MXPA05001641A

MXPA05001641A - Method of forming a 3-dimensional fiber and a web formed from such fibers.

Info

Publication number: MXPA05001641A
Application number: MXPA05001641A
Authority: MX
Inventors: Palani Raj Ramaswam Wallajapet
Original assignee: Kimberly Clark Co
Priority date: 2002-08-30
Filing date: 2003-07-24
Publication date: 2005-04-25
Also published as: KR20060006759A; WO2004020709A1; US20040043214A1; AU2003256753A1; BR0313446A; EP1532298A1; AR041041A1; JP2005537403A

Abstract

A method of forming 3-dimensional fibers is disclosed along with a web formed from such fibers. The method includes the steps of co-extruding a first component and a second component. The first component has a recovery percentage R1 and the second component has a recovery percentage R2, wherein R1 is higher than R2. The first and second components are directed through a spin pack to form a plurality of continuous molten fibers. The molten fibers are then routed through a quenching chamber to form a plurality of continuous cooled fibers. The cooled fibers are then routed through a draw unit to form a plurality of continuous, solid linear fibers. The solid fibers are then accumulated and stretched by at least about 50 percent. The plurality of stretched fibers are then cut and allowed to relax such that a plurality of 3-dimensional, coiled fibers is formed.

Description

METHOD FOR FORMING A THREE-DIMENSIONAL FIBER AND A TISSUE FORMED FROM SUCH FIBERS BACKGROUND OF THE INVENTION There are many methods known to those of ordinary skill in the art to spin fibers which can then be formed as a non-woven fabric. Most non-woven fabrics are useful for disposable absorbent articles to absorb body fluids and / or feces, such as urine, fecal matter, menstrual flow, blood, sweat, etc. The three-dimensional fibers are also useful for yarn-bonded materials that can be stretched in the transverse direction and in the machine direction, which can be formed as body side covers, linings and linings. Manufacturers of such items are always looking for new materials and ways to make or use such new materials in their articles to make them more functional for the application for which they are designed. The creation of a fabric of two-component and three-dimensional fibers, wherein the fibers are formed of at least one elastomeric material that can extend in at least one direction can be very beneficial. For example, a baby diaper containing an absorbent layer formed of cellulose pulp fibers interspersed in a three-dimensional non-woven fabric will allow the absorbent layer to retain a greater amount of body fluids, since the three-dimensional fibers can be expand. The absorbent layer can provide better protection against runoff for the user and probably should not be changed as frequently. In another example, a three-dimensional fiber-bonded nonwoven liner or liner can provide improved stretch and controllable shrinkage. Such liners or liners can provide an improved fit and greater comfort for the wearer of absorbent articles.

A fabric formed from the three-dimensional fibers can provide one or more of the following attributes: improved fit, improved lift, greater comfort, greater hollow volume, softer feel, improved elasticity, better stretch, controlled shrinkage and improved absorbency.

The exact method used to form a non-woven fabric can generate unique properties and characteristics in the fabric that can not be duplicated in any way.

Now, a new method has been invented to form a three-dimensional fiber, which allows the fibers that are ultimately formed inside the fabric to have very desirable properties, which are useful when the fabric is incorporated into a disposable absorbent article.

SYNTHESIS OF THE INVENTION In brief, the invention relates to a method for forming three-dimensional fibers together with a fabric formed of such fibers. The method includes the steps of co-extruding a first component and a second component. The first component has a recovery Rx percentage and the second component has a recovery percentage R2, where Ri is higher than R2. The first and second components are directed through a spin pack to form a plurality of continuous fused fibers. The plurality of molten fibers is then directed through a quenching chamber to form a plurality of cooled continuous fibers. The plurality of cooled fibers is then directed through a drawing unit to form a plurality of solid, continuous linear fibers. The plurality of solid fibers is accumulated on a reel which can then be unwound and stretched by at least 50 percent. The plurality of stretched fibers are cut and allowed to relax, this is how the plurality of rolled, three-dimensional fibers is formed.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic of the equipment necessary to extrude, spin, temper and stretch continuous solid fibers and accumulate them on a reel.

Figure 2 is a cross section of a bicomponent fiber.

Figure 3 is a diagram showing the unwinding of a plurality of linear, solid fibers, the stretching of the fibers, the cutting of the fibers and then allowing the fibers to relax to form a plurality of discontinuous fibers.

. Figure 4 is a side view of a helical fiber formed when the drawn fiber is cut into a discontinuous fiber and the fiber is allowed to relax.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, a scan of the equipment necessary to extrude, spin, temper and stretch a plurality of continuous solid fibers and accumulate them in a plurality of reels is illustrated. The method includes the steps of co-extruding a first component 10 and a second component 12. The first and second components, 10 and 12 respectively, can be in the form of solid resin granulates or as small particles. The first component 10 is placed in a funnel 14 from which it can be measured and directed through a conduit 16 to a first extruder 18. In the same way, the second component 12 is placed in a funnel 20 from which it can be measure and direct through a conduit 22 to a second extruder 24.

The first component 10 is a material that can be spun or otherwise formed into a continuous fiber. When the first component is formed in the fiber, the fiber must have the ability to stretch and has a recovery percentage Ri. The "Rx rate of recovery" is defined by the percentage by which the first component 10 recovers after it has stretched at least about 50% of its initial length and after the release of the force applied thereto. Desirably, the first component 10 is an elastomeric material. Suitable elastomeric materials that can be used for the first component include a molten thermoplastic elastomer, extrudable as a polyurethane elastomer, a copolyether ester, a polyether block polyamide copolymer, an ethylene and vinyl acetate elastomer ( EVA), a block copolymer of styrene, a block copolymer of amide ether, an olefinic elastomer, as well as other materials known to persons of ordinary skill in the art of polymers. Useful elastomeric resins include polyester polyurethane and polyether polyurethane. Examples of two commercially available elastomeric resins are sold under the brand names Polyurethanes PN 3429-219 and PS 370-200 of MORTHANE®. MORTHANE® is a registered trademark of Huntsman Polyurethanes with offices in Chicago, Illinois 60606. Another suitable elastomeric material is ESTAÑE®, a registered trademark of Noveno, Inc., with offices in Cleveland, Ohio 44040. Also, other suitable elastomeric material is PEARLTHANE ®, a registered trademark of Merquinsa, with offices in Boxford, Massachusetts 01921.

