JP7780950B2 - Laminate - Google Patents

Description

The present invention relates to a laminate including a remoistenable adhesive layer used for food packaging, etc., a multilayer laminate and adhesive body including the laminate, a bag made of the adhesive body, and packaging materials and secondary packaging materials such as labels, tapes and lid materials made of the laminate.

In food packaging, sealing of contents can be achieved by melting and adhering sealant layers together, such as with heat sealing or ultrasonic sealing, or by bonding with adhesive materials such as hot-melt adhesives. One such method involves the use of a remoistenable adhesive layer, as exemplified by postage stamps, which is primarily used for packaging secondary materials. For example, known remoistenable adhesive layers include those using acrylic polymers (Patent Document 1) and those using polyvinyl alcohol as the main component (Patent Document 2). Furthermore, food packaging requires functionality such as gas barrier properties to maintain food freshness, and in response to recent environmental concerns, there has been a significant increase in demand for biodegradable packaging materials.

Japanese Patent Application Laid-Open No. 2018-090319 Special Publication No. 61-39354

However, while synthetic polymers such as polyvinyl alcohol have high strength, they have the problem of not being able to meet the biodegradability requirements that have been particularly required for packaging materials in recent years. On the other hand, starch, which is most commonly used as a remoistenable adhesive layer, is relatively highly biodegradable and can soften and dissolve in the presence of water. However, the inventors' studies have revealed that such remoistenable adhesive layers become extremely brittle in the humidity environments in which food packaging materials are placed, particularly in low-humidity environments of 20 to 40% RH, and therefore do not provide sufficient adhesive strength.

An object of the present invention is to provide a laminate that is highly biodegradable and has excellent adhesive strength even when exposed to a low-humidity environment, a multilayer laminate and adhesive body containing the laminate, a bag made of the adhesive body, and a label, tape, and lid material made of the laminate.

As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that, in a laminate comprising a remoistenable adhesive layer (I) and a substrate layer (II), the remoistenable adhesive layer (I) contains a modified starch (A) and a water-soluble polymer (B), and the amylose content of the modified starch (A) is 45% by mass or more, thereby solving the above-mentioned problems and completing the present invention.

[1] A laminate comprising a remoistenable adhesive layer (I) and a substrate layer (II),
A laminate, wherein the remoistenable adhesive layer (I) comprises a modified starch (A) and a water-soluble polymer (B), and the amylose content of the modified starch (A) is 45% by mass or more.
[2] The laminate according to [1], wherein the water-soluble polymer (B) is polyvinyl alcohol.
[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 of the 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 substrate layer (II) is paper.
[5] A multilayer laminate comprising the laminate according to any one of [1] to [4] and a layer (III), wherein the remoistenable adhesive layer (I) of the laminate is on the outermost surface.
[6] An adhesive body formed by rewetting and bonding the remoistenable adhesive layer (I) of the laminate according to any one of [1] to [5] to a covering layer, wherein the covering layer is a layer selected from the remoistenable adhesive layer (I), the substrate layer (II), and the layer (III) contained in the laminate or another laminate, or a layer contained in an adherend other than these laminates.
[7] The adhesive body according to [6], wherein the covering layer is a remoistenable adhesive layer (I) contained in the laminate or the other laminate.
[8] A bag made of the adhesive material according to [6] or [7].
[9] A label comprising the laminate according to any one of [1] to [5], wherein printing is applied to the outermost surface of the laminate opposite to the remoistenable adhesive layer (I).
[10] A tape comprising the laminate according to any one of [1] to [5].
[11] A lid material comprising the laminate according to any one of [1] to [5].
[12] A method for producing an adhesive body according to [6], comprising a step of rewetting at least the remoistenable adhesive layer (I) of the laminate to remoisten and bond the remoistenable adhesive layer (I) and the covering layer.

The laminate of the present invention is highly biodegradable and can maintain excellent adhesive strength even when exposed to a low humidity environment.

1 is a schematic diagram showing a layer structure of a laminate according to one embodiment of the present invention. 1 is a schematic diagram showing an adhesive body (bag) and a method for producing the same in one embodiment of the present invention. 1 is a schematic diagram showing an adhesive body (bag) and a method for producing the same in one embodiment of the present invention. 1 shows a schematic diagram of a twin-screw extruder used in the examples.

[Laminate]
The laminate of the present invention is a laminate comprising a remoistenable adhesive layer (I) and a substrate layer (II).
<Rewetting adhesive layer (I)>
The remoistenable adhesive layer (I) is a layer that can be bonded by applying water. In the laminate of the present invention, the remoistenable adhesive layer (I) can be at least partially bonded by applying water.

The remoisturized adhesive layer (I) contains a modified starch (A) and a water-soluble polymer (B), and the amylose content of the modified starch (A) is 45% by mass or more. Therefore, the laminate of the present invention is highly biodegradable and can have excellent adhesive strength even when exposed to a low-humidity environment. Furthermore, it can also have excellent gas barrier properties. In this specification, adhesive strength refers to the adhesive strength when the remoisturized adhesive layer is bonded to an adherend (adhering layer) by rewetting. In this specification, remoistening means wetting (or wetting) the remoisturized adhesive layer with water, and remoist adhesion means bonding after wetting (or wetting) the remoisturized adhesive layer with water.

