Biodegradable laminate and method for manufacturing the same

Abstract

A biodegradable laminate comprises: a substrate layer; a first thermoplastic resin (A1) layer laminated on one side of the substrate layer and comprising a polyhydroxyalkanoate resin; and a second thermoplastic resin (A2) layer laminated on the other side of the substrate layer and comprising a polyhydroxyalkanoate resin. The first thermoplastic resin (A1) layer has a unit area weight of 10 g / m². 2 Above and 200g / m 2 Hereinafter, the unit area weight of the second thermoplastic resin (A2) layer is 0.1 g / m². 2 Above and 5g / m 2 the following.

Description

Technical Field

[0001] This invention relates to a biodegradable laminate having thermoplastic resin layers on both sides of a substrate layer and a method for manufacturing the same. Background Technology

[0002] In recent years, environmental problems caused by waste plastics have attracted much attention. Among them, marine pollution caused by waste plastics is particularly serious, and the widespread adoption of biodegradable plastics that can decompose naturally is anticipated. Various biodegradable plastics are known, among which the copolymer of 3-hydroxybutyrate (hereinafter sometimes referred to as "3HB") and 3-hydroxyhexanoate (hereinafter sometimes referred to as "3HH") (hereinafter sometimes referred to as "PHBH") is a thermoplastic polyester produced and accumulated within the cells of many microbial species as an energy storage substance. Because it is a material that can biodegrade not only in soil but also in seawater, it has attracted attention as a raw material for solving the aforementioned problems. Laminates made by water-based coating or lamination of such PHBH onto environmentally degradable substrates such as paper, where both the substrate and PHBH are environmentally degradable, are therefore very promising from an environmental protection perspective.

[0003] Generally, layers containing PHBH can be used for bonding to substrates such as paper. In addition, due to their excellent water and oil resistance, they also function as a barrier layer on the inner surface of molded bodies such as paper cups to prevent fillers from penetrating into the substrate.

[0004] However, PHBH's viscosity is difficult to decrease when heated and melted, making it difficult to wet and spread on substrates such as paper. To obtain a good molded body through adhesion to substrates such as paper, it must be heated to a temperature significantly above the melting point. As a result, the resin curing time is longer, leading to poor adhesion of molded bodies such as paper products and reduced production speed in continuous operation. From a processability point of view, there is still much room for improvement.

[0005] Patent document 1 discloses a biodegradable laminate in which a layer containing a polyhydroxyalkanoate resin and a layer containing a dicarboxylic acid and a diol polycondensed polyester are respectively laminated on both sides of a paper substrate.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 10-6444 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, in the biodegradable laminate described in Patent Document 1, even when water is applied to the laminate for the purpose of correcting warping that occurs during winding, the substrate cannot adequately contain the water, resulting in insufficient elimination of warping. Furthermore, when the laminate is molded into paper products, the resin layer disposed on the outer surface of the cup becomes adhesive when heated, causing it to stick to the molding die. From an operational point of view, there is still room for improvement.

[0011] Therefore, in view of the above, the object of the present invention is to provide a biodegradable laminate having thermoplastic resin layers comprising polyhydroxyalkanoate resin on both sides of a substrate layer and a method thereof, wherein the biodegradable laminate has sufficient water absorption to eliminate warping when the laminate is rolled into a roll, and can suppress adhesion to the mold of the forming machine when it is formed into paper products, etc., and has excellent adhesion even when processed at low temperature during forming.

[0012] Methods for solving problems

[0013] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that in a biodegradable laminate having thermoplastic resin layers containing polyhydroxyalkanoate resins on both sides of a substrate layer, the above-mentioned problems can be solved by setting the unit area weight of one thermoplastic resin layer to be sufficiently smaller than the unit area weight of the other thermoplastic resin layer, thereby completing the present invention.

[0014] That is, the present invention relates to a biodegradable laminate comprising:

[0015] Substrate layer;

[0016] A first thermoplastic resin (A1) layer, comprising a polyhydroxyalkanoate resin, is laminated on one side of the substrate layer; and

[0017] A second thermoplastic resin (A2) layer, which is laminated on the other side of the aforementioned substrate layer and comprises a polyhydroxyalkanoate resin,

[0018] The unit area weight of the first thermoplastic resin (A1) layer is 10 g / m². 2 Above and 200g / m 2 the following,

[0019] The weight per unit area of ​​the second thermoplastic resin (A2) layer is 0.1 g / m². 2 Above and 5g / m 2 the following.

[0020] The effects of the invention

[0021] According to the present invention, a biodegradable laminate having thermoplastic resin layers comprising polyhydroxyalkanoate resins on both sides of a substrate layer and a method thereof are provided. The biodegradable laminate exhibits sufficient water absorption to eliminate warping that occurs when the laminate is rolled into a roll, and can suppress adhesion to molding die when molded into paper products, etc. Furthermore, it possesses excellent adhesion even during low-temperature processing during molding. Using the biodegradable laminate manufactured by the method of the present invention improves the production efficiency and quality of molded articles. Attached Figure Description

[0022] Figure 1 The image shows the surface of the second thermoplastic resin (A2) layer in the biodegradable laminate manufactured in Example 1 and Comparative Example 1, and the surface of the paper substrate in the biodegradable laminate manufactured in Comparative Example 4, observed using a scanning electron microscope at 500x magnification.

