POLYURETHANE CARPET BACKING COMPOSITIONS AND A PROCESS FOR APPLYING A SECONDARY BACKING ON A SYNTHETIC PRIMARY BACKED CARPET SUBSTRATE

Abstract: The polyurethane carpet backing compositions are characterized by containing a non chlorinated thermoplastic polymer. This invention provides an improvement in edge curl or tuft lock for a synthetic primary backed carpet backed with a cured polyurethane composition as a secondary backing.

Description: POLYURETHANE CARPET BACKING COMPOSITIONS AND A PROCESS FOR APPLYING A SECONDARY BACKING ON A SYNTHETIC PRIMARY BACKED CARPET SUBSTRATE The present invention concerns polyurethane backed carpets wherein the backing composition contains a thermoplastic polymer incorporated therein. Synthetic based carpets backed with polyure- thane generally have a tendency to undergo curling at their periphery when moisture or certain organic sol¬ vents are absorbed. This edge curl phenomenon is believed to pertain directly to the back stitch loops of the carpet fibers that are firmly encapsulated with the polyure¬ thane backing material. Certain carpet fibers, such as nylon, are highly sensitive to moisture and organic solvents, yet their back stitch loops are the high strength member of the system. The polypropylene primary backing, which is impervious to moisture, is the high tension member of the system. When the surface fibers and/or back stitch loops absorb moisture or organic solvents present in installation adhesives, the loops tend to swell or enlarge. Collectively, the enlarged loops create a bending moment that is perpen- dicular to the primary backing and subsequently the carpet curls at its periphery and in extreme cases, buckles. However, in accordance with the present invention, woven synthetic, particularly polypropylene, primary backed carpets are provided with an improvement in one or more of its properties such as edge curl performance or tuft lock by incorporating minor amounts of a thermoplastic polymer of one or more ethylenically unsaturated monomers into a urethane forming composi¬ tion. The present invention pertains to a polyure¬ thane carpet backing composition containing (A) a polyol composition comprising (1) at least one relatively high molecular weight polyether polyol having an aver- age hydroxyl functionality from 2 to 8, preferably from 2 to 3 and an average hydroxyl equivalent weight of from 500 to 2200, preferably from 600 to 2000; (2) at least one relatively low molecular weight polyol having an average hydroxyl functionality of from 2 to 8, preferably from 2 to 3 and having an average hydroxyl equivalent weight of from 31 to 230, preferably from 31 to 200; (B) at least one polyisocyanate, polyisothio- cyanate or mixture thereof; (C) one or more catalysts; (D) at least one thermoplastic polymer prepared by polymerizing one or more ethylenically unsaturated monomers; and optionally (E) one or more inorganic filler materials; and wherein (1) components (A-l) and (A-2) are employed in quantities which provides a hydroxyl equivalent ratio of (A-2):(A-1) of from 0.8:1 to 5.5:1, preferably from 0.8:1 to 4:1; (2) component (A) is present in a quantity of from 25 to 45, preferably from 28 to 36 percent by weight based upon the combined weight of components (A), (D) and (E); (3) component (E) is employed in quantities of from zero to 75, preferably from 60 to 70 percent by weight of the combined weight of components (A), (D) and (E); and (4) components (A) and (B) are present in quantities which provides an NCX:OH equivalent ratio of from 0.95:1 to 1.5:1, preferably from 11:1 to 1.25:1 wherein X is oxygen and/or sulfur, characterized in that the thermoplastic polymer is a non-chlorinated thermo¬ plastic polymer having a density of from 0.75 to 1.60 g/cc, preferably from 0.90 to 1.3 g/cc; a melt index of up to 50 g/10 min. , preferably from 1.0 to 20 g/10 min. ; a flexural modulus of from 5,000 to 300,000 psi (34 to 2068 MPa), and an average particle size of from 5 to 150 micrometers, the non-chlorinated thermoplastic polymer is present in a quantity of from 0.05 to 25 percent by weight based upon the combined weights of components (A), (D) and (E). This invention also pertains to a process for applying a secondary backing on a synthetic primary backed carpet substitute comprising coating the substrate with a polyurethane carpet