Ocean biodegradation speed control method for biodegradable resin using waste

Abstract

To provide a technique for controlling ocean biodegradation speed for a biodegradable resin.SOLUTION: A biodegradable speed control method for a biodegradable resin in the ocean includes making shells of crustaceans or insects exist in the vicinity of a biodegradable resin or contact the biodegradable resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for controlling the rate of marine biodegradation of a biodegradable resin by utilizing waste materials, and more particularly to a method for controlling the rate of marine biodegradation of a biodegradable resin by utilizing the shells of crustaceans or insects. [Background technology]

[0002] Microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Polyesters are materials that exhibit excellent biodegradability even in marine environments. However, due to their excellent biodegradability, PHBV may biodegrade during use as a material, and its physical properties may not be guaranteed. In order to further popularize biodegradable plastics, it is necessary to develop technology to control the decomposition rate.

[0003] The following methods are known to slow down the decomposition rate of biodegradable plastics. Patent Document 1 proposes a method for controlling the decomposition of biodegradable plastics by applying a nonionic surfactant, which is an activity inhibitor of biodegradable plastic decomposition enzymes, to the surface of the biodegradable plastics at a concentration equal to or higher than the critical micelle concentration. Patent Documents 2, 3, and 4 propose a method for controlling the decomposition of biodegradable plastics by adding a carbodiimide compound, an ultraviolet absorber, and an antioxidant. Patent Document 5 proposes a method for controlling the decomposition of biodegradable plastics by blending a biodegradation rate control assistant and then irradiating it with active energy rays. Patent Document 6 proposes a method for controlling the biodegradation rate by adding antibacterial metal ions. Patent Document 7 proposes a method for suppressing decomposition by blending inorganic or organic fillers. Patent Document 8 discloses a biodegradable laminate obtained by laminating biodegradable resins, which is resistant to deterioration during use and quickly decomposes in the natural environment after use. Patent Documents 9 and 10 propose a method for reducing the decomposition rate by dispersing natural antibacterial agents in biodegradable plastics. Patent Document 11 proposes a method of suppressing biodegradability by increasing or decreasing the amount of biodegradable resin and carbon black added, while Patent Document 12 proposes a method of controlling the biodegradation rate by mixing a biodegradable resin with chitin.

[0004] In the method described in Patent Document 1, it is necessary to remove the surfactant in order to exhibit biodegradability. In the methods described in Patent Documents 2, 3, and 4, the biodegradability of the added compound is not guaranteed, and there is a possibility that some non-biodegradable substances remain. Similarly, in the method described in Patent Document 5, there is a possibility that the part crosslinked by irradiation with active energy remains. In the methods described in Patent Documents 6, 7, 9, 10, 11, and 12, there is a concern that the physical properties may decrease due to the addition of compounds or fillers to biodegradable plastics. In Patent Document 8, decomposition in the marine environment is not evaluated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2010-227006 [Patent Document 2] Patent Publication No. 2007-302758 [Patent Document 3] Patent Publication No. 2004-155993 [Patent Document 4] Patent Publication No. 2003-313436 [Patent Document 5] Patent Publication No. 2006-291091 [Patent Document 6] Patent Publication No. 05-117507 [Patent Document 7] Patent Publication No. 04-146953 [Patent Document 8] Patent Publication No. 2021-154559 [Patent Document 9] Patent Publication No. 2020-500792 [Patent Document 10] Patent Publication No. 2001-323177 [Patent Document 11] Patent Publication No. 2005-002165 [Patent Document 12] Patent Publication No. 2004-010749 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, an objective of the present invention is to develop a technique for controlling the marine biodegradation rate of a biodegradable resin. [Means for solving the problem]

[0007] As a result of intensive research by the present inventors to solve the above problems, they found that the marine biodegradation rate of a biodegradable resin can be controlled by placing crustacean or insect shells in the vicinity of the biodegradable resin or in contact with the biodegradable resin. More specifically, they found that by placing crustacean or insect shells in the vicinity of the biodegradable resin or in contact with the biodegradable resin, the growth of microorganisms that decompose the biodegradable resin is inhibited, and the marine biodegradability of the resin is inhibited. Based on this finding, the present invention has been completed. That is, the gist of the present invention relates to the following.

