Heat sealing agent and laminate

Abstract

To provide a heat sealing agent which enables formation of a heat seal layer having superior heat sealability and blocking resistance as well as superior water resistance.SOLUTION: A heat sealing agent contains resin particles (A) having glass transition temperatures in the range of 60 to 140°C and in the range of -50 to 20°C and having an acid value of 10 to 130 mgKOH / g. Preferably, the resin particles (A) include a polymer (A-1) having a glass transition temperature of 60 to 140°C and a polymer (A-2) having a glass transition temperature of -50 to 20°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat-sealing agent and a laminate.

Background Art

[0002] Conventionally, base materials such as paper and plastic films have been used as packaging materials for packaging clothes, foods, drugs, etc. After packaging the contents, heat sealing is frequently used to seal the opening (hereinafter also referred to as "sealing"). Packaging materials made of plastic films often have heat-sealing properties themselves, but packaging materials made of paper do not have heat-sealing properties themselves. Therefore, in order to impart heat-sealing properties, a plastic film such as a polyethylene film having heat-sealing properties is laminated on the entire inner surface of the packaging material or the opening to be sealed with a paper base material.

[0003] In recent years, from the viewpoints of resource saving, plastic reduction, and ease of recycling, the growth of packaging materials based on paper has been remarkable. However, packaging materials made of paper laminated with plastic films need to be separated from the plastic films during recycling, which is a burden in the recycling process. Therefore, instead of laminating a plastic film on a paper base material, there has been a study to obtain a packaging material based on paper by applying a heat-sealing agent having heat-sealing properties to the base material to form a heat-sealing layer.

[0004] However, if the seal strength of the opening is not sufficient, there is a risk that the opening of the sealed packaging material may open during transportation or handling of the package. In addition, when a heat-sealing layer is formed by applying a heat-sealing agent, a problem is that a so-called "blocking" phenomenon occurs in which a portion that is not intended to be sealed adheres to the heat-sealing layer. This blocking leads to a decrease in workability and a decrease in the quality of the packaging material. It is generally recognized among those skilled in the art that the ease of this blocking (blocking property) is a property that is contrary to the heat-sealing property. Furthermore, in the case of a packaging material using a paper substrate, since the paper itself has poor water resistance, when it gets wet with water, the water easily penetrates into the interior of the packaging material, causing problems such as contamination and deterioration of the contents.

[0005] Therefore, in the case of a packaging material using paper as a substrate, a method of obtaining a packaging material by applying a heat-sealing agent having excellent blocking resistance (the difficulty of blocking is referred to as "blocking resistance") and water resistance to the entire inner surface of the packaging material has been studied. However, it has been difficult to achieve both good heat-sealing properties and blocking resistance while imparting sufficient water resistance.

[0006] For example, Patent Document 1 discloses a material having a coating layer that exhibits water repellency, oil resistance, water vapor barrier properties, heat-sealing properties, and blocking resistance. However, it was insufficient from the viewpoint of achieving both heat-sealing properties, blocking resistance, and water resistance at a practical level.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a heat-sealing agent capable of forming a heat-sealing layer having good heat-sealing properties and blocking resistance and excellent water resistance.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have arrived at the present invention. That is, the present invention relates to a heat-sealing agent containing resin particles (A) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C, and an acid value of 10 to 130 mgKOH / g.

[0010] Further, the present invention relates to the above heat-sealing agent, wherein the resin particles (A) contain a polymer (A-1) having a glass transition temperature of 60 to 140°C and a polymer (A-2) having a glass transition temperature of -50 to 20°C.

[0011] Further, the present invention relates to the heat-sealing agent according to claim 1, wherein the resin particles (A) contain a polymer (A-3) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C.

[0012] Further, the present invention relates to the above heat-sealing agent, wherein the mass ratio of the polymer (A-1) to the polymer (A-2) (polymer (A-1) / polymer (A-2)) is 10 / 90 to 50 / 50.

[0013] Further, the present invention relates to the above heat-sealing agent, which further contains wax (B) having an average particle diameter of 0.03 to 10 μm.

