JPH0734860B2 - Moisture absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water absorbent, and more particularly to a water absorbent having excellent performance against ion-containing water and excellent durability.

(Prior Art) There have been many reports in recent years on superabsorbent materials, and typical examples thereof include ionic superabsorbent materials obtained by hydrolyzing starch graft-polymerized with polyacrylonitrile, and starch. Graft copolymerized with acrylic acid, cross-linked carboxymethyl cellulose, hydrolyzed cellulose grafted with polyacrylonitrile, hydrolysis of sodium polyacrylate, methyl methacrylic acid and vinyl acetate copolymer As a hydrolyzate of a polyacrylonitrile crosslinked product and a nonionic high water absorbent, a polyvinyl alcohol crosslinked polymer (hereinafter, also referred to as PVA water absorbent), a polyethylene oxide crosslinked polymer (hereinafter, also referred to as PEO water absorbent) Is known).

The applications of these highly water-absorbent materials include admixtures for concrete, cement, etc., dehydrating materials from water-immiscible organic solvents, sanitary materials such as diapers, paper filters, tampons, and napkins.
Sealing material for pure water and water containing ions, instant sandbags, cold insulation materials, knitted fabrics that lose breathability when wet with rain, curing film that makes good use of swelling when swelling, artificial soil, water moss, filter media, substitutes for ion exchange resins Application to a wide range of applications such as Among these applications, sanitary materials, applications relating to ion-containing water, etc. are required to absorb a large amount of ion-containing water.

However, most of the superabsorbents that have been reported so far are for water that does not contain ions (for example, distilled water), when measured by the tea bag method (referred to as TB method) described later,
It shows a very high swelling property of 50 to 1000 times, but its water absorption is greatly reduced in the case of water containing ions such as physiological saline, seawater, ammonia water, and imidazoline salt aqueous solution.

Among these water absorbents, nonionic water absorbents such as PVA water absorbents and PEO water absorbents are exceptional water absorbents that are not affected by ions. However, the water absorption of PVA-based water absorbent and PEO-based water absorbent is low, the TB method with a soaking time of 24 hours shows that the pure water and seawater are about 10 to 30 times, and the water absorption speed is slow. Most of the high water absorbents other than PVA and PEO water absorbents swell in 90% of the equilibrium value in a few seconds to a few minutes in the case of pure water, but it takes several hours in the case of PVA and PEO water absorbents. .

As one having improved high water absorption property against ion-containing water, carboxymethyl cellulose as disclosed in JP-A-52-155218 is known, which has high water absorption property and high water absorption speed. However, it has the drawbacks that it easily rots in a swollen state, and has poor durability under various conditions.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above problems and provide a high water-absorbing body having a large water absorption amount for ion-containing water, a high water-absorption rate, and excellent durability. To do.

(Means for Solving Problems) As a result of various investigations for achieving the above-mentioned object, the present inventors have found that by treating an ionic superabsorbent with a nonionic superabsorbent, The water absorption is large and the water supply rate becomes long, and especially when an acrylic polymer is used as the ionic high water absorbent, it becomes a nonionic high water absorbent.
It has been found that the use of the PEO-based high water-absorbing material makes it possible to obtain a highly water-absorbing material which is resistant to biological decay and has excellent durability, and has completed the present invention.

That is, the present invention is characterized in that the ionic superabsorbent is treated with the nonionic superabsorbent.

Further, in the present invention, particularly polyacrylate, as the ionic water-absorbing material, an acrylic water-absorbing material such as a copolymer of acrylate and acrylonitrile is used, and particularly as a nonionic water-absorbing material, a PEO-based water absorbing material. By using the body,
A highly water-absorbent body with excellent durability that is less susceptible to biological decay is obtained.

Acrylic superabsorbent is an ionic superabsorbent used in the present invention, a method of hydrolyzing polyacrylonitrile, a method of copolymerizing an acrylic monomer having a carboxyl group, acrylonitrile and acrylonitrile copolymerizable activity It is obtained by copolymerizing a monomer having a double bond and a carboxyl group.

