Biodegradable laminate, method for manufacturing the same, and molded body

Abstract

To provide a biodegradable laminate which is excellent in cooling roll releasability in manufacture, has sufficient interlayer adhesive strength, is free from warpage in a TD direction, and is composed of a paper base material layer and a thermoplastic resin layer.SOLUTION: A biodegradable laminate is formed by stacking a paper base material (A) layer, a first thermoplastic resin (B) layer and a second thermoplastic resin (C) layer containing PHBH as main components in this order, wherein the B layer and the C layer satisfy the following requirements 1 and 2. (Requirement 1) The B layer contains at least one kind of a low crystalline PHBH component having a ratio of a 3-hydroxyhexanoate (3HH) component of 10 mol% or more and less than 30 mol%, and a ratio of the low crystalline PHBH component with respect to the total amount of the PHBH component of the B layer is 50 wt.% or more. (Requirement 2) The C layer contains at least one kind of a high crystalline PHBH component having a ratio of a 3HH component of 2 mol% or more and less than 8 mol%, and a ratio of the high crystalline PHBH with respect to the total amount of the PHBH component of the C layer is 50 wt.% or more and less than 90 wt.%.SELECTED DRAWING: Figure 1

Description

[Technical Field] 【0001】 The present invention relates to a biodegradable laminate comprising a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, laminated in this order on one side thereof, a method for producing the same, and a molded article. [Background technology] 【0002】 In recent years, environmental problems caused by plastic waste have come into focus. In particular, marine pollution caused by plastic waste is serious, and the widespread use of biodegradable resins that decompose in the natural environment is highly anticipated. 【0003】 While various biodegradable resins are known, among them, the copolymer of 3-hydroxybutyrate (hereinafter sometimes referred to as "3HB") and 3-hydroxyhexanoate (hereinafter sometimes referred to as "3HH") (hereinafter sometimes referred to as "PHBH") is attracting attention as a material that can solve the above problems because it is a thermoplastic polyester that is produced and stored as an energy storage substance in the cells of many microbial species, and can biodegrade not only in soil but also in seawater. Among these, PHBH / paper composite materials, which are integrated with a base material such as paper, are of particular interest to society because they can be applied to food contact containers and other products that have a low environmental impact. 【0004】 Methods for integrating PHBH and paper include extrusion lamination and aqueous slurry coating methods. However, since the coating method does not easily provide sufficient mechanical strength for the resin layer, the extrusion lamination method is preferred. Patent Document 1 discloses a biodegradable laminate and its utilization technology that are superior in terms of adhesion to the substrate, neck-in characteristics, and peelability of the laminate layer from the cooling roll. [Prior art documents] [Patent Documents] 【0005】 [Patent Document 1] International Publication No. WO2021 / 100733 [Overview of the project] [Problems that the invention aims to solve] 【0006】 However, in the manufacturing method disclosed in Patent Document 1, after PHBH is laminated with paper by the extrusion lamination method, crystallization gradually progresses over time, and as a result the laminate layer shrinks, the resulting laminated paper can warp significantly towards the laminate layer, so improvement was needed. In particular, the warping of the laminated paper in the direction perpendicular to the flow direction (hereinafter sometimes referred to as the TD direction) during continuous production (hereinafter sometimes referred to as the MD direction) posed problems such as poor paper transport and poor molding during the secondary processing of cup molding. 【0007】 Therefore, in view of the above situation, the present invention aims to provide a biodegradable laminate comprising a paper substrate layer and a thermoplastic resin layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, wherein the laminate exhibits excellent cooling roll peelability of the thermoplastic resin layer during the manufacturing of the laminate, has sufficient adhesive strength between the paper substrate layer and the thermoplastic resin layer, and does not exhibit warping in the TD direction that causes transport defects or molding defects during cup molding, and a method for manufacturing the same. [Means for solving the problem] 【0008】 The present inventors, after diligent research to solve the above problems, have found that the above problems can be solved when a biodegradable laminate is formed by laminating a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate on one side thereof, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate in this order, and the copolymer molar ratio of 3-hydroxyhexanoate in the copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate contained in the first thermoplastic resin (B) and the second thermoplastic resin (C) is within a specific range, and have completed the present invention. 【0009】 In other words, the present invention relates to a biodegradable laminate comprising a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, laminated in this order on one side thereof, wherein the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer simultaneously satisfy the following requirements 1 and 2, and the present invention relates to a biodegradable laminate and a method for producing the same. (Requirement 1) The first thermoplastic resin (B) layer contains at least one low-crystalline PHBH component, with a 3-hydroxyhexanoate component content of 10 mol% or more and less than 30 mol%, and the proportion of the low-crystalline PHBH component to the total amount of PHBH component in layer B is 50 wt% or more. (Requirement 2) The second thermoplastic resin (C) layer contains at least one type of highly crystalline PHBH component, with a 3-hydroxyhexanoate component content of 2 mol% or more and less than 8 mol%, and the ratio of the highly crystalline PHBH component to the total amount of PHBH component in the C layer is 50 wt% or more and less than 90%. 