(Modified Starch (A))
As the modified starch (A), for example, at least one selected from the group consisting of etherified starch, esterified starch, cationized starch and crosslinked starch can be used.

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.

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 starches can also be used.

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, esterified starches having structural units derived from phthalic anhydride, and esterified starches having structural units derived from octenylsuccinic anhydride; and esterified starches having structural units derived from oxo acids, such as nitrate-esterified starch, phosphate-esterified starch, and urea-phosphate-esterified starch. Other examples include xanthate-esterified starch, acetoacetate-esterified starch, etc.

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

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

The modified starch (A) is preferably an etherified starch having a hydroxyalkyl group having 2 to 6 carbon atoms, an esterified starch having a structural unit derived from a dicarboxylic acid anhydride, or a combination thereof, and more preferably hydroxyethyl-etherified starch, hydroxypropyl-etherified starch, hydroxybutyl-etherified starch, an esterified starch having a structural unit derived from maleic anhydride, an esterified starch having a structural unit derived from phthalic anhydride, an esterified starch having a structural unit derived from octenylsuccinic anhydride, or a combination thereof. The modified starch (A) can be used alone or in combination of two or more kinds.

The modified starch (A) has an amylose content of 45% by mass or more. The inventors unexpectedly discovered that when the amylose content of the modified starch (A) contained in the remoistenable adhesive layer (I) is 45% by mass or more, the adhesive layer has excellent adhesive strength even when exposed to a low-humidity environment. Furthermore, an amylose content of 45% by mass or more is advantageous in terms of gas barrier properties and biodegradability. On the other hand, when the amylose content is less than 45% by mass, the adhesive layer is unlikely to exhibit sufficient adhesive strength in a low-humidity environment. When two or more types of modified starch are used, the amylose content of the modified starch (A) refers to the average amylose content calculated by weighting the amylose contents of the two or more types of modified starches. In this case, modified starches with an amylose content of less than 45% by mass may be included as long as the average amylose content is 45% by mass or more.

The amylose content in the modified starch (A) is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. When the amylose content in the modified starch (A) is equal to or greater than the above-mentioned lower limit, it is easy to increase the adhesive strength in a low-humidity environment, and it is easy to improve the gas barrier properties and biodegradability. The 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 coloration method described in "Starch 50 No. 4 158-163 (1998)".

The modified starch (A) preferably has a moisture content of 10 to 15% by mass.

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.

Commercially available modified starch (A) can also be used. A typical example of a commercially available modified starch (A) is ECOFILM (registered trademark), a hydroxypropyl etherified starch available from Ingredion.

(Water-soluble polymer (B))
The water-soluble polymer (B) is a polymer compatible with the modified starch (A). The water-soluble polymer (B) preferably has a melting point suitable for the processing temperature of the modified starch (A), and is preferably polyvinyl alcohol from the viewpoint of easily improving adhesive strength and gas barrier properties in a low-humidity environment. The water-soluble polymer (B) can be used alone or in combination of two or more types.

The saponification degree of polyvinyl alcohol is preferably 80 to 99.8 mol%. When the saponification degree of polyvinyl alcohol is within the above range, it tends to be easier to improve adhesive strength and gas barrier properties in low-humidity environments. 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. Polyvinyl alcohol is produced, for example, by hydrolysis of polyvinyl acetate obtained by polymerization of vinyl acetate monomer.

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, adhesive strength and gas barrier properties in low-humidity environments tend to be easily 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 35 mPa·s or less.

The polyvinyl alcohol 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 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.

The method for producing polyvinyl alcohol is not particularly limited. For example, a method can be used in which a vinyl alcohol 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, saponification can be performed 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.

The remoistenable adhesive layer (I) preferably contains 40 to 98 parts by mass of modified starch (A) and 2 to 60 parts by mass of water-soluble polymer (B) based on 100 parts by mass of the total of the modified starch (A) and the water-soluble polymer (B). When the contents of modified starch (A) and water-soluble polymer (B) are within the above ranges, adhesive strength, biodegradability, and gas barrier properties in a low-humidity environment are likely to be improved.

The content of modified starch (A) is preferably 45 parts by mass or more, more preferably 55 parts by mass or more, even more preferably 65 parts by mass or more, and is preferably 95 parts by mass or less, more preferably 93 parts by mass or less, and even more preferably 90 parts by mass or less, based on 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 is likely to be improved, and when it is at most the above upper limit, gas barrier properties and adhesive strength in low-humidity environments are likely to be improved.

The content of the water-soluble polymer (B) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, and is preferably 55 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 35 parts by mass or less, based on 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 and the adhesive strength in a low-humidity environment are likely to be improved, and when it is at most the above upper limit, the biodegradability is likely to be improved.

In the remoistenable adhesive layer (I), the total proportion of the modified starch (A) and the water-soluble polymer (B) is preferably 10% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, particularly preferably 80% by mass or more, and is preferably 100% by mass or less, based on the mass of the remoistenable adhesive layer (I). When the total proportion of the modified starch (A) and the water-soluble polymer (B) is within the above range, adhesive strength, biodegradability, and gas barrier properties in a low-humidity environment are likely to be improved.

The remoistenable adhesive 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.

When the remoisturized adhesive layer (I) contains a fatty acid having 12 to 22 carbon atoms and/or a fatty acid salt thereof, the content in the remoisturized adhesive 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 remoisturized adhesive 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.

