Laminate manufacturing method

Abstract

To provide a method capable of manufacturing a laminate in which an anchor layer is provided between a resin layer containing a poly(3-hydroxyalkanoate)-based resin and a paper base material layer, and which is good in all of heat seal adhesiveness, water resistance, and oil resistance.SOLUTION: A laminate manufacturing method includes: a process (i) in which a solution (I) containing aliphatic polyester resin (A) and a non-aqueous solvent is coated on a surface of a paper base material layer, and is dried, thereby forming an anchor layer; and a process (ii) in which a resin layer containing poly(3-hydroxyalkanoate)-based resin (B) is formed on the surface of the anchor layer. The aliphatic polyester resin (A) contains at least one kind selected from a group comprising polylactic acid resin, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate in which a resin layer containing a poly(3-hydroxyalkanoate) resin is laminated on a paper substrate layer. [Background technology]

[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] Poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species. They are also biodegradable not only in soil but also in seawater, and are therefore attracting attention as a material that can solve the above problems.

[0004] A laminate formed by laminating a resin layer whose main component is such a poly(3-hydroxyalkanoate)-based resin onto a biodegradable paper substrate is extremely promising from the perspective of environmental protection, since both the resin and the substrate are materials with excellent biodegradability.

[0005] In order to improve the adhesion between the resin layer and the paper substrate layer in such a laminate, Patent Document 1 describes providing a coating layer containing a polyester resin with a glass transition temperature of −25 to 46° C. as an anchor layer between the resin layer and the paper substrate layer. It also describes that the anchor layer is formed by coating the paper substrate with an aqueous dispersion of the polyester resin. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7285387 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the method described in Patent Document 1, the adhesion between the resin layer containing a poly(3-hydroxyalkanoate) resin as the main component and the paper substrate layer can be improved, and good heat seal adhesiveness can be achieved. However, the laminate produced by the method described in Patent Document 1 sometimes has insufficient water resistance or oil resistance.

[0008] In view of the above-mentioned current situation, the present invention aims to provide a method for producing a laminate in which an anchor layer is provided between a resin layer containing a poly(3-hydroxyalkanoate)-based resin and a paper base layer, and which is capable of producing a laminate having good heat seal adhesion, water resistance, and oil resistance. [Means for solving the problem]

[0009] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by selecting a specific resin as the resin that constitutes the anchor layer, applying the specific resin as a non-aqueous solution to the surface of a paper base layer and drying it to form an anchor layer, and then forming a resin layer containing a poly(3-hydroxyalkanoate) resin on top of the anchor layer, thereby completing the present invention.

[0010] That is, the present invention provides a method for producing a laminate including a paper base layer, (i) applying a solution (I) containing an aliphatic polyester resin (A) and a non-aqueous solvent to the surface of a paper substrate layer and drying the solution to form an anchor layer; and a step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B) on the surface of the anchor layer, The present invention relates to a method for producing a laminate, wherein the aliphatic polyester resin (A) comprises at least one selected from the group consisting of polylactic acid resin, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone. [Effects of the Invention]

[0011] According to the present invention, there is provided a method for producing a laminate in which an anchor layer is provided between a resin layer containing a poly(3-hydroxyalkanoate) resin and a paper base layer, and the method is capable of producing a laminate having good heat seal adhesion, water resistance, and oil resistance. When the laminate produced by the present invention is used as a packaging material for packaging oily foods, for example, it can inhibit the seepage of oil. Furthermore, the laminate produced by the present invention has good water resistance and can therefore be suitably used as paper tableware such as paper cups and paper plates. Furthermore, according to a preferred embodiment of the present invention, the biodegradability of the entire laminate can be improved. Furthermore, according to a preferred embodiment of the present invention, the laminate can be produced with good productivity. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] [Laminate] The laminate that can be produced by the present invention has an anchor layer and a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B) on at least one side of a paper substrate layer, with the paper substrate layer, anchor layer, and resin layer laminated in this order.

[0014] The anchor layer may be laminated directly on the paper base layer, or another layer may be further included between the anchor layer and the paper base layer as long as it does not impair adhesion.

[0015] The resin layer may be the outermost layer in the laminate, and in this case, the resin layer may function as a heat seal layer, a water-resistant layer, and / or an oil-resistant layer.

[0016] Furthermore, another layer may be laminated on the resin layer. The other layer is not particularly limited, and may be another resin layer or an inorganic layer.

[0017] The laminate may have the anchor layer and the resin layer on only one side of the paper base layer, or may have the anchor layer and the resin layer on each side of the paper base layer. When the paper substrate layer has an anchor layer and a resin layer on only one side, the other side of the paper substrate layer may be exposed without any other layer laminated thereon. Alternatively, for the purpose of imparting water resistance, glossiness, or adhesiveness, another layer may be laminated on the other side of the paper substrate layer.

[0018] When the paper base layer has an anchor layer and a resin layer on each side, the materials constituting the anchor layer on the front side and the anchor layer on the back side, as well as the basis weight and thickness, may be the same or different. The same applies to the resin layer on the front side and the resin layer on the back side. The basis weight refers to the dry weight (solid content) of the layer.

[0019] [Paper base layer] The paper base layer is composed of a sheet mainly made of pulp, and can be obtained by papermaking a stock containing pulp, fillers, various auxiliaries, etc. The type of paper that can be used is not particularly limited, and examples include cup base paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard.

[0020] 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.

[0021] 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, that discoloration is less likely to occur over time when recycled as waste paper raw material, that the high whiteness results in a good surface appearance when printed, and that this has high utility value particularly when used as a packaging material. Specifically, it is preferable that the amount of chemical pulp such as LBKP or NBKP in the pulp is 80% or more, and it is particularly preferable that the amount of chemical pulp is 100%.

[0022] 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.

[0023] 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.

