Packaging body and method for producing same

Abstract

This packaging body comprises a paper laminate and a resin film. The paper laminate includes a paper base material layer and a laminated adhesive resin layer. The resin film has: a seal region that is heat-sealed to the paper laminate via the adhesive resin layer; and a non-seal region that is not heat-sealed to the paper laminate. The resin film includes a poly(3-hydroxyalkanoate)-based resin (A). The resin (A) includes: (a-1) a copolymer of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content ratio of the other hydroxyalkanoate unit is 1-13 mol%; and (a-2) a copolymer of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content ratio of the other hydroxyalkanoate unit is 24 mol% or more.

Description

Packaging and manufacturing method thereof

[0001] The present invention relates to a packaging body including a paper laminate and a resin film, and a method for manufacturing the packaging body.

[0002] In recent years, the problem of marine pollution caused by discarded plastic packaging materials has come to the forefront, and environmentally friendly paper packaging materials have been attracting attention.

[0003] Paper used as a packaging material is usually laminated with a resin to impart water resistance, oil resistance, heat sealing properties, etc. As such a resin, it is preferable to laminate a biodegradable resin so as not to impair the biodegradability of the paper.

[0004] Among biodegradable resins, poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species, and are known to be biodegradable not only in soil but also in seawater.

[0005] A laminate obtained by laminating such a poly(3-hydroxyalkanoate) resin onto a paper substrate is extremely promising from the viewpoint of environmental protection. Patent Document 1 discloses such a laminate.

[0006] On the other hand, resin films made primarily from poly(3-hydroxyalkanoate) resins are also known, and Patent Document 2 discloses such films.

[0007] International Publication No. WO 2022 / 059592 International Publication No. WO 2022 / 004637

[0008] A package exhibiting good rigidity can be manufactured by integrating a paper laminate including the paper base layer and resin layer described above with a resin film by heat sealing. In this case, by providing an unsealed area in the resin film, a package (e.g., a three-sided seal, a standing pouch, etc.) can be constructed that allows the packaged item to be viewed from the outside through that area.

[0009] The present inventors have produced a package including the above-described heat-sealed portion using a paper laminate including a paper base layer and a biodegradable resin layer, and a resin film composed of a poly(3-hydroxyalkanoate)-based resin, and have found that curling (warping) may occur in the heat-sealed portion as time passes after heat sealing. Such curling occurs particularly when a thick resin film is used.

[0010] Such curling not only impairs the appearance of the package, but also poses problems in terms of handling, such as making it impossible to stack packages on top of each other when transporting or displaying the packages.

[0011] In view of the above, an object of the present invention is to provide a package including a portion where a paper laminate including a paper base layer and a biodegradable resin layer and a resin film including a poly(3-hydroxyalkanoate) resin are heat-sealed, wherein curling of the heat-sealed portion is suppressed while maintaining the adhesive strength of the heat-sealed portion, and to provide a method for producing the package.

[0012] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using two types of copolymers having specific monomer compositions in combination as a poly(3-hydroxyalkanoate)-based resin used in a resin film in a package including a heat-sealed portion as described above, and have completed the present invention.

[0013] Specifically, the present invention relates to a packaging body comprising a paper laminate and a resin film, wherein the paper laminate comprises a paper base layer and an adhesive resin layer containing a biodegradable polyester resin laminated on at least one side of the paper base layer, the resin film having a sealed area heat-sealed to the paper laminate via the adhesive resin layer and an unsealed area not heat-sealed to the paper laminate, the resin film comprising a poly(3-hydroxyalkanoate)-based resin (A), the poly(3-hydroxyalkanoate)-based resin (A) comprising a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer containing the other hydroxyalkanoate units having a ratio of 1 to 13 mol%, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units having a ratio of 24 mol% or more. The present invention also relates to a method for producing a packaging body, the method comprising at least the following steps: Step (i): A process for forming a raw material containing a poly(3-hydroxyalkanoate)-based resin (A) containing a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 1 to 13 mol%, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 24 mol% or more, into a resin film. Step (ii): A process for applying a coating liquid containing a biodegradable polyester resin to at least one surface of a paper base layer, and then heating to form a paper laminate containing a paper base layer and an adhesive resin layer. Step (iii): A process for overlapping the resin film and the paper laminate so that a portion of the surface of the resin film contacts the adhesive resin layer, and performing heat sealing, thereby obtaining a package in which a portion of the surface of the resin film is heat-sealed to the paper laminate.

[0014] According to the present invention, it is possible to provide a package including a heat-sealed portion between a paper laminate including a paper base layer and a biodegradable resin layer and a resin film including a poly(3-hydroxyalkanoate) resin, in which curling of the heat-sealed portion is suppressed while maintaining the adhesive strength of the heat-sealed portion, and a method for manufacturing the package.

[0015] FIG. 1 is a cross-sectional view showing an example of a layered structure constituting a packaging body according to the present disclosure; FIG. 2 is a cross-sectional view showing another example of a layered structure constituting a packaging body according to the present disclosure;

[0016] Embodiments of the present invention are described in detail below. However, the present invention is not limited to the embodiments described below, and various modifications are possible within the scope of the claims. Furthermore, the configurations described below can be combined arbitrarily, and such combinations can also be an aspect of the present invention. A packaging body according to the present disclosure includes at least a paper laminate including a paper base layer and an adhesive resin layer, and a resin film.

[0017] [Paper base layer] The paper base layer is not particularly limited as long as it is a commonly used paper whose main component is plant-derived pulp. The paper base can usually be obtained by papermaking a paper 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.

[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, that discoloration is less likely to occur over time when recycled 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 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%.

[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 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-retaining 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 layer can be appropriately selected depending on the desired quality and the use of the packaging material, but is preferably 30 to 350 g / m ２ It is preferable that the density is 40 to 300 g / m ２ More preferably, 50 to 200 g / m ２ By setting the content within this range, it becomes easy to impart practical mechanical strength to the package.

[0025] In conventional techniques, when the basis weight of the paper base layer is small, curling of the heat-sealed portion tends to occur easily. However, according to the present disclosure, curling can be suppressed even when the basis weight of the paper base layer is small. From this perspective, the basis weight of the paper base layer is set to 150 g / m ２ It may be less than 100 g / m ２ It may be the following:

[0026] [Adhesive Resin Layer] The adhesive resin layer may be laminated on only one side of the paper base layer or on both sides. The adhesive resin layer is located on the outermost surface of the paper laminate. At least a portion of the surface of the adhesive resin layer is bonded to the resin film described below by heat sealing.

