US20030211280A1 - Carpet, carpet backings and methods - Google Patents

Carpet, carpet backings and methods Download PDF

Info

Publication number
US20030211280A1
US20030211280A1 US10/418,227 US41822703A US2003211280A1 US 20030211280 A1 US20030211280 A1 US 20030211280A1 US 41822703 A US41822703 A US 41822703A US 2003211280 A1 US2003211280 A1 US 2003211280A1
Authority
US
United States
Prior art keywords
carpet
primary backing
backing material
back side
ethylene polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US10/418,227
Inventor
Julie Brumbelow
Von Moody
Wesley Mullinax
John Bieser
James Goins
David Kelley
Lichih Peng
Robert Turley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shaw Industries Inc
Original Assignee
Shaw Industries Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US3941297P priority Critical
Priority to US3958497P priority
Priority to US3958797P priority
Priority to US3941197P priority
Priority to US3921797P priority
Priority to US3240998A priority
Priority to US71550000A priority
Application filed by Shaw Industries Inc filed Critical Shaw Industries Inc
Priority to US10/418,227 priority patent/US20030211280A1/en
Publication of US20030211280A1 publication Critical patent/US20030211280A1/en
Application status is Abandoned legal-status Critical

Links

Images

Classifications

    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N7/00Flexible sheet materials not otherwise provided for, e.g. textile threads, filaments, yarns or tow, glued on macromolecular material, e.g. fibrous top layer with resin backing, plastic naps or dots on fabrics
    • D06N7/0063Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf
    • D06N7/0071Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04Interconnection of layers
    • B32B7/12Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • DTEXTILES; PAPER
    • D05SEWING; EMBROIDERING; TUFTING
    • D05CEMBROIDERING; TUFTING
    • D05C17/00Embroidered or tufted products; Base fabrics specially adapted for embroidered work; Inserts for producing surface irregularities in embroidered products
    • D05C17/02Tufted products
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N7/00Flexible sheet materials not otherwise provided for, e.g. textile threads, filaments, yarns or tow, glued on macromolecular material, e.g. fibrous top layer with resin backing, plastic naps or dots on fabrics
    • D06N7/0063Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf
    • D06N7/0071Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing
    • D06N7/0076Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing the back coating or pre-coat being a thermoplastic material applied by, e.g. extrusion coating, powder coating or laminating a thermoplastic film
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N7/00Flexible sheet materials not otherwise provided for, e.g. textile threads, filaments, yarns or tow, glued on macromolecular material, e.g. fibrous top layer with resin backing, plastic naps or dots on fabrics
    • D06N7/0063Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf
    • D06N7/0071Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing
    • D06N7/0078Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing the back coating or pre-coat being applied as a hot melt
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N7/00Flexible sheet materials not otherwise provided for, e.g. textile threads, filaments, yarns or tow, glued on macromolecular material, e.g. fibrous top layer with resin backing, plastic naps or dots on fabrics
    • D06N7/0063Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf
    • D06N7/0071Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing
    • D06N7/0081Floor covering on textile basis comprising a fibrous top layer being coated at the back with at least one polymer layer, e.g. carpets, rugs, synthetic turf characterised by their backing, e.g. pre-coat, back coating, secondary backing, cushion backing with at least one extra fibrous layer at the backing, e.g. stabilizing fibrous layer, fibrous secondary backing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2471/00Floor coverings
    • B32B2471/02Carpets
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2201/00Chemical constitution of the fibres, threads or yarns
    • D06N2201/02Synthetic macromolecular fibres
    • D06N2201/0254Polyolefin fibres
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2203/00Macromolecular materials of the coating layers
    • D06N2203/04Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D06N2203/042Polyolefin (co)polymers
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2205/00Condition, form or state of the materials
    • D06N2205/04Foam
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2209/00Properties of the materials
    • D06N2209/10Properties of the materials having mechanical properties
    • D06N2209/105Resistant to abrasion, scratch
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2213/00Others characteristics
    • D06N2213/03Fibrous web coated on one side with at least two layers of the same polymer type, e.g. two coatings of polyolefin
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N2213/00Others characteristics
    • D06N2213/06Characteristics of the backing in carpets, rugs, synthetic lawn
    • D06N2213/065Two back coatings one next to the other
    • DTEXTILES; PAPER
    • D10INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10BINDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2321/00Fibres made from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D10B2321/02Fibres made from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds polyolefins
    • D10B2321/022Fibres made from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds polyolefins polypropylene
    • DTEXTILES; PAPER
    • D10INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10BINDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2331/00Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products
    • D10B2331/02Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyamides
    • DTEXTILES; PAPER
    • D10INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10BINDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2331/00Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products
    • D10B2331/04Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyesters, e.g. polyethylene terephthalate [PET]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/23907Pile or nap type surface or component
    • Y10T428/23957Particular shape or structure of pile
    • Y10T428/23964U-, V-, or W-shaped or continuous strand, filamentary material
    • Y10T428/23971Continuous strand with adhesive bond to backing
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/23907Pile or nap type surface or component
    • Y10T428/23979Particular backing structure or composition
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/23907Pile or nap type surface or component
    • Y10T428/23986With coating, impregnation, or bond
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/23907Pile or nap type surface or component
    • Y10T428/23993Composition of pile or adhesive

Abstract

The present invention pertains to carpet and method of making it. In one aspect, the carpet includes (a) a primary backing which has a face and a back surface, (b) a plurality of fibers attached to the primary backing and extending from the face of the primary backing and exposed at the back surface of the primary backing, (c) an adhesive backing, (d) an optional secondary backing adjacent to the adhesive backing, and (e) at least one homogeneously branched linear ethylene polymer. The method includes extrusion coating at least one homogeneously branched linear ethylene polymer onto the back surface of a primary backing to provide an adhesive backing. The method can include additional steps or procedures, either separately or in various combinations. Additional steps and procedures include preheating the primary backing prior the extrusion step, multilayer adhesive backings, washing or scouring the primary backing prior the extrusion step, and utilizing adhesive polymeric additives, high heat content fillers, blowing agents and/or implosion agents. The constructions and methods described herein are particularly suited for making carpet tile.

Description

    CROSS-REFERENCE TO RELATED APPLICATIONS
  • This application is a continuation-in-part application from U.S. Provisional Application No. 60/039,217 filed Feb. 28, 1997, which application was in turn related to pending application Ser. No. ______, entitled “ETHYLENE POLYMER CARPET, CARPET BACKINGS AND METHODS”; Ser. No. ______ entitled “CARPET BACKINGS AND METHODS USING SUBSTANTIALLY LINEAR ETHYLENE POLYMERS METHODS”; Ser. No. ______ entitled “CARPETS, CARPET BACKINGS AND METHODS USING SUBSTANTIALLY LINEAR ETHYLENE POLYMERS METHODS”; and Ser. No. ______ entitled “CARPETS, CARPET BACKINGS AND METHODS USING HOMOGENEOUS LINEAR ETHYLENE POLYMERS,” all four of which were filed on Feb. 28, 1997, and the disclosures of which are incorporated herein by reference.[0001]
  • FIELD OF THE INVENTION
  • This invention relates to carpets and methods of making carpets, wherein, for each, the carpets comprise at least one flexible ethylene polymer backing material. In a particular instance, the invention relates to a carpet and a method of making a carpet by an extrusion coating technique, wherein for each the carpet comprises a backing material comprised of at least one homogeneously branched linear ethylene polymer. [0002]
  • BACKGROUND OF THE INVENTION
  • The present invention pertains to any carpet constructed with a primary backing material and includes tufted carpet and non-tufted carpet such as needle punched carpet. Although specific embodiments are amenable to tufted and non-tufted carpet, tufted carpet is preferred. [0003]
  • As illustrated in FIG. 1, tufted carpets are composite structures which include yam (which is also known as a fiber bundle), a primary backing material having a face surface and a back surface, an adhesive backing material and, optionally, a secondary backing material. To form the face surface of tufted carpet, yarn is tufted through the primary backing material such that the longer length of each stitch extends through the face surface of the primary backing material. Typically, the primary backing material is made of a woven or non-woven material such as a thermoplastic polymer, most commonly polypropylene. [0004]
  • The face of a tufted carpet can generally be made in three ways. First, for loop pile carpet, the yarn loops formed in the tufting process are left intact. Second, for cut pile carpet, the yam loops are cut, either during tufting or after, to produce a pile of single yarn ends instead of loops. Third, some carpet styles include both loop and cut pile. One variety of this hybrid is referred to as tip-sheared carpet where loops of differing lengths are tufted followed by shearing the carpet at a height so as to produce a mix of uncut, partially cut, and completely cut loops. Alternatively, the tufting machine can be configured so as to cut only some of the loops, thereby leaving a pattern of cut and uncut loops. Whether loop, cut, or a hybrid, the yarn on the back side of the primary backing material comprises tight, unextended loops. [0005]
  • The combination of tufted yarn and a primary backing material without the application of an adhesive backing material or secondary backing material is referred to in the carpet industry as raw tufted carpet or greige goods. Greige goods become finished tufted carpet with the application of an adhesive backing material and an optional secondary backing material to the back side of the primary backing material. Finished tufted carpet can be prepared as broad-loomed carpet in rolls typically 6 or 12 feet wide. Alternatively, carpet can be prepared as carpet tiles, typically 18 inches square in the United States and 50 cm. square elsewhere. [0006]
  • The adhesive backing material is applied to the back face of the primary backing material to affix the yarn to the primary backing material. Typically, the adhesive backing material is applied by a pan applicator using a roller, a roll over a roller or a bed, or a knife (also called a doctor blade) over a roller or a bed. Properly applied adhesive backing materials do not substantially pass through the primary backing material. [0007]
  • Most frequently, the adhesive backing material is applied as a single coating or layer. The extent or tenacity to which the yarn is affixed is referred to as tuft lock or tuft bind strength. Carpets with sufficient tuft bind strength exhibit good wear resistance and, as such, have long service lives. Also, the adhesive backing material should substantially penetrate the yarn (fiber bundle) exposed on the backside of the primary backing material and should substantially consolidate individual fibers within the yarn. Good penetration of the yarn and consolidation of fibers yields good abrasion resistance. Moreover, in addition to good tuft bind strength and abrasion resistance, the adhesive material should also impart or allow good flexibility to the carpet in order to facilitate easy installation of the carpet. [0008]
  • The secondary backing material is typically a lightweight scrim made of woven or non-woven material such as a thermoplastic polymer, most commonly polypropylene. The secondary backing material is optionally applied to the backside of the carpet onto the adhesive backing material, primarily to provide enhanced dimensional stability to the carpet structure as well as to provide more surface area for the application of direct glue-down adhesives. [0009]
  • Alternative backing materials may also be applied to the backside of the adhesive backing material and/or to the backside of the secondary backing material, if present. Alternative backing materials may include foam cushioning (e.g. foamed polyurethane) and pressure sensitive floor adhesives. Alternative backing materials may also be applied, for example, as webbing with enhanced surface area, to facilitate direct glue-down adhesive installations (e.g., in contract commercial carpeting, automobile carpet and airplane carpet where the need for cushioning is ofttimes minimal). Alternative backing materials can also be optionally applied to enhance barrier protection respecting moisture, insects, and foodstuffs as well as to provide or enhance fire suppression, thermal insulation, and sound dampening properties of the carpet. [0010]
  • Known adhesive backing materials include curable latex, urethane or vinyl systems, with latex systems being most common. Conventional latex systems are low viscosity, aqueous compositions that are applied at high carpet production rates and offer good fiber-to-backing adhesion, tuft bind strength and adequate flexibility. Generally, excess water is driven off and the latex is cured by passing through a drying oven. Styrene butadiene rubbers (SBR) are the most common polymers used for latex adhesive backing materials. Typically, the latex backing system is heavily filled with an inorganic filler such as calcium carbonate or Aluminum Trihydrate and includes other ingredients such as antioxidants, antimicrobials, flame retardants, smoke suppressants, wetting agents, and froth aids. [0011]
  • Conventional latex adhesive backing systems can have certain drawbacks. As one important drawback, typical latex adhesive backing systems do not provide a moisture barrier. Another possible drawback, particularly with a carpet having polypropylene yarn and polypropylene primary and secondary backing materials, is the dissimilar polymer of latex systems along with the inorganic filler can reduce the recyclability of the carpet. [0012]
  • In view of these drawbacks, some in the carpet industry have begun seeking suitable replacements for conventional latex adhesive backing systems. One alternative is the use of urethane adhesive backing systems. In addition to providing adequate adhesion to consolidate the carpet, urethane backings generally exhibit good flexibility and barrier properties and, when foamed, can eliminate the need for separate underlayment padding (i.e., can constitute a direct glue-down unitary backing system). However, urethane backing systems also have important drawbacks, including their relatively high cost and demanding curing requirements which necessitate application at slow carpet production rates relative to latex systems. [0013]
  • Thermoplastic polyolefins such as ethylene vinyl acetate (EVA) copolymers and low density polyethylene (LDPE) have also been suggested as adhesive backing materials due in part to their low cost, good moisture stability and no-cure requirements. Various methods are available for applying polyolefin backing materials, including powder coating, hot melt application and extruded film or sheet lamination. However, using polyolefins to replace latex adhesive backings can also present difficulties. For example, U.S. Pat. No. 5,240,530, Table A at Col. 10, indicates that ordinary polyolefin resins possess inadequate adhesion for use in carpet construction. Additionally, relative to latex and other cured systems, ordinary polyolefins have relatively high application viscosities and relatively high thermal requirements. That is, ordinary thermoplastic polyolefins are characterized by relatively high melt viscosities and high recrystallization or solidification temperatures relative to the typical aqueous viscosities and cure temperature requirements characteristic of latex and other cured (thermosetting) systems. [0014]
  • Even ordinary elastomeric polyolefins, i.e. polyolefins having low crystallinities, generally have relatively high viscosities and relatively high recrystallization temperatures. High recrystallization temperatures result in relatively short molten times during processing and, combined with high melt viscosities can make it difficult to achieve adequate penetration of the yarn, especially at conventional adhesive backing application rates. [0015]
  • One method for overcoming the viscosity and recrystallization deficiencies of ordinary polyolefins is to formulate the polyolefin resin as a hot melt adhesive which usually involves formulating low molecular weight polyolefins with waxes, tackifiers, various flow modifiers and/or other elastomeric materials. Ethylene/vinyl acetate (EVA) copolymers, for example, have been used in formulated hot melt adhesive backing compositions and other polyolefins compositions have also been proposed as hot melt backing compositions. For example, in U.S. Pat. No. 3,982,051, Taft et al. disclose that a composition comprising an ethylene/vinyl acetate copolymer, atactic polypropylene and vulcanized rubber is useful as a hot melt carpet backing adhesive. [0016]
  • Unfortunately, hot melt adhesive systems are generally considered not completely suitable replacements for conventional latex adhesive backings. Typical hot melt systems based on EVA and other copolymers of ethylene and unsaturated comonomers can require considerable formulating and yet often yield inadequate tuft bind strengths. However, the most significant deficiency of typical hot melt system is their melt strengths which are generally too low to permit application by a direct extrusion coating technique. As such, polyolefin hot melt systems are typically applied to primary backings by relatively slow, less efficient techniques such as by the use of heated doctor blades or rotating melt transfer rollers. [0017]
