Abstract:
A method of extruding a foamed plastic layer into a fabric carrier that relies on the use of dual expanding agents, a dispersed gas generant and thermally expandable micro-spheres. Upon deposit of the foaming melt onto the carrier, the composite textile is passed through a rotating gate wherein the expanding foam is contained between a roller and the carrier. Penetration and engagement of the foaming matrix with the carrier is thereby enhanced. The resulting product is resilient with good compression rebound.

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of textiles. In particular, it relates to textiles wherein a polymeric “plastic” layer is bonded to a fabric substrate, and the plastic layer is in the form of a foamed matrix. 
     BACKGROUND TO THE INVENTION 
     In the production of plastic coated textiles, the product has customarily been made by one of the following alternate procedures: 
     1) casting a molten plastic layer onto a fabric carrier; 
     2) bonding a pre-formed plastic layer onto a fabric carrier by calendering and/or use of adhesives; and 
     3) extruding a molten plastic layer onto a fabric carrier. 
     When it has been intended to provide a plastic layer that is “foamed” and resilient due to included gas-filled cells or voids, it has been customary to create the expanded plastic matrix in two stages. First a plastic layer containing a blowing agent in a quiescent state is cast onto a fabric carrier. Then the formed composite textile is exposed to heat which causes gas to evolve within the plastic layer—the process of “blowing”. 
     A disadvantage of this latter process is that the level of heat that is required to activate the blowing agent will cause carrier components in many types of fabric carriers to fuse, e.g. polyethylene will fuse at 175° F., whereas various types of chemical blowing agents require a temperature in excess of 300° F. to create foaming conditions. 
     Attempts have been made to incorporate a blowing agent into an extruded plastic to form a foamed plastic layer. However, with the use of conventional chemical blowing agents, this process produces often a textile wherein the foamed polymeric layer lacks resistance to crushing and results in a flattened polymeric layer that has almost no or little foam voids left in the structure after crushing. In a standard extrusion procedure, a chilled calendaring roll presses the extruded sheet of a melt into a fabric carrier and sets, and bonds, the plastic layer with the textile. Extruded textiles prepared with typical classic blowing agents have typically lacked the resilience to recover sufficiently from this compression step to provide a satisfactorily foamed textile. 
     A need exists for a foamed plastic composite textile that is formed on a permeable carrier, e.g. a woven, knitted or non-woven fabric, with a low fusing temperature, while exhibiting good recovery or resilience in response to applied pressure. This invention addresses this need as well as providing other advantages. 
     The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a method of producing a foamed sheet textile is provided: 
     1) extruding a heated, extrudable polymeric melt from a linear extrusion die in the form of a sheet with two faces, the melt containing as expanding agents: 
     1) a first extrusion activated gas source dispersed within said melt; and 
     2) thermally expandable micro-spheres having encapsulating shells each containing compressed gas and being dispersed within said melt 
     2) allowing the expanding agents to commence to expand, with the gas source generating gases to form a compressible foamed matrix in the melt and the micro-capsules expanding into resilient, compression resistant micro-spheres suspended within said foamed matrix, thereby providing a foaming melt; 
     3) depositing the foaming melt onto the surface of a permeable carrier that is in sheet form and into the surface of which the foaming melt partially penetrates; and 
     4) allowing the foaming melt so formed to set to provide a resilient, compression-resistant, foamed plastic/polymeric layer that is bonded to the carrier to form the resulting textile. 
     Preferably, the extrusion melt, upon being laid-down on the permeable carrier, is carried on the carrier through a rotating gate defined by a gap between two rollers, one of the rollers being cooled to set the melt. This establishes a constant height for the foamed layer on the textile. The roller delivering the carrier may be powered, and the second cooled roller may be traction-driven off of the powered roller by end-rims extending from the second roller. 
     The resulting product of the invention is a textile having a permeable carrier into the surface of which the foamed plastic layer has expanded while still molten and while the expanding agents, and particularly the encapsulated expanding agent, is still expanding. Thus, the boundary surface of the carrier is at least partially embedded within the foamed plastic/polymeric layer. Expansion of the foaming layer both above and within the carrier may continue after the formed textile exits the rotating gate, and particularly while the foaming melt is confined between the carrier and the second of the two rollers for an interval of rotation of the second roller. 
     By inclusion of thermally expandable micro-spheres in the melt the foamed plastic layer contains inclusions of thermally expanded hollow micro-spheres having encapsulating shells that are resiliently compressible. This enhances the crushability of the textile. 
     An advantage of this process is that polymers like PVC, polypropylene, polyethylene and other conventional polymers may be used to provide the foamed plastic layer. 
     Further, a textile may be produced with an integrally-formed skin region present at it&#39;s polymer surface, the skin region containing less voids than the intermediate region of the foamed layer lying between the skin region and the carrier. This is accomplished by cooling the extrusion die through which the melt is extruded and/or cooling the roller that contacts the foaming melt as such melt passes through and beyond the gap of the rotating gate. 
     An advantage of this process is that a textile can be produced at lower temperatures wherein the carrier would otherwise plastically deform at temperatures above, for example, 300 degrees Fahrenheit, or even 200 degrees Fahrenheit. 
     To produce the textile, the extruder is fed with a composition suitable for generating a foamed polymer comprising: 
     1) at least one expandable thermoplastic polymer capable of being extruded; 
     2) a first thermally activated gas generant dispersed within said polymer; and 
     3) thermally expandable resiliently compressible micro-spheres, disbursed within said polymer; 
     said generant and micro-spheres being capable on heating of expanding said polymer. 
    
