Manufacturing method of laminate

Abstract

To provide a method for manufacturing a biodegradable laminate including a paper base material layer and a resin layer, which suppresses blocking to a cooling roll of a P3HA-based resin and is excellent in adhesion between the paper base material layer and the P3HA-based resin layer, during manufacture of the laminate.SOLUTION: A method for manufacturing a laminate that is a method for manufacturing a laminate including a paper base material layer and a resin layer, includes: a step (step A) of forming a layer containing a first resin (A) on at least one surface of the paper base material layer; and a step (step B) of forming a layer containing a poly(3-hydroxybutyrate)-based resin (B) on the surface of the layer containing the first resin (A) by extrusion lamination or thermal lamination.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate having a paper substrate layer and a layer containing a poly(3-hydroxybutyrate) resin, and to the laminate. [Background technology]

[0002] In recent years, environmental problems caused by discarded plastics have been attracting attention. In particular, marine pollution caused by discarded plastics is serious, and there are high hopes for the widespread use of biodegradable plastics that decompose in the natural environment.

[0003] Various types of biodegradable plastics are known, but one in particular is poly(3-hydroxybutyrate) resin (hereinafter referred to as "P3HA resin"). This thermoplastic polyester is produced and accumulated as an energy storage substance within the cells of many microbial species, and is a material that can biodegrade not only in soil but also in seawater, so it is attracting attention as a material that can solve the above problems.

[0004] Laminated paper, which is produced by laminating such P3HA-based resin onto a paper substrate, is an extremely promising laminated paper from the perspective of environmental protection, as both the paper and the P3HA-based resin are environmentally degradable materials.

[0005] Generally, laminated paper is produced by laminating a paper substrate and a resin material using extrusion lamination or thermal lamination. However, P3HA-based resins tend to adhere to cooling rolls during lamination due to the resin's solidification speed, leaving room for improvement in terms of peelability from the roll. Furthermore, because of poor peelability from the roll, there is also room for improvement in terms of continuous lamination over long periods of time.

[0006] Patent Document 1 describes how blocking on a cooling roll can be prevented by co-extruding a P3HA-based resin and a polycondensation polyester of dicarboxylic acid and glycol, which has good processability, onto a paper substrate to produce a three-layer biodegradable laminate with the polycondensation polyester as the outermost layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-6444 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method of Patent Document 1 leaves room for improvement in practicality, as it is difficult to obtain adhesion between the paper substrate and the P3HA-based resin.In addition, the polycondensed polyester of the outer layer is generally less biodegradable than the P3HA-based resin, so there is also room for improvement in terms of environmental degradability. In view of the above-mentioned current situation, the present invention aims to provide a method for producing a biodegradable laminate comprising a paper base layer and a resin layer, which method suppresses blocking of the P3HA-based resin against a cooling roll during laminate production and has excellent adhesion between the paper base layer and the P3HA-based resin layer. [Means for solving the problem]

[0009] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that in a method for manufacturing a laminate, the above-mentioned problems can be solved by laminating and adhering a P3HA-based resin onto a layer containing a first resin that has been pre-formed on the surface of a paper base layer while heating, and thus completed the present invention.

[0010] That is, the present invention provides a method for producing a laminate including a paper base layer and a resin layer, A step (step A) of forming a layer containing a first resin (A) on at least one surface of a paper substrate layer; and The present invention relates to a method for producing a laminate, which includes a step (step B) of forming a layer containing a poly(3-hydroxybutyrate)-based resin (B) on the surface of the layer containing the first resin (A) by extrusion lamination or thermal lamination.

[0011] Preferably, in the step of forming the layer containing the poly(3-hydroxybutyrate)-based resin (B), the layer is formed by extrusion lamination or thermal lamination at a temperature equal to or higher than the melting point of the resin material containing the poly(3-hydroxybutyrate)-based resin (B) and lower than a temperature 30°C higher than the melting point.

[0012] Preferably, the layer containing the first resin (A) has an average thickness of 0.75 to 20 μm. Preferably, the layer containing the poly(3-hydroxybutyrate) resin (B) has an average thickness of 25 to 50 μm. Preferably, the first resin (A) is at least one selected from polycaprolactone, polybutylene succinate adipate, and poly(3-hydroxybutyrate)-based resins (A-1).

[0013] Preferably, the step of forming the layer containing the first resin (A) is a step of applying an aqueous coating liquid containing the poly(3-hydroxybutyrate)-based resin (A-1) to a paper substrate to form a coating film. Preferably, the poly(3-hydroxybutyrate)-based resin (B) is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units (BH). Preferably, the average content of the 3-hydroxyhexanoate unit (BH) is 3 to 20 mol %.

