Adhesive resin composition

Abstract

The present invention relates to an adhesive resin composition containing a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), the adhesive resin composition satisfying formula (1): 0.30 < Y / X < 0.99 (1) [in formula (1), X represents the mass of the polyvinyl alcohol resin (B) contained in a film having a thickness of 300 [mu] m formed from the adhesive resin composition, and X represents the mass of the polyvinyl alcohol resin (B) contained in the film having a thickness of 300 [mu] m; and Y represents the mass of the polyvinyl alcohol resin (B) extracted by hot water when the film is immersed in pure water at 80 DEG C for 1 hour.

Description

Technical Field

[0001] This patent application claims priority under the Paris Convention to Japanese Patent Application No. 2022-200517 (filing date: December 15, 2022) and Japanese Patent Application No. 2023-104831 (filing date: June 27, 2023), and the entire contents thereof are incorporated herein by reference.

[0002] The present invention relates to an adhesive resin composition, a laminate including an adhesive layer containing the adhesive resin composition, and a food packaging material or an agricultural film including the adhesive layer or the laminate. Background Art

[0003] Plastics are widely used as packaging materials because of their high formability, strength, water resistance, transparency, etc. However, plastics lack biodegradability, and if discarded into nature after use, they will remain for a long time and cause environmental damage. On the other hand, in recent years, biodegradable resins that are biodegradable or hydrolyzed in soil or water and are useful for preventing environmental pollution have attracted attention, and the practical application of packaging materials and the like using biodegradable resins is being promoted. Examples of such packaging materials and the like include laminates including 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 via an adhesive layer on at least one surface of a biodegradable resin layer, and the adhesive layer contains an adhesive composition obtained by graft-polymerizing an α,β-unsaturated carboxylic acid or its acid anhydride to a biodegradable polyester-based resin.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-212682 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, according to the research of the present inventors, the adhesive layer in the conventional biodegradable laminate is difficult to exhibit sufficient adhesive strength to both the polyvinyl alcohol-based resin layer and the biodegradable resin layer.

[0009] 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 containing the adhesive resin composition, and a food packaging material or an agricultural film including the adhesive layer or the laminate.

[0010] Means for Solving the Problems

[0011] In order to achieve the above object, the present inventors have repeatedly conducted in-depth research and found that, in an adhesive resin composition containing a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), if a specific parameter (Y / X) is within a specific range, the above problems can be solved, and thus the present invention has been completed. That is, the present invention includes the following preferred embodiments.

[0012] [1]An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), wherein the adhesive resin composition satisfies the formula (1):

[0013] 0.30 ≤ Y / X ≤ 0.99 (1)

[0014] [In the formula, X represents the mass of the polyvinyl alcohol resin (B) contained in a film having a thickness of 300 μm formed from the above adhesive resin composition, and Y represents the mass of the polyvinyl alcohol resin (B) extracted by hot water when the above film is immersed in pure water at 80°C for 1 hour for extraction treatment of soluble components].

[0015] [2]The adhesive resin composition according to [1], wherein the saponification degree of the polyvinyl alcohol resin (B) is 75 to 96 mol%.

[0016] [3]The adhesive resin composition according to [1] or [2], wherein the elongation at break of the biodegradable polyester resin (A) measured according to ISO 527-1 is 50% or more.

[0017] [4]The adhesive resin composition according to any one of [1] to [3], wherein the viscosity-average degree of polymerization of the polyvinyl alcohol resin (B) is 100 to 5000.

[0018] [5]The adhesive resin composition according to any one of [1] to [4], wherein the melting point of the biodegradable polyester resin (A) is 70°C or higher.

[0019] [6]The adhesive resin composition according to any one of [1] to [5], wherein the biodegradable polyester resin (A) contains an aromatic-aliphatic copolyester resin.

[0020] [7]The adhesive resin composition according to [6], wherein the aromatic-aliphatic copolyester resin is polybutylene adipate terephthalate.

[0021] [8] The adhesive resin composition according to any one of [1] to [7], wherein when a film having a thickness of 300 μm formed from the above adhesive resin composition is immersed in pure water at 80 °C for 1 hour to extract soluble components, the diameter of the pores formed is 10 μm or less.

[0022] [9] An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), and having a co-continuous structure formed of at least a phase containing the biodegradable polyester resin (A) and a phase containing the polyvinyl alcohol resin (B).

[0023]

[10] A laminate comprising an adhesive layer containing the adhesive resin composition according to any one of [1] to [9].

[0024]

[11] The laminate according to

[10] , which sequentially comprises a biodegradable resin layer, the above adhesive layer, and a polyvinyl alcohol resin layer.

[0025]

[12] The laminate according to

[11] , wherein the above biodegradable resin layer, the above adhesive layer, and the above polyvinyl alcohol resin layer all satisfy the criteria for biodegradability according to ISO14855.

[0026]

[13] A food packaging material comprising an adhesive layer containing the adhesive resin composition according to any one of [1] to [9], or the laminate according to any one of

[10] to

[12] .

[0027]

[14] An agricultural film comprising an adhesive layer containing the adhesive resin composition according to any one of [1] to [9], or the laminate according to any one of

[10] to

[12] .

[0028] Advantages of the Invention

[0029] The adhesive resin composition of the present invention has excellent adhesive strength to both the polyvinyl alcohol resin layer and the biodegradable polyester resin layer. Therefore, it can be suitably used as a packaging material for foods, etc., and an agricultural film. Brief Description of the Drawings

[0030] Figure 1 It is an image obtained by photographing the adhesive resin composition film after the hot water treatment of Example 2 with SEM.

[0031] Figure 2 It is an image obtained by photographing the adhesive resin composition film after the hot water treatment of Comparative Example 1 with SEM.

[0032] Figure 3 It is an image obtained by photographing the adhesive resin composition film after the hot water treatment of Example 13 with SEM. Detailed Embodiments

[0033] Hereinafter, the embodiments of the present invention will be described in detail. It should be noted that the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the gist of the present invention.

[0034] [Adhesive Resin Composition]

[0035] The adhesive resin composition of the present invention contains a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), and the adhesive resin composition satisfies the formula (1):

[0036] 0.30 ≤ Y / X ≤ 0.99 (1)

[0037] [In the formula, X represents the mass of the polyvinyl alcohol resin (B) contained in a film with a thickness of 300 μm formed from the above adhesive resin composition (sometimes referred to as an adhesive resin composition film), and Y represents the mass of the polyvinyl alcohol resin (B) extracted by hot water when the above film is immersed in pure water at 80°C for 1 hour.]

[0038] In this specification, the biodegradable polyester resin (A) is sometimes referred to as "component (A)", the polyvinyl alcohol resin (B) is sometimes referred to as "component (B)", and polyvinyl alcohol is sometimes abbreviated as PVA. In this specification, the upper limit value and the lower limit value can be arbitrarily combined.

[0039] In formula (1), for the adhesive resin composition film used to obtain X and Y, for example, the pellets of the adhesive resin composition are preheated at 180°C for 5 minutes using a compression molding machine, and then compressed and molded for 30 seconds under the condition of a load of 50 kgf / cm 2 is obtained.

[0040] X in formula (1) represents the mass of the polyvinyl alcohol resin (B) contained in the adhesive resin composition film. For example, the adhesive resin composition film is cut into 10 mm squares to obtain a mass measurement sample with a length of 10 mm × a width of 10 mm × a thickness of 300 μm, and is calculated by the following calculation formula (2). The proportion of the polyvinyl alcohol resin (B) contained in the adhesive resin composition can be obtained, for example, by the following method: freeze-grind the adhesive resin composition film and then perform hot water treatment, and measure the mass of the polyvinyl alcohol resin (B) contained in the extraction solution.

[0041] X = (mass of the mass measurement sample) × (proportion of the polyvinyl alcohol resin (B) contained in the adhesive resin composition (% by mass)) / 100 (2)

[0042] In formula (1), Y represents the mass of the polyvinyl alcohol-based resin (B) extracted by hot water when the adhesive resin composition film is immersed in pure water at 80°C for 1 hour to extract the soluble components. Specifically, when only polyvinyl alcohol (B) is dissolved out during the hot water treatment, a sample (sometimes referred to as the sample after hot water treatment) obtained by subjecting the sample for mass measurement to the treatment of being immersed in hot water at 80°C for 1 hour can be obtained, and it is calculated by the following formula (3).

[0043] Y = (mass of the sample for mass measurement) - (mass of the sample after hot water treatment) (3)

[0044] The above hot water treatment is, for example, the following treatment: Add the sample for mass measurement (about 0.03 g) into a 50 cc screw tube, and further add 20 ml of distilled water at 23°C. Place this screw tube into a hot air dryer set at 80°C. After 30 minutes, confirm that the distilled water reaches 80°C, and then let it stand for another 1 hour. Then, in order to remove the dissolved components located in the pores and on the surface, gently shake the sample with tweezers and then take out the sample for mass measurement from the screw tube. Furthermore, place the taken-out sample for mass measurement into a hot air dryer set at 80°C and let it stand for 1 hour.

[0045] Y / X in formula (1) is obtained by substituting the values of X and Y obtained above. In addition, X and Y are expressed in the same unit. For example, when the unit of X is gram (g), the unit of Y is gram (g). Y / X in formula (1) can be obtained, for example, by the method described in the examples.

[0046] The adhesive resin composition of the present invention contains a biodegradable polyester-based resin (A) and a PVA-based resin (B). Since component (A) is insoluble in pure water, Y / X can substantially refer to the proportion of the PVA-based resin (B) contained in the adhesive resin composition that is extracted in the form of soluble components when immersed in hot water at 80°C for 1 hour.

[0047] The present inventors studied the interlayer adhesion strength of the laminate, and as a result, it was found that, surprisingly, when Y / X as a specific parameter is in the range of 0.30 to 0.99, the adhesion strength to both the PVA-based resin and the biodegradable resin layer is significantly improved.

[0048] The reason is not yet certain, but it can be inferred that the reason for such an effect is that when the proportion of the PVA-based resin (B) reduced when immersed in 80°C hot water for 1 hour is within a specific range, a structure is presented in which the sea-island structure part (the PVA-based resin (B) corresponds to the island) and the co-continuous structure part of the PVA-based resin (B) are mixed well in balance. More specifically, since the co-continuous structure part is a structure formed by connecting the PVA-based resin (B), the adhesive force to the PVA-based resin layer as the adherend can be improved. On the other hand, in the sea-island structure part, since the PVA-based resin (B) is not connected, the strength and toughness of the composition itself can be improved, and it is also easy to exhibit good adhesive force to the biodegradable resin layer. Therefore, when these structures are mixed well in balance, as a result, it can be inferred that the adhesive strength to the PVA-based resin layer and the biodegradable resin layer is improved.

[0049] In addition, it can be inferred that there is the following trend: compared with the sea-island structure part, the co-continuous structure part presenting a structure formed by connecting the PVA-based resin (B) is more likely to dissolve the PVA-based resin (B) when immersed in hot water. On the other hand, compared with the co-continuous structure part, the sea-island structure part not presenting a connected structure is less likely to dissolve the PVA-based resin (B) when immersed in hot water. Therefore, it can be inferred that the larger the value of Y / X, the more the proportion of the co-continuous structure part increases, and the smaller the value of Y / X in the formula (1), the more the proportion of the sea-island structure part increases.

