JPH1171529A - Water-absorption resin and water-absorbing article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-absorbing resin that causes no pollution of the surroundings by its coloring components when absorbing liquid and can clearly show the presence of the water-absorbing resin, in addition to its coloring, by admixing a coloring component to a resin and specifying the absorption time under pressure and the water absorption rate. SOLUTION: The objective water-absorbing resin is obtained by admixing an adsorption component so as to set the absorption times under pressure to >=20 (g/g), preferably >=25 (g/g), more preferably >=30 (g/g), particularly >=35 (g/g) and the water absorption rate to <=40 seconds, preferably <=35 seconds more preferably <=30 seconds. This resin is obtained by adding (B) <=10 pts.wt. of a coloring component, preferably a food pigment, based on 100 pts.wt. of component A on the solid basis, to (A) a water-absorbing polymer with the absorption times under the pressure of >=20 (g/g) and the water absorption rate of <=40 seconds as a base polymer. The component A is obtained by surface crosslinking treatment of a precursor of the water-absorbing resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbent resin suitably used for sanitary materials such as paper diapers (disposable diapers) and sanitary napkins, so-called incontinence pads, and an absorbent article using the water-absorbent resin. It is.

[0002]

2. Description of the Related Art In recent years, sanitary materials such as disposable diapers and sanitary napkins, so-called incontinence pats, have been used as constituent materials thereof.
Examples of the above-mentioned water-absorbing resin in which the water-absorbing resin for absorbing body fluids is widely used include, for example, a crosslinked product of partially neutralized polyacrylic acid, a hydrolyzate of starch-acrylonitrile graft polymer, and starch. A neutralized product of an acrylic acid graft polymer, a saponified product of a vinyl acetate-acrylate copolymer, a hydrolyzed product of an acrylonitrile copolymer or an acrylamide copolymer, or a crosslinked product thereof, a crosslinked product of a cationic monomer, or the like. It has been known.

[0003] The above-mentioned water-absorbing resin should have the following characteristics: excellent water absorption amount, water absorption speed, gel strength, and suction power for sucking water from a base material containing an aqueous liquid when in contact with an aqueous liquid such as a body fluid. And so on. A water-absorbent resin exhibiting excellent performance (water-absorbing properties) when used in sanitary materials such as disposable diapers and sanitary napkins. Various bodies and absorbent articles have been proposed.

[0004] In recent years, absorbent articles such as disposable diapers and sanitary napkins have generally become more sophisticated and thinner, and the amount of water-absorbent resin used per absorbent article, or the amount of water-absorbent resin and fiber base material, Tend to increase the weight ratio of the water-absorbent resin to the total amount of In other words, by reducing the fiber base material having a small bulk specific gravity, being excellent in water absorbency, and increasing the water absorbent resin having a large bulk specific gravity, the ratio of the water absorbent resin in the absorber is increased, thereby reducing the water absorption. The sanitary material has been made thinner without causing it to shrink.

[0005]

In the manufacture of such an absorbent article containing a relatively large amount of a water-absorbent resin, a technique for making the presence of the water-absorbent resin more apparent in the absorbent layer has not yet been established. It has not been. That is, the conventional water-absorbent resin is generally a white powder, and the hydrophilic fibers used therewith are also white or pale yellow,
When manufacturing an absorbent article, there is a problem that a new analysis operation is required separately in order to check whether a predetermined amount of the water-absorbing resin is correctly added to the manufactured disposable diaper or the like. It is also recognized by general consumers that absorbent articles such as disposable diapers contain water-absorbent resin, but it is not known how much and how much is present, It has been difficult to show a sense of security.

The present inventors have studied various colored water-absorbing resins in view of the above-mentioned situation. However, when a water-soluble substance which does not generally give a problem to the absorption characteristics of the resin is used as a coloring component, the water-absorbing resin may have a disadvantage in absorbing the liquid. The present inventors have found a problem that the coloring component is released to contaminate the surroundings. Also, when an absorbent article containing such a water-absorbent resin is produced in a relatively large amount and an absorbing solution is added thereto, there is a problem that the released coloring component causes skin and clothing to be colored. Also found.

It is an object of the present invention to provide a colored water-absorbing resin, and the coloring component does not pollute the surrounding environment at the time of liquid absorption, and is colored. A water-absorbent resin and a water-absorbent resin which can be clearly described above, are particularly preferably used for quality control in a factory when manufacturing a water-absorbent article, and can sufficiently appeal to a consumer to the presence of the water-absorbent resin. To provide an absorbent article.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, they have a specific absorption capacity under pressure as a water-absorbing resin as a base polymer before adding a coloring component. The present inventors have found that the use of a resin having a specific water absorption rate eliminates contamination of the surroundings by the coloring component present in the water-absorbent resin during liquid absorption, and has completed the present invention.