【0010】 The present invention relates to a biodegradable laminate and a method for producing the same, wherein the copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate contained in the first thermoplastic resin (B) layer is heated and melted to a resin temperature of 180°C, and then cooled at a rate of 10°C / min, the recrystallization temperature is 50°C or higher and less than 90°C. Furthermore, the present invention relates to a biodegradable laminate and a method for producing the same that simultaneously satisfies the following conditions (a) to (c). 【0011】 (a) The average thickness (tB) of the first thermoplastic resin (B) layer is 5 μm or more. (b) The average thickness (tC) of the second thermoplastic resin (C) layer is 5 μm or more. (c) The sum of tB and tC is between 10 μm and 100 μm. (d) The value obtained by dividing tC by tB is between 1 and 10 (inclusive of 10). The present invention also relates to a molded article that includes the biodegradable laminate. [Effects of the Invention] 【0012】 According to the present invention, a biodegradable laminate comprising a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, laminated in this order on one side thereof, provides a biodegradable laminate and a method for manufacturing the same, which exhibits excellent peelability of the thermoplastic resin layer from the cooling roll during the manufacturing of the laminate, sufficient adhesive strength between the paper substrate layer and the thermoplastic resin layer, and no warping in the TD direction that would cause transport defects or molding defects during cup molding. The biodegradable laminate of the present invention makes it possible to improve the production efficiency and quality of molded products. [Brief explanation of the drawing] 【0013】 [Figure 1] This is a schematic cross-sectional view of a biodegradable laminate according to one aspect of the present invention. [Modes for carrying out the invention] 【0014】 Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. 【0015】 [Biodegradable laminate] The biodegradable laminate according to the present invention comprises a paper base material (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate on one side thereof, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, which are laminated in this order. Here, the first thermoplastic resin (B) layer may be directly laminated on the paper base material (A) layer, or may further include another resin layer as an intermediate layer as long as it does not inhibit adhesiveness. Further, an adhesive resin (D) layer may be laminated on the back surface of the paper base material (A) layer on the surface where the first thermoplastic resin (B) and the second thermoplastic resin (C) layers are laminated. Further, another resin layer may be laminated on the second thermoplastic resin (C) layer for the purpose of imparting water resistance, glossiness, etc. 【0016】 [Paper base material (A) layer] The paper base material layer according to the present invention is not particularly limited as long as it is mainly composed of paper, but it is preferably biodegradable. In addition to paper (the main component is cellulose), there are also paper base materials mixed with cellophane, cellulose ester; polyvinyl alcohol, polyamino acid, polyglycolic acid, pullulan, or those obtained by vapor-depositing inorganic substances such as aluminum and silica on these paper base materials. The type of paper is not particularly limited, and examples include cup base paper, kraft paper, high-quality paper, coated paper, tissue paper, glassine paper, cardboard, etc. The type of paper can be appropriately selected according to the use of the biodegradable laminate. To the paper, a water repellent, a water repellent agent, an inorganic substance, etc. may be added as necessary, or it may be one that has been surface-treated such as an oxygen barrier layer coating, a water vapor barrier coating. Further, the surface of the base material layer may be subjected to surface treatment such as corona treatment, ozone treatment, plasma treatment, frame treatment, anchor coat treatment, oxygen barrier layer coating, water vapor barrier coating, etc. These surface treatments may be performed alone or in combination of a plurality of surface treatments. 【0017】 The basis weight of the paper base material (A) layer is 30 g / m 2 or more and 300 g / m 2 less, preferably 60 g / m 2 or more and 250 g / m 2 less, more preferably 90 g / m 2 or more and 200 g / m 2 less, even more preferably. When the basis weight of the paper base material (A) layer is less than 30 g / m 2 the peelability from the cooling roll of the second thermoplastic resin (C) layer subjected to extrusion lamination may deteriorate due to the low elasticity of the paper base material. When it is 300 g / m 2 or more, not only does the total thickness of the biodegradable laminate become too large, making conveyance and winding during lamination difficult, but subsequent processing into a molded body may also become difficult. 【0018】 The Wang Ken air permeability resistance of the paper substrate (A) layer is preferably 10 seconds or more and less than 400 seconds, more preferably 30 seconds or more and less than 350 seconds, and even more preferably 50 seconds or more and less than 300 seconds. If the Wang Ken air permeability resistance is less than 10 seconds, the paper strength is low and it may not be suitable for molded products such as paper containers, and there is a risk of the paper breaking during transport due to low strength. If it is 400 seconds or more, the surface smoothness is high and the adhesion or lamination strength with the first thermoplastic resin (B) layer may be insufficient. 【0019】 [First thermoplastic resin (B) layer] The first thermoplastic resin (B) layer according to the present invention contains 50 wt% or more of a copolymer consisting of 3-hydroxybutyrate and 3-hydroxyhexanoate (hereinafter sometimes referred to as "PHBH" or "poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)"), and contains at least one low-crystalline PHBH component in an amount of 10 mol% or more and less than 30 mol% of the 3-hydroxyhexanoate component, in an amount of 50 wt% or more of the total weight of the PHBH. As the first thermoplastic resin (B), PHBH may be used alone, or as a minor component, for example, poly3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalate) (PHB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (PHB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (PHB3HOD), poly(3-hydroxybutyrate-co-3- In addition to hydroxydecanoate (PHB3HD) and poly(3-hydroxybutyrate-co-3-hydroxyvalate-co-3-hydroxyhexanoate) (PHB3HV3HH), the present invention may also contain one or more biodegradable resins other than P3HA, such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, polylactic