JP7788288B2 - Biodegradable film and biodegradable laminate - Google Patents

Description

The present invention relates to a biodegradable film, a biodegradable laminate containing the film, and a method for producing the laminate.

In recent years, environmental problems caused by discarded plastic have come into the spotlight, and it has become clear that large amounts of plastic, particularly plastic that has been dumped in the ocean or has entered the sea via rivers, are drifting in the oceans on a global scale. Because such plastic retains its shape for long periods of time, it has been pointed out that it has an impact on the ecosystem, such as trapping and capturing marine life (a practice known as ghost fishing), and that if ingested by marine life, it can become trapped in the digestive tract and cause feeding disorders.

Furthermore, it has been pointed out that microplastics, which are plastics that break down and break down into tiny particles due to ultraviolet rays and other factors, absorb harmful compounds in the ocean, and when these are ingested by marine organisms, harmful substances are introduced into the food chain.

The use of biodegradable plastics is expected to be a solution to this type of marine pollution caused by plastics, but a report compiled by the United Nations Environment Programme in 2015 pointed out that plastics that can be biodegraded through compost, such as polylactic acid, cannot be expected to decompose in the short term in the cold ocean temperatures, and therefore cannot be used to combat marine pollution.

Microbial poly(3-hydroxybutyrate) resins are materials that can biodegrade even in seawater, and are attracting attention as a material that can solve the above-mentioned problems. One example of a use for this resin is being considered: biodegradable films.

However, poly(3-hydroxybutyrate) resins can sometimes have a distinctive odor that limits their applications.

Patent Document 1 describes a biodegradable plastic made by adding a deodorizing agent such as hydrophobic zeolite to a biodegradable plastic such as a copolymer resin made of 3-hydroxybutyrate and 3-hydroxyvalerate.

Japanese Patent Application Publication No. 7-310005

Biodegradable films are required to be flexible so that they do not crack when bent. Furthermore, biodegradable films may be bonded by heat sealing, and in such cases, they are also required to have good heat-sealing adhesive strength.

However, when a biodegradable film is formed by adding a deodorizing agent such as hydrophobic zeolite to a biodegradable plastic using the method described in Patent Document 1, the flex resistance or heat sealability may be insufficient, and it has been found that it is difficult to obtain a biodegradable film that has good flex resistance and heat sealability while suppressing odor.

In light of the above-mentioned current situation, the present invention aims to provide a biodegradable film and biodegradable laminate that contain a poly(3-hydroxybutyrate)-based resin, has reduced odor, and has good flex resistance and heat sealability.

As a result of extensive research into resolving the above-mentioned issues, the inventors discovered that the above-mentioned issues could be resolved by constructing a biodegradable film from a resin composition in which a specific poly(3-hydroxybutyrate) resin with a specific molecular weight is blended with a specific amount of specific porous particles, thereby completing the present invention.

That is, the present invention provides a biodegradable film containing a thermoplastic resin (A) containing a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and porous particles (B) containing hydrophobic zeolite,
The weight average molecular weight of the copolymer is 400,000 to 650,000,
The copolymer has an average content of 3-hydroxyhexanoate of 3 to 20 mol %,
the pore diameter of the porous particles (B) is 0.7 to 1.5 nm,
The biodegradable film comprises 0.1 to 10 parts by weight of the porous particles (B) based on 100 parts by weight of the thermoplastic resin (A).
Preferably, the thermoplastic resin (A) contains at least one plasticizer (C) selected from the group consisting of glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoate ester compounds, phthalate ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds, in an amount of 0.5 parts by weight or more and less than 10 parts by weight per 100 parts by weight of the thermoplastic resin (A).
Preferably, the biodegradable film has a tensile modulus in the MD or TD direction of 300 MPa or more and less than 800 MPa.
Preferably, the biodegradable film has an Elmendorf tear strength in the MD or TD direction of 3.0 mN/μm or more and less than 35 mN/μm.
The present invention also relates to a biodegradable laminate obtained by laminating the biodegradable film and a substrate (D).
Preferably, the substrate (D) is paper.
The present invention also relates to a method for producing the biodegradable laminate, which comprises the step of forming the biodegradable film on at least one surface of the substrate (D) by extrusion lamination or thermal lamination.
Preferably, the biodegradable film is formed on at least one surface of the substrate (D) by extrusion lamination, and the temperature of the resin composition immediately after being extruded from the tip of the T-shaped die head is equal to or higher than the melting point of the thermoplastic resin (A) and equal to or lower than 170°C.
The present invention also relates to a molded article comprising the biodegradable laminate.

According to the present invention, it is possible to provide a biodegradable film and a biodegradable laminate that contain a poly(3-hydroxybutyrate)-based resin, have reduced odor, and have good flex resistance and heat sealability.
It is also possible to improve the laminate strength in a biodegradable laminate.
The biodegradable film and biodegradable laminate according to the present invention can be used in a wide range of applications, including foods, medicines, cosmetics, and other products that are sensitive to odors.

