Biodegradable resin composition

Abstract

To provide a biodegradable resin composition capable of improving a decomposition rate of a biodegradable resin.SOLUTION: A biodegradable resin composition includes a biodegradable resin and polysaccharides, and the polysaccharides are subjected to gelatinization or are insoluble when dissolved at a concentration of 10 mass% in water at 25°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a biodegradable resin composition.

Background Art

[0002] A biodegradable resin refers to a plastic that is decomposed by the decomposing ability of microorganisms in soil, water, etc. In addition to the good decomposability in soil, biodegradable resins generally generate less greenhouse gases such as carbon dioxide than petroleum-based resins even when incinerated, and also generate less calories during incineration. Therefore, they are materials friendly to the global environment.

[0003] In recent years, various developments have been made regarding biodegradable resins.

[0004] For example, in Patent Document 1, as a resin molded body capable of improving the biodegradation rate, there is disclosed a resin molded body comprising a molding substrate containing a biodegradable resin and a coating film formed on the surface of the molding substrate, and the coating film contains a growth promoter for promoting the growth of microorganisms.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 states that carbohydrates, amino acids, and both of them can be used as a growth promoter for promoting the growth of microorganisms. For example, it discloses that a carbohydrate containing polysaccharides, etc. is blended into a coating film together with a biodegradable resin, and thereby the biodegradation rate of the resin can be improved.

[0007] However, there is still a demand for further improving the degradation rate of biodegradable resins.

[0008] An object of the present invention is to improve the decomposition rate of a biodegradable resin.

Means for Solving the Problems

[0009] The present invention for achieving the above object is as follows.

[0010] 〈Aspect 1〉 A biodegradable resin composition comprising a biodegradable resin and a polysaccharide, and the polysaccharide is one that gels or is insoluble when dissolved in water at 25°C at a concentration of 10% by mass. Biodegradable resin composition. 〈Aspect 2〉 The composition according to Aspect 1, wherein the polysaccharide gels when dissolved in water at 25°C at a concentration of 10% by mass. 〈Aspect 3〉 The composition according to Aspect 1 or 2, wherein the polysaccharide has a branched structure. 〈Aspect 4〉 The composition according to any one of Aspects 1 to 3, wherein the biodegradable resin is selected from biodegradable polyester resins. 〈Aspect 5〉 The composition according to any one of Aspects 1 to 4, wherein the ratio of the polysaccharide to the total mass of the biodegradable resin and the polysaccharide (the polysaccharide / (the biodegradable resin + the polysaccharide)) is 1.0% by mass to 50% by mass. 〈Aspect 6〉 A molded body substrate made of a biodegradable resin, and The composition according to any one of Aspects 1 to 5 coating the surface of the molded body substrate. A biodegradable molded body having the same.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a biodegradable resin composition that further improves the decomposition rate of a biodegradable resin.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist of the invention.

[0013] 《Biodegradable Resin Composition》 The biodegradable resin composition of the present invention (hereinafter, also simply referred to as "the composition of the present invention") contains a biodegradable resin and a polysaccharide, and the polysaccharide gels or is insoluble when dissolved in water at 25°C at a concentration of 10% by mass. It is a biodegradable resin composition. That's it.

[0014] The biodegradable resin can be decomposed by microorganisms inhabiting in soil or water (hereinafter, simply referred to as "in soil"). More specifically, microorganisms release extracellular enzymes into the soil by secretion or cell lysis. By the action of this extracellular enzyme, the biodegradable resin is decomposed into low molecules, and when completely decomposed, it is converted into inorganic substances such as oxygen, nitrogen, hydrogen, carbon or their gases. The biodegradable resin decomposed into low molecules (for example, saccharides such as fructose and glucose and amino acids) can be food for microorganisms. And microorganisms grow and further proliferate by obtaining food. As a result, the extracellular enzymes from microorganisms also increase, which promotes the active biodegradation of the biodegradable resin.

[0015] So far, techniques for blending carbohydrates, amino acids, and both of them into biodegradable resins in order to promote the growth of microorganisms and improve the decomposition rate of biodegradable resins by microorganisms are known (for example, Patent Document 1).

