JP5510035B2 - Rice husk water retention mat for planting or planting and medium structure for planting or planting - Google Patents

Description

The present invention relates to a rice husk water retention mat for planting or greening and a culture medium structure for planting or greening. More specifically, the present invention relates to a rice husk water retention mat with improved water absorption speed used for rooftop greening, wall greening, greening of ground such as parks, indoor plant cultivation (hereinafter referred to as planting) and the like.

  Conventionally, when greening a rooftop or a park, greening was performed by laying a land of about 20 cm thick on the ground and planting a vegetation plant such as a lawn on the ground. . However, this method may cause problems such as outflow of the soil due to rain, poor drainage, and drying of vegetation plants. In particular, in rooftop greening, it is required to reduce the weight of the vegetation medium structure.

In order to solve such problems, a water-impervious sheet is laid on the ground, a fibrous plant-growing mat is laid on the ground, a lawn is planted on the plant-growing mat, and a water supply device on the water-impermeable sheet There has been proposed a vegetation medium structure provided with (for example, Patent Document 1). However, this vegetation medium structure has the disadvantage that the facilities are large and the cost required for the greening work increases.
Furthermore, in order to solve these problems, a soil layer is provided on the water retaining layer obtained by solidifying the rice husk with a urethane-based binder (for example, Patent Document 2) or a poval-based binder (for example, Patent Document 3). A method of vegetation is proposed. The water-retaining layer bonded with the urethane-based binder has a strength that does not dent even when stepped on the lawn.

Japanese Patent Laid-Open No. 9-308370 JP 2003-325037 A Special table 2010-504319

However, when the rice husk is entirely covered with the described urethane binder, the rice husk itself is hydrophobic, and the urethane binder described above is also hydrophobic. It takes a long time for water to soak into the water retention layer. Therefore, there is not enough water supply to the plants planted on the soil layer above the water reservoir, and it is necessary to supply water often in the early stage after the water reservoir is installed, and the problem is that the drainage is not sufficient when it rains. There is. In addition, when water is supplied to plants by immersing the bottom part of the water retaining layer in the water layer and sucking water by capillary action, the force of sucking water is weak because the hydrophobicity of the fixed rice husks is strong. Supply is not enough. In addition, the rice husk mat formed of a poval binder has a good water absorption rate, but has a problem that the mat is weak and easily collapses when stepped on.
The present invention relates to a rice husk water retention mat formed of a reactive urethane-based binder, having a strength that does not break or collapse even when stepped on with a foot, and has an improved water absorption rate, and planting using the same Or to provide a greening medium structure.

In view of the above problems, the present inventor, as a result of earnest research, if rice husks are combined with a reactive urethane binder composed of a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene glycol having a molecular weight of 200 to 4000, The present inventors have found that the balance between strength and water absorption speed can be achieved, and have completed the present invention.
The present invention relates to rice husk water retention for planting or greening in which rice husks are bonded with a reactive urethane-based binder composed of a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene glycol having a molecular weight of 200 to 4000, with improved water absorption rate. Matt.
Furthermore, the present invention is characterized in that at least one of poval and cellulose is further added to and bonded to the reactive urethane binder combined above.

The present invention also relates to a medium structure for planting or greening using the above-described rice husk water retaining mat, wherein the medium structure (I) is obtained by superimposing a soil layer in which plants are planted on the rice husk water retaining mat, or a rice husk water retaining mat. This is a medium structure for planting or greening of the medium structure (II) in which a hole is formed in the surface and a water-absorbing carrier is placed therein to plant a plant.
In addition, the present invention is a method for using a rice husk water retention mat for planting or greening, wherein the lower part of the planting or greening medium structure is immersed in an aqueous layer.

According to the present invention, the rice husk is formed by being bonded with a reactive urethane binder (hereinafter sometimes referred to simply as a binder) comprising a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene glycol having a molecular weight of 200 to 4000. The hydrophilicity of the coated film is improved, and the water absorption speed of the rice husk water retention mat is improved. As a result, the rice husk water retention mat sucks up water at the same time and the water retention is improved, so that the water supply to the plant on the rice husk water retention mat is sufficient. That is, the rice husk has a bag-like shape, and the binder does not easily enter the inside of the rice husk when mixed with the binder. This hole becomes a water storage hole, and the water retention amount of the rice husk water retention mat can be increased. In addition, since the formed coating contains polyethylene oxide groups, the hydrophilicity of the coating increases, water approaches the rice husk surface, and water is easily retained in the voids.

