MXPA01006748A - Polyurethane foams prepared from mechanically frothed polyurethane dispersions - Google Patents

Abstract

The present invention is polyurethane dispersion composition that can be mechanically frothed to yield a foam that has good resiliency. Frothed foams of the present invention can be useful in cushioned flooring applications such as attached cushion broadloom, carpet tiles, carpet underlay, or vinyl flooring. Frothed foams of the present invention can also be useful as coatings for various textiles and for diapers.

Description

POLYURETHANE FOAMS PREPARED FROM MECHANICALLY FOAMED POLYURETHANE DISPERSIONS This invention relates to polyurethane foams. In particular, this invention relates to polyurethane foams prepared from aqueous polyurethane dispersions and to a process for preparing them. US-A-5,104,693 and WO 97/43326 describe processes for preparing a substrate supported by polyurethane, such as carpets or textiles, where a reactive, uncured polyurethane-forming composition is applied to the surface of the substrate; It is calibrated and cured. Each of these relates to reactive polyurethane foam chemistries with side A (isocyanate) + B side (polyol), in which the respective polyurethane reaction is occurring in the foaming, as the foam is formed. Polyurethane dispersions are known and may be useful for preparing polyurethane polymers which, in turn, may be useful in various applications. Polyurethane dispersions can be used, for example, to prepare coatings for leather, wood finish, fiberglass sizing, textiles, adhesives, and automotive finishes and finishes. Polyurethane dispersions can be prepared by various processes, including, for example, those described in US Pat. No. 1,487,565; US-A- 4,742,095; US-1-4,879,322; US-A-3,437,624; US-A-5,037,864; US-A-5,221, 710; US-A-4,237,264 and US-A-4,092,286.

It is known that carpet backs can be prepared from polyurethane dispersions. For example, polyurethane dispersions prepared according to the process of US Application Serial No. 09/039978 may be useful for preparing polyurethane carpet backings and backs for polyurethane textiles. Typically, the mechanical foams of the dispersions, which are applied as a primary or secondary binder to a carpet backing, are unstable due to the high load concentration and the absence of foam stabilizers. Mechanical foaming to produce a stable foam requires less load and foam stabilizers to be used; and, therefore, a process clearly different from that conventionally used to coat the back of a carpet for primary or laminated structure applications. The mechanical foaming of commercially available polyurethane dispersions, using air, for example, can be effected using additives such as, for example, stabilizing soap, inorganic filler and wax dispersions. While foams can be prepared by casting and drying, having good properties and a fine, stable cellular structure, up to 10 mm thick, the foams thus prepared are not flexible. US-A-4,733,659 teaches a disposable bandage that includes a flexible polyurethane, liquid-permeable hydrophilic foam, which can be prepared by mechanically foaming a dispersion of fully reacted polyurethane polymers, emptying the dispersion on a substrate and curing the aqueous dispersion. Although the patent teaches that to increase the hydrophilicity in the preparation of the hydrophilic foam, the foam may include certain surfactants (column 3, rows 39-50, column 7, row 40 to column 8, row 4, column 11, rows) 11-12), the patent teaches the use of said surfactants in the foam not in the preparation of the polyurethane dispersion. The patent warns that the selection of the particular materials for incorporation into the laminated structure and the resulting foam bandages requires special care (column 3, lines 17-19) and that the polyurethanes which have utility in that invention are those recognized in the art as ionically dispersible in water, such as the cationic polyurethanes described in US 4,066,591, example XVIII, or the anionic polyurethanes described in US-A-4,171, 391. Both US-A-4,733,659, in column 4, lines 14-23 and US-1-4,171, 391, in column 3, lines 35-48, depart in their teachings from polyurethane dispersions prepared and dispersed in water , with the help of detergents and shear. Elasticity is a convenient feature for foams used in applications such as carpet backs. By increasing the elasticity of said foam, both the durability and the comfort of the foams can be increased. For example, a more flexible foam; or, put another way, an "elastic" foam is commonly considered to be more comfortable than a foam not flexible. A more flexible foam can also mechanically dissipate energy, by "springing", instead of as heat, which would occur with a non-flexible foam. Dispelling the energy as heat can eventually cause the degradation of the polymer; which, in turn, leads to the foam not returning to its original shape. When this occurs in a carpet application, the resulting pattern, evident on the surface of the carpet in normal traffic areas, may be perceived as premature wear. It would be convenient, in the technique of preparing polyurethane