KR20040072634A - Helically crimped, shaped, single polymer fibers and articles made therefrom - Google Patents

Abstract

Provided are nonwovens for use in personal care absorbent articles made from homopolymer spiral crimped fibers. This nonwoven provides economical production since only one polymer is used. These nonwovens have good porosity and elasticity and are useful in many applications, including as outercovers, liners, surge layers, and even as absorbent cores.

Description

Helical crimped molded homopolymer fibers and articles made therefrom {HELICALLY CRIMPED, SHAPED, SINGLE POLYMER FIBERS AND ARTICLES MADE THEREFROM}

The present invention relates to polymeric fibers and articles that can be made using the fibers. More specifically, these fibers can be used in absorbent articles useful in personal care products such as disposable sanitary napkins, diapers, training pants, incontinence garments, wound care hygiene products and the like. These articles typically have a structure comprising a bodyside liner, a liquid impermeable outer layer or "baffle", and an absorbent core between the liner and the baffle.

Crimp fibers have been found to be useful in personal care products because of their ability to provide increased thickness to the material, as well as other properties.

Previously, bicomponent fibers have been used to make crimped fibers. The fibers may have one side made from one polymer and the other side made from a different polymer and are also used as binder fibers. Others include having one polymer constituting the central region of the fiber and another polymer constituting the outer region, but the symmetrical fibers are less attractive for crimping. Another case is to make fibers with legs or lobes, in which different polymers make up different parts of the legs or lobes (US Pat. No. 5,707,735). These fibers are performed appropriately, but are relatively expensive to manufacture because they are made from more than one polymer. The apparatus for making these fibers is also relatively more expensive and complex compared to homopolymer fibers, since a number of channels have to be machined into fiber spinnerets.

While mechanical crimping of single component fibers is another known in the art, this is a slow and cumbersome manufacturing process. By crimping mechanically, the crimp type which is generally induced by passing the fibers between the interlocking rollers is generally a zig-zag crimp in only one plane.

Despite past developments in absorbent structures, there is still an improved absorbent structure that can adequately reduce leakage from absorbent products, such as feminine hygiene products and infant hygiene products, which is simpler to manufacture and even more cost effective. I need it. There is a need for an absorbent structure that can provide improved liquid surge handling by more effectively inhaling, distributing and retaining repeated loads of liquid. If the materials are made using spiral crimped fibers, the materials need to be produced economically and quickly for use in the absorbent structure. Such materials should have better liquid handling properties than those made from previously used fibers.

Summary of the Invention

In the face of the difficulties and problems discussed in the prior art, a novel structural material is provided comprising a nonwoven web with good thickness and elasticity to allow more efficient liquid handling. This is achieved by a material for use in a personal care absorbent article, made from a single component fiber having a spiral crimp. Although various polymers can be prepared using polyolefins, polyamides, polyesters, rayons, acrylics, superabsorbents, and regenerated cellulose, polyolefins are preferred, with polypropylene being most preferred. Nonwovens may be bonded by thermal point bonding, pointless bonding, aeration bonding with a binder, ultrasonic bonding and hydroentangling. The nonwovens of the present invention can be used in a variety of personal care products, including diapers, training pants, absorbent underpants, adult incontinence products, bandages and other wound care hygiene products and feminine hygiene products. The nonwovens of the present invention can be used, in particular, as hook components in surge materials, hook and loop fabrics, and as absorbent cores, outercovers, liners, filtration media, and wipers.

1 is a diagram of an apparatus for making spunbond fibers.

2 is a broken side view of a double capillary for making fibers.

3 is a cross-sectional view of a double capillary for making fibers showing different types of capillaries.

4 is a broken side view of a capillary for preparing homofilament spunbond fibers.

<Definition>

The following terms used herein have their definitions.

The term "disposable" includes those which are not intended to be washed and reused and that can be discarded after use.

As used herein, the term "nonwoven or nonwoven web" refers to a web that has a structure of individual fibers or yarns sandwiched between it, but not in an appreciable manner as in knitted fabrics. Nonwoven or nonwoven webs have been manufactured from many methods, such as meltblowing methods, spunbonding methods, and bonded carded web methods. The basis weight of nonwovens is usually expressed in ounces per square yard (osy) or grams per square meter (gsm), and useful fiber diameters are typically expressed in microns (33.91 in osy to convert from osy to gsm). Multiply).

As used herein, the term “spunbonded fiber” refers to, for example, US Pat. No. 4,340,563 to Appel et al. And US Pat. No. 3,692,618 to Dorschner et al., Matsuki et al. Extruded filaments, as in US Pat. Nos. 3,338,992 and 3,341,394 to Kinney, US Pat. Nos. 3,502,763 to Hartmann, and US Pat. No. 3,542,615 to Dobo et al. Refers to a small diameter fiber made by extruding a molten thermoplastic material as filaments from a number of generally circular fine capillaries of spinneret so that the diameter of the micron is then drastically reduced. Spunbond fibers are generally not tacky when they are deposited on a collecting surface. Spunbond fibers are generally continuous and have an average diameter (from at least 10 samples) of greater than 7 microns, more specifically about 10 to 30 microns. Fibers are also described in US Pat. No. 5,277,976 to Hogle et al., US Pat. No. 5,466,410 to Hills and US Pat. No. 5,069,970 to Largman et al., Which describe hybrids having unusual forms. And US Pat. No. 5,057,368.

