US3408709A - Method for softening fibrous sheet material - Google Patents

Description

Nov. 5, 1968 c. F. REITZ METHOD FOR SOFTENING PIBROUS SHEET MATERIAL Filed Dec. 29, 1964 2 Sheets-Sheet 1 INVENTCM C/M/FAEZS 195/72 ATTORNEY Nov. 5, 1968 c. F. REITZ 3,408,709

METHOD FOR SOFTENING FIBROUS SHEET MATERIAL Filed Dec. 29, 1964 2 Sheets-Sheet 2 009F155 FT m,

ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE i Continuous method for'softening an non-woven, polymeric, film-fibril sheet composed of cohesivelybonded, flash-spun, plexifilamentary material comprising stroking opposite sides of the sheet in transit viabutton breaker rolls while stretched between a for.

This invention relates to a method and apparatus for softening woven and nonwoven fibrous sheet materials.

A number of devices are known in the textile art for treating sheet materials to change aesthetic qualities such asv drape, flexibility, and softness. One of the devices, which is commonly referred to in the trade as a button breaker, consists of several free-running button rolls, the roll surfaces each carrying a multitude of small projections somewhat resembling knobs or buttons. The generally parallelspaced apartrolls are supported in bearings to permit easy turning in response to the frictional force exerted by fabric pulled over the rolls. The fabric transverses a meandering path by passing approximately one-half turn around each roll and follows then to the next roll, passing around to such rolls during the course of a normal treatment. After processing in. this fashion the sheet is finally wound up on a powerdriven windup roll. Tension is applied to the fabric during treatment by various means such as by controlling the amount of wrap around each roll or by applying a brake on the feed roll. While the fabric is under tension it is thus softened by the pushing action of the roll projections against small areas of the fabric.

While the button breaker as above described is satisfactory for treating many fibrous sheet materials, it is frequently inefficient and ineffective in treating others, e.g., nonwoven fibrous sheets or loose Woven fabrics. A common deficiency of the apparatus when applied to certain fabrics is that it fails to provide adequate softening, even with multiple passes, or else tends to form undesirable blisters or putts in the fabric. Accordingly one objective of the present invention is to provide a more efiicient process and apparatus for'softening fibrous sheets, i.e., one which requires less time, space, and labor for the softening operation to take place. A further objective is to provide an apparatus and process which will soften loose woven or nonwoven sheets without distorting the sheet or leaving blisters or other undesirable marks in the sheet.

In accordance with one embodiment of the invention there is provided a method for treating a web of fibrous material cohesively bonded into the form of a sheet which comprises advancing said sheet between unwind and windup positions, collecting said sheet at the windup position faster than its delivery from the unwind position thereby applying tension to said sheet and effecting stretching in the longitudinal dimension, intermediate said positions causing the sheet to be stroked in a predetermined pattern of small spaced apart areas across the width thereof to displace portions of the sheet from the general plane thereof and thereby soften the sheet, the stroking being directed first to one side of the sheet and then to the other and being applied successively, in

supply and take-up there- 3,408,709 Patented Nov. 5, 1968 "ice any order,'both with and against the direction of 'sheet travel. i

The web-treating apparatus of the invention includes a series of generally parallel spaced web-working rolls, means for advancing web in a path about the rollsin a tensioned condition, and drive means for rotating the rolls at different relative speeds than that of the web, said web-working rolls being provided with a pattern of spaced-apart rounded projections about the major portion of their curved surfaces for stroking the web as it passes in contact therewith. 1

The above described apparatus is somewhat similar to the ordinary button breaker but differs most notably in that the button rolls are rotated atfa different speed than the sheet which passes into contact with them. In terms of the process this means that the projections on the rolls gently but firmly strike and thra'sh repeatedly first against one side of the sheet and then against the other to work and partially loosen fibers therein. Instead of portions of the sheet being simply distended and stretched by the buttons, the whole sheet is effectively converted to a higher bulk form by the relative movement against the roll projections.

The process and apparatus of the invention will be further described with reference to the drawings wherein:

FIGURE 1 is a front .view of an assemblyof button rolls suitable for use in accordance with the invention.

FIGURE 2 shows an elevational view of the rolls of FIGURE 1 but further including web feeding and web windup rolls.

FIGURE roll.

FIGURE 4 is a cross-section of the button roll taken along the line 4-4 of FIGURE 3.

FIGURE 5 is a cross-section of the button roll taken along the line 55 of FIGURE 3 and greatly enlarged for ease of illustration.