foams, to have a polyurethane dispersion composition that can be foamed mechanically, so that a foam having a suitable structure of fine cells and good properties, including elasticity, can be prepared. It would also be convenient in the art to have a process for preparing a polyurethane foam having good elasticity, from a polyurethane dispersion, mechanically foaming the polyurethane dispersions. In one aspect, the present invention is a flexible polyurethane foam comprising a foam prepared by a process including the steps of foaming an aqueous polyurethane dispersion; apply the foam to a substrate, and dry the foam to make it foam; where the polyurethane dispersion is prepared by mixing water, a chain extender, a surfactant and a polyurethane prepolymer, under conditions of sufficient mixing to prepare a dispersion stable.; the polyurethane is prepared from a formulation including a polyisocyanate and a polyol, having a hydroxyl functionality greater than 2.2; and the polyurethane foam has an elasticity of 5 to 80 percent. In another aspect, the present invention consists of a substrate with foam backing, comprising a substrate and, adhered thereto, an elastic polyurethane foam, prepared by a process including the steps of foaming an aqueous polyurethane dispersion; apply the foam to a substrate; and dry it to form foam; wherein the polyurethane dispersion is prepared by mixing water, a chain extender, a surfactant and a polyurethane prepolymer, under sufficient mixing conditions to prepare a stable dispersion; the polyurethane is prepared from a formulation including a polyisocyanate and a polyol having a hydroxyl functionality greater than 2.2; and the polyurethane foam has an elasticity of 5 to 80%. The foamed foams of the present invention may be useful in cushioned floor applications, such as one-piece carpets with adhered cushioning; carpet mosaics, shades of carpet or vinyl floors. The foamed foams of the present invention could also be useful as a cushion or as absorbent layers for various textiles and disposable articles. In one embodiment, the present invention consists of an elastic polyurethane foam, prepared using a composition of aqueous polyurethane dispersion that can be mechanically foamed, to produce a polyurethane foam with good elasticity. A polyurethane dispersion useful in the practice of the present invention includes water and: a polyurethane; a mixture capable of forming a polyurethane; or a mixture of both ingredients. Polyurethane-forming materials, when used in the present invention, are materials that can be used to prepare polyurethane polymers. Polyurethane-forming materials include, for example, polyurethane prepolymers. Although polyurethane prepolymers can retain some isocyanate reactivity for a certain period of time after dispersion, for the purposes of the present invention a dispersion of polyurethane prepolymer should be considered as if it were a fully reacted polyurethane polymer dispersion. Also for the purposes of the present invention a polyurethane prepolymer or a polyurethane polymer may include other types of structures, such as, for example, urea groups. The polyurethane prepolymers useful in the practice of the present invention are prepared by reacting active hydrogen compounds with any amount of isocyanate, in stoichiometric excess with respect to the active hydrogen material. The isocyanate functionality in the prepolymers useful in the present invention may be present in an amount of 0.2 wt% to 20 wt%. A suitable prepolymer can have a weight molecular on the scale of 100 to 10,000. The prepolymers useful in the practice of the present invention should be substantially liquid under the conditions of dispersion. The prepolymer formulations of the present invention include a polyol component. Active hydrogen-containing compounds, most commonly used in the production of polyurethane, are those compounds having at least two hydroxyl groups or amine groups. These compounds are referred to herein as polyols. Representatives of suitable polyols are generally known and are described in publications such as High Polymers, Volume XVI, Polyurethanes, Chemistry and Technology, by Saunders and Frisch, Interscience Publishers, New York, Volume I, pages 32-42, 44-54 (1962). ) and Volume II, pages 5-6, 198-199 (1964); Organic Polymer Chemistry, by KJ Saunders, Chapman and Hall, London, pages 323-325 (1973) and Developments in Polyurethanes, Volume I, JM Burst, ed., Applied Science Publishers, pages 1-76 (1978). any compound containing active hydrogen may be used in the present invention Examples of those materials include those selected from the following classes of compositions, either alone or as a mixture: (a) adducts of polydroxyalkanes with alkylene oxide, (b) adducts of sugars non-reducing agents and derivatives of sugar, with alkylene oxide, (c) adducts of phosphorus and polyphosphorous acids with alkylene oxide, and (d) adducts of polyphenols with alkylene oxide.The polyols of these types are referred to herein "base polyols". Examples of polyhydroxyalkane adducts with alkylene oxide, useful herein, are the adducts of