US2316212A - Regenerated cellulose apparatus - Google Patents

Description

April 13, 1943.

F, P. ALLES REGENERATED CELLULOSE APPARATUS Filed Dec. 13, 1941 fidiZCf-FPAZAEJ INVENTOR I ATTORNEY Patented Apr. l3,

REGENERATED CELLULOSE' APPARATUS Francis P. Alles, Waynesboro, Va., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application December is, 1941, Serial No. 422,803

3 Claims. (01. 34-124) This invention relates to the drying of continuous non-fibrous cellulosic sheet material, espe- 1 cially to the removal of water from gel regenerated cellulose web in such a way that the dry product is substantially completely and uniformly flat; More particularly it appertains to improvements in the design, construction and operation "of the drier rolls employed in the drying operaoperation which fits the product for immediate use or storage. When the web is ready for this drying operation it contains 350% to 400% water, so it will be apparent that a very substantial volume change must, take place during the water removal. This change manifests itself in shrinkage (loss of area and thickness) of the web. The properties of the sheet wrapping material are dependent to a large extent upon how this shrinkage is regulated, and a host of patents relating to the drying stage, for example, U. S. A. Patents 1,606,824 (Brandenberger), 2,046,553 (Edwards), 2,099,160 (Charon), 2,099,162 (Eberlin), 2,115,132 (Alies 8: Edwards), and 2,141,377 (Chylinski) l The art has now developed to a point where drying the web by passing it around heated rolls is generally believed to be the most desirable scheme available for commercial scale operation. This method has had a major draw-back, in that no really satisfactory way of supplying heat to the rolls has been available. Under present day operating speeds it has heretofore been impossible to distribut the heat over the drying roll in a pattern which prevented over-drying of certain portions of the web. "As a result of the uneven heating, the final sheet material is not uniformly flat, and difficulty is encountered in operating w ppins hinery employing the same at high speeds. Cutting, slitting, laminating, crimping, and like operations must also be carried out at slower speeds than would be possible if a better material were available.

It was the primary object of this invention to.

prove continuous web. drier operation by special drier roll arrangements. Still further objects were to produce apparatus for drying continuous lengths of non-fibrous cellulosic web in which an even distribution of heat is provided and im proved uniformity of drying is obtained; to produce non-fibrous sheet material that is substantially uniformly flat and straight when'stretched without being placed under excessive tension: and to provide improved meansfor continuously drying gel non-fibrous webs. A general advance in the art, and other objects which will appear hereinafter, are also contemplated.

It has now been found that distributing steam in the interior of a drying roll in the manner described hereinafter in detail, accomplishes the aforementioned objects. Added improvement is obtained by arranging the drying rolls in a special sequence, also described in detail hereinafter. The present invention provides, inter alia, an improved steam distributor to. be positioned axially within the drying roll.

design improved drier rolls; to improve the results How the foregoing objects and related ends are accomplished will be apparent from the following exposition, in which are disclosed the principle and divers embodiments of the invention, including the best mode contemplated for carrying out the same. The written description is amplified by the accompanying drawing, in which:

Figure 1 is a scheme showing a roll drier and adjacent portions of a viscose-regenerated cellulose sheetcasting machine;

Figure 2 is a fragmentary elevation view partly in section of the drier roll and steam distribution unit of this invention;

Figure 3 is a fragmentary perspective view of th heating element of the present invention:

Figure 4 is a sectional view along the line 4-4 of Figure 2; and v Figure 5 is a fragmentary elevation view, partly in section, corresponding to Figure 2, of one end of the heating element.

Referringnow to the drawing, there is illustrated at MI in Figure 1 a tank containing the softening bath 33 l through which the continuous regenerated cellulose film 3 passes immediately before being transferred to the drier in the well known method of manufacturing regenerated cellulose sheet-wrapping material. The numerals MI and I indicate rolls which simultaneously.

2 numbers I through '21, after which the dried drier roll.

product passes to a winding mechanism comprising a driven (with friction clutch'and overdrive) core for the mill roll l6 supported on a bracket H, which is secured to an upright l8.

"As shown in Figure 2, the "individual rolls 32'! comprise an outer shell 325-supported on a tubular shaft 313 by means of a disc-like end closure piece 326. A pulley 3121s also mounted on the shaft 310 adjacent the aforementioned endof the A light friction means (not shown) connects the roll with the pulley in the actual machine. This permits some slippage in case the driving force exerted by the pulley should be greater than that desired. The pulley and the the disc 326 is imperforate so that the. heating steam and water condensed therefrom will not escape in the vicinity of the driving pulley. The corresponding piece 328 at the opposite end of the roll has openings 329 (or it may be replaced by a spider arrangement) to prevent the accumulation of water in the roll. a The shaft 310 rests on end supports (not shown). The end of this shaft, through which the heating steam or other liquid is admitted; is closed with a sleeve 4| and cooperating cap 42.

