Biodegradable laminate and method for producing same

Abstract

This biodegradable laminate includes: a substrate layer; a first thermoplastic resin (A1) layer including a polyhydroxyalkanoate-based resin, the first thermoplastic resin (A1) layer being laminated on one surface of the substrate layer; and a second thermoplastic resin (A2) layer including a polyhydroxyalkanoate-based resin, the second thermoplastic resin (A2) layer being laminated on the other surface of the substrate layer. The weight of the first thermoplastic resin (A1) layer is 10 g / m2 or greater and 200 g / m2 or less, and the weight of the second thermoplastic resin (A2) layer is 0.1 g / m2 or greater and 5 g / m2 or less.

Description

[Technical Field]

[0001] The present invention relates to a biodegradable laminate having a thermoplastic resin layer on each side of a substrate layer, and a method for producing the same. [Background technology]

[0002] In recent years, environmental issues caused by discarded plastics have been receiving increased attention. Marine pollution caused by discarded plastics is particularly serious, and biodegradable plastics that decompose in the natural environment are expected to become more widespread. Among various biodegradable plastics, a copolymer of 3-hydroxybutyrate (hereinafter referred to as "3HB") and 3-hydroxyhexanoate (hereinafter referred to as "3HH") (hereinafter referred to as "PHBH") is a thermoplastic polyester produced and accumulated as an energy storage substance within the cells of many microbial species. Because it can biodegrade not only in soil but also in seawater, it has attracted attention as a material that can solve the above-mentioned problems. Laminates produced by aqueous coating or laminating such PHBH onto environmentally degradable substrates such as paper are highly promising from an environmental protection perspective, as both the substrate and PHBH are environmentally degradable materials.

[0003] In general, a layer containing PHBH can be used for adhesion to a substrate such as paper, and because it has excellent water resistance and oil resistance, it also functions as a barrier layer on the inner surface of a molded product such as a paper cup to prevent the filling from penetrating into the substrate. However, because PHBH's viscosity does not decrease easily when heated and melted, it does not wet and spread easily on substrates such as paper, and when attempting to bond it to substrates such as paper to obtain high-quality molded products, it was necessary to heat it to a temperature well above its melting point. As a result, the resin took a long time to solidify, which led to poor adhesion of molded products such as paper containers and slower production speeds during continuous operation, leaving much room for improvement in terms of processability.

[0004] Patent Document 1 discloses a biodegradable laminate in which a layer containing a polyhydroxyalkanoate resin and a layer containing a polycondensation polyester of a dicarboxylic acid and a glycol are laminated on both sides of a paper substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-6444 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the biodegradable laminate described in Patent Document 1 had a problem in that even if water was applied to the laminate for the purpose of correcting warping that occurs when the laminate is wound into a roll, the base material was unable to absorb enough water, and the warping could not be fully eliminated. Also, when the laminate was formed into a paper container or the like, the resin layer arranged on the outer surface of the cup became sticky when heated, causing blocking against the molding machine mold, leaving room for improvement in terms of operability.

[0007] In view of the above-mentioned current situation, the present invention aims to provide a biodegradable laminate having thermoplastic resin layers containing a polyhydroxyalkanoate resin on both sides of a base layer, which has sufficient water absorbency to eliminate warping that occurs when the laminate is wound into a roll, which suppresses blocking of the molding machine mold when molded into paper containers, etc., and which has excellent adhesion even when processed at low temperatures during molding, and a method for producing the same. [Means for solving the problem]

[0008] As a result of intensive research into solving the above-mentioned problems, the inventors have discovered that in a biodegradable laminate having thermoplastic resin layers containing polyhydroxyalkanoate resin on both sides of a base layer, the above-mentioned problems can be solved by making the basis weight of one thermoplastic resin layer sufficiently smaller than the basis weight of the other thermoplastic resin layer, and have thus completed the present invention.

