Biodegradation accelerator for biodegradable resins

Abstract

[Problem] To provide a biodegradation accelerator that is for a biodegradable resin and that accelerates biodegradation of a biodegradable resin. [Solution] This biodegradation accelerator is for a biodegradable resin containing regenerated cellulose. The regenerated cellulose is selected from fibers, molded objects including films, powders, cotton-like objects, and mold intermediate products. As compared with cases where the biodegradation accelerator for the biodegradable resin is not used, the biodegradation accelerator for the biodegradable resin accelerates the biodegradation speed of the biodegradable resin.

Description

Technical Field

[0001] In its exemplary embodiments, the present disclosure relates to a biodegradability promoter for biodegradable resins. In other exemplary embodiments, the present disclosure also relates to a method for promoting the biodegradability of biodegradable resins, a biodegradable resin composition containing the biodegradability promoter for biodegradable resins, a biodegradable resin molded article made of the biodegradable resin composition, and a method for treating a discarded biodegradable resin molded article using the biodegradability promoter for biodegradable resins. Background Art

[0002] Environmental pollution of soil, rivers, oceans, etc. caused by garbage derived from discarded plastic products has become a problem. In order to solve such problems, it is important to separately collect and recycle garbage derived from plastic products or appropriately incinerate them, but at present, it cannot be solved only by that on a global scale.

[0003] Therefore, as one of the solutions to the above problems, the development and use of biodegradable resins that can be biodegraded in the natural environment are desired, and in particular, the development and use of biodegradable resins that can be biodegraded in the ocean are desired.

[0004] Japanese Patent Application Laid-Open No. 2010-241075 describes an invention of a method for manufacturing a biodegradable resin molded article by heat-melting and kneading a biodegradable resin composition containing an aliphatic polyester-based polymer to form a molded article. Specifically, it is described that 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH) is produced as the aliphatic polyester-based polymer (claims, examples).

[0005] HP (October 31, 2019), the applicant of Japanese Patent Application Laid-Open No. 2010-241075, discloses that the PHBH has marine biodegradability and is commercialized as a straw.

[0006] Japanese Patent Publication No. 2016-191021 discloses an invention of a composite molding substrate made of regenerated cellulose fibers and a thermoplastic resin containing polycarbonate and polylactic acid. However, the polycarbonate content is high, and the composite molding substrate itself is not biodegradable.

[0007] Japanese Patent Publication No. 3478299 discloses an invention of a biodegradable composite material comprising a thermoplastic polymer composition containing an aliphatic polyester, and cellulose selected from wood pulp, fibers made from wood pulp, and regenerated cellulose, cellulose esters, or cellulose ethers, excluding nonwoven fabrics and regenerated cellulose films, obtained by: 1) impregnating or coating the cellulose with the aliphatic polyester or a solution thereof; 2) mixing the fibrous or pulp-like aliphatic polyester with the cellulose fibers or pulp and pressing them together by heat; and 3) bonding the cellulose and a film of the aliphatic polyester by heat or adhesive.

[0008] Japanese Patent Publication No. 4357859 discloses a fiber composite resin article having a base layer of a composite material of a first fiber and a first thermoplastic resin, and a surface layer of a second composite material of a second fiber and a second thermoplastic resin on the base layer, wherein the first fiber is selected from the group consisting of glass, kenaf, hemp, bamboo, wood pulp, coconut husk, and rush, the fiber diameter of the second fiber is 15 μm to 50 μm, and the second fiber is selected from the group consisting of rayon, cotton, wool, straw, polyester, silk, nylon, and wool.

[0009] Japanese Patent Publication No. 6551726 discloses an invention for a composite molding fiber sheet comprising regenerated cellulose fibers and thermoplastic resin fibers, wherein the mixing ratio (mass ratio) of the regenerated cellulose fibers to the thermoplastic resin fibers is 20:80 to 60:40, the fineness of the regenerated cellulose fibers is 0.1 dtex or more and less than 1.0 dtex, and the fiber length is 1.0 mm or more. Examples of the thermoplastic resin fibers include polycarbonate fibers, polylactic acid fibers, polypropylene fibers, and polymethylpentene fibers. Summary of the Invention

[0010] In its exemplary embodiments, this disclosure aims to provide a biodegradation accelerator for biodegradable resins that can accelerate the biodegradation of biodegradable resins in a natural environment. In other exemplary embodiments, this disclosure also aims to provide a method for accelerating the biodegradation of a biodegradable resin using the biodegradation accelerator, a biodegradable resin composition containing the biodegradation accelerator for biodegradable resins, a biodegradable resin molded article made from the biodegradable resin composition, and a method for processing a biodegradable resin molded article using the biodegradation accelerator for biodegradable resins.

