Method for controlling marine biodegradation rate of biodegradable resin

Abstract

The present invention addresses the problem of developing a technique for accelerating the marine biodegradation rate of a biodegradable resin. The present invention provides a marine biodegradation rate accelerator for a biodegradable resin, the accelerator comprising 16-hydroxyhexadecanoic acid.

Description

Method for controlling the rate of marine biodegradation of biodegradable resins

[0001] The present invention relates to a method for controlling the rate of marine biodegradation of biodegradable resins using 16-hydroxyhexadecanoic acid (16HHD).

[0002] Many synthetic aliphatic polyesters, such as polybutylene succinate-co-adipate (PBSA) and polybutylene succinate (PBSu), are biodegradable materials with excellent physical properties and processability. However, their biodegradability varies significantly depending on the environment, and the biodegradation rate is particularly low in the marine environment.

[0003] Against this background, methods have been proposed for accelerating the decomposition of biodegradable resins in the marine environment. For example, Patent Documents 1 and 2 describe a method of adding polyhydroxyalkanoic acid (PHA) or polycaprolactone (PCL), which have high marine biodegradability, to materials such as PBSA or PBSu, which have low marine biodegradability. Patent Documents 3 and 4 describe a method of increasing the decomposition rate by adding the resin hydrolase to a resin article. Patent Document 5 describes a method of increasing the decomposition rate in the marine environment by adding a nitrogen compound and a phosphorus compound. However, there is a need for the development of further methods for accelerating the decomposition of biodegradable resins in the marine environment.

[0004] Patent Publication No. 2022-145600, Patent Publication No. 2022-037049, Patent Publication No. 2020-531671, Patent Publication No. 2022-526344, Patent Publication No. 2022-142016 (Patent No. 6976540)

[0005] In view of the above circumstances, an object of the present invention is to develop a technology for accelerating the rate of marine biodegradation of biodegradable resins.

[0006] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that contacting 16-hydroxyhexadecanoic acid with a biodegradable resin can accelerate the marine biodegradation rate of the biodegradable resin. Based on this finding, the present invention has been completed. That is, the gist of the present invention relates to the following.

[0007] [1] A marine biodegradation rate accelerator for a biodegradable resin, comprising 16-hydroxyhexadecanoic acid. [2] The marine biodegradation rate accelerator, wherein the biodegradable resin is a polyester resin. [3] The marine biodegradation rate accelerator, wherein the biodegradable resin is one or more selected from polybutylene succinate and polybutylene succinate / adipate. [4] A marine biodegradable resin composition having an accelerated marine biodegradation rate, comprising a biodegradable resin and the marine biodegradation rate accelerator. [5] A molded article formed from the marine biodegradable resin composition. [6] A method for accelerating the biodegradation rate of a biodegradable resin in a marine environment by contacting a biodegradable resin with the marine biodegradation rate accelerator. [7] A method for biodegrading a biodegradable resin in a marine environment by contacting a biodegradable resin with the marine biodegradation rate accelerator.

[0008] The present invention can also employ the following configurations. [8] Use of 16-hydroxyhexadecanoic acid for accelerating the marine biodegradation rate of a biodegradable resin. [9] 16-hydroxyhexadecanoic acid for use in accelerating the marine biodegradation rate of a biodegradable resin.

[10] Use of 16-hydroxyhexadecanoic acid in the production of an accelerator for the marine biodegradation rate of a biodegradable resin.

[11] Use of 16-hydroxyhexadecanoic acid in the production of a marine biodegradable resin composition having an accelerated marine biodegradation rate.

[12] A method for producing an accelerator for the marine biodegradable resin, comprising formulating 16-hydroxyhexadecanoic acid.

[13] A method for producing a marine biodegradable resin composition having an accelerated marine biodegradation rate, comprising mixing a biodegradable resin composition with 16-hydroxyhexadecanoic acid.