[0023] Figure 2 This is a schematic cross-sectional view of a biodegradable laminate according to one aspect of the present invention.

[0024] Symbol Explanation

[0025] 1 Biodegradable laminate

[0026] 2. Paper and other substrate layers

[0027] 3. First thermoplastic resin (A1) layer

[0028] 4. Second thermoplastic resin (A2) layer Detailed Implementation

[0029] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0030] [Layered Body]

[0031] One embodiment of the biodegradable laminate of this disclosure includes: a substrate layer such as paper; a first thermoplastic resin (A1) layer on one side and comprising a polyhydroxyalkanoate resin; and a second thermoplastic resin (A2) layer on the other side and comprising a polyhydroxyalkanoate resin, wherein the first thermoplastic resin (A1) layer, the substrate layer and the second thermoplastic resin (A2) layer are sequentially stacked together.

[0032] The first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer can be directly laminated onto a substrate such as paper, or they can be laminated with other layers in between.

[0033] In one embodiment of this disclosure, other adhesive layers may be further laminated on the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer.

[0034] The first thermoplastic resin layer (A1) and the second thermoplastic resin layer (A2) can be the outermost layers of the biodegradable laminate, respectively.

[0035] The components contained in the first thermoplastic resin (A1) layer and the components contained in the second thermoplastic resin (A2) layer may be the same or different. Furthermore, the proportions of the components contained in the first thermoplastic resin (A1) layer and the proportions of the components contained in the second thermoplastic resin (A2) layer may be the same or different.

[0036] (Substrate layer)

[0037] As the substrate layer of this disclosure, it is not particularly limited as long as it is biodegradable, and examples include: paper (mainly composed of cellulose), celluloid, cellulose ester; polyvinyl alcohol, polyamino acids, polyglycolic acid, pullulan, or materials formed by vapor-depositing inorganic substances such as aluminum or silica on these substrates. Among these, paper is preferred from the viewpoint of excellent heat resistance and low cost.

[0038] There are no specific limitations on the types of paper used; examples include: paper cup base paper, kraft paper, fully chemical pulp paper, coated paper, thin-layer paper, glassine paper, and cardboard. The type of paper can be appropriately selected based on the intended use of the laminate. Water-resistant agents, water-repellent agents, and inorganic substances can be added to the paper as needed, and surface treatments such as oxygen barrier coating and water vapor barrier coating can also be applied.

[0039] In addition, surface treatments such as corona treatment, ozone treatment, plasma treatment, flame treatment, tackifying coating treatment, oxygen barrier layer coating, and water vapor barrier coating can be applied to the surface of the substrate layer. These surface treatments can be performed individually or in combination.

[0040] (Thermoplastic resin 1 (A1) and thermoplastic resin 2 (A2))

[0041] The first thermoplastic resin (A1) and the second thermoplastic resin (A2) each contain one or more polyhydroxyalkanoate resins. The polyhydroxyalkanoate resins are biodegradable resins. The polyhydroxyalkanoate resins contained in the first thermoplastic resin (A1) and the polyhydroxyalkanoate resins contained in the second thermoplastic resin (A2) may be the same or different.

[0042] The resin components constituting the first thermoplastic resin (A1) and the resin components constituting the second thermoplastic resin (A2) preferably contain 50% by weight or more of a polyhydroxyalkanoate resin, more preferably 70% by weight or more, further preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. The above-mentioned resin components may each consist solely of a polyhydroxyalkanoate resin. It should be noted that, as resin components other than polyhydroxyalkanoate resins, biodegradable resins described later may be used.

[0043] The aforementioned polyhydroxyalkanoate resins (hereinafter sometimes simply referred to as PHA) refer to a general term for polymers in which hydroxyalkanoic acid is used as a monomer unit. The hydroxyalkanoic acid constituting PHA is not particularly limited, and examples include: 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxypropionic acid, 3-hydroxyvalerate, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, etc. PHA can be a homopolymer or a copolymer containing two or more monomer units.

[0044] From the viewpoint of seawater decomposability, PHA is preferably a homopolymer or copolymer having 3-hydroxybutyrate units, and more preferably a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0045] Specific examples of polymers having 3-hydroxybutyrate units include: poly(3-hydroxybutyrate) (abbreviated as PHB), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate) (abbreviated as PHBH), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate) (abbreviated as P3HB3HV), poly(3-hydroxybutyrate-copoly-4-hydroxybutyrate) (abbreviated as P3HB4HB), poly(3-hydroxybutyrate-copoly-3-hydroxyoctanoate) (abbreviated as P3HB3HO), poly(3-hydroxybutyrate-copoly-3-hydroxyoctadecanoate) (abbreviated as P3HB3HOD), poly(3-hydroxybutyrate-copoly-3-hydroxydecanoate) (abbreviated as P3HB3HD), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate-copoly-3-hydroxyhexanoate) (abbreviated as P3HB3HV3HH), etc. From the perspective of ease of industrial production, PHB, PHBH, P3HB3HV, and P3HB4HB are preferred.

