Laminate

Abstract

The invention described below is provided as a laminate that has excellent coextrusion moldability, oxygen barrier properties, and mechanical strength.　A laminate comprising at least two layers, including a resin composition layer α that contains a polyester-based resin (A) and a resin composition layer β that contains a polyvinyl-alcohol-based resin (B), wherein the melting point of the resin composition that contains the polyester-based resin (A) is 150°C or lower, and the melting point of the resin composition that contains the polyvinyl-alcohol-based resin (B) is 180°C or lower.

Description

Laminate

[0001] The present invention relates to a laminate, and more particularly to a laminate having good coextrusion moldability, oxygen barrier properties, and mechanical strength.

[0002] Conventionally, resin films such as polyamide resins, polyester resins, and polyolefin resins have been used as packaging materials. However, when it comes to foods, beverages, pharmaceuticals, chemicals, and other products whose quality is deteriorated by oxygen, films made of the above resins alone do not provide sufficient oxygen barrier properties. Therefore, laminated structures in which materials with oxygen barrier properties are combined by coating, laminating, co-extrusion, or the like are widely used.

[0003] For example, Patent Document 1 discloses a laminate structure having a layer containing a polyvinyl alcohol-based resin (hereinafter, polyvinyl alcohol may be referred to as "PVA") and a layer containing a thermoplastic resin (polyester-based resin), the layer containing a PVA-based resin obtained by modifying the PVA-based resin.

[0004] Furthermore, Patent Document 2 discloses a biodegradable laminate in which a PVA-based resin is laminated on at least one surface of an aliphatic polyester-based resin layer via an adhesive layer.

[0005] Furthermore, Patent Document 3 discloses a laminate comprising a gas barrier layer containing a PVA-based resin containing a specific structure as a main component, and an aliphatic polyester layer.

[0006] JP 2006-312313 A JP 2013-212682 A JP 2009-196287 A

[0007] In Patent Documents 1 and 2, laminates are produced by co-extrusion molding a polyester-based resin and a PVA-based resin. While typical PVA-based resins have a melting point of 185°C or higher, the inventors have found through their studies that the following problems may arise when a polyester-based resin having a melting point of 150°C or lower is used. In this case, the T-die processing temperature during co-extrusion molding must be 190°C or higher. The inventors have found that polyester-based resins, which have a lower melting point than the PVA-based resin, suffer from drawdown due to thermal decomposition, resulting in problems with co-extrusion moldability. Further studies by the inventors have revealed that, while it is conceivable to perform co-extrusion molding at a low temperature by lowering the melting point of the PVA-based resin, as in Patent Document 3, when the melting point of the polyester is 150°C or lower, there is a limit to how much the melting point of the PVA-based resin can be lowered, making it impossible to reduce the difference in melting points. This results in problems such as poor appearance and poor mechanical properties, making it difficult to achieve both co-extrusion moldability and barrier properties. Furthermore, if the viscosity of the PVA-based resin is too high during co-extrusion at low temperatures, poor appearance such as flow marks or orange peel will occur. On the other hand, if the viscosity is too low, the strength of the multilayer laminate will be weakened, raising concerns about the occurrence of cracks or breakage of the laminate.

[0008] Under these circumstances, the present invention provides a laminate having good co-extrusion moldability, oxygen barrier properties, and mechanical strength.

[0009] In view of the above circumstances, the present inventors have conducted extensive research and have found that a laminate comprising at least two layers, namely a resin composition layer containing a polyester-based resin and a resin composition layer containing a PVA-based resin, can be obtained that has good co-extrusion moldability, oxygen barrier properties, and mechanical strength by setting the melting points of the resin composition containing the polyester-based resin at a specific temperature or lower and the resin composition containing the polyvinyl alcohol-based resin at a specific temperature or lower.

[0010] That is, the present invention has the following aspects. [1] A laminate comprising at least two layers, a resin composition layer α containing a polyester-based resin (A) and a resin composition layer β containing a polyvinyl alcohol-based resin (B), wherein the resin composition containing the polyester-based resin (A) has a melting point of 150°C or less, and the resin composition containing the polyvinyl alcohol-based resin (B) has a melting point of 180°C or less. [2] The laminate according to [1], wherein the resin composition containing the polyvinyl alcohol-based resin (B) has a melt flow rate (210°C, 2160 g) of 3.0 to 60.0 g / 10 min. [3] The laminate according to [1] or [2], wherein the melting point of the polyester-based resin (A) is 150°C or less. [4] The laminate according to any one of [1] to [3], wherein the polyvinyl alcohol-based resin (B) has a melting point of 180°C or less and a melt flow rate (210°C, 2160 g load) of 3.0 to 60.0 g / 10 min. [5] The laminate has an oxygen permeability of 6 cc / m at 20°C and 65% RH. ２The laminate according to any one of [1] to [4], wherein the melting point difference between the polyester-based resin (A) and the polyvinyl alcohol-based resin (B) is 100°C or less. [7] The laminate according to any one of [1] to [6], wherein the polyester-based resin (A) comprises at least one resin selected from the group consisting of aliphatic polyester-based resins and aliphatic-aromatic polyester-based resins. [8] The laminate according to any one of [1] to [7], wherein the laminate has a layer γ between the layer α and the layer β, the layer γ comprising an adhesive resin composition (C), the adhesive resin composition (C) comprising an acid-modified polyester-based resin. [9] The laminate according to any one of [1] to [8], wherein the polyvinyl alcohol-based resin (B) comprises a polyvinyl alcohol-based resin having a primary hydroxyl group in a side chain.

[10] The laminate according to any one of [1] to [9], wherein the polyvinyl alcohol-based resin (B) contains a polyvinyl alcohol-based resin containing 7 to 12 mol% of primary hydroxyl groups in its side chains.

[11] The laminate according to any one of [1] to

[10] , wherein the polyvinyl alcohol-based resin (B) has a degree of saponification of 99.0 mol% or more.

[12] The laminate according to any one of [1] to

[11] , which is a co-extrusion laminate.

[13] A food packaging film comprising the laminate according to any one of [1] to

[11] .

[14] A food container comprising the laminate according to any one of [1] to

[11] .

[15] A beverage container comprising the laminate according to any one of [1] to

[11] .

[16] A resin composition comprising a polyvinyl alcohol-based resin containing 7 to 12 mol% of primary hydroxyl groups in side chains, having a degree of saponification of 99.0 mol% or more, and having a melt flow rate (210°C, 2160 g load) of 3.0 to 60.0 g / 10 min.

[17] The resin composition according to

[16] , which has a melting point of 180°C or less.

[18] The resin composition according to

[16] or

[17] , wherein the polyvinyl alcohol-based resin has a melting point of 180°C or less.

[0011] The present invention provides a laminate having good coextrusion moldability, oxygen barrier properties, and mechanical strength.

[0012] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0013] As used herein, "x and / or y (x and y are any configuration)" refers to at least one of x and y, and can mean three things: x only, y only, or x and y. In this specification, when "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it also means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." In this specification, when "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also means "preferably more than X" or "preferably less than Y." For numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described herein, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0014] In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and may be 100% by mass.

[0015] A laminate according to one embodiment of the present invention (hereinafter, sometimes referred to as "the laminate") is a laminate having a resin composition layer α containing a polyester-based resin (A) and a resin composition layer β containing a PVA-based resin (B), and preferably has a layer γ containing an adhesive resin composition (C) between the layer α and the layer β. Each layer will be described in detail below.

[0016] <Layer α> The layer α used in the present laminate is made of a resin composition containing a polyester-based resin (A). Such layer α preferably contains the polyester-based resin (A) as a main component. The layer α may be made of a single layer or two or more layers. Furthermore, when the layer α is made of two or more layers, the layers may be made of the same polyester-based resin as a main component, or may be made of different polyester-based resins as a main component.

[0017] Examples of the polyester resin (A) include condensation polymers mainly composed of aromatic dicarboxylic acids or their alkyl esters and glycols, and typically those containing ethylene terephthalate as the main repeating unit are preferred. Furthermore, copolymerization components can be contained within a range that does not significantly impair processability, strength, etc. Examples of such copolymerization components include acid components such as aromatic dicarboxylic acids and their ester-forming derivatives, such as isophthalic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, and succinic acid, aliphatic dicarboxylic acids and their ester-forming derivatives, cyclohexanedicarboxylic acid, and hexahydroterephthalic acid, alicyclic dicarboxylic acids and their ester-forming derivatives, p-hydroxybenzoic acid, hydroxycaproic acid, and their ester-forming derivatives, as well as trimellitic acid and pyromellitic acid.

