JPH1095810A - High water absorption resin and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high water absorption resin which is modified so that it not only can absorb a large amount of an aqueous liquid containing a high molecular weight substance, such as blood, but also does not release the liquid even when the resin is pressed after absorption, and therefore it can be suitably used for medical application as an absorber, and a method for producing the resin. SOLUTION: This high water absorption resin contains a carboxyl group and also at least one ion selected from among zinc, nickel, manganese, iron, cobalt and copper as a counter ion of the carboxyl group in an amount of 2 to 12wt.%, and is produced as follows. A treating liquid is prepared by mixing a water-soluble salt of at least one metal selected from among zinc, nickel, manganese, iron, cobalt and copper with a mixed solvent of water and an organic solvent miscible with water in a concentration of the organic solvent of 30 to 70wt.% and dissolving the metal salt in the mixed solvent. A high water absorption resin which contains a carboxyl group is mixed with the treating liquid while agitating, so that an ion of at least one metal selected from among zinc, nickel, manganese, iron, cobalt and copper is bonded to the high water absorption resin as a counter ion of the carboxyl group. After the reaction, the resulting resin is dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous solution containing a large amount of a high molecular weight substance such as blood, starch, aqueous solution of polyvinyl alcohol, etc., and which is difficult to absorb with a conventional superabsorbent resin. The present invention also relates to a highly water-absorbent resin which exhibits excellent liquid absorbability and is useful in various fields such as various medical materials, sanitary materials, civil engineering and construction materials, and a method for producing the same.

[0002]

2. Description of the Related Art Cotton, pulp, paper, cloth, nonwoven fabric, sponge, etc. are typical water-absorbing materials and are used in large quantities. There is a drawback that the amount is small and the water once absorbed is squeezed out when pressure is applied. on the other hand,
As a water-absorbing material for an aqueous solution containing salts such as water or saline, a group of materials called superabsorbent resins has been known in recent years, and has been put to practical use. These resin materials basically have a chemical structure in which a water-soluble polymer is slightly crosslinked and made insoluble in water. As such a highly water-absorbing material, a resin that is obtained by neutralizing an aqueous solution of acrylic acid with an alkali metal hydroxide such as sodium hydroxide until neutral and then polymerizing with a copolymerizable cross-linking agent becomes mainstream. However, a large number of products, such as a product obtained by graft polymerization of a metal acrylate to starch and a hydrolyzate of a methyl methacrylate-vinyl acetate copolymer, have been proposed and put into practical use.

There are many known methods for producing such a superabsorbent resin. For example, a powdery superabsorbent resin is obtained by partially neutralizing acrylic acid with an alkali and then subjecting it to reverse layer suspension polymerization ( JP-B-54-30710, JP-A-57-15
No. 8209, JP-A-59-62665), a method in which acrylic acid is partially neutralized with an alkali, polymerized in an aqueous solution, dried and pulverized into a powder (JP-A-55-1).
No. 08407, JP-A-57-34101 and JP-A-58-71907) are typical examples. Further, a product obtained by saponifying a vinyl acetate-methyl acrylate copolymer (Japanese Patent Publication No. 53-13495,
JP-A-3-50290), saponified isobutylene-maleic anhydride copolymer (JP-A-56-36504), starch obtained by graft polymerization of acrylic acid (JP-B-53-46199), polysaccharides (Japanese Patent Application Laid-Open No. 55-161813) are also known.

As a fibrous superabsorbent resin, a fiber made of a polyacrylonitrile-based polymer is hydrolyzed with an alkali to convert a nitrile group into a carboxyl group (Japanese Patent Laid-Open No.
No. 0-194173), an aqueous solution of a copolymer of acrylic acid and a vinyl monomer having an internal plasticizing action is spun and crosslinked (JP-A-63-159440).
And the like. As the superabsorbent resin composited with the fibrous substance, acrylic acid is impregnated or dispersed in a fiber base material and then polymerized (Japanese Patent Publication Nos. 6-55293 and 6-78402). , Tokuhei 6-890
No. 77, Japanese Patent Publication No. 7-10927) and the like.

