Abstract:
In various aspects the present application provides flooring materials and methods of making the same wherein the flooring material comprises an adhesion surface for attaching the flooring material to a substrate and an opposing bearing surface, wherein a cross-section of the flooring material has substantially the same composition along an axis from the bearing surface to the adhesion surface.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Flooring for commercial settings may be trodden by hundreds or even thousands of people every day. Most of those people will track dirt or other materials onto the floor or drop something on it. Every day, the flooring will also be worn by the action of people walking and also grinding the dirt and other rubbish into the floor. The flooring may also be cleaned daily, often using strong cleansers and solvents to remove the dirt.  
         [0002]     Particle reinforced rubbers offer a strong, wear resistant material that also provide a resilient walking surface. In comparison to wood or concrete, rubber flooring is less tiring to walk and stand on. The increased lifetime reduces maintenance costs. In a retail setting, this can help maintain the stamina of shoppers, keeping them from getting tired and increasing traffic for the retailers. In a medical setting, reduction of fatigue can prevent medical mistakes, and easily cleaned floors can help prevent diseases from being communicated from one patient to another.  
         [0003]     However, rubbers present unique fabrication challenges. Thus, it is desirable to have a method and formulation for production of rubber matrix flooring that eases production while maintaining or even augmenting the advantages of prior art rubber floors.  
       SUMMARY OF THE INVENTION  
       [0004]     In one aspect, the present inventions provide a flooring material comprising an adhesion surface for attaching the flooring material to a substrate and an opposing bearing surface, wherein a cross-section of the flooring material has substantially the same composition along an axis from the bearing surface to the adhesion surface. In various embodiments, the flooring material comprises between about 30 to about 40 weight percent of a rubber; between about 35 to about 50 weight percent of a clay; between about 1 to about 5 weight percent of a plasticizer; and one or more vulcanization agents. Preferably, the flooring material also comprises between about 1 to about 10 weight percent of a fire retardant. Further details and examples of the various suitable specific compounds are discussed below.  
         [0005]     In various embodiments, a cross-section of the flooring material has substantially the same composition and substantially the same color along an axis from the bearing surface to the adhesion surface. As used herein, “substantially the same color” refers to substantially the same distribution of one or more colors and is not limited to a single color. For example, flooring may have a primary color and one or more flakes of different color dispersed therein, the combination of the primary color and the flakes is considered a “color.” 
         [0006]     In one aspect, the present inventions provide methods for producing a flooring material, comprising: (a) providing a reservoir of uncured polymer particles having a size in the range between about 6 mesh and about 24 mesh; (b) disposing the uncured polymer particles from the reservoir between a first backing material and a second backing material to form a laminate; (c) compressing and heating the particles in the laminate to form a sheet of cured polymer, wherein the material from the heated particles flows to substantially fill spaces between the particles and bind substantially all of the particles together; and (d) separating the sheet of cured polymer from the first backing material and the second backing material. Preferably, the methods further comprise a step of sanding one or more sides of the cured polymer sheet until the cured rubber sheet has a substantially uniform thickness to within about ±0.001 inches.  
         [0007]     In various embodiments, the uncured polymer particles comprise between about 30 to about 40 weight percent of a rubber; between about 35 to about 50 weight percent of a clay; between about 1 to about 5 weight percent of a plasticizer; and one or more vulcanization agents. Preferably, the flooring material also comprises between about 1 to about 10 weight percent of a fire retardant. Further details and examples of the various suitable specific compounds are discussed below.  
         [0008]     In various embodiments, the methods of the present inventions provide methods for providing the uncured polymer particles having a size in the range between about 6 mesh and about 24 mesh. For example, in various embodiments, a sheet of uncured polymer material is feed through a granulator comprising: (a) at least one non-stationary blade for cutting the sheet; (b) at least one stationary blade for cutting the sheet; and a screen through which particles having a dimension less than a predetermined size can pass into a hopper. In various embodiments, the particles are drawn through the screen using a vacuum. The non-stationary blade is spaced at a predetermined distance from the screen and the stationary blade when the non-stationary blade is adjacent to the screen and the stationary blade to, for example, facilitate cutting and reduce tearing of the sheet of uncured polymer.  
