Biodegradable polymer composition, biodegradation accelerator for biodegradable polymers, and method for promoting the biodegradation of biodegradable polymers.

Abstract

To promote biodegradation of biodegradable polymers.SOLUTION: A biodegradable polymer composition contains biodegradable polymers and polyrotaxanes. In the biodegradable polymer composition, the content of the polyrotaxanes is 50 wt.% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a biodegradable polymer composition, a biodegradation accelerator for biodegradable polymers, and a method for promoting the biodegradation of biodegradable polymers. [Background technology]

[0002] Plastic is used in every aspect of daily life, from containers and packaging like PET bottles to household goods. Large amounts of improperly disposed plastic waste flow into the ocean, drifting and polluting the environment. Furthermore, plastic waste not only drifts, but over time it breaks down into microplastics smaller than 1 mm, creating a major problem of ecosystem destruction.

[0003] Reducing the amount of plastic used is a useful solution, but it is not possible to eliminate its use entirely. For this reason, various biodegradable plastics such as polylactic acid (PLA), polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoic acid (PHA), and polycaprolactone (PCL) have been developed (Non-Patent Literature 1).

[0004] On the other hand, Non-Patent Document 2 discloses that adding starch to polybutylene succinate adipate (PBSA) biodegradable fibers improves their biodegradability in seawater. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Adv. SCi. 2021, 8, 2001121, DOI: 10.1002 / advs.202001121 [Non-Patent Document 2] Aichi Industrial Science and Technology Research Center Research Report 2012, pp. 138-141 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a biodegradable polymer with improved degradability, a biodegradation accelerator for biodegradable polymers, and a method for promoting the biodegradation of biodegradable polymers. [Means for solving the problem]

[0007] This disclosure includes the embodiments described below.

[0008] Item 1. A biodegradable polymer composition comprising a biodegradable polymer and a polyrotaxane, wherein the polyrotaxane content in the biodegradable polymer composition is 50% by weight or less.

[0009] Item 2. The biodegradable polymer composition according to Item 1, wherein the biodegradable polymer comprises polyester, polyvinyl alcohol, or a combination thereof.

[0010] Item 3. The biodegradable polymer composition according to Item 1 or 2, wherein the amount of biodegradable polymer in the composition is equal to or greater than the amount of polyrotaxane.

[0011] Item 4. A biodegradable polymer composition according to any one of items 1 to 3, wherein the polyrotaxane content in the biodegradable polymer composition is 0.1% by weight or more and 50% by weight or less.

[0012] Item 5. Biodegradation accelerators for biodegradable polymers, including polyrotaxanes.

[0013] Item 6. A method for promoting the biodegradation of a biodegradable polymer, comprising adding a polyrotaxane to the biodegradable polymer.

[0014] Item 7. The method according to item 6, wherein the addition includes adding polyrotaxane to seawater. [Brief explanation of the drawing]

[0015] [Figure 1] Graph of the BOD biodegradation degree (%) of each sample over time. [Figure 2] Graph with the part up to 10 minutes in Fig. 1 enlarged. [Figure 3] Comparison of the BOD biodegradation degree (%) of each sample 5 days after the start of incubation. [Figure 4] Comparison of the BOD biodegradation degree (%) of each sample 30 days after the start of incubation. [Figure 5] Graph of the BOD biodegradation degree (%) of each sample with different concentrations of polycaprolactone-modified polylrotaxane over time. [Figure 6] Comparison of the BOD biodegradation degree (%) of each sample 30 days after the start of incubation [Figure 7] Comparison of the induction periods of each sample. [Figure 8] Graph of the BOD biodegradation degree (%) of each sample with different functional groups of α-cyclodextrin over time. [Figure 9] Comparison of the BOD biodegradation degree (%) of each sample 10 days after the start of incubation. [Figure 10] Comparison of the induction periods of each sample. [Figure 11] Comparison of the BOD biodegradation degree (%) of each sample with polylactic acid as the biodegradable polymer 10 days after the start of incubation. [Figure 12] Comparison of the BOD biodegradation degree (%) of each sample with poly(lactic acid-co-glycolic acid) as the biodegradable polymer 10 days after the start of incubation.

Mode for Carrying Out the Invention

[0016] The inventors of the present invention have found that the addition of polylrotaxane to a biodegradable polymer promotes the biodegradation of the biodegradable polymer, and thus reached the present invention.