Three other elastomeric materials include a polyether block polyamide copolymer which is available for sale in different grades under the brand name PEBAX®. PEBAX® is a registered trademark of Atofina Chemicals, Inc., with offices in Birdsboro, Pennsylvania 19508. A second elastomeric material is a copolyether-ester marketed under the brand name ARNITEL®. ARNITEL® is a registered trademark of DSM with offices in Het Overloon 1, NL-611 TE Heerlen, The Netherlands. The third elastomeric material is a copolyether ester marketed under the brand name HYTREL®. HYTREL® is a registered trademark of E.I. DuPont de Nemours with offices in ilmington, Delaware 19898.

The first component 10 can also be formed from a co-polymer in styrene block such as KRATON®. KRATON® is a registered trademark of Kraton Polymers with offices in Houston, Texas.

Also, the first component 10 can be formed of a biodegradable elastomeric material such as aliphatic polyester polyurethanes or polyhydroalkanoates. The first component 10 can be formed of an olefinic elastomeric material, as elastomers and plastomers. A plastomer is an ethylene-based polymer resin marketed under the brand name AFFINITY®. AFFINITY® is a registered trademark of Dow Chemical Company with offices in Freeport, Texas. AFFINITY® resin is an ethylene-octane elastomeric copolymer produced using the INSITE ™ restricted geometry catalyst technology from the Dow Chemical Company. Another plastomer is marketed under the brand name EXACT®, which includes copolymers derived from a single catalyzed site and terpolymers. EXACT® is a registered trademark of Exxon Mobil Corporation, which has offices at 5959 Las Colinas Boulevard, Irving, Texas 75039-2298. Other suitable elastomers that can be used to form the first component 10 include elastomers derived from polypropylene.

The first component 10 can also be formed as a non-elastomeric thermoplastic material, which has a sufficient recovery rate Ri after it has been stretched at a specific temperature. The non-elastomeric materials useful in forming the first component 10 are thermoplastic polymers which can be extruded as polyamides, nylons, polyesters, polyolefins and polyolefin blends. For example, a biodegradable, non-elastomeric polylactic acid can provide a sufficient recovery percentage cuando when stretched above the glass transition temperature of about 62 ° C.

The second component 12, like the first component 10, is a material that can be spun or otherwise formed into a continuous fiber. When the second component 12 is formed into a linear fiber, the linear fiber must have the ability to stretch and has a recovery rate of R2, where Ri is higher than R2. The "R2 recovery percentage" is defined as the percentage that the component can recover after it has been stretched at least 50% of its initial length and after releasing the force applied to it. When the first and second components, 10 and 12 respectively, are formed into a linear fiber, the fiber must have the ability to retract or contract from a stretched condition, so that the linear fiber can be used in an absorbent article. As referred to here, the term "retraction" means the same as "contraction". Desirably, the ratio of the R1 / R2 ranges is from at least about 2 to about 100. More preferably, the ratio of the R1 / R2 ranges from at least about 2 to 50. The reason for making Ri more High that R2 in a linear fiber is that after the retraction or contraction of the first and second components 10 and 12, respectively, the three-dimensional fiber will present a predetermined structural configuration, very desirable. This structural configuration of the three-dimensional fiber will exhibit exceptional elongation properties in at least one direction.

The linear fiber also obtains some of its unique properties when the first component 10 forms the volume percentage of about 30% to about 95% of the linear fiber and the second component 12 forms the volume percentage of about 5% to about 70% of the linear fiber. Desirably, the first component 10 forms the volume percentage of about 40% to 80% of the linear fiber and the second component 12 forms the volume percentage. from about 20% to 60% of the linear fiber. The volume of a solid linear fiber is calculated by using the following formula: wherein: V is the volume of the linear solid fiber; p is a transcendental number, approximately 3.14159, which represents the ratio of the circumference to the diameter of a circle, and appears as a constant in a wide range of mathematical problems; d is the diameter of the linear fiber; Y Li is the initial length of the linear fiber.

The above described ranges of volume percentages for the first component 10 and for the second component 12 allow the linear fiber to be stretched at least 50% to form a stretched linear fiber. The percentage of volume of each of the first and second components, 10 and 12 respectively, also fulfills a very important function in the retraction or contraction of the stretched fiber to a retracted length. By varying the volume percentage of each of the first and second components 10 and 12 respectively, a linear fiber can be manufactured which can be stretched and then retracted to a predetermined configuration, and with certain desirable characteristics. At another time, after the fibers are formed in a disposable absorbent article, contact with the body fluid can cause the absorbent article to swell, which allows the fibers to elongate in at least one direction before the fiber becomes linear. As the fibers lengthen, they can extend and allow the absorbent structure to receive and store the additional body fluids.

The first and second components, 10 and 12 respectively, adhere or join chemically, mechanically and / or physically with another to prevent the fiber from breaking when the fiber is stretched and relaxed. The relaxed fiber will retract in 'length. Desirably, the component 10 will adhere resistively to the second component 12. In the core / shell arrangement, the mechanical adhesion between the first and second components, 10 and 12 respectively, will be complemented by any chemical and / or physical adhesion. present and which helps to avoid breaking or separation of the first component 10 of the second component 12. This breaking or separation occurs because one component has the ability to retract to a greater limit than the other component. When mutual adhesion is not present, especially during retraction, the two components can break and this is not convenient. In a fiber formed of two components arranged in a side-by-side or wedge-shaped configuration, strong chemical and / or physical adhesion will prevent the first component 10 from breaking or separating from the second component 12.

The second component 12 can be formed of polyolefins, such as polyethylene or polypropylene, a polyester or a polyether. The second component 12 can also be a polyolefin resin, such as a fiber grade polyethylene resin marketed under the brand name ASPÜN® 6811a. ASPUN® is a registered trademark of the Dow Chemical Company having offices in Midland, Michigan 48674. The second component 12 may also be a polyolefin resin, such as a homopolymer polypropylene such as Himont PF 304 and PF 308, available from Basell North America, Inc. ., which has its offices at Three Little Falls Center, 2801 Centerville Road, Wilmington, De. 19808. Another example of polyolefin resin from which the second component 12 can be formed is PP 3445 polypropylene available from Exxon Mobil Corporation having offices at 5959 Las Colinas Boulevard, Irving, Texas 75039-2298. Also, other suitable polyolefin materials that can be used for the second component 12 include random copolymers, such as a random copolymer containing propylene and ethylene. A random copolymer is marketed under the brand name Exxon 9355, available from Exxon Mobil Corporation which has offices at 5959 Las Colinas Boulevard, Irving, Texas 75039-2298.

