Laminated materials, packaging materials and containers

Abstract

This invention provides a laminate comprising a substrate layer, a gas barrier layer, and a sealant layer. The sealant layer is located on the outermost surface of one side of the laminate. The sealant layer is a resin layer comprising poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate) and has at least one peak temperature (Tma) in the range of 130°C to 160°C in a crystallization melting curve obtained by differential scanning calorimetry.

Description

Technical Field

[0001] The present invention relates to a laminate comprising a gas barrier layer and a heat-sealable sealant layer, and a packaging material or container comprising the laminate. Background Technology

[0002] Packaging materials used for food, toiletries, and pharmaceuticals require gas barrier properties to prevent the contents from deteriorating due to air. Therefore, it is known that gas-barrier packaging materials are constructed by laminating layers such as aluminum foil or vapor-deposited layers onto a substrate layer like paper or resin film.

[0003] Furthermore, it is known that packaging materials possess both gas barrier and heat-sealing properties by providing a sealant layer formed of thermoplastic resin on one side of the aforementioned laminate. Polyesters and polyolefins are known as thermoplastic resins constituting such a sealant layer (see, for example, Patent Documents 1 and 2).

[0004] Furthermore, Patent Document 3 describes the use of biodegradable polymers as thermoplastic resins constituting the sealing layer of the aforementioned packaging material, specifically including poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate), polybutylene succinate, etc. (see paragraphs

[0029] and

[0030] ). Additionally, polylactic acid is widely known as a biodegradable polymer.

[0005] On the other hand, the environmental problems caused by discarded plastics have attracted much attention, especially the large quantities of plastics that are known to drift in the oceans globally through dumping and rivers. Because such plastics retain their shape for extended periods, they are pointed out to cause ecosystem impacts such as trapping and so-called ghost fishing that captures marine life, and the feeding difficulties caused by residues in the digestive organs of marine organisms when ingested. Furthermore, it has been pointed out that microplastics, formed by the degradation / micronization of plastics due to ultraviolet radiation, can adsorb harmful compounds from seawater, leading to the introduction of harmful substances into the food chain through ingestion by marine life.

[0006] For such marine pollution caused by plastics, the use of biodegradable plastics that demonstrate seawater decomposition properties is anticipated.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-210156

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-176441

[0011] Patent Document 3: Japanese Patent No. 5763776 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] Thermoplastic resins currently reported as sealant layers in packaging materials do not exhibit seawater decomposability. Furthermore, resins that do exhibit seawater decomposability typically suffer from low adhesion due to heat sealing.

[0014] When using a heat-sealing-based resin with low adhesion as the sealant layer in packaging materials that include a substrate layer such as paper and an air barrier layer, the substrate layer and air barrier layer can serve as insulation layers, thus requiring a higher heat-sealing temperature. However, when heat-sealing is performed at high temperatures, the melt viscosity of the resin-containing material constituting the sealant layer (hereinafter referred to as the sealant material) decreases significantly, leading to a problem where the sealant material overflows from the heat-sealing section and adheres to the sealing strip of machinery such as bag-making machines.

[0015] In view of the above, the object of the present invention is to provide a laminate comprising a substrate layer, a gas barrier layer and a sealant layer, wherein a resin exhibiting seawater decomposability is used as the resin constituting the sealant layer, and the laminate can ensure sufficient adhesive strength based on heat sealing and suppress the leakage of sealant material.

[0016] Methods for solving problems

[0017] The inventors discovered that by using a specific resin to form a sealant layer in a laminate comprising a substrate layer, a gas barrier layer, and a sealant layer, specific melting characteristics can be imparted, thereby solving the above-mentioned problems and completing the present invention.

[0018] That is, the present invention relates to a laminate comprising a substrate layer, a gas barrier layer and a sealant layer, wherein the sealant layer is located on the outermost surface of one side of the laminate, and the sealant layer is a resin layer comprising poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate) and has at least one peak temperature (Tma) in the range of 130°C to 160°C in the crystallization melting curve obtained by differential scanning calorimetry.

[0019] The effects of the invention

[0020] According to the present invention, a laminate comprising a substrate layer, a gas barrier layer and a sealant layer can be provided, wherein a resin exhibiting seawater decomposability is used as the resin constituting the sealant layer, and the laminate can ensure sufficient adhesive strength based on heat sealing and suppress leakage of sealant material. Attached Figure Description

[0021] Figure 1 This is a conceptual diagram illustrating the layer structure of a first-mode stack.

[0022] Figure 2This is a conceptual diagram illustrating the layer composition of a second type of laminate.

[0023] Figure 3 This is a conceptual diagram illustrating the layer structure of a third-party stack.

[0024] Figure 4 This is a conceptual diagram illustrating the layer composition of a fourth type of laminate.

[0025] Figure 5 This is a conceptual diagram illustrating the layer composition of a fifth type of laminate.

[0026] Figure 6 This is a diagram showing an example of a differential scanning calorimetry (DSC) spectrum.

[0027] Figure 7 This is another example of a differential scanning calorimetry (DSC) spectrum.

[0028] Symbol Explanation

[0029] 11, 21, 31, 41, 51 Sealant layers

[0030] 12, 22, 32, 42, 52 Gas barrier layers

[0031] 13, 23, 33, 43, 53 Substrate layers

[0032] 14, 14', 24, 34, 44 Adhesive layers

[0033] Printing layers 15, 25, 35, 45, 55

[0034] 16, 26, 36, 46, 56 protective layers Detailed Implementation

[0035] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0036] The laminate of this embodiment includes at least a substrate layer, a gas barrier layer, and a sealant layer. The sealant layer is located on the outermost surface of one side of the laminate so that the sealant layers can contact each other for heat sealing. Apart from this, the order of the layers is not particularly limited. That is, the layers can be laminated in the order of substrate layer, gas barrier layer, and sealant layer, or in the order of gas barrier layer, substrate layer, and sealant layer.

[0037] Additionally, an adhesive layer can be formed between the layers to bond them together, or the layers can be directly laminated without an adhesive layer. Furthermore, a printed layer can be formed on the surface opposite to the sealant layer. A protective layer can be formed on the printed layer to protect it. The layers will be described below.

