Aqueous dispersion composition for heat sealants, and heat seal material

Abstract

To provide an aqueous dispersion composition for heat sealants and a heat sealant that exhibits excellent heat sealability, blocking resistance of the heat seal layer, and anti-slip properties. [Solution] An aqueous dispersion composition for heat sealing agents containing copolymer latex and fatty acid amide.

Description

【Technical Field】 【0001】 The present invention relates to an aqueous dispersion composition for a heat-sealing agent and a heat-sealing material. 【Background Art】 【0002】 A method of adhering (i.e., heat-sealing) two sheets by overlapping and heating and pressing paper, films, etc. is used in various applications including packaging materials. As a means of imparting heat-sealing properties to paper, films, etc., for example, so-called laminated paper obtained by laminating a polyolefin resin, or a method of applying, laminating, or internally adding a polymer compound such as a copolymer containing vinyl chloride or vinylidene chloride to a substrate such as paper or film to develop heat-sealing properties is widely used because of the ease of production and low production cost. 【0003】 However, in recent years, due to the global trend of plastic reduction and resource conservation, the reuse of waste paper has been attempted. In the case of the above-mentioned laminated paper, etc., from the viewpoint of biodegradability and in the process of recycling waste paper into recycled paper, the laminated part remains in the ecosystem or remains undissociated during recycling, and the removal treatment of the residue becomes a problem. Therefore, the development of a technology that can be recycled such as collection and recycling and replaces lamination has been desired. 【0004】 Patent Document 1 discloses an aqueous dispersion composition for a heat-sealing agent that can improve the heat-sealing property and the blocking resistance of the heat-sealing layer without using lamination, and contains an aliphatic conjugated diene-based copolymer latex having an insoluble content in toluene and a glass transition temperature within a specific range. 【0005】 Patent Document 2 discloses an aqueous dispersion composition for heat sealants that can improve heat sealability and blocking resistance of the heat seal layer without using lamination, and addresses the objective of providing an aqueous dispersion composition for heat sealants that can improve heat sealability and blocking resistance of the heat seal layer without using lamination. The aqueous dispersion composition contains an aliphatic conjugated diene copolymer latex with toluene insoluble matter and a glass transition temperature within a specific range, and a polyolefin powder with an MFR (melt mass flow rate) within a specific range. [Prior art documents] [Patent Documents] 【0006】 [Patent Document 1] Japanese Patent Publication No. 2021-038381 [Patent Document 2] Japanese Patent Publication No. 2021-046539 [Overview of the Initiative] [Problems that the invention aims to solve] 【0007】 Incidentally, in addition to the aqueous dispersion compositions for heat sealants described in Patent Documents 1 and 2 mentioned above, various other aqueous dispersion compositions for heat sealants have been investigated. However, there is still a need for an aqueous dispersion composition for heat sealants that is excellent in heat sealability and resistance to blocking of the heat seal layer. Furthermore, the aqueous dispersion composition for heat sealants is required to have excellent anti-slip properties for the heat seal layer. 【0008】 The present invention aims to provide an aqueous dispersion composition for heat sealants and a heat seal material that exhibits excellent heat sealability, blocking resistance of the heat seal layer, and anti-slip properties. [Means for solving the problem] 【0009】 The present invention provides the following: [1] A water-dispersible composition for heat sealing agents, comprising copolymer latex and fatty acid amide. 【0010】 [2] The copolymer latex contains 5 to 32% by mass of aliphatic conjugated diene monomer units, 0.1 to 5% by mass of ethylene unsaturated carboxylic acid monomer units, 55 to 94.9% by mass of alkenyl aromatic monomer units, and 0 to 39.9% by mass of copolymerizable monomer units other than aliphatic conjugated diene monomers, ethylene unsaturated carboxylic acid monomers, and alkenyl aromatic monomers, as described in [1], for the aqueous dispersion composition for heat sealant. 【0011】 [3] The aqueous dispersion composition for heat sealing agents according to [1] or [2], wherein the fatty acid amide is alkylenebis fatty acid amide. 