[0046] For PHBH, by changing the composition ratio of repeating units, the melting point and crystallinity can be changed, resulting in the ability to adjust physical properties such as Young's modulus and heat resistance. Moreover, it can impart physical properties between polypropylene and polyethylene. In addition, it is easy to produce industrially and is a useful plastic in terms of physical properties. From this point of view, it is particularly preferred.

[0047] The resin components constituting the first thermoplastic resin (A1) and the resin components constituting the second thermoplastic resin (A2) preferably contain 50% by weight or more of PHBH, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. The aforementioned resin components may each consist solely of PHBH.

[0048] As a resin component other than PHBH, polyhydroxyalkanoate resins other than PHBH mentioned above can be used in combination with PHBH. Alternatively, biodegradable resins other than polyhydroxyalkanoate resins, such as polycaprolactone, polybutylene adipate, polybutylene succinate, polylactic acid, polybutylene adipate, and polybutylene azelaate, can also be used in combination with PHBH.

[0049] The specific manufacturing method of PHBH is described, for example, in International Publication No. 2010 / 013483. Furthermore, commercially available products of PHBH include Kaneka Corporation's "KANEKA Biodegradable Polymer Green Planet" (registered trademark).

[0050] The average content ratio of each constituent monomer in PHBH is preferably 3HB / 3HH = 97-75 / 3-25 (mol% / mol%), more preferably 3HB / 3HH = 94-82 / 6-18 (mol% / mol%). When the average content ratio of 3HH in PHBH is 3 mol% or more, good adhesion can be obtained even when low-temperature processing is performed during heat sealing. In addition, PHBH with an average content ratio of 3HH of 25 mol% or less does not crystallize too slowly, making it easier to manufacture.

[0051] It should be noted that the average content ratio of each constituent monomer in PHBH can be determined by methods known to those skilled in the art, such as the method described in paragraph

[0047] of International Publication No. 2013 / 147139, or by NMR determination. The aforementioned average content ratio refers to the molar ratio of 3HB to 3HH contained in PHBH. In the case where PHBH is a mixture containing at least two types of PHBH, or a mixture containing PHB and at least one type of PHBH, it refers to the molar ratio of each monomer contained in the total mixture.

[0052] As described above, PHBH with an average content of 3 to 25 mol% is particularly preferably composed of at least two PHBHs with different contents of each other constituting the monomers. In addition, it is also preferable to include PHB and at least one PHBH.

[0053] When at least two types of PHBH are included, it is preferable to include a highly crystalline PHBH with a monomer composition ratio of less than 6 mol% of 3HH and a low-crystalline PHBH with a monomer composition ratio of 3HH higher than that. With such a configuration, compared to the case composed of PHBH alone, during melt processing, the crystals of the highly crystalline PHBH with a 3HH composition ratio of less than 6 mol% do not completely dissolve and remain, acting as crystal nuclei, thereby accelerating crystallization and facilitating the formation of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer based on extrusion lamination, hot lamination, or coating.

[0054] Additionally, when PHB and at least one type of PHBH are included, PHB acts as a crystal nucleus, achieving the same effect. It should be noted that PHBH and PHB with an average 3HH content of less than 3 mol% can also be used in combination.

[0055] In the aforementioned highly crystalline PHBH, the proportion of 3HH relative to the total of 3HB and 3HH is preferably 5 mol% or less, more preferably 4 mol% or less, and even more preferably 3 mol% or less. Furthermore, in the aforementioned low-crystalline PHBH, the proportion of 3HH relative to the total of 3HB and 3HH is preferably 10 to 40 mol%, more preferably 15 to 30 mol%.

[0056] The amount of the above-mentioned highly crystalline PHBH or PHB 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 in the resin components contained in the thermoplastic resin (A1) layer or the thermoplastic resin (A2) layer.

[0057] From the viewpoint of balancing mechanical properties and processability, the weight-average molecular weight (hereinafter sometimes referred to as Mw) of the PHA contained in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 150,000 to 650,000, more preferably 250,000 to 550,000, and even more preferably 350,000 to 450,000. When the weight-average molecular weight of PHA is 150,000 or more, the mechanical properties are good; when it is 650,000 or less, a melt viscosity suitable for molding and processing can be easily achieved. The Mw of the PHA contained in the first thermoplastic resin (A1) and the Mw of the PHA contained in the second thermoplastic resin (A2) may be the same or different.

[0058] The weight-average molecular weight of the above-mentioned PHA can be determined using a gel permeation chromatography (GPC) system (Shodex GPC-101 manufactured by Showa Denko Corporation), with polystyrene gel (Shodex K-804 manufactured by Showa Denko Corporation) in the column and chloroform as the mobile phase, in the form of molecular weight after polystyrene conversion.

