US2591243A - Process for the manufacture of rayon from viscose with high elongation and spooling in centrifugal cups - Google Patents

Description

April 1, 1952 N. DRlscH ET AL 2,591,243 PROCESS FOR THR MANUFAOTURR OR RAYON FROM VISCOSE, WITH HIGH ELONGATION AND SPOOLING IN CENTRIFUGAL. CUPS Filed June 17, 1950 Snventors Patented Apr. 1, 1952 UNITED sTATEs PATENT 2,591,243 OFFICE PROCESS FOR THE MANUFACTURE OF RAYON FROM VISCOSE WITH HIGH ELONGATION AND SPOOLING IN CEN- TRIFUGAL CUPS Application June 17, 1950, Serial No. 168,674 In France February 21, 1947 4 Claims.

This invention relates to the spooling of rayon. In the manufacture of rayon from viscose, the

latter is commonly spooled, after congelation, by

means of suitable devices, such as bobbins or centrifugal cups.

This application is a continuation-in-part of our co-pendingfapplication Serial No. 9,115, nled February 18, 1948, for Process for the Manufacture of Rayon-from Viscose, With High Elongation and Spooling in Centrifugal Cups, now abandoned.

In spinning .accompanied by spooling in centrifugal cups, the thread leaving the bath passes over at leastone feed roller which delivers it at a definite speed, e. g. of the order of 60 to 100 meters per minute or more, whereupon the filament passes through a funnel into a rapidly revolving centrifugal cup. Owing to its mass, the filament is flung radially against the internal wall of the cup, and is wound up upon this wall. The funnel performs suitable vertical reciproeating movements, as a result of which the lament and to transformation of the cakes into secondary spoolings. the internal tensions referred to may prove prejudicial to proper formation of cakes and hence to the scientific mass production of rayon by these methods.

Attempts have been made to overcome the effect of these tensions by the application of a supplementary feed roller revolving at a lower speed than the last feed roller proper, but this expedient, in addition to complicating the equipment, has proved only partially eective.

The present invention provides a process for obtaining dense, perfectly uniform and heavy ment is' wound in intersecting helicoid spirals. l

This produces-ywhat is currently known as a filament cake, the thickness of the cake being greater or less according to the duration of the spooling. When the cake attains a certain diameter it is removed from the cup and the operation is repeated.

The rapid rotation of the cup produces a torsion in the filament, the value of which depends in principle on the linear speed of the lament and the number of turns in the cup. The magnitude of the centrifugal force exerted upon the filament depends on the speed of rotation of the cup. the mass of the filament, and the radial travel of the filament between the end of the funnel and the internal surface of the cake in Si".

process of formation. All other things being equal, this force decreases as the thickness of the cake increases.

Now, when, f according to one of the many known processes. atension is applied to the filament, whetl'lerin-Y the congelation bath, outside of the bath, or both, the feed roller (or the last feed roller if there are several) must theoretically overcome the resistance upstream and deliver filament at a tension determined by the force of the centrifugal cup. However, such internal tensions as are created by stretching may persist and reduce the centrifugal effect in the cup, since the two forces act in opposite directions.

Since obviously the cake will be more compact the higher the centrifugal effect, and since tightly packed cakes are desirable as affording longer periods of spooling and hence more eilicient utilization of the material, apart from other advantages relating to subsequent treatfilament increases.

filament cakes, e. g. 500,` to 600 grams, in conventional centrifugal cups.

This process is characterized by an extreme enlargement of the travel of the filament without stretching tension betweenthe point where the filament reaches the last feed roller and the spinning funnel, such that the duration of this travel becomes at least 3 seconds.

Such a duration of this travel (under nonstretching condition) allows time for the proaressive relief of internal stresses in the filament but without plastic deformation so that the filament loses the undesired internal tensions due to stretching before itis spooled, thus leaving the effectiveness of the centrifugal force unimpaired. The invention also provides an apparatus for fabricating rayon filament and spooling the same in a centrifugal cup, such apparatus representing an improvement relative to the previous processes and being characterized by comprising means for substantially enlarging the travel under non-stretching tension between the last feed roller or rollers and the funnel.

The travel between the point where the lament reaches the last feed roller and the funnel may, in pursuance to the invention, be increased three-, five-, or ten-fold, and more. This travel must be increased as the linear speed of the suitable travel for a linear speed of meters, at least 13.50 meters are required for a linear speed of 100 meters/min. so that the time required for the filament to cover the distance between the last feed roller and the funnel will be at least 3 seconds as aforesaid. ,y

The process may be applied with special advantage to spinning in baths containing more than 50% of sulfuric acid. The congelation of the viscose filament in a bath of at least 55% sulfuric acid is followed by subjection to extreme stretching in the presence of such acid acting as a plastifler, or alternatively in a secondary bath e. g. on an aqueous base at C. minimum. whereupon the filament is kept under non- If e. g. ten meters is the Y three seconds.

stretching tension between the last feed roller and the spooling means for a duration of at least This travel may include the time in the Wash bath.

