Vinyl-Backed Carpet Structure
BACKGROUND OF THE INVENTION
The -present invention relates to the field of carpet, more particularly to vinyl-backed carpet.
Vinyl-backed carpet has recently been gaining in popularity, especially for commercial installations. Vinyl backings are often used with carpet tile. Alternatively, vinyl backings can be used with rolled carpet, such as six-foot roll goods.
A common method of making a vinyl-backed carpet is to cast a layer of a vinyl polymer such as polyvinyl chloride (PVC) onto the back of a tufted carpet. For example, the desired weight of a PVC plastisol can be applied to the back of a tufted carpet using a doctor blade. PVC plastisol is typically made of PVC, plasticizers, viscosity reducers, pigments, and inorganic fillers such as calcium carbonate. The plastisol is cured by heat to provide a resilient layer of PVC on the back of the carpet.
One advantage of vinyl-backed carpet is provided when it is installed directly over an existing floor without a separate pad or underlayment. Naturally, when this is possible, material and labor costs are saved. However, some floor conditions do not permit this. For example, some floors that previously had a covering attached with an adhesive have much of that adhesive remaining after the old covering is removed. Often that adhesive is incompatible with the vinyl backing of carpet. Specifically, solvents and/or surfactants in the residual adhesive can have an affinity for the plasticizer in the vinyl backing. One solution to this problem is to spend the time and effort to remove the residual adhesive. Another is to spread some type of coating over the floor to
seal off any undesirable chemicals or odors before installing the vinyl-backed carpet. Naturally, both of these solutions add costs in labor and/or materials.
Another potential problem with vinyl-backed carpet structures is that the vinyl backings, particularly the plasticizers used in the vinyl backing, are often incompatible with the pressure sensitive adhesives used in making self- adhesive carpet. In particular, the plasticizers have a tendency to migrate down from the vinyl backing layer and degrade the pressure sensitive adhesive. One solution is reported in U.S. Patent No. 4,489,267 which teaches the use of a special oleophobic pressure-sensitive adhesive to avoid this compatibility problem. Naturally, this requirement for an oleophobic pressure-sensitive adhesive severely limits the choices of adhesives to use.
Finally, vinyl-backed carpet being laid directly on concrete floors can also experience some problems due to the harsh chemical environment, typically a high pH. In particular, this high pH can cause degradation in the vinyl backing layer.
SUMMARY OF THE INVENTION
Briefly stated, the invention is a vinyl-backed carpet structure with carpet pile affixed to a backing fabric. At least one vinyl backing layer is disposed below the backing fabric, which layer includes a vinyl polymer and at least one plasticizer. Below the vinyl backing layer is an oleophobic barrier layer which prevents chemical migration into or out of the vinyl backing layer.
In a second and preferred aspect, the carpet structure is made to be self-adhesive by incorporating a layer of pressure sensitive adhesive below the barrier layer. Also, a release sheet is applied to the pressure sensitive adhesive which is adapted to be pulled off to expose the pressure sensitive adhesive. In this preferred aspect, the oleophobic barrier layer prevents
migration of the plasticizer from the vinyl backing layer into the layer of pressure sensitive adhesive.
In accordance with a preferred embodiment, the carpet pile is tufted into a primary backing fabric. Preferably, the vinyl backing comprises polyvinyl chloride and a plasticizer. The oleophobic barrier layer preferably comprises polyurethane. In addition, the pressure sensitive adhesive is preferably applied directly to the barrier layer. In this preferred embodiment, the carpet is produced in the form of 6 foot wide roll goods.
An advantage of the present invention is that it allows the vinyl- backed carpet to be installed over old flooring adhesives without the use of a separate sealing coat or sheet.
An advantage of the second aspect of the invention is that it allows the use of a conventional pressure sensitive adhesive in making self-adhesive carpet structures.
Yet another advantage of the invention is that the barrier layer helps to isolate the vinyl backing layer from harsh chemical environments, such as that found when the vinyl-backed carpet is laid directly on top of concrete floors.
It should be noted that, as used herein, the term "carpet" is intended to have the relatively broad meaning of a floor covering with a pile surface, including without limitation carpet that is tufted, woven, fusion bonded or needle punched to create the pile surface.
It should also be noted that, as used herein, the term "vinyl-backed carpet" is intended to have the relatively broad meaning of a carpet with a vinyl backing whether or not that vinyl backing is directly adjacent the primary backing of the carpet, and whether or not the vinyl backing includes other components such as fiberglass scrims or the like.
Unless otherwise indicated, all percentages are intended to refer to percentages by weight.
The present invention, together with attendant objects and advantages, will be best understood with reference to the detailed description below in connection with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-sectional view through a vinyl-backed carpet made according to the first aspect of present invention.
Figure 2 is a cross-sectional view through a self-adhesive, vinyl- backed carpet made according to the second aspect and preferred embodiment of the present invention.
