JP2005517093A - Spiral crimped and shaped single polymer fibers and articles made therefrom - Google Patents

Abstract

A nonwoven fabric is provided for use in a personal care absorbent article, the fabric being made from a single polymer helical crimped fiber. Such fabrics are economical to manufacture because they use only one polymer. These fabrics have excellent void volume and elasticity and are useful for many applications, including applications as outer covers, liners, surge layers, and even absorbent cores.

Description

Detailed Description of the Invention

(Technical field)
The present invention relates to polymer fibers and articles that can be produced using such fibers. More particularly, these fibers can be used in absorbent articles useful in personal care products such as disposable sanitary napkins, diapers, training pants, incontinence clothing, wound care products and the like. These articles typically have a structure that includes a body side liner, a liquid-impermeable outer layer or “baffle”, and an absorbent core between the liner and the baffle.

(Background technology)
Crimped fibers have proven useful in materials for personal care products due to their ability to increase the thickness of the material as well as other properties.
Bicomponent fibers have long been used to produce crimped fibers. This fiber can have one side made from one polymer and another side made from a different polymer and is also used as a binder fiber. Another option is that symmetric fibers are not preferred for crimping, but one polymer constitutes the central region of the fiber and another polymer constitutes the outer region. Yet another option is to produce fibers with feet or protrusions such that different polymers make up different parts of the feet or protrusions (US Pat. No. 5,707,735). These fibers function properly, but are relatively expensive to manufacture because they are made from more than one polymer. The equipment for producing these fibers is also more expensive and complex than single polymer fibers because multiple channels must be machined into a fiber spinneret plate.
Mechanical crimping of single component fibers is another option known in the art, but this is a slow and unwieldy manufacturing method. A type of crimp that is brought about by mechanical crimping, generally by passing the fibers between the intermeshing rollers, is usually a zigzag crimp on only one side.
Despite previous developments of absorbent structures, leakage from absorbent products such as feminine hygiene products and infant care products can be sufficiently reduced, manufacturing can be simplified and even more cost effective. There remains a need for an absorbent structure. There is a need for an absorbent structure that can improve the handling of liquid surges by more effectively taking, distributing, and holding repeatedly loaded liquids. There continues to be a need for economical and quickly manufactured materials for use in such absorbent structures, where the materials are manufactured using spiral crimped fibers. Such materials should have better liquid handling properties than those produced from previously used fibers.

(Disclosure of the Invention)
In light of the aforementioned difficulties and problems faced by the prior art, a novel structural material is provided that includes a nonwoven web having good bulk and resilience characteristics that allow for more effective liquid processability. This is accomplished by a material for use in a personal care absorbent article, where the material is made with a single component fiber having a helical crimp. A variety of polymers can be used to make the nonwoven fabrics of the present invention, including polyolefins, polyamides, polyesters, rayon, acrylic fibers, superabsorbents, and regenerated cellulose, with polyolefins being preferred and polypropylene being most preferred. Nonwoven fabrics can be bonded by hot point bonding, point non-bonding, vent bonding using a binder, ultrasonic bonding and wet entanglement. The nonwoven fabrics of the present invention can be used in a variety of personal care products including diapers, training pants, absorbent underwear, adult incontinence products, bandages and other wound care products, and feminine hygiene products. The nonwoven fabrics of the present invention can be used as surge materials, hoop components in hook and loop fabrics, and among other things, as absorbent cores, outer covers, liners, filtration media, and wipes.

(Best Mode for Carrying Out the Invention)
(Definition)
As used herein, the following terms have the definitions given to them.
The term “disposable” encompasses what is discarded after use and is not intended to be cleaned and reused.
As used herein, the term “nonwoven or non-woven web” means a web having a structure of individual fibers or yarns that are entangled with each other but not identifiable like a knitted fabric. . Nonwoven or nonwoven webs are formed from a number of processes such as, for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of a nonwoven fabric is usually expressed in ounces per square yard (osy) or grams per square meter (gsm) and the effective fiber diameter is usually expressed in microns (converted from osy to gsm). Note that osy is multiplied by 33.91).
As used herein, the term “spunbond fiber” refers to extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries, of a spinneret having the diameter of the extruded filament, and then rapidly Refers to small diameter fibers formed by reducing the diameter, the methods of which are described, for example, in Appel et al. US Pat. No. 4,340,563, Dorschner et al. US Pat. No. 3,692,618. US Pat. No. 3,802,817 to Matsuki et al., US Pat. No. 3,338,992 to Kinney, US Pat. No. 3,341,394, US Pat. No. 3,502,763 to Hartmann, and Dobo. As in U.S. Pat. No. 3,542,615. Spunbond fibers are generally not sticky when they are deposited on the collection surface. Spunbond fibers are generally continuous and have an average diameter (from at least 10 samples) that is longer than 7 microns, and more particularly about 10-30 microns. The fibers are also Hogle et al., US Pat. No. 5,277,976, Hills US Pat. No. 5,466,410, and Largman et al., US Pat. 069,970 and US Pat. No. 5,057,368 may be used.

