Adhesive resin composition

Abstract

To provide an adhesive resin composition with superior adhesive strength to both a polyvinyl alcohol resin layer and a biodegradable resin layer.SOLUTION: An adhesive resin composition contains a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B). When the total of the biodegradable polyester resin (A) and the polyvinyl alcohol resin (B) is 100 pts.mass, the content of the biodegradable polyester resin (A) is 62-90 pts.mass, the content of the polyvinyl alcohol resin (B) is 10-38 pts.mass, and the degree of saponification of the polyvinyl alcohol resin (B) is 75-96 mol%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an adhesive resin composition, a laminate including an adhesive layer comprising the adhesive resin composition, and a food packaging material including the adhesive resin composition or the laminate. Regarding. [Background technology]

[0002] Plastics are widely used as packaging materials because of their high moldability, strength, water resistance, transparency, etc. However, plastics are poorly biodegradable, and if they are dumped in the natural world after use, they may remain for a long time and cause environmental destruction. In response to this, in recent years, biodegradable resins that are biodegraded or hydrolyzed in soil or water and are useful for preventing environmental pollution have attracted attention, and packaging materials using biodegradable resins have been put to practical use. Examples of such packaging materials include laminates containing a biodegradable resin layer, an adhesive layer, and a polyvinyl alcohol-based resin layer. For example, Patent Document 1 describes a biodegradable laminate in which a polyvinyl alcohol-based resin layer is laminated on at least one surface of a biodegradable resin layer via an adhesive layer made of an adhesive composition obtained by graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof to a biodegradable polyester-based resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-212682 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the investigations of the present inventors, it was found that it was difficult for the adhesive layer in the conventional biodegradable laminate to exhibit sufficient adhesive strength to both the polyvinyl alcohol-based resin layer and the biodegradable resin layer.

[0005] Therefore, an object of the present invention is to provide an adhesive resin composition having excellent adhesive strength to both a polyvinyl alcohol-based resin layer and a biodegradable resin layer, a laminate including an adhesive layer comprising the adhesive resin composition, and a food packaging material including the adhesive resin composition or the laminate. [Means for solving the problem]

[0006] As a result of intensive research aimed at achieving the above object, the present inventors have found that the above problems can be solved by setting the contents of components (A) and (B) and the degree of saponification of component (B) in a specific range in an adhesive resin composition containing a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), and have thus completed the present invention. That is, the present invention includes the following preferred embodiments.

[0007] [1] An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), wherein the content of the biodegradable polyester resin (A) is 42 to 90 parts by mass, the content of the polyvinyl alcohol resin (B) is 10 to 58 parts by mass, and the degree of saponification of the polyvinyl alcohol resin (B) is 75 to 96 mol%, based on a total of 100 parts by mass of the biodegradable polyester resin (A) and the polyvinyl alcohol resin (B). [2] The adhesive resin composition according to [1], wherein the biodegradable polyester resin (A) has a breaking elongation of 50% or more as measured in accordance with ISO 527-1. [3] The adhesive resin composition according to [1] or [2], wherein the polyvinyl alcohol-based resin (B) has a viscosity-average degree of polymerization of 100 to 5,000. [4] The adhesive resin composition according to any one of [1] to [3], wherein the biodegradable polyester resin (A) has a melting point of 70° C. or higher. [5] The adhesive resin composition according to any one of [1] to [4], wherein the biodegradable polyester resin (A) contains an aromatic-aliphatic copolymer polyester resin. [6] The adhesive resin composition according to [5], wherein the aromatic-aliphatic copolymer polyester resin is polybutylene adipate terephthalate. [7] A laminate comprising an adhesive layer comprising the adhesive resin composition according to any one of [1] to [6]. [8] The laminate according to [7], comprising a biodegradable resin layer, the adhesive layer, and a polyvinyl alcohol-based resin layer, in this order. [9] The laminate described in [8], wherein the biodegradable resin layer, the adhesive layer, and the polyvinyl alcohol-based resin layer all satisfy the biodegradability standards in accordance with ISO 14855.

[10] A food packaging material comprising an adhesive layer comprising the adhesive resin composition according to any one of [1] to [6], or a laminate according to any one of [7] to [9]. Effect of the Invention

[0008] The adhesive resin composition of the present invention has excellent adhesive strength to both a polyvinyl alcohol-based resin layer and a biodegradable polyester-based resin layer, and can therefore be suitably used as a packaging material for food and the like. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0010] [Adhesive resin composition] The adhesive resin composition of the present invention contains a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), and the content of the biodegradable polyester resin (A) is 42 to 90 parts by mass, the content of the polyvinyl alcohol resin (B) is 10 to 58 parts by mass, and the saponification degree of the polyvinyl alcohol resin (B) is 75 to 96 mol% based on 100 parts by mass of the total of the biodegradable polyester resin (A) and the polyvinyl alcohol resin (B). In this specification, the biodegradable polyester resin (A) may be referred to as "component (A)", the polyvinyl alcohol resin (B) may be referred to as "component (B)", and polyvinyl alcohol may be abbreviated as PVA. In this specification, the upper limit and the lower limit can be combined arbitrarily.

[0011] The present inventors have studied the interlayer adhesion of the laminate and have surprisingly found that, in an adhesive resin composition, by adjusting the contents of components (A) and (B) and the degree of saponification of component (B) to a specific range, the adhesive strength to both the polyvinyl alcohol-based resin layer and the biodegradable resin layer can be improved. This is presumably because the moderate degree of saponification of component (B) allows both good hydrogen bond formation with the PVA-based resin layer and fluidity during adhesion to be achieved, and the specific amounts of components (A) and (B) ensure the strength and toughness of the composition itself while maintaining biodegradability. Furthermore, it has been found that the adhesive resin composition of the present invention is also excellent in thermoformability, and the resulting laminate can be easily molded into a predetermined shape. In this specification, the adhesive strength can be evaluated by a peel test and means the peel strength between the adhesive resin composition (adhesive layer) and other layers such as the PVA-based resin layer and the biodegradable resin layer.

[0012] <Biodegradable polyester resin (A)> The adhesive resin composition of the present invention contains the biodegradable polyester resin (A). In the present invention, since the content of the biodegradable polyester resin (A) is 42 to 90 parts by mass, the adhesive strength, thermoformability and biodegradability can be improved. In this specification, "biodegradable" refers to a material that has a property of being chemically decomposable by, for example, hydrolysis, enzymatic decomposition, microbial decomposition, etc., and preferably refers to a material that meets the biodegradability standards specified in EN13432, ASTM6400, or ISO14855. That is, a material is considered to be biodegradable if, when placed in a compost environment, 90% of the material disintegrates into particles with an average size of less than 2 mm within 12 weeks, and at least 60% of the material in the case of ASTM6400, or at least 90% of the material in the case of EN13432, decomposes into carbon dioxide and / or water after 6 months.

[0013] The biodegradable polyester resin is not particularly limited as long as it is a biodegradable polyester resin, and may be a petroleum-derived biodegradable resin or a biologically derived biodegradable resin. Examples of the biodegradable polyester resin include aliphatic polyester resins, aromatic-aliphatic copolymer polyester resins, and aromatic polyester resins. The biodegradable polyester resin preferably contains at least one selected from the group consisting of aliphatic polyester resins and aromatic-aliphatic copolymer polyester resins, and more preferably contains an aromatic-aliphatic copolymer polyester resin from the viewpoint of having high biodegradability and easily increasing adhesive strength and thermoformability.

[0014] Examples of the aliphatic polyester resin include polyhydroxyalkanoates (abbreviated as PHA), polyalkylene monocarboxylates, and polyalkylene dicarboxylates.

[0015] PHA is a polymer that has hydroxyalkanoic acid as a monomer unit. More specifically, it includes polyglycolic acid, polylactic acid (sometimes abbreviated as PLA), poly(3-hydroxyalkanoate) (abbreviated as P3HA), poly(4-hydroxyalkanoate), etc.

[0016] P3HA is a polymer mainly composed of 3-hydroxyalkanoic acid as a monomer unit. Examples of 3-hydroxyalkanoic acid include 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, and 3-hydroxyoctanoate. P3HA may be a homopolymer or a copolymer containing two or more monomer units. When P3HA is a copolymer, it may be a copolymer of two or more 3-hydroxyalkanoic acids, or a copolymer of one or more 3-hydroxyalkanoic acids and a 4-hydroxyalkanoic acid such as 4-hydroxybutyrate.

