Patent Publication Number: US-2012027990-A1

Title: Article for wet applications

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation-in-part of U.S. Ser. No. 11/833,846, filed Aug. 3, 2007, which is a continuation-in-part of U.S. Ser. No. 09/982,741, filed Oct. 17, 2001, now U.S. Pat. No. 7,309,519, which is a continuation-in-part of U.S. Ser. No. 09/637,567, filed Aug. 11, 2000, now U.S. Pat. No. 6,610,382, which is a continuation-in-part of U.S. Ser. No. 09/166,837, filed Oct. 5, 1998, now U.S. Pat. No. 6,372,323. 
    
    
     FIELD 
     The present disclosure is directed to an article having a pleasant and soft feel, high friction properties, and good performance in wet conditions. 
     BACKGROUND 
     The development of enhanced grip and anti-slip surfaces typically centers around the materials and the surface topology of the article. Common materials include natural and synthetic rubbers, styrenic block co-polymers, latex, ethylene vinyl acetate, ethylene-propylene rubber, polyurethane, polyester co-polymers, polyimides, and the like. The surface topology can range from smooth to having exaggerated gripping structures. 
     U.S. Pat. No. 3,585,101 discloses a thin sheet of a soft, ductile, flexible material, such as aluminum, brass, plastic or the like, having a knurled pattern embossed to provide an improved gripping surface. The sheet can be applied to solid objects using an adhesive. 
     U.S. Pat. No. 4,488,918 discloses a plastic film having a non-slip surface comprising spaced, random patterns of rigid peaks and ridges formed of a second thermoplastic material co-extruded with and bonded to a plastic film. The surface has a pattern of relatively high, sharp, irregular plastic peaks and ridges, sufficiently sharp, hard and rough to effect a mechanical gripping with other surfaces. 
     U.S. Pat. No. 5,234,740 discloses a slip control surface with a structured surface. The structured surface includes an array of protrusions, typically triangular pyramids. The patent discloses that the sheeting may be applied to the handles of athletic equipment such as softball bats, golf clubs, tennis, racquetball, squash, badminton racquets, as well as the handles of tools. 
     SUMMARY 
     The present disclosure relates to an improved surface that has a pleasant and soft feel, high frictional properties and good performance (e.g. skin cleansing and exfoliation) in wet conditions. The surface is a soft micro-structured surface having an array of flexible upstanding stems of a variety of shapes produced from a thermoplastic elastomer. The size, spatial distribution, flexibility of the stems, stem array pattern, and the properties of the elastomer material all contribute to the soft feel of the surface, vibration dampening, and the performance under wet conditions. The various embodiments of the present article may include micro-channels, an absorbent layer and hydrophilic/hydrophobic regions all for directing fluids away from the upstanding stems, leaving them dry and providing high frictional performance even in wet conditions. 
     In one aspect, the present disclosure provides an article having frictional properties that do not substantially degrade when water is present, comprising a backing layer having a first surface with an array of at least 100 flexible, upstanding stems per square inch, that occupy no greater than 24.8% of a total area of the first surface of the backing layer, molded at least partially integrally to the first surface, each stem having an aspect ratio of at least 1.25 and having at least a portion of the stem formed of an elastomeric material having a Shore hardness of less than about 90 A, wherein the first surface has a static coefficient of friction when dry of at least 0.6 and a static coefficient of friction when wet within 20% of the static coefficient of friction when dry. In some embodiments, the elastomeric material is hydrophobic. In some embodiments, the static coefficient of friction when dry is at least 1.3, or even at least 2. 
     In some embodiments, the backing layer comprises additional layers of at least one of a reinforcing web, a foam layer, a substantially inelastic polymeric layer, or an adhesive layer. In some embodiments, the backing layer comprises a blend of polyurethane and a polystyrene material with elastomeric segments. In some embodiments, the backing layer comprises a compound selected from the group consisting of elastomeric materials, polyvinyl, polyurethane, polyester, polyacrylic, polycarbonate, and polyolefin. In some embodiments, the elastomeric material comprises at least one of a elastic block copolymer, styrene isoprene styrene, styrene butadiene styrene, styrene ethylene butadiene styrene, or a blend thereof. 
     In some embodiments, the presently disclosed article further comprises an array of upstanding stems of an elastomeric material located on a second surface of the backing layer. In some embodiments, the backing layer comprises holes between at least two of the upstanding stems. In some embodiments, the upstanding stems comprise one of hydrophobic or hydrophilic properties. In some embodiments, the upstanding stems have tips that are hydrophobic and the stem geometry provides that an individual water droplet placed on the surface beads up on the tips. In some embodiments, large amounts of water placed on the surface is distributed at the base of the stems while the tips of the stems remain exposed 
     In another aspect, the present disclosure provides an article having a first surface with a soft feel that has frictional properties that do not substantially degrade when water is present, comprising an array of upstanding stems of an elastomeric material on the first surface, the elastomeric material having a Shore hardness of less than about 60 A and a tensile modulus of less than about 4 MPa, wherein a stem geometry includes an aspect ratio of at least 1.25, a density of at least 100 stems per square inch, and a gap between adjacent stems of ranging from about 0.018 inches to about 0.1 inches, wherein the first surface has a static coefficient of friction when dry of at least 0.6 and a static coefficient of friction when wet within 20% of the static coefficient of friction when dry. In some embodiments, the stems have tips that are hydrophobic and the stem geometry provides that an individual water droplet placed on the surface beads up on the tips. In some embodiments, large amounts of water placed on the first surface is distributed at the base of the stems while the tips of the stems remain exposed. 
     In some embodiments, the elastomeric material comprises at least one of an elastic block copolymer, styrene isoprene styrene, styrene butadiene styrene, styrene ethylene butadiene styrene, or a blend thereof. 
     In some embodiments, the first surface defined by the array of flexible stems has an average dynamic shear strength of about 85% of its peak dynamic shear strength when engaged with a stem array of another article having the same defined characteristics. In some embodiments, the first surface defined by the array of flexible stems has an average dynamic shear strength of about 90% of its peak dynamic shear strength when engaged with a stem array of another article having the same defined characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side-sectional view of an article in accordance with the present disclosure. 
         FIG. 1A  is a side-sectional view of a two-sided article in accordance with the present disclosure. 
         FIG. 2  is a side-sectional view of an alternate article in accordance with the present disclosure. 
         FIG. 3  is a side-sectional view of co-extruded article in accordance with the present disclosure. 
         FIG. 3A  is a side-sectional view of an alternate co-extruded article in accordance with the present disclosure. 
         FIG. 4  is a side-sectional view of a article with an absorbent layer on the second surface in accordance with the present disclosure. 