[0018] Examples of the glycol component include aliphatic glycols such as diethylene glycol, trimethylene glycol, tetramethylene glycol, and neopentyl glycol; alicyclic glycols such as 1,4-cyclohexanedimethanol; aromatic glycols such as bisphenol A and alkylene oxide adducts of bisphenol A; polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; and glycerin, 1,3-propanediol, and pentaerythritol.

[0019] The content of ethylene terephthalate units is usually 75 to 100 mol %, preferably 85 to 100 mol %, and the intrinsic viscosity (measured in a 50% by mass / 50% by mass mixed solvent of phenol and tetrachloroethane at 30°C) is usually 0.5 to 1.3 dL / g, preferably 0.65 to 1.2 dL / g.

[0020] A typical example is one in which ethylene terenaphthalate is the main repeating unit. It is also possible to incorporate the same copolymerization components as above, and the ethylene terenaphthalate content is typically 75 to 100 mol %, preferably 85 to 98 mol %. The intrinsic viscosity is typically 0.4 to 1.2 dL / g, preferably 0.55 to 1.0 dL / g.

[0021] Furthermore, it is also preferable to use a blend of the ethylene terephthalate-based polyester resin and the ethylene terenaphthalate-based resin, in terms of improving the gas barrier property, ultraviolet blocking property, and melt moldability. In this case, the blend ratio is 5 to 90 mass%, or even 15 to 85 mass%, of the ethylene terephthalate-based polyester resin, and 95 to 10 mass%, or even 85 to 15 mass% of the ethylene terenaphthalate-based polyester resin.

[0022] In the present embodiment, the polyester resin (A) preferably contains at least one selected from the group consisting of aliphatic polyester resins and aliphatic aromatic polyester resins, from the viewpoint of biodegradability.

[0023] [Aliphatic polyester resin] The aliphatic polyester resin includes an aliphatic polyester resin having an aliphatic diol unit and an aliphatic dicarboxylic acid unit as main structural units, an aliphatic polyester resin having an aliphatic oxycarboxylic acid unit as main structural units, and a mixture thereof. Among these, an aliphatic polyester resin having an aliphatic diol unit and an aliphatic dicarboxylic acid unit as main structural units is preferred.

[0024] Here, "unit" refers to a structural unit derived from a monomer component used in the production of the aliphatic polyester resin and contained in the aliphatic polyester resin, and "main structural unit" refers to a structural unit derived from the target monomer component that accounts for 50 mol% or more of the total structural units of the aliphatic polyester resin. The content of the structural unit derived from the target monomer is preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 to 100 mol%. For example, it is preferable that the aliphatic polyester resin be produced by polymerizing raw materials that contain an aliphatic diol and an aliphatic dicarboxylic acid component in an amount of 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 to 100 mol% of the total monomer components used in the polymerization reaction of the aliphatic polyester resin.

[0025] (Aliphatic polyester resin having aliphatic diol units and aliphatic dicarboxylic acid units as main structural units) The aliphatic polyester resin having aliphatic diol units and aliphatic dicarboxylic acid units as main structural units is, for example, an aliphatic polyester resin having aliphatic diol units represented by the following formula (1) and aliphatic dicarboxylic acid units represented by the following formula (2) as main structural units.

[0026] -O-R 11 -O- (1) [In formula (1), R 11 represents a divalent chain aliphatic hydrocarbon group which may have an oxygen atom in the chain, and when copolymerized, the number of types is not limited to one.

[0027] -OC-R 21 -CO- (2) [In formula (2), R 21 represents a direct bond or a divalent chain aliphatic hydrocarbon group, and when copolymerized, the number of groups is not limited to one.

[0028] The aliphatic diol that provides the diol unit of formula (1) is not particularly limited, but is preferably an aliphatic diol having 2 to 10 carbon atoms, and more preferably an aliphatic diol having 4 to 6 carbon atoms. Specific examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. Of these, 1,4-butanediol is preferred. The aliphatic diols may be used alone or in combination of two or more.

[0029] The aliphatic dicarboxylic acid component that provides the aliphatic dicarboxylic acid unit of formula (2) is an aliphatic dicarboxylic acid or an aliphatic dicarboxylic acid derivative such as an alkyl ester thereof. The aliphatic dicarboxylic acid is not particularly limited, but is preferably, for example, an aliphatic dicarboxylic acid having 2 to 40 carbon atoms, more preferably an aliphatic dicarboxylic acid having 4 to 10 carbon atoms. Specific examples include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, etc. Among these, succinic acid, adipic acid, and sebacic acid are preferred, succinic acid and adipic acid are more preferred, and succinic acid is particularly preferred. The aliphatic dicarboxylic acid components may be used alone or in combination of two or more.

[0030] Specific examples of aliphatic polyester resins having aliphatic diol units and aliphatic dicarboxylic acid units as main constituent units include aliphatic polyester resins containing 1,4-butanediol and succinic acid, and aliphatic polyester resins containing 1,4-butanediol, adipic acid, and succinic acid. More specific preferred examples include polybutylene succinate and polybutylene succinate adipate.

[0031] When the aliphatic dicarboxylic acid is succinic acid, the proportion of the succinic acid-derived constituent units in all dicarboxylic acid units of the aliphatic polyester resin is usually 50 to 100 mol%, preferably 80 to 100 mol%, more preferably 90 to 100 mol%.

[0032] Furthermore, when the aliphatic dicarboxylic acids are succinic acid and adipic acid, the proportion of the succinic acid-derived constituent units in all dicarboxylic acid units of the aliphatic polyester resin is usually 50 to 95 mol%, preferably 60 to 93 mol%, more preferably 70 to 90 mol%, and the proportion of the adipic acid-derived constituent units in all dicarboxylic acid units is usually 5 to 50 mol%, preferably 7 to 40 mol%, more preferably 10 to 30 mol%.

[0033] (Aliphatic Polyester Resin Having an Aliphatic Oxycarboxylic Acid Unit as the Main Structural Unit) Specific examples of the aliphatic oxycarboxylic acid component that provides the aliphatic oxycarboxylic acid unit of the aliphatic polyester resin having an aliphatic oxycarboxylic acid unit as the main structural unit include, for example, lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, 3-hydroxyvaleric acid, malic acid, citric acid, etc., or lower alkyl esters or intramolecular esters thereof. Furthermore, lactone compounds such as ε-caprolactone are also included in the aliphatic oxycarboxylic acid of the present invention. When optical isomers exist, they may be in the D-form, L-form, or racemic form, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 6-hydroxycaproic acid, and 3-hydroxyvaleric acid are preferred. These aliphatic oxycarboxylic acids may be used alone or in combination of two or more.

[0034] Specific examples of aliphatic polyester resins having an aliphatic oxycarboxylic acid unit as the main constituent unit include polylactic acid, polyglycolic acid, poly 3-hydroxybutyrate, poly 4-hydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polycaprolactone, etc.

[0035] The molar ratio of lactic acid contained in polylactic acid is preferably D-lactic acid:L-lactic acid = 100:0 to 85:15, or 0:100 to 15:85. It is also possible to blend other polylactic acids with different ratios of D-lactic acid and L-lactic acid.

[0036] Furthermore, the polylactic acid may be a copolymer of the aforementioned polylactic acid with another hydroxycarboxylic acid, or may contain a small amount of units derived from a chain extender. Examples of other hydroxycarboxylic acids include optical isomers of lactic acid (D-lactic acid for L-lactic acid, and L-lactic acid for D-lactic acid), bifunctional aliphatic hydroxycarboxylic acids such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone. The units derived from such other hydroxycarboxylic acids are preferably used in an amount of less than 15 mol% of the total structural units of the polylactic acid.

[0037] [Aliphatic Aromatic Polyester Resin] The aliphatic aromatic polyester resin is an aliphatic aromatic polyester resin having an aliphatic diol unit, an aliphatic dicarboxylic acid unit, and an aromatic dicarboxylic acid unit as main structural units. The aliphatic aromatic polyester resin component has, for example, an aliphatic diol unit represented by the above formula (1), an aliphatic dicarboxylic acid unit represented by the above formula (2), and an aromatic dicarboxylic acid unit represented by the following formula (3) as essential components. It may further contain the above-mentioned oxycarboxylic acid unit.