[0017] Specific examples of P3HA include poly(3-hydroxybutyrate) homopolymer (abbreviated as PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviated as PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviated as PHBV), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as 3HB4HB).

[0018] Examples of polyalkylene monocarboxylates include ring-opening polymers of lactones (cyclic esters), and specific examples thereof include polycaprolactone (abbreviated as PCL).

[0019] Polyalkylene dicarboxylate is a polycondensate of an aliphatic diol (or a derivative thereof) and an aliphatic dicarboxylic acid (or a derivative thereof). Examples include polybutylene succinate (abbreviated as PBS), polyethylene succinate, and poly(butylene succinate-co-butylene adipate).

[0020] The aliphatic polyester resin is preferably at least one selected from the group consisting of PHA, polyalkylene monocarboxylate, and polyalkylene dicarboxylate, and from the viewpoint of easily increasing the adhesive strength, it is more preferably at least one selected from the group consisting of polyalkylene monocarboxylate and polyalkylene dicarboxylate.

[0021] Aromatic-aliphatic copolymer polyester resins are polyester resins having both aromatic and aliphatic moieties, and are condensates of aliphatic or aromatic diols (or their derivatives) and aromatic or aliphatic dicarboxylic acids (or their derivatives). Examples include polybutylene adipate terephthalate (abbreviated as PBAT), polybutylene succinate terephthalate (PBST), and polyethylene adipate terephthalate (PEAT). PBAT is preferred from the viewpoint of being highly biodegradable and easy to increase adhesive strength and thermoformability. These biodegradable polyester resins may be used alone or in combination of two or more kinds.

[0022] The biodegradable polyester resin (A) may be produced by a conventional method, or a commercially available product may be used. Commercially available biodegradable polyester resin (A) includes polycaprolactone (PCL) sold by UnionCarbide under the trade name Tone (e.g., Tone P-300, P-700, P-767, and P-787, each having a weight average molecular weight of about 10,000, 40,000, 43,000, and 80,000), or polycaprolactone (PCL) sold by Perstorf under the trade name CAPA 6800 and CAPA FB 100 (each having a molecular weight of 80,000 and 100,000 Daltons); polylactic acid (PLA) sold by Cargill under the trade name Natureworks (trade name) PLA; polyhydroxybutyrate (P) sold by Biomer (Germany) under the trade name Biocycle (trade name) or Biomer (trade name). HB); polyethylene succinate (PES) and polybutylene succinate (PBS) sold under the trade name Bionolle™ by Showa Polymer Co., Ltd. (e.g., Bionolle™ 1001 (PBS) and Bionelle™ 6000 (PES)); polybutylene adipate (PBA) sold under the trade name Skygreen™ SG100 by SK Chemicals (Korea); polybutylene adipate terephthalate (PBAT) aliphatic / aromatic copolyesters such as Ecoflex™ by BASF (Germany), or EnPOL™ G8060 and EnPOL™ 8000 by IreChemical Ltd (Seoul); poly(hydroxybutyrate valerate) (PHBV) by Metabolix Inc. (USA); and the like.

[0023] The biodegradable polyester resin (A) may be a modified biodegradable polyester resin or an unmodified biodegradable polyester resin. The modified biodegradable polyester resin is not particularly limited, but may be, for example, a modified biodegradable polyester resin obtained by graft-modifying a biodegradable polyester resin with an unsaturated carboxylic acid and / or its derivative. The unsaturated carboxylic acid used as a modifier is not particularly limited, but examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. Furthermore, the derivative of the unsaturated carboxylic acid is not particularly limited, but examples thereof include acid anhydrides, esters, amides, imides, metal salts, etc.

[0024] Specific examples of the derivative of an unsaturated carboxylic acid include maleic anhydride, himic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate, maleic acid monoethyl ester, maleic acid diethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N,N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, and potassium methacrylate. These unsaturated carboxylic acids and / or their derivatives can be used alone or in any combination and ratio of two or more. Among these, maleic acid or its anhydride is particularly preferred because of its low electron density and high reactivity.

[0025] The content of the modifier is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, even more preferably 0.03 mass% or more, and is preferably 3.0 mass% or less, more preferably 1.0 mass% or less, even more preferably 0.2 mass% or less, relative to the mass of the modified biodegradable polyester resin.

[0026] The adhesive resin composition of the present invention is an alloy of a biodegradable polyester resin (A) and a PVA resin (B) having a specific degree of saponification, and therefore can exhibit excellent adhesive strength to a PVA resin layer and a biodegradable resin layer without modifying the biodegradable polyester resin. Therefore, in a preferred embodiment of the present invention, the biodegradable polyester resin (A) is preferably an unmodified biodegradable polyester resin. When the resin is unmodified, it is possible to prevent a decrease in biodegradability due to modification and also to avoid the complication of production due to modification.

[0027] In a preferred embodiment of the present invention, the biodegradable polyester resin (A) has a breaking elongation measured in accordance with ISO 527-1 of preferably 50% or more, more preferably 100% or more, even more preferably 200% or more, even more preferably 400% or more, particularly preferably 600% or more, particularly more preferably 750% or more, particularly more preferably 850% or more, and particularly more preferably 1000% or more. If the breaking elongation is equal to or greater than the above lower limit, the toughness is increased, so that the adhesive strength is likely to be improved. The upper limit of the breaking elongation is usually 5000% or less, preferably 3000% or less, more preferably 2000% or less. If the breaking elongation is equal to or less than the above upper limit, the adhesive resin composition can be prevented from decreasing in elastic modulus and maximum strength, so that the adhesive strength is likely to be prevented from decreasing. The breaking elongation can be measured in accordance with ISO 527-1, for example, by the method described in the Examples.

[0028] In a preferred embodiment of the present invention, the melting point of the biodegradable polyester resin (A) is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 105°C or higher. When the melting point of the biodegradable polyester resin (A) is above the above lower limit, the thermoformability is more easily improved, so that the occurrence of wrinkles and the like of the obtained laminate is more easily suppressed or prevented, and the appearance is more likely to be good. The upper limit of the melting point is preferably 300°C or lower, more preferably 200°C or lower, even more preferably 150°C or lower, even more preferably 140°C or lower, and particularly preferably 130°C or lower. When the melting point is below the above upper limit, the thermoformability is easily improved, so that the obtained laminate can be easily molded into a predetermined shape. The melting point can be measured by a differential scanning calorimeter (DSC), for example, by the method described in the Examples.

[0029] In one embodiment of the present invention, the melt mass flow rate (MFR) of the biodegradable polyester resin (A) is preferably 1.0 g / 10 min or more, more preferably 3.0 g / 10 min or more, even more preferably 5.0 g / 10 min or more, even more preferably 10 g / 10 min or more, and preferably 30 g / 10 min or less, more preferably 25 / 10 min or less, and even more preferably 20 g / 10 min or less. When the MFR of the biodegradable polyester resin (A) is in the above range, it is easy to increase the adhesive strength and thermoformability. The MFR can be measured in accordance with JIS K 7210:2014 under conditions of a temperature of 200 ° C. and a load of 2.16 kg.

[0030] In one embodiment of the present invention, the weight average molecular weight (Mw) of the biodegradable polyester resin (A) is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more, and is preferably 500,000 or less, more preferably 200,000 or less, and even more preferably 100,000 or less. When the Mw of the biodegradable polyester resin (A) is within the above range, the adhesive strength and thermoformability are easily increased.

[0031] In one embodiment of the present invention, the number average molecular weight (Mn) of the biodegradable polyester resin (A) is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 20,000 or more, and is preferably 200,000 or less, more preferably 100,000 or less, and even more preferably 50,000 or less. When the Mn of the biodegradable polyester resin (A) is within the above range, the adhesive strength and thermoformability are easily increased. The Mw and Mn of the biodegradable polyester resin (A) can be determined by gel permeation chromatography (GPC) measurement and conversion into standard polystyrene, for example, by the method described in the Examples.

[0032] The content of the biodegradable polyester resin (A) is 42 to 90 parts by mass based on 100 parts by mass of the total of the components (A) and (B). If the content of the biodegradable polyester resin (A) is less than 42 parts by mass and exceeds 90 parts by mass, the adhesive strength tends to decrease. In the adhesive resin composition of the present invention, the content of the biodegradable polyester resin (A) is 42 parts by mass or more, preferably 45 parts by mass or more, more preferably 48 parts by mass or more, and 90 parts by mass or less, preferably 85 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 77 parts by mass or less, even more preferably 75 parts by mass or less, and particularly preferably 73 parts by mass or less. If the content of the biodegradable polyester resin (A) is the above lower limit or more, the biodegradability can be improved and the adhesive strength to the biodegradable resin layer can be increased. If the content of the biodegradable polyester resin (A) is the above upper limit or less, the adhesive strength to the PVA resin layer can be increased. The content of the biodegradable polyester resin (A) relative to the mass of the adhesive resin composition can also be selected from the above range.