[0024] The basis weight of the paper substrate can be selected appropriately depending on the desired quality and the use of the laminate, but is preferably 40 g / m 2 More than 400g / m 2 Preferably, it is 50 g / m or less. 2 More than 350g / m 2When 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 weight is more preferably 40 g / m 2 More than 150g / m 2 It is more preferable that the soft packaging material is a packaging material having a density of 40 g / m or less. 2 ~100g / m 2 It refers to a flexible packaging material made of thin paper of about 150 g / m². When the laminate is used for paper tableware such as paper cups, paper boxes, paper plates, paper trays, etc., or for lids and other paper containers, it is recommended that the thickness be 150 g / m². 2 More than 400g / m 2 It is more preferable that:

[0025] The density of the paper substrate can be selected appropriately depending on the desired quality, handling, etc., but is usually 0.5 g / cm 3 More than 1.0g / cm 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 applied to the surface of the paper layer. The paper base may be composed of a single layer, or two or more layers.

[0027] [Base layer] The paper base layer preferably has a primer layer on the surface of the paper body. In particular, it is preferable to have a primer layer on the surface on which the anchor layer is to be formed. This has the advantage of preventing the solution (I) used to form the anchor layer from penetrating into the paper base, making it easier to achieve the effect of improving oil resistance by the anchor layer.

[0028] The underlayer preferably contains at least a binder. The binder may be of a type generally used in the field of coated paper, etc. Examples of suitable binders include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, and polyvinyl alcohols such as ethylene-vinyl alcohol copolymers; (meth)acrylic acid and monomer components copolymerizable with (meth)acrylic acid (excluding olefins); Examples of binders include acrylic resins, ethylene-acrylic resins, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and acetyl cellulose, starches such as oxidized starch, etherified starch, and esterified starch, styrene-maleic anhydride copolymers, styrene-butadiene copolymers, casein, gum arabic, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polystyrose and copolymers thereof, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumarone resins. Only one type of binder may be used, or two or more types may be used in combination.

[0029] Among these, it is preferable to use a water-soluble polymer as the binder because it is highly effective in suppressing the impregnation of the paper substrate with the solution (I) used to form the anchor layer. Among these, polyvinyl alcohol, cellulose derivatives, and starches are more preferable, and polyvinyl alcohol or methyl cellulose is particularly preferable. Note that the polyvinyl alcohol referred to here includes saponified polyvinyl alcohol and various modified polyvinyl alcohols. Furthermore, by using a biodegradable binder such as polyvinyl alcohol, cellulose derivatives, starches, etc., the biodegradability of the entire laminate can be further increased.

[0030] The underlayer may further contain a pigment. 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, and satin white; and organic pigments such as solid, hollow, and core-shell pigments. Only one type of pigment may be used, or two or more types may be used in combination.

[0031] The undercoat layer may optionally contain a sizing agent, a water-resistant agent, a water-repellent agent, a dye, a surfactant, and the like.

[0032] When forming the underlayer, either aqueous coating using a solvent such as water or solvent-based coating using a solvent such as an organic solvent may be used. From the viewpoint of suppressing the impregnation of the paper substrate with the non-aqueous solution (I) used to form the anchor layer by the underlayer, it is preferable to form the underlayer using aqueous coating.

[0033] The undercoat layer can be formed using a known coating device, such as a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a reverse roll coater, a size press coater, or a gate roll coater.

[0034] The undercoat layer can be dried using, for example, a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer, or the like.

[0035] The basis weight of the undercoat layer is not particularly limited, but is, for example, 1.0 g / m2 in dry weight. 2More than 15.0g / m 2 The base layer may be one layer, or two or more layers. When the base layer is two or more layers, it is preferable that the total basis weight of the entire base layer is within the above range.

[0036] Anchor layer The anchor layer is a layer composed mainly of an aliphatic polyester resin (A). By providing such an anchor layer between the paper substrate layer and the resin layer, the adhesion between the resin layer and the paper substrate layer can be improved, and when the laminate is bonded by heat sealing, the adhesive strength (also called heat seal adhesion or heat sealability) can be improved. In addition, by providing an anchor layer, the oil resistance of the laminate is improved, and when it comes into contact with oily foods, etc., the seepage of oil can be suppressed. Furthermore, water resistance can be imparted to the laminate.

[0037] The aliphatic polyester resin (A) can be selected from those that have high adhesion to the poly(3-hydroxyalkanoate) resin (B) and are oil-resistant and water-resistant. Specifically, the aliphatic polyester resin (A) includes at least one selected from the group consisting of polylactic acid resin, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone. These aliphatic polyester resins are biodegradable and therefore preferred from the viewpoint of enhancing the biodegradability of the entire laminate.

[0038] Polylactic acid resin (abbreviated as PLA) is a polyester containing lactic acid as a constituent monomer. The polylactic acid resin is preferably a homopolymer of lactic acid, but may contain trace amounts of other monomers in addition to lactic acid.

[0039] The lactic acid constituting the polylactic acid resin may be either the L- or D-form, or may contain both. However, the polylactic acid resin is preferably a copolymer containing both L-lactic acid and D-lactic acid as repeating units. In this case, the ratio of the L- and D-forms is not particularly limited, but the content of each of the L-lactic acid and D-lactic acid is preferably less than 90 mol %. Within this range, an amorphous polylactic acid resin can be suitably formed.

[0040] Examples of the other monomers that may be contained in the polylactic acid resin include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, and polyfunctional polysaccharides. When the polylactic acid resin is a copolymer of lactic acid and other monomers, the content of the other monomers is preferably about 0 to 3 mol %, more preferably 0 to 2 mol %, relative to the total monomers contained in the polylactic acid resin.

[0041] The polylactic acid-based resin may be either a crystalline polylactic acid-based resin or an amorphous polylactic acid-based resin, but it is preferable to use an amorphous polylactic acid-based resin because it has good solubility in non-aqueous solvents and is easy to form a uniform anchor layer. The amorphous nature of a polylactic acid resin can be confirmed by the absence of a melting point peak in a DSC curve obtained by differential scanning calorimetry (DSC), which can be performed, for example, by heating the resin from 0°C to 200°C at a rate of 10°C / min using a differential scanning calorimeter.

[0042] The molecular weight of the polylactic acid resin is not particularly limited and may be set appropriately, but the weight-average molecular weight is preferably 1,000 to 700,000, more preferably 3,000 to 500,000, and even more preferably 5,000 to 300,000. In order to improve heat seal adhesiveness, oil resistance, and water resistance, the lower limit is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. The weight-average molecular weight of the polylactic acid resin can be measured as described below.