As used herein, the term “conjugate fiber” refers to fibers that are formed from at least two polymers that are extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. Although the polymers are usually different from each other, the conjugate fibers can be single component fibers. The polymer is disposed in distinguishable areas that are located approximately constant across the cross-section of the conjugate fiber and extends continuously along the length of the conjugate fiber. The configuration of such conjugate fibers can be, for example, a sheath / core arrangement in which one polymer is surrounded by the other polymer, or a side-by-side arrangement, a pie-like arrangement, or an “underwater islands” arrangement. Conjugate fibers are taught in US Pat. No. 5,382,400 to Pike et al., Using conjugate fibers, and using different expansion and contraction rates of two (or more) polymers Can make shrinkage.
As used herein, “bicomponent fiber” refers to a fiber that is formed from at least two polymers extruded from the same extruder as a blend. The term “blend” is defined below. In bicomponent fibers, the various polymer components are not placed in distinct areas located relatively constant across the cross-sectional area of the fiber, and the various polymers are usually continuous along the entire length of the fiber. Instead, it forms fibrils or protofibrils that usually start and end randomly. Bicomponent fibers are also sometimes referred to as multicomponent fibers.
As used herein, the term “blend” means a mixture of two or more polymers, while the term “alloy” is a subordinate concept of a blend, in which the components are immiscible, but are incompatible. It is solubilized. “Mixability” and “immiscibility” are defined as blends having negative and positive values, respectively, with respect to the mixing free energy. Furthermore, “compatibility” is defined as the process of modifying the interfacial properties of an immiscible polymer blend to produce an alloy.
“Single polymer fiber” means a fiber made from one polymer by one extruder. The nonwoven web of single polymer fibers may have only single polymer fibers or may be a blend of single polymer fibers and other fibers. Such webs can also have a layer of single polymer fibers and yet other types of fiber layers. A single polymer fiber may also be made from different polymers along its length as a two-component fiber blend rather than as a conjugate fiber. This means that at any point in the fiber (except for small areas of transition), the fiber is made of only one polymer, which is the same polymer as another section along the length of the fiber. It doesn't mean that.

As used herein, “bonded carded web” refers to sending staple fibers into a combing device or carding device to loosen and align them in the machine direction to form a fiber nonwoven web that is oriented in a generally machine direction. It refers to the web formed by doing so. Such fibers are a few millimeters to a few centimeters long and are usually purchased in bale packing and placed in a picker that separates the fibers before the carding machine. Once the web is formed, the web is then bonded by one or more of several known bonding methods. One such bonding method is powder bonding, in which a powdered adhesive binder is distributed throughout the web and then usually activated by heating the web and adhesive with hot air. Another suitable bonding method is pattern bonding, which uses heated calender rolls or ultrasonic bonding equipment to bond the fibers together, usually in a localized bonding pattern, if desired. Can be bonded across the entire surface of the web. Another suitable and well-known bonding method, especially when using staple length bicomponent fibers, is a breathable bond, in which one of the components acts as a binder.
As used herein, the term “hot air knife” or HAK refers to the step of pre-bonding or first bonding microfibers, especially spunbond webs, immediately after manufacture to provide sufficient integrity to the web for further processing. Does not mean a secondary bonding process that is a relatively strong bond such as TAB, thermal bonding and ultrasonic bonding. A hot air knife is a device that concentrates a heated air stream at a very high flow rate toward a freshly formed nonwoven web. This speed is typically about 1000 to about 10,000 feet per minute (fpm) (305 to 3050 meters per minute), or more specifically about 3000 to 5000 feet per minute (915 to 1525 m / min). The air temperature is usually within the melting point of at least one polymer used in the web, and typically about 200-550 ° F. (about 93-290 ° F. for thermoplastic polymers commonly used for spunbonds. ° C) range. Control of air temperature, speed, pressure, volume, and other factors helps to avoid damage to the web while increasing its integrity. The concentrated air flow of HAK is arranged and directed by at least one slot (or closely spaced hole) that acts as an outlet for heated air towards the web, which slot is directed to the web Operates substantially transversely across the entire width. Because the perforated wire from which the microfiber web polymer is formed generally moves at high speed, the time to expose the air released from the hot air knife to a particular part of the web is less than 0.1 seconds and is generally about 0.01 seconds. It is. HAK is further described in commonly assigned US Pat. No. 5,707,468.

  As used herein, “hot spot bonding” refers to bonding a fabric or web of fiber through a heated calendar roll and an anvil roll. Calendar rolls are usually, but not always, some kind of patterned so that the entire fabric is not bonded over the entire surface of the fabric, and anvil rolls are usually flat. . Thus, various patterns of calendar rolls have been developed for functionality and aesthetic reasons. An example of a pattern is one that has dots and has a bonding area of about 30% of about 200 bonds per square inch, as taught in US Pat. No. 3,855,046 to Hansen and Pennings. Pennings or “H & P” pattern. The H & P pattern has square dots or pin coupling areas, each pin is 0.038 inches (0.965 mm) on one side and 0.070 inches (1.778 mm) between each pin. The depth is 0.023 inches (0.584 mm). The resulting pattern has a bond area of about 29.5%. Another typical point bonding pattern has a side dimension of 0.037 inches (0.94 mm), pin spacing of 0.097 inches (2.464 mm), and a depth of 0.039 inches (0.991 mm). An extended Hansen Pennings or “EHP” bond pattern that gives a 15% bond area with square pins having Another exemplary point connection pattern, referred to as “714”, has a square pin connection area, each pin having a one-piece dimension of 0.023 inches and a spacing of 0.062 inches (1. 575 mm) and a bond depth of 0.033 inches (0.838 mm). The resulting pattern has a bond area of about 15%. Yet another common pattern is the C-Star pattern with a bond area of about 16.9%. The C-Star pattern has a horizontal bar or “corduroy” design that is interrupted by shooting stars. Another common pattern is a diamond pattern with approximately 16% bonded area, repeated diamonds and slightly offset, and approximately 19% bonded area reminiscent of, for example, a screen door. A wire weave pattern is included. Typically, the proportion of bonded area varies from about 10% to about 30% of the area of the fabric laminate web. As is well known in the art, point bonding not only holds the laminate layers together, but also provides integrity to each of the individual layers by bonding filaments and / or fibers within each layer. .