[0008] [1] A method for producing a crustacean or insect shell comprising placing the shell of a crustacean or insect in the vicinity of or in contact with a biodegradable resin, A method for controlling the rate of biodegradation of biodegradable resins in the ocean. [2] The method for controlling the biodegradation rate described in [1], wherein the shell of a crustacean or insect is a crab shell. [3] The method for controlling the biodegradation rate according to [1] or [2], wherein the biodegradable resin comprises one or more selected from polyhydroxyalkanoic acid, aliphatic polyester, aromatic polyester, and natural polymers and their derivatives. [4] The method for controlling the biodegradation rate according to any one of [1] to [3], wherein the biodegradable resin comprises one or more selected from poly(3-hydroxybutyrate) resin, polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, and cellulose. [5] A regulator of the rate of biodegradation of marine biodegradable resins, including crustacean or insect shells. [6] A biodegradable resin composition having a controlled rate of biodegradation in the ocean, comprising a biodegradable resin and the biodegradation rate control agent described in [5]. [7] The biodegradable resin composition according to [6], in which a biodegradable resin is laminated with a biodegradation rate regulator. [8] A molded article formed from the biodegradable resin composition according to [6] or [7].

[0009] The present invention can also employ the following configuration. [9] The use of crustacean or insect shells to control the rate of biodegradation of biodegradable resins in the ocean.

[10] Crustacean or insect shells for use in controlling the biodegradation rate of biodegradable resins in the ocean.

[11] The use of crustacean or insect shells in the manufacture of an agent for controlling the biodegradation rate of marine biodegradable resins.

[12] Use of crustacean or insect shells in the manufacture of a biodegradable resin composition having a controlled rate of biodegradation in the ocean.

[13] A method for producing an agent for controlling the biodegradation rate of marine biodegradable resins, the method comprising formulating crustacean or insect shells.

[14] A method for producing a biodegradable resin composition having a controlled rate of biodegradation in the ocean, comprising mixing the biodegradable resin composition with crustacean or insect shells. Effect of the Invention

[0010] According to the method of the present invention, it is possible to control the rate of marine biodegradation of a biodegradable resin. Furthermore, according to the present invention, there are provided an agent for controlling the rate of marine biodegradation of a biodegradable resin, a biodegradable resin composition having a controlled rate of marine biodegradation, and a molded article formed from the biodegradable resin composition. That is, according to the method of the present invention, by coexisting a biodegradable resin, which has excellent biodegradability but is therefore subject to a risk of deterioration in physical properties due to biodegradation during use, with the shells of crustaceans or insects, the bacterial flora on the surface of the biodegradable resin is changed, thereby decreasing the marine biodegradability of the biodegradable resin. Therefore, it is possible to control the biodegradability of a biodegradable resin with a high biodegradability rate, and provide a material that maintains its mechanical properties under normal use conditions but rapidly biodegrades under certain conditions. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the mass loss of the PHBV film versus seawater immersion time. [Diagram 2]Figure 2 shows SEM images of the surface of the PHBV film before and after immersion in seawater. The white scale bar represents 10 μm. [Diagram 3] FIG. 3 is a graph showing the relative abundance of the bacterial community at the class level for each sample. [Figure 4] FIG. 4 is a graph showing the NMDS plots of the bacterial communities of each sample. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will now be described. <Method of controlling biodegradation rate> One aspect of the present invention relates to a method for controlling the biodegradation rate of a biodegradable resin in the ocean, which comprises placing crustacean or insect shells in the vicinity of or in contact with a biodegradable resin (hereinafter sometimes referred to as the "method for controlling the biodegradation rate of the present invention").

[0013] In the present invention, the biodegradation rate of a biodegradable resin in the ocean can be controlled by having crustacean or insect shells in the vicinity of or in contact with the biodegradable resin. Specifically, for example, when there are sufficient crustacean or insect shells to inhibit the biodegradation rate of the biodegradable resin, the biodegradation rate can be decreased, and when there are not sufficient crustacean or insect shells to inhibit the biodegradation rate of the biodegradable resin, the biodegradation rate can be restored or improved.

[0014] As will be shown in the examples below, according to the method of the present invention, by placing crustacean or insect shells on or near the surface of a biodegradable resin, it is possible to change the microbial flora near the biodegradable resin (i.e., inhibit the growth of biodegradable resin-degrading microorganisms), thereby slowing down the biodegradation rate of the biodegradable resin in the ocean.

[0015] Therefore, by having a sufficient amount of crustacean or insect shells present in a region close enough to the biodegradable resin (i.e., in contact with or in close proximity to the biodegradable resin) to change the microflora near the biodegradable resin, the biodegradation rate of the biodegradable resin in the ocean can be controlled.

