Composite plastic and production method for same

Abstract

The purpose of the present invention is to provide a novel composite plastic and a production method for the same. The present invention provides, as a novel composite plastic, a composite plastic that contains one or more PGAICs and poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC). A production method for the composite plastic is characterized by comprising mixing molten plastic with PGA dissolved in an organic solvent and solidifying the mixture to produce a PGA-containing plastic.

Description

Composite plastic and its manufacturing method

[0001] The present invention relates to a composite plastic and a method for producing the same.

[0002] Poly-γ-glutamic acid ion complex (PGAIC) can be synthesized with a substantially 100% conversion rate by simply mixing poly-γ-glutamic acid (PGA) with a quaternary ammonium ion compound, which is the ion complex partner molecule, in a liquid phase (mainly aqueous solvent system) (International Publication WO 2010 / 014244). This reaction was achieved by utilizing the cooperative association ability unique to PGA.

[0003] PGAIC is known for its use as an antibacterial coating agent, but it has the problem that its functionality does not last for long periods of time because it is vulnerable to organic solvents widely used in daily life, such as alcohol.

[0004] Therefore, instead of coating PGAIC on plastic, attempts were made to mix PGAIC directly into plastic, but most PGAIC was not heat resistant and could not withstand the high temperatures that occur during plastic molding.

[0005] The present inventors have therefore conducted extensive research into methods for incorporating PGAIC into plastics, and have discovered that by first incorporating PGA into plastic and then immersing the solidified PGA-containing plastic in an aqueous solution of quaternary ammonium ions, PGAIC is generated from the area in contact with the aqueous solution, leading to the completion of the present invention. The present inventors call this method "in-situ transformation."

[0006] One embodiment of the present invention is a composite plastic containing poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC) and one or more PGAICs. The composite plastic may contain the PGA that does not form a PGAIC and the one or more PGAICs in a mass ratio of 0.01:99.99 to 99.99:0.01. The composite plastic may be in the form of a film, sheet, or fiber. The PGA that does not form a PGAIC and the one or more PGAICs may each be present in a compartmentalized form in the composite plastic. The two or more PGAICs may also be present in a compartmentalized form in the composite plastic.

[0007] Another embodiment of the present invention is a plastic containing poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC), wherein the PGA is dispersed within the plastic. The PGA-containing plastic may be in the form of a film, sheet, or fiber.

[0008] A further embodiment of the present invention is a method for producing the composite plastic, comprising the steps of melting a plastic, mixing the molten plastic with PGA dissolved in an organic solvent and solidifying the molten plastic, and partially converting the solidified PGA-containing plastic into a first PGAIC. ＋ and the first PGAIC is partially converted to the first PGAIC by contacting the first PGAIC with a salt having the formula ＋The salt having the formula (I) may be selected from quaternary ammonium compounds, cationic dye compounds, dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium). The method for producing a composite plastic may further include a step of dissolving PGA in an organic solvent to produce PGA dissolved in the organic solvent. In the method for producing a composite plastic, the PGA to be dissolved in the organic solvent may be aluminum ion-free. In the method for producing a composite plastic, the PGA to be dissolved in the organic solvent may be metal ion-free. In the method for producing a composite plastic, the organic solvent may be DMSO or acetone. The method for producing a composite plastic may further include a step of partially converting the solidified PGA-containing plastic into a second PGAIC. The solidified PGA-containing plastic may be converted into a second N ＋ is partially converted to a second PGAIC by contacting the second PGAIC with a salt having ＋ may be selected from quaternary ammonium compounds, cationic dye compounds, dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium).

[0009] A further embodiment of the present invention is a method for producing a PGA-containing plastic, comprising the steps of melting a plastic and mixing the molten plastic with PGA dissolved in an organic solvent and solidifying the mixture. The method for producing a PGA-containing plastic may further comprise dissolving PGA in an organic solvent to produce a PGA dissolved in the organic solvent. In the method for producing a PGA-containing plastic, the PGA to be dissolved in the organic solvent may be aluminum ion-free or metal ion-free. In the method for producing a PGA-containing plastic, the organic solvent may be DMSO or acetone.

[0010] A further embodiment of the present invention is a biodegradability-imparting agent for imparting biodegradability to plastics, the biodegradability-imparting agent containing PGA as an active ingredient.

[0011] A further embodiment of the present invention is a solution of PGA in an organic solvent, which may be DMSO or acetone.

[0012] A further embodiment of the present invention is an aluminum-free PGA, which may be metal ion-free.

[0013] ==Cross-reference to related literature== This application claims priority based on Japanese Patent Application No. 2024-67835, filed on April 18, 2024, and the basic application is incorporated herein by reference.

[0014] FIG. 1 is a diagram showing a method for producing a masterbatch as one embodiment of the present invention. (I) "Dispersion kneading method" and (II) "Localized kneading method" are exemplified. In one example of the present invention, this figure shows the appearance of a film made from a PGA-containing plastic. (A) Films made from PGA-containing polyethylene (B) PGA-containing polybutylene succinate (C) PGA-containing polybutylene terephthalate are exemplified. In a comparative example of the present invention, this figure shows the appearance of a film made from plastic. (A) Films made from polyethylene (B) polybutylene succinate (C) polyethylene terephthalate (D) anionized PET with sulfonic acid groups introduced are exemplified. In one example of the present invention, this figure shows the relationship between conversion efficiency and film thickness when in-situ transformation is performed on a PGA-containing plastic film using a cationic dye. (A) The appearance of dyed films made from PET (B) anionized PET (C) PE is exemplified. In one embodiment of the present invention, this figure shows the relationship between conversion efficiency and film thickness when in-situ transformation was performed on a PGA-containing plastic film using a cationic dye. (D) The appearance of a dyed film made of PGA-containing PE (E) PBS (F) PGA-containing PBS is illustrated. In one embodiment of the present invention, this figure shows the results of a dyeing test on films made from PGA-containing plastic and PGA-free plastic. (A) The appearance of a dyed film made of PET (B) anionized PET (C) PE (D) PGA-containing PE (E) PBS (F) PGA-containing PBS is illustrated. In one embodiment of the present invention, this figure shows the results of a multicolor dyeing test on a film made from PGA-containing PBS. (A, upper row) shows the absorption wavelength of the binding dye in the staining solution, (A, lower row) shows the absorption wavelength (400 nm to 800 nm) of the binding dye dissolved in a sodium chloride aqueous solution, and (B) shows the dyed appearance. 1 is a graph showing the results of an evaluation test on the mass loss rate conducted to evaluate the environmental compatibility of an embodiment of the present invention.CO was used to evaluate the environmental compatibility of an embodiment of the present invention. ２ 1 is a diagram showing the results of an evaluation test regarding the amount of generation.

