Sheet materials and method for producing them

Sheet materials and method for producing them

MINNESOTA MINING AND MANUFACTURING COMPANY

C: 77444

SHEET MATERIAL FOR FORMING THE LOOP PORTION FOR HOOK AND LOOP FASTENERS

Technical Field

The present invention relates to sheet materials adapted to be cut into pieces to form the loop portions for fasteners of the type including releasably engageable hook and loop portions, and methods for making such sheet materials.

Background of the Invention

Many sheet materials are known that are adapted to be cut into pieces to form the loop portions for fasteners of the type comprising releasably engageable hook and loop portions. Such sheet materials typically comprise a backing and a multiplicity of loops anchored in the backing and projecting a front surface of the backing so that they may be releasably engaged with the hooks on the hook portion of such a fastener, and can be made by many methods including conventional weaving, or knitting techniques. Such a sheet material in which the loops are stitched into the backing is described both in U.S. Patent No. 4,609,581, and in U. S. Patent Application No. 760,999. While the loop fastener portions made from many such loop materials work well with many different hook fastener portions, many of the processes by which they are made are more expensive than may be desired, particularly when the loop fastener portions are intended for a limited amount of use, such as to attach a disposable diaper to an infant, or to attach an abrasive disk to a backing pad by which it is driven.

Disclosure of Invention

The present invention provides a sheet material adapted to be cut into pieces to form the loop portions for fasteners of the type comprising releasably engageable hook and loop portions, which sheet material provides effective loop fastener portions for such fasteners while being very inexpensive to manufacture so that they are economical to use when the loop fastener portions are intended for a limited amount of use, such as to releasably attach a disposable diaper or other garment, or to attach an abrasive disk to a backing pad by which it is driven.

According to the present invention there is provided a sheet material adapted to be cut into pieces to form loop portions for fasteners, which sheet material comprises a backing, and a multiplicity of fibers having portions bonded to the backing along a front surface at spaced bonding locations to form arcuate portions of the fibers projecting from the front surface of the backing between the bonding locations. The arcuate portions have a height from the backing of less than about 0.64 centimeters (0.250 inch) and preferably less than about 0.318 centimeters (0.125 inch). The width of the bonding locations should be between about 0.005 and 0.075 inch, and the width of the arcuate portions of the fibers should be between about 0.06 and 0.35 inch. The fibers in the arcuate portions project to about the same height above the front surface, which height is at least one third, and preferably one half to one and one half the distance between the bonding locations, the individual fibers are less than 15 denier in size, and the fibers collectively have a basis weight in the range of 5 to 200 grams per square meter (and preferably in the range of 10 to 75 grams per square meter) measured along the front surface of the backing to provide sufficient open area between the fibers along the arcuate portions (i.e., between about 10 to 70 percent open area) to afford ready engagement of the fibers along the arcuate portions by the hook portion of the fastener.

Preferably the sheet material according to the present invention is made from the fibers and backing by forming the fibers into a sheet of fibers having arcuate portions projecting in the same direction from spaced anchor portions of the sheet of fibers, and bonding the spaced anchor portions of the sheet of fibers to the backing so that the arcuate portions project from the front surface of the backing. This forming of the fibers is preferably done by providing first and second generally cylindrical corrugating members each including a plurality of uniformly spaced ridges defining its periphery, mounting the corrugating members in axially parallel relationship with portions of the ridges of the corrugating members in mesh with each other, rotating at least one of the corrugating members, feeding the sheet of fibers between the meshed portions of the ridges of the rotating corrugating members to generally conform the sheet of fibers to the periphery of the first corrugating member, thereby forming the arcuate portions of the sheet of fibers in spaces between the ridges of the first corrugating member and the anchor portions of the sheet of fibers along outer surfaces of the ridges of the first corrugating member, and retaining the formed sheet of fibers along the periphery of the first corrugating member after it has moved past the meshing portions of the ridges. The anchor portions of the sheet of fibers are then bonded to the front surface of the backing while they are on the end surfaces of the ridges on the first corrugating member, and the thus formed sheet material is separated from the first corrugating member.