【0012】 [4] An aqueous dispersion composition for heat sealing agents according to any one of [1] to [3], wherein the melting point of the fatty acid amide is 110 to 170°C. 【0013】 [5] An aqueous dispersion composition for heat sealing agents according to any one of [1] to [4], containing 0.1 to 10 parts by mass (on a solid content basis) of fatty acid amide per 100 parts by mass (on a solid content basis) of copolymer latex. 【0014】 [6] An aqueous dispersion composition for heat sealing agents according to any one of [1] to [4], containing 0.5 to 6 parts by mass (on a solid content basis) of fatty acid amide per 100 parts by mass (on a solid content basis) of copolymer latex. 【0015】 A heat seal material having a heat seal layer formed from an aqueous dispersion composition for heat sealants described in any of [7][1] to [6]. [Effects of the Invention] 【0016】 According to the present invention, it is possible to provide an aqueous dispersion composition for heat sealants and a heat seal material that exhibits excellent heat sealability, blocking resistance of the heat seal layer, and anti-slip properties. [Modes for carrying out the invention] 【0017】 The aqueous dispersion composition for heat sealing agents of this embodiment contains copolymer latex and fatty acid amide. 【0018】 Examples of the copolymer latex include conjugated diene latex, (meth)acrylate ester emulsion, vinyl acetate emulsion, urethane emulsion, vinyl chloride emulsion, polyethylene terephthalate emulsion, ethylene vinyl acetate emulsion, vinylidene chloride emulsion, polyvinyl alcohol emulsion, etc., and one or more of these can be used. Among them, it is preferable to contain a conjugated diene latex. 【0019】 Examples of the conjugated diene latex include styrene-butadiene latex, acrylonitrile-butadiene latex, methyl methacrylate-butadiene latex, styrene-butadiene-vinyl pyridine latex, butadiene latex, natural rubber latex, etc., and one or more of these can be used. 【0020】 Examples of the conjugated diene latex include polymers of aliphatic conjugated diene monomers and copolymerizable monomers other than aliphatic conjugated diene monomers. 【0021】 Examples of the aliphatic conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side-chain conjugated hexadienes, etc., and one or more of these can be used. From the viewpoints of industrial ease of production, availability, and cost, the use of 1,3-butadiene is particularly preferred. 【0022】 Examples of copolymerizable monomers other than aliphatic conjugated diene monomers include ethylenically unsaturated carboxylic acid monomers, alkenyl aromatic monomers, vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, unsaturated monomers containing a hydroxyalkyl group, unsaturated carboxylic acid amide monomers, etc., and one or more of these can be used. Among them, from the viewpoint of better heat-sealing properties and blocking resistance of the heat-sealing layer, it is preferable to use at least one selected from the group consisting of ethylenically unsaturated carboxylic acid monomers and alkenyl aromatic monomers. 【0023】 Examples of ethylenically unsaturated carboxylic acid monomers include monobasic acids or dibasic acids (anhydrides) such as itaconic acid, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, etc., and one or more of these can be used in combination. 【0024】 Examples of alkenyl aromatic monomers include styrene, α-methylstyrene, methyl-α-methylstyrene, vinyltoluene, divinylbenzene, etc., and one or more of these can be used in combination. From the viewpoints of being industrially easily manufactured, easy availability, and cost, the use of styrene is particularly preferable. 【0025】 Examples of vinyl cyanide monomers include monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, etc., and one or more of these can be used in combination. From the viewpoints of being industrially easily manufactured, easy availability, and cost, the use of acrylonitrile or methacrylonitrile is particularly preferable. 【0026】 Examples of unsaturated alkyl carboxylate monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate, which can be used individually or in combination of two or more. Methyl methacrylate is particularly preferred from the viewpoint of being easily manufactured industrially, readily available, and cost-effective. 【0027】 Examples of unsaturated monomers containing hydroxyalkyl groups include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di-(ethylene glycol) maleate, di-(ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis(2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate. These can be used individually or in combination of two or more. 【0028】 Examples of unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, and N,N-dimethylacrylamide, which can be used individually or in combination of two or more. 