Manufacturing method of laminates

Abstract

The present invention provides a method for producing a multilayer body which comprises a base material layer and a resin layer that is formed on at least one surface of the base material layer and contains a poly(3-hydroxybutyrate) resin, while having a weight (dry weight) per unit area of 15 to 50 g / m2. This method has a step in which a coating film (a) is formed by coating the surface of the base material layer with an aqueous dispersion liquid (HB-A) that contains a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a dispersant (a2), which is composed of a water-soluble polymer, relative to 100 parts by weight of the component (a1), and a coating layer (A) that has a weight (dry weight) per unit area of 0.5 to 10 g / m2 is formed by heating the coating film (a). A coating film (b) is formed by coating the coating layer (A)-side surface with an aqueous dispersion liquid (HB-B) that contains a poly(3-hydroxybutyrate) resin (b1) and 0 to 0.5 part by weight of a dispersant (b2), which is composed of a water-soluble polymer, relative to 100 parts by weight of the component (b1), and a coating layer (B) is formed by heating the coating film (b).

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate having a base layer and a resin layer containing a poly(3-hydroxybutyrate) resin on at least one side of the base layer. [Background technology]

[0002] In recent years, environmental problems caused by plastic waste have come into sharp focus. In particular, marine pollution caused by plastic waste is serious, and the widespread use of biodegradable plastics that decompose in the natural environment is highly anticipated.

[0003] While various types of biodegradable plastics are known, poly(3-hydroxybutyrate) resins, in particular, are thermoplastic polyesters that are produced and stored as energy storage substances within the cells of many microbial species. Because they can biodegrade not only in soil but also in seawater, they are attracting attention as a material that can solve the aforementioned problems.

[0004] Laminates formed by layering a poly(3-hydroxybutyrate) resin onto a biodegradable substrate such as paper are extremely promising from an environmental protection standpoint because both the resin and the substrate are materials with excellent biodegradability.

[0005] While laminates in which paper is coated with an aqueous dispersion of resin have been known for some time, a laminate containing the poly(3-hydroxybutyrate) resin has been proposed in which an aqueous dispersion containing a polyhydroxybutyrate-polyhydroxyvaleric acid copolymer, polyvinyl alcohol, and a polycarboxylate-based dispersant is coated onto a substrate and then heat-treated to obtain the laminate (see Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-222421 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the method for producing a laminate by laminating a poly(3-hydroxybutyrate) resin layer onto a substrate as described in Patent Document 1, it is necessary to use a large amount of water-soluble polymer such as polyvinyl alcohol when dispersing the poly(3-hydroxybutyrate) resin in water, which results in insufficient water resistance of the laminate.

[0008] On the other hand, the inventors' investigations revealed that when attempting to obtain a laminate with a reduced amount of water-soluble polymer-based dispersant in an aqueous dispersion, and an increased dry weight per unit area (sometimes called basis weight) of the resin layer to enhance barrier properties against water and oil, a new problem arises: the coating layer peels off from the substrate during the heat treatment after applying the aqueous dispersion.

[0009] In view of the above situation, the present invention aims to provide a manufacturing method for producing a laminate comprising a substrate and a poly(3-hydroxybutyrate) resin layer by coating a substrate with an aqueous dispersion containing a poly(3-hydroxybutyrate) resin, using an aqueous dispersion that reduces the amount of water-soluble polymer dispersant which causes a decrease in the water resistance of the resin layer, thereby enabling the formation of a resin layer with a high basis weight while suppressing peeling between the resin layer and the substrate layer, or between the coating layer and the substrate layer, during manufacturing. [Means for solving the problem]

[0010] The inventors of the present invention have found that the above problem can be solved by first applying an aqueous dispersion of poly(3-hydroxybutyrate) resin containing a specific amount of dispersant to a substrate layer to form a first layer with a specific basis weight, and then forming a second layer, thereby completing the present invention.

[0011] That is, the present invention relates to a method for producing a laminate having a base material layer and a resin layer containing a poly(3-hydroxybutyrate) resin formed on at least one side of the base material layer, the weight per unit area (dry weight) being 15 to 50 g / m 2 and including sequentially performing at least the following steps (i) and (ii). Step (i): An aqueous dispersion (HB-A) containing a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a dispersant (a2) composed of a water-soluble polymer per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1) is applied to the surface of the base material layer to form a coating film (a), and the coating film (a) is heated so that the weight per unit area (dry weight) is 0.5 to 10 g / m 2 to form a coating layer (A). Step (ii): An aqueous dispersion (HB-B) containing a poly(3-hydroxybutyrate) resin (b1) and having a content of a dispersant (b2) composed of a water-soluble polymer of 0 to 0.5 parts by weight per 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1) is applied to the surface on the coating layer (A) side to form a coating film (b), and the coating film (b) is heated to form a coating layer (B).

[0012] The present invention also relates to a laminate having a base material layer and a resin layer containing a poly(3-hydroxybutyrate) resin formed on at least one side of the base material layer, the weight per unit area (dry weight) being 15 to 50 g / m 2 and comprising a base material layer, a poly(3-hydroxybutyrate) resin (a1) and a coating layer (A) containing 0.1 to 2.0 parts by weight of a dispersant (a2) composed of a water-soluble polymer per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1) and having a weight per unit area (dry weight) of 0.5 to 10 g / m 2 and A coating layer (B) containing a poly(3-hydroxybutyrate) resin (b1) and having a content of a dispersant (b2) composed of a water-soluble polymer of 0 to 0.5 parts by weight based on 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1). Also relates to a laminate including the above in this order.

Advantages of the Invention

[0013] According to the present invention, in a method for producing a laminate including a base material and a poly(3-hydroxybutyrate) resin layer by coating the base material with an aqueous dispersion containing a poly(3-hydroxybutyrate) resin, an aqueous dispersion with a reduced amount of a water-soluble polymer-based dispersant that causes a decrease in the water resistance of the resin layer is used, and a manufacturing method capable of suppressing peeling between the coating layer and the base material layer during manufacturing and forming a resin layer with a high basis weight can be provided.

[0014] According to a preferred embodiment of the present invention, a method for producing a laminate having a resin layer with excellent water resistance on a paper base material can be provided, and by using this manufacturing method, a laminate suitable for use as a container for containing liquids such as paper cups for beverages can be provided.