[0009] According to the present invention, the marine biodegradation rate of a biodegradable resin can be accelerated. Specifically, the present invention provides an accelerator for the marine biodegradation rate of a biodegradable resin, a marine biodegradable resin composition with an accelerated marine biodegradation rate, a molded article formed from the marine biodegradable resin composition, a method for accelerating the biodegradation rate of a biodegradable resin in a marine environment, and a method for biodegrading a biodegradable resin in a marine environment. Specifically, according to the present invention, the marine biodegradation rate of a biodegradable resin can be accelerated by coexisting a biodegradable resin with a low marine biodegradation rate with 16-hydroxyhexadecanoic acid. Therefore, it is possible to provide, at low cost, a composite material that retains its mechanical properties under normal use conditions but exhibits accelerated biodegradability when released into the environment after use and placed in an environment with few microorganisms, such as in the ocean.

[0010] Figure 1 shows the results of a test to measure the rate of resin weight loss in shallow water. The top row shows the test results for a PBSA-based resin, and the bottom row shows the test results for a PBSu-based resin. Figure 2 shows the results of a test to measure the rate of resin weight loss in deep water. The top row shows the test results for a PBSA-based resin, and the bottom row shows the test results for a PBSu-based resin. Figure 3 shows the results of a test to measure the rate of resin weight loss in sterile artificial seawater. The top row shows the test results for PBSA and PBSA with 16HHD added. Figure 4 shows the results of a test to measure the rate of resin weight loss in sterile artificial seawater. The top row shows the test results for PBSu and PBSu with 16HHD added. Figure 5 shows the results of observation of the surface morphology of a PBSA-based resin using a scanning electron microscope (SEM). The white bar is 10 μm long. Figure 6 shows the results of observation of the surface morphology of a PBSu-based resin using a scanning electron microscope (SEM). The white bar is 10 μm long. Figure 7 shows the BOD biodegradation curves for PBSA-based resin, 16HHD-added PBSA, PBSu-based resin, and 16HHD-added PBSu (90 days). Figure 8 shows the DNA / RNA content of 16HHD-added PBSA-based resin and PBSu-based resin before and after shallow water immersion tests.

[0011] The present invention will be described below. <Marine biodegradation rate enhancer> One aspect of the present invention relates to a marine biodegradation rate enhancer for a biodegradable resin, which comprises 16-hydroxyhexadecanoic acid (hereinafter, sometimes referred to as the "marine biodegradation rate enhancer of the present invention").

[0012] In the present invention, the biodegradation rate of a biodegradable resin in a marine environment, such as seawater or the ocean, can be accelerated by contacting 16-hydroxyhexadecanoic acid with the biodegradable resin. The marine biodegradation rate accelerator of the present invention can accelerate the biodegradation rate of a biodegradable resin in a marine environment by contacting the biodegradable resin with the biodegradable resin, for example, by mixing the marine biodegradation rate accelerator of the present invention with the biodegradable resin or by laminating the marine biodegradation rate accelerator on the biodegradable resin. For methods of using the marine biodegradation rate accelerator of the present invention, such as the method of contacting the marine biodegradation rate accelerator with the biodegradable resin and the amount used, please refer to the items explained below in the sections <Marine Biodegradable Resin Composition>, <Molded Article>, and <Method for Accelerating Biodegradation Rate and Biodegradation Method>.

[0013] <Biodegradable Resin> The "biodegradable resin" that is the target substance for accelerating the marine biodegradation rate of the marine biodegradation rate accelerator 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 either can be used. Biodegradable resins include, but are not limited to, polyester resins, natural polymers and their derivatives, etc. Polyester resins can be selected from, for example, aliphatic polyesters, aromatic polyesters, etc.; natural polymers can be selected from, for example, cellulose, starch, etc.; and derivatives of natural polymers can be selected from, for example, cellulose esters, cellulose ethers, cellulose ether esters, etc.

[0014] The aliphatic polyester may be, for example, polylactic acid (PLA), polyhydroxyalkanoic acid (PHA), polyethylene succinate (PESu), polybutylene succinate (PBSu), polyethylene succinate adipate (PESA), polybutylene succinate adipate (PBSA), polycaprolactone (PCL), polybutylene succinate carbonate (PEC), polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, or the like.

[0015] The aromatic polyester may be, for example, polybutylene adipate terephthalate (PBAT), polytetramethylene adipate terephthalate, polyethylene terephthalate succinate (CPE), and the like.