         [0009]     The foregoing and other aspects, embodiments, and features of the present inventions can be more fully understood from the following description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic diagram of an apparatus for granulating uncured rubber for use according to an embodiment of the invention.  
         [0011]      FIG. 2  is a schematic diagram of a process for making flooring according to an embodiment of the invention.  
         [0012]      FIG. 3  is a schematic diagram of rolled flooring of uneven thickness.  
         [0013]      FIGS. 4-8  are photographs of one embodiment of a granulator useful in various embodiments of the inventions. In various photographs can be seen a chopper having a rotating knife portion  414 , the stationary knives  416 , and the screen  418 .  
     
    
     DETAILED DESCRIPTION  
       [0014]     In one aspect, the present inventions provide a flooring material which in cross-section has substantially the same composition and substantially the same color along an axis from the bearing surface to the adhesion surface of the flooring material. The adhesion surface, for example, for attaching the flooring material to a substrate being on an opposing side of the material with respect to the bearing surface. The term “bearing surface” is used to refer to the surface of the flooring material which bears traffic, but such surfaces are also sometimes referred to as wear surfaces.  
         [0015]     The present inventions are not believed to be dependent on the specific substrate material used. Rather, it is believed that any substrate material normally employed in the field can be employed in the practice of the present inventions. Accordingly, a substrate can be chosen, e.g., on the basis of manufacturing convenience, physical properties of the end product, etc.  
         [0016]     The substrate is preferably composed of a strong, durable and flexible material. The substrate is preferably a relatively flat sheet of overlapping intersecting fibers. Examples of suitable substrates include, but are not limited to, felts, papers, textile material or fabrics made from cellulose, glass, natural organic fibers, synthetic organic fibers, natural inorganic fibers, synthetic inorganic fibers, and combinations thereof. The substrate can be woven, non-woven, knitted, or combinations thereof or otherwise fabricated. The substrate can be on a supported web, non-supported web, or combinations thereof.  
         [0017]     In one embodiment, the flooring material is produced from a rubber, for example, a nitrile butadiene rubber. The unvulcanized rubber material is combined with one or more other flooring components, e.g., fire retardant and reinforcing fillers, plasticizer, colorants, anti-oxidants, and vulcanizing agents, in a blender at a temperature above the glass transition point of the uncured polymer to facilitate even distribution of the components. The blended material is then sheeted on a mill and granulated. The resulting particles are sieved, and particles of different colors are blended to provide a desired color to the final product. The blended particles are spread on a carrier belt and covered with embossed paper to form a laminate. The laminate is compressed and cured in a continuous press following which the cured product is separated from the paper and the carrier belt. The side of the cured rubber sheet that had opposed the carrier belt is sanded to provide a better interface with an adhesive.  
         [0000]     Materials  
         [0018]     Practically any commercially available rubber material, including natural rubbers, polyisoprenes, chloroprene rubbers, butyl rubbers, ethylene-propylene-diene rubbers (EPDM), urethane rubbers, styrene butadiene rubbers, and nitrile rubbers can be used in an embodiment of the invention. One skilled in the art will recognize that these rubbers are available in various grades and specific compositions, e.g., the amount of acrylonitrile in nitrile rubbers. Examples of commercially available rubbers include, but are not limited to, Paracril Ozo™, available from Uniroyal Chemical, Krynac 3345C (34 E 50), and Krynac 4060 C (40 E 65), available from Bayer Material Science. The rubber can be blended with a small amount (e.g., 1 to 5 weight percent) of a plasticizer, e.g., phosphate ester plasticizers, phthalate plasticizers (e.g., benzyl phthalate, biphenyl phthalate, dioctyl phthalate, etc.). One example plasticizer is Santicizer available from Ferro Corporation.  