[0050] Figure 1 An image of the cross-section of the adhesive resin composition film after heat treatment in Example 2 of this specification was taken with a scanning electron microscope (abbreviated as SEM). Figure 2 An image was obtained by taking the adhesive resin composition film after heat treatment in Comparative Example 1 with SEM. Figure 3 An image was obtained by taking the adhesive resin composition film after heat treatment in Example 13 with SEM.

[0051] In Figure 1 、 Figure 2 and Figure 3 There are a large number of void parts in the SEM images of, and it can be said that the PVA-based resin (B) removed by hot water extraction originally existed in these void parts. And as shown in these SEM images, in the cases of Figure 1 and Figure 3 where Y / X is within the above range, the co-continuous structure part where the void parts are continuously connected and the sea-island structure part where the void parts form islands coexist. On the other hand, in Figure 2In this mode, the sea-island structure accounts for the majority. It should be noted that the present invention requires that Y / X be within a specific range. As long as the effects of the present invention are achieved, the structure of the adhesive resin composition is not limited.

[0052] Thus, since the adhesive resin composition of the present invention adjusts the value of Y / X in formula (1) to a moderate value of 0.30 to 0.99, it can exhibit excellent adhesive strength. It should be noted that in this specification, the adhesive strength can be evaluated by a peel test, and it refers to 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.

[0053] If Y / X in formula (1) is less than 0.30 or exceeds 0.99, the adhesive strength to the PVA-based resin layer is likely to decrease. In the present invention, Y / X in formula (1) is 0.3 or more, preferably 0.4 or more, more preferably 0.5 or more, further preferably 0.6 or more, still further preferably 0.66 or more, particularly preferably 0.7 or more, and especially more preferably 0.8 or more. For example, it can be 0.85 or more or 0.90 or more. The upper limit of Y / X in formula (1) is 0.99 or less, preferably 0.98 or less. If Y / X is above the above lower limit, the adhesive force to the PVA-based resin layer can be improved. In addition, if Y / X is below the above upper limit, the strength and toughness of the adhesive resin composition itself can be improved, and a good adhesive force to the biodegradable resin layer can also be exhibited. As a result, if Y / X is above the above lower limit and below the above upper limit, the adhesive strength to the PVA-based resin layer and the biodegradable resin layer can be improved.

[0054] Y / X in formula (1) only needs to be controlled within the above range by adjusting the values of X and Y. Here, X can be adjusted by the addition amount of the PVA-based resin (B) when preparing the adhesive resin composition film. Y substantially represents the reduction amount of the PVA-based resin (B) after being immersed in hot water for 1 hour, and can be adjusted to the above range according to the types and contents of components (A) and (B), the saponification degree and polymerization degree of component (B), and the manufacturing conditions of the adhesive resin composition. For example, Y / X in formula (1) can be adjusted to the above range by appropriately using the types and contents of the preferred components (A) and (B) described in this specification, the preferred saponification degree and polymerization degree of component (B), and the preferred manufacturing conditions, etc.

[0055] In one embodiment of the present invention, when a film with a thickness of 300 μm formed from the adhesive resin composition is immersed in pure water at 80°C for 1 hour, the diameter of the formed pores is preferably 10 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, and even more preferably 1 μm or less. If the diameter of the above-mentioned pores is below the above upper limit, it is easy to improve the adhesive strength between the polyvinyl alcohol-based resin layer and the biodegradable resin layer. In addition, the lower limit of the pore diameter is preferably 0.01 μm or more. The film with a thickness of 300 μm formed from the adhesive resin composition is the same as that described in the description of the above formula (1), and the treatment of immersing in pure water at 80°C for 1 hour is the same as the hot water treatment described in the description of the above formula (1). The diameter of the above-mentioned pores can be measured by SEM after the hot water treatment, for example, it can be measured by the method described in the examples.

[0056] <Biodegradable polyester resin (A)>

[0057] The adhesive resin composition of the present invention contains a biodegradable polyester resin (A). In this specification, "biodegradable" means having the property of being chemically decomposed by, for example, hydrolysis, enzymatic decomposition, microbial decomposition, etc., and preferably showing a material that conforms to the biodegradability criteria specified in EN13432, ASTM6400, or ISO14855. That is, when placed in a compost environment, 90% of it disintegrates into particles with an average size of less than 2 mm within 12 weeks, and in the case of ASTM6400, a material in which at least 60% of it decomposes into carbon dioxide and / or water after 6 months is biodegradable, or in the case of EN13432, a material in which at least 90% of it decomposes into carbon dioxide and / or water after 6 months is biodegradable.

[0058] The biodegradable polyester resin is not particularly limited as long as it is the above-mentioned biodegradable polyester resin, and it can be a petroleum-derived biodegradable resin or a bio-derived biodegradable resin. As the biodegradable polyester resin, for example, aliphatic polyester resins, aromatic-aliphatic copolyester resins, aromatic polyester resins, etc. can be mentioned. The biodegradable polyester resin preferably contains at least 1 selected from aliphatic polyester resins and aromatic-aliphatic copolyester resins. From the viewpoints of having high biodegradability and being easy to improve the adhesive strength and thermoformability, it is more preferably an aromatic-aliphatic copolyester resin.

[0059] As the aliphatic polyester resin, for example, polyhydroxyalkanoate (abbreviated as PHA), polyalkylene monocarboxylate, polyalkylene dicarboxylate, etc. can be mentioned.

[0060] PHA is a polymer with hydroxyalkanoic acid as monomer units. More specifically, polyglycolic acid, polylactic acid (sometimes abbreviated as PLA), poly(3-hydroxyalkanoate) (abbreviated as P3HA), poly(4-hydroxyalkanoate), etc. can be mentioned.

[0061] P3HA is a polymer mainly with 3-hydroxyalkanoic acid as monomer units. As 3-hydroxyalkanoic acid, for example, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxypentanoate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, etc. can be mentioned. P3HA can be a homopolymer or a copolymer containing two or more monomer units. In addition, when P3HA is a copolymer, it can be a copolymer formed by copolymerizing two or more 3-hydroxyalkanoic acids, or a copolymer formed by copolymerizing one or two or more 3-hydroxyalkanoic acids with 4-hydroxyalkanoic acids such as 4-hydroxybutyrate.

[0062] As specific examples of P3HA, poly(3-hydroxybutyrate) homopolymer (abbreviated as PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviated as PHBH), poly(3-hydroxybutyrate-co-3-hydroxypentanoate) (abbreviated as PHBV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as 3HB4HB), etc. can be mentioned.

[0063] As polyalkylene monocarboxylate esters, ring-opening polymers of lactones (cyclic esters) can be mentioned. As specific examples thereof, polycaprolactone (abbreviated as PCL), etc. can be mentioned.

[0064] Polyalkylene dicarboxylate esters are condensation polymers of aliphatic diols (or their derivatives) and aliphatic dicarboxylic acids (or their derivatives). As examples thereof, polybutylene succinate (abbreviated as PBS), polyethylene succinate (abbreviated as PES), poly(butylene succinate-co-butylene adipate), etc. can be mentioned.

[0065] The aliphatic polyester-based resin is preferably at least one selected from PHA, polyalkylene monocarboxylate esters, and polyalkylene dicarboxylate esters, and more preferably at least one selected from polyalkylene monocarboxylate esters and polyalkylene dicarboxylate esters from the viewpoint of easily improving the adhesive strength. In addition, from the viewpoint of thermoformability, PHA is more preferred.

[0066] An aromatic-aliphatic copolyester resin is a polyester resin having both an aromatic moiety and an aliphatic moiety, and is a condensate of an aliphatic or aromatic diol (or its derivative) and an aromatic or aliphatic dicarboxylic acid (or its derivative). As examples thereof, polybutylene adipate terephthalate (abbreviated as PBAT), polybutylene succinate terephthalate (PBST), polyethylene adipate terephthalate (PEAT), etc. can be cited, and PBAT is preferred from the viewpoints of high biodegradability and easy improvement of adhesive strength and thermoformability.

[0067] These biodegradable polyester resins can be used alone or in combination of two or more.

[0068] The biodegradable polyester resin (A) can be produced by a conventional method or a commercially available product can be used. As commercially available products of the biodegradable polyester resin (A), polycaprolactone (PCL) sold under the trade name of Tone (trademark) by Union Carbide (for example, Tone P-300, P-700, P-767, and P-787 have weight average molecular weights of about 10,000, 40,000, 43,000, and 80,000, respectively), or polycaprolactone (PCL) sold under the trade name of CAPA6800 and CAPAFB100 (having molecular weights of 80,000 and 100,000 daltons, respectively) by Perstorf; polylactic acid (PLA) sold under the trade name of Natureworks (trademark) PLA by Cargill; polyhydroxybutyrate (PHB) sold under the trade name of Biocycle (trademark) or Biomer (trademark) by Biomer (Germany); poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS) (for example, Bionolle (trademark) 1001 (PBS) and Bionelle (trademark) 6000 (PES)) sold under the trade name of Bionolle (trademark) by Showa Highpolymer Co., Ltd.; poly(butylene adipate) (PBA) sold under the trade name of Skygreen (trademark) SG100 by SK Chemicals (Korea); aliphatic / aromatic copolyesters of polybutylene adipate terephthalate (PBAT), for example, Ecoflex (trademark) from BASF (Germany), or EnPOL (trademark) G8060 and EnPOL (trademark) 8000 from Ire Chemical Ltd (Seoul); poly(hydroxybutyrate-co-valerate) (PHBV) from Metabolix Inc. (USA), etc.

[0069] The biodegradable polyester resin (A) can be a modified biodegradable polyester resin or an unmodified biodegradable polyester resin. There is no particular limitation on the modified biodegradable polyester resin. For example, it can be a modified biodegradable polyester resin obtained by graft-modifying a biodegradable polyester resin with an unsaturated carboxylic acid and / or its derivative. There is no particular limitation on the unsaturated carboxylic acid as the modifier. For example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. can be cited. In addition, there is no particular limitation on the derivative of the unsaturated carboxylic acid. For example, acid anhydrides, esters, amides, imides, metal salts, etc. can be cited.

[0070] Specific examples of the derivative of the unsaturated carboxylic acid include maleic anhydride, nadic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate, monoethyl maleate, diethyl maleate, monomethyl itaconate, diethyl itaconate, acrylamide, methacrylamide, monomaleamide, dimaleamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N,N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monamide, fumaric acid diamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butyl maleimide, N-phenyl maleimide, sodium acrylate, potassium acrylate, potassium methacrylate, etc.

[0071] These unsaturated carboxylic acids and / or their derivatives can be used alone only 1 kind, or 2 or more kinds can be used in any combination and ratio. Among them, maleic acid or its acid anhydride has a low electron density and high reactivity, so it is particularly suitable.

[0072] Relative to the mass of the modified biodegradable polyester resin, the content of the modifier is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.03% by mass or more, preferably 3.0% by mass or less, more preferably 1.0% by mass or less, and further preferably 0.2% by mass or less.

