Abstract:
Breathable and durable woven or knit ticking fabrics are prepared by foam-coating the fabric to provide good barrier properties to bacteria and liquids and post-cure treating the coated fabric to provide additional bacteriostatic or repellent properties.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to a unique type of barrier system used to produce high end durable ticking fabrics used to make hospital and institutional pillows and other similar articles. The barrier system utilized involves foam coating applied to the surface of a high quality fabric to impart fluid repellancy and bacteriostatic properties which are required for a durable hospital pillow. 
     In the hospital, durable pillows are exposed to numerous body fluids and cleaning solutions, thus requiring these articles to be repellant to such fluids as water, alcohol, oil, blood or solutions containing these fluids. Most of the high end durable ticking fabrics used today are either coated with vinyl type polymers and polyurethanes, or laminated with such products on woven fabrics. The result is a ticking fabric that is impermeable to fluids and can be wiped down very clean making stains an infrequent occurrence. The drawbacks of these high end durable pillows, however, are numerous. Since the pillows are impermeable, even under high pressures, they are not breathable, that is, air does not readily pass through the ticking structure. This causes several problems. Firstly, the pillows must be vented in order to collapse when someone rests their head on it. The venting is achieved by several methods including punching many very small holes in the material, using grommets, or leaving an uncoated or untreated area around the pillow. This venting serves to provide direct pathways for bacteria and fluids to pass directly through and into the pillow filling thus increasing the possibility of cross-contamination from patient to patient. 
     The result is a pillow that is repellant only in certain areas making a non-uniform barrier product. Secondly, by not being breathable, heat and moisture can build up between the patient and pillow ticking making it very uncomfortable. Thirdly, the products tend to be either stiff or noisy, again, creating an uncomfortable situation for a patient particularly one who is confined to the bed for extended periods of time. 
     The object of this invention is to produce a high end durable pillow ticking that displays uniform repellency to water, alcohol, oil and other hospital fluids, bacteriostatic properties and exhibit soil release properties when wiped or cleaned. 
     Another object is to provide a pillow ticking that is breathable without any artificial venting resulting in a softer, quieter, and more comfortable durable pillow than is currently available. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 Shows a ×100 photomicrograph of the foam coated side of the fabric of this invention, illustrating the porosity and distribution of open cell foam overlaying the fabric. 
     FIG. 2 A ×100 photomicrograph of the same fabric on the uncoated side, illustrating that this side is substantially devoid of foam. The only foam network visible is that which filled small gaps in the fabric. 
     FIG. 3 A ×150 cross-section photomicrograph of the same fabric, again illustrating that by far the majority of the foam is located on one surface of the substrate. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The fabric of this invention is based on any knit or woven fabric which is durable enough in nature to be used over an extended period of time and resistant to abrasion from being used which could compromise product performance. These fabrics may be composed of polyester, cellulosic, nylon, polypropylene, or combinations of such fibers. 
     Any suitable substrate must satisfy a number of requirements, listed below generally in order of priority. The fabric must be durable in nature and be quite strong with a grab tensile minimum of 30 pounds and a trap tear minimum of 5 pounds. It must be soft, quite, and flexible, with a hand that lends itself to this type of product. 
     While the fabric properties are very important, the main process by which the functionality of the product is achieved, is by foam coating with a stabilized foam. The coating is layed on the surface of an appropriate substrate forming a network of open cell foam distributed among and adhered to the surface fibers, and to a limited extent, penetrating the depth of the fabric. This open cell structure serves to fill gaps and holes in the substrate thus reducing the overall porosity of the fabric. In this manner, the foam acts as a physical barrier. In conjunction with the physical aspects, the foam compound itself can be given added chemical properties by adding or deleting property modifying chemicals such as, but not limited to, fluorocarbon repellants, flame retardant chemicals, antimicrobial agents, detackifying agents, etc. Thus, the foam coating acting both physically and chemically results in end use performance. 
     In addition to the foam barrier, an additional processing step may need to be utilized in order to achieve the stringent repellency requirements needed for a hospital pillow ticking. This process would involve the topical application of chemicals to the coated substrate. Again, the chemical applied could be any property modifying agent that is compatible with the other finish chemicals or the process in general. For the product of this invention, both a fluoropolymer repellant and an antimicrobial agent are applied topically to achieve the reported properties. 
     The coating composition is based upon a resin or combination of resins plus filler(s). Other necessary ingredients include a foaming aid or surfactant to assist in forming a stable foam plus any other reactants or auxiliaries required to cross-link the resin and form a foam that, upon drying and curing, remains stable and continues to exhibit the desired performance characteristics. 
     While not wishing to be limited exclusively to this group of polymers, a typical selection may be on acrylic, styrene-butadiene rubber, vinyl, acetate polyvinyl alcohol, urethane, vinyl chloride, vinylidene chloride or an acrylonitrile, with a preference being with those polymers which will exhibit flame resistance. 
     Common fillers such as titanium dioxide, clay and talc are used based on particular needs or requirements of the coating. 
     After all of the adjustments and additions are made, the foam compound should meet certain specifications. Total solids of the coating compound should range from 40% to 70% by weight. The pH of the composition may be adjusted by the addition of a suitable base, such as ammonia to maintain a pH in the range of 8-11. The coating composition, prior to foaming should have a viscosity from 400 to 2,900 centipoise. (mPa.S) The coating is maintained and applied at a temperature of 70° F. to 110° F. 
     The coating composition is mechanically foamed in a foam generator such as an Oaks foamer or a L.E.S.S. model 500 super foamer to achieve a ratio from three to twenty parts air to one part coating composition, with a ratio of 3:1-8:1 preferred. 
     The compound is then applied by any convenient means, such as a knife coater. The coater is adjusted to place a layer of foam on the surface of the substrate, known as a surface coating or gap coating. Some foam may penetrate into the substrate, however, the vast majority of the coating is on one side. The coating dry addon should be in the range of 0.7 to 2.5 oz. per square yard. 
     The fabric is then dried at 150° F.-300° F. in a conventional hot air tenter frame, infrared, belt, or drum dryer to a point where 2 to 15 percent moisture is retained, in other words it is not bone dry. This retained moisture allows the coating to be crushed between a set of rollers such as rubber over steel, steel over steel, or steel over rubber. Crushing compacts the foam onto the fabric thus effectively decreasing the porosity and pore size of the coating, while increasing the abrasion resistance. The substrate is then dipped through a finish bath and post cured at 230° F. to 325° F. depending on the type of fibers used in the fabric. The top finish could be omitted, and the fabric just cured if properties after curing were adequate for the end use. 
     The following is typical formulation for the foam compound prior to foaming. Amounts we expressed on a parts per hundred by weight. 
     
