CN101257871A - 3D porous membrane - Google Patents

Abstract

A three-dimensional apertured film comprising a first flat surface in a first imaginary plane, a second flat surface in a second imaginary plane, and a plurality of pores extending from the first flat surface to the second flat surface. The three-dimensional apertured membrane further includes at least one element spanning each of the plurality of pores, thereby defining a plurality of smaller pores, wherein the element spanning each of the plurality of pores has a top surface below.

Description

3D porous membrane

field of invention

The present invention generally relates to three-dimensional porous membrane materials suitable as components of personal care products such as sanitary napkins, diapers, incontinence products, tampons, surgical dressings, wound dressings, panty liners, wipes, and the like. More specifically, the present invention relates to three-dimensional porous polymer films having enhanced liquid handling and masking properties when used as component layers in disposable absorbent articles.

Background of the invention

The use of porous films in personal care products is well known in the art. These films can be used as body contacting topsheets, as liquid management layers, or as other components of personal care products. When using these films as body-contacting topsheets in feminine hygiene protection articles, it has generally been found that the greater the open area of the film, the more efficient it is at transferring menstrual fluid to the underlying layers of the article (e.g. transfer layer, absorbent core) . Unfortunately, it has also been found that the greater the open area of the film, the less effective it is at "stain masking" the absorbed menstrual fluid after it has been transferred to the underlying layer of the article. That is, the greater the open area of the film, the more visible the menstrual stain will be after the article absorbs menstrual fluid.

It is an object of the present invention to provide a porous film having improved liquid handling properties when used in disposable absorbent articles, such as feminine hygiene protection products. More specifically, it is an object of the present invention to provide a porous film capable of effectively transferring liquid to an underlying absorbent structure while exhibiting enhanced stain masking properties.

Summary of the invention

In view of the above, a first aspect of the present invention provides a three-dimensional porous membrane comprising: a first flat surface in a first imaginary plane, a second flat surface in a second imaginary plane, at least the planar surface extends to a plurality of holes of the second planar surface, and at least one element spanning each of the plurality of holes, wherein the element spanning each of the plurality of holes has a top surface lying in a third imaginary plane, The third imaginary plane is located below the first imaginary plane.

A second aspect of the present invention provides a three-dimensional porous membrane comprising: a first substantially planar surface lying in a first imaginary plane; a second substantially planar surface lying in a second imaginary plane; a plurality of interconnected framework portions , each frame portion has at least a first inner wall and a second inner wall arranged in a spaced manner relative to each other; a plurality of cross members, the cross members each extending from an inner wall of a frame portion to an opposite second inner wall of a frame portion , the intersecting elements each having a top surface in an imaginary plane below a first imaginary plane; and a plurality of holes extending at least from said first planar surface to said second planar surface, each hole defined by at least one frame portion and at least A cross element is bounded.

A third aspect of the present invention provides a three-dimensional porous membrane, the porous membrane comprising: a first flat surface in a first imaginary plane; a second flat surface in a second imaginary plane; a first plurality of pores; At least one element of each of the plurality of holes, thereby defining a plurality of smaller holes, each of the plurality of smaller holes communicates with a corresponding one of the first plurality of holes, wherein, across the first The elements of each of the plurality of apertures have a top surface lying in a third imaginary plane that is below the first imaginary plane.

A fourth aspect of the present invention provides a three-dimensional porous membrane, the porous membrane comprising: a first flat surface located in a first imaginary plane; a second flat surface located in a second imaginary plane below the first imaginary plane; holes; spanning at least one element of each hole in the first plurality of holes, thereby defining a plurality of smaller holes, each hole in the plurality of smaller holes corresponding to a corresponding one of the first plurality of holes communicating, wherein the member spanning each aperture of the first plurality of apertures has a top surface lying in a third imaginary plane below said first imaginary plane; and a second plurality of apertures.

A fifth aspect of the present invention provides a three-dimensional porous membrane comprising: a first substantially planar surface lying in a first imaginary plane; a second substantially planar surface lying in a second imaginary plane; a plurality of interconnected framework portions , each frame portion has at least a first inner wall and a second inner wall arranged in a spaced manner relative to each other; a plurality of cross members each extending from an inner wall of a frame portion to an opposite second wall of a frame portion an inner wall, the intersecting elements each having a top surface in an imaginary plane below the first imaginary plane; a first plurality of holes extending at least from the first planar surface to the second planar surface, each of the plurality of holes extending at least from the first planar surface to the second planar surface A framework portion and at least one intersection member define; and a second plurality of apertures.

A sixth aspect of the present invention provides a three-dimensional porous membrane, the porous membrane comprising: a first flat surface located in a first imaginary plane; a second flat surface located in a second imaginary plane; extending at least from the first flat surface to the second A plurality of holes of two planar surfaces; at least one element spanning each hole in the plurality of holes, wherein the element spanning each hole in the plurality of holes has a top surface lying in a third imaginary plane, the third imaginary plane located below the first imaginary plane; and a second plurality of apertures.

Brief description of the drawings

Figure 1a is a schematic diagram of a three-dimensional membrane according to one embodiment of the present invention.

Figure 1b is a partially cutaway perspective view of the membrane shown in Figure 1a taken along dashed line 1B in Figure 1a.

Figure 1c is an enlarged micrograph of the three-dimensional membrane shown in Figure 1a, showing its top surface.

Figure 1d is an enlarged micrograph of the 3D membrane shown in Figure 1c, showing its underside.

Figure 1e is a schematic diagram of a three-dimensional membrane according to a second embodiment of the invention.

Figure 1f is a partially cutaway perspective view of the membrane shown in Figure 1e taken along the dashed line "If" in Figure 1e.

Figure 1g is a photomicrograph of the top surface of the 3D membrane shown in Figure 1e.

Figure 1h is a photomicrograph of the underside of the 3D membrane shown in Figure 1g.

Figure 1i is an enlarged photomicrograph of a portion of the three-dimensional film shown in Figure 1g, which corresponds to the portion of the film circled by circle "1f" in Figure 1e.

Figure 1j is a photomicrograph of the portion of the three-dimensional membrane shown in Figure 1i, showing its underside.

Figure 2 is a schematic illustration of a three-dimensional topographical support element that can be used to make the membranes of the present invention.

Figure 3 is a schematic illustration of a processing apparatus that laser engraves a workpiece to form a support element that can be used to create the three-dimensional topography of the films of the present invention.

FIG. 4 is a schematic diagram of a computer control system for the apparatus of FIG. 3 .

Figure 5 is a pictorial representation of a document laser engraving a workpiece to produce a support element used to create the three-dimensional topography of the porous membrane shown in Figures 1a-1d.

Figure 5a is a graphical representation of the file shown in Figure 5, showing an enlarged portion thereof.

Figure 5b is a graphical representation of a file laser engraved on a workpiece to produce a support element for the fabrication of the three-dimensional topography of the porous membrane shown in Figures 1e-1j.

Figure 5c is an enlarged portion of the graphical representation of the document shown in Figure 5b, showing the portion of the document encircled by circle 5c in Figure 5b.

Figure 5d is an enlarged portion of the graphical representation of the document shown in Figure 5b, showing the portion of the document encircled by circle 5d in Figure 5b.

Figure 5e is an enlarged portion of the graphical representation shown in Figure 5d, showing the portion of the document encircled by circle 5e in Figure 5d.

FIG. 6 is a photomicrograph of the workpiece after it has been engraved using the file of FIG. 5 .

Figure 6a is a photomicrograph of the workpiece after it has been engraved using the files shown in Figures 5b-5e.

Fig. 6b is an enlarged portion of the workpiece shown in Fig. 6a, said enlarged portion corresponding to the area circled 6b in Fig. 6a.

Figure 7 is a view of a support member used to hold a film of the present invention in place on a film forming apparatus.

Fig. 8 is a schematic diagram of an apparatus for producing a porous membrane according to the present invention.

FIG. 9 is a schematic diagram of the circled part in FIG. 8 .

