FIELD OF INVENTION

This application relates generally to compositions comprising a polyurethane where such compositions are useful in the treatment of a substrate to impart desired properties onto the substrate.

BACKGROUND OF THE INVENTION

Poiyurethanes are used in numerous applications such as in coatings and adhesives. in coating applications poiyurethanes are used, for example, to coat substrates in automotive refinish and large vehicle coating areas, and are also used to coat metal, wood, plastic, concrete, rubber, paper, glass and textile suhstrates. They are also used in coating floors and pipelines. In most coating applications it is desirable that at least one of the following properties be transferred to the coated substrate: gloss, How, scratch resistance, abrasion resistance, chemical resistance (e.g. resistance to cleaning agents), flame retardation, light stability or weather stability. When used with textiles or fabrics in particular, the -polyurethane should also be compatible with the fabric or textile, transparent without obstructing the aesthetic or texture of the textile or fabric, resistant to light and weather, resistant to repeated washing or cleaning, resistant to chemical treatments and should have low toxic gas emissions and low expense in preparation and upkeep. It is also often desirable that the polyurethane contains some flame retardant characteristic.

As can be imagined, the methods and effects of coating substrates with polyurethane vary depending on numerous variables. These include the substrate and the type of polyurethane used, the solvents used in dissolving the polyurethane, as well as the desired aesthetics of the coated substrate. The durability of the coating and the coating properties depends on the ability of the coated substrate to resist one or more of light, heat, water, detergent, air pollutants and chemical degradation. These properties can in many instances be affected by the solvent used in dissolving the poiyurethanes.

The choice of coating application depends on the properties desired to be transferred to the substrate, the substrate itself and the intended use of the substrate. For example, textiles are used in a wide variety of applications such, as furniture and vehicle upholsteries. For many of these fabrics, flarnmabtlity is of concern. Consequently, flame retardation is one property that is often desirable to be transferred to the fabrics when coating them with polyurethane.

Approaches for coating fabrics include, for example, treating the fabric substrate with a coating of the polyurethane. Such coatings can be applied by knife back-coating (coating to the back of drapes, for exampl e) or front-coating (coating to the front of drapes, for example). Another means of coating the substrate is finishing. Finishing of the pol urethane .onto fabric substrates can be done, for example, either directly or using finish chemicals (resins), which chemically link the polyurethane to the fabric.

Before the polyurethane can be coated onto a substrate it must be dissolved in a solvent. The solvent in some instances will determine which properties will be transferred io the substrate and in some instances also affects how the polyurethane composition is cured.

Curing of the coated substrate is often done after the coating step, by evaporation or other means of removal of the solvent, which solvent was used to sohibilize the polyurethane before the coating step. Choice of solvent and solvent characteristics is also important considerations in preparing the polyurethane composition; especially the solvent ^' s boiling point. It is _. generally preferred to have solvents with low boiling points so that curing, for example, by evaporation, can be easily done without affecting the polyurethane's interaction with the substrate.

In the. coagulation method, for example, the polyurethane is often dissolved in

Dimethyiformamide (DMF), Other commonly used solvents include N-N Dimethylacetamide (DMA), Dimethylsulfoxi.de (DMSO), Tetrahydro.furan (THF), m-creso!, methyl ethyl ketone (ME ) and toluene. Tetrahydrofuran and Dimethyiformamide have relatively low boiling points of 64-65°C and 153°C, respectively, and are often used as solvents. Tetrahydrofuran has a low boiling point and is a useful solvent for soiubiiizing polyurethanes because Tetrahydrofuran has a shorter evaporation time, and therefore curing is easier compared to those solvents with higher boiling points. Unfortunately, it ha been suggested that although these solvents are effective for soiubiiizing polyurethanes, they may have toxicity and/or environmental concerns. Extra care is therefore suggested for handling these solvents. It is also important that all, or a significant portion of the solvent, be removed from the finished material before it is to be used. This requires carefully controlled drying operations and extensive washing with, for example, water to get the desired removal rate and/or desired amount of solvent to be removed. Such processes can be costly and time consuming. Beyond the cost and time concerns, when: polyurethane- Dimethylformamide solutions are used to coat a substrate, residual amounts of

Dimeihyiformamide are often left on the substrate which ma be of concern for the

aforementioned reasons.

Accordingly, there remains a need for polyurefhane compositions that are less costly to prepare and have fewer toxicity and/or environmental concerns. There also remains a need for polyurethane compositions having improved curing and interaction with the substrate.

SUMMARY OF THE INVENTION

The present disclosure provides a polyurethane solution wherein at least one of the following conditions are met: (1) the solvent is easily volatilized; (2) upon coating the solution to a substrate the solution does not stick to other surfaces, at least not in a significant way; (3) the solution has fewer toxicity and/or environmental concerns, relative to polyurethane compositions solubilized. in Dimeihyiformamide. solvents; {4} the solution increases the penetration of the coated material into the substrate; (5) the solution improves curing time; (6) the solution improves char integrity.

Surprisingly, it has now been found that solutions comprising a polyurethane solute and a trialkyl phosphate solvent provide at least, one, if not all, of these conditions. More specifically, it has been surprisingly found that a thermoplastic polyurethane solute can be dissolved in a trialkyl phosphate solvent to form a solution and that substrates coated with the solution demonstrate at least one, if not all, of the above conditions. Substrates coated with the solution can impart the above desired properties onto the substrate. Accordingly, in one aspect, Applicant has herein disclosed a polyurethane solution comprising a thermoplastic polyurethane solute in a trialkyl phosphate solvent where the trialkyl phosphate is of the general formula (I) as described herein.

In further aspects. Applicant also discloses herein a method of making the polyurethane solution and a method of coating a substrate with the polyurethane solution. In an embodiment of the method of making a polyureihane solution, the method comprises dissolving a polyurethane solute in a trialky! phosphate solvent, The polyurethane can be a thermoplastic polyurethane polymer or resin.

In an embodiment of the method of making a polyureihane coated substrate, the method comprises the steps of (a) forming a poiyurethane solution of a polyurethane in trialky! phosphate solvent, (b) coating the solution onto a substrate, and (c) curing the solution. Curing of the solution can be done after the solution is coated onto the substrate or at least partially before being coated onto the substrate or both.

