US2476293A - Artificial fiber - Google Patents

Description

July 19, 1949.

' J. W. HALL ETAL ARTIFICIAL FIBER Filed Oct. 3, 1944 INVENTORJ Patented July 19, 1949 UNITED STATE NT OFFICE ARTIFICIAL FBER Delaware Application October 3, 1944, Serial No. 557,004

This invention relatesv to novel hollow filaments of regenerated cellulose, products formed therefrom, and to processes for producing the same.

It has been proposed, heretofore, to produce hollow filaments by methods involving the emulsification of air in viscose prior to extrusion thereof, or the incorporation in the viscose of substances, commonly alkali carbonates, capable of reacting with acid to develop a gas, and extrusion of the mixture into an acid spinning bath.

All of the hollow regenerated cellulose fllaments of the prior. art, however, produced, have had a'common characteristic in that they have been tubular in cross-section, comprising either a hollow continuous canal, or a plurality of individual voids or lumens each taking up the entire cross-section area of the filament and spaced end to end along the length of the filament by transverse partitions. The hollow filaments oi the prior art have numerous disadvantages. Most importantly, such filaments have extremely low tensile strength and extensibility and, further, readily undergo considerable permanent collapse during manufacture, such as when they are passed over guides, about the godets, and under their own pressure as they are being collected on bobbins or in spinning buckets. Even after drying, should there be any appreciable residual inflation in the filaments having the tubular voids or lumens, additional permanent deflation occurs Whenever articles formed therefrom such as cushions, mattresses, wearing apparel, etc., are subjected to compression, with a noticeable loss -of buoyancy and increase in weight of the articles.

It is the purpose of our. invention to provide new hollow filaments. of. regenerated cellulose which do not exhibit the disadvantages associated with the hollow filaments heretofore known. It is a further object of our invention to provide hollow filaments which undergo substantially no loss in inflation when they are manipulated during production thereof. A still further object is to provide articles formed from our new hollow filaments which articles are not susceptible to deterioration in use due to loss of inflation in the filaments when they are compressed. Further objects and advantages will appear hereinafter.

In accordance with our invention, hollow filaments of regenerated: cellulose are obtained which in cross section, have a unique structure 2 Claims. (CI. 2882) by virtue of whichthey are sharply distinguishable from hollow filaments of the prior. art.

In the accompanying drawing illustrative oi the invention, g

Figure 1 is a cross-sectional view. of the file. ments of our invention;

Figure 2 is a view taken along the. length of the filaments of our invention; and.

Figure 3 is a cross-sectional view of a typical hollow filament of the ,prior art.

Referring to Figure 1, it will be seen that our new filaments have, in cross-section, a, cellular.

type structure, the cross-section area being occupied by a web-like network comprising a plurality of partitions 2 which separate. and define a plurality of voids or.lumens.3.' The partitions 2 radiate irregularly from the solidportion at one or more points 4 within thefilament, andconnect the solid portion 4 with what may be defined as the inner peripheral wall of. the fiber. The partitions lay more or less at random and may have a regular or irregular contour, and the voids or lumens, which may vary in size from extremely small to much larger voids, are of varying shape, some being more elongated than others, for example, as determined by the con tours of the dividing partitions. The solid portion 4 extends longitudinally of the fiber length along at least a substantial portion thereof. The voids 3 overlap one another and lie irregularly spaced along the fiber axis as shown in Figure 2. The separating partitions 2 present, as viewed in Figure 1, an essentially Web-like network or configuration. All of the partitions radiate from a point within the filament but not necessarily all from the same point and the partitions may have a more or less complex shape constituted by a branched structure, one or more partitions branching off from one or more others which radiate from a common point, as shown in Figure 1. The external walls of the hollow filaments are thus provided with an internal web-like support which enhances the rigidity of thefilaments so that while they are flexible enough to enable their being easily manipulated and adaptable to various textile working processes, they do not tend to collapse even under the influence of very high compressional forces. Under such conditions, the filaments give, but do not permanently collapse and upon removal or the compressing forces the inflated condition is immedi ately recovered.

We have discovered that filaments having the novel structure, in cross-section, described above and shown in Figure 1 can. be produced from viecose containing sodium carbonate only by a proper, selective control and correlation of the spinning conditions.

Generally, the viscose should analyze from about 1.9 to about 2.5% total sulfur, from about 6 to 9% sodium hydroxide (based on percent weight in viscose), from about 6 to 9% by weight cellulose, and should contain a large proportion of sodium carbonate, that is, from about to (based on the cellulose present). The viscose preferably should have a common salt (NaCl) point of from 5 to 6.

