JP7498029B2 - Agricultural shading agent - Google Patents

Description

The present invention relates to an agricultural light-shielding agent.

When plants grown in greenhouses or tunnels using the thermal energy of sunlight are exposed to strong light such as the strong sunlight of summer, there is a high risk of the leaves burning and other phenomena occurring. Such phenomena may have a negative impact on plant growth. As a method for suppressing the negative impact of strong light on plant growth, a method of covering the outer surface of sheet materials such as vinyl sheets that make up greenhouses for greenhouse cultivation or tunnels for tunnel cultivation with a shading net (hereinafter referred to as the "shading net covering method") and a method of spraying an agricultural shading agent on the outer surface of the sheet material to form a shading layer that can block light to a certain extent (hereinafter referred to as the "shading surface forming method") have been implemented.

In heat-retaining cultivation, the shading net covering method and shading surface formation method are usually implemented during specific periods when strong sunlight is pouring down on the earth's surface (around July to September in Japan). They are not implemented outside of these periods. Rather, during periods other than when strong sunlight is pouring down on the earth's surface, it is considered important to take in light efficiently in order to actively utilize the thermal energy of the sun's rays.

On the other hand, the shading net covering method has problems in that the process of covering with the shading net is complicated, and the shading net itself is expensive, resulting in high preparation costs. In addition, there is also the problem that the installed shading net is not easy to remove when the implementation is completed.

Due to these problems, the shading surface formation method has been widely used as a method for suppressing the adverse effects of strong light on plant growth. In the shading surface formation method, an agricultural shading agent for forming a shading layer is used that is composed of a composition containing water, a water-based binder, and a colorant. White calcium carbonate is mainly used as the colorant, and recently, one using titanium oxide is also known (Patent Document 1).
The shading layer formed using such agricultural shading agents has a white color derived from the coloring agent, and reduces the amount of light that passes through the sheet material and reaches the plants to a certain level, thereby suppressing the adverse effects of strong light on plant growth.

However, even in this case, the light-shielding layer needs to be removed when the light-shielding property is no longer required, and the removal of the light-shielding layer requires the use of a specific remover, which is not an easy task.
Therefore, the present applicant is developing an agricultural light-shielding agent that can gradually remove the light-shielding layer from the sheet material naturally by rainfall without using a specific remover (Patent Document 2). If the light-shielding layer is naturally removed by rainfall too early or too late, it affects plant growth, so it is difficult to adjust the light-shielding layer to remain on the surface of the sheet material for a certain period of time when light-shielding properties are required, and further improvements are required.

Agricultural shading agents are sold and stored in a concentrated state, and when spraying them on sheet materials, they are generally diluted with water or other liquids. For example, the agricultural shading agent and dilution water are added to a container and stirred with a mixer or other device until the colorant is uniformly dispersed, after which the shading agent is sprayed on the surface of the sheet material to form a shading layer.

JP 2015-6154 A JP 2020-68740 A

However, the agricultural shade agent after dilution had low viscosity, and the coloring agent settled, resulting in poor dispersibility. Therefore, it was necessary to dilute the agent on-site so that it could be sprayed immediately after dilution. However, if there was no water source on-site, water had to be transported separately, making the dilution work on-site cumbersome.
In addition, if the colorant settles when left unattended, it must be stirred again, which limits the working time from dilution to spraying. Furthermore, if the colorant is left in a settled state, it will aggregate and become difficult to mix, and even if it is stirred again, it may take a long time to disperse the colorant uniformly.
In particular, when a sprayer is used to apply the agricultural shading agent, the viscosity of the agricultural shading agent must be lower than when it is applied with a brush or roll, and there is an increasing need for agricultural shading agents that have excellent dispersibility so that the colorant does not settle out easily.

The present invention aims to provide an agricultural light-shielding agent that does not require dilution when used, has excellent dispersibility of coloring agents, and can be formed so that the light-shielding layer formed by spraying on the outer surface of the sheet material will exist while the light-shielding effect is required, but will naturally wash away due to rainfall or other factors after that period has passed, causing the light-shielding effect to be lost.

