US3718537A

US3718537A - Nonwoven fibrous product and method for producing same

Info

Publication number: US3718537A
Application number: US00070421A
Authority: US
Inventors: A Kawai; H Ohta; T Katsuyama; M Suzuki
Original assignee: Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Rayon Co Ltd
Priority date: 1969-09-12
Filing date: 1970-09-08
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27
Also published as: FR2061688A1; CH512616A; DE2045118B2; GB1329615A; NL7013507A; FR2061688B1; NL146554B; DE2045118C3; DE2045118A1; BE756032A

Abstract

SWELLING THE FORMED WEB, BONDING THE SWOLLEN VISCOSE FIBERS AND DECOMPOSITING THE HYDROXYMETHYL CELLULOSE ZANTHATE TO CELLULOSE.

A NONWOVEN FIBROUS PRODUCT HAVING EXCELLENT HAND IS PRODUCED WITHOUT USING ADHESIVE BY DISPERSING IN AN AQUEOUS MEDIUM VISCOSE FIBRES COMPRISING HYDROXYMETHYL CELLULOSE ZANTHATE, FORMING THE DISPERSED FIBRES INTO A WER,

Description

Feb. 21, 1973 I A H, KAWA. ETAL 3,71%;531

NONWOVEN FIBROUS' PRODUCT AND METHOD FOR PRODUCING SAME Filed Sept. 8, 1970 l I F/6.5

FIG 9 3,718,537 I p r NONWOVEN FIBROUS PRODUCT AND METHOD FOR PRODUCING SAME Atsushi Kawai, Takehiro Katsuyama, Migaku Suzuki,

and Hidenori ()hta, Ohtake, Japan, assignors to Mitsubishi Rayon Company, Ltd., Tokyo, Japan Filed Sept. 8, 1970, Ser. No.'70,421

Int. Cl. D2111 /12 3 US. Cl. 162-157 C w .14 Claims ABSTRACT on THE msctosonn A nonwoven fibrous product having excellent hand is produced without using adhesives by dispersing in an aqueous medium viscose fibers comprising hydroxymethyl cellulose xanthate, forming the dispersed fibers into a web, swelling the formed web, bonding the swollen. viscose fibers and decomposing the hydroxymethyl cellulose Xanthate to cellulose.

Conventionally, in the production of a nonwoven fibrous product by using the paper making technique, finely cut rayon filters or synthetic fibershave been used as a raw material. The cut fibers, various adhesives, dispersing agents and water are mixed to prepare an aqueous dispersion, from which the fiber is formed into a web and then dried.

Industrial production of non woven fibrous products by this technique results in increased production costs and moreover, products in which fibers are bonded with adhesives are hardened to a considerable extent, thus becoming paper-like. Therefore, products having fabric-like drape cannot be obtained.

The present invention effectively provides a non woven fibrous product having excellent hand by a process which combines web formation with fiber extrusion.

The method of the invention comprises dispersing in an aqueous medium fibers obtained by the viscose method and comprising the reaction product of cellulose xanthate and formaldehyde (the reaction product consisting essentially of hydroxymethyl cellulose xanthate), forming a web by a wet forming method, swelling the viscose fibers, bonding the swollen viscose fibers and decomposing the hydroxymethyl cellulose xanthate in the viscose fibers to the cellulose. Thereafter, the web, in a sheet form, is scoured and dried. I

FIG. 1 is a schematic view of an apparatus, showing an embodiment of a web dehydration step which may be used in accordance with this invention.

FIG. 2 shows, in cross section, a non woven fibrous product produced according to one embodiment of this invention, including the dehydration step shown in the FIG. 1.

FIG. 3 is a schematic view of an apparatus showing an embodiment of forming a web using an embossing roller.

FIG. 4 shows, in cross section, a non woven fibrous product produced according to one embodiment of this invention using the embossing roller of FIG. 3.

FIGS. 5, 6, 7 and 8 show, in cross section, non woven fibrous products produced according to the invention.

FIG. 9a is a plane view of a net having projections and FIG. 9b is a plane view of a net having meshes whose size is larger than the diameter of said projections.

FIG. 90 is a plane view of a net comprising combination of the net shown in FIGS. 9a and 9b.

FIG. 10 is a plane view of a nonwoven fibrous product produced using the net as shown in FIG. 90.

In FIG. 1, 1 is a portion which is subjected to an especially high degree of a reduced pressure, 2 is a portion which is subjected to a relatively low degree of reduced pressure, 3 is a web in which hydroXy-methyl cellulose xanthate is not yet decomposed and 4 is a net.

In FIG. 2, 5 and 6 correspond to 1 and 2 in FIG. 1, respectively.

In FIG. 3, 7 shows an embossing roller.

In FIG. 4, 8 is a portion of a web which is formed by the convex portion of the embossing roller and 9 is a portion of the web which is formed by the concave portion of the embossing roller.

In FIG. 10, 10 is a convex portion of a sheet and 11 and 12 are concave portions.

The starting material for use in the invention is filaments or fibers comprising the reaction product of formaldehyde and cellulose Xanthate (hydroxymethyl cellulose xanthate). To obtain this material, various means may be employed. For example, the filaments may be produced by extruding a viscose to which formaldehyde is added or by adding formaldehyde to a coagulation bath or by treating coagulated filaments comprising cellulose xanthate with an aqueous solution of formaldehyde.

Viscose used in this invention preferably contains 2 to 8% totalalkali. The viscose when spun should have a salt pointofat least 6, preferably of 8 to 24. When formaldehyde is added to viscose, the amount of the former is preferably 0.2 to 2% based on the weight of the viscose.

Excess amounts of low boiling point solvents such as carbon disulfide, methanol, acetone, etc. or materials capable of being decomposed in an acidic state to generate a gas such as ammonium carbonate, sodium bicarbonate etc. may be added to viscose to provide foaming effect and to occlude the gas in the subsequently formed web. Furthermore, phosphorus-containing compounds or halogen-containing compounds which provide a fiameproofing effect may also be incorporated into the viscose.

The coagulation bath contains 20 to 250 g./l. sodium sulfate, less than 0.3 g./l. zinc sulfate and 10 to g./l. sulfuric acid. In connection with development of crimps, the especially preferable range of concentration of sulfuric acid is shown by the following equation.

Minimum concentration of sulfuric acid (g./l.) 3A 8 Maximum concentration of sulfuric acid (g/l.) 8A 16 Wherein A is the total alkali concentration (percent) in the viscose.

When formaldehyde is not added to the viscose, the coagulation bath contains preferably 3 to 20 g./l. formaldehyde. When formaldehyde is added to the viscose, the formaldehyde concentration in the coagulation bath may be 0.5 to 6 g./l. The temperature of the coagulation bath is below 45 C., desirably 10 to 35 C.

Filaments comprising hydroxymethyl cellulose xanthate may also be obtained by extruding viscose into a cogulation bath containing 14 to 50 g./l. sulfuric acid, 20 to 250 g./l. sodium sulfate and less than 1 g./l. zinc sulfate at a temperature of lower than 35 C. and treating thus coagulated filaments with an aqueous solution containing 15 to 70 g./l. formaldehyde without adding formaldehyde to the viscose in the coagulation bath.