[0016] According to the intensive research of the present inventors, it has been found that simply blending any carbohydrates, amino acids, and both of them simultaneously with the biodegradable resin is insufficient to improve the degradation rate of the biodegradable resin by microorganisms. Therefore, through further intensive research by the present inventors, it has been found that the use of specific polysaccharides, that is, polysaccharides that gel or are insoluble when dissolved in water at 25 °C at a concentration of 10% by mass, can improve the degradation rate of the biodegradable resin, leading to the completion of the present invention.

[0017] Also, although not limited to theory, the reason why the effects of the present invention can be exerted by using the above-mentioned specific polysaccharides is analyzed as follows. That is, polysaccharides that gel or are insoluble when dissolved in water at 25 °C at a concentration of 10% by mass, when mixed with the biodegradable resin and buried in the soil, do not easily dissolve in the moisture in the soil, coexist with the biodegradable resin, serve as food for microorganisms, and are decomposed more quickly by the microorganisms grown there. On the other hand, when using polysaccharides that dissolve when dissolved in water at 25 °C at a concentration of 10% by mass, for example, they absorb and dissolve the moisture in the soil, flow out from the biodegradable resin, and separate from the biodegradable resin, so it is considered that it is difficult to obtain the growth effect of microorganisms in the vicinity of the biodegradable resin.

[0018] 〈Polysaccharide〉 Polysaccharides refer to those in which 10 or more monosaccharides are linked by glycosidic bonds.

[0019] The polysaccharides used in the present invention may gel or be insoluble when dissolved in water at 25 °C at a concentration of 10% by mass, but the former is preferred.

[0020] Here, "gelation" refers to a state in which polysaccharide molecules are intertwined to form a network-like network, water is retained in this network, and the entire polysaccharide aqueous solution loses fluidity.

[0021] In addition, "insoluble" refers to a state in which the polysaccharide is not completely dissolved. More specifically, it refers to a state in which the polysaccharide is not dissolved at all and exists in a suspended or precipitated form, or a state in which only a part of the polysaccharide is dissolved. Note that, in contrast to "insoluble", a state in which the polysaccharide is completely dissolved in water and forms a transparent solution is defined as "soluble".

[0022] In the present invention, the polysaccharide can have a linear, branched, branched-chain, or spherical structure. Among these, the polysaccharide preferably has a branched-chain structure. Here, the linear structure refers to a structure in which monosaccharides are linearly bonded and the polysaccharide has no side chains. The branched-chain structure refers to a structure having at least one side chain with respect to the linear main chain. The branched structure refers to a structure in which there is one or more side chains with respect to the linear main chain, and in any side chain, further one or more side chains are present and branched. The spherical structure refers to a spherical structure formed from the branched structure.

[0023] In the present invention, the molecular weight of the polysaccharide is not particularly limited, and may be, for example, 50,000 or more, 100,000 or more, 150,000 or more, 250,000 or more, 300,000 or more, 400,000 or more, 500,000 or more, or 1,000,000 or more, and may also be 3,000,000 or less, 2,500,000 or less, 2,000,000 or less, or 1,000,000 or less.

[0024] In the present invention, specific examples of the polysaccharide include, but are not limited to, tamarind seed gum (also referred to as "tamarind gum"), guar gum, cellulose, xanthan gum, chitosan, or starch, etc.

[0025] In the composition of the present invention, the content of the polysaccharide is not particularly limited, and may be, for example, 1.0% by mass or more, 5.0% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more with respect to the total mass of the composition, and may also be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. Also, within the range of these contents, a plurality of polysaccharides may be combined.

[0026] <Biodegradable resin> In the present invention, the biodegradable resin is not particularly limited and may be selected from any biodegradable resin.

[0027] The biodegradable resin may be selected from biodegradable polyester resins. More specifically, examples of the biodegradable polyester resin include polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate adipate terephthalate, polybutylene succinate terephthalate, polybutylene succinate carbonate, polybutylene adipate terephthalate, polyadipate terephthalate, and polytetramethylene adipate terephthalate, and combinations thereof, but are not limited thereto.

[0028] Other biodegradable resins used in the present invention include, for example, polylactic acid; hydroxycarboxylic acids such as glycolic acid, glyceric acid, 3-hydroxybutyric acid, tartaric acid, and citric acid, polycarboxylic acids such as succinic acid and adipic acid, lactones, and polyesters composed of copolymers of these monomers; polysaccharide-based polymer materials such as starch, cellulose (e.g., cellulose acetate, cellulose triacetate, etc.), chitosan, and pullulan; and polyvinyl alcohol, etc., but are not limited thereto.