As shown in FIGURE 1, rolls 11, 12, 13', 14 and 15 are supported in a rigid frame-work 16. The roll axles 30 pass through the frame-work and are supported in bearings 31. Sprockets 18 are provided at one end of each roll, and these are interconnected by means of roller chain 19. A second sprocket 20 is provided o'n'an extension of the axle 30 of roll 14.

As shown in FIGURE 2 the second sprocket 20 is in turn connected by roller chain 21 to the sprocket 22 of motor 23. The motor 23 therefore drives all of the five button rolls in this embodiment with a set speed ratio between each of the rolls and the motor. The ratios can be changed by changing the sprockets to provide ones with greater or lesser number of'teeth. Supply roll 40 is used to continuously supply sheet material .to the nip of feed rolls 27. Feed rolls'27 are power-driven at constant speed. The winding mechanism of windup roll 28 is provided with a conventional form of constant tension device, not shown. The constant tension windup roll ,28 working in conjunction with constant speed feed rolls draws, e.g., extends, the sheet lengthwise during treat: inent at least 0.5%, the sheet surface speed at the windup being essentially constant. An alternate system v may be used whereby the speed of the fabric at the windup roll 28 is controlled by means of a positivelydriven constant speed roll flexibly mounted above roll 28 and running against the top surface of the accumulated sheet on roll 28, sufficient frictional force being provided to avoid slipping by properly weighting the constant speed roll. A similar device may be used against supply roll 40, thereby making it a feed roll of constant speed. In this case rolls 27 may be omitted. Depending upon the amount of bonding in the sheet, the sheet may be drawn as much as 40% during treatment. The feed and windup speed ratios are adjusted to obtain between 0.5% and 40% stretch.

3 shows a detailed view of a single button The pair of feed rolls 27 and windup roll 28 are shown mounted separately from the button rolls in FIGURE 2. However, they could be mounted in the same frame-Work, provided means were included for adding or removing completed rolls of wound sheet material. In FIGURE 2 adjustable idler sprockets 24 are provided to allow the chain tension to be adjusted.

Rolls 11, 12, 13, 14 and are each provided with a multiplicity of spaced-apart rounded projections 32 disposed about the major portion of their curved surfaces (FIGURES 1 and 3) which independently displace and distend small areas of the fabric which contact them. In operation of the process the rolls move at a different speed from the fabric passing over them. Consequently the knobs on the rolls provide a stroking-action along the face of the sheet in addition to displacing small areas out of the plane of the sheet. I The sprockets 18 on rolls 11, 12, 13, 14 and 15 may all have the same number of teeth or the number of teeth may vary, depending upon the type of action needed at each point in the process. For example if more abrupt action is needed near the end of the process, rolls at the windup end of the apparatus may have sprockets with fewer teeth than the sprockets on any of the preceding rolls, thereby providing relatively faster rotation for the rolls at the windup end of the process.

In operation of the process, sheet material 26 passes from feed rolls 27 as shown in FIGURE 2 to button roll 11 at a set speed and then successively to rolls 12, 13, 14 and 15. With all of the rolls (feed rolls 27, button rolls 11, 12, 13, 14, 15 and windup roll 28), operating in clockwise direction as seen in FIGURE 2 fabric is passed over roll 11 in the direction of its rotation. The fabric then passes to the back side of roll 12 and is pulled over the roll surface in opposition to the surface movement of that roll. It passes then to roll 13 in conformance with roll 13 direction of movement. Then the fabirc passes to the back side of roll 14 against the direction of roll movement. Finally the fabric passes around the front side of roll 15 in the same direction as the roll surface is moving and is wound up at roll 28.

As shown in FIGURE 2, rolls 11, 13 and 15 alternately stroke one side of the sheet 26. The force of the roll projections 32 thereon (FIGURES 1 and 3) thus is applied in the direction of sheet travel. Rolls 12 and 14 contact the opposite side of the sheet with the force of the roll projections 32 thus stroking the sheet against the direction of sheet travel. The sequence in which the two sides of the sheet are contacted and the direction in which each roll is turning relative to the direction of sheet travel are not critical. It is only essential that the stroking of the sheet be applied sequentially to both sides and that part thereof is applied in the direction of sheet travel and the remainder against the direction of sheet travel.

