Biodegradable resin composition

Abstract

To provide a biodegradable resin composition or the like that can be used for the production of a molded article having high biodegradability particularly in the ocean.SOLUTION: A biodegradable resin composition contains a biodegradable resin and one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin, with the content of the biodegradable resin of 50 wt.% or greater.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biodegradable resin composition, and particularly to a biodegradable resin composition that is highly biodegradable in the ocean. [Background technology]

[0002] There are differences in the rate of biodegradation among biodegradable resins, and biodegradation can be extremely slow in environments with few microorganisms, such as the ocean. Known methods for improving the biodegradability of biodegradable resins in the ocean include mixing a compound that dissolves in seawater with the biodegradable resin, and incorporating resin-degrading bacteria into the biodegradable resin in advance. For example, Patent Document 1 discloses a molded article of biodegradable resin in which heavy calcium carbonate is contained in the biodegradable resin, causing the calcium carbonate to dissolve into the ocean and increasing the specific surface area of ​​the remaining resin, thereby improving biodegradability. Furthermore, Patent Document 2 discloses a biodegradable film material in which organic decomposition bacteria are mixed or coated and when the biodegradable film material comes into contact with soil or water, the organic decomposition bacteria are released, and the biodegradation of the resin in the film begins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-066721 [Patent Document 2] Japanese Patent Application Publication No. 2018-083946 Summary of the Invention [Problem to be solved by the invention]

[0004] The method described in Patent Document 1 has problems with compounds that dissolve readily in seawater dissolving when used in seawater, causing a deterioration in the physical properties of the molded product, and biodegradation is slow to progress due to the fact that microorganisms are unlikely to accumulate on the molded product itself in the ocean even if the specific surface area is large. Also, the method described in Patent Document 2 is less effective in promoting biodegradation in a marine environment because decomposing bacteria are released into the ocean and do not remain in the film. Therefore, an object of the present invention is to provide a biodegradable resin composition and the like that can be used to prepare molded articles that are highly biodegradable in the ocean. [Means for solving the problem]

[0005] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by mixing a specific component with a biodegradable resin, and have thus completed the present invention.

[0006] The present invention is as follows. [1] A biodegradable resin; one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin; A biodegradable resin composition having a content of the biodegradable resin of 50% by weight or more. [2] The biodegradable resin composition according to [1], wherein the biodegradable resin is polylactic acid or polybutylene succinate adipate. [3] The biodegradable resin composition according to [1] or [2], wherein the component is agarose or casein. [4] A molded article obtained by curing the biodegradable resin composition according to any one of [1] to [3]. [5] The molded article according to [4], which is for use in products that come into contact with seawater. [6] Use of the molded article according to [5] in products that come into contact with seawater. [7] A method for producing a biodegradable resin composition, comprising the step of mixing one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin with a biodegradable resin, so that the content of the biodegradable resin is 50% by weight or more. [8] Use of one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin for preparing a biodegradable resin composition containing 50% or more by weight of a biodegradable resin. [9] The use according to [8], wherein the biodegradable resin is polylactic acid or polybutylene succinate adipate.

[10] A method for improving the marine biodegradability of a cured product of a resin composition obtained by mixing one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin with a biodegradable resin.

[11] The method according to

[10] , wherein the biodegradable resin is polylactic acid or polybutylene succinate adipate. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a biodegradable resin composition that can be used to prepare molded articles that are highly biodegradable, particularly in the ocean. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described based on specific embodiments. In this specification, the term "highly biodegradable in the ocean" means that the biodegradability is excellent in the ocean or in contact with seawater for a certain period of time or more.

[0009] <Biodegradable resin> The biodegradable resin contained in the biodegradable resin composition of the present disclosure is not particularly limited as long as it is a resin known as a biodegradable resin. For example, one or more selected from the group consisting of polylactic acid, polybutylene succinate adipate, polybutylene succinate, polyethylene terephthalate succinate, polybutylene adipate, polybutylene terephthalate adipate, polyglycolic acid, and polyvinyl alcohol can be mentioned.

[0010] The polylactic acid is not particularly limited and may be a homopolymer of L-lactic acid or D-lactic acid, a copolymer of L-lactic acid and D-lactic acid, or a mixture of these homopolymers and / or copolymers. Polylactic acid with different crystallinity can be selected appropriately depending on the enantiomeric ratio of lactic acid, the method of copolymerization of the enantiomers (random, block, graft, etc.), the use of a method of adding a crystal nucleating agent, etc. Polylactic acid is known as a biodegradable resin, but this is mainly due to microbial decomposition in soil, and it is known to be less biodegradable in environments with low microbial density, such as the ocean. The polybutylene succinate is not particularly limited, and can be synthesized by dehydration polycondensation using succinic acid (HOCOCH2CH2COOH) and 1,4-butanediol (HO(CH2)4OH) as raw materials, or a commercially available product can be used. Polybutylene succinate adipate is an aliphatic polyester obtained by copolymerizing polybutylene succinate with adipic acid. Polybutylene succinate adipate may be synthesized as described above or may be a commercially available product. Polyethylene terephthalate succinate, polybutylene adipate, polybutylene terephthalate adipate, polyglycolic acid, and polyvinyl alcohol may be produced according to known production methods, or commercially available products may be used.

