Marine biodegradable polyester

Abstract

To develop a technique for controlling the marine biodegradability of a polyester such as a polyhydroxyalkanoic acid, and a marine biodegradable polyester using the technique.SOLUTION: The present invention provides a marine biodegradable polyester comprising a structure represented by the general formula (I) in the figure, where m represents an integer equal to or greater than 1, and n represents an integer equal to or greater than 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for controlling the marine biodegradability of polyesters such as polyhydroxyalkanoic acids, and to marine biodegradable polyesters. [Background technology]

[0002] In recent years, from the perspective of the SDGs, biodegradable polymers with low environmental impact, especially marine biodegradable polymers that decompose in the ocean, have been attracting increasing attention. This is because the ocean is the final destination of polymeric materials that are discharged, so it is important for biodegradable polymers to exhibit biodegradability in the ocean. However, the biodegradability of biodegradable polymers is highly dependent on the environment. Even if a polymer shows biodegradability in soil, there are few polymers that show biodegradability in the ocean. This is thought to be due to the fact that there are few microorganisms in the ocean, and the microbial flora is different from that in soil, making it difficult for microorganisms to attach and grow, and for enzymes to decompose the polymers to be produced.

[0003] Polyhydroxyalkanoic acid (PHA), an aliphatic polyester of hydroxycarboxylic acid, is well known as a biodegradable polymer. Polyhydroxyalkanoic acid with long methylene chains exhibits properties comparable to those of polyethylene (PE), and is therefore expected to be a substitute for PE (Non-Patent Document 1). However, only polycaprolactone (PCL) with five methylene chains has been evaluated for marine degradability (Non-Patent Document 2).

[0004] On the other hand, the relationship between biodegradability and molecular weight has been reported in the case of polylactic acid (PLA) through enzymatic hydrolysis, and it is known that the lower the molecular weight, the higher the biodegradability (Non-Patent Document 3). However, there is no description of its decomposition in seawater. Furthermore, no systematic research has been conducted on the biodegradability and molecular weight of PHA. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Ortmann, P.; Mecking, S. Long-Spaced Aliphatic Polyesters. Macromolecules 2013, 46 (18), 7213-7218. [Non-Patent Document 2] Hillmyer, MA; Tolman, WB Aliphatic Polyester Block Polymers: Renewable, Degradable, and Sustainable. Acc. Chem. Res. 2014, 47 (8), 2390-2396. [Non-Patent Document 3] Tsuji, H.; Miyauchi, S. Enzymatic Hydrolysis of Poly(Lactide)s: Effects of Molecular Weight, l -Lactide Content, and Enantiomeric and Diastereoisomeric Polymer Blending. Biomacromolecules 2001, 2 (2), 597-604. Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, there is a high demand for marine biodegradable polymers, but the technology for controlling marine biodegradability has not been fully established. In view of the above circumstances, an objective of the present invention is to provide a technology for controlling the marine biodegradability of polyesters such as polyhydroxyalkanoic acid, and to develop marine biodegradable polyesters using said technology. [Means for solving the problem]

[0007] The present inventors have conducted intensive research to solve the above problems. In other words, in order to develop PHA that can exhibit biodegradability in the ocean, PHAs with different molecular weights were prepared according to the methylene chain length, and their biodegradability was systematically evaluated by a microbial oxygen demand (BOD) biodegradability test. The present invention was completed based on the findings that "the dependence of HA biodegradation in the ocean on the number of methylene chains and molecular weight" was clarified, making it possible to create marine biodegradable polyesters. That is, the gist of the present invention relates to the following.

[0008] [1] A marine biodegradable polyester comprising a structure represented by the following general formula (I):

[0009] [ka]

[0010] (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more. [2] The marine biodegradable polyester according to [1], wherein m is an integer of 2 to 100. [3] The marine biodegradable polyester according to [1], wherein m is an integer of 4 to 45. [4] The marine biodegradable polyester according to [1], wherein m is an integer from 4 to 14. [5] The marine biodegradable polyester according to [1], wherein m is an integer of 4, 6 to 14. [6] The marine biodegradable polyester described in [1], wherein m is 7. [7] The marine biodegradable polyester according to any one of [1] to [6], wherein n is an integer from 2 to 100. [8] The marine biodegradable polyester according to any one of [1] to [7], having a number average molecular weight (Mn) of 10,000 or less. [9] A marine biodegradable resin composition comprising the marine biodegradable polyester according to any one of [1] to [8].

