JP2003525105A - Improved reinforced water-absorbing material and water-absorbing goods using it - Google Patents

Abstract

  (57) [Summary] The present invention relates to a reinforced water-absorbing composition using a non-neutral reinforced water-absorbing polymer, comprising at least 30% of a non-neutral reinforced polymer in which the functional groups are in a free acid form, and a layered double hydroxide anionic earth. . It is believed that the non-neutral reinforcing polymer captures NA +, and the layered double hydroxide anionite captures Cl-. These make it possible to remove the electrolyte from the solution and improve the water absorption capacity of the reinforced water-absorbing synthetic material. A preferred type of layered double hydroxide anionic soil useful in the present invention is hydrotalcite soil, most preferably rehydrated hydrotalcite. The present invention further discloses a water-absorbing article using the reinforced water-absorbing synthetic material.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a reinforced water absorbent material. The reinforced water absorbent material of the present invention is particularly useful for water absorbent articles, such as disposable diapers, adult incontinence pants, trousers, sanitary napkins, and the like. More precisely, the present invention relates to a reinforced water absorbing material comprising a non-neutral reinforced water absorbing polymer and a layered double hydroxide anionic soil.

BACKGROUND ART In general, water absorbent articles such as disposable diapers, adult incontinence trousers, trousers, sanitary napkins, etc., have an upper surface partially permeable to liquid and a non-impermeable back surface. And a water absorbent core. The water absorbent core is formed of (1) typically continuous soft wood pulp fibers (soft wool pulp) and (2) scattered reinforced water absorbent polymer pieces (SAP). The core portion is generally sandwiched between the top surface and the back surface. It is well known that water absorbent articles have one or more layers made of cellulose fibers, and these layers absorb or disperse various liquids or function as cushions. Has been.

To date, cost-effective, high-performance water-absorbent cores having liquid-absorbing property and liquid-holding property have been developed. A reinforced water-absorbing polymer made of fine particles, beads, flakes, small spherical particles, etc. was suitable for that purpose. These reinforced water-absorbing polymers are generally made of polymeric materials that are insoluble and swellable in water and are capable of absorbing at least 10 times as much liquid as dry weight.

[0004] One of the reinforced water-absorbing polymers is a piece or fiber that is chemically referred to as a salt-neutral polyacrylate that is cross-linked. These materials include salt neutral cross-linked polyacrylates and modified polymers such as cellulose, starch, or polysaccharides including carboxylated, phosphono-alkylated, sulfoxylated, phosphorylated regenerated cellulose. These are for making SAP highly hydrophilic. Further, such modified polymers are cross-linked to reduce their solubility in water.

The liquid absorption and liquid retention properties of the reinforced water-absorbing polymers are due to the polymer structure of the ionizable functional groups. These functional groups are usually carboxyl groups, for the majority of which the polymer retains its salt form in the dry state, which salt separates upon contact with water. In the separated state, various functional groups are added to the polymer chain, but since the functional groups have the same electric charge, they repel each other. This causes the polymer structure, which absorbs water molecules, to expand. However, its swelling itself is limited by the cross-linking of the polymer structure, which prevents degradation of the polymer.

It has already been discovered in the past that the water absorption performance of a reinforced water-absorbing polymer for body fluids such as urine is much lower than that for deionized water. This is commonly thought to be due to the electrolyte content in body fluids, an effect often referred to as "Salt poisoning". Especially because human urine has about 0.9 wt% NaCl (salt). These Na + ions and Cl − ions adversely affect the osmotic pressure around the reinforced water-absorbing polymer, and deteriorate the water absorption performance for urine far more than the water absorption performance for deionized water. For example, a salt solution containing 0.5 wt% of NaCl and 0.1 wt% of NaCl with respect to a solution having a pressurized water absorption capacity (AUL) of 40 g per SAP gram of NaCl solution containing 0.9 wt% of NaCl. Each AUL is 4
0 grams, 70 grams of solution.

Numerous efforts have been made to neutralize salt toxinization and improve the ability of toughened water-absorbing polymers to absorb electrolytes, including liquids such as human urine. In the past, Na + was used as the first approach to improve the water absorption capacity of reinforced water-absorbing polymers in NaCl solution.
Synthesis of reinforced water-absorbing polymers containing ionic functional groups that were not strongly affected by ions was performed. However, these approaches have proven costly.