Figure 10 is a histogram showing the average stain intensity of an absorbent article having the three-dimensional porous film of the present invention as its cover layer.

Figure 11 is a pictorial representation of a document using a raster scan drill to drill holes in a workpiece to produce a support element for creating a three-dimensional topography of a porous membrane.

Detailed description of the invention

The present invention relates to three-dimensional porous films particularly suitable for use in personal care products. These films can be used as body contacting topsheets, as liquid management layers, or as other components of personal care products. It has been found that the films of the present invention exhibit improved liquid handling when used in disposable absorbent articles, such as feminine hygiene products. In particular, it has been found that the membranes of the present invention provide enhanced stain masking properties while enabling more efficient transfer of fluids through the membrane as compared to conventional membranes.

Referring now to Figures 1a-1d, there is depicted a porous membrane 10 according to one embodiment of the present invention. Membrane 10 includes a plurality of repeating interconnected frameworks 12 . In the embodiment shown in Figures 1a-1d, each frame 12 includes opposing end regions 12a and 12b and opposing side walls 12c and 12d. Each of the end regions 12a and 12b are spaced from each other, as are each of the opposing side walls 12c and 12d. In the particular embodiment shown in FIGS. 1a-1d , each frame 12 is interconnected with adjacent frames 12 . More specifically, as shown, each frame 12 "shares" a common side wall 12c, 12d with the immediately adjacent frame 12 . Likewise, each frame 12 shares a common end region 12a, 12b with the immediately adjacent frame 12 . The porous membrane 10 further includes first and second cross members 14a and 14b. As shown, the cross member 14b extends from the first side wall 12c to the opposing side wall 12d of the frame 12 . Likewise, a cross member 14a extends from an end region 12a to an opposite end region 12b. In the embodiment of the invention shown in Figures 1a-1e, crossing elements 14a and 14b intersect at the center of the frame shown. Additionally, in the embodiment of the invention shown in Figures 1a-1e, the intersecting elements 14a and 14b are arranged in an orthogonal manner with respect to each other.

Although the embodiment of the invention shown in FIGS. 1a-1b shows porous membrane 10 having two intersecting elements 14a and 14b, only a single intersecting element may be used as long as the intersecting element extends through the open area defined by framework 12. Can. Also, while the frame 12 is shown to be generally hexagonal in shape, the frame 12 may take other shapes. Each of the intersecting elements 14a and 14b preferably has a width "a" of about 4.0-24.0 mils (1 mil = 0.001 inches) (see FIG. 1b ). Each of the intersecting elements 14a and 14b preferably has a length "b" of about 30.0-150.0 mils (see Figure Ib). Membrane 10 may optionally include a plurality of bumps 11 or similar elements arranged on the surface of the membrane, as best shown in Figure 1a.

Membrane 10 further includes a plurality of pores 16 . Each aperture 16 is bounded by at least a portion of the frame 12 and at least a portion of one of the cross members 14a and 14b. Referring now to FIG. 1b, which is a partially cutaway perspective view of the membrane 10 shown in FIG. 1 taken along the dashed line 1B of FIG. 1a. Each aperture is bounded by at least a portion of each of cross members 14a and 14b and a portion of frame 12 . More specifically, each aperture 16 is bounded by a corresponding inner wall 22, 24 of each side wall 12c, 12d of the frame 12, as best shown in FIG. 1b. Each aperture 16 is further bounded by a corresponding inner wall 26 or 28 of the intersecting element 14b and a corresponding inner wall 30, 32 of the intersecting element 14a. Finally, each hole 16 is bounded by a respective inner wall 34, 36 of the corresponding end region 12a, 12b.

Referring again to FIG. 1 b , film 10 generally includes a first generally planar top surface 18 in an imaginary plane 23 , and an opposing second generally planar bottom surface 21 in an imaginary plane 25 . Top surfaces 38 of side walls 12c and 12d , and top surfaces 40 of end regions 12a and 12b are coplanar with plane 23 . However, the top surfaces 42 and 44 of the cross members 14a and 14b are both recessed relative to the plane 23 . More specifically, top surfaces 42 and 44 of intersecting elements 14a and 14b both lie on plane 27 , which is below planes 23 and 25 . Preferably, the top surfaces 42 and 44 of the intersecting elements 14a and 14b are recessed relative to the top surface 18 of the film (ie, recessed relative to the plane 23) by a depth of about 3.0-17.0 mils. The top surfaces 42 and 44 of the intersecting elements 14a and 14b are preferably substantially parallel to the imaginary planes 23 and 25 .

The inner walls 22, 24 of the side walls 12c and 12d, the inner walls 26, 28 of the intersecting element 14a, the inner walls 30, 32 of the intersecting element 14b, and the inner walls 34, 36 of the end regions 12a, 12b, together define the aperture 16, of which Each extends below plane 25 such that the bottom opening of each well 16 is below the bottom planar surface 21 of the membrane (ie below imaginary plane 25 ). More specifically, the inner walls 22, 24 of the side walls 12c and 12d, the inner walls 26, 28 of the intersecting member 14a, the inner walls 30, 32 of the intersecting member 14b, and the inner walls 34, 36 of the end regions 12a, 12b, all extend downwardly. , so that the bottom opening of each hole is located on an imaginary plane 29 which is located below the imaginary planes 23 , 25 and 27 . It is to be noted that the imaginary planes 23, 25, 27 and 29 are all substantially parallel to each other.

Since the top surfaces 42, 44 of the intersecting elements 14a and 14b are recessed relative to the top surface 18 of the membrane 10 (i.e., are recessed relative to the imaginary plane 23), the first larger aperture is effectively defined as being from the top surface of the membrane 10. 18 to the top surfaces 42, 44 of the intersecting elements. Intersecting elements 14a and 14b divide the larger hole into four smaller holes which open into communication with the larger hole from the top surfaces 42 , 44 of the intersecting elements 14a and 14b down to the bottom of each hole 16 . Stated another way, within each framing element 12 a larger aperture is defined from plane 23 to plane 27 and a plurality of smaller apertures are defined from plane 27 to 29 which communicate with the larger apertures. In the embodiment shown in FIGS. 1 a - 1 d , the area of each of the smaller holes defined from planes 27 to 29 is less than a quarter of the total area of the larger holes defined from planes 23 to 27 . In embodiments employing a single intersecting element, the area of each smaller aperture defined by the intersecting element is less than one-half the total area of the larger apertures. For the sake of simplicity and clarity, the following explanations are proposed to the reader: the above-mentioned "smaller" and "larger" holes are all represented by reference numeral 16 in the accompanying drawings.

See Figures 1e-1j, which depict a porous membrane 100 according to a second embodiment of the present invention. In Figures 1e-1j, the same or similar reference numerals as in Figures 1a-1d are used to indicate the same and/or corresponding structures as in Figures 1a-1d and as described above.

As best shown in FIGS. 1e and 1g , film 100 includes at least a first portion 102 and at least a second portion 104 . The first portion 102 is defined by a plurality of repeating interconnected frameworks 12 defining a plurality of apertures 16 as described above. In the embodiment shown in Figures 1e-1j, each frame 12 includes opposing end regions 12a and 12b, and opposing side walls 12c and 12d. The porous membrane 100 also includes first and second cross members 14a and 14b. Intersecting elements 14a and 14b preferably have a width "a" of about 4.0-24.0 mils. Intersecting elements 14a and 14b each preferably have a length "b" of about 30.0-150.0 mils. Preferably, the top surfaces 42 and 44 of the intersecting elements 14a and 14b are recessed relative to the top surface 18 of the film (ie, recessed relative to the plane 23) by a depth of about 3.0-17.0 mils.

