JP2005074255A - Production method of granular water absorption material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method whereby a water absorption material consisting of a biodegradable polysaccharide having a high absorption performance is produced by a simple process not requiring a large amount of a volatile hydrophilic solvent. <P>SOLUTION: A method for producing a granular water absorption material composed of crosslinked galactomannan is provided. The method includes a process wherein a galactomannan powder is mixed with an aqueous crosslinker solution containing borate ion and/or a trivalent or higher polyvalent metallic ion to crosslink galactomannan and to granulate the powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a granular water-absorbing material having a low production cost, excellent biodegradability, and excellent absorption performance for body fluids such as blood and urine.

  The water-absorbing material is a resin that can absorb water several tens to several thousand times its own weight. For example, an acrylic water-absorbing material is known. These water-absorbing materials are widely used for disposable sanitary products because of their high water absorption. However, the conventional water-absorbing material is not biodegradable, and there has been a problem in the method for treating sanitary goods containing it.

  Examples of the water-absorbing material having biodegradability include, for example, a polyethylene oxide crosslinked body (for example, see Patent Document 1), a polyvinyl alcohol crosslinked body, a carboxymethylcellulose crosslinked body (for example, see Patent Document 2), an alginate crosslinked body, and a starch crosslinked body ( For example, patent document 3), a polyamino acid crosslinked body (for example, refer to patent documents 4 to 8), a galactomannan-metal ion crosslinked body (for example, refer to patent documents 9 to 11), and the like are known.

  By the way, when these water-degradable water-absorbing materials are compared with non-biodegradable synthetic polymer water-absorbing materials, the bio-degradable water-absorbing materials have higher production costs and lower water-absorbing performance. Due to problems such as weak gel strength after water absorption, it has not been put to practical use. Therefore, the present inventors have reported that a water-absorbing material composed of galactomannan and borate ions and / or trivalent or higher polyvalent metal ions is biodegradable and has excellent water absorption performance and gel strength after water absorption. (For example, see Patent Document 12 and Patent Document 13).

  The performance required for commonly used water-absorbing materials includes urine, blood, menstrual blood, sweat, and other body fluids containing monovalent or higher cations, as well as a large amount of environmental fluids such as mud, seawater, and river water. It is required to absorb and retain liquid. In particular, the present inventors have reported that a high specific surface area is effective in absorbing mucus containing a large amount of solids such as blood (see, for example, Japanese Patent Application No. 2002-253952).

  Although the water-absorbing material composed of galactomannan and borate ions and / or trivalent or higher polyvalent metal ions has excellent body fluid absorbability in this respect, it passes through a crosslinked hydrogel at the time of production. Have a process to do.

  In order to recover the crosslinked hydrogel as a water-absorbing material that maintains a high surface area by drying, it is necessary to efficiently dehydrate the water from the hydrogel. As a method for efficiently dehydrating the hydrogel, a volatile hydrophilic solvent typified by alcohol is directly brought into contact with the crushed hydrogel, the water in the gel is sufficiently substituted with alcohol, and solid liquid is obtained by centrifugation or the like. The method of drying the solid content after separation is most preferable, but a large amount of volatile hydrophilic solvent (10 to 25 times the amount of the water-absorbing material) is required as compared with the recovered mass of the water-absorbing material.

For this reason, the cost which a volatile hydrophilic solvent requires becomes huge, and there existed a problem that a water absorbing material will become expensive as a result.
JP-A-6-157795 U.S. Pat. No. 4,650,716 Japanese Patent Laid-Open No. 55-15634 JP 7-224163 A JP 7-309943 A JP-A-8-59820 JP-A-8-504219 JP-A-9-169840 JP-A-8-59891 Japanese Patent Publication No. 3-66321 JP 56-97450 A JP 2001-12992 A JP 2002-37924 A

  The object of the present invention is to solve the above-mentioned conventional problems, have biodegradability, do not require a large amount of volatile hydrophilic solvent in the production process, and have a granular water absorption having good absorption performance It is in providing a material and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have found that a granular crosslinked product can be obtained by adding and mixing an aqueous crosslinking agent solution directly to galactomannan, and to complete the present invention. It came.

  That is, the present invention includes a step of adding an aqueous solution of a cross-linking agent containing borate ions and / or trivalent or higher polyvalent metal ions to galactomannan powder to crosslink the galactomannan and granulate it into granules. The manufacturing method of the granular water absorbing material which consists of galactomannan crosslinked body characterized by including this is provided.

