JP7702840B2 - Biodegradable resin composition - Google Patents

Description

The present invention relates to a biodegradable resin composition.

Biodegradable resins are plastics that are decomposed by the decomposition ability of microorganisms in soil, water, etc. In addition to being easily decomposable in soil, biodegradable resins generally produce less greenhouse gases such as carbon dioxide and less calories when incinerated than petroleum-based resins, making them environmentally friendly materials.

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

For example, Patent Document 1 discloses a resin molded body capable of improving the biodegradation rate, which comprises a molded base containing a biodegradable resin and a coating film formed on the surface of the molded base, the coating film containing a growth promoter that promotes the growth of microorganisms.

JP 2007-106783 A

Patent Document 1 discloses that carbohydrates, amino acids, or both can be used as growth promoters that promote the growth of microorganisms, and that carbohydrates including polysaccharides, for example, can be blended with a biodegradable resin in a coating film, thereby improving the biodegradation rate of the resin.

However, there is still a need to further improve the decomposition rate of biodegradable resins.

The object of the present invention is to improve the decomposition rate of biodegradable resins.

The present invention, which achieves the above objective, is as follows:

<Aspect 1>
The composition comprises a biodegradable resin and a polysaccharide, and the polysaccharide is a substance 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 claim 1, wherein the polysaccharide forms a gel when dissolved in water at 25° C. at a concentration of 10% by mass.
Aspect 3
A composition according to any one of the preceding claims, wherein the polysaccharide has a side chain structure.
<Aspect 4>
Aspect 4. The composition of any one of aspects 1 to 3, wherein the biodegradable resin is selected from biodegradable polyester resins.
<Aspect 5>
A 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. The composition according to any one of claims 1 to 4.
Aspect 6
A molded body base made of a biodegradable resin; and the composition according to any one of aspects 1 to 5, which coats a surface of the molded body base.
A biodegradable molded body having the above structure.

The present invention provides a biodegradable resin composition that further improves the decomposition rate of a biodegradable resin.

The following describes in detail the embodiments of the present invention. Note that the present invention is not limited to the following embodiments, and can be modified in various ways within the scope of the invention.

《Biodegradable resin composition》
The biodegradable resin composition of the present invention (hereinafter also simply referred to as the "composition of the present invention") has the following properties:
The composition comprises a biodegradable resin and a polysaccharide, and the polysaccharide is a material that gels or is insoluble when dissolved in water at 25°C at a concentration of 10% by mass.
It is a biodegradable resin composition.

Biodegradable resins can be decomposed in soil or water (hereinafter simply referred to as "soil") by microorganisms living there. More specifically, microorganisms release extracellular enzymes into the soil by secretion or cell lysis. Through the action of these extracellular enzymes, biodegradable resins are decomposed into low molecular weight compounds, and when completely decomposed, they are converted into inorganic substances such as oxygen, nitrogen, hydrogen, and carbon, or into gases thereof. Biodegradable resins decomposed into low molecular weight compounds (e.g., sugars such as fructose and glucose, and amino acids) can become food for microorganisms. The microorganisms grow and further multiply by obtaining food. As a result, the amount of extracellular enzymes from the microorganisms also increases, which promotes biodegradation of the biodegradable resin.

To date, there are known techniques for blending carbohydrates, amino acids, or both with biodegradable resins in order to promote the growth of microorganisms and improve the rate at which the biodegradable resins are decomposed by microorganisms (e.g., Patent Document 1).

The inventors' intensive research has revealed that simply blending any carbohydrate, amino acid, or both with a biodegradable resin is insufficient to improve the decomposition rate of the biodegradable resin by microorganisms. Therefore, the inventors' further intensive research has revealed that the decomposition rate of the biodegradable resin can be improved by using a specific polysaccharide, i.e., a polysaccharide that gels or is insoluble when dissolved in water at 25°C at a concentration of 10% by mass, and this has led to the completion of the present invention.

Although not limited to theory, the reason why the effects of the present invention can be achieved by using the above-mentioned specific polysaccharides is analyzed as follows. That is, polysaccharides that gel when dissolved in water at 25°C at a concentration of 10% by mass, or insoluble polysaccharides, when mixed with biodegradable resin and buried in soil, do not easily dissolve in the moisture in the soil, but coexist with the biodegradable resin and become food for microorganisms, and the biodegradable resin is decomposed more quickly by the microorganisms that grow there. On the other hand, when using a polysaccharide that dissolves when dissolved in water at 25°C at a concentration of 10% by mass, for example, it absorbs moisture in the soil and dissolves, flows out of the biodegradable resin and separates from the biodegradable resin, so it is considered that the effect of growing microorganisms near the biodegradable resin is difficult to obtain.