ethylene glycol, propylene glycol, 1,3-dihydroxypropane, 1,4-dihydroxybutane and 1,6-dihydroxyhexane; glycerol, 1,4-trihydroxybutane, 1,2,6-trihydroxyhexane, 1,1,1-trimethylol ethane, 1,1-trimethylolpropane, pentaerythritol, polycaprolactone, xylitol, arabitol, sorbitol, mannitol. Preferred herein are polyhydroxyalkane adducts with alkylene oxide, propylene oxide adducts and propylene oxide adducts capped with ethylene oxide, dihydroxyalkanes and trihydroxylalkanes. Other useful alkylene oxide adducts include the adducts of ethylene diamine, glycerin, piperazine, water, ammonia, 1,2,3,4-tetrahydroxybutane, fructose, sucrose. Also useful in the present invention are poly (oxypropylene) glycols, thiols, tetroles and hexols, and any of them, which is capped with ethylene oxide. These polyols also include poly (oxypropylene oxyethylene) polyols. The oxyethylene content should preferably comprise less than 80 percent by weight of the total weight of the polyol and, more preferably, less than 40 percent by weight. When used, the ethylene oxide may be incorporated in any manner along the polymer chain, for example, as internal blocks, as terminal blocks, or as randomly distributed blocks, or any combination thereof. Another class of chicken that can be used with the present invention are the "copolymer polyols", which are polyols of base containing dispersed polymers, such as acrylonitrile-styrene copolymers. The production of those copolymer chicken may be from reaction mixtures comprising a variety of other materials, including, for example, catalysts such as azobisisobutyronitrile; copolymer polyol stabilizers, and chain transfer agents, such as isopropanol. Polyester polyols can be used to prepare the polyurethane dispersions of the present invention. The polyester polyols are generally characterized by repeating ester units, which may be aromatic or aliphatic, and by the presence of terminal, primary or secondary hydroxyl groups, but any polyester that ends in at least two active hydrogen groups may be used in the present invention. For example, the reaction product of the transesterification of glycols with poly (ethylene terephthalate) can be used to prepare the dispersions of the present invention. The polyamines, the amine-terminated polyethers, the polymercaptans and other isocyanate-reactive compounds, are also suitable in the present invention. Polyisocyanate polyaddition active hydrogen containing compounds (PIPA) can be used in the present invention. PIPA compounds are typically the reaction products of TDI and triethanolamine. A process for preparing PIPA compounds can be found, for example, in U.S. Patent 4,374,209, issued to Rowlands. In the practice of the present invention preferably the 50 weight percent of the active hydrogen compounds used to prepare the polyurethane or polyurethane prepolymer is a polyether polyol having a molecular weight of 600 to 20,000, preferably 1,000 to 10,000, most preferably 3,000 to 8,000. In the practice of the present invention, preferably this polyol has a hydroxyl functionality of at least 2.2. It is preferred that this polyol has a hydroxyl functionality of 2.2 to 5.0, more preferably, 2.3 to 4.0 and even more preferably, 2.5 to 3.8. It is highly preferable that the active hydrogen compounds used to prepare the polyurethane or the polyurethane prepolymer be a polyether polyol having a hydroxyl functionality of 2.6 to 3.5, and a molecular weight of 3,000 to 8,000. For the purposes of the present invention, functionality is defined as meaning the functionality calculated on average of all polyol initiators, further adjusted for any known side reactions, which affect functionality during the production of the polyol. The polyisocyanate component of the formulations of the present invention can be prepared using any organic polyisocyanate, modified polyisocyanate, isocyanate-based prepolymer, and mixtures thereof. These may include aliphatic and cycloaliphatic isocyanates, but aromatic isocyanates and especially multifunctional aromatics, such as the 2,4- and 2,6-toluene diisocyanates, and the corresponding mixtures; 4,4'-, 2,4'- and 2,2'- diisocyanates diphenylmethane (MDl) and the corresponding isomeric mixtures; mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and polyphenyl-polymethylene polyisocyanates (PMDI); and mixtures of PMDI and toluene diisocyanates. It is highly preferable that the polyisocyanate used to prepare the prepolymer formulation of the present invention be MDl or PMDI. The present invention includes a chain extender or interleaver. A chain extender is used to provide the molecular weight of the polyurethane prepolymer, by reaction of the chain extender with the isocyanate functionality in the polyurethane prepolymer; that is, it extends the chain of the polyurethane prepolymer. A suitable chain extender or interlayer is typically an active hydrogen-containing compound, of low equivalent weight, having 2 or more active hydrogen groups per molecule. The chain extenders typically have two or more active hydrogen groups, while the crosslinkers have three or more active hydrogen groups. The active hydrogen