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Publication numberUS3756232 A
Publication typeGrant
Publication dateSep 4, 1973
Filing dateNov 2, 1970
Priority dateNov 12, 1969
Publication numberUS 3756232 A, US 3756232A, US-A-3756232, US3756232 A, US3756232A
InventorsK Noguchi, M Saburi
Original AssigneeK Noguchi, M Saburi
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Sanitary napkins disposable in water closet bowl with the use of alkaline agent
US 3756232 A
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.
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United States Patent Noguchi et a1. 1 1 Sept. 4, 1973 1 SANITARY NAPKINS DISPOSABLE 111 3,407,814 10/1968 George et al. 128/290 R WATER CLOSET BOWL WITH THE USE OF 3,480,016 11/1969 Costanza et a1. 128/284 3,521,638 7/1970 Parrish 128/284 ALKALINE AGENT 3,563,241 2/1971 Evans et a1. 128/284 [75] Inventors: Koichi Noguchi, 54-6, l-chome, 3,575,173 4/1971 Loyer 128 290 R Yoyogi; Mme Saburi, both f 3,589,364 6/1971 Dean et a1. 128/296 X Japan FOREIGN PATENTS OR APPLICATIONS 1 1 Assigneer Said Nvsuchi, y Said Saburi 842,464 7/1960 Great 128/285 [22] Filed: Nov. 2, 1970 Primary Examiner-Charles F. Rosenbaum [21] Appl 86327 Attorney-Waters, Roditi, Schwartz and Nlssen [30] Foreign Application Priority Data [57] ABSTRACT N .12,1969 J 44 90156 9 1970 252: i 45130618 A water-d1spers1ble samtary napkm having an absor- June 12 1970 Japan rlin I TIM: 45150520 (a) a fibrous Pad of 5mm fibers of I less than 1 cm of fibrous carboxy methyl cellulose hav- 521 vs. c1 128/290 R a degree etherificatb" 0f and 51 1111. (:1. A611 13/16 degree Pdymerizam" than 100 a [58] Field of Search 128/284 285 287 mim'e these fibers with Pme"t of 6 treated short fibers and (b) a solid alkaline agent having a pH less than 10 at 0.1 mol concentration or a solid [56] Retemces Cited alkali carbonate and a solid acid. The absorbent may also contain up to 30 percent of alkaline cal-boxy UNITED STATES PATENTS methyl cellulose fibers. 2,626,214 H1953 Osborne l28/290R 3,055,369 9/1962 Graham, Jr. 128/285 23 Claims, 12 Drawing Figures PATENTEB SE? 4 I875 SEE! 1 0F 3 SANITARY NAPKINS DISPOSABLE IN WATER CLOSET BOWL WITH THE USE OF ALKALINE AGENT This invention relates to an improved sanitary napkin to be used for womens 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 ithas 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 alkalinewater 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 D5) 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, swellingdecomposition 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 dissolvesdisperses and swelldisperses 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 al kaline 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,CO,) the pH of which is ll.5. 0n the other hand, a CMC fibrous mass reacts very easily and dissolves, swells and disperses in a still water solution of NaHCO, (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,CO,, whose pHis higher than 10, are dangerous and unfit to be used for the napkin of this invention. However NaHCO, (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.

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 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 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, whose pH is 8.3, in order to maintain the pH of the liquid in the septic tank within the range of 6 8.

l-lereinunder the explained the features of the sani tary 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. l 5 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 between DP and within 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,O, )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 Nal-ICO, solution because its DP decreased to 243 by dipping in PLO, for 48 hours. Such being the case, a CMC fibrous mass does not dissolve-disperse in the case of normal DP but dissolvesdisperses 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 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 0, for 72 hours to decrease their DPs to the range of about DP 100 200 and the solubility-dispersibility was examined with the test pieces having small DEs. 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 dissolvedisperse. 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 as NaOl-l, Na,CO, 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. Nal-lCO, 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 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 dissolutiomdispersion 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 C0, 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 dissolvesdisperses 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, 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, 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 dissolutiondispersion of the absorbent easy. it is because C0, 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, 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, dissolutiondispersion 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 dissolvesdisperses 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, 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, 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 DB of the absorbent of the aforementioned napkin (about 0.3) because the reactivity of the absorbent is improved by C0, gas and, as provided in Experiment 6, it is about 0.!5. 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 DB 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 l. 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 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 dissolutiondispersion 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 parts of the cylinder.

