JPS6228641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing seed beds with good water resistance and growth. More specifically, water resistance is characterized by spraying on the soil surface a blended composition containing polyvinyl alcohol resin, water-insoluble polyisocyanate, water, seeds, and hydrogel with a water absorption rate of 50 to 1500 times by weight. Concerning a seed bed fixation method with good growth performance.

Many methods have been proposed for stably fixing seeds on artificially formed soil surfaces, and many chemicals are known for use in each method, but each method has its advantages and disadvantages. However, in reality, it is currently only used under very limited conditions. In view of the current situation, the present inventors have made earnest efforts to improve the shortcomings of conventionally known seed bed anchoring methods, and as a result, have developed a seed bed anchoring method that is superior in safety, workability, and economy, and has good water resistance and growth. completed.

Conventionally known seed bed fixing agents (hereinafter abbreviated as fixing agents) include acrylamide-based, polyamine-based, water-soluble urethane-based, water glass-based, cement-based, etc. There are some problems.

(b) Water-soluble components are strongly acidic, strongly alkaline, or highly toxic, so there are concerns about the safety of water systems.

(b) The gelation or solidification time after blending or mixing is too fast, which limits the freedom of construction work.

C. Physical properties such as elasticity, strength, water resistance, and water content of the solidified material cannot be widely controlled.

D. Adhesion to soil particles is low.

In addition, synthetic resin emulsions, rubber latex, bituminous emulsions, etc. are known as fixing agents for the seed bed fixing method, but all of these have poor water resistance, especially against rainfall immediately after construction. do not have.

On the other hand, when using a water-soluble urethane prepolymer, which has been used in some areas recently, an elastic foam with high water resistance is formed, and it is an excellent drug in terms of performance. However, it has its drawbacks, and in reality, it is only being used on a trial basis in a very limited number of areas. In other words, water-soluble urethane prepolymers gel by reacting with water, and the time from mixing water to gelation is
That is, since the gelation time is extremely short, ranging from several minutes to several tens of minutes, it is practically impossible to mix and spray in a tank. Therefore, it is necessary to use a special device that proportionally mixes the water-soluble urethane prepolymer and water near the nozzle tip.Furthermore, the resin raw material itself easily absorbs moisture and becomes thick and gelled due to moisture absorption, so the viscosity It has problems such as poor stability and the fact that proportional mixing is extremely difficult in practical terms.Although it has excellent performance, it is not easy to work on site, so it is not widely put into practical use. It is.

The present inventors have previously developed a new seed bed anchoring method that improves the drawbacks of these known seed bed anchoring methods.
Patent application for a seed bed fixing method with good water resistance consisting of spraying on the soil surface a composition containing a water-soluble polyvinyl alcohol resin, a water-insoluble polyisocyanate, water, and seeds as essential components.
A proposal was made as No. -95690. In this method, by changing the composition of each component, catalyst, and mixing conditions, it is possible to control the gelation time from several tens of minutes to several hours, and it is also possible to control the strength, elastic modulus, etc. of the gelled product. Physical properties can be changed over a wide range.

Furthermore, although it is a two-component mixture type, it has a long pot life after blending and can limit gelation time, making it easy to work on site. It has the advantage of not containing

However, when the composition proposed above is applied to the soil surface, a highly water-resistant film is formed, and the seeds are not washed away even by rain, which is a very remarkable advantage. Because the film has such good water resistance that even when it rains after construction, rainwater flows only through the top of the film and rarely penetrates into the soil inside the film, which slows down the growth rate after germination depending on the season. A slow case was recognized. Furthermore, as with conventional seed bed anchoring methods, germination rates decrease during periods of low rainfall, especially in midsummer, because sufficient water cannot be retained to satisfy germination conditions. It was found that there is a problem in that it is better to avoid construction work during the dry season.

Therefore, as a result of our efforts to improve the formulation in order to improve the germination rate during dry periods and the growth rate after germination, the present inventors added polyvinyl alcohol-based resin, water-insoluble polyisocyanate, water, and seeds. The seed bed fixing method of the present invention, which has good water resistance and growth performance, has been completed by spraying on the soil surface a compounded composition containing a hydrogel with a water absorption rate of 50 to 1,500 times by weight as an essential component.

