US 3427376 A
Description (OCR text may contain errors)
Feb. 11, 1969 J. .1. DEMPSEY SOFTENING NONWOVEN FABRICS Filed Sept. 27, 1966 al-II I nlvlllllll'l l ii INVENTOR JAMES JOSEPH DEMPSEY "F. T i
mu N a I! Q @v M ATTORNEY Feb. 11, 1969 J. J. DEMPSEY 3,427,376
SOFTENING NONWOVEN FABRICS Filed Sept. 27. 1966 FIG. 3 Sheet 2 of2 INVENTOR ATTORNEY JAMES JOSEPH DEMPSEY United States Patent 4 Claims ABSTRACT OF THE DISCLOSURE Point-bonded, nonwoven film-fibril sheets are softened by a three step process which includes, in order, button breaking, creping, and button breaking. The button breaker is modified to permit stroking of the sheets counter to the direction of sheet travel. This method permits attainment of a desired level of softness, without delamination, at a commercially practical rate of sheet throughput.
This invention relates to nonwoven fabrics, and more particularly to an improved process for softening a fibrous nonwoven sheet composed of film-fibril elements.
BACKGROUND A number of devices are known in the textile art for treating sheet materials to change aesthetic qualities such as drape, flexibility and softness. One of the devices is commonly referred to in the trade as a button breaker, which consists of several free-running button rolls, the roll surfaces each carrying a multitude of small projections somewhat resembling knobs or buttons. The generally parallel spaced-apart rolls are supported in bearings to permit easy turning in response to the frictional force exerted by fabric pulled over the rolls. In the traditional button breaker the button rolls are not powerdriven. The fabric traverses a meandering path by passing approximately one-half turn around each roll and follows then to the next roll, passing around to 20 such rolls during the course of a normal treatment. After processing in this fashion the sheet is finally wound up on a power-driven 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 inefiicient or ineffective in treating a new type of nonwoven fibrous sheet, namely film-fibril sheets. These are randomly laid nonwoven fibrous materials prepared by depositing layers of flash-spun plexifilamentary strand web on a moving belt as described in Steuber U.S. 3,169,899 issued Feb. 16, 1965. The preparation of the flash-spun plexifilamentary strand material is described in Blades and White, US. 3,081,519, issued Mar. 19, 1963.
A common deficiency of the conventional button breaker when applied to these film-fibril sheets is that it fails to provide adequate softening, even with multiple passes, or else tends to form undesirable blisters or puffs in the fabric. For this reason an improved driven-roll button breaker has been developed and has been described in a copending application of Reitz, US. patent application S.N. 421,902, filed Apr. 29, 1964 which is commonly assigned. It comprises a series of generally parallel spaced web-working rolls, means for advancing web in a path about the rolls in a tensioned condition, and drive means for rotating the rolls at different relative speeds than that of the web. The web-working rolls are ice 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. While the driven roll button breaker described in the Reitz application produces better results than earlier devices, further improvements are desirable for commercial operation. Thus an increase in sheet throughput rate results in decreased softness of the treated material. In order to obtain the desired softness at commercially acceptable throughput rates, therefore, multiple units must be provide-d, thus increasing the investment in equipment. Moreover, even with multiple units the results are not entirely satisfactory. Extensive treatment with the button breaker causes excessive delamination of the film-fibril sheet. Also the softening action of the button breaker is unequal in the two planar dimensions of the sheet. In other words, the sheet is not as soft in the machine (longitudinal) direction as it is in the cross (lateral) direction.
SUMMARY OF INVENTION According to this invention there is provided a process for preparing a soft textile-like material from a paperlike nonwoven film-fibril sheet. The process involves a sequence of operations utilizing (1) a driven roll button breaker; (2) a creping device wherein lateral folds are produced in the sheet; and (3) a drawing apparatus to remove part or all of the crepe elongation. In a preferred embodiment of the process the final drawing operation is accomplished on a driven roll button breaker with stroking accompanying the drawing.