The remoistenable adhesive layer (I) may further contain clay. Examples of the 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.

When the remoistenable adhesive layer (I) contains clay, the content of the clay in the remoistenable adhesive layer (I) is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.5 to 2% by mass, based on the mass of the remoistenable adhesive layer (I). A clay content within the above range tends to be advantageous in terms of transparency and strength.

The remoisturized adhesive layer (I) may further contain a plasticizer. The inclusion of a plasticizer is preferred because it facilitates improved film-forming and coating properties when forming the remoisturized adhesive layer (I), resulting in a layer with high gas barrier properties, remoisturized adhesion, and adhesive strength in low-humidity environments. 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. These plasticizers can be used alone or in combination. Among these plasticizers, water is preferred because it facilitates the formation of a layer with high gas barrier properties, remoisturized adhesion, and adhesive strength in low-humidity environments.

The water content (moisture content) in the remoisturized adhesive layer (I) is preferably 3 to 20% by mass, more preferably 4 to 18% by mass, and even more preferably 7 to 15% by mass, based on the mass of the remoisturized adhesive layer (I). A water content within this range is advantageous in terms of gas barrier properties, remoisturized adhesion, and adhesive strength in low-humidity environments. The water content is measured, for example, using a heat-drying moisture meter at 130°C for 30 minutes after conditioning at 23°C and 50% relative humidity for two weeks.

The remoistenable adhesive layer (I) may further contain additives such as fillers, processing stabilizers, weathering 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.

The remoisturized adhesive layer (I) is preferably in the form of a film or sheet. From the viewpoints of remoisturized adhesiveness, adhesive strength in a low-humidity environment, gas barrier properties, biodegradability, etc., the thickness of the remoisturized adhesive layer (I) is preferably 0.01 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and particularly preferably 1 μm or more, and is preferably 1000 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and particularly preferably 10 μm or less. One or more remoisturized adhesive layers (I) may be provided, and they may be single-layer or multi-layer. When the remoisturized adhesive layer (I) has two or more layers, the thickness and composition of each layer may be different or the same.

<Base material layer (II)>
The substrate layer (II) is not particularly limited, and examples thereof include paper or a resin film. Examples of paper include, but are not limited to, kraft paper, fine paper, construction paper, glassine paper, parchment paper, synthetic paper, white cardboard, Manila cardboard, milk carton base paper, cup base paper, ivory paper, and silver paper. Among these, kraft paper and glassine paper are preferably used from the viewpoint of easily improving adhesion with the remoisturized adhesive layer (I). Furthermore, examples of resin films include, but are not limited to, polyethylene terephthalate (PET) film, polypropylene (BOPP) film, polyethylene (PE) film (preferably low-density polyethylene (LDPE) film), and polylactic acid film. Among these, PET film is preferably used from the viewpoint of easily improving adhesion with the remoisturized adhesive layer (I). The substrate layer (II) is preferably paper from the viewpoint of easily improving adhesion with the remoisturized adhesive layer (I) and biodegradability, and kraft paper, cardboard, and glassine paper are even more preferable from the viewpoint of strength.

The thickness of the substrate layer (II) is not particularly limited and is preferably 1 to 1000 μm, more preferably 1 to 500 μm, even more preferably 5 to 300 μm, and particularly preferably 10 to 150 μm. One or more substrate layers (II) may be provided, and the substrate layer (II) may be a single layer or multiple layers. When the substrate layer (II) has two or more layers, the thickness and material of each layer may be different or the same.

The laminate of the present invention includes the remoistenable adhesive layer (I) and the substrate layer (II). Therefore, it is possible to achieve both high biodegradability and excellent adhesive strength after exposure to a low-humidity environment. Moreover, the laminate of the present invention also has excellent gas barrier properties.
The laminate of the present invention can exhibit adhesive function in the rewetted portion (water-applied portion) by partially or entirely rewetting the remoistenable adhesive layer (I) (e.g., by partially or entirely applying water). Furthermore, even when exposed to a low-humidity environment, it is possible to suppress a decrease in adhesive strength and maintain excellent adhesive strength. Therefore, for example, when the laminate is in the form of a film or sheet, it can be used to form packaging materials in various forms, or labels, stickers, lids, etc. Therefore, the laminate of the present invention is particularly useful as packaging materials and secondary packaging materials for food.

The laminate of the present invention may include one or more adhesive layers (X) other than the remoistenable adhesive layer (I) and the base layer (II). Examples of adhesives constituting the adhesive layer (X) include acrylic adhesives, urethane adhesives, epoxy adhesives, vinyl acetate adhesives, ethylene-vinyl acetate adhesives, vinyl chloride adhesives, silicone adhesives, nitrile cellulose adhesives, phenolic adhesives, polyvinyl alcohol adhesives, melamine adhesives, and styrene adhesives. From the viewpoint of adhesiveness, urethane adhesives are preferred. The thickness of the adhesive layer (X) is preferably 0.1 to 10 μm, more preferably 1 to 5 μm.