[0009] That is, the present invention provides a substrate layer, a first thermoplastic resin (A1) layer containing a polyhydroxyalkanoate resin laminated on one surface of the base material layer; a second thermoplastic resin (A2) layer containing a polyhydroxyalkanoate resin laminated on the other surface of the base material layer, The weight of the first thermoplastic resin (A1) layer is 10 g / m 2 More than 200g / m 2 is as follows: The weight of the second thermoplastic resin (A2) layer is 0.1 g / m 2 More than 5g / m 2 The present invention relates to the following biodegradable laminate. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a biodegradable laminate having a thermoplastic resin layer containing a polyhydroxyalkanoate resin on both sides of a base layer, which has water absorbency sufficient to eliminate warping that occurs when the laminate is wound into a roll, which suppresses blocking of the molding machine mold when molded into paper containers, etc., and which has excellent adhesion even at low temperature during molding, and a method for manufacturing the same. Use of a biodegradable laminate manufactured by the manufacturing method of the present invention makes it possible to improve the production efficiency and quality of molded articles. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 shows the surface of the second thermoplastic resin (A2) layer in the biodegradable laminates produced in Example 1 and Comparative Example 1, and the surface of the paper substrate in the biodegradable laminate produced in Comparative Example 4, observed at 500x magnification using a scanning electron microscope. [Figure 2] 1 is a schematic cross-sectional view of a biodegradable laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. [Laminate] A biodegradable laminate according to one embodiment of the present disclosure has a substrate layer such as paper, a first thermoplastic resin (A1) layer containing a polyhydroxyalkanoate resin on one side thereof, and a second thermoplastic resin (A2) layer containing a polyhydroxyalkanoate resin on the other side thereof, with the first thermoplastic resin (A1) layer, substrate layer, and second thermoplastic resin (A2) layer laminated in this order. The first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer may be laminated directly onto a substrate layer such as paper, or may be laminated via another layer. In one embodiment of the present disclosure, another adhesive layer or the like may be further laminated on the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer. The first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer may each be the outermost layer in the biodegradable laminate.

[0013] The components contained in the first thermoplastic resin (A1) layer and the components contained in the second thermoplastic resin (A2) layer may be the same or different, and the blending ratio of the components contained in the first thermoplastic resin (A1) layer and the blending ratio of the components contained in the second thermoplastic resin (A2) layer may be the same or different.

[0014] (base material layer) The substrate layer according to the present disclosure is not particularly limited as long as it is biodegradable, and examples thereof include paper (mainly composed of cellulose), cellophane, cellulose ester, polyvinyl alcohol, polyamino acid, polyglycolic acid, pullulan, or a substrate having an inorganic substance such as aluminum or silica vapor-deposited thereon. Among these, paper is preferred because of its excellent heat resistance and low cost. The type of paper is not particularly limited, and examples include cup base paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard. The type of paper can be appropriately selected depending on the application of the laminate. If necessary, a water-resistant agent, a water-repellent agent, an inorganic substance, etc. may be added to the paper, and the paper may be subjected to a surface treatment such as an oxygen barrier layer coating or a water vapor barrier coating. The surface of the substrate layer may be subjected to a surface treatment such as corona treatment, ozone treatment, plasma treatment, frame treatment, anchor coat treatment, oxygen barrier layer coating, or water vapor barrier coating. These surface treatments may be performed alone or in combination.

[0015] (First Thermoplastic Resin (A1) and Second Thermoplastic Resin (A2)) The first thermoplastic resin (A1) and the second thermoplastic resin (A2) each contain one or more polyhydroxyalkanoate resins. The polyhydroxyalkanoate resin is a biodegradable resin. The polyhydroxyalkanoate resin contained in the first thermoplastic resin (A1) and the polyhydroxyalkanoate resin contained in the second thermoplastic resin (A2) may be the same or different.

[0016] The resin components constituting the first thermoplastic resin (A1) and the resin components constituting the second thermoplastic resin (A2) each preferably contain 50% by weight or more of a polyhydroxyalkanoate resin, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. Each of the resin components may be composed solely of a polyhydroxyalkanoate resin. Furthermore, biodegradable resins, as described below, can be used as resin components other than the polyhydroxyalkanoate resin.

[0017] The polyhydroxyalkanoate resin (hereinafter sometimes abbreviated as PHA) is a general term for polymers containing hydroxyalkanoic acid as a monomer unit. The hydroxyalkanoic acid constituting PHA is not particularly limited, but examples thereof include 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid. PHA may be a homopolymer or a copolymer containing two or more types of monomer units.

[0018] From the viewpoint of seawater decomposability, the PHA is preferably a homopolymer or copolymer having 3-hydroxybutyrate units, and more preferably a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0019] Specific examples of polymers having 3-hydroxybutyrate units include poly(3-hydroxybutyrate) (abbreviation: PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), poly(3-hydroxybutyrate Examples of suitable poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH). Among these, PHB, PHBH, P3HB3HV, and P3HB4HB are preferred because of their ease of industrial production.

[0020] Among these, PHBH is particularly preferred from the viewpoints that its melting point and crystallinity can be changed by changing the composition ratio of repeating units, and as a result, its physical properties such as Young's modulus and heat resistance can be adjusted, it can be imparted with physical properties between those of polypropylene and polyethylene, it is easy to produce industrially, and it is a physically useful plastic.