[0043] The lactic acid raw material for producing polylactic acid resins is not particularly limited, and examples thereof include L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, meso-lactide, or a mixture thereof. Lactic acid obtained by microbial fermentation from renewable plant-derived raw materials such as starch can be suitably used. The method for producing the polylactic acid resin is not particularly limited, and known methods such as dehydration condensation polymerization and ring-opening polymerization can be used.

[0044] Polybutylene succinate (abbreviated as PBS) is an aliphatic polyester copolymer synthesized by esterification and / or transesterification of an aliphatic diol component, the main component of which is 1,4-butanediol, with an aliphatic dicarboxylic acid component, the main component of which is succinic acid and / or its derivatives, as well as by condensation polymerization. Commercially available products include "BioPBS FZ71" and "BioPBS FZ91" manufactured by Mitsubishi Chemical Corporation.

[0045] Polybutylene succinate adipate (abbreviated as PBSA) is an aliphatic polyester copolymer synthesized by esterification and condensation polymerization of an aliphatic diol component, primarily 1,4-butanediol, an aliphatic dicarboxylic acid component, primarily succinic acid such as succinic acid and / or its derivatives, and adipic acid. Commercially available products include Mitsubishi Chemical's BioPBS FD72 and BioPBS FD92.

[0046] Polycaprolactone (abbreviated as PCL) has the following formula: [-(CH2)5-CO-O-] PCL is a polymer having a monomer unit represented by the formula: PCL can usually be obtained by ring-opening polymerization of ε-caprolactone using a cationic or anionic initiator or an active hydrogen compound such as alcohol as an initiator, but the production method is not limited.

[0047] The end-capping structure of PCL is not particularly limited. PCL may typically have a melting point of 50 to 65° C., a crystallization temperature of 10 to 30° C., and a glass transition point of −50 to −60° C. The weight-average molecular weight of PCL is preferably 30,000 to 500,000, and more preferably 100,000 to 400,000, from the viewpoint of achieving both mechanical properties and processability.

[0048] Commercially available PCL products include, for example, Ingevity's "Capa 6506" (powder, Mw = 130,000), "Capa 6500" (pellet, Mw = 130,000), "Capa 6806" (powder, Mw = 230,000), "Capa 6800" (pellet, Mw = 230,000), and "FB100" (pellet, Mw = 300,000, contains PCL crosslinks).

[0049] As the aliphatic polyester resin (A), it is particularly preferable to use a polylactic acid resin from the viewpoints of heat seal adhesiveness, oil resistance, and water resistance.

[0050] The proportion of the aliphatic polyester resin (A) contained in the anchor layer is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more, based on the total amount (solid content) of the anchor layer. The upper limit may be 100% by weight or less, and may be 99% by weight or less.

[0051] When at least a polylactic acid resin is used as the aliphatic polyester resin (A), the proportion of the polylactic acid resin contained in the anchor layer is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more, of the total amount (solid content) of the anchor layer. The upper limit may be 100% by weight or less, and may be 99% by weight or less.

[0052] Components other than the aliphatic polyester resin (A) in the anchor layer include resins other than the aliphatic polyester resin (A), dispersants, viscosity improvers, water retention agents, antifoaming agents, water resistance agents, pH adjusters, UV absorbers, metal salts, lubricants, coloring dyes, and pigments.

[0053] As described below, the anchor layer is preferably a coating layer of a solvent-based coating liquid. This can improve the oil resistance of the laminate. In addition, the time required for the drying process after coating can be shortened, thereby improving the productivity of the laminate.

[0054] The basis weight of the anchor layer is not particularly limited, but is, for example, 0.1 g / m in dry weight. 2 More than 10g / m 2 The lower limit is 0.5 g / m2 or less, because the heat seal adhesive property, oil resistance, and water resistance are better. 2 It is preferable that the content is 1 g / m or more. 2 More preferably, 2 g / m 2 The upper limit is 8 g / m because this can shorten the time required for the drying step required for forming the anchor layer. 2 More preferably, it is 6 g / m or less. 2 The following is even more preferred:

[0055] [Resin layer] The resin layer contains a poly(3-hydroxyalkanoate)-based resin (B) (hereinafter also referred to as "P3HA-based resin (B)"). The resin layer may be the outermost layer in the laminate. In this case, the resin layer can be used for heat sealing (described below).

[0056] The P3HA resin is a biodegradable aliphatic polyester (preferably a polyester containing no aromatic ring), and is a polymer having at least one or more types of 3-hydroxyalkanoate units. The 3-hydroxyalkanoate units are preferably represented by the following general formula (1): [-CHR-CH2-CO-O-] (1)

[0057] In the general formula (1), R is C p H 2p+1 where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably 1 to 10, and more preferably 1 to 8.

[0058] The P3HA resin preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of the total structural units (monomer units). The poly(3-hydroxyalkanoate) resin may contain only one or more types of 3-hydroxyalkanoate units as structural units of the polymer, or may contain one or more types of 3-hydroxyalkanoate units as well as other units (e.g., 4-hydroxyalkanoate units).

[0059] The content of the P3HA-based resin (B) in the resin layer is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more of the total amount (solid content) of the resin layer. By using the P3HA-based resin as a main component, the resin layer can exhibit good biodegradability.

[0060] The P3HA resin is preferably a poly(3-hydroxybutyrate) resin (hereinafter also referred to as a P3HB resin). The P3HB resin contains poly(3-hydroxybutyrate) (b-1) and / or poly(3-hydroxybutyrate) copolymer (b-2) containing 3-hydroxybutyrate units and other hydroxyalkanoate units. From the viewpoint of seawater degradability, it is preferable to contain poly(3-hydroxybutyrate) copolymer (b-2).

[0061] The type of copolymerization in the copolymer is not particularly limited, and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc. Copolymers produced by microorganisms are usually random copolymers.

[0062] The hydroxyalkanoic acid that forms the other hydroxyalkanoate unit is not particularly limited, and examples thereof include 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid.

[0063] Specific examples of the poly(3-hydroxybutyrate) copolymer (b-2) include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxybutyrate) (abbreviation: P3HB4HB), Examples of copolymers include poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (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, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because of their ease of industrial production. As copolymer (b-2), one type may be used alone, or two or more types may be used in combination.