[0073] The adhesive resin composition of the present invention is an alloy of the biodegradable polyester resin (A) satisfying the formula (1) and the PVA-based resin (B). Therefore, the biodegradable polyester resin is not modified, and excellent adhesive strength to the PVA-based resin layer and the biodegradable resin layer can be exhibited. Therefore, in a preferred embodiment of the present invention, the biodegradable polyester resin (A) is preferably an unmodified biodegradable polyester resin. In the unmodified case, it is possible to prevent a decrease in biodegradability caused by modification, and it is also possible to avoid the complexity of manufacturing caused by modification.

[0074] In a preferred embodiment of the present invention, the elongation at break of the biodegradable polyester resin (A) measured according to ISO 527-1 is preferably 50% or more, more preferably 100% or more, further preferably 200% or more, still more preferably 400% or more, particularly preferably 600% or more, especially more preferably 750% or more, especially further preferably 850% or more, especially still more preferably 1000% or more. If the elongation at break is above the above lower limit, the toughness becomes higher, and thus the adhesive strength is likely to be improved. The upper limit of the above elongation at break is usually 5000% or less, preferably 3000% or less, more preferably 2000% or less. If the elongation at break is below the above upper limit, a decrease in the elastic modulus and maximum strength of the adhesive resin composition can be suppressed, and thus a decrease in the adhesive strength can be easily suppressed. It should be noted that the elongation at break can be measured according to ISO 527-1, for example, by the method described in the examples.

[0075] In a preferred embodiment of the present invention, the melting point of the biodegradable polyester resin (A) is preferably 70 °C or more, more preferably 80 °C or more, further preferably 90 °C or more, still more preferably 100 °C or more, particularly preferably 105 °C or more. If the melting point of the biodegradable polyester resin (A) is above the above lower limit, the thermoformability is likely to be further improved, and thus the generation of wrinkles and the like in the obtained laminate can be easily suppressed or prevented, and the appearance is likely to be good. The upper limit of the above melting point is preferably 300 °C or less, more preferably 200 °C or less, further preferably 150 °C or less, still more preferably 140 °C or less, particularly preferably 130 °C or less. If the above melting point is below the above upper limit, the thermoformability is likely to be improved, and thus the obtained laminate can be easily formed into a specified shape. It should be noted that the melting point can be measured using a differential scanning calorimeter (DSC), for example, by the method described in the examples.

[0076] In one embodiment of the present invention, the melt flow rate (MFR) of the biodegradable polyester resin (A) is preferably 1.0 g / 10 minutes or more, more preferably 3.0 g / 10 minutes or more, further preferably 5.0 g / 10 minutes or more, still more preferably 7.0 g / 10 minutes or more, particularly preferably 10 g / 10 minutes or more, preferably 30 g / 10 minutes or less, more preferably 25 g / 10 minutes or less, further preferably 20 g / 10 minutes or less. By making the MFR of the biodegradable polyester resin (A) within the above range, the adhesive strength and thermoformability are likely to be improved. The MFR can be measured according to JIS K 7210:2014 under the conditions of a temperature of 200 °C and a load of 2.16 kg.

[0077] 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, further preferably 50,000 or more, preferably 500,000 or less, more preferably 200,000 or less, and further preferably 100,000 or less. By making the Mw of the biodegradable polyester resin (A) within the above range, it is easy to improve the adhesive strength and thermoformability.

[0078] 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, further preferably 20,000 or more, preferably 200,000 or less, more preferably 100,000 or less, and further preferably 50,000 or less. By making the Mn of the biodegradable polyester resin (A) within the above range, it is easy to improve the adhesive strength and thermoformability.

[0079] It should be noted that the Mw and Mn of the biodegradable polyester resin (A) can be measured by gel permeation chromatography (GPC) and obtained by conversion with standard polystyrene. For example, they can be obtained by the method described in the examples.

[0080] Based on 100 parts by mass in total of the component (A) and the component (B), the content of the biodegradable polyester resin (A) is preferably 42 parts by mass or more, more preferably 45 parts by mass or more, further preferably 48 parts by mass or more, preferably 90 parts by mass or less, more preferably 85 parts by mass or less, further preferably 80 parts by mass or less, still more preferably 77 parts by mass or less, particularly preferably 75 parts by mass or less, especially more preferably 73 parts by mass or less or 70 parts by mass or less, and especially further preferably 67 parts by mass or less or 65 parts by mass or less, and extremely preferably 63 parts by mass or less. If the content of the biodegradable polyester resin (A) is above the above lower limit, it is easy to improve the biodegradability and the adhesive strength to the biodegradable resin layer is easily improved. If the content of the biodegradable polyester resin (A) is below the above upper limit, it is easy to improve the adhesive strength to the PVA-based resin layer. It should be noted that 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.

[0081] <Polyvinyl alcohol-based resin (B)>

[0082] The adhesive resin composition of the present invention contains a PVA-based resin (B).

[0083] 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 vinyl alcohol units as monomer units. In the case of the vinyl alcohol-based polymer, the saponified vinyl alcohol-based polymer obtained by saponifying a vinyl ester-based polymer polymerized from a vinyl ester monomer as its raw material monomer may contain vinyl ester units in addition to vinyl alcohol units.

[0084] The vinyl alcohol-based polymer may be a modified vinyl alcohol-based copolymer obtained by saponifying a copolymer obtained by copolymerizing a vinyl ester monomer as its raw material monomer with other monomers and containing other monomer units in addition to vinyl alcohol units and vinyl ester units. In addition, the PVA-based resin (B) may contain a plurality of vinyl alcohol-based polymers having different physical properties.

[0085] Examples of the vinyl ester monomer used as the raw material monomer for the vinyl alcohol-based polymer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among them, vinyl acetate is preferred from the viewpoints of ease of production and acquisition, cost, etc.

[0086] As described above, the vinyl alcohol polymer can be a modified vinyl alcohol copolymer containing other monomer units in addition to vinyl alcohol units and vinyl ester units, and other monomers can be appropriately selected according to the type of the PVA-based resin layer as the adherend. For example, α-olefins such as ethylene, propylene, n-butene, and isobutene can be mentioned; acrylic acid and its salts; acrylate esters; methacrylic acid and its salts; methacrylate esters; acrylamide; acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropylsulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or quaternary salts, and N-hydroxymethylacrylamide and its derivatives; methacrylamide; methacrylamide derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropylsulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts or quaternary salts, and N-hydroxymethylmethacrylamide and its derivatives; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-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 dihalides such as vinylidene dichloride and vinylidene difluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid and their salts or esters; vinylsilyl compounds such as vinyltrimethoxysilane; isopropyl acetate; vinyl compounds such as dimethylallyl vinyl ketone, N-vinylpyrrolidone, ethylene carbonate vinyl, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerol monoallyl ether, and 3,4-diacetoxy-1-butene. Among them, from the viewpoint of ease of industrial production, other monomers are preferably α-olefins such as ethylene. The content (modification amount) of these other monomer units varies depending on the purpose and use. In one embodiment, the content (modification amount) of other monomer units can be preferably 10 mol% or less, more preferably 5 mol% or less, preferably 0 mol% or more, and more preferably 0.1 mol% or more.

[0087] Some of the hydroxyl groups of the vinyl alcohol polymer can be crosslinked or not. In addition, some of the hydroxyl groups of the vinyl alcohol polymer can react with aldehyde compounds such as acetaldehyde and butyraldehyde to form an acetal structure, or can not react with these compounds to not form an acetal structure.

[0088] Depending on the type of the PVA-based resin layer as the adherend, the PVA-based resin (B) preferably contains at least one selected from an unmodified vinyl alcohol polymer and an α-olefin-vinyl alcohol copolymer as the vinyl alcohol polymer from the viewpoint of easily improving the adhesive strength and thermoformability, and more preferably contains an unmodified vinyl alcohol polymer.

[0089] The saponification degree of the PVA-based resin (B) contained in the adhesive resin composition of the present invention is preferably 75 mol% or more, more preferably 77 mol% or more, further preferably 79 mol% or more, still more preferably 80 mol% or more, and may be, for example, 81 mol% or more or 82 mol% or more. In addition, the saponification degree of the PVA-based resin (B) is preferably 96 mol% or less, more preferably 94 mol% or less, further preferably 92 mol% or less, still more preferably 90 mol% or less, particularly preferably 89 mol% or less, and particularly more 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 above the above lower limit, it is easy to form hydrogen bonds with the PVA-based resin layer as the adherend, and thus it is easy to improve the adhesive strength and gas barrier properties to the PVA-based resin layer. In addition, if the saponification degree of the PVA-based resin (B) is below the above upper limit, it is easy to exhibit moderate fluidity during adhesion, and thus it is easy to improve the adhesive strength and thermoformability. In the present specification, the saponification degree of the PVA-based resin (B) means the proportion (mol%) of the number of moles of vinyl alcohol units in the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification and vinyl alcohol units in the vinyl alcohol-based polymer. The saponification degree of the PVA-based resin (B) can be measured according to JIS K 6726:1994. In addition, regarding the saponification degree of the PVA-based resin (B), when the PVA-based resin (B) contains only one kind of vinyl alcohol-based polymer, the saponification degree of the vinyl alcohol-based polymer is the saponification degree of the PVA-based resin (B). When the PVA-based resin (B) contains two or more kinds of vinyl alcohol-based polymers, it means the average saponification degree calculated according to the saponification degrees and blending ratios of the respective vinyl alcohol-based polymers. It should be noted that when the PVA-based resin (B) contains two or more kinds of vinyl alcohol-based polymers, the saponification degree of the PVA-based resin (B) can be adjusted to the above range by mixing vinyl alcohol-based polymers having different saponification degrees at an appropriate blending ratio.

[0090] In one embodiment of the present invention, the viscosity-average degree of polymerization (sometimes referred to as the degree of polymerization) of the PVA-based resin (B) contained in the adhesive resin composition of the present invention may preferably be 5000 or less, 4000 or less, 3000 or less, or 2000 or less, more preferably 1500 or less, further preferably 1200 or less, still further preferably 900 or less, particularly preferably 700 or less, and especially more preferably 600 or less, and especially further preferably 480 or less, 400 or less, or 350 or less. If the degree of polymerization is below the above upper limit, it is easy to improve the adhesive strength to the PVA-based resin layer and the thermoformability. It is presumed that this is because, during adhesion, the PVA-based resin (B) as a polar component easily migrates to the interface, and the PVA-based resin (B) easily forms a co-continuous structure part. The viscosity-average degree of polymerization of the PVA-based resin (B) is preferably 100 or more, more preferably 150 or more, further preferably 200 or more, still further preferably 220 or more, particularly preferably 250 or more, and especially more preferably 270 or more. If the degree of polymerization is above the above lower limit, it is easy to improve the mechanical strength of the adhesive resin composition, and it is also easy to improve the adhesive strength to the biodegradable resin layer. It is presumed that this is because it is easy to form a sea-island structure. The degree of polymerization of the PVA-based resin (B) can be measured in accordance with JIS K 6726:1994. In addition, when the PVA-based resin (B) contains only one kind of vinyl alcohol-based polymer, the degree of polymerization of the vinyl alcohol-based polymer is the degree of polymerization of the PVA-based resin (B). When the PVA-based resin (B) contains two or more kinds of vinyl alcohol-based polymers, the degree of polymerization of the PVA-based resin (B) refers to the average degree of polymerization calculated based on the degree of polymerization and the blending ratio of each vinyl alcohol-based polymer. It should be noted that when the PVA-based resin (B) contains two or more kinds of vinyl alcohol-based polymers, the vinyl alcohol-based polymers with different degrees of polymerization are mixed at an appropriate blending ratio, and the degree of polymerization of the PVA-based resin (B) can be adjusted to the above range.