The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment.

The biodegradable film according to this embodiment is composed of a resin composition containing a thermoplastic resin (A) and porous particles (B).

[Thermoplastic resin (A)]
The thermoplastic resin (A) contains at least a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, i.e., poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), as a biodegradable aliphatic polyester. Hereinafter, this copolymer will also be referred to as PHBH.

From the viewpoint of balancing the flexibility and strength of the biodegradable film, the monomer composition ratio of the PHBH is such that the average content ratio of 3-hydroxyhexanoate units (hereinafter also referred to as 3HH units) out of all repeating units (100 mol%) constituting the PHBH is 3 to 20 mol%. An average content ratio of 3HH units of 20 mol% or less improves the rigidity of the PHBH and tends to facilitate purification without excessively low crystallinity. On the other hand, an average content ratio of 3HH units of 3 mol% or more tends to improve the flexibility of the PHBH. The average content ratio of the 3HH units is preferably 5 to 18 mol%, more preferably 8 to 15 mol%. The monomer composition ratio of PHBH can be measured by gas chromatography or the like (see, for example, WO 2014/020838).

Aeromonas caviae is known as a microorganism that produces PHBH. To increase PHBH productivity, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)), into which genes encoding P3HA synthases have been introduced, can be used. These microorganisms are cultured under appropriate conditions to allow PHBH to accumulate within the cells. In addition to the above, genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced may also be used, depending on the PHBH to be produced, or the culture conditions, including the type of substrate, may be optimized.

The weight-average molecular weight of PHBH is set to between 400,000 and 650,000 in order to improve both the flex resistance and heat sealability of the biodegradable film. It is preferably between 400,000 and 600,000, and more preferably between 450,000 and 550,000. By setting the weight-average molecular weight to 400,000 or more, the flex resistance of the biodegradable film can be improved. On the other hand, by setting the weight-average molecular weight to 650,000 or less, the seal strength (hereinafter also referred to as heat sealability) when heat-sealed with the biodegradable film can be improved. It can also improve the laminate strength (adhesion strength between the biodegradable film and the substrate) of the biodegradable laminate.

The weight-average molecular weight can be measured using gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) with a polystyrene gel column (Shodex K-804 manufactured by Showa Denko K.K.) and chloroform as the mobile phase, and can be calculated as the molecular weight converted into polystyrene. A calibration curve is prepared using polystyrenes with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. A column appropriate for measuring the molecular weight can be used for the GPC. The weight-average molecular weight is a value measured using the biodegradable film as a sample.

One type of PHBH can be used alone, or two or more types with different monomer composition ratios and/or molecular weights can be used in combination. When two or more types of PHBH are used in combination, the average content ratio of 3HH units and weight-average molecular weight described above are values indicated for the two or more types of PHBH as a whole, rather than values indicated for each individual PHBH.

The content of PHBH in the biodegradable film is not particularly limited, but is preferably 30% by weight or more, more preferably 50% by weight or more, even more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more. By making the PHBH content 30% by weight or more, the biodegradability of the biodegradable film tends to be good. There is no particular upper limit for the PHBH content, as long as it is less than 100% by weight. It may also be 99% by weight or less, or 95% by weight or less.

[Other P3HA]
The biodegradable film may contain only PHBH as the thermoplastic resin (A), but may also contain a poly(3-hydroxyalkanoate) resin other than PHBH (hereinafter also referred to as other P3HA). Since other P3HA is also biodegradable, it can be suitably used in combination.

Examples of such poly(3-hydroxybutyrate) resins include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

The content of the other P3HA in the biodegradable film is not particularly limited, but is preferably 250 parts by weight or less, more preferably 100 parts by weight or less, even more preferably 50 parts by weight or less, and particularly preferably 20 parts by weight or less, per 100 parts by weight of PHBH. It may also be 10 parts by weight or less, or 5 parts by weight or less. There is no particular lower limit for the content of the other P3HA, and it may be 0 parts by weight.

[Other thermoplastic resins]
The biodegradable film may contain, but is not limited to, other thermoplastic resins other than PHBH and P3HA (hereinafter also referred to as "other thermoplastic resins") as the thermoplastic resin (A). The other thermoplastic resins are not particularly limited as long as they do not significantly reduce the compatibility, moldability, or mechanical properties when producing the biodegradable film. However, biodegradable resins are preferred so that the biodegradability of the film is improved.

Examples of the other thermoplastic resins include aliphatic polyesters formed by the polycondensation of aliphatic diols and aliphatic dicarboxylic acids, and aliphatic-aromatic polyesters containing both aliphatic and aromatic compounds as monomers. Examples of the former include polyethylene succinate, polybutylene succinate (PBS), polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene succinate adipate (PBSA), polyethylene sebacate, and polybutylene sebacate. Examples of the latter include poly(butylene adipate-co-butylene terephthalate) (PBAT), poly(butylene sebacate-co-butylene terephthalate), poly(butylene azelate-co-butylene terephthalate), and poly(butylene succinate-co-butylene terephthalate) (PBST). These other thermoplastic resins can be used singly or in combination of two or more.

