Composite resin molded body and method for producing same

Abstract

A composite resin molded body containing a base resin, and a plurality of natural fibers dispersed in the base resin, wherein at least some of the plurality of natural fibers support spores and nutrients, the content of the plurality of natural fibers is 10 mass% to 99 mass% when the composite resin molded body is taken to be 100 mass%, and some of the plurality of natural fibers are exposed on the surface of the composite resin molded body.

Description

Composite resin molded body and its manufacturing method

[0001] The present disclosure relates to a composite resin molded article having excellent mechanical properties and an adjustable biodegradation rate in a humid environment, and a method for producing the same.

[0002] So-called "general-purpose plastics," such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), are not only very inexpensive, but also easy to mold and are a fraction of the weight of metals or ceramics. For this reason, general-purpose plastics are often used as materials for a variety of everyday items, such as bags, various types of packaging, various containers, and sheets, as well as industrial parts, such as automobile parts and electrical parts, and as materials for daily necessities and miscellaneous goods.

[0003] Under these circumstances, the amount of post-use plastic waste is increasing year by year, and because plastics are difficult to decompose, they accumulate in the natural environment, causing pollution problems such as environmental destruction and contamination.In recent years, biodegradable plastics, which decompose into water and carbon dioxide in the natural environment, have been proposed as one way to solve these problems, and it is expected that their use will expand, replacing general-purpose plastics made from petroleum-based materials.

[0004] However, biodegradable plastics have drawbacks compared to general-purpose plastics, such as insufficient mechanical strength, and therefore do not have the sufficient properties required for materials used in various industrial products, including mechanical products such as automobiles and electrical, electronic, and information products, and the range of their application is currently limited.

[0005] However, the rate at which biodegradable plastics decompose after disposal is greatly affected by the environment. In environments with few microorganisms, such as the ocean, it takes a significantly longer time for them to completely decompose, and their biodegradability is not fully utilized. To solve this problem, various methods have been proposed to accelerate the decomposition of biodegradable plastics after disposal.

[0006] To solve these problems, products have been disclosed in which biodegradable plastics are combined with microorganisms that have the enzymatic activity to decompose the same materials (see, for example, Patent Document 1), and methods have been disclosed in which spores, which are cell structures that are highly resistant to external stresses such as high temperature conditions, are combined with biodegradable plastics (see, for example, Patent Document 2).

[0007] JP 2013-209587 A International Publication No. 2013 / 180124

[0008] A composite resin molding according to one embodiment of the present disclosure is a composite resin molding containing a main resin and a plurality of natural fibers dispersed in the main resin, wherein at least a portion of the plurality of natural fibers carries spores and nutrients, and when the composite resin molding is taken as 100% by mass, the content of the plurality of natural fibers is 10% by mass or more and 99% by mass or less, and some of the plurality of natural fibers are exposed on the surface of the composite resin molding.

[0009] A method for manufacturing a composite resin molded body according to one aspect of the present disclosure includes the steps of preparing spores, nutrients, natural fibers, and a base resin; loading the natural fibers with the spores and nutrients; melt-kneading the natural fibers loaded with the spores and nutrients together with the base resin to proceed with defibration from the ends of the natural fibers in the fiber length direction, thereby obtaining a composite resin member with an increased specific surface area of ​​the defibrated portions at the ends; and molding the composite resin member to obtain a composite resin molded body.

[0010] Fig. 1 is a schematic diagram showing the cross-sectional structure of a composite resin molded body according to an embodiment. Fig. 2 is a schematic diagram showing the cross-sectional structure of a natural fiber that is a constituent member of the composite resin molded body according to an embodiment. Fig. 3 is a schematic cross-sectional view of a composite resin molded body containing natural fiber with defibrated portions according to an embodiment. Fig. 4 is a schematic diagram of a manufacturing process for a composite resin molded body according to an embodiment. Fig. 5 is a diagram showing the structure and measurement results of composite resin molded bodies in examples and comparative examples in the embodiment.

[0011] In the method described in Patent Document 1, the microorganisms are directly mixed into the biodegradable plastic, so the material is limited to a biodegradable plastic that can be molded at a temperature at which the microorganisms can survive.

[0012] On the other hand, the method described in Patent Document 2 has a problem in that the molded body needs to be physically destroyed in order for the spores to come into contact with water and germinate.