         FIG. 5A  is a side-sectional view of a article including micro-channels and an absorbent material in accordance with the present disclosure. 
         FIG. 5B  is a top view of the article of  FIG. 5A . 
         FIG. 6  is a schematic illustration of a water droplet interacting with a article in accordance with the present disclosure. 
         FIG. 7  is a schematic illustration of water being channeled away from the upstanding stems on an article in accordance with the present disclosure. 
         FIG. 8  is a perspective view of an exemplary article incorporating the article of the present disclosure. 
         FIG. 9  is a schematic illustration of an exemplary method of manufacturing the article in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side-sectional view of a article  20  in accordance with the present disclosure. The article  20  includes a backing layer  21  having a first surface  24  with an array of upstanding stems  26 . The stems may be arranged in a regular or an irregular array. Various patterns of stems may be used, such as hexagonal, diagonal, sinusoidal, etc. The upstanding stems  26  are constructed of an elastomeric material. The entire exterior surface of the upstanding stems  26  are an elastomeric material. In the embodiment of  FIG. 1 , the backing layer  21  is integrally formed with the upstanding stems  26  of an elastomeric material. The combination of the backing layer  21  and the upstanding stems  26  is sometimes referred to as a stem web. Although the illustrated embodiments show the stems  26  as being generally cylindrical, the sides of the stems  26  typically have a slight taper  35  to facilitate removal from the mold. A variety of non-cylindrical shapes can also be utilized, such as truncated cones or pyramids, rectangles, hemispheres, squares, hexagon, octagon, gum drops, and the like. 
     The present article  20  requires primarily upstanding stems  26  constructed of an elastomeric material and a backing layer  21  to hold the structure together. The elastomeric properties of the backing layer  21 , however, do not fulfill all requirements for some applications, such as when the article  20  is used as a gripping wrap. Therefore, additional backing layers  22 ,  34 ,  36  are optionally applied to the second surface  25  to reinforce the backing layer  21 . The additional backing layer  22  may serve to stabilize and reinforce the article  20 , to resist stretching and improving tear resistance, as well as a variety of other functions. Adhesive layer  34  and release liner  36  are optionally provided for attaching the present article  20  to another surface. As used herein, backing layer refers to an assembly having one or more layers supporting the upstanding stems, although typically at most one of these layers is integrally formed with the upstanding stems. 
     The backing layer is typically about 0.05 millimeters to about 0.38 millimeters (0.002 inches to 0.015 inches) thick. In some instances, the backing layer is sufficiently thick to bond a reinforcing web during extrusion, such as a sheet of fabric, to impart increased tear resistance and tensile strength. The reinforcing web is particularly useful when the article is attached to a flexible substrate via sewing. The backing layer may be a foamed or a solid polymeric material. In one embodiment, the backing layer may include a porous and/or absorbent layer, such as layers of fibrous material or fabric scrim which may be woven or nonwoven. A porous material is useful for absorbing moisture and/or directing moisture away from the upstanding stems. In one embodiment, the backing layer includes a substantially inelastic layer to prevent necking or stretching of the article. 
     It is desirable for the backing layer to be sufficiently compatible with the elastomeric material to keep the article together. Suitable backing layer materials include thermoplastic polyurethanes, polyvinyl chlorides, polyamides, polyimides, polyolefins (e.g., polyethylene and polypropylene), polyesters (e.g., polyethylene terephthalate), polystyrenes, nylons, acetals, block polymers (e.g., polystyrene materials with elastomeric segments, available from Shell Chemical Company of Houston, Tex., under the designation KRATON™, polycarbonates, thermoplastic elastomers (e.g. polyolefin, polyester or nylon types) and copolymers and blends thereof. The thermoplastic material may also contain additives, including but not limited to fillers, fibers, antistatic agents, lubricants, wetting agents, foaming agents, surfactants, pigments, dyes, coupling agents, plasticizers, suspending agents, hydrophilic/hydrophobic additives, and the like. 
     The optional adhesive layer typically comprises an adhesive selected to provide a bond to a substrate article to which the surface is to be applied, such as pressure sensitive adhesives, thermosetting or thermoplastic adhesives, radiation cured adhesives, adhesives activated by solvents, and blends thereof. The adhesive may include filaments. The backing layer can optionally be laminated or impregnated with the adhesive. One adhesive useful in the present disclosure is Adhesive Transfer Tape 950 available from Minnesota Mining and Manufacturing Company. Many suitable epoxy, urethane, synthetic or natural based rubber and acrylic adhesives are commercially available for this purpose as well. Depending upon the application, the adhesive may releasably bond or permanently bond the article to a surface. 
       FIG. 1A  is a sectional view of a two-sided article  20 ′ as generally illustrated in  FIG. 1 , without the additional backing layers  22 ,  34 ,  36 . The article  20 ′ includes a backing layer  21 ′ with an array of upstanding stems  26 ′ on both the first and second surfaces  24 ′,  25 ′. The upstanding stems  26 ′ are constructed of a single elastomeric material. In the embodiment of  FIG. 1A , the backing layer  21 ′ is integrally formed with the upstanding stems  26 ′ of an elastomeric material. In another embodiment, the upper and lower portions may be co-extruded from two different elastomeric materials. A two-side article in accordance with the present disclosure may be formed from the various disclosed embodiments. 
       FIG. 2  is a side-sectional view of an alternate article  40  in accordance with the present disclosure. Backing layer  42  defines lower portions  44  of the stems  46 . The upper portions  48  of the stems  46  are constructed of the elastomeric material. The backing layer  42  and lower portions of the stems  44  may be constructed of a variety of materials, elastomeric or non-elastomeric, depending upon the application for the article  40 . At a minimum, the exterior surface of the upper portions  48  is an elastomeric material. In one embodiment, the upper portions  48  of the stems  44  have hydrophobic properties. Hydrophobic properties may be obtained by constructing the upper portions  48  from a hydrophobic material or treating the upper portions  48  to achieve hydrophobic properties. For applications involving contact with non-polar liquids, the upper portions  48  of the stems  46  may be treated to achieve hydrophilic properties (e.g., corona treatment). 
       FIG. 3  is a side-sectional view of another alternate article  50  formed by co-extrusion in accordance with the present disclosure. The backing layer  52  protrudes into a center region  54  to add structural integrity to the elastomeric stems  56 . The backing layer  52  is typically a stiffer polymeric material. 
       FIG. 3A  is an alternate article  50 ′ formed by co-extrusion in accordance with the present disclosure. The stems  56 ′ and backing layer  52 ′ are constructed of an elastomeric material. The stems  56 ′ protrude through a center region  54 ′ of an additional backing layer  53 ′. The additional backing layer  53 ′ may provide structural stability, hydrophobic/hydrophilic properties or a variety of other functions. In one embodiment, the additional backing layer  53 ′ may be an elastomeric material with properties different from those used to construct the stems  56 ′. 