[0014] Further, the present invention relates to a laminate having a heat-sealing layer formed from the above heat-sealing agent on a substrate.

Advantages of the Invention

[0015] According to the present invention, it has become possible to provide a heat-sealing agent that is preferably used for a packaging material having a paper substrate and can form a heat-sealing layer that achieves both good heat-sealing properties and blocking resistance and is excellent in water resistance.

Embodiments for Carrying Out the Invention

[0016] The heat-sealing agent of the present invention contains resin particles (A) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C, and an acid value of 10 to 130 mgKOH / g. The resin particles (A) are preferably a polymer of an ethylenically unsaturated monomer (a) (hereinafter, also simply referred to as "monomer (a)").

[0017] The resin particles (A) preferably contain a polymer (A-1) having a glass transition temperature of 60 to 140°C and a polymer (A-2) having a glass transition temperature of -50 to 20°C. Further, the resin particles (A) preferably contain a polymer (A-3) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C. The polymer (A-3) may be in a form in which the polymer (A-1) and the polymer (A-2) are chemically bonded. Here, the chemical bond means a bond formed by the reaction of functional groups that can chemically react with each other, such as a carboxy group and an epoxy group, a carboxy group and a hydroxyl group, a carboxy group and an amino group, etc. Examples of the resin particles (A) containing the polymer (A-3) include resin particles (A) obtained by polymerizing a monomer mixture containing a monomer having a carboxy group such as (meth)acrylic acid, and then continuously polymerizing a monomer mixture containing a monomer having a glycidyl group such as glycidyl methacrylate.

[0018] Examples of the monomer (a) include carboxyl group-containing monomers such as (meth)acrylic acid (collectively referred to as "(meth)acrylic acid" for "acrylic acid" and "methacrylic acid"), maleic acid, fumaric acid, itaconic acid, citraconic acid, cinnamic acid, β-carboxyethyl (meth)acrylate, and anhydrides thereof; Chain alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, pentyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate;

[0019] Cyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate; Hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate;

[0020] (Meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide and other amide group-containing monomers; Ketone group-containing monomers such as diacetone (meth)acrylamide and acetoacetoxy (meth)acrylate;

[0021] Epoxy group-containing monomers such as glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and allyl glycidyl ether; Amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate, dimethylaminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate; Nitrile group-containing monomers such as (meth)acrylonitrile; Sulfonic acid group-containing monomers such as sodium 2-acrylamido-2-methylpropanesulfonate, methallylsulfonic acid, methallylsulfonic acid sodium salt, allylsulfonic acid, allylsulfonic acid sodium salt, allylsulfonic acid ammonium salt, and vinylsulfonic acid;

[0022] Phosphate group-containing monomers such as 2-(meth)acryloyloxyethyl acid phosphate; (Isocyanate group-containing monomers such as (meth)acryloyloxyethyl isocyanate; Heterocyclic ring-containing monomers other than epoxy groups such as tetrahydrofurfuryl (meth)acrylate and (meth)acryloylmorpholine; Alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and their alkylene oxide adducts; Aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate and their alkylene oxide adducts;

[0023] Methylol group-containing monomers such as N-methylol (meth)acrylamide, N,N-dimethylol (meth)acrylamide, and alkyl etherified N-methylol (meth)acrylamide Alkoxysilyl group-containing monomers such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane; Fluorine atom-containing monomers such as trifluoroethyl (meth)acrylate and heptadecafluorodecyl (meth)acrylate;

[0024] Allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, 1-butenyl (meth)acrylate, 2-butenyl (meth)acrylate, 3-butenyl (meth)acrylate, 1,3-methyl-3-butenyl (meth)acrylate, 2-chloroallyl (meth)acrylate, 3-chloroallyl (meth)acrylate, o-allylphenyl (meth)acrylate, 2-(allyloxy)ethyl (meth)acrylate, allyl lactyl (meth)acrylate, citronellyl (meth)acrylate, geranyl (meth)acrylate, rosinyl (meth)acrylate, cinnamyl (meth)acrylate, diallyl maleate, diallyl itaconate, vinyl (meth)acrylate, vinyl crotonate, vinyl oleate, vinyl linolenate, 2-(2'-vinyloxyethoxy)ethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, 1,1,1-tris(hydroxymethyl)ethane diacrylate, 1,1,1-tris(hydroxymethyl)ethane triacrylate, 1,1,1-tris(hydroxymethyl)propane triacrylate, divinylbenzene, divinyl adipate, diallyl isophthalate, diallyl phthalate, diallyl maleate, etc. Monomers having two or more ethylenically unsaturated groups;