[0064] Among P3HB-based resins, P3HB3HH is particularly preferred from the viewpoints that its melting point and degree of crystallinity can be altered by changing the composition ratio of the repeating units, thereby enabling adjustment of physical properties such as Young's modulus and heat resistance, and that it can be given physical properties intermediate between those of polypropylene and polyethylene. It is also easy to produce industrially and is a physically useful plastic.

[0065] The content of the P3HB resin in the resin layer is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more of the total amount (solid content) of the resin layer. By using a P3HB resin as a main component, the resin layer can exhibit good biodegradability.

[0066] The resin layer preferably contains poly(3-hydroxybutyrate) (b-1) (hereinafter also referred to as PHB (b-1)) as the P3HA-based resin (B). By including PHB (b-1), the P3HA-based resin (B) is rapidly solidified after melting in the heating step, thereby improving the productivity of the laminate.

[0067] PHB(b-1) refers to a homopolymer composed only of 3-hydroxybutyrate, or a polymer containing a trace amount of hydroxyalkanoate units other than 3-hydroxybutyrate units in addition to 3-hydroxybutyrate units. Specifically, PHB(b-1) preferably contains 3-hydroxybutyrate units in a proportion of more than 99 mol% and not more than 100 mol% of all of its constituent monomers.

[0068] The hydroxyalkanoate units other than 3-hydroxybutyrate units that can be contained in PHB (b-1) are not particularly limited as long as they are copolymerizable with 3-hydroxybutyrate units, and examples thereof include 3-hydroxyalkanoate units other than 3-hydroxybutyrate units and hydroxyalkanoate units other than 3-hydroxyalkanoate units (e.g., 4-hydroxyalkanoate units). In particular, 3-hydroxyhexanoate units are preferred.

[0069] The weight average molecular weight of PHB (b-1) is not particularly limited, but from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, and the mechanical properties of the resin layer, it is preferably 100,000 or more and less than 400,000, and more preferably 200,000 or more and 350,000 or less.

[0070] The weight-average molecular weight (hereinafter, sometimes referred to as Mw) of PHB (b-1) can be determined as the molecular weight converted into polystyrene 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.

[0071] The content of PHB (b-1) in the resin layer is preferably 12% by weight or more and 21% by weight or less, based on the total amount (100% by weight) of the P3HA resin (B), from the viewpoints of productivity of the laminate and water resistance and oil resistance of the resin layer. From the viewpoint of productivity of the laminate, the content is more preferably 13% by weight or more. From the viewpoint of oil resistance, the content is preferably 18% by weight or less, more preferably 16% by weight or less.

[0072] In addition to PHB (b-1), the resin layer preferably further contains a poly(3-hydroxybutyrate)-based copolymer (b-2) containing 3-hydroxybutyrate units and other hydroxyalkanoate units. The inclusion of copolymer (b-2) facilitates melting of the P3HA-based resin (B) during the heating process, facilitating homogenization of the resin layer by heating, thereby improving the water resistance and oil resistance of the laminate. However, the resin layer may also contain only copolymer (b-2) as the P3HA-based resin (B) without PHB (b-1).

[0073] Specific examples of the copolymer (b-2) include the copolymers mentioned above, and among them, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred.

[0074] The content of the other hydroxyalkanoate units out of 100 mol% of the total monomer units constituting the poly(3-hydroxybutyrate) copolymer (b-2) is preferably 10 mol% or more and less than 24 mol%, more preferably 10 mol% or more and less than 20 mol%, and even more preferably 10 mol% or more and less than 18 mol%, from the viewpoint of achieving both meltability in the heating step and productivity of the resin.

[0075] The average content of the other hydroxyalkanoate units out of 100 mol% of all monomer units contained in the entire P3HA-based resin (B) contained in the resin layer is preferably 5 mol% or more and 18 mol% or less, more preferably 6 mol% or more and 16 mol% or less, even more preferably 7 mol% or more and 14 mol% or less, and particularly preferably 8 mol% or more and 12 mol% or less, from the viewpoint of achieving both meltability in the heating step and productivity of the resin.

[0076] The average content ratio of each monomer unit relative to 100 mol% of all monomer units contained in the entire P3HA-based resin (B) 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. When the P3HA-based resin (B) is a mixture of two or more resins, the average content ratio refers to the average molar ratio of each monomer unit relative to 100 mol% of all monomer units contained in the entire mixture.

[0077] The weight-average molecular weight of the poly(3-hydroxybutyrate) copolymer (b-2) is not particularly limited, but is preferably 100,000 or more and less than 400,000, and more preferably 200,000 or more and 350,000 or less, from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, the mechanical properties of the resin layer, etc. The weight-average molecular weight can be measured by the method described above.

[0078] A specific method for producing poly(3-hydroxybutyrate) copolymer (b-2) is described in, for example, WO 2010 / 013483. Commercially available PHBH products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0079] The weight-average molecular weight of the entire P3HA resin (B) is not particularly limited, but is preferably from 100,000 to less than 1,000,000, and more preferably from 200,000 to 900,000, from the viewpoints of the productivity of the laminate, the water resistance and oil resistance of the resin layer, and the mechanical properties of the resin layer, etc. The weight-average molecular weight can be measured by the method described above.

[0080] The resin layer may contain, to the extent that the effects of the invention are not impaired, one or more of the following: resins other than the P3HA-based resin (B), adhesives, 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, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding improvers. However, these are optional components, and the resin layer may not contain these components.

[0081] Resins other than the P3HA-based resin (B) that can be used in the resin layer are not particularly limited, but are preferably biodegradable resins. Specific examples include aliphatic polyester-based resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate. The blend amount of such other resins may be 50 parts by weight or less, 30 parts by weight or less, or 10 parts by weight or less, per 100 parts by weight of the P3HA-based resin (B). It may also be 5 parts by weight or less, or 1 part by weight or less.

[0082] The weight of the resin layer can be appropriately determined in consideration of the performance and productivity required of the resin layer. Specifically, the weight of the resin layer is 1.0 g / m2 in dry weight. 2 More than 80g / m 2 Preferably, it is 5.0 g / m or less. 2 More than 60g / m 2 Less than 10 g / m is more preferable. 2More than 50g / m 2 When the basis weight of the resin layer is within the above range, defects such as pinholes can be prevented, the resin layer can have a strength sufficient for use, and functions such as water resistance and oil resistance can be efficiently exhibited.