[0021] The resin component constituting the first thermoplastic resin (A1) and the resin component constituting the second thermoplastic resin (A2) each preferably contains 50% by weight or more of PHBH, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. Each of the resin components may be composed solely of PHBH.

[0022] As a resin component other than PHBH, polyhydroxyalkanoate resins other than PHBH, as described above, can be used in combination with PHBH. Furthermore, biodegradable resins other than polyhydroxyalkanoate resins, such as aliphatic polyester resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate, can also be used in combination with PHBH.

[0023] A specific method for producing PHBH is described in, for example, International Publication No. 2010 / 013483. Commercially available PHBH products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0024] The average content ratio of the constituent monomers in PHBH is preferably 3HB / 3HH=97-75 / 3-25 (mol % / mol %), and more preferably 3HB / 3HH=94-82 / 6-18 (mol % / mol %). When the average content ratio of 3HH in PHBH is 3 mol % or more, good adhesiveness can be obtained even at low-temperature processing during heat sealing. Furthermore, PHBH with an average content ratio of 3HH of 25 mol % or less does not have an excessively slow crystallization rate and is relatively easy to produce.

[0025] The average content ratio of each constituent monomer in PHBH can be determined by methods known to those skilled in the art, such as the method described in paragraph

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

[0026] As described above, it is particularly preferable that the PHBH having an average content ratio of 3HH of 3 to 25 mol % contains at least two types of PHBH having different content ratios of constituent monomers, and it is also preferable that it contains at least one type of PHBH and PHB.

[0027] When at least two types of PHBH are included, it is preferable to include a highly crystalline PHBH having a 3HH monomer composition ratio of less than 6 mol% and a low-crystalline PHBH having a higher 3HH monomer composition ratio. With this configuration, compared to a case where only PHBH is used, the crystals of the highly crystalline PHBH having a 3HH composition ratio of less than 6 mol% are not completely dissolved during melt processing, and remain to act as crystal nuclei, thereby accelerating crystallization and facilitating the formation of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by extrusion lamination, thermal lamination, or coating. In addition, when at least one type of PHBH and PHB are contained, the PHB acts as a crystal nucleus, and the same effect can be obtained. Note that PHBH and PHB having an average 3HH content of less than 3 mol% may be used in combination.

[0028] The proportion of 3HH to the total of 3HB and 3HH in the highly crystalline PHBH is preferably 5 mol % or less, more preferably 4 mol % or less, and even more preferably 3 mol % or less. The proportion of 3HH to the total of 3HB and 3HH in the low crystalline PHBH is preferably 10 to 40 mol %, more preferably 15 to 30 mol %.

[0029] The amount of the highly crystalline PHBH or PHB blended is not particularly limited, but is preferably 1 to 60% by weight, more preferably 2 to 50% by weight, and even more preferably 4 to 15% by weight of the resin components contained in the thermoplastic resin (A1) layer or the thermoplastic resin (A2) layer.

[0030] The weight-average molecular weight (hereinafter sometimes referred to as Mw) of the PHA contained in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 150,000 to 650,000, more preferably 250,000 to 550,000, and even more preferably 350,000 to 450,000, from the viewpoint of achieving both mechanical properties and processability. When the weight-average molecular weight of the PHA is 150,000 or more, good mechanical properties are obtained, and when it is 650,000 or less, a melt viscosity suitable for molding can be easily achieved. The Mw of the PHA contained in the first thermoplastic resin (A1) and the Mw of the PHA contained in the second thermoplastic resin (A2) may be the same or different.

[0031] The weight-average molecular weight of the PHA can be determined as the molecular weight converted into polystyrene by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase.

[0032] In one embodiment of the present disclosure, a mixture of multiple PHAs with different weight-average molecular weights can be used in the first thermoplastic resin (A1) layer and / or the second thermoplastic resin (A2) layer. In particular, when two PHAs are mixed, for example, a PHA with a weight-average molecular weight of 150,000 to 350,000 and a PHA with a weight-average molecular weight of 450,000 to 650,000 can be mixed to achieve both good heat-sealability at low temperatures and high mechanical properties, thereby achieving the same effects as when PHBH with a single weight-average molecular weight is used alone.