As used herein, “pattern unbonded” or interchangeably “point unbonded” or “PUB” refers to a number of distinct non-bonds as illustrated in US Pat. No. 5,858,515 to Stokes et al. By fabric pattern having a continuous bond area defining the bond area. The fibers or filaments in the distinct non-bonded areas are dimensionally stabilized by a continuous bond area surrounding or surrounding each non-bonded area, thus eliminating the need for a film support layer or back layer or adhesive. The unbonded zone is strictly designed to provide space between the fibers or filaments in the unbonded zone.
“Hydrophilic” refers to a fiber or surface of a fiber that is wetted by an aqueous liquid that contacts the fiber. The wetness of a material can also be explained by the contact angle and surface tension between the liquid and the material involved. Equipment and techniques suitable for measuring the wettability of a particular fiber material can be provided by a Cahn SFA-222 surface force analyzer system or a system substantially equivalent thereto. When measured with this system, fibers having a contact angle of less than 90 degrees exhibit “wetting” or “hydrophilic”, and fibers having a contact angle equal to or greater than 90 degrees are “non-wetting”. That is, it shows hydrophobicity.
As used herein, “personal care product” or “personal care absorbent product” refers to diapers, training pants, absorbent underwear, adult incontinence products, bandages, other wound care products and feminine hygiene products. Means.

(Test method)
Compression test : The compression test measures the compression resistance and elasticity of a material. This relatively simple test uses a compression meter from Frazier Precision Instrument, Inc., located in Oakland Avenue 210, Gaithersburg, Maryland, 20760, and published by the Bureau of Commerce, Bureau of Research 56 10: June 1933, generally at pages 705-713. The compression meter has a 1 inch diameter foot on which the sample is placed. The force is applied perpendicular to the sample and monitored by a dial indicator. Thickness is measured at 0.1 psi load and is measured at multiple pressure points while increasing the load to 3 psi. After reaching 3 psi, the thickness is measured while gradually reducing the load to measure elasticity.
Opacity : This test measures the light transmission through the sample material. The test facility is a HunterLab color difference meter model D25 available from HunterLab, Naperville, Illinois 60540. The test specimen must be large enough to cover a 0.5 inch (1.27 cm) test opening or port, and the sample is tested at a location (in this case, the anvil side of the sample is tested). ), Rotate 90 degrees, retest, and average the results.

Peel test : Peel force value is a measure of the force required to peel a hook-and-loop fastening system at an angle of approximately 180 degrees, approved on September 15, 1991 and published in November 1991 Can be measured according to the standard procedure ASTM D5170, which is described in detail below. The loop material to be tested is cut into a laterally long 76 mm (3 inch) by 152 mm (6 inch) rectangle. The loop material is placed on the clamp plate of the roll-down device. The hook material is placed on top of the loop material and attached with its roll-down device using a 2 kg roller. A suitable roll-down device is part number HR-100 available from Chemsultants International, Mentor, Ohio. As the fasteners are engaged, the roller rolls on the test specimen for one cycle in the transverse “width” direction of the sample. Furthermore, the first manual peeling to “cause looping” is omitted. After the hooks and loops are properly attached, the combination is assembled into an Instron model 2712-004 tensile tester with a grip surface covered with 102 mm (4 inches) rubber (Instrument, 02021, Mass.). Ron Corp.). The hook bottom is inserted into the upper grip and the loop is inserted into the lower grip so that the two materials are peeled by the movement of the grip away from each other. Remove loosening and start the device. The tester is set so that the crosshead speed is 500 mm / min and the gauge length is 76 mm. The measurement starts at 10 mm and ends at 46 mm and is in grams. The value reported from the peel test result is the peel load value employing 2% peak reference MTS TESTWORKS software. Further, the peel force values are normalized and expressed as force per unit length of the “width” dimension of the test sample fastener, eg, grams per inch or grams per centimeter. MTS TESTWORKS software is available from MTS Systems, Inc., which has an office in Eden Prairie, Minnesota.
Shear force : The shear force test is used to test the force required to pull the hook and loop fasteners apart. A hookdown and loop material are engaged using a roll-down device (Cheminstruments) with a 2 kg weight. The sample was then inserted into an Instron ™ tester with a crosshead speed of 250 mm / min and pulled off in the same manner as used in the peel test. The width of the sample used was 2.54 mm (1 inch) and the hook used was VELCRO® HTH-851, but as long as all samples were tested with the same hook, 3M Company Other hooks such as CS-600 may be used.

Tensile : The tensile test measures the fabric's peak load and break load, as well as peak elongation% and break elongation%. This test measures load (strength) in grams and elongation in percent. In a tensile test, each of the two clamps has two jaws, each jaw having an opposing surface in contact with the sample, usually spaced 7.6 cm (3 inches) apart in the same plane. Hold the material and move away at a specific elongation rate. Using a sample measuring 3 inches by 15.2 cm (6 inches), strip tension at a constant extension rate of 300 mm / min with opposing jaws measuring 2.54 cm (1 inch) high by 3 inches wide Obtain strength and strip elongation values. This study included 27513 North Carolina, Cary, Shedron Dr. 1001 Sintech 2 testing machine available from Sintech, Massachusetts 02021, Canton, Washington St. Instron Model TM available from Instron, Inc., located at 2500, or 19154, Philadelphia, Pennsylvania, Duton Rd. A Thwing-Albert model INTERELL II available from Thwing-Albert Instrument, located at 10960, may be used. Results are reported as the average of 3 samples and can be done in the transverse direction (CD) or longitudinal direction (MD) of the sample.
The caliper of the bulk (thickness) material is a measure of thickness and is measured in millimeters at 146.3 grams per square centimeter (0.05 psi) using a Starret type bulk tester.