That is, in the present invention, in particular, the hydrogel having a water absorption rate of 50 to 1500 times by weight in the above-mentioned compounded composition,
It is thought that the germination rate and growth rate are improved by exerting its water absorption and water retention properties.

As the polyvinyl alcohol resin used in the present invention, any water-soluble resin that is a saponified product of a polymer whose main component is vinyl acetate can be used, but in particular, polyvinyl alcohol resins with a degree of polymerization of 300 or more,
So-called partially saponified polyvinyl alcohol resins having a degree of saponification of 95 mol% or less are preferred in terms of liquid stability, gelling properties, solubility, and the like. carboxyl group, sulfone group, and salts thereof, amide group,
So-called modified polyvinyl alcohol resins containing one or more types of long-chain alkyl ester groups, etc., and so-called so-called modified polyvinyl alcohol resins that are obtained by reacting aldehydes, acid anhydrides, vinyl monomers, etc. with the OH groups of polyvinyl alcohol resins. Post-modified polyvinyl alcohol resins and the like can also be suitably used. These modified polyvinyl alcohol resins have characteristic properties in terms of room temperature solubility, solution stability, emulsion stability of water-insoluble polyisocyanates, and the like. When the degree of polymerization of the polyvinyl alcohol resin is lower than 300, the gelation efficiency decreases and a large amount of polyisocyanate is required, which is not economical and generally not preferred. In addition, the degree of saponification of polyvinyl alcohol resins varies depending on the degree of modification, but in general, when the degree of saponification exceeds 95 mol%, it becomes difficult to emulsify and the solubility in water at room temperature decreases. This is not preferable because it impairs on-site workability.

In addition, the polyvinyl alcohol resin in the present invention refers not only to those used alone, but also to polyvinyl alcohol resins that are contained in various aqueous emulsions as emulsifiers, stabilizers, thickeners, or additives. It is included as one aspect of.

These aqueous emulsions containing polyvinyl alcohol resins include vinyl acetate, ethylene vinyl acetate, acrylic, styrene butadiene, styrene isoprene, styrene acrylic, vinyl chloride, vinylidene chloride, cloprene, and bitumen. Any aqueous emulsion such as rubber emulsion or natural rubber emulsion can be used. Furthermore, -OH groups, -COOH groups, -NH ₂ are present in the emulsion resin components.
More preferred is an aqueous emulsion containing a functional group having an active hydrogen that can react with an isocyanate, such as a group.

As water-insoluble polyisocyanates, aromatic diisocyanates such as m- and p-phenylene diisocyanate, 4-t-butyl-m-phenylene diisocyanate, 4-methoxy-m-
Phenyl diisocyanate, 4-phenoxy-
m-phenylene diisocyanate, 4-chloro-
m-phenylene diisocyanate, 2,4- and 2,6-toluene diisocyanate, m- and p-xylene diisocyanate, cumene-2,
4-diisocyanate, duyulene diisocyanate, 1,4-, 1,8- and 2,6-naphthylene diisocyanate, 1,5-tetrahydronaphthylene diisocyanate, diphenylmethane-
4,4'-diisocyanate, dianisidine diisocyanate, polymethylene polyphenyl isocyanates, toluene-2,4,6-triisocyanate, diphenyl-2,4,4'-triisocyanate, triphenylmethane-4,4', 4″-triisocyanates and aliphatic diisocyanates,
For example, many isocyanate compounds are included, such as hexamethylene diisocyanate, decamethylene diisocyanate, 2,3-dimethyltetramethylene diisocyanate, and alicyclic polyisocyanates such as hydrogenated methylene diisocyanate and isophorone diisocyanate.
From the viewpoint of stability and economy, liquid crude diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate are preferably used.

