JP7302086B1 - soil conditioner - Google Patents

Abstract

Kind Code: A1 A soil conditioner excellent in promoting plant growth is provided using a biodegradable resin. A soil conditioner of the present invention contains a biodegradable resin and an acidic polysaccharide. [Selection figure] None

Description

The present invention relates to soil conditioners.

At soil storage facilities and construction sites, there are concerns that the surface of the soil will be scattered by the wind and the soil will be washed away by the rain. . However, the work is complicated, the resin film of the sheet needs to be collected after use, and there are problems such as the deteriorated resin film scattering.

Therefore, it has been practiced to prevent the scattering and erosion of the soil by spraying a synthetic resin emulsion soil modifier. Furthermore, by means of spraying a mixture of soil modifier with seeds, the stability of the soil is also attempted by means of germinating and growing plants.

Conventionally, various soil conditioners using synthetic resin emulsions have been proposed (Patent Documents 1 to 5), but non-biodegradable synthetic resins remain in the soil without decomposing. Recently, biodegradable soil conditioners have also been provided from the viewpoint of environmental friendliness (Patent Documents 6 to 9).

However, polylactic acid, which is a representative biodegradable resin, has poor film-forming properties, making it difficult to form a film. Biodegradable resins generally have weak film strength and exhibit sufficient solidification performance. I have a problem that I can't. As a result, it cannot withstand slopes such as slopes and a large amount of rainwater such as torrential rain, and the environment in which it can be used is limited.

Techniques for adding thickeners to soil conditioners have also been proposed (Patent Documents 1 to 5 and 9). For example, Patent Documents 1 and 2 are for viscosity adjustment, Patent Documents 3 and 4 are for freeze-thaw stability, and Patent Document 5 is for water absorption.

JP 2019-218206 A Japanese Patent Application Laid-Open No. 2021-127380 WO2016/204290 WO2017/094747 JP 2003-261872 A JP-A-2000-159316 JP 2009-022179 A JP-A-2005-130732 JP 2019-218207 A

Specifically disclosed in these documents are guar gum (Patent Documents 1 and 2), hydroxyethyl cellulose and carboxymethyl cellulose (Patent Documents 3 and 4), and polyacrylamide (Patent Document 5), which are neutral polysaccharides. However, when biodegradable resin was used as a substitute for synthetic resin, the growth of plants was not good when mixed with seeds and sprayed onto soil. Patent Documents 1 and 9 also describe that guar gum, which is a neutral polysaccharide, improves the durability of the film. However, neutral polysaccharides such as guar gum could not exhibit sufficient effects.

The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a soil conditioner that uses a biodegradable resin and is excellent in promoting the growth of plants.

In order to solve the above problems, the present inventors conducted extensive studies and found that the use of acidic polysaccharides among polysaccharides improves the growth of plants, leading to the completion of the present invention.
That is, the soil conditioner of the present invention is characterized by containing a biodegradable resin and an acidic polysaccharide.

Since the soil conditioner of the present invention improves plant growth and decomposes in the environment after use, there is no need for collection work. In addition, by blending acidic polysaccharides, it exhibits high solidification performance even on steep slopes or when exposed to a large amount of rainwater, so it is excellent in preventing flying sand and erosion.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated concretely.

