CA1149380A - Alloy fibers of rayon and an alkali metal or ammonium salt of a copolymer of polyacrylic acid and methacrylic acid having improved absorbency - Google Patents

Abstract

Abstract of the Disclosure Cardable cellulosic fibers having improved water and fluid absorbency are made by incorporating therein an alkali metal or ammonium salt of a copolymer of acrylic acid and methacrylic acid prepared by a process wherein the two monomers are mixed together in ratios during the polymerization so that the amount of copolymer chains sub-stantially richer in methacrylic acid moieties than the total ratio of acrylic acid and methacrylic acid monomers included in the copolymerization process and the number of copolymer chains considerably lower in degree of polymeriza-tion than the copolymer average are minimized. These fibers are useful in the production of absorbent nonwoven articles such as diapers, tampons, sanitary napkins, medical sponges, soil mulches, wiping cloths, and the like.

Description

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This application is related to U.S. Patent No.
4,066,584, issued January 3, 1978, inventors Thomas C.
Allen and David B. Denning, and is concerned with highly absorbent fibers, for example, viscose rayon, hydroxy-propylcellulose, and hydroxyethylcellulose, made from wood pulp or other cellulosic materials, which are useful in the production of absorbent nonwoven articles such as diapers, tampons, sanitary napkins, medical sponges, soil mulches, wiping cloths, and the like. ~ach of these articles requires a material having a high capacity for absorbing and retaining water and other aqueous fluids, particularly, body fluids. As disclosed in U.S. 4,066,584, cellulosic fibers have found wide use in these and similar applications because of the hydrophilic nature of the cellulose molecule and its fibrous structure which contributes integrity, form, shape, wicking ability, and liquid retention to a nonwoven material.
It has been disclosed before, for example in U.S.
Patent No. 3,844,287, issued October 20, 1974, inventor Frederick R. Smith, that the incorporation of metal salts and ammonium salts of polyacrylic acid in regenerated cellu-lose fibers increases the fluid absorbency of the fibers over that of fibers produced from the same viscose solution but without the salts of the alloying polymer. Other examples of hydrophilic polymers incorporated into viscose to in-crease the hydrophilic properties of the fiber are carboxy-methylcellulose and carboxyethyl starch as described in U.S. Patents No. 3,423,167, issued January 21, 1969, inventor Joseph M. Kuzmak, and No. 3,847,636, issued November 12, 1974, inventor Frederick R. Smith, respectively.
U.S. 4,066,584 discloses that fibers containing copolymers of acrylic acid and methacrylic acid have certain advantages over the various homopolymers described above.

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These advantages are probably realized by the fact that the various comonomers offer a variety of properties necessary for the complex requirements necessary for the commercial utilization of a highly absorbent fiber in sophisticated formed products for a specific end use. For example, in the parent application, it is believed that the methacrylic acid units impart stiffness to the polymer chain, resulting in the observed improved absorbency and fiber processing due to increased fiber cohesion properties.
It is an object of this invention to improve the fluid absorbency of r~yon fibers.
Another object of the invention is to provide a process for making rayon fibers of improved absorbency which can be carded and otherwise processed on available apparatus and are adapted for making the absorbent articles listed above.
Another object of this invention is to provide a highly absorbent cellulosic fiber having incorporated into the cellulosic structure an alkali metal or ammonium salt of an azeotropic copolymer of acrylic acid and meth-acrylic acid.
Still another object of this invention relates to an article of manufacture comprising highly absorbent fibers comprising a matrix of regenerated cellulose and an alkali metal or ammonium salt of an azeotropic copolymer of acrylic acid and methacrylic acid.
The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a process for making rayon fibers containing as an alloying material a copolymer of acrylic acid and meth-acrylic acid which has been prepared by a copolymerizing process wherein the addition of the two monomers is con-9~