[0033] <Polyvinyl alcohol resin (B)> The adhesive resin composition of the present invention contains a PVA-based resin (B). The PVA-based resin (B) contained in the adhesive resin composition has a degree of saponification of 75 to 96 mol % and is contained in an amount of 10 to 58 parts by mass, so that the adhesive strength and thermoformability can be improved.

[0034] The PVA-based resin (B) is a resin containing a vinyl ester polymer or copolymer (collectively referred to as a vinyl alcohol-based polymer). The vinyl alcohol-based polymer is a polymer containing a vinyl alcohol unit as a monomer unit. The vinyl alcohol-based polymer is obtained by saponifying a vinyl ester-based polymer obtained by polymerizing a vinyl ester monomer, which is a raw material monomer, and the vinyl alcohol-based polymer after saponification may contain a vinyl ester unit in addition to the vinyl alcohol unit.

[0035] The vinyl alcohol polymer may be a modified vinyl alcohol copolymer containing other monomer units than vinyl alcohol units and vinyl ester units, which is obtained by saponifying a copolymer obtained by copolymerizing a vinyl ester monomer, which is a raw material monomer, with another monomer. The PVA resin (B) may contain a plurality of vinyl alcohol polymers having different physical properties.

[0036] Examples of vinyl ester monomers used as raw material monomers for vinyl alcohol polymers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among these, vinyl acetate is preferred from the viewpoints of production and availability, cost, and the like.

[0037] The vinyl alcohol polymer may be a modified vinyl alcohol copolymer containing, as described above, vinyl alcohol units and vinyl ester units as well as other monomer units other than the vinyl ester units. The other monomers can be appropriately selected according to the type of the PVA resin layer to be adhered, and may be, for example, α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and its salts; acrylic acid esters; methacrylic acid and its salts; methacrylic acid esters; acrylamide; acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamide propane sulfonic acid and its salts, acrylamide propyl dimethylamine and its salts or its quaternary salts, and N-methylol acrylamide and its derivatives; methacrylamide; methacrylamide derivatives such as N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic acid and its salts, methacrylamide propyl dimethylamine and its salts or its quaternary salts, and N-methylol methacrylamide and its derivatives; methyl vinyl Examples of suitable monomers include vinyl ethers such as ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids and their salts or esters such as maleic acid, itaconic acid, and fumaric acid; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; vinyl compounds such as dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene. Among these, from the viewpoint of ease of industrial production, it is preferable that the other monomer is an α-olefin such as ethylene. The content (modification amount) of these other monomer units varies depending on the purpose and application of the material.In one embodiment, the content (modification amount) of other monomer units is preferably 10 mol % or less, more preferably 5 mol % or less, and may be preferably 0 mol % or more, more preferably 0.1 mol % or more.

[0038] The vinyl alcohol polymer may or may not have a crosslinked hydroxyl group, and may or may not have a crosslinked hydroxyl group. The vinyl alcohol polymer may or may not have a crosslinked hydroxyl group. The vinyl alcohol polymer may or may not have a crosslinked hydroxyl group.

[0039] From the viewpoint of easily increasing adhesive strength and thermoformability, the PVA-based resin (B) preferably contains, as a vinyl alcohol-based polymer, at least one selected from the group consisting of unmodified vinyl alcohol polymers and α-olefin-vinyl alcohol copolymers, and more preferably contains an unmodified vinyl alcohol polymer, although this depends on the type of the PVA-based resin layer that is the adherend.

[0040] The saponification degree of the PVA-based resin (B) contained in the adhesive resin composition of the present invention is 75 to 96 mol%. If the saponification degree is less than 75 mol% and more than 96 mol%, the adhesive strength tends to decrease. The saponification degree of the PVA-based resin (B) in the present invention is preferably 77 mol% or more, more preferably 79 mol% or more, and even more preferably 80 mol% or more, and may be, for example, 81 mol% or more or 82 mol% or more. The saponification degree of the PVA-based resin (B) is preferably 94 mol% or less, more preferably 92 mol% or less, even more preferably 90 mol% or less, even more preferably 89 mol% or less, particularly preferably 88 mol% or less, and may be, for example, 85 mol% or less. If the saponification degree of the PVA-based resin (B) is the above lower limit or more, it is easy to form hydrogen bonds with the PVA-based resin layer that is the adherend, and therefore the adhesive strength to the PVA-based resin layer can be increased. In addition, when the saponification degree of the PVA resin (B) is equal to or less than the upper limit, it is easy to exhibit an appropriate fluidity during adhesion, and therefore the adhesive strength and thermoformability can be improved. In this specification, the saponification degree of the PVA resin (B) means the ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of the structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification and the vinyl alcohol unit that the vinyl alcohol polymer has. The saponification degree of the PVA resin (B) can be measured in accordance with JIS K 6726:1994. In addition, when the PVA resin (B) contains only one type of vinyl alcohol polymer, the saponification degree of the vinyl alcohol polymer is the saponification degree of the PVA resin (B). When the PVA resin (B) contains two or more types of vinyl alcohol polymers, the saponification degree means the average saponification degree calculated from the saponification degree and the blending ratio of each vinyl alcohol polymer. In addition, when the PVA-based resin (B) contains two or more kinds of vinyl alcohol-based polymers, the vinyl alcohol-based polymers having different degrees of saponification may be mixed in an appropriate mixing ratio to adjust the degree of saponification of the PVA-based resin (B) to fall within the above-mentioned range.

[0041] In one embodiment of the present invention, the viscosity average degree of polymerization (sometimes referred to as degree of polymerization) of the PVA resin (B) contained in the adhesive resin composition of the present invention may be preferably 5000 or less, 4000 or less, 3000 or less, or 2000 or less, more preferably 1500 or less, even more preferably 1200 or less, even more preferably 900 or less, particularly preferably 700 or less, especially more preferably 600 or less, especially more preferably 480 or less, 400 or less, or 350 or less. When the degree of polymerization is below the above upper limit, the adhesive strength and thermoformability to the PVA resin layer can be increased. This is presumably because the PVA resin (B), which is a polar component, is easily transferred to the interface during adhesion. The viscosity average degree of polymerization of the PVA resin (B) is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, even more preferably 220 or more, especially preferably 250 or more, and especially more preferably 270 or more. When the polymerization degree is equal to or higher than the lower limit, the mechanical strength of the adhesive resin composition is easily increased, and the adhesive strength to the biodegradable resin layer is easily increased. The polymerization degree of the PVA resin (B) can be measured according to JIS K 6726:1994. When the PVA resin (B) contains only one type of vinyl alcohol polymer, the polymerization degree of the vinyl alcohol polymer is the polymerization degree of the PVA resin (B). When the PVA resin (B) contains two or more types of vinyl alcohol polymers, the polymerization degree of the PVA resin (B) means the average polymerization degree calculated from the polymerization degree and blending ratio of each vinyl alcohol polymer. When the PVA resin (B) contains two or more types of vinyl alcohol polymers, the polymerization degree of the PVA resin (B) may be adjusted to the above range by mixing vinyl alcohol polymers having different polymerization degrees at an appropriate blending ratio.

[0042] The content of the PVA-based resin (B) is 10 to 58 parts by mass based on 100 parts by mass of the total of the components (A) and (B). If the content of the PVA-based resin (B) is less than 10 parts by mass and exceeds 58 parts by mass, the adhesive strength tends to decrease. In the adhesive resin composition of the present invention, the content of the PVA-based resin (B) is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 23 parts by mass or more, even more preferably 25 parts by mass or more, particularly preferably 27 parts by mass or more, and 58 parts by mass or less, preferably 55 parts by mass or less, more preferably 52 parts by mass or less, based on 100 parts by mass of the total of the components (A) and (B). If the content of the PVA-based resin (B) is the above lower limit or more, the adhesive strength to the PVA-based resin layer can be increased. If the content of the PVA-based resin (B) is the above upper limit or less, the adhesive strength to the biodegradable resin layer can be increased. The content of the PVA resin (B) relative to the mass of the adhesive resin composition can also be selected from the above range.

