Microbial degradation promoter for polymer compounds, environmentally friendly polymer compounds, environmentally friendly pellets, environmentally friendly plastic fibers, and use of the microbial degradation promoter

Abstract

To provide an eco-friendly plastic, an eco-friendly plastic fiber and a PGA ion complex which are mainly made of plastic but still have microbial decomposability.SOLUTION: An eco-friendly plastic according to the present invention comprises a polymeric compound, where the polymeric compound contains a poly-γ-glutamic acid (PGA) or a salt thereof. An eco-friendly plastic fiber according to the present invention comprises a polymeric compound with fiber-forming ability, where the polymeric compound contains a PGA or a salt thereof. A PGA ion complex according to the present invention comprises a PGA and polyvalent metallic ions.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to environmentally friendly plastics using aromatic polyesters or the like, environmentally friendly plastic fibers, and PGA ion complexes used therein. [Background technology]

[0002] Plastic molded products and plastic fibers are considered hygienic, and their full-scale use began in the 1950s, and they have become indispensable in modern life. However, these plastics are causing serious environmental problems. Although plastics are resistant to deterioration and highly durable, the microcrystalline structure of the material tends to turn into microplastics. As a result, microplastics remain in the ocean and soil, and are said to have a negative impact on the global environment that supports ecosystems and resource circulation.

[0003] For this reason, bioplastics have been attracting attention in recent years. In particular, environmentally compatible plastics that can be decomposed by microorganisms have been attracting attention. Environmentally compatible plastics can be made from either natural or petroleum-derived raw materials, and are effective as a measure against waste plastics that does not require incineration.

[0004] Incidentally, as an example of an environmentally compatible plastic fiber, Patent Document 1 describes a microbially degradable polylactic acid fiber. However, this polylactic acid fiber is compost degradable, not marine degradable. In addition, compared to ordinary polyester fibers, it has a lower melting point and is difficult to handle, and there have been product accidents in the past due to embrittlement of the bent parts of the fiber caused by long-term storage, making it difficult to use stably.

[0005] Patent Document 2 describes a fiber obtained by spinning poly-γ-glutamic acid (hereinafter sometimes referred to as PGA) and a PGA ion complex containing a quaternary ammonium ion compound. Patent Document 2 describes that the PGA ion complex may exhibit antibacterial properties depending on the type of quaternary ammonium ion compound, but exhibits microbial decomposition since it has poly-γ-glutamic acid as the main skeleton. Poly-γ-glutamic acid is a type of biopolymer and is known as the adhesive component of natto. It is extremely safe and has very high hydrophilicity, and therefore its use as a cosmetic ingredient, etc., is being considered. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4922232 [Patent Document 2] Patent No. 5709158 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, there are concerns that plastics will turn into microplastics and remain in the ocean and soil, causing adverse effects on ecosystems and the global environment. However, plastics such as polyamide (nylon), polyester, and polypropylene are resistant to deterioration and highly durable, and have been widely used for plastic molded products and textile applications such as clothing and industrial textile materials, so it is considered difficult to restrict the use of these plastics. However, if it were possible to decompose the above-mentioned petrochemically synthesized plastics using microorganisms, the impact of microplastics could be reduced. Also, from the perspective of reducing greenhouse gas emissions in the context of the Paris Agreement, it would be possible to move away from "carbon positive," which increases the amount of carbon dioxide in the atmosphere caused by the burning of plastics, to "carbon neutral," and even to innovate further to "carbon negative."

[0008] Therefore, there is a demand for environmentally friendly plastics and environmentally friendly plastic fibers that are synthetic plastics with microbial decomposition. It is also preferable that plastic products and fiber products are hygienic, but microbial decomposition is a property that attracts decomposing microorganisms, and it is considered difficult to achieve both microbial decomposition and antibacterial properties. Therefore, if environmentally friendly plastics can be given antibacterial properties and both microbial decomposition properties can be achieved, it is considered that the uses of plastics can be expanded.

[0009] A primary object of the present invention is to provide an environmentally compatible plastic and an environmentally compatible plastic fiber which are mainly made of plastic but have biodegradability, and a PGA ion complex for use therein. Another object of the present invention is to provide an environmentally friendly plastic, an environmentally friendly plastic fiber, and a PGA ion complex for use therein, which are both antibacterial and microbially degradable. [Means for solving the problem]

[0010] As a result of intensive research by the inventors to solve the above problems, they discovered that the nitrogen-containing polymeric compound poly-γ-glutamic acid (PGA) is itself a valuable nutrient for environmental microorganisms, but at the same time has the function of attracting chemotactic microorganisms, and its adhesiveness also acts advantageously as a foothold for microbial adhesion (hereinafter, this characteristic is referred to as microbial affinity). Therefore, by incorporating this microbially-compatible PGA as a functional filler into a polymeric compound, it becomes possible to accelerate the microbial degradation of plastics that have not been subject to microbial degradation in natural environments, including the ocean.