[10] A molded article formed from the marine biodegradable resin composition described in [9].

[11] A method for producing a marine biodegradable polyester comprising the structure represented by the following general formula (I): A method of manufacturing comprising controlling m and n.

[0011] [ka]

[0012] (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

[12] A method for controlling marine biodegradability of a polyester comprising a structure represented by the following general formula (I): A method of controlling comprising controlling m and n.

[0013] [ka]

[0014] (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

[0015] The present invention can also employ the following configuration.

[13] Use of the marine biodegradable polyester according to any one of [1] to [8] in the production of a marine biodegradable resin composition.

[14] A method for producing a marine biodegradable resin composition, comprising blending the marine biodegradable polyester according to any one of [1] to [8]. Effect of the Invention

[0016] According to the method of the present invention, it is possible to control the marine biodegradability of polyesters such as polyhydroxyalkanoic acid. Furthermore, the marine biodegradability control technique of the present invention makes it possible to produce marine biodegradable polyesters. [Brief description of the drawings]

[0017] [Figure 1] Figure 1 shows the BOD biodegradation curves of the prepared polyhydroxyalkanoates and hydroxycarboxylic acids. Figure 2 shows (a) PVL, (b) PCL, (c) PEL, (d) PCyL, (e) PPdL, (f) VL, EL, CL, (g) CyL and PdL. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will now be described. <Marine biodegradable polyester> One aspect of the present invention relates to a marine biodegradable polyester (hereinafter, sometimes referred to as "the marine biodegradable polyester of the present invention") comprising a structure represented by the following general formula (I).

[0019] [ka]

[0020] (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

[0021] Here, the marine biodegradability of the marine biodegradable polyester of the present invention means the property of the biodegradable resin being cut and fragmented into low molecular weight molecules under marine conditions by the action of hydrolases and the like of biodegradable polymer-degrading bacteria. Preferably, the marine biodegradability of the biodegradable resin may be the property of the biodegradable resin being cut and fragmented into low molecular weight molecules and mineralized under marine conditions. Marine biodegradability is evaluated by, for example, immersing a sample in seawater and measuring the weight of the sample after the seawater immersion test from the initial weight. More specifically, marine biodegradability can be confirmed by, for example, the test method specified in the marine biodegradability test (ASTM D6691-17). As an index of marine biodegradability, the marine biodegradable polyester of the present invention means that the biodegradability in a marine biodegradability test (ASTM D6691-17) is, for example, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. The method for calculating the biodegradability can be the same as that used in the examples.

[0022] In the present invention, as a result of extensive research aimed at developing marine biodegradable polymers, we have succeeded in creating marine biodegradable PHA by controlling the number of methylene chains and molecular weight of PHA.

[0023] The biodegradation of PHA proceeds in two steps: (First step) PHA undergoes enzymatic hydrolysis of the ester bond to produce a low molecular weight compound (ultimately a hydroxycarboxylic acid). (Second stage) The low molecular weight compounds are taken up and metabolized by microorganisms, resulting in biodegradation.

[0024] As shown in the examples below, the production rate and biodegradability of the low molecular weight compounds in the first stage are affected by the initial molecular weight of PHA. Therefore, it is predicted that biodegradability will be promoted by using a low molecular weight PHA. In addition, in enzymatic hydrolysis, the enzyme needs to adsorb to the polymer, but in high molecular weight substances, the hydrophobicity increases, preventing adsorption and reducing hydrolysis. In this respect, too, the use of a low molecular weight PHA is important for imparting biodegradability.

[0025] As will be shown in the Examples below, the rate at which the low molecular weight compounds are metabolized by microorganisms in the second step is strongly affected by the number of methylene chains in the PHA.

[0026] Thus, according to the present invention, a marine biodegradable polyester can be created by controlling the number of methylene chains m of PHA, which is a compound containing a structure represented by general formula (I), and the molecular weight (which can be controlled by controlling the number of methylene chains m and the degree of polymerization n of general formula (I)). By adjusting m and n in the marine biodegradable polyester of the present invention, a marine biodegradable polyester having the desired marine biodegradability can be produced depending on the purpose of use.