[0027] The adhesive resin layer may be a coating layer formed by applying a coating liquid to the surface of the paper substrate layer and drying it by heating, or may be a laminate layer formed by a lamination method, such as extrusion lamination, dry lamination, non-solvent lamination, and thermal lamination. The adhesive resin layer is preferably a coating layer because it has good adhesion to the paper substrate layer.

[0028] The adhesive resin layer is a resin layer composed mainly of a biodegradable polyester resin. By using a biodegradable polyester resin for the adhesive resin layer, the biodegradability of the entire package can be improved and the adhesive strength between the adhesive resin layer and the resin film can be improved.

[0029] As the biodegradable polyester resin, polyester resins generally known to be biodegradable can be used, and the type thereof is not particularly limited, but examples thereof include aliphatic polyester resins such as polyhydroxyalkanoate, polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate.

[0030] From the viewpoint of enhancing the biodegradability of the entire package, the proportion of the biodegradable polyester resin in the entire resin components contained in the adhesive resin layer is preferably 50% by weight or more and 100% by weight or less, more preferably 70% by weight or more, even more preferably 80% by weight or more, still more preferably 90% by weight or more, and particularly preferably 95% by weight or more, and may even be 99% by weight or more.

[0031] In particular, the adhesive resin layer preferably contains a poly(3-hydroxyalkanoate)-based resin (B) as the biodegradable polyester resin, which can further enhance the biodegradability of the entire package and can also improve the adhesive strength when heat-sealed with the resin film described below.

[0032] The proportion of the poly(3-hydroxyalkanoate) resin (B) in the entire resin components contained in the adhesive resin layer is preferably 50% by weight or more and 100% by weight or less, more preferably 70% by weight or more, even more preferably 80% by weight or more, still more preferably 90% by weight or more, and particularly preferably 95% by weight or more. It may even be 99% by weight or more.

[0033] In this specification, poly(3-hydroxyalkanoate) resin (hereinafter also referred to as P3HA resin) refers to a polymer having a 3-hydroxyalkanoate unit. Specifically, it is preferably a polymer containing a unit represented by the following general formula (1): [—CHR—CH ２ -CO-O-] (1) 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 an integer of 1 to 10, and more preferably an integer of 1 to 8.

[0034] As the poly(3-hydroxyalkanoate)-based resin, a poly(3-hydroxyalkanoate)-based resin produced by a microorganism is particularly preferred. In the poly(3-hydroxyalkanoate)-based resin produced by a microorganism, all of the 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0035] The poly(3-hydroxyalkanoate) 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. The poly(3-hydroxyalkanoate) resin may contain only 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).

[0036] The poly(3-hydroxyalkanoate) resin preferably contains a homopolymer having only 3-hydroxybutyrate units and / or a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units. In particular, from the viewpoint of seawater decomposability, it is preferable to contain a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0037] 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.

[0038] The hydroxyalkanoic acid forming 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.

[0039] Specific examples of P3HA-based resins include poly(3-hydroxybutyrate) (abbreviation: PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and poly(3-hydroxybutyrate-co- Examples of suitable P3HB include poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH). Among these, PHB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred due to their ease of industrial production. Only one type of P3HB may be used, or two or more types may be used in combination.

[0040] A specific method for producing poly(3-hydroxyalkanoate) resins is described in, for example, WO 2010 / 013483. Commercially available P3HB3HH products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0041] The poly(3-hydroxyalkanoate) resin (B) contained in the adhesive resin layer preferably contains a poly(3-hydroxybutyrate) copolymer (b-1) containing 3-hydroxybutyrate units and other hydroxyalkanoate units. The content of other hydroxyalkanoate units relative to the total monomer units in the copolymer (b-1) is preferably 6 mol% or more but less than 24 mol%, more preferably 8 mol% or more but less than 20 mol%, and particularly preferably 10 mol% or more but less than 16 mol%. Within this range, the resin component is easily melted during the heating process of the coating film described below, and the adhesive resin layer is easily homogenized by heating, thereby improving the water resistance and oil resistance of the paper laminate. Furthermore, the adhesive strength of the heat-sealed resin film described below can be further improved.

[0042] The average content ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin 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. The average content ratio means the molar ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin, and when the resin to be measured is a mixture of two or more resins, it means the molar ratio of each monomer unit contained in the entire mixture.

[0043] Specific examples of the copolymer (b-1) include the copolymers mentioned above, among which P3HB3HH, P3HB3HV and P3HB4HB are preferred, with P3HB3HH being particularly preferred.

[0044] The weight average molecular weight of the copolymer (b-1) is not particularly limited, but from the viewpoint of achieving both the coatability of the coating liquid and the mechanical properties of the adhesive resin layer, it is preferably 100,000 to 650,000, more preferably 150,000 to 450,000, and even more preferably 200,000 to 350,000.

[0045] The weight average molecular weight (hereinafter, sometimes referred to as Mw) of the polymer can be determined as the molecular weight in terms of 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.

[0046] The adhesive resin layer preferably further contains poly(3-hydroxybutyrate) (b-2) as the poly(3-hydroxyalkanoate)-based resin (B) in addition to the copolymer (b-1). This allows the resin component to be melted and then solidified quickly in the heating step of the coating film described below, thereby suppressing blocking.

[0047] Poly(3-hydroxybutyrate) (b-2) refers to a homopolymer composed only of 3-hydroxybutyrate, or a polymer containing, in addition to 3-hydroxybutyrate units, trace amounts of hydroxyalkanoate units other than 3-hydroxybutyrate units. Specifically, the content of 3-hydroxybutyrate units in the entire constituent monomers of poly(3-hydroxybutyrate) (b-2) is preferably more than 99 mol % and 100 mol % or less.

[0048] The hydroxyalkanoate unit other than the 3-hydroxybutyrate unit that can be contained in the poly(3-hydroxybutyrate) (b-2) is not particularly limited as long as it is copolymerizable with the 3-hydroxybutyrate unit, and examples thereof include a 3-hydroxyalkanoate unit other than the 3-hydroxybutyrate unit and a hydroxyalkanoate unit other than the 3-hydroxyalkanoate unit (for example, a 4-hydroxyalkanoate unit). In particular, a 3-hydroxyhexanoate unit is preferred.

[0049] The weight-average molecular weight of poly(3-hydroxybutyrate) (b-2) is not particularly limited, but from the viewpoint of achieving both the coatability of the coating liquid and the mechanical properties of the adhesive resin layer, it is preferably 100,000 to 400,000, and more preferably 200,000 to 350,000. The weight-average molecular weight can be measured by the method described above.