Modes for Carrying Out the Invention

[0015] Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0016] (Laminate) A laminate according to an embodiment of the present invention has a base material layer and a resin layer formed on at least one side of the base material layer, and the resin layer contains a poly(3-hydroxybutyrate) resin. The resin layer is formed by applying an aqueous dispersion containing a poly(3-hydroxybutyrate) resin to the surface of the base material layer and heating and drying.

[0017] The resin layer may be laminated on only one side of the base layer, or on both sides. Furthermore, the resin layer may be laminated to the base layer via other layers, or it may be laminated directly to the base layer without any other layers. Another layer may be laminated on top of the resin layer.

[0018] (base material layer) The base layer is not particularly limited as long as it is a layer on which a resin layer can be laminated, but it is preferably a biodegradable layer. Because the base layer is a biodegradable layer, the entire laminate, including the resin layer, becomes biodegradable, making it more advantageous as a material to solve the problem of marine pollution.

[0019] Furthermore, from the viewpoint of preventing the aqueous dispersion from flowing over the surface and forming a coating film of uneven thickness, it is preferable that the substrate layer be water-absorbent.

[0020] The biodegradable substrate layer is not particularly limited, but examples include paper (whose main component is cellulose), cellophane, cellulose ester; polyvinyl alcohol, polyamino acids, polyglycolic acid, pullulan, or these substrates with inorganic materials such as aluminum or silica deposited on them. Among these, paper is preferred due to its excellent heat resistance and low cost.

[0021] The type of paper is not particularly limited and includes cup paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and cardboard. The type of paper can be appropriately selected according to the application of the laminate. Water-resistant agents, water-repellent agents, inorganic substances, etc. may be added to the paper as needed, and surface treatments such as oxygen barrier coating and water vapor barrier coating may be applied. The weight per unit area of ​​the base material (basis weight of the base material) is not particularly limited, but is generally between 50 and 400 g / m². 2 Preferably, 100-300 g / m 2 More preferably, 150-250 g / m 2This is even more preferable. By setting the basis weight of the base material within this range, it is possible to suppress curling of the laminate that may occur when the resin layer is laminated with the basis weight described later.

[0022] The substrate layer may be subjected to surface treatments such as corona treatment, flame treatment, or anchor coating. These surface treatments may be performed individually or in combination.

[0023] (Resin layer and / or coating layer) The resin layer and coating layer included in the laminate according to one embodiment of the present invention include at least a poly(3-hydroxybutyrate) resin. In this specification, the poly(3-hydroxybutyrate) resin (hereinafter also referred to as P3HB resin) is an aliphatic polyester resin containing 3-hydroxybutyrate as a repeating unit.

[0024] The P3HB resin may be a poly(3-hydroxybutyrate) having only 3-hydroxybutyrate as repeating units, or it may be a copolymer of 3-hydroxybutyrate and other hydroxyalkanoates.

[0025] The P3HB resin may be a mixture of a homopolymer and one or more copolymers, or a mixture of two or more copolymers. The form of copolymerization is not particularly limited and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc.

[0026] Examples of P3HB-type resins include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvariate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvariate-co-3-hydroxyhexanoate) (P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0027] Furthermore, by changing the composition ratio of the repeating units, the melting point and degree of crystallinity can be changed, and as a result, physical properties such as Young's modulus and heat resistance can be changed, and it is possible to impart physical properties between polypropylene and polyethylene. From the viewpoint of being easy to produce industrially and being a physically useful plastic as described above, P3HB3HH, a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred. In addition, P3HB3HH is also preferred from the viewpoint that its melting point can be lowered, enabling molding and processing at low temperatures.

[0028] In this embodiment, the P3HB resin preferably contains at least one type of P3HB3HH, and is particularly preferably containing at least two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having different proportions of constituent monomers. It is also preferable that it contains at least one type of P3HB3HH and P3HB.

[0029] P3HB resins can be produced by microorganisms. These microorganisms are not particularly limited as long as they possess the ability to produce P3HB resins. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925. Other examples include natural microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus, Ralstonia eutropha), and Alcaligenes latus. It is known that P3HB accumulates within the cells of these microorganisms.

[0030] Furthermore, known microorganisms that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T.Fukui, Y.Doi, J.Bateriol., 179, p4821-4830 (1997)), into which genes for the P3HA synthase group have been introduced, are more preferable in order to increase the productivity of P3HB3HH. Microbial cells that have accumulated P3HB3HH in their cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, genetically modified microorganisms into which various P3HB resin synthesis-related genes may be introduced may be used, depending on the P3HB resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0031] Furthermore, P3HB3HH can also be produced by methods described, for example, in International Publication No. 2010 / 013483. Examples of commercially available P3HB3HH include Kaneka Corporation's "Kaneka Biodegradable Polymer PHBH®" (registered trademark).

[0032] The composition ratio of each constituent monomer in P3HB3HH is preferably 3HB / 3HH = 95-70 / 5-30 (mol% / mol%), and more preferably 3HB / 3HH = 90-82 / 10-18 (mol% / mol%). When the composition ratio of 3HH in P3HB3HH is 5 mol% or more, the melting point can be lowered relative to the thermal decomposition temperature of the resin, which is 180°C, making it easier to suppress the thermal decomposition of the resin layer during the heating process. Furthermore, P3HB3HH with a 3HH composition ratio of 30 mol% or less does not have an excessively slow crystallization rate and is relatively easy to manufacture. The composition ratio of 3HH is determined by measuring P3HB3HH by NMR.

[0033] P3HB3HH, in which the 3HH composition ratio is 5 to 30 mol%, can be obtained by culture and may be used as a standalone P3HB-based resin, or it may be used in combination with P3HB3HH or P3HB (a homopolymer of 3HB) in which the 3HH composition ratio is less than 5 mol%. This combination makes it easier to form a resin with the melting properties described later, compared to when used alone. The 3HH composition ratio in P3HB3HH with a 3HH composition ratio of less than 5 mol% is preferably 3 mol% or less, more preferably 2 mol% or less, and even more preferably 1 mol% or less.

[0034] The amount of P3HB3HH or P3HB blended, where the composition ratio of 3HH is less than 5 mol%, is not particularly limited, but is preferably 1 to 50% by weight, more preferably 3 to 30% by weight, even more preferably 4 to 20% by weight, and particularly preferably 5 to 15% by weight relative to the total P3HB-based resin contained in the resin layer and / or the coating layer.