[0027] In the general formula (I), m represents an integer of 1 or more. If the value of m is too small, the desired physical properties of the polyester may not be obtained, and if the value of m is too large, the desired marine biodegradability of the polyester may not be obtained. m is adjusted so as to exhibit the desired marine biodegradability according to the purpose of use. As long as the effects of the present invention are achieved, there is no limitation, but the value of m may be, for example, an integer of 1 or more, an integer of 2 or more, or an integer of 4 or more, an integer of 100 or less, an integer of 45 or less, or an integer of 14 or less, or a combination thereof that is not contradictory. The value of m may be, for example, an integer of 1 to 100, an integer of 2 to 100, an integer of 4 to 45, an integer of 4 to 14, or an integer of 4, 6 to 14.

[0028] In addition, in the general formula (I), n represents an integer of 2 or more. If the value of n is too small, the desired physical properties of the polyester may not be obtained, and if the value of n is too large, the desired marine biodegradability of the polyester may not be obtained. n is adjusted so as to exhibit the desired marine biodegradability depending on the purpose of use. Although not limited as long as the effects of the present invention are exhibited, the value of n may be, for example, an integer of 2 or more, an integer of 3 or more, or an integer of 4 or more, an integer of 500 or less, an integer of 400 or less, or an integer of 100 or less, or a combination thereof that is not contradictory. The value of n may be, for example, an integer of 2 to 500, an integer of 3 to 400, an integer of 4 to 100, or an integer of 2 to 100. The values ​​of m and n can be set independently.

[0029] A preferred embodiment of the marine biodegradable polyester of the present invention is a marine biodegradable polyester in which the value of m is an integer from 4 to 14 and the value of n is an integer from 2 to 100, from the viewpoint of being particularly excellent in marine biodegradability and usability.

[0030] The molecular weight of the marine biodegradable polyester of the present invention is not limited as long as the effects of the present invention are exhibited, but from the viewpoint of marine biodegradability, for example, the number average molecular weight (Mn) may be 300 to 50,000, 3,000 to 40,000, or 5,000 to 10,000. The weight average molecular weight (Mw) may be 300 to 50,000, 3,000 to 40,000, or 5,000 to 10,000. The molecular weight can be measured by size exclusion chromatography or the like.

[0031] A preferred embodiment of the marine biodegradable polyester of the present invention is a marine biodegradable polyester having a number average molecular weight (Mn) of 10,000 or less, from the viewpoint of particularly excellent marine biodegradability.

[0032] Specific examples of PHA, which is a compound containing a structure represented by general formula (I), include, but are not limited to, PGA: polyglycolic acid (a compound in general formula (I) where m = 1), PPL: poly(3-propiolactone) (a compound in general formula (I) where m = 2), PBL: poly(4-butyrolactone) (a compound in general formula (I) where m = 3), PVL: poly(5-valerolactone) (a compound in general formula (I) where m = 4), PCL: poly(6-caprolactone) (a compound in general formula (I) where m = 5), and the like. m = 5), PEL: poly(7-enantholactone) (compound in general formula (I) where m = 6), PCyL: poly(8-caprylolactone) (compound in general formula (I) where m = 7), PNL: poly(9-nonanolactone) (compound in general formula (I) where m = 8), PDL: poly(10-decanolactone) (compound in general formula (I) where m = 9), PUdL: poly(11-undecanolactone) (compound in general formula (I) where m = 10), PDdL: poly(12-dodecanolactone) (compound in general formula (I) where m = 11), PTrdL: poly(13-tridecanolactone) (compound in general formula (I) where m = 12), PTedL: poly(14-tetradecanolactone) (compound in general formula (I) where m = and PPdL: poly(15-pentadecanolactone) (a compound in which m = 14 in the general formula (I)).

[0033] <Manufacturing method for marine biodegradable polyester> A further aspect of the present invention relates to a method for producing a marine biodegradable polyester containing a structure represented by the above general formula (I), which includes controlling m and n (hereinafter, this method may be referred to as the "production method of the present invention"). Note that all of the matters described in the above section on <Marine biodegradable polyester> apply to the description of the production method of the present invention.

[0034] The production method of the present invention is characterized in that the number of methylene chains m and the degree of polymerization n in the general formula (I) are controlled to control the number of methylene chains and the molecular weight of the polyester. The number of methylene chains and the molecular weight of the polyester, as well as m and n, may be adjusted so as to obtain a marine biodegradable polyester having the desired marine biodegradability depending on the purpose of use. The specific ranges of the values ​​of m and n are the same as those explained in the section "Marine biodegradable polyester" above.