       FIG. 4  is a side-sectional view of an article  70  incorporating a plurality of holes  72  through the backing layer  74  in fluid communication with an absorbent layer  76 . The absorbent layer  76  draws moisture away from the elastomeric stems  78  to maintain good frictional properties in wet conditions. 
       FIGS. 5A and 5B  illustrate an article  80  incorporating micro-channels  82  on the backing layer  84  between the upstanding elastomeric stems  86 . The micro-channels  82  utilize capillary forces to cause the rapid transport of a fluid in a direction of a driving force. Absorbent layer  88  is located along the first surface  90  of the backing  84  to provide the driving force. Alternatively, the driving force may be gravity and/or hydrophilic areas on the stems  86 . 
     A number of mechanisms combine to give the present article exceptional frictional properties in both wet and dry conditions.  FIG. 6  is a schematic illustration of an individual water drop  60  residing on hydrophobic tips  62  of the stems  64 . The drop  60  is easily removed from the stem  64  by shaking or gripping of the article  66 . The redistribution of water is also impacted by stem density. 
     Deposition of large amounts of water  60  results in distribution of the liquid at the base of the stems  64  while the tips  62  remain dry, as illustrated in  FIG. 7 . When water or any other polar liquid is deposited on the surface of the article  66 , the tips  62  of the stems  64  remain exposed due to the hydrophobic nature of the thermoplastic elastomer polymer. Constructing the backing layer from a hydrophilic material assists in directing the water  60  away from the tips  62 . 
     The upstanding stems  64  grip with other surfaces primarily due to the frictional properties of the elastomeric material of the stems. Frictional performance does not require the stems  64  to protrude into the other surface (i.e. mechanical engagement is not required). Therefore, frictional contact can be made with both soft and rigid materials. 
     The present article provides high shear forces when engaged with another article, at minimal pressure. Since the upstanding stems are constructed substantially from a highly flexible elastomeric material, high shear forces are not derived from a mechanical interlock of the stems, such as on a mechanical fastener. Rather, the frictional properties of the upstanding stems are enhanced by the stem size, stem density, and stem pattern when two articles are engaged with each other. Possible applications include gloves having the present article located for gripping a surface also including the article. 
     Since the upstanding stems do not interlock, the present article has substantially zero peel and tensile force when engaged with the same or a similar stem web structure. This feature is important to safe use of the present article for gripping purposes, since the user must typically be free to quickly release the gripped item, without having to overcome any peel or tensile forces generated by the articles. For example, the present article can be wrapped around the handle bars of a bicycle and applied to bicycling gloves. When the user grips the handle bars of the bicycle, the two articles engage to provide excellent slip control properties in shear with minimal pressure. However, the substantially zero peel and tensile forces allows the user to release the handle bars with substantially zero resistance from the two articles. 
     The soft feel of the present article is due primarily to the nature of the elastomeric material and to stem geometry. The elastomeric material preferably has a Shore hardness of less than about 70 D (58091 under the trade designation “Estane”); more preferably less than about 90 A, and most preferably less than about 60 A. The tensile modulus is preferably less than about 12 MPa, more preferably less than about 6 MPa, and most preferably less than about 4 MPa. Stem height, stem diameter, and spacing between the stems (referred to as stem geometry) are significant factors in establishing a soft feel on the surface. Generally, longer stems result in a softer feel due to their flexibility. As for stem spacing, the average distance between the tactile points in fingertips is approximately 1.27 millimeters (0.050 inches). When the spacing between the objects is less than half the tactile distance, it becomes difficult to distinguish between the protrusions on the surface. Therefore, the best feel is typically obtained for a stem web with the highest available density of stem. A stem density in excess of 310 stems/centimeter 2  (2,000 stems per square inch) creates a unique soft and pleasant feel for skin contact. 
     Referring again to  FIG. 1 , the stems need to be substantially upstanding to optimize the performance of the article. The stems are kept upstanding by the stem diameter and the nature of the elastomeric material. The upstanding stems typically have a height  28  in the range of about 0.254 millimeters to about 1.27 millimeters (0.010 inches to about 0.050 inches), and more typically in the range of about 0.51 millimeters to about 1.02 millimeters (0.020 inches to 0.040 inches). The separation or gap  30  between adjacent stems  26  is generally in the range of about 0.254 millimeters and about 2.54 millimeters (0.01 inches to about 0.1 inches) and more typically in the range of about 0.46 millimeters to about 0.84 millimeters (0.018 inches to 0.033 inches). The stems  26  have a maximum cross sectional dimension  29  of about 0.076 millimeters to about 0.76 millimeters (0.003 inches to about 0.030 inches). The stems  26  are arranged on the backing in a density of at least 15.5 per centimeter squared (100 per square inch), and more typically about 54 per centimeter squared to about 1550 per centimeter squared (350 per square inch to about 10,000 per square inch). 
     The stems have an aspect ratio of at least 1.25, and preferably at least 1.5, and more preferably at least 2.0 and most preferably greater than 3.0, although aspect ratios in excess of 3.0 are possible for some applications. Aspect ratio refers to the ratio of pin height to the maximum cross sectional dimension. For pins with a circular cross section, the maximum cross sectional dimension is the pin diameter. 
       FIG. 8  is a perspective view of an exemplary article  100  incorporating the slip control surface  102  in accordance with the present disclosure. The article  100  is a molded grip having an opening  104  at one end, suitable for attachment to a variety of structures such as golf club, baseball bats, handles, and the like. The article  100  may be made using a variety of processes, such as injection molding, profile extrusion, roll extrusion forming, etc. 
     Elastomeric Materials 
     The elastomeric material can be any thermoplastic elastomer that can be heated to a state in which it can be flowed and molded, such as those described in G. Holden et al.,  Thermoplastic Elastomers,  (2 nd  ed. 1996). It is also within the scope of this disclosure to use two or more different thermoplastic elastomeric materials in either layered or blended form to define that portion of the article. 
     The term “elastomer” or “elastomeric” is used to refer to rubbers or polymers that have resiliency properties similar to those of rubber. In particular, the term elastomer reflects the property of the material that it can undergo a substantial elongation and then return to its original dimensions upon release of the stress elongating the elastomer. In all cases an elastomer must be able to undergo at least 10% elongation (at a thickness of 0.5 mm), and more preferably at least 30% elongation, and return to at least 50% recovery after being held at that elongation for 2 seconds and after being allowed 1 minute relaxation time. More typically, an elastomer can undergo 25% elongation without exceeding its elastic limit. In some cases elastomers can undergo elongation to as much as 300% or more of their original dimensions without tearing or exceeding the elastic limit of the composition. Elastomers are typically defined to reflect this elasticity as in ASTM Designation D883-96 as a macromolecular material that at room temperature returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress. ASTM Designation D412-98A can be an appropriate procedure for testing rubber properties in tension to evaluate elastomeric properties. 