The polyurethane coated substrate Is also within the scope of the present disclosure. As such, certain embodiments of the polyurethane coated substrate comprise a substrate and a polyurethane solution wherei the polyurethane solution is coated onto the substrate. The polyureihane solution is cured according to the methods disclosed herein.

Suitable substrates, poiyurethanes, and solvents are further described herein, it has been surprisingly found herein that polyurethane (e.g., thermoplastic

poiyurethanes) can be soluhilized by a trialky! phosphate solvent and that polyurethane solutions and polyurethane coated substrates can be prepared to have at least one, if not all, of conditions (1) - (6) described above when the solution is prepared with a triaikyl phosphate as the solvent for the polyurethane.

It has also been surprisingly found that polyurethane solutions, although free of

Dimethylformami.de or substantially free of Diraethylformamide, have satisfactory durability on coated substrates when the solvent used is a triaikyl phosphate or substantially is a triaikyl phosphate. These solutions described herein at least maintain the durability properties of Dimetliylfomiamide solubilized poiyurethanes while avoiding the suggested environmental and toxicity concerns. For example, in some embodiments, for substrates that aire coated with the polyurethane solutions of the present disclosure, the char stability of the coated substrate is improved. Curing rates (e.g., time and amount of solvent removed) are also improved by the methods disclosed herein. BRIEF DESCRIP TION OF THE FIGURES

Fig. 1 shows a comparison of the char stability of a cotton fiber textile substrate without a polyurethane coating, with a poIyurethane-DMF coaling and with a polyurethane-trialkyl phosphate solution coating of the subject disclosure.

DESCRIPTION OF PREFERED EMBODIMENTS OF THE IN VENTION

Disclosed herein are a written descriptiorh enablement, best mode and inventive steps of the ciaimed invention through the disclosure and descripiion of certain, preferred embodiments of the claimed invention. While Applicant, through these descriptions, seeks to disclose the invention through descriptions of particular embodiments such thai those of ordinary skill in the art may understand and practice Applicant's claimed invention, these embodiments are not exhaustive and are intended merely to provide illustrations of some of the presently preferred embodiments of the invention. The metes and bounds of the invention are defined by the claims and their equivalents and are supported by the. descriptions and disclosures presented in these exemplary embodiments, in general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those of ordinary skill in the art, unless otherwise defined herein.

The following definitions are provided to clarify their specific use in the context of the disclosed invention. All references cited herein are hereby incorporated by reference to the extent not inconsistent with the present disclosure.

The term "polyurethane," as used herein describes both polyurethane polymers and/or resins and in particular thermoplastic polyurethanes.

The term "solution," as used herein, describes a composition having a polyurethane solute in a trialkyi phosphate solvent wherein at least 50% of the polyurethane is dissolved in the solvent.

The expression "trialkyi phosphate solvent" as used herein, describes solvents that are free or substantially free of Dimemylforraaniide and contain at least one trialkyi phosphate solvent. The expression "substantially Dimethyl formamide tree" or "substantially fre of

.Dimethyl formamide"- are used interchangeably. As used herein, they are used to define scenarios, where, if present at all, Dimethylformamide is in an amount that does not exceed about 1000 ppm, an amount 900 ppm or less, 500 ppm or less, 100 ppm. or less or zero ppm in the cured coated substrates.

The expression "substantially comprised of a triaikyl phosphate," as used herein, defines solvent solutions wherein the triaikyl phosphate is the major solvent having a wt% of greater than about 90 wt%.

The terms "'a" and "an," as used herein are used to indicate one or more.

The term "about," as used herein to describe specific values, or ranges shall be construed to include the specifically recited value.

The term "char stability," as used herein, is used to indicate the ability of a coated substrate to retain its physical integrity even after exposure to flames.

All ranges herein are inclusive of endpoints and all values and sub-ranges within the explicitly disclosed ranges.

Disclosed herein are pol urethane sol tions that are at least substantially free of

Dimethylformamide and are comprised of a polyurethane solute and a triaikyl phosphate solvent. One embodiment of the polyurethane solution disclosed herein comprises a olyurethane solute and a triaikyl phosphate solvent wherein the triaikyl phosphate is of the general formula (I)

wherein, R ^! , R ² and R ^"1 are independently selected from linear or branched alk l

containing from 1 to about 12 carbon atoms. in some embodiments, the R\ R ² and R ³ linear or branched alky! groups of the Irialkyi phosphate may independently be the same or different. These groups can contain from 1 to 12 carbon atoms, specifically from 2 to 8 carbon atoms, more specifically from 2 to 6 carbons, including a linear or branched alkyl group such as ethyl, propyl, butyl n- ropyl, isopropyl, n-butyi, isobutyl, sec-butyl, tert-butyl, isopenty!, neopent l, isohexyl, isoheptyi.

cyclohexyl, and 2-methylpropyl. The trialkylphosphate is desirably triethyl phosphate (TEP). Combinations of solvents of 2 or more different trialkylphosphates may also be used as the solvent. The three alkyl groups (i.e., R\ R ^"? and R ^J ) of the irialkyi phosphate may be the same or different. The irialkyi phosphate solvents employed in the polyurethane solution, disclosed herein, are advantageous over solutions that contain Dhnethylfermamide at least because of the aforementioned concerns associated with DimethyMbrmamide.

