US3501811A - Continuous filament webs - Google Patents

Description

March 24, 1970 G. A. WATSON 3,501,811

CONTINUOUS FILAMENT WEBS Filed July 5, 1967 GEORGE A. WATSON ATTORNEY United States Patent 8 Claims ABSTRACT OF THE DISCLOSURE A method for producing a lightweight web of continuous filaments and the product produced thereby comprising deregistering a tow of continuous crimped filaments and subsequently subjecting the deregistered tow to a plurality of spreading stages to produce a web having a density of less than 1 ounce per square yard and preferably less than about /2 ounce per square yard.

BACKGROUND OF THE INVENTION This is a continuation-in-part of S.N. 382,263, filed July 13, 1964, now abandoned.

This invention relates to the production of extremely lightweight webs of low filament count from a tow of continuous crimped filaments.

The deregistration, or opening of a tow of continuous crimped filaments is known in the art. Previously, such deregistration was effected in the production of cigarette tow in a manner described by Dunlap et al. in US. 3,156,016.

It is an object of the present invention to provide a method for obtaining extremely lightweight webs from a deregistered crimped tow of continuous filaments. It is another object of this invention to provide a continuous filament web particularly suited for the production of soft cushioning products such as pillows, sleeping bags, fumiture batting and the like. These and other objects will become apparent to those skilled in the art from a description of the invention which follows.

SUMMARY OF THE INVENTION In accordance with the invention, a process is provided for the production of a lightweight web from a continuous filament tow comprising passing a traveling tow of crimped deregistered continuous filaments through a plurality of spreading stages, spreading the tow in each of said stages to thereby form a web having an average air space per fil of at least five times the average diameter of the filaments of the tow. Preferably, at least one of the spreading stages is an air spreading and more preferably all of the spreading stages are air spreading stages.

The present invention provides a ready means for producing high bulk, soft products such as cushioning materials. The light weight webs are very bulky and when cross lapped, crumpled, bunched and the like into a thicker batting, the soft bulky characteristics are retained.

The invention will be described more fully by reference to the drawings in which:

FIG. 1 is a schematic view of a process in accordance with the present invention illustrating tow opening and a plurality of tow spreading stages to form a lightweight web;

FIG. 2 is a sectional view of an air spreader particularly useful in the present invention;

FIG. 3 is a partial plan view showing the arrangement of openings in the air spreader of FIG. 2; and

FIGS. 4 and 5 are plan views along line 4-4 of FIG. 2 illustrating two alternative arrangements of the air openings of the air spreader.

3,501 ,8 l l Patented Mar. 24, 1970 'ice In a preferred embodiment of the invention, a lightweight web is produced by passing an opened tow of crimped continuous filaments through an air spreader in which the moving tow, in flattened condition, is confined between parallel walls while streams of air or other suitable gas are directed at the tow across its full width. It has been discovered that it is possible in this manner to spread the tow readily, and very evenly, to great widths to produce webs of extreme fineness, such as webs containing less than about 600, such as 500 filaments per inch of width, and in which the average air space per fil is appreciably greater than the diameter of the filaments.

The average air space per fil is the average space between the filaments of the web measured on a line in the plane of the web, perpendicular to the longitudinal direction of the filaments of the web, said space being calculated on the assumption that all the filaments are arranged in a single plane, with no filaments crossing other filaments. It may be calculated simply from a knowledge of the average diameter of the filaments (D the width (w) of the substantially uniform web and the number of filaments (n) in said width, according to the formula: Average Air Space Per Fil: (wnD +11.

In the preferred forms of the invention, the average air space per fil is a plurality of times (e.g., five, ten or more times) as great as the average filament diameter. Such webs may have densities well below one ounce per square yard, e.g., A to A or ounce per square yard.