[0011] Among the above biodegradable resins, polylactic acid and polybutylene succinate adipate are particularly effective in the present disclosure, and polylactic acid is the most effective. As described above, polylactic acid is known to have high biodegradability in soil, but low biodegradability in environments where it comes into contact with seawater, such as the ocean. In contrast, the biodegradable resin composition of the present disclosure contains a component that promotes marine degradability, as described below, so that molded articles thereof exhibit good biodegradability even in environments where they come into contact with seawater, such as the ocean.

[0012] The content of the biodegradable resin in the biodegradable resin composition of the present disclosure is 50% by weight or more to ensure adequate strength of molded articles of the biodegradable resin composition. At less than 50% by weight, the molded articles will not have sufficient strength. Even if the biodegradable resin composition of the present disclosure contains a high content of biodegradable resin, which is thought to have poor biodegradability in the ocean (as described below), at 50% by weight or more, sufficient biodegradability of the molded articles in the ocean can be ensured by including a component that promotes marine degradability (described below). Furthermore, if the content of the component that promotes marine degradability (described below) in the biodegradable resin composition is too high, the biodegradation of the component will proceed too quickly, hindering the biodegradation of the biodegradable resin. The content of the biodegradable resin is preferably 70% by weight or more, and more preferably 80% by weight or more. Meanwhile, the upper limit is preferably 97% by weight or less, more preferably 95% by weight or less, and even more preferably 93% by weight or less, taking into account the content of the component that promotes marine degradability (described below). Among biodegradable resins, polylactic acid has a high processing temperature, so its content in the biodegradable resin composition is preferably 70% by weight or more and 97% by weight or less to prevent deterioration of the components that promote marine biodegradability, which will be described later. Furthermore, polybutylene succinate has a lower processing temperature than polylactic acid, so its content in the biodegradable resin composition is preferably 50% by weight or more and 97% by weight or less.

[0013] <Ingredients that promote marine degradability> The biodegradable resin composition of the present disclosure contains, as a component other than the biodegradable resin, one or more selected from the group consisting of agarose, sodium alginate, casein, and keratin. By including the above components, the biodegradable resin composition of the present disclosure exhibits good biodegradability even in environments where it comes into contact with seawater, such as the ocean, for molded articles of biodegradable resin compositions containing biodegradable resins that have previously been focused on biodegradability only in soil. The inventors presume that the reason for this is that when the above-mentioned components are contained in the resin composition and the molded article thereof, microorganisms contained in seawater tend to aggregate on the surface of the molded article, allowing the microorganisms to efficiently assimilate the above-mentioned components and the biodegradable resin.

[0014] Agarose can be obtained by purifying agaropectin containing sulfate esters, or a commercially available product can be used. Agarose is preferred because it has good dispersibility in biodegradable resins and provides excellent product appearance and strength. Sodium alginate can be obtained by treating raw seaweed with acid to soften it, then heating it in the presence of alkali (sodium), and then separating and purifying it, or commercially available products can be used. Casein is the main component of milk proteins found in milk, and commercially available products can be used. Casein is a highly nutritious protein that is favored by microorganisms in seawater and is highly effective in promoting biodegradation, making it preferable. Keratin is the main fibrous structural protein present in hair, skin, and nails, and commercially available products can be used. The above components may be used alone or in combination of two or more. Among the above components, agarose or casein are preferred.

[0015] The content of each of the above components in the biodegradable resin composition of the present disclosure is preferably 3% by weight or more, more preferably 5% by weight or more, and even more preferably 7% by weight or more, from the viewpoint of increasing the aggregability of microorganisms on molded articles of the resin composition in environments that come into contact with seawater, such as the ocean, and thus increasing their biodegradability. Meanwhile, the upper limit is preferably 45% by weight or less, more preferably 30% by weight or less, and even more preferably 10% by weight or less, taking into account the content of the biodegradable resin described above. Because agarose is soluble in high-temperature water, its content in the biodegradable resin composition is preferably 3% by weight or more and 30% by weight or less. Because casein can cause a decrease in molecular weight when added to polyester and its high hygroscopicity can make the resin more susceptible to moisture absorption, its content in the biodegradable resin composition is preferably 3% by weight or more and 30% by weight or less.

[0016] In the biodegradable resin composition of the present disclosure, the weight ratio of the biodegradable resin to one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin, when the biodegradable resin is taken as 100, can be 0.5 to 40, preferably 1 to 30, and more preferably 3 to 10.

