Patent Application
20070254131
Referring to the figures, in which like numerals refer to like elements through the several figures,
The primary backing 110 is typically formed from a non-woven substrate. The non-woven substrate imparts stability to the carpet tile 100 and also provides the proper drape for the installation process. The non-woven substrate may be made from a polyester, such as poly(ethylene terephthalate) [PET], poly(trimethylene terephthalate) [PTT], poly(butylene terephthalate) [PBT], poly(ethylene terephthalate-co-isophthalate), poly(ethylene naphthalenedicaroxylate) [PEN], and copolymers thereof, with PET being preferred. The non-woven substrate may also be made from a polyester core surrounded by a polyamide sheath. Typically, the polyester core may be made from PET, PTT, PBT, PEN, poly(ethylene terephthalate-co-isophthalate) and copolymers thereof. The polyamide sheath may be made from polycaprolactam [nylon 6], poly(7-heptanamide) [nylon 7], polycapryllactam [nylon 8], poly(9-nonanamide) [nylon 9], poly(tetramethylene adipamide) [nylon 4,6], poly(hexamethylene adipamide) [nylon 6,6], poly(methylene-4,4′-dicyclohexylene dodecanediamede), poly(1,4-cyclohexylenedimethulene suberamide), poly(m-phenylene isophthalamide), and poly(p-phenylene terephthalamide), with polycaprolactam [nylon 6] being the preferred polyamide. Alternatively, the primary backing 110 may be formed using a woven substrate using any conventional natural or synthetic woven material, such as cotton, jute, rayon, paper, nylon, polypropylene and other polyolefins, polyamides, polyesters, and the like or from a combination of a non-woven substrate and a woven substrate.
The face yarn 105 may be tufted through the primary backing 110 so that the ends of the face yarn 105 extend in an outwardly direction from the topside of the primary backing 110. Typically the face yarn is tufted into the primary backing 110 at a weight of approximately 90 g/m2 to approximately 200 g/m2, and more preferably approximately 120 g/m2. The tufting may be performed using conventional techniques that are well known in the art. Furthermore, the tufted face yarn 105 loops may be left as uncut to form an uncut pile carpet, cut to form a cut pile carpet, or partially cut to form a tip sheared carpet, as is well known in the art.
The carpet tile 100 includes a pre-coat layer 115 that is applied on top of the primary backing 110. The main purpose of the pre-coat layer 115 is to penetrate the tufted face yarn 105 and encapsulate the individual ends of the fiber that make the yarn bundles and bind the tufted face yarn 105 to the primary backing 110. This prevents one end of an individual fiber from being pulled out of the carpet backing during the manufacturing process. The pre-coat layer 115 can also act as a tackifier to provide an acceptable binding surface for subsequent polymer layers and provide the right amount of flexibility (drape) to the carpet. In an exemplary embodiment, the pre-coat layer 115 consists of a hot melt adhesive (HMA) that contains a tackifying resin or agent alone or in combination with polyethylene. The tackifying agent preferably comprises at least approximately 20 wt % of the pre-coat layer 115, while the polyethylene comprises the remaining 0 wt % to approximately 80 wt % of the pre-coat layer 115. The tackifying agent more preferably comprises approximately 30 wt % to approximately 80 wt % of the pre-coat layer 115, while the polyethylene comprises the remaining approximately 20 wt % to approximately 70 wt % of the pre-coat layer 115. Most preferably, the tackifying agent comprises approximately 60 wt % of the pre-coat layer 115, while the polyethylene comprises the remaining approximately 40 wt % of the pre-coat layer 115.
The pre-coat layer 115 generally is applied on the primary backing in the range of approximately 2 oz/yd2 (68 g/m2) to approximately 20 oz/yd2 (680 g/m2), and more preferably in the range of approximately 8 oz/yd2 (272 g/m2) to approximately 12 oz/yd2 (408 g/m2). The pre-coat layer 115 has a viscosity between approximately 50 cps to approximately 5000 cps at a temperature between approximately 300° F. (149° C.) to approximately 350° F. (177° C.), and more preferably approximately 1,000 cps at approximately 335° F. (168° C.).
The tackifying agent component of the HMA used in the pre-coat layer 115 may be any suitable tackifying agent known generally in the art, such as natural and synthetic resins and rosin materials. Classes of tackifying resins that may be employed are the coumarone-indene resins, terpene resins, including also styrenated terpenes, butadiene-styrene resins, polybutadiene resins, and hydrocarbon resins. The tackifying agent may also include rosin materials, low molecular weight styrene hard resins, disproportionated pentaerythritol esters, and copolymers of aromatic and aliphatic monomer systems. The rosin material may be gum, wood or tall oil rosin. Also the rosin material may be a modified rosin such as dimerized rosin, hydrogenated rosin, disproportionated rosin, or esters of rosin.