    
     The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow. 
     SUMMARY OF THE FIGURES 
     FIG. 1 is a schematic side view of an extrusion coating line. 
     FIG. 2 is a cross-sectional side view of an extrusion screw. 
     FIG. 3 is an enlarged, detailed side-view of the extrusion die and dual counter-rotating rollers of FIG. 1 between which the foaming melt is being fed. 
     FIG. 4 is a diagrammatic cross-sectional side view of the foamed polymeric layer bonded to a fabric carrier. 
     FIG. 5 is a cross-sectional view through the pair of rollers receiving and combining the melt with the fabric. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 and 2 a powdered plastic composition  2  in powder/pellet form is fed into the feed-hopper  3  of a spiral extruder screw  4 . The gap around the spiraled flights  5  of the screw  4  decreases in width proceeding towards the extruder outlet  6  thus creating an increasing pressure on the melt  8  contained therein. Heat is applied externally from a heat source  7  such as hot oils, gas flames or electric radiant heating coils to convert the powdered composition  2  to a melt  8 . 
     Molten plastic composition or “melt”  8  passes from the extruder outlet  6  to the extrusion die  9  where the pressure that previously arrested the release of gas by the gas generants (not shown in FIG. 2) is relaxed, allowing the gas generants to “blow” and produce a foamed melt  10 . This foaming melt  10  is fed into the nip  15  between two counter rotating rollers  11 , 12 . 
     One of the rollers  11 , preferably a powered roller  11 , carries a sheet of a permeable, preferable fabric or fibrous matrix of porous, carrier material  13  from a carrier-source roller  14  to the nip  15 . The other roller  12 , preferably driven in a counter rotating direction by friction off of the powered roller  11 , provides a gap  16  having a pre-determined diameter at the nip  15  which services as a gate for metering the thickness of foaming melt  10  that is laid down on the carrier sheet  13 . Desirably, the roller  12  has a protruding circumferential end rim  25  positioned to bear against an interface  26  between the first and second rollers  11 , 12  whereby a traction drive effect occurs. Preferably, this “gating” roller  12  is temperature controlled, e.g. chilled as by circulating chilling fluid coolant, (not shown) or other suitable method of cooling in the normal manner known for extrusion processes. 
     Preferably, the die  9  is also cooled, as by cooling air, to form a skin  20  surface on the foamed melt  10  as it leaves the die lips  9 A. This skin  20  has less voids than the core of the foamed layer, e.g. 50% or less. 
     In the gap  16  the foaming melt  10  continues its expansion, having infiltrated or mixed with the boundary surface of the carrier  13  to thereafter set therein. The composite textile  17  exits the two rollers  11 ,  12  whereafter the foaming melt is preferably confined between the carrier and the second of said rollers. The composite textile  17  is then carried by a series of conveying and/or cooling rollers  18  to a textile take-up roll. Some partial expansion of the foamed layer  10  may occur while the textile  17  is proceeding to and is present on the conveying rollers  18 , as well as the expansion within the carrier  13  that continues after the composite textile  17  has passed beyond the gap. 
     In the above process, the powdered plastic compositions  2  may be a polymeric vinyl compound, a polypropylene compound, a polyethylene compound, thermoplastic polyurethane or other known and conventional polymeric material, or combinations thereof, for producing foamed plastic sheet textiles. In particular, the plastic composition  2  may include dual expansion agents, comprising: 
     1) a dispersed blowing agent or gas generant such as azodicarbonamide or other chemical blowing agents; 
     2) a micro-encapsulated expansion agent such as EXPANDCEL-™ (by Casco Nobel AB of Sweden cf U.S. Pat. No. 5,585,119) or such other encapsulated expansion agents which upon foaming provides compression-resistant micro-spheres within the plastic layer of the final textile  17 ; and 
     3) the compound may or may-not contain an additional, direct gas-injected blowing agent. 
     A typical composition of this invention which is extrudable may contain one or more conventional additives such as fillers, plasticisers, stabilizers, anti-oxidants, lubricants and processing aids. Such additives can be used in conventional quantities for formulating an extrudable composition. As additives, this composition  2  may include conventional binders, such as an acrylic and/or a nitrile rubber, or like elastomers that serve to constrain and delay the expansion of the foaming melt  10 . 
     By way of exemplification, the following table shows a typical composition which can be used in accordance with this invention. It is highly desirable that all additives and components of the composition be chlorine-free. 
     