The soil conditioner of the present invention contains a biodegradable resin and an acidic polysaccharide.
Examples of biodegradable resins include, but are not limited to, polylactic acid, copolymers of lactic acid and other hydroxycarboxylic acids, polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, polybutylene adipate, and the like. Dibasic acid polyesters, polycaprolactone, copolymers of caprolactone and other hydroxycarboxylic acids, polyhydroxybutyrate, copolymers of polyhydroxybutyrate and other hydroxycarboxylic acids, and the like . These may be used individually by 1 type, and may be used in combination of 2 or more type.
Among the biodegradable resins, the other hydroxycarboxylic acid in the copolymer is not particularly limited, but examples include glycolic acid, 2-hydroxybutyric acid, 2-hydroxyvaleric acid, 2-hydroxycaproic acid, 2- Hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxy-2-methylpropionic acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxy-2-ethylbutyric acid, 2-hydroxy-2-methylvaleric acid, 2- Hydroxy-2-ethylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2-butylvaleric acid, 2-hydroxy-2-methylcaproic acid, 2-hydroxy-2-ethylcaproic acid, 2- Hydroxy-2-propylcaproic acid, 2-hydroxy-2-butylcaproic acid, 2-hydroxy-2-pentylcaproic acid, 2-hydroxy-2-methylheptanoic acid, 2-hydroxy-2-ethylheptanoic acid, 2- Hydroxy-2-propylheptanoic acid, 2-hydroxy-2-butylheptanoic acid, 2-hydroxy-2-methyloctanoic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid , 7-hydroxyheptanoic acid and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.
Lactic acid and hydroxycarboxylic acid may take forms such as D form, L form, and D/L form, but they may be in any form without limitation. When polylactic acid is used, the D-lactic acid content is preferably 1 to 30 mol%, more preferably 5 to 20 mol%.

Among these, polylactic acid and polycaprolactone are preferable from the viewpoint of resin physical properties such as films.

The molecular weight of the biodegradable resin is not particularly limited, but the weight average molecular weight of polylactic acid is preferably 50,000 to 1,000,000, more preferably 100,000 to 800,000, and even more preferably 200,000 to 600,000. The weight average molecular weight of polycaprolactone is preferably 1,000 to 200,000, more preferably 10,000 to 150,000, even more preferably 50,000 to 100,000.
The weight average molecular weight (Mw) of polylactic acid and polycaprolactone can be determined by the method described in the Examples section below, for example, by gel permeation chromatography (GPC) and comparison with a standard substance of known molecular weight. can.

The soil conditioner of the present invention preferably has a low minimum film-forming temperature (MFT) from the viewpoint of forming a film on the soil surface and exhibiting high solidification performance. Considering that the film is formed at atmospheric temperature, the minimum film-forming temperature of the soil modifier is preferably 50°C or lower, more preferably 40°C or lower. When polylactic acid or the like having a high minimum film-forming temperature is contained as the biodegradable resin, it is preferable to use a plasticizer together. Polylactic acid has a minimum film-forming temperature of, for example, 160° C. or higher, but it can be lowered to 100° C. or lower by blending a plasticizer.

The soil conditioner of the present invention contains an acidic polysaccharide. Acidic polysaccharides have acidic functional groups such as carboxyl groups and sulfate groups. Soil particles have a negative charge at the interface, but acidic polysaccharides have a negative charge due to the dissociation of protons in water. This improves water retention. As a result, the plants grow well. In addition, the polysaccharide is sufficiently dissolved to assist the film-forming properties and exhibit high solidification performance. This is thought to contribute to the prevention of flying sand and erosion, as well as to the improvement of soil solidification performance as a secondary effect of plant rooting whose growth is promoted by the improvement in water retention.

Examples of acidic polysaccharides include, but are not limited to, xanthan gum, carrageenan, alginic acid, sodium alginate, gellan gum (such as deacylated gellan gum), pectin, gum arabic, karaya gum, tragacanth gum, and soybean polysaccharides. These may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, sodium alginate, gellan gum, xanthan gum, carrageenan, and pectin are preferable, sodium alginate, gellan gum, and xanthan gum are more preferable, and sodium alginate is particularly preferable, in terms of excellent water retention.

Although the molecular weight of the acidic polysaccharide is not particularly limited, it preferably has a number average molecular weight of 10,000 to 10,000,000, more preferably 100,000 to 5,000,000 in order to further exhibit the effects of the present invention. preferable.
Here, the number average molecular weight of acidic polysaccharides can be measured by the following method. In general, high-molecular-weight substances derived from natural products do not have a single molecular weight, but are aggregates of molecules with various molecular weights, so they are measured as a molecular weight distribution with a certain width. A typical measurement technique is gel filtration chromatography. Representative information on molecular weight distribution obtained by gel filtration chromatography includes weight average molecular weight (Mw), number average molecular weight (Mn), and dispersion ratio (Mw/Mn). Weight-average molecular weight emphasizes the contribution of high-molecular-weight polymers to the average molecular weight, and is expressed by the following formula.
Mw=Σ(WiMi)/W=Σ(HiMi)/Σ(Hi)
Number average molecular weight is calculated by dividing the total weight of the polymer by the total number of polymers.
Mn=W/ΣNi=Σ(MiNi)/ΣNi=Σ(Hi)/Σ(Hi/Mi)
Here, W is the total weight of the polymer, Wi is the weight of the i-th polymer, Mi is the molecular weight at the i-th elution time, Ni is the number of molecular weights Mi, and Hi is the height at the i-th elution time. .

