JP2018021090A - Absorptive resin particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide absorptive resin particles which are excellent in absorption performance conforming to actual circumstances because of having a quick speed of water absorption by Lockup method, and have a less amount of a residual volatile component without using a decomposable compound such as urea, and to provide a method for producing the same.SOLUTION: There are provided absorptive resin particles which contain a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) converted into the water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinking agent (b), as essential constitutional units, and porous hollow particles (B), where an absorption speed by Lockup method is 25-80 g/min; and a production method including obtaining the crosslinked polymer (A), and then mixing the porous hollow particles (B).SELECTED DRAWING: None

Description

  The present invention relates to absorbent resin particles and a method for producing the same.

  At present, water-absorbent resins made mainly of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbents in sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads. From the viewpoint of improving QOL (quality of life) in recent years, demand for these sanitary materials has been shifting to lighter and thinner materials, and accordingly, the use of hydrophilic fibers has been desired to be reduced. . Therefore, the water-absorbing resin itself is required to have the role of liquid diffusibility and initial absorption in the absorbent body, which has been carried out by hydrophilic fibers so far, and the water absorption in the table test, for example, liquid permeability under normal pressure. Although the performance and water absorption speed are good, it is difficult to ensure excellent absorption performance (absorption amount and absorption speed) under the conditions in which the absorbent article is actually used. It is strongly desired.

  As means for improving the absorption rate, for example, a method of adding a solid silicon compound such as silica (for example, see Patent Document 1 and Patent Document 2) or a hydrophobic substance has been proposed (for example, see Patent Document 3). Further, absorption is performed by a method of adding a foaming agent such as urea before the polymerization (for example, see Patent Document 4) or a method in which bubbles are included by performing high-speed strong stirring during the polymerization (for example, see Patent Document 5). A proposal has also been made to improve the absorption rate by foaming the conductive resin particles.

  However, when foaming is performed using a decomposable compound such as urea, there is a risk that a toxic gas such as ammonia is generated during the manufacturing process. Furthermore, the addition of a new manufacturing process not only causes high capital investment and increased costs due to its energy, but also requires industrially complicated operation, which may lead to lower productivity. . As a method without the above-mentioned concerns, the absorption rate may be improved by adding the above-mentioned silicon compound or hydrophobic substance. However, these are cases where the results of the DW method and the Vortex method are used as an index, and are more actual. The absorption rate was not improved in the lockup method according to the above.

JP 2005-095759 A JP 2012-012451 A JP 2013-231199 A Special table 2015-508836 gazette JP-A-10-251530

  An object of the present invention is to provide an absorbent resin particle having a high water absorption rate in the Lockup method and having excellent absorption performance in line with the actual situation, and having a small amount of residual volatile components without using a decomposable compound such as urea, and its production Is to provide a method.

The inventor of the present invention has arrived at the present invention as a result of intensive studies to achieve the above object.
That is, the present invention provides a water-soluble vinyl monomer (a1) and / or a cross-linked polymer comprising a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and a cross-linking agent (b) as essential constituent units ( A) and absorbent resin particles containing porous hollow particles (B) and having an absorption rate of 25 to 80 g / g / min according to the Lockup method defined by the following formula (a);
Lockup (g / g / min) = 40 / (t seconds ÷ 60 × mass of absorbent resin (g)) Formula (a)
(In the formula, t is a time when 40 g of physiological saline adjusted to 23 ° C. ± 2 ° C. is poured into a 100 ml beaker containing 1.00 g of the absorbent resin, and the poured physiological saline comes into contact with the absorbent resin. To the time (seconds) until the fluid of the absorbent resin or physiological saline solution does not leach from the absorbent resin when the beaker into which the physiological saline has been poured is tilted at an angle of about 90 °. Water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, and cross-linked polymer (A) and porous hollow containing cross-linking agent (b) as essential constituent units A method for producing the above-mentioned absorbent resin particles comprising a step of mixing particles (B); an absorbent body comprising the absorbent resin particles; and an absorbent article comprising the absorbent body.

  The absorbent resin particles of the present invention and the absorbent resin particles obtained by the production method of the present invention have a high absorption rate in the Lockup test method and are free from the risk of toxic gases such as ammonia being produced during the production process. Excellent handling at the time.

The schematic diagram which shows the apparatus used for the measurement of DW (Demand Wettability) method.

  The absorbent resin particle of the present invention comprises a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis and a cross-linking weight having a cross-linking agent (b) as essential constituent units. A coalescence (A) and porous hollow particles (B) are included.

  The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and is a known monomer, for example, at least one water-soluble substituent group disclosed in Japanese Patent No. 3648553, paragraphs 0007 to 0023 and an ethylenic group. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers, and cationic vinyl monomers), anionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A No. 2003-165883, nonionic Selected from the group consisting of a carboxylic group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982 At least one kind Vinyl monomers can be used.

  Vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis [hereinafter also referred to as hydrolyzable vinyl monomer (a2). ] Is not particularly limited, and known {for example, vinyl monomers having at least one hydrolyzable substituent which becomes a water-soluble substituent by hydrolysis disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553, At least one hydrolyzable substituent [1,3-oxo-2-oxapropylene (—CO—O—CO—) group, acyl group and cyano disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982 Vinyl monomer having a group etc.] can be used. The water-soluble vinyl monomer is a concept well known to those skilled in the art, but when expressed in terms of quantity, for example, it means a vinyl monomer that dissolves in 100 g of water at 25 ° C. The hydrolyzability in the hydrolyzable vinyl monomer (a2) is a concept well known to those skilled in the art. More specifically, for example, it can be expressed by the action of water and, if necessary, a catalyst (acid or base). It means the property of being hydrolyzed to become water-soluble. Hydrolysis of the hydrolyzable vinyl monomer (a2) may be performed either during polymerization, after polymerization, or both of them, but from the viewpoint of the absorption performance of the resulting absorbent resin particles, it is preferably after polymerization.

  Among these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance and the like, more preferably the above-mentioned anionic vinyl monomer, carboxy (salt) group, sulfo (salt) group, amino group, carbamoyl group, Vinyl monomers having an ammonio group or a mono-, di- or tri-alkylammonio group, more preferred are vinyl monomers having a carboxy (salt) group or a carbamoyl group, particularly preferred are (meth) acrylic acid (salt) and (Meth) acrylamide, particularly preferred is (meth) acrylic acid (salt), and most preferred is acrylic acid (salt).

The “carboxy (salt) group” means “carboxy group” or “carboxylate group”, and the “sulfo (salt) group” means “sulfo group” or “sulfonate group”. Moreover, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylate, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (such as lithium, sodium and potassium) salts, alkaline earth metal (such as magnesium and calcium) salts and ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferable from the viewpoint of absorption performance and the like, more preferable are alkali metal salts, and particularly preferable are sodium salts.