acid, and other aliphatic polyester resins, or polybutylene adipate terephthalate and polybutylene azelate terephthalate, as long as the effects of the present invention are not impaired. Furthermore, the first thermoplastic resin (B) may contain one or more other additives commonly added to resin materials, to the extent that they do not impede the effects of the present invention. These additives include, for example, inorganic fillers, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolites, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather-resistant modifiers, ultraviolet absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, sliding properties modifiers, and other secondary additives. However, these are optional components, and the first thermoplastic resin (B) may not contain any of these components.As optional components, the use of lubricants and inorganic fillers is preferred from the viewpoint of further improving the peelability from the pressing surface such as a cooling roll when laminating the first thermoplastic resin (B). 【0020】 Examples of the lubricant include saturated or unsaturated fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, and erucic acid amide, as well as aliphatic amide compounds such as alkylene fatty acid amides such as methylenebisstearic acid amide and methylenebisstearic acid amide, and pentaerythritol. 【0021】 The amount of lubricant added to the first thermoplastic resin (B) is preferably 0.1 to 2 parts by weight, and more preferably 0.2 to 1 part by weight, per 100 parts by weight of the first thermoplastic resin (B). By adding 0.1 parts by weight or more, the effect of improving release properties due to the addition of lubricant can be obtained. Conversely, if the amount exceeds 2 parts by weight, the lubricant bleeds out during pressing and adheres to the pressing surface such as the cooling roll, making it difficult to perform continuous processing for long periods of time. 【0022】 Examples of the inorganic filler include talc, calcium carbonate, mica, silica, clay, kaolin, titanium dioxide, alumina, and zeolite, all of which have an average particle size of 0.5 μm or more. 【0023】 The amount of inorganic filler in the first thermoplastic resin (B) is preferably 0.5 to 5 parts by weight, and more preferably 1 to 3 parts by weight, per 100 parts by weight of the first thermoplastic resin (B). By setting the amount to 0.5 parts by weight or more, the effect of improving release properties due to the inorganic filler can be obtained. Conversely, if the amount exceeds 5 parts by weight, cracks may easily occur in the first thermoplastic resin (B) layer. 【0024】 PHBH is a particularly useful plastic industrially because its melting point and degree of crystallinity can be changed by altering the composition ratio of repeating units, thereby easily adjusting physical properties such as Young's modulus and heat resistance, and it can also be given properties between those of polypropylene and polyethylene. 【0025】 The specific manufacturing method of PHBH is described, for example, in International Publication No. 2010 / 013483. Commercially available PHBH products include Kaneka Corporation's "Kaneka Biodegradable Polymer Green Planet" (registered trademark). 【0026】 The proportion of 3-hydroxyhexanoate (3HH) in the low-crystalline PHBH is 3HH = 10 mol% or more and less than 30 mol%, but it is more preferable that 3HB / 3HH = 15 mol% or more and 20 mol% or less. If the proportion of 3HH in the low-crystalline PHBH contained in the first thermoplastic resin (B) layer is 10 mol% or more, the crystallization is sufficiently slower compared to the highly crystalline PHBH described later, so that warping of the biodegradable laminate after lamination can be suppressed. In addition, PHBH with a 3HH proportion of less than 30 mol% does not have an excessively slow crystallization rate, and the production of pellet-shaped compounds containing PHBH is relatively easy. The proportion of 3HH is the monomer ratio of 3HH to the total monomers constituting the low-crystalline PHBH, and can be determined by methods known to those skilled in the art, for example, the method described in paragraph

[0047] of International Publication 2013 / 147139 or by NMR measurement. Furthermore, if multiple low-crystalline PHBHs are present, the percentage refers to the proportion of the total amount of constituent monomers contained in all components of the low-crystalline PHBH. In the case of a mixture of low-crystalline PHBH and other PHBHs, the ratio of the 3HH component to the total amount of constituent monomers in all PHBHs is referred to as the average content. 【0027】 The average content ratio of 3HH in the first thermoplastic resin (B) layer is preferably 10 mol% to 30 mol%, and more preferably 15 mol% to 20 mol%. As described above, the PHBH having an average 3HH content ratio of 10 to 30 mol% is particularly preferably composed of at least two types of PHBH having different content ratios of constituent monomers, and is also preferably composed of at least one type of PHBH and PHB. 【0028】 The recrystallization temperature (hereinafter sometimes referred to as "Tcc") when the PHBH contained in the first thermoplastic resin (B) layer is heated and melted to a resin temperature of 180°C and then cooled at a rate of 10°C / min is preferably 50°C or higher and less than 90°C, more preferably 60°C or higher and less than 80°C, and even more preferably 65°C or higher and less than 75°C. If the aforementioned Tcc is less than 50°C, solidification is too slow when making pellets from the powder raw material of PHBH, making it difficult to produce a high-quality compound. If it is 90°C or higher, for example, solidification during extrusion lamination is too fast, and the resulting biodegradable laminate may warp, making it difficult to obtain the effects of the invention. 【0029】 In the present invention, the weight-average molecular weight (hereinafter sometimes referred to as Mw) of PHBH contained in the first thermoplastic resin (B) layer is preferably 100,000 or more and less than 750,000, more preferably 200,000 or more and less than 650,000, and even more preferably 300,000 or more and less than 550,000, from the viewpoint of improving adhesion or lamination strength to the paper substrate (A) layer. If the weight-average molecular weight is less than 100,000, there is a possibility that a large amount of elute material will be produced when heated, which may make it unsuitable for use as a food container. Furthermore, during extrusion processing, the contribution of decomposition products will be large, which may reduce the lamination strength with the paper substrate (A) layer. If it exceeds 750,000, the melt viscosity will be high, which may reduce the adhesion or lamination strength to the paper substrate (A). In this application, the weight-average molecular weight of PHBH can be determined by gel permeation chromatography (GPC) (Shodex GPC-101, manufactured by Showa Denko Corporation), using a polystyrene gel column (Shodex K-804, manufactured by Showa Denko Corporation) with chloroform as the mobile phase, and expressed as the molecular weight in terms of polystyrene. 