[0091] Based on 100 parts by mass in total of component (A) and component (B), the content of the PVA-based resin (B) contained in the adhesive resin composition of the present invention is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, further preferably 20 parts by mass or more, still more preferably 23 parts by mass or more, particularly preferably 25 parts by mass or more, especially more preferably 27 parts by mass or more or 30 parts by mass or more, extremely preferably 33 parts by mass or more or 35 parts by mass or more, extremely still more preferably 37 parts by mass or more, and preferably 58 parts by mass or less, more preferably 55 parts by mass or less, further preferably 52 parts by mass or less. If the content of the PVA-based resin (B) is above the above lower limit, it is easy to improve the adhesive force to the PVA-based resin layer and easy to improve the adhesive strength. In addition, if the content of the PVA-based resin (B) is below the above upper limit, the adhesive strength to the biodegradable resin layer is easy to improve. It should be noted that the content of the PVA-based resin (B) relative to the mass of the adhesive resin composition can also be selected from the above range.

[0092] In one embodiment of the present invention, it is inferred that the more the content of component (B) is, the easier it is to form a co-continuous structure part, and there is a tendency for the value of Y / X to easily increase. On the other hand, it is inferred that the less the content of component (B) is, the easier it is to form a sea-island structure part, and there is a tendency for the value of Y / X to easily decrease. In addition, it is inferred that it is difficult to form a co-continuous structure part when the saponification degree of component (B) is too high or too low, and there is a tendency for the value of Y / X to easily increase due to an appropriate saponification degree. Furthermore, it is inferred that the lower the degree of polymerization of component (B) is, the easier it is to form a co-continuous structure part, and there is a tendency for the value of Y / X to easily increase. On the other hand, it is inferred that the higher the degree of polymerization of component (B) is, the easier it is to form a sea-island structure part, and there is a tendency for the value of Y / X to easily decrease.

[0093] <Manufacturing method of polyvinyl alcohol-based resin (B)>

[0094] As described above, the PVA-based resin (B) contains a vinyl alcohol-based polymer. The vinyl alcohol-based polymer can be obtained, for example, by polymerizing a vinyl ester monomer or a vinyl ester monomer and other monomers to obtain a vinyl ester polymer or copolymer, and then further subjecting it to saponification. As methods for polymerizing vinyl ester monomers and the like, known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be cited. Among them, bulk polymerization and solution polymerization, which are carried out in a solvent-free or in a solvent such as alcohol, are preferably used. As the alcohol used as a solvent in solution polymerization, lower alcohols such as methanol, ethanol, and propanol can be cited. As initiators used in copolymerization, known initiators such as azo-based initiators or peroxide-based initiators, such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl-pentanenitrile), benzoyl peroxide, and n-propyl peroxydicarbonate, can be cited. There is no particular limitation on the polymerization temperature, and a range of 0°C to 150°C is preferred. In addition, for example, when the vinyl alcohol-based polymer is an ethylene-vinyl alcohol copolymer or the like, it is preferred to copolymerize a vinyl ester monomer and a monomer such as ethylene using the above method.

[0095] The vinyl ester-based polymer obtained in the polymerization step can be saponified by an alcoholysis or hydrolysis reaction in an organic solvent in the presence of a catalyst. As the catalyst used in the saponification step, basic catalysts such as sodium hydroxide, potassium hydroxide, and sodium methoxide can be cited; or acidic catalysts such as sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid. The organic solvent used in the saponification step is not particularly limited, and alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene can be cited. They can be used alone or in combination of two or more. Among them, it is simple and preferred to carry out the saponification reaction in the presence of sodium hydroxide as a basic catalyst using methanol or a mixed solution of methanol and methyl acetate as a solvent. The usage amount of the saponification catalyst is preferably 0.001 to 0.5 in terms of the molar ratio relative to the vinyl ester monomer unit in the vinyl ester-based polymer. This molar ratio is more preferably 0.002 or more, preferably 0.4 or less, and more preferably 0.3 or less.

[0096] A preferred embodiment of the saponification step is as follows. First, a saponification catalyst such as sodium hydroxide is added to the vinyl ester-based polymer solution obtained in the polymerization step and mixed. The solvent at this time is preferably methanol. The initial mixture is a homogeneous liquid, and if the saponification reaction proceeds and the vinyl ester units in the polymer are saponified to vinyl alcohol units, the solubility in the solvent decreases and the polymer precipitates in the solution. At this time, methyl acetate generated by the alcoholysis of methanol is contained in the solution. As the saponification reaction proceeds, the precipitation amount of the polymer slowly increases and becomes slurry-like, and then loses fluidity. Therefore, in order to make the saponification reaction proceed uniformly, it is preferred to mix well until the fluidity is lost.

[0097] The method of mixing the vinyl ester polymer solution with the saponification catalyst is not particularly limited, and various methods such as a static mixer, a kneader, and stirring blades can be used. Using a static mixer enables continuous and uniform mixing, so it is preferred. In this case, it is preferred to add the saponification catalyst to the vinyl ester polymer solution after the polymerization step in the pipe connected to the polymerization tank, and then mix it through a static mixer to obtain a paste. The temperature of the reaction solution in the static mixer is usually 20 to 80 °C.

[0098] The method of subjecting the vinyl ester polymer in the paste passing through the static mixer to a saponification reaction is not particularly limited. A method of placing the paste on a moving belt and carrying out the saponification reaction while moving the belt in a tank maintained at a constant temperature is suitable. The paste on the belt loses fluidity and becomes a solid state, and then the saponification reaction proceeds in the solid state. By this method, the saponification reaction can be continuously carried out in the solid state to obtain a solid mass containing a vinyl alcohol polymer and a solvent. The saponification temperature is preferably 20 to 60 °C, more preferably 25 °C or higher, still more preferably 30 °C or higher, preferably 55 °C or lower, and more preferably 50 °C or lower. If the saponification temperature is above the above lower limit, it is easy to suppress the decrease in the reaction rate. If the saponification temperature is below the above upper limit, it is easy to suppress the decrease in the solvent content rate in the obtained solid mass and is easy to suppress the deterioration of 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 longer, further preferably 10 minutes or longer, more preferably 1.5 hours or shorter, and further preferably 1 hour or shorter.

[0099] If necessary, a cleaning step may be added to clean the vinyl alcohol polymer for the purpose of removing impurities such as sodium acetate. Examples of the cleaning liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, water, etc. Among them, a single or mixed liquid of methanol, methyl acetate, and water is more preferred. As the amount of the cleaning liquid, it is usually preferably 30 to 10,000 parts by mass, more preferably 50 to 3,000 parts by mass, relative to 100 parts by mass of the vinyl alcohol polymer. As the cleaning temperature, it is preferably 5 to 80 °C, more preferably 20 to 70 °C. As the cleaning time, it is preferably 20 minutes to 10 hours, more preferably 1 hour to 6 hours. As the cleaning method, known methods such as an intermittent method and a convection cleaning method can be applied. It should be noted that commercially available products of the vinyl alcohol polymer can also be used.

[0100] <Adhesive resin composition>

[0101] The adhesive resin composition of the present invention contains the above biodegradable polyester resin (A) and the above polyvinyl alcohol resin (B), and satisfies formula (1), and thus has excellent adhesive strength to both the PVA resin layer and the biodegradable resin layer. Therefore, it is useful as an adhesive layer between the PVA resin layer and the biodegradable polyester resin layer. In addition, the thermoformability of the adhesive resin composition of the present invention is also excellent, and the obtained laminate can be easily formed into a specified shape. Furthermore, the biodegradability is excellent. Therefore, the adhesive resin composition of the present invention can be suitably used as a packaging material for foods, etc., and an agricultural film.

[0102] The adhesive strength of the adhesive resin composition of the present invention to the PVA resin is preferably 4 N / 25 mm or more, more preferably 5 N / 25 mm or more, further preferably 7 N / 25 mm or more, still more preferably 10 N / 25 mm or more, particularly preferably 15 N / 25 mm or more, and especially more preferably 20 N / 25 mm or more. For example, it can be 25 N / 25 mm or more, 27 N / 25 mm or more, or 30 N / 25 mm or more. If the above adhesive strength is at least the above lower limit, it is easy to improve the strength of the obtained laminate. The adhesive strength to the PVA resin is usually 100 N / 25 mm or less. The adhesive strength to the PVA resin represents the peel strength between the adhesive layer and the PVA resin layer in the multi-layer sheet, and the multi-layer sheet includes an adhesive layer containing the adhesive resin composition and a PVA resin layer. This peel strength can be measured according to JIS K 6854-1:1999 using a peel tester under the conditions of a peel angle of 90°, a tensile speed of 50 mm / minute, and an ambient temperature of 23°C. The adhesive strength to the PVA resin can be obtained, for example, by the method described in the examples.

[0103] The adhesive strength of the adhesive resin composition of the present invention to a biodegradable resin (preferably PLA) is preferably 9 N / 25 mm or more, more preferably 15 N / 25 mm or more, further preferably 20 N / 25 mm or more, still more preferably 30 N / 25 mm or more, particularly preferably 40 N / 25 mm or more, especially more preferably 50 N / 25 mm or more, and especially further preferably 55 N / 25 mm or more. If the above adhesive strength is at or above the above lower limit, the strength of the resulting laminate can be improved. The adhesive strength to the biodegradable resin is usually 150 N / 25 mm or less. The adhesive strength to the biodegradable resin represents the peel strength between the adhesive layer and the biodegradable resin layer in a multi-layer sheet, and the multi-layer sheet includes an adhesive layer containing the adhesive resin composition and a biodegradable resin layer. This peel strength can be measured according to JIS K 6854-1:1999, using a peel tester, under the conditions of a peel angle of 90°, a tensile speed of 50 mm / minute, and an ambient temperature of 23°C. The adhesive strength to the biodegradable resin can be determined, for example, by the method described in the examples.

[0104] The adhesive resin composition of the present invention may contain additives other than component (A) and component (B) within the range that does not impair the object and effect of the present invention. Examples of the additives include fillers, processing stabilizers, weather 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, mildewproof agents, preservatives, crystal rate retardants, 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, and relative to the mass of the adhesive resin composition, it can be, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and can be preferably 0% by mass or more, more preferably 0.1% by mass or more. The adhesive resin composition of the present invention may contain additives that are insoluble in hot water among the above additives. Insoluble in hot water means that the mass does not decrease during the above hot water treatment. In one embodiment of the present invention, the adhesive resin composition of the present invention may contain component (A), component (B), and optionally additives that are insoluble in hot water.

[0105] From the viewpoints of easy improvement of hardness and rigidity and easy prevention of adhesion, it is preferable to add a filler. Examples of the filler include inorganic fillers such as mica, kaolin, kaolinite, clay, talc, acid clay, silica, alumina, diatomaceous earth, bentonite, montmorillonite, kibushi clay, frog-eye clay, pyrophyllite, alunite, pottery clay, feldspar, perlite, calcium carbonate, magnesium hydroxide, carbon black, vermiculite, titanium oxide, mica, zirconium oxide, boron nitride, aluminum nitride, shirasu, glass, glass fiber, etc., and organic fillers such as urea-formalin resin, melamine-formalin resin, etc. The filler can be used alone or in combination of two or more kinds.

