JPS6354755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates primarily to a covering for agriculture or plant growth, and particularly to a method for forming a continuous film-like covering layer on the soil surface.

Conventionally, the multi-film method has been widely used to raise the soil temperature or inhibit the growth of weeds by covering the soil surface with a black plastic film. but,
The disadvantage of this method is that it is time-consuming to install, as holes must be carefully punched in the film to expose the plants, and weights must be placed in places to prevent the film from flipping over in the wind. Furthermore, when it is no longer needed, it takes time and effort to remove it, and if it remains in the soil, it is too strong and difficult to tear, and it can get wrapped around the tiller, which is very troublesome. In addition, with this method, the film cannot be broken through and plants cannot grow, so it is not possible to cover with mulch at the same time as sowing. As another mulching method, a method of spraying asphalt has been proposed, but it has drawbacks such as not forming a continuous film unless a large amount is sprayed, and having undesirable effects if a large amount remains in the soil. To compensate for this drawback, it has been proposed to add a foaming agent to the asphalt emulsion; it has also been proposed to add a water-soluble resin such as polyvinyl alcohol as a thickener, but it is necessary to add a large amount of foaming agent. , which has an unfavorable effect on the growth of plants; and has other drawbacks such as being easily washed away by rainfall due to its poor water resistance, so it is currently hardly used in practice. Furthermore, in order to improve water resistance, foaming agents such as polyvinyl alcohol, emulsified asphalt or wax emulsion, and low-molecular surfactants, and gelling agents for polyvinyl alcohol when the pH becomes alkaline are used. By spraying an aqueous foam containing inorganic substances such as potassium titanium oxalate, fibrous potassium titanate, etc. on the soil surface and simultaneously spraying ammonia gas, the pH can be made alkaline.
A method of immobilizing an aqueous foam by gelling it simultaneously with spraying was proposed. Although this method is an extremely effective soil covering method, it requires the use of large amounts of foaming agents that are harmful to plants, and the stability of the foam is poor, so it is necessary to gel the aqueous foam at the same time as spraying. Therefore, it is necessary to inject ammonia gas at the same time, which makes the construction method extremely troublesome and poses safety problems. In fact, ammonia gas is toxic to humans;
Workers must wear gas masks.

In view of the above-mentioned circumstances of conventionally known soil covering methods, the present inventors have pursued a soil covering method that is easy to apply and has excellent water resistance and does not leave any harmful components harmful to plant growth. The present invention has been achieved. That is, the present invention is characterized in that a fluid composition containing highly foamable polyvinyl alcohol containing a hydrophobic group having 6 or more carbon atoms, a water-insoluble polyisocyanate, air bubbles, and water as essential components is sprayed onto the soil surface. This method is superior to conventional methods in terms of ease of construction, durability, and no residue pollution.

According to the method of the present invention, by changing the composition and mixing conditions, it is possible to control the gelation time from several tens of minutes to several hours, and furthermore, it is possible to control the strength, elastic modulus, etc. of the gelled product. Because its physical properties can be varied over a wide range, it can be advantageously used for a wide range of soil covering purposes, including heat retention, slope stabilization, seed establishment, weed growth prevention, and waterproofing. Furthermore, even though it is a two-component mixture type, it has a long pot life after mixing and can control gelation time, so it is easy to work on site and is free from water-soluble harmful substances. It has the advantage of not containing Furthermore, because the membrane that makes up the foam is made of a special highly foamable polyvinyl alcohol resin, it is extremely stable and retains the foam for a long time on the soil surface. contains a large amount of air bubbles, and the foamed layer thus formed can exhibit good heat retention. In addition, this coating layer has relatively low strength and can be easily destroyed by human power or the power of a cultivator.
Another advantage is that it does not get in the way much even if it is not removed. In other words, it can serve as a substitute for bedding.

The highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms used in the present invention includes vinyl acetate and an ethylenically unsaturated monomer having a hydrophobic group having 6 or more carbon atoms in its side chain. A saponified copolymer of , a common acetal of polyvinyl alcohol with a long-chain aldehyde, etc. can be used. As the ethylenically unsaturated monomer having a hydrophobic group having 6 or more carbon atoms in the side chain, dodecene-1,
α-olefins such as octadecene-1, long chain alkyl vinyl ethers such as lauryl vinyl ether and stearyl vinyl ether, vinyl lauric ester, vinyl stearate, 1,1,3,3-tetramethylvinyl acetate,
Examples include higher fatty acid vinyl esters such as 2,2,4,4-tetramethylvaleric acid vinyl ester and other saturated branched fatty acid vinyl esters. Among these, a saturated branched fatty acid vinyl ester having 10 carbon atoms (trade name: VeoVa-10, manufactured by Ciel Chemical Co., Ltd.) is preferred from the viewpoint of ease of copolymerization and stability in saponification. Examples of long-chain aliphatic aldehydes having 6 or more carbon atoms include lauryl aldehyde,
Examples include stearyl aldehyde. moreover,
The highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms used in the present invention includes, in addition to a hydroxyl group, a residual acetic acid group, and a hydrophobic group having 6 or more carbon atoms, a carboxyl group, a sulfone group, a tertiary Alternatively, it is permitted to contain a hydrophilic group such as a quaternary amine group or an amide group. Polyvinyl alcohol resins containing hydrophobic groups having 6 or more carbon atoms tend to lose water solubility when the content of hydrophobic groups exceeds 1 mol%, so in order to compensate for this, It is necessary to simultaneously introduce a polar group with stronger hydrophilicity.
As copolymerization components for this purpose, monomer components containing ionic groups such as carboxyl groups, sulfone groups, cationic groups, etc. are particularly suitable.
In order to maintain water solubility, especially water solubility at room temperature, and provide high aqueous solution viscosity and high foamability, the preferred amount of hydrophilic groups to be introduced is X/5 when the content of hydrophobic groups is X mol%. ~X/2 mol%. Further, the preferred range of X is 0.1 to 5, more preferably 0.3 to 3. Although it is possible to select an even larger X, it is not preferred for economic reasons. The polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms used in the present invention has high foamability and high aqueous solution viscosity. The reason for this is presumed to be that hydrophobic groups associate with each other in an aqueous solution. This phenomenon is similar to micelle formation of surfactants. The association between hydrophobic groups also greatly contributes to foam stabilization. High viscosity is also believed to have an advantageous effect on foam stabilization. On the other hand, the water-insoluble polyisocyanate used in the present invention must exist as fine emulsion particles in the composition, and if the particle size is large, it tends to float and separate, destabilizing the foam, and also reduces crosslinking efficiency. There is. The highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms used in the present invention has high surface activity and high emulsifying power, so it can stably emulsify and disperse water-insoluble polyisocyanate as a fine emulsion. It is possible to obtain high crosslinking efficiency. The saponification degree of the acetate vinyl ester moiety of the highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms used in the present invention is within the range of water solubility.
It can be selected arbitrarily, but from the viewpoint of film flexibility and cold water solubility, it is preferably lower, and is usually 95% or less, more preferably 80 mol% or less. The degree of polymerization is desirably 500 or more, more preferably 1000 or more from the viewpoint of thickening effect and foam stability.

Instead of using a highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms (hereinafter referred to as a hydrophobic group-modified polyvinyl alcohol resin) alone, a hydrophobic group-modified polyvinyl alcohol resin as described above can be used. It is also possible to use an aqueous emulsion containing.

Examples of aqueous emulsions containing hydrophobic group-modified polyvinyl alcohol resins as described above include vinyl acetate, ethylene-vinyl acetate, acrylic, styrene-butadiene, styrene-isoprene, styrene-acrylic, vinyl chloride,
Vinylidene chloride, chloroprene, bituminous,
Aqueous emulsions such as natural rubber-based emulsions containing polyvinyl alcohol-based resins containing hydrophobic groups having 6 or more carbon atoms as components of emulsifiers, stabilizers, thickeners, and additives as described above. , both can be used. More preferably, the aqueous emulsion contains a functional group having an active hydrogen that can react with isocyanate, such as -OH group, -COOH group, -NH ₂ group, etc. in the emulsion resin component.

As water-insoluble polyisocyanates, aromatic diisocyanates such as m- and p-phenylene diisocyanate, 4-t-butyl-m-phenylene diisocyanate, 4-methoxy-m-
Phenylene 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,
Many isocyanate compounds are included, such as hexamethylene diisocyanate, decamethylene diisocyanate, 2,3-dimethyltetramethylene diisocyanate, and alicyclic polyisocyanates such as hydroxide methylene diisocyanate and isophorone diisocyanate.
From the viewpoint of stability and economy, liquid crude diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate are preferably used. Furthermore, blocks, adducts, etc. of these polyisocyanate compounds can also be used as they have reactivity with hydroxyl groups. Further, in the case of a polyisocyanate that is solid at room temperature, it is desirable to liquefy it by mixing it with a water-insoluble inert liquid diluent.