The present invention relates to an agricultural light-shielding agent comprising water, an aqueous binder, a colorant, and a dispersant,
the aqueous binder is an aqueous resin emulsion having an acid value of 30 to 300, and the aqueous resin emulsion has a resin solid content of 0.1% by mass to 15% by mass relative to 100% by mass of the agricultural light-shielding agent;
the colorant contains calcium carbonate and/or titanium oxide, and the amount of the colorant added is 1% by mass or more and 50% by mass or less with respect to 100% by mass of the agricultural light-shielding agent;
The viscosity measured in accordance with JIS Z 8803 is 10 mPa·s or more and 100 mPa·s or less at room temperature.
Also, the amount of the dispersant added is preferably 0.01% by mass or more and 5% by mass or less relative to 100% by mass of the agricultural light-shielding agent.
The present invention also relates to an agricultural shade agent that can be sprayed with a sprayer.

The present invention provides an agricultural light-shielding agent that does not require dilution when used, has excellent dispersibility of coloring agents, and can be formed so that the light-shielding layer formed by spraying on the outer surface of the sheet material exists while the light-shielding effect is required, but after that period has passed, it naturally washes away due to rainfall or the like and loses its light-shielding effect.

The agricultural light-shielding agent of the present invention contains water, an aqueous binder, a colorant, and a dispersant.

The aqueous binder of the present invention is an aqueous resin emulsion having an acid value of 30 or more and 300 or less. Examples of resins constituting the aqueous resin emulsion include acrylic resins, urethane resins, vinyl resins, styrene resins, acrylic-styrene copolymer resins, polyester resins, and epoxy resins, but water-dispersible acrylic resins, water-dispersible styrene resins, and water-dispersible acrylic-styrene copolymer resins are preferably selected.

The acid value can be determined by potassium hydroxide titration using phenolphthalein or similar as an indicator.

In general, the acid value of a resin is a value related to the average number of free carboxylic acid groups per polymer chain that constitutes the resin. The higher the acid value of a resin, the less water resistant the resin is, i.e., the more easily it dissolves in water. The lower the acid value of a resin, the less water soluble the resin is. In consideration of this, the aqueous binder contained in the agricultural light-shielding agent is an aqueous resin emulsion, and the acid value of the resin component that constitutes the aqueous resin emulsion is set to 30 to 300, so that the aqueous binder can be effectively mixed in water, and when the agricultural light-shielding agent is sprayed on the outer surface of a specified sheet material to form a light-shielding layer and the outer surface side of the sheet material becomes a light-shielding surface, the light-shielding surface can be made to have water resistance for a certain period of time.

If the aqueous resin emulsion is an emulsion of a resin with an acid value of less than 30, the light-shielding layer is unlikely to wash away naturally due to rainfall, etc., and there is a risk that the light-shielding properties will continue even after the period when light-shielding properties are needed has passed. If the aqueous resin emulsion is an emulsion of a resin with an acid value of more than 300, the water resistance of the light-shielding layer will decrease and the light-shielding layer will be more likely to wash away from the sheet material due to rain and wind, and there is a risk that the light-shielding layer will not be able to be maintained for a specified period of time.

In the aqueous resin emulsion state, the average particle size of the resin is preferably 0.01 μm or more and 0.5 μm or less. If it is within this range, it can be maintained in a dispersed state as an emulsion in the agricultural shading agent even in the viscosity range of the present invention described later.