  • While unformulated high pressure low density polyethylene (LDPE) can be applied by a conventional extrusion coating technique, LDPE resins typically have poor flexibility which can result in excessive carpet stiffness. Conversely, those ordinary polyolefins that have improved flexibility, such as ultra low density polyethylene (ULDPE) and ethylene/propylene interpolymers, still do not possess sufficient flexibility, have excessively low melt strengths and/or tend to draw resonate during extrusion coating. To overcome extrusion coating difficulties, ordinary polyolefins with sufficient flexibility can be applied by lamination techniques to insure adequate yarn-to-backing adhesion; however, lamination techniques are typically expensive and can result in extended production rates relative to direct extrusion coating techniques. [0018]
  • Known examples of flexible polyolefin backing materials are disclosed in U.S. Pat. Nos. 3,390,035; 3,583,936; 3,745,054; and 3,914,489. In general, these disclosures describe hot melt adhesive backing compositions based on an ethylene copolymer, such as, ethylene/vinyl acetate (EVA), and waxes. Known techniques for enhancing the penetration of hot melt adhesive backing compositions through the yarn include applying pressure while the greige good is in contact with rotating melt transfer rollers as described, for example, in U.S. Pat. No. 3,551,231. [0019]
  • Another known technique for enhancing the effectiveness of hot melt systems involve using pre-coat systems. For example, U.S. Pat. Nos. 3,684,600; 3,583,936; and 3,745,054, describe the application of low viscosity aqueous pre-coats to the back surface of the primary backing material prior the application of a hot melt adhesive composition. The hot melt adhesive backing systems disclosed in these patents are derived from multi-component formulations based on functional ethylene polymers such as, for example, ethylene/ethyl acrylate (EEA) and ethylene/vinyl acetate (EVA) copolymers. [0020]
  • Although there are various systems known in the art of carpet backings, there remains a need for a thermoplastic polyolefin carpet backing system which provides adequate tuft bind strength, good abrasion resistance and good flexibility to replace cured latex backing systems. A need also remains for an application method which permits high carpet production rates while achieving the desired characteristics of good tuft bind strength, abrasion resistance, barrier properties and flexibility. Finally, there is also a need to provide a carpet structure having fibers and backing materials that are easily recyclable without the necessity of extensive handling and segregation of carpet component materials. [0021]
  • SUMMARY OF THE INVENTION
  • In accordance with one aspect of the present invention, a carpet comprises a plurality of fibers, a primary backing material having a face and a back side, an adhesive backing material and an optional secondary backing material, the plurality of fibers attached to the primary backing material and protruding from the face of the primary backing material and exposed on the back side of the primary backing material, the adhesive backing material disposed on the back side of the primary backing material and the optional secondary backing material adjacent to the adhesive backing material, wherein at least one of the plurality of fibers, the primary backing material, the adhesive backing material or the optional secondary backing material is comprised of at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent. [0022]
  • Another aspect of the present invention is a method of making a carpet, the carpet including a plurality of fibers, a primary backing material having a face and a back side, an adhesive backing material and an optional secondary-backing material, the plurality of fibers attached to the primary backing material and protruding from the face of the primary backing material and exposed on the back side of the primary backing material, the method comprising the step of extrusion coating the adhesive backing material or the optional secondary backing material onto the back side of the primary backing material, wherein the extrusion coated adhesive backing material or optional secondary backing material is comprised of at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent. [0023]
  • A third aspect of the present invention is a method of making a carpet, the carpet comprising (i) a greige good having a face surface comprised of a plurality of fibers attached to a primary backing material having a face and a back side and (ii) an adhesive backing material which comprises at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent and which is in intimate contact with the back side of the primary backing material and has substantially penetrated and substantially consolidated the fibers, the method comprising extrusion coating the adhesive backing material onto the back side of the primary backing material and at least one additional step selected from the group consisting of [0024]
  • (a) preheating the greige good prior to the application of the adhesive backing material, [0025]
  • (b) during the extrusion coating of the adhesive backing material, while at a temperature greater than or equal to the softening point of the adhesive backing material, subjecting the adhesive backing material to a vacuum to draw the adhesive backing material onto the back side of the primary backing material, [0026]
  • (c) during the extrusion coating of the adhesive backing material, while at a temperature greater than or equal to the softening point of the adhesive backing material, subjecting the adhesive backing material to a positive air pressure device in addition to nip roll pressure to force the adhesive backing material onto the back side of the primary backing material, and [0027]
  • (d) heat soaking the carpet after application of the adhesive backing material onto the back side of the primary backing material. [0028]
  • A fourth aspect of the present invention is a carpet comprising a primary backing material having a face and a back side, yarn attached to the primary backing material, an adhesive backing material and an optional secondary backing material, wherein the adhesive backing material comprises at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent and is in intimate contact with the back side of the primary backing material and has substantially penetrated the yarn, and wherein the adhesive backing material or optional secondary backing material is comprised of an effective amount of at least one additive selected from the group consisting of a blowing agent and high heat content filler with the proviso that where the blowing agent is selected, the adhesive backing material or the optional secondary backing material is further characterized as having a substantially foamed, frothed or expanded non-collapsed matrix. [0029]
  • A fifth aspect of the present invention is a method of making a carpet, the carpet comprising yarn attached to a primary backing material and an adhesive backing material, the adhesive backing material comprises at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent, and wherein the adhesive backing material is in intimate contact with the primary backing material and has substantially penetrated and substantially consolidated the yarn, the method comprising the step of adding an effective amount of a high heat content filler to the adhesive backing material to substantially extend the semi-molten or molten time of the adhesive backing material and enhance the penetration of the adhesive backing material into the yarn. [0030]
  • A sixth aspect of the invention is a method of making a carpet, the carpet comprising yarn attached to a primary backing material having a face and a back side and an adhesive backing material comprised of at least one first and at least one second ethylene polymer layers, wherein the at least one first ethylene polymer layer is in intimate contact with the back surface of the primary backing material and the at least one first ethylene polymer layer has substantially penetrated and substantially consolidated the yam, the at least one first ethylene polymer layer having a higher melt index than the at least one second ethylene polymer layer and one of the at least first or at least second ethylene polymer layer comprising at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent, the method comprising the steps of applying the at least one first ethylene polymer layer directly onto the back surface of the primary backing material and simultaneously or sequentially applying the at least one second ethylene polymer layer onto the at least one first ethylene polymer layer. [0031]
  • A seventh aspect of the present invention is a method of making a carpet, the carpet having a foamed, frothed or expanded adhesive backing material matrix and comprising yarn attached to a primary backing material, the adhesive backing material comprising at least one ethylene polymer and is in intimate contact with the primary backing material and has substantially penetrated and substantially consolidated the yarn, the method comprising the step of adding an effective amount of at least one blowing agent to the adhesive backing material and thereafter activating the blowing agent to foam, froth or expand the adhesive backing material. [0032]
  • An eighth aspect of the present invention is a method of making a carpet, the carpet having a collapsed, non-expanded adhesive backing material matrix and comprising yarn attached to a primary backing material, the adhesive backing material comprising at least one ethylene polymer and is in intimate contact with the primary backing material and has substantially penetrated and substantially consolidated the yarn, the method comprising the step of adding an effective amount of at least one implosion agent to the adhesive backing material and thereafter activating the implosion agent during an extrusion coating step such that molten or semi-molten polymer is forced into the free space of yarn exposed on the backside of the primary backing material. [0033]
  • A ninth aspect of the present invention is a method of making a carpet, the carpet having a face surface and comprising yarn, a primary backing material, an adhesive backing material and an optional secondary backing material, wherein the primary backing material has a back surface opposite the face surface of the carpet, the yarn is attached to the primary backing material, the adhesive backing material is applied to the back surface of the primary backing material and the optional secondary backing material is applied onto the adhesive backing material, the method comprising the step of scouring or washing the back surface of the primary backing material prior to the application of the adhesive backing material to substantially remove or displace processing materials. [0034]
  • A tenth aspect of the present invention is a carpet comprising a primary backing material having a face and a back side, yarn attached to the primary backing material, an adhesive backing material and an optional secondary backing material, wherein the adhesive backing material comprises at least one homogeneously branched ethylene polymer characterized as having a short chain branching distribution index (SCBDI) of greater than or equal to 50 percent, at least one adhesive polymeric additive and is in intimate contact with the back side of the primary backing material and has substantially penetrated the yarn. [0035]
  • An eleventh aspect of the present invention is a method of making a carpet, and the carpet so made, which includes the steps of providing a primary backing material having a face and a back side, tufting a yarn into the primary backing material to produce a carpet pile on the face side of the primary backing material and loops of the yarn on the back side of the primary backing material, providing an aqueous dispersion of polyolefin particles, applying the dispersion to the back side of the primary backing material, and then applying heat to the dispersion to dry the dispersion and to at least partially melt the polyolefin particles and thereby fix the loops of yarn to the primary backing material. [0036]
  • A twelfth aspect of the invention is a method of making a carpet, and the carpet so made, which method includes the steps of providing a primary backing material having a face and a back side, tufting a yarn into the primary backing material to produce a carpet pile on the face side of the primary backing material and loops of the yarn on the back side of the primary backing material, extruding a first sheet of a first thermoplastic material to the back side of the primary backing, and extruding a second sheet of a second thermoplastic material adjacent the first sheet. In this twelfth aspect, the melt viscosity of the thermoplastic material in the first sheet is lower than the melt viscosity of the thermoplastic material in the second sheet so as to provide for enhanced penetration of the thermoplastic material in the first sheet into at least one of the primary backing material or the loops of yarn on the back side of the primary backing material. [0037]
  • A thirteenth aspect of the present invention is a method of making a carpet with an extruded sheet as part of its backing wherein prior to the extruding step, at least the back side of the primary backing and loops of the yarn on the back side of the primary backing are treated to remove undesirable chemicals from the surface and thereby enhance the adhesion of the extruded sheet. [0038]
  • A fourteenth aspect of the present invention is a carpet tile with an extruded backing. Preferably, the carpet tile is made with a first and second extruded sheet and a reinforcing material embedded between the two sheets.[0039]
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is an illustration of a tufted carpet 10. [0040]
  • FIG. 2 is a schematic representation of an extrusion coating line [0041] 20 for making a carpet 70.
  • FIG. 3 consists of scanning electron microscopy photomicrographs at 20× magnification ([0042] 3 a) and 50× magnification (3 b) illustrating the interfaces of the various carpet components of Example 14.
  • FIG. 4 consists of scanning electron microscopy photomicrographs at 20× magnification ([0043] 4 a) and 50× magnification (4 b) illustrating the interfaces of the various carpet components of Example 22.
  • FIG. 5 is a X-Y plot of the effect of fiber bundle penetration by the adhesive backing material on the abrasion resistance performance of polypropylene and nylon carpet samples. [0044]
  • FIG. 6 is a cross-section showing the construction of a carpet tile in accordance with the present invention. [0045]
  • FIG. 7 is a schematic representation of an extrusion coating line for making carpet tile according to the present invention.[0046]
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • The terms “intimate contact,” “substantial encapsulation,” and/or “substantial consolidation” are used herein to refer to mechanical adhesion or mechanical interactions (as opposed to chemical bonding) between dissimilar carpet components, irrespective of whether or not one or more carpet component is capable of chemically interacting with another carpet component. With respect to the mechanical adhesion or interactions of the present invention, there may be some effective amount of intermixing or inter-melting of polymeric materials; however, there is no continuous or integral fusing of various components as determined from visual inspection of photomicrographs (at 20× magnification) of the various carpet interfaces. Within this meaning, fusion of yarn or fiber bundles or of individual fibers to one another within a fiber bundle is not considered integral fusion in itself since fibers are referred to herein as one carpet component. [0047]
  • The term “intimate contact” refers to the mechanical interaction between the back surface of the primary backing material and the adhesive backing material. The term “substantial encapsulation” refers to the adhesive backing material significantly surrounding the yam or fiber bundles at or in immediate proximity to the interface between the back surface of the primary backing material and the adhesive backing material. The term “substantial consolidation” refers to the overall integrity and dimensional stability of the carpet that is achieved by substantially encapsulating the yarn or fiber bundles and intimately contacting the back surface of the primary backing material with the adhesive backing material. A substantially consolidated carpet possesses good component cohesiveness and good delamination resistance with respect to the various carpet components. [0048]
  • The term “integral fusing” is used herein in the same sense as known in the art and refers to heat bonding of carpet components using a temperature above the melting point of the adhesive backing material. Integral fusing occurs when the adhesive backing material comprises the same polymer as either the fibers or primary backing material or both. However, integral fusing does not occur when the adhesive backing material comprises a different polymer than the fibers and primary backing material. By the term “same polymer,” it is meant that the monomer units of the polymers are of the same chemistry, although their molecular or morphological attributes may differ. Conversely, by the term “different polymer,” it is meant that, irrespective of any molecular or morphological differences, the monomer units of the polymers are of different chemistries. Thus, in accordance with the various definitions of the present invention, a polypropylene primary backing material and a polyethylene adhesive backing material would not integrally fuse because these carpet components are of different chemistries. [0049]
  • The term “carpet component” is used herein to refer separately to carpet fiber bundles, the primary backing material, the adhesive backing material and the optional secondary backing material. [0050]
  • The term “extrusion coating” is used herein in its conventional sense to refer to an extrusion technique wherein a polymer composition usually in pellet-form is heated in an extruder to a temperature elevated above its melt temperature and then forced through a slot die to form a semi-molten or molten polymer web. The semi-molten or molten polymer web is continuously drawn down onto a continuously fed greige good to coat the backside of the greige good with the polymer composition. FIG. 2 illustrates an extrusion process of the present invention wherein, at the nip, the face surface of the greige good is oriented towards the chill roll and the back surface of the adhesive backing material oriented is towards the nip pressure roll. Extrusion coating is distinct from a lamination technique. [0051]
  • The term “lamination technique” is used herein in its conventional sense refer to applying adhesive backing materials to greige goods by first forming the adhesive backing material as a solidified or substantially solidified film or sheet and thereafter, in a separate processing step, reheating or elevating the temperature of the film or sheet before applying it to the back surface of the primary backing material. [0052]
  • The term “heat content” is used herein to refer to the mathematical product of the heat capacity and specific gravity of a filler. Fillers characterized as having high heat content are used in specific embodiments of the present invention to extend the solidification or molten time of adhesive backing materials. The [0053] Handbook for Chemical Technicians, Howard J. Strauss and Milton Kaufmann, McGraw Hill Book Company, 1976, Sections 14 and 2-1 provides information on the heat capacity and specific gravity of select mineral fillers. The fillers suitable for use in the present invention do not change their physical state (i.e., remain a solid material) over the extrusion coating processing temperature ranges of the present invention. Preferred high heat content fillers possess a combination of a high specific gravity and a high heat capacity.