Referring to FIG. 1 f , the film 100 generally includes a substantially planar top surface 18 in an imaginary plane 23 , and an opposing substantially planar second bottom surface 21 in an imaginary plane 25 . End regions 12a and 12b, and portions 12c' and 12d' of sidewalls 12c and 12d where intersecting element 14b intersects sidewalls 12c and 12d are formed in such a manner that in these regions at least a portion of the top surface of the membrane Recessed relative to the imaginary plane 23 . In the particular embodiment of the membrane 100 shown in Figure 1f, the end regions 12a and 12b, and the portions 12c' and 12d' of the sidewalls 12c and 12d where the intersecting element 14b intersects the sidewalls 12c and 12d, have substantially The "w" shape, or having a sinusoidal shape, defines a cross-section of a pair of depressions 111 and peaks 113 arranged between the depressions 111 . As shown, the top surface of membrane 115 in the region of depressions 111 lies in plane 35 , which is recessed relative to imaginary plane 23 . Specifically, plane 35 is located between plane 23 and plane 25 . Preferably, depressions 111 have a depth of about 2-5 mils (relative to plane 23 ) at their most recessed point relative to plane 23 .

Although in embodiment 100, end regions 12a and 12b, and portions 12c' and 12d' of sidewalls 12c and 12d where intersecting member 14b meets sidewalls 12c and 12d, form a substantially "w" shaped cross-section. , however, these regions may also have other shapes and configurations, wherein at least part of the top surface of the membrane in the region where the cross members 14a and 14b intersect the framework 12 is recessed relative to the plane 23 . By forming the membrane 100 in the region where the intersecting element 14a intersects the end regions 12a and 12b and in the region where the intersecting element 14b intersects the side walls 12c and 12d, at least a portion of the membrane is recessed relative to the plane 23, thereby improving The perceived softness of the film. Although in the embodiment of the invention shown in Figure 1f, the membrane 100 is formed in the end regions 12a and 12b and in portions 12c' and 12d' of the side walls 12c and 12d such that at least a portion of the membrane surface is relative to the plane 23 is recessed, however, it is also possible to configure the membrane such that only one of these regions is recessed relative to plane 23 . For example, only portions 12c' and 12d' are recessed, or only end regions 12a and 12b are recessed.

As best shown in FIG. 1 e , the second portion 104 of the porous membrane 100 a includes second pores 106 that can be visually distinguished from the first pores 16 . The term "visually distinguishable" is used herein to mean that the shape and/or size of each of the second pores 106 is significantly different from the shape and/or size of each of the first pores 16 such that the Each of the second pores 106 can be distinguished from each of the first pores 16 at the same time. In one embodiment of the invention shown in Figures 1e-1j, each of the second pores 106 is generally elliptical, having a major axis "y" and a minor axis "z". The length of each of the major axis "y" and minor axis "z" is preferably about 5-150 mils. In one specific embodiment, the length of the major axis is about 43 mils and the length of the minor axis is about 16 mils. In a preferred embodiment of the invention, each of the second apertures 106 are spaced apart from each other by a distance "n" of about 10-100 mils along a horizontal line from the center of one aperture to the horizontally adjacent Measured at the center of the hole, each of the second porous holes 106 is separated from the vertically adjacent holes 106 by a distance "o" of about 10-70 mils along the diagonal line connecting the centers of each hole from Measured from the center of one hole to the center of the vertically adjacent hole. In a specific embodiment of the invention, the distance "n" is 40 mils and the distance "o" is 34 mils.

The second apertures 106 may be arranged in a pattern defining a design, indicia, text, etc., or a combination thereof. For example, in the embodiment of the invention shown in Figures 1e and 1g, the arrangement of the second apertures 106 defines a butterfly pattern. Although a butterfly pattern is depicted in the embodiments of the invention shown and described with reference to Figures 1e-1j, any other number of patterns may be used.

The membrane 100 shown in FIGS. 1e-1j also has a boundary 108 that separates the first pores 16 from the second pores 106 . The shape and size of the boundary are preferably such that the boundary can be distinguished from each of the first pores 16 and each of the second pores 106 when viewed with the naked eye. Preferably, the width "x" (see FIG. 1e) of border 108 is about 25-90 mils. In a preferred embodiment of the invention, border 108 is free of perforations. The membrane surface 109 located in the area defined by the boundary 108 is preferably recessed relative to the substantially planar top surface 18 of the membrane. In other words, the membrane surface 109 defined within the boundary 108 is recessed relative to the plane 23 . Preferably, the film surface 109 is recessed from plane 23 by an amount of about 2-5 mils. The membrane surface defining boundary 108 itself preferably lies within plane 23 .

Preferably the boundary 108 together with the second aperture 106 visually defines a design, indicia, text, etc. FIG. For example, in the illustrated embodiment of the membrane 100, the boundaries together with the second porous 106 define a butterfly pattern.

Although a single butterfly pattern is shown in Figure 1e for simplicity, multiple such elements may be spaced apart on the membrane surface. For example, in a specific embodiment, a plurality of such butterfly patterns may be arranged at intervals on the film material. Additionally, designs of different sizes may be used, for example, in one particular embodiment, multiple larger butterfly designs and multiple smaller butterfly designs may be used on the same film.

The porous membrane according to the present invention preferably has an open area of about 20-30%. The open area can be determined by using image analysis to measure the area of perforated and unperforated or "land". Essentially, image analysis converts optical images from an optical microscope into electronic signals suitable for processing. The image is scanned line by line using an electron beam. As each row is scanned, the output signal varies with illuminance. White areas produce higher voltages and black areas produce lower voltages. Images of the perforated film were produced in which the holes are white and the solid areas of thermoplastic material are various shades of gray.

The denser the solid area, the darker the gray area will be. Each line of the image being measured is divided into sampling points or pixels. The following equipment can be used to carry out the above analysis: Quantimet Q520 (QuantimetQ520) image analyzer (software version: 5.02B, with gray storage option), by LEICA/Cambridge Instruments Ltd. (LEICA/Cambridge Instruments Ltd.) For sale, the above image analyzer is used in conjunction with the Olympus SZH (Olympus SZH) microscope with transmitted light base, 1.0x flat objective and 2.50x eyepieces. Images can be produced with a DAGE MTI CCD72 camera.

A representative test piece of each material to be analyzed was placed on the microscope stage and imaged clearly on the video screen with the microscope zoom set to 10 times. The open area is determined by field measurement of a representative area. The Quantimet program output reports the mean and standard deviation for each sample.

A suitable starting film for the manufacture of the three-dimensional porous membrane according to the invention is a continuous uninterrupted film of thermoplastic polymer material. The stock film may be vapor permeable or vapor impermeable; may be embossed or unembossed; one or both major surfaces may be corona-discharge-treated or not-corona-discharge-treated; may be in The film may be treated with the surfactant after film formation by coating, spraying or printing the surfactant on the film, or the surfactant may be added as a blend to the thermoplastic polymer material prior to film formation. The stock film may comprise any thermoplastic polymer material including, but not limited to: polyolefins such as high density polyethylene, linear low density polyethylene, low density polyethylene, polypropylene; copolymers of olefins and vinyl monomers, Examples include copolymers of ethylene and vinyl acetate or vinyl chloride; polyamides; polyesters; polyvinyl alcohol; and copolymers of olefins and acrylate monomers, such as copolymers of ethylene and ethyl acrylate and ethylenemethacrylate of copolymers. Raw films comprising mixtures of two or more of these polymeric materials may also be used. The stock film to be perforated should have at least 100% elongation in the machine direction (MD) and cross direction (CD) according to ASTM Test No. D-882 at a crosshead speed of 50 inches/minute (127 cm/min) on Instron testing equipment. The thickness of the stock film is preferably uniform and may be about 0.5-5 mil or 0.0005-0.005 inch (0.0013-0.076 cm). Coextruded films can be used, as well as modified films, such as treated with surfactants. The raw film can be made by any known technique such as casting, extrusion or blow molding.

A method of perforating a film according to the invention comprises placing the film on the surface of a patterned support member. A high fluid pressure differential is applied to the membrane on the support element. The pressure differential of the fluid (which may be liquid or gas) causes the membrane to assume the surface pattern of the patterned support element. If the patterned support element has pores in it, the portion of the membrane covering the pores will be broken down by the fluid pressure differential, forming a porous membrane. One method of forming porous membranes is described in detail in US Patent 5,827,597 to James et al., which is hereby incorporated by reference.