         [0019]     In one embodiment, about 30-40 weight percent of the rubber is also blended with about 35-50 weight percent of clay particles as a reinforcement. Exemplary clays include aluminum silicate (kaolin) clays, e.g., Dover clay. Suitable commercially available products include, but are not limited to, Snobrite, available from Thompson, Weinman &amp; Co., East Orange, N.J., and Kaocal, available from Thiele Kaolin Company, Sandersville, Ga. Further description of Snobrite may be found in U.S. Pat. No. 4,260,534, the contents of which are incorporated herein by reference. Fire retardant clays may also be used as filler, or fire retardant materials may be added in addition to the reinforcing clays. For example, about 5-10 weight percent of hydrated alumina, e.g., Hydral 710, M632, or M932, can be included in the uncured formulation. Other fire retardants, for example about 5-10 percent Versamag (a magnesium hydroxide filler available from Rohm &amp; Haas), Cereclor 70, available from Brenntag Canada, Smokebloc AOM, available from Great Lakes Chemical Corporation, and/or about 1-5 weight percent antimony trioxide, can also be employed. Additional components that can be included in the uncured compound include colorants, fire retardants, anti-oxidants, and vulcanization agents. For example zinc stearate and Wingstay L, available from Goodyear, can be used as a processing aid and antioxidant, respectively. Phthalic anhydride can be employed as a plasticizer and/or retardant. Exemples of accelerators include, but are not limited, to zinc dimethyldithiocarbamate, e.g., Methasan™ or Methyl Zimate™, and cyclohexyl benzothiazole sulfonamide, e.g. Vulkazit™ CZ or Wescro™ CBS). Materials such as stearic acid and zinc oxide can be used as activators. Exemples of vulcanizing agents include, but are not limited to, sulfur and dithiodimorpholine, e.g., Naugex™ SD-1 or Accelerator™ R.  
         [0020]     The individual components are combined in any mixer appropriate for use with rubbers, for example, a Banbury mixer. The mixer provides a relatively uniform distribution of the various components. The mixture is then sheeted on a mill to a thin sheet, for example, about 200-250 mils, to form a sheet of precursor material. One skilled in the art will recognize that the width of the sheet is not essential to the invention but rather can be optimized for the various equipment in use. The sheet can be easily ground (e.g., it cuts instead of stretching and tearing), and the uniform mixing of the components provides improved chemical resistance to the final product. In addition, the aesthetic properties of the final product can be better controlled by granulating and then curing the precursor material instead of simply curing the sheet of uncured compound.  
         [0000]     Granulation and Blending  
         [0021]     The sheet of precursor material can be cut into particles with a granulator. A cross-sectional view of a granulator  10  is schematically depicted in  FIG. 1 . The granulator employs a chopper  12  having three rotating knives  14  and two stationary knives  16 . The sheet enters the granulator between the rotating knives and one of the stationary knives and proceeds into the granulator along a screen  18 . The screen can be a steel or other metallic plate about 1/16″ thick with ⅛″- 3/16 diameter holes about 3/32- 3/16″ in diameter spaced about the same distance apart. Larger holes can be used; but may need to be spaced sufficiently apart to maintain the strength of the metal in between. In some embodiments, at least 50% of the screen is open area. One skilled in the art will recognize that the optimal size and spacing of the holes may not be completely independent. One skilled in the art will recognize that the optimal surface density of the holes in the screen will depend in part on the strength of the material between the holes and the amount of material that is expected to pass through the screen. The holes may be tapered slightly away from the inlet side, for example, to facilitate the passage of material through the holes.  
         [0022]     The spacing between the rotating knives and the stationary knives, and the spacing between the rotating knives and the screen, may be adjusted to prevent jamming of the device. If the spacing between the rotating and stationary knives is too wide, the uncured compound sheet will not be cut efficiently. Then, the cut pieces of uncured compound will be too big and will tumble into the chopper, potentially clogging the screen holes because of friction generated by the rotating knives. One skilled in the art will recognize that the spacing between the various components and the rotational velocity of the non-stationary blades may be adjusted for uncured polymer sheets of different compositions or thicknesses. In one embodiment, the particles range in size from about 6 mesh to about 24 mesh. The cut particles may be sieved to remove fines and larger size particles.  