         ______________________________________Ingredients              Dry Parts______________________________________Aqueous polyermer dispersion (40-50% active)                    20-60melamine resin            .5-10.0filler: clay, talc, etc. 15-45ammonium stearate (21%)  1-7pigment                  as neededcatalyst                   1-1.5thickeners               as neededproperty modifiers       as needed(flame retardant, water repellent,antistat, etc.)______________________________________ 
    
     After foaming, coating, curing, and applying any top-finish needed, the fabric should exhibit the following range of properties for functional use. 
     
         ______________________________________base weight (oz/yd.sup.2)    2.0-5.0grab tensile (lbs)   MD      30 minimumINDA 110.0-70 (R82)  XD      30 minimumspray rating                  70-100INDA 80.1-70 (R82)Frazier air permeability (Ft.sup.3 /min/Ft.sup.2)                         30-120INDA 70.1-70 (R82)alcohol repellency            7-10INDA 80.9-74 (R82)oil repellency - 3M Scotchguard                        3-6INDA 80.8-70 (R82)Suter hydrostatic head (cm)  15 minimumINDA 80.6-70 (R82)Flammability: NFPA 702       PASS(pass/fail)antimicrobial presence       PASS(pass/fail)______________________________________ 
    
     EXAMPLE 
     A foam-coated durable pillow ticking was prepared. First a foamable composition containing the following ingredients was prepared in parts per hundred in weight: 
     
         ______________________________________                  Dry  Wet                  Parts                       Parts______________________________________foam compound            97.1   94.4(DG-1, High Point Chemical)fluoropolymer            2.3    4.7(Zonyl NWA, Dupont)Pigment                  .3     .4(Inmont Pad N. Blue 37 BASF)catalyst                 .3     .5(accelerator UTX, American Cyanamid)______________________________________ 
    
     This formulation was dispersed in air using a mechanical foam generator and then applied to a 3.25 oz. per square yard, polyester warp knit fabric using a knife-over-roll coater. The foam was applied to the surface of the substrate by setting a gap between the fabric and knife so as to end up with a 1.0 to 1.4 oz. per square yard dry add on. The fabric was dried in a hot air tenter frame at 275° F. for from 30 to 45 seconds. 
     The foam coated fabric was then post-treated to impart or enhance the bacteriostatic and repellent properties with a solution of: 
     
         ______________________________________            % on wt. of bath______________________________________isopropyl alcohol (penetrant)              1.2antimicrobial      2.4(DC 5700, Dow Corning)fluorochemical     3.8(FC-824: 3M)______________________________________ 
    
     This solution was applied in a pad bath, dried and cured at 300° F. for 45 seconds. The foam was crushed by the nip rollers of the pad. The photographs of FIGS. 1 &amp; 2 are of the product so produced. The finished product was tested and had the following properties: 
     
         ______________________________________basis weight (oz/yd.sup.2)    4.2-4.6grab tensile (lbs)     MD      82.3-109.6INDA 110.0-70 (R82)    XD      96.8-129.7spray rating                   90-100INDA 80.1-70 (R82)Frazier air permeability (ft.sup.3 /min/ft.sup.2)                         45-95INDA 70.1-70 (R82)Alcohol repellency            8-9INDA 80.9-74 (R82)oil repellency                4-6INDA 80.8-70 (R82)Suter Hydrostatic Head (cm)   16.1-22.3INDA 80.6-70 (R82)Flammability: NFPA 702        PASS(pass/fail)antimicrobial presence        PASS(pass/fail)______________________________________