The second approach is a reinforced water-absorbing polymer that combines anion / cation ion exchange synthetic resins. For example, EP-A-0210756 discloses a water-absorbing structure in which a reinforced water-absorbing polymer and a fibrous anion exchange medium, optimally a cation exchange medium, are combined. Attempts have been made to reduce salt toxin formation by combining an ion-exchange medium, generally both an anion-exchange medium and a cation-exchange medium, in combination with a reinforced water-absorbing polymer and an ion-exchange medium, thereby reducing salt content in the liquid. I'm trying to reduce. However, in this case, the ion exchange medium itself does not have a direct effect on the performance improvement of the reinforced water absorbing material, and the combination thereof cannot reduce the salt content to bring about a sufficient effect on the overall water absorbing capacity. It seems to be. Generally, the anion exchange medium is an anionic synthetic resin containing nitrogen anion groups having basic functional groups, ie, primary, secondary, tertiary amine groups and quaternary ammonia groups. These ion-exchange synthetic resins are sometimes expensive, they have no water-absorbing effect by themselves, they merely act as diluents for the reinforced water-absorbing polymers.

Among other things, the present invention seeks to improve the performance of toughened water-absorbing polymers in electrolyte solutions in a cost-effective manner.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an improved reinforced water-absorbing composition and a water-absorbing article using the same.

[0011] Another object of the present invention is to provide a reinforced water-absorbing compound having high water-absorbing performance especially in an electrolyte solution and being cost-effective, and a water-absorbing article using the same.

To this end, the present invention relates to a reinforced water-absorbing composition using a non-neutral reinforced water-absorbing polymer, wherein at least 30% of the functional groups are in the free acid form of the non-neutral reinforced polymer and a layered double hydroxide anion. It is composed of soil. It is believed that the non-neutral reinforcing polymer captures NA +, and the layered double hydroxide anion soil captures Cl-. They make it possible to remove the electrolyte from the solution and improve the water absorption capacity of the reinforced water absorbent composite.

In the present invention, certain combinations of non-neutral toughened water-absorbing polymer and layered double hydroxide anionic soil provide a solvent containing electrolyte compared to costly conventional toughened water-absorbing synthetic materials containing ion-exchange materials. Above all, it is based on the accidental discovery that it has a good water absorption capacity. Furthermore, in the reinforced water-absorbent synthetic material according to the present invention, the fact that even if a smaller amount of layered double hydroxide anionic soil is used, excellent water-absorption results can be obtained as compared with the reinforced water-absorbed synthetic material containing the conventional ion-exchange synthetic resin. , Have been discovered by chance.

The present invention further relates to a water-absorbing article, which is composed of a liquid-permeable top sheet, a liquid-impermeable back sheet, and a water-absorbent core portion placed therebetween. The water absorbent core is made of soft pulp (or other fiber material) and the reinforced water absorbent synthetic material according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION It is an object of the present invention to provide a reinforced water-absorbing composite material with improved performance in the presence of an electrolyte, especially NaCl (sodium chloride, salt). Is.

The present invention relates to (1) an unneutral reinforced water-absorbing polymer (uSAP) in which at least 30% of functional groups are in a free acid form, (2) a layered double hydroxide anionic soil (LDH anionic soil), To provide a reinforced water-absorbing material composed of a combination of

The above-mentioned uSAP has an anionic functional group, that is, a sulfo group, a sulfate group,
Any material having a water-absorbing property having a phosphoric acid group or a carboxyl group may be used. If possible, the functional group is preferably a carboxyl group. Generally, those functional groups are added to the slightly cross-linked acrylic acid-based polymer. For example, the base polymer is polyacrylamide, polyvinyl alcohol, ethylene-maleic anhydride copolymer, polyvinyl leather, polyvinylsulfonic acid, polyacrylic acid, polyvinylpyrovidone, and polyvinylmorpholine. It may be a copolymer of these monomers. Starch and cellulose-based polymers may also be used, for example hydroxypropyl cellulose, carboxymethyl cellulose, starch grafted with acrylic acid. Specific base polymers include cross-linked polyacrylates, hydrolyzed acrylonitrile grafted starch, starch polyacrylates, and isopretylene maleic anhydride copolymers. A particularly suitable base polymer is a polyacrylate cross-linked with starch polyacrylate.