[0035] Microbially produced P3HB3HH is a random copolymer. The 3HH composition ratio can be adjusted, for example, by selecting the microbial cells, selecting the carbon source as the raw material, blending P3HB3HH with different 3HH composition ratios, or blending homopolymers of 3HB.

[0036] According to this embodiment, the weight-average molecular weight of the P3HB resin is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more. When the weight-average molecular weight of the P3HB resin is 100,000 or more, the mechanical strength of the resin layer and / or coating layer is high, which has the advantage that the resin layer and / or coating layer are less likely to crack even when the laminate is bent during secondary processing.

[0037] Furthermore, the weight-average molecular weight of the P3HB resin is preferably 700,000 or less, more preferably 600,000 or less, and even more preferably 550,000 or less. When the weight-average molecular weight of the P3HB resin is 700,000 or less, the melt viscosity of the resin does not become too high, fusion between resin particles proceeds easily in the heating process described later, and the occurrence of pinholes in the resin layer and / or coating layer can be suppressed.

[0038] The weight-average molecular weight of P3HB resins can be determined by gel permeation chromatography (GPC) (Showa Denko's "Shodex GPC-101") using a polystyrene gel column (Showa Denko's "Shodex K-804") with chloroform as the mobile phase, and the molecular weight converted to polystyrene equivalent.

[0039] According to this embodiment, it is preferable that the P3HB resin has melting characteristics such as having at least one peak top temperature (Tma) in the range of 100 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in the crystal melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb being 10°C or more. Because the P3HB resin has a melting point peak in the relatively high temperature range of 150 to 170°C, the resin crystals having Tmb act as crystal nuclei, which accelerates the crystallization of the P3HB resin after the heating process, making it suitable for improving the productivity of laminates. Furthermore, it is possible to reduce blocking caused by adhesion between the base layer and the resin layer, or between the base layer and the coating layer, which occurs when the laminate is continuously manufactured and wound into a roll.

[0040] The temperature difference between Tma and Tmb is 10°C or more, preferably 15°C or more, more preferably 20°C or more, and even more preferably 25°C or more. When the temperature difference is 10°C or more, blocking in the roll-shaped laminate can be further reduced. There is no particular upper limit to the temperature difference between Tma and Tmb, but from the viewpoint of ease of manufacturing, for example, it is 60°C or less, more preferably 50°C or less.

[0041] In this specification, the peak top temperature of the crystal melting curve in differential scanning calorimetry is defined as follows: 2 to 5 mg of the resin to be measured is filled into an aluminum pan, and the resin is melted using a differential scanning calorimetry analyzer under a nitrogen stream at a rate of 10°C / min from 20°C to 190°C to obtain a crystal melting curve. In the obtained crystal melting curve, the top temperature of the melting point peak in the range of 100 to 150°C is defined as Tma, and the top temperature of the melting point peak in the range of 150 to 170°C is defined as Tmb. Furthermore, if multiple melting point peaks are observed in the range of 100 to 150°C, the top temperature of the peak with the highest height is defined as Tma, and if multiple melting point peaks are observed in the range of 150 to 170°C, the top temperature of the peak with the highest height is defined as Tmb.

[0042] The resin layer and / or coating layer may contain one or more resins other than the P3HB resin, to the extent that the effects of the invention are achieved. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate, polybutylene succinate adipate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. The amount of these resins added is preferably 20 parts by weight or less per 100 parts by weight of the P3HB resin in order to ensure the biodegradability of the resin layer. The resin layer does not have to contain resins other than the P3HB resin.

[0043] The resin layer and / or the coating layer may contain additives commonly used in the technical field within the scope where the effects of the invention can be achieved. Such additives include, for example, inorganic fillers such as talc, calcium carbonate, mica, silica, titanium oxide, alumina, kaolin, etc., organic fillers such as rice husks, wood powder, waste paper such as newsprint, various starches, cellulose, etc., colorants such as pigments, dyes, etc., odor absorbers such as activated carbon, zeolite, etc., fragrances such as vanillin, dextrin, etc., plasticizers, antioxidants, anti-oxidants, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, sliding property improvers, tackifiers, fillers, drugs, etc. As the additive, only one kind may be contained, or two or more kinds may be contained. The content of these additives can be appropriately set by those skilled in the art according to the purpose of use.

[0044] According to one embodiment of the present invention, the resin layer is composed of sequentially laminating coating layers (A) and (B), or coating layers (A), (C), and (B) from the base material layer side. Each P3HB-based resin contained in these coating layers (A) and (B), or (A), (B), and (C) may be the same as or different from each other. Also, the blending of resins and additives other than the P3HB-based resin, which is an optional component, into each layer can be appropriately set by those skilled in the art according to the purpose of use.

[0045] The resin layer may have layers other than the coating layers (A), (B), and (C).

[0046] The weight per unit area of the resin layer (when the laminate has resin layers on the front and back of the base material, it refers to the total dry weight of all coating layers including the poly(3-hydroxybutyrate)-based resin, and the total dry weight of all coating layers on one side. Sometimes it is referred to as the basis weight.) is preferably 15 - 50 g / m 2 and more preferably 20 - 40 g / m 2 and particularly preferably 25 - 35 g / m 2The weight per unit area of ​​the resin layer is within the above range. This prevents defects such as pinholes, gives the resin layer sufficient strength for use, and allows functions such as water resistance to be efficiently expressed. The dry weight per unit area of ​​the resin layer is measured by the method described in the examples (method for measuring the basis weight of the resin).

[0047] (aqueous dispersion) The aqueous dispersion containing poly(3-hydroxybutyrate) resin is not particularly limited, but can be produced by the following method. First, P3HB resin is produced within the cells of microorganisms, and then the microbial cells containing the P3HB resin are crushed in an aqueous dispersion state to separate the P3HB resin from within the cells.

[0048] Generally, when recovering P3HB resin from microbial cells, methods are used such as dissolving the P3HB resin with an organic solvent such as chloroform and then precipitating and recovering the P3HB resin with a P3HB resin-insoluble solvent such as methanol or hexane. However, with this method, the resulting P3HB resin does not become fine particles, requiring an additional step to make the P3HB resin into fine particles, which is economically disadvantageous. In contrast, by crushing microbial cells containing P3HB resin in an aqueous dispersion state and separating the P3HB resin from within the cells, it is possible to obtain an aqueous dispersion of P3HB resin fine particles that maintain a considerably fine particle size for the P3HB resin produced within the microbial cells.

