Title:
LIGHTWEIGHT NONPATTERNED NONWOVEN FABRIC
United States Patent 3620903
Abstract:
Lightweight, nonpatterned, nonwoven fabrics suitable for use as wearing apparel are produced by treating fibrous sheet materials with fine, essentially columnar streams of liquid jetted from orifices under high pressure. A layer of fibrous material is supported on a nonpatterning surface and traversed with the streams to entangle the fibers in a manner which imparts strength and stability without the need for binder. A smooth fabric surface is provided by use of broken streams or by rapid oscillation of the streams. 5 Claims, No Drawings
US Patent References:
TEXTILE-LIKE PATTERNED NONWOVEN FABRICS AND THEIR PRODUCTION
Evans - December 1969 - 3485706
NONPATTERNED,NONWOVEN FABRIC
Bunting, Jr. et al. - February 1970 - 3493462
TEXTILE-LIKE PATTERNED NONWOVEN FABRICS AND THEIR PRODUCTION
Evans - December 1969 - 3485706
NONPATTERNED,NONWOVEN FABRIC
Bunting, Jr. et al. - February 1970 - 3493462
Inventors:
William Wallar Jr., Bunting (Wilmington, DE)
Franklin James, Evans (Wilmington, DE)
David Ellis, Hook (Wilmington, DE)
Franklin James, Evans (Wilmington, DE)
David Ellis, Hook (Wilmington, DE)
Application Number:
05/006963
Publication Date:
11/16/1971
Filing Date:
01/29/1970
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
162/204, 162/115, 28/105, 428/359, 28/104
International Classes:
D04H1/42; D04H1/46; D04H3/08; D06C1/06
Field of Search:
161/72,80,153,154,169 28/72.2
Primary Examiner:
Robert, Burnett F.
Assistant Examiner:
Roger, May L.
Attorney, Agent or Firm:
Norris, Ruckman E.
Parent Case Data:
REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of applications, Ser. No. 834,788 filed June 19, 1969, now U.S. Pat. No. 3,508,308, and Ser. No. 712,070 filed Mar. 11, 1968, now U.S. Pat. No. 3,493,462, which is a continuation-in-part of application, Ser. No. 584,627 (now abandoned) filed Sept. 22, 1966, as a division of Ser. No. 208,136 filed July 6, 1962, and now abandoned
Claims:
1. A nonpatterned, smooth-surfaced, nonwoven fabric weighing 0.5 to 2.0 ounces per square yard, consisting of 20 percent to 100 percent by weight textile fibers and 80 percent to 0 percent papermaking fibers interentangled, at an entanglement frequency of 11 to 24 per inch for each of the two major fabric directions, in a substantially uniformly dense structure wherein fibers pass randomly about one another and interlock when the fabric is subjected to stress, thereby providing coherency and strength to the fabric, the fiber interlock value being at least 10 grams per gram/square meter of fabric, and the fabric having a strip tensile strength of at least 1.5 with a modulus of at least 1.0 pounds/inch per ounce/square yard in both major fabric directions, said textile fibers being selected from the group consisting of synthetic fibers and
2. A nonwoven fabric as specified in claim 1 wherein said textile fibers have a denier per filament of about 0.5 to 3 and an average length of
3. A nonwoven fabric as specified in claim 1 and weighing 0.5 to 1.5 ounces
4. A nonwoven fabric as specified in claim 1 wherein said entanglement
5. A nonwoven fabric as specified in claim 1 and having an internal bond value of at least 0.2 foot-pounds.
2. A nonwoven fabric as specified in claim 1 wherein said textile fibers have a denier per filament of about 0.5 to 3 and an average length of
3. A nonwoven fabric as specified in claim 1 and weighing 0.5 to 1.5 ounces
4. A nonwoven fabric as specified in claim 1 wherein said entanglement
5. A nonwoven fabric as specified in claim 1 and having an internal bond value of at least 0.2 foot-pounds.
Description:
This invention relates to novel textile products. More particularly, it relates to lightweight, nonpatterned, nonwoven fabrics obtained by subjecting bulk fibrous materials to the action of high pressure liquid streams.
The prior art discloses various processes in which fluids under pressure have been used to treat textile materials. For example, dispersed streams of water, provided by a solid cone spray nozzle supplied with water at 70 to 100 pounds per square inch gauge pressure (p.s.i.g.), have been applied through spaced apertures against a fibrous starting material so as to rearrange laterally the individual fibers into a pattern determined by the pattern of the apertures. These prior art products rely on binder to attain strength.
Guerin U.S. Pat. No. 3,214,819 issued Nov. 2, 1965, teaches the formation of felts by applying jets of liquid to a plurality of layers of loosely associated textile fibers to produce a reorientation of some fibers between laminations to provide a fiber-locking and entanglement, in the product, having a strength equal to a normal needle loomed fabric and with greater flexibility and diversification. The patent also discloses that when an adhesive such as resin in liquid form is added, the binder is permeated through the material to anchor the fibers in their new oriented form and increase the tensile strength and abrasion resistance.
The use of mechanical needle looms to produce relatively heavyweight feltlike products is well known.
However, attempts to use needle looms to produce lightweight products have not provided fabrics suitable for apparel use. Even when the number of needle punches per square inch is greatly increased beyond conventional values, the lightweight products are readily deformed and/or the appearance is quite poor, with a large number of visible holes from needle penetrations and blotchy, streaked non-uniformities. Lightweight needle loomed products of the prior art are characterized by low stress-strain moduli at 5 percent elongation, which is indicative of the ease with which they deform in use.
The products of the present invention are nonpatterned, smooth-surfaced nonwoven fabrics weighing 0.5 to 2.0 ounces per square yard (preferably 0.5 to 1.5 oz./yd. 2 ), consisting of 20 percent to 100 percent by weight textile fibers and 80 to 0 percent papermaking fibers interentangled, at an entanglement frequency of 11 to 24 per inch in each of the two major fabric directions, in a substantially uniformly dense structure wherein fibers pass randomly about one another and interlock when the fabric is subjected to stress, thereby providing coherency and strength to the fabric, the fiber interlock value being at least 10 grams per gram/square meter of fabric when evaluated as defined subsequently. These fabrics have a strip tensile strength of at least 1.5 with a 5 percent secant modulus of at least 1.0 pounds/inch per ounce/square yard in both major fabric directions, when determined as defined subsequently.
Synthetic textile fabric, cellulosic textile fibers and mixtures of synthetic textile fibers with cellulosic textile fibers are used in making the fabric. Papermaking fibers may also be present in amounts up to 80 percent of the total weight of fibers. Conventional papermaking fiberlengths are suitable. Preferably the textile fibers used will have a denier per filament of about 0.5 to 3 and an average length of about 0.5 to 2 inches.