[0013] One aspect of the present disclosure is intended to solve the above-described conventional problems, and aims to provide a composite resin molded body that maintains high rigidity during use and that, after disposal, is accelerated to biodegrade in humid environments such as the ocean or soil.

[0014] The composite resin molding of the first aspect is a composite resin molding containing a main resin and a plurality of natural fibers dispersed in the main resin, at least a portion of the plurality of natural fibers carrying spores and nutrients, and when the composite resin molding is taken as 100% by mass, the content of the plurality of natural fibers is 10% by mass or more and 99% by mass or less, and a portion of the plurality of natural fibers is exposed on the surface of the molding.

[0015] A composite resin molding according to a second aspect may be the composite resin molding according to the first aspect, wherein at least some of the plurality of natural fibers have a moisture content of 5% or more as measured by a method specified in JIS L0105:2020.

[0016] The composite resin molding according to the third aspect may be the composite resin molding according to the first or second aspect, wherein the main resin is a biodegradable resin containing any one selected from the group consisting of polyhydroxy acid, polyhydroxyalkanoate, polyalkylene dicarboxylate, and modified starch.

[0017] A composite resin molded product according to a fourth aspect is the product of any one of the first to third aspects, wherein the nutrients may include either peptones or extracts.

[0018] A composite resin molding according to a fifth aspect is any one of the first to fourth aspects, wherein at least some of the plurality of natural fibers may carry spores and nutrients on the surface of the fibers.

[0019] A composite resin molding according to a sixth aspect is the composite resin molding according to any one of the first to fifth aspects, wherein at least a part of the plurality of natural fibers may be cellulose.

[0020] A composite resin molding according to a seventh aspect is any one of the first to sixth aspects, wherein at least some of the plurality of natural fibers may have defibrated portions at ends in the fiber length direction.

[0021] The method for manufacturing a composite resin molded body according to the eighth aspect includes the steps of preparing spores, nutrients, natural fibers, and a main resin; loading the natural fibers with the spores and nutrients; melt-kneading the natural fibers loaded with the spores and nutrients together with the main resin, and proceeding with defibration from the ends of the natural fibers in the fiber length direction to obtain a composite resin member with an increased specific surface area of ​​the defibrated portions at the ends; and molding the composite resin member to obtain a composite resin molded body.

[0022] Hereinafter, a composite resin molding and a manufacturing method thereof according to an embodiment will be described with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals and the description thereof will be omitted where appropriate.

[0023] 1 is a schematic diagram showing a cross-sectional structure of a composite resin molded body 10 according to an embodiment. FIG. 2 is a schematic diagram showing a cross-sectional structure of a natural fiber that is a constituent member of the composite resin molded body 10 according to the embodiment.

[0024] The composite resin molded body 10 according to the embodiment is made of a melt-kneaded mixture of a base resin 1 and natural fibers 2 carrying spores 3 and nutrients 4. As shown in the schematic diagram showing the cross-sectional structure of Figure 1, the composite resin molded body 10 has the natural fibers 2 carrying spores 3 and nutrients 4 dispersed in the base resin 1.

[0025] At least one of the natural fibers 2 is exposed on the surface of the composite resin molding 10 .

[0026] 3, which is a schematic diagram showing the cross-sectional structure of a composite resin molding 10 containing natural fibers 2 with defibrated portions according to an embodiment, having defibrated portions at the ends of the natural fibers 2 increases the specific surface area of ​​the defibrated portions and increases the number of contact points between the natural fibers 2. This makes it possible for water to be absorbed into the composite resin molding 10 through the contact points between the natural fibers 2 in a humid environment.

[0027] In this composite resin molding 10, at least one natural fiber 2 is exposed on the surface of the composite resin molding, and the natural fibers 2 are in contact with each other, so that the molding has high elasticity and high water absorption. In a humid environment, the natural fibers 2 absorb water, causing the spores 3 to germinate, accelerating the decomposition of the base resin 1. This allows for the realization of a composite resin molding 10 that maintains high rigidity during use and exhibits excellent biodegradability in humid environments such as the ocean or soil after disposal.

[0028] Each of the components constituting this composite resin molded body will be described below.

