Sanitary Napkins Disposable In Water Closet Bowl With The Use Of Alkaline Agent

Abstract

A water-dispersible sanitary napkin having an absorbent composed of (a) a fibrous pad of short fibers of less than 1 cm of fibrous carboxy methyl cellulose having a degree of etherification of 0.15 - 1.50 and an average degree of polymerization of more than 100 or a mixture of these fibers with up to 70 percent of untreated short fibers and (b) a solid alkaline agent having a pH less than 10 at 0.1 mol concentration or a solid alkali carbonate and a solid acid. The absorbent may also contain up to 30 percent of alkaline carboxy methyl cellulose fibers.

Description

This invention relates to an improved sanitary napkin to be used for women's menstruation.

The feature of this napkin is that it comprises an absorbent pad of carboxy methyl cellulose short fibers, whose degree of etherification and average degree of polymerization being under control, and its combination with a solid weak alkali or an alkaline source consisting of a solid alkali carbonate and a solid acid, the said absorbent of the napkin being disposable by water flush in alkaline water solution in closet bowl by dissolution-dispersion and swelling-dispersion after its actual use for the purpose, by throwing the napkin and the above mentioned alkali agent or alkaline source into water in the bowl.

When cotton-wool napkins currently on the market are thrown into water in a water closet bowl, they tend to clog the drain of the water flush system because they do not swell-disperse nor dissolve-disperse and therefore they are not good for disposal into the water of a water closet bowl after their actual use. The essence of this invention is for the absorbent of the sanitary napkin to maintain its shape without dissolution by absorption and storing of menstrual fluid during its use and also to dissolve-disperse and swell-disperse quickly when the napkin is thrown into water in the closet bowl after its use. The basic feature with respect to the raw material for the absorbent in this invention to satisfy this objective is to use short fibers of fibrous glycolic acid as the raw material of the absorbent. Carboxy methyl cellulose (hereinafter abbreviated as CMC) is not soluble in water. However, in alkaline water solution, CMC becomes alkaline CMC and dissolves. This property is applied to the absorbent of the napkin in this invention.

The absorbent of the napkin is explained in detail hereunder:

It is necessary for the absorbent of the napkin to be basically a fibrous pad of CMC short-fibers. The reasons for it are that a fibrous pad of CMC does not give the wearer a disagreeable feeling during use because of its soft pliability and that it has the property of good absorption of menstrual fluid and good storage of menstrual fluid absorbed because of its large porous space and also that it has a good chemical property in that it dissolves and disperses instantly in weak alkaline water solution. It is generally very difficult to convert CMC to alkaline carboxy methyl cellulose (hereinafter called Na-CMC, taking sodium carboxy methyl cellulose as the most representative of alkaline carboxy methyl cellulose,) quickly and for this purpose, a strong alkali such as caustic soda (NaOH) and also some lengthy reaction time as well as such treatments as heating, stirring etc. are necessary. However, if the structure of CMC is a fibrous mass, it reacts well with weak alkaline water solution standing still at normal temperature, produced by a weak alkaline agent because of its very good property of reacting to alkaline water solution. The reason for this is that the structure of a fibrous mass being in the state that CMC short fibers are closely associated in a tangled mass but without being combined together and having large void spaces in it, alkaline water solution is absorbed all at once into the fibrous pad by wicking action when the fibrous pad is thrown into alkaline water solution and that when the fibrous pad absorbs alkaline water solution, the entire surfaces of the CMC short-fibers forming the fibrous pad contact the alkaline water solution and consequently the reactivity of the fibrous pad with the alkaline water solution is increased substantially.