  The method of adding and mixing the aqueous solution of the crosslinking agent is not particularly limited, but preferably, the aqueous solution of the crosslinking agent is sprayed on the galactomannan powder and stirred. According to the spraying, it is not necessary to stir the mixture of the galactomannan and the aqueous crosslinking agent solution at high speed, and the galactomannan powder can be uniformly contacted with the galactomannan powder.

  Also preferably, the aqueous crosslinking agent solution added to the galactomannan powder is 200% by mass or less based on the galactomannan powder.

  Further, when the crosslinking agent is borate ion, the amount of the crosslinking agent added is preferably 1 to 200 mmol as boric acid per 1 kg of galactomannan powder, and the crosslinking agent is trivalent or higher polyvalent metal ion. It is preferable to add 1 to 100 mmol of the metal per 1 kg of galactomannan powder.

  According to the present invention, it is possible to produce a biodegradable water-absorbing material at low cost without using a large amount of volatile hydrophilic solvent such as alcohol.

  The present invention is a method for producing a granular water-absorbing material having biodegradability, wherein an aqueous solution containing boric acid and / or trivalent or higher polyvalent metal ions is uniformly added to the galactomannan powder and crosslinked. It includes the steps of aggregating each other, granulating and drying.

  The galactomannan used in the present invention is a polysaccharide having a D-galactose side chain in the D-mannose main chain. The galactomannan used in the present invention is not particularly limited as long as it can crosslink with borate ions and / or trivalent or higher polyvalent metal ions.

  As such galactomannans, guar gum, locust bean gum, tara gum, acacia gum and the like are known, and any of them may be used, but guar gum is preferred because it is inexpensive.

  These galactomannans may be crosslinked alone with borate ions and / or trivalent or higher polyvalent metal ions, but these unmodified galactomannans are mixed with one or more galactomannan derivatives before crosslinking. May be. In this case, 50 mass% or more of all galactomannans should just be unmodified galactomannans.

  Examples of the galactomannan derivative that can be mixed with the unmodified galactomannan include carboxymethyl galactomannan, carboxymethylhydroxypropyl galactomannan, and hydroxypropyl galactomannan, and one or more galactomannan derivatives selected from these groups can be used. After adding in the range of 50% by mass or less of galactomannan, crosslinking may be performed with borate ions and / or trivalent or higher polyvalent metal ions.

  In addition, when a galactomannan derivative has a carboxyl group, a carboxyl group is contained in the structure of the water-absorbing material, and the water-absorbing ability is affected and lowered with respect to a cation concentration of 2 or less. Therefore, the mixing ratio of the galactomannan containing a carboxyl group is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total galactomannan.

  The molecular weight of the galactomannan used in the present invention is preferably 10,000 or more, more preferably 50,000 or more. When the molecular weight is 10,000 or less, it is not suitable because it is not crosslinked with polyvalent metal ions. The upper limit of the molecular weight is not particularly limited, but those having a molecular weight of up to 1,000,000, particularly those having a molecular weight of up to 250,000 are preferably used.

  As long as the water absorption performance is not reduced, organic compounds such as monosaccharides and chelating agents, inorganic salts, colloidal silica, layered silicates, zeolite, talc, white carbon, super Inorganic compounds such as fine-particle silica and titanium oxide powder may be added.

Further, a plasticizer, an oxidizing agent, an antioxidant, a reducing agent, an ultraviolet absorber, an antibacterial agent, a bactericidal agent, a fungicide, a fertilizer, a fragrance, a deodorant, a deodorant, a pigment, and the like may be mixed. In some cases, a crosslinking retarder can be added.
These additives are preferably mixed in advance in the galactomannan powder in advance, but if water-soluble organic compounds and inorganic salts do not react with the crosslinking agent or binder, they are dissolved in the aqueous crosslinking agent solution in advance. May be used.

  As the plasticizer used in the present invention, various hydrophilic compounds can be used. The purpose is to impart flexibility to the water absorbing material. The plasticizer used in the present invention is not particularly limited, but alcohols, carboxylic acids, sulfonic acids, glycols, water-soluble synthetic polymers, amino alcohols, monosaccharides, disaccharides, trisaccharides, 20 kinds of essential amino acids, amino acids And amino acid derivatives, nucleic acids and derivatives thereof, phospholipids, vitamins and coenzymes. Among these, a compound having abundant hydrophilic groups in the molecule is preferable because it can be easily mixed uniformly.

