Patent Application
20070000020
The present invention relates generally to elastomeric articles and their fabrication. The present invention relates to a method of modifying the surface characteristics of an elastomeric article, for example, a condom, or a glove for use in medical and/or scientific applications.
A common annoyance and complaint among surgeons and other operating room personnel is the tendency for conventional, elastomeric surgical gloves to slip or roll down the wear's forearms when in use. This problem can cause the glove to not fit properly, tending to gather around the surgeon's wrists, and sometimes making the glove a hindrance to the surgeon's manual dexterity and performance. The problem is particularly burdensome with surgical gloves, in view of the critical nature of the surgeon's activities, and also in view of the danger that sterile field on the gloves may be compromised by attempts to re-roll the glove backup along the surgeon's arm. Surgical gloves currently on the market experience significant cuff slippage during use.
Over the years a number of techniques have been put forward to counteract and/or solve this problem. For example, attempts that solving the glove-cuff slippage problem have traditionally focused on changing the physical shape or design of the glove. For instance, some commercially available gloves have cuff regions that have, individually or in combination, either relatively thick, circumferential or longitudinal bands, ribs, fluting, dentations or denticles, or a bead, in an attempt to minimize cuff roll-down.
Alternatively, others have suggested applying an adhesive strip to inside of the cuff, and still others have suggested employing rather cumbersome straps and pegs to secure the cuff tightly to the wear's wrist and forearm. Some manufactures have remedied this issue by narrowing the diameter of gloves at the cuff opening or its immediate area, which has resulted in more constrictive force on the arms producing discomfort and often a compression band on the skin. Hence, these efforts have not been very successful.
A need exists for a better alternative that does not constrict the glove cuff, nor substantially change the gross physical configuration of the glove from designs which medical, surgical, or laboratory workers have become accustomed. Additionally, a technique or method process is needed for either convenient, online or off-line production of an elastomeric article, like a glove with a higher coefficient of friction in the cuff region. The present invention satisfies these needs and can provide such an alternative.
In view of the needs, the present invention relates generally to a method of modifying the surface characteristics of an elastomeric article, for example, a glove (e.g., medical, surgical, and/or scientific) or a condom. More specifically, the present invention relates in part to a chemo-mechanical approach for modifying the surface characteristics of an elastomeric article, according to either an online, automation-friendly process, or an off-line production process. More particularly, according to an embodiment, the present invention involves a method or mechanism to enhance the wearer-contacting or inner surface about the cuff region of a glove in a post formation treatment. To the extent that a first region of a glove has anti-slip properties, the surface of the glove is modified to have a higher coefficient of friction (COF) relative to the second region or area of the glove that is not treated. The treatment creates a band or zone near or around the cuff that has either a surface with different and more pronounced texture, or higher COF to prevent slip-down than the rest of the interior surface of the glove.
The textured surface may comprise a roughened or dappled surface with micrometer-scale raised ridges and valleys or dimples (also referred to as microridges) to increase mechanical or frictional engagement of one surface with another surface or friction when worn, either against bare skin or a garment material. The micrometer-scale features can range from about 1 micron (μm) up to about 700 or 800 μm, but typically are less than 500 μm, and desirably, less than about 250 or 200 μm. Preferably, the features are in a range of about 5 μm to about 120 μm; more preferably about 10-50-80 μm.
The difference in relative coefficient of friction helps prevent the glove from slipping down off of a sleeve of a surgical gown or other garment surface. Hence, the anti-slip first region preferably should be situated at or near the cuff portion of the glove. The difference in relative coefficients of friction between the two regions or zones of the inner, wearer-contacting surface can be expresses as a ratio in a range of at least about 1:1.2, up to about 1:5.5, typically about 1:1.3 to about 1:4.5. For example, the band or zone near or around the cuff has a COF that is at least about 1.2 times greater (i.e., 20% greater) than the COF of the untreated section.