CMC short fibers to swell quickly when contacted with alkaline water solution and the degree of swelling (hereinafter called DS) of CMC short fibers, increases in proportion to the degree of etherification (hereinafter called DE) of CMC short-fibers. Therefore, CMC short-fibers of fibrous pad which absorbed alkaline water solution swell by contact with alkaline water solution and when the DE of CMC short fibers is large, the degree of swelling increases further whereby the lengths of CMC fibers are shortened and the linear structures of CMC short fibers are destroyed. In addition to swelling of CMC short fibers, CMC short fibers react with alkaline water solution and partly dissolve because of the change of CMC to Na-CMC. In summing up, CMC fibrous pad reacts with alkaline water solution thereby shrinkage of length, swelling-decomposition and dissolution of CMC short fibers take place simultaneously and the entanglement of CMC short fibers forming the fibrous pad is loosened and the entire entanglement of the fibrous mass is untied all at once and thus the fibrous pad dissolves-disperses and swell-disperses in the alkaline water solution. It is featured that such a dissolution-dispersion and swelling-dispersion of the fibrous pad take place easily and promptly in a weak alkaline water solution because the degree of reaction of the fibrous pad to alkaline water solution is very large. Contrary to this, it has been proven by experiments that such CMC materials of high density as CMC-paper or CMC gauze dissolved in strong alkaline solution (0.1 mol concentration at normal temperature - hereinafter, pH values are all stated on this basis) having a pH of more than 12 such as NaOH but did not dissolve for a long time at normal temperature in saturated alkaline water solution of sodium carbonate (Na.sub.2 CO.sub.3) the pH of which is 11.5. On the other hand, a CMC fibrous mass reacts very easily and dissolves, swells and disperses in a still water solution of NaHCO.sub.3 (pH 8.3 ) at normal temperature. Since the alkaline agent to be used with the napkin should be safe to the human body, strong alkaline agents such as NaOH or Na.sub.2 CO.sub.3 whose pH is higher than 10, are dangerous and unfit to be used for the napkin of this invention. However NaHCO.sub.3 (pH 8.3) which is safe to the human body, is effectively usable. This is because the absorbent of the napkin of this invention is formed by a CMC fibrous mass and this is the special feature of the napkin of this invention.

Firstly, it is necessary that the CMC fibers forming the fibrous pad be short fibers having a length less than 1 cm. It has been proven by experiments that if the CMC fibers forming a fibrous pad are more than 1 cm long, the CMC fibrous pad does not dissolve-disperse nor swell-disperse (hereinafter called, in combination, dissolve-disperse) in a weak alkaline water solution of an alkaline agent having a pH less than 10, due to tight entanglement of the fibers. Therefore, in order to ensure easy and prompt dissolution-dispersion of the CMC fibrous pad in alkaline water solution of the alkaline agent having a pH less than 10, it is necessary that the entanglement of CMC fibers of the fibrous pad be loose and for this, the length of the CMC fibers must be shorter than 1 cm.

Secondly, the effect of DE and average degree of polymerization (hereinafter called as DP) of the CMC fibers forming the fibrous pad to the pliability, dissolution-dispersibility and swelling-dispersibility of the fibrous pad is explained hereunder:

Regarding Relationship between DE and Pliability.

As the DE increases, the pliability becomes worse and the CMC-short fibers become harder and thus become unfit for the absorbent. In this sense, there should exist a maximum limit value for DE. When CMC short fibers become hard, their defibration becomes impossible. The maximum limiting value of DE is about 1.5. Of course, the smaller the DE, the better the pliability.

Regarding Relationship between DE and Solubility-Dispersibility.

With an increase in DE, the degree of reaction of CMC fibers to alkaline water solution increases. That is, DE and the reactivity are directly proportional i.e. DE and the solubility-dispersibility are directly proportional. On the other hand, when the DE decreases and falls below a certain limit, the reactivity between CMC fibers and alkaline water solution decreases and the dissolution-dispersion of the fibrous mass becomes impossible. Thus, there should exist a minimum limit for DE at which the CMC fibrous mass dissolves-disperses.

Regarding Relationship between DP and Pliability.

As the DP decreases, the fibers become fragile and lose pliability. Therefore, when the DP is decreased too much, the linear structure of the short fibers is destroyed. Thus, there should exist a minimum limit value for DP.

Regarding Relationship between DP and Solubility-Dispersibility.

As the DP decreases, the dispersibility increases.

Summing up the above, it is necessary to control the DE and DP in such a way as to maintain good pliability and solubility-dispersibility so as to make the fibrous mass suitable as the absorbent of the napkin.

