Composite elastic material

FIELD OF THE INVENTION

[0001] The present invention relates to a composite elastic material, uses of the composite elastic material and the method of making the composite elastic material.

BACKGROUND OF THE INVENTION

[0002] Composites of elastic and nonelastic materials have been made by bonding nonelastic materials to elastic materials in a manner that allows the entire composite material to stretch or elongate. These composites can be used in garment materials, pads, diapers, training pants and other personal care products where elasticity is needed.

[0003] In one such composite material, a nonelastic material is joined, for example pattern bonded, to an elastic sheet while the elastic sheet is in a stretched condition. These materials are often referred to as “stretch-bonded laminates.” When the elastic sheet is relaxed, the nonelastic material gathers between the locations where it is joined to the elastic sheet. The resulting composite elastic material is stretchable to the extent that the nonelastic material, gathered between the locations where the nonelastic and elastic materials are joined, allows the elastic sheet to elongate. An example of this type of composite material is disclosed by, for example, U.S. Pat. No. 4,720,415 to Vander Wielen et al. and U.S. Pat. No. 5,503,908 to Faass et al., both hereby incorporated by reference in their entirety.

[0004] In another stretched-bonded laminate described in U.S. Pat. No. 5,385,775, to Wright, which is hereby incorporated by reference in its entirety, the elastic layer contains an anisotropic elastic fibrous web having at least one layer of elastomeric meltblown fibers and at least one layer of substantially parallel rows of elastomeric filaments autogenously bonded to at least a portion of the elastomeric meltblown fibers. This elastic fibrous web is bonded to at least one gatherable layer joined at spaced apart locations to the anisotropic elastic fibrous web, so that the gatherable layer is gathered between the spaced-apart locations. The stretch-bonded laminate described in this patent has improved tenacity in one direction.

[0005] Hydraulic entangling is a process known in the art in which a high pressure liquid (usually water) entangles fibers or particles into a substrate. The entangling serves to “bond” or immobilize the fibers or particles in the substrate. Such a process and apparatus to accomplish the entanglement is described in U.S. Pat. No. 3,485,706 to Evans, which is hereby incorporated by reference in its entirety.

[0006] Further, it is known in the art to entangle nonelastic fibers into elastic filaments or an elastic substrate. In U.S. Pat. No. 4,775,579 to Hagy, which is hereby incorporated by reference in its entirety, the entangled material is prepared by forming a first layer of a web or net of an elastomeric material, stretching the elastomeric material, placing a layer of a nonelastic material on top of the web or net of the elastomeric material, subjecting the two layers to a hydraulic entangling process step and releasing the stretching to relax the elastomeric material. The resulting composite material is said to be usable in bandages, but suffers from the fact that the composite can be stretched to a point where “destructive elongation” occurs, resulting in a material that will no long recover, making unusable as a bandage material.

SUMMARY OF INVENTION

[0007] The present invention is directed to an elastic composite material having an elastic layer having a first side and a second side; at least one gatherable layer bonded to at least one of the first side and second side of the elastic layer; and a fibrous material entangled and intertwined with both the elastic layer and the gatherable layer. The resulting elastic composite provides a stretchable material which can conform to surfaces and has desirable properties of the fibrous material entangled and intertwined with both the elastic layer and the gatherable layer and does not suffer from the loss of the fibrous material from the stretchable substrate.

[0008] The elastic layer can be an elastomeric film, an elastomeric nonwoven web, a plurality of substantially continuous elastomeric filaments arranged in substantially parallel rows, or a laminate of an elastomeric nonwoven web and a plurality of substantially continuous elastomeric filaments arranged in substantially parallel rows. In addition, a gatherable layer, which can be a woven or nonwoven web, may be bonded to both sides of the elastic layer. Desirably, the gatherable layer is bonded to the elastic layer at spaced apart locations. The fibrous material entangled and intertwined imparts desirable properties to the elastic composite, such as, for example absorbency.

[0009] The present invention is also directed to a process of producing an elastic composite material of the present invention. The elastic composite may be prepared by a process including the steps of:

[0010] a. providing the elastic layer;

[0011] b. providing the gatherable layer;

[0012] c. applying a stretching force to the elastic layer to form a stretched elastic layer having a first side and a second side;

[0013] d. bonding the gatherable layer to the stretched elastic layer to at least the first side or the second side of the elastic layer to form a stretch-bonded laminate;

[0014] e. providing the fibrous material onto the gatherable layer of the stretch-bonded laminate;

[0015] f. entangling the fibrous material into the stretch bonded laminate; and

[0016] g. relaxing the stretching force.

[0017] In the present invention, the entangling of the fibrous material into the stretched-bonded laminate is desirable accomplished through hydraulic entangling.

[0018] The elastic composite has many utilities, especially in areas where a stretchable article with the properties of the fibrous material are desired. For example, the elastic composite may be used in applications such as bandages, durable wipes, durable mops, in personal care products, such as diapers and feminine napkins and/or agricultural products, such as a tree wrap for saplings or trees.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]
FIG. 1 shows a representative process for preparing a stretch-bonded laminate used in the present invention.

[0020]
FIG. 2 shows a representative process for preparing elastic composite of the present invention from a stretch-bonded laminate.

DEFINITIONS

[0021] As used herein, the term “comprising” is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps.

[0022] As used herein, the term “consisting essentially of” does not exclude the presence of additional materials which do not significantly affect the desired characteristics of a given composition or product. Exemplary materials of this sort would include, without limitation, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, particulates and materials added to enhance processability of the composition.

[0023] The term “elastic” is used herein to mean any material which, upon application of a biasing force, is stretchable in at least one direction, that is, elongatable at least about 50 percent (i.e., to a stretched, biased length which is at least about 150 percent of its relaxed unbiased length), and which, will recover at least 50 percent of its elongation upon release of the stretching, elongating force. A hypothetical example would be a 1.0 inch (2.54 cm) sample of a material which is elongatable to at least 1.50 inches (3.8 cm) and which, upon being elongated to 1.50 inches and released, will recover to a length of not more than 1.25 inches (3.13 cm) Many elastic materials may be elongated by much more than 50 percent (i.e., much more than 150 percent of their relaxed length), for example, elongated 100 percent or more, and many of these will recover to substantially their initial relaxed length, for example, to within about 105 percent of their original relaxed length, upon release of the stretching force.

