JPH0362184B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-absorbing composite useful as a water-retaining agent, a water-absorbing agent, a dehydrating agent, a desiccant, a wetting agent, a water-stopping material, etc., and a method for producing the same. Recently, various super-absorbent resins have been developed, and by taking advantage of their ability to absorb several hundred times their own weight in water, they can be used as water-retaining materials, water-absorbing agents, dehydrating agents, desiccants, wetting agents, water-stopping materials, etc. is used for this purpose. However, the water absorption capacity of these superabsorbent resins is significantly reduced by the metal ions present in the water they absorb, so they must be used with constant attention to the hardness of the water, and the areas where they can be used are limited. There was a drawback that it was difficult to use. In order to overcome this drawback, attempts have been made to increase the molecular weight of the superabsorbent resin, but even this method has not yielded a satisfactory product. The present inventors discovered that ion sequestering agents such as phosphates and aminocarboxylic acids remove metal ions from water faster than superabsorbent resins with large molecular weights, and based on this knowledge, further As a result of investigation, it was found that the above-mentioned drawbacks could be improved by using a mixture of a superabsorbent resin and an ion sequestering agent, but the effect lacked sustainability. As a result of various studies to improve the above-mentioned drawbacks, the present inventors discovered that by dispersing a certain type of ion sequestering agent over the entire surface of a specific super absorbent resin,
Recognizing the fact that the ion sequestering ability is stable and lasting,
The present invention has now been completed. That is, the present invention provides a super absorbent resin obtained by crosslinking an alkali-neutralized copolymer of α-olefin and maleic anhydride or its derivative, and a condensed phosphate and It is a water-absorbing complex consisting of an ion sequestering agent selected from the group consisting of aminocarboxylic acids or derivatives thereof. In the present invention, the water absorbent composite is composed of the superabsorbent resin and an ion sequestering agent dispersed throughout the resin, and achieves the initial purpose, but the ion sequestering agent If the powdered superabsorbent resin is simply mixed with the powders and the powders are in point contact, only the ion sequestering agent will selectively adsorb the metal, resulting in precipitation and separation phenomena. Therefore, the ion sequestration ability aimed at in the present invention cannot be maintained stably.
Additionally, if a superabsorbent resin powder is coated with an ion sequestering agent using a water-soluble binder, some of the binder will be eluted during water absorption and will separate from the ion sequestering agent, reducing the desired effect. Put it away. Therefore, it is important that the ion sequestering agent is dispersed over the entire surface of the superabsorbent resin. Surprisingly, adding an ion sequestering agent slightly increases the crosslinking efficiency and slightly decreases the water absorbing ability of the superabsorbent resin (hereinafter referred to as absorption performance). It is thought that this also partially contributes to crosslinking, making it possible to obtain a firmer resin that has never been seen before. In addition, if the absorption performance of the super absorbent resin is too small, the water absorbing performance as a water absorbent composite will be lost. On the other hand, if it is too large, the strength of the super absorbent resin when it contains water will be weakened, and the durability as a water absorbent composite will be affected. Not only will it disappear, but it will also be unable to maintain its shape.
Separation and recovery become difficult in systems where the absorbent complex is mixed with other solvents. Therefore, for super absorbent resins, the value obtained by dividing the weight of distilled water absorbed by the resin by the weight of the resin before water absorption (hereinafter referred to as water absorption capacity) is
It is preferably 5 to 800 times, particularly 10 to 500 times. The present invention also relates to a method for producing such a water-absorbing composite, which comprises α-
Ions selected from the group consisting of alkali-neutralized copolymers of olefin and maleic anhydride or derivatives thereof, crosslinking agents of alkali-neutralized copolymers, condensed phosphates, and aminocarboxylic acids or derivatives thereof. It consists in mixing the capping agent and the solvent and then desolventizing. Examples of α-olefins used in the present invention include linear or branched α-olefins having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, such as ethylene, propylene, isobutylene, butene-1, and diisobutylene. Examples of derivatives of maleic anhydride include maleic acid, maleic acid amide, maleic acid imide, and the like. The proportion of maleic anhydride or its derivative in the copolymer of α-olefin and maleic anhydride or its derivative is preferably 40 mol% or more, particularly 50 mol% or more. Copolymerization of α-olefin and maleic anhydride or its derivatives can be carried out according to a conventional method using a radical polymerization catalyst. The degree of polymerization is not particularly limited, but is preferably 10 to 5,000. The copolymer of α-olefin and maleic anhydride or its derivatives is a compound such as a hydroxide, oxide, or carbonate of an alkali metal or alkaline earth metal such as sodium, lithium, potassium, magnesium, calcium, or barium. It is made hydrophilic by reacting with a basic compound such as , ammonia, or an amine to form an alkali neutralized product. This reaction is carried out by dissolving the copolymer in a solvent, preferably water, and adding the basic compound thereto under stirring. In this reaction, sodium hydroxide, potassium hydroxide, and ammonia are preferably used from the viewpoint of reactivity and durability of the superabsorbent resin obtained. The proportion of the basic compound used is 40 to 100 mol% of the carboxyl group or group that can be induced into a carboxyl group in the copolymer.
