Resin composition

Abstract

The resin composition of the present invention comprises 40 to 98 parts by mass of a modified starch (A), 2 to 60 parts by mass of a polyvinyl alcohol (B) having a degree of saponification of 75.0 mol% or more, and optionally a clay (C), wherein the total content of (A), (B) and (C) is 100 parts by mass, and the peak temperature of tan δ when the dynamic viscoelasticity is measured in a range of 20°C to 150°C is 128°C or lower.

Description

Technical Field

[0001] The present invention relates to a resin composition used for food packaging and the like, a water-containing composition containing the resin composition, a coating containing the water-containing composition and a method for producing the same, a multilayer structure containing the coating, an adhesive containing the coating or the multilayer structure, and a packaging material made of the adhesive.

Background Art

[0002] Conventionally, resin compositions containing modified starch and water-soluble polymers have been widely used for containers for packaging food because of their excellent biodegradability and gas barrier properties (for example, Patent Document 1). However, when forming a container or the like using such a resin composition, it is necessary to use an adhesive material such as a hot melt adhesive, which is not only costly but also reduces biodegradability. Therefore, the resin composition is required to have heat sealability so that it can be adhered without an adhesive material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, according to the study by the present inventor, it has been found that the resin composition as described in Patent Document 1 has a relatively high gas barrier property but insufficient heat sealability. Further, if an attempt is made to improve the heat sealability, the gas barrier property may conversely decrease, and it has also been found that it is difficult to achieve both heat sealability and gas barrier property.

[0005] Accordingly, an object of the present invention is to provide a resin composition excellent in heat sealability and gas barrier properties, a water-containing composition containing the resin composition, a coating containing the water-containing composition and a method for producing the same, a multilayer structure containing the coating, an adhesive containing the coating or the multilayer structure, and a packaging material made of the adhesive. [Means for Solving the Problems]

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that in a resin composition containing 40 to 98 parts by mass of modified starch (A), 2 to 60 parts by mass of polyvinyl alcohol (B) having a saponification degree of 75.0 mol% or more, and optionally clay (C), when the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20°C to 150°C is adjusted to 128°C or less, the above problems can be solved, and the present invention has been completed. That is, the present invention includes the following aspects.

[0007] [1] A resin composition containing 40 to 98 parts by mass of modified starch (A), 2 to 60 parts by mass of polyvinyl alcohol (B) having a saponification degree of 75.0 mol% or more, and optionally clay (C), wherein the total content of (A), (B) and (C) is 100 parts by mass, and the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20°C to 150°C is 128°C or less. [2] The resin composition according to [1], wherein the total content of modified starch (A), polyvinyl alcohol (B), and clay (C) is 80% by mass or more based on the mass of the resin composition. [3] The resin composition according to [1] or [2], wherein the average amylose content of the modified starch (A) is 45% by mass or more. [4] The resin composition according to any one of [1] to [3], wherein the saponification degree of the polyvinyl alcohol (B) is 75.0 to 98.9 mol%. [5] The resin composition according to any one of [1] to [4], wherein the content of the clay (C) is 0 parts by mass or more and less than 2 parts by mass. [6] The modified starch (A) is at least one selected from the group consisting of etherified starch, esterified starch, cationized starch, and crosslinked starch, and the resin composition according to any one of [1] to [5]. [7] The modified starch (A) is at least one selected from the group consisting of etherified starch having a hydroxyalkyl group having 2 to 6 carbon atoms and esterified starch having a structural unit derived from a dicarboxylic anhydride, and the resin composition according to any one of [1] to [6]. [8] The polyvinyl alcohol (B) has a viscosity at 20 ° C of a 4% aqueous solution measured in accordance with JIS Z 8803 of 1 to 50 mPa·s, and the resin composition according to any one of [1] to [7]. [9] An aqueous composition containing the resin composition according to any one of [1] to [8], wherein the water content is 1 to 50% by mass, the aqueous composition.

[10] A coated product obtained by coating the aqueous composition according to [9] on paper or a film.

[11] A multilayer structure including the coated product according to

[10] and one or more layers (X).

[12] An adhesive obtained by thermally bonding the aqueous composition of the coated product according to

[10] or the multilayer structure according to

[11] to an adherend layer, wherein the adherend layer is the coated product, the multilayer structure, the aqueous composition contained in another coated product or another multilayer structure, the paper, the film, and the layer (X) A layer selected from the group consisting of: or a layer contained in an adherend other than these.

[13] The adhesive according to

[12] , wherein the adherend layer is the aqueous composition contained in a coated product, a multilayer structure, another coated product, or another multilayer structure.

[14] A packaging material comprising the adhesive according to

[12] or

[13] .

[15] A two-sided bag, a three-sided bag, a flat pouch, a standing pouch, a gusset pouch, a twin pouch, or a spout pouch, the packaging material according to

[14] .

[16] A method for producing the coated product according to

[10] , comprising a step of coating the aqueous composition according to [9] on a film or paper conveyed by a take-up machine using an extruder. [Effect of the Invention]

[0008] The resin composition of the present invention is excellent in heat sealability and gas barrier properties.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] [Resin Composition] The resin composition of the present invention contains 40 to 98 parts by mass of modified starch (A), 2 to 60 parts by mass of polyvinyl alcohol (B) with a saponification degree of 75.0 mol% or more, and optionally clay (C), and the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20°C to 150°C is 128°C or lower.

[0011] The present inventor has surprisingly found that when the modified starch (A) and polyvinyl alcohol (B) with a saponification degree of 75.0 mol% or more are contained in a specific ratio and the peak temperature of the tanδ is 128°C or lower, excellent heat sealability and excellent gas barrier properties can be achieved simultaneously.

[0012] [Modified Starch (A)] From the viewpoint of easily enhancing heat sealability, gas barrier properties, and biodegradability, the modified starch (A) is preferably at least one selected from the group consisting of, for example, etherified starch, esterified starch, cationized starch, and crosslinked starch.

[0013] Examples of starches include starches derived from cassava, corn, potato, sweet potato, sago, tapioca, sorghum, beans, bracken, lotus rhizome, water chestnut, wheat, rice, oats, kudzu, pea, etc. Among them, starches derived from corn and cassava are preferred, and starches derived from high amylose corn are more preferred. Starches can be used alone or in combination of two or more.

[0014] Examples of etherified starches include alkyl etherified starches such as methyl etherified starch; carboxyalkyl etherified starches such as carboxymethyl etherified starch; hydroxyalkyl etherified starches such as etherified starches having a hydroxyalkyl group with 2 to 6 carbon atoms, etc. Also, allyl etherified starch etc. can be used.

[0015] Examples of esterified starches include esterified starches having a structural unit derived from carboxylic acid such as esterified starch having a structural unit derived from acetic acid; esterified starches having a structural unit derived from dicarboxylic acid anhydride such as esterified starch having a structural unit derived from maleic anhydride, esterified starch having a structural unit derived from phthalic anhydride, esterified starch having a structural unit derived from octenyl succinic anhydride, etc.; esterified starches having a structural unit derived from oxo acid such as nitrate esterified starch, phosphate esterified starch, urea phosphate esterified starch, etc. Other examples include xanthic acid esterified starch, acetoacetic acid esterified starch, etc.

[0016] Examples of cationized starches include reaction products of starch and 2 - diethylaminoethyl chloride, reaction products of starch and 2,3 - epoxypropyltrimethylammonium chloride, etc.

[0017] Examples of the crosslinked starch include formaldehyde-crosslinked starch, epichlorohydrin-crosslinked starch, phosphoric acid-crosslinked starch, acrolein-crosslinked starch, and the like.