[0014] Preferably, the poly(3-hydroxybutyrate)-based resin (A) is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units (AH). Preferably, the average content of the 3-hydroxyhexanoate unit (AH) is 6 to 25 mol %.

[0015] The present invention also provides a laminate in which a paper substrate layer, a layer containing a first resin (A), and a layer containing a poly(3-hydroxybutyrate)-based resin (B) are laminated in this order, The present invention also relates to a laminate in which the layer containing the first biodegradable resin (A) is in contact with the paper substrate layer and the layer containing the poly(3-hydroxybutyrate)-based resin (B).

[0016] The present invention also relates to a molded article comprising the laminate. [Effects of the Invention]

[0017] According to the present invention, in a method for producing a laminate including a paper base layer and a resin layer, blocking of the P3HA-based resin against a cooling roll during laminate production can be suppressed, and a method for producing a biodegradable laminate with excellent adhesion between the paper base layer and the P3HA-based resin layer can be provided.When a laminate produced by the production method of the present invention is used, peeling between the paper base layer and the P3HA-based resin layer is unlikely to occur after heat sealing, making it possible to improve the production efficiency and quality of molded products. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0019] [Laminate] A laminate according to one embodiment of the present invention comprises a paper substrate layer, a layer containing a first resin (A) (hereinafter sometimes referred to as the "first resin (A) layer"), and a layer containing a poly(3-hydroxybutyrate)-based resin (B) (hereinafter sometimes referred to as the "P3HB-based resin (B) layer"). The paper substrate layer, the first resin (A) layer, and the P3HB-based resin (B) layer are laminated in this order, and the P3HB-based resin (B) layer is formed in contact with the surface of the first resin (A) layer.

[0020] (Paper base layer) The paper substrate layer according to the present invention is not particularly limited as long as it is biodegradable, and examples thereof include kraft paper, cup base paper, fine paper, coated paper, tissue paper, glassine paper, paperboard, cellophane cellulose ester, and the like. The paper substrate layer may contain a water-resistant agent, a water-repellent agent, an inorganic substance, etc., as required. The surface of the paper base layer may also be subjected to a surface treatment such as corona treatment, ozone treatment, plasma treatment, frame treatment, anchor coat treatment, oxygen barrier layer coating, or water vapor barrier coating. These surface treatments may be performed alone or in combination.

[0021] (1st resin (A) layer) The first resin (A) layer according to the present invention may be laminated on only one side or both sides of the paper substrate layer. The first resin (A) layer may be laminated on the paper substrate layer via another layer, or may be laminated directly on the paper substrate layer without another layer.

[0022] The first resin (A) is not particularly limited as long as it is a biodegradable resin that can be bonded to the P3HB resin (B) layer described below by heating, and examples thereof include polycaprolactone, polybutylene succinate adipate, and poly(3-hydroxybutyrate) resin (P3HB resin (A-1)).

[0023] In particular, P3HB resin (A-1) is preferably used because it is easy to bond the P3HB resin (B) layer by heating. The P3HB resin (A-1) of the present invention may be the same as or different from the P3HB resin (B). Furthermore, one type of poly(3-hydroxybutyrate) resin may be used, or multiple poly(3-hydroxybutyrate) resins may be used in combination.

[0024] When a P3HB-based resin (A-1) is used in the first resin (A) layer, it is preferable that the P3HB-based resin (A-1) content be 60 wt % or more of the total weight of the first resin (A) layer, as this makes it easier to adhere the P3HB-based resin (B) layer.

[0025] The poly(3-hydroxybutyrate)-based resin (A-1) is an aliphatic polyester resin that can be produced from a microorganism and contains 3-hydroxybutyrate as a repeating unit. The P3HB-based resin (A-1) may be a poly(3-hydroxybutyrate) containing only 3-hydroxybutyrate as a repeating unit, or may be a copolymer of 3-hydroxybutyrate and another hydroxyalkanoate.

[0026] The P3HB resin (A-1) may be a mixture of a homopolymer and one or more copolymers, or a mixture of two or more copolymers. The copolymerization method is not particularly limited and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, or the like. Examples of the P3HB resin (A-1) include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (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-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0027] Furthermore, P3HB3HH(AH), a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred because changing the composition ratio of the repeating units can change the melting point and crystallinity, thereby changing physical properties such as Young's modulus and heat resistance, and it can impart physical properties between those of polypropylene and polyethylene. Furthermore, P3HB3HH(AH) is also preferred because it can lower the melting point and enable molding at low temperatures.

[0028] In one embodiment of the present invention, the P3HB-based resin (A-1) preferably contains at least one type of P3HB3HH(AH), and particularly preferably contains at least two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with different monomer content ratios. It is also preferable to contain at least one type of P3HB3HH and P3HB.

