Laminate, structure, and method for producing laminate

Abstract

Provided is a paper laminate or the like in which a material having exceptional gas barrier properties and biodegradability is used in a heat seal layer, and which has excellent heat-sealing properties and blocking resistance. A laminate comprises a paper base material, and a heat seal layer (X) that is laminated on the paper base material and contains a vinyl-alcohol-based polymer, the laminate having at least one endothermic peak in each of the range from 150°C to lower than 190°C and the range of 190°C or higher in DSC measurement for the heat seal layer (X).

Description

Laminate, structure, and method for manufacturing laminate

[0001] The present invention relates to a laminate, a structure, and a method for manufacturing a laminate.

[0002] In recent years, environmental issues such as plastic waste and global warming have led to a growing global movement to move away from petroleum and plastics. As a result, there is a demand for a reduction in the use of materials derived from fossil resources and non-biodegradable materials, and paper packaging materials with gas barrier properties are attracting attention.

[0003] Patent Document 1 (JP 2020-163675 A) and Patent Document 2 (JP 2021-20398 A) describe paper packaging materials in which a water vapor barrier layer, a gas barrier layer, and a heat seal layer are laminated on a paper base material, and the gas barrier layer contains a vinyl alcohol-based polymer (hereinafter, the vinyl alcohol-based polymer will also be referred to as "PVOH").

[0004] JP 2020-163675 A JP 2021-20398 A

[0005] The paper packaging materials described in Patent Documents 1 and 2 use materials with poor biodegradability, such as olefin-unsaturated carboxylic acid copolymers, in the heat-seal layer. Considering environmental impact reduction, it is desirable to use materials with excellent biodegradability for the heat-seal layer as well. Therefore, the inventors considered using PVOH for the heat-seal layer. PVOH has excellent gas barrier properties and good biodegradability. A PVOH layer can potentially combine the functions of a gas barrier layer and a heat-seal layer, thereby reducing the number of layers in the laminate, which is useful in terms of cost reduction and productivity. However, when PVOH is used for the heat-seal layer, it is difficult to achieve both good heat-sealability and blocking resistance. Note that blocking resistance refers to the resistance to blocking (the phenomenon in which overlapping laminates stick to each other). When laminates are stacked, such as in a roll, and left under pressure, blocking can occur, resulting in peeling of the heat-seal layer or other components when peeling the stuck laminates. For this reason, it is desirable that a laminate provided with a heat seal layer or the like has high blocking resistance.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a paper laminate in which a material with excellent gas barrier properties and biodegradability is used for the heat seal layer, and which has good heat sealability and blocking resistance, a structure using such a laminate, and a method for manufacturing such a laminate.

[0007] The above-mentioned problems are solved by the following: [1] A laminate comprising a paper base material and a heat seal layer (X) laminated on the paper base material and containing a vinyl alcohol-based polymer, wherein, in a DSC measurement of the heat seal layer (X), at least one endothermic peak is observed in the range of 150°C or more and less than 190°C and at least one endothermic peak is observed in the range of 190°C or more; [2] The laminate of [1], wherein the heat seal layer (X) contains a component (A) corresponding to the endothermic peak in the range of 150°C or more and less than 190°C and a component (B) corresponding to the endothermic peak in the range of 190°C or more, and the mass ratio (A / B) of the components (A) to (B) is 10 / 90 to 70 / 30; [3] The laminate of [2], wherein the component (A) is a vinyl alcohol-based polymer (A) having a degree of saponification of 70.0 mol% or more and less than 86.0 mol%; [4] The laminate of [3], wherein a 4% aqueous solution of the vinyl alcohol-based polymer (A) has a viscosity of 2.0 to 20.0 mPa s; [5] The laminate of any one of [2] to [4], wherein the component (B) is a vinyl alcohol polymer (B) having a degree of saponification of 86.0 mol% or more and less than 99.9 mol%; [6] The laminate of [5], wherein the viscosity of a 4% aqueous solution of the vinyl alcohol polymer (B) is 2.0 to 20.0 mPa s; [7] The laminate of [2], wherein the component (A) is a vinyl alcohol polymer (A) having a degree of saponification of 70.0 mol% or more and less than 86.0 mol%, the component (B) is a vinyl alcohol polymer (B) having a degree of saponification of 86.0 mol% or more and less than 99.9 mol%, and the difference in the degree of saponification between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is 10 mol% or more and less than 29.9 mol%; [8] The total mass of the component (A) and the component (B) per unit area is 4 to 10 g / m ２[9] The laminate of any of [2] to [7], wherein the heat seal layer (X) comprises a vinyl alcohol polymer (A) corresponding to an endothermic peak in the range of 150°C or higher but lower than 190°C and a vinyl alcohol polymer (B) corresponding to an endothermic peak in the range of 190°C or higher, and wherein the difference in degree of saponification between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is 10 mol% or higher but 40 mol% or lower;

[10] The laminate of [9], wherein the degree of saponification of the vinyl alcohol polymer (A) is 70.0 mol% or higher but lower than 86.0 mol%, and the degree of saponification of the vinyl alcohol polymer (B) is 86.0 mol% or higher but lower than 99.9 mol%;

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

[10] , further comprising a pigment layer (Y) laminated on the side of the paper base opposite to the heat seal layer (X);

[12] A structure comprising a laminate of any one of [1] to

[11] , wherein the heat-sealable layers (X) are heat-sealed to each other;

[13] A structure comprising a laminate of any one of [1] to

[11] , wherein the heat-sealable layer (X) is disposed on the inner side, and wherein the heat-sealable layers (X) are heat-sealed to each other to form an airtight structure in which a gas is sealed inside;

[14] A method for producing a laminate comprising a paper base material and a heat-sealable layer (X) laminated on the paper base material and containing a vinyl alcohol-based polymer, the method comprising the steps of mixing a vinyl alcohol-based polymer (A) and a vinyl alcohol-based polymer (B) to prepare a coating liquid, and applying the coating liquid to form the heat-sealable layer (X), wherein the difference in degree of saponification between the vinyl alcohol-based polymer (A) and the vinyl alcohol-based polymer (B) is 10 mol % or more and 40 mol % or less.

