BACKGROUND OF THE INVENTION The present invention relates to a breathable film/nonwoven laminate having improved toughness (elongation) and greater retention of barrier properties. The present invention also relates to the process of producing the same using an anvil roll covered with a soft material.

Laminate materials have a wide variety of uses, especially in the areas of absorbent articles and disposable items. As used herein, the term "absorbent articles" refers to devices which absorb and contain body exudates and, more specifically, refers to devices that are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. The term "absorbent articles" is intended to include diapers, training pants, incontinence devices and the like. The term "disposable" is used herein to describe absorbent articles not intended to be laundered or otherwise restored or reused as an absorbent article.

Film/nonwoven laminates may be produced using thermal point bonding. Traditionally thermal point bonding entails passing the webs that are to be bonded together through the nip of two steel rolls. Generally, one of the steel rolls is engraved, or embossed, with a pattern. This roll is known as the "pattern roll." The non-engraved roll is known as the "anvil roll." During the lamination process, the pattern on the pattern roll is imparted to the laminated web. Use of steel anvil rolls tends to result in severe deformation of the nonwoven fibers, resulting in a weak laminate.

A need, therefore, exists for a method of producing a film/nonwoven laminate having improved toughness without causing severe deformation to the nonwoven fibers.

SUMMARY OF THE INVENTION It has now been found that lamination of breathable film using an anvil roll covered with a soft material produces laminates without the severe deformation of the nonwoven web that often results from using two steel rolls. The reduced deformation of the nonwoven web results in a laminate with improved tensile properties and improved laminate elongation.

Greater laminate elongation is important because it indicates a tougher material, i.e., one that is able to withstand pulling longer before breaking. The process of the present invention also maintains film integrity throughout the entire bonding procedure.

The lamination process of the present invention requires a pattern roll, an energy source and an anvil roll that is covered with a soft material that deforms under nip pressure but that also has adequate operational life.

Laminate materials produced according to the present invention may be used in personal care absorbent articles and in surgical gowns and drapes and other forms of protective apparel such as lab coats and workwear. Film/nonwoven laminates produced according to the present invention are especially useful in the outer coverings of personal care absorbent articles, particularly diapers.

The foregoing and other features and advantages of the present invention will become apparent from the following detailed description of the presently preferred embodiments, when read in conjunction with the accompanying examples.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspective view of a film/nonwoven laminate constructed in accordance with the present invention.

FIG. 2 is a schematic side view of the lamination process of the present invention.

FIG. 3 is a partially cut-away top view of an exemplary disposable garment which may utilize the laminate produced according to he present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to lamination of breathable film and nonwoven webs using an anvil roll covered with a soft material.

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 illustrated a film/nonwoven laminate 10 produced according to the present invention The laminate 10 includes a fibrous nonwoven web 12 and a polymeric film 14 bonded thereto.

The fibrous nonwoven web 12 may be, for example, necked polypropylene spunbond, crimped polypropylene spunbond, bonded carded webs, elastomeric spunbond or meltblown fabrics produced from elastomeric resins. Fibrous nonwoven webs can impart additional properties such as a softer, more cloth-like feel to polymeric film. A more cloth-like feel is particularly advantageous when the film is being used as a barrier layer in, for example, outer covers for personal care absorbent articles, surgical gowns and drapes, lab coats and other forms of protective apparel.

The manufacture of fibrous non-woven webs is known. Such webs may be formed from a number of processes including, but not limited to, spunbonding and meltblowing processes.

Meltblown fibers are fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, capillaries of a meltblowing die as molten threads or filaments into converging high-velocity, usually hot, gas (e.g., air) streams which are flowing in the same direction as ne extruded filaments or threads of the molten thermoplastic material so that the extruded filaments or threads are attenuated, i.e., drawn or extended, to reduce their diameter.

The threads or filaments may be attenuated to microfiber diameter which means the threads or filaments have an average diameter not greater than about 75 microns, generally from about 0.5 microns to about 50 microns, and more particularly from about 2 microns to about 40 microns. 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 disbursed meltblown fibers. The meltblown process is well-known and is described in various patents and publications, including NRL Report 4364, "Manufacture of Super-Fine Organic Fibers" by B.A. Wendt, E.L. Boone and D.D.

Fluharty; NRL Report 5265, "An Improved Device for the Formation of Super-Fine Thermoplastic Fibers" by K.D.

Lawrence, R.T. Lukas and J.A. Young; U.S. Patent No. 3,676,242 to Prentice; and U.S. Patent No. 3,849,241 to Buntin et al.