[0017] In this specification, "biodegradation" refers to "decomposition caused by enzymatic processing resulting from cellular activity," following the IUPAC definition (Pure Appl. Chem., Vol. 84, No. 2, pp. 377-410, 2012). Biodegradation includes decomposition by microorganisms.

[0018] In this specification, "microorganisms" may refer to microorganisms whose genes have not been artificially modified, or microorganisms whose genes have been artificially modified, but from an environmental perspective, naturally occurring microorganisms whose genes have not been artificially modified are preferred.

[0019] In this specification, "weight ratio" can be used interchangeably with "mass ratio," "weight %" can be used interchangeably with "mass %," and "parts by weight" can be used interchangeably with "parts by mass."

[0020] In other words, the present disclosure provides a biodegradable polymer composition containing a biodegradable polymer and a polyrotaxane, wherein the polyrotaxane content in the biodegradable polymer composition is 50% by weight or less.

[0021] Examples of biodegradable polymers include, but are not limited to, polyesters (aliphatic polyesters, aromatic polyesters) and polyvinyl alcohol. Biodegradable polymers can be used alone or in combination of two or more types.

[0022] Examples of polyesters include aliphatic polyesters, alicyclic polyesters, aromatic polyesters, and aliphatic-aromatic polyesters. In terms of promoting biodegradation, aliphatic polyesters, aromatic polyesters, and aliphatic-aromatic polyesters are preferred.

[0023] Polyesters can be prepared by condensation polymerization reactions of dicarboxylic acids and diols, hydroxycarboxylic acids, and dicarboxylic acids, diols, and hydroxycarboxylic acids. The dicarboxylic acid is preferably a saturated dicarboxylic acid.

[0024] Aliphatic polyesters include polycaprolactone (PCL), polypivalolactone, polylactic acid (PLA), polyglycolic acid (PGA), polyhydroxyalkanoic acid (PHA), copolymers thereof, or combinations thereof. Copolymers include polyhydroxyalkanoates (PHA) such as poly(3-hydroxybutyrate-co-hydroxyhexanoate) (3HB-co-3HH) and poly(3-hydroxybutyrate-co-3-hydroxyvalate) (3HB-co-3HV), polylactic acid-co-polyglycolic acid (PLA / PGA), polylactic acid-co-polycaprolactone, polyethylene succinate (PES), polybutylene succinate (PBS), and polybutylene succinate adipate (PBSA).

[0025] Examples of alicyclic polyesters include polyC2-6 alkylene C6-12 cycloalkanoates such as polyethylenecyclohexanoate.

[0026] Aromatic polyesters include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polytrimethylene naphthalate, and polytetramethylene naphthalate. 2-6 Polyalkylene C 6-12 Arylate (homopolyester), C 2-6 Polyalkylene C 6-12 Copolymers containing arylate units (e.g., C 2-6 Polyalkylene C 6-12 Examples include copolyesters obtained by copolymerizing arylate with aromatic dicarboxylic acids such as adipic acid, isophthalic acid, and phthalic acid.

[0027] Examples of aliphatic aromatic polyesters include polybutylene adipate-co-terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, and polyethylene terephthalate succinate (PETS).

[0028] The molecular weight of the biodegradable polymer is not particularly limited and may range from 500 to 2,000,000, for example, it may be a low molecular weight of about 500 to less than 10,000, or a high molecular weight of about 10,000 to 2,000,000. If the biodegradable polymer contains an aliphatic polyester, the molecular weight of the aliphatic polyester may range from 500 to 2,000,000, for example, it may be a low molecular weight of about 500 to less than 10,000, or a high molecular weight of about 10,000 to 2,000,000.

[0029] Polyrotaxanes are compounds having a structure in which linear molecules penetrate the opening of a cyclic molecule, and sealing molecules are bonded to both ends of the linear molecule to prevent the cyclic molecule from falling off. Polyrotaxanes may be manufactured based on known literature, or commercially available products from manufacturers such as Advanced Softmaterials Inc. may be used.