[0024] The term “nonelastic” as used herein refers to any material which does not fall within the definition of “elastic,” above.

[0025] The terms “recover” and “recovery” as used herein refer to a contraction of a stretched material upon termination of a biasing force following stretching of the material by application of the biasing force. For example, if a material having a relaxed, unbiased length of 1.0 inch (2.54 cm) is elongated 50 percent by stretching to a length of 1.5 inches (3.8 cm) the material would be elongated 50 percent or 0.5 inch (1.27 cm) and would have a stretched length that is 150 percent of its relaxed length. If this exemplary stretched material contracted, that is recovered to a length of 1.1 inches (2.8 cm) after release of the biasing and stretching force, the material would have recovered 80 percent or 0.4 inch (1.0 cm) of its 0.5 inch (1.27 cm) elongation. Recovery may be expressed as

% Recovery = \frac{(maximum stretch length - final sample length)}{(maximum stretch length - initial sample length)} \times 100

[0026] The term “machine direction” as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a nonwoven fibrous web.

[0027] The term “cross-machine direction” as used herein refers to the direction which is perpendicular to the machine direction defined above.

[0028] The term “stretch-to-stop” as used herein refers to the ratio determined from the difference between the unextended dimension of a composite elastic material and the maximum extended dimension of a composite elastic material upon application of a specified tensioning force and dividing that difference by the unextended dimension of the composite elastic material. If the stretch-to-stop is expressed in percent, this ratio is multiplied by 100. For example, a composite elastic material having an unextended length of 5 inches (12.7 cm) and a maximum extended length of 10 inches (25.4 cm) upon applying a force of 2000 grams has a stretch-to-stop (at 2000 grams) of 100 percent. Stretch-to-stop may also be referred to as “maximum non-destructive elongation”. Unless specified otherwise, stretch-to-stop values are reported herein at a load of 2000 grams.

[0029] The term “tenacity” as used herein refers to the resistance to elongation of a composite elastic material which is provided by its elastic component. Tenacity is the tensile load of a composite elastic material at specified strain (i.e., elongation) for a given width material divided by the basis weight of that composite material's elastic component as measured at about the composite material's stretch-to-stop elongation. For example, tenacity of a composite elastic material is typically determined in one direction (e.g., machine direction) at about the composite material's stretch-to-stop elongation. Elastic materials having high values for tenacity are desirable in certain applications because less material is needed to provide a specified resistance to elongation than a low tenacity material. For a specified sample width, tenacity is reported in units of force divided by the units of basis weight of the elastic component. This provides a measure of force per unit area and is accomplished by reporting the thickness of the elastic component in terms of its basis weight rather than as an actual caliper measurement. For example, reported units may be grams-force (for a specific sample width)/grams per square meter.

[0030] As used herein, the term “nonwoven web” means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable, repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes such as, for example, meltblowing processes, spunbonding processes and bonded carded web processes.

[0031] As used herein, the term “autogenous bonding” means bonding provided by fusion and/or self-adhesion of fibers and/or filaments without an applied external adhesive or bonding agent. Autogenous bonding may be provided by contact between fibers and/or filaments while at least portions of the fibers and/or filaments are semi-molten or tacky. Autogenous bonding may also be provided by blending a tackifying resin with the thermoplastic polymers used to form the fibers and/or filaments. Fibers and/or filaments formed from such a blend can be adapted to self-bond with or without the application of pressure and/or heat. Solvents may also be used to cause fusion of fibers and filaments which remains after the solvent is removed.

[0032] As used herein, the term “fiber” includes both staple fibers, i.e., fibers which have a defined length between about 19 mm and about 60 mm, fibers longer than staple fiber but are not continuous, and continuous fibers, which are sometimes called “substantially continuous filaments” or simply “filaments”. The method in which the fiber is prepared will determine if the fiber is a staple fiber or a continuous filament.

[0033] As used herein, the term “microfibers” means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, or more particularly, microfibers may have an average diameter of from about 4 microns to about 40 microns.

[0034] As used herein, the term “meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, which is hereby incorporated by reference in its entirety. Meltblown fibers are microfibers, which may be continuous or discontinuous, and are generally smaller than 10 microns in average diameter The term “meltblown” is also intended to cover other processes in which a high velocity gas, (usually air) is used to aid in the formation of the filaments, such as melt spraying or centrifugal spinning. As used herein the term “spunbond web” refers to a nonwoven web prepared from small diameter fibers of molecularly oriented polymeric material. Spunbond fibers may be formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as in, for example, U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,542,615 to Dobo et al, and U.S. Pat. No. 5,382,400 to Pike et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface and are generally continuous. Spunbond fibers are often about 10 microns or greater in diameter. However, fine fiber spunbond webs (having an average fiber diameter less than about 10 microns) may be achieved by various methods including, but not limited to, those described in commonly assigned U.S. Pat. No. 6,200,669 to Marmon et al. and U.S. Pat. No. 5,759,926 to Pike et al., each is hereby incorporated by reference in its entirety.

[0035] As used herein, the phrase “Bonded carded web” or “BCW” refers to webs that are made from staple fibers which are sent through a combing or carding unit, which separates or breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. Such fibers are usually purchased in bales which are placed in an opener/blender or picker which separates the fibers prior to the carding unit. Once the web is formed, it then is bonded by one or more of several known bonding methods. One such bonding method is powder bonding, wherein a powdered adhesive is distributed through the web and then activated, usually by heating the web and adhesive with hot air. Another suitable bonding method is pattern bonding, wherein heated calender rolls or ultrasonic bonding equipment are used to bond the fibers together, usually in a localized bond pattern, though the web can be bonded across its entire surface if so desired. Another suitable and well-known bonding method, particularly when using bicomponent staple fibers, is through-air bonding.