In all the above cases, the coagulation bath or the viscose may contain various surface active agents.

The swelling characteristics of the fibers comprising hydroxymethyl cellulose Xanthate in the following liquid media are utilized in making the fibrous products of the invention. That is, the fibers are highly swollen by treating them in, for example, the following media and under some conditions, whole fibers may be completely dissolved:

1) Substantially salt-free aqueous solutions having a pH of higher than 2.0 preferably 3.0-8.5, usually water which may contain a small amount of acid or surfactants.

(2) Aqueous solutions containing inorganic salts and/ or organic salts. Useful salts include alkali metal salts,

alkaline earth metal salts or ammonium salts of inorganic or organic acids or mixtures thereof. Examples of such salts are sodium acetate, potassium tartarate, sodium sulfate, potassium thiocyanate, potassium hydrogen phosphate, magnesium chloride, sodium chloride, etc. In such aqueous salt solutions, swelling of the fibers comprising hydroxymethyl cellulose xanthate is much greater than in an aqueous solution containing no salts and the effect of swelling can be attained even at about a pH of 1.0. However, salts of heavy metals such as zinc, cadmium, copper, nickel, etc. tend to restrain swelling of the fibers.

(3) Aqueous solutions of organic solvents. Examples of useful aqueous solutions of organic solvents are nitrogen containing solvents such as formamide, dimethylformamide, dimethylacetamide, pyridine, acetonitrile, glutaronitrile, etc.; cyclic ethers such as tetrahydrofurane, dioxane, etc.; sulfur containing solvents such as sulfoxide, dimethyl sulfoxide, dimethyl sulfone, ethylmethylsulfone, etc.; and water soluble ketones such as acetones, dioxyacetone, etc. In these media, hydroxymethyl cellulose xanthate is swollen or dissolved. As a liquid for swelling of the filaments comprising hydroxymethyl cellulose xanthate, the above mentioned solvents may be used alone or as mixtures with each other or as mixtures with water, preferably in the form of an aqueous solution.

The swelling speed of the fibers in said media is generally accelerated with increases of concentration and temperature, but it is abruptly reduced when temperature exceeds 80 C.

The swelling behavior of the fibers are different from those of regenerated cellulose fibers in aqueous alkaline solution or those of sodium cellulose xanthate in aqueous solution. The fibers consist of a portion rich in hydroxymethyl cellulose xanthate and a portion poor in hydroxymethyl cellulose xanthate and the swelling speed of the former portion is greater than that of the latter portion (swelling of the former portion is especially rapid in an aqueous solution of organic solvent). Therefore, the hydroxymethyl cellulose xanthate portion is selectively swollen and the portion partially begins to dissolve. That is, as is shown in Example 21, Table 4, when the apparent swelling degree in terms of weight of Water exceeds about 200%, a portion of the fibers begins to dissolve. The apparent swelling degree at which fibers begin to dissolve depends on the content of the hydroxymethyl cellulose xanthate in the fiber. The apparent swelling degree at which the fibers begin to dissolve decreases with an increase of the hydroxymethyl cellulose xanthate content. Conversely, with reduction of the content of hydroxymethyl cellulose xanthate, the apparent swelling degree at which the fibers begin to dissolve increases.

The swelling and dissolving characteristics are used to provide a self-bonding of the fibers. That is, the fibers comprising hydroxymethyl cellulose xanthate can be swollen or partially dissolved by the liquid treatment before or after formation of a web. Such characteristic can be used to bond the fibers in the web to each other. Accordingly, the viscose fibers in this invention can be formed into a web without using an adhesive. Furthermore, in cases where the viscose fibers are mixed with other natural or synthetic fibers and formed into a web, the swollen or partially dissolved viscose fibers can be used as fiber binder.

Latent crimpability or latent shrinkability of the viscose fibers comprising hydroxymethyl cellulose xanthate are utilized in providing bulk or soft hand to the fibrous product. That is, the abilities of the viscose fibers to develop crimps and to shrink are latent under such conditions that the hydroxymethyl cellulose xanthate is not swollen and not decomposed. Such conditions depends on the composition and temperature of an aqueous solution by which the viscose fibers are treated.

The hydroxymethyl cellulose xanthate is not swollen in (a) an aqueous solution containing no salt or no solvent at a pH of lower than 2.0, (b) an aqueous solution containing heavy metal ion having restraining effect on the swelling of the hydroxymethyl cellulose xanthate, or (c) an aqueous solution containing formaldehyde.

And the hydroxymethyl cellulose xanthate is not decomposed in aqueous solution at a temperature of lower than 50 C. and conversely, the hydroxymethyl cellulose xanthate is extremely decomposed in an aqueous solution at a temperature of higher than about 60 C. Accordingly, it is necessary to keep the hydroxymethyl cellulose xanthate from decomposition that the temperature of the aqueous solution is maintained at a temperature of lower than 50 0, preferably lower than 40 C.

Therefore, when the viscose fibers are treated in the aqueous solutions of (a) to (c) above described or the viscose fibers are treated at a temperature at which the hydroxymethyl cellulose xanthate is decomposed, shrinkage of fibers occurs. And under some conditions crimp development as well as shrinkage of the viscose fibers are observable.

It is necessary for developing crimps to form a heterogeneous structure in the fibers under the conditions described in US. Pat. 3,419,652 and British Patent 1,167, 555. The degree of shrinking depends on the content of hydroxymethyl cellulose xanthate and furthermore on the conditions under which the fibers are treated.

Because of the above mentioned swelling and dissolving, a wet-formed Web made according to the invention has excellent hand, bulkiness and high strength.

The filaments or fibers containing hydroxymethyl cellulose xanthate may be cut and dispersed directly in a dispersing medium and then formed into a web, but usually they are stretched before cutting. Any stretching medium such as air, water or steam may be used and furthermore any temperature may be used for the stretching medium provided that the absolute amount of the remaining hydroxymethyl cellulose xanthate is less than in terms of decomposition degree as explained hereinafter. Other conditions such as stretch ratio may also be optional, but in order to obtain fibers having sufficient latent crimpability, it is necessary to select production conditions as described in US. Pat. 3,19,652 taking conditions of stretching medium, stretching ratio, etc. into careful consideration.

The degree of decomposition of hydroxymethyl cellulose xanthate should be carefully considered during a heating treatment, such as stretching. The content of hydroxymethyl cellulose xanthate in the fibers is very important in connection with dispersibility of the fibers, the self-bonding ability of the fibers before or after formation of a web, the crimpability, the shrinkability, etc. The content of hydroxymethyl cellulose xanthate is expressed herein as a relative value by the amount of the chemically bonded carbon disulfide because, by actual measurement, the portion of the chemically bonded formaldehyde in the fibers cannot exactly be distinguished from that of non-bonded formaldehyde and further because the amount of the bonded carbon disulfide (7- value) in the fibers is substantially that of hydroxymethyl cellulose xanthate under the conditions employed in this invention.