【0030】 In one embodiment of the present invention, the first thermoplastic resin (B) layer can be made by mixing multiple types of PHBH with different weight-average molecular weights. 【0031】 Furthermore, when using a mixture of multiple types of PHBH, or when mixing with other resin components, the weight-average molecular weight of the resin components in the first thermoplastic resin (B) layer refers to the weight-average molecular weight of the entire PHBH component. 【0032】 [Second thermoplastic resin (C) layer] The proportion of 3HH monomer in the highly crystalline PHBH contained in the second thermoplastic resin (C) layer according to the present invention is 2 mol% or more and less than 8 mol%, but preferably 4 mol or more and less than 6 mol% (mol% / mol%). When the proportion of 3HH in the highly crystalline PHBH contained in the second thermoplastic resin (C) layer is 2 mol% or more, a sufficient temperature can be ensured between the decomposition temperature and the melting point, allowing for easy extrusion processing while suppressing the thermal decomposition of PHBH. Furthermore, when the average content ratio of 3HH is less than 8 mol%, crystallization is sufficiently fast, and peelability from the cooling roll after lamination is excellent. In addition, the second thermoplastic resin (C) layer is not particularly limited as long as it contains at least one of the aforementioned highly crystalline PHBH components and the total proportion of highly crystalline PHBH components contained in the total PHBH components is 50 wt% or more and less than 90 wt%, and the same as those used in the first thermoplastic resin (B) layer can be used as auxiliary components other than PHBH. 【0033】 [Adhesive resin (D)] The resin component contained in the adhesive resin (D) layer in the present invention is not particularly limited as long as it is commonly used in the coated paper or resin film fields, but it is desirable that at least one type of resin with high affinity to the paper substrate and PHBH be included, and examples include ester resins, acrylic resins, methacrylic resins, vinyl chloride resins, styrene-acrylic resins, styrene-butadiene resins, styrene-isoprene resins, polycarbonate resins, urea resins, melamine resins, epoxy resins, phenolic resins, urethane resins, diallyl phthalate resins, imine resins, etc. These can be used individually, or two or more types of resins can be mixed in any proportion as needed. 【0034】 Furthermore, each resin may be water-soluble or soluble in organic solvents. However, if the resin is insoluble in water, for example, other additives may be added to improve its dispersibility and coating properties in water. When coating with an aqueous dispersion emulsion, dispersion slurry, or water-soluble resin, the solid content concentration of the resin is not particularly limited, but it is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more, in order to keep the amount of heat required for drying low. In addition, it is preferable that the solid content be 60% or less, as sedimentation of the dispersed resin may adversely affect the coating properties. 【0035】 [Method for manufacturing laminates] The method for manufacturing the laminate according to the present invention is not particularly limited as long as a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate are laminated on one side thereof in this order. However, from the viewpoint of improving heat sealability during cup molding, it is preferable to include a step of laminating an adhesive resin (D) layer on the back surface of the paper substrate (A) layer where the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer are laminated. In this case, the adhesive resin (D) layer may be laminated on the other side after the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer have been laminated on the paper substrate (A) layer, or it may be laminated on one side of the paper substrate (A) layer first, and then the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer may be laminated on the other side. 【0036】 Furthermore, the method of applying the solution or aqueous dispersion according to the present invention to a substrate is not particularly limited as long as a desired coating layer is substantially formed on the substrate. For example, known methods such as spraying, application, slit coater, air knife coater, roll coater, bar coater, comma coater, blade coater, screen printing, and gravure printing can be used individually or in combination. Before applying the solution or aqueous dispersion, the substrate may be subjected to a surface treatment such as the corona treatment described above. 【0037】 The heat treatment during drying can be carried out using known heating methods, such as hot air heating, infrared heating, microwave heating, roll heating, and hot plate heating, which can be used individually or in combination of two or more. 【0038】 From the viewpoint of increasing the lamination strength between the paper substrate (A) layer and the first thermoplastic resin (B) layer, or between the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer, it is preferable that at least one of the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer is formed by an extrusion lamination method. Furthermore, from the viewpoint of further increasing the lamination strength between the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer while suppressing warping in the TD direction of the resulting biodegradable laminate, it is preferable that the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer are formed simultaneously on the paper substrate (A) layer by a co-extrusion lamination method. Furthermore, from the viewpoint of making it easier to create biodegradable laminates of any desired configuration by performing melt extrusion and bonding processes in separate steps, it is also preferable to form the first thermoplastic resin (B) layer on the paper substrate (A) layer by a coating method or an extrusion lamination method, and then form the second thermoplastic resin (C) layer by a heat lamination method. In addition, corona treatment or the like can be performed on the surface of the coating layer or extrusion lamination layer for purposes such as improving adhesion with the paper substrate (A) on which the first thermoplastic resin (B) layer is formed. 