JP2001276124A - Humor absorptive article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent leak preventive effect to a large quantity of urination or repeated urination and moderate the going-back of urine or sticky feeling after urine absorption. SOLUTION: This humor absorptive article comprises a liquid impermeable back sheet, a liquid permeable surface sheet and an absorber consisting of pulp and a highly absorptive polymer and interposed between both the sheets. In the absorber, the ratio of the highly absorptive polymer to the total weight of pulp and highly absorptive polymer is set to 10-9 wt.%. In the highly absorptive polymer, the humor sucking and absorbing performance for transferring the humor retained in the pulp fiber voids to the highly absorptive polymer side is 5 g/g or more for 15 second from absorption start.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a body fluid absorbing article such as a disposable diaper, a sanitary napkin, an incontinence pad and the like. The present invention relates to a body fluid-absorbing article that eliminates the return to the surface and the stickiness of the topsheet.

[0002]

2. Description of the Related Art Since body fluid absorbent articles such as disposable diapers, sanitary napkins and incontinence pads have been introduced to the market, various improvements have been made on absorbents using superabsorbent polymers.

[0003] As is well known, superabsorbent polymers have properties such as absorption of water and swelling upon contact with water to form a gel, and once they absorb water, they do not separate even if some pressure is applied. It shows tremendous water absorption, for example, reaching several tens to several thousand times its own volume.

Although the superabsorbent polymer alone exhibits the above-mentioned absorption power alone, it cannot exhibit water absorption power unless it is wet to some extent, and has a low absorption rate.
It is mixed in the pulp constituting the absorbent body of the body fluid absorbing article, for example, in a state of being aggregated into granular powder, crushed powder or grape. As a result, problems unique to bodily fluid absorbent articles such as reversion from pulp and reabsorbability arise.

For example, in recent years, this type of body fluid absorbing article has been made thinner and more compact, but even if it is made thinner and more compact, the water absorption cannot be reduced. Therefore, the blending ratio of the superabsorbent polymer is necessarily increased. However, if the compounding ratio of the superabsorbent polymer is increased, the so-called "gel blocking" in which the gap between the swollen polymer particles is extremely reduced occurs, and the required water absorbing power cannot be exhibited. As a result, the penetration between the urine is inhibited by the bond between the polymer particles, and a phenomenon in which the urine whose penetration is inhibited returns again and flows out is observed. In the past, as a method of preventing this gel blocking, a method of gradually increasing the mixing density of the superabsorbent polymer from the upper layer side and mixing the same so as to prevent gel blocking on the upper layer side (Japanese Patent Laid-Open No.
No.-45703) and the super absorbent polymer having a central particle size of 4
Those having a thickness of 100 to 700 μm and comprising an absorbent body by mixing a superabsorbent polymer and a hydrophilic fiber (US Pat.
No. 5061259). On the other hand, there is a tendency to cope with a reduction in thickness by reducing the number of hydrophilic fibers having a low bulk specific gravity and using a highly absorbent polymer having a large bulk specific gravity.

Furthermore, in order to prevent the pulp from absorbing and deforming when it absorbs water, the pulp itself is compressed or densified in order to prevent the water absorbing space between fibers from becoming extremely small (Japanese Patent Publication No. 1-333176). Japanese Patent Application Laid-Open No. 63-264971) and those obtained by crosslinking pulp with a suitable crosslinking agent in order to prevent the pulp from twisting when wet (JP-A-63-264971).

[0007]

Although each of the above-mentioned technologies has been effective to some extent with respect to the individual problems, a questionnaire survey on the use of disposable diapers showed that the amount of urination was large and the urination speed was high. In the case of older children and adults, it has been confirmed that leaks and reversals often occur, causing dissatisfaction to the wearer. Has been confirmed to leak.

[0008] In view of such a situation, when reconsidering the technologies proposed in the past, each of the proposed technologies has its own problems, such as leakage prevention, prevention of reversion, suppression of gel blocking, prevention of pulp twisting due to improved absorption performance. Proposal of a solution to the problem, each of which has been effective, but it is not lacking a comprehensive viewpoint on the composite function of the pulp and superabsorbent polymer constituting the absorber and the role sharing of the function The question was raised. That is, to increase the absorption performance, the mixing ratio of the superabsorbent polymer may be increased, but if the mixing ratio is excessively increased, gel blocking occurs. As a result, in order to achieve reciprocal effects such as reversal, from the viewpoint of comprehensively considering the composite function and function allotment of pulp and superabsorbent polymer, and taking into account the balance of these, high absorbency is considered. It is necessary to define the blending ratio of the polymer and the absorption performance.

