US3684648A - Multicomponent filamentary material formed from waste material - Google Patents

Abstract

A CONJUGATE FIBER COMPRISING DISTINCT ZONES OF CELLULOSE TRIACETATE AND A BLEND OF SECONDARY CELLULOSE ACETATE WTIH CELLULOSE TRIACETATE, SAID FIBER BEING PRODUCED BY A METHOD WHICH COMPRISES INJECTING INTO DOPE STREAM OF SECONDARY CELLULOSE ACETATE A SOLUTION OF "WASTE" MULTICOMPONENT FILAMENTARY MATERIAL OF CELLULOSE TRIACETATE AND SECONDARY CELLULOSE ACETATE, CONTACTING THE SO-MODIFIED CELLULOSE ACETATE DOPE STREAM WITH A DOPE STREAM OF CELLULOSE TRIACETATE TO FORM A COMPOSITE STREAM, PASSING THE COMPOSITE DOPE STREAM BY LAMINAR FLOW TO A JET, AND EXTRUDING THE COMPOSITE DOPE STREAM THROUGH THE JET TO FORM MULTICOMPONENT FILAMENTARY MATERIAL. THEREAFTER MAY SLECTIVELY SAPONIFY SO AS TO REGENERATE CELLULOSE FROM THE CELLULOSE ACETATE, RESULTING IN MULTICOMPONENT FILAMENTS OF CELLULOSE TRIACETATE AND REGENERATED CELLULOSE.

Description

United States Patent US. Cl. 161-175 2 Claims ABSTRACT OF THE DISCLOSURE A conjugate fiber comprising distinct zones of cellulose triacetate and a blend of secondary cellulose acetate with cellulose triacetate, said fiber being produced by a method which comprises injecting into dope stream of secondary cellulose acetate a solution of waste multicomponent filamentary material of cellulose triacetate and secondary cellulose acetate, contacting the so-modified cellulose acetate dope stream with a dope stream of cellulose triacetate to form a composite stream, passing the composite dope stream by laminar flow to a jet, and extruding the composite dope stream through the jet to form multicomponent filamentary material. Thereafter may selectively saponify so as to regenerate cellulose from the cellulose acetate, resulting in multicomponent filaments of cellulose triacetate and regenerated cellulose.

BACKGROUND OF THE INVENTION (1) Field of the invention This application, which is a divisional application of application S.N. 857,564, filed Sept. 12, 1969, and now Pat. No. 3,584,089, relates to the production of multicomponent filamentary material. More particularly, it relates to a method of utilizing waste multicomponent filamentary material, which waste has heretofore been discarded, by adding a solution of such waste to a selected dope stream containing one of the components for the multicomponent filaments.

(2) Description of the prior art Methods for producing multicomponent or conjugate filaments are well known in the art. In US. Pat. 3,039,173, there is described a method involving spinning together two or more cellulosic derivatives, at least one of which is fiberforming, in such a way that the derivatives are not appreciably blended together but rather form over the cross section of the single composite filament two or more distinct zones which extend through the entire length of the filament, whereby only one or, alternatively part of or all of the components form the surface of the single composite filament. The extrusion may be such that the components are localized and held together in a sideby-side arrangement in which both components form part of the composite, or the extrusion may be such that one component forms a core and the other a sheath to form a sheath-core composite. In this latter instance, only the sheath contributes to the surface of the composite. See also US. Pat. 3,209,402, which describes method and apparatus suitable for producing multicomponent filaments and yarns. The' contents of each of the foregoing patents are incorporated hereby by reference: Thus, the term multicomponent filaments as used herein refers to filaments formed from 2 or more fiber-forming masses wherein distinct zones of each mass remain segregated in co-extensive relationship throughout at least a portion of the fiber as opposed to the homogeneity associated with fibers formed from a blend of two or more fiber-forming Ice,

components. Multicomponent and conjugate are used interchangeably herein to describe such fibers.

Multicomponent filaments that have proven to be of considerable importance commercially are those made up of cellulose triacetate and regenerated cellulose. It has been found desirable in preparing such bicomponent filaments to utilize two separate dope streams, one of cellulose triacetate and the other of secondary cellulose acetate (hereinafter referred to as cellulose acetate). These two dope streams are brought together in surface to surface contact, e.g., as by side-by-side arrangement, sheath-core arrangement, or the like, and the resulting composite dope stream is caused to flow by laminar or viscous flow to a jet or spinnerette. The composite dope stream is extruded through the jet so as to form a multicomponent (in this instance a bicomponent) filamentary material made up of cellulose triacetate and cellulose acetate. Inasmuch as the cellulose acetate is more readily regenerated to cellulose than is the cellulose triacetate, the composite material may be selectively saponified under mildly alkaline conditions whereby the cellulose acetate will be converted to regenerated cellulose without significantly affecting the cellulose triacetate, thus resulting in a bicomponent filamentary material made up of cellulose triacetate and regenerated cellulose.