[0016] Contacting the shell of a crustacean or insect with a biodegradable resin means, for example, laminating the shell of a crustacean or insect or the biodegradation rate control agent of the present invention described below onto a biodegradable resin, but it may also mean placing the shell of a crustacean or insect or the biodegradation rate control agent of the present invention described below in a state of contact with the biodegradable resin.

[0017] The presence of the shells of crustaceans or insects or the regulator of the biodegradation rate of the present invention described below in the vicinity of the biodegradable resin means, for example, arranging the shells or regulator and the biodegradable resin so that the shortest distance between the shells or regulator and the biodegradable resin is 50 cm or less, 30 cm or less, or 10 cm or less, but it may also mean, for example, adding the shells of crustaceans or insects or the regulator of the biodegradation rate of the present invention described below and the biodegradable resin to the same environment, etc. The addition of the shells of crustaceans or insects or the regulator of the biodegradation rate of the present invention described below may be done simultaneously, or either may be added first.

[0018] ≪Biodegradable resin≫ The "biodegradable resin" which is the target substance for promoting biodegradation in the ocean in the control method of the present invention is not particularly limited as long as it is a polymer that can be biodegraded by biodegradable polymer-degrading bacteria. Biodegradable resins include those derived from living organisms and those derived from chemical synthesis, and both can be used. Biodegradable resins include, but are not limited to, polyester resins, natural polymers and derivatives thereof, and the polyester resins can be selected from, for example, aliphatic polyesters, aromatic polyesters, polyhydroxyalkanoic acids (PHAs), and the like; the natural polymers can be selected from, for example, cellulose, starch, and the like; and the derivatives of natural polymers can be selected from, for example, cellulose esters, cellulose ethers, cellulose ether esters, and the like.

[0019] Aliphatic polyesters include, for example, polylactic acid (PLA), polyethylene succinate (P ESu), polybutylene succinate (PBSu), polyethylene succinate adipate The polylactic acid / polycaprolactone copolymer may be poly(lactic acid / polyether copolymer), poly(lactic acid / polyether copolymer), poly(butylene succinate) (PESA), poly(butylene succinate adipate) (PBSA), polycaprolactone (PCL), poly(butylene succinate carbonate) (PEC), polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, and the like.

[0020] The aromatic polyester may be, for example, polybutylene adipate terephthalate (PBAT), polytetramethylene adipate terephthalate, polyethylene terephthalate succinate (CPE), and the like.

[0021] The polyhydroxyalkanoic acid (PHA) may be, for example, a poly-3-hydroxybutyrate (PHB)-based resin containing 3-hydroxybutyrate, specifically, poly-3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate / 3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate / 3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate / 4-hydroxybutyrate), etc.

[0022] Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Examples of cellulose ethers include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and cyanoethyl cellulose. Examples of cellulose ether esters include hydroxypropyl methylcellulose acetate and hydroxypropyl methylcellulose acetate succinate (it is intended that in this specification, cellulose ether esters are encompassed by the concepts of both cellulose ether and cellulose ester).

[0023] Of these, preferred are poly(3-hydroxybutyrate) resins, polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, and cellulose. The biodegradable resin may include one type or two or more types. The biodegradable resin can be prepared, for example, by a conventional method for preparing a polymer, and commercially available products can also be used.

[0024] The molecular weight of the biodegradable resin used in the present invention is not particularly limited as long as it does not impair the effects of the present invention. For example, the number average molecular weight (Mn) may be 20,000 to 10,000,000. The weight average molecular weight (Mw) may be 20,000 to 10,000,000. The molecular weight can be measured by gel permeation chromatography (GPC) or the like.

[0025] Here, the biodegradability of a biodegradable resin means the property of the biodegradable resin being cleaved and fragmented into low molecular weight molecules by the action of hydrolases of biodegradable polymer-degrading bacteria, etc. Also, preferably, the biodegradability of a biodegradable resin may be the property of the biodegradable resin being cleaved and fragmented into low molecular weight molecules and inorganicized. The biodegradability of a biodegradable resin in the ocean can be confirmed, for example, by immersing a sample in seawater and observing a decrease in weight from the initial weight after a seawater immersion test.

[0026] <<Crustacean or insect shells>> The shells of crustaceans or insects used in the present invention contain chitin. There are no particular limitations on the species of crustaceans or insects, so long as they contain chitin and do not impair the effects of the present invention.