In one embodiment of the present invention, when the laminate of the present invention has an adhesive layer (X), the adhesive layer (X) is preferably disposed between the remoistened adhesive layer (I) and the substrate layer (II). In a preferred embodiment of the present invention, the laminate has the remoistened adhesive layer (I), the adhesive layer (X), and the substrate layer (II) in this order, or has the remoistened adhesive layer (I) and the substrate layer (II) adjacent to each other. Figure 1 shows a laminate 2 that is a preferred embodiment of the present invention, i.e., a laminate having a remoistened adhesive layer (I) 3, an adhesive layer (X) 5, and a substrate layer (II) 4 laminated in this order.

The laminate of the present invention has excellent gas barrier properties, particularly oxygen barrier properties. The oxygen permeability (mL.20 μm/m ² day atm) of the laminate of the present invention at 23° C. and 50% RH is preferably 8.0 or less, more preferably 5.0 or less, even more preferably 4.0 or less, even more preferably 3.0 or less, particularly preferably 2.0 or less, and most preferably 1.0 or less. When the oxygen permeability of the laminate is below the above upper limit, excellent oxygen barrier properties can be exhibited. Furthermore, the oxygen permeability (mL.20 μm/m ² day atm) is usually 0.1 or more. The oxygen permeability of the laminate can be measured using an oxygen permeation amount measuring device after storing and regulating the humidity at 23° C. and 50% RH for two weeks, and can be measured, for example, by the method described in the examples.

The laminate of the present invention exhibits excellent adhesive strength (adhesion) when the remoistened adhesive layer (I) is remoistened and can maintain sufficient adhesive strength even when exposed to a low-humidity environment. The seal strength of an adhesive body obtained by remoistening and bonding the laminate of the present invention after storage and conditioning in a low-humidity environment of 23°C and 20% RH for three days is preferably 5 N/15 mm or more, more preferably 8 N/15 mm or more, and even more preferably 10 N/15 mm or more. The seal strength is measured by preparing an adhesive body by remoistening and bonding the laminate, preferably two identical laminates, applying water to the remoistened adhesive layer (I) of one laminate, and then overlapping and press-bonding the water-coated portion with the remoistened adhesive layer (I) of the other laminate to form an adhesive body, storing the adhesive body at 23°C and 20% RH for three days and conditioning the humidity, and then measuring the interlayer peel strength using a tensile tester under conditions of a speed of 50 mm/min, an initial chuck distance of 50 mm, and a peel angle of 180°. This can be measured, for example, by the method described in the Examples.

[Method of manufacturing laminate]
The method for producing the laminate of the present invention is not particularly limited, but examples include a method in which a remoistened adhesive layer (I) is produced, an adhesive layer (X) is formed on the obtained remoistened adhesive layer (I), and a substrate layer (II) is formed on the adhesive layer (X).

The remoistened adhesive layer (I) can be produced, for example, by a method including at least the steps of: (1) mixing the modified starch (A) and the water-soluble polymer (B) to obtain a mixture; (2) extruding the mixture; and (3) cooling and drying the extruded mixture.

Step (1) is a step of mixing at least the modified starch (A) and the 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 also be mixed together.

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.

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 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 more, more preferably 100 rpm or more. 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, these components may be premixed using a mixer and then introduced into the extruder.

In step (1), from the viewpoint of the film-forming ability and gas barrier properties of the mixture, it is preferable to mix a plasticizer 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, with an upper limit of 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. A preferred plasticizer is water. Here, the mass of the mixture refers to the total mass of the mixture including the plasticizer. In step (1), the plasticizer may be introduced at the initial stage of extrusion, or before the temperature reaches the temperature at which the cooking treatment described below is performed, 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, and can be gelatinized (gelated). Furthermore, by separately introducing a plasticizer, preferably water, the water-soluble polymer (B) can be dissolved, the mixture can be softened, and the modulus and brittleness can be reduced.

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 stepwise temperature to each barrel, heating to the target temperature is possible. Cooking at a temperature above 120°C is advantageous in terms of processability.

The cooked mixture is preferably forced towards the die while the temperature is reduced to preferably 85 to 120°C, more preferably 90 to 110°C, to prevent foaming. Also, venting the barrel prevents foaming and removes moisture.

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.

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.

In step (3) of cooling and drying the extruded mixture, the mixture is extruded into a film or sheet to form a remoistenable adhesive layer (I). The extruded mixture is usually in the form of a melt.

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. Cooling between the die and the roller is preferred to prevent the mixture from sticking to the roller. 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 stream to prevent film blocking.

The method for forming the adhesive layer (X) on the remoistened adhesive layer (I) is not particularly limited, but examples thereof include a method in which an adhesive constituting the adhesive layer (X) is applied to the remoistened adhesive layer (I) and then dried.

The method for forming the substrate layer (II) on the adhesive layer (X) is not particularly limited, and examples thereof include a method in which the substrate layer (II) is laminated on the adhesive layer (X) and then laminated. The laminate of the present invention may be produced by extruding the mixture onto the substrate layer (II) using the above-mentioned extruder. Alternatively, the laminate may be produced by a sand lamination method in which the adhesive layer (X) is extruded between the remoistenable adhesive layer (I) and the substrate layer (II).

[Multilayer laminate]
The present invention encompasses a multilayer laminate comprising the above-described laminate (comprising the remoistenable adhesive layer (I) and the substrate layer (II)) and a layer (III), with the remoistenable adhesive layer (I) of the laminate on the outermost surface. Because the multilayer laminate of the present invention has the remoistenable adhesive layer (I) on the outermost surface, it can be partially or entirely bonded to an adherend by rewetting (for example, by applying water).