[0030] Examples of linear molecules constituting polyrotaxanes include molecules that can penetrate the rings of multiple cyclic molecules. Preferably, the linear molecules are polymers having repeating monomer units. Examples of linear molecules include polyalkylenes, polyesters, polyethers, polyamides, polyacrylics, and linear molecules having benzene rings. More specifically, examples of linear molecules include polyethylene glycol, polyethylene oxide, polypropylene glycol, polylactic acid, polycaprolactone, polyethylene, polypropylene, polyvinyl acetal, polyvinyl methyl ether, polyvinylpyrrolidone, polyacrylamide, polymethyl polyacrylate, polymethyl methacrylate, and polystyrene. The linear molecules may have branched chains, as long as they are configured to penetrate the rings of the above-mentioned cyclic molecules.

[0031] A particularly preferred linear molecule is a water-soluble linear molecule. The water-soluble linear molecule is not particularly limited, as long as it has the property of being able to dissolve at a concentration of 1 g per liter.

[0032] Examples of water-soluble linear molecules include, but are not limited to, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, water-soluble cellulose derivatives such as hydroxypropyl cellulose, polyvinylpyrrolidone, polypeptides, and copolymers containing polyethylene glycol. The water-soluble linear molecule is at least one selected from the group consisting of the polymer species listed above, preferably at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, polyethyleneimine, and copolymers containing one or more of these, and more preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polyethylene glycol.

[0033] The linear molecule may be a polymer in which the entire structure is a repeating structure of the same monomer, or it may be a block copolymer having at least two blocks, or it may be a block copolymer having at least three blocks.

[0034] Preferably, each block of the "block copolymer" consists of only one repeating unit, but a first spacer group may be present between one repeating unit and the next. Furthermore, a second spacer group, which may be the same as or different from the first spacer group, may be present between adjacent blocks of the "block copolymer".

[0035] Examples of first and / or second spacer groups include, but are not limited to, linear or branched alkyl groups having 1 to 20 carbon atoms, such as methylene, ethylene, propylene, butylene, and pentylene groups (which may be partially substituted with aromatic rings such as phenyl groups); linear or branched ethers having 1 to 20 carbon atoms; linear or branched esters having 1 to 20 carbon atoms; and aromatic groups having 6 to 24 carbon atoms, such as phenyl groups.

[0036] Examples of the skeletons forming at least two or at least three blocks include, but are not limited to, copolymers containing polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, water-soluble cellulose derivatives such as hydroxypropyl cellulose, polyvinylpyrrolidone, polypeptides, and polyethylene glycol.

[0037] For example, if the linear molecule is a water-soluble linear molecule composed of one type of polymer, it may be a polymer composed solely of polyethylene glycol, solely of polypropylene glycol, solely of polyvinyl alcohol, solely of polyethyleneimine, or solely of polyethylene glycol. If the linear molecule is a linear molecule composed of three blocks, the central block may be polypropylene glycol, with polyethylene glycol on both sides.

[0038] The molecular weight of the linear molecule is not particularly limited, but is more preferably, by number average molecular weight, for example, 3,000 to 500,000, more preferably 7,000 to 200,000, and even more preferably 10,000 to 100,000. Alternatively, by weight average molecular weight, for example, is more preferably 3,000 to 500,000, more preferably 7,000 to 200,000, and even more preferably 10,000 to 100,000. The number average molecular weight and weight average molecular weight as used herein can be determined from polyethylene glycol equivalent values ​​obtained by gel permeation chromatography (GPC) measurement.

[0039] Preferably, both ends of the linear molecule have reactive groups that can react with a chelating group to prevent the detachment of the cyclic molecule from the linear molecule, thereby facilitating the binding of the chelating group to both ends of the linear molecule. Examples of reactive groups include amino groups, hydroxyl groups, carboxyl groups, thiol groups, disulfide groups, vinyl groups, acryloyl groups, methacryloyl groups, and sulfo groups. Preferably, amino groups and alboxyl groups are used.

[0040] The blocking group bonded to the linear molecule of the polyrotaxane is not particularly limited as long as it functions to prevent the cyclic molecule from detaching from the linear molecule. For example, as the blocking group, a dinitrophenyl group, cyclodextrin, adamantane group, trityl group, fluorescein, silsesquioxane, pyrene, substituted benzene (substituents include, but are not limited to, alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, phenyl, etc. One or more substituents may be present.), optionally substituted polynuclear aromatic (substituents include, but are not limited to, the same as those described above. One or more substituents may be present.), and steroids. Preferably, it is selected from the group consisting of a dinitrophenyl group, cyclodextrin, adamantane group, trityl group, fluorescein, silsesquioxane, and pyrene, and more preferably an adamantane group or cyclodextrin.