trolled so that the amount of copolymer chains which aresubstantially richer in methacrylic acid moieties than the total ratio of acrylic acid and methacrylic acid monomers included in the copolymerization process and the number of copolymer chains considerably lower in degree of polymeri-zation than the copolymer average are minimized.
For example, if a 50/50 copolymer of acrylic acid and methacrylic acid is included in the rayon fiber, the copolymer is prepared by a process wher~in the amount of each monomer at the beginning of the polymerization and the addition of more of each monomer to the polymerizing mixture are controlled so that the ratio of the acrylic acid and methacrylic acid moieties is substantially the same as the total ratio of acrylic acid and methacrylic acid monomers included in the copolymerization process. Various methods for copolymerizing acrylic acid and methacrylic acid to make the copolymer contemplated for use in practicing the invention described in U.S. 4,066,584 are described in that U.S. Patent. One of these methods involves controlled mono-mer addition. My continued research has now established thatcopolymers produced in this way when included in rayon fibers especially at higher concentrations, i.e. from about 10 to 40 percent CIV, improve the fluid absorbing of the fiber more per unit weight of copolymer than copolymers of acrylic and methacrylic acids produced by adding all of the comonomers at the beginning of the copolymerization process. As dis-closed in U.S. 4,066,584, 50/50 acrylic acid-methacrylic acid copolymers are preferred but copolymers prepared in ratios of from 90 mole acrylic acid and 10 mole methacrylic acid to ratios of 10 mole acrylic acid to 90 mole methacrylic acid may be used as alloying materials in practicing the invention provided the monomer addition is controlled so that the ratio 9;3~3~

of the acrylic acid and methacrylic acid moieties in sub-stantially all of the copolymer chains is substantially the same as the total ratio of acrylic acid and methacrylic acid monomers included in the copolymerization process.
It has now been found that when using copolymers of acrylic acid and methacrylic acid made by adding all of the monomers at the beginning of the copolymerization process, the increase in absorbency obtained by adding more copolymer to the fiber levels off at a certain p~int. This point will vary with the ratio of acrylic acid to methacrylic acid and with the molecular weight of the copolymer.
It is well known in basic copolymerization theory that due to different rates of reactivity of the different comonomers with either of the terminal free radical species, the comonomers will not enter the copolymer chains in the same ratio as their molar composition in the monomer mixture.
Therefore, the 50~50 by weight copolymer of acrylic acid and methacrylic acid in Example 3 of U.S. 4,066,584 may have the equal amount weightwise of the two comonomers averaged among all the copolymer chains, but the individual chains will vary greatly in regard to monomer composition.
The exact accepted method of variation can be calculated from known equations. The data necessary for such calculations are the molar fractions of the two mono-mers and their reactivity ratios. The reactivity ratios can be found in the literature for a number of monomer combina-tions. These values were determined experimentally, but sinGe the acrylic acid-methacrylic acid combination is not common, the reactivity ratios were estimated from the Price-Alfrey Q and e parameters. Table I shows a computer programoutput of instantaneous concentrations of acrylic acid in the feed and the copolymer for the system of 50/50 weight~

weight of acrylic acid and methacrylic acid. Note that only 40 molar percent of the copolymer chains contain between 60~40 and 40/60 weight percent of acrylic to meth-acrylic acid, a reasonable bracket for the desired 50~50 ratio. In the second part of Table I it is seen that start-ing with a 65/35 weight ratio of acrylic to methacrylic acid produces roughly a 50/50 weight ratio of the two monomers up until about 40 percent weight cohesion. Past this point, the methacrylic acid monomer has been d,epleted so that the chains now become increasingly richer in acrylic acid.
As shown in Table I, the methacrylic acid moieties tend to enter the chains faster than the acrylic acid moieties so that the ratio of acrylic acid to methacrylic acid in the monomer supply tends to drift in favor of acrylic acid.
There are several possible ways to control the monomer addi-tion so that the amounts of acrylic acid to methacrylic acid in the monomer supply stays at the desired ratio. The pre-ferred method is to begin the polymerization with a monomer supply richer in acrylic acid so that the ratio of the two monomers is greater than that desired in the copolymer. The withheld methacrylic acid is then added later in the poly-merization to compensate for the drift in favor of acrylic acid in the monomer feed. The exact procedure for control-ling the monomer addition must be worked out by experiment by one skilled in the art depending on the time and temperature of polymerization, the initiator type and amount, and the particular equipment used in the polymerization process.
However, a starting point can be obtained by using basic copolymerization theory. For example, as shown in Table IB, a 65/35 weight ratio of acrylic acid to methacrylic acid produces an approximate 50/50 weight ratio of the two mono-mers in the copolymer until the drift in monomer composition 3~