[0038] (Substrate layer)

[0039] The aforementioned substrate layer is not particularly limited as long as it is capable of being laminated with both the gas barrier layer and the sealant layer. However, from the viewpoint of improving the overall biodegradability of the laminate, a biodegradable substrate layer is preferred. Examples of biodegradable substrate layers are not particularly limited, but include: paper (main component is cellulose), celluloid, cellulose esters; polyvinyl alcohol, polyamino acids, polyglycolic acid, pullulan, etc. From the viewpoint of excellent heat resistance and low cost, paper or celluloid is preferred, and paper is particularly preferred. The type of paper is not particularly limited and can be appropriately selected according to the application of the laminate; specific examples include: paper cup base paper, kraft paper, fully chemical pulp paper, coated paper, thin-layer paper, glassine paper, and board paper. Water-resistant agents, water-repellent agents, inorganic additives, etc., can be added to the paper as needed.

[0040] The aforementioned substrate layer can be pre-treated with surface treatments such as corona treatment, flame treatment, and primer coating. These surface treatments can be performed individually or in combination.

[0041] (Gas barrier layer)

[0042] The aforementioned gas barrier layer is a layer that prevents gas from passing through. It is not particularly limited to any layer whose gas permeability is lower than that of the substrate layer and the sealant layer. Existing known gas barrier layers can be used, such as metal foil, vapor-deposited film, resin film, and coatings formed from inorganic materials. Only one type of gas barrier layer can be used, or two or more types can be layered together.

[0043] Examples of metal foils include aluminum foil.

[0044] The vapor-deposited film only needs to contain inorganic materials and can be composed solely of inorganic materials. Examples of such inorganic materials include metals or inorganic oxides. Examples include: aluminum, alumina, silicon oxide (e.g., silicon monoxide, silicon dioxide, silicon nitride, etc.), cerium oxide, calcium oxide, diamond-like carbon, etc., but there are no particular limitations. These can be used alone or in combination of two or more. From the viewpoint of vapor deposition adhesion, the above-mentioned vapor-deposited film is preferably a metal vapor-deposited film, a metal oxide vapor-deposited film, or a silicon oxide vapor-deposited film, and particularly preferably an aluminum vapor-deposited film or a silicon oxide vapor-deposited film.

[0045] The thickness of the vapor-deposited film is not particularly limited, but from the viewpoints of productivity, operability, and appearance, 5–100 nm is preferred, and 5–60 nm is more preferred. When the thickness of the vapor-deposited film is 5 nm or more, defects in the vapor-deposited layer are less likely to occur, and the gas barrier properties are good. In addition, when the thickness of the vapor-deposited film is less than 100 nm, the cost of vapor deposition is low, the coloring of the vapor-deposited layer is not obvious, and the appearance is good.

[0046] Examples of resin films constituting the aforementioned gas barrier layer include: polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, polyethylene glycol, and polyolefins (e.g., polyethylene, polypropylene).

[0047] Examples of inorganic materials that constitute the aforementioned gas barrier layer include talc, clay, montmorillonite, and vermiculite plate-like crystals.

[0048] The aforementioned gas barrier layer is preferably selected from at least one of metal foil, metal vapor-deposited film, metal oxide vapor-deposited film, silicon oxide vapor-deposited film, polyvinyl alcohol film, and ethylene-vinyl alcohol copolymer film, and more preferably from at least one of metal foil, metal vapor-deposited film, metal oxide vapor-deposited film, and silicon oxide vapor-deposited film. It should be noted that the thickness of the aforementioned gas barrier layer can be appropriately determined considering the desired gas barrier properties.

[0049] (Sealant layer)

[0050] The aforementioned sealant layer comprises at least poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate) (hereinafter also referred to as P3HB3HH). P3HB3HH is a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate. The copolymerization form is not particularly limited and can be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc., with random copolymerization being preferred.

[0051] Polylactic acid (PLA) and polybutylene succinate (PBS), widely used as biodegradable resins, do not exhibit sufficient biodegradability in seawater. In contrast, P3HB3HH displays excellent seawater degradability. Furthermore, compared to poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate), which is also known to be seawater degradable, P3HB3HH offers the advantage of increased adhesive strength achieved through heat sealing, and can be heat-sealed at lower temperatures, thus avoiding the problem of substrate discoloration due to heat during heat sealing.

[0052] P3HB3HH alters the melting point and crystallinity by changing the composition ratio of its constituent monomers, resulting in changes to properties such as Young's modulus and heat resistance. It can also impart properties between polypropylene and polyethylene, and offers the advantage of easy industrial production. Furthermore, P3HB3HH can lower the melting point, allowing for processing at lower temperatures.

[0053] The aforementioned sealant layer may contain only one type of 3HB3HH, but preferably contains at least two types of P3HB3HH with different compositions of the monomers.

[0054] P3HB3HH is an aliphatic polyester resin that can be produced by microorganisms. One known P3HB3HH producing bacterium is *Alcaligenes eutrophus* AC32 (FERMBP-6038), which has been introduced with genes containing the P3HA synthase genome (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)). Alternatively, P3HB3HH can be manufactured, for example, by the method described in International Publication No. 2010 / 013483. Commercially available P3HB3HH products include, for example, "KANEKA Biodegradable Polymer PHBH (registered trademark)" from Kaneka Corporation.

[0055] The aforementioned sealant layer exhibits at least one peak temperature (Tma) in the crystallization melting curve obtained by differential scanning calorimetry within the range of 130–160°C. The presence of Tma indicates that the sealant layer contains a high-melting-point resin component with a melting point in the range of 130–160°C. During heat sealing, the crystals of this high-melting-point resin component do not completely melt and remain, acting as crystal nuclei, thereby accelerating the curing of the sealant material during heat sealing. This ensures sufficient adhesive strength based on heat sealing and prevents sealant material from overflowing from the sealed area. The temperature range in which Tma is present is more preferably 135–158°C, and even more preferably 140–156°C.

[0056] The aforementioned sealant layer may be a sealant layer that does not have a peak temperature in the temperature range below 130°C in the crystallization melting curve obtained by differential scanning calorimetry.

[0057] However, according to a preferred embodiment, the sealant layer, in the crystallization melting curve obtained by differential scanning calorimetry, preferably has at least one peak temperature (Tmb) in the range of 40°C or higher and below 130°C, in addition to the aforementioned Tma, and the temperature difference between Tma and Tmb is 10°C or higher.

[0058] The presence of Tmb refers to the inclusion of a low-melting-point resin component in the sealant layer, with a melting point between 40°C and 130°C. This low-melting-point resin component exhibits thermal tack during heat sealing, further improving the heat-sealed bond strength. The temperature range in which Tmb is present is more preferably 45–125°C, more preferably 70–120°C, and even more preferably 75–115°C.

