Foam formed webs constructed from ultra-fine fibers

Abstract

Nonwoven materials are disclosed that contain cellulose pulp fibers combined with ultra-fine fibers. The ultra-fine fibers also have a relatively long length. By utilizing a foam forming process, the fibers can be homogeneously mixed together to produce webs having dramatically high strength properties. By using ultra-fine fibers, the number of fibers per area can be greatly increased for producing a fibrous network within the nonwoven structure.

Description

[0001] FOAM FORMED WEBS CONSTRUCTED FROM ULTRA-FINE FIBERS

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] The present application is related and has right of priority to U.S. Provisional Patent Application No. 63 / 594,090 filed on October 30, 2023, which is incorporated by reference in its entireties for all purposes.

[0004] BACKGROUND

[0005] Domestic and industrial wipers are often used to pick up and absorb both polar liquids and non-polar liquids. The wipers should be constructed to have a sufficient absorption capacity to hold a liquid within the wiper structure. In addition, the wipers should also possess good physical strength and abrasion resistance to withstand the tearing, stretching and abrading forces often applied during use.

[0006] Conventional wiping products have been made from woven and knitted fabrics. Such wipers have been used in all different types of industries, such as for industrial applications, food service applications, health and medical applications, and for general consumer use.

[0007] In the past, nonwoven wipers have also been constructed from pulp fibers alone or in combination with synthetic fibers. For example, in the past, spunbond webs made from continuous filaments have been hydroentangled with pulp fibers in order to produce a resilient wiping product. In many instances, these webs are for single use applications and then disposed. Although these wipers possess good levels of strength and absorbency, the wipers typically do not possess the same cleaning characteristics as woven and knitted fabrics, particularly when wiping up oil and grease.

[0008] In view of the above, a need currently exists for a disposable nonwoven wiper having increased strength characteristics while having a basis weight much lower than conventional textile rags. In one aspect, a need exists for a disposable wiping product that has a very high ratio of fibers to basis weight for not only increasing strength, but for also improving many other properties and characteristics of the product.

[0009] SUMMARY

[0010] In general, the present disclosure is directed to nonwoven webs containing ultra-fine fibers. In one aspect, the nonwoven web is formed through a foam forming process that is capable of not only processing the ultra-fine fibers but also capable of combining the ultra-fine fibers with other fibers, such as pulp fibers, for producing nonwoven webs that have an unexpectedly better balance of properties at lower basis weights. In the past, such nonwoven webs were not capable of being formed through conventional wetlaid papermaking processes. In one aspect, for instance, the present disclosure is directed to a nonwoven product comprising a nonwoven web containing ultra-fine fibers blended with cellulose pulp fibers. The ultrafine fibers can have an average length of greater than about 8 mm, such as greater than about 10 mm, such as greater than about 11 mm, and less than about 50 mm, such as less than about 20 mm. The ultra-fine fibers can have a fiber size of less than about 1 .8 denier, such as less than about 1 .4 denier, such as less than about 1 .2 denier, such as less than about 1 denier, such as less than about 0.8 denier, such as less than about 0.7 denier, such as less than about 0.6 denier, and greater than about 0.25 denier, such as greater than about 0.3 denier. The ultra-fine fibers can comprise synthetic polymer fibers or regenerated cellulose fibers. The web can have a basis weight of less than about 100 gsm, such as less than about 80 gsm, such as less than about 70 gsm, and greater than about 25 gsm, such as greater than about 40 gsm, such as greater than about 50 gsm. In one aspect, the nonwoven web can have a basis weight of from about 52 gsm to about 68 gsm.

[0011] In accordance with the present disclosure, the nonwoven web can contain the ultra-fine fibers in an amount of greater than about 2.8 million fibers / m2, such as greater than about 5 million fibers / m2, such as greater than about 10 million fibers / m2, such as greater than about 20 million fibers / m2, such as greater than about 30 million fibers / m2, such as greater than about 40 million fibers / m2, such as greater than about 50 million fibers / m2, such as greater than about 60 million fibers / m2. The ultra-fine fibers can also be contained in the nonwoven web in an amount greater than about 50,000 linear meters / m2, such as greater than about 100,000 linear meters / m2, such as greater than about 150,000 linear meters / m2, such as greater than about 200,000 linear meters / m2, such as greater than about 300,000 linear meters / m2, such as greater than about 400,000 linear meters / m2, such as greater than about 500,000 linear meters / m2, and generally less than about 1 .5 million linear meters / m2.

[0012] The nonwoven web can display a density of greater than about 0.07 g / cm3, such as greater than about 0.09 g / cm3, such as greater than about 0.1 g / cm3, such as greater than about 0.11 g / cm3, and less than about 0.2 g / cm3.

[0013] As described above, in one aspect, the nonwoven web can comprise a foam formed web. The nonwoven web can also be subjected to at least one hydroentangling step. For instance, in one aspect, the foam formed web can include a first surface and a second and opposite surface and wherein the first surface has been subjected to hydroentangling and the second surface has been subjected to hydroentangling. The foam formed web can comprise a single ply web that is nonlayered. The resulting web can contain residual amounts of a foaming agent. The foaming agent, for instance, can comprise lauryl sulfate, a glycoside, sodium dodecyl sulfate, ammonium lauryl sulfate, a fatty acid amine, an amide, an amine oxide, or a fatty acid quaternary compound. The ultra-fine fibers can be present in the nonwoven web generally in an amount from about 10% by weight to about 50% by weight depending upon the size of the fibers. The ultra-fine fibers can comprise, in one embodiment, polymer synthetic fibers, such as polyester fibers or polyolefin fibers. Alternatively, the ultra-fine fibers can comprise regenerated cellulose fibers, such as viscose fibers, lyocell fibers, or the like. In one aspect, the ultra-fine fibers can comprise crimped fibers. For instance, the fibers can contain greater than about 2 crimps per cm.

[0014] Nonwoven webs made according to the present disclosure can display an excellent balance of physical properties. For instance, the nonwoven web can display a tensile strength in a machine direction of greater than about 5,000 gf, such as greater than about 6,000 gf, such as greater than about 7,000 gf, such as greater than about 8,000 gf, such as greater than about 9,000 gf, and less than about 20,000 gf. The nonwoven web can display a tensile strength in a cross-direction of greater than about 2,500 gf, such as greater than about 3,000 gf, such as greater than about 3,500 gf, such as greater than about 4,000 gf, such as greater than about 4,500 gf, and less than about 10,000 gf. The nonwoven web can display a wet tensile strength in the machine direction of greater than about 2,500 gf, such as greater than about 3,500 gf, such as greater than about 4,000 gf, such as greater than about 4,500 gf, such as greater than about 5,000 gf, such as greater than about 5,500 gf, and less than about 12,000 gf. The nonwoven web can display a wet tensile strength in a cross-direction of greater than about 1 ,500 gf, such as greater than about 2,000 gf, such as greater than about 2,500 gf, such as greater than about 3,000 gf, such as greater than about 3,200 gf, and less than about 10,000 gf.

[0015] The nonwoven web can also display a trapezoidal tear strength in a machine direction of greater than about 1 ,000 gf, such as greater than about 1 ,500 gf, such as greater than about 2,000 gf, such as greater than about 2,200 gf, and less than about 6,000 gf. The nonwoven web can display a trapezoidal tear strength in a cross-direction of greater than about 500 gf, such as greater than about 1 ,000 gf, such as greater than about 1 ,500 gf, and less than about 5,000 gf.

[0016] Nonwoven webs made according to the present disclosure have numerous and diverse applications and uses. In one particular embodiment, the nonwoven web can be an industrial wiper The wiper can include a plurality of individual sheets stacked together or can comprise a spirally wound product. In one aspect, the nonwoven product can be pre-saturated with a cleaning solvent.

[0017] The present disclosure is also directed to a nonwoven web containing ultra-fine synthetic polymer fibers blended with cellulose pulp fibers. The ultra-fine synthetic fibers can have an average length of greater than about 8 mm and can have a fiber size of less than about 0.8 denier. The ultrafine synthetic polymer fibers can be present in the nonwoven web in an amount from about 10% by weight to about 50% by weight. In one aspect, the ultra-fine synthetic polymer fibers can comprise crimped fibers.