Referring more particularly to FIG. 1, a band of crimped continuous filament tow 10 is drawn from bale 12 through a banding jet 13 comprising a stationary cylinder 14, having one or more slits running lengthwise of the cylinder and a curved bafile member 16 parallel to, and spaced about the thickness of the tow 10, from the adjacent surface of said cylinder, so that the tow band 10 passes between said bafiie member 16 and cylinder 14. Air under pressure is supplied to the interior of cylinder 14 and emerges as a stream-from the slit of said cylinder, the slit being cut at an angle such that the air stream has a component in a direction opposing the forward motion of the stream. The air jet preconditions the tow for further processing by removing snags, false twists, straightens and flattens the tow and, if desired, spreads the tow somewhat to provide a uniform thickness.

Tow band 10 is hence passed around stationary tensioning bars 17 and 18 to help smoooth and uniformly pretension the band, said bars being adjustably mounted, so that their angle to the horizontal may be varied, to adjust the position of the band on subsequent processing equipment with which the band comes into contact downstream of the bars.

After leaving bars 17 and 18 the band passes into the tow opening zone. The tow may be conveniently opened or deregistered, to prepare it for spreading stages by subjecting it while moving in a predetermined path, to a differential gripping action between a plurality of points spaced from one another both longitudinally and transversely in the path so that certain laterally spaced sections of the tow are positively gripped relative to other lateral spaced sections of the tow, alternating with the grip sections, which are not gripped at all or are gripped at different relative points. In this manner there is produced a relative shifting of the adjacent filaments longitudinally along the tow whereby the crimps are moved out of-registry with one another. The shifting action is a fluction of the differential positive gripping of the tow. Preferably, although not necessarily, the differential gripping action is such that a relative lateral displacement between adjacent filaments of the tow is also effected, so that the combination of two transverse filament movements brings about the complete opening of the tow.

Several methods for effecting the differential gripping action are known in the art as well as several different apparatuses for effecting the differential gripping, which apparatuses deregister the tow with varying degrees of success. A preferred apparatus is disclosed in the aforementioned Dunlap et al. patent, U.S. 3,156,016.

Typically, the differential gripping action is achieved by using at least one pair of rollers, one of which is smooth surfaced and the other of which is patterned over its entire periphery. The most preferred apparatus comprises a plurality of such pair of rollers arranged in tandem wherein one of each pair of rollers comprises a smooth surfaced roll coated with a resilient material such as rubber, and the other roller has alternating lands and grooves. Preferably, the lands and grooves form helical threads of about 8 to 20 per inch.

Thus, the tow is passed through the nip of a pair of rolls 19 and 21 prior to being passed through a second pair of rolls 22 and 23. In the most preferred embodiment, rolls 19 and 23 are the patterned rolls, such as threaded steel rolls and rolls 21 and 22 are resilient surfaced rolls.

Each pair of rolls is individually driven at a predetermined controlled speed. Generally, only one roll of each pair is positively driven while the other is in yieldable compressive contact with the driven roll and rotates due to the passing of the tow between the rollers. The differential gripping and deregistering action is produced by driving the second pair of rollers at a faster rate of speed than the first pair. Thus, the second pair of rollers is typically driven at a rate of about 1.1 to about 8 times, and more preferably, at a rate of about 1.2 to about 3.0 times that of the first pair.

On leaving the deregistration zone, the crimp in adjacent filaments of the tow is out of registry.

After deregistering the tow, the tow is subjected to a plurality of spreading stages. Various spreading means can be used to spread the deregistered tow into a uniform web. Such means include mechanical spreading bars, diverging belts, air jets and the like. The most preferred means is the air jet, also known as a banding jet. Therefore the invention will be described more particularly with reference to air spreaders although it is to be understood that other types of spreaders can be used with correspondingly good results.