     For some applications, thermoset elastomers may be used. Generally, such compositions include relatively high molecular weight compounds which, upon curing, form an integrated network or structure. The curing may be by a variety of methods, including chemical curing agents, catalysts, and/or irradiation. 
     The final physical properties of the material are a function of a variety of factors, most notably: number and weight average polymer molecular weights; the melting or softening point of the reinforcing domains (hard segment) of the elastomer (which, for example, can be determined according to ASTM Designation D1238-86); the percent by weight of the elastomer composition which comprises the hard segment domains; the structure of the toughening or soft segment (low Tg) portion of the elastomer composition; the cross-link density (average molecular weight between crosslinks); and the nature and levels of additives or adjuvants, etc. 
     Examples of classes of elastomers include anionic triblock copolymers, polyolefin-based thermoplastic elastomers, thermoplastic elastomers based on halogen-containing polyolefins, thermoplastic elastomers based on dynamically vulcanized elastomer-thermoplastic blends, thermoplastic polyether ester or polyester based elastomers, thermoplastic elastomers based on polyamides or polyimides, ionomeric thermoplastic elastomers, hydrogenated block copolymers in thermoplastic elastomer interpenetrating polymer networks, thermoplastic elastomers by carbocationic polymerization, polymer blends containing styrene/hydrogenated butadiene block copolymers, and polyacrylate-based thermoplastic elastomers. Some specific examples of elastomers are natural rubber, butyl rubber, EPDM rubber, silicone rubber such as polydimethyl siloxane, polyisoprene, polybutadiene, polyurethane, ethylene/propylene/diene terpolymer elastomers, chloroprene rubber, styrene-butadiene copolymers (random or block), styrene-isoprene copolymers (random or block), acrylonitrile-butadiene copolymers, mixtures thereof and copolymers thereof. The block copolymers may be linear, radial or star configurations and may be diblock (AB) or triblock (ABA) copolymers or mixtures thereof. Blends of these elastomers with each other or with modifying non-elastomers are also contemplated. Commercially available elastomers include block polymers (e.g., polystyrene materials with elastomeric segments), available from Shell Chemical Company of Houston, Tex., under the trade designation “KRATON”. 
     Method of Manufacture 
     The process illustrated in  FIG. 9  shows a three-roll vertical stack molding apparatus  150  which includes an extruder and extrusion die  152  adapted for extruding one or more layers of molten thermoplastic material  154  into a mold  156 . In this case, the mold  156  is a roll  158 , which has on its outer cylindrical surface a desired surface pattern for transference to the molten thermoplastic material  154  as it passes over the cylindrical surface of the roll  158 . In the illustrated embodiment, the surface of the roll  158  has a plurality of arranged cavities  160  adapted to form a like plurality of upstanding stems  162 . The cavities may be arranged, sized and shaped as required to form a suitable surface stem structures from the thermoplastic material  154 . In one embodiment, a sufficient additional quantity of molten thermoplastic material  154  is extruded into the mold  156  to form a portion of the backing layer (see  FIGS. 1 and 3 ). 
     The roll  158  is rotatable and forms a nip  166 , along with an opposed roll  168 . The nip  166  between the roll  158  and opposed roll  168  assists in forcing the flow of molten thermoplastic material  154  into the cavities  160  and provides a uniform backing layer thereon. The spacing of the gap forming the nip  166  can be adjusted to assist the formation of a predetermined thickness of the backing layer of thermoplastic material  154 . Optionally, backing layer  164  is simultaneously brought into the nip  166 . Depending upon the composition of the elastomeric material and the geometry of the upstanding stems  162 , the backing layer  164  may be useful in efficiently remove the article  172  from the mold  156 . 
     As illustrated in  FIG. 9 , the article  172  may traverse a third roll  170  after exiting the roll  158 . In this process, the temperatures of all three rolls  158 ,  168 ,  170  may be selectively controlled to achieve desired cooling of the thermoplastic material  154 . The third roll  170  also serves to define the further path traversed by the article  172 . 
     The mold  158  may be of the type used for either continuous processing (such as a tape, a cylindrical drum or a belt), or batch processing (such as an injection mold or a compression mold). When making a mold  158  for forming the upstanding stems  162 , the cavities  160  of the mold  158  may be formed in any suitable manner, such as by drilling, machining, laser drilling, water jet machining, casting, etching, die punching, diamond turning, engraving, knurling and the like. The placement of the cavities determines the spacing and orientation of the article. The stems  162  typically have shapes corresponding to the shape of the cavities  160 . The mold cavities can be open at the end of the cavity opposite the surface from which the molten thermoplastic material is applied to facilitate injection of the thermoplastic material into the cavity. If the cavity is closed, a vacuum can be applied to the cavity so that the molten thermoplastic material fills substantially the entire cavity. Alternatively, closed cavities can be longer than the lengths of the stem structures being formed so that the injected material can compress the air in the cavities. The mold cavities should be designed to facilitate release of the surface stem structures therefrom, and thus may include angled side walls, or a release coating (such as a Teflon material layer) on the cavity walls. The mold surface may also include a release coating thereon to facilitate release of the thermoplastic material backing layer from the mold. In some embodiments, the cavities can be angled relative to the surface of the roll. 
     The mold can be made from suitable materials that are rigid or flexible. The mold components can be made of metal, steel, ceramic, polymeric materials (including both thermosetting and thermoplastic polymers such as silicone rubber) or combinations thereof. The materials forming the mold must have sufficient integrity and durability to withstand the thermal energy associated with the particular flowable thermoplastic material used to form the backing layer and surface topographies. In addition, the material forming the mold preferably allows the cavities to be formed by various methods, is inexpensive, has a long service life, consistently produces material of acceptable quality, and allows for variations in processing parameters. 
     The molten thermoplastic material is flowed into the mold cavity, and over the surface of the mold to form the layer of cover material. To facilitate flow of the molten thermoplastic material, the thermoplastic material typically must be heated to an appropriate temperature, and then coated into the cavities. This coating technique can be any conventional technique, such as calendar coating, cast coating, curtain coating, die coating, extrusion, gravure coating, knife coating, spray coating or the like. In  FIG. 9 , a single extruder and extrusion die arrangement is shown. However, the use of two (or more) extruders and associated dies allows simultaneous extrusion into the nip  166  of a plurality of thermoplastic materials to achieve a multi-component (layered or blended) laminate cover material. 