[0059] Furthermore, by maintaining a temperature difference of 10°C or more between Tma and Tmb, while allowing the high-melting-point resin component to crystallize and remain, the low-melting-point resin component is easily melted. This improves the bond strength and facilitates the suppression of sealant material overflow. The temperature difference between Tma and Tmb is preferably 20°C or more, more preferably 25°C or more, further preferably 30°C or more, and particularly preferably 35°C or more. While there is no particular upper limit to the temperature difference between Tma and Tmb, from the viewpoint of ease of preparing a resin exhibiting this temperature difference, it is preferably 120°C or less, more preferably 90°C or less, and further preferably 60°C or less.

[0060] On the other hand, it is preferable that the aforementioned sealant layer does not have a peak temperature in the crystallization melting curve obtained by differential scanning calorimetry in a temperature range exceeding 160°C. When it has a Tma in the range of 130–160°C, and further has a peak temperature in the temperature range exceeding 160°C, there is an excessive amount of residual crystal nuclei of the high-melting-point resin component during heat sealing, resulting in a decrease in heat-sealing performance. If the heat-sealing temperature is increased without excessive residual crystal nuclei, the thermal decomposition of the resin proceeds significantly, posing a potential risk of reduced heat-sealing strength due to a decrease in the mechanical strength of the sealant layer.

[0061] In this specification, Tma and Tmb in the crystallization melting curve obtained by differential scanning calorimetry are defined as follows.

[0062] Four to ten mg of the sealant layer sample obtained from the other layers was filled into an aluminum disk. The sample was then melted using a differential scanning calorimeter under a nitrogen flow, with the temperature increased from 20°C to 190°C at a rate of 10°C / min, to obtain a crystallization melting curve. In the obtained crystallization melting curve, for the melting point peak existing in the range of 130–160°C, the peak temperature at which the maximum heat endothermic effect was observed was designated as Tma. Conversely, for the melting point peak existing in the range above 40°C but below 130°C, the peak temperature at which the maximum heat endothermic effect was observed was designated as Tmb.

[0063] When multiple melting point peaks are identified within the range of 130–160°C, the peak temperature of the highest peak is set as Tma. Similarly, when multiple melting point peaks are identified within the range of above 40°C and below 130°C, the peak temperature of the highest peak is set as Tmb.

[0064] Figure 6 A representative example of a crystallization melting curve containing Tma is shown. Figure 7 A representative example of crystallization melting curves including Tma and Tmb is shown.

[0065] A sealant layer that meets the above melting characteristics can be achieved by appropriately adjusting the P3HB3HH used in the layer. To meet the above melting characteristics, the selection of the bacterial cells used to produce P3HB3HH, the selection of the carbon source used in the bacterial cell culture, the mixing of various P3HB3HH with different 3HH ratios, and the mixing of 3HB homopolymer (hereinafter also referred to as P3HB) can be implemented appropriately.

[0066] The P3HB3HH used as a sealant layer can be obtained by using P3HB3HH derived from a single microorganism alone, or by using a mixture of P3HB3HH derived from multiple microorganisms.

[0067] When the P3HB3HH used in the sealant layer is composed of P3HB3HH alone, the proportion of 3HH in the P3HB3HH relative to the total of 3HB and 3HH is preferably 3 to 9 mol%, more preferably 3 to 7 mol%. When the proportion of 3HH in P3HB3HH is 3 to 9 mol%, a sealant layer with the above-mentioned melting characteristics can be easily formed. It should be noted that the proportion of 3HH can be determined by measuring P3HB3HH using NMR.

[0068] When the P3HB3HH used in the sealant layer is composed of a mixture of various P3HB3HH, it is preferable to mix highly crystalline P3HB3HH and low-crystalline P3HB3HH. Alternatively, P3HB can be mixed in to replace the highly crystalline P3HB3HH. This makes it easy to achieve a sealant layer that simultaneously possesses the aforementioned Tma and Tmb.

[0069] In the aforementioned highly crystalline P3HB3HH, the proportion of 3HH relative to the total of 3HB and 3HH is preferably 3 mol% or less, more preferably 2 mol% or less, and even more preferably 1 mol% or less. Furthermore, in the aforementioned low-crystalline P3HB3HH, the proportion of 3HH relative to the total of 3HB and 3HH is preferably 10 to 40 mol%, more preferably 10 to 30 mol%.

[0070] The amount of the above-mentioned highly crystalline P3HB3HH or P3HB 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, relative to the total amount of P3HB3HH and P3HB contained in the above-mentioned sealant layer.

[0071] The weight-average molecular weight of P3HB3HH contained in the above-mentioned sealant layer is preferably 100,000 to 700,000, more preferably 150,000 to 650,000, and even more preferably 200,000 to 600,000. By making the weight-average molecular weight of P3HB3HH within the above range, the sealant layer can exhibit high adhesive strength due to heat sealing. It should be noted that the weight-average molecular weight of P3HB3HH can be determined by using a gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko Corporation), using polystyrene gel (Shodex K-804 manufactured by Showa Denko Corporation) in the column, with chloroform as the mobile phase, and in the form of the molecular weight converted from polystyrene.

[0072] The aforementioned sealant layer may contain one or more P3HB3HH resins and any resin other than P3HB within the scope of achieving the effects of the invention. Examples of such other resins include: poly(3-hydroxybutyrate) resins other than P3HB3HH, polybutylene succinate, polycaprolactone, polylactic acid, and other aliphatic polyester resins; polybutylene adipate terephthalate, polybutylene sebacic acid, polybutylene azelaic terephthalate, and other aliphatic aromatic polyester resins. To ensure the seawater biodegradability of the sealant layer, the amount of these other resins added is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 1 part by weight or less, relative to 100 parts by weight of the total amount of P3HB3HH and P3HB. The aforementioned sealant layer may not contain P3HB3HH or any resin other than P3HB.

[0073] The aforementioned sealant layer may include additives commonly used in this technical field to achieve the effects of the invention. Examples of such additives include: inorganic fillers such as talc, calcium carbonate, mica, silica, titanium dioxide, and alumina; organic fillers such as rice husks, wood flour, and waste paper such as newspapers; various starches and celluloses; colorants such as pigments and dyes; odor absorbers such as activated carbon and zeolite; fragrances such as vanillin and dextrin; plasticizers; antioxidants; weather-resistant modifiers; ultraviolet absorbers; nucleating agents; lubricants; release agents; water-repellent agents; antibacterial agents; slip-modifying agents; tackifiers; fillers; and pharmaceuticals. The additive may contain only one type or more. Those skilled in the art can appropriately determine the content of these additives according to their intended use.

[0074] The thickness of the sealant layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 50 μm, and even more preferably 20 to 30 μm. When the thickness is within the above range, defects such as pores can be prevented, sufficient flexibility can be ensured, and it has the strength to withstand use, and can efficiently and well exhibit functions such as water resistance.