Length of CMC short fiber materials 2 to 4 millimeters. DP of material Alkaline agent H,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) l. 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.

NaHCO, 10 grams.

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,O, 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 11 30 percent concentration, 500 cc. DP and DB of material before immersion in I-I,0

DE 0.27 DP 564 Alkaline agent NaHCO, H O 1,000 cc Time of dipping of material Immediately after throwing the alkaline agent into water and stirring up the liquid.

10 grams 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 11,0, 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 DP of material 100 200 Alkaline agent NaHCO, 11,0 1,000 cc Time of clipping of material Immediately after throwing alkaline agent into water and stirring up the liquid.

2 to 4 millimeters.

10 grams (DE of CMC) (State of dissolution-dispersion) 1. 0.043 No dissolution-dispersion even after 30 minutes. 2. 0.148 Same as above. p 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 NaCMC 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 Length of Na-CMC short fibers Alkaline agent NaHCO, H O 1,000 cc.

Time of dipping of material Immediately after throwing alkaline agent into water and stirring up the liquid.

2 to 4 millimeters 2 to 4 millimeters 10 grams (Na-CMC mixing ratio (Durability of maintaining in k the form of the material) 10 When 14,0 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 \vs 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 Length of untreated short fibers Alkaline agent NaI-ICO, H30 1,000 CC Time of dipping of material Immediately after throwing alkaline agent into water 2 to 4 millimeters 2 to 6 millimeters 10 grams 40 and stirring up the liquid.

(Mixing ratio of chemicaluntreated short (Solubilityibers in Dispenability) 10 Good 20 Good 30 Good 40 Good Hardly dissolution-dispersion.

but dispersed by stirring the liquid 50 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 percent, the absorbent does not dissolvedisperse. 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, state etc. of material the same as those in Experiment 1 Length of CMC short fibers DP of material 500 600 2 4 millimeters Alkali carbonate salt NallCO Acid Citric acid grams H,O 1,000 cc Time of dipping of material Immediately after throwing alkali source into water.

grams The minimum value of DE falls within a range between 0.18 and 0.14. It is about 0.15.

Experiment 7.

Experiment on dissolution-dispersion of CMC fibrous mass of low DE, having also low DP of 100 200 as result of immersion of CMC short fiber fibrous mass of DP more than 500 in I-I,O, for 72 hours.

Kind, size, form, weight, state etc. of material The same as those in Experiment 1. Length of CMC short fibers DP of material 100 200 Alkaline carbonate salt Nal-ICO,

2 4 millimeters 10 grams Acid Citric acid 5 grams H,O 1,000 cc Time of dipping of material Immediately after throwing alkali source into water.

(DB of CMC) (State of dissolution-dispersion) 1. 0.043 No dissolution-dispersion 2. 0.148 Dissolved-dispersed within about 2 secends. 3. 0.197 Dissolved-dispersed within about 1 second. Comment:

The minimum value of DE falls within a range between 0.148 and 0.043. It is about 0.10. Ninthly, the figures, structures and the features of the napkin are explained hereunder:

FIG. 1 is a perspective view of the absorbent pad of the claimed invention.

FIGS. 2, 3 and 4 are perspective views of the absorbent pad partially cut away to show in cross section alternative embodiments of the arrangement of the alkaline source within the pad.

FIGS. 50, 5b and 5c are cross-sectional views which illustrate alternative embodiments of the arrangement of the alkaline source within a water-soluble bag.

FIGS. 6a, 6b and 6c are cross-sectional views which illustrate alternative embodiments of the arrangement of the alkaline source within waterproof bags tied with water-soluble tie material.