[0036] “Airlaying” or “airlaid” is a well known process by which a fibrous nonwoven layer can be formed. In the airlaying process, bundles of small fibers having typical lengths ranging from about 3 to about 19 millimeters (mm) are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. The randomly deposited fibers then are bonded to one another using, for example, hot air or a spray adhesive.

[0037] As used herein, the term “polymer” generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.

[0038] As used herein, the term “superabsorbent” refers to absorbent materials capable of absorbing at least 10 grams of aqueous liquid (e.g. distilled water per gram of absorbent material) while immersed in the liquid for 4 hours and holding substantially all of the absorbed liquid while under a compression force of up to about 1.5 psi.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention provides an elastic composite material having an elastic layer with a first side and a second side; at least one gatherable layer bonded to at least one of the first side and second side of the elastic layer; and a fibrous material entangled and intertwined with both the elastic layer and the gatherable layer. The resulting elastic composite provides a stretchable material which can conform to surfaces and has desirable properties of the fibrous material entangled and intertwined with the elastic layer and does not suffer from the loss of the fibrous material from the stretchable substrate.

[0040] A variety of materials may be employed as the elastic layer. The elastic layer can be an elastomeric film, an elastomeric nonwoven web, a plurality of substantially continuous elastomeric filaments arranged in substantially parallel rows, or a laminate of an elastomeric nonwoven web and a plurality of substantially continuous elastomeric filaments arranged in substantially parallel rows.

[0041] Desirably, the elastic layer contains a meltblown nonwoven web prepared from an elastomeric polymer such as, for example, elastomeric polyesters, elastomeric polyurethanes, elastomeric polyamides, elastomeric copolymers of ethylene and at least one vinyl monomer, and elastomeric A-B-A′ block copolymers wherein A and A′ are the same or different thermoplastic polymer, and wherein B is an elastomeric polymer block. The elastomeric polymer may be blended with a processing aid.

[0042] For example, the elastomeric meltblown fibers may be made from elastomeric block copolymers. Exemplary elastomeric block copolymers may have the general formula A-B-A′ where A and A′ are each a thermoplastic polymer endblock which contains a styrenic moiety such as a poly (vinyl arene) and where B is an elastomeric polymer midblock such as a conjugated diene or a lower alkene polymer. The block copolymers may be, for example, (polystyrene/poly(ethylene-butylene)/polystyrene) block copolymers available from the Kraton Polymers, under the trademark KRATON® G. One such block copolymer may be, for example, KRATON® G-1657.

[0043] Other exemplary elastomeric materials which may be used include polyurethane elastomeric materials such as, for example, those available under the trademark ESTANE from Noveon., polyamide elastomeric materials such as, for example, those available under the trademark PEBAX from Atofina Chemicals, and polyester elastomeric materials such as, for example, those available under the trade designation Hytrel from E.I. DuPont De Nemours & Company. Formation of elastomeric meltblown fibers from polyester elastic materials is disclosed in, for example, U.S. Pat. No. 4,741,949 to Morman et al., hereby incorporated by reference. Useful elastomeric polymers also include, for example, elastic copolymers of ethylene and at least one vinyl monomer such as, for example, vinyl acetates, unsaturated aliphatic monocarboxylic acids, and esters of such monocarboxylic acids. The elastic copolymers and formation of elastomeric meltblown fibers from those elastic copolymers are disclosed in, for example, U.S. Pat. No. 4,803,117 to Daponte, hereby incorporated by reference.

[0044] Processing aids may be added to the elastomeric polymer. For example, a polyolefin may be blended with the elastomeric polymer (e.g., the elastomeric block copolymer) to improve the processability of the composition. The polyolefin must be one which, when so blended and subjected to an appropriate combination of elevated pressure and elevated temperature conditions, is extrudable, in blended form, with the elastomeric polymer. Useful blending polyolefin materials include, for example, polyethylene, polypropylene and polybutene, including ethylene copolymers, propylene copolymers and butene copolymers. Extrudable blends of elastomeric polymers and polyolefins are disclosed in, for example, previously referenced U.S. Pat. No. 4,663,220.

[0045] Desirably, the elastomeric meltblown fibers should have some tackiness or adhesiveness to enhance autogenous bonding. For example, the elastomeric polymer itself may be tacky when formed into fibers or, alternatively, a compatible tackifying resin may be added to the extrudable elastomeric compositions described above to provide tackified elastomeric fibers that autogenously bond. In regard to the tackifying resins and tackified extrudable elastomeric compositions, note the resins and compositions as disclosed in U.S. Pat. No. 4,787,699, hereby incorporated by reference.

[0046] Any tackifier resin can be used which is compatible with the elastomeric polymer and can withstand the high processing (e.g., extrusion) temperatures. If the elastomeric polymer (e.g., elastomeric block copolymer) is blended with processing aids such as, for example, polyolefins or extending oils, the tackifier resin should also be compatible with those processing aids. Generally, hydrogenated hydrocarbon resins are preferred tackifying resins, because of their better temperature stability. REGALREZ® and ARKON® P series tackifiers are examples of hydrogenated hydrocarbon resins. ZONATAK®501 lite tackifier resin is an example of a terpene hydrocarbon. REGALREZ® hydrocarbon resins are available from Eastman Chemical Company. ARKON® P series resins are available from Arakawa Chemical (U.S.A.) Incorporated. Of course, the present invention is not limited to use of such three tackifying resins, and other tackifying resins which are compatible with the other components of the composition and can withstand the high processing temperatures, can also be used.

[0047] Typically, the blend used to form the elastomeric fibers include, for example, from about 40 to about 80 percent by weight elastomeric polymer, from about 5 to about 40 percent polyolefin and from about 5 to about 40 percent resin tackifier. For example, a particularly useful composition included, by weight, about 61 to about 65 percent KRATON® G-1657, elastomer about 17 to about 23 percent polyethylene NA 601, and about 15 to about 20 percent REGALREZ® 1126 tackifying resin.