[0029] A specific method for producing P3HB3HH is described in, for example, WO 2010 / 013483. Commercially available P3HB3HH products include Kaneka Biodegradable Polymer PHBH (registered trademark) manufactured by Kaneka Corporation.

[0030] The average content ratio of each constituent monomer in P3HB3HH is preferably 3HB / 3HH = 94-75 / 6-25 (mol % / mol %), and more preferably 3HB / 3HH = 90-82 / 10-18 (mol % / mol %). When the average 3HH content in P3HB3HH is 6 mol % or more, a resin layer exhibiting good thermal fusion properties can be formed when heated to the lamination temperature described below. Furthermore, P3HB3HH with an average 3HH content of 25 mol % or less does not exhibit an excessively slow crystallization rate and is relatively easy to produce. The average content ratio of each constituent in P3HB3HH can be determined by methods known to those skilled in the art, such as the method described in paragraph

[0047] of WO 2013 / 147139 or by NMR measurement. The average content ratio refers to the molar ratio of 3HB and 3HH contained in P3HB3HH. When P3HB3HH is a mixture containing two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or at least one type of P3HB3HH and P3HB, the average content ratio refers to the molar ratio of each monomer contained in the entire mixture.

[0031] As described above, P3HB3HH having an average 3HH content of 6 to 25 mol% preferably contains at least two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having different constituent monomer contents, and also preferably contains at least one type of P3HB3HH and P3HB. When two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) are contained, it is preferable that the constituent component is P3HB3HH having a 3HH monomer composition ratio of less than 6 mol%. This configuration allows for faster crystallization during melt processing compared to when the composition is composed solely of P3HB3HH, by leaving crystals of P3HB3HH or P3HB having a 3HH composition ratio of less than 6 mol% instead of completely dissolving them, allowing them to act as crystal nuclei. This facilitates the formation of the first resin (A) layer by the extrusion lamination, thermal lamination, or coating method. When at least one type of P3HB3HH and P3HB are contained, the P2HB component acts as a crystal nucleus, and a similar effect can be obtained. Note that P3HB3HH and P3HB may be used in combination at less than 6 mol %.

[0032] The composition ratio of 3HH in P3HB3HH in which the composition ratio of 3HH is less than 6 mol % is preferably 3 mol % or less, more preferably 2 mol % or less, and even more preferably 1 mol % or less.

[0033] The amount of P3HB3HH or P3HB in which the composition ratio of 3HH is less than 6 mol % is not particularly limited, but is preferably 1 to 50 wt % of the total P3HB-based resin (A-1) contained in the resin layer, more preferably 2 to 30 wt %, even more preferably 3 to 20 wt %, and particularly preferably 4 to 15 wt %.

[0034] The weight-average molecular weight (hereinafter sometimes referred to as Mw) of the P3HB resin (A-1) used in the present invention is not particularly limited, but is preferably 100,000 to 700,000, more preferably 120,000 to 400,000, and even more preferably 150,000 to 250,000. A weight-average molecular weight of less than 100,000 results in excessively low mechanical strength, which may cause cracking of the first resin (A) layer during processing. A weight-average molecular weight exceeding 700,000 results in excessively high melt viscosity, which may result in poor wetting of the first resin (A) layer or lamination of the P3HB resin (B) layer, resulting in insufficient adhesive strength. In the present application, the weight-average molecular weight of the P3HB resin can be determined by gel permeation chromatography (GPC) (Shodex GPC-101, manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804, manufactured by Showa Denko K.K.) column and chloroform as the mobile phase, as a polystyrene-equivalent molecular weight.

[0035] Examples of methods for forming the first resin (A) layer include extrusion lamination and thermal lamination, which will be described later, and a method in which a coating liquid in which the first resin (A) is dissolved or dispersed in a liquid such as water is applied to one or both sides of a paper substrate layer, and then heated to dry and form a film (hereinafter sometimes referred to as a "coating method"). In particular, when the first resin (A) layer is laminated directly to the paper substrate layer without any other layer in between, a portion of the coating liquid penetrates into the paper substrate layer during the process of forming the first resin (A) layer, making it easy to bond the first resin (A) layer to the paper substrate layer. Therefore, the coating method can be preferably used.

[0036] The lower limit of the thickness of the first resin (A) layer is preferably 0.75 μm or more, more preferably 1 μm or more, and particularly preferably 3 μm or more. The upper limit of the thickness is preferably 20 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. By forming the first resin (A) layer in the range of 0.75 μm to 20 μm, the first resin (A) layer is completely melted in a short time by heating when laminating the P3HB resin (B) layer, and good adhesion to the P3HB resin (B) layer can be obtained without reducing productivity during lamination.