[0005] Since the principle of water absorption is osmotic pressure, these superabsorbent resins absorb much more water than water-absorbing materials based on the capillary phenomenon, such as cotton, pulp, paper, cloth, nonwoven fabric and sponge. Such a highly water-absorbent resin has an excellent feature that it does not easily release water even when pressure is applied in a water-absorbing state. For this reason, disposable disposable diapers using super-absorbent resin have high water absorption,
The absorbed liquid does not return and requires less absorbing material, so that it has an advantage that it can be made thinner as a whole, and plays a major role in the spread of disposable disposable diapers. The superabsorbent resin is also used in the field of agricultural materials such as soil water retention agent and seedling raising sheet, food field such as food freshness preserving material and dewatering material, preventing sludge from excavation during tunnel excavation, and sheeting such as sheet for preventing dew condensation in buildings. -Widely used as a building material.

As described above, a superabsorbent resin is the most excellent as a water absorbing material for an aqueous solution containing water or salts, but there are also aqueous liquids which are hardly absorbed by the superabsorbent resin. For example, an aqueous solution containing a high-concentration salt or acid is, of course, inferior in water absorption from the principle of water absorption of a highly water-absorbent resin. Aqueous liquids that cannot be absorbed regardless, for example, human and animal blood,
Examples include plasma, serum, or an aqueous solution containing a high concentration of a water-soluble polymer such as starch or polyvinyl alcohol. For these aqueous liquids, the water absorption of the superabsorbent resin is surprisingly reduced, and is almost useless as a water absorbing material. In particular, blood is an aqueous liquid that is most difficult to absorb, but in the medical field, absorbent materials for absorbing blood are:
It is indispensable. In such a case, a water-absorbing material based on a capillary phenomenon such as cotton, pulp, paper, cloth, nonwoven fabric, and sponge will be used.
It has the disadvantages of low water absorption and the release of blood once absorbed when pressure is applied.

[0007]

In view of this background, the present inventors have made intensive studies to solve the disadvantages of the conventional superabsorbent resin, and as a result, have found that the counter ion of carboxyl group in sodium, potassium, ammonium and the like. When the conventional superabsorbent resin having a high molecular weight substance comes into contact with a liquid containing a high molecular weight substance, it immediately absorbs only water and swells, so that the high molecular weight substance is concentrated around the superabsorbent resin. Obtained the finding that a wall that is difficult to penetrate water is formed, resulting in further impairment of water absorption, and focusing on this finding, the water-absorbent resin having a carboxyl group swells due to water absorption. In order not to dissolve a specific metal ion in a solvent system composed of water and an organic solvent formed at a specific ratio, and to prepare a counter ion such as sodium, potassium, and ammonium of the resin, The superabsorbent resin, in which a specific metal ion is replaced by ion exchange and contains a specific amount of a metal ion as a counter ion of a carboxyl group, does not swell for a while even when it comes into contact with a liquid containing a high molecular weight substance. By its action, the aqueous liquid can penetrate into every corner between the particles of the superabsorbent resin, and after the permeation ends, water absorption occurs, so that a liquid containing a high molecular weight substance, For example, they have found that they exhibit extremely excellent performance in absorbing starch aqueous solution and blood, and have completed the present invention. An object of the present invention is to eliminate the drawbacks of conventional superabsorbent resins that cannot absorb liquids containing high molecular weight substances, such as human or animal blood, concentrated aqueous solutions of starch and polyvinyl alcohol, and have a high molecular weight. Modified superabsorbent resin as an absorbent material that absorbs a large amount of liquid containing a substance and does not re-release even if pressure is applied after absorption, and can be suitably used for applications in a wide range of fields, especially medical applications And a method for manufacturing the same.