In a first aspect, a polyurethane solution is disclosed herein. The polyurethane solution is a solution wherein at least 50% by weight of a polyurethane solute is dissolved in a trialkyl phosphate solvent to form a polyurethane solution, in one embodiment of the polyurethane solution, the polywethane is substantially dissolved in the trialkyl phosphate solvent such that at least .60%, more specifically at least 75%, even more specifically at least 85%, yet even more specifically at least 95%, and most specifically at least 99% of the polyurethane is dissolved in the trialkyl phosphate solvent, in some embodiments of the polyurethane solution, between 50 and 99.9% of the polyurethane solute is dissolved in the trialkyl phosphate solvent. The term "dissolved" is understood to mean that the solution containing the respective amount of solute does not contain any visibly precipitated solute material when mixed at room temperature. in another aspect, Applicant herein discloses a method for producing the polyurethane solution disclosed herein. In one embodiment of the method for producing the polyurethane solution, a polyurethane solute is mixed into a trialkyl phosphate solvent to form a polyurethane solution. Where a polyurethane mixture is formed, a polyurethane solution can be subsequentl formed from further processing of the polyurethane mixture. For example, where less than 50% of the polyurethane is dissolved in the trialkyl phosphate solvent, a mixture is formed. Where at least 50% (i.e., a major portion) of the polyurethane is dissolved, in the trialkyl phosphate solvent a solution is formed. Further processing of the polyurethane solution can be performed to obtain a polyurethane solution with a substantial portion of the polyurethane dissolved in the trialkyl phosphate solvent. In one embodiment, the method of producing a polyurethane solution comprises dissolving at least a substantial portion of the polyurethane (i.e., at least 60%) in a trialkyl phosphate solvent to form a polyureihane solution. In a specific embodiment, a thermoplastic polyurethane is mixed into a trialkyl phosphate solvent to form a mixture or solution as described above. The polyurethane solution described herein can be formed by- methods known to those of ordinary skill in the art such as by adding the polyurethane to a container with the trialkyl phosphate. Addition of the polyurethane can be done at elevated temperatures with stirring, such as by magnetic rod, until the mixture or desired solution is formed.

In a further aspect, a polyurethane coated substrate is also disclosed herein. In a general embodiment of the polyurethane coated substrate, the coated substrate comprises a substrate and a polyurethane solution wherein the polyurethane solution is coated onto the substrate. The polyurethane solution is free or substantially free of Dimethylfonnamide. The polyurethane solution used to coat the substrate can then be cured. The coated substrate demonstrates at least one of the (1) to (6) conditions described herein. For example, the coated substrate has less of the toxicity and environmental concerns of Dimethylfonnamide. in a specific embodiment of the polyurethane coated substrate, the coated substrate comprises a textile substrate wherein the textile substrate further comprises a polyurethane solution coated thereon. The polyurethane coated textile substrate demonstrates improved char stability over similar substrates coated with solution of polyurethane in Dimethyiformaniide solvent. The polyurethane coated substrate also has an improved interaction between the polyurethane solution and the substrate, due at least in part to the solvent and/or the viscosity of the polyurethane solution. Suitable substrates are described herein, though other suitable substrates may be employed depending on the desired application. In some embodiments, the thickness of the coating can be adjusted by known methods and by the methods disclosed further herein, Polyurethane solutions suitable for coating the substrate are disclosed herein.

A method of coating a substrate with the polyurethane solution i also provided herein. In one embodiment of the method of preparing a poly urethane coated substrate, the polyurethane solution is coated onto a substrate using known coating techniques. In one embodiment the substrate is a textile substrate and the textile substrate is coated with the poly urethane solution disclosed herein. In a furthe embodiment, the solution is cured. Curing of the poiyurethane solution removes most of the sol vent from the solution. The poiyurethane solution is cured and in more specific embodiments is cured on the substrate. While curing on the substrate is preferred, it is contemplated within the present disclosure thai the solution may be cured, at least in part, before being coated onto the substrate. In a specific embodiment of the method of coating substrate, a poiyurethane solution is formed as disclosed herein; a textile substrate is then coated with a poiyurethane solution where the poiyurethane solution comprises at least a thermoplastic poiyurethane and a irialkyl phosphate solvent. After coating the poiyurethane solution onto the textile substrate, the solution is cured on the substrate to form a poiyurethane coated substrate. in another embodiment a method is provided for the preparation of a poiyurethane coated substrate where there are at least two coating steps. A poiyurethane solution as described herein is prepared, by for example, the methods described herein. The poiyurethane solution is then coated onto a substrate, using coating methods known to those of skill in the art, in at least, two coating steps. Curing can be accomplished by the methods disclosed further herein. For example, curing can be done by alternating each coating step with a curing step. Alternatively, curing may be accomplished after a series of coating steps or after the final coating step in a series of coating steps. In preferred embodiments, curing is alternated with each coating step. While curing on the substrate is preferred, it is contemplated within the present disclosure that the poiyurethane solution may be cured, at least in part, before being coated onto the substrate. In a specific embodiment, a thermoplastic poiyurethane and trialkyl phosphate solvent is used in the preparatio of the poiyurethane solution and a textile substrate is coated with the

poiyurethane solution.

Any art recognized method, of coating the poiyurethane solution onto the substrate may be used, in coating applications using poiyurethane, the poiyurethane may be coated onto a substrate by using direct coating, coagulation coating, reverse coating, a simple solution dipping technique, spray coating or knife coating, grayure, foam coating, finishing or printing.

In a reverse, coating method the coating is, by contrast to direct coating, first applied to an intermediate substrate where the coating is laminated to a release paper. The coating and release paper are then laminated to the substrate followed by a delamination step where the release paper Is removed. This method is a preferred method for textile substrates that are not suitable for high tensile stresses during coating or for textile substrates that are open fabrics with low density. For the coagulation method, a textile substrate is usually coaled with a polyurethane solution. Often, this is thermoplastic polyurethane.

The thickness of the coating can be controlled by utilizing a coating implement that is held at a predetermined distance from the substrate. The polyurethane solution can also be mechanically pressed into the substrate. Pressing may improve the interaction (i.e., bonding) between the polyurethane and the substrate and, also, between sequentially added coatings of polyurethane. Rollers, platens, scrapers, knives, and the like can be used in the process of this invention as coating implements, as well as coating machines. Spraying the solution onto the substrate can also be effective, especially if the force of the spray is sufficient to result in good penetration and bonding.

