Laminate, molded body, and method for producing laminate

Abstract

Provided is a laminate comprising a paper substrate layer and a first resin layer disposed on at least one surface of the paper substrate layer. The first resin layer contains a poly(3-hydroxybutyrate)-based resin and a polyvinyl alcohol having a saponification degree of less than 90 mol%. The weight ratio of the poly(3-hydroxybutyrate)-based resin / the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.0 in terms of solid content. The laminate can be produced by applying a water-based coating liquid to at least one surface of a paper substrate and drying the resultant to form a first resin layer on the paper substrate.

Description

Laminate, molded body, and method for manufacturing laminate

[0001] The present invention relates to a laminate having a resin layer containing a poly(3-hydroxybutyrate)-based resin, and a molded article containing the laminate.

[0002] In recent years, environmental problems caused by discarded plastics have been attracting attention. In particular, marine pollution caused by discarded plastics is serious, and there are high hopes for the widespread use of biodegradable plastics that decompose in the natural environment.

[0003] Various types of biodegradable plastics are known, but among them, poly(3-hydroxybutyrate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species, and because they are capable of biodegrading not only in soil but also in seawater, they have attracted attention as a material that can solve the above-mentioned problems.

[0004] A laminate obtained by laminating a layer containing a poly(3-hydroxybutyrate)-based resin onto a biodegradable paper substrate is extremely promising from the viewpoint of environmental protection, since both the resin and the substrate are materials with excellent biodegradability.

[0005] As an example of such a laminate, Patent Document 1 describes a coated paper having a coating layer on a paper substrate, the coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), a type of poly(3-hydroxybutyrate) resin, and an adhesive such as polyvinyl alcohol in a specific ratio, with the aim of reducing coating defects.

[0006] International Publication No. 2021 / 256381

[0007] The coated paper described in Patent Document 1 has a certain degree of water resistance and heat sealability, but the adhesion between the coating layer and the paper substrate is insufficient, and the coating layer tends to peel off easily from the paper substrate, which can result in poor heat sealability, for example, depending on the heating conditions during heat sealing. Furthermore, when the coated paper is used in the form of paper containers such as paper tableware, a high level of water resistance (e.g., long-term water resistance in hot water) is sometimes required, but Patent Document 1 does not consider such a high level of water resistance.

[0008] In view of the above-described current situation, an object of the present invention is to provide a laminate having a resin layer containing a poly(3-hydroxybutyrate)-based resin on a paper substrate, which laminate has both good binding properties and water resistance.

[0009] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by blending polyvinyl alcohol having a specific degree of saponification with a resin layer containing a poly(3-hydroxybutyrate)-based resin in a specific ratio, and have thus completed the present invention.

[0010] Specifically, the present invention relates to a laminate comprising a paper substrate layer and a first resin layer provided on at least one surface of the paper substrate layer, wherein the first resin layer contains a poly(3-hydroxybutyrate)-based resin and a polyvinyl alcohol having a saponification degree of less than 90 mol%, and the solids weight ratio of the poly(3-hydroxybutyrate)-based resin to the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.0. The present invention also relates to a laminate manufacturing method comprising the steps of applying an aqueous coating liquid to at least one surface of the paper substrate and drying the liquid to form a first resin layer on the paper substrate, wherein the aqueous coating liquid contains a poly(3-hydroxybutyrate)-based resin and a polyvinyl alcohol having a saponification degree of less than 90 mol%, and the solids weight ratio of the poly(3-hydroxybutyrate)-based resin to the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.0.

[0011] According to the present invention, it is possible to provide a laminate having a resin layer containing a poly(3-hydroxybutyrate)-based resin on a paper substrate, which laminate has both good binding properties and water resistance. A preferred embodiment of the laminate exhibits long-term water resistance in hot water and can be formed into paper containers such as paper tableware. A preferred embodiment of the laminate exhibits good heat sealing properties even when heat-sealed at a relatively low heating temperature. Another embodiment of the laminate further includes a second resin layer, and exhibits good adhesion (lamination properties) between the paper substrate layer and the second substrate layer.

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0013] [Laminate] A laminate according to one embodiment of the present disclosure includes at least a paper substrate layer and a first resin layer laminated on one or both sides of the paper substrate layer. The laminate as a whole can exhibit biodegradability. The first resin layer may be laminated directly on the paper substrate layer or may be laminated via another layer, but it is preferably laminated directly on the paper substrate layer.

[0014] In one embodiment of the present disclosure, the first resin layer may be the outermost layer in the laminate, and in this case, the first resin layer may function as a heat seal layer, a water-resistant layer, and / or an oil-resistant layer, etc.

[0015] In another embodiment of the present disclosure, another layer may be laminated on the first resin layer. In this case, the first resin layer may function as an anchor coat layer between the paper substrate layer and the other layer. The other layer is not particularly limited and may be a resin layer or an inorganic layer, but one example is the second resin layer described below.

[0016] The surface of the paper base layer opposite to the side on which the first resin layer is laminated may be the outermost layer, or may have any other layer laminated thereon. The layer may be a layer that can correspond to the first resin layer, or may be a layer other than the first resin layer.

[0017] (Paper base layer) The paper base layer is composed of a sheet mainly made of pulp. The paper base can be obtained by papermaking a paper stock containing pulp, fillers, various auxiliaries, etc. The type of paper that can be used as the paper base is not particularly limited, and examples include cup base paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard.

[0018] The pulp is not particularly limited, and examples thereof include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp; mechanical pulps such as stone-ground pulp and thermomechanical pulp; wood fibers such as deinked pulp and recycled paper pulp; and non-wood fibers obtained from kenaf, bamboo, hemp, etc. These can be used in appropriate combinations.

[0019] Among these, it is preferable to use chemical pulp or mechanical pulp made from wood fibers, and it is more preferable to use chemical pulp, for reasons such as the fact that foreign matter is less likely to be mixed into the paper base material, that discoloration over time is less likely to occur when recycled and used as a waste paper raw material, that the high whiteness results in a good surface appearance when printed, and that the value is particularly high when used as a packaging material. Specifically, it is preferable that the blending amount of chemical pulp such as LBKP or NBKP in the pulp is 80% or more, and it is particularly preferable that the blending amount of chemical pulp is 100%.

[0020] The filler is not particularly limited, and examples thereof include inorganic fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, and calcium sulfate; and organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, and hollow microparticles. Note that fillers are not essential materials and may not be used.

[0021] The various auxiliaries are not particularly limited and include, for example, sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA), polyacrylamide polymers, polyvinyl alcohol polymers, cationized starch, various modified starches, dry strength agents such as urea-formalin resin and melamine-formalin resin, wet strength agents, retention aids, drainage aids, coagulants, aluminum sulfate, bulking agents, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, UV inhibitors, anti-fading agents, pitch control agents, slime control agents, etc. These may be selected and used as needed.