[0027] Examples of crustaceans include marine crustaceans, such as crabs and shrimp. Examples of insects include silkworms, flies, grasshoppers, etc. The shells (exoskeletons) of crustaceans and insects contain a lot of chitin, and are therefore suitable for use in the present invention. In particular, the shells of crustaceans usually contain about 20 to 30% by mass of chitin, and therefore are preferably used in the present invention.

[0028] The shells of crustaceans or insects may include those derived from one or more types of organisms. The shells of crustaceans or insects may be collected from crustacean or insect organisms and used as is, or may be purified, crushed, or the like as necessary, or may be commercially available products.

[0029] The amount of crustacean or insect shells used in the method for controlling the biodegradation rate of the present invention is not limited, but for example, the amount of crustacean or insect shells applied can be approximately 0.01 to 500 parts by weight, 1 to 100 parts by weight, or 15 to 50 parts by weight per part by weight of biodegradable resin.

[0030] In the method for controlling the biodegradation rate of the present invention, a nutrient source necessary for the growth of the biodegradable resin-degrading microorganism may be added as desired. Examples of the nutrient source include nitrogen-containing compounds, inorganic and organic phosphorus-containing compounds, etc.

[0031] The nitrogen-containing compound may be any compound containing nitrogen, and may be inorganic or organic nitrogen-containing compounds. For example, inorganic nitrogen-containing compounds include various ammonium salts such as ammonium chloride, ammonium sulfate, and ammonium nitrate, and organic nitrogen-containing compounds include various amino acids and their derivatives, polymers of various amino acids, peptides, proteins, urea, and the like, but are not limited thereto. In addition, compounds containing both nitrogen and phosphorus may be used as the nitrogen-containing compound, and examples thereof include inorganic compounds such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, as well as organic compounds such as nucleic acids such as ribonucleic acid and deoxyribonucleic acid. As the nitrogen-containing compound, ammonium salts are preferred, and ammonium chloride is more preferred. The nitrogen-containing compound may contain one or more types.

[0032] Nitrogen-containing compounds (in terms of nitrogen) are expressed as concentrations in 1 L of the environment containing biodegradable resin, e.g. , 0.1 to 10 g / L, 0.5 to 5 g / L, or 0.65 to 1.5 g / L.

[0033] Inorganic phosphorus compounds include various phosphates such as sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and various polymers such as polyphosphoric acids. Organic phosphorus compounds include various alkyl and alkenyl phosphate esters, sugar phosphate esters such as phytic acid, and nucleic acids, but are not limited to these.

[0034] The phosphorus compound (in terms of phosphorus) can be applied so that the concentration in 1 L of the environment containing the biodegradable resin is, for example, about 0.001 to 10 g / L, 0.01 to 5 g / L, or 0.1 to 1 g / L.

[0035] Here, the control of the biodegradation rate of the biodegradable resin in the ocean can be confirmed by, but is not limited to, for example, a decrease in the biodegradation rate of the biodegradable resin to which the shells of crustaceans or insects have been added, compared to the biodegradation rate of the biodegradable resin to which the shells of crustaceans or insects have not been added, and, but is not limited to, for example, the biodegradation rate of the biodegradable resin to which the shells of crustaceans or insects have been added can be 0.8 times or less, 0.7 times or less, 0.6 times or less, 0.5 times or less, 0.4 times or less, 0.3 times or less, 0.2 times or less, or 0.1 times or less of the biodegradation rate of the biodegradable resin to which the shells of crustaceans or insects have not been added. Whether or not the biodegradation rate of the biodegradable resin has decreased can be confirmed by a degradation test such as that shown in the examples below. For example, the amount of weight loss is calculated from the difference between the initial weight of the sample and the weight after the seawater immersion test, and the decomposition rate is calculated by dividing the amount of weight loss by the surface area of ​​the sample and the immersion time.If the biodegradation rate of a biodegradable resin containing crustacean or insect shells is slower than that of a biodegradable resin not containing crustacean or insect shells, it can be determined that the biodegradation rate of the biodegradable resin has decreased.

[0036] <Biodegradation rate control agent> Another aspect of the present invention relates to an agent for controlling the biodegradation rate of marine biodegradable resins, including shells of crustaceans or insects (hereinafter, sometimes referred to as the "biodegradation rate controller of the present invention"). Note that all of the matters explained in the section "Method for controlling biodegradation rate" above are applicable to the explanation of the biodegradation rate controller of the present invention.