Coating of the substrate generates a %-add-on amount of the solution onto the substrate. As used herein, the term "%-add-on" refers to the percent of the total weight of the coated substrate that is attributable to the polyurethane solution added to the substrate. The %-add-on can be determined by suitable methods. For example, the %-add-on can be determined by first measuring and then calculating the difference in weight of a "bone-dry' ⁵ (conditioned at 105 for 30 minutes) substrate (i.e., fabric) sample and one that is coated and fully cured, %-add-on - (weight of the fully cured coated substrate minus {-) the weight of the "bone-dry"

substrate)/(weight of the ^' "bone-dry" substrate) X 100, In some embodiments, the %-add-on is between about 4 and 25 percent, preferably between about 10 and 20 percent. In other embodiments, the %-add-on is between about 15 and 20 percent.

In some embodiments where multiple coating steps are employed, a first coat is applied having a %-add-on of about 5 to about 15 percent, more preferably between about 7 to 12 percent. In a second coating step, the %-add-on is about 5 to about 1 5 percent more preferabl between about 6 and 13 percent. In some embodiments, where multiple coatings are employed, the total average %-add-on is between about 15 to about 25 percent, more preferabl about 20 percent. The coated polyurethane layer, in some embodiments, has a thickness of about ί μτη to about 600 μηι, preferably about 1 μη» to about 400 urn and more preferably about 1 μηι to about 200 μιη.

The polyurethane solutions and polyurethane coated substrates disclosed herein contain a solvent such as a trialkyl phosphate solvent or a combination trialk l phosphate solvent. In certain embodiments, a curing step is used to remove at least a portion of the solvent from the polyurethane solution or coated substrate. Ev aporation or removal of the sol vent is controlled by system temperature, pressure, drying gas flow rate, and solvent boiling point. The evaporation rate wi ll affect the composition and characteristics of the coating, especially for very thin coatings. A slow evaporation rate will allow for pseudo-equilibrium to be established during evaporation, The non-equilibrium conditions achieved during rapid evaporation - such as under high vacuum or high gas flow rates— may result in unusual bulk and surface morphologies. Control of the residual amounts of solvent is important and consequently the solvent is therefore important in how the polyurethane coating composition behaves. Poiyurethanes require relatively pola solvents for solubilization. In certain embodiments, the curing step is performed after the polyurethane solution is coated onto a substrate. In certain embodiments, where multiple coating steps are employed in the coating of the substrate, the curing step is alternated after each coating step. In other embodiments, the curing step is applied after multiple coating steps in a series of coating steps. In further embodiments, the curing step takes place after the final coating step in a series of coating steps.

In a curing step, at least a portion of the trialkyl phosphate solvent or combination trialkyl phosphate solvent is removed from the solution to form a cured solution. In some embodiments at least a portion of the trialkyl phosphate solvent is removed from the solution. In other embodiments where a combination solvent is employed, at least a portion of the combination solvent is removed from the solution, such as at least one of an organic solvent or at least one of a trialkyl phosphate solvent.

Curing, in some embodiments, is performed by introducing the coating solution or the coated substrate to an oven. The oven is used to promote evaporation of at least a portion of the solvent from the solution or the coated substrate. It is contemplated by the present invention that azeotropes of the trialky l phosphates are, in some embodiments, incorporated. into the polyurethane solution such that the boiling point of the trialkyl phosphate is reduced. An exemplary azeotrope is phosphoric acid. A reduction in boiling point wi ll improve the evaporation rates such that curing rates are improved. Curing in some embodiments is done at from about 100°C to about 200°C, or from about 150°C to about 175X: specifically at about 160°C.

In spite of the significantly higher boiling point of trialkyl phosphates (i.e., 209°C for triethyl phosphate) compared to Dimethylformamide (i.e., 153°C) it has been surprisingly found that polyurethane solutions comprising a polyurethane (e.g., thermoplastic polyurethane) and a trialkyl phosphate solvent can be cured relatively easy because the trialkyl phosphates in polyurethane solutions volatilize relatively easy. In some embodiments the trialkyl phosphate volatilized in less than 5 minutes and more specifically between about 2 to about 3 minutes. These trialkyl phosphates also advantageously provide non-sticking polyurethane coatings. Furthermore, it has been surprisingly found that some flame- retardation characteristics have been transferred to the coated substrate by residual trialkyl phosphates foll owing the curing of the solution. For example, residual triethyl phosphate remaining in the coating after curing provides additional flame retardant benefits.

The polyurethanes used in forming the polyurethane solution disclosed herein are suited for or formulated for dissolution in a trialkyl phosphate solvent. For example, thermoplastic polyurethanes are suited for dissolution in the trialkyl phosphate solvent to form the

polyurethane solution. In a more specific embodiment, the polyurethane is a thermoplastic polyurethane and may be a polymer or resin. It is within the scope of the present disclosure that the solvent used for solubilizing the polyurethane is a combination trialkyl phosphate solvent having a first trialkyl phosphate solven and at least one other solvent component. When the solvent is a combination trialkyl phosphate solvent, the polyurethane is suited or is formulated such that at least a major portion of the polyurethane is sol uble in at least one component of the combination trialkyl phosphate solvent. In preferred embodiments, the polyurethane is soluble in a trialkyl phosphate solvent component of the combination trialkyl phosphate solvent.

The polyurethane, in certain embodiments, can be an aliphatic or aromatic polyurethane resin, in certain embodiments the polyurethane resin may be a one-component system (i.e., I K) or two-component system (i.e., 2K). Exemplary polyurethanes include, for example, polyether polyurethane, polyester polyurethane, polycarbonate polyurethane, polyeiherester polyurethane, polyethercarbonate polyurethane, polycaprolactone polyurethane, hydrocarbon polyurethane, alicycHc polyurethane, aromatic polyurethane, or a combination thereof. Although the present invention contemplates polyurethane resin having a weight average molecular weight (Mw) of from 10,000 to 700,000; from 10,000 to 100,000; from 20,000 to 80,000; from 40,000 to 60,000; the present invention is however not limited thereto.

Processes for the preparation of the polyurethane resins and polymers are known in the art and it is contemplated that those of ordinary skill in the art would be able to prepare, without undue experimentation, the resins or polymers suitabl for dissolution in the desired solvent. Polyurethane polymers can be prepared, for example, by reacting a polymeric polyol with a diisocyanate to form a capped -polyol, dissol ving the capped polyol (in a suitable solvent), and then reacting the capped polyol with a di-functionat chain extender having active hydrogen atoms. Polyo.Is contemplated within the scope of this disclosure include glycols. Polyurethane resins can be formed from processes known to those of ordinary skill in the art and men dissolved in the solvents described herei to form the polyurethane-trialkyl phosphate PUTP solutions disclosed herein.