That is, the present invention relates to a water-absorbing resin containing a coloring component, having an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less, and having an object color L = 80 or less and a Value is 2 or more, or the absolute value of b satisfies at least one value of 10 or more, the absorption capacity under pressure is 20 (g / g) or more, and the water absorption rate is 4
Water-absorbent resin of 0 seconds or less, and absorption capacity under pressure of 20 (g
/ g) a method for producing a water-absorbent resin characterized by adding a coloring component to a water-absorbent resin as a base polymer having a water absorption rate of 40 seconds or less, and the total amount of the water-absorbent resin and the fiber base material An absorbent layer containing an absorbent having a weight ratio α of the water-absorbent resin of 0.3 or more, a surface sheet having liquid permeability,
An absorbent article comprising a back sheet having liquid impermeability, which is colored so as to contain a coloring component as the water-absorbing resin and have an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. And an absorbent layer comprising an absorbent having a weight ratio α of the water-absorbent resin to the total amount of the water-absorbent resin and the fibrous base material of 0.3 or more, and a liquid-permeable surface. Sheet, an absorbent article comprising a back sheet having liquid impermeability, the object color as the water-absorbing resin L = 80 or less, the absolute value of a is 2 or more, or the absolute value of b is at least 10 or more Satisfies one value and absorbency against pressure is 20 (g / g)
The present invention relates to an absorbent article including those having a water absorption rate of 40 seconds or less.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The water-absorbing resin as a base polymer that can be used in the present invention must satisfy two conditions: an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. It is. When the value is less than 20 (g / g), the coloring component is not easily transferred to the surrounding environment when absorbing the liquid, even if the value of the water absorption rate satisfies the range of the present invention. If the water absorption rate exceeds 40 seconds, the coloring component is also likely to migrate to the surrounding environment when absorbing the liquid, even if the absorption capacity under pressure satisfies the range of the present invention. Preferably the absorption capacity under pressure is 25 (g / g) or more, more preferably 3
The resin is 0 (g / g) or more, more preferably 35 (g / g) or more. The water absorption rate is preferably 35 seconds or less, more preferably 30 seconds or less.

The water-absorbing resin as such a base polymer is generally obtained by a production method of subjecting a water-absorbing resin precursor to a surface crosslinking treatment. The above-mentioned water-absorbent resin precursor preferably has an average particle diameter in the range of 100 μm to 600 μm, and has a specific surface area by a BET method of 0.020 (m2 / g) or more. More preferably, the average particle size is from 100 μm to 40
It has a specific surface area of 0.025 (m2 / g) or more by the BET method within the range of 0 μm.

The water-absorbing resin precursor is synthesized, for example, by aqueous solution polymerization or reverse phase suspension polymerization. Specific examples of the water-absorbent resin precursor include, for example, a crosslinked product of partially neutralized polyacrylic acid, a hydrolyzate of starch-acrylonitrile graft polymer, a neutralized product of starch-acrylic acid graft polymer, and acetic acid. Saponified vinyl-acrylate copolymer, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer or cross-linked product thereof, carboxyl group-containing cross-linked polyvinyl alcohol-modified product, cross-linked isobutylene-maleic anhydride copolymer, etc. Is mentioned.

The above-mentioned water-absorbing resin precursors include, for example, unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, β-acryloyloxypropionic acid and the like. After polymerizing or copolymerizing one or more monomers selected from neutralized products of the above, the polymer is subjected to operations such as pulverization and classification as necessary to adjust the average particle size to the above. can get. Among the above monomers, (meth) acrylic acid and their neutralized products are more preferable.

Further, the water-absorbing resin precursor may be a copolymer of the above monomer and another monomer copolymerizable with the monomer. As the other monomer, specifically,
For example, vinyl sulfonic acid, styrene sulfonic acid, 2-
(Meth) acrylamide-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2-
Anionic unsaturated monomers such as (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, N
-N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) ) Nonionic hydrophilic group-containing unsaturated monomers such as acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine; N, N-dimethylaminoethyl ( (Meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, and quaternary salts thereof And cationic unsaturated monomers such.

The water absorbing resin precursor is preferably internally crosslinked by reacting or copolymerizing with a crosslinking agent having a plurality of polymerizable unsaturated groups or a plurality of reactive groups. Further, the water-absorbing resin precursor may be a self-crosslinking type that does not require a crosslinking agent. Specific examples of the crosslinking agent include N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and trimethylolpropane. Di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide-modified trimethylolpropane tri (meth)
Acrylate pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl Examples include ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) acrylate, and the like. These crosslinking agents may be used alone or as a mixture of two or more. Among the compounds exemplified above, it is more preferable to use a compound having a plurality of polymerizable unsaturated groups as a crosslinking agent.

The amount of the crosslinking agent to be used is preferably in the range of 0.005 mol% to 2 mol%, and
More preferably, it is in the range of 05 mol% to 1 mol%. If the amount of the cross-linking agent is less than 0.005 mol%, the stability of the swollen gel of the water-absorbent resin to urine may be undesirably reduced.

At the start of the polymerization in the above polymerization reaction, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide,
A radical polymerization initiator such as hydrogen peroxide and 2,2′-azobis (2-amidinopropane) dihydrochloride, or an active energy ray such as an ultraviolet ray or an electron beam can be used. When an oxidizing radical polymerization initiator is used, redox polymerization may be performed using a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, or L-ascorbic acid in combination. The amount of these polymerization initiators used is preferably in the range of 0.001 mol% to 2 mol%, more preferably in the range of 0.01 mol% to 0.5 mol%.