[0022] The surface of the paper substrate may be treated with various chemicals. The chemicals are not particularly limited, and examples thereof include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retention agents, thickeners, lubricants, etc. Only one type of chemical may be used, or two or more types may be used in combination. Furthermore, these chemicals may be used in combination with pigments.

[0023] The pigment is not particularly limited, and examples thereof include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, satin white, etc.; organic pigments such as solid, hollow, or core-shell type pigments, etc. Only one type of pigment may be used, or two or more types may be used in combination.

[0024] The basis weight of the paper substrate can be appropriately selected depending on the desired quality and the use of the laminate, but is usually 20 g / m ２ More than 600g / m ２ Preferably, the weight is 25 g / m or less. ２ More than 600g / m ２ When the laminate is used for packaging materials such as wrapping paper, paper bags, lids, liner papers, and soft packaging materials, or posters to be used outdoors, the preferred weight is 30 g / m ２ 150g / m or more ２It is more preferable that the soft packaging material has a density of 30 g / m or less. ２ ~100g / m ２ When the laminate is used for paper tableware such as paper cups, paper boxes, paper plates, paper trays, and other paper containers, it is recommended that the thickness be 150 g / m or less. ２ More than 300g / m ２ It is more preferable that:

[0025] The density of the paper substrate can be appropriately selected depending on the desired quality, handling, etc., but is usually 0.5 g / cm ３ 1.0g / cm or more ３ It is preferable that:

[0026] The method for producing the paper base (papermaking) is not particularly limited, and can be carried out by appropriately selecting a known papermaking machine, such as a Fourdrinier papermaking machine, a cylinder papermaking machine, a short wire papermaking machine, or a twin-wire papermaking machine such as a gap former type or a hybrid former type (on-top former type). The pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking). After papermaking in the acidic range, an alkaline agent may be coated on the surface of the paper layer. The paper base may be composed of a single layer, or two or more layers.

[0027] When treating the surface of a paper substrate with a chemical, the method of surface treatment is not particularly limited, and known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, or a curtain coater can be used.

[0028] (First Resin Layer) The first resin layer provided on at least one surface of the paper substrate layer contains at least a poly(3-hydroxybutyrate) resin and a polyvinyl alcohol exhibiting a specific degree of saponification. The resin components contained in the first resin layer may consist only of the poly(3-hydroxybutyrate) resin and the polyvinyl alcohol, or may further contain another resin. The other resin may be a biodegradable resin, as described below.

[0029] The first resin layer preferably contains 50% by weight or more of a poly(3-hydroxybutyrate)-based resin (hereinafter sometimes abbreviated as P3HB), more preferably 70% by weight or more, even more preferably 80% by weight or more, and even more preferably 90% by weight or more. By using a poly(3-hydroxybutyrate)-based resin as a main component, the first resin layer can exhibit biodegradability, particularly seawater degradability.

[0030] P3HB refers to a homopolymer having 3-hydroxybutyrate units and / or a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units. From the viewpoint of seawater degradability, it is preferable to include a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0031] The hydroxyalkanoic acid constituting the copolymer is not particularly limited, and examples thereof include 3-hydroxybutanoic acid, as well as 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid.

[0032] Specific examples of P3HB include poly(3-hydroxybutyrate) (abbreviation: PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Examples of suitable poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH). Among these, PHB, PHBH, P3HB3HV, and P3HB4HB are preferred because of their ease of industrial production.

[0033] Among these, PHBH is particularly preferred from the viewpoints that its melting point and crystallinity can be changed by changing the composition ratio of repeating units, and as a result, its physical properties such as Young's modulus and heat resistance can be adjusted, it can be imparted with physical properties between those of polypropylene and polyethylene, it is easy to produce industrially, and it is a physically useful plastic.

[0034] The first resin layer preferably contains 50 wt % or more of PHBH, more preferably 70 wt % or more, even more preferably 80 wt % or more, and even more preferably 90 wt % or more. The resin component contained in the first resin layer may be only PHBH and the polyvinyl alcohol, or may further contain another resin.

[0035] Examples of resins other than PHBH and polyvinyl alcohol include P3HB other than PHBH, and biodegradable resins other than P3HB, such as aliphatic polyester resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate.

[0036] A specific method for producing PHBH is described in, for example, International Publication No. 2010 / 013483. Commercially available PHBH products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0037] The average content ratio of the constituent monomers in PHBH is preferably 3HB / 3HH = 97 to 75 / 3 to 25 (mol % / mol %), and more preferably 3HB / 3HH = 94 to 82 / 6 to 18 (mol % / mol %). When the average content ratio of 3HH in PHBH is 3 mol % or more, good adhesion can be obtained by heat sealing. Furthermore, PHBH with an average content ratio of 3HH of 25 mol % or less does not have an excessively slow crystallization rate and is relatively easy to produce.

[0038] The PHBH having an average content ratio of 3HH of 3 to 25 mol% may be composed of one type of PHBH, may be composed of a mixture of at least two types of PHBH having different content ratios of constituent monomers, or may be composed of a mixture of at least one type of PHBH and PHB.

[0039] The average content ratio of each constituent monomer in PHBH can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139 or by NMR measurement. The average content ratio means the molar ratio of 3HB to 3HH in the entire PHBH contained in the first resin layer, and when the PHBH is a mixture containing at least two types of PHBH, or a mixture containing at least one type of PHBH and PHB, it means the molar ratio of each monomer contained in the entire mixture.

[0040] The weight-average molecular weight (hereinafter sometimes referred to as Mw) of P3HB contained in the first resin layer can be selected as appropriate, but from the viewpoint of achieving both mechanical properties and processability, it is preferably 50,000 to 700,000, more preferably 100,000 to 600,000, and even more preferably 150,000 to 550,000. When the weight-average molecular weight of P3HB is 50,000 or more, good mechanical properties are obtained, and when it is 700,000 or less, good adhesiveness can be obtained by heat sealing.

[0041] The weight average molecular weight of P3HB can be determined as a polystyrene-equivalent molecular weight by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase.

[0042] (Polyvinyl alcohol) In addition to P3HB, the first resin layer contains polyvinyl alcohol (hereinafter, sometimes abbreviated as PVA). By including PVA in the first resin layer, the binding strength between the paper base layer and the first resin layer can be improved.

[0043] PVA is typically a saponified vinyl ester polymer (a polymer containing at least a vinyl ester monomer as a constituent monomer). In the laminate according to the present disclosure, a PVA with a saponification degree of less than 90 mol% is used. PVA with a relatively low saponification degree like this has slightly reduced hydrophilicity, and improved compatibility with P3HB further improves the adhesiveness between the paper substrate layer and the first resin layer, resulting in improved heat-sealability or lamination properties of the laminate. On the other hand, PVA with a saponification degree of 90 mol% or more has extremely high hydrophilicity, which reduces compatibility with P3HB and tends to result in insufficient adhesiveness between the paper substrate layer and the resin layer.