The second component 12 can also be formed as a molten thermoplastic material that can be extruded which provides sufficient permanent deformation after stretching. This material includes, but is not limited to, aliphatic and aromatic polyesters, copolyesters, polyethers, polyolefins such as polypropylene and polyethylene, mixtures or copolymers thereof, polyamides and nylons. The second component 12 can also be formed of biodegradable resins, such as aliphatic polyesters. An aliphatic polyester is polylactic acid (PL7A). Other biodegradable resins include polycaprolactone, polybutylene adipate succinate, and polybutylene succinate. Polybutylene succinate adipate resins and polybutylene succinate resins are marketed under the brand name BIONOLLE® which is a registered trademark of Showa High Polymers having sales offices in New York, New York 10017. Other biodegradable resins they include copolyester resin marketed under the brand name EASTAR BIO®. EASTAR BIO® is a registered trademark of Eastman Chemical Company having offices in Kingsport, Tennessee 37662. Also, other biodegradable resins that can be used for the second component 12 include polyhydroxyalkanoates (PHA) of a variable composition and structure and copolymers and mixtures of the previous polymers. Specific examples of the appropriate biodegradable polymer resins include BIONOLLE® 1003, 1020, 3020 and 3001 resins, available for sale from Itochu International, BIONELLE® is a registered trademark of Showa High Polymers with offices in New York, New York 10017.

The second component 12 can also be formed of an inflatable and water-soluble resin. Examples of such water-soluble and inflatable resins include polyethylene oxide ((PEO) and polyvinyl alcohol (PVOH).) Grafted polyethylene oxide (gPEO) or chemically modified PEO can also be used. Mix with a biodegradable polymer to provide better processing, performance and interactions with liquids.

It should be noted that the PEO resin can be chemically modified by a reactive extrusion, graft, or block polymerization or by branching to improve its processability. The PEO resin can be modified by reactive extrusion or grafting as described in U.S. Patent No. 6,172,177 issued to ang et al. On January 9, 2001.

Finally, the second component 12 has a lower recovery rate R2 than the first component 10. The second component 12 can be formed of a material having a low elastic recovery. The materials from which the second component 12 can be formed include, but are not limited to, resins of polyolefin, polypropylene, polyethylene, polyethylene oxide (PEO), polyvinyl alcohol (PVOH), polyester and polyether. The second component 12 can be treated or modified with hydrophilic or hydrophobic surfactants. The treatment of the second component 12 with a hydrophilic surfactant will form a surface that can be wetted to increase the interaction with a body fluid or liquor. For example, when the surface of the second component 12 is treated to be hydrophilic, it will become more wettable when it contacts body fluid, especially urine. Treating the second component 12 with a hydrophobic surfactant will cause it to reject the body fluid or fluid. A similar treatment for the first component 10 can also be carried out to control its hydrophilic and hydrophobic characteristics.

Referring again to Figure 1, the first and second components, 10 and 12 respectively, are co-extruded separately into two extruders 18 and 24. Extruders 18 and 24 operate in a manner known to persons of ordinary skill. in art. In short, the solid resin granules or small particles are heated above their melting temperature and advance along a path by means of a rotary piston. The first component 10 is directed through a conduit 26 while the second component 12 is directed simultaneously through a conduit 28 and both flow streams are directed into a spin pack 30. A melt pump, not shown, may be placed through one or both conduits 26 and 28 to regulate the volumetric distribution, as necessary. The spin pack 30 is a device for making synthetic fibers. The spin pack 30 includes a bottom plate having a plurality of holes or openings through which the extruded material flows. The number of openings per square inch in the spin pack 30 may vary from about 5 to 500 openings per square inch. Desirably, the number of openings per square inch in the spin pack 30 is from about 25 to 250. More preferably, the number of openings per square inch in the spin pack 30 is from about 125 to 225. The size of each 'opening _ in the spin pack 30 may vary. A typical opening size can vary from about 0.1 millimeter to 2.0 millimeters in diameter. Desirably, the size of each of the openings in the spin pack 30 may range from about 0.3 mm to 1.0 mm in diameter.

It should be noted that the openings in the bundle 30 of thread do not have to be round or circular in cross section, but may have a configuration of two lobes, three lobes, square, triangular, rectangular, oval or any other desired geometric cross section.

With reference to Figures 1 and 2, the first and second components, 10 and 12 respectively, are directed within the spin pack 30 and are directed through the openings formed in the lower plate, such that the first component 10 will form a core 32 while the second component 12 will form a cover 34 that surrounds the outer circumference of the core 32. It should be noted that the first component 10 can form the cover while the second component 12 can form the core, if desired . This roof / core arrangement produces a configuration of a bicomponent, linear fiber 36. The bicomponent fibers have other cross-sectional configurations that can also be produced when using the spin pack 30. For example, the bicomponent fibers may have a side-by-side configuration or a cover / core design wherein the core is displaced coaxially from the cover.

A bicomponent fiber 36 will be formed for each opening formed in the plate within the spin pack 30. This allows a plurality of continuous fused fibers 36, each with a predetermined diameter, to exit simultaneously from the spin pack 30 at a first speed. Each linear bicomponent fiber 36 will be separated from the adjacent fibers 36. The diameter of each bicomponent fiber 36 will be governed by the size of the openings formed in the bottom plate of the spin pack 30. For example, as mentioned above, when the diameter of the holes or openings in the lower plate is within the range of about 0.1 to 2.0 mm, then each of the melted fibers 36 will have a diameter ranging from about 0.1 mm to 2.0. mm. There is a tendency for the molten fibers 36 to swell in their cross-sectional area once they leave the aperture formed in the plate but this expansion is relatively small.

The plurality of continuous, fused fibers 36 is directed through a quenching chamber 38 to form a plurality of cooled, linear, bicomponent fibers 40. Desirably, the molten fibers 36 are directed down from the spin pack 30 into the quench chamber 38. The reason for directing the melted fibers 36 downwards is that gravity can be used to cooperate in moving the melted fibers 36. In addition, the downward vertical movement can help in keeping the fibers 36 separated from each other.