The decomposition degree is a value represented by the ratio of the 'y-value when the decomposition degree of viscose when spun is taken as 0% and that of completely decomposed cellulose xanthate is Thus, for example, if the 'y-value of viscose is 80 and that of the fibers dispersed in a dispersing bath after spinning and stretching is 32, the decomposition degree of the fibers is 100=60 (percent) lulose xanthate is preferably more than 20 in terms of -value and more than 3% on the weight of fiber in terms of apparent bonded formaldehyde.

The dispersing methods are roughly classified as described below. The choice of a particular method depends upon the type of contemplated products, the way of bonding the formed web, the way of various surface treatments such as embossing or the way of development of crimps and shrinkage. The methods are:

(l) Swelling during dispersion is restricted or suppressed to a swelling degree of lower than 200% and after forming the web, swelling and shrinking of the fibers in sheet form are carried out to complete the bonding.

(2) Swelling of the fibers is carried out during dispersion by selecting conditions under which the dispersing medium causes swelling of more than 200% of the fibers. In this case, a part of the fibers begins to dissolve. Wet forming and bonding of the fibers are simultaneously carried out.

(3) The fibers are partly swollen during dispersion and formed into a web (the first bonding). The formed web is subjected to swelling and shrinking treatment during the following step (the second bonding). Thus, the bonding of the fibers is carried out in two stages.

In order to obtain a product of excellent hand utilizing development of crimps and shrinkage in accordance with above mentioned method (1), conditions under which crimpability and shrinkability are latent are required. That is, in this case, decomposition of hydroxymethyl cellulose xanthate in the dispersing bath should be suppressed, and the bonding of the fibers during the web forming stage should be controlled, thereby providing high mobility of the fibers in a web in the following stage. For this purpose, an aqueous solution should be used as a dispersing medium and pH of the solution is preferably kept at less than 2.0. When pH of the aqueous solution is higher than 2.0 or when salts, solvents, etc. which are capable of swelling hydroxymethyl cellulose xanthate as mentioned above are present in the medium, it is necessary to add heavy metal ions such as Zn++, Cd++, Mn++ and Al+++ or a small amount of formaldehyde to the dispersing medium to suppress swelling of the fibers and decomposition of hydroxymethyl cellulos xanthate. The dispersing medium is kept at a temperature of lower than 50 0., preferably lower than 40 C. In general, a dispersing medium maintained at a high temperature results in conspicuous reduction of dispersibility due to development of crimps or shrinkage. Thus, the dispersion should be carried out at a temperature lower than 50 C.

When the dispersing conditions of method (2) above are selected, a non woven fibrous product having a high strength, especially a high Wet strength can be obtained. However, the hand of the product becomes hard and the product is apt to become paper-like. Therefore, it is necessary to prevent such a drawback by surface treatments. such as embossing and crepe treatment. However, dispersing method (2) is extremely effective when fibrous having no self bending ability are mixed with the fibers comprising hydroxymethyl cellulose xanthate using this method, care should be taken if a paper making machine is used, because the freeness of the fiber dispersion is reduced and release of the sheet from net felt becomes rather difficult. Furthermore, loss of the fiber due to partial dissolution is also increased. For the dispersing medium of method (2), liquids containing salts or solvents which can swell and dissolve the fibers comprising hydroxymethyl cellulose xanthate or a solution to control the pH value may be used.

The dispersing method (3) described above, according to which bonding of the fibers is carried out by a first bonding during web forming and a second bonding during after treatment, may be carried out by controlling the degree of swelling of the fibers in the dispersing medium.

For example, when fibers comprising a large amount of hydroxymethyl cellulose xanthate are used, they are partially swollen using an aqueous solution containing a small amount of sodium sulfate as a dispersing medium during the dispersing step. The first bonding is done at the step of web formation and the thus obtained web is subsequently subjected to a second treatment to strengthen the bonding.

As additives for the dispersing medium, dispersing agents such as polyethylene oxide, carboxymethylcellulose, sodium polyacrylate, and polyacrylic amide and various lateXes may be used.

The concentration of fibers in the dispersing medium is preferably 0.01 to 1%. Various paper making machines may be used as apparatus for forming a web from the fibers dispersed in liquid. For example, a Fourdrinier paper making machine or a cylinder type paper making machine may be used. In a special case, it is possible to simultaneously carry out formation and surface treatments of a web by using the combined net as shown in FIG. 9 as a net of a paper making machine.

Wet web obtained by wet-forming according to the invention is subjected to surface treatments such as embossing, crepe treatment, etc. in a swollen and high water content state, namely, in a state of high mobility of the fiber in the web. This is because the wet web comprising hydroxymethyl cellulose xanthate has a wet strength sufficient to withstand various treatments and further because after such treatments, hydroxymethyl cellulose xanthate is decomposed to cellulose with an acidic aqueous solution or steam at a high temperature and set the -web structure resulting from the surface treatments.

If the fibers of the Web are completely and strongly bonded due to swelling or partial dissolving of the fibers comprising hydroxymethyl cellulose xanthate, the remaining hydroxymethylcellulose xanthate is decomposed to cellulose to set the web structure at a high temperature. On the other hand, if much of the hydroxymethyl cellulose xanthate remains in the fibers in the web and the bonding of the fibers is not completed, after-treatments are used which utilize the mobility, latent crimpability or latent shrinkability of the fibers in the web. One of these treatments is a surface treatment such as embossing and another is the dipping treatment for development of crimps and shrinkage to impart bulkiness, drape, etc. to the web.

The characteristics of the surface treatments of this invention may be summarized as follows:

(1) Because of the plasticity of the fibers in swollen state, the web has a high processability. Therefore, a Web structure having a great difference in apparent specific gravity of the web between the bonded part and the other part can be formed by embossing. For this purpose, the water content in the web is preferably more than 300%, desirably 500 to 1,000%.

(2) Bonding ability of the fibers is increased with a surface treatment such as embossing thereby increasing the strength of the web.

(3) The bonding state of the fibers in the web are set by decomposing hydroxymethyl cellulose xanthate to cellulose after surface treatments.