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 isocyanate reaction, while acidic substances such as phosphoric acid, hexametaphosphoric acid, sulfuric acid, etc. It is a negative catalyst that suppresses When using crude diphenylmethane diisocyanate as the water-insoluble polyisocyanate, it is better to use a negative catalyst such as hexametaphosphoric acid to keep the PH of the composition on the acidic side, which will increase gelation time and improve field workability. This is generally convenient.

The concentration of the hydrophobic group-modified 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 0.05 to 5% by weight. It is appropriate to select from the range of %. When using the hydrophobic group-modified polyvinyl alcohol resin of the present invention, a water-resistant film can be formed with a much smaller amount added than when using ordinary polyvinyl alcohol.
It also has the advantage that the amount of water-insoluble polyisocyanate used can be greatly reduced.

In the present invention, the amount of water-insoluble polyisocyanate contained in the fluid composition also needs to be appropriately increased or decreased depending on the type of isocyanate, purpose of use, conditions of use, etc., but generally polyvinyl alcohol An appropriate range is 1 to 1000% by weight, preferably 10 to 200% by weight, based on the amount of the system resin present.

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.

It has been found that the polyvinyl alcohol resin of the present invention containing a hydrophobic group having 6 or more carbon atoms is extremely useful for such purposes.

The hydrophobic group-modified polyvinyl alcohol resin used in the present invention has high emulsifying power and extremely high aqueous solution viscosity. For example, the viscosity of a 4% aqueous solution at 20°C is less than 100 c.ps even with a degree of polymerization of 2400 in the case of ordinary PVA, but in the case of hydrophobic group-modified polyvinyl alcohol, it is easy to obtain an aqueous solution with a viscosity of 100 c.ps or more. can be obtained. Therefore, although it is not particularly necessary to use a thickener in combination, there is no problem in using it in combination.

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. However, the best thickening and filling agent is air bubbles. The air bubbles reduce the density of the system and improve the "riding" of the flowable composition on the soil surface, while also reducing the fluidity of the system. Furthermore, the covering film formed on the soil surface after gelation and drying has a cellular structure, which significantly increases the volume, thereby increasing the covering efficiency and increasing the heat insulation effect. The bubble component is usually air, but may also be nitrogen, carbon dioxide, oxygen gas, etc. As described above, air bubbles are an extremely important essential component in the fluid composition of the present invention. Another essential ingredient is water. The role of water is not only as a solvent for the hydrophobic group-modified polyvinyl alcohol resin, but also as a dispersion medium for the water-insoluble polyisocyanate and air bubbles.

As described above, the four components of the highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms, water-insoluble polyisocyanate, air bubbles, and water are the fluid composition for soil coating of the present invention. It is an essential component of a porous hydrating material in the composition;
For example, it is effective to incorporate foam, straw waste, wood flour, cotton waste, grain, pulp, water absorbency, resin, etc.

In preparing the compounded composition used in the present invention, first, an aqueous solution containing the hydrophobic group-modified polyvinyl alcohol resin is prepared, and then, if necessary, thickeners and fillers dispersed or diluted in water are added. The recommended method is to mix fertilizers and other additives with stirring, and finally add water-insoluble polyisocyanate along with a water-insoluble diluent if necessary, and then thoroughly mix and mix, but this method is not limited to this method. It's not a thing. Next, whisk the mixture. For whipping, any conventionally known method can be used. Examples include a method of blowing fine air bubbles into a liquid mixture, a method of introducing a composition capable of generating gas into a liquid, a method of entraining air into a liquid by strong stirring, and dividing it into even finer particles. . The simplest method is to mechanically disperse air into the liquid.

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 inexpensive.
Furthermore, the gelation time can be delayed by selecting a highly hydrophobic polyisocyanate, or by dissolving the polyisocyanate in a highly hydrophobic water-insoluble diluent and then adding it to water. be able to. Examples of water-insoluble diluents include toluene, xylene, chlorinated paraffin, dioctyl adipate, and the like.

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 (for example, known emulsifying dispersants) and stirring conditions that make the dispersed particles of isocyanate finer.

In particular, when it is desired to enhance the effect of raising the temperature of the soil or when it is desired to suppress the growth of weeds that germinate due to light, it is suitable to add black substances such as carbon fine particles. More specifically, it is effective to add 5 to 200% of commercially available carbon black to the equivalent weight of the hydrophobic group-modified polyvinyl alcohol resin. Furthermore, clay, titanium dioxide,
Although it is possible to change the light transmittance by adding an inorganic pigment such as calcium carbonate, care must be taken so as not to inhibit the foamability. In order to control light transmittance, ultraviolet absorbers, coloring pigments, etc. can also be added. In addition, fungicides, insecticides,
Pesticides such as herbicides can also be added.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. Unless otherwise indicated in each example, parts mean parts by weight.