The PEO superabsorbent used in the present invention is obtained by the method described in Japanese Examined Patent Publication (Kokoku) No. 50-36280, that is, water-soluble polyethylene oxide having an average molecular weight of 100,000 or more, and 0.01 to 5% by weight of mono- and polyisocyanate. It can be obtained by reacting a compound. The water-soluble polyethylene oxide may have an average molecular weight of 100,000 or more. When the molecular weight is smaller than this range, even a similar reaction product is fragile and does not form a film, and has a low swelling property with respect to water or is dispersed in small particles, resulting in poor practicality. Further, propylene oxide, butylene oxide and other polymerizable components may be contained as a copolymer to the extent that water solubility is not lost, and within the range, a alkylene group or an alkyl group is contained in the main chain or the side chain. May be. These may be used alone or as a mixture of two or more kinds. It is also possible to appropriately adjust the properties of the resin produced by using these appropriate copolymers or mixtures, such as water swelling property.

On the other hand, mono- and polyisocyanate compounds are organic compounds containing one or more isocyanate groups in the same molecule, for example, n-propyl isocyanate, n-butyl isocyanate, n-hexyl isocyanate, Dodecyl Isocyanate, Octadecyl Isocyanate, Cyclohexyl Isocyanate, Benzyl Isocyanate, Phenyl Isocyanate, p-Chlorophenyl Isocyanate, p-Nitrophenyl Isocyanate, 2-Chloroethyl Isocyanate, Stearoyl Isocyanate, p-Toluol Sulfo Nyl isocyanate, propane diisocyanate, hexane diisocyanate, decane isocyanate, ω ・ ω'-dipropyl ether diisocyanate, thiodiethyl diisocyanate, hexafluoro Propane diisocyanate, 1,3
-Dimethylbenzene-ω ・ ω'-diisocyanate, 1,
4-dimethylnaphthalene, ω-ω'-diisocyanate, 2,4-toluylene diisocyanate, 1,3-dimethylbenzene-2,4-diisocyanate, naphthalene-1,4 diisocyanate, biphenyl-4 , 4'-diisocyanate, 2-nitrobiphenyl-4,4 'diisocyanate,
3,3'-dimethoxybiphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,
3'-dichlorodiphenyldimethylmethane-4,4'-diisocyanate, 1-methylbenzene-2,4,6-triisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4, 4'-triisocyanate, triphenylmethane-4,4 ', 4 "-triisocyanate, TDI trimer (Desmodur 1L), polymethylene polyphenyl isocyanate (Apjon Corporation), trimethylolpropane Examples include urethane triisocyanate compounds (decimodur L) obtained by reacting a polyol such as the above with a molar number of diisocyanate corresponding to the number of active hydrogens.

Furthermore, even if these mono- and polyisocyanate compounds are masked with a suitable masking agent, it does not matter if they can be raised above the regeneration temperature during the reaction. Further, these may be used alone or in a mixture of two or more for the reaction. The amount of the mono- and polyisocyanate compounds used in the reaction is preferably 0.01 to 5% by weight based on the polyethylene oxide resin, and is preferably 0.05 to 2% by weight, although it varies depending on the type of each reaction composition.

As a method for reacting a polyethylene oxide resin with a mono- or polyisocyanate compound, it is usual to react in a solution form in an appropriate solvent, but in a dispersion form in a solvent, or in a powder form or a solid form. It is also possible to uniformly mix the two and then heat the mixture to a predetermined temperature for reaction. The reaction temperature is generally preferably 50 ° C to 150 ° C.

The shape of the acrylic superabsorbent material used in the present invention is powdery,
Fruit-like, film-like, or sheet-like cloth, nonwoven fabric, yarn-like fibrous structures and / or surfaces holding a powdery material of acrylic superabsorbent, fruit-like material, film-like material Things are good. The fibrous structure may be short fibers, long fibers, or a combination thereof.

As a method of treating the ionic superabsorbent with the nonionic superabsorbent, for example, when the ionic superabsorbent is a polymer powder, the nonionic superabsorbent dissolved in a volatile organic solvent and the ionic superabsorbent The water absorbent of the present invention can be obtained by mixing and stirring the polymer powder, volatilizing and removing the organic solvent, and then pulverizing the obtained lump.