Therefore, when water is supplied to the rice husk water retaining mat from the top or the bottom, the water absorption speed of the rice husk water retaining mat is improved. There is no need to do it.
Even if you dig a hole in the surface of the rice husk water retention mat, put a water-absorbing carrier there, plant a plant and immerse the rice husk water-retaining mat in the lower water layer, the water absorption speed is high. Water supply to the sex carrier is sufficient, and a rice husk water retention mat for planting or greening suitable for plant growth can be obtained. Thereby, even when there is no rainfall for a long period of time, it is not necessary to replenish water separately, and even when it is raining, drainage is good and vegetation management becomes easy.
Moreover, since the mat is lightweight because it is formed of rice husk, the entire rice husk water retaining mat can be reduced in weight.

In addition, the rice husks are bonded with a reactive urethane binder and the space between the rice husks serves as a cushion. There is no sense of incongruity with ordinary lawn even if you walk with the customer layer. Therefore, the rice husk water retention mat is suitable for greening where there is no soil. Moreover, since it has great strength, durability is also good.

According to the present invention, since the reactive urethane-based binder is a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene oxide adduct having two or more hydroxyl groups, the reaction occurs very quickly and the bond becomes strong, A rice husk water retention mat with high strength is produced. Further, the rice husk water retaining mat has a water absorption rate that can be put to practical use by improving the water absorption rate.

  According to the present invention, since at least one of poval and cellulose is further added to react with the reactive urethane-based binder, the isocyanate group of the isocyanate group-terminated urethane prepolymer is bonded to the hydroxyl group of poval or cellulose, and poval or cellulose Is incorporated into the rice husk coating. Poval or cellulose has many hydroxyl groups, and the remaining hydroxyl groups that are not bonded have high hydrophilicity, so that the water absorption rate of the rice husk water retention mat is further improved.

According to the present invention, the rice husk water retaining mat has a high water absorption rate and is excellent in strength. Therefore, the rice husk water retaining mat has a medium structure (I) in which a customer soil layer planted with plants is stacked on the rice husk water retaining mat, or a rice husk water retaining water. A medium structure (II) in which a hole is formed on the surface of the mat and a water-absorbing carrier such as soil is placed therein to plant a plant, so that water can permeate the inside quickly and water supply to the plant is sufficient. It is possible to drain water even when it rains. In addition, since it is lightweight, it can be used for rooftop greening, wall greening, and the like.
According to the present invention, the rice husk retention mat has a high water absorption speed, so that even if the lower part of the medium structure for planting or greening is immersed in an aqueous layer, water can be quickly sucked up and supplied to the plant. . If an aqueous layer is provided under the medium structure, it is often unnecessary to spray water.

It is sectional drawing of the culture medium structure (I) which concerns on one Embodiment of this invention. It is sectional drawing of the culture medium structure (II) which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

The rice husk in the present invention refers to the hull of glutinous rice, which can be used as a by-product of natural products in rice cultivation. The rice husk contains, for example, about 28.7% by weight of cellulose, about 21.6% by weight of lignin, about 17.3% by weight of silica, and about 14.4% by weight of pentosan, and contains a large amount of fiber components. You may mix | blend some extenders with this rice husk. Examples of the bulking agent include sawdust and buckwheat. Moreover, an inorganic extender may be sufficient. The content of the extender is preferably 10% by weight or less.

  Examples of the reactive urethane-based binder include a two-component type reactive curable binder and a one-component type moisture curable binder. The reaction curable binder is a binder that is reacted by mixing two liquids such as polyol and polyisocyanate. Known polyols such as polyether polyols and polyester polyols can be used as polyols, and 2,4′-diphenylmethane diisocyanate (2,4′-MDI) and 4,4′-diphenylmethane can be used as polyisocyanates. In addition to aromatic polyfunctional isocyanates such as diisocyanate (4,4'-MDI), tolylene diisocyanate (TDI), and naphthalene diisocyanate, known polyisocyanates such as aliphatic polyfunctional isocyanates such as hexamethylene diisocyanate and isophorone diisocyanate are used. it can.