[0033] To the first thermoplastic resin (A1) and / or the second thermoplastic resin (A2), one or more of other additives that are usually added to resin materials may be added, as long as the effects of the invention are not impaired. For example, one or more of colorants such as inorganic fillers, 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, and other secondary additives may be added. These are optional components, and the first thermoplastic resin (A1) and / or the second thermoplastic resin (A2) may not contain these components. As the optional components, it is preferable to use a lubricant and / or an inorganic filler, from the viewpoint of further improving the releasability from the pressure bonding surface of a cooling roll or the like when laminating the first thermoplastic resin (A1) and the second thermoplastic resin (A2).

[0034] 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, and alkylene fatty acid amides such as methylene bisstearic acid amide and methylene bisstearic acid amide, and aliphatic amide compounds, and pentaerythritol.

[0035] Examples of the inorganic filler include talc, calcium carbonate, mica, silica, clay, kaolin, titanium oxide, alumina, and zeolite, all of which have an average particle size of 0.5 μm or more.

[0036] The amount of lubricant in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1 part by weight, per 100 parts by weight of the first thermoplastic resin (A1) and the second thermoplastic resin (A2). By setting the amount to 0.1 part by weight or more, the effect of improving releasability due to the addition of the lubricant can be obtained. By setting the amount to 2 parts by weight or less, bleeding of the lubricant and adhesion to the pressing surface of a cooling roll or the like during pressing can be suppressed, enabling long-term continuous processing.

[0037] The amount of inorganic filler in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of the first thermoplastic resin (A1) and the second thermoplastic resin (A2). By setting the amount to 0.5 parts by weight or more, the effect of improving releasability due to the addition of the inorganic filler can be obtained. By setting the amount to 5 parts by weight or less, the occurrence of cracks in the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer can be suppressed.

[0038] Examples of methods for forming the first thermoplastic resin (A1) layer and / or the second thermoplastic resin (A2) layer include extrusion lamination, thermal lamination, and a method in which an aqueous coating liquid, in which the first thermoplastic resin (A1) and the second thermoplastic resin (A2) are dissolved or dispersed in a liquid such as water, is applied to the surface of a substrate layer such as paper, and then heated to dry and form a film (hereinafter sometimes referred to as a "coating method"). In particular, when a thermoplastic resin layer is directly laminated to a substrate layer such as paper without any other layer interposed therebetween, a portion of the coating liquid penetrates into the substrate layer such as paper, making it easy to increase the adhesive strength between each thermoplastic resin layer and the substrate layer such as paper. The coating method is preferably used.

[0039] The heating temperature when carrying out extrusion lamination or thermal lamination may be set appropriately from among known conditions, but is preferably a temperature equal to or higher than the melting point of the resin material (the resin material that comprises the thermoplastic resin and includes PHA) and lower than the melting point + 30° C. Carrying out extrusion lamination or thermal lamination at a temperature within this range makes it possible to form a thermoplastic resin layer while avoiding decomposition of the PHA.

[0040] In the coating method, an aqueous coating liquid is applied to the surface of a substrate to form a coating film, and then the coating film is preferably heated to a temperature equal to or higher than the melting point of the resin material but lower than the melting point + 30° C. using at least one method selected from the group consisting of hot air blowing, infrared radiation, ultrasonic radiation, and contact with a heated roll. By forming the film at a temperature within this range, the PHA can be melted on the surface of the substrate while avoiding decomposition of the PHA, thereby forming a highly uniform thermoplastic resin layer.

[0041] The lower limit of the basis weight of the first thermoplastic resin (A1) layer is 10 g / m 2 It is preferable that the weight is 20 g / m or more. 2 More preferably, 30 g / m 2 The upper limit of the weight per unit area is 200 g / m 2 Less than 100 g / m 2 Less than 50 g / m 2 The following is particularly preferred: The basis weight of the first thermoplastic resin (A1) layer is 10 g / m 2 More than 200g / m 2 Within the following ranges, the first thermoplastic resin (A1) layer can function as a barrier layer, and good adhesiveness can be obtained when heat-sealing to form paper containers and the like.

[0042] The lower limit of the basis weight of the second thermoplastic resin (A2) layer is 0.1 g / m 2 It is preferable that the content is 0.5 g / m or more. 2 More preferably, 1 g / m 2 The upper limit of the weight per unit area is 5 g / m 2 Less than 3g / m is preferred 2 Less than 2g / m is preferred 2 The following is particularly preferred: The basis weight of the second thermoplastic resin (A2) layer is 0.1 g / m 2 More than 5g / m 2Within the following range, at least a portion of the substrate surface is not covered by the resin layer and the substrate is exposed, thereby ensuring water absorption sufficient to eliminate warping that occurs when the laminate is wound into a roll, while suppressing blocking of the molding machine die when forming paper containers, etc., and also enabling excellent adhesion to be exhibited even at low temperatures when heat-sealing.