In order to carry out surface treatments, it is necessary that the web is in a swollen state and, when the web is not sufficiently swollen, a swelling treatment is required. Such swelling of the web may be carried out by spraying or applying to the web a liquid capable of swelling and dissolving the fibers comprising hydroxymethyl cellulose Xanthate as mentioned above. The swelling of the web may also be carried out by previously treating the web at a low temperature with a liquid capable of swelling and dissolving the fibers at a higher temperature and then heating the web with a high frequency heating apparatus. The swollen web is then subjected to surface treatment such as embossing. Such surface treatment is carried out by using an embossing apparatus provided with rotary projection part and rotary concave part or by passing the wet web together with a stainless steel or plastic net between press rollers. One of the press rollers may be heated. In this case the part corresponding to meshes of the net are changed into film state or melted. It is also possible to simultaneously carry out surface treatment and partial decomposition of hydroxymethyl cellulose xanthate by using an apparatus provided with a heated projection part. In this case also, the part corresponding to the projection part are changed to film state or melted. Furthermore, it is also possible to effect bonding at points or in lines by limiting the area of such heat treatments. In some special cases, a wet web is inserted between nets made of cotton yarns of thick count, into which a solution of swelling agent for hydroxymethyl cellulose xanthate is absorbed and the resultant laminate is pressed to simultaneously carry out partial swelling and bonding. Latent crimpability and latent shrinkability are generally developed by treating the web in acidic warm water at a temperature higher than 40 C. in substantially tensionless state. The acidic warm water may contain a swelling agent, but, when the temperature of the acidic water is high, presence of the swelling agent is not necessary for developing only shrinkage. Furthermore, a highly porous web can be produced by occluding in the web a gas generated simultaneously with development of crimps and shrinkage of the fibers.

The purpose of these treatments is to produce a non woven fibrous product having excellent hand, high bulkiness and excellent drapability by utilizing crimp development and shrinkage of the fibers comprising hydroxymethyl cellulose xanthate. In order to achieve this purpose, it is necessary that a sufficient amount of hydroxymethyl cellulose xanthate remains in the fibers in the Web and that there are spaces in which the fibers can move during development of crimps and shrinkage. Thus, if bonding of the web is substantially complete, development of crimps and shrinkage of the fibers is extremely limited, even if a large amount of hydroxymethyl cellulose xanthate remains. On the contrary, if bonding is extremely weak, crimp development and shrinkage treatments in an aqueous solution cause breaking up of the web.

Therefore, in order to carry out crimp development and shrinkage treatments as mentioned above, it is essential to control the swelling and bonding degree of the fibers in the wet web. The fibers in the web, after being subjected to crimp development and shrinkage treatments, are in a strongly bonded state due to a self-bonding ability and a felting effect.

The bonded structure of the web is fixed by decomposing hydroxymethyl cellulose xanthate contained in the web to the cellulose. The structure of non woven fibrous product is set by this decomposition. For such treatments, an acidic aqueous solution of a temperature of higher than 70 C. is preferable, but, alternatively the web may be heated in glycerine or liquid paraffin, or may be treated with steam at high temperature. The regenerated cellulose fibers in web form are then scoured and dried. Souring includes a bleaching step, a neutralizing step, washing step, and other treating steps which are conventional in the art. The souring step may be followed by treatment with softening agents, fireproofing agents, sanitary finishing treatment, dyeing and various latex treatments.

The method of this invention has many practical applications, as illustrated in the examples that follow. The web can be bonded to formed materials, films or nets utilizing the self-bonding ability of the fibers comprising hydroxymethyl cellulose xanthate to produce a composite material such as bonded fabric. Furthermore, a web comprising hydroxymethyl cellulose xanthate can be cut into tapes of about 20 mm. in width, which are subjected to twisting to form ropes, and then heated to shrink and decompose, thereby providing an extremely cord-like material, useful for twine, etc.

As mentioned above, according to the method of this invention, various commercially valuable materials can be produced at low cost. Especially, the nonwoven fabric obtained utilizing development of crimps and shrinkage of the fiber has excellent drapability, high bulkiness and excellent hand and closely resembles woven fabric.

The non woven fibrous product has an extremely wide range of uses such as wall materials, auxiliary material for civil engineering and construction industry, sanitary goods such as tampon and pad, sheets, baby wear, curtains, and the like.

The following examples serve to further illustrate the invention:

EXAMPLE 1 A viscose containing a 6.5% cellulose and 4% alkali and having a viscosity of 160 seconds, a salt point of 21.5 and a 'y-value of 8 was extruded into a coagulation bath containing 40 g./l. sulfuric acid, 75 g./l. sodium sulfate and 6 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 275% of their original length in a stretching bath containing 2 g./l. sulfuric acid at 65 C. The content of hydroxymethyl cellulose xanthate in the thus stretched filaments was 40 in terms of -value and the decomposition degree was 52.5%. The fineness of the filaments was 3 deniers.

The strenched filaments were cut to 15 mm. lengths and immediately were dispersed in water at 20 C. The dispersed fibers were formed into a web on a stainless steel net without using adhesive. The fibers in the web were subjected to swelling treatment in a swelling bath containing 0.2 g./l. sulfuric acid, 10 g./l. sodium sulfate and 4 g./l. formaldehyde at 55 C. for 2 minutes. Thereafter, the fibers were completely regenerated in a regenerating bath containing 2 g./l. sulfuric acid at C. Then, the web was scoured and dried to obtain a highly bukly, non woven fabric having many micro-crimps and crisp hand.

EXAMPLE 2 The extrusion and the stretching of Example 1 were repeated with the following modifications. A viscose containing 9% cellulose and 5.5% alkali and having a viscosity of seconds, a salt point of 20 and a 'y-value of 78 was extruded to form filaments of 1.5 denier. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 30 in term of 'y-value and the decomposition degree was 61.5%.

The stretched filaments were cut into 10 mm. lengths and then dispersed in water at 10 C. The dispersed fibers were formed into a web on a stainless steel net without using adhesives. The fibers in the web were treated in an aqueous solution having a pH of 5.0 at 60 C. for 2 minutes. Regeneration of the fibers was completed under the same conditions as in Example 1 and then the web was scoured and dried to obtain a non woven fabric having a felt-like hand.

EXAMPLE 3 The same viscose as used in Example 1 was extruded into a coagulation bath containing 30 g./l. sulfuric acid, 60 g./l. sodium sulfate and 10 g./l. formaldehyde at 30 C. The filaments withdrawn from the coagulation bath were immediately stretched to 350% of the original length in a stretching box filled with saturated steam at 102 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 25 in terms of 'y-value and the decomposition degree was 70%. The fineness of the filaments was 3 deniers.

The stretched filaments were cut to 15 mm. lengths and were dispersed in an aqueous solution containing 7% dimethylsulfoxide at 20 C. The dispersed fibers were formed into a web on a stainless steel net without using adhesives. Then, the fibers in the web were swollen in an aqueous solution containing 12% dimethylsulfoxide at 9 55 C. and completely regenerated in a regenerating bath containing g./l. sulfuric acid at 90 C. Subsequently, the Web was scoured and dried to obtain a non woven fabric having soft and bulky hand.

EXAMPLE 4 The same viscose as used in Example 2 was extruded into a coagulation bath containing 35 g./l. sulfuric acid, 90 g./l. sodium sulfate and 8 g./l. formaldehyde at 25 C. The fineness of the filaments thus obtained was 1.5 denier. The filaments withdrawn from the coagulation bath were immediately stretched to 250% of the original length in air at 50 C. The content of hydroxymethyl cellulose xanthate of the stretched filaments was 43 in terms of 'y-v'a'lue and the decomposition [degree was 45%.