In the present invention, as a general observation an inner surface of a glove that has a higher coefficient of friction is more desirable because of friction to retain the glove against the material of a garment. Yet, this observation has caveats that were surprisingly unexpected. Gloves, especially surgeon's gloves, should not restrict the natural movement and flex of a wearer's hands and wrist. Hence, the glove should not be too stiff and the coefficient of friction ratio should not be too large. In our experience, an excessively high COF can overly restrict the ability of the user to freely move and flex the user's hands and wrists, such as one can experience with rubber bands, large-area arrays of rigid or non-flexible hook-n-loop attachments, or adhesive tapes used to prevent glove slip-down. These techniques have been disfavored. Further, a COF that is too high can hinder the ability of the wearer to easily don the glove, especially under damp-skin conditions. The wear's hand will catch against the high friction surface of the cuff region. To strike a balance between maintaining a natural feel, without binding the movement of hands and wrists, and better donning, while preventing the glove-cuff from slipping down, a desirable range for the COF ratio is between about 1:1.3 up to about 1:5.0, preferably about 1:1.4-1:4.8, or about 1:5.0-1:4.0.
The first region, depending on the physical dimensions or size of the glove, can cover a distance or width that extends inwardly, from the terminal edge of the glove cuff, about 1 inch (2 cm) to about 5 or 6 inches (12-13 cm), and around laterally over a surface area that encompasses the entire periphery of the cuff area.
According to certain embodiments, the surface of the first region can be left substantially bare of any coating. That is, the elastomeric material (e.g., natural rubber or synthetic polymer) surface is exposed and roughened to create either a scabrous surface or a surface topography with peaks and valleys. Depending on the type of elastomeric material, such a roughened surface may have an intrinsic low level of tack. The roughened region further can be coated with a layer of adhesive or tackifying agents (e.g., tackifying resins, rubber cement), to increase the level of tack. Typically, the elastomeric material or coating should be relatively low tack; that is, the polymer material should not have an “aggressive” initial adhesive quality that instantly creates a level of tack that would make the elastomeric article difficult to remove, readjust, or separate from bare skin or a garment fabric material The “low-tack” materials should be capable of providing slip resistance without forming a permanent bond between the elastomeric surface and bare skin or garment fabric during the time the elastomer is in contact with skin or fabric, under normal temperature and humidity conditions (e.g., 20-25° C. and 50-60% relative humidity), and contact pressures. Typically, this time can range from less than an hour to several hours (e.g., 2-6 hrs.). It is contemplated that the contact time period without bonding can be more than 10 or 12 hours.
In some other embodiments, the higher COF may be achieved by either providing a more tacky surface in the first region or generating a slicker surface in the second region, each of which may involve the application or removal of a coating, such as of a hydrogel or other lubricating cover, to the respective zone.
According to an embodiment, the present invention uses a chemical-mechanical manufacturing process for creating or modifying a surface property or characteristic of an elastomeric material, the process comprising: a) providing an elastomeric workpiece; b) providing a colloidal slurry, the slurry having non-agglomerated single or multi-component particles of a single or mixed-metal or metaloid oxide, oxyfluoride, or oxynitride composition, c) abrading a surface of the workpiece with the single or multi-component particles. Terms “abrade” or “abrading,” as used herein, refer to the relatrive action or motion of the particles under sufficient pressure to erode the elastomeric matrix, stripping away the fine micro or nano-scale layers of the surface material to roughen the elastomeric surface. Abrade can also refer to “buffing,” “rubbing to wear away,” “texturize” and/or “polish” as forms of roughening or making “scabrous.” In particular, the single and/or mixed component particles buff or abrade what will become an inner surface of an elastomeric article to a predetermined and desired surface texture.