[0018] From the viewpoint of easily enhancing heat sealability, gas barrier properties, and biodegradability, the modified starch (A) is preferably at least one selected from the group consisting of etherified starch having a hydroxyalkyl group having 2 to 6 carbon atoms and esterified starch having a structural unit derived from a dicarboxylic anhydride, more preferably at least one selected from the group consisting of hydroxyethyl etherified starch, hydroxypropyl etherified starch, hydroxybutyl etherified starch, esterified starch having a structural unit derived from maleic anhydride, esterified starch having a structural unit derived from phthalic anhydride, and esterified starch having a structural unit derived from octenyl succinic anhydride. The modified starch (A) can be used alone or in combination of two or more. In the present specification, the number of carbon atoms described before "starch" represents the number of carbon atoms of the group substituted for one hydroxyl group in the starch (the group formed by modifying one hydroxyl group in the starch). For example, etherified starch having a hydroxyalkyl group having 2 to 5 carbon atoms indicates that the number of carbon atoms of the hydroxyalkyl group formed by modifying one hydroxyl group in the starch is 2 to 5.

[0019] The etherified starch having a hydroxyalkyl group having 2 to 6 carbon atoms may be obtained, for example, by the reaction of an alkylene oxide such as ethylene oxide, propylene oxide, or butylene oxide with starch. The average number of hydroxy groups used for modification is preferably 0.05 to 2 per glucose unit in the starch.

[0020] The modified starch (A) preferably has an average amylose content in the modified starch (A) of 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, and even more preferably 60% by mass or more. When the average amylose content is at least the above lower limit, it is easy to enhance heat sealability, gas barrier properties, and biodegradability. The content of the average amylose in the modified starch (A) is usually 90% by mass or less. In this specification, the amylose content can be measured, for example, by the iodine colorimetric method described in "Starch 50 No.4 158-163 (1998)". The average amylose content indicates the amylose content of one type of modified starch when there is one type of modified starch, and when two or more types of modified starches are used, it is a weighted average of the amylose contents of two or more types of modified starches. Therefore, for example, when two or more types of modified starches are used and the average amylose content is 45% by mass or more, a modified starch with an amylose content of less than 45% by mass may be included.

[0021] The modified starch (A) may preferably have a water content in the modified starch (A) of 5 to 15% by mass.

[0022] Commercially available modified starches can also be used as the modified starch (A). Examples of typical commercial products of the modified starch (A) include, for example, ECOFILM (trademark) and National1658 (trademark), which are hydroxypropyl etherified starches manufactured by Ingredion.

[0023] The content of the modified starch (A) is 40 to 98 parts by mass with respect to a total of 100 parts by mass of the components (A), (B), and (C). When the content of the modified starch (A) is less than 40 parts by mass or exceeds 98 parts by mass, the heat sealability, gas barrier properties, and biodegradability tend to decrease. The content of the modified starch (A) is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 65 parts by mass or more, and preferably 95 parts by mass or less. When the content of the modified starch (A) is not less than the above lower limit, it is easy to improve the heat sealability and biodegradability, and when the content of the modified starch (A) is not more than the above upper limit, it is easy to improve the gas barrier property and heat sealability.

[0024] <Polyvinyl alcohol (B)> Polyvinyl alcohol (B) is a polymer having structural units derived from vinyl alcohol (sometimes referred to as vinyl alcohol units). The saponification degree of polyvinyl alcohol (B) is 75.0 mol% or more. When the saponification degree of polyvinyl alcohol (B) is less than 75.0 mol%, the gas barrier property tends to decrease. Since the saponification degree of polyvinyl alcohol (B) in the resin composition of the present invention is 75.0 mol% or more, the gas barrier property can be improved. The saponification degree of polyvinyl alcohol (B) is preferably 78 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and preferably 98.9 mol% or less, more preferably 98 mol% or less, even more preferably 97 mol% or less. When the saponification degree of polyvinyl alcohol (B) is not less than the above lower limit, it is easy to enhance the gas barrier property, and when the saponification degree of polyvinyl alcohol (B) is not more than the above upper limit, it is easy to enhance the heat sealability. The saponification degree indicates the molar fraction of hydroxyl groups with respect to the total of hydroxyl groups and ester groups in polyvinyl alcohol. The saponification degree can be measured in accordance with JIS K 6726 (Polyvinyl Alcohol Test Method), for example, by the method described in the examples. Polyvinyl alcohol is produced, for example, by hydrolysis of polyvinyl acetate obtained by polymerization of vinyl acetate monomer.

[0025] Polyvinyl alcohol (B) preferably has a viscosity at 20 °C of a 4% aqueous solution measured in accordance with JIS Z 8803 of 1 mPa·s or more, more preferably 3 mPa·s or more, still more preferably 5 mPa·s or more, and preferably 50 mPa·s or less, more preferably 45 mPa·s or less, still more preferably 35 mPa·s or less. When the viscosity of polyvinyl alcohol (B) is within the above range, heat sealability, gas barrier properties, and biodegradability are likely to be enhanced. The viscosity can be measured by the method described in the examples.

[0026] Polyvinyl alcohol (B) can further contain monomer units other than vinyl alcohol units. Examples of other monomer units include monomer units derived from ethylenically unsaturated monomers. Examples of ethylenically unsaturated monomers include α-olefins such as ethylene, propylene, n-butene, isobutylene, 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylate group; methacrylic acid and its salts; unsaturated monomers having a methacrylate group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts (e.g., quaternary salts); vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile, methacrylonitrile; vinyl halides such as vinyl chloride, vinyl fluoride; vinylidene halides such as vinylidene chloride, vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid and their salts or esters; vinyl silyl compounds such as vinyltrimethoxysilane, isopropenyl acetate; vinyl ester monomers such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl carlylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate. The content of other monomer units is preferably 10 mol% or less, more preferably 5 mol% or less, based on the total molar amount of the constituent units constituting polyvinyl alcohol (B).

[0027] The method for producing polyvinyl alcohol is not particularly limited. For example, a method of polymerizing a vinyl acetate monomer and optionally another monomer, and saponifying the obtained polymer to convert it into vinyl alcohol units can be mentioned. Examples of the polymerization method during polymerization include batch polymerization, semi-batch polymerization, continuous polymerization, semi-continuous polymerization, etc. Examples of the polymerization method include known methods such as bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. For the saponification of the polymer, known methods can be applied. For example, it can be carried out in a state where the polymer is dissolved in an alcohol or a hydrous alcohol. The alcohol that can be used at this time is a lower alcohol such as methanol, ethanol, etc. Polyvinyl alcohol (B) can be used alone or in combination of two or more.

[0028] The content of polyvinyl alcohol (B) is 2 to 60 parts by mass based on 100 parts by mass in total of components (A), (B) and (C). When the content of polyvinyl alcohol (B) is less than 2 parts by mass or more than 60 parts by mass, the heat sealability, gas barrier property and biodegradability tend to decrease. The content of polyvinyl alcohol (B) is preferably 5 parts by mass or more, more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. When the content of polyvinyl alcohol (B) is at least the above lower limit, the gas barrier property and heat sealability are likely to be improved, and when the content of polyvinyl alcohol (B) is at most the above upper limit, the heat sealability and biodegradability are likely to be improved.