[0106] 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, (meth)acrylate resins such as polymethyl methacrylate resin, etc. Other resins can be used alone or in combination of two or more kinds.

[0107] The form of the adhesive resin composition of the present invention is not particularly limited and can be pellets, sheets or films. That is, it can be pellets, sheets or films containing or composed of the adhesive resin composition. The thickness of the sheet or film can be appropriately selected according to the use, preferably 5 to 1000 μm, more preferably 10 to 500 μm. The thickness of the film or sheet can be measured using a thickness gauge, for example, by the method described in the examples. In addition, the adhesive resin composition of the present invention can contain a solvent and can also be in the form of a solution or dispersion. As the solvent, a known solvent capable of dissolving or dispersing the components in the composition can be used.

[0108] The method for producing the adhesive resin composition of the present invention is not particularly limited. For example, it can be a method of mixing a biodegradable polyester resin (A), a PVA resin (B) and optional additives, etc. Mixing can be suitably carried out using a conventional mixer, preferably a melt-kneader. In a preferred embodiment of the present invention, an extruder can be used for melt-kneading to obtain the adhesive resin composition.

[0109] As the extruder, a twin-screw extruder can preferably be used. The twin-screw extruder can be either co-rotating or counter-rotating. The rotational speed (revolution speed) of the screw is preferably 20 rpm or more, more preferably 70 rpm, further preferably 150 rpm or more, and generally 1000 rpm or less. The barrel temperature is preferably 40 °C or more, more preferably 80 °C or more, further preferably 100 °C or more, preferably 300 °C or less, and more preferably 200 °C or less. Each component can be directly introduced into the extruder separately. Alternatively, a mixer or the like can be used to premix these components, and the resulting substance can be introduced into the extruder.

[0110] The molten mixture that is extruded in the extruder while being melt-kneaded is extruded from the die head. The temperature of the die head can preferably be 100 to 200 °C, more preferably 100 to 150 °C.

[0111] The specific mechanical energy (SME: Specific Mechanical Energy) (unit: kJ / kg) during melt-kneading is not particularly limited, preferably 400 kJ / kg or more, more preferably 500 kJ / kg or more, preferably 900 kJ / kg or less, and more preferably 800 kJ / kg or less. If the specific mechanical energy is within the above range, it is easy to adjust X / Y to the above range and easy to improve the adhesive strength of the adhesive resin composition. The specific mechanical energy (Ψ) can be calculated by the following formula.

[0112] Ψ = N(RUN) / N(MAX) × Φ / φ(MAX) × Kw / Q (4)

[0113] [In Formula 1, N(RUN) represents the screw rotational speed (unit: rpm), N(MAX) represents the maximum screw rotational speed (unit: rpm), Φ represents the motor torque during the test (unit: N·m), φ(MAX) represents the maximum motor torque (unit: N·m), Kw represents the motor power (unit: kJ / h), and Q represents the discharge rate (unit: kg / h)]

[0114] The extruded mixture (melt) can be extruded into a sheet shape, a film shape, or a wire harness shape. At this time, the mixture (melt) is cooled and dried.

[0115] In the case of extruding the mixture into a wire harness shape, by extruding from a porous wire harness nozzle and cutting with a rotary cutter, the wire harness can be made into a pellet shape. To prevent the pellets from sticking, vibration can be applied regularly or frequently, and moisture in the pellets can be removed by hot air, dehumidified air, or an infrared heater.

[0116] In the case of extruding the mixture into a sheet or film form, the mixture can be extruded from a film-forming die, and then cooled and dried while being wound by a take-up roll. Between the die and the roll, cooling is preferably performed to prevent the mixture from adhering to the roll. It should be noted that a sheet or film form can be produced by forming a film of a solution or dispersion of the adhesive resin composition of the present invention by a conventional film-forming method (such as casting film formation, etc.).

[0117] [Adhesive Resin Composition Containing a Co-continuous Structure]

[0118] The present invention also includes an adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), and having a co-continuous structure formed at least by a phase containing the biodegradable polyester resin (A) and a phase containing the PVA resin (B) (or at least including these phases). Since the adhesive resin composition of the present invention has a specific co-continuous structure, the adhesive strength to both the PVA resin layer and the biodegradable resin layer is excellent. Therefore, it is useful as an adhesive layer between the PVA resin layer and the biodegradable polyester resin layer. In addition, the thermoformability of the adhesive resin composition of the present invention is also excellent, and the obtained laminate can be easily formed into a specified shape. Furthermore, the biodegradability is excellent. Therefore, the adhesive resin composition of the present invention can be suitably used as a packaging material for foods, etc., and an agricultural film.

[0119] In the present specification, the co-continuous structure refers to a network structure (or three-dimensional continuous structure) in which two or more components respectively form continuous phases and are mixed with each other, and can be distinguished from the sea-island structure, columnar structure, and layered structure. This network structure (or three-dimensional continuous structure) does not need to be entirely connected and can be partially interrupted.

[0120] In the present invention, the co-continuous structure is formed by at least 2 phases, the first phase contains the biodegradable polyester resin (A), and the second phase contains the PVA resin (B). In the case where the adhesive resin composition contains additives such as the above-mentioned other resins, etc., the co-continuous structure may also contain other phases, but from the viewpoint of improving the adhesive strength and thermoformability of the adhesive resin composition, this co-continuous structure is preferably formed only by a phase containing the biodegradable polyester resin (A) and a phase containing the PVA resin (B).

[0121] In one embodiment of the present invention, the adhesive resin composition of the present invention preferably has both the above-mentioned co-continuous structure and the above-mentioned sea-island structure, more preferably mainly has the above-mentioned co-continuous structure, and a part thereof has a sea-island structure. In the above-mentioned sea-island structure, the sea part is a biodegradable polyester-based resin (A), and the island part is a PVA-based resin (B). By having such a structure, excellent adhesive strength can be exhibited for both the PVA-based resin layer and the biodegradable resin layer. It is considered that this is because, in the co-continuous structure part, since the PVA-based resin (B) is connected, the adhesive force to the PVA-based resin layer as the adherend can be improved. On the other hand, in the sea-island structure part, since the PVA-based resin (B) is not connected, the strength and toughness of the composition itself can be improved, and a good adhesive force to the biodegradable resin layer can be easily exhibited. The co-continuous structure can be measured by platinum evaporation coating on the cross-section of the sample (adhesive resin composition film) that has undergone the above-mentioned hot water treatment and using SEM, for example, it can be measured by the method described in the examples.

[0122] In the obtained SEM image, as described above, the PVA-based resin (B) is eluted by hot water treatment, and thus, the part where the PVA-based resin (B) exists becomes a void part. For example, in Fig. 13, it can be confirmed that the phase containing the biodegradable polyester-based resin (A) other than the voids and the phase containing the PVA-based resin (B) equivalent to the voids form a co-continuous structure. In addition, it can be confirmed that a part of the sea-island structure is included, in which the phase containing the biodegradable polyester-based resin (A) other than the void part is the sea part, and the phase containing the PVA-based resin (B) equivalent to the void part is the island part.

[0123] As a method for preparing the co-continuous structure, for example, the same method as the method for adjusting Y / X in formula (1) can be cited. That is, by adjusting the types and their contents of component (A) and component (B), the saponification degree and polymerization degree of component (B), and the manufacturing conditions of the adhesive resin composition, etc., for example, appropriately using the types and their contents of the preferred component (A) and component (B), the preferred saponification degree and polymerization degree of component (B), and the preferred manufacturing conditions, etc. described in this specification, an adhesive resin composition having a co-continuous structure can be obtained. In one embodiment of the present invention, the more the content of component (B), the more appropriate the saponification degree of component (B), or the lower the polymerization degree, the easier it is to form a co-continuous structure.

[0124] [Laminated body]

[0125] The present invention includes a laminate comprising an adhesive layer containing the adhesive resin composition of the present invention. The laminate of the present invention may include one or two or more adhesive layers of the present invention. When two or more adhesive layers are included, the compositions of the respective adhesive layers may be the same or different. The form of the adhesive layer is not particularly limited. For example, it may be in the form of a film or a sheet. The laminate may include other layers other than the adhesive layer of the present invention. Examples of the other layers include a resin layer, paper, and other adhesive layers. It should be noted that the resin layer is a resin layer having a composition different from that of the adhesive layer. In addition, the adhesive layer preferably has the "biodegradability" defined above.

[0126] The resin constituting the resin layer is not particularly limited. For example, polyester resins such as polyethylene terephthalate (PET); polyolefin resins such as polypropylene (PP) [preferably biaxially oriented polypropylene (BOPP)], polyethylene (PE) [preferably low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE)]; ethylene-vinyl acetate copolymer; polyvinyl alcohol-based resins such as polyvinyl alcohol and ethylene-α-olefin copolymer; biodegradable resins such as biodegradable polyester resins; and resins obtained by modifying them with modifiers such as maleic anhydride. The resin layers may be used alone or in combination of two or more.

[0127] Since the adhesive layer in the laminate of the present invention contains an adhesive resin composition satisfying formula (1), it can exhibit excellent adhesive strength to both the biodegradable resin layer and the polyvinyl alcohol-based resin layer. Therefore, the laminate of the present invention preferably includes a biodegradable resin layer and / or a polyvinyl alcohol-based resin layer as the resin layer, and more preferably includes a biodegradable resin layer and a polyvinyl alcohol-based resin layer as the resin layer. In addition, from the viewpoint of exhibiting excellent biodegradability, the resin layer in the laminate of the present invention preferably consists only of a biodegradable resin layer and a polyvinyl alcohol-based resin layer. Furthermore, by including the adhesive layer, the laminate of the present invention can improve thermoformability, biodegradability, and gas barrier properties.

[0128] The above biodegradable resin layer is a resin layer having biodegradability as defined above. The biodegradable resin layer is preferably a layer containing a biodegradable resin as a main component. Examples of the biodegradable resin include, in addition to the biodegradable polyester resin described in the above item <Biodegradable polyester resin (A)>, casein, modified starch, cellulose acetate, etc. Among them, from the viewpoint of easily improving the adhesive strength and biodegradability with the adhesive layer, the biodegradable resin is preferably the above biodegradable polyester resin. In addition, from the viewpoints of versatility, biodegradability, and mechanical properties, it is more preferably at least one selected from PLA, PHB, PHBV, 3HB4HB, PHBH, PBAT, PBS, and PCL. In addition, from the viewpoints of strength, heat resistance, and water resistance, it is further preferably PLA and / or PBAT.

[0129] The above PVA-based resin layer is not particularly limited as long as it contains a PVA-based resin as a main component. Examples thereof include the PVA-based resins described in the above item <Polyvinyl alcohol-based resin (B)>. In addition, in one embodiment of the present invention, the PVA-based resin layer may contain a plasticizer such as a polyol (such as trehalose) in addition to the PVA-based resin.

[0130] It should be noted that in this specification, the "main component" means a component contained in an amount of 40% by mass or more, preferably 50% by mass or more, based on the mass of the layer. The amount may be, for example, 55% by mass or more, 70% by mass or more, or 90% by mass or more. In addition, the PVA-based resin layer preferably has the biodegradability defined above.