Accordingly, the main object of the present invention is to provide a disposable diaper,
For body fluid absorbent articles such as sanitary napkins and incontinence pads, by defining the superabsorbent polymer element focusing on the performance of the superabsorbent polymer used and the cooperation between pulp and superabsorbent polymer Another object of the present invention is to provide a body fluid-absorbing article which is excellent in the effect of preventing leakage of a large amount of urine or repeated urination, and in which the return to the topsheet after urine absorption and the stickiness of the topsheet are reduced.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a liquid-impermeable backing sheet, a liquid-permeable topsheet, and an absorbent made of pulp and a superabsorbent polymer inside these two sheets. In the body fluid absorbing article having a body interposed therebetween, the absorbent has a ratio of the superabsorbent polymer to the total weight of the pulp and the superabsorbent polymer of 10 to 9;
0% by weight, and the superabsorbent polymer has a bodily fluid suction / absorbing performance of transferring the bodily fluid retained in the pulp fiber voids to the superabsorbent polymer side of 5 g / g or more for 15 seconds from the start of absorption. It is characterized by the following.

In this case, the ratio of the superabsorbent polymer to the total weight of pulp and superabsorbent polymer is preferably 30 to 60% by weight. The superabsorbent polymer desirably has an irregularity of polymer particle shape of not more than 0.3 to 0.5 g / ml in bulk density evaluation, and has a polymer particle size distribution of not less than 500 μm.
% By weight, 250-500 μm is 70% by weight, 250 μm
Those having the following 20% by weight are preferably used.

To reconsider the mechanism of water absorption between the pulp and the superabsorbent polymer (hereinafter simply referred to as a water-absorbing polymer) and the cooperative action at that time, it is assumed that urine is discharged to the absorber. However, because the water-absorbing polymer cannot exert its water-absorbing power unless it is moistened to some extent, and the absorption speed is relatively slow, it is instantly absorbed by pulp whose absorption speed is significantly faster than that of the water-absorbing polymer. Will be. Then, the urine retained in the pulp voids takes an absorption form in which the urine transferred to the water-absorbing polymer side is delayed. Urinary leakage was considered to be due to the delay in the transfer speed to the water-absorbing polymer side, and the amount of water retained in the pulp void had reached the limit, and it was recognized that the transfer speed from the pulp void to the water-absorbing polymer side and its amount were problems. Below, as described below, assuming that the urination time is 15 seconds, if the suction absorption performance of the water-absorbing polymer in this 15 seconds is 5 g / g or more, the amount of water retained in the pulp void does not reach the limit value, The entire amount of the excreted urine can be absorbed by the absorber.

In view of the properties of the water-absorbing polymer, urine once retained does not easily separate from water even when pressurized.
In addition to the condition that the transition to the water-absorbing polymer is made quickly, if the content of the water-absorbing polymer is preferably 30% by weight or more and less than 60% by weight, as demonstrated by the experiment described later, the reversion occurs. Generation can be effectively suppressed.

Furthermore, since the reabsorbing performance is determined by the water retention capacity of the pulp after urine absorption and the degree of gel blocking, the transfer to the water-absorbing polymer side should be performed promptly, In the present invention, the problem is solved by using a water-absorbing polymer of 0.3 to 0.5 g / ml in evaluation of bulk density.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The body fluid-absorbing articles to which the present invention is directed are adult paper diapers, infant paper diapers, sanitary napkins, incontinence pads, etc. Specifically, liquid-impermeable back sheets, liquid-permeable top sheets, Any body fluid absorbing article may be used as long as an absorbent made of pulp and a water-absorbing polymer is interposed between these two sheets.