[0043] <Production method of polyvinyl alcohol resin (B)> As described above, the PVA resin (B) contains a vinyl alcohol polymer. The vinyl alcohol polymer can be obtained, for example, by polymerizing a vinyl ester monomer or a vinyl ester monomer with another monomer to obtain a vinyl ester polymer or copolymer, and then saponifying the vinyl ester polymer or copolymer. Methods for polymerizing vinyl ester monomers and the like include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these, bulk polymerization and solution polymerization, which are polymerized without a solvent or in a solvent such as alcohol, are preferably used. Examples of alcohols used as a solvent during solution polymerization include lower alcohols such as methanol, ethanol, and propanol. Examples of initiators used in copolymerization include known initiators such as azo initiators or peroxide initiators, such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl-valeronitrile), benzoyl peroxide, and n-propyl peroxydicarbonate. There is no particular limitation on the polymerization temperature, but a range of 0°C to 150°C is preferred. Furthermore, for example, when the vinyl alcohol polymer is an ethylene-vinyl alcohol copolymer or the like, it is preferable to copolymerize a vinyl ester monomer with a monomer such as ethylene by the above-mentioned method.

[0044] The vinyl ester polymer obtained in the polymerization step can be saponified in an organic solvent by alcoholysis or hydrolysis in the presence of a catalyst. Examples of the catalyst used in the saponification step include basic catalysts such as sodium hydroxide, potassium hydroxide, and sodium methoxide; or acid catalysts such as sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid. The organic solvent used in the saponification step is not particularly limited, and examples thereof include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; and aromatic hydrocarbons such as benzene and toluene. These can be used alone or in combination of two or more. Among them, it is preferable to use methanol or a mixed solution of methanol and methyl acetate as a solvent and perform the saponification reaction in the presence of sodium hydroxide, which is a basic catalyst, because it is simple. The amount of the saponification catalyst used is preferably 0.001 to 0.5 in terms of a molar ratio to the vinyl ester monomer unit in the vinyl ester polymer. The molar ratio is more preferably 0.002 or more, more preferably 0.4 or less, and even more preferably 0.3 or less.

[0045] A preferred embodiment of the saponification step is as follows. First, a saponification catalyst such as sodium hydroxide is added to the vinyl ester polymer solution obtained in the polymerization step and mixed. The solvent at this time is preferably methanol. At the beginning of mixing, the mixture is a homogeneous liquid, but as the saponification reaction progresses and the vinyl ester units in the polymer are saponified and converted to vinyl alcohol units, the solubility in the solvent decreases and the polymer precipitates in the solution. At this time, the solution contains methyl acetate produced by alcoholysis with methanol. As the saponification reaction progresses, the amount of polymer precipitated gradually increases, becoming a slurry, and then losing fluidity. Therefore, in order to uniformly proceed with the saponification reaction, it is preferable to mix thoroughly until the fluidity is lost.

[0046] The method of mixing the vinyl ester polymer solution and the saponification catalyst is not particularly limited, and various methods such as a static mixer, a kneader, and an agitator blade can be used, but it is preferable to use a static mixer because it can mix continuously and uniformly. In this case, it is preferable to add the saponification catalyst to the vinyl ester polymer solution after the polymerization step in a pipe connected to the polymerization tank, and then pass the mixture through a static mixer to mix and obtain a paste. The temperature of the reaction solution in the static mixer is usually 20 to 80°C.

[0047] The method of proceeding with the saponification reaction of the vinyl ester polymer in the paste that has passed through the static mixer is not particularly limited, but a method in which the paste is placed on a moving belt and the saponification reaction is proceeded while the belt is moved in a tank maintained at a constant temperature is preferred. The paste on the belt loses fluidity and becomes solid, and the saponification reaction proceeds in the solid state. This method allows the saponification reaction to proceed continuously in the solid state, and a solid block containing the vinyl alcohol polymer and the solvent is obtained. The saponification temperature is preferably 20 to 60°C, preferably 25°C or higher, more preferably 30°C or higher, and preferably 55°C or lower, more preferably 50°C or lower. When the saponification temperature is equal to or higher than the lower limit, it is easy to suppress a decrease in the reaction rate. When the saponification temperature is equal to or lower than the upper limit, it is easy to suppress a decrease in the content of the solvent in the obtained solid block, and to suppress a deterioration in the solubility of the obtained vinyl alcohol polymer. The saponification time is preferably 5 minutes to 2 hours. The saponification time is more preferably 8 minutes or more, even more preferably 10 minutes or more, more preferably 1.5 hours or less, and even more preferably 1 hour or less.

[0048] If necessary, a washing step may be added to wash the vinyl alcohol polymer for the purpose of removing impurities such as sodium acetate. Examples of the washing liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, and water, and among these, methanol, methyl acetate, and water alone or in a mixture are more preferable. The amount of the washing liquid is usually preferably 30 to 10,000 parts by mass, and more preferably 50 to 3,000 parts by mass, relative to 100 parts by mass of the vinyl alcohol polymer. The washing temperature is preferably 5 to 80°C, and more preferably 20 to 70°C. The washing time is preferably 20 minutes to 10 hours, and more preferably 1 hour to 6 hours. As the washing method, known methods such as a batch method and a countercurrent washing method can be applied. In addition, a commercially available vinyl alcohol polymer can also be used.

[0049] <Adhesive resin composition> The adhesive resin composition of the present invention contains the biodegradable polyester resin (A) and the polyvinyl alcohol resin (B) in a specific ratio, and therefore has excellent adhesive strength to both the PVA resin layer and the biodegradable resin layer. Therefore, it is useful as an adhesive layer between a PVA resin layer and a biodegradable polyester resin layer. In addition, the adhesive resin composition of the present invention has excellent thermoformability, and the obtained laminate can be easily molded into a predetermined shape. Furthermore, it has excellent biodegradability. Therefore, the adhesive resin composition of the present invention can be suitably used as a packaging material for food and the like.

[0050] The adhesive strength of the adhesive resin composition of the present invention to a PVA-based resin is preferably 4N / 25mm or more, more preferably 5N / 25mm or more, even more preferably 7N / 25mm or more, even more preferably 10N / 25mm or more, particularly preferably 15N / 25mm or more, particularly preferably 20N / 25mm or more, and may be, for example, 25N / 25mm or more or 30N / 25mm or more. When the adhesive strength is equal to or more than the lower limit, the strength of the resulting laminate can be improved. The adhesive strength to a PVA-based resin is usually 100N / 25mm or less. The adhesive strength to a PVA-based resin indicates the peel strength between an adhesive layer and a PVA resin layer in a multilayer sheet including an adhesive layer made of an adhesive resin composition and a PVA resin layer. The peel strength can be measured using a peel tester according to JIS K 6854-1:1999 under the conditions of a peel angle of 90°, a tensile speed of 50mm / min, and an environmental temperature of 23°C. The adhesive strength to a PVA-based resin can be determined, for example, by the method described in the Examples.

[0051] The adhesive strength of the adhesive resin composition of the present invention to a biodegradable resin (preferably PLA) is preferably 9N / 25mm or more, more preferably 15N / 25mm or more, even more preferably 20N / 25mm or more, even more preferably 30N / 25mm or more, particularly preferably 40N / 25mm or more, particularly preferably 50N / 25mm or more, and particularly preferably 55N / 25mm or more. When the adhesive strength is equal to or greater than the lower limit, the strength of the resulting laminate can be improved. The adhesive strength to a biodegradable resin is usually 150N / 25mm or less. The adhesive strength to a biodegradable resin indicates the peel strength between the adhesive layer and the biodegradable resin layer in a multilayer sheet comprising an adhesive layer made of the adhesive resin composition and a biodegradable resin layer. The peel strength can be measured using a peel tester according to JIS K 6854-1:1999 under the conditions of a peel angle of 90°, a tensile speed of 50mm / min, and an environmental temperature of 23°C. The adhesive strength to a biodegradable resin can be determined, for example, by the method described in the Examples.

[0052] The adhesive resin composition of the present invention may contain additives other than the component (A) and the component (B) within a range that does not impair the purpose and effects of the present invention. Examples of additives include fillers, processing stabilizers, weathering stabilizers, colorants, ultraviolet absorbers, heat stabilizers, light stabilizers, antioxidants, antistatic agents, flame retardants, plasticizers, lubricants, fragrances, foaming agents, deodorants, extenders, release agents, mold release agents, reinforcing agents, fungicides, preservatives, crystallization rate retarders, and other resins other than the biodegradable polyester resin (A) and the PVA resin (B). These additives can be used alone or in combination of two or more. The content of the additives is not particularly limited, but may be, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and preferably 0% by mass or more, more preferably 0.1% by mass or more, based on the mass of the adhesive resin composition.