[0034] FIG. 1 is a diagram showing the results of a microparticle binding test for a PGAIC-containing PE film in one embodiment of the present invention.

[0035] FIG. 1 shows the results of photographing fluorescent microplastics captured in a PE film (PE), a PGA-containing PE film (PGA / PE), and a PGAIC-containing PE film (PGAIC / PE) using a fluorescence observation device. The white glowing areas indicate fluorescence emitted by fluorescent microplastics.

[0036] FIG. 1 is a diagram showing the results of an evaluation test regarding the amount of generation.

[0037] FIG. 1 shows the results of a microparticle binding test for a PGAIC-containing PE film in one embodiment of the present invention.

[0038] FIG. 1 shows the results of photographing fluorescent microplastics captured in a PE film (PE), a PGA-containing PE film (PGA / PE), and a PGAIC-containing PE film (PGAIC / PE) using a fluorescence observation device. The white glowing areas indicate fluorescence emitted by fluorescent microplastics.

[0039] FIG. 1 shows the results of an evaluation test regarding the amount of generation.

[0039] (A) Aluminum ion-bound PGA; (B) Aluminum ion-free PGA.

[0015] The objectives, features, advantages, and concepts of the present invention will be apparent to those skilled in the art from the description herein, and those skilled in the art will be able to easily reproduce the present invention from the description herein. The following embodiments and specific examples of the present invention are intended to illustrate and explain preferred embodiments of the present invention and are not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and adaptations can be made based on the description herein within the spirit and scope of the present invention. ==Composite Plastic== The composite plastic disclosed herein is a plastic containing poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC) and one or more PGAICs. In this specification, this composite plastic is also referred to as a PGAIC-containing plastic. Specific PGAIC-containing plastics will also be referred to by prefixing the name of the plastic with "PGAIC-containing" (e.g., PGAIC-containing polyester).

[0016] Here, PGAIC means PGA and N ＋ It is an ion complex formed by hydrophobic bonding with a salt having the formula: ＋The salt having the formula (I) is preferably selected from quaternary ammonium compounds of the formula (I) and (II), cationic dye compounds of the formula (I), dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium).

[0017]

[0018] (In the formula, R １ H and C １－２ alkyl groups (i.e., hydrogen, methyl, or ethyl), preferably methyl; R ２ and R ３ is independently C １－１５ alkyl groups, R ４ and R ５ is independently C １－２０ alkyl groups.)

[0019]

[0020]

[0021]

[0022] The PGA that does not form a PGAIC and one or more PGAICs may be contained in a mass ratio of 0.01:99.99 to 99.99:0.01, preferably 0.1:99.9 to 99.9:0.1, more preferably 1:99 to 99:1, even more preferably 5:95 to 95:5, even more preferably 10:90 to 90:10, and even more preferably 20:80 to 20:80. That is, the total mass of PGAIC relative to the total mass of PGA and PGAIC that do not form PGAIC is preferably 0.01% or more, more preferably 0.1% or more, even more preferably 1% or more, even more preferably 5% or more, even more preferably 10% or more, even more preferably 20% or more, and preferably 99.99% or less, more preferably 99.9% or less, even more preferably 99% or less, even more preferably 95% or less, even more preferably 90% or less, even more preferably 80% or less.

[0023] The ratio of the total mass of the plastic to the PGA and PGAIC that do not form PGAIC relative to the total mass of the composite plastic is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, and even more preferably 0.4% or more, and is preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and even more preferably 2.5% or less.

[0024] The ratio of PGAIC in the composite plastic is preferably such that the total mass of PGAIC is 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, and even more preferably 0.4% or more, relative to the mass of the entire composite plastic, and is preferably 8.0% or less, more preferably 4.0% or less, even more preferably 2.0% or less, and even more preferably 1.0% or less.

[0025] The shape of the composite plastic is not particularly limited, and may be a cube, a rectangular parallelepiped, a sphere, a plate, or a film, sheet, fiber, or the like. Here, a film refers to a film with a thickness of less than 200 μm, and a sheet refers to a film with a thickness of 200 μm or more. The thickness of the film may be less than 100 μm or less than 50 μm. The thickness of the sheet may be 250 μm or more, 300 μm or more, 500 μm or more, or 1000 μm or more.

[0026] In the composite plastic, PGA and PGAIC that do not form PGAIC may exist in a compartmentalized manner. For example, the PGAIC may form part or all of the surface of the composite plastic, may form part of the interior of the composite plastic, or may form part of the composite plastic extending from the surface to the interior.

[0027] Furthermore, the PGAIC may contain multiple types of PGAIC, or multiple types of PGAIC may be present in a compartmentalized state. This allows the composite plastic to have multiple functions. For this purpose, it is preferable that multiple types of PGAIC are present in a compartmentalized state.