The amount of the aqueous binder added to the agricultural light-shielding agent is 0.1% by mass or more and 15% by mass or less of the resin solid content of the aqueous resin emulsion relative to 100% by mass of the agricultural light-shielding agent. If the resin solid content of the aqueous resin emulsion in the agricultural light-shielding agent is less than 0.1% by mass, the colorant will not be sufficiently fixed to the surface of the sheet material, and the light-shielding layer will easily flow off the sheet material due to rain and wind, and the light-shielding layer may not be able to be maintained for a specified period of time. If it exceeds 15% by mass, the viscosity of the agricultural light-shielding agent will be high, the workability of spraying will decrease, and it may take a long time to dry after spraying, and it will be difficult to naturally wash off due to rainfall, etc. The specified period during which the light-shielding property of the present invention is required may be set appropriately depending on the crop and region, but is, for example, a period of about three months from July to September in Japan when strong sunlight falls on the ground. However, the present invention does not exclude cases where light-shielding property is required only for a shorter period of time.

In the present invention, white calcium carbonate and/or titanium oxide are used as the colorant.
The average particle size of the colorant of the present invention is preferably from 0.01 μm to 1 μm.
If the average particle size of the colorant exceeds 1 μm, it tends to settle in the agricultural light-shielding agent, and once it settles, the colorant aggregates and becomes difficult to mix, and when sprayed using a sprayer, it may clog and the spraying workability may be deteriorated. Also, if the average particle size of the colorant is less than 0.01 μm, it is difficult to exhibit light-shielding properties, and there is a risk that the desired light-shielding properties will not be realized.

In the present invention, the amount of the colorant added is from 1% by mass to 50% by mass based on 100% by mass of the agricultural light-shielding agent.
If the content is less than 1% by mass, sufficient light-shielding properties will not be obtained, and if the content exceeds 50% by mass, the viscosity of the agricultural light-shielding agent will be high, making it difficult to spray without diluting it, and there is a risk of poor spraying workability.
In addition, if the amount of colorant added is 1% by mass or more and 30% by mass or less relative to 100% by mass of the agricultural shading agent, it is preferable because this provides an agricultural shading agent with a viscosity suitable for application using a sprayer or the like.

In the present invention, a colorant that has been subjected to a surface treatment may be used as necessary.
For example, examples include methods of modification with special polymers, fatty acids, sulfonic acids, aluminum compounds, zinc compounds, silica, etc. When titanium oxide is subjected to a surface hydrophilization treatment in this way, the wettability of the surface is improved, making it easier to form a dispersed state in water.

In the present invention, colorants other than calcium carbonate and titanium oxide may be contained. Examples include talc, clay, silica, mica, and barium sulfate, and colorants other than white may also be used.

The dispersant of the present invention is used to physically or chemically adsorb to the surface of the colorant and disperse the colorant in water by a protective colloid or electrostatic repulsion in water. Various surfactants such as commonly used cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants and polymeric surfactants can be used, and one or a mixture of two or more types may be used.

Examples of anionic surfactants include sulfate ester salts, sulfonate salts, phosphate ester salts, and fatty acid salts, and more specifically, alkali metal alkyl sulfates such as sodium dodecyl sulfate and potassium dodecyl sulfate; ammonium alkyl sulfates such as ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate, sodium sulfocinoate, and alkali metal salts of sulfonated paraffin; alkyl sulfonates such as ammonium salts of sulfonated paraffin; sodium laurate, triethanolamine oleate, fatty acid salts of triethanolamine abietate, sodium dodecylbenzenesulfonate, and alkylaryl sulfonates such as alkali metal sulfates of alkaliphenol hydroxyethylene; higher alkylnaphthalenesulfonates, naphthalenesulfonic acid formalin condensates, dialkyl sulfosuccinates, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkylaryl sulfate salts, sodium propenyl-2-ethylhexylbenzenesulfosuccinate, (meth) Examples include sulfate esters of polyoxyethylene acrylate, ammonium sulfate salts of polyoxyethylene alkylpropenyl ether, phosphate esters of polyoxyethylene (meth)acrylate, sodium laurate, triethanolamine oleate, and fatty acid salts of triethanolamine abietate.

Cationic surfactants include alkylpyridinyl chloride, alkylammonium chloride, etc.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid monoglycerides such as glycerol monolaurate, polyoxyethylene oxypropylene copolymers, and condensation products of ethylene oxide with fatty acid amines, amides, or acids.