The foregoing references are incorporated herein in by reference in their entirety. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter and are generally tacky when deposited onto a collecting surface.

Preferably the fibrous nonwoven web is polypropylene spunbond. Spunbonded fibers are small diameter fibers that are formed by extruding a 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 by, for example, non- eductive or eductive fluid-drawing or other well-known spunbonding mechanisms. The production of spunbonded non- woven webs is illustrated in patents such as, for example, U.S. Patent No. 4,340,563 to Appel et al.; U.S. Patent No.

3,802,817 to Matsuki et al.; U.S. Patent No. 3,692,618 to Dorschner et al; U.S. Patent No. 3,542,615 to Dobo; U.S.

Patent No. 3,502,763 to Hartman; U.S. Patent No. 3,502,538 to Peterson; U.S. Patent Nos. 3,341,394 and 3,338,992 to Kinney; U.S. Patent No. 3,276,944 to Levy; and Canadian Patent No.

803,714 to Harmon. The disclosures of these patents are herein incorporated by reference in their entirety.

Spunbonded fibers generally are not tacky when deposited onto a collecting surface. Spunbonded fibers generally are continuous and have average diameters (from a sample of at least 10) larger than 7 microns and, more particularly, from about 10 microns to about 20 microns.

For the film 14 that is laminated to the nonwoven web 12, a wide variety of thermoplastic films are useful. Such ilms include, but are not limited to, polypropylene and/or polyethylene-based polyolefins in mono- or coex-execututions.

Polypropylene films are preferred for lamination to polypropylene spunbond.

A process for forming polymeric film 14 is shown in FIG.

2 of the drawings. Referring now to that figure, polymeric ilm 14 is formed from an extrusion film apparatus 20 such as a cast or blown unit. Typically, the apparatus 20 includes an extruder 22. The polymeric material is prepared in a mixer 24 and directed to the extruder 22. The film 14 is extruded into a pair of nip rollers 26, 28 one of which may be patterned so as to impart an embossed pattern to the newly formed film 14.

From the extrusion film apparatus 20, film 14 is directed =o a film stretching unit 30 such as a machine direction oriented which is commercially available from vendors such as The Marshall and Williams Company of Providence, Rhode Island.

Such an apparatus 30 has a plurality of stretching rollers 32 that move at progressively faster speeds relative to the pair disposed before it. These rollers 32 apply an amount of stress and thereby progressively stretch film 14 to a second length in the machine direction of the film, which is the direction of travel of film 14 through the process as shown in FIG. 2. The stretch rollers 32 may be heated for better processing. Film stretching unit 30 may also include rollers ;not shown) upstream and/or downstream from the stretch rollers 32 that can be used to preheat the film 14 before orienting it and/or to cool the film 14 after stretching it.

Preferably, the second, or stretched, length is from about two to about six times, more preferably from about three times to about four times, the original length of the film 14 prior to stretching.

Film 14 is then directed out of stretching unit 30 so that the stress is removed and the film 14 is allowed to relax. Preferably, a permanent elongation length of from about 1.5 times the original length is retained after the stretched film is allowed to relax.

Lamination reinforces and protects the film. During the laminating process, the film 14 is attached to the nonwoven web 12 to form a laminate 10.

Referring again to FIG. 2, there is also illustrated a side view of the lamination process of the present invention.

A conventional fibrous nonwoven web-forming apparatus 40, such as a pair of spunbond machines, is used to form the fibrous nonwoven web 12. The long, essentially continuous fibers 42 are deposited onto a forming wire 44 as an unbonded web 46.

The unbonded web 46 is then sent through a pair of bonding rolls 48, 50 to bond the fibers together and increase the tear strength of the resultant web 12. One or both of the rolls 48, 50 are often heated to aid bonding. Typically, one of the rolls 48, 50 is also patterned so as to impart a discrete bond pattern with a prescribed bond surface area to the web 12.

The other roll is usually a smooth anvil roll, but this roll also may be patterned if desired.

Once the film 14 has been sufficiently stretched and the fibrous nonwoven web 12 has been formed, the two layers are brought together and laminated using thermal point bonding.

Thermal point bonding involves passing the film 14 and the fibrous nonwoven web 12 through the nip formed between a pair of rolls 52, 54. As with the bonding rolls 48, 50 at least one of the laminating rolls is patterned to create a discrete bond pattern upon the resultant laminate 10. If desired, bonding rolls 48, 50 may be omitted or used for light compaction and the laminating nip between rolls 52, 54 may serve to simultaneously bond the nonwoven web 12, as well as form the laminate 10. Generally, the maximum bond point surface area for a given area of surface on one side of the laminate 10 will not exceed about 50t of the total surface area. Any of a number of discrete bond patterns may be used.