Disposed on top of the pre-coat-layer 115 is a first extruded polymer layer 120 whose primary function is to permanently bond the tufted face yarn 105 to the primary backing 110. In an exemplary embodiment, the first extruded polymer layer 120 comprises a HMA, examples of which include but are not limited to ethylene-vinyl acetate copolymers (EVA), styrene-isoprene-styrene copolymers (SIS), styrene-butadiene-styrene copolymers (SBS), ethylene-ethyl acrylate copolymers (EEA), ultra-low density polyethylene (ULDPE), low density polyethylene (LDPE), polypropylene, ethylene-propylene diene monomer (EPDM), and blends of any of the foregoing (e.g., a blend of polypropylene and EPDM), with EVA being preferred.
When the first extruded polymer layer 120 is an EVA hot melt adhesive, the poly(vinyl acetate) content of the EVA may be approximately 2 wt % to approximately 40 wt % of the EVA, and more preferably approximately 8 wt % to approximately 30 wt % of the EVA. The EVA hot melt adhesive has a melt flow index of approximately 0.2 grams per minute (g/min) to approximately 25 g/min, and more preferably about 2.5 g/min. The melting point of the EVA hot melt adhesive is about 140° F. (60° C.) to approximately 450° F. (232° C.), depending on the relative amounts of each component of the copolymer, and more preferably about 180° F. (82° C.), which is above the melting point of the HMA used for the pre-coat layer 115. Generally, approximately 25 oz/yd2 (850 g/m2) of the EVA is extruded onto the back of the pre-coat layer 115, however the EVA can extruded onto the pre-coat layer in a range from approximately 10 oz/yd2 (340 g/m2) to approximately 50 oz/yd2 (1700 g/m2). The extrusion temperature of the EVA hot melt adhesive is preferably approximately 350° F. (177° C.) to approximately 385° F. (196° C.), with acceptable extrusion temperatures being between approximately 275° F. (135° C.) and approximately 450° F. (232° C.). The viscosity of the EVA hot melt adhesive can lie in the range of approximately 250,000 cps to approximately 1,500,000 cps at temperatures between 390° F. (199° C.) and 430° F. (221° C.). More preferably, the EVA hot melt adhesive has a viscosity of approximately 521,000 cps at 390° F. (199° C.), approximately 402,000 cps at 410° F. (210° C.), and approximately 320,000 cps at 430° F. (221° C.).
Beneath the first extruded polymer layer 120 is a second extruded polymer layer 125, which is also a solventless hot melt adhesive. The hot melt adhesive of the second extruded polymer layer 125 can be identical to the composition of the hot melt adhesive used for the first extruded polymer layer 120. However, the hot melt adhesive of the second extruded polymer layer 125 has a heavier application than the first extruded polymer layer 120. In an exemplary embodiment, approximately 20 oz/yd2 (680 g/m2) to approximately 70 oz/yd2 (2380 g/m2), and more preferably approximately 45 oz/yd2 (1530 g/m2) of the hot melt adhesive is extruded onto the back of the first extruded polymer layer 120.
The composition of the hot melt adhesive of either or both the first and second extruded polymer layers can also contain other components. In particular, the hot melt adhesive may include an inert filler material. In one exemplary embodiment, the hot melt adhesive contains approximately 60 wt % inert filler material, while the polymeric component comprises approximately 40 wt % of the hot melt adhesive. In preferred embodiments, the polymeric component comprises approximately 10 wt % to approximately 95 wt %, while the remaining component is filler. For example, a filled EVA HMA will preferably comprise approximately 30 wt % to approximately 40 wt % EVA, with the filler comprising the remainder of the mixture.
The inert filler material may be made from carbonates such as calcium carbonate (CaCO3), cesium carbonate (CsCO3), strontium carbonate (SrCO3), and magnesium carbonate (MgCO3); sulfates such as barium sulfate (BaSO3); oxides such as iron oxide (Fe2O3 or Fe3O4), aluminum oxide (Al2O3), tungsten oxide (WO3), titanium oxide (TiO2), silicon oxide (SiO2), silicates, such as clay; metal salts, and the like. Additionally, the inert filler material may be a flame retardant such as, but not limited to, aluminum trihydrate (ATH) or magnesium hydroxide (MgOH) for applications where flame-retardancy is desired.