The moisture curable binder is mainly composed of a urethane prepolymer obtained by reacting a polyol and an isocyanate compound so as to leave an isocyanate group at the terminal, and a conventionally known isocyanate group-terminated urethane prepolymer can be used. As the reactive urethane-based binder, it is preferable to use a moisture-curable urethane-based binder from the viewpoint of ease of use.
In the moisture curable urethane-based binder, the equivalent ratio NCO / OH between the isocyanate group contained in the polyisocyanate and the hydroxyl group contained in the polyol is preferably 2-6. Within this range, a rice husk water retention mat that reacts sufficiently and has excellent strength can be obtained.

The polyethylene oxide group (hereinafter sometimes referred to as PEO group) refers to a product obtained by addition polymerization of ethylene oxide. Preferably, it is a block addition of 3 mol or more of ethylene oxide, more preferably a block addition of 10 mol or more. Moreover, what added the block to 100 mol or less is preferable, and what added the block to 50 mol or less is especially preferable. The rice husk water retaining mat is hydrophilic when it is added with a block of 3 mol or more, and the water absorption rate can be improved. If it is added with a block of 10 mol or more, the water absorption rate is sufficiently high. If the block is added to 100 mol or less, the strength of the rice husk water retaining mat is high, and if it is added to the block to 50 mol or less, the mat is further excellent in strength. Further, random addition products of ethylene oxide and propylene oxide, which are water-soluble, are considered to partially satisfy the above-described conditions, and therefore are included in the addition polymer of ethylene oxide in the present invention. The amount of the PEO group is preferably 5% or more and 70% or less by weight with respect to the entire binder (solid content). If it is 5% or more, the effect of increasing the water absorption speed of the rice husk water retention mat can be confirmed, and if it is 70% or less, the strength of the formed rice husk water retention mat is sufficiently large, and it may be broken or collapse even if it is stepped on from above. Absent. More preferably, it is 15% or more and 50% or less by weight.

The PEO group may be present in a binder, and is a polyethylene oxide adduct that is used in combination with an isocyanate-terminated urethane prepolymer and reacts with an isocyanate group, that is, a polyethylene oxide adduct having two or more hydroxyl groups. May be. In the present invention, a polyethylene oxide adduct having two or more hydroxyl groups used in combination with an isocyanate-terminated urethane prepolymer is also included in the reactive urethane-based binder of the present invention. Even if an isocyanate-terminated urethane prepolymer having a PEO group introduced is not specially prepared, it is blended with an isocyanate-terminated urethane prepolymer that does not contain a PEO group and heated together with rice husk to react and be incorporated into the film to bind the rice husk. Can do.

As the isocyanate-terminated urethane prepolymer, a commercially available moisture-curable urethane adhesive is also effective as the urethane binder in the present invention. However, since such commercially available binders often do not contain a PEO group, it is preferable to use a polyethylene oxide adduct having two or more hydroxyl groups as described above. Examples of such polyethylene oxide adducts having two or more hydroxyl groups include water; low molecular polyols such as ethylene glycol, propylene glycol, and hexylene glycol; and polyamines obtained by addition polymerization of ethylene oxide to low molecular amines such as ammonia and dimethylamine. Ethylene oxide adducts can be used. As the polyethylene oxide adduct having two or more hydroxyl groups, a divalent or trivalent polyol is preferable. More preferred is a diol. Particularly preferred is polyethylene glycol. When polyethylene glycol is used in combination, a rice husk water retention mat that is more likely to react and is more firmly bonded. The molecular weight of the polyol containing such a PEO group is preferably 150 to 4000. When it is 150 or more, the reaction with the isocyanate group is sufficiently fast and the water absorption rate is high, and when it is 4000 or less, the strength of the rice husk water retaining mat is high. In particular, polyethylene glycol having a molecular weight of 236 to 1000 has a quicker reaction with an isocyanate-terminated prepolymer and a higher strength rice husk water retention mat. Further, the water absorption rate may be further increased by blending a monovalent polyethylene oxide adduct with a bivalent to trivalent polyethylene oxide adduct.

Specifically as said commercially available urethane type binder, "UR-143", "UR-145", "UR-20" (a brand name, the product made by Mizushima Science Promotion Co., Ltd.); "Diabond DA3154H" "Diabond DU296" (trade name, manufactured by Nogawa Chemical Co., Ltd.); "Dino Grip 303" (trade name, manufactured by No Tape Industrial Co., Ltd.); "Cement U" (trade name, manufactured by Tajima Co., Ltd.); “-100”, “Cemedine UM-200”, “Cemedine UM-300” (trade name, manufactured by Cemedine Co., Ltd.); “Panel Bond KU” (trade name, manufactured by Konishi Co., Ltd.); “Samprene BD-55” (commercial product) Name, manufactured by Sanyo Chemical Industries, Ltd.).

