WO2008103159A1

WO2008103159A1 - Floor covering and process for making it

Info

Publication number: WO2008103159A1
Application number: PCT/US2007/024759
Authority: WO
Inventors: Randall C. Jenkines; James K. Jennings; Larry W. Mobley
Original assignee: Dow Global Technologies, Inc.
Priority date: 2007-02-23
Filing date: 2007-12-03
Publication date: 2008-08-28

Abstract

Carpet tile is produced having a polyurethane tie (4) layer which adheres a reinforcing scrim (5) to a primary backing, and also adheres facing fibers (3) to the primary backing (2). A process for making the carpet tile is also disclosed.

Description

FLOOR COVERING AND PROCESS FOR MAKING IT

This application claims benefit of United States Provisional Application No. 60/903,189, filed 23 February 2007.

The invention relates to certain multilayer floor covering products which have a facing, a reinforcing scrim and a capcoat. Floor covering products of particular interest are carpet tiles.

Carpet tiles are often multi-layered products, in which each layer performs some specific function. An example of a common carpet tile construction is shown, for example, in U. S. Patent No. 5,540,968. A carpet tile product often contains a primary backing; fibers that are tufted through the primary backing to form a pile; an adhesive coating which secures the facing fibers to the primary; a reinforcing scrim which provides dimensional stability; a bitumen or other adhesive which secures the reinforcing scrim to the primary backing; a cushion backing, which provides cushioning and aesthetic attributes, another adhesive layer which binds the cushion backing to the reinforcing scrim, and a felt or adhesive layer attached to the bottom of the cushion backing.

Because of their complex construction, carpet tiles are manufactured in multi- step processes. The multiplicity of processing steps means that manufacturing costs are high. It would be desired to provide a carpet product and a method of manufacturing it which is less expensive, but still provides good product attributes. For carpet tile, a key attribute is dimensional stability, as the aesthetic attributes of installed carpet tile depend heavily on how well they will lay flat and fit closely to adjacent tiles.

In one aspect, this invention is a floor covering product, comprising; a) a carpet fabric having a face side and an underside, and facing fibers woven or tufted into a primary backing to form a pile on the face side of the carpet fabric; b) a reinforcing scrim having a first side and a second side; c) a substantially non-cellular polyurethane tie layer, the tie layer being in direct contact with the underside of the carpet fabric such that the tie layer bonds the facing fibers to the primary backing, the tie layer further being in direct contact with and adhered to the first side of the reinforcing scrim to bond the reinforcing scrim to the carpet facing; d) a polymeric cap coat layer attached to the second side of the reinforcing scrim. In a second aspect, this invention is a process for manufacturing a floor covering product, comprising a) forming a layer of an uncured polyurethane tie coat composition between and in direct contact with a reinforcing scrim and an underside of a carpet fabric, wherein the carpet fabric has facing fibers woven or tufted into a primary backing to form a pile on an opposing face side, and curing the polyurethane tie coat composition to form a substantially noncellular polyurethane tie layer that adheres the facing fibers to the primary backing of the carpet fabric and adheres to a first side of the reinforcing scrim to bond the reinforcing scrim to the carpet facing; and, prior to, simultaneously with or after step a), b) applying a layer of a polymeric cap coat to a second side of the reinforcing scrim.

The figure is a cross- sectional side view of an embodiment of a floor covering product according to the invention. An embodiment of the floor covering product of the invention is illustrated in

Figure 1. In Figure 1, floor covering product 1 includes carpet fabric 8, which includes primary backing 2. Primary backing 2 defines multiple openings through which facing fibers 3 are tufted or woven to produce a pile on a face side of the carpet fabric. Facing fibers 3 form fiber bundles on the underside of primary backing 2. Reifnorcing scrim 5 forms a layer attached to the underside of carpet fabric 8 via polyurethane tie layer 4. Polyurethane tie layer 4 is directly adhered to both the underside of carpet fabric 8 and to the top side of reinforcing scrim 5. Thus, polyurethane tie layer 4 serves to adhere facing fibers 3 to primary backing 2, and to adhere scrim 5 to primary carpet fabric 8. In this manner, a construction assembly is formed, having, in order, carpet fabric 8, tie layer 4 and scrim 5. In Figure 1, tie layer 4 is shown in an idealized manner, with sharp boundaries at primary backing 2 and scrim 5. In practice, it is contemplated that tie layer 4 will penetrate somewhat into primary backing 2, scrim 5, or both. As shown, tie layer 4 penetrates between the fiber bundles formed on the underside of primary backing 2, to adhere facing fibers 3 to primary backing 2. Tie layer 4 is substantially noncellular. It preferably has a coating weight in the range of from 20 to 60 ounces/square yard (0.68 — 2.05 kg/m³), and more preferably from 30 to 50 ounces/square yard (1.05- 1.73 kg/m³).

Polymeric cap coat 6 is adhered to the underside of scrim 5. Polymeric cap coat 6 may be cellular, but is preferably substantially noncellular. Polymeric cap coat suitably has a coating weight of -from 20 to 50 ounces/square yard (0.68-1.73 kg/m³); and more preferably from 30 to 40 ounces/square yard (1.05-1.39 kg/m³).

The embodiment shown in Figure 1 further includes optional layer 7, which may be, for example, an adhesive layer, a woven or nonwoven fabric layer, another reinforcing scrim layer, or other functional layer that is applied for use in particular applications.