[0018] The present disclosure is also directed to a nonwoven product comprising a nonwoven web containing ultra-fine synthetic fibers blended with cellulose pulp fibers. The ultra-fine synthetic fibers can have an average length of greater than about 8 mm and can have a fiber size of less than about 0.8 denier. The nonwoven web can display a tensile strength in a machine direction of greater than about 7,000 gf, can display a tensile strength in a cross-direction of greater than about 3,500 gf, can display a wet tensile strength in a machine direction of greater than about 4,000 gf, can display a wet tensile strength in a cross-direction of greater than about 2,500 gf, can display a trapezoidal tear strength in a machine direction of greater than about 2,000 gf, can display a trapezoidal tear strength in a cross-direction of greater than about 1 ,500 gf, and can have a basis weight of from about 45 gsm to about 70 gsm.

[0019] Other features and aspects of the present disclosure are discussed in greater detail below.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A full and enabling disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

[0022] Figure 1 is a diagram of one embodiment of a process for producing base sheets in accordance with the present disclosure;

[0023] Figure 2 is a diagram of an enlarged portion of the process illustrated in Figure 1 ;

[0024] Figure 3 is a perspective view of a wiping product made in accordance with the present disclosure;

[0025] Figure 4 is a perspective view of another embodiment of a wiping product made in accordance with the present disclosure; and

[0026] Figure 5 is a diagram of bonded and unbonded fibers for purposes of explaining nonwoven materials made in accordance with the present disclosure.

[0027] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

[0028] DEFINITIONS

[0029] The term "machine direction" as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a nonwoven web.

[0030] The term "cross-machine direction" as used herein refers to the direction which is perpendicular to the machine direction defined above.

[0031] The term "cellulose pulp fibers" as used herein refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. “Pulp fibers” refers to delignified cellulose fibers and can include hardwood fibers, softwood fibers, and mixtures thereof.

[0032] The term "average fiber length" as used herein refers to an average length of fibers, fiber bundles and / or fiber-like materials determined by measurement utilizing microscopic techniques. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of fibers. The fibers are set up on a microscope slide prepared to suspend the fibers in water. A tinting dye is added to the suspended fibers to color cellulose-contain ing fibers so they may be distinguished or separated from synthetic fibers The slide is placed under a Fisher Stereomaster II Microscope-S19642 / S19643 Series. Measurements of 20 fibers in the sample are made at 20X linear magnification utilizing a 0-20 mils scale and an average length, minimum and maximum length, and a deviation or coefficient of variation are calculated. In some cases, the average fiber length will be calculated as a weighted average length of fibers (e.g . , fibers, fiber bundles, fiber-like materials) determined by equipment such as, for example, a Kajaani fiber analyzer Model No. FS-200, available from Kajaani Oy Electronics, Kajaani, Finland. According to a standard test procedure, a sample is treated with a macerating liquid to ensure that no fiber bundles or shives are present. Each sample is disintegrated into hot water and diluted to an approximately 0.001% suspension. Individual test samples are drawn in approximately 50 to 100 ml portions from the dilute suspension when tested using the standard Kajaani fiber analysis test procedure. The weighted average fiber length may be an arithmetic average, a length weighted average or a weight weighted average and may be expressed by the following equation: where k=maximum fiber length xrfiber length n(-number of fibers having length xi n=total number of fibers measured.

[0033] One characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not discriminate between different types of fibers. Thus, the average length represents an average based on lengths of all different types, if any, of fibers in the sample.

[0034] As used herein, the term "staple fibers" means discontinuous fibers made from synthetic polymers such as polypropylene, polyester, post-consumer recycle (FOR) fibers, polyester, nylon, and the like, or cellulose fibers such as cotton fibers, bast fibers, regenerated cellulose fibers (e.g. viscose, rayon, etc.), and the like. Staple fibers may be cut fibers or the like. Staple fibers can have crosssections that are round, bicomponent, multicomponent, shaped, hollow, or the like.

[0035] As used herein, the term “nonwoven web or material” refers to a web having a structure of individual fibers that are interlaid, but not in an identifiable manner as in a knitted or woven fabric. Nonwoven materials include, for example, carded webs, wet-laid webs, airlaid webs, foam-formed webs, and the like.

[0036] As used herein the term “caliper” is the representative thickness of a single sheet (caliper of sheet products comprising two or more plies is the thickness of a single sheet of sheet product comprising all plies) measured in accordance with TAPPI test method T402 using an EMVECO 200-A Microgage automated micrometer (EMVECO, Inc., Newberg, Oreg.). The micrometer has an anvil diameter of 2.22 inches (56.4 mm) and an anvil pressure of 132 grams per square inch (per 6.45 square centimeters) (2.0 kPa).

[0037] As used herein the term “sheet bulk” refers to the quotient of the caliper (generally having units of pm) divided by the bone dry basis weight (generally having units of gsm).

[0038] As used herein, “tensile testing” was done in accordance with TAPPI test method T-576 “Tensile properties of towel and tissue products (using constant rate of elongation)" wherein the testing is conducted on a tensile testing machine maintaining a constant rate of elongation and the width of each specimen tested is 3 inches. More specifically, samples for dry tensile strength testing were prepared by cutting a 3 ± 0.05 inch (76.2 ± 1 .3 mm) wide strip in either the machine direction (MD) or cross-machine direction (CD) orientation using a JDC Precision Sample Cutter (Thwing-Albert Instrument Company, Philadelphia, PA, Model No. JDC 3-10, Serial No. 37333) or equivalent. The instrument used for measuring tensile strengths was an MTS Systems Sintech 11 S, Serial No. 6233. The data acquisition software was an MTS TestWorks® for Windows Ver. 3.10 (MTS Systems Corp., Research Triangle Park, NC). The load cell was selected from either a 50 Newton or 100 Newton maximum, depending on the strength of the sample being tested, such that the majority of peak load values fall between 10 to 90 percent of the load cell's full scale value. The gauge length between jaws was 4 ± 0.04 inches (101 .6 ± 1 mm) for facial tissue and towels and 2 ± 0.02 inches (50.8 ± 0.5 mm) for bath tissue. The crosshead speed was 10 ± 0.4 inches / min (254 ± 1 mm / min), and the break sensitivity was set at 65 percent. The sample was placed in the jaws of the instrument, centered both vertically and horizontally. The test was then started and ended when the specimen broke. The peak load was recorded as either the "MD tensile strength" or the "CD tensile strength" of the specimen depending on direction of the sample being tested. Ten representative specimens were tested for each product or sheet and the arithmetic average of all individual specimen tests was recorded as the appropriate MD or CD tensile strength of the product or sheet in units of grams of feree per 3 inches of sample. The geometric mean tensile (GMT) strength was calculated and is expressed as grams-force per 3 inches of sample width. Tensile energy absorbed (TEA) and slope are also calculated by the tensile tester. TEA is reported in units of gn cm / cm2. Slope is recorded in units of kg. Both TEA and Slope are directionally dependent and thus MD and CD directions are measured independently. Geometric mean TEA and geometric mean slope are defined as the square root of the product of the representative MD and CD values for the given property.

[0039] As used herein, “wet tensile strength” measurements are conducted on a tensile testing machine maintaining a constant rate of elongation and the width of each specimen tested is one (1) inch. Generally products are tested in their product forms. The tensile tester, which is the same as described above, parameters are as follows:

[0040] Wet tensile strength measurements can be performed on pre-moistened wipes or can be performed on dry base sheets. When testing dry base sheets, prior to testing, samples are soaked in tap water at room temperature. In such instances, 5 dry sheets of a sample are weighed and combined with 220% of water based on the weight of the sheets. The water is added to the sheets so that the sheets are saturated. The water can be applied to each side of the dry sheets using a syringe. The saturated sheets are then placed in a ZYPLOK bag and stored for a week. After a week, the samples are removed, cut into 1 inch strips, and tested immediately.

