JPH09302339A - Water retaining agent for soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water retaining agent for soil having approximately no change in volume in water supply and drainage, having no defects of causing soil clogging in wetting and cracking in drying in spite of the possession of large water retaining power and excellent characteristics of supplying and draining water corresponding to the change in temperature. SOLUTION: This water retaining agent is obtained by blending heat-sensitive water absorbing polymer powder consisting essentially of N-isopropylacrylamide, having particle diameters in shrinkage smaller than the void of a porous material with the porous material and water at a temperature equal to or higher than the temperature-sensing point of the hat-sensitive water absorbing polymer, then swelling the heat-sensitive water absorbing polymer by lowering the temperature to a temperature equal to or lower than the temperature-sensing point and removing the excessive water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil water retention agent used for modifying vegetation soil.

[0002]

2. Description of the Related Art When a plant is to be grown on a soil which tends to lack water such as a soil for slope greening, a soil for urban space, a planter and a pot, it is effective to add a water retention agent to the soil.
One of the water retention agents is a temperature-sensitive water absorbent polymer. The temperature-sensitive water-absorbent polymer absorbs and swells water at a temperature below a specific set temperature (hereinafter referred to as the temperature-sensitive point), and shrinks and drains at temperatures above the temperature-sensitive point, so water is supplied and drained according to changes in the ground temperature. It becomes an effective soil water retention agent and has an excellent function as a water retention agent for vegetation soil.

However, when the raw powder of the temperature-sensitive water-absorbing polymer is mixed with soil, there are problems that the gel blocks the soil space during swelling and the soil surface rises as the swelling occurs.
Also, mixing powder with soil is difficult to work.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems and is excellent in workability and, when mixed with water and absorbed into the soil, does not block the soil space and causes a change in the volume of the soil. The purpose of the present invention is to obtain a soil water retention agent that supplies and drains water according to changes in temperature, which is rare.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the problems can be solved by combining a temperature-sensitive water-absorbing polymer with a porous material, and completed the present invention. Came to do. That is, the present invention, a temperature-sensitive water-absorbing polymer powder having a particle size at the time of shrinkage smaller than the diameter of the pores of the porous material is mixed with the porous material and water at a temperature not lower than the temperature-sensitive point of the temperature-sensitive water-absorbing polymer, and then It is a soil water retention agent comprising a composite material of a temperature-sensitive water-absorbent polymer and a porous material, which is obtained by lowering the temperature below the temperature-sensitive point to swell the temperature-sensitive water-absorbent polymer and then removing excess water.

The temperature-sensitive water-absorbing polymer used in the present invention is obtained by crosslinking a polymer having a lower critical solution temperature in water. Specifically, the main component is an N-alkyl-substituted acrylamide monomer such as N-isopropyl (meth) acrylamide, N-n-propyl (meth) acrylamide, N, N-diethylacrylamide, acryloylpiperidine, acryloylpyrrolidine, etc. It is obtained by adding a polyfunctional monomer and polymerizing. Other vinyl monomers may be copolymerized, if necessary, such as controlling the temperature-sensitive point and improving the rate of water absorption. Examples of vinyl monomers to be copolymerized include (meth) acrylic acid and salts thereof, (meth) acrylamide, obutylacrylamide, diacetone acrylamide, and the like.

The porous material used in the present invention must be a hard material having pressure resistance and the pores must be continuous pores. Specifically, an inorganic porous material such as pearlite, pumice, vermiculite, A plant-derived natural organic substance porous body such as a buckwheat rattle or a monigar and a synthetic resin porous body such as an open-cell type foamed steel can be used.

The particle size of the temperature-sensitive water-absorbent polymer must be smaller than the pore size of the porous material in the non-swelling state. If the particle size of the temperature-sensitive water-absorbent polymer in the non-swollen state is larger than the pore size of the porous material, it does not enter the pores of the porous material and does not make sense of complexation. It creates a meaningless space. In reality, both the porous material and the temperature-sensitive water-absorbing polymer have a pore size distribution and a particle size distribution, so it is difficult to define a strict quantitative definition. However, the temperature-sensitive water-absorbing polymer generally has an average particle size of 1 of the average pore size of the porous material. / 3 or less is suitable. For example, when pearlite perlite having an average pore diameter of 100 μm is used as the porous body, a temperature-sensitive water-absorbing polymer having a particle diameter of 33 μm or less is used.

When the temperature-sensitive water-absorbing polymer having such a particle size is mixed with the porous material in the presence of water at a temperature above the temperature-sensing point (non-swelling state), the temperature-sensitive water-absorbing polymer is mixed with water in the pores of the porous material. Break into. The amount of water used at this time is not particularly limited, but is preferably 50 to 500 times the temperature-sensitive water-absorbing polymer and 1 to 2 times the total pore volume of the porous material. After mixing, by lowering the temperature below the temperature-sensitive point of the temperature-sensitive water-absorbent polymer, the temperature-sensitive water-absorbent polymer swells, the particle size becomes 4 to 6 times, and at the same time adhesive contact is generated, which makes it difficult to desorb from the porous material. Become. The desired soil water retention agent can be obtained by physically removing excess water from the complex thus obtained by filtration or the like.