[0029] <Clay (C)> The resin composition of the present invention may optionally contain clay (C). In this specification, "optionally contain" means that the component may or may not be contained. The clay (C) may be natural clay, synthetic clay, or organic clay. Examples of the clay include synthetic or natural layered silicate clays such as montmorillonite, bentonite, beidellite, mica, hectorite, saponite, nontronite, sauconite, vermiculite, ledikite, magadiite, kenyaite, stevensite, and volkonskoite. The clay (C) can be used alone or in combination of two or more kinds.

[0030] The organic clay is obtained by subjecting the above-mentioned clay to an organic treatment (or modification) with an organic agent (or modifier). The organic agent is not particularly limited, and examples thereof include quaternary ammonium salts having an alkyl group, a benzyl group, a pyridyl group, animal fat, or hydrogenated animal fat obtained by hydrogenating animal fat; tertiary ammonium salts, secondary ammonium salts, and the like. Examples of the alkyl group include alkyl groups having 1 to 20 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, and decyl group.

[0031] Commercially available products may be used for the clay (C). The commercially available products are not particularly limited, and examples thereof include CLOISITE (registered trademark) 20A (montmorillonite organically treated with dimethyldi(hydrogenated tallow) quaternary ammonium salt, manufactured by Southern Clay Industries).

[0032] The content of the clay (C) is preferably less than 2 parts by mass, more preferably 1.5 parts by mass or less, still more preferably 1 part by mass or less, even more preferably 0.5 part by mass or less, particularly preferably 0.2 part by mass or less, and preferably 0 part by mass or more with respect to 100 parts by mass in total of the components (A), (B), and (C). When the content of the clay (C) is below the above upper limit, it is easy to adjust the peak temperature of tanδ to 128°C or lower, and excellent heat sealability is likely to be exhibited.

[0033] <Additive> (Polyoxyalkylene (D)) The resin composition of the present invention can optionally contain polyoxyalkylene (D). Polyoxyalkylene (D) refers to polyalkylene oxide and polyalkylene glycol and has a structural unit (also referred to as structural unit (1)) represented by the following formula (1). Polyoxyalkylene (D) may have two or more different structural units (1). [Chemical formula] [In the formula, R is an alkylene group and n is 1 or more]

[0034] In formula (1), examples of the alkylene group include alkylene groups having 2 to 10 carbon atoms such as ethylene group, propylene group, trimethylene group, butylene group, isobutylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, and decylene group. Among these, from the viewpoints of heat sealability and gas barrier properties, an alkylene group having 2 to 6 carbon atoms is preferable, and an ethylene group and / or a propylene group is more preferable. When n is 2 or more, these alkylene groups can be used alone or in combination of two or more.

[0035] From the viewpoints of heat sealability and gas barrier properties, n in formula (1) is preferably 5 or more, more preferably 50 or more, still more preferably 100 or more, and preferably 120,000 or less, more preferably 70,000 or less. When polyoxyalkylene (D) contains different structural units (1), the repeating number n of each structural unit may be the same or different.

[0036] Examples of the polyalkylene oxide include polymers having structural units derived from alkylene oxides having 2 to 6 carbon atoms, specifically polyethylene oxide, polypropylene oxide, polytrimethylene oxide (polyoxetane), polybutylene oxide, polyisobutylene oxide, or copolymers of monomers constituting these. Examples of the polyalkylene glycol include polymers having structural units derived from alkylene glycols having 2 to 6 carbon atoms, specifically polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polybutylene glycol, polyisobutylene glycol, or copolymers of monomers constituting these. Among these, from the viewpoints of heat sealability and gas barrier properties, polyoxyalkylene (D) is preferably polyethylene oxide, polypropylene oxide, polyethylene glycol, polypropylene glycol, or a copolymer of monomers constituting these. Preferred examples of the copolymer include copolymers of ethylene oxide and propylene oxide, copolymers of ethylene glycol and propylene glycol, and the like.

[0037] Polyoxyalkylene (D) may contain structural units derived from other monomers than the structural unit (1) as long as the effects of the present invention are not impaired. When polyoxyalkylene (D) is a copolymer, the polymerization form of the copolymer is not particularly limited and may be any of random, block, graft, or tapered forms. Polyoxyalkylene (D) can be used alone or in combination of two or more.

[0038] From the viewpoints of heat sealability and gas barrier properties, the weight average molecular weight of polyoxyalkylene (D) is preferably 10,000 or more, more preferably 50,000 or more, preferably 5,000,000 or less, and more preferably 3,000,000 or less.

[0039] Polyoxyalkylene (D) can also be a commercially available product. Examples of representative commercially available products of polyoxyalkylene (D) include Alcox (trademark) E-75G, Alcox (trademark) L-11, Alcox (trademark) L-6, Alcox (trademark) EP1010N manufactured by Meisei Chemical Industry Co., Ltd., Peo (trademark) PEO-1, PEO-2 manufactured by Sumitomo Seika Chemicals Co., Ltd., and the like.

[0040] From the viewpoints of heat sealability and gas barrier properties, the content of polyoxyalkylene (D) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and preferably 0 parts by mass or more, based on the mass of the resin composition.

[0041] (Polyol plasticizer (E)) The resin composition of the present invention can optionally contain a polyol plasticizer (E). The polyol plasticizer (E) is not particularly limited. For example, sorbitol, maltitol, xylitol, erythritol, sucrose, mannitol, lactitol, arabinose, xylose, fructose, glucose, galactose, ribose, trehalose, glycerol, ethylene glycol, propylene glycol, etc. can be mentioned. These polyol plasticizers (E) can be used alone or in combination of two or more. Among these, from the viewpoints of heat sealability and oxygen barrier properties, the polyol plasticizer (E) preferably contains at least one selected from the group consisting of sorbitol, maltitol, xylitol, erythritol, sucrose, mannitol, lactitol, arabinose, xylose, fructose, glucose, galactose, ribose, trehalose, and glycerol, and more preferably contains at least one selected from the group consisting of sorbitol, xylitol, and sucrose. Note that, for example, commercially available products can be used as the polyol plasticizer (E). The commercially available products are not particularly limited, and for example, Sorbitol SP manufactured by Bussan Food Science Co., Ltd. can be mentioned.

[0042] From the viewpoints of heat sealability and gas barrier properties, the content of the polyol plasticizer (E) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, and preferably 0 parts by mass or more, based on the mass of the resin composition.

[0043] (Other additives) The resin composition of the present invention may contain a fatty acid having 12 to 22 carbon atoms and / or its fatty acid salt. Examples of the fatty acid having 12 to 22 carbon atoms and its fatty acid salt include stearic acid, calcium stearate, sodium stearate, palmitic acid, lauric acid, myristic acid, linoleic acid, behenic acid, etc. Among these, from the viewpoint of processability, stearic acid, calcium stearate, and sodium stearate are preferable. The fatty acid having 12 to 22 carbon atoms and its fatty acid salt can be used alone or in combination of two or more.

[0044] When the resin composition of the present invention contains a fatty acid having 12 to 22 carbon atoms and / or its fatty acid salt, the content thereof is preferably 0.01 to 3% by mass, more preferably 0.03 to 2% by mass, still more preferably 0.1 to 1% by mass, based on the mass of the resin composition. When the content of the fatty acid having 12 to 22 carbon atoms and / or its fatty acid salt is within the above range, it tends to be advantageous in terms of processability.

[0045] The resin composition of the present invention may contain other plasticizers (F) other than the polyol plasticizer (E). Examples of the plasticizer (F) include water, glyceryl trioleate, epoxidized linseed oil, epoxidized soybean oil, tributyl citrate, acetyltriethyl citrate, glyceryl triacetate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. The plasticizer (F) can be used alone or in combination of two or more. Among these plasticizers (F), water is preferable from the viewpoint of obtaining good film-forming properties and coatability.