[0053] The filler may be added from the viewpoint of easily increasing hardness and stiffness, easily preventing blocking, etc. Examples of the filler include inorganic fillers such as mica, kaolin, kaolinite, clay, talc, acid clay, silica, alumina, diatomaceous earth, bentonite, montmorillonite, wood-bush clay, frog's eye clay, rosewood, alumite, china clay, feldspar, perlite, calcium carbonate, magnesium hydroxide, carbon black, vermiculite, titanium oxide, mica, zirconium oxide, boron nitride, aluminum nitride, shirasu, glass, and glass fiber, and organic fillers such as urea-formalin-based resins and melamine-formalin-based resins.

[0054] Examples of other resins include polyphenylene ether resins, polycarbonate resins, polyamide resins such as nylon 66 and nylon 11, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, styrene resins such as polystyrene, and (meth)acrylate resins such as polymethyl methacrylate resins.

[0055] The form of the adhesive resin composition of the present invention is not particularly limited, and may be a pellet, a sheet, or a film. The thickness of the sheet or film containing the adhesive resin composition can be appropriately selected depending on the application, and is preferably 5 to 1000 μm, more preferably 10 to 500 μm. The thickness of the film or sheet can be measured by a thickness meter, for example, by the method described in the Examples. In addition, the adhesive resin composition of the present invention may contain a solvent and may be in the form of a solution or dispersion, and the solvent may be a known solvent in which the components in the composition can be dissolved or dispersed.

[0056] The method for producing the adhesive resin composition of the present invention is not particularly limited, but may be, for example, a method of mixing the biodegradable polyester resin (A), the PVA resin (B), and optionally additives. A conventional mixer, preferably a melt kneader, can be suitably used for mixing. In a preferred embodiment of the present invention, the adhesive resin composition can be obtained by melt kneading using an extruder.

[0057] As the extruder, a twin screw extruder can be preferably used. The twin screw extruder may be either co-rotating or counter-rotating. The rotation speed of the screw is preferably 20 rpm or more, more preferably 70 rpm or more, and even more preferably 150 rpm or more, and usually 1000 ppm or less. The cylinder temperature is preferably 40° C. or more, more preferably 80° C. or more, and even more preferably 100° C. or more, and preferably 300° C. or less, and more preferably 200° C. or less. Each component can be directly introduced into the extruder. Also, each component may be premixed using a mixer or the like and then introduced into the extruder.

[0058] The molten mixture that has been forced through the extruder while being melt-kneaded is extruded from a die. The die temperature may be preferably 100 to 200°C, more preferably 100 to 150°C.

[0059] The specific mechanical energy (SME) (unit: kJ / kg) during melt kneading is not particularly limited, but is preferably 400 kJ / kg or more, more preferably 500 kJ / kg or more, and is preferably 900 kJ / kg or less, more preferably 800 kJ / kg or less. When the specific mechanical energy is in the above range, the adhesive strength of the adhesive resin composition is easily increased. The specific mechanical energy (Ψ) is calculated by the following formula. Ψ=N(RUN) / N(MAX)×Φ / Φ(MAX)×Kw / Q (Formula 1) [In Equation 1, N(RUN) indicates the screw rotation speed (unit: rpm), N(MAX) indicates the maximum screw rotation speed (unit: rpm), Φ indicates the motor torque during the test (unit: N m), Φ(MAX) indicates the maximum motor torque (unit: N m), Kw indicates the motor power (unit: kJ / h), and Q indicates the discharge rate (unit: kg / h)]

[0060] The extruded mixture (melt) can be extruded into a sheet, film or strand shape, during which the mixture (melt) is cooled and dried.

[0061] When the mixture is extruded in the form of strands, it can be extruded through a strand nozzle with multiple holes and cut with a rotary cutter to form the strands into pellets. To prevent the pellets from sticking together, vibration can be applied periodically or constantly, and moisture in the pellets can be removed by hot air, dehumidified air, or an infrared heater.

[0062] When the mixture is extruded into a sheet or film, the mixture can be extruded through a film forming die and then cooled and dried while being taken up by a take-up roller. Between the die and the roller, it is preferable to cool the mixture to prevent it from adhering to the roller. The solution or dispersion of the adhesive resin composition of the present invention may be formed into a sheet or film by a conventional film forming method (for example, cast film formation, etc.).

[0063] [Laminate] The present invention encompasses a laminate comprising an adhesive layer comprising the adhesive resin composition of the present invention. The laminate of the present invention may comprise one or more adhesive layers of the present invention, and when it comprises two or more layers, the compositions of the adhesive layers may be the same or different. The laminate may comprise layers other than the adhesive layer of the present invention. Examples of the other layers include a resin layer, paper, and other adhesive layers. The resin layer is a resin layer having a different composition from the adhesive layer. In addition, it is preferable that the adhesive layer has the "biodegradability" defined above.

[0064] The resin constituting the resin layer is not particularly limited, and examples thereof include polyester-based resins such as polyethylene terephthalate (PET), polyolefin-based resins such as polypropylene (PP) [preferably biaxially oriented polypropylene (BOPP)] and polyethylene (PE) [preferably low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE)], ethylene-vinyl acetate copolymers, polyvinyl alcohol-based resins such as ethylene-α-olefin copolymers, biodegradable resins such as biodegradable polyester-based resins, and resins obtained by modifying these with a modifier such as maleic anhydride. The resin layer can be used alone or in combination of two or more kinds. Since the adhesive layer in the laminate of the present invention can exhibit excellent adhesive strength to both the biodegradable resin layer and the polyvinyl alcohol-based resin layer, the laminate of the present invention preferably contains a biodegradable resin layer and / or a polyvinyl alcohol-based resin layer as the resin layer, and more preferably contains a biodegradable resin layer and a PVA-based resin layer. In addition, from the viewpoint of exhibiting excellent biodegradability, the resin layer in the laminate of the present invention is preferably composed of only a biodegradable resin layer and a polyvinyl alcohol-based resin layer. Furthermore, by including an adhesive layer, the laminate of the present invention can improve thermoformability and biodegradability.

[0065] The biodegradable resin layer is a resin layer having biodegradability, and the biodegradability is as defined above. The biodegradable resin layer is preferably a layer containing a biodegradable resin as a main component, and examples of the biodegradable resin include the biodegradable polyester resins described in the above section <Biodegradable polyester resin (A)> as well as casein, modified starch, cellulose acetate, etc., and among these, from the viewpoint of easily increasing the adhesive strength and biodegradability with the adhesive layer, the biodegradable resin is preferably the biodegradable polyester resin, and from the viewpoints of versatility, biodegradability, and mechanical properties, it is more preferable that the biodegradable resin is at least one selected from the group consisting of PLA, PHB, PHBV, 3HB4HB, PHBH, PBAT, PBS, and PCL, and from the viewpoints of strength, heat resistance, and water resistance, it is even more preferable that the biodegradable resin is PLA.

[0066] The PVA-based resin layer is not particularly limited as long as it contains a PVA-based resin as a main component, and examples thereof include the polyvinyl alcohol-based resins described in the above section <Polyvinyl alcohol-based resin (B)>. In one embodiment of the present invention, the PVA-based resin layer may contain a plasticizer such as a polyol (e.g., trehalose) in addition to the PVA-based resin. In this specification, the term "main component" refers to a component that is contained in an amount of 40% by mass or more, preferably 50% by mass or more, based on the mass of the layer, and the amount may be, for example, 55% by mass or more, 70% by mass or more, or 90% by mass or more. In addition, it is preferable that the PVA-based resin layer has the biodegradability defined above.

[0067] The paper is not particularly limited, and examples thereof include kraft paper, unglazed kraft paper, woodfree paper, imitation paper, glassine paper, parchment paper, synthetic paper, white cardboard, Manila cardboard, milk carton base paper, cup base paper, ivory paper, and white silver paper.