[0083] [Method for manufacturing laminate] The method for producing a laminate according to this embodiment includes step (i) of forming an anchor layer on at least one side of a paper substrate, and step (ii) of forming a resin layer containing a P3HA-based resin (B) on the surface of the formed anchor layer. In an embodiment in which the paper substrate has an underlayer, a paper substrate having a pre-formed underlayer on its surface may be obtained, and steps (i) and (ii) may be carried out on the paper substrate. Alternatively, a separate step of providing an underlayer on at least one surface of the paper substrate may be carried out before step (i).

[0084] [Step (i): Formation of anchor layer] In step (i), the solution (I) containing the aliphatic polyester resin (A) and a non-aqueous solvent described above is applied to one or both sides of the paper substrate and dried to form an anchor layer.

[0085] The solution (I) containing the aliphatic polyester resin (A) and a non-aqueous solvent is a solvent-based coating liquid in which the aliphatic polyester resin (A) is dissolved in a non-aqueous solvent. The use of a solvent-based coating liquid instead of a water-based coating liquid can improve the oil resistance of the laminate. This is presumably because the anchor layer is less likely to be eroded and the oil resistance of the anchor layer is less likely to be impaired in the step (ii) of forming the resin layer, which will be described later. Furthermore, by using a solvent-based coating liquid, the time required for the drying step after coating can be shortened, and the productivity of the laminate can also be improved.

[0086] The non-aqueous solvent usable in solution (I) can be appropriately selected from solvents commonly used in the field of coated paper, etc., taking into consideration the solubility of the aliphatic polyester resin (A) and the drying speed. Specific examples include, but are not limited to, non-halogenated organic solvents such as ethyl acetate, butyl acetate, toluene, xylene, methyl ethyl ketone, acetone, and acetonitrile; and halogenated organic solvents such as chloroform and methylene chloride. Only one type of non-aqueous solvent may be used, or two or more types may be used in combination.

[0087] From the viewpoint of forming a uniform anchor layer and shortening the drying step, it is preferable that the solution (I) contains substantially no water. Specifically, the water content in the solution (I) is preferably less than 1% by weight, more preferably less than 0.1% by weight.

[0088] The solid content concentration of the aliphatic polyester resin (A) in the solution (I) is not particularly limited, but may be, for example, within the range of 1% by weight to 60% by weight.

[0089] When the paper substrate layer has a primer layer, it is preferable to apply solution (I) onto the primer layer, which prevents solution (I) from penetrating into the paper substrate and makes it easier to achieve the oil resistance improving effect of the anchor layer.

[0090] The method for applying solution (I) to the paper substrate is not particularly limited, and any known method capable of forming a coating layer on the paper substrate can be used as appropriate. Specifically, methods such as spraying, scattering, slit coating, air knife coating, roll coating, bar coating, comma coating, blade coating, screen printing, and gravure printing can be used. Before applying solution (I), the paper substrate may be subjected to a surface treatment such as the above-mentioned corona treatment.

[0091] The drying treatment after coating can be carried out using a known heating method, such as hot air heating, infrared heating, microwave heating, roll heating, or hot plate heating, which can be used alone or in combination of two or more.

[0092] The heating temperature in the drying treatment is not particularly limited as long as it is a temperature at which the non-aqueous solvent contained in solution (I) can be evaporated. Specifically, it is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. The upper limit may be less than 130°C and may be 125°C or lower. The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably about 30 seconds to 5 minutes.

[0093] [Step (ii): Formation of Resin Layer] Next, step (ii) is carried out to form a resin layer containing a P3HA-based resin (B) on the surface of the formed anchor layer. The resin layer may be formed by applying an aqueous dispersion (II) containing the P3HA resin (B) to the surface of the anchor layer and drying the applied dispersion to form the resin layer, or by laminating a resin composition containing the P3HA resin (B) on the surface of the anchor layer.

[0094] [Formation of resin layer by coating method] In the embodiment in which the resin layer is formed by applying an aqueous dispersion (II) containing a P3HA-based resin (B) to the surface of an anchor layer and drying it, first, the aqueous dispersion (II) is prepared. The aqueous dispersion (II) containing the P3HA resin (B) refers to a liquid in which at least resin particles containing the P3HA resin (B) are dispersed in water. The aqueous dispersion (II) may contain other components dissolved or dispersed therein, as necessary.

[0095] The aqueous dispersion (II) contains an aqueous solvent. The aqueous solvent may be water alone or a mixed solvent of water and an organic solvent. The organic solvent is preferably an organic solvent that is compatible with water. The concentration of the organic solvent is preferably equal to or less than the solubility of the organic solvent in water.

[0096] The solids concentration of the P3HA resin (B) in the aqueous dispersion (II) is not particularly limited, but is preferably 20% by weight or more and 60% by weight or less. When the solids concentration is within this range, the viscosity of the dispersion is not too high, allowing for uniform application, and the required coating thickness can be maintained, thereby preventing coating defects. The lower limit of the solids concentration is preferably 30% by weight or more, and more preferably 40% by weight or more.

[0097] The average particle size of the P3HA resin (B) in the aqueous dispersion (II) may be, for example, 0.1 to 50 μm, from the viewpoint of achieving both productivity of the P3HA resin (B) and uniformity during application.

[0098] The aqueous dispersion (II) may not contain an emulsifier, but preferably contains an emulsifier to stabilize the dispersion. Examples of emulsifiers include anionic surfactants such as sodium lauryl sulfate and sodium oleate, cationic surfactants such as lauryl trimethylammonium chloride, nonionic surfactants such as glycerin fatty acid esters and sorbitan fatty acid esters, polyvinyl alcohol derivatives such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonated polyvinyl alcohol, and ethylene-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, starch derivatives such as starch, oxidized starch, and etherified starch, and water-soluble polymers such as chitin, chitosan, casein, and gum arabic. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol is preferred.

[0099] The amount of emulsifier added is not particularly limited, but is preferably, for example, about 1 to 10 parts by weight per 100 parts by weight of the solid content of the P3HA resin (B).