[0011] This disclosure, in an exemplary embodiment, provides a biodegradation accelerator for biodegradable resins containing regenerated cellulose, The regenerated cellulose is selected from fibers, molded articles including films, powders, cotton-like materials and molding intermediates. The present invention provides a biodegradation accelerator for biodegradable resins that accelerates the biodegradation rate of the biodegradable resin compared to the case in which the biodegradation accelerator for the biodegradable resin is not used.

[0012] In other exemplary embodiments, this disclosure provides a method for accelerating the biodegradation of a biodegradable resin using the biodegradation accelerator. In other exemplary embodiments, this disclosure provides a biodegradable resin composition comprising the biodegradation accelerator for the biodegradable resin. In other exemplary embodiments, this disclosure provides a biodegradable resin molded article comprising the biodegradable resin composition. In other exemplary embodiments, this disclosure provides a method for processing a biodegradable resin molded article using the biodegradation accelerator for the biodegradable resin.

[0013] The biodegradation accelerator for biodegradable resins according to the examples of this disclosure has a biodegradation-promoting effect on biodegradable resins. A similar promoting effect can be obtained in a method for promoting the biodegradation of biodegradable resins produced using this biodegradation accelerator, a biodegradable resin composition containing the biodegradation accelerator for biodegradable resins, and a biodegradable resin molded article made from the biodegradable resin composition. [Brief explanation of the drawing]

[0014] [Figure 1] Front view of the test apparatus for conducting seawater biodegradability tests used in the examples of this disclosure. However, a portion is shown in cross-sectional view to show the internal structure. Modes for carrying out the invention

[0015] <Biodegradation accelerator for biodegradable resins> For example, a biodegradation accelerator for a biodegradable resin may contain regenerated cellulose, and the biodegradation rate of the biodegradable resin is accelerated compared to the case where the biodegradation accelerator for the biodegradable resin is not used.

[0016] The biodegradation accelerator for biodegradable resins may consist solely of regenerated cellulose, or it may consist of a combination of regenerated cellulose and other components.

[0017] Regenerated cellulose may be obtained by dissolving cellulose or its derivatives into a liquid and then molding it into a desired shape. A key difference between regenerated cellulose and natural cellulose is that its size and shape can be controlled according to the purpose, such as the rate of biodegradation.

[0018] Regenerated cellulose may be selected from fibers, molded articles including films, powders, cotton-like materials, and molding intermediates.

[0019] The regenerated cellulose may have a preferred degree of crystallinity of 80% or less, or a preferred degree of crystallinity of 60% or less. In addition, amorphous regenerated cellulose with a degree of crystallinity of 10% or less can also be used.

[0020] Regenerated cellulose fibers can be any known fibers such as viscose rayon, cupro (copper ammonia rayon), fortisan, lyocell (solvent-spun cellulose fiber), BIOMID (solvent-spun cellulose fiber), or Bocel.

[0021] Cellophane and other materials can be used as regenerated cellulose films. Viscopearl (Rengo Co., Ltd.) and NanoAct (Asahi Kasei Corporation) can be used as regenerated cellulose particles, and crushed regenerated cellulose fibers and films can also be used.

[0022] Viscose rayon, cellophane, and Viscoparl have the problem of using carbon disulfide, which is highly toxic and flammable, during their manufacture. Therefore, as a method for producing regenerated cellulose, it is preferable to dissolve cellulose directly in a solvent, and then produce it by spinning, forming a film, powdering, or making it into a cotton-like substance.

[0023] The regenerated cellulose used in this disclosure can also be obtained by dissolving cellulose in one of the following solvents 1 to 4 and then adding the solution to a poor solvent. Solvents 1 to 4 may be used individually or in combination.

[0024] 1. Ionic liquid An ionic liquid refers to a liquid that is liquid at 150°C or lower and contains organic ions.

[0025] In the present disclosure, the anion part of the ionic liquid is not particularly limited, and those generally used for the anion part of ionic liquids can be used.

[0026] Preferred examples of the anion part of the ionic liquid in the present disclosure include halogen anions, carboxylate anions, phosphate anions, cyanide anions, and the like.

[0027] In the present disclosure, the cation part of the ionic liquid is not particularly limited, and those generally used for the cation part of ionic liquids can be used.

[0028] Preferred examples of the cation part of the ionic liquid in the present disclosure include phosphonium cations, nitrogen-containing aromatic cations, and the like.