[0011] That is, the environmentally compatible plastic of the present invention is made of a polymer compound, and contains PGA or a salt thereof in the polymer compound. The PGA is preferably contained in the form of a PGA ion complex. For example, the PGA ion complex may contain the poly-γ-glutamic acid and a polyvalent metal ion. This can impart antibacterial properties and microbial decomposition to the resulting plastic.

[0012] The environmentally friendly plastic fiber of the present invention is made of a polymeric compound having fiber-forming ability, and contains poly-γ-glutamic acid (PGA) or a salt thereof in the polymeric compound. The environmentally friendly plastic fibers are obtained, for example, by melt spinning a polymer compound containing PGA. The PGA ion complex of the present invention contains poly-γ-glutamic acid (PGA) and a polyvalent metal aluminum ion. Effect of the Invention

[0013] The environmentally compatible plastic and environmentally compatible plastic fiber of the present invention have the effect of promoting microbial decomposition of the polymer compound by containing PGA in the polymer compound. Furthermore, when poly-γ-glutamic acid is contained in the form of a PGA ion complex, the PGA ion complex has antibacterial properties and has the effect of microbial decomposition due to the above-mentioned microbial affinity of PGA in seawater, soil, etc. Furthermore, when the PGA ion complex contains the poly-γ-glutamic acid and a polyvalent metal ion, it can impart heat resistance in addition to antibacterial properties and microbial decomposition properties. [Brief description of the drawings]

[0014] [Figure 1A] 1 is a graph showing the results of an accelerated test of marine microbial decomposition of PGA-containing pellets in Example 1 (changes over time in biochemical oxygen demand (BOD) in natural seawater). [Figure 1B] FIG. 1B is a side view of the state of the PGA-containing pellet in FIG. 1A after 15 days. [Figure 1C] FIG. 1C is a photograph of the microbial growth state after culturing the biofilm obtained from the PGA-containing plastic shown in FIG. 1B after 15 days. [Figure 1D] FIG. 1B shows the state of the PGA-free pellets (control) in FIG. 1A after 15 days. [Figure 2A] 1 is a graph showing the change over time in biochemical oxygen demand (BOD) in artificial seawater for PGA-containing pellets. [Figure 2B] FIG. 2B is a side view of the state of the PGA-containing pellet in FIG. 2A after 15 days. [Figure 2C] FIG. 2C is a photograph of the microbial growth state after culturing the deposits on the PGA-containing plastic surface after 15 days have elapsed, as shown in FIG. 2B. [Figure 2D] FIG. 2B shows the state of the PGA-free pellets (control) in FIG. 2A after 15 days. [Diagram 3] 1 is a graph showing the results of an accelerated test of marine microbial decomposition of the PGA-containing PBT fiber in Example 2 (changes over time in biochemical oxygen demand (BOD) in natural seawater). [Figure 4] 1 is a graph showing the change over time in biochemical oxygen demand (BOD) in natural seawater for pellets containing a PGA ion complex in Example 3. [Diagram 5] 1 is a graph showing the change over time in biochemical oxygen demand (BOD) in natural seawater for an aromatic polyester fiber containing a PGA ion complex in Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Environmentally friendly plastics> The environmentally compatible plastic of the present invention is made of a polymer compound, and contains poly-γ-glutamic acid (PGA) in the polymer compound. Here, the concept of environmentally compatible plastics includes not only pellets for use in molding, which will be described later, but also various plastic molded articles that can become products.

[0016] The polymer compound is preferably a synthetic polymer compound that is not easily decomposed by microorganisms and is a thermoplastic resin that melts when heated when mixed with PGA, such as polyamide, polyester, polyethylene, polypropylene, ABS resin, etc. The polymer compound in the present invention is not limited to a thermoplastic resin that melts when heated, and a thermosetting resin can also be used.

[0017] Examples of polyamides include nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 56, and polyparaphenylene terephthalamide. Examples of polyesters include aromatic polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN). Aliphatic polyesters such as polylactic acid (PLA), polycaprolactone (PCL), and polybutylene succinate (PBS) are also applicable. As long as the performance is not impaired, copolymerized components may be used, and titanium dioxide may be added as a matting agent or ultraviolet ray shielding agent. Examples of other copolymerization components include polycarboxylic acids and derivatives thereof, such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, trimellitic acid, pyromellitic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic 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 ethylene glycol ether of bisphenol A.