As used herein, the term “composite fiber” means a fiber formed from two or more polymers extruded from separate extruders but spun together to form one fiber. Composite fibers are often called multicomponent or bicomponent fibers. Although composite fibers may be monocomponent fibers, the polymers are generally different from one another. The polymers are arranged in separate zones positioned substantially uniformly across the cross section of the composite fibers and extend continuously along the length of the composite fibers. The coordination of such composite fibers may be, for example, a sheath / core arrangement in which one polymer is surrounded by another or may be in a parallel arrangement, a pie arrangement or an "islands-in-the-sea" arrangement. Composite fibers are disclosed in US Pat. No. 5,382,400 to Pike et al. And can be used to produce crimps in fibers using different expansion and contraction rates of two (or more) polymers.

The term “bicomponent fiber” as used herein refers to a fiber formed from two or more polymers extruded into a blend from the same extruder. The term "blend" is defined below. Bicomponent fibers do not have a variety of polymer components arranged in separate zones located relatively constant over the cross-sectional area of the fiber and the various polymers are generally not continuous along the entire length of the fiber, but instead generally start and end randomly. To form fibrils or protofibrils. Bicomponent fibers are often referred to as multicomponent fibers.

As used herein, the term "blend" refers to a mixture of two or more polymers, while the term "alloy" refers to a subclass of the blend in which the components are immiscible but are compatible. do. "Mixable" and "immiscible" are defined as blends having negative and positive values, respectively, for mixed free energy. "Commercialization" is also defined as a method of modifying the interfacial properties of an immiscible polymer blend to produce an alloy.

"Single polymer fiber" means a fiber made from one extruder from one polymer. The nonwoven web of homopolymer fibers may have only homopolymer fibers or may be a blend of homopolymer fibers and other fibers. The web may also have one layer of homopolymer fibers and also layers of other types of fibers. Homopolymer fibers may also be prepared from different polymers along their length and as bicomponent fiber blends, but not as composite fibers. This means that at any point in the fiber (except for the small transition region), the fiber is made from only one polymer, but this need not be the same polymer as in other zones along the length of the fiber.

As used herein, the term “bonded carded web” is used from staple fibers sent through a combing or carding unit, which divides the staple fibers in the machine direction to align them to form a machine direction oriented fibrous nonwoven web. It means the web produced. The fibers are several millimeters to several centimeters long. It is usually purchased as a package placed on a picker that separates the fibers before the carding unit. Once the web is formed, it is then joined by one or more of several known bonding methods. One such bonding method is powder bonding in which a powder adhesive binder is distributed throughout the web and then generally heated and activated by heating the web and adhesive. Another suitable bonding method is a pattern bonding method in which a heated calender roll or ultrasonic bonding device is generally used to bond the fibers together in a local bonding pattern, although the web can be bonded over its entire surface if desired. Another suitable known bonding method, particularly when using bicomponent staple fibers, is a breathable bonding method in which one of the components acts as a binder.

The term "hot air knife" or HAK, as used herein, is a process of pre- or preliminary bonding of a just-prepared microfiber, in particular a spunbond web, to provide sufficient gathering for further processing. It does not mean relatively strong bonding of secondary bonding processes such as TAB, hot spot bonding and ultrasonic bonding. Hot air knives are devices that concentrate a very high flow rate of heated air stream in a nonwoven web immediately after formation of the nonwoven web. This flow rate is generally about 1000 to about 10000 feet / minute (fpm) (305 to 3050 meters / minute) or more specifically about 3000 to 5000 feet / minute (915 to 1525 m / minute). The air temperature is usually about 200 to 550 ° F. (93 to 290 ° C.) for thermoplastic polymers commonly used in spunbonding, generally within the melting point of at least one of the polymers used in the web. Control of air temperature, speed, pressure, volume and other factors helps to prevent damage to the web while increasing the cohesiveness of the web. The HAK concentrated stream of air is arranged and oriented by one or more slots (or closely spaced holes) used as outlets for the web of heated air, wherein the slots are substantially transverse across the width of the web. -Extend in the direction of the machine; Since the perforated wires on which the microfiber web polymer is formed travel generally at high speeds, the exposure time to the air discharged from the hot air knife of any particular portion of the web is less than 1/10 second, generally approximately 1 / 100 seconds. HAKs are further described in commonly assigned US Pat. No. 5,707,468.

As used herein, “thermal point bonding” includes passing a web of fabric or fiber to be bonded between heated calender rolls and anvil rolls. Calender rolls, although not always, are generally patterned in some way such that the entire fabric does not bond through its entire surface. As a result, various patterns of calendar rolls have been developed for both functional and aesthetic reasons. An example of that pattern is the point, Hansen Penning with about 30% bond area having about 200 bonds / square inch, as disclosed in US Pat. No. 3,855,046 to Hansen and Pennings. Or "H & P" pattern. The H & P pattern has a rectangular point or pin engagement area where each pin has a lateral dimension of 0.038 inch (0.965 mm), a spacing between pins of 0.070 inch (1.778 mm) and a depth of engagement of 0.023 inch (0.584 mm). The resulting pattern has a binding area of about 29.5%. Another representative point bonding pattern is an enlarged Hansen Pennings or "EHP" bonding pattern, which has a lateral dimension of 0.037 inches (0.94 mm), a pin spacing of 0.097 inches (2.464 mm) and a depth of 0.039 inches (0.991 mm) Create a 15% bond area with square pins. Another representative dot bonding pattern, denoted by "714," is a rectangular pin bonding area where each pin has a lateral dimension of 0.023 inches, a spacing between pins of 0.062 inches (1.575 mm), and a depth of engagement of 0.033 inches (0.838 mm). Have The resulting pattern has about 15% bonded area. Another common pattern is a C-Star pattern with about 16.9% binding area. The C-stellar pattern has a "corduroy" design that is interrupted by shooting cross-shaped bars or constellations. Other common patterns include diamond patterns with about 16% bond area, with repeated and slightly misaligned diamonds, and wires with a bond area of about 19%, as indicated by the name, for example, a window screen. A weaving pattern is mentioned. Typically, the percent bond area varies from about 10% to about 30% of the fabric laminate web area. As is known in the art, spot bonding not only secures the laminate layers together but also imparts aggregation to each individual layer by joining the filaments and / or fibers within each layer.