Preferably, the amount is within a range of 50 to 80% as salt. Among the alkali-neutralized copolymers, reaction products of isobutylene-maleic anhydride copolymers and sodium hydroxide, potassium hydroxide, or ammonia are particularly preferred from the viewpoint of water absorption and water resistance. Examples of the crosslinking agent in the present invention include polyvalent epoxy compounds, polyvalent amines, polyhydric alcohols, amino alcohols, polyisocyanates, and polyvalent halohydrins. Examples of polyvalent epoxy compounds include glycerin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycidyl ether, glycerin triglycidyl ether, propylene diglycidyl ether, polypropylene diglycidyl ether, and trimethylolpropane triglycidyl ether; Examples include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine having a molecular weight of 5000 or less. The proportion of the crosslinking agent to be used varies depending on the alkali neutralized product of the copolymer to be crosslinked and the type of crosslinking agent, the crosslinking conditions, the water absorption capacity of the resulting water absorbent composite, and even its use, but it is generally The amount is preferably in the range of 0.0001 to 10 parts by weight, particularly preferably in the range of 0.005 to 5 parts by weight, per 100 parts by weight of the alkali-neutralized copolymer. In the present invention, condensed phosphates and aminocarboxylic acids or derivatives thereof are used as ion sequestering agents, and these have the effect of collecting metal ions in water. Here, condensed phosphate refers to the general formula xMO−
It is expressed as yP ₂ O ₂ . In the formula, M represents a monovalent or divalent metal, and particularly good results are obtained when it is potassium or sodium. Examples of condensed phosphates include orthophosphates, polyphosphates, methanoates, and ultraphosphates. Examples of aminocarboxylic acids or derivatives thereof include imidinoacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetrahexaacetic acid,
cyclohexane-1,2-diaminotetraacetic acid,
N-hydroxyethylethylenediaminetriacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, ethylenediaminetetrapropionic acid, and alkali metal salts, ammonium salts, or amine salts thereof. These ion sequestering agents are used in powder form. Two or more types of ion sequestering agents can be used in combination, and by using them in combination, it becomes possible to control the ion adsorption capacity or ion adsorption rate for various metals. The amount of the ion sequestering agent used is preferably in the range of 0.2 to 200 parts by weight, particularly 0.5 to 100 parts by weight, based on 100 parts by weight of the superabsorbent resin in the water absorbent composite. As mentioned above, the water-absorbing composite of the present invention is prepared by mixing an ion sequestering agent, an alkali neutralized product of the copolymer, and a crosslinking agent, and performing a crosslinking treatment. alkali neutralized product as its solvent,
Preferably, after dissolving in water or a mixture of water and other solvent, the crosslinking agent is dissolved therein, and then the ion sequestering agent is dispersed, followed by drying and heat treatment. It is then ground into particles of a desired particle size and used for various purposes. If the amount of alkali neutralized copolymer used in the crosslinking treatment is too small, a water-absorbing composite with sufficient water absorption capacity cannot be obtained, while if it is too large, the water-absorbing composite will not absorb water. When shear force is applied, the superabsorbent resin falls off from the composite. In this way, a composite consisting of a superabsorbent resin and an ion sequestering agent dispersed therein is obtained. The water-absorbent composite of the present invention obtained in this way has various water absorption capacities similar to those of the superabsorbent resin, depending on the proportions of the alkali neutralized copolymer, crosslinking agent, and ion sequestrant. It is effectively used as a water retaining agent, water absorbing agent, dehydrating agent, wetting agent, desiccating agent, water stopping material, etc. either alone or mixed with soil, plastic, etc. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples at all. In addition, "parts" in Examples and Comparative Examples means "parts by weight" unless otherwise specified. Example 1 100 parts of isobutylene-maleic anhydride copolymer with a molecular weight of 160,000 (Isoban-10 manufactured by Clareisoprene Chemical Co., Ltd.), 32 parts of sodium hydroxide (approximately 60 moles of carboxyl groups based on maleic anhydride in the copolymer) % salt) and water
Stir 500 parts at a temperature of 80°C and add isobutylene to
A homogeneous aqueous solution of the sodium salt of maleic anhydride copolymer was prepared. Next, polyethyleneimine (Nippon Shokubai) with a molecular weight of 1200, which is a crosslinking agent, was added to this aqueous solution.
Polyethyleneimine SP-012 (manufactured by Co., Ltd.) and sodium tripolyphosphate (reagent manufactured by Wako Pure Chemical Industries, Ltd.), an ion sequestering agent, were mixed in the proportions shown in Table 1, and approximately
After drying on a hot plate at 110°C, it was further heat-treated in a hot air dryer at 170°C for 8 hours. Crush this to 16
A water-absorbing composite was obtained by forming particles through mesh wire mesh. Put 1g of this complex in 1 beaker, 1000
After adding 1.5 g of distilled water and allowing it to stand for 2 hours, the dispersion was filtered through a 200 mesh nylon cloth. In addition, in order to investigate the influence of ions in water, 1 g of this complex was mixed with pre-prepared calcium chloride.
Add to 1000g of 0.3% aqueous solution and leave for 2 hours.
It was passed through a nylon cloth in the same manner as above. By measuring the weight of the water-containing composite thus obtained, the water absorption capacity of the water-absorbing composite was determined. The results are shown in Table 1.