Thirdly, the alkaline agent is explained hereunder:

It is necessary that the alkaline agent be solid. As the alkaline agent is required to be present always together with the napkin, it is necessary that it be a solid alkaline agent convenient to be carried and to be incorporated in the napkin.

Also, it is necessary that the alkaline agent be safe to human body and clothing. Since the alkaline agent is to be used by an infinite number of persons, it should always be positively safe. Therefore, an agent having a pH higher than 10 can not be used.

Also, it must be a weak alkaline agent which will not cause the death of bacteria which promote putrefaction of night soil in a septic tank. Since it is said that the pH necessary to keep bacteria alive in a septic tank is within the range of about 6 - 8, it should be a weak alkaline agent such as NaHCO.sub.3 whose pH is 8.3, in order to maintain the pH of the liquid in the septic tank within the range of 6 - 8.

Hereinunder the explained the features of the sanitary napkins comprising the combination of napkin and alkaline agent covered by this invention:

Sanitary napkins consisting of a combination of (a) an absorbent which is a fibrous pad of short fibers of less than 1 cm of fibrous glycolic acid of degree of etherification of 0.15 - 1.50 and of average degree of polymerization of more than 100 or is a fibrous pad made by mixing untreated short fibers not subjected to chemical treatment with the above mentioned fibrous pad within 70 percent and (b) a solid alkaline agent whose pH is lower than 10 at 0.1 mol concentration and at room temperature, the said napkin being disposable by water flushing by combined use of an alkaline agent, featured by being designed for easy disposal by dissolution-dispersion of the absorbent of the napkin in an alkaline water solution when the used napkin and the above mentioned alkaline agent are thrown into water in a water closet bowl.

This napkin is explained in detail hereunder:

When the napkin is disposed in this combination, there is a problem in that, since the solid alkaline agent, when thrown into water in a closet bowl, sinks to the bottom of the water and commences dissolution there, the water in the upper part does not become alkaline for a short while after throwing the alkaline agent into water, it being still. Therefore, in this case, it is necessary to make the entire water alkaline quickly by stirring the water after throwing in the alkaline agent or to delay the throwing of the napkin for a until the upper part of the water becomes alkaline.

As for the DE and DP of the absorbent of the napkin in this invention, the maximum value of DE is 1.50 as aforementioned since the absorbent fibrous pad is made of difibrated short fibers and the minimum value of DE which is, as aforementioned, the lowest capable of dissolving-dispersing the fibrous pad quickly, is within the range of 0.34 - 0.27 and generally about 0.30 in case of normal degree of polymerization (DP's of more than 500 are called normal degree of polymerization) as illustrated in Experiment 1.