[0131] The paper is not particularly limited. For example, kraft paper, coarse kraft paper, fine paper, imitation paper, glassine paper, parchment paper, synthetic paper, white cardboard, Manila cardboard, milk carton base paper, cup base paper, ivory paper, silver paper, etc. can be cited.

[0132] Examples of the laminate of the present invention include a laminate sequentially including a biodegradable resin layer / an adhesive layer; a laminate sequentially including a PVA-based resin layer / an adhesive layer; a laminate sequentially including a biodegradable resin layer / an adhesive layer / PVA-based resin layer, etc. Among them, the laminate of the present invention is preferably a laminate sequentially including a biodegradable resin layer / an adhesive layer / PVA-based resin layer (sometimes referred to as laminate A). These laminates may include other layers other than the biodegradable resin layer and the PVA-based resin layer between each layer and on the outside, but it is preferred that no such other layer is included between each layer, that is, each layer is adjacent. For example, in laminate A, the biodegradable resin layer, the adhesive layer, and the PVA-based resin are preferably arranged adjacent to each other in sequence (i.e., in contact). The adhesive strength and biodegradability of the biodegradable resin layer and the adhesive layer, and the adhesive layer and the PVA-based resin layer in laminate A are excellent.

[0133] The thickness of the adhesive layer in the laminate of the present invention can be appropriately selected according to the type of the laminate, and there is no particular limitation. It is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, still further preferably 10 μm or more, particularly preferably 15 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, further preferably 200 μm or less, still further preferably 100 μm or less, particularly preferably 50 μm or less. If the thickness of the adhesive layer is within the above range, it is easy to improve the adhesive strength, thermoformability, biodegradability, and gas barrier properties. In the case where two or more adhesive layers are included in the laminate, the thickness of the above-mentioned adhesive layer represents the thickness of one layer.

[0134] The thickness of other layers (for example, the biodegradable resin layer or the PVA-based resin layer) other than the adhesive layer in the laminate of the present invention can be appropriately selected according to the type of the laminate, and there is no particular limitation. It is preferably 15 to 1000 μm, more preferably 20 to 500 μm, further preferably 30 to 400 μm. If the thickness of the other layer is within the above range, it is easy to improve the adhesive strength, thermoformability, biodegradability, and gas barrier properties. In the case where two or more other layers are included in the laminate, the thickness of the above-mentioned other layer represents the thickness of one layer.

[0135] The thickness of the laminate of the present invention is not particularly limited. It is preferably 50 μm or more, more preferably 70 μm or more, further preferably 100 μm or more, particularly preferably 200 μm or more, especially more preferably 300 μm or more, preferably 5000 μm or less, more preferably 3000 μm or less, further preferably 1000 μm or less. If the thickness of the laminate is within the above range, it is easy to improve the strength, thermoformability, biodegradability, and gas barrier properties of the laminate.

[0136] 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 above-mentioned adhesive layer. In addition, the thickness of the biodegradable resin layer in the laminate A is not particularly limited, preferably 30 μm or more, more preferably 50 μm or more, further preferably 100 μm or more, still more preferably 200 μm or more, preferably 1000 μm or less, more preferably 500 μm or less. In addition, the thickness of the PVA-based resin layer in the laminate A is not particularly limited, preferably 15 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, further preferably 200 μm or less, still more preferably 100 μm or less, particularly preferably 50 μm or less. If the thickness of each layer is within the above range, it is easy to improve the adhesive strength, thermoformability, biodegradability, and gas barrier properties. Regarding the thickness of each layer (biodegradable resin layer, adhesive layer, and PVA-based resin layer) in the above-mentioned laminate A, when there are two or more layers of the same layer in the laminate A, it represents the thickness of one layer. The thickness of each of the above layers and the thickness of the laminate can be measured using a thickness gauge, for example, by the method described in the examples.

[0137] As a specific layer structure of the laminate A of the present invention, the following layer structures can be exemplified.

[0138] Biodegradable resin layer / adhesive layer / PVA-based resin layer; biodegradable resin layer / adhesive layer / PVA-based resin layer / adhesive layer / biodegradable resin layer; biodegradable resin layer / regrind layer / adhesive layer / PVA-based resin layer / adhesive layer / regrind layer / biodegradable resin layer; biodegradable resin layer / adhesive layer / PVA-based resin layer / adhesive layer / paper.

[0139] 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 biodegradable resin layer, the adhesive layer, and the PVA-based resin layer is biodegradable based on ISO 14855, and more preferably at least two layers, and further preferably all layers are biodegradable based on ISO 14855.

[0140] The laminate of the present invention can be manufactured by laminating other layers such as resin layers and the adhesive layer using conventional methods such as co-extrusion molding (co-extrusion lamination method, co-extrusion sheet molding method, co-extrusion blow molding method, co-extrusion blow molding method, etc.), co-injection molding method, extrusion lamination method, dry lamination method, etc. For example, it can be a method of co-extruding or laminating other layers and the adhesive layer; a method of forming a film of an adhesive resin composition on other layers. During lamination, the adhesive resin composition can be coated on the surface of other layers or extrusion-coated on the surface of other layers.

[0141] The manufacturing method of laminate A as a preferred embodiment of the present invention is not particularly limited. A method of co-extruding a granular adhesive resin composition forming an adhesive layer, a granular biodegradable resin (or biodegradable resin composition) forming a biodegradable resin layer, and a granular PVA-based resin (or PVA-based resin composition) forming a PVA-based resin layer using a co-extruder is preferred. More specifically, each resin (or each resin composition) can be introduced into the hopper of each extruder for melt-kneading, and co-extrusion can be performed using a feedblock die. The barrel temperature of each extruder can be appropriately selected according to the melting temperature of the resin (or resin composition). Although not limited, for example, the barrel temperature of the extruder for the adhesive layer can be, for example, 120 to 300°C, preferably 150 to 250°C, the barrel temperature of the extruder for the biodegradable resin layer is, for example, 150 to 300°C, preferably 180 to 250°C, and the barrel temperature of the extruder for the PVA-based resin layer can be, for example, 150 to 300°C, preferably 190 to 260°C.

[0142] In one embodiment of the present invention, a crosslinking agent can be added to the adhesive resin composition of the present invention when obtaining the laminate of the present invention. Examples of the crosslinking agent include epoxy compounds, isocyanate compounds, aldehyde compounds, silica compounds, aluminum compounds, zirconium compounds, boron compounds, etc. Among them, silica compounds such as colloidal silica and alkyl silicate are preferred. The addition amount of the crosslinking agent can be 5 to 60 parts by mass, preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass based on 100 parts by mass of the PVA-based resin. In addition, in one embodiment of the present invention, a stretching treatment can be performed on the laminate of the present invention for the purpose of improving gas barrier properties and mechanical properties.

[0143] The laminate of the present invention also has excellent thermoformability and can be easily formed into a specified shape. In a preferred embodiment, even when thermoformed, wrinkles or the like do not occur, so the appearance is excellent. The forming method is preferably melt forming. As the melt forming method, there is no particular limitation, and examples thereof include an extrusion forming method, an injection molding method, an extrusion film forming method from a T die, a blown film forming method, a compression molding method, a transfer molding method, a reinforced plastic molding method, a hollow molding method, a pressure molding method, a blow molding method, a calendering method, a foaming molding method, a vacuum forming method, a pressure air forming method, and the like. Other thermoplastic resins can also be laminated by methods such as a coextrusion forming method and a lamination forming method according to expectations. By these methods, molded articles of any shape such as films, sheets, tubes, bottles, capsules, non-woven fabrics, and fibers can be obtained. In one embodiment of the present invention, in the case of forming by a vacuum forming method, the laminate can be formed into a desired shape by a vacuum forming machine after heating. The forming temperature is not limited and can be appropriately selected according to the type of the laminate. It is preferably 100 °C or higher, more preferably 130 °C or higher, further preferably 150 °C or higher, preferably 300 °C or lower, and more preferably 200 °C or lower. In such a forming temperature range, it is easy to form a molded article having excellent thermoformability.

[0144] [Food packaging material]

[0145] The uses of the adhesive resin composition and the laminate of the present invention are not particularly limited and can be suitably used as packaging materials, particularly food packaging materials. 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. Since the food packaging material of the present invention contains the adhesive layer or the laminate in the present invention, it has excellent adhesive strength, thermoformability, biodegradability, and gas barrier properties. As the food packaging material, there is no particular limitation, and examples thereof include containers for packaging foods such as meat, fresh noodles, processed foods, black tea, coffee powder, coffee beans, and pickles. In addition, in a preferred embodiment of the present invention, the food packaging material can be a garbage bag for organic waste, a container used in various activities, a tea bag, a coffee capsule, etc., and is particularly suitable for use as a coffee capsule.

[0146] [Agricultural film]

[0147] The adhesive resin composition and the laminate of the present invention have decomposability in the natural environment and excellent gas barrier properties, so they can be suitably used as agricultural films. Therefore, the present invention includes an agricultural film including an adhesive layer containing the adhesive resin composition of the present invention or a laminate of the present invention. As the agricultural film, examples include a mulch film (Japanese: マルチフィルム), a fumigation film, a seedling raising film, a covering film, etc. Among them, it is particularly useful as a fumigation film.

[0148] [Examples]

[0149] Hereinafter, the present invention will be described in further detail by way of examples and comparative examples, but the present invention is not limited by any of these examples.

[0150] It should be noted that the respective measurement methods and evaluation methods in the following examples and comparative examples are shown below.

[0151] [Saponification degree]

[0152] The saponification degrees of the PVA-based resins (B) were determined by the method described in JIS K 6726:1994, respectively.

[0153] [Viscosity-average degree of polymerization]

[0154] The viscosity-average degrees of polymerization of the PVA-based resins (B) were determined by the method described in JIS K 6726:1994, respectively. Specifically, after re-saponifying and purifying each polymer, the intrinsic viscosity [η] (l / g) measured in water at 30°C was used to calculate according to the following formula. It should be noted that in the following formula, the degree of polymerization is denoted as P.

[0155] P = ([η]×10 4 / 8.29) （1 / 0.62）

[0156] [Elongation at break]

[0157] The biodegradable polyester-based resin (A) was hot-pressed to obtain a sheet, and the sheet was cut into a width of 15 mm and a length of 100 mm, and the elongation at break was measured in accordance with ISO527-1.

[0158] [Melting point]

[0159] 10 mg of the adhesive resin composition pellets obtained in each example and comparative example were sealed in an aluminum pan (manufactured by TA Instrument), and after heating from -30°C to 220°C at a rate of 10°C / minute, it was rapidly cooled to -30°C at a rate of 10°C / minute, and then heated from -30°C to 220°C again at a rate of 10°C / minute, thereby performing DSC measurement. In the obtained DSC curve, the melting point Tm (°C) was determined from the peak top temperature in the temperature range from the start to the end of melting during the second heating.

[0160] [MFR]

[0161] For the biodegradable polyester-based resin (A), MFR was measured in accordance with JIS K 7210:2014 at 200°C under a load of 2.16 kg.

[0162] [Mw, Mn]

[0163] The Mw and Mn of the biodegradable polyester resin (A) were measured by the following analytical method for relative molecular weight based on GPC analysis.