【0029】 In addition to the monomers mentioned above, any monomer commonly used in emulsion polymerization, such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, and vinylidene chloride, can be used. 【0030】 From the viewpoint of obtaining better film-forming properties of the aqueous dispersion composition for heat sealants and better blocking resistance of the heat seal layer, the content of aliphatic conjugated diene monomer units in the polymer is preferably 5 to 32% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 28% by mass. 【0031】 The content of copolymerizable monomer units other than aliphatic conjugated diene monomers is preferably 68 to 95% by mass, more preferably 70 to 90% by mass, and even more preferably 72 to 85% by mass in the polymer. 【0032】 From the viewpoint of improving the dispersion stability of the aqueous dispersion composition for the heat sealant and the heat sealability of the heat seal material, the content of ethylene-based unsaturated carboxylic acid monomer units in the polymer is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 2.5% by mass. 【0033】 From the viewpoint of providing superior blocking resistance of the heat seal layer, the content of alkenyl aromatic monomer units in the polymer is preferably 55 to 95% by mass, more preferably 60 to 94.9% by mass, even more preferably 65 to 85% by mass, and particularly preferably 70 to 75% by mass. 【0034】 The content of copolymerizable monomer units other than aliphatic conjugated diene monomers, ethylene unsaturated carboxylic acid monomers, and alkenyl aromatic monomers is preferably 0 to 40% by mass, more preferably 0.1 to 39.9% by mass, even more preferably 0.5 to 30% by mass, and particularly preferably 1 to 20% by mass in the polymer. 【0035】 From the viewpoint of achieving superior polymerization stability, the content of unsaturated monomer units containing hydroxyalkyl groups is preferably 0.1 to 4% by mass, more preferably 0.4 to 3% by mass, and even more preferably 0.7 to 2% by mass in the polymer. 【0036】 Conjugated diene latex can be obtained, for example, by emulsion polymerization of monomer components constituting a polymer. In addition to monomer components, the emulsion polymerization reaction system may contain emulsifiers (surfactants), polymerization initiators, and, if necessary, chain transfer agents, reducing agents, etc. There are no particular restrictions on the method of adding the various components; any of the following methods can be used: batch addition, divided addition, continuous addition, or power feed method. Batch polymerization, semi-batch polymerization, seed polymerization, etc., can also be used. 【0037】 Examples of emulsifiers (surfactants) include anionic surfactants such as sulfate ester salts of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, aliphatic sulfonates, aliphatic carboxylates, dehydroabiethinates, formalin condensates of naphthalene sulfonic acid, and sulfate ester salts of nonionic surfactants; and nonionic surfactants such as alkyl ester types, alkylphenyl ether types, and alkyl ether types of polyethylene glycol. These can be used individually or in combination of two or more. 【0038】 Examples of polymerization initiators include water-soluble polymerization initiators such as lithium persulfate, potassium persulfate, sodium persulfate, and ammonium persulfate; and oil-soluble polymerization initiators such as cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide, diisopropylbenzene hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. The polymerization initiator is preferably at least one selected from the group consisting of potassium persulfate, sodium persulfate, cumene hydroperoxide, and t-butyl hydroperoxide. The amount of polymerization initiator used is not particularly limited and can be appropriately adjusted considering the monomer composition, the pH of the polymerization reaction system, and the combination with other additives. 【0039】 Chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; xanthogene compounds such as dimethylxanthogene disulfide and diisopropylxanthogene disulfide; thiram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide; and 2,6-di-t-butyl-4-methylphenol. Examples of chain transfer agents include phenolic compounds such as ethylene phenol; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide; vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, and α-benzyloxyacrylamide; and chain transfer agents such as triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, terpinolene, and α-methylstyrene dimer. These can be used individually or in combination of two or more. The amount of chain transfer agent can be adjusted as appropriate, taking into account the combination with other additives. 