  If necessary, the plasticizer used in the present invention may be mixed with two or more other plasticizers. Although the usage-amount of these plasticizers is not specifically limited, 0.1-70 mass% is preferable with respect to a water absorbing material, and 0.1-30 mass% is more preferable.

  The above-described galactomannan used in the present invention needs to be a powder. The size of the galactomannan powder is preferably 30 to 250 μm, more preferably 50 to 200 μm, and most preferably 100 to 150 μm. When the galactomannan is a powder larger than the above range, it can be crushed by a known pulverizer such as a milling mill, jet mill, roller mill, etc. to obtain a powder within the above range.

  The aqueous crosslinking agent solution used in the present invention needs to be an aqueous solution containing borate ions and / or trivalent or higher polyvalent metal ions as a crosslinking agent.

  Although it does not specifically limit as a form (chemical structure of a compound) of the borate ion used for this invention, Sodium borate, orthoboric acid, metaboric acid, etc. are illustrated. In addition, since a boric-acid compound is cheap, sodium tetraborate hydrate or an anhydride is preferable.

  The “trivalent or higher polyvalent metal ion” used in the present invention is an ion of a compound containing a trivalent or higher polyvalent metal having two or more functional groups capable of reacting with the functional group of galactomannan. . “Trivalent or higher polyvalent metal ions” do not contain borate ions. Examples of the trivalent or higher polyvalent metal ions include titanium ions, zirconium ions, aluminum ions, yttrium ions, and cerium ions, but titanium ions and zirconium ions are most preferable because they are inexpensive and highly safe.

  The form of titanium ions, zirconium ions, etc. (chemical structure of the compound) is not particularly limited, but for titanium compounds and zirconium compounds, the pH in the aqueous solution is neutral to weakly alkaline, and the stability in water is high. To alkoxide compounds are preferred.

  Titanium alkoxide compounds include DuPont's products Tyzor131, TyzorTE (titanium IV triethanolamate isopropoxide), TyzorAA (titanium IV diisopropoxide bisacetylaminate), TyzorGBA, TyzorTOT (titanium IV tetra-2). -Ethyl hexoxide), TyzorTPT (titanium IV tetraisopropoxide), a product of Nisso, TAT (titanium IV di-n-butoxy bistriethanolamate), TOG (titanium IV isopropoxy octylene glycolate), Examples include TEAT (titanium IV bistriethanolamate diisopropoxide) and TAA (titanium IV bisacetylacetonate diisopropoxide) manufactured by Mitsubishi Gas Chemical Company.

  Examples of the zirconium alkoxide compound include zirconyl ammonium acetate, zirconyl ammonium carbonate, zirconium IV tetra-n-butoxide, and zirconium IV tetra-n-propoxide.

  These alkoxide compounds have different stability depending on conditions such as the solvent to be used and pH, and therefore may be appropriately selected.

  The cross-linking agent used in the present invention needs to contain borate ions and / or trivalent or higher polyvalent metal ions, but other cross-linking agents as long as they do not cause deterioration in biodegradability and water absorption performance. Aldehyde compounds such as glutaraldehyde and glyoxal, amine compounds such as ethylenediamine and polyamide resin, aziridine compounds such as 2,2-bishydroxymethylbutanol tri [3- (1-aziridine)] propionic acid, tolylene diisocyanate, Isocyanate compounds such as hexamethylene diisocyanate and toluene diisocyanate, polyhydric alcohols such as glycerol, propylene glycol and ethylene glycol, epoxy compounds such as epichlorohydrin, ethylene glycol diglycidyl ether and diethylene glycol diglycidyl ether It is also possible to use in admixture with like.

  When the crosslinking agent is borate ion, the amount of the crosslinking agent required for crosslinking the galactomannan powder is preferably 1 to 200 mmol, particularly preferably 5 to 60 mmol, as boric acid per 1 kg of the total galactomannan mass.

  When the cross-linking agent is a trivalent or higher polyvalent metal ion, it varies depending on the type of metal ion and its form, but about 1 to 100 mmol is preferable as the metal per kg of galactomannan mass, and 5 to 50 mmol is preferable. Particularly preferred.

