Laminate

Abstract

A laminate comprising: a gas barrier layer (I) containing a modified starch (A) having an average amylose content of 45% by mass or more and a water-soluble polymer (B); and a substrate (II) adjacent to the gas barrier layer (I), the laminate exhibiting a degree of biodegradation of 80% or more in a biodegradability test in accordance with ISO 14855-1.

Description

[Technical Field]

[0001] The present invention relates to a laminate used for food packaging and the like, a multilayer structure including the laminate, and a packaging material or lid material including the multilayer structure. [Background technology]

[0002] Imparting gas barrier properties (particularly oxygen barrier properties) to packaging materials is an important function for protecting various packaged products from gas-induced deterioration, such as oxidation by oxygen, and has been imparted by metal deposition on aluminum foil or plastic substrates, or by forming a multilayer with a gas barrier resin such as EVOH. For example, Patent Document 1 discloses a gas barrier laminate having a gas barrier layer made of a water-soluble polymer and an inorganic layered compound on a paper substrate. On the other hand, from the viewpoint of reducing the environmental load, film materials containing starch as a main component have been studied. For example, Patent Document 2 discloses a multilayer film in which a starch layer is laminated on a substrate via an adhesive, and the adhesive can ensure the adhesive strength between the substrate and the starch layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-184138 [Patent Document 2] Special Publication No. 2015-508341 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the inventors' investigations, although the laminate described in Patent Document 1 has gas barrier properties, it does not have sufficient disintegration properties, making it difficult to reuse the laminate. Furthermore, the laminate described in Patent Document 2 uses an adhesive to ensure good adhesive strength between the base material and the starch layer, and the adhesive causes poor disintegration. Thus, it has been found that it is difficult to increase disintegration properties while maintaining gas barrier properties and adhesive strength between layers.

[0005] Therefore, an object of the present invention is to provide a laminate having excellent gas barrier properties, adhesive strength and disintegration properties, a multilayer structure including the laminate, and a packaging material or lid material including the multilayer structure. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by adjusting the average amylose content of the modified starch (A) to 45% by mass or more, arranging the gas barrier layer (I) containing a modified starch (A) and a water-soluble polymer (B) adjacent to the substrate (II), and adjusting the biodegradability of the laminate to 80% or more, thereby completing the present invention. That is, the present invention includes the following aspects.

[0007] [1] A laminate comprising: a gas barrier layer (I) containing a modified starch (A) having an average amylose content of 45% by mass or more and a water-soluble polymer (B); and a substrate (II) adjacent to the gas barrier layer (I), wherein the degree of biodegradation is 80% or more in a biodegradation test in accordance with ISO14855-1. [2] The laminate according to [1], wherein the water-soluble polymer (B) is polyvinyl alcohol and / or polyoxyalkylene. [3] The laminate according to [1] or [2], wherein the content of the modified starch (A) is 40 to 98 parts by mass and the content of the water-soluble polymer (B) is 2 to 60 parts by mass, based on 100 parts by mass in total of the modified starch (A) and the water-soluble polymer (B). [4] The laminate according to any one of [1] to [3], wherein the gas barrier layer (I) has a thickness of 1 to 600 μm. [5] The laminate according to any one of [1] to [4], wherein the substrate (II) is paper. [6] A multilayer structure having a heat seal layer or a moisture-proof layer on at least one surface of the laminate according to any one of [1] to [5]. [7] A packaging material or a lid material comprising the laminate according to any one of [1] to [5] or the multilayer structure according to [6]. [Effects of the Invention]

[0008] The laminate of the present invention has excellent gas barrier properties, adhesive strength, and disintegration properties, and is therefore suitable for use as a packaging material or lid material for food and the like. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a twin-screw extruder used in the examples. [Figure 2] FIG. 2 is a schematic diagram of a laminate manufacturing apparatus used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Laminate] The laminate of the present invention comprises a gas barrier layer (I) and a substrate (II) adjacent to the gas barrier layer (I).

[0011] <Gas barrier layer (I)> The gas barrier layer (I) in the laminate of the present invention is a layer having gas barrier properties and contains a modified starch (A) and a water-soluble polymer (B).

[0012] (Modified starch (A)) The modified starch (A) is preferably at least one selected from the group consisting of etherified starch, esterified starch, cationized starch, and crosslinked starch, from the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability, and disintegrability.

[0013] Examples of starches include starches derived from cassava, corn, potato, sweet potato, sago, tapioca, sorghum, beans, bracken, lotus, water chestnut, wheat, rice, oats, arrowroot, and peas. Among these, 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 types.

[0014] Examples of etherified starches include alkyl-etherified starches such as methyl-etherified starch, carboxyalkyl-etherified starches such as carboxymethyl-etherified starch, and hydroxyalkyl-etherified starches such as etherified starches having a hydroxyalkyl group having 2 to 6 carbon atoms. Allyl-etherified starch can also be used.

[0015] Examples of esterified starches include esterified starches having structural units derived from carboxylic acids, such as esterified starches having structural units derived from acetic acid; esterified starches having structural units derived from dicarboxylic acid anhydrides, such as esterified starches having structural units derived from maleic anhydride, phthalic anhydride, and octenylsuccinic anhydride; and esterified starches having structural units derived from oxoacids, such as nitrate-esterified starch, phosphate-esterified starch, and urea-phosphate-esterified starch. Other examples include xanthate-esterified starch, acetoacetate-esterified starch, and the like.

[0016] Examples of the cationized starch include a reaction product of starch with 2-diethylaminoethyl chloride, and a reaction product of starch with 2,3-epoxypropyltrimethylammonium chloride.

[0017] Examples of crosslinked starches include formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphate crosslinked starch, and acrolein crosslinked starch.

[0018] From the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability, and disaggregability, the modified starch (A) is preferably at least one selected from the group consisting of etherified starches having a hydroxyalkyl group having 2 to 6 carbon atoms and esterified starches having structural units derived from dicarboxylic acid anhydrides, and more preferably at least one selected from the group consisting of hydroxyethyl etherified starch, hydroxypropyl etherified starch, hydroxybutyl etherified starch, esterified starch having structural units derived from maleic anhydride, esterified starch having structural units derived from phthalic anhydride, and esterified starch having structural units derived from octenylsuccinic anhydride. The modified starches (A) can be used alone or in combination of two or more. In this specification, the number of carbon atoms listed before "starch" refers to the number of carbon atoms in the group substituted with 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 with 2 to 5 carbon atoms indicates that the hydroxyalkyl group formed by modifying one hydroxyl group in the starch has 2 to 5 carbon atoms.

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

[0020] The average amylose content of the modified starch (A) contained in the gas barrier layer (I) is 45% by mass or more. If the average amylose content of the modified starch (A) is less than 45% by mass, the gas barrier properties tend to decrease. The laminate of the present invention can improve gas barrier properties because the modified starch (A) contained in the gas barrier layer (I) has an average amylose content of 45% by mass or more. The average amylose content of the modified starch (A) is preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and even more preferably 60% by mass or more. When the average amylose content is equal to or greater than the above-mentioned lower limit, gas barrier properties are more likely to be improved. The average amylose content 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 coloring method described in "Starch 50 No. 4 158-163 (1998)." When one type of modified starch is used, the average amylose content refers to the amylose content of that one type of modified starch. When two or more types of modified starches are used, the average amylose content refers to the weighted average of the amylose contents of the two or more types of modified starches. Therefore, for example, when two or more types of modified starches are used to provide an average amylose content of 45% by mass or more, the starch may contain a modified starch with an amylose content of less than 45% by mass.