【0040】 Examples of reducing agents include reducing sugars such as dextrose and saccharose; amines such as dimethylaniline and triethanolamine; carboxylic acids and their salts such as L-ascorbic acid, erythorbic acid, tartaric acid, and citric acid; sulfites, bisulfites, pyrosulfites, nithinites, nithinites, thiosulfates, formaldehyde sulfonates, and benzaldehyde sulfonates. The reducing agent is preferably L-ascorbic acid or erythorbic acid. The amount of reducing agent used can be appropriately adjusted considering the monomer composition, the pH of the polymerization reaction system, and the combination with other additives. 【0041】 Furthermore, to control the molecular weight and crosslinking structure of the polymer, hydrocarbon compounds such as saturated hydrocarbons (pentane, hexane, heptane, octane, cyclohexane, cycloheptane), unsaturated hydrocarbons (pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene), and aromatic hydrocarbons (benzene, toluene, xylene) can be added. These can be used individually or in combination of two or more. Of these, cyclohexene and toluene are preferred. 【0042】 Furthermore, if necessary, additives such as electrolytes, oxygen scavengers, chelating agents, dispersants, defoaming agents, antioxidants, preservatives, antibacterial agents, flame retardants, and UV absorbers may be added to the reaction system. These additives can be used in appropriate amounts and types as appropriate. 【0043】 The average particle size of the copolymer latex is preferably 70 to 250 nm, more preferably 80 to 220 nm, and even more preferably 90 to 200 nm, from the viewpoint of achieving superior dispersion stability, viscosity, and film-forming properties of the aqueous dispersion composition for heat sealing agents. The average particle size of the copolymer latex can be adjusted by appropriately adjusting the type, amount, and method of addition of the emulsifier used during polymerization of the copolymer latex, as well as the proportion of water. The average particle size of the copolymer latex can be measured by dynamic light scattering using the photon correlation method in accordance with JIS Z8826. 【0044】 The toluene-insoluble content of the copolymer latex is preferably 2 to 60% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, from the viewpoint of superior heat sealability and surface strength of the heat seal layer. The toluene-insoluble content can be adjusted by appropriately adjusting the amount of chain transfer agent used during polymerization of the copolymer latex. The toluene-insoluble content can be measured by the method described in the examples below. 【0045】 The glass transition temperature of the copolymer latex is preferably 10 to 80°C, more preferably 20 to 70°C, and even more preferably 25 to 60°C, from the viewpoint of superior film-forming properties of the aqueous dispersion composition for the heat sealant and better blocking resistance of the heat seal layer. The glass transition temperature can be adjusted by appropriately adjusting the type, amount, and method of addition of monomers used during polymerization of the copolymer latex. The glass transition temperature can be measured by the method described in the examples below. 【0046】 Copolymer latex may contain additives such as dispersants, preservatives, antioxidants, printability enhancers, surfactants, pH adjusters, crosslinking agents, and viscosity modifiers, as needed. These additives can be used in appropriate amounts and of varying types. 【0047】 Examples of fatty acid amides include fatty acid monoamides, alkylenebis fatty acid amides, alkylol fatty acid amides, and N-alkyl fatty acid amides, and one or more of these can be used. Among these, alkylenebis fatty acid amides are preferred from the viewpoint of providing superior slip resistance to the heat seal layer. 【0048】 Examples of alkylenebis fatty acid amides include methylenebislaurate, methylenebismyristicate, methylenebispalmitate, methylenebisstearamide, methylenebisoleate, methylenebislinoleate, methylenebislinolenate, methylenebisarachidamide, methylenebisarachidonic acid amide, methylenebisbehenamide, methylenebislignoceramide, methylenebiscerotinamide, methylenebismontanamide, methylenebismelisinamide, methylenebis-12-hydroxystearamide, methylenebisricinoleamide, and ethylenebis Examples include lauric acid amide, ethylenebismyristic acid amide, ethylenebispalmitic acid amide, ethylenebisstearate amide, ethylenebisoleic acid amide, ethylenebislinoleic acid amide, ethylenebislinolenic acid amide, ethylenebisarachidic acid amide, ethylenebisarachidonic acid amide, ethylenebisbehenic acid amide, ethylenebislignoceric acid amide, ethylenebiscerotinic acid amide, ethylenebismontanic acid amide, ethylenebismericinic acid amide, ethylenebis-12-hydroxystearic acid amide, and ethylenebisricinoleic acid amide, and one or more of these can be used. In particular, it is preferable to include ethylenebisstearate amide from the viewpoint of having a better balance between blocking resistance and slip resistance of the heat seal layer. 