[0037] The biodegradation rate regulator of the present invention contains crustacean or insect shells as an active ingredient. By placing the biodegradation rate regulator containing the active ingredient, crustacean or insect shells, in the vicinity of a biodegradable resin or in contact with the biodegradable resin, the biodegradation rate of the biodegradable resin in the ocean can be controlled. As the active ingredient, crustacean or insect shells, those described in the above section <Method for controlling biodegradation rate> can be used. In addition, the method of using the biodegradation rate regulator of the present invention is the same as the method of using crustacean or insect shells, and the method of using crustacean or insect shells described in the above section <Method for controlling biodegradation rate> can be referred to.

[0038] The biodegradation rate control agent of the present invention may be composed of only the active ingredient, but may optionally contain additives for formulation, such as solvents, excipients, binders, stabilizers, etc. Also, it may optionally contain a nutrient source necessary for the proliferation of biodegradable resin-degrading microorganisms. Examples of nutrient sources include nitrogen-containing compounds, inorganic and organic phosphorus-containing compounds, etc. As the nitrogen-containing compounds, inorganic and organic phosphorus-containing compounds, those described in the above section on <Method for controlling biodegradation rate> can be used. The biodegradation rate regulator may contain the crustacean or insect shells and the nutrient source separately, or may contain the crustacean or insect shells and the nutrient source in combination.

[0039] The blending ratio of crustacean or insect shells in the biodegradation rate regulator of the present invention is not limited, but can be, for example, about 0.1 to 100% by weight, 1 to 99.9% by weight, or 10 to 50% by weight relative to the total amount of the biodegradation rate regulator.

[0040] The dosage form of the biodegradation rate control agent of the present invention is not particularly limited, and it may be in the form of a powder, pellet, film-like solid, or dissolved or dispersed in a hydrophilic or lipophilic liquid, sol, or gel. The biodegradation rate control agent can be formulated according to a conventional method.

[0041] <Biodegradable resin composition> Another aspect of the present invention relates to a biodegradable resin composition having a controlled biodegradation rate in the ocean, which contains a biodegradable resin and the biodegradation rate control agent of the present invention (hereinafter, may be referred to as the "biodegradable resin composition of the present invention"). Note that all of the matters explained in the above sections "Method for controlling biodegradation rate" and "Biodegradation rate control agent" are applicable to the explanation of the biodegradable resin composition of the present invention.

[0042] The biodegradable resin composition of the present invention contains a biodegradable resin and the biodegradation rate regulator of the present invention, and the biodegradability is controlled by adding a small amount of the biodegradation rate regulator to the biodegradable resin. That is, the biodegradation rate is suppressed during use of the biodegradable resin composition, without impairing the mechanical properties, etc. of the biodegradable resin, and when biodegradation in the ocean is required, the biodegradation rate of the biodegradable resin can be restored by reducing the amount of the biodegradation rate regulator or making it nonexistent.

[0043] As the biodegradable resin, those explained in the section <Method of controlling biodegradation rate> above can be used. The blending ratio of the biodegradable resin of the present invention and the biodegradation rate regulator is not limited, but for example, the biodegradation rate regulator may be 0.01 to 500 parts by weight, 1 to 100 parts by weight, or 15 to 50 parts by weight, in terms of the amount of crustacean or insect shells, per 1 part by weight of the biodegradable resin.

[0044] The biodegradable resin composition of the present invention may consist only of a biodegradable resin and a biodegradation rate regulator, but may also contain, if necessary, various additives that are usually used in biodegradable resin compositions, such as a plasticizer for the biodegradable resin, a stabilizer (antioxidant, heat stabilizer, light resistance stabilizer, etc.), a surfactant, a lubricant, a colorant, a filler, an antistatic agent, a silane coupling agent, a dispersant, a dispersion aid, a release agent, etc. The additives may be used alone or in combination of two or more kinds.