Figure 3 is a schematic view of a processing line for adding a vinyl backing to carpet.
Figure 4 is a schematic view of a processing line for making the self-adhesive, vinyl-backed carpet of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, Figure 1 is a schematic cross-sectional view through a carpet structure 11 made according to the first aspect of the invention. The carpet structure includes yarn 13 which have been tufted into a backing fabric 15. After the yarn is tufted into the primary backing, the material is typically referred to as greige goods. The yarn 13 shown here is in the form of loops made in the tufting operation. Alternatively, the loops from the tufting operation may be cut to form a cut-pile carpet. The type of yarn is not deemed critical to the invention. Suitable materials for the yarn include nylon, polypropylene, polyester and wool. Currently, nylon yarn is preferred.
While tufting is the preferred method of affixing the carpet pile to the backing fabric, other methods, such as fusion bonding or needle punching, are also available. One fusion bonding process is taught in U.S. Patent No. 5,198,277, the entire disclosure of which is incorporated herein by reference. Another fusion bonding process is described in PCT Patent Publication No. WO 93/0779, the entire disclosure of which is incorporated by reference.
Needle punch carpet is made by known techniques, basically, by taking a volume of fibers and needling them into a primary backing.
The type of backing fabric 15 is not deemed critical to the invention. Suitable materials include polypropylene and polyester. Currently, a slit-film polypropylene fabric, such as that sold to Shaw Industries, Inc. under the designation Polybac® from Amoco is preferred.
In the preferred construction, an adhesive precoat layer 17 is applied directly to the underside of the backing fabric 15. This adhesive precoat layer serves the purpose of locking the loops of yarn 13 into the backing fabric 15. Typically, the layer 17 is applied to the bottom of the backing fabric 15 when it is facing up. The layer is typically applied in the form of a frothed latex of a polymer such as ethylene vinyl acetate (EVA), polyvinylidine chloride or polyvinyl acetate. Most often, the latex composition is heavily filled with an inorganic filler such as calcium carbonate, aluminum trihydrate, barium sulfate, talc, dolomitic limestone, silica or mica. Currently a latex with about 50 percent of EVA (TX-83500 from National Starch) with about 45 percent inorganic filler. Preferably the latex is applied so as to result in an application of about 35 OSY wet, or about 30 OSY dry. After application of the wet latex, the carpet is dried in an oven, preferably at about 138-160°C for about 4 minutes. After curing, the carpet is allowed to cool and preferably rolled up for subsequent application of the vinyl backing. Alternatively, the vinyl backing can be applied in the same processing line.
The construction of the carpet 11 also includes a vinyl backing layer 19. The vinyl backing 19 comprises a polymer selected from the group consisting of polyvinyl chloride (PVC), vinyl chloride and vinyl acetate, and copolymers of vinyl chloride and vinyl esters. Preferably, the vinyl backing layer comprises a blend of a vinyl chloride/vinyl ester copolymer and polyvinyl chloride
The vinyl backing composition in the layer 19 also includes a plasticizer. Preferable plasticizers include, but are not limited to, diisoheptyl phthalate, diisononyl phthalate, butylbenzyl phthalate and di-2-ethyl, hexyl phthalate. Most preferably, the plasticizer is diisoheptyl phthalate. Preferably, the level of plasticizer will range from about 20 to about 30 percent, more preferably between about 20 and about 23 percent, most preferably about 23 percent.
The vinyl backing composition in the layer 19 also preferably includes an inorganic filler, such as calcium carbonate, aluminum trihydrate, barium sulfate, talc, dolomitic limestone, silica or mica. Preferably, the layer is filled to between about 40 and about 60 percent, most preferably about 55 percent.
The vinyl backing layer 19 also preferably includes a scrim 20 which is embedded in the layer 19 so as to enhance the dimensional stability of the carpet structure. Most preferably, the scrim is a nonwoven fiberglass sheet with a basis weight of about 2.2 OSY.
Optional ingredients in the vinyl backing include antioxidants, organometaliic heat stabilizers, thixatropes, viscosity reducers, and pigments. Most preferably, the vinyl backing layer includes 0.11 percent heat stabilizer (plastistab 2150 from OMG), 0.75 percent viscosity reducer (Soya Lecithin from American Lecithin Co.), and 1.3 percent pigment (for example 0.65 percent SR Black from Adchem and 0.65 percent clay from M & M clays).