It is also preferable to increase the specific surface area by adding a foaming agent such as a carbonate or an azo compound or an inert gas to the monomer at the time of polymerization, and forming the resulting water-absorbent resin precursor into a porous structure. .

The above-mentioned water-absorbent resin precursor may be granulated in a predetermined shape, or may be in various shapes such as a spherical shape, a scale-like shape, an irregular crushed shape, and a granular shape. Further, the water absorbing resin precursor may be primary particles,
Granules of secondary particles may be used.

The above water-absorbent resin precursor generally has an absorption capacity under pressure that does not satisfy the range in the present invention.
For this reason, it is necessary to use a specific surface cross-linking agent to make the cross-linking density near the surface of the water-absorbent resin precursor higher than that inside. That is, by cross-linking the vicinity of the surface of the water-absorbent resin precursor using the specific surface cross-linking agent, a water-absorbent resin as a base polymer usable in the present invention can be obtained.

That is, the water-absorbent resin as the base polymer according to the present invention has a specific surface area by a so-called BET method.
0.02 (m2 / g) or more, more preferably 0.025 (m2 / g) or more, preferably a water-absorbent resin precursor obtained by the aqueous solution polymerization described above, that is, the average particle size is 100 μm to 60
0 μm, more preferably the average particle size is 100 μm
After adjusting by polymerization, classification and the like so as to have a diameter within the range of 400 μm, it can be obtained by heat treatment in the presence of a surface crosslinking agent.

The surface cross-linking agent is not particularly limited, and has a functional group of the water-absorbing resin precursor, for example, a functional group capable of reacting with an acidic group, and is usually used for the purpose. Known crosslinking agents are exemplified.

When the functional group of the water absorbent resin precursor is, for example, a carboxyl group, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, 1,3-propanediol, Dipropylene glycol, 2,2,4-trimethyl-1,3-pentadiol, polypropylene glycol, glycerin, polyglycerin, 2-butene-
1,4-diol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,2
Polyhydric alcohol compounds such as cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethyleneoxypropylene block copolymer, pentaerythritol and sorbitol; ethylene glycol diglycidyl Ether, polyethylene diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyhydric epoxy compounds such as glycidol; ethylenediamine, diethylenetriamine, Triethylenetetramine, tetraethylenepentamine, pentae Renhekisamin, polyallylamine, polyamine compounds such as polyethyleneimine; 2,4
Polyvalent isocyanate compounds such as tolylene diisocyanate and hexamethylene diisocyanate; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline;
1,3-dioxolan-2-one, 4-methyl-1,3
-Dioxolan-2-one, 4,5-dimethyl-1,3
Dioxolan-2-one, 4,4-dimethyl-1,3
-Dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-
Dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,
6-dimethyl-1,3-dioxan-2-one, 1,3
Alkylene carbonate compounds such as dioxopan-2-one; epichlorohydrin, epibromohydrin, α
-A haloepoxy compound such as methyl epichlorohydrin;
Zinc, calcium, magnesium, aluminum, iron,
One or more compounds selected from hydroxides such as zirconium and polyvalent metal compounds such as chlorides; silane coupling agents; and the like can be exemplified. Preferably polyvalent alcohol
And at least one selected from the group consisting of a polyamine compound, a polyamine compound, a polyepoxy compound, and an alkylene carbonate compound.

The amount of the surface cross-linking agent used depends on the compound to be used and the combination thereof, but is preferably in the range of 0.001 to 5 parts by weight based on 100 parts by weight of the solid content of the water-absorbing resin precursor. And more preferably in the range of 0.01 to 1 part by weight. By using the above surface cross-linking agent, the water-absorbing resin precursor, that is, the cross-linking density in the vicinity of the surface of the water-absorbing resin can be higher than that inside, and the absorption capacity under pressure required for the resin of the present invention can be increased. Can be. When the amount of the surface cross-linking agent exceeds 10 parts by weight, not only is it uneconomical, but also because the amount of the surface cross-linking agent becomes excessive in forming the optimum cross-linked structure in the water absorbent resin, The rolling absorption capacity is undesirably reduced. Also, the amount of surface cross-linking agent
When the amount is less than 0.001 part by weight, it is difficult to obtain the effect of improving the absorbency against pressure of the water-absorbent resin, so that it is not preferable.

When mixing the water-absorbing resin precursor and the surface crosslinking agent, it is preferable to use water as a solvent. The amount of water used depends on the type and particle size of the water-absorbing resin precursor, but is 0% based on 100 parts by weight of the solid content of the water-absorbing resin precursor.
And preferably not more than 20 parts by weight, more preferably in the range of 0.5 to 10 parts by weight.