The stretched filaments were cut to mm. lengths and were formed into a web on a stainless steel net in an aqueous solution containing 0.5 g./l. carboxymethyl cellulose at 10 C. Thereafter, the web was treated in a swelling bath containing 0.4 g./l. sulfuric acid and 8 g./l. sodium sulfate at 50 C. for 2 minutes. Then, regeneration of the fibers was completed in a regeneration bath containing 2 g./l. sulfuric acid at 85 C. and subsequently the fibers were scoured and dried to obtain a non woven fabric having many micro-crimps and a bulky and somewhat hard hand.

EXAMPLE 5 Extrusion, stretching and cutting were carried out in the same manner as in Example 4 with the same viscose as used in Example 4. The cut filaments were homogeneously dispersed in water at 24 C. together with 10% (based on the weight of cellulose) of fibrous binder of heat soluble polyvinyl alcohol and 50% (based on the weight of cellulose) of Wood pulp and thereafter formed into a web at 24 C. Then, the web was treated with the same swelling bath as in Example 4 and was completely regenerated with a regeneration bath containing 2 g./l. sulfuric acid acid at 75 C. Thereafter, the fibers were scoured and dried to obtain a non woven fibrous product having a somewhat hard hand.

EXAMPLE 6 The same viscose as used in Example 2 was extruded into a coagulation bath containing 30 g./l. sulfuric acid, 80 g./l. sodium sulfate, 0.1 g./l. zinc sulfate and 12 g./l. formaldehyde at 25 C. The filaments withdrawn from the coagulation bath were immediately stretched to 350% of the original length in a stretching bath containing 5 g./l. sulfuric acid at 75 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 27 in terms of 'y-value and the decomposition degree was 65.5.

The fineness of the filaments was 1.5 denier. The stretched filaments were cut to 10 mm. lengths and dispersed in an aqueous sulfuric acid solution (pH about 1) at 24 C. The dispersed fibers were formed into a web on a stainless steel net Without using adhesives. The fibers in the web were subjected to wet heat treatment in a steam atmosphere. Then, the fibers wereswollen and regenerated in the same swelling bath and regeneration bath as in Example 1 and thereafter scoured and dried to obtain a soft and bulky non woven fibrous product. The fibers on the surface of the web were fused to from a film layer and the fibers in the inner portion of the web were not fused.

EXAMPLE 7 A viscose containing 7% cellulose and 4% alkali and having a salt point of 16.0, a -value of 71 and a viscosity of 280 seconds was extruded into a coagulation bath containing 25 g./l. sulfuric acid, 70 g./l. sodium sulfate, 0.2 g./l. zinc sulfate and 8 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 250% of the original length in a stretching bath containing 5 g./l. sulfuric acid at 70 C. The content of hydroxymethyl cellu- 10 lose xanthate in the stretched filaments was 32 terms of -value and decomposition degree was 55%. The fineness of the filaments was 3 deniers.

The stretched filaments were cut to 15 mm. lengths and immediately dispersed in water at 15 C. and formed into a web on a stainless steel net. The web was dipped in boiling water for 2 minutes and was completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at C. Then, the web was scoured and dried to obtain a soft and bulky non woven fibrous product having a felt-like hand. The stretched filaments were shrunk 45% during the boiling treatment.

EXAMPLE 8 A viscose containing 9% cellulose and 5.4% alkali and having a salt point of 6.0, 'y-value of 33 and a viscosity of 43 seconds was extruded into a coagulation bath containing 38 g./l. sulfuric acid, 75 g./l. sodium sulfate and 7 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stertched to 270% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 30 C. The content of hydroxymethyl cellulose xanthate in the filaments was 20 in terms of 'y-value and the decomposition degree was 39.4%. The apparent content of bonded formaldehyde in the filaments was 4.2% based on the weight of cellulose. The fineness of the filaments was 3 deniers.

The stretched filaments were cut to 15 mm. lengths. Thereafter, they were immediately dispersed in water at 30 C. and formed into a web on a stainless steel net. The fibers in the web were dehydrated under reduced pressure to strengthen bonding of the fibers. Then, in an aqueous acidic solution containing 2 g./l. sulfuric acid at 90 C., the remaining hydroxymethyl cellulose xanthate was decomposed completely. Subsequently, the web was bleached by treatment with an aqueous solution of sodium hypochloride and neutralized, and washed with water. Thereafter a fireproofing agent was applied to the web by dipping it in a 20% aqueous solution of fireproofing agent of phosphorus-nitrogen compounds (Flameproof No. 270 manufactured by Nihon Senka Kogyo K. K.) and then the web was squeezed and dried. The thus obtained non woven fibrous product had a paper-like hand, with excellent strength and fireproofing properties.

The apparent content of the bonded formaldehyde was measured as follows: 1 g. (calculated as dry weight) of the filaments containing hydroxymethyl cellulose xanth ate after stretching was sampled, placed in 200 cc. of water having a pH of 1.0 at 20 C., washed with water with striring for 1 minute and then squeezed. Thereafter,

from which the apparent content of bonded formaldehyde (percent) was calculated.

EXAMPLE 9 A viscose containing 9% cellulose and 5.5% alkali and having a salt point of 8, a -value of 42 and a viscosity of 45 seconds was extruded into a coagulation bath containing 48 g./l. sulfuric acid, 75 g./l. sodium sulfate and 12 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to of their original length in air at normal temperature. The 'y-value of the stretched filaments was 28 and the decomposition degree was 33%. The apparent content of the bonded formaldehyde was 5.7% based on the weight of the cellulose.

The stretched filaments were then cut to 20 mm. lengths and then dispersed in an aqueous solution containing g./l. sodium sulfate having a pH of 4.0 at 20 C. for 2 minutes with stirring. The dispersed fibers were formed into a web on a net of 20 x 20 meshes made by polyethylene and simultaneously the formed web was dehydrated under a reduced pressure of 600 mm. Hg in such a way as shown in FIG. 1. The dispersed fibers during the forming were partially dissolved; the degree of dissolution being 4.8 g. based on the weight of cellulose. Then, the incompletely decomposed fibers of the web, which was shaped into embossed form, were completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. and scoured and dried to obtain a nonwoven fibrous product having a good hand and embossed form as shown in FIG. 3. The physical properties of the nonwoven fibrous product thus obtained are shown in Table 1.