The process of this invention permits production of a sheet of given softness at a commercially acceptable rate without excessive delamination of the sheet. In addition, the three step process gives a specified level of softness at a higher sheet throughput rate than a two step process involving a creping operation either preceded or followed by a single button breaker operation. Softness measurements indicate that sheets treated in accordance with this invention are about equally soft in their two planar dimensions. Also, the sheets exhibit improved drape characteristics after treatment according to the invention.
The process of the invention comprises passing a bonded film-fibril sheet in sequence through three stages.
Stage 1.Comprises passing the sheet through a stretching and mechanical agitation zone between a feed position and a take-up position, the speed of the sheet at the take-up position being faster than the speed at the feed position so that sufficient tension is applied to the sheet to stretch it between 0.1 and 10% in the longitudinal dimension of the sheet, intermediate said positions causing the sheet to be stroked in a predetermined pattern of small spaced apart areas across the width thereof to dis place portions of the sheet from the general plane thereof, the stroking being directed first to one side of the sheet and then to the other and being applied successively, in any order, both with and against the direction of sheet travel.
Sta-ge 2.-Comprises passing the sheet from the take-up position of Stage 1 through a creping position where the sheet is mechanically detained by the application of pressure exterted normal to the sheet between the two faces of the sheet, the pressure, input speed, and output speed move at least 80% of the crepe elongation. Crepe elongation, as used herein is defined as the precentage increase in length upon stretching the creped material just to remove all of the crepe. This'stage may be a simple drawing operation, or the stretching may be and preferably is, accompanied by mechanical agitation as in Stage 1.
LIST OF FIGURES FIGURE 1 is a schematic diagram showing three apparatus components arranged in sequence, the combined apparatus being useful for operating the process of the present invention.
FIGURE 2 is an end view of a power-driven button breaker which is useful for performing the operation of both Stage 1 and Stage 3 shown in FIGURE 1.
FIGURE 3 is a perspective view of a creping apparatus which in conjunction with a retarding member is useful for performing the operation of Stage 2 shown in FIG- URE 1.
FIGURE 4 is an enlarged cross-sectional diagram of the sheet passing through the creping area between the dried roll, web contacting member, and the retarding member.
FIGURE 5 is a front view of a button roll.
PROCESS DETAILS FIGURE 1 shows schematically the three stages of the process. While these three operations may be conducted separately, the figure shows one embodiment in which the three stages are coupled together. In any case the first stage of the process is conducted by passing the filmfibril sheet through a power driven button breaker as shown schematically in the area marked Stage 1, the second stage is performed in a creping apparatus, this portion being labeled Stage 2 in FIGURE 1. The final process element comprises passing through a stretching device, in this embodiment a power-driven button breaker as shown in the block marked Stage 3.
Considering first the power-driven button breaking operation of Stage 1 a roll of bonded film-fibril sheet 1 provides sheet 2 at a constant rate by means of the drive roll 3. The sheet material 2 passes from the feed position to an idler roll 4 and then passed through the series of power-driven button rolls 5 and 6. The action of the button breaker will be described in subsequent paragraphs in more detail. For the moment it should be observed that in the embodiment shown in FIGURE 1 the rolls on the right side of the machine rotate counter clockwise and those on the left side of the machine rotate clockwise. These rolls are power driven. This is, of course, not true with the commonly used button breaker of the textile trade. Each of the rolls 5 and 6 is provided with numerous protrusions or bosses otherwise known as buttons on the roll surface. Because of the manner in which the sheet is threaded into the machine some of these button rolls stroke the sheet material in the direction of passage through the machine, namely rolls 5, while others rolls 6 stroke the sheet counter to its direction of movement. Idler rolls 7 at the top of the machine simply transfer the sheet from one side of the machine to the other side. It is obvious, however, that one of these rolls could be a spreader roll to remove wrinkles. Likewise roll 8 may be either an idler or spreader roll.
Take-up rolls 9 provide a positive nip for applying tension to the sheet during passage through the button breaker rolls. The take-up rolls are positively driven at a peripheral speed which is 0.1 to 10% faster than the feed roll 1. The successive stroking operations both with and against the direction of movement of the sheet at a multitude of points throughout the sheet area provides a softer sheet and one which is more responsive to further softening operations in the creper.