[0048] The elastomeric nonwoven web may also include a substantially homogenous mixture of meltblown fibers and other fibrous materials and/or particulates. Exemplary materials and processes are disclosed in, for example, U.S. Pat. Nos. 4,209,563 and 4,741,949.

[0049] In one aspect of the present invention, the elastic layer is an anisotropic elastic fibrous web containing at least one layer of elastomeric meltblown fibers and at least one layer of substantially parallel rows of elastomeric filaments. The substantially parallel rows of elastomeric filaments are autogenously bonded to at least a portion of the meltblown fibers. This autogenous bonding may take place, for example, by forming molten elastomeric filaments directly on a layer of meltblown fibers. Likewise, a layer of meltblown fibers may be formed directly on a layer of substantially parallel rows of elastomeric filaments to provide the desired autogenous bonding.

[0050] When the elastic layer contains at least two layers of materials, at least one layer is a layer of elastomeric meltblown fibers and at least one other layer is a layer containing substantially parallel rows of elastomeric filaments autogenously bonded to at least a portion of the elastomeric meltblown fibers. These elastomeric filaments have an average diameter ranging from about 40 to about 750 microns and extend along length (i.e. machine direction) of the fibrous web to improve the tenacity of the fibrous web in that direction.

[0051] Desirably, the elastomeric filaments may have an average diameter in the range from about 50 to about 500 microns, for example, from about 100 to about 200 microns. These elastomeric filaments extend along length (i.e. machine direction) of the fibrous web so that the tenacity of the elastic fibrous web is greater in that direction than the tenacity of a substantially nonwoven web without the continuous filaments of about the same basis weight. For example, the tenacity of the elastic fibrous web with the continuous filaments may be about 20 to about 90 percent greater in the machine direction than the tenacity of a substantially nonwoven web of about the same basis weight containing only elastomeric meltblown fibers.

[0052] Typically, the elastic fibrous layer will contain at least about 20 percent, by weight, of continuous elastomeric filaments. For example, the elastic fibrous web may contain from about 20 percent to about 80 percent, by weight, of the elastomeric filaments. Desirably, the continuous elastomeric filaments will constitute from about 40 to about 60 percent, by weight, of the elastic fibrous layer. The elastic layer may also be composed of only of the continuous filaments.

[0053] The elastomers used to produce the meltblown filaments may also be used to form the continuous elastomeric filaments. The meltblown fibers and the continuous filaments may be prepared from the same elastomeric material or from different elastomeric materials.

[0054] The gatherable layer, or layers if two gatherable layers are present in the elastic composite, may be a woven, knit material or a nonwoven web from a thermoplastic polymer. By selecting a woven, knit of nonwoven webs of thermoplastic polymers, the gatherable may be easily bonded to the elastic layer. Desirably, the gatherable layer can be a nonwoven web of fibers, such as, for example, a web of spunbond fibers, a web of meltblown fibers, a bonded carded web of fibers, a multilayer material including at least one of a spunbond layer, a meltblown layer and/or a bonded carded web. Optionally, the gatherable layer can be a composite material composed of a mixture of fibers and one or more other materials such as, for example, wood pulp, staple fibers, particulates or super-absorbent materials. Medicinal materials may be mixed with the fibrous materials of the gatherable layer. Such mixtures may be formed by adding fibers and/or particulates to the gas stream in which meltblown fibers are carried so that an intimate entangled commingling of meltblown fibers and other materials, e.g., wood pulp, staple fibers and particulates such as, for example, hydrocolloid (hydrogel) particulates commonly referred to as superabsorbent materials, occurs prior to collection of the meltblown fibers upon a collecting device to form a coherent web of randomly dispersed meltblown fibers and other materials such as disclosed in U.S. Pat. No. 4,100,324, the disclosure of which is hereby incorporated by reference. In order to provide strength to the stretch-bonded laminate, desirably the gatherable layer contains a spunbond nonwoven web. The gatherable layer may also be a multilayer material having two of more of the above mentioned gatherable layer laminated together. For example, at least one layer of a spunbond web may be joined to at least one layer of meltblown web, bonded carded web or other suitable material.

[0055] In the practice of the present invention, the gatherable layer may be joined to one side of the elastic layer or to both sides of the elastic layer. Desirably, the gatherable layer is joined to both sides of the elastic material. The gatherable layer or layers are joined to the elastic layer by any suitable means, such as, for example, thermal bonding or ultrasonic bonding, which will soften at least portions of at least one of the materials, usually the a material of the elastic layer, the elastomeric materials used for elastic layer have a lower softening point than the components of the gatherable layers. Joining may be produced by applying heat and/or pressure to the overlaid elastic layer and the gatherable layer or layers by heating these portions (or the overlaid layer) to at least the softening temperature of the material with the lowest softening temperature to form a reasonably strong and permanent bond between the re-solidified softened portions of the elastic layer and the gatherable layers. It is desirable that the gatherable layer (or layers) is bonded to the elastic layer at spaced apart locations, so that the gatherable layer will pucker when the elastic layer is in a relaxed condition.

[0056] The bonder roller arrangement may be a smooth anvil roller and a patterned calender roller, such as, for example, a pin embossing roller arranged with a smooth anvil roller. One or both of the smooth anvil roller and the calender roller may be heated and the pressure between these two rollers may be adjusted by well-known means to provide the desired temperature, if any, and bonding pressure to join the gatherable layers to the elastic fibrous web. As can be appreciated, the bonding between the gatherable layers and the elastic sheet is a point bonding. Various bonding patterns can be used, depending upon the desired tactile properties of the final composite laminate material. When the gatherable layer is a material such as, for example, spunbond polypropylene, the bonding can be performed at temperatures as low as 60° F. A range of temperatures for the calender rolls during bonding between a gatherable layer such as, for example, spunbond polypropylene and an elastic sheet is 60° to 180° F.

[0057] With regard to thermal bonding, one skilled in the art will appreciate that the temperature to which the materials, or at least the bond sites thereof, are heated for heat bonding will depend not only on the temperature of the heated roll(s) or other heat sources but on the residence time of the materials on the heated surfaces, the compositions of the materials, the basis weights of the materials and their specific heats and thermal conductivities. However, for a given combination of materials, and in view of the herein contained disclosure the processing conditions necessary to achieve satisfactory bonding can be readily determined by one of skill in the art.