[0016] The polyhydroxyalkanoic acid (PHA) may be, for example, a poly-3-hydroxyalkanoate-based resin containing 3-hydroxyalkanoate, specifically a poly-3-hydroxybutyrate (PHB)-based resin containing 3-hydroxybutyrate, more specifically poly-3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate / 3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate / 3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate / 4-hydroxybutyrate), etc.

[0017] 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 methyl cellulose, and cyanoethyl cellulose; and examples of cellulose ether esters include hydroxypropyl methyl cellulose acetate and hydroxypropyl methyl cellulose acetate succinate (it is intended that in this specification, cellulose ether esters are encompassed by the concepts of both cellulose ether and cellulose ester).

[0018] Although not limited thereto, polyester resins are preferred, aliphatic polyester resins are more preferred, polyethylene succinate, polybutylene succinate, polyethylene succinate / adipate, and polybutylene succinate / adipate are even more preferred, and polybutylene succinate and polybutylene succinate / adipate are particularly preferred. The biodegradable resin may contain one type or two or more types. The biodegradable resin can be prepared, for example, by a conventional polymer preparation method. Commercially available products can also be used.

[0019] 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.

[0020] Here, the biodegradability of a biodegradable resin means that the biodegradable resin has the property of being cut and fragmented into low-molecular-weight compounds by the action of hydrolytic enzymes and the like of biodegradable polymer-degrading bacteria, and then mineralized. The biodegradability of a biodegradable resin in a marine environment (marine biodegradability) can be confirmed, for example, by immersing a sample in seawater and observing the weight loss from the initial weight after a seawater immersion test, as well as the biochemical oxygen demand (BOD) during the test.

[0021] <16-Hydroxyhexadecanoic Acid> The marine biodegradation rate accelerator of the present invention contains 16-hydroxyhexadecanoic acid as an active ingredient.

[0022] 16-Hydroxyhexadecanoic acid is an aliphatic hydroxycarboxylic acid having 16 carbon atoms, and can be synthesized by a known chemical synthesis method, and purified as necessary, or a commercially available product such as 16HHD manufactured by Sigma-Aldrich or Fujifilm Wako Pure Chemical Industries, Ltd. can be used.

[0023] The blending ratio of 16-hydroxyhexadecanoic acid in the marine biodegradation rate accelerator is not limited, but can be, for example, about 0.001 to 100% by weight, 0.01 to 90% by weight, 0.1 to 80% by weight, 1 to 70% by weight, 10 to 60% by weight, or 20 to 50% by weight relative to the total amount of the marine biodegradation rate accelerator.

[0024] The marine biodegradation rate accelerator may be composed of 16-hydroxyhexadecanoic acid, but may optionally contain additives for formulation, such as solvents, excipients, stabilizers, etc. In other words, the marine biodegradation rate accelerator can also be referred to as a "marine biodegradation rate accelerator composition." The additives can be used alone or in combination of two or more. Optionally, the accelerator may also contain a nutrient source necessary for the growth of biodegradable resin-degrading microorganisms.

[0025] The formulation of the marine biodegradation rate accelerator is not particularly limited, and 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 marine biodegradation rate accelerator can be formulated according to conventional methods.

[0026] <Marine biodegradable resin composition> Another aspect of the present invention relates to a marine biodegradable resin composition having an accelerated marine biodegradation rate, comprising a biodegradable resin and the marine biodegradation rate accelerator of the present invention (hereinafter, sometimes referred to as the "marine biodegradable resin composition of the present invention"). Note that all of the matters explained in the above section <Marine biodegradation rate accelerator> apply to the explanation of the marine biodegradable resin composition of the present invention.

[0027] The marine biodegradable resin composition of the present invention contains the biodegradable resin and a marine biodegradation rate accelerator, and can significantly accelerate biodegradation even when the ratio of the marine biodegradation rate accelerator to the biodegradable resin is small. Therefore, the biodegradability of the biodegradable resin can be improved or accelerated without significantly impairing the mechanical properties, etc. of the biodegradable resin. Furthermore, the biodegradability of the biodegradable resin can be controlled by the amount of marine biodegradation rate accelerator used.

[0028] The blending ratio of the marine biodegradation rate accelerator in the marine biodegradable resin composition is not limited, but may be, for example, 1 to 500 parts by weight, 10 to 100 parts by weight, or 1 to 50 parts by weight of 16-hydroxyhexadecanoic acid per 100 parts by weight of the biodegradable resin.