  • The term “implosion agent” is used herein to refer to the use of conventional blowing agents or other compounds which out-gas or cause out-gassing when activated by heat, usually at some particular activation temperature. In the present invention, implosion agents are used to implode or force adhesive backing material into the free space of yarn or fiber bundles. [0054]
  • The term “processing material” is used herein to refer to substances such as spin finishing waxes, equipment oils, sizing agents and the like, which can interfere with the adhesive or physical interfacial interactions of adhesive backing materials. Processing materials can be removed or displaced by a scouring or washing technique of the present invention whereby improved mechanical bonding is accomplished. [0055]
  • The terms “polypropylene carpet” and “polypropylene greige goods” are used herein to mean a carpet or greige goods substantially comprised of polypropylene fibers, irrespective of whether the primary backing material for the carpet or greige good is comprised of polypropylene or some other material. [0056]
  • The terms “nylon carpet” and “nylon greige goods” are used herein to mean a carpet or greige goods substantially comprised of nylon fibers, irrespective of whether the primary backing material for the carpet or greige good is comprised of nylon or some other material. [0057]
  • The term “linear” as used to describe ethylene polymers is used herein to mean the polymer backbone of the ethylene polymer lacks measurable or demonstrable long chain branches, e.g., the polymer is substituted with an average of less than 0.01 long branch/1000 carbons. [0058]
  • The term “homogeneous ethylene polymer” as used to describe ethylene polymers is used in the conventional sense in accordance with the original disclosure by Elston in U.S. Pat. No. 3,645,992, to refer to an ethylene polymer in which the comonomer is randomly distributed within a given polymer molecule and wherein substantially all of the polymer molecules have substantially the same ethylene to comonomer molar ratio. As defined herein, both substantially linear ethylene polymers and homogeneously branched linear ethylene are homogeneous ethylene polymers. [0059]
  • Homogeneously branched ethylene polymers-are homogeneous ethylene polymers that possess short chain branches and that are characterized by a relatively high short chain branching distribution index (SCBDI) or relatively high composition distribution branching index (CDBI). That is, the ethylene polymer has a SCBDI or CDBI greater than or equal to 50 percent, preferably greater than or equal to 70 percent, more preferably greater than or equal to 90 percent and essentially lack a measurable high density (crystalline) polymer fraction. [0060]
  • The SCBDI or CDBI is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content and represents a comparison of the comonomer distribution in the polymer to the comonomer distribution expected for a Bernoullian distribution. [0061]
  • The SCBDI or CDBI of polyolefins can be conveniently calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation (abbreviated herein as “TREF”) as described, for example, by Wild et al., [0062] Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), L. D. Cady, “The Role of Comonomer Type and Distribution in LLDPE Product Performance,” SPE Regional Technical Conference, Quaker Square Hilton, Akron, Ohio, October 1-2, pp. 107-119 (1985), or in U.S. Pat. Nos. 4,798,081 and 5,008,204. However, the preferred TREF technique does not include purge quantities in SCBDI or CDBI calculations. More preferably, the comonomer distribution of the polymer and SCBDI or CDBI are determined using 13C NMR analysis in accordance with techniques described, for example, in U.S. Pat. No. 5,292,845 and by J.C. Randall in Rev. Macromol. Chem. Phys., C29, pp. 201-317.
  • The terms “homogeneously branched linear ethylene polymer” and “homogeneously branched linear ethylene/[0063] a-olefin polymer” means that the olefin polymer has a homogeneous or narrow short branching distribution (i.e., the polymer has a relatively high SCBDI or CDBI) but does not have long chain branching. That is, the linear ethylene polymer is a homogeneous ethylene polymer characterized by an absence of long chain branching. Such polymers can be made using polymerization processes (e.g., as described by Elston in U.S. Pat. No. 3,645,992) which provide a uniform short chain branching distribution (i.e., homogeneously branched). In his polymerization process, Elston uses soluble vanadium catalyst systems to make such polymers, however others, such as Mitsui Petrochemical Industries and Exxon Chemical Company, have reportedly used so-called single site catalyst systems to make polymers having a homogeneous structure similar to polymer described by Elston. U.S. Pat. No. 4,937,299 to Ewen et al. and U.S. Pat. No. 5,218,071 to Tsutsui et al. disclose the use of metallocene catalysts, such as catalyst systems based on hafnium, for the preparation of homogeneously branched linear ethylene polymers. Homogeneously branched linear ethylene polymers are typically characterized as having a molecular weight distribution, Mw/Mn, of less than 3, preferably less than 2.8, more preferably less than 2.3. Commercial examples of suitable homogeneously branched linear ethylene polymers include those sold by Mitsui Petrochemical Industries as Tafmer™ resins and by Exxon Chemical Company as Exact™ resins and Exceed™ resins.
  • The terms “homogeneous linearly branched ethylene polymer” or “homogeneously branched linear ethylene/[0064] a-olefin polymer” do not refer to high pressure branched polyethylene which is known to those skilled in the art to have numerous long chain branches. The term “homogeneous linear ethylene polymer” generically refers to both linear ethylene homopolymers and to linear ethylene/a-olefin interpolymers. A linear ethylene/a-olefin interpolymer possesses short chain branching and n the a-olefin is typically at least one C3-C20 a-olefin (e.g., propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene).
  • When used in reference to an ethylene homopolymer (i.e., a high density ethylene polymer not containing any comonomer and thus no short chain branches), the term “homogeneous ethylene polymer” or “homogeneous linear ethylene polymer” means the polymer was made using a homogeneous catalyst system such as, for example, that described Elston or Ewen or those described by Canich in U.S. Pat. Nos. 5,026,798 and 5,055,438, or by Stevens et al. in U.S. Pat. No. 5,064,802. [0065]
  • The term “substantially linear ethylene polymer” is used herein to refer specially to homogeneously branched ethylene polymers that have long chain branching. The term does not refer to heterogeneously or homogeneously branched ethylene polymers that have a linear polymer backbone. For substantially linear ethylene polymers, the long chain branches have the same comonomer distribution as the polymer backbone, and the long chain branches can be as long as about the same length as the length of the polymer backbone to which they are attached. The polymer backbone of substantially linear ethylene polymers is substituted with about 0.01 long chain branches/1000 carbons to about 3 long chain branches/1000 carbons, more preferably from about 0.01 long chain branches/1000 carbons to about 1 long chain branches/1000 carbons, and especially from about 0.05 long chain branches/1000 carbons to about 1 long chain branches/1000 carbons. [0066]
  • Long chain branching is defined herein as a chain length of at least 6 carbons, above which the length cannot be distinguished using [0067] 13C nuclear magnetic resonance spectroscopy. The presence of long chain branching can be determined in ethylene homopolymers by using 13C nuclear magnetic resonance (NMR) spectroscopy and is quantified using the method described by Randall (Rev. Macromol. Chem. Phys., C29, V. 2&3, p. 285-297).
  • Although current [0068] 13C nuclear magnetic resonance spectroscopy cannot determine the length of a long chain branch in excess of six carbon atoms, there are other known techniques useful for determining the presence of long chain branches in ethylene polymers, including ethylene/1-octene interpolymers. Two such methods are gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS) and gel permeation chromatography coupled with a differential viscometer detector (GPC-DV). The use of these techniques for long chain branch detection and the underlying theories have been well documented in the literature. See, e.g., Zimm, G. H. and Stockmayer, W. H., J. Chem. Phys., 17,1301 (1949) and Rudin, A., Modern Methods of Polymer Characterization, John Wiley & Sons, New York (1991) pp. 103-112.
  • A. Willem deGroot and P. Steve Chum, both of The Dow Chemical Company, at the Oct. 4, 1994 conference of the Federation of Analytical Chemistry and Spectroscopy Society (FACSS) in St. Louis, Mo., presented data demonstrating that GPC-DV is a useful technique for quantifying the presence of long chain branches in substantially linear ethylene polymers. In particular, deGroot and Chum found that the level of long chain branches in substantially linear ethylene homopolymer samples measured using the Zimm-Stockmayer equation correlated well with the level of long chain branches measured using [0069] 13C NMR.
  • Further, deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can account for the molecular weight increase attributable to octene short chain branches by knowing the mole percent octene in the sample. By deconvoluting the contribution to molecular weight increase attributable to 1-octene short chain branches, deGroot and Chum showed that GPC-DV may be used to quantify the level of long chain branches in substantially linear ethylene/octene copolymers. [0070]
  • DeGroot and Chum also showed that a plot of Log(I[0071] 2, melt index) as a function of Log(GPC Weight Average Molecular Weight) as determined by GPC-DV illustrates that the long chain branching aspects (but not the extent of long branching) of substantially linear ethylene polymers are comparable to that of high pressure, highly branched low density polyethylene (LDPE) and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts such as titanium complexes and ordinary homogeneous catalysts such as hafnium and vanadium complexes.
  • For substantially linear ethylene polymers, the long chain branch is longer than the short chain branch that results from the incorporation of the [0072] a-olefin(s) into the polymer backbone. The empirical effect of the presence of long chain branching in the substantially linear ethylene polymers used in the invention is manifested as enhanced rheological properties which are quantified and expressed herein in terms of gas extrusion rheometry (GER) results and/or melt flow, I10/I2, increases.
  • Substantially linear ethylene polymers are homogeneously branched ethylene polymers and are disclosed in U.S. Pat. No. 5,272,236 and U.S. Pat. No. 5,278,272. Homogeneously branched substantially linear ethylene polymers are available from The Dow Chemical Company as AFFINITY™ polyolefin plastomers and from Dupont Dow Elastomers JV as ENGAGE™ polyolefin elastomers. Homogeneously branched substantially linear ethylene polymers can be prepared via the solution, slurry, or gas phase polymerization of ethylene and one or more optional [0073] a-olefin comonomers in the presence of a constrained geometry catalyst, such as the method disclosed in European Patent Application 416,815-A. Preferably, a solution polymerization process is used to manufacture the substantially linear ethylene polymer used in the present invention.
  • The terms “heterogeneous” and “heterogeneously branched” mean that the ethylene polymer is characterized as a mixture of interpolymer molecules having various ethylene to comonomer molar ratios. Heterogeneously branched ethylene polymers are characterized as having a short chain branching distribution index (SCBDI) less than about 30 percent. Heterogeneously branched linear ethylene polymers are available from The Dow Chemical Company as DOWLEX™ linear low density polyethylene and as ATTANE™ ultra-low density polyethylene resins. Heterogeneously branched linear ethylene polymers can be prepared via the solution, slurry or gas phase polymerization of ethylene and one or more optional alpha-olefin comonomers in the presence of a Ziegler Natta catalyst, by processes such as are disclosed in U.S. Pat. No. 4,076,698 to Anderson et al. Heterogeneously branched ethylene polymers are typically characterized as having molecular weight distributions, M[0074] w/Mn, in the range of from 3.5 to 4.1 and, as such, are distinct from substantially linear ethylene polymers and homogeneously branched linear ethylene polymers in regards to both compositional short chain branching distribution and molecular weight distribution.
  • The substantially linear ethylene polymers used in the present invention are not in the same class as homogeneously branched linear ethylene polymers, nor heterogeneously branched linear ethylene polymers, nor are substantially linear ethylene polymers in the same class as traditional highly branched low density polyethylene (LDPE). The substantially linear ethylene polymers useful in this invention surprisingly have excellent processability, even though they have relatively narrow molecular weight distributions (MWDs). Even more surprising, the melt flow ratio (I[0075] 10/I2) of the substantially linear ethylene polymers can be varied essentially independently of the polydispersity index (i.e., molecular weight distribution (Mw/Mn)). This is contrasted with conventional heterogeneously branched linear polyethylene resins which have rheological properties such that as the polydispersity index increases, the I10/I2 value also increases. The rheological properties of substantially linear ethylene polymers also differ from homogeneously branched linear ethylene polymers which have relatively low, essentially fixed I10/I2 ratios.
  • We have discovered that substantially linear ethylene polymers and homogeneously branched linear ethylene polymers (i.e., homogeneously branched ethylene polymers) offer unique advantages for extrusion coated carpet backing applications, especially for commercial and residential carpet markets. Homogeneously branched ethylene polymers (including substantially linear ethylene polymers in particular) have low solidification temperatures, good adhesion to polypropylene, and low modulus relative to conventional ethylene polymers such as low density polyethylene (LDPE), heterogeneously branched linear low density polyethylene (LLDPE), high density polyethylene (HDPE), and heterogeneously branched ultra low density polyethylene (ULDPE). As such, homogeneously branched ethylene polymers are useful for making carpet fibers, primary backing materials, adhesive backing materials and optional secondary backing materials. However, homogeneously branched ethylene polymers are particularly useful as adhesive backing materials for tufted carpet and non-tufted carpet (e.g., needle-punched carpet) and are especially useful for tufted carpets. [0076]
  • In the present invention, during extrusion coating of the backside of carpet to apply an adhesive backing material, properly selected substantially linear ethylene polymers and homogeneously branched linear ethylene polymers show good penetration of carpet yarns (fiber bundles) and also allow good consolidation of the fibers within the yarn. When used for tufted carpets, the tuft bind strength and abrasion resistance of the carpet is increased by the penetration of substantially linear ethylene polymers and homogeneously branched linear ethylene polymers into the yarn. Preferably, a tuft bind (or tuft lock) strength of 3.25 pounds (1.5 kg) or more is achieved, more preferably 5 pounds (2.3 kg) or more and most preferably 7.5 pounds (3.4 kg) or more. In addition to improved penetration of the yarn, tuft bind strength can be also be increased by increasing the molecular weight of the polymer. However, a higher polymer molecular weight selected for improved tuft bind strength is contra to the requirement of a lower polymer molecular weight which is generally needed for good yarn penetration and good extrusion coatability. Also, higher polymer densities are desirable for improved chemical and barrier resistance, yet higher densities invariably yield stiffer carpets. As such, polymer properties must be chosen such that a balance is maintained between extrusion coatability and abrasion resistance as well as between chemical resistance and carpet flexibility. [0077]
  • When carpet greige goods are backed with properly selected substantially linear ethylene polymers or homogeneously branched linear ethylene polymers the low flexural modulus of these polymers offers advantages in ease of carpet installation and general carpet handling. Substantially linear ethylene polymers, in particulars when employed as an adhesive backing material show enhanced mechanical adhesion to polypropylene which improves the consolidation and delamination resistance of the various carpet layers and components, i.e., polypropylene fibers, fiber bundles, the primary backing material, the adhesive backing material and the secondary backing material when optionally applied. Consequently, exceptionally good abrasion resistance and tuft bind strength can be obtained. Good abrasion resistance is especially important in commercial carpet cleaning operations as good abrasion resistance generally improves carpet durability. [0078]
  • Properly selected substantially linear ethylene polymers can allow the elimination of secondary backing materials and as such can result in significant manufacturing cost savings. In addition, carpets adhesively backed with a substantially linear ethylene polymer or homogeneously branched linear ethylene polymer can provide a substantial fluid and particle barrier which enhances the hygienic properties of carpet. [0079]
  • A substantially linear ethylene polymer or homogeneously branched linear ethylene polymer adhesive backing material can allow totally recyclable carpet products particularly where the carpet comprises polypropylene fibers. In addition, the mixture of a substantially linear ethylene polymer or a homogeneously branched linear ethylene polymer with a fiber-grade polypropylene resin can result in an impact modified recycle composition which is useful for injection molding and other molding applications as well as reuse in carpet construction, for example, as the primary backing material or as a blend component of the adhesive backing material polymer composition. That is, polyolefin polymer mixtures can involve sufficiently similar polymer chemistries, compatibilities, and/or miscibilities to permit good recyclability without having sufficient similarities to permit integral fusion. [0080]
  • The preferred homogeneously branched ethylene polymer has a single melting peak between −30° C. and 150° C., as determined using differential scanning calorimetry. The most preferred homogeneously branched ethylene polymer for use in the invention is a substantially linear ethylene polymer characterized as having [0081]
  • (a) a melt flow ratio, I[0082] 10/I2≧5.63,
  • (b) a molecular weight distribution, M[0083] w/Mn, as determined by gel permeation chromatography and defined by the equation:
  • (M w /M n)≦(I10 /I 2)−4.63,
  • (c) a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the linear ethylene polymer has a homogeneously branched short chain branching distribution and no long chain branching, and wherein the substantially linear ethylene polymer and the linear ethylene polymer are simultaneously ethylene homopolymers or interpolymers of ethylene and at least one C[0084] 3-C20 a-olefin and have the same I2 and Mw/Mn and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer.