Primary backing 2 is generally in the form of a woven or nonwoven scrim, and can be made of any convenient material, such as, for example, jute, polypropylene, nylon, a polyester, a polyacrylate, cotton, wool, a blend of two or more of these, or other material. Facing fibers 3 also can be of any convenient material, such as wool, cotton, nylon, a polyester, an acrylic fiber, polypropylene, polyethylene, a blend of any two or more of these, or the like. The primary backing and the facing fibers should be thermally and hydrolytically stable under the conditions at which the tie coat compositionally is applied and cured, so the carpet fabric does not degrade or become permanently distorted. The facing fibers are typically in the form of fiber bundles that are tufted or woven through the primary backing to produce a carpet face and an opposing underside. The facing fibers may be twisted or entangled together to form a yarn.

Reinforcing scrim 5 is a woven or non-woven fiber mat that is stiffer than the carpet facing. Reinforcing scrim 5 imparts dimensional stability, and in particular contributes dimensional stability during changes in temperature and humidity that are encountered during use. Reinforcing scrim 5 preferably is thermally and hydrolytically stable to 100⁰C or more and is preferably is composed of one or more hydrophobic materials that exhibit little or no ability to absorb moisture. Preferred fibers for use in reinforcing scrim 3 include glass, polyester (particularly polyethylene terephthalate), graphite, carbon, and the like. Glass fibers are particularly preferred. The fibers in reinforcing scrim 3 may be held together with a binder such as an acrylic polymer, a urea-formaldehyde resin, or other suitable material. Reinforcing scrim 3 may consist of multiple plies of woven or non-woven materials as just described. The floor covering product of the invention is prepared by forming a layer of an uncured polyurethane tie coat composition between and in direct contact with the reinforcing scrim and the underside of the carpet fabric. The tie coat composition is then cured to form a substantially noncellular polyurethane tie layer. The tie layer adheres the facing fibers to the primary backing of the carpet fabric. In addition, it adheres one side of the reinforcing scrim to the carpet fabric.

The polymeric cap coat is applied to the other side of the reinforcing scrim. This step may be done prior to, simultaneously with or after the assembly of the carpet facing, tie coat and reinforcing scrim is prepared. Thus, in one embodiment, the assembly is formed, the tie coat composition is cured, and the cap coat is subsequently applied to the exposed side of the reinforcing scrim. In an alternative embodiment, the cap coat is first applied to the reinforcing scrim, leaving one side of the scrim exposed. The assembled product is then created by forming the layer of the uncured tie coat composition between the carpet facing and the reinforcing scrim/cap coat assembly, and the tie coat composition is cured as described before. In a third embodiment, the cap coat is applied to the reinforcing scrim at the same time as the assembly is prepared involving the carpet facing, tie coat composition and reinforcing scrim. In still another embodiment, in which the cap coat is formed from a curable polyurethane cap coat composition, an assembly of carpet facing, layer of uncured tie coat composition, reinforcing scrim and uncured cap coat composition is prepared, and the tie coat and cap coat compositions are cured simultaneously.

The polyurethane tie coat composition is preferably applied directly to the underside of the carpet facing, to wet out the fiber bundles and adhere them to the primary backing. This is conveniently done by creating a puddle of the tie coat composition on the underside of the carpet facing and mechanically spreading the composition over the back surface. It is preferred to froth the tie coat composition before applying it, as frothing makes it easier to control coating weight. A suitable froth density is from about 400 kg/m³ to about 800 kg/m³. It is preferred to use a doctor blade or similar apparatus to spread the tie coat composition, as this method mechanically pushes the tie coat composition into and between the fiber bundles and into contact with the primary backing, thereby improving the bond between the fibers and primary backing. Another suitable apparatus for applying the tie coat composition is an application roll. Once the tie coat composition is applied and spread onto the carpet facing, the reinforcing scrim can be brought into contact with the layer of the tie coat composition. The tie coat composition then is allowed to cure to form a polyurethane polymer. Alternatively, more of the tie coat composition can be applied separately to the reinforcing scrim, in the same manner as just described, and the coated carpet facing and coated reinforcing scrim- can be joined, tie coat layer-to-tie coat layer, followed by curing the tie coat composition, to form the assembly. This latter method has the advantage of getting excellent penetration of the tie coat composition into both the carpet facing and the reinforcing scrim, although capital and operating costs may tend to be higher. In addition, the tie coat composition can be applied simultaneously to the carpet facing and reinforcing scrim. This can be done by depositing the reinforcing scrim onto the tie coat layer as it is being formed into a layer on the carpet facing. For example, the reinforcing scrim can be fed under a doctor blade or application roll which is used to apply and gauge the tie coat composition to form a layer on the carpet facing. It is also within the scope of the invention to apply the tie coat composition to the reinforcing scrim, in the manner described, and then to bring the carpet facing into contact with the layer of the tie coat composition. This method is generally less preferred, as good penetration of the fiber bundles may not be achieved. As a result, the facing fibers may not be secured to the primary backing as well as desired. The tie coat composition can be cured at about room temperature (-22⁰C), but it is generally desirable to apply heat to accelerate the cure. A suitable curing temperature is from 100 to 200⁰C, such as from 110 to 15O⁰C. It is desired that the curing temperature be such that the formulation cures to a tack-free state in 4 minutes or less, preferably 2.5 minutes or less and more preferably in 2 minutes or less. The spreading and curing process generally will remove gasses entrapped in the tie coat composition, even if the composition is frothed prior to application, unless the tie coat composition contains a surfactant or other foam stabilizer. As it is highly preferred to produce a noncellular tie layer, the tie coat composition preferably does not contain an effective amount of a surfactant or foam stabilizer. The lack of surfactant or foam stabilizer permits trapped gasses to escape more easily. If necessary, an antifoam or cell opener can by added to the tie coat composition to promote collapse of the entrapped gasses to form a substantially noncellular tie layer.