[0045] The form of the biodegradable resin composition of the present invention is not particularly limited, and may be a powder, pellet, fiber, or film-like solid, or may be dissolved or dispersed in a hydrophilic or lipophilic liquid, sol, or gel.Preferably, the biodegradation rate regulator is formed into a film on a biodegradable resin, or the biodegradation rate regulator is laminated by coating the surface of a biodegradable resin film, for example. The lower limit of the thickness of the laminated layers may be, for example, 0.75 μm or more, 1 μm or more, or 3 μm or more, and the upper limit may be, for example, 100 μm or less, 50 μm or less, or 10 μm or less. The marine biodegradable resin composition can be produced by a conventional method. For example, a method of forming a film on one or both surfaces of a biodegradable resin by a lamination method using a coating liquid prepared by dissolving or dispersing crushed crustacean or insect shells and a binder in a liquid such as water, and laminating the film, can be mentioned. Specifically, for example, an extrusion lamination method is used in which a molten coating liquid is extruded from a T-die into a film shape, and then a cooling roll is used to cool and press the biodegradable resin laminated on a separately unwound substrate, or a method of forming a film using a coating liquid prepared in advance is used. A thermal lamination method is used in which a film formed on the substrate is heated and pressure-bonded to a biodegradable resin laminated on a substrate. Another method is to apply a coating liquid prepared by dissolving or dispersing crushed crustacean or insect shells in a liquid such as water onto one or both surfaces of a biodegradable resin, and then heat and dry the resulting film.

[0046] <Molded products> Another aspect of the present invention relates to a molded article formed from the biodegradable resin composition of the present invention (hereinafter, may be referred to as "molded article of the present invention"). Note that the matters explained in the above sections "Method for controlling biodegradation rate", "Agent for controlling biodegradation rate", and "Biodegradable resin composition" all apply to the explanation of the molded article of the present invention.

[0047] The biodegradable resin composition of the present invention can be molded into films, sheets, and other molded articles such as tools, containers, nonwoven fabrics, and the like having shapes suitable for the intended use.

[0048] The method for obtaining a film or sheet made of the biodegradable resin composition of the present invention is not particularly limited, and the composition is molded into a film or sheet by a known molding method. For example, the composition may be molded into a film or sheet by a T-die molding method, an inflation molding method, a calendar molding method, a heat press molding method, etc. In addition, these films or sheets may be stretched in at least one direction. The stretching method is not particularly limited, and examples thereof include a roll stretching method, a tenter method, and an inflation method.

[0049] There are no particular limitations on the method for obtaining a molded article having a shape suitable for the intended use, which is made from the biodegradable resin composition of the present invention, and the article can be produced by any known method, such as extrusion molding or injection molding in a mold. The thickness of the molded article of the biodegradable resin composition of the present invention is preferably thin in order to enhance its water disintegrability and biodegradability, but can be freely adjusted to satisfy strength, flexibility, etc. The preferred thickness of the film is 5 to 300 μm, more preferably 10 to 100 μm. The preferred thickness of the sheet or container-shaped molded article is 0.1 to 5 mm, more preferably 0.2 to 2 mm. The tensile modulus is not particularly limited, but is usually preferably 1200 MPa or less, more preferably 600 MPa or less. The tensile strength is not particularly limited, but is preferably in the range of 10 to 100 MPa. The pressure is preferably in the range of 15 to 70 MPa, more preferably in the range of 20 to 50 MPa.

[0050] The method for obtaining a nonwoven fabric of the biodegradable resin composition of the present invention is not particularly limited, and the fabric can be produced by a known method, for example, a dry method, a spunbond method, a meltblowing method, a wet method, etc. That is, the nonwoven fabric can be obtained by spinning the biodegradable resin composition of the present invention, forming a web, and bonding the web by a known method.

[0051] The uses of the molded article made of the biodegradable resin composition of the present invention are not particularly limited, and it can be used, for example, as a member (part) constituting a sanitary product, an agricultural and horticultural material, a civil engineering and construction material, a fishing material, etc. That is, it is possible to manufacture a sanitary product, an agricultural and horticultural material, a civil engineering and construction material, a fishing material, etc., using a material containing the biodegradable resin composition of the present invention.

[0052] Sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc. can be produced by molding the biodegradable resin composition of the present invention into a desired shape, and the molded products can be further bonded and fixed to each other by known methods such as hot melt bonding or thermal bonding.

[0053] Examples of the sanitary products include disposable diapers, incontinence pads, sanitary napkins, etc. Examples include: Examples of the agricultural and horticultural materials include mulch films, seedling pots, gardening tapes, fruit cultivation bags, stakes, fumigation sheets, films for vinyl greenhouses, and fertilizer covering materials. Examples of the civil engineering and construction materials include vegetation nets, vegetation pots, three-dimensional net structures, civil engineering fibers, stakes, and heat insulating materials. Examples of the fishing materials include fishing nets, aquaculture equipment, fishing tackle, mooring ropes, fenders, sea anchors, floats, and the like. EXAMPLES

[0054] The present invention will be specifically described below with reference to examples. However, these are merely illustrative of the present invention and the scope of the present invention is not limited to these examples.