The amount of the acidic polysaccharide to be added is 0.05 parts by mass or more based on 100 parts by mass of the biodegradable resin from the viewpoint of good plant growth and soil improvement such as prevention of flying sand and erosion. It is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and particularly preferably 2 parts by mass or more. In addition, from the point that the growth of the plant is not hindered by the thickening, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, further preferably 8 parts by mass or less, and 6 parts by mass with respect to 100 parts by mass of the biodegradable resin. Part or less is particularly preferred.

From the viewpoint of dispersibility, the soil conditioner of the present invention is preferably an aqueous dispersion of a biodegradable resin. Therefore, it is preferable to incorporate a dispersant that enhances the dispersibility of the biodegradable resin in the aqueous medium and stably disperses the resin particles of the biodegradable resin.

The dispersant is not particularly limited, and examples thereof include ionic dispersants such as nonionic surfactants, polymeric surfactants, anionic surfactants and cationic surfactants.

Examples of nonionic surfactants include polyvinyl alcohol, polyoxyalkylene condensates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and the like. mentioned. Among these, polyvinyl alcohol, which itself is biodegradable and can well disperse the biodegradable resin, is preferred.

The polyvinyl alcohol may be partially saponified. In addition, unmodified polyvinyl alcohol and modified polyvinyl alcohol can be used.
Examples of modified polyvinyl alcohol include, but are not limited to, ethylene-modified polyvinyl alcohol, carbonyl-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, alkyl ether-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, acetamide-modified polyvinyl alcohol, and diacetone group-modified polyvinyl alcohol. , acrylonitrile-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The molecular weight of the polyvinyl alcohol is not particularly limited, but from the viewpoint of the dispersibility of the biodegradable resin particles and the solidification performance due to film formation, the average molecular weight according to the viscosity average polymerization degree is preferably 10,000 or more, preferably 30,000. It is more preferably 50,000 or more, more preferably 50,000 or more, particularly preferably 70,000 or more, and particularly preferably 90,000 or more. From the viewpoint of handleability of the aqueous biodegradable resin dispersion, the average molecular weight based on the viscosity average degree of polymerization is preferably 200,000 or less, more preferably 180,000 or less, and further preferably 160,000 or less. It is preferably 140,000 or less, particularly preferably 120,000 or less.

The average molecular weight of polyvinyl alcohol can be calculated from the viscosity average degree of polymerization, the degree of saponification, and the molecular weights of vinyl acetate units and vinyl alcohol units.
The degree of polymerization of polyvinyl alcohol, as described in JIS K 6726, is obtained from the intrinsic viscosity [η] (unit: liter/g) measured in water at 30°C after resaponification of polyvinyl alcohol with sodium hydroxide. , can be calculated based on the following formula:
Viscosity average degree of polymerization = ([η] × 10000/8.29) ^(1/0.62)
The average molecular weight is obtained by converting the viscosity average degree of polymerization to the molecular weight of the vinyl acetate unit and the vinyl alcohol unit according to the ratio of the degree of saponification.
In the case of modified polyvinyl alcohol, it is calculated in the same manner as above from the viscosity-average degree of polymerization.

The amount of polyvinyl alcohol is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the biodegradable resin, from the viewpoint of improving the dispersibility of the biodegradable resin. preferable. In addition, from the viewpoint of good handling of the biodegradable resin aqueous dispersion and good plant growth, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, relative to 100 parts by mass of the biodegradable resin. Preferably, 20 parts by mass or less is more preferable.