[0075] [Method for forming the sealant layer]

[0076] The sealant layer can be a pre-made resin film containing P3HB3HH, or it can be a resin layer formed on the surface of the substrate layer or the gas barrier layer by melt extrusion or coating of the resin material.

[0077] The resin film containing P3HB3HH can be manufactured using various molding methods such as T-die extrusion, blow molding, and calendering. Specific conditions can be set appropriately.

[0078] (Extrusion lamination method)

[0079] According to one method, the sealant layer can be formed by extrusion lamination. Specifically, molten resin material is extruded from a die, cooled using cooling rollers, and pressed onto the surface of the target film (substrate layer or gas barrier layer), then immediately peeled off from the cooling rollers to form the sealant layer. The target film (especially metal foil, celluloid) may have been pre-treated with a primer.

[0080] When using common poly(3-hydroxybutyrate) resins for extrusion lamination, the laminate (resin layer) is not easily peeled off from the cooling roller, and temporary adhesion of the laminate to the cooling roller can easily occur. As a result, when the adhered area is peeled off from the roller, stress occurs, causing a cloudy, uneven (fine roughness) appearance on the laminate surface at that location. However, by using P3HB3HH, which exhibits the aforementioned melting properties, the peelability from the cooling roller can be improved, resulting in a sealant layer with a good surface finish.

[0081] The heating temperature during extrusion lamination is more preferably set to Tma + 5°C to 10°C, so that some of the resin crystals remain in the molten resin. By using a lower heating temperature, it is possible to appropriately improve the neck-in and peelability from the roll. From the viewpoint of ensuring adhesion to the substrate layer or the gas barrier layer, the lower limit of the heating temperature is preferably 160°C or higher, more preferably 165°C or higher.

[0082] The surface temperature of the cooling roller used in the extrusion lamination process is not particularly limited, as long as it is sufficient to cool and press the laminated layers together. The surface temperature of the cooling roller is preferably 35–70°C, more preferably 40–60°C. When the surface temperature of the cooling roller is within the above range, the crystallization of P3HB3HH is promoted, resulting in reduced adhesion of the laminated layers to the cooling roller and enabling faster curing.

[0083] (Applying method)

[0084] According to another method, the sealant layer can be formed by coating. Specifically, it can be formed by applying a coating liquid (preferably an aqueous coating liquid) containing P3HB3HH to one side of the substrate layer or the gas barrier layer and then heating and drying it.

[0085] The coating method can be implemented using known methods without particular limitation, and may include, for example, the following steps: (a) manufacturing process of aqueous coating liquid, (b) delivery process of substrate layer or gas barrier layer, (c) coating process of the aqueous coating liquid onto the substrate layer or gas barrier layer, and (d) drying and film formation process of coating layer.

[0086] The above step (a) is not particularly limited and can be carried out by the following method. That is, step (a) includes the following steps: P3HB3HH is produced by microorganisms, the microbial cells containing the above P3HB3HH are broken in an aqueous dispersion state, and the P3HB3HH in the cells is separated.

[0087] Generally, when recovering P3HB3HH from microbial cells, methods such as dissolving P3HB3HH with organic solvents like chloroform or precipitating it with insoluble solvents like methanol or hexane can be used. However, in these methods, the obtained P3HB3HH cannot be in particulate form, requiring an additional step to make it into particulate particles, which is economically disadvantageous. In contrast, a process that involves breaking down microbial cells containing P3HB3HH into an aqueous dispersion and separating the P3HB3HH from the cells can yield an aqueous dispersion of P3HB3HH particles that retain a considerably fine particle size.

[0088] In the process of breaking down microbial cells containing P3HB3HH in an aqueous dispersion and separating P3HB3HH from the cells, it is preferable to simultaneously break down and add alkali while stirring the microbial cells containing P3HB3HH. The advantages of this method are: (i) it prevents an increase in the viscosity of the dispersion due to cell components other than P3HB3HH leaking from the microbial cells; (ii) by preventing an increase in the viscosity of the cell dispersion, the pH can be controlled, allowing for further processing at lower alkali concentrations through continuous or intermittent addition of alkali; and (iii) it suppresses the decrease in the molecular weight of P3HB3HH, enabling the separation of high-purity P3HB3HH. The pH of the cell dispersion after adding alkali is preferably 9 to 13.5. When the pH is 9 or higher, P3HB3HH is easily separated from the cells, while when the pH is 13.5 or lower, the decomposition of P3HB3HH tends to be inhibited.

[0089] Microbial cell disruption can be achieved using methods such as ultrasonic disruption, emulsifying dispersers, high-pressure homogenizers, and mills. Among these methods, considering the efficient disruption of nucleic acids (which are the main cause of viscosity increase) by effectively dissolving P3HB3HH from the cells through alkali treatment, and the thorough dispersion of insoluble substances other than P3HB3HH, such as cell walls, cell membranes, and insoluble proteins, emulsifying dispersers are preferred, such as Silverson Mixer (manufactured by Silverson Corporation), ClearMix (manufactured by M-Technique Corporation), and Ebara Milder (manufactured by Ebara Corporation), but are not limited to these. Furthermore, the preferred temperature conditions for microbial cell disruption and alkali addition are room temperature to 50°C. Temperatures exceeding 50°C easily lead to the decomposition of P3HB3HH; therefore, temperatures near room temperature are preferred. Additionally, setting temperatures below room temperature requires cooling operations, which is uneconomical.

[0090] A dispersion can be obtained by breaking down and alkali-treating the microbial cells, from which a precipitate is obtained by centrifugation. The precipitate is then washed with water, followed by methanol washing as needed, and finally an appropriate amount of water is added to obtain an aqueous coating solution containing the desired concentration of solid components of P3HB3HH.

[0091] Following the above steps, it is preferable to perform a step of applying mechanical shear to the aqueous coating liquid to separate some of the agglomerated P3HB3HH particles from each other. From the viewpoint of obtaining an aqueous coating liquid containing P3HB3HH with substantially no agglomerates and uniform particle size, applying mechanical shear is preferred. The mechanical shearing applied to the aqueous coating liquid can be performed using, for example, a mixer, homogenizer, or ultrasonic equipment. At this point, the agglomeration of P3HB3HH particles is not very strong; therefore, from the viewpoint of simplicity, it is preferable to use a mixer with a conventional stirring paddle.