The fabrication process can involve, first either providing or forming an elastic membrane on a mould surface; drying the membrane to at least partially set and have a firm degree of structural integrity; applying a liquid-mediated treatment (i.e., liquid carrier) containing at least one kind of either mixed or mono-metallic of metalloid oxide, oxyfluoride, or oxynitride particles to the elastic membrane surface; applying an amount of pressure (e.g., between about 5 or 10 dynes/cm2 up to about 3 or 5 pounds/inch2 (psi)) to the particles suspended in the slurry for a predetermined duration, to permit the particles to abrade or rub against the membrane surface utilizing a treatment applicator or transfer substrate. The transfer substrate may be formed from any suitable material, and in some instances, may include an open cell material, a nonwoven material, a flexible bristle, and so forth. The elastic membrane desirably is cured before the transfer substrate or pad is applied to the surface of the elastic membrane, but if an uncured membrane is structurally sufficiently resilient to abrasion, the treatment may be applied before curing. After roughening or texturizing the surface, the elastomeric article can be rinsed in either water or a dilute acid wash to remove any residue oxide particles and then oven dried. The elastomeric article can be further coated with emollients, other material solutions, or a donning coat. A preferred protocol would be to texturize the surface after the addition of coatings or other treatments so that the texturing will not be diminished by the additional coating or treatment.
The invention also includes a reagent solution system for processing an elastomeric material substrate. The reagent system involves at least two parts, a slurry for roughening the elastomeric surface and an acidic wash solution.
In another embodiment, an abrasive substrate can be dragged or rubbed against the cuff region of each glove while the glove substrate membrane is mildly tacky either still uncured or just after curing the glove substrate. In such a fashion one can create a surface that is lightly textured or has a series of slightly elevated and depressed ridges or score marks, arrayed either parallel to each other, randomly, or in a desirable cross-hatching pattern. The abrasive substrate is a material or article that includes features adapted to roughen or texturize a softer glove substrate or elastomeric article. For example, an abrasive substrate may be a roughened sheet, fabric strip, or set of bristles, impregnated or studded with a layer of abrasives composed of, for example, a) silicates, such as silica (SiO2) or garnet, b) aluminum oxides (Al2O3), such as corundum or fused alumina, and/or c) silicon carbide. Other alternative embodiments, may include a wire brush or similar article with or without the abrasive agents coated on the surface. These abrasive agents can be applied singly or in combination. The abrasive substrate can be operated against the elastomeric membrane under either dry or wet conditions using water or a dilute alcohol. An extrinsic force or pressure can be applied to the abrasive agent against the surface of the workpiece. Alternatively, the pressure can result from the intrinsic weight of the abrasive media against the workpiece. The pressure should be sufficient to cause surface texture but not enough to damage the overall structural integrity of the polymer material or film properties.
Additional features and advantageous of the present invention will be revealed in the following detailed description. Both the foregoing summary and the following detailed description and examples are merely representative of the invention, and are intended to provide an overview for understanding the invention as claimed.
The present invention provides, in part, an elastic or elastomeric article having a modified surface that is adapted to better attach to either skin or garment materials. The invention also provides a method of producing or creating the surface modification in an elastomeric article. As used herein, the terms “elastic” or “elastomeric article” refers to a product, article or substrate membrane having at least one surface formed predominantly from an elastomeric material. An “elastic” or “elastomeric material” refers to a natural latex or synthetic polymer-based material that is capable of being easily stretched or expanded, and substantially returns to its previous shape or configuration upon release of the distorting force. As a non-limiting example, upon application of a level of stretching or biasing force easily achievable by a human adult, an elastic material can be readily stretched at least about 150% of its original, relaxed, unstretched dimensions and has a tendency, for example, to retract to within about 110% or 120% of the original, relaxed, unstretched dimensions after release of a stretching or biasing force.
In particular, the invention pertains to methods for modifying surfaces to improve the staying power of elastomeric substrates, such as work or surgical gloves from slipping down when worn. Specifically, the present technique contemplates treating a surface of the article to modify the local surface topography for enhanced attachment to gloves or other garments to prevent slippage when worn. The term “treatment” refers to any chemical or other agent that can alter chemically or mechanically the physical or chemical properties of the treated surface. The technique contemplated by the present invention enables a surface of the article to be treated without having to resort to more cumbersome, traditional techniques mentioned above, such as bands, ribs, fluting or adhesive strips or patches. Furthermore, the treatment may be applied to one surface without the risk of inadvertently treating another surface, such as the case when a bulk off-line halogenation process is used. Often, the halogenation solution is likely to enter the glove in the cuff area and reduce the coefficient of friction in that area.