If the tie layer is thermoformable, it is possible to collapse cells contained in the tie layer after it is cured, by compressing the tie layer with applied heat. Care should be taken to minimize mechanical stresses on the carpet during the application and curing of the tie coat layer, as these stresses often lead to subsequent dimensional instability. The carpet facing and reinforcing scrim each are preferably stretched no more than 2% in either the weft (cross machine) or warp (machine) direction, and more preferably no more than 0.75%, during the process of applying and curing the tie coat composition. To achieve this, the carpet may be held in a tenter frame or simply laid on a moving belt when the tie coat composition is applied and cured. The carpet may be heated slightly prior to applying the tie coat composition, in order to drive off absorbed moisture. The carpet is preferably dry, as residual moisture can react with the polyisocyanate component of the tie coat composition to generate a gas. Gas generation can form a cellular structure in the tie layer or at the interface of the tie and the carpet facing or reinforcing scrim, which is generally undesirable.

The polyurethane tie layer is substantially noncellular. The tie layer preferably is thermoformable and exhibits a significant amount of creep at room temperature (22⁰C). The tie layer preferably exhibits a tan delta value, on dynamic thermal mechanical analysis, of at least 0.1 at 100⁰C and more preferably at least 0.2 at 100⁰C. The tie layer also is preferably highly filled. The fillers can modify physical properties somewhat and also reduce the overall cost of the composition.

The polyurethane tie coat composition is one that cures to form a polyurethane and/or polyurea polymer. The tie coat composition includes at least one polyisocyanate component and at least one polyol component. It preferably contains a filler and one or more other components as described more fully below.

The polyisocyanate component includes at least one organic polyisocyanate, which may be an aromatic, cycloaliphatic, or aliphatic isocyanate. Examples of suitable polyisocyanates include m-phenylene diisocyanate, toluene-2,4-dϋsocyanate, toluene-2,6- diisocyanate, hexamethylene-l,6-diisocyanate, tetramethylene-l,4-diisocyanate, cyclohexane-l,4-diisocyanate, hexahydrotoluene diisocyanate, naphthylene-1,5- diisocyanate, methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 4,4'- biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4-4'- biphenyl diisocyanate, 3,3'-dimethyldiphenyl methane-4,4'-diisocyanate, 4,4',4"- triphenyl methane triisocyanate, a polymethylene polyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate. Preferably the polyisocyanate is diphenylmethane-4,4'-dϋsocyanate, diphenylmethane- 2,4'-diisocyanate, PMDI, toluene-2-4-diisocyanate, toluene-2-6-diisocyanate or mixtures thereof. Diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate and mixtures thereof are generically referred to as MDI, and all can be used. Toluene-2,4- diisocyanate, toluene-2,6-dϋsocyanate and mixtures thereof are generically referred to as TDI, and all can be used. Prepolymers made by reacting a stoichiometric excess of any of the foregoing polyisocyanates with an isocyanate-reactive compound such as those described below can be used as well. Isocyanate functionalities preferably are as indicated above with respect to the polyisocyanate compounds. The polyol component includes one or more isocyanate-reactive compounds. The isocyanate-reactive materials preferably include at least one high equivalent weight polyol having a hydroxyl equivalent weight of at least 400, especially from about 500 to about 2000 and preferably from 800 to 1200, or a mixture thereof. The high equivalent weight polyol may be a polyether polyol, such as a polymer of ethylene oxide, propylene oxide, tetrahydrofuran or butylene oxide, or a mixture of two or more of these. Particularly suitable polyether polyols include homopolymers of propylene oxide and random copolymers of a mixture of from 70 to 99% by weight propylene oxide and from 30 to 1% by weight ethylene oxide, especially those random copolymers containing up to about 15% by weight randomly polymerized ethylene oxide. These polyols are conveniently prepared by adding the corresponding alkylene oxide to an initiator material such as a low molecular weight compound containing two or more hydroxyl and/or primary or secondary amine groups.

Polyester polyols such as polycaprolatone and butanediol/adipate polyesters can also be used as all or part of the high equivalent weight polyol. Similarly, hydroxymethyl-containing polyester polyol(s) can be used as all or part of the high equivalent weight polyol. Suitable such hydroxymethyl-containing polyester polyols are described in detail in WO 04/096882 and WO 04/096883; their use in preparing certain polyurethane carpet backings is described in WO 2006/047432A1. Hydroxymethyl-containing polyester polyols of this type are conveniently prepared by reacting a hydroxymethyl-group containing fatty acid having from 12 to 26 carbon atoms, or an ester of such a hydroxymethylated fatty acid, with a polyol, hydroxylamine or polyamine initiator compound having an average of at least 2.0 hydroxyl, primary amine and/or secondary amine groups/molecule. Proportions of starting materials and reaction conditions are selected such that the resulting hydroxymethyl-containing polyester polyol contains an average of at least 1.3 repeating units derived from the hydroxmethyl-group containing fatty acid or ester thereof for each hydroxyl, primary amine and secondary amine group in the initiator compound, and the hydroxymethyl- containing polyester polyol has an equivalent weight of at least 400 up to about 15,000. One or more chain extenders are also preferably present in the polyol component of the tie coat composition. For purposes of this invention, a chain extender is a material having two isocyanate-reactive groups/molecule and an equivalent weight per isocyanate-reactive group of from about 30 to 399, preferably from about 30 to 250. Chain extenders having two hydroxyl groups are preferred. Examples of suitable chain extenders include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-dimethylolcyclohexane, diethyltoluene diamine, 1,4-butane diol, 1,6-hexane diol, 1,3-propane diol, amine-terminated polyethers such as Jeffamine D-400 (from Huntsman Chemical Company), amino ethyl piperazine, 2-methyl piperazine, l,5-diamino-3-methyl-pentane, isophorone diamine, ethylene diamine, hexane diamine, hydrazine, piperazine, mixtures thereof and the like. Amine chain extenders can be blocked, encapsulated, or otherwise rendered less reactive. Preferred chain extenders are propylene glycol, dipropylene glycol and tripropylene glycol. Another type of preferred chain extender is an alkoxylated aniline, especially an adduct of one mole of aniline and from 2 to 8 moles of ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide. In especially preferred embodiments, the chain extender is a mixture of an alkoxylated aniline as just described at least one of propylene glycol, dipropylene glycol and tripropylene glycol.