[0046] The water content (moisture content) in the resin composition is preferably 3 to 20% by mass, more preferably 4 to 18% by mass, still more preferably 7 to 15% by mass, based on the mass of the resin composition, from the viewpoint of facilitating the improvement of the film-forming property and gas barrier property of the resin composition. The water content can be determined, for example, by measuring at 130 °C for 60 minutes using a heated drying type moisture meter.

[0047] The resin composition of the present invention may further contain additives (G) such as a filler, a processing stabilizer, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, another thermoplastic resin, a lubricant, a fragrance, an antifoaming agent, a deodorant, a bulking agent, a release agent, a mold release agent, a reinforcing agent, a crosslinking agent, a fungicide, a preservative, a crystallization rate retardant, etc., as required.

[0048] In the resin composition of the present invention, the total content of the modified starch (A), polyvinyl alcohol (B) and clay (C) is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 85% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less, based on the mass of the resin composition. When the total content of components (A), (B) and (C) is within the above range, it is easy to enhance the heat sealability and gas barrier property.

[0049] <Resin composition> The resin composition of the present invention contains 40 to 98 parts by mass of the modified starch (A), 2 to 60 parts by mass of the polyvinyl alcohol (B), and optionally contains the clay (C), and the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20 °C to 150 °C is 128 °C or lower, so that excellent heat sealability and excellent gas barrier property can be achieved simultaneously. Furthermore, the resin composition is also excellent in biodegradability. Therefore, by using the resin composition of the present invention, a packaging material for food or the like can be easily formed without using an adhesive material. Moreover, such a packaging material can have excellent biodegradability and gas barrier property. In this specification, the heat sealability indicates the property of being able to adhere by heat.

[0050] The tanδ represents the loss tangent (E” / E’), which is the ratio of the storage modulus (E’) to the loss modulus (E”) obtained in the dynamic viscoelasticity measurement. Also, the peak temperature of tanδ indicates the temperature at the peak of tanδ in a graph (with the horizontal axis being temperature (°C) and the vertical axis being tanδ) obtained when measuring the dynamic viscoelasticity in the range of 20°C to 150°C. The measurement of the dynamic viscoelasticity can be carried out by using a dynamic viscoelasticity measuring device and pulling the resin composition (sheet) with a sine wave of 11 Hz while raising the temperature at a rate of 3°C / min in the range of 20°C to 150°C. In the graph in the range of 20°C to 150°C (sometimes referred to as the tanδ curve), when there are two or more peaks of tanδ, the temperature at the peak existing on the highest temperature side is taken as the peak temperature of tanδ. Also, in order to prevent the volatilization of water in the resin composition due to the temperature rise, vaseline or the like can be applied to both sides of the resin composition (sheet) before the measurement. Such a peak temperature of tanδ can be calculated, for example, by the method described in the examples.

[0051] The resin composition of the present invention has a peak temperature of tanδ of 128°C or less. When the peak temperature of tanδ exceeds 128°C, the gas barrier property and heat sealability, particularly the heat sealability, tend to significantly decrease. The resin composition of the present invention preferably has a peak temperature of tanδ of 125°C or less, more preferably 120°C or less, still more preferably 118°C or less, and preferably 50°C or more, more preferably 70°C or more, still more preferably 80°C or more. When the peak temperature of tanδ is within the above range, it is easy to improve the gas barrier property and heat sealability, particularly the heat sealability.

[0052] The peak temperature of tanδ in the resin composition of the present invention can be adjusted by appropriately changing, for example, the types and contents of the modified starch (A), polyvinyl alcohol (B) and clay (C), the saponification degree of the polyvinyl alcohol (B), the amylol content in the modified starch (A), etc. For example, the lower the content of the modified starch (A), the content of the clay (C) and the saponification degree of the polyvinyl alcohol (B), or the higher the content of the polyvinyl alcohol (B), the more likely the peak temperature of tanδ is to decrease. In particular, when the content of the clay (C) is high, the peak temperature of tanδ tends to increase significantly. Therefore, the content of the clay (C) is preferably adjusted to 1% by mass or less in the resin composition.

[0053] The resin composition of the present invention is excellent in gas barrier properties, particularly oxygen barrier properties. The oxygen permeability (mL·20μm / [m 2 ·atm·24hr]) of the resin composition of the present invention at 23°C and 50% RH is preferably 8.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, even more preferably 3.5 or less, and particularly preferably 3.0 or less. When the oxygen permeability in the resin composition is below the above upper limit, excellent oxygen barrier properties can be exhibited. Also, the oxygen permeability (mL·20μm / [m 2 ·atm·24hr]) is usually 0.01 or more. The oxygen permeability of the resin composition can be measured by an oxygen permeation measuring device after storing and conditioning it at 23°C and 50% RH for two weeks, for example, by the method described in the examples. In this specification, an improvement or increase in oxygen barrier properties means a reduction in oxygen permeability, and excellent oxygen barrier properties mean a low oxygen permeability.

[0054] The resin composition of the present invention can exhibit excellent heat sealability even in a low humidity environment, which is disadvantageous for resin compositions containing modified starch (A). Therefore, the resin composition of the present invention is excellent in heat seal strength in a low humidity environment. The heat seal strength of the resin composition of the present invention at 20°C and 30% RH is preferably 1.0 N / 15 mm or more, more preferably 3.0 N / 15 mm or more, still more preferably 4.0 N / 15 mm or more, even more preferably 5.0 N / 15 mm or more, and particularly preferably 5.5 N / 15 mm or more. When the heat seal strength is equal to or higher than the above lower limit, it is easy to exhibit excellent heat sealability. The upper limit of the heat seal strength is usually 30 N / 15 mm or less. The heat seal strength at 20°C and 30% RH can be measured, for example, by the method described in the examples.

[0055] The resin composition of the present invention may be in the form of pellets and films or sheets. When the resin composition of the present invention is used as a film or sheet, the thickness of the film is generally 5 μm to 100 μm, and the thickness of the sheet is generally 100 μm to 1000 μm. Also, the film or sheet may be a single layer or a multilayer. In this specification, the term "sheet" can be substituted with "film", and the term "film" can be substituted with "sheet".

[0056] [Method for producing resin composition] The resin composition of the present invention can be produced, for example, by a method including at least a step (1) of mixing the modified starch (A) and the polyvinyl alcohol (B) to obtain a mixture, a step (2) of extruding the mixture, and a step (3) of cooling and drying the extruded mixture.

[0057] Step (1) is at least a step of mixing the modified starch (A) and the polyvinyl alcohol (B), and optionally, at least one selected from the group consisting of the clay (C), polyoxyalkylene (D), polyol plasticizer (E), and other additives (for example, the fatty acid having 12 to 22 carbon atoms and / or its fatty acid salt, the plasticizer (F), the additive (G), etc.) can be mixed together.

[0058] Step (1) is usually carried out using an extruder. In the extruder, each component is subjected to shear stress by a screw and homogeneously mixed while being heated by the application of external heat to the barrel.

[0059] As the extruder, for example, a twin-screw extruder can be used. The twin-screw extruder may be either co-rotating or counter-rotating. The screw diameter may be, for example, 20 to 150 mm, and the ratio of the extruder length (L) to the screw diameter (D), i.e., the L / D ratio, may be, for example, 20 to 50. The rotational speed of the screw is preferably 80 rpm or more, more preferably 100 rpm or more. Also, the extrusion molding pressure is preferably 5 bar (0.5 MPa) or more, more preferably 10 bar (1.0 MPa) or more. Each component can be directly introduced into the extruder. Alternatively, a premixed product of these components using a mixer may be introduced into the extruder.