[0035] As a method for controlling the number of methylene chains m and the degree of polymerization n in general formula (I) and adjusting the number of methylene chains and molecular weight of the polyester, m can be adjusted, for example, by selecting and using a lactone or hydroxyalkanoic acid having the desired number of methylene chains m as the raw material for PHA. The degree of polymerization n can be adjusted by adjusting the polymerization conditions of the PHA (e.g., polymerization time, temperature, amount of initiator, amount of catalyst, etc.). The polymerization conditions can be adjusted based on known methods. Alternatively, a commercially available PHA may be hydrolyzed to a desired degree of polymerization n. Alternatively, a PHA having a predetermined degree of polymerization n may be prepared by molecular weight fractionation.

[0036] The production method of the present invention can be carried out in the same manner as a conventional polymer production method, except for adjusting the number of methylene chains and the molecular weight of the polyester. The polymer production method may be a method using a microorganism or a method using chemical synthesis. More specifically, for example, as shown in the examples below, a marine biodegradable polyester containing a structure represented by general formula (I) can be synthesized by ring-opening polymerization of lactone having a desired methylene chain number m, which serves as a monomer raw material, under conditions that can achieve a desired degree of polymerization n, using a catalyst such as an organotin catalyst. The ring-opening polymerization reaction conditions are not limited, but examples include reaction conditions of 80 to 240°C and 0.5 to 72 hours. The lactone or hydroxyalkanoic acid that is the raw material of the marine biodegradable polyester can be a commercially available product or a chemically synthesized product.

[0037] <Method of controlling marine biodegradability of polyester> A further aspect of the present invention relates to a method for controlling the marine biodegradability of a polyester containing a structure represented by the above general formula (I), which comprises controlling m and n (hereinafter, may be referred to as the "control method of the present invention"). Note that all of the matters explained in the above sections "Marine biodegradable polyester" and "Method for producing marine biodegradable polyester" are also applicable to the explanation of the control method of the present invention.

[0038] The control method of the present invention is characterized in that the number of methylene chains m and the degree of polymerization n in the general formula (I) are controlled to control the number of methylene chains and the molecular weight of the polyester. The method of controlling m and n to adjust the molecular weight of the polyester is the same as that described in the above section <Production method of marine biodegradable polyester>. That is, m and n may be adjusted so as to obtain a marine biodegradable polyester having the desired marine biodegradability depending on the purpose of use.

[0039] <Marine biodegradable resin composition> A further aspect of the present invention relates to a marine biodegradable resin composition containing the marine biodegradable polyester of the present invention (hereinafter, may be referred to as the "marine biodegradable resin composition of the present invention"). Note that the matters explained in the above sections "Marine biodegradable polyester", "Method for producing marine biodegradable polyester", and "Method for controlling marine biodegradability of polyester" all apply to the explanation of the marine biodegradable resin composition of the present invention.

[0040] The marine biodegradable resin composition of the present invention is a composition that contains the marine biodegradable polyester of the present invention and has marine biodegradability. The marine biodegradable resin composition of the present invention may contain one or more marine biodegradable polyesters.

[0041] The marine biodegradable resin composition of the present invention may consist only of the marine biodegradable polyester, but may also contain, if necessary, various additives that are usually used in biodegradable resin compositions, such as plasticizers for biodegradable resins, stabilizers (antioxidants, heat stabilizers, light resistance stabilizers, etc.), surfactants, lubricants, colorants, fillers, antistatic agents, silane coupling agents, dispersants, dispersion aids, release agents, etc. The additives may be used alone or in combination of two or more.

[0042] The blend ratio of the marine biodegradable polyester in the marine biodegradable resin composition 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 composition.

[0043] The marine biodegradable polyester in the marine biodegradable resin composition of the present invention is a readily degradable bond. It is also possible to link multiple marine biodegradable polyesters together, and the blend ratio of the marine biodegradable polyester in this form 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 weight of the composition.

[0044] The form of the marine biodegradable resin composition 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 marine biodegradable resin composition can be produced according to a conventional method.