The selective saponification of the cellulose acetate/ cellulose triacetate bicomponent fiber wherein only the cellulose acetate is appreciably saponified is desired for a number of reasons. Of primary concern is the degree of crimp developable during selective saponification, enabling use of the fiber in textile end-use manufacturing processes, i.e., knitting: and Weaving operations, without further texturing and/or bulking. Additionally, regenerated cellulose, along with its superior dyeability with respect to direct dyes over secondary cellulose acetate, increases the safe ironing temperature of textile structures constructed of the bicomponent fiber.

Inevitably, in the production of multicomponent filamentary material, some wastage of filamentary material occurs. For instance, with respect to the production of cellulose acetate/cellulose triacetate bicomponent filaments, it has been found that the amount of such material that has heretofore been discarded as waste is generally of the order of from about 1 to 20 percent by weight, based upon total spinning dope utilized. Such waste results from such varied factors as short bobbins, quality deficiencies, etc.

In processing either cellulose acetate or cellulose triacetate alone, waste would be redissolved. With mixed material, however, the waste was dilferent from each stream of dope and it was not thought possible to utilize the waste cellulose triacetate-cellulose acetate bicomponent filamentary material which therefore was discarded as scrap even though it would obviously be beneficial from an economic viewpoint to be able to re-use such material. In greater detail, it had previously been thought by those of skill in the art that the addition of cellulose acetate to the triacetate phase would impair crystallization of that segment of the bicomponent fiber, preventing sufiicient crimping while conversely addition of triacetate to the secondary acetate would retard saponification of that component resulting in a markedly elevated acetyl value, less crimping and general decline in the desirable attributes of regenerated cellulose being imparted to the bicomponent fiber. Therefore, it is an object of this invention to provide a method to economically produce a regenerated cellulose/ cellulose triacetate bicomponent fiber. Another object of the invention is to provide a method to produce a regenerated cellulose/cellulose triacetate bicomponent fiber by selective saponification techniques from a secondary cellulose acetate/cellulose triacetate bicomponent fiber wherein bicomponent waste material is recycled to be incorporated into the partially saponified heterofilarnent without deleteriously affecting desired fiber properties, and particularly crimp levels. A further object of the invention is to provide a novel cellulose acetate/cellulose triacetate precursor and the selectively saponified fiber produced therefrom. Other objects of the invention will appear obvious to those of skill in the art from the detailed description of the invention hereinafter.

SUMMARY OF THE INVENTION By virtue of the present invention, there has been found a method for reusing waste cellulose triacetatesecondary cellulose acetate multicomrponent filamentary material. [In essence, the method of the invention involves dissolving such waste, adding the resulting solution to the secondary cellulose acetate dope stream, bringing the resulting cellulose acetate dope stream (containing waste solution below a critical weight percent level of triacetate therein) into face to face contact with a dope stream of cellulose triacetate, passing the resulting composite stream by viscous flow to a jet, and extruding the composite stream therethrough to form bicomponent filaments. More particularly, it has been found that the amount of Waste solution in the cellulose acetate dope stream must be such that the cellulose triacetate level in the cellulose acetate dope stream does not exceed about 30 percent by weight, such value assuring adequate selective saponification of the secondary cellulose acetate phase of the bicomponent fiber to produce a highly crimped fiber displaying the combined desired properties of both regenerated cellulose triacetate. In one aspect of the invention which may be considered as a preferred embodiment thereof, there is provided a spun composite precursor fiber containing coextensive secondary cellulose/acetate/cellulose triacetate phases wherein the secondar'y cellulose acetate zone includes up to about 30 percent by weight cellulose triacetate i.e., about 15 to 30 percent, based on total weight of secondary cellulose acetate and cellulose triacetate in said secondary acetate zone, and the selectively saponified fiber obtainable therefrom.