The method adapts chemo-mechanical techniques to modify part of an inner surface of an elastic membrane, such as the surface of surgical or examination gloves, so as to generate a differentiated surface with higher coefficient of friction. As used herein, chemo-mechanical refers, for example, to an adjustment of the either the pH and rheology, or hardness of abrasive particles to keep the particle non-agglomerated and in a stable dispersion so they can more efficiently roughen and scarify the surface of an elastic article when applied and mechanically moved against the article under an applied pressure. Using a transfer substrate such as described in U.S. patent application Ser. No. 10/429,502, the contents of which are incorporated herein by reference, a slurry of abrasive colloidal particles are applied against the elastomeric material surface. The abrasive colloidal particles can have either a single or multi-component composition comprising mixed 1) metal or metalloid oxides, 2) oxyfluorides, or 3) oxynitrides, each grouping (1, 2, or 3) individually alone or in combination thereof. The metal or metalloid oxides abrasive can including at least one, or a combination of the following, silica, ceria, titania, zirconia, germania, and germania-doped silica. The term “multi-component,” as used herein, refers to a composition having at least two, preferably three or more constituents in a single particle. Variable compositions of the abrasive materials can be used to generate colloidal particles with different surface charges and dispersion behaviors. The surface chemistry of the multi-component particle is modified relative to the surface chemistry performance of the individual, original base constituents of the particles, where in embodiments, the isoelectric point of the particle is displaced toward an alkaline pH value. Each multi-component particle exhibits a modified surface chemistry in which it has an isoelectric point (pH IEP) greater than or equal to about 5-6 with a stabilized particle dispersion at pH values of interest for chemo-mechanical processing (CMP) operations. Typically the pKIEp is greater than or equal to about pH 6.5 or 7. Preferably, the pH values are alkaline, in a range from about 7.5-10 or 10.5. Occasionally, the pH may be as high as about 11-14. This is not to exclude the possibility that one may do the counterpart, in which one fashions particles from compositions with desirable chemical and physical properties that can overcome current dispersion difficulties associated with CMP operations in the range of alkaline pH values.
The particles exhibit a modified surface chemistry performance and have an isoelectric point (pHIEP) greater than the pH of the dispersed particles in solution, and with a stabilized particle dispersion at pH values of interest for chemo-mechanical processing (CMP) operations.
The slurry mixture incorporating the single or multi-component particles has a solution chemistry that enhances the CMP effects by in-part adjusting the pH of the solution away from the pHIEP of the media to maximize dispersion. Problems associated with agglomeration of the colloidal particles can be addressed by adjusting the pH of the slurry solution. As described in U.S, Patent Publication No. 2004/0132,306, A1, incorporated herein, multi-component colloidal particles that have compositions which may be adjusted as desired, in regard to their chemical or physical properties such as surface chemistry, hardness, solubility, or degree of compatibility with the workpiece material can be used for chemo-mechanical processes. The particles' multi-component composition is believed to generate an advantageous effect for better dispersion in solution. This effect shifts the multi-component particles' isoelectric point (i.e., point of zero charge on the particles), such that the pHIEP can be raised or lowered as desired. This feature can reduce the likelihood of agglomeration at operational pH values, thus enhancing the efficiency and operation, even at smaller particle sizes.