changes the ratio. Therefore, in order to obtain an approxi-mate 50/50 weight ratio copolymer of acrylic acid and meth-acrylic acid among all polymer ehains, an initial charge of 65~35 weight ratios of monomer can be made. After the polymerization is 25 to 35 percent complete, the monomer ratio is then adjusted baek from about 70~30 to the 65~35 ratio. After about 50 and 75 percent conversion of monomer to polymer, further adjustments back to the 65h 5 ratio are made.
Another property of polymers that is an average among all polymer chains and will usually vary greatly is degree of polymerization (D.P.). It has been found that the same factors that tend to cause wide variations in monomer unit composition among the copolymer chains also causes wide variations in the degree of polymerization among the eo-polymer ehains. It is believed that eontrolling the monomer addition during the polymerization process also gives a more narrow distribution of degree of polymerization among polymer ehains. Lower moleeular weight polymer ehains not only tend to come out of the fiber more in the spinbath and fiber puri-fieation process, causing pollution and economy efficiency problems, and in actual use such as in a tampon in the human body, eausing possible tissue irritation, but there is also evidenee that lower D.P. moleeular polymer chains cause lower absorbency when the fiber is in tampon form. Increas-ing the average degree of polymerization greatly will decrease the amount of lower D.P. material but a significant increase in viscosity will result. Although there is no known upper limit to the degree of polymerization of polymer ehains in regard to this invention, the viscosity may be too high for praetieal handling of the polymer in regard to pumping for injection into the viscose and transfer from the polymeriza-a tion vessel. It is believed that controlling the monomeraddition in the copolymerizatio~ of acrylic and methacrylic acid also reduces the amount of lower molecular weight material, giving added benefits in regard to economy, toxicology, pollution, and absorbency.

TABLE I

INSTANTANEOUS COMPOSITION OF ACRYLIC
ACID IN COMONOMER FEED AND COPOLYMER

FROM V.E. MAYER AND R.K.S. CHAN, POLYMER
PREPRINTS 8 (1), 209-215, AMERICAN CHEMICAL
SOCIETY, 1967.

A. 50/50 WEIGHT/WEIGHT ACRYLIC ACID AND METHACRYLIC ACID
Ml= Acrylic acid M2= Methacrylic acid rl= 0.448 r2= 2.20 ~Ml]= 0.554= Molar Frac- [M2]= 0.456 tion of Ml WEIGHT CONVERSION Ml/M2 IN COPOLYMER Ml/M2 IN MONOMER FEED
(percent) (weiqht percent) (weiqht percent) 0 32/68 50~50 9 35/65 53~47 34 40/60 58~42 47 45/55 63~37 56 50/50 67~33 71 60/40 75~25 78 70~30 80~20 83 75/25 84~16 80~20 86~14 TABLE I (CON T) B. 65~35 WEIGHT/WEIGHT ACRYLIC ACID AND METHACRYLIC ACID
Ml= Acrylic acid M2= Methacrylic acid rl= 0.448 r2= 2.20 [Ml]= 0.69 [M2]= 0-31 WEIGHT CONVERSION Ml/M2 IN COPOLYMER Ml~M2 IN MONOMER FEED
(percent) (weiqht percent) (weiqht percent) 0 47~53 65~35 49 48~52 ' 66~34 14 51~49 68~32 55~45 72~28 44 61~39 75~25 53 65~35 78~22 61 69~31 80~20 71 76~24 85~15 78 81~19 88~12 82 84/16 90~10 89 90~10 92~8 94 94~6 94~6 The fibers of the invention can be prepared by adding, at any stage of viscose aging, but preferably by injecting into a fully ripened viscose solution, any suit-able amount of the contemplated copolymer but preferably by injecting from about 2% to about 40% by weight of the co-polymer into the viscose solution, based on the weight of cellulose in the viscose solution (hereinafter all percent-ages are given on this basis and referred to as CIV). A range of 10-20% CIV is preferred, based on a balance between in-creasing absorbency, economic factors, and processing con-ditions. The viscose solution containing the copolymer is spun or extruded through spinneret openings into an acid ~ 8 ~