Preferably the fibers are interentangled at an entanglement frequency of at least 14, as subsequently defined. An internal bond value of at least 0.2 foot-pounds is also desirable for durable fabrics.
The products of this invention are termed "textile fabrics" as they compare favorably in strength, appearance and handle with conventional fabrics used for wearing apparel. An elongation at the break of between 20 and about 100 percent in both major directions is readily provided.
The phase "textile fibers" includes the conventional synthetic fibers, e.g., polyesters, polyamides, acrylics, etc., and cellulosic fibers such as rayon and cotton. The conventional "papermaking fibers" are wood pulp and cotton linters, and short synthetic fibers are sometimes used. The synthetic textile fibers and the cellulosic textile fibers will generally have a denier per filament of about 0.5 to 3 although both finer and coarser fibers may be sometimes used, and will preferably have an average length of about 0.5 to 2 inches. Shorter fibers may be included with the textile fibers to increase the modulus and surface stability of the products. Long fibers up to and including continuous filaments may be used to provide added strength.
The products of the invention are made by traversing a layer of fibrous material on a nonpatterning support member with essentially columnar streams of liquid jetted from orifices. Suitable streams include broken streams (which may be produced as disclosed in example 1 of Dworjanyn U.S. Pat. No. 3,403,862) and solid streams. The solid streams may be oscillated rapidly, or interrupted (as by an oscillating screen) in their passage toward the layer, so that they will not introduce a regular pattern of entanglement in the product.
Suitable apparatus and discussion of the process is disclosed in Bunting, Evans and Hook U.S. application, Ser. No. 712,070, filed Mar. 11, 1968.
Preferred orifices are shown in U.S. Pat. No. 3,403,862 to Dworjanyn. Orifice diameters of 5 and 7 mil are especially preferred. Preferably the orifices are spaced 10 per inch and more preferably 20 to 40 or more per inch.
The nonpatterning support member may be a screen or other apertured support or a solid surface such as a flat plate or bar. Preferably a plain woven screen of 80×80 mesh per inch or finer is used in conjunction with the preferred orifices.
The high-strength nonwoven fabrics of the present invention are obtained by traversing the exposed face of the initial fibrous layer, on the support, with streams of a noncompressible fluid at sufficiently high energy flux and for a sufficient amount of treatment to entangle the fibers thereof as specified above. The energy flux (EF) of the streams will depend upon the jet device used, the pressure of the liquid supplied to the jet orifice, and the orifice-to-web spacing during treatment. The liquid initially forms a "solid" stream, i.e., an unbroken, homogeneous liquid stream. The initial energy flux, in foot-poundals/inch 2 second, is readily calculated by the formula:
EF i =77 PG/a where: P=the liquid pressure in p.s.i.g. (pounds per square inch gauge pressure), G=the volumetric flow of the stream in cu.ft./minute, and a=the initial cross-sectional area of the stream in square inches.
The value of G for use in the above formula can be obtained by measuring the flow rate of the stream. The initial cross-sectional area (a) which is inside the jet device, can be determined by measuring the actual orifice area and multiplying by the discharge coefficient (usually 0.64), or it can be calculated from measured flow rates. Since the area (a) corresponds to solid stream flow, the above formula gives the maximum value of energy flux which can be obtained at the pressure and flow rate used. The energy flux will usually decrease rapidly as the stream travels away from the orifice, even when using carefully shaped orifices. The stream diverges to an area (A) just prior to impact against the web and the kinetic energy of the stream is spread over this larger area. The cross-sectional area (A) can be estimated from photographs of the stream with the web removed, or can be measured with micrometer probes. The energy flux is then equal to the initial energy flux times the stream density ratio (a/A). Therefore, the formula for energy flux at the web being treated is:
EF w =77 PG/A ft.-poundals/in. 2 sec.
The value of (A) increases with the orifice-to-web spacing and, at a given treatment distance, the value depends upon the jet device and the liquid supply pressure used. A pressure of 200 p.s.i.g. can provide sufficient energy flux for several inches when using a highly efficient jet device, e.g. as in examples 1 to 10. With other jet devices, the energy flux of a stream may become too low in a relatively short distance even when using higher pressures, due to the stream breaking up and losing its columnar form. When this occurs there is a sudden increase in the value of (A) and the energy flux drops rapidly. Since the stream may become less stable when higher pressures are used, the energy flux at a given treatment distance may actually decrease when the jet orifice pressure is increased to provide a higher initial energy flux (PG/a).
By "essentially columnar" is meant that the streams have a total divergence angle of not greater than about 5°. Particularly, strong and surface-stable fabrics are obtained with high-pressure liquid streams having an angle of divergence of less than about 3°.
The amount of treatment must be sufficient and is measured by energy expended per pound fabric produced. The energy (E 1 ) expended during one passage under a manifold in the preparation of a given nonwoven fabric, in horsepower-hours per pound of fabric, may be calculated from the formula:
E 1 =0.125 (YPG/sb) where: Y=number of orifices per linear inch of manifold, P=pressure of liquid in the manifold in p.s.i.g., G=volumetric flow in cu.ft./min. per orifice, s=speed of passage of the web under the streams, in ft./min., and b=the weight of the fabric produced, in oz./yd. 2 . The total amount of energy expended in treating the web is the sum of the individual energy values for each pass under each manifold, if there is more than one.
It has been observed that the entanglement of the fibers is related to the products of this energy (E) of treatment and the impact force (I) (in pounds) of the water stream, where (I) is calculated by multiplying the cross-sectional area (A) of the stream in square inches by the pressure (P) on the orifice in p.s.i.g.
The process of the present invention may be used to produce entangled nonwoven fabrics from any type of loose fibrous web, batt, or sheet. The ease with which a given web can be entangled is dependent upon many factors, and process conditions may be chosen accordingly. Fiber mobility also has a bearing on the ease with which a web can be processed. Factors which influence fiber mobility include, for example, the density, modulus stiffness, surface-friction properties, denier, crimp and/or length of the fibers in the web. In general, fibers which are highly wettable, or have a high degree of crimp, or have a low modulus or low denier, can also be processed more readily.
Suitable fibrous material includes all manner of textile fibers and combinations of textile fibers and papermaking fibers such as wood pulp, cotton linters and the like. The textile fibers can be of any convenient length ranging from short staple (e.g., 0.25 inch) to continuous lengths. Deniers of from 1 to 3 are readily processed but smaller and larger deniers can be used. The fibers can be straight or crimped. Blends of various fibers can be used and the fibrous layer can contain layers of different composition.
Papermaking fibers can be present in the initial layer as a paper sheet or an intimate blend with the textile fibers. The fibrous material should contain at least about 20 percent of textile fibers to obtain the desired integrity of a nonwoven fabric.