[0008] According to the present invention, a material having excellent gas barrier properties and biodegradability is used for the heat seal layer, and it is possible to provide a paper laminate having good heat seal properties and blocking resistance, a structure using such a laminate, and a method for manufacturing such a laminate.

[0009] In this specification, a numerical range expressed as "A to B" means that A is the lower limit and B is the upper limit. Furthermore, the lower limit means that the numerical value is included, and the upper limit means that the numerical value is included. In other words, "A to B" is equal to greater than or equal to A and less than or equal to B.

[0010] <Laminate> A laminate according to one embodiment of the present invention comprises a paper base material and a heat seal layer (X) laminated on the paper base material and containing a vinyl alcohol polymer (PVOH), and in DSC measurement of the heat seal layer (X), it has at least one endothermic peak in the range of 150°C or higher and lower than 190°C and at least one endothermic peak in the range of 190°C or higher.

[0011] A laminate according to one embodiment of the present invention uses PVOH, a material with excellent gas barrier properties and biodegradability, for the heat seal layer (X). The laminate exhibits both excellent heat sealability and blocking resistance. The following reasons are presumed to be the reasons for this. The heat seal layer (X) of the laminate contains a component (A) that exhibits an endothermic peak in the range of 150°C or higher but lower than 190°C in DSC measurement. Because the heat seal layer (X) contains the component (A) with such a relatively low melting point, it can exhibit excellent heat sealability. Meanwhile, the heat seal layer (X) further contains a component (B) that exhibits an endothermic peak in the range of 190°C or higher in DSC measurement. Because the heat seal layer (X) contains the component (B) with a relatively high melting point, the outermost heat seal layer (X) is less likely to stick to other layers, even when the laminate is stacked and pressure is applied, thereby exhibiting excellent blocking resistance.

[0012] A laminate according to one embodiment of the present invention has a paper substrate and a heat seal layer (X). The laminate may have layers other than the paper substrate and the heat seal layer (X). For example, the laminate may have a pigment layer (Y) and may further have other layers. Each component of the laminate will be described in detail below.

[0013] (Paper substrate) The paper substrate is a paper layer that serves as the base material in the laminate. The paper substrate may be the outermost layer on one side of the laminate. Note that the outermost layer does not mean to distinguish between the front and back of the laminate, but means a layer that has an exposed surface. In other words, no other layer may be laminated on one side of the paper substrate. Other layers may be laminated on both sides of the paper substrate. The paper substrate may have a single-layer structure or a multi-layer structure.

[0014] The paper base material can be a common paper whose main component is plant-derived pulp. In this specification, the term "main component" refers to the component with the highest content by mass. In addition to pulp, the paper base material may contain sizing agents, fillers, paper strength agents, retention aids, pH adjusters, drainage aids, waterproofing agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes, pigments, etc.

[0015] Examples of paper substrates include kraft paper, bleached kraft paper, fine paper, medium-quality paper, alkaline paper, paperboard, glassine paper, semi-glassine paper, and parchment paper.

[0016] The lower limit of the basis weight (mass per unit area) of the paper substrate is 40 g / m ２ is preferred, and 45 g / m ２ More preferably, 50 g / m ２ More preferably, 55 g / m ２ , 60 g / m ２ or 65 g / m ２ By setting the basis weight of the paper substrate to the above lower limit or more, the strength and shape retention of the laminate can be improved. On the other hand, the upper limit of the basis weight is 120 g / m ２ is preferred, and 110 g / m ２ More preferably, 100 g / m ２ More preferably, 90 g / m ２ , 80 g / m ２ or 70 g / m ２ When the basis weight of the paper substrate is equal to or less than the upper limit, flexibility, heat sealability, etc. can be improved and weight can be reduced. The basis weight of the paper substrate is a value measured in accordance with JIS P8124:2011.

[0017] The lower limit of the thickness of the paper substrate is preferably 50 μm, more preferably 60 μm, even more preferably 70 μm, and may be 80 μm, 90 μm, 100 μm, 110 μm, or 120 μm. When the thickness of the paper substrate is equal to or greater than the above lower limit, the strength, workability, shape retention, etc. of the laminate can be improved. On the other hand, the upper limit of the thickness is preferably 160 μm, more preferably 150 μm, even more preferably 140 μm, and may be 130 μm or 120 μm. When the thickness of the paper substrate is equal to or less than the above upper limit, flexibility, processability, workability, heat sealability, etc. can be improved. The thickness of the paper substrate is a value measured in accordance with JIS P8118:2014.

[0018] The lower limit of the density of the paper base material is 0.60 g / cm ３ is preferred, and 0.65 g / cm ３ When the density of the paper substrate is equal to or higher than the lower limit, the strength, workability, shape retention, etc. of the laminate can be improved. On the other hand, the upper limit of the density is 0.80 g / cm ３ is preferred, and 0.75 g / cm ３ More preferably, 0.70 g / cm ３ When the density of the paper substrate is equal to or less than the above upper limit, flexibility, processability, heat sealability, etc. can be improved. The density of the paper substrate is a value calculated from the basis weight and thickness.

[0019] The paper substrate can be produced by a known method, and commercially available paper substrates can also be used.

[0020] (Heat-seal layer (X)) The heat-seal layer (X) (hereinafter, the heat-seal layer (X) will also be referred to as "layer (X)") is laminated to the paper substrate directly or via another layer. From the viewpoints of productivity, weight reduction, etc., the layer (X) may be laminated directly to the paper substrate. Alternatively, another layer may be provided between the paper substrate and the layer (X). The layer (X) is usually a layer formed by coating (coating layer). Furthermore, the layer (X) is the outermost layer of the laminate from the viewpoint of exerting heat-sealing properties and blocking resistance. The heat-seal layer (X) means a layer having a heat-sealing function, and is not limited by whether or not it is actually heat-sealed.