[0038] -OC-R 31 -CO- (3) [In formula (3), R 31represents a divalent aromatic hydrocarbon group, and when copolymerized, the number of types is not limited to one.

[0039] The aliphatic diol that provides the diol unit of formula (1) and the aliphatic dicarboxylic acid component that provides the aliphatic dicarboxylic acid unit of formula (2) are the same as those exemplified in the above description of [Aliphatic polyester resin having aliphatic diol units and aliphatic dicarboxylic acid units as main structural units], and the preferred examples are also the same.

[0040] The aromatic dicarboxylic acid component that provides the aromatic dicarboxylic acid unit of formula (3) is not particularly limited, but examples thereof include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid. These may be acid anhydrides. Furthermore, examples of aromatic dicarboxylic acid derivatives include lower alkyl esters of these aromatic dicarboxylic acids. Among these, terephthalic acid, isophthalic acid, or lower alkyl (e.g., alkyl having 1 to 4 carbon atoms) ester derivatives thereof are preferred. These may be used alone or in combination of two or more. Terephthalic acid and / or a methyl ester of terephthalic acid, or a mixture containing terephthalic acid and / or a methyl ester of terephthalic acid and isophthalic acid and / or a methyl ester of isophthalic acid, are particularly preferred.

[0041] Specific examples of aliphatic aromatic polyester resins include polybutylene alkylate terephthalate, more preferably polybutylene adipate terephthalate or polybutylene succinate terephthalate, and particularly preferably polybutylene adipate terephthalate.

[0042] In the present embodiment, the aliphatic polyester resin and the aliphatic aromatic polyester resin may be used alone or in combination of two or more thereof. For example, two or more aliphatic polyester resins having different diol units or dicarboxylic acid units may be mixed and used.

[0043] The weight average molecular weight (Mw) of the polyester resin (A) is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 50,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably 400,000 or less. The range of the weight average molecular weight (Mw) is preferably 10,000 or more and 1,000,000 or less. The weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0044] The melt flow rate (MFR) of the polyester resin (A), measured at 190°C and 2.16 kg, is usually 0.1 g / 10 min or more, preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and usually 1000 g / 10 min or less, preferably 500 g / 10 min or less, more preferably 100 g / 10 min or less, and even more preferably 50 g / 10 min or less. The range of such melt flow rate (MFR) is usually 0.1 g / 10 min or more and 1000 g / 10 min or less.

[0045] The layer α used in the present laminate is composed of a resin composition containing a polyester-based resin (A), and the melting point of the resin composition containing the polyester-based resin (A) is 150°C or lower, preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower. The lower limit is not particularly limited, but is usually 70°C. The melting point of the resin composition containing the polyester-based resin (A) is usually in the range of 70°C or higher and 150°C or lower. If the melting point is too low, coextrusion moldability tends to deteriorate.

[0046] The melting point of the polyester resin (A) is preferably 150°C or lower, more preferably 140°C or lower, even more preferably 130°C or lower, and particularly preferably 120°C or lower. The lower limit is not particularly limited, but is usually 70°C. If the melting point is too low, co-extrusion moldability tends to deteriorate. The melting point range of the polyester resin (A) is usually 70°C or higher and 150°C or lower.

[0047] The acid value of the polyester resin (A) is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.8 or less, and is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 1.0 or more. The acid value ranges from 0.3 to 2.5. When the acid value of the polyester resin (A) is equal to or higher than the lower limit, thermal decomposition tends to be suppressed, and when the melting point is equal to or lower than the upper limit, stability during melt molding tends to be improved.

[0048] Furthermore, it is preferable that the polyester resin (A) does not contain a polyester resin having an acid value higher than that of the adhesive resin composition (C) described below. Specifically, the acid value of the polyester resin (A) is preferably lower than that of the adhesive resin composition (C) by 0.5 or more, more preferably by 2.0 or more.

[0049] The melt flow rate (MFR) of the resin composition containing the polyester resin (A), measured at 190°C and 2.16 kg, is usually 0.1 g / 10 min or more, preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and usually 1000 g / 10 min or less, preferably 500 g / 10 min or less, more preferably 100 g / 10 min or less, and even more preferably 50 g / 10 min or less. The range of such melt flow rate (MFR) is usually 0.1 g / 10 min or more and 1000 g / 10 min or less.

[0050] Layer α can further contain other thermoplastic resins and additives to the extent that the various properties are not significantly impaired. Examples of thermoplastic resins include MXD-6 nylon, polycarbonate, polyarylate, and liquid crystal polymers. Examples of additives include heat stabilizers, antioxidants, ultraviolet absorbers, crystal nucleating agents, antistatic agents, flame retardants, plasticizers, lubricants, fillers, lubricants, and crystal nucleating agents. These can be used alone or in combination of two or more. When other thermoplastic resins or additives are added, the content thereof is typically 10% by mass or less, and more preferably 5% by mass or less, relative to Layer α.

[0051] <Layer β> The layer β used in the present laminate contains a PVA-based resin (B). The layer β preferably contains the PVA-based resin (B) as a main component. If the content of the PVA-based resin (B) is too low, the oxygen barrier property tends to be insufficient. The layer β may be composed of a single layer or two or more layers. Furthermore, when the layer β is composed of two or more layers, the layers may be composed of the same PVA-based resin as a main component, or may be composed of PVA-based resins having different degrees of saponification, ethylene contents, etc. as main components.

[0052] The PVA-based resin (B) is a resin mainly composed of vinyl alcohol structural units, which is obtained by saponifying a polyvinyl ester-based resin obtained by polymerizing a vinyl ester-based monomer, and is composed of vinyl alcohol structural units and vinyl ester structural units in amounts corresponding to the degree of saponification.

[0053] Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl versatate, with vinyl acetate being economically preferred.

[0054] The average degree of polymerization of the PVA-based resin (B) (measured in accordance with JIS K6726-1994) is preferably 200 to 1,800, more preferably 300 to 1,500, and even more preferably 300 to 1,000.

[0055] The melt flow rate (MFR) (210°C, 2160 g load) of the PVA-based resin (B) is usually 3.0 to 63.0 g / 10 min, preferably 3.0 to 60.0 g / 10 min, more preferably 3.5 to 50.0 g / 10 min, even more preferably 4.0 to 45.0 g / 10 min, and particularly preferably 4.5 to 40.0 g / 10 min. Having an MFR value within the above range tends to suppress the occurrence of poor appearance or the occurrence of breakage or cracking of the laminate.

[0056] The layer β used in the present laminate is made of a resin composition containing a PVA-based resin (B). The melt flow rate (MFR) (210°C, 2160 g load) of the resin composition containing the PVA-based resin (B) is typically 3.0 to 63.0 g / 10 min, preferably 3.0 to 60.0 g / 10 min, more preferably 3.5 to 50.0 g / 10 min, even more preferably 4.0 to 45.0 g / 10 min, and particularly preferably 4.5 to 40.0 g / 10 min. Having an MFR value within the above range tends to suppress the occurrence of poor appearance or the occurrence of breakage or cracking of the laminate. The MFR can be measured, for example, by the method described in the Examples below.

[0057] The melting point of the resin composition containing the PVA-based resin (B) is 180°C or lower, preferably 178°C or lower, more preferably 175°C or lower, even more preferably 173°C or lower, and particularly preferably 170°C or lower. The lower limit is 150°C or higher. The melting point of the resin composition containing the PVA-based resin (B) is usually in the range of 150°C or higher to 180°C or lower. A melting point of 180°C or lower tends to make it difficult for unmelted material to be generated during melt molding. The melting point can be measured, for example, by the method described in the Examples below.

[0058] The melting point of the PVA-based resin (B) is usually 180°C or lower, preferably 178°C or lower, more preferably 175°C or lower, even more preferably 173°C or lower, and particularly preferably 170°C or lower. The lower limit is 150°C or higher. If the melting point is too high, unmelted material tends to be generated during melt molding. The melting point of the PVA-based resin (B) is usually in the range of 150°C or higher and 180°C or lower. The melting point can be measured, for example, by the method described in the Examples below.

[0059] The melting point difference between the resin composition containing the polyester-based resin (A) and the resin composition containing the PVA-based resin (B) is usually 100° C. or less, preferably 95° C. or less, more preferably 90° C. or less, even more preferably 85° C. or less, and particularly preferably 80° C. or less. The melting point difference is usually in the range of 0° C. or more and 100° C. or less. When the melting point difference is within the above range, the resin temperature difference during processing can be reduced, which tends to result in good moldability.