  When either the water-soluble vinyl monomer (a1) or the hydrolyzable vinyl monomer (a2) is used as a structural unit, one kind of each may be used alone as a structural unit, and if necessary, two or more kinds may be used as a structural unit. good. The same applies when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units. Further, when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as structural units, the molar ratio [(a1) / (a2)] is preferably 75/25 to 99/1. The ratio is more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.

  As a structural unit of the crosslinked polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith are used as the structural unit. Can do. Other vinyl monomers (a3) may be used alone or in combination of two or more.

Other vinyl monomers (a3) that can be copolymerized are not particularly limited, and are known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883). 0025 paragraph and vinyl monomer disclosed in JP-A-2005-75982, paragraph 0058) can be used. Specifically, for example, the following vinyl monomers (i) to (iii) Can be used.
(I) C8-C30 aromatic ethylenic monomer Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylenic monomer Alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkadienes (butadiene, isoprene, etc.) and the like.
(Iii) C5-C15 alicyclic ethylenic monomer Monoethylenically unsaturated monomer (such as pinene, limonene and indene); and polyethylene vinyl monomer [such as cyclopentadiene, bicyclopentadiene and ethylidene norbornene].

  The content (mol%) of the other vinyl monomer (a3) unit is based on the total number of moles of the water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit from the viewpoint of absorption performance and the like. 0 to 5 is preferable, more preferably 0 to 3, particularly preferably 0 to 2, particularly preferably 0 to 1.5. From the viewpoint of absorption performance and the like, the content of other vinyl monomer (a3) units is Most preferably, it is 0 mol%.

  The cross-linking agent (b) is not particularly limited and is known (for example, it reacts with a cross-linking agent having two or more ethylenically unsaturated groups and water-soluble substituents disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553. Crosslinking agent having at least one functional group and at least one ethylenically unsaturated group, and crosslinking agent having at least two functional groups capable of reacting with a water-soluble substituent, Japanese Patent Application Laid-Open No. 2003-165883 The crosslinking agent having two or more ethylenically unsaturated groups, the crosslinking agent having an ethylenically unsaturated group and a reactive functional group, and the crosslinking agent having two or more reactive substituents disclosed in paragraphs 0028 to 0031 of , A crosslinkable vinyl monomer disclosed in paragraph 0059 of JP-A-2005-75982, and paragraphs 0015 to 0016 of JP-A-2005-95759. Crosslinking agents such as disclosed crosslinkable vinyl monomer) can be used. Among these, from the viewpoint of absorption performance and the like, a crosslinking agent having two or more ethylenically unsaturated groups is preferable, and more preferable is triallyl cyanurate, triallyl isocyanurate, and a poly (poly (2 to 40 carbons) polyol). Meta) allyl ethers, particularly preferred are triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, polyethylene glycol diallyl ether and pentaerythritol triallyl ether, most preferred is pentaerythritol triallyl ether. A crosslinking agent (b) may be used individually by 1 type, or may use 2 or more types together.

  The content (mol%) of the crosslinking agent (b) unit is preferably 0.001 to 5, based on the total number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Preferably it is 0.005-3, Most preferably, it is 0.01-1. Within this range, the absorption performance is further improved.

  Examples of the polymerization method of the crosslinked polymer (A) include known aqueous solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.), known suspension polymerization method and reverse phase suspension. Suspension polymerization (Japanese Patent Publication No. 54-30710, Japanese Patent Laid-Open No. 56-26909, Japanese Patent Laid-Open No. 1-5808, etc.) can be mentioned.

  The crosslinked polymer (A) is obtained by polymerizing a monomer composition containing water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and crosslinking agent (b) as essential components. However, a solution polymerization method is preferable as the polymerization method, and it is advantageous in terms of production cost because it is not necessary to use an organic solvent or the like. Therefore, an aqueous solution polymerization method is particularly preferable, and a water retention amount is large. An aqueous solution absorptive polymerization method is most preferable because an aqueous liquid absorbent resin having a small amount of water-soluble components can be obtained and temperature control during polymerization is unnecessary.

When aqueous solution polymerization is performed, a mixed solvent containing water and an organic solvent can be used. Examples of the organic solvent include methanol, ethanol, acetone, methyl ethyl ketone, N, N-dimethylformamide, dimethyl sulfoxide, and two or more of these. A mixture of
When aqueous solution polymerization is performed, the amount (% by weight) of the organic solvent used is preferably 40 or less, more preferably 30 or less, based on the weight of water.

In the case of using an initiator for polymerization, conventionally known initiators for radical polymerization can be used. For example, azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid and 2,2′-azobis (2-amidinopropane) Hydrochloride, etc.], inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides [benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinate Acid peroxide and di (2-ethoxyethyl) peroxydicarbonate, etc.] and redox catalyst (alkali metal sulfite or bisulfite, ammonium sulfite, ammonium bisulfite, ascorbic acid and the like, and alkali metal persulfate) Such as salt, ammonium persulfate, hydrogen peroxide and organic peroxide And those comprising a combination with an oxidizing agent). These catalysts may be used alone or in combination of two or more thereof.
The amount (% by weight) of the radical polymerization initiator used is that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), when the other vinyl monomer (a3) is used (a1) to (a3). Based on the total weight, 0.0005 to 5 is preferable, and 0.001 to 2 is more preferable.

At the time of polymerization, a polymerization control agent typified by a chain transfer agent may be used as necessary. Specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptans, alkyl halides. And thiocarbonyl compounds. These polymerization control agents may be used alone or in combination of two or more thereof.
The amount (% by weight) of the polymerization control agent used is that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), in the case of using other vinyl monomers (a3) (a1) to (a3), Based on the total weight, 0.0005 to 5 is preferable, and 0.001 to 2 is more preferable.

  When a suspension polymerization method or a reverse phase suspension polymerization method is used as the polymerization method, the polymerization may be carried out in the presence of a conventionally known dispersant or surfactant, if necessary. In the case of the reverse phase suspension polymerization method, polymerization can be carried out using a conventionally known hydrocarbon solvent such as xylene, normal hexane and normal heptane.

  The polymerization start temperature can be appropriately adjusted depending on the type of catalyst used, but is preferably 0 to 100 ° C, more preferably 2 to 80 ° C.

  When using a solvent (such as an organic solvent and water) for the polymerization, the solvent is preferably distilled off after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Is 0-3, most preferably 0-1. Within this range, the absorbent performance of the absorbent resin particles is further improved.

  When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, based on the weight of the crosslinked polymer (A). Most preferably, it is 3-8. Within this range, the absorption performance is further improved.

By the above polymerization method, the crosslinked polymer (A) can obtain a water-containing gel-like product containing water (hereinafter abbreviated as a water-containing gel), and the water-containing gel is further dried to obtain the crosslinked polymer (A). Can be obtained.
When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the hydrogel may be neutralized with a base. The neutralization degree of the acid group is preferably 50 to 80 mol%. When the degree of neutralization is less than 50 mol%, the resulting water-containing gel polymer has high tackiness, and the workability during production and use may deteriorate. Further, the water retention amount of the obtained aqueous liquid absorbent resin may be reduced. On the other hand, when the degree of neutralization exceeds 80%, the pH of the obtained resin becomes high, and there is a concern that the safety of human skin may be concerned.
The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (A) in the production of the absorbent resin particles. For example, a method such as neutralization in the state of a hydrogel is preferable. Illustrated.
As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogen carbonate and potassium carbonate can be used.