[0037] (P3HB resin (B) layer) The P3HB resin (B) layer according to the present invention contains at least a poly(3-hydroxybutyrate) resin (B). The P3HB resin (B) is an aliphatic polyester resin that contains 3-hydroxybutyrate as a repeating unit and can be produced from a microorganism. The P3HB resin (B) may be a poly(3-hydroxybutyrate) containing only 3-hydroxybutyrate as a repeating unit, or may be a copolymer of 3-hydroxybutyrate and another hydroxyalkanoate.

[0038] The P3HB resin (B) may be a mixture of a homopolymer and one or more copolymers, or a mixture of two or more copolymers. The copolymerization method is not particularly limited and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, or the like.

[0039] Examples of the P3HB resin (B) include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (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-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0040] Furthermore, P3HB3HH(BH), a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred because changing the composition ratio of the repeating units can change the melting point and crystallinity, thereby changing physical properties such as Young's modulus and heat resistance, and it can impart physical properties between those of polypropylene and polyethylene. Furthermore, P3HB3HH is also preferred because it can lower the melting point and enable molding at low temperatures.

[0041] In one embodiment of the present invention, the P3HB-based resin (B) preferably contains at least one type of P3HB3HH (BH), and particularly preferably contains at least two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with different monomer content ratios. It is also preferable to contain at least one type of P3HB3HH and P3HB.

[0042] The average content ratio of the constituent monomers in P3HB3HH is preferably 3HB / 3HH=97-80 / 3-20 (mol % / mol %), more preferably 3HB / 3HH=95-75 / 5-15 (mol % / mol %), and even more preferably 3HB / 3HH=92-78 / 7-13 (mol % / mol %), from the viewpoints of preventing adhesion to cooling rolls during laminate production and facilitating molding and processing of molded articles using the obtained laminate. As described above, P3HB3HH having an average 3HH content of 3 to 20 mol% is particularly preferably at least two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with different constituent monomer content ratios. It is also preferable to include at least one type of P3HB3HH and P3HB. When composed of two types of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), it is preferable to combine a high-crystalline P3HB3HH with a low-crystalline P3HB3HH. Alternatively, P3HB may be blended in place of the high-crystalline P3HB3HH, or a combination of a high-crystalline P3HB3HH and a P3HB may be used. This blending allows the high-crystalline P3HB3HH, which easily crystallizes, to suppress adhesion to the cooling roll during heated lamination onto the first resin (A) layer, while the low-crystalline P3HB3HH provides hot tackiness, further improving adhesive strength to the first resin (A) layer. The proportion of 3HH relative to the total of 3HB and 3HH in the high-crystalline P3HB3HH is preferably 3 mol % or less, more preferably 2 mol % or less, and even more preferably 1 mol % or less.The proportion of 3HH relative to the total of 3HB and 3HH in the low-crystalline P3HB3HH is preferably 10 to 40 mol %, more preferably 15 to 30 mol % or less.

[0043] The amount of the highly crystalline P3HB3HH or P3HB blended is not particularly limited, but is preferably 1 to 60% by weight, more preferably 2 to 50% by weight, and even more preferably 4 to 15% by weight, based on the P3HB resin (B).

[0044] The weight-average molecular weight (hereinafter sometimes referred to as Mw) of the P3HB resin (B) used in the present invention is not particularly limited, but is preferably 100,000 to 700,000, more preferably 150,000 to 600,000, and even more preferably 200,000 to 400,000. If the weight-average molecular weight is less than 100,000, the mechanical properties may be poor, while if it exceeds 700,000, the melt viscosity may be too high, making molding difficult, and there may be problems such as reduced wetting to the first resin (A) layer, making it difficult to obtain sufficient adhesive strength.

[0045] The P3HB resin (B) layer may contain one or more biodegradable resins other than P3HA, such as aliphatic polyester resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate, as long as the effects of the present invention are not impaired.

[0046] The P3HB resin (B) layer may contain one or more of the following additives typically added to resin materials, provided they do not impair the effects of the present invention: inorganic fillers, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, sliding properties improvers, and other secondary additives. However, these are optional components, and the P3HB resin (B) layer may not contain these components. Lubricants and inorganic fillers are preferred optional components, as they can further improve the releasability of the P3HB resin (B) from the pressure surface of a cooling roll or the like during lamination.

[0047] Examples of the lubricant include saturated or unsaturated fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, and erucic acid amide, and alkylene fatty acid amides such as methylene bisstearic acid amide and methylene bisstearic acid amide, and aliphatic amide compounds, and pentaerythritol.

[0048] Examples of the inorganic filler include talc, calcium carbonate, mica, silica, clay, kaolin, titanium oxide, alumina, and zeolite, all of which have an average particle size of 0.5 μm or more.