[0029] The marine biodegradable resin composition may contain, as necessary, various additives that are commonly used in biodegradable resin compositions, such as plasticizers for the biodegradable resin, stabilizers (antioxidants, heat stabilizers, light resistance stabilizers, etc.), surfactants, lubricants, colorants, fillers, antistatic agents, silane coupling agents, dispersants, dispersing aids, mold release agents, etc. The additives can be used alone or in combination of two or more.

[0030] The marine biodegradable resin composition may be in the form of a mixture of a biodegradable resin and a marine biodegradation rate accelerator, or may be in the form of an integrated mixture of the biodegradable resin and the marine biodegradation rate accelerator (for example, powder or pellets).

[0031] The mixture of the biodegradable resin and the marine biodegradation rate enhancer may be in the form of a film formed on the biodegradable resin or coated on the surface of the biodegradable resin, thereby forming a laminate. The lower limit of the thickness of the laminated layer may be, for example, 0.75 μm or more, 1 μm or more, or 3 μm or more. The upper limit may be, for example, 100 μm or less, 50 μm or less, or 10 μm or less.

[0032] The marine biodegradable resin composition can be produced by conventional methods, including, for example, laminating a film onto one or both surfaces of a biodegradable resin using a coating solution prepared by dissolving or dispersing a marine biodegradation rate accelerator and a binder in a liquid such as water. Specific examples include extrusion lamination, in which a molten coating solution is extruded through a T-die into a film, and then cooled and pressure-bonded to a separately unwound biodegradable resin laminated on a substrate using a cooling roll. Other examples include thermal lamination, in which a film formed from a pre-prepared coating solution is heated and pressure-bonded to the biodegradable resin laminated on the substrate. Another example is a method in which a coating solution prepared by dissolving or dispersing a marine biodegradation rate accelerator in a liquid such as water is applied to one or both surfaces of a biodegradable resin, followed by heating, drying, and film formation.

[0033] The form in which the biodegradable resin and the marine biodegradation rate enhancer are kneaded together to form an integrated body may be a form in which the marine biodegradation rate enhancer is kneaded together with the biodegradable resin to form an integrated body.

[0034] The marine biodegradable resin composition can be produced by a conventional method, for example, by adding at least the biodegradable resin and the marine biodegradation rate accelerator to an extruder and melt-kneading the components. In the melt-kneading step, the biodegradable resin, the marine biodegradation rate accelerator, and optional additives may be added separately to the extruder, or the components may be mixed and then added to the extruder. The melt-kneading in the melt-kneading step can be carried out using, for example, an extruder (single-screw extruder, twin-screw extruder), a kneader, or the like.

[0035] The marine biodegradable resin composition can be produced in the same manner as in the production of ordinary polymer compositions, except that it contains a marine biodegradation rate accelerator in addition to the biodegradable resin.

[0036] <Molded Article> Another aspect of the present invention relates to a molded article formed from the marine biodegradable resin composition of the present invention (hereinafter, sometimes referred to as the "molded article of the present invention"). Note that all of the matters explained in the sections <Marine biodegradation rate accelerator> and <Marine biodegradable resin composition> above apply to the explanation of the molded article of the present invention.

[0037] The marine biodegradable resin composition of the present invention can be molded into films, sheets, and other molded articles such as instruments, containers, and nonwoven fabrics having shapes suitable for the intended use.

[0038] There are no particular limitations on the method for obtaining a film or sheet made from the marine biodegradable resin composition of the present invention, and the composition can be molded into a film or sheet by a known molding method. Examples include T-die molding, inflation molding, calendar molding, and hot press molding. These films and sheets may also be stretched in at least one direction. There are no particular limitations on the stretching method, and examples include roll stretching, tenter molding, and inflation molding.