[0059] In one embodiment of this disclosure, multiple PHAs with different weight-average molecular weights can be mixed in the first thermoplastic resin (A1) layer and / or the second thermoplastic resin (A2) layer. Particularly in the case of mixing two PHAs, for example, by mixing a PHA with a weight-average molecular weight of 150,000 to 350,000 and a PHA with a weight-average molecular weight of 450,000 to 650,000, good heat-sealing properties at low temperatures and high mechanical properties can be achieved, thus obtaining the same effect as using a single PHBH with a single weight-average molecular weight.

[0060] To the extent that it does not impair the effects of the invention, the first thermoplastic resin (A1) and / or the second thermoplastic resin (A2) may contain one or more other additives commonly added to resin materials, such as inorganic fillers, pigments, dyes and other colorants, activated carbon, zeolite and other odor absorbers, vanillin, dextrin and other fragrances, plasticizers, antioxidants, weather resistance modifiers, ultraviolet absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, slip modifiers, and other minor additives.

[0061] These are arbitrary components, and the first thermoplastic resin (A1) and / or the second thermoplastic resin (A2) may not contain these components. As arbitrary components, from the viewpoint that the peelability of the cooling roller and the like from the pressing surface can be further improved when the first thermoplastic resin (A1) and the second thermoplastic resin (A2) are laminated, lubricants and / or inorganic fillers are preferred.

[0062] Examples of such lubricants include: saturated or unsaturated fatty acid amides such as lauryl amide, myristyl amide, palmitamide, stearamide, behenyl amide, oleamide, and erucamide; aliphatic amide compounds such as methylene distearate amide and methylene distearate amide; and pentaerythritol.

[0063] The aforementioned inorganic filler materials include, for example, talc, calcium carbonate, mica, silica, clay, kaolin, titanium dioxide, alumina, zeolite, etc., with an average particle size of 0.5 μm or more.

[0064] Relative to 100 parts by weight of the first thermoplastic resin (A1) and the second thermoplastic resin (A2), the amount of lubricant in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1 part by weight. By setting the amount to 0.1 parts by weight or more, the improved peelability due to the lubricant can be obtained. By setting the amount to 2 parts by weight or less, the lubricant leakage and adhesion to the pressing surface such as the cooling roller during pressing can be suppressed, enabling continuous processing over a long period of time.

[0065] Relative to 100 parts by weight of the first thermoplastic resin (A1) and the second thermoplastic resin (A2), the amount of inorganic filler in the first thermoplastic resin (A1) and the second thermoplastic resin (A2) is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight. By setting the amount to 0.5 parts by weight or more, the improved peelability due to the addition of inorganic filler can be obtained. By setting the amount to 5 parts by weight or less, cracking of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer can be suppressed.

[0066] Methods for forming the aforementioned first thermoplastic resin (A1) layer and / or second thermoplastic resin (A2) layer include: extrusion lamination, hot lamination, and a method of forming the layer by applying an aqueous coating liquid, obtained by dissolving or dispersing the first thermoplastic resin (A1) and the second thermoplastic resin (A2) in a liquid such as water, onto the surface of a substrate layer such as paper, and then heating, drying, and forming a film (hereinafter, sometimes referred to as "coating method"). In particular, when the thermoplastic resin layer is directly laminated onto the substrate layer such as paper without passing through other layers, since a portion of the coating liquid will penetrate into the substrate layer such as paper, the coating method is preferred from the viewpoint of easily improving the adhesive strength between each thermoplastic resin layer and the substrate layer such as paper.

[0067] The heating temperature for extrusion lamination or hot lamination can be appropriately set from known conditions, preferably above the melting point of the resin material (a resin material containing PHA constituting a thermoplastic resin) and less than 30°C above that melting point. When extrusion lamination or hot lamination is performed at a temperature within this range, the formation of a thermoplastic resin layer can be achieved from the perspective of avoiding PHA decomposition.

[0068] Preferably, in the coating method, after the aqueous coating liquid is applied to the surface of the substrate to form a coating film, the coating film is heated to a temperature above and below the melting point of the resin material by at least one method selected from hot air blowing, infrared irradiation, ultrasonic irradiation, and contact with a heated roller to form a film. By forming the film at a temperature within this range, the decomposition of PHA is avoided and PHA is melted on the surface of the substrate, thereby forming a highly uniform thermoplastic resin layer.

[0069] The lower limit of the unit area weight of the first thermoplastic resin (A1) layer is preferably 10 g / m². 2 The above, more preferably 20g / m 2 The above, especially preferred, is 30g / m 2 The above is the upper limit for weight per unit area, preferably 200 g / m². 2 The following is preferred: 100g / m 2 The following is particularly preferred: 50g / m2 The following is a description of the first thermoplastic resin (A1) layer, with a unit area weight of 10 g / m². 2 Above and 200g / m 2 Within the following range, the first thermoplastic resin (A1) layer can function as a barrier layer and achieve good adhesion when heat-sealed for molding into paper products, etc.