(Detailed explanation)
The present invention relates to personal care absorbent articles such as disposable sanitary napkins, diapers, incontinence clothing and the like. The materials of the present invention can also find use as wipes and in the field of filtration. Nonwoven fabrics prepared using single polymer helical crimped fibers provide improved properties in many areas useful for such articles.
Absorbent articles typically have at least a liquid permeable body side liner, a liquid impermeable baffle, and an absorbent core between the liner and the baffle. The filter and wipe may be a single layer fabric or may have multiple layers with different specific characteristics.
Nonwoven materials such as carded webs and spunbond webs have been used as body side liners for absorbent products. Open porous liner structures have been used to help liquids pass through them quickly and help keep the wearer's skin isolated from the wet absorbent pad under the liner. Some structures perform surfactant treatment on selected portions of the selected liner area to increase the wettability of the selected area, thereby controlling the amount of liquid wetting back onto the wearer's skin. It was.
The outer cover or baffle is designed to be liquid impermeable so as not to soil the wearer's clothing or bedding. Impervious baffles are often made from thin films and are usually made from plastic, although other materials may be used. Nonwoven webs, films, or film-coated nonwoven webs may be used as baffles as well. The baffle can optionally comprise 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 including superabsorbents and / or cellulosic fibers. Certain absorbent garments can be configured to have absorbent gelling particles and can include multiple layers of absorbent core arrangements with different compositions.
In addition, other material layers such as those composed of thick, bulky fabric structures, liners and absorbent cores to reduce wetting back, distribute liquid, and provide retention or “surge” retention capability. Was inserted between.

Spiral crimped fibers can be produced by a number of means. FIG. 1 shows a general type of apparatus used for the production of filaments or fibers according to a patent application assigned to the applicant. The apparatus 10 has a first extrusion assembly 12 for producing spunbond fibers according to known methods (see also Pike et al. US Pat. No. 5,382,400). The spinneret 14 supplies a molten polymer resin from a resin supply source (not shown). The spinneret 14 produces fine denier fibers from an outlet 16 that is quenched by an air flow supplied by a quench blower 18. The air flow can cool one side of the fiber flow differentially from the other, thereby creating fiber bending and crimping. By crimping, for example, the fiber linearity between the bonding points generated in the thermal bonding process is reduced, so that a more flexible fiber can be formed. Various parameters of the quench blower 18 can be controlled to control the quality and amount of crimping. Fiber composition and resin selection also determine the crimping properties imparted.
The filament is drawn into a fiber stretcher or suction device 20 with a venturi / channel 22 through which the fiber passes. The tube is supplied with temperature-controlled air, and the filament is thinned as it is drawn through the fiber stretcher 20 in a plastic state. The thinned fibers are then deposited on the perforated movable collection belt 24 and held on the belt 24 by the vacuum force created by the vacuum box 26. The belt 24 rotates around the guide roller 27. As the fiber moves along the belt 24, a compression roll 28 on the belt actuated by one of the guide rollers 27 under the belt compresses the spunbond mat so that the fiber is sufficiently integral to withstand the manufacturing process. It has. A hot air knife may be used in place of the compression roll.
A layer of meltblown fibers composed of a diameter of from 1 to about 10 microns, preferably less than 5 microns, can be introduced onto a spunbond layer from a previously prepared meltblown fiber roll 30. Alternatively, meltblown fibers can be formed and deposited so that they are formed directly on the spunbond layer. The meltblown fibers are formed of a resin that is preferably a thermoplastic polymer such as, but not limited to, polyolefins, polyesters, polyamides, polyurethanes, copolymers and mixtures thereof.
The second layer of spunbond fibers can be produced by the spunbond apparatus 32 in a manner similar to that described for the spunbond apparatus 12, that is, the spinneret 34 produces a filament and quenches the filament. The blower 36 is rapidly cooled and crimped, and is thinned by the suction device 38. Next, the fibers deposited on the meltblown layer are compressed by the second compression device 40 to form a three-layer laminate (SMS laminate) 42 composed of spunbond-meltblown-spunbond fibers.

In general, spunbond nonwovens are bonded in a specific way that they are manufactured to give the spunpond fibers sufficient structural integrity to withstand the rigors of further processing into the final product. Bonding can be done by a number of methods such as wet entanglement, needle, ultrasonic bonding, adhesive bonding, stitch bonding, vent bonding and thermal bonding. A preferred method is by thermal bonding. The SMS laminate 42 is moved away from the belt 24 and passed through the nip between the pair of heat bonding rolls 44 and 46. The bonding roll 44 is a conventional smooth anvil roll. The coupling roll 46 is a conventional pattern roll having a plurality of pins 48. Pins create bond points in the fabric matrix. The number and size of bond points is related to the stiffness of the fabric, i.e., a wider bond area per unit area or more bond points will result in a more rigid fabric. Pins 48 pattern on SMS laminate 42 by passing the SMS laminate between rolls 44 and 46 and pressing against anvil roll 44 that is controlled so that the nip pressure is uniform.
Rolls 44 and 46 can be heated to form fiber bonds more efficiently. Rolls 44 and 46 may be heated to different temperatures. The optimum temperature range and roll differences depend on the denier, fiber composition, web mass, and web density, and whether to use single component fibers or conjugate fibers. For a single component polypropylene fiber of about 3 dpf produced at about 500 feet per minute, the temperature range is about 270 ° F. (132 ° C.) to about 340 ° F. (171 ° C.), with preferred pattern and anvil rolls. The difference is from about 10 ° F. (5.5 ° C.) to about 30 ° F. (17 ° C.). For a single component polypropylene fiber of about 1 dpf at the same production rate, the temperature range is about 240 ° F. (115 ° C.) to about 290 ° F. (143 ° C.) with a preferred difference of about 40-50 ° F. (22 ~ 28 ° C). For smaller denier fibers, the overall temperature range is lower because heat transfer is more efficient. For a given raw material, the temperature range is approximately the same, but it is made warmer or cooler depending on the conveyor speed, which has a significant impact on the mass and density of the web. It is preferred to heat the pattern roll to a higher temperature than the anvil. Lowering the temperature of the anvil roll 44 reduces the possibility of secondary fiber-to-fiber bonding between the fiber shed and bonding points. By varying the temperature of the bonding roll in this manner, secondary fiber-fiber bonding is reduced without affecting the integrity of the primary bond, thereby improving fabric drape.
Laminate 42 is passed through bond rolls 44 and 46 and optionally through a neck extension assembly 50 comprising nip roll pairs 52 and 54. The rolls 52 and 54 operate under tension at a controlled speed that is faster than the speed of the bonding rolls 44 and 46 so that the SMS laminate 42 is stretched in the same direction as the fabric path, known as the machine direction. Neck extension breaks the fiber-fiber bond and distorts the fibers between the bond points, thereby reducing the stiffness of the fabric. The roll can be heated or cooled as necessary to obtain the desired matting properties and dimensional stability.
The neck stretched SMS laminate 42 is then optionally applied to a non-neck assembly 56 and a collection roll 66 known to those skilled in the art as generally shown in US Pat. No. 5,810,954 to Jacobs et al. Passed.