[0028] Such composite plastics possess antibacterial and adhesive properties due to the presence of PGAIC. Furthermore, as described below, PGA functions as a microbial affinity enhancer, and the PGAIC reverts to PGA after long-term use, subsequent disposal, or exposure to the natural environment, enhancing biodegradability. ==Method for Producing Composite Plastics== The method for producing composite plastics disclosed herein includes a first step of melting plastic, a second step of mixing the molten plastic with PGA dissolved in DMSO and solidifying it, and a third step of partially converting the solidified PGA-containing plastic into a first PGAIC. A fourth step may also be included in which the solidified PGA-containing plastic is partially converted into a second PGAIC. Repeating these steps allows the production of composite plastics containing PGA that does not form PGAIC and 3 to n types of PGAIC (n is an integer of 4 or greater). (1) First Step Examples of plastic materials include thermoplastic polymers such as polyester, polyolefin, polyamide, and ABS resin; thermosetting polymers such as acrylic resin; natural fibers made of sugars such as polysaccharides that are neither thermoplastic nor hardenable; and biosynthetic polymers such as cellulose, alginic acid, and polylactic acid.

[0029] Examples of polyesters include aromatic polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); aromatic polyester copolymers such as polybutylene adipate terephthalate (PBAT); and aliphatic polyesters such as polyhydroxyalkanoic acid (PHAs), polylactic acid (PLA), polycaprolactone (PCL), and polybutylene succinate (PBS). Various copolymerization components may be used, as long as they do not impair performance, and may contain additives such as matte finishes or UV blocking agents. Recycled polyester may also be used.

[0030] Examples of the copolymerization component include polycarboxylic acids and derivatives thereof, such as isophthalic acid, orthophthalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, trimellitic acid, and pyromellitic acid; dicarboxylic acids and derivatives thereof, including sulfonates, such as 5-sodium sulfoisophthalic acid and 5-sodium dihydroxyethyl sulfoisophthalate; 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, polyethylene glycol, trimethylolpropane, pentaerythritol, 4-hydroxybenzoic acid, ε-caprolactone, and copolymerized ethylene glycol ether.

[0031] Examples of polyolefins include polyethylene (PE), polypropylene (PP), PE-methyl acrylate copolymer (EMMA), PE-vinyl acetate copolymer (EVA), etc. Recycled polyolefins may also be used.

[0032] Examples of polyamides include nylon 6, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 5,6, polyparaphenylene terephthalamide, etc. Recycled polyamides may also be used.

[0033] Examples of polysaccharides include highly crystalline natural cellulose (e.g., Avicel), amorphous cellulose acetate, and composite polymers containing edible amylose, hemicellulose, lignin, etc. Recycled pulp may also be used. (2) Second Step: Next, PGA dissolved in an organic solvent is mixed with the molten plastic and solidified. This step may include a step of dissolving PGA in the organic solvent.

[0034] PGA is a biopolyamide formed by the polymerization of the natural amino acid glutamic acid through the bonding of each α-amino group and γ-carboxy group, and is known to have stereochemical diversity. As the polymer, homopolymers of L-glutamic acid, homopolymers of D-glutamic acid, and copolymers containing L-glutamic acid and D-glutamic acid have been disclosed and known, and any of these may be used.

[0035] There are no particular limitations on the shape or molecular weight of PGA, but the molecular weight is preferably 10 kD or more, more preferably 30 kD or more, even more preferably 90 kD or more, and preferably 1,000 kD or less, more preferably 300 kD or less, and even more preferably 100 kD or less.

[0036] PGA may be commercially available, chemically synthesized, or isolated from organisms that produce it. In the case of chemical synthesis, PGA is polymerized under typical conditions to form poly-α-glutamic acid. Examples of organisms that produce PGA include Bacillus subtilis and Bacillus megaterium, as well as Bacillus anthracis, Bacillus halodurans, Natrialba aegyptiaca, and Hydra, and PGA may be isolated from these organisms.

[0037] Conventionally, PGA has been known to be water-soluble but insoluble in other solvents. However, the present invention uses a PGA that is soluble in organic solvents but insoluble in water (also referred to herein as organic solvent-soluble PGA). PGA can be made soluble in organic solvents but insoluble in water by being aluminum ion-free. This organic solvent-soluble PGA is preferably metal ion-free. Here, "free of aluminum ions" does not simply mean that the aluminum ion content is completely absent; it may be 30 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less, per mole of PGA carboxyl groups. Furthermore, "metal ion-free" does not simply mean that the total amount of all types of metal ions is completely zero; it may be 30 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less.

[0038] By using PGA dissolved in an organic solvent in this manner, it is possible to create a highly dispersed state even in a solid-phase solvent such as molten plastic. The organic solvent for dissolving PGA is not particularly limited, but examples include dimethyl sulfoxide (DMSO), acetone, dimethylacetamide, dimethylformamide, hexamethylphosphoric triamide (HMPA), and N-methyl-2-pyrrolidone, with DMSO being preferred. The organic solvent may contain an aqueous solvent such as water. The proportion of the aqueous solvent is not particularly limited, but is preferably 90% or less, more preferably 70% or less, even more preferably 50% or less, even more preferably 30% or less, even more preferably 10% or less, even more preferably 5% or less, even more preferably 2% or less, and even more preferably 1% or less, and most preferably does not contain an aqueous solvent.

[0039] Specific methods for kneading PGA dissolved in an organic solvent into plastic include, for example, the general "dispersion kneading method" shown in Figure 1(I), as well as the "localized kneading method" shown in Figure 1(II), which allows for more surface concentration. In the "dispersion kneading method," plastic is melted in a mold, PGA dissolved in an organic solvent is added thereto, and the mixture is quickly stirred and mixed. On the other hand, the "localized kneading method" is more preferable in that the inner surface of the mold is covered with PGA dissolved in DMSO, and then heated and melted plastic is poured into the mold, allowing the PGA to be quickly dispersed into the molten plastic while maintaining surface localization.