The abrasive particles can have an average particle dimension (e.g., diameter) of up to about 500 or 600 nanometers (0.5-0.6 microns), with a distribution having a variable mean particle size of between about 10-400 nm. Preferably the average dimension of each particle may range from about 10 nm to about 200 or 300 nm, more preferably about 25 or 30 nm to about 150 or 180 nm. Silicate-based particles are fumed soot particles, preferably, ranging from about 1 nm to up to about 200 nm, preferably about 25-150 nm. Alternatively, as in the case of fused silica particles, the dimensions can be much larger, of greater than 1 or 5 microns. The resulting particles have either a spherical, near-spherical, elongated, or amorphous (non-crystalline) morphology. Other morphologies, such as dendritic, non-spherical, regular or irregular crystalline forms, may be used, but are less desired.
When applied in a slurry, the particle size distribution may take the form of a single mode distribution, or alternatively, may be a multi-modal distribution as the desired use may dictate. That is, within a slurry mixture, the multi-component particles may have a particle-size distribution with two or more modes each with a mean particle size. The distribution of particle sizes may have a normal (gaussian) distribution or skewed distribution. Although the overall particle size distribution may span the entire range of average particle dimensions (˜10-600 nm), preferably, the variation in particle size is relatively small, such that the size of individual particles is clustered closely round a mean value. For instance, in a single distribution curve the average dimensions of about 68-95% (two standard deviations) of the particles are within about ±30-50 nm (preferably within about ±25 nm) of a mean value. Particle-size distribution can be adjusted to control the final surface finish as well as the ability to clean residue abrasive particles from workpiece surfaces after processing. The particles in solution are preferably selected for chemical and physical properties that reduce agglomeration under predetermined pH conditions employed.
The method includes providing an abrasive transfer substrate, providing the elastomeric matrix on a former, the elastomeric matrix having an exposed surface, and contacting the matrix and the transfer substrate such that an abrading treatment is applied to the exposed surface. The pressure of the abrasive transfer substrate against the exposed elastomeric surface can vary depending, in part on the kind of elastomeric material (e.g., natural vs. synthetic polymer lattices), or whether the elastomer has been cured to not. The pressure that an abrasive substrate exerts against the elastomeric workpiece may range between about 40 dynes/cm up to about 1-5 psi, depending on the resilience of the elastomer and the desired degree of roughening or texturizing for enhanced friction on the exposed surface. Desirably, the pressure is about 100 or 150 dynes/cm2 to about 2 psi; and, more desirably about 500 dynes/cm2 to 1 psi.
According to an embodiment of the present method, to apply a surface-modifying treatment a glove, for example, an elastomeric matrix on a hand-shaped glove former is brought into contact with a transfer substrate. Through a conduit the colloidal slurry is supplied in metered fashion to the abrading, active, or matrix-contacting surface of the transfer substrate, which serves as the polishing or abrasive substrate applied. The particles in the slurry work against the matrix. As used herein, “matrix” refers to a coating of an elastomeric material on the surface of the former that has significantly gelled and has a firm degree of structural integrity. When the transfer substrate and matrix are in contact, the abrading action can occur when either: 1) the transfer substrate remains stationary as the former rotates about on its longitudinal axis, 2) the transfer substrate revolves about the former with the matrix, and/or move in a circular motion against the matrix, or 3) a combination of 1 and 2 motions with respect to both former and transfer substrate. It is further contemplated that the abrading action may be carried out by other motions or combinations of motions. For example, reciprocating linear motions and/or other motions may be used alone or in combination with one or more of the previously identified motions.
After abrading for a predetermined period of time, the matrix on the former is withdrawn and moved to a wash or rinse to remove any residual colloidal particles. An acid wash (e.g., pH ˜1.5 or 2 up to ˜6, desirably pH ˜4-5) can follow over either the whole or only the part of the elastomeric membrane that is abraded. The elastomeric article is then dried, in ambient air or through an oven, or the article may be further subject to other post-processing steps or surface treatments. As mentioned previously, a preferred method is to have all processing completed prior to the abrasion so the post treatments will not adversely affect the abraded area. Once the abrasion process is completed the elastomeric article can be stripped from the former, inverted roughened-side-in, without backend processing, and packed for shipping.