DETAILED DESCRIPTION OF THE INVENTION As previously noted, heretofore it has been known to prepare bicomponent filamentary materials made up of cellulose triacetate and regenerated cellulose. This method has comprised bringing together a dope stream of cellulose triacetate with a dope stream of cellulose acetate, joining the two streams so as to form a single composite stream wherein the interface between the separate dope streams has remained discrete and identifiable, passing the composite stream by laminar flow to a jet, and extruding the composite stream through the jet so as to form cellulose triacetate-cellulose acetate bicomponent filaments. Thereafter such bicomponent filamentary material can be subjected to selective saponification so as to regenerate cellulose from the cellulose acetate without significantly altering the chemical composition of the cellulose triacetate.

'In accordance with one aspect of our invention, we have found that waste bicomponent material made up of cellulose triacetate and cellulose acetate may be dissolved and the resulting solution injected into a dope stream of cellulose acetate prior to joining such cellulose acetate dope stream with a cellulose triacetate dope stream. The cellulose acetate dope stream containing the waste solution therein is then united with the cellulose triacetate dope stream, the resulting composite stream is extruded to form bicomponent filaments, and these filaments may be then subjected to selective saponification so as to form cellulose triacetate-regenerated cellulose bicomponent filamentary material.

The foregoing is surprising, inasmuch as one would expect that the presence of cellulose triacetate in the cellulose acetate dope stream (arising from the introduction of a solution of cellulose acetate-cellulose triacetate waste thereto) would tend to impede saponification and regeneration of the cellulose acetate to form regenerated cellulose. On the contrary, however, we have found that so long as the level of cellulose triacetate in the dope stream of cellulose acetate does not exceed about 30 percent by weight, then the resulting bicomponent filament (formed by extruding the composite dope stream through the jet) may be readily selectively saponified to give a bicomponent filament of cellulose triacetate and regenerated cellulose, the properties of such bicomponent filament being essentially identical to those exhibited by a similar bicomponent but wherein no filamentary waste of cellulose acetate-cellulose triacetate had been added to the cellulose acetate dope stream.

Our discovery is all the more surprising inasmuch as the converse approach does not work. That is, if the cellulose acetate-cellulose triacetate waste filaments are dissolved and the solution is added to the dope stream of cellulose triacetate, one does not obtain satisfactory results. Specifically, if a solution of waste filaments of cellulose triacetate-cellulose acetate is injected into the cellulose triacetate dope stream, even in such minor quantity that the relative amount of cellulose acetate is only about 15 percent by weight, and if thereafter the triacetate dope is joined with a cellulose acetate dope to form a composite dope stream which is extruded, then we have found that the resulting bicomponent filaments, upon being subjected to mild conditions of saponification, regenerate to cellulose, i.e., not only the cellulose acetate component (derived from the dope stream of cellulose acetate), but also the cellulose triacetate component (derived from the cellulose triacetate dope stream). The reason for this appears to be that the presence of cellulose acetate (with its numerous hydroxy groups) in the triacetate dope stream renders the triacetate far more readily regenerable to cellulose upon being subjected to conditions thought to lead to selective saponification.

The particular spinning techniques employed will vary, being the type normally employed to extrude the conjugate filament, i.e., melt spinnning, solution spinning, etc. Although melt spinning, that is, a spinning technique wherein a melted fiber-forming material is extruded, is usually not employed for the forming of cellulose acetate-containing fibers, if so desired the waste material within the defined weight percentages can be added to an appropriate secondary cellulose acetate melt prior to joining the two fiber-forming streams. In most instances, solution spinning processes are involved, and particularly dry spinning; that is, a solution of the fiberforming materials is spun into a heated chamber wherein the solvent evaporates as opposed to spinning into a coagulent, as in wet-spinning methods. Obviously, the particular solvent used is not critical to the invention as long as the waste material containing cellulose triacetate is either soluble in the solvent medium selected for the secondary cellulose acetate dope stream or, alternatively, a solution of the waste material is compatible with the secondary cellulose acetate dope within the proportions used. In the preferred methods of the invention, the waste material is dissolved or dispersed in a solvent miscible with the solvent used in the secondary cellulose acetate dope stream and, in most instances, the same solvent will be employed as used in the secondary cellulose acetate solution.

Thus, the solvent for either dope stream will most often be that routinely employed within the cellulose acetate dry spinning art. As examples of suitable solvents, there may be mentioned acetate, methanol, ethanol, methylene chloride, methyl chloride and mixtures thereof such as methylene chloride/methanol admixtures. The various spinning solvents are well known in the art. If one preferred solvent may be mentioned, it is a mixture of methylene chloride and methanol within the ratio of about 80:20 to 99:1 and, most preferably, about 90:10 to 92:8 with the identical solvent mixture being employed for both the secondary cellulose acetate and cellulose triacetate dope streams.