[0040] After the PGA is mixed and dispersed in the molten plastic, the molten plastic is solidified to produce a masterbatch. In this state, the masterbatch is a plastic containing PGA that has not formed a PGAIC, and the PGA is dispersed within the masterbatch. In this specification, such a masterbatch is also referred to as a PGA-containing plastic. Specific PGA-containing plastics will also be referred to by adding "PGA-containing" before the name of the plastic (e.g., PGA-containing polyester).

[0041] The method for molding the masterbatch is not particularly limited, and injection molding, extrusion molding, blow molding, inflation molding, T-die molding, inflation molding, vacuum molding, pressure molding, etc. can be used. The shape and size of the masterbatch are not particularly limited, and examples of shapes include pellets, blocks, powder, and particles. For example, pellets can be formed by kneading PGA into molten plastic, immediately extruding it from an extruder, and cutting it to a predetermined size. In the case of pellets, the length is preferably 2 mm to 6 mm and the diameter is preferably 1 mm to 3 mm. (3) Third and Fourth Steps In the third step, the masterbatch is partially converted into the first PGAIC. The method for converting the PGA contained in the masterbatch into the first PGAIC is not particularly limited, and known methods can be used. For example, the masterbatch can be kneaded with the first N ＋ The compound may be contacted with a salt having the formula:

[0042] The PGA in the masterbatch is the first N ＋ In the fourth step, the masterbatch is reacted with the salt having the formula (I) to partially produce the first PGAIC. ＋ This step can be repeated for the third to nth N ＋ (n is an integer of 4 or more), a composite plastic containing PGA that has not formed PGAIC and 3 to n types of PGAIC can be produced.

[0043] The first to nth numbers used here are ＋ The salt having the formula (I) is not particularly limited as long as it is a compound capable of converting PGA to PGAIC, but is preferably independently selected from quaternary ammonium compounds of the following formulas (I) and (II), cationic dye compounds of the following formulas, dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium).

[0044]

[0045] (In the formula, R １ H and C １－２ alkyl groups (i.e., hydrogen, methyl, or ethyl), preferably methyl; R ２ and R ３ is independently C １－１５ alkyl groups, R ４ and R ５ is independently C １－２０ alkyl groups.)

[0046]

[0047]

[0048]

[0049] Masterbatch N ＋ The method for contacting the salt having the formula (I) is not particularly limited, and examples thereof include ＋and a method of supporting quaternary ammonium ions on a carrier and bringing the carrier into contact with the masterbatch. ＋ When a solution of a salt having the formula: ＋ Depending on the type of salt having the formula (I), a protophilic organic solvent, such as an alcohol solvent such as methanol or ethanol, an ether solvent such as THF, or an amide solvent such as dimethylformamide or dimethylacetamide, may be mixed with the aqueous solvent. ＋ The concentration of the solution of the salt having the formula (I) is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0050] By immersing this PGAIC-containing plastic in a high salt concentration aqueous solution, ＋ The salt having the formula (I) can be dissociated from the PGAIC-containing plastic and returned to the PGA-containing plastic. The type of salt in the high-salt aqueous solution used here is not particularly limited, but sodium chloride, magnesium chloride, potassium chloride, etc. can be used. The salt concentration is preferably 500 mM or more, more preferably 600 mM or more, even more preferably 700 mM or more, and even more preferably 800 mM or more. The salt concentration is preferably 1300 mM or less, more preferably 1200 mM or less, even more preferably 1100 mM or less, and even more preferably 1000 mM or less.

[0051] N ＋Colored PGAIC-containing plastics can be produced by using a cationic dye as a salt having the formula (I) as the dyeing molecule. Examples of dyeing molecules include safranine (red), methylene blue (blue), Basic Yellow 1 (yellow), and Basic Green 1 (green), as mentioned above. As mentioned above, colored PGAIC-containing plastics can be decolorized by using a high-salt aqueous solution to return them to PGA-containing plastics. ==Method of Using PGA-Containing Plastics== As mentioned above, PGA-containing plastics are plastics that contain PGA that has not formed PGAIC, in which the PGA is dispersed. The PGA-containing plastics may be in the form of a film, sheet, or fiber.

[0052] PGA has the property of microbiophilicity, allowing it to attract and colonize microorganisms. This PGA-containing plastic also has microbiophilicity. That is, PGA not only possesses microbiophilicity itself, but also imparts microbiophilicity to plastics, thereby making the PGA-containing plastic itself microbiophilic, and can therefore function as an active ingredient in a biodegradable agent. == Organic Solubility-Soluble PGA == As mentioned above, PGA has traditionally been known to be water-soluble and insoluble in other solvents. However, the PGA disclosed herein is soluble in organic solvents and insoluble in water. PGA can be made soluble in organic solvents and insoluble in water by being aluminum ion-free. This organic solvent-soluble PGA is preferably metal ion-free. Here, "aluminum ion-free" does not simply mean that it is completely free, but rather that the aluminum ion content is 30 mol% or less per mole of PGA carboxyl group, preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less. Also, "metal ion-free" does not simply mean that the total amount of all types of metal ions is completely zero, but rather that the total amount is 30 mol% or less, preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less.

[0053] By using a solution of PGA dissolved in an organic solvent in this way, it is possible to create a highly dispersed state even in a solid-phase solvent such as molten plastic. The organic solvent for dissolving PGA is not particularly limited, but examples include dimethyl sulfoxide (DMSO), acetone, dimethylacetamide, dimethylformamide, hexamethylphosphoric triamide (HMPA), and N-methyl-2-pyrrolidone, with DMSO being particularly preferred. The organic solvent may contain an aqueous solvent such as water. The proportion of the aqueous solvent is not particularly limited, but is preferably 90% or less, more preferably 70% or less, even more preferably 50% or less, even more preferably 30% or less, even more preferably 10% or less, even more preferably 5% or less, even more preferably 2% or less, and even more preferably 1% or less, and most preferably does not contain an aqueous solvent.