Examples of the liquid-impervious back sheet include a liquid-impervious sheet made of a polyethylene sheet or the like, a water-permeable / moisture-permeable sheet having moisture permeability from the viewpoint of preventing stuffiness, and a composite sheet of a nonwoven fabric and a waterproof sheet. On the other hand, as the liquid-permeable surface sheet, a perforated or non-porous nonwoven fabric or a porous plastic sheet is preferably used. The material fibers constituting the nonwoven fabric can be synthetic fibers such as olefins such as polyethylene or polypropylene, polyesters, polyamides, etc., recycled fibers such as rayon and cupra, and natural fibers such as cotton. A nonwoven fabric obtained by an appropriate processing method such as a method, a spun bond method, a thermal bond method, a melt blown method, and a needle punch method can be used.

The absorber interposed between the liquid-impermeable back sheet and the liquid-permeable top sheet is composed of pulp and a water-absorbing polymer. Specifically, it is mixed in the pulp constituting the absorber, for example, as a granular powder.

Examples of the pulp include cellulose fibers such as chemical pulp and dissolved pulp obtained from wood, and artificial cellulose fibers such as rayon and acetate. Softwood pulp having a longer fiber length than hardwood pulp is used. Are preferably used in terms of function and price.

On the other hand, the water-absorbing polymer used in the main body liquid-absorbing article has a body fluid suction-absorbing performance of transferring body fluid retained in the pulp fiber voids to the water-absorbing polymer side at 5 g / g or more for 15 seconds from the start of absorption. Some are used.

Assuming that urine is discharged into an absorbent made of pulp and a water-absorbing polymer, the water-absorbing polymer cannot exert its water-absorbing power unless it is in a wet state to some extent, and its absorption speed is slow. Water is absorbed between the fibers by capillary action with some diffusion on the pulp side having a high speed, and then urine retained between the fibers is transferred to the water-absorbing polymer side.

On the other hand, according to the investigation by the present inventors, the urination speed and volume are completed in 10 to 15 seconds, and the volume is found to be 50 to 200 ml. If it is assumed that a large amount of urine leaks during the urination time, the amount of urine retained in the voids between the pulp fibers will exceed the limit value.To ensure leakage prevention, water is retained between the pulp fibers. As soon as urine is transferred to the water-absorbing polymer side and the water-absorbing polymer content (also referred to as water-absorbing polymer content ratio) does not cause reversion, the total amount of urine excreted without the pulp fiber gap reaching the water retention limit. Can be absorbed in the absorber, and reversion can be prevented.

Therefore, in order to prevent urine leakage, the amount of absorption at the urination site (about 100 cm ² ) is about 1 /
Since it is known that it is desirable to set it to 4 or more, if the urination volume is 200 ml, the absorption amount at the urination site should be 50 ml or more. 50 ml of urine in 1
Table 1 shows a trial calculation study table for absorption by the pulp and the water-absorbing polymer for 5 seconds. In Table 1, the pulp weight per 100 cm ² was 2.95 g, and the weight of the water-absorbing polymer was 1.25 g (the water-absorbing polymer content ratio was 0.1%).
3) and the pulp absorption capacity is 15 g / g,
This is a trial calculation of required suction and absorption performance of a water-absorbing polymer when 0 ml of urine is absorbed by pulp and a water-absorbing polymer.

[0024]

[Table 1]

According to the calculation results in Table 1, in order to make the total absorption amount after 15 seconds equal to or more than 50 ml, the water-absorbing polymer needs to absorb 5 g / g or more in 15 seconds from the start of absorption. found.

As a test method for measuring the body fluid suction absorption performance, for example, the test method shown in FIG. 1 is suitably employed. First, 3 g of pulp is spread flat on a cylindrical body 1 having an opening with a diameter of 50 mm at the upper part and a filter 1a of 300 mesh at the lower part, and the weight W of Group A
Measure o. Next, 0.3 g of the water-absorbing polymer is spread evenly on the upper surface of the filter paper 3 with the filter paper 2 interposed therebetween so as to be uniform. Then, as shown in FIG. 1, the filter paper 3, the filter paper 2, and the Group A are placed on the tray 4 in this order, and the artificial urine 8 ml is placed.
Is injected using a burette. The weight Wt of Group A was measured at intervals determined after the injection of 8 ml, and the absorption amount of the water-absorbing polymer at each interval was calculated from the following equation (1). Water absorption polymer absorption amount (g / g) = (Wo + artificial urine weight-Wt) / water absorption polymer weight ... (1)

