US2986446A - Crimped regenerated cellulose fibres - Google Patents

Description

May 30, 1961 J. 0. SMITH ET AL CRIMPED REGENERATED CELLULOSE FIBRES Filed July 25, 1957 3 Sheets-Sheet 1 M y 1961 J. 0. SMITH ET AL 2,986,446

CRIMPED REGENERATED CELLULOSE FIBRES Filed July 25, 1957 3 Sheets-Sheet 2 57/00 60/7/00'G0rd/7e/ By .fhe/r qf/omeys y 1961 J. 0. SMITH ET AL 2,986,446

CRIMPED REGENERATED CELLULOSE FIBRES Filed July 25, 1957 3 Sheets-Sheet 3 FIG. 4.

gf'ii FIG. 5.

//7 van 20/5 John O/Wer Sm/f/i Br/an Con/0d Gardner By fhe/r afforneys United States Patent 2,986,446 CRIMPED REGENERATED CELLULOSE FIBRES John Oliver Smith, Coventry, and Brian Conrad Gardner, Kenilworth, England, assignors to Courtaulds Limited, London, England, a British company Filed July 25, 1957, Ser. No. 674,196

Claims priority, application Great Britain Aug. 1, 1956 9 Claims. (Cl. 18-54) This invention relates to the production of fibres by the viscose process.

United States of America patent specification No. 2,517,694 describes the production of crimped filaments of denier less than ten by extruding viscose into an aqueous acid coagulating bath having a high total salt content, subsequently stretching the filaments, and then relaxing the filaments so that they acquire a permanently recoverable crimp. The cross-section of such a filament when difierentially dyed as described in the Textile Research Journal 1945, page 443, shows an irregular shape with a skin-core structure in which the skin is much thicker around one part of the periphery than another part which has a thin skin or none at all. Typical crosssections are shown in Figure 1 of the accompanying drawings, in which the skin appears dark and the core light.

We have now found that regenerated cellulose fibres can be obtained capable of assuming to a high degree a permanently recoverable crimp upon relaxation in aqueous solution and having a cross-section part of which has a smooth exterior and is oval or bean shaped having a high proportion of skin, the remainder having a lobed periphery and consisting largely of cellulose having a core structure. In addition to an unusually high degree of crimp, the smoother surface increases the resistance of the fibre to soiling.

The invention also consists therefore in a process for producing such fibres by extruding viscose containing from 5.0 percent to 10.0 percent cellulose and from 5.0 percent to 10.0 percent caustic soda into a bath containing between 5 percent and 14 percent sulphuric acid, 0.5 percent and 4 percent zinc sulphate, and more than 12 percent sodium sulphate, in the presence of more than 0.05 percent on the weight of viscose of polyethylene glycol having an average molecular weight of between 600 and 6,000, or other polyoxyethylene derivatives of comparable molecular weight, at a salt figure between 3.0 and 14.0 and subjecting the filaments to a high degree of stretching, at least 50 percent. Stretching may be carried out, if desired, in a hot dilute acid bath. If this is done, a higher degree of stretch can be used, and results in an increased amount of crimp.

In a preferred form, the invention consists in extruding viscose containing from 7.5 percent to 8.3 percent of cellulose, caustic soda such that the ratio of caustic soda to cellulose is between 0.9 and 1, and 0.1 percent to 0.3 percent by weight of a polyoxyethylene derivative having a molecular weight between 600 and 6,000, at a salt figure of 5.5 to 8.5 into a coagulating and regenerating liquor containing, among other compounds, sulphuric acid, the concentration of which is dependent on the cellulose and caustic soda contents of the viscose and is best demonstrated by example. Thus, in the extrusion of viscose containing 7.0'percent of caustic soda and 7.5 percent of cellulose the sulphuric acid concentration in the liquor should be from 7.5 percent to 9.5 percent, whereas viscose containing 8.3 percent of cellulose and 2,986,446 Patented May 30, 1961 5.8 percent of caustic soda requires and acid concentration of from 5.5 percent to 6.5 percent in the liquor. The coagulating and regenerating liquor should also contain from 1 percent to 2 percent of zinc salts and from 22 percent to 24 percent of sodium sulphate, and be heated to a temperature of 55 C. Subsequently the regenerated cellulose filaments should be stretched by at least 60 percent and this may be accomplished in a hot dilute acid bath.