In operation of the process the forward moving rolls (relative to fabric) have speeds well above that of the fabric (e.g., 2 to 50 times). Reverse turning rolls 12 and 14 may move more slowly, however. The overall fabric speed is controlled by the feed and windup speeds. In order to avoid tearing the fabric or excessive stretching thereof, the tension of the fabric against the button rolls 11 to '15 must be controlled at a suitable level. In the embodiment of FIGURE 2 this can be achieved most readily by control of the surface speed ratio of windup roll to feed rool. A windup/feed speed ratio of about 1.005 is satisfactory for a machine having button rolls of 4 inch diameter with centers 9 inches apart and the roll axes parallel as well as lying in a single plane. Other methods of varying tension will be apparent. For example to reduce tension the amount of contact of fabric to roll surface can be adjusted by arranging the rolls to allow the fabric to follow a path more nearly planar. Regardless of the means used for tension control, however, the tension on the sheet as it is wound up on roll 28 is advantageously between .05 and 2.0 lbs. per inch of sheet width.

The reversal in stroking direction which is afforded by passage from roll-to-roll gives great extremes in tension within the fabric. It will be apparent from FIGURE 2 that the fabric .will be under tensionbetween feed roll 27 and roll 11, will be'relatively relaxed between rolls 11 and 12, tensioned between rolls 12 and 13 relatively relaxed between rolls-13 and 14 and tensioned between rolls 14 and 15. It is wound up under tension at roll 28. The alternate tensioning and relaxing in conjunction with the distortion caused by local pressure of the moving projections 32 works, disrupts and relocates the fibers into freer positions to give a very soft fabric structure.

Now considering FIGURE 3, a button roll which is suitable for this invention is shown in detail. In this embodiment the projections 32 are arranged spirally about the major portion of the curved surface of the roll. The spiral pattern is initiated at one end 33 of the roll, the projections being arranged on a ,line which at any point forms an angle of 15 with the roll axis. As shown in FIGURE 4, there are 6 separate rows of projections in: itiated at the end 33 of the roll, these being started at points 60 apart around the 'roll circumference (4 in. diameter roll).

FIGURE 4 is a cross-section taken along the line 4-4 of FIGURE 3. Detail of the cross-section of individual projections is shown in FIGURE 5 which is a partial section taken along the lines 5-5 of FIGURE 3. The geometry of the projections should be as to prevent tearing or cutting of the sheet and to this end are rounded at the shoulders.

The projections can be very close together but should not form a substantially continuous spiral bar or ridge as this is less efficient in giving the desired softening effect. In general the projections have a height h approximately equivalent to the diameter d of the projection at the base to provide high resistance to bending and breaking. The distance 0 between centers of adjacent projections is greater than the diameter d of a single projection at its base.

While a specific pattern for the button roll has been shown in FIGURE 3, it will be apparent that wide variations and size and placement of projections can be employed as long as the rolls give the necessary local relaxation and tensioning of the fabric during treatment.

In terms of other variations that can be made, it is also possible to provide separate drives for each of the rolls. A particularly useful form of the apparatus utilizes variable motor drives for each roll so that the speed of each roll can be varied independently.

A preferred form of the apparatus has been shown in FIGURE 1 with five button rolls in addition to the feed and windup rolls. However, as many as ten to twenty button rolls may be provided where desired. A minimum of two button rolls is necessary to accomplish an adequate degree of softening at practical operating speeds. Depending upon the number ,of button rolls employed as well as certain other factors, operating speeds up to 650 ft./min. or more can be realized.

It will be understood that among other variations, the apparatus may alternatively be constructed with all forward-treating rolls on one frame and reverse-treating rolls on another frame, the distance from frame to frame being adjustable thereby providing another means for adjusting tension.

The invention is applicable to the treatment of any web formed of a fibrous material cohesively bonded into the form of a sheel. The bonding may be achieved by a separate binder material applied to a web of fibers, or by the use of solvents, heat and/or pressure and other means. In the case of woven fabrics the bonding is achieved simply by the weave of the structure. For use with nonwoven products, as is preferred, these should be bonded in a pattern of spaced binder areas "extending through the web thickness but occupying less than 35% of the sheet area. Fusion bonded points, diagonal lines and a variety of other geometrical shapes are suitable. An impregnated sheet with binders distributed throughout the sheet may of course also be used if the total amount of binder is less than 35% of the treated sheet weight. Although all forms of conventional textile fibers and filaments are useful for producing webs to be treated in accordance with the invention, a preferred product is a polyolefin film-fibril sheet as disclosed in US. patent applicaiton of Steuber, Ser. No. 97,496, filed Mar. 27, 1961. Bonded film-fibril sheets, preferably having been deposited in random overlapping arrangement, represent a preferred form of product.