         [0023]     Particles of different colors can then be blended in pre-set proportions to provide a desired design for the final product. For example, a mixture of different colored particles can be used to form a speckled design in the final product. Because the particles are uncured, they may stick together during mixing if they are compressed. A double cone blender or other blender with no internal moving parts can be employed to combine the particles. About 0.1% to about 1% by weight of calcium carbonate, a clay, talc, zinc stearate, etc., can be added to the blend to facilitate blending and avoidance of clogging.  
         [0000]     Spreading and Curing of Rubber  
         [0024]     A rotocure press may then be employed to produce the cured rubber sheet. A carrier belt is unwound and the blended particles spread over it, for example, at a rate of 3.5-4 lbs/linear foot for a 64 inch wide belt, to achieve a final product thickness, after sanding, of, e.g., about 80 mils. The thickness of the particle layer can be controlled by the flow rate of the feeder and the gap opening of the gate feeder for the hopper from which the granules are distributed, and the optimal flow rate will be determined by the desired thickness and the speed of the carrier belt. The carrier belt should be flexible but relatively stiff in tension (e.g., it should not stretch significantly). It should be able to withstand the curing temperatures that will be applied and should not stick to the cured rubber sheet. The carrier belt may be fabricated from nylon; other suitable materials will be readily apparent to those of skill in the art. Standard equipment to control particle flow, such as the use of a spreader with moving walls to prevent particle bridging in the hopper or an angle serrated wiper of urethane or other appropriate material to prevent lumps from clogging the opening of the spreader, can be employed.  
         [0025]     Heating units can be used to preheat, by radiation, the surface of the particles to a temperature of about 200° F. An embossed paper can then be distributed over the particles to form a laminate with them. The paper can have an acrylic coating that, e.g., may provide a textured design to the final product. In one embodiment, the paper may be Warren release paper, available from Sappi. The laminate can be cured by winding it around a rotating drum. In one embodiment, the laminate is cured around an arc of about 11.5′ long at a rate of about 3.0-3.5 feet/minute at about 330°-360° F. ( FIG. 2 ). A continuous steel belt compresses the laminate against the drum. The paper is removed from the cured product and may be reused. The carrier belt is also removed after the curing, and the side of the cured product that was against the carrier belt is preferably sanded. The belt may then be rewound for a subsequent curing run. The sanding roughens the surface, providing, e.g., a better surface for adhesion, and also removes excess material to produce a cured rubber sheet with a substantially uniform thickness. If the thickness is not substantially uniform, e.g., too thick or too thin, the rolled sheet could develop bumps, grooves, or ridges ( FIG. 3 ) that could be detrimental to the aesthetic appearance of the installed product and make proper installation more difficult, since the product may not lay flat on the subfloor and may exhibit uneven seams. In one embodiment, the cured sheet is taken up between a pinch roll and a sanding roll. The sanding roll is maintained at a fixed height from the pinch roll. The cured material is thus sanded to the proper thickness. In one embodiment, the cured material is sanded to a thickness accuracy of about ±0.001″ both crossweb and downweb, to, for example, help prevent visible joints in the flooring and reduces tripping.  
         [0026]     The finished product may be used for flooring in practically any setting. Nitrile rubbers and many other rubbers are resistant to oils and staining and are thus easy to clean. In various embodiments, the use of a “thruchip” structure instead of a separate surface layer can provide, e.g., a more uniform color and texture to the product. As the product wears, there is no surface layer to wear through, which would expose a different material disposed underneath the surface layer. Thus, wear is less noticeable than on a multilayer material. In addition, the surface aesthetics of the finished product may be dictated by the embossed paper, which may be selected to provide not only a particular surface texture but a visually pleasing sheen.  
         [0027]     The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in any way.  
         [0028]     While the present inventions have been described in conjunction with various embodiments and examples, it is not intended that the present inventions be limited to such embodiments or examples. On the contrary, the present inventions encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art.  
         [0029]     While the inventions have been particularly shown and described with reference to specific illustrative embodiments, it should be understood that various changes in form and detail may be made without departing from the spirit and scope of the present inventions. Therefore, all embodiments that come within the scope and spirit of the present inventions, and equivalents thereto, are claimed.