38~3 bath where the cellulose fiber is regenerated. The regenerat-ed fiber is stretched in air from O-100~/o~ or even higher, if desired, preferably from about 30 to 50/O and then run through a hot aqueous bath which can be maintained at a temperature of from ambient to 100C, preferably from 90C
to 97C. The hot aqueous bath may contain various amounts of dilute sulfuric acid, sodium sulfate, and zinc sulfate.
The fiber is subjected to a second stretching of from 0 to 100~/o in the hot bath. The total stret~h in both steps is preferably in the range of 50-70%. The stretching, as is well known, imparts the necessary strength to the finished fiber. The fibers, now a large bundle of continuous fila-ments or tow, from the combined output of a number of spinnerets is cut into short fibers of any desired length and washed and dried to a moisture content of around 11%
and baled.
After the fiber is regenerated, the copolymer occluded in the fiber will be in acid form. The copolymer must be in the form of the alkali metal or ammonium salt in order to achieve the highest degree of absorbency. The copolymer of acrylic acid and methacrylic acid may be con-verted to the salt form during an alkaline sodium sulfide wash bath which is conventionally used to remove metal and sulfur impurities. In some instances, it may be desirable, particularly, if an acid wash follows the sulfide, to treat the fiber with a base such as a dilute solution of sodium bicarbonate, sodium hydroxide, and the like, to complete the conversion, and insure that a high percentage of the co-polymer is in the salt form. It may be necessary to limit the amount of conversion to the salt form for certain appli-cations where the material may come into contact with the body, since a pH which is much higher than 7 to 7.5 can cause 3~C~

irritation of delicate membranes and serves to promote the growth of harmful microorganisms. Finally, a conventional finish, such as a surfactant, may be applied and the staple fiber may be dried in a continuous drier to a predetermined moisture content suited to the particular end use of the fiber.
The dried fiber may be baled or carded for process-ing into one of the final products mentioned previously. A
particularly suitable use for the fiber~of the invention is for tampons, which may be made, for example, by one of the methods referred to in U.S. Patent ~o. 3,699,965, issued October 24, 1972, inventor Zdenek Denny Dostal, or by other well-known methods.
The copolymers of the invention may be prepared by any method which will produce a uniform arrangement of the monomer moieties among the polymer chains as contemplated by this invention. For example, copolymers may be prepared by adding the proper weight ratio of the two monomers to a water solution at the beginning of the polymerization. As discussed above, due to different rates of polymerization among mono-mers, two different comonomers will not enter a growing polymer chain in equal amounts. Therefore, the 50~50 co-polymer of acrylic acid and methacrylic acid may have an equal amount weightwise of the two comonomers averaged among all the copolymer chains, but the individual copolymer chains will vary greatly in regard to monomer composition. The in-dividual chains may vary in composition from a range of very rich in methacrylic acid to very rich in acrylic acid. It might be thought that acrylic acid will be depleted from a monomer mixture at a faster rate than methacrylic acid since the rate of polymerization of acrylates is generally about ten times greater than that of the methacrylates. However, 3B~
in copo]ymerization the rate of polymerization is not the controlling factor in determining how a monomer will enter a growing polymer chain. For this reason, it is necessary to maintain a proper ratio of monomers throughout the poly-merization. It has been found that in copolymerization of acrylic acid and methacrylic acid, both the acrylic acid moieties and the methacrylic acid moieties tend to polymerize with methacrylic acid moieties in preference to acrylic acid moieties. Hence, there is a tendency f~or that part of the chain first formed to contain a preponderance of methacrylic moieties leaving excess acrylic acid moieties for polymeriza-tion at the terminal end of the chain. This may be avoided by withholding some of the methacrylic acid until near the end of the polymerization so it will not be used up too early in the polymerization.
The absorbency of the fibers can be determined by various test methods. One common measure of absorbency is the Water Retention Value or Secondary Swelling ("Q") which is determined in the following manner.
After soaking 2 to 3 g. of previously washed and dried rayon fiber in water, the excess water is removed by centrifuging at a force of 2500 to 3500 times gravity for 15 minutes in stainless steel sample holders. These holders are 22 mm. I.D. x 25 mm. deep, with screw caps to cover both ends. Space is provided in the centrifuge cup below the sample holder to contain the excess water which is removed from the yarn during centrifuging. The extracted fiber is placed in a preweighed weighing bottle the weight of the swollen fiber is obtained and, after drying overnight at 105C., the weight of the dry fiber is obtained. The per-cent swelling is then determined by use of the following equation.