Examples of amphoteric surfactants include lauryl betaine, stearyl betaine, and lauryl dimethylamine oxide.

Examples of polymer surfactants include polyvinyl alcohol, sodium poly(meth)acrylate, potassium poly(meth)acrylate, ammonium poly(meth)acrylate, polyhydroxyethyl(meth)acrylate, polyhydroxypropyl(meth)acrylate, copolymers of two or more of the polymerizable monomers that are the structural units of these polymers, or copolymers with other monomers. In particular, polycarboxylate-type anionic surfactants, such as alkali metal salts of polycarboxylates such as poly(meth)acrylic acid and acrylic acid-olefin copolymers, such as sodium and potassium salts, and alkaline earth metal salts of magnesium and calcium salts, are preferred because they are easy to disperse calcium carbonate and titanium oxide.

In the present invention, the amount of the dispersant added is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the agricultural light-shielding agent.
If the content is less than 0.01% by mass, the colorant is likely to settle, and even if stirred, the dispersibility of the colorant is poor, so that once it settles, the colorant aggregates and becomes difficult to mix, which may result in poor spraying workability. If the content exceeds 5% by mass, although the dispersibility of the colorant is excellent, the fixation of the colorant to the surface of the sheet material is hindered, and the light-shielding layer is likely to flow off the sheet material due to rain and wind, and the light-shielding layer may not be maintained for a certain period of time. The dispersibility of the agricultural light-shielding agent of the present invention will be described later.

In addition to the above-mentioned components, various additives may be added to the agricultural shading agent as necessary within the range that does not impair the effects of the present invention. Examples of additives include hardeners, preservatives, thickeners, viscosity reducers, antioxidants, UV absorbers, light stabilizers, alcohols, etc.

The agricultural light-shielding agent of the present invention has a viscosity of 10 mPa·s or more and 100 mPa·s or less at room temperature, as measured using a single cylindrical rotational viscometer (Brookfield B-type rotational viscometer) in accordance with JIS Z 8803. If the viscosity is within this range, the agricultural light-shielding agent does not require dilution when used, and can be simply stirred and sprayed directly onto the surface of the sheet material to form a light-shielding layer.

The dilution process when using the agricultural light-shielding agent refers to the process of diluting the agricultural light-shielding agent stock solution with water to an appropriate ratio to prepare a diluted solution when the agricultural light-shielding agent is sprayed to form a light-shielding layer, and this diluted solution is usually used as the agricultural light-shielding agent to be sprayed. If the coloring agent is uniformly dispersed in the diluted agricultural light-shielding agent, a light-shielding layer without uneven coating can be formed by spraying the light-shielding agent on the surface of the sheet material.
However, the viscosity of the agricultural shade agent after dilution is low, and the coloring agent is prone to settling. Therefore, if the coloring agent is left to settle, it must be stirred again, which limits the work time from dilution to spraying. Furthermore, if the coloring agent is left in a settled state, it will aggregate and become difficult to mix, and even if it is stirred again, it may take time to disperse the coloring agent uniformly. Moreover, the dilution work must be done on-site, which is a cumbersome work in itself.

In contrast, the agricultural shading agent of the present invention contains water, an aqueous binder, a dispersant, and a colorant, and even though its viscosity, measured in accordance with JIS Z 8803, is relatively low at room temperature, ranging from 10 mPa·s to 100 mPa·s, it has excellent dispersibility of the colorant, so that an agricultural shading agent in which the colorant is uniformly dispersed can be easily obtained by simply stirring without the need for dilution.

Here, in the present invention, excellent dispersibility of the colorant means that the colorant can be easily restored to a uniformly dispersed state simply by stirring even after settling.
Specifically, 200 mL of the agricultural light-shielding agent is placed in a 250 mL plastic bottle, left to stand at room temperature for one week, and then the container is shaken. If the number of times the colorant reaches a dispersed state is less than 20, the container is evaluated as having excellent dispersibility. The colorant is considered to be dispersed when the plastic bottle is turned upside down and the colorant remaining at the bottom of the bottle is visually observed, with no colorant remaining at the bottom being visible.