Such three-dimensional porous membranes are preferably formed by placing a thermoplastic membrane on the surface of a porous support element having a pattern corresponding to the desired final membrane shape; directing a stream of hot air at the membrane, It is heated and softened; a vacuum is then applied to the membrane so that it conforms to the surface shape of the support element; the portions of the membrane located on the pores of the support element are further elongated until these portions are broken down, forming in the membrane hole.

A suitable porous support element for making these three-dimensional porous membranes is a three-dimensional topographical support element produced by laser engraving a workpiece. A schematic illustration of an exemplary workpiece of a support element laser-engraved to form a three-dimensional topography is shown in FIG. 2 .

The workpiece 102 includes a thin tubular cylinder 110 . The workpiece 102 has a raw surface region 111 and a laser-engraved central portion 112 . A preferred workpiece for the manufacture of the support element of the present invention is an acetal thin wall seamless tube which has been relieved of all residual internal stresses. The wall thickness of the workpiece is 1-8 mm, more preferably 2.5-6.5 mm. Exemplary workpieces for forming the support elements have a diameter of 1-6 feet and a length of 2-16 feet. However, these dimensions can be selected by design. Workpieces can be made of other shapes and materials such as acrylics, urethanes, polyesters, high molecular weight polyethylene, and other polymers that can be processed with a laser beam.

Referring now to Figure 3, there is shown a schematic diagram of an apparatus for laser engraving a support member. The stock blank tubular workpiece 102 is secured on suitable rolls or mandrels 121, holding it in a cylindrical shape so that the workpiece can rotate in bearings 122 about its longitudinal axis. A rotary drive 123 is provided to rotate the mandrel 121 at a controlled rate. Connected to a rotary pulse generator 124, the rotation of the spindle 121 is monitored so that its exact radial position is known at all times.

One or more rails 125 are secured in parallel outside the maximum swing of the mandrel 121 to enable the carriage 126 to move back and forth along the entire length of the mandrel 121 while maintaining continuous clearing of the top surface 103 of the workpiece 102. Carriage drive 133 moves the carriage along rail 125 while carriage pulser 134 registers the lateral position of the carriage relative to workpiece 102 . The focusing platform 127 is fixed on the sliding frame. The focusing platform 127 is fixed in the focusing rail 128 . The focusing platform 127 can move in a direction orthogonal to the direction of movement of the carriage 126 , providing a means of focusing the lens 129 relative to the top surface 103 . A focus drive 132 is provided to position the focus stage 127 to bring the lens 129 into focus.

The lens 129 is fixed on the focusing platform 127 , and the lens 129 is fixed in the nozzle 130 . The nozzle 130 has a component 131 that introduces pressurized gas into the nozzle 130 to cool the lens 129 and keep it clean. A preferred nozzle 130 for this purpose is described in US Patent 5,756,962 to James et al., which is hereby incorporated by reference.

Finally a bending mirror 135 is also fixed on the bracket 126 , the bending mirror 135 directs the laser beam 136 towards the focusing lens 129 . A laser 137 is located at the distal end with an optional laser beam bending mirror 138 for directing the laser beam towards a final bending mirror 135 . While it is possible to mount the laser 137 directly on the carriage 126 without the use of a laser beam bending mirror, space constraints and the laser's ancillary connections make it most preferable to mount the laser at the distal end.

When the laser 137 is powered on, the emitted laser beam 136 is reflected by the first beam bending mirror 138 , and then reflected by the final laser beam bending mirror 135 , leading to the lens 129 . The path of the laser beam 136 is arranged such that the laser beam passes through the longitudinal centerline of the mandrel 121 if the lens 129 is removed. When lens 129 is in place, the laser beam may be focused above, below, at, or near top surface 103 .

While a variety of lasers can be used with this device, the preferred laser is a high-flux _CO2 laser capable of producing a laser beam rated up to 2500 watts. However, low-flow _CO2 lasers rated at 50 watts can also be used.

FIG. 4 is a schematic diagram of a control system of the laser engraving device of FIG. 3 . During operation of the laser engraving device, control variables regarding focus position, rotational speed and traverse speed are transmitted from host computer 142 to drive computer 140 via connection 144 . The drive computer 140 controls the focus position through the focus platform driver 132 . The drive computer 140 controls the rotational speed of the workpiece 102 through the rotational driver 123 and the rotational pulse generator 124 . The driving computer 140 controls the back and forth moving speed of the carriage 126 through the carriage driver 133 and the carriage pulse generator 134 . Drive computer 140 also reports drive status and possible errors to host computer 142 . The system provides aggressive position control, and actually divides the surface of the workpiece 102 into small regions, called pixels, each pixel consisting of a fixed number of rotational driver pulses and a fixed number of traversing driver pulses. Host computer 142 also controls laser 137 via connection 143 .

Laser-engraved three-dimensional topographical support elements can be produced in a number of ways. One method of manufacturing such support elements combines laser drilling and laser milling of the workpiece surface.

Methods for laser drilling workpieces include percussion drilling, fire-on-the-fly drilling, and raster scanning drilling.

The preferred method is raster scan drilling. In this method, the pattern is reduced to a rectangular repeating unit 141 , an example of which is shown in FIG. 11 . This repeating unit contains all the information needed to form the desired pattern. When repeating units are used like tiles, while placing them end-to-end and juxtaposed, larger required patterns are formed.

The repeating unit 141 is further subdivided into smaller rectangular unit cells or “pixels” 142 . Although usually square, for some purposes it is more convenient to use non-proportional pixels. A pixel itself has no size, the actual size of the image is set during processing, ie the width 145 and length 146 of a pixel are only set during the actual drilling operation. During drilling, the length of the pixel is set to a size corresponding to a selected number of pulses from carriage pulse generator 134 . Similarly, the width of a pixel is set to a size corresponding to the number of pulses from the rotary pulse generator 124 . Therefore, for ease of illustration, the pixels are represented as squares in FIG. 5a; however, it is not required that the pixels be square, as long as the pixels are rectangular.

Each column of pixels represents a pass of the workpiece past the laser focus. This sequence is repeated as many times as required to reach the full extent of the workpiece 102 . White pixels represent an "off" command to the laser, and each black pixel represents an "on" command to the laser. The result is a simple binary file of 1s and 0s, where a 1 or white is an instruction for the laser to be off and a 0 or white is an instruction for the laser to be on.

Referring to FIG. 4, this figure shows the content of the engraving file transmitted by the host computer 142 to the laser 137 through the connection 143. The file is transmitted in binary form, wherein 1 means off and 0 means on. By varying the time between commands, the duration of the commands is adjusted to match the size of the pixel. After each column file is complete, process that column again or repeat until the entire range is complete. When executing a column of instructions, the lateral drive moves slightly. The speed of moving back and forth is set so that after the engraving on the periphery is completed, the lateral drive moves the focusing lens by a distance of the width of one column of pixels to process the next column of pixels. Continue this step until the end of the file is reached, repeating the file again in the axial dimension until the full required width is reached.

In this method, each operation creates many narrow cuts in the material rather than large pores. Since these cuts are all aligned precisely side-by-side and overlap slightly, the cumulative effect is the hole.

Fabrication of laser-engraved three-dimensional topographical support elements by laser modulation is the preferred method. Laser modulation is performed by gradually varying laser power on a pixel-by-pixel basis. In laser modulation, the simple on-off instruction of raster scan drilling is replaced by an instruction to gradually adjust the laser power for each individual pixel of the laser modulation file. In this way, the workpiece can be formed into a three-dimensional structure with a single operation of the workpiece.

Laser modulation has several advantages over other methods of fabricating three-dimensionally topographical support elements. Laser modulation produces a one-piece seamless support element without pattern mismatch due to the presence of seams. Using laser modulation, the support element can be completed in a single operation instead of multiple operations, thus improving efficiency and reducing costs. Laser modulation eliminates issues with pattern alignment that arise in multi-step sequential operations. Laser modulation also allows the generation of topographical features with complex geometries over longer distances. By varying the command to the laser, the depth and shape of features can be precisely controlled, and features that vary continuously in cross-section can be formed. Furthermore, the fixed positioning of the holes relative to each other can be maintained during laser engraving.