The sheet product from the first button breaker operation passes to Stage 2 where it undergoes a creping treatment.
The sheet product fed at a constant speed from rolls 9 passes then under an idler roll 10 to the driving roll 11 of a creper. Pressure is applied to the sheet by the head member of the creper indicated by 12.
A sheet-contacting member 13 presses the sheet into knurls of the creper drive roll 11 to assure that there is no slip of sheet relative to roll. This sheet-contacting member has an extended portion that projects in the form of a cantilever forwardly over roll 11. The head member is supported by frame-work not shown through a hinge or pivot 14. A retarding member 15 working in conjunction with the sheet-contacting member 13 provides a retarding action to the forward motion. The position of the retarding member 15 can be adjusted relative to the lip of the sheet-contacting member 13 to establish the dimensions of a cavity wherein the creping action occurs. Air piston 16 or other pressurizing device regulates the pressure on the sheet-contacting member 13. The pressure at this point is adjusted to provide in the sheet fault lines which are no farther than 0.5 inch apart on the average along the length of the sheet. These fault lines will run laterally in the sheet. The pressure required depends on the location of the retarding member 15 relative to the sheet-contacting member 13. However, when the pressure exerted by piston 16 is increased, the distance between fault lines becomes smaller-and-smaller and the amount of crepe elongation in the sheet product becomes larger-and-larger.
The input speed for the creper is governed by drive roll 11. In the coupled process it is the same as the output speed of the take-up position represented by rolls 9 in Stage 1. Considerably more versatility can be obtained, of course, by providing a separate wind-up for collecting the product of Stage 1. This intermediate may then be fed at a convenient operating time from an unwind (not shown) to a separate creping machine. On the other hand the coupled machine offers certain savings in labor and transfer costs. The output speed of the creper is adjusted at a level sutficient to give a product with 2 to 50% crepe elongation. This level of elongation is obtained by setting the relative speeds of roll pair 17 and of drive roll 11. In other words drive roll 11 should have a surface speed 2 to 50% faster than roll pair 17. Again, it should be noted that if Stages 2 and 3 are separated, then a separate set of take-up rolls must be provided for Stage 2. In FIGURE 1, roll 18 is an idler roll, but it could be supplemented with a second driven roll to provide a nip if the operations are separated.
In Stage 3 as shown in FIGURE 1 the creped sheet passes through a pair of nip rolls l7 and then to a set of button rolls 19 similar to those of Stage 1. This operation differs in part from Stage 1, since the higher crepe elongation will initially provide considerable more stretch to the sheet product than was available in Stage 1. Stage 3 is then operated to remove at least of the crepe elongation available in the sheet issuing from the creping position. In FIGURE 1 the percent stretch removed is determined by the speed ratio between wind-up rolls 20 and nip rolls 17 While FIGURE 1 shows removal of the crepe elongation by means of a button breaker, other stretching apparatus may be used to prepare a satisfactory soft product. Still the use of a driven-roll button breaker with the accompanying mechanical agitation of the sheet is much preferred when the products of still greater softness are desired.
In one variation of the process the nip rolls 17 are used simply as idler rolls and the crepe elongation is removed by controlling the speed of wind-up rolls 20 relative to the speed of drive roll 11. If this method is used sheet passing from Stage 2 to Stage 3 can with certain speed settings show no appreciable crepe elongation, since this is removed immediately upon formation at the sheet-contacting apparatus. Nevertheless it should be understood that such a process falls within the scope of the present invention. In any case, fault lines will be evident in products made by the process of this invention. Fault lines are tiny creases which run for varying distances across the width of the sheet. They will be present on the average at intervals not more than 0.5 inch apart and preferably not more than 0.2 inch apart. If all of the crepe elongation is removed in Stage 3, then the fault lines may be the only visual evidence that creping has occurred. The existence of fault lines may be observed simply by pushing two ends of the sheet together along its length while holding with the fingers of both hands, leaving up to about 1 inch of the sheet between the two hands. When the sheet is relaxed in this manner, the fault lines become more pronounced and waves show up in the sheet.