【0049】 Fatty acid amides may be provided, for example, in the form of a dispersion (emulsion, latex, suspension, etc.) produced by dispersing the fatty acid amide in an aqueous medium. As a method for dispersing the fatty acid amide, the method for producing an emulsified dispersion described in Japanese Patent Application Publication No. 2019-93383 can be employed. Specifically, as a method for dispersing the fatty acid amide, for example, the fatty acid amide powder is dispersed in an aqueous medium by a wet dispersion method using a surfactant. 【0050】 Examples of surfactants include the emulsifiers mentioned above. 【0051】 The surfactant is blended in an amount of, for example, 6 parts by mass or more, preferably 7 parts by mass or more, more preferably 8 parts by mass or more, for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 13 parts by mass or less, and more preferably 11 parts by mass or less, per 100 parts by mass of fatty acid amide powder. 【0052】 The aqueous medium is blended with 100 parts by mass or more, preferably 120 parts by mass or more, more preferably 130 parts by mass or more, for example, 500 parts by mass or less, preferably 350 parts by mass or less, and more preferably 250 parts by mass or less, per 100 parts by mass of fatty acid amide powder. 【0053】 Preferably, an antifoaming agent and a preservative are added to the fatty acid amide dispersion. 【0054】 Examples of defoaming agents include polyglycols, fatty acid esters, phosphate esters, silicone oils, and silica. One type of defoaming agent or two or more types can be used in combination. 【0055】 The defoaming agent is contained in an amount of, for example, 0.05 parts by mass or more, and for example, 0.5 parts by mass or less, per 100 parts by mass of fatty acid amide powder. 【0056】 Examples of preservatives include butylparaben, 5-chloro-2-methyl-4-isothiazolin-3-one, sorbic acid, potassium sorbate, p-chloro-m-xylenol, 1,2-benzoisothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol, 2-methyl-4-isothiazolin-3-one, and 2-n-octyl-4-isothiazolin-3-one. Preservatives can be used individually or in combination of two or more. 【0057】 The preservative is contained in an amount of, for example, 0.05 parts by mass or more, and for example, 0.3 parts by mass or less, per 100 parts by mass of fatty acid amide powder. 【0058】 The fatty acid amide dispersion may contain additives such as oxygen scavengers, chelating agents, dispersants, antioxidants, antibacterial agents, flame retardants, and UV absorbers, as needed. 【0059】 The melting point of the fatty acid amide is preferably 110 to 170°C. A melting point within this range provides superior slip resistance to the heat seal layer. The melting point can be measured by the method described in the examples below. From the viewpoint of superior slip resistance to the heat seal layer, the melting point is more preferably 125 to 160°C, and even more preferably 140 to 150°C. 【0060】 The water-dispersible composition for heat sealants preferably contains 0.1 to 10 parts by weight (solid content) of fatty acid amide per 100 parts by weight (solid content) of copolymer latex. Containing 0.1 parts by weight or more of fatty acid amide provides superior blocking resistance of the heat seal layer. Containing 10 parts by weight or less of fatty acid amide provides superior heat sealability. Since the blocking resistance of the heat seal layer is superior, it is more preferable to contain 0.3 parts by weight or more of fatty acid amide, and even more preferable to contain 0.5 parts by weight or more. Since the heat sealability is superior, it is more preferable to contain 8 parts by weight or less of fatty acid amide, and even more preferable to contain 6 parts by weight or less. 【0061】 The water-dispersible heat sealant composition may be mixed with other binders, etc., as needed. Additives such as preservatives, anti-aging agents, printability enhancers, and surfactants may also be added as needed. These additives can be used in appropriate amounts and types as appropriate. 【0062】 The total amount of solids contained in the aqueous dispersion composition for heat sealing agents, for example, may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of solids in the aqueous dispersion composition for heat sealing agents. 