[0008]

The first aspect of the present invention is a super water-absorbing resin having a carboxyl group, wherein at least one ion selected from zinc, nickel, manganese, iron, cobalt and copper is converted to a carboxyl group. 2 as a counter ion of
It is a highly water-absorbent resin characterized by containing 12% by weight.
The second aspect of the present invention is that the concentration of the organic solvent compatible with water is 3%.
At least one water-soluble metal salt selected from zinc, nickel, manganese, iron, cobalt, and copper is mixed and dissolved in 0 to 70% by weight of a mixed solvent of water and an organic solvent compatible with water. The super-absorbent resin having a carboxyl group is mixed and stirred with the treated solution, and zinc,
A highly water-absorbent resin characterized in that 2 to 12% by weight of at least one ion selected from nickel, manganese, iron, cobalt, and copper is bound as a counter ion of a carboxyl group of the highly water-absorbent resin, followed by drying. It is a manufacturing method of.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The superabsorbent resin used in the present invention may be any one in which a linear polymer in which a monomer having a carboxyl group is polymerized forms a three-dimensional network structure by crosslinking. . Also, as another super absorbent resin,
A linear polymer obtained by copolymerizing a monomer having a carboxyl group and a monomer having no carboxyl group may form a three-dimensional network structure by cross-linking.
The form of the superabsorbent tree of the present invention is not particularly limited, and powdery ones, fibrous ones, composites with fibrous substances, and the like can be used. These superabsorbent resins having a carboxyl group can be produced by the above-mentioned known method, or commercially available resins can be used.

In most cases, the counter ions of the carboxyl groups of the above-mentioned known superabsorbent resins are sodium ions and protons, but sometimes potassium ions, ammonium ions or other ions are used as counter ions instead of sodium ions. Some superabsorbent resins also exist. The highly water-absorbent resin containing the metal ion of the present invention and having excellent absorbability of an aqueous solution containing a high molecular weight substance is the sodium,
It is produced by ion exchange using a known superabsorbent resin having potassium, ammonium, etc. as a counter ion of a carboxyl group, but such a resin has a high water absorbency, so that it absorbs a very large amount of water and swells. Therefore, it is necessary to prevent swelling when carrying metal ions. Therefore, in order to produce the superabsorbent resin containing the metal ion of the present invention, first, a treatment liquid in which an organic solvent compatible with water, water and a water-soluble metal salt are mixed, is prepared. To the liquid, sodium, potassium,
A superabsorbent resin having an ammonium ion or the like as a carboxyl group counter ion is added, mixed and stirred, and during that time, a metal ion is bonded as a carboxyl group counter ion of the superabsorbent resin by an ion exchange reaction.

Examples of the organic solvent compatible with water include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, acetone, dioxane, acetonitrile, tetrahydrofuran and the like. Good to use. Metal ions used in the present invention for ion exchange include zinc, nickel, manganese, and iron (divalent or trivalent).
), Cobalt and copper salts, but any water-soluble salts can be used. As the salt form, sulfates, nitrates, chlorides, acetates and the like can be suitably used because of their high solubility. More specifically, these compounds include zinc sulfate, zinc nitrate, zinc chloride, zinc acetate, nickel sulfate, nickel nitrate, nickel chloride, nickel acetate, manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, Iron, ferric sulfate, ferrous nitrate, ferric nitrate, ferrous chloride, ferric chloride, ferrous acetate, ferric acetate, cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, sulfuric acid Copper, copper nitrate, copper chloride, copper acetate and the like can be mentioned, and these are appropriately selected and used from these. These metal salts are usually used in a form containing water of crystallization, but of course, anhydrous salts may be used. Since zinc and nickel are most effective in increasing blood absorption, it is preferable to use water-soluble salts of these metals alone or in combination.

In the present invention, the mixing ratio of water and an organic solvent compatible with water for dissolving the water-soluble metal salt is such that the concentration of the organic solvent is from 30 to 70 per total weight.
% By weight, preferably in the range of 40-60% by weight. Within this range, it has been found that the superabsorbent resin only swells slightly, and that the ion exchange reaction can be carried out smoothly. When the concentration of the organic solvent is 7
If it exceeds 0% by weight, the ion exchange reaction hardly occurs. Conversely, when the concentration of the organic solvent is less than 30% by weight, the ion exchange reaction is accelerated, but swelling due to water absorption of the highly water-absorbing resin occurs, so that an enormous amount of water must be removed by drying, Not a realistic way.