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

[0022] Commercially available modified starch (A) can also be used. Typical commercially available examples of modified starch (A) include ECOFILM (trademark) and National 1658 (trademark), which are hydroxypropyl etherified starches manufactured by Ingredion.

[0023] The content of modified starch (A) is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, still more preferably 70 parts by mass or more, particularly preferably 75 parts by mass or more, and is preferably 98 parts by mass or less, more preferably 95 parts by mass or less, relative to 100 parts by mass of the total of modified starch (A) and water-soluble polymer (B). When the content of modified starch (A) is at least the above lower limit, biodegradability and disaggregability are likely to be improved, and when the content of modified starch (A) is at most the above upper limit, gas barrier properties are likely to be improved.

[0024] (Water-soluble polymer (B)) The water-soluble polymer (B) is a polymer compatible with the modified starch (A). The water-soluble polymer (B) is not particularly limited, but preferably has a melting point suitable for the processing temperature of the modified starch (A). From the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability, and disintegrability, the water-soluble polymer (B) is preferably polyvinyl alcohol and / or polyoxyalkylene, more preferably polyvinyl alcohol.

[0025] The polyvinyl alcohol preferably has a saponification degree of 80 to 99.8 mol%. When the saponification degree of polyvinyl alcohol is within the above range, gas barrier properties, adhesive strength, biodegradability, and disintegrability are likely to be improved. The saponification degree is more preferably 85 mol% or more, even more preferably 88 mol% or more, and particularly preferably 90 mol% or more. The saponification degree indicates the molar fraction of hydroxyl groups relative to the total of hydroxyl groups and ester groups in polyvinyl alcohol. The saponification degree can be measured in accordance with JIS K 6726 (Testing Methods for Polyvinyl Alcohol), for example, by the method described in the Examples. Polyvinyl alcohol is produced by hydrolysis of polyvinyl acetate, which is obtained, for example, by polymerization of vinyl acetate monomer.

[0026] The viscosity of a 4% aqueous solution of polyvinyl alcohol at 20°C, measured in accordance with JIS Z 8803, is preferably 1 to 50 mPa·s. When the viscosity of polyvinyl alcohol is within the above range, gas barrier properties, adhesive strength, biodegradability, and disintegrability tend to be improved. The viscosity is more preferably 3 mPa·s or more, even more preferably 5 mPa·s or more, and more preferably 45 mPa·s or less, even more preferably 40 mPa·s or less.

[0027] The polyvinyl alcohol (B) may further contain other monomer units in addition to vinyl alcohol units, such as monomer units derived from ethylenically unsaturated monomers. Examples of ethylenically unsaturated monomers include α-olefins such as ethylene, propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic ester 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); 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, vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid, and salts or esters thereof; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; and vinyl ester monomers such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl carboxylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate and vinyl benzoate. The content of other monomer units is preferably 10 mol % or less, and more preferably 5 mol % or less, based on the total molar amount of the structural units constituting the polyvinyl alcohol.

[0028] The method for producing polyvinyl alcohol is not particularly limited. For example, a method can be used in which vinyl acetate monomer and optionally other monomers are polymerized, and the resulting polymer is saponified to convert it into vinyl alcohol units. Polymerization methods include batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Polymerization methods include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Known methods can be used for saponification of the polymer. For example, the saponification can be carried out in a state in which the polymer is dissolved in alcohol or aqueous alcohol. Examples of alcohols that can be used in this case include lower alcohols such as methanol and ethanol. Polyvinyl alcohols can be used alone or in combination of two or more types.

[0029] Polyoxyalkylene refers to polyalkylene oxide and polyalkylene glycol, and has a structural unit represented by the following formula (1) (also referred to as structural unit (1)). The polyoxyalkylene may have two or more different types of structural unit (1). [ka] wherein R is an alkylene group and n is 1 or greater.

[0030] In formula (1), examples of the alkylene group include alkylene groups having 2 to 10 carbon atoms, such as ethylene, propylene, trimethylene, butylene, isobutylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene. Among these, from the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability, and disintegrability, alkylene groups having 2 to 6 carbon atoms are preferred, and ethylene and / or propylene are more preferred. When n is 2 or more, these alkylene groups can be used alone or in combination of two or more.

[0031] In terms of facilitating enhancement of gas barrier properties, adhesive strength, biodegradability, and disintegrability, n in formula (1) is preferably at least 5, more preferably at least 50, and even more preferably at least 100, and is preferably at most 120,000, more preferably at most 70,000. When the polyoxyalkylene contains different structural units (1), the repeating number n of each structural unit may be the same or different.

[0032] Examples of polyalkylene oxides include polymers having structural units derived from alkylene oxides having 2 to 6 carbon atoms, such as polyethylene oxide, polypropylene oxide, polytrimethylene oxide (polyoxetane), polybutylene oxide, polyisobutylene oxide, and copolymers of monomers constituting these. Examples of polyalkylene glycols include polymers having structural units derived from alkylene glycols having 2 to 6 carbon atoms, such as polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polybutylene glycol, polyisobutylene glycol, and copolymers of monomers constituting these. Among these, from the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability, and disintegrability, the polyoxyalkylene is preferably polyethylene oxide, polypropylene oxide, polyethylene glycol, polypropylene glycol, or a copolymer of monomers constituting these. Examples of such copolymers include copolymers of ethylene oxide and propylene oxide, and copolymers of ethylene glycol and propylene glycol.

[0033] The polyoxyalkylene may contain structural units derived from monomers other than the structural unit (1) as long as the effects of the present invention are not impaired. When the polyoxyalkylene is a copolymer, the polymerization form of the copolymer is not particularly limited and may be any of random, block, graft, or tapered. The polyoxyalkylene may be used alone or in combination of two or more types.

[0034] The weight average molecular weight of the polyoxyalkylene is preferably 10,000 or more, more preferably 50,000 or more, and preferably 5,000,000 or less, more preferably 3,000,000 or less, from the viewpoint of easily improving gas barrier properties, adhesive strength, biodegradability and disintegrability.

[0035] Commercially available polyoxyalkylenes can also be used. Typical examples of commercially available polyoxyalkylenes include ALKOX (trademark) E-75G, ALKOX (trademark) L-11, ALKOX (trademark) L-6, and ALKOX (trademark) EP1010N manufactured by Meisei Chemical Industry Co., Ltd., and PEO (trademark) PEO-1 and PEO-2 manufactured by Sumitomo Seika Chemicals Co., Ltd.

[0036] The content of the water-soluble polymer (B) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less, relative to 100 parts by mass of the total of the modified starch (A) and the water-soluble polymer (B). When the content of the water-soluble polymer (B) is at least the above lower limit, the gas barrier property is easily improved, and when the content of the water-soluble polymer (B) is at most the above upper limit, the biodegradability and disaggregability are easily improved.

[0037] In the gas barrier layer (I), the total proportion of the modified starch (A) and the water-soluble polymer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, still more preferably 90% by mass or more, and is preferably 100% by mass or less, relative to the mass of the gas barrier layer (I). When the total proportion of the modified starch (A) and the water-soluble polymer (B) is within the above range, it is easy to improve the gas barrier properties, adhesive strength, biodegradability, and disaggregability.

[0038] (Other ingredients) In the laminate of the present invention, the gas barrier layer (I) may further contain a fatty acid having 12 to 22 carbon atoms and / or a fatty acid salt thereof. Examples of fatty acids having 12 to 22 carbon atoms and fatty acid salts thereof include stearic acid, calcium stearate, sodium stearate, palmitic acid, lauric acid, myristic acid, linoleic acid, and behenic acid. Among these, stearic acid, calcium stearate, and sodium stearate are preferred from the viewpoint of processability. The fatty acids having 12 to 22 carbon atoms and fatty acid salts thereof can be used alone or in combination of two or more.