[0060] In step (1), from the viewpoint of easily enhancing the film-forming property and oxygen barrier property of the resin composition, it is preferable to mix a plasticizer (F) and preferably water. The lower limit is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 10% by mass or more, particularly preferably 15% by mass or more, and most preferably 20% by mass or more, and the upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, based on the mass of the mixture. Here, the mass of the mixture indicates the total mass of the mixture containing the plasticizer (F). In step (1), the plasticizer (F) may be introduced at the initial stage of extrusion, and the plasticizer (F) can be introduced before reaching the above heating temperature, for example, when it is 100 °C or lower. The modified starch (A) can be subjected to a cooking treatment by a combination of moisture, heat, and shear stress to be gelatinized (gelled). Also, by separately introducing a plasticizer (F) and preferably water, a water-soluble polymer such as polyvinyl alcohol (B) can be dissolved, the resin composition can be softened, and the modulus and brittleness can be reduced.

[0061] In step (1), the cooking process is preferably carried out by heating to a temperature above 100°C and below 150°C, more preferably above 115°C and below 140°C. Here, the cooking process is a process of crushing and gelling starch granules. Heating can be carried out by applying heat from the outside to the barrel of the extruder. By applying gradually changed temperatures to each barrel, heating can be achieved up to the target temperature. When the cooking process is carried out at a temperature above 120°C, it is advantageous in terms of processability.

[0062] In order to prevent foaming, the cooked mixture is preferably pushed forward toward the die while decreasing in temperature to a temperature of preferably 85 to 120°C, more preferably 90 to 110°C. Also, foaming can be prevented and moisture can be removed by exhausting from the barrel.

[0063] The residence time in the extruder can be set according to the temperature profile and screw speed, and is preferably 1 to 2.5 minutes.

[0064] In step (2) of extruding the mixture, the molten mixture that has been pushed forward in the extruder while being melt-kneaded is extruded from the die. The temperature of the die is preferably 85 to 120°C, more preferably 90 to 110°C.

[0065] In step (3) of cooling and drying the extruded mixture (melt), the mixture (melt) can be extruded in the form of a film, sheet, or strand.

[0066] When extruding the mixture in film form, the mixture can be extruded from a film-forming die and then cooled and dried while being wound up by a take-up roller. Between the die and the roller, it is preferable to cool so as to prevent the mixture from adhering to the roller. A forming roll may be installed between the die and the roller. The material of the forming roll is, for example, rubber, resin, or metal. For drying, the roll may be heated, or dehumidified air may be supplied during winding. In the case of the blowing tube method, the dehumidified air can be used to expand the film when the film exits the die. It is also possible to prevent film blocking by entraining talc in the air stream.

[0067] When extruding the mixture in strand form, it can be extruded from a multi-hole strand nozzle and cut with a rotary cutter to form strands into pellet shape. To prevent sticking of the pellets, vibration can be applied periodically or constantly, and moisture in the pellets can be removed by hot air, dehumidified air, or an infrared heater.

[0068] [Hydrous composition] The present invention includes a hydrous composition containing the resin composition and having a water content of 1 to 50% by mass. In one embodiment of the present invention, when forming a coating described later using the resin composition, in order to enhance the film-forming property of the resin composition, for example, when coating the resin composition on paper or a film, water may be added to the resin composition to prepare a hydrous composition. The water content can be determined by measuring with a heat drying type moisture meter at 130°C for 60 minutes for the resin composition or hydrous composition pulverized to a maximum particle size of 1 mm or less. In this specification, the hydrous composition means all those having a water content of 1 to 50% measured by the above method in a resin composition containing water. That is, the hydrous composition means not only those obtained by adding water to the resin composition to adjust the water content to the above range, but also resin compositions having a water content in the above range at the time of production.

[0069] The water content of the aqueous composition of the present invention is preferably 5% by mass or more, more preferably 8% by mass or more, preferably 45% by mass or less, and more preferably 40% by mass or less. When the water content is within the above range, it is easy to enhance the gas barrier property and the drawability during the formation of the coating.

[0070] In a preferred embodiment of the present invention, the aqueous composition of the present invention can be obtained by adding water to the resin composition and, for example, stirring and mixing. In order to prevent adhesion between the resin compositions and adsorb water throughout the pellets, it is preferable to perform stirring while adding water in two or more portions. Further, in order to keep the water content constant, the aqueous composition may be stored in a sealed container.

[0071] [Coating and Method for Producing the Same] The present invention includes a coating obtained by coating the aqueous composition of the present invention on paper or a film (or sheet). That is, the coating becomes a laminate having a layer made of the aqueous composition and a layer made of paper or a film (or sheet). The coating of the present invention is excellent in gas barrier property and biodegradability, and can exhibit heat sealability. Therefore, for example, a packaging material or the like can be easily and efficiently produced by heat without using an adhesive material.

[0072] When coating the aqueous composition on paper, the paper is not particularly limited, and examples thereof include kraft paper, high-quality paper, imitation paper, glassine paper, parchment paper, synthetic paper, white cardboard, manila board, milk carton base paper, cup base paper, ivory paper, silver paper, tissue paper, cardboard, rayon paper, and the like. The thickness of the paper in the coating is not particularly limited, and is preferably 1 to 500 μm, more preferably 10 to 300 μm. When the thickness of the paper in the coating is within the above range, the draw speed during coating production can be increased, and productivity is likely to be improved.

[0073] When coating a film with an aqueous composition, the film is not particularly limited. For example, polyethylene terephthalate (PET) film, biaxially oriented polypropylene (BOPP) film, polyethylene (PE) film (preferably low-density polyethylene (LDPE) film), and polylactic acid film can be mentioned. The thickness of the film in the coating is not particularly limited, preferably 1 to 500 μm, more preferably 10 to 300 μm, and even more preferably 50 to 100 μm.

[0074] The thickness of the aqueous composition in the coating of the present invention is preferably 1 to 300 μm, more preferably 5 to 100 μm, and even more preferably 10 to 50 μm. When the thickness of the aqueous composition in the coating is within the above range, good film-forming properties, heat-sealing properties, and gas barrier properties are easily obtained.

[0075] The coating of the present invention is excellent in gas barrier properties, particularly oxygen barrier properties. The oxygen permeability of the coating can be selected from the same range as the oxygen permeability of the resin composition.

[0076] The method for producing the coating of the present invention is not particularly limited as long as it can coat an aqueous composition on paper or a film. In a preferred embodiment, the coating of the present invention can be produced by a method including a step of coating the aqueous composition on a film or paper conveyed by a take-up machine using an extruder (referred to as step (A)).

[0077] In one embodiment of the present invention, in step (A), the aqueous composition is charged into an extruder. Examples of the extruder include a single-screw extruder and a twin-screw extruder. The screw diameter of the extruder is, for example, 20 to 150 mm, the ratio of the extruder length (L) to the screw diameter (D) (L / D ratio) is, for example, 15 to 50, and the rotational speed of the screw is preferably 80 rpm or more, more preferably 100 rpm or more. The cylinder temperature in the extruder can be, for example, 80 to 120°C, preferably 90 to 110°C.