In the tempering chamber 38, the continuous, fused fibers 36 come into contact by one or more air streams. Under normal conditions, the temperature of the melted, continuous fibers 36 that come out of the spin pack 30 and enter the quench chamber 38 will be within the range of about 150 ° C to 250 ° C. The actual temperature of the melted fibers 36 will depend on the material with which they were made, the melting temperature of such material, the amount of heat applied during the extrusion process, as well as other factors. Within the quench chamber 38, the continuous, fused fibers 36 come into contact and are surrounded by an air with a lower temperature. The air temperature can vary from about 0 ° C to 120 ° C. Desirably, the air is cooled or frozen to rapidly cool the molten fibers 36. However, for certain materials used to form the bicomponent fibers 36, it is advantageous to use ambient air and even hot air. However, for most elastomeric materials, the air is cooled or frozen at a temperature of about 0 ° C to 40 ° C. More preferably, the air is cooled or frozen at a temperature of about 15 ° C to 30 ° C. The air with lower temperature can be directed towards the fibers 36 melted at different angles but it seems that a vertical or horizontal angle works better. The incoming air velocity can be maintained or used to effectively cool the molten fibers 36.

Chilled or frozen air will cause the continuous, fused fibers 36 to crystallize, adopt a crystalline structure or separate phase and form a plurality of cooled, continuous fibers 40. The cooled fibers 40 remain in the linear configuration in this step. After leaving the tempering chamber 38, the temperature of the cooled fibers 40 can vary from about 15 ° C to 100 ° C. More preferably, the temperature of the cooled fibers 40 will vary from about 20 ° C to 80 ° C. More preferably, the temperature of the cooled fibers 40 will vary from about 25 ° C to 60 ° C. The . cooled fibers 40 will be at a temperature below the melting temperature of the first and second components, 10 and 12 respectively, from which the fibers 40 are formed. The cooled fibers 40 may have a soft plastic consistency in this step.

The plurality of cooled, continuous fibers 40 is then directed towards an extraction unit 42. The extraction unit 42 can be located vertically below the tempering chamber 38 to take advantage of gravity. The extraction unit 42 may be a rotating roller around which all the fibers 40 are cooled down to form a rope or tow and are stretched as they are wound at least once around the outer periphery of the rotating roll. The plurality of wound fibers 40 can be wound one or more times around the outer periphery of the rotating roller. Desirably, the plurality of cooled fibers 40 can be wound 1½ times around the outer periphery of the rotating roller, where the fibers 40 accumulate in a rope or tow of solid fibers 44. Mechanical stretching involves subjecting the cooled fibers to a mechanical force that will pull or stretch the molten material that leaves the spin pack 30.

The cooled fibers 40 are. they stretch downward mainly from the molten state and not from the cooled state. The downward force in the extraction unit 42 will cause the molten material to elongate and stretch to form solid fibers. The elongation of the molten material will usually shape, narrow, distort or otherwise change the cross-sectional area of the fibers 44. For example, when the molten material has a circular or round cross-sectional area after leaving the package 30. of spinning, the external diameter of the solid '44 fibers will be reduced. The amount that is reduced in diameter from the solid linear fibers 44 will depend on several factors, including the amount of stretched molten material, the distance over which the fibers are stretched, the mechanical force used to stretch the fibers, the tension in the line of spinning, etc. Desirably, the diameter of the solid linear fibers 44 will vary from about 5 microns to about 100 microns. More desirable, the diameter of the solid linear fibers 44 will vary from about 10 microns to 50 microns. More preferably, the diameter of the solid linear fibers 44 will vary from about 10 microns to 30 microns.

The extraction unit 42 will pull the cooled fibers 40 at a second speed faster than the first speed deployed by the continuous fused fibers 36 coming out of the spin pack 30. This change in speed between the. continuous fused fibers 36 and continuous cooled fibers 40 allow the molten material to be elongated and also reduce in cross-sectional area. After leaving the extraction unit 42, the cooled fibers 40 will be the solid fibers 44.

The plurality of solid fibers 44 exiting the extraction unit 42 is then directed in bulk around the roller 45 to a reel 46. The advance fibers 44 are wound circumferentially on the periphery of the reel 46 in the form of a rope. The spool 46 can be mounted on a support 48 and rotatable as the advance fiber 44 is directed on the reel 46. The reel 46 can have the proper shape and dimensions to accumulate a predetermined amount of the solid fibers 44. The solid linear fibers 44 will accumulate on the reel 46 until the reel 46 is filled. At this time, the plurality of solid fibers 44 are cut or separated in bulk by a cutter 50. The solid advance fibers 44 can be directed onto another empty reel 46 that can be supported on the support 48. The process of removing a reel 46 full and replacing it with an empty reel 46, on which the advancing fibers 44 can accumulate, is known to persons of ordinary skill in the art. The process can be automated so that the forward linear fibers 44 can be directed instantaneously and sequentially to the next empty reel 46.

Each of the empty reels 46 can be stacked and stored for later use in another facility or transported to another location. A feature of the invention is that the solid linear fibers 44 do not have to be processed into folded discontinuous fibers or formed into a fabric in a continuous process. Instead, the method allows for an interruption, so that solid linear fibers 44 can also be processed at a later time and at a remote location, as appropriate. Alternatively, a continuous method may be employed, wherein the reels 46 need not be present. 1 With reference to Figure 3, a scheme showing the unwinding of a plurality of linear fibers, stretching the fibers, cutting the fibers and then allowing the fibers to relax to form a plurality of three-dimensional discontinuous fibers is illustrated. The method allows the plurality of linear fibers 44 which was wound on the outer periphery of the reel 46 to be unwound and directed towards a heater 52. The heater 52 is optional, but when present, it will heat the plurality of linear fibers 44 at a temperature elevated The exact temperature will depend on the composition of the first and second components, 10 and 12 respectively, the diameter of the fibers 44, the amount of fibers 44 to be stretched, the speed of the fibers 44, etc. Also, at this time it is possible to apply a treatment to the surface of the plurality of linear fibers 44, if desired. The application of a surface treatment, either by spraying a chemical composition into the fibers 44 or immersing fibers 44 in a liquid bath, is well known to those of ordinary skill in the art. Several types of surface treatments can be applied to the fibers 44.