[0049] When separating P3HB resin from microbial cells containing P3HB resin by crushing them in an aqueous dispersion, it is preferable to crush and add alkali simultaneously while stirring the microbial cells containing P3HB resin. The advantages of this method are that (1) it prevents an increase in the viscosity of the dispersion due to microbial components other than P3HB resin leaking from the microbial cells, (2) by preventing an increase in the viscosity of the microbial dispersion, it becomes possible to control the pH and further perform treatment at a low alkali concentration by continuously or intermittently adding alkali, and (3) it is possible to suppress the decrease in molecular weight of P3HB resin and separate high-purity P3HB resin.

[0050] The pH of the bacterial cell dispersion after alkali addition is preferably between 9 and 13.5. When the pH is 9 or higher, the P3HB resin is easily separated from the bacterial cells, and when the pH is 13.5 or lower, the decomposition of the P3HB resin tends to be suppressed.

[0051] Methods for disrupting microbial cells include ultrasonic disruption, and the use of emulsifiers, homogenizers, mills, etc. Among these, it is preferable to use an emulsifier, such as a Silverson Mixer (manufactured by Silverson), Clear Mix (manufactured by M-Tech), or Ebara Milder (manufactured by Ebara Corporation), because it allows for the elution of P3HB resin from within the microbial cells through alkaline treatment, efficiently disrupting nucleic acids which are the main cause of viscosity increase, and sufficiently dispersing insoluble substances other than P3HB resin, such as cell walls, cell membranes, and insoluble proteins. However, the method is not limited to these.

[0052] Furthermore, the temperature conditions during microbial cell crushing and alkali addition are preferably within the range of room temperature to 50°C. If the above temperature conditions exceed 50°C, decomposition of the P3HB resin is more likely to occur, so temperatures near room temperature are preferable. Also, attempting to lower the temperature below room temperature would require a cooling operation, which is not economical.

[0053] A precipitate can be obtained by centrifugation from a dispersion obtained by crushing and alkaline treatment of microbial cells. This precipitate is then washed with water, and if necessary, with methanol. Finally, an appropriate amount of water is added to obtain an aqueous dispersion containing a P3HB resin with the desired solid content concentration.

[0054] A step may be taken to subject the obtained aqueous dispersion to mechanical shearing to separate the partially aggregated P3HB resin particles from each other. Applying mechanical shearing is preferable because it substantially eliminates aggregates and allows for obtaining an aqueous dispersion containing P3HB resin with a uniform particle size. Mechanical shearing of the aqueous dispersion can be performed using, for example, a stirrer, homogenizer, or ultrasound. At this point, the aggregation of P3HB resin particles is not very strong, so for simplicity, it is preferable to use a stirrer equipped with a standard stirring blade.

[0055] The solid content concentration of the P3HB resin in the aqueous dispersion is preferably 25 to 65% by weight, more preferably 30 to 55% by weight, and particularly preferably 35 to 50% by weight. When the solid content concentration of the P3HB resin in the aqueous dispersion is within the above range, the viscosity of the aqueous dispersion is not too high, uniform application is possible, and the required film thickness can be maintained, resulting in the effect of minimizing defects in the coating film.

[0056] Furthermore, the solid content concentrations of the P3HB resin in each aqueous dispersion may be the same or different, and can be appropriately set by those skilled in the art depending on the intended use.

[0057] The average particle size of the P3HB resin in the aqueous dispersion is, for example, 0.1 to 50 μm, preferably 0.5 to 30 μm, and more preferably 0.8 to 20 μm, from the viewpoint of achieving both productivity of the P3HB resin and uniformity during coating. An average particle size of 0.1 μm or more allows for easy acquisition of the P3HB resin by either microbial production or chemical synthesis methods. An average particle size of 50 μm or less helps to avoid uneven coating. The average particle size of the P3HB resin in the aqueous dispersion can be calculated using a general-purpose particle size analyzer such as a Microtrac particle size analyzer (manufactured by Nikkiso, FRA), by adjusting the aqueous dispersion containing the P3HB resin to a predetermined concentration and determining the particle size corresponding to the 50% accumulation of all particles in a normal distribution.

[0058] Examples of water-soluble polymer dispersants usable in this embodiment include polyvinyl alcohol derivatives such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonated polyvinyl alcohol, and ethylene-modified polyvinyl alcohol; cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose; starch derivatives such as starch, oxidized starch, or etherified starch; chitin, chitosan, casein, and gum arabic. These can be used individually or in combination of two or more.

[0059] The amount of water-soluble polymer dispersant (a2) used in the aqueous dispersion of poly(3-hydroxybutyrate) resin (HB-A) is preferably 0.1 to 2.0 parts by weight, more preferably 0.3 to 1.8 parts by weight, and particularly preferably 1.0 to 1.5 parts by weight, per 100 parts by weight of poly(3-hydroxybutyrate) resin (a1) contained in the aqueous dispersion (HB-A). By setting the amount within this range, it is possible to suppress the peeling of the coating layer (A) from the substrate layer during heat treatment after application of the aqueous dispersion (HB-A), and to maintain good adhesion strength between the substrate layer and the poly(3-hydroxybutyrate) resin after heat treatment.

[0060] The aqueous dispersion of poly(3-hydroxybutyrate) resin (HB-B) does not necessarily have to contain substantially no water-soluble polymer dispersant (b2), but it may contain water-soluble polymer dispersant (b2) to the extent that it does not impair the water resistance of the coating layer (B) in order to suppress aggregation of the poly(3-hydroxybutyrate) resin (b1) contained in the aqueous dispersion (HB-B) and stabilize the dispersion.