【0039】 The average thickness (tB) of the first thermoplastic resin (B) layer is preferably 5 μm or more. If tB is less than 5 μm, the warping in the TD direction that occurs due to the crystallization of the second thermoplastic resin (C) layer may not be sufficiently buffered, and the warping of the entire biodegradable laminate may not be suppressed. 【0040】 The average thickness (tC) of the second thermoplastic resin (C) layer is preferably 5 μm or more. If tC is less than 5 μm, cracks may occur in the resin layer when bending or other processes are performed during cup molding. 【0041】 The sum of the average thickness (tB) of the first thermoplastic resin (B) layer and the average thickness (tC) of the second thermoplastic resin (C) layer (tB + tC) is preferably 10 μm or more and less than 100 μm, and the value obtained by dividing tC by tB (tC / tB) is preferably 1 or more and less than 10. If tB + tC is 100 μm or more, warping may occur in the paper substrate (A), which may worsen the moldability of molded products such as cups. 【0042】 Furthermore, it is more preferable that the average thickness of the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer simultaneously satisfy the following conditions (a) to (d). 【0043】 (a) The average thickness (tB) of the first thermoplastic resin (B) layer is 5 μm or more. (b) The average thickness (tC) of the second thermoplastic resin (C) layer is 5 μm or more. (c) The sum of tB and tC is between 10 μm and 100 μm. (d) The value obtained by dividing tC by tB is between 1 and 10 (inclusive of 10). [Molded body] A molded article according to one embodiment of the present invention (hereinafter sometimes referred to as "the molded article") includes the biodegradable laminate of the present invention (hereinafter sometimes referred to as "the laminate"). Since the molded article is formed from a laminate in which the surface condition of the laminate layer containing PHBH is good, it is advantageous in various applications. 【0044】 The molded article is not particularly limited as long as it includes the laminate, but examples include paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, part, etc. From the viewpoint of countermeasures against marine pollution, the molded article is preferably a bag or bottle container. 【0045】 In one embodiment of the present invention, the molded article may be the laminate itself, or it may be a product of secondary processing using the laminate. 【0046】 Because this laminate is subjected to secondary processing, the molded product containing it can be suitably used as various packaging container materials such as shopping bags, various types of bags, food and confectionery packaging materials, cups, trays, and cartons (in other words, in various fields such as food, cosmetics, electronics, medical, and pharmaceuticals). Because this laminate contains a resin composition that has high adhesion to the substrate and good heat resistance, it is more preferable as a container for liquids, especially as a container for hot contents such as cups for instant noodles, instant soup, coffee, and other food and beverages, and trays used for prepared foods, bento boxes, and microwaveable foods. 【0047】 The various secondary processing steps described above can be performed using the same methods as for conventional resin-laminated paper or coated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Processing can also be done using equipment such as paper cup molding machines, die-cutting machines, and box presses. For these processing machines, known techniques can be used for bonding this biodegradable laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and flame sealing. 【0048】 The heat sealing temperature of this laminate varies depending on the bonding method. For example, when using a heated heat sealing tester with a sealing bar, the resin temperature is usually set to 180°C or lower, preferably 170°C or lower, and more preferably 160°C or lower. Within this range, it is possible to avoid the melting of the resin near the sealed area and to ensure an appropriate resin layer thickness and seal strength. Furthermore, when using a heated heat sealing tester with a sealing bar, the lower limit is usually 100°C or higher, preferably 110°C or higher, and more preferably 120°C or higher. Within this range, it is possible to ensure appropriate adhesion at the sealed area. 【0049】 The heat sealing pressure of this laminate varies depending on the bonding method, but for example, when using a heated heat sealing tester with a sealing bar, the heat sealing pressure of this laminate is usually 0.1 MPa or higher, preferably 0.5 MPa or higher. Within this range, adequate adhesion at the sealed portion can be ensured. Furthermore, the upper limit when using a heated heat sealing tester with a sealing bar is usually 1.0 MPa or lower, preferably 0.75 MPa or lower. Within this range, thinning of the film thickness at the seal edge can be avoided, and seal strength can be ensured. 【0050】 Furthermore, in order to improve its physical properties, this molded body can be compounded with a molded body made of a different material (for example, fibers, yarn, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, board, rod, container, bag, part, foam, etc.). It is preferable that these materials are also biodegradable. 【0051】 The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A biodegradable laminate formed by laminating a paper base material (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate on one side thereof, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate in this order, wherein the first thermoplastic resin (B) and the second thermoplastic resin (C) simultaneously satisfy the following requirements 1 to 2. (Requirement 1) The first thermoplastic resin (B) contains at least one type of low-crystalline PHBH component in which the proportion of the 3-hydroxyhexanoate component is 10 mol% or more and less than 30 mol%, and the proportion of the low-crystalline PHBH component with respect to the total amount of the PHBH components constituting the first thermoplastic resin (B) layer is 50 wt% or more. (Requirement 2) The second thermoplastic resin (C) contains at least one type of high-crystalline PHBH component in which the proportion of the 3-hydroxyhexanoate component is 2 mol% or more and less than 8 mol%, and the proportion of the high-crystalline PHBH component with respect to the total amount of the PHBH components constituting the second thermoplastic resin (C) layer is 50 wt% or more and less than 90%. [Item 2] The biodegradable laminate according to Item 1, wherein when the copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate contained in the first thermoplastic resin (B) layer is heated and melted so that the resin temperature becomes 180°C and then cooled at a rate of 10°C / min, the recrystallization temperature is 50°C or more and less than 90°C. [Item 3] The biodegradable laminate according to any one of Items 1 to 3, which simultaneously satisfies the following (a) to (d). 