[0060] The melting point difference between the polyester resin (A) and the PVA resin (B) is usually 100° C. or less, preferably 95° C. or less, more preferably 90° C. or less, even more preferably 85° C. or less, and particularly preferably 80° C. or less. The melting point difference is usually in the range of 0° C. or more and 100° C. or less. When the melting point difference is within the above range, the resin temperature difference during processing can be reduced, which tends to improve moldability.

[0061] The saponification degree (measured in accordance with JIS K6726-1994) of the PVA-based resin (B) used in the present embodiment is preferably 70 mol% or more as a lower limit, more preferably 90 mol% or more, even more preferably 98 mol% or more, and particularly preferably 99 mol% or more. The upper limit is preferably 100 mol% or less, more preferably 99.9 mol% or less. The saponification degree is preferably in the range of 70 mol% or more and 100 mol% or less. When the saponification degree is equal to or more than the lower limit, the gas barrier property tends to be improved.

[0062] In this embodiment, the PVA-based resin (B) may be a resin obtained by copolymerizing various monomers during the production of a polyvinyl ester-based resin and then saponifying the copolymer, or a modified PVA-based resin obtained by post-modifying an unmodified PVA to introduce various functional groups.

[0063] Examples of monomers used for copolymerization with vinyl ester monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, and derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, salts thereof, monoesters thereof, and dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; and diacetone acrylate. olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof; alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, 3,4-diacetoxy-1-butene or other vinyl compounds; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,4-diacetoxy-2-butene, vinylene carbonate, and the like.

[0064] Examples of modified PVA-based resins into which functional groups have been introduced by post-modification include those having acetoacetyl groups by reaction with diketene, those having polyalkylene oxide groups by reaction with ethylene oxide, those having hydroxyalkyl groups by reaction with an epoxy compound, and those obtained by reacting PVA with an aldehyde compound having various functional groups.

[0065] The content of modified species in the modified PVA-based resin, i.e., structural units derived from various monomers in the copolymer or functional groups introduced by post-modification, is preferably 1 to 40 mol %, more preferably 2 to 35 mol %, although it is difficult to generalize because the properties vary greatly depending on the modified species.

[0066] Among these various modified PVA-based resins, in the present embodiment, a PVA-based resin containing a primary hydroxyl group in a side chain, i.e., a PVA-based resin having a structural unit having a 1,2-diol structure in a side chain (hereinafter, sometimes referred to as a "1,2-diol structural unit") represented by the following general formula (1) is preferably used.

[0067]

[0068] R in the 1,2-diol structural unit represented by general formula (1) 1 ~R 4 each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.

[0069] Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. The alkyl group may have a functional group such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, as necessary.

[0070] Furthermore, X in the 1,2-diol structural unit represented by general formula (1) represents a single bond or a bonding chain. Examples of such bonding chains include hydrocarbons such as linear or branched alkylene groups having 1 to 6 carbon atoms, linear or branched alkenylene groups having 1 to 6 carbon atoms, linear or branched alkynylene groups having 1 to 6 carbon atoms, phenylene groups, and naphthylene groups (these hydrocarbons may be substituted with halogens such as fluorine, chlorine, and bromine), as well as -O-, -(CH ２ O) ｔ -, -(OCH ２ ) ｔ -, -(CH ２ O) ｔ CH ２ -, -CO-, -COCO-, -CO(CH ２ ) ｔ CO-, -CO(C ６ H ４ )CO-, -S-, -CS-, -SO-, -SO2-, -NR-, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO ４ -, -Si(OR) ２ -, -OSi(OR)２ -, -OSi(OR) ２ O-, -Ti (OR) ２ -, -OTi(OR) ２ -, -OTi(OR) ２ Examples include O-, -Al(OR)-, -OAl(OR)-, -OAl(OR)O-, etc. (each R is independently an arbitrary substituent and represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and t represents an integer of 1 to 5). Among these, from the viewpoint of stability during production or use, the bonding chain is preferably a linear or branched alkylene group having 1 to 6 carbon atoms, particularly a methylene group, or -CH ２ OCH ２ - is preferred.

[0071] In general formula (1), X is most preferably a single bond in terms of thermal stability and stability under high temperatures and acidic conditions.

[0072] In addition, among the 1,2-diol structural units represented by general formula (1), R 1 ~R 4 A structural unit represented by the following general formula (1') in which all of are hydrogen atoms and X is a single bond is most preferred.

[0073]

[0074] Examples of methods for producing such PVA-based resins having 1,2-diol structural units in their side chains include the methods described in paragraphs

[0026] to

[0034] of JP-A-2015-143356.

[0075] The content of 1,2-diol structural units in such PVA-based resins, i.e., the content of primary hydroxyl groups in the side chains, is preferably 1 to 20 mol%, more preferably 2 to 15 mol%, even more preferably 3 to 13 mol%, particularly preferably 7 to 12 mol%, and most preferably 7 to 9 mol%. When this content is 1 mol% or more, the effect of the 1,2-diol structure in the side chains is sufficiently obtained, and when this content is 20 mol% or less, there is a tendency that deterioration of gas barrier properties at high humidity can be suppressed.

[0076] The content of 1,2-diol structural units in the PVA-based resin is １ H-NMR (300 MHz proton NMR, d ６ The content can be calculated from the integrated value measured in a 1,2-diol structural unit (a 1,2-dimethyl-1,2-diol-1,2-diol-1,2-diol-2 ...

[0077] In the present laminate, it is particularly preferable to use, as the PVA-based resin (B), a PVA-based resin which contains 7 to 12 mol % of primary hydroxyl groups in its side chains, has a degree of saponification of 99 mol % or more, and has a melt flow rate (210°C, 2160 g load) of 3.0 to 60.0 g / 10 min.

[0078] The PVA-based resin (B) may be one type or a mixture of two or more types. When the PVA-based resin (B) is a mixture of two or more types, the PVA-based resins may be a combination of the above-mentioned unmodified PVAs, an unmodified PVA and a PVA-based resin having the structural unit represented by general formula (1), PVA-based resins having the structural unit represented by general formula (1) but differing in saponification degree, polymerization degree, modification degree, etc., an unmodified PVA, or a PVA-based resin having the structural unit represented by general formula (1) and another modified PVA-based resin, etc.

[0079] In addition to the PVA-based resin (B), the layer β may contain a heat stabilizer, an antioxidant, an ultraviolet absorber, a crystal nucleating agent, an antistatic agent, a flame retardant, a plasticizer, a lubricant, a filler, a lubricant, or a crystal nucleating agent. These may be used alone or in combination of two or more. When other thermoplastic resins or additives are added, the content thereof is usually 10% by mass or less, and more preferably 5% by mass or less, relative to the layer β.

[0080] The resin composition containing the PVA-based resin (B) can be subjected to co-extrusion molding as it is. However, in consideration of workability and extrusion stability during molding, it is preferable to knead the resin composition in a molten state, then cool and solidify it into pellets or the like.

[0081] Although known kneading devices such as a kneader-ruder, an extruder, a mixing roll, a Banbury mixer, and a blast mill can be used as the kneading means, it is usually industrially preferable to use a single-screw or twin-screw extruder, and it is also preferable to provide a vent suction device, a gear pump device, a screen device, a strand support belt, a dry fog generator, etc., as necessary. In particular, by providing one or more vent holes in the extruder to perform suction under reduced pressure in order to remove moisture and by-products (such as low-molecular-weight pyrolyzed products), or by continuously supplying an inert gas such as nitrogen into the hopper in order to prevent oxygen from entering the extruder, it is possible to obtain high-quality pellets of the resin composition containing the PVA-based resin (B) with reduced thermal discoloration and thermal degradation.

[0082] The laminate has a layer β and a layer α, and can be produced by laminating the layer α on one or both sides of the layer β. Examples of lamination methods include melt-extrusion laminating a resin composition containing the polyester-based resin (A) onto a film or sheet of a resin composition containing the PVA-based resin (B), melt-extrusion laminating a resin composition containing the PVA-based resin (B) onto a substrate of a resin composition containing the polyester-based resin (A), co-extruding a resin composition containing the PVA-based resin (B) with a resin composition containing the polyester-based resin (A), or dry-laminating a film or sheet of a resin composition containing the PVA-based resin (B) with a film or sheet of a resin composition containing the polyester-based resin (A) using a known adhesive resin such as an organotitanium compound, an isocyanate compound, a polyester compound, or a polyurethane compound. Co-extrusion molding is particularly preferred in terms of achieving the effects of the present invention.