backing composition and curing the composition, characterized in that the polyurethane carpet backing composition is the composi¬ tion described hereinbefore. This invention provides an improvement in edge curl or tuft lock for a synthetic primary backed carpet substrate backed with a cured polyurethane com¬ position as a secondary backing. Suitable relatively high molecular weight polyether polyols which can be employed in the present invention include adducts of one or more compounds containing 2 to 8 hydroxyl groups per molecule and one or more hydrocarbylene or halogen substituted hydrocar- bylene oxides. Suitable hydroxyl-containing compounds include those having from 2 to 20, preferably from 2 to 6, carbon atoms such as, for example, water, ethylene glycol, diethylene glycol, propylene glycol, 1,2-butane diol, 1,3-butane diol, 1,4-butane diol, glycerine, tri- methylol propane, p,p'-isopropylidine diphenol, and mixtures thereof. Suitable hydrocarbylene or halogen substituted hydrocarbylene oxides which can be employed to prepare polyether polyols include those having from 2 to 12, preferably from 2 to 4, carbon atoms such as, for example, ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, 3-methyl-l,2-butylene oxide, 3,3-dimethyl- 1,2-butylene oxide, and mixtures thereof. Other relatively high molecular weight polyols which can be employed herein include polymer-containing polyols such as, for example, those disclosed in U.S. Patents RE 29,118 (Stamberger), RE 28,715 (Stamberger), RE 29,014 (Pizzini et al), 3,869,413 (Blankenship et al), U.S. 4,390,649 (Hoffman et al) and U.S. 4,394,491 (Hoffman). Suitable low molecular weight polyols include, for example, ethylene glycol, propylene glycol, 1,3-propane diol, 1,4-butane diol, 1,6-hexane diol, dipropylene glycol, diethylene glycol, triethylene glycol, tetra- ethylene glycol, tripropylene glycol, tetrapropylene glycol, heptapropylene glycol, and mixtures thereof. Also suitable as low molecular weight polyols are adducts of initiator compounds having from 2 to 8 active hydrogen atoms per molecule and a hydro- carbylene oxide as hereinbefore described so long as the resultant adduct has the desired equivalent weight for the low equivalent weight polyol. Particularly suitable initiator compounds include, for example, water, ethylene glycol, propylene glycol, glycerine, trimethylol propane, aniline, ammonia, ethylene diamine, diethylenetriamine, aminoethylethanol amine, pentaerythritol, glucose, fructose, sucrose, sorbitol, and mixtures thereof. When adducts of initiator compounds having more than 8 active hydrogen atoms per molecule are employed, they must be employed in admixture with polyols having less than 8 hydroxyl groups per molecule in quantities so as to result in an average of from 2 to 8 hydroxyl groups per molecule. Suitable organic polyisocyanates include, for example, 2,4-toluenediisocyanate, 2,6-toluenediisocyanate, xylylenediisocyanate, p,p'-diphenylmethanediisocyante, p-phenylenediisocyanate, naphthalenediisocyanate, dianisodine diisocyanate. polymethylene polyphenyl- isocyanate, hexamethylenediisocyanate, and mixtures thereof. Also suitable are the isocyanate terminated prepolymers prepared from one or more of the above mentioned polyisocyanates and one or more of the above mentioned polyols. Suitable also are the trimerized diisocyanates and crude diisocyanates. Also suitable are the corresponding polyiso- thiocyanates. including isothiocyanate terminated prepolymers. Suitable catalysts which can be employed include, for example, tertiary amines, organometallic compounds, particularly metal carboxylates, and mixtures thereof. Particularly suitable catalysts include, for example, di-n-butyl tin-bis(mercaptoacetic acid isooctyl ester), dimethyl tin dilaurate, dibutyl tin dilaurate, stannous octoate, lead octoate, triethylenediamine, N-methyl morpholine, and mixtures thereof. Suitable non-chlorinated thermoplastic polymers which can be employed herein include those polymers pre¬ pared from one or more polymerizable ethylenically unsat- urated monomers, said polymer having density of from 0.75 to 1.60, preferably from 0.90 to 1.3 g/cc; a melt index of up to 50 g/10 min., preferably from 1.0 to 20 g/10 min.; a flexural modulus of from 5,000 to 300,000 psi (34 to 2068 MPa) and an average particle size of from 5 to 