The uSAP described above is preferably partially sodium-neutralized with sodium hydroxide. Further preferably, less than about 70% of the uSAP functional groups are sodium neutralized and at least about 30% in the free acid form. Moreover, less than about 50% of the functional groups of uSAP are sodium neutralized and at least about 50% may be in the free acid form. Still more preferably, less than about 40% of the uSAP functional groups are sodium neutralized and at least about 60% are in the free acid form. Here, "unneutral reinforced water-absorbing polymer" or "uSAP
The term "refers to at least about 30% of the functional groups in the free acid form,
This can be contrasted with standard reinforced water-absorbing polymers in which about 30% or less of the functional groups are in the free acid form.

Further, the uSAP according to the present invention preferably has a pH value of about 6.0 or less, preferably about 4.5 to about 6.0.

The LDH anionic soil useful in the present invention is a synthetic material composed of two metals, which contains a reaction layer capable of binding and exchanging anions. LDH anion soil is composed of multiple layers of metal cations (M2 + and M3 +) with similar ionic radii and is octagonally coordinated with six oxygen anions. The LDH anion soil is composed of two-dimensional sheets stacked by hydrogen bonding between the hydroxyl groups of adjacent sheets. The LDH anion soil maintains electrical neutrality by using CO 32 −, NO 3 −, OH −, etc. as charge balance anions between adjacent layers which are reaction layers. The LDH ionic soil functions as an anion exchange material by exchanging anions existing between these layers. Further, when the LDH ion soil is hydroxylated, the reaction layer may contain water. The most preferred LDH ionic soil type of the present invention is hydrotalcite-like ionic soil. This hydrotalcite-like ionic soil contains hydrotalcite, hydrotalcite, manaceite, pyrophyllite, joglenite, styrolite, barbertolite,
The one with tacobite, ribesite, and desoutersite is good,
Furthermore, the re-hydroxylated form of hydrotalcite (containing 50% moisture) is even better.

It has been surprisingly discovered by the present invention that the combination of uSAP and LDH anionic soil described above is particularly effective for a reinforced water-absorbing composite for solutions containing electrolytes such as human urine. Further, u in the reinforced water-absorbing synthetic material according to the present invention
Due to the synergistic effect of both SAP and LDH anionic soil, a more efficient and cheaper water absorbent material can be compared with the standard water absorbent polymer reinforced water absorbent composite material that uses the usual basic anion exchange material. It has been discovered by chance that is produced.

Without being bound by any particular theory, it is believed that the reinforced water-absorbent synthetic material of the present invention has the following two merging effects when it comes into contact with a solution containing an electrolyte. (1) uSAP has a cation (Na +) exchange property, which binds Na + and thereby deionizes the solution, and (2) LDH anionic soil has an anion (Cl-) exchange property. Having, restraining Cl-and thereby deionizing the solution. The functional group of the uSAP is typically a carboxyl group, which is weakly acidic and does not separate, for example in sodium chloride solution. However, the presence of LDH ionic soil has the effect of adding sodium ions from the sodium chloride solution. As a result, the balance can be broken and uSAP can be converted into a salt state, and uSAP can be converted into the original high-performance reinforced water-absorbing polymer.

When this uSAP is brought into contact with a solution containing an electrolyte, it is converted into a salt state, and
The effect of LDH anion soil to restrain sodium ions has an excellent effect for desalting the solution, and thereby the salt toxin-forming effect can be reduced and the performance of the reinforced water-absorbing material can be improved. Compared to desalinating a solution using an ion-exchange synthetic resin in combination with a reinforced water-absorbing material already in salt form (see EP-A-
(See 0210756), this uSAP also has a solvent desalting effect. Therefore, the present invention is further superior to the desalination effect obtained by using an ion exchange material and a normal reinforcing water-absorbing polymer in a salt state. It is important to note that the effect of the electrolyte-enhanced water-absorbing polymer of the electrolyte on the ability to absorb the solvent is not linear, as the water-absorption capacity simply decreases as the salt content increases. . Therefore, if the concentration is above a certain range, the water absorption capacity can be improved significantly by reducing the salt content in the solution by a relatively small amount.

In the reinforced water-absorbing synthetic material according to the present invention, the composition ratio of uSAP and LDH anionic soil is generally in the range of 1: 1 to 1:20, preferably in the range of 1: 1 to 1:10, and further, The most preferable range is 1: 1 to 1: 4.