When the ionic superabsorbent is a film-like or sheet-like fabric, a non-woven fabric, a structure such as a yarn, a method of squeezing the structure with a mangle after dipping the structure, or a fabric in the case of a yarn. The water-absorbing material of the present invention can be obtained by a method based on gluing warping, a method by single gluing (for example, Unisizer; trade name of Kaji Seisakusho Co., Ltd.), and the like.

(Effects of the Invention) The water absorbent of the present invention has a large water absorption amount even for ion-containing water, a high water absorption speed, and excellent durability.

(Example) Hereinafter, the present invention will be described in more detail with reference to Examples. All percentages in the examples are weight percentages.

The evaluation methods of the characteristic values in the examples are as follows.

Water absorption: a) Method TB The sample placed in a polyester net is immersed in water at 20 ° C for a certain period of time, suspended in the air for 10 minutes, and then taken out from the net and weighed. The weight at this time is taken as A, and the water absorption capacity is determined by the following formula. However, C in the formula is the weight after drying in a hot air dryer adjusted to 80 ° C. until there is no change in weight.

B) CB method The sample weighed by the TB method is returned to the polyester net again, dehydrated by a centrifugal dehydrator with a force of 100 G for a predetermined time, and then the sample is taken out from the net and weighed. The weight at this time is defined as B, and the water absorption capacity is determined by the following formula.

Example 1 20 parts of a polyethylene oxide resin having an average molecular weight of 500,000 and 0.05 part of triethyldiamine were added to 380 parts of nitromethane and completely dissolved in a nitrogen atmosphere at 30 to 40 ° C.,
1-Methylbenzol and 0.1 part of 2,5-diisocyanate were added, and a PEO-based high water-absorber (water absorption ratio of film: 30 times by TB method) obtained by reacting at 70 ° C. for 5 hours was prepared. This P
10 parts of the EO-based water absorbent was mixed with 45 parts of toluene and 45 parts of ethylene dichloride and stirred to obtain a liquid PEO-based high water absorbent. This liquid P
To 100 parts of EO-based super absorbent body, 10 parts of powdered aqua keep 10SH (manufactured by Steel Chemical Industry Co., Ltd., trade name), which is a polyacrylate based super absorbent polymer, was added and thoroughly mixed and stirred.
Evaporated to dryness. This solid was crushed to prepare a powdery high water absorbent. The absorption performance of the powdery water-absorbent material thus obtained is shown in Table 1 in comparison with the powdery aquakeep 10SH single material and the powdery material comprising the above PEO-based water-absorbing material.

As shown in Example 1, the product of the present invention has a significantly improved absorption capacity for artificial seawater as compared with Comparative Examples 1 and 2. It was confirmed that the product of the present invention did not decompose even after long-term use.

Example 2 Poester Spunbond E5030 (manufactured by Asahi Chemical Industry Co., Ltd.,
Polyester long-fiber non-woven fabric (trade name) coated with acrylic adhesive, powdered Aqua Keep 10SH (trade name, manufactured by Steel Chemical Industry Co., Ltd.), which is an ionic water absorbent,
g / m ^{2 was} uniformly dispersed and held, and then polyester spun bond E5030 coated with an acrylic adhesive was overlaid, and pressure was applied by a roller to bond them. This sheet-like material was immersed in the liquid toluene / ethylene chloride-based liquid PEO superabsorbent material of Example 1, squeezed with a mangle to a squeezing ratio of 200%, and dried. The sheet material thus obtained and PEO
The absorption ratio of the sheet-shaped material before processing to artificial seawater is second
Shown in the table.

As shown in Example 2, the product of the present invention has a significantly improved water absorption capacity for artificial seawater as compared with Comparative Example 3.

Claims (2)

[Claims] 1. A water absorbent material, which is obtained by treating an ionic water absorbent material or an absorbent material containing the same with a nonionic water absorbent material. 2. The water absorbing material according to claim 1, wherein the ionic superabsorbent is an acrylic copolymer and the nonionic superabsorbent is a polyethylene oxide crosslinked polymer. .