[0029] <Main Resin> In this embodiment, the main resin 1 is preferably a biodegradable plastic containing any one selected from the group consisting of polyhydroxy acid, polyhydroxyalkanoate, polyalkylene dicarboxylate, and modified starch. Furthermore, to ensure good moldability, a thermoplastic resin is preferred, and the above resins may be used alone or in combination of two or more. Note that the main resin 1 is not limited to the above materials as long as it is biodegradable.

[0030] In the present embodiment, "biodegradable plastic" refers to "resins that have the same functions as conventional petroleum-derived resins during use, and that are ultimately decomposed into water and carbon dioxide by microorganisms in the soil or oceans in nature after use." Specific examples include polyester resins such as polyhydroxyalkanoates, such as polyhydroxybutyrate and polyhydroxyvalerate; polyhydroxy acids, such as polylactic acid, polyglycolic acid, and polycaprolactone; polyalkylene dicarboxylates, such as polybutylene adipate terephthalate, polyethylene succinate, and polybutylene succinate; polyamides; and modified starch. Biodegradable plastics include the above resins, including homopolymers of the monomers, as well as copolymers of the monomers, such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and copolymers of the monomers with other copolymerizable monomers.

[0031] <Natural Fiber> Next, the natural fiber 2 will be described. The first main purpose of adding the natural fiber 2 (hereinafter, sometimes simply referred to as "fiber") contained in the composite resin molded body 10 in this embodiment is to allow the composite resin molded body 10 to absorb water in soil or the ocean without placing a burden on the environment when it is discarded after use, thereby bringing the spores 3 into contact with water and causing them to germinate. For this purpose, the natural fiber 2 preferably has high water absorption properties, and the moisture content of the natural fiber 2 is preferably 5% or more as determined by the method specified in JIS L0105:2020. Specifically, pulp, cellulose, cellulose nanofiber, lignocellulose, lignocellulose nanofiber, cotton, silk, hemp, or the like is preferred.

[0032] The second purpose of adding natural fibers 2 is to improve mechanical properties and dimensional stability by reducing the linear expansion coefficient. For this purpose, it is preferable that the natural fibers 2 have a higher elastic modulus than the base resin 1. Specific examples include pulp, cellulose, cellulose nanofibers, lignocellulose, lignocellulose nanofibers, cotton, silk, wool, and hemp. Among these, celluloses are particularly preferable from the viewpoints of availability, high elastic modulus, and low linear expansion coefficient. However, the natural fibers 2 are not limited to the above materials as long as they can improve mechanical properties and have water absorbency.

[0033] After the spores 3 and nutrients 4 are supported on the natural fibers 2, the content of the natural fibers 2 supporting the spores 3 and nutrients 4 in the composite resin molded body 10 is preferably 10% by mass or more and 99% by mass or less, when the composite resin molded body 10 is taken as 100% by mass. If the content of the natural fibers 2 supporting the spores 3 and nutrients 4 is less than 10% by mass, the natural fibers 2 are less likely to come into contact with each other inside the composite resin molded body 10, and the composite resin molded body 10 does not have sufficient water absorbency. On the other hand, if the content of the natural fibers 2 supporting the spores 3 and nutrients 4 is more than 99% by mass, the proportion of the main resin 1 becomes smaller, which eliminates the effect of adhering the natural fibers 2 together and reduces moldability.

[0034] The form of the natural fibers 2 in the composite resin molding 10 will now be described. To improve the water absorption of the composite resin molding 10, it is preferable that a portion of the natural fibers 2 be exposed on the surface of the composite resin molding 10. By exposing a portion of the natural fibers 2 on the surface of the composite resin molding 10, the natural fibers 2 absorb water from the exposed portion, and the water is absorbed into the composite resin molding 10 due to capillary action of the fibers that make up the natural fibers. The smaller the specific surface area of ​​the exposed portion of the natural fibers 2 on the surface of the composite resin molding, the higher the water absorption. This is because when the specific surface area of ​​the exposed portion of the natural fibers 2 on the surface is large, the water repellency is enhanced due to the effect of fine unevenness. Furthermore, as shown in Figure 3, by having defibrated portions at the ends of the natural fibers 2, the specific surface area of ​​the defibrated portions increases, increasing the number of contact points between the natural fibers 2, making it possible to increase the water absorption rate through the contact points between the natural fibers 2 in humid environments.