[0061] The amount of water-soluble polymer dispersant (b2) used is preferably 0 to 0.5 parts by weight per 100 parts by weight of poly(3-hydroxybutyrate) resin (b1) contained in the aqueous dispersion (HB-B). By keeping it within this range, the amount of aqueous dispersion (HB-B) applied can be increased without impairing the water resistance of the coating layer (B), and the basis weight of the coating layer (B) and the resin layer can be increased. When using water-soluble polymer dispersant (b2), the amount used is preferably 0.1 to 0.5 parts by weight. The upper limit may be 0.4 parts by weight or less, or 0.3 parts by weight or less. Furthermore, in this application, "substantially free of water-soluble polymer dispersants" means that water-soluble polymer dispersants are not added in order to obtain the effect of stabilizing the dispersion of the resin.

[0062] The aqueous dispersion (HB-A) and / or (HB-B) may optionally contain a dispersant other than a water-soluble polymer. The type of dispersant other than the water-soluble polymer is not particularly limited, but examples include anionic surfactants such as sodium lauryl sulfate and sodium oleate, cationic surfactants such as lauryltrimethylammonium chloride, and nonionic surfactants such as glycerin fatty acid esters and sorbitan fatty acid esters. These can be used individually or in combination of two or more types.

[0063] The poly(3-hydroxybutyrate) resin aqueous dispersion (HB-C) is an aqueous dispersion that forms a coating layer (C) which is an intermediate layer between the coating layer (A) and the coating layer (B). The dispersant contained in the aqueous dispersion (HB-C) may be the same as or different from the dispersant contained in the aqueous dispersions (HB-A) and (HB-B), and can be appropriately selected according to the coating method.

[0064] The aforementioned dispersant can be added to an aqueous dispersion after crushing and alkaline treatment of microbial cells, followed by centrifugation and washing with water. If methanol washing is performed, the dispersant can be added before or after adjusting the solid content concentration of the P3HB resin by adding an appropriate amount of water after methanol washing.

[0065] (Method of manufacturing a laminate) In one embodiment of this product, the manufacturing method involves applying the aqueous dispersion (HB-A) to one or both sides of a substrate layer, heating and drying to form a film, thereby forming a first coating layer (A), and then applying the aqueous dispersion (HB-B) again, heating and drying to form a film, thereby forming a coating layer (B). By forming the resin layers in multiple steps in this manner, it becomes easy to form a water-resistant coating layer (B) on the outermost surface while suppressing peeling between the substrate and the resin layer.

[0066] The weight per unit area (dry weight: basis weight) of the coating layer (A) is 0.5 to 10 g / m². 2 Preferably, it is 1-8 g / m 2 More preferably, 3-7 g / m 2 This is particularly preferable. By forming a coating layer with a relatively low basis weight on the substrate surface in this way, and then forming coating layer (B) (or (B) and (C)), it becomes possible to form a resin layer with a high overall basis weight while suppressing peeling between the resin layer and the substrate layer.

[0067] The basis weight of the coating layer (A) is 0.5 g / m². 2 If the amount is less than 10 g / m², the thickness of the coating layer (A) becomes uneven, and the coating layer (B) tends to peel off from the substrate when the aqueous dispersion (HB-B) is applied and the heat treatment described later is performed. On the other hand, 10 g / m² 2 Beyond a certain point, the adhesion strength between the coating layer (A) and the substrate tends to weaken.

[0068] The weight per unit area (dry weight: basis weight) of coating layer (B) is calculated by considering the weight per unit area of ​​coating layer (A), and the weight per unit area of ​​the resin layer is 15-50 g / m². 2 You should adjust the settings accordingly. The weight per unit area of ​​the resin layer should be 50g / m². 2 Beyond this point, it becomes not only uneconomical, but the resin melts insufficiently, making it difficult to form a uniform resin layer.

[0069] In another embodiment of this model, the manufacturing method can also be carried out by forming the coating layer (A) on one or both sides of the substrate layer, then applying an aqueous dispersion (HB-C) containing a poly(3-hydroxybutyrate) resin (c1), heating and drying to form a film, thereby forming a coating layer (C) as an intermediate layer, and then forming the coating layer (B). By providing the coating layer (C) as an intermediate layer, the occurrence of pinholes is further suppressed, and it becomes easier to ensure the barrier properties of the resin layer against water and oil.

[0070] The weight per unit area (dry weight: basis weight) of the coating layer (C) is 5-10 g / m². 2 This is preferable. The coating layer (C) may be formed by repeatedly applying an aqueous dispersion (HB-C), drying by heating, and forming a film multiple times.

[0071] The method of applying each aqueous dispersion to the substrate is not particularly limited as long as a desired coating layer is substantially formed on the substrate. For example, known methods such as spraying, application, slit coater, air knife coater, roll coater, bar coater, comma coater, blade coater, screen printing, and gravure printing can be used individually or in combination. Before applying the aqueous dispersion (HB-A), the substrate may be subjected to a surface treatment such as the corona treatment described above.

[0072] Each coating layer is formed by heating each coating film, which has been formed on the substrate by applying each aqueous dispersion, to a temperature above the melting point of the P3HB resin, thereby evaporating the water and fusing the P3HB resin particles contained in the aqueous dispersion together. The melting point of the P3HB resin mentioned above refers to the peak top temperature of the highest temperature in the crystal melting curve in the differential scanning calorimetry. For example, if Tma and Tmb are present, it refers to Tmb.

[0073] This heat treatment can be carried out using known heating methods, such as hot air heating, infrared heating, microwave heating, roll heating, and hot plate heating, which can be used individually or in combination of two or more.

[0074] The heating temperature in the heat treatment should be above the melting point of the P3HB resin, but it is preferably 10 to 40°C above the melting point of the P3HB resin, and more preferably 20 to 30°C above. Specifically, the heating temperature is preferably 160°C or higher, more preferably 165°C or higher, and particularly preferably 170°C or higher. Furthermore, the heating temperature is preferably 200°C or lower. By setting the heating temperature to 200°C or lower, it is possible to avoid problems such as a decrease in the mechanical strength of the laminate and breakage caused by excessive drying of the base layer or thermal decomposition of the P3HB resin. Note that the heating temperature in the heat treatment refers not to the actual temperature of the laminate, but to the set temperature of the equipment used in the heat treatment, such as the drying oven or rolls.

[0075] The heating time in the heat treatment can be set appropriately considering the drying of the coating film and the melting state of the resin, but it is preferably 3 seconds to 3 minutes, more preferably 5 to 60 seconds, and even more preferably 10 to 30 seconds.