[0029] In the composition of the present invention, the content of the biodegradable resin is not particularly limited and may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and may also be 99% by mass or less, 95% by mass or less, 90% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total mass of the composition.

[0030] In the composition of the present invention, the ratio of the above-described polysaccharide to the total mass of the biodegradable resin and the above-described polysaccharide (polysaccharide / (biodegradable resin + polysaccharide)) may be, for example, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more, and may also be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less.

[0031] 〈Other Components〉 In addition to the above-described biodegradable resin and polysaccharide, the composition of the present invention may further optionally contain other components as long as the effects of the present invention are not impaired.

[0032] Examples of other components include additives that can serve as food for microorganisms such as biostimulants. Here, more specifically, examples of biostimulants include polysaccharides other than the above-described polysaccharides, oligosaccharides, disaccharides, and carbohydrates such as monosaccharides, amino acids, humic substances, organic acid materials (e.g., humic acid, fulvic acid, etc.), seaweeds, seaweed extracts, peptides, trace minerals, vitamins, and microbial materials (e.g., Bacillus subtilis, Trichoderma, yeast, etc.), but are not limited thereto. Further, examples of other components include various additives such as paints, pigments, plasticizers, antistatic agents, antioxidants, ultraviolet absorbers, modifiers, or fillers, but are not limited thereto.

[0033] 〈Method for Producing Biodegradable Composition〉 The composition of the present invention is not particularly limited and can be produced, for example, by kneading a biodegradable resin and a polysaccharide at a certain mass ratio.

[0034] The kneading can be carried out, for example, by conical kneading, mixer kneading, or the like. The temperature during kneading is not particularly limited and may be appropriately adjusted to a temperature higher than the melting point of the biodegradable resin according to the types of the biodegradable resin and polysaccharide used. For example, it may be 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, and may also be 200°C or lower, or 150°C or lower. Also, the kneading time is not particularly limited and may be appropriately adjusted according to the amounts of the biodegradable resin and polysaccharide used.

[0035] In addition to the kneading described above, the composition of the present invention can also be produced, for example, by coating a polysaccharide on the surface of a biodegradable resin using a bar coater or the like.

[0036] 《Biodegradable Molded Article》 The present invention can also provide a biodegradable molded article.

[0037] The biodegradable molded article of the present invention a molded article substrate composed of a biodegradable resin, and the composition of the present invention described above that coats the surface of the molded article substrate, has.

[0038] When the biodegradable molded article of the present invention is buried in the soil, microorganisms can first decompose the composition of the present invention that coats the surface of the molded article substrate and then reach the molded article substrate and decompose the biodegradable resin that constitutes it.

[0039] Since the composition of the present invention can improve the decomposition rate of conventional biodegradable resins by microorganisms, the biodegradable molded article using the composition of the present invention can improve the decomposition rate by microorganisms compared to conventional molded articles.

[0040] Therefore, the biodegradable molded article of the present invention can have various uses as shown below.

[0041] 1. Use as a material for the agricultural, forestry, and fisheries industries As materials for the agricultural, forestry, and fisheries industries, more specifically, for example, multi-films, seedling pots, cell trays, runner pins, root pouches, pesticide and fertilizer coating materials, sheets for pest control smoke, fishing lines, fishing nets, etc. can be mentioned, but it is not limited to these.

[0042] 2. Applications as civil engineering and construction materials As civil engineering and construction materials, more specifically, for example, heat insulation materials, formworks for civil engineering works, greening sheets such as earth retaining materials, sandbags, vegetation nets, green bags, etc. can be mentioned, but it is not limited to these.

[0043] 3. Applications as outdoor leisure products As outdoor leisure products, more specifically, for example, disposable products for golf, fishing, marine sports, mountain climbing, etc. can be mentioned, but it is not limited to these.

[0044] 4. Applications as films and containers for food packaging As films and containers for food packaging, more specifically, for example, trays for fresh food, instant food containers, fast food containers, lunch boxes, etc. can be mentioned, but it is not limited to these.