150 micrometers. Particularly suitable non-chlorinated thermo¬ plastic polymers include, for example, ethylene-acrylic acid interpolymers, ethylene carbon monoxide inter- polymers, high density polyethylene, linear low density polyethylene, low density polyethylene, ethylene-butene interpolymers, ethylene-2-methylpentene interpolymers, ethylene-hexene interpolymers, ethylene-octene inter¬ polymers, polypropylene, ethylene-vinyl acetate inter¬ polymers, ethylene-methyl acrylate interpolymers, ethylene-methacrylic acid interpolymers, ethylene- methyl methacrylate interpolymers, ethylene-ethyl acrylate interpolymers, ethylene-acrylic acid-carbon monoxide interpolymers, ethylene-acrylic acid- vinyl acetate interpolymers, and mixtures thereof. Suitable inorganic fillers which can be employed herein includes, for example, alumina tri- hydrate, calcium carbonate, talc, calcium sulfate, aluminum silicate, kaloin, silion dioxide, bentonite, and mixtures thereof. The urethane backing compositions may also contain, if desired, dyes, pigments, fire retardant agents, foaming agents, silicone surfactants, or combinations thereof. The following examples are illustrative of the invention, but are not to be construed as to limiting the scope thereof in any manner. GLOSSARY OF TERMS doctor = to spread a puddle of froth or mixed components evenly across the width of a carpet with a draw down bar. coating weight = the weight of the foam that is applied to the carpet. greige weight = the weight of fibers and primary backing, tuft lock = the amount of force needed to pull a tuft of carpet fiber from the foam backing, primary backing = the material through which the carpet fibers are tufted. GENERAL PROCEDURE To a 400 ml cup, 100 grams of the desired polyol mixture was added. The appropriate amount of filler and thermoplastic polymer was then added to the polyol mixture and admixed for 2 minutes (120 s) using a high speed stirrer. Based on the desired index, the effective amount of isocyanate was added and mixed until the uncatalyzed compo¬ sition reached ~93°F(34°C). The catalyst(s) was/were then added and mixed. The catalyzed mixture was then "doctored" onto the back of the carpet within 45 seconds from the time the catalyst was administered and allowed to cure for about 8 minutes (420 s) at a temperature between 100° and 120°C. The following procedures were employed to determine the properties of the urethane backed carpet or reaction mixtures. Determination of Coating Weight A 6.75" x 6.75" (171.45 mm x 171.45 mm) square was cut from the carpet sample and weighed to the nearest 0.1 gram. This weight minus the greige weight of the carpet specimen was the actual coating weight in oz/yd 2 (kg/m 2 ). Determination of Moisture Edge Curl Moisture edge curl was determined by thoroughly saturating a 6" x 2" (152.4 mm x 50.8 mm) urethane backed sample with water and placing the sample, backing down on a flat surface. A heavy weight was used to hold the first 2 inches (50.8 mm) of the test specimen firmly down on the surface. The sample was left undis¬ turbed for 90 minutes (5400 s). After this time, the extent of curl or the distance from the flat surface to the back side of the outer edge of the carpet was measured in millimeters. Because edge curl is a function of time, it is pertinent that all measurements be taken at the specified time. Determination of Adhesive Edge Curl A 2" x 6" (50.8 mm x 152.4 mm) sample of carpet cut in the warp direction was covered on the backing side with a polyethylene film of equivalent dimensions. The carpet was then positioned face-up on a 2" x 8" x 7/16" (50.8 mm x 203.2 mm x 11.1 mm) piece of transite so that 2 inches (50.8 mm) was extended over the end of the transite. Masking tape was used to secure the carpet to the transite. The polyethylene film was pulled back to expose the backing. Adhesive was applied to the urethane backing after which the backing was immediately covered with the polyethylene film. After 4 hours (14400 s), the distance of the end of the carpet above the transite planar surface was measured in millimeters. Determination of Toluene Edge Curl The toluene edge curl test was developed to measure the actual amount of curl a urethane backing can experience when saturated with toluene, a solvent in many adhesives. In this test a 2" x 6" (50.8 mm x 152.4 