US2597577A - Rayon yarn - Google Patents

Description

im E952 N. DRlscH ETAL, 2,597,577

RAYON YARN original Filed May 14,v 1949 Patented May 20, v1952 RAYON YARN Nicolas Drisch and Roland Brepson, Paris, France, assignors, by mesne assignments, to Textile and Chemical Research Co mpany Limited, St. Peter Port, Guernsey, Channel Islands, a corporation of Great Britain Original application May 14, 1949, Serial No. Y 93,416. Divided and this applicationDecember 8, 1951, Serial No. March 4, 1949 1 Claim. (Cl. 57-140) This invention relates to the production of rayon yarns composed of short V.bers twisted together.

, This application is a division of Serial No. 93,416 led May 14, 1949 for Rayon Yarns.

In United States Letters Patent No. 2,586,796, dated February 26, 1952, a process is described for the production of viscose rayon having in the airdry condition a tenacity greater than 4.8 g. per denier, an elongation at breaking point greater than 8%, a work-till-rupture value of at least 30 gm. cm. meter/denier and other remarkable properties. The process disclosed in said application comprises extruding into a bath oi sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerization below 500 and less than 4% by weight of molecular chains with a degree of polymerization below 250, said viscose being prepared from alkali-cellulose of which the mean degree of polymerization after ripening is greater than 450, which viscose has a degree of xanthogenation (y) (as hereinafter dened) between 40 and 50, the concentration of sulphuric acid in the said bath being defined by the formula: Percentage concentration by weight of sulphuric acid =1.26'yI-8i3, thereafter subjecting the extruded lament to a stretching operation to increase their length by 150 to 280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition, finishing and drying, and then winding or winding and twisting the laments thus obtained.

The degree of xanthogenation of the cellulose, represented by the symbol 7, is the number of hydroxyl groups substituted by -CSS- groups per 100 glucose units (i. e. Cel-1100s units). fy-values below 40 are impracticable since they yield products of low extensibility and an upper limit is set by the fact that sulphuric acid of strength much greater than 72% has so strong a dissolving action on the viscose filaments that very rapid washing indeed becomes necessary. Also in that patent a process is described for the production of viscose rayon yarn having in the air-dry condition a tenacity greater than 5.0 gm. per denier, an elongation at breaking point greater than 8.5 and having a work-till-rupture value greater than 20 gm. cm. meter/denier.

These types of rayon, whose base consists of very ne filaments, for example of from 0.5 denier to 0.1 denier have many valuable uses, but for certain purposes it is desirable to employ yarns 260,704. In Great Britain Y .Y

made up of short fibers. The neness of the elementary filaments produced by the processes of the foregoing United States applications is such that they cannot be cut by the usual method and then worked by the usual means, such as card or a comb since it is very difcult using such material to obtain regular yarns formed of discontinuous bers when the bers are presented in ock form, owing to the fragile nature of the bers.

According to a further featurev of the present invention yarns made up of short :bers and being of very high `tenacity are obtained' from continuous filaments produced a's described above by continuously directly converting the lilaments into rovings of short fibers and thereafter drawing and twisting the rovings, for example on normal frames or on very high-draft frames of the Casablancas or Leblanc type. It is thus possible to obtain particularly line yarns of good regularity, for example up to 25 denier or even ner.

Any method for the continuous direct conversion of laments into rovings may be employed and in particular that in which the laments undergo a draft to breaking point between an assemblage of rolls. for example in accordance with French patent specification No. 702,745.

In one particular embodiment of the present invention, for example, a bundle I of untwisted viscose rayon yarns comprising 1000 filaments totalling 300 denier and having a tenacity of 5.5 g. per denier, produced in accordance with the process of this invention is drawn in apparatus as illustrated diagramatically in the accompanying drawing. The bundle of continuous filaments 'I is fed between three superimposed tangential rolls I, 2 and 3 having a peripheral velocity of 40 meters per minute, roll I being driven and the rolls 2 and 3 resting on roll I and being driven by it. The bundle is then fed through three other superimposed tangential rolls 4, 5 and 6 rotating at meters per minute, roll 6 being driven and rolls 4 and 5 resting on roll 6 and being dri v e;n by it. The axial planes of the rolls are 20 cm. apart. The bundle 'I is fed as illustrated to the bottom of the first set of rolls I, 2 and 3, passes successively between the nip of such rolls and then successively through the nips of the second set of rolls 4, 5 and vIi and emerges as a roving 9 of broken bers at the bottom of the second set of rolls. The breakage of the filaments occurs between the rolls at 8.

This roving is condensed, drawn and twisted with a coeicient of twist of from 50 to 70 for a yarn having a nal count of deniers.

The irregularity of the tenacity when wet is of the order of from 6% to 10%.

The yarn thus obtained can be readily used to very great advantage for knitting, either on circular frames or chain frames, or for the production of stockings. The yarn displays no tendency to slip during knitting, and the high tenacity re sults in very strong products. The wearing qualities are excellent. Stockings withstand long wear with daily washing without running into holes. Another very important use for the yarn is as sewing thread, in which case the high tenacity and the good sewing behavior constitute important advantages.

By applying higher drafts on a Casablancastype frame it is possible to obtain, for example from a count of 30 denier with a tenacity when dry of 3.3 g. per denier and when wet of 2.7' g. per denier, an elongation when dry of 7.0% and when wet of 8%. The present invention thus makes it possible to obtain yarns which cannot be produced from any other comparable artiiicial textile material, other known artiiicial yarns of very high tenacity, comprising very fine iibers not having sufiicient elongation.

What is claimed is:

A iine yarn of low shrinkage characteristics and of a tenacity when dry of at least 3.5 per denier, said yarn being formed by twisting a roving of staple bers, said staple fibers being formed by cracking a bundle of viscose rayon filaments of at most 0.5 denier having in the air-dry condition a tenacity greater than 4.8 g. per denier, an elongation at breaking point greater than 8% and a work-till-rupture value of at least 20 g. cm. meter/denier, said laments being prepared by extruding into a bath of sulphuric acid at normal room temperature a Viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerization below 500 and less than 4% by weight of molecular chains with a degree of polymerization below 250, said viscose being prepared from alkali cellulose of which the mean degree of polymerization after ripening is greater than 450, which viscose has a degree of xanthogenation (fy) between and 50, the concentration of sulphuric acid in the said bath being deiined by the formula: Percentage concentration by weight of sulphuric acid =1.26y+8i3, the extruded filaments being stretched to increase their length by to 280% while they are still wet from the spinning bath, being washed in a more dilute acid bath, relaxed while still in the acid condition and iinished and dried.

Y NICOLAS DRISCH.

ROLAND BREPSON.

No references cited.

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