groups may be hydroxyl, mercaptyl or amino groups. An amine chain extender can be blocked, encapsulated or otherwise reactive. Other materials, particularly water, can function to extend the chain length and, therefore, can be chain extenders for the purposes of the present invention. Polyamines are the preferred chain extenders. It is particularly preferred that the chain extenders is selected from the group consisting of polyethers terminated with amine, such as, for example, JEFFAMINE D-400 from Huntsman Chemical Company, amlnoethylpiperazine, 2-methylpiperazine, 1,5-diamino-3-methylpentane, isophorone diamine, ethylenediamine, diethylenetriamine, aminoethylethanolamine, triethylenetetramine, triethylenepentamine, ethanolamine, lysine in any of its stereoisomeric forms, and its salts; hexane diamine, hydrazine and piperazine. In the practice of the present invention, the chain extender can be used as an aqueous solution. In the practice of the present invention, a chain extender is used in an amount sufficient to react with from zero (0) up to 100 percent of the isocyanate functionality present in the prepolymer, based on an isocyanate equivalent that reacts with an equivalent of chain extender. It may be desirable to allow the water to act as a chain extender and to react with some of the isocyanate functionality present, or with all of it. A catalyst can optionally be used to promote the reaction between a chain extender and an isoclanate. When the chain extenders of the present invention have more than two active hydrogen groups, then they also function concurrently as interleavers. A polyurethane formulation, suitable for preparing a foam of the present invention (hereinafter the compound) can be prepared from a polyurethane dispersion and a foam stabilizer. In addition to a polyurethane dispersion and a foam stabilizer, a compound of the present invention may optionally include: interlayers, surfactants, fillers, dispersants, thickeners, fire retardants, absorbers, fragrances and / or other materials known in the art to be useful in the preparation of products of polymer foam. The term "compound" means particularly the material placed in a frothing device to produce a foam that can be dried to a foam product. A compound of the present invention optionally includes a filler. The filler material may include conventional fillers, such as ground glass, calcium carbonate, aluminum trihydrate, talc, bentonite, antimony trioxide, kaolin, ash powder or other known fillers. In the practice of the present invention a suitable filler, which is charged in a polyurethane dispersion, can be from 0 to 500 parts of filler per 100 parts of polyurethane. It is preferred to load the filler in an amount of less than 250 parts per hundred parts of resin, more preferably less than 200 parts per hundred parts of resin, most preferably less than 150 parts per hundred parts of resin. The present invention optionally includes a charge wetting agent. A charge dampening agent can generally help make the polyurethane filler and dispersion compatible. Useful wetting agents include phosphate salts, such as sodium hexametaphosphate. A charge wetting agent may be included in a compound of the present invention, at a concentration of at least 0.5 parts per 100 parts of filler, by weight. The present invention optionally includes thickeners. Thickeners may be useful in the present invention to increase the viscosity of low viscosity polyurethane dispersions. Thickeners suitable for use in the practice of the present invention can be any of those known in the art. For example, suitable thickeners include ALCOGUM ™ VEP-II (commercial designation of Aleo Chemical Corporation) and PARAGUM ™ 241 (commercial designation of Para-Chem Southern, Inc.). The thickeners can be used in any amount necessary to prepare a compound of the desired viscosity. The present invention may include other optional components. For example, a formulation of the present invention may include surfactants, foaming agents, dispersants, thickeners, fire retardants, pigments, antistatic agents, reinforcing fibers, antioxidants, preservatives, biocides, acid scavengers. Examples of suitable foaming agents include: gases and / or gas mixtures, such as, for example: air, carbon dioxide, nitrogen, argon, helium. While optional for the purposes of the present invention, some components may be highly advantageous for the stability of the product during the manufacturing process and after it. For example, the inclusion of antioxidants, biocides and Conservatives can be extremely advantageous in the practice of the present invention. It is preferred in the practice of this invention to use a gas, as a foaming agent. The use of air as a foaming agent is particularly preferred. Foaming agents are typically introduced by mechanical introduction of a gas into a liquid to form the foam; that is, by mechanical foaming. When preparing a foamed polyurethane backing, it is preferred to mix all the components and then mix the gas in the mixture, using equipment such as an OAKES or FI RESTONE skimmer. The surfactants may be useful for preparing