mm) carpet sample was placed backing side down on a flat surface. The sample was then saturated with toluene and left undisturbed for 30 minutes (1800 s). After this time, the extent of curl or the actual distance from the flat surface to the outer edge of the carpet sample was measured in centimeters. Determination of Tack The relative tackiness and embossability of the urethane backing systems was determined by "finger contact" utilizing a polypropylene glove. After the samples were placed in the oven to cure they were finger-touched at 1 to 2 minute (60-120 s) time spans for tack. Any up-take of material onto the glove was considered to be indicative of excessive tackiness. If there was no up-take of material yet embossment occurred, the system was considered "embossable" and the time it retained this quality was noted. The following materials were employed in the examples. RELATIVELY HIGH MOLECULAR WEIGHT POLYOL A was an adduct of dipropylene glycol and propylene oxide. The resultant diol had an average hydroxyl equivalent weight of 1000. RELATIVELY LOW EQUIVALENT WEIGHT POLYOL A was dipropylene glycol having an average hydroxyl equivalent weight of 67. ISOCYANATE A was an 80/20 mixture of 2,4-/2,6-toluene diisocyanate having an average NCO equivalent weight of 87. ISOCYANATE B was a prepolymer prepared by reacting isocyanate A with dipropylene glycol in an equivalent NCO:OH ratio of 1.25:1. The resultant prepolymer contained 28% NCO by weight and had an average NCO equivalent weight of 150. CATALYST A was dimethyl tin dilaurate FILLER A was alumina trihydrate. FILLER B was calcium carbonate. CARPET SUBSTRATE A was Antron brand nylon fibers weighing 2 about 22 oz/yd 2 (0.75 kg/m ) tufted through a woven polypropylene primary backing at a rate of 7.5 stitches per inch (0.295 stiches per mm). This greige good had a pile height of 0.156 inches (3.96 mm), a WDF (Weight Density Factor) of 111,000 and a greige weight of 25 oz/yd 2 (0.85 kg/m 2 ). CARPET SUBSTRAT 2 E B was Antr 2 on brand nylon fibers weighing about 26 oz/yd (0.88 kg/m ) tufted through a woven polypropylene primary backing at a rate of 9.0 stitches per inch (0.354 stitches per mm). This greige good had a pile height of 0.125 inches (3.17 mm), a WDF of 194,000 and a greige weight of 29 oz/yd (0.98 kg/m 2 ). THERMOPLASTIC POLYMER A was an ethylene-acrylic acid copolymer containing 6.5% acrylic acid by weight and having a melt index (I,) of 2.5 and a density of 4 0.9325 g/cc. Flexural Modulus of 2.6 x 10 psi (179 MPa), average particle size <_ 75 micrometer. THERMOPLASTIC POLYMER B was an ethylene-carbon monoxide copolymer containing 12% carbon monoxide by weight and having a melt index (I 2 ) of 10, g/10 min. a density of 0.9040 g/cc, a flexural modulus of 4 2.8x10 psi (193 MPa), and an average particle size 75 micrometer. THERMOPLASTIC POLYMER C was a high density polyethylene homopolymer having a melt index (I 2 ) of 5 g/10 min. a density of 0.935 g/cc, a flexural modulus of 5 1.9x10 psi (137 MPa), and an average particle size <75 micrometer. THERMOPLASTIC POLYMER D was a high density polyethylene homopolymer having a melt index (I 2 ) of 0.7 g/10 min. a density of 0.965 g/cc, a flexural modulus of 5 1.85x10 psi (128 MPa), and an average particle size 75 micrometer. THERMOPLASTIC POLYMER E was a linear low density copolymer of ethylene-butene-1 containing 6.5% butene-1 by weight and having a melt index (I 2 ) of 1.5 g/10 min., a density of 0.920 g/cc, a flexural 4 modulus of 3.0x10 psi (207 MPa), and an average particle size 75 micrometer. THERMOPLASTIC POLYMER F was a high density polyethylene homopolymer having a melt index (I 2 ) of 0.46 g/10 min. a density of 0.935 g/cc, a flexural modulus of 1.8xl0 5 psi (124 MPa), and an average particle size £75 micrometer. THERMOPLASTIC POLYMER G was a high density polyethylene homopolymer having a melt index (I 2 ) of 5 g/10 min., a density of 0.945 g/cc, a flexural modulus of 2.1x10 s psi (145 MPa), and an average particle size £75 micrometer. EXAMPLES 1 THROUGH 10 AND COMPARATIVE EXPERIMENTS A AND B A series of urethane backed carpet sub¬ strates were prepared by the general procedure. In Examples 1 through 10 and Comparative Experiment A and B, 85 parts by weight of Relatively High Molecular Weight (RHMW) Polyol A (0.085 equivalent OH), 15 parts by weight of Relatively Low