When the slurry and abrasion treatment is applied, the elastomeric matrix can be either in its pre- or post-cured state, depending on subsequent processing parameters or steps. Desirably, the matrix has already been cured. To better understand the present invention, the entirety of the process is described below.
An elastomeric article, for example, a glove, may be formed using a variety of processes, for example, dipping, spraying, tumbling, drying, and curing. An exemplary dipping process for forming a glove is described herein, though other processes may be employed to form various articles having different shapes and characteristics. For example, a condom may be formed in substantially the same manner, although some process conditions may differ from those used to form a glove. It should also be understood that a batch, semi-batch, or a continuous process may be used with the present invention.
Although the accompanying figures depict a transfer substrate contacting the entire elastomeric matrix of a glove, other embodiments as contemplated according to the present invention can be configured to limited contact of the transfer substrate to only certain, specific areas of the glove surface, such as along the cuff, palm, or fingers, without affecting the other portions of the glove. The accompanying figures are intended to be illustrative of the general concept of contacting an elastomeric substrate with a transfer substrate for delivering a treatment, and should not be limiting the invention to anyone particular depiction or embodiment.
A glove 20 (
The former 22 is coated with an elastomeric material, often using a dipping process, to form an elastomeric matrix 28 on the surface of the former. Any suitable elastomeric material or combination of materials may be used to form the elastomeric glove matrix. In one embodiment, the elastomeric material may include natural rubber, which may generally be provided as natural rubber latex. In another embodiment, the elastomeric material may include nitrile butadiene rubber, and in particular, may include carboxylated nitrile butadiene rubber. In other embodiments, the elastomeric material may include a styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene block copolymer, styrene-butadiene block copolymer, synthetic isoprene, chloroprene rubber, polyvinyl chloride, silicone rubber, or a combination thereof. The former may be subjected to multiple dipping processes to build up the desired glove thickness on the former, or to create layers of the glove having various properties, and so forth.
In many cases, the exposed surface becomes the interior surface (wearer-contacting) of the glove, so it may be advantageous to apply a treatment that enhances the interior surface of the resulting glove. However, it should be understood that the exposed surface may become the exterior surface of the glove when donned, depending on the number of times the glove is inverted during post formation processes, and it therefore may be advantageous to apply a treatment that enhances the exterior surface of the resulting glove.
While traditional treatment processes involve stripping the glove from the former and subjecting the glove to cumbersome immersion processes, the method of the present invention allows the surface-modification treatment to be applied while the glove matrix is still on the former. As depicted in
The treatment to be applied may be metered to the substrate from a supply source 36, for example, a tank or other suitable vessel, during the treatment process (
The method also contemplates removing excess treatment from the transfer substrate where needed or desired (not shown). In some instances, removal of excess treatment may be performed to ensure that the proper quantity of treatment is available for transfer to the next matrix to be coated. In other instances, removal of treatment may be performed to ensure that the treatment transferred to the matrix is of a consistent quality.
The transfer substrate may be formed from any material capable of delivering the treatment to the matrix without compromising the physical integrity of the matrix. The transfer substrate may be flexible, compressible, and/or deformable, depending on the needs of the application. The size of the transfer substrate can be may depend on the dimensions of the area on the substrate to be subject to treatment. For the purposes of the present surface-modification uses, the transfer substrate, desirably, is within dimensions that contain a gross area sufficient to cover either a narrow band (e.g., 0.5-1-2 cm width) along an edge of a glove or the entire cuff region (e.g., 2-5 inches width) of the glove.
The transfer substrate can also be configured with alternating ridges and valleys, in which the ridges contact the elastomeric matrix while the valleys avoid contact. Thus, one creates alternating bands of modified and unmodified surface, when the elastomeric substrate is rubbed against the transfer substrate in a unidirectional or straight back and forth motion, either horizontally, diagonally, or vertically over the exposed surface. In other words, the abrasion is not applied in a circular or arching motion when abrading the surface.