[0076] After heat treatment, it is preferable to perform a heat retention treatment at a temperature below the melting point of the P3HB resin. The heat retention temperature is preferably 35 to 70°C, and more preferably 40 to 60°C. By maintaining the temperature at this level, the crystallization of the P3HB resin after heat treatment is accelerated, which is suitable for improving the productivity of laminates. Furthermore, it is possible to reduce blocking caused by adhesion between the base layer and the resin layer, or between the base layer and the coating layer, which occurs when the laminates are continuously manufactured and wound into a roll.

[0077] This heat retention treatment can be carried out using the same heating methods as the aforementioned heat treatment, such as hot air heating, infrared heating, microwave heating, roll heating, and hot plate heating, which can be used individually or in combination of two or more types. In particular, in order to make the surface properties of the resin layer uniform, it is preferable to use a roll adjusted to a specific temperature and bring the resin coated surface into contact with the roll, and furthermore, to provide a roll on the base layer side as well, sandwiching the laminate from both sides. Note that the heat retention temperature in the heat retention process refers not to the actual temperature of the laminate, but to the set temperature of the equipment used in the heat retention process, such as the drying oven or rolls.

[0078] The processing time for the heat retention treatment can be set appropriately considering the effects of the heat retention treatment, but it is preferably 3 seconds to 1 minute, more preferably 5 to 30 seconds, and even more preferably 10 to 20 seconds.

[0079] If the substrate is paper, the moisture content of the paper substrate may be adjusted as needed by applying water to the paper substrate after heat treatment and any heat retention treatment, a so-called humidity control treatment. Planarization treatment using a machine calender or soft calender may also be performed in conjunction with this.

[0080] The method for applying water to a paper substrate is not particularly limited as long as it can be applied uniformly to the paper substrate. For example, known methods such as spraying, scattering, slit coater, air knife coater, roll coater, bar coater, comma coater, blade coater, screen printing, and gravure printing can be used individually or in combination. Among these, the spraying method is preferred because it can be applied uniformly and evenly with a small amount of water. Water spraying can be carried out, for example, using a commercially available liquid coating device characterized by non-contact coating. Furthermore, water may contain additives such as humectants like glycerin and propylene glycol, various fragrances, and preservatives, to the extent that it does not impair its purpose.

[0081] The series of steps for forming the coating layer may be carried out on a substrate that has been cut into a plate shape in advance, or the substrate may be prepared as a roll and carried out continuously while being continuously fed and conveyed using a general sheet, film, paper, or other conveying device.

[0082] (Application) The laminate obtained by this embodiment can be molded into various types of molded articles by secondary processing. Examples of such molded articles include tubes, plates, rods, packaging materials (e.g., bags), containers (e.g., bottles), and parts. In particular, the molded articles can be suitably used as various packaging container materials such as shopping bags, various types of bags, food and confectionery packaging materials, cups, trays, and cartons (in other words, in various fields such as food, cosmetics, electronics, medical, and pharmaceuticals). Furthermore, since the molded articles have a resin layer formed on one side of the paper substrate that has high adhesion to the substrate and good heat resistance, they can be particularly suitably used as containers for liquids, especially food and beverage cups for instant noodles, instant soup, coffee, etc., and trays used for prepared foods, bento boxes, microwaveable foods, etc., as containers for hot contents.

[0083] The aforementioned secondary processing can be carried out using any method known in the art, such as various bag-making machines, filling and packaging machines, etc. Alternatively, processing can be done using equipment such as paper tray press molding machines, paper cup molding machines, die-cutting machines, and box presses. When bonding the laminates using these processing machines, known techniques can be used, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing. The heat sealing may be performed between the substrate layer and the resin layer, or between the resin layers themselves.

[0084] The aforementioned molded article may also be compounded with another molded article made of a different material (for example, fibers, yarn, rope, fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, board, rod, container, bag, part, foam, etc.) in order to improve its physical properties. These materials are also preferably biodegradable.

[0085] The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A base layer and a poly(3-hydroxybutyrate) resin formed on at least one side of the base layer, with a weight (dry weight) per unit area of ​​15 to 50 g / m². 2 A method for manufacturing a laminate having a resin layer, comprising sequentially performing at least the following steps (i) and (ii). Process (i): A coating film (a) is formed by applying an aqueous dispersion (HB-A) containing a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a water-soluble polymer dispersant (a2) per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1) to the surface of the substrate layer, and then heating the coating film (a) to obtain a weight per unit area (dry weight) of 0.5 to 10 g / m². 2 Step of forming a coating layer (A) Step (ii): The process involves applying an aqueous dispersion (HB-B) containing a poly(3-hydroxybutyrate) resin (b1), wherein the content of a dispersant (b2) made of a water-soluble polymer is 0 to 0.5 parts by weight per 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1) to the surface of the coating layer (A) to form a coating film (b), and then heating the coating film (b) to form the coating layer (B). [Item 2] The method for producing the poly(3-hydroxybutyrate) resin (a1) and (b1) according to item 1, wherein at least one of them has a weight-average molecular weight of 100,000 to 700,000. [Item 3] The manufacturing method according to item 1 or 2, wherein at least one of the poly(3-hydroxybutyrate) resins (a1) and (b1) has at least one peak top temperature (Tma) in the range of 100 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in the crystal melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or more. [Item 4] The manufacturing method according to any one of items 1 to 3, wherein at least one of the poly(3-hydroxybutyrate) resins (a1) and (b1) comprises at least one type of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). [Item 5] The manufacturing method according to any one of items 1 to 4, wherein at least one of the aqueous dispersions (HB-A) and (HB-B) has a solid content concentration of the poly(3-hydroxybutyrate) resin (a1) or (b1) of 25 to 65% by weight. [Item 6] A manufacturing method according to any one of items 1 to 5, further comprising the following step (iii) between step (i) and step (ii). Step (iii): The process involves applying an aqueous dispersion (HB-C) containing a poly(3-hydroxybutyrate) resin (c1) to the surface of the coating layer (A) to form a coating film (c), and then heating the coating film (c) to form a coating layer (C). [Item 7] The manufacturing method according to item 6, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) has a weight-average molecular weight of 100,000 to 700,000. [Item 8] The manufacturing method according to item 6 or 7, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) has at least one peak top temperature (Tma) in the range of 100 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in the crystal melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or more. [Item 9] The manufacturing method according to any one of items 6 to 8, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) comprises at least one type of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). [Item 10] The manufacturing method according to any one of items 6 to 9, wherein at least one of the aqueous dispersions (HB-A), (HB-B), and (HB-C) has a solid content concentration of 25 to 65% by weight of the poly(3-hydroxybutyrate) resin (a1), (b1), or (c1). [Item 11] The manufacturing method according to any one of items 1 to 10, wherein the base material layer is biodegradable. [Item 12] The manufacturing method according to item 11, wherein the base material layer is paper. [Item 13] A base layer and a poly(3-hydroxybutyrate) resin formed on at least one side of the base layer, with a weight (dry weight) per unit area of ​​15 to 50 g / m². 2 A laminate having a resin layer, base material layer, The material contains a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a water-soluble polymer dispersant (a2) per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1), with a weight per unit area (dry weight) of 0.5 to 10 g / m². 2 The coating layer (A), and A coating layer (B) comprising a poly(3-hydroxybutyrate) resin (b1), wherein the content of a dispersant (b2) consisting of a water-soluble polymer is 0 to 0.5 parts by weight per 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1), A laminate containing these elements in this order. [Item 14] The laminate according to item 13, further comprising a coating layer (C) containing a poly(3-hydroxybutyrate) resin (c1) between the coating layer (A) and the coating layer (B). [Item 15] A molded body comprising the laminate described in item 13 or 14. [Item 16] The molded body according to item 15, wherein the molded body is a container for food and beverages. [Examples]