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 
               
               
                   
                   
               
               
                   
                   
                 WEIGHT IN 
               
               
                   
                   
                 MIXTURE 
               
               
                   
                 COMPOUND 
                 Preferred 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Polymer: - PVC 
                 136 
                 pounds 
               
               
                   
                 Filler: 
                 40.7 
                 pounds 
               
               
                   
                 e.g. (Omyacarb) (TM) 
               
               
                   
                 Micro-encapsulating blowing 
                 1.0 
                 pounds 
               
               
                   
                 agent: 
               
               
                   
                 e.g. (Expancel 092) (TM) 
               
               
                   
                 Dispersed blowing agent: 
                 4.1 
                 pounds 
               
               
                   
                 e.g. (Celogen 754A) (TM) 
               
               
                   
                 Plasticizer/Co-stabilizer: 
                 102 
                 pounds 
               
               
                   
                 e.g. (Soy Bean Oil) 
               
               
                   
                 Stabilizer: 
                 3.7 
                 pounds 
               
               
                   
                 e.g. (Nuostabe) (TM) 
               
               
                   
                 Anti-oxident: 
                 0.3 
                 pounds 
               
               
                   
                 e.g. (Irganox) (TM) 
               
               
                   
                 Lubricants: 
                 3.3 
                 pounds 
               
               
                   
                 e.g. (Internal/external-stearic 
               
               
                   
                 acid, “Loxiol (TM) ”and 
               
               
                   
                 Hostalub (TM) 
               
               
                   
                 Process Aid: 
                 6.8 
                 pounds 
               
               
                   
                 e.g. Paralord- (K12ON) (TM) 
               
               
                   
                   
               
             
          
         
       
     
     The resulting textile  17  is thereby rendered resilient and crush resistant. This textile may be further processed by pressure and/or vacuum-forming or injection molding without the foam layer being crushed or destroyed. 
     A sample textile  17  is depicted in FIG. 4 wherein the foamed layer  10  is bonded to the carrier  13 . Within the foamed layer  10  are two types of voids: voids  21  in the foamed matrix produced by the dispersed gas generant; and voids  22  present within expanded micro-spheres  23 . Each micro-sphere  23  has an encapsulating shell of resilient, compression resistant material. The presence of two types of voids  21 ,  22  improves the character and “feel” of the final textile product  17 . 
     CONCLUSION 
     The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects, is further described and defined in the claims which now follow. 
     These claims, and the language used therein, are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.