The degree of softness obtained in the product increases with increasing amount of stretch in Stage 3. However, if stretching is excessive, delamination of the nonwoven sheet may occur. Considering this limitation, it has been found that a preferred high level of softness is achieved when all of the crepe elongation has been removed provided that any additional stretching is less than based on the de-creped sheet. Products made by removing all crepe elongation are useful for garments such as disposable swim wear which is acceptable for motel or resort use.
In the event that a simple nip roll draw is used for Stage 3, the resulting sheet is characterized by high drape in one direction as measured by the drape flex method. It has a combination of drape and softness which is desirable for many uses such as in industrial garments.
REQUIREMENTS FOR THE INITIAL SHEET This invention is particularly effective when applied to randomly laid film-fibril sheets which have been point bonded by exposure to hot bosses as on an embossing roll and/or by coating with polymeric material on each side of the sheet. In such pretreatments it is important to obtain a sheet with sufiicient surface stability to resist the heating action of the driven-roll button breaker and with suflicient resistanec to delamination. In any case, however, the bonding should be mild enough so that fiber mobility is maintained at the center of thickness. Materials which have been thoroughly bonded throughout their thickness, for example, by a hot palmer treatment with the sheet kept at about the melting point,
are unsatisfactory because of excessive bonding. Cold rolled sheet is unsatisfactory because of insufficient surface stability when subjected to the softening operation.
By point-bonding is meant any type of discrete area bonding from resin treatment or from hot fusion, with or without the application of pressure which bonds fibrils at points all the way through the sheet thickness. The fibers in the point bonded sheets are firmly attached to one another Within the discrete bonding areas, but can be worked loose from one another in other areas of the sheet. Where film-fibril sheets have been point bonded by heat and fusion, the material is translucent within the bonded areas. About 2 to 50% of the area is bonded. The over-all density of the sheet after point bonding is preferably between 0:19 and 0.40 g./cm. (1 1.8 to 25 lbs./ft. The bonded areas may be in the form of various shapes such as circles, lines, or rectangles, and they may be placed in such a way as to provide geometric designs in the sheet. They also may exist as annular bonds surrounding perforated areas in the sheet. The point bonded patterns are advantageously applied to the cold contact bonded sheet by passing the sheet through one or more pair of rolls, one of each pair being a hard rubber roll and the other being an embossed roll with raised points over its entire surface. A variety of specific point bonding procedure are well known in the art.
6 EQUIPMENT DETAILS A modified button breaker which is particularly useful for operation of the process of this invention has been described in Reitz, U.S. patent application Ser. No. 421,902, filed -Dec. 29, 1964. A simplified form of the apparatus is shown in FIGURE 2 there being only five button rolls in this version. In the figure rolls 5 and 6 are interconnected by means of roller chain 21 through sprockets 22. A second sprocket 23 is provided on an extension of the axle of one button roll 6.
As shown in FIGURE 2 the second sprocket 23 is in turn connected by roller chain 24 to the sprocket 25 of motor 26. The motor 26 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 27 is used to continuously supply sheet material to the nip of feed rolls 28. Feed nip rolls 28 are power-driven at constant speed. The winding mechanism of windup roll 29 is provided with a conventional form of constant tension device, not shown. The constant tension windup roll 29 working in conjunction with constant speed feed rolls draws, e.g. extends, the sheet lengthwise during treatment at least 0.1%, the sheet surface speed at the windup being essentially constant. .An alternate system may be used whereby the speed of the fabric at the windup roll 29 is controlled by means of a positively driven constant speed roll flexibly mounted above roll 29 and running against the top surface of the accumulated sheet on roll 29, suflicient frictional force being provided to avoid slipping by properly weighting the constant speed roll. A similar device may be used against supply roll 27, thereby making it a feed roll of constant speed. In this case feed nip rolls 28 may be omitted. Depending upon the amount of bonding and crepe elongation in the sheet, the sheet may be drawn as much as 10% during treatment. The feed and windup speed ratios are adjusted to provide the required amount of stretch, depending upon whether Stage -1 or Stage 3, and upon the type of product desired.
Rolls 5 and 6 are each provided with a multiplicity of spaced-apart rounded projections 31 buttons, knobs or bosses) disposed about the major portion of their curved surfaces as shown in FIGURE 5 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.
In operation of Step 1 and optionally of Step 3 of the process of this invention, sheet material 30 passes at a set speed from feed roll 27 as shown in FIGURE 2 to button rolls 5 and 6. The take-up speed of the sheet is controlled by the speed of take-up roll 29. With the button rolls 5 and 6 operating in a clockwise direction as seen in FIGURE 2 fabric is passed over the first, third, and fifth rolls in the direction of their rotation, and over the second and fourth rolls in a direction opposite their direction of rotation. The fabric passes around the front side of the fifth button roll and is wound up at roll 29.
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 be 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 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 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 roll. A windup/feed speed ratio of at least 1.001 is satisfactory for a machine having buttons rolls of 4 inch diameter with centers 9% inches apart and the roll axis 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 roll 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 29 is advantageously between 0.05 and 2.0 lbs. per inch of sheet Width.
A creping apparatus which develops lateral folds or fault lines is required for the process. Such a creper permits a sheet of high elongation in the longitudinal direction to be obtained. The mechanical action which accompanies substantial crepe removal is especially beneficial in developing softness. The lateral folds are desirable too because they may be removed by longitudinal stretching which is a simple and inexpensive operation. One satisfactory creping machine is described in US. Patent 3,260,778.
One suitable form of the apparatus is shown in FIG- URE 3. In the figure roll 11 is driven by means 32. A gripping surface 33 is provided on the roll, preferably comprising projections and indentations, for example knurled bosses or ribs and grooves.
A pressing apparatus arranged above the roll, has arms 34 that pivot about axle 14, this axle being parallel to the roll axis. On these arms 34 is mounted a head member 12 which vertically moves toward and away from the roll 11.
A holder 35 mounted on the head member 12 supports a sheet-contacting member 13. This sheet-contacting member has an extended portion that projects in the form of a cantilever forwardly over roll 11. Also mounted on the head member 12 is a pressing member 36, secured to forward portion 37 of the head member by mounting plate 38.
Preferably, as shown, the pressing member 36 is a plate that projects forwardly from its mounting as a cantilever, and this plate is resiliently yieldable in the direction perpendicular to its sides. The lower side of the pressing plate 36 can be fiat, as shown and at the free end it can intersect plate end surface 39 to define a continuous, straight pressing edge 40 that is parallel to the axis 35 of roll 11. This edge 40 is pressed against the forward margin 41 of sheet-contacting member 13.
A number of air cylinders 16 are mounted above the head member 12 and are provided with adjustment devices 42 which enable an adjustable downward force to be applied through piston rods 43 to the head member 12.
FIGURE 4 shows a preferred arrangement of roll 11, sheet-contacting member 13, and retarding member 15. The sheet-contacting member 13 comprises a plurality of spring metal layers 13a, 13b, and 130. The layer adjacent the sheet (130) has a resilient lip portion, and the pointed leading edge of retarding member is located under this lip portion. Metal layer 13b extends beyond the lip of layer 130, defining, with the surface of retarding member 15 a convergent passage which the sheet must traverse.
For further details of design, operation, and materials of construction for the creping apparatus, reference can be had to US. Patent 3,260,778. The entire disclosure of that patent is hereby incorporated by reference.
Example 1 A film-fibril sheet weighing about 1.3 oz./yd.'- was prepared from linear polyethylene (LPE). The sheet was prepared from networks of material flash spun by the method of US. Patent 3,081,519 using trichlorofluoromethane as solvent. The material was randomly deposited on a moving belt by the method of US. Patent 3,169,899. A 67 inch wide sheet was obtained. The sheet was lightly consolidated by passing through a pair of cold rolls which exerted a pressure of about 10 lbs./in. of axial length. The rolls 'were 1214 inches in diameter.