TABLE 1 Weight (g./m. 50 Thickness (mm.) 0.198 Apparent specific gravity (g./cm. 0.250 Cantilever bending resistance (cm.) 8.6 KGSC strength (kg./cm./g./cm. 730

EXAMPLE A viscose containing 6.5% cellulose and 4% alkali and having a salt point of 21.5, a 'y-value of 84 and a viscosity of 160 seconds was extruded into a coagulation bath containing 35 g./l. sulfuric acid, 75 g./l. sodium sulfate and 8 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 275% of the original length in a stretching bath containing 2 g./l. sulfuric acid at 60 C. The regeneration degree of the filaments was 50 in terms of 'y-value and the decomposition degree was 41% The stretched filaments were cut to 10 mm. lengths and immediately dispersed in an aqueous solution containing 10 g./l. dimethyl formamide and having a pH of 4.5 at 25 C. with stirring. Thereafter, the dispersed fibers were formed into a web on a net of polypropylene. The apparent primary swelling degree of the fibers was 350% based on the weight of cellulose and the dissolved part of the fibers was as high as based on the weight of cellulose. The web containing water and incompletely regenerated fibers was dehydrated to a water content of 700% based on the weight of the fibers. Then, the web was treated in a swelling and crimping bath containing 0.5 g./l. sulfuric acid, g./l. sodium sulfate and 0.1 g./l. zinc sulfate at 55 C. to develop crimps and thereafter dehydrated to a water content of 700%. This web was pressed by an embossing roller as shown in FIG. 3. Then, the web was completely regenerated in a regeneration bath containing 2 g./l. sulfuric acid at 85 C. The web was then scoured and dried to obtain a highly stretchable nonwoven fabric having a form as shown in FIG. 4. The fibers of the web had many micro-crimps.

EXAMPLE 1 1 A web containing hydroxymethyl cellulose xanthate, produced by carrying out the spinning, forming, swelling, crimping treatment and dehydration steps in the same way as in Example 10 was pressed as shown by 5 in FIG. 2 by an embossing roller heated to about 80 C. The web was completely regenerated in a regeneration bath containing 2 g./l. sulfuric acid at 85 C. and scoured and dried to obtain a nonwoven fabric having a form 'as shown in FIG. 4, and being characterized by a high stretchability. In FIG. 4, 8 shows a strongly bonded portion.

EXAMPLE 12 A viscose was prepared by using 60% carbon disulfide on the weight of cellulose. The viscose containing 7% cellulose and 4% alkali and having a salt point of 23, a 'yvalue of 83.5 and a viscosity of 170 seconds (in which the amount of by-product such as trithiocarbonate was 1%) was extruded into a coagulation bath containing 35 g./l. sulfuric acid, g./l. sodium sulfate and 7 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath was immediately stretched to 275% of the original length in a stretching bath containing 2 g./l. sulfuric acid at 65 C. The content of hydroxymethyl cellulose xanthate in the stretched fil aments was 46 in terms of 'y-value and the decomposition degree was 45%. The fineness of the filaments was 3 deniers.

The stretched filaments were cut to 15 mm. lengths and immediately dispersed in water having a pH of 6.5 at 20 C. Then, the fibers dispersed were formed in to a web on a stainless steel net without using adhesives. The web was then squeezed to a water content of 600% and thereafter was treated in a swelling bath containing 0.2 g./l. sulfuric acid and 10 g./l. sodium sulfate at 55 C. Then, the web was completely regenerated in a regeneration bath containing 10 g./l. sulfuric acid at C. and scoured and dried to obtain a highly bulky and crisp non woven fibrous product as shown in FIG. 4 containing a gas within the fiber structure.

EXAMPLE 13 A viscous containing 6.5% cellulose and 4% alkali and having a salt point of 20, a 'y-value of 75 and a viscosity of 200 seconds, to which sodium bicarbonate was added in an amount of 15% by weight of cellulose, was extruded into a coagulation bath containing 40 g./l. sulfuric acid, 80 g./l. sodium sulfate and 5 g./l. formaldehyde at 20 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 250% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 55 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 28 in terms of 'y-value and the decomposition degree was 62.5%. The fineness of the filaments was 1.5 denier. The stretched filaments were cut to 12 mm. length and immediately dispersed in a 2% dimethylsulfoxide aqueous solution having a pH of 5 at 20 C. The fibers dispersed were shaped into a web on a stainless steel net without using adhesives. The web was squeezed to a water content of 600% and was swollen in a 2% dimethylsulfoxide aqueous solution at 55 C. Thereafter, the web was completely regenerated in a regeneration bath containing 10 g./l. sulfuric acid at C. and scoured and dried by a conventional method to obtain an extremely soft and bulky non woven fibrous product as shown in FIG. 6, containing a gas within the fiber structure and having a very low apparent specific gravity.

EXAMPLE 14 A viscose was prepared by using 70% carbon disulfide based on the weight of cellulose. The viscose containing 8.0% cellulose and 5% alkali and having a salt point of 14, a 'y-value of 62 and a viscosity of 220 seconds (in which the amount of by-product such as trithiocarbonate was 1.8%) was extruded into a coagulation bath containing 32 g./l. sulfuric acid, 70 g./l. sodium sulfate and 7 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 250% of the original length in air at 50 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 40 in terms of 'y-value and the decomposition degree was 35%. The fineness of the filaments was 1.5 denier.

The stretched filaments were cut to 15 mm. lengths and then were dispersed in an aqueous solution containing 0.5 g./l. of carboxymethyl cellulose having a pH of 7.5 at 22 C. The dispersed fibers were formed into a web on a stanless steel net without using adhesives. The web was then squeezed to a water content of 500% and thereafter was treated in a swelling bath containing 0.5 g./l. sulfuric acid and 10 g./l. sodium sulfate at 60 C. Then, the

Web was completely regenerated in a regeneration bath containing 10 g./l. sulfuric acid at 85 C. and was scoured and dried by conventional methods to obtain a relatively hard non woven fibrous product as shown in FIG. 7; the product being characterized by a high bulkiness and crisp hand and containing gas in the web structure.

EXAMPLE 15 A viscose containing 6.5% celluose and 4% alkali and having a salt point of 16, a 'y-value of 71 and a viscosity of 160 seconds, to which 30% by weight of cellulose of formaldehyde and 20% by weight of cellulose of methylene chloride were added, was extruded into a coagulation bath containing 38 g./l. sulfuric acid, 100 g./1. sodium sulfate and 2 g./l. of formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were stretched to 250% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 50 C. The content of hydroxymethyl celluose xanthate in the stretched filaments was 26 in terms of 'y-value and the decompositionv degree was 63%. The fineness of the filaments was 2 deniers.

The stretched filaments were cut to 12 mm. lengths and immediately dispersed in an aqueous solution containing 5 g./l. formaldehyde and having a pH of 6 at 23 C. together with heat-fusible polyethylene fibers which were cut to mm. lengths.

The proportion of cellulose to the polyethylene was 8/2 by weight. The mixed fibers dispersed in the formaldehyde aqueous solution were formed into a web on a stainless steel net without using adhesives. The sheet was then dehydrated to a moisture content of 1000% and treated in a crimping bath containing 0.5 g./l. sulfuric acid and 10 g./l. sodium sulfate at 55 C. Thereafter, the web was completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. and scoured and dried by conventional methods. Subsequently, theweb was heat treated in a high temperature drier at 140 C. for 4 minutes to obtain a highly bulky non woven fibrous product as shown in FIG. 8, containing a gas and being characterized by an extremely low apparent specific gravity and excellent physical properties.