The mixing amount of the water-soluble metal salt in the mixed solvent of the organic solvent and water depends on conditions such as the target value of the metal content in the superabsorbent resin, the type of the resin, and the salt concentration. Although determined, the weight ratio of the water-soluble metal salt to the superabsorbent resin is selected from the range of 10 to 200% by weight in terms of anhydride. It is good to use the water-soluble metal salt after completely dissolving it in the mixed medium of the organic solvent and water, since the time required for ion exchange can be shortened. Since the dissolution rate is low, it is more convenient to avoid this by first dissolving the water-soluble metal salt in water in advance, and then adding and mixing an organic solvent. Depending on the conditions, this method may not completely dissolve due to the limitation of the solubility, but may be used as it is if a sufficient time is taken for the ion exchange reaction.

The organic solvent thus prepared, water,
And a treatment liquid comprising a mixture of a water-soluble metal salt, a superabsorbent resin for ion exchange is added and mixed, and the mixture is sufficiently stirred to bring the treatment liquid into contact with the superabsorbent resin so that metal ions are ion-exchanged. As a counter ion of the carboxyl group of the superabsorbent resin. The amount of the treatment liquid added to the superabsorbent resin is 20 to 200 kg / kg of the resin.
If the amount is small, uniform mixing becomes difficult, and if too large, the cost of the organic solvent increases, which is not preferable. It should be noted that, depending on the type of the superabsorbent resin, when mixed with the processing liquid, the resin may swell to form a partial lump, and may be poorly dispersed in the processing liquid. In that case, the amount of water in the processing liquid was temporarily reduced, the organic solvent concentration was increased and mixed with the superabsorbent resin, and when the superabsorbent resin was sufficiently dispersed, the amount was temporarily reduced. It is sufficient to return the concentration of the organic solvent to a predetermined concentration by adding water. Since the ion exchange reaction takes place rapidly, there is no need to particularly heat, and it is only necessary to continue stirring at room temperature of 15 to 35 ° C. for 10 minutes to 5 hours.

The highly water-absorbing resin after the ion exchange reaction is
Pressing, centrifugal dehydration, filtration using a filter or decantation removes the treatment liquid, and may be dried.
The superabsorbent resin at this stage contains a small amount of water and unreacted water-soluble metal salts that have not been bonded to the superabsorbent resin, so that when dried, they are agglomerated and cannot be obtained in powder or fibrous form. . To avoid this, the superabsorbent resin after filtration is washed with a mixture of water and an organic solvent compatible with water to first remove unreacted water-soluble metal salts, and then to remove water-soluble metal salts. After washing with a soluble organic solvent to remove water and drying, a powdery or fibrous product is obtained. Zinc, contained in the ion-exchanged dried superabsorbent resin,
The total content of at least one metal selected from nickel, manganese, iron, cobalt, and copper is in the range of 2 to 12% by weight, preferably 3.5 to 10% by weight, based on the total weight of the bone dry. If the metal content is less than 2% by weight, the absorption of blood is hardly improved as a representative of a liquid containing a high molecular weight substance. When the amount of absorption becomes maximum and exceeds 12% by weight, the amount of blood absorbed reaches a plateau again and is not so much improved or conversely tends to decrease, which is not economical.

In the present invention, the reason why a superabsorbent resin excellent in the amount of absorbed blood is obtained is not clear, but is considered as follows. That is, blood components are red blood cells, white blood cells, blood cells such as platelets, and other liquid components,
That is, it is divided into plasma. Many components are dissolved in plasma, and the most common components are water-soluble proteins such as albumin and globulin. The proportion of water-soluble protein in plasma is about 8% in human blood. On the other hand, the conventional superabsorbent resin containing sodium, potassium, and ammonium ions as carboxyl group counterions has a three-dimensional network structure formed by cross-linking of a linear polymer, so that it has a three-dimensional network structure. When the superabsorbent resin comes into contact, the superabsorbent resin absorbs moisture, gels and tries to swell, but water-soluble proteins such as albumin and globulin are high molecular weight substances, It cannot penetrate due to the larger size of the molecular structure.