[0083] Specific examples of the co-extrusion method include the inflation method, T-die method, multi-manifold die method, feed block method, and multi-slot die method. Die shapes that can be used for the die-exterior bonding method include T-dies and round dies. The melt molding temperature during melt extrusion is usually 140°C to 210°C, and preferably 150°C to 200°C.

[0084] As an example of the layer structure of this laminate, when layers α and β are written as α and β, not only the two-layer structure of α / β is possible, but also any combination such as α / β / α, β / α / β, β1 / β2 / α, β / α1 / α2, α1 / α2 / β / α2 / α1, α1 / α2 / β / α3 / α4, β1 / α1 / β2 / α2, etc., and a layer structure of α / β / α or α1 / α2 / β / α2 / α1 is particularly preferred.

[0085] <Layer γ> In addition, in the layer configuration, an adhesive resin layer can be provided in each layer configuration as necessary. That is, it is preferable to have a layer γ containing the adhesive resin composition (C) between the layer α and the layer β. Such layer γ preferably contains the adhesive resin composition (C) as a main component. The layer γ may consist of either a single layer or two or more layers. Furthermore, when the layer γ consists of two or more layers, the layers may contain the same adhesive resin composition as a main component, or different adhesive resin compositions as main components.

[0086] From the viewpoint of biodegradability of the present laminate, the adhesive resin composition (C) preferably contains an acid-modified polyester resin.

[0087] The acid-modified polyester resin is obtained by graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof onto an aliphatic polyester resin or an aliphatic aromatic polyester resin.

[0088] The aliphatic polyester resin used in the acid-modified polyester resin is the same as the aliphatic polyester resin exemplified in the polyester resin (A) and preferred examples thereof are also the same.

[0089] The aliphatic aromatic polyester resin used in the acid-modified polyester resin is the same as the aliphatic aromatic polyester resin exemplified in the polyester resin (A) and the preferred examples are also the same.

[0090] Specific examples of the α,β-unsaturated carboxylic acid include α,β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and α,β-unsaturated dicarboxylic acids or anhydrides thereof such as maleic acid, fumaric acid, itaconic acid, citrus acid, tetrahydrophthalic acid, crotonic acid, and isocrotonic acid, and preferably an anhydride of an α,β-unsaturated dicarboxylic acid, more preferably maleic anhydride. Note that these α,β-unsaturated carboxylic acids may be used alone or in combination of two or more.

[0091] The method for graft polymerizing the α,β-unsaturated carboxylic acid to the aliphatic polyester resin and / or the aliphatic aromatic polyester resin is not particularly limited, and known methods can be used. Although a thermal reaction alone is also possible, it is preferable to use a radical initiator to enhance reactivity. Furthermore, examples of the reaction method include a solution reaction, a reaction as a suspension, and a reaction in a molten state without using a solvent, among which a reaction in a molten state is preferable.

[0092] Examples of the melting method that can be used include a method in which an aliphatic polyester resin and / or an aliphatic aromatic polyester resin is mixed in advance with an α,β-unsaturated carboxylic acid compound and a radical initiator, and then the mixture is melt-kneaded in a kneader to cause a reaction, and a method in which an α,β-unsaturated carboxylic acid compound and a radical initiator are blended with an aliphatic polyester resin and / or an aliphatic aromatic polyester resin in a molten state in a kneader.

[0093] Examples of mixers used when premixing the raw materials include a Henschel mixer and a ribbon blender, and examples of kneaders used for melt-kneading include a single-screw or twin-screw extruder, a roll, a Banbury mixer, a kneader, and a Brabender mixer. The temperature during melt-kneading may be set appropriately within a temperature range that is equal to or higher than the melting point of the aliphatic polyester resin and / or the aliphatic aromatic polyester resin and that does not cause thermal degradation. Melt-mixing is preferably performed at 100 to 270°C, more preferably 160 to 250°C.

[0094] The amount of α,β-unsaturated carboxylic acid used is typically 0.0001 to 5 parts by mass, preferably 0.001 to 2 parts by mass, and more preferably 0.02 to 1 part by mass, per 100 parts by mass of the aliphatic polyester resin and / or the aliphatic aromatic polyester resin. If the blending amount is too small, a sufficient number of polar groups will not be introduced into the aliphatic polyester resin and / or the aliphatic aromatic polyester resin, and interlayer adhesion, particularly adhesion to the layer β containing the PVA resin, tends to be insufficient. On the other hand, if the blending amount is too large, ungrafted α,β-unsaturated carboxylic acid may remain in the resin, which tends to result in poor appearance and the like.

[0095] The radical initiator is not particularly limited, and known radical initiators can be used. Examples thereof include organic and inorganic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis(t-butyloxy)hexane, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxybenzoate, benzoyl peroxide, m-toluoyl peroxide, dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, and hydrogen peroxide; azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(isobutylamido)dihalide, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and azodi-t-butane; and carbon radical generators such as dicumyl. These may be used alone or in combination of two or more.

[0096] The amount of radical initiator blended is usually 0.00001 to 2.0 parts by mass, preferably 0.0001 to 1.0 part by mass, and more preferably 0.002 to 0.5 parts by mass, relative to 100 parts by mass of the resin component such as the aliphatic polyester-based resin. If the amount of radical initiator blended is too small, graft polymerization does not occur sufficiently, tending to result in insufficient adhesive strength. If the amount is too large, decomposition of the polyester-based resin leads to a decrease in molecular weight, and insufficient cohesive strength tends to result in insufficient adhesive strength.

[0097] The amount of polar groups introduced by the α,β-unsaturated carboxylic acids relative to the acid-modified polyester resin is usually 0.0001 to 6 mol %, preferably 0.001 to 1 mol %, and more preferably 0.025 to 0.6 mol %. If the amount introduced is too small, the adhesive strength with the layer β containing the PVA resin tends to be insufficient. On the other hand, if the amount introduced is too large, the stability during hot melt molding tends to decrease. Here, the amount of polar groups introduced is １ It can be determined from a spectrum obtained by H-NMR measurement or IR measurement.

[0098] The adhesive resin composition (C) may contain any additives, such as heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, neutralizing agents, rust inhibitors, and pigments. These additives may be used alone or in combination of two or more.

[0099] The acid value of the acid-modified polyester resin is usually 8.0 or less, preferably 7.0 or less, more preferably 6.0 or less, and even more preferably 5.5 or less, and is usually 3.0 or more, preferably 3.3 or more, and more preferably 3.6 or more. The acid value ranges from 3.0 to 8.0. When the acid value of the acid-modified polyester resin is equal to or higher than the lower limit, thermal decomposition tends to be suppressed, and when the acid value is equal to or lower than the upper limit, stability during hot melt molding tends to be improved.

[0100] A preferred embodiment of the present laminate is a laminate including a layer α, a layer β, and a layer γ, and the number of layers is not limited, but is, for example, 3 to 15 layers, more preferably 3 to 7 layers, and particularly preferably 5 to 7 layers.

[0101] The configuration of the laminate of the present invention is not particularly limited, but when the adhesive resin composition (C) layer is γ, the layer containing the PVA-based resin (B) is β, and the polyester-based resin (A) layer is α, any combination such as α / γ / β, α / γ / β / γ / α, α / β / γ / β / γ / β / α / α is possible. When multiple layers α are present in the laminate, the multiple layers α may be the same or different. The same applies when multiple layers β and multiple layers γ are present in the laminate.

[0102] In general, in order to prevent deterioration of gas barrier performance due to moisture absorption by the resin composition layer β containing the PVA-based resin (B), it is preferable to provide an α-layer in a portion of the layer β that comes into contact with the outside air or a moisture-containing content.

[0103] The thickness of the present laminate is preferably 1 to 30,000 μm, more preferably 3 to 13,000 μm, and even more preferably in the range of 10 to 3,000 μm.

[0104] With regard to the thickness of each layer constituting the present laminate, the thickness of layer α is preferably 0.4 to 14,000 μm, more preferably 1 to 6,000 μm, and particularly preferably 4 to 1,400 μm. If the thickness of layer α is 14,000 μm or less, the laminate can be prevented from becoming too hard. Furthermore, if the thickness of layer α is 0.4 μm or more, the laminate can be prevented from becoming brittle. When multiple layers α are present, the thickness of layer α is the total thickness of these layers.