  The water-containing gel obtained by polymerization can be shredded as necessary before drying. The size (longest diameter) of the gel after chopping is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved.

  Shredding can be performed by a known method, and can be performed using a shredding device (for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer).

  In addition, the content and water content of the organic solvent were measured using an infrared moisture meter [JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specifications 100V, 40W ] Is obtained from the weight loss of the measurement sample when heated.

  As a method of distilling off the solvent (including water) of the hydrogel and drying it, a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a drum dryer heated to 100 to 230 ° C., etc. A thin film drying method, a (heating) vacuum drying method, a freeze drying method, a drying method using infrared rays, decantation, filtration, and the like can be applied.

  After the hydrogel is dried to obtain the crosslinked polymer (A), it can be further pulverized. The pulverization method is not particularly limited, and a pulverizer (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a shet airflow pulverizer) can be used. The pulverized crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

  The weight average particle size (μm) of the crosslinked polymer (A) when screened as necessary is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, Most preferably, it is 350-450. Within this range, the absorption performance is further improved.

  In the present invention, the weight average particle size is determined by using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook, 6th edition (Mac Glow Hill Book). -It is measured by the method described in Kanbany, 1984, page 21). That is, JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and a tray from the top. About 50 g of the measured particles are put in the uppermost screen and shaken for 5 minutes with a low-tap test sieve shaker. Weigh the measured particles on each sieve and pan, and calculate the weight fraction of the particles on each sieve with the total as 100% by weight. This value is the logarithmic probability paper [horizontal axis is sieve aperture (particle size ), The vertical axis is plotted in the weight fraction], and then a line connecting the points is drawn to obtain the particle diameter corresponding to the weight fraction of 50% by weight, which is defined as the weight average particle diameter.

  Further, when pulverized, the smaller the content of the fine particles contained in the crosslinked polymer (A) after pulverization, the better the absorption performance. Therefore, 106 μm or less (preferably 150 μm) of the total weight of the crosslinked polymer (A). The content (% by weight) of the following fine particles is preferably 3 or less, more preferably 1 or less. The content of the fine particles can be determined using a graph created when determining the above-mentioned weight average particle diameter.

  When pulverized, the shape of the crosslinked polymer (A) after pulverization is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The crosslinked polymer (A) may contain some other components such as a residual solvent and a residual crosslinking component as long as the performance is not impaired.

  The absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked by the surface crosslinking agent (d), but it is not essential. By cross-linking the surface of the cross-linked polymer (A), the gel strength of the absorbent resin particles can be improved, and the desired water retention amount and absorption amount under load of the absorbent resin particles can be satisfied. Examples of the surface cross-linking agent (d) include known polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyvalent isocyanate compounds described in JP 59-189103 A, JP 58-180233 A. And polyhydric alcohols described in JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, and JP-A-5-508425. Use is made of a surface crosslinking agent or the like of an alkylene carbonate, a polyvalent oxazoline compound described in JP-A-11-240959, and a polyvalent metal described in JP-A-51-136588 and JP-A-61-257235) it can. Of these surface cross-linking agents, from the viewpoint of economy and absorption properties, polyvalent glycidyl compounds, polyhydric alcohols and polyhydric amines are preferred, polyvalent glycidyl compounds and polyhydric alcohols are more preferred, and many are particularly preferred. Valent glycidyl compounds, most preferred are ethylene glycol diglycidyl ethers. A surface crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

  In the case of surface cross-linking, the amount (% by weight) of the surface cross-linking agent (d) is not particularly limited because it can be variously changed depending on the type of surface cross-linking agent, the conditions for cross-linking, the target performance, and the like. From the viewpoint of absorption characteristics, etc., 0.001 to 3 is preferable, more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5 with respect to 100 parts by weight of the absorbent resin.

  Surface crosslinking of the crosslinked polymer (A) can be performed by mixing the crosslinked polymer (A) and the surface crosslinking agent (d) and heating as necessary. As a mixing method of the crosslinked polymer (A) and the surface crosslinking agent (d), a cylindrical mixer, a screw mixer, a screw extruder, a turbulator, a nauter mixer, a double arm kneader, a flow Cross-linked polymer using a mixing device such as a mixing mixer, a V-type mixer, a minced mixer, a ribbon-type mixer, a fluid-type mixer, an airflow-type mixer, a rotating disk-type mixer, a conical blender, and a roll mixer. A method of uniformly mixing A) and the surface cross-linking agent (d) can be mentioned. At this time, the surface crosslinking agent (d) may be used after diluted with water and / or an arbitrary solvent.

  Although the temperature at the time of mixing a crosslinked polymer (A) and a surface crosslinking agent (d) is not specifically limited, 10-150 degreeC is preferable, More preferably, it is 20-100 degreeC, Most preferably, it is 25-80 degreeC. .

  After mixing the cross-linked polymer (A) and the surface cross-linking agent (d), heat treatment is performed. The heating temperature is preferably 100 to 180 ° C., more preferably 110 to 175 ° C., and particularly preferably 120 to 170 ° C. from the viewpoint of breakage resistance of the resin particles. Heating at 180 ° C. or lower is advantageous in terms of equipment because indirect heating using steam is possible, and absorption performance may deteriorate at heating temperatures below 100 ° C. Moreover, although heating time can be suitably set with heating temperature, from a viewpoint of absorption performance, Preferably it is 5 to 60 minutes, More preferably, it is 10 to 40 minutes. The absorbent resin obtained by surface cross-linking can be further subjected to surface cross-linking using the same or different type of surface cross-linking agent as the first used surface cross-linking agent.

  After the surface of the crosslinked polymer (A) is crosslinked with the surface crosslinking agent (d), the particle size is adjusted by sieving as necessary. The weight average particle size of the obtained particles is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of fine particles is preferably small, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

  When surface cross-linking is performed with the surface cross-linking agent (d) of the cross-linked polymer (A), even if surface cross-linking is performed before mixing with the porous hollow particles (B), mixing with the porous hollow particles (B) Although surface crosslinking may be performed simultaneously or after mixing with the porous hollow particles (B), the surface crosslinking agent (d) may be used from the viewpoint of absorption performance of the absorbent resin particles under pressure. The surface crosslinking of the crosslinked polymer (A) is preferably performed before mixing with the porous hollow particles (B).

  In the absorbent resin particle of the present invention, the crosslinked polymer (A) may be further treated with a hydrophobic substance. As a method of treating with a hydrophobic substance, a method described in JP2013-231199A or the like is used. I can do it.