The ridges can be elongate and generally parallel so that the bonding locations are also elongate and generally parallel and are continuous in one direction across the front surface of the backing so that continuous rows of the arcuate portions extend across the backing of the sheet material; or alternately the ridges can be elongate, generally parallel, and in a regular pattern of discontinuous lengths so that the parallel bonding locations are also in a regular pattern of discontinuous lengths to to form a regular pattern of discontinuous rows of the arcuate portions along the front surface of the backing. Also it is contemplated that the ridges of the first corrugating member can form interlocking closed patterns (e.g., circular, diamond shaped, octagonal, etc.) to form corresponding patterns for the arcuate portions of the fibers along the front surface of the backing, in which case the second corrugating member will be formed with post like ridges to press the fibers into the centers of the closed patterns.

Elongate ridges on the corrugating members can be oriented at any angle in the range of 0 to 90 degrees with respect to their axes so that the rows of arcuate portions, whether continuous or discontinuous, can be oriented along or transverse to the sheet of fibersfed between the corrugating member or at any angle therebetween.

The backing could be a woven, knitted, random woven, nonwoven or other layer of intertwined fibers, but preferably is a continuous polymeric film in the range of about 0.0025 to 0.013 centimeters (0.001 to 0.005 inch) thick which is generally less expensive than a backing of entwined fibers and allows the backing to be printed by conventional methods along one of its surfaces with graphics (such as advertising, instructions or locating marks)״which will be visible through the loop portions of the fibers due to their large percentage of open area. The film may be a single layer of a polymeric material such as polypropylene, polyester, or polyamide, or may have a plurality of layers such as a central layer of a relatively high strength material such as polyester, a layer defining the first surface of a material more easily bonded to the fiber such as ethylene vinyl acetate or polyethylene, and a layer defining its second surface adapted to adhere the backing to a substrate such as polyethylene or a bonding layer of room-temperature non-tacky thermoplastic material adapted to adhere a fastener portion to a polyolefin layer (such as may be found on a disposable diaper) that can be bonded to the polyolefin layer under heat and pressure that leaves the polyolefin layer substantially undeformed and will hold the fastener portion to the polyolefin layer with greater force than that which is required to separate an engaged fastener, which bonding layer of room-temperature non-tacky thermoplastic material is described in U.S. Patent application No. 126,746 filed November 30, 1987, and can include from about 40% to about 100% of a thermoplastic material having a softening point of generally below 120 degrees Centigrade and preferably below 100 degrees Centigrade, and from about 60% to about 0% of a tackifying resin that has a softening point below about 105 degrees Centigrade and preferably below 95 degrees Centigrade. Suitable thermoplastic materials include ethylene and propylene based copolymers such as ethylene/vinyl acetate copolymers, ethylene/acrylic acid copolymers, and ethylene/methacrylic acid copolymers. Preferred thermoplastic materials include ethylene/vinyl acetate copolymers, especially those with a melt flow index from about 40 to about 2500, and preferably with a melt flow index between about 50 and about 1000. Such materials are available commercially as Elvax 40W, Elvax 150, Elvax 210W, Elvax 220W, Elvax 310, Elvax 410, and Elvax 4980W from E. I. DuPont de Nemours and Co. of Wilmington, Delaware; Escorene UL7710 and Escorene UL7720 from Exxon Chemical Co., Houston, Texas,. and Ultrathene 639-35 and Ultrathene 649-04, available from USI Chemical Co. of Cincinnati, Ohio. Suitable tackifying resins are preferably solid or semisolid, however liquid tackifying resins can also be used. The tackifying resin, when used, should be compatible with the thermoplastic material and may include rosin esters, rosin acids, and derivatives of these; hydrogenated rosin esters and rosin acids and derivatives of these; aliphatic hydrocarbon resins; mixed aliphatic/aromatic hydrocarbon resins, polyterpene resins; resins made from the polymerization and hydrogenation of a dicyclopentadiene feed stream; polyterpene resins and aromatic-modified polyterpene resins; resins made from the polymerization and hydrogenation of a C9 hydrocarbon stream; and resins made from the polymerization and hydrogenation of a mixture of alphamethyl styrene, styrene, and vinyl toluene. Preferred tackifying resins include aliphatic hydrocarbon resins such as Escorez 1580 and Escorez 1310, available from Exxon

