GB2040955A - Rayon Fibers Containing Starch - Google Patents

Abstract

Rayon fibers are made by spinning a viscose containing dissolved starch. Starch grains may be slurried in water, then made alkaline with NaOH to form a solution which is then added to viscose.

Description

SPECIFICATION Rayon Fibers Containing Starch This invention relates to rayon fibers containing from about 5% to about 100% of starch b.o.c.

("b.o.c." is used herein as an abbreviation for: based on the weight of the cellulose). Preferably, the proportion of starch is below about 60% b.o.c., such as about 5 to 25% b.o.c.

According to the invention, starch-containing rayon fibers are prepared by forming a slurry of starch granules in an aqueous medium, adding sodium hydroxide to the solution, the NaOH concentration in the solution being preferably higher than about 2% and less than about 4-1/2%, based on the total weight of water and NaOH. In such a solution, the proportion of starch may be, for instance, in the range of about 6 to 20% (based on the total weight of the solution). The solution is blended with viscose in such an amount that the proportion of starch is about 5100% b.o.c., the starch containing viscose is extruded in fiber form, and the cellulose in the viscose is regenerated to form the fibers. The starch has an amylopectin content of at least 60% and preferably is corn starch.

By using appropriate proportions within the ranges indicated above, one forms a viscous, but ungelatinized, starch solution having a ball fall viscosity usually less than about 200 seconds, preferably less than 1 50 seconds, e.g., in the range of about 30 to 100 seconds. This is very suitable for incorporation into a viscose solution, e.g., by injection into the viscose solution just before spinning.

or by addition to the "viscose mixer" or other zone in which the viscose is "aged" before spinning.

To determine the optimum concentration of alkali for forming the starch solutions, the following experiment (hereinafter termed the "microscope method") was carried out, using a microscope fitted with polarizer and analyzer: (a) place grains of starch (between 50 and 100 grains), as received, on a plain glass microscope slide; (b) cover the starch with a cover glass; (c) place the slide on the microscope stage; (d) focus the microscope and adjust the polarizing means to show the Maltese Cross characteristic of natural starch grains; (e) by means of a medicine dropper, and while observing the grains through the microscope, introduce aqueous alkali solution of different NaOH i concentrations (1-1/2, 2, 2-1/2. 3. 3-li2, 4,4-1/2, 5,5-1/2 6%) to the space around the starch grains; (f) record observations as to swelling, disappearance of the Maltese Cross and the disappearance of grain boundaries. Concentrations of NaOH in water up to six percent were used in tests on corn starch.

With grains of ordinary corn starch, it was found that the Maltese Cross disappeared in all concentrations of alkali used; the rate of swelling and of the disappearance of the Maltese Cross was very rapid, almost identical with the rate of wetting of the grains; even though the grains swelled, and the Maltese Cross disappeared, the outline of swollen grains was discernible at or below 2% NaOH and at or above 4-1/2% NaOH; but in the range of from 2-1/2% to 4%, no grain boundaries were visible.

The invention yields starch solutions, as well as starch-viscose mixtures, of very good filterability.

By slurrying the starch granules in the aqueous medium, before the NaOH is mixed with the starch, one insures against formation of gels or lumps in the starch solution. The starch solutions produced in this way may contain air bubbles; when the bubbles are removed (as by vacuum deaeration), the solution is translucent.

The aqueous medium in which the granules are slurried may be ordinary tap water, or water containing small amounts of alkali (e.g., 0.01 N NaOH solution) or acid, or other ingredient. The preferred type of slurrying medium is one which has substdntially no effect on the integrity of the grains, and in which the grains have substantially no tendency to clump together (which clumping tendency could be due, for instance, to induced surface tackiness of the grains).