The content of the other thermoplastic resin in the biodegradable film is not particularly limited, but is preferably 250 parts by weight or less, more preferably 100 parts by weight or less, even more preferably 50 parts by weight or less, and particularly preferably 20 parts by weight or less, relative to 100 parts by weight of PHBH. It may also be 10 parts by weight or less, or 5 parts by weight or less. There is no particular lower limit for the content of the other resin, and it may be 0 parts by weight.

[Porous particles (B)]
The porous particles (B) contained in the biodegradable film according to this embodiment have porosity, which allows them to adsorb odor-causing substances and provide deodorizing properties. The porous particles may be made of an organic material, an inorganic material, or an organic-inorganic hybrid material.

Examples of the organic material include polymeric porous particles, such as nylon particles, polyamide particles, acrylic particles, polymethyl methacrylate particles, polystyrene particles, silicone particles, cyclic silicone particles, urethane particles, polyethylene particles, and phospholipid particles. These particles may be crosslinked or non-crosslinked, but crosslinked particles are preferred because they are less likely to be destroyed by shear during molding.

Examples of such inorganic materials include activated carbon, activated clay, acid clay, natural zeolite, hydrophobic zeolite, hydrophilic zeolite, silica gel, bentonite, smectite, mica, talc, pyroferrite, vermiculite, chlorite, kaolinite and serpentine, silica, titanium oxide, a mixture of magnesium oxide and silicon dioxide, and a composite of magnesium oxide and silicon dioxide.

The porous particles (B) contain at least hydrophobic zeolite. The biodegradable film may contain only hydrophobic zeolite as the porous particles (B), or may contain hydrophobic zeolite and porous particles other than hydrophobic zeolite. Hydrophobic zeolite is preferred because it has excellent deodorizing properties against the odor specific to PHBH and good dispersibility in PHBH.

The proportion of hydrophobic zeolite in the entire porous particles (B) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and particularly preferably 90 to 100% by weight.

Zeolite is an inorganic compound mainly composed of tetrahedral coordinated SiO ₂ and Al ₂ O _3. The hydrophobic zeolite is a zeolite that contains a large amount of SiO ₂ and has a SiO ₂ /Al ₂ O ₃ molar ratio of 35 or more.

The inventors have discovered that, among porous particles, porous particles (B) having a pore diameter of 0.7 nm or more and 1.5 nm or less are particularly excellent at deodorizing the odor specific to PHBH, and are less likely to impair the flex resistance or heat sealability of the biodegradable film. If the pore diameter is less than 0.7 nm or more than 1.5 nm, the deodorizing effect per unit amount of porous particles decreases, making it necessary to increase the amount of porous particles added to achieve the desired deodorizing effect. This tends to reduce the flex resistance or heat sealability of the biodegradable film.

The pore diameter of the porous particles (B) is preferably 0.7 nm or more and 1.2 nm or less, more preferably 0.7 nm or more and 1.0 nm or less, and particularly preferably 0.8 nm or more and 1.0 nm or less.

The pore diameter of the porous particles (B) is a value measured by a constant volume gas adsorption method. Examples of adsorbed gases used in the constant volume gas adsorption method include nitrogen, carbon dioxide, methane, and hydrogen.

The particle size of the porous particles (B) is not particularly limited, but it is preferable that the average particle size be 0.1 μm or more and 10 μm or less. By setting the average particle size to 0.1 μm or more, the dispersibility of the porous particles (B) in the thermoplastic resin (A) is improved, and the deodorizing effect tends to be improved. On the other hand, by setting the average particle size to 10 μm or less, the mechanical strength of the biodegradable film tends to be improved. The average particle size is more preferably 0.3 μm or more and 8 μm or less, and even more preferably 0.5 μm or more and 6 μm or less.

The average particle diameter of porous particles (B) is a value obtained by observation using a scanning electron microscope (SEM). 100 or more particles that are not overlapping with other particles are selected, the lengths of the major and minor axes of each particle are measured, and the arithmetic mean of these particle diameters is used as the particle diameter of each particle. The average particle diameter can then be calculated as the arithmetic mean of these particle diameters.

The amount of porous particles (B) blended is 0.1 to 10 parts by weight per 100 parts by weight of thermoplastic resin (A). If the amount of porous particles (B) blended is less than 0.1 part by weight, the deodorizing effect of the porous particles blended cannot be fully achieved. On the other hand, if the amount blended exceeds 10 parts by weight, the bending resistance or heat sealability of the biodegradable film tends to decrease. The amount of porous particles (B) blended is preferably 0.5 to 8 parts by weight, more preferably 1 to 7 parts by weight, and even more preferably 2 to 6 parts by weight.

[Additives]
The biodegradable film may contain additives as long as the effects of the invention are not impaired. Examples of additives that can be used depending on the purpose include nucleating agents, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, and hydrolysis inhibitors. Biodegradable additives are particularly preferred.

Examples of the crystal nucleating agent include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, etc. Among these, pentaerythritol is preferred because it has a particularly excellent effect of promoting the crystallization of PHBH.
The amount of the nucleating agent used is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, relative to 100 parts by weight of PHBH. One type of nucleating agent or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, polycondensates of ethylenediamine, stearic acid, and sebacic acid, etc. Among these, behenamide or erucamide is preferred because of its particularly excellent lubricating effect on PHBH.
The amount of the lubricant used is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, relative to 100 parts by weight of PHBH. One type of lubricant may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

By incorporating a plasticizer (C), the elastic modulus of the biodegradable film can be reduced, improving its flex resistance. In particular, when the amount of porous particles (B) incorporated is relatively high, it is preferable to incorporate a plasticizer to improve flex resistance.

As the plasticizer (C), it is preferable to use glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoic acid ester compounds, phthalic acid ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds, because they have a good plasticizing effect on PHBH. Among these, glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, and dibasic acid ester compounds are preferred. One or more types of plasticizers may be used, and the ratio of their use can be adjusted appropriately depending on the purpose.

Examples of glycerin ester compounds include glycerin diacetomonolaurate. Examples of citrate ester compounds include acetyl tributyl citrate. Examples of sebacic acid ester compounds include dibutyl sebacate. Examples of dibasic acid ester compounds include benzyl methyl diethylene glycol adipate.

When a plasticizer is used, its amount is not particularly limited, but is preferably 0.5 parts by weight or more but less than 10 parts by weight, more preferably 0.8 to 8 parts by weight, and even more preferably 1 to 6 parts by weight, per 100 parts by weight of thermoplastic resin (A).

[Resin composition]
The resin composition containing the thermoplastic resin (A) and the porous particles (B) can be easily produced using a known melt kneader as long as it is an apparatus capable of heating and kneading the thermoplastic resin (A) to a temperature equal to or higher than the melting point of the thermoplastic resin (A). For example, the thermoplastic resin (A), the porous particles (B), and, if necessary, other components can be melt-kneaded using an extruder, a roll mill, a Banbury mixer, or the like to form pellets, which can then be molded; or a method in which a masterbatch containing a high concentration of the porous particles (B) is prepared in advance, which is melt-kneaded with the thermoplastic resin (A) in a desired ratio, and then molded, can be used.

The thermoplastic resin (A) and porous particles (B) may be added to the kneader simultaneously, or the thermoplastic resin (A) may be melted first and then the porous particles (B) may be added.

To prepare pellets of the resin composition, first, the thermoplastic resin (A), porous particles (B), and other components, if necessary, are added and melt-kneaded using an extruder, kneader, Banbury mixer, roll, or the like to prepare a resin composition, which is then extruded into a strand and cut to obtain pellets in particle shapes such as cylindrical, elliptical, spherical, cubic, or rectangular. The prepared pellets are then preferably thoroughly dried at 40-80°C to remove moisture before being used for film molding.

The temperature at which the melt-kneading is carried out cannot be generally determined as it depends on the melting point, melt viscosity, etc. of the resin used, but it is preferable that the resin temperature at the die outlet of the molten kneaded product be approximately 135 to 200°C.

[Biodegradable film]
The biodegradable film according to this embodiment can be produced by various molding methods, such as T-die extrusion, inflation molding, and calendar molding. Specific conditions can be set as appropriate. For example, the temperature during extrusion molding can be set as appropriate depending on the melting point and MFR of the resin material. From the viewpoint of resin fluidity and solidification speed, the temperature is preferably 150 to 180°C, and more preferably 155 to 170°C.

The biodegradable film preferably exhibits a tensile modulus of 300 MPa or more and less than 800 MPa when measured in the MD or TD direction of the film. Within this range, the film can exhibit good flex resistance while maintaining sufficient heat sealability. If the tensile modulus is too high, flex resistance tends to decrease; conversely, if it is too low, heat sealability tends to decrease. The tensile modulus is more preferably 350 MPa or more and 800 MPa or less, and even more preferably 400 MPa or more and 780 MPa or less.

The tensile modulus value is calculated from the stress-strain curve between two points where the strain is 0.05% and 0.25% using a tensile testing machine in accordance with JIS standard K7161-1.

In a preferred embodiment, the biodegradable film exhibits high tear strength. The tear strength exhibited by the biodegradable film is preferably 3.0 mN/μm or more and less than 35 mN/μm, as measured in the machine direction or transverse direction of the film, using the Elmendorf tear strength.

The Elmendorf tear strength value is measured using an Elmendorf tear tester in accordance with JIS standard K7128-2.

The thickness of the biodegradable film is not particularly limited, but is preferably 10 μm or more and 1 mm or less, more preferably 15 μm or more and 500 μm or less, and even more preferably 20 μm or more and 300 μm or less. Biodegradable films in this application may also include those with thicknesses that are generally referred to as sheets.

[Biodegradable laminate]
The biodegradable laminate according to this embodiment includes the biodegradable film and a substrate laminated on at least one surface of the film.

The biodegradable film may be laminated on only one side of the substrate, or on both sides. The biodegradable film may be laminated on the substrate via another layer, or may be laminated directly on the substrate layer without any other layer in between. Another layer may be laminated on top of the biodegradable film.

(Base material)
The substrate is not particularly limited, but is preferably biodegradable. When the substrate has biodegradability, the entire laminate has biodegradability, making it more advantageous as a material for solving the problem of marine pollution.

Biodegradable substrates are not particularly limited, but examples include paper (mainly composed of cellulose), cellophane, cellulose esters, polyvinyl alcohol, polyamino acids, polyglycolic acid, pullulan, and substrates such as these onto which inorganic substances such as aluminum and silica have been vapor-deposited. Of these, paper is preferred because of its excellent heat resistance and low cost.

The type of paper is not particularly limited, and examples include cup base paper, kraft paper, fine paper, coated paper, tissue paper, glassine paper, and paperboard. The type of paper can be selected appropriately depending on the application of the laminate. If necessary, water-resistant agents, water-repellent agents, inorganic substances, etc. may be added to the paper, and the paper may be surface-treated with an oxygen barrier layer coating, a water vapor barrier coating, etc.

The substrate may be subjected to surface treatments such as corona treatment, flame treatment, and anchor coating. These surface treatments may be performed alone or in combination with other surface treatments.

The biodegradable film and the substrate may be directly laminated together, or an adhesive layer may be sandwiched between the two layers. There are no particular restrictions on the adhesive used to form the adhesive layer, and conventionally known adhesives can be used. The bonding method is also not particularly limited, but examples include the dry lamination method, in which a two-component curing urethane adhesive is used for bonding, and the non-solvent dry lamination method, in which a solvent-free adhesive is used for bonding.

The biodegradable laminate according to this embodiment can be manufactured by extrusion lamination. Extrusion lamination is a method in which a molten resin material is extruded onto the surface of a substrate to form a film. Specifically, the molten resin material is extruded through a die, cooled using a cooling roll, and pressed onto the surface of the target film (substrate), and then immediately thereafter, the resin material is peeled off from the cooling roll.

The heating temperature during extrusion lamination is not particularly limited and may be set as appropriate. However, from the perspective of successfully carrying out extrusion lamination while avoiding resin decomposition, it is preferable that the heating conditions be such that the temperature of the resin composition immediately after being extruded from the tip of the T-die head is equal to or higher than the melting point of the thermoplastic resin (A) and equal to or lower than 170°C. Note that these heating conditions can also be applied when producing biodegradable films by T-die extrusion molding.

Furthermore, the surface temperature of the cooling roll during extrusion lamination is not particularly limited and may be set as appropriate, but may be, for example, 35 to 70°C.

The biodegradable laminate according to this embodiment can also be produced by molding the biodegradable film alone using a method such as T-die extrusion or inflation molding, and then integrating the biodegradable film with a substrate using a thermal lamination method. If another layer is included between the biodegradable film and the substrate, the biodegradable film and the substrate can also be integrated via the other layer using a thermal lamination method.

In the thermal lamination method, the lamination temperature can be set appropriately depending on the melting point and MFR of the resin material, but from the perspective of film dimensional stability, a temperature of, for example, 90 to 130°C is preferred, and 95 to 120°C is even more preferred.

[Molded body]
A molded article according to one aspect of the present embodiment includes the biodegradable laminate.
The molded article is not particularly limited as long as it contains the laminate, and examples thereof include paper, film, sheet, tube, plate, rod, packaging material (e.g., bag), container (e.g., bottle container), parts, etc. From the viewpoint of measures against marine pollution, the molded article is preferably a packaging material or a container.

The molded article may be the biodegradable laminate itself.
The biodegradable laminate contained in the molded article may be a secondary processed one. By processing the biodegradable laminate, 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). The laminate can also be used as a container for holding liquids, particularly as a container for hot contents, such as a cup for food and beverages such as instant noodles, instant soup, and coffee, or a tray for prepared meals, bento boxes, and microwaveable foods.

The secondary processing can be carried out by any method known in the art, such as various bag-making machines, filling and packaging machines, etc. Processing can also be carried out using devices 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. It is particularly preferred that the molded product be secondary processed using a heat sealing method, i.e., that it includes a heat-sealed portion using a biodegradable film layer. The heat sealing may be carried out between the base layer and the biodegradable film layer, or between the biodegradable film layers.

The heat sealing temperature when heat sealing the biodegradable laminate varies depending on the adhesive method, substrate, and coating thickness, but may be, for example, approximately 120°C to 180°C. The heat sealing pressure when heat sealing the biodegradable laminate varies depending on the adhesive method, but may be, for example, 0.1 MPa or more.

To improve its physical properties, the molded article according to this embodiment can also be composited with another molded article (e.g., fiber, thread, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, part, foam, etc.) made from a different material. It is preferable that these materials are also biodegradable.

The present invention will be explained in detail below using examples, but the technical scope of the present invention is not limited to these examples.

(Resin powder with PHBH as the main component)
All of the PHBH powders used in the examples and comparative examples were produced in accordance with the method described in International Publication No. 2019-142845. The molecular weight and monomer ratio of PHBH contained in each powder are shown below.
PHBH powder 1: PHBH powder having a weight-average molecular weight of 550,000, and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 15.3 mol%. PHBH powder 2: PHBH powder having a weight-average molecular weight of 550,000, and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 5.3 mol%. PHBH powder 3: PHBH powder having a weight-average molecular weight of 250,000, and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 15.3 mol%. PHBH powder 4: PHBH powder having a weight-average molecular weight of 250,000, and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 5.3 mol%. PHBH powder 5: PHBH powder having a weight-average molecular weight of 750,000, and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 15.3 mol%. PHBH powder 6: PHBH powder having a weight average molecular weight of 750,000 and a ratio of 3HH to the total of 3HB and 3HH in the PHBH of 5.3 mol%

(Ingredients other than PHBH powder)
Porous particle 1: Hydrophobic zeolite, average particle size 3 to 5 μm, pore size 0.9 nm, ABSCENTS-2000 POWDER (manufactured by Union Showa Co., Ltd.)
Porous particle 2: Hydrophobic zeolite, average particle size 3 to 5 μm, pore size 0.6 nm, ABSCENTS-3000 POWDER (manufactured by Union Showa Co., Ltd.)
PETL: Pentaerythritol, Neuraizer P (manufactured by Mitsubishi Chemical Corporation)
BA: Behenic acid amide, BNT-22H (manufactured by Nippon Fine Chemical Co., Ltd.)
Plasticizer: glycerin fatty acid ester, Biocizer (manufactured by Riken Vitamin Co., Ltd.)

(Method for producing resin pellets containing PHBH as the main component)
PHBH pellet 1: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 part by weight), pentaerythritol (1.0 part by weight), and porous particle 1 (1.0 part by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellets 2: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), and porous particles 1 (5.0 parts by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellet 3: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 part by weight), pentaerythritol (1.0 part by weight), porous particle 1 (5.0 parts by weight), and glycerin fatty acid ester (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 extruded strands were then passed through warm water at 40°C to solidify them, and then cut into pellets.
PHBH pellet 4: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), porous particle 1 (5.0 parts by weight), and glycerin fatty acid ester (5.0 parts 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 extruded strands were then passed through warm water at 40°C to solidify them, and then cut into pellets.

PHBH pellets C1: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 part by weight), and pentaerythritol (1.0 part by weight), and the mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellets C2: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), and porous particles 1 (11.0 parts by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellets C3: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), porous particles 1 (11.0 parts by weight), and glycerin fatty acid ester (5.0 parts 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 extruded strands were then passed through warm water at 40°C to solidify them, and then cut into pellets.
PHBH pellets C4: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), porous particles 1 (11.0 parts by weight), and glycerin fatty acid ester (11.0 parts 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 extruded strands were then passed through warm water at 40°C to solidify them, and then cut into pellets.
PHBH pellet C5: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 part by weight), pentaerythritol (1.0 part by weight), and porous particle 2 (1.0 part by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellets C6: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), and porous particles 2 (5.0 parts by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellet C7: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), and porous particles 2 (11.0 parts by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.
PHBH pellets C8: PHBH powder 1 (80 parts by weight) was dry-blended with PHBH powder 2 (20 parts by weight), behenic acid amide (0.5 parts by weight), pentaerythritol (1.0 part by weight), porous particles 2 (11.0 parts by weight), and glycerin fatty acid ester (5.0 parts 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 extruded strands were then passed through warm water at 40°C to solidify them, and then cut into pellets.
PHBH pellet C9: PHBH powder 3 (80 parts by weight) was dry-blended with PHBH powder 4 (20 parts by weight), behenic acid amide (0.5 part by weight), pentaerythritol (1.0 part by weight), and porous particle 1 (1.0 part by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into a strand shape, passed through warm water at 40°C to solidify, and cut into pellets.
PHBH pellets C10: PHBH powder 5 (80 parts by weight) was dry-blended with PHBH powder 6 (20 parts by weight), behenic acid amide (0.5 part by weight), pentaerythritol (1.0 part by weight), and porous particle 1 (1.0 part by weight). The mixture was melt-kneaded using a twin-screw extruder at a set temperature of 150°C and a screw rotation speed of 100 rpm, extruded into strands, solidified by passing through warm water at 40°C, and cut into pellets.

<Production of PHBH film by extrusion method and production of paper laminate by thermal lamination method>
Example 1
The PHBH pellets 1 were extruded using a single-screw extruder equipped with a T-die so that the resin temperature immediately after leaving the T-die head would be 168°C, and then taken up with a cooling roll set at 60°C to obtain a 30 μm-thick PHBH film 1. Subsequently, a paper substrate with a basis weight of 210 g/ ^m2 and the PHBH film 1 were sandwiched between a heating roll on the paper side and a cooling roll on the film side to obtain a paper laminate 1.
Example 2
A PHBH film 2 and a laminate 2 were obtained in the same manner as in Example 1, except that PHBH pellets 1 were changed to PHBH pellets 2.
Example 3
A PHBH film 3 and a laminate 3 were obtained in the same manner as in Example 1, except that PHBH pellets 1 were changed to PHBH pellets 3.
Example 4
A PHBH film 4 and a laminate 4 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets 4.
Example 5
PHBH film 5 and laminate 5 were obtained in the same manner as in Example 1, except that the resin was extruded so that the temperature of the resin immediately after it came out of the T-type die head was 158°C.

(Comparative Example 1)
A PHBH film C1 and a laminate C1 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C1.
(Comparative Example 2)
A PHBH film C2 and a laminate C2 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C2.
(Comparative Example 3)
A PHBH film C3 and a laminate C3 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C3.
(Comparative Example 4)
A PHBH film C4 and a laminate C4 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C4.
(Comparative Example 5)
A PHBH film C5 and a laminate C5 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C5.
(Comparative Example 6)
A PHBH film C6 and a laminate C6 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C6.
(Comparative Example 7)
A PHBH film C7 and a laminate C7 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C7.
(Comparative Example 8)
A PHBH film C8 and a laminate C8 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C8.
(Comparative Example 9)
A PHBH film C9 and a laminate C9 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C9.
(Comparative Example 10)
A PHBH film C10 and a laminate C10 were obtained in the same manner as in Example 1, except that the PHBH pellets 1 were changed to PHBH pellets C10.

[Evaluation method]
The evaluations in the examples and comparative examples were carried out by the following methods.
(Measurement of weight average molecular weight of PHBH)
The weight-average molecular weight of PHBH contained in the PHBH film was determined as a polystyrene-equivalent molecular weight by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase.

(Measurement of tensile modulus of PHBH film)
The tensile modulus of the PHBH film was calculated from the stress-strain curve between two points where the strain was 0.05% and 0.25% according to JIS standard K7161-1. Here, the tensile test was performed using a Shimadzu Autograph EZ-LX (manufactured by Shimadzu Corporation).

(Measurement of tear strength of PHBH film)
The tear strength of the PHBH film was evaluated as the Elmendorf tear strength in the machine direction of the film in accordance with JIS standard K7128-2. Here, the tear test was performed using an analog Elmendorf tear tester (manufactured by Toyo Seiki Co., Ltd.).

(Odor evaluation of paper laminate)
The paper laminate was cut into a rectangle 20 mm wide and 50 mm long, and sealed in a glass bottle. The sealed glass bottle was then left to stand in an oven at 80°C for 1 hour, after which the lid was removed and three people were asked to smell the odor and evaluate it based on the following criteria.
<Evaluation criteria>
×: The odor was so strong that 3 out of 3 people could clearly detect it. ○: Of the 3 people, some could detect the odor and some could not, and even if they could detect the odor, it was not bothersome. ◎: The odor was so strong that none of the 3 people could detect it. If the evaluation result is ◎ or ○, it can be said that the odor is suppressed.

(Evaluation of Lamination Strength of Paper Laminate)
A laminate strength test was conducted on the day after the paper laminate was produced. Specifically, a thin cross-cut was made on the PHBH film surface of the paper laminate with a cutter blade, and Nichiban No. CT-17 tape was firmly attached to the cut portion, and then gently peeled off by hand to create a starting point. A piece was then cut out to a width of 15 mm, and the PHBH film layer and paper layer were gripped with a jig so that they were at an angle of 180°, and a peel strength test was conducted. The tensile speed was 200 mm/min. A Shimadzu Autograph EZ-LX (manufactured by Shimadzu Corporation) was used as the peel tester.
<Evaluation criteria>
⊚: 3.0 N/15 mm or more ◯: 2.5 N/15 mm or more and less than 3.0 N/15 mm ×: less than 2.0 N/15 mm When the evaluation result is ⊚ or ◯, it can be said that the laminate strength is good.

(Evaluation of bending resistance of paper laminate)
The flexural resistance of the paper laminate was evaluated the day after its production. Specifically, the paper laminate was bent at a 90° angle so that the PHBH film surface faced outward, and the bent portion was observed under a scanning electron microscope at 500x magnification to check for the presence of streaky cracks on the resin surface. Furthermore, a red food coloring solution adjusted to a solids concentration of 10% was applied to the bent portion, which was left to stand for 1 minute. After that, the red food coloring was wiped off with a cloth, and it was checked whether the bent portion was dyed red.
<Evaluation criteria>
◎: No streak-like cracks, and no staining with red food coloring is observed. ○: Streak-like cracks are observed, but no staining with red food coloring is observed. ×: Streak-like cracks are observed, and staining with red food coloring is also observed. When the evaluation result is ◎ or ○, it can be said that the bending resistance is good.

(Evaluation of heat sealability)
The heat seal test was conducted on the day after the paper laminate was produced. Using a heat sealer (TP-701-B, manufactured by Tester Sangyo Co., Ltd.), the PHBH film surface and the paper surface of the paper laminate were overlapped and heated and pressed at 0.4 MPa for 5 seconds. The maximum temperature of the resin surface during adhesion was 140°C.
According to JIS standard Z0238, a 15 mm wide piece was cut out and subjected to a 180° peel strength test to evaluate heat sealability. The test was performed with a chuck distance of 100 mm and a pulling speed of 300 mm/min. The peel tester used was a Shimadzu Autograph EZ-LX (manufactured by Shimadzu Corporation).
<Evaluation criteria>
⊚: 3.0 N/15 mm or more ◯: 2.5 N/15 mm or more and less than 3.0 N/15 mm ×: less than 2.0 N/15 mm When the evaluation result is ⊚ or ◯, it can be said that the heat sealability is good.

The following can be seen from Table 1: In Comparative Example 1, in which no porous particles (B) were blended, the bending resistance and heat sealability were good, but a clear odor was detected.
In Comparative Example 2, in which the blending amount of porous particles (B) was large, odor was suppressed but flex resistance deteriorated. In Comparative Examples 3 and 4, in which a plasticizer was blended in contrast to Comparative Example 2, flex resistance was improved but heat sealability deteriorated.
In Comparative Examples 5 and 6, which used porous particles with a pore size as small as 0.6 nm, odor could not be suppressed, and in Comparative Example 7, in which the blending amount of the porous particles was increased, odor was suppressed but flex resistance deteriorated. In Comparative Example 8, in which a plasticizer was blended in addition to Comparative Example 7, flex resistance was improved but heat sealability deteriorated.
Comparative Example 9, in which a low molecular weight PHBH was used, had insufficient flex resistance, and Comparative Example 10, in which a high molecular weight PHBH was used, had insufficient heat sealability and also a decrease in lamination strength (adhesion strength between layers in a paper laminate).
In contrast to these comparative examples, Examples 1 to 5 show that odor is suppressed and both bending resistance and heat sealability are good. It is also clear that the laminate strength is good.

Claims (9)

A biodegradable film comprising a thermoplastic resin (A) containing a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, and porous particles (B) containing hydrophobic zeolite,
The weight average molecular weight of the copolymer is 400,000 to 650,000,
The copolymer has an average content of 3-hydroxyhexanoate of 3 to 20 mol %,
the pore diameter of the porous particles (B) is 0.7 to 1.5 nm,
the proportion of the hydrophobic zeolite in the entire porous particles (B) is 50 to 100% by weight,
A biodegradable film, wherein the blending amount of the porous particles (B) is 0.1 to 10 parts by weight per 100 parts by weight of the thermoplastic resin (A). The biodegradable film according to claim 1, further comprising at least one plasticizer (C) selected from the group consisting of glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoate ester compounds, phthalate ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds, in an amount of 0.5 parts by weight or more but less than 10 parts by weight per 100 parts by weight of the thermoplastic resin (A). The biodegradable film according to claim 1 or 2, wherein the tensile modulus of the biodegradable film in the MD or TD direction is 300 MPa or more and less than 800 MPa. The biodegradable film according to any one of claims 1 to 3, wherein the Elmendorf tear strength of the biodegradable film in the MD or TD direction is 3.0 mN/μm or more and less than 35 mN/μm. A biodegradable laminate comprising the biodegradable film according to any one of claims 1 to 4 and a substrate (D). The biodegradable laminate according to claim 5, wherein the substrate (D) is paper. A method for producing the biodegradable laminate described in claim 5 or 6, comprising the step of forming the biodegradable film on at least one surface of the substrate (D) by extrusion lamination or thermal lamination. The biodegradable film is formed on at least one surface of the substrate (D) by extrusion lamination,
The method according to claim 7, wherein the temperature of the resin composition immediately after being extruded from the tip of the T-die head is equal to or higher than the melting point of the thermoplastic resin (A) and equal to or lower than 170°C. A molded article comprising the biodegradable laminate according to claim 5 or 6.