[0055] <Experimental Method> (material) Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (Mw = 114 × 10) was purchased from HighChem Co., Ltd. 3 ) was placed in a stainless steel mold with a thickness of 0.1 mm, and the tape was The shells were sandwiched between two 1 mm thick stainless steel plates and a pressure of 15 MPa was applied for 1 minute using a Mini Test Press MP-SCH (Toyo Seiki Seisakusho). After quenching in an ice bath for 10 minutes, the shells were removed from the mold and cut into 2 cm squares to give PHBV films. Crab shells were purchased from Kitayama Suisan Co., Ltd. Seawater was collected from the Japan Agency for Marine-Earth Science and Technology (35°31'27.63”, 139°65'43.83”) in Yokosuka, Kanagawa Prefecture.

[0056] (Biodegradation rate test) PHBV film (0.081g) was placed in a bag made of polyethylene mesh (mesh count 24 / inch). Crab shells (1.5 g) were placed between the films. The samples were immersed in a tank containing seawater (7 L) to which potassium dihydrogen phosphate (0.1 g / L) and ammonium chloride (0.5 g / L) had been added. As a negative control, a PHBV film without crab shells was immersed in seawater to which inorganic salts had been added in the same way. Seawater was circulated using a pump. The tank containing the samples was placed at room temperature (20°C), and the samples were collected after 1, 2, 3, 4, and 8 weeks. The PHBV film was washed with methanol and ultrapure water in that order, dried under reduced pressure, and then its mass was measured. The difference between the initial mass of each polyester film and the mass after the seawater immersion test was calculated based on the surface area (8 cm) of the film. 2 ) to get the film size of 1 cm 2 The mass loss per unit area was calculated.

[0057] (Observation of film surface morphology) After the seawater immersion test, the PHBV film was immersed in a 2.5% glutaraldehyde solution for 1 hour. After washing the PHBV film with ultrapure water, it was immersed in 50%, 60%, 70%, 80%, 90%, and 100% ethanol for 20 minutes each. The dehydrated film was immersed in t-butyl alcohol for 1 hour. After that, it was dried in vacuum. Au was evaporated onto the surface of the PHBV film using a DII-29010SCTR Smart Coater (manufactured by JEOL Ltd.). The surface morphology of the PHBV film was observed under high vacuum conditions at an accelerating voltage of 10 kV using a JCM-7000 NeoScope TM tabletop scanning electron microscope (manufactured by JEOL Ltd.).

[0058] (Analysis of microbial community structure) The seawater before and after the sample immersion was filtered using a vacuum pump (As One Corporation, DRY SAPIRATOR DAS-01) and a membrane filter (Advantec, pore size 0.45 μm). The PHBV film after immersion in seawater, crab shells (chitin), and the membrane filter through which the seawater had been filtered were then filtered using ZymoBIOMICS TM DNA and total RNA were extracted using the DNA / RNA Miniprep Kit (ZYM RESEARCH). The extracted DNA solution was stored at -20°C, and the total RNA solution was stored at -80°C.

[0059] The extracted DNA was subjected to sequencing analysis using the 16s rDNA V4 region amplicon sequencing method with the MiSeq Reagent Kit v3 (Illumina) under the condition of 2x300 bp. After removing the primer sequence using fastx_trimer of lkit, the dada2 primer of Qiime2 (ver. 2022.8) was used. Chimeric sequences and noise sequences were removed using the plug-in. Representative sequences and ASV (Amplicon Sequence Variants) tables were output. The representative sequences were also classified into Phylogenetic inference was performed by comparing the sequence with 97% OTUs in Greengene (ver. 13_8).

[0060] Non-metric multidimensional scaling (NMDS) was used to compare the microbial community structure among samples based on the Bray-Curtis index calculated from the ASV data. All analyses were performed using the ggplot2, MASS, and vegan packages in the statistical software R (v.4.2.2).

[0061] <Result> Figure 1 shows the mass loss of the PHBV film as a function of immersion time (μg / cm 2 ) (n=5). All immersions The mass loss of the PHBV film immersed with the crab shells was 0.084-0.52 times smaller than that of the PHBV film alone. The weight loss of the PHBV film immersed in water was higher than that after 4 weeks. This is thought to be due to shell wear.