Instead of polyoxyethylene derivatives, other known additives which modify the sections of the fibres so as to produce a smoother surface and thicker skin, may be used, such as primary and secondary monoor polyamines and derivatives thereof, such as thiocarbamates and quaternary ammonium compounds.

Four typical cross sections of fibres produced according to the invention are shown in Figures 2, 3, 4 and 5 of the accompanying drawings. The skin portions are represented by the dark parts of the sections and the core by the lighter parts. It will be seen that at least half of each section has an oval or bean like shape with a thick skin, and that the remainder is mainly core, in some cases bound by a thin skin, and is lobed. The whole section has the appearance of a thick-skinned bean or oval shape, the core of which has burst through the skin at one or more points to form thin-skinned lobes. Figure 3 shows sections obtained by spinning into a bath containing 8.5 percent sulphuric acid at a salt figure of 7. Figures 2 and 5 show sections obtained by spinning viscose of a high salt figure and it will be seen that this has resulted in a more irregular outline to the thin skinned part of the section, which also appears to have cavities due to the higher proportion of carbon disulphide in the Viscose. Sections in which the bean shaped or oval parts have a still thicker skin are obtained by reducing the proportion of acid in the bath.

The following examples in which proportions are by weight show a typical process for obtaining such fibres:

Example 1 Viscose containing 7.5 percent cellulose, 7.0 percent caustic soda and 0.1 percent polyethylene glycol of average molecular weight 1,500 was extruded through a jet having holes of 0.006 inch diameter at a salt figure of 10.0 into a regenerating bath containing 9.0 percent sulphuric acid, 2 percent zinc sulphate and 22 percent sodium sulphate at 55 C. The length of immersion was 60 inches and the spinning speed was 32.5 metres per minute. After passing round a godet the filaments while still wet were subjected to 60 percent stretching by passing over a second godet driven at a greater peripheral speed than the first. The filaments were then cut into short lengths to form staple.

Upon relaxing the filaments in water, or an aqueous solution, the filaments assumed a high degree of crimp. This normally occurs in the process of washing free of acid, but may take place prior to this, when the filaments are in the form of tow or when out into staple.

After drying, the product, with a filament denier of 15.0, had a very high degree of crimp. The filaments, which when pulled out straight had a length of 4 inches, had a total of 22 crimps, and in their contracted state, had a length of about 2% inches.

Example 2 Viscose containing 7.5 percent of cellulose, 7.0 percent of NaOH, 0.1 percent of polyethylene glycol of average molecular weight 1,500 and at a salt figure of 7.0, was extruded at a rate of 480 grams per minute through a jet containing 1,400 holes each of 0.0065 inch diameter, into a coagulating and regenerating bath containing 8.50 percent of sulphuric acid, 1.92 percent of zinc sulphate and 23.2 percent of sodium sulphate maintained at a temperature of 50 C. The tow so formed emerged from the bath at a point 24 inches away from the jet and passed round a godet rotating at a peripheral speed of 26.2 metres per minute; and thence to a second godet with a peripheral speed of 42 metres per minute, so that the tow was stretched by 60 percent. The tow was passed through a cutter, where it was cut into tufts 2% inches in length. These tufts were transferred to a continuous wash machine, where, after being freely suspended in Water in a well at the entry of the machine for a few minutes to permit full development of the crimp, they were washed free from acid, salts, sulphur and other impurities. After drying, the filaments had a denier of 8.0 and a straight length of 2 /2 inches. Crimp measurements gave the following figures:

Initial crimp percent 12 Final crimp do 6 Waves/cm. 3.8

These tests for crimp were carried out in the following manner.

Single fibres were wetted and dried while held straight, to remove temporary or mechanical crimp. They were then rewetted and redried in a completely relaxed state to allow full development of the permanent, or chemical crimp. The length of each fibre was then measured under a load of 1 milligramme/denier (L applied by a torsion balance. In a similar manner the length under a load of 50 milligrammes/denier was measured (L This load is sufiicient to remove the crimp from the fibre without producing a permanent extension. The initial percent crimp is then given by the formula:

Each fibre was then given 4 cycles of loading and unloading, each load being applied for 30 seconds", with intervals of 30 seconds between. Using the lengths measured in the 4th and final cycle, the final percent crimp is obtained by the formula above.