[0018] The type of PGA contained in the polymer compound is not particularly limited, and may be, for example, one consisting of only L-glutamic acid, one consisting of only D-glutamic acid, or one containing both, and any of them may be used in the present invention. However, the higher the ratio of one, the better the stereoregularity and the higher the strength, and if thoroughly dried, the melting point (about 208°C) will be. This melting point becomes clearer by forming an ion complex as described below. Furthermore, since PGA consisting of L-glutamic acid has excellent microbial decomposition properties, it is preferable to use one having an L-glutamic acid content of 90% or more, more preferably 95% or more, even more preferably 98% or more, and particularly preferably 100%. The ratio of 100% means that when PGA is hydrolyzed under conditions that do not cause racemization and analyzed with a chiral column, the L-glutamic acid is below the detection limit.

[0019] The molecular size of the PGA used is not particularly limited, but an average molecular mass of 10 kDa or more is preferable. Generally, the larger the molecular size, the higher the performance such as strength. On the other hand, PGA with an excessively large molecular size is expensive to manufacture and may be technically difficult to manufacture, so it is usually 10000 kDa or less. The average molecular mass of PGA is more preferably 100 kDa or more, more preferably 500 kDa or more, particularly preferably 800 kDa or more, more preferably 5,000 kDa or less, more preferably 2,000 kDa or less, and particularly preferably 1500 kDa or less. In addition, when using a commercially available PGA, the average molecular weight may be referred to the catalog value, but may also be a measured value by gel filtration chromatography or the like.

[0020] PGA may be used if it is commercially available, or may be produced separately. However, since poly-α-glutamic acid is obtained by polymerizing glutamic acid under normal conditions, it is preferable to use microorganisms for biosynthesis. Microorganisms capable of producing PGA with a large molecular size include the hyperhalophilic archaea Natrialba aegyptiaca and the bacillus subtilis (eubacteria).

[0021] PGA may be used in the form of a salt. Examples of the salt include alkali metal salts such as sodium salts and potassium salts, and alkaline earth metal salts such as calcium salts and magnesium salts. Even when a salt is used, it is not necessary for all carboxyl groups to be in the form of a salt, and only a portion of the carboxyl groups may be in the form of a salt.

[0022] To incorporate PGA (or a salt thereof) into a polymeric compound, PGA may be kneaded into a molten polymeric compound. To produce an environmentally friendly plastic product (molded article) or fiber, PGA may be directly incorporated into the raw polymeric compound, but it is preferable to prepare pellets of the polymeric compound containing PGA in advance and mix the pellets with the raw polymeric compound to produce the environmentally friendly plastic product (molded article) or fiber. PGA-containing pellets (hereinafter sometimes referred to as PGA-containing pellets) are made by mixing PGA at a relatively high concentration with the raw polymer compound in an amount that will give a specified PGA concentration. This allows accurate measurement of PGA, improves dispersion of PGA, prevents scattering during work, and improves dispersion of additives such as PGA during molding.

[0023] PGA may be mixed in the form of powder with the polymer compound melted. Alternatively, PGA may be dissolved in a solvent such as water, mixed with the polymer compound, and then dried. The PGA in the PGA pellets is at a relatively high concentration, specifically, for example, at a concentration of 0.05% by mass or more, and preferably at a concentration of 20% by mass or less. The shape and size of the PGA-containing pellets are not particularly limited, but for example, the length is preferably 2 mm to 6 mm and the diameter is preferably 1 mm to 3 mm. The PGA-containing pellets may be prepared by passing the PGA through a filter to adjust the particle size to a predetermined size, mixing the PGA with the polymer pellets, extruding the PGA from an extruder, and cutting the PGA into a predetermined size. The filter should be 40 mesh or larger (opening size of about 500 μ or less).

[0024] The PGA-containing pellets are subjected to various molding processes, including conventional injection molding, extrusion molding, blow molding, inflation molding, T-die molding, inflation, vacuum molding, and pressure molding.

[0025] During molding, the amount of PGA-containing pellets mixed is adjusted so that the PGA is mixed in a predetermined amount relative to the base polymer compound. Specifically, the amount of PGA-containing pellets mixed is adjusted so that the PGA is mixed in a predetermined amount in the polymer compound, with the amount being 0.05% by mass or more, preferably 0.1% by mass or more. This accelerates and promotes the microbial decomposition of the polymer compound due to the bioaffinity. The amount of PGA mixed in the polymer compound is preferably 20% by mass or less. The PGA-containing pellets may be in the form of powder or granules.