Fourthly, it was mentioned before that the dispersibility of the CMC fibrous mass increases in accordance with the decrease in DP and it was then examined in Experiment 2 to find out how far the minimum DE among those capable of dissolving-dispersing the CMC fibrous pad may be decreased from the DE (about 0.3) of normal degree of polymerization, by lowering the DP less than the normal degree of polymerization. Also in Experiment 2, the optimum point in respect of the pliability of the CMC fibrous mass suitable for napkins was examined since the pliability of the fibrous mass is worsened when the DP is decreased. There are various methods to decrease DP. For industry purpose for making CMC fibers, the DP may be arbitrarily controlled by adjusting dipping time of raw material cellulose in NaOH solution in the process of making alkaline cellulose, i.e., the longer the dipping time, the smaller the DP. In Experiment 2, CMC fibers were dipped in hydrogen peroxide (H.sub.2 O.sub.2)AND DP's were controlled by length of this dipping time. In Experiment 2, a CMC fibrous mass of DE 0.27 and of DP 564 was used as a test piece and this fibrous mass did not dissolve-disperse in alkaline water solution as mentioned in Experiment 1 but it dissolved-dispersed within about two seconds after being thrown into NaHCO.sub.3 solution because its DP decreased to 243 by dipping in H.sub.2 O.sub.2 for 48 hours. Such being the case, a CMC fibrous mass does not dissolve-disperse in the case of normal DP but dissolves-disperses at decreased DP. Using this property, Experiment 3 was exercised to find out the lowest DE at which the CMC fibrous mass was dissolved-dispersed under the state of its DP being extremely lowered but within such a limit of DP that the shape of the CMC fibrous mass is maintained (DP about 100 - 200). The test pieces used in this Experiment consisted of a CMC fibrous mass having a DP more than 500 which were dipped in H.sub.2 O.sub.2 for 72 hours to decrease their DP's to the range of about DP 100 - 200 and the solubility-dispersibility was examined with the test pieces having small DE's. In this experiment, a CMC fibrous mass of DE 0.197 dissolved-dispersed quickly but those of DE 0.148 and DE0.043 did not dissolve-disperse. From this, it has been ascertained that the minimum value of DE at which a CMC fibrous mass of DP 100 - 200 dissolves-disperses, was within the range of DE 0.197 - 0.148 and was about 0.15. As for the cases in which untreated short fibers not subjected to chemical treatment are evenly mixed with the CMC fibrous pad of the napkin in this paragraph, it has been confirmed in Experiment 5 that the absorbent could dissolve-disperse when the mixing proportion was less than 70 percent. The effect of mixing untreated short fibers is that it is naturally economical to mix as much untreated short fibers as possible because untreated short fibers are cheaper than CMC short fibers. Those fibers which are mentioned here as chemically untreated short fibers are all the fibers other than the CMC fibers essentially relating to swelling-dispersion and dissolution-dispersion of the absorbent of the napkin of this invention and Na-CMC fibers. For example, alkaline cellulose fibers are the fibers which are chemically treated but which do not dissolve-disperse by themselves in water or alkaline water solution. Therefore, they are deemed here as chemically untreated fibers. Also even when additive(s) are applied to the fibers, those fibers are regarded as chemically untreated fibers as long as they do not dissolve-disperse in water nor in alkaline water solution by themselves.

As for the alkaline agent to be used in combination with the napkin in this invention, it is necessary that it be a solid alkaline agent which, as mentioned before in the paragraph concerning the conditions of alkali, is positively safe to the human body and clothing and does not cause death of bacteria in septic tank. For this reason, many strong alkaline agents having a pH more than 10 as NaOH, Na.sub.2 CO.sub.3 etc. may not be used in combination with he napkin in this invention because of their likely hazard and trouble. Alkaline agents of pH lower than 10 are suitable as alkaline agents to be used in combination with the napkin in this invention because they are safe to the human body and also, the pH in the septic tank will be lowered by the large quantity of used for flushing. NaHCO.sub.3 is one of the most suitable examples of the alkaline agent for this use.

Fifthly, explanations are made about a sanitary napkin consisting of a combination of (a) an absorbent which is a fibrous pad made by mixing alkaline carboxy methyl cellulose fibers within 30 percent, with the fibrous mass of short fibers of less than 1 cm of fibrous glycolic acid having a degree of etherification of 0.15 - 1.50 and an average degree of polymerization of more than 100 or with the fibrous mass made by mixing untreated short fibers not subjected to chemical treatment within 70 percent with the above mentioned latter CMC fibrous mass and (b) a solid alkaline agent whose pH is lower than 10 at 0.1 mol concentration and at room temperature, the said napkin being disposable by water flushing by combined use of an alkaline agent, featured by being designed for easy disposal by dissolution-dispersion of the absorbent of the napkin in alkaline water solution when the used napkin and the above mentioned alkaline agent are thrown into water in a water closet bowl, as follows:

The absorbent of this napkin maintains its shape during its use with absorption of menstrual fluid as long as the proportion of Na-CMC short fibers in the absorbent is within 30 percent but it is featured that this mixing has an effect to prevent the binding of the short fibers of the absorbent caused by coagulation of menstrual fluid to some extent. (Since it has been ascertained by results of the actual application tests exercised by the inventor that the part of the short fibers of the absorbent which are bound together by coagulation of menstrual fluid is only 5 percent of all short fibers of the absorbent and so it does not cause any trouble to the disposal of the napkin in its practical use). The experiment regarding the maximum permissible proportion of Na-CMC fibers is illustrated in Experiment 4.