The waves/ cm. were measured by counting the number of peaks visible on fibres, which had been treated to remove temporary crimp, lying horizontally in a completely relaxed state, and dividing by the relaxed length.

Each figure given is the average of measurements on twenty fibres selected at random from a given sample.

Cross-sections of the fibres when stained in accordance with the Textile Journal page 443 were similar to those shown in Figure 4.

Example 3 Viscose containing 7.5 percent of cellulose, 7 .0 percent of NaOH, 0.2 percent of polyethylene glycol of average molecular weight 1,500 and at a salt figure of 7.5, was extruded through a jet containing 674 holes each of 0.01 inch diameter into a coagulating and regenerating bath containing 9.25 percent of sulphuric acid, 2.0 percent of zinc sulphate, and 23 percent of sodium sulphate, maintained at 55 C.

The viscose flow was such as to give a final denier of 35. The tow so formed was conducted through the bath for a distance of 75 inches, then led on to a god'et rotating with a peripheral speed of 20.3 metres per minute, and thence to a second godet with a peripheral speed of 32.5 metres per minute, so that the tow was stretched by 60 percent. The tow was then cut into short lengths and washed as in Example 1. Crimp measurements on the dried product gave the following results:

4 Example 4 Viscose containing 8.3 percent of cellulose, 5.8 percent of caustic soda and 0.13 percent of polyethylene glycol (of average molecular weight 1,500) and having a salt figure of 8.0 was extruded through a jet containing 674 holes each of 0.006 inch diameter into a coagulating and regenerating bath containing 6.25 percent of sulphuric acid, 2.0 percent of zinc sulphate and 24 percent of sodium sulphate, at 55 C. The rate of extrusion was such that the tow so formed, after stretching, washing and drying had a denier of 15. The tow was led through the coagulating and regenerating bath for a distance of 60 inches, before being withdrawn round a guide, and passed on to a godet rotating with a peripheral speed of 20.3 metres per minute. 7

From this point it was passed round a second godet with a peripheral speed of 32.5 metres per minute, thus having been stretched by 60 percent. The freshly spun tow, when allowed to relax in water, contracted, due to the development of crimp, to 45 percent of the original length and had 3% crimps per inch of contracted length, a crimp being defined as a complete wave, peak to Peak.

Example 5 Viscose containing 7.5 percent of cellulose, 7.0 percent of caustic soda, and 0.1 percent of polyethylene glycol (of average molecular weight 1,500), and with a salt figure of 7.5 was extruded through a jet containing 1,400 holes each of 0.0065 inch diameter, at a rate of 690 grams per minute, into a bath containing 8.5 percent of sulphuric acid, 1.2 percent of zinc sulphate, and 24.0 percent of sodium sulphate at 50 C. The threads were led through the bath for a distance of 60 inches, then withdrawn, passed round a godet with a peripheral speed of 20.3 metres per minute and led to a second godet with a peripheral speed of 32.5 metres per minute, being stretched by 60 percent. The freshly spun tow, when relaxed in water, contracted to 32 percent of its original length and developed 7 crimps per inch of contracted length. After cutting the tow to staple, washing and drying in the usual manner, the product gave the following results when subjected to crimp measurements:

Viscose containing 7.5 percent of cellulose, 7.0 percent of caustic soda and 0.4 percent of polyethylene glycol 1,500, at a salt figure of 12.3, was extruded at a rate of 690 grams per minute through a jet containing 1,400 holes each of 0.0065 inch diameter. The tow, so formed, was withdrawn from the bath after an immersion of 60 inches and passed round a godet with a peripheral speed of 20.3 metres per minute, and thence round another godet'with a peripheral speed of 32.5 metres per minute the stretch applied between them being 60 percent. The final filament denier Was 15.0. When the freshly spun tow was relaxed in water, it contracted to 45 percent of its original length, and developed 5 crimps per inch of contracted length.

The fibres'had cross-sections which, when stained, appeared similar to those shown in Figure 5.