The blending ratio of rice husk and urethane-based binder is not particularly limited, but the binder is preferably mixed in an amount of 20% to 100% by weight with respect to the rice husk in a dry state. If it is 20% or more, there is no inconvenience that rice husks are sufficiently bonded and the rice husk water retention mat is weak in strength. When it is 100% or less, it is economical. More preferably, the amount of binder is 30-60%. Within this range, the rice husk water retention mat is further balanced in water absorption speed and strength.

A rice husk water retaining mat obtained by further combining at least one of poval and cellulose with the reactive urethane binder combined as described above is preferable. Although it will not specifically limit if it is poval or a cellulose, As a cellulose, carboxymethylcellulose (CMC), a hydroxy alkoxy cellulose, a hydroxyalkyl cellulose, starch etc. are mentioned, for example. If the rice husks are combined only with a combination of poval or cellulose and an isocyanate-terminated urethane prepolymer, sufficient strength does not come out, but a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene oxide adduct having two or more hydroxyl groups can be combined with poval or The rice husk water retention mat to which at least one of cellulose is added and bonded exhibits sufficient strength and also has a sufficiently high water absorption rate.
The blending amount of at least one of poval or cellulose is preferably 5 to 30% by weight with respect to the reactive urethane binder. If it is 5% or more, an effect of improving the water absorption rate is recognized, and if it is 30% or less, the strength is not hindered.

The method for producing the rice husk water retaining mat of the present invention is not particularly limited, but it is preferable to prepare a kneaded product of rice husk and the reactive urethane binder and then heat it, and if necessary, add water vapor to cure. . The temperature is preferably 50 to 150 ° C, more preferably 100 to 130 ° C. The time is preferably 1 to 10 hours. If it is within the range of this temperature and time, a sufficiently strong reaction and a strong mat can be obtained.

The isocyanate group reacts with the hydroxyl group to form a urethane bond to be linked. In addition, the isocyanate group is converted into an amino group and carbon dioxide by water, and the carbon dioxide is released into the atmosphere, and the amino group reacts with another isocyanate group to form a urea bond and connect. When using a moisture curable urethane-based binder and not using a polyol, water vapor is essential, but when using a polyol, water vapor is not essential. However, it is preferable to react with water vapor simultaneously with the reaction of the isocyanate group and the polyol or after the reaction to eliminate the remaining isocyanate group.

The rice husk water retention mat thus obtained has an improved water absorption speed and has a strength that does not break or collapse even when stepped on. The water absorption rate is preferably within 5 hours, more preferably within 3 hours, and particularly preferably within 2 hours in the following water absorption rate test method. When the water absorption speed is within 5 hours, the rice husk water retaining mat absorbs water quickly, and the surface of the rice husk water retaining mat with a medium structure (I) in which the soil layer planted with plants is stacked is provided with water absorption therein. Even if it is used as a medium structure (II) in which a plant is planted with a sex carrier, water can be sufficiently supplied to the plant without often watering.
(Test method for water absorption rate)
The obtained rice husk water retaining mat is cut into 2 cm square pieces and floated on tap water at room temperature (15-25 ° C.). At first, about half of the cubic piece sinks in water, and the time until the rice husk water retaining mat absorbs water and 80% of the total volume sinks in water is measured by observing with the naked eye every 30 minutes. In order to average the variation depending on the location, it is preferable to average the measured values at the three locations.

The strength of the rice husk water retention mat is expressed by bending strength. The bending strength (average of three locations) measured by preparing a test piece according to JIS K 6911 is preferably 5 MPa or more, more preferably 10 MPa or more. Even if it is stepped on when the bending strength is 5 MPa or more, it does not break or collapse. The density is preferably 0.1 to 0.5 g / m ³ .

The rice husk water retention mat of the present invention is preferably manufactured in a sheet shape or a block shape. The size and thickness of the sheet or block are not particularly limited, and are determined as necessary and in consideration of production. The thickness is preferably 2 to 20 cm and the width is preferably 30 cm to 1 m.