[0041] The trapezoid or “trap” tear test is a tension test applicable to the nonwoven web. The entire width of the specimen is gripped between clamps, thus the test primarily measures the bonding or interlocking and strength of individual fibers directly in the tensile load, rather than the strength of the composite structure of the fabric as a whole. The test measures the fabric resistance to tear propagation under a constant rate of extension. A fabric cut on one edge is clamped along nonparallel sides of a trapezoidal shaped specimen and is pulled, causing a tear propagation in the specimen perpendicular to the load. The test can be conducted in either the MD or CD direction. In conducting the trap tear test, an outline of a trapezoid is drawn on a 3 by 6 inch (75 by 152 mm) specimen with the longer dimension in the direction being tested, and the specimen is cut in the shape of the trapezoid. The trapezoid has a 4 inch (102 mm) side and a 1 inch (25 mm) side which are parallel and which are separated by 3 inches (76 mm). A small preliminary cut of % inches (15 mm) is made in the middle of the shorter of the parallel sides The specimen is clamped in, for example, an Instron Model™ (a constant-rate-of-extension tester), available from the Instron Corporation, 2500 Washington St., Canton, Mass., or a Thwing-Albert Model INTELLECT II available from the Thwing-Albert Instrument Co., 10960 Dutton Rd., Phila., Pa. 19154, which have 3 inch (76 mm) long parallel clamps. The specimen is clamped along the non-parallel sides of the trapezoid so that the fabric on the longer side is loose and the fabric along the shorter side taut, and with the cut halfway between the clamps. A continuous load is applied on the specimen such that the tear propagates across the specimen width. It should be noted that the longer direction is the direction being tested even though the tear is perpendicular to the length of the specimen. The force required to completely tear the specimen is recorded in pounds with higher numbers indicating a greater resistance to tearing. The test method used conforms to ASTM Standard test D1117-14, except that the tearing load is calculated as the average of the first and highest peaks recorded rather than the lowest and highest peaks. Five specimens for each sample are typically tested. The data presented include first and high peak values.

[0042] As used herein, “resistance to linting" or “Gelbo Lint Value” is determined in accordance with INDA Standard Procedure 160.1 .RO (12) using the counting method C. This test determines the relative number of particles released from a nonwoven material when it is subjected to a flexing and twisting movement.

[0043] As used herein, the “Martindale Abrasion” test can measure the relative resistance of a sample to abrasion according to Worldwide Strategic Partners (“WSP") Standard Test No. 20.5 (08). A circular specimen of 165 mm±6.4 mm in diameter with an area of 18,258 sq mm is subjected to a requested number of cycles (10 or 60) with an abradant under a pressure of 9 kilopascals (kPa). The abradant is a 36 inch by 4 inch by 0.05 thick silicone rubber wheel reinforced with fiberglass having a rubber surface hardness 81 A Durometer, Shore A of 81 ±9. The specimen is examined for the presence of surface fuzzing (fiber lofting), pilling (small dumps of fibers), roping, delamination or holes and assigned a numerical rating of 1 , 2, 3, 4, or 5 based on comparison to a set of standard photographs similarly numbered, with "1” showing the greatest wear and "5” the least. The test is carried out with a Martindale Wear and Abrasion Tester such as Model No. 103 or 403 from James H. Heal & Company, Ltd. of West Yorkshire, England.

[0044] As used herein, the term “thermal point bonding” generally refers to a process performed, for example, by passing a material between a patterned roll (e.g ., calender roll) and another roll (e.g., anvil roll), which may or may not be patterned. One or both of the rolls are typically heated.

[0045] As used herein, the term “ultrasonic bonding” generally refers to a process performed, for example, by passing a material between a sonic horn and a patterned roll (e.g., anvil roll). For instance, ultrasonic bonding through the use of a stationary horn and a rotating patterned anvil roll is described in U.S. Patent Nos. 3,939,033 to Grgach, et al., 3,844,869 to Rust Jr., and 4,259,399 to Hill, which are incorporated herein in their entirety by reference thereto for all purposes. Moreover, ultrasonic bonding through the use of a rotary horn with a rotating patterned anvil roll is described in U.S. Patent Nos. 5,096,532 to Neuwirth, et al., 5,110,403 to Ehlert, and 5,817,199 to Brennecke, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Of course, any other ultrasonic bonding technique may also be used in the present disclosure.

[0046] As used herein, “vertical absorbent capacity” is a measure of the amount of water absorbed by a nonwoven product (single ply or multi-ply) or a sheet, expressed as water or oil per gram of fiber (dry weight). In particular, the vertical absorbent capacity is determined by cutting a sheet of the product to be tested (which may contain one or more plies) into a square measuring 100 millimeters by 100 millimeters (±1 mm.) The resulting test specimen is weighed to the nearest 0.01 gram and the value is recorded as the “dry weight.” The specimen is attached to a 3-point clamping device and hung from one corner in a 3-point clamping device such that the opposite corner is lower than the rest of the specimen, then the sample and the clamp are placed into a dish of water or oil and soaked in the water or oil for 3 minutes (±5 seconds). The water should be distilled or de-ionized water at a temperature of 23±3° C. At the end of the soaking time, the specimen and the clamp are removed from the water or oil. The clamping device should be such that the clamp area and pressure have minimal effect on the test result. Specifically, the clamp area should be only large enough to hold the sample and the pressure should also just be sufficient for holding the sample, while minimizing the amount of water removed from the sample during clamping. The sample specimen is allowed to drain for 3 minutes (±5 seconds). At the end of the draining time, the specimen is removed by holding a weighing dish under the specimen and releasing it from the clamping device. The wet specimen is then weighed to the nearest 0.01 gram and the value recorded as the “wet weight”. The vertical absorbent capacity in grams per gram=[(wet weight-dry weigh t) / d ry weight]. At least five (5) replicate measurements are made on representative samples from the same, roll or box of product to yield an average vertical absorbent capacity value. The same test can be also done horizontally.

[0047] As used herein, the “vertical wicking” test is used to measure the height of water that can be vertically wicked by a sample in a given period of time. A reservoir containing purified distilled / deionized water is provided. One end of a 25 mm x 203 mm (1 in x 8 in) specimen is clamped and the other end is placed in the fluid such that it extends 2.5 cm therein. An apparatus as shown in FIG. 7 of U.S. Patent Publication No. 2007 / 0010153 is used. A paperclip or other weight may be used to weigh the lower end of the specimen and prevent the specimen from curling and allow the lower end of the specimen to readily submerge into the water. Support blocks maintain the specimen at a fixed height. The degree of liquid migration in centimeters is measured at 15 second, 30 second, 45 second, and 60 second intervals. A ruler or other device may be used to determine the degree of liquid migration of the specimen. Tests are conducted in a laboratory atmosphere of 23 ± °C and 50 ± 5% RH. The vertical wicking value for a sample is given as the average of at least three specimens. The vertical wicking test may be performed on specimens taken along the machine direction or the cross-direction of the sample.

[0048] As used herein, the “static and dynamic coefficient of friction’’ testing may be performed in accordance with ASTM D 1894-08 using a high gloss smooth vinyl tile sliding surface. A sled, which has the test specimen attached thereto, may be pulled over a high gloss smooth vinyl tile surface. The test specimen and the vinyl tile surface are in surface-to-surface contact with each other. The coefficient of friction value is defined as the measure of the relative difficulty when the surface of the test specimen slid over the fixed vinyl tile surface. The “static” coefficient of friction is the highest instantaneous value obtained to begin movement between the surfaces and “dynamic” coefficient of friction is the average of the values obtained during the 60 seconds of the test (6 inch travel distance). The testing apparatus may be a LAB MASTER Slip and Friction Model 32-90 with a model number 32.90-06 test sled; both of which are available from Testing Machines, Inc. of Islanda, N.Y., 11722, U.S.A.

[0049] The sled used for the testing may have a weight of 200 grams. Testing occurs in a room having a temperature of between about 22°C. and about 24°C., and a relative humidity of about 50%. The test material is mounted to the platen (table) had a length of about 305 millimeters and a width of about 102 to 127 millimeters using a double-sided tape. The test specimen has a length of about 100 millimeters and a width of about 63 millimeters. The sled is lowered by the test equipment before testing and positioned lightly onto the test material when the test was started to prevent any unnatural bond from developing. The length of the sled and the length the plane-mounted are parallel. The moving platen is then put in motion at a velocity of 6 inches per minute. The gauge takes readings and continues to do so for about 60 seconds (6 inches of travel). The gauge measures and stored the "static” value for the highest instantaneous coefficient of friction value obtained to begin the movement between the surfaces within the first inch of pull. The “dynamic" value is obtained and stored as the average of the values obtained during the 60 seconds of the test (6 inch travel distance).

[0050] As used herein, the amount of fibers in linear meters / m2 and the number of fibers per m2 are calculated from the measured basis weight of the nonwoven web and the known weight percent of the ultra-fine fibers in the web. The number of fibers per square meter is calculated based on the above and based on the average weight of the specific fiber (ultra-fine fiber). Once the number of fibers per square meter is calculated, the amount of fibers in linear meters per square meter can be calculated based on the average fiber length (through multiplication).