[0026] <PGAイオンコンプレックス> The PGA in the present invention is preferably contained in the polymer compound in the form of a PGA ion complex (hereinafter, sometimes referred to as PGAIC). PGAIC has antibacterial or bacteriostatic activity (hereinafter, sometimes simply referred to as antibacterial activity), and since it has PGA as the main skeleton, it also has properties as a functional filler that contributes to accelerating decomposition by marine microorganisms. In other words, if plastics that have been given antibacterial properties in addition to synthetic polymer compounds that have semi-permanent environmental durability from the viewpoint of public health are discarded and released into the natural world, there is a risk that they will fundamentally deplete the vitality of the microorganisms that decompose them. In particular, in the ocean, where the majority of microorganisms are difficult to culture, such antibacterial and antiviral products could trigger another dimension of ocean destruction. PGAIC makes it possible to achieve both antibacterial activity and microbial decomposition, which are mutually contradictory properties.

[0027] Known PGAICs include PGA ion complexes containing PGA and a quaternary ammonium ion compound represented by the following formula (I) or (II) (see the above-mentioned Patent Document 2 and JP-A-2010-222496). [ka] [In the formula, R 1 ~R 3 each independently represents a C1-C2 alkyl group; R 4 ~R 5 is independently C 12 ~C 20 indicates an alkyl group]

[0028] Here, C1-C2 means an aliphatic hydrocarbon having 1 to 2 carbon atoms, i.e., a methyl group or an ethyl group. 12 ~C 20 The alkyl group refers to a linear or branched aliphatic hydrocarbon having 12 to 20 carbon atoms. Examples of the alkyl group include linear alkyl groups such as dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups; and branched alkyl groups such as isotetradecyl, isopentadecyl, isohexadecyl, isoheptadecyl, isooctadecyl, sec-tetradecyl, sec-pentadecyl, sec-hexadecyl, sec-heptadecyl, sec-octadecyl, t-tetradecyl, t-pentadecyl, t-hexadecyl, t-heptadecyl, t-octadecyl, neotetradecyl, neopentadecyl, neohexadecyl, neoheptadecyl, and neooctadecyl groups. R 4 As the 15 -C 20 is an alkyl group, more preferably C 16 -C 20 is an alkyl group, most preferably C 17 -C 20 R is an alkyl group. 5 As the 13 -C 20 is an alkyl group, more preferably C 14 -C19 is an alkyl group, most preferably C 15- C 18 It is an alkyl group.

[0029] PGAIC contains glutamic acid and a quaternary ammonium ion compound in equimolar amounts, is water-insoluble, has a melting point, and contains 90% or more of L-glutamic acid in the glutamic acid that constitutes PGA. PGAIC can be easily prepared by mixing PGA with a quaternary ammonium ion compound in a solvent such as water. Such PGAIC can be incorporated into a polymer compound in the same manner as the above-mentioned PGA to produce pellets, which can then be used to produce plastics or the fibers described below.

[0030] Another PGAIC in the present invention is a PGA ion complex containing PGA and a polyvalent metal ion. The polyvalent metal ion includes an ion of a divalent or higher metal element. The divalent or higher metal elements are exemplified below. Divalent metallic elements: Magnesium (Mg), Calcium (Ca), Manganese (Mn), Iron (Fe), Zinc (Zn), Copper (Cu) Trivalent metallic elements: Aluminum (Al), Gallium (Ga), Indium (In), Thallium (Tl) Tetravalent metallic elements: silicon (Si), manganese (Mn), titanium (Ti), tin (Sn), zirconium (Zn), cerium (Se), thorium (Th) Pentavalent metallic elements: niobium (Nb), tantalum (Ta), antimony (Sb) Hexavalent metallic elements: molybdenum (Mo), tungsten (W) In the present invention, a PGA ion complex containing PGA and a trivalent metal ion is particularly preferred, and a PGA ion complex containing PGA and an aluminum ion (hereinafter sometimes referred to as PGAAL) is preferred. PGAIC, which contains PGA and polyvalent metal ions, is a polymer metal soap type that has excellent heat resistance, for example, heat resistance even in the melting temperature range of PET or PBT. Therefore, it is suitable for hot molding (extrusion molding, etc.) and melt spinning using PET or PBT. In addition, this PGAIC has excellent antibacterial and antiviral properties, which can dramatically increase the possibility of applying PGAIC as a filler. In the following explanation, PGAAL is used as a representative example, but other PGAICs can be applied in the same way.

