JPS5938271A - Water-holding agent - Google Patents

Abstract

PURPOSE:To provide a water-holding agent with good stability with time and heat resistance even in a state of water pickup, by incorporating a water-absorbing resin contg. carbon black and/or active carbon. CONSTITUTION:A water-holding agent which comprises a water-absorbing resin (e.g., hydrolyzate of starch/acrylonitrile graft copolymer) contg. carbon black and/or active carbon, wherein the content of carbon black and/or active carbon is pref. 0.01-70wt% and water absorption is pref. 10 times or above. It is excellent in stability with time and heat resistance even in a state of water pickup. It finds extensive uses as water-holding agents for agriculture and horticulture, sweating-proof agents for building materials, water-holding agents for sweet- smelling gels, heat/cold insulators, waterstop agents for civil engineering and construction, adsorbents for heavy metals, dehydrating agents for org. solvents, sanitary goods, controlled release agents for medicines, deodorizers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water retention agent that has excellent durability and light resistance. Specifically, the present invention relates to a water-retaining agent made of a water-absorbing resin containing carbon black and/or activated carbon, which has excellent durability and light resistance in a water-absorbed state.

In recent years, water-absorbing resins that absorb tens to hundreds of times their own weight in water have been developed, and are used as absorbents in sanitary products, disposable diapers, etc., water retention agents for agriculture and horticulture, coagulants for sludge, and construction materials. The use of this product as a sushi prevention agent, desiccant agent, etc. is being developed.

Examples of such water-absorbing resins include hydrolysates of starch-acrylonitrile graft subpolymers, neutralized starch-acrylic acid graft polymers, saponified products of vinyl acetate-acrylic acid esters themselves, and acrylonitrile copolymers. Alternatively, hydrolysates of acrylamide copolymers, crosslinked products thereof, self-crosslinked sodium polyacrylate obtained by reverse phase suspension polymerization, crosslinked partially neutralized polyacrylic acids, etc. are known. There is.

However, although these conventional water-absorbing resins have great stability in a dry state, their drawback is that they have poor stability in a water-absorbing state. For example, if a gel-like material made by absorbing several hundred times as much water as a water-absorbing resin is left indoors for a long period of time, the gel-like material may gradually become solubilized to 1 or more and finally become a completely aqueous solution. Furthermore, when a gel-like material that has absorbed water is exposed to sunlight, it may become solubilized and disappear within just a few hours. When these water-absorbing resins are used as a water-retaining agent for gardening, when soil and water-absorbing resin are mixed together, plants are planted in pots, and watered, a water-absorbing gel is formed, because its specific gravity is smaller than that of soil. When water forms on the surface of the soil, it becomes exposed to IfC, becomes soluble and loses its water-holding ability. Although water-absorbing gel in soil exhibits water-holding capacity for a relatively long period of time, it tends to gradually become solubilized and lose its water-holding capacity over many years. Even when used as a dew-preventing agent for building materials, long-lasting durability is required.

As described above, the current situation is that conventional water-absorbing resins cannot meet the requirements of stability i<1 in the water-absorbing state.

The inventor of the present invention possesses a conventionally known water-absorbing resin.
As a result of intensive research to solve the above-mentioned problems, the present invention has been completed.

Therefore, an object of the present invention is to provide a water retaining agent that is durable even in a water-absorbed state, that is, has good stability over time and good light exchange properties even in a water-absorbed state.

The water retention agent (-1) of the present invention is made of a water-absorbing resin containing carbon black and/or activated carbon.

As the water-absorbing resin used in the present invention, conventionally known water-insoluble water-absorbing resins such as V can be used.

In the present invention, the water absorbent resin is carbon black and/or
Alternatively, the state containing activated carbon includes, for example, a state in which carbon black and/or activated carbon powder is uniformly dispersed inside water-absorbing resin particles, a state in which carbon black and/or activated carbon powder is coated with a water-absorbing resin, or carbon black. and/or a state in which activated carbon powder is impregnated with a water-absorbing resin. A simple mixture of water-absorbing resin powder and carbon black and/or activated carbon has poor durability and heat resistance, and the object of the present invention cannot be achieved.