The aqueous slurrying medium may contain ingredients which reduce the molecular weight of one or both of the polymeric components (amylose and amylopectin) of the starch. For instance, one may include hydrogen peroxide (H2O2) (which may be present in very small amounts, such as 0.01 and 0.05% H202 based on the weight of water). The H202 is relatively inactive in the slurry but, when the mixture is made alkaline, it acts quite rapidly to decrease the molecular weight of the starch polymer. It.

has been found that this makes it possible to prepare starch solutions which have higher concentrations of starch, e.g., above 14% such about 18% or more, but are still readily pumpable and otherwise processable, having ball fall viscosities of below 200 (which is about 225 poises at 1 80C.

and preferably below 1 50 (about 1 70 poises), e.g., in the range of about 30-100 (about 35-11 10 poises)). The degree to which the molecular weight reduction (e.g., chain scission) is carried out may be readily controlled by the concentration of chain-splitting agent. The reduction of molecular weight can be effected in other ways, such as by storing the alkaline solution under conditions in which atmospheric oxygen acts on it, or by including NaOCI instead of H202 in the slurry. The use of the higher starch concentrations makes for economy of operation in that the amount of water in the viscose-starch blend is reduced and the polymer: NaOH ratio is also more economical. Fibers of very good properties are obtained with the "degraded" starch solutions.

The formation of the starch solutions used herein (with or without molecular weight reduction) may be carried out readily without heating (e.g., at temperature well below 350C.) and, therefore, without the need for cooling before mixing with the viscose. In the starch solutions, the number of moles of NaOH per anhydroglucose unit of the starch is at least about 0.5, such as about 1.

According to a preferred feature of this invention, the viscose is spun under conditions effecting a substantial orientation of the cellulose molecules, i.e., the fiber, while in a plastic state, is stretched by fifty percent (50%) or more to form fibers having a conditioned tenacity of at least about 2 grams per denier, such as 2.5 grams per denier or more.The stretching is preferably effected, after the fibers have been initially coagulated into a plastic condition, in a hot aqueous stretch bath, containing preferably well below 5% H2SO4 (e.g., about 3% H2SO4), at a temperature above 700C., such as 90-1 000C. The initial coagulation may be effected,for example, by spinning into an acidic aqueous spin bath containing about 6-13% H2SO4, about 12-25% Na2SO4 and about 0.5-5% ZnSO4, According to another preferred feature of this invention, polymeric additives which markedly increase the fluid-holding capacity of the fibers may be dispersed in the starch-containing viscose.

Examples of such materials are anionic polymers, such as polymeric acids or salts (e.g., alkali metal salts) thereof, e.g., salts of carboxyalkyl celluloses (such as sodium carboxymethyl or carboxyethyl cellulose), salts of polyacrylic acids, (including polyacryic acid or polymethacrylic acid homopolymer, or copolymers of acrylic and/or methacrylic acid with one or more other monomers such as acrylamide or alkyl acrylates, e.g., ethyl acrylate), salts of copolymers of maleic or itaconic acid with other monomers such as methyl vinyl ether, or naturaily occurring polycarboxylic polymers, such as algin.Before their addition to the viscose, these materials are preferably dissolved in aqueous medium preferably forming an alkaline solution, e.g., they may be made with an amount of alkali, such as NaOH, stoichiometrically equivalent to the amount of acidic (e.g., carboxyl) groups of the polymer or with an excess of alkali.

Less desirably, these materials may be added in acid form (again preferably as aqueous solutions) and be converted to salt form by the action of the alkali present in the viscose. In a preferred form of the invention, the starch is incorporated into the viscose before (or during) the aging of the viscose (e.g., in the viscose "mixer") and the solution of anionic polymer is injected into the starch-containing viscose just before spinning. It is also within the broader scope of the invention to add an alkaline solution containing both the starch and anionic polymer, preferably by injecting it into the viscose just before spinning, or to separately (consecutively with either one first, or simultaneously) inject an alkaline starch solution and an anionic polymer solution into the viscose.The anionic polymers preferably have at least 0.2 (and preferably above about 0.5) gram equivalent of salt-forming anionic groups per 1 0Q grams of such polymer, for instance in sodium polyacrylate there is, ideally, one gram equivalent of -COONa per 94 grams (94 is the molecular weight of sodium acrylate). Examples of specific anionic polymers which may be used and descriptions of the uses of the resulting fibers are given in U.S. patent numbers 3,187,747; 3,844,287; 3,847,636 and 3,919,385. The same materials may be employed in the starch-containing fibers, and the resulting fibers containing cellulose, starch and anionic polymer may be used for the same purposes as described in those patents. The fibers containing anionic polymer are preferably finished so that they are distinctly alkaline, as described, for instance, in U.S.

patent no. 3,844,287.