[0105] The thickness of layer β is preferably 0.1 to 1000 μm, more preferably 0.3 to 500 μm, and even more preferably 1 to 100 μm. If the thickness of layer β is 1000 μm or less, the laminate can be prevented from becoming hard and brittle. If the thickness of layer β is 0.1 μm or more, the gas barrier properties are improved. When multiple layers β are present, the thickness of layer β is the total thickness of these layers.

[0106] The thickness of the layer γ is preferably 0.1 to 500 μm, more preferably 0.15 to 250 μm, and particularly preferably 0.5 to 50 μm. If the thickness of the layer γ is 500 μm or less, the appearance is good. If the thickness of the layer γ is 0.1 μm or more, a decrease in adhesive strength can be suppressed. When multiple layers γ are present, the thickness of the layer γ is the total thickness of these layers.

[0107] The laminate of the present invention can be produced by a conventionally known molding method, specifically, a melt molding method or a molding method from a solution state can be used.

[0108] Examples of the melt molding method include a method of melt-extrusion laminating a film or sheet of a resin composition containing a polyester-based resin (A) with an adhesive resin composition (C) and a resin composition containing a PVA-based resin (B) in that order or simultaneously; conversely, a method of melt-extrusion laminating a film or sheet of a resin composition containing a PVA-based resin (B) with an adhesive resin composition (C) and a resin composition containing a polyester-based resin (A) in that order or simultaneously; and a method of co-extrusion of a resin composition containing a polyester-based resin (A), an adhesive resin composition (C), and a resin composition containing a PVA-based resin (B).

[0109] Further, examples of the molding method from a solution state include a method in which a solution of the adhesive resin composition (C) dissolved in a good solvent is solution-coated onto a film or sheet containing the polyester-based resin (A), and after drying, an aqueous solution containing the PVA-based resin (B) is solution-coated thereon.

[0110] Among these, the melt molding method is preferred, and the co-extrusion method is particularly preferred, since it can be produced in one step and can give a laminate with excellent interlayer adhesion. When using such a melt molding method, it is preferred to use a PVA-based resin having a 1,2-diol structural unit in the side chain as the PVA-based resin (B).

[0111] Specific examples of the co-extrusion method include the inflation method, T-die method, multi-manifold die method, feed block method, and multi-slot die method. Dies such as T-dies and round dies can be used. The melt molding temperature during melt extrusion is preferably 140°C to 210°C, more preferably 150°C to 200°C. For resin compositions containing polyester-based resin (A), the temperature is preferably 120°C to 180°C, more preferably 130°C to 170°C; for resin compositions containing PVA-based resin (B), the temperature is preferably 160°C to 200°C, more preferably 170°C to 190°C; and for adhesive resin composition (C), the temperature is preferably 140°C to 210°C, more preferably 150°C to 200°C.

[0112] The laminate of the present invention may be further subjected to a heat stretching treatment, and such a stretching treatment tends to be expected to improve the strength and gas barrier properties.

[0113] In particular, in the laminate of the present invention, when a PVA-based resin having a 1,2-diol structural unit in the side chain is used as the PVA-based resin (B), the stretchability tends to be good.

[0114] For the stretching treatment, etc., known stretching methods can be used. Specific examples include uniaxial stretching and biaxial stretching, in which both edges of a multilayer structure sheet are gripped and expanded; mold forming methods such as deep drawing, vacuum forming, pressure forming, and vacuum pressure forming, in which a multilayer structure sheet is stretched using a mold; and methods in which a preformed multilayer structure such as a parison is processed by a tubular stretching method, stretch-blow method, etc.

[0115] As such a stretching method, when a film or sheet-like molded product is intended, it is preferable to employ a uniaxial stretching method or a biaxial stretching method.

[0116] In addition, in the case of a mold forming method such as deep drawing, vacuum forming, pressure forming, or vacuum pressure forming, it is preferable to uniformly heat the laminate using a hot air oven, a heater oven, or a combination of both, and stretch it using a chuck, plug, vacuum force, compressed air force, or the like.

[0117] When a molded article such as a cup or a tray is intended to have a drawing ratio (depth of molded article (mm) / maximum diameter of molded article (mm)) of usually 0.1 to 3, it is preferable to employ a mold forming method in which a mold is used for stretching, such as deep drawing, vacuum forming, pressure forming, or vacuum pressure forming.

[0118] The oxygen permeability of this laminate at 20°C and 65% RH is 6 cc / m ２ ·day·atm or less, preferably 5 cc / m ２ ·day·atm or less, more preferably 4cc / m ２ ·day·atm or less, more preferably 3 cc / m ２ ·day·atm or less, and particularly preferably 2 cc / m ２ The lower limit is not limited, but is, for example, 0.01 cc / m ２ The oxygen permeability can be measured, for example, by the method described in the Examples below.

[0119] The oxygen permeability of layer β at 20°C and 65% RH is 6 cc 20 μm / m ２ · day · atm or less, preferably 5 cc · 20 μm / m ２ · day · atm or less, more preferably 4 cc · 20 μm / m ２ · day · atm or less, more preferably 3 cc · 20 μm / m ２ · day · atm or less, and particularly preferably 2 cc · 20 μm / m ２ The lower limit is not limited, but is, for example, 0.01 cc 20 μm / m ２ The oxygen permeability can be measured, for example, by the method described in the Examples below.

[0120] The tensile strength of the present laminate is usually 25 MPa or more, preferably 27 MPa or more, and more preferably 30 MPa or more. The tensile strength can be measured, for example, by the method described in the Examples below.

[0121] The laminate has good coextrusion moldability, oxygen barrier properties, and mechanical strength, and is useful as various packaging materials for foods and pharmaceuticals, food packaging films, food containers, beverage containers, agricultural films, etc. Specific applications include injection-molded articles (e.g., trays for fresh food, fast food containers, coffee capsule containers (capsule containers for capsule coffee makers and capsule tea makers, cutlery, outdoor leisure products, etc.)), extrusion-molded articles (e.g., films, sheets, fishing lines, fishing nets, vegetation nets, secondary processing sheets, water-retaining sheets, etc.), and hollow-molded articles (e.g., bottles). Other examples include agricultural films, coating materials, fertilizer coating materials, seedling pots, laminated films, plates, stretched sheets, monofilaments, nonwoven fabrics, flat yarns, staples, crimped fibers, creased tape, split yarns, composite fibers, blown bottles, shopping bags, garbage bags, compost bags, cosmetic containers, detergent containers, bleach containers, ropes, binding materials, sanitary cover stock, insulated boxes, cushioning films, multifilaments, synthetic paper, and medical applications such as surgical thread, sutures, artificial bones, artificial skin, DDS (Disposable Disposal Systems) such as microcapsules, and wound dressings. The molded article is particularly suitable for food containers such as food packaging films, fresh food trays, fast food containers, and lunch boxes. Among the above, the laminate is biodegradable and therefore suitable for use in compostable containers, such as food and beverage containers, including coffee capsules and shrink film.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are based on mass.

[0123] First, the raw materials of the laminates prepared in the examples and comparative examples will be described in detail.

[0124] <Polyester-based resins (A)> Polyester-based resin (A1): PBS (BioPBS FZ91PM, manufactured by Mitsubishi Chemical Corporation, melting point 115°C, acid value 1.1) Polyester-based resin (A2): PBSA (BioPBS FD92PM, manufactured by Mitsubishi Chemical Corporation, melting point 84°C, acid value 1.3) Polyester-based resin (A3): PBAT (Ecoflex (registered trademark) C1200, manufactured by BASF, melting point: 115°C, acid value 0.6) was used.

[0125] [Method for measuring melting point] The melting point was measured using a differential scanning calorimeter (DSC, Q2000, manufactured by TA Instrument) as follows. The sample amount was 5 mg. The measurement was carried out under a nitrogen atmosphere. First, the sample was heated from -30°C to 250°C at a heating rate of 10°C / min and held at that temperature for 1 minute to dissolve (1st run). Subsequently, the sample was cooled to -30°C at a heating rate of 10°C / min, held at that temperature for 1 minute, and then heated again to 250°C at a heating rate of 10°C / min (2nd run). The melting point (Tm) and glass transition point (Tg) were read from the thermograph in the 2nd run.