Additionally, the inert filler material may be made from post-consumer products, such as post-consumer glass, post-consumer carpets and/or other post-consumer recycled materials. In cases where the inert filler is made from post-consumer glass, the post-consumer glass is ground into a fine glass powder before it is added as filler. The glass cullet may be made from automotive and architectural glass, also known as plate glass, flint glass, E glass, borosilicate glass, brown glass (bottle glass), green glass (bottle glass), and coal fly ash, or a combination thereof. In the case where post-consumer carpet is used as the inert filler material, the post-consumer carpet maybe ground into a fine cullet and added to the hot melt adhesive. In addition to the post-consumer carpet, remnants and trimmings of carpet, fine waste fibers that are a result of the shearing process, and the like, that are produced as a by-product during the manufacturing process may also be used to form the inert filler material. Specific examples of post-consumer compositions include post-consumer densified polypropylene carpets comprising approximately 52 wt % polypropylene, approximately 40 wt % CaCO3 (or other inert filler listed hereinabove), and approximately 8 wt % of a styrene-butadiene-rubber (SBR) latex residue; post-consumer polypropylene fibers that comprise approximately 93 wt % polypropylene, less than approximately 5 wt % nylon, less than approximately 2 wt % ash, and approximately 0.3 wt % of a SBR latex residue; post-consumer densified polyethylene stretch wrap films consisting essentially of polyethylene; post-consumer bottle caps that comprise less than approximately 50 wt % polyethylene, less than approximately 50 wt % polypropylene and less than approximately 1 wt % ash; or a mixture of any of the foregoing post-consumer compositions. The use of post-consumer products provides environmental benefits, as materials that were destined for landfills may be diverted to make new, useful products, such as carpet and carpet tiles 100.
To ensure that the hot melt adhesive flows properly through the extruder, steric acid may be added to act as a lubricant. In addition to providing lubrication, the steric acid also increases the tear strength of the hot melt adhesive. Typically, the steric acid may be added in an amount up to approximately 1 wt % of the filled or unfilled hot melt adhesive, and more preferably approximately 0.2 wt % of the hot melt adhesive.
The filled or unfilled hot melt adhesive may also contain a pigment, such as carbon black or another colorant(s) to provide color and increase the opaqueness of the hot melt adhesive. Typically, the pigment may be present in an amount less than or equal to approximately 1 wt % the filled or unfilled hot melt adhesive, and more preferably approximately 0.1 wt % of the hot melt adhesive.
When certain hot melt adhesives are heated, they may become susceptible to thermo-oxidation degradation. Therefore, to reduce the possibility of thermo-oxidation degradation, the hot melt adhesive may also contain an antioxidant. Some suitable antioxidants include, but are not limited to 2,2′-methylene bis-(4-methyl-6-tert-butylphenol), 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,4′-thio-bis-(6-tert-butyl-m-cresol), butylated hydroxy anisole, and butylated hydroxy toluene. Typically, the antioxidant may be present in the filled or unfilled hot melt adhesive in an amount less than or equal to approximately 2 wt % of the adhesive, and preferably approximately 0.01 wt % to approximately 1 wt % of the filled or unfilled hot melt adhesive.
The carpet tile 100 can include an optional scrim 130 disposed between the first extruded polymer layer 120 and the second extruded polymer layer 125. The purpose of the scrim 130 is to impart dimensional stability to the finished carpet tile 100. Typically, the scrim 130 is made from a non-woven material such as fiberglass. However, the non-woven fiber may also be made from polymers such as polyesters, polyamides, polyurethanes, copolymers thereof, blends thereof, and the like. The scrim 130 can also be woven from fiberglass fibers using a leno weave attachment to impart stability to the resultant carpet tile 100.
Beneath the second extruded polymer layer, 125, the carpet tile 100 can contain an optional cushioned backing 135, which can be formed from any conventional thermoplastic material. For example, the cushioned backing 135 may be made from any natural or synthetic rubber such as foam, rubber, polychloroprene, acrylonitrile-butadiene copolymers, ethylene-propylene-diene rubbers, and the like. The cushioned backing 135 may also be made from another polymeric material, such as petroleum resins, vinyl-based polymers, polybutylene resins, polyisobutene-butadiene resins and copolymers thereof, polyvinyl chloride, polyvinylidine chloride, poly(vinyl acetate), poly(vinyl acetal), poly(vinyl butyral), copolymers thereof, and blends thereof The cushioned backing 135 may further include various indentations or corrugations to provide friction between the bottom of the carpet tile 100 and the floor, which provides increased resistance of the carpet tile 100 to movement after it is installed.