[0092] The concentration of solid component P3HB3HH in the above-mentioned aqueous coating solution is preferably 25-65% by weight, more preferably 30-55% by weight, and particularly preferably 35-50% by weight. When the concentration of solid component P3HB3HH in the above-mentioned aqueous coating solution is within the above range, the viscosity of the solution is moderate, so uniform coating can be performed, and the necessary coating thickness can be maintained, thereby reducing the likelihood of coating defects.

[0093] From the viewpoint of balancing the productivity of P3HB3HH and the uniformity of coating, the average particle size of P3HB3HH in the above-mentioned aqueous coating solution is, for example, 0.1 to 50 μm, preferably 0.5 to 30 μm, and more preferably 0.8 to 20 μm. By making the average particle size 0.1 μm or more, P3HB3HH can be easily obtained by any method, including microbial production and chemical synthesis. By making the average particle size 50 μm or less, uneven coating can be avoided. It should be noted that the average particle size of P3HB3HH in the aqueous coating solution can be calculated using a common particle size analyzer such as a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd., FRA), by adjusting the aqueous suspension containing P3HB3HH to a given concentration, in the form of particle size corresponding to 50% accumulation of all normally distributed particles.

[0094] The above-mentioned aqueous coating solution may be free of emulsifiers, but it is preferable to include an emulsifier to stabilize the coating solution. Examples of emulsifiers include: anionic surfactants such as sodium lauryl sulfate and sodium oleate; cationic surfactants such as lauryl trimethylammonium chloride; nonionic surfactants such as fatty acid glycerides and sorbitan fatty acid esters; water-soluble polymers such as polyvinyl alcohol, ethylene-modified polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. The amount of emulsifier added is not particularly limited, but is preferably 1 to 10% by weight relative to the solid content of P3HB3HH. When the amount of emulsifier added is 1% by weight or more, there is a tendency to obtain a stabilizing effect from the emulsifier; when it is 10% by weight or less, it is possible to avoid the reduction in physical properties and coloring caused by excessive emulsifier mixing into P3HB3HH.

[0095] The emulsifier described above can be added to the aqueous dispersion after centrifugation and water washing following microbial cell disruption / alkali treatment. In the case of methanol washing, it can be added after methanol washing, either before or after adjusting the solid component concentration of P3HB3HH with an appropriate amount of water.

[0096] The above steps (b) and (c) are not particularly limited and can be performed by any method known in the art.

[0097] In one embodiment of the present invention, the heating temperature in the drying and film-forming process of the coating layer in step (d) is preferably 130–180°C, more preferably 135–175°C, and even more preferably 140–170°C. By heating the coating layer at such a temperature and drying and forming a film thereon, a sealant layer exhibiting the above-described melting characteristics can be formed, thereby obtaining the above-described laminate.

[0098] The method for manufacturing the above-described laminate may include a winding step (e) of the laminate after step (d). Step (e) is not particularly limited and may be performed by any method known in the art.

[0099] (Adhesive layer)

[0100] In the laminate of this embodiment, the adhesive layer is any layer. The adhesive layer may be formed between the substrate layer and the gas barrier layer, between the gas barrier layer and the sealant layer, or between the substrate layer and the sealant layer.

[0101] There are no particular limitations on the adhesive used to form the adhesive layer; any known adhesive may be used. As for the bonding method, there are no particular limitations; examples include dry lamination using a two-component curing urethane adhesive and solvent-free dry lamination using a solvent-free adhesive.

[0102] (Printed layer and protective layer)

[0103] In the laminate of this embodiment, the printed layer is any layer. When the laminate has a printed layer, it is preferable to form the printed layer on the side opposite to the sealant layer. The printed layer can be formed on the surface of the substrate layer or on the surface of the gas barrier layer.

[0104] The details of the printed layer are not particularly limited and can be formed using known printing methods and known printing inks. Examples of printing methods include gravure printing, offset printing, gravure-offset printing, flexographic printing, and inkjet printing. The printing ink can be any solvent-based or water-based ink. Furthermore, the printed layer can be a single layer or composed of multiple layers.

[0105] A protective layer can be formed on the printed layer to protect it. This protective layer can be selected from known materials; for example, solvent-based or water-based paints containing resins and additives can be used.

[0106] The following describes the specific configuration of the laminate in this embodiment, but the configuration of the laminate in this embodiment is not limited to the following configuration.

[0107] (First method)

[0108] like Figure 1 As shown, in the first embodiment of this invention, the laminate 1 is sequentially stacked with a sealant layer 11, a first adhesive layer 14, a gas barrier layer 12, a second adhesive layer 14', a substrate layer 13, a printing layer 15, and a protective layer 16.

[0109] It should be noted that protective layer 16 can be omitted. Furthermore, both printed layer 15 and protective layer 16 can be omitted. This also applies to the methods described below.

[0110] The sealant layer 11 is preferably a resin film containing P3HB3HH. The gas barrier layer 12 is preferably a metal foil such as aluminum foil. The first adhesive layer 14 and the second adhesive layer 14' are preferably formed of adhesives that can be used in dry lamination processes, and are particularly preferably formed of urethane adhesives.

[0111] The method for manufacturing the laminate 1 is not particularly limited, but a method involving two dry lamination processes is preferred. Here, dry lamination refers to a process in which an adhesive is applied to one film and allowed to dry temporarily before being bonded to another film. For example, firstly, a resin film constituting the sealant layer 11 is bonded to a metal foil constituting the gas barrier layer 12 by dry lamination with a first adhesive layer 14 sandwiched between them. Then, a second dry lamination is performed to bond paper or celluloid, etc., located on the substrate layer 13, to the gas barrier layer 12 side of the resulting laminate structure consisting of the sealant layer 11, the first adhesive layer 14, and the gas barrier layer 12, with a second adhesive layer 14' sandwiched between them. The order of the two dry lamination processes can be reversed. Then, printing can be performed on the substrate layer 13 to form a printed layer 15, and a protective layer 16 can be further formed as needed. Through the above, the laminate 1 can be manufactured.

[0112] (Second method)

[0113] like Figure 2 As shown, in the second embodiment of this invention, the laminate 2 is sequentially stacked with a sealant layer 21, a gas barrier layer 22, an adhesive layer 24, a substrate layer 23, a printing layer 25, and a protective layer 26.

[0114] The sealant layer 21 is preferably a resin film containing P3HB3HH. The gas barrier layer 22 is preferably a vapor-deposited film such as a metal vapor-deposited film, a metal oxide vapor-deposited film, or a silicon oxide vapor-deposited film. The adhesive layer 24 is preferably formed of an adhesive that can be used in dry lamination processes, and is particularly preferably formed of a urethane adhesive.