[0051] DETAILED DESCRIPTION

[0052] It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure.

[0053] In the past, attempts have been made to combine pulp fibers, such as cellulose fibers, with longer, staple fibers. Such fiber mixtures, however, are very difficult to handle in a conventional wetlaid forming process because only relatively short, straight fibers are able to be transported in a water medium during formation of the web. Longer fibers have a tendency to clump and flock together when combined with a sufficient amount of water to produce the web. The present disclosure, however, uses a foam forming process in order to combine cellulose fibers with ultra-fine and relatively long synthetic fibers. Through the foam forming process, an integrated and entangled fiber matrix is created that produces nonwoven materials having an excellent balance of properties at relatively low basis weights.

[0054] More particularly, it was discovered that relatively long, ultra-fine fibers, when combined with cellulose fibers, can provide numerous benefits and advantages in producing nonwoven materials. In the past, ultra-fine fibers, such as microfibers, have been used to produce yarns for making woven fabrics that can then be used to produce garments. Their use in nonwoven materials, however, has been limited due to the difficulties encountered in handling and processing the fibers. When used in a foam forming process, however, the ultra-fine fibers can be combined with cellulose fibers for producing nonwoven materials that are homogeneous and uniform in properties.

[0055] It was discovered that incorporating ultra-fine fibers into nonwoven materials can result in a nonwoven web containing a greater amount of fibers at the same basis weight. When producing nonwoven webs containing synthetic staple fibers combined with cellulose pulp fibers, increasing the ratio of staple fibers to basis weight can be controlled in three different ways: 1) adding a greater proportion of staple fibers to the nonwoven material in relation to the cellulose pulp fibers; 2) cutting the staple fibers to shorter lengths; or 3) decreasing the size of the fibers at the same proportion of staple fibers to cellulose pulp fibers.

[0056] Incorporating synthetic staple fibers into nonwoven materials in combination with cellulose fibers can improve product characteristics. Staple fibers, however, are relatively more expensive and therefore minimizing the overall proportion of the staple fibers in the web is preferred. Thus, adding a greater proportion of staple fibers under (1) above can not only unnecessarily create added cost but also produces nonwoven materials that are less sustainable and can require greater amounts of time for biodegradation. Cutting the staple fibers to shorter lengths ((2) above) in order to increase the amount of fibers per basis weight is also not preferred. Shorter fibers, however, result in a decrease in bond points and a web with less strength and less integrity.

[0057] Thus, the present disclosure is directed to using finer or lower denier fibers which according to the present disclosure, can produce uniform webs that reach critical fiber mass at lower weights. Although unknown, it is believed that the ultra-fine fibers of the present disclosure produce a percolating fiber network within the nonwoven material. A fiber percolation network refers to the behavior of randomly distributed fibers within a matrix or medium. In a fiber percolation network, a random distribution of fibers is present within a given space and the concept of percolation refers to the formation of continuous paths or clusters of interconnected fibers. Although unknown, it is believed that nonwoven materials made according to the present disclosure containing ultra-fine fibers produce a percolation fiber network that results in extremely high strength and other physical property values due to reaching a fiber density at which the fibers start to form a connected network spanning the entire system. By using ultra-fine fibers, a percolation network can be formed without having to increase the basis weight of the material from conventional amounts. For example, FIG. 5 shows the differences between reaching a fiber critical mass that results in a fiber percolation network. As shown in FIG. 5, for instance, a fiber percolation network 500 is illustrated in which all of the fibers are interconnected at a plurality of bond points. The bottom diagram 600, however, shows where a threshold of critical mass or density of fibers is not reached resulting in clusters of fibers that are not connected.

[0058] Because the longer, ultra-fine fibers of the present disclosure can be present in a nonwoven web at greater fiber numbers and / or densities at lower basis weights, a percolating fiber network is believed to be produced that creates materials with extremely high strength values. For instance, nonwoven webs having a basis weight of less than 100 gsm, such as even less than about 70 gsm, can display a tensile strength in a machine direction of greater than about 5,000 gf, such as greater than about 6,000 gf, such as greater than about 7,000 gf, such as greater than about 8,000 gf, such as even greater than about 9,000 gf, and can display a tensile strength in a cross-direction of greater than about 2,500 gf, such as greater than about 3,000 gf, such as greater than about 3,500 gf, such as greater than about 4,000 gf, such as greater than about 4,500 gf.

[0059] The nonwoven web as described above can display a wet tensile strength in a machine direction of greater than about 2,500 gf, such as greater than about 3,500 gf, such as greater than about 4,000 gf, such as greater than about 4,500 gf, such as greater than about 5,000 gf, such as even greater than about 5,500 gf. The nonwoven web can display a wet tensile strength in a crossdirection of greater than about 1 ,500 gf, such as greater than about 2,000 gf, such as greater than about 2,500 gf, such as greater than about 3,000 gf, such as greater than about 3,200 gf.

[0060] In one aspect, the strength in the machine direction and the cross-direction can be relatively uniform. For instance, the tensile strength ratio of the machine direction to the cross-direction can be about 2.5 or less, such as less than about 2.3, such as less than about 2, and about 1 or greater.

[0061] The nonwoven web can also display excellent tear properties. For instance, the nonwoven web can display a trapezoidal tear strength in a machine direction of greater than about 1 ,000 gf, such as greater than about 1 ,500 gf, such as greater than about 2,000 gf, such as greater than about 2,200 gf. The nonwoven web can display a trapezoidal tear strength in a cross-direction of greater than about 500 gf, such as greater than about 1 ,000 gf, such as greater than about 1 ,500 gf.

[0062] As described above, the above properties can be obtained at relatively low basis weights. For instance, the basis weight of the nonwoven web can be less than about 100 gsm, such as less than about 90 gsm, such as less than about 80 gsm, such as less than about 70 gsm, and greater than about 30 gsm, such as greater than about 40 gsm, such as greater than about 45 gsm. In one aspect, the basis weight of the nonwoven material can be from about 40 gsm to about 70 gsm, such as from about 52 gsm to about 68 gsm.

[0063] In addition, by using ultra-fine, long fibers, the amount of synthetic fibers incorporated into the nonwoven material can be relatively low while still obtaining an interconnected fibrous network that produces dramatically enhanced strength properties. For instance, the amount of ultra-fine fibers contained in the nonwoven material can be less than about 50% by weight, such as less than about 45% by weight, such as less than about 40% by weight, such as less than about 35% by weight, such as less than about 30% by weight, such as less than about 25% by weight, and generally greater than about 10% by weight, such as greater than about 15% by weight. In one aspect, the nonwoven web can contain the ultra-fine fibers in an amount of from only about 15% by weight to about 25% by weight. The weight percentage or proportion of the ultra-fine fibers contained in the nonwoven web can remain relatively low because greater numbers of fiber or a greater fiber density is achieved by using the ultra-fine fibers. More particularly, the present inventors discovered that it is the number of fibers and the linear length of fibers contained in the nonwoven web per area that results in the improved properties, as opposed to examining the weight percentage of the fibers present in the web. For instance, nonwoven webs made in accordance with the present disclosure can contain the ultrafine fibers in an amount greater than about 2.8 million fibers / m2. For instance, the nonwoven web can contain greater than about 5 million fibers / m2, such as greater than about 8 million fibers / m2, such as greater than about 10 million fibers / m2, such as greater than about 12 million fibers / m2, such as greater than about 15 million fibers / m2, such as greater than about 17 million fibers / m2, such as greater than about 20 million fibers / m2, such as greater than about 25 million fibers / m2, such as greater than about 30 million fibers / m2, such as greater than about 35 million fibers / m2, such as greater than about 40 million fibers / m2, such as greater than about 45 million fibers / m2, such as greater than about 50 million fibers / m2, such as greater than about 55 million fibers / m2, such as greater than about 60 million fibers / m2, and generally less than about 300 million fibers / m2. The actual number of fibers per area can depend upon the size of the fibers, the length of the fibers, and the product being constructed.