[0126] <PVA-based resin (B)> [PVA-based resin (b1)] A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 68.5 parts of vinyl acetate, 20.5 parts of methanol, and 11.0 parts of 3,4-diacetoxy-1-butene (8 mol % relative to the charged vinyl acetate) at an initial vinyl acetate charge ratio of 40%, with vinyl acetate and 3,4-diacetoxy-1-butene being added dropwise at a constant rate for 9 hours, followed by the addition of 0.3 mol % (relative to the charged vinyl acetate) of azobisisobutyronitrile, and the temperature was raised under a nitrogen stream with stirring to initiate polymerization. When the conversion of vinyl acetate reached 95%, 10 ppm of m-dinitrobenzene relative to the monomer mass was added to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing in methanol vapor to obtain a methanol solution of the copolymer. Next, the methanol solution was diluted with methanol to a concentration of 55%, and a methanol solution of sodium hydroxide with a sodium concentration of 2% was added at a ratio of 10.5 mmol per mole of the total amount of vinyl acetate structural units and 3,4-diacetoxy-1-butene structural units in the copolymer. The mixture was uniformly mixed and poured onto a belt, and saponification was carried out while maintaining the ambient temperature at 40°C. As the saponification proceeded, gelation progressed, and when a plate-like shape was obtained, the resin was scraped off with a rubber cutter and a comb cutter, thoroughly washed with methanol, and dried in a hot air dryer at 70°C for 12 hours to obtain a PVA-based resin (b1) having 1,2-diol structures in the side chains. The degree of saponification of the resulting PVA-based resin (b1) having 1,2-diol structures in the side chains was analyzed based on the amount of alkali consumption required for hydrolysis of the remaining vinyl acetate and 3,4-diacetoxy-1-butene structural units in the resin, and was found to be 99 mol%. The average degree of polymerization was analyzed in accordance with JIS K 6726 and found to be 450. The melting point was measured by a differential scanning calorimeter (DSC) and found to be 169°C. The content of the 1,2-diol structural unit represented by the general formula (1) was 1The content was calculated from the integrated value measured by H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard: tetramethylsilane, 50°C), and was found to be 8 mol%. [PVA-based resin (b2)] A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 68.5 parts of vinyl acetate, 20.5 parts of methanol, and 11.0 parts of 3,4-diacetoxy-1-butene (8 mol% relative to the charged vinyl acetate) at an initial vinyl acetate charge rate of 10%, with vinyl acetate and 3,4-diacetoxy-1-butene being added dropwise at a constant rate for 9 hours, followed by the addition of 0.3 mol% azobisisobutyronitrile (relative to the charged vinyl acetate), and the temperature was raised under a nitrogen stream with stirring to initiate polymerization. When the conversion of vinyl acetate to polymerization reached 90%, 10 ppm of m-dinitrobenzene was added relative to the monomer mass to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing in methanol vapor to obtain a methanol solution of the copolymer. The methanol solution was then diluted with methanol to a concentration of 55%, and a methanol solution of sodium hydroxide with a sodium concentration of 2% was added at a ratio of 10.5 mmol per mole of the total amount of vinyl acetate structural units and 3,4-diacetoxy-1-butene structural units in the copolymer. The mixture was mixed uniformly and poured onto a belt. While maintaining the ambient temperature at 40°C, saponification was carried out. As saponification progressed, gelation progressed, and when the resin became plate-like, it was scraped off with a rubber cutter and a comb cutter, thoroughly washed with methanol, and dried in a hot air dryer at 70°C for 12 hours to obtain a PVA-based resin (b2) having a 1,2-diol structure in the side chain. The degree of saponification of the obtained PVA-based resin (b2) having a 1,2-diol structure in the side chain was analyzed based on the amount of alkali consumed for hydrolysis of the structural units of vinyl acetate and 3,4-diacetoxy-1-butene remaining in the resin, and was found to be 99 mol%. The average degree of polymerization was analyzed in accordance with JIS K 6726 and was found to be 300. The melting point was measured using a differential scanning calorimetry (DSC) and was found to be 169°C. The content of the 1,2-diol structural unit represented by the general formula (1) was also found to be 169°C. 1The content was calculated from the integrated value measured by H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard: tetramethylsilane, 50°C), and was found to be 8 mol%. [PVA-based resin (b3)] A reaction vessel equipped with a reflux condenser and a stirrer was charged with 76.6 parts of vinyl acetate (initial charge: 40%), 14.2 parts of methanol, and 9.2 parts of 3,4-diacetoxy-1-butene (initial charge: 40%). Azobisisobutyronitrile was then added in an amount of 0.068 mol% relative to the vinyl acetate content. The temperature was increased under a nitrogen stream while stirring, and polymerization was initiated by adding the remaining amounts of vinyl acetate and 3,4-diacetoxy-1-butene dropwise at a constant rate for 13.5 hours. When the conversion of vinyl acetate reached 91%, m-dinitrobenzene was added to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing in methanol vapor, and a methanol solution of the copolymer was obtained. Next, the methanol solution was further diluted with methanol to a concentration of 50% and charged into a kneader. While maintaining the solution temperature at 35°C, a methanol solution of sodium hydroxide with a sodium concentration of 2% was added at a ratio of 4.5 mmol per mole of the total amount of vinyl acetate structural units and 3,4-diacetoxy-1-butene structural units in the copolymer, thereby carrying out saponification. As the saponification proceeded, the saponified product precipitated. When it became particulate, it was filtered out, thoroughly washed with methanol, and dried in a hot air dryer to obtain PVA-based resin (b3) having 1,2-diol structures in its side chains. The degree of saponification of the resulting PVA-based resin (b3) having 1,2-diol structures in its side chains was analyzed based on the amount of alkali consumed for hydrolysis of the remaining vinyl acetate and 3,4-diacetoxy-1-butene in the resin, and was found to be 99 mol%. Furthermore, the average degree of polymerization was found to be 450 when analyzed in accordance with JIS K 6726. The melting point was measured by a differential scanning calorimeter (DSC) and found to be 188° C. The content of the 1,2-diol structural unit represented by the general formula (1) was: 1 The content was calculated from the integrated value measured by H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard: tetramethylsilane, 50° C.), and was found to be 6 mol %.

[0127] [Preparation of PVA-based resin (B) pellets] The PVA-based resins (b1) to (b3) obtained above were fed to a twin-screw extruder and pelletized under the following conditions to obtain pellets of PVA-based resin (B): (Pelletization conditions) Screw inner diameter: 32 mm L / D: 56 Screw rotation speed: 350 rpm Discharge rate: 15 kg / h Extrusion temperatures: C1 / C2 / C3 / C4 / C5 / C6 / C7 to C16 / H / D = 50 / 50 / 100 / 160 / 190 / 210 / 220 / 220 / 220°C

[0128] PVA-based resin (B1): 80 parts of PVA-based resin (b1) and 20 parts of PVA-based resin (b2) were dry-blended, and then pellets of PVA-based resin (B1) were obtained by the method described above. PVA-based resin (B2): 50 parts of PVA-based resin (b1) and 50 parts of PVA-based resin (b2) were dry-blended, and then pellets of PVA-based resin (B2) were obtained by the method described above. PVA-based resin (B3): PVA-based resin (b2) was prepared, and pellets of PVA-based resin (B3) were obtained by the method described above. PVA-based resin (B4): PVA-based resin (b3) was prepared, and pellets of PVA-based resin (B4) were obtained by the method described above.

[0129] The melting point and melt flow rate (MFR) of the resulting pellets of PVA resins (B1) to (B4) were measured under the following conditions, and the results are shown in Table 1 below.

[0130] <Measurement of Melting Point> The melting point was measured using a differential scanning calorimeter (DSC) (Q2000, manufactured by TA Instrument).