Although a single polyurethane may be used -in forming the polyurethane solution, mixtures of polyurethanes (polymers and/or resins) are also contemplated within the scope of the present disclosure as suitable for use in forming the polyurethane solutions disclosed herein. Accordingly, it is within the scope of this disclosure that me polyurethane solution can, in some embodiments, contain combination poly urethanes having mixtures of polyurethanes. For example, in some embodiments, the polyurethane solution contains i, 2, 3, 4, 5, 6, 7, 8, 9 or 10 different polyurethane types. In other specific embodiments, the polyurethane solution contains i, 2, 3 or 4 polyurethane types, In some embodiments, the polyurethanes or combination polyurethanes provided are soluble in a single trialfcyl phosphate solvent or respective solvent .components of a combination tr-ialk l phosphate solvent. Single solvents substantially comprise a trialk I phosphate. Combination solvents comprise at least one trialkyl phosphate solvent and at least one other different trialkyl phosphate solvent and/or at least one organic solvent.

Whether a single solvent or a combination solvent, the solvent is at least substantially free of Dimethyl formarnide free or in preferred embodiment is free of Dimeihylformamide. In some embodiments, suitable polyurethanes include LARiPURs (i.e., LPR5860), which are polyurethane resins available from COIM USA, inc. located in West Deptford, NJ, USA. These resins may be formed into small, clear balls of 100 gm and abou 5mm in diameter.

LARIPURS are thermoplastic polyurethanes and combine the working technology of thermoplastic products together with well known features of polyurethanes. For example, they have excellent abrasion resistance, great flexibility and consistency at various temperatures, good compression set resistance, good water and light resistance, good resistance to hydrolysis, resistance to microbiological attack, good cold flexibility, good resistance to oils, fats and many types of solvents.

It has been surprisingly found that polyurethane solutions and substrates coated therewith can be formed. More surprisingly, it has been found that a trialkyl phosphate solvent can so!ubiiize a polyurethane to form a polyurethane solution as described herein. Thermoplastic polyurethane solutions can be formed by dissolving a thermoplastic polyurethane in a trialkyl phosphate solvent. The trialkyl phosphate solvents of the present disclosure are either free of Dimethyl formamide or substantially tree of Dimethylformamide.

The trialkyl phosphate, in some embodiments, is a polar solvent wherein the trialkyl phosphate has the general phosphate ester structure of formula (I) as defined above.

Trialkyl phosphates may be produced by conventional methods known by those of ordinary skill in the art such as those methods described in the US Patent No. 2,636,648 and those recited in US Patent No. 3.342,909, the contents of which are herein incorporated by reference in their entireties. It is contemplated within the present disclosure that various methods may be employed in producing the trialkyl phosphates.

The trialkyl phosphate solvent, in some embodiments, may be a combination trialkyl phosphate solvent and may comprise an optional organic solvent that is Dimethylformamide free or substantially Dimethylformamide tree, in some other embodiments, the combination trialkyl phosphate solvent and the polyurethane are selected such that at least a portion of the

polyurethane is soluble in at least one of the solvent components of the combination trialkyl phosphate solvent. In some embodiments the polyurethane is soluble in a trialkyl phosphate solvent and at least one of an organic solvent or residual amount of Dimethylformamide. Suitable organic solvents include, 2-methoxyethyl acetate, diethyiene glycol monomethyi ether, btrtyrolatone, 2- methoxy~l,3-dioxolane, dipropylene glycol methyl ether, propylene glycol n-propyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, propyl cellosolve including ethylene glycol propyl ether, butyl triglycol including ethylene glycol n- buty! ether, and/or dimethylacetamide; such as 2-methoxyethyl acetate, butyrolatone, 2- methoxy-l,3-dioxolane, dipropylene glycol methyl ether, propylene glycol n-propyl ether, dipropylene glycol dimethyl ether, and/or tripropylene glycol methyl ether; such as 2- methoxy- 1,3-dioxolane, dipropylene glycol methyl ether, and/or propylene glycol n-propyl ether; for example dipropylene glycol methyl ether and/or propylene glycol n-propyl ether, in some embodiments, the organic solvent is miscibie in water at 20°C or greater; preferably from about 25°C to about 95°C,

The viscosity of the polyurethane solution can influence the degree of penetration of the polymer into the subs trate and the amount of the solution t hat i s delivered to the substrate , it has been surprisingly found that formulating the polyurethane solutions disclosed herein to have viscosities within about 500 cps to about 15000 cps imparts an advantageous effect to the substrates coated with the present polyurethane solution. When the viscosity is too. low, reduced amounts of the polyurethane can be deposited in the substrate while causing increased

penetration into the substrate. When the solution viscosity is too high, penetration of the solution into the substrate can be reduced, thereby inhibiting interaction (i.e., bonding) of the

polyurethane with the substrate. This can adversely affect the durability in the coated substrate. In certain embodiments of the present invention, the polyurethane solution at about 25°C has a solution viscosity between about 500 cps and about 15000 cps. Specifically, the viscosity is between about 1000 cps and about 4000 cps. More specifically, the viscosity is between about 1000 cps and about 2000 cps. In some embodiments, the viscosity of the polyurethane solution is from about 1500 to about 1600 cps. Surprisingly, it has been found advantageous that when the viscosity is between about 500 to about 5000 cps or preferably between about 1 00 cps and about 4000 cps and more preferably between about 1 00 cps and about 1600 cps, that the polyurethane solution has improved absorption into the substrate. Viscosity can be determined by Brookfield Viscometer, model DV-Πί. This improved absorption is advantageous in mat the char stability of the coated substrate is improved, at least in comparison to substrates coated with poiyurethanes dissolved in Dimethyl formamide solvents. in some embodiments, a poiyurethane solution is formulated to have a viscosity between 48 cps and about 20,000 cps at 25°C; preferably between about 1000 cps and about 4000 cps. in further embodiments, the weighted amounts of the poiyurethane are dissolved in a trialkyl phosphate solvent to obtain the given viscosity of between about 1000 cps and about 2000 cps at 2S"C In certain preferred embodiments, the poiyurethane solution is 14 wt. % poiyurethane in trialkyl phosphate solvent and the viscosity, at 25°C, is between about 1 100 cps and about 1600 cps; more preferably from about 1500 to about 1600 cps. it has also been found advantageous that poiyurethane solutions described herein have unexpected and/or improved curing rates relative to poiyurethane solutions that are not Dimethylformanude-free or substantially

Di me t hy 1 form am ide- fre .