The layer (III) is not particularly limited as long as it is a layer other than the remoistenable adhesive layer (I), the substrate layer (II), and the adhesive layer (X). Examples of such a layer include a protective layer, a gas barrier layer other than the remoistenable adhesive layer (I), a moisture-proof layer, a light-shielding layer, a printed layer, a reinforcing layer, etc. Examples of materials for forming the layer (III) include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, EVOH, polyvinyl chloride, polyurethane, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon, polyacrylonitrile, cellulose or its derivatives, glass, and wood. One or more layers (III) may be provided, and the layer (III) may be a single layer or multiple layers. When the layer (III) has two or more layers, the thickness and material of each layer may be different or the same. The layer (III) may be laminated to the remoistenable adhesive layer (I) or the substrate layer (II) via the adhesive layer (X).

In the multilayer laminate of the present invention, at least one layer (III) is preferably disposed on the outermost surface opposite the remoistenable adhesive layer (I). In such an embodiment, by providing decoration such as letters or a pattern on the surface of layer (III), it is possible to form labels, stickers, packages with letters or decorations, and the like.

The layer structure of the multilayer laminate of the present invention is not particularly limited, but examples thereof include a layer structure having a remoistenable adhesive layer (I)/adhesive layer (X)/substrate layer (II)/adhesive layer (X)/layer (III) in this order, a layer structure having a remoistenable adhesive layer (I)/substrate layer (II)/adhesive layer (X)/layer (III) in this order, and a layer structure having a remoistenable adhesive layer (I)/substrate layer (II)/layer (III) in this order. The thickness of layer (III) is not particularly limited, but is preferably 1 to 1000 μm, more preferably 5 to 500 μm.

[Bonded body, its manufacturing method and bag]
The present invention encompasses an adhesive formed by rewetting and bonding the remoistenable adhesive layer (I) of the laminate (including a multilayer laminate) to a covering layer. Examples of the covering layer include a layer selected from the remoistenable adhesive layer (I), substrate layer (II), and layer (III) contained in the laminate or another laminate, or a layer contained in an adherend other than these laminates. In other words, examples of the covering layer include a layer selected from the remoistenable adhesive layer (I), substrate layer (II), and layer (III) contained in the laminate; a layer selected from the remoistenable adhesive layer (I), substrate layer (II), and layer (III) contained in a laminate other than the laminate; and a layer contained in an adherend other than the laminate or the other laminate.
The present invention also includes a bag made of the adhesive product. When two or more laminates of the present invention are used, the other laminate refers to the laminate that is to be adhered.

The adhesive structure of the present invention is a laminate of the present invention, in which the remoistenable adhesive layer (I) and the covering layer are remoistened and bonded together. The adhesive structure of the present invention can maintain sufficient adhesive strength even when exposed to a low-humidity environment, and can therefore exhibit high strength even in such an environment. Furthermore, it has excellent biodegradability and gas barrier properties.

The present invention also encompasses a method for producing the bonded article, which includes a step of rewetting at least the remoistenable adhesive layer (I) of a laminate to remoisten and bond the remoistenable adhesive layer (I) to the adhesive layer. The method for remoistening the remoistenable adhesive layer (I) in this step is not particularly limited, but includes applying water to the surface of the remoistenable adhesive layer (I), spraying water, and storing under high humidity. Among these, applying water is preferred from the viewpoint of easily increasing the adhesive strength of the resulting adhesive article. When the adhesive layer is a remoistenable adhesive layer (I) contained in the same laminate and another laminate, the remoistenable adhesive layer (I) on the adhesive layer side may also be remoistened. The degree of remoistening can be appropriately adjusted by the amount of water used for remoistening. The amount of water used is not particularly limited, but may be, for example, 0.1 to 1,000 g/m ² , preferably 1 to 100 g/m ² .
As described above, after rewetting at least the remoistenable adhesive layer (I) of the laminate, the remoistened portion is brought into contact with the covering layer, thereby rewetting and bonding the remoistenable adhesive layer (I) and the covering layer of the laminate. Simultaneously with or after the contact, pressure may be applied inward. Applying pressure tends to increase adhesive strength. The pressure can be adjusted appropriately depending on the type and thickness of the remoistenable adhesive layer (I) and the substrate layer (II) contained in the laminate, and may be, for example, 0.1 to 50 kg/cm ² , preferably 0.5 to 10 kg/cm ² .

The bonded body (bag) of the present invention will be described below with specific examples, but the bonded body (bag) is not limited to the following embodiments.

The adhesive product shown in Fig. 2 is a two-sided bag made of a single laminate (film or sheet), in which the laminate 2a is folded in two and both ends are rewet-adhered. The laminate 2a has the layer structure shown in Fig. 1.
2, the bonded body 1a is obtained by folding a laminate 2a in half, applying water to the corresponding two sides on one side of the laminate 2a from the remoistenable adhesive layer (I) 3a side to form coated areas 6a, and then folding the laminate 2a in half to remoisten and bond the coated areas 6a to the bonded areas 7a in the other remoistenable adhesive layer (I) 3a (covering layer 8a) opposite the coated areas 6a. The bonded body 1a functions as a bag because both ends are bonded by remoistenable adhesive areas 9a.

