JPH02135263A - Water absorbing gel composition having excellent light resistance and heat resistance - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent light resistance and heat resistance and suitable for water-retaining agent for enjoying horticulture by absorbing a dispersion obtained by uniformly dispersing a fine powder of water insoluble iron oxide or titanium oxide into an aqueous dispersing medium into a highly water-absorbing resin. CONSTITUTION:A dispersion obtained by dispersing a fine powder of water insoluble iron oxide or titanium oxide into an aqueous dispersing medium is applied to a highly water-absorbing resin (e.g., hydrolysate of starch-acrylonitrile graft copolymer) to absorb an aqueous dispersing medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background of the Invention] Field of Application The present invention relates to a water-absorbing gel composition that is stable with very little deterioration over time even when exposed to sunlight and in a high temperature atmosphere.

The water-absorbing gel composition of the present invention is obtained by allowing a superabsorbent resin to absorb water from a dispersion obtained by uniformly dispersing water-insoluble iron oxide or titanium oxide fine powder in an aqueous dispersion medium, and It is also extremely stable against heat, so it can be used as a water retaining agent for horticultural ornamentals, air fresheners and deodorizing gels, water stop agents for outdoor civil engineering work, lubricants for excavation work, cold storage agents, heat storage agents, artificial snow, and chemical warmers. Durability of hygroscopic components, etc. (light resistance, heat resistance)
It can be effectively used in various fields of use as a material that requires

BACKGROUND OF THE INVENTION In recent years, various highly water-absorbing polymeric materials have been proposed that absorb water tens to hundreds of times their own weight. For example, starch graft polymers (Japanese Patent Publication No. 53-46199, etc.), cellulose modified materials (Japanese Patent Publication No. 50-80376, etc.), crosslinked water-soluble polymers (Japanese Patent Publication No. 43-23462, etc.), There are self-crosslinking type acrylic acid alkali metal salt polymers (Japanese Patent Publication No. 30710/1983), etc., which are used as absorbents for sanitary products, disposable diapers, etc., as water retention agents for gardening, and for other industrial uses. It is being developed for use as a material in a wide range of fields.

However, although these superabsorbent polymer materials have excellent ability to absorb a large amount of water and excellent stability over time when dry, they have extremely poor stability in a water-absorbed state. For example, if a gel-like material that has absorbed water is exposed to sunlight, it often deteriorates and becomes fluid within just a few hours, making it impossible to maintain its gel-like shape. In addition, if a gel-like material is filled into a sealed container etc. without physical water evaporation and left in a high temperature (80°C or higher) atmosphere, it may take several hours to 2 hours.
There is a problem in that it similarly deteriorates after about 4 hours.

Therefore, such super-absorbent resins (water-absorbing gels) can be used, in particular, as water-retaining agents for gardening, aromatic and deodorizing gels, water-stopping agents for outdoor civil engineering work, lubricants for excavation work, cold storage agents, heat storage agents,
When used in fields that require light resistance or heat resistance, such as artificial snow or moisture-absorbing ingredients for chemical body warmers, the gel does not have sufficient durability, which poses a problem in practical use.

Conventionally, methods for improving the light resistance or heat resistance of water-absorbing gels include mixing carbon black or activated carbon with super absorbent resin (Japanese Patent Laid-Open No. 59-38271), and adding acrylic acid monomers to the water-absorbing gel. Sulfoalkyl (
Water-insoluble water-absorbent resin obtained by polymerizing together with a crosslinking agent in the presence of a meth)acrylate monomer (Japanese Patent Application Laid-open No. 1986-
36309) etc. have been proposed to be effective.

However, as far as the present inventors know, the effects of improving the light resistance and heat resistance of water-absorbing gels by these methods are still small and insufficient, and they are not satisfactory for use in each of the above fields of application. It was hard to say.

Generally, in order to synthesize and obtain a water-absorbing resin, a mixture (carbon black or activated carbon) and a copolymerizable monomer (sulfoalkyl (meth)acrylate There is a natural limit to the amount of additives such as monomers, etc.), and when the above mixtures or monomers for copolymerization are added to improve light resistance and heat resistance to a level that does not cause practical problems, these additives Another problem emerges.