In another exemplary embodiment, rather than providing a separate cushioned layer 135, the second extruded polymer layer 125 may contain a foaming agent to produce a foam backing on the carpet. If used, any conventional foaming agent, such as but not limited to, azodicarbonamide, toluene sulfonyl seimcarbazide, and oxy bis(benzene sulfonyl)hydrazide may be used. Normally, the amount of foaming agent depends upon the amount of foaming desired in the adhesive compound. Typically, the foaming agent may be present in the second extruded polymer layer 125 in an amount between approximately 0.1 wt % and approximately 2 wt % of the total weight of the hot melt adhesive (either filled or unfilled), and more preferably approximately 0.75 wt % of the total weight of the hot melt adhesive.
The griege good is then fed into an accumulator where one or more operators join the ends of each form to one another. Typically, the accumulator may contain j-boxes, roll accumulators, or a combination of both to collect the individual forms. The accumulator allows the operators to sew the ends of the forms together while maintaining a line speed between approximately 10 feet per minute (fpm), which is approximately 3 meters per minute (mpm), and approximately 80 fpm (24 mpm). At this point, the griege good is oriented so that the tufted face fibers 105 are facing upward.
At 210 the tufted face fibers 105 are treated with one or more topical chemicals. The topical chemicals applied to the tufted face fibers 105 may include of stain blockers, such as phenolic resin, methacrylic acid resin, and styrene-maleic anhydride co-polymer, soil release agents, such as hydrophilic colloids like carboxymethylcellulose, synthetic hydrophilic polymers like polyacrylic acid, and fluorochemical-based systems, or anti-static agents, or a combination thereof.
The topical chemicals may be applied onto the tufted face fibers 105 by a sprayer unit or applied as foam. Typically, the topical chemicals are applied to the tufted face fibers 105 at approximate 10 wt % to approximately 14 wt %, based on the overall weight of the fibers. The griege good then proceeds to a topical oven to cure the chemicals to the tufted face fibers 105. Normally, the topical oven operates at a temperature of approximately 250° F. (121° C.) to approximately 350° F. (177° C.), which is well below the melting point of the face fibers 105.
Next, at 215, the griege good is inverted by an inversion unit, which orients the griege good so that the backside of the primary backing 110 is facing upward. Once inverted, the griege good passes through an optional weft straightener at 220. The weft straightener insures that the patterns in the face fibers 105 are properly aligned before the polymer layers are applied to the backside of the griege good.
Once the griege good leaves the weft straightener, the griege good enters a first coating station at 225, in which a first polymer layer 115 is applied to the backside of the griege good. The first polymer layer 115 is generally a hot melt pre-coat adhesive. The hot melt pre-coat layer 115 encapsulates the individual ends of the fibers that make up the yarn bundle to prevent the fibers from “fuzzing” and provide a level of tuft bind strength to prevent one end of the yarn from being pulled out when subjected to normal wear. In addition, the pre-coat layer 115 also acts as a tackifying agent for any additional backing layers that may be applied to the carpet tile 100. The pre-coat layer 115 includes a tackifying agent and, optionally, polyethylene. In an exemplary embodiment, the pre-coat layer 115 comprises approximately 20 wt % to approximately 100 wt % of the tackifying agent, and approximately 0 wt % to approximately 80 wt % polyethylene. The pre-coat adhesive layer 115 is typically applied to the backside of the primary backing 110 at a temperature between approximately 250° F. (121° C.) and approximately 450° F. (232° C.), and more preferably at approximately 350° F. (177° C.). At this temperature, the hot melt layer 115 has a viscosity of approximately 500 cps. The pre-coat layer 115 is applied at a rate of approximately 2 oz/yd2 (68 g/m2) to approximately 20 oz/yd2 (680 g/m2), and more preferably at a rate of approximately 8 oz/yd2 (272 g/m2) to approximately 10 oz/yd2 (340 g/m2) using a roll coater.
At 230, the griege good travels to a first extrusion station, in which a first extruded polymer layer 120 is applied onto the top of the hot melt pre-coat layer 115. To provide the optimum tuft bind and adhesion performance, the first extruded polymer layer 120 is applied while the hot melt pre-coat layer 115 is slightly “tacky.” That is, the first extruded polymer layer 120 is applied while the temperature of the hot melt pre-coat layer 115 is still above its softening point, which may be approximately 250° F. (121° C.) to approximately 450° F. (232° C.). In an exemplary embodiment, the first extruded polymer layer 120 is a hot melt adhesive composition. Preferably, the hot melt adhesive composition is EVA. The content of the poly(vinyl-acetate) is between approximately 2 wt % and approximately 40 wt % of the EVA hot melt adhesive and more preferably between approximately 19 wt % and approximately 20 wt % of the EVA, with polyethylene comprising the remaining portion.