Examples of polymeric surfactants include anionic polymers, cationic polymers, nonionic polymers, and amphoteric polymers. These polymeric surfactants may be water-soluble, for example, polyacrylates, polymethacrylates, polyacrylamides, alkyl acrylate/methacrylate copolymers, acrylate/acrylamide copolymers. , maleated polybutene, maleated polybutadiene, polymethyl vinyl ether, polyvinylpyrrolidone, polystyrene sulfonate, cationized cellulose, carboxymethyl cellulose, cationized cellulose, and the like.

Examples of anionic surfactants include fatty acid salts, higher alcohol sulfates, liquid fatty acid oil sulfates, sulfates of fatty amines and aliphatic amides, fatty alcohol phosphates, alkylbenzene sulfonates, fatty acid group amide sulfonates, sulfonates of dibasic fatty acid esters, and the like.

Examples of cationic surfactants include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, fatty acid triethanolamine monoester salts, and alkylpolyoxyethyleneamines.

The mass ratio of the acidic polysaccharide to the dispersant (acidic polysaccharide/dispersant) is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.01 or more, from the viewpoint of solidification performance by film formation. , is particularly preferably 0.05 or more, and particularly preferably 0.1 or more. In addition, the mass ratio of the acidic polysaccharide to the dispersant (acidic polysaccharide/dispersant) is preferably 3 or less from the viewpoint that the biodegradable resin aqueous dispersion has good handling properties and good plant growth. , is more preferably 1 or less, more preferably 0.8 or less, particularly preferably 0.6 or less, and particularly preferably 0.4 or less.

The mass ratio of acidic polysaccharide to polyvinyl alcohol (acidic polysaccharide/polyvinyl alcohol) is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.01 or more, from the viewpoint of solidification performance by film formation. , is particularly preferably 0.05 or more, and particularly preferably 0.1 or more. In addition, the mass ratio of the acidic polysaccharide to polyvinyl alcohol (acidic polysaccharide/polyvinyl alcohol) is preferably 3 or less from the viewpoint of good handling of the biodegradable resin aqueous dispersion and good plant growth. , is more preferably 1 or less, more preferably 0.8 or less, particularly preferably 0.6 or less, and particularly preferably 0.4 or less.

The soil conditioner of the present invention may contain a plasticizer. Plasticizers improve the film properties of biodegradable resins.
Examples of plasticizers include, but are not limited to, diisopropyl adipate, diisobutyl adipate, dioctyl adipate, diethylhexyl adipate, diisononyl adipate, diisodecyl adipate, dibutoxyethoxyethyl adipate, adipic acid and 2-( adipic acid derivatives such as esters of 2-methoxyethoxy)ethanol and benzyl alcohol; phthalic acid derivatives such as ethyl phthalyl ethyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl butyl glycolate; triethyl citrate, tributyl citrate , citric acid derivatives such as acetyl triethyl citrate, acetyl tributyl citrate, ether ester derivatives such as diethylene glycol diacetate, triethylene glycol diacetate, triethylene glycol dipropionate, glycerin triacetate, glycerin tripropionate, glycerin tributyrate and glycerin derivatives such as Among these, those using an adipic acid derivative or a citric acid derivative are preferable because they are highly effective in improving film-forming properties.

A plasticizer is suitably blended when polylactic acid or the like having a high minimum film-forming temperature is contained as a biodegradable resin. Polylactic acid has a minimum film-forming temperature of, for example, 160° C. or higher, but it can be lowered to 100° C. or lower by blending a plasticizer.

When the plasticizer is blended, the amount is preferably such that the minimum film-forming temperature of the aqueous biodegradable resin dispersion is 50° C. or lower, more preferably 40° C. or lower.
Although it depends on the type of biodegradable resin, the blending amount of the plasticizer, including the case where polylactic acid is blended, is 5 parts by mass per 100 parts by mass of the biodegradable resin from the viewpoint of improving the film properties by plasticization. 1 part or more is preferable, and 20 parts by mass or more is more preferable. From the viewpoint of suppressing the occurrence of bleeding out of the plasticizer, the amount is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, relative to 100 parts by mass of the biodegradable resin.