  The absorbent resin particles of the present invention contain porous hollow particles (B). It does not specifically limit as a porous hollow particle (B), An organic particle may be sufficient and an inorganic particle may be sufficient. Examples of the organic particles include organic resin balloons that are made of a synthetic resin as a raw material and foamed inside to form a hollow structure. Examples of inorganic particles include foaming by firing glassy fine particles at a high temperature. Inorganic balloon with hollow structure, pearlite obtained by firing fine particles of obsidian and pearlite at high temperature and foamed, hillstone obtained by firing and burning vermiculite at high temperature, graphite with added substances to scaly graphite Examples thereof include expanded graphite obtained by rapidly heating an intercalation compound. These porous hollow particles may be used alone or in combination of two or more. These porous hollow particles may be those produced by foaming during the manufacturing process of the absorbent resin particles.

  The organic resin balloon is preferably an acrylic resin, a phenol resin, a vinylidene chloride resin, a urea resin, or a resin balloon composed of a mixture of two or more of these from the viewpoint of improving the absorption rate, and among them, an acrylonitrile resin balloon is preferable. Moreover, these may be made of a synthetic resin as a raw material and foamed inside to form a hollow structure.

  The inorganic balloon is preferably a glass balloon, a shirasu balloon, a silica balloon (fly ash balloon), an alumina balloon, or an aluminosilicate balloon, and more preferably a shirasu balloon, from the viewpoint of improving the absorption rate.

  It is preferable that the surface of the porous hollow particle (B) has a through-hole of any appropriate size as long as the effects of the present invention are not impaired. By having a through-hole, many water flow paths are generated inside the absorbent resin, the absorption rate can be improved by the capillary effect, and the absorption performance is improved.

The weight average particle size of the porous hollow particles (B) was measured using a digital image analysis type particle size distribution measuring device (CAMSIZER manufactured by Retsch Co., Ltd.). Specifically, when the minimum diameter (Martin diameter) that bisects the area obtained from the projected image of the particle is obtained as the particle diameter of each particle, and the volume cumulative particle size distribution is obtained, the cumulative particle size in the volume cumulative particle size distribution The 50% particle size (D50) was taken as the weight average particle size.
The weight average particle diameter of the porous hollow particles (B) is preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. Further, from the viewpoint of handling, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, and particularly preferably 2 μm or more. By adjusting the average particle diameter of the porous hollow particles within the above range, absorbent resin particles having a sufficient absorption rate and excellent absorption performance can be provided.

The apparent specific gravity of the porous hollow particles (B) is preferably 0.2 to 0.8 g / cm ^3, still more preferably from 0.2 to 0.7 g / cm ^3, particularly preferably 0.2 0.6 g / cm ³ . By adjusting the apparent specific gravity of the porous hollow particles within the above range, sufficient absorbent resin particles can be provided. If the apparent specific gravity of the porous hollow particles is smaller than 0.2 g / cm ³ , sufficient pressure strength cannot be obtained, and there is a possibility that breakage occurs during compounding and molding. Further, when the apparent specific gravity of the porous hollow particles is larger than 0.8 g / cm ³ , an excellent absorption rate may not be obtained.

  The absorbent resin of the present invention can be obtained by mixing the crosslinked polymer (A) and the porous hollow particles (B). As a mixing method, a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a nauter type mixer, a double arm type kneader, a fluid type mixer, a V type mixer, a minced mixer, a ribbon type The method of uniformly mixing using well-known mixing apparatuses, such as a mixer, a fluid-type mixer, an airflow type mixer, a rotary disk type mixer, a conical blender, and a roll mixer, is mentioned.

In mixing the crosslinked polymer (A) and the porous hollow particles (B), the porous hollow particles (B) are preferably added to the stirred crosslinked polymer (A). The porous hollow particles (B) to be added may be added simultaneously with water and / or a solvent.
When the porous hollow particles (B) are added simultaneously with water and / or a solvent, it is preferable to add a dispersion in which the porous hollow particles (B) are dispersed in water and / or a solvent, from the viewpoint of workability and the like. More preferably, a dispersion is added. When the dispersion is added, it is preferably added by spraying or dropping.

  Although the temperature at the time of mixing a crosslinked polymer (A) and porous hollow particle (B) is not specifically limited, 10-150 degreeC is preferable, More preferably, it is 20-100 degreeC, Most preferably, it is 25-80 degreeC. .

After mixing the crosslinked polymer (A) and the porous hollow particles (B), a heat treatment may be further performed. The heating temperature is preferably 25 to 180 ° C., more preferably 30 to 175 ° C., and particularly preferably 35 to 170 ° C. from the viewpoint of breakage resistance of the resin particles. Heating at 180 ° C. or lower is advantageous in terms of equipment because indirect heating using steam is possible. Moreover, when not heating, the water and solvent used together will remain excessively in the absorbent resin, and the absorption performance may deteriorate.
In the case of heating after mixing the crosslinked polymer (A) and the porous hollow particles (B), the heating time can be appropriately set depending on the heating temperature, but from the viewpoint of absorption performance, preferably 5 to 60 minutes, Preferably it is 10 to 40 minutes. The absorbent resin obtained by mixing the crosslinked polymer (A) and the porous hollow particles (B) is the same or different kind of porous hollow particles (B) from the porous hollow particles (B) used first. It is also possible to use it for further surface treatment.

  The absorbent resin particles of the present invention may be used after mixing with the crosslinked polymer (A) and the porous hollow particles (B), and sieving to adjust the particle size. The average particle size of the particles obtained by adjusting the particle size is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of fine particles is preferably small, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

  In the absorbent resin particles of the present invention, the content of the porous hollow particles (B) can be adjusted according to the use of the absorbent resin particles, but it is 0 based on the weight of the crosslinked polymer (A). The content is preferably 0.01 to 5.0% by weight, more preferably 0.10 to 3.0% by weight. When it is in this range, the absorption rate of the absorbent resin particles becomes good, which is more preferable.

  The absorbent resin particle of the present invention contains the crosslinked polymer (A) and the porous hollow particle (B), and may further contain a polyvalent metal salt (e). By containing the polyvalent metal salt (e), the blocking resistance and liquid permeability of the absorbent resin particles are improved. As the polyvalent metal salt (e), at least one metal selected from the group consisting of magnesium, calcium, zirconium, aluminum and titanium and an inorganic acid (for example, sulfuric acid, hydrochloric acid, hydrobromic acid nitric acid, sulfuric acid, sulfamic acid) , Phosphoric acid, etc.) or organic acids (eg acetic acid, propionic acid, succinic acid, glycolic acid, stearic acid, lactic acid, malic acid, tartaric acid, citric acid, ascorbic acid, pamoic acid, maleic acid, hydroxymaleic acid, phenylacetic acid , Glutamic acid, benzoic acid, salicylic acid, sulfanilic acid, 2-acetoxy-benzoic acid, fumaric acid, toluenesulfonic acid, methanesulfonic acid, ethanedisulfonic acid, oxalic acid, isethionic acid, trifluoroacetic acid (TFA), etc.) Is mentioned.