In this case, the form of the superabsorbent resin is as follows:
Although the average particle diameter is often a fine powder of 50 to 300 μm, in an absorbent article to which a large amount of superabsorbent resin is added for the purpose of increasing the amount of water absorbed, the water absorbent resin has one particle per particle. The particles do not exist in a dispersed state, but are in an aggregated state in which the particles are in contact with each other. When the superabsorbent resin powder in such an aggregated state comes into contact with blood, only water is absorbed by the superabsorbent resin, and as a result, the remaining protein forms a thick layer outside the aggregate to form the aggregate. This thick layer is difficult to penetrate water, so that the liquid cannot penetrate inside (so-called "mamako"), and the highly water-absorbent resin inside cannot even come into contact with blood. Extremely low. The present inventors have experimentally confirmed that not only blood but also a concentrated aqueous solution of starch or polyvinyl alcohol has an extremely small absorption amount of the conventional superabsorbent resin, which is similar to the case of blood. It seems to be due to the mechanism.

The modified superabsorbent resin containing the metal ion of the present invention as a counter ion of a carboxyl group exhibits high absorbency not only for blood but also for concentrated aqueous solutions of starch and polyvinyl alcohol. Seems to have its unique swelling behavior. That is, a superabsorbent resin containing at least one ion selected from zinc, nickel, manganese, iron, cobalt, and copper as a counter ion of 2 to 12% by weight of a carboxyl group is immersed in an aqueous solution to be absorbed. Thus, even if the resin comes into contact with the liquid, swelling does not start for a while. This time is usually from a few seconds to a few minutes, but in extreme cases ones which do not swell in the aqueous solution for more than one hour can also be produced. When a conventional superabsorbent resin is immersed in an aqueous solution, it starts swelling from the moment it comes into contact with the liquid, and as described above, when the object to be absorbed is blood, blood is absorbed inside the superabsorbent resin aggregate. A thick layer of protein is formed outside of the aggregate before it penetrates, thereby blocking the liquid inlet so that no more blood is absorbed.

However, the modified superabsorbent resin of the present invention contains a specific divalent metal ion and can form an ionic bond with two carboxyl groups. Swelling is suppressed for a while even if it comes into contact with blood.
Therefore, since "mamako" is not formed, blood can penetrate into every corner between the particles of the superabsorbent resin forming the aggregate, and after the permeation is completed, the ionic crosslinking is cut off. Since the swelling of the superabsorbent resin occurs, the superabsorbent resin inside the aggregate and at the center can also absorb blood,
As a result, a large amount of blood can be absorbed.

[0020]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the Examples and Comparative Examples, “%” means “% by weight” unless otherwise specified.

Example 1 Nickel sulfate hexahydrate (special grade reagent) in 21.4 g of water
23 g was dissolved, and 39.3 g of methanol (special grade reagent) was mixed. A commercially available particulate polyacrylic acid-based superabsorbent resin (trade name: Diamond Wet US50, particle diameter 100)
5 g of ２００200 μm, manufactured by Mitsubishi Chemical Corporation) were mixed, and 28.6 g of water was added with stirring to adjust the methanol concentration to 44%. The mixture was stirred at 25 ° C. for 1 hour to bind nickel ions to the carboxyl groups of the superabsorbent resin by an ion exchange reaction, and then allowed to stand to settle the superabsorbent resin, followed by decantation to remove the treatment liquid. . Next, water 3
After adding a mixed solvent of 0 g and 55 g of methanol and stirring at 25 ° C. for 1 hour, the mixture was allowed to stand to settle the superabsorbent resin,
The solvent was removed by decantation to remove unreacted nickel sulfate. Finally, 100% methanol 78.
7 g was added, the mixture was stirred at 25 ° C. for 1 hour, filtered to remove water, and then completely dried with a 50 ° C. vacuum dryer. Using the modified superabsorbent resin thus obtained, the amount of cow blood absorbed and the content of metal were measured by the following test methods, and the quality was evaluated.