Referring again to FIG. 4, during the laser modulation process, the host computer 142 may send commands to the laser 137 other than a simple "on" or "off" format. For example, an 8-bit (byte) format can be used instead of a simple binary file, which allows the power emitted by the laser to be varied at 256 possible levels. When using the byte format, a command like "11111111" commands the laser to shut down, "00000000" commands the laser to deliver full power, and something like "10000000" commands the laser to deliver half of the full available laser power.

Laser modulation files can be generated in many ways. One such approach is to graphically construct the document using a computer image with 256 gray levels of gray. In this grayscale image, black can represent full power, white can represent no power, and various shades of gray in between represent intermediate power levels. Such laser engraved files can be visualized or generated using a number of computer graphics programs. Using this file, the power emitted by the laser is modulated on a pixel-by-pixel basis, allowing the direct engraving of three-dimensional topographical support elements. Although an 8-bit byte format is described herein, other levels such as 4-bit, 16-bit, 24-bit, or other formats may be used instead.

A suitable laser in a laser modulation system for laser engraving is a high flow _CO2 laser with a power output of 2500 watts, although lower power output lasers can also be used. The main consideration is that the laser must be able to switch power levels as fast as possible. A preferred slew rate is at least 10 kHz, and a more preferred slew rate is 20 kHz. A high energy transfer rate is required to process as many pixels as possible per second.

Figure 5 is a graphical representation of a laser modulation file comprising repeating units 141a for forming a support element that can be used to form the porous membrane shown in Figures 1a-1e. Figure 5a is an enlarged portion of the laser modulation file shown in Figure 5.

Figure 5b is a graphical representation of a laser modulation file comprising repeating units 141b for forming a support element that can be used to form the porous membrane shown in Figures 1e-1j. Figure 5c is an enlarged portion of the laser modulation file shown in Figure 5b, corresponding to the portion of the file circled "5c" in Figure 5b. Figure 5d is an enlarged portion of the laser modulation file shown in Figure 5b, corresponding to the portion of the file circled "5d" in Figure 5b. Figure 5e is an enlarged portion of the laser modulation file shown in Figure 5b, corresponding to the portion of the file circled "5e" in Figure 5d.

In Figures 5-5e, black areas 154a represent pixels where the laser is commanded to deliver full power, thereby forming holes in the support member corresponding to holes 16 in the three-dimensional porous membrane 10 shown in Figures 1a-1d. Light gray areas 155 represent pixels where the laser was instructed to apply very low levels of power such that the surface of the support element was substantially unchanged. These areas of the support element correspond to the projections 11 shown in FIG. 1a. The other regions shown in FIGS. 5-5e (these regions are shown in various levels of gray) represent corresponding levels of laser power and correspond to the various levels of the films 10 and 100 shown in FIGS. 1a-1d and 1e-1j, respectively. feature. For example, regions 157 and 159 correspond to intersecting elements 14 a and 14 b of membrane 10 and membrane 100 .

FIG. 6 is a photomicrograph of a portion 161 of the support element after it has been engraved using the file shown in FIG. 5 . The pattern on this part of the support element shown in Figure 6 is repeated on the surface of the support element, thereby forming the repeating pattern of the membrane 10 shown in Figures 1a-1d.

Figure 6a is a photomicrograph of a portion 162 of the support element after it has been engraved using the file shown in Figure 5 . The pattern on this part of the support element shown in Figure 6a is repeated on the surface of the support element, thereby forming a film with a repeating butterfly pattern of the kind shown in Figures 1e-1j. Figure 6b is an enlarged portion of the support element shown in Figure 6a, which corresponds to the portion of the support element circled "6b" in Figure 6a. After the laser engraving of the workpiece is completed, the workpiece can be assembled into the structure shown in FIG. 7 and used as a support element. Two end bells 235 are fitted inside a workpiece 236 with a laser engraved area 237 . The two end bells may be shrink fit, press fit, secured by mechanical means such as a narrow band 238 and screw 239 as shown, or by other mechanical means. The end bell provides a means of holding the workpiece in a circular shape, driving the finished assembly, and securing the finished structure in the piercing device.

A preferred apparatus for making such a three-dimensional porous membrane is shown in FIG. 8 . As shown, the support element is a rotatable drum 753 . In this particular device, the drum rotates in a counterclockwise direction. Hot air nozzles 759 are positioned outside the drum 753 to provide a curtain of hot air to directly impinge on the film carried on the laser engraved support element. Provision is made to retract the hot air nozzle 759 to avoid overheating the membrane when stationary or moving at a slow speed. The blower 757 works together with the heater 758 to supply hot air to the nozzle 759 . Vacuum head 760 is positioned inside drum 753 directly opposite nozzle 759 . Vacuum head 760 may be radially adjusted and positioned to contact the inner surface of drum 753 . A vacuum source 761 is provided to continuously evacuate the vacuum head 760 .

A cooling zone 762 is provided inside the drum 753 at a location contacting its inner surface. Cooling zone 762 houses cooling vacuum source 763 . In the cooling zone 762, a cooling vacuum source 763 draws ambient air through the holes formed in the film, thereby setting the pattern formed in the perforated zone. The vacuum source 763 also provides a means to hold the film in place in the cooling zone 762 of the drum 753 and to isolate the film from the tension caused by winding the film after perforation.

A continuous uninterrupted film 751 of thermoplastic polymer material is placed on a laser engraved support element 753 .

An enlarged view of the area circled in FIG. 8 is shown in FIG. 9 . As shown in this embodiment, vacuum head 760 has two vacuum slits 764 and 765 that extend across the width of the film. For some purposes, however, it may be preferable to use a separate vacuum source for each vacuum slot. As shown in FIG. 23 , vacuum slot 764 provides an area for the stock film to remain down as it approaches air knife 758 . Vacuum slot 764 is connected to a vacuum source through passage 766 . This design anchors the incoming film 751 firmly to the drum 753 and is immune to tension in the incoming film due to unwinding of the film. This design also lays the membrane 751 flat on the outer surface of the drum 753 . The second vacuum slot 765 defines the vacuum perforation area. The middle support rod 768 is located in the middle of the slots 764 and 765 . The position of the vacuum head 760 is such that the point of impact of the hot air curtain 767 is directly above the middle support rod 768 . The hot air is provided at a sufficient temperature, at a sufficient angle of incidence to the film, and at a sufficient distance from the film that the film becomes soft and deformable due to the applied force. The geometry of the device ensures that the membrane 751, while softened by the hot air curtain 767, is free from the tension created by holding down the slit 764 and cooling zone 762 (FIG. 22). Vacuum porous region 765 is in close proximity to hot air curtain 767, thereby minimizing the time to heat the membrane and preventing excessive heat transfer to support member 753.

Referring to FIGS. 8 and 9 , the flexible film 751 is fed from a supply roll 750 and passes over an idler roll 752 . Roller 752 may be connected to a load cell or other mechanical device to control the feed tension into film 751. The membrane 751 is then placed in close contact with the support element 753 . Next, the membrane and support member are passed through vacuum zone 764 . In the vacuum region 764 , the pressure differential further forces the membrane into intimate contact with the support element 753 . Vacuum pressure keeps the membrane free from feed tension. The membrane and support element combination is then passed under a curtain of hot air 767 . A curtain of hot air heats the combination of the membrane and support element, thereby softening the membrane.

The heat-softened membrane and support element combination is then passed into vacuum region 765 where the pressure differential deforms the heated membrane and assumes the topography of the support element. The heated film region lying on the region of the opening in the support element deforms further into the region of the opening of the support element. If there is sufficient heat and deformation force, the membrane on the open area of the support element ruptures, forming a hole.

The still hot porous membrane and support element combination then passes through cooling zone 762 . In the cooling zone, sufficient ambient air is sucked through the freshly apertured membrane to cool the membrane and support element.