[0021] The layer (X) contains PVOH. PVOH is a material that has excellent gas barrier properties and biodegradability. Therefore, the laminate according to one embodiment of the present invention can be a laminate with high gas barrier properties. In addition, the laminate can also be a laminate with high biodegradability. PVOH is a vinyl alcohol unit (—CH ２ PVOH is a polymer having the formula —CHOH—. PVOH is usually obtained by saponifying a vinyl ester polymer.

[0022] In DSC measurement of the layer (X) of the laminate, there is at least one endothermic peak in the range (A) of 150° C. or higher and lower than 190° C. and at least one endothermic peak in the range (B) of 190° C. or higher.

[0023] The lower limit of range (A) is preferably 155°C, and more preferably 160°C, 165°C, 170°C, or 172°C. The upper limit of range (A) is preferably 186°C, more preferably 183°C, and even more preferably 181°C. When range (A) is within the above range, that is, when the low-temperature endothermic peak appears within the above range, it is possible to improve heat-sealability, etc. Note that when the low-temperature endothermic peak appears in a relatively high temperature range, blocking properties tend to increase, and when the low-temperature endothermic peak appears in a relatively low temperature range, heat-sealability tends to increase.

[0024] The lower limit of range (B) is preferably 195°C, more preferably 200°C. When range (B) is equal to or higher than the lower limit, that is, when the endothermic peak on the higher temperature side appears in a range equal to or higher than the lower limit, blocking properties can be improved. The upper limit of range (B) may be, for example, 400°C, 350°C, 300°C, 250°C, 240°C, or 235°C.

[0025] The lower limit of the difference between the peak temperature of the endothermic peak on the lower temperature side (the endothermic peak appearing in range (A)) and the peak temperature of the endothermic peak on the higher temperature side (the endothermic peak appearing in range (B)) is preferably 5° C., more preferably 10° C., even more preferably 15° C., and even more preferably 20° C. The upper limit of the difference may be, for example, 200° C., 150° C., 100° C., 80° C., or 60° C.

[0026] DSC measurement of layer (X) of the laminate is performed according to the following procedure. Approximately 2 mg of the measurement sample (laminate) is punched out with a 5 mm diameter punch, filled into an aluminum pan, and set in a DSC measurement device. First, to remove moisture from the measurement sample, the sample is preheated from 0°C to 150°C, and then held at that temperature for 1 minute. Next, the measurement sample is cooled from 150°C to 0°C, held at that temperature for 1 minute, and then reheated from 0°C to 400°C. Note that if the components of layer (X) are known and it is clear that an endothermic peak will not appear above a predetermined temperature, the upper limit of the reheating temperature may be set to a temperature lower than 400°C (e.g., 260°C). The preheating heating rate is 200°C / min, and the cooling and reheating rates are 10°C / min. Furthermore, if the laminate has layers other than the paper substrate and layer (X), layer (X) is peeled off, and approximately 2 mg of the sample is placed in an aluminum pan and subjected to DSC measurement.

[0027] The layer (X) typically contains a component (A) corresponding to an endothermic peak in the range (A) of 150°C or higher but lower than 190°C, and a component (B) corresponding to an endothermic peak in the range (B) of 190°C or higher.

[0028] The lower limit of the mass ratio (A / B) of component (A) to component (B) is preferably 10 / 90, more preferably 15 / 85, and may be 20 / 80, 30 / 70, 35 / 65, 40 / 60, or 50 / 50. When the mass ratio (A / B) is equal to or greater than the above lower limit, the proportion of component (A) increases, and heat sealability tends to be further improved. On the other hand, the upper limit of the mass ratio (A / B) is preferably 70 / 30, more preferably 60 / 40, and may be 50 / 50 or 45 / 55. When the mass ratio (A / B) is equal to or less than the above upper limit, the proportion of component (B) increases, and blocking resistance tends to be further improved.

[0029] The lower limit of the total content of component (A) and component (B) in layer (X) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 97%, or 99% by mass. The upper limit of the total content may be 100% by mass.

[0030] Each of component (A) and component (B) may consist of one kind of component or two or more kinds of components. It is preferable that both component (A) and component (B) are PVOH. For example, it is preferable that the PVOH contains two kinds of PVOH (A) and PVOH (B) having different degrees of saponification, and it is more preferable that the PVOH consists of two kinds of PVOH (A) and PVOH (B) having different degrees of saponification.

[0031] Component (A) may be PVOH (A). The saponification degree of PVOH (A) may be, for example, 60 mol% or more and less than 86.0 mol%, preferably 70.0 mol% or more and less than 86.0 mol%. Using PVOH (A) with a relatively low saponification degree can improve heat sealability, etc. The upper limit of the saponification degree of PVOH (A) is preferably 83.0 mol%, and may be 80.0 mol% or 75.0 mol%. The lower limit of the saponification degree of PVOH (A) is preferably 71.0 mol%, more preferably 72.0 mol%, and in some cases, 75.0 mol%, 78.0 mol%, or 80.0 mol% may be even more preferable. When the saponification degree of PVOH (A) is equal to or greater than the above lower limit, blocking resistance, barrier properties, etc. tend to be improved. The saponification degree of PVOH is measured in accordance with JIS K6726:1994.

[0032] The viscosity of a 4% aqueous solution of PVOH (A) is preferably 2.0 to 20.0 mPa·s, more preferably 2.2 to 10.0 mPa·s, and even more preferably 2.4 to 7.0 mPa·s. Having the viscosity of a 4% aqueous solution of PVOH (A) within the above range can improve coatability, etc. The viscosity of a 4% aqueous solution of PVOH is adjusted by the degree of saponification, degree of polymerization, and whether or not the PVOH is modified. The viscosity of a 4% aqueous solution of PVOH is measured using a Brookfield viscometer at 60 rpm for the aqueous solution at 20°C.

[0033] Component (B) may be PVOH (B). The saponification degree of PVOH (B) may be, for example, 86.0 mol% or more and 100.0 mol% or less, but is preferably 86.0 mol% or more and less than 99.9 mol%. The lower limit of the saponification degree of PVOH (B) is preferably 86.5 mol%, and may also be 90.0 mol%, 93.0 mol%, 95.0 mol%, or 97.0 mol%. When the saponification degree of PVOH (B) is equal to or more than the above lower limit, blocking resistance, barrier properties, etc. can be improved. The upper limit of the saponification degree of PVOH (B) may be 99.5 mol%, 99.0 mol%, 98.0 mol%, 95.0 mol%, or 90.0 mol%.

[0034] The viscosity of a 4% aqueous solution of PVOH (B) may be, for example, 2.0 to 30.0 mPa s, preferably 2.0 to 20.0 mPa s, more preferably 2.5 to 10.0 mPa s, and even more preferably 3.0 to 7.0 mPa s. When the viscosity of the 4% aqueous solution of PVOH (B) is in the above range, it is possible to improve the coatability, etc.

[0035] Typically, the degree of saponification of PVOH (A) is lower than the degree of saponification of PVOH (B). The difference in the degree of saponification between PVOH (A) and PVOH (B) (the degree of saponification of PVOH (B) - the degree of saponification of PVOH (A)) may be, for example, 5 mol% or more, preferably 10 mol% or more and 40 mol% or less, and more preferably 10 mol% or more and less than 29.9 mol%. The lower limit of the difference in the degree of saponification may be 12 mol%. The upper limit of the difference in the degree of saponification may be 28 mol%.

[0036] The lower limit of the mass ratio (A / B) of PVOH (A) to PVOH (B) is preferably 10 / 90, more preferably 15 / 85, and may be 20 / 80, 30 / 70, 35 / 65, 40 / 60, or 50 / 50. The upper limit of the mass ratio (A / B) is preferably 70 / 30, more preferably 60 / 40, and may be 50 / 50 or 45 / 55.

[0037] The PVOH (PVOH (A) and PVOH (B)) may have monomer units derived from other monomers than vinyl alcohol units and vinyl ester units. PVOH having monomer units derived from other monomers than vinyl alcohol units and vinyl ester units is also referred to as modified PVOH, and PVOH not having monomer units derived from other monomers than vinyl alcohol units and vinyl ester units is also referred to as unmodified PVOH. Other monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; (meth)acrylic acid and its salts; (meth)acrylic acid esters; (meth)acrylamide; (meth)acrylamide derivatives such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid and its salts, (meth)acrylamidopropyldimethylamine and its salts or quaternary salts, and N-methylol(meth)acrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, and i-propyl vinyl ether. Examples of the other monomer include vinyl ethers such as butyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinyl halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and salts or esters thereof; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; 1,4-diacetoxybutene; 3,4-diacetoxy-1-butene; vinylformamide; and vinylpyrrolidone. As the other monomer, an α-olefin is preferred, and ethylene is more preferred.

[0038] The PVOH is preferably unmodified PVOH or α-olefin modified PVOH, and more preferably unmodified PVOH or ethylene modified PVOH.

[0039] The total content of vinyl alcohol units, vinyl ester units, and any α-olefin units relative to all monomer units of PVOH is preferably 95 mol % or more, more preferably 99 mol % or more, and may be 100 mol %.

[0040] The lower limit of the content of α-olefin units relative to all monomer units in the α-olefin-modified PVOH is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol% or 3 mol%. On the other hand, the upper limit of this content is preferably 19 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol% or 8 mol%. The lower limit of the content of ethylene units relative to all monomer units in the ethylene-modified PVOH is preferably 0.1 mol%, more preferably 0.5 mol%, even more preferably 1 mol%, and may be 2 mol% or 3 mol%. On the other hand, the upper limit of this content is preferably 19 mol%, more preferably 15 mol%, even more preferably 13 mol%, and may be 10 mol% or 8 mol%.

[0041] When the other monomer is other than an α-olefin, the upper limit of the content of monomer units derived from the other monomer relative to all monomer units in the PVOH is preferably 19 mol%, more preferably 15 mol%, and still more preferably 13 mol%, and may be 10 mol%, 8 mol%, 5 mol%, 3 mol%, or 1 mol%.

[0042] In one embodiment of the present invention, the PVOH may be substantially free of a monomer unit (1a) represented by the following formula (1), or may not have any monomer unit (1a).

[0043]

[0044] In formula (1), R １ ~R ６ are each independently a hydrogen atom or an organic group. X is a single bond or a linking group.

[0045] PVOH is represented by R in the above formula (1). １ ~R ６are all hydrogen atoms and X is a single bond, or the PVOH may be free of monomer units (1b). In addition, the PVOH may be free of monomer units (1c) having a 1,2-diol structure, or the PVOH may be free of monomer units (1c).

[0046] The upper limit of the content of the monomer unit (1a), the monomer unit (1b), or the monomer unit (1c) relative to the total monomer units in the PVOH is preferably 5 mol%, more preferably 3 mol%, even more preferably 1 mol%, and even more preferably 0.1 mol%. On the other hand, it may be preferable for the PVOH to contain a certain amount of the monomer unit (1a), the monomer unit (1b), or the monomer unit (1c). The monomer unit (1a), the monomer unit (1b), and the monomer unit (1c) are monomer units derived from hydroxy group-containing α-olefins, acylated products thereof, etc.

[0047] The lower limit of the PVOH content in layer (X) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass, and may be 95%, 97%, or 99% by mass. The upper limit of the content may be 100% by mass.

[0048] The layer (X) may contain components other than PVOH. Examples of such components include resins other than PVOH, inorganic particles, dispersants, surfactants, antifoaming agents, dyes, preservatives, interlayer adhesives, thickeners, and the like. These components may be component (A) or component (B). For example, inorganic particles may effectively function as component (B). Furthermore, when the layer (X) contains a PVOH (A) with a relatively low degree of saponification, the layer (X) preferably contains an antifoaming agent. Generally, PVOH with a low degree of saponification is prone to foaming. Therefore, when the layer (X) containing PVOH (A) is formed by coating, adding an antifoaming agent to the coating solution forming the layer (X) can ensure good coating. The antifoaming agent may be a surfactant.

[0049] The layer (X) may be a single layer or a laminate structure of multiple layers. When the layer (X) has a laminate structure of multiple layers, the compositions of the layers may be the same or different. In one embodiment of the present invention, the layer (X) is preferably a single layer.

[0050] The lower limit of the mass per unit area of ​​the layer (X) is 4 g / m ２ is preferred, and 5 g / m ２ By setting the mass per unit area of ​​the layer (X) to the above lower limit or more, the gas barrier property, heat sealability, etc. can be further improved. The upper limit of the mass per unit area of ​​the layer (X) is 10 g / m ２ is preferred, and 8 g / m ２ By setting the mass per unit area of ​​the layer (X) to the above upper limit or less, it is possible to reduce the thickness of the laminate.

[0051] The lower limit of the total mass of the component (A) and the component (B) per unit area in the layer (X) is 4 g / m ２ is preferred, and 5 g / m ２ By setting the total mass to the above lower limit or more, it is possible to further improve the gas barrier property, heat sealability, etc. The upper limit of the total mass of the component (A) and the component (B) per unit area in the layer (X) is 10 g / m ２ is preferred, and 8 g / m ２ By setting the total mass to the upper limit or less, it is possible to reduce the thickness of the laminate.

[0052] The lower limit of the mass of PVOH per unit area in the layer (X) is 4 g / m ２ is preferred, and 5 g / m ２ By setting the mass of the PVOH to the above lower limit or more, it is possible to further improve the gas barrier property, heat sealability, etc. The upper limit of the mass of PVOH per unit area in the layer (X) is 10 g / m ２ is preferred, and 8 g / m ２ By setting the mass of the PVOH to the above upper limit or less, it is possible to reduce the thickness of the laminate.

[0053] (Pigment Layer (Y)) A laminate according to one embodiment of the present invention may have a pigment layer (Y) (hereinafter, the pigment layer (Y) will also be referred to as "layer (Y)") laminated on the opposite side of the paper substrate to layer (X). Layer (Y) is a layer containing a pigment. Typically, a pigment layer is provided on a paper substrate for the purposes of improving printability, aesthetics, smoothness, and the like. However, in a laminate having a pigment layer as one outermost layer and a heat-seal layer as the other outermost layer, if the laminate is stacked, for example, in a roll, and left under pressure, the pigment layer and the heat-seal layer are likely to stick together. When the laminate is removed from such a state, the pigment layer may peel off while still attached to the heat-seal layer, resulting in defects in the pigment layer and / or the heat-seal layer. This phenomenon occurs more prominently in laminates with low blocking resistance. In contrast, the laminate of the present invention has good blocking resistance, and therefore, even when a pigment layer (Y) is provided, the pigment layer (Y) and the heat seal layer (X) are unlikely to stick to each other, and the occurrence of defects when the laminate is left in a rolled state or the like can be suppressed.

[0054] The layer (Y) may be laminated directly on the paper substrate, or may be laminated via another layer. The layer (Y) may be laminated on both sides of the paper substrate. The pigment contained in the layer (Y) is not particularly limited, and for example, known pigments used in coated paper can be used. The pigment may be an organic pigment or an inorganic pigment, and inorganic pigments are preferred. Examples of pigments include light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, engineered kaolin, clay, talc, silica, colloidal silica, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, calcium silicate, magnesium silicate, aluminum hydroxide, alumina, magnesium carbonate, magnesium hydroxide, kaolinite, antigorite, smectite, vermiculite, and mica. Among these, clay is preferred. One or more pigments can be used.

[0055] The content of the pigment in the layer (Y) is preferably from 60% by mass to 99% by mass, more preferably from 70% by mass to 95% by mass, and may be from 75% by mass to 90% by mass.

[0056] Layer (Y) usually contains a binder together with the pigment. Examples of binders that can be used include known binders used in coated paper. Examples of binders include vinyl alcohol polymers, acrylic polymers, cellulose derivatives, starches, styrene polymers, ester polymers, olefin polymers, fluororesins, silicone resins, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polystyrene, and polyamide. One or more binders can be used.

[0057] The content of the binder in layer (Y) is preferably from 1 to 40% by mass, more preferably from 5 to 30% by mass, and may be from 10 to 25% by mass. The total content of the pigment and binder in layer (Y) is preferably from 80 to 100% by mass, and may be from 90 to 100% by mass.

[0058] The layer (Y) may further contain other components in addition to the pigment and binder, such as a dispersant, a viscosity improver, a water retention agent, an antifoaming agent, a water resistance agent, a fluorescent dye, a coloring dye, a surfactant, a pH adjuster, an ultraviolet absorber, and a metal salt.

[0059] (Other Layers, Layer Structure, etc.) The laminate according to one embodiment of the present invention may further include layers other than the paper substrate, the heat-seal layer (X), and the pigment layer (Y). Examples of such layers include a precoat layer provided between the paper substrate and the heat-seal layer (X). The precoat layer may be a layer containing, as a main component, a resin such as an olefin polymer, a styrene polymer, or a polyester polymer. The precoat layer may be a coating layer. Further, other layers may include other resin layers, layers other than resin layers, etc. In one embodiment of the present invention, the laminate may not include any layers other than the paper substrate, the heat-seal layer (X), and the pigment layer (Y). When the laminate does not include any layers other than the paper substrate, the heat-seal layer (X), and the pigment layer (Y), biodegradability, productivity, etc. tend to be improved.