The present invention further relates to a water absorbent article using the reinforced water absorbent synthetic material described above. As shown in FIGS. 1 and 2, the water absorbent article according to the present invention can take the form of a disposable diaper 10. Furthermore, the disposable diaper 10 has an approximate size from an infant size to an adult size. If the size is for adults, the disposable diaper 10 is also called incontinence pants. Objects to which the present invention can be applied are widely applicable to wound bandages and other water absorbent articles well known in the industry, such as trepanes, adult incontinence pants, sanitary napkins, and other similar articles. is important.

The disposable diaper 10 according to the present invention generally comprises a liquid permeable top sheet 12,
It is composed of a liquid-impermeable backsheet 14 connected to the topsheet 12, and a water-absorbent core portion 16 sandwiched between the topsheet 12 and the backsheet 14. The disposable diaper 10 is further provided with a tape fastener 18, an elastic waist band 20, and other functions well known to those skilled in the art. Top sheet 12
The back sheet 14 is glued to the outer edge 22 of the disposable diaper 12 to accommodate the water absorbent core 16. The topsheet 12 is also referred to as the topsheet and is made of polymeric fibers such as polyphephine. The backsheet 14 is made of a synthetic polymer film, such as polyester film.

Except as specifically shown or described in detail, the disposable diaper 10 is described in US Pat.
Essentially similar to the disposable ome disclosed in the 301 Huffman patent and the 5,891,120 Chmiewewski patent. Note that both of these patents have already been assigned to the assignee of the present invention, and the disclosures thereof can be referred to in a unified manner with the present invention. In the embodiment shown in FIG. 2, the absorbent core 16 includes a central water-absorbing structure 32 having an elongated central portion 40 which further includes a front end 42, a rear end 44, and a front end. The part 44 is provided with two ears 45, 46.

In one embodiment, the water absorbent core 16 comprises (1) soft fibrous fibers, typically powdered softwood pulp fibers (soft fur pulp) or other fibrous material, 2) Dispersed small pieces of the reinforced water-absorbing synthetic material according to the present invention.

The reinforced water-absorbent synthetic material according to the present invention may be dispersed and arranged in the water-absorbent core by any method known in the art, and a single reinforced water-absorbent core is used. It may be used as a water absorbing material or as an additive to a conventional reinforced water absorbing polymer. The amount of the reinforced water-absorbent synthetic material according to the present invention is in the range of about 1 gram to 20 grams per gram of soft hair of the water absorbent core. Preferably, the reinforced water-absorbing synthetic material is in the range of about 1 to 10 grams per gram of vellus hair, and more preferably in the range of about 1 to 5 grams per gram of vellus hair.

The following examples illustrate specific embodiments of the present invention and disclose the reinforced water-absorbent composite material and the water-absorbing article according to the present invention for comparing a normal reinforced water-absorbing agent and the water-absorbing article thereof. is there.

In general, the important performance attributes of the absorbent core of a diaper (all other absorbent clothing) are functional performance, water absorption, and strength of the core during use. Pressurized water absorption value of core (AUL
) Is a good measure of functional performance and water absorption. Therefore, this AUL value is used in comparison with the following example.

Example 1 Various water absorbent core materials were tested and AUL values (pressure 0.5 psi) were measured to demonstrate the efficiency of the present invention. This AUL test consists of a standard test cylinder with first a round (50 mm) metered regular first pulp fiber (60 mm).
0 mg) sheet was placed. Next, on the upper surface of the circular pulp fiber sheet, a reinforced water-absorbent synthetic material having a constant weight composed of uSAP and an ion exchange material shown in Table 1 is placed. A second constant weight (600 mg) pulp fiber sheet is then placed on top of the reinforced water absorbent composite. And with a stainless steel cylinder, 40 at one end
Mesh stainless steel wire mesh fixed to the pulp-reinforced water-absorbent synthetic material-
The wire mesh is adhered to the uppermost pulp layer on a sandwich-shaped sample called pulp. A cylindrical 0.5 psi weight is placed on the other end of the stainless steel cylinder. After that, synthetic urine (sodium chloride 0.87% by weight, 50 g)
Is poured into the stainless steel cylinder, and the sample is absorbed for 20 minutes through the above 40 mesh stainless steel wire mesh. The synthetic urine remaining above the wire mesh is then removed with a dropper and weighed. This determines the amount of synthetic urine absorbed by the test sample absorbent core from the remaining amount. The tested reinforced water absorbent composites are as follows:

Comparative Sample 1: Zero ion exchange material; and SAP IM4500 (Hoechst Cela
Nese) 600 mg, which is cross-linked polyacrylic acid, 65% of the functional groups have been neutralized with sodium hydroxide, and 35% of the functional groups appear to be in the free acid state.