  If the addition amount of the crosslinking ions is too small, gelation does not occur even if water is absorbed, so that the handleability is poor, and if the addition amount is large, the water absorption amount decreases. The temperature at which galactomannan and borate ions and / or trivalent or higher polyvalent metal ions are cross-linked is not particularly limited, but is preferably 5 to 90 ° C and more preferably 20 to 70 ° C in order to promote the reaction. The reaction time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes. The pH of the aqueous crosslinking agent solution is preferably 7.5 to 12.0, and more preferably 8.5 to 11.0. When the pH of the aqueous crosslinking agent solution is 7.5 or less, borate ions cannot undergo a crosslinking reaction with the hydroxyl group of galactomannan. If the pH is 12 or more, the crosslinked galactomannan cannot be swollen appropriately and granulation becomes difficult.

In the present invention, the above-described aqueous crosslinking agent solution is added to and mixed with the galactomannan powder.
1. A method in which the galactomannan powder is fluidized in a fluid bed granulator and then sprayed or dripped with an aqueous solution of the crosslinking agent, and crosslinking, granulation and drying are performed simultaneously.
2. A method of spraying or dropping an aqueous solution of a crosslinking agent on a galactomannan powder stirred at high speed in a granulator, simultaneously performing crosslinking and granulation, and then drying,
3. There is a method in which, after the crosslinking and granulation are performed at the same time in 2 above, the mixture is further granulated into an appropriate granule state by an extrusion molding machine and then dried.

  When spraying these aqueous solution of the crosslinking agent onto the galactomannan powder, the spray amount of the aqueous solution is preferably 200% or less of the mass of the galactomannan powder as the total mass of the aqueous solution.

  When the spray amount is 200% or more, the cross-linked galactomannan powder absorbs moisture and swells, and is fused and gelled. When gelled under stirring, it becomes a lump, which makes it difficult to control the particle size and requires a crushing step for the lump gel, which is disadvantageous.

  Addition of 200% or more of water requires energy for the drying process, and if the gel obtained in such a state is dried with hot air as it is, the gel is remarkably contracted and the water absorption performance is deteriorated.

  Depending on the production method and conditions, for example, in the case of a fluid bed granulator, the spray amount is preferably about 30 to 60% of the weight of the galactomannan powder.

  Further, the operation of adding and mixing the aqueous crosslinking agent solution can be repeated by changing the kind of the crosslinking agent. When mixing repeatedly, it is preferable that the total amount of the aqueous crosslinking agent solution to be added is 200% or less of the galactomannan powder mass as the mass of the entire aqueous solution.

  When spraying the crosslinker solution onto the galactomannan powder, the stirring conditions of the galactomannan powder depend on the production method and the stirring efficiency (shape of the stirring blade and stirring tank) of the applied machinery. In the case of a machine, the stirring speed is preferably 1500 to 5000 rpm, more preferably 2000 to 3500 rpm.

  In the case of a stirring speed of 1500 rpm or less, when the crosslinker liquid comes into contact with the galactomannan powder, only the contact portion swells and crosslinks, resulting in a nonuniform crosslinked state as a whole. In addition, stirring at 5000 rpm or more generates heat due to friction caused by the collision between the galactomannan powder, the mechanical device, and the galactomannan powder, so that the powder temperature rises and the thermal decomposition of the galactomannan and the hydrolysis of the cross-linking agent component are significantly accelerated. Therefore, it is not preferable.

  In the case of a fluidized bed granulator, it is affected by the size and shape of the apparatus, the input amount and particle size of the galactomannan powder, so the fluid air supply amount may be appropriately selected by visually confirming the powder flow state. . The amount of air that can flow the galactomannan powder moderately is optimal as appropriate because it is affected by the volume and shape of the granulator, floor area, position of the air outlet, the amount of galactomannan powder input and the particle size, etc. What is necessary is just to select the appropriate ventilation volume.