Chemical of Houston, Texas; Hercotac 95, available from Hercules Chemical Co. of Wilmington, Delaware; and wingtack Plus and Wingtack 95, available from the Goodyear Tire and Rubber Company of Akron, Ohio. Additional preferred solid tackifying resins include the aromatic-modified polyterpene resins such as Wingtack 86, available from Goodyear; Zonatac 105, available from Arizona Chemical Co. of Panama City, Florida; and Res D-2083, available from Hercules; resins made from the polymerization and hydrogenation of a dicyclopentadiene feed stream such as Escorez 5380, available from Exxon; resins made from the polymerization and hydrogenation of a C9 hydrocarbon stream such as Arkon P-90, available from Arakawa Chemical Co. USA of Chicago, Illinois; and resins made from the polymerization and hydrogenation of mixtures of alphamethyl styrene, styrene, and vinyl toluene such as Regalrez 1065, Regalrez 1078, and Regalrez 1094, available from Hercules. Conventional additives for hot-melt adhesives may also be incorporated into the bonding layer, including, but not limited to, waxes, fillers, oils, pigments, antioxidants, ultraviolet light stabilizers, and heat stabilizers.

The individual fibers may be of many polymeric materials such as polypropylene, polyethylene, polyester, or polyamide, or combinations of such materials such as a core of polyester and a sheath of polypropylene which provides relatively high strength due to its core material and is easily bonded due to its sheath material. Fibers of one material or fibers of different materials or material combinations may be used in the same sheet material.

The sheet of fibers may be fed between the meshed ridges of the corrugating members in the form of a non woven or random woven sheet or web in which the fibers may or may not be bonded together. In such a sheet the fibers may be disposed in various directions with respect to the direction the sheet of fibers is fed between the corrugating members so that in the resultant sheet material the fibers are disposed in various directions with respect to the spaced bonding locations. In such a sheet to be fed between corrugating members with spaced parallel ridges, preferably a majority of the fibers (e.g., over 90 percent) project in one direction along the web and the web is fed between the corrugating members with that direction at about a right angles to the ridges on the corrugating members so that in the resultant sheet material a majority of the fibers project generally at about right angles to the parallel bonding locations.

Alternatively, the fibers may be provided in the form of yarns in the range of 50 to 300 denier, the yarns distributed to provide a sheet of generally uniformly distributed fibers by passing them through a comb, and the sheet of fibers fed between corrugating members having elongate parallel ridges oriented in the range of 0 to 45 degrees with respect to their axes in a direction perpendicular to their axes, which results in a sheet material in which the fibers all extend in directions at about the same angles with respect to the parallel bonding locations.

When the contacting portions of the backing and the fibers are of the same thermoplastic material, bonding of the fibers to the backing can be done by sonic welding or other means of applying heat and pressure to fuse the fibers to the backing at the bonding location. Alternatively, or when the contacting portions of the backing and the fibers are of different materials, the fibers may be adhesively bonded to the backing such as by softening a thermoplastic adhesive layer of the backing by sonic energy or other means of applying heat and pressure to adhere the fibers to the backing at the bonding locations.

Brief Description of Drawing

The present invention will be further described with reference to the accompanying drawing wherein like reference numerals refer to like parts in the several views, and wherein:

Figure 1 is a perspective view of a sheet material according to the present invention;

Figure 2 is a much enlarged top plan view of the sheet material of Figure 1;

Figure 3 is a much enlarged end view of the sheet material of Figure 1;

Figure 4 is a schematic view illustrating an apparatus and a method according to the present invention for making the sheet material of Figure 1;

Figures 5 and 6 are top and side views respectively illustrating a first alternate embodiment of the apparatus of Figure 4;

Figures 7 and 8 are top and side views respectively illustrating a second alternate embodiment of the apparatus of Figure 4; and

Figures 9 and 10 are top and side views respectively of an alternate embodiment of a sheet material according to the present invention made by the apparatus of Figures 7 and 8.

Detailed Description

Referring now to the drawing, there is shown in Figures 1, 2 and 3 a sheet material according to the present invention, generally designated by the reference numeral 10, which sheet material 10 is adapted to be cut into pieces to form the loop portions for fasteners of the type having releasably engageable hook and loop portions.