[0025] Aromatic (meth)acrylates such as benzyl (meth)acrylate; Aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene; Vinyl ester monomers such as vinyl acetate; Vinyl ether compounds, α-olefins, etc. can be mentioned.

[0026] Among these, the monomer (a) preferably contains a carboxyl group-containing monomer and / or its anhydride, and preferably contains styrene or 2-ethylhexyl (meth)acrylate from the viewpoint of water resistance.

[0027] Resin particles (A) having a glass transition temperature of 60 to 140 °C and -50 to 20 °C and an acid value of 10 to 130 mgKOH / g can be obtained by appropriately selecting these monomers and polymerizing them alone or copolymerizing two or more of them in the presence of a radical polymerization initiator. In the polymerization, conventional known methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.

[0028] As the radical polymerization initiator, known oil-soluble polymerization initiators or water-soluble polymerization initiators can be used, and these may be used alone or in combination of two or more. Examples of the oil-soluble polymerization initiator include organic peroxides such as benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), tert-butyl peroxy-3,5,5-trimethylhexanoate, and di-tert-butyl peroxide; azo-bis compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 1,1'-azobis-cyclohexane-1-carbonitrile; and the like can be mentioned. Examples of the water-soluble polymerization initiator include ammonium persulfate (abbreviation: APS), potassium persulfate (abbreviation: KPS), hydrogen peroxide, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the like. The radical polymerization initiator is preferably used in an amount of 0.1 to 4 parts by mass based on 100 parts by mass of the monomer (a).

[0029] When performing emulsion polymerization, a water-soluble polymerization initiator is preferably used, and a reducing agent may also be used in combination therewith. By using a reducing agent in combination, the emulsion polymerization rate can be accelerated and emulsion polymerization at low temperatures becomes easier. Examples of the reducing agent include reducing organic compounds such as ascorbic acid, erythorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate; reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite; ferrous chloride, Rongalit, thiourea dioxide, etc.

[0030] One glass transition temperature of the resin particles (A) is importantly 60 to 140°C, preferably 70 to 130°C. If the glass transition temperature is 60°C or higher, the heat-sealing layer formed has excellent blocking resistance. If the glass transition temperature is 140°C or lower, the heat-sealing layer formed has excellent heat-sealing properties.

[0031] Also, the other glass transition temperature of the resin particles (A) is importantly -50 to 20°C, preferably -40 to 10°C. If the glass transition temperature is -50°C or higher, the heat-sealing layer formed has excellent blocking resistance. If the glass transition temperature is 20°C or lower, the heat-sealing layer formed has excellent water resistance.

[0032] In the present invention, it is sufficient that the resin particles (A) are contained, and the method for obtaining them is not particularly limited. For example, organic solvent solutions of the polymer (A-1) and the polymer (A-2) are prepared respectively, and after mixing the two, an aqueous medium such as water and, if necessary, an emulsifier are added and the solvent is removed to obtain the resin particles (A). Also, the resin particles (A) can be obtained by polymerizing a monomer in the presence of the polymer (A-1). This method is advantageous in terms of production cost and efficiency and is preferably used.

[0033] It is important that the acid value of the resin particles (A) is 10 to 130 mgKOH / g, preferably 15 to 120 mgKOH / g, and more preferably 20 to 110 mgKOH / g. If the acid value of the resin particles (A) is 10 mgKOH / g or more, the emulsion has excellent stability. If the acid value is 130 mgKOH / g or less, the heat-sealing layer has excellent water resistance.