The high equivalent weight polyol(s) will in general constitute from about 50 to about 95%, preferably from 75 to 90%, of the total weight of the isocyanate-reactive materials in the tie coat composition. One or more chain extenders will in general constitute from 5 to 30%, preferably from 10 to 25%, of the total weight of the isocyanate-reactive materials in the tie coat composition.

It is within the scope of the invention to include a crosslinker in the tie coat composition. A crosslinker, for purposes of this invention, is a compound having three or more isocyanate reactive groups and an equivalent weight per isocyanate-reactive group of 150 or less. However, the use of crosslinkers in the tie coat composition is generally discouraged because their use tends to increase edge curl. Therefore, crosslinkers are most preferably eliminated or used in small quantities, such as less than 5% of the total weight of the isocyanate-reactive materials. The isocyanate-reactive groups may be hydroxyl, primary amine or secondary amine groups.

The average functionality (number of reactive groups/molecule) of the reactive materials (polyisocyanates and isocyanate-reactive materials) in the tie coat composition can in some cases significantly affect the dimensional stability of the floor covering product. It is desirable that the - average functionality of the reactive materials be - maintained close to 2.0, such as from 1.95 to 2.05 and more preferably from 1.97 to 2.03. Average functionality of the reactive materials can be calculated using the relationship

∑(Eq_x * F_t)

F = x=\

∑Eq_χ

X=]

wherein F represents the average functionality of the reactive materials, n represents the number of different reactive materials (polyisocyanates, high equivalent weight polyols, chain extenders, crosslinkers and others, if present), Eq_x represents the number of equivalents of the x^th component in the composition, and F_x represents the functionality of the x^th component.

For high equivalent weight polyols, it is actual functionality rather than nominal functionality that is used in the calculation. The "nominal" functionality is the number of functional groups expected to be present on the polyol based on the composition of the starting materials. The actual functionality is sometimes somewhat lower than the nominal functionality. This is especially with polyether polyols, which tend to contain monofunctional materials that reduce average functionality somewhat.

High equivalent weight polyols used in the tie coat composition preferably have, in the aggregate, an actual functionality of from 1.8 to 2.3, preferably from 1.8 to 2.2. Chain extenders have actual functionalities of 2. Polyisocyanates preferably have, in the aggregate, a functionality of from 1.8 to 2.2, especially from 1.9 to 2.1 isocyanate- group s/molecule .

The isocyanate index can also affect the amount of crosslinking that forms when the tie coat composition is cured, as a significant excess of polyisocyanate can result in the formation of isocyanurate, biuret or similar linkages. The isocyanate index (100 times the ratio of isocyanate groups to isocyanate-reactive groups in the composition) is preferably from 85 to 125, and more preferably from 90 to 110.

The tie coat composition preferably contains a filler, which reduces overall cost and may improve flame resistance and other physical properties. It is often convenient to express the amount of filler that is used in relation to the amount of isocyanate- reactive materials in the tie coat formulation. Filler loadings of from 100 to 450 parts by weight per 100 parts by weight isocyanate-reactive materials are suitable, but highly loaded systems are preferred. Accordingly, a preferred filler loading is from 300 to 450 parts per 100 parts isocyanate-reactive materials. Suitable fillers include talc, mica, montmorillonite, marble, milled glass granite, milled glass, calcium carbonate, aluminum trihydrate, carbon, aramid, silica, silica-alumina, zirconia, talc, bentonite, antimony trioxide, kaolin, coal-based fly ash and boron nitride. Reclaimed and/or reground scrap polymer, especially a reclaimed or reground thermoset polyurethane polymer, can be used as a particulate filler, as well.

The tie coat composition also preferably contains one or more catalysts, which promote the reaction of the polyisocyanate with the isocyanate-reactive materials. Suitable catalysts include tertiary amines, organometallic compounds, or mixtures thereof. Specific examples of these include di-n-butyl tin bis(mercaptoacetic acid isooctyl ester), dimethyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, stannous octoate, lead octoate, ferric acetylacetonate, bismuth carboxylates, triethylenediamine, N-methyl morpholine, like compounds and mixtures thereof. An amine-blocked tin (IV) catalyst, such as those described in U. S. Patent No. 5,491,174, can be used. A particularly preferred catalyst is a delayed action catalyst, such as the dialkyltin sulfide catalysts described in U. S. Patent No. 5,646,195. Of the last types, dimethyl-, dibutyl- and dioctyltin sulfide catalysts are of particular interest. Even more preferred is a mixture of such a dimethyl-, dibutyl- and dioctyltin sulfide catalyst with a nickel- or ferric acetylacetonate catalyst.