In some embodiments herein, curing is done at from about I00°C to about 200°C.

Specifically, curing is done at from about 125°C to about 175 ^Q C. More specifically, curing is done at irom about 150°C to about 170°C. In some embodiments, curing is done at 160°C. The curing time in some embodiments is from about 1 minute to about. 5 minutes. In some specific embodiments, the curing time is from about 2 minutes to about 3 minutes. In some embodiments the curing time is about 3 minutes. After curing, the solvent remaining in the poiyurethane solution, the residual solvent, is less than about 900 ppm. Specifically, the residual solvent is less than about 500 ppm, about 400 ppm, about 300 ppm, about 200 ppm. In more specific embodiments, the residual solvent is less than about 1 10 ppm after curing for about 3 minutes at about 160°C.

In some embodiments, the poiyurethane solution comprises a trialkyl phosphate solvent having a concentration of between about 70% to about 95% such tha it substantially comprises a trialkyl phosphate. In certain specific embodiments, the trialkyl phosphate solvent comprises from about 75 wt. % to about 95 wt. % of trialkyl phosphate such that it substantially comprises a trialkyl phosphate. In more specific embodiments, the trialkyl phosphate solvent comprises from about 80 wt, % to about 90 wt. % of trialkyl phosphate such that it substantially comprises a trialkyl phosphate. In some embodiments the trialkyl phosphate solvent comprises 95 wt. %, 90 wt. %, 87 wt. %, 86 wt. %, 85 wt. % or 80 wt. % of a trialkyl phosphate such that it substantially comprises a trialkyl phosphate, in these embodiments, the trialkyl phosphate solvent is substantially free of Dimethyl forma nide such that it comprises less than 5 wt. % DMF. In certain specific embodiments, the tri alky 1 phosphate solvent comprises less than 0.05 wt. %, 0.1 wt. %, 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, L0 t. % DMF. In more specific embodiments, the solvent comprises 0 wt. % Dimeth Iformamide such that it is

Dimethylformamide free. in polyurethane solutions or mixtures, the solvent is present in amounts of from about 50% to about 95% by weight of the solution or mixture. In other embodiments, the solvent comprises from about 70% to about 95% of the composition. In some embodiments of the polyurethane solution, the polyurethane is from about 5% to about 20% by weight of the solution. In some specific embodiments, the polyurethane solution comprises from about 10% to about 20% polyurethane; more specifically from about 10% to about 15% polyurethane by weight of the solution or mixture. in embodiments comprising an organic solvent, the organic solvent, and the polyurethane resin and/or polymer may be combined at a weight ratio of the polyurethane to the organic solvent of from about 1 : 1.4 to about 1 :1 ,8 and are mixed along with the trialkyi phosphate to form the polyurethane solution with, polyurethane in a trialkyi phosphate solvent.

Additives may be incorporated into the polyurethane solution . In some embodiments, suitable additives include pigments, colorants, deforming reagents, or further fire retardants. Here, a pigment ma be an one known in the art, for example, a pigment containing an organic or inorganic component, without limitation. In some embodiments pigments are added to the polyurethane solution or mixture in an amount of from about 0.1 to about 0.6 wt. %. More preferably, the pigment is added in an amount of from about 0.1 to about 0.3 wt. %. In other embodiments, the additive is added to the coated substrate. Other additives suitable to those of skill in the art may also be added to desirable characteristics.

Optionally incorporated additives can be incorporated into the polyurethane solution or coated substrate to provide color, pigment, texture, flame retardation and durability. It is contemplated that the incorporation of additi ves will be added by methods known to those of ordinary skill in the art. The additives can be added during the mixing steps of the polyurethane and the solvent, or can be added after mixing of the polyurethane and solvent, or can be added

47- after coating to the substrate before or after curing. In some embodiments, pigments in an amount from about 0.4 to about I wt. % are added to the solution.

In. some embodiments, the poiyurethane solution disclosed herein imparts a flame retardant characteristic to a substrate coated with the poiyurethane solution. In some

embodiments the flame retardant characteristic is, for example, an improved char stability. In some embodiments the flame retardant characteristic _. is improved char stability relative to poiyurethane compositions formed from poiyurethane in Dimetky Iformamide solvents (i.e., not Dimethylformamide-free or substantially Dimethyiformamide-i ee). In some embodiments, the flame retardant characteristic is imparted by the poiyurethane solution. For example, in some embodiments residual components from the trialkyl phosphate solvent or combination trialkyl phosphate solvent impart the flame retardant characteristic to the coated substrate. In specific embodiments, residual trialkyl phosphate from the trialkyl phosphate solvent imparts the flame retardant characteristic to the coated substrate. Contemplated flame retardant characteristics include improve char stability.

Although the present invention surprisingly provided flame retardant characteristics to coated substrates disclosed herein, it is further contemplated that said flame retardant characteristic (i.e., char stability) can. be provided or supplemented by additives to a poiyurethane solution or poiyurethane coated substrate. Flame retardation in compliance with NFPA-701 ^• flammability criteria may further be imparted to the substrate by an additive. It is therefore contemplated within the scope of some embodiments of the present invention that a poiyurethane solution includes a further flame retardant additive. For instance, the amount of trialkyl phosphate remaining after curing may be adjusted to further increase char stability. In other embodiments, the NFPA-701 flame retardation compliance characteristic may be imparted by the inclusion of other additives, including for example, known flame retardants additives.