EXAMPLE 16 A viscose containing 6.5% cellulose and 4% alkali and having a salt point of 21.5, a 'y-value of 80 and a viscosity of 160 seconds was extruded into a coagulation bath containing 35 g./l. sulfuric acid, 75 g./l. sodium sulfate and 8 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 275% of the original length in a stretching bath containing 2 g. l. sulfuric acid at 60 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 36 in terms of -value and the decomposition degree was 55%. The fineness of the filaments was 3 deniers.

The filaments were cut to mm. lengths and immediately dispersed in an aqueous solution containing 2 g./l. formaldehyde and 0.1 g./l. polyacrylamide (molecular weight8,000,000 and degree of hydrolysis20%) and having a pH of 6.0 at 15 C.

The dispersed fibers were formed into a web by a cylinder paper-making machine with a cylinder wire part of 50 cm. in diameter and 45 cm. in width. The swelling degree of unregenerated fibers in the web was 180%. Then, the web was passed through a shower of an aqueous solution containing 10 g./l. sodium sulfate at 30 C. for 10 seconds to swell the unregenerated fibers. The web was then squeezed to a moisture content of 700%. The thus treated web was then transferred on a stainless steel net of 20 x meshes and was subjected to a pressure of 25 kg./cm. on the net. The thus obtained unregenerated fiber web was treated in a crimping bath containing 0.2 g./l. sulfuric acid and 10 g./1. sodium sulfate at 60 C.

14 to shrink it to the extent of 20% in area. The shrunken web was completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. and then scoured by the conventional method. Before drying, it was treated with a 10% solution of copolymerized latex of acrylonitrile and butadiene. The excess latex was removed by a squeeze roller so that the amount of the latex applied to the web was 8% based on the weight of the fibers. Then, the web was dried to obtain a non-woven fibrous product having a high strength, excellent drape and a flannel-like hand. The physical properties thereof are shown in Table 2.

TABLE 2 Weight (g./m. 45 Thickness (mm.) 1.8 Apparent specific gravity (g./cm. 0.189 Cantilever bending resistance (cm.) 5.3 KGSC strength (kg./cm./g./cm. 670

EXAMPLE 17 An unregenerated web produced and transferred on a wet felt by the same procedure as in Example 16 and was passed through a hot water shower at 32 C. for 10 seconds to swell the web. The web was then squeezed to a water content of 400%. A net of 8 mm. meshes of 0.96 count (cotton count) cotton yarn, which was wetted with a 50% aqueous solution of dimethylformamide at 60 C., was placed on the web and immediately a pressure of 23 kg./cm. was applied thereto. Thus, the dimethylformamide solution was permeated in the form of meshes into the web to cause bonding of the fibers in the form of meshes. Thereafter, the web was treated in a crimping bath containing 0.2 g./l. sulfuric acid and 10 g./l. sodium sulfate at 55 C. to cause shrinking of area to the extent to 10%. Then, the web was completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. and scoured and dried by the conventional methods to obtain a very soft and highly strong non-woven fibrous product in which the fibers were strongly bonded to each other in the form of meshes of the cotton yarns. The physical properties thereof are shown in Table 3.

TABLE 3 Weight (g./m. 40 Thickness (mm) 0.157 Apparent specific gravity (g./cm. 0.191 Cantilever bending resistance (cm.) 5.5 KGSC strength (kg./cm./g./cm. 830

EXAMPLE 18 A viscose containing 7% cellulose and 4% alkali and having a salt point of 22.0, a 'y-value of 80.5 and a viscosity of 200 seconds was extruded into a coagulation bath containing 30 g./l. sulfuric acid, 70 g./l. sodium sulfate and 10 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 320% of the original length in a stretching bath containing 5 g./l. sulfuric acid at C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 28 in terms of 'y-value and the decomposition degree was 65%. The fineness of the filaments was 3 deniers.

The stretched filaments were cut to 20 mm. lengths and immediately thereafter were dispersed in water at 23 C. The dispersed fibers were formed into a web by the same cylinder paper-making machine as used in Example 16. The swelling degree of the dispersed fibers at this point was 220%. The unregenerated web was transferred on the wet felt and squeezed to a water content of 380% Thereafter, the web was passed in a high frequency heating apparatus of output 550 w. and frequency of 2450 mHz. for 0.5 second to cause shrinking of area to the extent of 25%, whereby crimps were developed and bonding of the fibers was attained. Thereafter, the web was completely regenerated in a regeneration bath containing 2 g./l. sulfuric acid at 85 C. and then scoured and dried by conventional methods to obtain a strong non-woven fibrous product having a flannel-like hand and a hlgh stretchability.

EXAMPLE 19 A viscose containing 6.5% cellulose and 4% alkali and having a salt point of 19, a 'y-value of 70 and a viscosity of 180 seconds was extruded into a coagulation bath containing 29 g./l. sulfuric acid, 75 g./l. sodium sulfate and 12 g./l. formaldehyde at 25 C. to from filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 350% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 60 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 30 in terms of 'y-value and the decomposition degree was 54.5%. The fineness of the filaments was 1.5 denier.

The stretched filaments were cut to 20 mm. lengths and immediately dispersed in an aqueous solution containing 0.5 g./l. formaldehyde and 0.01 g./l. polyethylene oxide (molecular weight 3,600,000) having a pH of 6.0 at 18 C. The dispersed fibers were formed into a web by a cylinder paper-making machine having a cylinder wire part of 50 cm. in diameter and 45 cm. in width. The swelling degree of the dispersed fibers at this point was 220%.

Then, the unregenerated web was passed through a shower of an aqueous solution containing 10 g./l. sodium sulfate at 30 C. for 1 second to swell the web, which was then squeezed to a moisture content of 280%. The web was pressed under a load of 23 kg./cm. with a pressure roller. Thus pressed unregenerated fiber web containing hydroxymethyl cellulose xanthate was cut into tapes of 1 cm. in width. Three of the tapes were formed into a rope with a conventional twisting machine. The number of twists was 60/m. (second twist) and 150/m. (first twist). Then, the rope was subjected to the regeneration treatment in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. to cause shrinking to the extent of 50%. Thereafter, the rope was scoured and dried by conventional methods to obtain a cord of regenerated cellulose having a tenacity of 7 kg/0.2 count (cotton count).

EXAMPLE 20 A viscose containing 7% cellulose and 4% alkali and having a salt point of 14, a -value of 64 and a viscosity of 180 seconds was extruded into a coagulation bath containing 30 g./l. sulfuric acid, 65 g./l. sodium sulfate and 6 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 230% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 50 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 30 in terms of 'y-value and the decomposition degree was 53%. The fineness of the filaments was 1.5 denier.

The stretched filaments were cut to 12 mm. lengths and immediately dispersed in water having a pH of 6.5 at 20 C. The dispersed fibers were formed into a Web on a combined net characterized by the combination of a net having projections (FIG. 9a) and a net having meshes of a size larger than the diameter of the projections (FIG. 9b). The swelling degree of the unregenerated fibers at this point was 200% based on the weight of cellulose. The unregenerated fiber web was squeezed and thereafter the web was completely regenerated in a regeneration bath containing 5 g./l. sulfuric acid at 85 C. and scoured and dried by the conventional methods to obtain a non woven fibrous product, which had a ringlike convex form as shown in FIG. 10. The product had little difference in strength between the machine direction and the cross direction and was excellent in drape. In FIG. 10, 1 shows the convex part and 2 and 3 show the concave part.