[0035] The central portion of the undefibrated natural fibers 2, which has a small specific surface area, is less entangled with the main resin 1 and is more likely to be exposed on the surface of the composite resin molded body depending on the molding conditions. Conversely, the tip portions of the defibrated natural fibers 2 are more entangled with the main resin 1 and penetrate into the interior together with the main resin 1. This allows for the production of a composite resin molded body 10 in which the central portions of the natural fibers 2, excluding both end portions, are exposed on the surface.

[0036] The combined length of the tip defibrated portions at both ends of the natural fibers 2 is preferably 5% or more and 50% or less of the fiber length L of the entire natural fibers 2. If the defibrated portions are less than 5% of the entire fiber length L, the specific surface area is small and no improvement in the elastic modulus is observed, and if they are longer than 50%, the defibrated portions with a large aspect ratio are exposed on the surface of the composite resin molding, resulting in a deterioration in water absorbency.

[0037] Next, the characteristics of the natural fibers 2 will be described. The types of the base resin 1 and the natural fibers 2 are as described above. However, if the natural fibers 2 are too soft relative to the base resin 1, i.e., if the natural fibers 2 have a low modulus of elasticity, the composite resin molding 10 will have a low overall modulus of elasticity, resulting in reduced strength. On the other hand, if the natural fibers 2 are too hard relative to the base resin 1, i.e., if the natural fibers 2 have a high modulus of elasticity, shock waves generated upon impact will not propagate but will be absorbed at the interface between the base resin 1 and the natural fibers 2, making cracks and crazes more likely to occur near the interface, resulting in reduced impact strength. Therefore, the relationship between the modulus of elasticity of the base resin 1 and the natural fibers 2 is such that the modulus of elasticity of the natural fibers 2 is higher than that of the base resin 1, and the difference between them should preferably be as small as possible. The optimal relationship was calculated from simulation results, and the difference in modulus of elasticity between the base resin 1 and the natural fibers 2 is preferably within 20 GPa.

[0038] Furthermore, these natural fibers 2 may be surface-treated for the purpose of improving adhesion to the main resin 1 or dispersibility in the composite resin molding 10, but if the surface treatment impairs the water absorption properties of the natural fibers 2, it is preferable not to perform the surface treatment in advance.

[0039] <Additives> Additives may be used as needed. For example, a compatibilizer may be added to improve the affinity between the base resin 1 and the natural fibers 2, or the natural fibers 2 may be coated with a water-soluble or hydrolyzable resin to protect the spores 3 and nutrients 4 contained therein. This protects the spores and nutrients from heat damage caused by the molten base resin during melt-kneading in the production stage of the composite resin molded body. Any additive that is commonly used may be used.

[0040] <Spores> Next, the spores 3 will be described. Spores are durable cells with a highly durable cell structure that bacteria form when the growth environment deteriorates. They are also sometimes called spores. In this embodiment, the spores 3 are used for the purpose of accelerating the decomposition of the composite resin molded body 10 in a humid environment. Specific examples of the spores 3 in this embodiment include spores of bacteria from the genus Bacillus, Paenibacillus, Brevibacillus, Clostridium, and Sporsarcinia. Examples of spores for decomposing biodegradable plastics such as aliphatic polyesters and aliphatic aromatic polyesters include spores of bacteria from the genus Bacillus, Paenibacillus, and Brevibacillus. The above spores may be used alone or in combination of two or more types. Note that the spores are not limited to the above materials as long as they are degradable in the base resin 1 and form spores.

[0041] <Nutrients> Next, nutrient 4 will be described. Nutrient 4 in this embodiment is used for the purpose of promoting germination of spores 3 in a humid environment. In this embodiment, nutrient 4 is preferably a peptone or extract that serves as a phosphorus source, sulfur source, mineral source, or vitamin source to promote nutrient absorption by microorganisms. Examples of peptones include casein peptone, meat peptone, fungal peptone, soybean peptone, etc. Examples of extracts include meat extract, yeast extract, malt extract, potato extract, etc. The above nutrients may be used alone or in combination of two or more. Note that the materials are not limited to those listed above as long as they contain components that promote spore germination.

[0042] <Method for Manufacturing Composite Resin Molded Product> Next, a method for manufacturing the composite resin molded product 10 according to the embodiment will be described. Fig. 4 is a flow diagram illustrating an example of a manufacturing process for the composite resin molded product 10 according to the present embodiment.