[0068] The laminate of the present invention includes a laminate including a biodegradable resin layer / adhesive layer in this order; a laminate including a PVA-based resin layer / adhesive layer in this order; and a laminate including a biodegradable resin layer / adhesive layer / PVA-based resin layer in this order. Among these, the laminate of the present invention is preferably a laminate including a biodegradable resin layer / adhesive layer / PVA-based resin layer in this order (sometimes referred to as laminate A). These laminates may include other layers between or on the outside of each layer, but it is preferable that no other layers are included between each layer, that is, each layer is adjacent. For example, it is preferable that the laminate A has a biodegradable resin layer, an adhesive layer, and a PVA-based resin adjacent to each other (i.e., in contact with each other) in this order. The laminate A has excellent adhesive strength between the biodegradable resin layer and the adhesive layer, and between the adhesive layer and the PVA-based resin layer, and excellent biodegradability.

[0069] The thickness of the adhesive layer in the laminate of the present invention can be appropriately selected according to the type of laminate, and is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. When the thickness of the adhesive layer is within the above range, it is easy to increase the adhesive strength, thermoformability, and biodegradability. The above thickness of the adhesive layer indicates the thickness of one layer when two or more adhesive layers are included in the laminate.

[0070] The thickness of the other layer in the laminate of the present invention can be appropriately selected depending on the type of laminate, and is not particularly limited, but is preferably 10 to 3000 μm, more preferably 15 to 1000 μm, and even more preferably 20 to 500 μm. When the thickness of the other layer is within the above range, the adhesive strength, thermoformability, biodegradability, and gas barrier property are easily improved. When two or more other layers are included in the laminate, the thickness of the other layer indicates the thickness of one layer.

[0071] The thickness of the laminate of the present invention is not particularly limited, but is preferably 20 μm or more, more preferably 50 μm or more, even more preferably 100 μm or more, even more preferably 200 μm or more, particularly preferably 300 μm or more, and is preferably 5000 μm or less, more preferably 3000 μm or less, even more preferably 1000 μm or less. When the thickness of the laminate is within the above range, the strength, thermoformability, biodegradability, and gas barrier property of the laminate are easily improved.

[0072] In one embodiment of the present invention, the thickness of the adhesive layer in the laminate A of the present invention is the same as the thickness of the adhesive layer described above. The thickness of the biodegradable resin layer in the laminate A is not particularly limited, but is preferably 50 μm or more, more preferably 100 μm or more, even more preferably 200 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less. The thickness of the PVA-based resin layer in the laminate A is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. When the thickness of each layer is within the above range, it is easy to increase the adhesive strength, thermoformability, biodegradability, and gas barrier property. The thickness of each layer (biodegradable resin layer, adhesive layer, and PVA-based resin layer) in the laminate A indicates the thickness of one layer when the laminate A has two or more layers of the same layer. The thickness of each layer and the thickness of the laminate can be measured using a thickness meter, for example, by the method described in the Examples.

[0073] Specific examples of the layer structure of the laminate A of the present invention are as follows. Biodegradable resin layer / adhesive layer / PVA resin layer; Biodegradable resin layer / adhesive layer / PVA resin layer / adhesive layer / biodegradable resin layer; Biodegradable resin layer / regrind layer / adhesive layer / PVA resin layer / adhesive layer / regrind layer / biodegradable resin layer; Biodegradable resin layer / adhesive layer / PVA resin layer / adhesive layer / paper.

[0074] In one embodiment of the present invention, in the laminate of the present invention, it is preferred that at least one layer selected from the group consisting of a biodegradable resin layer, an adhesive layer, and a PVA-based resin layer is biodegradable according to the ISO 14855 standard, more preferably at least two layers, and even more preferably all layers are biodegradable according to the ISO 14855 standard.

[0075] The laminate of the present invention can be produced by laminating another layer such as a resin layer and an adhesive layer by a conventional method such as a coextrusion molding method (coextrusion lamination method, coextrusion sheet molding method, coextrusion inflation molding method, coextrusion blow molding method, etc.), a coinjection molding method, an extrusion lamination method, a dry lamination method, etc. For example, it may be a method of coextruding or laminating another layer and an adhesive layer, or a method of forming a film of an adhesive resin composition on another layer. When laminating, the adhesive resin composition may be applied to the surface of the other layer, or extrusion coated on the surface of the other layer.

[0076] The method for producing the laminate A, which is a preferred embodiment of the present invention, is not particularly limited, but is preferably a method in which a pellet-shaped adhesive resin composition forming the adhesive layer, a pellet-shaped biodegradable resin (or a biodegradable resin composition) forming the biodegradable resin layer, and a pellet-shaped PVA-based resin (or a PVA-based resin composition) forming the PVA-based resin layer are co-extruded by a co-extruder. More specifically, each resin (or each resin composition) can be introduced into the hopper of each extruder, melt-kneaded, and co-extruded by a feed block die. The cylinder temperature of each extruder may be appropriately selected according to the melting temperature of the resin (or the resin composition). Although not limited, for example, the cylinder temperature of the extruder for the adhesive layer may be, for example, 120 to 300°C, preferably 150 to 250°C, the cylinder temperature of the extruder for the biodegradable resin layer may be, for example, 150 to 300°C, preferably 180 to 250°C, and the cylinder temperature of the extruder for the PVA-based resin layer may be, for example, 150 to 300°C, preferably 190 to 260°C.

[0077] In one embodiment of the present invention, when obtaining the laminate of the present invention, a crosslinking agent may be added to the adhesive resin composition of the present invention. Examples of the crosslinking agent include epoxy compounds, isocyanate compounds, aldehyde compounds, silica compounds, aluminum compounds, zirconium compounds, and boron compounds. Among these, silica compounds such as colloidal silica and alkyl silicates are preferred. The amount of the crosslinking agent added may be 5 to 60 parts by mass, preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass, relative to 100 parts by mass of the PVA-based resin. In one embodiment of the present invention, the laminate of the present invention may be subjected to a stretching treatment for the purpose of improving gas barrier properties and mechanical properties.

[0078] The laminate of the present invention is also excellent in thermoformability and can be easily molded into a predetermined shape. In a preferred embodiment, the laminate is excellent in appearance because it does not cause wrinkles or the like even when thermoformed. The molding method is preferably melt molding, and the melt molding method is not particularly limited, but examples thereof include extrusion molding, injection molding, extrusion film formation from a T-die, inflation film formation, compression molding, transfer molding, reinforced plastic molding, hollow molding, press molding, blow molding, calendar molding, foam molding, vacuum molding, and pressure molding. If desired, other thermoplastic resins can be laminated by methods such as co-extrusion molding and lamination molding. These methods can provide molded products of any shape, such as films, sheets, tubes, bottles, capsules, nonwoven fabrics, and fibers. In one embodiment of the present invention, when molding by vacuum molding, the laminate can be heated and then molded into a desired shape by a vacuum molding machine. The molding temperature is not limited and can be appropriately selected depending on the type of laminate, and is preferably 100° C. or higher, more preferably 130° C. or higher, and even more preferably 150° C. or higher, and is preferably 300° C. or lower, and more preferably 200° C. or lower. When the molding temperature is in this range, a molded product having excellent thermoformability is easily formed.

[0079] [Food packaging materials] The adhesive resin composition and laminate of the present invention are not particularly limited in use, but can be suitably used as a packaging material, particularly as a food packaging material. Therefore, the present invention includes a food packaging material including an adhesive layer containing the adhesive resin composition of the present invention, or a laminate of the present invention. The food packaging material of the present invention is excellent in adhesive strength, thermoformability, biodegradability, and gas barrier properties because it contains the adhesive layer or laminate of the present invention. The food packaging material is not particularly limited, but examples thereof include containers for packaging foods such as meat, raw noodles, processed foods, black tea, coffee powder, coffee beans, and pickles. In a preferred embodiment of the present invention, the food packaging material may be a garbage bag for organic waste, a container used in various events, a tea bag, a coffee capsule, or the like, and is particularly suitably used as a coffee capsule. EXAMPLES

[0080] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way. The measurement methods and evaluation methods used in the following examples and comparative examples are shown below.

[0081] [Saponification degree] The degree of saponification of the PVA-based resin (B) was determined by the method described in JIS K 6726:1994.

[0082] [Viscosity average degree of polymerization] The viscosity average degree of polymerization of the PVA-based resin (B) was determined by the method described in JIS K 6726: 1994. Specifically, each polymer was resaponified and purified, and then calculated from the intrinsic viscosity [η] (l / g) measured in water at 30°C by the following formula. In the following formula, the degree of polymerization is represented as P. P = ([η] × 10 4 / 8.29) (1 / 0.62)

[0083] [Elongation at break] The biodegradable polyester resin (A) was hot-press molded into a sheet, which was then cut into a piece having a width of 15 mm and a length of 100 mm, and the breaking elongation was measured in accordance with ISO527-1.