Test Method (1) Method of Measuring Blood Absorption 0.8 g of the test material was sealed in a 10-cm square, 250-mesh nylon wire bag, and this was filled with bovine blood (500 ml of fresh bovine blood). (10 ml of a 10% aqueous solution of sodium citrate as an anticoagulant) was absorbed for 10 minutes to absorb blood. After being lifted and suspended for 10 minutes, it is placed on a horizontal laboratory table with 10 filter papers (diameter 16 cm, Advantech Toyo, No. 2 filter paper) sandwiched between each of the upper and lower sides, and placed on a horizontal laboratory table. A stainless steel plate having a weight of 100 g was overlaid, a 1 kg weight was placed thereon, and a pressure was applied for 5 minutes to completely absorb the blood remaining in the nylon bag. afterwards,
The weight was measured, and the amount of absorption was indicated by the weight of the bovine blood absorbed per 1 g of the dried sample.

(2) Metal Content Measurement Method 0.3 g of the test material was precisely weighed and placed in a 200 ml tall beaker, and nitric acid (nitric acid 1: water 2) 10 m
l and 10 ml of concentrated sulfuric acid were added, and the mixture was heated with an electric heater. When the content turned dark brown, concentrated nitric acid was added dropwise, and after the color changed to yellow, the addition was stopped. Subsequently, heating was further continued, and when the content changed to dark brown again, concentrated nitric acid was added dropwise, and when the content changed to yellow, the operation of stopping the addition was repeated. If the contents are pale yellow even when the white smoke of sulfuric acid starts to appear, the decomposition has been completed, so the heating was stopped, cooled, and diluted with pure water to make 100 ml. This decomposed liquid was further diluted 100 times with 0.1% nitric acid, the metal concentration was quantified by atomic absorption spectrometry, and the amount of metal in the test material was calculated and obtained.

Example 2 1.37 g of anhydrous zinc sulfate (special grade reagent) was dissolved in 21.4 g of water, and 39.3 g of methanol (special grade reagent) was mixed. The same commercially available polyacrylic acid-based superabsorbent resin as used in Example 1 (trade name: DiaWet US50,
5 g of water and 28.6 g of water while stirring.
g was added to adjust the methanol concentration to 44%. After the mixture was stirred at 25 ° C. for 1 hour to bind zinc ions to the carboxyl groups of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. . Next, 30 g of water and 5
After adding 5 g of a mixed solvent and stirring at 25 ° C. for 1 hour, the mixture was allowed to stand to settle the superabsorbent resin, and the solvent was removed by decantation to remove unreacted zinc sulfate. Finally, 78.7 g of 100% methanol was added, and 2
After stirring at 5 ° C. for 1 hour and filtering to remove water, 50
It dried with the vacuum dryer of ° C. Using the obtained superabsorbent resin, the absorption amount of bovine blood and the metal content in the resin were measured by the test method described above, and the quality was evaluated.

Example 3 Manganese sulfate pentahydrate (special grade reagent) in 21.4 g of water
04 g was dissolved, and 39.3 g of methanol was mixed. 5 g of the same commercially available polyacrylic acid-based superabsorbent resin (trade name: DiaWet US50, manufactured by Mitsubishi Chemical Corporation) as used in Example 1 was mixed, and 28.6 g of water was added while stirring to reduce the methanol concentration. Adjusted to 44%. Mixture at 25 ° C
After the manganese ion was bonded to the carboxyl group of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. Next, a mixed solvent of 30 g of water and 55 g of methanol was added, and the mixture was stirred at 25 ° C. for 1 hour. Then, the mixture was allowed to stand to settle the superabsorbent resin, and the solvent was removed by decantation to remove unreacted manganese sulfate. Removed.
Finally, 78.7 g of 100% methanol was added, and the mixture was added at 25 ° C.
After stirring for 1 hour and removing water by filtration, the mixture was completely dried with a vacuum dryer at 50 ° C. Using the obtained superabsorbent resin, the absorption amount of bovine blood and the metal content in the resin were measured by the test method described above, and the quality was evaluated.