Q = Swollen weiaht - dry wei~ht x 100 dry weight U.S. Patent 3,670,069, issued June 13, 1972, inventor Reid L. Mitchell, column 6, details a prior art procedure for making this determination. Briefly, the test measures the amount of water retained by the fiber after centrifuging for 15 minutes at 2500-3000 times gravity from which the per-centage of water retained in the sample is calculated (based on dry weight by the fiber sample). A more recent test which correlates well with actual end use evaluations has been developed. As disclosed in U.S. 4,066,584, the so-called Demand Wettability Test (Lichstein, Bernard, International Nonwovens and Disposables Association, 2nd Annual Symposium on Non-Woven Product Development, March 5-6, 1974, Washington, D.C.), uses a novel apparatus which allows the measure of volume and rate of absorption of a fluid by m~intaining the absorbent material at a zero hydrostatic head so that wetting occurs purely on demand by the absorbent material. Thus, the absorption of liquid occurs only by virtue of the ability of the absorbent material to imbibe liquid with the flow of liquid abruptly stopping at the point of saturation. Varia-tions in the method can be made to allow for end product simulation, e.g., the fibrous mass can be compressed to simulate a tampon. Testing of the compressed fiber can then be conducted on the apparatus using a variety of external pressures and testing fluids. A third method which involves actual formation of tampons is described by GoW~ Rapp in a paper "A Comparison of The Absorptive Efficiency of the Commercial Tampons" published June 1958, by the Department of Research, Loyola University, Chicago, Illinois and in the parent application.
In order to describe the invention in greater detail, ~1 ~, lqj~
embodiments thereof are described in the following examples:
EXAMPLE I
A. A solution of a 50/50 copolymer of acrylic acid and methacrylic acid wherein substantially all copolymer chains contain substantially equal amounts of acrylic acid and methacrylic acid moieties is partially neutralized with sodium hydroxide to a pH of about 5.2 and injected into a viscose solution at a concentration of about 15% CIV, thoroughly mixed with the viscose and spun into a conventional acid spinbath containing about 5% sulfuric acid, about 20%
sodium sulfate, about 1% zinc sulfate and about 25 ppm lauryl pyridinium chloride at 56-58C. to coagulate and regenerate the cellulose to give a 22 ~488 denier fiber tow containing 7 ~496 filaments. The resulting tow is stretched 40% in air, run through a second bath at 92-97C. containing 3.2% sulfuric acid and about 6.15% total salts (~aS04 +
ZnS04) and stretched 18% in the bath. The tow is then cut - into 1-9/16" staple fiber lengths. The staple is washed with water, then with 0.30/0 sodium sulfide solution, followed 20 with water, then with a 0.175% sulfuric acid solution, followed with water, and then followed by a 0.2C% sodium bicarbonate wash. A finish solution consisting of 0.30%
aqueous solution of ethoxylated sorbitan monolaurate is applied before the fibers are dried for about 1/2 hour in a continuous oven set at about 80C. ~ for about 1/2 hour at about 70C. ~ and for about another 1/2 hour at about 50C ~ The final moisture content is about 11%.
B. The process of Example IA is repeated to prepare a fiber containing a 50/50 copolymer of acrylic acid and methacrylic acid wherein the ratio of acrylic acid and methacrylic acid moieties among the copolymer chains varies widely from the average 50/50 weight ratio as predicated ~ 13 ~

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in Table IA. Samples of fibers produced by the process of Examples IA and IB were transmitted to an established tampon which performed its usual syngyna absorbency tests and reported the results back. These results were obtained with a test liquid of 60 parts by volume of human blood and 40 parts by volume water and are shown in Table II.
TABLE II

Brookfield Viscosity Syngyna of Copolymer Fiber pH Absorbéncy (Spindle ~water) (g/g) No. 2) Example IA 8.0 6.2 2900 Example IB 7.7 5.6 95 EXAMPL_ II
Example IA is repeated with a 50/50 by weight co-polymer produced by withholding a portion of methacrylic acid from the initial monomer charge and adding the withheld methacrylic acid incrementally throughout the polymerization process. This polymerization procedure produces a copolymer with the monomer moieties distriDuted as in Example IA. The fiber is carded into a fiber pad, from which discs are made by compressing and heating one gram of ~hese fibers in a one-inch diameter tube. Samples of these discs were tested in the Demand Wettability Test using about 0.2 psi external weight and a 1% sodium chloride solution as the test fluid. The results of this evaluation are shown in Table III.