16 EXAMPLE 21 A viscose containing 6.5% cellulose and 4% alkali and having a salt point of 21.5, a 'y-value of 84 and a viscosity of 162 seconds was extruded into a cogulation bath containing 31 g./l. sulfuric acid, g./l. sodium sulfate and 10 g./l. formaldehyde at 25 C. to form filaments. The filaments withdrawn from the coagulation bath were immediately stretched to 175% of the original length in a stretching bath containing 1 g./l. sulfuric acid at 60 C. The content of hydroxymethyl cellulose xanthate in the stretched filaments was 44 in terms of 'y-value and the decomposition degree was 48%. The swelling degree of the stretched filaments and the dissolving degree of the unregenerated filaments in aqueous solutions containing 10 g./l. sodium sulfate and having a pH ranging from 1.5 to 8 at 20 C. are shown in Table 4.

TABLE 4 pH M 1. 5 2. 5 4 6 6 7 8 Dissolving degree (percent) 0 0.8 6.4 12.5 12.8 13.4 14.0 Swelling degree (percent) The swelling degree was measured as follows:

A given amount of the unregenerated fibers (corresponding to about 1 g. as dried cellulose) was dipped in the aqueous solution and thereafter dehydrated with a centrifugal hydroextractor under a centrifugal force of 1000G for 3 minutes. The weight of the sample after the treatment was obtained as W and the weight of the sample which was regenerated, washed and dried was obtained as D. The swelling degree was calculated by the following formula.

Swelling degree (percent) X (percent) EXAMPLE 22 Filaments comprising hydroxymethyl cellulose xanthate obtained by extrusion and stretching in the same manner as in Example 21 were cut to 20 mm. length and immediately thereafter were dispersed in water at a pH of 6.0 and at 20 C. The dispersed fibers were formed into a web without using adhesives on a plastic net. The swelling degree of the web was 240%. The wet web was squeezed to a water content of 500%. Thereafter, the web was passed through embossing rollers heated at C. at a speed of 5 m./min. under a pressure of 5 kg./cm. to obtain a sheet having a non-woven fabric form wherein heat adhered portions were converted into transparent film state and other portions remain bulky state. Thus obtained sheet was subjected to the decomposition treatment of hydroxymethyl cellulose xanthate and scouring treatment. The apparent specific gravity of the film portions of the sheet was 1.2 and that of the other portions was 0.2.

What is claimed is:

1. A method for producing a non-woven fibrous product of viscose fibers comprising:

(a) dispersing spun and stretched viscose fibers comprising hydroxymethyl cellulose xanthate in an aqueous medium at a temperature lower than 40 C. under conditions which control the degree of swelling and dissolving of the fibers, said fibers prior 17 to dispersion having a decomposition degree of less than 90% and a hydroxymethyl cellulose xanthate content of a v-value after spinning and stretching of greater than 20;

(b) forming the dispersed fibers into a web;

(c) swelling and partially dissolving said fibers such that said fibers are self-bonding; and

(d) subsequent to the above steps, subjecting the hydroxyrnethyl cellulose xanthate in the fibers to decomposition to form cellulose, thereby fixing the structure of the web.

2. A method according to claim 1, wherein the viscose fibers are dispersed in an aqueous medium having low swelling ability to the viscose fibers and the viscose fibers are subsequently treated with a liquid medium having high swelling ability to the viscose fibers, after the formation of the web, but prior to the decomposition.

3. A method according to claim 2, wherein the web is introduced into an aqueous solution having high swelling ability to the viscose fibers and the web is maintained in this solution at low tension to cause shrinking of the viscose fibers and development of crimps.

4. A method according to claim 1, wherein the viscose fibers are dispersed in a liquid medium having high swelling ability to the viscose fibers to cause simultaneous swelling of the viscose fibers.

5. A method according to claim 4, wherein web forming and bonding of the fibers are carried out simultaneously.

'6. A method according to claim 4, wherein the viscose fibers are partially swollen prior to web formation and swelling and bonding are completed subsequent to web formation but prior to regeneration.

7. A method according to claim 1, wherein the swelling of the viscose fibers is performed by using a liquid medium selected from the group consisting of (1) substantially salt-free aqueous solutions having a pH of greater than 2, (2) aqueous solutions of an alkali, alkaline earth or ammonium salt of an organic or inorganic acid, and (3) an aqueous solution containing organic solvent selected from the group consisting of nitrogen-containing solvents, sulfur-containing solvents and water soluble ketones.

8. A method according to claim 1, wherein only a part of the surface of the formed web is compressed to bond the fibers to each other.

9. A method according to claim 8, wherein the partial compression is carried out using a heated roll.

10. A method according to claim 1, wherein the viscose fibers are obtained by extruding a viscose containing 2 to 8% total alkali and having a salt point of at least 6 into a coagulation bath containing 3 to 20 g./l. formaldehyde, 20 to 250 g./l. sodium sulfate, at most 0.3 g./l. zinc sulfate and 10 to 120 g./l. sulfuric acid.

11. A method according to claim 1, wherein the viscose fibers are produced by extruding a viscose containing 2 to 8% total alkali and 0.2 to 2% formaldehyde and having a salt point of at least 6 into a coagulation bath containing 1 to 6 g./l. formaldehyde, 20 to 250 g./l. sodium sulfate, at most 0.3 g./l. zinc sulfate and 10 to 120 g./l. sulfuric acid.

12. A method according to claim 1, wherein the viscose fibers are obtained by extruding a viscose containing 2 to 8% total alkali and having a salt point of at least 6 into a coagulation bath containing 14 to g./l. sulfuric acid, 20 to 250 g./l. sodium sulfate and at most 1 g./l. zinc sulfate and kept at a temperature of lower than 35 C. and thus obtained filaments are treated with an aqueous solution containing 15 to g./l. formaldehyde.

13. A method according to claim 1, wherein the temperature of said aqueous medium for dispersing said viscose fibers is less than 30 C.

14. A non-Woven fibrous product obtained by the method of claim 1.

References Cited UNITED STATES PATENTS 3,320,1 17 5/1967 Aoki 162157 C 3,511,751 5/1970 Fukumura 162-157 C X 3,419,652 12/1968 Kubota ct al. 264-189 X 3,539,679 11/1970 Kimura et al 264197 3,574,812 4/1971 Kubota et al. 264--189 X 3,574,813 4/1971 Kubota et al 264189 X FOREIGN PATENTS 1,167,555 10/1969 Great Britain l5683 ROBERT F. BURNETT, Primary Examiner H. F. EPSTEIN, Assistant Examiner US. Cl. X.R.

813l; l5683; 264-l88, 189