The plurality of solid linear fibers 44 is then directed to a stretching unit 54 where the plurality of linear fibers 44 stretch at least about 50%. The term "stretched" refers to the linear, solid, continuous fibers 44 being stretched or stretched while in a solid state. The stretching is caused by the axial tension exerted on the plurality of linear fibers 44. As the linear fibers 44 are stretched, the cross-sectional area of the linear fibers 44 will be reduced. Desirably, the amount of stretch imparted to the solid fibers 44 can vary from about 75% to 1,000%. More preferably, the amount of stretching imparted on the solid fibers 44 can vary from about 100% to 500%. More preferably, the amount of stretch imparted on the solid fibers 44 can vary from about 150% to about 300%.

The stretching unit 54 is shown as including two pairs of separate rollers. It should be noted that other forms of mechanical stretching apparatus can be used. The first pair of rollers includes a first roller 56 and a second roller 58. The first and second rollers, 56 and 58, respectively, can be arranged in close contact with another in order to form a contraction point 60 between them. The plurality of linear fibers 44, unwound from the reel 46, are directed around a portion of the periphery of the first roll 56, through the shrinkage point 60 and around a portion of the periphery of the second roll 58. The dot 60 of The shrinkage can be adjusted so that little or no pressure is exerted on the fibers 44. At least one of the first and second rollers, 56 and 58 respectively, is a drive roller that is adjusted to rotate at a first predetermined surface velocity. . This surface velocity caused the plurality of linear fibers 44 to advance at this speed. The surface velocity may vary depending on the unique independent requirements. However, a speed between approximately 10 meters per minute (m / min) to 1, 000 m / min will be sufficient for most applications. Conveniently, the surface velocity will be equal to or less than about 500 m / min. In general, a higher surface velocity than a lower surface velocity is preferred, in order to reduce the manufacturing cost. However, at higher speeds the fibers may lose their stretch capacity and become brittle. This can cause the fibers to break before they reach the desired percentage of elongation.

At a distance downstream of the first pair of rollers is the second pair of rollers. The second pair of rollers includes a first roller 62 and a second roller 64. The first and second rollers 62, and 64 respectively, can be arranged in close contact with each other to form a contraction point 66 therebetween. The plurality of linear fibers 44 emerging from the first pair of rollers is directed around a portion of the periphery of the first roller 62 through the contraction point 66 and around a portion of the periphery of the second roller 64. Point 66 of FIG. The shrinkage can be adjusted in such a way that little or no pressure is exerted on the fibers 44. At least one of the first and second rollers, 62 and 64 respectively, is a drive roller which is adjusted to rotate at a second surface speed. default The second predetermined speed is faster than the first predetermined speed. This difference in velocity caused the plurality of fibers 44 to be stretched in their length between the two pairs of rollers to form a plurality of linear, stretched fibers 68.

It should be noted that you can also use multiple > rollers or pairs .d t rollers to rotate at different speeds and preferably, increasing surface speeds.

Optionally, between the two pairs of rollers 56 and 58 and 60 and 62 respectively, is a heater 70. The heater 70 has the ability to heat a plurality of linear fibers 44 at an elevated temperature. The exact temperature will depend on the composition of the first and second components, 10 and 12 respectively, the diameter of the fibers 44, the amount of fibers 44 to be stretched, the speed of the fibers 44, etc.

Stretching the plurality of fibers 44 within the stretching unit 54 will cause the cross-sectional area of each of the linear fibers 44 to be reduced from about 5% to 90% in the cross-sectional area of the linear fibers 44 unrolled from the reel 46. Desirably, the cross-sectional area of each of the linear fibers 44 is reduced from about 10% to 60% of the cross-sectional area of the unrolled linear fibers 55 of the reel 46. More preferably, the cross-sectional area of each of the linear fibers 44 is reduced from about 20% to 50% of the cross-sectional area of the unwound linear fibers 44 of the reel 46.

The linear, continuous, stretched fibers 68 will have a relatively small cross-sectional diameter or area. Desirably, the diameter of the stretched linear fibers 68 will vary from about 5 microns to 50 microns. More preferably, the diameter of the stretched fibers 68 will vary from about 5 microns to 30 microns. More preferably, the diameter of the stretched linear fibers 68 will vary from about 10 microns to 20 microns.

It should be noted that the linear, stretched fibers 68 that leave the second pair of rollers 62 and 64 can be set with heat, if desired before being cut into discontinuous fibers.

Still with reference to Figure 3, after leaving the stretching unit 54, the plurality of drawn linear fibers 68 are cut or separated by a rotary cutter 72 having at least one blade 74 secured thereto. The rotary cutter 72 cooperates with an anvil roll 76 and the cutter 72 and the anvil roll 76 are arranged so that the linear, stretched fibers 68 pass between them. The rotary cutter 72 and the anvil roll 76 maintain the linear fiber 68 stretched in tension until it has been cut by the knife 74. It should be noted that other types of cutting mechanisms can be used, which are well known to people with ordinary skill in art. Also, it is possible to place a current cutter. under a pair of cooperating rollers to hold the fibers 68 stretched in a plurality of discontinuous fibers 68, each with a predetermined length. The plurality of stretched fibers 68 can be cut to a discontinuous length of about 5 millimeters to 500 millimeters. Desirably, the plurality of stretched fibers 68 can be cut to a discontinuous length of about 10 millimeters to 50 millimeters. More preferably, the plurality of stretched fibers 68 can be cut to a discontinuous length of about 12 millimeters to 25 millimeters. The plurality of interrupted discontinuous fibers 78 will initiate their relaxation. Relaxation allows the discontinuous fibers 78 to relax or contract into a plurality of three-dimensional coiled fibers 80. The rolled fibers will have a shorter length than the fiber 78 stretched cut. The '80 coiled fibers will have a length ranging from about 3 millimeters (mm) to about 50 mm. Desirably, the rolled fibers 80 will have a length ranging from about 5 mm to 25 mm. More preferably, the rolled fibers 80 will have a length ranging from about 5 mm to 15 mm. These rolled fibers 80 are collected in a funnel or container 82.