[0054] [Example 1] Production and Testing of PGA-Containing Plastics [1] Production of PGA-Containing Plastics PGA-containing plastic films (1) to (3) were produced as follows and used in the following experiments. This PGA-containing plastic contains PGA that does not form PGAICs, with the PGA dispersed within. Films (4) to (7) were also produced as comparative examples. (1) Production of PGA-Containing Polyethylene Pellets and Film Formation 18 g of polyethylene (PE) pellets (manufactured by Japan Polyethylene Co., Ltd.) were melted on a hot plate set to 180°C, and then kneaded with 2 g of PGA dissolved in DMSO to a final PGA concentration of 10% by mass. The solidified material was then molded into pellets. The pellets were then filmed using a press set to 180°C. Films of various thicknesses ranging from 50 to 250 μm were produced. Figure 2A shows the appearance of the resulting film (thickness: 100 μm). The method for producing PGA dissolved in DMSO will be described later. In the following experiments, tests were performed using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0055] (2) Preparation of PGA-Containing Polybutylene Succinate Pellets and Film Formation. 18 g of polybutylene succinate (PBS) pellets (Nature3D) were melted on a hot plate set to 180°C, and then 2 g of PGA dissolved in DMSO was kneaded to a final PGA concentration of 10% by weight. The resulting solid was then molded into pellets. The pellets were then filmed using a press set to 180°C. Films were prepared in thicknesses ranging from 50 to 250 μm. Figure 2B shows the appearance of the resulting film (thickness: 100 μm). In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0056] (3) Preparation of PGA-Containing Polybutylene Terephthalate Pellets and Film Formation. 18 g of polybutylene terephthalate (PBT) pellets (manufactured by Polyplastics Co., Ltd.) were melted on a hot plate set to 290°C, and then 2 g of PGA dissolved in DMSO was kneaded to a final PGA concentration of 10% by mass. The resulting solid was then molded into pellets. The pellets were then filmed using a press set to 250°C. Films were prepared in various thicknesses ranging from 50 to 250 μm. Figure 2C shows the appearance of a film (thickness: 100 μm) obtained using PBT. In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0057] (4) Film Formation of PE Pellets The PE pellets were pressed into a press set at 180°C to form films. Films with various thicknesses ranging from 50 to 250 μm were produced. Figure 3A shows the appearance of the resulting film (thickness: 100 μm). In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0058] (5) Film Formation from PBS Pellets The PBS pellets were pressed into a press set at 180°C to form films. Films with various thicknesses ranging from 50 to 250 μm were prepared. Figure 3B shows the appearance of the resulting film (thickness: 100 μm). In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0059] (6) Film Formation from PET Pellets Films were formed from the PET pellets in a press set at 250°C, with various thicknesses ranging from 50 to 250 μm. Figure 3C shows the appearance of the resulting film (thickness: 100 μm). In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0060] (7) Film Formation from Anionized PET Pellets Anionized PET pellets (manufactured by Sanyo Chemical Industries, Ltd.) to which sulfonic acid groups had been introduced were subjected to a press set at 250°C to form films. Films with various thicknesses ranging from 50 to 250 μm were produced. Figure 3D shows the appearance of the resulting film (thickness: 100 μm).

[0061] In the following experiments, tests were conducted using square films with sides of 2 cm or circular films with a diameter of 12 mm.

[0062] [2] Test (1) In-situ transformation of PGA-containing plastics The thickness and weight of the film prepared in [1] were measured, and the film was immersed in a 0.0067% aqueous solution of safranine. Then, 30 μL of the aqueous solution was taken and diluted with 470 μL of distilled water, and the absorbance at 492 nm was measured. The measured values ​​were substituted into the following formula to calculate the in-situ transformation efficiency (based on the net amount converted to chromogenic PGAIC): y = (640x / 0.062979w) × 100, where y is the in-situ transformation efficiency (mol%), x is the measured absorbance at 492 nm, and w is the film mass (μg).

[0063] The relationship between the thickness of each film and the in-situ transformation efficiency is shown in Figure 4. As a control, no in-situ transformation occurred when using any of the pan-films made of PET, PBS, PE, or anionized PET (Figures 4A-C, E).

[0064] On the other hand, in-situ transformation occurred in films prepared by mixing PGA with PE or PBS (Figures 4D and 4F). Furthermore, as shown in Figure 4, the efficiency of in-situ transformation can be easily controlled by adjusting the film thickness and processing time. In this example, the final concentration of PGA mixed into the plastic was set to 10% by mass, and it is clear that the efficiency of in-situ transformation can also be controlled by adjusting this concentration.

[0065] (2) Coloring Performance Test of PGA-Containing Plastics 2 cm square films (100 μm thick) made of PET, anionized PET, PE, PGA-containing PE, PBS, and PGA-containing PBS were prepared and immersed in 4 mL of safranine aqueous solution (250 μmol / L) at room temperature for 1 hour. After immersion, the films were washed twice with distilled water and their dyeability was observed. The results are shown in Figure 5.

[0066] The films without PGA blended in (Figs. 5A-C, E) were not stained, but the films with PGA blended in (Figs. 5D, F) were easily stained. Although dyeing plastics is generally difficult, dyeing of PGA-containing plastics was easy.

[0067] Next, heat-resistant PGAAL was directly mixed with PBS without dissolving it in DMSO to form a film, which was then dyed in the same manner. However, as shown in Figure 5G, the resulting plastic was non-uniform and had low dispersibility.