[0031] PGAAL can be easily produced, for example, by mixing PGA and alum in a solvent such as water. Aluminum chloride, aluminum hydroxide, etc. may be used instead of alum. When using a polyvalent metal ion other than aluminum, the corresponding metal compound or salt may be used. The obtained PGAAL contains aluminum ions in an amount of 1 / 6 or more by mol, preferably 1 / 3 or more by mol and 1 / 2 or less by mol, based on the amount of glutamic acid constituting the PGA. It is particularly preferable that the aluminum ions are 1 / 3 by mol, based on the amount of glutamic acid constituting the PGA.

[0032] <Environmentally friendly plastic fibers> The environmentally friendly plastic fiber of the present invention is made of a polymeric compound having fiber-forming ability, and contains poly-γ-glutamic acid (PGA) as a filler in the polymeric compound. PGA is preferably used in the form of a PGA complex. The polymer compound capable of forming fibers refers to one that can be made into fibers by a spinning process. The spinning method is not particularly limited, and solution spinning (dry-wet spinning, wet spinning, dry spinning, gel spinning, etc.), melt spinning, charged spinning, etc. can be applied. The environmentally compatible plastic fiber of the present invention is particularly suitable for production by the melt spinning method.

[0033] Specific examples of polymer compounds include polyamide, polyester, polyethylene, polypropylene, ABS resin, acrylic resin, etc. Examples of polyamide include nylon 6, nylon 11, nylon 12, nylon 66, etc. Examples of polyester include aromatic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN).

[0034] The PGA content in the fiber is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. This allows the degradation of polymeric compounds by microorganisms to be promoted based on the microbial affinity of PGA. In addition, the use of a PGA ion complex can also impart antibacterial properties to the fiber.

[0035] The manufacturing method of the environmentally friendly plastic fiber of the present invention will be described in detail below, taking the melt spinning method as an example. In melt spinning, the polymer compound containing PGA may be added directly to the raw material, but it is preferable to use the above-mentioned PGA-containing pellets mixed with the raw polymer compound. In other words, the PGA-containing pellets containing a high concentration of PGA are diluted with the raw polymer compound. This allows the PGA to be measured accurately, prevents it from scattering during the process, and improves the dispersion of the PGA during spinning. The polymer compound contained in the PGA-containing pellets and the polymer compound used as the raw material for melt spinning may be the same or different. When using different polymer compounds, it is preferable to use those that are compatible with each other. For example, PET and PBT can be used as described in the examples below.

[0036] In the melt spinning method, a polymer compound is heated and melted, spun from a spinning machine nozzle, and cooled by a gas flow while applying tension with a take-up roller to form a fiber. The resulting yarn may then be stretched. The melting temperature may be appropriately determined taking into consideration the melting point and thermal decomposition point of the polymer compound, but is usually in the range of melting point +5°C or more and +100°C or less, preferably melting point +30°C or more and +50°C or less.

[0037] The distance from the spinneret to the take-up may be determined as appropriate within the range that allows cooling, but is usually 0.5 m to 15 m. The take-up speed may also be determined as appropriate depending on the fiber thickness, but is usually 1 m / min to 8 km / min. The cooling atmosphere may be 5°C to 35°C.

[0038] In the melt spinning method, it is preferable that the PGA does not decompose at the heating and melting temperature of the polymer compound. In the present invention, it is preferable to use PGAAL, which has excellent heat resistance. PGAAL has heat resistance that does not decompose even at temperatures close to 240°C.

[0039] <Application> The environmentally friendly plastic of the present invention can be suitably used for general-purpose plastic products such as plastic bottles and plastic films, and various industrial plastic products. The environmentally friendly plastic fiber of the present invention can be suitably used as a material for general clothing and various industrial textile materials. In particular, the environmentally friendly plastic and plastic fiber containing the PGA ion complex can be applied to wearable products and general-purpose plastic products that require antibacterial properties.

[0040] The environmentally friendly plastic, the environmentally friendly plastic fiber, and the PGA ion complex of the present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples. EXAMPLES

