JPS63210109A - Highly water-absorptive water-retentive material - Google Patents

Abstract

PURPOSE:To provide a highly water-absorptive water-retentive material superior in water absorption properties, water retention properties, shape retention properties, etc. and useful for agriculture, horticulture, etc., by mixing a monomer having an alpha,beta-unsaturated bond with an inorganic and/or organic powder, granulating and shaping followed by polymerizing. CONSTITUTION:A monomer (e.g., acrylic acid or acrylamide) having an alpha,beta-unsaturated bond, and an inorganic and/or organic powder are mixed. As preferred examples of the inorganic powder, bentonite, zeolite, alumina, silica, barite, kaoline, etc. can be mentioned. As preferred examples of the organic powder, wood powder, pulp powder, etc. can be mentioned. Then, the mixture is granulated or shaped followed by polymerization of the monomer to provide the aimed highly water-absorptive water-retentive material. When this material is used as an agricultural or horticultural water retentive material, the air flows smoothly through it since the material maintains its shape so that root rot or the like would not occur.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a highly water-absorbent water-retaining agent, and more specifically, granules, pellets, and Regarding highly absorbent water retaining agents having a block shape, etc., the purpose is to provide water absorbing agents and water retaining agents useful as soil water retention improvers in agriculture and horticulture, and water stop agents in civil engineering works. .

[Conventional technology]

Conventionally, the most widely used fields of superabsorbent resins are paper diapers, sanitary products, etc., and most of the superabsorbent resins used in these products are fine powders with a particle size of 111111 or less. Therefore, the main objective of conventional techniques for improving this type of resin is to omit the pulverization step and to polymerize water-soluble monomers as finely as possible. In addition, it has also been proposed to mix these finely powdered superabsorbent resins with rubber, paint, etc., and use them for purposes such as water-swellability and prevention of dew condensation.

However, it is extremely difficult to use conventional super-absorbent resin fine powder as it is as a soil water-retaining agent for agriculture and horticulture, or as a water-stopping agent for civil engineering work. In other words, in these applications, superabsorbent resin fine powder is used as is or mixed with soil, but when used as is in the form of fine powder, it is easily affected by wind and cannot be uniformly dispersed. Moreover, it is difficult to mix uniformly with soil, so water absorption and water retention in the soil are not uniform, and the effect of improving water retention is small. Furthermore, for agricultural and horticultural purposes, it is important to maintain air circulation in the soil, not only to improve water retention, but also to prevent so-called boarding. However, the conventional finely powdered water-absorbing resins cannot sufficiently prevent this root wetting, and currently cannot be used for most agricultural and horticultural purposes. Therefore, there is currently a strong demand for the development of a water-absorbing and water-retaining agent that is highly water-absorbent and does not have the above-mentioned drawbacks in place of the conventional finely powdered water-absorbing resin.

[Problems to be Solved by the Invention] The problems to be solved by the present invention are to solve each of the above-mentioned difficulties of the conventional fine powder water absorbent resin. In addition, it is possible to obtain sufficient uniformity even when mixed with soil, and it is difficult to cause rooting.
The objective is to develop a highly absorbent water retaining agent for horticultural use.

[Means for solving problems]

A means to solve this problem is to mix inorganic or (and) organic powder and a polymerizable monomer, granulate or shape the mixture, and then polymerize the monomer and further crosslink it if necessary. be done. That is, as a result of various studies to improve the above-mentioned conventional drawbacks, the present inventor has developed a method for granulating or forming inorganic or (and) organic powder using a monomer having α,β-unsaturated bonds as a binder. It is possible to easily produce a water-absorbing resin by integrating powder and monomer into granules, pellets, blocks, etc., polymerizing them, and crosslinking them if necessary. The present invention was completed based on the discovery that the original purpose of the invention can be achieved.

