JPS6295138A - Water retention material - Google Patents

Abstract

PURPOSE:To keep high water absorption performance and water retention performance for a long period and to improve air permeability by packing polymer having high water absorption properties into a continuous pore of a porous supporter having the continuous pore and forming a water retention material. CONSTITUTION:A water retention material is formed by packing polymer having high water absorption properties with a dry method or a wet method to the inside of the continuous pores of a porous supporter which has the continuous pores having >=50% porosity and >=50% porosity and >=100mum pore diameter. An organic or an inorganic supporter is used as the porous supporter having the continuous pores and polyurethane foam or the like is shown as the organic supporter and porous ceramic is shown as the inorganic supporter. Polymer dissolving in both of water and a solvent, for example, polyvinyl ethyl ether, polyethylene oxide, etc., are shown as polymer for binding the powder of polymer having high water absorption properties.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a water retaining material that is effective for plant growth in dry areas and areas where irrigation is difficult.

[Conventional technology]

When it comes to greening drylands and agricultural development, problems include lack of irrigation water, high-temperature solar radiation, and temperature differences between day and night, but lack of irrigation water is considered to be the most important problem among these. There is. Irrigation in dry areas in particular is extremely difficult due to the relationship between irrigation water and soil. In other words, water is precious in dry areas, and even if a large amount of water is applied at once, most of it is lost as gravity water because the soil itself lacks water retention. If the water quality is poor, problems such as salt accumulation in the soil also occur. Therefore, in such dry areas, water retaining materials are mixed into the soil, which prevents irrigation water from penetrating deep into the ground and being lost, and allows small amounts of irrigation water to work effectively. I am planning to do so. This allows valuable irrigation water to be retained in the crop root zone and used effectively.
A sufficient effect can be obtained even with a small amount of irrigation water, and when there is a shortage of irrigation water, the water retaining material supplies the retained water to the crop roots to compensate for the lack of water.

As described above, the action of water-retaining materials is particularly important in dry areas, but water-retaining materials are also effective in areas other than such dry areas where shrubs are difficult to grow. In other words, trees in road median strips and green belts between sidewalks and driveways are often left unirrigated except when planted, and they suffer great damage from lack of water during summer droughts. ing. Therefore, when planting these trees, it is possible to prevent the above-mentioned damage during droughts in the summer by adding a water retaining material to the soil.

As described above, water-retaining materials are particularly effective in dry areas and areas where irrigation is difficult, and organic and inorganic water-retaining materials have been developed as this type of water-retaining materials. As the organic water-retaining material, highly water-absorbing polymers such as sodium polyacrylate and polyvinyl alcohol, or mixtures thereof with pulp and clay are used. The characteristic of organic water-retaining materials is their high water absorption capacity, which is 200 to 1000 times their own weight, and because they retain the absorbed water as hydration water, they have long-term water-retention performance. have. However, with organic water-retaining materials, the resin in a state of absorbing water becomes gel-like, exhibiting semi-fluidity due to low gel strength, and may lose its shape.Also, since it does not have air permeability, This has the disadvantage that the ventilation at the roots of the plant deteriorates, causing root rot.

On the other hand, as inorganic water-retaining materials, vermiculite, porous ceramics, perlite, etc. are used, and although their water absorption capacity is not so high, they are characterized by having both water-retaining properties and air permeability. However, since the absorbed water is retained in the voids within the porous body under capillary pressure, it is easy to release the water, but it has the disadvantage that the water retention time is insufficient.

Therefore, it is desired to provide a water-retaining material that eliminates the drawbacks of both organic water-retaining materials and inorganic water-retaining materials and has only the advantages of both.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a water-retaining material that has high water-absorbing ability and long-term water-retaining performance, and also has good air permeability.

[Means for solving problems]

In order to achieve the above object, the water retaining material of the present invention has a structure in which the continuous pores of a porous support having continuous pores are filled with a superabsorbent polymer.

In other words, since the above-mentioned water-retaining material has a porous support filled with a superabsorbent polymer, the porous support itself maintains its own air permeability, and the highly water-absorbing ability of the superabsorbent polymer and its long-term durability. It maintains water retention performance, eliminates the drawbacks of organic water retention materials and inorganic water retention materials, and has well-balanced performance that takes advantage of the strengths of both.

As described above, the water retaining material of the present invention is composed of a porous support having continuous pores and a super absorbent polymer.

Examples of the porous support having continuous pores include organic types and inorganic types. Examples of organic materials include polyurethane foam, and examples of inorganic materials include common porous ceramics. Such a porous support must have continuous pores, and preferably has a porosity of 50% or more. Since the continuous pores of this porous support are filled with a superabsorbent polymer, it is preferable that the continuous pores have a pore diameter of 100 μm or more, and more preferably I
It has a pore diameter of R or more.