The agricultural shading agent of the present invention can be used by being sprayed on the outer surface of a sheet material (sometimes called an agricultural sheet material) that can be used in heat-retaining cultivation. The method of spraying the agricultural shading agent is not particularly limited, and various sprayers such as a manual sprayer, an engine-powered sprayer, a motor-powered sprayer, and a sprayer equipped with a pump or a dolly can be used. In addition to spraying, a coating method using a brush or a roll can also be used.
Since the agricultural shading agent of the present invention has a relatively low viscosity, the shading agent may be repelled by the surface of the sheet when applied by a coating method, and therefore it is suitable for use with various sprayers since it is easy to form a uniform shading layer.

Agricultural sheet materials that can be used for heat retention cultivation are preferably selected from vinyl chloride resin films, olefin resin films, fluorine-based films, etc., and may have a single-layer structure or a multi-layer structure. The agricultural shading agent of the present invention can be used on glass surfaces as well as agricultural sheet materials.

Examples of vinyl chloride resins include polyvinyl chloride homopolymers and vinyl chloride copolymers such as vinyl chloride-vinyl acetate copolymers, vinyl chloride-ethylene copolymers, vinyl chloride-propylene copolymers, vinyl chloride-isobutylene copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-styrene-maleic anhydride terpolymers, copolymers of vinyl chloride with alkyl, cycloalkyl, or alkylmaleimide, vinyl chloride-styrene-acrylonitrile copolymers, vinyl chloride-butadiene copolymers, vinyl chloride-isoprene copolymers, vinyl chloride-vinylidene chloride-vinyl acetate terpolymers, vinyl chloride-acrylic acid ester copolymers, vinyl chloride-maleic acid ester copolymers, vinyl chloride-methacrylic acid ester copolymers, vinyl chloride-acrylonitrile copolymers, and vinyl chloride-urethane copolymers.

Olefin-based resins include polyethylenes such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polyethylene polymerized using a metallocene catalyst; polypropylenes such as random-polymerized polypropylene, block-polymerized polypropylene, isotactic polypropylene, and syndiotactic polypropylene; and ethylene-based copolymers such as ethylene-vinyl acetate, ethylene-acrylic acid, ethylene-acrylic acid ester, ethylene-methacrylic acid, and ethylene-methacrylic acid ester. These can be used alone or in mixtures.

The amount of agricultural shading agent to be applied to a sheet material that can be used in heat retention cultivation is not particularly limited, but the amount of agricultural shading agent applied is preferably an amount such that the solid content of the agricultural shading agent is 0.1 g/ ^m2 or more and 10 g/ ^m2 or less. If the amount is less than 0.1 g/ ^m2 , it may be difficult to obtain a sufficient shading effect. If the amount exceeds 10 g/ ^m2 , there is a risk of loss due to dripping of the agricultural shading agent from the sheet material during the spraying operation.

When the agricultural light-shielding agent is sprayed onto the sheet material in this manner, a light-shielding layer is formed on the surface of the sheet material, and the surface of the sheet material becomes a light-shielding surface. The light-shielding layer may be a structure in which many fine granular structures are attached to the surface of the sheet material, or may be formed in the form of a film on the surface of the sheet material.

The shading layer of the present invention has high shading properties immediately after the agricultural shading agent is sprayed, and while it maintains its shading properties while it is necessary, it naturally washes off due to rainfall when it is no longer necessary, eliminating the need to remove it with an alkaline remover as in the past. In the present invention, the period during which shading properties are necessary is the period during which the crop is exposed to strong sunlight in the summer, which is assumed to be about three months, but does not exclude cases where shading properties are required only for a shorter period of time. For example, there are cases where after the hottest period has passed, another crop is planted without a shading layer, where an agricultural shading agent has been sprayed once but the shading layer has fallen off due to heavy rain and the layer is sprayed again, where it is known that a standard three-month type of agricultural shading agent will not fall off in areas with little rain, and where the temperature has risen just before harvest and shading is desired for about one month until harvest.