[0045] <Molded products> Another aspect of the present invention relates to a molded article formed from the marine 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 "Marine biodegradable polyester", "Method for producing marine biodegradable polyester", "Method for controlling marine biodegradability of polyester", and "Marine biodegradable resin composition" all apply to the explanation of the molded article of the present invention.

[0046] The marine 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.

[0047] There is no particular limitation on the method for obtaining a film or sheet made of 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. For example, the composition can be molded into a film or sheet by a T-die molding method, an inflation molding method, a calendar molding method, a hot press molding method, or the like. These films or sheets may be stretched in at least one direction. There is no particular limitation on the stretching method, and examples thereof include a roll stretching method, a tenter method, and an inflation method.

[0048] 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 marine 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.

[0049] The thickness of the molded article of the marine 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.

[0050] There is no particular limitation 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, 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 marine 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 marine 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. In other words, it is possible to manufacture sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc. using a material containing the marine biodegradable resin composition of the present invention.

[0052] As for the method of producing sanitary products, agricultural and horticultural materials, civil engineering and construction materials, fishing materials, etc., they can be produced by molding and processing the marine biodegradable resin composition of the present invention into desired shapes, and further by bonding and fixing the molded products to each other by known methods such as hot melt bonding or thermal bonding.

[0053] Examples of the sanitary products include disposable paper diapers, incontinence pads, sanitary napkins, and the like. 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] [material and method] <Reagents> Tin(II) ethylhexanonate (Sn(Oct)2), 15-pentadecanolactone, and 15-hydroxypentadecanoic acid were purchased from Tokyo Chemical Industry Co., Ltd. Valerolactone, caprolactone, enantholactone, and caprylolactone were purified by distillation. 5-Hydroxypentanoic acid sodium salt and Chloroform-d were purchased from Fujifilm Wako Pure Chemical Industries. Chloroform used in chromatography was purchased from Kishida Chemical.

[0056] <Instrumental analysis> ( 1 H NMR measurement) 1 For the 1 H NMR measurements, a superconducting Fourier transform nuclear magnetic resonance spectrometer (ECX400, 400 MHz) manufactured by JEOL Ltd. was used. 1 H NMR measurements were performed by dissolving the sample in 0.05 v / v % TMS-containing deuterated chloroform (0.6 mL) and measuring the chemical shifts using TMS as the internal standard at 0.0 ppm.

[0057] (GPC measurement) The molecular weight of the synthesized polymer was calculated by size exclusion chromatography. The sample solution was prepared by dissolving the sample (5 mg) in chloroform (1 mL) and filtering the solution through a membrane filter. For GPC measurement, an LC-4000 system (JASCO Corporation) was used, and the flow rate was 1.0 mL min -1 The measurements were performed at 40°C. A calibration curve was created using a Tosoh TSK standard polystyrene (number average molecular weight = 2890000, 706000, 355000, 96400, 37900, 10200, 2630, 433) was used. The columns used were TSKgel guardcolumnMP (XL) and TSKgel MultiporeHXL-M connected together, and detection was performed using an RI detector.

[0058] <Method> (Synthesis of low molecular weight PHA) Triphenylphosphine PPh3 (262 mg, 1.0 mmol), lactones (10 mmol) and Tin(II)bis(2-Ethylhexane) (320 mL, 1.0 mmol) were placed in a 50 mL reaction vessel under a nitrogen atmosphere. Distilled water H2O (18 μL, 1.0 mmol) was added to the reaction vessel as a polymerization initiator under a nitrogen atmosphere at room temperature. The reaction vessel was then heated to 140-200°C and stirred for 1 hour to obtain the corresponding reaction mixture. The resulting reaction mixture was subjected to molecular weight fractionation by size exclusion chromatography (chloroform), and the solvent was distilled off and vacuum dried to obtain polyhydroxycarboxylic acids with the desired molecular weight.

[0059] (Synthesis of high molecular weight PHA) Triphenylphosphine PPh3 (2.4 mg, 0.009 mmol), lactone (88 mmol), and Tin(II)bis(2-Ethylhexane) (3.6 mg, 0.009 mmol) were placed in a 50 mL reaction vessel under a nitrogen atmosphere. Distilled water H2O (1.0 mL, 0.056 mmol) was added to the reaction vessel as a polymerization initiator under a nitrogen atmosphere at room temperature. The reaction vessel was then heated to 140-200 °C and stirred for 1 h to obtain the corresponding reaction mixture. The resulting reaction mixture was dissolved in chloroform (40 mL) and reprecipitated using methanol (400 mL). The resulting white solid was dried in vacuum to obtain polyhydroxycarboxylic acid with the desired molecular weight.