[0086] The present invention will be described in detail below based on examples, but the technical scope of the present invention is not limited by these examples.

[0087] (Method for measuring resin basis weight) The laminates obtained in each example and comparative example were cut into 10cm x 10cm sections, their weight was measured, and the weight of the base material was subtracted from this weight and multiplied by 100 to obtain the resin basis weight (dry weight per unit area of ​​the resin layer or coating layer).

[0088] (Adhesion between the base material (paper) and the resin layer) The adhesion between the substrate layer and the resin layer was evaluated for the laminates obtained in each example and comparative example according to the following criteria. For the cross-cut evaluation within the evaluation criteria, a 30 mm long cross-cut was made in the resin layer with a utility knife, cellophane tape (registered trademark, model number: Nichiban, CT-18) was applied to the cut surface and peeled off by hand to evaluate the peel strength of the resin layer from the substrate layer. <Rating> ◎: The resin layer does not peel off from the substrate after heat treatment, but paper fibers adhere to the resin layer when it is peeled off by cross-cut evaluation. ○: The resin layer does not peel off from the substrate after heat treatment, and although there is resistance when peeling off the resin layer in a cross-cut evaluation, no paper fibers adhere to the resin layer. ×: After heat treatment, the resin layer has peeled off from the substrate, and cracks have appeared across the entire resin layer.

[0089] (Method for producing P3HB3HH aqueous dispersion) Following the method described in International Publication No. 2015 / 146195, an aqueous dispersion containing 50% by weight of P3HB3HH was obtained, which has a 3-hydroxyhexanoate unit content of 11 mol% (weight-average molecular weight of 550,000), a top melting point peak temperature Tma in the range of 100-150°C of 110°C, and a top melting point peak temperature Tmb in the range of 150-170°C of 160°C. Tma and Tmb were measured by filling an aluminum pan with 2-5 mg of the dried material obtained by drying the resulting aqueous dispersion in a hot air dryer at 60°C, and then melting the dried material by heating it from 20°C to 190°C at a rate of 10°C / min under a nitrogen stream using a differential scanning calorimetry analyzer.

[0090] (Method for producing aqueous dispersion) HB-A1, HB-B2: For every 100 parts by weight of resin contained in the P3HB3HH aqueous dispersion, methylcellulose (Metholose SM-400, manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a water-soluble polymer dispersant to a total of 0.3 parts by weight. This mixture was then stirred with water to obtain an aqueous dispersion containing 40% by weight of solids (39.9% by weight of P3HB3HH) from the combined P3HB3HH and dispersant. HB-A2 was prepared in the same manner as HB-A1, except that 1.0 part by weight of methylcellulose was added to 100 parts by weight of P3HB3HH resin, to obtain an aqueous dispersion containing a combined solid content of 40% by weight (39.6% by weight of P3HB3HH) of P3HB3HH and dispersant. HB-A3 and HB-C1 were prepared in the same manner as HB-A1, except that 1.5 parts by weight of methylcellulose was added to 100 parts by weight of P3HB3HH resin, to obtain an aqueous dispersion containing a combined solid content of 40% by weight (39.4% by weight of P3HB3HH) of P3HB3HH and dispersant. HB-B1: Water was added to the P3HB3HH aqueous dispersion to obtain an aqueous dispersion containing 40% by weight of solids of P3HB3HH.

[0091] [Example 1] Weight: 200g / m 2 On one side of the cup base paper, the resin basis weight after drying is 3g / m². 2 After applying the aqueous dispersion HB-A1 using a bar coater, the coating layer (A) was formed by heating it in a hot air drying oven set to 180°C for 1 minute. Then, on top of the coating layer (A), a resin weight of 15 g / m² after drying was applied. 2 After applying the aqueous dispersion HB-B1 using a bar coater, the material was heated in a hot air drying oven set to 180°C for 2 minutes to form the coating layer (B), completing the formation of the resin layer. The adhesion between the substrate (paper) and the resin layer of the resulting laminate was evaluated. The results are shown in Table 1.

[0092] [Examples 2-4] Except for the types of aqueous dispersions used to form coating layers (A) and (B) and the amount of resin after drying being as described in Examples 2 to 4 of Table 1, the procedure was the same as in Example 1 to obtain laminates, and the adhesion between the substrate (paper) and the resin layer of the obtained laminates was evaluated. The results are shown in Table 1.

[0093] [Example 5] Weight: 200g / m 2 On one side of the cup base paper, the resin basis weight after drying is 1g / m². 2 After applying the aqueous dispersion HB-A3 using a bar coater, the coating layer (A) was formed by heating it in a hot air drying oven set to 180°C for 30 seconds. Next, on top of the coating layer (A), a resin weight of 10 g / m² after drying was applied. 2 After applying the aqueous dispersion HB-C1 using a bar coater, the mixture was heated in a hot air drying oven set to 180°C for 1 minute to form a coating layer (C). Furthermore, on top of the coating layer (C), a resin basis weight of 25 g / m² after drying was applied. 2 The aqueous dispersion HB-B2 was applied using a bar coater, and the resin layer was completed by heating in a 180°C hot air drying oven for 2 minutes. The adhesion between the substrate (paper) and the resin layer of the resulting laminate was evaluated. The results are shown in Table 1.