[0043] (1) The spores 3 and nutrients 4 are first supported on the surface of the natural fibers 2. Methods for supporting the spores 3 and nutrients 4 include physical adsorption by dry blending, impregnation of natural fibers using a dispersion solvent, crosslinking, and entrapment. The support method is not limited to the above, as long as it can retain the spores 3 and nutrients 4 on the surface of the natural fibers 2.

[0044] (2) The base resin 1 and the natural fibers 2 carrying spores 3 and nutrients 4 are dry-blended, then loaded into a melt-kneading processing device and melt-kneaded within the device. Some of the spores 3 and nutrients 4 carried by the natural fibers 2 fall off the natural fibers 2 and are dispersed in the base resin 1. The shearing action of the device promotes defibration of the natural fiber 2 agglomerates, allowing the natural fibers 2 to be finely dispersed within the base resin 1. By adjusting the shearing conditions, it is possible to defibrate the ends of the natural fibers 2, as shown in Figure 3, and obtain defibrated areas. For example, as shown in Example 1 described below, the spores and nutrients are unlikely to be thermally damaged by the molten base resin if the material temperature is 180°C for approximately 5 minutes.

[0045] Conventionally, when fibers are compounded with resin, fibers are first defibrated through pretreatment such as wet dispersion. However, when natural fibers are defibrated in the solvent used in wet dispersion, the fibers swell due to the solvent. Therefore, in order for the natural fibers to fully absorb water and expand in the composite resin molding, it is necessary to dry out the solvent in the natural fibers before kneading them with the base resin. Furthermore, because the fibers are more easily defibrated by wet dispersion than when defibrated in a molten base resin, it is difficult to defibrate only the ends, and the entire natural fiber ends up in a defibrated state. Furthermore, adding pretreatment increases the number of processes, resulting in problems such as reduced productivity.

[0046] In contrast, in the manufacturing process for the composite resin molded body 10 in this embodiment, the natural fibers 2 are melt-kneaded together with the base resin 1 (all-dry method) without undergoing pretreatment by wet dispersion for the purpose of defibrating the natural fibers 2. In this method, by not performing wet dispersion treatment of the natural fibers 2, swelling of the natural fibers 2 during the manufacturing process can be suppressed, and the water absorption rate of the natural fibers 2 in the composite resin molded body 10 can be improved. By drying the natural fibers 2 beforehand or during kneading, the water absorption rate in a humid environment in the composite resin molded body 10 can be further improved. Furthermore, since the natural fibers 2 have defibrated regions as described above, there are many contact points between the fibers within the composite resin molded body 10, and the water absorption rate of the composite resin molded body 10 can be increased via the contact points between the fibers.

[0047] To produce the natural fibers 2 of this embodiment using an all-dry method, it is preferable to apply high shear stress during kneading. Specific kneading methods include a single-screw kneader, a twin-screw kneader, a roll kneader, a Banbury mixer, and combinations thereof. From the viewpoint of ease of applying high shear and high mass productivity, a continuous twin-screw kneader and a continuous roll kneader are particularly preferred. Other kneading methods may also be used as long as they can apply high shear stress.

[0048] (4) The composite resin composition extruded from the melt kneading device is injection molded to produce the composite resin molding 10 as an injection molded product.

[0049] Hereinafter, examples and comparative examples of the experiments conducted by the inventors will be described.

[0050] Example 1 In Example 1, a cellulose-composite poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) resin molded article was produced by the following production method.

[0051] Softwood pulp (manufactured by Mitsubishi Paper Mills, product name: NBKP Celgar) was used as the starting material for natural fibers. Spores formed by Bacillus bacteria were used as PHBV-degrading spores. Casein peptone (manufactured by Nacalai Tesque) was used as a nutrient. Softwood pulp, spores, and nutrients were dry-blended in a mass ratio of 97.8:1.1:1.1 to obtain a cellulose filler loaded with spores and nutrients.