Nonwoven fabrics having particularly high levels of drape and conformability may be obtained by using crimpable, shrinkable, spontaneously elongatable, or elastic fibers as one of the components of the fibrous sheet material and developing the latent properties of the fiber after formation of the nonwoven fabric.
TESTS FOR EVALUATING PHYSICAL PROPERTIES
The tensile properties are measured on an Instron tester at 70° F. and 65 percent relative humidity. Strip tensile strength, elongation and modulus are determined for a sample 1.0-inch wide, using a 2-inch gauge length and elongating at 50 percent per minute. The measured stresses in pounds and corresponding elongations are plotted to give a stress-strain curve. Strip tensile strength is the value at break divided by the fabric weight in oz./yd. 2 . The 5 percent secant modulus is defined by American Society for Testing and Materials Standards E6-61, Sec. 20 (1969, Part 27). It is determined by reading the stress at 5 percent elongation from the stress-strain curve, multiplying this by 20, and dividing by the fabric weight in oz./yd. 2 .
Tensile properties are determined in the two major directions of the products; the machine direction (MD), which is the direction of travel of the web during treatment, and the cross direction (XD), which is 90° to the machine direction. Each value is the average of five determinations.
Density is calculated from the weight of the fabric and its thickness.
Thickness is measured under a total pressure 0.22 lb./in. 2 with a 2-inch diameter disc on a thickness gauge.
FIBER-INTERLOCK TEST
The fiber-interlock value is the maximum force in grams per unit fabric weight needed to pull apart a given sample between two hooks.
Samples are cut 0.5 inch × 1.0 inch and weighed, and each sample is marked with two points 0.5 inch apart symmetrically along the midline of the fabric so that each point is 0.25 inch from the sides and end of the fabric.
The eye end of a hook (Carlisle-6 fish hook with the barb ground off or a hook of similar wire diameter and size) is mounted on the upper jaw or an Instron tester so that the hook hangs vertically from the jaw. This hook is inserted through one marked point on the fabric sample.
A second hook is inserted through the other marked point on the sample, and the eye end of the hook is clamped in the lower jaw of the Instron. The two hooks are now opposed but in line, and hold the sample at 0.5-inch interhook distances.
The "Instron" tester is set to elongate the sample at 0.5 inch per minute (100 percent elongation/minute) and the force in grams to pull the sample apart is recorded. The maximum load in grams divided by the fabric weight in grams per square meter is the single fiber interlock value. The average of 3 determinations in the machine direction and 3 in the cross direction (samples cut in directions at 90° to each other) is reported to two significant figures as the fiber interlock value.
ENTANGLEMENT FREQUENCY
Samples of the nonwoven fabrics are characterized according to the frequency of the fiber entanglement in nonbonded fabric, as determined from strip tensile breaking data using an "Instron" tester.
Entanglement frequency is a measure of the frequency of occurrence of entanglement sites along individual lengths of fiber in the nonwoven fabric. The higher the value of entanglement frequency the greater is the surface stability of the fabric, i.e., the resistance of the fabric to the development of pilling and fuzzing upon repeated laundering.
Entanglement frequency is calculated from strip tensile breaking data, using strips of the following sizes: Strip Strip "Instron" Gauge Elongation Width Symbol Width Length Rate (in.) (in.) (in./min.) ____________________________________________________________ _____________ _ w 1 0.3 1.5 5 w 2 1.9 1.5 5 ____________________________________________________________ _____________ _
In cutting the strips from fabrics having a repeating pattern of ridges or lines of high and low basis weight, integral numbers of repeating units are included in the strip width, always cutting through the low basis weight portion and attempting in each case to approximate the desired widths (w 1 , w 2 ) closely. Ten or more specimens are tested at w 1 , and five or more at w 2 using an "Instron" tester with standard rubber coated, flat jaw faces and the gauge lengths and elongation rates listed above. Average tensile breaking forces for each width (w 1 and w 2 ) are correspondingly reported as T 1 and T 2 . It is observed that: It is postulated that the above inequalities occur because there is a border zone of width D at the cut edges of the long gauge length specimens, which zone is ineffective in carrying stress.
In certain cases (D) may be nearly zero and even a small experimental error can result in the measured (D) being negative. Strips are cut in two directions: (a) in the machine direction, and (b) in the direction at 90° to the direction specified in (a). Entanglement frequency (f) per inch is defined as 1/D. If the measured (D) turns out to be zero or negative, it is proper to assume that the actual (D) is less than 0.01 inch and (f) is therefore greater than 100 per inch.
INTERNAL BOND VALUE TEST
It has been found that the following "internal bond" test is a measure of the extent of three-dimensional entanglement. It is believed that this test measures the ability of the fibers that penetrate the entangled fiber regions at substantial angles to the plane of the fabric to prevent delamination in the test.
A. The internal bond value of the nonwoven fabric is determined by a procedure described in Technical Association of the Pulp and Paper Industrial (TAPPI) "RC-308 Test for Interfiber Bond Using the Internal Bond Tester." Further information regarding this procedure, particularly about the equipment used, is disclosed by Blockman and Wikstrand, TAPPI, Mar. 1958, Volume 41, Number 3, pages 190A to 194A, "Interfiber Bond Strength of Paper." The faces of the steel anvils, striking bar, samples of nonwoven fabric and double-faced pressure-sensitive tape are each one inch square. The samples are mounted at 200 p.s.i. for one second. Five samples are tested in the machine direction of the fabric and five in the cross direction, and the average value is reported in foot-pounds.
Routine Control Method RC-308 specifies the use of "Scotch Brand type 400 double-faced pressure-sensitive tape" in the test. In case such a commercial produce is not available, its characteristics are as follows: Double-faced pressure-sensitive tape, 1-inch wide with combined thickness of adhesive layers of 0.0015±0.0005 inch (measured under about 1 p.s.i. pressure) and with an adhesion to steel within 35±5 ounces/inch (measured according to Federal Specification UU-T-91C of May 10, 1961).
It should be a routine practice to check the tape each day by running the test on two layers of tape between the bottom steel anvil and the aluminum angle pressed together at 200 p.s.i. These tests should give a value of at least 0.5 foot-pounds. If they do not, some tape is stripped off the roll and the tape calibration is repeated with fresh tape until proper values are obtained. It is obvious that, since the test is designed to measure internal bond values as high as 0.5, the adhesion of the tape to the anvil and angle must be at least 0.5 foot-pounds. This fact could be overlooked by an operator that might be accustomed to obtaining values below 0.5.
The tape-contacting surfaces of the anvil and the angle must be clean. Preferably they should be cleaned with a minimum of acetone and dried between each set of determinations.
Meaningful results may not be obtained by the above Method (A) on (1) netlike products having an open area of more than about 15 percent or (2) very thin fabrics having a fabric weight of less than 1.0 oz./yd. 2 due to adhesion of the two layers of tape to each other. For these products the following Method (B) should be used:
B. The sample is fastened to the lower fixed steel plate with the tape. This assembly is then pressed (sample face down) into a thin, flat bed of aluminum oxide (grade 400 "Lionite Floated Flour" made by General Abrasive Co., Inc., of Little Rock, Arkansas) at a pressure of 100 p.s.i. The assembly is removed from the bed and the bottom of the steel plate held firmly against the vertical shaft of a laboratory vibrator (providing an amplitude of 0.5 mm. at a frequency of 60 cycles per second) for 30 seconds. This treatment effectively removes the aluminum oxide from the fabric but not from any tape face exposed through openings in the fabric.
If the sample is vibrated face up, then it should be gently blown by mouth after the vibration treatment to remove any loose aluminum oxide from the sample, and aluminum oxide remaining on the steel surfaces of the anvil should be removed with a brush to avoid contaminating the apparatus.
The assembly is replaced in the mounting jig and fastened to the upper striking bar with tape at 200 p.s.i. and tested as in Method A.
Although the instrument has a dual range, all measurements in the application were made on the high range of from 0.100-0.500 ft.-lb.
The open area of a fabric can be estimated by measuring the size of the openings and counting for a given area.
It is observed that Method B gives substantially the same results as Method A on fabrics of low open area and weights greater than 1 oz./yd. 2 .
Preferred products of this invention have an internal bond value of at least 0.2 foot-pounds.
EXAMPLES 1-4
These examples illustrate a preferred process for preparing products of the invention from polyester textile fibers, using a final treatment with broken streams of water.
Webs containing a random array of fibers are made by air deposition of 1.5 denier polyester staple fibers of 1.5 inches in length except for example 4 where 0.75-inch fibers are used. The fiber lengths given are nominal average values for the starting fiber, but the actual fiber lengths are somewhat lower, e.g., when measured the 1.5 -inch polyester fiber has an average length of 1.2 inches.
The webs are placed on a plain woven metal screen of 80×80 mesh per inch (31 percent open area), and passed under a row of vertical jet streams of water at 20 y.p.m. (30 y.p.m. for example 1).
The water streams are produced by a row of 7 mil diameter orifices spaced 40/inch located 2 inches above the web and constructed similar to FIG. 3 of U.S. Pat. No. 3,403,862 to Dworjanyn.
a. Each web is given 1 pass under the streams at 200, 500 and 800 p.s.i.g., in order, plus optional treatments at 1400 p.s.i.g. as indicated below. (b) The products are then flipped on the screen and the above treatments are repeated for the web face which previously contacted the screen. The total treatment energy used in the process is given in table I.
The use of 1,400 p.s.i.g. with the above orifices and perforated plate filter located above the orifices affords an essentially columnar (i.e., less than 5° total divergence angle) stream of water which is broken at 2 inches from the orifice. The treatment entangles the fibers without producing a pattern of entanglement.
The properties of the products shown in table I, wherein pairs of values are for XD and MD, respectively. All products are strong, with moduli of at least 1.4, and have a uniform appearance, with no pattern or apertures and a smooth surface.
FINAL TREATMENT WITH BROKEN STREAMS Example No. 1 2 3 4 Web face a b a b a b a b Number of Passes 0 1 1 1 1 3 1 3 (1,400 p.s.i.g.)
EXAMPLES 5-8
The process described in examples 1-4 is used for treating webs of rayon instead of polyester fibers.
Each starting web consists of a random array of 1.5 denier rayon fibers averaging 1.56 inches in length. The webs are supported on plain-weave metal screens of 80×80 mesh per inch (31 percent open area), except for examples 6 and 7 where 150×150 mesh (2.6 mil wire diameter) screens are used; and passed under the water streams at 20 y.p.m. (30 y.p.m. for example 6). The web is treated on both faces with the streams at 200, 500 and 800 p.s.i.g., in order, except for the webs of examples 5 and 7 which are treated on one face only. The webs are also given a final treatment on at least one face with 1,400 p.s.i.g. streams as follows: Example No. 5 6 7 8 Web face a a b a a b Passes 1 0 1 3 1 1
The properties of the products are given in table II. All products are strong, with moduli of at least 1.4 and having a uniform appearance, with no pattern or apertures and a smooth surface.
EXAMPLE 9
This example shows the preparation of a product of the invention composed of polyester textile fibers and cellulosic papermaking fibers.
Webs containing random arrays of 1.5 inch polyester fiber of 1.5 d.p.f. (weighing 0.5 oz./yd. 2 ) are placed on an 150 × 150 mesh screen and covered with a layer of tissue-grade paper of wood-pulp fibers (weighing 0.6 oz./yd. 2 ) and passed under a row of vertical jet streams of water at 4 y.p.m.
The water streams are produced by a row of 5-mil diameter orifices constructed similarly to those of examples 1-4 , spaced 40/inch, located 3.25 inches above the paper/fiber layer.
The web is given one treatment at 200 p.s.i.g. with the vertical water jets, followed by four treatments at 200 p.s.i.g. in which a 30×30 mesh screen (49 percent open area) placed about 2.5 inches above the webs and below the orifices is oscillated at 200 cycles per minute with a 0.25-inch amplitude. The resulting fabric is turned over and given one treatment at 100 p.s.i.g. using the above oscillating screen. Properties of the product are given in table II.
The dried, nonforaminous product has no regular pattern of entanglement. Properties are given in table II.
EXAMPLE 10
This example shows the preparation of a product of the invention composed of polyester textile fibers and papermaking fibers. The starting web and paper of example 9 are used with the apparatus of example 9.
One layer of paper placed between two random webs of polyester fibers is placed on a 150-mesh screen and passed under a row of jet streams of water at 2 y.p.m. The composite web is given one treatment with the uninterrupted vertical jet streams at each of 100, 200 and 300 p.s.i.g. Then the web is given four treatments at 200 p.s.i.g. using oscillating jets and an oscillating top screen. The web is turned over and given one additional treatment at 200 p.s.i.g. with the oscillating jets and top screen.
The jets are mechanically oscillated, laterally to the direction of web movement at 50 oscillations per minute with an amplitude of 0.5 inch. A 30-mesh screen placed 0.75 inch below the orifices and 2.5 inches above the web is manually oscillated, laterally to the web movement, about 200 oscillations per minute with an amplitude of about 0.25 inch.
The dried, nonforaminous product has a substantially uniform appearance. Properties are given in table II.
COMPARISON EXAMPLE
This example illustrates the properties obtained in attempts to prepare similar products by needle punching.
The polyester fibers of examples 1-4, but cut to an average length of 2.0 inches, are processed into a card web on a sample roller card made by Davis and Furber Co. of North Andover, Massachusetts, for items a-i. Random webs of polyester fiber identical with those of examples 1-4 are plied to give the starting webs for items j and k.
The webs are processed on a small-scale needle loom("Hunter Fiber Locker" made by James Hunter Machine Co., North Adams, Massachusetts). The needle board (10 inches long × 12 inches wide) carries 600 needles and affords 300 needle penetrations per square inch for each pass through the machine. The web is advanced 0.19 inch per stroke. The stripper plate and the bed plate have a normal separation of 0.50 inch. A needle penetration of 12 mm. is used on all items. Felting needles used are a very small needle (15×18×46×3CB carrying 3 rows of barbs) and a small size needle for commercial operation (15×18×38×3CB with 2 rows of barbs) designated Needle Gauge 46 and 38, respectively, in table III. The top roll of the feed rolls is not used. All webs are processed for an even number of passes through the needle loom with alternate sides being needled on each successive pass.
Process conditions and properties of the products are are given in table III.
The products made with the finer (46 gauge) needles (items a-f) have a fluffy, feltlike appearance with some visible holes from the needles. The extremely low moduli with average values of less than 0.5 indicates the ease with which these felts can be deformed. The elongations at the break range from 109 to 220 percent and from 90 to 118 percent for XD and MD, respectively.
The use of the larger 38 gauge needle (items g- i) affords moduli that give a more useful fabric, and densities more comparable to fabrics, since the web is simultaneously stretched as these larger needles penetrate the web. The elongations range from 75 to 86 percent and from 61 to 84 percent, respectively, for the XD and MD. However, the larger needle causes randomly spaced visible holes of about 0.5 mm. diameter at a frequency of typically 80/inch 2 , and the stretching action imparts a very blotchy, nonuniform, streaked appearance.
Items j and k are included to illustrate the relatively poor physical properties--especially moduli--obtained from lightweight webs of random fibers. ##SPC1## ##SPC2##
The prior art discloses various processes in which fluids under pressure have been used to treat textile materials. For example, dispersed streams of water, provided by a solid cone spray nozzle supplied with water at 70 to 100 pounds per square inch gauge pressure (p.s.i.g.), have been applied through spaced apertures against a fibrous starting material so as to rearrange laterally the individual fibers into a pattern determined by the pattern of the apertures. These prior art products rely on binder to attain strength.
Guerin U.S. Pat. No. 3,214,819 issued Nov. 2, 1965, teaches the formation of felts by applying jets of liquid to a plurality of layers of loosely associated textile fibers to produce a reorientation of some fibers between laminations to provide a fiber-locking and entanglement, in the product, having a strength equal to a normal needle loomed fabric and with greater flexibility and diversification. The patent also discloses that when an adhesive such as resin in liquid form is added, the binder is permeated through the material to anchor the fibers in their new oriented form and increase the tensile strength and abrasion resistance.
The use of mechanical needle looms to produce relatively heavyweight feltlike products is well known.
However, attempts to use needle looms to produce lightweight products have not provided fabrics suitable for apparel use. Even when the number of needle punches per square inch is greatly increased beyond conventional values, the lightweight products are readily deformed and/or the appearance is quite poor, with a large number of visible holes from needle penetrations and blotchy, streaked non-uniformities. Lightweight needle loomed products of the prior art are characterized by low stress-strain moduli at 5 percent elongation, which is indicative of the ease with which they deform in use.
The products of the present invention are nonpatterned, smooth-surfaced nonwoven fabrics weighing 0.5 to 2.0 ounces per square yard (preferably 0.5 to 1.5 oz./yd. 2 ), consisting of 20 percent to 100 percent by weight textile fibers and 80 to 0 percent papermaking fibers interentangled, at an entanglement frequency of 11 to 24 per inch in each of the two major fabric directions, in a substantially uniformly dense structure wherein fibers pass randomly about one another and interlock when the fabric is subjected to stress, thereby providing coherency and strength to the fabric, the fiber interlock value being at least 10 grams per gram/square meter of fabric when evaluated as defined subsequently. These fabrics have a strip tensile strength of at least 1.5 with a 5 percent secant modulus of at least 1.0 pounds/inch per ounce/square yard in both major fabric directions, when determined as defined subsequently.
Synthetic textile fabric, cellulosic textile fibers and mixtures of synthetic textile fibers with cellulosic textile fibers are used in making the fabric. Papermaking fibers may also be present in amounts up to 80 percent of the total weight of fibers. Conventional papermaking fiberlengths are suitable. Preferably the textile fibers used will have a denier per filament of about 0.5 to 3 and an average length of about 0.5 to 2 inches.
Preferably the fibers are interentangled at an entanglement frequency of at least 14, as subsequently defined. An internal bond value of at least 0.2 foot-pounds is also desirable for durable fabrics.
The products of this invention are termed "textile fabrics" as they compare favorably in strength, appearance and handle with conventional fabrics used for wearing apparel. An elongation at the break of between 20 and about 100 percent in both major directions is readily provided.
The phase "textile fibers" includes the conventional synthetic fibers, e.g., polyesters, polyamides, acrylics, etc., and cellulosic fibers such as rayon and cotton. The conventional "papermaking fibers" are wood pulp and cotton linters, and short synthetic fibers are sometimes used. The synthetic textile fibers and the cellulosic textile fibers will generally have a denier per filament of about 0.5 to 3 although both finer and coarser fibers may be sometimes used, and will preferably have an average length of about 0.5 to 2 inches. Shorter fibers may be included with the textile fibers to increase the modulus and surface stability of the products. Long fibers up to and including continuous filaments may be used to provide added strength.
The products of the invention are made by traversing a layer of fibrous material on a nonpatterning support member with essentially columnar streams of liquid jetted from orifices. Suitable streams include broken streams (which may be produced as disclosed in example 1 of Dworjanyn U.S. Pat. No. 3,403,862) and solid streams. The solid streams may be oscillated rapidly, or interrupted (as by an oscillating screen) in their passage toward the layer, so that they will not introduce a regular pattern of entanglement in the product.
Suitable apparatus and discussion of the process is disclosed in Bunting, Evans and Hook U.S. application, Ser. No. 712,070, filed Mar. 11, 1968.
Preferred orifices are shown in U.S. Pat. No. 3,403,862 to Dworjanyn. Orifice diameters of 5 and 7 mil are especially preferred. Preferably the orifices are spaced 10 per inch and more preferably 20 to 40 or more per inch.
The nonpatterning support member may be a screen or other apertured support or a solid surface such as a flat plate or bar. Preferably a plain woven screen of 80×80 mesh per inch or finer is used in conjunction with the preferred orifices.
The high-strength nonwoven fabrics of the present invention are obtained by traversing the exposed face of the initial fibrous layer, on the support, with streams of a noncompressible fluid at sufficiently high energy flux and for a sufficient amount of treatment to entangle the fibers thereof as specified above. The energy flux (EF) of the streams will depend upon the jet device used, the pressure of the liquid supplied to the jet orifice, and the orifice-to-web spacing during treatment. The liquid initially forms a "solid" stream, i.e., an unbroken, homogeneous liquid stream. The initial energy flux, in foot-poundals/inch 2 second, is readily calculated by the formula:
EF i =77 PG/a where: P=the liquid pressure in p.s.i.g. (pounds per square inch gauge pressure), G=the volumetric flow of the stream in cu.ft./minute, and a=the initial cross-sectional area of the stream in square inches.
The value of G for use in the above formula can be obtained by measuring the flow rate of the stream. The initial cross-sectional area (a) which is inside the jet device, can be determined by measuring the actual orifice area and multiplying by the discharge coefficient (usually 0.64), or it can be calculated from measured flow rates. Since the area (a) corresponds to solid stream flow, the above formula gives the maximum value of energy flux which can be obtained at the pressure and flow rate used. The energy flux will usually decrease rapidly as the stream travels away from the orifice, even when using carefully shaped orifices. The stream diverges to an area (A) just prior to impact against the web and the kinetic energy of the stream is spread over this larger area. The cross-sectional area (A) can be estimated from photographs of the stream with the web removed, or can be measured with micrometer probes. The energy flux is then equal to the initial energy flux times the stream density ratio (a/A). Therefore, the formula for energy flux at the web being treated is:
EF w =77 PG/A ft.-poundals/in. 2 sec.
The value of (A) increases with the orifice-to-web spacing and, at a given treatment distance, the value depends upon the jet device and the liquid supply pressure used. A pressure of 200 p.s.i.g. can provide sufficient energy flux for several inches when using a highly efficient jet device, e.g. as in examples 1 to 10. With other jet devices, the energy flux of a stream may become too low in a relatively short distance even when using higher pressures, due to the stream breaking up and losing its columnar form. When this occurs there is a sudden increase in the value of (A) and the energy flux drops rapidly. Since the stream may become less stable when higher pressures are used, the energy flux at a given treatment distance may actually decrease when the jet orifice pressure is increased to provide a higher initial energy flux (PG/a).
By "essentially columnar" is meant that the streams have a total divergence angle of not greater than about 5°. Particularly, strong and surface-stable fabrics are obtained with high-pressure liquid streams having an angle of divergence of less than about 3°.
The amount of treatment must be sufficient and is measured by energy expended per pound fabric produced. The energy (E 1 ) expended during one passage under a manifold in the preparation of a given nonwoven fabric, in horsepower-hours per pound of fabric, may be calculated from the formula:
E 1 =0.125 (YPG/sb) where: Y=number of orifices per linear inch of manifold, P=pressure of liquid in the manifold in p.s.i.g., G=volumetric flow in cu.ft./min. per orifice, s=speed of passage of the web under the streams, in ft./min., and b=the weight of the fabric produced, in oz./yd. 2 . The total amount of energy expended in treating the web is the sum of the individual energy values for each pass under each manifold, if there is more than one.
It has been observed that the entanglement of the fibers is related to the products of this energy (E) of treatment and the impact force (I) (in pounds) of the water stream, where (I) is calculated by multiplying the cross-sectional area (A) of the stream in square inches by the pressure (P) on the orifice in p.s.i.g.
The process of the present invention may be used to produce entangled nonwoven fabrics from any type of loose fibrous web, batt, or sheet. The ease with which a given web can be entangled is dependent upon many factors, and process conditions may be chosen accordingly. Fiber mobility also has a bearing on the ease with which a web can be processed. Factors which influence fiber mobility include, for example, the density, modulus stiffness, surface-friction properties, denier, crimp and/or length of the fibers in the web. In general, fibers which are highly wettable, or have a high degree of crimp, or have a low modulus or low denier, can also be processed more readily.
Suitable fibrous material includes all manner of textile fibers and combinations of textile fibers and papermaking fibers such as wood pulp, cotton linters and the like. The textile fibers can be of any convenient length ranging from short staple (e.g., 0.25 inch) to continuous lengths. Deniers of from 1 to 3 are readily processed but smaller and larger deniers can be used. The fibers can be straight or crimped. Blends of various fibers can be used and the fibrous layer can contain layers of different composition.
Papermaking fibers can be present in the initial layer as a paper sheet or an intimate blend with the textile fibers. The fibrous material should contain at least about 20 percent of textile fibers to obtain the desired integrity of a nonwoven fabric.
Nonwoven fabrics having particularly high levels of drape and conformability may be obtained by using crimpable, shrinkable, spontaneously elongatable, or elastic fibers as one of the components of the fibrous sheet material and developing the latent properties of the fiber after formation of the nonwoven fabric.
TESTS FOR EVALUATING PHYSICAL PROPERTIES
The tensile properties are measured on an Instron tester at 70° F. and 65 percent relative humidity. Strip tensile strength, elongation and modulus are determined for a sample 1.0-inch wide, using a 2-inch gauge length and elongating at 50 percent per minute. The measured stresses in pounds and corresponding elongations are plotted to give a stress-strain curve. Strip tensile strength is the value at break divided by the fabric weight in oz./yd. 2 . The 5 percent secant modulus is defined by American Society for Testing and Materials Standards E6-61, Sec. 20 (1969, Part 27). It is determined by reading the stress at 5 percent elongation from the stress-strain curve, multiplying this by 20, and dividing by the fabric weight in oz./yd. 2 .
Tensile properties are determined in the two major directions of the products; the machine direction (MD), which is the direction of travel of the web during treatment, and the cross direction (XD), which is 90° to the machine direction. Each value is the average of five determinations.
Density is calculated from the weight of the fabric and its thickness.
Thickness is measured under a total pressure 0.22 lb./in. 2 with a 2-inch diameter disc on a thickness gauge.
FIBER-INTERLOCK TEST
The fiber-interlock value is the maximum force in grams per unit fabric weight needed to pull apart a given sample between two hooks.
Samples are cut 0.5 inch × 1.0 inch and weighed, and each sample is marked with two points 0.5 inch apart symmetrically along the midline of the fabric so that each point is 0.25 inch from the sides and end of the fabric.
The eye end of a hook (Carlisle-6 fish hook with the barb ground off or a hook of similar wire diameter and size) is mounted on the upper jaw or an Instron tester so that the hook hangs vertically from the jaw. This hook is inserted through one marked point on the fabric sample.
A second hook is inserted through the other marked point on the sample, and the eye end of the hook is clamped in the lower jaw of the Instron. The two hooks are now opposed but in line, and hold the sample at 0.5-inch interhook distances.
The "Instron" tester is set to elongate the sample at 0.5 inch per minute (100 percent elongation/minute) and the force in grams to pull the sample apart is recorded. The maximum load in grams divided by the fabric weight in grams per square meter is the single fiber interlock value. The average of 3 determinations in the machine direction and 3 in the cross direction (samples cut in directions at 90° to each other) is reported to two significant figures as the fiber interlock value.
ENTANGLEMENT FREQUENCY
Samples of the nonwoven fabrics are characterized according to the frequency of the fiber entanglement in nonbonded fabric, as determined from strip tensile breaking data using an "Instron" tester.
Entanglement frequency is a measure of the frequency of occurrence of entanglement sites along individual lengths of fiber in the nonwoven fabric. The higher the value of entanglement frequency the greater is the surface stability of the fabric, i.e., the resistance of the fabric to the development of pilling and fuzzing upon repeated laundering.
Entanglement frequency is calculated from strip tensile breaking data, using strips of the following sizes: Strip Strip "Instron" Gauge Elongation Width Symbol Width Length Rate (in.) (in.) (in./min.) ____________________________________________________________ _____________ _ w 1 0.3 1.5 5 w 2 1.9 1.5 5 ____________________________________________________________ _____________ _
In cutting the strips from fabrics having a repeating pattern of ridges or lines of high and low basis weight, integral numbers of repeating units are included in the strip width, always cutting through the low basis weight portion and attempting in each case to approximate the desired widths (w 1 , w 2 ) closely. Ten or more specimens are tested at w 1 , and five or more at w 2 using an "Instron" tester with standard rubber coated, flat jaw faces and the gauge lengths and elongation rates listed above. Average tensile breaking forces for each width (w 1 and w 2 ) are correspondingly reported as T 1 and T 2 . It is observed that: It is postulated that the above inequalities occur because there is a border zone of width D at the cut edges of the long gauge length specimens, which zone is ineffective in carrying stress.
In certain cases (D) may be nearly zero and even a small experimental error can result in the measured (D) being negative. Strips are cut in two directions: (a) in the machine direction, and (b) in the direction at 90° to the direction specified in (a). Entanglement frequency (f) per inch is defined as 1/D. If the measured (D) turns out to be zero or negative, it is proper to assume that the actual (D) is less than 0.01 inch and (f) is therefore greater than 100 per inch.
INTERNAL BOND VALUE TEST
It has been found that the following "internal bond" test is a measure of the extent of three-dimensional entanglement. It is believed that this test measures the ability of the fibers that penetrate the entangled fiber regions at substantial angles to the plane of the fabric to prevent delamination in the test.
A. The internal bond value of the nonwoven fabric is determined by a procedure described in Technical Association of the Pulp and Paper Industrial (TAPPI) "RC-308 Test for Interfiber Bond Using the Internal Bond Tester." Further information regarding this procedure, particularly about the equipment used, is disclosed by Blockman and Wikstrand, TAPPI, Mar. 1958, Volume 41, Number 3, pages 190A to 194A, "Interfiber Bond Strength of Paper." The faces of the steel anvils, striking bar, samples of nonwoven fabric and double-faced pressure-sensitive tape are each one inch square. The samples are mounted at 200 p.s.i. for one second. Five samples are tested in the machine direction of the fabric and five in the cross direction, and the average value is reported in foot-pounds.
Routine Control Method RC-308 specifies the use of "Scotch Brand type 400 double-faced pressure-sensitive tape" in the test. In case such a commercial produce is not available, its characteristics are as follows: Double-faced pressure-sensitive tape, 1-inch wide with combined thickness of adhesive layers of 0.0015±0.0005 inch (measured under about 1 p.s.i. pressure) and with an adhesion to steel within 35±5 ounces/inch (measured according to Federal Specification UU-T-91C of May 10, 1961).
It should be a routine practice to check the tape each day by running the test on two layers of tape between the bottom steel anvil and the aluminum angle pressed together at 200 p.s.i. These tests should give a value of at least 0.5 foot-pounds. If they do not, some tape is stripped off the roll and the tape calibration is repeated with fresh tape until proper values are obtained. It is obvious that, since the test is designed to measure internal bond values as high as 0.5, the adhesion of the tape to the anvil and angle must be at least 0.5 foot-pounds. This fact could be overlooked by an operator that might be accustomed to obtaining values below 0.5.
The tape-contacting surfaces of the anvil and the angle must be clean. Preferably they should be cleaned with a minimum of acetone and dried between each set of determinations.
Meaningful results may not be obtained by the above Method (A) on (1) netlike products having an open area of more than about 15 percent or (2) very thin fabrics having a fabric weight of less than 1.0 oz./yd. 2 due to adhesion of the two layers of tape to each other. For these products the following Method (B) should be used:
B. The sample is fastened to the lower fixed steel plate with the tape. This assembly is then pressed (sample face down) into a thin, flat bed of aluminum oxide (grade 400 "Lionite Floated Flour" made by General Abrasive Co., Inc., of Little Rock, Arkansas) at a pressure of 100 p.s.i. The assembly is removed from the bed and the bottom of the steel plate held firmly against the vertical shaft of a laboratory vibrator (providing an amplitude of 0.5 mm. at a frequency of 60 cycles per second) for 30 seconds. This treatment effectively removes the aluminum oxide from the fabric but not from any tape face exposed through openings in the fabric.
If the sample is vibrated face up, then it should be gently blown by mouth after the vibration treatment to remove any loose aluminum oxide from the sample, and aluminum oxide remaining on the steel surfaces of the anvil should be removed with a brush to avoid contaminating the apparatus.
The assembly is replaced in the mounting jig and fastened to the upper striking bar with tape at 200 p.s.i. and tested as in Method A.
Although the instrument has a dual range, all measurements in the application were made on the high range of from 0.100-0.500 ft.-lb.
The open area of a fabric can be estimated by measuring the size of the openings and counting for a given area.
It is observed that Method B gives substantially the same results as Method A on fabrics of low open area and weights greater than 1 oz./yd. 2 .
Preferred products of this invention have an internal bond value of at least 0.2 foot-pounds.
EXAMPLES 1-4
These examples illustrate a preferred process for preparing products of the invention from polyester textile fibers, using a final treatment with broken streams of water.
Webs containing a random array of fibers are made by air deposition of 1.5 denier polyester staple fibers of 1.5 inches in length except for example 4 where 0.75-inch fibers are used. The fiber lengths given are nominal average values for the starting fiber, but the actual fiber lengths are somewhat lower, e.g., when measured the 1.5 -inch polyester fiber has an average length of 1.2 inches.
The webs are placed on a plain woven metal screen of 80×80 mesh per inch (31 percent open area), and passed under a row of vertical jet streams of water at 20 y.p.m. (30 y.p.m. for example 1).
The water streams are produced by a row of 7 mil diameter orifices spaced 40/inch located 2 inches above the web and constructed similar to FIG. 3 of U.S. Pat. No. 3,403,862 to Dworjanyn.
a. Each web is given 1 pass under the streams at 200, 500 and 800 p.s.i.g., in order, plus optional treatments at 1400 p.s.i.g. as indicated below. (b) The products are then flipped on the screen and the above treatments are repeated for the web face which previously contacted the screen. The total treatment energy used in the process is given in table I.
The use of 1,400 p.s.i.g. with the above orifices and perforated plate filter located above the orifices affords an essentially columnar (i.e., less than 5° total divergence angle) stream of water which is broken at 2 inches from the orifice. The treatment entangles the fibers without producing a pattern of entanglement.
The properties of the products shown in table I, wherein pairs of values are for XD and MD, respectively. All products are strong, with moduli of at least 1.4, and have a uniform appearance, with no pattern or apertures and a smooth surface.
FINAL TREATMENT WITH BROKEN STREAMS Example No. 1 2 3 4 Web face a b a b a b a b Number of Passes 0 1 1 1 1 3 1 3 (1,400 p.s.i.g.)
EXAMPLES 5-8
The process described in examples 1-4 is used for treating webs of rayon instead of polyester fibers.
Each starting web consists of a random array of 1.5 denier rayon fibers averaging 1.56 inches in length. The webs are supported on plain-weave metal screens of 80×80 mesh per inch (31 percent open area), except for examples 6 and 7 where 150×150 mesh (2.6 mil wire diameter) screens are used; and passed under the water streams at 20 y.p.m. (30 y.p.m. for example 6). The web is treated on both faces with the streams at 200, 500 and 800 p.s.i.g., in order, except for the webs of examples 5 and 7 which are treated on one face only. The webs are also given a final treatment on at least one face with 1,400 p.s.i.g. streams as follows: Example No. 5 6 7 8 Web face a a b a a b Passes 1 0 1 3 1 1
The properties of the products are given in table II. All products are strong, with moduli of at least 1.4 and having a uniform appearance, with no pattern or apertures and a smooth surface.
EXAMPLE 9
This example shows the preparation of a product of the invention composed of polyester textile fibers and cellulosic papermaking fibers.
Webs containing random arrays of 1.5 inch polyester fiber of 1.5 d.p.f. (weighing 0.5 oz./yd. 2 ) are placed on an 150 × 150 mesh screen and covered with a layer of tissue-grade paper of wood-pulp fibers (weighing 0.6 oz./yd. 2 ) and passed under a row of vertical jet streams of water at 4 y.p.m.
The water streams are produced by a row of 5-mil diameter orifices constructed similarly to those of examples 1-4 , spaced 40/inch, located 3.25 inches above the paper/fiber layer.
The web is given one treatment at 200 p.s.i.g. with the vertical water jets, followed by four treatments at 200 p.s.i.g. in which a 30×30 mesh screen (49 percent open area) placed about 2.5 inches above the webs and below the orifices is oscillated at 200 cycles per minute with a 0.25-inch amplitude. The resulting fabric is turned over and given one treatment at 100 p.s.i.g. using the above oscillating screen. Properties of the product are given in table II.
The dried, nonforaminous product has no regular pattern of entanglement. Properties are given in table II.
EXAMPLE 10
This example shows the preparation of a product of the invention composed of polyester textile fibers and papermaking fibers. The starting web and paper of example 9 are used with the apparatus of example 9.
One layer of paper placed between two random webs of polyester fibers is placed on a 150-mesh screen and passed under a row of jet streams of water at 2 y.p.m. The composite web is given one treatment with the uninterrupted vertical jet streams at each of 100, 200 and 300 p.s.i.g. Then the web is given four treatments at 200 p.s.i.g. using oscillating jets and an oscillating top screen. The web is turned over and given one additional treatment at 200 p.s.i.g. with the oscillating jets and top screen.
The jets are mechanically oscillated, laterally to the direction of web movement at 50 oscillations per minute with an amplitude of 0.5 inch. A 30-mesh screen placed 0.75 inch below the orifices and 2.5 inches above the web is manually oscillated, laterally to the web movement, about 200 oscillations per minute with an amplitude of about 0.25 inch.
The dried, nonforaminous product has a substantially uniform appearance. Properties are given in table II.
COMPARISON EXAMPLE
This example illustrates the properties obtained in attempts to prepare similar products by needle punching.
The polyester fibers of examples 1-4, but cut to an average length of 2.0 inches, are processed into a card web on a sample roller card made by Davis and Furber Co. of North Andover, Massachusetts, for items a-i. Random webs of polyester fiber identical with those of examples 1-4 are plied to give the starting webs for items j and k.
The webs are processed on a small-scale needle loom("Hunter Fiber Locker" made by James Hunter Machine Co., North Adams, Massachusetts). The needle board (10 inches long × 12 inches wide) carries 600 needles and affords 300 needle penetrations per square inch for each pass through the machine. The web is advanced 0.19 inch per stroke. The stripper plate and the bed plate have a normal separation of 0.50 inch. A needle penetration of 12 mm. is used on all items. Felting needles used are a very small needle (15×18×46×3CB carrying 3 rows of barbs) and a small size needle for commercial operation (15×18×38×3CB with 2 rows of barbs) designated Needle Gauge 46 and 38, respectively, in table III. The top roll of the feed rolls is not used. All webs are processed for an even number of passes through the needle loom with alternate sides being needled on each successive pass.
Process conditions and properties of the products are are given in table III.
The products made with the finer (46 gauge) needles (items a-f) have a fluffy, feltlike appearance with some visible holes from the needles. The extremely low moduli with average values of less than 0.5 indicates the ease with which these felts can be deformed. The elongations at the break range from 109 to 220 percent and from 90 to 118 percent for XD and MD, respectively.
The use of the larger 38 gauge needle (items g- i) affords moduli that give a more useful fabric, and densities more comparable to fabrics, since the web is simultaneously stretched as these larger needles penetrate the web. The elongations range from 75 to 86 percent and from 61 to 84 percent, respectively, for the XD and MD. However, the larger needle causes randomly spaced visible holes of about 0.5 mm. diameter at a frequency of typically 80/inch 2 , and the stretching action imparts a very blotchy, nonuniform, streaked appearance.
Items j and k are included to illustrate the relatively poor physical properties--especially moduli--obtained from lightweight webs of random fibers. ##SPC1## ##SPC2##