[0064] As described above, the ultra-fine fibers can be combined with shorter cellulose pulp fibers. Suitable cellulose pulp fibers include, but are not limited to, nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and woody or pulp fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, and aspen. Pulp fibers can be prepared in high-yield or low-yield forms and can be pulped in any known method, including kraft, sulfite, high-yield pulping methods and other known pulping methods. Fibers prepared from organosolv pulping methods can also be used, including the fibers and methods disclosed in U.S. Pat. No. 4,793,898, U.S. Pat. No. 4,594,130, U.S. Pat. No. 3,585,104. Useful fibers can also be produced by anthraquinone pulping, exemplified by U.S. Pat. No. 5,595,628.

[0065] Chemically treated natural cellulosic fibers can be used such as mercerized pulps, chemically stiffened or crosslinked fibers, or sulfonated fibers. For good mechanical properties, it can be desirable that the fibers be relatively undamaged and largely unrefined or only lightly refined. Suitable cellulose pulp fibers can also include recycled fibers, virgin fibers, or mixes thereof. In certain embodiments capable of high bulk and good compressive properties, the fibers can have a Canadian Standard Freeness of at least 200, more specifically at least 300, more specifically still at least 400, and most specifically at least 500.

[0066] Other cellulose fibers that can be used in the present disclosure include high yield fibers. High yield pulp fibers are those papermaking fibers produced by pulping processes providing a yield of about 65% or greater, more specifically about 75% or greater, and still more specifically about 75% to about 95%. Yield is the resulting amount of processed fibers expressed as a percentage of the initial wood mass. Such pulping processes include bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP), pressure / pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high yield sulfite pulps, and high yield Kraft pulps, all of which leave the resulting fibers with high levels of lignin. High yield fibers are well known for their stiffness in both dry and wet states relative to typical chemically pulped fibers.

[0067] The cellulose pulp fibers can be present in the nonwoven web generally in an amount from about 50% by weight to about 95% by weight including all increments of 1% by weight therebetween. For instance, cellulose pulp fibers can be present in the nonwoven web in an amount greater than about 70% by weight, such as in an amount greater than about 75% by weight, such as in an amount greater than about 77% by weight, and in an amount less than about 90% by weight, such as in an amount less than about 85% by weight, such as in an amount less than about 83% by weight.

[0068] The cellulose pulp fibers are combined with ultra-fine fibers in accordance with the present disclosure. In one aspect, the ultra-fine fibers comprise synthetic polymer fibers. Alternatively, the ultra-fine fibers comprise synthetic cellulose fibers, such as regenerated cellulose fibers. The ultra-fine fibers can be staple fibers that are straight or crimped.

[0069] The size of the ultra-fine fibers can vary depending upon the particular application. The ultrafine fibers have a size of about 1 .8 denier or less. For instance, the ultra-fine fibers can have a size of less than about 1 .6 denier, such as less than about 1 .4 denier, such as less than about 1 .2 denier, such as less than about 1 denier, such as less than about 0.9 denier, such as less than about 0.8 denier, such as less than about 0.7 denier, such as less than about 0.6 denier. The ultra-fine fibers can have a size of greater than about 0.09 denier, such as greater than about 0.2 denier, such as greater than about 0 3 denier. It was discovered that decreasing the size of the fiber can also allow for a decrease in the weight percentage of fibers incorporated into the nonwoven web while still retaining a desired level of number of fibers per area or linear length of fibers per area.

[0070] The ultra-fine fibers have an average fiber length of greater than about 6 mm, such as greater than about 8 mm, such as greater than about 10 mm. The average fiber length can be less than about 100 mm, such as less than about 80 mm, such as less than about 60 mm, such as less than about 40 mm, such as less than about 25 mm, such as less than about 20 mm, such as less than about 15 mm.

[0071] As described above, the ultra-fine fibers can be polymer synthetic fibers, regenerated cellulose fibers, or mixtures thereof. Synthetic polymer fibers include, for instance, polyester fibers, such as fibers containing polyethylene terephthalate. Other synthetic polymer fibers include polyolefin fibers, such as polypropylene fibers, polyethylene fibers, and copolymers thereof. The synthetic polymer fibers can comprise monofilament fibers or bi-component fibers.

[0072] Regenerated cellulose fibers can include man-made filaments obtained by extruding or otherwise treating regenerated or modified cellulosic materials from woody or non-woody plants. For example, the regenerated cellulose fibers may include lyocell fibers, viscose fibers, rayon fibers, and the like. The regenerated cellulose fibers can be produced by dissolving cellulose in a suitable solvent and then extruding the solution through a suitable fiber-making device, such as a spinneret, to produce filaments that then can be cut to a desired length.

[0073] As described above, in one aspect, the ultra-fine fibers can comprise crimped fibers. Crimped fibers exhibit a waviness in which the axis of a fiber departs from a straight line and follows a simple, complex, or irregular wavy path. In its simplest form, a crimp is uniplanar and regular, e.g., it resembles a sine wave, but is frequently much more complicated and irregular. An example of a three-dimensional crimp is a helical crimp. The crimp can be expressed numerically as the number of crimps per unit length or as the difference between the distances between two points on the fiber when it is relaxed and when it is straightened under suitable tension.

[0074] Synthetic fibers can be curled or crimped using various different techniques. In one embodiment, for instance, the fiber can be a monocomponent fiber formed from a polymer or mixture of polymers that cause the fiber to curl or crimp when heat treated. In other embodiments, however, the synthetic fibers can be curled or crimped using chemical means or mechanical means. The three- dimensional synthetic fibers can include fibers that are curled in two dimensions and / or helically- shaped fibers.

[0075] In one embodiment, the crimped fibers may comprise multi-component fibers, such as bicomponent fibers. The bi-component fibers can contain dissimilar polymers in a side-by-side configuration or in an island-in-the-sea configuration. When heat treated or subjected to mechanical means, the presence of the two different polymers can cause the fibers to crimp or curl. The fibers, for instance, can be heat treated by traversal under a hot air knife or hot air diffuser. Crimping can result due to differential cooling of the polymer components of the fibers. After the fibers are crimped or curled, the fibers can optionally be subjected to a further heat treating step in order to lock in the three- dimensional conformation. The synthetic fibers can be made from all different types of polymers including polyolefin polymers such as polyethylene and / or polypropylene, polyester polymers, polyamide polymers, and the like. In one embodiment, the synthetic fibers are bi-component fibers made from a polyethylene and a polypropylene. In one embodiment, the polyethylene may have greater crystallinity which causes the polyethylene chains to recrystallize upon cooling and results in the polyethylene polymer shrinking and inducing crimp or curl into the fiber.

[0076] Other multi-component fibers that may be used in accordance with the present disclosure include bi-component fibers having a sheath-core configuration in which a polyethylene polymer is used to form the sheath while the core is made from a polyester polymer, such as a polyethylene terephthalate polymer. In another aspect, the bi-component fibers can include a first polyester polymer to form the sheath while the core is made from a second polyester polymer. Both polyester polymers can comprise polyethylene terephthalate polymers. Many of the above described bi-component fibers also can be used as binder fibers if desired. When subjected to a certain amount of thermal energy, for instance, the sheath polymer on one fiber can bond to the sheath polymer on an adjacent fiber.

[0077] In still another embodiment, the crimped fiber may comprise a bi-component fiber containing a first polymer composition separated from a second polymer composition. The first polymer composition may contain a crimp enhancement additive that causes the fiber to crimp. The crimp enhancement additive, for instance, can comprise a polymer that has a rapid crystallization rate. For example, in one embodiment, the crimp enhancement additive can comprise a polypropylene homopolymer.

[0078] Synthetic cellulose fibers, such as regenerated cellulose fibers, can be crimped using any suitable mechanical or chemical method. In one aspect, for instance, the regenerated cellulose fibers can be crimped with the aid of dry steam.

[0079] Crimped fibers in accordance with the present disclosure can generally contain greater than

[0080] 1.5 crimps per cm, such as from about 2 crimps per cm to about 15 crimps per cm. For instance, the fibers can contain greater than about 2 crimps per cm, such as greater than about 2.2 crimps per cm, such as greater than about 2.7 crimps per cm, such as greater than about 3 crimps per cm, such as greater than about 3.2 crimps per cm, such as greater than about 3.5 crimps per cm, such as greater than about 3.8 crimps per cm, such as greater than about 4 crimps per cm, such as greater than about 4.2 crimps per cm, such as greater than about 4.5 crimps per cm, such as greater than about 4.8 crimps per cm, such as greater than about 5 crimps per cm, such as greater than about 5.2 crimps per cm, such as greater than about 5.5 crimps per cm, such as greater than about 5.7 crimps per cm, such as greater than about 6 crimps per cm. In other embodiments, the crimp fibers can contain greater than about 6.5 crimps per cm, such as greater than about 7 crimps per cm, such as greater than about

[0081] 7.5 crimps per cm, such as greater than about 8 crimps per cm, such as greater than about 10 crimps per cm, such as greater than about 12 crimps per cm, and generally less than about 20 crimps per cm, such as less than about 15 crimps per cm.