[0041] Examples of the cyclic molecule constituting the polyrotaxane include various cyclodextrins (α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, their derivatives or modified forms), crown ethers, benzo crowns, dibenzo crowns, dicyclohexano crowns, and their derivatives.

[0042] Examples of the cyclodextrin derivative include at least one or more hydroxyl groups of cyclodextrin or a hydrogen atom of the hydroxyl group being -O-(CHR 1 ) n -CHR 2 -OH (where R 1 is H, a methyl group, or an ethyl group, and R 2Compounds substituted with a hydrocarbon group having a hydroxyl group (where n is an integer from 1 to 6), a hydrocarbon group having a hydroxyl group, or a hydrocarbon group having an amino group are examples. Specific examples of hydrocarbon groups having a hydroxyl group include hydroxymethyl group, hydroxyethyl group, and hydroxypropyl group. Specific examples of hydrocarbon groups having an amino group include aminomethyl group, aminoethyl group, and aminopropyl group.

[0043] In cyclodextrin derivatives, -O-(CHR) per cyclodextrin molecule 1 ) n -CHR 2 The number of hydrocarbon groups having an -OH group, a hydroxyl group, or an amino group is preferably 2 to 80%, more preferably 3 to 50%, when the state in which all -OH groups are substituted is considered 100%. -O-(CHR 1 ) n -CHR 2 Among the substituents represented by the -OH group, R 1 is H and R 2 Is it a methyl group, or R 1 is a methyl group and R 2 It is preferable that it is H.

[0044] The cyclic molecule preferably has a reactive group. The reactive group of the cyclic molecule may originate from the structure originally present in the cyclic molecule, or it may be introduced separately. Furthermore, the reactive group is preferably one that does not react with the choke group described later. Examples of such reactive groups include hydroxyl groups, carboxyl groups, amino groups, epoxy groups, isocyanate groups, thiol groups, and aldehyde groups. Among these, hydroxyl groups, carboxyl groups, amino groups, and epoxy groups are preferred, with hydroxyl groups and carboxyl groups being more preferred.

[0045] Additional functional groups other than the reactive groups described above can be introduced into the cyclic molecule. Examples of additional functional groups include acetyl groups, propyl groups, hexanoyl groups, methyl groups, ethyl groups, propyl groups, 2-hydroxypropyl groups, cyclohexyl groups, butylcarbamoyl groups, hexylcarbamoyl groups, phenyl groups, polycaprolactone groups, alkoxysilane groups, acryloyl groups, methacryloyl groups or cinnamoyl groups, polymers (such as polycaprolactone groups, polycarbonate groups, polyester groups, polyamide groups, polyurethane groups, etc.), or derivatives thereof. The additional functional groups may be directly bonded to the cyclic molecule or bonded to the cyclic molecule via groups other than the reactive groups. The additional functional groups may also be substituted for the reactive groups described above.

[0046] If a cyclic molecule has additional functional groups, such functional groups can be selected based on the desired properties, such as compatibility with biodegradable polymers.

[0047] In this specification, inclusion ratio refers to the ratio of the amount of cyclic molecules inclusion of linear molecules to the maximum amount of cyclic molecules inclusion of linear molecules. The inclusion ratio can be determined, for example, by nuclear magnetic resonance spectroscopy (NMR) or gel permeation chromatography (GPC).

[0048] The inclusion rate of polyrotaxane is preferably 0.1 to 100%, more preferably 0.1 to 50%, even more preferably 1 to 50%, and most preferably 1 to 30%.

[0049] The polyrotaxane content in a biodegradable polymer composition is preferably 50% by weight or less, and more preferably 40% by weight or less, because if the content is too high, the mechanical strength of the biodegradable polymer composition decreases, impairing the effect of promoting the degradation of the biodegradable polymer and the mechanical strength of the biodegradable polymer composition.

[0050] Furthermore, in terms of promoting the biodegradation of the biodegradable polymer, the polyrotaxane content in the biodegradable polymer composition is preferably 0.1% by weight or more, and more preferably 1% by weight or more.

[0051] In a biodegradable polymer composition, the weight ratio of the biodegradable polymer to the polyrotaxane (biodegradable polymer:polyrotaxane) is preferably 99.9:0.1 to 1:1, more preferably 99:1 to 1:1, more preferably 95:5 to 1:1, more preferably 9:1 to 1:1, and more preferably 4:1 to 3:2. When the amount of biodegradable polymer in the biodegradable polymer composition is equal to or greater than the amount of polyrotaxane, the biodegradation of the biodegradable polymer is advantageously promoted.