As used herein, "pattern unbound" or interchangeably "point unbound" or "PUB" refers to a number of discrete unbounds as illustrated in US Pat. No. 5,858,515 to Stokes et al. By a fabric pattern having continuous joined areas forming areas. The fibers or filaments in the separated unbonded regions are dimensionally stabilized by successive bonded regions that completely surround or surround each unbonded region so that no support or backing layer of adhesive or film is required. Unbonded regions are specifically designed to provide space between the fibers or filaments within the unbonded regions.

"Hydrophilic" describes the fiber or surface of the fiber that is wetted by the aqueous solution in contact with the fiber. The degree of wetting of the materials can in turn be described in terms of the surface tensions and contact angles of the materials and liquids involved. Apparatus and techniques suitable for measuring the wettability of particular fiber materials may be provided by the Cahn SFA-222 Surface Force Analyzer System or a substantially equivalent system. Fibers with a contact angle of less than 90 °, as measured by this system, are labeled "wettable" or "hydrophilic", while fibers with a contact angle of greater than 90 ° are labeled "non-wetting" or "hydrophobic".

The term "personal hygiene product" or "personal hygiene absorbent product" as used herein refers to diapers, training pants, absorbent underpants, adult incontinence products, bandages and other wound care hygiene products and feminine hygiene products.

<Test method>

Compression Test : The compression test measures the resistance and elasticity of a material to compress. This relatively simple test uses a Compressometer, Frazier Precision Instrument Co., Inc., 20760 Gaithersburg, Oakland, MD, USA, generally referred to in literature. The US Department of Commerce, Bureau of Standards Research Paper RP561 published in the Bureau of Standards Journal of Research, Vol. 10, June 1933, p. 705-713]. The compression system has a 2.54 cm (1 inch) diameter foot, under which the sample is placed. Force is applied perpendicular to the sample and monitored by a dial indicator. Thickness was measured at 0.1 psi load and at multiple pressures with increasing load to 3 psi. After reaching 3 psi, the thickness was measured while gradually reducing the load to provide an elastic measure.

Opacity : This test measures the light transmittance through the sample material. The test apparatus is the HunterLab Color Difference Meter Model D25 available from HunterLab, 60540 Naperville, Illinois, USA. This specimen should be large enough to cover a 0.5 inch (1.27 cm) test opening or port, and the sample was tested at one location, in this case the anvil side of the sample, rotated 90 degrees and retested to average the results.

Peel Test : Peel force value measures the force required to peel detach a hook and loop fastening system at an angle of about 180 degrees, and is a standard method approved September 15, 1991 and published November 1991 with the following: Can be measured according to ASTM D5170: The loop material to be tested is cut into 76 mm (3 inches) x 152 mm (6 inches) rectangles with longer dimensions in the transverse machine direction. The roof material is placed under the stationary plate of the rolldown machine. The hook material was placed on top of the loop material and attached by a roll down machine using a 2 kg roller. A suitable roll down machine is Part Number HR-100, available from Chemsultants International of Mentor, Ohio, USA. During fastening of the fastener components, the roller is rolled over the test piece over one cycle in the transverse "width" direction of the sample. In addition, initial peeling by the hand "raising the loop" is omitted. After the hook-and-loop is properly attached, the combination is placed on an Instron Model 2712-004 tensile tester with a 102 mm (4 inch) rubberized grip face (Instron Corporation, Canton, 02021 Canton, USA). Was placed in a test apparatus. The hook base was inserted into the upper grip and the loop into the bottom in such a way that the movement of the grips away from each other would cause peeling separation of the two materials. Loose parts were removed and the machine started. The tester is set to have a crosshead speed of 500 mm / min and a gauge length of 76 mm. Measurements start at 10 mm and end at 46 mm, with measurements in grams. Reported values for peel test results are peak load values using MTS TESTWORKS software with a peak criterion of 2%. In addition, the peel force values are normalized to express in terms of force per unit length of the “width” dimension of the fastener component, such as grams / inch or grams / centimeters. MTS TESTWORKS software is available from MTS Systems Corporation, a business with offices in Eden Prairie, Minnesota, USA.

Shear : Shear test is used to test the force required to pull the hook and loop fasteners apart. Hook and loop material is fastened using a roll down machine (Cheminstruments Inc.) with a 2 kg weight. The sample is then inserted into an Instron ™ tester with a crosshead speed of 250 mm / min and pulled apart in a similar manner as used in the peel test. The sample width used was 2.54 cm (1 inch), and the hook used was VELCRO® HTH-851, but if all samples were tested with the same hook, another hook such as 3M's CS-600 could be used. Can be.

Tensile : The tensile test measures the peak and break load and peak and break elongation of the fabric. This test measures load (strength) in grams and elongation in%. In the tensile test, two clamps, each with two jaws and the side where each jaw contacts the sample, generally hold the material in the same plane spaced 7.6 cm (3 inches) vertically, and at a specified extension rate. Move the roll. Strip tensile strength and strip elongation using a sample size of 3 inches x 15.2 cm (6 inches), with a rough surface size of 2.5 inches (1 inches) high by 3 inches wide, and a constant extension speed of 300 mm / min. Get the value of Sintech 2 tester, available from Sintech Corporation, Carrie Sheldon Drive 1001, 27513, North Carolina, USA; Instron Model TM, available from Instron Corporation, Washington Street 2500, Canton, MA 02021, USA; or The Swing-Albert Model INTELLECT II, available from Swing-Albert Instrument Co., Duton Road 10960, Philadelphia, 19154, can be used for this test. The results are reported as the average of three specimens and can be performed with the specimen in the transverse direction (CD) or machine direction (MD).