FIGS. 7 and 8 are perspective views of a sanitary napkin partially cut away to show in cross section alternative embodiments of the arrangement of the absorbent pad within the napkin. CMC made from celluloses such as wood pulp, linter pulp etc. were defibrated and made to short fibers of less than 1 cm (1) which were put together and entangled to form a fibrous mass. This fibrous mass was then pressed into such a form as desired which is the absorbent (2) of the napkin. FIG. 2 is a perspective view of an actual example of the central part of a napkin incorporating in itself an alkali source consisting of alkali carbonate and citric acid. The absorbent (2), the water-proof material (3) set outside the absorbent to prevent menstrual fluid from leakage, methyl cellulose film bag (4), in which alkali carbonate (5) and citric acid (6) are enclosed, are illustrated.

In case of the previously mentioned napkin, the napkin and the alkaline agent are to be thrown separately in water in a closet bowl but the incorporation of alkaline material (alkaline agent and/or alkali source) in the napkin is an improved method in which the disposal of the napkin is more convenient, certain and quick. The reasons are: When the napkin and the alkaline agent are thrown away separately, two actions are required, however, in case of this incorporation system, only one natural action of throwing the napkin itself will suffice for disposal: Moreover, in case of separate throwing of napkin and alkaline agent, it is necessary to increase the quantity of alkaline agent to throw in if the quantity of water in the closet bowl is big, however, in case of this incorporation system, only such a fixed quantity of alkaline agent as to match the quantity of the CMC absorbent, irrespective of the water quantity, is sufficient because the CMC absorbent of the napkin reacts only to the alkaline solution locally generated inside the napkin by reaction of the alkaline agent to the water which has entered into the napkin: Also, there is a feature of prompt dissolution-dispersion of the napkin because the alkaline agent dissolves very quickly in absence of the effect of common ions so that the water in the napkin becomes alkaline easily to cause a reaction with the CMC absorbent: And in addition, when an alkali source consisting of an alkali carbonate and an acid is employed as alkaline agent in case of this incorporation system, there is a feature of instant and positive dissolution-dispersion of the absorbent because of an increased reaction of the CMC absorbent to alkaline solution on account of the generation of a large quantity of CO, gas. FIG. 3 is a perspective view of central part of a sanitary napkin incorporating in itself an alkali source consisting of alkali carbonate and citric acid. The absorbent (2), the waterproof material (3) set outside the absorbent to prevent menstrual fluid from leakage, and the alkali carbonate (5) and citric acid (6) mixed in with the fibers of the absorbent (2) are illustrated.

For incorporating said alkaline material in the napkin, it is necessary to devise the position and the method in such a manner that the alkaline material will not react with the fibers of the absorbent before they are thrown into water. For prevention of dissolutiondispersion of the absorbent while being worn, a thin water-proof sheet is placed between the alkaline material and the absorbent so that the alkaline material is separated from the fibers of the absorbent. To achieve this, the alkaline material is positioned on the other side of a water-proof sheet than the side where menstrual fluid is supposed to be absorbed and retained, for instance, the solid alkaline material is wrapped in one or two bags, made of a thin water soluble sheet or a thin moisture proof sheet tied with water soluble ties, which bags are then placed on the other side of the water-proof sheet than the side where the menstrual fluid is supposed to be absorbed and retained.

Various bags enclosing an alkaline material and to be incorporated in the napkin as shown in FIG. 4 and are further illustrated in detail in FIGS. 5 and 6 which will be explained below.

The bag (4) in FIG. 4 corresponds to FIG. 5a. Except FIG. 5a, the following five kinds of incorporation of the bag or the bags containing an alkaline material in the style of FIG. 4 are possible, i.e., a bag of FIG. 5b only, a combination of a bag of FIG. 5b and a bag of FIG. So, a bag of FIG. 6a only, a bag of FIG. 6b only and a combination of a bag of FIG. 6b and FIG. 60.