[0029] Examples of nitrogen-containing aromatic cations include pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, oxazolium cations, 1,2,3-triazolium cations, 1,2,4-triazolium cations, thiazolium cations, piperidinium cations, pyrrolidinium cations, and the like.

[0030] Specific examples of such ionic liquids include 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium phosphinate, 1-butyl-3-methylimidazolium methylphosphonate, 1-ethyl-3-methylimidazolium methylphosphonate, 1-ethyl-3-methylimidazolium chloride, and the like.

[0031] 2. Aqueous solution of alkali metal hydroxide Aqueous solutions of alkali metal hydroxides such as sodium hydroxide or potassium hydroxide can be used. Preferably, it is a 35-60% by mass aqueous solution of sodium hydroxide. Urea and thiourea may be added as solubilizers.

[0032] 3. Aqueous solution of onium compounds An aqueous solution of onium compounds can be used.

[0033] Onium compounds include quaternary phosphonium compounds and quaternary ammonium compounds.

[0034] As the quaternary phosphonium compound, quaternary phosphonium hydroxides are preferred. Typical examples of quaternary phosphonium hydroxides include tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydroxide, and tetraalkylphosphonium hydroxides having an alkyl group with 2 to 8 carbon atoms, such as tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, and tetrahexylphosphonium hydroxide.

[0035] As the quaternary ammonium compound, quaternary ammonium hydroxides are preferred. Typical examples of quaternary ammonium hydroxides include tetraalkylammonium hydroxides having an alkyl group with 2 to 8 carbon atoms, such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetrahexylammonium hydroxide.

[0036] The onium compound may be a salt of an onium cation with an anion such as a halide anion, tetrafluoroborate anion, tetrafluorophosphate anion, or trifluoromethanesulfonate anion, but onium hydroxide is preferred.

[0037] 4. Other solvents Other solvents include amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide and hexamethylene sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aqueous solutions of N-methylmorpholine-N-oxide; cyclic ether solvents such as 1,3-dioxolane and tetrahydrofuran; amine solvents such as pyridine; aqueous solutions of N-methylmorpholine-N-oxide; and water.

[0038] These solvents may contain solubilizers. Examples of solubilizers include, but are not limited to, lithium chloride and lithium bromide.

[0039] The fineness and fiber length of the regenerated cellulose fibers are not particularly limited, and known values ​​within the numerical range described in, for example, Japanese Patent Publication No. 2016-191021 can be used.

[0040] Examples of regenerated cellulose fibers include powder of regenerated cellulose fibers, shredded or beaten regenerated cellulose fibers, woven fabric made of regenerated cellulose fibers or cut or beaten pieces thereof, nonwoven fabric made of regenerated cellulose fibers or cut or beaten pieces thereof, knitted fabric made of regenerated cellulose fibers or cut or beaten pieces thereof, yarn made of regenerated cellulose fibers or cut or beaten pieces thereof, and cord made of regenerated cellulose fibers or cut or beaten pieces thereof.

[0041] (i) As an example of regenerated cellulose fibers, regenerated cellulose fibers cut (for example, to about 3 mm) can be mixed with biodegradable resin in an extruder, extruded into strands, cooled, and cut in a pelletizer.

[0042] (ii) Alternatively, instead of cutting the regenerated cellulose fibers, the continuous fibers can be taken from the creel, the fiber bundles can be coated with resin using an extruder equipped with a coating die, and the resin-coated fiber bundles can be cut with a pelletizer to obtain pellets.

[0043] (iii) Alternatively, these pellets can be fed further into an extruder to produce pellets with more uniformly dispersed fibers.

[0044] (iv) As an example of regenerated cellulose fibers, a bundle of long regenerated cellulose fibers aligned in the length direction can be used, which is then coated or impregnated with a molten biodegradable resin to form an integrated bundle, and then cut into lengths of 3 to 30 mm. This regenerated cellulose fiber bundle can be manufactured, for example, in the same manner as in Manufacturing Example 1 of Japanese Patent No. 6711876 and Manufacturing Example 1 of Japanese Patent No. 6453575.

[0045] The length of the fibers dispersed in the biodegradable resin can be controlled by selecting one of the above mixing methods (i) to (iv). According to some examples, the fiber lengths in the resulting composition are in the order of (iv) > (ii) > (i), and (iii), from longest to shortest.

[0046] Further control can be achieved by adjusting the processing conditions. For example, in (i), the length of the fibers in the resulting composition can be shortened by first shortening the cutting length of the regenerated cellulose fibers.

[0047] As molded articles containing film, films, film-processed products, etc., can be used.