[0062] Figure 2 shows SEM images of the PHBV film surface before and after immersion in seawater. The surface of the PHBV film before immersion was smooth, but after immersion, rods of spherulites were observed due to preferential decomposition of the amorphous portion. On the other hand, the surface of the PHBV film immersed with crab shells had small holes, but was smoother than the surface of the PHBV film without crab shells.

[0063] The relative abundance of bacterial communities at the class level in seawater before the immersion test (0d-SW-July), the PHBV surface (PHBV), the PHBV surface immersed with crab shells (PHBV+Chitin), the crab shell surface (Chitin), and seawater after the immersion test (afSW-PHBV, afSW-PHBV+Chitin) is shown (Figure 3).

[0064] The microbiota on the PHBV surface was dominated by Alphaproteobacteria and Gammaproteobacteria at all immersion periods. The microbiota on the PHBV surface immersed with crab shells after 1 to 4 weeks and on crab shells at all immersion periods was dominated by Gammaproteobacteria and Deltaproteobacteria. On the other hand, the microbiota on the PHBV film surface immersed with crab shells for 8 weeks was dominated by Alphaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria.

[0065] Based on the Bray-Curtis index, the dissimilarity of bacterial communities between samples was illustrated by NMDS (Figure 4). The distance between the points compared on the plot represents the similarity of the bacterial communities. Here, P represents PHBV, PC represents PHBV + crab shell, C represents crab shell, SW represents seawater before immersion, and the numbers represent the immersion period (weeks). SW.P and SW.C represent PHBV film and seawater after immersion of PHBV film together with crab shell, respectively. The bacterial community structures of PHBV alone and on the crab shell surface were significantly different from those of the seawater before immersion. In addition, PHBV Differences were observed between the bacterial community structure of PHBV and that of PHBV soaked with crab shells. Furthermore, the bacterial community structure of PHBV soaked with crab shells was similar to that of crab shells.

[0066] From the above results, it was suggested that placing crustacean or insect shells such as crab shells near biodegradable resins such as PHBV would change the microbial flora on the surface of the PHBV film and inhibit the decomposition of PHBV. Crab shells are natural products and are biodegradable in the marine environment. Since the biodegradation of PHBV is inhibited while crab shells are present near PHBV, it is considered possible to control the biodegradation rate of PHBV by the amount of crab shells. In addition, the present invention utilizes industrial waste as a biodegradation control material, and is considered to be a technology that contributes to adding value to waste. [Industrial Applicability]

[0067] According to the method of the present invention, the shells of crustaceans or insects are placed on or near the surface of a biodegradable resin. This makes it possible to inhibit the proliferation of biodegradable resin-degrading microorganisms and reduce the marine biodegradability of the resin. After the shells of the crustaceans or insects are completely biodegraded, the biodegradable resin begins to decompose. The present invention can be used in a variety of fields as a biodegradable resin product, but it can be preferably applied to materials that are expected to be used in the environment, such as fishing equipment, fishing tackle, agricultural mulch films, and fertilizer covering materials.

Claims

1. The method includes placing a shell of a crustacean or insect in the vicinity of or in contact with a biodegradable resin. A method for controlling the rate of biodegradation of biodegradable resins in the ocean.

2. The method for controlling the biodegradation rate according to claim 1 , wherein the shell of a crustacean or insect is a crab shell.

3. 2. The method for controlling a biodegradation rate according to claim 1, wherein the biodegradable resin comprises one or more selected from the group consisting of polyhydroxyalkanoic acid, aliphatic polyester, aromatic polyester, and natural polymers and derivatives thereof.

4. 2. The method for controlling a biodegradation rate according to claim 1, wherein the biodegradable resin comprises one or more selected from the group consisting of poly(3-hydroxybutyrate)-based resin, polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, and cellulose.

5. An agent for controlling the rate of biodegradation of marine biodegradable resins, including crustacean or insect shells.

6. A biodegradable resin composition having a controlled rate of biodegradation in the ocean, comprising a biodegradable resin and the biodegradation rate control agent according to claim 5.

7. The biodegradable resin composition according to claim 6, wherein a biodegradation rate regulator is laminated on the biodegradable resin.

8. A molded article formed from the biodegradable resin composition according to claim 6 or 7.

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