The cooled film is then removed from the support element around idler rolls 754 . Idler rollers 754 may be connected to load cells or other mechanical devices to control winding tension. The porous membrane is then conveyed to finish roll 756 where the membrane is rolled up.

Construction of test components

Test assemblies #1 and #5 of the present invention were fabricated to illustrate the enhanced properties of porous membranes according to the present invention. Comparative assemblies #2, #3 and #4 were also manufactured. Test assemblies #1-#5 each included a cover layer, a transfer layer, an absorbent core, and a barrier layer. The transfer layer, absorbent core and barrier layer used in test assemblies #1-#5 are as follows:

(a) transfer layer - 100 gsm 3003 Visorb (100 gsm 3003 Visorb) product (air laid) available from Buckeye Technologies Inc. (Buckeye Technologies Inc., Memphis TN), Memphis TN;

(b) Absorbent core - available from Rayonier Inc., Jessup GA, 208 gsm Novathin product (No. 080525);

(c) Conventional polyethylene monolithic film barrier layer.

The layers of the test assembly are bonded to each other in a conventional manner using conventional and commercially available structural adhesives.

Each of the cover materials described in the following test assemblies #1-#3 and #5 consisted of a commercially available base film, product number DPD81715, available from Tredegar Corporation, Sao Paulo, Brazil. Sao Paulo, Brazil).

Composition of Test Component #1:

A porous membrane according to the present invention was first formed, as shown in Figures 1a-1d and as described above (hereinafter referred to as Membrane #1). Film #1 was constructed such that the upper surface of intersecting elements 14a and 14b were recessed 15 mils relative to the upper surface of the film, each of intersecting elements 14a and 14b having a width "a" of 10 mils. Each intersecting element 14a is 100 mils long and each intersecting element 14b is 60 mils long. The average open area of Membrane #1 was found to be 26%. Film #1 was applied on top of the transfer layer described above to form a test assembly consisting from top to bottom of the cover layer, transfer layer, absorbent core and barrier layer, completing Test Assembly #1.

Composition of Test Component #2:

A porous membrane identical in all respects to Membrane #1 (hereinafter referred to as Membrane #2) is first formed, with the difference that the intersecting elements 14a and 14b are arranged so that they are coplanar with the top surface of the membrane, i.e., the intersecting elements are opposite There is no recess on the top surface of the membrane. The average open area of Membrane #2 was found to be 26%. Film #2 was applied on top of the transfer layer described above to form a test assembly consisting from top to bottom of the cover layer, transfer layer, absorbent core and barrier layer, completing Test Assembly #2.

Composition of Test Component #3:

A porous membrane identical in all respects to Membrane #1 (hereinafter referred to as Membrane #3) was first formed, with the difference that intersecting elements 14a and 14b were omitted entirely, ie, the membrane comprised many hexagonal pores. The average open area of Membrane #3 was found to be approximately 39%. Film #3 was applied on top of the transfer layer described above to form a test assembly consisting from top to bottom of the cover layer, transfer layer, absorbent core and barrier layer, completing Test Assembly #3.

Composition of Test Component #4:

Removal of the porous membrane cover from the Semper Livre ultra-thin product with wings, manufactured by Johnson & Johnson Ind. E. Com. Ltda., Brazil layer (hereinafter referred to as film #4). Film #4 was applied on top of the transfer layer described above to form a test assembly consisting from top to bottom of the cover layer, transfer layer, absorbent core and barrier layer, completing Test Assembly #4.

Composition of test component #5:

A porous membrane according to the present invention was first formed as shown in Figures 1e-1j and as described above (hereinafter referred to as Membrane #5). The upper surfaces of the intersecting elements 14a and 14b were recessed by 4.5 mils relative to the upper surface of the film, and the width "a" of each of the intersecting elements 14a and 14b was 5 mils and 9 mils, respectively. The lengths of each of cross members 14a and 14b are 100 mils and 60 mils, respectively. The film included a plurality of larger butterfly patterns of the kind shown in Figure 1e and a plurality of smaller butterfly patterns of the kind shown in Figure 1e. For larger butterflies, measure 1.0 inches from the most distal end of one wing to the most distal end of the other and 0.6 inches at the narrowest point of the butterfly's waist. For smaller butterflies, measure 0.6 inches from the most distal end of one wing to the most distal end of the other and 0.4 inches at the narrowest point of the butterfly's waist. The larger and smaller butterflies are equally spaced such that a 9 inch (length) x 6 inch (width) porous film sample has 9 large and 9 small butterflies equally spaced on the film sample. Each of the large and small butterflies includes a border 108 and a plurality of apertures 106 arranged within the area defined by the border. The width of the border 108 for each large butterfly is 78 mils, and the width of the border 108 for each small butterfly is 31 mils. For both the larger and smaller butterflies, the film surface within film region 109 defined by boundary 108 was recessed about 4.5 mils from the top film surface. The area 109 defined by the boundaries of the smaller and larger butterflies has a plurality of holes 106, each of which is elliptical in shape with a major axis of 43 mils and a minor axis of 16 mils. The distance "n" between horizontally adjacent holes 106 was 40 mils, and the distance "o" between vertically adjacent holes was 34 mils.

Five samples of each of the above Test Assemblies #1-5 were fabricated and tested for Fluid Penetration Time (FPT), Rewet (in grams) and Masking Value. Therefore, a total of 25 samples (5 for each test assembly) were produced. Test methods for determining fluid penetration time (FPT), rewet, and masking values are discussed in more detail below. The same 5 samples were used for each test. That is, instead of using a clean sample for each test, the same sample is used for liquid penetration, followed by a rewet test, and then a masking value test.

The test fluid for the Liquid Penetration Test, Rewet Test, and Masking Value Test may be any synthetic menstrual fluid having the following properties: (1) viscosity of approximately 30 centipoise; (2) Hunter ( Hunter) color value: L is about 17, a is about 7, and b is about 1.5. A certain amount of test liquid is placed in a glass dish with a depth of 0.25", and the L Hunter value of the test liquid is measured.

Fluid Penetration Time (FPT)

The sample to be tested is placed under the liquid penetration test orifice plate, and the liquid penetration time is measured. The test panels were rectangular, manufactured by Lexan, 25.4 cm (10.0 inches) long, 7.6 cm (3.0 inches) wide, and 1.27 cm (0.5 inches) thick. A concentric, oval hole was formed through the plate with a major axis (length) of 3.8 cm parallel to the long side of the plate and a minor axis (width) of 1.9 cm parallel to the short side of the plate.

The orifice plate is located in the center of the sample to be tested. A graduated 10 cubic centimeter syringe containing 7 ml of test fluid is suspended above the orifice so that the outlet of the syringe is approximately 3 inches above the orifice. The syringe is held horizontally, parallel to the surface of the test plate, and liquid is then expelled from the syringe at a rate such that the liquid flows into the well in a stream perpendicular to the test plate, a stopwatch is started when the liquid initially contacts the sample to be tested. The stopwatch can be stopped when the surface of the sample is first seen in the well. The elapsed time on the stopwatch is the liquid penetration time. The average fluid penetration time (FPT) was calculated from the test results of 5 samples. The average liquid penetration time for each of the test assemblies #1-#5 was determined by testing 5 samples for each test assembly.

rewetting potential

The rewet potential is a measure of the ability of a sanitary napkin or other article to retain liquid within its structure when it contains a substantial amount of liquid and is subjected to external mechanical pressure. The rewetting potential was determined and determined by the following method.

The equipment required for this test includes a stopwatch accurate to 1 second and lasting at least 5 minutes, a glass graduated cylinder with a capacity of 10 milliliters and an internal diameter of approximately 12 millimeters, a volume of test fluid, and a liquid penetration test orifice.