[0044] The saponification degree of the PVA may be 89 mol% or less. It may also be 85 mol% or less, 80 mol% or less, or 75 mol% or less. There is no particular lower limit, but a lower limit of 60 mol% or more is preferred, 65 mol% or more is more preferred, and 70 mol% or more is even more preferred. Commercially available PVAs exhibiting such a saponification degree can be used. The saponification degree of PVA can be measured, for example, by the method specified in JIS K6726.

[0045] Incidentally, 28-98 manufactured by Kuraray Co., Ltd., which is a fully saponified PVA used in Example 1 of Patent Document 1, has a degree of saponification of about 98 to 99 mol%, while RS1713 manufactured by Kuraray Co., Ltd., which is a partially saponified ethylene-vinyl acetate copolymer (ethylene-modified PVA) used in Example 9 of the same document, has a degree of saponification of 92 to 94 mol%, both of which are outside the above-mentioned ranges of the numerical value of the saponification degree.

[0046] The average degree of polymerization of the PVA is not particularly limited, but may be, for example, 100 or more, preferably 200 or more, more preferably 300 or more, and even more preferably 500 or more. The upper limit may be, for example, 4000 or less, preferably 3000 or less, more preferably 2000 or less, and even more preferably 1000 or less. The average degree of polymerization of the PVA can be measured, for example, by the method specified in JIS K6726.

[0047] The PVA may have units derived from monomers other than vinyl alcohol and vinyl ester monomers (i.e., may be modified with other monomers). However, since olefin-modified (e.g., ethylene-modified) PVA has increased lipophilicity, which may reduce its affinity with the paper substrate and reduce the adhesive strength between the paper substrate layer and the resin layer, it is preferable to use PVA that has not been olefin-modified.

[0048] The content ratio of P3HB to PVA in the first resin layer is set so that the solids weight ratio of P3HB / PVA is within the range of 99.8 / 0.2 to 95.0 / 5.0. Using both resins in such a ratio can achieve the effects of using PVA with a specific degree of saponification while ensuring good water resistance of the laminate. It also achieves good biodegradability derived from P3HB. If the PVA content is too low, the adhesion between the paper substrate layer and the first resin layer will be reduced, resulting in insufficient heat sealability or lamination of the laminate. Conversely, if the PVA content is too high, the laminate will have insufficient water resistance and may also have reduced biodegradability.

[0049] The solids weight ratio of P3HB / PVA is preferably 99.5 / 0.5 to 95.0 / 5.0, more preferably 99.0 / 1.0 to 96.0 / 4.0, still more preferably 98.5 / 1.5 to 96.5 / 3.5, and particularly preferably 98.0 / 2.0 to 97.0 / 3.0.

[0050] The first resin layer may contain, to the extent that the effects of the invention are not impaired, one or more of the following: dispersants or emulsifiers, pH adjusters, inorganic fillers, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding property improvers, etc. However, these are optional components, and the first resin layer may not contain these components.

[0051] The thickness of the first resin layer is not particularly limited and can be appropriately determined taking into consideration the performance and productivity desired for the first resin layer, but specifically, it is preferably 0.5 to 30 μm, more preferably 1 to 20 μm, and even more preferably 2 to 15 μm. Having such a thickness allows the first resin layer to fully exhibit its performance. Furthermore, it reduces production costs and makes handling and molding of the laminate relatively easy.

[0052] The first resin layer may be formed by extrusion lamination or thermal lamination, but is preferably formed by applying an aqueous coating liquid, in which a resin component containing at least P3HB and PVA is dissolved or dispersed in a liquid such as water, to the surface of the paper substrate and then heating and drying (hereinafter sometimes referred to as a "coating method"). In particular, when the first resin layer is directly laminated on the paper substrate layer without any other layer in between, a portion of the coating liquid penetrates into the paper substrate layer, making it easier to improve the adhesion between the paper substrate layer and the first resin layer, so the coating method is preferred.

[0053] The aqueous coating liquid can be prepared by referring to, for example, International Publication No. 2021 / 075412.

[0054] The method for applying the aqueous coating liquid to the paper substrate is not particularly limited, and any known method capable of forming a resin layer on a substrate can be used as appropriate. Specifically, a spraying method, a scattering method, a slit coater method, an air knife coater method, a roll coater method, a bar coater method, a comma coater method, a blade coater method, a screen printing method, a gravure printing method, etc. can be used. Before applying the aqueous coating liquid, a step of subjecting the paper substrate to a surface treatment such as a corona treatment may be carried out.

[0055] The drying treatment after coating can be carried out using a known heating method, such as hot air heating, infrared heating, ultrasonic irradiation, microwave heating, roll heating, or hot plate heating, which can be used alone or in combination of two or more.

[0056] In the drying treatment after application, it is preferable to form a film by heating at a temperature at which the resin components contained in the first resin layer, particularly the main resin component P3HB, can melt. This causes the P3HB in the first resin layer to melt and then cool and solidify, smoothing the surface of the first resin layer (the surface not facing the paper base layer) and further improving the bonding between the paper base layer and the first resin layer, thereby further improving heat-sealing properties or lamination properties.

[0057] From the above viewpoints, the heating temperature in the drying treatment after application is preferably 130° C. or higher, more preferably 140° C. or higher, even more preferably 150° C. or higher, and particularly preferably 160° C. or higher. From the viewpoint of avoiding thermal decomposition of P3HB, the upper limit of the heating temperature is preferably 180° C. or lower.

[0058] The heating time in the drying treatment after application is not particularly limited and can be set appropriately, but may be, for example, 10 seconds to 10 minutes, and preferably about 30 seconds to 5 minutes.

[0059] The surface of the first resin layer (the surface opposite to the paper substrate layer), whose smoothness has been increased by the drying treatment after application, can exhibit a high gloss. Specifically, the gloss of the surface of the first resin layer, measured at an incident angle of 60° in accordance with the "Specular Gloss - Measurement Method" specified in JIS Z 8741:1997, is preferably 5% or more. A laminate including a first resin layer exhibiting such a gloss has improved adhesion between the paper substrate layer and the first resin layer, and can further improve heat-sealing properties or lamination properties.

[0060] The gloss value is preferably 7% or more, more preferably 8% or more, even more preferably 9% or more, and particularly preferably 10% or more. The upper limit is not particularly limited, but may be, for example, 20% or less, or 15% or less. If the heating temperature in the drying treatment after application is not sufficiently high, the gloss value of the surface of the first resin layer is usually less than 5%.