When mixing the water-absorbing resin precursor with the surface crosslinking agent, a hydrophilic organic solvent may be used as a solvent, if necessary. As the above hydrophilic organic solvent,
For example, lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol; ketones such as acetone;
Ethers such as dioxane and tetrahydrofuran;
Amides such as N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; and the like. The amount of the hydrophilic organic solvent used depends on the type and particle size of the water-absorbing resin precursor, but is preferably 20 parts by weight or less, and more preferably 0.1 part by weight, based on 10 parts by weight of the solid content of the water-absorbing resin precursor. More preferably, it is within the range of 10 to 10 parts by weight.

When mixing the water-absorbing resin precursor and the surface crosslinking agent, for example, after dispersing the water-absorbing resin precursor in the above-mentioned hydrophilic organic solvent, the surface crosslinking agent is mixed. However, the mixing method is not particularly limited. Among various mixing methods, a method in which a surface cross-linking agent dissolved in water and / or a hydrophilic organic solvent, if necessary, is directly sprayed or dropped onto the water-absorbent resin precursor and mixed. In the case of mixing using water, fine powder insoluble in water, a surfactant or the like may be allowed to coexist.

The mixing device used for mixing the water-absorbing resin precursor and the surface cross-linking agent preferably has a large mixing force in order to mix both uniformly and reliably. As the mixing device, for example, a cylindrical mixer,
Double wall conical mixer, V-shaped mixer, ribbon mixer,
Suitable examples include a screw mixer, a fluid-type furnace rotary desk mixer, an airflow mixer, a double-arm kneader, an internal mixer, a pulverizing kneader, a rotary mixer, and a screw extruder.

After mixing the water-absorbent resin precursor and the surface cross-linking agent, a heat treatment is performed to crosslink the vicinity of the surface of the water-absorbent resin precursor. The temperature of the heat treatment depends on the surface cross-linking agent used, but is preferably from 40 ° C. to 250 ° C. When the treatment temperature is lower than 40 ° C., a uniform crosslinked structure is not formed, so that a water-absorbent resin having an absorption capacity under pressure falling within the range of the present invention may not be obtained. Processing temperature
When the temperature exceeds 250 ° C., the water-absorbent resin is deteriorated, and the performance of the water-absorbent resin is deteriorated.

The above heat treatment can be carried out using a usual dryer or heating furnace. Examples of the dryer include a groove-type mixing dryer, a rotary dryer, a desk dryer, a fluidized-bed dryer, a flash dryer, and an infrared dryer.

The water-absorbing resin of the present invention can be obtained by adding a coloring component to the water-absorbing resin as a base polymer obtained as described above.

The coloring component which can be used in the present invention includes those which exhibit a hue by being dispersed and dissolved in an aqueous liquid containing hydrophilic water or a hydrophilic organic solvent. These include, for example, Food Red No. 2, Food Red No. 2 Aluminum Lake, Food Red No. 3, Food Red No. 3 Aluminum Lake, Food Red No. 102, Food Red No. 104, Food Red No. 105
No., Food Red No. 106, Food Yellow No. 4, Food Yellow No. 4 Aluminum Lake, Food Yellow No. 5, Food Yellow No. 5 Aluminum Lake, Food Green No. 3, Food Green No. 3 Aluminum Lake, Food Blue No. 1, Food Blue No. 1 aluminum lake, Food Blue No. 2, Food Blue No. 2 aluminum lake, water-soluble annatto, food irons such as iron iron chlorophyllin, sodium copper chlorophyllin, copper chlorophyll, alizarin red, xylenol orange, xylene cyanol FF, crystal violet , Congo Red,
Indicators such as titanium yellow, ninhydrin, methyl orange, methyl thymol blue and toluidine blue; nitroso dyes such as naphthol green B; nitro dyes such as naphthol yellow S; azo dyes such as amaranth; stilbene dyes such as chrysophenin G; Diphenylmethane dyes, triarylmethane dyes such as malachite green, xansen dyes such as rhodamine B, acridine dyes such as acridine orange R, quinoline dyes such as quinoline yellow, thiazole dyes such as thioflavin T, and indophenol dyes such as indophenol blue , Azine dyes such as safranin T, oxazine dyes such as gallocyanine, thiazine dyes such as methylene blue, sulfur dyes such as sulfur black T, herringdon yellow C
Aminoketone dyes such as G; anthraquinone dyes such as alizanin cyanine green G; indigoid dyes such as indigo; and phthalocyanine dyes such as pontamine fast tercoass 8GL. Among these, food dyes are preferred for safety.

The amount of these coloring components varies depending on the purpose of coloring the water-absorbing resin, but it is usually sufficient if the desired coloring strength is imparted to the water-absorbing resin as the base polymer. The amount varies greatly depending on the type of the coloring component used, but generally, the amount added is based on 100 parts by weight of the solid content of the water-absorbent resin as the base polymer.
It is preferably at most 10 parts by weight, more preferably at most 1 part by weight, even more preferably in the range of 0.000001 parts by weight to 0.1 part by weight.

It is preferable that the coloring component is generally added as an aqueous liquid adjusted so that a desired amount is added to the water absorbing resin as the base polymer. The addition amount of the aqueous liquid is preferably not more than 10 parts by weight, based on 100 parts by weight of the solid content of the water-absorbent resin as the base polymer,
The range of 0.1 to 5 parts by weight is more preferable.