Bulk (Thickness ): The caliper of the material is a measure of thickness, measured in millimeters at 146.3 grams per square centimeter (0.05 psi) with a Starret type bulk tester.

The present invention relates to personal care absorbent articles such as disposable sanitary napkins, diapers, incontinence garments, and the like. The materials of the present invention may also find use as wipers and in the filtration area. Nonwovens made from homopolymers, spiral crimped fibers, provide improved properties in many areas useful for these articles.

Absorbent articles typically have a liquid permeable bodyside liner, a liquid impermeable baffle, and an absorbent core between the liner and the baffle. The filter and wiper may be a single layer fabric or may have multiple layers with different special properties.

Nonwoven materials such as carded webs and spunbond webs have been used as bodyside liners in absorbent articles. An open porous liner structure could be used to allow liquid to pass quickly and to help keep the wearer's skin isolated from the wet absorbent pad just below the liner. Some structures have included a banding surfactant treatment in selected areas of the liner to increase the wettability of selected areas to control the amount of liquid that is rewet onto the wearer's skin.

The outer cover or baffle is designed to be liquid impermeable to prevent the wearer's clothing or bedding from being contaminated. Impermeable baffles are often made from thin films and generally from plastic resins, although other materials may be used. Nonwoven webs, films or film coated nonwoven webs may also be used as the baffles. The baffle may optionally be composed of a vapor or gas permeable microporous “breathable” material that is permeable to vapor or gas but substantially impermeable to liquid.

Absorbent articles have used various types of absorbent cores comprised of superabsorbents and / or cellulose fibers. Certain absorbent garments may be constructed with absorbent gelling particles and may comprise a multilayer absorbent core arrangement of varying composition.

In addition, other layers of material have been disposed between the liner and the absorbent pad, such as consisting of a thick lofty fabric structure for reduced rewet, distribution and storage of liquids, or to provide "surge" retention capabilities.

Spiral crimped fibers can be produced by many means. 1 shows a general type of device used in the manufacture of filaments or fibers according to a co-assigned patent application. Apparatus 10 has a first extruder assembly 12 for making spunbond fibers according to known methods (see also US Pat. No. 5,382,400 to Pike et al.). The spinneret 14 is supplied with a molten polymer resin from a resin source (not shown). The spinneret 14 produces fine denier fibers from the outlet 16, which are quenched by the air stream supplied by the quench blower 18. The air stream may cool one side of the fiber stream differentially relative to the other side, resulting in bending and crimping of the fiber. Crimping results in a softer fabric, for example by reducing the linearity of the fiber between the bond points resulting from the thermal bonding step. Various parameters of the quench blower 18 can be adjusted to adjust the amount and quality of the crimping. Fiber composition and resin selectivity also determine the crimping properties imparted.

The filament is directed into a fiber drawing device or aspirator 20 having a Venturi tube / channel 22 through which the fiber passes. The tube is supplied with temperature controlled air, which thins the filaments as the filaments are pulled through the fiber drawing device 20 in their plastic state. The tapered fibers are then deposited on the hole moving collection belt 24 and retained on the belt 24 by the vacuum force exerted by the vacuum box 26. The belt 24 moves around the guide roller 27. As the fiber moves on the belt 24, the compression roll 28 on the belt works with one of the guide rollers 27 directly below the belt, so that the fiber has sufficient gatherability to pass the manufacturing process. Compress the spunbond mat to allow An open knife may be used as an alternative to compression rolls.

A layer of meltblown fibers having a diameter of 1 to about 10 microns, preferably less than 5 microns, can be introduced on top of the spunbond layer from a previously rolled roll of meltblown fibers. Alternatively, it is also possible to form meltblown fibers and deposit them directly on the spunbond layer as they are formed. Meltblown fibers are preferably made of a resin which is a thermoplastic polymer, including but not limited to polyolefins, polyesters, polyamides, polyurethanes, copolymers and mixtures thereof.

The second layer of spunbond fibers can be made by the spunbond device 32 in a similar manner as described for the spunbond device 12. That is, the spinneret 34 produces a filament, which is quenched and crimped by the quench blower 36 and tapered by the aspirator 38. The fibers deposited on the meltblown layer are then compressed by a second compression mechanism 40 to form a three layer laminate (SMS laminate) 42 composed of spunbond-meltblown-spunbond fibers.

Spunbond nonwovens are generally bonded in some way when they are manufactured to provide sufficient structural integrity to withstand the harsh conditions of further processing leading to the finished product. Bonding can be accomplished in many ways, such as hydroentangling, needling, ultrasonic bonding, adhesive bonding, stitch bonding, aeration bonding, and thermal bonding. The preferred method is by thermal bonding. The SMS laminate 42 leaves the belt 24 and passes between a pair of nibbed thermal bond rolls 44 and 46. The bonding roll 44 is a conventional smooth anvil roll. The engagement roll 46 is a conventional pattern roll with a pair of pins 48. The pin creates bond points in the fabric matrix. The number and size of bond points is associated with fabric stiffness. That is, the higher the bond area or the more bond points per unit area, the more rigid the fabric. As the SMS laminate passes between the rolls 44 and 46, the pin 48 stamps the pattern on the SMS laminate 42 by pressing against the anvil roll 44 where the nip pressure is adjusted for uniformity.