When such a porous support having continuous pores with a large pore diameter is used, it has the advantage that it can be filled with a powdered superabsorbent polymer as it is.

The superabsorbent polymer to be filled into the continuous pores of the porous support is not particularly limited, and conventionally known organic water retaining materials can be used. Among these, it is particularly preferable to use those having a maximum water absorption capacity of 200 times or more, and those exhibiting a gel-like form that are insoluble in water. Typical examples of such polymers include polyvinyl alcohol and sodium polyacrylate.

The water retaining material of this invention can be manufactured as follows. That is, a porous support having continuous pores as described above and a super absorbent polymer are prepared, and the continuous pores of the porous support are filled with the super absorbent polymer by a dry method or a wet method. The dry method is a method in which water-absorbing polymer powder is directly filled into the continuous pores of a porous support, while the wet method is a method in which a slurry containing super-absorbent polymer powder is filled into the continuous pores of a porous support. The method is to dry it. When using a wet method, it is preferable to apply an adhesive substance such as butyl polyacrylate to the continuous pores of the porous support by means such as coating, so that the polymer powder is firmly fixed. Become so. In the case of a wet method, a slurry is prepared by dispersing the superabsorbent polymer powder in a solvent, and the porous support is filled by immersing the porous support into the slurry.

In this case, it is necessary to select a solvent for dispersing the polymer powder that does not dissolve or swell the polymer powder. For example, when using sodium polyacrylate as the polymer powder, use ethanol or acetone as the organic solvent.

Toluene, hexane, etc. can be used. In addition, when dispersing a superabsorbent polymer in a solvent as described above, another polymer may be dissolved in the solvent as a fixing component for fixing the superabsorbent polymer powder into the continuous pores of the porous support. It is also possible to keep it. In this case, as the polymer for fixing the superabsorbent polymer powder, it is preferable to use a polymer that is soluble in both water and the above-mentioned solvent. Examples of such polymers include polyvinyl methyl ether, polyvinylethyl ether, polyethylene oxide, polyacrylic acid, polydimethylaminoethyl methacrylate, and the like. By using such a fixing polymer that dissolves in both organic solvents and water, when using a water retaining material, the fixing polymer dissolves and disappears due to water, so the water retaining property of the super absorbent polymer itself is reduced to the above fixing property. It does not cause any adverse effects such as those caused by other polymers.

The water-retaining material obtained in this way has a structure in which the continuous pores of a porous support are filled with a highly water-absorbing polymer, and has the air permeability of the porous support itself, and also has high water-absorbency. It is ideal because it also has the high water absorption capacity and long-term water retention performance of the polymer itself. In addition, this water-retaining material has a porous support filled with a superabsorbent polymer, and the porous support forms the basic skeleton, so there is no risk of the superabsorbent polymer itself losing its shape even when water is absorbed. Uruchino has excellent water retention properties.

〔Effect of the invention〕

As described above, the water retaining material of the present invention has a structure in which the continuous pores of a porous support having continuous pores are filled with a highly water-absorbing polymer, so that it has better air permeability than conventional inorganic water retaining materials. It is an ideal material that has both the high water absorption capacity and long-term water retention performance of organic water retention materials, and is suitable as a water retention material that supports plant growth in dry areas and areas where irrigation is difficult.

Next, examples will be described.

〔Example〕

Porous ceramics with an average pore diameter of 1.2U+ and a porosity of 85% are immersed in a slurry consisting of 90 parts by weight of sodium polyacrylate (hereinafter referred to as "parts"), 1 part of polyethylene oxide, and 90 parts of acetone. The slurry was completely impregnated into the continuous pores. Next, this impregnated body was placed in an oven at 60° C. and dried to obtain a water-retaining material in which the continuous pores inside the porous ceramic were filled and fixed with a superabsorbent polymer.

Next, the water retention performance of the water retention material thus obtained was measured. That is, when 20 g of the obtained water retaining material, 300 g of river sand of 20 mesh passes, and 100 g of water were placed in a petri dish and maintained at 20°C and 60% RH, the water retention rate, which was initially 100%, decreased to about 15%. After a few days, the water retention rate dropped to 20%.

By the way, the porous ceramics used in the above example was used as a control sample, and 20g of this was mixed with 300g of river sand.
When a test similar to the above was conducted using 100 g of water in a Petri dish, the water retention rate decreased to 20% after about 5 days. Furthermore, even when no water retention material was added, the water retention rate decreased to 20% in about 5 days.

From the above results, it can be seen that the water retention performance of the example is superior to that of the control example.

Claims (2)

[Claims] (1) A water-retaining material characterized in that the continuous pores of a porous support having continuous pores are filled with a highly water-absorbing polymer. (2) The water retaining material according to claim 1, wherein the porous support is ceramic.