[0039] When the gas barrier layer (I) contains a fatty acid having 12 to 22 carbon atoms and / or a fatty acid salt thereof, the content in the gas barrier layer (I) is preferably 0.01 to 3 mass%, more preferably 0.03 to 2 mass%, and even more preferably 0.1 to 1 mass%, relative to the mass of the gas barrier layer (I). A content of the fatty acid having 12 to 22 carbon atoms and / or a fatty acid salt thereof within the above range tends to be advantageous in terms of processability.

[0040] The gas barrier layer (I) may further contain clay. Examples of clay include synthetic or natural layered silicate clays such as montmorillonite, bentonite, beidellite, mica, hectorite, saponite, nontronite, sauconite, vermiculite, ledikite, magadite, kenyaite, stevensite, and vulkonskoite. The clays can be used alone or in combination.

[0041] When the gas barrier layer (I) contains clay, the content of the clay in the gas barrier layer (I) is preferably 0.1 to 5 mass%, more preferably 0.1 to 3 mass%, and even more preferably 0.5 to 2 mass%, relative to the mass of the gas barrier layer (I). A clay content within the above range tends to be advantageous in terms of transparency and strength.

[0042] If the water-containing composition (described below) forming the gas barrier layer (I) contains a plasticizer, the film-forming and coating properties of the gas barrier layer (I) are improved when the layer is formed directly on the substrate (II), and the adhesive strength and gas barrier properties between the substrate (II) and the gas barrier layer (I) are easily increased. Therefore, the gas barrier layer (I) in the laminate preferably contains a plasticizer. Examples of plasticizers include water, sorbitol, glycerol, maltitol, xylitol, mannitol, glycerol trioleate, epoxidized linseed oil, epoxidized soybean oil, tributyl citrate, acetyltriethyl citrate, glyceryl triacetate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, polyethylene oxide, and polyethylene glycol. Plasticizers can be used alone or in combination. Among these plasticizers, water is preferred from the viewpoint of easily increasing the adhesive strength and gas barrier properties of the laminate.

[0043] The moisture content (water content) in the gas barrier layer (I) is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more, relative to the mass of the gas barrier layer (I), and is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less. A moisture content within the above range facilitates improved gas barrier properties and adhesive strength. The moisture content is measured using a heat-drying moisture meter at 130°C for 60 minutes after pulverizing the material to a maximum particle size of 1 mm or less using a Wonder Blender WB-1.

[0044] The gas barrier layer (I) may further contain additives such as fillers, processing stabilizers, weather resistance stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, fragrances, antifoaming agents, deodorizers, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, mildew inhibitors, preservatives, and crystallization rate retarders, as required.

[0045] The gas barrier layer (I) is preferably in the form of a film or sheet. From the viewpoint of easily improving gas barrier properties, biodegradability, and disintegrability, the thickness of the gas barrier layer (I) is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, particularly preferably 10 μm or more, and is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 450 μm or less. Furthermore, one or more gas barrier layers (I) may be provided, and may be single-layer or multi-layer. When the gas barrier layer (I) is two or more layers, the thickness and composition of each layer may be different or the same.

[0046] <Base material (II)> The laminate of the present invention includes a substrate (II) adjacent to the gas barrier layer (I). The substrate (II) is not particularly limited as long as it allows the resulting laminate to have a biodegradability of 80% or more, and examples thereof include paper and biodegradable polyester.

[0047] (Paper base material) The paper substrate may be, for example, a film or sheet containing pulp, fillers, chemicals, and pigments. Examples of pulp include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp; mechanical pulps such as stone-ground pulp and thermomechanical pulp; wood fibers such as deinked pulp and recycled paper pulp; and non-wood fibers obtained from kenaf, bamboo, hemp, and the like. These pulps can be used alone or in combination. Among these, chemical pulp, mechanical pulp, and wood fiber are preferred, with chemical pulp being more preferred, from the viewpoints of easily preventing the incorporation of foreign matter into the base paper and the occurrence of discoloration over time when used paper containers are recycled, and of easily achieving a good surface appearance when printed.

[0048] Examples of fillers include known fillers such as white carbon, talc, kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium oxide, zeolite, and synthetic resin fillers. Fillers can be used alone or in combination. Examples of chemicals include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents (e.g., neutral sizing agents), water-resistant agents, water retention agents, thickeners, lubricants, retention aids, drainage aids, and paper strength agents. These may be used alone or in combination. Examples of retention aids include aluminum sulfate and various anionic, cationic, nonionic, and amphoteric agents. Examples of dry strength agents include polyacrylamide and cationized starch, and examples of wet strength agents include polyamidoamine epichlorohydrin. These chemicals are added to a level that does not affect formation or runnability. Neutral sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and neutral rosin sizing agents. Pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, and core-shell pigments. These can be used alone or in combination. Furthermore, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control agents, and the like can also be added as needed. The surface of the paper substrate may also be treated with various chemicals or pigments.

[0049] The method for producing the paper base material (papermaking) is not particularly limited, and the paper base material can be produced by acidic papermaking, neutral papermaking, or alkaline papermaking using a known Fourdrinier former, on-top hybrid former, gap former machine, or the like.

[0050] The method for treating the surface of the paper substrate is not particularly limited, but known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used.

[0051] Examples of paper substrates obtained in this manner include various known types such as fine paper, medium-quality paper, coated paper, one-side glossy paper, kraft paper, one-side glossy kraft paper, bleached kraft paper, unbleached kraft paper, rayon paper, tissue paper, glassine paper, paperboard, white paperboard, cellophane, and liner.

[0052] The paper substrate may have a transparent coating layer on one or both sides of the base paper as part of the paper substrate. By applying a transparent coating to the base paper, it is easy to improve the surface strength and smoothness of the base paper, and it is also easy to improve the coatability when coating a pigment. The transparent coating layer may contain a starch-derived polymer compound as a binder. The amount of the transparent coating is 0.1 to 4.0 g / m2 in solids content per side. 2 is preferable, and 0.5 to 2.5 g / m 2 is more preferable. For example, a coating liquid containing as its main component starch, various starches such as oxidized starch, polyacrylamide, polyvinyl alcohol, or other water-soluble polymers may be applied to the base paper using a coater (coating machine) such as a size press, gate roll coater, premetering size press, curtain coater, or spray coater. In order to ensure a uniform coating layer after coating, it is preferable to pre-calender the base paper before coating using an online soft calender, online chilled calender, or the like to smooth the base paper in advance.

[0053] The paper substrate may be subjected to a smoothing treatment as required. For the smoothing treatment, a smoothing treatment device such as a normal super calender, gloss calender, soft calender, heat calender, or shoe calender can be used. The smoothing treatment device is used on-machine or off-machine as appropriate, and the shape of the pressure device, the number of pressure nips, heating, etc. are also adjusted as appropriate.

[0054] (biodegradable polyester base) The biodegradable polyester substrate is not particularly limited as long as it is made of a biodegradable polyester, and examples thereof include polyhydroxybutyrate, polyhydroxyhexanoate, polylactic acid (PLA), polycaprolactone, polybutylene succinate, polyadipate, polybutylene adipate, polytetramethylene adipate, polyethylene succinate, polyglycolic acid, poly(butylene adipate terephthalate) (PBAT), and poly(butylene succinate adipate) (PBSA).

[0055] The substrate (II) is preferably paper (paper substrate) from the viewpoint of making it easier to improve the biodegradability, disintegrability, and adhesive strength of the laminate.