Comparative Sample 2: 7.5 g of Dowex 50W-X8, which is a normal strong acid ion exchange material; Am
Berlite IRA-400-7.5 g, which is a normal strong barthic ion exchange material; and SAP IM4500 600 mg.

Comparative Sample 3: 7.5 g of Dowex 1-X8, a conventional strong acid ion exchange material; and S
600 mg of AP IM4500.

Sample 1: Rehydrated FloMag HAC-P (Martin Marietta Magn)
Esia Specialties, Baltimore MD) 7.5
g, which is the rehydrated hydrotalcite material: and 600 mg SAP IM4500.

Sample 2: 7.5 g of rehydrated FloMag HAC-P, which was rehydrated hydrotalcite material: and 600 mg of HSAP40. This is cross-linked polyacrylic acid with 40% of the functional groups neutralized with sodium hydroxide and 60% of the functional groups appear to be in the free acid state.

Note: The hydrotalcites used in Samples 1 and 2 were obtained by soaking dried hydrotalcite overnight in deionized water and rehydrating.
Unabsorbed water was removed and the remaining solids were tapped dry on a paper towel (50% humidity).

[0039]

[Table 1]

As shown in the results in Table 1, the LDH anionic soil of the example and the free acid capacity were about 35%.
It was accidentally found that a combination of either (Sample 1) or 60% SAP (Sample 2) gave a much better AUL value than the reinforced water absorbent containing uSAP alone (Comparative Sample 1). It has been done.

Example 2 Various materials for the water-absorbent core were tested, and the time-dependent AUL value (pressure 0.5 psi) was measured. This aging AUL value test was performed to compare the performance of uSAP in combination with an ion exchange material with different degrees of neutralization with sodium.
The AUL test was performed on the standard test cylinder described in Example 1. The tested reinforced water absorbent composites are as follows:

Comparative Sample 4: 7.5 g of Dowex 1-X8, which is a conventional strong acid ion exchange material; and as shown in the table, SAP IM4500 (Hoechst Celane).
Se) 600 mg, which is cross-linked polyacrylic acid, 65% of the functional groups have been neutralized with sodium hydroxide, and 35% of the functional groups appear to be in the free acid state, or HSAP40 600 mg, which is cross-linked polyacrylic acid, 40% of the functional groups have been neutralized with sodium hydroxide, and 60% of the functional groups appear to be in the free acid state.

Sample 3: Rehydrated FloMag HAC-P (Martin Marietta Mag)
7. Nesia Specialties, Baltimore MD).
5 g of this rehydrated hydrotalcite material: and 600 mg SAP IM4500 or 600 mg HSAP40 as shown in the table.

Sample 4: Rehydrated FloMag HAC-P 4.0 g: and S as shown in the table
600 mg of AP IM4500 or 600 mg of HSAP40.

Note: The hydrotalcite used in Samples 3 and 4 was rehydrated by soaking dried hydrotalcite overnight in deionized water.
Unabsorbed water was removed and the remaining solids were tapped dry on a paper towel (50% humidity).

[0046]

[Table 2]

As shown in Table 2, the reinforced water-absorbing synthetic material according to the present invention is superior to the reinforced water-absorbing material which is a comparative sample containing a usual anion exchange material both from the beginning and after the passage of time. Further, as shown in Sample 4, even when a significantly smaller amount of LDH anion soil is used as compared with a normal ion exchange material, the same result can be obtained even after a lapse of time.

Table 2 further shows that the combination of uSAP and LDH anionic soil produces a surprising synergistic effect. For example, when an HSAP material (uSAP in which many of the functional groups are in a free acid state) is used in combination with a hydrotalcite material, the AUL value is slightly improved after a lapse of time. However, the HS
No such improvement is seen when AP is used in combination with conventional ion exchange materials. In fact, when the proportion of functional groups in the free acid state increased in the comparative sample, AU
The L value decreases slightly.