Suitable flame retardant additives and means of preparing them are provided in

International Patent Application WO 2012/061373 to Jeffrey Stowell, et al.; which is

incorporated herein by reference in. its entirety. For example, a suitable flame retardant additive comprises a phosphate ester of the general formula (II); wherein R ⁴ , R ³ , R ⁶ and ⁷ of formula (ΪΪ) are each independently an aryl, or.arylalkyl each independently containing up to about 30 carbon atoms, optionally interrupted with heteroatoms, X is a divalent aryl or arylalkyl group, containing up to about 20 carbon atoms and n has an average value of from about 1.0 to about 2.0, In some preferred embodiments, the phosphate ester is selected from the group consisting of hydroquinone ^" bis(diphenyl phosphate); resorcinol bis(di-2,6-xyly! phosphate); 4,4'-biphenol bis(2,6-xyknol phosphate); and combinations thereof. The flame retardant is incorporated in a flarae retardant effective amount. This amount will vary depending on the phosphate ester, textile and other parameters. However, one of skill in the art, without undue experimentation, will be able to adjust the amounts to obtain an effective amount. The further flame retardant may be applied to the polyureihane solution or polyureihane coated substrate. In some embodiments the flame retardant is incorporated with the substrate in a separate step from the coating of the polyureihane solution onto the substrate,, such as by coating a previous or subsequent layer of flame retardant onto the substrate. The flame retardant, incorporated in the polyurethane solution or substrate (i.e., before or after coating with the polyurethane solution) of the present disclosure can be coated and cured by methods known to those of ordinary skill in the art, including the methods presented herein for coating and curing the polyurethane solution disclosed elsewhere in this application.

Polyurethane solutions according to the present invention remain stable solutions for at least 2 days, preferably at least 3 days and more preferably for at least 4 days. Polyurethane solutions can, in some embodiments, be prepared by mixing a polyurethane, such as a thermoplastic polyurethane (TPU) like LARIPUR 5860 in a trialkyj phosphate solvent, such as triethyl phosphate solvent (i.e., 5 wt, %, 10 wt. %, 14 wt. %, 15 wt. % o 20 wt. %) to form a mixture. The mixture is heated to about 300°C, then shaken and stirred then allowed to sit and cooled. The mixture is subsequently heated again to around 100°C and treated in warm water to form the solution, in some embodiments, the warm water is provided in an ultrasonic bath for about 30 minutes. The solution becomes cloudy/yellowish. The solution remains stable for at least 1 day, preferable at least 2 days and more preferably at least 3 days. In■some embodiments, the solution remains stable for up to 90 days.

It has been surprisingly found, that the solutions described herein are suitable for coating applications onto various substrates. In some embodiments the substrates are metal, wood, plastic, concrete, rubber, paper, glass and textile substrates. They are also used in coating floors and pipelines, in some embodiments, conventional woven or non-woven textile substrates known to those skilled in the art are used. Textile substrates are in this context, to be understood as including woven or nonwoven fabrics formed from fiber materials. The woven or non-woven fabric may be prepared with synthetic resin fibers such as a polyester fiber, a viscose rayon fiber, a polyamide fiber, a polyurethane fiber, an acrylic fiber, a polyolefin fiber and a cellulose fiber, alone or in combination; cotton (e. g. , thread made of cotton); or a combination of the synthetic resin fiber and cotton. It is also contemplated within the scope of the present disclosure that woven fabrics composed of 100% cellulosic fibers, for example woven cotton fabrics may be used as substrates. Cotton fibers are particularly suited for chemically linking the polyurethane to a substrate using the polyurethane solutions of the present invention, Examples of articles which can be produced from woven fabrics suitable for the present invention are weatherproof (water-resistant) clothing, textiles used in transportation and seat covers for automobiles and airplanes, tents, tarpaulins and home textiles such as, for example, paddings, draperies, linens, clothes curtains, seat covers, floor covers and the like. Substrates described herein, while not exhaustive, are exemplary of substrates that are suitable for use in forming the polyurethane coated substrate.

The solutions, coated substrates, and methods provided by the present disclosure are advantageous in that they at least substantially eliminate the environmental and human health concerns of polyurethane solutions comprising a Dimethylformamide solvent. The present disclosure, in providing a polyurethane solution where the polyurethane is dissolved in a trialkyl phosphate solvent advantageously provides the benefit of improved environmental, ecosystemic and human health. The process of forming the coated substrate compositions of the present invention improves the process in that the solutions when coated can be easily volatilized even though the boiling point of the trialkyl phosphate is significantly higher than for

Dimethylformamide; providing time and cost savings. The improved volatilization provides viscosity that allows the coated solution to have better interaction with the substrate such as by penetrating deeper into the substrate. This improves the char stability. Residual trialkyl phosphates in the cured coating also provide improved flarne retardation, as evidenced at least by the improved char stability, compared to cured substrates coated with solutions having

Dimethyiformamide.

EXAMPLES

Example 1 : Preparation of Polyurethane- Trialkyl Phosphate Solutions

A polyurethane solution was prepared by mixing a trialkyl phosphate solvent and a polyurethane resin solute until the solute is dissolved in the solvent. The trialkyl phosphate is trieihyl phosphate. The polyurethane is LARiPUR 5860, formed into clear balls of

approximately 5mm diameter. The concentration of polyurethane is 10 wt. ¾. The LARiPUR 5860 was added to the triethyi phosphate sol vent in a glass containe to form a mix. The mix was then heated up to 100°C then shaken and stirred with magnetic rod. The small balls were peeled off. The mix stood for 3 days at room temperature. The whole balls dissolved to form a small layer in the container. The mix was then heated up to around 100°C again, shaken and treated in warm water in an ultrasonic bath for about 30 min. The mix became a little cloudy/yellowish with all balls in solution. The solution remained stable for 1 day at room temperature.