The equipment further includes: a scale or balance capable of weighing accurately to ±0.001 grams; a certain amount of NuGauze universal porous material (sponge) (10 cm x 10 cm) (4 inches x 4 inches) from Johnson & Johnson 4-ply gauze from Johnson & Johnson Medical Inc., product number: 3634 (available from Johnson & Johnson Hospital Services, order number: 7634); 2.22 kg (4.8 lbs. ), the dimensions are: 5.1 cm (2 inches) by 10.2 cm (4.0 inches) by approximately 5.4 cm (2.13 inches), the weight is on a surface of 5.1 cm by 10.2 cm (2 inches by 4 inches) A pressure of 4.14 kilopascals (0.6 psi) is applied.

The two pieces of porous material were folded so that the folded edges were placed against each other to form a multilayer structure of approximately 5 cm x 10 cm x 16 layers. The 16 layers of porous material used in each sanitary napkin sample to be tested were weighed to the nearest 0.001 gram. Lay the preconditioned sanitary napkin or other article on a level surface without removing the release paper and with the cover facing up.

Immediately after application of the test liquid in the orifice plate in the FPT test described above, the stopwatch is started and the time measured for 5 minutes as soon as the top surface of the liquid reveals the coversheet of the sanitary napkin. After 5 minutes, remove the perforated plate and place the napkin on a firm, level surface with the cover facing up. A pre-weighed piece of 16-ply multilayer porous material was placed over and centered on the wetted area and a standard 2.22 kg weight was placed on top of the 16-ply multilayer porous material. After placing the porous material and weight on the sanitary napkin, start the stopwatch immediately, and after 3 minutes, quickly remove the standard weight and 16 layers of multi-layer porous material. Measure and record the wet weight of the 16-layer multilayer porous material, and record to the nearest 0.001 gram. The rewet value was then calculated as the weight difference (in grams) between the wet 16-layer multilayer porous material and the dry 16-layer multilayer porous material.

Repeat the above measurements for 5 samples, wiping the weights clean before each operation if necessary. The values obtained for the 5 test samples were averaged to obtain the average rewet potential. Therefore, the average rewet potential for each of the test assemblies #1-#5 was determined by testing 5 samples for each test assembly.

When carrying out the above method, it is very important to conduct the test under the conditions of temperature 21±1°C and relative humidity 65±2%.

masking value

The ability of a facing material to reduce the revealing of product stains after use, ie, masking value, is determined by the following method. Immediately following liquid testing, each of the assemblies #1-5 were imaged at 50X magnification after liquid penetration testing and rewetting testing using a Scalar USB microscope, model UM02 -SUZ-01, using its own light source. Set the Sculler microscope to Hue Saturation and Intensity with Auto Exposure turned on. Take 5 images of the stained area of each sample, and save them as 24-bit true-color graphic files (in bmp format) with 640×480 pixels. A total of 25 images were thus acquired (5 images were taken for each of the 5 samples).

Then open the original bmp image with Image Pro Plus version 4.0 software (product of Media Cybermetics, LP (Media Cybermetics, LP)). The image is then converted from the original 24-bit true color format to an 8-bit grayscale image using the image poroparas. Apply the histogram function of the image Pole Paras to the image to construct the histogram of the image grayscale. This method counts the number of pixels at a specific grayscale value, from 0 (black) to 255 (white). Data from the histograms were converted into Microsoft Excel 2000 worksheets using DDE (Windows Dynamic Data Exchange).

When DDE is converted into Excel 2000, a worksheet with 25 columns and 256 rows in each column is formed. The columns in the worksheet contain the histogram values for a single image. Each column consists of 256 values, which are counts of the number of pixels in the image, which correspond to numbers in the range 0-255. Rows are then averaged to produce a material-specific average histogram.

A typical mean histogram exhibits a bimodal distribution with gray areas representing the stained areas of the test components and white areas representing the unstained areas of the test components. Observation of the average histogram demonstrates the presence of a plateau between the gray and white areas, with all stained areas defined by a gray value equal to or less than 90. Thus, the stained area of a material can be determined by summing the grayscale values from 0-90, with lower numbers representing less gray area and thus better masking. The sum of grayscale values equal to or less than 90 is the "masked value". The masking values obtained for each of the 5 test samples of the test assembly were averaged to obtain an average masking value for each test assembly. Figure 10 is a representative averaged histogram showing the stain density of an absorbent article having a porous film according to the present invention as its coversheet.

Table 1 below lists the average liquid breakthrough time, average rewet (in grams), and masking values for test assemblies #1-#5.

test component Average liquid penetration time (seconds) Average rewetting (grams) average masking value #1 38.50 0.032 50841.26 #2 45.52 0.040 78587.00 #3 21.55 0.052 114930.20 #4 46.50 0.024 111959.93 #5 30.43 0.037 55794.13

As shown in the table above, test assemblies #1 and #5 constructed using porous membranes according to the present invention provided a unique combination of liquid handling capabilities and masking properties.

While specific embodiments of the present invention have been described above, this application is intended to cover modifications and variations of this invention. As long as these modifications and changes are within the scope of the appended claims and their equivalents.

Claims (63)