[0043] In one embodiment of the present disclosure, the substrate layer such as paper has a thickness of 150 to 350 g / m 2 When the cup base paper is used, the basis weight of the first thermoplastic resin (A1) layer is 20 g / m 2 More than 100g / m 2 It is preferable that the density is 30 g / m or less. 2 More than 50g / m 2 By setting the thickness within the above range, it is possible to maintain good secondary processability, such as punching properties and heat sealing properties, in the laminate according to one embodiment of the present disclosure (hereinafter, sometimes referred to as "the laminate").

[0044] [Molded body] A molded article according to an embodiment of the present disclosure (hereinafter, sometimes referred to as the "present molded article") includes the present laminate. The present molded article is advantageous in various applications because it is formed from a laminate in which the surface condition of the PHA-containing resin layer is good.

[0045] The present molded article is not particularly limited as long as it contains the present laminate, and examples thereof include paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, part, etc. From the viewpoint of measures against marine pollution, the present molded article is preferably a bag or a bottle container.

[0046] In one embodiment of the present disclosure, the present molded article may be the present laminate itself, or may be a product obtained by subjecting the present laminate to secondary processing.

[0047] Because the laminate has been subjected to secondary processing, the molded article containing it can be suitably used as various packaging container materials such as shopping bags, various bags, food and confectionery packaging materials, cups, trays, cartons, etc. (in other words, in various fields such as food, cosmetics, electronics, medicine, and pharmaceuticals.) Because the laminate contains a resin composition that has high adhesion to substrates and good heat resistance, it is more suitable as a container for holding liquids, particularly containers for holding hot contents, such as cups for food and beverages such as instant noodles, instant soup, and coffee, and trays for prepared meals, boxed lunches, and microwaveable foods.

[0048] The various secondary processes described above can be carried out in the same manner as conventional resin-laminated paper or coated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Processing can also be carried out using machines such as paper cup forming machines, punching machines, and box making machines. In these processing machines, known techniques can be used to bond the present laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing.

[0049] The heat-sealing temperature of the present laminate varies depending on the bonding method. For example, when a heating-type heat-sealing tester equipped with a sealing bar is used, the heat-sealing temperature of the present laminate is usually set so that the surface temperature of at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer is 180°C or less, preferably 170°C or less, and more preferably 160°C or less. Within the above range, melting of the resin near the sealed portion can be avoided, and an appropriate resin layer thickness and seal strength can be ensured. Since the present laminate can achieve good adhesion even when heat-sealed at a low temperature, the surface temperature may be 150°C or less, or 140°C or less. Furthermore, when a heating-type heat-sealing tester equipped with a seal bar is used, the lower limit is usually 100° C. or higher, preferably 110° C. or higher, and more preferably 120° C. or higher. Within the above range, appropriate adhesion at the sealed portion can be ensured.

[0050] The heat-sealing pressure of the present laminate varies depending on the bonding method. For example, when a heat-sealing tester equipped with a seal bar is used, the heat-sealing pressure of the present laminate is typically 0.1 MPa or higher, preferably 0.5 MPa or higher. Within this range, adequate adhesion at the sealed portion can be ensured. Furthermore, when a heat-sealing tester equipped with a seal bar is used, the upper limit is typically 1.0 MPa or lower, preferably 0.75 MPa or lower. Within this range, thinning of the film thickness at the sealed edge can be avoided, ensuring sufficient seal strength.

[0051] Furthermore, in order to improve the physical properties of the present molded article, it can also be composited with a molded article made of a material different from the present molded article (for example, fiber, thread, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, part, foam, etc.). These materials are also preferably biodegradable.