[0058] The fibrous material which is entangled with the gatherable layer and the elastic layer of the present invention may include absorbent fibers or non-absorbent fibers. This material may generally be made up of fibers such as polyester fibers, polyamide fibers, cellulosic derived fibers such as, for example, rayon fibers and wood pulp fibers, multi-component fibers such as, for example, sheath-core multi-component fibers, natural fibers such as silk fibers, wool fibers or cotton fibers or electrically conductive fibers or blends of two or more of such secondary fibers. Other types of fibrous material such as, for example, polyethylene fibers and polypropylene fibers, as well as blends of two or more of other types of fibrous material may be utilized. The fibers may be microfibers, i.e. fibers having a fiber diameter less than 75 microns or the secondary fibers may be macrofibers having an average diameter of from about 75 microns to about 1,000 microns.

[0059] The selection of the fibrous material will determine the properties of the resulting the resulting composite. For example, the absorbency of the composite material can be improved by using an absorbent material as the fibrous material. In the case were absorbency is not necessary or not desired, non-absorbent material may be selected as the secondary material.

[0060] The absorbent materials useful in the present invention include absorbent fibers. Examples of the absorbent material include, but are not limited to, fibrous organic materials such as woody or non-woody pulp from cotton, rayon, recycled paper, pulp fluff, inorganic absorbent materials, treated polymeric staple fibers and so forth. Desirably, although not required, the absorbent material is pulp.

[0061] The pulp fibers may be any high-average fiber length pulp, low-average fiber length pulp, or mixtures of the same. Preferred pulp fibers include cellulose fibers. The term “high average fiber length pulp” refers to pulp that contains a relatively small amount of short fibers and non-fiber particles. High fiber length pulps typically have an average fiber length greater than about 1.5 mm, preferably about 1.5-6 mm. Sources generally include non-secondary (virgin) fibers as well as secondary fiber pulp which has been screened. The term “low average fiber length pulp” refers to pulp that contains a significant amount of short fibers and non-fiber particles. Low average fiber length pulps typically have an average fiber length less than about 1.5 mm.

[0062] Examples of high average fiber length wood pulps include those available from Georgia-Pacific under the trade designations Golden Isles 4821 and 4824. The low average fiber length pulps may include certain virgin hardwood pulp and secondary (i.e., recycled) fiber pulp from sources including newsprint, reclaimed paperboard, and office waste. Mixtures of high average fiber length and low average fiber length pulps may contain a predominance of low average fiber length pulps. For example, mixtures may contain more than about 50% by weight low-average fiber length pulp and less than about 50% by weight high-average fiber length pulp. One exemplary mixture contains about 75% by weight low-average fiber length pulp and about 25% by weight high-average fiber length pulp.

[0063] The pulp fibers may be unrefined or may be beaten to various degrees of refinement. Crosslinking agents and/or hydrating agents may also be added to the pulp mixture. Debonding agents may be added to reduce the degree of hydrogen bonding if a very open or loose nonwoven pulp fiber web is desired. Exemplary debonding agents are available from the Quaker Oats Chemical Company, Conshohocken, Pa., under the trade designation Quaker 2028 and Berocell 509ha made by Akzo Nobel, Inc. Marietta, Ga. The addition of certain debonding agents in the amount of, for example, 1-4% by weight of the pulp fibers may be added to the pulp fibers. The debonding agents act as lubricants or friction reducers. Debonded pulp fibers are commercially available from Weyerhaeuser Corp. under the designation NB 405.

[0064] In addition, non-absorbent fibrous material can be incorporated into the stretch-bonded laminate, depending on the end use of composite material. For example, in end uses where absorbency is not an issue, non-absorbent secondary materials may be used. Examples of the fibers include, for example, staple fibers of untreated thermoplastic polymers, such as polyolefins and the like.

[0065] The elastic composite of the present may be prepared by a process including the steps of providing the elastic layer; providing the gatherable layer; applying a stretching force to the elastic layer to form a stretched elastic layer having a first side and a second side; bonding the gatherable layer to the stretched elastic layer to at least the first side or the second side of the elastic layer to form a stretch bonded laminate; providing the fibrous material onto the gatherable layer of the stretch bonded laminate; entangling the fibrous material into the stretch bonded laminate; and relaxing the stretching force. Although not necessary, the stretch-bonded laminate may be prepared on a separate line and transported to the entangling line.

[0066] Referring now to the drawings wherein like reference numerals represent the same or equivalent structure and, in particular, to FIG. 1 of the drawings there is schematically illustrated a process 10 for forming a stretch-bonded laminate which includes an elastic web 12 and two gatherable layers 24 and 26. The elastic layer 12 is unwound from a supply roll 14 and travels in the direction indicated by the arrow associated therewith as the supply roll 14 rotates in the direction of the arrows associated therewith. The elastic layer 12 passes through a nip 16 of the S-roll arrangement 18 formed by the stack rollers 20 and 22.

[0067] The elastic web 12 may also be formed in-line in a continuous process, using a known process in the art, and passed directly through the nip 16 without first being stored on a supply roll. A first gatherable layer 24 is unwound from a supply roll 26 and travels in the direction indicated by the arrow associated therewith as the supply roll 26 rotates in the direction of the arrows associated therewith. Optionally, a second gatherable layer 28 is unwound from a second supply roll 30 and travels in the direction indicated by the arrow associated therewith as the supply roll 30 rotates in the direction of the arrows associated therewith. The first gatherable layer 24 and second gatherable layer 28 pass through the nip 32 of the bonder roller arrangement 34 formed by the bonder rollers 36 and 38. The first gatherable layer 24 and/or the second gatherable layer 28 may be formed by extrusion processes such as, for example, meltblowing processes, spunbonding processes and passed directly through the nip 32 without first being stored on a supply roll. Both the elastic layer and the gatherable layers may be formed in-line without the need to first store the layers on a supply roll.