Figure 3 schematically shows a typical processing line 70 for applying a PVC backing to carpet. Carpet 73 is unrolled from roll 71. Preferably, the carpet is tufted carpet with an EVA latex adhesive precoat applied in a separate operation. The carpet 73 is unrolled so as to have the back side with the EVA precoat facing up. A first layer of PVC plastisol is applied at station 75. The PVC plastisol is made up of a dispersion of a plastisol grade (emulsion or paste) PVC resin in plasticizer. Upon fusion, the PVC resin is completely dissolved by the plasticizer. A plastisol is liquid at ambient temperature. Station 75 is a roll over roll application. Preferably, the station 75, as well as stations 81 and 85 comprise a pump with multiple nozzles which supply a puddle of PVC behind a doctor blade. Preferably, between about 30-35 OSY of PVC is applied at station 75. A second layer of PVC, preferably about 20-24 OSY is applied by station 81. The carpet then passes through an infrared oven 83 by which the PVC is fused. The oven is set at about 157 °C and has a dwell time of about 45 seconds. The PVC is actively cooled before a third layer of PVC, preferably about 20-25 OSY, is applied at station 85. The carpet then passes through another infrared oven 87 in which the final layer of PVC is fused. The temperature and dwell time of the oven 87 is preferably the same as that for oven 83. The carpet is embossed, cooled and preferably rolled up on take up roll 89. Alternatively, the vinyl backing line 70 can be designed to be in-line with the line 90 described below so that no take up roll is required at this point.
Preferably, the total vinyl backing applied to the carpet is between 70-80 OSY based on dry weight, most preferably about 80 OSY. This results in a backing which is between 1.5-2.0 mm thick, most preferably about 1.5 mm thick.
In an alternative embodiment, the vinyl backing layer is foamed in sheet form and then laminated to a heat activated adhesive precoat so as to provide extra cushion for the carpet structure. Still alternatively, the vinyl
material in the backing layer can be foamed in place, for example with a heat activated blowing agent. In particular, the PVC may be foamed by addition of a heat activated foaming agent such as azodicarbamid. Such foamed backings are taught in U.S. Patent Nos. 3,560,284 and 3,695,987, the entire disclosures of which are incorporated by reference.
In accordance with the invention, an oleophobic barrier layer 21 is provided adjacent the vinyl backing layer 19. An important feature of this layer 21 is that it is oleophobic, meaning that it is substantially impervious to oils and is likewise not degraded by oils, such as the oils used as plasticizers in the vinyl backing layer, and such as the oils present in some flooring adhesives. Preferably, the barrier layer is also not susceptible to degradation by exposure to high or low pH conditions. Suitable materials for the barrier layer include, but are not limited to, polyurethane, epoxies, silicone polymers, acrylic polymers, acrylonitrile polymers, and vinylidine chloride derivatives. Currently, polyurethane is the preferred polymer used in the barrier layer. The polyurethanes can be applied from various dispersions, aqueous or nonaqueous. The polyurethane can also be thermoset or thermoplastic.
Presently, the most preferred polyurethane is an aliphatic waterbome polyurethane with 41 percent solids such as that sold by Soluol Corp. under the designation ASolucote 1012-HS.@ Alternative polyurethanes are available from Ur-Cryl Corp under the designation Ur-Cryl 3200, and from Miles Corp. under the designation Bayhydrol 101. Preferably, a surfactant system is included with each of these waterborne polyurethane systems. Most preferably, the dispersion includes 0.15 percent of a surfactant from 3M Corp. called "FC-129" and 0.07 percent of a surfactant from Byk Chemie called "Byk- 346."
As an alternative to coating the vinyl backing with a polymer in liquid form followed by drying and/or curing, the oleophobic layer can be
provided as a preformed sheet of polyurethane or the like which is laminated to the vinyl backing of the carpet. Such a preformed sheet may be affixed to the vinyl backing through the use of a heat process or an adhesive.
The thickness of the barrier layer 21 can vary so long as the layer does in fact act as an oleophobic barrier. Preferably, the barrier layer will be between about 0.2 and about 0.6 mm. thick, more preferably between about 0.2 and 0.4 mm. thick, most preferably about 0.3 mm. thick.
In an alternative embodiment, the barrier layer is expanded to make a closed-cell foam. In this way, extra padding is provided to the carpet structure while still providing a barrier layer.
Figure 2 is a schematic cross-section of a carpet structure 31 of the second aspect of the invention. This second aspect includes the same components as the first aspect, namely the yarn 33, fabric backing 35, pre-coat layer 37 vinyl backing 39 and barrier layer 41. In addition, this second aspect includes a layer of pressure sensitive adhesive 43 and a release sheet 45.
The pressure sensitive adhesive can be any of a variety of such adhesives. Preferably, the pressure sensitive adhesive is selected from the group consisting of polyalkyl acrylates, polyacrylate/acrylonitrile blends, ethylene vinylacetate hot melts, and polyurethane pressure sensitive adhesives. Most preferably, the pressure sensitive adhesive is a polyalkyl acrylate and is applied at between about 2 and about 4 OSY.