【0052】 (a) The average thickness (tB) of the first thermoplastic resin (B) layer is 5 μm or more. (b) The average thickness (tC) of the second thermoplastic resin (C) layer is 5 μm or more. (c) The sum of tB and tC is 10 μm or more and less than 100 μm. (d) The value obtained by dividing tC by tB is 1 or more and less than 10. [Item 4] The basis weight of the paper base material (A) layer is 30 g / m 2More than 300g / m 2 A biodegradable laminate described in any of items 1-3, which is less than [amount missing]. [Item 5] A biodegradable laminate according to any of items 1 to 4, wherein the air permeability resistance of the paper substrate (A) layer is 10 seconds or more and less than 400 seconds according to the Oken method. [Item 6] A method for producing a biodegradable laminate according to any one of items 1 to 5, wherein the first thermoplastic resin layer (B) and the second thermoplastic resin layer (C) are simultaneously formed on the paper substrate layer (A) by a co-extrusion lamination method. [Item 7] A molded body containing a biodegradable laminate as described in any of items 1 to 5. [Examples] 【0053】 The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples. 【0054】 [Manufacturing example] (Method for producing resin powder with PHBH as the main component) The PHBH powders used in the examples and comparative examples were all manufactured in accordance with the method described in International Publication WO2019-142845. The specific formulations are shown below. 【0055】 PHBH Powder 1: A low-crystallinity PHBH powder with a weight-average molecular weight of 400,000 and a 3HH content of 11 mol% relative to the total of 3HB and 3HH in the PHBH. PHBH Powder 2: A low-crystalline PHBH powder with a weight-average molecular weight of 400,000 and a 3HH content of 16 mol% relative to the total of 3HB and 3HH in PHBH. PHBH Powder 3: A highly crystalline PHBH powder with a weight-average molecular weight of 400,000 and a 3HH content of 1.5 mol% relative to the total of 3HB and 3HH in the PHBH. PHBH Powder 4: A highly crystalline PHBH powder with a weight-average molecular weight of 400,000 and a 3HH content of 3 mol% relative to the total of 3HB and 3HH in the PHBH. PHBH Powder 5: A highly crystalline PHBH powder with a weight-average molecular weight of 400,000 and a 3HH content of 6 mol% relative to the total of 3HB and 3HH in PHBH. (Method for manufacturing resin pellets with PHBH as the main component) The PHBH pellets used in the examples and comparative examples were prepared by blending each PHBH powder and additive in the proportions shown in Table 1. The specific manufacturing method is described below. 【0056】 PHBH Pellet 1: 100 parts by weight of the above low-crystalline PHBH powder 1 was dry-blended with behenamide (0.5 parts by weight), and the mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm to extrude it into strands. The mixture was then solidified by passing it through 40°C hot water and cut into pellets. The temperature (Tcc) was determined by differential thermal analysis to be 71°C. 【0057】 PHBH Pellet 2: The above low-crystallinity PHBH powder 2 (100 parts by weight) was dry-blended with behenamide (0.5 parts by weight), and the mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm to extrude it into strands. The mixture was then solidified by passing it through 40°C hot water and cut into pellets. The temperature (Tcc) was determined by differential thermal analysis to be 60°C. 【0058】 PHBH pellet 3: The above-mentioned low-crystallinity PHBH powder 1 (75 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 5 (25 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through 40°C hot water, and cut into pellets. The Tcc was determined by differential thermal analysis and found to be 85°C. 【0059】 PHBH pellets 4: The above-mentioned low-crystallinity PHBH powder 1 (25 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 5 (75 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through 40°C hot water, and cut into pellets. The Tcc was determined by differential thermal analysis and found to be 95°C. 【0060】 PHBH pellet 5: The above-mentioned low-crystallinity PHBH powder 1 (40 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 5 (60 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into a strand, solidified by passing through 40°C hot water, and cut into pellets. Differential thermal analysis determined the Tcc to be 105°C. 【0061】 PHBH pellets 6: The above-mentioned low-crystallinity PHBH powder 1 (20 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 5 (80 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through 40°C hot water, and cut into pellets. 【0062】 PHBH pellets 7: The above-mentioned low-crystallinity PHBH powder 1 (40 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 4 (60 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through 40°C hot water, and cut into pellets. 【0063】 PHBH pellets 8: The above-mentioned low-crystallinity PHBH powder 1 (40 parts by weight) was dry-blended with the above-mentioned high-crystallinity PHBH powder 3 (60 parts by weight) and behenamide (0.5 parts by weight). Using a twin-screw extruder, the mixture was melt-kneaded at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through 40°C hot water, and cut into pellets. 【0064】 [Table 1] <Manufacturing of laminates by co-extrusion lamination method> (Example 1) PHBH pellets 1 and 5 were extruded using a single-screw extruder equipped with a two-layer T-type die, with the conditions adjusted so that the resin temperature directly below the die reached 175°C for each pellet, resulting in a basis weight of 200 g / m². 2 A laminate (S) was obtained by laminating a paper substrate (A) with a Wang-Lan smoothness score of 35 seconds on its surface, with the paper substrate (A), a first thermoplastic resin (B) layer consisting of PHBH pellets 1, and a second thermoplastic resin (C) layer consisting of PHBH pellets 5 in that order. At this time, the thickness of the first thermoplastic resin (B) layer was 10 μm, and the thickness of the second thermoplastic resin (C) layer was 30 μm. The structure of the obtained biodegradable laminate is shown in Table 2. 