     The flow of the molten thermoplastic material  154  into the mold  158  may also be facilitated by the application of pressure between opposing rolls  168 . When the backing layer  164  includes a porous material, the three-roll vertical molding apparatus  150  controls the degree of penetration of the molten thermoplastic material  154 . In this fashion, the quantity of molten thermoplastic material  154  can be controlled to barely penetrate the surface coating of the backing layer  164 , to penetrate the porous backing layer  164  on the opposite side of introduction of thermoplastic material  154  so as to almost encapsulate the backing layer  164 . The penetration of the molten thermoplastic material  154  into the porous backing layer  164  may also be controlled by the temperature of the molten thermoplastic material  154 , the quantity of thermoplastic material  154  in the nip  166 , and/or by extruder flow rates in conjunction with the line speed of the mold cavities. 
     After the molten thermoplastic material  154  has been coated into the mold cavities  160  and over the mold surface  156 , the thermoplastic material is cooled to solidify and form the desired exterior surface topography thereon (e.g., upstanding stems  162 ). The solidified thermoplastic material is then separated from the mold  158 . The thermoplastic material  154  will often shrink when it is solidified, which facilitates release of the material (e.g., surface stem structures and backing layer) and integral film layer from the mold (see  FIG. 1 ). Part or all of the mold may be cooled to aid in solidifying the surface stem structures and backing layer. Cooling can be effected by the use of water, forced air, heat transfer liquids or other cooling processes. 
     Some molding processes, such as injection molding, may utilize thermoset elastomeric polymers. When thermosetting resins are used as the molten material, the resin is applied to the mold as a liquid in an uncured or unpolymerized state. After the resin has been coated onto the mold, it is polymerized or cured until the resin is solid. Generally, the polymerization process involves either a setting time, or exposure to an energy source, or both, to facilitate the polymerization. The energy source, if provided, can be heat or radiation energy such as an electron beam, ultraviolet light or visible light. After the resin is solidified, it is removed from the mold. In some instances, it may be desired to further polymerize or cure the thermosetting resin after the surface stem structures are removed from the mold. Examples of suitable thermosetting resins include melamine, formaldehyde resins, acrylate resins, epoxy resins, urethane resins and the like. The formation of a backing layer having upstanding stem structures on at least one side thereof can be performed by injection molding or profile extrusion, such as is disclosed in U.S. Pat. No. 4,290,174 (Kalleberg); U.S. Pat. No. 5,077,870 (Melbye et al.); and U.S. Pat. No. 5,201,101 (Rouser et al.). 
     Test Procedure for Measuring Static and Dynamic Coefficients of Friction 
     The static and dynamic coefficient of friction for each film sample was measured on a Thwing-Albert Model 225-1 Friction/Peel Tester available from Thwing-Albert Instrument Company, Philadelphia, Pa. Equipment operation is specified in the Thwing-Albert Instruction Manual, Friction/Peel Tester, Model #225-1 revised May 1994, Software version 2.4. This analysis for the static coefficient of friction measured the horizontal force required to cause movement of a weighted 5.08 cm by 5.08 cm (2 inch by 2 inch) sample of the article against a sample of artificial leather sold under the trade designation “Ultrasuede” HP available from Toray Ultrasuede America located in Manhattan, N.Y. 
     The friction test specimen were prepared by anchoring a 5.08 cm by 5.08 cm (2 inch by 2 inch) sample of the article to a 5.08 cm by 5.08 cm (2 inch by 2 inch) metal test sled. The test specimen were attached to the sled with a two sided pressure sensitive adhesive such as SCOTCH 9851, available from Minnesota Mining and Manufacturing Company, St. Paul, Minn. The metal test sled weighed 500 grams. An additional weight of 500 grams was applied to the top of the block making the total weight 1000 grams. 
     To prepare the artificial leather sample for the friction test a sample approximately 10.16 cm by 30.48 cm (4 inches by 12 inches) was anchored to a metal sheet with a two sided pressure sensitive adhesive tape, such as SCOTCH 9851 to prevent movement and wrinkling of the sample during the test. 
     The metal sheet with the sample adhered was clamped on to the metal platen testing surface with the provided spring clip. The metal test sled with film sample on bottom of the sled and additional weight weighing 1000 grams in total was placed on the fabric and pulled for 10 seconds at a speed of 5.1 cm (2 inches) per minute across the fabric per instructions specified in the instructions manual. The static coefficient of friction was then calculated by the machine wherein the measured horizontal force to cause slippage on the sample was divided by the 1000 gram normal force of the sled. At least five measurements were recorded for each friction test sample and article. Arithmetic averages were calculated by the friction/peel tester. 
     Test Method for Dynamic Shear Strength 
     The dynamic shear strength was measured on an I-mass peel tester. The tester was set up in the 180° Peel Mode. A sample about 3.8 cm×12.7 cm (1.5 inches×5 inches) of stem web was attached using a double sided tape, such as 3M 404, and centered lengthwise to about 1.6 mm ( 1/16 inch) thick, 6.35 cm×22.9 cm (2.5 inches wide×9 inches long) aluminum test panel. Similarly, a sample about 2.54 cm×2.54 cm (1 inch×1 inch) of stem web was attached to the center of about 1.6 mm ( 1/16 inch) thick, 6.35 cm×22.9 cm (2.5 inches wide×9 inches long) aluminum test panel. The panels were then placed together with the stems of each sample in contact with each other. The engaged thickness of the two samples without any pressure applied including the aluminum panels was measure using a digital caliper gauge. The weight of the upper panel was approximately 53 grams. 
     An aluminum panel with the larger sample of stem web was attached to the moving platform of the I-mass tester with the stem web side up. The aluminum panel with the sample about 2.54 cm×2.54 cm (1 inch×1 inch) of stem web was placed on top so that the stem web was in an engaged position. The stem web was positioned so that it was at the end farthest away from the force gauge so that the sample on the upper panel would be pulled through the lower sample. A bar was placed over the engaged pair with a gap approximately 0.13 mm-0.254 mm (0.005-0.010 inches) greater than the engaged thickness. This bar is designed to prevent the samples from disengaging without exerting undue pressure to engage the two stem web samples. The end of the upper aluminum panel was attached to the force gauge in a position so that the gauge would measure a force directly parallel to the moving platform. 
     The I-mass tester was balanced, zeroed and adjusted to measure a 2 second averaging time. The position of the spacing bar was adjusted so that it would be directly above the stem web sample during the 2 second averaging time. The platform rate was set at 30.5 cm/minute (12 inches/minute). The peak, valley, and average forces were measure for each sample. Each sample was tested three times and the average values were calculated. 
     Materials Used in the Examples 
     A variety of elastomeric materials were used in the preparation of the samples of the examples. These materials are summarized in Table 1. Some properties of some of the samples are summarized in Table 2. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Material 
                 Description 
               