[0084] [Melting point] Among the adhesive resin composition pellets obtained in each of the examples and comparative examples, 10 mg was sealed in an aluminum pan (manufactured by TA Instrument), heated from -30°C to 220°C at a rate of 10°C / min, then rapidly cooled to -30°C at a rate of 10°C / min, and DSC measurement was carried out by heating again from -30°C to 220°C at a rate of 10°C / min. The melting point Tm (°C) was determined from the peak apex temperature in the temperature range from the start to the end of melting during the second heating in the obtained DSC curve.

[0085] [MFR] For the biodegradable polyester resin (A), the MFR was measured at 200°C under a load of 2.16 kg in accordance with JIS K 7210:2014.

[0086] [Mw, Mn] The Mw and Mn of the biodegradable polyester resin (A) were measured using the relative molecular weight analysis method by GPC analysis shown below. [Sample preparation] Approximately 5 mg of powder sample of the biodegradable polyester resin (A) was collected and precisely weighed. To the collected sample, hexafluoroisopropanol (HFIP) added with 1 ml of 20 mM sodium trifluoroacetate per 1 mg of the sample was added, and heated at 40°C for 3 hours to dissolve. Using this solution, GPC analysis was performed under the following conditions. The calculation of the relative molecular weight distribution curve was performed by converting the relative molecular weight obtained from the RI detector using the analysis software attached to the analyzer. The analysis was performed 3 times for the same sample, and the average value was taken as the analysis result.

[0087] [GPC analysis conditions] Measuring device: HLC-8320GPC (manufactured by TOSOH) Analysis software: Empower (manufactured by Waters) Sample concentration: 0.1 mg / ml Mobile phase solvent: Hexafluoroisopropanol added with 20 mM sodium trifluoroacetate Injection volume: 10μl Flow rate: 0.2ml / min Measurement temperature: 40℃ Sample dissolution conditions: 40℃ x 3 hours Filter filtration: 0.45μm PTFE filter Column: 2 GMMHR-H(S) (TOSOH) Detector: RI detector included with the device Equipment calibration standard: PMMA (manufactured by Agilent)

[0088] Thickness The thicknesses of the films made of the adhesive resin compositions, the laminates, and the layers in the laminates in the examples and comparative examples were measured with a digital micrometer.

[0089] [Adhesive strength of adhesive resin composition to PVA-based resin layer] The adhesive resin composition pellets obtained in the examples and comparative examples were preheated at 180°C for 5 minutes using a compression molding machine, and then subjected to a load of 50 kgf / cm 2 The adhesive resin composition was compressed and molded for 30 seconds under the conditions described above to obtain a film (also referred to as an adhesive layer) made of the adhesive resin composition. A film made of the adhesive resin composition (length 150 mm × width 150 mm × thickness 0.3 mm), a polyimide film ("Kapton film" manufactured by Toray DuPont Co., Ltd., length 75 mm × width 150 mm × thickness 0.05 mm), and a film made of polyvinyl alcohol resin (also referred to as a PVA resin layer) ("Mobiflex C17" manufactured by Kuraray Co., Ltd., length 150 mm × width 150 mm × thickness 0.5 mm) were stacked in this order and placed at the center of a metal spacer with inner dimensions of 150 mm × 150 mm and a thickness of 0.8 mm. The stacked films and metal spacer were sandwiched between polytetrafluoroethylene sheets and further sandwiched between metal plates from the outside, and compressed at 180°C and a load of 50 kgf / cm using a compression molding machine. 2 The mixture was compressed at RT for 30 seconds to obtain a multilayer sheet including an adhesive layer and a PVA resin layer. The multilayer sheet was cut into a width of 25 mm to prepare a test piece for measuring adhesive strength, and the peel strength between the adhesive layer and the PVA resin layer was measured in accordance with JIS K 6854-1:1999 using a peel tester (Shimadzu Corporation's "AGS-X") under conditions of a peel angle of 90°, a tensile speed of 50 mm / min, and an environmental temperature of 23°C, which was taken as the adhesive strength of the adhesive resin composition. The adhesive strength was evaluated using the following indices. The results are shown in Table 2. ◎: Peel strength is 20N / 25mm or more ○: Peel strength is 10N / 25mm or more and less than 20N / 25mm △: Peel strength is 4N / 25mm or more and less than 10N / 25mm ×: Peel strength is less than 4N / 25mm

[0090] [Adhesive strength of adhesive resin composition to biodegradable resin layer] The adhesive resin composition pellets obtained in the examples and comparative examples were preheated at 180°C for 5 minutes using a compression molding machine, and then subjected to a load of 50 kgf / cm 2 The adhesive resin composition was compressed and molded for 30 seconds under the conditions to obtain a film (also referred to as an adhesive layer) made of the adhesive resin composition. A film made of the adhesive resin composition (length 150 mm × width 150 mm × thickness 0.3 mm), a polyimide film ("Kapton film" manufactured by Toray DuPont Co., Ltd., length 75 mm × width 150 mm × thickness 0.05 mm), and a film made of a biodegradable resin (also referred to as a biodegradable resin layer) ("Ingeo (registered trademark) biopolymer 2003D" manufactured by Natureworks, 150 mm × width 150 mm × thickness 0.5 mm) were stacked in this order and placed at the center of a metal spacer with inner dimensions of 150 mm × 150 mm and a thickness of 0.8 mm. The stacked films and metal spacer were sandwiched between polytetrafluoroethylene sheets and further sandwiched between metal plates from the outside, and compressed at 180 ° C. and a load of 50 kgf / cm using a compression molding machine. 2 The mixture was compressed and molded at room temperature for 30 seconds to obtain a multilayer sheet including an adhesive layer and a biodegradable resin layer. The multilayer sheet was cut into a width of 25 mm to prepare a test piece for measuring adhesive strength, and the peel strength between the adhesive layer and the biodegradable resin layer was measured in accordance with JIS K 6854-1:1999 using a peel tester (Shimadzu Corporation's "AGS-X") under conditions of a peel angle of 90°, a tensile speed of 50 mm / min, and an environmental temperature of 23°C, which was taken as the adhesive strength of the adhesive resin composition. The adhesive strength was evaluated using the following indices. The results are shown in Table 2. ◎: Peel strength is 55N / 25mm or more ○: Peel strength is 15N / 25mm or more and less than 55N / 25mm △: Peel strength is 9N / 25mm or more and less than 15N / 25mm ×: Peel strength is less than 9N / 25mm

[0091] [Thermoformability] The laminates obtained in the examples and comparative examples were heated to 160°C using a vacuum forming machine (Formech508DT manufactured by Formech) and then molded into capsule shapes with a diameter of 5 cm and a depth of 3 cm. The molded products obtained were visually observed, and the thermoformability was evaluated using the following indices. 〇: Forming possible without problems △: Capsule shape formed, but some wrinkles occurred ×: Difficult to mold

[0092] [Production Example 1] [Production of vinyl alcohol polymer (B1)] A 250L reaction tank equipped with a stirrer, a nitrogen inlet, and an initiator addition port was charged with 630 parts by mass of vinyl acetate and 2520 parts by mass of methanol, and the temperature was raised to 60°C, after which the system was replaced with nitrogen by nitrogen bubbling for 30 minutes. The internal temperature of the flask was adjusted to 60°C, and then 0.5 parts by mass of AIBN was added to start polymerization. When the polymerization rate reached 60% 3.2 hours after the start of polymerization, 1000 parts by mass of methanol was added, and then the polymerization was stopped by cooling. Unreacted vinyl acetate monomer was removed to obtain a methanol solution of PVAc. Methanol was added to the obtained PVAc solution to adjust the concentration to 25% by mass, and an alkali solution (10% by mass of NaOH in methanol) was added at 4.6 mass (molar ratio [MR] to vinyl acetate units in PVAc: 0.01) to 400 parts by mass of a methanol solution of PVAc (100 parts by mass of PVAc in the solution), and saponification was performed at 40°C. After the alkali was added, the gel was pulverized in a pulverizer, and the saponification reaction was carried out for a total of 1 hour, after which 1000 parts by mass of methyl acetate was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, 1000 parts by mass of methanol was added to the white solid PVA polymer obtained by filtration, and the polymer was left to stand at room temperature for 3 hours for washing. After repeating the above washing operation three times, the PVA polymer obtained by centrifugal deliquor was left to stand in a dryer at 70°C for 2 days to dry, thereby obtaining a vinyl alcohol polymer (B1) (referred to as PVA1) having a viscosity average polymerization degree of 300 and a saponification degree of 88.0 mol%.