The method according to US Provisional Patent Application No. 60 / 257,973 (Docket No. 15272) is substantially hemispherical or semicircular, polymer that flows into the capillary half, and non-hemispherical or shaped. A single shaped capillary is used that produces a differential shear force with the polymer flowing in half of the capillary. The method further includes cooling the filament differentially or directionally with cooling air directed toward a shaped portion of the fiber.
A single shaped capillary has a cut-out portion that is no more than 25% of the overall cross-sectional area of the capillary's substantially round circumference. Removing less than 25% of the capillary cross-sectional area helps to maintain a substantially circular cross-section while at the same time creating the necessary differential shear between the round and non-round half of the capillary, It is believed that tough fibers can be obtained.
Others such as “X” or “Y” shapes or multi-leaf shapes made from a single polymer and subjected to differential cooling treatment, as taught, for example, in US Patent Application No. 60 / 257,983 The shape of is considered to produce satisfactory fibers.
US patent application Ser. No. 09 / 747,278 (Docket No. 15274) teaches the production of single polymer crimped fibers by merging polymer streams exiting a two-capillary spinneret design. The capillaries share a parallel boundary, where the capillaries are specially shaped to maximize the induced shear forces adjacent to each other. Different shear forces are induced in different polymer streams, resulting in different tensions for each seamed half of the filament. The filament may further be subjected to a differential or directional cooling process provided to create a crimp on the filament to further induce crimp. Desirably, the filaments can also be drawn during the spinning process to achieve a substantially round shape, resulting in a tough, expected filament.

As shown in FIG. 2, the die chip 70 defines a polymer feed path 72 that terminates in an additional path defined by a counterbore 74 connected to the capillary 76. Although essentially schematic, it will be appreciated that FIG. 2 shows the two capillaries 76 that are the individual paths formed in the die chip 70. The different capillary shapes are more clearly shown in FIG. In general, the capillaries of the present invention preferably have a length to width ratio of about 4: 1 to about 12: 1, more preferably about 6: 1 to about 10: 1, the length being defined by the flow direction of the polymer. And the width is the diameter of the capillary.
Each fiber is therefore produced by two capillaries of a two-capillary design. FIG. 3 details an exemplary embodiment of such a two-capillary design. When producing single fibers using differently shaped capillaries, increased shear forces result in fiber surfaces having lower viscosity and lower melt strength, and substantially higher orientation within the fiber segment. It is considered to have sex. It is believed that the different polymer structures between the two capillaries will also have different cooling rates between the fiber segments, further helping to produce crimps.
As can be seen from FIG. 3, the two-capillary design 112 has a first capillary 114 and a second capillary 116. The first capillary 114 has an outer boundary 118 and an inner boundary 120 that is sufficient to extrude the polymer from the first and second capillaries to mix or bond into a single fiber. A close distance is disposed adjacent to the second capillary 116. The outer boundary 118 is arcuate and extends over about 120 degrees. The inner boundary 120 is also arcuate and extends over about 120 degrees but has a smaller radius than the outer boundary. The second capillary 116 is shown as substantially circular so that the inner boundary 122 opposite and adjacent to the first capillary 114 is arcuate. The distal boundary 124 of the second capillary is distal from the first capillary and, of course, is also arcuate. The second capillary is shown as circular, but may be substantially oval if desired.

  US patent application Ser. No. 09 / 746,858 (Docket No. 16170) merges polymer streams from two capillaries, each having a different length-to-diameter ratio (L / D), and melts the merged polymer streams Teaching the production of single polymer crimped fibers by exiting from a single exit or hole of a spinning die head. Because different capillary structures induce different shear forces in different polymer streams, the polymer orientation, crystallinity, and resulting tension will be different in the spliced half of the filament. The filaments may be further subjected to a cooling step provided to create crimps on the filaments to further induce crimps. The filaments of certain embodiments retain a substantially round shape by exiting a round hole, resulting in a tougher and expected filament, but the fiber shape need not be limited to this.

FIG. 4 shows in detail a portion of a typical die head 80 set up for the production of polypropylene homofilament spun pound crimped filaments. The counterbore 82 is located in the die head between the polymer feed channel 84 and the extrusion end or knife edge 86 and thus has a longitudinal axis in the direction of flow of the polymer as indicated by arrow 88, or the polymer Specifies the flow direction of The counterbore 82 does not reach the knife edge 86, i.e. does not communicate. In the polymer flow direction, the counterbore 82 has a first channel 90 with a diameter of about 4.00 mm connected adjacent to the polymer feed channel 84. The first channel 90 leads to a first conical supply chamber 92 whose walls are inclined about 2.16 mm inward and downward at a 60 degree angle, with a diameter of about 1.50 mm and a length of 7.43 mm. Leading to two narrower channels 94. The second channel 94 terminates in a second conical feed chamber 96, its wall also tilts inward about 60 degrees and terminates at a flat bottom about 0.54 mm from the knife edge 86.
A first capillary 98 having a diameter of about 0.60 mm is connected to the first supply chamber 92 at approximately the midpoint of the supply chamber, extends parallel to the major axis of the counterbore, and communicates with the air at the knife edge 86. The total length is about 6.36 mm.
A second capillary 100 having a diameter of about 0.20 mm and a length of about 0.30 mm is connected to the conical wall of the second supply chamber 96 and extends downward at an angle of about 45 degrees to provide a knife edge or first It is connected to the first capillary 98 at about 0.41 mm above the capillary outlet hole 102.
In this embodiment, the first capillary has an L / D ratio of about 10-1 and the second capillary has an L / D ratio of about 1.5-1. The L / D ratio of the capillary may be varied to achieve the desired durability, processability, and crystallization ratio within the fiber. The crystallization ratio is represented by the amount or ratio of crystals formed in the polymer chain. The capillary tube or outlet hole may be non-rounded to further induce crimp.
The greater shear forces that occur in the polymer by passing the shorter, narrower second capillary are greater than the polymer that passes through the larger, wider first capillary, reducing the viscosity of the polymer melt and making the polymer chains more Highly oriented. The polymer in the first capillary has a higher viscosity and a lower polymer chain orientation, resulting in a more amorphous polymer stream. As the mixed polymer stream exits the spinneret into the air, it is preferred to cool from both sides to fix the extrudate orientation. The more highly oriented surface shrinks more and causes fiber crimp.