That is, if the above mixture or monomer for copolymerization is added in order to impart sufficient light resistance and heat resistance according to the conventional method, the solubility in the solvent, reactivity (copolymerizability), etc. are insufficient. This makes it difficult to synthesize superabsorbent resins, and even if it were possible to synthesize them, the resulting superabsorbent resins (including mixtures) would have significantly lowered their original water absorption ability. This is because it will be put away. Furthermore, it is difficult to say that the addition of such a large amount of mixture is advantageous in terms of cost.

[Summary of the invention]

Summary The present inventors have completed the present invention as a result of extensive research in order to solve the above-mentioned problems.

Therefore, the water-absorbing gel composition of the present invention with excellent light resistance and heat resistance can be obtained by dispersing water-insoluble iron oxide or titanium oxide fine powder in an aqueous dispersion medium and applying it to a superabsorbent resin. It is characterized by being obtained by absorbing water in a medium.

Effects Conventional methods attempt to improve the light resistance of the water-absorbing gel obtained by improving the superabsorbent resin itself, whereas the present invention improves the superabsorbent resin itself. By using any ordinary material as it is and making the resin absorb a dispersion of iron oxide or titanium oxide fine powder, which has an ultraviolet and infrared shielding effect, the fine powder can be applied to the surface of the water-absorbing gel. According to the present invention, a dispersion in which iron oxide or titanium oxide is dispersed is applied to a super absorbent resin. Excellent light resistance and heat resistance can be imparted to the water-absorbing gel using an extremely simple method, which is advantageous in terms of cost. Therefore, it is easy to adjust its texture (color) and durability time. Therefore, a water-absorbing gel composition suitable for the purpose can be obtained simply and easily.

[Detailed description of the invention]

Super Water Absorbent Resin The super water absorbent resin used in the present invention can be any water-insoluble super water absorbent resin.

Specific examples of preferred highly aqueous resins include hydrolysates of starch-acrylonitrile graft copolymers, neutralized starch-acrylic acid graft copolymers, saponified acrylic ester-vinyl acetate copolymers, Crosslinked polyvinyl alcohol modified product, crosslinked polyethylene Oquinde modified product, partially neutralized poly(meth)acrylate crosslinked product,
Examples include crosslinked isobutylene-maleic anhydride copolymer.

Among these, superabsorbent resins containing carboxyl groups based on acrylic acid and/or methacrylic acid and/or alkali metal carboxylate groups are particularly preferred in the present invention.

Super absorbent resins are often obtained in the form of granules or blocks, but the super absorbent resins targeted by the present invention are not limited to these types of resins. The material may be fixed in a sheet form or a fixed form by appropriate treatment. For example, a fibrous sheet is impregnated with an aqueous solution of a monomer that provides a superabsorbent resin, such as (meth)acrylic acid in which 20 to 80% of the carboxyl groups are neutralized with an alkali metal, and polymerized by an appropriate method (for example, Examples include those obtained by decomposition of a radical polymerization initiator or a part thereof (for example, an oxidizing agent component of a redox initiator) dissolved in the aqueous solution.

Water-insoluble iron oxide or titanium oxide fine powder Any water-insoluble iron oxide or titanium oxide used in the present invention can be used as long as it is opaque and has an ultraviolet and infrared shielding effect.

Such materials include, for example, Fe2O3, Fe
Examples include OT io 2 or a mixture thereof.

Further, the particle size may be fine enough to maintain a substantially uniform dispersion state until the dispersion liquid in which the particles are dispersed is applied to the superabsorbent resin. The specific particle size varies depending on the type, particle size, condition, or purpose of the superabsorbent resin to be applied, and generally, particles of 5 μm or less can be suitably used.

Manufacturing method of water-absorbing gel composition The water-absorbing gel composition of the present invention with excellent light resistance and heat resistance can be produced by first adding the water-insoluble iron oxide or titanium oxide fine powder to an aqueous liquid and stirring, for example. It can be produced by dispersing and then applying this dispersion to a superabsorbent resin. The dispersion may be applied by adding the super absorbent resin into it while stirring continuously, or by pouring the dispersion into the water absorbent resin. The application amount of the dispersion liquid is also arbitrary, and the desired light resistance and A water-absorbing gel composition with excellent heat resistance can be obtained. The dispersion medium constituting the dispersion of iron oxide or titanium oxide is preferably one that is absorbed by the superabsorbent resin, and is therefore preferably an aqueous liquid, that is, an aqueous solution of water or a water-soluble organic solvent. .