Methods for producing the water retention agent of the present invention include, for example, a method of polymerizing a crosslinkable monomer and an acrylate monomer in the presence of carbon black and/or activated carbon; A method of polymerizing an acid salt monomer in an aqueous solution to form a hydrogel, mechanically kneading carbon black and/or activated carbon thereto, and then drying it; carbon black and/or activated carbon added to a linear water-soluble polymer A method of obtaining a water retaining agent through a reaction process; mixing carbon black and/or activated carbon with a powdered water-absorbing resin, adding water or a binder, and firmly cross-linking. Examples include a method of coating or impregnating carbon black and/or activated carbon with a water-absorbing resin.

In addition, in these methods, if a surfactant is present when adding carbon black and/or activated carbon,
It may be preferable to improve the affinity between carbon black and/or activated carbon and the water-absorbing resin.

The method for producing the water retention agent of the present invention is more specifically shown in the following items 0 to 0, but the present invention is of course not limited to these examples.

(5) Crosslinkable half-moon, body (B) An aqueous dispersion of acrylic acid and/or acrylic acid water-soluble salt (Q carbon black and/or), activated carbon and 0 water in the presence of a radical polymerization initiator. Water retention agent obtained by polymerization.

■ Acrylic acid and/or a water-soluble salt of acrylic acid containing carbon black and/or activated carbon, a water-soluble radical polymerization initiator, and optionally a crosslinking monomer in an alicyclic and/or aliphatic hydrocarbon solvent. HLB 3 aqueous solution
A water-retaining agent obtained by dispersion and suspension polymerization in the presence of a surfactant as described in F.12.

(2) A water retention agent obtained by copolymerizing a vinyl ester with an ethylenically unsaturated carboxylic acid and/or a derivative thereof in the presence of carbon black and/or activated carbon, followed by saponification.

■ Starch and/or cellulose, monomers having carboxyl groups or producing υ carboxyl groups by hydrolysis, in the presence of carbon black and/or activated carbon;
A water retention agent obtained by polymerizing a crosslinkable monomer in an aqueous medium and further hydrolyzing it if necessary.

■ Carbon black and/or A water retention agent obtained by mixing activated carbon and further reacting the resulting mixture with a polyvalent epoxy compound if necessary.

The water retention agent of the present invention preferably has a water absorption capacity of 10 times or more. If the water absorption capacity is less than 10 times, for example, if /l' is used as a water retention agent for gardening, it will be necessary to use a water retention agent for a long time in order to be effective, and it will be economical. Not desirable.

The carbon black or activated carbon used in the present invention is usually commercially available and can be used in powder or granular form, but those with a small particle size are preferred. The content of carbon black or activated carbon is 0.0% of the water retention agent in the dry state.
It is preferable that the weight ratio is 1 to 70. If the content of carbon black and/or activated carbon is less than 0.01% by weight, the durability and light resistance will be poor, and if it exceeds 70% by weight, the water absorption capacity will be low, both of which are not preferred. Carbon black and activated carbon may be used alone or in combination. Further, an inorganic filler other than carbon black or activated carbon may be used in combination.

The water retention agent of the present invention obtained in the above manner has excellent durability and light resistance in a water-absorbed state compared to conventionally known water-absorbing resins.

In the water-retaining agent of the present invention, the water-absorbing resin encloses particles of carbon black and/or activated carbon, so even if the water-retaining agent absorbs water and swells, the carbon black and activated carbon remain in the swollen hydrogel. For this reason, even if the swollen hydrogel is watered or rained, the carbon black and activated carbon will not wash away or separate, and it is believed that the light resistance and durability will last for a long time. On the other hand, such an effect cannot be expected from a simple mixture of a water-absorbing resin and carbon black or activated carbon.

The water retention agent of the present invention is a water retention agent for agriculture and horticulture, a dew condensation prevention agent for building materials, a water retention agent for aromatic gel, a heat insulation/cold insulation material, a water stop agent for civil engineering and construction, an adsorbent for heavy metals, a dehydration agent for organic solvents, Sanitary items,
It can be used in a wide range of applications, such as a controlled release agent for drugs and a deodorizing agent.

Hereinafter, the present invention will be explained in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples. In the example, unless otherwise specified, the person in charge is the person in charge,
Each part indicates a part by weight.