1. A three-dimensional porous membrane, comprising: a first planar surface in a first imaginary plane; a second planar surface in a second imaginary plane, said second imaginary plane being located below said first imaginary plane; first plurality of holes; at least one element spanning each of the first plurality of holes, thereby defining a plurality of smaller holes, each of the plurality of smaller holes corresponding to a corresponding one of the first plurality of holes The apertures are connected, wherein said element spanning each of said apertures has a top surface lying in a third imaginary plane, said third imaginary plane being below said first imaginary plane. 2. The three-dimensional porous membrane of claim 1, wherein the first plurality of pores is defined from the first imaginary plane to the third imaginary plane. 3. The three-dimensional porous membrane of claim 1 , wherein the top surface of the member spanning each of the plurality of holes is substantially parallel to the first imaginary plane and the second imaginary plane. imaginary plane. 4. The three-dimensional porous membrane of claim 1, wherein the third imaginary plane is located below the first and second imaginary planes. 5. The three-dimensional porous membrane of claim 1, wherein said at least one element spanning each of said plurality of pores comprises: a first intersecting member spanning each of the plurality of holes; A second intersecting member spanning each of the plurality of holes. 6. The three-dimensional porous membrane of claim 5, wherein the first intersecting element intersects the second intersecting element. 7. The three-dimensional porous membrane of claim 6, wherein the first intersecting elements and the second intersecting elements are arranged orthogonally to each other. 8. The three-dimensional porous membrane of claim 1, wherein the porous membrane has a plurality of bumps arranged on the first flat surface. 9. The three-dimensional porous film of claim 1, wherein the elements spanning each hole in the first plurality of holes each have a width of about 4.0-24.0 mils. 10. The three-dimensional porous membrane of claim 5, wherein the first and second intersecting elements each have a width of about 4.0-24.0 mils. 11. The three-dimensional porous membrane of claim 1, wherein the membrane has an open area of about 20-30%. 12. A three-dimensional porous membrane comprising: a first substantially planar surface lying in a first imaginary plane; a second substantially planar surface lying in a second imaginary plane; a plurality of interconnected frame portions each having at least a first inner wall and a second inner wall spaced apart from each other; a plurality of intersecting elements each extending from one said inner wall of one said frame portion to said opposite second inner wall of one said frame portion, said intersecting elements each having an apex lying in an imaginary plane surface, the imaginary plane is located below the first imaginary plane; A plurality of apertures extending from at least the first planar surface to the second planar surface, each aperture being bounded by at least one of the frame portions and at least one of the intersecting members. 13. The three-dimensional porous membrane of claim 12, wherein said top surfaces of said intersecting elements are substantially parallel to said first imaginary plane and said second imaginary plane. 14. The three-dimensional porous membrane according to claim 13, wherein the top surfaces of the crossing elements are located in a third imaginary plane, and the third imaginary plane is located between the first imaginary plane and the Below the second imaginary plane. 15. The three-dimensional porous membrane of claim 12, wherein each frame portion includes oppositely spaced end regions and oppositely spaced sidewalls. 16. The three-dimensional porous membrane of claim 15, wherein the plurality of intersecting elements comprises: a first plurality of intersecting elements, each of said first plurality of intersecting elements extending from one said end region of said framework to an opposite end region of said framework; A second plurality of intersecting elements each extending from one side wall of the frame to an opposite side wall of the frame. 17. The three-dimensional porous membrane of claim 16, wherein each of the first plurality of intersecting elements intersects one of the second plurality of intersecting elements. 18. The three-dimensional porous membrane of claim 17, wherein each of the first plurality of intersecting elements is arranged orthogonally relative to one of the second plurality of intersecting elements. 19. The three-dimensional porous membrane of claim 12, wherein each frame portion is substantially hexagonal. 20. The three-dimensional porous membrane of claim 12, further comprising: A plurality of bumps extending upwardly from the first planar surface of the membrane. 21. The three-dimensional porous membrane of claim 12, wherein the membrane has an open area of about 20-30%. 22. A three-dimensional porous membrane comprising: a first planar surface in a first imaginary plane; a second planar surface in a second imaginary plane; a plurality of holes extending at least from said first planar surface to said second planar surface; At least one element spanning each of the plurality of holes, wherein the element spanning each of the holes has a top surface lying in a third imaginary plane, the third imaginary plane lying on the first below an imaginary plane. 23. The three-dimensional porous membrane of claim 22, wherein said top surface of said element spanning each of said plurality of holes is substantially parallel to said first imaginary plane and said second imaginary plane. imaginary plane. 24. The three-dimensional porous membrane of claim 22, wherein the third imaginary plane is located below the first and second imaginary planes. 25. The three-dimensional porous membrane of claim 22, wherein said at least one element spanning each of said plurality of pores comprises: a first intersecting member spanning each of the plurality of holes; A second intersecting member spanning each of the plurality of holes. 26. The three-dimensional porous membrane of claim 25, wherein the first intersecting element intersects the second intersecting element. 27. The three-dimensional porous membrane of claim 26, wherein the first intersecting elements and the second intersecting elements are arranged orthogonal to each other. 28. The three-dimensional porous membrane of claim 22, wherein the porous membrane has a plurality of bumps arranged on the first planar surface. 29. The three-dimensional porous film of claim 22, wherein the elements spanning each hole in the first plurality of holes each have a width of about 4.0-24.0 mils. 30. The three-dimensional porous membrane of claim 25, wherein the first and second intersecting elements each have a width of about 4.0-24.0 mils. 31. The three-dimensional porous membrane of claim 22, wherein said membrane has an open area of about 20-30%. 32. The three-dimensional porous film of claim 1, wherein the porous film is a coversheet in an absorbent article. 33. The three-dimensional porous film of claim 12, wherein the porous film is a cover sheet in an absorbent article. 34. The three-dimensional porous film of claim 22, wherein the porous film is a cover sheet in an absorbent article. 35. A three-dimensional porous membrane comprising: a first planar surface in a first imaginary plane; a second planar surface in a second imaginary plane, said second imaginary plane being located below said first imaginary plane; first plurality of holes; spanning at least one element of each hole in the first plurality of holes, thereby defining a plurality of smaller holes, each hole in the plurality of smaller holes corresponding to a corresponding hole in the first plurality of holes wherein said element spanning each of said holes has a top surface lying in a third imaginary plane, said third imaginary plane being below said first imaginary plane; second plurality of holes. 36. The three-dimensional porous film of claim 35, wherein the second plurality of pores is visually distinguishable from the first plurality of pores. 37. The three-dimensional porous membrane of claim 35, wherein said membrane comprises at least one first portion and at least one second portion, said first portion comprising said first plurality of pores, said second portion comprising said second plurality of holes, Wherein, the surface of the membrane in the second portion is located below the first imaginary plane. 38. The three-dimensional porous membrane of claim 36, wherein the second plurality of pores together define one of a pattern and indicia, or a combination thereof. 39. The three-dimensional porous membrane of claim 35, wherein the second plurality of pores is surrounded by a boundary separating the first plurality of pores from the second plurality of pores. 40. The three-dimensional porous film of claim 35, wherein the at least one element spanning each hole in the first plurality of holes each has a length of about 30.0-150.0 mils. 41. The three-dimensional porous film of claim 39, wherein the at least one element spanning each hole in the first plurality of holes each has a width of about 4.0-24.0 mils. 42. The three-dimensional porous membrane of claim 35, wherein said membrane has an open area of about 20-30%. 43. The three-dimensional porous film of claim 35, wherein the third imaginary plane is located about 3.0-17.0 mils below the first imaginary plane. 44. A three-dimensional porous membrane comprising: a first substantially planar surface lying in a first imaginary plane; a second substantially planar surface lying in a second imaginary plane, said second imaginary plane being located below said first imaginary plane; a plurality of interconnected frame portions each having at least a first inner wall and a second inner wall spaced apart from each other; a plurality of intersecting elements each extending from one said inner wall of one said frame portion to said opposite second inner wall of one said frame portion, said intersecting elements each having an apex lying in an imaginary plane surface, the imaginary plane is located below the first imaginary plane; a first plurality of apertures extending at least from said first planar surface to said second planar surface, said apertures being bounded by at least one of said framework portions and at least one of said intersecting members; second plurality of holes. 45. The three-dimensional porous film of claim 44, wherein the second plurality of pores is visually distinguishable from the first plurality of pores. 46. The three-dimensional porous membrane of claim 44, wherein said membrane comprises at least one first portion and at least one second portion, said first portion comprising said first plurality of pores, said second portion comprising said second plurality of holes, Wherein, the surface of the membrane in the second portion is located below the first imaginary plane. 47. The three-dimensional porous membrane of claim 44, wherein the second plurality of pores together define one of a design and indicia. 48. The three-dimensional porous membrane of claim 44, wherein the second plurality of pores is surrounded by a boundary separating the first plurality of pores from the second plurality of pores. 49. The three-dimensional porous film of claim 44, wherein the at least one element spanning each hole in the first plurality of holes each has a length of about 30.0-150.0 mils. 50. The three-dimensional porous film of claim 44, wherein the at least one element spanning each hole in the first plurality of holes each has a width of about 4.0-24.0 mils. 51. The three-dimensional porous membrane of claim 44, wherein said membrane has an open area of about 20-30%. 52. The three-dimensional porous film of claim 44, wherein the third imaginary plane is located about 3.0-17.0 mils below the first imaginary plane. 53. The three-dimensional porous membrane of claim 44, wherein at least a portion of a surface of each framing member is recessed relative to the first imaginary plane. 54. The three-dimensional porous membrane of claim 53, wherein said portion of said framing member is recessed from said first imaginary plane by about 2.0-5.0 mils. 55. A three-dimensional porous membrane comprising: a first planar surface in a first imaginary plane; a second planar surface in a second imaginary plane; a plurality of holes extending at least from said first planar surface to said second planar surface; At least one element spanning each of the plurality of holes, wherein the element spanning each of the holes has a top surface lying in a third imaginary plane, the third imaginary plane lying on the first below an imaginary plane; second plurality of holes. 56. The three-dimensional porous film of claim 55, wherein the second plurality of pores is visually distinguishable from the first plurality of pores. 57. The three-dimensional porous membrane of claim 55, wherein said membrane comprises at least one first portion and at least one second portion, said first portion comprising said first plurality of pores, said second portion comprising said second plurality of holes, Wherein, the surface of the film in the second portion is located below the first imaginary plane. 58. The three-dimensional porous membrane of claim 56, wherein the second plurality of pores together define one of a design and indicia. 59. The three-dimensional porous membrane of claim 55, wherein the second plurality of pores is surrounded by a boundary, the boundary separating the first plurality of pores from the second plurality of pores. 60. The three-dimensional porous film of claim 55, wherein the at least one element spanning each hole in the first plurality of holes each has a length of about 30.0-150 mils. 61. The three-dimensional porous film of claim 55, wherein the at least one element spanning each hole in the first plurality of holes each has a width of about 4.0-24.0 mils. 62. The three-dimensional porous membrane of claim 55, wherein said membrane has an open area of about 20-30%. 63. The three-dimensional porous film of claim 55, wherein the third imaginary plane is located about 3.0-17.0 mils below the first imaginary plane.

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