a stable dispersion of the present invention, and / or a surfactant useful for preparing a stable foam. Surfactants useful for preparing a stable dispersion are optional in the practice of the present invention, and may be cationic surfactants, anionic surfactants or a nonionic surfactant. Examples of anionic surfactants include sulfonates, carboxylates and phosphates. Examples of cationic surfactants include quaternary amines. Examples of nonionic surfactants include block copolymers containing ethylene oxide and silicone surfactants. The surfactants useful in the practice of the present invention can be external surfactants or internal surfactants. The agents External surfactants are surfactants that are not chemically reacted in the polymer during the preparation of the dispersion. Examples of external surfactants, useful herein, include the salts of dodecylbenzenesulfonic acid and the salt of lauryl sulphonic acid. The internal surfactants are surfactants that are chemically reacted in the polymer during the preparation of the dispersion. An example of an internal surfactant, useful herein, includes 2,2-dimethylolproplonic acid and its salts. A surfactant may be included in a formulation of the present invention, in an amount ranging from 0.01 to 8 parts per 100 parts by weight of the polyurethane component. Surfactants useful in preparing a stable foam are called foam stabilizers herein. Foam stabilizers are essential in the practice of the present invention. In addition to the surfactants described above, foam stabilizers may include, for example: sulfates, succinamates and sulfosuccinamates. Any foam stabilizer known to be useful to those skilled in the art of preparing polyurethane foams can be used in the present invention. The catalysts are optional in the practice of the present invention. Catalysts suitable for use in the preparation of the polyurethanes and polyurethane prepolymers of the present invention include the tertiary amines and the organometallic compounds, as compounds and their mixtures. For example, suitable catalysts include di (n-butyltin) bis (isocyclic ester of mercaptoacetic acid), dimethyltin dilaurate, dibutyltin dilaurate, dibutyltin sulfide, stannous octoate, ferric acetylacetonate lead octoate, bismuth carboxylates, triethylene diamine, N -methylmorpholine, similar compounds and their mixtures. An amount of catalyst is advantageously employed so that a relatively rapid cure to a stick-free state can be obtained. If an organometallic catalyst is employed, said cure can be obtained using from 0.01 to 0.5 parts per 100 parts of the polyurethane prepolymer, by weight. If a tertiary amine catalyst is employed, preferably the catalyst provides adequate cure using 0.01 to 3 parts of tertiary amine catalyst per 100 parts of the polyurethane-forming composition, by weight. Both an amine type catalyst and an organometallic catalyst can be used in combination. In general any method known to those skilled in the art of preparing polyurethane dispersions, for preparing polyurethane dispersion material, suitable for preparing, for example, a carpet of the present invention, can be used in the practice of the present invention. A suitable polyurethane dispersion, stable during storage, as defined herein, is any polyurethane dispersion having an average particle size of less than 5 microns. A polyurethane dispersion which is not stable during storage may have average particle sizes greater than 5 microns. For example, a suitable dispersion can be prepared by mixing a polyurethane polymer prepolymer with water and dispersing the prepolymer in the water, using a mixer. Alternatively a suitable dispersion can be prepared by feeding a prepolymer in a static mixing device, together with water, and dispersing the water and the prepolymer in the static mixer. Continuous methods for preparing aqueous polyurethane dispersions are known, and can be used in the practice of the present invention. For example, U.S. Patent Nos. 4,857,565, 4,742,095, 4,879,322, 3,437,624, 5,037,864, 5,221, 710, 4,237,264 and 4,092,286 describe continuous processes useful for preparing polyurethane dispersions. Additionally, a polyurethane dispersion having a high internal phase ratio can be prepared by a continuous process, such as that described in U.S. Patent No. 5,539,021. Other types of aqueous dispersions may be used in combination with the polyurethane dispersions of the present invention. Suitable dispersions, useful for mixing with polyurethane dispersions of the present invention include: styrene-butadiene d ispersions; styrene-butadiene-vinylidene chloride dispersions; alkyl styrene-acrylate dispersions; ethylene-vinyl acetate dispersions; polychloropropylene latex; polyethylene copolymer latex; Latex ethylene-styrene copolymer; polyvinyl chloride latex, or acrylic dispersions; similar compounds, and mixtures of them. The polyurethane foams of the present invention are elastic. For the purposes of the present invention, an elastic foam is one that has a minimum elasticity of 5 percent, when tested by the sphere drop method. This method, ASTM D1564-64T, generally consists