FIGS. 50, 5b and 5c are cross-sectional views of actual examples of water-soluble bags each enclosing an alkaline agent or alkali source as a means of incorporating alkaline material in the napkin of this invention.

FIG. 5a illustrates the state in which a solid alkali carbonate (5) and a solid acid (6) are mixed together and enclosed in a water-soluble bag (4). In this case, a solid alkali carbonate and a solid acid may also be mixed to formulate into tablets which are then enclosed in a bag or bags.

FIG. 5b illustrates the state in which only a solid alkali carbonate (5) is enclosed in a water-soluble bag FIG. 5c illustrates the state in which only a solid acid (6) is enclosed in a water-soluble bag (4).

Since the bag is water-soluble, the alkaline material enclosed in the bag comes into contact with water easily to produce an alkaline aqueous solution, when the napkin of this invention is thrown into water in a water closet bowl.

FIGS. 60, 6b and 6c are cross-sectional views of actual examples of moisture-proof bags each enclosing an alkaline agent or alkali source as a means of incorporating alkaline material in the napkin of this invention said bags being tied with water soluble ties.

FIG. 6a illustrates the state in which the inside of moisture-proof bag (13) is made into two enclosures by binding the bag tightly at its middle and both ends each with a tie made of a water-soluble material (10) and a solid alkali carbonate (5) and a solid acid (6) are enclosed separately each in one of the enclosures of the bag. In this case, a solid alkali carbonate and a solid acid may be also mixed to formulate into tablets which are then enclosed in a moisture-proof bag made by binding only its two ends with a water-soluble tie.

FIG. 6b illustrates the state in which a solid alkaline agent is enclosed in a moisture-proof bag (13) made by binding its two ends with a water-solubletie (10).

FIG. 6a illustrates the state in which a solid acid is enclosed in a moisture-proof bag (13) made by binding its two ends with a water-soluble tie (10).

The special feature in these cases of FIG. 6a, FIG. 6b and FIG. 60 is that, although the bag or the bags are moisture-proof, each of the both ends of the bag is open and only bound by a water-soluble tie and the alkaline material in the bag comes into contact with water by dissolution of the water-soluble tie binding both ends and the middle of the bag to produce easily an alkaline aqueous solution when the napkin is thrown into water.

The reason for using a moisture-proof sheet or film for the major material of the bag in these cases is that solid acid for the alkali source. Citric acid has hygroscopic property but the citric acid employed will not cause trouble with dissolution of the bag or disintegration of CMC fibers in case it is enclosed in such a moisture-proof bag as illustrated in FIG. 6a and/or FIG. 6c.

As for the water-proof sheet (3) of FIGS. 2, 3 and 4, employed in this improved napkin to prevent spread and permeation of menstrual fluid absorbed and retained, in the absorbent of the napkin, the characteristics of its structure and its function are explained be low.

The water-proof sheet is essentially composed of a methyl cellulose sheet as a water-soluble base sheet and a very thin film of linseed oil as a water-proof material, the later being applied onto the surface of one side of the former. This water-proof sheet functions in such a way that said linseed oil film, being water-repellent, prevents permeation of menstrual fluid absorbed and retained in the absorbent of the napkin while the napkin is worn and once the napkin is thrown into water, said methyl cellulose sheet dissolves into water by contact of the water with one side of the methyl cellulose sheet where linseed oil is not coated and subsequently, said linseed oil film loses its flat shape, disintegrates and disperses in the water. Since it has been well known that linseed oil does not react chemically with methyl cellulose under normal conditions even after prolonged contact, said water-proof sheet maintains the abovementioned function for a long time. By use of said water-proof sheet in conjunction with incorporation of an alkaline material in the napkin of this invention, a quick reaction of CMC fibers of the absorbent to the alkaline aqueous solution penetrating into the absorbent which absorhs and retains menstrual fluid, in achieved as a result of disintegration of the water-proof sheet in alkaline aqueous solution.