[0070] The lower limit of the unit area weight of the second thermoplastic resin (A2) layer is preferably 0.1 g / m². 2 The above, more preferably 0.5 g / m 2 The above is particularly preferred, with a concentration of 1g / m³. 2 The above is the upper limit for weight per unit area, preferably 5 g / m². 2 The following is preferred: 3g / m 2 The following is particularly preferred: 2g / m 2 The following is a partial sentence: The unit area weight of the second thermoplastic resin (A2) layer is 0.1 g / m². 2 Above and 5g / m 2 In the following range, at least a portion of the substrate surface is not covered by the resin layer, exposing the substrate. Therefore, it can be ensured that only the water absorption caused by warping when the laminate is rolled into a roll can be eliminated, and adhesion to the forming machine mold can be suppressed when forming paper, etc. In addition, excellent adhesion can be maintained even at low temperatures during heat sealing.

[0071] In one embodiment of this disclosure, as a substrate layer such as paper, a layer with a density of 150–350 g / m³ is used. 2 In the case of paper cup base paper, the unit area weight of the first thermoplastic resin (A1) layer is preferably set to 20 g / m². 2 Above and 100g / m 2 The following is more preferably 30g / m 2 Above and 50g / m 2 The following describes how, by setting the thickness within the range described above, the die-cutting properties, heat-sealing properties, and other secondary processing properties of the laminate (hereinafter sometimes referred to as "this laminate") of one embodiment of the present disclosure can be well maintained.

[0072] [Molded body]

[0073] A molded body (hereinafter sometimes referred to as "this molded body") according to one embodiment of the present disclosure comprises this laminate. This molded body is formed from a laminate with a good surface condition containing a resin layer of PHA, and is therefore advantageous in various applications.

[0074] This molded body can be any material containing this laminate and is not particularly limited. Examples include: paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, component, etc. From the viewpoint of countermeasures against marine pollution, this molded body is preferably a bag or bottle container.

[0075] In one embodiment of this disclosure, the molded body may be the laminate itself, or it may be obtained by processing the laminate twice.

[0076] By performing two processing steps on this laminate, the molded body containing it can be preferably used as a packaging container material for various products such as shopping bags, bags of various kinds, food / snack packaging materials, cups, plates, and cartons (in other words, in various fields such as food, cosmetics, electronics, medical, and pharmaceuticals). This laminate contains a resin composition with high adhesion to the substrate and good heat resistance, therefore, it is more preferably used as a container for holding liquids, especially for beverage cups such as instant noodles, instant soup, and coffee, as well as for plates used for dishes, boxed meals, microwaveable foods, etc., to hold warm contents.

[0077] The aforementioned secondary processing can be performed using the same methods as existing resin-laminated or coated paper, i.e., using various bag-making machines, filling and packaging machines, etc. Alternatively, it can be processed using paper cup forming machines, punching machines, box-making machines, etc. In these processing machines, the bonding method of this laminate can use known techniques, such as heat sealing, pulse sealing, ultrasonic sealing, high-frequency sealing, hot air sealing, flame sealing, etc.

[0078] The heat-sealing temperature of this laminate varies depending on the bonding method. For example, when using a heated heat-sealing tester with a sealing strip, the surface temperature of at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer is typically set to 180°C or lower, preferably 170°C or lower, and more preferably 160°C or lower. Within this range, resin leaching near the sealing portion can be avoided, ensuring appropriate resin layer thickness and sealing strength. This laminate achieves good adhesion even when heat-sealed at low temperatures; therefore, the surface temperature can be 150°C or lower, or even 140°C or lower.

[0079] Furthermore, when using a heated heat-sealing tester with a sealing strip, the lower limit is typically 100°C or higher, preferably 110°C or higher, and more preferably 120°C or higher. Within these ranges, proper adhesion of the seal can be ensured.

[0080] The heat-sealing pressure of this laminate varies depending on the bonding method. For example, when using a heated heat-sealing tester with a sealing strip, the heat-sealing pressure is typically 0.1 MPa or higher, preferably 0.5 MPa or higher. Within this range, proper adhesion of the seal is ensured. Furthermore, when using a heated heat-sealing tester with a sealing strip, the upper limit is typically 1.0 MPa or lower, preferably 0.75 MPa or lower. Within this range, thinning of the film at the sealing end is avoided, ensuring sealing strength.

[0081] In addition, to improve the physical properties of this molded body, it is also possible to composite it with a molded body made of a different material (e.g., fiber, filament, rope, fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, component, foam, etc.). These materials are also preferably biodegradable.

[0082] Preferred embodiments of this disclosure are set forth in the following items, but the invention is not limited to the following items.

[0083] [Project 1]

[0084] A biodegradable laminate comprising:

[0085] Substrate layer;

[0086] A first thermoplastic resin (A1) layer, comprising a polyhydroxyalkanoate resin, is laminated on one side of the substrate layer; and

[0087] A second thermoplastic resin (A2) layer, which is laminated on the other side of the aforementioned substrate layer and comprises a polyhydroxyalkanoate resin,

[0088] The unit area weight of the first thermoplastic resin (A1) layer is 10 g / m². 2 Above and 200g / m 2 the following,

[0089] The weight per unit area of ​​the second thermoplastic resin (A2) layer is 0.1 g / m². 2 Above and 5g / m 2 the following.