With reference to Figure 4, a portion of the discontinuous, three-dimensional fiber 80 is illustrated in the form of a helical coil or helix having a longitudinal central x-x axis. The term "three-dimensional fiber" refers to a fiber having a component x, y, and z that is formed by virtue of spirals and / or regular or irregularly spaced curves, the ends of which, the planes x, y and z form a geometric dotted point that define a greater volume than a linear fiber. The coiled, three-dimensional fibers 80 will have a generally helical configuration. The helical configuration may extend along the entire length L of each of the three-dimensional fibers 80 or may occur over a portion of the length of the three-dimensional fibers 80. Desirably, the rolled configuration extends over at least half the length of each of the three-dimensional fibers 80. More desirably, the coiled configuration extends from about 50% to 90% of the length of each of the three-dimensional fibers 80. More preferably, the coiled configuration extends from about 90% to 100% of each of the three-dimensional fibers 80. It should be noted that the spirals may be formed in the clockwise or counterclockwise directions along at least a portion of the length of the discontinuous, three-dimensional fibers 80. It should also be noted that the configuration in each spiral may vary along the length of each of the discontinuous, three-dimensional fibers 80.

Each of the discontinuous, three-dimensional fibers 80 has spirals circumscribing 360 degrees. The helical spirals may be continuous or non-continuous over a portion or the entire length of the discontinuous, three-dimensional fibers. Preferably, the discontinuous, three-dimensional fibers 80 will exhibit a continuous helical spiral. The discontinuous, three-dimensional fibers 80 differ from a Two-dimensional fiber in that the two-dimensional fiber has only two components, for example, a component wx "and a component w and"; a component "x" and "o" or a component "y" and "z" The discontinuous, three-dimensional fiber 80 has three components, a component "" ", a component" and "and a component" z ". Many folded fibers are two-dimensional fibers that are flat and extend only in two directions. Typically, a folded fiber is a fiber that is pressed or punctured into small loins or folds, regular. A folded fiber usually has a fold along its length.

The discontinuous, three-dimensional fiber 80 has a non-linear configuration when a helical spiral is formed. The discontinuous, three-dimensional fiber 80 also has an amplitude "A" that is measured perpendicular to a portion of its length L. The amplitude "A" of the discontinuous, three-dimensional fiber 80 may vary from about 10 microns to 5,000 microns. Desirably, the "" amplitude of discontinuous, three-dimensional fiber 80 ranges from about 30 microns to 1,000 microns. More preferably, the amplitude "A" of the discontinuous, three-dimensional fiber 80 may vary from about 50 microns to 500 microns. Fiber 80, three-dimensional also has a frequency "F" measured at two locations spaced 360 degrees between the adjacent helical spirals. The frequency "F" is used to denote the number of spirals or loops formed in each inch of the length of the wound fiber. The frequency "F" may vary from about 10 to about 1,000 spirals per inch. Desirably, the frequency "F" may vary from about 50 to 500 loops per inch. It should be noted that the amplitude "" A "and / or the frequency" F "may vary or remain constant over at least a portion of the length L, or over the entire length of the discontinuous, three-dimensional fiber 80. Desirably, the amplitude "A" and the frequency "F" will remain constant over most of the length L. The amplitude "A" of the discontinuous three-dimensional fiber 80 and the frequency "" F "of the helical spirals forming the discontinuous, three-dimensional fiber 80 affects the total reduction in the length of discontinuous, three-dimensional fiber 80 of its stretched condition.

It should be noted that the deformation properties of the first and second components, 10 and 12 respectively, will affect the configuration and size of the helical coils developed as the stretched fibers 78 are retracted into three-dimensional coiled fibers 80.

The first and second components, 10 and 12 respectively, adhere together in the spin pack 30 to form a plurality of continuous bicomponent fibers. The adhesion of the first component 10 with the second component 12 can be chemical, physical and / or mechanical. This ability of the first and second components, 10 and 12 respectively, to adhere to each other will prevent the division of the components 10 and 12 at a later time when one component retracts more than the other component. The first component 10 in the solid linear fiber 44 has an elongation of at least 50% of the deformation. The first component 10 has the ability to recover at least about 20% of the stretch deformation imparted thereto, with base, on its length after deformation. Desirably, the first component 10 in the solid, linear fiber 44 has the ability to recover at least about 50% of its stretch deformation. When the first component 10 has an elongation below at least about 50%, the recovery or relaxation energy may not be sufficient to activate the helical spiral of the discontinuous, three-dimensional fiber 80. The repetitive helical spirals in discontinuous, three-dimensional '80 fiber are more convenient. A greater elongation of at least about 50% for the first component 10 is desirable. For example, the elongation of at least about 100% is good, an elongation exceeding 300% is better and an elongation exceeding 400. % is even better.

The second component 12 in the linear, solid fiber 44 has a total deformation that includes a non-recoverable permanent strain value and a recoverable strain value. The irretrievable permanent deformation value in a solid state, as a result of stretching, plastic flexibility and / or extraction is at least about 40%. The recoverable deformation value is at least about 0.1%. A deformation higher than at least about 50% for the second component is desirable. A deformation of at least about 100% is good and a deformation exceeding 300% is even better. Plastic flexibility and stretching result in thinning of the second component 12. Stretching in a solid state means that the second component 12 is stretched below its melting temperature. When the total deformation of the second component 12 is below at least about 50%, the second component 12 will fail and break during the stretching process. Also, with low deformation, the second component 12 does not provide a sufficient level of permanent plastic flexibility and the desired thinning for the formation of repetitive helical coils in the discontinuous, three-dimensional fibers 80. Stretching should not occur at low temperatures because the fibers can become brittle and break. In the same way, the fibers should not stretch rapidly since this can cause the fibers to break before reaching the desired percentage of elongation.

The elongation percentage of the length of rolled, three-dimensional fiber 80 is defined as the change in percentage in length by which rolled, three-dimensional fiber 80 was wound before being straight or linear. The percentage of elongation can be expressed by the following formula: % E = 100 x (Li-L) / L t where:% E is the percentage of fiber elongation 80 discontinuous, three-dimensional; L is the retracted length of discontinuous, three-dimensional fiber 80; Li is the final length of discontinuous, three-dimensional fiber 80 once it is stretched in a straight or unwound configuration.

. The discontinuous, three-dimensional fiber 80 has the ability to subsequently stretch to at least 100% of its retracted length. With more convenience, the discontinuous, retracted fiber 80 can be stretched more than about 150% to about 900% of its retracted length. More preferably, discontinuous, three-dimensional fiber 80 can be stretched more than about 250% to 500% of its retracted length. More preferably, the discontinuous, three-dimensional fiber 80 can be stretched more than about 300% to 400% of its retracted length.