[0048] A molding intermediate is a product that is in the process of forming fibers, films, etc., from cellulose or its derivatives, and is, for example, in the form of a solution.

[0049] According to several examples, biodegradation accelerators for biodegradable resins may contain biodegradable resin in addition to regenerated cellulose.

[0050] Examples of biodegradable resins include one or more selected from cellulose esters, starch polyesters, polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), polylactic acid / polycaprolactone copolymer, polyglycolic acid (PGA), polylactic acid / polyether copolymer, butanediol / long-chain dicarboxylic acid copolymer, polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, polyethylene terephthalate succinate (PETS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyvinyl alcohol (PVA).

[0051] When the biodegradable resin is a cellulose ester, examples of biodegradable resins include those selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, polycaprolactone grafted cellulose acetate, acetylmethylcellulose, acetylethylcellulose, acetylpropylcellulose, acetylhydroxyethylcellulose, and acetylhydroxypropylcellulose.

[0052] In one preferred embodiment of this disclosure, the biodegradable resin may be cellulose acetate.

[0053] Furthermore, from the viewpoint of acting as a biodegradation accelerator for biodegradable resins, the cellulose acetate preferably has a degree of substitution of 2.8 or less, more preferably 2.5 or less, and even more preferably 2.1 or less.

[0054] Even if the biodegradation accelerator for biodegradable resins contains regenerated cellulose fibers and biodegradable resins, it is preferable that it does not contain non-biodegradable resins. However, a small amount of non-biodegradable resin may be included for reasons such as sharing the production line with products that use non-biodegradable resins.

[0055] When a biodegradation accelerator for a biodegradable resin contains a small amount of non-biodegradable resin, the proportion of non-biodegradable resin in the total 100% by mass of biodegradable resin and non-biodegradable resin is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0056] Biodegradation accelerators for biodegradable resins act to accelerate the biodegradation of biodegradable resins. Therefore, they can be mixed with biodegradable resins as molding materials and used as molding materials for various applications. In addition, they can be used when disposing of existing biodegradable resin molded products by mixing them with the aforementioned biodegradable resin molded products.

[0057] Biodegradation accelerators for biodegradable resins can act to promote the biodegradation of biodegradable resins in seawater, freshwater, and soil.

[0058] While biodegradable resins exhibit sufficient biodegradability in freshwater and soil, many have a low biodegradation rate in seawater. A key feature of the biodegradation accelerator for biodegradable resins described in this disclosure is its ability to accelerate marine biodegradation.

[0059] <Method for accelerating the biodegradation of biodegradable resins> One example is a method for accelerating the biodegradation of a biodegradable resin, which involves preparing a biodegradable resin composition or molded article containing the biodegradation accelerator for the biodegradable resin and the biodegradable resin, such that the content ratio of the biodegradation accelerator for the biodegradable resin is 0.1 to 80% by mass as regenerated cellulose.

[0060] In some cases, a biodegradable resin composition or a molded article thereof can be obtained by mixing a biodegradation accelerator, a biodegradable resin, and, if necessary, known additives, using a mixer or the like, or by melt-kneading the mixture using an extruder or the like to form a desired shape.

[0061] In some cases, the biodegradable resin used in a biodegradable resin composition or its molded article may be the same biodegradable resin used in a method for accelerating the biodegradation of a biodegradable resin.

[0062] The content ratio of the biodegradability accelerator for the biodegradable resin in the biodegradable resin composition or its molded article (content ratio as regenerated cellulose) is preferably 0.1 to 80% by mass, more preferably 1 to 60% by mass, even more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass.

[0063] A method for promoting the biodegradation of a biodegradable resin involves adjusting the content ratio of the biodegradation accelerator for the biodegradable resin in the biodegradable resin composition or its molded body to a predetermined range, thereby promoting the biodegradation of the biodegradable resin and its molded body in seawater, freshwater, and soil.

[0064] <Biodegradable resin composition> For example, a biodegradable resin composition may contain the biodegradation accelerator for the biodegradable resin and the biodegradable resin itself.

[0065] Examples of biodegradable resins include one or more selected from cellulose esters, starch polyesters, polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), polylactic acid / polycaprolactone copolymers, polyglycolic acid (PGA), polylactic acid / polyether copolymers, butanediol / long-chain dicarboxylic acid copolymers, polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, polyethylene terephthalate succinate (PETS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyvinyl alcohol (PVA).

[0066] When the biodegradation accelerator for the biodegradable resin described above contains a biodegradable resin, the biodegradable resin contained in the biodegradable resin composition and the biodegradable resin contained in the biodegradation accelerator may be the same or different.