[0094] [Comparative Example 1] Weight: 200g / m 2 On one side of the cup base paper, the resin basis weight after drying is 15g / m². 2 After applying the aqueous dispersion HB-B1 using a bar coater, the resin layer was formed by heating in a hot air drying oven set to 180°C for 2 minutes. The adhesion between the substrate (paper) and the resin layer of the resulting laminate was evaluated. The results are shown in Table 1.

[0095] [Comparative Example 2] Using aqueous dispersion HB-B2, the resin basis weight after drying was 25 g / m². 2 The laminate was obtained by performing the same procedure as in Comparative Example 1, except for the following adjustments, and the adhesion between the substrate (paper) and the resin layer was evaluated. The results are shown in Table 1.

[0096] [Table 1]

[0097] 〔result〕 As shown in Table 1, in Examples 1 to 5, where a coating layer (A) with a predetermined basis weight was pre-applied to the paper substrate, peeling of the resin layer after heat treatment of the coating film was suppressed, and laminates with a resin layer with a high basis weight were manufactured.

[0098] On the other hand, in Comparative Examples 1 and 2, where a resin layer with a high basis weight was formed in a single step, peeling of the resin layer from the substrate layer occurred, and cracks developed across the entire resin layer. Poly(3-hydroxybutyrate) resins have low affinity for other materials, and it is presumed that if a high basis weight resin is applied directly to the substrate layer without first forming a low basis weight coating layer (A) as in the example, the resin will not wet and spread on the substrate during the heat treatment, and instead, aggregation and fusion of resin particles will occur first, leading to peeling of the resin layer.

Claims

1. A base layer and a poly(3-hydroxybutyrate) resin formed on at least one side of the base layer, with a weight (dry weight) per unit area of ​​15 to 50 g / m². ２ A method for manufacturing a laminate having a resin layer, comprising sequentially performing at least the following steps (i) and (ii). Process (i): A coating film (a) is formed by applying an aqueous dispersion (HB-A) containing a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a water-soluble polymer dispersant (a2) per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1) to the surface of a substrate layer, and then heating the coating film (a) to obtain a weight per unit area (dry weight) of 0.5 to 10 g / m². ２ Step of forming a coating layer (A) Step (ii): The process involves applying an aqueous dispersion (HB-B) containing a poly(3-hydroxybutyrate) resin (b1), wherein the content of a dispersant (b2) made of a water-soluble polymer is 0 to 0.5 parts by weight per 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1) to the surface of the coating layer (A) to form a coating film (b), and then heating the coating film (b) to form the coating layer (B).

2. The manufacturing method according to claim 1, wherein at least one of the poly(3-hydroxybutyrate) resins (a1) and (b1) has a weight-average molecular weight of 100,000 to 700,000.

3. The manufacturing method according to claim 1 or 2, wherein at least one of the poly(3-hydroxybutyrate) resins (a1) and (b1) has at least one peak top temperature (Tma) in the range of 100 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in the crystal melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or more.

4. The manufacturing method according to claim 1 or 2, wherein at least one of the poly(3-hydroxybutyrate) resins (a1) and (b1) comprises at least one type of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

5. The manufacturing method according to claim 1 or 2, wherein at least one of the aqueous dispersions (HB-A) and (HB-B) has a solid content concentration of the poly(3-hydroxybutyrate) resin (a1) or (b1) of 25 to 65% by weight.

6. The manufacturing method according to claim 1, further comprising the following step (iii) between step (i) and step (ii). Step (iii): The process involves applying an aqueous dispersion (HB-C) containing a poly(3-hydroxybutyrate) resin (c1) to the surface of the coating layer (A) to form a coating film (c), and then heating the coating film (c) to form a coating layer (C).

7. The manufacturing method according to claim 6, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) has a weight-average molecular weight of 100,000 to 700,000.

8. The manufacturing method according to claim 6 or 7, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) has at least one peak top temperature (Tma) in the range of 100 to 150°C and at least one peak top temperature (Tmb) in the range of 150 to 170°C in the crystal melting curve obtained by differential scanning calorimetry, and the temperature difference between Tma and Tmb is 10°C or more.

9. The manufacturing method according to claim 6 or 7, wherein at least one of the poly(3-hydroxybutyrate) resins (a1), (b1), and (c1) comprises at least one type of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

10. The manufacturing method according to claim 6 or 7, wherein at least one of the aqueous dispersions (HB-A), (HB-B), and (HB-C) has a solid content concentration of the poly(3-hydroxybutyrate) resin (a1), (b1), or (c1) of 25 to 65% by weight.

11. The manufacturing method according to claim 1 or 6, wherein the base material layer is biodegradable.

12. The manufacturing method according to claim 11, wherein the base material layer is paper.

13. A base layer and a poly(3-hydroxybutyrate) resin formed on at least one side of the base layer, with a weight (dry weight) per unit area of ​​15 to 50 g / m². ２ A laminate having a resin layer, base material layer, The material contains a poly(3-hydroxybutyrate) resin (a1) and 0.1 to 2.0 parts by weight of a water-soluble polymer dispersant (a2) per 100 parts by weight of the poly(3-hydroxybutyrate) resin (a1), with a weight per unit area (dry weight) of 0.5 to 10 g / m². ２ The coating layer (A), and A coating layer (B) comprising a poly(3-hydroxybutyrate) resin (b1), wherein the content of a dispersant (b2) consisting of a water-soluble polymer is 0 to 0.5 parts by weight per 100 parts by weight of the poly(3-hydroxybutyrate) resin (b1), A laminate containing these elements in this order.

14. The laminate according to claim 13, further comprising a coating layer (C) containing a poly(3-hydroxybutyrate) resin (c1) between the coating layer (A) and the coating layer (B).

15. A molded article comprising the laminate described in claim 13 or 14.

16. The molded body according to claim 15, wherein the molded body is a container for food and beverages.

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