FIG. 2 shows the results of the above-mentioned test conducted on a plurality of types of water-absorbing polymers A to C. As a result of conducting tests on three types of water-absorbing polymers, it was found that the water-absorbing polymer A was usable in the present invention. The water-absorbing polymer A is obtained by dispersing and suspending an acrylic acid or an alkali metal acrylate aqueous solution containing a reaction initiator (catalyst) in a petroleum solvent containing a surfactant, crosslinking with a crosslinking agent, and then drying and drying. It is manufactured by classification, and its particle form has large irregularities on the surface of each particle,
Each particle shape has an irregular shape. Table 2 shows the bulk density and particle size distribution of the water-absorbing polymers A to C used in the experiment.

[0028]

[Table 2]

The content of the water-absorbing polymer with respect to the total weight of the pulp and the superabsorbent polymer is 0.1%.
It is desirable to set it to 0.9. When the content of the water-absorbing polymer is less than 0.1, the bodily fluid is not sufficiently transferred from the pulp voids to the water-absorbing polymer, causing the bodily fluid to flow on the top sheet of the absorbent article at the time of repeated absorption, and leakage is likely to occur. When the content of the water-absorbing polymer exceeds 0.9, a phenomenon in which gel blocking becomes remarkable is observed.

In order to find a more preferable range of the content of the water-absorbing polymer, the content of the water-absorbing polymer which does not revert was examined by using the water-absorbing polymer A suitable for the body fluid absorbing article of the present specification. The exam is
Five kinds of absorption specimens were prepared in which the polymer mixing ratio a was varied between 0.2 and 0.6, made into a plate shape, and after injecting 200 cc of artificial urine, the kitchen was weighed in advance. The paper was placed thereon, and after a certain period of time, a 5 kg weight was loaded for 10 seconds. After the loading, the kitchen paper weight was measured again, and the amount of reversion was calculated from the difference in kitchen paper weight before and after loading. The result is shown in FIG.

As a result of the test, the water-absorbing polymer content ratio a was found to be 0.
When it is lower than 3, the amount of absorption per unit weight of the water-absorbing polymer increases, and the artificial urine is not sufficiently sucked from the pulp gap, and the reversion phenomenon is rapidly increasing. Therefore, it was found that the water-absorbing polymer content was desirably 0.3 or more. Although the upper limit is not shown in the experiment, gel blocking may occur depending on the type of the body fluid absorbing article, which may adversely affect the amount of reversion, and therefore, the preferred upper limit of the water-absorbing polymer content is 0. .6.

Next, a disposable diaper was actually manufactured by using the water-absorbing polymer A suitable for the body fluid absorbing article of the present specification,
An absorption test and a reabsorption test were performed. The water-absorbing polymer A used had an irregular shape of particle shape of 0.40 g / bulk density evaluation.
ml. In the body fluid absorbing article of the present invention, those having a bulk density in the range of 0.3 to 0.5 g / ml are preferably used. When the bulk density is less than 0.3 g / ml, the strength of the water-absorbing polymer is reduced, and the gel is broken by the shearing force applied during production and use, so that the absorption performance is reduced. On the other hand, if the bulk density exceeds 0.5 g / ml, the surface area of the water-absorbing polymer tends to decrease, so that the contact area with the body fluid also decreases, and sufficient body fluid absorption performance cannot be obtained.

The polymer particle size distribution is 10% by weight for 500 μm or more, 70% by weight for 250 to 500 μm,
What was adjusted to 20% by weight of 0 μm or less was used. Considering that the bulk density of a normally used water-absorbing polymer is around 0.6 g / ml, this water-absorbing polymer with a low bulk density ensures gel blocking, as demonstrated in the reabsorption test described below. It has been confirmed that they prevent and exhibit very high resorption performance.

The bodily fluid absorbent article used in the experiment was a pants-type paper diaper having an absorbent body interposed between a liquid-permeable top sheet and a liquid-impermeable back sheet, wherein the absorbent body was composed of an upper absorbent body and a lower absorbent body sheet. Absorber structure of upper and lower two layers with the body, the lower absorber has a substantially hourglass shape with a constricted part on both sides in the longitudinal direction, the longitudinal dimension is 500 mm, the width of the constricted part is 100 mm, and one upper layer absorbent The body is exactly the shape of a rice scoop, about 300 mm long, about 150 mm wide, and about 50 mm narrow. As shown in Table 3, the water-absorbing polymer content ratio was set to 0.5 for both the lower layer and the upper layer absorber, and a polymer using water-absorbing polymer C was produced for comparison.