[0164] <Adjustment of sample>

[0165] Collect about 5 mg of powder sample of the biodegradable polyester resin (A) and weigh it accurately. To the collected sample, add 1 ml of hexafluoroisopropanol (HFIP) containing 20 mM sodium trifluoroacetate per 0.1 mg of the sample, and heat it at 40 °C for 3 hours to dissolve it. Using this solution, GPC analysis was performed under the following conditions. The calculation of the relative molecular weight distribution curve was carried out by converting the relative molecular weight determined by the RI detector using the analysis software attached to the analytical device. The same sample was analyzed 3 times, and the average value was taken as the analysis result.

[0166] <GPC analysis conditions>

[0167] Measuring device: HLC-8320GPC (manufactured by TOSOH Corporation)

[0168] Analysis software: Empower (manufactured by Waters Corporation)

[0169] Sample concentration: 0.1 mg / ml

[0170] Mobile phase solvent: Hexafluoroisopropanol containing 20 mM sodium trifluoroacetate

[0171] Injection volume: 10 μl

[0172] Flow rate: 0.2 ml / min

[0173] Measuring temperature: 40 °C

[0174] Sample dissolution conditions: 40 °C × 3 hours

[0175] Filter filtration: 0.45 μm PTFE filter

[0176] Column: 2 pieces of GMMHR-H(S) (manufactured by TOSOH Corporation)

[0177] Detector: RI detector attached to the device

[0178] Standard for device calibration: PMMA (manufactured by Agilent Corporation)

[0179] [Thickness]

[0180] The thicknesses of the films, laminates formed from the adhesive resin composition, and each layer in the laminate in Examples and Comparative Examples were measured using a digital micrometer.

[0181] [Measurement of (Y / X)]

[0182] Regarding Y / X, the measurement is performed as follows.

[0183] First, the pellets of the adhesive resin composition obtained in the examples and comparative examples were preheated at 180 °C for 5 minutes using a compression molding machine, and then compression molded for 30 seconds under the condition of a load of 50 kgf / cm 2 to obtain a film formed of the adhesive resin composition with a thickness of 300 μm. The above film was cut into 10 mm squares to obtain a sample for mass measurement with a length of 10 mm × a width of 10 mm × a thickness of 300 μm. At this time, the value obtained by the following calculation formula (2) was set as X.

[0184] X = (mass of the sample for mass measurement) × (proportion of the polyvinyl alcohol-based resin (B) contained in the adhesive resin composition (mass%)) / 100 (2)

[0185] The obtained sample for mass measurement (about 0.03 g) was added to a 50 cc screw tube, and 20 ml of distilled water at 23 °C was further added. The screw tube containing the sample for mass measurement and 20 ml of distilled water was placed in a hot air dryer set at 80 °C. After 30 minutes, when it was confirmed that the distilled water reached 80 °C, it was further left standing for 1 hour. Then, in order to remove the eluted components located in the pores and on the surface, the sample was gently shaken with tweezers, and the sample for mass measurement was taken out from the screw tube and further placed in a hot air dryer set at 80 °C and left standing for 1 hour to obtain a sample after heat treatment with hot water. At this time, the value obtained by the following calculation formula (3) was set as Y. In the examples and comparative examples, since the component eluted during the heat treatment with hot water was only polyvinyl alcohol (B), the value Y obtained according to the following calculation formula (3) can be regarded as the mass of polyvinyl alcohol (B) extracted into the hot water.

[0186] Y = (mass of the sample for mass measurement) - (mass of the sample after heat treatment with hot water) (3)

[0187] Using the obtained values of X and Y, Y / X representing the proportion of the polyvinyl alcohol-based resin (B) contained in the adhesive resin composition that decreased during the heat treatment with hot water was calculated. The results are shown in Table 2.

[0188] [SEM image]

[0189] In Example 2, Example 13, and Comparative Example 1, the SEM images of the above samples after heat treatment with hot water were measured under the following conditions. The sample after heat treatment with hot water having platinum vapor-deposited on the cross section was placed on the sample stage of an SEM (VE9800, manufactured by KEYENCE CORPORATION), and observed under the condition of an acceleration voltage of 5 kV. Each SEM image is shown in Figures 1 to 3 . In Example 2 ( Figure 1), and Example 13 ( Figure 3 ), it was confirmed that the phase containing the biodegradable polyester resin (A) other than the void portion and the phase containing the PVA resin (B) corresponding to the void portion formed a co-continuous structure. In addition, it was confirmed that a sea-island structure (sea: biodegradable polyester resin (A), island: PVA resin (B)) partially coexisted. In Comparative Example 1 ( Figure 2 ), it was confirmed that a sea-island structure was formed.

[0190] [Diameter of pores]

[0191] Except for Example 2, Example 13, and Comparative Example 1, SEM images were also obtained for Examples 1, 4, and 5 by the above method. Ten pores were randomly selected from the SEM images observed in Examples 1, 2, 4, 5, and Comparative Example 1, and their diameters were measured, and the average value was taken as the diameter of the pores. It should be noted that in the case of the structure of Example 2 as in Figure 1 , sometimes multiple pores were connected, and the diameters of the pores that were circular in the SEM image were measured.

[0192] [Adhesive strength of the adhesive resin composition to the PVA resin layer]

[0193] Using a compression molding machine, the pellets of the adhesive resin composition obtained in the examples and comparative examples were preheated at 180 °C for 5 minutes, and then compression molded for 30 seconds under the condition of a load of 50 kgf / cm 2 . Thus, a film (also referred to as an adhesive layer) formed of the adhesive resin composition was obtained. A film formed of the adhesive resin composition (150 mm in length × 150 mm in width × 0.3 mm in thickness), a polyimide film ("Kapton film" manufactured by Du Pont-Toray Co., Ltd., 75 mm in length × 150 mm in width × 0.05 mm in thickness), and a film containing a polyvinyl alcohol resin (also referred to as a PVA resin layer) ("Mowiflex C17" manufactured by Kuraray Co., Ltd., 150 mm in length × 150 mm in width × 0.5 mm in thickness) were sequentially overlapped and placed at the center of a metal spacer having an inner size of 150 mm × 150 mm and a thickness of 0.8 mm. The overlapped film and the metal spacer were clamped with a polytetrafluoroethylene sheet, and further clamped with a metal plate from the outside. Using a compression molding machine, compression molding was performed at 180 °C and a load of 50 kgf / cm 2 for 30 seconds. Thus, a multilayer sheet containing an adhesive layer and a PVA resin layer was obtained.

[0194] The multi-layer sheet was cut into 25 mm in width to obtain test pieces for measuring the adhesive strength. According to JIS K 6854-1:1999, using a peel tester ("AGS-X" manufactured by Shimadzu Corporation), the peel strength between the adhesive layer and the PVA resin layer was measured under the conditions of a peel angle of 90°, a tensile speed of 50 mm / minute, and an ambient temperature of 23°C, and this was taken as the adhesive strength of the adhesive resin composition. In addition, the adhesive strength was evaluated using the following criteria. The results are shown in Table 2.

[0195] ◎: The peel strength is 20 N / 25 mm or more

[0196] ○: The peel strength is 10 N / 25 mm or more and less than 20 N / 25 mm

[0197] △: The peel strength is 4 N / 25 mm or more and less than 10 N / 25 mm

[0198] ×: The peel strength is less than 4 N / 25 mm

[0199] [Adhesive strength of the adhesive resin composition to the biodegradable resin layer]

[0200] Using a compression molding machine, the pellets of the adhesive resin compositions obtained in the examples and comparative examples were preheated at 180°C for 5 minutes and then compression molded for 30 seconds under the condition of a load of 50 kgf / cm 2 to obtain a film formed of the adhesive resin composition (also referred to as the adhesive layer). A film formed of the adhesive resin composition (150 mm in length × 150 mm in width × 0.3 mm in thickness), a polyimide film ("Kapton film" manufactured by DU PONT-TORAY Co., Ltd., 75 mm in length × 150 mm in width × 0.05 mm in thickness), and a film containing a biodegradable resin (also referred to as the biodegradable resin layer) (manufactured by Natureworks LLC, "Ingeo (registered trademark) biopolymer 2003D", 150 mm in length × 150 mm in width × 0.5 mm in thickness) were sequentially overlapped and placed at the center of a metal spacer having an inner size of 150 mm × 150 mm and a thickness of 0.8 mm. The overlapped films and the metal spacer were clamped with a PTFE sheet and further clamped with a metal plate from the outside, and using a compression molding machine, compression molding was performed at 180°C and a load of 50 kgf / cm 2 for 30 seconds to obtain a multi-layer sheet including an adhesive layer and a biodegradable resin layer.

[0201] The multi-layer sheet was cut into 25 mm widths to obtain test pieces for measuring the adhesive strength. In accordance with JIS K 6854-1:1999, using a peel tester ("AGS-X" manufactured by Shimadzu Corporation), the peel strength between the adhesive layer and the biodegradable resin layer was measured under the conditions of a peel angle of 90°, a tensile speed of 50 mm / minute, and an ambient temperature of 23°C, and this was taken as the adhesive strength of the adhesive resin composition. In addition, the adhesive strength was evaluated using the following criteria. The results are shown in Table 2.

[0202] ◎: The peel strength is 55 N / 25 mm or more

[0203] ○: The peel strength is 15 N / 25 mm or more and less than 55 N / 25 mm

[0204] △: The peel strength is 9 N / 25 mm or more and less than 15 N / 25 mm

[0205] ×: The peel strength is less than 9 N / 25 mm

[0206] [Thermoformability]

[0207] After heating the laminates obtained in the examples and comparative examples to 160°C using a vacuum forming machine ("Formech508DT" manufactured by Formech), they were formed into a capsule shape with a diameter of 5 cm and a depth of 3 cm. The obtained formed products were visually observed, and the thermoformability was evaluated according to the following criteria.

[0208] 〇: It can be formed without problems

[0209] △: It becomes a capsule shape, but some wrinkles are generated

[0210] ×: It is difficult to form

[0211] [Production Example 1]

[0212] [Production of vinyl alcohol polymer (B1)]

[0213] 630 parts by mass of vinyl acetate and 2520 parts by mass of methanol were charged into a 250 L reaction vessel equipped with a stirrer, a nitrogen inlet, and an initiator addition port. After heating to 60 °C, nitrogen replacement of the system was carried out by nitrogen bubbling for 30 minutes. After adjusting the internal temperature of the above flask to 60 °C, 0.5 parts by mass of AIBN was added to initiate 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 cooling was carried out to stop the polymerization. The 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 400 parts by mass of a methanol solution of PVAc (100 parts by mass of PVAc in the solution) was obtained. 4.6 parts by mass (molar ratio [MR] 0.01 relative to the vinyl acetate units in PVAc) of an alkali solution (10% by mass methanol solution of NaOH) was added thereto, and saponification was carried out at 40 °C. After adding the alkali, the gelled substance was pulverized with a pulverizer. After a total of 1 hour of saponification reaction, 1000 parts by mass of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 parts by mass of methanol was added to the white solid PVA polymer obtained by filtration, and it was left to wash at room temperature for 3 hours. After repeating the above washing operation 3 times, the PVA polymer obtained by centrifugal dewatering was placed in a dryer at 70 °C for 2 days for drying, and thus an ethylene alcohol polymer (B1) (referred to as PVA1) having a viscosity-average degree of polymerization of 300 and a saponification degree of 88.0 mol% was obtained.