Pipe 2| carries the steam through the cap into the interior of the roll shaft. This pi-pe extends a considerable distance into the shaft, and is an important part of the steam distribution arrangement As shown in Figure 2, thepipe is supported on one side of the roll by disc-like member 32, and atits end on the opposite side of the roll by a member 22, which also serves as a gastight closure for the end. Surrounding pipe 2| is a cylinder 3| closely fitting inside the shaft, and

'closed at one end by the disc 34. The closed space within this tube is defined by the member 34 and the previously mentioned member 32.

The steam entering through the pipe 2| (Figure.

with the slot 3'" in the shaft 310 into the interior of the drying roll.

In Figure 5, a shaft and steam distribution arrangement similar to that of Figure 3, is shown,

but in this case an aperture 23a is used in .the

ventionalmanner, and as a final step in the wet treatment, passed through an aqueous bath of 5%. glycerol.

At this stage were 12 inches in outside diameter and 76 inches long, and were supported on trunnions, one of which was hollow to permit access to the interior of the roll. The shafts 310 upon which the rolls and driving pulleys rotated, were iron tubes 3 inches in diameter. The slot 3' extended for 52 inches, and was centered on the center line of the roll. The shafts were lined with brass tubes 3|, and

= taining it in position at the center of the drying roll.

The orifices 23 and 2311 were spaced 27% inches from the center line of the roll. The

perforations in the tube 3| were spacedat 2 inch intervals opposite the slot 3' in the shaft.

The steam delivery pipes 2| entered all rolls on the same side, but as previously pointed out, the steam was delivered to the distribution tube and lower rolls. As a further refinement, all

, the tubes 3| in which steam entered from the place of the previously described aperture .23 for the purpose of admitting the steam to the tube 3|- at the opposite end. In the drier these two types of steam distributors alternate. This is indicated by the indicia on the rolls in Figure 1. As there shown, the steam is admitted at the right end of the tube 3| in roll I, at the right end of tube 3| in roll 2, at the left endv of tube 3| in roll 3, at the left end of tube 3| in roll 4, at the right end of tube 3| in roll 5, etc. In this way,any uneven distributionofl the heatin the rolls is alternated back and forth across the web 3| as it passes through the drier. The arrangement just described has the additional advantage that the surfaces of the web alternate in contacting pairs of rolls having opposed steam inlet arrangements. In one specific embodiment of the invention, a viscose solution comprising 8.5% cellulose and 5.5% sodium hydroxide, was extruded into a coby desulfuring, bleaching and washing in the contube 2| on the left side (3L, etc.) of the machine, as illustrated in the drawing, had a hole in the tube 3| centered on the center .line of the roll, and all the tubes 3| in which steam entered on the right side had the series of perforations displaced one inch from the center line."

distances of 38 inches and 40 inches, respectively. In this manner the area's of-the regenerated cellulose web treated by the heat from the two sets of perforations were staggered, so that the effective distance between areas of maximum heatingwere one inch, a distance so smallthat no band streaks on the film were apparent.

The steam entering the distributor tubes was controlled in flow,.temperature and pressure by conventional apparatus, the characteristics and adjustments of which are well knownin the art. v

Aluminum and its alloys are the preferred materials of construction for the drier rolls because of their light weight, high heat conductivity, etc. Other .metals such 'asiron and its alloys, for example, stainless steel, copper, brass, etc., may be employed somewhat less satisfactorily for the construction of the roll itself. The steam distributor tubes 3| on the interior of the roll shaftmay be made of any suitable non-corroding metals and alloys, such as stainless steel, brass, aluminum, etc, Special devices such as those already knownin the art may be employed to remove the water of condensathe web contained 350% waterand 15% glycerol, based on the'cellulose, and was The perforations in the tubes 3| extended over and satisfactorily operative arrangement for draining off the water. In some cases it has been found desirable to operate the rolls with about one inch of water in the bottom, in order to further equalize the heat distribution. An inwardly projecting bead or collar of comparable terial beingprocessed and the use to whichit is to be put.

Steamis very convenient for. heating the drying rolls, but'other heating fluids may be employed if desired. In ordinary operation the heating fluid temperature is regulated sothat the roll surface is kept within the temperature range 90-l00 C., but other temperatures may be emdimensions at the open end of the roll accomplishes this purpose satisfactorily. Where the rolls are operated relatively free of water, the steam may be directed in a downward direction so as to play upon the lowest part of the roll. Where considerable water is desired at the bottom of theroll, the steam projected upwardly.

or in any desired direction. The diameter of the orifices 33 in the distributor 23!, and their general arrangement, are. to some extent determined by the drying pattern desired for the type of film'being manufactured by the particular conditions of operation encountered. A full discussion of drying patterns will be found in the Charch & Alles application mentioned above, and there is no need to burden this specification with such details at this time. Suflice it to say that adjustment and regulation of the steam controllin apparatus, to secure the desired variations, is with n the skill of those versed in the art having familiarity with the foregoing disclosure.