The soil water retention agent of the present invention exhibits a high water retention capacity at low temperatures, and most of it is discharged as water that can be used by plants at a temperature above the temperature sensitive point. In other words, when mixed in soil, it shows an increase in the water retention capacity of the theoretical water absorption capacity of the temperature-sensitive water-absorbing polymer. In addition, it does not block the space of the soil or change the volume of the soil. Furthermore, since this soil water retention agent also retains and drains the fertilizer component dissolved in water, the effective utilization rate of fertilizer is also improved. The present invention will be specifically described below with reference to examples.

[0011]

Example 1 Method for Producing Soil Water Retaining Agent (Temperature-Sensitive Water-Absorbing Polymer / Perlite Composite Material) Temperature-sensitive water-absorbing polymer having a particle size of 20 μm or less (polymerized cross-linked body containing N-isopropylacrylamide as a main component; temperature-sensitive point) (30 ° C.) 10 g was dispersed in 40 ° C. warm water 2ι. This was poured into a container containing 1 pearl pearlite (average pore size 100 μm) while stirring, and then the system temperature was adjusted to 2
It was cooled to 0 ° C. and left for 2 hours. The solid content was collected by filtration and dried to obtain a temperature-sensitive water-absorbing polymer / perlite composite material (1ι).

Example 2 Measurement of Water Retaining Amount of 300 cc of the temperature-sensitive water-absorbent polymer / perlite composite material produced in Example 1 was put into a cylindrical container equipped with a bottoming cock.
Up to (65 g), 500 cc of water at 20 ° C. was added and left for 1 hour. During this period, the surface of the composite material did not rise and the increase in volume was hardly observed. Then, the bottom venting cock was opened, the water was drained, the mixture was allowed to stand overnight, and the weight was measured. Water retention capacity is 175g / 30
It was 0 cc (580 g / ι).

Comparative Example 1 The same test as in Example 2 was carried out except that perlite alone was used instead of the temperature-sensitive water-absorbing polymer / perlite composite material. As a result, the water retention capacity is 180g / 300cc (38
It was 3 g / ι).

Comparative Example 2 As a temperature-sensitive water-absorbing polymer, N having a particle size of 100 to 500 μm was used.
-A thermosensitive water-absorbing polymer in the same manner as in Example 1 except that 3 g of a polymerized crosslinked product containing isopropylacrylamide as a main component (temperature-sensitive point 30 ° C) and 300 cc of perlite (average pore size 100 µm) as a porous material were used. / Perlite composite material was obtained. When the same test as in Example 2 was conducted using the obtained composite material, the surface of the composite material was elevated and the volume was 80 when water was absorbed in 500 cc of water at 20 ° C.
It was confirmed that cc increased. The weight increase after standing overnight after drainage was 220 g (water retention capacity 517 g /
ι).

Example 3 Mixing Test with Soil 500 cc (350 g) of dried black soil was mixed with the temperature-sensitive water-absorbing polymer / perlite composite material 500 c obtained in Example 1.
c (105 g) were mixed. This was placed in a container equipped with a bottoming cock, 1 water was added, and the mixture was allowed to stand for 2 hours. Then, the bottoming cock was opened to drain excess water. The total soil weight at this stage was 880 g and the water content was 425 g / ι. At this time, the container remained unchanged at 1000 cc. Next, raise the environmental temperature to 35 ° C and supplement the water discharged from the bottom for 5 hours,
The weight was calculated. The weight of water discharged was 165 g.

Comparative Example 3 Black soil 1ι (700 g) was used in place of the mixture of the black soil of Example 3 and the temperature-sensitive water-absorbing polymer / perlite composite material.
The same test as in Example 3 was performed, except that 5 g of the temperature-sensitive water-absorbent polymer used in Example 1 was mixed and used. The total soil weight was 1050 g and the water retention capacity was 350 g / ι. At this point the volume of soil increased to 1120 cc. The amount of wastewater at elevated temperature was 90 g.

Comparative Example 4 Instead of the mixture of the black soil of Example 3 and the temperature-sensitive water-absorbing polymer / perlite composite material, 1 soil of black soil (700 g) was used.
The same test as in Example 3 was performed, except that was used alone. The water retention capacity was 260 g / ι, and no drainage of elevated temperature was observed.

[0018]

EFFECTS OF THE INVENTION The soil water retention agent of the present invention has a large water retention ability and has excellent characteristics of supplying and discharging water in response to temperature changes, while there is almost no volume change during water supply and drainage, and when wet. It is an excellent soil water retention agent that does not cause defects such as clogging the soil or cracking when dried, and can greatly save water management of soil in the vegetation field.

Claims (3)

[Claims] 1. A temperature-sensitive water-absorbent polymer powder having a particle size at the time of shrinkage smaller than the pore diameter of the porous material is mixed with the porous material and water at a temperature equal to or higher than the temperature-sensitive point of the temperature-sensitive water-absorbent polymer, and then, A soil water retention agent comprising a composite material of a temperature-sensitive water-absorbing polymer and a porous material, which is obtained by swelling the temperature-sensitive water-absorbing polymer by lowering the temperature to a temperature below the temperature-sensitive point and then removing excess water. 2. The soil water retention agent according to claim 1, wherein the temperature-sensitive water-absorbing polymer is a polymerized cross-linked product containing N-isopropylacrylamide as a main component. 3. The soil water retention agent according to claim 1, wherein the porous material is pearlite perlite.