  The reaction conditions between the galactomannan powder and the crosslinking agent may be within a range in which decomposition of the galactomannan and the crosslinking agent component, that is, thermal decomposition of the galactomannan and hydrolysis of the crosslinking agent component does not occur. It is preferably carried out at a temperature of 5 to 90 ° C, particularly preferably 20 to 70 ° C. The reaction time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes. The pH of the aqueous crosslinking agent solution is preferably 7.5 to 12.0, and more preferably 8.5 to 11.0. When the pH of the aqueous crosslinking agent solution is 7.5 or less, borate ions cannot undergo a crosslinking reaction with the hydroxyl group of galactomannan. If the pH is 12 or more, the crosslinked galactomannan cannot be swollen appropriately and granulation becomes difficult.

  In the present invention, the method for drying the galactomannan cross-linked product is not limited to any drying method as long as it does not reduce the water absorption performance after drying. Examples include freeze drying, reduced pressure drying, vacuum drying, fluidized drying and the like.

  As other drying methods, water in the cross-linked product may be monovalent alcohol having 1 to 5 carbon atoms (methanol, ethanol, isopropanol, etc.), ketone having 3 to 6 carbon atoms (acetone, etc.), or a mixture thereof. A method of drying after substituting with a hygroscopic and volatile anhydrous hydrophilic organic solvent as described above may be employed.

  According to the method of the present invention, it is possible to dry without using alcohols, but the case of drying using a volatile hydrophilic solvent such as alcohol is also included in the scope of the present invention.

  A granular water-absorbing agent having a desired particle size can be obtained by the production method of the present invention. Although it depends on the application, a water absorbing agent having a particle size in the range of 200 to 1000 μm, more preferably in the range of 300 to 800 μm is preferably used.

  If the particle size is less than 200 μm, not only will mamas easily occur during water absorption, but dust may also be generated in the process of producing products containing these, and for example, paper diapers absorb water from the gaps in the nonwoven fabric used for the top sheet. Since the material leaks out, it is not preferable.

  Further, if the particle size exceeds 1000 μm, in the case of disposable diapers and sanitary products containing these, not only the water absorption speed is lowered, but also the water absorbing material is too large and uncomfortable when worn, which is not preferable.

  When the obtained dried product has a desired particle size, for example, less than 200 μm, it is sprayed with an aqueous solution of a biodegradable binder component, dried again after granulation, and water absorption within the above range. It is possible to obtain a material. If a binder component that does not react with the crosslinking agent is used, it is possible to dissolve the binder component in an aqueous solution containing the crosslinking agent in advance, and simultaneously perform crosslinking and granulation of galactomannan and drying. In this case, the concentration of the binder component is preferably 0.2 to 5% by mass.

  Examples of the binder component that can be mixed in advance to form an aqueous solution by not reacting with a cross-linking agent, that is, borate ions and / or trivalent or higher polyvalent metal ions include starch and derivatives thereof.

  In addition, as a binder component for particle diameter adjustment, you may use a guar gum, locust bean gum, glucomannan, xanthan gum, carrageenan, sodium alginate, etc., for example. However, since these react with borate ions and / or trivalent or higher polyvalent metal ions, they cannot be mixed with an aqueous crosslinking agent solution in advance. That is, when these are mixed in advance, the binder component reacts with the cross-linking agent to cross-link and gel, and therefore cannot be fed and sprayed with a pump.

  The granular water-absorbing material obtained by the production method of the present invention has excellent absorption performance. For example, in the tea bag method, the water absorption amount of 0.9 mass% sodium chloride aqueous solution after 1 hour is 15 times its own weight. The absorption performance is as described above and the vortex water absorption speed is within 90 seconds.

In the tea bag method, 1 g of a water-absorbing material was put into a 255 mesh nylon tea bag, the tea bag was immersed in 1 L of a 0.9 mass% sodium chloride aqueous solution for 60 minutes, the tea bag was pulled up and drained for 10 minutes. Later, the weight is measured.
The water absorption amount of the water-absorbing material is the weight of the tea bag without water-absorbing material soaked in water for 60 minutes, and the weight of the water-absorbing material before swelling from the weight of the tea bag containing the water-absorbing material absorbed and swollen And the value obtained by dividing the weight of the blank by the weight of the water-absorbing material before swelling is defined as the water absorption (g / g resin).

  The vortex water absorption speed is a method in which 50 g of a 0.9% by mass aqueous sodium chloride solution is added with 2 g of water absorbing material while stirring with a stirrer at 600 rpm, and the time until fluidity (water swirl) disappears is measured.