               
                   
               
             
            
               
                 ESTANE ™ 58661 
                 available from B.F. Goodrich, Cleveland, OH 
               
               
                 ESTANE ™ 58238 
                 available from B.F. Goodrich, Cleveland, OH 
               
               
                 VECTOR ™ 4111 
                 available from Exxon Chemical Co., Houston, TX 
               
               
                 ESTANE ™ 5740-820 
                 available from B.F. Goodrich, Cleveland, OH 
               
               
                 KRATON ™ G1657 
                 available from Shell Oil Co., Houston, TX 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Tensile 
                   
                   
                   
               
               
                   
                   
                   
                 set 
                   
                   
                 Hard- 
               
               
                   
                 Modulus 
                   
                 200% 
                   
                 Tensile 
                 ness, 
               
               
                   
                 @ 100%, 
                 Ultimate 
                 elon- 
                 Friction 
                 strength 
                 Shore 
               
               
                 Material 
                 MPa 
                 elongation 
                 gation 
                 Coef. 
                 MPa 
                 A 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Polyurethane 
                 4.5 
                 680% 
                 3% 
                 1.35 
                 48.3 
                 75 
               
               
                 Estane ™ 
               
               
                 58238 
               
               
                 Polyurethane 
                 5.86 
                 640% 
                 3% 
                 1.4 
                 52.4 
                 80 
               
               
                 Estane ™ 
               
               
                 58661 
               
               
                 Polyurethane 
                 3.8 
                 750% 
                 5.6%   
                 1.5 
                 24.9 
                 79 
               
               
                 Estane ™ 
               
               
                 5740 × 820 
               
               
                 Vector ™ 
                 1.9 
                 1200% 
                 15%  
                 2.55 
                 29 
                 38 
               
               
                 4111 
               
               
                 Kraton ™ 
                 2.4 
                 750% 
                 10%  
                 2.1 
                 23.4 
                 65 
               
               
                 G1657 
               
               
                 MPR 
                 6.45 
                 280% 
                 8% 
                 .9-2.6 
                 13 
                 77 
               
               
                 Alcryn ™ 
               
               
                 2080-BK 
               
               
                   
               
            
           
         
       
     