<Polysaccharide>
A polysaccharide is a compound consisting of 10 or more monosaccharides linked together via glycosidic bonds.

The polysaccharides used in the present invention may be those that gel when dissolved in water at 25°C at a concentration of 10% by mass, or may be insoluble, with the former being preferred.

Here, "gelation" refers to a state in which polysaccharide molecules become entangled with each other, forming a mesh-like network, water is retained within this network, and the entire polysaccharide aqueous solution loses its fluidity.

"Insoluble" refers to a state in which the polysaccharide is not completely dissolved, and more specifically refers to a state in which the polysaccharide is not completely dissolved and exists in the form of a suspension or precipitate, or a state in which the polysaccharide is only partially dissolved. In contrast to "insoluble," the state in which the polysaccharide is completely dissolved in water and forms a transparent solution is defined as "soluble."

In the present invention, the polysaccharide may have a linear, side-chain, branched, or spherical structure, but among these, it is preferable that the polysaccharide has a side-chain structure. Here, the linear structure refers to a polysaccharide structure formed by linearly bonding monosaccharides and having no side chains. The side-chain structure refers to a structure having at least one side chain with respect to a linear main chain. The branched structure refers to a structure having one or more side chains with respect to a linear main chain, and any side chain is further branched so that one or more side chains are present. In addition, the spherical structure refers to a spherical structure formed from a branched structure.

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 million or more, and may be 3 million or less, 2.5 million or less, 2 million or less, or 1 million or less.

Specific examples of polysaccharides in the present invention include, but are not limited to, tamarind seed gum (also called "tamarind gum"), guar gum, cellulose, xanthan gum, chitosan, and starch.

In the composition of the present invention, the content of polysaccharides 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, relative to the total mass of the composition, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. Furthermore, multiple polysaccharides may be combined as long as they are within these content ranges.

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

The biodegradable resin may be selected from biodegradable polyester resins, and more specifically, examples of biodegradable polyester resins include, but are not limited to, 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, as well as combinations thereof.

Other biodegradable resins that can be used in the present invention include, but are not limited to, 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 polymer materials such as starch, cellulose (e.g., cellulose acetate, cellulose triacetate, etc.), chitosan, and pullulan; and polyvinyl alcohol.

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 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, relative to the total mass of the composition.

In addition, in the composition of the present invention, the ratio of the above-mentioned polysaccharides to the total mass of the biodegradable resin and the above-mentioned polysaccharides (polysaccharides/(biodegradable resin+polysaccharides)) 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 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.

<Other Ingredients>
In addition to the above-mentioned biodegradable resin and polysaccharide, the composition of the present invention may further contain other components as desired, so long as the effects of the present invention are not impaired.

Other components include, for example, additives such as biostimulants that can serve as food for microorganisms. More specifically, biostimulants include, for example, carbohydrates such as polysaccharides other than the above-mentioned polysaccharides, oligosaccharides, disaccharides, and monosaccharides, amino acids, humus, organic acid materials (for example, humic acid, fulvic acid, etc.), seaweed, seaweed extracts, peptides, trace minerals, vitamins, and microbial materials (for example, Bacillus subtilis, Trichoderma fungi, yeast, etc.), but are not limited to these. Other components include, for example, various additives such as paints, pigments, plasticizers, antistatic agents, antioxidants, and ultraviolet absorbers, as well as modifiers and fillers, but are not limited to these.

<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 in a certain mass ratio.

The kneading can be carried out, for example, by conical kneading or mixer kneading. The kneading temperature is not particularly limited and may be appropriately adjusted to a temperature higher than the melting point of the biodegradable resin depending on the type of biodegradable resin and polysaccharide used, and may be, for example, 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, and may be 200°C or lower, or 150°C or lower. The kneading time is not particularly limited and may be appropriately adjusted depending on the amount of biodegradable resin and polysaccharide used.

In addition to the above-mentioned kneading method, the composition of the present invention can also be produced, for example, by applying a polysaccharide to the surface of a biodegradable resin using a bar coater or the like.

《Biodegradable molded body》
The present invention can also provide a biodegradable molded article.

The biodegradable molded article of the present invention is
A molded body base made of a biodegradable resin, and the above-mentioned composition of the present invention coating the surface of the molded body base,
has.

When the biodegradable molded body of the present invention is buried in soil, microorganisms first decompose the composition of the present invention that covers the surface of the molded body base, and then reach the molded body base and decompose the biodegradable resin that constitutes it.

The composition of the present invention can improve the rate of decomposition by microorganisms of conventional biodegradable resins, so biodegradable molded bodies using the composition of the present invention can improve the rate of decomposition by microorganisms compared to conventional molded bodies.