[0090] [Project 2]

[0091] According to the biodegradable laminate described in Project 1, the weight-average molecular weight of the aforementioned polyhydroxyalkanoate resin is 150,000 to 650,000.

[0092] [Project 3]

[0093] The biodegradable laminate according to item 1 or 2, wherein the polyhydroxyalkanoate resin comprises a polymer having 3-hydroxybutyrate units.

[0094] [Project 4]

[0095] According to the biodegradable laminate described in Project 3, the polyhydroxyalkanoate resin comprises a copolymer of 3-hydroxybutyrate units and 3-hydroxyhexanoate units.

[0096] [Project 5]

[0097] A method for manufacturing a biodegradable laminate, which is a method for manufacturing the biodegradable laminate as described in any one of items 1 to 4, the method comprising:

[0098] The process of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by extrusion lamination or hot lamination at a temperature above and below the melting point of the resin material plus 30°C.

[0099] [Project 6]

[0100] A method for manufacturing a biodegradable laminate, which is a method for manufacturing the biodegradable laminate as described in any one of items 1 to 4, the method comprising:

[0101] The process of applying an aqueous coating liquid containing polyhydroxyalkanoate resin to a substrate to form a coating film; and

[0102] The process of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by heating the coating film to a temperature above and below the melting point of the resin material by using at least one method selected from hot air blowing, infrared irradiation, ultrasonic irradiation, and contact with a heating roller.

[0103] [Project 7]

[0104] A molded body comprising any one of items 1 to 4 of the biodegradable laminate.

[0105] [Project 8]

[0106] A method for manufacturing a molded article, which is the method for manufacturing a molded article described in Item 7, the method comprising:

[0107] A process of heating at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer at a temperature of 100°C or higher and lower than 170°C.

[0108] Example

[0109] The present invention will be specifically described below through embodiments, but the present invention is not limited to its technical scope by these embodiments.

[0110] [Manufacturing Example]

[0111] (Method for manufacturing an aqueous dispersion with PHBH as the main component)

[0112] A resin dispersion of PHBH (3HH ratio 11.0 mol%, melting point 120°C) with a solid content concentration of 50 wt% was obtained according to the method described in International Publication No. 2004 / 041936. The resin dispersion was diluted with pure water as needed to adjust the solid content concentration before use. Furthermore, the weight-average molecular weight of PHBH is 620,000.

[0113] (Adjustment of the weight-average molecular weight of PHBH in aqueous dispersion)

[0114] The above resin dispersion was kept at 60°C and hydrolyzed to obtain a dispersion of PHBH with a weight-average molecular weight of 230,000.

[0115] (Aqueous mixed dispersion of multiple resin dispersions with different weight-average molecular weights)

[0116] Equal weights of the above-mentioned aqueous dispersions of PHBH with a weight average molecular weight of 620,000 and 230,000 were measured and mixed to obtain an aqueous mixed dispersion.

[0117] (Manufacturing method of water-based coating solution)

[0118] To obtain an aqueous coating solution, 0.3 parts by weight of PHBH sedimentation inhibitor (OptigelMW, manufactured by BYK) and 30 parts by weight of 2% methylcellulose (Metolose SM-400, manufactured by Shin-Etsu Chemical Co., Ltd.) aqueous solution were added to each of the above dispersions for 100 parts by weight and stirred.

[0119] [Evaluation Method]

[0120] The evaluations in the examples and comparative examples were conducted according to the following methods.

[0121] (Evaluation of 180° peel strength)

[0122] A heat-sealing test was conducted the day after the film-forming treatment. Using a heat-sealing machine (TP-701-B, manufactured by TESTERSANGYO), the surface of the first thermoplastic resin layer (A1) was overlapped with the surface of the second thermoplastic resin layer (A2), and pressed together at 0.4 MPa for 5 seconds. The maximum temperature reached by the resin surface during bonding was set to 106°C, 127°C, or 141°C.

[0123] Cut to a width of 15mm according to JIS standard Z0238, a peel strength test was conducted. The test was performed with a clamping distance of 100mm and a tensile speed of 300mm / min. The peel testing machine used was the Shimadzu Autograph EZ-LX (manufactured by Shimadzu Corporation).

[0124] <Evaluation>

[0125] ○:3.0N / 15mm or more

[0126] △: 2.5N / 15mm or more and less than 3.0N / 15mm

[0127] ×: Less than 2.0N / 15mm

[0128] When the above evaluation result is ○ or △, it has sufficient adhesion to obtain a good molded body.