The cold consolidated sheet was then passed through the nip of a pair of rolls to develop a fine point bonded pattern on one side of the sheet only. One of the rolls was a smooth, hard rubber backup roll while the other roll had a steel surface which carried an embossing pattern. The embossing pattern on the steel roll consisted of tiny raised ridges which followed the circumference of the roll. The circumferential ridges were disposed every 0.158 cm. inch) across the axial length of the roll. Within the ridges were individual points which were 0.025 cm. (0.01 inch) high relative to the roll surface and which were 0.091 cm. inch) apart. In preparing the embossed film-fibril sheet the cold consolidated sheet was passed at 20 yds./min. through the roll pair with the steel roll maintained at 158 C. The sheet was trimmed to 52 inches width. Next the sheet was coated on both sides with a dispersion of an ethylene/methacrylic acid (/10) copolymer. The dispersion was applied by use of a two-side gravure coating method using 44% polymer in the dispersion. The resulting sheet contained 35% polymeric coating approximately evenly divided between the two sides. The center of thickness of the sheet still had movable fibers, the major part of the bonding being at the two surfaces of the sheet. The sheet was trimmed to 47 inches width.
The above prepared sheet was then subjected to a button braking operation using an apparatus similar to that of FIGURE 1, Stages 2 and 3 only. The apparatus consisted of a tandem arrangement of creper and button breaker. Treatment was provided in this apparatus by running first with the creper head lifted out of operating position so that the sheet fed directly to the button breaker. The sheet was then run through the coupled creper and button breaker to provide Stage 2 and 3 treatment.
In the first pass (Stage 1) through the button breaker the sheet Wind-up speed was yards per minute. The button breaker used in this experiment had 10 rolls of 4 inch diameter turning in the direction of the sheet at a speed of 600 revolutions per minute (r.p.m.) and 8 rolls of 4 inch diameter running counter to the direction of the sheet at 320 r.p.m. The take-up roll of the button breaker was set at a speed 1.9% faster than the feed troll speed. Due to slippage the actual draw was 1.5%.
In the Stage 2 and 3 operation of the sheet the feed and wind-up speed was 150 yds./min. The overfeed was 11.1% in the creping step, nip rolls 17 of FIGURE 1 being run at a speed of yds/min. The sheet was passed continuously through the operating creper head, through a pair of nip rolls and directly to the powerdriven button breaker.
In this Stage '3 pass through the button breaker the forward running rolls were rotated at 750 r.p.m. and the counter-rotating rolls at 400 r.p.m.
The sheet product from Stages 1, 2, and 3 in this experiment had no crepe elongation, all of the original 11.1% crepe elongation having already been removed in the last button breaker step. A soft product suitable for use in swimwear was obtained. The final sheet weighed 1.75 oz./yd. The softness of the sheet was measured by means of the Handle-O-Meter using TAPPI Method T498-SU65. Lower values indicate greater softness.
Handle-O-Meter (HOM) results taken after each step during the production are shown in Table I. These data indicate that during the softening operation, softness directionally (MD/CD) increased in the button breaking step, but was reduced almost to that of the base material by the subsequent creping-button breaking step. The ulti- Process CD HOM MD HOM MD/CD Before Button Breaking 138. 9 176. 9 1. 3 After 1 Pass Button Break 43. 8 104. 4 2. 4 After Button Break/Crepe] Button Break 36. 1 54. 9 1.
In the table the results are expressed in grams force.
CD indicates cross-direction measurement and MD indicates machine direction.
Other physical properties for this product are shown in Table II.
TABLE II.PROPERTIES OF SHEET FROM EXAMPLE I Final basis weight, oz./yd. 1.75 Tensile strength MD/ CD,
lbs./in./oz./yd. 7.9/5.9 Elongation MD/ CD, percent at break 22.8/28.6 Modulus MD/CD, lbs./in. 29070/ 17043 Tongue tear MD/CD, lbs./in. 3.12/3.09 Delamination resistance MD/CD, lbs./ in 0.17/ 0.11 Drape flex MD/CD, cm 3.66/ 3.53
Example II A cold-consolidated film-fibril sheet was prepared as in Example I by depositing LPE plexifilamentary material on a moving belt and cold rolling. The belt speed was adjusted to produce a sheet weighing 1.5 oz./yd. This sheet was hot embossed on one side by the embossing roll described in Example I, the roll temperature being 160 C., whereby a rib pattern was impressed on one side of the sheet. A linen pattern was impressed on the other side of the sheet by a similar technique. The sheet was coated on both sides as in Example I, using the same coating material. This sheet was then subjected to driven-roll button breaker operation with the feed roll operating slower than the take-up roll. It was then passed through a creper with 11.1% overfeed. Finally all of the crepe elongation was removed by drawing between a pair of rolls without benefit of mechanical stroking. In the drawing operation the first pair of rolls was set at about 64.5 yds./min. and the wind-up at about 70 yds./min. The product had improved softness based on Handle-O-Meter data as shown in Table III. In addition it showed a very favorable drape flex value (low values being desirable).
is not as good. This example demonstrates the preferred process wherein all of the crepe elongation is removed and wherein this operation is accompanied by mechanical stroking action. In other tests it has been shown that Handle-O-Meter data correlate well with subjective evaluations on softness and these data are more reliable for softness measurement than drape flex values.
Examples IV and V A linear polyethylene film-fibril sheet weighing 1.3 oz./yd. was embossed on one side only using the rib pattern described in Example I. The sheet was coated on both sides with the same polymeric coating. In both Examples IV and V, the Stage 1 operation comprised treatment on the roll driven button breaker with the feed roll running 5.5% slower than the take-up roll. Stage 2 comprised creping with 11.1% overfeed to provide 11.1% crepe elongation. Finally in Stage 3 the sheet of Example IV was subjected to a simple drawing operation to remove all of the crepe elongation. In Example V the Stage 3 operation comprised treatment on a driven roll button breaker to remove all of the available crepe elongation. Both products had improved softness. However, as shown by the Handle-O-Meter data in Table III, the Stage 3 operation involving the button breaker gave a. softer sheet than was obtained in the simple drawing operation.
Examples VI and VII These two examples demonstrate treatment of the filmfibril sheets without the use of coatings. Sheets weighing 1.3 oz./yd. were embossed on one side with the rib pattern and on the other side with the linen pattern and treated in Stages 1 and 2 as in Example II through V. In Stage 3 the simple drawing operation of Examples II and IV was used; for Example VI the button breaker drawing operation of Examples III, and V was used for Example VII. The product prepared by mechanical button breaking for Stage 3 was exceptionally soft and was therefore useful for industrial garments. Handle-O-Meter data for the two examples are given in Table III. Both of the products were much softer than the untreated embossed sheet.
Example VIII linen pattern using the method of Example II. It was coated on both sides as in Example II. The efiiciency of DRAWING ON BUTTON ROLLS Example Softening Drape-flex v Handle-O-Meter,
N Initial Sheet 8 Process b Avg.
MD CD 1.5 oz./yd. II R X L BondBtL. BB-CI-D 3.30 3.80 94. 5
2-Side Coated HI Same as Ex. 11 BB-Cr-BB 3. 51 3. 65. 0
1.3 ozJyd. IV R X 0 Bonded..." BB-Cr-D 2.72 2.92 59.0
2-Side Coated V Same as Ex IV BB-Or-BB 3. 84 3. 04 43. 0
1.3 oz./yd. VI R X L Bonded BB-Cr-D 3. 40 3. 30 44. 0
Uncoated VII Same as Ex. VI BB-Cr-BB 8. 47 3. 22 33. 5
d HandIe-O-Meter data in grams iorce (units), average of cross-direction and machine direction.
Example III the three-stage process was compared to a process using multiple passes through a power-driven button breaker of the type described in Reitz, US. patent application Ser. No. 421,902. The softening process was the same as in Example III. This process was then compared to that using simply multiple passes of the Stage 1 operation until obtained than in Example 11 but machine direction drape the same level of Handle-O-Meter softness was obtained.