Therefore, the biodegradable molded body of the present invention can have a variety of uses, as shown below.

1. Use as agricultural, forestry and fishery materials More specifically, agricultural, forestry and fishery materials include, but are not limited to, mulch films, seedling pots, cell trays, runner pins, root pouches, pesticide and fertilizer covering materials, pest smoking sheets, fishing lines, fishing nets and the like.

2. Use as civil engineering and construction materials More specifically, examples of civil engineering and construction materials include, but are not limited to, heat insulation materials, civil engineering formwork, greening sheets for retaining soil, sandbags, vegetation net green bags, etc.

3. Use as an Outdoor Leisure Product More specifically, examples of outdoor leisure products include disposable products for golf, fishing, marine sports, mountain climbing, and the like, but are not limited thereto.

4. Use as food packaging films and containers More specifically, examples of food packaging films and containers include, but are not limited to, trays for fresh food, containers for instant food, containers for fast food, and lunch boxes.

5. Use as a Hygiene Product More specifically, examples of the hygiene product include disposable diapers, sanitary products, etc., but are not limited thereto.

6. Use as office supplies, daily necessities, stationery, and miscellaneous goods More specifically, examples of office supplies, daily necessities, stationery, and miscellaneous goods include, but are not limited to, pen cases, lead cases, razors, toothbrushes, cups, and garbage bags.

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

Examples 1 to 7 and Comparative Examples 2 and 3
Preparation of Samples for Examples and Comparative Examples
As the biodegradable resin, FORZEAS (registered trademark) DM9B01 (a biodegradable resin compound based on BioPBS (registered trademark); pellet-shaped; white; melting point 84° C.) manufactured by Mitsubishi Chemical Corporation was used.

The various polysaccharides shown in Table 1 were used. In addition, each polysaccharide was dissolved in water at 25°C at a concentration of 10% by mass to evaluate whether it was gelling, insoluble, or soluble. In Table 1, the corresponding column for "solubility in water" is indicated as "gelling," "insoluble," or "soluble."

The biodegradable resin and the polysaccharide were kneaded in a conical kneader so that the mass ratio (biodegradable resin:polysaccharide) was 70:30 to obtain a biodegradable resin composition. The kneading conditions were as follows:
(Mixing conditions)
Equipment: Vertical conical twin-screw kneading extruder Kneading time: 10 minutes Rotation speed: 100 rpm
Kneading temperature: 120° C. (Note that kneading was performed at 125° C. only in the case of Example 3 (kneading was performed at 125° C. because the torque value of the device increased when kneading was performed at 120° C. The temperature conditions for the heat press described below were also set to match those of the kneading.)

The obtained biodegradable resin composition was heat-pressed under the following conditions to obtain a film sample having a size of 4 cm x 4 cm. The thickness of each film is shown in Table 1.
(Heat press conditions)
Equipment: Heat press Time: 30 seconds Pressure: 30 MPa
Temperature: 120° C. (Note that, in the case of Example 3, the temperature was 125° C.)

Comparative Example 1
A sample of Comparative Example 1 was prepared in the same manner as in the above-mentioned Example, except that no polysaccharide was added.

Evaluation of decomposition by microorganisms
Soil (Hyponex (registered trademark) manufactured by Hyponex Japan Co., Ltd.) was placed in a commercially available seedling pot, water was appropriately added, and each sample obtained above was buried in an environment of 23° C. and 60% RH (relative humidity). The samples were taken out every week and visually observed for the presence or absence of decomposition.

The decomposition results after 2 weeks for the samples of each of the Examples and Comparative Examples were evaluated according to the following criteria and are shown in Table 1.
(Decomposition evaluation criteria)
S: The film has completely disappeared (i.e., completely decomposed by microorganisms);
A: The film shape is destroyed;
B: The film still had its shape, but decomposition had begun;
C: No change.

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

Claims (4)

The composition comprises a biodegradable resin and a polysaccharide, and the polysaccharide is a substance that gels or is insoluble when dissolved in water at 25° C. at a concentration of 10% by mass,
The polysaccharide has a side chain structure, and
The ratio of the polysaccharide to the total mass of the biodegradable resin and the polysaccharide (polysaccharide/(biodegradable resin+polysaccharide)) is 20% by mass to 50% by mass;
Biodegradable resin composition. The composition according to claim 1, wherein the polysaccharide gels when dissolved in water at 25°C at a concentration of 10% by mass. The composition according to claim 1 or 2 , wherein the biodegradable resin is selected from biodegradable polyester resins. A molded body base made of a biodegradable resin, and the composition according to any one of claims 1 to 3 , which coats the surface of the molded body base.
A biodegradable molded body having the above structure.