[0082] As described above, the nonwoven webs of the present disclosure can be made through a foam forming process. It was discovered that a foam forming process, for instance, can successfully process the ultra-fine fibers, even if the fibers have a relatively long length and are crimped. Optionally, the nonwoven web can also be subjected to one or more bonding steps, such as one or more hydroentangling steps and / or a thermal bonding step during formation.

[0083] There are many advantages and benefits to a foam forming process. During a foam forming process, water is replaced with foam as the carrier for the fibers that form the web. The foam, which represents a large quantity of air, is blended with the cellulose and / or ultra-fine fibers. Since less water is used to form the web, less energy is required in order to dry the web. In addition, foam forming processes are more amenable to producing nonwoven materials containing different types of fibers, especially longer and / or crimped fibers. In addition, surface topography can be incorporated into the nonwoven material in which raised elements have a greater basis weight than the surrounding area of the web. In addition, foam forming processes can create unique fiber orientation. For example, when producing nonwoven materials from a combination of shorter fibers (such as pulp fibers) and longer fibers (such as synthetic ultra-fine fibers), the shorter fibers tend to accumulate in the raised elements while the longer fibers can have a greater density along the base surface. This structure produces a nonwoven material having greater fiber density and absorbency in the raised elements while having significant strength in between the raised elements.

[0084] In one particular embodiment, as shown in FIGS. 1 and 2, for exemplary purposes only, the nonwoven material of the present disclosure can be produced using a foam forming process and optionally in combination with a hydroentangling step. The hydroentangling step, for instance, can occur on a patterned forming surface that creates topography on the nonwoven material. Not shown, the nonwoven material can also be subjected to a thermal bonding process, such as a thermal point bonding process in addition to or instead of hydroentangling the material.

[0085] Initially, a fiber furnish is selected for producing the nonwoven material. As described above, the fiber furnish can contain cellulose pulp fibers combined with ultra-fine fibers. During foam forming, the fiber furnish is combined with a foam created by blending water with a foaming agent.

[0086] The foaming agent, for instance, may comprise any suitable surfactant. In one embodiment, for instance, the foaming agent may comprise sodium lauryl sulfate, which is also known as sodium laureth sulfate or sodium lauryl ether sulfate. In one embodiment, the foaming agent is a nonionic surfactant which may comprise an alkyl polyglycoside. The foaming agent, for instance, can be a C8 alkyl polyglycoside, a C10 alkyl polyglycoside, or a mixture of C8 and C10 alkyl polyglycosides.

[0087] Other foaming agents include sodium dodecyl sulfate or ammonium lauryl sulfate. In other embodiments, the foaming agent may comprise any suitable cationic and / or amphoteric surfactant. For instance, other foaming agents include fatty acid amines, amides, amine oxides, fatty acid quaternary compounds, and the like.

[0088] The foaming agent is combined with water generally in an amount greater than about 0.1 % by weight, such as in an amount greater than about 1 % by weight, such as in an amount greater than about 2% by weight, such as in an amount greater than about 3% by weight. One or more foaming agents are generally present in an amount less than about 50% by weight, such as in an amount less than about 10% by weight, such as in an amount less than about 8% by weight, such as in an amount less than about 4% by weight.

[0089] Once the foaming agent and water are combined, the mixture is blended or otherwise subjected to forces capable of forming a foam. A foam generally refers to a porous matrix, which is an aggregate of hollow cells or bubbles which may be interconnected to form channels or capillaries.

[0090] The foam density can vary depending upon the particular application and various factors including the fiber furnish used. In one embodiment, for instance, the foam density of the foam can be greater than about 200 g / L, such as greater than about 250 g / L, such as greater than about 300 g / L. The foam density is generally less than about 600 g / L, such as less than about 500 g / L, such as less than about 400 g / L, such as less than about 350 g / L. In one embodiment, for instance, a lower density foam is used having a foam density of generally less than about 350 g / L, such as less than about 340 g / L, such as less than about 330 g / L. The foam will generally have an air content of greater than about 30%, such as greater than about 40%, such as greater than about 50%, such as greater than about 60%. The air content is generally less than about 80% by volume, such as less than about 70% by volume, such as less than about 65% by volume.

[0091] In order to form the nonwoven web, the foam is combined with the selected fiber furnish in conjunction with any auxiliary agents. The foamed suspension of fibers is then pumped to a tank and from the tank is fed to a headbox. FIGS. 1 and 2, for instance, show one embodiment of a process in accordance with the present disclosure for forming the web. As shown particularly in FIG. 2, the foamed fiber suspension can be fed to a tank 312 and then fed to the headbox 310. From the headbox 310, the foamed fiber suspension is issued onto an endless traveling forming fabric 326 supported and driven by rolls 328 in order to form a web 210. As shown in FIG. 2, a forming board 314 may be positioned below the web 210 adjacent to the headbox 310. Once formed on the forming fabric 326, the foam formed web can have a consistency of less than about 50%, such as less than about 20%, such as less than about 10%, such as less than about 5%. In fact, the forming consistency can be less than about 2%, such as less than about 1 .8%, such as less than about 1 .5%. The forming consistency is generally greater than about 0.5%, such as greater than about 0.8%. The forming consistency indicates the ability to produce webs according to the present disclosure while minimizing the amount of water needed during formation.

[0092] Once the wet web is formed on the forming fabric 326, the web is conveyed downstream and dewatered. For instance, the process can optionally include a plurality of vacuum devices 316, such as vacuum boxes and vacuum rolls. The vacuum boxes assist in removing moisture from the newly formed web 210.

[0093] As shown in FIG. 2, the forming fabric 326 may also be placed in communication with a steambox 318 positioned above a pair of vacuum rolls 320. The steambox 318, for instance, can increase dryness and reduce cross-directional moisture variance. The applied steam from the steambox 318 heats the moisture in the wet web 210 causing the water in the web to drain more readily, especially in conjunction with the vacuum rolls 320. From the forming fabric 326, the newly formed web 210, in the embodiment shown in FIG. 1 , is conveyed downstream, optionally subjected to hydroentangling, and dried on a through-air dryer.

[0094] After the foam formed web has been produced, the web is optionally subjected to one or more hydroentangling steps. In the embodiment illustrated in FIG. 2, for instance, the web 210 is subjected to two different hydroentangling steps. In particular, in FIG. 2, the web 210 is hydroentangled on a first surface during a first hydroentangling step and then hydroentangled on a second and opposite surface during a second hydroentangling step. As shown in FIG. 2, for example, the process can include a first hydroentangling device 330 and a second hydroentangling device 332. The hydroentangling that occurs at each hydroentangling station may be accomplished utilizing conventional hydroentangling equipment. The hydroentangling of the foam formed web may be carried out with any appropriate working fluid such as, for example, water. The working fluid flows through a manifold which evenly distributes the fluid through a series of individual holes or orifices. Exemplary holes or orifices, for example, can have a diameter of from about 0.003 inches to about 0.015 inches. For example, the manifold may include a strip of orifices having a diameter of 0.007 inches. The manifold may contain about 20 to about 40 holes per inch and can include 1 to 3 rows of holes. Many other manifold configurations and combinations may be used. In the embodiment illustrated in FIG. 2, for instance, the hydroentangling device 330 includes a plurality of injectors 334, while the hydroentangling device 332 includes a plurality of injectors 336. The injectors 334 and 336 can be part of the manifold and can be in communication with a working fluid supply.

[0095] During the hydroentangling process, the working fluid can pass through the orifices at pressures ranging from about 200 psig to about 3,500 psig. At the upper ranges of the described pressures, it is contemplative that the web may be processed at speeds of from about 500 ft / min to about 2000 ft / min. The fluid impacts the material or web which can be supported on a foraminous surface or wire or may be supported on a porous drum surface. In the embodiment illustrated in FIG. 2, for instance, hydroentangling occurs on a first drum 338 and a second drum 340.