[0045] 5. Applications as sanitary products As sanitary products, more specifically, for example, paper diapers, sanitary products, etc. can be mentioned, but it is not limited to these.

[0046] 6. Applications as office supplies, daily necessities, stationery, and miscellaneous goods As office supplies, daily necessities, stationery, and miscellaneous goods, more specifically, for example, pen cases, refill cases, razors, toothbrushes, cups, garbage bags, etc. can be mentioned, but it is not limited to these.

Examples

[0047] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these.

[0048] 《Examples 1 to 7, and Comparative Examples 2 and 3》 <Preparation of Samples for Each Example and Comparative Example> As the biodegradable resin, FORZEAS (registered trademark) DM9B01 (a biodegradable resin compound based on BioPBS (registered trademark); pellet form; white; melting point 84°C) manufactured by Mitsubishi Chemical Corporation was used.

[0049] As the polysaccharides, various ones shown in Table 1 were used. Also, regarding whether each polysaccharide gels, is insoluble, or is soluble, the polysaccharide was dissolved in water at 25°C at a concentration of 10% by mass and evaluated. In Table 1, in the column of the item "solubility in water", the corresponding part is indicated as "gels", "insoluble", or "soluble".

[0050] The biodegradable resin and the polysaccharide were kneaded with a conical kneader so that the mass ratio (biodegradable resin: polysaccharide) was 70:30 to obtain a biodegradable resin composition. The kneading conditions are as follows: (Kneading Conditions) Apparatus: Vertical conical twin-screw kneading extruder Kneading time: 10 minutes Rotation speed: 100 rmp Kneading temperature: 120°C (in the case of Example 3 only, it was carried out at 125°C (when kneading at 120°C, the torque value of the apparatus increased, so kneading was carried out at 125°C. The following hot press was also adjusted to the temperature condition of kneading.))

[0051] The obtained biodegradable resin composition was hot-pressed under the following conditions to obtain a film sample with a size of 4 cm × 4 cm. The thickness of each film is shown in Table 1. (Hot Press Conditions) Apparatus: Hot press Time: 30 seconds Pressure: 30 MPa Temperature: 120°C (in the case of Example 3 only, it was carried out at 125°C)

[0052] <<Comparative Example 1>> A sample of Comparative Example 1 was prepared in the same manner as the above examples, except that no polysaccharide was blended.

[0053] "Evaluation of Degradation by Microorganisms" Commercially available seedling pots were filled with soil (Hyponex (registered trademark) manufactured by Hyponex Japan Co., Ltd.), and after adding water as appropriate, each sample obtained above was buried under an environment of 23°C and 60% RH (relative humidity). It was taken out every week and visually observed for the presence or absence of degradation.

[0054] The degradation results of the samples of each example and comparative example after two weeks were evaluated according to the following criteria and shown in Table 1. (Evaluation Criteria for Degradation) S: The state where the film completely disappeared (i.e., completely decomposed by microorganisms); A: The state where the shape of the film has collapsed; B: The state where the shape of the film exists but degradation has started; C: The state where there is no change.

[0055] [Table 1]

[0056] As is clear from Table 1, when dissolved in water at 25°C at a concentration of 10% by mass, Examples 1 to 7 using polysaccharides that gel or are insoluble were all able to further improve the degradation rate of the biodegradable resin compared to Comparative Example 1 that does not contain polysaccharides, and Comparative Examples 2 and 3 using other polysaccharides.

Claims

1. A biodegradable resin composition comprising a biodegradable resin and a polysaccharide, and when the polysaccharide is dissolved in water at 25 °C at a concentration of 10% by mass, it gels or is insoluble, the polysaccharide has a branched structure, and the ratio of the polysaccharide to the total mass of the biodegradable resin and the polysaccharide (the polysaccharide / (the biodegradable resin + the polysaccharide)) is 20% by mass to 50% by mass. A biodegradable resin composition.

2. The composition according to claim 1, wherein the polysaccharide gels when dissolved in water at 25 °C at a concentration of 10% by mass.

3. The composition according to claim 1 or 2, wherein the biodegradable resin is selected from biodegradable polyester resins.

4. A molded body substrate made of a biodegradable resin, and the composition according to any one of claims 1 to 3 covering the surface of the molded body substrate, A biodegradable molded body having the same.

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