  In addition to the water-absorbing material thus obtained, if necessary, deodorants, fragrances, various inorganic powders, foaming agents, pigments, dyes, antibacterial agents, foaming agents, hydrophilic short fibers, plasticizers, adhesives, interfaces An activator, a fertilizer, an oxidizing agent, a reducing agent, water, salts, and the like may be added to thereby impart various functions to the water absorbing material.

  Examples of the inorganic powder include substances that are inert to aqueous liquids, such as fine particles of various inorganic compounds, fine particles of clay minerals, and the like. The inorganic powder preferably has an appropriate affinity for water and is insoluble or hardly soluble in water.

  Specific examples include metal oxides such as silicon dioxide and titanium oxide, silicic acid (salts) such as natural zeolite and synthetic zeolite, kaolin, talc, clay, bentonite and the like. Among these, silicon dioxide and silicic acid (salt) are more preferable, and silicon dioxide and silicic acid (salt) having an average particle diameter measured by a Coulter counter method of 200 μm or less are more preferable.

  The amount of the inorganic powder used depends on the combination of the water-absorbing material and the inorganic powder, but is in the range of 0.001 to 10 parts by mass, more preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the water-absorbing material. It should be inside. The mixing method of the water-absorbing material and the inorganic powder is not particularly limited, and for example, a dry blend method, a wet mixing method, or the like can be employed, but it is preferable to employ the dry blend method.

  The granular water-absorbing material obtained by the production method of the present invention can be combined with (combined with) a fibrous material such as pulp to produce an absorbent article. Applicable absorbent articles include disposable sanitation materials such as paper diapers, sanitary napkins, simple toilet pods, portable toilets, incontinence pads, ostomy bags, surgical products such as wound protection materials and wound healing materials, and pets Pet supplies such as toilet sand and sheets, construction materials and soil water retaining materials, water-stopping materials, packing materials, civil engineering and construction materials such as gel water sacs, drip absorbent materials and freshness retaining materials, food items such as cold insulation materials, oil water Examples include various industrial articles such as separation materials, anti-condensation materials, coagulants, and agricultural and horticultural articles such as water retention materials such as plants and soil.

  For example, when making disposable paper diapers, a back sheet (back surface material) made of a liquid-impermeable material, a core layer containing the water-absorbent resin of the present invention, and a top sheet (surface material) made of a liquid-permeable material Are laminated in this order and fixed to each other, and a gather (elastic portion), a so-called tape fastener or the like is attached to the laminate. Paper diapers also include pants with paper diapers that are used when urinating or defecation is performed on infants.

By using biodegradable materials such as polylactic acid and polyvinyl alcohol as materials other than the water-absorbing material used for these absorbent articles, it becomes possible to create all-biodegradable absorbent articles, reducing the amount of incinerated garbage and landfills It is possible to contribute to the prolongation of life. Furthermore, if the biodegradable material is a renewable resource such as polylactic acid made from plant materials, absorbent articles made from these materials are also renewable products, which can reduce the amount of newly generated carbon dioxide. It can contribute to the solution of the global warming problem.
(Example)

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

  The water absorption was measured by the tea bag method. That is, 1 g of a water absorbing material is put into a 255 mesh nylon tea bag, the tea bag is immersed in 1 L of 0.9 mass% sodium chloride aqueous solution for 60 minutes, the tea bag is pulled up, drained for 10 minutes, It was measured. The water absorption amount of the water-absorbing material is the weight of the tea bag without water-absorbing material soaked in water for 60 minutes, and the weight of the water-absorbing material before swelling from the weight of the tea bag containing the water-absorbing material absorbed and swollen. And the value obtained by dividing the weight of the blank by the weight of the water-absorbing material before swelling is the water absorption amount (g / g resin).

  The water absorption rate was measured by the vortex water absorption rate method. That is, this is a method of measuring the time until fluidity (water swirl) disappears by adding 2 g of a water-absorbing material while stirring 50 ml of a 0.9 mass% sodium chloride aqueous solution at 600 rpm with a stirrer.