[0060] In the laminate according to one embodiment of the present invention, the number of paper substrates may be only one or may be multiple. In the laminate according to one embodiment of the present invention, the number of paper substrates is preferably only one.

[0061] In a laminate according to one embodiment of the present invention, the heat seal layer (X) and the pigment layer (Y) may each be a single layer or two or more layers. In a laminate according to one embodiment of the present invention, the heat seal layer (X) is preferably a single layer. When either the heat seal layer (X) or the pigment layer (Y) has two or more layers, the compositions, thicknesses, etc. of the layers may be the same or different.

[0062] Examples of the layer structure of the laminate according to one embodiment of the present invention are as follows: X represents the heat seal layer (X), Y represents the pigment layer (Y), and Z represents other layers. Paper substrate / X Paper substrate / Z / X Y / paper substrate / X Y / paper substrate / Z / X Y / paper substrate / Y / X Y / paper substrate / Y / Z / X X / paper substrate / X X / Z / paper substrate / Z / X X / Z / Y / paper substrate / Y / Z / X

[0063] The laminate according to one embodiment of the present invention can be suitably used as gas barrier paper, packaging material, etc. The laminate can also be used in a state where it has been formed into a predetermined shape (for example, a bag shape) by heat-sealing the heat-sealable layers (X) together. The heat-sealing method is not particularly limited, and known methods can be used, such as a hot plate heat sealer, impulse sealer, ultrasonic sealer, frictional heat sealer, or dielectric heating sealer.

[0064] <Method for producing laminate> The method for producing a laminate according to one embodiment of the present invention is not particularly limited, but the following method for providing a heat-sealable layer (X) by coating is preferred. That is, the production method includes a step of preparing a coating liquid and a step of forming a heat-sealable layer (X) by applying the coating liquid. The laminate according to one embodiment of the present invention may be coated paper.

[0065] The coating liquid contains PVOH and, as components other than the PVOH or PVOH, components (A) and (B). The coating liquid preferably contains PVOH (A) and PVOH (B). That is, the coating liquid is preferably prepared by mixing PVOH (A) and PVOH (B). The difference in degree of saponification between PVOH (A) and PVOH (B) used in preparing the coating liquid is preferably 10 mol% or more and 40 mol% or less. The specific and preferred forms of each component (PVOH, etc.) used in preparing the coating liquid are the same as the specific and preferred forms of each component contained in layer (X).

[0066] The solid content (solid content concentration) of the coating liquid is not particularly limited, but can be, for example, 3% by mass to 70% by mass, 5% by mass to 50% by mass, or 10% by mass to 30% by mass. The solvent for the coating liquid is not particularly limited, but water is preferred.

[0067] The viscosity of the coating liquid at 20° C. is preferably 2,000 mPa·s or less. When the viscosity of the coating liquid is equal to or less than the upper limit, good coatability can be exhibited.

[0068] The coating liquid can be applied by a conventionally known method, for example, using a blade coater, a flexo coater, a comma coater, a metering rod size press, a two-roll size press, a shim sizer, a bar coater, an air knife coater, a slit die coater, a gravure coater, a reverse gravure coater, a microgravure coater, a gate roll coater, or a curtain coater.

[0069] The method for drying the applied coating liquid is not particularly limited, and can be carried out using, for example, a hot air dryer, an infrared dryer, a gas burner, a hot plate, or the like.

[0070] When producing a laminate having a pigment layer (Y), the pigment layer (Y) can also be provided by coating, similar to the heat seal layer (X). Alternatively, a paper substrate provided with a pigment layer (Y) can also be used. Commercially available coated paper may be purchased and used as the paper substrate provided with the pigment layer (Y).

[0071] <Structure> A structure according to one embodiment of the present invention includes a laminate according to one embodiment of the present invention, in which the heat-sealable layers (X) are heat-sealed to each other. The structure may be made of a laminate according to one embodiment of the present invention. The structure may be made by stacking two laminates according to one embodiment of the present invention so that the heat-sealable layers (X) face each other and heat-sealing them, or by folding one laminate according to one embodiment of the present invention so that the heat-sealable layer (X) is on the inner side and heat-sealing it. The structure may have at least a portion where the heat-sealable layers (X) are heat-sealed to each other, and may also have a portion that is not heat-sealed. The method for heat-sealing the laminate is as described above. The structure may be in the shape of a bag, a box, a container, or the like. The structure may be a sealed structure or an unsealed structure.

[0072] The structure may have a sealed structure in which the heat seal layer (X) is disposed on the inner side and the heat seal layers (X) are heat-sealed to each other, and a gas (e.g., air) is sealed inside. The inside of the structure may further contain other components together with the gas.

[0073] The structure can be used for packaging containers for food, agricultural chemicals, medicines, cosmetics, medical supplies, electronic parts, clothing, etc., bags, cushioning materials, toys, etc.

[0074] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way.

[0075] (Viscosity Measurement) The viscosity was measured using a Brookfield viscometer at a rotation speed of 60 rpm while maintaining the liquid temperature at 20° C. The viscosity of the coating liquid was evaluated according to the following criteria: A: less than 2000 mPa·s B: 2000 mPa·s or more

[0076] (Measurement of endothermic peak by DSC) The endothermic peak of layer (X) in the laminate was measured by the following procedure. Approximately 2 mg of the measurement sample (laminate) was punched out with a 5 mmφ punch, filled into an aluminum pan, and set in a DSC measurement device "DSC2500" (manufactured by TA Instruments, Inc.). First, to remove moisture from the measurement sample, the sample was preheated by heating from 0°C to 150°C, and then the temperature was held for 1 minute. Next, the sample was cooled from 150°C to 0°C, held for 1 minute, and then reheated from 0°C to 260°C. The heating rate for preheating was 200°C / min, and the cooling rate and reheating rate were 10°C / min.