In the soil conditioner of the present invention, the water-based solvent is not particularly limited, but examples thereof include water and a mixed solvent of an organic solvent compatible with water.
The ratio of water in the mixed solvent is not particularly limited, but is preferably 90% by mass or more, more preferably 95% by mass or more, based on the total amount of the mixed solvent.

In the mixed solvent, the organic solvent is not particularly limited, and examples thereof include monohydric alcohols and polyhydric alcohols. Examples of monohydric alcohols include methanol, ethanol, butanol, isopropyl alcohol (IPA), normal propyl alcohol and butanol, and examples of polyhydric alcohols include glycerin and butylene glycol. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The soil conditioner of the present invention may contain other components than those shown above within the range that does not impair the effects of the present invention. Examples of other components include, but are not particularly limited to, surfactants, organic solvents, viscosity modifiers, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The solid content of the soil conditioner of the present invention is preferably 20% by mass or more, more preferably 25% by mass or more, and 30% by mass or more based on the total amount of the soil conditioner. is more preferable, and 35% by mass or more is particularly preferable. When the solid content is within this range, the ratio of the resin particles in the water dispersion is high, so the drying efficiency is improved. In addition, the resin particles are stably dispersed by adjusting the viscosity of the aqueous dispersion to an appropriate range. Also, the solid content is preferably 50% by mass or less, more preferably 45% by mass or less. When the solid content is within this range, the viscosity of the water dispersion does not become too high, and the handling property of the soil conditioner is improved. Here, the solid content is the mass percentage obtained by subtracting the amount of water-based solvent such as water from the total amount of the soil conditioner.

In the soil conditioner of the present invention, the viscosity (20° C.) of the aqueous dispersion is 100 to 5000 mPa s from the viewpoint of good handling of the soil conditioner and good growth of plants. is preferred, 200 to 3000 mPa·s is more preferred, and 300 to 1500 mPa·s is even more preferred.

The method for producing the soil conditioner of the present invention is not particularly limited. , by mixing and stirring with an aqueous solvent, a biodegradable resin aqueous dispersion can be produced.

Specifically, for example, using a closed tank equipped with a stirring device, a biodegradable resin, an acidic polysaccharide, a dispersant, a plasticizer, and water are charged simultaneously, and pressure is applied while heating and stirring to disperse the biodegradable resin. A direct dispersion method in which a melt containing a biodegradable resin, an acidic polysaccharide, a dispersant, and a plasticizer is added and stirred to disperse in hot water held under pressure; Biodegradation A phase inversion method in which a biodegradable resin and a plasticizer are heated and melted, and an aqueous solution containing a dispersant and an acidic polysaccharide is added and stirred to disperse the biodegradable resin in water; organic solvent, water, biodegradable resin, acid A method in which the organic solvent is removed after the polysaccharide, dispersant, and plasticizer are added and dispersed by stirring; A method of removing the organic solvent after adding and stirring to disperse may be mentioned.

Considering the fact that it can be applied to a wide variety of biodegradable resins and the progress of hydrolysis, an organic solvent, water, a biodegradable resin, an acidic polysaccharide, a dispersant, and a plasticizer are placed in a closed tank with a stirring device. is charged, the temperature is raised while stirring, the solid raw material is dissolved and dispersed, the mixture is cooled, and then the organic solvent is removed under reduced pressure.

Alternatively, an organic solvent, a biodegradable resin, and a plasticizer are placed in a closed tank equipped with a stirrer, and the mixture is stirred and heated to dissolve to prepare a biodegradable resin-dissolved solution. A preferable method is to charge the dispersant, add the dissolved aqueous solution to the closed tank, disperse the mixture while raising the temperature to the resin dissolution temperature or more under stirring, cool, and then remove the organic solvent under reduced pressure. .

Examples of the organic solvent include, but are not limited to, formic acid esters such as methyl formate, ethyl formate, propyl formate, and butyl formate; ester organic solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; Examples thereof include solvents, chlorine-based organic solvents such as chloroform and carbon tetrachloride, and aromatic hydrocarbons such as benzene, toluene and xylene. Among these, ester-based organic solvents, particularly formic acid esters and acetic acid esters, are preferred because they have good resin solubility. Considering sufficient dissolution of the resin, dispersant, etc., the ratio of the organic solvent to water is preferably organic solvent:water = 1:9 to 9:1, preferably 7:3 to 3:7. is more preferred.