[0035]

[Table 3]

(Leak Test) Regarding the leak, artificial urine was injected at a rate of 15 ml with a doll simulating the shape of an old man in a sideways state, and the amount of absorption when the leak occurred was taken as a measured value. Table 4 shows the results.

[0037]

[Table 4]

From Table 4, it was 321 ml for the product of the present invention and 220 ml for the comparative product. In this absorbent, it was confirmed that urine retained in the pulp voids immediately migrated to the water-absorbing polymer side, so that the pulp did not reach the water retention limit, resulting in the absorption of a large amount of urine.

(Reabsorption test) In the reabsorption test, the mannequin was placed in a horizontal position, and artificial urine was absorbed 150 ml in advance, then 10 m
Artificial urine was injected at a water injection rate of 1 / sec, and the amount of additional absorption at the time of leakage (subtracting the first 150 ml) was measured. Table 5 shows the results.

[0040]

[Table 5]

From Table 5, it was confirmed that the product of the present invention exhibited a high numerical value also in terms of resorption performance. This is because urine retained in the pulp voids is promptly transferred to the water-absorbing pulp side, leaving water retention capacity in the pulp voids, and because a low-bulk density polymer is used as the water-absorbing polymer, it swells. Even so, it is considered that the result is that the gap is not filled and the absorption power is maintained for a long time.

[0042]

As described above in detail, according to the present invention, the performance of the superabsorbent polymer used and the performance of the pulp and the superabsorbent polymer are related to body fluid absorbing articles such as disposable diapers, sanitary napkins and incontinence pads. By specifying the water-absorbing polymer element focusing on the cooperative action, it is possible to improve the effect of preventing leakage of large amounts of urine and repeated urination, as well as to return to the top sheet after urine absorption and to make the top sheet sticky. It can be alleviated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a suction absorption test capacity of a water-absorbing polymer.

FIG. 2 is a graph showing the results of a suction absorption test.

FIG. 3 is a graph showing a reversion test result.

[Explanation of symbols]

 1 ... cylindrical body, 2/3 ... filter paper, 4 ... saucer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor, Mitsuhiro Otani 4776-4, Suginosawa, Shizu-gun, Kitsuregawa-cho, Shioya-gun, Tochigi Prefecture F-term in Eliel Papertech Co., Ltd. 3B029 BA05 BA12 BA18 4C003 AA07 AA09 AA18 AA22 4C098 AA08 CC03 DD05 4F100 AK01A AK01B AK04C AL05B AP00B AT00A AT00C BA03 BA10A BA10C DG02B DG15A DJ00A GB72 JA13B JA20B JD14B YY00B

Claims (4)

[Claims] 1. A bodily fluid absorbent article comprising a liquid-impermeable back sheet, a liquid-permeable top sheet, and an absorbent made of pulp and a high-absorbent polymer interposed between the two sheets. The ratio of the superabsorbent polymer to the total weight of the pulp and the superabsorbent polymer is 10 to 90% by weight
And the superabsorbent polymer is characterized in that the bodily fluid suction and absorption performance for transferring the bodily fluid held in the pulp fiber voids to the superabsorbent polymer side is 5 g / g or more for 15 seconds from the start of absorption. Body fluid absorbing article. 2. The body fluid absorbent article according to claim 1, wherein the ratio of the superabsorbent polymer to the total weight of the pulp and the superabsorbent polymer is 30 to 60% by weight. 3. The body fluid-absorbing article according to claim 1, wherein the superabsorbent polymer has an irregularity of polymer particle shape of 0.3 to 0.5 g / ml in bulk density evaluation. 4. The superabsorbent polymer has a polymer particle size distribution of not less than 500 μm at 10% by weight, 250 to 500 μm.
The body fluid absorbent article according to any one of claims 1 to 3, wherein 70% by weight and 20% by weight of 250 µm or less.