[0017] <Other added ingredients> The biodegradable resin composition of the present disclosure may further contain other components, such as pigments, fillers, leveling agents, surfactants, dispersants, UV absorbers, flame retardants, antioxidants, plasticizers, colorants, and crosslinking agents, as long as the components do not impair the functions of the composition.

[0018] <Method for producing biodegradable resin composition> The method for producing the biodegradable resin composition of the present disclosure is not particularly limited, and known methods can be used. For example, a method can be used in which a mixture of the components is melt-kneaded using a single-screw or multi-screw extruder at a predetermined temperature, for example, a temperature between about 150 and 200°C. The components can be kneaded all at once, or an optional component can be kneaded first, and then the remaining components can be added and kneaded.

[0019] <Molded products> The biodegradable resin composition of the present disclosure can be used to produce a molded article. There are no limitations on the method for producing the molded article, and the molded article can be produced by heating the biodegradable resin composition prepared by the above method to a temperature above its softening point, molding it into a desired shape and size, and cooling it. The uses of the molded articles are not particularly limited, and examples include general-purpose products such as films, sheets, trays, and garbage bags. These general-purpose products include those that may be disposed of in the ocean after use, even if they do not come into contact with seawater. Films may have a thickness of 1 μm or more and 100 μm or less, and sheets may have a thickness of 100 μm or more and 2000 μm or less. Garbage bags may have a thickness of 1 μm or more and 20 μm or less. Furthermore, the molded articles may be used in products that come into contact with seawater. Examples of products that come into contact with seawater include products used in the fishing industry, such as fishing gear including fishing lines and fishing nets. When molded articles obtained using the biodegradable resin composition of the present disclosure are used in products that come into contact with seawater, they do not decompose immediately during use. On the other hand, if they are lost in the ocean due to an unexpected event, they will decompose in the ocean due to their excellent marine biodegradability, making it less likely that molded articles will remain in the ocean, a problem that has become a recent issue.

[0020] Regarding the decomposition rate in the ocean of molded articles obtained using the biodegradable resin composition of the present disclosure, when the articles are immersed in seawater maintained at 25°C under light-shielded conditions for three months, the decomposition rate is reduced by 4% by weight or more when polylactic acid is used, and by 10% by weight or more when polybutylene is used, based on the original weight of a 50 μm film. When succinate adipate is used, the reduction can be 30% by weight or more. More specifically, in molded articles made from resin compositions in which polylactic acid is used as the biodegradable resin and agarose is added, the weight loss is reduced by 25% or more by weight, and in cases where casein is used, the weight loss is reduced by 29% or more by weight. Furthermore, in molded articles made from resin compositions in which polybutylene succinate adipate was used as the biodegradable resin and agarose was added, the reduction was 31% by weight or more, and when casein was used, the reduction was 90% by weight or more. For the above reasons, molded articles made from the biodegradable resin composition of the present disclosure are suitable for use in products that may accidentally be released into the ocean (e.g., the general-purpose products described above) and products that are intentionally brought into contact with seawater (e.g., the products used in the fishing industry described above).

[0021] Furthermore, based on the above explanation, it can be seen that according to the present disclosure, a preferred embodiment is to use one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin when preparing a biodegradable resin composition containing a biodegradable resin. When the above-mentioned predetermined components are used in preparing the biodegradable resin composition, a resin composition can be provided that can be used to obtain molded articles with high marine biodegradability. The type of biodegradable resin composition, the amount of the biodegradable resin composition, and the amount of one or more selected from the group consisting of agarose, sodium alginate, casein, and keratin added to the resin composition can be the same as those described in the "Biodegradable Resin Composition" section above. Among these conditions, it is preferable to use polylactic acid or polybutylene succinate adipate as the biodegradable resin.

[0022] The present disclosure also includes a method for improving the marine biodegradability of a cured product of a biodegradable resin composition by mixing one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin with a biodegradable resin. As explained above, by adding one or more components selected from the group consisting of agarose, sodium alginate, casein, and keratin to a resin composition containing a biodegradable resin that has been recognized as not having particularly high marine biodegradability, the marine biodegradability of a molded article made from the resin composition can be clearly improved. The type of biodegradable resin composition, the amount of the biodegradable resin composition, and the amount of one or more selected from the group consisting of agarose, sodium alginate, casein, and keratin added to the resin composition can be the same as those described in the "Biodegradable Resin Composition" section above. Among these conditions, it is preferable to use polylactic acid or polybutylene succinate adipate as the biodegradable resin. Furthermore, the details explained in the above section on <Molded Articles> can be applied to the molding method of the resin composition obtained using the above method and the uses of the molded articles. [Example]

[0023] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0024] Example 1: Kneading of polylactic acid (PLA) and agarose 90 parts by mass of polylactic acid (Ingeopolymer 2003D: Natureworks) and agarose (product core) 10 parts by mass of Sigma-Aldrich A9639 (Sigma-Aldrich) were mixed in a lab mixer at 180°C. The mixture was kneaded under these conditions for 6 minutes to obtain a resin composition.