[0061] The coating amount of the first resin layer is not particularly limited and can be appropriately determined in consideration of the performance and productivity required of the first resin layer. Specifically, the coating amount of the first resin layer is 1 to 30 g / m as the basis weight measured in accordance with JIS P 8124. ２ It is preferable that the density is 2 to 20 g / m ２ More preferably, 3 to 15 g / m ２ When the basis weight is within this range, the performance of the first resin layer can be fully exhibited, production costs can be reduced, and handling and molding of the laminate can be made relatively easy.

[0062] In a laminate according to one embodiment of the present disclosure, the first resin layer may constitute the outermost layer. In this case, the first resin layer may function as a heat seal layer, a water-resistant layer, and / or an oil-resistant layer, etc. In this embodiment, the thickness of the first resin layer may be 0.5 to 30 μm as described above, but is preferably 3 to 25 μm, and more preferably 5 to 20 μm.

[0063] The heat seal layer is a layer having heat sealing suitability, specifically, a layer that can be bonded to an object by heat and pressure bonding. The object may be the same heat seal layer, a paper substrate layer, or an article made of another material. The laminate according to the present disclosure can achieve good heat sealing properties even at a relatively low heating temperature during heat sealing. Such a heating temperature is not limited, but may be, for example, about 110 to 160°C, preferably 120 to 150°C, and more preferably 125 to 140°C.

[0064] According to a preferred embodiment of the present disclosure, the water-resistant layer has a water absorption (Cobb value) of 20 g / m2 measured using hot water at 90°C for a contact time of 1800 seconds in accordance with "Paper and board - Water absorption test method - Cobb method" specified in JIS P 8140:1998. ２ Since the first resin layer exhibits long-term water resistance against hot water, the laminate according to the present disclosure can be formed into paper containers such as paper tableware and used. ２ Preferably, it is 5 g / m or less.２ More preferably, it is:

[0065] According to a preferred embodiment of the present disclosure, the oil-resistant layer refers to a layer having an average kit number of 10 or more measured at any five points on the surface of the layer in accordance with "Paper and paperboard - Oil repellency test method - Kit method" specified in JAPAN TAPPI No. 41:2000. The average kit number is preferably 11 or more, and more preferably 12.

[0066] (Second Resin Layer) In a laminate according to another aspect of the present disclosure, a second resin layer may be further laminated on the first resin layer. In this aspect, the paper base layer, the first resin layer, and the second resin layer are laminated in this order.

[0067] In this embodiment, the first resin layer functions as an anchor coat layer between the paper substrate layer and the second resin layer, and since the adhesiveness between the paper substrate layer and the first resin layer is good, the lamination property (lamination strength) between the paper substrate layer and the second resin layer can also be improved. Furthermore, by providing the second resin layer, it is possible to impart a high level of water resistance and oil resistance to the laminate. In this embodiment, it is sufficient that the first resin layer has adhesive properties between the paper substrate layer and the second resin layer. As described above, the thickness of the first resin layer may be 0.5 to 30 μm, but is preferably 0.7 to 15 μm, and more preferably 1 to 10 μm. The second resin layer may be the outermost layer in the laminate, or another layer may be laminated on top of the second resin layer.

[0068] The second resin layer preferably contains a biodegradable resin and exhibits biodegradability. This can enhance the biodegradability of the entire laminate. Usable biodegradable resins include the resins described above for the first resin layer, specifically, P3HB, aliphatic polyester resins, aliphatic aromatic polyester resins, and the like.

[0069] From the viewpoint of affinity with the first resin layer, the second resin layer preferably contains at least P3HB. This can further improve adhesion between the first resin layer and the second resin layer. However, the second resin layer does not need to contain the aforementioned PVA. The second resin layer preferably contains 50 wt% or more of P3HB, more preferably 70 wt% or more, even more preferably 80 wt% or more, and even more preferably 90 wt% or more. It may also be 95 wt% or more. The resin component contained in the second resin layer may be only P3HB, or it may further contain another resin. The aforementioned biodegradable resin can be used as the other resin.

[0070] The type of P3HB that can be used in the second resin layer is the same as the P3HB that can be used in the first resin layer, and detailed description thereof will be omitted. Although not particularly limited, the P3HB that can be used in the second resin layer preferably includes a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units, with PHBH being particularly preferred. The second resin layer preferably contains 50% by weight or more of PHBH, more preferably 70% by weight or more, even more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may also be 95% by weight or more. The resin component contained in the second resin layer may be only PHBH, or may further contain another resin.

[0071] The average content ratio of the constituent monomers and the weight average molecular weight of the P3HB that can be used in the second resin layer are also similar to those of the P3HB that can be used in the first resin layer, and therefore detailed description thereof will be omitted.

[0072] The second resin layer may contain additives typically added to resin materials, provided that the effects of the present invention are not impaired. Examples of such additives include inorganic fillers, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolites, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding properties improvers. These additives may be used alone or in combination. However, additives are optional components, and the second resin layer may not contain these additives. It is preferable to use at least one additive selected from the group consisting of lubricants and inorganic fillers, as this improves releasability from the pressure-bonding surface of a cooling roll or the like during lamination of the second resin layer.

[0073] Examples of the lubricant include saturated or unsaturated fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, and erucic acid amide; alkylene fatty acid amides such as methylene bisstearic acid amide and methylene bisstearic acid amide; and aliphatic amide compounds such as pentaerythritol.

[0074] The amount of lubricant in the second resin layer is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1 part by weight, per 100 parts by weight of the total amount of resin components contained in the second resin layer. By setting the amount to 0.1 part by weight or more, the effect of improving releasability due to the addition of the lubricant can be obtained. If the amount is 2 parts by weight or less, the problem of the lubricant bleeding and adhering to the pressing surface of the cooling roll or the like during pressing is suppressed, and long-term continuous processing can be performed.

[0075] Examples of the inorganic filler include talc, calcium carbonate, mica, silica, clay, kaolin, titanium oxide, alumina, zeolite, etc. The average particle size of these inorganic fillers is preferably 0.5 μm or more.

[0076] The amount of inorganic filler in the second resin layer is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of the total amount of resin components contained in the second resin layer. By setting the amount to 0.5 parts by weight or more, the effect of improving releasability due to the incorporation of the inorganic filler can be obtained. If the amount is 5 parts by weight or less, the occurrence of cracks in the second resin layer can be suppressed.

[0077] The thickness of the second resin layer is not particularly limited and can be appropriately determined taking into consideration the performance and productivity required of the second resin layer, but may be, for example, about 5 to 100 μm, preferably 10 to 80 μm, and more preferably 20 to 60 μm. The second resin layer is preferably thicker than the first resin layer.

[0078] The method for forming the second resin layer on the first resin layer may be the coating method described above, but from the viewpoints of adhesion to the first resin layer, productivity, and suppression of thermal degradation, it is preferable to form the second resin layer on the surface of the first resin layer by extrusion lamination or thermal lamination.

