ethylhexyl acrylate · MA: Methyl acrylate · MMA: Methyl methacrylate · AN: Acrylonitrile · HEA: 2-Hydroxyethyl acrylate · MAA: Methacrylic acid · AA: Acrylic acid · NMMA: N-Methoxymethylacrylamide · DAAM: Diacetoneacrylamide

[0083] 2. Production and Evaluation of Aqueous Binder Composition (Examples 1 to 16 and Comparative Examples 1 and 2) (1) Production of Aqueous Binder Composition The aqueous resin dispersion, surfactant, and tackifier obtained in the production example were mixed at the compounding ratios shown in Table 2. As a result, an aqueous binder composition was obtained as a binder aqueous dispersion in which the (meth)acrylic polymer was dispersed in water. Each component was blended so that the nonvolatile content in the aqueous binder composition was around 18.0%.

[0084] (2) Evaluation Test pieces were prepared using each aqueous binder composition, and the tensile physical properties and adhesion to a hot melt adhesive were evaluated. The production procedure and evaluation method of the test pieces are as follows. The evaluation results are shown in Table 2.

[0085] <Preparation of Test Pieces for Evaluation> Japanese paper without being processed by a binder was prepared, and the mass of the Japanese paper was measured. The aqueous binder composition was poured into a vat, and then the above-mentioned Japanese paper was immersed in the aqueous binder composition in the vat for several seconds and then taken out. After taking out the Japanese paper, the excess aqueous binder composition adhering to the Japanese paper was gently squeezed out with two metal bars. Thereafter, the Japanese paper impregnated with the aqueous binder composition was dried at 130°C for 3 minutes to obtain a test piece for evaluation as an organic fiber aggregate. When obtaining the test piece for evaluation, the mass Wa of the Japanese paper before immersion in the aqueous binder composition and the mass Wb of the test piece for evaluation dried after immersion in the aqueous binder composition were measured respectively, and the squeezing method was adjusted so that the adhesion amount of the binder obtained from the masses Wa and Wb was 12 - 14 g / m 2 ².

[0086] <Evaluation of Tensile Physical Properties> The above-mentioned test piece for evaluation was cut into strips with a width of 15 mm. In an environment at 25°C, it was set on a tensile testing machine (Strograph VG, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a distance of 20 mm between chucks, and the test was conducted at a speed of 250 mm / min to obtain the maximum stress (N / 15 mm) and the elongation rate (%) at the maximum stress. In the evaluation of the tensile physical properties, the maximum stress was the stress with respect to the width of 15 mm of the test piece.

[0087] <Evaluation of Adhesion to Hot Melt Adhesive> The above evaluation test pieces were cut into strips with a width of about 45 mm. Subsequently, an adhesive tape coated with a styrene-isoprene-styrene (SIS)-based hot melt adhesive with a width of 40 mm was bonded to the cut evaluation test pieces. Thereafter, using a 2 kg roller, pressure bonding was performed at a speed of 5 mm / second. Subsequently, heating was carried out at 130 °C for 30 minutes and then cooling was performed for 30 minutes. After cooling, in an environment of 25 °C, a 180° peel test was performed at a speed of 250 mm / minute using a tensile testing machine (Strograph VG, manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the peel strength (N / 15 mm) was determined.

[0088]

Table 2

[0089] The details of the compounds used in Table 2 are shown below. · E-900NT: Emulsion-type rosin-based tackifier, Super Ester E-900NT (non-volatile content 50%) manufactured by Arakawa Chemical Industries, Ltd. · E-100: Emulsion-type terpene phenol-based tackifier, Tamanol E-100 (non-volatile content 53%) manufactured by Arakawa Chemical Industries, Ltd. · OT-P: Sodium di-2-ethylhexyl sulfosuccinate, Perex OT-P (non-volatile content 70%) manufactured by Kao Corporation. · ADH: Adipic acid dihydrazide, ADH (non-volatile content 99% or more) manufactured by Nippon Fine Chemical Co., Ltd.

[0090] As shown in Table 2, by using the aqueous binder compositions of Examples 1 to 19, an organic fiber aggregate having good tensile physical properties (maximum stress, elongation rate at maximum stress) and showing good adhesion to the hot melt adhesive could be obtained. On the other hand, in the aqueous binder composition of Comparative Example 1 containing a (meth)acrylic polymer and not containing a tackifier, the adhesion to the hot melt type adhesive was insufficient. Further, in the aqueous binder composition of Comparative Example 2 in which the content of the tackifier was 70 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer, the elongation rate at the maximum stress was low, and the adhesion to the hot melt type adhesive was insufficient.

Claims

1. A (meth)acrylic polymer and, a tackifier (excluding the (meth)acrylic polymer), contained therein, wherein the glass transition point of the (meth)acrylic polymer is 10°C or lower, and the content of the tackifier with respect to 100 parts by mass of the (meth)acrylic polymer is 0.1 to 50 parts by mass, an aqueous binder composition for organic fibers.

2. The aqueous binder composition for organic fibers according to claim 1, which is for non-woven fabric or papermaking.

3. The aqueous binder composition for organic fibers according to claim 1, having a surface tension of 35 mN / m or lower.

4. The aqueous binder composition for organic fibers according to any one of claims 1 to 3, wherein the (meth)acrylic polymer contains a structural unit derived from an ethylenically unsaturated monomer having a nitrile group.

5. The aqueous binder composition for organic fibers according to any one of claims 1 to 3, wherein the (meth)acrylic polymer contains a structural unit derived from an ethylenically unsaturated monomer having a carboxyl group.

6. The aqueous binder composition for organic fibers according to any one of claims 1 to 3, wherein the (meth)acrylic polymer contains a structural unit derived from N-alkoxyalkyl (meth)acrylamide in an amount of 0.1% by mass or more and 2.5% by mass or less based on all the structural units constituting the (meth)acrylic polymer.

7. The aqueous binder composition for organic fibers according to any one of claims 1 to 3, wherein the tackifier contains a rosin ester.

8. An organic fiber aggregate in which organic fibers are adhered to each other with the aqueous binder composition for organic fibers according to any one of claims 1 to 3.

9. An organic fiber layer formed from the organic fiber aggregate according to claim 8, and an adhesive layer formed from a hot-melt adhesive, comprising a pressure-sensitive adhesive sheet.

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