  Among these, from the viewpoint of easy availability and solubility, inorganic acid salts of aluminum and inorganic acid salts of titanium are preferable, and aluminum sulfate, aluminum chloride, potassium aluminum sulfate, and sodium aluminum sulfate are particularly preferable. Are aluminum sulfate and sodium aluminum sulfate, most preferably sodium aluminum sulfate. These may be used alone or in combination of two or more.

  The use amount (parts by weight) of the polyvalent metal salt (e) is preferably 0.05 to 5, more preferably 0.1 to 100 parts by weight of the absorbent resin from the viewpoint of absorption performance and blocking resistance. 3, particularly preferably 0.2-2.

When the absorbent resin particles further contain a polyvalent metal salt (e), the absorbent resin particles of the present invention comprise a crosslinked polymer (A), porous hollow particles (B), and a polyvalent metal salt (e). Although it can be obtained by mixing, the polyvalent metal salt (e) may be mixed before mixing the porous hollow particles (B) with the crosslinked polymer (A). You may mix, and after mixing a porous hollow particle (B) and a crosslinked polymer (A), you may mix. Moreover, after mixing a crosslinked polymer (A) and a polyvalent metal salt (e), you may mix a porous hollow particle (B), and also mix a polyvalent metal salt (e). Among these, from the viewpoint of absorption performance of the absorbent resin particles under pressure, the polyvalent metal salt (e) should be mixed with the crosslinked polymer (A) before being mixed with the porous hollow particles (B). Is preferred.
When the polyvalent metal salt (e) is mixed with the cross-linked polymer (A) before being mixed with the porous hollow particles (B), the polyvalent metal salt (e) is the surface cross-linking agent (d) described above. However, from the viewpoint of the absorption performance of the absorbent resin particles under pressure, the surface cross-linking with the surface cross-linking agent (d) may be carried out simultaneously with the surface cross-linking with the surface cross-linking agent (d). It is preferable to mix.

  The mixing method of the polyvalent metal salt (e) can be performed in the same manner as the porous hollow particles (B), and the mixing temperature is also the same. Heat treatment may be performed after mixing the polyvalent metal salt (e), and the conditions are the same as the heating conditions after mixing the porous hollow particles (B), and the preferable conditions are also the same. The absorbent resin particles containing the polyvalent metal salt (e) may be used after adjusting the particle size, and the adjusting method is the same as the particle size adjustment after adding the porous hollow particles (B). The diameter is the same.

  The absorbent resin particles of the present invention may further contain water-insoluble inorganic particles (f). By including the water-insoluble inorganic particles (f), the surface of the particles contained in the absorbent resin particles is surface-treated with the water-insoluble inorganic particles (f), so that the absorbent resin particles have blocking resistance and liquid permeability. improves.

  Examples of the water-insoluble inorganic particles (f) include colloidal silica, fumed silica, clay and talc. Colloidal silica and silica are preferable and more preferable from the viewpoints of availability, ease of handling, and absorption performance. Is colloidal silica. One type of water-insoluble inorganic particles (f) may be used alone, or two or more types may be used in combination.

  The amount (parts by weight) of the water-insoluble inorganic particles (f) used is preferably from 0.01 to 5, more preferably from 0.05 to 1, particularly preferably from 100 parts by weight of the absorbent resin from the viewpoint of absorption performance. Is 0.1 to 0.5.

  When the water-insoluble inorganic particles (f) are contained, it is preferable to mix the absorbent resin particles and the water-insoluble inorganic particles (f). The mixing is performed in the same manner as the mixing of the porous hollow particles (B). The conditions are the same.

  The absorbent resin particles after mixing the water-insoluble inorganic particles (f) may be used after adjusting the particle size, and the particle size adjustment is performed in the same manner as the particle size adjustment performed after mixing the porous hollow particles (B). The same applies to the particle size after particle size adjustment.

  The absorbent resin particles of the present invention may be added with additives (for example, known preservatives, fungicides, antibacterial agents, oxidation agents (for example, described in JP-A-2003-225565 and JP-A-2006-131767, etc.)) An inhibitor, an ultraviolet absorber, a colorant, a fragrance, a deodorant, a liquid permeability improver, and an organic fibrous material). When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Preferably it is 0.05 to 1, most preferably 0.1 to 0.5.

  The absorbent resin particle of the present invention comprises a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinking agent (b) as essential constituent units. It can obtain suitably by the manufacturing method which has the process of mixing the crosslinked polymer (A) and porous hollow particle (B) which are made into.

  In the mixing of the crosslinked polymer (A) and the porous hollow particles (B), the crosslinked polymer (A) and the dispersion of the porous hollow particles (B) in oil are preferably mixed.

  The dispersion of the porous hollow particles (B) in oil can be obtained by an ordinary production method. For example, the porous hollow particles (B) are mixed in an organic solvent, and the system is stirred with a stirrer in the presence of an inert gas. A method such as stirring and mixing may be used.

  The step of mixing the crosslinked polymer (A) with the dispersion of the porous hollow particles (B) in oil includes the step of mixing the crosslinked polymer (A) with the dispersion of the porous hollow particles (B) in oil as described above. It can carry out by mixing using the mixing apparatus of. The temperature during mixing is the same as described above.

  The apparent density (g / ml) of the absorbent resin particles of the present invention is preferably 0.50 to 0.80, more preferably 0.52 to 0.75, and particularly preferably 0.54 to 0.70. . Within this range, the anti-fogging property of the absorbent article is further improved. The apparent density of the absorbent resin particles is measured at 25 ° C. according to JIS K7365: 1999.

  The water retention amount (g / g) of 0.9% by weight saline solution per unit weight of the water-absorbent resin particles of the present invention is preferably 30 or more, more preferably 34 or more, from the viewpoint of anti-fogging property of the absorbent article. Especially preferably, it is 36 or more. The upper limit is not particularly limited as the water retention amount is higher, but it is preferably 50 or less, more preferably 46 or less, and particularly preferably 44 or less, in view of balance with other physical properties.

In the present invention, the water retention amount is measured by the following measurement method.
<Measurement method of water retention amount>
1.00 g of a measurement sample is placed in a tea bag (20 cm long, 10 cm wide) made of a nylon net having a mesh size of 63 μm (JIS Z8801-1: 2006) and in 1,000 ml of physiological saline (saline concentration 0.9%). After stirring for 1 hour without stirring, pull up and hang for 15 minutes to drain. Thereafter, each tea bag is placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag is measured, and the water retention amount is obtained from the following equation. In addition, the temperature of the used physiological saline and measurement atmosphere shall be 25 degreeC +/- 2 degreeC. (H2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.
Water retention amount (g / g) = (h1)-(h2)

  The absorption amount (ml / g) of the water-absorbent resin particles of the present invention by the DW method (5-minute value) is preferably 45 or more, more preferably 50 or more, particularly preferably 55 from the viewpoint of the surface dryness of the absorbent article. That's it.