Molecular Weight (RLMW) Polyol A (0.224 equivalent OH), 0.1 part by weight of Catalyst A, and 53.4 parts by weight of Isocyanate B (0.356 equivalents NCO) were employed. The hydroxyl equivalent ratio of RLMW Polyol A:RHMW Polyol A was 2.6:1 and the NCO:OH equivalent ratio was 1.15:1. In Examples 1 though 10, 90 parts by weight of Filler A and 95 parts by weight of Filler B were employed. Each thermoplastic polymer was employed at 5 parts by weight. The polyols were 34.5 weight percent, the thermoplastic polymer was 1.7 weight percent, and the inorganic fillers were 63.8 weight percent, of the combinded weights of the polyols, the thermoplastic polymer and the inorganic fillers. In Comparative Experiments A and B, 100 parts by weight of Filler A and 105 parts by weight of Filler B were employed. The polyols were 32.8 weight percent and the inorganic fillers were 67.2 weight percent, of the combined weights of the polyols and the inorganic fillers. In Examples 1 though 6 and Comparative Experiment A, carpet substrate A was employed. In Examples 7 through 10 and Comparative Experiment B, carpet substrate B was employed. The thermoplastic polymers for each example and the properties of the coated carpet substrate for Examples 1 through 10 and Comparative Experiments A and B are shown in Table I. TABLE I COMPONENTS EXAMPLE OR COMPARATIVE EXP AND PROPERTIES THERMOPLASTIC POLYMER, none B . 2 COATING weight, oz/yd 2 36.18 28.35 36.03 36.71 (kg/m ) (1.227) (0.961) (1.222) (1.245) ( TACK FREE TIME, min., 10 8 8.5 9 sec. 600 480 510 540 EDGE CURL Moisture, mm 16 3 4 0 Adhesive, mm 19 neg. neg. neg. Toluene, mm 4 0 0 0 TABLE I continued. COMPONENTS AND PROPERTIES EXAMPLE OR COMPARATIVE EXPERIMENT B 10 THERMOPLASTIC POLYMER, none D B 2 COATING weight, oz/yd 36.15 31 63 29 ,35 28 18 34.74 (kg/m 2 ) (1.226) (1 072) (0 ,995) (0 955) (1.178) EDGE CURL Moisture, mm 15

Claims: 1. A polyurethane carpet backing composition containing (A) a polyol composition comprising (1) at least one relatively high molecular weight polyether polyol having an average hydroxyl functionality from 2 to 8, and an average hydroxyl equivalent weight of from 500 to 2200; (2) at least one relatively low molecular weight polyol having an average hydroxyl functionality of from 2 to 8 and having an average hydroxyl equivalent weight of from 31 to 230; (B) at least one polyisocyanate, polyisothiocyanate or mixture thereof; (C) one or more catalysts; (D) at least one thermoplastic polymer prepared by polymerizing one or more ethylenically unsaturated monomers; and optionally (E) one or more inorganic filler materials; and wherein (1) components (A-l) and (A-2) are employed in quantities which provides a hydroxyl equivalent ratio of (A-2):(A-1) of from 0.8:1 to 5.5:1; (2) component (A) is present in a quantity of from 25 to 45 percent by weight based upon the combined weight of components (A), (D) and (E); (3) component (E) is employed in quantities of from zero to 75 percent by weight of the combined weight of components (A), (D) and (E); and (4) components (A) and (B) are present in quantities which provides an NCX:OH equivalent ratio of from 0.95:1 to 1.5:1 and X is oxygen or sulfur, characterized in that thermoplastic polymer is a non-chlorinated thermo¬ plastic polymer having a density of from 0.75 to 1.60 g/cc, a melt index of up to 50 g/10 min. , a flexural modulus of from 5,000 to 300,000 psi (34 to 2068 MPa) and an average particle size of from 5 to 150 micrometers, the non-chlorinated thermoplastic polymer is present in a quantity of from 0.05 to 25 percent by weigh based upon the combined weights of components (A), (D), and (E). 2. The composition of Claim 1 characterized in that the thermoplastic polymer has a density of from 0.90 to 1.3 g/cc, and a melt index of from 1.0 to 20 g/10 min. 3. A process for applying a secondary backing on a synthetic primary backed carpet sub¬ strate comprising coating the substrate with a polyurethane carpet backing composition and curing the composition, characterized in that the poly¬ urethane carpet backing composition is the compo¬ sition of either Claim 1 or Claim 2.

Inventors: MCKINNEY LINDA MARIE, MCKINNEY OSBORNE KELLY, MCKINNEY, LINDA, MARIE, MCKINNEY, OSBORNE, KELLY
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1985
Main classification: B32B3
IPC codes: C09D175, D06N7