[0060] (Synthesized PHA 1 H NMR spectrum data) Poly(5-valerolactone) (PVL): 1 H NMR (400MHz, CDCl3, 292 K, δ) = 4.06 (t, J = 6.8, 2H), 2.32 (t, J = 7.2, 2H), 1.72-1.35 (m, 4H). Poly(6-caprolactone) (PCL): 1H NMR (400MHz, CDCl3, 292 K, δ) = 4.06 (t, J = 6.8, 2H), 2.31 (t, J = 7.6, 2H), 1.69-1.34 (m, 6H). Poly(7-enantholactone) (PEL): 1 H NMR (400MHz, CDCl3, 291 K, δ) = 4.05 (t, J = 6.8, 2H), 2.33 (t, J = 7.4 Hz, 2H), 1.63-1.30 (m, 8H). (New compound) Poly(8-caplyrolactone) (PCyL): 1 H NMR (400MHz, CDCl3, 292 K, δ) = 4.03 (t, J = 6.8 Hz, 2H), 2.27 (t, J = 7.6 Hz, 2H), 1.61-1.32 (m, 10H). Poly(15-pentadecanplactone) (PPdL): 1 H NMR (400MHz, CDCl3, 292 K, δ) = 4.06 (t, J = 7.0 Hz, 2H), 2.29 (t, J = 7.6 Hz, 2H), 1.81-1.27 (m, 24H).

[0061] (BOD biodegradability test) The BOD biodegradability was measured using a BOD measuring device Oxitop IS12 (WTW). Seawater collected in Yokosuka, Kanagawa Prefecture in May 2022 was filtered through filter paper and left to stand overnight. The filtered seawater (2 L) was suction filtered through a membrane filter, the filter was removed and suspended in seawater (20 mL) to prepare 100-fold concentrated seawater. 100-fold concentrated seawater (1.0 mL), 5.0 g of seawater, and 1.0 mL of seawater were placed in a medium bottle. L -1 N-allylthiourea aq. (200 μL) was added to the filtered seawater, and potassium dihydrogen phosphate was added. (0.10 g L -1 ) and ammonium chloride (5.0 g L-1 ) was added to the seawater to make up to 200 mL. As controls, two medium bottles were prepared without the carbon source sample, and one medium bottle was prepared with the carbon source sample added. An appropriate amount of Yabashiri lime was added to the carbon dioxide absorbent container and attached to the top of the medium bottle. The adjusted medium bottle was placed in a BOD TESTER and stirred in a dark room at 30°C, and the amount of oxygen consumed was measured periodically.

[0062] Calculation of BOD biodegradability (%) The degree of biodegradation of a sample can be calculated using the following formula (1).

[0063] BOD biodegradability (%) = measured oxygen consumption (mL) / theoretical oxygen demand (mL) x 100 (Equation 1)

[0064] -Calculation of biodegradation rate The biodegradation rate in the biodegradation curve was calculated from the maximum slope of the biodegradation curve.

[0065] Here, BOD biodegradability (%) is defined as follows: Biodegradability at the end of the degradation test in the biodegradability curve (60 days for PHA, 14 days for hydrolyzate).

[0066] [result] (synthesis) PHAs were synthesized by ring-opening polymerization of lactones with various methylene chain numbers, and PHAs with various molecular weight ranges were prepared by fractionating them by size exclusion chromatography. The names, molecular weights, molecular weight distributions, and degrees of polymerization of the prepared PHAs are summarized in Table 1. The names of PHAs are based on the number average molecular weight (M n ) as a suffix to form PHA (M n / 1000).

[0067] [Table 1]

[0068] (Biodegradability evaluation) The biodegradability of each PHA was evaluated through a BOD biodegradation test in a marine environment. Figure 1 shows the BOD biodegradation curves of PHA obtained from the BOD biodegradation test. In addition, since it is expected that hydroxycarboxylic acids will ultimately be derived during the biodegradation process of PHA, the biodegradability of each lactone hydrolysate was also evaluated. The names of the hydrolysates were taken from the corresponding polymer with the "P" removed. (For example, 5-hydroxypentanoic acid, the hydrolysate of 5-valerolactone, is abbreviated as VL.) The biodegradation rate was calculated from the maximum slope of the BOD biodegradation curve. The biodegradation rates (at the end of the test) and biodegradation rates of hydroxycarboxylic acids and PHAs are summarized in Table 2.