While Fig. 2 shows an embodiment in which the coating layer 8a is a remoistenable adhesive layer (I) contained in the same laminate, the formation location of the application portion 6a of the remoistenable adhesive layer (I) may be appropriately changed to produce an adhered body (e.g., a bag) using a substrate layer (II) contained in the same laminate as the coating layer. Also, in Fig. 2, water is not applied to the adherend portion 7a, but water may be applied to the adherend portion 7a. Furthermore, by changing the laminate 2a to a multilayer laminate and appropriately adjusting the formation location of the application portion, an adhered body (e.g., a bag) may be produced using a remoistenable adhesive layer (I), substrate layer (II), or layer (III) contained in the same multilayer laminate as the coating layer.

The bonded product (bag) shown in Fig. 3 is a three-sided bag made of two laminates (films or sheets), 2b and 2c, which are rewet-bonded together near three sides. The laminates 2b and 2c each have the layer structure shown in Fig. 1.
3, the bonded body 1b is obtained by applying water to the vicinity of three sides of one laminate 2b from the remoistenable adhesive layer (I) 3b side to form coated portions 6b, and then superimposing the other laminate 2c from the remoistenable adhesive layer (I) 3c side, thereby rewetting and bonding the coated portions 6b to the adherend portions 7c in the remoistenable adhesive layer (I) 3c (adhering layer 8c) of the other laminate 2c that face the coated portions 6b. The bonded body 1b functions as a bag because the vicinity of the three sides are bonded by the remoistenable adhesive portions 9b.

While Fig. 3 shows an embodiment in which the coating layer 8c is a remoistenable adhesive layer (I) contained in another laminate, by appropriately adjusting the formation location of the application portion 6b of the remoistenable adhesive layer (I), an adhered body (e.g., a bag) may be produced using the substrate layer (II) contained in the other laminate 2c as the coating layer. Also, while water is not applied to the adherend portion 7c in Fig. 3, water may be applied to the adherend portion 7c. Furthermore, by changing at least the laminate 2c to a multilayer laminate and appropriately adjusting the formation location of the application portion, an adhered body (e.g., a bag) may be produced using the remoistenable adhesive layer (I), substrate layer (II), or layer (III) contained in the other multilayer laminate as the coating layer.

A laminate can also be formed using an adherend other than the laminate or multilayer laminate of the present invention, and for example, such an adherend may be used in place of one of the laminates in the embodiment shown in Figure 3. The adherend does not have at least a remoistenable adhesive layer (I), and may be, for example, a film or the like comprising a substrate layer (II) (particularly paper).

The number of laminates forming the adhesive body of the present invention is not particularly limited, and is preferably 1 to 3, more preferably 1 or 2. Furthermore, in the adhesive body of the present invention, from the viewpoint of easily increasing remoistenability and adhesive strength in low-humidity environments, the covering layer is preferably a remoistenable adhesive layer (I) contained in the above-mentioned laminate or another laminate. In the embodiment shown in Fig. 2, the covering layer is a remoistenable adhesive layer (I) contained in a laminate, and in the embodiment shown in Fig. 3, the covering layer is a remoistenable adhesive layer (I) contained in another laminate. Although Figs. 2 and 3 show a bag as an example, the adhesive body is not limited to a bag.

The bag of the present invention comprises an adhesive body formed by rewetting and bonding the rewettable adhesive layer (I) of the laminate to the covering layer (see, for example, FIGS. 2 and 3). In the bag of the present invention, the area of the rewettable adhesive layer (I) of the laminate that is rewet-bonded to the covering layer is preferably 1 to 90%, more preferably 5 to 40%, of the total area of the rewettable adhesive layer (I). When this area is within the above range, the volume of the bag can be secured while maintaining adhesive strength.

The shape of the bag of the present invention is not particularly limited, and may be, for example, any of the following shapes: a two-sided bag (FIG. 2), a three-sided bag (FIG. 3), a three-sided bag with a zipper, a palm-shaped bag, a gusset bag, a bottom gusset bag, a stand-up bag, a stand-up zipper bag, a two-sided bag, a four-pillar flat-bottom gusset bag, a side-sealed bag, and a bottom-sealed bag.

[Labels, tapes and lids]
The present invention includes a label comprising the laminate and having printing applied to the outermost surface of the laminate opposite to the remoistenable adhesive layer (I).The present invention also includes a tape or a lid material comprising the laminate.

The label of the present invention functions as an adhesive label due to the rewet adhesion of the rewettable adhesive layer (I). Furthermore, the decoration, such as printed characters or patterns, is not particularly limited. The printing method used to form the label of the present invention is not particularly limited, and examples thereof include screen printing, flexographic printing, and gravure printing. The label and tape of the present invention have excellent rewet adhesion due to the presence of the rewettable adhesive layer (I).

The use of the lid material of the present invention is not particularly limited, and it is suitable for use as, for example, a container lid material. When used as a container lid material, it can seal the inside of the container by combining it with the container body. In particular, the lid material of the present invention is useful as a lid material for food containers because of its excellent gas barrier properties. Furthermore, the lid material of the present invention is also excellent in biodegradability, which can reduce the environmental burden.