Catalysts that promote or suppress the reaction of isocyanate, such as organic tin compounds, basic compounds, and acidic compounds, may also be added as appropriate. Generally, organic tin compounds such as dibutyltin dilaurate, tin octylate, triethylamine, triethylenediamine,
Basic compounds such as lime, soda carbonate, caustic soda, and other alkaline substances are positive catalysts that promote the reaction of isocyanate, while acidic substances such as phosphoric acid, hexametaphosphoric acid, sulfuric acid, etc. suppress the reaction of isocyanate. It is a negative catalyst. When using crude diphenylmethane diisocyanate as the water-insoluble polyisocyanate, it is better to use hexametaphosphoric acid in combination to keep the PH of the composition on the acidic side, which will take a longer time to gel and give more room for on-site workability. , which is generally convenient.

The hydrogel with a water absorption rate of 50 to 1,500 times its weight used in the present invention refers to a substance that absorbs 50 to 1,500 times its dry weight of water and swells when a dry resin is placed in water at room temperature. These can be manufactured by various methods. Such hydrogels can be produced, for example, by (1) a method in which starch is graft-polymerized with acrylonitrile and then hydrolyzed and neutralized; (2) a method in which acrylic acid or methacrylic acid is graft-polymerized on a polyvinyl alcohol resin and then neutralized with an alkali. (3) A method of reacting polyvinyl alcohol resin powder with a cyclic acid anhydride and neutralizing it with an alkali, (4) A method of saponifying and drying a copolymer of vinyl acetate and ethylenically unsaturated carboxylic acid, ( 5) A method in which microscopically added ethylenically unsaturated carboxylic acid is added to polyvinyl alcohol-based resin and neutralized with an alkali, (6) A method in which an aqueous solution of a hydrophilic polymer is irradiated with radiation, gelled, and then crushed. Any resin can be used as long as it has the ability to absorb 50 to 1500 times its own weight of water at room temperature, but polyvinyl alcohol-based resins are particularly preferred. Although the form of the hydrogel is not particularly limited,
From the viewpoint of on-site workability and the expression of effects for the purpose of the present invention, particles having a major diameter in the water-absorbed state in the range of 0.01 to 10 mm are suitable. Particles that are too large are not suitable because they tend to clump up during spraying or fall off slopes. Furthermore, if the particles are too small, the hydrogel particles will be buried inside the film and will not be able to absorb water quickly, which is disadvantageous. When the hydrogel is fibrous, the dispersibility and effectiveness are good even if the length is slightly longer than 10 mm.

The blending ratio of the hydrogel material in the compounded composition of the present invention should be appropriately selected depending on the water absorption rate of the hydrogel, the concentration of other coexisting components, the viscosity of the system, etc.
It is appropriate to select from the range of 0.001 to 1% by weight. If the amount of hydrogel added is too small, water absorption,
Water retention is insufficient and the effect is insufficient. On the other hand, if the amount of hydrogel added is too large, the viscosity of the system becomes too high, making the spraying operation difficult, which is not preferable.

The concentration of the polyvinyl alcohol resin contained in the compounded composition used in the present invention should be appropriately selected depending on the purpose of use, the concentration of other additives, etc., but is usually in the range of 0.1 to 20% by weight. It is appropriate to choose from. If the concentration is too low, the gelation efficiency will decrease, and only local gels will be formed instead of forming a gel overall, and the gelation rate will also be extremely slow, making it necessary to add a large amount of water-insoluble polyisocyanate. This method does not meet the purpose of the present invention because it has many disadvantages such as the following.

The amount of water-insoluble polyisocyanate contained in the composition used in the present invention also needs to be appropriately increased or decreased depending on the type of isocyanate, purpose of use, usage conditions, etc., but generally polyvinyl alcohol-based 1 to 1000 relative to the amount of resin present
A range of weight % is suitable, preferably 10 to 100
It is safe to choose from a range of weight %.

Since the polyisocyanate in the compounded composition used in the present invention is insoluble in water, it is necessary to be in a finely dispersed state in the composition, but in general, when left standing for a long time, the density of the polyisocyanate increases. Due to the difference, it tends to sink or float, resulting in an uneven state.
In order to prevent such phase separation, the following measures are effective.