The viscose is extruded into an acid bath having a regenerating capacity equivalent to not less than 11% sulfuric acid, mixed with a large proportion, not less than 5%, of a zinc salt, and a large proportion of sodium sulfate, that is not less than 21%. Preferably, the bath contains from about 11.3 to 12.5% sulfuric acid; from about 5 to 6% zinc sulfate; and from about 21 to 25% sodium sulfate. The viscose may contain special modifying agents, if desired, such as dyes, pigments, etc., or any mixture of such materials.

The spinning bath should have a temperature between 40 to 60 C. The immersion depends, to some extent, upon the denier of the filaments, longer immersion periods being productive of better results in the case of filaments of larger total denier and denier per filament.

If desired, the filaments may be given a stretch up to about 40 to of their length, by passing them between godets or rollers operating at different speeds, or by means of any other equivalent stretching procedure, and preferably the filaments are stretched soon after leaving the coagulating medium. When necessary, the stretching may be facilitated by passing the filaments through a plasticizing bath, such as hot water, hot acids, and the like.

Generally, the various factors involved in producing the fibers are correlated as indicated, and the various ingredients of the viscose and the spinning bath are used in proportions within the ranges stated, but when the sodium carbonate is present in the viscose in the higher amounts, the sulfuric acid, zinc sulfate, and sodium sulfate contents of the spinning bath are not quite as critical as when the smaller quantities of sodium carbonate are employed.

For illustrative purposes, the following specific examples are given.

Example I A viscose aged to a common salt point of 5.5 and having 8.4% by weight sodium hydroxide, 7.3% cellulose, 2.3% total sulfur and to which had been added 25% by Weight of sodium carbonate (based on cellulose) was extruded through a spinneret to produce a 120-filament thread having a total denier of 300, into a spinning bath maintained at 50 C. and containing 12.3% sulfuric acid, 22% sodium sulfate and 5.3% zinc sulfate.

The immersion was 24". After leaving the bath the filaments were passed over two godets in succession having a differential in speed which effected a 40% stretch of the filaments. Filaments which along their entire length showed, in cross-section, a cellular type structure were obtained.

Example If A viscose aged to a sodium chloride salt point of 5.3, and having 8.1% by weight sodium hydroxide, 7.4% by weight cellulose, 2.3% by Weight total sulfur and to which had been added 20% of sodium carbonate (based on cellulose present) was extruded through a spinneret to produce a 200 filament thread having a total denier of 300, into a spinning bath maintained at about 45 C., and containing 12% sulfuric acid; 22.5% sodium sulfate, and 5.3% zinc sulfate. The immersion was 14 inches. The filaments were stretched 40% between godets. Filaments which along of the fiber axis showed, in cross-section, a cellulartype structure, were obtained.

Example III A viscose aged to a sodium chloride salt point of 5, and having 9% by weight sodium hydroxide, 7.6% by weight cellulose, 2.3% by weight total sulfur and to which had been added 25% of sodium carbonate (based on the cellulose) was extruded through a spinneret to produce a 490- filament thread of 1200 total denier, into a spinning bath maintained at 50 C., and containing 11.4% sulfuric acid, 23% sodium sulfate, and 5.5% zinc sulfate. The immersion was 14", The filaments were stretched 40% between godets. Filaments were obtained which, along 95% of their length showed, in cross-section, a cellulartype structure.

Example IV A aged to a SOdlllIIl chloride salt point 5.5, and having 8.5% by weight sodium hydroxide, 7.2 cellulose, 2.3% total sulfur and to which had been added 25% sodium carbonate ased on the cellulose present) was extruded through a spinneret to produce a 24 filament structure of 300 total denier, into a spinning bath containing 12% sulfuric acid, 22.5% sodium sulfate, and 6% zinc sulfate. The immersion was 64". The filaments leaving the bath were given a stretch of 40%. The filaments thus obtained showed, in cross-section, at all points along the filament length, a cellular type structure.

The filaments obtained as described have dry tensile strengths of approximately 2 or more grams per denier, and wet extensibilities of about 30%.

The individual filaments produced in accordance with this invention have in cross-section a cellular type structure at points along at least a substantial portion of the filament length which comprises a plurality of voids or gas pockets which are separated by partitions forming an internal support for the filaments.