Further, the present invention provides a structure (I) in which a soil layer in which plants are planted is stacked on the rice husk water retaining mat obtained as described above, or a hole is formed in the surface of the rice husk water retaining mat so as to absorb water. This is a medium structure for planting or greening the structure (II) in which a plant is planted with a carrier.

In the case of the structure of (I) above, “custom soil layer” refers to a layer where vegetation is planted, such as black soil, red ball soil, Kanuma soil, river sand, Fuji sand, humus soil, peat moss, vermiculite, perlite, Asama sand, Or what mixed fertilizer with these is used, However, It is preferable to use a material with high water permeability. Furthermore, in order to increase the porosity of the soil layer and maintain the shape of the soil layer, a fiber agent may be mixed into the soil layer. In particular, when using the medium structure in rooftop greening where lightening is required, it is required to have good water retention, drainage, fertilizer, air permeability, etc., so humus soil and fertilizer components should be added to perlite. It is preferable to use lightweight artificial soil mixed and stirred.
It is preferable to use low grass plants such as Japanese turf, western turf, alfalfa, sedum, etc. for this soil layer.

With this configuration, the roots of the lawn are intricately spread over the soil layer, so that the shape of the soil layer is stabilized and scattering and outflow of the soil within the soil layer are prevented. Moreover, the water retention of a customer soil layer improves by planting a lawn in a customer soil layer.

In addition, the rice husk water retaining mat is in the form of a sheet or block, and at the same time, because the rice husk is used for the rice husk water retaining mat, the greening mat is extremely lightweight, and the rice husk water retaining mat can be easily stored, transported and laid. In addition, since it is lightweight, it is not necessary to reinforce the building even when a rice husk water retaining mat is laid on the roof or roof of the building, and rooftop greening can be easily performed. By transporting the rice husk water retaining mat to the construction site and laying the sheet or block-shaped rice husk water retaining mat, the vegetation medium structure can be easily constructed on the upper surface of the ground. The rice husk water retention mat can be used by being laminated.
A planting plant is grown in advance on the customer soil layer on the surface of the rice husk water retaining mat at a location other than the construction site, and the rice husk water retaining mat on which the planted plant has grown sufficiently is transported to the construction site and laid. Therefore, the ground on the construction site can be greened in a very short period of time.

During rainfall, the water poured into the top surface of the soil layer penetrates the soil layer, and the rice husk retention mat contains many rice husks with voids. At the same time as it is stored, the water absorption speed is high, so that water can penetrate quickly and can be discharged from the lower part of the rice husk water retaining mat.
A water shielding sheet may or may not be provided under the rice husk water retaining mat. Usually, it is preferable to lay a water-impervious sheet, place a rice husk water retaining mat thereon, and further provide a guest soil layer. This water shielding sheet is made of water-impermeable rubber, vinyl chloride sheet, polypropylene sheet or the like.

  Moreover, the culture medium structure of (II) makes a hole in a part of rice husk water retention mat, puts a water absorbing carrier in it, and grows a plant. The size and depth of the hole are not limited and are determined by the method of use. For example, the size of the hole is, for example, 1 cm to 1 m, and the depth is preferably smaller than the thickness of the rice husk water retaining mat. The rice husk water retention mat may be laminated. When the lower part of this structure is immersed in the water layer, the water absorption speed of the rice husk retention mat is improved, so the water in the water layer rises to or near the water-absorbent carrier in the hole. Water can be supplied to the plant. You may mix | blend fertilizer etc. with a water layer.

The water-absorbing carrier is not particularly limited as long as it is generally used as a water-absorbing substance suitable for plant growth. For example, inorganic and / or organic substance powders, porous bodies, pellets, fibers And one or more water-insoluble solid substances selected from the group consisting of foams can be used. As inorganic substances, inorganic powders (soil, sand, fly ash, diatomaceous earth, clay, talc, kaolin, bentonite, dolomite, calcium carbonate, alumina, etc.); inorganic fibers (rock wool, glass fibers, etc.); inorganic porous materials [ Filton (porous ceramic, kuntan), calcined vermiculite, pumice, volcanic ash, zeolite, shirasu balloon, etc.]; inorganic foam (perlite, etc.). Preferred is soil.