An amount of catalyst is advantageously employed such that a relatively rapid cure to a tack-free state can be obtained, while providing enough open time that the tie coat composition can be dispensed and spread over the carpet back before curing. If an organometallic catalyst is employed, such a cure can be obtained using from about 0.01 to about 0.5 parts per 100 parts of the tie coat composition, by weight. If a tertiary amine catalyst is employed, the catalyst preferably provides a suitable cure using from about 0.01 to about 3 parts of tertiary amine catalyst per 100 parts of the tie coat composition, by weight. An amine type catalyst and an organometallic catalyst can be employed in combination. Because of the higher filler loadings used in the preferred embodiments, the tie coat composition can become very viscous. For that reason, the tie coat composition preferably contains at least one filler wetting agent, which can help to reduce viscosity. Suitable filler wetting agents include ethoxylated phosphate esters, which are generally available in an organic carrier. Examples of such wetting agents include those sold under the trade names Maphos™ 56 (available from BASF) and Code 5027 (Fibro Chem, Inc.). About 0.5 to 1.5 parts by weight of such a filler wetting agent, per 100 parts by weight isocyanate-reactive materials, is usually effective.

Because the presence of water in the tie coat composition can lead to undesired bubble formation, the tie coat composition is preferably substantially devoid of water which is available to react with the polyisocyanate compound(s). It is preferred to incorporate a water scavenger into the tie coat composition to tie up small amounts of water that may be carried into the composition with one or more of the other ingredients. Various types of molecular sieves are suitable for this purpose. A particular molecular sieve that is useful is commercially available as Molsiv™ 5A (available from UOP). About 1 to 10 parts by weight of a water scavenger, per 100 parts by weight isocyanate-reactive materials, are suitably used. Alternatively, water can be removed from the tie coat composition by placing it under vacuum. This can be done to the individual components or various subcombinations therefore before the tie coat composition is formed.

Other additives may be used in the tie coat composition, including fire retardants, pigments, antistatic agents, reinforcing fibers, antioxidants, preservatives, acid scavengers, and the like. It is preferred not to include a blowing agent. Components are preferably dried to remove residual water. The tie coat composition preferably contains less than 0.1% by weight water, so as to avoid a gas-generating reaction with the polyisocyanate. In order to provide a non-cellular coating, it is preferred to eliminate or minimize the presence of surfactants and foam stabilizers. The elimination of these materials permits the formulation to be frothed in order to help control coating weight, while then allowing the entrapped gases to escape before the tie coat composition is cured.

The tie composition is conveniently formed into a blended polyol component, which includes all isocyanate-reactive materials, and a polyisocyanate component. The filler is typically blended into the polyol component, as are the filler wetting agent and the water scavenger. The mixing of the filler into the polyol is suitably done under high shear conditions, so that the filler is finely and uniformly dispersed into the polyol. A convenient approach to doing this is to mix the polyol and filler at about room temperature, and continue applying shear until the temperature of the composition is raised to about 49°C by the generation of waste heat from the mixing process. Catalysts may be added to either the polyol or polyisocyanate component (preferably the polyol component) or added as one or more separate streams.

Some fillers may tend to affect the pH of the tie coat composition, which may in turn adversely affect catalyst performance. It is generally preferred to adjust the pH of the formulated polyol/filler blend to within the range of 7.5 to 11.5. Phosphoric acid can be added to lower pH, as can other mineral and organic acids.

The cap coat may be formed from a wide variety of polymers, including, for example, polyethylene, polypropylene, polyvinylchloride, a styrene-butadiene copolymer, an ethylene vinyl acetate resin, a polyester, and the like. A preferred cap coat is a polyurethane, which is conveniently prepared by forming a layer of a cap coat composition, and curing the composition. The layer of the cap coat composition can be formed in various ways. For example, it can be formed onto a release backing or an endless belt that has a non-stick surface, in which case the reinforcing scrim or the carpet facing/tie layer/reinforcing scrim assembly can be brought into contact with it, followed by curing the cap coat composition. Alternatively, the cap coat can be applied to the back of the carpet facing/tie layer/reinforcing scrim assembly or to one side of the reinforcing scrim, again followed by a curing step. As mentioned before, curing of the cap coat composition can be done simultaneously with the curing of the tie coat composition. It is also possible to form the cap coat layer separately, and laminate it to the reinforcing scrim (or the carpet facing/tie layer/reinforcing scrim assembly) through the use of a suitable adhesive.

A polyurethane cap coat is conveniently made from a curable cap coat composition that contains at least one polyol and at least one polyisocyanate. The cap coat composition is preferably filled, as described with respect to the tie coat composition. In general, the average functionality of the reactive components of the cap coat composition is not as important as in the tie coat composition. Therefore, a wider range of polyol and polyisocyanate components can be used in the cap coat composition.

Suitable polyisocyanates for use in the cap coat composition include those described before with regard to the tie coat composition, provided, however, that the average isocyanate functionality may be broader, such as from 2.0 to 3.0, and especially from about 2.2 to 2.7, isocyanate groups/molecule. Preferred polyisocyanates for the cap coat composition include TDI, MDI, PMDI, mixtures of two or more thereof, and prepolymers made from one or more thereof. A preferred prepolymer is prepared from a dipropylene glycol and/or tripropylene glycol and MDI or MDI/PMDI mixture having an isocyanate content of from 20 to 25% by weight and an isocyanate functionality of from 2.1 to 2.5.