[0052] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] a substrate layer; a first thermoplastic resin (A1) layer containing a polyhydroxyalkanoate resin laminated on one surface of the base material layer; a second thermoplastic resin (A2) layer containing a polyhydroxyalkanoate resin laminated on the other surface of the base material layer, The weight of the first thermoplastic resin (A1) layer is 10 g / m 2 More than 200g / m 2 is as follows: The weight of the second thermoplastic resin (A2) layer is 0.1 g / m 2 More than 5g / m 2 A biodegradable laminate comprising: [Item 2] Item 2. The biodegradable laminate according to item 1, wherein the polyhydroxyalkanoate resin has a weight-average molecular weight of 150,000 to 650,000. [Item 3] 3. The biodegradable laminate according to item 1 or 2, wherein the polyhydroxyalkanoate resin comprises a polymer having a 3-hydroxybutyrate unit. [Item 4] 4. The biodegradable laminate according to item 3, wherein the polyhydroxyalkanoate resin comprises a copolymer of 3-hydroxybutyrate units and 3-hydroxyhexanoate units. [Item 5] A method for producing a biodegradable laminate according to any one of items 1 to 4, A method for producing a biodegradable laminate, comprising the step of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by extrusion lamination or thermal lamination at a temperature equal to or higher than the melting point of a resin material and lower than the melting point + 30°C. [Item 6] A method for producing a biodegradable laminate according to any one of items 1 to 4, a step of applying an aqueous coating liquid containing a polyhydroxyalkanoate resin to a substrate to form a coating film; and heating the coating film to a temperature equal to or higher than the melting point of the resin material and lower than the melting point + 30°C using at least one method selected from the group consisting of blowing hot air, irradiating with infrared rays, irradiating with ultrasonic waves, and contact with a heated roll, thereby forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer. [Item 7] A molded article comprising the biodegradable laminate according to any one of items 1 to 4. [Item 8] Item 7. A method for producing a molded body according to Item 7, comprising a step of heating the surface temperature of at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer to 100°C or higher and lower than 170°C. [Example]

[0053] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0054] [Manufacturing example] (Method for producing aqueous dispersion containing PHBH as the main component) A resin dispersion with a solids concentration of 50% by weight of PHBH (3HH ratio 11.0 mol%, melting point 120°C) was obtained according to the method described in International Publication No. 2004 / 041936. The resin dispersion was diluted with pure water as needed to adjust the solids concentration. The weight-average molecular weight of PHBH was 620,000.

[0055] (Adjustment of weight-average molecular weight of PHBH in aqueous dispersion) The resin dispersion was kept at 60° C. and hydrolyzed to obtain a dispersion of PHBH having a weight average molecular weight of 230,000.

[0056] (Aqueous mixed dispersion of multiple resin dispersions with different weight average molecular weights) The same weights of the aqueous dispersion of PHBH having a weight-average molecular weight of 620,000 and the aqueous dispersion of PHBH having a weight-average molecular weight of 230,000 were weighed out and mixed to obtain an aqueous mixed dispersion.

[0057] (Method of manufacturing aqueous coating liquid) To 100 parts by weight of each of the above dispersions, 0.3 parts by weight of an anti-settling agent for PHBH (Optigel MW, manufactured by BYK) and 30 parts by weight of a 2% aqueous solution of methylcellulose (Metolose SM-400, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and stirred to obtain aqueous coating solutions.

[0058] [Evaluation method] The evaluations in the examples and comparative examples were carried out by the following methods.

[0059] (180° peel strength evaluation) A heat seal test was conducted the day after the film formation treatment. Using a heat sealer (TP-701-B, manufactured by Tester Sangyo Co., Ltd.), the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer were overlapped and heated and pressed together at 0.4 MPa for 5 seconds. The maximum temperature of the resin surface during adhesion was 106°C, 127°C, or 141°C. According to JIS standard Z0238, a 15 mm wide piece was cut out and subjected to a peel strength test. The chuck distance was 100 mm and the pulling speed was 300 mm / min. The peel tester used was a Shimadzu Autograph EZ-LX (Shimadzu Corporation). <Evaluation> 〇: 3.0N / 15mm or more △: 2.5N / 15mm or more, less than 3.0N / 15mm ×: Less than 2.0N / 15mm If the evaluation result is ◯ or Δ, the adhesiveness is sufficient to obtain a good quality molded product.

[0060] (Blocking evaluation during heating) The upper heat seal bar of a heat sealer (TP-701-B, manufactured by Tester Sangyo Co., Ltd.) was heated to 180°C, and the biodegradable laminate was placed so that the surface of the second thermoplastic resin (A2) layer was in contact with the upper heat seal bar, followed by heat compression bonding at 0.4 MPa for 5 seconds. After compression bonding, it was observed whether the biodegradable laminate adhered to the heat seal bar and fell off, and this was repeated three times. <Evaluation> ○: The tape did not stick and fell off in all three attempts (no blocking) △: Sticking occurred at least once out of three times, but the film fell off all three times (no blocking occurred) ×: Sticking occurred at least once out of three times, and the film did not fall off (blocking occurred). If the evaluation result is ◯ or Δ, the laminate has little adhesion when heated, and blocking to the mold does not pose a problem.