[0079] As the extrusion lamination method, a general extrusion lamination method can be used. Specifically, a molten resin material is extruded into a film form from a T-shaped die, and is pressed onto the surface of the laminate on the side of the first resin layer while being cooled using a cooling roll, and immediately thereafter, the resin material is peeled off from the cooling roll to form the second resin layer, thereby producing a three-layer laminate.

[0080] When the second resin layer is formed by the extrusion lamination method, it is preferable that the temperature of the resin immediately after being melt-extruded from the tip of the T-shaped die is equal to or higher than the melting point of the resin component contained in the second resin layer and lower than the decomposition temperature of the resin component.

[0081] The thermal lamination method can be a general thermal lamination method. Specifically, first, a molten resin material is extruded, for example, through a T-shaped die, and cooled using a cooling roll to obtain a molded film containing the resin material. Next, the obtained molded film is pressed onto the surface of the first resin layer side of the laminate using a heated roll or the like, thereby producing a three-layer laminate.

[0082] When the second resin layer is formed by the thermal lamination method, it is preferable that when obtaining the molded film that constitutes the second resin layer, the resin temperature immediately after being melt-extruded from the tip of the T-shaped die is equal to or higher than the melting point of the resin component contained in the second resin layer and lower than the decomposition temperature of the resin component.

[0083] For the purpose of improving the adhesion between the second resin layer and the first resin layer, the surface of the first resin layer may be subjected to corona treatment, flame treatment, ozone treatment, etc. [Molded Product] A molded product according to one embodiment of the present disclosure (hereinafter, sometimes referred to as the "present molded product") includes the present laminate and has a desired size and shape. Since the present molded product is formed from a laminate including a first resin layer containing P3HB, it is advantageous in various applications.

[0084] The present molded article is not particularly limited as long as it contains the present laminate, and examples thereof include paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, part, etc. From the viewpoint of measures against marine pollution, the present molded article is preferably a bag or a bottle container.

[0085] In one embodiment of the present disclosure, the present molded article may be the present laminate itself, or may be a product obtained by subjecting the present laminate to secondary processing.

[0086] Because the laminate has been subjected to secondary processing, the molded article containing it can be suitably used as various packaging container materials such as shopping bags, various bags, food and confectionery packaging materials, cups, trays, cartons, etc. (in other words, in various fields such as food, cosmetics, electronics, medicine, and pharmaceuticals.) Because the laminate contains a resin that has high adhesion to substrates and good heat resistance, it is more suitable as a container for holding liquids, particularly containers for holding hot contents such as cups for food and drink such as instant noodles, instant soup, and coffee, and trays for prepared meals, boxed lunches, and microwaveable foods.

[0087] The various secondary processes described above can be carried out in the same manner as conventional resin-laminated paper or coated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Processing can also be carried out using machines such as paper cup forming machines, punching machines, box making machines, etc. In these processing machines, known techniques can be used to bond the present laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing.

[0088] The heat sealing temperature of the present laminate varies depending on the adhesion method. For example, when a heating-type heat sealing tester equipped with a sealing bar is used, the heat sealing temperature of the present laminate can usually be set so that the surface temperature of the first resin layer or the second resin layer is 180°C or less, preferably 170°C or less, and more preferably 160°C or less. Within the above range, melting of the resin near the sealed portion can be avoided, and an appropriate resin layer thickness and seal strength can be ensured. Since the present laminate can achieve good adhesion even when heat-sealed at low temperatures, the surface temperature may be 150°C or less or 140°C or less. Furthermore, when a heating-type heat sealing tester equipped with a sealing bar is used, the lower limit of the surface temperature is usually 100°C or more, preferably 110°C or more, and more preferably 120°C or more. Within the above range, appropriate adhesion at the sealed portion can be ensured.

[0089] The heat-sealing pressure of the present laminate varies depending on the bonding method. For example, when a heat-sealing tester with a seal bar is used, the heat-sealing pressure of the present laminate is usually 0.1 MPa or more, preferably 0.5 MPa or more. Within this range, appropriate adhesion at the sealed portion can be ensured. Furthermore, when a heat-sealing tester with a seal bar is used, the upper limit of the heat-sealing pressure is usually 1.0 MPa or less, preferably 0.75 MPa or less. Within this range, thinning of the film thickness at the sealed end can be avoided, and seal strength can be ensured.

[0090] Furthermore, in order to improve the physical properties of the present molded article, it can also be composited with a molded article made of a material different from the present molded article (for example, fiber, thread, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, part, foam, etc.). These materials are also preferably biodegradable.

[0091] The following items list preferred aspects of the present disclosure, but the present invention is not limited to them. [Item 1] A laminate comprising a paper base layer and a first resin layer provided on at least one surface of the paper base layer, wherein the first resin layer contains a poly(3-hydroxybutyrate)-based resin and a polyvinyl alcohol having a saponification degree of less than 90 mol%, and wherein the solids weight ratio of the poly(3-hydroxybutyrate)-based resin to the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.0. [Item 2] The laminate according to item 1, wherein the poly(3-hydroxybutyrate)-based resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 3] The laminate according to item 2, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units. [Item 4] The laminate according to any one of Items 1 to 3, wherein the surface of the first resin layer that is not facing the paper base layer has a gloss of 5% or more as measured at an incident angle of 60° in accordance with "Specular Gloss - Measurement Method" specified in JIS Z 8741:1997. [Item 5] The laminate according to any one of Items 1 to 4, wherein the first resin layer has a thickness of 0.5 to 30 μm. [Item 6] The laminate according to any one of Items 1 to 5, further comprising a second resin layer provided on the first resin layer, wherein the second resin layer contains a poly(3-hydroxybutyrate)-based resin. [Item 7] The laminate according to any one of Items 1 to 6, which is used for packaging. [Item 8] The laminate according to any one of Items 1 to 6, which is used for paper containers. [Item 9] A molded product comprising the laminate according to any one of Items 1 to 8. [Item 10] A method for manufacturing a laminate, comprising the steps of applying an aqueous coating liquid to at least one surface of a paper substrate and drying the liquid to form a first resin layer on the paper substrate, wherein the aqueous coating liquid contains a poly(3-hydroxybutyrate) resin and a polyvinyl alcohol having a saponification degree of less than 90 mol%, and the solids weight ratio of the poly(3-hydroxybutyrate) resin to the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.0.[Item 11] The first resin layer has a basis weight measured in accordance with JIS P 8124 of 1 to 30 g / m. ２ Item 12: The manufacturing method according to item 10 or 11, wherein the drying is carried out by heating to a temperature of 130 to 180°C. [Item 13] The manufacturing method according to any one of items 10 to 12, further comprising a step of forming a second resin layer on the first resin layer, wherein the second resin layer contains a poly(3-hydroxybutyrate)-based resin. [Item 14] The manufacturing method according to item 13, wherein the second resin layer is formed by extrusion lamination or thermal lamination.