[0093] [Manufacturing Examples 2 to 7] [Production of vinyl alcohol polymers (B2) to (B7)] By changing the ratio of vinyl acetate to methanol, the polymerization conditions for the polymerization rate, and the saponification conditions for the amount of alkaline solution added, vinyl alcohol polymers (B2) to (B7) (referred to as PVA1 to 7) with the polymerization degrees and saponification degrees shown in Table 2 were obtained.

[0094] [Production Example 8] [Production of ethylene-vinyl alcohol copolymer (B8)] A continuous polymerization vessel equipped with a reflux condenser, a raw material supply line, a reaction liquid withdrawal line, a thermometer, a nitrogen inlet, an ethylene inlet, and an agitator was used. Vinyl acetate was continuously supplied to the continuous polymerization vessel at 626 L / hr, methanol at 216 L / hr, and a 1% methanol solution of n-propyl peroxydicarbonate as an initiator at 30.3 L / hr, each of which was continuously supplied to the continuous polymerization vessel using a metering pump. The ethylene pressure in the polymerization vessel was adjusted to 0.69 MPa. The polymerization liquid was continuously removed from the continuous polymerization vessel so that the liquid level in the polymerization vessel was constant. The polymerization rate at the outlet of the continuous polymerization vessel was adjusted to 67%. The residence time of the continuous polymerization vessel was 5 hours. The temperature at the outlet of the continuous polymerization vessel was 60°C. The polymerization liquid was recovered from the continuous polymerization vessel, and the remaining vinyl acetate was removed by introducing methanol vapor into the polymerization liquid while heating it to 75°C in a hot water bath, to obtain a methanol solution of an ethylene-vinyl ester copolymer. Then, at 40°C, the water content of the system to be subjected to the saponification step was 0.5%, and sodium hydroxide was used as a saponification catalyst in a molar ratio of 0.02 relative to the ethylene-vinyl ester copolymer, and the saponification reaction was carried out for 1 hour. The obtained polymer was immersed in methanol and washed. The solvent was then removed by centrifugation, and the mixture was dried to obtain an ethylene-vinyl alcohol copolymer (B8) having an ethylene unit content of 10 mol%, a viscosity average polymerization degree of 400, and a saponification degree of 98.5 mol%.

[0095] [Example 1] <Adhesive resin composition> As the biodegradable polyester resin (A), 80 parts by mass of polybutylene adipate terephthalate (BASF "Ecoflex C1200", melting point: 118 ° C., elongation at break: 1012%, MFR: 15.8 g / 10 min, Mw: 72000, Mn: 24500) and as the PVA resin (B), 20 parts by mass of PVA1 obtained in Production Example 1 were melt-kneaded under the following conditions using a twin-screw extruder KZW15-45MG (D = 15 mm φ, L / D = 45, Technovel Co., Ltd.). After the melt-kneaded product was extruded from the strand nozzle, the obtained strand was cooled and cut to obtain pellets of the adhesive resin composition. The specific mechanical energy (SME) during melt-kneading was measured to be 526 kJ / kg. [Table 1] Screw rotation speed: 250 rpm Discharge: 3.5kg / h Operation method: Same direction, same rotation, fully meshed type

[0096] <Laminate> A three-kind, five-layer laminate in which a biodegradable resin layer / adhesive layer / polyvinyl alcohol-based resin layer / adhesive layer / biodegradable resin layer were laminated in this order was produced by the following method. The pellets of the adhesive resin composition obtained above, the pellets of the polyvinyl alcohol resin composition (a composition obtained by kneading 100 parts by mass of ethylene-vinyl alcohol copolymer (B8) / 67 parts by mass of trehalose with a twin-screw extruder), and the pellets of polylactic acid (Natureworks, Ingeo (registered trademark), biopolymer 2003D) were each put into the hopper of a single-screw extruder (GM ENGINEERING, VGM25-28EX), and co-extruded at a flow rate of 5 kg / h using a feed block die to obtain a 20 cm wide three-type five-layer laminate. At this time, the cylinder temperatures set were as follows. (Cylinder temperature) Adhesive layer: 180°C, polyvinyl alcohol resin layer: 210°C, biodegradable resin layer: 220°C

[0097] The resulting laminate had a structure of polylactic acid layer / adhesive layer / polyvinyl alcohol-based resin layer / adhesive layer / polylactic acid layer=250 μm / 20 μm / 30 μm / 20 μm / 250 μm (thickness) from the outside.

[0098] [Examples 2 to 7 and Comparative Examples 1 to 4] Except for changing the types and amounts of the biodegradable polyester resin (A) and the PVA resin (B) when preparing the adhesive resin composition as shown in Table 2, an adhesive resin composition and a laminate were obtained in the same manner as in Example 1. In Table 2, PCL indicates polycaprolactone (Ingevity's "Capa@6800", melting point: 60°C, elongation at break: 800%, MFR: 2.4g / 10min). The PBAT and PCL used in the examples and comparative examples meet the biodegradability standards specified in EN13432, ASTM6400 and ISO14855. Furthermore, in the laminates obtained in the examples and comparative examples, the biodegradable resin layer, adhesive layer, and polyvinyl alcohol resin layer all meet the biodegradability standards in ISO14855.

[0099] According to the above method, the adhesive strength of each adhesive resin composition obtained in the examples and comparative examples was evaluated by measuring the peel strength of the PVA-based resin layer and the biodegradable resin layer. In addition, the thermoformability of each laminate obtained in the examples and comparative examples was evaluated. The results are shown in Table 2. In Table 2, *1 indicates that the film (adhesive layer) made of the adhesive resin composition was damaged before peeling in the peel test, that is, that it was cohesively broken. The value in the peel strength column of *1 indicates the strength at the time of cohesive failure before peeling, and since the peel strength is an even larger value, the peel strength in the case of cohesive failure is expressed as "value <". [Table 2]

[0100] As shown in Table 2, it was confirmed that the adhesive resin compositions of Examples 1 to 7 were evaluated as having higher adhesive strength to the PVA-based resin layer and the biodegradable resin layer than those of Comparative Examples 1 to 4. Thus, the adhesive resin composition of the present invention has excellent adhesive strength to both the polyvinyl alcohol-based resin layer and the biodegradable resin layer. Furthermore, it was confirmed that the laminates of Examples 1 to 7 could be easily molded into a desired shape, and in particular, the laminates of Examples 1 to 6 could be molded into a desired shape without the occurrence of wrinkles, etc. Thus, the laminates containing the adhesive resin composition of the present invention have excellent thermoformability.

Claims

1. An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), wherein based on a total of 100 parts by mass of the biodegradable polyester resin (A) and the polyvinyl alcohol resin (B), the content of the biodegradable polyester resin (A) is 42 to 90 parts by mass, the content of the polyvinyl alcohol resin (B) is 10 to 58 parts by mass, and the saponification degree of the polyvinyl alcohol resin (B) is 75 to 96 mol%.

2. The adhesive resin composition according to Claim 1, wherein the biodegradable polyester resin (A) has an elongation at break of 50% or more measured in accordance with ISO 527-1.

3. The adhesive resin composition according to Claim 1, wherein the viscosity average degree of polymerization of the polyvinyl alcohol resin (B) is 100 to 5000.

4. The adhesive resin composition according to Claim 1, wherein the melting point of the biodegradable polyester resin (A) is 70°C or higher.

5. The adhesive resin composition according to Claim 1, wherein the biodegradable polyester resin (A) contains an aromatic-aliphatic copolyester resin.

6. The adhesive resin composition according to Claim 5, wherein the aromatic-aliphatic copolyester resin is polybutylene adipate terephthalate.

7. A laminate comprising an adhesive layer comprising the adhesive resin composition according to any one of Claims 1 to 6.

8. The laminate according to Claim 7, comprising a biodegradable resin layer, the adhesive layer, and a polyvinyl alcohol resin layer in this order.

9. The laminate according to Claim 8, wherein all of the biodegradable resin layer, the adhesive layer, and the polyvinyl alcohol resin layer satisfy the biodegradability criteria based on ISO 14855.

10. A food packaging material comprising an adhesive layer comprising the adhesive resin composition according to any one of Claims 1 to 6.