Organic substances include organic powders [coconut shells, rice straw, peanut shells, mandarin shells, wood chips, wood flour, dried coconut powder; organic fibers [natural fibers (cellulosic materials (cotton, sawdust, straw, etc.) And others, grass charcoal, wool, etc.), artificial fibers (cellulosic, such as rayon, acetate, etc.), pulp (mechanical pulp (pulverized wood pulp, asprund method, etc.), chemical pulp (sulfite pulp, soda pulp, sulfuric acid) Salt pulp, nitrate pulp, chlorine pulp, etc.), semi-chemical pulp, recycled pulp (for example, mechanically crushed or pulverized paper made by making pulp once, or recycled waste paper pulp that is mechanically crushed or pulverized waste paper) Etc.), other waste materials (such as waste materials from the production of paper diapers), etc.]; Activated carbon, etc.]; organic foam [cereals, hydrophilic synthetic resin or rubber foam (polyvinyl acetal sponge, rubber sponge, urethane foam, etc.)]; organic pellet [rubber and synthetic resin pellets, etc.] .

The above water-absorbing carriers may be used alone or in combination of two or more as required. Among these, preferred are inorganic powder, inorganic porous body, inorganic foam, organic powder, organic fiber, and organic foam, and particularly preferred are inorganic powder, inorganic porous body, inorganic foam, and organic powder. Body, organic fiber. The form is not particularly limited.

As described above, since the plant vegetated on the soil layer or the water-absorbing carrier in the hole is always supplied with an appropriate amount of water, a medium structure with good plant growth can be provided. In addition, rice husk is produced as a by-product in rice cultivation, so that resources can be effectively used and purchased at a very low cost. Therefore, the medium structures (I) and (II) can be produced at a low price.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, it is not limited to this.

(Production Example 1 of isocyanate-terminated urethane prepolymer)
In a 5 L planetary mixer, “Takelac P-21” (trade name, bifunctional polypropylene glycol having a molecular weight of 2000, manufactured by Takeda Pharmaceutical Co., Ltd.) 500 parts by mass, “Takelac P-31” (trade name, molecular weight 3000) was dehydrated in advance. 100 parts by mass of trifunctional polypropylene glycol Takeda Pharmaceutical Co., Ltd.), 200 parts by mass of “Adeka New Ace F7-67” (trade name, bifunctional polyester polyol having a molecular weight of 2000, manufactured by Asahi Denka Kogyo Co., Ltd.) 591 parts by mass of “Lupranate MI” (trade name, a mixture of 4,4-MDI and 2,4′-MDI, manufactured by BASF Japan Ltd.) was added, and urethanization reaction was performed at 90 ° C. for 4 hours. The urethane reaction conditions at this time were an NCO content of 10% and an NCO / OH ratio of 4.8. After cooling to room temperature, 10 parts by mass of “U-CAT2041” (trade name, bis (2,6-dimethylmorpholinoethyl) ether, manufactured by San Apro) was added to obtain an isocyanate-terminated urethane prepolymer A.

Example 1
Into a 3 L mixing vessel, 600 g of rice husk, 300 g of the isocyanate-terminated urethane prepolymer A obtained in Production Example 1 above, “PEG 300” (polyethylene glycol having a molecular weight of 300, manufactured by Sanyo Kasei Kogyo Co., Ltd.) 100 g and 10 g of water were added and mixed. A kneaded product was obtained. This is placed in a 3 cm deep, 30 cm × 40 cm mold container, lightly pressed, heated at 120-130 ° C. for 3 hours, then blown with water vapor, left to stand at the same temperature for 1 hour, then cooled and taken out. A water retention mat was obtained. The water absorption rate measured by the above water absorption rate test method of this rice husk water retention mat was within 2 hours, and the bending strength was 18 MPa.

(Examples 2-9)
As described in Table 1, a kneaded product was obtained in the same manner as in Example 1 using another polyethylene glycol instead of PEG 300, and further using polyvinyl alcohol or corn starch in the same manner as in Example 1. Thus, the rice husk water retention mats of Examples 2 to 9 were obtained. When polyvinyl alcohol or corn starch was used in combination, the mixture was heated to the melting point or higher and kneaded. Similarly, the results of measuring the water absorption rate and bending strength are shown in Table 1.

(Comparative Examples 1-3)
Moreover, the rice husk water retention mat | matte of the comparative example 1 was obtained like Example 1 except not using "PEG300" in Example 1. FIG. Moreover, the rice husk water-retaining mats of Comparative Examples 2 and 3 were obtained in the same manner as in Examples 5 and 6 except that polyvinyl alcohol and corn starch were not used in Examples 5 and 6. Similarly, the results of measuring the water absorption rate and bending strength are shown in Table 1.