[0061] (Evaluation of warpage after decal processing) The biodegradable laminate was cut into a rectangular shape measuring 65 mm in length and 240 mm in width. Next, the surface of the second thermoplastic resin (A2) layer was subjected to a humidity conditioning / decal treatment by exposing it to steam from boiling water for 1 minute, and then left to stand for 1 hour in an environment at room temperature and normal pressure (27°C, humidity 65%). The biodegradable laminate was then placed on a flat surface, and the heights of the four corners from the flat surface were recorded. <Evaluation> ○: The average height of the four corners is 2 mm or less △: The average height of the four corners is over 2 mm and 5 mm or less ×: The average height of the four corners exceeds 5 mm If the evaluation result is ◯, it can be determined that the warping has been eliminated due to sufficient water absorption.

[0062] (PHBH basis weight) The biodegradable laminates obtained in the examples and comparative examples were cut into 10 cm x 10 cm pieces and weighed. The weight was then subtracted from the weight by the weight of the base paper or the sum of the weight of the base paper and the weight of the thermoplastic resin layer on the back side, and multiplied by 100 to obtain the basis weight.

[0063] (Observation of the surface of the thermoplastic resin (A2) layer) The coating surface was observed at a magnification of 500 times using a scanning electron microscope (SEM JSM-6060LA, manufactured by JEOL Ltd.).

[0064] Example 1 Weight 210g / m 2 An aqueous coating solution containing PHBH with a weight-average molecular weight of 620,000 and a solids concentration of 48% by weight was coated onto an A4-sized base paper using a bar coater No. 40. After drying at room temperature for 5 minutes, the coating was heated in a hot air drying oven to a resin temperature of 137°C, and a film-forming process was carried out to produce a first thermoplastic resin (A1) layer. Next, an aqueous coating solution containing PHBH with a weight-average molecular weight of 620,000 and a solids concentration of 13% by weight was applied to the surface opposite the first thermoplastic resin (A1) layer using a bar coater No. 7, and dried at room temperature for 5 minutes. Further, the film was heated in a hot air drying oven to a resin temperature of 137°C, and a film-forming process was performed to produce a second thermoplastic resin (A2) layer. The basis weight of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer was 48 g / m 2 , 1.2g / m 2 It was. The biodegradable laminate obtained above was heat-sealed by heating to a resin temperature of 141°C and a pressure of 0.4 MPa, and after 48 hours, the 180° peel strength test described below was performed. In addition, a blocking test and an evaluation of warpage after decal processing were also performed.

[0065] Example 2 The same procedure as in Example 1 was carried out, except that the resin was heated to a resin temperature of 127°C and heat-sealed.

[0066] Example 3 The same procedure as in Example 3 was carried out, except that the resin was heated to a temperature of 106°C for heat sealing.

[0067] Example 4 To prepare the second thermoplastic resin (A2) layer, the same procedure as in Example 1 was carried out, except that an aqueous coating liquid containing PHBH with a weight average molecular weight of 230,000 and a solid content concentration of 13% by weight was used.

[0068] Example 5 The same procedure as in Example 4 was carried out, except that the resin was heated to a resin temperature of 127°C for heat sealing.

[0069] Example 6 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 2 was carried out, except that an aqueous coating liquid containing PHBH with a weight average molecular weight of 230,000 and a solid content concentration of 48% by weight was used.

[0070] Example 7 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 5 was carried out, except that an aqueous coating liquid containing PHBH with a weight average molecular weight of 230,000 and a solid content concentration of 48% by weight was used.

[0071] Example 8 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 5 was carried out, except that an aqueous mixed dispersion of PHBH having a weight average molecular weight of 620,000 and 230,000 was used.

[0072] Example 9 The same procedure as in Example 1 was carried out to prepare the first thermoplastic resin (A1) layer, except that bar coater No. 14 was used instead of bar coater No. 40. At this time, the basis weight of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer was 18 g / m 2 , 1.2g / m 2 It was.

[0073] Example 10 To prepare a second thermoplastic resin (A2) layer, the same procedure as in Example 9 was carried out, except that an aqueous coating liquid containing PHBH with a weight average molecular weight of 230,000 and a solid content concentration of 13% by weight was used.

[0074] Example 11 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 5 was carried out, except that bar coater No. 14 was used instead of bar coater No. 40.

[0075] Example 12 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 6 was carried out, except that bar coater No. 14 was used instead of bar coater No. 40.

[0076] Example 13 To prepare the first thermoplastic resin (A1) layer, the same procedure as in Example 11 was carried out, except that an aqueous coating liquid containing PHBH with a weight average molecular weight of 230,000 and a solid content concentration of 48% by weight was used.

[0077] Comparative Example 1 To prepare the second thermoplastic resin (A2) layer, the same procedure as in Example 1 was carried out, except that bar coater No. 25 was used instead of bar coater No. 7.