[0056] The basis weight of the substrate (II) is preferably 1 g / m 2 More preferably, 10 g / m 2 or more, preferably 500 g / m 2 Less than 400 g / m 2 More preferably, 300 g / m or less 2 When the basis weight of the substrate (II) is within the above range, the gas barrier properties, adhesive strength, biodegradability and disintegrability are likely to be improved.

[0057] The substrate (II) may be one or more, and may be a single layer or multiple layers. When the substrate (II) has two or more layers, the thickness and material of each layer may be different or the same.

[0058] <Laminate> The laminate of the present invention comprises a gas barrier layer (I) containing a modified starch (A) having an average amylose content of 45% by mass or more and a water-soluble polymer (B), and a substrate (II) adjacent to the gas barrier layer (I). The laminate exhibits a biodegradability of 80% or more in a biodegradation test in accordance with ISO 14855-1, and thus exhibits excellent biodegradability, gas barrier properties, adhesive strength, and disintegration properties. Therefore, the laminate is suitable for use as a packaging material or lid material for food, etc. Here, "adjacent" means that the gas barrier layer (I) and the substrate (II) are in contact with each other, and more specifically, means that the gas barrier layer (I) is laminated directly on the surface of the substrate (II) without any other layer interposed therebetween. In the present invention, a specific gas barrier layer (I) is used, and no adhesive is used between the substrate (II) and the gas barrier layer (I), so that the present invention can achieve high biodegradability and excellent disintegrability. Furthermore, even without the use of such an adhesive, sufficient adhesive strength can be achieved between the layers. In this specification, "disintegrability" refers to the property of being able to be disintegrated, more specifically, the property of being easily separated into fibers in a disintegrating solution, and can be evaluated, for example, by the method described in the section "(3) Measurement of disintegrability of laminate" in the Examples. Furthermore, "adhesion strength" refers to the strength of adhesion between the gas barrier layer (I) and the substrate (II).

[0059] The laminate of the present invention has a biodegradability of 80% or more in a biodegradability test in accordance with ISO 14855-1. A biodegradability of less than 80% tends to result in a decrease in not only biodegradability but also disintegrability. In the present invention, a biodegradability of 80% or more allows for excellent disintegrability. The biodegradability is preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 97% or more. A biodegradability equal to or greater than the lower limit described above facilitates improved disintegrability. The upper limit of the biodegradability is 100% or less. The biodegradability can be measured by a biodegradability test in accordance with ISO 14855-1, and the biodegradability can be determined preferably after 168 days. The biodegradability can be measured by the method described in the Examples. The biodegradability can be adjusted, for example, by using a highly biodegradable component as the substrate (II) or by appropriately adjusting the amounts of the modified starch (I) and the water-soluble polymer (II) in the gas barrier (I).

[0060] The laminate of the present invention has excellent gas barrier properties, particularly oxygen barrier properties. The oxygen permeability (cc / [m 2 ·atm·24hr]) is preferably 10 or less, more preferably 8.0 or less, even more preferably 5.0 or less, even more preferably 3.0 or less, and particularly preferably 1.0 or less. When the oxygen permeability is equal to or less than the above upper limit, excellent oxygen barrier properties are likely to be exhibited. In addition, the oxygen permeability (cc / [m 2 The oxygen permeability (atm·24 hr) is usually 0.01 or more. The oxygen permeability of the resin composition can be measured with an oxygen permeability measuring device after storing it at 23°C and 50% RH for two weeks and adjusting the humidity, and can be measured, for example, by the method described in the Examples. In this specification, "improved or enhanced oxygen barrier properties" means that the oxygen permeability is reduced, and "excellent oxygen barrier properties" means that the oxygen permeability is low.

[0061] The laminate of the present invention has excellent adhesive strength between the substrate (II) and the gas barrier layer (I) even without the use of an adhesive. The adhesive strength is preferably 1 N / 15 mm or more, more preferably 2 N / 15 mm, even more preferably 3 N / 15 mm or more, even more preferably 4 N / 15 mm or more, and particularly preferably 5 N / 15 mm or more. The upper limit of the adhesive strength is usually 100 N / 15 mm or less, preferably 50 N / 15 mm or less. The adhesive strength can be measured using a tensile tester at a peel angle of 180° and a peel rate of 100 mm / min after conditioning the laminate at 23°C and 50% RH for two weeks, for example, by the method described in the Examples. The adhesive strength may be adjusted to fall within the above range, for example, by appropriately adjusting the type of base material (I) or the types and proportions of the components in the gas barrier layer (I), particularly by using the above-mentioned preferred components and adjusting the proportions thereof to fall within the above-mentioned preferred ranges; by adjusting the water content of the gas barrier layer (I) in the laminate to fall within the above range, i.e., by producing the laminate using a water-containing composition having a predetermined water content; or by employing the below-mentioned method for producing the laminate.

[0062] The moisture content (water content) in the laminate of the present invention is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 7% by mass or more, and preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less, relative to the mass of the laminate. When the moisture content of the laminate is within the above range, the gas barrier properties and adhesive strength are easily improved. The moisture content is measured, for example, by pulverizing the material to a maximum particle size of 1 mm or less using a Wonder Blender WB-1 (Osaka Chemical Co., Ltd.) and measuring the moisture content at 130°C for 60 hours using a heat-drying moisture meter, and can be measured by the method described in the Examples.

[0063] Specific examples of the layer structure of the laminate include, but are not limited to, gas barrier layer (I) / substrate (II); substrate (II) / gas barrier layer (I) / substrate (II); gas barrier layer (I) / substrate (II) / gas barrier layer (I); and the like.

[0064] [Method of manufacturing laminate] The method for producing the laminate of the present invention is not particularly limited, but a preferred method includes, for example, a step (sometimes referred to as step (X)) of coating the substrate (II) with a water-containing composition containing the modified starch (A) and the water-soluble polymer (B). By using such a method, the gas barrier layer (I) can be laminated on the substrate (II) without using an adhesive, which can improve biodegradability and disintegratability and also ensure sufficient adhesive strength.

[0065] <Production of Water-Containing Composition> The water-containing composition includes a resin composition containing the modified starch (A) and the water-soluble polymer (B), and has a water content of 1 to 50% by mass. The water content is preferably 5% by mass or more, more preferably 8% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less. A water content within the above range facilitates improved application and film-forming properties when coating the substrate (II) with the water-containing composition, and facilitates increased adhesive strength between the substrate (II) and the gas barrier layer (I) in the resulting laminate. Furthermore, the gas barrier properties are also likely to be improved. The water content of the water-containing composition is measured, for example, using a heat-drying moisture meter at a temperature of 130°C for 60 minutes, and can be measured by the method described in the Examples. In this specification, the water-containing composition refers to all water-containing resin compositions having a water content of 1 to 50% by mass as measured by the above method. That is, the water-containing composition is preferably a resin composition obtained by adding water to the resin composition to adjust the water content to the above range, but also includes resin compositions whose water content is within the above range at the time of production.

[0066] The resin composition can be produced, for example, by a method comprising at least step (1) of mixing the modified starch (A) and the water-soluble polymer (B) to obtain a mixture, step (2) of extruding the mixture, and step (3) of cooling and drying the extruded mixture. The components contained in the resin composition are the same as the components contained in the gas barrier layer (I), but their moisture contents may be the same or different from each other, and can preferably be selected from the same range as the moisture content of the gas barrier layer (I).

[0067] Step (1) is a step of mixing at least modified starch (A) and water-soluble polymer (B), and optionally other components, such as the fatty acid having 12 to 22 carbon atoms and / or its fatty acid salt, the clay, the plasticizer, and the additives, can be mixed together.