[0067] In some examples, the content of regenerated cellulose in the total 100% by mass of the biodegradable resin (including the biodegradable resin contained in the biodegradation accelerator) and the biodegradation accelerator in the biodegradable resin composition is preferably 0.1 to 80% by mass, more preferably 1 to 60% by mass, even more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass.

[0068] The regenerated cellulose in the biodegradation accelerator acts to promote the biodegradation of the biodegradable resin, and does not act to improve mechanical strength or physical properties as described in Japanese Patent Publication No. 2016-191021, Japanese Patent No. 3478299, Japanese Patent No. 4357859, or Japanese Patent No. 6551726. Therefore, even when the content is reduced within the range of the above-mentioned content ratio, the biodegradation-promoting effect of the biodegradable resin can be exhibited.

[0069] Furthermore, by increasing the content within the aforementioned range, the biodegradability-promoting effect of the biodegradable resin can be further enhanced, and the regenerated cellulose itself exhibits a reinforcing effect as a filler, thereby improving the mechanical strength of the molded article obtained from the biodegradable resin composition. The improvement in the mechanical strength of the molded article obtained from the biodegradable resin composition is particularly enhanced when regenerated cellulose fibers are used as the regenerated cellulose.

[0070] In some cases, it is preferable that the biodegradable resin composition does not contain non-biodegradable resins, but it may contain a small amount of non-biodegradable resin for reasons such as sharing the production line with products that use non-biodegradable resins.

[0071] When a biodegradable resin composition contains a small amount of non-biodegradable resin, the proportion of non-biodegradable resin in the total 100% by mass of biodegradable resin and non-biodegradable resin is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0072] In some cases, biodegradable resin compositions may contain known resin additives depending on the application. Examples of known resin additives include carbon black, inorganic pigments, organic pigments, dyes, colorants, dispersants, stabilizers, plasticizers, modifiers, UV absorbers or light stabilizers, antioxidants, antistatic agents, lubricants, mold release agents, crystallization accelerators, crystal nucleating agents, and elastomers for improving impact resistance.

[0073] When using organic additives as resin additives, it is possible to use organic additives that are themselves biodegradable.

[0074] In some examples, the content of known resin additives in the biodegradable resin composition may be preferably 8% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of promoting biodegradation.

[0075] However, the aforementioned content ratio is not particularly limited when the known resin additive is biodegradable or derived from natural products and does not adversely affect the natural environment.

[0076] <Biodegradable resin molded body> In one example, a biodegradable resin molded article is obtained by molding the above-mentioned biodegradable resin composition into a desired shape.

[0077] In some cases, biodegradable resin molded products can be made into various shapes depending on the application, such as film, sheet, plate, sphere, hollow, pin, rod, tubular, thread, rope, mesh, or irregular shape.

[0078] In some cases, biodegradable resin molded products can be made into foams for purposes such as weight reduction or buoyancy.

[0079] In some cases, biodegradable resin molded products are biodegradable in seawater, freshwater, and soil. For example, even if a biodegradable resin molded product is released into the sea, or into the sea via rivers or lakes connected to rivers, it will not cause marine pollution or adverse effects on marine life.

[0080] However, when biodegradable resin molded products are used in indoor applications or machine parts where they are not exposed to wind and rain, biodegradation is not accelerated. Sufficient mechanical strength can be provided by adjusting the content ratio of regenerated cellulose (preferably regenerated cellulose fibers).

[0081] In some cases, biodegradable resin molded products are suitable for short-term use or disposable applications, rather than for durable articles intended for long-term use.

[0082] However, in some cases, the biodegradability rate of a biodegradable resin molded product can be adjusted depending on the application by exposing regenerated cellulose on the surface to promote biodegradation, or by keeping the regenerated cellulose embedded without being exposed on the surface to suppress biodegradation.

[0083] Methods for exposing regenerated cellulose on the surface include polishing the surface with a file after molding, lowering the mold temperature during injection molding, laminating a regenerated cellulose film onto the surface of the molded body, coating with regenerated cellulose, and using the in-mold method.

[0084] In some cases, biodegradable resin molded products can be used in films, sheets, bottles, tubes, woven fabrics, nonwoven fabrics, various containers (for cosmetics, general merchandise, etc.), lunch boxes, cups, straws, spoons, forks, chopsticks, toothpicks, plates, bags, boxes, smartphone cases, eyeglass frames, stationery, household goods, fishing gear mainly for leisure, fishing gear used in fisheries, and articles including containers for holding caught marine products.