The cap coat composition contains at least one high equivalent weight polyol. High equivalent weight polyols as described before with regard to the tie coat composition are suitable, again with the proviso that a wider range of functionalities can be used. Preferred high equivalent weight polyols include homopolymers of propylene oxide, and random copolymers of a mixture of from 70 to 99% by weight propylene oxide and from 30 to 1% by weight ethylene oxide, especially those random copolymers containing up to about 15% by weight randomly polymerized ethylene oxide. However, other types of high equivalent weight polyols as describe before can be used.

It is sometimes preferable to use a mixture of two or more high equivalent weight polyols. One such mixture includes at least one polyether polyol as just described, and at least one hydroxymethyl-containing polyol as described before or at least one hydroxyl-containing vegetable oil that has an average hydroxyl functionality of at least 1.5 (of which castor oil is of particular interest). The presence of the hydroxymethyl- containing polyol or hydroxyl-containing vegetable oil often imparts some hydrophobic character to the cured cap coat. Hydrophobic character in the cap coat often helps the product be more resistant to moisture.

The cap coat composition may contain one or more chain extenders and/or one or more crosslinkers as described before. However, it is possible to omit chain extenders and crosslinkers form the cap coat composition. This has the advantage of increasing overall equivalent weight, which reduces the amount of the relatively expensive polyisocyanate that is needed, and in that way reduces raw material costs.

A preferred polyol component for the cap coat composition includes (1) from 50 to 80% by weight of a homopolymer of propylene oxide or a random copolymer of a mixture of from 70 to 99% by weight propylene oxide and from 30 to 1% by weight ethylene oxide, (2) from 5 to 50% by weight of castor oil, (3) from 0 to 20% by weight of propylene glycol, dipropylene glycol or tripropylene glycol, and (4) from 5 to 20% of an alkoxylated aniline chain extender, the percentages being based on the weight of all isocyanate- reactive components. Another preferred polyol component for the cap coat composition includes (1) from 35 to 60% by weight of a homopolymer of propylene oxide or a random copolymer of a mixture of from 70 to 99% by weight propylene oxide and from 30 to 1% by weight ethylene oxide, (2) from 5 to 50% by weight of castor oil, (3) from 0 to 20% by weight of a 150-250 equivalent weight poly(propylene oxide) diol, and (4) from 5 to 20% of an alkoxylated aniline chain extender, the. percentages again being based on the weight of all isocyanate-reactive components.

The cap coat composition is preferably filled. Fillers and amounts thereof as described with regard to the tie coat composition are suitable. Similarly, the cap coat composition preferably contains a filler wetting agent, as described with regard to the tie coat composition. Catalysts as described with respect to the tie coat composition are preferably used. A preferred catalyst is a delayed action catalyst, such as the dialkyltin sulfide catalysts described in U. S. Patent No. 5,646,195, and especially the dimethyl-, dibutyl- and dioctyltin sulfide catalysts. As before, the dimethyl-, dibutyl- and dioctyltin sulfide catalyst can be used as a mixture with a nickel- or ferric acetylacetonate catalyst. The cap coat composition can also contain other optional components as described with regard to the tie coat composition.

It is within the scope of the invention to form a cellular cap coat, but the cap coat is preferably substantially non-cellular. If the cap coat is to be cellular, the cap coat composition is frothed, contains a blowing agent, or both, and will also include a surfactant or other foam stabilizer. A cellular cap coat is preferably prepared by frothing the cap coat composition before forming it into a layer. Organosilicone surfactants, such as those described in U. S. Patent No. 4,483,894, are preferred, when a cellular cap coat is desired. Typically, about 0.5 to about 3 parts of surfactant are used per 100 parts by weight polyols.

The cap coat composition can be formulated and applied in the same general manner as described before with respect to the tie coat composition.

The effectiveness of the tie layer in binding the facing fibers to the primary backing can be expressed in terms of tuftbind. The finished floor covering product of the invention advantageously exhibits a tuftbind, measured according to ASTM D 1335, of at least 10 Ib (44.5N), more preferably at least 13 Ib (58N) and even more preferably at least 15 Ib (67N). Wet tuftbind values are advantageously at least 5.5 Ib (24N), more preferably at least 8.8 Ib (39N) and even more preferably at least 11 Ib (49N). Wet tuftbind is measured according to ASTM D 1335 after soaking the carpet sample in room temperature tap water for 20 minutes. Another indication of the effectiveness of the tie layer is edge ravel. The floor covering product of the invention preferably exhibits an edge ravel of greater than 78N, especially greater than 98N or greater than 108N on the test described below. The dimensional stability of a floor covering product is often indicated by edge curl. The floor covering product of the invention suitable exhibits an edge curl of no greater than 2.54 cm, preferably no greater than 1.8 cm, more preferably no greater than 1.3 cm and even more preferably no greater than 0.8 cm, in each of the machine and cross machine direction.

For some applications, the floor covering product should exhibit a "hand punch" (a measure of flexibility described below) of 133N or less. The floor covering product also advantageously exhibits good flame retardancy, antimicrobial/antifungal activity, low 24-hour total volatile organic components (TVOC), good liquid barrier functionality as measured by the British spill passage test (United Kingdom Health Care Specifications Method E), and excellent castor chair resistance to backing delamination and zippering (measured according to ASTM D6962 using the Feingerate Baumberg Roller Chair Testing Device).

The floor covering of the invention have particular applicability in the residential and commercial carpet industry as well as in carpeting for recreational use, such as for use in ships and boats, cars, patios, synthetic turf, etc. An application of particular interest is carpet tile. Carpet tile is preferably produced in accordance with the invention by forming a broadloom floor covering product, and then cutting the broadloom down into smaller tiles. Carpet tiles are typically no larger than 2 square yards (1.672 m²) in area, preferably not greater than 1 square yard (0.836 m²), and have smooth and regular edges that allow them to be placed adjacent to and fit tightly against other tiles. The tiles are usually rectangular or square, but may be of any suitable shape. Good quality carpet tiles will, if laid correctly, look very similar to a laid broadloom carpet. The following example is provided to illustrate the invention, but is not intended to Limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Unless stated otherwise, all molecular weights expressed herein are weight average molecular weight.

EXAMPLE

The following materials are employed in these examples:

Polyether Polyol A is a 2000 molecular weight, nominally trifunctional poly(propylene oxide). It is available commercially as Voranol® 9120A polyol from Dow Chemical. It has an actual functionality of about 1.8. Polyether Polyol B is a 3000 molecular weight, nominally trifunctional random copolymer of about 87% propylene oxide and 13% ethylene oxide, available commercially as Voranol® 9137CA polyol from Dow Chemical. It has an actual functionality of approximately 2.7. Propoxylated Aniline A is an adduct of 1 mole of aniline and 2 moles of propylene oxide, available commercially from as Voranol® SH9100A polyol from Dow Chemical.

Code 5027 is an ethoxylated phosphate ester, which is available commercially from Fibro Chem, Inc.

LC5614 is an organosilicone surfactant available from GE Advanced Materials. LC5615 is a nickel acetonylacetonate catalyst available from GE Advanced

Materials. It is used in these examples as a 25% solution in a 2000 MW poly(propylene oxide) diol having a 13% EO end-cap.

Polyisocyanate A is a blend of 60% of an MDI/dipropylene glycol/tripropylene glycol prepolymer and 40% MDI. It has an isocyanate functionality of about 2.05. Polyisocyanate A is commercially available as Isonate® 7560 isocyanate from Dow Chemical.

Polyisocyanate B is a 50/50 blend of a 23%-NCO soft-segment MDI prepolymer and a polymeric MDI prepolymer. Polyisocyanate B is commercially available as Isonate®7045A isocyanate from Dow Chemical. Catalyst A is a blend of 10% of a dibutyltin dϋsooctylmercaptoacetate delayed action catalyst, commercially available as Fomrez™ UL6 from GE Advanced Materials, in Polyether Polyol B.

Catalyst B is a blend of 20% dibutyltin dilaurate (Dabco™ T12, from Air Products and Chemicals, Inc.) in Polyether Polyol B.

A 2-inch (5 cm) Oakes frother equipped to process multiple component streams is used to prepare a mechanically frothed tie coat formulation. The composition of the tie coat composition is as shown in Table 1: Table 1

The polyols, dipropylene glycol, propoxylated aniline, phosphoric acid, fly ash, molecular sieves and LC5615 catalyst are combined and mixed with a Cowles blade until the compound reaches a temperature of 49°C. It is then cooled to 29.4°C. The compounded polyol, polyisocyanate, surfactant solution and dibutyltindisulfide solution are metered separately into an Oakes frother and frothed with compressed air to a froth density of 600 g/L. The frothed mixture is then delivered to the backside of a 888.4 g/m² tufted greige fabric (style Midnight Sparkle, from Milliken), simultaneously with a 43.7 g/m² fiber glass mat. A drawdown bar set to a gap opening of 0.63 cm is used to apply a layer of the frothed mixture to the carpet, and the fiber glass mat is fed under the drawdown bar as the froth is gauged. The result is a sandwich assembly of the carpet facing, tie coat compostion and fiber glass mat. This assembly is cured at 130⁰C for 6 minutes and then cooled to 65.5°C.

A polyurethane cap coat composition is prepared from the components listed in Table 2: Table 2

These components, except for the dibutyltindisulfi.de solution and polyisocyanate, are compounded by mixing with a Cowles blade until the compound temperature reaches 49°C. The compound is then cooled to about 29°C and mixed with the dibutyltindisulfi.de solution and polyisocyanate (without frothing) and gauged onto the exposed fiberglass side of the assembly made before, using a drawdown bar set to a gap opening of 0.075 cm. The cap coat composition is then cured by inverting the assembly and placing the inverted assembly into a 135°C oven for 6 minutes. The assembly is then removed from the oven and cooled to room temperature. 45.7 X 45.7 cm tiles are die -cut from the assembly and allowed to condition for 24 hours under conditions as specified below for specific tests.

The tiles are then evaluated for tuftbind and wet tuftbind in accordance with ASTM D1335. Edge ravel is measured on samples conditioned at ~21°C and -50% humidity for

24 hours. Tuft rows are pulled from the sample until two complete rows are pulled out. About I-V2 to 2 inches (4-5 cm) of a third row is pulled out, leaving the resulting partially pulled row otherwise attached to the carpet. The sample is placed in the lower jaw of an Instron 4465 tensile tester equipped with 100 Ib (45 kg) tension cell, and the free end of the partially pulled tuft row is placed in a hemostat that is attached to the upper jaw. The jaws are then pulled apart at the rate of 10 inches (25.4 cm)/minute. The force is measured on three duplicate samples and the average reported as edge ravel.

Hand punch is measured using a test that measures the force needed to bend and flex a textile, as may be necessary to install it into corners or over uneven substrates, or to bend the textile around a stair nose. A 9" X 12" (21.6 cm X 30.5 cm) sample of the carpet is conditioned at 50% relative humidity and 25°C for two hours. The carpet is placed face up over a hollow cylinder with a 5.5" (14 cm) internal diameter. An Instron 4465 tensile tester is equipped with a IkN compression/extension load cell and a compression foot having a 2.25" (5.7 cm) outside diameter. The compression foot is then forced 0.65 inch (1.65 cm) into the carpet at a rate of 12 inches/minute (30 cm/minute). The force at 0.5 inch (1.27 cm) deflection is reported. The test is repeated three more times, with the carpet being reversed each time. "Hand" is the average of the four measurements. ' British spill passage testing (United Kingdom Health Care Specifications Method E) is performed on the sample, and wear resistance is evaluated according ASTM D6962 using the Feingerate Baumberg Roller Chair Testing Device,.