[0041] (1) Preparation of PGA-containing pellets The PGA used was in powder form with an average molecular weight of 1000 kDa. The polymer compound used was PBT resin (NOVADURAN (registered trademark) manufactured by Mitsubishi Engineering Plastics Corporation). The PBT was heated and melted, and PGA was kneaded into the mixture at a ratio of 10 mass% relative to the total amount, and passed through a 150 mesh (opening 109 μm) filter. The mixture was then extruded from the nozzle hole of the extruder and cut to a length of about 3 mm to obtain pellets containing PGA with a diameter of about 2 mm. Hereinafter, the obtained PGA-containing pellets are referred to as PT[PGA 10% / PBT] will be displayed. (2) Accelerated biodegradation test of PGA-containing pellets by marine microorganisms Pellet-shaped PT[PGA 10% We investigated whether marine microbial communities show microbial affinity for PT[PGA / PBT]. 10% / PBT] was added at 550 cm 3 The fish were placed in an airtight space, and the oxygen consumption in the airtight space was measured to examine the change in BOD over a 15-day period. The temperature in the airtight space was maintained at 20±5°C, close to the average seawater temperature off the coast of Kochi Prefecture. The oxygen consumption was measured using a BOD measuring device (a pressure sensor manufactured by VELP SCIENTIFICA). As a control, 2.5 g of pellet-shaped PBT resin (PBT) not containing PGA was used in the same manner. 10% A similar test was also performed on 0.25 g of PG powder alone, which corresponds to the PGA content in 2.5 g of [PBT / PBT]. The test results are shown in Figures 1A to 1D. As shown in FIG. 1A, 15 days after the start of measurement, PT[PGA 10% In the [Water / PBT] water, the BOD is high, indicating that marine microbial activity is increased. Figure 1B shows the PT[PGA 10%After 15 days, the adhesion of microorganisms to the pellet surface was significant, and the formation of a biofilm, an aggregate of microorganisms, was observed. 10% The pellets were then taken out of the container and washed with water to remove any attached matter from the pellet surface. A portion of the washing water was transferred to a petri dish containing a specified medium, and the dish was sealed and cultured at 20±5°C for one week. As a result, as shown in Figure 1C, microbial growth was observed on the surface of the medium. The medium used was a modified LB medium with the composition shown in Table 1 below to which 1 L of deionized water had been added. The sodium chloride concentration was adjusted to approximately the same as that of seawater (3.5%). [Table 1] On the other hand, in the sample containing only PBT (PBT, 2.5 g; shown by square in Fig. 1A), the BOD hardly changed, and no biofilm formation was observed, as shown in Fig. 1D. 10% In the sample containing only PGA (0.25 g; indicated by a triangle in Figure 1A), which corresponds to the PGA content in 2.5 g of [PBT / PBT], the PGA content was so low that it did not cause a change in the BOD. As a negative control, artificial seawater was used to ensure the absence of microorganisms, and the test was conducted in the same manner as for natural seawater. The artificial seawater used was MAERINE ART SF-1, a research reagent sold by Tomita Pharmaceutical Co., Ltd. The specific composition of the artificial seawater was 22.1 g / L sodium chloride, 9.9 g / L magnesium chloride, 1.5 g / L calcium chloride, 3.9 g / L anhydrous sodium sulfate, 0.61 g / L potassium chloride, 0.19 g / L sodium bicarbonate, 0.096 g / L potassium bromide, 0.078 g / L borax, 0.013 g / L anhydrous strontium chloride, 0.003 g / L sodium fluoride, and 0.001 g lithium chloride. The test consisted of 0.000081 g / L potassium iodide, 0.0000006 g / L manganese chloride, 0.000002 g / L cobalt chloride, 0.000008 g / L aluminum chloride, 0.000005 g / L ferric chloride, 0.000002 g / L sodium tungstate, and 0.000018 g / L ammonium molybdate, which were dissolved in the required amount of deionized water and then sterilized. The test results are shown in Figures 2A to 2D. From these test results, it was found that in natural seawater, PT[PGA 10% It can be seen that the decomposition by marine microorganisms is accelerated by the inclusion of PGA, whereas PBT accounts for the majority of PT[PGA / PBT] (see Figures 1A-1C). 10% It was suggested that [PBT / PBT] showed microbial affinity and was significantly degraded by microorganisms. On the other hand, when microorganisms were grown in artificial seawater, as shown in Figure 2A, PT[PGA 10%In the case of [PBT / PBT] (2.5 g; indicated by ●), no biofilm formation was observed after 15 days, and no biofilm formation was observed even after 30 days of follow-up from the start of the test. Figure 2C, like Figure 1C, shows the results of removing pellets from the medium in Figure 2B after 15 days of culture, washing off any attached matter from the pellet surface, transferring them to a petri dish, and culturing them under the same conditions. As shown in the figure, it is clear that microbial decomposition of PBT has hardly progressed in the artificial seawater. Furthermore, there was almost no change in the BOD of the sample containing only PBT (PBT, 2.5 g; indicated by □ in Figure 2A), and no biofilm formation was observed, as shown in Figure 2D. Furthermore, in the case of PT[PGA 10% Similar results were obtained for a sample containing only PGA (0.25 g; indicated by △ in Figure 2A), which corresponds to the PGA content in 2.5 g of [PBT / PBT]. EXAMPLES