In particular embodiments, the transfer or treatment substrate may include an open cell material, for example, an open cell foam, sponge, pad, or the like. In such an embodiment, the open cell material 42 may be affixed to or mounted onto a rigid or semi-rigid plate 34 to which the treatment 30 is supplied (
Where the matrix 28 is especially delicate, it may be beneficial to provide the treatment 30 to the transfer substrate 32 as a chemical foam 48 (
In another embodiment, the transfer substrate 32 may include flexible bristles or fiber-like materials (
In another embodiment, the transfer substrate may include a nonwoven material, for example, nonwoven strips. In one embodiment, transfer substrate includes a strip of nonwoven material, for example, spunbond or combinations of spunbond and meltblown material that is secured to a rigid or semi-rigid plate/backing to which the treatment is supplied. In another embodiment, multiple strips 52 of a nonwoven material may be used as the transfer substrate 32 (
As used herein, the term “spunbond” or “spunbond fibers” or “spunbonded fibers” refers to small diameter fibers that are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced, for example, as in U.S. Pat. No. 4,340,563 to Appel et al.
As used herein, the term “meltblown” or “meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams that attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin et al.
The nonwoven transfer substrate may be formed from a single layer of material or a composite of multiple layers. In the case of multiple layers, the layers may generally be positioned in a juxtaposed or surface-to-surface relationship and all or a portion of the layers may be bound to adjacent layers. The multiple layers of a composite may be joined to form a multilayer laminate by various methods, including but not limited to adhesive bonding, thermal bonding, or ultrasonic bonding. One composite material suitable for use with the present invention is a spunbond/meltblown/spunbond (SMS) laminate. Other examples include wovens, films, foam/film laminates and combinations thereof, for example, a spunbond/film/spunbond (SFS) laminate.
The treatment may be supplied to the transfer substrate at any suitable rate and by any suitable method, for example, a pump, a gravity feed tank, or any other suitable means. The treatment may be supplied to the transfer substrate at a constant rate or a variable rate as desired. Furthermore, the treatment may be supplied continuously or discontinuously as needed to provide the desired amount of treatment to the transfer substrate. Where the transfer substrate is mounted to a rigid or semi-rigid plate, the plate may include features that enable the treatment to be uniformly delivered to the entire transfer substrate. Such features may include, for example, distribution channels or baffles, multiple supply inlets, and so forth.
The abrasive colloidal slurry can be applied at room temperature (i.e., ˜20-23° C.). For some other applications, however, one may desire to heat the treatment during the surface modification process. For instance, treatments having a reduced viscosity at lower temperatures, heating the treatment may improve transfer of the treatment from the substrate to the glove matrix. For some applications, the temperature of the treatment may be maintained at about 25-30° C. to about 80° C. For other applications, the temperature of the treatment may be maintained at about 40° C. to about 70° C. In yet other applications, the temperature of the treatment may be maintained at about 45° C. to about 60° C. Where it is desirable to heat the treatment during the treatment process, the transfer substrate may be selected to be resistant to degradation at the temperature to which it will be exposed.
The present invention has a number of advantages. For example, the fabrication process is automation compatible and can be a cost-effective technique for modifying the surface characteristics of an elastomeric substrate that allows one to address and target or treat one surface of an article without inadvertently treating another. The method includes providing a conveyable assembly including a plurality of formers, each former coated with an elastomeric matrix, metering a treatment to a transfer substrate, and advancing the assembly to bring each elastomeric matrix into contact with the transfer substrate such that the surface-modifying treatment is applied from the transfer substrate to each elastomeric matrix.
According to another embodiment, in a variation of abrading to modify the surface features, one can provide an elastomeric matrix or workpiece, apply under either dry or irrigated wet conditions a substrate with a surface impregnated or studded with an abrasive agent. The substrate can be a pad, a paper or fabric strip, or bristle fibers.