[0085] As a cosmetic container, it is suitable for use with sun oils and sunscreens, which are often used at the beach.

[0086] Examples of recreational fishing equipment include fishing rods, fishing lines, floats, lures, hand nets, and fishing tackle cases. Compared to fishing equipment used by commercial fishermen, these items are used less frequently and do not require high durability. However, because there is a risk that all or part of them may be discarded or released into the sea or rivers, they are effective in preventing marine pollution and adverse effects on marine life.

[0087] Examples of fishing gear and containers used in fisheries (fishing goods) include pipes used in oyster farming, planks that make up floating islands used in aquaculture, hollow floats, foam floats, octopus traps, cylindrical containers for catching eels and conger eels, and baskets for holding caught fish, shellfish, seaweed, and other marine products.

[0088] These fishing equipment are constantly in contact with seawater, or are frequently in contact with it. Even when placed on land or fixed in the sea, they may be washed into the sea by high waves, storm surges, or storms, or partially damaged, resulting in fragments being released into the sea. Therefore, if the resin material used has high marine biodegradability, it will decompose during normal use, which is undesirable in terms of durability.

[0089] Therefore, in some cases, as the biodegradable resin for the biodegradable resin molded body that will be used for fishing purposes, it is preferable to use a biodegradable resin with a low marine biodegradation rate among the biodegradable resins mentioned above in order to obtain durability while maintaining marine biodegradability, and among these, polylactic acid is preferred.

[0090] Biodegradable resin molded products containing regenerated cellulose fibers and polylactic acid resin have enhanced mechanical strength due to the reinforcing effect of the regenerated cellulose fibers, providing the necessary durability for normal use. However, if they are damaged by being carried out to sea, or if damaged products are carried out to sea, the regenerated cellulose fibers inside the biodegradable resin molded product come into contact with the ocean, accelerating the decomposition of the polylactic acid resin.

[0091] Thus, biodegradable resin molded articles are preferable as fishing articles because they are difficult to decompose under normal use, and decomposition is accelerated when damaged.

[0092] <Disposal method for biodegradable resin molded products to be discarded> For example, a method for processing discarded biodegradable resin molded products is a method for processing existing biodegradable resin molded products that are no longer needed and are to be discarded.

[0093] In some cases, the method for disposing of biodegradable resin molded articles involves leaving them in contact with a biodegradation accelerator for biodegradable resins.

[0094] As for the biodegradable resin molded articles to be discarded, in order to increase the contact area between the biodegradable resin and the biodegradation accelerator and promote biodegradation, mechanically crushed or mechanically shredded articles can be used, or articles that have been reduced to fine particles by other methods such as beating or pulverization can be used.

[0095] Examples of biodegradable resin molded articles to be discarded include those made from one or more biodegradable resins selected from cellulose ester, starch polyester, polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), polylactic acid / polycaprolactone copolymer, polyglycolic acid (PGA), polylactic acid / polyether copolymer, butanediol / long-chain dicarboxylic acid copolymer, polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, polyethylene terephthalate succinate (PETS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyvinyl alcohol (PVA).

[0096] In some examples, methods for bringing a biodegradable resin molded product to be discarded into contact with a biodegradation accelerator for biodegradable resins include mixing the biodegradable resin molded product to be discarded with the biodegradation accelerator for biodegradable resins to form a mixture, or wrapping the biodegradable resin molded product to be discarded or the mixture with a sheet made of the biodegradation accelerator for biodegradable resins.

[0097] In some examples, the content of regenerated cellulose in the total 100% by mass of the biodegradable resin molded article and biodegradation accelerator to be discarded may preferably be 0.1 to 80% by mass, more preferably 1 to 60% by mass, even more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass.

[0098] Each embodiment disclosed herein can be combined with any other features disclosed herein. The configurations and combinations thereof in each embodiment are examples, and additions, omissions, substitutions, and other modifications are permitted as appropriate, without departing from the spirit of the disclosure of the present invention. This disclosure is not limited by the embodiments, but is limited only by the claims. Examples

[0099] Examples 1-5, Comparative Examples 1-4 As examples and comparative examples, a total of 30g of samples were prepared, with each component in the proportions shown in Table 1.

[0100] 30g of each sample was melt-kneaded using a Laboplast Mill 4M150 manufactured by Toyo Seiki Seisakusho Co., Ltd., and the melt-kneaded mixture was then pulverized using a freeze-mill (SPEX Freezer / Mill6700: manufactured by SPEX).