[0050] From the viewpoint of achieving both blocking suppression and adhesion strength, the content of poly(3-hydroxybutyrate) (b-2) in the adhesive resin layer is preferably 1% by weight or more and 50% by weight or less of the total of copolymer (b-1) and poly(3-hydroxybutyrate) (b-2). From the viewpoint of blocking suppression, the content is more preferably 3% by weight or more, and even more preferably 5% by weight or more. Furthermore, from the viewpoint of improving adhesion strength, the content is preferably 30% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.

[0051] The average content ratio of other hydroxyalkanoate units in all monomer units contained in the entire poly(3-hydroxyalkanoate) resin (B) contained in the adhesive resin layer is preferably 5 mol% or more and 18 mol% or less, more preferably 7 mol% or more and 15 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.

[0052] The weight average molecular weight of the entire poly(3-hydroxyalkanoate) resin (B) contained in the adhesive resin layer is not particularly limited, but from the viewpoint of achieving both the coatability of the coating liquid and the mechanical properties of the adhesive resin layer, it is preferably 100,000 to 400,000, and more preferably 200,000 to 350,000.

[0053] The adhesive 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 poly(3-hydroxyalkanoate) 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, ultraviolet absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, sliding property improvers, etc. However, these are optional components, and the adhesive resin layer may not contain these components.

[0054] The thickness of the adhesive resin layer is not particularly limited and can be appropriately determined taking into consideration the performance and productivity required of the adhesive resin layer, but may be, for example, 0.5 to 100 μm or 1 to 50 μm. In particular, from the viewpoint of achieving both adhesive strength by heat sealing and flexibility as a package, a thickness of 5 to 30 μm is preferred.

[0055] The adhesive resin layer preferably has melting characteristics such that, in a crystalline melting curve measured by differential scanning calorimetry, it has at least one peak top temperature (Tma) in the range of 90 to 150° C. and at least one peak top temperature (Tmb) in the range of 150 to 170° C., and the temperature difference between Tma and Tmb is 10° C. or more. When the adhesive resin layer has such melting characteristics, heat sealing between the adhesive resin layer and the resin film becomes easy, and good adhesive strength can be exhibited in a short time after heating.

[0056] It is presumed that the adhesive resin layer has a melting point peak in the relatively high temperature range of 150 to 170°C, and resin crystals having Tmb act as crystal nuclei, accelerating the solidification of the molten resin during heat sealing, making it possible to develop good adhesive strength in a short time after heat sealing.

[0057] The temperature difference between Tma and Tmb is 10°C or more, preferably 15°C or more, more preferably 20°C or more, and even more preferably 25°C or more. When the temperature difference is 10°C or more, heat sealing becomes easy and good adhesive strength tends to be exhibited in a short time after heating. The upper limit of the temperature difference between Tma and Tmb is not particularly limited, but from the viewpoint of ease of production, it is, for example, 60°C or less, more preferably 50°C or less.

[0058] In this specification, the peak top temperature of a crystalline melting curve in differential scanning calorimetry is defined as follows. 2 to 5 mg of the adhesive resin layer separated from the substrate layer is placed in an aluminum pan, and using a differential scanning calorimetry analyzer, the temperature is raised from 20°C to 190°C at a rate of 10°C / min under a nitrogen stream to melt the adhesive resin layer, thereby obtaining a crystalline melting curve. In the obtained crystalline melting curve, the top temperature of the melting peak present in the range of 90 to 150°C is defined as Tma, and the top temperature of the melting peak present in the range of 150 to 170°C is defined as Tmb. Furthermore, if multiple melting peaks are observed in the range of 90 to 150°C, the top temperature of the highest peak is defined as Tma, and if multiple melting peaks are observed in the range of 150 to 170°C, the top temperature of the highest peak is defined as Tmb.

[0059] The weight per unit area (basis weight) of the poly(3-hydroxyalkanoate) resin (B) in the adhesive resin layer is preferably 3 to 100 g / m ２ , more preferably 5 to 50 g / m ２ , particularly preferably 10 to 30 g / m ２ Within this range, defects such as pinholes can be prevented, strength sufficient for use can be provided, and functions such as water resistance can be efficiently exhibited. The weight per unit area of ​​the resin (B) in the adhesive resin layer is measured and evaluated by the method described in the Examples.

[0060] The thickness of the entire paper laminate including the paper base layer and adhesive resin layer is not particularly limited, but is preferably 50 to 500 μm, more preferably 60 to 350 μm.

[0061] [Method for manufacturing a paper laminate] The method for manufacturing a paper laminate containing a paper base layer and an adhesive resin layer is not particularly limited, but a method in which a coating liquid containing a biodegradable polyester resin is applied to one or both sides of the base layer and then heated is preferred.

[0062] The coating liquid containing the biodegradable polyester resin is preferably an aqueous coating liquid. The production method is not particularly limited, and may be, for example, a production method by mixing and dispersing a powdered biodegradable polyester resin in water. Furthermore, when a poly(3-hydroxyalkanoate)-based resin (B) is used as the biodegradable polyester resin, an aqueous coating liquid containing a P3HA-based resin (B) with a desired solids concentration can be obtained by crushing microbial cells containing the resin in an aqueous dispersion, obtaining a precipitate by centrifugation, washing the precipitate with water, methanol, or the like, and finally adding an appropriate amount of water.

[0063] The solids concentration of the biodegradable polyester resin in the coating liquid is not particularly limited, but from the viewpoints of realizing a uniform coating, achieving a desired coating film thickness, and preventing the occurrence of coating film defects, the solids concentration is preferably 25 to 65 wt %, more preferably 30 to 55 wt %, and particularly preferably 35 to 50 wt %.

[0064] The coating liquid does not necessarily contain an emulsifier, but preferably contains one to stabilize the coating liquid. 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 and its derivatives, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, polyvinylpyrrolidone, starch, starch derivatives such as oxidized starch and etherified starch, and water-soluble polymers such as chitin, chitosan, casein, and gum arabic. The amount of emulsifier added is not particularly limited, but is preferably about 1 to 10 parts by weight per 100 parts by weight of the biodegradable polyester resin.

[0065] The method for applying the coating liquid to the paper substrate layer is not particularly limited, and any known method can be used as appropriate, such as spraying, scattering, slit coating, air knife coating, roll coating, bar coating, comma coating, blade coating, screen printing, gravure printing, etc.