[0049] The amount of lubricant in the P3HB resin (B) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1 part by weight, per 100 parts by weight of the P3HB resin (B). By using an amount of 0.1 part by weight or more, the effect of improving releasability due to the addition of the lubricant can be obtained. Conversely, if the amount exceeds 2 parts by weight, the lubricant will bleed during compression and adhere to the compression surface of the cooling roll, etc., making long-term continuous processing difficult. The amount of inorganic filler in the P3HB resin (B) is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of the P3HB resin (B). By setting the amount to 0.5 parts by weight or more, the effect of improving releasability due to the addition of the inorganic filler can be obtained. Conversely, if the amount exceeds 5 parts by weight, cracks may easily occur in the P3HB resin (B).

[0050] In the present invention, the P3HB resin (B) layer is formed by laminating a paper substrate layer and a first resin (A) layer formed on one or both sides of the paper substrate layer to form a laminate. The lamination method involves pressing a resin material containing the P3HB resin (B) onto a laminate containing a paper substrate layer using a pressure-bonding surface such as a chill roll, and then peeling the resin material containing the P3HB resin (B) from the pressure-bonding surface to produce a laminate. The lamination method is not particularly limited as long as it uses a pressure-bonding surface to bond a resin material containing the P3HB resin (B) to a laminate containing a paper substrate layer. Specific examples include extrusion lamination, in which a molten resin material containing the P3HB resin (B) is extruded from a T-die into a film and then cooled and pressed onto a separately unwound laminate containing a paper substrate layer using a chill roll, and thermal lamination, in which a pre-prepared film containing the P3HB resin (B) is heated and pressed onto the paper substrate layer. The bonding surface here may be any surface that can bond a laminate including a resin material containing a P3HB resin (B) and a paper substrate layer to the bonding surface, and examples thereof include a plate-like surface and the surface of a roll.

[0051] When forming the P3HB resin (B) layer by the lamination method, the heating temperature during lamination is preferably within a range of a temperature equal to or higher than the melting point (Tm) of the resin material containing the P3HB resin (B) and less than 30°C higher than the melting point (Tm). In the present invention, the melting point refers to the top temperature of the highest melting point peak on the crystalline melting curve obtained by differential scanning calorimetry. At temperatures below the melting point, the resin does not flow sufficiently, and the adhesive strength to the first resin (A) tends to be insufficient. Furthermore, at temperatures equal to or higher than 30°C higher than the melting point, the solidification rate of the P3HB resin (B) layer after lamination tends to be slow, resulting in insufficient peelability from the chill roll. Specifically, the lamination temperature is preferably 160°C or higher, more preferably 165°C or higher, and particularly preferably 170°C or higher. The upper limit of the heating temperature is preferably 180°C or lower. When the lamination temperature is 180° C. or less, it is possible to avoid a decrease in the mechanical strength of the P3HB resin (B) layer due to thermal decomposition of the P3HB resin.

[0052] In the present invention, the lamination temperature may be set so that the temperature of the resin material containing the P3HB resin (B) during lamination falls within the above-mentioned range. For example, in the case of extrusion lamination, the temperature of the T-die may be adjusted, and in the case of thermal lamination, the temperature of the heating roll used to bond the films may be adjusted. Furthermore, the surface temperature of the cooling roll in the lamination method is not particularly limited as long as it is a temperature at which the laminate layer can be cooled and pressure-bonded, and can be determined appropriately. The surface temperature of the cooling roll is, for example, 20 to 70°C, and preferably 40 to 60°C. When the surface temperature is within the above range, crystallization of the P3HB resin (B) is promoted, which results in reduced adhesion to the cooling roll and allows solidification to be achieved in a short time.

[0053] The thickness of the P3HB resin (B) layer in the present laminate is not particularly limited, but from the viewpoint of preventing water absorption into the paper base layer while ensuring sufficient flexibility, it is preferably 5 to 300 μm, more preferably 10 to 200 μm.

[0054] In one embodiment of the present invention, when a cup base paper of 150 to 350 g / m2 is used as the paper base layer, the thickness of the laminate layer is preferably 20 to 100 μm, more preferably 30 to 70 μm. By keeping the thickness within this range, it is possible to maintain good secondary processability such as punching properties and heat sealing properties in the laminate according to one embodiment of the present invention (hereinafter sometimes referred to as "this laminate").

[0055] [Molded body] A molded article according to one embodiment of the present invention (hereinafter sometimes referred to as "the molded article") includes the laminated article. The molded article is formed from a laminated article having a good surface condition of the laminate layer, and is therefore advantageous in various applications.

[0056] The present molded article is not particularly limited as long as it contains the present laminate, and examples thereof include paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, part, etc. From the viewpoint of measures against marine pollution, the present molded article is preferably a bag or a bottle container.