     Rheology and Morphology of the Blends 
     Viscosities of both Estate™ 58661 and Vector™ 4111 were measured over several decades of shear rate using both a DSR and a capillary rheometer (CR) at 204° C. (400° F.), the temperature used in the stem web extrusion. It is apparent that at higher shear rates (&gt;10 s−1), the viscosity and elasticity modulus of Vector™ 4111 are approximately twice that of Estane™ 58661. 
     Scanning electron microscopy (SEM) was used to investigate the morphology of blends of various compositions. The blends were mixed using a Brabender mixer and pressed into a silicone mold using a hot press method at about 216° C. (420° F.) at 6.9 MPa (1000 psi) for 60 seconds. The tool containing the material was cooled on dry ice. The sample was peeled from the mold. Only hot-pressed blends, described below, were studied. Micrographs were taken near the sample surface. A dispersed morphology was present in nearly every sample. Only in the 60/40 Estane™ 58661/Vector™ 4111 sample were any co-continuous structures present. 
     EXAMPLES 
     Example 1  
     A 50:50 by weight of polyurethane resin Estane™ 58661 and a styrenic triblock copolymer Vector™ 4111 was dry blended as pellets. Polyurethane provided durability and resiliency of the structure while Vector improved frictional performance. The Estane™ 58661 was dried at about 82.3° C. (180° F.) for at least 4 hours. The mixture of pellets was mixed with about 2 wt % of carbon black/polyurethane blend. The content of carbon black in the final blend did not exceed 1 wt %. 
     The mixture was extruded as generally illustrated in  FIG. 9 , except that the tooling was configured as a belt rather than a roll. The extruder as a Davis Standard single screw extruder with about 6.35 cm (2.5 inches) screw diameter designed for polyolefin processing. At about 8 revolutions per minute (rpm), the melt was discharged through the die at melt pressure of about 13.8 MPa (2000 psi). The temperature in the last zone of the extruder was about 216° C. (420° F.). The temperature of the die was about 232° C. (450° F.). The opening of the die lip was about 0.51 millimeters (0.020 inches). 
     The melt was pressed into a silicone belt/tool with a metal roll at a nip pressure of about 345,705 Pa (50 psi). One of the rolls had a tooled surface that was heated to about 65.6° C. (150° F.). The surface contained an array of holes about 0.254 mm (0.010 inches) in diameter and about 0.46 cm (0.018 inches) apart. A backing layer of double coated tape available from Minnesota Mining and Manufacturing Company under product designation 404 was introduced into the nip and bonded to the side of the web opposite the upstanding stems. The web and double coated tape was removed from the tooled surface at a speed of about 1.5 meters/minute (5 feet per minute). 
     The resulting stem web had about 490/centimeters 2  (3159 stems per square inch). The center-to-center spacing of the stems was about 0.439 mm (0.0173 inches) in the x-direction and about 0.465 mm (0.0183 inches) in the y-direction. Stem diameter was about 0.15 mm (0.0059 inches) and the stem height was about 0.625 mm (0.0246 inches). The gap between adjacent stems was about 0.127 mm (0.005 inches). Using the size of the tool diameter holes (0.010 inches) to define the largest possible individual stem cross-sectional area (0.00007854 inches 2 ), the area of each square inch of the stem web made up of stems (at about 3159 stems/inch 2 ) is thus no greater than about 24.8% of the total area. 
     Wetting capability of water was estimated by measuring a contact angle between a drop of water and flat substrate with the same composition as the stem web. The contact angle was measured to be about 65°, which was expected for a hydrophobic material (see generally  FIG. 6 ). A large amount of water was then applied to the structured surface of the stem web and viewed in optical microscope. Water completely filled the space between the stems. The tips of the stems were exposed due to hydrophobic nature of the elastomer, as shown in  FIG. 7 . As a result of the exposed tips, frictional properties were improved when compared to flat sheet performance, when tested under the same conditions. 
     The gripping performance was evaluated using two approaches. The first set of experiments included direct measurements of the frictional properties of the stem web. The results were compared to the performance of the flat substrate made of the same polymer blend as the stem web. The second approach involved direct application of the stem web to an article. A 68.6 cm×2.54 cm (27 inches×1 inch) strip of the web was wrapped around a golf shaft and compared to the existing golf grips performance in both wet and dry conditions. A panel of evaluators took a series of swings with the golf club with the new grip. The performance of the presently disclosed article was believed to be superior to the control sample in wet conditions. A similar test was conducted with a tennis racket. 
     Example 2 
     For more consistent removal of the stem web from the tooled surface and uniform application the articles, a two-layer construction was created using a co-extrusion process. The tooling and processing parameters were as described in Example 1 unless otherwise specified. Rather than the backing layer of the double coated tape in Example 1, a backing layer made of a 80:20 wt % blend of polyurethane Estane™ 58137 and Vector™ 4111 was co-extruded with the stem web. The polyurethane had hardness of 70 Durometer and the modulus of about 22 MPa (3200 psi). The stiffer backing layer was extruded using about 6.35 cm (2.5 inches) diameter screw at about 5 rpm. The top layer which formed the stemmed portion of the construction was extruded using about a 3.2 cm (1.25 inches) diameter screw extruder operating at about 15 rpm. The temperature profile was the same as described in Example 1. The polymer melt was discharged at a minimum pressure of about 6.9 MPa (1000 psi) and at the temperature in the front zone of about 216° C. (420° F.). 
     Both melts were combined in Cloeren feed block model no. 86-120-398 at about 232° C. (450° F.). A Cloeren extrusion die with a deckle system, model no. 89-12939, was used. The construction was removed from the tooled surface at about 1.5 meters/minute and about 3 meters/minute (5 fpm and 10 fpm). The resulting thickness of the each layer (not including the stems), at about 5 fpm take-up speed was about 0.254 mm (0.010 inches). 
     Example 3  
     A stem web was made generally according to Example 2 using a tool with different stem geometry and a pressure of about 68,941 Pa (10 psi), resulting in shorter stems. The stem web was a 80:20 by weight of polyurethane resin Estane™ 58661 and a styrenic triblock copolymer Vector™ 4111. The backing layer was made of a 80:20 wt % blend of polyurethane Estane™ 58137 and Vector™ 4111, co-extruded with the stem web as in Example 2. 
     The resulting stem web had about 235/centimeters 2  (1516 stems per square inch). The center-to-center spacing of the stems was about 0.676 mm (0.0266 inches) in the x-direction and about 0.630 mm (0.0248 inches) in the y-direction. Stem diameter was about 0.198 mm (0.0078 inches) and the stem height was about 0.307 mm (0.0121 inches). The gap between adjacent stems was about 0.127 mm (0.005 inches). 
     Example 4  
     A stem web with a single layer construction and a density of about 139 stems/cm 2  (900 stems/square inch) was created using a tool with different stem geometry and the same processing conditions and polymer blend formulation as in Example 1. The stems had about 50% larger diameter than the stems on the about 465 stems/cm 2  (3000 stems/square inch) construction of Example 1, which lead to better durability of the construction. Stem height was about 0.56 mm to about 0.61 mm (0.022 inches to 0.024 inches). At a distance between the pins of about 0.84 mm (0.033 inches), individual pins could be felt. Thicker pins are also less flexible, which also contributed to a more rough, or coarse feel of the surface. This surface is most suited for non-skin contact applications. 
     Example 5  
     A stem web was made using a tool with different stem geometry and substantially according to Example 1 with a 80:20 by weight of polyurethane resin Estane™ 58661 and a styrenic triblock copolymer Vector™ 4111. The resulting stem web had about 46/centimeters 2  (299 stems per square inch). The center-to-center spacing of the stems was about 1.68 mm (0.066 inches) in the x-direction and about 1.29 mm (0.0507 inches) in the y-direction. Stem diameter was about 0.459 mm (0.0195 inches) and the stem height was about 0.617 mm (0.0243 inches). The gap between adjacent stems was about 0.254 mm (0.010 inches). The higher percentage of polyurethane increased durability of the resulting article. 
     Example 6  
     Stem web sheets were made using silicone tooling similar to Example 1 and the hot press method discussed above. The formulations are set forth in Table 3, where the ratios refer to percentage of Estane™ 58661 to Vector™ 4111. The resulting stem web had about 490/centimeters 2  (3159 stems per square inch). The center-to-center spacing of the stems was about 0.439 mm (0.0173 inches) in the x-direction and about 0.465 mm (0.0183 inches) in the y-direction. Stem diameter was about 0.15 mm (0.0059 inches) and the stem height was about 0.625 mm (0.0246 inches). The gap between adjacent stems was about 0.127 mm (0.005 inches). 
     In order to quantitatively compare the group properties of various blend compositions in both wet and dry conditions, a Thwing-Alber friction/peel tester was used to measure both static (SFC) and dynamic (DFC) friction. In addition, friction coefficients for flat sheets, i.e. the other side of the stem web, were also measured for a few of the blend compositions. The average SFC and DFC values for stem webs prepared in a batch process using a heated press of various formulations are given in Table 3. 
                     TABLE 3                  Frictional properties of blended stem webs in dry and wet conditions.                                 Formulation   SFC Dry   DFC Dry   SFC Wet   DFC Wet                                         Estane 58661   1.3   1.25   1.2   1.1       80/20   1.5   1.5   1.4   1.4       60/40   1.8   1.75   1.7   1.6       50/50   1.85   1.75   1.7   1.6       40/60   2.1   2.0   2.0   1.9       20/80   2.3   2.11   2.1   1.8       Vector 4111   2.5   2.3   2.3   2.1                    
Stem samples made from pure Vector™ 4111 have the highest DFC and SFC, and pure Estane™ 58661 stem samples have the lowest DFC and SFC. Mixtures are somewhere in between with a nearly linear relationship. In addition, SFC and DFC for each blend decreases with the addition of water between the stems and the Ultrasuede™ substrate. In fact, the addition of water causes an only about a 7% decrease in stem web friction for every blend composition. Small differences in friction performance are found for 50/50 and 60/40 blends. Based on frictional performance, the 60/40 formulations will lead to better wear properties since it possess a larger volume fraction of polyurethane.
 