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

<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 permeability measuring device to measure the oxygen permeability. The measurement conditions were as follows:
Equipment: Modern Control "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

(2) Biodegradability of Remoisturized Adhesive Layer (I) For the remoisturized adhesive layers (I) obtained in the Examples and Comparative Examples, the following biodegradability was calculated from the amount of carbon dioxide generated during biodegradation under aerobic conditions in accordance with ISO 14885-1.
Biodegradation degree (%) = (CO ₂ )T-(CO ₂ )B/MToT×CToT×44/12×100
(CO ₂ )T: cumulative amount of CO ₂ emitted from the compost container (g)
(CO ₂ )B: cumulative amount of CO ₂ emitted from the empty test container (g)
MToT: Amount of dry solids of the 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)

(3) Seal Strength at Low Humidity The adhesive bonded specimens (pressed pieces) obtained in the Examples and Comparative Examples were stored at 23°C and 20% RH for three days to condition the humidity, and then cut into 15mm x 150mm strips including the 15mm x 50mm adhesive surface at the edges to prepare test specimens. Interlayer peel strength measurements were carried out using a tensile tester (Instron 3367, manufactured by Instron) at a speed of 50mm/min, an initial chuck distance of 50mm, and a peel angle of 180°. The same test was carried out five times, and the average value was used as the seal strength value.

(4) Materials used <Modified starch (A)>
ECOFILM®: Corn starch modified with propylene oxide, amylose content 70% by weight, available from Ingredion. National7®: Cassava starch modified with propylene oxide, amylose content 20% by weight, available from Ingredion.

Example 1
(Rewetting adhesive layer)
The raw materials, ECOFILM® (9.00 kg) and polyvinyl alcohol (solution viscosity 30 mPa s, saponification degree 99%, 1.00 kg), 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 4 shows a schematic diagram of the twin-screw extruder used in Example 1, and the screw diameter, L/D ratio, screw rotation speed, operating mode, and temperature profile of the extruder (Table 1) are shown below.

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

When the above mixture was fed into the twin-screw extruder, it was fed into the barrel through a hopper at C1 at a rate of 3.5 kg/hr via the twin-screw extruder's weight feeder. Water was injected into the barrel at a flow rate of 26 g/min through a liquid pump (L) at C4. The temperature ranges C5 to C9 were cooking zones, and complete gelatinization was achieved within these zones. The take-up speed was set so that the film extruded from the die would have a thickness of 20 μm after cooling and drying. In this way, a remoisturized adhesive layer (I) was obtained. The water content in the remoisturized adhesive layer (I) was 12% by mass relative to the mass of the remoisturized adhesive layer (I). The water content was measured using a heat-drying moisture meter at 130°C for 30 minutes after conditioning at 23°C and 50% relative humidity for two weeks.

(Laminate)
An adhesive layer (X) was formed on the resulting remoistened adhesive layer (I) so that the thickness after drying would be 3 μm, and a laminate was obtained by laminating kraft paper (basis weight 100 g/m ² , thickness 120 μm) as a substrate layer (II) onto the adhesive layer (X). The adhesive layer (X) 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.

(Adhesive body)
The resulting laminate was cut into two pieces measuring 150 mm x 150 mm. 5 g/ ^m2 of water was applied to the remoistenable adhesive surface of one of the two pieces in an area measuring 150 mm x 50 mm from one edge, and then the remoistenable adhesive surface of the other piece was placed on top of the other piece so that their sides overlapped, and the pieces were pressed together at a pressure of ¹ kg/cm2 to bond them together, yielding an adhesive bond. In the resulting adhesive bond, the covering layer was the remoistenable adhesive layer (I) contained in the other laminate (one of the two pieces cut out).

Example 2
A remoistened adhesive layer (I), a laminate, and an adhesive were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (4.00 kg) and polyvinyl alcohol (solution viscosity 30 mPa s, saponification degree 99%, 6.00 kg) were used as raw materials.

Example 3
A remoistened adhesive layer (I), a laminate, and an adhesive were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (9.80 kg) and polyvinyl alcohol (solution viscosity 30 mPa s, saponification degree 99%, 0.20 kg) were used as raw materials.

Example 4
A remoistened adhesive layer (I), a laminate, and an adhesive were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (5.40 kg), National 7 (3.6 kg), and polyvinyl alcohol (solution viscosity 30 mPa s, saponification degree 99%, 1.00 kg) were used as raw materials.

Example 5
A remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 1, except that glassine paper (70 g/m ² , thickness 70 μm) was used as the substrate layer (II).

Example 6
A remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 1, except that cardboard (400 g/m ² , thickness 570 μm) was used as the substrate layer (II).

Example 7
A remoistenable adhesive layer (I), a laminate, and an adhesive were obtained in the same manner as in Example 1, except that a stretched polyethylene terephthalate film, "Lumirror (registered trademark) P60" (thickness 12 μm) manufactured by Toray Industries, Inc., was used as the base layer (II).

Example 8
A remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 1, except that when two laminates were superimposed, the remoistenable adhesive surface of one laminate was superimposed on the substrate surface of the other laminate. In the obtained adhesive body, the covering layer was the substrate layer (II) contained in the other laminate (one of the two laminates cut out).