Example 1 A 37% sodium acrylate aqueous solution 956F and an 80% acrylic acid aqueous solution J1 were placed in a double-arm kneader with a total capacity of 2.5 tons.
3F, methylene bisacrylamide 0.8f, and carbon black (Columbian Carbon Co., Ltd. "Neo Spectra Mark nJ) c+r" were added.

Stirring speed: 50 r, p, m, under nitrogen atmosphere
Heat to 0°C and add 50 l of 10% ammonium persulfate aqueous solution.
2 and 10 sodium bisulfite aqueous solutions 201 were added and polymerized. Heat was generated with the start of polymerization, and the temperature reached 80° C. about 10 minutes after the start of polymerization.

At the same time, the aqueous monomer solution turned into a hydrogel, which was gradually divided into smaller pieces by stirring. Stop stirring 80 minutes after starting,
Finely divided black hydrogel polymer (average particle size approximately 3 tones)
was taken out and dried in a hot air dryer at 7.180°C to obtain a water retention agent (1). This water retention agent tfIN1m is in the form of black particles with an average particle size of approximately 2 particles, and has a water absorption capacity of 2.
It was 70 times more. The method for measuring water absorption capacity is as follows. (The same applies to Example 2 and subsequent examples) Water-absorbing resin 1
2 was immersed in deionized water + 000 me for 24 hours, filtered through a 200-mesh wire mesh, drained for 10 minutes, measured the weight of the water-absorbing gel present on the 200-mesh wire mesh, and calculated the number of grams as the water absorption capacity. shall be.

Example 2 154 parts of isobutylene-male-inic acid anhydride copolymer, 64 parts of caustic soda and 398 parts of water were mixed and heated and stirred at 90°C for 2 hours to prepare a uniform aqueous solution. Next, powdered activated carbon (white, manufactured by Takeda Pharmaceutical Co., Ltd.) XM was added to this aqueous solution.
J) 20 parts and glycerin diglycidyl needle 2.
5 parts were added, and after mixing, the mixture was poured into a vat, a crosslinking reaction was caused in a hot air dryer at 110°C, and the mixture was dried to obtain a black water retention agent (2). The water absorption capacity of the water retention agent (2) was 200 times.

Example 3 100 parts of starch and 100 parts of water were charged into a polymerization reaction vessel, stirred at 55°C for 30 minutes under a nitrogen stream, cooled to 30°C, and mixed with 200 parts of acrylic acid, trimethylolpropane triacrylate, carbon black ( Mitsubishi Carbon Black #600J) 29 manufactured by Mitsubishi Chemical Industries, Ltd. and 2 parts of ammonium persulfate and 0.5 parts of t-ascorbic acid were added as polymerization initiators, and the mixture was stirred at 40°C for 3 hours to polymerize. The reaction solution became an elastic black solid. The obtained black solid was dried and ground to obtain a black water retention agent (3). The water absorption capacity of the water retention agent (31) was 220 times.

Comparative Example 1 Polymerization and drying were carried out in the same manner as in Example 1 except that carbon black was not added. The water absorption capacity of the obtained pale yellow granules (comparative water retention agent (1)) was 280 times.

Comparative Example 2 A crosslinking reaction was carried out in the same manner as in Example 2 except that activated carbon was not added to obtain a comparative water retention agent (2). The water absorption capacity of the comparative water retention agent (2) was 250 times.

Comparative Example 3 A comparative water retention agent (3) was obtained by polymerizing, drying, and pulverizing in the same manner as in Example 3 except that carbon black was not added. The water absorption capacity of Comparison water retention agent 31 was 200 times.

Example 4 (Durability test) After adding 100 f of deionized water to 1 f of each water retention agent obtained in Examples 1 to 3 and Comparative Examples 1 to 3 to absorb water, this was placed in a glass bottle, covered with a lid, and heated for 70 minutes. The water-absorbing gel was placed in a constant temperature bath and observed over time.

As is clear from Tables 1 and 2, the water retention agent of the present invention has excellent durability and light resistance.

Claims (1)

[Claims] 1. A water retaining agent made of a water-absorbing resin containing carbon black and/or activated carbon. 2. The water retention agent according to claim 1, which has a water absorption capacity of 10 times or more. 3. The content of carbon black and/or activated carbon is 0.
The water retention agent according to claim 1, which has an IP content of 0.01 to 70% by weight.