To improve the fluid holding capacity of the starch-containing fibers polyvinylpyrrolidone (PVP) may also be included therein instead of, or together with, the anionic polymer (e.g., in an approximate ratio of PVP: anionic polymer of 10:90, 20:80, 30:70, 50:50, 70:30 or 80:20). The PVP preferably has a high molecular weight, such as well above 10,000. Very good results have been attained with PVP of average molecular weight ranging from 100,000 to 400,000 and, more desirably, from 160,000 to 360.000, and a preferred K-value of from 50 to 1 00.The procedure for determining the K-value of such polymers is disclosed in Modern Plastics,1945, No. 3, starting on Page 1 57. PVP is described in the Encyclopedia of Polymer Science and Technology, published in 1 971 by John Wiley 8 Sons, in the article on "N-Vinyl Amide Polymers" in Volume 14 pages 239-251. In place of all or part of the PVP one may use one or more other N-vinyl amide polymers, e.g., N-vinyl lactam polymers, N-vinyl-2oxazolidinone polymers or N-vinyl-3-morpholinone polymers, such as the polymers (including copolymers) listed in U.S. patent no. 2,931,694.

The proportion of anionic polymer and/or PVP included in the starch-containing viscose should be such as to impart improved fluid holding capacity to the rayon. Preferably it is such as to produce fibers whose fluid holding capacity (as measured by the "Syngyna" method as described in Example VI below) is at least 5 cc per gram, more preferably at least 5.5 cc. per gram. In general, the total proportion of added polymer is within the range of about 6 to 40% b.o.c. and more desirably in the range of about 10 or 20 to 35%, b.o.c. Higher proportions, e.g., about 50 to 70% b.o.c. may also be used. Expressed in terms of the total of cellulose, starch and added polymer (hereinafter termed "the total") the proportion of added polymer is generally in the range of about 7 to 30%, although higher proportions may be employed.

The process of this invention gives outstanding "yields" of fiber. For instance, in one extended run, the weight of fiber (calculated on a dry basis) obtained was over 99% of the total weight of cellulose, starch and TiO2 used to make the spinning solution; the analytically determined starch content (b.o.c.) of these fibers was substantially the same as the proportion of starch included in the spinning solution.

The starch-containing rayon fibers produced in accordance with this invention are suitable for a great many uses. Fabrics made entirely therefrom have been found to be capable of being washed repeatedly (e.g., 50 washes with household detergent in an automatic washing machine, using standard laundering conditions). The effects of such washing have been found not to differ significantly from those with ordinary rayon. Under the light microscope, the starch-containing fibers appear to be of a homogeneous chemical nature; e.g., on iodine staining (indicating the presence of starch), the staining is found to be uniform throughout the cross-section of the fiber. With ordinary rayon dyes, the starch-containing fibers dye well, usually more intensely than ordinary rayon and with more substantivity, thus requiring less dyestuff to attain a given desired change.Moisture regain (measured at 240 C. and fifty-eight percent relative humidity) is, for fibers containing about ten percent starch (b.o.c.), in the range of about eleven to twelve percent (ordinary rayon is usually within the same range).

The fibers are resistant to removal of the starch. For instance, when a mass of the fibers (of 10% starch content b.o.c.) is soaked for about 1/2 hour at room temperature in about thirty times its weight of a 1 N aqueous solution of NaOH, the fibers swell to a considerably greater extent than. ordinary rayon fibers; but when the soak liquid is then poured off, neutralized with HCI or H2SO4 and tested for the presence of starch by the conventional iodine test, it shows only a very faint color, indicating that the starch content of the soak liquid is less than 50 p.p.m.

The fibers behave well in processing, such as in high-speed carding, to form a card web suitable for bonding into a non-woven fabric (e.g., by impregnation with a latex of polymeric bonding agent).

The fibers maybe used to form yarns or fabrics in which they are the sole fibers or they may be blended with other fibers.

The fibers may be in the form of staple fibers or continuous filaments.

The-follokving Examples illustrate this invention further, all proportions being by weight unless otherwise indicated.

Example i Alkaline starch solution was prepared by mixing a slurry of corn starch grains in water with an 18% NaOH aqueous solution at about 20 to 250C, to give a translucent viscous solution comprising 13% starch and 4% NaOH.

In a conventional viscose mixer, viscose containing 9.2% cellulose, 6.2% NaOH, 32% CS2 b.o.c., and about 1/2% TiO2 b.o.c., was prepared by dissolving xanthated alkali cellulose in aqueous NaOH and mixing for about 2 hours. A quantity of the alkaline starch solution was then added to the viscose in an amount such that the resulting viscose-starch blend contained 10% starch b.o.c.