[Table] As the amount of sodium tripolyphosphate, an ion sequestering agent, used increases, the water absorption capacity of the water-absorbing composite decreases, but there is almost no difference between the water absorption capacity of distilled water and the water absorption capacity of 0.3% calcium chloride aqueous solution. It showed extremely stable ion sequestration performance. The water-absorbing composite in a hydrated state was transparent, and when redispersed in water, it settled in 2 to 3 minutes, and did not feel slimy even when it was passed through a nylon cloth and then squeezed. This shows that the water absorbent composite obtained in this example has excellent gel strength. Example 2 Glycerin diglycidyl ether (manufactured by Nagase Sangyo Co., Ltd.) was added to the homogeneous solution of the sodium salt of the isobutylene-maleic anhydride copolymer used in Example 1 in the amount shown in Table 2. Ethylenediaminetetraacetic acid (Krewatsu TAA, manufactured by Nagase Sangyo Co., Ltd.) was mixed with this aqueous solution in the proportion shown in Table 2, and the mixture was heated to about 111°C.
After drying on a hot plate, it was further heat treated in a hot air dryer at 120°C for 2 hours. This was pulverized into particles of 16 meshes to obtain a water-absorbing composite. The water absorption capacity of the water absorbent composite was determined in the same manner as in Example 1. The results are shown in Table 2.

【table】

[Table] Maleic anhydride aminetet diglycidi

Claims (1)

[Scope of Claims] 1. A water-absorbing resin obtained by crosslinking an alkali-neutralized copolymer of α-olefin and maleic anhydride or its derivative, and a condensed phosphate salt dispersed in the resin. and an ion sequestering agent selected from the group consisting of aminocarboxylic acids or derivatives thereof. 2. An alkaline neutralized product of a copolymer of α-olefin and maleic anhydride or a derivative thereof, an alkali neutralized product of the copolymer selected from the group consisting of a crosslinking agent, a condensed phosphate, and an aminocarboxylic acid or a derivative thereof. A method for producing a water-absorbing composite, which comprises mixing a selected ion sequestering agent and a solvent, and then removing the solvent. 3. The manufacturing method according to claim 2, wherein the solvent is water.