Example 3 Various materials for the water-absorbent core were tested, and the time-dependent AUL value (pressure 0.5 psi) was measured. This time course AUL value test was performed on various types of L in the dry and rehydrated states.
It was done to compare the performance of DH anion soil. The AUL test was performed on the standard test cylinder described in Example 1. The tested reinforced water absorbent composites are as follows:

Sample 5: FloMag42 (Martin Marietta Magnesia Sp)
2.0 g of Baltimore MD) manufactured by E. Earliest, which is a rehydrated hydrotalcite material, dry and rehydrated as shown in the table; and SAP IM4500 (manufactured by Hoechst Celanese) 6
00 mg, which is cross-linked polyacrylic acid, with 65% of the functional groups neutralized with sodium hydroxide, and 35% of the functional groups appear to be in the free acid state.

Sample 6 FloMag42A (Martin Marietta Magnesia)
Specialties, Baltimore MD) 2.0 g, which is a rehydrated hydrotalcite material, dry and rehydrated as shown in the table; and 600 mg SAP IM4500.

Sample 7 FloMag02 (Martin Marietta Magnesia S
Specialties, Baltimore MD) 2.0 g, which is a rehydrated hydrotalcite material, dry and rehydrated as shown in the table; and 600 mg SAP IM4500.

Note: The hydrotalcite used in Samples 6 and 7 was rehydrated by soaking dried hydrotalcite overnight in deionized water.
Unabsorbed water was removed and the remaining solids were tapped dry on a paper towel (50% humidity).

[0054]

[Table 3]

As shown in Table 3, certain hydrotalcite materials in the rehydrated state generally have higher AUL values than hydrotalcite materials in the dry state. Table 3 also shows that a particularly preferred type of LDH anionic soil material useful in the present invention is FloMag4.
2A is shown. Furthermore, the reinforced water-absorbing composite material according to the present invention has been shown to be effective even at relatively low levels of LDH anionic soil material.

Example 4 Various materials for the water-absorbent core were tested, and the time-dependent AUL value (pressure 0.5 psi) was measured. This aging AUL value test was conducted to evaluate the efficiency of the reinforced water-absorbing composite material particularly suitable for the present invention and to evaluate how the AUL value depends on the level of the LDH anionic soil material. . The AUL test was performed on the standard test cylinder described in Example 1. The tested reinforced water absorbent composites are as follows:

Comparative Sample 5: Zero Ion Exchanger; and SAP IM4500 (Hoechst Cela
Nese) 600 mg, which is cross-linked polyacrylic acid, 65% of the functional groups have been neutralized with sodium hydroxide, and 35% of the functional groups appear to be in the free acid state.

Sample 8: Rehydrated FloMag42A (Martin Marietta Mag)
nesia Specialties, Baltimore MD).
5 g, this is the rehydrated hydrotalcite material. ; And SAP IM
4500 to 600 mg.

Sample 9; 1.0 g rehydrated FloMag42A; and 600 mg SAP IM4500.

Sample 10; 2.0 g rehydrated FloMag42A; and 600 mg SAP IM4500.

[0061]

[Table 4]

As shown in Table 4, as the rehydrated FloMag42A increases, the AUL value in the examples of the present invention also increases. Furthermore, even with a small amount of FloMag42A such as 0.5 g, the reinforced water-absorbing synthetic material according to the present invention is superior to the normal reinforced water-absorbing material.

Although the present invention has been mainly disclosed as described above, these examples are not intended to limit the scope of the invention. As described in the appended claims, various modifications can naturally be made by those skilled in the art without departing from the scope and spirit of the invention.

[0064]

[Brief description of drawings]

FIG. 1 is a partial external view of a disposable diaper that is a usage example of a water absorbent material according to the present invention.

FIG. 2 is a partial external view when the disposable diaper shown in FIG. 1 is unfolded.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), OA (BF , BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, G M, KE, LS, MW, MZ, SD, SL, SZ, TZ , UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, B Z, CA, CH, CN, CR, CU, CZ, DE, DK , DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, J P, KE, KG, KP, KR, KZ, LC, LK, LR , LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, R O, RU, SD, SE, SG, SI, SK, SL, TJ , TM, TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZW F-term (reference) 3B029 BA18                 4C003 AA23                 4C098 AA09 CC02 CE06 DD16 DD24                       DD27 DD30                 4G066 AA66B AC17B AD15B AE01B                       AE20B BA03 CA43 DA11                       DA13 EA05 FA37