[0131] <Melt flow rate (MFR) measurement> A melt indexer conforming to JIS K 7210-1:2014 is used. 5 g of sample is placed in a cylinder set to 210°C and charged within 30 seconds. 4 minutes and 30 seconds after sample addition, a 2160 g weight is placed on the cylinder, and the strand extruded 5 minutes after sample addition is cut and discarded. Subsequently, the strand is cut 6 minutes, 7 minutes, and 8 minutes after sample addition, and a total of three strands are collected. The masses of the three collected strands are measured and the average is calculated. The MFR is calculated from the average mass calculated using the following formula. [Formula] MFR (g / 10 min) = W x 10 W: average mass (g) of three strands 10: coefficient for converting grams per minute to grams per 10 minutes

[0132] <Adhesive resin composition (C)> Adhesive resin composition (C1): 100 parts of adipic acid / 1,4-butanediol condensation polymer (Ecoflex (registered trademark) C1200 manufactured by BASF) as a raw material biodegradable polyester resin, 0.35 parts of maleic anhydride, and 0.25 parts of 2,5-dimethyl-2,5-bis(t-butyloxy)hexane (Perhexa 25B manufactured by NOF Corporation) as a radical initiator were dry-blended, and the resultant mixture was melt-kneaded in a twin-screw extruder under the conditions described below, extruded into a strand shape, cooled with water, and cut with a pelletizer to obtain cylindrical pellets of an adhesive resin composition (C1) containing an acid-modified polyester resin composition (acid value 4.6). (Twin-screw extruder conditions) Diameter (D): 20 mm L / D: 45 Screw rotation speed: 200 rpm Mesh: 90 / 90 mesh Processing temperature: 210°C

[0133] <Preparation of laminate> Using the polyester resin (A), PVA resin (B), and adhesive resin composition (C) prepared above, a three-kind five-layer multilayer film device equipped with four extruders was used to prepare a three-kind five-layer structure of layer α / layer γ / layer β / layer γ / layer α, a three-kind five-layer structure of layer α1 / layer α2 / layer β / layer α2 / layer α1 using two kinds of polyester resins (A), or a two-kind three-layer structure of layer α / layer β / layer α. The thickness of the obtained laminate was 100 μm, and the thickness of each layer was as follows: Layer α / Layer γ / Layer β / Layer γ / Layer α = 30 μm / 10 μm / 20 μm / 10 μm / 30 μm Layer α1 / Layer α2 / Layer β / Layer α2 / Layer α1 = 20 μm / 20 μm / 20 μm / 20 μm / 20 μm Layer α / Layer β / Layer α = 40 μm / 20 μm / 40 μm The set temperatures for each extruder and roll are as follows: Polyester resin (A) temperature condition I: C1 / C2 / C3 / C4 / H / AD = 150 / 160 / 160 / 160 / 160 / 160°C Polyester resin (A) temperature condition II: C1 / C2 / C3 / H / AD = 150 / 160 / 160 / 160 / 160 / 160°C PVA resin (B): C1 / C2 / C3 / C4 / H / AD = 180 / 180 / 180 / 180 / 180 / 180°C Adhesive resin composition (C): C1 / C2 / C3 / H / AD = 190 / 200 / 200 / 200 / 200°C Feed block: FB1 / FB2 = 180 / 180°C Die: D1 / D2 / D3 / D4 / D5 / D6 = 170°C or 180°C Roll: 30°C

[0134] [Example 1] A laminate was produced using the polyester resin (A2), PVA resin (B1), and adhesive resin composition (C1) prepared above, with a die temperature of 170°C and the temperature of the polyester resin (A2) under the temperature condition I described above.

[0135] Examples 2 to 9, Comparative Examples 1 to 5 Laminates were prepared in the same manner as in Example 1, except that the type of resin and the processing temperature conditions were changed to those shown in Table 1 below.

[0136] The laminates prepared in the above Examples and Comparative Examples were subjected to the following various measurements and evaluations, the results of which are shown in Table 1 below.

[0137] <Evaluation of formability> The appearance of the obtained laminate was evaluated based on the following criteria. Thickness: Measured with a contact film thickness meter Appearance: Visually confirmed for the presence or absence of appearance defects due to flow marks [Evaluation criteria] ◯: There were no parts where the thickness of the laminate was uneven, and the appearance was good. Δ: There were some parts where the thickness of the laminate was uneven, or partial appearance defects were observed. ×: Due to the occurrence of flow marks and orange peel, parts of the thickness of the laminate were uneven, and overall appearance was poor. Or drawdown occurred, resulting in poor molding.

[0138] <Measurement of oxygen barrier property> The oxygen permeability of the obtained laminate was measured under conditions of 20°C and 65% RH using an oxygen permeability measuring device (OX-TRAN2 / 21, manufactured by MOCON Corporation) in accordance with JIS K 7126-2 (2006).

[0139] <Measurement of Tensile Strength> The tensile strength of the laminates obtained in the Examples and Comparative Examples was measured according to JIS K 7127:1999. Test specimens were prepared by cutting out rectangular specimens from the laminates, each specimen having a length of 150 mm in the measurement direction and a width of 15 mm. Both ends of the specimen in the longitudinal direction were chucked with a chuck distance of 50 mm, and the specimen was stretched at a crosshead speed of 500 mm / min. The stress at the breaking point was measured five times as the tensile strength, and the average value was calculated.

[0140]

[0141] The results in Table 1 above demonstrate that the laminates of Examples 1 to 9, which used PVA-based resins having specific melting points, exhibited excellent moldability and oxygen gas barrier properties. Furthermore, the laminates of Examples 1 and 2, which used PVA-based resins having specific melting points, also exhibited excellent tensile strength. On the other hand, the laminates of Comparative Examples 1 and 3 to 5, which contained PVA-based resins with melting points above the specific range, exhibited good oxygen barrier properties. However, the die processing temperature of 180°C destabilized the moldability of the polyester-based resin outer layer, resulting in uneven thickness of the laminate in some areas and poor appearance in some areas. Furthermore, the laminate of Comparative Example 2, which used a PVA-based resin with a melting point above the specific range, exhibited flow marks and poor overall appearance due to the die processing temperature of 170°C. Because the laminates of Examples 1 to 9 exhibited excellent moldability and oxygen gas barrier properties, food packaging films, food containers, and beverage containers containing these laminates also exhibited excellent moldability and oxygen gas barrier properties.

[0142] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0143] The laminate of the present invention has good coextrusion moldability, oxygen barrier properties, and mechanical strength, and is useful as various packaging materials for foods and pharmaceuticals, food packaging films, food containers, beverage containers, and agricultural films.

Claims

1. A laminate comprising at least two layers: a resin composition layer α containing a polyester-based resin (A) and a resin composition layer β containing a polyvinyl alcohol-based resin (B), wherein the resin composition containing the polyester-based resin (A) has a melting point of 150°C or less, and the resin composition containing the polyvinyl alcohol-based resin (B) has a melting point of 180°C or less.

2. The laminate according to claim 1, wherein the resin composition containing the polyvinyl alcohol-based resin (B) has a melt flow rate (210°C, 2160 g) of 3.0 to 60.0 g / 10 min.

3. The laminate according to claim 1, wherein the melting point of the polyester resin (A) is 150°C or lower.

4. The laminate according to claim 1, wherein the polyvinyl alcohol resin (B) has a melting point of 180°C or less and a melt flow rate (210°C, 2160g load) of 3.0 to 60.0g / 10min.

5. The oxygen permeability of the laminate at 20°C and 65% RH is 6 cc / m 2 2. The laminate according to claim 1, wherein the thermal expansion coefficient is 0.5×day·atm or less.

6. The laminate according to claim 1, wherein the difference in melting point between the polyester resin (A) and the polyvinyl alcohol resin (B) is 100°C or less.

7. The laminate according to claim 1, wherein the polyester resin (A) comprises at least one selected from the group consisting of aliphatic polyester resins and aliphatic-aromatic polyester resins.

8. The laminate according to claim 1, which has a layer γ between the layer α and the layer β, the layer γ comprising an adhesive resin composition (C), wherein the adhesive resin composition (C) comprises an acid-modified polyester resin.

9. The laminate according to claim 1, wherein the polyvinyl alcohol resin (B) comprises a polyvinyl alcohol resin containing a primary hydroxyl group in the side chain.

10. The laminate according to claim 1, wherein the polyvinyl alcohol resin (B) contains a polyvinyl alcohol resin containing 7 to 12 mol % of primary hydroxyl groups in the side chains.

11. The laminate according to claim 1, wherein the polyvinyl alcohol resin (B) has a degree of saponification of 99.0 mol % or more.

12. The laminate according to any one of claims 1 to 11, which is a coextruded laminate.

13. A food packaging film comprising the laminate according to any one of claims 1 to 11.

14. A food container comprising a laminate according to any one of claims 1 to 11.

15. A beverage container comprising a laminate according to any one of claims 1 to 11.

16. A resin composition containing a polyvinyl alcohol resin having 7 to 12 mol% of primary hydroxyl groups in its side chains, a degree of saponification of 99.0 mol% or more, and a melt flow rate (210°C, 2160 g load) of 3.0 to 60.0 g / 10 min.

17. The resin composition according to claim 16, having a melting point of 180°C or less.

18. The resin composition according to claim 16 or 17, wherein the melting point of the polyvinyl alcohol resin is 180°C or lower.

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