The weight ratio of iron oxide or titanium oxide and super absorbent resin is:
There is no particular limitation unless it goes against the spirit of the present invention. The larger the weight ratio, the better the light resistance and heat resistance of the water-absorbing gel composition, but if it becomes too large, it will not be advantageous in terms of cost. A preferable weight ratio in the present invention is 0.1 to 1 water absorbent resin. 1-1.

The water-absorbing gel composition thus obtained is one in which iron oxide or titanium oxide fine powder is attached to the surface of a water-absorbing resin, or a mixture of iron oxide or titanium oxide fine powder and water-absorbing gel.

[Experiment example]

Example 1 0.3 g of ferric oxide powder (average particle size of 2 μm or less) was added to 100 g of ion-exchanged water and stirred to prepare a uniform dispersion. Next, a commercially available super-absorbent resin (trade name "Diawet" manufactured by Mitsubishi Yuka Co., Ltd.) I containing a partially neutralized sodium polyacrylate crosslinked product as a main component is added to the dispersion.
g was added, and all 100 g of the dispersion liquid was absorbed. The obtained water-absorbing gel (1) was an aggregate of small spherules with a reddish-brown color.

Example 2 The same method as in Example 1 was used except that titanium oxide powder (rutile type, average particle size 2 μm or less) was used instead of the ferric oxide powder in Example 1, to form small white spherical water absorbers. A gel (water-absorbing gel (2)) was obtained.

Titanium oxide powder (anatase type, average particle size 2 μm or more F)
A white small spherical water-absorbing gel (water-absorbing gel (3)) was obtained using the following method.

Example 3 Instead of using the super absorbent resin Diawet in Example 1, a commercially available super absorbent resin (trade name: Sunwet-IMJ) containing a hydrolyzate of starch-acrylic acid graft polymer as the main component was used. A reddish-brown, irregularly shaped water-absorbing gel (water-absorbing gel (4)) was obtained in the same manner as in Example 1, except that water-absorbing gel (manufactured by Sanyo Chemical Industries, Ltd.) was used.

Comparative Example 1 1 g of super absorbent resin "Diawet" similar to that used in Example 1 was added to 100 g of ion-exchanged water to absorb water, and a transparent small spherical water absorbing gel (comparative gel (1 ))
I got it.

Comparative Example 2 A super absorbent resin similar to that used in Example 3 [Sunwet Jig was added to 100 g of ion-exchanged water to absorb water to obtain a transparent small spherical water absorbing gel (comparative gel (2)). Ta.

[Evaluation test method]

Light resistance test (1) 50 g of each of the scale water-absorbing gels of Examples 1 to 4 and Comparative Example 1.2 was placed in a transparent polyethylene bag with a thickness of 30 μm, and placed in a bag made of transparent polyethylene in the summer (July to August). exposed to sunlight. The appearance of the water-absorbing gel was observed over time. Table 1 shows the results obtained.

Heat resistance test (2) 5 each of the various water-absorbing gels of Examples 1 to 4 and Comparative Examples 1.2
0 g each was placed in a glass bottle, capped, and placed in a constant temperature bath at 90°C, and the appearance of the water-absorbing gel was observed over time. Table-2 shows the results obtained.Table-1 Light resistance test (1) Table-2 Heat resistance test (2) The symbols in Table-1 and Table-2 above indicate the state of the water-absorbing gel. The meaning is as follows.

Hard gel-like Soft gel-like Partially dissolved (Retains initial state) (Starts to deteriorate slightly) (Deterioration has progressed to a large extent including soft gel-like state) (Turns into aqueous solution) ing)

Claims (1)

[Claims] It is characterized by being obtained by applying a dispersion obtained by dispersing water-insoluble iron oxide or titanium oxide fine powder in an aqueous dispersion medium to a super absorbent resin to absorb the aqueous dispersion medium.
A water-absorbing gel composition with excellent light resistance and heat resistance.