[0057] In one embodiment of the present invention, the present molded article may be the present laminate itself, or may be a secondary processed product using the present laminate.

[0058] Because the laminate has been subjected to secondary processing, the molded article containing it can be suitably used as various packaging container materials such as shopping bags, various bags, food and confectionery packaging materials, cups, trays, cartons, etc. (in other words, in various fields such as food, cosmetics, electronics, medicine, and pharmaceuticals.) Because the laminate contains a resin composition that has high adhesion to substrates and good heat resistance, it is more suitable as a container for holding liquids, particularly containers for holding hot contents, such as cups for food and beverages such as instant noodles, instant soup, and coffee, and trays for prepared meals, boxed lunches, and microwaveable foods.

[0059] The various secondary processes described above can be carried out in the same manner as conventional resin-laminated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Processing can also be carried out using machines such as paper cup forming machines, punching machines, and box making machines. In these processing machines, known techniques can be used to bond the laminate, such as heat sealing, impulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, and frame sealing.

[0060] The heat-sealing temperature of the present laminate varies depending on the adhesion method. When a heat-sealing tester equipped with a seal bar is used, the heat-sealing temperature of the present laminate is usually 250°C or lower, preferably 200°C or lower, and more preferably 180°C or lower. Within the above range, melting of the resin near the sealed portion can be avoided, and an appropriate resin layer thickness and seal strength can be ensured. Furthermore, when a heat-sealing tester equipped with a seal bar is used, the lower limit is usually 130°C or higher, preferably 140°C or higher, and more preferably 150°C or higher. Within the above range, appropriate adhesion at the sealed portion can be ensured.

[0061] The heat-sealing pressure of the present laminate varies depending on the bonding method. When a heat-sealing tester with a seal bar is used, the heat-sealing pressure of the present laminate is usually 0.1 MPa or more, preferably 0.3 MPa or more. Within this range, appropriate adhesion at the sealed portion can be ensured. Furthermore, when a heat-sealing tester with a seal bar is used, the upper limit is usually 0.5 MPa or less, preferably 0.45 MPa or less. Within this range, thinning of the film thickness at the sealed end can be avoided, and seal strength can be ensured.

[0062] Furthermore, in order to improve the physical properties of the present molded article, it can also be composited with a molded article made of a material different from the present molded article (for example, fiber, thread, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, part, foam, etc.). These materials are also preferably biodegradable. [Example]

[0063] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0064] The substances used in the examples and comparative examples and the method for measuring the melting point of the P3HA-based resin are shown below.

[0065] P3HB3HH(AH)-1: average content ratio 3HB / 3HH=89 / 11 (mol% / mol%, weight average molecular weight was 200,000 g / mol, content of PHB in the composition was 5.7% by weight) It was produced in accordance with the method described in Example 6 of International Publication WO2015-14619, and obtained as a 50% Sc aqueous dispersion. P3HB3HH(AH)-2: average content ratio of 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 200,000 g / mol) It was produced in accordance with Example 1 of Japanese Patent No. 4553733 and obtained as a 50% Sc dispersion in water. P3HB3HH(BH)-1:(Average content ratio 3HB / 3HH= 97 / 3 (mol% / mol%), weight average molecular weight is 400,000 g / mol) It was produced in accordance with the method described in Example 2 of International Publication WO2019-142845. P3HB3HH(BH)-2: (average content ratio of 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 400,000 g / mol) It was produced in accordance with the method described in Example 1 of International Publication WO2019-142845. P3HB3HH(BH)-3: A blend of 70 wt% P3HB3HH(BH)-1 and 30 wt% P3HB3HH(CH) (average 3HB / 3HH ratio throughout the blend: 89 / 11 (mol% / mol%)). P3HB3HH( CH ): Average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight is 660,000 g / mol): Produced in accordance with Example 9 of WO 2019 / 142845 P3HB3HH(BH)-4: A blend of 70 wt% P3HB3HH(BH)-2 and 30 wt% P3HB3HH(CH) (average 3HB / 3HH ratio throughout the blend: 87 / 13 (mol% / mol%)).

[0066] When a mixture of two or more resins is used as the polyhydroxyalkanoate resin component, the average content ratio (3HB / 3HH) is an average value calculated from the average 3HB / comonomer content ratio in each resin and the weight proportion of each resin. Lubricant: Behenamide (Nippon Fine Chemical Co., Ltd. "BNT-22H") Pentaerythritol (Mitsubishi Chemical's "Neuraizer P")

[0067] (Method for measuring the melting point of P3HA resin) The melting point (Tm) of the P3HA resin used in this example was measured by the following method. The measurement results are shown in Tables 1 and 2.