[0068] Step (1) is usually carried out using an extruder in which the components are mixed homogeneously while being subjected to shear stress by the screw and heated by applying external heat to the barrel.

[0069] The extruder may be, for example, a twin-screw extruder. 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 L / D ratio, which is the ratio of the extruder length (L) to the screw diameter (D), may be, for example, 20 to 50. The screw rotation speed is preferably 80 rpm or higher, more preferably 100 rpm or higher. The extrusion molding pressure is preferably 5 bar (0.5 MPa) or higher, more preferably 10 bar (1.0 MPa) or higher. Each component may be directly introduced into the extruder. Alternatively, the components may be premixed using a mixer and then introduced into the extruder.

[0070] In step (1), from the viewpoint of easily improving film-forming properties and gas barrier properties, it is preferable to mix a plasticizer, preferably water, in an amount of preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 10% by mass or more, particularly preferably 15% by mass or more, and most preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, based on the mass of the mixture. Here, the mass of the mixture refers to the total mass of the mixture including the plasticizer. In step (1), the plasticizer may be added at the initial stage of extrusion, or before the heating temperature is reached, for example, when the temperature is below 100°C. The modified starch (A) is subjected to a cooking treatment by a combination of moisture, heat, and shear stress, resulting in gelatinization (gelation). Furthermore, by separately adding a plasticizer, preferably water, the water-soluble polymer (B) is dissolved, the resin composition is softened, and the modulus and brittleness can be reduced.

[0071] In step (1), the cooking treatment is preferably carried out by heating to a temperature of more than 100°C and not more than 150°C, more preferably from 115°C to 140°C. Here, the cooking treatment is a treatment for crushing and gelling starch granules. Heating can be carried out by applying heat externally to the barrels of the extruder. By applying a temperature that is changed stepwise to each barrel, heating to the desired temperature is possible. Cooking at a temperature above 120°C is advantageous in terms of processability.

[0072] To prevent foaming, the cooked mixture is preferably forced toward the die while the temperature is lowered to preferably 85 to 120°C, more preferably 90 to 110°C. In addition, foaming can be prevented and moisture can be removed by venting the barrel.

[0073] The residence time in the extruder can be set depending on the temperature profile and the screw speed, and is preferably 1 to 2.5 minutes.

[0074] In the step (2) of extruding the mixture, the molten mixture that has been forced through the extruder while being melt-kneaded is extruded through a die at a temperature of preferably 85 to 120°C, more preferably 90 to 110°C.

[0075] In step (3) of cooling and drying the extruded mixture (melt), the mixture (melt) can be extruded into a film, sheet, or strand shape.

[0076] When the mixture is extruded into a film, it can be cooled and dried while being extruded through a film-forming die and then wound up on a take-up roller. It is preferable to cool the mixture between the die and the roller to prevent it from sticking to the roller. A forming roll may be installed between the die and the roller. The forming roll may be made of, for example, rubber, resin, or metal. For drying, the roll may be heated, and dehumidified air may be supplied during winding. In the case of the blown tube method, dehumidified air can be used to expand the film as it exits the die. Talc can also be entrained in the air flow to prevent film blocking.

[0077] When the mixture is extruded into strands, it can be extruded through a strand nozzle with multiple holes and cut with a rotary cutter to form pellets. To prevent the pellets from sticking together, vibration can be applied periodically or constantly, and moisture in the pellets can be removed using hot air, dehumidified air, or an infrared heater.

[0078] In a preferred embodiment of the present invention, after the resin composition is formed, water is added to form a water-containing composition, and therefore the resin composition is preferably in the form of pellets.

[0079] In a preferred embodiment of the present invention, water can be added to the obtained resin composition (preferably a pellet-shaped resin composition) and, for example, stirred and mixed to obtain a water-containing composition. To prevent the resin composition from sticking together and to allow the water to be adsorbed throughout the pellets, it is preferable to add water in two or more batches while stirring. To maintain a constant water content, the water-containing composition may be stored in a sealed container.

[0080] <Manufacturing of laminate> The step (X) is preferably a step of using an extruder to coat the water-containing composition onto the substrate (II) transported by a take-off machine.

[0081] In step (A), the water-containing composition is preferably introduced into an extruder. Examples of extruders include single-screw extruders and twin-screw extruders. The extruder has a screw diameter of, for example, 20 to 150 mm, an L / D ratio of the extruder length (L) to the screw diameter (D) of, for example, 15 to 50, and a screw rotation speed of, preferably, 80 rpm or higher, more preferably, 100 rpm or higher. The cylinder temperature in the extruder may be, for example, 80 to 120°C, preferably 90 to 110°C.

[0082] The water-containing composition introduced into the extruder is plasticized and discharged from the die outlet. Meanwhile, the substrate (II) is conveyed by a take-up machine, preferably a roller-type take-up machine. The water-containing composition discharged from the die outlet is coated onto the conveyed substrate (II), thereby obtaining a laminate. The obtained laminate is conveyed while being pressed against the substrate (II) between multiple rolls, including a metal roll, and can be wound into a roll by a winder. Examples of the multiple rolls include a pressure roll, a cast roll, and a touch roll. In this manner, a laminate having a gas barrier layer (I) and a substrate (II) adjacent to the gas barrier layer (I) can be obtained.

[0083] In the step (X), the draw ratio represented by the following formula is preferably 5 to 20. Draw ratio = (take-off speed of take-off machine) / (flow rate at die exit of extruder) When a laminate is produced at such a draw ratio, productivity is improved and a laminate having excellent adhesive strength between the substrate (II) and the gas barrier layer (I) and excellent gas barrier properties is easily obtained. The flow rate at the die outlet of the extruder is expressed as (discharge rate) / ((lip opening)×(die width)). When the discharge rate is expressed as mass per unit time, the discharge rate 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, since the water in the water-containing composition evaporates during the production process, the moisture content of the gas barrier layer (I) in the resulting laminate is lower than that of the water-containing composition. The resulting laminate may also be dried to adjust the moisture content.

[0084] In another embodiment of the present invention, the method for producing the laminate of the present invention includes a step (sometimes referred to as step (Y)) of coating the gas barrier layer (I) with a material for forming the base material (II). In this embodiment, the gas barrier layer (I) can be formed from the water-containing composition using the extruder, and can be formed into, for example, a sheet or film. The material for forming the base material (II) is not particularly limited, and examples thereof include the biodegradable polyesters described above.

[0085] The step (Y) is preferably a step of using an extruder to coat the gas barrier layer (I) conveyed by a take-off machine with the material.

[0086] In step (Y), the material is preferably fed into an extruder. Examples of the extruder include a single-screw extruder and a twin-screw extruder. The screw diameter, L / D ratio, and screw rotation speed of the extruder may be the same as those in the ranges described in step (X). The cylinder temperature in the extruder can be appropriately selected depending on the type of material, and may be, for example, 100 to 270°C, preferably 150 to 250°C.

[0087] The material fed into the extruder is discharged from the die outlet. Meanwhile, the gas barrier layer (I) is transported by a take-up machine, preferably a roller-type take-up machine. The material discharged from the die outlet is coated onto the transported gas barrier layer (I), thereby obtaining a laminate. The obtained laminate is transported between multiple rolls, including a metal roll, while being pressed against the gas barrier layer (I), and can be wound into a roll by a winder.

[0088] In the method for producing the laminate of the present invention, the method including step (X) can be suitably used when the substrate is a paper substrate, and the method including step (Y) can be suitably used when the substrate is a biodegradable polyester substrate.