[0100] The method for producing aqueous dispersion (II) containing P3HA resin (B) is not particularly limited, but may involve first producing P3HA resin (B) within the cells of a microorganism, then disrupting the microbial cells in an aqueous dispersion state containing the P3HA resin (B). A precipitate is obtained by centrifugation from the aqueous dispersion of P3HA resin (B) obtained by disruption. This precipitate is washed with water and, if necessary, with methanol, and finally an appropriate amount of water is added to obtain aqueous dispersion (II) containing P3HA resin (B) with a desired solids concentration.

[0101] Alternatively, the microbial cells may be disrupted to obtain an aqueous dispersion of the P3HA resin (B), which may then be washed appropriately and spray-dried to obtain a powder of the P3HA resin (B), which may then be dispersed in water to obtain the aqueous dispersion (II). Alternatively, the P3HA resin (B) may be obtained in powder form and dispersed in water to obtain the aqueous dispersion (II).

[0102] The aqueous dispersion (II) described above is applied to the surface of the anchor layer to form a coating film. The application method is not particularly limited, and known methods can be used as appropriate. Specifically, spraying, scattering, slit coating, air knife coating, roll coating, bar coating, comma coating, blade coating, screen printing, gravure printing, etc. can be used.

[0103] After the coating film is formed, the coating film is heated and dried to form a resin layer. This drying step may be a step aimed solely at evaporating the aqueous medium contained in the aqueous dispersion (II), or may be a step aimed at fusing the particles of the P3HA resin (B) together to increase the uniformity of the resin layer, in addition to the evaporation.

[0104] When the drying step is intended solely to evaporate the aqueous medium, the heating temperature of the coating film in the drying step is not particularly limited, but may be a temperature lower than the melting point of the P3HA resin (B). Specifically, the upper limit of the heating temperature may be less than 130°C and may be 125°C or lower. The lower limit of the heating temperature is not particularly limited, but may be, for example, 70°C or higher, preferably 90°C or higher, and more preferably 100°C or higher. The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably 30 seconds to 5 minutes.

[0105] On the other hand, if the drying step is intended to evaporate the aqueous medium and fuse the P3HA resin (B) particles together, the heating temperature of the coating film in the drying step is preferably equal to or higher than the melting point of the P3HA resin (B). Heating at such a temperature melts at least a portion of the P3HA resin (B), and the molten portion cools and solidifies after heating, fusing the resin particles together and integrating the resin components, resulting in the formation of a more uniform resin layer. This improves the adhesion of the resin layer to the paper substrate layer and anchor layer, as well as the water and oil resistance of the resin layer.

[0106] The heating temperature is preferably 10 to 40°C higher than the melting point of the P3HA resin (B), and more preferably 20 to 30°C higher. Specifically, the heating temperature is preferably 160°C or higher, more preferably 165°C or higher, and particularly preferably 170°C or higher. The heating temperature is also preferably 200°C or lower. A heating temperature of 200°C or lower can avoid excessive drying of the paper substrate and thermal decomposition of the P3HA resin (B). The heating time is not particularly limited, but may be, for example, 10 seconds to 10 minutes, and preferably 30 seconds to 5 minutes. The melting point of the P3HA resin (B) refers to the highest peak top temperature in the crystal melting curve in differential scanning calorimetry.

[0107] This drying step 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.

[0108] After the drying step, a humidity control step may be carried out to adjust the moisture content of the dried paper base layer.

[0109] [Formation of resin layer by lamination method] In the embodiment in which the resin layer is formed by lamination, extrusion lamination or thermal lamination can be used. The extrusion lamination method may be a general extrusion lamination method. Specifically, a molten resin material (i.e., a resin composition containing the P3HA resin (B)) is extruded into a film form through a T-die, and is pressed onto the surface of the anchor layer while being cooled using a cooling roll. Immediately thereafter, the resin material is peeled off from the cooling roll to form a resin layer, thereby producing a laminate.

[0110] The thermal lamination method can be a general thermal lamination method. Specifically, first, a molten resin material (i.e., a resin composition containing the P3HA-based resin (B)) is extruded, for example, through a T-shaped die, and cooled using a cooling roll to form a film containing the resin material. Next, the obtained film is pressed onto the surface of the anchor layer using a heated roll or the like, to produce a molded product.

[0111] For the purpose of improving the adhesion between the resin layer and the paper substrate layer on which the anchor layer is formed, the surface of the anchor layer may be subjected to corona treatment, flame treatment, ozone treatment, or the like.

[0112] [Molded body] The molded article according to one aspect of the present embodiment includes the laminate described above and has a desired size and shape. The molded article is advantageous in a variety of applications because it is formed from a laminate including a resin layer containing a P3HA-based resin (B).

[0113] The molded article is not particularly limited as long as it contains the laminate, and examples thereof include paper, film, sheet, tube, plate, rod, container (for example, bottle container), bag, and part.

[0114] The molded article may be the laminate itself, or may be a product of secondary processing of the laminate. By subjecting the laminate to secondary processing, the molded article 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 molded article contains a resin layer that has high adhesion to substrates and good heat resistance, it can be more suitably used as containers for holding liquids, particularly containers for hot contents, such as cups for food and beverages such as instant noodles, instant soup, and coffee, and trays for prepared meals, bento boxes, and microwaveable foods. Because the laminate has excellent water resistance and oil resistance, it can be suitably used as a packaging material for packaging food and beverages that contain water or oil.

[0115] The secondary processing 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, and box making machines. In these processing machines, known techniques can be used to bond the laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing.

[0116] The heat-sealing temperature of the laminate varies depending on the adhesion method, but when using, for example, a heating-type heat-sealing tester equipped with a seal bar, the resin temperature can usually be set to 180° C. or lower, preferably 170° C. or lower, and more preferably 160° C. or lower. The lower limit of the resin temperature is usually 100° C. or higher, preferably 110° C. or higher, and more preferably 120° C. or higher.

[0117] The heat-sealing pressure for the laminate varies depending on the bonding method, but when a heating-type heat-sealing tester equipped with a seal bar is used, it is usually 0.1 MPa or more, preferably 0.5 MPa or more, and the upper limit of the heat-sealing pressure is usually 1.0 MPa or less, preferably 0.75 MPa or less.

[0118] In order to improve the physical properties of the molded article, the molded article can be composited with another molded article made of a material different from the 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.