(1) The system must be constantly stirred.

(2) Improve the dispersion stability of water-insoluble polyisocyanate by using a polyvinyl alcohol resin with strong emulsifying power or by using a small amount of emulsifier.

(3) Increase the viscosity of the system and slow down the sedimentation or floating speed of dispersed particles.

Polyvinyl alcohol resins with strong emulsifying power have as low a degree of saponification as possible, and residual acetic acid groups are arranged in a block-like manner, or modified polyvinyl alcohols obtained by copolymerizing a small amount of long-chain alkyl vinyl esters. etc. are suitable.

An effective way to increase the viscosity of the system is to add a thickener and/or filler to the system. Examples of thickeners include methyl cellulose, carboxymethyl cellulose, methyl vinyl ether, polyacrylamide, polyethylene oxide, and starch. In addition, as fillers, clay, calcium carbonate, titanium oxide,
In addition to inorganic powders such as silicon oxide, zinc oxide, gypsum, and perlite, organic materials such as pulp, waste paper, resin powder, fiber waste, straw waste, grains, wood flour, dried sludge, livestock manure, and sponge waste can also be used. Available as required. In short, anything that can reduce the fluidity of the system can be used as appropriate.

The hydrogel having a water absorption rate of 50 to 1,500 times by weight used in the present invention is also effective as a system thickener, and when the hydrogel is used in an appropriate amount, the other thickeners mentioned above are not particularly necessary.

In formulating the compounded composition used in the present invention, first, an aqueous solution containing a polyvinyl alcohol resin is prepared, and then the hydrogel material and seeds are dispersed or diluted in water, if necessary, with a thickening agent. The recommended method is to mix the ingredients with fillers, fertilizers and other additives under stirring, and finally add the water-insoluble polyisocyanate and then thoroughly stir and knead, but the method is not limited to this method.

The gelation time of the compounded composition used in the present invention can be controlled within the range of 30 minutes to several hours after preparation, but the addition of acidic substances, especially phosphoric acids, can delay the gelation time. Effective and straightforward.
Furthermore, the gelation time can be delayed by selecting a highly hydrophobic polyisocyanate, or by dissolving the polyisocyanate in a highly hydrophobic organic solvent and then adding it to water. .

On the other hand, in order to accelerate the gelation time, it is effective to use catalysts such as organic tin compounds and amines, and to add basic substances. It is effective to use additives and stirring conditions that make the isocyanate particles more finely dispersed.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but these Examples are not intended to limit the present invention in any way.

Example 1 A spray composition for a seed bed fixing method was prepared with the following blending ratio and sprayed onto a soil slope.

Blend composition Component Amount (per 1000) A. Polyvinyl alcohol 10Kg (polymerization degree 1700, saponification degree 88 mol%) B Waste paper pulp 20Kg C Chemical fertilizer 20Kg D Seed; Kentucky 31 13Kg E Organic soil 200Kg F Hydrogel material ( Note) 2.5Kg G Crude diphenylmethane diisocyanate 15Kg nate (Millionate MR-100 manufactured by Nippon Polyurethane Co., Ltd.) (Note) Powder (100 mesh pass) of polyvinyl alcohol (degree of polymerization 1700, degree of saponification 88 mol%) in dioxane. 20, which was obtained by suspending the mixture in
A hydrogel material with a water absorption of 240 times its weight at °C.

After spraying, the seeds germinated in about 10 days and grew to an average length of 7.5 cm in 30 days. During this period, no runoff due to rain was observed.

As a comparative experiment, spraying was carried out at the same site using a formulation in which the hydrogel material was excluded from the above formulation, but in this case, the germination status was almost the same, but the average body length after 30 days was 4.5 cm
It was clearly observed that growth was slow.

Claims (1)

[Claims] 1 Polyvinyl alcohol resin, water-insoluble polyisocyanate, water, seeds and water absorption rate 50-1500
A seed bed fixing method with good water resistance and growth performance, which is characterized by spraying a compounded composition containing twice the weight of hydrogel as an essential component onto the soil surface.