[0039] There are no particular limitations on the method for obtaining molded articles of the marine biodegradable resin composition of the present invention in a shape suitable for the intended use, and they can be produced by known methods, such as extrusion molding or injection molding in a mold. The thickness of molded articles of the marine biodegradable resin composition of the present invention is preferably thin to enhance their water-disintegrability and biodegradability, but can be freely adjusted to satisfy requirements such as strength and flexibility. The preferred thickness of films is 5 to 300 μm, more preferably 10 to 100 μm. The preferred thickness of sheet- or container-shaped molded articles is 0.1 to 5 mm, more preferably 0.2 to 2 mm. The tensile modulus is not particularly limited, but is generally preferably 1200 MPa or less, and more preferably 600 MPa or less. The tensile strength is not particularly limited, but is preferably in the range of 10 to 100 MPa, more preferably 15 to 70 MPa, and even more preferably 20 to 50 MPa.

[0040] There are no particular limitations on the method for obtaining a nonwoven fabric of the marine biodegradable resin composition of the present invention, and it can be produced by a known method, such as a dry method, a spunbond method, a meltblowing method, a wet method, etc. That is, the nonwoven fabric can be obtained by spinning the marine biodegradable resin composition of the present invention or a composition containing the marine biodegradable resin composition and an additive, forming a web, and bonding the web by a known method.

[0041] The uses of molded articles containing the marine biodegradable resin composition of the present invention are not particularly limited, and they can be used, for example, as members (components) constituting sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc. That is, it is possible to produce sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc. using materials containing the marine biodegradable resin composition of the present invention.

[0042] Sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc. can be produced by molding a composition containing the marine biodegradable resin composition of the present invention into a desired shape, and then the molded products can be bonded and fixed to each other by known methods such as hot melt bonding or thermal bonding.

[0043] Examples of the hygiene products include disposable diapers, incontinence pads, sanitary napkins, etc. Examples of the agricultural and horticultural materials include mulch films, seedling pots, gardening tapes, fruit cultivation bags, stakes, fumigation sheets, and greenhouse films. Examples of the civil engineering and construction materials include vegetation nets, vegetation pots, three-dimensional netting 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, and floats.

[0044] <Method for Accelerating Biodegradation Rate and Biodegradation Method> Another aspect of the present invention relates to a method for accelerating the biodegradation rate of a biodegradable resin in a marine environment by contacting the biodegradable resin with the marine biodegradation rate accelerator of the present invention (hereinafter sometimes referred to as the "biodegradation rate acceleration method of the present invention"). Another aspect relates to a method for biodegrading the biodegradable resin in a marine environment by contacting the biodegradable resin with the marine biodegradation rate accelerator of the present invention (hereinafter sometimes referred to as the "biodegradation method of the present invention"). As described above, by contacting the biodegradable resin with the marine biodegradation rate accelerator of the present invention, the biodegradation rate of the biodegradable resin in a marine environment can be accelerated and the biodegradable resin can be biodegraded. The step of contacting the biodegradable resin with the marine biodegradation rate accelerator of the present invention in the biodegradation rate acceleration method and biodegradation method of the present invention can be carried out under the conditions and by the procedures described above in the <Marine Biodegradation Rate Accelerator> and <Marine Biodegradable Resin Composition> of the present invention. That is, for example, by adding, mixing, or blending the marine biodegradation rate accelerator of the present invention to a biodegradable resin (or by adding, mixing, or blending a biodegradable resin to the marine biodegradation rate accelerator of the present invention), the biodegradation of the biodegradable resin can be accelerated when the biodegradable resin is placed in a marine environment, allowing the biodegradation of the biodegradable resin to be biodegraded. That is, the biodegradation rate acceleration method of the present invention may be, for example, a method for accelerating the biodegradation of a biodegradable resin in a marine environment, comprising a step of adding, mixing, or blending the marine biodegradation rate accelerator of the present invention to a biodegradable resin. Furthermore, the biodegradation method of the present invention may be, for example, a method for biodegrading a biodegradable resin in a marine environment, comprising a step of adding, mixing, or blending the marine biodegradation rate accelerator of the present invention to a biodegradable resin.

[0045] The marine biodegradation rate accelerator of the present invention may be added to, mixed with, or blended with a biodegradable resin in such a manner that the marine biodegradation rate accelerator is formed into a film on the biodegradable resin, or that the marine biodegradation rate accelerator is laminated onto the surface of the biodegradable resin by coating, etc. Furthermore, the marine biodegradation rate accelerator of the present invention may be added to, mixed with, or blended with a biodegradable resin in such a manner that the marine biodegradation rate accelerator is kneaded and integrated with the biodegradable resin, etc. Furthermore, the marine biodegradation rate accelerator of the present invention may be added to, mixed with, or blended with a biodegradable resin in such a manner that the biodegradable resin and the marine biodegradation rate accelerator are brought into contact with each other during use.