[0034] In the resin particles (A), the mass ratio of the polymer (A-1) to the polymer (A-2) (polymer (A-1) / polymer (A-2)) is preferably polymer (A-1) / polymer (A-2) = 10 / 90 to 50 / 50, and more preferably 15 / 85 to 40 / 60. If the proportion of the polymer (A-1) is more than 10% by mass, the heat-sealing layer formed has better blocking resistance. If it is less than 50% by mass, the heat-sealing layer formed has better heat-sealing properties.

[0035] The average particle diameter of the resin particles (A) is preferably 20 to 300 nm, and more preferably 40 to 150 nm. If the average particle diameter is within this range, the dispersion stability of the emulsion particles and the coatability of the heat-sealing agent are excellent.

[0036] The heat-sealing agent of the present invention preferably contains a wax (B) having an average particle diameter of 0.03 to 10 μm (hereinafter, also simply referred to as "wax (B)"). By containing the wax (B), the water resistance of the heat-sealing layer formed is further improved, and the blocking resistance is easily improved without reducing the heat-sealing properties. Furthermore, it can impart appropriate slipperiness, which is suitable when processing the packaging material.

[0037] Examples of the type of wax (B) include carnauba wax, beeswax, paraffin wax, modified paraffin wax, polyethylene wax, oxidized polyethylene wax, modified polyethylene wax, polypropylene wax, oxidized polypropylene wax, modified polypropylene wax, ethylene vinyl acetate copolymer wax, modified ethylene vinyl acetate copolymer wax, fatty acid amide, microcrystalline wax, Fischer-Tropsch wax, polytetrafluoroethylene, etc. From the viewpoint of improving water resistance, paraffin wax, modified paraffin wax, polyethylene wax, and oxidized polyethylene wax are preferred.

[0038] Wax (B) is preferably blended in a proportion of 50 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the total amount with the resin particles (A).

[0039] The heat-sealing agent of the present invention may contain additives such as extender pigments, defoamers, leveling agents, preservatives, solvents, neutralizing agents, fillers, etc. as optional components, if necessary.

[0040] The laminate of the present invention can be obtained by coating the heat-sealing agent of the present invention on a substrate such as a plastic film or paper to form a heat-sealing layer, and performing molding processing or the like as necessary.

[0041] Examples of the substrate include paper, non-woven fabric, a sheet having a porous surface state for woven fabric, polyethylene film, polypropylene film, polyester film, nylon film, and aluminum foil. Paper is preferred. Since the substrate is a paper substrate, the coating agent wets the substrate sufficiently and penetrates into the substrate, so that the substrate and the coating agent are more firmly bonded. Therefore, the water resistance and heat-sealability of the laminate can be improved.

[0042] Examples of the coating device include a knife coater, comma coater, roll coater, bar coater, gravure coater, flexo coater, etc.

[0043] The heat-sealing agent of the present invention is particularly preferably used for a paper substrate. In addition, the heat-sealing agent of the present invention may be applied in multiple coats as necessary to obtain desired heat-sealing properties and water resistance.

Examples

[0044] Hereinafter, the present invention will be specifically described with reference to examples. In the examples, unless otherwise specified, “parts” represents “parts by mass” and “%” represents “% by mass”.

[0045] <Glass transition temperature> The glass transition temperature (hereinafter also referred to as “Tg”) was measured using a DSC (Differential Scanning Calorimeter, manufactured by TA Instruments). Specifically, 3 mg of the dried polymer was precisely weighed and placed in an aluminum pan, and an empty aluminum pan as a reference was set in a DSC measurement holder. The temperature at the intersection of the baseline on the low-temperature side of the endothermic phenomenon in the DSC curve obtained by measurement under the temperature-rising condition of 10 °C / min and the tangent line at the inflection point was defined as the glass transition temperature (Tg). For the example where polymerization is carried out in two steps, sampling was performed after the completion of the first-stage polymerization reaction, and DSC measurement was carried out. The obtained Tg was designated as Tg1. Then, sampling was performed again after the completion of the second-stage polymerization reaction, and DSC measurement was carried out. The newly appeared Tg different from Tg1 was designated as Tg2.

[0046] <Acid value> For the dried resin particles (A), potentiometric titration was carried out with a potassium hydroxide-ethanol solution in accordance with the method described in JIS K2501 and calculated.