[0077] (Heat sealability) The heat sealability of the laminate was evaluated by the following procedure. The surfaces of the layers (X) of a 15 mm wide laminate were overlapped and heat-sealed using a thermal gradient device under conditions of a temperature of 155°C, a time of 5 seconds, and a pressure of 3 MPa. A peel test was then performed using an autograph. The peeling speed was 100 mm / min. The peel strength at this time was taken as the heat seal strength and was used as an index of heat sealability.

[0078] (Blocking Resistance) The blocking resistance of the laminate was evaluated by the following procedure. The laminate was cut into a size of 1.5 cm x 21.0 cm in the TD direction. The coated surface (the exposed surface of layer (X)) and the uncoated surface (the exposed surface opposite layer (X)) of the cut laminate were overlapped, pressed at 1 MPa, and left in a thermo-hygrostat at 40°C x 90% RH for 24 hours. Thereafter, the blocking strength was confirmed using an autograph. The blocking resistance was evaluated based on the degree of peeling of layer (X) and the strength of the peel resistance, according to the following criteria: A: No peeling of layer (X). B: Slight peeling of layer (X) occurred, and strong peel resistance was felt. C: Almost all of layer (X) peeled, and strong peel resistance was felt.

[0079] Example 1 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 40 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content, 60 parts by mass of a vinyl alcohol polymer ("5-88" manufactured by Kuraray Co., Ltd.: saponification degree 86.6 mol %, 4% aqueous solution viscosity 4.7 mPa s) solids content, and water to prepare a coating solution with a solids concentration of 15% by mass. The viscosity of the obtained coating solution (X) was less than 2000 mPa s. The viscosity of coating solution (X) was low and excellent in coatability. Therefore, productivity was also good. The paper substrate had a basis weight of 68 g / m ２ PPC paper, the coating amount after drying was 6 g / m ２ The coating solution (X) was applied using a wire bar so that the thickness of the coated film was 100°C, and the coated film was dried at 100°C for 5 minutes to provide a layer (X). A laminate was thus obtained. The endothermic peak of the obtained laminate was measured by DSC, and the heat sealability and blocking resistance were evaluated using the methods described above. The results are shown in Table 1.

[0080] Example 2 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 40 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 60 parts by mass of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, 4% aqueous solution viscosity 5.4 mPa s) solids content as component (B), and water to adjust the concentration to 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0081] Example 3 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 60 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol%, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 40 parts by mass of a vinyl alcohol polymer ("28-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.0 mol%, 4% aqueous solution viscosity 29.8 mPa s) solids content as component (B), and water to adjust the concentration to 15% by mass. The resulting coating solution (X) had a high viscosity of 2000 mPa s or more. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0082] Example 4 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 60 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 40 parts by mass of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, 4% aqueous solution viscosity 5.4 mPa s) solids content as component (B), and water to adjust the concentration to 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0083] Example 5 As the coating solution (X) for forming layer (X), as shown in Table 1, 60 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 40 parts by mass of a vinyl alcohol polymer ("RS-2117" manufactured by Kuraray Co., Ltd.: saponification degree 97.5 mol %, 4% aqueous solution viscosity 25.2 mPa s) solids content as component (B), and water were mixed to prepare a coating solution adjusted to a concentration of 15% by mass. The viscosity of the resulting coating solution (X) was 2000 mPa s or more, and thus was high. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were carried out. The results are shown in Table 1.

[0084] Example 6 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 60 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol%, 4% aqueous solution viscosity 5.1 mPa·s) solids content as component (A), 40 parts by mass of a vinyl alcohol polymer ("Ultiloc 5003" manufactured by Sekisui Specialty Chemicals America, LLC: saponification degree 99.0 mol%, 4% aqueous solution viscosity 5.4 mPa·s) solids content as component (B), and water to a concentration of 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa·s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0085] Example 7 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing 30 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 70 parts by mass of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, 4% aqueous solution viscosity 5.4 mPa s) solids content as component (B), and water to adjust the concentration to 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0086] Example 8 As the coating solution (X) for forming layer (X), as shown in Table 1, 60 parts by mass of a vinyl alcohol polymer ("3-80" manufactured by Kuraray Co., Ltd.: saponification degree 81.2 mol %, 4% aqueous solution viscosity 2.8 mPa s) solids content as component (A), 40 parts by mass of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, 4% aqueous solution viscosity 5.4 mPa s) solids content as component (B), and water were mixed to prepare a coating solution adjusted to a concentration of 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0087] Example 9 As the coating solution (X) for forming layer (X), as shown in Table 1, 20 parts by mass of a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol %, 4% aqueous solution viscosity 5.1 mPa s) solids content as component (A), 80 parts by mass of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, 4% aqueous solution viscosity 5.4 mPa s) solids content as component (B), and water were mixed to prepare a coating solution adjusted to a concentration of 15% by mass. The viscosity of the resulting coating solution (X) was less than 2000 mPa s. The coating solution (X) had a low viscosity and excellent coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1, except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0088] Comparative Example 1 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing a vinyl alcohol polymer ("5-74" manufactured by Kuraray Co., Ltd.: saponification degree 72.8 mol%, viscosity of 4% aqueous solution 5.1 mPa s) and water to a concentration of 15% by mass. The viscosity of the obtained coating solution (X) was less than 2000 mPa s. The viscosity of coating solution (X) was low and it was excellent in coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1 except that the above coating solution (X) was used, and measurements and evaluations were carried out. The results are shown in Table 1.