[0096] The web 210 can be placed directly onto the surface of the drum 338 and on the surface of the drum 340 during hydroentangling. Each drum can include a plurality of openings or vacuum passages for withdrawing excess water. These openings or vacuum passages can also create a pattern into the web 210 during the hydroentangling process. For example, a pattern can be formed into one surface of the web at the first hydroentangling station and a pattern can be formed into the second and opposite surface of the web at the second hydroentangling station.

[0097] In addition to forming a desired topography and improving the cleaning properties of the nonwoven material 210, the one or more hydroentangling stations can also significantly improve various physical properties of the web 210, such as the integrity of the web. For example, the columnar jets of working fluid which directly impact the surfaces of the web serve to entangle and intertwine the fibers contained in the web. The hydroentangling processes ultimately form a coherent entangled matrix. The hydroentangling steps also further serve to create a substantially homogeneous fiber mixture within the web. The resulting hydroentangled web, for instance, is “nonlayered" and contains no distinguishable separate fibrous layers over the thickness of the web.

[0098] Once the foam formed web 210 is hydroentangled one or more times, the web can be dried using a non-compressive drying operation. For example, as shown in FIG. 1, the foam formed web can be dried using a through-air dryer.

[0099] Referring to FIG. 1, the foam formed and hydraulically entangled web 210 is transferred from the drum 340 to a throughdrying fabric 344 with the aid of a vacuum transfer roll 346 or a vacuum transfer shoe. If desired, the throughdrying fabric can be run at a slower speed than the web 210 to further enhance stretch. Transfer can be carried out with vacuum assistance to ensure deformation of the sheet to conform to the throughdrying fabric, thus yielding desired bulk and appearance if desired.

[0100] In the embodiment illustrated in FIG. 1, the foam formed web 210 is transferred to a throughdrying fabric 344. Alternatively, the foam formed web can be transferred to a metal, porous sleeve that forms the circumference of the throughdryer 348. The use of a metal sleeve instead of a fabric may provide various advantages. For instance, a porous metal sleeve may further create porosity for increasing the liquid absorbent properties of the web.

[0101] Alternatively, the foam formed web 210 can be conveyed on the throughdrying fabric 344 over the circumference of the throughdryer 348.

[0102] The level of vacuum used for the web transfers can be from about 3 to about 15 inches of mercury (75 to about 380 millimeters of mercury), preferably about 5 inches (125 millimeters) of mercury. The vacuum shoe or roll (negative pressure) can be supplemented or replaced by the use of positive pressure from the opposite side of the web to blow the web onto the next fabric in addition to or as a replacement for sucking it onto the next fabric with vacuum.

[0103] The web is finally dried to a consistency of about 94 percent or greater by the throughdryer 348 and thereafter transferred to a carrier fabric 350. The dried basesheet 352 is transported to the reel 354 using carrier fabric 350 and an optional carrier fabric 356. An optional pressurized turning roll 358 can be used to facilitate transfer of the web from carrier fabric 350 to fabric 356. Suitable carrier fabrics for this purpose are Albany International 84M or 94M and Asten 959 or 937, all of which are relatively smooth fabrics having a fine pattern.

[0104] Instead of or in addition to hydroentangling the nonwoven material, the nonwoven material can be thermally bonded. Thermal bonding can be accomplished using heat and pressure or through applying ultrasonic energy.

[0105] In one aspect the nonwoven material can be subjected to thermal point bonding. As an example, thermal point bonding often involves passing a nonwoven material containing fibers to be bonded through a nip between a pair of heated bonding calender rolls. One of the bonding rolls is usually, though not always, patterned in some way so that the entire material is not bonded across its entire surface, and the second or anvil roll is usually a smooth surface. As a result, various patterns for calender rolls have been developed for functional as well as aesthetic reasons. One example of a pattern has points and is the Hansen Pennings or "H&P" pattern with about a 30% bond area with about- 200 bonds / square inch as taught in U.S. Patent 3,855,046 to Hansen and Pennings. The resulting pattern has a bonded area of about 29.5%. Another typical point bonding pattern is the expanded Hansen Pennings or "EHP" bond pattern which produces a 15% bond area. Yet another common pattern is the C-Star pattern which has a bond area of about 16.9%. The C-Star pattern has a cross-directional bar or "corduroy” design interrupted by shooting stars. Other common patterns include a diamond pattern with repeating and slightly offset diamonds with about a 16% bond area and a wire weave pattern, having generally alternating perpendicular segments, with about a 19% bond area. Typically, the percent bonding area varies from around 10% to around 30% of the area of the nonwoven material.

[0106] The process of the present disclosure can produce webs with good bulk characteristics. The bulk, for instance, can generally be greater than about 3 cc / g, such as greater than about 5 cc / g, such as greater than about 8 cc / g, such as greater than about 10 cc / g, such as greater than about 12 cc / g, and generally less than about 20 cc / g, such as less than about 15 cc / g. The nonwoven web can also display an enhanced caliper per basis weight of greater than about 0.009 mm / gsm, such as greater than about 0.010 mm / gsm, such as greater than about 0.011 mm / gsm. For example, the caliper of the base sheet can be greater than about 0.4 mm, such as greater than about 0.5 mm, such as greater than about 0.6 mm, and less than about 3 mm at a basis weight of from about 55 gsm to about 70 gsm.

[0107] In the embodiment illustrated in FIGS. 2 and 3, the foam formed web can be hydroentangled on a patterned forming surface in order to form a pattern of raised elements. In other embodiments, however, a suction force positioned below the forming surface can be used to form the raised elements. These processes produce raised elements where the raised elements have an increased basis weight in comparison to the base surface of the web. Texture can also be imparted to a web through embossing. When a web is embossed, however, the basis weight of the web remains uniform and does not create raised elements with increased basis weight.

[0108] Nonwoven webs made according to the present disclosure can generally have a smooth surface or can include a pattern of raised elements based on the hydroentangling conditions.

[0109] Nonwoven materials made according to the present disclosure can generally have a density of greater than about 0.08 g / cm3when tested at a pressure of 0.05 psi. The density of the nonwoven web, for instance, can be greater than about 0.1 g / cm3and less than about 2 g / cm3, such as less than about 1 .8 g / cm3, such as less than about 0.14 g / cm3.

[0110] The basis weight of nonwoven materials made in accordance with the present disclosure can be anywhere from about 20 gsm to about 200 gsm, including all increments of 1 gsm therebetween. In one aspect, the basis weight can be less than about 100 gsm, such as less than about 90 gsm, such as less than about 80 gsm, such as less than about 70 gsm, such as less than about 68 gsm, such as less than about 65 gsm. The basis weight is generally greater than about 40 gsm, such as greater than about 50 gsm, such as greater than about 52 gsm, such as greater than about 55 gsm, such as greater than about 58 gsm.

[0111] As described above, nonwoven webs made according to the present disclosure generally contain cellulose pulp fibers combined with ultra-fine fibers. In one aspect, the cellulose pulp fibers and the ultra-fine fibers comprise substantially all of the fibers contained in the nonwoven web. For instance, the cellulose pulp fibers and the ultra-fine fibers can account for greater than about 90% by weight, such as greater than about 95% by weight, such as greater than about 98% by weight of the fibers contained in the nonwoven web. In this regard, the nonwoven web can be constructed without containing any other synthetic polymer staple fibers, such as binder fibers and the like.

[0112] The nonwoven materials made according to the present disclosure can be used in numerous different products and applications. In one aspect, the nonwoven web can be used as a wiper in an as-is state. For instance, referring to FIG. 3, a spirally wound product 10 is shown in accordance with the present disclosure. The spirally wound product 10 is made up of individual sheets separated by perforation lines 12.

[0113] Alternatively, the nonwoven material of the present disclosure can be cut into individual sheets and sold in a stack. For instance, as shown in FIG. 4, a stack 20 of individual sheets is illustrated. In one embodiment, the individual sheets can be interfolded as shown.

[0114] In other embodiments, the nonwoven material of the present disclosure can be incorporated into a product and used as a layer within the product. For instance, the nonwoven webs can be incorporated into personal care products, such as absorbent articles including diapers, pullups, incontinence products, feminine care products, and the like.

[0115] The present disclosure may be better understood with reference to the following example.

[0116] Example

[0117] The following example demonstrates some of the advantages and benefits of the present disclosure.