In US Provisional Patent Application No. 60 / 257,982 (Docket No. 15620), a spiral crimped homofilament is treated with a sufficiently high temperature air stream to promote a natural tendency to produce fiber crimp. Is taught. This document also creates crimps without essentially melt-bonding or relaxing the crimped fibers to maintain the bulky structure of this layer of the laminate. Various other layers can then be bonded, for example by hot spot bonding, to produce a laminate that retains the essential properties of each layer.
For example, the layers are bonded together to provide sufficient integrity to produce a laminate that can withstand high speed web moving processes without harming the processing equipment or materials. This method is preferably described in a high temperature air knife, Arnold et al., US Pat. No. 5,707,468, now using equipment known to those skilled in the art, which is fitted with a diffusion mechanism, which is HAK. Rather than as an internal concentrating line, it can end up with a plate with many holes that allow hot air to escape.
The pause time, air temperature and flow rate of the hot air knife are adjusted by the polymer type and fiber morphology of the crimped fiber. A typical homofilament polypropylene spiral spunbond layer has been processed to achieve the desired result by a diffused air flow. The flow rate was about 275 meters per minute over a length of 45.72 cm (18 inches) at a material crossing speed of 61-366 mpm (200-1200 fpm), ie mpm (900 feet per minute, or fpm). It was. Further satisfactory results are: longitudinal diffuser plenum extension of 20.32 cm (8 inches), air temperature of 132-143 ° C. (270-290 ° F.), 2.54 cm (1 inch) from the forming wire Air flow rates of 213 to 259 mpm (700 to 850 fpm) and material crossing speeds of 91 to 244 mpm (300 to 800 fpm) were obtained.

US Provisional Patent Application No. 60 / 257,972 (Docket No. 15814) describes a first layer of nonwoven filaments deposited on a forming belt or perforated wire, an optional intermediate layer, and, for example, a first layer and a predetermined location. Teaches a layer of bulky nonwoven filaments, such as spiral crimped homofilaments, deposited on any intermediate layer. The first layer is processed, such as by a known high temperature air knife process, to combine the first layers into a web that has sufficient integrity to withstand a high speed web moving process. The optional intermediate layer may or may not be heat treated depending on the fiber type, the desired laminating function, or morphology. The layer of bulky nonwoven filaments is processed inline on the forming belt and treated with sufficient heat to create a crimp, to maintain the bulky structure of this layer of laminate There is no substantial melt bonding or crimp relaxation. The various web layers, ie, the first layer for mechanical integrity, the second bulky spiral crimped layer, and the optional intermediate layer are then bonded together, such as by hot point bonding, so The layers are bonded so that they retain their proper properties and have sufficient integrity to produce a laminate that can withstand high speed web transfer processing without harming processing equipment or materials. The production speed depends on the material being formed, but the invention should be practically unlimited in this respect and can be adjusted to a web speed of 200-2000 feet per minute for illustration purposes only. Is understood. Crystallize or make a crimp of a single component crimped thermoplastic fiber web and maintain bulk by low temperature application as in Slack US Pat. No. 6,123,886. Slack generates turbulence in a thermoplastic material intended to form a filament at the glass transition phase temperature and maintains a turbulent flow during the crystallization of the polymer to produce a substantial amount of spiral in the continuous filament. Teaches how to make crimps. However, this process adds little web integrity for modern high-speed line transfer manufacturing, and as taught by Slack, this process is a slow off-line process that is undesirable in terms of economic manufacturing speed.
Crimped fiber laminate material produced in this manner can be useful for bulky and bulky applications such as the loop portion of hook and loop fasteners. The fibers can be designed to produce fabrics with good flexibility and drape while maintaining sufficient bulk and bulk to promote a cloth-like feel.

  The materials of the present invention can be made from synthetic polymers. Synthetic fibers include those made from polyolefins, polyamides, polyesters, rayon, acrylic fibers, superabsorbents, LYOCELL® regenerated cellulose, and other suitable synthetic fibers known to those skilled in the art. Many polyolefins are available for fiber production, and polyethylene such as Dow Chemical's ASPUN® 6811A liner low density polyethylene, 2553LLDPE, and 25355 and 12350 high density polyethylene are such suitable polymers. Polyethylene has melt flow rates of about 26, 40, 25, and 12, respectively. Examples of the fiber-forming polypropylene include EXCORE Chemical's ESCORENE (registered trademark) PD3445 polypropylene and Himont Chemical's PF304. Other polyolefins are also available.