[0129] (Evaluation of adhesion during heating)

[0130] The upper heat-sealing strip of a heat-sealing machine (TP-701-B, manufactured by TESTER SANGYO) was heated to 180°C. The biodegradable laminate was then prepared by contacting the surface of the second thermoplastic resin (A2) layer with the upper heat-sealing strip, and then pressed at 0.4 MPa for 5 seconds. After pressing, it was observed whether the biodegradable laminate adhered to the heat-sealing strip and whether it fell off. This process was repeated three times.

[0131] <Evaluation>

[0132] ○: In all three attempts, the adhesive failed and fell off (it was not stuck on).

[0133] △: At least one of the three attempts resulted in the item sticking together, but it fell off (did not stick) in all three attempts.

[0134] ×: In at least one of the three instances, the item was stuck together and did not fall off (remain stuck).

[0135] When the above evaluation result is ○ or △, the adhesion of the heated laminate is reduced, but there is no problem with the adhesion of the mold.

[0136] (Evaluation of warp after decurving)

[0137] The biodegradable laminate was cut into rectangular shapes with a length of 65 mm and a width of 240 mm. Next, the surface of the second thermoplastic resin (A2) layer was subjected to humidification / de-curling treatment by contacting it with steam generated from boiling hot water for 1 minute, and then left to stand for 1 hour at room temperature and pressure (27°C, 65% humidity). Then, the biodegradable laminate was placed on a flat surface, and the height of each of the four corners from the plane was recorded.

[0138] <Evaluation>

[0139] ○: The average height of the four corners is less than 2mm.

[0140] △: The average height of the four corners is greater than 2mm and less than 5mm.

[0141] ×: The average height of the four corners is greater than 5mm

[0142] When the above evaluation result is ○, it can be determined that the warping has been eliminated through sufficient water absorption.

[0143] (Weight per unit area of ​​PHBH)

[0144] The biodegradable laminates obtained in the examples and comparative examples were cut into 10cm×10cm pieces and their weights were measured. The weight of the base paper, or the sum of the weight of the base paper and the weight of the thermoplastic resin layer on the back side, was subtracted from the weight value and then multiplied by 100. The resulting value was taken as the weight per unit area.

[0145] (Surface observation of the thermoplastic resin (A2) layer)

[0146] The coating surface was observed at 500x magnification using a scanning electron microscope (SEM JSM-6060LA, manufactured by Nippon Electron Ltd.).

[0147] [Example 1]

[0148] relative to the weight per unit area of ​​210g / m² 2 A4-sized base paper was coated with an aqueous coating solution of PHBH with a weight-average molecular weight of 620,000 and a solid content concentration of 48% by weight using a rod coater No. 40. After drying at room temperature for 5 minutes, the resin was heated in a hot air drying oven at 137°C to form a film, thus producing the first thermoplastic resin (A1) layer.

[0149] Next, on the side opposite to the first thermoplastic resin (A1) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 620,000 and a solid content concentration of 13% by weight was applied using a bar coater No. 7 and dried at room temperature for 5 minutes. Further, the resin was heated in a hot air drying oven to a temperature of 137°C for film formation, thus creating the second thermoplastic resin (A2) layer.

[0150] The unit area weights of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer are 48 g / m². 2 1.2g / m 2 .

[0151] The biodegradable laminate obtained above was heat-sealed by heating the resin at a temperature of 141°C and a pressure of 0.4 MPa. After 48 hours, a 180° peel strength test (described later) was performed. In addition, an adhesion test and a warpage evaluation after decurving treatment were also conducted.

[0152] [Example 2]

[0153] The resin was heated to 127°C for heat sealing, and otherwise the same operation as in Example 1 was performed.

[0154] [Example 3]

[0155] The resin was heated to a temperature of 106°C for heat sealing, and otherwise the same operation as in Example 3 was performed.

[0156] [Example 4]

[0157] To prepare the second thermoplastic resin (A2) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 230,000 and a solids concentration of 13% by weight was used, and the same procedures as in Example 1 were performed.

[0158] [Example 5]

[0159] The resin was heated to 127°C for heat sealing, and otherwise the same operation as in Example 4 was performed.

[0160] [Example 6]

[0161] To prepare the first thermoplastic resin (A1) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 230,000 and a solid content concentration of 48% by weight was used, and the same procedures as in Example 2 were performed.

[0162] [Example 7]

[0163] To prepare the first thermoplastic resin (A1) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 230,000 and a solid content concentration of 48% by weight was used, and the same procedures as in Example 5 were performed.

[0164] [Example 8]

[0165] To prepare the first thermoplastic resin (A1) layer, an aqueous mixed dispersion of PHBH with a weight average molecular weight of 620,000 and 230,000 was used, and the same procedures as in Example 5 were performed.

[0166] [Example 9]

[0167] To prepare the first thermoplastic resin (A1) layer, a bar coater No. 14 was used instead of bar coater No. 40, and all other operations were performed the same as in Example 1. At this time, the unit area weights of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer were 18 g / m². 2 1.2g / m 2 .

[0168] [Example 10]

[0169] To prepare the second thermoplastic resin (A2) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 230,000 and a solid content concentration of 13% by weight was used, and the same procedures as in Example 9 were performed.