Sixthly, explanations are made about a sanitary napkin consisting of a combination of (a) an absorbent which is a fibrous pad of short fibers of less than 1 cm of fibrous glycolic acid having a degree of etherification of 0.10 - 0.15 and an average degree of polymerization of more than 100 or a fibrous pad made by mixing untreated short fibers not subjected to chemical treatment within 70 percent with the above mentioned fibrous mass and (b) an alkali source composed of a solid alkali carbonate and a solid acid, the said napkin being disposable by water flushing by combined use of an alkali source, featured by being designed for easy disposal by dissolution-dispersion of the absorbent of the napkin in alkaline water solution when the used napkin and the above mentioned alkali source are thrown into water in a closet bowl, as follows:

For some time after the alkaline agent used for disposal of the previously mentioned napkin is thrown into water in a closet bowl, the upper part of the water does not change to the alkaline state. Therefore, there is a defect that even when the napkin is thrown into water after the alkaline agent is put into water, the absorbent of the napkin does not dissolve-disperse for a long time because it absorbs the water of the upper part and, the water staying still, the exchange of water in it with alkaline water solution does not take place. However, when an alkali source composed of an alkali carbonate and an acid is used in combination with the napkin in this invention, a large amount of CO.sub.2 gas is generated by reaction of the alkali carbonate and acid in water which agitates the water in the closet bowl and changes the water evenly to an alkaline state. Therefore, in the case of the napkin of this invention, the absorbent dissolves-disperses quickly because, when the napkin is thrown into water after the alkali source is put into water, an alkaline solution is forced into the absorbent by CO.sub.2 gas. In this way, the alkali source in this invention has a feature that, when put into water in a closet bowl, it generates actively CO.sub.2 gas, agitates the water, thus bringing the water quickly to an even alkaline state and also, accelerates dissolution-dispersion of the absorbent by compulsory forcing alkaline water solution into the absorbent. Additionally, the alkali source in this paragraph has the following features useful for disposal of napkins:

It has an effect to push out the menstrual fluid absorbed in the absorbent and thus to make dissolution-dispersion of the absorbent easy. It is because CO.sub.2 gas generated in a large quantity penetrates forcefully into the absorbent and pushes out the menstrual fluid already absorbed in the absorbent and, instead, delivers alkaline solution into the absorbent so that the absorbent may be dissolved-dispersed quickly. It has also an effect to improve the reaction between the absorbent and the alkaline solution because CO.sub.2 gas generated in a large quantity penetrates forcefully and continuously into the absorbent and as a result of this, the CMC absorbent fibrous pad contacts continuously fresh alkaline solution and, the reactivity of the absorbent with alkaline solution being improved, dissolution-dispersion of the absorbent becomes easy. Also, even when the alkalinity of the alkaline solution is weak, the absorbent dissolves-disperses easily in the alkaline solution.

Also, it has an effect that the absorbent dissolves-disperses in alkaline solution easily even when, the order of throw-in being reversed, the napkin is thrown into the water in the closet bowl prior to the alkali source. As mentioned before, when the napkin is thrown into water prior to the alkali agent, the water penetrates into the absorbent and, even with subsequent throw-in of alkali agent into the water, the exchange of the water in the absorbent with the alkaline solution does not take place since the alkaline solution stays still and the absorbent does not dissolve-disperse for a long time. However, in case of the alkali source in this invention, it is featured that, even when the napkin is thrown into water prior to the alkali source, the generation of a large amount of CO.sub.2 gas causes quick exchange of the water in the absorbent with the alkaline solution and the absorbent dissolves-disperses quickly.

Also, since this alkali source contains an acid, it has a feature that the alkalinity due to alkaline agent is reduced and thus, the lives of bacteria in domestic septic tanks are saved.

This alkali source is entirely safe to the lives of bacteria in septic tanks because the pH of the water in the closet bowl may be perfectly controlled within a range of about 7.0 - 7.5 by adjusting the quantity of the acid to that of the alkali carbonate.