[0069] Biodegradability of PVL The biodegradability of PVL8.9, PVL5.4 and PVL3.2 in the marine environment was 1%, 44% and 86%, respectively. Therefore, in PVL, biodegradability can be imparted by making it a low molecular weight substance. In addition, the biodegradation rate is faster for compounds with lower molecular weights, including hydroxycarboxylic acids. Biodegradability of PCL The biodegradability of PCL4.1, PCL8.4 and PCL44 in the marine environment was 87%, 55% and 81%, respectively. Therefore, PCL shows a biodegradability of 50% or more regardless of molecular weight. There was no molecular weight dependency in the biodegradation rate. Biodegradability of PEL The biodegradability of PEL8.0, PEL10 and PEL31 in the marine environment was 43%, 33% and 55%, respectively. Therefore, PEL shows a biodegradability of 30% or more regardless of molecular weight. In addition, a certain tendency was observed regarding the biodegradation rate. Overall, low molecular weight compounds, including hydroxycarboxylic acids, The rate of biodegradation tends to be faster. Biodegradability of PCyL The biodegradability of PCyL4.4, PCyL9.9 and PCyL22 in the marine environment was 44%, 34% and 22%, respectively. Therefore, the molecular weight dependence of biodegradability was confirmed for PCyL. The lower the molecular weight, the faster the biodegradation rate. Biodegradability of PPdL The biodegradability of PPdL3.5, PPdL9.0 and PPdL12 in the marine environment was 8%, 8% and 0%, respectively. Therefore, PPdL is not easily biodegradable.

[0070] (Biodegradability of Hydroxycarboxylic Acids) In the marine environment, the VL, CL, EL, CyL and PdL were 50%, 80%, 72%, 75% and 79%, respectively. Therefore, all hydroxycarboxylic acids corresponding to the smallest unit of the polymer are biodegradable.

[0071] [Table 2]

[0072] As described above, the results of the BOD biodegradation test for PHA with each methylene chain length and molecular weight showed that the low molecular weight It was observed that the smaller the number of methylene chains, the easier the biodegradation. In other words, biodegradability depended on the number of methylene chains and molecular weight. Based on these findings, it was found that by controlling the number of methylene chains and molecular weight, it was possible to successfully create marine biodegradable PHA. [Industrial Applicability]

[0073] The PHA provided by the present invention can be used as an alternative biodegradable polymer to polyethylene, polypropylene, polystyrene, ethylene vinyl acetate resin, ABS resin, AS resin, etc., and can be introduced into all products in which they are used. Considering its marine biodegradability, it can be preferably applied to fishing gear, etc. Furthermore, the PHA provided by the present invention can also be used as a biodegradable unit of a stimuli-responsive polymer in a copolymer or the like.

Claims

1. A marine biodegradable polyester comprising a structure represented by the following general formula (I): 【Chemistry 1】 (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

2. The marine biodegradable polyester according to claim 1, wherein m is an integer from 2 to 100.

3. The marine biodegradable polyester according to claim 1, wherein m is an integer from 4 to 45.

4. The marine biodegradable polyester according to claim 1, wherein m is an integer from 4 to 14.

5. The marine biodegradable polyester according to claim 1, wherein m is an integer of 4, 6 to 14.

6. The marine biodegradable polyester according to claim 1, wherein m is 7.

7. The marine biodegradable polyester according to claim 1, wherein n is an integer from 2 to 100.

8. The marine biodegradable polyester according to claim 1, having a number average molecular weight (Mn) of 10,000 or less.

9. A marine biodegradable resin composition comprising the marine biodegradable polyester according to claim 1.

10. A molded article formed from the marine biodegradable resin composition according to claim 9.

11. A method for producing a marine biodegradable polyester comprising the structure represented by the following general formula (I): A method of manufacturing comprising controlling m and n. 【Chemistry 2】 (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

12. A method for controlling marine biodegradability of a polyester comprising a structure represented by the following general formula (I): A method of controlling comprising controlling m and n. 【Chemistry 3】 (In the formula, m represents an integer of 1 or more, n is an integer of 2 or more.

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