[0078] The water-containing composition introduced into the extruder is plasticized and discharged from the die outlet. On the other hand, a paper or film is conveyed by a take-up machine, preferably a roller-type take-up machine. A coating is obtained by coating the conveyed paper or film with the water-containing composition discharged from the die outlet. The obtained coating is conveyed while being pressure-bonded to the paper or film between a plurality of rolls including a metal roll, and can be wound into a roll shape by a winder. Examples of the plurality of rolls include a pressure roll, a casting roll, and a touch roll.

[0079] In the process, it is preferable that the draw ratio represented by the following formula is 5 to 20. When a coating is produced with such a draw ratio, productivity is improved, and a coating excellent in adhesion between the paper or film and the water-containing composition and oxygen barrier properties is easily obtained. The flow rate at the die outlet of the extruder is represented by (discharge amount) / ((lip opening)×(die width)). When the discharge amount is expressed as the mass per unit time, the discharge amount is preferably 1 to 500 kg / hr, more preferably 5 to 200 kg / hr, the lip opening is preferably 0.01 to 5 mm, more preferably 0.1 to 1 mm, and the die width is preferably 100 to 3000 mm, more preferably 200 to 2000 mm. In the present invention, in the above manufacturing process, since the water in the water-containing composition evaporates, the water content rate of the water-containing composition in the obtained coating is reduced compared to before manufacturing. Draw ratio = (take-up speed of the take-up machine) / (flow rate at the die outlet of the extruder)

[0080] [Multi-layer structure] The present invention encompasses a multilayer structure including the coating and one or more layers (X). Examples of the layer (X) include a protective layer, a gas barrier layer different from the aqueous composition, a moisture-proof layer, a light-shielding layer, a printing layer, a reinforcing layer, and the like. Examples of the material for forming the layer (X) include polyesters such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, EVOH, polyvinyl chloride, polyurethane, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon; polyacrylonitrile; cellulose or its derivatives; glass; wood; and the like. One or two or more layers (X) may be provided, and the layer may be a single layer or a multilayer. When there are two or more layers (X), the thickness and material of each layer may be different or the same. Note that the layer (X) may be laminated on the aqueous composition, paper, or film via an adhesive layer (Y).

[0081] The adhesive for forming the adhesive layer (Y) is not particularly limited, and examples thereof include acrylic adhesives, urethane adhesives, epoxy adhesives, vinyl acetate adhesives, ethylene-vinyl acetate adhesives, vinyl chloride adhesives, silicone adhesives, nitrile cellulose adhesives, phenol adhesives, polyvinyl alcohol adhesives, melamine adhesives, styrene adhesives, and the like.

[0082] The multilayer structure of the present invention includes the coating (the aqueous composition coated on paper or film) and one or more layers (X). In a preferred embodiment of the present invention, the outermost surface has an aqueous composition (a layer composed of the aqueous composition). In such an embodiment, since the outermost aqueous composition can be adhered by heat, it is possible to easily form a packaging material for food or the like using the multilayer structure.

[0083] In a preferred embodiment of the present invention, in the multilayer structure of the present invention, at least one layer (X) is preferably disposed on the outermost surface on the side opposite to the aqueous composition with respect to the paper or film. In such an embodiment, by applying decorations such as letters and patterns on the surface of the layer (X), it is possible to form labels, seals, packaging materials with letters or decorations, and the like.

[0084] Although the layer structure of the multilayer structure of the present invention is not particularly limited, for example, a layer structure having a water-containing composition / paper or film / adhesive layer (Y) / layer (X) in this order; a layer structure having a water-containing composition / paper or film / layer (X) in this order, etc. may be mentioned. The thickness of layer (X) is not particularly limited, but is preferably 1 to 1000 μm, more preferably 5 to 500 μm.

[0085] [Adhesive body and packaging material] The present invention includes an adhesive body formed by thermally bonding the water-containing composition of the coating or multilayer structure and an adherend layer. Examples of the adherend layer include a layer selected from the group consisting of the coating, the multilayer structure, the water-containing composition contained in another coating or another multilayer structure, the paper, the film, and the layer (X), or a layer contained in an adherend other than these. In other words, examples of the adherend layer include a layer selected from the group consisting of the water-containing composition, paper, film, and layer (X) contained in the coating or the multilayer structure; a layer selected from the group consisting of the water-containing composition, paper, film, and layer (X) contained in another coating other than the coating; a layer selected from the group consisting of the water-containing composition, paper, film, and layer (X) contained in another multilayer structure other than the multilayer structure; and a layer contained in an adherend that is not the coating, the multilayer structure, the other coating, or the other multilayer structure. Note that the other coating means the coating on the side to be adhered when two or more coatings of the present invention are used, and the other multilayer structure means the multilayer structure on the side to be adhered when two or more multilayer structures of the present invention are used. The adherend layer is preferably the water-containing composition contained in the coating, multilayer structure, other coating, or other multilayer structure. When the adherend layer is the water-containing composition contained in the coating or multilayer structure, an adhesive body can be created using a single sheet. When the adherend layer is the water-containing composition contained in another coating or another multilayer structure, an adhesive body can be created using two or more sheets.

[0086] Heat adhesion (heat sealing) can be performed using a conventional heat sealing machine. Since the adhesive of the present invention is formed by heat adhesion of a water-containing composition having excellent heat sealability, it can have sufficient adhesive strength even in a low humidity environment. Furthermore, it also has excellent gas barrier properties and biodegradability.

[0087] The adhesive (two-sided bag) shown in FIG. 2 is a two-sided bag composed of one covering, and is obtained by folding the covering 2a in half and heat-sealing (heat sealing) both ends. The covering 2a is a covering having the layer structure shown in FIG. 1. As shown in FIG. 2, the adhesive 1a can be obtained by folding the covering 2a in half with the water-containing composition 3a side on the inside, and then heat-pressing the heat-pressing portions 6a at both ends from the paper or film 4a side. Since the heat-pressing portions 6a are adhered by heat-pressing to form a heat-adhesive portion, the adhesive 1a functions as a two-sided bag.

[0088] In addition, the adhesive (two-sided bag) 1a has an opening, and for example, after putting the contents into the bag, it can be sealed by heat-sealing the vicinity of the opening.

[0089] In FIG. 2, an embodiment is shown in which the adherend layer 5a is the above-mentioned water-containing composition contained in the same covering. However, by appropriately changing the location of heat adhesion, an adhesive can be produced with the paper or film contained in the same covering as the adherend layer; by changing the covering 2a to a multilayer structure and appropriately changing the heat-pressing portion (heat-adhesive portion), an adhesive can be produced with the water-containing composition, paper or film, or layer (X) contained in the same multilayer structure as the adherend layer.

[0090] The adhesive 1b shown in FIG. 3 is a three-sided bag composed of two coverings, and the three-side vicinity portions of the two coverings 2b and 2c are heat-adhered to each other. The coverings 2b and 2c each have the layer structure shown in FIG. 1. As shown in Fig. 3, the adhesive body 1b can be obtained by superposing two coverings 2b and 2c with the water-containing compositions 3b and 3c inside each other, and then thermocompression bonding the thermocompression bonding portions 6b located near three sides of the superposed laminate from the paper or film 4b and 4c sides. Since the thermocompression bonding portions 6b are bonded by thermocompression bonding to form thermoadhesive portions, the adhesive body 1b functions as a three-sided bag.

[0091] Also, the adhesive body (three-sided bag) 1b has an opening, but for example, after putting the contents into the bag, it can be sealed by thermoadhesively bonding the vicinity of the opening.