Generally the sheet material 10 comprises a transparent thermoplastic film backing 12 (e.g., of polypropylene or polyester) in the range of about 0.0025 to 0.013 centimeters (0.001 to 0.005 inch) thick having front and rear major surfaces 13 and 14, and a multiplicity of fibers 16 having portions bonded (i.e., by being fused or adhesively attached) to the front surface 13 of the backing 12 at spaced elongate generally parallel bonding locations 18 that are continuous in one direction along the front surface 13 to form arcuate portions 20 of the fibers 16 projecting from the front surface 13 of the backing 12 between the bonding locations 18 in continuous rows transversely across the sheet material 10. The arcuate portions 20 of the fibers 16 have a generally uniform height from the backing 12 of less than about 0.64 centimeters (0.250 inch) and preferably less than about 0.318 centimeters (0.125 inch), the height of the fibers 16 is at least one third, and preferably one half to one and one half times the distance between the bonding locations 18, the individual fibers 16 are less than 15 denier (preferably in the range of 1 to 10 denier) in size, and the fibers 16 without the backing 12 have a basis weight in the range of 5 to 200 grams per square meter (and preferably in the range of 10 to 75 grams per square meter) measured along the first surface 13 to provide sufficient open area between the fibers 16 along the arcuate portions 20 (i.e., between about 10 and 70 percent open area) to afford ready engagement of the fibers 16 along the arcuate portions 20 by the hook portion of the fastener.

The fibers 16 can be disposed in various directions with respect to the parallel bonding locations 18 and may or may not be bonded together at crossover points in the arcuate portions 20; can be disposed in various directions with respect to the parallel bonding locations 18 with the majority of the fibers 16 (i.e., over 90 percent) extending in directions at about a right angle to the bonding locations 18; or all of the fibers 16 can extend in directions generally at right angles to the spaced generally parallel bonding locations 18.

The backing 12 may have printing 22 along either one or both of its surfaces 13 or 14 applied by conventional printing techniques, which printing 22 is readily visible through the arcuate portions 20 of the fibers 16.

Figure 4 schematically illustrates a method according to the present invention for forming the sheet material 10 which generally comprises forming the fibers 16 into a sheet of fibers having arcuate portions projecting in the same direction from spaced generally parallel anchor portions 24 of the sheet, and bonding the spaced generally parallel anchor portions 24 of the sheet of fibers 16 to the front surface 13 of the backing 12 with the arcuate portions of the fibers 16 projecting from the front surface 13 of the backing 12. This method is preferably performed by providing first and second heated (e.g., 280 degrees F) corrugating members or rollers 26 and 27 each having an axis and including a plurality of circumferentially spaced generally axially extending ridges 28 around and defining its periphery, with the ridges 28 having outer surfaces and defining spaces between the ridges 28 adapted to receive portions of the ridges 28 of the other corrugating member in meshing relationship with the sheet of fibers between the meshed ridges 28 and to afford rolling engagement between the ridges 28 and spaces of the corrugating members in the manner of gear teeth. The corrugating members 26 and 27 are mounted in axially parallel relationship with portions of the ridges 28 of the corrugating members 26 and 27 meshing generally in the manner of gear teeth; at least one of the corrugating members 26 or 27 is rotated; and the sheet of fibers is fed between the meshed portions of the ridges 28 of the corrugating members 26 and 27 to generally conform the sheet of fibers to the periphery of the first corrugating member 26 and form the arcuate portions of the fibers 16 in the spaces between the ridges 28 of the first corrugating member 26 and the generally parallel anchor portions 24 of the sheet of fibers along the outer surfaces of the ridges 28 on the first corrugating member 26. The formed sheet of fibers is retained along the periphery of the first corrugating member 26 after it has moved past the meshed portions of the ridges 28; the backing 12 is bonded to the parallel anchor portions 24 of the sheet of fibers on the end surfaces of the ridges 28 on the first corrugating member 26 as by the action of a sonic welder 30 or by other sources of heat and pressure such as heat from within the first corrugating member 26; and the bonded backing 12 and fibers 16 or sheet material 10 is separated from the first corrugating member 26.