Example 2: Preparation of a Polyureihane-Trialkyl Phosphate Solutions

A polyurethane solution was prepared by mixing a trialkyl phosphate solvent and a polyurethane resin solute until the solute dissolved in the solvent. The trialkyl phosphate was trieihyl phosphate. The polyurethane resin was LARiPUR 5860, formed into clear balls of approximately 5mm diameter. The concentration of the polyurethane in the riethylphosphate solvent was 15 wt. %. The LARIPUR 5860 was added to the triethyi phosphate solvent in a glass container to form a mix. The mix was then heated up to 100°C then shaken and stirred with magnetic rod. The small balls were peeled off. The mix stood for 3 days at room temperature. The whole balls dissol ved to form a small layer in the container. The mi -was then heated up to around 100°C again, shaken and treated in warm water in an ultrasonic bath for about 30 mill. The mix became a little cloudy/yellowish with all balls in solution. The solution remained stable for 1 day at room temperature,

Example 3: Preparation of a Polyurethane-Trialkyl Phosphate Solution

A poiyurethane solution was prepared by mixing a trialkyl phosphate solvent and a poiyurethane resin solute until the solute dissolved in the solvent. The trialkyl phosphate was triethyl phosphate. The poiyurethane was LARIPUR .5860, formed into clear balls of approximately 5mm diaraeter. The concentration of the poiyurethane in the triethyl phosphate solvent was 20 wt. ¾. The LARIPUR 5860 was added to the triethyl phosphate solvent in a glass container to form a mix. The mix was then heated up to 100°C then shaken and. stirred with magnetic rod. The small balls were peeled off, The mix stood for 3 days at room temperature. The whole balls dissolved to form a small layer in the container. The mix was then heated up to around i00°C again, shaken and treated with warm water in an ultrasonic bath for about 30 min. The mix became a little cloudy/yellowish -with all balls in solution. The solution remained stable for 1 day at room temperature.

Example 4; Preparation of Polyurethane-Trialkyl Phosphate .Solutions

A poiyurethane solution was prepared by mixing a trialkyl phosphate solvent and a poiyurethane resin solute until the solute is dissolved in the solvent. The trialkyl phosphate is triethyl phosphate. The poiyurethane was LARIPUR 5860, formed into clear balls of approximately 3mm diameter. The concentration of the poiyurethane in the triethylphosphate solvent was 15 wt. %. The LARiPUR 5860 was added to the triethyl phosphate solvent in a glass container to form a mix. The mix was then heated up to 80°C and stirred with magnetic rod for about 1 hour. The small balls were peeled off and dissolved to form a stable solution. The solution remained stable for 4 days at room temperature. The solution was nearly clear. Example 5: Preparation of Polyurethane-Trialkyl Phosphate Solutions

A poiyurethane solution was prepared by mixing a trialkyl phosphate solvent and a poiyurethane resin solute until the poiyurethane is dissolved in the solvent. The trialkyl phosphate was diethyl phosphate. The poiyurethane is LARJPUR 5860, a thermoplastic poiyurethane resin formed into clear balls of approximately 5mm diameter. The concentration. of the poiyurethane was 20 wi. %. The LARJPUR 5860 was added to the triethyl phosphate solvent in a glass container to form a mix. The mix was then heated up to 80°C and stirred with magnetic rod for about 1 hour. The small balls were peeled off and dissolved to form a stable solution.. The solution remained stable for 4 days at room temperature. The solution is nearly clear.

Example 6: Comparative Example of the Viscosity of Poiyuretane-Trialkyl Phosphate Solutions and Polyurethane-Dimethy!formamide Solutions

A solution of thermoplastic poiyurethane was made with Dimethyiformaraide (DMP) as the solvent and a solution made with triethyl phosphate (TEP) as the solvents. Varying amounts of thermoplastic poiyurethane were added to solutions with Dimethylforniamide solvent and varying amounts of thermoplastic poiyurethane were added to solutions with TEP as the solvent. Table I below the shows the viscosities, measured in a Brookfield viscomete at 25°C of the various solutions.

Table 1 : Viscosities of DMF and TEP ormu at ons w t vary ng amounts of thermoplastic polyurethane

Example 7: Comparative Example of the %-add-ons for TPU-TEP and TPU-DMF Solutions

Four substrate specimens coated with TPU-DMF solutions were compared to 4 substrate specimens coated with TPU-TEP solutions as reflected in Table 2. The substrate was a cotton fabric. The TPU-DMF solution contained about 20% polyurethane. The TPU-TEP contained 14% polyurethane. In each of the eight substrate compositions two coating steps were used to coat the iabric The final %-add-ons for the TPU-TEP solution coated substrates are higher than that for the TPU-DMF coated substrates. The %-add-on on the fabrics were not uniform for the two groups of compositions and may be attributed to the differences in viscosity. The viscosity difference (1560 cps for TPU-TEP and 3243 for TPU-DMF) between the solutions may be responsible for increased substrate penetration. The solution was coated by back-coating with a knife.

Table 2 : %-add on per coating step

Example 8 : Curing of the coated substrates

After the substrates were double coated, the substrates were cured at 160°C for various times as reflected in Table 3. The curing times, when equal, produced cured substrates with substantially less residual solvent for the TPU-TEP solutions. While both Dimethy!formamide and the trialkyl phosphate solvent could be evaporated, the tria!kyl phosphate solvent was more readily evaporated and reached residual solvent levels of about 45 times less, The TPU-DMF coated substrate had to be cured substantially longer to gain the ppm of the cured TPU-TEP substrate.

Table 3: Residual Solvent after curing Example 9: Fiammability Performance

Both the TPU-TEP and TPU-DMF coated substrates were tested for fiammability performance as depicted in Table 4. While neither coated substrates passed the NFPA-701 test standards, the TPU-TEP coated substrate had a better performance in fiammability (i.e., flame retardation). On average the TPU-DMF had a weight loss of 96,09% while the TPU-TEP had a weight loss of just 90.44%.

Table 4: Fiammability Performance

Example 10: Char Stability

The char stability of uncoated cotton substrates were compared t coated cotton substrate as in example 7 for TPU-DMF and TPU-TEP, as depicted in Figure 1. The TPU-TEP coated cotton substrate demonstrated superior char stability by maintaining it's physical character. The thermal stability of the TPU-TEP coated substrate had was better (Td— 5 wt.% loss - 89°C) compared to TPU-DMF coated substrate (Td-5 -wt.% - 59°C).