When the water-absorbing resin as the base polymer and the coloring component are added, the coloring component dissolved in the aqueous liquid is directly sprayed or dropped onto the water-absorbing resin as the base polymer and mixed. Is preferred. In addition, in the case of adding and mixing using water, a fine powder insoluble in water, a surfactant or the like may be allowed to coexist.

The mixing device used for adding the water-absorbing resin as the base polymer and the coloring component preferably has a large mixing power in order to uniformly and surely mix the two. As the above mixing device, for example,
Cylindrical mixer, double-wall conical mixer, V-shaped mixer, ribbon mixer, screw mixer, fluidized furnace rotary desk mixer, air-flow mixer, double-arm kneader, internal mixing A machine, a pulverizing kneader, a rotary mixer, a screw extruder and the like are suitable.

After adding the water-absorbing resin as the base polymer and the coloring component, a heat treatment may be performed. The treatment temperature of the above-mentioned heat treatment depends on the coloring component used, but 4
The temperature is preferably from 0 ° C to 120 ° C.

The water-absorbing resin obtained by the above production method is a colored water-absorbing resin having an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. Such a resin generally satisfies at least one value in which the object color is L = 80 or less, the absolute value of a is 2 or more, or the absolute value of b is 10 or more. Absorbent articles containing an absorbent comprising a large amount of such a water-absorbent resin, the water-absorbent resin is colored, but the presence of the water-absorbent resin can be more clearly defined on the absorbent article, It is particularly preferably used for quality control in factories in the case of manufacturing, etc., and can sufficiently appeal to consumers to the presence of the water-absorbent resin, and at the time of liquid absorption, the coloring component oozes out of the absorbent article. It does not pollute the environment and is particularly preferable as a sanitary material such as disposable diapers.

The absorbent article of the present invention comprises an absorbent layer containing an absorbent having a weight ratio α of the water-absorbent resin to the total amount of the water-absorbent resin and the fiber base of 0.3 or more, a liquid-permeable topsheet, An absorbent article comprising a back sheet having liquid permeability, containing a coloring component as the water-absorbing resin, having an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. It is characterized by. Further, the absorbent article of the present invention has an absorbent layer containing an absorbent having a weight ratio α of the water-absorbent resin to the total amount of the water-absorbent resin and the fiber base material of 0.3 or more, a surface sheet having liquid permeability, an impermeable liquid. An absorbent article comprising a backing sheet having a property, the object color of the water-absorbent resin is L = 80.
Hereinafter, the absolute value of a is 2 or more, or the absolute value of b satisfies at least one value of 10 or more, and the absorbency against pressure is 20 (g / g).
g) and those having a water absorption rate of 40 seconds or less are included.

Specific examples of such absorbent articles include, but are not particularly limited to, sanitary materials such as paper diapers and sanitary napkins, so-called incontinence pads. It has the feature that the water-absorbing resin present in the article can be more clearly recognized.

The absorbent of the absorbent article of the present invention contains, in addition to the water-absorbent resin, a fiber base such as a hydrophilic fiber, and the amount of the water-absorbent resin relative to the total amount of the water-absorbent resin and the fiber base. The weight ratio α is 0.3 or more. When α is less than 0.3, the amount of the water-absorbing resin used is relatively small, and the effect of clarifying its existence is small.

When the absorber comprises, for example, a water-absorbent resin and hydrophilic fibers, the structure of the absorber includes, for example, a structure including a mixture of a water-absorbent resin and hydrophilic fibers uniformly. It is preferable in that the effect of the above can be sufficiently exhibited. Examples of such a material include a structure in which a water-absorbent resin and a hydrophilic fiber are uniformly mixed; a structure in which a water-absorbent resin and a hydrophilic fiber are uniformly mixed to form a layer, and a layer formed on the hydrophilic layer. A configuration in which fibers are stacked; a configuration in which a water-absorbent resin and hydrophilic fibers are uniformly mixed to form a layer, and a water-absorbent resin is sandwiched between the layer and the hydrophilic fibers formed in a layer. Can be. In addition, a configuration in which a water-absorbing resin is sandwiched between hydrophilic fibers formed in layers may be used.

Examples of the above-mentioned fiber base material include, for example, cellulose fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp obtained from wood; and hydrophilic fibers such as artificial cellulose fibers such as rayon and acetate. No. Among the fibers exemplified above, cellulose fibers are preferred. Further, the hydrophilic fiber may contain a synthetic fiber such as polyamide, polyester, or polyolefin. In addition, the fiber base material is not limited to the fibers exemplified above.

When the ratio of the fiber base material such as hydrophilic fibers in the absorber is relatively small, the absorbers, that is, the hydrophilic fibers may be bonded to each other by using an adhesive binder. By adhering the hydrophilic fibers to each other, the strength and shape retention of the absorber before and during use of the absorber can be increased.