【0063】 For example, a water-dispersible composition for heat sealing agents can be prepared by mixing a dispersion of copolymer latex and a fatty acid amide at room temperature (23°C), and additives or aqueous media can be added as needed during mixing. 【0064】 Aqueous media basically contain water such as distilled water, deionized water, tap water, or industrial water, and may further contain water-soluble components (various additives, organic solvents, etc.). 【0065】 The heat seal material of this embodiment has a heat seal layer formed from the aqueous dispersion composition for heat sealants of this embodiment. For example, the heat seal layer can be provided by coating and drying the aqueous dispersion composition for heat sealants of this embodiment onto a substrate. [Examples] 【0066】 The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. Unless otherwise specified, percentages and parts are based on mass. 【0067】 <Measurement of average particle size of copolymer latex> The average particle size of copolymer latex was measured by dynamic light scattering using the photon correlation method. The number-average particle size was measured using an FPAR-1000 (manufactured by Otsuka Electronics). 【0068】 <Measurement of insoluble content of copolymer latex in toluene> A film was prepared using copolymer latex in an atmosphere of 50°C and 85% humidity. Approximately 1 g of the prepared film was weighed (weighing value: X (g)), and this was placed in 400 mL of toluene and left for 48 hours to swell and dissolve. After that, it was filtered through a 300 mesh wire mesh, and the toluene-insoluble matter captured on the wire mesh was dried and weighed (weighing value: Y (g)). The toluene-insoluble content of the copolymer latex was calculated from the percentage of the weighing value Y of the toluene-insoluble matter relative to the weighing value X of the prepared film. Insoluble matter in toluene (mass%) = (Y / X) × 100 【0069】 <Measurement of glass transition temperature of copolymer latex> Copolymer latex was cast onto a glass plate and dried at 70°C for 4 hours to produce a film. This film was packed into an aluminum pan and placed in a differential scanning calorimeter (DSC6200: Seiko Instruments). After cooling the apparatus to a temperature approximately 50°C lower than the expected glass transition temperature, the temperature was increased at a heating rate of 10°C / min to obtain a DSC curve. Next, the differential curve of the obtained DSC curve was obtained. The peak top temperature of the obtained differential curve was taken as the glass transition temperature of the copolymer latex. If the shape of the peak in the differential curve was broad and there was no portion that could be recognized as a peak top, the temperature at the center of the peak was taken as the glass transition temperature instead of the peak top temperature. Furthermore, if there were two or more peaks in the differential curve, the peak top temperature of the peak with the largest area was taken as the glass transition temperature, and if the shape of the peak in the differential curve was broad, the temperature at the center of the peak with the largest area was taken as the glass transition temperature. 【0070】 <Preparation of copolymer latex> 10% by mass of a monomer mixture consisting of 26.0% by mass of 1,3-butadiene, 71.2% by mass of styrene, 1.0% by mass of hydroxyethyl acrylate, 0.6% by mass of fumaric acid, and 1.2% by mass of acrylic acid, along with 0.6 parts by mass of sodium dodecylbenzenesulfonate, 1.0 part by mass of t-dodecyl mercaptan, 1.0 part by mass of potassium persulfate, and 90 parts by mass of polymerization water were charged into a pressure-resistant polymerization reactor. After thorough stirring, the remaining components of the monomer mixture were continuously added over 360 minutes starting when the reactor temperature reached 65°C. Subsequently, the temperature inside the polymerization reactor was raised to 80°C, and polymerization was terminated when the polymerization conversion rate exceeded 95%. Then, the pH was adjusted to 9.0 with NaOH to obtain copolymer latex (average particle size: 150 nm, insoluble content in toluene: 50% by mass, glass transition temperature: 27°C). 【0071】 <Measurement of the melting point of fatty acid amides> The melting point of fatty acid amides is measured by differential scanning calorimetry (DSC) in accordance with JIS K7121. The melting point of fatty acid amides is the melting peak temperature of the DSC curve drawn by differential scanning calorimetry. First, the fatty acid amide is heated to 200°C in differential scanning calorimetry, and then cooled to 0°C at a rate of 10°C / min to obtain a sample. Next, the obtained sample is heated from 0°C at a rate of 10°C / min to obtain a DSC curve. The melting peak temperature of the obtained DSC curve is the melting point of the fatty acid amide. If there are two or more melting peaks, the melting peak temperature of the melting peak with the largest area is the melting point of the fatty acid amide. 