[0115] The method for manufacturing the laminate 2 is not particularly limited, but a method of sequentially performing vapor deposition and dry lamination is preferred. For example, firstly, the resin film constituting the sealant layer 21 is vapor deposited, and a gas barrier layer 22 is directly formed on the sealant layer 21. A paper or celluloid, etc., located on the substrate layer 23, is then bonded to the gas barrier layer 22 side of the resulting laminate structure composed of the sealant layer 21 and the gas barrier layer 22 using a dry lamination method with an adhesive layer 24 in between. Then, a printing layer 25 and a protective layer 16 can be formed on the substrate layer 23 as needed. Thus, the laminate 2 can be manufactured.

[0116] (Third method)

[0117] like Figure 3 As shown, the third-party laminate 3 of this embodiment is sequentially stacked with a sealant layer 31, a gas barrier layer 32, an adhesive layer 34, a substrate layer 33, a printing layer 35, and a protective layer 36.

[0118] The sealant layer 31 is preferably a resin layer formed on the gas barrier layer 32 by extrusion lamination or coating. The gas barrier layer 32 is preferably a metal foil such as aluminum foil. The adhesive layer 34 is preferably formed of an adhesive that can be used in dry lamination processing, and is particularly preferably formed of a urethane adhesive.

[0119] The method for manufacturing the laminate 3 is not particularly limited, but preferably it is a method in which a sealant layer 31 is formed on the gas barrier layer 32 by extrusion lamination or coating, and then the substrate layer 33 is bonded to one side of the gas barrier layer 32 by dry lamination. The order of the processes can be reversed.

[0120] For example, firstly, a resin material containing P3HB3HH is melted and extruded from a die, forming a sealant layer 31 of the resin material on one side of the metal foil constituting the gas barrier layer 32 by extrusion lamination. Alternatively, a coating liquid containing P3HB3HH can be prepared, applied to one side of the metal foil constituting the gas barrier layer 32, and then dried to form the sealant layer 31. A paper or celluloid, etc., located on the substrate layer 33, is bonded to the gas barrier layer 32 side of the resulting laminated structure consisting of the sealant layer 31 and the gas barrier layer 32 by dry lamination with an adhesive layer 34. Then, a printed layer 35 and a protective layer 36, used as needed, can be formed on the substrate layer 33. Through the above, the laminate 3 can be manufactured.

[0121] In the first, second, and third methods described above, the substrate layer is located on the side opposite to the sealant layer in each laminate. Therefore, when constructing a packaging bag comprising each laminate, since the sealant layer is located on the inside of the bag and the substrate layer is located on the outside of the bag, it has the advantage of being able to identify the feel of the substrate layer from the outside of the packaging bag.

[0122] (Fourth method)

[0123] like Figure 4 As shown, in the fourth embodiment of this invention, the laminate 4 is sequentially stacked with a sealant layer 41, a substrate layer 43, an adhesive layer 44, a gas barrier layer 42, a printing layer 45, and a protective layer 46.

[0124] The sealant layer 41 is preferably a resin layer formed on the substrate layer 43 by extrusion lamination or coating. The adhesive layer 44 is preferably formed of an adhesive that can be used in dry lamination processes, and particularly preferably of a urethane adhesive. The gas barrier layer 42 is preferably a metal foil such as aluminum foil.

[0125] The method for manufacturing the laminate 4 is not particularly limited, but preferably a dry lamination process is performed after forming the sealant layer 41 on the substrate layer 43 by extrusion lamination or coating. The order of the processes can be reversed.

[0126] For example, firstly, a resin material containing P3HB3HH is melted and extruded from a die, forming a sealant layer 41 made of the resin material on one side of the paper or celluloid located on the substrate layer 43 by extrusion lamination. Alternatively, a coating liquid containing P3HB3HH can be prepared, applied to one side of the paper or celluloid located on the substrate layer 43, and then dried to form the sealant layer 41. A metal foil constituting the gas barrier layer 42 is bonded to one side of the substrate layer 43 of the resulting laminated structure consisting of the sealant layer 41 and the substrate layer 43 by dry lamination with an adhesive layer 44. Then, a printed layer 45 and a protective layer 46, used as needed, can be formed on the substrate layer 43. Through the above, the laminate 4 can be manufactured.

[0127] (Fifth method)

[0128] like Figure 5 As shown, in the fifth embodiment of this invention, the laminate 5 is sequentially stacked with a sealant layer 51, a substrate layer 53, a gas barrier layer 52, a printing layer 55, and a protective layer 56. The sealant layer 51 is preferably a resin layer formed on the substrate layer 53 by extrusion lamination or coating. The gas barrier layer 52 is preferably a coating layer containing resin and / or inorganic substances.

[0129] The method for manufacturing the laminate 5 is not particularly limited, but preferably it is a method in which a sealant layer 51 is formed on the substrate layer 53 by extrusion lamination or coating, and then a gas barrier layer 52 is formed on the substrate layer 53 by coating. The order of the processes can be reversed.

[0130] For example, firstly, a sealant layer 51 is formed on the substrate layer 53 by extrusion lamination or coating, similar to the fourth method. Next, a coating liquid containing resin and / or inorganic materials (e.g., talc, clay) is prepared, applied to the substrate layer 53, and allowed to dry, forming a gas barrier layer 52 composed of resin and / or inorganic materials. Then, a printed layer 45 and a protective layer 56, if desired, can be formed on the gas barrier layer 52. Through the above, a laminate 5 can be manufactured.

[0131] Alternatively, a paper with an air barrier layer 52 on its surface can be prepared, and a sealant layer 51 can be formed on the surface of the paper without the air barrier layer 52 by extrusion lamination or coating to manufacture a laminate 5.

[0132] (use)

[0133] The laminated body of this embodiment can constitute a molded body. The molded body can be the laminated body itself, or it can be a molded body formed by processing the laminated body in a given shape or structure. The molded body is not particularly limited as long as it includes the laminated body; examples include paper, film, sheet, tube, plate, rod, packaging materials (e.g., bags), containers (e.g., bottle containers), components, etc. From the viewpoint of countermeasures against marine pollution, the molded body is preferably a packaging material or container.

[0134] The molded body described above can be formed by heat-sealing and bonding the sealant layers together as a secondary processing step. Such molded bodies are not particularly limited, and examples include: side-sealed packaging bodies, three-side-sealed packaging bodies, pillow-type packaging bodies, stand-up pouches, and other packaging bags. The molded body described above can exhibit high adhesive strength through heat sealing; however, because heat sealing can be performed at relatively low temperatures, discoloration of the substrate layer, etc., due to the heat during heat sealing can be avoided.