Rolls 44 and 46 may be heated to form fiber bonds more efficiently. Rolls 44 and 46 may be heated to different temperatures. Optimal temperature ranges and roll differences depend on denier, fiber composition, web mass and web density, and whether single fiber or composite fiber is used. For monocomponent polypropylene fibers having approximately 3 dpf made at about 500 feet / minute, the temperature range is about 270 ° F. (132 ° C.) to about 340 ° F. (171 ° C.), and the difference between the pattern and the anvil roll is about It is preferably between 10 ° F. (5.5 ° C.) and about 30 ° F. (17 ° C.). For monocomponent polypropylene fibers with approximately 1 dpf of the same production rate, the temperature ranges from about 240 ° F. (115 ° C.) to about 290 ° F. (143 ° C.), with a difference of about 40-50 ° F. (22-28 ° C.) Is preferably. Smaller denier fibers have a lower overall temperature range because heat transfer is more efficient. If a raw material is specified, the temperature range will generally be the same, but it will move towards a warmer or cooler direction depending on the conveyor speed, which significantly affects the web mass and density. Preferably, the pattern roll is heated to a higher temperature than the anvil roll. Lower temperatures on the anvil roll 44 reduce the likelihood of secondary fiber to fiber bonding and fiber gloss between the bond points. As a result of this differential bond roll temperature, secondary fiber-to-fiber bonds are reduced without affecting the aggregation of the primary bonds, thereby improving fabric drape.

After the laminate 42 passes through the bond rolls 44 and 46, it is sent to a neck stretching assembly 50, which optionally includes a pair of nibbed rolls 52 and 54. The rolls 52 and 54 are operated under tension at a controlled rate faster than the speed of the bond rolls 44 and 46 to stretch the SMS laminate in the same direction as the path of the fabric, known as the machine direction. Neck stretching breaks fiber-to-fiber bonds and twists fibers between bond points, reducing fabric stiffness. The rolls can be heated or cooled as needed to achieve the desired mat properties and dimensional stability.

The neck stretched SMS laminate 42 is then optionally unnecked assembly as known to those of ordinary skill in the art, as generally described in US Pat. No. 5,810,954 to Jacobs et al. 56 and collection roll 66 are sent.

The method according to U.S. Provisional Application No. 60 / 257,973 (reference number 15272) provides a differential shear between a polymer flowing in a substantially hemispherical or semicircular half of the capillary and a polymer flowing in a non-semi-shaped or shaped half of the capillary One molded capillary is used to induce. This method further includes differential or regulated quenching of the filaments, where the regulated quench air is fitted to the molded part of the fiber.

One shaped capillary has a cutout of 25% or less of the total cross sectional area of the substantially round circumference of the capillary. Removal of less than 25% of the cross-sectional area of the capillary is believed to provide a strong fiber by inducing the necessary shear difference between the rounded and non-rounded half of the capillary while retaining a substantially circular cross section.

Other forms, such as the "X" or "Y" form or the multileaf form, also made from homopolymers and subjected to differential quenching, as disclosed, for example, in US Patent Application 60 / 257,983, also provide satisfactory fibers. I think it will be manufactured.

US patent application Ser. No. 09 / 747,278 (reference number 15274) discloses the production of homopolymer crimped fibers by the connection of polymer streams exiting through a double capillary spinneret design. Capillaries are specifically shaped to share parallel borders and to maximize induced shear in adjacent to each other. Differentially induced shear in different polymer streams results in differential tension in the connected halves of the filament. The filaments may further undergo differential or regulated quenching, which cures the crimps in the filaments to further induce crimps. The filaments are also preferably stretched in the spinning process to achieve a substantially rounded shape that produces a strong predictable filament.

As shown in FIG. 2, the die tip 70 forms a polymer feed passage 72 that terminates in an additional passage formed by a counterbore 74 that is connected to the capillary 76. While in fact schematic, it will be seen that FIG. 2 shows a dual capillary 76, an individual passageway formed within the die tip 70. The differential capillary morphology is shown more clearly in FIG. 3. In general, the capillary of the present invention preferably has a length to width ratio of about 4: 1 to about 12: 1, more preferably about 6: 1 to about 10: 1, with the length being the direction of the polymer flow. And the width is the capillary diameter.

Thus, each fiber is made by two capillaries of a double capillary design. 3 details an exemplary embodiment of these dual capillary designs. Using differentially shaped capillaries to produce a single fiber allows the face of the fiber with increased shear to have lower viscosity and lower melt strength, and then higher orientation within that segment of the fiber. To have it. It is contemplated that the differential polymer structure between the two capillaries may further lead to differential cooling rates between the fiber segments, which may aid in the creation of crimps.

As shown in FIG. 3, the dual capillary design 112 has a first capillary 114 and a second capillary 116. The first capillary 114 has an outer rim 118 and an interior positioned adjacent to the second capillary 116 at a close enough distance to allow the polymer extrudate from the first and second capillaries to mix or merge into a single fiber. Has a border 120. The outer rim 118 is arcuate and extends by at least about 120 degrees. The inner rim 120 is also arcuate and extends about 120 degrees or more but has a smaller radius than the outer rim. The second capillary 116 is shown in a substantially circular shape such that its inner rim 122 is arcuate toward and adjacent to the first capillary 114. The second capillary end border 124 distal from the first capillary is of course also arcuate. The second capillary may be substantially oval in some cases, although shown as circular.