EXAMPLE III
Example IB is repeated with a 50/50 by weight co-polymer produced by adding all of the monomers at the begin-ning of the polymerization. This polymerization procedure produces a copolymer with the monomer moieties distributed as in Example IB~ The fiber is then carded, compressed, and 3~3~
evaluated for absorbency as in Example II. The results of this evaluation are shown in Table III.
EXAMPLE IV
The copolymer from Example III is air-dried to remove the water, extracted at ambient temperature with methyl alcohol to remove polymer chains very rich in meth-acrylic acid and of lower degree of polymerization. The extracted copolymer is then redissolved in water and in-corporated into fiber as in Example IA. The fiber is then carded, compressed, and evaluated for absorbency as in Example II. The results of this evaluation are shown in Table III.
TABLE III

Brookfield Demand Viscosity Fiber pH Wettability (Spindle ~o.2) (water) (g/g) (cps) Example II 7.3 6.6 1900 Example III 7.4 5.9 1925 Example IV 7.4 6.4 290 EXAMPLE V
Example II is repeated except on a larger scale staple fiber machine. The fibers are then sent to the tampon manufacturer and tested for absorbency as in Example IA. The results of this evaluation are shown in Table IV.

EXAMPLE VI
Example III is repeated except on a larger scale staple fiber machine. The fibers are tested as in Example V. The results of this evaluation are shown in Table IV.

EXAMPLE VII
Example VI is repeated except that a homopolymer of acrylic acid is used in place of a copolymer of acrylic acid and methacrylic acid. The results of this evaluation e9~380 are shown in Table IV.
EXAMPLE VIII
Example VI is repeated except that a 65/35 by weight copolymer of acrylic acid and methacrylic acid was substituted for the 50/50 copo]ymer. The copolymer of this example was made by the contlnuous addition of the monomer mixture through-out the polymerization process. The results oE this evaluation are shown in Table IV.

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!~Q ~

~ ) cq r~l t~) ~ d' s~ ~ a) Ln o~ O OD

,:' O ~ ~ ~5) O O LO
~t '14 1` OD t~ C~) O O ~:
O rl ~ CS`\ ~1 0 O~) .,1 ~ .n W In In U~
, ~ ~ LO
s-, a) . . . .
OD
~, ~5 H HH
~q H H H
s~
~ ~1 P~ ~

3~3E3~) The copolymer contemplated by the invention is an azeotropic copolymer of acrylic acid and methacrylic acid of the kind described in "Encyclopedia of Polymer Science and Technology", Volume 4, pages 165 and 166, published by John Wiley & Sons, Inc., New York, New York, in 1965.
Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A highly absorbent cellulosic fiber having incorporated into the cellulosic structure an alkali metal or ammonium salt of an azeotropic copolymer of acrylic acid and methacrylic acid, wherein the ratio of the salt of acrylic acid to the salt of methacrylic acid is from about 10:90 to about 90:10 by weight.

2. The fiber of claim 1 wherein the cellulosic fiber is regenerated from a viscose solution and the copolymer is incorporated into the viscose solution in an amount ranging from about 2 to about 30% by weight based on the weight of cellulose in the viscose solution.

3. The fiber of claim 2 wherein the weight ratio is about 50:50.

4. An absorbent, non-woven article of manufacture comprising highly absorbent fibers comprising a matrix of regenerated cellulose and an alkali metal or ammonium salt of an azeotropic copolymer of acrylic acid and methacrylic acid, wherein the weight ratio of the salt of acrylic acid to the salt of methacrylic acid ranges from 10:90 to 90:10.

5. The article of claim 4 wherein the cellulose is regenerated from a viscose solution and the copolymer is incorporated into the regenerated cellulose in an amount ranging from about 2 to about 30 by weight, based on the weight of cellulose in the viscose solution.

6. The article of claim 5 wherein the weight ratio is about 50:50.

7. The article of claim 6 in the form of a tampon.