     Example 7  
     A stem web of 50:50 by weight of polyurethane resin Estane™ 58661 and a styrenic triblock copolymer Vector™ 4111 was made according to Example 1. The stem geometry is as set forth in Example 1. A flat sheet was also made using this formulation. The average SFC and DFC values for stem web and the flat sheet are given in Table 4. 
                     TABLE 4                  Stem web and flat film comparison.                                         Sample ID   SFC Dry   DFC Dry   SFC Wet   DFC Wet                                                     Flat Film   2.12   2.08   1.3   1.3           Stem web   2.1   2.0   2.05   1.95                        
From Table 4 it is evident that both static and dynamic coefficients of friction are comparable for the stem web (60% Estane™ 58661 and 40% Vector™ 4111) and flat sheet when measured in dry conditions. However, when some water was added to the stem web, coefficient of friction of the flat sheet decreased by 30%, while stem web maintained its high friction, within the experimental error. This result is consistent with the mechanism of wetting described on  FIGS. 6 and 7 .
 
     Example 8 
     Three samples of the stem webs of Examples 1, 3 and 5 were examined for dynamic shear strength using the test method described above. A summary of the results is found in Table 5. 
                     TABLE 5                  Dynamic Shear Strength - Dynes/cm 2  (ounces/inch 2 )                                 Exam-   Sam-                   ple   ple   Peak   Valley   Average               1   1   168,481   140,904   157,709               (39.1 oz/sq. in.)   (32.7 oz/sq. in.)   (36.6 oz/sq. in.)       1   2   144,351   140,904   143,489               (33.5 oz/sq. in.)   (32.7 oz/sq. in.)   (33.3 oz/sq. in.)       1   3   202,523   81,009   136,595               (47.0 oz/sq. in.)   (18.8 oz/sq. in.)   (31.7 oz/sq. in.)       1   Aver-   171,929   121,082   146,075           age   (39.9 oz/sq. in.)   (28.1 oz/sq. in.)   (33.9 oz/sq. in.)       3   1    18,959    14,650    16,805                (4.4 oz/sq. in.)    (3.4 oz/sq. in.)    (3.9 oz/sq. in.)       3   2    23,268    18,959    21,545                (5.4 oz/sq. in.)    (4.4 oz/sq. in.)    (5.0 oz/sq. in.)       3   3    35,333    21,114    31,886                (8.2 oz/sq. in.)    (4.9 oz/sq. in.)    (7.4 oz/sq. in.)       3   Aver-    25,854    18,097    23,268           age    (6.0 oz/sq. in.)    (4.2 oz/sq. in.)    (5.4 oz/sq. in.)       5   1   168,051   107,725   133,148               (39.0 oz/sq. in.)   (25.0 oz/sq. in.)   (30.9 oz/sq. in.)       5   2   152,969    80,578   135,733               (35.5 oz/sq. in.)   (18.7 oz/sq. in.)   (31.5 oz/sq. in.)       5   3   152,538    81,009   112,034               (35.4 oz/sq. in.)   (18.8 oz/sq. in.)   (26.0 oz/sq. in.)       5   Aver-   157,709    89,627   127,115           age   (36.6 oz/sq. in.)   (20.8 oz/sq. in.)   (29.5 oz/sq. in.)                    
The stem webs made according to Examples 1 and 5 had the best dynamic shear strength. The samples from Examples 1 and 3 were more similar in stem density and stem diameter than those of Example 5. However, the stem height of the samples of Example 3 was approximately half the height of the stems of Examples 1 and 5. Even the relatively low density stem web of Example 5 outperformed the samples of Example 3. Therefore, stem height appears to be a significant factor in dynamic shear strength.
 
     Patents and patent applications disclosed herein are hereby incorporated by reference. Other embodiments of the present disclosure are possible. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the present disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.