Edge curl is measured by first conditioning 3 carpet samples at 14°C and 20% relative humidity for 24 hours. A panel is applied over the sample, leaving a 2" X 2" (5 cm X 5 cm) portion exposed. After 30 minutes, the distance from the flat surface to the underside of the outer exposed edge of the carpet sample is measured. The average of the three measurements is reported as the edge curl. Testing is repeated for samples conditioned at 35°C and 80% relative humidity, and for samples conditioned at 100⁰C and 100% relative humidity. Results of this testing are as indicated in Table 3.

Table 3

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the true spirit and scope of the novel concepts of the invention.

Claims

WHAT IS CLAIMED IS:

1. A floor covering product, comprising;

a) a carpet fabric having a face side and an under side, having facing fibers woven or tufted into a primary backing to form a pile on the face side of the carpet fabric;

b) a reinforcing scrim having a first side and a second side;

c) a substantially non-cellular polyurethane tie layer, the tie layer being in direct contact with the underside of the carpet fabric such that the tie layer bonds the facing fibers to the primary backing, the tie layer further being in direct contact with and adheresdto the first side of the reinforcing scrim to bond the reinforcing scrim to the carpet facing;

d) a polymeric cap coat layer attached to the second side of the reinforcing scrim.

2. The floor covering product of claim 1, in the form of a carpet tile.

3. The floor covering product of claim 2, wherein the polymeric cap coat layer is attached directly to the second side of the reinforcing scrim.

4. The floor covering product of claim 3, wherein the polymeric cap coat layer is a polyurethane.

5. The floor covering product of claim 4, wherein the polymeric cap coat layer is substantially noncellular.

6. The floor covering product of claim 5, further comprising e) an adhesive or fabric layer attached to the polymeric cap coat layer opposite to the reinforcing scrim.

7. A process for manufacturing a floor covering product, comprising a) forming a layer of an uncured polyurethane tie coat composition between and in direct contact with a reinforcing scrim and an under side of a carpet fabric, wherein the carpet fabric has facing fibers woven or tufted into a primary backing to form a pile on a face side that is opposed to the underside, and curing the polyure thane tie coat composition to form a substantially noncellular polyurethane tie layer that adheres the facing fibers to the primary backing of the carpet fabric and adheres to a first side of the reinforcing scrim to bond the reinforcing scrim to the carpet facing; and, prior to, simultaneously with or after step a), b) applying a layer of a polymeric cap coat to a second side of the reinforcing scrim.

8. The process of claim 7, wherein the polyurethane tie layer is a filled polymer.

9. The process of claim 8, wherein the polyurethane tie coat composition includes at least one polyether polyol having a hydroxyl equivalent weight of from 500 to 2000, at least one chain extender, and at least one polyisocyanate, wherein the average functionality of all polyol(s), chain extender(s) and polyisocyanate(s) is from 1.97 to 2.03.

10. The process of claim 9, wherein the polyurethane tie coat composition contains from 300 to 450 parts by weight of a particulate filler per 100 parts by weight isocyanate-reactive components.

11. The process of claim 10, wherein the polyurethane tie coat composition contains at least one alkoxylated aniline chain extender.

12. The process of claim 11, wherein the polyether polyol(s) are homopolymers of propylene oxide or random copolymers of a mixture of from 70 to 99% by weight propylene oxide and from 30 to 1% by weight ethylene oxide.

13. The process of claim 12, wherein the polyurethane tie coat composition contains propylene glycol, dipropylene glycol or tripropylene glycol.

14. The process of claim 13, wherein the polyurethane tie coat composition contains at least one viscosity reducing agent and at least one water scavenger.

15. * The process of claim 7, wherein the polyurethane tie coat composition is first applied to the reinforcing scrim to form a coated reinforcing scrim, the coated reinforcing scrim is married to the under side of the carpet fabric, and the polyurethane tie coat composition is then cured.

16. The process of claim 7, wherein the polyurethane tie coat composition is first applied to the under side of the carpet fabric to form a coated carpet fabric, the coated carpet fabric is married to the reinforcing scrim, and the polyurethane tie coat composition is then cured.

17. The process of claim 7, wherein the polymeric cap coat layer is a polyurethane.

18. The process of claim 17, wherein the polymeric cap coat layer is formed by applying a polyurethane cap coat composition to the second side of the reinforcing scrim and curing the polyurethane cap coat composition.

19. The process of claim 18, wherein the polymeric cap coat layer is crosslinked.

20. The process of claim 19, wherein the polyurethane cap coat composition includes at least one polyether polyol having an equivalent weight of from 500 to 2000, a particular filled in an amount of from 300 to 450 parts by weight per 100 parts by weight of isocyanate-reactive components, and at least one polyisocyanate.

21. The process of claim 20, wherein the polyurethane cap coat composition further comprises at least one hydroxymethyl-containing polyester polyol or a hydroxyl- containing vegetable oil, or both.

22. The process of claim 21, wherein the polyurethane cap coat composition contains castor oil

23. The process of claim 22, wherein the polyurethane tie coat composition contains at least one viscosity reducing agent and at least one water scavenger.