of dropping a sphere with known weight, from a standard height, onto a sample of the foam, and then measuring the bounce of the sphere as a percentage of the height from which it is measured. let fall. Preferably, the foams of the present invention have an elasticity of 5 to 80 percent, more preferably, of 10 to 60 percent, and most preferably, of 15 to 50 percent. The elasticity of the foams of the present invention can impart greater durability and greater comfort to products that include them, as compared to conventional polyurethane foams, prepared from aqueous polyurethane dispersions. A polyurethane dispersion of the present invention can be stored for subsequent application to the back of a substrate, such as, for example, a carpet. Storage for this purpose requires that the dispersion be stable during storage. Alternatively, the polyurethane dispersion can be applied continuously to the back of a carpet substrate, that is, the dispersion can be applied to the back of a carpet as the dispersion is prepared. according to the practice of the present invention. In the practice of the present invention, a foamed polyurethane layer is dried to prepare a foam. For the purposes of the present invention this means that the foam is treated in such a way that the structural integrity of the foam is maintained and after the foam is substantially free of water, the resulting material is an elastic cellular polyurethane foam. The drying can be done at room temperature but, preferably, it is done in an oven at temperatures of 50 to 200 ° C. In preparing carpets with polymer backing, according to the present invention, a polyurethane dispersion is applied as a layer of preferably uniform thickness over the hairless surface of the properly prepared carpet substrate. The polyurethane precoats, the laminated structure coatings and the foam coatings can be prepared by methods known to those of ordinary skill in the art of preparing such backings. The precoats, the laminated structure coatings and the foam coatings, prepared from dispersions are described in P. L. Fitzgerald, Integral Foam Carpet Cushining Dispersion, J. Coat. Fab., 1977, volume 7 (pages 107-120) and in R. P. Brentin, Dispersion Coating Systems for Carpet Backing, J. Coat. Fab. 1982, volume 12 (pages 82-91). A reactive polyurethane backing, also known as backing A + B, as formed by the reaction of a polyisocyanate and a polyol, in the presence of a catalyst and a blowing agent, can be applied to a surface of a carpet substrate before curing to the stick-free state, to form a carpet. Alternatively, in the practice of the present invention, a polyurethane dispersion containing no unreacted isocyanate functionality can be advantageously applied to the surface of a carpet substrate, thereby eliminating the need to react polyurethane precursors in situ. to form the polyurethane polymer. Typically the polyurethane dispersion, usually in the form of a compound, is applied as a stable foam to a carpet surface that has been coated with a primary backing or precoat. The polyurethane dispersion can be applied to a suitable substrate, using equipment such as a spatula or roller; an air knife or an extruder, to apply and calibrate the layer. The amount of polyurethane dispersion used to coat a textile can vary widely, from 53 g / m2 to 10.7 kg / m2 dry weight, depending on the characteristics of the textile. It is preferable that the foams of the present invention be applied at a level of 170 g / m2 to 1.8 kg / m2 by weight of dry polymer. After applying and calibrating the layer, the layer can be dried using heat from any suitable thermal source, such as an Infrared oven, a convection oven or heating plates. In preparing the substrates with polyurethane foam backing of the present invention, in general, and textiles with backing, in particular, it is advantageous to dry the polyurethane dispersion as quickly as possible after applying it to the substrate. It has been found that by using a slow heating process a thicker cell structure can be obtained at the center of the foam. It is particularly advantageous to carry out at least the initial drying of a polyurethane dispersion of the present invention using an infrared heater, since this practice can promote the formation of a smooth skin on the surface of the foam facing the heater, which It is convenient from the aesthetic point of view and can also be drawn or submitted to any other form of marker process. A unique property of the polyurethane foams of the present invention is that they are resistant to yellowing. Conventional polyurethane foams, in particular those prepared with aromatic starting materials, such as MDl or TDI, may yellow when exposed to air and ultraviolet light. The foams of the present invention have a surprising ability to resist yellowing under conditions that would cause a conventional polyurethane foam to yellow. The following examples are given for illustrating the present invention. The examples are not intended to limit the scope of the present invention and should not be construed as such. All percentages are by weight, unless noted otherwise.