Claims (20)

[Claims] 1. In a reinforced water-absorbing synthetic material: a non-neutral reinforced water-absorbing polymer in which at least 30% of functional groups of the polymer are in a free acid state; and a layered double hydroxide anionic soil. Characterized reinforced water-absorbing synthetic material. 2. The pH value of the non-neutral reinforcing water-absorbing polymer is about 4.5 to about 6.
． The reinforced water-absorbent synthetic material according to claim 1, wherein the reinforced water-absorbent synthetic material has a range of 0. 3. About 70% or less of the functional groups of the non-neutral reinforcing water-absorbing polymer are neutralized with sodium. The reinforced water-absorbent synthetic material according to claim 1, wherein at least 30% is in a free acid state. 4. About 50% or less of the functional groups of the non-neutral reinforced water-absorbing polymer are neutralized with sodium. The reinforced water-absorbent synthetic material according to claim 1, wherein at least 50% is in a free acid state. 5. About 40% or less of the functional groups of the non-neutral reinforcing water-absorbing polymer are neutralized with sodium. The reinforced water-absorbent synthetic material according to claim 1, wherein at least 60% is in a free acid state. 6. The reinforced water-absorbent synthetic material according to claim 1, wherein the layered double hydroxide anionic soil is hydrotalcite. 7. The reinforced water-absorbing synthetic material according to claim 6, wherein the hydrotalcite is rehydrated. 8. The composition ratio of the non-neutral reinforcing water-absorbing polymer and the layered double hydroxide anionic soil is in the range of about 1: 1 to about 1:20. Reinforced water-absorbing synthetic material as described in the item. 9. The composition ratio of the non-neutral reinforced water-absorbing polymer and the layered double hydroxide anionic soil is in the range of about 1: 1 to about 1:10. Reinforced water-absorbing synthetic material as described in the item. 10. A water absorbent article comprising: a liquid-permeable top sheet; a liquid-impermeable back sheet connected to the top sheet 12; sandwiched between the top sheet 12 and the back sheet 14. A water-absorbent core; the water-absorbent core contains soft hair and a reinforced water-absorbing synthetic material, and the reinforced water-absorbing synthetic material is a non-neutral reinforced water-absorbing polymer and a layered double hydroxide anionic soil. A water-absorbing article, which is characterized in that at least 30% of the functional groups of the non-neutral reinforcing water-absorbing polymer are in a free acid state. 11. The reinforced water-absorbing synthetic material is contained in the range of about 0.2 to about 0.8 gram per gram of soft hair of the water-absorbent core. The water-absorbing article according to item 10. 12. The reinforced water-absorbent synthetic material according to claim 10, wherein the reinforced water-absorbent synthetic material is contained in the range of about 3 to about 10 grams per gram of the fiber material of the water-absorbent core. Water absorbent article. 13. The reinforced water absorbent composite according to claim 10, wherein the pH value of the non-neutral reinforced water absorbent polymer is in the range of about 4.5 to about 6.0. 14. About 70% or less of the functional groups of the non-neutral reinforced water-absorbing polymer are neutralized with sodium. The reinforced water absorbent synthetic material according to claim 10, wherein at least 30% is in a free acid state. 15. About 50% or less of the functional groups of the non-neutral reinforcing water-absorbing polymer are neutralized with sodium. 11. The reinforced water-absorbing synthetic material according to claim 10, wherein at least 50% is in a free acid state. 16. About 40% or less of the functional groups of the non-neutral reinforced water-absorbing polymer are neutralized with sodium. The reinforced water-absorbent synthetic material according to claim 10, wherein at least 60% is in a free acid state. 17. The reinforced water-absorbing synthetic material according to claim 10, wherein the layered double hydroxide anion soil is hydrotalcite. 18. The reinforced water absorbent synthetic material according to claim 17, wherein the hydrotalcite is rehydrated. 19. The composition according to claim 10, wherein the composition ratio of the non-neutral reinforcing water-absorbing polymer and the layered double hydroxide anionic soil is in the range of about 1: 1 to about 1:20. Reinforced water-absorbing synthetic material as described in the item. 20. The composition according to claim 10, wherein the composition ratio of the non-neutral reinforcing water-absorbing polymer and the layered double hydroxide anionic soil is in the range of about 1: 1 to about 1:10. Reinforced water-absorbing synthetic material as described in the item.