[0092] In Fig. 3, an embodiment is shown in which the adherend layer 5c is the water-containing composition contained in the other covering. However, by appropriately changing the location of thermoadhesion, an adhesive body may be produced with the paper or film contained in the other covering as the adherend layer; by changing at least the covering 2c to a multilayer structure and appropriately changing the thermocompression bonding portion (thermoadhesive portion), an adhesive body may be produced with the water-containing composition, paper or film, or layer (X) contained in the other multilayer structure as the adherend layer.

[0093] An adhesive body can also be formed using an adherend other than the covering or multilayer structure of the present invention. For example, in the embodiment shown in Fig. 3, the adherend may be used instead of one of the coverings. The adherend may have a water-containing composition or may not have a water-containing composition, and may be, for example, the paper or film described above.

[0094] The total number of the coating and the multilayer structure for forming the adhesive body of the present invention is not particularly limited, preferably 1 to 3, more preferably 1 or 2. In a preferred embodiment of the present invention, the adherend layer is the water-containing composition contained in a coating, a multilayer structure, another coating, or another multilayer structure. The adhesive body in such an embodiment is formed by heat-sealing the water-containing composition of the coating or the multilayer structure and the water-containing composition contained in the coating, the multilayer structure, the other coating, or the other multilayer structure, and thus can have more excellent adhesive strength. The embodiment shown in FIG. 2 is a water-containing composition in which the adherend layer is contained in the same coating, and the embodiment shown in FIG. 3 is a water-containing composition in which the adherend layer is contained in another coating. In addition, although a bag is shown as an example in FIGS. 2 and 3, the embodiment of the adhesive body is not limited to a bag.

[0095] The present invention includes a packaging material comprising the adhesive body. Since the packaging material of the present invention is composed of the adhesive body, it can have sufficient adhesive strength even in a low-humidity environment, and is also excellent in gas barrier properties and biodegradability. The shape of the packaging material of the present invention is not particularly limited, but a two-sided bag (see FIG. 2), a three-sided bag (see FIG. 3), a flat pouch, a standing pouch, a gusset pouch, a twin pouch, or a spout pouch is preferred.

[0096] In one embodiment of the present invention, in the packaging material of the present invention, the area that thermally adheres to the adherend layer within the total area of the water-containing composition of the coating or the multilayer structure is preferably 1 to 90%, more preferably 5 to 40%. When the area is within the above range, it is easy to secure the volume as a packaging material while maintaining the adhesive strength.

Examples

[0097] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these embodiments.

[0098] <Test method> (1) Measurement of oxygen permeability After storing the sheets obtained in the examples and comparative examples at 23°C and 50% RH for two weeks for humidity conditioning, they were attached to an oxygen permeability measuring device and the oxygen permeability was measured. The measurement conditions were as follows. Apparatus: "MOCON OX-TRAN2 / 20" manufactured by Modern Controls Temperature: 23°C Humidity on the oxygen supply side and the carrier gas side: 50% RH Oxygen pressure: 1.0 atm Carrier gas pressure: 1.0 atm

[0099] (2) Measurement of heat seal strength The sheets obtained in the examples and comparative examples were stored at 20°C and 30% RH for two weeks for humidity conditioning. A strip-shaped sheet cut to 15 mm × 300 mm was folded in half in the longitudinal direction. A length of 30 mm from the fold (area 15 mm × 30 mm) was heat-sealed under the conditions of a gauge pressure of 0.2 MPa, a temperature of 100°C, and 2 seconds. The heat seal strength was measured by peeling the sealed portion with a tensile tester. Heat sealer: "YSS Heat Sealer" manufactured by Yasuda Seiki Seisakusho, sealer area 20 mm × 300 mm Tensile tester: "INSTRON3367" manufactured by Instron, load cell 100 N

[0100] (3) Measurement of the saponification degree of polyvinyl alcohol (B) In accordance with JIS K 6726 (Polyvinyl Alcohol Test Method), the dissolution titration of polyvinyl alcohol in the examples and comparative examples was carried out, and the saponification degree was calculated.

[0101] (4) Measurement of the viscosity of polyvinyl alcohol (B) In accordance with JIS Z 8803 (Falling Ball Viscometer) and JIS K 6726 (Polyvinyl Alcohol Test Method), a 4% aqueous solution of polyvinyl alcohol in the examples and comparative examples was prepared, and the viscosity at 20°C was measured using a Heppler viscometer, and the viscosity (20°C) in the 4% aqueous solution of polyvinyl alcohol (B) was used.

[0102] (5) Measurement of dynamic viscoelasticity The sheets obtained in the examples and comparative examples were stored at 23°C and 50% RH for two weeks for humidity conditioning, and then cut into small pieces of 5 mm × 30 mm. After installing the sample in a dynamic viscoelasticity measuring device (RHEOGEL-E4000, manufactured by UBM), vaseline was applied to both sides to prevent volatilization of water due to temperature rise. While raising the temperature at a rate of 3°C / min in the range of 20°C to 150°C, tensile tests were performed with a sine wave of 11 Hz, and the dynamic viscoelasticity was measured. In the obtained tanδ curve (the horizontal axis is temperature (°C), and the vertical axis is tanδ), the peak temperature of tanδ was recorded. When there are two or more peaks in tanδ, the peak existing on the highest temperature side was taken as the peak temperature of tanδ.

[0103] (5) Materials used <Modified starch (A)> · (A-1): ECOFILM (registered trademark); corn starch modified with propylene oxide, amylose content 70% by mass, obtained from Ingredion · (A-2): National1658 (registered trademark): corn starch modified with propylene oxide, amylose content 20% by mass, obtained from Ingredion

[0104] <Polyvinyl alcohol (B)> · (B-1): Kuraray Poval (registered trademark) 3-80; polyvinyl alcohol resin, saponification degree 79.8 mol%, viscosity 3 mPa·s (20°C, 4% aqueous solution), obtained from Kuraray · (B-2): Kuraray Poval (registered trademark) 5-88; polyvinyl alcohol resin, saponification degree 88.2 mol%, viscosity 5 mPa·s (20°C, 4% aqueous solution), obtained from Kuraray · (B-3): Kuraray Poval (registered trademark) 7-92; polyvinyl alcohol resin, saponification degree 91.5 mol%, viscosity 7 mPa·s (20°C, 4% aqueous solution), obtained from Kuraray · (B-4): Kuraray Poval (registered trademark) 17-94; polyvinyl alcohol resin, saponification degree 93.8 mol%, viscosity 17 mPa·s (20°C, 4% aqueous solution), obtained from Kuraray ·(B-5): Kuraray POVAL (registered trademark) 27-96; polyvinyl alcohol resin, saponification degree 96.0 mol%, viscosity 27 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-6): Kuraray POVAL (registered trademark) 5-98; polyvinyl alcohol resin, saponification degree 98.8 mol%, viscosity 5 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-7): ELVANOL (registered trademark) 71-30; polyvinyl alcohol resin, saponification degree 99.5 mol%, viscosity 30 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-8): Kuraray POVAL (registered trademark) 25-100; polyvinyl alcohol resin, saponification degree 99.9 mol%, viscosity 25 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-9): Kuraray POVAL (registered trademark) L-8; polyvinyl alcohol resin, saponification degree 71.2 mol%, viscosity 5 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-10): Kuraray POVAL (registered trademark) 22-88; polyvinyl alcohol resin, saponification degree 88.0 mol%, viscosity 22 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray ·(B-11): Kuraray POVAL (registered trademark) 5-88; polyvinyl alcohol resin, saponification degree 88.0 mol%, viscosity 5 mPa·s (20 °C, 4% aqueous solution), obtained from Kuraray

[0105] <Clay (C)> ·(C-1): CLOISITE (registered trademark) 20A; natural montmorillonite organically treated (modified) with dimethyldi(hydrogenated tallow) quaternary ammonium chloride, obtained from Southern Clay Industries

[0106] <Polyoxyalkylene (D)> ·(D-1): Alcox (trademark) L-11; polyethylene oxide resin, weight average molecular weight 100,000, obtained from Meisei Chemical Industry Co., Ltd.