[0170] [Example 11]

[0171] To prepare the first thermoplastic resin (A1) layer, a bar coater No. 14 was used instead of a bar coater No. 40, and otherwise the same operations as in Example 5 were performed.

[0172] [Example 12]

[0173] To prepare the first thermoplastic resin (A1) layer, a bar coater No. 14 was used instead of a bar coater No. 40, and otherwise the same operations as in Example 6 were performed.

[0174] [Example 13]

[0175] To prepare the first thermoplastic resin (A1) layer, an aqueous coating solution of PHBH with a weight-average molecular weight of 230,000 and a solid content concentration of 48% by weight was used, and the same procedures as in Example 11 were performed.

[0176] [Comparative Example 1]

[0177] To prepare the second thermoplastic resin (A2) layer, a bar coater No. 25 was used instead of bar coater No. 7, and otherwise the same operations as in Example 1 were performed.

[0178] [Comparative Example 2]

[0179] To prepare the second thermoplastic resin (A2) layer, a bar coater No. 75 was used instead of bar coater No. 7, and otherwise the same operations as in Example 6 were performed.

[0180] [Comparative Example 3]

[0181] To prepare the second thermoplastic resin (A2) layer, a bar coater No. 25 was used instead of bar coater No. 7, and otherwise the same operations as in Example 4 were performed.

[0182] [Comparative Example 4]

[0183] The second thermoplastic resin (A2) layer was not formed on the side opposite to the first thermoplastic resin (A1) layer; otherwise, the same operation as in Example 2 was performed.

[0184] [Comparative Example 5]

[0185] The second thermoplastic resin (A2) layer was not formed on the side opposite to the first thermoplastic resin (A1) layer. Otherwise, the same operation as in Example 9 was performed.

[0186] [Comparative Example 6]

[0187] The second thermoplastic resin (A2) layer was not formed on the side opposite to the first thermoplastic resin (A1) layer. Otherwise, the same operation as in Example 12 was performed.

[0188]

[0189] <Results>

[0190] As shown in Table 1, in each embodiment, the adhesion of the heat seal at low temperature is good, there is no risk of sticking to the heat seal strip, and it has sufficient water absorption to eliminate warping of the laminate by contact with steam.

[0191] On the other hand, it can be seen that in each comparative example, it is impossible to simultaneously achieve adhesion, prevention of heat sealing strip adhesion, and sufficient water absorption.

[0192] In addition, according to Figure 1 It can be seen that, regarding the surface of the second thermoplastic resin (A2) layer in the biodegradable laminate of Example 1, compared with the surface of the substrate of Comparative Example 4, the entire surface of the substrate is not covered by resin; the resin only adheres to a portion of the substrate. Therefore, it can be considered that the biodegradable laminate of Example 1 has sufficient water absorption to eliminate warping of the laminate through decurving treatment.

[0193] On the other hand, it can be seen that, for the surface of the second thermoplastic resin (A2) layer in the biodegradable laminate of Comparative Example 1, the entire surface of the substrate is coated with resin. Therefore, the water absorption is insufficient, and it can be considered that it is difficult to eliminate warping by decurving treatment.

[0194] Therefore, according to the present invention, a biodegradable laminate and a method thereof can be provided that have water absorption that can eliminate warping caused when the laminate is rolled into a roll, suppress adhesion to the die of the forming machine during the forming of paper products, and have excellent adhesion even when the forming process is carried out at low temperature.

Claims

1. A biodegradable laminate comprising: Substrate layer; A first thermoplastic resin (A1) layer, comprising a polyhydroxyalkanoate resin, is laminated on one side of the substrate layer; and A second thermoplastic resin (A2) layer, which is laminated on the other side of the substrate layer and comprises a polyhydroxyalkanoate resin, The substrate layer is paper. The unit area weight of the first thermoplastic resin (A1) layer is 10 g / m². 2 Above and 200g / m 2 the following, The unit area weight of the second thermoplastic resin (A2) layer is 0.1 g / m². 2 Above and 5g / m 2 the following.

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

3. The biodegradable laminate according to claim 1 or 2, wherein, The polyhydroxyalkanoate resin comprises a polymer having 3-hydroxybutyrate units.

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

5. A method for manufacturing a biodegradable laminate, which is a method for manufacturing the biodegradable laminate according to claim 1 or 2, the method comprising: The process of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by extrusion lamination or hot lamination at a temperature above and below the melting point of the resin material by +30°C.

6. A method for manufacturing a biodegradable laminate, which is a method for manufacturing the biodegradable laminate according to claim 1 or 2, the method comprising: The process of applying an aqueous coating liquid containing polyhydroxyalkanoate resin to a substrate to form a coating film; as well as The process of forming at least one of the first thermoplastic resin (A1) layer and the second thermoplastic resin (A2) layer by heating the coating film to a temperature above and below the melting point of the resin material by using at least one method selected from hot air blowing, infrared irradiation, ultrasonic irradiation, and contact with a heated roller.

7. A molded body comprising the biodegradable laminate of claim 1 or 2.

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

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