Through the combination of such' congelation bath with prolonged maintenance under tension in air before fixation and spooling, filaments are obtained with a tensile strength in grams denier of 4 or 5 and more, with ultimate elongations definitely above those obtained without such prolonged aerial travel, namely of the order of 9 to l instead of 7 to 8 per cent. The knot strength and loop strength are likewise improved by l0 to 20 per cent.

The invention is not confined to spooling in centrifuges, the same improvement in certain characteristics of the filament being obtained with any method of spooling, as e. g. on bobbins or spools.

The effect is probably connected with the phenomena of relaxation in the lament While kept under non-stretching tension over an extended travel during a substantially longer time than that of the usual travel. During such a prolonged travel, the internal tensions are considerably relieved, and after shrinking of the gel in the aqueous wash bath, the molecular equilibrium is appreciably better than that of a filament spooled immediately after drawing.

In the accompanying drawings, which are given only by way of example,

Fig. l is a schematic representation of the portion of an apparatus designed in pursuance to the invention included between the feed rollers and the centrifugal cup; and

Fig. 2 is a schematic representation of an apparatus according to the invention including an acid bath and a wash bath between which the filament is tensioned.

According to the example shown in Fig. l, the

filament 3, after passing over the feed rollers l and 2, describes a zig-zag path as it passes over a series of guide means 4, 5, 6, 1 and B, before entering the funnel 9 of the centrifugal cup I0 where the filament is spooled to form a cake H. The guide means 4 to 8 may comprise pins, rollers, reels, etc. whose number may be varied according to the length of travel desired. The travel may be further increased by allowing the filament 3 to describe several helicoid spirals about the roller 2, and thereafter to follow a zig-zag course or any other devious path.

According to Fig. 2, the spinneret 2l is shown as immersed in a bath 22 containing 975 grams of sulfuric acid per liter and having a temperature of 20 C. The spinneret 23, having e. g. 1000 holes, is charged with a suitable volume of viscose at 6% of cellulose and 9% of soda, so that the resulting yarn runs 900 deniers for a spinning speed of 20 meters. The travel through the bath is to 60 centimeters in length. The filament 3 passes over a guide roller 24 and is led over a feed roller 25, whence it proceeds to the final feed roller 2. Between these two rollers, separated by about l meter, the filament 3 is drawn out 200%, reducing the rating' to 300 deniers per thousand strands. The filament describes a certain number of parallel spirals (e. g. 10) ori a roller 2 associated for the purpose with a rod 25 with axis slightly inclined to that of the roller 2, for effecting automatic uniform spacing of the spirals. This winding in several spirals greatly increases cohesion and facilitates uniform drawing. VOne or more Vcomplete spirals may additionally be wound on the roller 25 to 'improve traction on th' .roller also, and reduce slippage.

Subsequent to the extended path over the final roller 2, the lament passes through an aqueouswash bath 2l and then over a guide 8, whereupon it goes down through the funnel 9 and iscollected at il in the cup l0. The cup i0 may be replaced by other spooling means, as a bobbin or spool 'if desired.

The path of travel between the last feed roller 2 of Fig. 2 through the bath 2l to the funnel is such as to provide the above mentioned three second dwell under non-stretching conditions before spooling.

In each case the entire stretching takes place prior. to the last feed roller 2 and the filament between the feed roller; 2 and the funnel 9 is under only the non-stretching tension which is necessaryforfeeding purposes and is produced by the centrifugal spooling action. Hence the internal tensions are relieved before spooling and are not present to oppose the centrifugal force in the cup. A more compact cake is thus formed. 4

Although a specific embodiment has been shown for purposes of illustration, the invention is not to be restricted thereto, but is to be limited only in accordance with the scope of the following claims.

What is claimed is:

l. The method of making rayon lament from viscose which comprises feeding the rayon fila.- ment through a coagulating bath without stretching, removing the filament from the coagulating bath, then stretching the filament at a stretchingstation and subsequently holding the stretched filament under non-stretching conditions for a period of at least three seconds while conveying the stretched filament from the stretching station to a winding station so as to allow complete relaxation and relief of internal strains before winding and then winding the said filament.

2. The method of making rayon filament from l viscose which comprises feeding the rayon filament without stretching through a coagulating bath containing at least 55% sulfuric acid, removing the filament from the coagulating bath, then stretching the filament at a stretching station and subsequently holding the stretched filament under non-stretching conditions for a period of atleast three seconds while conveying the stretched filament from the stretching station to a winding station so as to allow complete relaxation and relief of internal strains before winding, and then winding the said filament.

3. The method, as set forth in claim l, in which the extreme drawing is effected prior. to washing and in the'presence of an acid. as a plasticizer.

4'. The method, as set forth in claim l, inY

y which-the extreme drawing is eected in an aqueous medium at about C.

, NICOLAS DRSCH. Y ROLAND BREPSON.

@REED The following references are of record in the file of this patent: Y

UNITED STATES PATENTS Number Name Y Date Re. 18,170 vf .ilienfeld T Aug. 25, 1931 2,309,072V `Burkholder T Jan. 19,1943 2,348,415 Polak ug May 9; 1944

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