A homomixer, a high-pressure emulsifier, or the like may be used as a dispersing and agitating device in the production of a soil conditioner. , propeller blades, paddle blades, turbine blades, anchor blades, and ribbon blades. Also, the stirring speed and rotation speed may be the conditions used in normal dispersion or mixing. For example, a stirring blade having a ratio of the blade diameter (d1) to the inner diameter (d2) of the stirring tank during dispersion (blade ratio: d1/d2) of 0.5 to 0.85 can be used. Also, the peripheral speed of the stirring blade can be 1 to 8 m/s.

The soil modifier of the present invention can be obtained, for example, by mixing the soil modifier with water, seeds, and, if necessary, soil, fertilizer, seed spraying curing agent, etc., and spraying it on the outdoor slope. Immediately after spraying, the solidification of the soil surface by the soil modifier can prevent temporary soil erosion, and the plants that germinate and grow thereafter can stabilize the soil. Since the soil modifier contains an acidic polysaccharide, it promotes permeation of rainwater into the soil due to its water retention capacity, reduces the amount of rainwater that is washed away as surface water, and causes poor germination and dryness of plants due to dryness of the soil. Prevents withering, improves growth, and prevents erosion.

Objects to which the soil modifier is applied are not particularly limited, but examples thereof include bare land slopes, embankments, reclaimed land and developed land caused by tunnel construction, road construction, and the like.
The method of applying the soil modifier to the soil surface is not particularly limited, and can be carried out by spraying or the like. For example, considering the workability and spraying efficiency at the time of spraying, a soil modifier diluted with water may be sprayed as necessary, or the soil is mainly used, and the soil modifier and, if necessary, seeds It is also possible to spread the soil mixed with the above. The method of application to the soil is not particularly limited, and can be applied by a conventionally known method using a shower nozzle, sprayer, sprinkler, or the like.

The soil conditioner of the present invention can be suitably used as a growth base material containing seeds, such as a greening base material and a vegetation base material. Growth bases such as greening bases and vegetation bases are used on slopes such as embankments and cuttings associated with the construction of reclaimed land, roads, dams, etc. The purpose is to regenerate the topsoil that has been created in difficult-to-green areas, etc., where plants can grow. The growth base material containing the soil modifier of the present invention can form a growth base by spraying or the like, and allows plants to grow densely through germination and growth. From the viewpoint of exerting the effects of the present invention, the growth base material such as a vegetation base material preferably contains at least one selected from bark compost, peat moss, and black soil, and more preferably contains all three. .

For sand prevention applications, for example, by diluting a soil conditioner with water and spraying it on an outdoor slope surface, the sprayed soil conditioner forms a film on the surface of the soil, causing the sprayed surface to harden. and prevent dust from scattering from the surface layer of the soil. By adding the acidic polysaccharide in addition to the biodegradable resin, a strong surface adhesion layer is formed on the surface of the soil, effectively preventing dust scattering. Since the soil conditioner of the present invention uses an acidic polysaccharide, it has the effect of promoting plant growth, and as a secondary effect of plant rooting, it can further improve soil solidification performance.

Similarly, for erosion prevention applications, for example, by diluting a soil conditioner with water and spraying it on an outdoor slope, the sprayed soil conditioner forms a film on the surface of the soil. It hardens and prevents sudden erosion due to wind and rain. By adding the acidic polysaccharide in addition to the biodegradable resin, a strong surface-fixing layer is formed on the surface of the soil, which effectively prevents rapid erosion due to wind and rain.

That is, since the soil conditioner contains an acidic polysaccharide, it is possible to form a sufficient film even if the soil conditioner is diluted with water contained in the soil. For example, when the water content of the soil is high, such as immediately after a rainfall, it is conceivable that the sprayed soil modifier will be diluted by the water in the soil, or that the material components will flow out without remaining on the soil surface. By adding the acidic polysaccharide, it is difficult to soak into the soil, and a film is formed on the surface of the soil to prevent dust scattering and erosion. Furthermore, since the soil conditioner of the present invention uses an acidic polysaccharide, it has the effect of promoting the growth of plants, and as a secondary effect of plant rooting, it can further improve the erosion prevention performance of the soil.