The hot melt adhesive may also contain an inert filler material. In an exemplary embodiment, the hot melt adhesive has a composition of approximately 60 wt % of the inert filler material and approximately 40 wt % of the polymer. However, acceptable concentrations of the inert filler material can range between approximately 60 wt % and 95 wt % of the hot melt adhesive. This provides the hot melt adhesive with a melt index in the range of approximately 0.2 g/min to approximately 25 g/min, and more preferably approximately 2.5 g/min. For example, a filled EVA will have a melt index of approximately 1 g/min.
The extruder station is preferably a single screw-type extruder with a barrier screw. However, other types of extrusion processes, such as multi-screw extruders, disc extruders, ram extruders, and the like may be used without departing from the scope of the invention. Normally, the weight of the hot melt adhesive that is extruded onto the backside of the pre-coat layer 115 is approximately 25 oz/yd2 (850 g/m2). However, the acceptable weight may range between approximately 10 oz/yd2 (340 g/m2) and 50 oz/yd2 (1700 g/m2). The hot melt adhesive is preferably extruded through a die so that it forms a sheet of molten HMA that is at least as wide as the griege good. The sheet of molten HMA encapsulates and adheres to the loops of the tufted yarn 105 to permanently lock both the individual fibers and the yarn to the primary backing 110, while maintaining sufficient flexibility and drape required for the carpet tile 100.
At 235, while the temperature of the first extruded polymer layer 120 is still between approximately 150° F. (66° C.) and 450° F. (232° C.), an optional scrim 130 may be placed on top of the first extruded polymer layer 120. The scrim 130 is preferably made of a non-woven fiber, such as fiberglass, which imparts dimensional stability to the carpet.
The griege good next proceeds to a second extrusion station at 240, where a second extruded polymer layer 125 is extruded onto the first extruded polymer layer 120 or the optional non-woven fiberglass scrim 130. In an exemplary embodiment, the second extruded polymer layer 125 is composed of the same hot melt adhesive used for the first extruded layer 120. However, the second extruded layer 125 is applied at a slightly heavier weight than the first extruded layer and has a target weight of approximately 20 oz/yd2 (680 g/m2) to approximately 70 oz/yd2 (2380 g/m2) and more preferably between approximately 40 oz/yd2 (1360 g/m2) and approximately 45 oz/yd2 (1530 g/m2).
Next at 245, a cushioned backing 135 may optionally be applied to the griege good. In an exemplary embodiment, the cushioned backing 135 may be laminated to the second extruded polymer layer 125. The cushioned backing 135 may be made of a non-woven material or more preferably a foam backing made from a high density polyurethane, styrene butadiene, poly vinyl-chloride, ethylene vinyl-acetate, and the like. The cushioned backing 135 has have a density in the range of approximately 12 pounds per cubic foot (lbs/ft3), which corresponds to 0.19 grams per cubic centimeter (g/cm3), to 24 lbs/ft3 (0.38 g/cm3), but preferably the density of the cushioned backing 135 is about 18 lbs/ft3 (0.29 g/cm3).
Rather than applying a separate cushioned backing 135, the second extruded polymer layer 125 may contain a foaming agent to produce a foam backing. Any conventional foaming agent, such as but not limited to, azodicarbonamide, toluene sulfonyl seimcarbazide, and oxy bis(benzene sulfonyl) hydrazide may be used. Typically, the foaming agent may be present in the adhesive in an amount between approximately 0.1 wt % and approximately 2.0 wt %, and preferably in an amount of approximately 0.75 wt % of the second extruded polymer layer 125. Once the cushioned backing 135 is in place, the griege good can be cooled by passing the griege good through a series chilled rollers to an exit accumulator so allow the polymer layers to cool to a nominal temperature of approximately 75° F. (24° C.) to approximately 80° F. (27° C.).
Finally, at 250, the griege good is then fed into a die cutter, where the griege good is die cut into the appropriate market-size (e.g., 18″×18″, 24″×24″, or 36″×36″) carpet tiles 100. Alternatively, the griege good may also be taken onto a large diameter (i.e., 8′ diameter) drum where it can be taken to an off-line die cutting station for further processing into carpet tiles 100.
While the invention has been disclosed in its preferred forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/745,793 filed 27 Apr. 2006, and entitled “Hot Melt Carpet Tile and Process for Making Same,” which is hereby incorporated by reference in its entirety as if fully set forth below.
| Number | Date | Country | |
|---|---|---|---|
| 60745793 | Apr 2006 | US |