[0068] The elastic layer web 12 passes through the nip 16 of the S-roll arrangement 18 in a reverse-S path as indicated by the rotation direction arrows associated with the stack rollers 20 and 22. From the S-roll arrangement 18, the elastic layer web 12 passes through the pressure nip 32 formed by a bonder roller arrangement 34. Additional S-roll arrangements (not shown) may be introduced between the S-roll arrangement and the bonder roller arrangement to stabilize the stretched material and to control the amount of stretching. Because the peripheral linear speed of the rollers of the S-roll arrangement 18 is controlled to be less than the peripheral linear speed of the rollers of the bonder roller arrangement 34, the elastic layer web 12 is tensioned between the S-roll arrangement 18 and the pressure nip of the bonder roll arrangement 32. By adjusting the difference in the speeds of the rollers, the elastic layer web 12 is tensioned so that it stretches a desired amount and is maintained in such stretched condition while the first gatherable layer 24 and second gatherable layer 28 is joined to the anisotropic elastic fibrous web 12 during their passage through the bonder roller arrangement 34 to form a composite elastic material 40.

[0069] The composite elastic material 40 immediately relaxes upon release of the tensioning force provided by the S-roll arrangement 18 and the bonder roll arrangement 34, whereby the first gatherable layer 24 and the second gatherable layer 28 are gathered in the composite elastic material 40. The composite elastic material 40 is then wound up on a winder 42. Processes of making composite elastic materials of this type are described in, for example, U.S. Pat. No. 4,720,415, the disclosure of which is hereby incorporated by reference.

[0070] With regard to bonding, one or both of the bonder rolls 36 and/or 38 may be heated. Both rolls may have a bond pattern or one roll may have a bond pattern and the other roll will have a smooth surface and act as an anvil-type roll. As is noted above, one skilled in the art will appreciate that the temperature to which the materials, or at least the bond sites thereof, are heated for thermal bonding will depend not only on the temperature of the heated roll(s) or other heat sources but on the residence time of the materials on the heated surfaces and the pressure exerted by these rolls, the compositions of the materials, the basis weights of the materials and their specific heats and thermal conductivities. However, for a given combination of materials, and in view of the herein contained disclosure the processing conditions necessary to achieve satisfactory bonding can be readily determined by one of skill in the art.

[0071] Conventional drive means and other conventional devices which may be utilized in conjunction with the apparatus of FIG. 1 are well known and, for purposes of clarity, have not been illustrated in the schematic view of FIG. 1.

[0072] Once the stretch-bonded laminate is formed, the fibrous material to be entangled with the stretch-bonded laminate is contacted with the stretch-bonded laminate. Any method known in the art use to entangle a fibrous material with a substrate can be used. Of the known methods, desirably hydraulic entangling is used. In hydraulic entangling, the jetting of a plurality of high pressure liquid streams towards the material is used so that the material is intertwined with both the elastic layer and the gatherable layer.

[0073] An exemplary hydraulic entangling process is shown in FIG. 2. In FIG. 2, an embodiment of the present invention for hydraulically entangling a fibrous material with the stretch-bonded laminate is illustrated. As shown, a fibrous slurry containing fibrous material is conveyed to a conventional papermaking headbox 112 where it is deposited via a sluice 114 onto a conventional forming fabric or surface 116. The suspension of fibrous material may have any consistency that is typically used in conventional papermaking processes. For example, the suspension may contain from about 0.01 to about 1.5 percent by weight fibrous material suspended in water. Water is then removed, using a known technique, such as a suction box, from the suspension of fibrous material to form a uniform layer of the fibrous material 118.

[0074] The stretch-bonded laminate 120 is also unwound from a supply roll 122 and travels in the direction indicated by the arrow associated therewith as the supply roll 122 rotates in the direction of the arrows associated therewith. The stretch-bonded laminate 120 passes through a nip 124 of an S-roll arrangement 126 formed by the stack rollers 128 and 130 which causes the stretched-bonded laminate to be stretched in the machine direction. The guide rollers 131 help maintain the tension of the stretched stretch-bonded laminate 120. In the stretched state, the stretch-bonded laminate 120 is then placed upon a foraminous entangling surface 132 of a conventional hydraulic entangling machine where the cellulosic fibrous layer 118 is then laid on the stretch-bonded laminate 120. Although not required, it is typically desired that the fibrous layer 118 be between the stretch-bonded laminate 120 and the hydraulic entangling manifolds 134. The fibrous layer 118 and stretch-bonded laminate 120 pass under one or more hydraulic entangling manifolds 134 and are treated with jets of fluid to entangle the fibrous material with the fibers of the gatherable layer and the elastic layer of the stretch-bonded laminate 120. The jets of fluid also drive fibrous material into the stretch-bonded laminate 120 to form the composite fabric 136.

[0075] Alternatively, hydraulic entangling may take place while the fibrous layer 118 and stretch-bonded laminate 120 are on the same foraminous screen (e.g., mesh fabric) that the wet-laying took place. The present invention also contemplates superposing a dried fibrous sheet on a nonwoven web, rehydrating the dried sheet to a specified consistency and then subjecting the rehydrated sheet to hydraulic entangling. The hydraulic entangling may take place while the fibrous layer 118 is highly saturated with water. For example, the fibrous layer 118 may contain up to about 90% by weight water just before hydraulic entangling. Alternatively, the fibrous layer 118 may be an air-laid or dry-laid layer.

[0076] Hydraulic entangling may be accomplished utilizing conventional hydraulic entangling equipment such as described in, for example, in U.S. Pat. No. 3,485,706 to Evans, which is incorporated herein in its entirety by reference. Hydraulic entangling may be carried out with any appropriate working fluid such as, for example, water. The working fluid flows through a manifold that evenly distributes the fluid to a series of individual holes or orifices. These holes or orifices may be from about 0.003 to about 0.015 inch in diameter and may be arranged in one or more rows with any number of orifices, e.g., 30-100 per inch, in each row. For example, a manifold produced by Honeycomb Systems Incorporated of Biddeford, Me., containing a strip having 0.007-inch diameter orifices, 130 holes per inch, and 1 row of holes may be utilized. However, it should also be understood that many other manifold configurations and combinations may be used. For example, a single manifold may be used or several manifolds may be arranged in succession.