[0042] (1) Preparation of PGA-containing PBT fibers The same PT[PGA 10% / PBT] was mixed with the same PBT resin as used in Example 1, and short fibers were produced by melt spinning. 10% The amount of [PGA / PBT] mixed into PBT was set to a PGA content of 0.5 mass% (i.e., equivalent to diluting PGA with PBT 20 times) and 0.1 mass% (i.e., equivalent to diluting PGA 100 times) relative to the total amount of fiber. Next, the PBT resin was heated and melted at 275°C, and then spun out from the nozzle of the spinning device, and spun by cooling with air flow in a cooling atmosphere of 20°C while applying tension with a take-up roller at a take-up speed of 800 m / min. The distance from the nozzle to the take-up was 10 m. This undrawn yarn was drawn in a 60°C liquid bath, mechanically crimped by a pushing method, and then subjected to a relaxation heat treatment at 120°C. The fiber bundle was then cut to obtain short fibers. The fibers obtained are hereafter referred to as FB[PGA 0.5% / PBT] and FB[PGA 0.1% The fibers obtained had a single fiber size of 6.7 dtex and a cut fiber length of 51 mm. (2) Accelerated decomposition test of marine microorganisms on PGA-containing PBT fibers FB[PGA 0.5% / PBT]2.5g and FB[PGA 0.1% The change in BOD over time for 2.5 g of [PGA pellets / PBT] in natural seawater was measured in the same manner as for the PGA-containing pellets in Example 1. As a negative control for marine recalcitrance, 2.5 g of short PET fiber manufactured by Toray Industries, Inc. (fiber length 38 mm, single fiber fineness 1.3 dtex; hereafter referred to as FB[G403(PET)]) was used, and the change in BOD over time was measured in the same manner. As another marine biodegradable positive control, 2.5 g of CiCLO staple fiber (fiber length 38 mm, single fiber fineness 1.4 dtex; hereafter referred to as FB[CiCLO]) made of biodegradable polyester manufactured by SUNFLAG Public Company, Ltd. in Thailand was used, and the change in BOD over time was measured in the same manner. The results are shown in Figure 3. From Figure 3, FB[PGA 0.5% / PBT] and FB[PGA 0.1% It was suggested that CiCLO fiber FB[CiCLO] has marine biodegradation properties equivalent to or superior to those of CiCLO fiber FB[CiCLO]. EXAMPLES

[0043] (1) Preparation of PGA ion complex (PGAAL) 1 kg of PGAAL was prepared by the following procedure. (i) Using an electronically controlled stirrer (IKA's "EUROSTAR60 Digital") and a spiral-type stirring blade (IKA's "R3003.2"), 1 kg of PGA powder (average molecular weight 1000 kDa) was dissolved in 20 L of water at room temperature (~25°C) and a stirring speed of 140 rpm. (ii) Using the same apparatus and conditions as in (i) above, 1.23 kg of alum powder was dissolved in 1.23 L of water. (iii) The 10% aqueous alum solution (ii) was added dropwise to the 5% aqueous PGA solution (i) above, and the mixture was mixed for 5 minutes using a stirrer. (iv) After mixing, the mixture was confirmed to become cloudy, and then excess water was removed using a filter cloth. (v) After thoroughly draining the water, place in a -80°C ultra-low temperature freezer and freeze overnight. (vi) After confirming that the mixture was frozen, it was transferred to a freeze dryer (FDU-1200) and dried to obtain a PGAAL powder. The water-insoluble material obtained was subjected to acid hydrolysis and then analyzed by chiral resolution HPLC in the usual manner. It was found that more than 90% of the PGA used as the raw material had been modified into an ion complex. (2) Preparation of PGA ion complex 10 g of the same PGA salt as in (1) above was dissolved in purified water to prepare a 2 w / v% solution. To this solution, an equal amount of a 0.2 M aqueous solution of hexadecylpyridium bromide (HDPB) kept at 60°C was added. After confirming that a water-insoluble material was formed immediately after the addition of HDPB, the solution was further kept at 60°C for 4 hours. The resulting water-insoluble material was collected by filtration and washed with 100 mL of hot water three times. It was further dehydrated by washing with acetone and then vacuum dried. The water-insoluble material obtained was subjected to acid hydrolysis and then analyzed by chiral resolution HPLC in the usual manner. It was found that more than 90% of the PGA used as the raw material had been modified into an ion complex. (3) Heat resistance test The heat resistance of the PGAAL powder obtained in (1) above and the PGAIC powder obtained in (2) above was evaluated. In the test, a given amount of the PGAIC powder and the PGAAL powder were placed in a heat-resistant container and heated in an oven. As a result, the PGAIC powder melted at 240℃, whereas the PGAAL powder did not melt and remained in a solid state, indicating that PGAAL has high heat resistance. (4) Preparation of Pellet of Aromatic Polyester Containing PGAAL In the same manner as in Example 1(1), PGAAL powder was mixed into PBT resin so as to give a concentration of 3.8% by mass to prepare pellets containing PGAAL powder (hereinafter sometimes referred to as PGAAL pellets). Hereafter, this PGAAL pellet is referred to as PT[PGAAL 3.8% / PBT] will be displayed. EXAMPLES