[0101] The pulverized material was sieved using two screen meshes, screen mesh 60 (mesh opening 250 μm) and screen mesh 120 (mesh opening 125 μm), to obtain samples (biodegradable resin composition) with particle sizes ranging from 125 to 250 μm.

[0102] The ingredients used were as follows: PCL: Polycaprolactone, Praxel HIP [(Manufactured by Daicel Corporation)] PHBH (3-hydroxybutyrate-co-3-hydroxyhexanoate): Seven Cafe straws made from Kaneka's biodegradable polymer PHBH were used. EC210: Cellulose acetate resin (manufactured by Daicel Mirise Co., Ltd.) PLA (Polylactic Acid): LUMINY L-105 (manufactured by TotalCorbion PLA Co., Ltd.) Regenerated cellulose fiber 1: CR500, 2700 filaments (viscose rayon manufactured by Cordenka GmbH & Co.KG), cut to a length of 5 mm. Regenerated Cellulose Fiber 2: TENCEL (Fiber spun using N-methylmorpholine-N-oxide as a solvent) FCP (Lenzing) (Fiber length 0.6 mm)

[0103] (Marine biodegradability test) Approximately 10 mg of each sample was placed in the test apparatus (capacity 0.5 L, BOD tester 10D, manufactured by Taitec Co., Ltd.) shown in Figure 1, which contained 0.1 L of seawater (collected in July 2020 from the sea in front of the Hirohata Plant of Daicel Mirise Co., Ltd., Himeji City, Hyogo Prefecture). Each sample was completely immersed in the seawater (liquid phase) 2. In this state, the samples were maintained at 25°C ± 1°C for 64 days, and the biodegradability level was tested after 35 days and 64 days.

[0104] The degree of biodegradation was evaluated by absorbing carbon dioxide generated by the biodegradation of the resin sample by microorganisms using an absorbent, and measuring the oxygen consumption (Amg) from the pressure change inside the container. As a blank, the oxygen consumption (A1mg) in a test apparatus containing only seawater without the sample was also measured and evaluated. A higher oxygen consumption indicates a better degree of biodegradation. The degree of biodegradation was calculated using the following formula.

[0105] Biodegradability (%)=(A-A1) / (B×10)×100 B: This is the amount of oxygen (mg) required to completely decompose the resin sample placed in the test apparatus, and is calculated as a theoretical value based on the molecular structure.

[0106] [Table 1]

[0107] As is clear from the results in Table 1, the biodegradation of the biodegradable resin was accelerated by using a biodegradation accelerator (regenerated cellulose fiber). The biodegradation rate of the reference cellulose after 64 days was 75%.

[0108] Examples 6-8, Comparative Example 5 A fiber bundle consisting of rayon long fibers (CR500, 2700 filaments) was passed through a crosshead die. At that time, molten component (A) shown in Example 6 of Table 2 was supplied to the crosshead die from a twin-screw extruder (cylinder temperature 230°C), and the molten material was impregnated into the rayon fiber bundle.

[0109] Subsequently, the material was shaped using a shaping nozzle at the crosshead die outlet, then refined with a shaping roll, and finally cut to a predetermined length (7 mm) using a pelletizer to obtain pellet-shaped (cylindrical) resin-impregnated long fiber bundles (biodegradable resin composition).

[0110] When the resin-impregnated long fiber bundle obtained in this way was cut and examined, it was found that in Example 6, the rayon fibers were almost parallel in the length direction, and the resin had penetrated to the center.

[0111] The test pieces (biodegradable resin molded products) were manufactured by injection molding under the following conditions. Pellet drying conditions: 100°C, 4 hours Cylinder temperature: 210℃ Mold temperature 40℃

[0112] In Example 6, the resin-impregnated long fiber bundle (biodegradable resin composition) produced in Example 6 was injection molded. In Examples 7 and 8, the resin-impregnated long fiber bundle (biodegradable resin composition) produced in Example 6 and PLA pellets were dry blended in the ratios shown in Table 2, dried, and then injection molded to obtain test pieces (biodegradable resin molded bodies).

[0113] The obtained test pieces (biodegradable resin molded articles) were used to perform the evaluation tests shown in Table 2. The marine biodegradability test was conducted using 0.1 L of seawater (collected in July 2021 from the sea in front of Daicel Mirise Co., Ltd.'s Hirohata Plant in Himeji City, Hyogo Prefecture) in the same manner as in Examples 1-5.

[0114] The ingredients used were as follows: PLA: Luminy130 (manufactured by TotalCorbion PLA) Regenerated cellulose fiber 3: CR500, 2700 filaments (viscose rayon manufactured by Cordenka GmbH & Co.KG) PLA-RF40: A composite consisting of 60% by mass of PLA (Luminy130) and 40% by mass of recellulose fiber (manufactured in Example 6)

[0115] [Table 2]

[0116] As is clear from Table 2, the biodegradable resin composition of the present invention and the molded articles obtained therefrom can have their mechanical properties adjusted by adjusting the content of regenerated cellulose fibers.

[0117] A comparison of Table 1 and Table 2 confirms that it is possible to impart strength appropriate for the application while ensuring biodegradability in marine environments. The biodegradation rate of the reference cellulose after 64 days was 63%.

[0118] Note that while Comparative Example 4 in Table 1 and Comparative Example 5 in Table 2 used the same PLA, there were differences in the degree of biodegradation after 35 days and 64 days. This is thought to be because the seawater samples were collected in different years, resulting in differences in the amount and types of microorganisms contained in the seawater. Industrial applicability

[0119] The biodegradation accelerators for biodegradable resins according to the examples of this disclosure can act to accelerate the biodegradation of biodegradable resins, and can therefore be used to incorporate them into various products using biodegradable resins or to accelerate the biodegradation of biodegradable resin products to be discarded. [Explanation of symbols]

[0120] 1. Test apparatus 2 Liquid phase (seawater phase) 3. Gas phase (air phase) 4 CO2 absorbent

Claims

1. A biodegradable resin composition comprising a biodegradation accelerator for biodegradable resins and a biodegradable resin, The biodegradation accelerator for the biodegradable resin contains regenerated cellulose and biodegradable resin. The regenerated cellulose is selected from fibers, molded articles including films, powders, cotton-like materials and molding intermediates. Compared to the case where no biodegradation accelerator is used for the biodegradable resin, the biodegradation rate of the biodegradable resin is accelerated. A biodegradable resin composition for a biodegradable resin molded article, wherein the content of the biodegradation accelerator for the biodegradable resin in the biodegradable resin composition is 0.1 to 15% by mass as regenerated cellulose.

2. The biodegradable resin composition according to claim 1, wherein the biodegradable resin is selected from cellulose ester, starch polyester, polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), polylactic acid / polycaprolactone copolymer, polyglycolic acid (PGA), polylactic acid / polyether copolymer, butanediol / long-chain dicarboxylic acid copolymer, polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, polyethylene terephthalate succinate (PETS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyvinyl alcohol (PVA).

3. The biodegradable resin composition according to claim 2, wherein the biodegradable resin is a cellulose ester selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, polycaprolactone grafted cellulose acetate, acetylmethylcellulose, acetylethylcellulose, acetylpropylcellulose, acetylhydroxyethylcellulose, and acetylhydroxypropylcellulose.

4. A biodegradable resin molded article comprising the biodegradable resin composition according to any one of claims 1 to 3.

5. The biodegradable resin molded article according to claim 4, which is biodegradable in seawater, freshwater, and soil.

6. The biodegradable resin molded article according to claim 4, which includes fishing gear used in fisheries and containers for holding caught marine products.

7. The biodegradable resin molded article according to claim 6, wherein the biodegradable resin is polylactic acid.

8. A method for disposing of a biodegradable resin molded body, comprising leaving the biodegradable resin molded body to be disposed of in contact with a biodegradation accelerator for biodegradable resin, The biodegradation accelerator for the biodegradable resin contains regenerated cellulose and biodegradable resin. The regenerated cellulose is selected from fibers, molded articles including films, powders, cotton-like materials and molding intermediates. Compared to the case where no biodegradation accelerator is used for the biodegradable resin, the biodegradation rate of the biodegradable resin is accelerated. A method for disposing of a biodegradable resin molded article, wherein the content of regenerated cellulose in the total of 100% by mass of the biodegradable resin molded article to be disposed of and the biodegradation accelerator for the biodegradable resin is 0.1 to 15% by mass.

9. The method for processing a biodegradable resin molded body to be discarded according to claim 8, wherein the biodegradable resin molded body to be discarded is mechanically crushed or mechanically shredded.

10. A method for disposing of a biodegradable resin molded article according to claim 8 or 9, wherein the biodegradable resin molded article to be disposed of is made of a biodegradable resin selected from cellulose ester, starch polyester, polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), polylactic acid / polycaprolactone copolymer, polyglycolic acid (PGA), polylactic acid / polyether copolymer, butanediol / long-chain dicarboxylic acid copolymer, polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate-co-terephthalate, polyethylene terephthalate succinate (PETS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyvinyl alcohol (PVA).

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