[0046] The amount of marine biodegradation rate accelerator used in the biodegradation rate acceleration method and biodegradation method of the present invention is not limited, but can be, for example, about 1 to 500 parts by weight, 10 to 100 parts by weight, or 30 to 50 parts by weight of 16-hydroxyhexadecanoic acid per 100 parts by weight of biodegradable resin.

[0047] Another aspect of the present invention may be, for example, a method for producing the marine biodegradable resin composition of the present invention, which includes a step of adding, mixing, or blending the marine biodegradation rate accelerator of the present invention to a biodegradable resin.

[0048] The matters explained in the sections <Marine biodegradation rate accelerator>, <Marine biodegradable resin composition>, and <Molded article> above all apply to the explanation of the method for accelerating the biodegradation rate and the biodegradation method of the present invention.

[0049] Here, "accelerating the biodegradation rate of a biodegradable resin in a marine environment" is not limited to, but may mean that the biodegradation rate of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has been added is increased compared to the biodegradation rate of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has been added in a marine environment, and is not limited to, for example, that the biodegradation rate of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has been added is at least 1.25 times, at least 1.5 times, at least 2 times, or at least 5 times the biodegradation rate of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has not been added. Whether or not the biodegradation rate of a biodegradable resin has increased 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 weight loss rate is calculated by dividing the amount of weight loss by the surface area of ​​the sample and the immersion period. Using this as an indicator, if the biodegradation rate of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has been added is faster than that of a biodegradable resin to which the marine biodegradation rate accelerator of the present invention has not been added, it can be determined that the biodegradation rate of the biodegradable resin has increased.

[0050] The present invention will be specifically described below with reference to examples, but these are merely examples of the present invention and the scope of the present invention is not limited to these examples.

[0051] <Experimental method> <Sample preparation> Poly(butylene succinate-co-adipate) (PBSA) (Mw=1.5×10 6 ) and poly(butylene succinate) (PBSu) (Mw=1.8×10 6 ) was purchased from Mitsubishi Chemical Corporation. 16HHD was purchased from Sigma-Aldrich and Fujifilm Wako Pure Chemical Industries, Ltd.

[0052] <Environmental samples> Seawater was collected from the Yokosuka Headquarters of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokosuka City, Kanagawa Prefecture (N35°31'27.63", E139°65'43.83") and marine mud was collected from the Hiroshima University Marine Biological Station, Graduate School of Integrated Life Sciences, Onomichi City, Hiroshima Prefecture (N34°21'54", E133°13'0").

[0053] Biodegradation Rate Test: 10 wt% 16HHD was added to PBSA and PBSu. The mixture was mixed at 150 °C and 50 rpm using a MiniLab 3. For comparison, the same procedure was performed without adding anything to PBSA or PBSu. The mixed strand was placed in a 0.5 mm thick stainless steel mold and sandwiched between polyimide films (Kapton, Toray DuPont Co., Ltd.). The strand was then sandwiched between stainless steel plates and pressed at 150 °C, 5 MPa for 1 min, and 15 MPa for 1 min using a press (Mini Test Press MP-SCH, TOYOSEIKI). After gradual cooling, the strand was removed from the mold to obtain a film.

[0054] (Shallow water test) One sheet of each film (2 cm x 2 cm) was placed in a polystyrene petri dish with multiple holes drilled at the top and bottom. The sides of the dish were wrapped with polyvinyl chloride tape. This dish was then secured to a nylon trical net with cable ties. Ropes were passed through both sides of the trical net, with concrete blocks attached to the ends. This was installed 2-3 m above the seabed on the quay of JAMSTEC Yokosuka Headquarters (Natsushima-cho, Yokosuka City, Kanagawa Prefecture, N35°31'27.63", E139°65'43.83"). The installation periods were November 2019 to January-March 2020 for PBSA and March-May-July 2020 for PBSu.