Mixing was continued for one hour and the solution was aged for about 24 hours at about 1 90C., (including a period of about 12 hours for vacuum deaeration). The solution was filtered both before deaeration and after, and directly pumped (e.g., within a half hour) through the spinnerette. At the spinnerette, the ball fall viscosity of the viscose-starch blend was about 90 and its salt test value was about 8. The solution was spun (through 12,000 circular spinnerette holes 0.0635 mm in diameter) into an aqueous spin bath containing seven to eight percent H2SO4, about 1.5% ZnS04, and about twenty-one percent Na2SO4 at 550C.

The tow formed in the spin bath was passed around a driven roll and then pulled (by a second driven roli) through a stretch bath containing 3% H2S04 aqueous solution at about 900C. The stretch bath is continuously replenished by spin bath carried into it by the tow, and by additions of water from time to time. The exit speed (i.e., the speed at the surface of the second driven roll) was 60 meters/minute, and the speed ratio of the first and second driven rolls was such that the tow was stretched about 60 to 75% in the stretch bath.

The length of travel of the two in the spin bath was about 1/2 meter and in the stretch bath about 2 meters. After leaving the driven roll, the tow dropped into a cutter and the resulting cut fibers dropped into flowing hot water (about 85 to 900C.) where relaxation (and crimping) occurred. The fibers were taken up as a blanket, washed with hot water and desulfurized (with a conventional solution of sodium polysulfide), rewashed, treated with a conventional staple finish solution (made from "Red Oil"), and the fibers were then dried in hot air (e.g., at about 900C.).

Forty-one samples, each comprising 10 single fibers, were tested for tensile properties. The results (averaged) are set forth in Table 1.

Additional tests showed crimps ranging from 9.4 to 12.6 per 25 mm, for an average of 10.95.

The denier per filament of the fibers was about 1.5.

In this Example I, the starch was a common industrial grade of unmodified corn starch, being simply the original starch granules, isolated from the corn kernel by wet milling, filtering, and drying with heated air. The source of the corn starch was regular corn (e.g., yellow dent corn; the term "corn" as used herein is synonymous with maize, e.g., zea maize). The literature indicates that the amylose constitutes a minor proportion (such as 27% of the starch) and amylopectin constitutes a major proportion (such as 73%); these proportions are on an anhydrous basis. The starch grains normally contain about 1012% moisture, but the amounts of starch specified herein are on an anhydrous basis.

The viscose was prepared in conventional manner by treatment of pulp sheets (93% alpha cellulose, dissolving pulp) with NaOH (by steeping the sheets in aqueous NaOH, then draining away NaOH solution for re-use, then pressing the mass of alkali cellulose pulp to press out "reject soda", which is a solution of hemicelluloses in aqueous NaOH), shredding the resulting alkali cellulose, xanthating the alkali cellulose and dissolving it-in dilute aqueous NaOH in the mixture. The "reject" soda, after clarification (by standing to allow fibers to settle), is used to make the dilute NaOH solution which is added to the viscose mixer; thus hemicelluloses are included in the viscose.

Example II In this example the alkaline starch solution was injected into the viscose just before it was extruded through the spinnerette (e.g., less than 1/2 hour, such as 1 5 to 20 minutes, before such extrusion).

A viscose solution containing 9% cellulose, 6% caustic soda and 31% carbon disulfide.(b.o.c.) was aged and filtered in the conventional manner at 1 90C. for about 24 hours until it had a sodium chloride salt test of 6.2 to 7.2 and a ball fall viscosity of 75 to 109 seconds. It was then pumped at a controlled flow rate into a blender (high shear).

The alkaline starch solution prepared as described in Example I, was filtered, before and after deaeration, and then pumped at a controlled flow rate into the same blender, so that the thoroughly mixed solution contained 10% starch, b.o.c.

The resulting blend was spun and stretched as in Example I and the degree of stretching was approximately 68%. The spinning speed of the second driven roll is given in Table II. The lengths of the paths in the spinning bath and stretch baths were about 1/2 meter and 3.7 meters, respectively.