EXAMPLES Materials used in the examples: VORANOL 4701 * - A triol with a molecular weight of 4950, having a 15% coronation with OE (* commercial designation from The Dow Chemical Company). ISONATE 125M * - 4,4'-methylenediphenyl isocyanate, having a functionality of 2.0 and an equivalent weight of 125 g / equivalent (* commercially available debasing from The Dow Chemical Company). ISONATE 50 OP * - A 50% blend of socianato 4,4'-methylenediphenyl, and 50% 2,4'-methylenediphenyl isocyanate, having a functionality of 2.0 and an equivalent weight of 125 g / equivalent (* commercial designation from The Dow Chemical Company). MPEG 950 * - Monol produced by reacting ethylene oxide with methanol, at an equivalent weight of 950 g / equivalent (* commercial breakdown from The Dow Chemical Company). BIO-TERGE AS-40 * - Mixed Olefin Sulfonate (14-16 carbon atoms) -sodium (* commercial name of Stepan Corporation). EMPIMIN MK / B * - Disodium N-sebosulfosuccinamate, obtainable as a 35% active solution in water (* commercial designation by Albright &Wilson, United Kingdom).

Thickener ACUSOL A810 * - Acrylate thickener, obtainable as a 19 percent solution in water (* commercial designation of Rohm and Haas Co.). Antioxidant L - an emulsion of 54 parts of beta.beta-ditridecyl thiodipropionate, 40 parts of water and 6 parts of WINGSTAY L *, which is a butylated reaction product of p-cresol and dicyclopentadiene (* commercial designation of Goodyear Rubber Company).

EXAMPLE 1 Preparation of a prepolymer: A prepolymer is prepared by adding 504 g of VORANOL 4701, 14 g of MPEG 950, 9.1 g of diethylene glycol, 86.45 g of ISONATE 125M and 86.45 g of ISONATE 50 OP, to a glass bottle; where the threads of the glass bottle are wrapped with TEFLON * tape to prevent the lid from adhering to the bottle (* commercial designation of DUPONT). The bottle is sealed, vigorously shaken until the homogeneity of the components is obtained, and then rolled in an apparatus for rolling bottles for about 10 minutes. The bottle is then placed in an oven maintained at 70 ° C for 15 hours, after which it is removed and allowed to cool to room temperature before use. Preparation of an aqueous dispersion of polyurethane: We weigh 75 g of prepolymer in a 0.24 liter glass bottle, which has an internal diameter of 5.6 cm. The bottle is immobilized and an INDCO type A mixing blade is inserted into the prepolymer (4.3 cm in INDCO diameter), INC.), So that the blade is barely covered by the liquid. Water is fed to the prepolymer at a rate of 14 g / minute for 2 minutes and 19 seconds, while stirring at 3,000 r.p.m. After 30 seconds in the water supply, 6.1 g of BIO-TERGE AS-40 is introduced for a period no longer than 5 seconds, through a syringe. After the addition of the water is complete, a 10 percent solution of piperazine in water (32.9 g, 80% stoichiometric, based on the isocyanate equivalents of the prepolymer) is added through the syringe over a period of 15 seconds The resulting dispersion is then poured into a plastic triple weir beaker, hermetically covered with aluminum foil and left stirring moderately overnight with a magnetic stirrer. The next day 55 percent of the solids dispersion is filtered through a thick paint filter. Preparation of the foamed polyurethane foam, elastic: 200 g of the aqueous polyurethane dispersion is mixed with 4.7 g of a 25% aqueous solution of sodium lauryl sulfate, 18.7 g of EMPIMIN MK / B and 3.6 g of ACUSOL A810 thickener using a mixer, until foam formation is observed. It pours the foam on a sheet of polyester film and heated in an oven at 150 ° C for 20 minutes, to produce an elastic, low density foam.