[0052] In certain embodiments, the polyrotaxane content in the biodegradable polymer composition is 5% by weight or more and 50% by weight or less, in terms of more significantly promoting the biodegradation of the biodegradable polymer.

[0053] In certain embodiments, the polyrotaxane content in the biodegradable polymer composition is 10% by weight or more and 50% by weight or less, in terms of more significantly promoting the biodegradation of the biodegradable polymer.

[0054] In certain embodiments, the polyrotaxane content in the biodegradable polymer composition is 20% by weight or more and 40% by weight or less, in terms of more significant acceleration of the biodegradation of the biodegradable polymer.

[0055] The total amount of biodegradable polymer and polyrotaxane in the biodegradable polymer composition is not particularly limited, but is preferably 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In a particular embodiment, the total amount of biodegradable polymer and polyrotaxane in the biodegradable polymer composition is 95% by weight or more or 98% by weight or more. In a particular embodiment, the total amount of biodegradable polymer and polyrotaxane in the biodegradable polymer composition is 100% by weight.

[0056] The biodegradable polymer composition may contain, in addition to the biodegradable polymer and polyrotaxane, other additives such as plasticizers, surfactants, lubricants, organic or inorganic fillers, dispersants, antioxidants, light stabilizers, UV absorbers, and colorants. These additives can be used individually or in combination of two or more.

[0057] As described above, a biodegradable polymer composition containing a biodegradable polymer and a polyrotaxane, wherein the polyrotaxane content in the biodegradable polymer composition is 50% by weight or less, exhibits improved biodegradability of the biodegradable polymer compared to a biodegradable polymer alone or a biodegradable polymer composition containing a biodegradable polymer, differing only in that it does not contain a polyrotaxane.

[0058] While we do not wish for the present invention to be constrained by any particular hypothesis or theory, this unexpected effect of further improving the degradability of biodegradable polymers by adding polyrotaxane is presumed to be because, by adding polyrotaxane to biodegradable polymers, the polyrotaxane acts as food for degrading bacteria, promoting the formation of biofilms (high-concentration microbial communities) in the plant source, and the high-concentration polymer-degrading bacteria in this biofilm enzymatically degrade the biodegradable polymer, thus advancing the degradation reaction.

[0059] The biodegradable polymer composition containing the biodegradable polymer and polyrotaxane disclosed herein will be partially or completely decomposed by the action of microorganisms in the environment when left for a certain period of time after being immersed in water (sea, lake) or buried in soil. However, compared to a biodegradable polymer alone or a biodegradable polymer composition containing a biodegradable polymer, which differ only in that it does not contain polyrotaxane, the biodegradability is improved, making it even more environmentally friendly.

[0060] The biodegradable polymer compositions of this disclosure are obtained by mixing a biodegradable polymer with a polyrotaxane. The mixing may be carried out using conventional mixing equipment such as a mixer and an extruder.

[0061] In some embodiments, the biodegradable polymer composition is obtained by melt-mixing a biodegradable polymer with a polyrotaxane.

[0062] In some embodiments, the biodegradable polymer composition comprises mixing a biodegradable polymer and a polyrotaxane in a solvent. Mixing the biodegradable polymer and polyrotaxane in a solvent may involve dissolving the polyrotaxane in the solvent and then mixing the solvent containing the polyrotaxane with the biodegradable polymer, or with a solution of the biodegradable polymer dissolved in another solvent. The solvent for dissolving the polyrotaxane and the solvent for dissolving the biodegradable polymer may be the same or different. Preferably, the two solvents are the same. Examples of such solvents include, but are not limited to, tetrahydrofuran, chloroform, acetone, methyl ethyl ketone, and methylene chloride.

[0063] After mixing the biodegradable polymer and polyrotaxane, the solvent is removed to obtain a solid of the biodegradable polymer composition of this disclosure. Known methods for removing the solvent can be used, such as drying with a heating device such as an oven or drying under reduced pressure.

[0064] The biodegradable polymer composition of this disclosure can be molded into any three-dimensional shape, such as a film, sheet, tube, or case, by known molding techniques such as extrusion molding, press molding, vacuum molding, injection molding, blow molding, inflation molding, and foam molding, to form a molded article.