As in Example I, the fibers were cut and relaxes to form staple fiber (here, as in Example I, the fiber length was nominally about 4 cm) and, before drying, were washed with water, desulfurizing solution, water, and treated with a finish solution. Details as to the starch level and spinning conditions, and the properties of the resulting fiber are set forth in Table II.

A comparison of properties of fibers obtained in the two examples indicates that the results were similar.

Example II produces a "bright" (undelustered) fiber, while the fiber of Example I is "dull" (owing to the presence of the TiO2).

Example III This example illustrates the preparation of an alkaline solution of starch of decreased molecular weight for mixing with viscose in a manner such as described above. The molecular weight reduction is effected by including a small amount of 30% aqueous solution of H202 in the slurry of starch grains. A convenient proportion is about 0.003 to 0.01 5 moles of H202 per mole of starch.Spinning was effected under the following conditions: viscose containing 9.0% cellulose; 6.0% NaOH; 31% CS2 (b.o.c.) is prepared; the starch solution is filtered, deaerated, again filtered and then injected into viscose less than 5 minutes before spinning; spinning is done by spinning 980 filaments into spin bath of 7.1% H2SO4, 1.1% ZnS04, 18.3% Na2SO4 at 500 C.; then stretching is 60% in stretch bath containing 2.4% H2SO4 at 900 C.; path length is 0.6 meter in spin bath; 0.7 meter in stretch bath; speed of second driven roll (takeup speed) is 40 meters per minute.

Table III gives the proportions used in making up the slurry into alkaline starch solution as well as the viscosity values of the solution (after deaeration), and an indication of the filterability and the properties of the fibers made by injection of 20% starch b.o.c.

Example IV While best starch solutions are obtained when the alkali concentration is above 2% NaOH and below 4-1/2% NaOH, it is within the broader aspects of this invention to use higher concentrations of alkali, e.g., 6%. Processes using such concentrations are illustrated in this example.

A. A starch solution was prepared by mixing 635 grams of corn starch in 3365 ml. of water and then pouring in slowly, while mixing, 1 680 ml. of 18% NaOH. The resulting starch solution, after filtration followed by deaeration, was injected into viscose just before spinning.

The viscose was prepared to have the following composition: 9.0% cellulose; 6.0% NaOH; 32% CS2 (b.o.c.), and was aged to have a ball fall viscosity of 50 to 80, and a spinning salt test value of 6-to 7. The spinning process was as in Examples land lIthe spin bath contained 7.5% H2SO4,3.5% ZnSO4, 18% Na2SO4, and was at 500C.

The stretch bath contained 3% H2SO4 at 900 C. The degree of stretch was 60% and the spinning speed was 40 meters per minute. The resulting staple fibers had a denier per filament of about 1-1/2.

Before drying, an adhesion-inhibiting finish (such as aqueous 1/2% solution of a fatty acid ester of an hexitol anhydride, a lauric ester of soribitan, or an oxyethylated sorbitan ester). was applied to the fibers to overcome their tendency to stick together.

The proportion of starch and the fiber properties are set forth in Table IV.

B. Using the same procedure as in "A" above, but with 43 percent starch b.o.c., fibers of various deniers were prepared by appropriate changes in the rate of delivery of the solution being spun, and/or changes in the size or number of spinnerette holes. Table V gives data obtained in these runs.

Example V In this Example, 1 0% starch b.o.c. was incorporated (as an aqueous solution containing 13% starch and 4% NaOH) into viscose (containing 9% cellulose, 6.0% NaOH and 31% CS2 b.o.c.) being mixed in the viscose mixer.After aging, there was injected, into the starch-containing viscose just before spinning through a 980 hole spinnerette to form 3 d/f fibers, a solution of sodium polyacrylate made by diluting a 25% aqueous solution of a polyacrylic acid with sufficient water and an excess (e.g., 10% more than the stoichiometric amount) of NaOH to form a solution whose content of sodium polyacrylate (calculated as if all carboxyl groups are in -COONa form) is 15.7%; simple calculation shows this corresponds to a polymer content, calculated as polyacrylic acid, of 12%. The amount of injected solution was varied to give the proportions tabulated below. The spin bath composition was 7.35% H2S04, 0.61% ZnS04,21.8% Na2SO4 and was kept at 550C.The aqueous stretch bath contained 2.5% sulfuric acid and was kept at 90-950C; the percent stretch in that bath was about 55%. After stretching, the yarn was washed thoroughly with water and the resulting wet yarn was cut to staple fibers (37 mm long) which were made distinctly alkaline by the following procedure: The fibers were immersed in an aqueous 1/2% NaOH solution at 250C. for 1 5 minutes, then showered with soft water for 10 minutes, centrifuged to remove excess liquid, immersed in 0.19/0 aqueous solution of Span 20 at 650C. for 5 minutes, centrifuged again and dried at 700C.