[Structure and operation of the invention]

The inorganic and/or organic powder used in the present invention may be any powder that can be granulated using a binder.
Typical examples of inorganic powders include bentonite, zeolite, alumina, silica, barride, kaolin, and various other inorganic powders, and examples of organic powders include wood flour, pulp powder, various synthetic resin powders, etc. Various organic powders are used. Moreover, two or more types can also be used in combination. Furthermore, inorganic pigments such as red iron oxide and titanium oxide, and organic pigments such as cyanine blue and benzidine yellow can also be used, and various dyes can also be appropriately added for coloring. The particle size of the powder at this time can be appropriately selected from a wide range, but usually 1
~1000 microns, preferably 30-900 microns, particularly preferably about 30-300 microns.

Among these powders, in particular, powders that themselves have a water absorbing or water-retaining effect, such as bentonite, have a synergistic effect with a water-absorbing resin, which further improves the water-retaining or water-absorbing effect.

As monomers used in the present invention, monomers having α,β-unsaturated bonds can be widely used, such as acrylic acid, methacrylic acid, and metal salts thereof, preferably sodium salts, potassium salts, or the like. Examples include ammonium salts such as acrylamide, methacrylamide, and their N-methylol derivatives. In order to obtain the superabsorbent water retention agent of the present invention, these water-soluble monomers may be used alone, but in order to improve the water absorption rate and water absorption capacity of the water retention agent, two or more types may be mixed. It can also be used as

As the initiator used in the present invention, a water-soluble radical polymerization initiator is preferably used. These include potassium peroxonisulfate, ammonium peroxonisulfate, tert-butyl hydroperoxide, cumene hydroperoxide, etc., with potassium peroxonisulfate and ammonium peroxonisulfate being preferred. Furthermore, these initiators can also be used as a so-called redox system in combination with a suitable reducing agent, as is generally done in radical polymerization. Combinations of potassium peroxodisulfate or ammonium peroxodisulfate with sodium sulfite, sodium bisulfite, triethanolamine, ferric salts, etc., respectively, are known.
A combination of potassium peroxonisulfate and sodium sulfite or sodium bisulfite is easy to handle. The amount of initiator used is in the range of 0.005 to 5% by weight, preferably 0.1 to 2% by weight, based on the monomer.

Although it is not necessary to use a crosslinking agent in the present invention, the use of a crosslinking agent improves the gel strength after water absorption. As the crosslinking agent, a wide variety of agents that participate in the crosslinking reaction of the monomers mentioned above can be used. For example, N.

N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trieglycol dimecacrylate, tetraethylene glycol diacrylate, tetraethylene glycol Examples include dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, and the like. The usage ratio of the crosslinking agent varies depending on the type of monomer, the type of crosslinking agent, the water absorption capacity, etc., but it can be varied within 20% of the monomer, but it is usually 0.01 to 10%. range.

When preparing the superabsorbent water retention agent of the present invention, first, a monomer and an initiator are mixed with an inorganic or (and) organic powder, and if necessary, a crosslinking agent is added and the resulting mixture is granulated. It is shaped into a desired shape such as granules, pellets, lumps, grains, etc. The monomer in this case is
It is sufficient that the monomers are substantially liquid at the time of mixing; for example, the monomers are used in the form of an aqueous solution, or liquid ones are used as they are. Moreover, if it becomes liquid by heating, it may be used in the liquid state by heating. The same applies to the initiator and the crosslinking agent used if necessary.

Further, when a salt of acrylic acid or methacrylic acid is used as a monomer, these acids and a compound to be formed into a salt may be used in combination to form a salt at the time of mixing.

The monomers present in the molded body are then polymerized. The polymerization conditions at this time are not limited in any way, and may be any conditions as long as the monomers can be sufficiently polymerized, for example, 40 to 200
A typical example is a condition in which the polymerization is carried out by heating at about .degree. C. for about 5 minutes to 6 hours. After polymerization is completed, it is dried and used as the desired water-retaining agent. In this case, for example, if a Redos I-based initiator is used or a powder having a catalytic action is used, the reaction can be allowed to proceed simultaneously with granulation by heating the product to the same temperature or slightly heating it.

In addition, in the present invention, the above-mentioned monomers, initiators, etc. are repeatedly absorbed and impregnated into granules, pellets, blocks, etc., or polymerized and dried, and the reaction is repeated. , it is also possible to improve water retention capacity.