[0068] A 4-10 mg sample of each P3HA-based resin dried at 60°C was placed in an aluminum pan and heated from 20°C to 190°C at a rate of 10°C / min under a nitrogen stream using a differential scanning calorimeter to melt the sample and obtain a crystalline melting curve. The top temperature of the highest melting point peak on the obtained crystalline melting curve was taken as the melting point Tm.

[0069] <Manufacturing laminates by extrusion lamination method> Example 1 A 5% aqueous solution of partially saponified polyvinyl alcohol (Kuraray Poval PVA205, manufactured by Kuraray Co., Ltd.) was added to an aqueous dispersion containing P3HB3HH(AH)-1 so that the amount was 3 parts by weight per 100 parts by weight of the resin, and the mixture was stirred to obtain an aqueous coating solution containing 40% by weight of P3HB3HH in solids. 2 The aqueous coating liquid was coated on one side of the cup base paper, and then the cup base paper was passed through a drying oven set at 180° C. to form a first resin (A) layer having a thickness of 3 μm. P3HB3HH(BH)-1 (100 parts by weight) was dry-blended with behenamide (0.2 parts by weight) and pentaerythritol (1.0 part by weight), and the mixture was melt-kneaded and extruded into strands using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm. The strands were then passed through 40°C hot water to solidify them, and cut into pellets. Next, the obtained pellets were extruded using a single-screw extruder equipped with a T-type die, adjusting the conditions so that the resin temperature directly below the die was 175°C, and then laminated to a thickness of 30 μm onto the cup base paper with the first resin (A) layer prepared above to obtain a laminate.

[0070] Example 2 A laminate was obtained in the same manner as in Example 1, except that P3HB3HH(BH)-2 was used instead of P3HB3HH(BH)-1 and the resin temperature directly below the die was set to 170°C.

[0071] Example 3 A laminate was obtained in the same manner as in Example 1, except that P3HB3HH(BH)-3 was used instead of P3HB3HH(BH)-1.

[0072] Example 4 A laminate was obtained in the same manner as in Example 1, except that P3HB3HH(BH)-4 was used instead of P3HB3HH(BH)-1 and the resin temperature directly below the die was set to 170°C.

[0073] Examples 5 to 7 Laminates were obtained in the same manner as in Example 3, except that the thicknesses of the first resin (A) layers were set to 1 μm, 10 μm, and 20 μm, respectively.

[0074] Example 8 A laminate was obtained in the same manner as in Example 3, except that P3HB3HH(AH)-2 was used instead of P3HB3HH(AH)-1.

[0075] Example 9 A laminate was obtained in the same manner as in Example 2, except that the resin temperature immediately below the die was set to 178°C.

[0076] (Comparative Example 1) Weight 200g / m 2 A laminate was obtained in the same manner as in Example 3, except that the cup base paper was used without forming the first resin (A) layer.

[0077] (Comparative Example 2) A laminate was obtained in the same manner as in Comparative Example 1, except that P3HB3HH(AH)-4 was used instead of P3HB3HH(AH)-3 and the resin temperature directly below the die was set to 178°C.

[0078] (Manufacturing laminates by thermal film lamination) Example 10 The aqueous coating containing P3HB3HH(AH)-1 used in Example 1 was applied to a substrate having a basis weight of 150 g / m 2 The aqueous coating liquid was coated on one side of the unbleached kraft paper, and then the paper was passed through a drying oven set at 180° C. to form a first resin (A) layer having a thickness of 3 μm. P3HB3HH(BH)-3 (100 parts by weight) was dry-blended with behenamide (0.2 parts by weight) and pentaerythritol (1.0 part by weight), and the mixture was melt-kneaded and extruded into strands using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm. The strands were then passed through 40°C hot water to solidify them, and the mixture was cut into pellets. The resulting pellets were then taken up by a single-screw extruder equipped with a T-die and formed into a 30 μm-thick film using a cooling roll set at 60° C. The kraft paper on which the P3HB3HH(AH)-1 layer had been formed and the P3HB3HH(BH)-3 film were sandwiched so that the paper side was in contact with the heating roll and the film side was in contact with the cooling roll, and conditions were adjusted so that the surface temperature of the P3HB3HH(BH)-3 film was 170° C., yielding a laminate.

[0079] Example 11 A laminate was obtained in the same manner as in Example 10, except that the raw material for the P3HB3HH(BH) film was changed to P3HB3HH(BH)-4 and the lamination conditions were changed so that the lamination temperature was 165°C.

[0080] (Comparative Example 3) Weight 150g / m 2 A laminate was obtained in the same manner as in Example 10, except that the unbleached kraft paper was used without forming a first resin (A) layer.

[0081] Comparative Example 4 A laminate was obtained in the same manner as in Comparative Example 3, except that the raw material for the P3HB3HH(BH) film was changed to P3HB3HH(BH)-4 and the lamination temperature was changed to 165°C.