[0066] After applying the coating liquid to the paper substrate layer, the coating film is heated to form an adhesive resin layer, thereby obtaining a paper laminate. This heating process evaporates water and fuses the resin particles contained in the coating liquid to form an adhesive resin layer with relatively high uniformity. This allows the formation of an adhesive resin layer that satisfies the specific melting characteristics described above.

[0067] The heating temperature in the heating step is not particularly limited, but is, for example, preferably 120 to 180° C., more preferably 130 to 170° C., and particularly preferably 140 to 160° C. By heating the coating film at such a temperature, it becomes easier to form an adhesive resin layer that satisfies the above-mentioned melting characteristics.

[0068] The heating time in the heating step is not particularly limited and can be set appropriately, but may be, for example, 30 seconds to 10 minutes, and preferably 1 to 5 minutes.

[0069] The heating step can be carried out using a known heating method, such as hot air heating, infrared heating, microwave heating, roll heating, hot plate heating, etc. These can be used alone or in combination of two or more.

[0070] [Resin Film] The packaging according to the present disclosure includes the above-described paper laminate and a resin film containing a poly(3-hydroxyalkanoate)-based resin (A) as an essential component. Because the resin film is made of a poly(3-hydroxyalkanoate)-based resin, the biodegradability of the entire packaging can be improved.

[0071] From the viewpoint of biodegradability, the proportion of the poly(3-hydroxyalkanoate) resin (A) in the entire resin film is preferably 50% by weight or more and 100% by weight or less, more preferably 70% by weight or more, even more preferably 80% by weight or more, still more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0072] The poly(3-hydroxyalkanoate) resin (A) contains a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 1 to 13 mol %, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 24 mol % or more. By using these copolymers in combination, the adhesive strength of the heat-sealed portion can be maintained while suppressing the curling of the heat-sealed portion.

[0073] Copolymer (a-1) with a low content of other hydroxyalkanoate units is a P3HA-based resin with high crystallinity, while copolymer (a-2) with a high content of other hydroxyalkanoate units is a P3HA-based resin with relatively low crystallinity. Generally, highly crystalline P3HA-based resins have excellent processability but poor mechanical strength, while low-crystalline P3HA-based resins have poor processability but excellent mechanical properties. By using these resins in combination, a P3HA-based resin (A) with excellent processability and mechanical properties can be obtained.

[0074] It is presumed that by using copolymer (a-2) having a high content of other hydroxyalkanoate units of 24 mol% or more as the P3HA-based resin (A) constituting the resin film, crystallization of the P3HA-based resin (A) is less likely to proceed after thermal melting during heat sealing, so the resin film does not shrink, and as a result, curling of the heat-sealed portion is less likely to proceed. On the other hand, if copolymer (a-2) is not used, it is presumed that crystallization of the P3HA-based resin (A) proceeds after thermal melting during heat sealing, causing the resin film to shrink, and the difference in shrinkage rate with the paper base layer causes curling of the heat-sealed portion.

[0075] Furthermore, the combined use of copolymer (a-1) and copolymer (a-2) can improve the processability of the P3HA resin (A). Furthermore, the use of copolymer (a-2) can increase the strength of the resin film and, in turn, the strength of the package.

[0076] Specific examples of copolymer (a-1) and copolymer (a-2) include the copolymers described above in the section on P3HA-based resin (B), of which P3HB3HH, P3HB3HV, and P3HB4HB are preferred, with P3HB3HH being particularly preferred. The types of constituent monomers in copolymer (a-1) and copolymer (a-2) may be the same or different.

[0077] In the copolymer (a-1), the composition ratio of the monomer units, 3-hydroxybutyrate units / other hydroxyalkanoate units, is in the range of 87 / 13 to 99 / 1 by molar ratio, preferably 88 / 12 to 98 / 2.

[0078] As the copolymer (a-1), only one type may be used, or two or more types having different monomer unit composition ratios within the above range may be used. In the latter case, it is preferable to use a copolymer (a-1-1) having a 3-hydroxybutyrate unit / other hydroxyalkanoate unit ratio of 97 / 3 to 99 / 1 in combination with a copolymer (a-1-2) having a 3-hydroxybutyrate unit / other hydroxyalkanoate unit ratio of 87 / 13 to 95 / 5 in order to achieve an excellent effect of suppressing curling of the heat-sealed portion.

[0079] When the copolymer (a-1-1) and the copolymer (a-1-2) are used in combination, the weight ratio of (a-1-1) to the total weight of both copolymers, i.e., (a-1-2) / [(a-1-1) / (a-1-2)], is preferably 5 to 40% by weight, more preferably 10 to 20% by weight, from the viewpoint of suppressing curling.

[0080] In the copolymer (a-2), the composition ratio of the monomer units, 3-hydroxybutyrate units / other hydroxyalkanoate units, is, in molar ratio, from 76 / 24 to 1 / 99, preferably from 76 / 24 to 50 / 50, more preferably from 75 / 25 to 65 / 35, and particularly preferably from 74 / 26 to 70 / 30.

[0081] The weight average molecular weight of the copolymer (a-1) is not particularly limited, but from the viewpoint of the balance between mechanical properties and productivity, it is preferably from 200,000 to 1,000,000, more preferably from 250,000 to 700,000, and even more preferably from 300,000 to 650,000.

[0082] The weight average molecular weight of the copolymer (a-2) is not particularly limited, but from the viewpoint of the balance between mechanical properties and productivity, it is preferably from 100,000 to 1,500,000, more preferably from 150,000 to 1,000,000, and even more preferably from 200,000 to 700,000.

[0083] The blending ratio of copolymer (a-1) and copolymer (a-2) can be set as appropriate, but from the viewpoint of achieving a well-balanced effect of each copolymer, the proportion of copolymer (a-1) in the total of copolymer (a-1) and copolymer (a-2) is preferably 40 to 80% by weight and the proportion of copolymer (a-2) is 60 to 20% by weight, more preferably 45 to 75% by weight and 55 to 25% by weight, and even more preferably 50 to 70% by weight and 50 to 30% by weight, of copolymer (a-1) and copolymer (a-2).

[0084] Furthermore, the P3HA-based resin (A) may further contain, in addition to the copolymers (a-1) and (a-2), other P3HA-based resins that do not meet the definition of these copolymers. The proportion of the total of the copolymers (a-1) and (a-2) in the entire P3HA-based resin (A) is preferably 70 to 100 wt%, more preferably 80 to 100 wt%, even more preferably 90 to 100 wt%, and particularly preferably 95 to 100 wt%.