The invention will be further illustrated by the following example.

Example A nonwoven film-fibril sheet was prepared by flash spinning linear polyethylene according to the method of Blades and White US. Patent 3,081,519 using trichloro fiuoromethane as a solvent. The solution was spun through a spinneret at a temperature well above the boiling point of the solvent, and a plexifilamentary network was obtained. This network of fibril material was collected on a moving belt in random overlapping arrangement to form a nonwoven sheet as described in U.S. patent application of Steuber Ser. No. 97,496, filed Mar. 22, 1961. The sheet was consolidated by cold rolling with a pressure of 10 lbs/in. of roll axis. The roll diameter was 11 inches. This sheet was then bonded by passing through a pair of rolls, one of which was a steel roll with a multitude of conical points arranged in diamond patterns throughout the entire roll surface. The second roll was a neoprene rubber-coated steel roll with 80 durometer hardness (Shore A). The surface of the first roll had a conical point every 0.125 inch across the width of the roll. Around the circumference there were points every 0.100 inch. The points extended .040 inch from the roll surface. The first roll was maintained at a temperature of 208 C. which was above the melting point of the nonwoven sheet. The pressure on each point during rolling was about 600 p.s.i. When the sheet (.006.007 inch thick) was passed through the nip between the two rolls, it became both perforated and point embossed. A fused embossed ring appeared around each of the perforations. The hole diameter was about .020 inch and the outer diameter of the fused ring was about .030 inch.

The point perforated and embossed sheet was coated with a latex of vinyl resin and inert filler to obtain a sheet with 25% coated material after drying. The resulting sheet was quite film-like in feel. It had a drape flex of 6.1 cm. in the machine direction and 5.8 cm. in the transverse direction using a Drape-Flex Tester*.

The coated, point-embossed, perforated sheet was then treated in an apparatus of the type shown in FIGURES 1 and 2. The projections n the roll were similar to those shown in FIGURE being gently rounded to avoid tearing the sheet. The height h of each projection was 0.375 inch and the diameter d at the base was 0.375 inch. The

Sold by Fabric Development Test, Brooklyn, N.Y.

distance 0 between centers about 1 inch, the projections being arranged in spiral pattern as in FIGURE 3. The angle between the projections and the roll surface at the point of juncture was approximately Rolls 1, 3 and 5 were rotated in the direction of sheet travel at a speed of 120, 126 and 135 yds./min. respectively. Rolls 2 and 4 operated counter to the direction of the sheet at speeds of and 131 yds./min. The sheet itself was fed into the machine at the rate of l5 yds./min. and was wound-up at 15.75 yds./min. giving an overall stretch of 5%. The resulting fabric showed no evidence of blisters or distortion from the points of the button rolls. During the above treatment the sheet became smaller in width because of the drawing operation. The original width was 48 in. and the final Width after treatment was 46 in. The resulting sheet was very soft and had the feel of soft kid leather. Drape flex was 4.5 cm. in the machine direction and 4.3 cm. in the transverse direction. This material was later cross-stretched to its original width. The fabric produced in this method was suitable for fabricating swimming trunks and soft disposable garments. The material was useful for a multitude of other soft fabric uses, including spring wrap used to enclose individual coil springs in a mattress, dust covers for chair bottoms, and pillow covers.

What is claimed is:

1. A method for softening a non-woven polymeric film-fibril sheet which is composed of random overlapping layers of flash-spun plexifilamentary material and which has been cohesively bonded by fusion at spaced points over its surface, the method comprising advancing said sheet between unwind and windup positions, collecting said sheet at the windup position faster than its delivery from the unwind position thereby stretching the sheet between about 0.5% and 40% in the longitudinal dimension, intermediate said positions causing the sheet to be positively stroked in at least five zones in a predetermined pattern of small spaced apart areas across the width of the sheet to displace portions of the sheet from the general plane thereof, the stroking being applied alternately in either order to one side of the sheet in the direction of sheet travel and to the other side of the sheet against the direction of sheet travel, whereby the sheet is alternately tensioned and relaxed as it travels between said unwind and windup positions.

References Cited UNITED STATES PATENTS 1,238,143 8/1917 Hodgkins 2651 1,730,520 10/1929 McMurray 2627 XR 2,705,497 4/1955 Johnson et al. 128-290 FOREIGN PATENTS 9,908 12/1908 France.

580 1883 Great Britain. 41,565 9/ 1907 Switzerland.

ROBERT. R. MACKEY, Primary Examiner.

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