[0119] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A method for producing a laminate including a paper substrate layer, comprising: (i) applying a solution (I) containing an aliphatic polyester resin (A) and a non-aqueous solvent to the surface of a paper substrate layer and drying the solution to form an anchor layer; and a step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B) on the surface of the anchor layer, The method for producing a laminate, wherein the aliphatic polyester resin (A) comprises at least one selected from the group consisting of polylactic acid resin, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone. [Item 2] Item 2. The method for producing a laminate according to item 1, wherein the step (ii) is a step of applying an aqueous dispersion (II) containing the poly(3-hydroxyalkanoate)-based resin (B) to a surface of the anchor layer and drying the applied dispersion to form the resin layer. [Item 3] Item 2. The method for producing a laminate according to item 1, wherein the step (ii) is a step of forming the resin layer on the surface of the anchor layer by a lamination method using a resin composition containing the poly(3-hydroxyalkanoate)-based resin (B). [Item 4] 4. The method for producing a laminate according to any one of items 1 to 3, wherein the paper substrate layer has an underlayer containing a water-soluble polymer on the surface on which the solution (I) is applied. [Item 5] 5. The method for producing a laminate according to item 4, wherein the water-soluble polymer is polyvinyl alcohol or methyl cellulose. [Item 6] 6. The method for producing a laminate according to any one of items 1 to 5, wherein the aliphatic polyester resin (A) contains a polylactic acid resin, and the polylactic acid resin is an amorphous polylactic acid resin. [Item 7] 7. The method for producing a laminate according to any one of items 1 to 6, wherein the poly(3-hydroxyalkanoate) resin (B) contains poly(3-hydroxybutyrate) (b-1). [Item 8] 8. The method for producing a laminate according to Item 7, wherein the content of the poly(3-hydroxybutyrate) (b-1) is 12% by weight or more and 21% by weight or less, based on 100% by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin (B). [Item 9] 9. The method for producing a laminate according to any one of items 1 to 8, wherein the poly(3-hydroxyalkanoate) resin (B) comprises a poly(3-hydroxybutyrate) copolymer (b-2) having a 3-hydroxybutyrate unit and another hydroxyalkanoate unit. [Item 10] Item 10. The method for producing a laminate according to Item 9, wherein the content of the other hydroxyalkanoate units is 10 mol% or more and less than 24 mol% of the total amount of monomer units constituting the poly(3-hydroxybutyrate)-based copolymer (b-2), 100 mol%. [Item 11] 11. The method for producing a laminate according to any one of items 1 to 10, wherein the poly(3-hydroxyalkanoate) resin (B) has a weight average molecular weight (Mw) of 100,000 or more and less than 1,000,000. [Example]

[0120] The present invention will be explained in more detail below by showing examples and comparative examples, but the technical scope of the present invention is not limited to these examples.

[0121] In the examples and comparative examples, the following raw materials were used. [Water-soluble polymer] Polyvinyl alcohol (PVA): Poval L508W (Kuraray)

[0122] [Polylactic acid resin] Polylactic acid (PLA-1): Ingeo 4060D (Natureworks), amorphous, weight-average molecular weight: 1.8 × 10 5 Polylactic acid (PLA-2): PLA-1 was treated at 120°C and 100% humidity for 3 hours to produce PLA-2. Amorphous, weight-average molecular weight: 5.0 x 10 3

[0123] [Poly(3-hydroxyalkanoate) resin] P3HB3HH-11: P3HB3HH (average content ratio of 3HB / 3HH = 87.1 / 11 (mol% / mol%), weight average molecular weight is 260,000 g / mol)

[0124] [PVA aqueous solution] 12.5 g of PVA was dissolved in 87.5 g of hot water and then cooled to obtain an aqueous PVA solution.

[0125] [PLA water dispersion] 47.2 g of PLA-1 was mixed with an aqueous solution of 2.8 g of PVA dissolved in 50 g of water, and a PLA aqueous dispersion was prepared by a general phase inversion emulsification method.

[0126] [P3HB3HH water dispersion] According to the method described in WO 2015 / 1461965, an aqueous dispersion of P3HB3HH with a solids concentration of P3HB3HH-11 of 50% by weight was prepared.

[0127] The measurement and evaluation methods used in the examples and comparative examples are described below. [Method for measuring the basis weight of the base layer, anchor layer, and resin layer] The basis weight of the base layer, anchor layer, and resin layer was determined by cutting out a sample with each layer formed into a size of 10 cm x 10 cm, measuring its weight, subtracting the weight of the sample before each layer was formed from that weight value, and multiplying the result by 100 to obtain the basis weight of each layer (dry weight of each layer per unit area).

[0128] [water resistance] In accordance with JIS P 8140:1998, "Paper and board - Water absorption test method - Cobb method," the water absorption [Cobb value (g / m2)] of room temperature water at any two points on the resin layer surface of the laminate after a contact time of 1800 seconds was measured. 2 )] was measured.

[0129] [Oil resistance] Ageless Check Liquid (Color Check Liquid, manufactured by Taseto) was evenly applied to the surface of the resin layer of the laminate. After 1 minute, the liquid on the surface was wiped off, and the degree of penetration to the back side of the sprayed surface was evaluated according to the following criteria. 〇: No stain △: Stains are observed, but are reduced compared to Comparative Example 3 ×: Stains equivalent to or greater than those in Comparative Example 3 are observed

[0130] [Heat sealability] The laminate was cut into a width of 25 mm, and the resin layers of the laminate were pressed together using a heat sealer (TP-701-B, manufactured by Tester Sangyo Co., Ltd.) at a pressing temperature of 130°C, a pressing pressure of 0.5 MPa, and a pressing time of 1 second. The resulting heat seal paper was subjected to a T-peel test at a tensile speed of 100 mm / min using a tensile tester (Eztest Ez-LX manufactured by Shimadzu Corporation), and the peelability was evaluated according to the following criteria. ○: The paper substrate was destroyed when peeled off. △: No damage to the paper substrate was observed, but adhesion was observed ×: Not adhered

[0131] Example 1 [Formation of base layer] A PVA aqueous solution was applied to bleached kraft paper [Kujira, basis weight: 50 g / m] using a bar coater (No. 7 AS ONE). 2 The paper was coated onto a paper sheet (Oji Materia) and then heated in an oven set at 100°C for 1 minute to obtain a paper substrate with a primer layer. The basis weight of the primer layer was 2.8 g / m 2 It was.