The tow is spread as shown in FIG. 1 by means of a first spreader 24. The tow is pulled through spreader 24 by the action of driven rollers 36 and 37 about which tow is S wrapped. In passing through spreader 24, the tow is spread about 2 to 4 times the width of the tow exiting from the deregistration zone. As is preferred in the present invention, the tow is preferably again spread, such as in second spreader 38 wherein the spread band is again spread 2 to about 4 times the width of the web drawn through rollers 36 and 37. Again, the web is drawn through spreader 38 by means of another set of driven rollers 39 and 41. Thus, the spreading action preferably spreads the tow into a web at least twice the original width of the tow and more preferably 2 to about 10 times the original tow width to produce a web of less than 1 ounce per square yard and more preferably about 0.005 to 0.5 ounce per square yard and most preferably about 0.01 to 0.25 ounce per square yard.

From rolls 39 and 41, the tow falls in a freely hanging shallow catenary 42 onto a horizontal moving surface of a wide, endless belt 43. Idler roll 44, mounted on lever arms 46 pivoted at 47, extends across the full width of the web on belt 43. The idler roll serves to bring the tow web into firm contact with belt 43 to define the shape and position of catenary 42 and also to keep any loose ends in the catenary portion from being drawn around roll 41. Catenary 42 also serves to relax the spread web which relaxation partially restores crimping which was stretched during the deregistration and spreading operation. The relaxation by passing through a catenary further serves as a self healing process by removing striations which may have formed during the spreading operation. A static bar preferably contacts the web at the catenary to remove static electricity.

Referring more specifically to the air spreaders used in the present invention as illustrated in FIGS. 2, 3, 4 and 5, tow 10 is passed through space 26 which separates air chamber 28 of plenum box 30 from back plate 27. Air pressure is exhausted through slit 31 thereby impinging upon the fibrous web as it is passed through space 26. Thus, the spreading operation is effected on the tow as it is passed through the air spreader in a flattened condition between parallel walls while a stream of suitable gas is directed onto the tow at a right angle across its full width. Advantageously, the air spreading is efiected in a plurality of stages as described above, each of which spread the tow to a greater width than in the preceding stage. For best results, the tow in any one stage is isolated from the effect of the following stage by passing the tow through drawing rollers such as 36 and 37, and 39 and 41 between each spreading stage.

The air spreaders themselves advantageously have air delivery slits or other suitable openings in one or both of the parallel walls between which the tow passes. The slits lead from a plenum box or air chamber supplied with air at a constant pressure. In one highly effective appartaus, a series of slits is provided, each running in a direction transverse to the direction of movement of the tow and so arranged that all portions of the tow are subjected to the air stream from said slits. Surprisingly, it has been found that even when the width of the air spreader is 8 feet or more, the tow spreads uniformly to the outer edges of the tow, where the resistance to air would be expected to be less, to attain substantially the same density as the central portions of the tow.

The pressure in the plenum chamber may vary considerably. One suitable range is about 1 to 5 pounds per square inch gauge pressure. Higher pressures, such as about pounds per square inch gauge can be used, but these are generally not necessary and are economically wasteful. Surprisingly, little air is needed to expand the tow. Despite the fineness of the webs, the walls of the towcnfining zones of the air spreaders need not be correspondingly close together. Thus, very good results have been obtained with tow confining slots one tenth inch in width.

Advantageously, the webs are spread to such an extent that when further air spreading is attempted, with the length of the web kept constant, the web strongly resists such spreading and returns to its previous width. Thus, if a graph is plotted relating the air pressure in the spreader to the degree of lateral spreading of the moving Web, it is found that there is substantially no additional pressure needed to effect spreading up to a certain width, after which the air pressure required rises sharply. The web density at which the sharp change occurs is termed herein the potential web density. This potential web density will varv depending on the type of tow which is employed and particularly on the degree of intermingling and crossing over of the tow filaments. In general, optimum tows have potential web densities below about one ounce per square yard and preferably less than about /2 ounce per square yard. Surprisingly, webs of such densities are easily handled and maintain their unity without disintegration during ordinary handling.