[0052] The cellulose filler carrying spores and nutrients and PHBV (manufactured by TianAn Biopolymer, product name: Y1000P) as the base resin were weighed to a mass ratio of 90:10 and dry-blended. The mixture was then melt-kneaded in a twin-screw kneader (KRC Kneader, manufactured by Kurimoto Iron Works). The screw was a medium shear type. The melt-kneading conditions were a material temperature of 180 ° C and a rotation speed of 50 min. -１ The composite resin composition discharged from the twin-screw kneader was hot-cut to obtain cellulose-composite PHBV resin pellets having a mass ratio of base resin, natural fiber, spores, and nutrients of 10:88:1:1.

[0053] Then, test pieces of cellulose-composite PHBV resin molded bodies were prepared using an injection molding machine (180AD manufactured by Japan Steel Works). The test piece preparation conditions were: base resin temperature 200°C, mold temperature 50°C, injection speed 100 mm / s, and holding pressure 100 Pa. The total heating time for the melt-kneading and injection molding was set to within 5 minutes. The shape of the test piece was changed depending on the evaluation items described below.

[0054] (Evaluation of Water Absorbency of Fibers) The water absorbency of fibers was evaluated by measuring the moisture content of the fibers according to the method specified in JIS L0105:2020. Specifically, the weight of the fibers dried at 80°C for 24 hours was measured, and this was used as the reference weight. Then, the weight of the fibers maintained at a temperature of 20°C and a humidity of 65% for 24 hours was measured. The weight increase from the reference weight was taken as the moisture content, and the moisture content was calculated. A moisture content of less than 5% was rated B, and a moisture content of 5% or more was rated A. In the composite resin molding according to Example 1, the moisture content of the softwood pulp was 6.5%, and the evaluation was A.

[0055] (Fiber end defibration) The obtained cellulose-composite PHBV resin molded body was immersed in chloroform to dissolve the PHBV, and the shape of the remaining cellulose fibers was observed by SEM. In the composite resin molded body of Example 1, the fiber ends were defibrated.

[0056] (Evaluation of Elastic Modulus of Composite Resin Molded Article) A three-point bending test was carried out using the obtained JIS K7139 Type A12 size dumbbell-shaped test piece. Here, the evaluation method for the elastic modulus was such that a value less than 200 MPa was rated as B and a value 200 MPa or more was rated as A. The elastic modulus of the composite resin molded article of Example 1 was 683 MPa, and the evaluation was A.

[0057] (Biodegradability Evaluation of Composite Resin Molded Articles) A ​​biodegradation test was conducted using bar-shaped test pieces made of the obtained cellulose composite resin molded articles. 50 g of compost inoculum (YK-11 manufactured by Yawata Bussan) was placed in a plastic container, and a bar-shaped test piece measuring 20 mm in height, 10 mm in width, and 3 mm in thickness, the weight of which had been measured in advance, was buried in the inoculum. The test piece was kept at a temperature of 58°C and a humidity of 50%, and the weight loss after two months was evaluated. The biodegradation rate was evaluated as follows: AA for a weight loss of 50% or more, A for a weight loss of 40% or more but less than 50%, and B for a weight loss of less than 40%. The biodegradation rate of the composite resin molded article of Example 1 was 42%, and the test piece was rated A.

[0058] (Example 2) In Example 2, the mass ratio of the base resin, natural fiber, spores, and nutrients was changed to 60:38:1:1, and the other material conditions and process conditions were the same as in Example 1 to produce a cellulose-composite PHBV resin molded body. Evaluations similar to those in Example 1 were also performed.

[0059] (Comparative Example 1) In Comparative Example 1, natural fibers were not used, and the mass ratio of the base resin to the spores and nutrients was changed to 98:1:1. The other material conditions and process conditions were the same as in Example 1 to produce a PHBV resin molded body. Evaluations similar to those in Example 1 were also performed.

[0060] In Comparative Example 2, PET fibers with a fiber diameter of 20 μm and a fiber length of 100 μm were used instead of softwood pulp to produce PET fibers carrying spores and nutrients. The other material and process conditions were the same as in Example 1 to produce a PET fiber-composite PHBV resin molding. Evaluations similar to those in Example 1 were also performed.

[0061] (Comparative Example 3) In Comparative Example 3, nutrients were not used, and the mass ratio of the base resin, natural fiber, and spores was changed to 11:88:1. The other material conditions and process conditions were the same as in Example 1 to produce a cellulose-composite PHBV resin molded body. Evaluations similar to those in Example 1 were also performed.