[0089] Comparative Example 2 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing a vinyl alcohol polymer ("5-88" manufactured by Kuraray Co., Ltd.: degree of saponification 86.6 mol %, viscosity of 4% aqueous solution 4.7 mPa s) and water to a concentration of 15 mass %. The viscosity of the obtained coating solution (X) was less than 2000 mPa s. The viscosity of coating solution (X) was low and it was excellent in coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1 except that the above coating solution (X) was used, and measurements and evaluations were carried out. The results are shown in Table 1.

[0090] Comparative Example 3 As shown in Table 1, a coating solution (X) for forming layer (X) was prepared by mixing a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol%, viscosity of 4% aqueous solution 5.4 mPa s) and water to a concentration of 15% by mass. The viscosity of the obtained coating solution (X) was less than 2000 mPa s. The viscosity of coating solution (X) was low and it was excellent in coatability. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1 except that the above coating solution (X) was used, and measurements and evaluations were carried out. The results are shown in Table 1.

[0091] Comparative Example 4 As the coating solution (X) for forming layer (X), as shown in Table 1, 50 parts by mass of solids of a vinyl alcohol polymer ("5-88" manufactured by Kuraray Co., Ltd.: saponification degree 86.6 mol %, viscosity of 4% aqueous solution 4.7 mPa s) as component (A), 50 parts by mass of solids of a vinyl alcohol polymer ("5-98" manufactured by Kuraray Co., Ltd.: saponification degree 98.9 mol %, viscosity of 4% aqueous solution 5.4 mPa s) as component (B), and water were mixed to prepare a coating solution adjusted to a concentration of 15% by mass. The viscosity of the obtained coating solution (X) was less than 2000 mPa s. The viscosity of coating solution (X) was low and the coating properties were excellent. Therefore, productivity was also good. A laminate was obtained in the same manner as in Example 1 except that the above coating solution (X) was used, and measurements and evaluations were performed. The results are shown in Table 1.

[0092]

[0093] As shown in Table 1, in the DSC measurement, each of the laminates of Examples 1 to 9, which had a low-temperature endothermic peak in the range of 150°C or higher but lower than 190°C and a high-temperature endothermic peak in the range of 190°C or higher, had a heat seal strength of 0.9 N / 15 mm or higher and was evaluated as A or B in blocking resistance. Each of the laminates of the Examples had good heat sealability and blocking resistance.

[0094] The laminate of the present invention can be suitably used as a packaging material or the like.

Claims

1. A laminate comprising a paper substrate and a heat seal layer (X) laminated on the paper substrate and containing a vinyl alcohol polymer, wherein, in DSC measurement of the heat seal layer (X), there is at least one endothermic peak in the range of 150°C or higher but lower than 190°C and at least one endothermic peak in the range of 190°C or higher.

2. The laminate according to claim 1, wherein the heat seal layer (X) comprises a component (A) corresponding to the endothermic peak in the range of 150°C or higher but lower than 190°C, and a component (B) corresponding to the endothermic peak in the range of 190°C or higher, and the mass ratio (A / B) of the components (A) to (B) is 10 / 90 to 70 / 30.

3. The laminate according to claim 2, wherein component (A) is a vinyl alcohol polymer (A) having a degree of saponification of 70.0 mol % or more and less than 86.0 mol %.

4. The laminate according to claim 3, wherein the viscosity of a 4% aqueous solution of the vinyl alcohol polymer (A) is 2.0 to 20.0 mPa·s.

5. The laminate according to any one of claims 2 to 4, wherein component (B) is a vinyl alcohol polymer (B) having a degree of saponification of 86.0 mol % or more and less than 99.9 mol %.

6. The laminate according to claim 5, wherein the viscosity of a 4% aqueous solution of the vinyl alcohol polymer (B) is 2.0 to 20.0 mPa·s.

7. The laminate according to claim 2, wherein component (A) is a vinyl alcohol polymer (A) having a degree of saponification of 70.0 mol% or more and less than 86.0 mol%, component (B) is a vinyl alcohol polymer (B) having a degree of saponification of 86.0 mol% or more and less than 99.9 mol%, and the difference in the degree of saponification between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is 10 mol% or more and less than 29.9 mol%.

8. The total mass of component (A) and component (B) per unit area is 4 to 10 g / m ２ The laminate according to any one of claims 2 to 4 and 7, 9. The laminate according to claim 1, wherein the heat seal layer (X) comprises a vinyl alcohol polymer (A) corresponding to an endothermic peak in the range of 150°C or higher but lower than 190°C, and a vinyl alcohol polymer (B) corresponding to an endothermic peak in the range of 190°C or higher, and the difference in degree of saponification between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is 10 mol% or higher but 40 mol% or lower.

10. The laminate described in claim 9, wherein the degree of saponification of the vinyl alcohol polymer (A) is 70.0 mol% or more and less than 86.0 mol%, and the degree of saponification of the vinyl alcohol polymer (B) is 86.0 mol% or more and less than 99.9 mol%.

11. The laminate according to any one of claims 1 to 4, 7, 9 and 10, further comprising a pigment layer (Y) laminated on the side of the paper substrate opposite to the heat seal layer (X).

12. A structure comprising the laminate according to any one of claims 1 to 4, 7, 9 and 10, wherein the heat-sealable layers (X) are heat-sealed to each other.

13. A structure comprising the laminate according to any one of claims 1 to 4, 7, 9 and 10, wherein the heat seal layer (X) is disposed on the inner side, the heat seal layers (X) are heat sealed together to form a sealed structure, and a gas is sealed inside.

14. A method for producing a laminate comprising a paper substrate and a heat seal layer (X) laminated on the paper substrate and containing a vinyl alcohol polymer, the method comprising the steps of mixing a vinyl alcohol polymer (A) and a vinyl alcohol polymer (B) to prepare a coating liquid, and applying the coating liquid to form the heat seal layer (X), wherein the difference in degree of saponification between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is 10 mol% or more and 40 mol% or less.

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