What we claim is:

1. A process for the production of regenerated cellulose fibres having a high degree of crimp, comprising the steps of extruding viscose containing from 5 percent to 10 percent cellulose, from 5 percent to 10 percent caustic soda, at a salt figure of from 3 to 14, into a coagulating and regenerating bath containing between 5 percent and 14 percent sulphuric acid, 0.5'percent and 3 percent zinc sulphate and more than 12 percent sodium sulphate, in the presence of more than 0.05 percent on the weight of the viscose of polyoxyethylene glycol having an average molecular weight of between 600 and 6,000, subjecting the filaments to at least a 50 percent stretch, and relaxing said filaments.

2. A process for the production of regenerated cellulose fibers as defined in claim 1, including the step of cutting the filaments into short lengths to form staple following the stretching of said filaments.

3. A process, as claimed in claim 1, in which the viscose contains from 7.5 percent to 8.3 percent cellulose.

4. A process, as claimed in claim 1, in which the ratio of caustic soda to cellulose by weight in the viscose is between 0.9 and 1.

5. A process, as claimed in claim 1, in which the viscose has a salt figure of from 5.5 to 8.5.

6. A process, as claimed in claim 1 which includes adding the polyoxyethylene glycol, to the extent of from 0.1 percent to 0.3 percent on the weight of the viscose, to the viscose before extrusion.

7. A process, as claimed in claim 1, in which the zinc sulphate content of the coagulating and regenerating bath liquor is between 1.0 percent and 2.0 percent by weight on the liquor.

8. A process for the production of regenerated cellulose fibres having a high degree of crimp, comprising the steps of extruding viscose containing from 7.5 persent to 8.3 percent of cellulose, caustic soda such that the ratio of caustic soda to cellulose by weight is between 0.9 and l, and from 0.1 percent to 0.3 percent on the weight of the viscose of polyoxyethylene glycol, at a salt figure of from 5.5 to 8.5, into a coagulating and regenerating bath containing from 5 percent to 14 percent sulphuric acid, 1 percent to 2 percent of zinc sulphate and from 22 percent to 24 percent sodium sulphate at a temperature of from to C., stretching the filaments so formed by at least 50 percent and relaxing said filaments.

9. A process for the production of high denier regenerated cellulose fibers having a high degree of crimp, comprising the steps of extruding viscose containing from 5 to 10 percent cellulose and from 5 to 10 percent caustic at a salt figure of from 3 to 14 into a coagulating and regenerating bath containing between 5 and 14 percent sulphuric acid, between 0.5 and 3 percent zinc sulphate and more than 12 percent sodium sulphate, in the presence of more than 0.05 percent on the weight of viscose of a polyoxyethylene glycol having an average molecular weight of between 600 and 6,000, subjecting said filaments to at least a 50 percent stretch, and relaxing said filaments, thereby forming crimped filaments having a denier of at least 15.

References Cited in the file of this patent UNITED STATES PATENTS 2,517,694 Merion Aug. 8, 1950 2,674,025 Ladis'ch Apr. 6, 1954 2,705,184 Drisch Mar. 29, 1955 2,732,279 Tachikawa Jan. 24, 1956 2,852,333 Cox et a1 Sept. 16, 1958

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF REGENERATED CELLULOSE FIBERS HAVING A HIGH DEGREE OF CRIMP, COMPRISING THE STEPS OF EXTRUDING VISCOSE CONTAINING FROM 5 PERCENT TO 10 PERCENT CELLULOSE, FROM 5 PERCENT TO 10 PERCENT CAUSTIC SODA, AT A SALT FIGURE OF FROM 3 TO 14, INTO A COAGULATING AND REGENERATING BATH CONTAINING BETWEEN 5 PERCENT AND 14 PERCENT SULPHURIC ACID, 0.5 PERCENT AND 3 PERCENT ZINC SULPHATE AND MORE THAN 12 PERCENT SODIUM SULPHATE, IN THE PRESENCE OF MORE THAN 0.05 PERCENT OF THE WEIGHT OF THE VISCOSE OF POLYOXYETHYLENE GLYCOL HAVING AN AVERAGE MOLECULAR WEIGHT OF BETWEEN 600 AND 6,000, SUBJECTING THE FILAMENTS TO AT LEAST A 50 PERCENT STRETCH, AND RELAXING SAID FILAMENTS.

Images