In similar fashion as described with regard to the foregoing colloidal particle abrasion, after the elastomeric membrane is gelled to a satisfactory physical integrity, the former with the exposed elastomeric surface is brought in contact with the abrading substrate. The exposed elastomeric matrix surface rubs against the substrate when the former is rolled against the abrading substrate. The substrate may be either held in a fixed, angled position or be allowed to hang like a strip of flap fabric. Since the elastomeric surface is back-supported by a rigid former, one can set the abrasive substrate to apply a constant, predetermined amount of pressure against the exposed elastomeric surface when the substrate is in a largely fixed, rigid position at an angle that can accommodate the rounded form of the former. Alternatively, the abrasive substrate can be flexible. In such a situation, the abrasive substrate would rise and fall against the exposed elastomeric surface corresponding with the rolling of a former against the substrate. In the second situation, however, force applied to the exposed elastomeric surface is likely to be minimal. The desired amount of pressures exerted against the elastomeric surface should be sufficient to create a textured impression on the surface, while avoiding damaging the structural integrity of the elastic membrane. For example, 15-90 dynes/cm2 may be suitable for an uncured elastomeric surface, while forces greater than about 150 dynes/cm2 up to about 2 or 3 psi, may be suitable for a post-cured surface.
According to an alternative expression, the abrasive substrate may be characterized in terms of “grit,” as is common with abrasive sheets. For instance, the abrasives on the abrading substrate have a density and size analogous or comparable to a conventional sheet with from 500 to 1200 grit for fine abrasion, or 100 to 500 grit for more aggressive abrasion.
It is believed that the modification of the inner surface of a glove, according to the present invention can greatly reduce the tendency for elastomeric gloves to slip when worn, especially when in contact with an article of protective clothing. A portion of the glove, not coated with donning layer, but a roughened and/or tacky surface engages with the material of the protective clothing. As such, one creates a good glove-gown interface region. In other words, due to the combination the silicone emulsion over the latex substrate which generates a higher COF at the cuff region than over the hand-donning region of the glove. The cuff sticks to gown surface and reduces slip down.
An elastomeric surface, treated according to either the colloidal slurry process or the abrasive-impregnated substrate, has a first region or zone that has a higher coefficient of friction relative to that of a second region or zone. The abraded or roughened elastomeric surface can have an average coefficient of friction ratio in a range of typically about 1:1.3 to about 1:4.0, and preferably about 1:1.4 to about 1:3.5 or 1:3.8. More desirably, the coefficient of friction ratio is about 1:1.5 to about 1:2.75. The COF ratios can be derived from a comparative measurement of the first and second regions of the inner surface of the elastomeric article according to the Kawabata Method. This test is described in Standardization Analysis of Hand Evaluation, by Sueo Kawabata; July, 1980, 2nd Edition, pp 31-35, 48-50.
For measuring the coefficient of friction on rough surfaces or surfaces with small areas, the Kawabata test is more reliable than the Classical Inclined Plane and Weight Method, which measures coefficient of friction via a determination of the angle at which the test sample, weighted down in a standard manner, slides down an inclined plane. (Principles of Physics, by J. B. Marion et al., chapter 7-1, Saunders College Publishing, New York, N.Y., 1984.) According to the Kawabata method, the test material is moved from left to right while a contacting element (of specific dimensions, and under constant force) touches the surface of the material. A transducer connected to the detector is used to measure frictional force as the test material is moved. The coefficient of friction is determined on the cuff and palm areas of the samples. In the test zone A is defined as the surface of the glove within 1.25 to 2 inches from the cuff edge or bead, and zone B is the surface of the donning areas of the glove, in particular the palm region.
Treatment techniques for chemo-mechanically modifying a surface of an elastomeric material substrate has been described in the present invention. Persons skilled in the art will understand that the invention is not limited necessarily to the specific embodiments disclosed. Modifications and variations may be made without departing from the scope of the invention as defined by the following claims or their equivalents, including equivalent components presently known, or to be developed, which may be used within the scope of the present invention. Hence, unless changes otherwise depart from the scope of the invention, the changes should be construed as being included herein.