In the present invention, the amount of absorption by the DW method (5-minute value) is measured by the following measurement method.
<Measurement method of absorption amount (DW method) of absorbent resin particles>
The DW (Demand Wettability) method is a measurement method performed using the apparatus shown in FIG. 1 in a room at 25 ° C. and a humidity of 50%. The measuring apparatus shown in FIG. 1 includes a burette part (2) {scale capacity 50 ml, length 86 cm, inner diameter 1.05 cm,}, conduit {inner diameter 7 mm}, and measuring table (6). The burette part (2) is connected to the rubber stopper (1) at the upper part, the intake introduction pipe (9) {tip inner diameter 3 mm} and the cock (7) at the lower part, and the upper part of the intake introduction pipe (9) is There is a cock (8). A conduit is attached from the burette part (2) to the measurement table (6). At the center of the measurement table (6), there is a hole with a diameter of 3 mm as a physiological saline supply unit, and a conduit is connected. Using the measuring device of this configuration, first, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are closed, and a predetermined amount of physiological saline (salt) adjusted to 25 ° C. (Concentration 0.9 wt%) from the top of the burette part (2), and after plugging the top of the buret with the rubber plug (1), the cock (7) of the burette part (2) and the cock of the air introduction pipe (9) Open (8). Next, after wiping off the physiological saline overflowing the measurement table (6), the upper surface of the measurement table (6) and the surface of the saline solution coming out from the conduit port at the center of the measurement table (6) The height of the measurement table (6) is adjusted so that it is the same height. While wiping the physiological saline from the physiological saline supply part, the surface of the physiological saline in the burette part (2) is adjusted to the top (0 ml line) of the burette part (2) scale.

Subsequently, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are closed, and the plain weave nylon mesh (on the measurement table (6) is placed so that the physiological saline supply part is at the center. 5) (Opening 63 μm, 5 cm × 5 cm) is placed on this plain weave nylon mesh (5), and 0.50 g in a range of 2.7 cm in diameter with the physiological saline supply part of the measuring table (6) as the center. The absorbent resin particles (4) are uniformly dispersed. Thereafter, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are opened. When the absorbent resin particles (4) begin to absorb water and the first bubble introduced from the air introduction tube (9) reaches the surface of the physiological saline in the burette portion (2) (burette portion (2) The measurement start time is defined as the time when the physiological saline water in the inside drops, and the amount of physiological saline (3) in the burette portion (2) is continuously reduced (the physiological state in which the absorbent resin particles (4) have absorbed water). Saline amount) M (ml) is read. The absorption amount of the absorbent resin particles (4) after the elapse of a predetermined time from the start of water absorption is determined by the following equation. In this application, the 5-minute value is used as an index of the absorption rate.
Absorption by DW method (ml / g) = M ÷ 0.50

  The absorption rate (seconds) of the water-absorbent resin particles of the present invention by the Vortex method is preferably 60 or less, more preferably 50 or less, and particularly preferably 40 or less from the viewpoint of the surface dryness of the absorbent article. The lower the lower limit value is, the higher the absorption rate by the Vortex method is, and the lower limit is not particularly limited.

In the present invention, the absorption rate (second) by the Vortex method is measured by the following measurement method.
<Measurement Method of Absorption Rate of Absorbent Resin Particles (Vortex Method)>
After sufficiently shaking the container containing the absorbent resin particles so as to eliminate the uneven distribution of the particle size distribution, the absorbent resin particles are weighed with an accuracy of 2.00 ± 0.001 g. Next, 50 g of 0.900 ± 0.001 wt% physiological saline adjusted to 25 ± 1 ° C. and a stirrer chip are placed in a 100 ml beaker, the beaker is placed on a magnetic stirrer, and the vortex becomes the center of the beaker. Stir at a rotation speed of 600 ± 60 rpm. At this time, it is performed in an atmosphere of room temperature 23 ± 2 ° C. and relative humidity 50 ± 5%. Next, 2.00 g of the weighed absorbent resin particles are collectively put into the center of the vortex formed in the beaker, and at the same time, measurement is started with a stopwatch. Along with the absorption of the saline by the absorbent resin particles, the point where the vortex begins to disappear and the liquid level becomes horizontal is taken as the end point, and the time (unit: seconds) required until the end point is measured. The time (unit: second) measured as described above is taken as the absorption rate in the Vortex method.

  The absorption rate (g / g / min) of the water-absorbent resin particles of the present invention by the Lockup method is 25 or more, preferably 28 or more, more preferably 30 or more, from the viewpoint of the surface dryness of the absorbent article. The absorption rate (Lockup) measurement method is a test method for measuring the absorption rate under stationary conditions, rather than the Vortex method for measuring under stirring conditions or the DW method for defining the absorption rate from a single absorption spot. It is more suitable as an evaluation method because it is in line with the actual use situation, for example, the situation where body fluid such as urine is absorbed. The upper limit is not particularly limited as the absorption rate by the Lockup method is faster, but it is preferably 80 or less, more preferably 60 or less, and particularly preferably 50 or less, from the balance with liquid diffusibility in the absorbent article. When the absorption rate (g / g / min) by the Lockup method is less than 25, the liquid diffusibility when used as an absorbent article is inferior. As a result, the liquid return amount increases, which is not preferable from the viewpoint of anti-fogging property. On the other hand, if it exceeds 80, blocking is likely to occur, liquid diffusibility is deteriorated, and the liquid return amount of the absorbent article is increased.

In the present invention, the absorption rate (Lockup) is measured by the following measurement method.
<Measurement Method of Absorption Rate (Lockup) of Absorbent Resin Particles>
Place 1.00 g of the absorbent resin in a 100 ml glass beaker (with a flat bottom as defined in JIS R 3503). At this time, the upper surface of the absorbent resin placed in the beaker is made to be horizontal (if necessary, the surface of the absorbent resin may be made horizontal by carefully tapping the beaker or the like). Next, 40 g of physiological saline adjusted to 23 ° C. ± 2 ° C. is weighed into a 100 ml glass beaker and poured quickly and carefully into a 100 ml beaker containing an absorbent resin. Time measurement is started at the same time as the poured physiological saline comes into contact with the absorbent resin. Then, when the beaker into which the physiological saline is poured is inclined at an angle of about 90 °, the time measurement is finished when the fluid of the absorbent resin or the physiological saline does not ooze from the surface of the absorbent resin (t Seconds). The absorption rate (Lockup) is calculated by the following equation (a).
Lockup (g / g / min) = 40 / (t seconds ÷ 60 × mass of absorbent resin (g)) Formula (a)

  The weight average particle diameter of the water-absorbent resin particles of the present invention is preferably 280 μm or more, more preferably 300 μm or more, and particularly preferably 320 μm or more from the viewpoint of blocking resistance. Further, it is preferably 600 μm or less, more preferably 500 μm or less, and particularly preferably 450 μm or less.