EXAMPLES 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. Preparation of soil conditioner In the examples and comparative examples, the following ingredients were used for the soil conditioner.
(biodegradable resin)
Polylactic acid-1 Weight average molecular weight about 400,000 Polylactic acid-2 Weight average molecular weight about 120,000 Polycaprolactone-1 Weight average molecular weight 64,000
Polycaprolactone-2 weight average molecular weight 2,000

Average Molecular Weight The average molecular weight of the biodegradable resin, that is, the weight average molecular weight (Mw) is the polystyrene-equivalent average molecular weight measured by gel permeation chromatography using the following equipment and conditions.
[GPC measurement device]
Column: manufactured by JASCO Corporation Detector: RI detector for liquid chromatography RI-1530 manufactured by JASCO Corporation
[Measurement condition]
Solvent: Chloroform (special grade)
Measurement temperature: 50°C
Flow rate: 1.0 ml/min Sample concentration: 15 mg/ml
Injection volume: 2 μl
Calibration curve: Universal Calibration
Analysis program: ChromNAV (Ver.1.19.02)

(dispersant)
PVA-1 Polyvinyl alcohol Molecular weight: 100,000 Degree of saponification: 80%
PVA-2 Polyvinyl alcohol Molecular weight: 16,000 Degree of saponification: 80%
Copolymer of ethylene oxide (EO) and propylene oxide (PO) Number average molecular weight 3300 EOPO ratio (EO:PO) = 46:54
The average molecular weight of polyvinyl alcohol is a value calculated from the viscosity average degree of polymerization, the degree of saponification, and the molecular weights of vinyl acetate units and vinyl alcohol units described in JIS K 6726 as described above.

(Plasticizer)
Diisopropyl adipate Diisobutyl adipate Diisooctyl adipate

(polysaccharide)
Xanthan gum: acidic polysaccharide Gellan gum: acidic polysaccharide Sodium alginate: acidic polysaccharide Carrageenan: acidic polysaccharide Pectin: acidic polysaccharide Gum arabic: acidic polysaccharide Karaya gum: acidic polysaccharide Gum tragacanth: acidic polysaccharide Guar gum: neutral polysaccharide Locust bean Gum: Neutral polysaccharide Agar: Neutral polysaccharide Chitosan: Basic polysaccharide

(High molecular)
Sodium polyacrylate
acrylamide copolymer

Each component was placed in a closed dispersion tank at the component ratios shown in Tables 1A to 1C, heated to 65°C, dispersed by a dispersion method using a predetermined stirring and dispersing device, and then rapidly cooled to 40°C. Thereafter, ethyl acetate was removed under reduced pressure to obtain a soil modifier and a biodegradable resin aqueous dispersion.

The minimum film-forming temperature of the soil modifier was measured with a film-forming temperature measuring instrument IMC-1538 manufactured by Imoto Seisakusho.

2. Evaluation The soil conditioners of Examples and Comparative Examples were evaluated as follows.

(1) Growth acceleration test A vegetation base material was prepared on a stainless steel bat with the following composition ratio (mass), and using them, the extra soil spraying method and the thick layer base material spraying method were applied without giving an inclination angle to the stainless steel bat. carried out. The thickness of the sprayed surface was 5 mm at each of the locations.
Vegetation base material composition Bark compost: 50%
Peat moss: 20%
Black soil: 30%

Various raw materials were mixed with the following compositions with respect to 100 parts by mass of the vegetation base material.
Fertilizer (High Control 700 (trade name) manufactured by Asahi Kasei Corporation): 0.3%
Seed (grass: Kentucky 31 fescue): 0.05%
Soil conditioner of Examples and Comparative Examples: 5%

Using pasture grass (Kentucky 31 fescue), the germination rate and the state of growth after germination after 30 days were measured and evaluated according to the following criteria.
[Growth: germination rate]
◎ ++: 99% or more ◎ +: 95% or more and less than 99% ◎: 90% or more and less than 95% ○: 80% or more and less than 90% △: 70% or more and less than 80% ×: less than 70%