[0047] <Average particle diameter> The resin particles (A) obtained in each example were diluted 500-fold with water, and approximately 5 ml of the diluted solution was measured by the dynamic light scattering measurement method (the measuring device is NanoTrack UPA; manufactured by Microtrac Bell), and the median diameter (median value) was taken as the average particle diameter.

[0048] <Heat seal strength> Two test pieces obtained by cutting the resulting laminate into 15 mm widths were prepared. The coated surface of one test piece was overlapped with the coated surface of the other test piece, and it was pressure-bonded under the conditions of 120 °C - 2 kgf / cm 2 - 1 second using a HEATSHEEL&IMPULSE TESTER (manufactured by Nichiris Kagaku Kogyo Co., Ltd., upper and lower plate heating), and this was used as the evaluation sample. Regarding this evaluation sample, the peel strength was measured under the following conditions to evaluate the heat seal strength (heat sealability). Testing equipment: Tensile tester (manufactured by Tester Sangyo Co., Ltd.) Peeling conditions: 180° peeling, 300 mm / min [Evaluation criteria] S: 6 N or more (extremely good) A: 4 N or more and less than 6 N (good) B: 2 N or more and less than 4 N (usable) C: Less than 2 N (not usable)

[0049] <Blocking resistance> Two of the resulting laminates were prepared. The coated surface of one laminate was overlapped with the non-coated surface of the other laminate, and the evaluation was conducted according to the following testing equipment and conditions. Testing equipment: CO-201 permanent distortion tester (manufactured by Tester Sangyo Co., Ltd., upper and lower plate heating) Pressure: 4 kg / cm 2 [Evaluation criteria] S: After compression for 24 hours in an environment of 40 °C - 80% RH, there is no sense of resistance during peeling, and the laminate is not damaged (extremely good) A: After compression for 24 hours in an environment of 40 °C - 40% RH, there is no sense of resistance during peeling, and the laminate is not damaged (good) B: After compression for 24 hours in an environment of 40 °C - 40% RH, there is a slight sense of resistance during peeling, but the laminate is not damaged (usable) C: After compression for 24 hours in an environment of 40 °C - 40% RH, there is a sense of resistance during peeling, and the laminate is also damaged (not usable)

[0050] <Water absorption resistance> For the coated surface of the obtained laminate, a water resistance test was conducted with reference to JIS P8140 (Water Absorbency Test Method: Cobb Method). To evaluate more strictly, the test was carried out using water heated to 80 °C for 30 minutes. [Evaluation Criteria] S: Water absorbency after 30 minutes is less than 10 g / m 2 (Extremely good) A: Water absorbency after 30 minutes is 10 g / m 2 or more and less than 20 g / m 2 (Good) B: Water absorbency after 30 minutes is 20 g / m 2 or more and less than 30 g / m 2 (Usable) C: Water absorbency after 30 minutes is 30 g / m 2 or more (Unusable)

[0051] [Sealability when wet with water] Two test pieces obtained by cutting the obtained laminate into 15 mm widths were prepared, and the coated surfaces of each were overlapped, and those subjected to a pressure bonding treatment under the same conditions as the heat seal strength test were used as evaluation samples. After immersing the evaluation samples in water at 25 °C for 10 seconds, the presence or absence of peeling at the bonded portion was visually observed. [Evaluation Criteria] 〇: No peeling ×: Peeling exists

[0052] [Example 1] 60.0 parts of butyl alcohol was charged into a reaction vessel (reaction tank) equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, and while performing nitrogen substitution, the internal temperature of the reaction vessel was raised to 110 °C. Next, 40.0 parts of styrene, 30.0 parts of α-methylstyrene, and 30.0 parts of acrylic acid were charged into the dropping funnel, and further, 5 parts of azoisobutyronitrile was charged and dissolved, and it was dropped over 2 hours. After completion of dropping, the reaction was carried out at 110 °C for 4 hours. After the reaction, it was cooled to 80 °C, neutralized with 28.3 parts of 25% aqueous ammonia, diluted with 220.0 parts of water, and then butyl alcohol was distilled off and adjusted to a non-volatile content of 30% to obtain an aqueous solution of polymer (A-1). The Tg of the obtained polymer (A-1) was 120 °C.