[0135] The heat-sealed molded body described above can be appropriately used as a packaging container material for various purposes, such as shopping bags, various types of bags, food / snack packaging materials, cups, trays, and cartons (in other words, in various fields such as food, cosmetics, electronics, medical, and pharmaceuticals). Because the molded body possesses a gas barrier layer and includes a sealant layer with high adhesion to the substrate layer and good oxygen and water vapor barrier properties, it is particularly preferred as a packaging material for dry foods (instant noodles, nuts, dried fruits, etc.), various solid seasonings, chocolate, tea, and other contents that require preservation of aroma and flavor.

[0136] The aforementioned secondary processing can be performed using any method known in the art, such as various bag-making machines and filling packaging machines. Alternatively, paper cup forming machines, punching machines, and box-making machines can also be used. In these processing machines, the bonding method for the molded body can use known techniques; besides the conventional heat sealing method, methods such as pulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and flame sealing can also be used. It is particularly preferred that the molded body is formed using a heat sealing method, i.e., it preferably includes a heat-sealed portion formed by a sealant layer. This heat sealing is preferably performed between sealant layers, but it can also be performed between the sealant layer and other layers.

[0137] The heat-sealing temperature for heat-sealing the molded body varies depending on the bonding method, the thickness of the sealant layer, and the type of layers to be bonded. For heat-sealing the sealant layers together when the substrate layer is paper, the typical heat-sealing temperature is 150–200°C, preferably 160–190°C, and more preferably 170–180°C when using a heated heat-sealing tester with a sealing strip for double-sided heating. Within these ranges, leakage of sealant material during heat sealing can be suppressed, and sufficient bond strength based on heat sealing can be ensured.

[0138] For the heat-sealing temperature when heat-sealing the sealant layer of the above-mentioned laminate to the paper as the substrate layer, when using a heated heat-sealing tester with a sealing strip for double-sided heating, it is typically 140–190°C, preferably 150–180°C, and more preferably 160–170°C. Within this range, leakage of sealant material during heat sealing can be suppressed, and sufficient adhesive strength based on heat sealing can be ensured.

[0139] The heat-sealing pressure during the heat sealing of the molded body varies depending on the bonding method. When using a heated heat-sealing testing machine with a sealing strip, the heat-sealing pressure of the molded body is typically 0.1 MPa or higher, preferably 0.3 MPa or higher. Values ​​above these values ​​ensure sufficient bond strength based on the heat seal.

[0140] In order to improve the physical properties of the molded body of this embodiment, it may also be composited with other molded bodies made of different materials (e.g., fibers, filaments, ropes, fabrics, knitted fabrics, nonwoven fabrics, paper, films, sheets, tubes, plates, rods, containers, bags, components, foams, etc.). These materials are also preferably biodegradable.

[0141] Preferred embodiments of this disclosure are set forth in the following items, but the invention is not limited to the following items.

[0142] [Project 1]

[0143] A laminate comprising a substrate layer, a gas barrier layer, and a sealant layer, wherein,

[0144] The aforementioned sealant layer is located on the outermost surface of one side of the aforementioned laminate.

[0145] The aforementioned sealant layer is a resin layer comprising poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate) and has at least one peak temperature (Tma) in the range of 130°C to 160°C in the crystallization melting curve obtained by differential scanning calorimetry.

[0146] [Project 2]

[0147] According to the laminate described in Project 1, the aforementioned substrate layer is biodegradable.

[0148] [Project 3]

[0149] According to the laminate described in Project 2, the substrate layer is paper.

[0150] [Project 4]

[0151] The laminate according to any one of items 1 to 3, wherein the gas barrier layer is selected from at least one of metal foil, metal vapor deposition film, metal oxide vapor deposition film, silicon oxide vapor deposition film, polyvinyl alcohol film, and ethylene-vinyl alcohol copolymer film.

[0152] [Project 5]

[0153] According to any one of items 1 to 4, the laminate of the sealant layer further has at least one peak temperature (Tmb) in the crystallization melting curve obtained by differential scanning calorimetry in the range of 40°C or higher and 130°C or lower, and the temperature difference between Tma and Tmb is 10°C or higher.

[0154] [Project 6]

[0155] The laminate according to any one of items 1 to 5 further has a printed layer on the side opposite to the aforementioned sealant layer.

[0156] [Project 7]

[0157] A packaging material comprising any one of items 1 to 6.

[0158] [Project 8]

[0159] The packaging material according to Item 7 includes portions in which the aforementioned sealant layers are heat-sealed together.

[0160] [Project 9]

[0161] A container comprising the laminate as described in any one of items 1 to 6.

[0162] [Project 10]

[0163] The container according to Project 9 includes a portion in which the aforementioned sealant layers are heat-sealed together.

[0164] Example

[0165] The present invention will be specifically described below based on embodiments, but the present invention is not limited to its technical scope by these embodiments.

[0166] In Examples 1-4 and Comparative Examples 1-2, 30 μm thick P3HB3HH films were used, which were molded using the resin material shown below. The films were produced by feeding granules obtained from melt mixing in a twin-screw extruder into a single-screw extruder, extruding them using a T-die mounted at the front end, and stretching them with metal rollers.

[0167] (Example 1)

[0168] P3HB3HH(a): Average ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight-average molecular weight 600,000 g / mol: X131A (KANEKA biodegradable polymer PHBH (registered trademark))

[0169] (Example 2)

[0170] P3HB3HH(b): Average ratio 3HB / 3HH = 97 / 3 (mol% / mol%), weight-average molecular weight 660,000 g / mol): manufactured according to Example 2 of International Publication No. 2019 / 142845

[0171] (Example 3)

[0172] The mixture used in Example 2 was 55% by weight of P3HB3HH(b) and 45% by weight of P3HB3HH(c) (the average ratio of the total mixture was 3HB / 3HH = 85 / 15 (mol% / mol%)).

[0173] P3HB3HH(c): Average ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight-average molecular weight 660,000 g / mol): manufactured according to Example 9 of International Publication No. 2019 / 142845.

[0174] (Example 4)

[0175] The composition comprising P3HB3HH and PHB shown in Example 6 of International Publication No. 2015 / 146195 (average ratio of 3HB / 3HH in P3HB3HH = 89.0 / 11.0 (mol% / mol%), and the composition contains 4.2% by weight of PHB)

[0176] (Comparative Example 1)

[0177] P3HB3HH(d): Average ratio 3HB / 3HH = 99.2 / 0.88 (mol% / mol%): Manufactured according to Comparative Example 1 of International Publication No. 2004 / 041936

[0178] (Comparative Example 2)

[0179] P3HB3HH(e): Average ratio 3HB / 3HH = 83 / 17 (mol% / mol%): According to paragraph

[0022] and Table 4 of Japanese Patent No. 3537274, it was manufactured by culturing Aeromonas guinea pig FA440 in a culture medium containing a yeast extract with the concentration of oleic acid as a carbon source adjusted to 2% by weight.