[0085] From the viewpoint of the balance between mechanical strength such as flexibility and solidification speed, the average composition ratio of monomer units in the entire P3HA-based resin (A) is preferably 3-hydroxybutyrate units / other hydroxyalkanoate units (mol % / mol %) = 93 / 7 to 83 / 17, more preferably 92 / 8 to 84 / 16, and even more preferably 90 / 10 to 85 / 15. When the ratio of 3-hydroxybutyrate units is 93 mol % or less, sufficient mechanical properties tend to be easily obtained. Furthermore, when the ratio of 3-hydroxybutyrate units is 83 mol % or more, the solidification speed of the P3HA-based resin (A) tends to be fast, and the productivity of the resin film tends to be good.

[0086] The weight average molecular weight of the entire P3HA resin (A) is not particularly limited, but from the viewpoint of the balance between mechanical properties and productivity, it is preferably from 100,000 to 1,500,000, more preferably from 150,000 to 1,000,000, and even more preferably from 200,000 to 700,000.

[0087] The method for obtaining a blend of two or more P3HA-based resins is not particularly limited, and may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Also, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, etc., or by dissolving two or more resins in a solvent, mixing, and drying the resins.

[0088] The resin film may contain one or more resins other than the P3HA-based resin (A) as long as the effects of the invention are achieved. Such other resins are preferably biodegradable resins, such as aliphatic polyester-based resins such as polybutylene succinate, polycaprolactone, and polylactic acid; aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebate terephthalate, and polybutylene azelate terephthalate; and polybutylene succinate adipate-based resins such as copolymers of polybutylene succinate adipate and polybutylene succinate adipate with lactic acid, terephthalic acid, malic acid, or sebacic acid.

[0089] To ensure the biodegradability of the resin film, the amount of these other resins added is preferably 30 parts by weight or less per 100 parts by weight of the P3HA-based resin (A). It may also be 20 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less. There is no particular lower limit for the content of the other resins, and it may even be 0 parts by weight.

[0090] The resin film may contain additives that can be used with the P3HA-based resin (A) to the extent that they do not impair the effects of the invention. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, fillers, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding properties improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use. Crystal nucleating agents, lubricants, fillers, and plasticizers are described in more detail below.

[0091] (Crystal nucleating agent) The resin film may contain a crystal nucleating agent. Examples of crystal nucleating agents include polyhydric alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, pentaerythritol is preferred because it has a particularly excellent effect of promoting the crystallization of the P3HA resin (A). One type of crystal nucleating agent may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

[0092] When a nucleating agent is used, its amount is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, per 100 parts by weight of the P3HA-based resin (A).

[0093] (Lubricant) The resin film may contain a lubricant. Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide or erucamide is preferred because of its particularly excellent lubricating effect on the P3HA-based resin (A). One type of lubricant may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

[0094] When a lubricant is used, the amount thereof is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, per 100 parts by weight of the P3HA-based resin (A).

[0095] (Filler) The resin film may contain a filler. By including a filler, the film can have higher strength. The filler may be either an inorganic filler or an organic filler, or both may be used in combination. The inorganic filler is not particularly limited, but examples thereof include silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Only one type of inorganic filler may be used, or two or more types may be used in combination.

[0096] When the filler is used, its content is not particularly limited, but is preferably 1 to 100 parts by weight, more preferably 3 to 80 parts by weight, even more preferably 5 to 70 parts by weight, and even more preferably 10 to 60 parts by weight, per 100 parts by weight of the P3HA-based resin (A). However, the resin film may be substantially free of filler. "Substantially no filler" means that the amount of filler blended is less than 1 part by weight per 100 parts by weight of the P3HA-based resin (A). It may also be less than 0.1 parts by weight.

[0097] (Plasticizer) The resin film may contain a plasticizer. Examples of plasticizers include glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoate ester compounds, phthalate ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds. Among them, glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, and dibasic acid ester compounds are preferred because of their particularly excellent plasticizing effect on the P3HA resin (A). Examples of glycerin ester compounds include glycerin diacetomonolaurate. Examples of citrate ester compounds include acetyl tributyl citrate. Examples of sebacic acid ester compounds include dibutyl sebacate. Examples of dibasic acid ester compounds include benzyl methyl diethylene glycol adipate. One type of plasticizer may be used, or two or more types may be used, and the ratio of use can be adjusted appropriately depending on the purpose.

[0098] When a plasticizer is used, the amount used is not particularly limited, but is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight, per 100 parts by weight of the P3HA-based resin (A). However, the resin film may be substantially free of plasticizer. "Substantially free of plasticizer" means that the amount of plasticizer blended is less than 1 part by weight per 100 parts by weight of the P3HA-based resin (A). It may also be less than 0.1 part by weight.

[0099] The thickness of the resin film can be appropriately selected depending on the desired quality, the use of the package, etc., but a thicker resin film is preferable from the viewpoint of imparting sufficient strength to the resin film. A specific thickness value of 50 to 400 μm is preferable. This can impart strength suitable for use as the package, and when the package is a standing pouch, for example, it can impart self-standing ability.

[0100] On the other hand, the thicker the resin film, the more likely it is that curling will occur at the heat-sealed portion. However, according to the present invention, curling can be suppressed even when the resin film is 50 μm or thicker. The thickness is preferably 70 μm or thicker. The upper limit may be 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 90 μm or less, or 80 μm or less.

[0101] The ratio of the thickness of the paper laminate to the thickness of the resin film (thickness of the paper laminate / thickness of the resin film) is preferably 0.45 to 3.5, more preferably 0.8 to 3.0, since this makes it easier to suppress curling of the packaging body.

[0102] The method for producing the resin film is not particularly limited as long as it can mold a raw material containing the P3HA-based resin (A) into a film. However, it is preferable to use an extrusion molding method in which a film raw material containing the P3HA-based resin (A) and, if necessary, other components is melted and extruded through a T-die. The extrusion molding method makes it easy to produce a resin film with a uniform thickness. In the extrusion molding, a single-screw extruder, a twin-screw extruder, or the like can be used as appropriate.

[0103] The conditions for melting the film raw material may be any conditions that allow the P3HA resin (A) to melt, and the temperature of the molten film raw material may be, for example, about 140 to 210°C.

[0104] The molten film material is then extruded onto a casting roll to form a film. The molten film material comes into contact with the casting roll and moves along the surface of the casting roll, whereby it is cooled and solidified, forming a resin film.

[0105] Alternatively, a stretched film obtained by stretching a molded resin film in the MD direction and / or the TD direction may be used.

[0106] The resin film may be a resin film composed of an independent single layer, or may be a resin film having other layers laminated on one or both sides thereof, such as other resin layers, inorganic layers, metal layers, metal oxide layers, printed layers, etc.