[0089] [Multilayer structure] The laminate of the present invention can be formed into a multilayer structure by laminating another layer on at least one surface of the laminate, such as a resin layer.

[0090] Resins that form the resin layers included in the multilayer structure of the present invention include fossil-derived resins such as polyester, polyvinyl alcohol, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, polymethylpentene, polyvinyl chloride, acrylonitrile-butadiene-styrene, acrylonitrile-styrene, polymethyl methacrylic, polyvinylidene chloride (PVDC), polyamide (nylon), polyacetal, and polycarbonate; and bio-derived resins such as polylactic acid (PLA), esterified starch, cellulose acetate, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), bio-polyethylene, bio-polyethylene terephthalate, and bio-polyurethane. Bio-derived resins include renewable organic-resource-derived materials, preferably polymeric materials with a number-average molecular weight (Mn) of 1,000 or more, obtained by chemical or biological synthesis.

[0091] In addition, as fossil resource-derived resins and bio-derived resins, any of biodegradable resins such as polylactic acid (PLA), esterified starch, cellulose acetate, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), etc., and non-biodegradable resins such as polyethylene, polypropylene, polyester, polyethylene terephthalate, polyamide (nylon), biopolyethylene, etc. Using a biodegradable resin as the resin constituting the resin layers tends to exhibit higher biodegradability and disintegrability, even in a multilayer structure. The term "biodegradable resin" refers to a resin that can be decomposed to the molecular level by the action of microorganisms, ultimately turning into carbon dioxide and water, which are then circulated back into nature.

[0092] In the present invention, examples of the method for laminating the resin layer include extrusion coating, extrusion lamination, and film attachment methods using barrier films, vapor-deposited films, etc. In the case of the extrusion coating method, the above-mentioned various resins are extrusion coated onto at least one surface of the gas barrier layer (I) / substrate (II), or laminated via an adhesive resin and a primer layer. In the case of the film lamination method, a film of the above-mentioned various resins is laminated as a resin laminate layer onto at least one surface of the gas barrier layer (I) / substrate (II) by dry lamination, sand lamination, or the like.

[0093] In the film lamination method, in addition to the films made of the various resins described above, the films used for the lamination layer may include barrier films such as films obtained by laminating a metal foil made of various metals such as aluminum onto a film made of the various resins described above, and vapor-deposited films obtained by vapor-depositing various metals such as aluminum or inorganic oxides such as silicon oxide or aluminum oxide onto a film made of the various resins described above.

[0094] Examples of adhesives used in the film lamination method 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, and styrene adhesives, with urethane adhesives being preferred from the standpoint of adhesiveness. The thickness of the adhesive layer is preferably 0.1 to 30 μm, more preferably 1 to 20 μm. The thickness of the adhesive layer can be measured using an optical microscope, a film thickness meter, or the like.

[0095] In the multilayer structure of the present invention, it is preferable not to use the adhesive when achieving higher biodegradability and disintegrability. In such cases, it is preferable to laminate the resin layer directly (adjacently) to at least one surface of the gas barrier layer (I) and the substrate (II) by extrusion coating, extrusion lamination, or the like. The multilayer structure of the present invention may have one or two or more resin layers, and when two or more resin layers are present, the types of the resin layers may be the same or different.

[0096] The resin layer contained in the multilayer structure of the present invention may be, for example, a biodegradable resin layer, a heat seal layer, a moisture-proof layer, an inorganic vapor deposition layer, or a light-shielding layer, and is more preferably a heat seal layer or a moisture-proof layer. That is, in a preferred embodiment of the present invention, the multilayer structure of the present invention has a heat seal layer or a moisture-proof layer on at least one surface of the laminate of the present invention. The heat seal layer is a layer formed from the resin and capable of thermal bonding (heat sealing). The moisture-proof layer is a layer formed from the resin and has moisture-proof properties.

[0097] Specific examples of the layer structure of the multilayer structure of the present invention are shown below. In the multilayer structure having the following layer structure, the gas barrier layer (I) and the substrate (II) are adjacent to each other, but an adhesive layer or other layer may be included at a position other than between these layers. In the following layer structure, it is preferable that the layers other than the gas barrier layer (I) and the substrate (II) function as a heat seal layer or a moisture-proof layer. The gas barrier layer (I) is (I), the substrate (II) is (II), and the polyester layer is (L1), and the following configurations can be given. (I) / (II) / (L1);(L1) / (I) / (II);(L1) / (I) / (II) / (L1); Furthermore, the polyolefin layer (L2) may have the following structure. (I) / (II) / (L2);(L2) / (I) / (II);(L2) / (I) / (II) / (L2);(L1) / (I) / (II) / (L2);(L2) / (I) / (II) / (L1); Furthermore, the biodegradable resin layer (L3) may have the following structure. (L3) / (I) / (II);(I) / (II) / (L3);(L3) / (I) / (II) / (L3);(L1) / (I) / (II) / (L3);(L2) / (I) / (II) / (L3);(L3) / (I) / (II) / (L1);(L3) / (I) / (II) / (L2); Furthermore, the inorganic vapor deposition layer (L4) may have the following structure. (I) / (II) / (L4) / (L2);(I) / (II) / (L4) / (L1);(I) / (II) / (L4) / (L3);(L2) / (I) / (II) / (L4) / (L2);(L1) / (I) / (II) / (L4) / (L2);(L3) / (I) / (II) / (L4) / (L2);(L1) / (I) / (II) / (L4) / (L1);(L3) / (I) / (II) / (L4) / (L1);(L3) / (I) / (II) / (L4) / (L3) ;(L2) / (L4) / (I) / (II);(L1) / (L4) / (I) / (II);(L3) / (L4) / (I) / (II);(L2) / (L4) / (I) / (II) / (L2);(L1) / (L4) / (I) / (II) / (L2);(L3) / (L4) / (I) / (II) / (L2);(L1) / (L4) / (I) / (II) / (L1);(L3) / (L4) / (I) / (II) / (L1);(L3) / (L4) / (I) / (II) / (L3)

[0098] The multilayer structure of the present invention has excellent gas barrier properties and adhesive strength because it contains the laminate of the present invention. Furthermore, the multilayer structure in a preferred embodiment of the present invention also has excellent biodegradability and disintegrability.

[0099] The laminate or multilayer structure of the present invention can be used, for example, as a barrier packaging material used in packaging applications such as packaging materials for food, containers, cups, etc., or as industrial materials. Among these, it can be suitably used as a barrier packaging material used in packaging applications such as packaging materials for food, containers, cups, etc., and is particularly suitably used as a flexible packaging material for food, etc. Note that the term "flexible packaging material" refers to a packaging material made of a highly flexible material, and generally refers to a packaging material made of thin, flexible materials such as paper, film, aluminum foil, etc., either alone or laminated together. In terms of shape, it refers to a packaging material such as a bag that maintains a three-dimensional shape when contents are placed inside. When the laminate or multilayer structure of the present invention is used as a packaging material for food and the like, particularly as a soft packaging material, laminating or incorporating a resin layer having heat sealing properties (the heat sealing layer) therein can improve the airtightness of the packaging material, protect the contents from deterioration due to oxidation by oxygen, and make it easy to extend the shelf life. Furthermore, when the composition is used as a laminate or multilayer structure for industrial materials, etc., it is possible to prevent putrefaction and deterioration by suppressing the intrusion of oxygen, and it is also expected to have effects such as a flavor barrier property that prevents the odor of the solvent from leaking out.