EXAMPLE 2 Preparation of a prepolymer A polyurethane prepolymer is prepared using a formulation consisting of 2 parts of MPEG 950, 72 parts of VORANOL 4701, 1.3 parts of diethylene glycol, 12.35 parts of each of ISONATE 50 OP and ISONATE 125M. Preparation of a polyurethane dispersion: A polyurethane dispersion is prepared by extending the prepolymer chain of this example in water with piperazine, to a stoichiometry of 0.75 with respect to a solids content of 52.7 percent. The dispersion is prepared with 3% of surfactant BIO-TERG AS-40, based on the prepolymer solids. The polyurethane dispersion has an average particle size by volume of 0.229 microns. Preparation of an elastic foamed polyurethane foam: A composite is prepared using 215 parts of the polyurethane dispersion of this example; 2.1 parts of Antioxidant L, 10 parts of EMPIMIN MK / B and 3.6 parts of a 25% aqueous solution of sodium lauryl sulfate. The compound is foamed using a COWIE RIDING FOAM MACH INE * (* commercial designation of Cowie and Riding Ltd.) And is emptied on a sheet of TEFLON. The foam is dried for 30 seconds, under infrared heat, and then for 20 minutes in an oven at 150 ° C. The foam is tested and the results of the tests are given in the list of the following table.

EXAMPLE 3 A foam is prepared and tested substantially in identical manner to Example 2, except that the compound also includes 180 parts of calcium carbonate.

PICTURE 1 Determined by measuring the thickness of the foam after drying and reported as% of the original thickness of the foam, when applied to the substrate 2 ASTM D 1564 G 3 DIN 53571 A 4 DIN 53571 A

Claims (14)

2. What is claimed is: 1. A process for forming an elastic polyurethane foam, comprising the steps of (1) foaming a fully reacted aqueous polyurethane dispersion in the presence of a foam stabilizer; (2) applying the foam to a substrate, and (3) drying the foam to a foam product; where: (a) the polyurethane dispersion is prepared by mixing water, a chain extender and a polyurethane prepolymer, under sufficient mixing conditions to prepare a stable dispersion; and (b) preparing the polyurethane from a formulation including a polyisocyanate and a polyol having a hydroxyl functionality of more than 2.2; characterized in that: (i) the polyurethane dispersion includes an external surfactant; and (ii) the polyurethane foam has an elasticity of 5 to 80%. 2. The process of claim 1, wherein the foam includes a filler.
3. 3. The process of claim 2, wherein the foam is adhered to the substrate.
4. 4. The process of claim 2, wherein the substrate is a cushioned floor.
5. 5. - The process of claim 1, wherein step (3) includes exposing a surface of the foam to infrared heat to promote the formation of a smooth skin on the surface of the foam facing the heater; and adsorptively dry the foam at a temperature of 50 ° C to 200 ° C.
6. 6. The process of claim 5, wherein the substrate is a carpet and where the foam has an elasticity of 15 to 50%.
7. 7. The process of claim 1, wherein the polyisocyanate comprises at least one multifunctional aromatic isocyanate and the pollol having a hydroxyl functionality of more than 2.2 is a polyether polyol having a molecular weight of 600 to 20,000.
8. 8. The process of claim 7, wherein the polyurethane prepolymer is prepared from a formulation including MDl as the sole polyisocyanate.
9. 9. The process of claim 7, wherein the foam is resistant to yellowing.
10. 10. The process of claim 1, wherein the external surfactant used to prepare the polyurethane dispersion is at least one salt of lauryl sulphonic acid or dodecylbenzenesulfonic acid or sodium sulfonate of 14 to 16 carbons.
11. 11. The process of claim 1, wherein the polyurethane is prepared from a formulation that includes a polyol having an hydroxyl functionality of 2.6 to 3.5 and that polyol is the only one polyol included in the formulation.
12. 12. The foam produced by the process of any of claims 1, 2, 3, 7, 8, 9, 10 or 11.
13. 13. The foam on a substrate article, produced by the process of any of the claims 3, 4 or 6.
14. 14. The use in the manufacture of coverings for floor or cushioned textiles, of the foam produced by the process of any of claims 1, 2, 5, 7, 8, 9, 10 or 11. SUMMARY The present invention is a polyurethane dispersion composition that can be foamed mechanically to produce a foam having good elasticity. The foamed foams of the present invention may be useful in cushioned floor applications, such as one-piece carpeting with included cushioning; carpet mosaics, low carpets or vinyl floors. The foamed foams of the present invention may also be useful as coatings for various textiles and for diapers.