Discontinuous, three-dimensional fiber 80 exhibits elongation properties in at least one direction before the fiber becomes linear. The elongation is defined as the percentage of length at which the discontinuous, three-dimensional fiber 80 can be stretched before it becomes linear or straight. The direction of the elongation property of the discontinuous, three-dimensional fiber 80 is usually in the same direction as the linear fiber 44 was stretched. In other words, the direction in which the discontinuous, three-dimensional fiber 80 has the ability to elongate subsequently will be opposite to the direction of its retraction. It is possible that discontinuous, three-dimensional fiber 80 has elongation properties in two or more directions. For example, discontinuous, three-dimensional fiber 80 can be lengthened later in both directions, x and y.

Discontinuous, three-dimensional fiber 80 is obtained once the stretched fiber 78 is allowed to relax or retract. The discontinuous, three-dimensional fiber 80 has the ability to acquire its helical profile by the difference in the percentage Ri of recovery of the first component 10 compared to the recovery percentage of the second component 12. For example, since the first component 10 has a If the percentage Ri of recovery is higher than the percentage R2 of recovery of the second component 12, it is convenient that the first component 10 retract to a greater degree than the second component 12. However, both the first and second components, 10 and 12 respectively, the same proportion will be retracted or contracted, since they adhere or join physically, chemically or mechanically to each other. The combination of the volume percentage and the recovery percentage of the first and second components, 10 and 12 respectively, create a unique three-dimensional configuration of the fiber 80. Retraction or recovery of the first and second components, 10 and 12 respectively, establishes the twisting or rolling effect on discontinuous, three-dimensional fiber 80. The winding ratio obtained, as well as the shape and location of the winding, can be controlled by the selection of materials that are used to build the linear fiber. These three variables: the winding rate, the shape and the location of the winding, can also be controlled by the volume of each component, as well as the proportion in which the linear fiber 44 is stretched. The conditions of time and temperature under which the solid fibers 44 are stretched and allowed to retract can affect the final profile of the discontinuous, three-dimensional fiber 80.

The first component 10 has a recovery percentage Ri higher than the recovery rate R2 of the second component 12 and therefore the material from which the first component 10 is formed tends to be more viscous and elastic. For this reason, the material with the highest recovery percentage Ri is used to form the inner core while the material having the lowest recovery percentage R2 tends to be used to form the outer cover. As the first and second components, 10 and 12 respectively, attempt to retract from the stretched condition, the outer cover will retract and contract less. This means that the first component 10 will not have the capacity to completely retract a certain amount, of what it could on its own. This containment force creates the effect of helical spiral or twist in discontinuous, three-dimensional fiber 80 retracted. By varying the materials used to form the linear fiber 44 and by controlling the conditions at which it was stretched and then retracted, discontinuous shaped fibers 80 can be manufactured which will subsequently be elongated in a predetermined manner. This feature has been identified as extremely useful when constructing disposable absorbent articles. This feature also shows beneficial aspects in other articles.

The following Table 1 shows the recovery percentage of individual materials that have been stretched at varying percentages. The material forming each sample was separated from a thin sheet of a particular thickness in the form of a dumbbell or a bone. The bone sample had an initial length of 63 millimeters (mm) measured from a first elongated end to a second elongated end. In the middle of the two elongated and aligned opposite ends was a narrow section with a length of 18 mm and a width of 3 mm. The material was then placed in a tension tester and stretched at a rate of 5 inches per minute, in the machine direction of the material. This stretching caused the narrow section of the sample to lengthen. The force used to stretch the sample was then released and the sample allowed to retract or recover. The retracted length of the narrow section, known as the completed recovery length, was measured and recorded as a percentage of the stretched length. This information can be extrapolated that when this kind of material is combined with another material to form a linear fiber, the similar intervals of recovery or contraction can be known.

TABLE 1 In Table 1, the bone-shaped sample has a section 1? narrow, located between its first and second elongated ends. Each of the elongated ends of the bone-shaped sample was secured in a tension tester and a force was applied which caused the material to be stretched in the machine direction of the material, at a predetermined ratio at a specific temperature. When stretching the sample, the narrow section was stretched to a length 12. The length 12 is greater than the length 1? initial. The force exerted on the sample was then released and the sample allowed to retract, so that the narrow section was reduced to a length I3. The retracted length I3 is less than the stretched length I2, but it is greater than the initial li length. The percentage (R%) of recovery can be calculated with the following formula: % Recovery = [I2-I3] x 100 where: I2 is the stretched length of the narrow section of the sample; Y I3 is the retracted length of the narrow section of the sample.

It should be noted that the rolled fibers 80 can be mixed with other types of fibers, such as cellulose fibers, wood pulp fibers, other synthetic fibers, etc., and / or a superabsorbent to form a fabric. The fabric can be a fabric stretched to the air, a fabric formed by air, a fabric of conformation, a fabric laid wet, etc. The fabric can be used in different products. The fabric is especially useful when used in a disposable absorbent article, such as a baby diaper, a trainer brief, an incontinence garment, which includes a bearing, a pantyhose, a restrainable pant and pant, a sanitary tampon or tampon, a wet towel product, etc. The method of mixing such fibers and / or superabsorbent particles is known to those of ordinary skill in the art. The percentage of each kind of fiber used to form a fabric can vary to meet the particular needs. It should be noted that the superabsorbent material, preferably in the form of particles, can be mixed with one or more kinds of fibers to form an absorbent fabric. The fabric can also be stabilized and / or joined by using the different methods known to those of ordinary skill in the art.

A well-known limitation of bound and stabilized absorbent fabrics is that the superabsorbent material present in the fabric is restricted to swell to its full capacity. The use of three-dimensional fibers of this invention will allow the structure of the absorbent fabric containing the superabsorbent material to expand and adapt to the total limit at which the superabsorbent material can swell.

It should be noted that the rolled fibers 80 can be laminated to form a stretchable material, an elastic film or elastic fibers to form a thin, absorbent or non-absorbent material. This laminated material can be used as the body side cover or cover layer in a disposable absorbent article, such as a diaper, a training pant, an incontinence garment, sanitary napkin, etc. This laminated material can also be used in health care products, such as bandages, surgical gowns, gloves, etc.

Although the invention was described along with various specific embodiments, it should be understood that for those with ordinary skill in the art many alternatives, modifications and variations will be apparent by virtue of the foregoing description. Accordingly, this invention has the purpose of covering all these alternatives, modifications and variations that are within the spirit and scope of the appended claims.