[0118] Foam formed base sheets were produced according to the present disclosure containing cellulose pulp fibers in combination with ultra-fine fibers. The cellulose pulp fibers included Southern softwood kraft fibers. Two different nonwoven materials were made in accordance with the present disclosure. The first nonwoven material contained ultra-fine fibers having a size of 0.5 denier (Sample No. 1). The second nonwoven material contained ultra-fine fibers having a size of 1 .5 denier (Sample No. 2). The ultra-fine fibers each comprised polyester fibers having an average length of 12 mm. The nonwoven materials each contained the cellulose pulp fibers in an amount of 80% by weight and the ultra-fine fibers in an amount of 20% by weight. Each nonwoven material had a basis weight of 60 gsm.

[0119] The nonwoven materials were made using a foam forming process including a hydroentangling step similar to the process illustrated in FIGS. 1 and 2.

[0120] The nonwoven materials were subjected to various different tests and the following results were obtained:

[0121] Table No. 1

[0122] Table No. 2

[0123] As shown above, the nonwoven materials displayed unexpectedly high strength and durability properties when only containing 20% by weight of the ultra-fine fibers. These dramatically improved strength properties were demonstrated in both the wet and dry states. The samples also displayed excellent tear properties while producing little to no lint.

[0124] Sample No. 1 containing the 0.5 denier fibers contained greater than about 30 million ultrafine fibers / m2, such as greater than about 35 million ultra-fine fibers / m2. Sample No. 1 also contained greater than about 300,000 linear meters of ultra-fine fibers / m2. Sample No. 2 contained greater than about 3 million ultra-fine fibers / m2and contained greater than about 60,000 linear meters of ultra-fine fibers / m2.

[0125] The ability of the nonwoven materials to absorb liquids was also tested and the following results were obtained:

[0126] Table No. 3

[0127] It is believed that by lowering the fiber to basis weight ratio, greater void space is created within the structure which accounts for the extremely high wicking rates above and absorbing capacity.

[0128] The nonwoven webs were also tested for friction properties and the following results were obtained:

[0129] Table No. 4

[0130] These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention so further described in such appended claims.

Claims

What Is Claimed:1 . A nonwoven product comprising: a nonwoven web containing ultra-fine fibers blended with cellulose pulp fibers, the ultra-fine fibers having an average length of greater than about 8 mm and having a fiber size of less than about1 .8 denier, the ultra-fine fibers comprising synthetic polymer fibers or regenerated cellulose fibers; the web having a basis weight of less than 100 gsm; and wherein the nonwoven web contains the ultra-fine fibers in an amount of greater than about2.8 million fibers per m2.2 A nonwoven product as defined in claim 1 , wherein the ultra-fine fibers are contained in the nonwoven web in an amount of greater than 50,000 linear meters per m2, such as greater than about 100,000 linear meters per m2, such as greater than about 150,000 linear meters per m2, such as greater than about 200,000 linear meters per m2, such as greater than about 300,000 linear meters per m2, such as greater than about 400,000 linear meters per m2, such as greater than about 500,000 linear meters per m2, and less than about 1 ,500,000 linear meters per m2.

3. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers are contained in the nonwoven web in an amount of greater than about 5 million fibers per m2, such as greater than about 10 million fibers per m2, such as greater than about 20 million fibers per m2, such as greater than about 30 million fibers per m2, such as greater than about 40 million fibers per m2, such as greater than about 50 million fibers per m2, such as greater than about 60 million fibers per m2.

4. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven web displays a density of greater than about 0.07 g / cm3, such as greater than about 0.09 g / cm3, such as greater than about 0.1 g / cm3, such as greater than about 0.11 g / cm3.

5. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven web displays a tensile strength in a machine direction of greater than about 5000 gf, such as greater than about 6000 gf, such as greater than about 7000 gf, such as greater than about 8000 gf, such as greater than about 9000 gf, and less than about 20,000 gf and displays a tensile strength in a cross direction of greater than about 2500 gf, such as greater than about 3000 gf, such as greater than about 3500 gf, such as greater than about 4000 gf, such as greater than about 4500 gf, and less than about 10,000 gf.

6. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven web displays a wet tensile strength in a machine direction of greater than about 2500 gf, such as greater than about 3500 gf, such as greater than about 4000 gf, such as greater than about 4500 gf, such as greater than about 5000 gf, such as greater than about 5500 gf and less than about 12,000 gf and displays a wet tensile strength in a cross direction of greater than about 1500 gf, such as greaterthan about 2000 gf, such as greater than about 2500 gf, such as greater than about 3000 gf, such as greater than about 3200 gf, and less than about 10,000 gf.

7. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven web displays a trapezoidal tear strength in a machine direction of greater than about 1000 gf, such as greater than about 1500 gf, such as greater than about 2000 gf, such as greater than about 2200 gf, and less than about 6,000 gf and displays a trapezoidal tear strength in a cross direction of greater than about 500 gf, such as greater than about 1000 gf, such as greater than about 1500 gf and less than about 5,000 gf.8 A nonwoven product as defined in any of the preceding claims, wherein the web comprises a foam formed web.

9. A nonwoven product as defined in any of the preceding claims, wherein the web has been hydroentangled and / or thermally bonded.

10. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers comprise polyester fibers.

11. A nonwoven product as defined in any of claims 1 through 9, wherein the ultra-fine fibers comprise polyolefin fibers.

12. A nonwoven product as defined in any of claims 1 through 9, wherein the ultra-fine fibers comprise regenerated cellulose fibers13. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers comprise crimped fibers.

14. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers have a fiber size of less than about 1 denier, such as less than about 0.8 denier, such as less than about 0.6 denier and greater than about 0.25 denier.

15. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers have an average fiber length of greater than about 10 mm, such as greater than about 11 mm, and less than about 20 mm.

16. A nonwoven product as defined in any of the preceding claims, wherein the ultra-fine fibers are present in the web in an amount from 10% to about 50% by weight, such as from about 15% to about 25% by weight and wherein the nonwoven web has a basis weight of from about 40 gsm to about 70 gsm, such as from about 52 gsm to about 68 gsm.

17. A nonwoven product as defined in any of the preceding claims, wherein the foam formed web has a first surface and a second and opposite surface and wherein the first surface has been subjected to hydroentangling and the second surface has been subjected to hydroentangling.

18. A nonwoven product as defined in any of the preceding claims, wherein the foam formed web is a single ply web and is non-layered.

19. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven web contains a foaming agent.

20. A nonwoven product as defined in claim 19, wherein the foaming agent comprises lauryl sulfate, a glycoside, sodium dodecyl sulfate, ammonium lauryl sulfate, a fatty acid amine, an amide, an amine oxide, or a fatty acid quaternary compound.21 . A nonwoven product as defined in any of the preceding claims, wherein the nonwoven product comprises an industrial wiper22. A nonwoven product as defined in claim 21 , wherein the industrial wiper includes a plurality of individual sheets stacked together or comprises a spirally wound product.

23. A nonwoven product as defined in any of the preceding claims, wherein the nonwoven product is presaturated with a cleaning solvent.

24. A nonwoven product comprising: a nonwoven web containing ultra-fine synthetic polymer fibers blended with cellulose pulp fibers, the ultra-fine synthetic fibers having an average length of greater than about 8 mm and having a fiber size of less than about 0.8 denier, the ultra-fine synthetic polymer fibers being present in the nonwoven web in an amount of from about 10% by weight to about 50% by weight25. A nonwoven product as defined in claim 24, wherein the ultra-fine synthetic polymer fibers comprise crimped fibers.

26. A nonwoven product comprising: a nonwoven web containing ultra-fine synthetic fibers blended with cellulose pulp fibers, the ultra-fine synthetic fibers having an average length of greater than about 8 mm and having a fiber size of less than about 0.8 denier, and wherein the nonwoven web displays a tensile strength in a machine direction of greater than about 7000 gf, displays a tensile strength in a cross direction of greater than about 3500 gf, displays a wet tensile strength in a machine direction of greater than about 4000 gf, displays a wet tensile strength in a cross direction of greater than about 2500 gf, displays a trapezoidal tear strength in a machine direction of greater than about 2000 gf, and displays a trapezoidal tear strength in a cross direction of greater than about 1500 gf, and wherein the nonwoven web has a basis weight of from about 45 gsm to about 70 gsm.

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