[0107] [Packaging] The packaging according to the present disclosure includes at least the paper laminate and the resin film, and a portion of the surface of the resin film is heat-sealed to the paper laminate via an adhesive resin layer. The heat-sealed portion is also referred to as the "sealed area" below. The paper laminate and the resin film are connected and integrated by this sealed area.

[0108] At the same time, the resin film also includes a non-sealed area that is not heat-sealed to the paper laminate. In the non-sealed area, the resin film is not laminated with the paper laminate and exists as a single layer. The paper laminate may also include a non-sealed area that is not heat-sealed to the resin film.

[0109] The heat sealing means that the resin film and the adhesive resin layer are bonded by thermal fusion between at least a part of the resin component contained in the resin film and at least a part of the resin component contained in the adhesive resin layer. Such heat sealing can be performed by superposing the resin film and the paper laminate so that a part of the surface of the resin film contacts the adhesive resin layer, applying heat and / or pressure to thermally melt the resin component, and then cooling and solidifying it.

[0110] As the heat sealing, in addition to a general heat sealing method, for example, an impulse sealing method, an ultrasonic sealing method, a high frequency sealing method, a hot air sealing method, a frame sealing method, etc. may be used.

[0111] The heat sealing temperature when heat sealing is performed varies depending on the type of heat sealing method, the types of components contained in the resin film and adhesive resin layer, the thickness of the resin film and adhesive resin layer, etc. For example, when using a heating type heat sealing tester with a sealing bar, the heat sealing temperature is usually 220°C or less, preferably 210°C or less, more preferably 200°C or less. Within the above range, melting of the resin near the sealed portion can be avoided and good adhesion strength can be ensured. In addition, the lower limit of the heat sealing temperature is usually 120°C or more, preferably 140°C or more. Within the above range, appropriate adhesion at the sealed portion can be ensured.

[0112] The heat sealing pressure when heat sealing is performed also varies depending on the conditions of the heat sealing method, etc. For example, when using a heating type heat sealing tester with a seal bar, the pressure is usually 0.1 MPa or more, preferably 0.3 MPa or more. Within this range, appropriate adhesion at the sealed portion can be ensured. Furthermore, 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 sealed portion can be avoided and good adhesion strength can be ensured.

[0113] The package according to the present disclosure has at least a heat-sealed region between the P3HA-based resin (A)-containing resin film and the adhesive resin layer, but may also have other heat-sealed regions, such as heat-sealed regions between adhesive resin layers, between resin films, and between the adhesive resin layer and the paper substrate layer.

[0114] According to a preferred embodiment, heat sealing is preferably performed by stacking the P3HA-based resin (A)-containing resin film, adhesive resin layer, and paper base layer in this order, and then heating from the paper base layer side. In this case, heating is not performed from the resin film side. This method is suitable for suppressing deformation of the resin film due to excessive heat and suppressing warping at the heat-sealed portion. Furthermore, it prevents the resin film from fusing to the seal bar, enabling stable production of the package according to the present disclosure.

[0115] Specific examples of packaging materials include shopping bags, bags, packaging materials for food, beverages, and confectionery, blister packaging materials for storing miscellaneous goods, cups, trays, cartons, and the like.

[0116] Among the packaging materials, the present invention can be suitably used as a packaging material configured so that the packaged item can be seen through the resin film in the non-sealed area. In this packaging material, for example, a space is formed surrounded by the resin film in the non-sealed area and the paper laminate or the resin film in the sealed area, and the packaged item is stored in such a space. The packaged item can be seen from outside the packaging material through the transparent resin film.

[0117] Specific examples of such packages include three-sided sealed bags, four-sided sealed bags, standing pouches, pillow packaging bags, gusset bags, envelope-type bags, square-bottom bags, etc. The specific structure of each package is not particularly limited and can be selected appropriately by the manufacturer. The package according to the present disclosure may contain a packaged item inside, or may be in a state before the packaged item is contained therein.

[0118] Specific examples of laminate structures in packaging according to the present disclosure will be described with reference to the drawings. In Fig. 1 and Fig. 2, packaging 10 includes a paper laminate 11 and a resin film 12. Paper laminate 11 includes a paper substrate layer 11a and an adhesive resin layer 11b, with adhesive resin layer 11b formed on the surface of paper substrate layer 11a. A portion of resin film 12 contacts adhesive resin layer 11b, and in this sealed region 21, the resin film is heat-sealed to the surface of adhesive resin layer 11b. Meanwhile, resin film 12 also includes a region 22 that is not in contact with adhesive resin layer 11b, which corresponds to a non-sealed region.

[0119] In Figure 1, there is a space 13 surrounded by a paper laminate 11 and a resin film 12 in the non-sealed area 22. An item to be packaged can be placed in this space (not shown). In this case, the item to be packaged can be seen through the resin film 13 in the non-sealed area 22. Specific examples of packages of this type include three-sided sealed bags and four-sided sealed bags.

[0120] In Figure 2, two paper laminates 11 are shown separated into left and right. In this embodiment, for example, this laminate structure is formed into a bag shape with the resin film 12 on the inside, and the resin films are appropriately heat-sealed between to form a space surrounded by the resin film 22, within which the packaged item can be placed (not shown). In this case, too, the packaged item can be seen through the resin film 13 in the non-sealed area 22. In the formed bag, the position of the non-sealed area is not particularly limited. Furthermore, one bag may include multiple non-sealed areas. Specific examples of packages of this embodiment include stand-up pouches and pillow packaging bags.

[0121] It should be noted that the layered structure shown in FIG. 1 or FIG. 2 is merely one embodiment, and the layered structure of the package according to the present disclosure is not limited to that shown in FIG. 1 or FIG.