[0053] Subsequently, the internal temperature of the reaction vessel was adjusted to 80°C, and 100 parts of water was charged into the reaction tank. Next, 94.0 parts of styrene and 100.0 parts of 2-ethylhexyl acrylate were charged into the dropping funnel as monomer (a-2). After raising the internal temperature of the reaction vessel to 80°C and thoroughly performing nitrogen substitution, 17.0 parts of a 10% aqueous solution of ammonium persulfate was added, and 5 minutes later, the mixed solution of monomer (a-2) charged into the dropping funnel was added dropwise over 2 hours to conduct the reaction. After completion of the dropwise addition, the reaction was further carried out at 80°C for 3 hours to obtain resin particles (A). The Tg of the polymer (A-2) portion of the obtained resin particles (A) was -12°C, the average particle diameter of the resin particles (A) was 85 nm, and the acid value of the non-volatile content of the resin particles (A) was 78 mgKOH / g. To the obtained resin particles (A), 58.8 parts of ChemPearl W400 (a polyethylene wax manufactured by Mitsui Chemicals, non-volatile content: 40%, melting point: 110°C, average particle diameter: 4 μm) as wax (B) and a predetermined amount of water were added, and the non-volatile content was adjusted to 40% to obtain the target heat sealant. Using the obtained heat sealant as a base material, it was coated on one side of a commercially available paper (weight 100 g) using a bar coater #12. After coating, it was dried in a hot air oven at 100°C for 30 seconds to obtain a laminate.

[0054] [Examples 2 to 5, 8 to 10, 13 to 20, Comparative Examples 2 to 6] Resin particles (A) were prepared in the same manner as in Example 1 with the composition shown in Table 1. Regarding water, it was adjusted so that the non-volatile content of the heat sealant became 40%. For the obtained resin particles (A), the Tg, acid value, and average particle diameter were measured in the same manner as in Example 1. In Table 1, the blanks indicate that they are not blended or not contained. Also, in Example 2, AQUACER539 (a modified paraffin wax manufactured by BYK, non-volatile content: 35%, melting point: 90°C, average particle diameter: 0.06 μm) was used instead of ChemPearl W400 as wax (B), and in Example 3, ChemPearl W410 (a polyethylene wax manufactured by Mitsui Chemicals, non-volatile content: 40%, melting point: 110°C, average particle diameter: 9.5 μm) was used instead of ChemPearl W400 as wax (B).

[0055] [Example 6] Into a reaction vessel (reaction tank) equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 230.0 parts of water and 0.6 part of Perlex OT-P (sodium dioctyl sulfosuccinate manufactured by Kao Corporation, active ingredient 70%) as a surfactant were charged. Separately, 80.0 parts of methyl methacrylate, 7.0 parts of n-butyl acrylate, 13.0 parts of methacrylic acid, 3.0 parts of t-dodecyl mercaptan, 0.4 part of Perlex OT-P, and 65.0 parts of water as monomer (a-1) were mixed and stirred in advance to prepare an emulsion of the monomer to be dropped in the first stage (the dropping tank of the first stage). After raising the internal temperature of the reaction vessel to 85°C and sufficiently replacing the nitrogen, 2.5 parts of a 10% aqueous solution of ammonium persulfate as a polymerization initiator was added, and the emulsion of the monomer to be dropped in the first stage was dropped over 2 hours while maintaining the internal temperature at 85°C to carry out emulsion polymerization. After completion of the dropping of the monomer in the first stage, the temperature was maintained at 85°C for 30 minutes, and then 10.3 parts of 25% aqueous ammonia was added with stirring to neutralize. The Tg of the obtained polymer (A-1) was 91°C.