  • (d) a single differential scanning calorimetry, DSC, melting peak between −30° and 150° C. [0085]
  • Determination of the critical shear rate in regards to melt fracture as well as other rheology properties such as “rheological processing index” (PI), is performed using a gas extrusion rheometer (GER). The gas extrusion rheometer is described by M. Shida, R. N. Shroff and L. V. Cancio in [0086] Polymer Engineering Science, Vol. 17, No. 11, p. 770 (1977), and in “Rheometers for Molten Plastics” by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pp. 97-99. GER experiments are performed at a temperature of 190° C., at nitrogen pressures between about 250 and about 5500 psig (about 1.7 and about 37.4 MPa) using a 0.0754 mm diameter, 20:1 L/D die with an entrance angle of about 180°. For the substantially linear ethylene polymers used herein, the PI is the apparent viscosity (in kpoise) of a material measured by GER at an apparent shear stress of 2.15×106 dyne/cm2 (2.19×104 kg/m2). The substantially linear ethylene polymer for use in the invention have a PI in the range of 0.01 kpoise to 50 kpoise, preferably 15 kpoise or less. The substantially linear ethylene polymers used herein also have a PI less than or equal to 70 percent of the PI of a linear ethylene polymer (either a Ziegler polymerized polymer or a homogeneously branched linear polymer as described by Elston in U.S. Pat. No. 3,645,992) having an I2 and Mw/Mn, each within ten percent of the substantially linear ethylene polymer.
  • An apparent shear stress versus apparent shear rate plot is used to identify the melt fracture phenomena and quantify the critical shear rate and critical shear stress of ethylene polymers. According to Ramamurthy in the [0087] Journal of Rheology, 30(2), 337-357, 1986, above a certain critical flow rate, the observed extrudate irregularities may be broadly classified into two main types: surface melt fracture and gross melt fracture.
  • Surface melt fracture occurs under apparently steady flow conditions and ranges in detail from loss of specular film gloss to the more severe form of “sharkskin.” Herein, as determined using the above-described GER, the onset of surface melt fracture (OSMF) is characterized at the beginning of losing extrudate gloss at which the surface roughness of the extrudate can only be detected by 40× magnification. As described in U.S. Pat. No. 5,278,272, the critical shear rate at the onset of surface melt fracture for the substantially linear ethylene interpolymers and homopolymers is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having essentially the same I[0088] 2 and Mw/Mn.
  • Gross melt fracture occurs at unsteady extrusion flow conditions and ranges in detail from regular (alternating rough and smooth, helical, etc.) to random distortions. For commercial acceptability to maximize the performance properties of films, coatings and moldings, surface defects should be minimal, if not absent The critical shear stress at the onset of gross melt fracture for the substantially linear ethylene polymers used in the invention, especially those having a density >0.910 g/cc, is greater than 4×10[0089] 6 dynes/cm2. The critical shear rate at the onset of surface melt fracture (OSMF) and the onset of gross melt fracture (OGMF) will be used herein based on the changes of surface roughness and configurations of the extrudates extruded by a GER.
  • The homogeneous ethylene polymers used in the present invention are characterized by a single DSC melting peak. The single melting peak is determined using a differential scanning calorimeter standardized with indium and deionized water. The method involves 5-7 mg sample sizes, a “first heat” to about 140° C. which is held for 4 minutes, a cool down at 10°/min. to −30° C. which is held for 3 minutes, and heat up at 10° C./min. to 150° C. for the “second heat”. The single melting peak is taken from the “second heat” heat flow vs. temperature curve. Total heat of fusion of the polymer is calculated from the area under the curve. [0090]
  • For polymers having a density of 0.875 g/cc to 0.910 g/cc, the single melting peak may show, depending on equipment sensitivity, a “shoulder” or a “hump” on the low melting side that constitutes less than 12 percent, typically, less than 9 percent, and more typically less than 6 percent of the total heat of fusion of the polymer. Such an artifact is observable for other homogeneously branched polymers such as Exact™ resins and is discerned on the basis of the slope of the single melting peak varying monotonically through the melting region of the artifact. Such an artifact occurs within 34° C., typically within 27° C., and more typically within 20° C. of the melting point of the single melting peak. The heat of fusion attributable to an artifact can be separately determined by specific integration of its associated area under the heat flow vs. temperature curve. [0091]
  • Whole polymer product samples and individual polymer components are analyzed by gel permeation chromatography (GPC) on a Waters 150 high temperature chromatographic unit equipped with three mixed porosity columns (Polymer Laboratories 10[0092] 3, 104, 105 and 106 Å), operating at a system temperature of 140° C. The solvent is 1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions of the samples are prepared for injection. The flow rate is 1.0 milliliters/minute and the injection size is 100 microliters.
  • The molecular weight determination with is deduced by using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in conjunction with their elution volumes. The equivalent polyethylene molecular weights are determined by using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in [0093] Journal of Polymer Science, Polymer Letters, Vol. 6, p. 621, 1968) to derive the following equation:
  • M polyethylene =a*(M polystyrene)b.
  • In this equation, a=0.4316 and b=1.0. Weight average molecular weight, M[0094] w, and number average molecular weight, Mn, are calculated in the usual manner according to the following formula: Mj=(Swi(Mi j))j; where wi is the weight fraction of the molecules with Mi eluting from the GPC column in fraction i and j=1 when calculating Mw and j=−1 when calculating Mn.
  • The molecular weight distribution (M[0095] w/Mn) for the substantially linear ethylene polymers and homogeneous linear ethylene polymers used in the present invention is generally from about 1.8 to about 2.8.
  • However, substantially linear ethylene polymers are known to have excellent processability, despite having a relatively narrow molecular weight distribution. Unlike homogeneously and heterogeneously branched linear ethylene polymers, the melt flow ratio (I[0096] 10/I2) of substantially linear ethylene polymers can be varied essentially independently of their molecular weight distribution, Mw/Mn.
  • Suitable homogeneously branched ethylene polymers for use in the present invention include interpolymers of ethylene and at least one [0097] a-olefin prepared by a solution, gas phase or slurry polymerization process or combinations thereof. Suitable a-olefins are represented by the following formula:
  • CH2═CHR
  • where R is a hydrocarbyl radical. Further, R may be a hydrocarbyl radical having from one to twenty carbon atoms and as such the formula includes C[0098] 3-C20 a-olefins. Suitable a-olefins for use as comonomers include propylene, 1-butene, 1-isobutylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene, as well as other comonomer types such as styrene, halo- or alkyl-substituted styrenes, tetrafluoro-ethylene, vinyl benzocyclobutane, 1,4-hexadiene, 1,7-octadiene, and cycloalkenes, e.g., cyclopentene, cyclohexene and cyclooctene. Preferably, the comonomer will be 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, or mixtures thereof, as adhesive backing materials comprised of higher a-olefins will have especially improved toughness. However, most preferably, the comonomer will be 1-octene and the ethylene polymer will be prepared in a solution process.
  • The density of the substantially linear ethylene polymer or homogeneously branched linear ethylene polymer, as measured in accordance with ASTM D-792, does not exceed 0.92 g/cc, and is generally in the range from about 0.85 g/cc to about 0.92 g/cc, preferably from about 0.86 g/cc to about 0.91 g/cc, and especially from about 0.86 g/cc to about 0.90 g/cc. [0099]
  • The molecular weight of the homogeneously branched linear ethylene polymer or substantially linear ethylene polymer is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition 190° C./2.16 kg (formerly known as “Condition (E)” and also known as I[0100] 2). Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear. The melt index for the homogeneously branched linear ethylene polymer or substantially linear ethylene polymer is generally from about 1 grams/10 minutes (g/10 min) to about 500 g/10 min, preferably about 2 g/10 min. to about 300 g/10 min., more preferably from about 5 g/10 min to about 100 g/10 min., especially from about 10 g/10 min. to about 50 g/10 min., and most especially about 25 to about 35 g/10 min.
  • Another measurement useful in characterizing the molecular weight of the homogeneous linear ethylene polymer or the substantially linear ethylene polymer is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition 190° C./10 kg (formerly known as “Condition (N)” and also known as I[0101] 10). The ratio of the I10 and the I2 melt index terms is the melt flow ratio and is designated as I10/I2. For the substantially linear ethylene polymer, the I10/I2 ratio indicates the degree of long chain branching, i.e., the higher the I10/I2 ratio, the more long chain branching in the polymer. The I10/I2 ratio of the substantially linear ethylene polymer is at least 6.5, preferably at least 7, especially at least 8. The I10/I2 ratio of the homogeneously branched linear ethylene polymer is generally less than 6.3.
  • Preferred ethylene polymers for us in the present invention have a relative low modulus. That is, the ethylene polymer is characterized as having a 2% secant modulus less than 24,000 psi (163.3 MPa), especially less than 19,000 psi (129.3 MPa) and most especially less than 14,000 psi (95.2 MPa), as measured in accordance with ASTM D790. [0102]
  • Preferred ethylene polymers for use in the a present invention are substantially amorphous or totally amorphous. That is, the ethylene polymer is characterized as having a percent crystallinity less than 40 percent, preferably less than 30 percent, more preferably less than 20 and most preferably less than 10 percent, as measured by differential scanning calorimetry using the equation percent crystallinity=H[0103] f/292*100, where Hf is the heat of fusion in Joules/gram.
  • The homogeneously branched ethylene polymer can be used alone or can be blended or mixed with one or more synthetic or natural polymeric material. Suitable polymers for blending or mixing with homogeneously branched ethylene polymers used in the present invention include, but are not limited to, another homogeneously branched ethylene polymer, low density polyethylene, heterogeneously branched LLDPE, heterogeneously branched ULDPE, medium density polyethylene, high density polyethylene, grafted polyethylene (e.g. a maleic anhydride extrusion grafted heterogeneously branched linear low polyethylene or a maleic anhydride extrusion grafted homogeneously branched ultra low density polyethylene), ethylene acrylic acid copolymer, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, polystyrene, polypropylene, polyester, polyurethane, polybutylene, polyamide, polycarbonate, rubbers, ethylene propylene polymers, ethylene styrene polymers, styrene block copolymers, and vulcanates. [0104]
  • The actual blending or mixing of various polymers may be conveniently accomplished by any technique known in the art including, but not limited to, melt extrusion compounding, dry blending, roll milling, melt mixing such as in a Banbury mixer and multiple reactor polymerization. Preferred blends or mixtures include a homogeneously branched ethylene polymer and a heterogeneously branched ethylene [0105] a-olefin interpolymer wherein the a-olefin is a C3-C8 a-olefin prepared using two reactors operated in parallel or in series with different catalyst systems employed in each reactor. Multiple reactor polymerizations are described in copending application U.S. Ser. No. 08/544,497, filed Oct. 18, 1995 and U.S. Ser. No. 08/327,156, filed Oct. 21, 1994. However, preferred multiple reactor polymerizations comprise non-adiabatic solution loop reactors as described in provisional applications U.S. S No. 60/014,696 and U.S. S No. 60/014,705, both filed Apr. 1, 1996.
  • A range of resin properties, processing conditions and equipment configurations have been discovered for extrusion coatable carpet backing systems that deliver performance similar or better than incumbent latex and polyurethane systems. [0106]
  • FIG. 1 is an illustration of a tufted carpet [0107] 10. The tufted carpet 10 is made of a primary backing material 11 with yarn 12 tufted therethrough; an adhesive backing material 13 which is in intimate contact with the back surface of the primary backing material 11, substantially encapsulates the yarn 12 and penetrates the yarn 12 and binds individual carpet fibers; and an optional secondary backing material 14 applied to the back surface of the adhesive backing material 13.
  • FIG. 2 is an illustration of an extrusion coating line [0108] 20 for making a carpet 70. The line. 20 includes an extruder 21 equipped with a slot die 22, a nip roll 24, a chill roll 23, an exhaust hood 26, a greige good feeder roll 28 and a pre-heater 25. As illustrated, the nip roll is preferably equipped with a vacuum slot 29 to draw a vacuum across about 60 degrees or about 17 percent of its circumference and is equipped with a vacuum pump 27. The slot die 22 dispenses an adhesive backing material in the form of a semi-molten or molten polymer web 30 onto greige good 40 with the polymer web 30 towards the chill roll 23 and the greige good 40 towards the optional vacuum nip roll 24. As illustrated, an optional secondary backing material 50 is applied onto the polymer web 30. The point where the nip roll 24 and the chill roll 23 are closest to one another is referred to as the nip 60.