[0055] (Deep-sea test) Each film (4 cm x 4 cm) was placed in a plastic container protected by polyethylene mesh (mesh 24#, 924 μm opening) and perforated with numerous holes. The container was covered with a net and deployed on the deep seafloor off Misaki (N 35°04.21', E 139°33.20', water depth 757 m) and on the abyssal plain west of KEO (N 32°34.79', E 143°46.15', water depth 5502 m). The Shinkai 6500 was used for deployment and retrieval in the deep sea. The deployment period was June to November 2022.

[0056] (Test in aquarium) Seawater (35 L) was placed in an aquarium (Leglass Flat F-3050, Kotobuki Kogei Co., Ltd.) and circulated using an electric pump (Megapower 2045, Gex Co., Ltd.). One sheet of each film (2 cm x 2 cm) was placed in a bag (3 cm x 3 cm) made of stainless steel mesh (mesh size 90) and hung from the top of the aquarium with nylon fishing line. 0.175 g of ammonium chloride was added to the seawater in the aquarium every two weeks. The test temperature was 20°C. The installation period was from December 2019 to January-March 2020.

[0057] (Test using sterilized artificial seawater) Artificial seawater (200 mL) was prepared according to ASTM D1141-98 and placed in a polypropylene bottle. The artificial seawater was sterilized using a high-pressure steam sterilizer (Hirayama Manufacturing Co., Ltd.). Films (1 cm x 1 cm) wrapped in polyethylene mesh that had been sterilized with methanol and washed with sterile distilled water were submerged in the artificial seawater. The films were collected every two weeks.

[0058] The number of tests was N=5. Each recovered film was washed with methanol and distilled water, dried under reduced pressure, and then weighed. The rate of weight loss of each film was calculated using the following formula from the weight loss amount, surface area, and immersion period of each film.

[0059]

[0060] <Observation of Film Surface Morphology> The film was immersed in a 2.5% glutaraldehyde solution for 1 hour. The film was then immersed in solutions with gradually increasing ethanol concentrations (50, 60, 70, 80, 90, and 99.5%) for 20 minutes each to dehydrate. The film was then immersed in tert-butyl alcohol for 1 hour and then freeze-dried. The film was gold-coated using a DII-29010SCTR Smart Coater (JEOL Ltd.) and observed under a scanning electron microscope (JCM-7000 NeoScope™, JEOL Ltd.).

[0061] <BOD Biodegradability Test and TOC Test> Biodegradability based on BOD of each sample in seawater was measured using a BOD tester OxiTOP (WTW) according to ASTM D6691-17. 100 g of sea mud was added to 600 mL of seawater and ultrasonicated for 10 seconds using an ultrasonic cleaner (AS ONE Corporation). The solution was then filtered using qualitative filter paper (Advantec No. 2) to prepare a sea mud extract. The soil extract (200 mL) was supplemented with ammonium chloride (0.5 g / L), potassium dihydrogen phosphate (0.1 g / L), and an allylthiourea aqueous solution (5 g / L, 200 μL) to prepare a media solution. The media (200 mL), sample, and a stir bar were placed in a 250 mL flan bottle. A carbon dioxide absorbent (Yabashi Lime®-f, Yabashi Industries Co., Ltd.) was placed on top of the flan bottle to absorb carbon dioxide generated by microbial respiration. The BOD tester OxiTOP was attached and the mixture was stirred in a constant temperature bath at 30°C. A sample without the sample was used as a negative control. Cellulose and PHBV were used as positive controls. The chemical composition of the sample was determined by elemental analysis using a carbon, hydrogen, and nitrogen simultaneous determination device (J Science Lab, MICRO CORDER JM 10). The BOD biodegradability was calculated using the following formula.

[0062]

[0063] where BOD b , B.O.D. t , ThOD represent the BOD of the blank (15 minutes after media preparation), the BOD of the test solution, and the theoretical oxygen demand, respectively.

[0064] <DNA / RNA Measurement> After the BOD test, the test solution was filtered through an Advantec membrane filter with a pore size of 0.45 μm to recover microorganisms. DNA / RNA was extracted from the membrane filter using ZymoBIOMICS DNA / RNA Miniprep Kits according to the product protocol. DNA / RNA concentrations were measured using a Nabi ultra-microspectrophotometer.