  The absorbent resin particles of the present invention can be used as an absorbent body together with a fibrous material. The structure and manufacturing method of the absorber are the same as those known in the art (Japanese Patent Laid-Open Nos. 2003-225565, 2006-131767, and 2005-097569, etc.). Moreover, it is preferable that this absorber comprises absorbent articles {paper diapers, sanitary napkins, etc.}.

The water-absorbent resin particles of the present invention constitute an absorbent used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, medical pads, etc., and are suitably used for absorbent articles containing the absorbent. It is done.
The water absorbent body using the water absorbent resin particles of the present invention is excellent in absorption amount, excellent in liquid uptake speed, excellent in dry touch under pressure after absorption, and suppresses cracking and deformation of the absorbent body. Can do.

  The absorber using the water absorbent resin particles of the present invention is composed of, for example, water absorbent resin particles and hydrophilic fibers. Specific examples of the hydrophilic fiber include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood, and artificial cellulose fibers such as rayon and acetate. A preferred hydrophilic fiber is wood pulp fiber. These hydrophilic fibers may partially contain synthetic fibers such as nylon and polyester.

  The content of the water-absorbent resin particles in the absorber is preferably 5 to 95% by mass, more preferably 20 to 90% by mass, and 30 to 80% by mass from the viewpoint of light weight and thin film formation. More preferably it is.

  As the constitution of the absorbent body, the water-absorbent resin particles are sandwiched between the mixed dispersion obtained by mixing the water-absorbent resin particles and the hydrophilic fibers so as to have a uniform composition, and the layered hydrophilic fibers. And a sandwich structure, a structure in which water-absorbent resin particles and hydrophilic fibers are wrapped with a tissue, and the like. The absorbent body may contain other components, for example, an adhesive binder such as a heat-fusible synthetic fiber, a hot melt adhesive, and an adhesive emulsion for enhancing the shape retention of the absorbent body. .

  Also, the absorbent body using the water-absorbent resin particles is held between a liquid-permeable sheet (top sheet) through which liquid can pass and a liquid-impermeable sheet (back sheet) through which liquid cannot pass. Thus, an absorbent article can be obtained. The liquid permeable sheet is disposed on the side in contact with the body, and the liquid impermeable sheet is disposed on the opposite side in contact with the body.

  Examples of the liquid permeable sheet include air-through type, spun bond type, chemical bond type, needle punch type nonwoven fabrics and porous synthetic resin sheets made of fibers such as polyethylene, polypropylene, and polyester. Examples of the liquid impermeable sheet include synthetic resin films made of resins such as polyethylene, polypropylene, and polyvinyl chloride.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, parts indicate parts by weight and% indicates% by weight.

<Example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mole parts), crosslinking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Corporation } 0.6225 parts (0.0024 mole part) and 340.27 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to reduce the dissolved oxygen amount to 1 ppm or less, and then 0.62 part of 1% aqueous hydrogen peroxide solution, 1.1625 part of 2% aqueous ascorbic acid solution and 2% 2,2′-azobis [ 2.325 parts of 2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., polymerization was carried out at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1).
Next, the water-containing gel (1) 502.27 parts was shredded with a mincing machine (12 VR-400K manufactured by ROYAL), and 128.42 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed. Hollow particles (B-1) {Marlite 713D (manufactured by Marunaka Shirato Co., Ltd.), apparent density 0.25, average particle diameter 40-50 μm} 1.0 part was added and mixed, and the chopped gel (2) was added. Obtained. Further, the chopped gel (2) was dried with a ventilation band dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster Co., Ltd.), and then adjusted to a particle size of 150 to 710 μm using a sieve having openings of 150 μm and 710 μm to obtain dried particles. While stirring 100 parts of the dry particles (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30). 4 parts were added while being sprayed and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes to cross-link the surface to obtain the absorbent resin particles (P-1) of the present invention. The weight average particle diameter of the absorbent resin particles (P-1) was 385 μm, and the water retention amount was 39.9 g / g. Further, the absorption amount after 5 minutes in the DW method was 55.4 ml / g, the absorption rate in the Vortex method was 25 seconds, and the absorption rate in the Lockup method was 28.6 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 2>
“Porous hollow particles (B-1) 1.0 part” is replaced with “Porous hollow particles (B-2) {Winlite MSB3011 (manufactured by Axes Chemical Co., Ltd.), apparent density 0.28-0.33, average particles Absorbent resin particles (P-2) of the present invention were obtained in the same manner as in Example 1 except that the diameter was changed to 35 parts by 1.0 μm. The weight average particle diameter of the absorbent resin particles (P-2) was 378 μm, and the water retention amount was 40.1 g / g. Further, the absorption amount after 5 minutes in the DW method was 56.2 ml / g, the absorption rate in the Vortex method was 22 seconds, and the absorption rate in the Lockup method was 29.6 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 3>
“Porous hollow particles (B-1) 1.0 part” is referred to as “porous hollow particles (B-3) {Winlite MSB3011S (manufactured by Axes Chemical Co., Ltd.), apparent density 0.5-0.8, average particles Absorbent resin particles (P-3) of the present invention were obtained in the same manner as in Example 1, except that the diameter was changed to 25 parts by weight of 1.0 part. The weight average particle diameter of the absorbent resin particles (P-3) was 380 μm, and the water retention amount was 40.3 g / g. Further, the absorption amount after 5 minutes in the DW method was 54.7 ml / g, the absorption rate in the Vortex method was 26 seconds, and the absorption rate in the Lockup method was 28.2 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 4>
“Porous hollow particles (B-1) 1.0 part” is replaced with “Porous hollow particles (B-4) {Winlite MSB3011SS (manufactured by Axes Chemical Co., Ltd.), apparent density 0.2-0.3, average particle Absorbent resin particles (P-4) of the present invention were obtained in the same manner as in Example 1 except that the diameter was changed to 2.8 μm} 1.0 part ”. The weight average particle diameter of the absorbent resin particles (P-4) was 399 μm, and the water retention amount was 40.3 g / g. Further, the absorption amount after 5 minutes in the DW method was 55.5 ml / g, the absorption rate in the Vortex method was 27 seconds, and the absorption rate in the Lockup method was 30.0 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 5>
“Porous hollow particles (B-1) 1.0 part” is replaced with “Porous hollow particles (B-5) {Glass Bubbles S42XHS (manufactured by Sumitomo 3M), apparent density 0.28, average particle diameter 22 μm} 1” Absorbent resin particles (P-5) of the present invention were obtained in the same manner as in Example 1 except that the content was changed to “0.0 parts”. The weight average particle diameter of the absorbent resin particles (P-5) was 401 μm, and the water retention amount was 38.2 g / g. Further, the absorption amount after 5 minutes in the DW method was 53.1 ml / g, the absorption rate in the Vortex method was 30 seconds, and the absorption rate in the Lockup method was 26.1 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 6>
“Porous hollow particles (B-1) 1.0 part” is replaced with “porous hollow particles (B-6) {Matsumoto Microsphere F-48 (manufactured by Matsumoto Yushi Co., Ltd.), average particle size 9-16 μm} 1” Absorbent resin particles (P-6) of the present invention were obtained in the same manner as in Example 1 except that the content was changed to "0.0 parts". The weight average particle diameter of the absorbent resin particles (P-6) was 406 μm, and the water retention amount was 39.7 g / g. Further, the absorption amount after 5 minutes in the DW method was 56.8 ml / g, the absorption rate in the Vortex method was 29 seconds, and the absorption rate in the Lockup method was 29.3 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Example 7>
“Porous hollow particles (B-1) 1.0 part” is replaced with “porous hollow particles (B-7) {Matsumoto Microsphere F-30 (manufactured by Matsumoto Yushi Co., Ltd.), average particle size 10-18 μm} 1. Absorbent resin particles (P-7) of the present invention were obtained in the same manner as in Example 1 except that the content was changed to ".0 part". The weight average particle diameter of the absorbent resin particles (P-7) was 400 μm, and the water retention amount was 39.9 g / g. Further, the absorption amount after 5 minutes in the DW method was 51.2 ml / g, the absorption rate in the Vortex method was 30 seconds, and the absorption rate in the Lockup method was 26.7 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Comparative Example 1>
Absorbent resin particles (R-1) for comparison were obtained in the same manner as in Example 1 except that 1.0 part of “porous hollow particles (B-1)” was not added. The weight average particle diameter of the absorbent resin particles (R-1) was 390 μm, and the water retention amount was 40.5 g / g. Further, the absorption amount after 5 minutes in the DW method was 47.6 ml / g, the absorption rate in the Vortex method was 35 seconds, and the absorption rate in the Lockup method was 19.0 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Comparative example 2>
Implementation other than changing “porous part (B-1) 1.0 part” to “MS-KY (manufactured by Nippon Talc Co., Ltd.), apparent density 0.55, average particle diameter 25 μm, 1.0 part” In the same manner as in Example 1, comparative absorbent resin particles (R-2) were obtained. The weight average particle diameter of the absorbent resin particles (R-2) was 381 μm, and the water retention amount was 38.1 g / g. Further, the absorption amount after 5 minutes in the DW method was 56.5 ml / g, the absorption rate in the Vortex method was 25 seconds, and the absorption rate in the Lockup method was 24.2 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