[0082] (Comparative Example 5) A laminate was obtained in the same manner as in Comparative Example 4, except that the lamination temperature was set to 178°C.

[0083] (Laminate evaluation method) The laminates of Examples 1 to 11 and Comparative Examples 1 to 5 were evaluated for roll peelability during laminate production and adhesion between the paper substrate layer and the P3HB-based resin layer (B).

[0084] (Roll peelability) The peelability from the cooling roll during lamination was evaluated by observing the state of the laminate when it was taken off the cooling roll, and the results are shown in Table 1. ◯: The P3HB resin layer (B) did not stick to the cooling roll, and the surface appearance of the P3HB resin layer (B) of the laminate was good △: The P3HB resin layer (B) sticks to the cooling roll, but the surface appearance of the P3HB resin layer (B) of the laminate is good ×: The P3HB resin layer (B) sticks to the cooling roll, a peeling sound from the cooling roll is heard, and irregularities occur on the surface of the P3HB resin layer (B).

[0085] (Adhesion between paper substrate and P3HB resin layer (B)) A 30 mm cross-cut was made in the resin layer with a cutter knife, the P3HB resin layer (B) was peeled off by hand, and the state of the peeled surface was visually inspected and evaluated according to the following criteria. The results are shown in Table 2. ◎: Cohesive failure of the paper occurs, and paper fibers adhere to the entire surface of the P3HB resin layer (B). ○: Cohesive failure of the paper occurs, and paper fibers adhere to part of the P3HB resin layer (B) surface. △: No cohesive failure of the paper occurs, and there is interfacial peeling between the first resin (A) layer and the P3HB-based resin layer (B), but there is resistance when peeling. ×: Cohesive failure of the paper did not occur, and the P3HB resin layer (B) was easily peeled off without resistance.

[0086] [Table 1]

[0087] [Table 2]

[0088] <Result> As can be seen from Tables 1 and 2, in the Examples, the P3HB resin layer had good adhesion to the paper substrate layer, and the P3HA resin had good releasability from the roll during the production of the laminate.

[0089] On the other hand, in the comparative examples, it was difficult to achieve both releasability from the roll and adhesion, and in comparative examples 2 and 5, adhesion did not improve even when the lamination temperature was increased, and further, the P3HA-based resin was prone to adhere to the roll during laminate production. Therefore, according to the production method of the present invention, in the production of a laminate including a paper base layer and a resin layer, blocking of the P3HA-based resin against the cooling roll during laminate production can be suppressed, and a biodegradable laminate with excellent adhesion between the paper base layer and the P3HA-based resin layer can be produced.

Claims

1. A method for producing a laminate including a paper substrate layer and a resin layer, comprising: A step (step A) of forming a layer containing a first resin (A) on at least one surface of a paper substrate layer; and and forming a layer containing a poly(3-hydroxybutyrate)-based resin (B) on the surface of the layer containing the first resin (A) by extrusion lamination or thermal lamination (step B), the first resin (A) is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units (AH); In the step of forming the layer containing the first resin (A), an aqueous coating liquid containing the copolymer containing the 3-hydroxybutyrate unit and the 3-hydroxyhexanoate unit (AH) is applied to a paper substrate to form a coating film; In the step of forming the layer containing the poly(3-hydroxybutyrate)-based resin (B), the layer is formed by extrusion lamination or thermal lamination at a temperature that is equal to or higher than the melting point of the resin material containing the poly(3-hydroxybutyrate)-based resin (B) and is lower than a temperature that is 30°C higher than the melting point.

2. 2. The method for producing a laminate according to claim 1, wherein the layer containing the first resin (A) has an average thickness of 0.75 to 20 μm.

3. 3. The method for producing a laminate according to claim 1, wherein the layer containing the poly(3-hydroxybutyrate)-based resin (B) has an average thickness of 25 to 50 μm.

4. The method for producing a laminate according to any one of claims 1 to 3, wherein the poly(3-hydroxybutyrate)-based resin (B) is a copolymer containing a 3-hydroxybutyrate unit and a 3-hydroxyhexanoate unit (BH).

5. 5. The method for producing a laminate according to claim 4, wherein the average content of the 3-hydroxyhexanoate units (BH) is 3 to 20 mol %.

6. The method for producing a laminate according to any one of claims 1 to 5, wherein the average content of the 3-hydroxyhexanoate units (AH) is 6 to 25 mol%.

7. A method for manufacturing a laminate described in any one of claims 1 to 6, wherein a layer containing the first resin (A) is laminated directly onto the paper base layer without any other layer in between.

8. A method for producing a laminate described in any one of claims 1 to 7, wherein the weight average molecular weight of the copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units (AH) is 150,000 to 250,000.

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