  • The present invention is useful in producing carpets with face yarn made from various materials including, but not limited to, polypropylene, nylon, wool, cotton, acrylic, polyester and polytrimethylenetheraphthalate (PTT). However, again because one of the objects of the present invention is to provide a recyclable carpet such as, for example, a 100% polyolefin carpet, the most preferred yarn comprises a polyolefin, more preferably, polypropylene. Most preferably, the yam used in the present invention is an air entangled 2750 denier polypropylene yarn such as that produced by Shaw Industries, Inc. and sold under the designation “Permacolor 2750 Type 015.”[0109]
  • The preferred primary backing material comprises a polyolefin, more preferably polypropylene. Most preferably, the primary backing material is a slit film polypropylene sheet such as that sold by AMOCO or Synthetic Industries. Alternatively, other types of primary backing materials, such as non-woven webs, can also be used. Although other materials, such as polyesters or polyamides can be used for the primary backing material, it is preferred to use a polyolefin so that the objective of producing a carpet made entirely from polyolefins is achieved. In addition, polypropylene primary backing materials are typically lower in cost. [0110]
  • The method of tufting or needle-punching the yarn is not deemed critical to the present invention. Thus, any conventional tufting or needle-punching apparatus and stitch patterns can be used. Likewise, it does not matter whether tufted yarn loops are left uncut to produce a loop pile; cut to make cut pile; or cut, partially cut and uncut to make a face texture known as tip sheared. [0111]
  • After the yam is tufted or needle-punched into the primary backing material, the greige good is typically rolled up with the back side of the primary backing material facing outward and held until it is transferred to the backing line. [0112]
  • In a preferred embodiment, the greige good is scoured or washed before it has an adhesive backing material extruded thereon. In particular, yam that is tufted or needle-punched to make carpet often has varying quantities of processing materials, most commonly oily or waxy chemicals, known as spin-finish chemicals, remaining thereon from the yarn manufacturing processes. It has been found to be preferable to remove or displace all or substantially all of these processing materials prior to extruding the adhesive backing material onto the back surface of the primary backing material. A preferred scouring or washing method includes passing the greige good through a bath containing an aqueous detergent solution at about 64 to about 70° C. (e.g., 67° C.). Suitable detergents include, but are not limited to, STA which is available from American Emulsions. After the detergent washing processing step, the greige good is dried or preheated. Drying can be accomplished at a temperature of about 108° C. to about 112° C. (e.g., 110° C.) for about 1-0.8 to about 2.2 minutes (e.g., 2 minutes). [0113]
  • Another preferred scouring or washing method includes using a wet vacuum cleaner system that initially dispenses ambient temperature water or heated water (either optionally containing a detergent or cleaning solution) onto the primary backing material side of the greige good and then sequentially vacuums up the water and retained amounts of processing materials. The wet vacuum system is suitably adapted with a dispensing and vacuum wand or head such that the entire width of the greige good can be wet vacuumed at least once on a continuous extrusion coating line. After the wet vacuuming processing step, the greige good is suitably dried and/or preheated. Suitable detergents, cleaning solutions or cleaning concentrates for use in a wet vacuuming method includes, but is not limited to, aqueous alkaline solutions, for example, those consisting of ethylene diamine tetracetic acid tetrasodium salt. One suitable wet vacuum cleaner system is the Rinsevac™ carpet cleaning system and one suitable cleaning concentrate is the Rinsevac™ Professional Carpet Cleaner both supplied by Blue Lustre Products, Inc., Indianapolis, In. [0114]
  • Other suitable methods of the present invention for scouring or washing processing materials, adaptable to an extrusion coating line such as, for example, the one illustrated in FIG. 2, include steam cleaning, flashing at elevated temperatures and/or under vacuum, and solvent chemical washing of the greige good. [0115]
  • It is also contemplated that the use of polyolefin waxes (rather than conventional organic and mineral oils) as processing materials would allow improved adhesive backing material performance in itself or at least less demanding scouring or washing requirements. Nevertheless, practitioners will find that scouring or washing requirements may vary with the amount and specific type of processing materials present. That is, higher quantities of process materials and/or higher molecular processing materials may require more stringent scouring and washing techniques such as, for example, multiple washing and drying steps using concentrated washing solutions based on softened or deionized water. Practitioners will also recognize that scouring and washing requirements for effectively removing or displacing processing materials may be more extensive than ordinary washings or other cleaning procedures performed for cosmetic or decorative purposes or performed to simply remove loose fibers, primary backing material or other debris that ordinarily result from tufting, needle-punch and/or cutting operations. [0116]
  • In another aspect of the present invention, the greige good is coated with an aqueous pre-coat material, either as a final backing or preferably before an adhesive backing material is extruded thereon. The particles in this dispersion can be made from various polyolefin materials such as ethylene acrylic acid (EAA), ethylene vinyl acetate (EVA), polypropylene or polyethylene (e.g., low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or substantially linear ethylene polymer, or mixtures thereof). Presently, polyethylene particles are preferred. Most preferably, the polyethylene particles are those sold by Quantum USI Division under the designation “Microthene FN500.”[0117]
  • Preferably, the polyolefin particles are present in an amount between about 10 and 75 percent by weight of the dispersion, more preferably between about 20 and about 50 percent, and most preferably between about 25 and about 33 percent. [0118]
  • The particle size of the polyolefin particles is important both to ensure that a good dispersion is achieved and also to ensure that the polyolefin particles penetrate the yarn and primary backing so as to provide good abrasion resistance. Preferably, the average particle size of the polyolefin particles is between about 1 and about 1000 microns, and more preferably between about 5 and 40 microns. The most preferred polyethylene particles referred to above have an average particle size of about 18 to about 22 microns (e.g., 20 microns). [0119]
  • Preferably, the polyolefin particles have a Vicat softening point (as measured in accordance with ASTM D1525) between about 50 and about 100° C., and more preferably between about 75 and 100° C. The most preferred polyethylene particles referred to above have a softening point of about 80° to about 85° C. (e.g., 83° C.). [0120]
  • When polypropylene particles are used, they preferably have a melt flow (ASTM D-1238 Condition 210/2.16) between about 1 to about 80, most preferably between about 60 and about 80. When polyethylene particles are used, they preferably have an I[0121] 2 melt index (ASTM D-1238 Condition 19012.16) between about 1 and about 100 g/10 minutes, and more preferably between about 20 and about 25 g/10 minutes. The most preferred polyethylene particles referred to above have an I2 melt index of t 22 g/10 minutes.
  • Ethylene acrylic acid (EAA) may be used for the polyolefin particles, preferably in combination with polyethylene or polypropylene particles. It has been found that EAA can increase the adhesion of the pre-coat to the yarn and primary backing, as well as to a thermoplastic sheet extruded thereon. [0122]
  • The aqueous dispersion preferably contains other ingredients. For example, a surfactant is preferably included to aid in keeping the polyolefin particles dispersed. Suitable surfactants are nonionic, anionic, cationic and fluorosurfactants. Preferably, the surfactant is present in an amount between about 0.01 and about 1 weight percent based on the total weight of the dispersion. More preferably, the surfactant is anionic. Most preferably, the surfactant is one sold by Ciba Geigy under the designation “Igepal C0430” and is present at 0.1 weight percent based on the total weight of the dispersion. [0123]
  • A thickener is also preferably included to provide a suitable viscosity to the dispersion. Preferably, the thickener is one selected from the group consisting of sodium and ammonium salts of polyacrylic acids and is present in an amount between about 0.1 and about 2 weight percent based on the total weight of the dispersion. Most preferably, the thickener is a salt of a polyacrylic acid such as that sold by Sun Chem International under the designation “Print Gum 600” and is present at about 0.8 weight percent based on the total weight of the dispersion. [0124]
  • Preferably, the viscosity of the dispersion measured on a Brookfield RVT viscometer is between about 3000 cP (centipoises) at 20 rpm with a No. 5 spindle and about 50,000 cP at 2.5 rpm with a No. 5 spindle measured at 23° C. Most preferably, the viscosity of the dispersion is between about 10,000 and 20,000 cP at 2.5 rpm with a No. 5 spindle. [0125]
  • In addition, the dispersion preferably includes a defoaming agent. Preferably, the defoaming agent is a non-silicone defoaming agent and is present in an amount between about 0.01 and about 1.0 weight percent based on the total weight of the dispersion. Most preferably the defoamer is one such as that sold by LENMAR Chemical Corporation under the designation “MARFOAM N-24A” and is present at about 0.1 weight percent based on the total weight of the dispersion. [0126]
  • Preferably, the aqueous dispersion further includes a dispersion enhancer, such as fumed silica which has been found to act as a compatibilizer for the dispersion, thus allowing the use of larger polyolefin particles. Preferably, the fumed silica is present at between about 0.1 and about 0.2 weight percent based on the total weight of the dispersion. Most preferably, the fumed silica is one such as that sold by DeGussa under the designation “Aerosil 300.”[0127]
  • The aqueous dispersion of polyolefin particles can be made up in various ways. Preferably, the ingredients are added to the water in the following order: surfactant, defoamer, polyolefin, thickener. The mixture is then agitated in a homogenous mixer, preferably with high shear mixing, until all lumps have dispersed, typically for about 8 to about 12 minutes (e.g., 10 minutes). [0128]
  • The dispersion can be applied to the carpet in various ways. For example, the dispersion can be applied directly, such as with a roll over roller applicator, or a doctor blade. Alternatively, the dispersion can be applied indirectly, such as with a pan applicator. Preferably, a roll over roller applicator is used with the top roller turning at about 22 to about 27 percent of line speed (e.g., 25 percent of line speed). [0129]
  • The amount of dispersion applied and the concentration of the particles can be varied depending on the desired processing and product parameters. Preferably, the amount of dispersion applied and the concentration of the particles are selected so as to apply between about 4 and about 12 ounces per square yard (OSY) (about 141.5 and about 424.4 cm[0130] 3/m2) of carpet. Most preferably, this is achieved by using a dispersion containing about 50 weight percent polyolefin particles (based on the total weight of the dispersion) and applying between about 8 and about 10 OSY (about 283 and about 353.7 cm3/m2) of the dispersion.
  • After application of the dispersion, heat is applied to the back side of the primary backing so as to dry the dispersion and to at least partially melt the particles. As a result, the loops of yarn are fixed to the primary backing. Preferably, the heat is applied by passing the product through an oven. Such an oven is preferably set at a temperature between about 100 and about 150° C. and the product spends between about 2 and about 5 minutes passing through the oven. Also, since the object is to at least partially melt the particles, the temperature of the oven is set at between about 5 and about 75° C. above the Vicat softening point of the polyolefin particles. [0131]
  • After treatment with the dispersion of polyolefin particles, the carpet may be used as is or, more preferably, may have an additional backing applied thereto. Additional backings can be applied by various methods with the preferred method, as described above, involving the use of an extruded sheet of a thermoplastic material, preferably the homogeneously branched ethylene polymer described above, onto which a conventional secondary backing is laminated In particular, a molten thermoplastic material is preferably extruded through a die so as to make a sheet which is as wide as the carpet. The molten, extruded sheet is applied to the back side of the primary carpet backing. Since the sheet is molten, the sheet will conform to the shape of the loops of yarn and further serve to fix the loops in the primary backing. [0132]
  • Extrusion coating configurations include a monolayer T-type die, single-lip die coextrusion coating, dual-lip die coextrusion coating, and multiple stage extrusion coating. Preferably, the extrusion coating equipment is configured to apply a total coating weight of between about 4 and about 30 ounces/yd[0133] 2 (OSY) (about 141.5 and about 1061.1 cm3/m2), with between about 18 OSY (about 636.7 cm3 μm2) and about 22 OSY (about 778.1 cm3/m2), e.g., 20 OSY, (707.4 cm3/m2) being most preferred.
  • Measured another way, the thickness of an unexpanded, collapsed extrusion coated adhesive backing material is in the range from about 6 to about 80 mils, preferably from about 10 to about 60 mils (about 0.25 to about 1.52 mm), more preferably from about 15 to about 50 mils (about 0.38 to about 1.27 mm), and most preferably from about 20 to about 40 mils (about 0.51 to about 1.02 mm). [0134]
  • The line speed of the extrusion process will depend on factors such as the particular polymer being extruded, the exact equipment being used, and the weight of polymer being applied. Preferably, the line speed is between about 18 and about 250 ft./min. (about 5.5 and about 76.2 m/min.), more preferably between about 80 and about 220 ft./min. (about 24.4.and about 67.1 m/min.), most preferably between about 100 and about 200 ft./min. (about 30.5 and about 61 m/min.). [0135]
  • The extrusion coating melt temperature principally depends on the particular polymer being extruded. When using the most preferred substantially linear polyethylene described above, the extrusion coating melt temperature is greater than about 450° F. (232° C.), preferably greater than or equal to about 500° F. (about 260° C.), or is between about 450° (about 232° C.) and about 650° F. (about 343° C.), more preferably between about 475° (about 246° C.) and about 600° F. (about 316° C.), most preferably between about 500° and about 550° F. (about 2600 and about 288° C.). [0136]
  • Preferably, two layers of resin, each layer comprising a different resin, are extruded with the layer applied directly onto the backside of the primary backing material (first layer) having a higher melt index than the second layer which is applied onto the backside of the first layer. Since it is the first layer which is relied on to encapsulate and penetrate the yam, this layer should have a melt index high enough (melt viscosity low enough) to promote encapsulation and penetration of the yarn. The second layer, which is generally not relied on to encapsulate and penetrate the yarn, may be used either as the bottom surface of the carpet or to facilitate the application of an optional secondary backing material. For both of these uses, it is preferred to have a lower melt index to provide higher strength after cooling. In addition, because it is not relied on for encapsulating or penetrating the fiber bundles, a resin of lower quality and/or less tightly controlled properties may be used in the second layer. In a preferred embodiment, the second layer is a recycled feedstock. [0137]
  • Also, the first and second layers may consist of different polymer chemistries or compositions. For example, the first layer can be comprised of an adhesive polymer (as an additive or as the composition of the entire layer) such as, but not limited to, an ethylene vinyl acetate copolymer, an ethylene acrylic acid copolymer or a maleic anhydride/ethylene polymer graft (preferably, a substantially linear ethylene polymer/maleic anhydride extrusion graft or a high density polyethylene/maleic anhydride extrusion graft) and the second layer can be comprised of a non-polar polymer such as a homogeneously branched ethylene polymer, a low density polyethylene or ultra low density polyethylene. Alternately, the first layer can be comprised of a non-polar polymer and the second layer can be comprised of an adhesive polymer. [0138]
  • Preferably, the first layer has an I[0139] 2 melt index between about 30 and about 175 g/10 min. and the second layer has an I2 melt index between about 1 and about 70 g/10 min. Most preferably, the first layer has an I2 melt index between about 30 and about 70 g/10 min and the second layer has an I2 melt index between about 10 and about 30 g/10 min.
  • It is also preferred to extrude two layers of a single polymer composition so as to have greater control over the thickness or weight of the resin applied to the carpet. In alternative embodiments, three or more layers of the resin can be extruded on the back surface of the primary backing material to achieve even higher coat weights and/or to obtain a more gradual transition between the first and last layer applied. Preferably, a dual lip die is used to apply two layers. Alternatively, two or more extrusion stations or a single lip coextrusion die can be used to apply these two or more layers. [0140]
  • Another aspect of the present invention is the use of modified homogeneously branched ethylene polymers. In particular, in certain aspects of the invention the at least one homogeneously branched ethylene polymer that is employed as the adhesive backing material, primary backing material or yarn, preferably as the adhesive backing material, is modified by the addition of at least one adhesive polymeric additive. Suitable adhesive polymeric additives include polymer products comprised of (1) one or more ethylenically unsaturated carboxylic acids, anhydrides, alkyl esters and half esters, e.g., acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, crotonic acid and citraconic acid, citraconic anhydride, succinnic acid, succinnic anhydride, methyl hydrogen maleate, and ethyl hydrogen maleate; esters of ethylenically unsaturated carboxylic acids, e.g., ethyl acrylate, methyl methacrylate, ethyl methacrylate, methyl acrylate, isobutyl acrylate, and methyl fumarate; unsaturated esters of carboxylic acids, e.g., vinyl acetate, vinyl propionate, and vinyl benzoate; and ethylenically unsaturated amides and nitriles e.g., acrylamide, acrylonitrile, methacrylonitrile and fumaronitrile; and (2) one or more ethylenically unsaturated hydrocarbon monomers such as aliphatic [0141] a-olefin monomers, e.g., ethylene, propylene, butene-1 and isobutene; conjugated dienes, e.g., butadiene and isoprene; and monovinylidene aromatic carbocyclic monomers, e.g., styrene, a-methylstyrene, toluene, and t-butylstyrene. Suitable adhesive polymeric additives can be conveniently prepared by known techniques such as, for example, by interpolymerization or by a polymerization procedure followed by a chemical or extrusion grafting procedure. Suitable grafting techniques are described in U.S. Pat. Nos. 4,762,890; 4,927,888; 4,230,830; 3,873,643; and 3,882,194.