[0214] [Production Examples 2 to 8]

[0215] [Production of ethylene alcohol polymers (B2) to (B8)]

[0216] By changing the ratio of vinyl acetate to methanol, the polymerization conditions of the polymerization rate, and the saponification conditions of the alkali solution addition amount, ethylene alcohol polymers (B2) to (B8) (referred to as PVA2 to 8) having the degree of polymerization and saponification degree shown in Table 2 were thus obtained.

[0217] [Production Example 9]

[0218] [Production of ethylene-vinyl alcohol copolymer (B9)]

[0219] A continuous polymerization tank equipped with a reflux condenser, a raw material supply pipeline, a reaction liquid discharge pipeline, a thermometer, a nitrogen inlet, an ethylene inlet, and stirring blades was used. Vinyl acetate was continuously supplied to the continuous polymerization tank 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, respectively, using metering pumps. The ethylene pressure in the polymerization tank was adjusted to 0.69 MPa. The polymerization liquid was continuously withdrawn from the continuous polymerization tank in such a way that the liquid level in the polymerization tank was constant. Adjustment was made so that the polymerization rate at the outlet of the continuous polymerization tank became 67%. The residence time of the continuous polymerization tank was 5 hours. The temperature at the outlet of the continuous polymerization tank was 60 °C. The polymerization liquid was recovered from the continuous polymerization tank, and while being heated to 75 °C in a warm water bath, methanol vapor was introduced into the polymerization liquid to remove the remaining vinyl acetate, obtaining a methanol solution of an ethylene-vinyl ester copolymer. Then, at 40 °C, the water content of the system to be supplied to the saponification process was set to 0.5%, and sodium hydroxide was used as a saponification catalyst at a ratio of 0.02 in terms of molar ratio with respect to the ethylene-vinyl ester copolymer, and a saponification reaction was carried out for 1 hour. The obtained polymer was immersed in methanol for washing. Then, after centrifugally separating and removing the solvent, drying was carried out, thereby obtaining an ethylene-vinyl alcohol copolymer (B9) having an ethylene unit content of 10 mol%, a viscosity-average degree of polymerization of 400, and a saponification degree of 98.5 mol%.

[0220] [Example 1]

[0221] <Adhesive resin composition>

[0222] Using a twin-screw extruder KZW15-45MG (D = 15 mmφ, L / D = 45, manufactured by TECHNOVEL Co., Ltd.), 80 parts by mass of polybutylene adipate terephthalate (BASF's "Ecoflex C1200", melting point: 118 °C, elongation at break: 1012%, MFR: 15.8 g / 10 min, Mw: 72000, Mn: 24500) as a biodegradable polyester resin (A) and 20 parts by mass of PVA1 obtained in Production Example 1 as a PVA resin (B) were melt-kneaded under the following conditions. After the melt-kneaded product was extruded from a 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, and the result was 526 kJ / kg.

[0223]

Table 1

[0224]

[0225] Screw rotation speed: 250 rpm

[0226] Discharge: 3.5 kg / h

[0227] Operation mode: same-direction same-rotation fully meshing type

[0228] <Laminate>

[0229] A 3-kind 5-layer laminate in which a biodegradable resin layer / adhesive layer / polyvinyl alcohol-based resin layer / adhesive layer / biodegradable resin layer are laminated in sequence is produced by the following method.

[0230] Pellets of the above-obtained adhesive resin composition, pellets of a polyvinyl alcohol-based resin composition (a composition obtained by kneading 100 parts by mass of ethylene-vinyl alcohol copolymer (B9) / 67 parts by mass of trehalose with a twin-screw extruder), and pellets of polylactic acid (manufactured by Natureworks, Ingeo (registered trademark), biopolymer 2003D) are respectively put into the hopper of a single-screw extruder (manufactured by G.M. ENGINEERING, VGM25-28EX), and co-extruded at a flow rate of 5 kg / h using a feedblock die to obtain a 3-kind 5-layer laminate with a width of 20 cm. At this time, the set barrel temperatures are as follows.

[0231] (Barrel temperature)

[0232] Adhesive layer: 180 °C, polyvinyl alcohol-based resin layer: 210 °C, biodegradable resin layer: 220 °C

[0233] The structure of the obtained laminate is from the outside: 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).

[0234] [Examples 2 to 10, 12, 13 and Comparative Examples 1 to 4]

[0235] The types and blending amounts of the biodegradable polyester resin (A) and the PVA resin (B) were changed as shown in Table 2 during the production of the adhesive resin composition. Other than that, the adhesive resin composition and the laminate were obtained in the same manner as in Example 1. It should be noted that in Table 2, PCL represents polycaprolactone ("Capa6800" manufactured by Ingevity Corporation, melting point: 60°C, elongation at break: 800%, MFR: 2.4 g / 10 min), and PLA represents polylactic acid ("Ingeo (trademark) Biopolymer 2003D" manufactured by NatureWorks, melting point: 153°C, elongation at break: 6%, MFR: 6 g / 10 min). In addition, PBAT, PCL, and PLA used in the examples and comparative examples meet the biodegradability criteria specified in EN13432, ASTM6400, and ISO14855. Furthermore, in the laminates obtained in the examples and comparative examples, the biodegradable resin layer, the adhesive layer, and the polyvinyl alcohol resin layer all meet the biodegradability criteria in ISO14855.

[0236] [Example 11]

[0237] The blending amounts and specific mechanical energy (SME) of the biodegradable polyester resin (A) and the PVA resin (B) were changed as shown in Table 2 during the production of the adhesive resin composition. Other than that, the adhesive resin composition and the laminate were obtained in the same manner as in Example 1. It should be noted that when changing the specific mechanical energy (SME) as shown in Table 2, the discharge amount was changed to 2.0 kg / h.

[0238] According to the above method, (Y / X) was measured for each adhesive resin composition obtained in the examples and comparative examples, and the peel strength with respect to the PVA resin layer and the biodegradable resin layer was measured to evaluate the adhesive strength. In addition, the thermoformability of each laminate obtained in the examples and comparative examples was evaluated. The results are shown in Table 2. It should be noted that in Table 2, ※1 indicates that the film (adhesive layer) formed from the adhesive resin composition was damaged before peeling in the peel test, that is, cohesive failure. The value in the peel strength column of ※1 represents the strength at the time of cohesive failure. Since the peel strength is a larger value, the peel strength at the time of cohesive failure is expressed as "value <".

[0239]

Table 2

[0240]

[0241] As shown in Table 2, it was confirmed that the evaluation of the adhesive strength of the adhesive resin compositions of Examples 1 to 13 with respect to the PVA resin layer and the biodegradable resin layer was higher than that of Comparative Examples 1 to 4. Therefore, the adhesive strength of the adhesive resin composition of the present invention is excellent.

[0242] In addition, it was confirmed that the laminates of Examples 1 to 13 could be easily formed into a desired shape. In particular, the laminates of Examples 1 to 8, 10, and 11 to 13 could be formed into a desired shape without generating wrinkles or the like. Therefore, the thermoformability of the laminate containing the adhesive resin composition of the present invention is excellent.

[0243] [Example 14]

[0244] <Laminate>

[0245] A 5-layer laminate composed of a biodegradable resin layer / adhesive layer / polyvinyl alcohol-based resin layer / adhesive layer / biodegradable resin layer laminated in this order was produced by the following method.

[0246] Pellets of the adhesive resin composition obtained in Example 2, pellets of a polyvinyl alcohol-based resin composition (a composition obtained by kneading 100 parts by mass of ethylene-vinyl alcohol copolymer (B9) and 67 parts by mass of trehalose with a twin-screw extruder), and pellets of polybutylene adipate terephthalate (PBAT) ("Ecoflex C1200" manufactured by BASF) were respectively put into the hopper of a single-screw extruder (VGM25-28EX manufactured by G.M. ENGINEERING), and co-extruded at a flow rate of 1 kg / h using a feed block die to obtain a 5-layer laminate with a width of 15 cm. At this time, the set barrel temperatures were as follows.

[0247] (Barrel temperature)

[0248] Adhesive layer: 180 °C, Polyvinyl alcohol-based resin layer: 210 °C, Biodegradable resin layer: 180 °C

[0249] The structure of the obtained laminate was PBAT layer / adhesive layer / polyvinyl alcohol-based resin layer / adhesive layer / PBAT layer = 35 μm / 5 μm / 15 μm / 5 μm / 35 μm (thickness) from the outside.

[0250] In the above evaluation of [Thermoformability], the heating temperature was changed from "160 °C" to "110 °C", and the thermoformability of the laminate obtained in Example 14 was evaluated by the same method except for this.

[0251]

Table 3

[0252]

[0253] As shown in Table 3, the laminate of Example 14 does not generate wrinkles or the like and can be formed into a desired shape, so it has excellent thermoformability. In the laminate of Example 12, the biodegradable resin layer (PBAT layer), the adhesive layer, and the polyvinyl alcohol-based resin layer all satisfy the biodegradability standard in ISO 14855. In addition, the laminate of Example 14 has a high adhesive strength between the PVA-based resin layer and the biodegradable resin layer (PBAT layer).

Claims

1. An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), wherein the adhesive resin composition satisfies formula (1): 0.30 ≤ Y / X ≤ 0.99 (1) In formula (1), X represents the mass of the polyvinyl alcohol resin (B) contained in a film with a thickness of 300 μm formed from the adhesive resin composition, and Y represents the mass of the polyvinyl alcohol resin (B) extracted by hot water when the film is immersed in pure water at 80°C for 1 hour for extraction treatment of soluble components.

2. The adhesive resin composition according to claim 1, wherein the saponification degree of the polyvinyl alcohol resin (B) is 75 mol% to 96 mol%.

3. The adhesive resin composition according to claim 1 or 2, wherein the elongation at break of the biodegradable polyester resin (A) measured according to ISO 527-1 is 50% or more.

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

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

6. The adhesive resin composition according to any one of claims 1 to 5, wherein the biodegradable polyester resin (A) contains an aromatic-aliphatic copolyester resin.

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

8. The adhesive resin composition according to any one of claims 1 to 7, wherein when a film with a thickness of 300 μm formed from the adhesive resin composition is immersed in pure water at 80°C for 1 hour for extraction treatment of soluble components, the diameter of the pores formed is 10 μm or less.

9. An adhesive resin composition comprising a biodegradable polyester resin (A) and a polyvinyl alcohol resin (B), having a co-continuous structure formed at least by a phase containing the biodegradable polyester resin (A) and a phase containing the polyvinyl alcohol resin (B).

10. A laminate comprising an adhesive layer containing the adhesive resin composition according to any one of claims 1 to 9.

11. The laminate according to claim 10, which sequentially comprises a biodegradable resin layer, the adhesive layer, and a polyvinyl alcohol resin layer.

12. The laminate according to claim 11, wherein the biodegradable resin layer, the adhesive layer, and the polyvinyl alcohol resin layer all meet the criteria for biodegradability according to ISO14855.

13. A food packaging material comprising an adhesive layer containing the adhesive resin composition according to any one of claims 1 to 9, or the laminate according to any one of claims 10 to 12.

14. An agricultural film comprising an adhesive layer containing the adhesive resin composition according to any one of claims 1 to 9, or the laminate according to any one of claims 10 to 12.

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