<Comparative Example 3>
Except for changing “porous hollow particles (B-1) 1.0 part” to “Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.), apparent density 0.05, average particle diameter 14 nm, 1.0 part”. In the same manner as in No. 1, comparative absorbent resin particles (R-3) were obtained. The weight average particle diameter of the absorbent resin particles (R-3) was 376 μm, and the water retention amount was 37.9 g / g. Further, the absorption amount after 5 minutes in the DW method was 56.9 ml / g, the absorption rate in the Vortex method was 28 seconds, and the absorption rate in the Lockup method was 17.8 g / g / min. The measuring method of these characteristics was based on the above-mentioned method.

  Table 1 shows the performance evaluation results of the absorbent resin particles (P-1) to (P-7) of Examples 1 to 7 and the absorbent resins (R-1) to (R-3) of Comparative Examples 1 to 3. Shown in

From the results in Table 1, there is a clear difference between the measurement results in the comparative examples and the examples of the absorption rate of the Vortex method that measures under stirring conditions and the DW method that defines the absorption rate from one absorption spot. However, it was found that the absorbent resin particles of the present invention showed a clear and excellent absorption rate in the Lockup method relative to the comparative example. The Lockup method for measuring under static conditions more accurately reflects the actual use situation, for example, the situation of absorbing bodily fluids such as urine. Therefore, it is suitable as a performance evaluation method under actual use conditions that cannot be correctly evaluated by the Vortex method or the DW method.
When the absorption rate (g / g / min) by the Lockup method is less than 25, the liquid diffusibility when used as an absorbent article is inferior. As a result, the liquid return amount increases and the anti-fogging property deteriorates. On the other hand, if it exceeds 80, blocking tends to occur, and therefore liquid diffusibility tends to deteriorate, and the amount of liquid return of the absorbent article increases, so that anti-fogging property also deteriorates. The absorption rate (g / g / min) by the Lockup method of the examples was all within this range, while the value of the comparative example was outside this range.

  The absorbent resin particles of the present invention have an excellent absorption rate in the Lockup method and an excellent absorption performance. Because of the above effects, the absorbent resin particles of the present invention can be used for absorbent articles having a large amount of absorption and excellent reversibility and surface dryness when applied to various absorbers. Suitable for hygiene items such as children's disposable diapers and adult disposable diapers), napkins (such as sanitary napkins), paper towels, pads (such as incontinence pads and surgical underpads), and pet sheets (pet urine absorbing sheets) Used, especially for disposable diapers.

DESCRIPTION OF SYMBOLS 1 Rubber stopper 2 Bullet part 3 Saline 4 Absorbent resin particle 5 Plain weave nylon mesh 6 Measuring stand 7 Cock 8 Cock 9 Intake pipe

Claims (10)

Water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, cross-linked polymer (A) having cross-linking agent (b) as an essential constituent unit, and porous Resin particles containing a porous hollow particle (B) and having an absorption rate of 25 to 80 g / g / min according to the Lockup method defined by the following formula (a).

Lockup (g / g / min) = 40 / (t seconds ÷ 60 × mass of absorbent resin (g)) Formula (a)

(In the formula, t is a time when 40 g of physiological saline adjusted to 23 ° C. ± 2 ° C. is poured into a 100 ml beaker containing 1.00 g of the absorbent resin, and the poured physiological saline comes into contact with the absorbent resin. To the time (seconds) until the fluid of the absorbent resin or physiological saline does not leach from the absorbent resin when the beaker into which physiological saline is poured is tilted at an angle of about 90 °.   The absorbent resin particle according to claim 1, wherein the porous hollow particle (B) is an inorganic particle.   The absorbent resin particle according to claim 2, wherein the inorganic particles are at least one selected from the group consisting of a glass balloon, a shirasu balloon, a silica balloon, an alumina balloon, and an aluminosilicate balloon.   The absorbent resin particle according to claim 3, wherein the inorganic particle is a shirasu balloon.   The absorbent resin particles according to any one of claims 1 to 4, wherein the porous hollow particles (B) have a weight average particle diameter of 0.1 to 50 µm.   The absorbent resin particles according to any one of claims 1 to 5, wherein the content of the porous hollow particles (B) is 0.01 to 5.00% by weight based on the weight of the crosslinked polymer (A). .   The absorbent resin particles according to any one of claims 1 to 6, wherein a water retention amount of 0.9 wt% saline of the absorbent resin particles is 30 to 50 g / g per unit weight.   Water-soluble vinyl monomer (a1) and / or vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis, and cross-linked polymer (A) and porous hollow containing cross-linking agent (b) as essential constituent units The manufacturing method of the absorptive resin particle in any one of Claims 1-7 which has the process of mixing particle | grains (B).   The absorber containing the absorptive resin particle in any one of Claims 1-7.   An absorbent article comprising the absorbent body according to claim 9.

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