[0065] Molded articles made from the obtained biodegradable polymer composition, or molded articles containing the biodegradable polymer composition, can be used for various applications such as containers, films, sheets, and household goods. In this specification, "film" refers to a thin film with a thickness of less than 250 μm, and "sheet" refers to a plate-like member with a thickness of 250 μm or more.

[0066] This disclosure further provides biodegradation accelerators for biodegradable polymers, including polyrotaxanes. The polyrotaxanes and biodegradable polymers are as described above with respect to the polyrotaxanes and biodegradable polymers contained in the biodegradable polymer compositions.

[0067] The amount of the biodegradation accelerator containing polyrotaxane added to the biodegradable polymer is not particularly limited, but from the viewpoint of the mechanical strength of the biodegradable polymer composition during use, it is preferable that the amount of the biodegradation accelerator be 0.1 to 50 parts by weight, and more preferably 0.1 to 20 parts by weight, per 100 parts by weight of the biodegradable polymer.

[0068] Alternatively, or in addition to the above, the mass ratio of the biodegradable polymer to the polyrotaxane (biodegradable polymer:polyrotaxane) is preferably 99.9:0.1 to 1:1, more preferably 99:1 to 1:1, more preferably 95:5 to 1:1, more preferably 9:1 to 1:1, and more preferably 4:1 to 3:2.

[0069] This disclosure further provides a method for accelerating the degradation of a biodegradable polymer, comprising adding a polyrotaxane to the biodegradable polymer. The polyrotaxane and biodegradable polymer are as described in relation to the polyrotaxane and biodegradable polymer contained in the biodegradable polymer composition described above. The amount of polyrotaxane added to the biodegradable polymer is as described in relation to the amount of biodegradation accelerator added above.

[0070] In one embodiment, the addition includes adding polyrotaxane to seawater. When polyrotaxane is added to seawater and comes into contact with the biodegradable polymer, the biodegradation of the biodegradable polymer by microorganisms in the seawater is further accelerated.

[0071] In another embodiment, the addition includes adding polyrotaxane to the soil. When polyrotaxane is added to the soil and comes into contact with the biodegradable polymer, the biodegradation of the biodegradable polymer by microorganisms in the soil is further accelerated.

[0072] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Examples]

[0073] Test Example 1 We investigated the effect of polyrotaxanes added to biodegradable polymers on their biodegradability.

[0074] Marine sediment and surface seawater were collected at Miyagawa Beach in Miura City, Kanagawa Prefecture. 100g of sediment and 600ml of seawater were mixed in a glass container, and the mixture was ultrasonically irradiated for 10 seconds to filter out the sediment and obtain extracted seawater. Polymer samples were immersed in the extracted seawater and incubated. The degree of biodegradation (%) of the polymer samples was measured over time using a biochemical oxygen demand (BOD) meter. The seawater temperature was controlled in a low-temperature incubator and was approximately 25°C.

[0075] The polymer samples were as follows. Polycaprolactone-modified polyrotaxane (PR-g-PCL) is a molecule (SH3400P, Advanced Softmaterials Inc., in which polyethylene glycol chains (molecular weight 35,000) are inserted through the openings of α-cyclodextrin in a skewer-like manner, and the hydroxyl groups of α-cyclodextrin are substituted with polycaprolactone (molecular weight approximately 1,000)). Sample 1: A polymer blend of polycaprolactone (PCL) (molecular weight 80,000) and polycaprolactone-modified polyrotaxane (PR-g-PCL) mixed in a weight ratio of 80:20. Sample 2: Single resin of polycaprolactone (PCL) (molecular weight 80,000) Sample 3: Cellulose The BOD biodegradability (%) was calculated according to formula (1).

[0076]

number

[0077] BODs: Sample BODs BPDb: Blank BOD ThOD: Theoretical Oxygen Demand *Theoretical oxygen demand is calculated from the decomposition formula of each component. Example) C6H 10 O2+ 7.5O2→ 6CO2+ 5H2O (PCL decomposition formula)

[0078] (result) As shown in Figure 1, the BOD biodegradation rate of the polymer blend was higher than that of the single PCL resin throughout the entire period. The plateau in BOD biodegradation rate of the polymer blend at approximately 60% indicates the end of the reaction.