The sheet of fibers fed between the meshed portions of the ridges 28 of the corrugating members 26 and 27 can be in the form of a non woven web or sheet, or, as illustrated in Figure 4, in the form of yarns 33 distributed to provide a sheet of uniformly distributed fibers by passing the yarns 33 through a comb 34 and fed between the meshed portion of the ridges 28 of the corrugating members 26 and 27 with all of the fibers 16 extending generally perpendicular to the axes of the corrugating members 26 and 27. Corrugating members 26 and 27 adapted to have such a sheet of fibers 32 fed into them can have their ridges 28 oriented generally in the range of 0 to 45 degrees with respect to their axes, but preferably have their ridges 28 oriented at about 5 degrees with respect to their axes so that the sonic welder 30 will always be adjacent and heating the parallel portions 24 of the sheet of fibers along a portion of at least one of the ridges 28 to help even out the energy output of the sonic welder 30 and so that the fibers 16 in the sheet material 10 all extend in directions at about right angles (i.e., 85 degrees) to the parallel bonding locations 18.

Additionally, the method can further include printing the backing along one of its surfaces prior to the bonding step, as along its rear surface 14 with a printer 36, which may preferably be done at a location remote from the corrugating members 26 and 27.

Figures 5 and 6 schematically illustrate a first alternate way to perform the method according to the present invention for forming a sheet material 40 according to the present invention, which method generally comprises forming fibers 38 into a sheet having arcuate portions 41 projecting in the same direction from spaced generally parallel anchor portions of the sheet, and bonding the spaced anchor portions of the sheet of fibers with the fibers along a front surface of a backing 43 with the arcuate portions 41 projecting from the front surface of the backing 43. As illustrated, the method can be performed by providing first and second cylindrical heated corrugating members or rollers and 45 each having an axis and including a plurality of generally annular, circumferentially extending, axially spaced ridges 46 around and defining its periphery, with the ridges 46 having outer surfaces and defining spaces between the ridges 46 adapted to receive portions of the ridges 46 of the other corrugating member 44 or 45 in meshing relationship with the sheet of fibers between the meshed portions of the ridges 46. The corrugating members 44 and are mounted in axially parallel relationship to mesh portions of the ridges 46 of the corrugating members 44 and 45; at least one of the corrugating members 44 or 45 is rotated; and the sheet of fibers is fed between the meshed portions of the ridges 46 of the corrugating members 44 and to generally conform the sheet of fibers to the periphery of the first corrugating member 44 and form the arcuate portions 41 of the fibers in the spaces between the ridges of the first corrugating member 44 and the generally parallel anchor portions of the fibers along the outer surfaces of the ridges 46. The formed sheet of fibers is retained along the periphery of the first corrugating member 44 after separation of the ridges 46; the backing 43 is bonded to the parallel anchor portions 42 of the sheet of fibers on the end surfaces of the ridges 46 of the first corrugating member 44 at spaced elongate generally parallel bonding locations corresponding to the end surfaces of the ridges 46 on the first corrugating member 44 as by the action of a sonic welder 50 or by other sources of heat and pressure such as heat from within the first corrugating member 44; and the thus completed sheet material 40 is separated from the first corrugating member 44.

The fibers 38 fed between the meshed ridges 46 of the corrugating members 44 and 45 can be in the form of a non woven web formed by adhering the fibers together, or another sheet formed of the fibers that has sufficient internal strength so that the sheet of fibers will corrugate longitudinally to conform to the ridges 46 as it is pulled into the nip between the meshing ridges 46 of the corrugating members 44 and 45. Preferably a majority of the fibers 38 in such a non woven sheet of fibers are oriented transversely of the direction the sheet of fibers is fed between the corrugating members 44 and 45 so that a majority of the fibers in the resultant sheet material 40 extend in directions at about right angles to the parallel bonding locations. Additionally, the method can further include printing the backing along one of its surfaces prior to the bonding step (not shown).

Like the sheet material 10, the sheet material 40 made by the method illustrated in Figures 5 and 6 comprises the backing 43 (which can be a thermoplastic film), and the fibers 38 which are bonded (i.e., by being fused or adhesively attached) to the backing 43 at the spaced elongate generally parallel bonding locations along the. front surface, which bonding locations are continuous in one direction across the sheet material 40 to form arcuate portions 54 of the fibers 38 projecting from the front surface of the backing 43 between the bonding locations in continuous rows, except that the continuous rows of arcuate portions 54 in the sheet material 40 extend longitudinally along the sheet material 40 instead of transversely across the sheet material as in the case of the sheet material 10.