  Zircozol AC7 (Zirconyl ammonium carbonate manufactured by Daiichi Rare Elemental Chemical Co., Ltd.) 18.9 ml of the stock solution was made up to 300 ml with distilled water to prepare an aqueous crosslinking agent solution. Separately, 1 kg of guar gum (Guacoal manufactured by Sanei Pharmaceutical Trading Co., Ltd.) 1 kg is blown from the lower part of the device with a fluid bed granulator (volume 2 L, the same shall apply below) in advance to flow moderately. Oita. Next, 300 ml of the aqueous crosslinking agent solution was supplied to a fluidized bed granulator at 15 ml / min with a peristaltic pump and sprayed. At this time, the amount of zirconium added to guar gum was 25 mmol / kg.

  When this apparatus is used, granulation can be performed simultaneously with the crosslinking of the guar gum powder, and after the spraying of the crosslinking agent, it can be dried by allowing it to flow until the exhaust temperature reaches 30 ° C. The particle size distribution was measured by classifying the particle size of the collected granulated dried product with a sieve. The water absorption performance test was conducted by classifying the granulated dried product and using only the one in the range of 200 to 1000 micrometers. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

  Using the same method as in Example 1, 37.7 ml of zircozol AC7 stock solution was made up to 300 ml with distilled water, and 300 ml of this was spray-added to 1 kg of guar gum, so that a guar gum cross-linked product having a zirconium addition amount of 50 mmol / kg to guar gum. Got.

  1 kg of this cross-linked product was put into a fluidized bed dryer and fluidized, and further, 300 ml of 0.4 mass% guar gum aqueous solution was sprayed at a rate of 13 g / min for granulation. After spraying, the granulated dried product was collected after the exhaust temperature reached 30 ° C. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

  Zircozol AC7 stock solution 18.9ml and 0.5M sodium borate aqueous solution 30ml were mixed and further diluted to 300ml with distilled water. Using this 300 ml, the same operation as in Example 1 was carried out to obtain a granulated dried product. The amount of zirconium added to guar gum at this time was 25 mmol / kg, and boric acid was 15 mmol / kg. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

  Zircozol AC7 stock solution (18.9 ml) was made up to 300 ml with 5% by weight potato starch aqueous solution. 300 ml of the mixture was operated in the same manner as in Example 1 to obtain a granulated dried product. At this time, the amount of zirconium added to guar gum was 25 mmol / kg. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

  90 ml of 0.5M sodium borate aqueous solution was diluted with distilled water to 300 ml. Using this 300 ml, the same operation as in Example 1 was carried out to obtain a granulated dried product. The amount of boric acid added to guar gum at this time was 45 mmol / kg. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

  Zircozol AC7 stock solution 18.9ml was made up to 1L with distilled water to make a crosslinker aqueous solution. 1 kg of guar gum was put into a horizontal rotary granulator and this aqueous solution of the crosslinking agent was sprayed at 4 ml / min while stirring the guar gum at 3000 rpm to obtain a wet crosslinked product. This wet cross-linked product is then put into an extrusion molding machine, granulated into pellets with a nozzle diameter of 0.5 mm, and further this granulated product is dried with a fluid bed dryer at an intake air temperature of 80 ° C. A dry grain was obtained. The results of the particle size distribution are shown in Table 1, and the water absorption performance is shown in Table 2.

Claims (6)

A step of adding an aqueous solution of a crosslinking agent containing borate ions and / or trivalent or higher polyvalent metal ions to the galactomannan powder and mixing it to crosslink the galactomannan and granulate it in a granular form. A method for producing a granular water-absorbing material comprising a crosslinked galactomannan. The method for producing a granular water-absorbing material according to claim 1, wherein the method of adding and mixing the aqueous solution of the crosslinking agent is spraying and stirring the aqueous solution of the crosslinking agent on the galactomannan powder. The method for producing a granular water-absorbing material according to claim 1 or 2, wherein the aqueous solution of the crosslinking agent added to the galactomannan powder is 200% by mass or less based on the galactomannan powder. The method for producing a granular water-absorbing material according to any one of claims 1 to 3, wherein 1 to 200 mmol of boric acid aqueous solution containing borate ions is added as boric acid to 1 kg of galactomannan powder. The granular water-absorbing material according to any one of claims 1 to 3, wherein an aqueous solution of a crosslinking agent containing a trivalent or higher polyvalent metal ion is added as 1 to 100 mmol of the metal per 1 kg of galactomannan powder. Production method. Furthermore, starch or its derivative (s) is added to crosslinking agent aqueous solution as a binder component, The manufacturing method of the granular water absorbing material in any one of Claims 1-5 characterized by the above-mentioned.