Carpet backing that provides dimensional stability

Abstract: A tufted carpet is made by tufting yarn through a primary backing of at least two layers, including a first backing layer (14) and a second backing layer (15). The first backing layer (14) is formed of a woven material, a non-woven material, a plastic sheet material, a plastic extrusion, or a composite of a woven or non-woven material and a plastic sheet material. The second backing layer (15) is formed of a woven material of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene, a woven fiber glass material, a leno weave material, an open weave material, a plastic net or a plastic sheet material. A plurality of tufts(21) of yarn that are sewn through the primary backing are exposed on one side of the primary backing for forming face yarns, and also form a plurality of back stitches (22) on the opposite side of the primary backing. At least a major portion of the back stitches secure each layer of the primary backing to each other layer.

Description: This invention relates generally to tufted carpeting and,more particularly to tufted carpeting having an improved primary backing which includes two or three backing components or layers. This primary backing construction provides dimensional stability to the carpet without the necessity for a secondary backing. In the past, tufted carpeting was made by tufting yarn into a backing of woven jute or the like. Because the jute backing was heavy and stable, it was coated on the back with latex or another adhesive to lock in the tufts, and the carpet was ready to install. More recently, however, various light weight materials have been used as a primary backing through which yam is tufted, and a secondary backing of a heavier or more stable material is adhered to the back of the primary backing by an adhesive. Currently, the most popular primary backings are made of polypropylene materials, either woven or non-woven. Such backings are preferred because they are inexpensive, and the material has an oily quality that provides for smooth entry and exit of the tufting needles. In addition, the material is quite elastic so the hole tends to close around the yarn after the tufting needle is withdrawn. However, the polypropylene backings have some disadvantages as well. Polypropylene is a thermoplastic elastomer, so the backing is subject to degradation by excess heat and is rather easily stretched through the application of tension. Typically, after face yarns are tufted into a primary backing, the unfinished carpet is back coated with an adhesive to lock in the stitches. Without the back coating, the tufts are very easy to pull out, so the back coating is an important finishing step. During the coating process, however, the carpet is dimensionally unstable because of the presence of only the light-weight primary backing. Consequently, it is not uncommon to have elongation in the carpet in the range of 5% - 20% during the back coating process. While this elongation may appear to "create" more carpet, it does so by reducing the amount of face yarn per unit area, so the resulting carpet will not be as densely tufted. Another problem with elongation is that the backing may not stretch uniformly, with the result that any pattern in the carpet will be distorted. Efforts have been made to physically prevent elongation of the carpet, but such efforts require additional equipment, time and effort, and still do not entirely solve the basic problem of stretching of the primary backing. It is known to make rugs and carpets having a plurality of backings. For example, US-A- 2,713,012 of Hartstein discloses a tufted rug having dual primary backings of cotton and jute or the like. The Hartstein reference does not contemplate back coating of the rug, and instead relies on the double backing to assist in holding in the tufts. Furthermore, the jute backing is heavy enough to stabilize the rug so that elongation is minimized. US-A- 4,426,415 of Avery discloses a carpet in the nature of artificial turf having a plurality of primary backings and a conventional back coating. These backings varying in fineness from the bottom to the top of the carpet. All of the Avery backings are of the same material, and polypropylene is specifically mentioned. Since the Avery reference contemplates back coating of the carpet, the problem of elongation of the carpet and the resulting distortion of any pattern will still be present, though perhaps to a lesser degree because of the greater strength inherent in multiple backings. US-A- 4,705,706 of Avery discloses a multiple-layer primary backing of nylon or the like. Face yams of polyethylene are tufted through this backing and the back stitch is set by heat, rather than by a separately applied adhesive. The multiple layers of backing described in this patent allow sand to infiltrate when the carpet is used as outdoor turf. It is also known, as described in US-A- 4,096,302 of Thibodeau et al., to provide a carpet backing comprising non-woven fiber material that is needle punched into plastic netting. The fiber material, comprised of nylon, rayon, or similar fibers having a fiber length of about one to six inches, is deposited on the plastic net with the fibers aligned in the weft direction. The fibers are then secured to the net by needle punching them through the net. The fibers may be deposited and punched through the net serially one side at a time, or they may be deposited on both sides of the net and simultaneously needle punched through both sides of the net with a double acting loom. After the backing has been formed in this manner, carpet yarn is tufted into the backing. The tufts are held in the backing primarily by the fibers, but a back coating of adhesive may also be applied to the tufted carpet. It is also known to provide a backing system for carpet comprising a primary backing and a secondary backing, with a thin film of liquid-impervious thermoplastic material bonded either to the back of the primary backing or the back of the secondary backing. U S-A-5,612,113 describes such a backing system in which yarn is tufted into a conventional primary backing such as is generally comprised of polypropylene. A conventional secondary backing or foam cushion is thereafter bonded to the primary backing to lock in the back stitches, by application of latex or other adhesive. In addition, however, a thin liquid-impervious film is applied either to the back of the primary backing or to the back of the secondary backing by use of an adhesive. US-A-3,542,632 discloses a tufted pile carpet having a primary backing through which pile yarns are tufted, a layer of latex adhering the pile yarn to the primary backing and a secondary backing which is applied on top of the latex and forms the actual bottom layer of the carpet. US-A-5,962,101, entitled Dimensionally Stable Tufted Carpet, describes a tufted carpet having a double-layer primary backing, the first part of such backing being formed of a woven or non-woven material, preferably a conventional woven ribbon polypropylene, and the second part having warp yams and fill yams, with at least the warp yams having greater strength and less stretchability than the first part of the primary backing. The face yams are tufted through both parts of the double-layer backing, which secures the two parts together, with the second part forming the back side of the carpet. Because the second part of the backing is of an open weave material, at least some of the back stitches protrude from the back of the carpet, so that an applied adhesive can truly encapsulate such stitches for maximum strength. WO-A-98/49000 discloses a two-part primary backing with an upper, or face, backing of conventional woven or non-woven polypropylene and a lower, or back, backing of a stronger, open weave fabric. Tufts of yarn are sewn through both parts of the primary backing which causes some of the back stitches to protrude for better coating with adhesive. The resulting carpet may be fully back coated and may have a secondary backing adhered thereto. US-A-5,654,066 discloses a carpet structure comprising (i) a first carpet part having a primary layer with pile substantially covering a first side of the layer, the pile tufted through the primary layer to leave tuft bundles on a second side of the primary layer and a binder encapsulating the tuft bundles, the first part having a predetermined force of expansion and contraction under cycling conditions of temperature and moisture; (ii) a second part in layered relationship to the first carpet part, the second carpet part constructed from one or more layers to have a predetermined resistance to expansion and contraction at least equal to or greater than the force of expansion and contraction of the first carpet part under cycling conditions of temperature and moisture and traffic loads on the carpet pile. With the dual-layer primary backing, it has been found that the tufts are held more securely, even without back coating of the carpet, so the carpet can be handled as necessary without fear of loss of any substantial amount of face yarns. During back coating or other processing of the carpet, the non-stretchable part of the backing in the carpet prevents elongation or other stretching of the carpet. However, further research has revealed that dimensional stability may be obtained regardless of which of the first or second backing layers forms a first side of the primary backing (on which the tufts of yarn form face yarns) or the opposite (or back) side of the primary backing (on which the back stitches are formed), provided that suitable materials are selected for use as the first and second backing layers. Other research has revealed that several other materials may be incorporated into the primary backing for further improvement in the dimensional stability and overall quality of the carpet. The present invention consists in a tufted carpet comprising: (a) a primary backing comprised of at least two layers, including: (i) a first backing layer which comprises: (1) a non-woven material, or (2) a composite of a woven or non-woven material and a plastic sheet material; and (ii) a second backing layer, and (b) a plurality of tufts of yarn sewn through the primary backing, said tufts of yarn: (i) being exposed on one side of the primary backing for forming face yarns; and (ii) forming a plurality of back stitches on the opposite side of the primary backing: wherein at least a major portion of the back stitches secure each layer of said primary backing to each other layer, characterised in that said second backing layer comprises: (I) a woven material comprised of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene, or (2) a plastic sheet material, or (3) an extruded, oriented plastic net. Tufted carpet embodying the invention provides among its advantages greater dimensional stability than has been previously available. Another advantage is that the quality of the carpet, including the integrity of the pattern and the density of face yarns per unit area, is consistently high. Still another advantage of an embodiment of the invention in which the first layer and the second layer of the primary backing are bonded together prior to tufting is a simplification of the tufting process. Yet another advantage of an embodiment of the invention in which the first backing is comprised of a plastic sheet material or a composite of a woven or non-woven material and a plastic sheet material is a carpet with improved dimensional stability and moisture resistance. Still another advantage of an embodiment of the invention which includes a third layer in the primary backing is a carpet with even greater dimensional stability. As used herein, a plastic sheet material includes pliable sheets and films of any thickness that are comprised of any of various nonmetallic compounds that are synthetically produced, usually by polymerization, and which may be either thermosetting or thermoplastic. The term film is used synonymously with the term sheet herein. As used herein, a composite of a woven or non-woven material and a plastic sheet material includes any of various combinations of woven or non-woven materials and a plastic sheet material. Such combinations include woven or non-woven materials to which a plastic sheet is bonded by use of an adhesive, by heat, or by extrusion of the plastic material thereon, as well as laminates and co-extrusions of such materials. A composite may also comprise a woven or a non-woven material and a plastic sheet material which are in intimate contact substantially across the area of the sheet material. As used herein, a plastic extrusion refers to a backing layer comprised of a plastic material, of any type or thickness, which is extruded or otherwise applied as a coating onto another backing layer. As used herein, pardiculate material includes powders and granules of various particle sizes. As used herein, thermofusible particulate materials are those that may be deposited, dispensed or applied as particulate materials, which upon heating will coalesce and subsequently fuse together. At least a major portion of the back stitches secure each layer of the primary backing to each other layer. A method for making a tufted carpet having the characteristics set out above is also described herein. The presently preferred embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which: Figure 1 is a perspective view of a piece of carpet that is partially broken away to show its construction, said carpet having been made according to a first embodiment of the present invention, in which the first backing layer is the upper layer and the second backing layer is the lower layer. Figure 2 is a schematic illustration showing the tufting of carpet according to one embodiment of the present invention. Figure 3 is a schematic illustration similar to that of Figure 2, showing the tufting of carpet according to another embodiment of the present invention. Figure 4 is a highly enlarged cross-sectional view showing the construction of the embodiment of the carpet illustrated in Figure 1. Figure 5 is a view similar to that of Figure 4, but showing the construction of another embodiment of the carpet of the present invention. Figure 6 is a view similar to that of Figure 4, but showing a back coating in place to lock in the stitches. Figure 7 is a view similar to that of Figure 6 but showing a secondary backing placed over the back coating. Figure 8 is a schematic illustration showing a plan view of the back of a carpet made according to the embodiment of the invention illustrated in Figure 1. Figure 9 is a perspective view of a piece of carpet that is partially broken away to show its construction, said carpet having been made according to a second embodiment of the present invention, in which the first backing layer is the upper layer, the second backing layer is the lower layer and a third backing layer is interposed between the first backing layer and the second backing layer. Figure 10 is a highly enlarged cross-sectional view showing the construction of the embodiment of the carpet illustrated in Figure 9. Figure 11 is a highly enlarged cross-sectional view showing the construction of a third embodiment of the present invention, in which the first backing layer is the lower layer and the second backing layer is the upper layer. Figure 12 is a view similar to that of Figure 11, but showing a back coating in place to lock in the stitches. Figure 13 is a view similar to that of Figure 4, but showing the construction of another embodiment of the carpet of the present invention. Figure 14 is a schematic illustration of an apparatus for applying a preferred back coating to carpet made according to the invention. Referring now more particularly to the drawings, and to those embodiments of the invention here presented by way of illustration, Figure 1 shows a piece of carpet generally designated at 10, the carpet 10 comprising face yams 11 and a primary backing 12. The primary backing comprises at least two layers, an upper backing layer and a lower backing layer. The term "upper backing layer" as used herein indicates the backing adjacent to the face of the carpet. Similarly, the term "lower backing layer" indicates the backing on the bottom when the carpet is laid. The back side of the lower backing layer, or the side on the bottom when the carpet is laid, may also be referred to as the "back" of the primary backing. Either the upper or lower backing layer may be designated as the first backing layer, and the other may be designated as the second backing layer. In Figures 1, 2, 4 through 10 and 13, the first backing layer will be the upper layer and the second backing layer will be the lower layer, although as mentioned above, the first backing layer and the second backing layer may be interchangeable between upper and lower locations. Examples I through III and V through XV illustrate embodiments of the invention in which the first backing layer is the upper layer and the second backing layer is the lower layer. Figures 11 and 12, on the other hand, show an embodiment of the invention in which the first backing layer is the lower layer and the second backing layer is the upper layer. Example IV is illustrative of this construction. Typical woven materials and non-woven materials that are suitable for use as the first backing layer include those made from polypropylene, polyester, polyamide, jute and viscose rayon. Typical plastic extrusions and sheet materials that are suitable for use as or in connection with the first backing layer include those made from polyethylene, polypropylene, polyurethane, polyester and polyvinyl chloride (PVC). A preferred sheet material for use in connection with the first backing layer is a polyethylene film having a thickness of about 1.5 mm. In one embodiment of the invention, first backing layer 14 comprise a non-woven, spun-bonded material comprised of polyester, polypropylene or nylon. In such event, it is preferred that the first backing layer is comprised of a spun-bonded fabric such as the "LUTRADUR" brand of spun-bonded polyester that is sold by Freudenberg Spunweb Company, or the "COLBAC" brand of spun-bonded nylon-coated polyester that is sold by Akzo Fibers B.V. The first backing layer may also be a composite of a woven or non-woven material and a plastic sheet material, such as, for example, a composite of a plastic sheet that is extruded onto woven or non-woven materials. Preferably, in this embodiment of the invention, the first layer is comprised of a high density polyethylene film that is extruded onto or otherwise applied as a coating to woven ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene. Such a material as is known for use in bagging and general purpose tarps is sold by Fabrene Inc. of Mississauga, Ontario, Canada as a "Type KKN1" industrial synthetic fabric. The second backing layer may be a woven material, such as a conventional primary-type backing material woven from polypropylene ribbons, polyethylene ribbons or ribbons comprised of combinations of polypropylene and polyethylene. If such material is used for the second backing layer, one preferred embodiment of the invention includes a first backing layer comprising a non-woven, spun-bonded material comprised of polyester, polypropylene or nylon such as the "LUTRADUR" brand of spun-bonded polyester that is sold by Freudenberg Spunweb Company, or the "COLBAC" brand of spun-bonded nylon-coated polyester that is sold by Akzo Fibers B.V. Spun-bonded backings have not generally been used as primary backings for broadloom carpet, because they can easily stretch and because the needle holes do not close around the yarn after tufting. Furthermore, conventional backings woven from polypropylene ribbbons and the like are also stretchable and subject to degradation by excessive heat. However, it has been found that a primary backing comprised of a non-woven spun-bonded material and a woven material of conventional primary-type ribbons may provide advantageous dimensional stability. Second backing layer 15 may also be a plastic sheet or a plastic net material comprised of either a thermoplastic or a thermosetting material. If a plastic sheet material, the second backing layer is preferably comprised of a sheet of polyethylene, polypropylene, polyurethane, polyester or PVC. If a plastic net material, the second backing layer is preferably comprised of a thermoplastic material such as polypropylene, having a strand count of from 472 x 472 per square metre (12 x 12 per square inch) to 157 x 157 per square metre (4 x 4 per square inch) and a weight of from 9.76 to 48.8 kg per thousand square metres (2 to 10 pounds per thousand square feet). Preferably, the net material used in connection with the invention is comprised of strands which are integrally extruded at the joints. Furthermore, it is preferred that the net be oriented after it is extruded. By orienting, it is meant that the net is heated and stretched at a temperature above its second glass transition temperature so that the net will take a permanent stretch to a dimension at least three times as great as its unoriented dimension. Orienting the net increases its tensile strength and reduces its weight and cost. Such net materials as are preferred for use as the second backing layer may be obtained from Conwed Corporation of St. Paul, Minnesota. As illustrated in Figure 2, the carpet of the present invention is tufted in a generally conventional way. The first backing layer 14 of the primary backing of the invention is mounted on roll 16, and passes through tufting machine 17 to exit rolls 18. In accordance with the present invention, the second layer 15 of the primary backing is mounted on a roll 19, and is held against the first backing layer 14 by roll 20. With the two parts of primary backing 12 held together, tufting machine 17 sews tufts of yarn through the primary backing 12, so that said tufts are exposed on one side of the primary backing for forming face yams 11. It will therefore be understood that the carpet, immediately on being tufted, has the strength and stability attributes described above. Those skilled in the art to which the invention relates will realize that carpet may be subject to stretching and distortion as it emerges from the tufting machine, but the present invention substantially eliminates any such stretch and distortion. Figure 3 illustrates another embodiment of the invention in which the first backing layer and the second backing layer are bonded together prior to tufting to form the primary backing. This bonding may be accomplished by application of an adhesive such as is known to those skilled in the art to which the invention relates, or it may be accomplished by selection of first and second layers that are capable of being bonded together by the application of heat. If the two layers are to be bonded by application of heat, it is preferred that both layers include a component comprised of polypropylene, polyester or polyamide. To bond the first and second layers together with heat, the layers are placed into intimate contiguous relationship and heated to a temperature at or near the melting point of at least one of the layers. In another embodiment of the invention, the two layers may be co-extruded sheets or films, such as of polyethylene, with the first layer being comprised of a low-density, low-melting point formulation and the second layer being comprised of a high-density, high-melting point formulation. In still another embodiment of the invention that is illustrated in Figure 13 (and discussed hereinafter in more detail), the first layer may comprise a woven or a non-woven material and the second layer may comprise a plastic extrusion, a plastic material that is extruded onto the first layer. Preferably, the bonding of the first and second layers, whether by application of an adhesive, by heating, by extrusion or by other means, is carried out in a separate process, so that the bonded primary backing 112, comprised of first and second layers, may be mounted on roll 16 and held in place for passage through the tufting machine by roll 20. The primary backing 112 is then passed through tufting machine 17, which sews tufts of yarn therethrough. Such carpet will have the same strength and stability attributes as that of the embodiment of Figure 2. The second layer of the primary backing of the present invention may include open weave fabrics of a hard polypropylene and even fiber glass. The use of such materials would not be expected to provide satisfactory results by those having ordinary skill in the art to which the invention relates, because of a fear of needle deflection in the tufting process. In conventional tufting processes, if some of the needles engage "hard" fibers or the like in the backing material, they may move laterally in attempting to penetrate the backing. There is also a danger of breaking a needle in conventional tufting through "hard" backings, and there is a great danger of producing deviant stitches that reduce the quality of the finished goods. Those skilled in the art to which the invention relates have always believed that it was not possible to tuft into "hard" backings comprised of many of the materials that may be freely used in backing 15 because of needle deflection. Consequently, very soft polypropylene ribbons, or spun fibers, or soft non-woven polypropylene, or other spun-bonded fabrics (such as the "LUTRADUR" brand of spun-bonded polyester that is sold by Freudenberg Spunweb Company, or the "COLBAC" brand of spun-bonded nylon-coated polyester that is sold by Akzo Fibers B.V.) are generally used in a conventional primary backing, although some of these, such as for example, the spun-bonded fabrics, are not commonly used in broadloom carpet construction. In contrast, the carpet of the present invention may be made by tufting through a primary backing including a second layer of open weave fabric of "hard" polypropylene or even fiber glass without significant needle deflection. A more thorough understanding of the construction of the carpet of one embodiment of the present invention may be obtained by examination of Figure 4. As shown therein, tufts 21 of face yarn 11 pass through both the first backing layer 14 and the second backing layer 15 of primary backing 12 in such manner that back stitches 22 loop over the strands of the second backing layer 15. Since backing layer 15 may be comprised of a woven ribbon material, a leno weave material or an open weave material, some of the stitches are likely to miss the strands of backing layer 15 and engage only backing layer 14. As shown in Figure 4, the yams of tufts 24 pass through only the first backing layer 14, and the resulting back stitches 25 lie against the lower side of backing layer 15. This phenomenon is further illustrated in Figure 8 where back stitches 22 are shown looping over the strands of second backing layer 15, while back stitches 25 are shown between the strands of backing layer 15, and engaged with only the first backing layer 14. Figure 5 shows carpet of a similar construction to that of Figure 4. In Figure 5, first backing layer 14 is comprised of a woven or non-woven material 114 to which a moisture-impervious sheet or film 13 has been applied, either in a separate process (such as by application of an adhesive, by heating or by co-extrusion) or by a separate feed of film that is placed in intimate contact with non-woven material 114 (not shown). Otherwise, the construction of the carpet of Figure 5 is identical to that of Figure 4. In view of the construction described above, it will be understood that the tufts of yarn are mechanically locked into the system. In the conventional tufted carpet, the tufts, like tuft 24, extend only through the soft and stretchable material (comparable in some respects to first layer 14), but without the additional fabric layer 15 to hold them. Carpet 10, made according to the invention with a dual-layer primary backing (including layer 15), does not stretch or distort noticeably, but is dimensionally stable even as it leaves the tufting machine. In the above and foregoing discussion, it should be understood that the term "primary backing" indicates a sheet of material through which yarns are inserted. The term "secondary backing" indicates a sheet of material that is fixed to the back of the tufted carpet, such material not having yams inserted therethrough. Those skilled in the art will realize that, even with the mechanical lock for tufts 21 and 24, it is desirable to back coat the carpet to assure that the tufts will not pull out. One common form of back coating utilizes a small amount of adhesive, and the adhesive is allowed to coat the back stitch very lightly. The carpet of the present invention works well with such back coating system, because the back stitches such as stitches 22 stand out from the backing, allowing the adhesive to coat the sides of the stitches. Many adhesives used do not actually adhere well to the fiber, but depend on simply encapsulating the stitches to prevent their pulling out. With the protruding back stitches 22, the yarns can be well encapsulated and thereby firmly anchored to the primary backing and the fibers of the yams can be locked into place so as to prevent pilling and fuzzing. Sometimes it is preferable to back coat the carpet to provide a smooth rear surface, as shown in Figure 6. The carpet of Figure 6 is like that of Figure 4, except that there is a coating of adhesive or other back coating 26 on the primary backing. Back coating 26 is thick enough that the entire back stitch is covered, and the back of the carpet is smooth. It should also be noted that if the primary backing includes a moisture impervious sheet, it will be necessary to back coat the carpet to preserve the fluid barrier characteristic, since tufts of yarn will pierce the primary backing during the tufting process. Figure 7 shows a modified form of the carpet of Figure 6. In Figure 7, adhesive coating 26 is also used to adhere a secondary backing 28 to the carpet. While a secondary backing will not be required on the carpet of the present invention for most uses, one may wish to use a tricot as a secondary backing for installations in which hook and loop fasteners are used to hold the carpet in place. In this event, the tricot secondary backing performs the function of the loop portion of the hook and loop fastener for holding the carpet in place on a floor. The carpet of Figure 7 may have other sheet materials adhered thereto as a secondary backing. For example, one might select any of the conventional woven or non-woven materials or a sheet of foamed material as a secondary backing. The foamed material may be mechanically frothed and applied, may be foamed in place, or may be formed as a sheet and subsequently adhered to the carpet. All these techniques are known in the art to which the invention relates. In addition, a waterproof barrier film may also be applied as a secondary backing as disclosed in US-A- 5,612,113. Still other secondary backings will suggest themselves to those skilled in the art. Figure 9 shows another embodiment of the invention in the form of a piece of carpet generally designated at 210 which comprises face yams 11 and a primary backing 212. The primary backing includes a first backing layer 14, a second backing layer 15 and a third backing layer 23. First backing layer 14 may be formed of a non-woven or plastic sheet material, a plastic extrusion, or a composite of a woven or non-woven material and a plastic sheet material, such as is employed in the embodiment of the invention illustrated in Figure 1. Second backing layer 15 is also comparable to that employed in the embodiment of Figure 1, and may comprise a woven material of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene, plastic net or plastic sheet material. Third backing layer 23, which is interposed between the first backing layer and the second backing layer, preferably comprises a material that is different from the material which comprises the first and second layers. Such material is preferably selected from woven material of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene, a woven fiber glass material, a leno weave material, an open weave material or a non-woven, spun-bonded material comprised of polyester, polypropylene or nylon-coated polyester. Preferably, the first backing layer is comprised of a spun-bonded fabric (such as the "LUTRADUR" brand of spun-bonded polyester that is sold by Freudenberg Spunweb Company, or the "COLBAC" brand of spun-bonded nylon-coated polyester that is sold by Akzo Fibers B.V.), the second backing layer is comprised of a woven material of polypropylene ribbons and the third layer is comprised of an open weave or leno weave material. As shown in Figures 10 and 11, the third backing layer 23 is interposed between first backing layer 14 and second backing layer 15, and the yarn 21 is tufted through the first, second and third backing layers of the primary backing, so that at least a major portion of the back stitches secure first backing layer 14 to second backing layer 15 with third backing layer 23 interposed therebetween. This embodiment of the invention will likely provide maximum dimensional stability, especially when the preferred materials are used for the various backing layers, as described above. Figures 11 and 12 illustrate the construction of a carpet made according to the invention in which the first backing layer 214 is the lower layer and the second backing layer 215 is the upper layer. As shown in Figure 11, tufts 21 of face yarn 11 pass through both the first backing layer 214 and the second backing layer 215 of the primary backing in such manner that back stitches 22 loop over the strands of the second backing layer 215. However, some of the stitches may only pass through and engage second backing layer 215. Thus, as shown in Figure 11, the yarns of tufts 24 pass through only the second backing layer 215, and the resulting back stitches 25 lie against the lower side of first backing layer 214. This phenomenon is also illustrated in Figure 12, which shows a coating of adhesive or other back coating 26 on the primary backing. Back coating 26 is thick enough that the entire back stitch is covered, and the back of the carpet is smooth. Figure 13 shows another embodiment of the invention comprising a carpet of construction similar to that of Figure 4. In Figure 13, the first backing layer 314 is the upper layer and the second backing layer 315 is the lower layer. Second backing layer 315 comprises a woven material such as a leno weave material, and first backing layer 314 comprises a plastic extrusion, preferably of polyethylene, that is extruded or otherwise coated onto the second layer. In this embodiment of the invention, the first layer is applied to the second layer prior to tufting. Such layer may be on the order of 25.4 to 254 µm (1-10 mils) in thickness, and need not span the gaps between the individual strands of the leno weave material. After extrusion of the first layer to the second, tufts 21 of face yarn 11 are tufted through the second backing layer 315 with the first backing layer 314 thereon in such manner that back stitches 22 loop over the strands of the second backing layer 315. Figure 14 illustrates the application of a preferred type of back coating to carpet made according to the invention. As shown therein, a roll 30 of carpet made by tufting yarn through the primary backing of the invention is passed beneath a powder scattering or coating head 32, which deposits a quantity of thermofusible particulate material on the back of the primary backing. Suitable thermofusible particulate materials for use in connection with the invention include powders and granules of thermoplastic polymers such as polyethylene, ethylene vinyl acetate, ethylene vinyl acrylate, low-melting point polyamides and syndiotactic polypropylene. Such materials should have a melting point lower than that of the materials of either the first or second layer of the primary backing. If it is desired to provide a secondary backing sufficient to obtain fiber lock and tuft bind, 203 to 509 g of thermofusible particulate material may be applied for each square metre of carpet (6 to 15oz/sq.yd). If it is desired that the secondary backing of thermofusible material serve also as a fluid barrier, 678 to 1695 g/m 2 (20 to about 50 ounces per square yard) of particulate material should be deposited on the back of the primary backing. The amount of particulate material used will depend on the carpet construction and the fiber face weight. After deposition of the thermofusible particulate materials on the back of the primary backing, the carpet is conveyed through infrared sintering oven 34 where the thermofusible materials are heated so as to coalesce and cover or encapsulate the back stitches. The carpet with the thermofusible materials thereon then passes over tensioning rolls 36 and 38 and is stored on reel 40. A secondary backing material may also be applied to the back coating from roll 42 by application of nip pressure by roll 44. Preferably, any such secondary backing is applied before the thermofusible materials have fully cured, so that the secondary backing will adhere to the thermofusible material back coating on the primary backing. Suitable secondary backing materials may include any of those known to those having ordinary skill in the art to which the invention relates, and may also include moisture impervious sheets, preferably those comprised of polyethylene and co-extruded polyethylene films. If co-extruded polyethylene films are employed, it is preferred that one component of the co-extruded film has a lower melting point than the other component, and that the component with the lower melting point be placed next to the adhesive or other coating on the primary backing. The invention will be understood better from consideration of the following examples: Example I A carpet was tufted at 1.9 kg/m 2 (56 ounces per square yard) of face yarn, with a nylon fiber having a denier of 4400. The primary backing included a first backing layer comprising a 4.6 m (15 foot) wide "Poly ABC" style 2225 from Amoco Fabric and Fibers Company and a second backing layer of fiber glass, style 4802 from CSX Fiberglass Products. The tufting was performed on a 3/16 gauge tufting machine. No shrinkage was observed in this carpet, but at 5.1 to 7.6 cm (two- to three-inch) shrinkage was observed when a similar carpet was made without the second backing layer of fiber glass. The tufted carpet described above was back coated with a polyurethane having the following formulation: Ingredient Parts/Hundred Arco Chemical Froth Polyol 92.0 Diethylene Glycol 8.0 Catalyst LC-5615 1.0 Silicone L-5614 0.5 Black 0.05 Aluminum trihydrate 200.0 Water 0.2 Isocyanate Bayer E-448 64.0 The process for applying the polyurethane coating is well known in the art, and is described in the following patents assigned to Union Carbide:US-A-3,772,224, 3,849,156, 3,947,386, and 4,022,941, as well as in the following patents assigned to Dow Chemical: US-A-5,104,693 and 4,853,054, as well as in US-A-4,035,529 assigned to Bayer. Example II The carpet of Example I was tufted using as the second backing layer an open weave polypropylene "Action Bac" style 3870 from Amoco Fabrics and Fibers Company, instead of the fiberglass. Example III The carpet of Example I was tufted using as the second backing layer an open weave polyester fabric instead of the fiberglass. The tensile and elongation properties of the carpets made according to Example I, Example II and Example III are as follows: EXAMPLE I EXAMPLE II EXAMPLE III Tensile Strength MPa (psi) - Warp 2.792 (405) 1.091 (158.3) 2.475 (359) Elongation - Warp 6.0 17.11 25.7 Tensile Strength MPa (psi) - Fill 2.586 (375) 0.819 (118.8) 2.387 (346.2) Elongation - Fill 5.5 17.11 25.2 Example IV A carpet was tufted at 1085 g/m 2 (32 ounces per square yard) with a nylon fiber having a denier of 3750. The primary backing was comprised of a first backing layer of a 3.7 m (12 foot) wide "Poly Bac" style 2200 from Amoco Fabrics and Fibers Company and a second backing layer of an open weave fabric of polypropylene, style 3870, from Amoco Fabrics and Fibers Company. The carpet was tufted on a 1/8 gauge tufting machine. No shrinkage was measured. The resulting carpet was back coated with a latex containing 125 parts calcium carbonate at 1085 g/m 2 (32 ounces per square yard). During the back coating process, the carpet shrank by only) 6 mm (1/4 inch), as opposed to 7.6 to 15.2 cm (3 to 6 inches) for conventional carpet. In addition, the carpet had a tuft bind of 10.16 kg (22.4 pounds), versus 7.98 kg (17.6 pounds) for the same carpet with a single-layer primary backing. Example V A cut pile carpet for residential use was tufted at 1.53 kg/m 2 (45 ounces per square yard) of a nylon BCF yarn. The first backing layer of the primary backing was comprised of woven polypropylene (15 pick). The second backing layer of the primary backing was an open weave backing, . style 850, from Synthetic Industries. The resulting carpet was back coated with 475 g/m 2 (14 ounces per square yard) of a hot melt adhesive supplied by Barrier-Bac, Inc. of Calhoun, Georgia and applied using a well-known hot melt pan system. The carpet exhibited fiber lock near 100%. Example VI Prior to back coating of the carpet of Example V, a 1.5 mm fluid-impervious film was bonded to the back of the second layer of the primary backing according to the process of U.S. -A-5,612,113. The dimensional stability and fiber lock exhibited by this carpet were comparable to that of the carpet of Example V. Example VII A carpet was tufted at 1.19 kg/m 2 (35 ounces per square yard) with a nylon fiber having a denier of 3750. The primary backing was comprised of a first backing layer of a 3.7 µm (12 foot wide) "Poly Bac", style 2200, from Amoco Fabrics and Fibers Company and a second backing layer of an extruded oriented polypropylene webbing sold under the designation "Conwed OV-7100" by Conwed Corporation of St. Paul, Minnesota. The carpet was tufted on a 1/8 gauge tufting machine. The resulting carpet was back coated with a polyurethane as described in Example I. No shrinkage was measured either before or after back coating. Example VIII A cut pile carpet for residential use was tufted at 1.53 kg/m 2 (45 ounces per square yard) of a nylon BCF yarn. The first backing layer of the primary backing was comprised of woven polypropylene (15 pick). The second backing layer of the primary backing was an open weave backing, style 850, from Synthetic Industries. The resulting carpet was back coated by applying twelve ounces per square yard of "Epolene C10" polyethylene granules having a melt index of 2,250 at 190° C., such as may be obtained from Eastman Chemical Company, and heating the thermofusible granules to a temperature at or near their melting point. Upon melting of the granules, a calendaring roll was applied so as to cause the granules to coalesce and cover or encapsulate the back stitches. The resulting back coated carpet exhibited near 100% fiber lock. Example IX An unbacked residential carpet such as is described in Example VIII was back coated by applying 305 g/m 2 (nine ounces per square yard) of "Epolene C13P" polyethylene powder having a melt index of 200 at 190° C., such as may be obtained from Eastman Chemical Company, and heating the thermofusible powder to a temperature at or near its melting point so as to cause the powder to coalesce and cover or encapsulate the back stitches. The resulting back coated carpet exhibited near 100% fiber lock, even though no calendaring roll was used in the application of the back coating. Example X An unbacked residential carpet such as is described in Example VIII was back coated by applying 1017 g/m 2 (thirty ounces per square yard) of "Epolene C10P" polyethylene powder having a melt index of 2,250 at 190° C., such as may be obtained from Eastman Chemical Company, and heating the thermofusible powder to a temperature at or near its melting point. Upon melting of the powder, a calendaring roll was applied so as to cause the powder to coalesce and cover or encapsulate the back stitches. The resulting carpet exhibited a smooth, liquid-impermeable back surface. Example XI A low density polyethylene film having a thickness of 1.5 mm was applied prior to application of the calendaring roll to a residential carpet such as is described in Example X so as to produce a back-coated carpet having an additional liquid-impermeable barrier. Example XII A residential berber-style loop carpet of 90% polypropylene fibers and 10% nylon fibers was tufted at a face fiber weight of 1085 g/m 2 (32 ounces per square yard). The primary backing was comprised of a first backing layer of polypropylene woven material, style 12546, from Wayn-Tex, Inc. of Dalton, Georgia and a second backing layer of an open weave fabric of polypropylene, style 3870, from Amoco Fabrics and Fibers Company. This carpet was back coated by applying 373 g/m 2 (eleven ounces per square yard) of "Epolene C13P" polyethylene powder having a melt index of 200 at 190° C., such as may be obtained from Eastman Chemical Company, and heating the thermofusible powder to a temperature at or near its melting point so as to cause the powder to coalesce and cover or encapsulate the back stitches. The resulting back coated carpet exhibited near 100% fiber lock, even though no calendaring roll was used in the application of the back coating. Example XIII A carpet was tufted at 1187 g/m 2 (35 ounces per square yard) with an olefin fiber having a denier of 8800 Dtex. The primary backing was comprised of a first backing layer of a 3.7 m (12 foot) wide "Poly Bac" material having a 15 pick, from Amoco Fabrics and Fibers Company, and a second backing layer of an open weave fabric of polypropylene, style 3870, from Amoco Fabrics and Fibers Company. Interposed between the first backing layer and the second backing layer was a third backing layer of a non-woven spun-bonded polyester sold under the designation "Colbac GFT-80" by Akzo Fibers B.V. The tufted carpet was back coated with 814 g/m 2 (24 ounces per square yard) of polyurethane as described in Example I. No shrinkage was measured. Example XIV A carpet was tufted at 1187 g/m 2 (35 ounces per square yard) with an olefin fiber having a denier of 8800 Dtex. The primary backing was comprised of a first backing layer which formed the lower layer and a second backing layer which formed the upper layer. The first backing layer comprised a non-woven spun-bonded polyester sold under the designation "COLBAC GFT-80" by Akzo Fibers B.V., and the second backing layer comprised a 3.7 m (12 foot) wide "Poly Bac" material having a 15 pick from Amoco Fabrics and Fibers Company. The tufted carpet was back coated with 814 g/m 2 (24 ounces per square yard) of polyurethane as described in Example I. No shrinkage was measured. Example XV A cut pile carpet for residential use was tufted at 1017 g/m 2 (30 ounces per square yard) of a nylon BCF yarn. The primary backing was comprised of a leno weave material from Simplex Products Division of Jacksonville, Florida on which a layer of polyethylene had been extruded. The resulting carpet was back coated by applying 407g/m 2 (twelve ounces per square yard) of "Epolene C10" polyethylene granules having a melt index of 2,250 at 190° C., such as may be obtained from Eastman Chemical Company, and heating the thermofusible granules to a temperature at or near their melting point. Upon melting of the granules, a calendaring roll was applied so as to cause the granules to coalesce and cover or encapsulate the back stitches. The resulting back coated carpet exhibited near 100% fiber lock. From the foregoing it will be understood that the present invention provides a carpet having a superior dimensional stability from the time of tufting, through coating, and through installation and use. The carpet is not as severely affected by stress during coating, nor by heat during coating or curing. Even without the application of a secondary backing, the carpet of the present invention can be stretched into place or can be glued down, without fear of stretch causing unsightly bulges or interfering with any pattern therein.