[0092] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0093] (Method for evaluating film-forming properties of coated paper) To evaluate the film-forming properties of the coating layer, the gloss of the coating layer surface was measured using a glossmeter (HORIBA, IG-320) at an incident angle of 60° in accordance with "Specular gloss - measuring method" specified in JIS Z 8741: 1997. A higher gloss value indicates a smoother coating layer surface.

[0094] (Method for evaluating water resistance of coated paper or laminated paper) According to "Paper and board - Water absorption test method - Cobb method" specified in JIS P 8140:1998, the water absorbency (Cobb value) was measured at any two points on the surface of the coating layer or laminate layer with hot water at 90°C for a contact time of 1800 seconds. The average value of the water absorbency (Cobb value) measured at the two points was used as the value of water resistance, and water resistance was evaluated according to the following criteria. If the evaluation was ⊚, ◯, or △, it was determined that there was no problem in practical use. [Evaluation criteria] ⊚: The average water absorbency (Cobb value) was 5 g / m or more. ２ ◯: The average water absorbency (Cobb value) is 5 g / m or less. ２ More than 10 g / m ２ △: The average water absorption (Cobb value) is 10 g / m or less. ２ More than 20 g / m ２ x: The average water absorbency (Cobb value) is 20 g / m or less. ２ Exceeds.

[0095] (Method for evaluating oil resistance of coated paper or laminated paper) Kit numbers were measured at any five points on the surface of the coating layer or laminated layer in accordance with "Paper and paperboard - Oil repellency test method - Kit method" specified in JAPAN TAPPI No. 41:2000. The average value of the kit numbers measured at the five points was used as the oil resistance value, and the oil resistance was evaluated according to the following criteria. If the evaluation is ◎, ◯, or △, it can be determined that there is no problem in practical use. [Evaluation criteria] ◎: The average kit number is 12. ◯: The average kit number is 11 or more and less than 12. △: The average kit number is 10 or more and less than 11. ×: The average kit number is less than 10.

[0096] (Method for evaluating adhesion between coating layer and paper substrate) Cellophane tape (25 mm wide) was applied to the surface of the coating layer, and a 130 mm wide, 1.8 kg rubber roller was rolled back and forth five times under its own weight on the cellophane tape to adhere the cellophane tape to the surface of the coating layer. Immediately afterwards, the cellophane tape was vigorously peeled off, and the ratio of the area where the coating layer adhered to the cellophane tape and peeled off from the paper substrate surface (area of ​​interfacial failure) to the area where the cellophane tape was applied was calculated, or the ratio of the area where a portion of the paper substrate adhered to the cellophane tape together with the coating layer and the paper substrate was destroyed (area of ​​internal paper substrate failure) was calculated. Adhesion to the paper substrate was evaluated according to the following criteria. A rating of ◎, ○, or △ indicated that there was no practical problem. When the evaluations of the percentage of the coating layer peeled off area and the percentage of the paper substrate destroyed area differed, the more stringent evaluation was adopted. [Evaluation criteria] ◎: The percentage of the area where the coating layer peeled off was less than 5%, or the percentage of the area where the paper base was destroyed was 95% or more. ○: The percentage of the area where the coating layer peeled off was 5% or more but less than 10%, or the percentage of the area where the paper base was destroyed was 90% or more but less than 95%. △: The percentage of the area where the coating layer peeled off was 10% or more but less than 30%, or the percentage of the area where the paper base was destroyed was 70% or more but less than 90%. ×: The percentage of the area where the coating layer peeled off was 30% or more, or the percentage of the area where the paper base was destroyed was less than 70%.

[0097] (Method for evaluating the heat sealability of coated paper) Two 25 mm wide strips were cut out from the obtained coated paper, and the coated layers were brought into contact with each other and pressed at a temperature of 130°C and a pressure of 2 kgf / cm. ２ The heat seal was performed with a pressure application time of 0.5 seconds. To measure the heat seal strength of the test piece, an autograph was used, and both sides of the paper substrate were gripped with a chuck and peeled at 180°. The peeled area was visually observed and the heat sealability was evaluated according to the following criteria. If the evaluation is ◯ or △, it can be determined that there is no problem in practical use. [Evaluation criteria] ◯: Peeling occurs within the paper substrate (paper substrate is destroyed). △: Peeling occurs mostly within the paper substrate (paper substrate is destroyed). ×: Peeling occurs between the paper substrate and the coating layer, or between the coating layers, without destroying the paper substrate.

[0098] (Method for evaluating lamination properties of laminated paper) A 25 mm wide strip was cut out from the obtained laminated paper (with an unlaminated portion remaining). To evaluate the lamination properties of the test piece, an autograph was used to grasp the unlaminated portion of the paper substrate and the unlaminated portion of the film with a zipper and perform a 180° peel. The peeled portion was visually observed and the lamination properties were evaluated according to the following criteria. A rating of ◯ indicates that there is no practical problem. [Evaluation criteria] ◯: Cohesive failure of the paper occurs, with paper fibers adhering to the film side. Δ: Cohesive failure of the paper occurs, with paper fibers adhering to part of the film side. ×: No cohesive failure of the paper occurs, with the film side easily peeling off without resistance.

[0099] (Evaluation of biodegradability of coating layer components) Dry powders of the coating layer components were passed through a 100-mesh filter and subjected to biodegradation in seawater using a BOD measuring device (OXITOP series, manufactured by Central Chemical) at an incubator temperature of 30±1°C (with stirring) for 180 days. The biodegradability was calculated from the amount of oxygen consumed by the bacteria and evaluated according to the following criteria: [Evaluation criteria] ◯: Biodegradation of 90% or more within 180 days ×: Biodegradation of less than 90% within 180 days