[0079] In Figure 2, a closer examination of the period from the start of incubation to 10 days after the start of incubation, enclosed by the square frame in the graph of Figure 1, reveals that the induction period, which is the time it takes for the BOD biodegradation rate to reach 10%, was 5 days for PCL single resin (B in the graph), while it was 2 days for polymer blends (A in the graph).

[0080] The addition of PR-g-PCL tended to shorten the induction period, and it was confirmed that the blend of PCL and PR-g-PCL induced degradation by degrading bacteria more effectively than PCL alone.

[0081] As shown in Figure 3, the BOD biodegradation rates of each sample after 5 days of incubation were 9.8%, 16.4%, and 12.8%, respectively, with the polymer blend showing a 67% increase in BOD biodegradation compared to PCL resin. Unexpectedly, the polymer blend showed a higher BOD biodegradation rate than cellulose, which is known to decompose quickly.

[0082] As shown in Figure 4, the BOD biodegradability of each sample after 30 days from the start of incubation was 32.0%, 50.5%, and 48.3%, respectively, with the polymer blend showing a 57% increase in BOD biodegradability compared to PCL resin. Even after 30 days from the start of incubation, the polymer blend showed higher BOD biodegradability not only compared to single PCL resin but also compared to cellulose.

[0083] Test Example 2 The effect of the amount of polyrotaxane added to biodegradable polymers on their biodegradability was investigated. The biodegradability of each of the following samples was evaluated under the same conditions as in Test Example 1. Sample 4: A polymer blend of polycaprolactone (PCL) (molecular weight 80,000) and polycaprolactone-modified polyrotaxane (PR-g-PCL) mixed in a weight ratio of 80:20. Sample 5: A polymer blend of polycaprolactone (PCL) (molecular weight 80,000) and polycaprolactone-modified polyrotaxane (PR-g-PCL) mixed in a weight ratio of 60:40. Sample 6: A polymer blend of polycaprolactone (PCL) (molecular weight 80,000) and polycaprolactone-modified polyrotaxane (PR-g-PCL) mixed in a weight ratio of 20:80. Sample 7: Single resin of polycaprolactone (PCL) (molecular weight 80,000) Sample 8: Polycaprolactone-modified polyrotaxane (PR-g-PCL) only Sample 9: Cellulose

[0084] (result) As shown in Figure 5, in the period immediately following the start of incubation, the BOD biodegradation rates of samples 4-6 were all higher than those of samples 7 and 8.

[0085] As shown in Figure 6, the BOD biodegradation rates of samples 7, 4, 5, and 6 30 days after the start of incubation were 32.0%, 50.5%, 44.6%, and 29.3%, respectively. Samples 4 (20% by weight of PR-g-PCL) and 5 (40% by weight of PR-g-PCL) showed increased biodegradation rates compared to sample 7 (PCL), with sample 4 (20% by weight of PR-g-PCL) having the highest biodegradation rate. However, the biodegradation rate of sample 6 (80% by weight of PR-g-PCL) decreased to a similar level as sample 7 (PCL).

[0086] As shown in Figure 7, the induction period for samples 7, 4, 5, and 6 was 6 days for sample 7 (PCL) and sample 6 (PR-g-PCL amount of 80% by weight), while it was 2 days for sample 4 (PR-g-PCL amount of 20% by weight) and sample 5 (PR-g-PCL amount of 40% by weight).

[0087] Test Example 3 The effect of cyclic molecule modification in polyrotaxanes on the affinity between biodegradable polymers and polyrotaxanes was investigated. The biodegradability of each of the following samples was evaluated under the same conditions as in Test Example 1.

[0088] Polyvinyl alcohol (PVA) was used as the biodegradable polymer to prepare the following samples. The linear molecules of the polyrotaxane were polyethylene glycol chains (molecular weight 35,000), and the inclusion ratio was 28%. For a method of producing polyrotaxane in which the hydroxyl group of α-cyclodextrin is substituted with -O-CH2CH(CH3)OH, please refer to WO2018 / 021267.