On injection, the sodium polyacrylate solution formed a dispersed phase in the starch-containing viscose, and the anionic polymer was present as a dispersed phase, visible under the microscope, in the final fibers.

The fibers from each run were tested for fluid holding capacity as follows. The fibers were carded into webs, each having a length of about 1 5 cm and a weight of 2-1/2 grams. Each of these webs was individually rolled in the direction of its width to provide a six inch roll and a string was looped about the center thereof. Each such roll was then folded on itself at the string loop and drawn into a 12 mm tube within which it was compressed by a clamp and plunger. After compression, the resulting tampons were removed, allowed to stand for a period of about 30 minutes during which the tampons recovered to a bulk density of about 0.4 g/cc. and were then evaluated for their capacity to hold water by the Syngyna Method, as described by G. W. Rapp in a June 1 958 publication of the Department of Research, Loyola University, Chicago, Illinois.

The following results were obtained: % Na polyacrylate* Fluid holding Run injected b.o.c. Capacity cc/g A 0 3.95 B 10.9 5.05 C 16.6 5.48 D 22.4 5.76 Calculated as if all carboxyl groups are in -COONa form.

Example VI In this Example a solution of starch and PVP was injected into viscose just before spinning. The injection solution was prepared by slurrying 31 8 g of corn starch in 4380 ml water, adding 700 g of an 1 8% aqueous solution of NaOH while stirring and then, after five minutes, adding 600 g of PVP and mixing thoroughly. This solution was injected at three different rates as tabulated below. The viscose contained 9.0% cellulose, 6.0% NaOH and 32% CS2. The spin bath contained 7.5% H2S04, 1.5% ZnS04 and 20% Na2SO4 and was kept at 50"C. while the stretch bath containing 2% H2S04 was kept at 900C.

The percent stretch in the stretch bath was 60%. After washing, the fibers were tested for water retention, with the following results: % injected, b.o.c. Water Run Starch PVP Retention % A O 0 122 B 5 5 144 C 10 10 169 D 15 15 204 While the invention has been illustrated with ordinary corn starch, it is within the broader scope of the invention to employ other starches, of at least 60% amylopectin content, alone or in various combinations with each other or with corn starch. Examples of these are rice starch, wheat starch, barley starch, tapioca (casava) and potato starch.

It is also within the broader scope of the invention to use grains of starches of higher (e.g., above 90%) amylopectin contents, such as those of waxy corn, waxy sorghum, and waxy (or glutinous) rice.

In using starches other than ordinary corn starch, it is desirable to check the behaviour of the starch in alkaline solutions of different NaOH content (using the "microscope method" described above) in order to determine the optimum concentrations of alkali. For instance, for potato starch, the optimum concentration of the NaOH in water is, as indicated by the "microscopic method", in the range of about 4 to 8%. For some starches, the grain boundaries remain at all NaOH concentrations: for these one may determine the NaOH concentration at which maximum visible grain swelling occurs (e.g., to 4% for tapioca starch and 1-1/2 to 6% for rice starch), and employ mechanical action (e.g., high shear) to break the grain boundaries.

TABLE I Conditioned RASTA 24 OC., Property 57% Relative Humidity Wet Tenacity, g/d 2.84 1.55 Elongation, % 19.15 23.83 Breaking Energy, g.cm./cm./denier 0.33 0.19 TABLE II Data on Starch-containing Rayon Staple

Conditionedd at 24 C. and 59% R.H. Water Crimps Spin Starch Ball Fall Salt Spin Bath Tenacity % Breaking Retention Per 24 RUN Speed** % b.o.c. Seconds Test Acid Conc. g/d Elong. Energy*** % mm (C.P.l.) A 85 10 109 7.2 10.6 2.74 20.9 0.34 147 7.6 *B' 40 20 100 7.5 7.6 2.76 19.9 0.33 9.0 B'' 40 20 97 6.2 7.1 2.88 18.2 0.31 # 126 (Avg.) 12.5 B''' 40 20 83 6.7 6.3 2.78 18.4 0.31 15.0 C 40 10 75 6.4 8.5 3.00 18.0 0.32 124 16.0 *Run B is subdivided according to salt test and spin bath acid values.