[0122] The following items list preferred aspects of the present disclosure, but the present invention is not limited to them. [Item 1] A packaging body comprising a paper laminate and a resin film, wherein the paper laminate comprises a paper base layer and an adhesive resin layer comprising a biodegradable polyester resin laminated on at least one side of the paper base layer, the resin film has a sealed area that is heat-sealed to the paper laminate via the adhesive resin layer and a non-sealed area that is not heat-sealed to the paper laminate, the resin film comprises a poly(3-hydroxyalkanoate)-based resin (A), and the poly(3-hydroxyalkanoate)-based resin (A) comprises a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of the other hydroxyalkanoate units being 1 to 13 mol %, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of the other hydroxyalkanoate units being 24 mol % or more. [Item 2] The package according to Item 1, wherein the biodegradable polyester resin comprises a poly(3-hydroxyalkanoate)-based resin (B), and the resin (B) comprises a copolymer (b-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of the other hydroxyalkanoate units being 10 to 16 mol %. [Item 3] The package according to Item 1 or 2, wherein the adhesive resin layer has, in a crystalline melting curve measured by differential scanning calorimetry, at least one peak top temperature (Tma) in the range of 90 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C, and the temperature difference between Tma and Tmb is 10°C or more. [Item 4] The package according to any one of items 1 to 3, wherein the proportion of the copolymer (a-1) in the poly(3-hydroxyalkanoate) resin (A) is 45 to 75% by weight, and the proportion of the copolymer (a-2) is 55 to 25% by weight. [Item 5] The package according to any one of items 1 to 4, wherein the thickness of the resin film is 50 to 400 μm. [Item 6] The package according to any one of items 1 to 5, wherein the thickness of the adhesive resin layer is 5 to 30 μm. [Item 7] The basis weight of the paper base layer is 30 to 350 g / m ２[Item 8] The package according to any one of items 1 to 7, wherein the package is configured so that the packaged item can be seen through the resin film in the non-sealed region. [Item 9] A method for manufacturing a package, comprising at least the following steps: Step (i): A process for forming a raw material containing a poly(3-hydroxyalkanoate)-based resin (A) containing a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 1 to 13 mol%, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 24 mol% or more, into a resin film. Step (ii): A process for applying a coating liquid containing a biodegradable polyester resin to at least one surface of a paper base layer, and then heating to form a paper laminate containing a paper base layer and an adhesive resin layer. Step (iii): A process for overlapping the resin film and the paper laminate so that a portion of the surface of the resin film contacts the adhesive resin layer, and performing heat sealing, thereby obtaining a package in which a portion of the surface of the resin film is heat-sealed to the paper laminate. [Item 10] Item 11: The method according to Item 9, wherein the biodegradable polyester resin comprises a poly(3-hydroxyalkanoate)-based resin (B), and the resin (B) comprises a copolymer (b-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of the other hydroxyalkanoate units being 10 to 16 mol %. [Item 12] The method according to Item 9 or 10, wherein the heat-sealing in step (iii) is performed by heating from the paper base layer side in a state where the resin film, the adhesive resin layer, and the paper base layer are superimposed in this order.

[0123] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0124] The raw materials used for the resin films in the examples and comparative examples are as follows. [Poly(3-hydroxyalkanoate) (P3HA)-based resin (A)] P3HB3HH-1: P3HB3HH (average content ratio 3HB / 3HH = 98 / 2 (mol% / mol%), weight average molecular weight 600,000 g / mol): Produced in accordance with the method described in Comparative Example 2 of International Publication WO 2019 / 142845. P3HB3HH-2: P3HB3HH (average content ratio 3HB / 3HH = 97 / 3 (mol% / mol%), weight average molecular weight 600,000 g / mol): Produced in accordance with Example 2 of International Publication WO 2019 / 142845. P3HB3HH-3: P3HB3HH (average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight 600,000 g / mol): Produced in accordance with the method described in Example 1 of International Publication WO2019 / 142845. P3HB3HH-4: P3HB3HH (average content ratio 3HB / 3HH = 89 / 11 (mol% / mol%), weight average molecular weight 600,000 g / mol): Produced in accordance with the method described in Comparative Example 1 of International Publication WO2015 / 146195. P3HB3HH-5: P3HB3HH (average content ratio 3HB / 3HH = 72 / 28 (mol% / mol%), weight average molecular weight 600,000 g / mol): Produced in accordance with the method described in Example 9 of International Publication WO2019 / 142845.

[0125] [Nucleating Agent] Pentaerythritol (manufactured by Mitsubishi Chemical Corporation: Neuraizer P)

[0126] [Lubricant] Behenamide (manufactured by Nippon Fine Chemical Co., Ltd.: BNT-22H)

[0127] (Production of aqueous coating liquid containing P3HB3HH) Cultivation was carried out in accordance with the method described in the examples of WO 2015 / 146195, and the weight-average molecular weight was adjusted and purified in accordance with the method described in WO 2004 / 041936, to obtain an aqueous suspension containing 50% by weight of a P3HB3HH composition (P3HB3HH-6: average ratio of 3HB / 3HH in the entire composition = 89.5 mol% / 10.5 mol%, PHB content in the composition was 6.3 wt%) containing P3HB3HH and PHB and having a weight-average molecular weight of 220,000, in terms of solids concentration. Partially saponified polyvinyl alcohol (Kuraray Poval: 5-88, manufactured by Kuraray Co., Ltd.) as a dispersant was added together with water so that the amount was 3 parts by weight relative to 100 parts by weight of the resin contained in the aqueous suspension, and the mixture was stirred to obtain an aqueous coating liquid containing P3HB3HH, PHB, and the dispersant at a combined solids concentration of 40% by weight.

[0128] (Production of P3HB3HH coated paper) Basis weight 50 g / m ２ The aqueous coating solution containing P3HB3HH-6 was applied to one side of an A4-size bleached kraft paper at a dry weight of 10 g / m ２ The adhesive resin was applied to the paper in the longitudinal direction of an A4 size sheet using a bar coater so that the thickness was 8 to 10 μm, and then heated for 2 minutes in a hot air drying oven set at 180° C. to form an adhesive resin layer, thereby obtaining coated paper. The dry weight of the adhesive resin layer was calculated by cutting the coated paper into 100 mm square pieces, measuring the weight, subtracting the weight of the base paper from the measured weight, and multiplying the result by 100.

[0129] (Differential Scanning Calorimetry) The aqueous coating solution containing P3HB3HH-6 was applied to a 50 μm-thick PET film in a dry weight of 10 g / m ２ After applying the coating using a bar coater so that the coating was uniform, the coating was heated for 2 minutes in a hot air drying oven set at 180°C to form a resin layer. 2 to 5 mg of the resin layer peeled from the PET film was placed in an aluminum pan, and the resin layer was melted using a differential scanning calorimeter by increasing the temperature from 20°C to 190°C at a rate of 10°C / min under a nitrogen stream to obtain a crystalline melting curve. Tma was 115°C, and Tmb was 162°C.