In this way, in order to maintain the light-shielding property while it is necessary, and to allow it to naturally wash off with rainfall when it is no longer necessary, the present invention contains water, a water-based binder, a colorant, and a dispersant, and the water-based binder uses a water-based resin emulsion with an acid value of 30 to 300, and the resin solid content of the water-based resin emulsion and the amount of the colorant added are adjusted within a specific range. The light-shielding property can also be maintained for a specified period by adjusting the amount of the dispersant added within a specific range. Moreover, since the viscosity of the present invention measured in accordance with JIS Z 8803 is 10 mPa·s to 100 mPa·s at room temperature, it is possible to easily obtain an agricultural light-shielding agent in which the colorant is uniformly dispersed, without the need for dilution, by simply stirring.

The present invention will be described in more detail below using examples and comparative examples. The present invention may not be limited to these examples.

[Examples 1 to 7, Comparative Examples 1 to 6]
As shown in Tables 1 and 2, each raw material constituting the agricultural light-shielding agent was weighed and stirred with a stirrer for 10 minutes to mix the agricultural light-shielding agent, and the viscosity was measured at room temperature using a single cylindrical rotational viscometer (Brookfield B-type rotational viscometer) in accordance with JIS Z 8803. Note that the unit of the blending amount of the raw materials constituting the agricultural light-shielding agent in the tables is mass %, and in the column for aqueous resin emulsion, the blending amount of the aqueous resin emulsion and the value obtained by converting the amount of resin solids in the aqueous resin emulsion into the blending amount of resin solids relative to 100 mass % of the agricultural light-shielding agent are shown in parentheses.
Next, a vinyl chloride resin agricultural film (manufactured by Achilles, product name "Sky Sky") having a length of 200 mm, width of 200 mm, and thickness of 0.1 mm was used, and 0.6 cc of each agricultural shading agent was sprayed once from a position 20 cm away from the surface using a mister (sprayer), and dried for one day to obtain a test film with a shading layer formed on the surface. At this time, each agricultural shading agent was used in the evaluation of [dispersibility] described below, and was used in a state in which the coloring agent was dispersed. Note that since the evaluation of [dispersibility] of Comparative Example 1 was x, and since the agricultural shading agent could not be sprayed in Comparative Example 3, the evaluation of shading property was not performed.

The raw materials that make up agricultural shading agents are as follows:
[Water-based resin emulsion]
Water-dispersible acrylic copolymer (manufactured by BASF, product name "JONCRYL PDX-7700", resin acid value: 60, resin solid content: 48% by mass)
[Coloring Agent]
Calcium carbonate (manufactured by Maruo Calcium Co., Ltd., product name "Luminous", average particle size: 0.1 μm)
Titanium oxide (manufactured by Teika Corporation, product name "JR600A", average particle size: 0.25 μm)
[Dispersant]
Polycarboxylic acid type anionic surfactant (manufactured by ADEKA CORPORATION, product name "ADEKACOL W-193")

The following evaluations were carried out for each of the agricultural shading agents and test films obtained. The results are shown in Tables 1 and 2.

[Dispersibility]
200 mL of each agricultural light-shielding agent was placed in a 250 mL plastic bottle, left to stand at room temperature for one week, and then the container was shaken to count the number of times the colorant reached a dispersed state, and evaluated according to the following criteria. The colorant was considered to be dispersed when the plastic bottle was turned upside down and the colorant remaining at the bottom of the bottle was visually observed, with no colorant remaining at the bottom being visible.

○ The number of times the colorant was shaken until it was dispersed was less than 20 times. × The number of times the colorant was shaken until it was dispersed was 20 or more times.