【0065】 (Example 2) A biodegradable laminate was obtained in the same manner as described in Example 1, except that the thickness of the second thermoplastic resin (C) layer was adjusted to 60 μm. The composition of the obtained biodegradable laminate is shown in Table 2. 【0066】 (Example 3) A biodegradable laminate was obtained in the same manner as described in Example 1, except that the thickness of the second thermoplastic resin (C) layer was adjusted to 90 μm. The composition of the obtained biodegradable laminate is shown in Table 2. 【0067】 (Example 4) A biodegradable laminate was obtained in the same manner as in Example 1, except that PHBH pellet 3 was used instead of PHBH pellet 1. The composition of the obtained biodegradable laminate is shown in Table 2. 【0068】 (Example 5) A biodegradable laminate was obtained in the same manner as described in Example 1, except that the thickness of the first thermoplastic resin (B) layer was adjusted to 5 μm. The composition of the obtained biodegradable laminate is shown in Table 2. 【0069】 (Example 6) A biodegradable laminate was obtained in the same manner as described in Example 1, except that the thickness of the first thermoplastic resin (B) layer was adjusted to 20 μm. The composition of the obtained biodegradable laminate is shown in Table 2. 【0070】 (Example 7) A biodegradable laminate was obtained in the same manner as described in Example 1, except that the thickness of the first thermoplastic resin (B) layer was adjusted to 20 μm and the thickness of the second thermoplastic resin (C) layer to 60 μm. The composition of the obtained biodegradable laminate is shown in Table 2. 【0071】 (Example 8) A biodegradable laminate was obtained in the same manner as in Example 1, except that PHBH pellet 2 was used instead of PHBH pellet 1. The composition of the obtained biodegradable laminate is shown in Table 2. 【0072】 (Example 9) A biodegradable laminate was obtained in the same manner as in Example 1, except that PHBH pellet 6 was used instead of PHBH pellet 5. The composition of the obtained biodegradable laminate is shown in Table 2. 【0073】 (Example 10) A biodegradable laminate was obtained in the same manner as in Example 1, except that PHBH pellet 7 was used instead of PHBH pellet 5. The composition of the obtained biodegradable laminate is shown in Table 2. 【0074】 (Example 11) A biodegradable laminate was obtained in the same manner as described in Example 1, except that a paper substrate (A) with a Wang-Lan smoothness score of 200 seconds was used. The composition of the obtained biodegradable laminate is shown in Table 2. 【0075】 (Example 12) Basis weight 50g / m² 2 A biodegradable laminate was obtained in the same manner as described in Example 1, except that a paper substrate (A) was used. The composition of the obtained biodegradable laminate is shown in Table 2. 【0076】 (Comparative Example 1) A biodegradable laminate was obtained in the same manner as described in Example 1, except that PHBH pellets 4 were used as the first thermoplastic resin (B) layer. The composition of the obtained biodegradable laminate is shown in Table 2. 【0077】 (Comparative Example 2) A biodegradable laminate was obtained in the same manner as described in Example 1, except that PHBH pellets 5 were used as the first thermoplastic resin (B) layer. The composition of the obtained biodegradable laminate is shown in Table 2. 【0078】 (Comparative Example 3) A biodegradable laminate was obtained in the same manner as described in Example 1, except that PHBH pellets 3 were used as the second thermoplastic resin (C) layer. The composition of the obtained biodegradable laminate is shown in Table 2. 【0079】 (Comparative Example 4) A biodegradable laminate was obtained in the same manner as described in Example 1, except that PHBH pellets 8 were used as the second thermoplastic resin (C) layer. The composition of the obtained biodegradable laminate is shown in Table 2. 【0080】 (Comparative Example 5) A biodegradable laminate was obtained in the same manner as described in Example 1, except that PHBH pellets 1 were used as the second thermoplastic resin (C) layer. The composition of the obtained biodegradable laminate is shown in Table 2. 【0081】 [Evaluation Method] The biodegradable laminates obtained in the examples and comparative examples were evaluated for laminate strength, cooling roll peelability, warping in the TD direction, and flexural resistance, and the results are shown in Table 3. The evaluations were performed using the following methods. 【0082】 (Evaluation of lamination strength) To evaluate the lamination strength, the adhesion (peel strength) between the paper substrate (A) and the laminated resin was assessed. 【0083】 The laminate strength test was performed the day after the extrusion lamination. Specifically, a thin cross-cut was made on the extruded laminated thermoplastic resin surface with a cutter blade, and Nichiban No. CT-17 tape was firmly attached to the cut area. The tape was then lightly peeled off by hand to create a starting point. After that, the strip was cut to a width of 15 mm, and the peeled laminate layer and paper were held at a 180° angle using a jig, and the peel strength test was performed. The tensile speed was 200 mm / min. A Shimadzu Autograph EZ-LX (manufactured by Shimadzu Corporation) was used as the peel tester. 【0084】 <Evaluation Criteria> ◎: 3.5N / 15mm or more ○: 2.5N / 15mm or more, less than 3.5N / 15mm △: 1.5N / 15mm or more, less than 2.5N / 15mm ×: 1.5N / less than 15mm If the above evaluation result is ◎, ○, or △, then the laminate strength is sufficient. 【0085】 (Evaluation of cooling roll peelability) After adjusting the lamination speed to 20 m / min and the cooling roll temperature to 40°C, the peelability of the laminated surface from the cooling roll of the extrusion laminating machine was visually evaluated. 【0086】 <Evaluation Criteria> ◎: The laminated surface does not stick to the cooling roll and is picked up smoothly. ○: The laminated surface is starting to stick to the cooling roll, but it is being picked up smoothly. △: The laminated surface is starting to stick to the cooling roll, but it was accepted without any problems. ×: The laminated surface sticks to the cooling roll, preventing proper collection. If the above evaluation result is ◎, ○, or △, then the cooling roll release properties are sufficient. 