To the contrary, in case an entirely non-watersoluble sheet such as polyethylene sheet is used as a water proof sheet to prevent permeation of menstrual fluid in the napkin, an alkaline aqueous solution produced by contact of water and the alkaline material incorporated in the napkin at its previously explained place, has difficulty reacting with CMC fibers of the absorbent by being separated from them by said waterproof sheet and thus the said water-proof sheet tends to delay dissolution-dispersion of the napkin and causes a defect that it becomes an obstacle to speedy disposal of the napkin. This defect is completely removed by use of the aforementioned water-proof sheet prepared by applying a very thin linseed oil film onto one side of a methyl cellulose sheet and therefore, the use of the water-proof sheet of said structure and function is very meaningful in that it enhances the practical value of the incorporation of alkaline material in the napkin of this invention.

FIG. 7 illustrates an actual example of a suspender napkin incorporating in the napkin an alkaline material wherein a moisture-proof bag enclosing in it an alkali source is attached to a suspender of the napkin of this invention to form a particular product. (2) is an absorbent, (7) is a suspender made of a paper reinforced by CMC, (8) is a part of the joint of the suspender, (9) is a part of a water soluble film connecting the joints of the suspender and (1 l) and (12) are the bags enclosing an alkali source illustrated in FIG. 6a.

The position where said bag is attached to said suspender may be either on the inside or on the outside of the suspender having a tubular form. (11) in FIG. 7 illustrates said bag attached to the outside of the suspender and (12) in FIG. 7 illustrates said bag attached to the inside of the suspender. In case the bag is attached to the outside of the suspender, the napkin may be used as such or with the bag taken off from the napkin. When the napkin is used with the bag attached to it, the napkin may be thrown away as such into water in a water closet bowl for its disposal. When the napkin is used with the bag taken off from it, said removed bag may be used for disposal of a used napkin, at the time of replacing the latter napkin with a new one. That is, said removed bag may be used one turn ahead i.e., said bag taken off from the napkin to be newly worn may be thrown into water in a closet bowl together with the napkin previously worn, for disposal of the latter napkin. In case the bag is attached to the inside of the suspender, the napkin may be worn with the bag attached to it and the napkin may be thrown away as such into water in a water closet bowl for its disposal. However, it is also possible that the bag attached to the inside of a suspender may be taken off from the suspender and used for disposal of a previously used napkin at the time of changing napkins.

In order for the water-soluble material binding the bag made of water-proof sheet not to dissolve by perspiration while the napkin is worn, the bag is wrapped with a water-proof film or sheet but so loosely that the binding water-soluble material may contact the water when the napkin is thrown into water.

The bag enclosing the alkaline material is attached to the said suspender with a paste.

FIG. 8 is a perspective view of an actual example of the suspender napkin with certain parts being shown in local section. A suspender (7) made of the paper reinforced by CMC impregnation has a role to place at the center, wrap and suspend the absorbent (2). The seams (8) of the suspender are joined together by watersoluble film (9) of methyl cellulose, poly-vinyl alcohol etc. It is devised so that, when the napkin is thrown into water, the water-soluble film dissolves in water and the paper of the napkin opens wide and then the absorbent dissolves-disperses outside the suspender. But in this case, it is necessary to devise so that this water-soluble film may not dissolve by perspiration of the wearer during use, by making the one side of the film water-proof or by putting in layers on the water-soluble film another water-soluble film, its one side being made water-proof, or putting on the water-soluble film a water-proof material which can be decomposed in septic tank. The location of the seam joint of the suspender with watersoluble film need not be necessarily on the rear side of the suspender but it is more convenient to locate the seam joint at the flank side of the suspender because of the location of alkali source to be incorporated. This suspender napkin is to be used by tying its both ends with a suspender belt. It is featured in that there is no fear of its split by perspiration of the wearer because the paper forming it is reinforced by CMC impregnation and also these papers do not accumulate in septic tank because CMC reinforcement loses its reinforcing function due to its swelling in the septic tank and decomposes in accordance with the decomposition of the paper by bacteria in the septic tank. It is also obvious that the absorbent dissolves-disperses in a weak alkaline solution as it is a CMC fibrous mass and therefore, even when the suspender itself does not dissolve in water, it does not cause trouble with its disposal in a water closet bowl as long as the absorbent which consists of the most part of the quantity of the napkin, dissolvesdisperses in water.

