Stock material or miscellaneous articles – Pile or nap type surface or component – Composition of pile or adhesive
Reexamination Certificate
1998-07-14
2001-01-09
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Pile or nap type surface or component
Composition of pile or adhesive
C428S095000, C156S078000
Reexamination Certificate
active
06171678
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to tufted carpeting with improved tuft bind and cracking resistance characteristics. More particularly, the present invention pertains to reactive polyurethane formulations which can be used to prepare tufted carpet with improved tuft bind while retaining good carpet feel and resistance to cracking.
DESCRIPTION OF THE RELATED ART
Tufted carpeting is manufactured by tufting yarns into a woven primary backing. The tufts are secured by applying at least one adhesive formulation to the primary backing side of the carpet/primary backing (“greige good”). In the past, SBR latexes have seen widespread use as adhesives for such purposes. However, such latexes have numerous drawbacks. First, neither the hydrolytic stability nor the durability of the cured elastomer is entirely satisfactory. Second, as the latex is applied in the form of an aqueous dispersion, considerable energy is expended in evaporating the aqueous component.
Polyurethanes have been considered as alternatives to SBR latex. Polyurethanes, in general, exhibit greater chemical and physical stability as compared to SBR latexes. Furthermore, polyurethanes may be applied either as an expandable or as a frothed foam, and may perform the dual function of tuft binding and cushioning. However, acceptable polyurethane systems have been difficult to formulate to achieve balanced properties. For example, tuft bind is known to be improved by increasing the hard segment content of the polyurethane polymer. However, increased hard segment content decreases the elastomer elongation, and alters both the feel of the carpet as well as its resistance to “cracking” when rolled.
U.S. Pat. Nos. 4,696,849 and 4,853,054 attest to the difficulties experienced in preparing polyurethane carpet backings. In U.S. Pat. No. 4,696,849, for example, improvements in the tuft bind are achieved by use of two distinct high primary hydroxyl polyols, one having an actual functionality of 1.4-1.95 and a second having an actual functionality greater than 2.05, admixed such that the average functionality is within the very narrow range of 2.00±0.03. Tuft bind is said to be increased, but no comparative formulations are included to verify any increase. In the U.S. Pat. Nos. 4,853,054 , blends of polyoxyalkylene polyether diols and triols, each having an equivalent weight between 1000 Da and 5000 Da, and the blend having an average actual functionality between 1.8 and 2.2, are used in conjunction with a polyisocyanate having a functionality between 1.9 and 2.4. Carpet splits are said to be reduced by the latter formulations, although the effect on tuft bind is unclear. When precoat adhesives are used, the average actual polyol blend functionality range is yet more narrow.
In general, it has been found that in order to be suitable for use as a carpet backing adhesive, the elongation of the polyurethane is desirably greater than 60%, with higher values more desirable, although the range between 40% and 60% may be acceptable for certain carpet styles and the degree of bending expected. Elongations lower than 60% often result in excessive cracking when the carpet is rolled or bent, for example during installation. Elongation less than 40% is clearly unacceptable. The lower acceptable limit for tuft bind is approximately 12 lbs, again with higher values much desired. As tuft bind is influenced by numerous factors such as the yarn denier, the nature of the backing, and the number of tufts per inch, limiting the polyurethane formulation window to resin components with functionalities close to two unacceptably limits the formulation window and the carpet properties which may be achieved.
It would be desirable to increase the tuft bind in polyurethane-backed carpeting. It would be further desirable to increase tuft bind without decreasing elongation of the polyurethane polymer. However, the competing effects of increasing the hard segment content, necessary to increase tuft bind, and increasing elongation which requires decreased high hard segment content, have thus far been unable to be reconciled.
SUMMARY OF THE INVENTION
It has now been surprisingly discovered that increases in tuft bind and elongation may be achieved by substituting 2-methyl-1,3-propanediol for all or part of the chain extender portion of polyurethane carpet backing adhesives, and that improvements in elongation and hence, cracking resistance, can be obtained by substituting low unsaturation polyols for all or part of the polyol component. The use of low unsaturation polyols allows the hard segment content to be raised, thus increasing tuft bind. Surprisingly, use of low unsaturation polyols does not require that a polyol functionality close to 2 be maintained. Preferably, 2-methyl-1,3-propanediol and low unsaturation polyol components are used simultaneously to provide both exceptional tuft bind and elongation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The tufted carpets of the subject invention are initially prepared in the conventional manner, the greige good being constructed by tufting yarns into a primary woven backing of jute, polypropylene, or the like. The primary backing side of the greige good is then contacted with the reactive polyurethane precoat adhesive, generally in the form of a frothed foam. If desired, two precoat adhesives, one being a lower density foam or liquid, non-foam precoat adhesive, preferably containing 2-methyl-1,3-propanediol as chain extender and low unsaturation polyol as the polyol component, may be applied to yet more effectively wet out the protruding tuft ends and achieve higher tuft bind.
The precoat adhesive(s) may be applied by conventional methods, including dipping, spraying, etc. Frothed foam may be supplied from a frothing apparatus, for example an Oakes or Firestone froth head. The thickness of the adhesives may be gauged by a doctor blade, roller, air blade, etc., all well known to the art. Preferably, the reactive polyurethane components are mixed in a high pressure mixhead prior to being introduced into the frothing head, and fillers, when used, introduced into the polyol side through an in-line mixer rather than being with polyol in a holding tank, all as disclosed in U.S. Pat. No. 5,604,267, which is herein incorporated by reference.
The reactive polyurethane systems comprise one or more di- or polyisocyanates (A-side), and a B-side which comprises one or more polyols, generally polyols having nominal functionalities of from 2 to 8, a low molecular weight chain extender, one or more polyurethane-promoting catalysts, and optionally suitable surfactants, crosslinkers, plasticizers, pigments, and other well known polyurethane additives. In general, a filler is also employed, particularly in froth foam.
The di- and polyisocyanates which are useful include the conventionally used isocyanates such as toluene diisocyanate, including the 2,4- and 2,6-isomers individually or in any admixture, preferably in the common 65/35 and 80/20 mixtures; methylene diphenylene diisocyanates (MDI), in the form of the individual 2,2′-, 2,4′-, and 4,4′-isomers, and mixtures thereof; crude or polymeric MDI having a functionality greater than 2 and comprising mixtures of 2-ring diisocyanates and their higher ring polyfunctional analogs; aliphatic diisocyanates such as 2,4- and 2,6-methylcyclohexane diisocyanate (hydrogenated TDI); 2,2′-, 2,4′-, and 4,4′-dicyclohexylmethane diisocyanates and mixtures of these isomers (hydrogenated MDI); 1,6-hexane diisocyanate, isophorone diisocyanate; and urethane, urea, biuret, uretonimine, uretdione, carbodiimide, isocyanurate, and allophanate modified isocyanates. TDI and MDI or their admixtures are preferred, either as individual isomers or as mixtures.
Isocyanate-terminated prepolymers and quasi-prepolymers are also useful. Isocyanate-terminated prepolymers are prepared by reacting a stoichiometric excess of one or more di- or polyisocyanates with a polyoxyalkylene polyol having a functionality of 2 or higher and an equivalent weight greater than 300
Duffy Robert D.
Gibala David
Holeschovsky Ulrich B.
Robbins Jeffrey L.
Bayer Antwerp N.V.
Brooks & Kushman P.C.
Morris Terrel
Torres Norca L.
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