[Light blocking effect: immediately after spraying]
The obtained test film was attached to a table inclined at 30 degrees with respect to the installation surface with the light-shielding surface facing up, and 6 ml/ ^cm2 of water (2400 ml since the area of the test film is 400 ^cm2 ) was sprayed over the entire surface of the test film using a watering can. Thereafter, the test film and an agricultural film (blank film) made of polyvinyl chloride resin without a light-shielding layer were irradiated with artificial light source light (xenon light, 500 W) from the thickness direction, and the illuminance of the transmitted light was measured using an illuminometer (Mother Tools, product name "LX-105"). The transmitted light intensity (B) measured for the test film relative to the transmitted light intensity (A) measured for the blank film, that is, the value (%) of (1-B/A) x 100 (referred to as the light-shielding rate (%)), was specified. In the present invention, a light-shielding rate of about 10 to 50% immediately after spraying of the agricultural light-shielding agent is judged to be practical.

[Light blocking ability: after 3 months, after 6 months]
The obtained test film was attached to a table inclined at 30 degrees from the installation surface with the shading surface facing up, and left outdoors (an environment where it is not exposed to natural rain and is exposed to sufficient sunlight). At this time, 6 ml/ ^cm2 of water (2400 ml because the area of the test film is 400 ^cm2 ) was sprayed on the entire surface of the test film using a watering can every week, and this was repeated for 6 months, and the shading rate was measured after 3 months and 6 months. This was evaluated by assuming an annual precipitation of 3000 mm, based on the annual precipitation of 3659 mm in Kochi Prefecture, which has a high precipitation rate, in 2014, and by referring to this, the shading layer was washed away by natural rainfall.
In the present invention, it is determined that the light-shielding layer is prone to fall off if the light-shielding rate after six months is 65% or less of the rate immediately after application, and it is preferably 50% or less.

As can be seen from Table 1, the agricultural shading agents of Examples 1 to 7 have excellent dispersibility of colorants and do not require dilution when used, and can be directly sprayed onto the surface of a sheet material to form a shading layer.
In addition, in the present invention, the light-shielding rate after six months was 65% or less of the rate immediately after application, and it was found that a light-shielding layer that easily fell off was obtained. In Example 4, the light-shielding rate after three months was as low as 6%, but a product was obtained that could be used even in a short period of one month in which the light-shielding properties were maintained.

As can be seen from Table 2, since Comparative Example 1 did not contain a dispersant, the colorant aggregated and became difficult to mix, and even when stirred again, it took a long time to disperse the colorant uniformly.
In Comparative Example 2, the amount of colorant was too small to obtain the desired light-shielding properties, and when the amount of colorant was too much as in Comparative Example 3, the viscosity of the agricultural light-shielding agent was too high to allow spraying.
Comparative Example 4 is an example that does not contain a water-based binder, and the light-shielding layer was not fixed on the film, and the desired light-shielding properties were not obtained.
In Comparative Example 5, the amount of the aqueous binder added was large and the viscosity was high, and although the coating was able to be spread, the light-shielding layer was difficult to remove even after six months had passed.
In Comparative Example 6, even though the amount of dispersant added was increased compared to Comparative Example 5, the viscosity was high and the light-shielding layer was not easily removed even after 6 months.

Claims (2)

An agricultural light-shielding agent comprising water, an aqueous binder, a colorant, and a dispersant,
the aqueous binder is an aqueous resin emulsion having an acid value of 30 to 300, and the aqueous resin emulsion has a resin solid content of 0.1% by mass to 15% by mass relative to 100% by mass of the agricultural light-shielding agent;
the colorant contains calcium carbonate and/or titanium oxide, and the amount of the colorant added is 1% by mass or more and 50% by mass or less with respect to 100% by mass of the agricultural light-shielding agent;
the dispersant contains a polycarboxylic acid type anionic surfactant, and the amount of the dispersant added is 0.01% by mass or more and 5% by mass or less relative to 100% by mass of the agricultural light-shielding agent;
1. An agricultural light-shielding agent, characterized in that the viscosity measured in accordance with JIS Z 8803 at room temperature is 10 mPa·s or more and 100 mPa·s or less. 2. The agricultural shade agent according to claim 1 , which can be applied by a sprayer.