**Speed of second driven rollin meters per minute.

***g.cm./cm./denier.

In the products of RUNS B" through C the level and type of crimp is such that the trade would consider these to be "crimped" staple fibers.

TABLE III A B C D E F G H Slurry Mls.H2O 3737 3604 3472 3341 1870 1870 1870 1870 Mls. 30% H2O2 2 2.5 3 3.5 0 1 2 4 Grams Starch. as is 928 1081 1193 1328 464 464 464 464 NaOH Solution Grams 18% NaOH 1333 1333 1333 1333 666 666 666 666 alkaline starch solution %Starch (anhydrous basis) 14 16 18 20 14 14 14 14 %NAOH 4 4 4 4 4 4 4 4 Properties of Starch Solution (after one day storsge) Ball Fall Viscosity.

Seconds 31 36 45 68 77 41 24 14 Relative rate of buildup of pressure on filtration 36.7 26.3 32.6 25.3 - - - Properties of Conditioned Fiber (20% starch b.o.c.) Tenacity g/d 2.71 2.75 2.76 2.85 2.71 2.79 2.70 2.62 Elongation % 20.7 20.8 19.3 18.3 18.3 19.4 19.4 19.6 Breaking Energy.g.cm./cm./denier .36 .37 .35 .31 .32 .34 .33 .33 TABLE IV %Starch Tenacity g/d Elongation,% Breaking Energy* %Water Sample b.o.c. DDenier Conditioned Wet Condditlonedd Wet Conditioned Wet Retention A 33 1.63 2.49 1.21 18.6 27.3 0.28 0.18 129 B 54 1.64 2.17 .92 18.6 24.7 0.24 0.13 148 *g.cm./cm./denier TABLE V Dry Sample 1 2 3 4 5 6 Denier 5 8 15 15 5 8 % Water Retention 127 128 126 132 141 140

Claims (9)

Claims

1. Process for preparing starch-containing rayon fibers, characterized by forming a slurry of granules of a starch having an amylopectin content of at least 60% in an aqueous medium, adding sodium hydroxide (NaOH) to the slurry to produce an aqueous alkaline solution of starch, the NaOH concentration in the solution being preferably such that the grain boundaries disappear in the "microscope method" (as herein described), blending the solution with viscose in an amount such that the proportion of starch is about 5100% b.o.c., for example, at least 10% and no more than 25%, and extruding the starch-containing viscose in fiber form and regenerating the cellulose in the extruded viscose in a known manner to form the fibers.

2. Process according to claim 1, characterized in that the starch is corn starch, the NaOH concentration in the solution is between 2% and 4-1/2%, based on the weight of water and NaOH, and the concentration of the starch in the solution preferably is about 620%.

3. Process according to claim 1 or 2, characterized in that the slurry contains a starch-splitting agent active in alkaline medium, such as hydrogen peroxide, preferably present in a concentration of at least 0.01%, based on the weight of water, the proportion of the chain-splitting agent being preferably such that the alkaline starch solution has a concentration of 1420% starch and a viscosity of 35 1 70 poises, the viscosity being lower than that of a corresponding starch solution which has not been subjected to the chain-splitting agent.

4. Process according to any one of claim 1-3, characterized in that the extruded fibers are stretched in their plastic form at least 50% to form fibers having a tenacity of at least about 2 grams per denier.

5. Process according to claim 4, characterized in that the viscose contains a regeneration retarder and the fibers are stretched at least 100% to obtain fibers having a wet modulus above 7.

6. Process according to any one of claims 1-5, characterized in that the viscose contains dispersed therein an anionic polymer, preferably in an amount of at least about 10% b.o.c., to increase the fluid holding capacity of the fibers.

7. Process according to claim 6, characterized in that the anionic polymer has at least about 0.2 gram equivalent of salt forming anionic groups per 100 grams.

8. Process according to any one of claims 1-5, characterized in that the viscose contains polyvinylpyrollidone to increase the fluid holding capacity of the fibers.

9. Any novel feature or combination of features described herein.