Examples are disclosed in U.S. Patent No. 4,041,203 to Brock et al., which is incorporated herein by reference. The pattern roll 52 is a metal roll, preferably steel.

During lamination, the film is oriented against the non- engraved roll 54, which is also known as the anvil roll. Such orientation assists force distribution and prevents damage to the film during the bonding process.

The anvil roll 54 is also made of metal, again preferably steel. The anvil roll 54, however, is covered with a soft material that deforms under nip pressure but that also has an adequate operational life. The soft material generally has a surface roughness (Ra) of about 5 to about 250. Surface roughness is measured with a surface roughness tester such as, for example, the Surftest 211 produced by MTI Corporation.

The soft material must be softer and more conformable than steel, such as rubber Rubber-containing compounds may also be useful such as, for example, a silicone rubber compound with a Shore-A hardness of about 80-95. Preferably, a sleeve (not shown) slides over the metal anvil roll 54 to provide the soft, conformable surface. The sleeve deforms under the nip pressure of lamination thereby creating a larger area over which a constant nipping force is distributed. This, in turn, results in a lower pressure required for lamination. The pressure used during lamination according to the present invention is from about 170 to about 230 psi, depending on the relative softness of the sleeve covering the anvil roll 54.

The lower pressure, while enough to laminate the incoming film 14 and nonwoven web 12, eliminates the severe deformation of the nonwoven web 12 that generally occurs during lamination.

The resulting laminate 10 also shows improved tensile properties and laminate elongation, thus indicating a tougher laminate material.

Preferably, the energy source used to assist lamination is infrared heaters. Other sources, such as a hot air knife, may also be used. The temperature on the pattern roll 52 is between about 2306F and about 260"F. The anvil roll 54 picks up heat and runs at about 150OF during steady state processing.

Once the laminate 10 exists, it may be wound up into a roll 58 for subsequent processing. Alternatively, the laminate 10 may continue in line for further processing or conversion.

The process shown in FIG. 2 may also be used to create a three layer laminate. The only modification to the previously described process is to feed a supply 60 of a second fibrous nonwoven web 12a into the pattern roll 52 and the anvil roll 54 on the side of the film 14 opposite that of the other nonwoven web 12. One or both of the nonwoven webs 12 and 12a may be formed directly in line, as illustrated with nonwoven web 12 in FIG. 2. Alternatively, one or both of the nonwoven webs 12 and 12a may be in the form of a pre-formed roll 62 as illustrated in FIG. 2 by nonwoven web 12a. In any event, the second nonwoven web 12a is fed between the nip of the pattern roll 52 and the anvil roll 54 and is laminated to film 14 in the same manner as the first fibrous nonwoven web 12.

As previously stated, the laminate 10 produced according to the present invention may be used in a wide variety of applications including personal care absorbent articles such as diapers, training pants, incontinence garments, surgical gowns and drapes and protective apparel such as lab coats and other workwear. A disposable garment 70, in this case a diaper, is shown in FIG. 3. Although a diaper is shown in FIG. 3, it will be understood that use of the laminate 10 produced according to the present invention is not limited to such articles and may also be used in a wide variety of applications. Referring again to FIG. 3, the disposable garment 70 includes a liquid permeable top sheet or liner 72, a back sheet or outer cover 74 and an absorbent core 76 disposed between and contained by the liner 72 and the outer cover 74. Disposable garment 70 may also include some type of fastening means 78 such as adhesive fastening tapes or mechanical hook and loop type fasteners and stretch region 80.

Laminate 10 may be used to form various portions of disposable garment 70 including, but not limited to, liner 72, outer cover 74 and stretch region 80. Preferably, laminate 10 is used to form the outer cover 74 of disposable garment 70.

The advantages and other characteristics of the present invention are best illustrated by the following examples. It should be understood that the following examples are illustrative and are not limiting.

Two sets of film/spunbond laminates were produced using rubber and steel anvil rolls. The laminates bonded with the rubber anvil roll displayed greater elongation compared to the laminates bonded with the steel anvil roll. An analysis of the resultant laminates by a scanning electron microscope indicated that the increase in elongation in the material laminated with the rubber anvil roll is due to the fact that the spunbond fibers in the area of the bond points in those materials were flattened and indented into the film rather than fused into the film as shown in the samples bonded with the steel anvil roll.

Of course, it should be understood that a wide range of changes and modifications can be made to the embodiments described above. It is, therefore, intended that the foregoing description illustrate rather than limit this invention and that it is the following claims, including all equivalents, that define this invention.