The features regarding the effects of using an alkali source in combination with the napkin are mentioned above and explanations are made hereinafter about the solid alkali carbonate and the solid acid composing this alkali source. Of course, a solid alkali carbonate and a solid acid very safe to human body and clothing should be employed and their dosages for use should be formulated beforehand to make the alkalinity of the water in the closet bowl within a pH range of about 7.0 - 7.5. The best example is to use a combination of NaHCO.sub.3 as the alkali carbonate and citric acid as the acid.

Next, as for the DE of the absorbent of the napkin in this invention the minimum value of DE at which the absorbent can dissolve-disperse is lower than that of the DE of the absorbent of the aforementioned napkin (about 0.3) because the reactivity of the absorbent is improved by CO.sub.2 gas and, as provided in Experiment 6, it is about 0.15. The DP in this case is a normal degree of polymerization i.e. about 500 - 600 but if the DP is decreased to lower than normal degree of polymerization, the DE is further lowered and it has been proven as provided in Experiment 7, that the DE is about 0.10. The fact that the DE of the absorbent may be decreased by the use of an alkali source means that the pliability and sponginess of the absorbent is fully secured.

Seventhly, explanations are made about a sanitary napkin consisting of a combination of (a) an absorbent which is a fibrous pad made by mixing alkaline carboxy methyl cellulose fibers within 30 percent with the fibrous mass of short fibers of less than 1 cm of fibrous glycolic acid of degree of etherification of 0.10 - 1.50 and of average degree of polymerization of more than 100 or with the fibrous mass made by mixing untreated short fibers not subjected to chemical treatment within 70 percent with the above mentioned latter CMC fibrous mass and (b) an alkali source composed of a solid alkali carbonate and a solid acid, the said napkin being disposable by water flushing by combined use of an alkali source, featured by being designed for easy disposal by dissolution-dispersion of the absorbent of the napkin in alkaline water solution when the used napkin and the above mentioned alkali source are thrown into water in a closet bowl, as follows:

The special feature of this napkin is that, although the effect of mixing Na-CMC is the same as that of the previously mentioned napkin, the dissolution-dispersion of the absorbent is quicker and more positive than that of the previously mentioned napkin since the alkali source is employed.

Eighthly, the inventor illustrates hereunder the experiments on which the foregoing explanations are based:

Experiment 1.

Experiment on DE of CMC fibers, the absorbent fibrous pad of these CMC short fibers of less than 1 cm being capable to dissolve-disperse by combined use of the napkin and the alkaline agent.

Kind of material Wood-pulp of defibrated short fibers.

Size, form and weight of material

1 gram in a cylindrical form of 2 cm in diameter and 2 cm in height.

State of material

Under pressed condition, water is absorbed in more than 2/3 parts of the cylinder.

Length of CMC short fiber materials

2 to 4 millimeters.

Dp of material 500 - 600.

Alkaline agent NaHCO.sub.3 10 grams.

H.sub.2 o 1,000 cc

Time of dipping of material

Immediately after throwing alkaline agent into water and stirring up the liquid.

(DE of CMC) (State of dissolution-dispersion)

1. 0.27 No dissolution-dispersion even after 30 minutes.

2. 0.34 Dissolved-dispersed within about 2 seconds.

3. 0.45 Dissolved-dispersed within about 1 second.

4. 0.50 The same as above.

5. 0.70 The same as above.

6. 0.90 The same as above.

Comment:

The minimum value of DE at which the material dissolves-disperses is between 0.27 and 0.34. It is about 0.30.

Experiment 2.

Experiment on dissolution-dispersion of CMC fibrous pad of CMC short fibers of DE 0.27 and DP 564, this DP having been decreased by immersion in H.sub.2 O.sub.2 and this fibrous pad on being thrown into water in combination with an alkaline agent.

Material of DE 0.27 in Experiment 1 was employed in this experiment.

Kind of material, size, form and state of material etc. were the same as those in Experiment 1.

Weight of Material 5 grams.

Length of CMC short fibers 2 to 4 millimeters

H.sub.2 o.sub.2 30 percent concentration, 500 cc.

Dp and DE of material before immersion in H.sub.2 O.sub.2

De 0.27 dp 564

alkaline agent NaHCO.sub.3 10 grams

H.sub.2 o 1,000 cc

Time of dipping of material

Immediately after throwing the alkaline agent into water and stirring up the liquid.