  • Preferred adhesive polymeric additives for use in the present invention are maleic anhydride grafts wherein maleic anhydride is grafted onto an ethylene polymer at a concentration of about 0.1 to about 5.0 weight percent, preferably about 0.5 to about 1.5 weight percent. The use of ethylene polymer/maleic anhydride grafts as adhesive polymeric additives in the present invention significantly improves the performance and operating window of extrusion coated homogeneously branched ethylene polymers as the adhesive backing material, especially for polar polymer such as for example, but not limited to, nylon and polyester faced carpets. The improvement pertained to substantially higher comparative abrasion resistance and tuft bind strength. The improvement was surprising in that graft adhesives are generally known to require extended molten or semi-molten contact times for improved performance and function as interlayer adhesives for films and coatings where there is a continuous substrate as opposed to the discontinuous interface existent in carpet construction. [0142]
  • Preferred ethylene polymers for use as the grafted host polymer include low density polyethylene (LDPE), high density polyethylene (HDPE), heterogeneously branched linear low density polyethylene (LLDPE), homogeneously branched linear ethylene polymers and substantially linear ethylene polymers. Preferred host ethylene polymers have a polymer density greater than or equal to 0.915 g/cc and most preferably greater than or equal to 0.92 g/cc. Substantially linear ethylene polymers and high density polyethylene are the preferred host ethylene polymers. [0143]
  • In this aspect of the present invention, the adhesive polymeric additive is added to the homogeneously branched ethylene polymer at a level in the range of from about 0.5 to about 30 weight percent, preferably from about 1 to about 20 weight percent, more preferably from about 5 to about 15 weight percent based on the total weight of the polymer. For the preferred ethylene polymer maleic anhydride grafts, additions should provide a final maleic anhydride concentration in the range of from about 0.01 to about 0.5 weight percent, preferably from about 0.05 to about 0.2 weight percent based on the total weight of the polymer. [0144]
  • Auxiliary equipment such as a pre-heater can be used. In particular, a heater, such as a convection oven or infrared panels can be used to heat the back of the greige good before the adhesive backing material is extruded thereon. In doing so, it has been found that the encapsulation and penetration of the yarn bundles can be enhanced. Preferably, the pre-heater is an infrared unit set at between about 200 and about 1500° C. and the greige good is exposed to this heating for between about 3 and about 30 seconds. Most preferably, the heater is set at about 1000° C. and the greige good is exposed to this heating for about 5 to about 7 seconds (e.g., 6 seconds). [0145]
  • In addition to or as an alternative to pre-heating, the process of the invention may also employ a post-heat soaking process step to lengthen the molten time for the adhesive backing material to thereby improve the encapsulation and penetration of the yarn or fiber bundles by the adhesive backing material. Preferably, after the adhesive backing material is applied to the greige good, it is heated by a convection oven or infrared radiation at a temperature between about 200 and about 1500° C. for between about 3 and 30 seconds, most preferably at 1000° C. for about 5 to about 7 seconds (e.g., 6 seconds). [0146]
  • As another piece of auxiliary or optional equipment, a vacuum nip roll can be used to draw the adhesive backing material extrudate (i.e., semi-molten or molten polymer web) onto the greige good. In a properly configured extrusion coating operation, the pile face of the greige good is positioned towards the vacuum nip roll and the polymer web is draw down onto the back surface of the primary backing material of the greige good. Vacuum nip roll [0147] 24 (which is illustrated in FIG. 2 and is available from Black Clawson Corporation) is suitable for vacuum drawing the adhesive backing material web. Vacuum nip roll 24 can be adapted from a conventional nip roll wherein a portion of the hollow internal of the roll is partitioned, dedicated and coupled to a external vacuum pump 27 to provide a vacuum surface. The surface of the vacuum portion is perforated but machined flush and continuously with the remaining surface of the roll. Suitable vacuum nip rolls can have a complete 360 degree vacuum surface; however, a vacuum surface of from about 10 to about 180 degrees is preferred, most preferably about 60 degrees. To effectively draw the adhesive backing material web onto the greige good and maximize to the penetration of the yarn or fiber bundles, the vacuum is set to greater than 15 inches of H2O (3.7 Pa), preferably greater than or equal to 25 inches of H2O (6.1 Pa) and more preferably greater than or equal to 40 inches of H2O (9.8 Pa), or from between about 15 and about 50 inches of H2O (about 3.7 and about 12.3 Pa), preferably from between about 20 and about 45 (about 4.9 and about 11.1 Pa).
  • The length of time the greige good is actually subjected to the vacuum will primarily depend on the extrusion coating line speed and the extent of draw on the adhesive backing material web will largely depend on the level of vacuum and the porosity of the greige good. As such, higher vacuum levels will be required for higher extrusion coating line speeds and/or denser greige good to effectively the draw the adhesive backing material. [0148]
  • In addition to or as an alternative to a vacuum nip roll, a high pressure positive air device such as an air blade or knife can also be used to force the adhesive backing material web onto the back surface of the primary backing material. Preferably, the positive air pressure device is set to provide an air pressure greater than 20 psi (0.14 MPa), preferably greater than or equal to 40 psi (0.27 MPa), more preferably greater than or equal to 60 psi (0.41 MPa), or between about 20 and about 120 psi (about 0.14 and about 0.82 MPa), most preferably between about 30 and about 80 psi (about 0.20 and about 0.54 MPa) Preferably, the positive air pressure device is positioned at the extrusion coating nip, extends across the entire width of the polymer web and is positioned behind the polymer web towards the chill roll so to force the polymer web onto the greige good and press the polymer web into the yarn or fiber bundles. [0149]
  • The extruded polymer(s) can either be used neat, or can have one or more additive included. A preferred additive is an inorganic filler, more preferably, an inorganic filler with a high heat content. Examples of such fillers include, but are not limited to, calcium carbonate, aluminum trihydrate, talc, barite. High heat content fillers are believed to be advantageous in the invention because such fillers allow the extrudate to remain at elevated temperatures longer with the beneficial result of providing enhanced encapsulation and penetration. That is, normally fillers are added to carpet backing materials to merely add bulk (i.e. as extenders) or to impart insulating and sound dampening characteristics. However, we have found that inorganic mineral fillers that have high heat contents surprisingly improve yarn encapsulation and penetration which in turn improves the performance of the abrasion resistance and tuft bind strength of extrusion coated carpet samples. [0150]
  • Preferably, a high heat content filler is added at a level of between about 1 and about 75 weight percent of the total extrudate, more preferably between about 15 and about 60 weight percent and most preferably between about 20 weight percent and 50 weight percent. Such fillers will have a specific heat content of greater than or equal to 0.4 cal-cc/° C. (1.8 Joules-cc/° C.), preferably greater than or equal to 0.5 cal-cc/° C. (2 Joules-cm[0151] 3/° C.), more preferably greater than or equal to 0.6 cal-cc/° C. (2.5 Joules-cm3/° C.), and most preferably greater than or equal to about 0.7 cal-cc/° C. (2.9 Joules-cm3/° C.). Representative examples of high heat content fillers for use in the present invention include, but are not limited to, limestone (primarily CaCO3), marble, quartz, silica, and barite (primarily BaSO4). The high heat content fillers should be ground or precipitated to a size that can be conveniently incorporated in an extrusion coating melt stream. Suitable particle sizes range from about 1 to about 50 microns.
  • If a foamed backing is desired on the carpet, a blowing agent can be added to the adhesive backing material and/or the optional secondary backing material. If used, the blowing agents are preferably conventional, heat activated blowing agents such as azodicarbonamide, toluene sulfonyl semicarbazide, and oxy bis(benzene sulfonyl) hydrazide. The amount of blowing agent added depends on the degree of foaming sought. A typical level of blowing agent is between about 0.1 and about 1.0 weight percent. [0152]
  • Implosion in the present invention is accomplished by restricting expansion of the adhesive backing material in the direction opposite the primary backing material during activation of the implosion agent such that the molten polymer is forced into the interior and free space of the yarn or fiber bundles. An imploded adhesive backing material will have a collapsed, non-expanded matrix (relative to a foamed backing) and be of essentially the same thickness (measured from the plane of the back surface of the primary backing material) as would be the case without the use of the implosion agent That is, the adhesive backing material layer would be characterized as not being expanded by the implosion agent. [0153]
  • The implosion agent is selected and formulated into the adhesive backing material and extrusion conditions are set such that the activation of the implosion agent occurs at the instant of nip while the adhesive backing material is still semi-molten or molten. With improved yarn penetration accomplished with the use of an implosion agent, the carpet will exhibit comparatively improved abrasion resistance. Thus, the use of an implosion agent can allow the use of polymer compositions having lower molecular weights to provide improved extrusion coatability yet maintain higher abrasion resistance (i.e., comparable to adhesive backing materials based on higher molecular weight polymer compositions). An effective amount of implosion agent would be between about 0.1 and about 1.0 weight percent based on the weight of the adhesive backing material. [0154]
  • Conventional blowing agents or any material that ordinarily functions as a blowing agent can be used as an implosion agent in the present invention providing expansion of the adhesive backing material matrix is suitably restricted or confined when the material is activated such that molten polymer is forced into the interior and free space of the yarn or fiber bundles and there is no substantial expansion of the adhesive backing material as a result of having used the implosion agent. However, preferably, an imploded adhesive backing material will be characterized as having a closed cell structure that can be conveniently identified by photomicrographs at 50× magnification. [0155]
  • Other additives can also be included in the adhesive backing material, to the extent that they do not interfere with the enhanced properties discovered by Applicants. For example, antioxidants such as sterically hindered phenols, sterically hindered amines and phospites may be used. Suitable antioxidants include Irganox® 1010 from Ciba-Geigy which is a hindered phenol and Irgafos® 168 from Ciba-Geigy which is a phosphite. Other possible additives include antiblock additives, pigments and colorants, anti-static agents, antimicrobial agents (such as quaternary ammonium salts) and chill roll release additives (such as fatty acid amides). [0156]
  • As noted above, and shown in FIG. 2, the carpet of the invention preferably also includes a secondary backing material. Preferably, the secondary backing material is laminated directly to the extruded layer(s) while the extrudate is still molten after extrusion coating. It has been found that this technique can improve the penetration of the extrusion coating into the primary backing. [0157]
  • Alternatively, the secondary backing material can be laminated in a later step by reheating and/or remelting at least the outermost portion of the extruded layer or by a coextrusion coating technique using at least two dedicated extruders. Also, the secondary backing material can be laminated through some other means, such as by interposing a layer of a polymeric adhesive material between the adhesive backing material and the secondary backing material. Suitable polymeric adhesive materials include, but are not limited to, ethylene acrylic acid (EAA) copolymers, ionomers and maleic anhydride grafted polyethylene compositions. [0158]
  • The material for the secondary backing material can be a conventional material such as the woven polypropylene fabric sold by AMOCO under the designation Action Bac®. This material is a leno weave with polypropylene monofilaments running in one direction and polypropylene yarn running in the other. More preferably, the secondary backing material used with the present invention is a woven polypropylene fabric with monofilaments running in both directions. A suitable example of such a material is sold by Amoco under the designation Style 3878. This material has a basis weight of 2 OSY (70.7 cm[0159] 3/m2). This material with monofilaments running in both directions has been found beneficial in providing enhanced dimensional stability to the carpet.
  • In an alternatively preferred embodiment, the secondary backing material is a material known as fiber lock weave or “FLW.” FLW is a fabric which includes fibers needle punched into it. Sometimes FLW is used as a primary backing material on a carpet with a low pile weight. In such carpet, the fibers protrude on the pile side so as to help keep the primary backing material from showing through the pile. However, in this alternatively preferred embodiment, FLW is used as the secondary backing material with the needle punched fibers protruding away from the carpet. Doing so has been found to enhance the adhesion of the carpet when installed with a glue-down adhesive. In particular, the surface area for contacting the glue-down adhesive is increased and the protruding fibers help to anchor the carpet backing to the glue-down adhesive. [0160]
  • Alternatively, the secondary backing material can be a non-woven fabric. Several types are available, including, but not limited to, spun-bond, wet-laid, melt-blown, and air entangled. As noted above, it is preferred that the secondary backing is made from a polyolefin to facilitate recycling. [0161]
  • In an alternatively preferred embodiment, the non-woven fabric is spun-bond polypropylene fabric, such as that available from Don & Low Non-wovens under the name “Daltex.” Typically, spun-bond fabric is made from extruded and air-drawn polymer filaments which are laid down together and then point bonded, for example by a heated calendar roll. The basis weight of such a spun-bond secondary backing can be varied, preferably between 35 and 80 grams/m[0162] 2 (gsm) more preferably between 60 and 80 gsm. Most preferably, the basis weight is 77-83 gsms (e.g., 80 gsm). One factor favoring a higher basis weight for the spun-bond fabric is that the higher basis weight fabric is less likely to be melted when brought into contact with the molten extruded backing.
  • It has been found that a spun-bond non-woven fabric is advantageous to use as a secondary backing in the present invention because the porous nature of the fabric increases the surface area of the carpet for gluing the carpet to the floor. [0163]
  • In still another alternatively preferred embodiment, the secondary backing is a woven polypropylene fabric such as Action Bac® from Amoco which has been enhanced by having 2 OSY (70.7 cm[0164] 3/m2) of polypropylene fibers needle punched onto one side of it. This needle punched fabric is laminated so as to have the polypropylene fibers embedded within the adhesive backing layer. As a result, the strands of the woven polypropylene fabric exposed. This embodiment has been shown to have improved glue down properties as compared to an embodiment without the needle punched fibers because, without the needle punched fibers, the strands of the woven polypropylene fabric are at least partially embedded in the adhesive backing layer. As such, the surface area for gluing is reduced. It was also noted that the back of the carpet made in this embodiment was much less abrasive than that found with traditional latex backed carpet. The carpet is also more flexible than traditional latex backed carpet. Consequently, this embodiment is preferred for making areas rugs and the like.
  • Still other materials can be used for the secondary backing. For example, if an integral pad is desired, a polyurethane foam or other cushion material can be laminated to the back side of the carpet Such backings can be used for broadloom carpet as well as for carpet tile. [0165]
  • The extrusion backed carpet construction and the methods described herein are particularly suited for making carpet tile. FIG. 6 shows a cross-section of a carpet tile [0166] 100 made according to the present invention. A yarn 103, preferably made of polypropylene, is tufted into a primary backing 101, which is also preferably made of polypropylene, so as to leave a carpet pile face 104 on top of the primary backing 101 and back stitches 105 below the primary backing. Applied to the back of the primary backing 101 and the back stitches 105 is an adhesive layer 107. Preferably, this adhesive layer is made from a polyolefin. More preferably, the adhesive layer is made from the ethylene polymers described in detail above. Most preferably, this adhesive layer 107 is made from a substantially linear ethylene polymer with the additives described in Example 194 below.