The present invention is useful with all continuous filament materials which have been crimped prior to deregistration. The process is particularly useful with filaments of polyethylene terephthalate polyester and cellulose acetate of the usual acetyl content of about 54 to 55 percent calculated as acetic acid. However, the invention is also equally applicable to other tows such as those made of other polyesters such as polyesters of 70/30 isophthalic and terephthalic acids and other glycols such as dimethylolcyclohexane; linear super polyamides such as nylon 6 and nylon 66; polyacrylonitrile and copolymers of acrylonitrile; olefinic polymers and copolymers such as isotactic polypropylene; other organic derivatives of cellulose such as esters and/or ethers of cellulose, for example cellulose propanate and cellulose acetate propanate and the like; highly esterified cellulose containing less than 0.29 free hydroxyl groups per anhydroglucose units such as cellulose triacetate, rayon and the like.

The number of filaments in the starting tow can vary within wide limits and may range up to as high as about one million with a denier per filament as high as about 25, that is, in the range of about 0.5 to about 25 and more preferably in the range of l to 20 denier per filament. The number of crimps per inch of tow may range up to as high as about 80, but for most end products a crimp of about 3 to 50 crimps per inch, preferably about 3 to 20 crimps per inch of starting tow are found to be exceptionally satisfactory.

The invention will be described more fully by reference to the examples which show certain preferred embodiment of the present invention.

EXAMPLE 1 A lightweight web was made in accordance with FIG. 1 by deregistering and spreading a band of crimped cellulose acetate tow having a total denier of 42,000 and made up of 3 denier continuous filaments of cellulose acetate. The filaments were crimped at a rate of 8 /2 crimps per inch. The tow band was drawn from a bale through a banding jet and pretensioning bars prior to being fed to a deregistration zone comprising two pairs of rollers in tandem. In the deregistration zone the tow was fed into the nip of of a pair of rollers, one of which was a rubber surfaced roller and the other a helically grooved steel roller having 14 turns per inch, cut about inch deep. The rollers were in pressure contact with each other. The first pair of rolls was driven at a peripheral speed of about 45 feet per minute. From the first pair of rollers, the band was passed horizontally to the nip of the second pair of rollers corresponding to the first pair, which second pair was driven at a peripheral speed of 66 feet per minute. The tow exiting from the deregistration zone was about 8 inches wide.

From the deregistration zone, the deregistered tow was passed into a first air spreader which had a passage for the tow 24 inches in width and inch between the confining walls. The air spreader was supplied with air under a constant pressure of about 4 pounds per square inch. The air exited from air slits on one wall which were tapered to 0.007 inch wide at their outlet at an angle of 45 degrees. The slits were each 5 inches long and arranged as shown in FIGS. 3 and 4, thus supplying air across the full 24 inch width of the air spreader. The slits were arranged at a small angle, about 5 degrees to a line perpendicular to the direction of movement of the tow.

In passing through the first air spreader, the tow band was diverged uniformly from its 8 inch width to the full 24 inch width of the air spreader. From the first air spreader, the tow was drawn by means of drive rollers operated at a peripheral speed of 44 feet per minute whlch serve the additional function of also holding the tow in the spread state.

The tow was then fed to a second air spreader of the same design as the first air spreader with the exception that it was 50 inches in width. The second air spreader was operated under the same air pressure as the first air spreader. In passing through the second air spreader, the tow was again spread uniformly to the full 50 inch Width of the second spreader. The 50 inch width was maintained by drawing the tow through the spreader by means of another pair of drive rollers driven at a peripheral speed of 42 feet per minute. The lightweight web was then dropped freely to form a hanging shallow catenary onto the horizontal moving surface of a wide endless belt operated at a speed of 46 feet per minute. The catenary drop relaxed the spread web, partially restored lost crimps and removed striations. The web retained substantially its 50 inch width. The belt was used to convey the produced lightweight web to further processing steps wherein the web could be bonded, cross lapped into heavier weight battings, formed into pillows, cushioning materials and the like as may be desired. The produced web was about 50 inches in width and was of a Weight of 6.01 grams per square yard.