Example 4 Ferrous sulfate heptahydrate (special grade reagent) in 21.4 g of water 2.3
6 g was dissolved, and 39.3 g of methanol was mixed. 5 g of the same commercially available polyacrylic acid-based superabsorbent resin (trade name: DiaWet US50, manufactured by Mitsubishi Chemical Corporation) as used in Example 1 was mixed with the mixture, and 28.6 g of water was added while stirring, followed by addition of methanol. The concentration was adjusted to 44%. Mix 25
After stirring at 1 ° C. for 1 hour to bind ferrous ions to the carboxyl group of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. During the ion exchange reaction, ferrous ions were oxidized by oxygen in the air, and the superabsorbent resin was colored brown. Next, a mixed solvent of 30 g of water and 55 g of methanol was added, and the mixture was stirred at room temperature for 1 hour. Then, the mixture was allowed to stand to settle the superabsorbent resin, and the solvent was removed by decantation to remove unreacted ferrous sulfate. Was removed. Finally 10
After adding 78.7 g of 0% methanol, the mixture was stirred at 25 ° C. for 1 hour, filtered to remove water, and then completely dried with a 50 ° C. vacuum dryer. Using the obtained superabsorbent resin, the absorption amount of bovine blood and the metal content in the resin were measured by the test method described above, and the quality was evaluated.

Example 5 Cobalt sulfate heptahydrate (special grade reagent) in 21.4 g of water
38 g was dissolved, and 39.3 g of methanol was mixed. 5 g of the same commercially available polyacrylic acid-based superabsorbent resin (trade name: DiaWet US50, manufactured by Mitsubishi Chemical Corporation) as used in Example 1 was mixed with the mixture, and 28.6 g of water was added while stirring, followed by addition of methanol. The concentration was adjusted to 44%. Mix 2
After stirring at 5 ° C. for 1 hour to bind the cobalt ions to the carboxyl groups of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. Next, 30 g of water and 55 g of methanol
g of the mixed solvent was added, and the mixture was stirred at room temperature for 1 hour, and then allowed to stand to settle the superabsorbent resin. The solvent was removed by decantation to remove unreacted cobalt sulfate.
Finally, 78.7 g of 100% methanol was added, and the mixture was added at 25 ° C.
After stirring for 1 hour and removing water by filtration, the mixture was completely dried with a vacuum dryer at 50 ° C. Using the obtained superabsorbent resin, the absorption amount of bovine blood and the metal content in the resin were measured by the test method described above, and the quality was evaluated.

Example 6 2.12 g of copper sulfate pentahydrate (special grade reagent) in 21.4 g of water
Was dissolved, and 39.3 g of methanol was mixed. 5 g of the same commercially available polyacrylic acid-based superabsorbent resin (trade name: DiaWet US50, manufactured by Mitsubishi Chemical Corporation) as used in Example 1 was mixed with the mixture, and 28.6 g of water was added while stirring, followed by addition of methanol. The concentration was adjusted to 44%. Mixture at 25 ° C
After stirring for 1 hour to bind the copper ions to the carboxyl groups of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. Next, a mixed solvent of 30 g of water and 55 g of methanol was added, and the mixture was stirred at 25 ° C. for 1 hour, and then allowed to stand to settle the superabsorbent resin. The solvent was removed by decantation to remove unreacted copper sulfate. Removed. Finally 100%
78.7 g of methanol was added, and the mixture was stirred at 25 ° C. for 1 hour, filtered to remove water, and then completely dried with a 50 ° C. vacuum dryer. Using the modified superabsorbent resin thus obtained, the amount of bovine blood absorbed was measured by the following test method, and the quality was evaluated.