UP-A: Isocyanate-terminated urethane prepolymer A
PEG200: Polyethylene glycol with a molecular weight of 200, manufactured by Sanyo Chemical Industries PEG300: Polyethylene glycol with a molecular weight of 300, manufactured by Sanyo Chemical Industries PEG1000: Polyethylene glycol with a molecular weight of 1000, manufactured by Sanyo Chemical Industries PEG4000: Polyethylene glycol with a molecular weight of 4000, Sanyo Chemical Industries PVA-217E: Polyvinyl alcohol, Kuraray

From Table 1, when rice husks are bonded with a binder having a polyethylene oxide group, a rice husk water retention mat with good bending strength and improved water absorption speed is obtained, and those bonded with polyvinyl alcohol or corn starch with a binder have low bending strength. I understand that.

(Example 10, comparative example 4)
Nine rice husk water retaining mats of Example 1 were arranged on the outdoor concrete to prepare a continuous rice husk water retaining mat of 90 cm × 120 cm. A soil layer with a thickness of 3 cm on which lawns were planted was placed thereon to produce a medium structure of the above structure (I). The cross section is shown in FIG. On the three rice husk water retention mats 1 (indicated by bold lines), there is a customer soil layer 2 in which lawns 3 are planted. Water was thoroughly sprinkled from above. Ten hours later, walking on the rice husk water retention mat did not get drenched, and the drainage was good. Looking at the rice husk water retention mat from the side, it was found that water was absorbed. Also, when the clear sky lasted for 10 days, the lawn was lively without watering.
In addition, using the rice husk water retention mat of Comparative Example 1, a medium structure of the above structure (I) was produced in the same manner, and water was sprayed in the same manner. Ten hours later, when I walked on the rice husk water retention mat, there was a lot of water in the soil and the water was badly drained. Looking at the rice husk water retention mat from the side, it was found that it did not absorb much water. Also, when the clear sky lasted for 10 days, if the water did not sprinkle during that time, the lawn was withered.

(Example 11, Comparative Example 5)
A rice husk water retaining mat having a thickness of 9 cm was produced by stacking the rice husk water retaining mat of Example 1 in three layers. 3cm in diameter from the top of the rice husk water retention mat. Drill a 5cm deep cylindrical hole, put soil in it, plant a small plant, Masaki, make the medium structure of the above structure (II), put water into the aquarium and put the water into the rice husk water retaining mat The lower 1 cm was immersed in water in a water tank container. This cross section is shown in FIG. Rice husk water retaining mat 1 (indicated by a thick line) is placed in three layers, and three cylindrical holes 7 are dug, and soil 8 is put therein, and plant 4 is planted there. This medium structure is put in a water tank container 9 and immersed in water 6, and a portion 9 where water ascends the rice husk water retaining mat 1 and penetrates to the middle is shown by hatching. This was left indoors for 10 days without watering, but the planted plants were not wilted.
Moreover, the culture medium structure of the said structure (II) was similarly produced using the rice husk water retention mat of the comparative example 1, and the lower part 1cm of the rice husk water retention mat was similarly immersed in water. When this was left indoors and left for 10 days without watering, the planted plants withered and withered.

1 Rice husk water retention mat 2 Customer soil layer 3 Lawn 4 Plant 5 Aquarium container 6 Water 7 Hole 8 Soil 9 Portion of water penetration in rice husk water retention mat

Claims (4)

A rice husk water retention mat for planting or greening in which rice husk is bonded with a reactive urethane-based binder composed of a combination of an isocyanate group-terminated urethane prepolymer and a polyethylene glycol having a molecular weight of 200 to 4000, with improved water absorption rate. 2. The rice husk water retaining mat according to claim 1, further comprising at least one of poval and cellulose bonded thereto. A medium structure for planting or greening using the rice husk water retaining mat according to claim 1 or 2 , wherein the rice husk water retaining mat is overlaid with a soil layer in which plants are planted, or the rice husk water retaining mat. A medium structure for planting or greening of the medium structure (II) in which a hole is formed on the surface of the medium and a water-absorbing carrier is placed therein to plant a plant. A method of using a rice husk water retention mat for planting or greening, wherein the lower part of the planting or greening medium structure according to claim 3 is immersed in an aqueous layer.

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