【0072】 A: Ethylene bis-stearamide (melting point: 145°C) B: Stearamide (melting point: 100°C) C: Calcium fatty acid (melting point: 120℃) D: Polyethylene emulsion (melting point: 105°C) E: Paraffin wax (melting point: 60°C) 【0073】 <Preparation of aqueous dispersion composition for heat sealant> The copolymer latex and A to E were mixed according to the formulations shown in Table 1, and the solid content was adjusted to 45% by mass with water to obtain the aqueous dispersion compositions for heat sealants of Examples 1 to 6 and Comparative Examples 1 to 5. 【0074】 [Table 1] 【0075】 <Evaluation of heat sealability> Basis weight 70g / m 2 A water-dispersible heat-sealing agent composition is applied to one side of commercially available double-sided kraft paper at a rate of 6 g / m². 2After applying the coating and overlapping the coated surfaces, heat sealing was performed using a TP-701C heat seal tester manufactured by Tester Sangyo Co., Ltd., with a heat seal width of 15 mm, a sealing temperature of 140°C, a sealing pressure of 0.2 MPa, and a sealing pressure of 0.5 seconds. The adhesive strength was then measured using a T-shaped peel test. Based on the obtained results, the heat sealability was determined according to the following criteria. The results are shown in Table 1. A: 2.5N or higher B: 1.0N or more and less than 2.5N C: Less than 1.0N 【0076】 <Evaluation of blocking resistance> Basis weight 70g / m 2 A water-dispersible heat-sealing agent composition is applied to one side of commercially available double-sided kraft paper at a rate of 13 g / m². 2 Apply the coating, overlapping the coated surfaces, with a basis weight of 157 g / m². 2 Ten sheets each of commercially available high-quality paper are placed on top and bottom, and a weight is placed on top to create a 100gf / cm² load. 2 The specimens were left standing for 5 days under a load at 40°C and 90% humidity, and then left standing for another 24 hours at 23°C and 50% humidity. After that, the test specimens were cut into 15mm wide strips, and the degree to which they could be peeled off by hand was used to determine their blocking resistance according to the following criteria. The results are shown in Table 1. A: Not glued B: Although it is glued, it can be easily peeled off. C: It is strongly bonded, and if you try to peel it off, both sides of the kraft paper will tear. 【0077】 <Evaluation of slip resistance> Basis weight 70g / m 2 A water-dispersible heat-sealing agent composition is applied to one side of commercially available double-sided kraft paper at a rate of 13 g / m². 2 The coating was applied, and the static friction coefficient between the coated surfaces was measured in accordance with JIS P 8147:2010. The anti-slip properties were determined from the results according to the following criteria. The results are shown in Table 1. A: 0.8 or higher B: 0.5 or higher, less than 0.8 C: Less than 0.5

Claims

[Claim 1] A water-dispersible composition for heat sealing agents, containing copolymer latex and fatty acid amide. [Claim 2] The aqueous dispersion composition for heat sealant according to claim 1, wherein the copolymer latex contains 5 to 32% by mass of aliphatic conjugated diene monomer units, 0.1 to 5% by mass of ethylene-unsaturated carboxylic acid monomer units, 55 to 94.9% by mass of alkenyl aromatic monomer units, and 0 to 39.9% by mass of copolymerizable monomer units other than aliphatic conjugated diene monomers, ethylene-unsaturated carboxylic acid monomers, and alkenyl aromatic monomers. [Claim 3] The aqueous dispersion composition for heat sealants according to claim 1, wherein the fatty acid amide contains alkylenebis fatty acid amide. [Claim 4] The aqueous dispersion composition for heat sealing agents according to claim 1, wherein the melting point of the fatty acid amide is 110 to 170°C. [Claim 5] The aqueous dispersion composition for heat sealing agents according to claim 1, comprising 0.1 to 10 parts by mass (on a solid content basis) of fatty acid amide per 100 parts by mass (on a solid content basis) of copolymer latex. [Claim 6] The aqueous dispersion composition for heat sealing agents according to claim 1, comprising 0.5 to 6 parts by mass (on a solid content basis) of fatty acid amide per 100 parts by mass (on a solid content basis) of copolymer latex. [Claim 7] A heat seal material having a heat seal layer formed from an aqueous dispersion composition for heat sealants according to any one of claims 1 to 6.

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