  • In a preferred embodiment of carpet tile, the carpet included from about 5 to about 200 OSY (about 176.8 to about 7,074 cm[0167] 3 μm2) of extruded adhesive backing. More preferably, the carpet for tile includes from about 30 to about 80 OSY (about 1061 to about 2,830 cm3 μm2) of extruded backing, most preferably, 50 OSY (1,768 cm3 μm2).
  • Preferably, the carpet for carpet tile receives its extruded backing in two passes, i.e., to apply two layers of the extruded backing. The first pass applies the layer [0168] 107 in FIG. 6. Preferably this layer 107 is between about 2.5 and about 100 OSY (about 88.4 to about 3,537 cm3/m2) of the extruded polymer, more preferably between about 15 and about 40 OSY (about 530.5 to about 1,415 cm3/m2), and most preferably 25 OSY (884 cm3/m2). The second pass adds the layer 111. Preferably the second layer 111 is about 2.5 and about 100 OSY (about 88.4 to about 3,537 cm3/m2), more preferably between about 15 and 40 OSY (about 530.5 to about 1,415 cm3/m2), and most preferably 25 OSY (884 cm3/m2).
  • Applying the extruded backing in two passes allows the opportunity to apply a first and second layer which have different physical and/or chemical properties. As noted above, it is sometimes preferable to apply a polymer with a higher melt index adjacent the primary backing, and a polymer with a lower melt index below that. In addition, it can also be preferably to use an extrudate with a lower filler content in the layer next to the primary backing and an extrudate with a higher filler content in the layer below that. In one preferred embodiment, the layer next to the primary backing includes a filler loading of 30 percent by weight and the layer below that includes a filler loading of 60 percent by weight. The lower filler content is believed to provide better penetration of the primary backing and back stitches in the carpet by the extrudate. [0169]
  • When making carpet tile, it is preferable to embed a layer of reinforcing material [0170] 109 between the first and second layers of extruding backing. An important property of carpet tile is dimensional stability, i.e., the ability of the tile to maintain its size and flatness over time. The inclusion of this layer of reinforcing material has been found to enhance the dimensional stability of carpet tile made according to this preferred embodiment. Suitable reinforcing materials include dimensionally and thermally stable fabrics such as non-woven or wet-laid fiberglass scrims, as well as woven and non-woven thermoplastic fabrics (e.g. polypropylene, nylon and polyester). Most preferably, the reinforcement layer is a polypropylene non-woven fabric sold by Reemay as “Typar” with a basis weight of 3.5 OSY (124 cm3/m2). Alternatively, a preferred reinforcement layer is a fiberglass scrim sold by ELK Corp. as “Ultra-Mat:” with a basis weight of 1.4 OSY (49.5 cm3/m2).
  • The carpet tile may include a secondary backing fabric [0171] 113 below the second layer of extruded backing 111. Suitable materials for the secondary backing fabric include those described above. However, it is presently not preferred to include a secondary backing fabric on carpet tile.
  • FIG. 7 schematically shows a preferred line [0172] 120 for making carpet tile according to the present invention. A length of greige good 121, i.e. yarn tufted into a primary backing, is unrolled from the roll 123. The greige good 121 passes over the rollers 125 and 127 with the primary backing toward the roller 123. Between rollers 125 and 127 is a pre-heater 129 as described above.
  • An extruder [0173] 131 is mounted so as to extrude a sheet 135 of the polymeric backing through the die 133 onto the back of the greige good at a point between the roller 127 and the nip roll 141. The exact location at which the sheet 135 contacts the greige good can be varied depending on the line speed and the time desired for the molten polymer to rest on the greige good before passing between the nip roll 141 and the chill roll 143. At present it is preferred that the sheet 135 contact the greige good so as to lie on the greige good for between about 0.5 and about 2 seconds, most preferably about 1 second, before passing between the nip roll 141 and the chill roll 143.
  • In this preferred depicted embodiment, a scrim of non-woven polypropylene [0174] 139 is fed from roll 137 so as to contact the chill roll 143 at a point just prior to the nip roll 141. As a result, the scrim 139 which will act as a reinforcing fabric in the finished carpet tile is laminated to the greige good through the polymer.
  • The pressure between the nip roll [0175] 141 and the chill roll 143 can be varied depending on the force desired to push the extruded sheet. Most preferably, there is 60 psi (0.41 MPa) of air pressure pushing the rolls together. Also, as described in connection with FIG. 2, it may be desirable to include a vacuum slot in the nip roll. In addition, a jet of pressurized air may also be used to push the extruded sheet into the carpet backing.
  • The size of the chill roll [0176] 143 and the length of time the carpet rolls against it can be varied depending on the level of cooling desired in the process. Preferably the chill roll 143 is cooled by simply passing ambient water through it.
  • After passing over the chill roll [0177] 143, the carpet is brought over rollers 145 and 147 with the carpet pile toward the rollers. A second extruder 149 extrudes a sheet of polymer 153 through its die 151 on to the back of the scrim 139. Again the point at which the extruded sheet 153 contacts the scrim 139 can be varied as described above.
  • At this point, if a secondary backing fabric is desired for the carpet tile, that fabric can be introduced from a roll similar to that shown at [0178] 137 so as to contact the be laminated to the carpet through the extruded sheet 153 as it passes between the nip roll 155 and the chill roll 153. Such a secondary backing fabric is not currently preferred for carpet tile construction.
  • The carpet passes between the nip roll [0179] 155 and the chill roll 157. Again, the pressure applied between the two rolls 155 and 157 can be varied. At present, 60 psi (0.41 MPa) of air pressure is preferably applied against the nip roll 155.
  • After passing around the chill roll [0180] 157, the carpet passes around roll 159 and is preferably passed over an embossing roll (not shown) to print a desired pattern on the back of the carpet.
  • While the apparatus shown in FIG. 7 is preferred for making a carpet tile with two layers of extruded backing and a reinforcing fabric in between, the same construction can be made with a single extrusion die, nip roll and chill roll. In particular, the first layer of extruded backing and the reinforcing fabric can be applied in a first pass through the line after which the carpet is rolled up. The second layer of extruded backing can be applied on top of the reinforcing fabric in a second pass through the same line after which the carpet is ready to be cut into carpet tiles. [0181]
  • Carpet tile is typically made by producing a length of backed carpet and then cutting the carpet into the appropriate sized squares. In the United States, the most common size is 18 inches (45.7 cm) square. In the rest of the world, the most common size is 50 cm square. [0182]
  • In still another alternative embodiment, a pressure sensitive adhesive is applied to the bottom surface of the backed carpet and a release sheet is included. In this way, a “peel and stick” carpet is produced. This is particularly beneficial when the carpet is to be cut into tiles. Examples of suitable pressure sensitive adhesives include ethylene vinyl acetate copolymers and substantially linear ethylene polymers formulated with tackifiers and polymeric waxes. The release sheet can be made from conventional polymers and/or paper products. Preferably, the release sheet is made of polyester/wax formulation. [0183]
  • It has been determined that the pressure sensitive adhesive is best applied directly to the adhesive backing material while the adhesive backing material is still at an elevated temperature from the extrusion coating process. A preferred technique is to extrusion laminate the pressure sensitive adhesive with the adhesive backing material; that is, to apply the pressure sensitive adhesive at nip. Alternately, the adhesive backing material can be reheated before the pressure sensitive adhesive is applied. [0184]
  • Another preferred embodiment of the present invention, exclusive of an optional secondary backing material, involves the combination of the various process steps described herein together with the use of at least one substantially linear ethylene polymer with an effective amount of an implosion agent formulated therein in the first layer of a two layer adhesive backing material. The a preferred combination of process steps at least includes pre-coating with an aqueous polyolefin system; removal of processing materials by washing or scouring the greige good with an aqueous detergent solution heated to at least 67° C.; drying and pre-heating the greige good by subjecting it to infra-red radiation set at about 1000° C. for about 1 to about 6 seconds; extrusion coating the adhesive backing material onto the back surface of the pre-heated, washed primary backing material by utilizing extrusion melt temperatures of greater than or equal to 615° F. (324° C.); subjecting the semi-molten or molten adhesive backing material web to a vacuum of greater than 40 inches H[0185] 2O (9.8 Pa) while at the extrusion coating nip; subjecting the semi-molten or molten adhesive backing material to a positive air pressure device set at greater than about 60 psi (0.41 MPa) at the extrusion coating nip; activating an implosion agent while at the extrusion coating nip; and heat soaking of the carpet by subjecting it to infra-red radiation set at about 1000° C. for about 1 to about 6 seconds.
  • Various embodiments of the present invention were evaluated and, in specific instances, compared to prior art embodiments. However, the Examples shown should in no way limit the scope of the present invention to such Examples. [0186]
  • EXAMPLES
  • Test Methods [0187]
  • The primary performance criteria determined for the various Examples included: tuft bind, abrasion resistance, Velcro rating, flexibility and lamination strength. Tuft bind testing was conducted in accordance with ASTM D-1335-67. [0188]
  • Moduli for the ethylene polymers used in the present invention were measured in accordance with ASTM-790. [0189]
  • Abrasion resistance was based on a qualitative Velcro fuzzing test. In this test, a 2 inch (5.1 cm) diameter, 2 pound (0.91 kg) roller coated with the loop side of standard Velcro was passed 10 times over the face side of coated carpet samples. The fuzz on the abraded carpet was then compared to a set of carpet standards and rated on a 1-10 scale wherein a rating of 10 denoted zero fuzzing. [0190]
  • Flexibility rating was also based on a qualitative assessment. Lamination strength was based on manual qualitative assessment in which a good delamination rating was given if the various layers of a carpet sample could not be manually pulled apart (i.e., separation of the adhesive backing material from the primary backing material), while a poor rating was given if layers delaminated. [0191]
  • The Aachen test is used to determine the dimensional stability of carpet tile. The Aachen test used herein is ISO Test Method 2551. Briefly described, carpet tiles are first measured in the machine and cross-machine dimensions and then exposed to heat (140° F. (60° C.) for 2 hours) and moisture (submerged in water for 2 hours). The carpet tiles are dried for 16 hours in a drying oven. The tiles are then put into a conditioning room for 48 hours, after which each tile is measured in the machine and cross-machine directions. The results are given in terms of a percent change from the original dimensions. [0192]
  • Resins [0193]
  • Table 1 lists the various ethylene polymers used to prepare the various Examples. [0194] TABLE 1 Melt Index Density Modulus Resin Type (gm/10 min) (gm/cc) psi (MPa) A SLEP 30 0.871  2.560 (17.4) B SLEP 30 0.885  5.400 (36.7) C SLEP 30 0.900 13.700 (93.2) D SLEP 10 0.900 ND E SLEP 13 0.871 ND F SLEP 75 0.871 ND G SLEP 75 0.900 ND H SLEP 175 0.900 ND I HBLEP 35 0.882 ND J* LLDPE 5.4 0.921 ND K* LDPE 12 0.916 23.500 (160) L* LDPE 120 0.922 43.000 (293) M* LDPE 150 0.913 ND N* ULDPE 6 0.911 ND O* ULDPE 1 0.912 26.700 (182) P* LLDPE 1 0.920 38.000 (259) Q* HDPE 10 0.960 182.000 (1238) R* ULDPE 30 0.913 28.400 (193) S* LDPE 55 0.922 41.000 (279)
  • Examples 1-12
  • Table 2 summarizes the polymers, extrusion conditions and carpet sample performance results for Inventive Examples 1-8 and Comparative Runs 9-12. The extrusion coating equipment consisted of a two-extruder Black Clawson coextrusion line equipped with a 3½ inch (8.9 cm) diameter primary extruder having a 30:1 L/D and a 2½ inch (6.4 cm) diameter secondary extruder with a 24:1 L/D. For these examples, only the large extruder was operated at 90 rpms (250 lbs./hr). A 76 cm slot die was attached to the extruder and was deckled to 69 cm with a 20-mil (0.51 mm) die gap and a 6-inch (15.2 cm) air/draw gap. The nip roll pressure was set at 85 psi (0.58 MPa) and the chill roll was controlled at 60° F. (15.6° C.). The targeted extrusion temperatures, line speed and coating thicknesses are listed in Table 2. [0195]