[0180] (Differential Scanning Calorimetry)

[0181] 4–10 mg of each P3HB3HH film sample was packed into an aluminum disk. Using a differential scanning calorimeter under a nitrogen flow, the temperature was increased from 20 °C to 190 °C at a rate of 10 °C / min, melting the sample to obtain a crystallization melting curve. In the obtained crystallization melting curve, the peak temperature of the melting point peak existing in the range of 130–160 °C was designated as Tma. Furthermore, the peak temperature of the melting point peak existing in the range above 40 °C but below 130 °C was designated as Tmb.

[0182] 〔result〕

[0183] The Tma of the P3HB3HH membrane in Example 1 was 144°C.

[0184] The Tma of the P3HB3HH membrane in Example 2 was 152°C.

[0185] The Tma of the P3HB3HH membrane in Example 3 was 156°C, and the Tmb was 48°C.

[0186] The Tma of the P3HB3HH membrane in Example 4 was 157°C, and the Tmb was 107°C.

[0187] The P3HB3HH film of Comparative Example 1 did not have Tma and Tmb, and a melting point peak was observed at 165 °C.

[0188] The P3HB3HH membrane in Comparative Example 2 did not have Tma, and Tmb was 119°C.

[0189] In each embodiment / comparative example, a laminate of the first type was manufactured by dry lamination of the substrate layer, the sealant layer and the gas barrier layer.

[0190] Sealant layer: the aforementioned 30μm thick P3HB3HH film

[0191] First adhesive layer: a urethane adhesive layer formed by dry lamination.

[0192] Gas barrier layer: 9μm thick aluminum foil

[0193] Second adhesive layer: a urethane adhesive layer formed by dry lamination.

[0194] Substrate layer: 50g / m²2 Unbleached kraft paper

[0195] The following evaluations were performed on each laminate. The results are shown in Table 1.

[0196] (Evaluation method for adhesive properties based on heat sealing)

[0197] Sealant layers cut to 15mm width were overlapped and pressed together using a heat sealant tester (TESTERSANGYO TP-701-B) with a 20mm wide heat sealant strip at a heating temperature of 180℃, a gauge pressure of 0.2MPa, and a sealing time of 1 second. After the resulting laminate was allowed to cool naturally to room temperature, the sealing surface was peeled off by hand, and the peeled surface was visually inspected and evaluated according to the following evaluation criteria.

[0198] <Evaluation Criteria>

[0199] ○: The paper suffered material damage.

[0200] ×: The paper did not suffer material damage, but peeling occurred at the interface.

[0201] (Evaluation method for sealant material overflow during heat sealing)

[0202] The heat-sealed strips, after being crimped using the above method, were visually inspected and evaluated according to the following evaluation criteria.

[0203] <Evaluation Criteria>

[0204] ○: Resin not adhered to the heat seal strip

[0205] ×: Resin adheres to the heat seal strip

[0206] [Table 1]

[0207] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Tma 144 152 156 157 - - Tmb - - 48 107 - 119 Peak temperatures other than Tma and Tmb - - - - 165 - Based on heat-sealed adhesive properties ○ ○ ○ ○ × ○ Sealant material overflow ○ ○ ○ ○ ○ ×

[0208] The following results can be obtained from Table 1. In Examples 1 and 2, which used a P3HB3HH film with Tma as the sealant layer, and in Examples 3 and 4, which used a P3HB3HH film with both Tma and Tmb as the sealant layer, good adhesion was achieved through heat sealing, and no leakage of sealant material was observed.

[0209] On the other hand, in Comparative Example 1, which used a P3HB3HH film with a melting point peak temperature as high as 165°C as a sealant layer, although no overflow of sealant material was observed, the adhesion of the heat seal was insufficient.

[0210] In addition, in Comparative Example 2, which used a P3HB3HH film with a melting point peak as low as 119°C as the sealant layer, although the heat-sealed adhesion was good, sealant material overflow was observed.

Claims

1. A laminate comprising a substrate layer, a gas barrier layer, and a sealant layer, wherein the sealant layer is located at the most surface on one side of the laminate, the sealant layer is a resin layer comprising poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and has at least one peak top temperature (Tma) in the range of 130°C to 160°C in a crystalline melting curve obtained by differential scanning calorimetry, the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) contained in the sealant layer is composed of solely poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a proportion of 3-hydroxyhexanoate relative to the total of 3-hydroxybutyrate and 3-hydroxyhexanoate in the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) of 3 to 9 mol%, or the sealant layer contains high-crystallinity poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or a 3-hydroxybutyrate homopolymer, and low-crystallinity poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), the high-crystallinity poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) has a proportion of 3-hydroxyhexanoate relative to the total of 3-hydroxybutyrate and 3-hydroxyhexanoate of 3 mol% or less, the low-crystallinity poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) has a proportion of 3-hydroxyhexanoate relative to the total of 3-hydroxybutyrate and 3-hydroxyhexanoate of 10 to 40 mol%, and the high-crystallinity poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or the 3-hydroxybutyrate homopolymer is blended in an amount of 1 to 60% by mass relative to the total amount of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and 3-hydroxybutyrate homopolymer contained in the sealant layer.

2. The laminate according to claim 1, wherein the substrate layer has biodegradability.

3. The laminate according to claim 2, wherein the substrate layer is paper.

4. The laminate according to claim 1 or 2, wherein the gas barrier layer is at least one selected from the group consisting of a metal foil, a metal vapor deposition film, a metal oxide vapor deposition film, a silicon oxide vapor deposition film, a polyvinyl alcohol film, and an ethylene-vinyl alcohol copolymer film.

5. The laminate according to claim 1 or 2, wherein the sealant layer further has at least one peak top temperature (Tmb) in the range of 40°C or higher and lower than 130°C in a crystalline melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or higher.

6. The laminate according to claim 1 or 2, further comprising a print layer on the side opposite to the sealant layer.

7. A packaging material comprising the laminate according to claim 1 or 2.

8. The packaging material according to claim 7, comprising portions where the sealant layers are heat-sealed together.

9. A container comprising the laminate according to claim 1 or 2.

10. The container according to claim 9, comprising portions where the sealant layers are heat-sealed together. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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