The dimensions given in the specific example are not necessarily critical. Rolls from 50 inches to 120 inches long and from 10 to 15 inches.

indiameter are often encountered in the art, and proportionate variations in the dimensions of the steam distributing apparatus may be made to produce aim-action satisfactory for pressure may be employed with suitable modifications of the controls, orifices, etc. i

. Where the ends of the roll are opened, it is preferable to operate under such conditions that the steam will be reduced to water rather than in escape in large quantities into the surrounding 7 atmosphere.

Gel materials other than regenerated cellulose web, for example, low substituted methyl cellulose and the 1lke..may be successfully dried on the previously described' apparatus. Webs of different thicknesses may be dried with suitable adjustment of the conditions, and the number of drying rolls employed will depend upon the. material being produced and various operating conditions encountered. i

It is not intended by the preceding tolimit the invention to the drying of cellulosic film.

since it is as applicable to gelatin, caseinand' the like as it is to celluloseethers, for example, glycol cellulose, and cellulose esters, for example, cellulose acetate. I

Similarly, it is not intended to limit the invention to, the employment of glycerol as a soft ener. Other softeners and combinations of softeners may be employed, depending upon the ma Thisfactor should be observed in designing sult desired.

ployed, depending upon the results desired.

It will be appreciated that any specific pattern or arrangement of the right and left heating fluid feeds may be employed, depending upon the re- The arrangement illustrated in Figure 1, wherein the steam is admitted to the central distributor tubes in rolls l and 2 from the right side, in 3 and 4 from the left side, etc.,

has been found to give the fiattest sheet, and since a fiat sheet is the present desideratum, it was most convenient to illustrate the corresponding drier roll arrangement.

Most of the advantages of the present invention are believed to be obvious. The drier apparatus provides a more uniform distribution of heat, and provides a process of compensation of factors influencing the distribution of heat with out necessitating complicated apparatus.

Regenerated cellulose film dried according to the preferred embodiments of this invention is substantially completely and-uniformly flat, and of substantially uniform moisture 7 content throughout. Because of its uniform flatness, the film so produced can be run through subsequent processing operations such as coating, slitting, laminating, crimping, etc., at less cost and greater production rates. The product is especially well suited for use in modern high speed wrapping machinery, and ensures rapid operation and perfect packaging.

Because of the efficient and uniform applica tion of the heating medium in the present meth-- The fact that the elements 2|, 3i, 4| and 42- form a unit which may be bodily removed from the shaft 310, is an important advantage in the I construction and maintenance of the apparatus;

.As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. A steam distributor for a web drying roll compising three concentric tubes, the innermost tube being connected to a source of heating fluid at one end and closed at the other end, the intermediatetube being larger than the innermost tube whereby a compartment therebetween is formed, the said' compartment being closed at both ends, an opening through thewall of the innermost tube to provide communication beopenings in the wall of the intermediate tube.

and a slot in the outer tube registering with the said line "of discharge openings to permit direct access of the heatingfluid from the aforementioned compartment to the chamberbetween the exterior of the outer tube' and the inside of drying roll.

. 2. A drier roll for regenerated cellulose web including 9, hollow 'cyiindrical aluminum shell tributor shaft upon which said shell is mounted for tree rotation, said shaft comprising three concentric tubes, the innermost tube being connected to a source of heating fluid at one end and closed at the other end, the intermediate tube being larger than the innermost tube whereby a compartment therebetween is formed, the said compartmentbeing closed at both ends, an opening through the wall of the innermost tube-to provide communication between its interior and the said compartment near one end of said compartment, a line of discharge openings in the wall of the intermediate tube, and a slot in the outer tube registering with the said line of discharge openings to permit direct access or the heating fluid from the aforementioned compartment to the chamber between the exterior of v the outer tube and the inside of said shell.

3. In a continuous web drier, a series of drier rolls, each roll including a hollow cylindrical shell for supporting the 'web and a heating fluid distributor shaft upon which said shell is mounted for tree'rotation, said shaft comprising three concentric tubes, the innermost tube being confor supporting theweb and a heating fluid dis- -nected to a source of heating fluid at one end and closed at the other end, the intermediate tube being larger than the innermost tube whereby a compartment therebetween is formed, the

said compartment being closed at both ends. an

opening through the wall of the innermost tube to provide communication between its interior and the said compartment near one end of said compartment, a line of discharge openings in the wall 01 the intermediate tube, and a slot in the outer tube registering with the said line of discharge' openings to permit direct access ofthe,

heating fluid from the aforementioned compartment to the chamber between the exterior of the outer tube and the inside of said shell, the adjacent upper and lower rolls in the operating sequence being. arranged to have the heating

Images