1 1 The delamination resistance was observed after each pass. Data are shown in Table IV.
TABLE IV.-COMPARISON OF PROCESS OF THE INVEN- iIgON WITH MULTIPLE PASS BUTTON BREAKERPROC- Softening Method Speed HOM Visual Delamination y.p.rn.
BB/Crepe/BB 75 65 Acceptable. 1 Pass, Button Breaker 50 116 No delamination. 2 Pass, Button Breaker 75 89 Acceptable. 3 Pass, Button Breaker b 75 75 Questionable. 4 Pass, Button Breaker b 75 65 Not acceptable. 5 Pass, Button Breaker... b 75 56 Totally delaminated.
a ROM means Handle-O-Meter measurement in grams force. b First pass for each was 50 y.p.rn. Lower sheet speeds in driven roll button breaker gives increased softness.
Basis weight-TAPPI Method T410OS61 Handle-O-Meter-TAPPI Method T498-SU65 Drape fieXASTM Test D1388-64 (Option A) Tensile strengthTAPPI Method T404-M-50 Elongation at breakSame Tongue tearTAPPI T4l4--M49 For simplicity in measurement crepe elongation is considered to be the same as the percentage overfeed in the creper.
Delamination resistance is measured using an Instron Tester, 1 inch x 3 inch line contact clamps, and an Instron Integrator, all manufactured by Instron Engineering Inc., Canton, Mass, Delamination of a 1 inch x 7 inch specimen is manually started across a 1 inch x 1 inch edge area (so that the remaining 1 inch x 6 inch portion remains unseparated) by splitting the sheet with a pin. With a C load cell, the following settings are used: gauge length of 4.0 inch, crosshead speed of 5.0 inch/ minute chart speed of 2.0 inch/ minute and full scale load of 2 lbs. One split end is placed in each of the clamps and the force is measured which is required to pull the sheet apart. Delamination resistance (lbs./ in.) equals the integrator reading divided by 2500.
1. A process for producing a soft textile-like sheet from a. paper-like, point-bonded film-fibril sheet which comprises:
(1) passing the sheet through a stretching and mechanical agitation zone between a feed position and a take-up position, the speed of the sheet at the take-up position being faster than the speed at the feed position so that sufiicient tension is applied to the sheet to stretch it between 0.1 and 10% in the longitudinal dimension of the sheet, 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, the stroking being directed first to one side of the sheet and then to the other, and being applied successively in any order both with and against the direction of sheet travel; then,
(2) passing the sheet from the take-up position of Step (1) through a creping position where the sheet is mechanically detained by the application of pressure exerted normal to the sheet between the two faces of the sheet, the pressure, input speed, and output speed being adjusted to provide numerous lateral fault lines across the sheet such that the spacing between fault lines along the length of the sheet is no greater than about 0.5 inch; then,
(3) passing the sheet through a stretching and mechanical agitation zone between a feed position and a take-up position, the speed of the sheet at the takeup position being faster than the speed at the feed position so that suflicient tension is applied to the sheet to remove at least of the crepe elongation, 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, the stroking being directed first to one side of the sheet and then to the other, and being applied successively in any order both with and against the direction of sheet travel.
2. A process as defined in claim 1 wherein the stretching of the sheet in Step (3) is sufficient to remove all of the crepe elongation.
3. A process as defined in claim 2 wherein the stretching of the sheet in Step (3) is accompanied by mechanical agitation as in Step (1).
4. A process as defined in claim 1 wherein in Step (2) the input speed to the creping position is between about 2% and about 50% greater than the output speed.
References Cited UNITED STATES PATENTS Re. 25,335 2/1963 Hamilton 162-l 13 2,705,497 4/1955 Johnson 128-290 3,047,444 7/1962 Harwood 154--46 3,203,850 8/1965 McCarty 162---l13 3,260,778 7/1966 Walton 264-282 ROBERT F. WHITE, Primary Examiner.
RICHARD R. KUCIA, Assistant Examiner.
U.S. Cl. X.R.