US patent application Ser. No. 09 / 746,858 (reference number 16170) discloses the preparation of a single polymer crimped fiber by the connection of polymer streams from two capillaries, each having a different length to diameter ratio (L / D). The stream exits through a single outlet or hole in the meltspun die head. Because of the different capillary structures, differentially induced shear in different polymer streams results in differential polymer orientation, percent crystallinity and differential tension at the connected halves of the filaments. The filament may be further quenched, which cures the crimp in the filament to further induce the crimp. The filament in one embodiment has a substantially rounded shape that exits through the round hole, creating a stronger predictable filament, but the fiber shape need not be so limited.

4 details a portion of an exemplary die head 80 set up for polypropylene homofilament spunbond crimped filament fabrication. Counter bore 82 is located in the die head between polymer feed channel 84 and extrusion or knife edge 86 and has its longitudinal axis defining or in the direction of polymer flow as indicated by arrow 88. . The counter bore 82 does not reach or open to the knife edge 86. In the polymer flow direction, the counter bore 82 is connected to the polymer feed channel 84 and has a first channel 90 of diameter of about 4.00 mm adjacent thereto. The first channel 90 leads to a first conical feed chamber 92 whose walls are inclined inwards and downwards by about 2.16 mm at a 60 degree angle so as to have a second more than about 1.50 mm diameter and 7.43 mm length. It leads to a narrow channel 94. The second channel 94 leads to the second conical feed chamber 96, the wall of which is inclined inwardly at a 60 degree angle and ends at a flat bottom within about 0.54 mm from the knife edge 86.

A first capillary tube 98 of about 0.60 mm in diameter is connected to the first supply chamber 92 at approximately its midpoint and parallel to the counterbore major axis for a total length of about 6.36 mm to open into the air at the knife edge 86. Is extended.

A second capillary tube 100 of about 0.20 mm in diameter and 0.30 mm in length is connected to the conical wall of the second supply chamber 96 and with the first capillary tube or the first capillary discharge hole 102 at about 0.41 mm above the knife edge. It extends downward at an angle of about 45 degrees to connect.

In this embodiment, the first capillary has an L / D ratio of about 10 to 1 and the second capillary has an L / D ratio of about 1.5 to 1. The L / D ratio of the capillary can be varied to achieve the desired durability, processability and percent crystallinity in the fiber. Crystallinity% refers to the amount, or%, of crystals formed in the polymer chain. The capillary or outlet hole may take a form other than round to induce further crimping.

It is believed that the higher the shear produced in the polymer by the shift through the shorter, narrower second capillary, the lower the viscosity of the polymer, leading to higher polymer chain orientation than the polymer shift through the larger and wider first capillary. The polymer in the first capillary has a higher viscosity and lower polymer chain orientation, resulting in a more amorphous polymer stream. Preferably, the mixed polymer stream is quenched on both sides to fix the orientation of the extrudate as it exits the spinneret and exits the air. The highly oriented side will contract more, causing crimping of the fibers.

U.S. Patent Application 60 / 257,982 (reference number) discloses treating spiral crimped homofilaments with sufficient heat flow to accelerate the natural crimping tendency of the fibers. It also cures the crimp without substantial melt bonding or loosening of the crimped fibers to retain the lofty structure of this layer of laminate. Various other layers can then be joined, for example by thermal point bonding, to produce laminates that retain the essential properties of each layer. The layers can, for example, be joined together to have sufficient cohesion to create a laminate that will withstand a high speed web delivery process without harm to the processing apparatus or material. This method is preferably described in US Pat. No. 5,707,468 to Arnold et al., Which is attached to a diffusion mechanism that can end in a plate with multiple perforations for escape of heat, rather than as a concentrated line in HAK. Now use an open knife, an instrument known to those of ordinary skill in the art.

The residence time, air temperature and flow rate of the hot air knife are adjusted depending on the fiber type and the polymer type of the crimped fiber. Exemplary homofilament polypropylene helical spunbond layers have been treated to have desired results by diffusion airflow. The flow rate is about 275 meters / minute or mpm (99 feet / minute) over 45.72 cm (18 inches) in the machine direction at a material transverse speed between 61 and 366 meters / minute or mpm (200 to 1200 feet / minute or fpm). Minutes or fpm). A more satisfactory result is 1 inch 2.54 cm (1 inch) from the forming wire, at an air temperature between 132-143 ° C. (270-290 ° F.), with a diffuser plenum extending 20.32 cm (8 inch) in the machine direction. At a flow rate between 213 and 259 mpm (700 to 850 fpm) supplied at a distance of) and at a material transverse speed between 91 and 244 mpm (300 fpm to 800 fpm).

US Provisional Patent Application No. 60 / 257,972 (reference number 15814) discloses a first layer, an optional intermediate layer, and, for example, a middle layer of a nonwoven filament deposited on a forming belt or perforated wire. Disclosed is a lofty nonwoven filament layer, such as a spiral crimped homofilament, deposited on the layer. The first layer is processed, for example by known hot knife processing, to join the first layer into a web having sufficient aggregate to withstand high speed web delivery handling. The optional intermediate layer may or may not be heat treated depending on the fiber type, the desired laminate function or form, and the like. The layer of lofty nonwoven filament is inlined with sufficient heat to cure the crimp without substantial melt bonding or crimp relaxation of the crimped fibers to retain the lofty structure of this layer of laminate on the forming belt. The various web layers, ie, the first layer for mechanical gathering, the second lofty spiral crimping layer and any intermediate layers, for example by thermal point bonding, are combined to retain the essential properties of each layer and to provide sufficient gathering properties. Together, the layers have been joined together to produce a laminate that will withstand a high speed web delivery process without harm to the processing apparatus or material. The manufacturing speed will depend on the material to be molded, but the present invention has little practical limitation in this regard and can only accept web speeds in the range of 200 to 2000 feet / minute, for example. Crimps of single component crimped thermoplastic fiber webs can be crystallized or cured to retain their loft through low application of heat, as in US Pat. No. 6,123,886 to Slack. Slack discloses a method for making substantial spiral crimps in continuous filaments by generating turbulence in the thermoplastic material intended to form the filaments and maintaining turbulence while the polymer is crystallizing when they are at their glass transition phase temperature. However, this process is a slow off-line method that hardly increases the aggregate of the web in the case of modern high-speed line-delivery production and, as disclosed in Slack, is not suitable for economical manufacturing speeds.