[Growth: growth state after germination]
A test section of the vegetation base prepared in the same manner as described above except that the seeds were sown without using the soil modifier was used as a blank. After 30 days from spraying, the grass height compared to the blank was evaluated according to the following criteria.
◎ ++: 120% or more ◎ +: 115% or more and less than 120% ◎: 110% or more and less than 115% ○: more than 100% and less than 110% △: 90% or more and 100% or less ×: less than 90%

(2) Flying Sand Prevention Test Masago soil (particle size: 10 mm or less) was placed in a stainless steel bat, and the soil modifiers of Examples and Comparative Examples were applied so that the active ingredient was 250 g/m ² and cured.
[Strength]
Using a digital force gauge, the strength (N) was measured after 60 days and 180 days had passed, and evaluated according to the following criteria.
◎ ++: 40 or more ◎ +: 30 or more and less than 40 ◎: 20 or more and less than 30 ○: 10 or more and less than 20 △: 5 or more and less than 10 ×: less than 5

[Amount of dust scattering]
After 60 days and 180 days of elapsed time, a blower was operated on the test body (wind speed 10 m/s x 5 minutes), and the amount of scattered dust was measured.
The amount of dust scattering was measured and evaluated according to the following criteria.
◎ ++: less than 5% ◎ +: 5% or more and less than 10% ◎: 10% or more and less than 30% ○: 30% or more and less than 50% △: 50% or more and less than 70% ×: 70% or more

(3) Erosion prevention test Vegetation base materials were prepared on stainless steel bats with the following composition ratios (mass), and using them, the additional soil spraying method and the thick layer base material spraying method were carried out. At the places where the spraying was applied, the inclination angle was about 45° C., and the thickness of the sprayed surface was 5 mm.
Vegetation base material composition Bark compost: 50%
Peat moss: 20%
Black soil: 30%
Various raw materials were mixed with the following compositions with respect to 100 parts by mass of the vegetation base material.
Fertilizer (High Control 700 (trade name) manufactured by Asahi Kasei Corporation): 0.3%
Seed (grass: Kentucky 31 fescue): 0.05%
Soil conditioner of Examples and Comparative Examples: 5%

[Presence or absence of collapse]
After leaving it outdoors for 30 days, it was subjected to a rainfall test of 100 mm/hr×5 minutes from a height of 1 m.
◎ ++: less than 5% ◎ +: 5% or more and less than 10% ◎: 10% or more and less than 30% ○: 30% or more and less than 50% △: 50% or more and less than 70% ×: 70% or more

[Soil Runoff]
After being left outdoors for 30 days, a rainfall test of 100 mm/hr×5 minutes from a height of 1 m was conducted, and then the amount of soil runoff was measured and evaluated according to the following criteria.
◎ ++: less than 5% ◎ +: 5% or more and less than 10% ◎: 10% or more and less than 30% ○: 30% or more and less than 50% △: 50% or more and less than 70% ×: 70% or more

The results of the above evaluations are shown in Tables 1A-1C.

Claims (4)

Containing a biodegradable resin, a dispersant for dispersing the biodegradable resin in an aqueous medium, and an acidic polysaccharide,
An aqueous dispersion of resin particles of a biodegradable resin,
Biodegradable resins include polylactic acid, copolymers of lactic acid and other hydroxycarboxylic acids, polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, polybutylene adipate, polycaprolactone, caprolactone and other hydroxycarboxylic acids. A soil conditioner which is at least one selected from copolymers with acids, polyhydroxybutyrate, and copolymers of polyhydroxybutyrate and other hydroxycarboxylic acids. The soil conditioner according to claim 1, wherein the acidic polysaccharide is at least one selected from xanthan gum, carrageenan, alginic acid, sodium alginate, gellan gum, pectin, gum arabic, karaya gum, tragacanth gum, and soybean polysaccharides. The soil conditioner according to claim 1, wherein the amount of said acidic polysaccharide is 0.05 to 15 parts by mass with respect to 100 parts by mass of said biodegradable resin. 2. The soil conditioner according to claim 1, which is used in a seed-containing growth substrate.