[0056] Subsequently, an emulsion of the monomer in the second stage (the dropping tank of the second stage) was prepared by mixing 90.0 parts of methyl methacrylate, 104.0 parts of 2-ethylhexyl acrylate, 0.4 part of Perlex OT-P, and 100.0 parts of water in advance as monomer (a-2) and stirring. 10.0 parts of a 10% aqueous solution of ammonium persulfate was added, and the emulsion of monomer (a-2) to be dropped in the second stage was dropped over 2 hours while maintaining the internal temperature at 85°C to carry out emulsion polymerization. After completion of the dropping, the reaction was carried out at 85°C for another 2 hours to obtain resin particles (A). The Tg of the polymer (A-2) part of the obtained resin particles (A) was -14°C, the average particle diameter of the resin particles (A) was 40 nm, and the acid value of the non-volatile content of the resin particles (A) was 28 mgKOH / g. To the obtained resin particles (A), 29.4 parts of Chemparl W400 as wax (B) and a predetermined amount of water were added, and the non-volatile content was adjusted to 40% to obtain the target heat-sealing agent. The obtained heat-sealing agent was coated on one side of a commercially available paper (weight 100 g) as a substrate using a bar coater #12. After coating, the laminate was obtained by drying in a hot air oven at 100°C for 30 seconds.

[0057] [Example 7, Comparative Example 1] An aqueous dispersion of resin particles was prepared in the same manner as in Example 5 with the composition shown in Table 1. Regarding water, it was adjusted so that the nonvolatile content of the heat-sealing agent would be 40%. For the obtained polymer (A-1) and polymer (A-2), the Tg, acid value, and average particle diameter were measured in the same manner as in Example 1.

[0058] [Example 11] Into a reaction vessel (reaction tank) equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 230.0 parts of water and 0.6 part of Perlex OT-P (sodium dioctyl sulfosuccinate manufactured by Kao Corporation, active ingredient 70%) as a surfactant were charged. Separately, 88.0 parts of methyl methacrylate, 10.0 parts of methacrylic acid, 2.0 parts of 2-hydroxyethyl methacrylate, 3.0 parts of t-dodecyl mercaptan, 0.4 part of Perlex OT-P, and 65.0 parts of water as monomer (a-1) were mixed and stirred in advance to prepare an emulsion of the monomer to be added dropwise in the first stage (the dropping tank for the first stage). After raising the internal temperature of the reaction vessel to 85°C and sufficiently purging with nitrogen, 3.0 parts of a 10% aqueous solution of ammonium persulfate as a polymerization initiator was added, and while maintaining the internal temperature at 85°C, the emulsion of the monomer to be added dropwise in the first stage was added dropwise over 2 hours to conduct emulsion polymerization. After completion of the dropwise addition of the monomer in the first stage, the temperature was maintained at 85°C for 30 minutes, and then 7.9 parts of 25% aqueous ammonia was added with stirring for neutralization. The Tg of the obtained polymer (A-1) was 106°C.

[0059] Subsequently, as the monomer (a-2), 200.0 parts of methyl methacrylate, 250.0 parts of 2-ethylhexyl acrylate, 5.0 parts of glycidyl methacrylate, 0.4 part of Perex OT-P, and 200.0 parts of water were mixed in advance and stirred to prepare an emulsion of the second-stage monomer (the dropping tank of the second stage). 20.0 parts of a 10% aqueous solution of ammonium persulfate was added, and the emulsion of the monomer (a-2) to be dropped in the second stage was dropped over 2 hours while maintaining the internal temperature at 85°C to conduct emulsion polymerization. After completion of the dropping, the reaction was continued at 85°C for another 2 hours to obtain resin particles (A) containing a polymer (A-3) in which the carboxyl group of the polymer (A-1) and the glycidyl group of the polymer (A-2) were chemically bonded. The Tg of the polymer (A-2) portion of the obtained resin particles (A) was -17°C, the average particle diameter of the resin particles (A) was 80 nm, and the acid value of the non-volatile content of the resin particles (A) was 12 mgKOH / g. To the obtained resin particles (A), 249.8 parts of Chemparl W400 as the wax (B) and a predetermined amount of water were added, and the non-volatile content was adjusted to 40% to obtain the target heat-sealing agent. The obtained heat-sealing agent was used as a base material and coated on one side of a commercially available paper (weight 100 g) using a bar coater #12. After coating, the laminate was obtained by drying in a hot air oven at 100°C for 30 seconds.

[0060] [Example 12] 60.0 parts of butyl alcohol was charged into a reaction vessel (reaction tank) equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, and while performing nitrogen substitution, the internal temperature of the reaction vessel was raised to 110°C. Next, 29.0 parts of styrene, 29.0 parts of α-methylstyrene, and 42.0 parts of methacrylic acid were charged into the dropping funnel as the monomer (a-1), and further 5 parts of azoisobutyronitrile was charged and dissolved, and then dropped over 2 hours. After completion of the dropping, the reaction was carried out at 110°C for 4 hours. After the reaction, it was cooled to 80°C, neutralized with 39.6 parts of 25% aqueous ammonia, diluted with 220.0 parts of water, and then butyl alcohol was distilled off and adjusted to a non-volatile content of 30% to obtain an aqueous solution of the polymer (A-1). The Tg of the obtained polymer (A-1) was 120°C.

[0061] Subsequently, the internal temperature of the reaction vessel was adjusted to 80°C, and 80 parts of water was charged into the reaction tank. Next, 65.0 parts of styrene, 81.0 parts of 2-ethylhexyl acrylate, and 4.0 parts of glycidyl methacrylate were charged into a dropping funnel as monomer (a-2). After raising the internal temperature of the reaction vessel to 80°C and sufficiently performing nitrogen substitution, 15.0 parts of a 10% aqueous solution of ammonium persulfate was added, and 5 minutes later, the mixed solution of monomer (a-2) charged into the dropping funnel was added dropwise over 2 hours to conduct the reaction. After completion of the dropwise addition, the reaction was further carried out at 80°C for 3 hours to obtain resin particles (A) containing polymer (A-3) in which the carboxyl group of polymer (A-1) and the glycidyl group of polymer (A-2) were chemically bonded. The Tg of the polymer (A-2) portion of the obtained resin particles (A) was -17°C, the average particle diameter of the resin particles (A) was 75 nm, and the acid value of the non-volatile content of the resin particles (A) was 127 mgKOH / g. To the obtained resin particles (A), 50.0 parts of Chem Pearl W400 as wax (B) and a predetermined amount of water were added, and the non-volatile content was adjusted to 40% to obtain the target heat sealant. The obtained heat sealant was coated on one side of a commercially available paper (weight 100 g) as a substrate using a bar coater #12. After coating, a laminate was obtained by drying in a hot air oven at 100°C for 30 seconds.

[0062]

Table 1

[0063]

Table 1

[0064]

Table 1

[0065] As can be seen from Table 1, the heat sealability, blocking resistance, water absorption resistance, and sealability during water staining of the laminates using the heat sealants obtained in Examples 1 to 20 were extremely excellent, and the performance fully satisfied the practical level. On the other hand, the heat sealability, blocking resistance, water absorption resistance, and sealability during water staining of the laminates using the heat sealants obtained in Comparative Examples 1 to 6 were extremely inferior in any of the physical properties, and it was difficult to say that they met the practical level.

Claims

1. A heat-sealing agent containing resin particles (A) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C, and an acid value of 10 to 130 mg KOH / g.

2. The heat-sealing agent according to Claim 1, wherein the resin particles (A) contain a polymer (A-1) having a glass transition temperature of 60 to 140°C and a polymer (A-2) having a glass transition temperature of -50 to 20°C.

3. The heat-sealing agent according to Claim 1, wherein the resin particles (A) contain a polymer (A-3) having a glass transition temperature in the range of 60 to 140°C and in the range of -50 to 20°C.

4. The heat-sealing agent according to Claim 2, wherein the mass ratio of the polymer (A-1) to the polymer (A-2) (polymer (A-1) / polymer (A-2)) is 10 / 90 to 50 / 50.

5. The heat-sealing agent according to Claim 1, further comprising a wax (B) having an average particle diameter of 0.03 to 10 μm.

6. A laminate having a heat-sealing layer formed from the heat-sealing agent according to any one of Claims 1 to 5 on a substrate.

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