[0077] Fluid can impact the fibrous material of the fibrous layer 118 and the stretched stretch-bonded laminate 120, which are supported by a foraminous surface, such as a single plane mesh having a mesh size of from about 40×40 to about 100×100. The foraminous surface may also be a multi-ply mesh having a mesh size from about 50×50 to about 200×200. As is typical in many water jet treatment processes, vacuum slots 138 may be located directly beneath the hydro-needling manifolds or beneath the foraminous entangling surface 132 downstream of the entangling manifold so that excess water is withdrawn from the hydraulically entangled composite material 136.

[0078] Although not held to any particular theory of operation, it is believed that the columnar jets of working fluid that directly impact cellulosic fibers 118 laying on the stretch-bonded laminate 120 work to drive those fibers into and partially through the matrix or network of fibers in the stretch-bonded laminate 120. When the fluid jets and cellulosic fibers 18 interact with a stretch-bonded laminate 120, the cellulosic fibers 118 are also entangled with fibers of the nonwoven web 120 and with each other. To achieve the desired entangling of the fibers, it is typically desired that hydroentangling be performed using water pressures from about 100 to 3000 psig, and in some embodiments from about 1200 to 2000 psig. When processed at the upper ranges of the described pressures, the composite fabric 136 may be processed at speeds of up to about 1000 feet per minute (fpm).

[0079] The pressure of the jets in the entangling process is typically at least about 100 psig because lower pressures often do not generate the desired degree of entanglement. However, it should be understood that adequate entanglement may be achieved at substantially lower water pressures. In addition, greater entanglement may be achieved, in part, by subjecting the fibers to the entangling process two or more times. Thus, it may be desirable that the web be subjected to at least one run under the entangling apparatus, wherein the water jets are directed to the first side and an additional run wherein the water jets are directed to the opposite side of the web.

[0080] After the fluid jet treatment, the resulting composite fabric 136, the stretched bonded laminate is released from its stretched condition and may then be transferred to a non-compressive drying operation. A differential speed pickup roll 140 may be used to transfer the material from the hydraulic needling belt to a non-compressive drying operation. Alternatively, conventional vacuum-type pickups and transfer fabrics may be used. If desired, the composite fabric 136 may be wet-creped before being transferred to the drying operation. Non-compressive drying of the fabric 136 may be accomplished utilizing a conventional rotary drum through-air drying apparatus 142. The through-dryer 142 may be an outer rotatable cylinder 144 with perforations 146 in combination with an outer hood 148 for receiving hot air blown through the perforations 146. A through-dryer belt 150 carries the composite fabric 136 over the upper portion of the through-dryer outer cylinder 140. The heated air forced through the perforations 146 in the outer cylinder 144 of the through-dryer 142 removes water from the composite fabric 136. The temperature of the air forced through the composite fabric 136 by the through-dryer 142 may range from about 200° F. to about 500° F. Other useful through-drying methods and apparatus may be found in, for example, U.S. Pat. No. 2,666,369 to Niks and U.S. Pat. No. 3,821,068 to Shaw, which are incorporated herein in their entirety by reference thereto for all purposes.

[0081] The resulting composite material exhibits durability, texture, elasticity, absorbency, is low linting, has high strength and a durable wet texture. These properties make the composite material in applications were these properties are needed or desired, such as, for example, in wet and dry wipe applications, bandages, absorbent bandages, floor mops, personal care products such as diapers, training pants and feminine care products, agricultural products, such as a tree wrap for saplings or trees, or sorbents.

[0082] One particularly notable use of the composite is in the area of bandages. When used as a bandage material, it is usually desirable to have the bandage to be self adhesive. In order to make the bandage self adhesive, a coating of a self-adhesive material is added to at least a portion of at least one exterior surface of the elastic composite material so that the peel strength of the self-adhesive material is less than the peel strength of the layers which bind the elastic composite material. It is very desirable that the peel strength of the self-adhesive material be less than the peel strength which binds the elastic composite material to prevent delamination (i.e., separation of the layers) of the elastic composite material.

[0083] For example, the peel strength of the self-adhesive material may be at least about 5 percent less than the peel strength which binds the elastic composite material. As another example, the peel strength of the self-adhesive material may be from about 10 to about 98 percent less than the peel strength which binds the elastic composite material. As a further example, the peel strength of the self-adhesive material may be from about 20 to about 95 percent less than the peel strength which binds the elastic composite material. Desirably, the peel strength of the self-adhesive material will be from about 0.1 to about 1.0 pound per inch. For example, the peel strength of the self-adhesive material may be from about 0.3 to about 0.5 pound per inch. Desirably, the amount of force required to unwind a roll of the self-adhesive material will be from about 0.3 to about 2.0 pounds per inch. For example, the amount of force required to unwind a roll of the self-adhesive material may be from about 0.5 to about 1.2 pounds per inch.

[0084] The coating of self-adhesive material may be located on the gatherable material. In some embodiments, the coating of self-adhesive material may be located only on raised portions of the gathers present in the gatherable material. Where the composite material is composed of one layer of gatherable material and a layer of an elastomeric fibrous web, the coating of self-adhesive material can be located on the elastomeric fibrous web.

[0085] While it is contemplated that the self-adhesive material may be an organic solvent based adhesive or water based adhesive (e.g., latex adhesive) that can be printed, brushed or sprayed onto the elastic composite material, it is desirable that the coating of self adhesive material be in the form of a randomly scattered network of hot-melt adhesive filaments and/or fibers produced by conventional hot-melt adhesive spray equipment. The coating of hot-melt self-adhesive material may also desirably be applied in patterns such as, for example, semi-cycloidal patterns. For example, a self-adhesive material such as a hot-melt self adhesive material may be applied to a composite elastic material as generally described by U.S. Pat. No. 4,949,668 to Heindel, et al., issued Aug. 21, 1990, which is hereby incorporated by reference. Desirably, the hot-melt adhesive coating should be applied while the stretch-bonded laminate material is under a relatively small amount of tension. For example, the hot-melt adhesive coating can be applied while the elastic composite material is under only enough tension needed to have the material travel through the adhesive application process.