[0100] (Preparation of an aqueous suspension containing PHBH isolated from a microorganism) First, Ralstonia eutropha (formerly Alcaligenes eutrophus AC32 (deposit number FERM BP-6038)) into which Aeromonas caviae-derived 3-hydroxyalkanoic acid copolymer synthase group genes had been introduced was cultured by the method described in J. Bacteriol., 179, pp. 4821-4830 (1997), to obtain bacterial cells containing approximately 67% by weight of PHBH. In this PHBH, the composition ratio of repeating units (composition ratio of 3-hydroxybutyrate units / 3-hydroxyhexanoate units) was 89 / 11 (mol / mol). Next, paste-like bacterial cells were separated from the culture broth by centrifugation (5000 rpm, 10 min). Water was added to the bacterial cells to prepare a suspension of 75 g dry bacterial cells / L, and aqueous sodium hydroxide solution was added as an alkali to maintain the pH at 11.7. The bacterial constituents other than PHBH were solubilized by stirring and physical disruption, and the mixture was centrifuged (3,000 rpm, 10 min) to obtain a precipitate. The precipitate was further washed with water to separate PHBH with a weight-average molecular weight of approximately 260,000, a 3HH molar fraction of 11%, and a purity of 91%, yielding a suspension containing 75 g / L of PHBH. The suspension was placed in a stirring tank equipped with a pH electrode and maintained at 70°C. The pH electrode was connected to a Marubishi Bioengine Lab Controller Model MDL-6C, and was set so that when the pH fell below the set value, a peristaltic pump would operate and sodium hydroxide aqueous solution would enter the suspension until the set value was reached. The pH of the lab controller was set to 10, and 30% aqueous hydrogen peroxide was added to the suspension so that the hydrogen peroxide concentration was 5 wt% relative to the polymer weight (0.375 wt% relative to the suspension weight), followed by stirring for 1 hour. The suspension was then centrifuged, washed twice with water, and then washed twice with methanol. Furthermore, 30% aqueous hydrogen peroxide was added to the solids (PHBH) of the aqueous suspension as a preservative treatment so that the hydrogen peroxide concentration was 0.1 wt%. Through these processes, an aqueous suspension (A) with a PHBH concentration of 52 wt% was obtained. The protein content of the aqueous suspension (A) was 1,500 ppm based on the solids, and the purity of the PHBH was 99.8% or higher.

[0101] Example 1 (Preparation of Coating Solution 1 for Coating Layer) PHBH aqueous suspension (A) was mixed with an adhesive (polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: L-10, saponification degree 71.5-73.5 mol%) so that the solids weight ratio was 98.0 / 2.0, and water was further added and stirred to prepare Coating Solution 1 for Coating Layer, with a combined solids concentration of PHBH and adhesive of 40 wt %. (Preparation of Coated Paper) A paper substrate (basis weight 50 g / m ２ Coating solution 1 for coating layer was applied to one side of the sheet of paper (single-sided gloss paper) to a basis weight of 10.0 g / m2 in dry weight. ２ The coating was applied by a bar coater so as to give a thickness of 8 μm, and then dried at a drying temperature of 160° C. for 2 minutes to obtain a coated paper.

[0102] Example 2 A coated paper was obtained in the same manner as in Example 1, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 1 for coating layer was changed to 95.0 / 5.0.

[0103] Example 3 A coated paper was obtained in the same manner as in Example 1, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 1 for coating layer was changed to 99.5 / 0.5.

[0104] Example 4 (Preparation of Coating Solution 2 for Coating Layer) PHBH aqueous suspension (A) was mixed with an adhesive (polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: 5-74, saponification degree 72.5-74.5 mol%) so that the solids weight ratio was 98.0 / 2.0, and water was further added and stirred to prepare Coating Solution 2 for Coating Layer, with a combined solids concentration of PHBH and adhesive of 40 wt %. (Preparation of Coated Paper) Coated paper was obtained in the same manner as in Example 1, except that Coating Solution 1 for Coating Layer was changed to Coating Solution 2 for Coating Layer.

[0105] Example 5 A coated paper was obtained in the same manner as in Example 4, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 2 for coating layer was changed to 95.0 / 5.0.

[0106] Example 6 (Preparation of Coating Solution 3 for Coating Layer) PHBH aqueous suspension (A) was mixed with an adhesive (polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: 5-88, saponification degree 86.5-89.0 mol%) so that the solids weight ratio was 98.0 / 2.0, and water was further added and stirred to prepare Coating Solution 3 for Coating Layer, which had a combined solids concentration of PHBH and adhesive of 40 wt %. (Preparation of Coated Paper) Coated paper was obtained in the same manner as in Example 1, except that Coating Solution 1 for Coating Layer was changed to Coating Solution 3 for Coating Layer.

[0107] Example 7 A coated paper was obtained in the same manner as in Example 6, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 3 for coating layer was changed to 95.0 / 5.0.

[0108] Comparative Example 1 Preparation of Coating Solution 4 for Coating Layer Water was added to the PHBH aqueous suspension (A) and stirred to prepare Coating Solution 4 for Coating Layer with a solids concentration of 40 wt %. Preparation of Coated Paper Coated paper was obtained in the same manner as in Example 1, except that Coating Solution 1 for Coating Layer was replaced with Coating Solution 4 for Coating Layer.

[0109] Comparative Example 2 A coated paper was obtained in the same manner as in Example 1, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 1 for coating layer was changed to 90.0 / 10.0.

[0110] Comparative Example 3 (Preparation of Coating Solution 5 for Coating Layer) PHBH aqueous suspension (A) was mixed with an adhesive (polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: 5-98, saponification degree 98.0-99.0 mol%) so that the solids weight ratio was 98.0 / 2.0, and water was further added and stirred to prepare Coating Solution 5 for Coating Layer, which had a combined solids concentration of PHBH and adhesive of 40 wt %. (Preparation of Coated Paper) Coated paper was obtained in the same manner as in Example 1, except that Coating Solution 1 for Coating Layer was changed to Coating Solution 5 for Coating Layer.

[0111] The coated papers obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated for film-forming properties, water resistance, oil resistance, adhesion between the coating layer and the paper substrate, and heat-sealability using the methods described above. The results are shown in Table 1.

[0112]

[0113] Table 1 shows that the coated papers of Examples 1 to 7 contain a coating layer containing P3HB and PVA meeting a specific saponification degree in a specific ratio, exhibiting good water resistance, strong adhesion between the coating layer and the paper substrate, and good heat sealability. On the other hand, the coated paper of Comparative Example 1 does not contain PVA, exhibiting poor adhesion between the coating layer and the paper substrate and insufficient heat sealability. The coated paper of Comparative Example 2 contains PVA meeting a specific saponification degree, but at a high PVA content, resulting in insufficient water resistance. Furthermore, the high PVA content also reduced the biodegradability of the coating. The coated paper of Comparative Example 3 contains PVA that does not meet the specific saponification degree, exhibiting somewhat poor adhesion between the coating layer and the paper substrate and insufficient heat sealability.

[0114] [Example 8] (Preparation of laminate by extrusion lamination method) A paper substrate having a basis weight of 200 g / m ２ The solid content of coating solution 1 for the coating layer was changed to 25% by weight, and the coating amount of coating solution 1 for the coating layer was changed to a basis weight of 3.0 g / m2 in dry weight. ２ Except for changing the thickness of the PHBH powder (weight average molecular weight 650,000 and a composition ratio of 3-hydroxybutyrate units to 3-hydroxyhexanoate units of 85 / 15 (mol / mol)), 100 parts by weight of PHBH powder was dry-blended with 0.2 parts by weight of behenic acid amide and 1.0 part by weight of pentaerythritol. The mixture was melt-kneaded and extruded into strands using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm. The strands were then passed through 40°C hot water to solidify them, and the extruded strands were cut into pellets. Next, the obtained pellets were extruded using a single-screw extruder equipped with a T-type die, adjusting the conditions so that the resin temperature directly below the die was 175°C, and laminated to a thickness of 30 μm as a second resin layer on the first resin layer of the coated paper with the first resin layer prepared above, thereby obtaining laminated paper, which is a laminate including the first resin layer and the second resin layer.