[0107] <Polyol plasticizer (E)> ·(E-1): Sorbitol SP: Sorbitol, obtained from Kisan Food Science Co., Ltd.

[0108] <Example 1> 90 parts by mass of modified starch (A-1) and 10 parts by mass of polyvinyl alcohol (B-1) were mixed in a tumbler mixer for 2 hours, and the resulting mixture was fed into a twin-screw extruder connected to a liquid pump. Figure 4 shows a schematic diagram of the twin-screw extruder used in Example 1, and the screw diameter, L / D ratio, rotational speed, operation mode, and temperature profile (Table 1) of the extruder are shown below.

[0109]

Table 1

[0110] Screw diameter: 27 mm L / D ratio: 48 Screw rotational speed 500 rpm Operation mode: Co-rotating (meshing self-wiping) mode

[0111] Specifically, the resulting mixture was fed into the barrel through the hopper at C1 at a rate of 3.5 kg / h via the gravimetric feeder of the twin-screw extruder. Water was injected into the barrel at a flow rate of 26 g / min through the liquid pump at C4 (10 in Figure 4). The temperature ranges of C5 to C9 are the cooking zones, and complete gelatinization was completed within these zones. The resin composition extruded from the die was taken up at a take-up speed such that the thickness became 120 μm after cooling and drying, and a film with a thickness of 120 μm was obtained. The moisture content of the resin composition (film) was 11%. The moisture content was determined by measuring at 130 °C for 60 minutes using a heat drying type moisture meter. When measuring the moisture content, the resin composition (film) was pulverized to a maximum particle size of 1 mm or less with a wonder blender WB-1 (Osaka Chemical Co., Ltd.) and then measured.

[0112] <Examples 2 to 14 and Comparative Examples 1 to 9> A resin composition (sheet) was obtained in the same manner as in Example 1, except that the types and amounts of the modified starch (A), polyvinyl alcohol (B), and other substances were adjusted as shown in Table 2. In Example 10, a mixture of 81 parts by mass of modified starch (A-1) and 9 parts by mass of modified starch (A-2) was used as the modified starch (A). In Example 11, a mixture of 54 parts by mass of modified starch (A-1) and 36 parts by mass of modified starch (A-2) was used. Except for Examples 10 and 11, modified starch (A-1) was used as the modified starch (A) in the same manner as in Example 1.

[0113] Using the resin compositions (sheets) obtained in Examples 1 to 14 and Comparative Examples 1 to 9, the peak temperature of tanδ, oxygen permeability, and heat seal strength in dynamic viscoelasticity were measured. The results are shown in Table 2.

[0114]

Table 2

[0115] As shown in Table 2, it was confirmed that the resin compositions (sheets) obtained in Examples 1 to 14 had low oxygen permeability and high heat seal strength. On the other hand, it was confirmed that the resin compositions (sheets) obtained in Comparative Examples 1 to 9 were significantly inferior in either both or one of the oxygen permeability and heat seal strength compared to the Examples. Therefore, it was found that the resin composition of the present invention is excellent in heat sealability and gas barrier properties.

Explanation of Symbols

[0116] 1a, 1b... Adherends 2, 2a, 2b, 2c... Coatings 3, 3a, 3b, 3c... Hydrous Compositions 4, 4a, 4b, 4c... Paper or Film 5a, 5c... Adhesive Layers 6a, 6b... Thermocompression Bonding Parts (Thermal Adhesion Parts) 8... Twin-Screw Extruder 9... Hopper 10…Liquid addition nozzle 11…Resin thermometer 12…Resin pressure gauge 13…Adapter 14…Die

Claims

1. A water-containing composition having a water content of 1 to 50% by mass, which contains 40 to 98 parts by mass of modified starch (A), 2 to 60 parts by mass of polyvinyl alcohol (B) having a saponification degree of 75.0 to 98.9 mol%, and optionally clay (C), and the total content of (A), (B), and (C) is 100 parts by mass, and the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20°C to 150°C is 50 to 128°C. The coating is obtained by coating a paper or a film with the water-containing composition.

2. The total content of the modified starch (A), polyvinyl alcohol (B), and clay (C) is 80 to 100% by mass based on the mass of the resin composition. The coating according to Claim 1.

3. The average amylose content of the modified starch (A) is 45 to 90% by mass. The coating according to Claim 1 or 2.

4. The content of the clay (C) is 0 parts by mass or more and less than 2 parts by mass. The coating according to any one of Claims 1 to 3.

5. The modified starch (A) is at least one selected from the group consisting of etherified starch, esterified starch, cationized starch, and crosslinked starch. The coating according to any one of Claims 1 to 4.

6. The modified starch (A) is at least one selected from the group consisting of etherified starch having a hydroxyalkyl group having 2 to 6 carbon atoms and esterified starch having a structural unit derived from a dicarboxylic acid anhydride. The coating according to any one of Claims 1 to 5.

7. The polyvinyl alcohol (B) has a viscosity of 1 to 50 mPa·s at 20°C in a 4% aqueous solution measured in accordance with JIS Z 8803. The coating according to any one of Claims 1 to 6.

8. The thickness of the water-containing composition in the coating is 1 to 300 μm. The coating according to any one of Claims 1 to 7.

9. The paper is kraft paper, high-quality paper, imitation paper, glassine paper, parchment paper, synthetic paper, white cardboard, manila board, milk carton base paper, cup base paper, ivory paper, silver paper, tissue paper, cardboard, or rayon paper. The coating according to any one of Claims 1 to 8.

10. The film is a polyethylene terephthalate (PET) film, biaxially oriented polypropylene (BOPP) film, polyethylene (PE) film, or polylactic acid film. The coating according to any one of Claims 1 to 9.

11. A multilayer structure comprising the coating according to any one of claims 1 to 10 and one or more layers (X).

12. An adhesive body formed by thermally bonding a water-containing composition of the coating according to any one of claims 1 to 10 or the multilayer structure according to claim 11 and an adherend layer, wherein the adherend layer is the coating, the multilayer structure, the water-containing composition contained in another coating or another multilayer structure, the paper, the film, and the layer selected from the group consisting of (X), or a layer contained in an adherend other than these.

13. The adhesive body according to claim 12, wherein the adherend layer is the water-containing composition contained in a coating, a multilayer structure, another coating or another multilayer structure.

14. A packaging material comprising the adhesive body according to claim 12 or 13.

15. The packaging material according to claim 14, which is a two-sided bag, a three-sided bag, a flat pouch, a standing pouch, a gusset pouch, a twin pouch, or a spout pouch.

16. Using an extruder, 40 to 98 parts by mass of modified starch (A), 2 to 60 parts by mass of polyvinyl alcohol (B) having a saponification degree of 75.0 to 98.9 mol%, and optionally clay (C) are included, and the total content of (A), (B), and (C) is 100 parts by mass. A method for producing a coating according to any one of claims 1 to 10, comprising a step of coating a film or paper conveyed by a take-up machine with a water-containing composition having a water content of 1 to 50% by mass and containing a resin composition in which the peak temperature of tanδ when measuring the dynamic viscoelasticity in the range of 20°C to 150°C is 50 to 128°C.

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