While it is preferred to apply the pressure sensitive adhesive in a continuous layer across the entire back of the carpet, it may also be applied in non-continuous patterns. For example, the adhesive may be applied in stripes or other patterns on the back of the carpet. Whether a continuous spread, or discontinuous patterns, both are considered a layer of adhesive for purposes of this application.
The release sheet 45 can be selected from various materials, such as polymeric or coated paper sheets. Preferably, the release sheet is a polyolefin film, such as polyethylene film that is about 0.4 mm. thick.
While the first aspect of the invention provides the advantage of preventing chemical migration into or out of the vinyl backing layer, the second aspect is particularly advantageous in preventing the plasticizers from the vinyl backing layer from migrating into the layer of pressure sensitive adhesive 43 and thus degrading the performance of the pressure sensitive adhesive.
Figure 4 is a schematic representation of a processing line 90 configured to make a self-adhesive, vinyl-backed carpet of the present invention. At the beginning of the line 90, carpet 93, which received a vinyl backing in a separate processing line, is unrolled from roll 91. Alternatively, the vinyl backing line 70 and the line 90 can be made in-line. A layer of polyurethane is applied at station 95. Preferably, the station 95 is a roll over roll applicator which applies between about 3 and about 7 OSY wet polyurethane is applied. Preferably, the thickness of the dry polyurethane layer is about .2 to .3 mms. The polyurethane layer is preferably cured by passing through the convection oven 97 at between about 82 and about 144 °C with a dwell time of about 3 minutes. After cooling the vinyl-backed carpet with a barrier layer can be rolled up and used as is.
More preferably, the carpet can have a pressure sensitive adhesive and release sheet applied in accordance with the second aspect of the invention. In particular, after the layer of polyurethane is cooled, a layer of pressure sensitive adhesive is applied at station 99. Preferably, station 99 is a roll over roll applicator which applies between about 2 and about 6 OSY of one of the pressure sensitive adhesives noted above. Most preferably, 4 OSY of a polyalkyl acrylate is applied. The adhesive is preferably dried by passing through convection oven 101 at between about 82 and about 144 °C for about 3 minutes. After the adhesive is cured, a release sheet 103 is applied over it.
Preferably, the release sheet is applied between two rollers with only light pressure applied in order to avoid wrinkling. The carpet is then taken up on roll 105.
The vinyl-backed, self-adhesive carpet is preferably used in a 6 foot wide roll. Alternatively, the carpet can be cut into carpet tile, for example, 18 inch square tiles for use in the U.S. or 50 cm square tiles for use in Europe.
EXAMPLES
The following examples are provided by way of illustration and explanation and as such are not to be viewed as limiting the scope of the present invention.
EXAMPLE 1
Example 1 was carried out according to the most preferred embodiment of the first aspect of the present invention except that the oleophobic barrier layer was applied by hand. In particular, a vinyl-backed six- foot width product was obtained from Shaw Industries, Inc. under the designation Momentum ® Spec 6 ®. This carpet has a tufted face of nylon yarn and a PVC backing as described above.
A polyurethane coating system was obtained from Soluol Corp. under the designation Solucote 1012-HS. The dispersion included 0.15 percent FC-129 surfactant from 3M Corp. and 0.07 percent Byk-346 surfactant from Byk Chemie. This dispersion was applied to the back of the carpet tile through the use of a cushioned roller and puddle. The coating was dried in a convection oven at between 82 and 144 °C for about 3 minutes. The coating thickness was 2-3 mils, when cured.
The carpet so made was observed to have good dimensional stability and no plasticizer migration from the PVC layer through the barrier layer.
One test involved application of an adhesive known as "cutback" to a floor. This adhesive is known to degrade the vinyl backing on typical vinyl- backed carpet. The adhesive was allowed to dry for two days and then the carpet made above was laid directly on top of it. The carpet was observed at various intervals, including one month, and found to have no degradation of the vinyl backing due to the adhesive on the floor.
Another test involved laying the carpet made above directly on top of fresh concrete. Again, the carpet was observed at various intervals, including one month, and found to have no degradation of the vinyl backing.
EXAMPLE 2
Example 2 was carried out in accordance with the most preferred embodiment of the second aspect of the invention. In particular, a layer of polyurethane was applied to a Shaw Momentum ® Spec 6 ® as in Example 1. After the polyurethane layer was cooled, a layer of a waterbome acrylic adhesive ("Tacky Back" adhesive from Textile Rubber and Chemical) was applied with a cushioned roller. This adhesive is known to be incompatible with the plasticizers in the typical vinyl-backed carpet. The adhesive was dried in a convection oven at between 82 and 144 °C for about 3 minutes. After cooling, a release sheet of polyethylene film was applied over the surface of the adhesive.
This product was also observed to have good dimensional stability and no plasticizer migration into the pressure sensitive adhesive layer. In particular, the carpet was observed to have no degradation in the vinyl backing layer or in the adhesive layer for over a month.