In the present invention, no matter which production method is adopted, the amount of the polymer obtained from the monomer in the final water retention agent is usually 1 to 95% by weight, preferably 5 to 95% by weight. It is about 85% by weight, particularly preferably about 5 to 75% by weight. In this case, if the amount of polymer from the monomer does not reach 1% by weight, not only will granulation or shaping be difficult, but the resulting water retention agent will also have low mechanical strength and absorbency, making it impractical for practical use. isn't it. Conversely, if the amount exceeds 95% by weight, shaping tends to become difficult.

The water retention agent obtained by the method of the present invention may be in the form of secondary particles, or these secondary particles may aggregate to form secondary particles.

C Effects of the Invention] The superabsorbent water retention agent of the present invention thus obtained has water absorption and water retention properties as a water retention agent for agriculture and horticulture, and also maintains a constant shape, so air circulation is prevented. It's good, and it's useful without being grounded. It also has the advantage of being easier to handle at outdoor construction sites than fine powder as a water sealing agent for civil engineering work.

〔Example〕

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. however,
In the following examples, parts indicate parts by weight.

Example 1 60 parts of a 20% aqueous sodium hydroxide solution was gradually added dropwise to 28 parts of acrylic acid while cooling. To this solution, 0.07 part of ethylene glycol diacrylate and 0.2 part of potassium belloxonisulfate were added and dissolved. The above solution was gradually added to 100 parts of zeolite powder (average particle size: 74 microns) to form granules with a particle size of approximately 1 to 3 mm. This product was reacted by heating at 80℃ for 1 hour to prevent the shape of the granules from collapsing, and then the remaining solution was absorbed and heated to 80℃ for 1 hour.
A granular water retention agent was obtained by heating and polymerizing at C for 3 hours. The water absorption amount per gram of this water retention agent was 33g.

Example 2 In Example 1, ethylene glycol diacrylate as a crosslinking agent was not used at all, and the other processes were the same as in Example 1. The obtained water retaining agent was almost the same as in Example 1, except that the mechanical strength tended to decrease slightly upon water absorption.

Examples 3 to 9 The water retention agent of the present invention was obtained in the same manner as in Example 1 except that the zeolite powder in Example 1 was changed to bentonite, alumina, silica, baride, kaolin, wood flour, and pulp powder. . The average particle size of each powder, the particle size and water absorption amount of the obtained water retention agent are shown in Table 1 below.

Table 1 Example 10 50 parts of acrylamide, 10 parts of methacrylic acid, N, N'
-0.08 part of methylenebisacrylamide and 0.4 part of ammonium beroxonisulfate were dissolved in 60 parts of water.

On the other hand, a powder was prepared by mixing 60 parts of kaolin and 0.5 parts of cyanine blue, and the above monomer aqueous solution was added dropwise to the powder for granulation. When the particle size reached 1 to 5 mm, a 1% aqueous solution of sodium bisulfite was sprayed on the particles, and when the particles were left to stand at room temperature for several minutes, they generated heat and reacted.

The remaining monomer aqueous solution was absorbed and reacted with the material whose shape did not collapse in this way. Finally 80-85
It was dried at ℃ for 5 hours to obtain a water retaining agent colored blue. The water absorption amount of this material was 78 g/g.

(that's all)

Claims (4)

[Claims] (1) At least one of inorganic and organic powders and α, β
- A highly water-absorbing water-retaining agent characterized by granulating or shaping a mixture with a monomer having an unsaturated bond, and then polymerizing the monomer. (2) The water retention agent according to claim 1, wherein the inorganic powder is at least one of bentonite, zeolite, alumina, silica, baride, and kaolin. (3) The organic powder is at least one of wood flour and pulp powder.
The water retention agent according to claim 1, which is a seed. (4) The monomer having α,β-unsaturated bonds is at least one of acrylic acid, methacrylic acid, alkali metal salts or ammonium salts thereof, acrylamide, methacrylamide, and N-methylol derivatives of these amides. The water retention agent according to claim 1.