Figure 7 and 8 schematically illustrate a second alternate way to perform the method according to the present invention for forming a sheet material 60 illustrated in Figures 9 and 10, which method illustrated in Figures 7 and 8 generally comprises forming fibers 59 into a sheet having arcuate portions 61 projecting in the same direction from spaced generally parallel anchor portions 62 of the sheet of fibers, and bonding the spaced generally parallel anchor portions 62 of the sheet of fibers to a front surface 58 of a backing 63 to form bonding locations 68 with the arcuate portions 61 projecting from the front surface 58. As illustrated, the method can be performed by providing first and second cylindrical heated corrugating members or rollers 64 and 65 each having an axis and including a plurality of circumferentially spaced generally axially extending discontinuous ridges 66 around and defining its periphery, with the ridges 66 on each corrugating member 64 or 65 having outer surfaces and defining spaces between the ridges 66 adapted to receive a portion of the ridges 66 of the other corrugating member 64 or 65 in meshing relationship in the manner of a pair of gears with the sheet of fibers 59 between the meshed portions of the ridges 66. The corrugating members 64 and 65 are mounted in axially parallel relationship to mesh portions of the ridges 66 of the corrugating members 64 and 65 in the manner of gear teeth; at least one of the corrugating members 64 or 65 is rotated; and the sheet of fibers 59 is fed between the meshed portions of the ridges 66 of the corrugating members and 65 to generally conform the sheet of fibers to the periphery of the first corrugating member 64 and form the arcuate portions 61 of the fibers in the spaces between the ridges 66 of the first corrugating member 64 and the generally parallel anchor portions 62 of the sheet of fibers along the outer surfaces of the ridges 66. The formed sheet of fibers is retained along the periphery of the first corrugating member 64 after it moves past the meshing portions of the ridges 66; the backing 63 is bonded to the parallel anchor portions 62 of the sheet of fibers on the end surfaces of ridges 66 of the first corrugating member 64 as by the action of a sonic welder 67 or by other sources of heat and pressure such as heat from within the first corrugating member 64; and the thus completed sheet material 60 is separated from the first corrugating member 64.

The fibers 59 can be fed between the meshed portions of the ridges 66 of the corrugating members 64 and in the form of yarns 70 distributed to provide a sheet of uniformly distributed fibers 59'by passing the yarns 70 through a comb 72 and fed between the meshed ridges 66 of the corrugating members 64 and 65 with all of the fibers extending generally perpendicular to the axes of the corrugating members 64 and 65» in which case the corrugating members 64 and 65 can have their ridges 66 oriented in the range of 0 to 45 degrees with respect to their axes, but preferably have their ridges 66 oriented at about 5 degrees with respect to their axes so that the sonic welder 67 will always be adjacent and heating the parallel anchor portions of fibers along a portion of one of the ridges 66 to help even out the energy output of the welder 67 and so that in the sheet material 60 the fibers all extend in directions at about right angles (i.e., 85 degrees) to parallel bonding locations 68 between the fibers 59 and the backing 63. Alternatively, the fibers 59 fed between the meshed ridges 66 of the corrugating members 64 and 65 can be in the form of a non woven or random woven web formed by adhering fibers together or laying unattached fibers together. In that case the ridges 66 may be oriented at any angle with respect to the axes of the corrugating members 64 and 65, and preferably a majority of the fibers in such a sheet of fibers are oriented at right angles to the ridges 66 so that a majority of the fibers in the resultant sheet material 60 extend in directions at about right angles to the parallel bonding locations 68. Additionally, the method can further include printing the backing along one of its surfaces prior to the bonding step (not shown). Additionally, the method can further include printing the backing along one of its surfaces prior to the bonding step (not shown).

Like the sheet materials 10 and 40, the sheet material 60 made by the method illustrated in Figures 7 and 8 and illustrated in Figures 9 and 10 Comprise the backing (which can be a thermoplastic film), and the fibers 59 which are bonded (i.e., by being fused or adhesively attached) to the front surface 58 of the backing 63 at the spaced elongate generally parallel bonding locations 68 to form rows of the arcuate portions 61 of the fibers 59 projecting from the front surface 58 of the backing 63 between the bonding locations 6Θ, except that the rows of arcuate portions 69 are discontinuous and form a regular pattern along the sheet material 60 instead of being continuous in one direction across the sheet material as in the case of the sheet materials 10 and 40,

The following are illustrative examples of sheet materials according to the present invention formed by the method described above.