  • Greige good swatches of polypropylene (26 OSY (919.6 cm[0196] 3/m2), tufted, loop pile, straight stitch greige goods available from Shaw Industries under the designation of Volunteer) were cut and slip sheeted onto Kraft paper for each Example and candidate resins were extrusion coated onto the backside of the greige goods. Secondary backing material (2.8 OSY (99 cm3/m2) woven polypropylene scrim known as Action Bac® available from Amoco Chemical Company, Fabrics and Fibers Division) was added to the backside of greige goods after the disposition of the extrudate at the die and before the nip pressure rollers to form a laminate structure. FIG. 2 shows the extrusion coating method and the sequence of application of an extrusion coated adhesive backing material followed by the application of an optional secondary backing material. In some instances, greige good swatches were first preheated in a convection oven at 200° F. (93° C.) for 30 min. After coated samples were aged for 24 hours at ambient room temperature and 70% relative humidity, tuft bind, abrasion resistance and delamination were determined. TABLE 2 Pre- Coat Melt Line Tuft Temp Thick Wt Temp Speed Lamin- Bind ° F. mil OSY ° F. ft/min ation lbs. Ex. Resin (° C.) (mm) (cm3/m2) (° C.) (m/min) Flex Strength (kg)  1 C Ambient 21 14.5 500 22 Good Good 8.0 (0.53) (513) (260) (6.7) (3.6)  2 D Ambient 20 ND 500 22 Good Good 7.6 (0.51) (260) (6.7) (3.4)  3 D Ambient  7 ND 500 65 Good Good 5.0 (0.18) (260) (19.8)  (2.3)  4 A 140 ND 15.5 500 22 Good Good 4.6 (60) (548) (260) (6.7) (2.1)  5 G 140 ND 13.1 500 22 Good Good 7.0 (60) (463) (260) (6.7) (3.2)  6 F 150 ND 11.9 500 30 Good Good 7.0 (66) (421) (260) (9.1) (3.2)  7 E 160 ND 18.9 500 22 Good Good 10.4  (71)  669) (260) (6.7) (4.7)  8 A 160 ND 11.8 550 30 Good Good 7.6 (71) (417) (288) (9.1) (3.4)  9* R 140 ND 17.6 500 22 Stiff Poor 7.1 (60) (623) (260) (6.7) (3.2) 10* J Ambient 20 ND 500 22 Stiff Poor ND (0.51) (260) (6.7) 11* L Ambient 20 ND 500 22 Stiff Poor ND (0.51) (260) (6.7) 12* S Ambient 20 ND 500 22 Stiff Poor ND (0.51) (260) (6.7)
  • Inventive Examples 1-8 show that homogeneously branched ethylene polymers result in carpet samples with good flexibility and good cohesion of the carpet components and that tuft bind and abrasion resistance are dependent on processing conditions. Two high pressure LDPE, a heterogeneously branched LLDPE, and a heterogeneously branched ULDPE extrusion coating (Comparative Runs 9-12) resulted in relatively stiff carpet samples and relatively poor carpet component cohesiveness. [0197]
  • One indication of poor component cohesiveness was relatively low adhesiveness of the backing material to the primary backing material. Another indication was relatively low penetration of the yarn or fiber bundles with the LDPE, LLDPE and ULDPE extrusion coating resins. [0198]
  • Examples 13-22
  • Table 3 summarizes the polymers, extrusion conditions, and carpet performance results for Inventive Examples 13-22. These examples used the same extrusion equipment, extrusion conditions and greige goods listed for Examples 1-12. [0199] TABLE 3 Pre- Melt Line Tuft Temp Thick Temp Speed Bind ° F. mil ° F. ft/min Lamination lbs. Ex. Resin (° C.) (mm) (° C.) (m/min) Flex Strength (kg) 13 C 175  7 425 65 Good Good 3.6 (79) (0.18) (218) (19.8) (1.6) 14 C 175  7 500 65 Good Good 5.4 (79) (0.18) (260) (19.8) (2.4) 15 C 175  7 550 65 Good Good 6.3 (79) (0.18) (288) (19.8) (2.9) 16 C 175  7 575 65 Good Good 6.6 (79) (0.18) (302) (19.8) (3.0) 17 C 175  7 600 65 Good Good 5.3 (79) (0.18) (316) (19.8) (2.4) 18 C 175 15 425 30 Good Good 6.9 (79) (0.38) (218)  (9.1) (3.1) 19 C 175 15 500 30 Good Good 6.8 (79) (0.38) (260)  (9.1) (3.1) 20 C 175 15 550 30 Good Good 8.3 (79) (0.38) (288)  (9.1) (3.8) 21 C 175 15 575 30 Good Good 6.2 (79) (0.38) (302)  (9.1) (2.8) 22 C 175 15 600 30 Good Good 6.2 (79) (0.38) (316) (2.8)
  • Inventive Examples 13-22 show the effect of coating thickness and extrusion temperature on carpet backing performance. In certain aspects of the present invention, coating thicknesses greater than 7 mils (0.18 mm), preferably greater than or equal to 11 mils (0.38 mm), more preferably greater than or equal to about 15, and most preferably greater than or equal to 22 mils (0.56 mm) are preferred for extrusion melt temperatures greater than 550° F. (288° C.), preferably greater than or equal to 575° F. (302° C.), more preferably greater than or equal to 600° F. (316° C.) and most preferably greater than or equal to 615° F. (324° C.). Practitioners will appreciate that extrusion melt temperature and extrusion line speed are inversely related. That is, lower extrusion temperatures will generally require slower extrusion line speeds to achieve good penetration of the yarn. Practitioners will also appreciate that at elevated temperatures, thermal stabilization additives such as Irganox® 1010 and Irgafos® 168 (both supplied by Ciba-Geigy) may be required to achieve the full benefit of the present invention such as, for example, adhesive backing material penetration of the yarn or fiber bundles greater than 40 percent. Practitioners will also appreciate that excessive chemical stabilization may adversely effect draw down performance, thus additive selection and concentration must be balanced against draw down requirements and penetration requirements. However, in general, higher additive concentrations will be required at higher extrusion melt temperatures. [0200]
  • Examples 23-54
  • Table 4 summarizes the polymers, extrusion conditions and carpet performance results for Examples 23-54. In this evaluation, the extrusion coating equipment consisted of a 3½ inch (8.9 cm) diameter Black Clawson Model 435 extruder equipped with a 30:1 L/D screw, a 150 hp (311 Joules/hr) Electro Flight drive system, a Cloreren 3-layer feedblock, and a Black Clawson Model 300 XLHL 30″ coat hanger die externally deckled to 24 inches (61 cm) using a 20 mil (0.51 mm) die gap and a 6 inch (15.2 cm) air/draw gap. The targeted extrusion temperatures, screw speed, line speed and coating thicknesses are listed in Table 4. [0201]
  • Samples of polypropylene greige goods (26 OSY (920 cm[0202] 3/m2), tufted, loop pile, straight stitch greige goods supplied by Shaw Industries under the designation of Volunteer) were used. Candidate ethylene polymers were extrusion coated onto the backside of greige goods that were run continuously through the extrusion coater rather than slip sheeted as individual greige good swatches. Electric and gas-fired infrared heaters were installed prior to the coating station to preheat the greige goods. A partitioned vacuum pressure roll with a 45° vacuum section was installed and attached to a variable vacuum pump. The vacuum section was positioned at the contact point of extrudate and greige goods. The nip roll pressure was set at 80 psi and the chill roll was controlled at 120° F. (49° C.). Secondary backing material (2.8 OSY 99 cm3/m2) woven polypropylene scrim or Action Bac® available from Amoco Chemical Company, Fabrics and Fibers Division) was added to the backside of the carpet samples after disposition of the extrudate at the die and before the nip pressure rollers to form a laminate structure. After coated samples were aged for 24 hours at ambient and 70% relative humidity, tuft bind, abrasion resistance and delamination resistance were determined. TABLE 4 Pre- Coat Melt Line Tuft Temp Weight Temp Screw Speed Vac Bind ° F. Thick OSY ° F. Speed ft/min in H2O Lamination lbs. Ex. Resin (° C.) mil (cm3/m2) (° C.) rpm (m/min) (Pa) Flex Strength (kg) 23 C Ambient ND 11.6 500 20 18 0 Good Good 8.6 (410) (260) (5.5) (3.9) 24 C Ambient ND 14.2 500 25 18 0 Good Good 7.9 (502) (260) (5.5) (3.6) 25 C Ambient ND 17.8 500 30 18 0 Good Good 10.1 (630) (260) (5.5) (4.6) 26 B Ambient ND  9.7 500 20 18 0 Good Good 9.0 (343) (260) (5.5) (4.1) 27 B Ambient ND 13.0 500 25 18 0 Good Good 7.0 (460) (260) (5.5) (3.2) 28 B Ambient ND 14.2 500 30 18 0 Good Good 9.1 (502) (260) (5.5) (4.1) 29 G 200 ND  6.9 400 ND 18 0 Good Good 6.6  (93) (244) (204) (5.5) (3.0) 30 G 200 ND 11.8 400 ND 18 0 Good Good 8.4  (93) (417) (204) (5.5) (3.8) 31 H 200 ND 10.2 400 ND 18 0 Good Good 7.3  (93) (361) (204) (5.5) (3.3) 32 B 150 ND  8.0 500 24 26 20 Good Good ND  (66) (283) (260) (7.9) (4.9) 33 B 150 ND  7.7 500 24 26 10 Good Good ND  (66) (272) (260) (7.9) (2.5) 34 B 150 ND  7.8 500 24 26 0 Good Good ND  (66) (276) (260) (7.9) 35 B 150 ND  3.9 500 48 26 0 Good Good ND  (66) (138) (260) (7.9) 36 B 150 ND 15.8 500 48 26 10 Good Good 8.7  (66) (559) (260) (7.9) (2.5) (3.9) 37 B 150 ND 15.4 500 48 26 25 Good Good 9.6  (66) (545) (260) (7.9) (6.1) (4.4) 38 B 150 ND 14.8 550 48 26 25 Good Good 7.6  (66) (523) (288) (7.9) (6.1) (3.4) 39 B 150 ND 18.0 550 48 26 20 Good Good 8.2  (66) (637) (288) (7:9) (4.9) (3.7) 40 G 175 ND 10.7 400 26 26 25 Good Good ND  (79) (378) (204) (7.9) (6.1) 41 G 175 ND  9.2 400 26 26 10 Good Good ND  (79) (325) (204) (7.9) (2.5) 42 G 175 ND  9.5 400 26 26 2.5 Good Good ND  (79) (336) (204) (7.9) (0.6) 43 G 175 ND 27.2 400 55 26 25 Good Good 10.9 (79) (962) (204) (7.9) (0.6) (4.9) 44 G 175 ND 26.0 400 55 26 10 Good Good 8.8  (79) (920) (204) (7.9) (2.5) (4.0) 45 G 175 ND 17.8 400 55 26 25 Good Good 10.2  (79) (630) (204) (7.9) (6.1) (4.6) 46 C 250 ND  9.8 500 24 26 25 Good Good 10.9 (121) (347) (260) (7.9) (6.1) (4.9) 47 C 250 ND  9.6 500 24 26 10 Good Good 9.9 (121) (340) (260) (7.9) (2.5) (4.5) 48 C 250 ND  9.3 500 24 26 2.5 Good Good ND (121) (329) (260) (7.9) (0.6) 49 C 250 ND 16.6 500 51 26 2.5 Good Good 6.8 (121) (587) (260) (7.9) (0.6) (3.1) 50 C 250 ND 17.5 500 51 26 10 Good Good 7.0 (121) (619) (260) (7.9) (2.5) (3.2) 51 C 250 ND 16.6 500 51 26 25 Good Good 7.6 (121) (587) (260) (7.9) (6.1) (3.4) 52 C 245 ND 10.2 500 50 26 50 Good Good 7.8 (118) (361) (260) (7.9) (12.3) (3.5) 53 C 245 ND 19.8 500 50 26 50 Good Good 10.8 (118) (700) (260) (7.9) (12.3) (4.9)  54* L 200 15 ND 400 ND 18 0 Stiff Poor ND (93) (0.38) (204) (5.5)
  • These Examples show that homogeneously branched ethylene polymers result in carpet samples with good flexibility and good cohesion of carpet components, and that tuft bind strength and abrasion resistance are dependent on processing conditions. These Examples also show the improvement in carpet backing performance is attainable by the utilization of a carpet preheating process step, optimized coating thickness, and/or a vacuum nip pressure process step. [0203]
  • The high pressure LDPE extrusion coating resin resulted in stiff carpet with poor component cohesiveness. [0204]
  • Examples 55-77
  • Table 5 summarizes the polymers, extrusion conditions and carpet performance results for Examples 55-77. These examples employed the same extrusion equipment and extrusion conditions listed for Examples 23-54, with the exception that nylon greige goods (26 OSY (920 cm[0205] 3/m2), tufted, loop pile, straight stitch greige goods available from Shaw Industries under the designation of Vocation™) were used instead of polypropylene greige goods. TABLE 5 Pre- Coat Melt Line Temp Weight Temp Screw Speed Vacuum ° F. OSY ° F. Speed ft/min in H2O Lamination Ex. Resin (° C.) (cm3/m2) (° C.) RPM (m/min) (Pa) Flex Strength 55 C Ambient 18.4 500 25 18 0 Good Good (651) (5.5) 56 C Ambient 18.9 500 30 18 0 Good Good (668) (5.5) 57 C Ambient 20.2 500 35 18 0 Good Good (714) (5.5) 58 B Ambient 12.1 500 25 18 0 Good Good (428) (5.5) 59 B Ambient 17.2 500 30 18 0 Good Good (608) (5.5) 60 B Ambient 18.1 500 35 18 0 Good Good (640) (5.5) 61 G 200  8.4 400 ND 18 0 Good Good  (93) (297) (5.5)  62* L 200 13.6 400 ND 18 0 Poor Poor  (93) (481) (5.5) 63 B 150 17.6 550 48 26 22 Good Good  (66) (623) (7.9) (5.4) 64 B 150 15.1 550 48 26 11 Good Good  (66) (534) (7.9) (2.7) 65 B 150 16.4 550 48 26 2.5 Good Good  (66) (580) (7.9) (0.6) 66 G 175 16.9 400 26 26 25 Good Good  (79) (598) (7.9) (6.1) 67 G 175 16.6 400 26 26 10 Good Good  (79) (587) (7.9) (2.5) 68 G 175 17.3 400 26 26 2.5 Good Good  (79) (612) (7.9) (0.6) 69 G 175  8.0 400 55 26 2.5 Good Good  (79) (283) (7.9) (0.6) 70 G 175  8.4 400 55 26 10 Good Good  (79) (297) (7.9) (2.5) 71 G 175  8.3 400 55 26 25 Good Good (79) (294) (7.9) (6.1) 72 C 260 18.8 500 24 26 25 Good Good (127) (665) (7.9) (6.1) 73 C 260 16.6 500 24 26 10 Good Good (127) (587) (7.9) (2.5) 74 C 260 16.6 500 24 26 2.5 Good Good (127) (587) (7.9) (0.6) 75 C 260  8.1 500 51 26 2.5 Good Good (127) (286) (7.9) (0.6) 76 C 260  8.1 500 51 26 10 Good Good (127) (286) (7.9) (2.5) 77 C 260  7.9 500 51 26 25 Good Good (127) (279) (7.9) (6.1)
  • Inventive Examples 55-77 show also that homogeneously branched ethylene polymers result in carpet samples with good flexibility and good cohesion of the carpet components, and that tuft bind strength and abrasion resistance are dependent on processing conditions. Like Examples 23-53, these examples also show that improvements in carpet backing performance are attainable by employing a preheat process step, optimum coating thickness and/or a vacuum nip pressure process step. [0206]
  • Examples 78-86
  • Table 6 summarizes the polymers, extrusion conditions and carpet performance results for Examples 78-86. These examples used the same extrusion equipment and extrusion conditions listed for Examples 1-12, with the exceptions that cross stitch polypropylene greige goods (20 OSY (707 cm[0207] 3/m2), tufted, loop pile available from Shaw Industries under the style name of “Proton”) were used instead of straight stitch goods TABLE 6 Pre- Coat Melt Line Tuft Temp Weight Temp Speed Bind ° F. OSY ° F. ft/min Lamination lbs. Abrasion Velcro Ex. Resin (° C.) (cm3/m2) (° C.) (m/min) Flex Strength (kg) Resistance Test 78 C Ambient  7.7 500 48 Good Good  8.5 Good 8 (272) (260) (14.6) (3.9) 79 C 175 16.9 500 22 Good Good 14.3 Good 9 (79) (598) (260)  (6.7) (6.5) 80 E 175  9.9 500 48 Good Good 10.2 Good 9 (79) (350) (260) (14.6) (4.6) 81 E 175 17.3 500 22 Good Good 13.2 Good 9 (79) (612) (260)  (6.7) (6.0) 82 D 175 17.8 500 22 Good Good 12.9 Good 9 (79) (630) (260)  (6.7) (5.9) 83 D 175  9.2 500 48 Good Good  7.6 Good 9 (79) (325) (260) (14.6) (3.4)  84* J 175  9.7 500 48 Stiff Poor  8.7 Good 9 (79) (343) (260) (14.6) (3.9)  85* J 175 16.3 500 22 Stiff Poor 10.4 Good 9 (79) (577) (260)  (6.7) (4.7)  86* J Ambient 18.6 500 22 Stiff Poor  9.1 Good 9 (658) (260)  (6.7) (4.1)
  • Inventive Examples 78-83 show that homogeneously branched ethylene polymers result in cross-stitched carpet samples with good flexibility and good cohesion of the carpet components. The LLDPE extrusion coating resin used for Comparative Runs 84-86 resulted in stiff cross-stitched carpet samples. [0208]
  • <