Example 9
A remoistenable adhesive layer (I) and a laminate were obtained in the same manner as in Example 1. The obtained laminate and glassine paper (70 g/ ^m2 , 70 μm thick) were each cut into 150 mm x 150 mm pieces, and 5 g/ ^m2 of water was applied to the remoistenable adhesive surface of the laminate slice in an area 150 mm x 50 mm from one edge. The remoistenable adhesive surface and the glassine paper surface were then overlapped so that each side overlapped the glassine paper slice, and the pieces were pressed together at a pressure of 1 kg/ ^cm2 to obtain an adhesive structure. In the obtained adhesive structure, the adherend layer was a layer contained in an adherend other than the same laminate or another laminate.

Example 10
Except for using cardboard (400 g/m ² , thickness 570 μm) instead of glassine paper, a remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 9. In the obtained adhesive body, the adherend layer was a layer contained in an adherend other than the same laminate and other laminates.

<Comparative Example 1>
Polyvinyl alcohol (solution viscosity 30 mPa s, saponification degree 99%, 1.00 kg) was dissolved in hot water to a concentration of 10 wt %, and then the solution was placed in a flat mold and the water was evaporated to obtain a 20 μm film, which was used as remoistenable adhesive layer (I). A laminate and an adhesive body were obtained in the same manner as in Example 1, except that the remoistenable adhesive layer (I) obtained was used instead of the remoistenable adhesive layer (I) of Example 1.

<Comparative Example 2>
A remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 1, except that National 7 (10.0 kg) was used as the raw material.

<Comparative Example 3>
A remoistenable adhesive layer (I), a laminate, and an adhesive body were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (10.0 kg) was used as the raw material.

<Comparative Example 4>
A remoistened adhesive layer (I), a laminate, and an adhesive were obtained in the same manner as in Example 1, except that National 7 (9.0 kg) and polyvinyl alcohol (solution viscosity 30 mPa·s, saponification degree 99%, 1.00 kg) were used as raw materials.

The laminates of Examples 1 to 10 and Comparative Examples 1 to 4 were measured for their structure, oxygen permeability (mL. 20 μm/m ² .day.atm) and biodegradability (%) of the remoistened adhesive layer (I), and the results are shown in Table 2. Table 2 also shows the results of measuring the seal strength of the adhesives obtained in Examples 1 to 10 and Comparative Examples 1 to 4 under 20% RH humidity control, as well as the adhesive layer.

As shown in Table 2, it was confirmed that the laminates obtained in Examples 1 to 10 had higher biodegradability than Comparative Example 1, and that the resulting adhesive bodies had higher seal strength under low humidity conditions than Comparative Examples 2 to 4. Therefore, it was confirmed that the laminates obtained in Examples 1 to 10 had high biodegradability and excellent rewet adhesion even in low-humidity environments. Furthermore, it was confirmed that the laminates obtained in Examples 1 to 10 also had excellent oxygen barrier properties.

<Making bags>
A two-sided bag as shown in Figure 2 was produced using the laminate obtained in Example 1. More specifically, the laminate obtained in Example 1 was cut into a 150 mm x 300 mm piece and folded in the long direction with the rewettable adhesive layer (I) facing inward. Next, 5 g/ ^m2 of water was applied to the entire area 6a shown in Figure 2 over a width of 10 mm. Then, the rewettable surfaces of the two pieces were placed together so that each side overlapped (the coated portion 6a overlapped the adherend portion 7a), and the two pieces were pressed together at a pressure of 1 kg/ ^cm2 to form a two-sided bag. This bag was also confirmed to be highly biodegradable and to have excellent rewettable adhesion even in a low-humidity environment.

1, 1a, 1b... Adhesive body 2, 2a, 2b, 2c... Laminated body 3, 3a, 3b, 3c... Rewetting adhesive layer (I)
4, 4a, 4b...Base material layer (II)
5...Adhesive layer (X)
6a, 6b...applied part 7a, 7c...adhered part 8a, 8c...adhered layer 9a, 9b...rewet adhesion part

Claims (10)

A laminate comprising a remoistenable adhesive layer (I) and a substrate layer (II),
the remoistenable adhesive layer (I) contains a modified starch (A) and a water-soluble polymer (B), and the modified starch (A) has an amylose content of 45% by mass or more;
the water-soluble polymer (B) is polyvinyl alcohol;
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);
Laminate. The laminate according to claim 1 , wherein the substrate layer (II) is paper. A multilayer laminate comprising the laminate according to claim 1 or 2 and a layer (III),
A multilayer laminate having the remoistenable adhesive layer (I) of the laminate on the outermost surface. An adhesive body formed by rewetting and bonding a remoistenable adhesive layer (I) of the laminate according to any one of claims 1 to 3 to a covering layer, wherein the covering layer is a layer selected from the remoistenable adhesive layer (I), the substrate layer (II), and the layer (III) contained in the laminate or another laminate, or a layer contained in an adherend other than these laminates. 5. The adhesive body according to claim 4 , wherein the covering layer is a remoistenable adhesive layer (I) contained in the laminate or the other laminate. A bag made of the adhesive material according to claim 4 or 5 . A label comprising the laminate according to any one of claims 1 to 3 , wherein printing is applied to the outermost surface of the laminate opposite to the remoistenable adhesive layer (I). A tape comprising the laminate according to any one of claims 1 to 3 . A lid material comprising the laminate according to any one of claims 1 to 3 . 5. A method for producing an adhesive body according to claim 4 , comprising the step of rewetting at least the rewettable adhesive layer (I) of the laminate to rewet and bond the rewettable adhesive layer (I) and the covering layer.