Actual example of application:

The absorbent of the napkin was prepared by making 15 grams of fibrous mass of CMC short fibers of DE 0.50 and DP 560 made from a raw material of wood pulp, into an oval form (15 cms in length, 8 ems in width and 2 cms in thickness). Then, this absorbent was wrapped by a suspender (50 cms in length and 12 cms in width) it being located at the center of the suspender. Then, a water-proof material coated thinly with linseed oil on the surface of the paper impregnated with CMC was inserted at the bottom of the absorbent to prevent leakage of menstrual fluid and outside of it (between the suspender and the water-proof material), a bag made of methyl cellulose film enclosing an alkali source consisting of 10 grams of NaHCO, and 5 grams of citric acid was placed. Thus a suspender napkin was completed. When this was thrown into water of about 2,000 cc in a water closet bowl after its actual use, the water-soluble film applied to the seam joint of the paper of the suspender dissolved at first and the suspender was split. Then, the alkali source incorporated in the suspender contacted H,O and an active reaction took place, generating a large quantity of CO, gas. Subsequently, the CMC absorbent began dissolutiondispersion and completely dispersed outside the suspender. The time required from the throw-in of the napkin to the dissolution-dispersion was about 10 seconds. It was then confirmed that, although the suspender did not dissolve-disperse, it did not cause trouble with disposal in a water closet bowl because the suspender is a soft thin paper. I

What I claim is:

l. A sanitary napkin comprising in combination a. an absorbent for menstrual fiuid comprising a mass of fibers of less than 1 cm. in length of fibrous carboxymethyl cellulose having a degree of etherification of 0.15 1.50 and an average degree of polymerization of more than 100, optionally containing less than percent by weight of chemically untreated short fibers and also optionally containing up to 30 percent by weight of alkaline carboxymethyl cellulose and b. a solid alkaline agent having a pH less than 10 at 0.1 mol concentration at room temperature, said agent being so disposed in relation to said absorbent that no menstrual fluid from said absorbent comes in contact with said alkaline agent during use of said napkin, said napkin being disposable by water flushing and being designed for easy disposal by dissolution-dispersion of said absorbent in aqueous alkaline solution when said napkin is thrown into water in a water closet bowl.

2. A sanitary napkin according to claim 1 further comprising a waterproof sheet located on the side of said napkin other than the side intended for absorption of menstrual fluid, a suspender for said napkin, and a water-breakable bag located between said waterproof sheet and said suspender on the side of said napkin other than the side intended for absorption of menstrual fluid and wherein said bag contains said alkaline agent.

3. A sanitary napkin according to claim 2 wherein said bag is made of a moisture proof material and has two open ends tightly bound by a water soluble tie material.

4. A sanitary napkin according to claim ll further comprising a waterproof sheet located within said mass of fibers and a water-breakable bag disposed within said mass of fibers on the other side of said waterproof sheet than the side where menstrual fluid is to be absorbed and retained and wherein said alkaline agent is contained in said bag.

5. A sanitary napkin according to claim 4 wherein said bag is made of a moisture proof material and has two open ends tightly bound by a water-soluble tie material.

6. A sanitary napkin according to claim 1 further comprising a waterproof sheet within said mass of tibers wherein said alkaline agent is mixed in with said fibers on the other side of said waterproof sheet than the side where menstrual fluid is to be absorbed and retained.

7. A sanitary napkin according to claim 2 wherein said suspender is made of paper reinforced by carboxymethyl cellulose and serves to wrap and suspend said absorbent and said alkaline agent in said bag.