[0065] <Results> <Biodegradation rate test in shallow waters> Figure 1 shows the weight loss rate of each film placed in coastal waters (shallow waters). The addition of 16HHD increased the weight loss rate of PBSA. The addition of 16HHD also increased the weight loss rate of PBSu.

[0066] <Deep-sea biodegradation rate test> Figure 2 shows the weight loss rate of each film placed in the deep sea (Miura and KEO). The addition of 16HHD increased the weight loss rate of PBSA. The addition of 16HHD also increased the weight loss rate of PBSu.

[0067] <Biodegradation rate test using sterilized artificial seawater> The weight loss rate of each sample in sterilized artificial seawater is shown in Figures 3 and 4. For all samples, the weight loss rate in sterilized artificial seawater was slower than the weight loss rate in shallow water or aquariums. This suggests that the decomposition of PBSA and PBSu with added 16HHD occurs through biological action.

[0068] <Observation of film surface morphology> Figures 5 and 6 show SEM images of the film surface before and after the shallow seawater immersion test. The film surface became rough after seawater immersion. The surface roughness increased particularly for PBSA and PBSu containing 16HHD.

[0069] <BOD biodegradability test and TOC test> Figure 7 shows the BOD biodegradability curves for PBSA-based resin, PBSu-based resin, and each 16HHD-added resin. After 90 days, PBSA and PBSu showed no biodegradability. After 90 days, PBSA + 16HHD showed a biodegradability of over 80%, and PBSu + 16HHD showed a biodegradability of over 90%.

[0070] Table 1 shows the results of TOC tests on samples of 16HHD-added resin 90 days after the BOD test. The TOC values ​​of the samples were compared with those of a blank solution without added sample after the BOD test, and the proportion of carbon derived from the resin in the BOD test solution was calculated. All results were less than 1%. This indicates that the 16HHD-added resin had been completely mineralized.

[0071]

[0072] <DNA / RNA amount measurement> Figure 8 shows the DNA / RNA amounts in the BOD test systems for PBSA-based resin and PBSu-based resin. After the test, an increase in DNA / RNA amounts was observed in PBSA+16HHD and PBSu+16HHD compared to before the test. This suggests that the addition of 16HHD to the resin caused the resin to be metabolized by microorganisms, increasing the amount of microorganisms in the system.

[0073] These results demonstrate that contacting 16HHD with biodegradable resins accelerates the rate of biodegradation of the resins in the ocean.

[0074] According to the method of the present invention, it is possible to accelerate the rate of marine biodegradation of biodegradable resins by contacting them with 16-hydroxyhexadecanoic acid. It is believed that contacting a biodegradable resin with 16-hydroxyhexadecanoic acid causes biodegradable resin-degrading microorganisms to accumulate on the surface of the biodegradable resin, thereby accelerating the rate of marine biodegradation of the biodegradable resin. The present invention can be used in a variety of fields as a biodegradable resin product, but is preferably applied to materials that are expected to be used in or washed away from the environment, such as fishing gear, fishing tackle, agricultural mulch film, and fertilizer covering materials.

Claims

1. An accelerator for promoting the marine biodegradation rate of biodegradable resins, containing 16-hydroxyhexadecanoic acid.

2. The accelerator for promoting the marine biodegradation rate according to claim 1, wherein the biodegradable resin is a polyester resin.

3. The accelerator for promoting the marine biodegradation rate according to claim 1, wherein the biodegradable resin is one or more selected from polybutylene succinate and polybutylene succinate / adipate.

4. A marine biodegradable resin composition with an accelerated marine biodegradation rate, comprising a biodegradable resin and the accelerator for promoting the marine biodegradation rate according to any one of claims 1 to 3.

5. A molded article formed from the marine biodegradable resin composition according to claim 4.

6. A method for promoting the biodegradation rate of a biodegradable resin in a marine environment by bringing the biodegradable resin into contact with the accelerator for promoting the marine biodegradation rate according to any one of claims 1 to 3.

7. A method for biodegrading a biodegradable resin in a marine environment by bringing the biodegradable resin into contact with the accelerator for promoting the marine biodegradation rate according to any one of claims 1 to 3.

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