[0062] The structures and measurement results of the composite resin moldings in Examples 1 and 2 and Comparative Examples 1 to 3 are shown in FIG.

[0063] As is clear from Figure 5, in Examples 1 and 2 in which spores and nutrients were carried on natural fibers, the elastic modulus was high at 200 MPa or more, and Example 1, which had a higher proportion of natural fibers, showed a higher elastic modulus compared to Example 2. Biodegradation was promoted compared to Comparative Example 1.

[0064] As described above, it was confirmed that if natural fibers carrying spores and nutrients are combined, the fibers are exposed on the surface of the composite resin molding, and the natural fibers have a high water absorption rate, a composite resin with a high elastic modulus and high biodegradability can be obtained.

[0065] Comparative Example 1, which was produced without using natural fibers, had a lower elastic modulus and was rated B. Because the natural fibers did not absorb water into the composite resin molding, spore germination did not progress, and the biodegradation rate was lower than in Example 1, resulting in a rating of B.

[0066] In Comparative Example 2, which was made using PET fiber instead of softwood pulp, the moisture content of the PET fiber was low and it was not water absorbent, so in the biodegradability evaluation, spore germination did not progress and the biodegradation rate was lower than in Example 1, resulting in a rating of B.

[0067] In Comparative Example 3, which was produced without using nutrients, spore germination did not progress and the biodegradation rate was lower than in Example 1, resulting in an evaluation of B.

[0068] From the above evaluations, it was confirmed that if absorbent natural fibers and biodegradable plastics are used, spores and nutrients are carried on the surface of the natural fibers, and the fibers are exposed on the surface of the composite resin molding, a composite resin molding with a high elastic modulus and high biodegradability can be obtained.

[0069] It should be noted that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example.

[0070] According to one aspect of the present disclosure, a composite resin molding can be realized that not only has a higher elastic modulus but also an accelerated biodegradation rate in a humid environment compared to a resin alone.

[0071] According to one aspect of the present disclosure, a composite resin molded body can be provided that has better mechanical strength and a more controllable biodegradation rate than conventional biodegradable plastics. Because one aspect of the present disclosure can improve the properties of the base resin, the composite resin molded body can be used as a substitute for petroleum-derived general-purpose plastics. Therefore, the environmental impact of various industrial products or household goods made from petroleum-derived general-purpose plastics can be significantly reduced. Furthermore, the composite resin molded body can be used for packaging materials, daily necessities, home appliance housings, building materials, etc.

[0072] 1 Base resin 2 Natural fiber 3 Spore 4 Nutrients 10 Composite resin molded body

Claims

1. A composite resin molding containing a base resin and a plurality of natural fibers dispersed in the base resin, At least a portion of the plurality of natural fibers are carrying spores and nutrients; When the composite resin molding is taken as 100% by mass, the content of the plurality of natural fibers is 10% by mass or more and 99% by mass or less, A composite resin molding, wherein some of the plurality of natural fibers are exposed on the surface of the composite resin molding.

2. The composite resin molding according to claim 1, wherein the moisture content of at least a portion of the plurality of natural fibers is 5% or more as determined by the method specified in JIS L0105:2020.

3. 2. The composite resin molding according to claim 1, wherein the base resin is a biodegradable resin containing any one selected from the group consisting of polyhydroxy acid, polyhydroxyalkanoate, polyalkylene dicarboxylate, and modified starch.

4. The composite resin molding according to claim 1 , wherein the nutrients include either peptones or extracts.

5. The composite resin molding according to claim 1 , wherein at least some of the plurality of natural fibers carry the spores on the surface of the fibers.

6. The composite resin molding according to claim 1 , wherein at least a part of the plurality of natural fibers is cellulose.

7. The composite resin molding according to claim 1 , wherein at least some of the plurality of natural fibers have defibrated portions at ends in the fiber length direction.

8. Providing spores, nutrients, natural fibers, and a base resin; loading the spores and the nutrients onto the natural fibers; a step of melting and kneading the natural fibers carrying the spores and the nutrients together with the base resin, defibrating the natural fibers from the ends in the fiber length direction, and obtaining a composite resin member with an increased specific surface area of ​​the defibrated portions at the ends; a step of molding the composite resin member to obtain a composite resin molded body; A method for producing a composite resin molded product, comprising: