Patent Application
20070178790
The invention relates generally to secondary carpet backings and carpets made therefrom. More particularly, the invention relates to an improved secondary carpet backing, as well as carpets made therefrom, whereby the secondary backing is made with a special class of fill yarns that imparts increased dimensional stability to carpet.
Carpet is a multi-component material produced in many forms. It provides comfort, warmth, slip resistance, sound abatement, and is an integral part of the room decor. More than 80% of all tufted carpet is made with woven carpet backing. In the United States, the most common type of carpet is tufted broadloom carpet, which is made by inserting pile yarns into a fabric (i.e., the “primary carpet backing”), applying a filled latex to anchor the pile yarns (i.e., the “binder”), attaching a second fabric (i.e., the “secondary carpet backing”) to the binder, and then curing the composite in an oven.
Typically, the primary backing consists of yarns oriented in the warp and fill direction and woven together in a plain weave construction. The warp and fill yarns are commonly made from polypropylene. In comparison, conventional secondary carpet backings are leno weave fabrics made of polypropylene resin. The warp yarns are oriented tapes, and the fill yarns are spun yarns made from staple fibers. Secondary carpet backings provide additional strength to support the carpet as it cures in the oven and when it is “stretched in” over carpet tack strips. Additionally, when the carpet is glued in place, the secondary carpet backing provides an anchoring point for the adhesive.
Conventional secondary carpet backings may comprise oriented polypropylene tapes in the warp direction and open-end polypropylene spun yarn in the filling direction. The spun yarns are made in several steps. First, the fibers are spun into a tow composed of tens of thousands of filaments. Next, the fibers are subjected to a drawing step to increase strength and stiffness, heated and compressed to create crimp, and then cut into short segments (e.g., 2 inches). After the fibers are carded and converted to sliver, they are twisted by an open-end spinning process into a yarn of about 1700 denier. The spun yarn is then woven into fabric with the warp tapes. The fabric is brushed to create hairiness (i.e., nap) on the surface and is wound on long rolls.
Some secondary carpet backings use fill yarns other than open-end spun yarns as the filling yarns. Alternative filling yarns include core-spun yarns, bulked continuous filament yarns, and yarns made by a stretch breaking process described in a publication by Dupont® entitled, Specialty Technologies: Uniplex™ Spun Yarn Technology. In particular, core-spun yarn is formed by taking a central yarn and surrounding it by a cover of staple fibers that have been brought together at the spinning frame and spun into a composite structure as described in B. C. G
Secondary carpet backings with core-spun filling yarns are commercially available. Such fabrics have an open leno weave construction and a filling yarn in which the core component is an oriented polypropylene tape yarn of about 500 denier covered by a sheath of polypropylene staple fibers. The total denier of the core-spun yarn used in the secondary backing is about 1600. Examples of such core-spun yarns can be found in technical publications by Dr. E. Fehrer AG, Linz, Austria (now part of the Saurer Group), the manufacturer of the yarn spinning equipment used to make core-spun yarn.
Core-spun yarn may be produced by DREF spinning, a variation of friction spinning being so titled because it is spun by a machine invented by Dr. Ernst Fehrer, i.e., a DREF spinning system. The publications for DREF spun fill yarns for secondary carpet backings disclose that a polypropylene tape yarn should be used as the core component yarn and that polypropylene staple fiber should be used as the fiber sheath. See M. Gsteu, Yarn Production from Polypropylene Fibers for Secondary Carpet Backings as an Alternative to Jute, I
Carpets comprising a tufted primary backing, a binder layer, and a secondary backing are routinely tested following manufacture to verify that they possess minimum properties for satisfactory performance. Two key tests measure tuft bind and delamination (or peel) strength. Tuft bind measures the force required to remove a pile yarn from the face of the carpet. Peel strength test measures the force required to separate the secondary carpet backing from the filled latex binder layer. A minimum level of performance in both of these tests is required for all carpets. The US Department of Housing and Urban Development (HUD), in its Use of Materials Bulletin 44d, issued Aug. 15, 1993, has set the minimum tuft bind (for cut pile carpets) and peel strength at 3.0 lbs and 2.5 lbs/inch, respectively, for carpets installed in homes qualifying for HUD financing. Therefore, many carpets manufactured today meet these requirements.
Although most carpets have satisfactory tuft bind and peel strength, they often develop buckles (i.e., wrinkles) in use. Buckling occurs when the carpet is stretched in over a foam or fibrous pad and subjected to rolling or foot traffic. Most commonly the buckles show up as a series of ridges that run in the machine (warp) direction of the carpet. Many homeowners experience buckles in stretched-in carpet. These buckles can be very unsightly. More importantly, buckles can be a tripping hazard. Therefore, to prevent and remove buckles, the manufactured housing industry, as well as many homeowners, spend thousands of dollars per year to re-stretch buckled carpet.
Researchers have spent many years looking for ways to eliminate buckling. However, because the tendency of a carpet to buckle depends on many factors, including the extent of trafficking, carpet construction, carpet cushion properties, and installation quality, researchers have had limited success. Adding further complication, carpet construction variables, including carpet backing types, binder type and amount, and tufting patterns, also affect the tendency of a carpet to buckle. Therefore, because so many factors affect buckling, few definitive studies have been done to understand the impact of carpet construction variables on buckling.
In addition to the above, for any modified carpet backing to be adopted for commercial use, the new fabric must impart the same performance characteristics as the conventional fabric provides and also advance the level of performance in at least one area. Further, the improved product should add no complexity and little cost to the current operations for making the fabric and carpet.
One approach to reducing or eliminating buckling is to modify the primary carpet backing fabric. In US Patent Application Publication 2004/0077242, published Apr. 22, 2004, it has been proposed to interweave reinforcing yarns into a primary backing to improve carpet properties. However, this approach involves additional materials (i.e., reinforcing yarns) and involves a more expensive and complex manufacturing process. For example, the manufacturing process is more complex because it involves multiple types of warp yarns.
Other approaches, such as U.S. Pat. No. 3,817,817, issued Jun. 18, 1974, propose that fibers be needlepunched into a fabric normally used as a primary backing to construct a modified secondary carpet backing to improve dimensional stability. While this approach can lead to improved stability, the modified fabric requires a separate manufacturing step after weaving. In addition, a secondary carpet backing modified in this way does not permit the same rate of water removal from the latex binder as does a common 16 warp ends/inch by 5 pick ends/inch (also referred to as “16×5”) leno weave secondary carpet backing. Thus, such a modified secondary carpet backing may increase manufacturing costs due to reduced carpet manufacturing speeds.
For the reasons described above, conventional approaches to reducing carpet buckling have yet to prove satisfactory. Therefore, there exists a need in the art for a secondary carpet backing fabric that imparts improved buckling resistance to a carpet made therefrom, that may be manufactured utilizing conventional weaving processes, that may be laminated to carpet in a process identical to that routinely used with conventional secondary backings, and that exhibits performance qualities, such as tuft bind and peel strength, which may be similar to or better than conventional secondary carpet backings.
After extensive research and experimentation, the inventors have developed a novel secondary carpet backing fabric that can provide the performance of conventional secondary carpet backings (e.g., similar peel strength, tuft bind, ease of handling), and that does not require post processing after weaving before the secondary carpet backing is used to make carpet. The improved secondary carpet backing can be laminated to carpet at speeds and using equipment designed for conventional secondary backings and can provide improved buckling resistance to carpets.
The inventive secondary carpet backing may comprise a core-spun filling yarn with specific properties. Yarns in the warp direction of the inventive secondary carpet backing may comprise tape or multifilament yarns comprised of materials such as, but not limited to, polypropylene, polyester or fiberglass. The secondary carpet backing may preferably be woven in a leno or plain weave; however, one of ordinary skill in the art will appreciate that numerous other weaves may be utilized with the inventive secondary carpet backing, such as, but not limited to, satin and twill weaves.
Compared to conventional secondary carpet backings, the inventive secondary carpet backing can lead to reduced carpet growth in cyclic tensile testing carried out under British Standard 4682, Part 1, 1971. The reductions in carpet growth after cyclic testing may be seen in common secondary carpet backing constructions, such as 16×5 construction, as well as in many other common secondary carpet backings with different end and pick counts.
Specifically, as explained in more detail in the Examples to follow, carpets made with the inventive secondary carpet backing may display reduced unrecovered extension and reduced total extension in cyclic tensile tests as compared to carpets made with conventional secondary carpet backings. Thus, carpets made from the inventive secondary carpet backing may be less prone to buckling than conventional carpets, thereby contributing to a carpet that requires less re-stretching. Further, exemplary embodiments of the inventive secondary carpet backing can impart delamination and tuft bind strengths comparable to those of carpets manufactured with standard secondary carpet backings.
The inventive secondary carpet backings of this invention may comprise a special class of core-spun yarns as the filling yarns. The inventive secondary carpet backing may further comprise between about 3 and 20 picks/inch of fill yarns. According to an exemplary embodiment of the inventive secondary carpet backing, the fill yarn comprises a core-spun fill yarn, such as a DREF spun yarn. The total denier of the core-spun fill yarn, as measured according to ASTM D-1907, can range between from about 800 denier to about 3,000 denier. The core-spun fill yarn can have a tenacity, as measured according to ASTM D-2256, of about 3 grams per denier to about 7 grams per denier. The core-spun fill yarn can have an elongation at peak load, as measured by ASTM D-2256, from about 8% to about 30%. Additionally, the core-spun fill yarn may comprise a core component yarn denier, as measured according to ASTM D-1907, of less than about 50% of the total denier. Further, the core component of the fill yarn of the inventive secondary carpet backing may have a tenacity of at least 7 grams per denier, a shrinkage of 8% or less, and a denier range of 400 to 1500.
More broadly described, the inventive secondary carpet backing may comprise a high tenacity, low shrinkage core-spun filling yarn with a core component of at least one high stiffness continuous filament yarn wrapped with a sheath of staple fibers. The core component yarn can be a high tenacity, low shrink polyester yarn, a high tenacity polypropylene continuous filament yarn or a combination of continuous fibers containing fiberglass, and the sheath can be polypropylene staple fibers or polyester staple fibers.
An inventive carpet made from the inventive secondary carpet backing can comprise a primary backing, the inventive secondary carpet backing, and a binder. A range of carpet styles, binders or primary carpet backings may be utilized with the current invention. For example, the carpets may include, but are not limited to, cut pile, loop pile, or cut/loop pile carpets. The binder for the carpet can include, but is not limited to, latex, polyurethane, hot melt, and thermoplastic polyolefin (e.g., polyethylene or polypropylene).
These and other aspects, objects, and features of the exemplary invention will become apparent from the following detailed description of the exemplary embodiments, read in conjunction with, and reference to, the accompanying tables and drawings.
After extensive research and experimentation, the inventors have developed a novel secondary carpet backing fabric that has the performance of at least conventional secondary carpet backings (e.g., similar peel strength, tuft bind, ease of handling), that is capable of being produced in a simple weaving process, converted into carpet using current carpet making techniques, and that imparts improved buckling resistance to carpet.
The present invention can include an improved woven secondary carpet backing that may be used to form an inventive carpet. The inventive secondary carpet backing allows the carpet to better withstand the rigors of typical carpet manufacturing processes, the stretch-in installation process, and rolling and foot traffic. Compared to carpets made with conventional secondary carpet backings, carpets manufactured according to an exemplary embodiment of the inventive secondary carpet backing have reduced growth in dimensions in tests, such as the cyclic tensile test described in British Standard 4682, Part 1, 1971. Accordingly, a carpet comprising the inventive secondary carpet backing is less prone to buckling than conventional carpets, thereby providing a carpet that requires less re-stretching.
Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings in which like reference numerals represent like elements.
The primary backing 120 may comprise a woven or nonwoven fabric. Specifically, fabrics with woven polypropylene tapes are common and preferred. Other suitable fabrics include nonwoven polyester primary backings sold under the names Lutradur® from Freudenberg AG and Colback® from Colbond B. V. Woven primary backings can be made with polyester (PET) and poly trimethylene terephthatlate (PTT) resins, nylon, and polyolefin resins. Composite primary backings 120 with woven and nonwoven layers, such as Matrix primary backings from Propex Fabrics Inc., may also be used.
The carpet yarn 110 typically comprises synthetic yarns such as nylon, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polypropylene, and natural fibers such as wool or cotton. Other fiber types include polylactic acid (PLA). While the carpet yarn 110 is illustrated in
The inventive carpet 100 further comprises a binding layer 140 used to bind the primary backing 120 to an inventive secondary carpet backing 150. The binding layer 140 is typically an inert particulate-filled aqueous latex of an organic polymer, such as carboxylated styrene butadiene latex (XBSR). One of ordinary skill in the art recognizes that other materials may be used as the binder 140 in order to bond the inventive secondary carpet backing 150 to the primary backing 120. Examples of other possible binders 140 include, but are not limited to other aqueous lattices, such as styrene acrylate copolymers, ethylene vinyl acetate copolymers, and thermoplastic polyurethanes or 100 percent solids binder systems such as hot melt adhesives based on ethylene vinyl acetate, thermoplastic polyolefins, reactive urethanes, and combinations thereof, all of which are commercially available and known to one of ordinary skill in the art. The filler content of the binder can range from about 0 to 85% by weight. Typical fillers are ground calcium carbonate, treated fly ash from coal—fired power plants, and aluminum trihydrate.
The inventive carpet is made using the same processes as are used with conventional leno weave secondary backings, except that the inventive secondary backings are substituted the conventional backings. For example, typical processes using filled latex binders are described in R. L. Scott, Journal of Coated Fabrics, Volume 19 Jul. 1989, pp 35-52. In a common process, the tufted primary backing is contacted with about 20 to 28 ounces per square yard of filled latex (i.e., the precoat) while the secondary backing is contacted with about 8 ounces per square yard of filled latex. The binder layers are combined using a “marriage roll” at the entrance to a forced air oven. As the laminated structure moves through the oven on tenter pins, the edges are held on a tenter frame to prevent the backings from shrinking as the latex layer is dried. At the end of the oven, the carpet is passed through a cool-out box and then released from the tenter frame and wound up on a roll. Typical oven air temperatures are 300 to 340° F., and residence times are one to three minutes.
Carpets can be made with 100 percent solid binder systems as well. For example, U.S. Pat. No. 6,849,565 and British Patent 971,958, hereby incorporated herein by reference, describe such carpets with a polyethylene binder system. Carpets with hot melt adhesive binder systems are described in U.S. Pat. Nos. 3,551,231; 3,684,600; 3,745,054 and 3,914,489, hereby incorporated herein by reference.
The inventive secondary carpet backing fabric 150 may have a weight of 1 to 10 ounces/sq yd, a warp count of 8 to 30 ends/inch, a fill count of 3 to 20 picks/inch, and a grab tensile strength, according to ASTM D-5034, of between 20 and 150 lbs in both the warp and fill directions. Further, this inventive secondary carpet backing fabric 150 may comprise an elongation at peak load, according to ASTM D-5034, of between 8 and 40 percent, and a shrinkage according to ASTM D-2646 of less than 10% after 20 minutes at 270° F.
The inventive secondary carpet backing 150 preferably comprises a plain weave or leno weave fabric comprised of a warp yarn 160 and a fill yarn 180. The warp yarns can be tapes, continuous filament yarns, core-spun yarns, stretch-broken yarns, open end spun yarns, or combinations thereof. They may be made of polypropylene, PET, PTT, or fiberglass, however, polypropylene and PET are the most preferred materials. The warp yarns may also be made from high strength continuous filament yarns with deniers from about 200 to 800 and, preferably, about 250 to 600 denier. The warp yarn density may be from about 4 to 28 ends/inch.
Although the most preferred weave is a leno weave, one of ordinary skill in the art will recognize that other weaves, including plain weaves, twill weaves, and satin weaves with higher or lower warp and fill counts may be used without departing from the scope and spirit of the current invention.
In addition to secondary carpet backings in which all of the fill yarns are of the specific type of core-spun fill yarns described below, other secondary backings in which the fill yarns are a mixture of both the core-spun fill yarn of this invention and other fill yarns, such as conventional open end spun yarn are possible. Such secondary backings can be easily made on looms that have the capability to weave two types of filling yarn using a programmable filling yarn insertion device. The core-spun fill yarns may comprise at least 20 percent of total number of picks in the secondary backing fabric, preferably at least 30 percent of the total number of picks.
The total denier of the core-spun fill yarn 180 of the inventive secondary carpet backing 150, as measured according to ASTM D-1907, may have a weight from about 800 denier to about 3,000 denier. The core-spun fill yarn 180 of the inventive secondary carpet backing 150 can have a tenacity, as measured according to ASTM D 2256, of about 3 grams per denier to about 7 grams per denier. The fill yarn 180 of the inventive secondary carpet backing 150 can comprise an elongation at peak load, as measured by ASTM D 2256, from about 8% to about 30%. The preferred core-spun yarns have deniers from about 1400 to 2400, tenacity above 3.5 g/denier, and elongation at break between 12 to 27%. Further, the fill yarn 180 of the inventive secondary carpet backing 150 may possess an initial modulus of at least 15 grams per denier and a thermal shrinkage of 8% or less at 270° F.
According to an exemplary embodiment of the inventive secondary carpet backing 150, the fill yarn 180 comprises a core-spun yarn. A preferred process for making the core-spun yarn 180 is by friction spinning.
The sheath 220 of the core-spun fill yarn 180 can be made from polypropylene, PET, PTT, or nylon staple fiber or combinations thereof. The fiber can have a denier of 0.8 to 15, preferably 1 to 6 and a cut length from 0.5 to 6 inches. For filled latex binder systems, PET staple fiber with a 1.5 denier by 1.2 inch cut length and 3 denier polypropylene staple fiber with a 2-inch cut length are the preferred sheath 220 fibers according to one exemplary embodiment. According to another exemplary embodiment of the inventive carpet 100, the denier of the core component 210 of the core-spun fill yarn of the secondary backing 150, as measured according to ASTM D 1907, is less than or equal to about 50% of the total denier of the entire core-spun fill yarn 180 as a whole. For example, if the total denier of the core-spun fill yarn 180 were sixteen hundred (1600), the denier of the core component 210, according to an exemplary embodiment, would be less than eight hundred (800) (i.e., less than or equal to about 50% of the denier of the whole core-spun fill yarn 180).
Turning to another exemplary embodiment of the inventive carpet 100, the inventive secondary carpet backing 150 may comprise a high tenacity, low shrinkage core-spun fill yarn 180 with a core component 210 of at least one high stiffness continuous filament yarn wrapped with a sheath 220 of staple fibers. According to this exemplary embodiment, the core component 210 can comprise high tenacity, low shrink polyester or fiberglass continuous filament yarn, and the sheath 220 can comprise polypropylene staple fibers or polyester staple fibers. The core component 210 may also comprise combinations of yarns, such as fiberglass yarns and nylon yarns. When fiberglass and polyaramid continuous filaments are used for the core component 210, they are preferably used in combination with high tenacity PET or nylon continuous filament yarns.
Specific examples of commercially available filament yarns that may be used as the core component 210 comprise E-glass (fiberglass) and high tenacity PET continuous filament yarns, and high tenacity nylon continuous filament yarns. Preferred core components 210 comprise high tenacity, low shrinkage, continuous filament PET yarns types 784, 711, 792, and 710 in deniers of 200, 500, 840, 1000, and 1300 from Invista Inc. Other suitable high tenacity, low shrinkage continuous filament PET yarns used for the core component 210 include, but are not limited to, DSP® yarns types 1X30, 1X50, and 1X90, in deniers of 1000 and 1300 manufactured by Performance Fibers, Inc., Colonial Heights, Va.
For illustrative purposes, exemplary and comparative yarns, secondary carpet backings, and carpets are presented below with reference to tabulated test results in Tables 1 through 5.
Exemplary and Comparative Yarns
Table 1 illustrates the characteristics of the core-spun fill yarn 180 according to several exemplary embodiments of the inventive secondary carpet backing 150 and inventive carpet 100 as compared to conventional fill yarns and alternative core-spun yarns that do not possess the specific property profiles of the core-spun yarns suitable for this invention. All core-spun yarns 180 in Table 1 were produced on a DREF-2 spinning frame manufactured by Fehrer AG using procedures known to one of ordinary skill in the art. Further, yarn physical properties in Table 1 were determined according to the following tests:
3. Tenacity and Peak Elongation were measured according to ASTM D-2256.
Yarns A, B, and C in Table 1 comprised core-spun fill yarns 180 according to an exemplary embodiment of the inventive secondary carpet backing 150 and inventive carpet 100. More specifically, these exemplary Yarns A, B, and C comprised high tenacity, low shrinkage continuous filament polyester yarns used for core component 210, each yarn of the core component 210 comprising less than 50% of the total core-spun yarn 180 weight. Exemplary Yarns A, B, and C further comprised the following exemplary properties: total denier 800 to 3000; less than 50% for the core component 210; tenacity above 3 g/den; and elongation between about 8% and 30%. Specifically, the yarns used for the core component 210 for exemplary Yarns A, B, and C were of type 784 continuous filament polyester yarn manufactured by Invista Inc., with deniers of 500, 1000, and 1000, respectively. The sheath fiber 220 in Yarn A was 3 denier by 2 inch polypropylene fiber, the sheath fiber 220 in Yarn B was 1.5 denier by 1.5 inch low shrinkage PET staple fiber, and the sheath fiber 220 in Yarn C was 1.2 denier by 1.5 inch low shrinkage PET staple fiber. The polypropylene fiber was manufactured by FiberVisions, Inc., and the polyester staple fiber was manufactured by Wellman, Inc. Yarns D-K are listed in Table 1 for comparative purposes. Yarns D and E comprised open-end spun yarns. Sample D comprised a 1714 denier open-end polypropylene spun yarn used in conventional secondary carpet backing. This yarn was spun from 4.6 denier by 2 inch staple fiber. Yarn E comprised a heavier open end spun yarn made with 100% polyester staple fibers (1.5 denier by 1.5 inch staple length). Yarn F comprised a core-spun yarn 180 with a polypropylene tape used for the core component 210. Yarn G comprised a core-spun yarn 180 with fiberglass used as the core component 210. Yarns H and J were comprised of core-spun yarns 180 with a combination of continuous filament yarns used for the core component 210 (i.e., fiberglass plus polyester core-spun yarns). In Yarn H, the core component 210 consisted of 598 denier fiberglass continuous filament yarn and 150 denier PET continuous filament yarn. In Yarn J, the core component 210 consisted of 298 denier fiberglass continuous filament yarn and 150 denier PET continuous filament yarn.
Yarn K was comprised of a core-spun yarn 180 having an identical yarn of Yarn C used for the core component 210; however, the yarn used for core component 210 of Yarn K accounted for over 50% of the total denier of the core-spun fill yarn 180 as a whole.
The sheath fibers used for sheath 220 in Yarns F, G, and H were 3 denier by 2 inch polypropylene fiber. The sheath fiber 220 in Yarn J was 1.5 denier by 1.5 inch low shrinkage PET staple fiber. The sheath fiber 220 in Yarn K was 1.2 denier by 1.5 inch low shrinkage PET staple fiber. As above, the polypropylene fiber was manufactured by from FiberVisions, Inc., and the polyester staple fiber was manufactured by from Wellman, Inc.
Exemplary and Comparative Secondary Carpet Backing Fabrics
Table 2 shows the properties of exemplary embodiments of the inventive secondary carpet backing 150 of the inventive carpet 100 as well as comparative secondary carpet backings. As used in Tables 1 through 5 below, the term “osy” is an abbreviation for “ounces/sq yard.” All of the secondary carpet backings in Table 2, except Comparative 5, had a 16×5 leno weave construction. Comparative 5 had a construction of 18 warp ends/inch by 13 picks/inch. Surprisingly, Comparative 5 performed poorly despite its high end and pick count.
The tests used to measure fabric properties in Table 2 were as follows:
2. Tensile Strength and Peak Elongation were measured according to ASTM D-5034.
Secondary carpet backings S1, S2, and S3 are exemplary embodiments of the inventive secondary carpet backing 150. Secondary carpet backings Comp. 1 through Comp. 6 are shown in Table 2 for comparative purposes.
All of the secondary carpet backing fabrics in Table 2 were woven on a Sulzer 430 mm PU projectile weaving machine. To manufacture the secondary carpet backings, the loom was set to run the standard fill yarn (1714 denier OES PP spun yarn—Yarn D in Table 1) at about 230 picks/min, and then small adjustments were made to weave other fill yarns. The fill yarns were either core-spun or open-end spun (OES) yarns.
Exemplary embodiment S1 comprised a 16×5 leno construction using core-spun Yarn A. The fill yarns utilized in the secondary carpet backings discussed in Table 2 are described by their like referenced letter in Table 1. Thus, Fill Yarn A in Table 2 is the same as Yarn A in Table 1. Exemplary embodiment S1 of the inventive secondary carpet backing 150, as illustrated in Table 2, had a weight of 2.2 ounces per square yard, a shrinkage of 7.3% in the warp direction and 4.0% in the fill direction, a grab tensile strength of 68 lbs at 35% elongation in the warp direction, and a grab tensile strength of 48 lbs at 31% elongation in the fill direction.
Exemplary embodiment S2 of the inventive secondary carpet backing 150 comprised a 16×5 leno weave using Yarn B. Yarn B had a 1000 denier yarn for the core component 210 of Invista 784 polyester continuous filament yarn and a sheath 220 made with 1.5 denier by 1.5 inch low shrinkage polyester staple fiber. Exemplary embodiment S2 had a warp direction tensile strength of 72 lbs at a peak elongation of 34%, a fill direction tensile strength of 82 lbs at a peak elongation of 18%, and a fill direction shrinkage of 2.8%.
The fill yarn in exemplary secondary carpet backing S3 (i.e., Yarn C) comprised the same yarn used for the core component 210 as in Yarn B, but with a different polyester staple fiber sheath (1.2 denier by 1.5 inch low shrinkage staple fiber). Exemplary embodiment S3 of the inventive secondary carpet backing 150 had a warp direction tensile strength of 67 lbs at a peak elongation of 30%, a fill direction tensile strength of 70 lbs at a peak elongation of 16%, and a fill direction shrinkage of 2.6%.
Comparative 1 (Comp. 1) secondary carpet backing comprised a 16×5 leno weave construction with Yarn D—a 3.1 cc OES polypropylene yarn—as the filling yarn. This yarn had a weight and shrinkage similar to those of S1. Comp. 1is representative of the most common secondary carpet backing used in the industry today.
Comparative 2 (Comp. 2) secondary carpet backing comprised the same construction and warp yarn as SI, but with a different filling yarn—Yarn F.
Comparative 3 (Comp. 3) secondary carpet backing comprised the same construction and warp yarn as S1, but with a different filling yarn—Yarn G. Yarn G had a 500 denier fiberglass core component and could not be woven without excessive stops. Thus, it did not produce a satisfactory secondary carpet backing. The inability to weave fabric at high efficiency is consistent with the low elongation at break for this yarn.
Comparative 4 (Comp. 4) secondary carpet backing comprised the same construction and warp yarn as SI, but a different filling yarn—Yarn E. This filling yarn was an open end spun yarn made from polyester staple fiber.
Comparative 5 (Comp. 5) secondary carpet backing comprised a 1714 denier OES (the same filling yarn as Comp. 1, i.e., Yarn D), but a high end count and pick count. Comp. 5 is an example of a heavyweight, high pick count commercial leno weave secondary carpet backing. This fabric is available as ActionBac style 3872 from Propex Fabrics Inc., Austell, Ga. The warp count in this fabric is 18 ends/inch, and the pick count is 13 ends/inch.
Comp. 5 secondary carpet backing fabric had higher grab strengths in the warp direction and in the filling direction than any other secondary carpet backing fabric in Table 2. The fill direction grab strength was 145 lbs, more than 60% higher than the grab strengths of inventive secondary carpet backings S1, S2, and S3. Surprisingly, however, as will be illustrated in reference to Table 4 below, despite the increased grab strengths, secondary carpet backing Comp. 5 did not produce a carpet any less prone to buckling. Specifically, the carpet made from secondary carpet backing Comp. 5 had greater total and unrecovered extensions, as determined according to British Standard 4682, Part 1, 1971, than did the exemplary carpets of this invention.
Comparative 6 (Comp. 6) secondary carpet backing was identical to S3, except for the filling yarn. Comp. 6 comprised Yarn K as its filling yarn; S3 comprised Yarn C as its filling yarn. In Yarn K, the percentage of core component yarn was 56%; in Yarn C, the percentage was 49%.
Carpets
With the secondary carpet backings listed in Table 2, three carpet manufacturing runs were carried out. A pre-coat of about 16 to 22 ounces of 550-load carboxylated styrene butadiene latex was applied to the back of the tufted primary backing, and an adhesion coat of about 8 ounces of 400-load carboxylated styrene butadiene latex was applied to the secondary carpet backing. The filler used for these secondary carpet backings was ground calcium carbonate.
Following the above, the backings were pressed together, attached to a tenter frame, and passed through a forced air oven approximately 80 feet long. The oven air temperature was 320° F., and the line speed was about 60 feet per minute. After the carpet samples cooled, they were tested. Tables 3-5 represent the results from the three different carpet runs. The tests used to measure certain carpet properties in Tables 3-5 are as follows:
The first manufacturing run involved exemplary secondary carpet backing S1, along with comparative secondary carpet backings Comp. 1 and Comp. 2. The three secondary carpet backings, S1, Comp. 1, and Comp. 2, were laminated with a common tufted primary backing to make carpets C1, Comp. 1 and Comp. 2, respectively. The carpets were made back-to-back to minimize the differences caused by changes in latex binder application rates, oven temperatures, and other processing variables. Each carpet comprised a tufted primary backing with a face weight of 39 oz/sq yd of ⅜ inch high nylon cut pile ( 1/10th gauge, 10 stitches inch in a straight stitch pattern). The primary backing was a 24×18 woven polypropylene tape backing sold as PolyBac® 2218 by Propex Fabrics Inc., Austell, Ga. Table 3 below summarizes the properties of exemplary carpet C1 and comparative carpets Comp. 1 and Comp. 2 following measurement of the carpets.
The inventive carpet 100 in exemplary embodiment C1 comprised a core-spun fill yarn 180 with a 16×5 leno weave secondary carpet backing 150 using fill Yarn A. As is illustrated in Table 3, all tested carpets had peel strengths above 3 pounds per inch. However, as can be seen from Table 3, the exemplary embodiment C1, which was comprised of a secondary carpet backing 150 with core-spun fill Yarn A, had the highest tuft bind. Further, in the cyclic loading test, the exemplary embodiment C1 had smaller total extension (7.0%) and unrecovered extension (1.4%) than comparative carpets Comp. 1 and Comp. 2.
The second manufacturing run involved exemplary secondary carpet backing S2, along with comparative secondary carpet backings Comp. 3, Comp. 4, and Comp. 5. The four secondary carpet backings, S2, Comp. 3, Comp. 4, and Comp. 5, were laminated with a common tufted primary backing to make carpets C2, Comp. 3, Comp. 4, and Comp. 5, respectively. Each carpet comprised a tufted primary backing with 54 oz/sq yd of nylon cut pile face yarn ( 1/10th gauge, 10 stitches/inch, and ⅝ inch pile height) and a 24×18 PolyBac® 2218 woven tape primary backing. Carpets with this type of face construction are typically used in commercial buildings. The small pile denier and dense tufting pattern limit the tuft binds that can be achieved.
Table 4 below summarizes the properties of exemplary carpet C2 and the comparative carpets following measurement of the carpets.
The inventive carpet 100 in exemplary embodiment C2 comprised exemplary secondary carpet backing S2 with core-spun fill Yarn B. Carpets Comp. 3and Comp. 4were comprised of a 16×5 leno weave secondary carpet backing made from open end spun fill yarns. All carpet samples had excellent peel strengths; however, exemplary carpet C2 had a much lower total extension (5.5%) and unrecovered extension (0.9%) than did comparative carpets Comp. 3 and Comp. 4.
To test the effect of using more ends and picks in a conventional secondary carpet backing with open end spun polypropylene yarn, the 18×13 leno weave secondary carpet backing, Comp. 5, was used to make a carpet. This carpet is denoted in Table 4 as Comp. 5. Surprisingly and unexpectedly, cyclic testing of Comp. 5 revealed that it had a higher total extension (7.7%) and unrecovered extension (1.6%) than any of the other carpets in the group. This result was unexpected, because additional fill yarns would be expected by one of ordinary skill in the art to give increased dimensional stability to the carpet; however, as is illustrated in Table 4, this was not the case. Therefore, even though carpet Comp. 5 would be expected to be the least likely carpet to buckle, it was actually the most likely carpet to buckle. These observations of unexpected results demonstrate the necessary iterations and experimentation that were required by the inventors in arriving at the present invention.
The third series of carpet samples were prepared in the same manner as the first two. In this series, the tufted primary backing contained 24 osy of polyester cut pile ( 3/16 gauge, 8 stitches/inch tufting pattern, ⅝ inch pile height). The primary backing (PolyBac® 2205 from Propex Fabrics Inc., Austell, Ga.) had a 24×13 construction.
The face construction of this style of carpet would typically not qualify for United States Housing and Urban Development financing because the amount of pile yarn is below the minimum required for polyester cut pile carpet.
Nevertheless, the property profiles of carpets made with this tufted primary backing can be used for to compare the effects of different secondary backings.
Further, this carpet style is typical one that frequently buckles after installation.
Table 5 below summarizes the properties of exemplary carpet C3 and the comparative carpets following measurement of the carpets.
The inventive carpet 100 of exemplary carpet C3 comprised a 16×5 leno weave secondary carpet backing 150 with a core-spun polyester fill yarn, Yarn C.
As can be seen from Table 5, exemplary carpet C3 with inventive secondary carpet backing S3 had an excellent peel strength (5.7 lbs/inch) and much lower total extension (5.1%) and unrecovered extension (0.9%) than did carpet Comp. 6, which was made from secondary carpet backing Comp. 1 with a 3.1 cc OES polypropylene fill yarn. Additionally, although comparative carpet Comp. 7 had similar dimensional stability to the exemplary embodiment C3, the peel strength was only 2.1 lbs/inch, much lower than the peel strength achieved with the secondary backing S3, and well below industry normal values or norms. The low peel strength of comparative carpet Comp. 7 is surprising, considering the fact that comparative carpet Comp. 7 had a filled latex binder weight of 34 osy, while exemplary embodiment C3 comprised a filled latex binder weight of only 25 osy.
As is illustrated by Tables 3, 4 and 5, exemplary embodiments C1, C2 and C3 of the inventive carpet 100 exhibit necessary peel strength and comparable tuft bind strength while outperforming the comparative carpets in cyclic tensile tests that predict carpet buckling resistance. This combination of good tuft bind and peel strength with improved dimensional stability in cyclic testing is unexpected given that: (1) the only change between carpets is the secondary carpet backing; (2) the inventive secondary carpet backing can be made by a simple one-step weaving process—just like conventional, widely used secondary backings; and (3) the inventive secondary carpet backing can be converted into carpet using the same manufacturing steps as conventional secondary backings. Thus, the current invention allows for a carpet to possess the added requirements without suffering slower carpet manufacturing line speeds.
As illustrated by comparative carpet Comp. 5, one of ordinary skill in the art would believe that a carpet having increased fill yarns would be one solution to the problem of buckling, whereas increasing the number of fill yarns actually has the opposite effect.
As previously stated, buckling in carpets depends on many variables. Therefore, the inventors necessarily considered many factors to create the unexpected secondary carpet backings that are capable of being made by a simple one-step weaving process. In doing so, the inventors performed many trials and experimentations to produce a carpet exhibiting the proper characteristics to reduce buckling.
Many modifications, features and embodiments of the inventive carpet comprising the inventive secondary carpet backing will become evident to one of ordinary skill in the art. Many aspects of the invention were described above by way of example only and are not intended as required or essential elements of the invention. Accordingly, it should be understood that the foregoing relates only to certain embodiments of the invention and that numerous changes may be made therein without departing from the spirit and scope of the invention as defined by the following claims. It is also understood that the invention is not restricted to the illustrated embodiments and that various modifications may be made without leaving the scope of the following claims.