(Example)
A number of examples were prepared using different fibers to test the fabrics of the present invention. The fibers used were a spiral crimped single polymer fiber, a spiral crimped bicomponent fiber and a mechanically crimped polypropylene fiber made according to US Pat. No. 6,123,886. Met.
A single crimped single polymer fiber (Fiber 1) had 7 denier and was made from polypropylene. These fibers were produced as continuous fibers and subsequently cut to a staple length of approximately 50 mm.
The bicomponent crimped fiber (Fiber 2) had about 6 denier and was made from polypropylene and polyethylene. These fibers were cut to a staple length of 50 mm.
Mechanically crimped fibers (fiber 3) also had about 6 denier and were cut to a staple length of about 50 mm.
Each fiber was processed into a nonwoven web at two different basis weights according to the known bonded carded web process. All webs were bonded in a point-unbonded pattern. Six nonwoven webs were tested for bulk, shear and peel strength, compression, elasticity and density. The results are shown in Table 1. In Table 1, basis weight is given in grams per square meter, bulk is given in mm, shear force and peel measured in the transverse direction, given in grams, and compression is 292.7 grams per square centimeter (. Tested using a 1 inch diameter foot with a pressure of 1 psi), given in mm, elasticity is the difference between loaded height and unloaded height, and density is given in grams per cubic centimeter .

表１からわかるように、単一ポリマーの螺旋捲縮加工繊維ウェブの剪断力及び剥離特性は、３１．９ｇｓｍにおける繊維１の剪断力以外は２成分捲縮加工繊維に比べて優れている。単一ポリマーの螺旋捲縮加工繊維ウェブの嵩はかなり大きく、個人用ケア製品における流体処理用途に、並びにフック・ループ式ファスナ用途のループ材料として有利であることが示された。単一ポリマーの螺旋捲縮加工繊維ウェブの大きい嵩及び良好な弾性はまた、好結果の流体処理層についての肯定的な指標でもある空隙体積が高い（低密度である）ことを示している。
別の実施例は、螺旋捲縮加工繊維を用いて行われたが、それはスパンボンドプロセスに従って製造された。使用された繊維は、単一成分の螺旋捲縮加工されたスパンボンド繊維及び螺旋捲縮加工された２成分繊維であった。
螺旋捲縮加工された単一ポリマー繊維（繊維４）は、７デニールを有し、ポリプロピレンから製造された。これらの繊維は、米国特許仮出願第６０／２５７，９７３号に従って製造され、剪断力を誘導するために取り除かれた毛細管の断面積は約２５％であった。 (Table 1)

As can be seen from Table 1, the shear and peel properties of the single polymer helical crimped fiber web are superior to the two component crimped fibers except for the shear force of fiber 1 at 31.9 gsm. The bulk of a single polymer helical crimped fiber web is quite large and has been shown to be advantageous for fluid treatment applications in personal care products and as a loop material for hook and loop fastener applications. The large bulk and good elasticity of the single polymer helical crimped fiber web also indicates high void volume (low density), which is also a positive indicator for successful fluid treatment layers.
Another example was performed using a spiral crimped fiber, which was produced according to a spunbond process. The fibers used were single component spiral crimped spunbond fibers and spiral crimped bicomponent fibers.
A single crimped crimped polymer fiber (Fiber 4) had 7 denier and was made from polypropylene. These fibers were made according to US Provisional Patent Application No. 60 / 257,973, and the capillary cross-sectional area removed to induce shear was about 25%.

The bicomponent crimped fiber (fiber 5) had about 6 denier and was made from side-by-side polyethylene and polypropylene. These fibers were made according to US Pat. No. 5,382,400 to Pike et al.
Each fiber was processed into a nonwoven web at two different basis weights according to a known spunbond process. All webs were thermally bonded using a point-nonbonded pattern. Four nonwoven webs were tested for shear and peel strength,% opacity, longitudinal tensile strength, transverse tensile strength, compression and elasticity using the procedures herein. The results are shown in Table 2. In Table 2, basis weight is given in grams per square meter, shear force and peel measured laterally, given in grams, and compression is 292.7 grams per square centimeter (0.1 psi) pressure in diameter. Tested with a 2.54 cm (1 inch) foot, given in mm, elasticity is the difference between the loaded height and the unloaded height.

単一成分の螺旋捲縮加工繊維の弾性は、２成分繊維の弾性よりも大きく、特に坪量について規格化した場合、引張強度についても同様であった。単一成分の螺旋捲縮加工繊維の不透明度も、より大きく、個人用ケア製品の外側カバー又はライナにおけるように染みを隠す特性が所望される、この布の潜在的な用途が示された。
約４．７デニールで製造された繊維４及び５のテナシティ試験では、それぞれ１．９及び１．４ｇｍ／デニールのテナシティを示し、それは本発明に従う繊維が同等の捲縮加工された２成分繊維よりも強いことを示している。
単一ポリマーの螺旋捲縮加工繊維ウェブの試験は、個人用ケア製品における良好なサージ材料となることを示している。サージ制御材料は、入ってくる排泄物を素早く受け入れ、液体を吸収、保持、導き又は管理するために設けられ、それによって液体が物品の外側に漏れない。サージ層はまた、取り込み層、移動相、輸送層等と呼ばれることもある。サージ材料は、通常、例えば幼児の場合約５〜２０ｃｃ／秒の体積流速にて約６０〜１００ｃｃの入ってくる排泄物を処理できなければならない。
超吸収性ポリマーも、本発明の不織ウェブに使用するための単一ポリマー螺旋捲縮加工繊維を製造するのに使用できる。超吸収体は、その重量の何倍もの液体を吸収するので、吸収性コアにおいて粒子状形態で通常使用される。粒子状超吸収体を使用する以前の吸収性コアに関する特定の問題は、「ゲルブロッキング」であり、これは超吸収体粒子が膨潤し、吸収されるべき追加の液体の侵入を防止又は禁止する状態のことである。粒子状超吸収体はまた繊維状超吸収体よりもかなり容易に製品から漏れることがある。螺旋捲縮加工繊維に関連する大きい空隙体積及び良好な弾性は、ゲルブロッキングの問題を大部分解決し、従来の吸収性コアよりも長い時間連続的に液体を取り込む吸収構造体中の開放孔を維持するのである。 (Table 2)