[0044] (1) Preparation of aromatic polyester fibers containing PGAAL pellets A PET resin (manufactured by Hyosung Co., Ltd., IV value 0.64) was used as a substrate, and the PT[PGAAL 3.8% / PBT] was mixed (i.e., it corresponds to diluting PGAAL with PET). Next, the mixture was heated and melted at 295°C, and spun out from the nozzle of the spinning device, and spun by cooling with air flow in a cooling atmosphere of 25°C while applying tension with a take-up roller at a take-up speed of 800 m / min. The distance from the nozzle to the take-up was 10 m. This undrawn yarn was drawn with a heating roller at 75°C, heat-treated at 155°C, and then wound up to obtain a long fiber (84 dtex / 24f, single yarn fineness 3.5 dtex). PT[PGAAL 3.8% The amount of [PGA / PBT] mixed into the PET was adjusted so that the PGA content was 0.1 mass % relative to the total amount of fibers. Hereafter, the obtained fiber is referred to as FB[PGAAL 0.1% / PET] will be displayed. (2) Antibacterial testing FB[PGAAL 0.1% / PET] was subjected to antibacterial testing according to JIS-L-1902 (bacterial liquid absorption method, Staphylococcus aureus). The result was an antibacterial activity value of 5.8, which is significantly higher than the antibacterial activity value of ≥ 2.2 that is the standard for "antibacterial and deodorizing processing." (3) Accelerated marine microbial decomposition test (a) Microbial degradation of PGAAL pellets In the same manner as in Example 1, PT[PGAAL 3.8% We investigated whether marine microbial communities exhibited microbial affinity for 2.5 g of [PGAAL / PBT]. As a negative control, 2.5 g of PBT pellets not containing PGAAL were used and tested in the same manner. The test results are shown in Figure 4. (b) Microbial degradation of fibers In the same manner as in Example 2, FB[PGAAL 0.1%We investigated whether marine environment microorganisms exhibited microbial affinity for 2.5g of [FB[PET]. As a negative control, we used PET fiber that did not contain PGAAL (FB[PET]2.5g, 167dtex / 48f, single yarn fineness 3.5dtex). The test results are shown in Figure 5. From the above test results, it was confirmed that both the PGAAL-containing pellets and their fiber molded products were decomposed accelerated by marine microorganisms. EXAMPLES

[0045] <Production of environmentally friendly plastic molded products> As the base resin, pellets of a copolyester resin (Tritan® manufactured by Eastman Chemical Co.) were used, to which the pellet-shaped PT[PGAAL 3.8% / PBT] was mixed and a PET bottle with a wall thickness of 1.1 mm was prepared according to the usual method. 3.8% The mixing amount of [PGAA / PBT] was adjusted so that the PGAAL content in the molded PET bottles was 0.1% by mass (corresponding to a 38-fold dilution of PGAA with PET resin), 0.2% by mass (19-fold dilution), and 0.4% by mass (9.5-fold dilution). As a result, PET bottles could be obtained with any mixing amount.

[0046] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and improvements are possible within the scope of the present invention. For example, in the above example, microbial decomposition in seawater has been described, but microbial decomposition is also possible in soil such as compost, or in water such as rivers and lakes.

Claims

1. A microbial decomposition promoter for polymer compounds, comprising an alkali metal salt of poly-γ-glutamic acid (PGA).

2. An environmentally friendly polymer compound comprising the microbial decomposition promoter described in claim 1.

3. An environmentally friendly plastic comprising the environmentally friendly polymer compound described in claim 2.

4. An environmentally friendly pellet comprising the environmentally friendly polymer compound described in claim 2.

5. An environmentally friendly plastic fiber comprising a polymeric compound having fiber-forming ability and the microbial decomposition promoter described in claim 1.

6. An environmentally friendly plastic fiber as described in claim 5, wherein the polymer compound having fiber-forming ability is polyester.

7. Use of the microbial degradation promoter according to claim 1 for promoting microbial degradation of plastics or plastic fibers produced from polymer compounds.

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