[0068] (3) Antibacterial Test of PGAIC-Containing Plastics Films made of PET, anionized PET, PE, PGA-containing PE, PBS, PGA-containing PBS, and PGAAL-containing PBS, each with a diameter of 12 mm and a thickness of 100 μm, were treated with hexadecylpyridinium cation (HDP). ＋ The film was then immersed in a 0.1% aqueous solution (30°C) of HDP to prepare a PGAIC-containing plastic. The film was then kept at 30°C and immersed for 10 or 60 minutes, after which it was washed with 1 mL of warm water at 70°C. Finally, the film was dried in a space adjusted to 22°C until all excess water was removed, and used as a test film. ＋ A test film was also used that was not treated with the aqueous solution but was otherwise treated identically.

[0069] For the antibacterial test in this example, Escherichia coli and Bacillus subtilis were used. These bacteria were cultured in Luria-Bertani (LB) liquid medium at 37°C, and the OD ６００ When the pH reached 0.6, the bacteria were collected by centrifugation and suspended in an appropriate amount of physiological saline to prepare an "indicator bacteria solution." The concentration of E. coli in the indicator bacteria solution was 6.9 x 10 ４ / μL, and the concentration of Bacillus subtilis was 1.1 × 10 ４ / μL. 20 μL of this indicator bacteria solution was dropped into a petri dish, and a test film was placed on top of it to bring the two into contact. After incubation at room temperature for 1 hour, the bacteria in the petri dish were recovered with 2 mL of physiological saline. The recovered bacteria were again inoculated onto an LB plate medium and subsequently cultured at 37°C for 24 hours, after which the number of colonies (CFU) that appeared was counted. The following formula was used to calculate the antibacterial activity value (LRS). The results are shown in Tables 1 and 2. PET, PE, PBS, and PBS were used as controls for anionized PET, PGA-containing PE, PGA-containing PBS, and PGAAL-containing PBS, respectively. LRS=(log C ｔ -log C ０ ) - (log T ｔ -log T ０ ) Log C ０ : CFU Log C in the target area immediately after sowing ｔ : CFU LogT in the control group after incubation ０ : CFU LogT in the test plot immediately after sowingｔ : CFU in test group after incubation As shown in Tables 1 and 2, the PGA-containing PE and PGA-containing PBS exhibited significant antibacterial activity compared to the PGA-free PE and PBS, respectively.

[0070]

[0071] In this way, in situ transformation can impart antibacterial properties to plastics.

[0072] (4) Water Resistance Test of PGA-Containing Plastics. A film (2 cm square, 100 μm thick) composed of PGA-containing PE and PBS was immersed in 3 mL of distilled water. After 24 hours, 10 μL of the solution was removed and mixed with PGA quantification reagent (50 μL of physiological saline; 20 μL of 60 mM sodium citrate buffer (pH 6.8); 20 μL of 0.1% safranine solution). The mixture was left at room temperature for 10 minutes and then centrifuged (13,000 rpm; 10 minutes). 10 μL of the supernatant was collected and diluted 50-fold with distilled water, and the absorbance at 492 nm was measured. The leached PGA concentration (%) was calculated using the equation "y = x / 0.9106" (x, measured absorbance at 492 nm).

[0073] As a result, even when samples with different film masses and thicknesses were used, no PGA leaching was detected after 24 hours of treatment. Although PGA is considered a water-soluble polymer, the PGA present in PGA-containing plastics was highly water-resistant. Thus, PGA-containing plastics can be used stably in environments where they are exposed to water for long periods of time.

[0074] (5) Resistance test of PGAIC-containing plastics to organic solvents PGAIC was prepared by conventional methods by dissolving PGA in an aqueous solvent. ＋It can be prepared by reacting with PGAIC. Hereinafter, the PGAIC obtained by the conventional method will be referred to as "PGA / HDP." PGA / HDP is soluble in organic solvents such as ethanol and can be used as a coating agent that can impart antibacterial properties. First, a 1% PGA / HDP ethanol preparation dissolved at a high concentration in ethanol was prepared using the conventional method. Then, circular PE and PBS films (12 mm diameter, 100 μm thickness) were prepared, and 10 μL of the 1% PGA / HDP ethanol preparation was dropped onto both sides. Finally, the coated PGA / HDP ethanol preparation was dried in a space adjusted to 22°C until the ethanol in the PGA / HDP ethanol preparation was completely evaporated.

[0075] The PE film, PBS film, PGAIC-containing PE film, and PGAIC-containing PBS film thus prepared were immersed in an ethanol solution (2 mL) and then removed, and this procedure was repeated once, five times, or ten times. Finally, the film was dried in a space adjusted to 60°C until the ethanol had completely evaporated.

[0076] The thus treated film was subjected to an antibacterial test as follows. In this example, Escherichia coli was used, and an "indicator bacteria solution" was prepared in the same manner as in (3). 50 μL of the indicator bacteria solution was dropped into a petri dish, and the test film was placed on top of it to bring the two into contact. After incubation at room temperature for 1 hour, the indicator bacteria cells were recovered with 500 μL of physiological saline. The cells were plated on an LB plate and cultured at 37°C for 24 hours, after which the number of colonies (CFU) that appeared was counted, and the antibacterial activity value was calculated in the same manner as in (3). Tables 3 and 4 summarize the results of comparing the antibacterial durability of each film.

[0077]

[0078] In the case of PE films and PBS films coated with pre-synthesized antibacterial PGAIC, the antibacterial activity decreased after one ethanol wash and disappeared after five washes, as shown in Table 3. On the other hand, in the case of PGAIC-containing PE films and PBS films, the antibacterial activity was confirmed even after the 10th ethanol wash, as shown in Table 4, demonstrating excellent durability of the antibacterial activity.

[0079] Thus, PGAIC-containing plastics exhibit excellent durability even in environments where they are exposed to organic solvents.

[0080] (6) Dyeing Test of PGAIC-Containing Plastics This example demonstrates that PGAIC-containing plastics can be dyed to desired colors.