The elasticity of the single component spiral crimped fiber was greater than the elasticity of the bicomponent fiber, especially when normalized for basis weight, as was the tensile strength. The opacity of single component helical crimped fibers is also greater, indicating a potential use for this fabric where the property of hiding stains is desired as in the outer cover or liner of a personal care product.
Tenacity tests for fibers 4 and 5 made at about 4.7 denier show tenacities of 1.9 and 1.4 gm / denier, respectively, which indicates that the fibers according to the present invention are more comparable than crimped bicomponent fibers. Is also strong.
Tests of single polymer helical crimped fiber webs have shown good surge materials in personal care products. Surge control material is provided to quickly receive incoming waste and absorb, hold, direct or manage the liquid so that the liquid does not leak outside the article. The surge layer may also be referred to as an acquisition layer, a mobile phase, a transport layer, and the like. The surge material must typically be able to handle about 60-100 cc of incoming waste at a volumetric flow rate of about 5-20 cc / sec, for example for infants.
Superabsorbent polymers can also be used to produce single polymer helical crimped fibers for use in the nonwoven webs of the present invention. Superabsorbents absorb liquids many times their weight and are therefore typically used in particulate form in the absorbent core. A particular problem with previous absorbent cores that use particulate superabsorbents is “gel blocking”, which prevents or prohibits the intrusion of additional liquid to be absorbed, where the superabsorbent particles swell. It is a state. Particulate superabsorbers can also leak from the product much more easily than fibrous superabsorbents. The large void volume and good elasticity associated with spiral crimped fibers largely solves the gel blocking problem and creates open pores in the absorbent structure that continuously take up liquid for longer periods of time than conventional absorbent cores. To maintain.

  Superabsorbers useful in the present invention can be selected from a classification based on chemical structure and physical form. These include superabsorbers with low gel strength, superabsorbers with high gel strength, surface cross-linked superabsorbers, uniformly cross-linked superabsorbers or superabsorbers with various crosslink densities throughout the structure. It is done. Superabsorbents can be based on chemicals including but not limited to acrylic acid, isobutylene / maleic anhydride, polyethylene oxide, carboxymethylcellulose, polyvinylpyrrolidone, and polyvinyl alcohol. Superabsorbents can range from slow to fast speed. Superabsorbents must be able to be made into fibers. The superabsorber may have various degrees of neutralization. Neutralization occurs through the use of counter ions such as Li, Na, K, Ca. Examples of superabsorbers obtained from Camellot are shown as FIBERDRI® 1241 and FIBERDRI® 1161. Examples of such types of superabsorbents obtained from Technical Absorbents are those referred to as OASIS® 101 and OASIS® 111. Another example of this type of superabsorber is obtained from Chemtall, which is designated as FLOSORB® 60 Lady. Another example of this type of superabsorber is obtained from Sumitomo Seika and is recognized as SA60N Type 2. Other types of superabsorbents that are generally available and known to those skilled in the art but not listed herein may also be useful in the present invention.

The nonwoven fabric of the present invention can be manufactured according to various physical parameters depending on the end use. The fabric can be manufactured to have a basis weight of, for example, about 20-80 gsm for lighter applications and 80-150 gsm for heavier applications. Lighter applications include, for example, liners, loop materials and outer covers, and heavier applications include surge and absorbent core materials, filtration media and wipes. The density of the web can vary from about 0.002 to 0.05 g / cm ³ . The degree of crimp can be controlled using variables such as cooling temperature, L / D ratio, capillary shape, polymer type, and polymer flow rate. The denier of the fibers used to produce the nonwoven web of the present invention can also be adjusted to change the properties of the web. Denier affects, for example, web wicking characteristics. Web properties can also be affected by chemical treatment. Examples of these treatments include a surfactant for the purpose of preventing static electricity and changing the hydrophilicity of the fiber.
As will be appreciated by those skilled in the art, variations and modifications of the present invention are considered to be within the scope of those skilled in the art. Examples of such variations are included in the patents identified above, each of which is incorporated herein by reference in its entirety to the extent that it is consistent with the present specification. We intend that such variations and modifications are within the scope of the present invention.

FIG. 1 is a diagram of an apparatus for producing spunbond fibers. FIG. 2 is a cut-away side view of a double capillary for fiber production. FIG. 3 is a cross-sectional view of a two-capillary tube for fiber production, showing different shaped capillaries. FIG. 4 is a cut-away side view of a capillary tube for producing homofilament spunbond fibers.

Claims (14)

  Nonwoven fabric for use in personal care absorbent articles consisting of single polymer helical crimped fibers.   The nonwoven fabric according to claim 1, wherein the polymer is selected from the group consisting of polyolefin, polyamide, polyester, rayon, acrylic, superabsorbent, and regenerated cellulose.   The nonwoven fabric according to claim 2, wherein the polymer is a polyolefin.   The nonwoven fabric according to claim 3, wherein the polyolefin is polypropylene.   The nonwoven fabric according to claim 1, wherein the fabric is bonded by a method selected from the group consisting of thermal point bonding, point non-bonding, ventilation bonding, ultrasonic bonding, and hydraulic entanglement.   The nonwoven fabric according to claim 5, wherein the fabric is bonded by hot spot bonding.   The nonwoven fabric according to claim 5, wherein the fabric is bonded by air-flow bonding.   The nonwoven fabric according to claim 5, wherein the fabric is bonded by hydraulic entanglement.   The nonwoven fabric according to claim 1, wherein the fibers are staple fibers.   The nonwoven fabric according to claim 1, wherein the fibers are continuous fibers.   The personal care of claim 1, wherein the article is selected from the group consisting of diapers, training pants, absorbent underwear, adult incontinence products, bandages and other wound care products, and feminine hygiene products. Nonwoven fabric for absorbent articles.   Absorbent core for personal care absorbent articles formed from superabsorbent polymers and made of spiral crimped fibers.   A loop material for a hook-and-loop type fastener characterized by comprising a single component helical crimped fiber.   The loop material of claim 13, wherein the loop material is bonded in a point unbonded pattern.

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