Likewise, the respective ratios by weight of secondary cellulose acetate and cellulose triacetate within the component fiber as extruded will vary within ranges well known in the art, i.e., about 1:3 to 3:1, and preferably about 1:1 or about 50 weight percent of each ester in the bicomponent fiber. Regardless of the percentage of secondary cellulose acetate in the extrudate, the critical parameter is the limitation on the Weight percent of cellulose triacetate which may be included within the secondary acetate dope stream without impairing desired fiber properties, with only that amount of waste material being added thereto to supply up to 30 percent by weight triacetate based upon the total amount of cellulose triacetate and secondary cellulose acetate within the secondary acetate zone of the fiber.

The following example will further illustrate our invention. All parts are by weight unless otherwise stated.

EXAMPLE A normal 50/50 cellulose acetate-cellulose triacetate conjugate yarn is dry spun as the control with both fiber-forming materials being dissolved (22% solids) in methylene chloride/methanol solvent 91/9. The bicomponent filaments are of the sheath-core type, with the sheath being cellulose triacetate and the core being cellulose acetate.

The run is repeated with the addition of the cellulose triacetate dope to the secondary cellulose acetate system to produce secondary cellulose acetate dopes of 15, 30, and 50 percent cellulose triacetate content. These dopes are then spun as the cellulose acetate half, i.e., the core, of the bicomponent filaments. Dry spinning techniques are employed throughout the example.

Table 1 hereinafter sets forth the spinning conditions employed and the observed physical properties wherein CTA designates cellulose triacetate and CA designates secondary cellulose acetate. The 50 percent CTA in CA level would correspond to the use of 100 percent recycled waste material from 50/50 bicomponent fiber as the CA phase.

TABLE 1 Spinning conditions:

Take-up speed: 500 mJmin. Jet: 40 holes each 010.036 mm. diameter Dope:

Core: 0, 15, 30, 50% CTA in CA CTA.

Sheath:

CTA in GA side, percent;

Physical properties Control 15 30 50 Denier 197. 1 199. 5 197. 4 197. 8 Tenacity, g./d 1. 1.27 1.32 1.3 Elongation, percent 31. 6 32.4 32. 6 32.6

pared with the control as a standard. All samples exhibit adequate bulkiness except for the 50 percent CTA sample which shows a deficient crimp level rendering the fabric unsuitable as a bulky knit fabric without subjection to further texturing operations. Calculation of acetyl values of all fabrics reveals an elevated value for the 50 percent CTA fabric which would account in part for the lower crimp level as a consequence of less relative saponification occuring in the secondary cellulose acetate zone of the bicomponent fiber.

The precursor and saponified fibers resulting from the method of the invention will contain a certain percent by weight of cellulose triacetate in the secondary acetate part of the composite fiber. While the above example demonstrates the invention indicating maximum permissible values, obviously lower amounts of cellulose triacetate may be incorporated into the secondary cellulose acetate dope stream, i.e., about 5 to 10, or even about 1 percent by Weight based on the weight of secondary acetate and triacetate in said stream.

The inclusion of triacetate in both phases of the multicomponent fiber is advantageous for reasons in addition to economics. For example, the resulting fiber exhibits less fibrillation during the tensions applied thereto in textile manufacturing operations, i.e., knitting and weaving processes, fiber integrity being markedly improved because of the increased relative afiinity of both fiber phases to one another due to the presence of the triacetate in both dope streams. Another surprising saponified fiber characteristic is that acetyl values remain relatively constant up to the 30 percent CTA level, indicating that the triacetate content of the secondary acetate phase is also selectively saponified; that is, the presence of secondary acetate increases the saponifiability of triacetate.

Variations can, of course, be made without departing from the spirit of our invention.

Having thus disclosed the invention, what is claimed is:

1. A conjugate fiber comprising distinct zones of (a) cellulose triacetate and (b) a blend of secondary cellulose acetate with cellulose triacetate, said blend (b) containing more than 30 percent by weight of blended cellulose triacetate based on total weight of cellulose triacetate and secondary cellulose acetate in said blend (b).

2. The fiber of claim 1 wherein said blend (b) contains at least 15 percent by weight of cellulose triacetate based on total weight of cellulose triacetate and secondary cellulose acetate in said blend (b).

References Cited UNITED STATES PATENTS 3,039,173 2/1958 Mchler, Jr. et al. 161-173 3,103,732 9'/ 1963 Woodell l6l--173 3,414,644 12/1968 Myles et a1. 264'207 3,584,089 6/1971 Kunkel et a1 106--196 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. X.R.