[0081] Aqueous solutions of the cationic dyes safranine (red) and methylene blue (blue) were prepared, and mixed dye solutions were prepared at various mixing ratios to achieve a total molar concentration of 250 μmol / L, as shown in Figure 6. The absorption wavelengths (400-800 nm) of the various mixed dye solutions were analyzed using an infrared-visible spectroscopy (UV-VIS). The results are shown in Figure 6A (top).

[0082] Next, a PGA-containing PBS film (2 cm square, 100 μm thick) was immersed in 4 mL of the mixed staining solution at room temperature for 1 hour to stain it. It was then washed with distilled water and dried to prepare a dyed film specimen. A photograph of its appearance is shown in Figure 6B. When the proportion of safranine in the staining solution was high, the amount of safranine-binding PGAIC increased, resulting in a reddish color; when the proportion of methylene blue in the staining solution was high, the amount of methylene blue-binding PGAIC increased, resulting in a blueish color. When the blending conditions were such that the proportions of the two in the staining solution were competitive, the film was stained purple.

[0083] Furthermore, the film can be decolorized by exposure to high-salt conditions. In this example, the film was decolorized to almost its original state by immersing each film in 1 mL of 4% sodium chloride aqueous solution and stirring for 20 minutes, and almost all of the binding dye was recovered in the sodium chloride aqueous solution. The absorption wavelength (400 nm to 800 nm) of the binding dye eluted in the sodium chloride aqueous solution was measured, and the results are shown in the lower panel of Figure 6A. The absorption wavelength was almost identical to that of the staining solution used.

[0084] In this way, the color of the plastic can be adjusted by selecting the type of colorable PGAIC contained in the film, and decolorization is easy by using an aqueous solution.

[0085] (7) PGAIC-Containing Plastic Having Both Dyeability and Antibacterial Properties This example demonstrates that PGAIC-containing plastic can have both dyeability and antibacterial properties.

[0086] First, 0.1% HDP aqueous solution, 0.04% safranine aqueous solution, and a mixed solution (0.1% HDP, 0.04% safranine) were prepared. PGA-containing PBS films (12 mm diameter, 100 μm thick) were immersed in 1 mL of each solution at room temperature for 1 hour, then washed with 1 mL of hot water at 70°C and dried. The staining test was performed by measuring absorbance (492 mm), and the antibacterial activity test was performed as in (3).

[0087] As shown in Figure 7, PGAIC-containing plastics stained red when treated with a safranine aqueous solution, PGAIC-containing plastics stained red when treated with a HDP aqueous solution exhibited antibacterial properties, and PGAIC-containing plastics stained with a mixed HDP and safranine aqueous solution possessed both dyeability and antibacterial properties.

[0088] In this way, by producing a PGAIC-containing plastic using a plurality of quaternary ammonium ions, it is possible to prepare a PGAIC-containing plastic having two different functions.

[0089] (8) Environmental compatibility evaluation method I (evaluation test on mass loss rate) In this example, the mass loss rate before and after treatment was calculated as an index of biodegradability by leaving the sample in seawater for a long period of time.

[0090] First, each film (2 cm square, 100 μm thick) was placed in a polypropylene basket and immersed in seawater at a depth of approximately 10 m off the coast of Kochi Prefecture for six months. After removal, the basket was washed with distilled water to completely remove any attached matter and then dried at room temperature. The weights were measured before and after immersion, and the weight loss rate was calculated. The results are shown in Figure 8.

[0091] Mass loss was observed in the control plastic (a) kneaded with cellulose and the marine biodegradable PHBH (b), but no clear mass loss was observed in the chemically synthesized polyester "CiCLO" (c) kneaded with PHBH and the compostable "Bio-PBS" (d). However, the PGA-containing PBT showed the greatest mass loss, comparable to or even greater than those of the other plastics.

[0092] Thus, PGA can impart biodegradability to PGA-containing plastics in the natural environment.

[0093] (9) Environmental compatibility evaluation method II (CO ２ In this example, as an index of biodegradability, the amount of CO generated during treatment was measured by leaving the sample in seawater for a long period of time. ２ The amount generated was measured and the biodegradation rate was calculated.

[0094] First, the weight of carbon in the total weight was calculated from the weight ratio of elements in the composition formula of the sample polymer, and all carbon was CO ２ The amount of oxygen required to convert carbon dioxide into carbon dioxide was calculated. Next, 400 mL of seawater collected from the coast of Kochi Prefecture was placed in a brown bottle. Each sample was placed in the bottle, and a 2 mol / L aqueous solution of sodium hydroxide was used as a carbon dioxide reservoir to measure the net biochemical oxygen demand (BOD). Measurements were performed using a BOD measurement sensor (BOD EVO system, VELP SCIENTIFICA), and the biodegradation rate (%) was calculated from the measurement results over one month. Biodegradation rate (%) = ((B-C) / A) x 100 A: The rate at which all carbon contained in the sample is converted to CO ２ B: BOD value in seawater in which the sample was immersed (test group) C: BOD value in seawater that had no contact with the sample (control group) The results are shown in Figure 9.

[0095] Mass loss was observed in the control plastic (a) kneaded with cellulose and the marine biodegradable PHBH (b), but no clear mass loss was observed in the chemically synthesized polyester "CiCLO" (c) kneaded with PHBH and the compostable "Bio-PBS" (d). However, the PGA-containing PBT showed the greatest mass loss, comparable to or even greater than those of the other plastics.

[0096] Thus, PGA can impart biodegradability to PGA-containing plastics in the natural environment.