[0100] [Packaging or lid material] The present invention encompasses packaging materials or lid materials comprising the laminate or multilayer structure of the present invention. Examples of packaging materials include, but are not limited to, the barrier packaging materials described above. Examples of lid materials include, but are not limited to, container lid materials. When used as a container lid material, it can seal the inside of the container by combining it with the container body.

[0101] The packaging material or lid material of the present invention contains the laminate and therefore has excellent gas barrier properties, interlayer adhesive strength and disintegration properties, making it suitable for use in food applications and reducing the environmental load. [Example]

[0102] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0103] <Test Method> (1) Measurement of oxygen permeability The laminates obtained in the examples and comparative examples were stored at 23°C and 50% RH for two weeks to condition the humidity, and then attached to an oxygen transmission rate measuring device to measure the oxygen transmission rate. The measurement conditions were as follows: Equipment: Modern Controls "MOCON OX-TRAN2 / 20" Temperature: 23℃ Humidity on the oxygen supply side and carrier gas side: 50% RH Oxygen pressure: 1.0 atm Carrier gas pressure: 1.0 atm

[0104] (2) Measurement of biodegradability of laminate The laminates obtained in the examples and comparative examples were cut into 1 x 1 cm pieces, and the following biodegradability was calculated from the amount of carbon dioxide generated during biodegradation after 168 days under aerobic conditions in accordance with ISO14855-1. Biodegradation rate (%)=((CO2)T-(CO2)B) / (MToT×CToT×44 / 12)×100 (CO2)T: Total CO2 emitted from the compost bin (g) (CO2)B: Total CO2 emitted from the empty test vessel (g) MToT: dry solids mass of test material placed in the compost bin (g) CToT: Relative amount of total organic carbon (TOC) in the dry solids of the test material (g / g)

[0105] (3) Measurement of the decomposability of the laminate According to JAPAN Tappi No. 39, the laminate was disintegrated in a standard disintegrator (Kumagaya Riki Kogyo Co., Ltd.) at a paper concentration of 4.5%, a temperature of 50-60°C, and with the addition of 1.0% sodium hydroxide (to paper), 2.0% No. 3 silicic acid (to paper), and 1.0% hydrogen peroxide (to paper). Unbleached kraft paper (Taiou Atlas, basis weight 50 g / m) was used. 2 ) was used as a comparison and evaluated visually according to the following criteria. A = Disintegrated within 5 minutes compared to the control, and undisintegrated pieces disappeared. B = Disintegrated in 5 minutes or more compared to the control, and undisintegrated pieces disappeared within 1 hour from the completion time of A. Undissociated fragments remained even one hour after the completion time of C=A.

[0106] (4) Measurement of adhesive strength of laminate The laminates obtained in the Examples and Comparative Examples were conditioned at 23°C and 50% RH for two weeks, and then cut into strips 150 mm long and 15 mm wide. The gas barrier layer (I) and the substrate (II) were then peeled off, and the adhesive strength (N / 15 mm) was measured by pulling at an angle of 180° at a rate of 100 mm / min using the tensile tester described below. The arithmetic average of five measurements for each sample was taken as the adhesive strength. Tensile testing machine: Instron "INSTRON3367", load cell 500N

[0107] (5) Measurement of the degree of saponification of polyvinyl alcohol (B) In accordance with JIS K 6726 (Testing method for polyvinyl alcohol), dissolution titration of the polyvinyl alcohol in the examples and comparative examples was carried out, and the degree of saponification was calculated.

[0108] (6) Viscosity measurement of polyvinyl alcohol (B) In accordance with JIS Z 8803 (falling ball viscometer) and JIS K 6726 (polyvinyl alcohol test method), 4% aqueous solutions of polyvinyl alcohol in the examples and comparative examples were prepared, and the viscosity at 20°C was measured using a Hoebler viscometer, and this was taken as the viscosity (20°C) of the 4% aqueous solution of polyvinyl alcohol (B).

[0109] (7) Measurement of moisture content (water content) The moisture content (the proportion of water in the total mass of the laminate) of the water-containing compositions and laminates obtained in the examples and comparative examples was confirmed by crushing the compositions using a Wonder Blender WB-1 (Osaka Chemical Co., Ltd.) to a maximum particle size of 1 mm or less, and then measuring the moisture content at 130°C for 60 minutes using a Mettler-Toledo heat-dry moisture meter "HR73."

[0110] (8) Materials used <Modified starch (A)> (A-1): ECOFILM®; corn starch modified with propylene oxide, amylose content 70% by weight, obtained from Ingredion (A-2): National 1658 (registered trademark); corn starch modified with propylene oxide, amylose content 20% by mass, obtained from Ingredion

[0111] <Water-soluble polymer (B)> (B-1): ELVANOL (registered trademark) 71-30; polyvinyl alcohol resin, saponification degree 99.5 mol%, viscosity 30 mPa·s (20°C, 4% aqueous solution), manufactured by Kuraray Co., Ltd. (B-2): Alcox (registered trademark) L-11; polyethylene oxide resin, weight average molecular weight 100,000, manufactured by Meisei Chemical Industry Co., Ltd.

[0112] <Other Materials (C)> (C-1): PVDC film; Saran (registered trademark) film 700, 43 μm thick, manufactured by Asahi Kasei Corporation (C-2): EVOH film; EVAL (registered trademark) film EF-XL, 12 μm thick, manufactured by Kuraray Co., Ltd. (C-3): Aluminum foil; commercial-use My Foil, 12 μm thick, manufactured by UACJ Foil Corporation <Base material (II)> Unbleached kraft paper: Taiou Atlas, basis weight 50g / m 2 , manufactured by Daio Paper Co., Ltd. Bleached kraft paper: Snow Queen G40, basis weight 50g / m 2, manufactured by Daio Paper Co., Ltd. One-sided glossy kraft paper: Star White, basis weight 40 g / m 2 , manufactured by Marusumi Paper Co., Ltd. Glassine paper: Thick glassine, basis weight 31 g / m 2 , manufactured by Nippon Paper Industries Co., Ltd. ·Thin paper: food paper, basis weight 21g / m 2 , manufactured by Shirakawa Paper Co., Ltd. Rayon paper: Rayon paper <208> , basis weight 14g / m 2 , manufactured by Okura Paper Co., Ltd. White paperboard: Hokuetsu Art Post, basis weight 233g / m 2 , manufactured by Hokuetsu Corporation High-quality paper: Shiraoi, 110g / m 2 , manufactured by Nippon Paper Industries Co., Ltd. Coated paper: Ryuo Coat, basis weight 55g / m 2 , manufactured by Daio Paper Co., Ltd. Cellophane: Plain cellophane PL, basis weight 20g / m 2 , manufactured by Futamura Chemical Co., Ltd. PBAT / PLA blend: Ecovio F2341, basis weight 50g / m 2 , manufactured by BASF Hereinafter, the trade name and manufacturer of the substrate (II) will be omitted.

[0113] Example 1 (Resin composition) As raw materials, 90 parts by mass of modified starch (A-1) and 10 parts by mass of water-soluble polymer (B-1) were mixed in a tumbler mixer for 2 hours, and the resulting mixture was fed to a twin-screw extruder connected to a liquid pump. Figure 1 shows a schematic diagram of the twin-screw extruder used in Example 1, and the screw diameter, L / D ratio, rotation speed, operating mode, and temperature profile of the extruder (Table 1) are shown below.

[0114] [Table 1]

[0115] Screw diameter: 27mm L / D ratio: 48 Screw rotation speed: 500 rpm Operation method: Co-rotation (meshing self-wiping) method

[0116] Specifically, the resulting mixture was fed into the barrel through a hopper at C1 via a weight feeder of a twin-screw extruder at a rate of 3.5 kg / hr. Water was injected into the barrel at a flow rate of 26 g / min via a liquid pump (L) at C4. The temperature ranges from C5 to C9 were the cooking range, and complete gelatinization was achieved within these zones. The strand die was located after C11. The resin composition was extruded through a multi-hole strand nozzle and cut with a rotary cutter to form strands into pellets. Because the pellets contained excess moisture, the moisture was removed with hot air while constantly vibrating to prevent sticking.

[0117] (Water-containing composition) Water was added to the resulting pellet-shaped resin composition until the water content reached 35% by mass relative to the mass of the resin composition. During the water addition, the pellets were stirred for 15 minutes in a tumbler mixer while adding the water in multiple batches to prevent the pellets from sticking together and to ensure that the water was uniformly absorbed throughout the pellets. After stirring, the pellets were placed in a polyethylene bag, sealed, and left to stand at room temperature for 6 hours to prevent water evaporation. In this way, a water-containing composition (water-containing pellets) with a water content of 35% by mass was obtained.

[0118] (Laminate) The obtained water-containing composition (pellet-like) 1 was charged into a single-screw extruder 2 shown in Fig. 2 and extruded through a film-forming die 3. Next, the water-containing composition 4 extruded from the outlet of the die 3 was transferred to a substrate 5 (unbleached kraft paper, basis weight 50 g / m) conveyed by a roller-type take-up machine (not shown). 2). The laminate 6 obtained by coating was immediately pressed onto the substrate 5 through a pressure roll (rubber) 7a, a cast roll (metal) 7b, and a touch roll (rubber) 7c, and then taken up into a roll using a winder (not shown). The details of the single-screw extruder used and its operating conditions, as well as the temperature profile (Table 2), are shown below. The obtained laminate was placed in a hot-air dryer at 90°C and dried until the moisture content reached 12% by mass. In this way, a laminate consisting of a gas barrier layer (I) and a substrate (II) adjacent to the gas barrier layer (I) was obtained. The thickness of the gas barrier layer was 20 μm. Single-screw extruder: Extruder manufactured by the Institute of Plastics Engineering (40 mm diameter, L / D = 25) ·Set temperature: [Table 2] ·Discharge amount: 20kg / hr Die: 450mm wide coat hanger die, lip opening 0.2mm Distance between die and casting roll (air gap): 150 mm

[0119] <Example 2> A laminate was obtained in the same manner as in Example 1, except that 79 parts by mass of modified starch (A-1), 20 parts by mass of water-soluble polymer (B-1), and 1 part by mass of water-soluble polymer (B-2) were used as raw materials for the resin composition.

[0120] <Examples 3 to 18 and Comparative Examples 1 to 4 and 8> A laminate was obtained in the same manner as in Example 1, except that the contents of the modified starch (A) and the water-soluble polymer (B), the types and contents of other substances, the thickness of the gas barrier layer (I), and the type and basis weight of the substrate (II) were adjusted to be as shown in Table 3. In Example 5, 54 parts by mass of modified starch (A-1) and 36 parts by mass of modified starch (A-2) were used as the modified starch (A), and in Comparative Examples 2 and 4, modified starch (A-2) was used as the modified starch (A). In the other Examples and Comparative Examples, modified starch (A-1) was used as the modified starch (A). As the water-soluble polymer (B), the water-soluble polymer (B-1) was used.

[0121] Example 19 The water-containing composition obtained in Example 1 was formed into a film using a single-screw extruder to obtain a rolled sheet (gas barrier layer (I)) having a thickness of 120 μm. The obtained rolled sheet was placed on an unwinder and conveyed by a take-up machine while a PBAT / PLA blend was applied at 50 g / m to one side. 2 In this way, a laminate consisting of the gas barrier layer (I) and the substrate (II) adjacent to the gas barrier layer (I) was obtained. The coating equipment and conditions are as follows: Single-screw extruder: Extruder manufactured by the Institute of Plastics Engineering (40 mm diameter, L / D = 25) ·Set temperature: [Table 3] ·Discharge amount: 20kg / hr Die: 450mm wide coat hanger die, lip opening 0.2mm Distance between die and casting roll (air gap): 150mm

[0122] <Comparative Example 5> An adhesive layer was formed on a PVDC film (other material (C) in Table 3) so that the thickness after drying was 3 μm, and unbleached kraft paper (basis weight 50 g / m) was placed on the adhesive layer. 2 ) to obtain a laminate. The adhesive layer was formed by applying a two-component adhesive using a bar coater and drying it. The two-component adhesive was a two-component reactive polyurethane adhesive consisting of "Takelac (registered trademark) A-520" manufactured by Mitsui Chemicals, Inc. and "Takenate (registered trademark) A-50" manufactured by Mitsui Chemicals, Inc.

[0123] <Comparative Examples 6 and 7> A laminate was obtained in the same manner as in Comparative Example 5, except that the other materials (C) and the thickness of the gas barrier layer were as shown in Table 3.

[0124] <Comparative Example 8> A laminate was obtained in the same manner as in Comparative Example 5, except that the sheet (gas barrier layer (I)) obtained in Example 19 was used instead of the other material (C).

[0125] The biodegradability, adhesive strength, oxygen permeability, and disintegrability of the laminates obtained in the examples and comparative examples were measured. The results are shown in Table 4. In Table 4, an * in the adhesive strength column indicates that material failure occurred in the substrate, and that sufficient adhesive strength was maintained. [Table 4]

[0126] The laminates obtained in Examples 1 to 19 were evaluated as A in terms of disintegrability, and were confirmed to have low oxygen permeability and high adhesive strength. In contrast, the laminates obtained in Comparative Examples 1 and 5 to 8 were evaluated as B or C in terms of disintegrability, and the laminates obtained in Comparative Examples 2 to 5 were confirmed to have higher oxygen permeability than the Examples. Therefore, it was found that the laminate of the present invention is excellent in gas barrier properties, adhesive strength and defibration properties. [Explanation of symbols]

[0127] 1...Water-containing composition (pellet form) 2...Single screw extruder 3...Die 4...Water-containing composition 5...Base material 6...Laminate 7a...Pressure roll 7b…Cast Roll 7c...Touch Roll 8...Twin-screw extruder 9. Hopper 10...Liquid addition nozzle 11...Resin thermometer 12...Resin pressure gauge 13...Adapter 14...Die

Claims

1. a gas barrier layer (I) containing a modified starch (A) having an average amylose content of 45% by mass or more and a water-soluble polymer (B); and a substrate (II) adjacent to the gas barrier layer (I), a moisture content of the gas barrier layer (I) of 4% by mass or more and 20% by mass or less, based on the mass of the gas barrier layer (I); the substrate (II) is paper; and the degree of biodegradation in a biodegradation test in accordance with ISO 14855-1 is 80% or more.

2. The laminate according to claim 1 , wherein the water-soluble polymer (B) is polyvinyl alcohol and / or polyoxyalkylene.

3. 3. The laminate according to claim 1, wherein the content of the modified starch (A) is 40 to 98 parts by mass and the content of the water-soluble polymer (B) is 2 to 60 parts by mass, based on 100 parts by mass in total of the modified starch (A) and the water-soluble polymer (B).

4. 4. The laminate according to claim 1, wherein the gas barrier layer (I) has a thickness of 1 to 600 μm.

5. A multilayer structure comprising the laminate according to any one of claims 1 to 4, having a heat seal layer or a moisture-proof layer on at least one surface thereof.

6. A packaging material or a lid material comprising the laminate according to any one of claims 1 to 4 or the multilayer structure according to claim 5.

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