[0078] Comparative Example 2 To prepare a second thermoplastic resin (A2) layer, the same procedure as in Example 6 was carried out, except that bar coater No. 75 was used instead of bar coater No. 7.

[0079] Comparative Example 3 To prepare the second thermoplastic resin (A2) layer, the same procedure as in Example 4 was carried out, except that bar coater No. 25 was used instead of bar coater No. 7.

[0080] Comparative Example 4 The same procedure as in Example 2 was carried out, except that the second thermoplastic resin (A2) layer was not formed on the surface opposite to the first thermoplastic resin (A1) layer.

[0081] Comparative Example 5 The same procedure as in Example 9 was carried out, except that the second thermoplastic resin (A2) layer was not formed on the surface opposite to the first thermoplastic resin (A1) layer.

[0082] Comparative Example 6 The same procedure as in Example 12 was carried out, except that the second thermoplastic resin (A2) layer was not formed on the surface opposite to the first thermoplastic resin (A1) layer.

[0083] [Table 1]

[0084] <Result> Table 1 shows that in each example, the adhesiveness by heat sealing at low temperatures is good, there is no concern about sticking to the heat seal bar, and the laminate has sufficient water absorbency to eliminate warping by applying steam. On the other hand, it is clear that the comparative examples are unable to achieve both adhesiveness, prevention of sticking to the heat seal bar, and sufficient water absorbency.

[0085] 1, it can be seen that the surface of the second thermoplastic resin (A2) layer in the biodegradable laminate of Example 1 is not entirely covered with resin, but is only partially adhered to the substrate, in comparison with the surface of the substrate of Comparative Example 4. For this reason, it is believed that the biodegradable laminate of Example 1 has sufficient water absorbency to eliminate warping of the laminate by decal treatment. On the other hand, it is clear that the entire substrate surface is covered with resin on the surface of the second thermoplastic resin (A2) layer in the biodegradable laminate of Comparative Example 1. This is thought to result in insufficient water absorption, making it difficult to eliminate warping by decal treatment.

[0086] Therefore, according to the present invention, it is possible to provide a biodegradable laminate and a method for producing the same that has sufficient water absorbency to eliminate warping that occurs when the laminate is wound into a roll, suppresses blocking of the molding machine mold when forming paper containers, etc., and has excellent adhesive properties even when processed at low temperatures during molding. [Explanation of symbols]

[0087] 1 Biodegradable laminate 2. Base layer such as paper 3. First thermoplastic resin (A1) layer 4. Second thermoplastic resin (A2) layer

Claims

1. A base layer and a first thermoplastic resin (A1) layer containing a polyhydroxyalkanoate resin laminated on one surface of the base material layer; a second thermoplastic resin (A2) layer containing a polyhydroxyalkanoate resin laminated on the other surface of the base material layer, The basis weight of the first thermoplastic resin (A1) layer is 10 g / m². ２ More than 200g / m ２ is as follows: The weight of the second thermoplastic resin (A2) layer is 0.1 g / m ２ 5g / m or more ２ A biodegradable laminate comprising:

2. 2. The biodegradable laminate according to claim 1, wherein the polyhydroxyalkanoate resin has a weight average molecular weight of 150,000 to 650,000.

3. 3. The biodegradable laminate according to claim 1, wherein the polyhydroxyalkanoate resin contains a polymer having a 3-hydroxybutyrate unit.

4. 4. The biodegradable laminate according to claim 3, wherein the polyhydroxyalkanoate resin contains a copolymer of 3-hydroxybutyrate units and 3-hydroxyhexanoate units.

5. A method for producing the biodegradable laminate according to claim 1 or 2, A method for producing a biodegradable laminate, comprising a step of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by extrusion lamination or thermal lamination at a temperature equal to or higher than the melting point of a resin material and lower than the melting point + 30°C.

6. A method for producing the biodegradable laminate according to claim 1 or 2, a step of applying an aqueous coating liquid containing a polyhydroxyalkanoate resin to a substrate to form a coating film; and heating the coating film to a temperature equal to or higher than the melting point of the resin material and lower than the melting point + 30°C using at least one method selected from the group consisting of blowing hot air, irradiating with infrared rays, irradiating with ultrasonic waves, and contact with a heated roll, thereby forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer.

7. A molded article comprising the biodegradable laminate according to claim 1 or 2.

8. 8. A method for producing a molded body according to claim 7, comprising a step of heating a surface temperature of at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer to 100°C or higher and lower than 170°C.

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