Claims: A tufted carpet (10) comprising: (a) a primary backing (12, 112) comprised of at least two layers, including: (i) a first backing layer (14) which comprises: (1) a non-woven material, or (2) a composite of a woven or non-woven material (114) and a plastic sheet material (13); and (ii) a second backing layer (15), and (b) a plurality of tufts of yarn (21) sewn through the primary backing, said tufts of yarn: (i) being exposed on one side of the primary backing for forming face yarns (11); and (ii) forming a plurality of back stitches (22) on the opposite side of the primary backing: wherein at least a major portion of the back stitches secure each layer of said primary backing to each other layer, characterised in that said second backing layer comprises: (1) a woven material comprised of ribbons of polypropylene; polyethylene or combinations of polypropylene and polyethylene, or (2) a plastic sheet material, or (3) an extruded, oriented plastic net. The tufted carpet (210) of claim 1, wherein the primary backing (212) includes a third backing layer (23) that is interposed between the first backing layer (14) and the second backing layer (15), said third backing layer comprising a material that is different from the materials which comprise the first and the second layers, which material of the third backing layer is selected from the group consisting of: (a) a woven material of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene, (b) a woven fibre glass material, (c) a nylon-coated non-woven, spun-bonded material comprised of polyester, polypropylene or polyester, (d) an open weave material. The tufted carpet of claim 1 or claim 2 wherein the first backing layer (14) comprises a nylon-coated non-woven, spun-bonded polyester material, and the second backing layer (15) comprises a woven material comprised of ribbons of polypropylene, polyethylene or combinations of polypropylene and polyethylene. The tufted carpet of claim 3 wherein the primary backing includes a third backing layer (23) that is interposed between the first backing layer and the second backing layer, said third backing layer comprising an open weave or leno weave material. The tufted carpet of claim 1, 2, 3 or 4 which includes a back coating (26) that covers and encapsulates the back stitches and locks in the fibres. The tufted carpet of claim 5 wherein the back coating (26) is comprised of a quantity of particulate thermofusible material having a melting point lower than that of the materials comprising the first and second layers of the primary backing, which material has been applied to the back of the primary backing and heated so that it coalesces and encapsulates the back stitches. The tufted carpet of claim 6 wherein the particulate thermofusible'material comprising the back coating (26) is selected from powders and granules of polyethylene, ethylene vinyl acetate, ethylene vinyl acrylate, low-melting point polyamide and syndiotactic polypropylene. The tufted carpet of claim 5, 6 or 7 which includes a secondary backing material (28) which has been applied to the back of the back coating (26) on the primary backing. The tufted carpet of claim 8 which includes a secondary backing material (28) comprised of a co-extruded polyethylene film comprised of a first component and a second component, wherein the first component of the co-extruded film has a lower melting point than the second component, and wherein the first component of the co-extruded film is applied to the back of the back coating on the primary backing. The tufted carpet of any preceding claim wherein the first backing layer is comprised of a non-woven material (114) to which a moisture-impervious sheet (13) is applied. The tufted carpet of any preceding claim wherein the first backing layer and the second backing layer are bonded together to form the primary backing. The tufted carpet of any preceding claim wherein the plastic net is comprised of material selected from polypropylene, polyethylene and nylon. The tufted carpet of any preceding claim wherein the plastic net comprises extruded strands having integral intersections and having a strand count of from 157 x 157 per square metre (12 x 12/inch 2 ) to 472 x 472 per square metre (4 x 4/inch 2 ) and a weight of from 9.76 to 48.8 kg per thousand square metres (2 to 10 pounds per thousand square feet).

Inventors: IRWIN DONALD A SR, IRWIN, DONALD A. SR
Applicants: DARWIN ENTPR INC, DARWIN ENTERPRISES, INC.
Application year: 2000
Main classification: D05C17
IPC codes: D05C17, B32B5, D06N7