Claims

R E I V I N D I C A C I O N S

1. A method for forming three-dimensional fibers, comprising the steps of: a) Extruding with unilaterally a first and a second component, said first component has a recovery percentage R and said second component has a recovery percentage i, where ¾ is greater than R2; b) directing said first and second components through a spin pack to form a plurality of continuous cast fibers each having a predetermined diameter; c) directing said plurality of melted fibers through a quench chamber to form a plurality of cooled fibers; d) directing said plurality of cooled fibers through a pull unit to form a plurality of said solid fibers each having a diameter smaller than that of said melted fibers; e) accumulating said plurality of solid fibers and stretching said fibers by at least about 50%; f) cutting said stretched fibers into a plurality of short fibers each t having a predetermined length; and g) allowing said short fibers to relax thereby forming fibers 'rolled up,. said first component of said wound fibers has a strong mutual adhesion for said second component of said wound fiber to avoid division.

2. The method as claimed in clause 1 characterized in that said rolled fibers are fibers of components.

3. The method as claimed in clause 1 characterized in that each of said wound fibers has a cross-sectional configuration of core / sheath.

4. The method as claimed in clause 1 characterized in that said first and second components are mechanically adhered to each other.

5. The method as claimed in clause 1 characterized in that the first and second components are chemically adhered to one another.

6. The method as claimed in clause 1 characterized in that the first and second components are physically adhered to each other.

7. The method as claimed in clause 1 characterized in that said solid fibers are heated before being stretched.

8. The method as claimed in clause 1 characterized in that said solid fibers are heated while being stretched.

9. The method as claimed in clause 1 characterized in that said plurality of stretched fibers are cut by a rotary cutter in predetermined lengths of from about 5 mm to about 500 mm.

10. A method for forming fibers of two-dimensional bicomponents, comprising the steps of: . a) extruding with first and second components, said first component | has a recovery percentage ¾ and said second component has a recovery percentage] ¾, where ¾ is greater than R2; b) directing said first and second components through a spin pack at a first speed to form a plurality of continuous melt fibers each having a predetermined diameter; c) directing said plurality of melted fibers through a cooling chamber to form a plurality of cooled fibers; d) directing said plurality of cooled fibers through a pulling unit at a second speed, said second speed being greater than said first speed, to form a plurality of solid fibers each having a diameter smaller than that of said melted fibers; e) accumulating said plurality of solid fibers and stretching said fibers by at least about 75 percent; f) cutting said stretched fibers into a plurality of short fibers each having a predetermined length; g) allowing said short fibers to relax thereby forming coiled fibers, said first component of said coiled fibers having a strong mutual adhesion for said second component of said coiled fiber to prevent division.

11. The method as claimed in clause 10 characterized in that each of said wound fibers has a predetermined length of from about 5 mm to about 50 mm.

12. The method as claimed in clause 11 characterized in that said wound fibers have a predetermined length of from about 5 mm to about 25 mm.

13. The method as claimed in clause 10 characterized in that said solid fibers are stretched by from about 50% to about 1,000% ..

14. The method as claimed in clause 10 characterized in that said coiled fibers have a spiral amplitude of from about 10 microns to about 5,000 microns.

15. The method as claimed in clause 10 characterized in that each of said wound fibers have a frequency of windings ranging from about 10 microns to about 1,000 rolls per inch.

16. The method as claimed in clause 10 characterized in that said second component is a polyolefin.

17. A method for forming three-dimensional bicomponent fibers, comprising the steps of a) extruding jointly a first and a second component, said first component has a recovery percentage R2 and said second component has a recovery percentage R2, where Ri is greater than R2; b) directing said first and second components through a spin pack at a first speed to form a plurality of continuous fused fibers each having a predetermined diameter; c) directing said plurality of melted fibers through a cooling chamber to form a plurality of cooled fibers; d) directing said plurality of cooled fibers through a pulling unit at a second speed, said second speed being greater than said first speed, to form a plurality of solid fibers each having a diameter smaller than that of said melted fibers; e) accumulating said plurality of solid fibers on a reel and cutting said plurality of solid fibers when said reel is filled; f) unrolling said plurality of solid fibers from said reel and heating said fibers to an elevated temperature; g) stretching said heated fibers by at least about 50 percent; h) cutting said stretched fibers into a plurality of short fibers each having a predetermined length; and i) allowing said short fibers to relax thereby forming coiled fibers, said first component of said coiled fibers having strong mutual adhesion for said second component of said coiled fiber to prevent division.

18. The method as claimed in clause 17 characterized in that said wound fibers have a helical configuration.

19. The method as claimed in clause 17 characterized in that each of said rolled fibers has a roll width of from about 10 microns to about 5,000 microns.

20. The method as claimed in clause 17 characterized each of said fibers are stretched from between about 50% to about 1,000%.

21. The method as claimed in clause 17 characterized in that each of said wound fibers has a roll frequency ranging from about 10 to about 1,000 rolls per inch.

22. The method as claimed in clause 21 characterized in that said wound fibers have a roll frequency ranging from about 25 to about 250 rolls per inch.

23. A fabric formed of said three-dimensional fibers as claimed in clause 1.

24. The fabric as claimed in clause 23 characterized in that the fabric is placed by air.

25. The fabric as claimed in clause 23, characterized in that said fabric is formed by air.

26. The fabric as claimed in clause 23 characterized in that said fabric is a coform fabric.

27. The fabric as claimed in clause 23 characterized in that said fabric is a wet laid fabric.

28. The fabric as claimed in clause 23 characterized in that said superabsorbent material is present in said fabric.

29. A fabric 'formed of' three-dimensional fibers as claimed in clause 17.

30. The fabric as claimed in clause 29 characterized in that the 'superabsorbent material is present in said fabric. SUMMARIZES A method for forming three-dimensional fibers together with a fabric formed of such fibers is described. The method includes the steps of extruding together a first component and a second component. The first component has a recovery percentage Ri and the second component has a recovery percentage R2, where Ri, is greater than R2. The first and second components are directed through a spin pack to form a plurality of continuous fused fibers. The molten fibers are then directed through a cooling chamber to form a plurality of continuous cooled fibers. The cooled fibers are then directed through a pull unit to form a plurality of continuous solid linear fibers. The solid fibers are then accumulated and stretched by at least about 50%. The plurality of drawn fibers are then cut and allowed to relax so that the plurality of three-dimensional coiled fibers is formed.