The hollow continuous filaments initially obtained may be cut to staple length, as well as continuous or broken filament yarns. For example, the filament bundles proceeding from several spinnerets over stretching godets may be combined into tows of 1200 up to 400,000 or so denier. The tows while still Wet are cut to staple fiber, which is allowed to fall into a liquid bath which may serve merely to effect opening of the fiber clumps, or may also serve the purpose of an additional liquid treatment, such as washing or desulfurizing. The opened staple fibers are wettreated, and finally dried in any appropriate manner.

The filaments have a delustered appearance, give full, deep dyeings in dull shades, and are characterized by a soft hand and feel, excellent water retentivity, light weigh-t, and enhanced covering power. Those filaments that are made without much stretching are generally substantially cylindrical or long and oval in cross-section,

depending upon the type of spinneret utilized, while those which have been given a greater amount of stretching exhibit numerous points of necking down along their length, and due to this irregularity of configuration possessed by some of the filaments they exhibit fulling and felting properties resembling natural wool.

The new hollow fibers, either as continuous filaments or as staple fibers may be used in the production of textile yarns and knitted or woven fabrics which are especially useful in the manufacture of wearing apparel or bed clothing where lightness in weight, buoyancy, and protection from cold or heat are important factors. Carded mats of the material may be used as fillers for the production of comforts, wearing apparel, cushions, life preservers, vibration damping, sound insulating or generally as a heat insulating material for filling spaces between the walls of buildings or other structures to be insulated, such as ice boxes, cold rooms, ships, railway cars, automobiles, airplanes, and the like, and for any of these uses, Where desired or necessary, the mats may be provided with a water-proof wrapping or the filaments may be impregnated with a resin, such as phenol-aldehyde and phenol-ketone resins, for example, phenol-formaldehyde resins, phenol-diphenylol propane-formaldehyde or ketone resins, phenol-furfural resins, aromatic sul-= fonamide-aldehyde resins, benzophenone aldehyde resins, and the polymerized vinyl resins.

The novel hollow filaments of the present invention, may be incorporated in filamentary bundles of the type described in the copending application of Robert J. Taylor, Serial No. 530,682, filed April 12, 1944, now Patent No. 2,461,094, Feb-- ruary 8, 1949.

The filaments either per se or in the form of a yarn-like bundle, or in the form of a mat, carded or otherwise, may be crimped by efiecting shrinkage, which increases the bulk of the products. Further the filaments may be rendered potentially self-crimpable by stretching them while in a plasticized condition, removing the plasticizer while the stretched condition is maintained, fabricating the stretched filaments or fibers and permitting the development of crimp therein in situ in the fabricated structure by activating the filaments, as during a fulling or felting operation, and permitting the crimped filaments or fibers to dry while relaxed.

Since many variations and modifications may be made in practicing the present invention, it is to be understood that we are not to be limited except b the spirit and scope of the appended claims.

We claim:

1. A yarn comprising a bundle of inflated regenerated cellulose fibers, a plurality of which show in cross-section, along at least a substantial portion of its length, a web-like network constituted by a plurality of distinct radiating partitions which separate and define a plurality of distinct individual voids between an internal point and the periphery wall of the fiber, the partitions constituting an internal support for the peripheral wall of the inflated fiber.

2. A stretched, inflated regenerated cellulose fiber of from about 1 to 15 deniers and showing, in cross-section, along at least a substantial portion of its length, a web-like network constituted by a plurality of distinct radiating partitions which separate and deflne a plurality of distinct individual voids between an internal point and the peripheral Wall of the fiber, the partitions constituting an internal support for the peripheral wall of the inflated fiber, and the fiber having a dry tenacity of approximately 2 gm. per denier.

JAMES W. HALL. ALFRED W. HUNTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 20,953 Stoeckly Dec. 20, 1938 1,487,807 Rousset Mar. 25, 1924 1,867,298 Zart July 12, 1932 2,136,463 Picard Nov. 15, 1938 2,136,464 Picard Nov. 15, 1938 2,171,805 Picard Sept. 5, 1939 2,339,950 Sackner Jan. 25, 1944 2,399,260 Taylor Apr, 30, 1946 FOREIGN PATENTS Number Country Date a 260,872 Great Britain Nov. 11, 1926 282,973 Great Britain Jan. 5, 1928 318,632 Great Britain Sept. 5, 1929 343,604 Great Britain Mar. 5, 1931 OTHER REFERENCES Rayon Textile Monthly, Oct, 1942, page 33, Continuous Cellophane Bubble Yarn.

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