[0115] Example 9 A laminated paper was obtained in the same manner as in Example 8, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 1 for coating layer was changed to 95.0 / 5.0.

[0116] [Example 10] The coating amount of coating solution 1 for coating layer was 1.0 g / m2 in terms of dry weight. ２ A laminated paper was obtained in the same manner as in Example 8, except that the thickness was changed to 0.8 μm.

[0117] Example 11 A laminated paper was obtained in the same manner as in Example 8, except that Coating Liquid 3 for Coating Layer was used instead of Coating Liquid 1 for Coating Layer.

[0118] Example 12 A laminated paper was obtained in the same manner as in Example 11, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 3 for coating layer was changed to 95.0 / 5.0.

[0119] [Example 13] (Production of laminate by thermal lamination method) Coated paper with a first resin layer was obtained in the same manner as in Example 8. To prepare the second resin layer, the same PHBH powder (100 parts by weight) used in Example 8 was dry-blended with behenic acid amide (0.2 parts by weight) and pentaerythritol (1.0 parts by weight), and the mixture was melt-kneaded and extruded into a strand using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm. The strand was then passed through hot water at 40°C to solidify it, and cut into pellets. The resulting pellets were then taken up using a single-screw extruder equipped with a T-die and a cooling roll set at 60°C to obtain a film molded product with a thickness of 30 μm. Then, the film molding was sandwiched between the first resin layer of the coated paper with the first resin layer so that the heating roll was on the paper side and the cooling roll was on the film side, and thermal lamination was performed by adjusting the conditions so that the surface temperature of the film molding was 170°C, thereby obtaining laminated paper containing the film molding as a second resin layer.

[0120] Comparative Example 4 A laminated paper was obtained in the same manner as in Example 8, except that Coating Liquid 4 for Coating Layer was used instead of Coating Liquid 1 for Coating Layer.

[0121] Comparative Example 5 A laminated paper was obtained in the same manner as in Example 8, except that Coating Liquid 5 for Coating Layer was used instead of Coating Liquid 1 for Coating Layer.

[0122] Comparative Example 6 A laminated paper was obtained in the same manner as in Comparative Example 5, except that the solids weight ratio of the PHBH aqueous dispersion and adhesive in Coating Solution 5 for coating layer was changed to 95.0 / 5.0.

[0123] The laminated papers obtained in Examples 8 to 13 and Comparative Examples 4 to 6 were evaluated for film-forming properties, water resistance, oil resistance, and lamination properties by the methods described above. The results are shown in Table 2.

[0124]

[0125] Table 2 shows that the laminated papers of Examples 8 to 13, which are laminates including a first resin layer and a second resin layer, have good lamination properties because the first resin layer contains a specific ratio of PVA that satisfies a specific degree of saponification. On the other hand, the laminated paper of Comparative Example 4 does not contain PVA in the first resin layer, and therefore has insufficient lamination properties. Furthermore, the laminated papers of Comparative Examples 5 and 6 have insufficient lamination properties because the PVA contained in the first resin layer does not satisfy the specific degree of saponification.

[0126] (Reference Example) Coated papers with a first resin layer were obtained in the same manner as in Example 8, except that the drying temperature of the first resin layer was 80°C, 100°C, 120°C, 140°C, 160°C, or 180°C and heating was performed for 2 minutes. The 60° gloss of the coating layer surface of the obtained coated papers was measured using the method described above. The results are shown in Table 3.

[0127]

[0128] Table 3 shows that when the drying temperature of the coating layer is between 80 and 120°C, there is almost no change in the gloss of the coating layer, but when the temperature is 140°C or higher, the gloss increases with increasing temperature. This is thought to be because the PHBH in the coating layer melts when heated during drying, and then cools and solidifies, improving the smoothness of the coating layer surface. Furthermore, melting the PHBH in the coating layer when heated during drying can also improve the adhesion between the coating layer and the paper substrate, as well as heat-sealing and laminating properties.

Claims

1. A laminate including a paper base layer and a first resin layer provided on at least one surface of the paper base layer, the first resin layer contains a poly(3-hydroxybutyrate)-based resin and polyvinyl alcohol having a saponification degree of 85 mol % or less, The laminate has a solids weight ratio of the poly(3-hydroxybutyrate) resin to the polyvinyl alcohol of 99.8 / 0.2 to 95.0 / 5.

0.

2. 2. The laminate of claim 1, wherein the poly(3-hydroxybutyrate)-based resin comprises a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

3. 3. The laminate of claim 2, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

4. The laminate according to any one of claims 1 to 3, wherein the gloss of a surface of the first resin layer that is not facing the paper base layer is 5% or more, as measured at an incident angle of 60° in accordance with "Specular gloss measurement method" specified in JIS Z 8741:1997.

5. The laminate according to any one of claims 1 to 3, wherein the first resin layer has a thickness of 0.5 to 30 µm.

6. Further comprising a second resin layer provided on the first resin layer, The laminate according to any one of claims 1 to 3, wherein the second resin layer contains a poly(3-hydroxybutyrate)-based resin.

7. The laminate according to any one of claims 1 to 3, which is used as a packaging material.

8. The laminate according to any one of claims 1 to 3, which is for a paper container.

9. A molded article comprising the laminate according to any one of claims 1 to 3.

10. A method for producing a laminate, comprising: applying an aqueous coating liquid to at least one surface of a paper substrate and drying the aqueous coating liquid to form a first resin layer on the paper substrate, the aqueous coating liquid contains a poly(3-hydroxybutyrate)-based resin and polyvinyl alcohol having a saponification degree of 85 mol % or less; A solids weight ratio of the poly(3-hydroxybutyrate) resin to the polyvinyl alcohol is 99.8 / 0.2 to 95.0 / 5.

0.

11. The first resin layer has a basis weight of 1 to 30 g / m2 measured in accordance with JIS P 8124. ２ The method according to claim 10, wherein

12. The method according to claim 10 or 11, wherein the drying is carried out by heating at a temperature of 130 to 180° C.

13. The method further includes forming a second resin layer on the first resin layer, The method according to claim 10 or 11, wherein the second resin layer contains a poly(3-hydroxybutyrate)-based resin.

14. The method according to claim 13, wherein the second resin layer is formed by extrusion lamination or thermal lamination.