The crimped fiber laminate material produced in this manner can be useful for high loft and high thickness applications, for example as the loop portion of a hook and loop fastener. The fibers can be designed to produce fabrics with good flexibility and drapes while maintaining sufficient bulk and loft to aid in cotton feel.

The materials of the present invention can be made from synthetic polymers. Synthetic fibers are made from polyolefins, polyamides, polyesters, rayons, acrylics, superabsorbents, LYOCELL® regenerated cellulose and any other suitable synthetic fibers known to those of ordinary skill in the art. Include. Many polyolefins can be used to make fibers, such as polyethylene such as Dow Chemical's Asun® 6811 linear low density polyethylene, 2553 LLDPE and 25355 and 12350 high density polyethylene. Suitable polymers. Polyethylenes have melt flow rates of about 26, 40, 25 and 12, respectively. Fibers forming the polypropylene include ESCORENE® PD 3445 polypropylene from Exxon Chemical Company and PF304 from Himont Chemical Co. Other polyolefins are also available.

In order to test the fabric of the present invention, many examples were made using different fibers. The fibers used are spiral crimped homopolymer fibers, spiral crimped bicomponent fibers and mechanical crimped polypropylene fibers made according to US Pat. No. 6,123,886.

Spiral crimped homopolymer fibers (fiber 1) had 7 deniers and were made from polypropylene. These fibers were made as continuous fibers and then cut to a staple length of about 50 mm.

The bicomponent crimped fiber (fiber 2) had a denier of about 6 and was made from polypropylene and polyethylene. These fibers were cut to a staple length of 50 mm.

The mechanical crimped fiber (fiber 3) had a denier of about 6 and was cut to a staple length of about 50 mm.

Each fiber was processed into a nonwoven web according to known bonded carded web processes at two different basis weights. All webs were joined in a point-unbound pattern. Six nonwoven webs were tested for bulk, shear and peel strength, compression, elasticity and density. The results are provided in Table 1. In Table 1, the basis weight is given in grams per square meter, the bulk is given in mm, the shear and peeling are measured in the transverse machine direction and are in grams, and the compression is 292.7 gram-square centimeters (0.1 psi) For tests using a 2.54 cm (1 inch) diameter foot in mm, elasticity is the difference between the loaded and unloaded heights, and the density is given in grams / cubic centimeters.

Fiber 1 Fiber 1 Fiber 2 Fiber 2 Fiber 3 Fiber 3 Basic weight 48.5 31.9 52.3 23.3 51.2 26.8 thickness 13.7 8.6 9.4 5.1 7.6 4.6 shear 2724 2510 2493 2390 2914 2593 Peeling 76 28 48 45 51 49 Compression (Load) 1.12 0.58 0.71 0.33 0.66 0.41 Compression (no load) 0.71 0.38 0.48 0.15 0.51 0.25 Shout 0.64 0.65 0.68 0.46 0.77 0.63 density 0.0035 0.0037 0.0056 0.0046 0.0067 0.0059

As can be seen from Table 1, the shear and peel properties of the homopolymer helical crimped fibrous web are superior to that of the bicomponent crimped fibers, except for the shear of fiber 1 at 31.9 gsm. The bulk is much larger in the case of homopolymer spiral crimped fibrous webs, which represents an advantage as a loop material in fluid handling applications, personal care products, as well as hook and loop fastening applications. The high bulk and good elasticity of the homopolymer helical crimped fibrous web also show high porosity (and low density), and also positive indicators for successful fluid handling layers.

Another example was performed using spiral crimped fibers but made according to the spunbonding process. The fibers used were single component spiral crimped spunbond fibers and spiral crimped bicomponent fibers.

Spiral crimped homopolymer fibers (fiber 4) had 7 deniers and were made from polypropylene. These fibers were made according to US patent application 60 / 257,973, with the capillary removed to induce shear having about 25% of the cross sectional area.

The bicomponent crimped fiber (fiber 5) had a denier of about 6 and was made in parallel arrangement from polypropylene and polyethylene. These fibers were made according to US Pat. No. 5,382,400 to Pike et al.

Each fiber was processed into a nonwoven web according to known spunbonding processes at two different basis weights. All webs were thermally bonded using a point-unbonded pattern. Four nonwoven webs were tested for shear and peel strength, percent opacity, machine direction tensile strength, transverse machine direction tensile strength, compression, and elasticity using the process procedures herein. The results are provided in Table 2. In Table 2, the basis weight is given in grams per square meter, shear and peel are measured in the transverse machine direction and are in grams, and the compression is 2.54 cm (1 inch) diameter at a pressure of 292.7 gram-square centimeters (0.1 psi) For tests with foot, provided in mm, elasticity is the difference between the loaded height and the unloaded height.

Fiber 4 Fiber 4 Fiber 5 Fiber 5 Basic weight 48.8 23.4 52.5 25.4 shear 1210 585 872 993 Peeling 115 58 161 176 Opacity 55.4 38.8 44.8 25.3 Compression (Load) 0.61 0.36 0.58 0.41 Compression (no load) 0.46 0.23 0.41 0.23 Shout 0.75 0.64 0.70 0.56 Tensile MD 12.4 8.2 7.7 2.5 Tensile CD 8.1 5.0 3.7 1.1

The elasticity of single component helical crimped fibers is greater than that of bicomponent fibers, especially when standardized to basis weight, and so is the tensile strength. The opacity of the single component spiral crimp fibers is also greater, which means that they are applicable to fabrics where stain hiding properties are desired, such as in outer covers or liners for personal care products.