Examples of the adhesive binder include heat-fusible fibers such as polyolefin fibers such as polyethylene, polypropylene, ethylene-propylene copolymer, and 1-butene-ethylene copolymer, and emulsions having adhesive properties. . These adhesive binders may be used alone or as a mixture of two or more. The weight ratio between the hydrophilic fiber and the adhesive binder is 50 / 50-99.
/ 1, preferably in the range of 70/30 to 95/5, and more preferably in the range of 80/20 to 95/5.

In the absorbent article of the present invention, the absorbent layer containing such an absorbent is sandwiched between a liquid-permeable top sheet and a liquid-impermeable back sheet. A diffusion layer made of nonwoven fabric, cellulose, cross-linked cellulose, or the like, which assists liquid diffusion, can be disposed on the back surface of the top sheet and the top surface of the top sheet. The liquid-permeable sheet (hereinafter, referred to as a liquid-permeable sheet) is made of a material having a property of transmitting an aqueous liquid. Examples of the material of the liquid-permeable sheet include a nonwoven fabric and a woven fabric; a porous synthetic resin film made of polyethylene, polypropylene, polyester, polyamide, or the like. The sheet having the liquid impermeability (hereinafter, referred to as a liquid impermeable sheet) is made of a material having a property of impermeable to an aqueous liquid. As a material of the liquid impermeable sheet, for example, a synthetic resin film made of polyethylene, polypropylene, ethylene vinyl acetate, polyvinyl chloride, or the like; a film made of a composite material of these synthetic resin and nonwoven fabric; And the like. The liquid impermeable sheet may have a property of transmitting vapor.

[0048]

As described above, the water-absorbing resin satisfying the constitution of the present invention is a colored water-absorbing resin. It is a water-absorbent resin that is particularly preferably used for quality control in factories when manufacturing articles, and that can sufficiently appeal to consumers to the presence of the water-absorbent resin. It has an excellent feature of no contamination. In addition, the absorbent article of the present invention is such that the water-absorbent resin present therein is colored, so that producers and consumers can easily recognize the presence of the water-absorbent resin, and even when absorbing the liquid. Since the coloring component is not easily transferred, it can be particularly preferably used for sanitary materials such as disposable diapers and sanitary napkins, so-called incontinence pads, for which high functionality and thinness are desired.

[0049]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The various properties of the water-absorbent resin were measured by the following methods.

(A) Absorption Capacity Under Pressure First, a measuring apparatus used for measuring the absorption capacity under pressure will be briefly described with reference to FIG.

As shown in FIG. 1, the measuring device is a balance 1
And a container 2 having a predetermined capacity mounted on the balance 1, an outside air suction pipe 3, a conduit 4, a glass filter 6, and a measuring unit 5 mounted on the glass filter 6. I have. The container 2 has an opening 2a at the top and an opening 2b at the side surface thereof.
The outside air suction pipe 3 is fitted into the opening a, and the conduit 4 is attached to the opening 2b. The container 2 contains a predetermined amount of physiological saline solution 11 (aqueous solution of 0.9% by weight of sodium chloride). The lower end of the outside air suction pipe 3 is submerged in the physiological saline 11. The glass filter 6 has a diameter of 70 mm. The container 2 and the glass filter 6 are in communication with each other by the conduit 4. The upper part of the glass filter 6 is fixed at a position slightly higher than the lower end of the outside air suction pipe 3. The measuring unit 5 includes a filter paper 7, a support cylinder 8, a wire mesh 9 attached to a bottom of the support cylinder 8,
And a weight 10. Then, the measuring unit 5 places the filter paper 7 and the support cylinder 8 (that is, the wire mesh 9) on the glass filter 6 in this order, and places the weight 10 inside the support cylinder 8, that is, on the wire mesh 9. It has been. The support cylinder 8 has an inner diameter of 60 mm. The wire mesh 9 is made of stainless steel and has a mesh of 400 mesh (mesh size of 38 μm).
m). Then, a predetermined amount of the water-absorbing resin is evenly spread on the wire mesh 9. Weight 1
0 is 20 g / cm 2 with respect to the wire mesh 9, that is, the water absorbent resin.
The weight is adjusted so that a uniform load can be applied.

The absorption capacity under pressure was measured using the measuring apparatus having the above-mentioned structure. The measuring method will be described below.

First, predetermined preparation operations such as putting a predetermined amount of physiological saline 11 into the container 2 and fitting the outside air suction pipe 3 into the container 2 were performed. Next, the filter paper 7 was placed on the glass filter 6. On the other hand, in parallel with these placing operations, 0.9 g of the water-absorbing resin was evenly sprayed on the inside of the support cylinder, that is, on the wire mesh 9, and the weight 10 was placed on the water-absorbing resin.

Next, on the filter paper 7, the supporting cylinder 8 on which the wire mesh 9, that is, the water-absorbing resin and the weight 10 was mounted, was placed.

Then, the weight W2 (g) of the physiological saline solution 11 absorbed by the water-absorbent resin was measured using the balance 1 for 60 minutes after the support cylinder 8 was placed on the filter paper 7. Then, from the above weight W2, the absorption capacity under pressure 60 minutes after the start of absorption according to the following equation: absorption capacity under load (g / g) = weight W2 (g) / weight of water absorbent resin (g).
(g / g) was calculated.

(B) Water Absorption Rate In a 100 ml beaker, 50 g of physiological saline (0.9% NaCl aqueous solution) adjusted to 30 ° C. and a stirrer were put in advance, and the mixture was stirred with a magnetic stirrer at a speed of 600 rpm.
When 2 g of the water-absorbent resin is introduced into the mixture, gelation occurs, the fluidity of the liquid decreases, and the vortex around the stirring center disappears. The time required until the rotating stirrer, which was initially visible, disappeared due to the rise of the vortex when the vortex disappeared after the sample was introduced was measured, and this was taken as the water absorption rate.

(C) Object color SZ-Σ (Sigma) 80 type COLOUR M manufactured by Nippon Denshoku Industries Co., Ltd.
After calibrating the XYZ values with a standard white plate using the EASURING SYSTEM, apply about 3 g of water-absorbent resin to an inner diameter of about 30 mm and a height of about 1
The sample was placed in a 4 mm cylindrical cell, and L, a, and b of the water-absorbing resin were measured.

(D) Transferability of coloring components 50 parts by weight of a water-absorbent resin and 50 parts by weight of ground wood pulp are
Dry mixing was performed using a mixer. Next, the resulting mixture was air-formed on a wire screen formed into a 400 mesh (mesh size of 38 μm) using a batch-type air-forming device to form a web having a size of 100 mm × 100 mm. . Further, the web is subjected to a pressure of 2 kg / cm2.
For 5 seconds to obtain an absorbent having a basis weight of about 360 g / m2.

Subsequently, a back sheet (liquid-impermeable sheet) made of liquid-impermeable polypropylene, the above-mentioned absorber, and a top sheet (liquid-permeable sheet) made of liquid-permeable polypropylene are placed in this order. By mounting, an absorbent article was obtained. The weight of this absorbent article is 3.6
g.

40 g of physiological saline was added to the absorbent article, and one minute later, 10 kitchen towels folded into four pieces were placed on the top sheet, and a load of 10 kg was applied for 1 minute to pass through the top sheet. The presence or absence of coloring components that migrated to kitchen towels was examined.

REFERENCE EXAMPLE 1 4.96 g of polyethylene glycol diacrylate (average number of added moles of ethylene oxide: 8) was dissolved in 5,500 g of an aqueous solution of sodium acrylate having a neutralization ratio of 75 mol% (monomer concentration: 33%). This was used as a reaction solution. Next, this reaction solution was degassed for 30 minutes under a nitrogen gas atmosphere. Next, the reaction solution was supplied to a reactor formed by attaching a lid to a jacketed stainless steel double-armed kneader having two sigma-type blades and having an internal volume of 10 L, and while maintaining the reaction solution at 30 ° C., the system was purged with nitrogen. The gas was replaced.
Subsequently, while stirring the reaction solution, sodium persulfate 2.4 g
When 6 g and 0.10 g of L-ascorbic acid were added, polymerization started about 1 minute later. And 30 ℃ ~ 80 ℃
, And the hydrogel polymer was taken out 60 minutes after the initiation of the polymerization. The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product was pulverized using a vibration mill, and further classified by a 20-mesh wire mesh,
An amorphous crushed water-absorbent resin precursor (a) having an average particle size of 280 µm and a specific surface area of 0.027 m2 / g was obtained.

A surface cross-linking agent composed of 0.5 parts by weight of glycerin, 2 parts by weight of water, and 1 part by weight of isopropyl alcohol was mixed with 100 parts by weight of the obtained water-absorbent resin precursor (a). The mixture was heat-treated at 190 ° C. for 50 minutes to obtain a water-absorbent resin (1) as a base polymer. The water absorbing resin (1) as a base polymer had an absorption capacity under pressure of 29 (g / g) and a water absorption rate of 34 seconds.

Reference Example 2 Propylene glycol 1 was added to 100 parts by weight of the water-absorbent resin precursor (a) obtained in Reference Example 1.
Parts by weight and ethylene glycol diglycidyl ether
A surface cross-linking agent consisting of 0.05 parts by weight, 3 parts by weight of water, and 1 part by weight of isopropyl alcohol was mixed. The mixture was heat-treated at 210 ° C. for 45 minutes to obtain a water-absorbent resin (2) as a base polymer. The absorption capacity under pressure of the water absorbent resin (2) as the base polymer is 38.
(g / g) and the water absorption rate was 22 seconds.

Reference Example 3 A dried product of the hydrogel polymer obtained in the same manner as in Reference Example 1 was pulverized by changing the pulverization conditions of a vibration mill, and further classified by a 20-mesh wire net. An amorphous crushed water-absorbent resin precursor (b) having an average particle size of 400 μm and a specific surface area of 0.014 m 2 / g was obtained. The obtained water-absorbent resin precursor (b) was subjected to the same surface treatment as in Reference Example 1 to obtain a water-absorbent resin (3) as a comparative base polymer. The water absorbing resin (3) as a base polymer had an absorption capacity under pressure of 30 (g / g) and a water absorption rate of 62 seconds.

[Reference Example 4] The water-absorbent resin precursor (a) obtained in Reference Example 1 was used as a water-absorbent resin (4) as a comparative base polymer, and its physical properties were measured. g / g), and the water absorption rate was 31 seconds.

Example 1 A water-absorbent resin obtained by adding 5 parts by weight of a 0.06% aqueous solution of Food Red No. 3 as a coloring component to 100 parts by weight of the water-absorbent resin (1) as a base polymer obtained in Reference Example 1 1) was obtained. The object color of the water-absorbent resin (1) is L = 48.1, a = 16.6, b = 1.18, and the absorption capacity under pressure is 27 (g /
g), the water absorption rate was 31 seconds, and no transfer of coloring components to the kitchen towel was observed at all.

Example 2 A water-absorbent resin obtained by adding 5 parts by weight of a 0.1% aqueous solution of Edible Yellow No. 4 as a coloring component to 100 parts by weight of the water-absorbent resin (2) as a base polymer obtained in Reference Example 2 ( 2) got. The object color of the water absorbent resin (2) is L = 67.
2, a = 19.1, b = 38.7, absorption capacity under pressure was 36 (g / g), water absorption rate was 25 seconds, and no transfer of coloring components to the kitchen towel was observed at all.

Example 3 Water-absorbing resin (3) obtained by adding 2 parts by weight of a 5% aqueous solution of iron chlorophyllin as a coloring component to 100 parts by weight of the water-absorbing resin (1) as a base polymer obtained in Reference Example 1 I got Water-absorbent resin (3)
Object color is L = 45.4, a = -4.95, b = 9.60, absorption ratio under pressure is 3
0 (g / g), the water absorption rate was 29 seconds, and no transfer of the coloring component to the kitchen towel was observed.

Example 4 A water-absorbent resin obtained by adding 2 parts by weight of a 0.01% aqueous solution of Edible Red No. 3 as a coloring component to 100 parts by weight of the water-absorbent resin (2) as a base polymer obtained in Reference Example 2 ( 4) got. The object color of the water absorbent resin (4) is L = 81.
4, a = -11.7, b = -4.77, absorbency against pressure was 37 (g / g), water absorption rate was 22 seconds, and no migration of coloring components was observed.

[Comparative Example 1] For comparison, a 0.06% aqueous solution of Food Red No. 3 was added as a coloring component in an amount of 5 parts by weight to 100 parts by weight of the water-absorbing resin (3) as a comparative base polymer obtained in Reference Example 3. Water absorbent resin (1) was obtained. The absorbency against pressure of the comparative water absorbent resin (2) was 27 (g / g), the water absorption rate was 56 seconds, and the coloring component was transferred to the kitchen towel.

[Comparative Example 2] For comparison, 100 parts by weight of the water-absorbing resin (4) as a comparative base polymer obtained in Reference Example 4 was added with 5 parts by weight of a 0.06% aqueous solution of Edible Red No. 3 as a coloring component. Water absorbent resin (1) was obtained. The absorbency against pressure of the comparative water-absorbent resin (2) was 8 (g / g), the water absorption rate was 30 seconds, and the coloring component was transferred to the kitchen towel.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a measuring device used for measuring an absorption capacity under pressure, which is one of the properties exhibited by a water-absorbent resin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Balance 2 Container 3 External air suction pipe 4 Conduit 5 Measurement part 6 Glass filter 7 Filter paper 8 Support cylinder 9 Wire mesh 10 Weight 11 Physiological saline

Claims (5)

[Claims] (1) The composition contains a coloring component and has an absorption capacity under pressure of 20 (g / g).
g) a water-absorbent resin having a water absorption speed of 40 seconds or less. 2. The object color satisfies at least one value of L = 80 or less, the absolute value of a is 2 or more, or the absolute value of b is 10 or more, the absorption capacity under pressure is 20 (g / g) or more, and Water-absorbent resin with a water absorption speed of 40 seconds or less. 3. A method for producing a water-absorbent resin, comprising adding a coloring component to a water-absorbent resin as a base polymer having an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. 4. An absorbent layer containing an absorbent having a weight ratio α of the water-absorbent resin to the total amount of the water-absorbent resin and the fiber substrate of 0.3 or more, a liquid-permeable topsheet, and a liquid-impermeable material. An absorbent article comprising a back sheet, comprising a coloring component as the water-absorbing resin, having an absorption capacity under pressure of 20 (g / g) or more and a water absorption rate of 40 seconds or less. Products. 5. An absorbent layer containing an absorbent having a weight ratio α of the water-absorbent resin to the total amount of the water-absorbent resin and the fiber base of 0.3 or more, a liquid-permeable topsheet, and a liquid-impermeable material. An absorbent article comprising a back sheet, wherein the water-absorbent resin has an object color satisfying at least one value of L = 80 or less, an absolute value of a of 2 or more, or an absolute value of b of 10 or more, and under pressure. An absorbent article comprising an absorbent article having an absorption capacity of 20 (g / g) or more and a water absorption rate of 40 seconds or less.