(Time of immer (Average degree of (State of dissolu sion in H.sub.2 O.sub.2) polymerization: DP) tion-dispersion) hours (1) 44 319 No dissolution-dis persion. (2) 48 243 Dissolved-dispersed within about 2 - 3 seconds. (3) 52 227 Dissolved-dispersed within about 1 - 2 seconds. (4) 56 213 Dissolved-dispersed within about 1 second. Most of material completely dissolved within about 1 minute. (5) 61 205 The same as above. (6) 69 151 The same as above. (7) 81 132 The same as above. (8) 95 110 The same as above.

Comment:

Immersion for 48 hours provides DP 243 and from this DP, dissolution-dispersion begins and all the materials of DP lower than this dissolve-disperse but the lowest limit of DP at which the pliability is suitable for the absorbent of the napkin is about 110.

Experiment 3.

Experiment on dissolution-dispersion of CMC fibrous pad, these CMC short fibers being of low DE and having low DP within a range of 100 - 200 as result of immersion of CMC short fiber cotton-wool congregation in H.sub.2 O.sub.2 for 72 hours.

Kind, size, form, state etc. of material the same as those in Experiment 1.

Weight of material 5 grams.

Length of CMC short fibers 2 to 4 millimeters.

Dp of material 10 100 - 200

Alkaline agent NaHCO.sub.3 10 grams

H.sub.2 o 1,000 cc

Time of dipping of material

Immediately after throwing alkaline agent into water and stirring up the liquid.

(DE of CMC) (State of dissolution-dispersion)

1. 0.043 No dissolution-dispersion even after 30 minutes.

2. 0.148 Same as above.

3. 0.197 Dissolved-dispersed within about 3 seconds.

Comment:

It has been known from this that the minimum value of DE at which CMC fibrous mass of DP 100 - 200 fell within a range between 0.197 and 0.148.

It is about 0.150.

Experiment 4.

Experiment on durability of maintaining forms of the absorbent during use when Na-CMC short fibers are evenly mixed in the absorbent of CMC short fibers.

Kind, form, weight, state etc. of material the same as those in Experiment 1

Length of CMC short fibers 2 to 4 millimeters

Length of Na-CMC short fibers 2 to 4 millimeters

Alkaline agent NaHCO.sub.3 10 grams

H.sub.2 o 1,000 cc.

Time of dipping of material

Immediately after throwing alkaline agent into water and stirring up the liquid.

(Na-CMC mixing ratio (Durability of maintaining in % ) the form of the material) 10 When H.sub.2 O was soaked in the material, its form was not decomposed. 20 The same as above. 30 The form of the material was somewhat destroyed. 40 The form of the material was completely destroyed.

Comment:

When Na-CMC is mixed at 40 percent, the form is completely destroyed by water. Therefore, the practical limit is 30 percent.

Experiment 5.

Experiment on solubility-dispersability of the absorbent when chemically untreated short fibers are evenly mixed in the absorbent of CMC short fibers.

Kind, size, form, weight, state etc. of material the same as those in Experiment 1

Length of CMC short fibers 2 to 4 millimeters

Length of untreated short fibers 2 to 6 millimeters

Alkaline agent NaHCO.sub.3 10 grams

H.sub.2 o 1,000 cc

Time of dipping of material

Immediately after throwing alkaline agent into water and stirring up the liquid.

(Mixing ratio of chemical- ly untreated short (Solubility- fibers in %) Dispersability) 10 Good 20 Good 30 Good 40 Good 50 Hardly dissolution-dispersion but dispersed by stirring the liquid 60 The same as above. 70 No dissolution-dispersion even with agitation of the liquid.

Comment:

When the chemically untreated short fibers are mixed at 70 percent, the absorbent does not dissolve-disperse. Therefore, the practical limit of the chemically untreated fibers is 70 percent.

Experiment 6.

Experiment on DE of CMC fibrous mass the CMC short fiber absorbent of which dissolves-disperses under combined use of the napkin with an alkali source composed of an alkali carbonate and acid.

Kind, size, form, weight, 850000000000000000000000000000000000000000000000000000000000000000