In the same manner, mechanical spreaders can be used in one or more of the spreading stages. However, mechanical spreaders normally do not yield as high a uniformity as the air spreading. Also, in the same manner, 3, 4 or more spreaders can be used to further spread the web to its potential web density or more, such as by the ustle of higher air pressures, with correspondingly good resu ts.

EXAMPLE 2 The process of Example 1 was again operated utilizing a polyethylene terephthalate tow having a total denier of 128,000 and containing 5 denier filaments of 12 crimps per inch. The tow was deregistered and air spread in 2 stages to a width of 50 inches. The deregistration was effected by operating the first pair of rollers in the deregistration zone at 60 feet per minute and the second pair of rollers at 102 feet per minute. The spreading was effected in two stages using air spreaders operating at 3 pounds per square inch gauge pressure.

The resulting web was uniformly spread over the 50 inch width to produce a lightweight web of 14 grams per square yard.

EXAMPLE 3 A lighter weight web having a density of 2.5 grams per square yard was produced following the procedure of Example 1 and that illustrated in FIG. 1 of the drawing, using a tow of 20,000 total denier and 5 denier per filament of crimped cellulose acetate. The tow was deregistered and subsequently air spread in two stages to a width of 50 inches. This lightweight web was particularly useful for the production of cushioning materials.

While there have been described various embodiments of the present invention, the method described is not intended to be understood as limiting the scope of the invention as it is realized that changes therein are possible. It is intended that each element recited in the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same equivalent manner. It is intended to cover the invention broadly in whatever form its principles may be utilized.

What is claimed is:

1. A process for the production of a lightweight web from a crimped continuous filament tow comprising deregistering the crimp of said continuous filament tow, passing a traveling tow of crimped deregistered continuous filaments through a first spreading stage and spreading the tow to a width of about 2 to 4 times the width of the tow just after deregistration, passing the tow through a second spreading stage and spreading the tow to a width of about 2 to 4 times the width after the first spreading stage, to thereby form a web having an average air space per fil of at least five times the average diameter of the filaments of the tow.

2. The process of claim 1 wherein the spreading is elfected by air pressure.

3. The process of claim 1 comprising spreading a tow containing about 500 to 1,000,000 filaments having about 3 to crimps per inch, said tow being spread to a density of less than about /2 ounce per square yard and an average air space per fil in the spread tow of more than 10 times the average diameter of its filaments.

4. The process of claim 1 wherein at least one spreading step is effected by air pressure by passing the traveling tow in a flattened condition in a confined zone while 7 subjecting it to a stream of air directed at the tow across its full width.

5. The process of claim .1 wherein said tow of said intermediate width is firmly drawn from said first spreading zone at a controlled rate prior to entering said second spreading zone.

6. The process of claim 5 wherein the tow is relaxed after being spread in the second spreading zone.

7. The process of claim 1 wherein the tow, after being spread, is advanced under a low tension insufficient to remove the crimp from said tow and said tow is relaxed without substantial change in width by moving said tow continuously in a free shallow catenary thereby increasing the degree of crimp per unit length in said filaments and removing striations in said spread tow.

8. A process for the production of a lightweight web from a crimped continuous filament tow comprising deregistering the crimp of said continuous filament tow, passing a traveling tow of crimped deregistered continuous filaments through a first spreading stage and spreading the tow to a width of about 2 to 4 times the width of the tow just after deregistration, passing the tow through a second spreading stage to produce tow having a final width of from 2 to 10 times the width just after deregistration and thereafter advancing said spread tow under a low tension insufficient to remove the crimp from said tow, relaxing said tow without substantial change in width by moving said tow continuously in a free shallow catenary, thereby increasing the degree of crimp per unit length in said filaments and removing striations in said spread tow.

References Cited UNITED STATES PATENTS 3,380,131 4/1968 Gray 281 2,215,112 9/1940 Beck et al. 1965 2,657,433 11/ 1953 Merriman. 3,032,829 5/1962 Mahoney et al. 1965 3,081,951 3/1963 Dyer et al.

DORSEY NEWTON, Primary Examiner US. Cl. X.R. 28-1

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