Example 1 Vinyl acetate 97 mol%, branched saturated branched fatty acid vinyl ester having 10 carbon atoms (trade name: VeoVa
-10, Ciel Chemical Co., Ltd.) 2 mol%, itaconic acid 1
Degree of saponification obtained by saponifying a terpolymer containing mol% in methanol using caustic soda as a catalyst
One part of hydrophobically modified polyvinyl alcohol having a viscosity of 88 mol % and a 4% aqueous solution at 20°C of 550 centipoise was put into 25 parts of water and dissolved with stirring at room temperature to prepare an aqueous polyvinyl alcohol solution. Next, liquid crude diphenylmethane diisocyanate (Millionate MR manufactured by Nippon Polyurethane Co., Ltd.
-100) and 0.5 part of chlorinated paraffin were added, and stirring was continued to obtain a yellow-white emulsion. Next, stirring was continued while increasing the stirring speed to entrain air into the liquid, and the volume was expanded to about 5 times. The dispersion composition still had sufficient fluidity and could be pumped. While this fluid composition is being pumped, it is combined with a high-pressure air line in the coating of the liquid-feeding hose, and then passed through a line mixer to further split the air bubbles, resulting in approximately 12 times the foaming at the hose outlet. A flowable composition with multiple ratios was obtained. After spraying the fluid composition on the soil surface (slope) to a thickness of about 3 to 5 cm, it was left to stand, and after 3 hours, water was sprayed at about 20 m/m in a shower, but no water was formed on the soil surface. The foamed layer was slightly destroyed and mostly maintained the form of an open foamed film. After 3 days, a nearly dry film was formed, but it was observed that it still had a foamed structure. I took a portion of this film and put it into water, but
It did not disintegrate for three months.

Example 2 Hydrophobic group-modified polyvinyl alcohol with a degree of saponification of 99 mol% and a 4% aqueous solution viscosity of 210 centipoise at 20°C obtained by saponifying a copolymer consisting of 99.2 mol% of vinyl acetate and 0.8 mol% of lauryl vinyl ether. was dissolved in water to create a 10% aqueous solution. At this time, heating by steam injection was required. 700ml of the 10% aqueous solution was put into a tank of a special vehicle equipped with a horizontal stirring blade pump with a capacity of 5000ml, and headed for the outdoor test site.On the way, the tank was filled with river water to bring the volume to 4500ml. After arriving at the site, while rotating the stirring blade, add 5 kg of carbon black, 1 kg of hexametaphosphoric acid, and 40 kg of crude diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., Millionate MR-200).
was added and stirring was continued for 20 minutes. Next, the liquid is started to be fed through the pump, sent to the centrifugal foam generator, and air pressurized by the air compressor is sent from another line, and the two are mixed to achieve a fluidity with a foaming ratio of 8 to 10 times. A foam was sprayed onto the soil surface to form a covering layer. A covering layer was applied in a circular pattern around young trees in an orchard (Unshu mandarin oranges), covering almost all of one foot. The cover layer withstood wind, rain and summer sunlight, and was extremely effective in inhibiting weed growth for about 200 days. The number of days to inhibit weed growth is approximately 30 days with a mower.
Since the herbicide spraying time is 60 days, it can be seen that the method of the present invention is an extremely labor-saving and effective method.

Claims (1)

[Claims] 1. Spraying a fluid composition containing a highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms, a water-insoluble polyisocyanate, air bubbles, and water as essential components on the soil surface. A soil covering method characterized by: 2 The highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms contains at least 200
The soil coating method according to claim 1, wherein the soil coating method has a viscosity of 4% aqueous solution of centipoise. 3. The soil coating method according to claim 1, wherein the highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms is soluble at room temperature. 4 Highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms is obtained by saponifying a copolymer of an ethylenically unsaturated monomer, an ethylenically unsaturated carboxylic acid compound, and vinyl acetate. The soil covering method according to claim 1, which is a soluble soil covering method. 5 A highly foamable polyvinyl alcohol resin containing a hydrophobic group having 6 or more carbon atoms is obtained by saponifying a copolymer of a branched fatty acid vinyl ester having 10 or more carbon atoms, an ethylenically unsaturated dicarboxylic acid, and a vinyl acetate. 4% of room temperature solubility at 20℃
The soil coating method according to claim 1, wherein the aqueous solution viscosity is 200 centipoise or more.