[0025] <Examples 2 to 4> Resin compositions were obtained in the same manner as in Example 1, except that the agarose in Example 1 was changed to sodium alginate (Chimica Algin: Chimica Co., Ltd.), casein (Kanto Chemical Co., Ltd.), and keratin (reagent: Tokyo Chemical Industry Co., Ltd.), respectively.

[0026] Example 5: Kneading of polybutylene succinate adipate (PBSA) and agarose 90 parts by mass of polybutylene succinate adipate (FD92PM: Mitsubishi Chemical Corporation) and 10 parts by mass of agarose (reagent: Sigma-Aldrich Co.) were kneaded using a lab mixer at 140°C for 6 minutes to obtain a resin composition.

[0027] <Examples 6 to 8> Resin compositions were obtained in the same manner as in Example 5, except that the agarose in Example 5 was changed to sodium alginate (Chimica Algin: Chimica Co., Ltd.), casein (reagent: Kanto Chemical Co., Ltd.), and keratin (reagent: Tokyo Chemical Industry Co., Ltd.), respectively.

[0028] <Comparative Examples 1 and 2> Polylactic acid (Ingeopolymer 2003D: Natureworks), polybutylene succinate adipate 100 parts by weight of ethylene glycol acrylate (FD92PM: Mitsubishi Chemical Corporation) was kneaded using a lab mixer at 180° C. and 140° C. for 6 minutes to obtain resin compositions.

[0029] Comparative Example 3: Kneading of polylactic acid and cellulose 90 parts by mass of polylactic acid (Ingeopolymer 2003D: Natureworks) and cellulose (reagent: Ten parts by mass of a cellulose ester copolymer (Fujifilm Wako Pure Chemical Industries, Ltd.) was kneaded using a lab mixer at 180° C. for 6 minutes to obtain a resin composition.

[0030] <Comparative Examples 4 and 5> Comparative Example 3 Cellulose in chitin (product code 034-13632 Fujifilm Wako Pure Chemical Co., Ltd.), and calcium alginate (product code: A0738, Tokyo Chemical Industry Co., Ltd.), respectively. A resin composition was obtained in the same manner except for the above.

[0031] Comparative Example 6: Kneading of polybutylene succinate adipate and cellulose A resin composition was obtained by kneading 90 parts by mass of polybutylene succinate adipate (FD92PM (product name) Mitsubishi Chemical Corporation) and 10 parts by mass of cellulose (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) using a lab mixer at 140°C for 6 minutes.

[0032] <Comparative Examples 7 and 8> Comparative Example 6 Cellulose in chitin (product code 034-13632 Fujifilm Wako Pure Chemical Co., Ltd.), and calcium alginate (product code: A0738, Tokyo Chemical Industry Co., Ltd.), respectively. A resin composition was obtained in the same manner except for the above.

[0033] <Marine biodegradability test> The melt-kneaded resin composition was pressed onto a plate at a temperature above its softening point to produce a sheet approximately 300 μm thick, from which 20 mm square sheets were then cut. Each sheet was washed with ethanol, vacuum dried, weighed, wrapped in a wire mesh, and immersed in a tank of seawater. After three months had passed, the wire mesh was removed, and the sheet was washed and dried in the same manner as before the test, and then weighed to determine the rate of weight loss. The rate ratio was calculated by setting the weight loss rate of a molded product (sheet) of a resin composition to which no component promoting marine biodegradability had been added to each biodegradable resin as 1.0. The results are shown in Table 1. The numbers in parentheses in Table 1 indicate the amount of weight loss (μg) per square centimeter per day (unit: μg / cm 2 / day). The figures in the table A negative value indicates that the molded article did not decompose and instead the weight increased.

[0034] [Table 1]

[0035] As can be seen from the evaluation results shown in Table 1, it was found that marine biodegradability can be significantly improved by mixing specific components that promote marine biodegradability into biodegradable resins. These results suggest that by including specific components in the resin composition that promote marine biodegradability, microorganisms present in seawater accumulate in large quantities in the biodegradable resin of the molded product, improving biodegradability. [Industrial Applicability]

[0036] According to the present invention, it is possible to provide a biodegradable resin composition that can be used to prepare molded articles that are highly biodegradable, particularly in the ocean.

Claims

[Claim 1] A method for improving the marine biodegradability of a cured resin composition obtained by mixing one or more components selected from the group consisting of casein and keratin with polylactic acid, wherein the component is mixed in an amount of 7% by weight or more relative to the resin composition.

Images