[0097] (10) Particle Capture Test of PGAIC-Containing Films A 0.1% TOA solution was prepared by dissolving methyltri-n-octylammonium chloride (TOA) in a 20% aqueous ethanol solution. The PGA-containing PE film prepared in [1] was immersed in the 0.1% TOA solution. After 3 hours, the film was washed with warm water at 60°C to produce a PGAIC-containing film. For the particle capture test in this example, fluorescent microplastic powder was prepared as follows. First, acrylic resin powder (300 mesh or less) was dispersed in distilled water to prepare a 10% acrylic resin dispersion. Next, Nile Red was dissolved in acetone to prepare a Nile Red solution. The Nile Red solution was added to the 10% acrylic resin dispersion to a final Nile Red concentration of 10 ppm, and the mixture was allowed to stand. After 5 minutes, the mixture was centrifuged (130,000 rpm; 5 minutes) and the supernatant was removed to obtain fluorescent microplastic powder. A fluorescent microplastic dispersion was prepared by suspending fluorescent microplastic powder in distilled water to a final concentration of 0.1%. PE film, PGA-containing PE film, and PGAIC-containing PE film were immersed in this fluorescent microplastic dispersion (50 mL) and shaken. After 1 hour, the fluorescent microplastics captured by each film were observed using a fluorescence observation device (excitation wavelength: 480-520 nm, orange filter) (Figure 10). As shown in Figure 10, the PGAIC-containing PE film had more fluorescent microplastics attached than the PE or PGA-containing PE films. Thus, the PGAIC-containing PE film has a strong microparticle-trapping function.

[0098] [Example 2] Manufacturing method of PGA dissolved in DMSO PGA can be dissolved in an organic solvent by making it aluminum ion-free. In this example, DMSO was used as the organic solvent to manufacture PGA dissolved in DMSO.

[0099] First, 10 mL of aqueous PGA solution (concentration: 10% by mass) was mixed with 0.63 g of aluminum chloride hexahydrate to prepare a 10% PGA suspension. This suspension (10 mL) was placed in a dialysis tube and dialyzed against 1 L of 25 mM hydrochloric acid. After 1.5 hours, the dialysate was replaced with fresh solution four times. Once the bound aluminum ions were removed, the precipitate was recovered by centrifugation. When 0.3 g of this precipitate was placed in 10 mL of water or 10 mL of DMSO and stirred, it did not dissolve in water but dissolved in DMSO (Figure 11(B)).

[0100] By removing aluminum ions from PGA in this way, PGA becomes soluble in organic solvents. However, dialysis using pure water cannot remove aluminum ions from PGA, so PGA cannot be dissolved in DMSO (FIG. 11(A)).

[0101] The present invention makes it possible to provide a novel composite plastic and a method for producing the same.

Claims

1. A composite plastic containing poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC) and one or more types of PGAIC.

2. The composite plastic according to claim 1, wherein the one or more PGAs that do not form PGAIC and the one or more PGAIC are contained in a mass ratio of 0.01:99.99 to 99.99:0.

01.

3. The composite plastic according to claim 1 or 2, which is in the form of a film, sheet, or fiber.

4. The composite plastic according to claim 1 or 2, wherein the PGA not forming a PGAIC and the one or more PGAICs are each present in a compartmentalized state.

5. The composite plastic according to claim 1 or 2, wherein the two or more types of PGAICs are present in a compartmentalized state.

6. A plastic containing poly-gamma glutamic acid (PGA) that does not form a poly-gamma glutamic acid ion complex (PGAIC), wherein the PGA is dispersed within the plastic.

7. A method for producing a composite plastic according to claim 1, comprising the steps of: melting a plastic; mixing the molten plastic with PGA dissolved in an organic solvent and solidifying the mixture; and partially converting the solidified PGA-containing plastic into a first PGAIC.

8. The method for producing a composite plastic according to claim 7, wherein the solidified PGA-containing plastic is ＋ is partially converted to a first PGAIC by contacting the first PGAIC with a salt having ＋ wherein the salt having the formula (I) is selected from quaternary ammonium compounds, cationic dye compounds, dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium).

9. A method for producing a composite plastic according to claim 7 or 8, further comprising the step of dissolving PGA in an organic solvent to produce PGA dissolved in said organic solvent.

10. The method for producing a composite plastic according to claim 9, wherein the PGA to be dissolved in an organic solvent is free of aluminum ions.

11. The method for producing a composite plastic according to claim 10, wherein the PGA to be dissolved in an organic solvent is free of metal ions.

12. A method for producing a composite plastic according to any one of claims 7 to 11, wherein the organic solvent is DMSO or acetone.

13. A method for producing a composite plastic according to any one of claims 7 to 12, further comprising a step of partially converting the solidified PGA-containing plastic into a second PGAIC.

14. The method for producing a composite plastic according to claim 13, wherein the solidified PGA-containing plastic is ＋ is partially converted to a second PGAIC by contacting the second PGAIC with a salt having the formula ＋ wherein the salt having the formula (I) is selected from quaternary ammonium compounds, cationic dye compounds, dequalinium cations, and N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium).

15. A method for producing a PGA-containing plastic according to claim 6, comprising the steps of: melting a plastic; and mixing the molten plastic with PGA dissolved in an organic solvent, followed by solidification.

16. A method for producing a PGA-containing plastic according to claim 15, further comprising the step of dissolving PGA in an organic solvent to produce PGA dissolved in said organic solvent.

17. A method for producing a PGA-containing plastic according to claim 16, wherein the PGA to be dissolved in an organic solvent is free of aluminum ions.

18. A method for producing a PGA-containing plastic according to claim 17, wherein the PGA to be dissolved in an organic solvent is free of metal ions.

19. A method for producing a PGA-containing plastic according to any one of claims 15 to 18, wherein the organic solvent is DMSO or acetone.

20. A biodegradability imparting agent that imparts biodegradability to plastics, the agent containing PGA as an active ingredient.

21. A solution of poly-gamma glutamic acid (PGA) dissolved in an organic solvent.

22. The solution of claim 21, wherein the organic solvent is DMSO or acetone.

23. Aluminum-free poly-gamma glutamic acid (PGA).

24. The PGA according to claim 23, which is a metal ion-free PGA.

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