Example 7 Nickel sulfate hexahydrate (special grade reagent) in 34.4 g of water
23 g was dissolved by stirring, and 51.6 g of methanol was mixed. The same commercially available polyacrylic acid-based superabsorbent resin as used in Example 1 (trade name: Diamond Wet US5)
0, manufactured by Mitsubishi Chemical Corporation). At this time, the methanol concentration was 60%. After the mixture was stirred at 25 ° C. for 4 hours to bind nickel ions to the carboxyl groups of the superabsorbent resin by ion exchange reaction, the mixture was allowed to stand to settle the superabsorbent resin, and the treatment liquid was removed by decantation. . Next, a mixed solvent of 30 g of water and 55 g of methanol was added, and the mixture was stirred at room temperature for 1 hour. Then, the mixture was allowed to stand to settle the superabsorbent resin, and the solvent was removed by decantation to remove unreacted nickel sulfate. did. Finally, 78.7 g of 100% methanol was added, and the mixture was stirred at 25 ° C. for 1 hour.
After removing water by filtration, the product was completely dried with a vacuum dryer at 50 ° C. Using the obtained superabsorbent resin, the absorption amount of bovine blood and the metal content in the resin were measured by the test method described above, and the quality was evaluated.

Comparative Example 1 The same commercially available polyacrylic acid-based superabsorbent resin (trade name: Diamond Wet US50, manufactured by Mitsubishi Chemical Corporation) as used in Examples 1 to 6 was treated as described above without any treatment. The blood absorption and the metal content of the cow were measured by the test method, and the quality was evaluated.

Comparative Example 2 A super water-absorbent resin having a reduced nickel ion binding amount was produced in the same manner as in Example 1 except that the amount of nickel sulfate hexahydrate was reduced to 0.5 g. did. Using the resulting superabsorbent resin, the amount of cow blood absorbed and the content of metal were measured by the test method described above, and the quality was evaluated.

Comparative Example 3 A superabsorbent resin having an increased nickel ion binding amount was produced in the same manner as in Example 1 except that the amount of nickel sulfate hexahydrate was increased to 3.0 g. did. Using the resulting superabsorbent resin, the amount of cow blood absorbed and the content of metal were measured by the test method described above, and the quality was evaluated.

Table 1 shows the results obtained in Examples and Comparative Examples.

[0034]

[Table 1]

As can be seen from Table 1, the untreated commercial superabsorbent resin has a remarkably low absorption of bovine blood (Comparative Example 1).
On the other hand, all of the highly absorbent resins according to the present invention have high blood absorption (Examples 1 to 7). However, if the content of nickel is too small even in the superabsorbent resin to which nickel is bound, the amount of absorbed blood is extremely low (Comparative Example 2),
Conversely, even if the nickel content was too large, the blood absorption was reduced (Comparative Example 3).

[0036]

According to the present invention, there is provided a modified superabsorbent resin which absorbs a large amount of a liquid containing a high molecular weight substance and does not re-release even if pressure is applied after absorption, and a method for producing the same. It works.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C08J 7/00 CEY A41B 13/02 S C08L 33/02 LHR A61F 13/18 307A

Claims (2)

[Claims] 1. A super-absorbent resin having a carboxyl group, comprising at least one ion selected from zinc, nickel, manganese, iron, cobalt and copper as a counter ion of the carboxyl group in an amount of 2 to 12% by weight. Highly water absorbent resin characterized by the following. 2. The concentration of an organic solvent compatible with water is 30.
~ 70% by weight of a mixed solvent of water and an organic solvent compatible with water, zinc, nickel, manganese, iron, cobalt,
Mixing at least one water-soluble metal salt selected from copper,
A superabsorbent resin having a carboxyl group is mixed and stirred with the dissolved processing solution, and at least one ion selected from zinc, nickel, manganese, iron, cobalt, and copper is ion-exchanged into carboxyl of the superabsorbent resin. A method for producing a highly water-absorbent resin, comprising bonding 2 to 12% by weight as a counter ion of a group, followed by drying.