Toughness tests of fibers 4 and 5 made of about 4.7 denier showed toughness of 1.9 and 1.4 gm / denier, respectively, showing that the fibers according to the invention are stronger than comparable crimped bicomponent fibers.

Testing of homopolymer spiral crimped fibrous webs shows that they can be good surge materials in personal care products. The surge control material is provided to quickly receive the incoming inlet and to absorb, retain, channel or otherwise process the liquid so that it does not leak out of the article. Surge layers may also be referred to as suction layers, transfer layers, transport layers, and the like. Surge materials should typically be able to handle incoming inlets between about 60 and 100 cc, for example at a volume flow rate of about 5 to 20 cc / sec for infants.

Superabsorbent polymers may also be used to make homopolymer helical crimped fibers for use in the nonwoven webs of the present invention. Superabsorbents are usually used in particulate form in the absorbent core because they absorb liquids many times their weight. A specific problem with prior art absorbent cores using particulate superabsorbents is "gel blocking", which is a state in which the superabsorbents swell and block or prevent the ingress of additional liquid that must be absorbed. Particulate superabsorbents may also leak from the product much more easily than fibrous superabsorbents. The large porosity and good elasticity associated with helical crimped fibers should greatly alleviate the blocking problem and maintain open pores in the absorbent structure for continued liquid absorption for longer periods of time than conventional absorbent cores.

Superabsorbents useful in the present invention may be selected from several groups based on chemical structure, as well as physical form. These include low gel strength, superabsorbents with high gel strength, surface crosslinked superabsorbents, and superabsorbents whose crosslink density varies throughout the structure. Superabsorbents can be based on chemicals including, but not limited to, acrylic acid, iso-butylene / maleic anhydride, polyethylene oxide, carboxy-methyl cellulose, polyvinyl pyrrolidone, and polyvinyl alcohol. Superabsorbents can have a range in flow rate from slow to fast. The superabsorbent should be one that can be made from fibers. The superabsorbent may be neutralized to varying degrees. Neutralization occurs through the use of counter ions such as Li, Na, K, and Ca. Examples of superabsorbents obtained from Camelot are indicated by FIBERDRI® 12241 and Fiberdry® 1161. Examples of these types of superabsorbents obtained from Technical Absorbents, Ltd. are represented by OASIS® 101 and Oasis® 111. Another example included in these types of superabsorbents was obtained from Chemtall Inc. and is represented by FLOSORB® 60 Lady. Another example included in these types of superabsorbents is from Sumitomo Seika and is recognized as SA60N type 2. Additional types of superabsorbents that are generally available and known to those of ordinary skill in the art, not listed here, may also be useful in the present invention.

The nonwovens of the present invention can be made to have a variety of physical parameters depending on their end use. Fabrics can be made, for example, with a basis weight of about 20 to 80 gsm for lighter weight applications and a basis weight of about 80 to 150 gsm for heavier weight applications. Examples of lighter weight applications include liners, loop materials and outer covers, and examples of heavier weight applications include surge and absorbent core materials, filtration media and wipers. The density of the web can vary from about 0.002 to 0.05 g / cm ³ . Crimp degree can be adjusted using variables of quench temperature, L / D ratio, form of capillary, polymer type and polymer flow rate. The denier of the fibers used to make the nonwoven web of the present invention can also be adjusted to change the behavior of the web. Denier affects the wicking properties of the web, for example. The nature of the web is also affected by chemical treatment. These treatments include surfactants and antistatics designed to change the hydrophilicity of the fibers.

As will be appreciated by one of ordinary skill in the art, changes and variations to the invention are considered to be within the ability of one of ordinary skill in the art. Examples of such changes are included in the above cited patents, each of which is incorporated by reference in its entirety as consistent with the present specification. Such changes and variations are intended to be within the scope of the present invention by the inventors.

Claims (14)

A nonwoven fabric for use in personal care absorbent articles, comprising homopolymer spiral crimped fibers. The nonwoven fabric of claim 1, wherein the polymer is selected from the group consisting of polyolefins, polyamides, polyesters, rayons, acrylics, superabsorbents, and regenerated cellulose. The nonwoven fabric of claim 2 wherein said polymer is a polyolefin. The nonwoven fabric of claim 3 wherein said polyolefin is polypropylene. The nonwoven fabric of claim 1, wherein the fabric is bonded by a method selected from the group consisting of thermal point bonding, pointless bonding, aeration bonding, ultrasonic bonding, and hydroentangling. 6. The nonwoven fabric of claim 5, wherein the fabric is joined by thermal point bonding. 6. The nonwoven fabric of claim 5, wherein the fabric is joined by breathable bonding. 6. The nonwoven fabric of claim 5, wherein the fabric is joined by hydroentangling. The nonwoven fabric of claim 1 wherein the fibers are staple fibers. The nonwoven fabric of claim 1 wherein the fibers are continuous fibers. The nonwoven fabric of claim 1, wherein the article is selected from the group consisting of diapers, training pants, absorbent underpants, adult incontinence products, bandages and other wound care hygiene products, and feminine hygiene products. An absorbent core for personal care absorbent articles comprising helical crimped fibers made from superabsorbent polymers. Loop material for hook and loop fasteners comprising a single component spiral crimped fiber. The loop material of claim 13, wherein the loop material is joined in a point unbonded pattern.