[0089] Sample 10: PVA only (molecular weight 90,000) Sample 11: A polymer blend obtained by mixing PVA (molecular weight 90,000) and polyrotaxane (referred to as APR), in a weight ratio of 80:20, where the cyclic portion of the polyrotaxane is an unmodified α-cyclodextrin. Sample 12: A polymer blend obtained by mixing PVA (molecular weight 90,000) and polyrotaxane (referred to as HAPR), which is an α-cyclodextrin in which the cyclic portion of the polyrotaxane has its hydroxyl group replaced with -O-CH2CH(CH3)OH, in a weight ratio of 80:20. Sample 13: A polymer blend obtained by mixing PVA (molecular weight 90,000) and a polyrotaxane (referred to as PR-g-PCL, the same as the PR-g-PCL used in Test Example 1) in a weight ratio of 80:20. This polyrotaxane is an α-cyclodextrin in which the cyclic portion of the polyrotaxane has its hydroxyl groups replaced with polycaprolactone (PCL, molecular weight approximately 1000).

[0090] (result) As shown in Figure 8, the PVA samples 11-13 with added polyrotaxane all showed faster PVA biodegradation than the PVA-only resin sample 10 throughout the entire period from the start of incubation to 10 days later. PVA degraded slowly in seawater, and measurable biodegradation was observed from the 4th day of incubation.

[0091] As shown in Figure 9, the BOD biodegradation rates of samples 10, 13, 12, and 11 10 days after the start of incubation were 14.5%, 20.6%, 23.9%, and 32.1%, respectively.

[0092] As shown in Figure 10, the induction periods for samples 10, 13, 12, and 11 were 9 days, 5 days, 3 days, and 4 days, respectively.

[0093] The hydrophilicity of the polyrotaxanes was highest for HAPR, followed by APR, and then PR-g-PCL (HAPR > APR >> PR-g-PCL), which also coincided with the order of degradation levels. This suggests that the compatibility between the biodegradable polymer PVA and the polyrotaxane is related to the degree of degradation.

[0094] Test Example 4 The effect of polyrotaxanes added to various biodegradable polymers, different from those used in Test Examples 1-3, on their biodegradability was investigated. The biodegradability of each of the following samples was evaluated under the same conditions as in Test Example 1.

[0095] Sample 14: Polylactic acid (racemic mixture: PDLA) only (molecular weight 100, 422) Sample 15: A polymer blend of polylactic acid (PDLA) and PR-g-PCL (SH3400P, Advanced Softmaterials Inc.) mixed in a weight ratio of 60:40. Sample 16: Polylactic acid-co-polyglycolic acid (racemic mixture: PDLA / PGA = 50 / 50) only (molecular weight 38,000-54,000) Sample 17: A polymer blend of polylactic acid-co-polyglycolic acid (PDLA / PGA) and PR-g-PCL (SH3400P, Advanced Softmaterials Inc.) mixed in a weight ratio of 60:40.

[0096] (result) As shown in Figure 11, the BOD biodegradation rates of sample 14 and sample 15 10 days after the start of incubation were 0% and 10%, respectively.

[0097] Unexpectedly, PDLA, which generally does not exhibit biodegradability in seawater (under low concentrations of degrading bacteria), showed degradability upon the addition of polyrotaxane. These data suggest an increase in the density of degrading bacteria due to biofilm formation.

[0098] As shown in Figure 12, the BOD biodegradability of sample 16 and sample 17 after 10 days of incubation was 4.7% and 8.2%, respectively. This also demonstrated that the biodegradability of polylactic acid-co-polyglycolic acid improved with the addition of polyrotaxane.

Claims

1. A biodegradable polymer composition containing a biodegradable polymer and a polyrotaxane, wherein the polyrotaxane content in the biodegradable polymer composition is 20% by weight or more and 40% by weight or less.

2. The biodegradable polymer composition according to claim 1, wherein the biodegradable polymer comprises polyester, polyvinyl alcohol, or a combination thereof.

3. The biodegradable polymer composition according to claim 1 or 2, wherein the amount of biodegradable polymer in the composition is equal to or greater than the amount of polyrotaxane.

4. A biodegradation accelerator for biodegradable polymers, containing polyrotaxane, A biodegradation accelerator for biodegradable polymers, used in such a weight ratio of biodegradable polymer to polyrotaxane as 99:1 to 1:

1.

5. A method for promoting the biodegradation of a biodegradable polymer, comprising adding a polyrotaxane to the biodegradable polymer, A method for using a biodegradable polymer in a weight ratio of 99:1 to 1:1 relative to polyrotaxane.

6. A method for promoting the biodegradation of a biodegradable polymer, comprising adding a polyrotaxane to the biodegradable polymer, wherein the addition includes adding a polyrotaxane to seawater.

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