[0086] The coating of self-adhesive material may be a coating of any suitable conventional commercially available hot-melt adhesive such as, for example, hot melt adhesives which may contain a blend of thermoplastic polymers (e.g., thermoplastic polyolefins), adhesive resins, and waxes.

[0087] Exemplary hot-melt self-adhesive materials which may be used include auto-adhesive 6631-117-1 and auto-adhesive 6631-114-4 available from the National Starch & Chemical Company, Adhesives Division, Bridgewater, N.J. Other self-adhesive materials may be, for example, Hot Melt Adhesive H-9140 available from Findley Adhesives, Incorporated, Wauwatosa, Wis. These self-adhesive materials may be blended with other materials such as, for example antioxidants, stabilizers, surfactants, flow promoters, particulates and materials added to enhance processability of the composition.

EXAMPLE

[0088] The elastic layer of the composite is prepared in accordance with the Example of U.S. Pat. No. 5,385,775. A four-bank meltblowing process in which each bank was a conventional meltblown fiber forming apparatus was setup to extrude an elastomeric composition which contained about 63 percent, by weight, KRATON® G-1657, about 17 percent, by weight, polyethylene NA 601, and about 20 percent, by weight, REGALREZ® 1126. Meltblowing bank 1 was set-up to produce meltblown fibers; banks 2 and 3 were set-up to produce continuous filaments; and bank 4 was set-up to produce meltblown fibers. Each bank contained an extrusion tip having 0.016 inch diameter holes spaced at a density of about 30 capillary per lineal inch. The polymer was extruded from the first bank at a rate of about 0.58 grams per capillary per minute (about 2.3 pounds per liner inch per hour) at a height of about 11 inches above the forming surface. A primary air-flow of about 14 ft3/minute per inch of meltblowing die at about 3 psi was used to attenuate the extruded polymer into meltblown fibers and microfibers that were collected on a foraminous surface moving at a constant speed. The meltblown fibers were carried downstream on the foraminous surface to the second bank which was an identical meltblown system except that the primary air flow was eliminated. The polymer was extruded at the same temperature and throughput rates into substantially parallel continuous filaments at a density of 30 filaments per lineal inch. A secondary air flow chilled to about 50 degrees Fahrenheit was used to cool the filaments. The difference in speed between the continuous filaments leaving the die tips and the foraminous surface aided the alignment of the continuous filaments into substantially parallel rows. The laminate of meltblown fibers and continuous filaments was carried to the third bank where an identical layer of substantially parallel continuous filaments was deposited at the same process conditions. This material was then carried to a fourth bank where a final layer of elastomeric meltblown fibers was deposited onto the multi-layer structure at the same conditions as the first bank. The layers of the structure were joined by autogenous bonding produced by directly forming one layer upon the other and enhanced by the tackifier resin added to the polymer blend. This material had 2 layers of meltblown fibers and 2 layers of substantially parallel continuous filaments (for a total filament density of about 60 filaments per lineal inch), a basis weight of about 60 gsm, and weight ratio of filaments to fibers of about 50:50. The tensile test revealed a strength index (i.e., machine direction tension versus cross-machine direction tension) from about 3 to about 5 when the tension was measured at an elongation of about 400 percent.

[0089] The four-layer elastic fibrous web was moved along at a rate of about 100 feet/minute by the foraminous wire, lifted off the wire by a pick-off roll moving at a rate about 50% faster and then drawn to a ratio of 2:1(200%). At this extension the drawn elastic fibrous web was fed into a calender roller along with upper and lower non-elastic gatherable facings. Each gatherable facing was a conventional polypropylene spunbond web having a basis weight 0.35 ounces per square yard (about 12 gsm) which was joined to the anisotropic elastic fibrous web at spaced apart locations to form a stretch-bonded laminate structure. The stretched-bonded laminate was relaxed as it exited the nip so that gathers and puckers would form. The laminate was wound onto a driven wind-up roll under slight tension and has a basis weight of about 2.5 osy (85 gsm)

[0090] Next the stretch-bonded laminate was hydroentangled with pulp at a pulp addition of about 1.0 osy (34 gsm) and 2.0 osy (68 gsm). A wet slurry of pulp fibers was formed using conventional paper making process conditions. The wet slurry of pulp fibers was transported on a wire. The stretch-bonded laminate prepared above was removed from the storage roll and stretched to about 100%. The wet slurry of pulp fibers was placed onto the stretched stretch-bonded laminate and the two layers were moved via a forming wire into a hydroentangling unit having two manifolds. The pulp was hydraulically entangled into a composite material utilizing 2 manifolds. Each manifold was equipped with a jet strip having one row of 0.007 inch holes at a density of 30 holes per inch. Water pressure in the manifold was 1800 psi (gage). The layers were supported on a C-9 coarse forming wire which traveled under the manifolds at a rate of about 45 fpm. The composite fabric was dried utilizing conventional through-air drying equipment. The composites had a total basis weight of about 120 gsm (34 gsm pulp add-on) and 154 gsm (68 gsm pulp add-on).

Example 2

[0091] The 120 gsm composite of Example 1 was coated onto both sides with about 2 gsm of an Ato Findley H 2174-01 hot melt adhesive, while in the relaxed condition. The adhesive containing composite was cut into a bandage 3 inches wide and 20 inches long. With the adhesive coated on the composite and cut to size, the composite was useful as an absorbent bandage.

[0092] While the invention has been described in detail with respect to specific embodiments thereof, and particularly by the example described herein, it will be apparent to those skilled in the art that various alterations, modifications and other changes may be made without departing from the spirit and scope of the present invention. It is therefore intended that all such modifications, alterations and other changes be encompassed by the claims.

Composite elastic material

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