[0130] Example 1 70 parts by weight of P3HB3HH-3 as copolymer (a-1), 30 parts by weight of P3HB3HH-5 as copolymer (a-2), and 100 parts by weight of copolymer (a-1) and copolymer (a-2) in total were dry-blended with 1 part by weight of pentaerythritol and 0.5 parts by weight of behenic acid amide (resin components were mixed in a non-molten state), and then melt-kneaded and extruded in a twin-screw extruder into a strand shape. The extrusion was passed through a water bath heated to 40°C to crystallize and solidify, and then cut with a pelletizer to prepare P3HA-based resin pellets. The obtained pellets were extruded using a single-screw extruder ("20C200" Labo Plastomill" manufactured by Toyo Seiki Seisaku-sho) equipped with a T-die having a width of 150 mm and a lip opening width of 0.25 mm, with the cylinder temperature set to 140 to 160°C and the die temperature set to 170°C, and the extruded pellets were taken up on a cooling roll controlled to 40°C. Both ends of the film were trimmed and the film was taken up to produce a P3HA-based resin film having a width of 100 mm and a thickness of 80 μm. The resulting resin film and the coated paper were cut into 25 mm wide and 100 mm long pieces (100 mm in the film unwinding direction for the resin film, and 100 mm in the direction of coating with the bar coater for the coated paper). The resin film and the coated paper were stacked so that their adhesive resin layers were in contact with each other, and placed in a heat sealer (TP-701-B, manufactured by Tester Sangyo Co., Ltd.) equipped with a heating plate above the pressure-bonding section and a natural rubber plate below, in the following order: heating plate, paper base layer, adhesive resin layer, resin film, and natural rubber plate. The heat-bonding was performed under the following conditions: heating plate temperature setting: 150°C, surface pressure: 0.4 MPa, sealing time: 0.5 seconds, to obtain a package including a heat-sealed area. The size of the heat-sealed area was 20 mm (width of the heating plate) × 25 mm (width of the test piece).

[0131] (Examples 2 to 7, Comparative Examples 1 and 2) Packages including a heat seal region were obtained in the same manner as in Example 1, except that the type of copolymer (a-1) and the compounding ratio (parts by weight) of copolymer (a-1) and (a-2) were changed as shown in Table 1 or 2.

[0132] (Examples 8 to 21) The type of copolymer (a-1) and the blending ratio (parts by weight) of copolymer (a-1) and (a-2) were the same as in Example 4, and packages including a heat seal region were obtained in the same manner as in Example 1, except that the thickness of the resin film, the basis weight of the paper, the dry weight and thickness of the adhesive resin layer, and the set temperature of the heating plate during heat sealing were changed as shown in Table 1 or 2.

[0133] The curling property and adhesive strength between the paper substrate layer and the resin film were evaluated for each of the packages obtained in the Examples and Comparative Examples according to the following methods. The results are shown in Tables 1 and 2.

[0134] [Curling] The packages obtained in each Example or Comparative Example were aged at room temperature for one day, and a 20 mm x 25 mm heat-sealed portion was cut out. The edge of one 25 mm long side was pressed with a finger, and the maximum height to which the opposite 25 mm long side rose above the reference surface was taken as the curl height, and evaluation was performed according to the following criteria: <Evaluation criteria> ⊚: Curl height 5 mm or less ◯: Curl height more than 5 mm to 10 mm or less ×: Curl height more than 10 mm

[0135] [Adhesion strength between paper substrate layer and resin film] The packages obtained in each example or comparative example were aged at room temperature for one day, and the heat-sealed portions were peeled off by manually holding the edges of the paper substrate layer and resin film in the non-heat-sealed area, and evaluated according to the following criteria. <Evaluation> ◯: Material destruction of the paper substrate layer ×: Material destruction of the paper substrate layer was not observed

[0136]

[0137]

[0138] Tables 1 and 2 show that the packages of each Example had good adhesion strength between the paper base layer and the resin film and suppressed curling at the heat-sealed portion. On the other hand, the packages of each Comparative Example did not use copolymer (a-2) in the resin film, and although the adhesion strength between the paper base layer and the resin film was good, significant curling occurred at the heat-sealed portion.

Claims

1. A packaging product comprising a paper laminate and a resin film, wherein the paper laminate comprises a paper base layer and an adhesive resin layer comprising a biodegradable polyester resin laminated on at least one side of the paper base layer, the resin film having a sealed area that is heat-sealed to the paper laminate via the adhesive resin layer and an unsealed area that is not heat-sealed to the paper laminate, the resin film comprising a poly(3-hydroxyalkanoate) resin (A), the poly(3-hydroxyalkanoate) resin (A) comprising a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer containing the other hydroxyalkanoate units being 1 to 13 mol%, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer containing the other hydroxyalkanoate units being 24 mol% or more.

2. The package according to claim 1, wherein the biodegradable polyester resin comprises a poly(3-hydroxyalkanoate)-based resin (B), and the resin (B) comprises a copolymer (b-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 10 to 16 mol %.

3. The package according to claim 1 or 2, wherein the adhesive resin layer has at least one peak top temperature (Tma) in the range of 90 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in a crystalline melting curve determined by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or more.

4. A package according to claim 1 or 2, wherein the proportion of said copolymer (a-1) in said poly(3-hydroxyalkanoate) resin (A) is 45 to 75% by weight, and the proportion of said copolymer (a-2) is 55 to 25% by weight.

5. The package according to claim 1 or 2, wherein the thickness of the resin film is 50 to 400 μm.

6. The package according to claim 1 or 2, wherein the adhesive resin layer has a thickness of 5 to 30 μm.

7. The paper base layer has a basis weight of 30 to 350 g / m ２ The package according to claim 1 or 2, 8. A package according to claim 1 or 2, wherein the package is configured so that the packaged item can be seen through the resin film in the non-sealed area.

9. A method for producing a package, comprising at least the following steps: Step (i): forming a raw material containing a poly(3-hydroxyalkanoate)-based resin (A) containing a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 1 to 13 mol %, and a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 24 mol % or more, into a resin film; Step (ii): applying a coating liquid containing a biodegradable polyester resin to at least one surface of a paper substrate layer, followed by heating to form a paper laminate comprising a paper substrate layer and an adhesive resin layer; Step (iii): overlapping the resin film and the paper laminate so that a portion of the surface of the resin film contacts the adhesive resin layer, and heat-sealing to obtain a package in which a portion of the surface of the resin film is heat-sealed to the paper laminate.

10. The manufacturing method according to claim 9, wherein the biodegradable polyester resin comprises a poly(3-hydroxyalkanoate)-based resin (B), and the resin (B) comprises a copolymer (b-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 10 to 16 mol %.

11. A manufacturing method according to claim 9 or 10, wherein the heat sealing in step (iii) is carried out by superimposing the resin film, the adhesive resin layer, and the paper base layer in this order and then heating from the paper base layer side.

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