【0087】 (Evaluation of warping in the TD direction) The warping in the TD direction was evaluated the day after the fabrication of the biodegradable laminate. Specifically, a rectangle with a length of 300 mm in the TD direction and a length of 100 mm in the MD direction was cut out with scissors. After placing it on a flat table with the paper substrate (A) layer facing downwards, the distance between the end that was warped in the TD direction and the flat table was measured. 【0088】 <Evaluation Criteria> ◎: The distance between the edge in the TD direction and the flat table is less than 1 mm. ○: The distance between the edge in the TD direction and the flat desk is 1 mm or more and less than 5 mm. △: The distance between the edge in the TD direction and the flat desk is 5 mm or more and less than 10 mm. ×: The distance between the edge in the TD direction and the flat desk is 10 mm or more. If the evaluation result is ◎, ○, or △, it can be said that warping in the TD direction is suppressed. 【0089】 (Evaluation of bending resistance) The bending resistance of the biodegradable laminate was evaluated the day after its fabrication. Specifically, the biodegradable laminate was bent at a 90° angle so that the PHBH film surface faced outwards. The bent portion was then observed at 500x magnification using a scanning electron microscope to check for the occurrence of streaky cracks on the resin surface. Additionally, food coloring solution adjusted to a solid content concentration of 10% was applied to the bent portion, left for 1 minute, and then wiped off with a cloth to check whether the bent portion was stained red. 【0090】 <Evaluation Criteria> ◎: No streaky cracks are present, and no staining with food coloring solution is observed. ○: There are some streaky cracks, but no staining from food coloring is observed. △: There are clearly visible streaky cracks, but no staining from food coloring is observed. ×: There are streaky cracks, and staining with food coloring is also visible. If the evaluation result is ◎, ○, or △, it can be said that the bending resistance is good. 【0091】 [Table 2] 【0092】 [Table 3] <Result> Tables 1 and 2 show that the examples obtained a biodegradable laminate with sufficient lamination strength between the paper substrate (A) layer and the first thermoplastic resin (B) layer, excellent peelability from the cooling roll, suppressed warping in the TD direction, and high mechanical strength to withstand bending. 【0093】 On the other hand, in the comparative example, it is not possible to achieve sufficient lamination strength between the paper substrate (A) layer and the first thermoplastic resin (B) layer, peelability from the cooling roll, suppression of warping in the TD direction, and high mechanical strength to withstand bending. Therefore, according to the present invention, in a biodegradable laminate in which a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and a second thermoplastic resin (C) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate are laminated in this order on one side thereof, a biodegradable laminate and a method for manufacturing the same can be provided, in which sufficient lamination strength is achieved between the paper substrate (A) layer and the first thermoplastic resin (B) layer, peelability from the cooling roll is excellent, warping in the TD direction is suppressed, and high mechanical strength to withstand bending. [Explanation of symbols] 【0094】 1 Biodegradable laminate 2.Paper base material (A) layer 3. First thermoplastic resin (B) layer 4. Second thermoplastic resin (C) layer

Claims

[Claim 1] A biodegradable laminate comprising a paper substrate (A) layer, a first thermoplastic resin (B) layer mainly composed of a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate (hereinafter, the copolymer is referred to as "PHBH"), and a second thermoplastic resin (C) layer mainly composed of PHBH, laminated in this order on one side thereof, wherein the first thermoplastic resin (B) layer and the second thermoplastic resin (C) layer simultaneously satisfy the following requirements 1 and 2. (Requirement 1) The first thermoplastic resin (B) layer contains at least one low-crystalline PHBH component, the proportion of the 3-hydroxyhexanoate component is 10 mol% or more and less than 30 mol%, and the weight-average molecular weight is 100,000 or more and 400,000 or less, and the proportion of the low-crystalline PHBH component to the total amount of PHBH components constituting the first thermoplastic resin (B) layer is 50 wt% or more. (Requirement 2) The second thermoplastic resin (C) layer contains at least one type of highly crystalline PHBH component, with a 3-hydroxyhexanoate component content of 2 mol% or more and less than 8 mol%, and the proportion of the highly crystalline PHBH component to the total amount of PHBH components constituting the second thermoplastic resin (C) layer is 50 wt% or more and less than 90%. [Claim 2] The biodegradable laminate according to claim 1, wherein the recrystallization temperature of the copolymer with PHBH contained in the first thermoplastic resin (B) layer, after being heated and melted to a resin temperature of 180°C and then cooled at a rate of 10°C / min, is 50°C or higher and less than 90°C. [Claim 3] A biodegradable laminate according to claim 1 or 2, which simultaneously satisfies (a) to (d) below. (a) The average thickness (tB) of the first thermoplastic resin (B) layer is 5 μm or more. (b) The average thickness (tC) of the second thermoplastic resin (C) layer is 5 μm or more. (c) The sum of tB and tC is 10 μm or more and less than 100 μm. (d) The value obtained by dividing tC by tB is 1 or greater and less than 10. [Claim 4] The basis weight of the paper substrate (A) layer is 30 g / m². ２ More than 300g / m ２ A biodegradable laminate according to claim 1 or 2, wherein the amount is less than [amount missing]. [Claim 5] The biodegradable laminate according to claim 1 or 2, wherein the air permeability resistance of the paper substrate (A) layer is 10 seconds or more and less than 400 seconds according to the Ogan method. [Claim 6] A method for producing a biodegradable laminate according to claim 1 or 2, wherein the first thermoplastic resin layer (B) and the second thermoplastic resin layer (C) are simultaneously formed on the paper substrate layer (A) by a co-extrusion lamination method. [Claim 7] A molded article comprising the biodegradable laminate described in claim 1 or 2.

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