[0132] [Anchor layer formation] 10.0 g of PLA-1 was dissolved in a mixed solvent of 18.0 g of ethyl acetate and 72.0 g of chloroform to obtain a non-aqueous solution. The non-aqueous solution was applied to the surface of the underlayer using a bar coater (No. 7 AS ONE), and then heated in an oven set at 105°C for 1 minute to form an anchor layer. The basis weight of the anchor layer was 2.8 g / m 2 It was.

[0133] [Formation of resin layer] The P3HB3HH aqueous dispersion was applied to the surface of the anchor layer using a bar coater (No. 14 AS ONE), and then heated in an oven set to 180°C for 2 minutes to form a resin layer, yielding a laminate. The resulting laminate was evaluated for Cobb value, oil resistance, and heat sealability, and the results are shown in Table 1.

[0134] Example 2 A laminate was obtained in the same manner as in Example 1, except that a non-aqueous solution containing PLA-2 (a solution in which 10.0 g of PLA-2 was dissolved in 90.0 g of ethyl acetate) was used to form the anchor layer. The Cobb value, oil resistance, and heat sealability of the obtained laminate were evaluated, and the results are shown in Table 1.

[0135] (Comparative Example 1) A laminate was produced in the same manner as in Example 1, except that an aqueous PVA solution was used to form the anchor layer, and after coating, the solution was heated in an oven set to 100° C. for 1 minute. The Cobb value, oil resistance, and heat sealability of the obtained laminate were evaluated, and the results are shown in Table 1.

[0136] (Comparative Example 2) Except for forming the resin layer directly on the underlayer without forming an anchor layer, a laminate was produced in the same manner as in Example 1. The obtained laminate was evaluated for Cobb value, oil resistance, and heat sealability, and the results are shown in Table 1.

[0137] (Comparative Example 3) A laminate was produced in the same manner as in Example 1, except that the resin layer was formed directly on the bleached kraft paper without forming the base layer and anchor layer. The Cobb value, oil resistance, and heat sealability of the obtained laminate were evaluated, and the results are shown in Table 1.

[0138] Comparative Example 4 A laminate was produced in the same manner as in Example 1, except that, without forming a primer layer, the aforementioned PLA aqueous dispersion was directly coated on bleached kraft paper instead of the PLA-1 solution, and after coating, the coated product was heated for 1 minute in an oven set to 130°C (drying was insufficient at 100°C). The Cobb value, oil resistance, and heat sealability of the resulting laminate were evaluated, and the results are shown in Table 1.

[0139] (Comparative Example 5) A laminate was produced in the same manner as in Example 1, except that a PLA emulsion (Landy PL-1000, manufactured by Miyoshi Oil & Fats) was used instead of the PLA-1 solution in forming the anchor layer, and after coating, the layer was heated for 1 minute in an oven set to 130°C (drying was insufficient at 100°C). The Cobb value, oil resistance, and heat sealability of the resulting laminate were evaluated, and the results are shown in Table 1.

[0140] [Table 1]

[0141] 〔result〕 Table 1 shows that in Examples 1 and 2, in which the anchor layer was formed using a non-aqueous solution of polylactic acid resin, the Cobb value was relatively low and water resistance was good, and good results were also obtained in terms of oil resistance and heat sealability. On the other hand, in Comparative Example 1, in which an aqueous solution of polyvinyl alcohol was used to form the anchor layer, the Cobb value was high and the water resistance was insufficient. Similar results were obtained in Comparative Example 2, in which no anchor layer was formed. Furthermore, in Comparative Example 3, in which neither the undercoat layer nor the anchor layer was formed, the water resistance was high but the oil resistance was insufficient. Furthermore, in Comparative Examples 4 and 5, in which the anchor layer was formed using an aqueous dispersion of a polylactic acid resin, the oil resistance was also insufficient.

Claims

1. A method for producing a laminate including a paper substrate layer, comprising: a step (i) of applying a solution (I) containing an aliphatic polyester resin (A) and a non-aqueous solvent to the surface of a paper substrate layer and drying the solution to form an anchor layer; and a step (ii) of forming a resin layer containing a poly(3-hydroxyalkanoate)-based resin (B) on the surface of the anchor layer, The method for producing a laminate, wherein the aliphatic polyester-based resin (A) comprises at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone.

2. 2. The method for producing a laminate according to claim 1, wherein the step (ii) is a step of applying an aqueous dispersion (II) containing the poly(3-hydroxyalkanoate)-based resin (B) to a surface of the anchor layer and drying the applied dispersion to form the resin layer.

3. 2. The method for producing a laminate according to claim 1, wherein the step (ii) is a step of forming the resin layer on the surface of the anchor layer by a lamination method using a resin composition containing the poly(3-hydroxyalkanoate)-based resin (B).

4. The method for producing a laminate according to any one of claims 1 to 3, wherein the paper substrate layer has an underlayer containing a water-soluble polymer on the surface on which the solution (I) is applied.

5. The method for producing a laminate according to claim 4, wherein the water-soluble polymer is polyvinyl alcohol or methyl cellulose.

6. The method for producing a laminate according to any one of claims 1 to 3, wherein the aliphatic polyester-based resin (A) contains a polylactic acid-based resin, and the polylactic acid-based resin is an amorphous polylactic acid-based resin.

7. The method for producing a laminate according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate)-based resin (B) contains poly(3-hydroxybutyrate) (b-1).

8. 8. The method for producing a laminate according to claim 7, wherein the content of the poly(3-hydroxybutyrate) (b-1) is 12% by weight or more and 21% by weight or less, based on 100% by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin (B).

9. The method for producing a laminate according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) resin (B) comprises a poly(3-hydroxybutyrate) copolymer (b-2) having a 3-hydroxybutyrate unit and another hydroxyalkanoate unit.

10. The method for producing a laminate according to claim 9, wherein the content of the other hydroxyalkanoate units is 10 mol% or more and less than 24 mol% of the total amount (100 mol%) of monomer units constituting the poly(3-hydroxybutyrate)-based copolymer (b-2).

11. The method for producing a laminate according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) resin (B) has a weight average molecular weight (Mw) of 100,000 or more and less than 1,000,000.

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