8. A sanitary napkin according to claim ll wherein said alkaline agent is NaHCO;,.

9. A sanitary napkin comprising in combination a. an absorbent for menstrual fluid comprising a mass of fibers of less than 1 cm. in length of fibrous carboxymethyl cellulose having a degree of etherification of 0.10 1.50 and an average degree of polymerization of more than 100, optionally containing less than 70 percent by weight of chemically untreated short fibers and also optionally containing up to 30 percent by weight of alkaline carboxymethyl cellulose and b. an alkali source consisting essentially of a solid alkali carbonate and a solid acid being so disposed in relation to said absorbent that no menstrual fluid from said absorbent comes in contact with said alkali source during use of said napkin, said napkin being disposable by water flushing and being designed for easy disposal by dissolution-dispersion of said absorbent in aqueous alkaline solution when said napkin is thrown into water in a water closet bowl.

10. A sanitary napkin according to claim 9 further comprising a waterproof sheet located on the side of said napkin other than the side intended for absorption of menstrual fluid, a suspender for said napkin, and a water-breakable bag located between said waterproof sheet and said suspender on the side of said napkin other than the side intended for absorption of menstrual fluid and wherein said bag contains said alkali source.

11. A sanitary napkin according to claim 10 wherein said bag is made of a moisture proof material and has two open ends tightly bound by a water-soluble tie material.

12. A sanitary napkin according to claim ill wherein the middle portion of said bag is bound with a water soluble tie material to form two sections, the first section containing said alkali carbonate and the second section containing said acid.

13. A sanitary napkin according to claim 9 further comprising a waterproof sheet located on the side of said napkin other than the side intended for absorption of menstrual fluid, a suspender for said napkin and two water-breakable bags located between said waterproof sheet and said suspender on the side of said napkin other than the side intended for absorption of men strual fluid and wherein one bag contains said alkali carbonate and the second bag contains said acid.

14. A sanitary napkin according; to claim 13 wherein each of said bags is made of a moisture proof material and has two open ends tightly bound by a water-soluble tie material.

l5. A sanitary napkin according to claim 9 further comprising a waterproof sheet located within said mass of fibers and a water-breakable bag disposed within said mass of fibers on the other side of said waterproof sheet than the side where menstrual fluid is to be absorbed and retained, wherein said alkali source is contained in said bag.

16. A sanitary napkin according; to claim 15 wherein said bag is made of a moisture pnoof material and has two open ends tightly bound by a water soluble tie material.

17. A sanitary napkin according to claim 16 wherein the middle portion of said bag is bound with a watersoluble tie material to form two sections, the first sec tion containing said alkali carbonate and the second section containing said acid.

18. A sanitary napkin according to claim 9 further comprising a waterproof sheet located within said mass of fibers and two water-breakable bags disposed within said mass of fibers on the other side of said waterproof sheet than the side where menstrual fluid is to be absorbed and retained, wherein said alkaline carbonate is contained in one bag and said acid is contained in the second bag.

19. A sanitary napkin according to claim 18 wherein each of said bags is made of a moisture proof material and has two open ends tightly bound by a water-soluble tie material.

20. A sanitary napkin according to claim 9 further comprising a waterproof sheet within said mass of f1- bers wherein said alkali source is mixed in with said fibers on the other side of said waterproof sheet than the side where menstrual fluid is to be absorbed and retained.

21. A sanitary napkin according to claim 12 wherein said bag is attached to said suspender by means of a binding material.

22. A sanitary napkin according to claim 10 wherein said suspender is made of paper reinforced by carboxymethyl cellulose and serves to wrap and suspend said absorbent and said alkali source in said bag.

acid.

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US5080657 *Dec 1, 1989Jan 14, 1992Korea Research Institute Of Chemical TechnologyAlginic
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Classifications
U.S. Classification604/359, 604/365, 604/376, 604/364
International ClassificationA61F13/15, A61L15/28
Cooperative ClassificationA61F2013/530145, A61F2013/51409, A61F2013/530131, A61F2013/15227, A61F13/15211, A61L15/28
European ClassificationA61L15/28, A61F13/15J2