Technical field of invention:

The present invention relates to sulphur functionalized polyurea composite of Formula (I) and Formula (II) that provides an insoluble solid support for effective removal of metal residues from solvent streams and other reservoirs. The invention further relates to the process for preparation of same thereof.

Background of the invention:

Metal catalysed reactions have become a cornerstone of modern organic chemistry. Recent advances in catalysis have demonstrated how molecules can be assembled and diversified to suit a variety of applications. Widely used catalysts in organic synthesis involve the use of metals from the platinum group such as palladium, platinum, ruthenium, rhodium, iridium and osmium. Another group referred to as rare earth metals have now ubiquitous use in electronic materials. However, the use of these metals is expensive and dependence on them for industrial and commercial applications is not only increasing costs of the processes but also is potentially contaminating the product. The only way to make such catalytic technologies sustainable is to ensure both low loadings during use and efficient recoveries to enable reuse.

Metal scavenging technology is now widely used to reduce or remove metals from processes such as mining, refining, chemical production. They also find application in pharmaceutical industry in the manufacture of API where their presence may have deleterious effects for use or consumption of the products. Metal scavengers are a class of functionalised metal adsorption media that exhibit ability to bond to or "scavenge" metal compounds dissolved in solution. Metal scavengers known in the art include polymers, functionalized silica polymers and resins. The chemical functionality depends on the scavenger in question, as their affinity to different metals varies although sulphonic acid, vinyl pyridine and mercapto groups are commonly used.

However, the disadvantage in use of the inorganic polymers, modified and functionalized silica as metal scavengers is that the extraction of metals bound to such systems require further chemical treatments which add to the cost and time making the process cumbersome and not economical.

Therefore, there is still a need in the art for simpler, quicker and more cost effective metal scavenger that will not only hold on to the metals effectively but also provide easy recovery through simple combustion processes.

Summary of the invention:

In accordance with the above, it is an object of the present invention to provide sulphur containing polyurea composite as effective metal scavengers and to the process for preparation thereof.

In one aspect, the present invention provides sulphur functionalized polyurea of formula (I) composed of polyisocyanate and amino thiol useful as metal scavengers;

Formula I):

wherein, A is selected from di or poly (un)substituted or substituted aromatic or aliphatic hydrocarbons;

R is selected from independently from (un) substituted or substituted alkyl, (un) substituted or substituted aryl; carboxyl, ester or ether;

B is selected from linear or branched chain comprising of (un) substituted or substituted alkyl, (un) substituted or substituted alkenyl, (un) substituted or substituted alkynyl, (un) substituted or substituted aryl, (un) substituted or substituted heteroaryl, wherein the linear or branched chain may be interspersed with oxygen or nitrogen;

Z is selected from independently from hydrogen, (un) substituted or substituted alkyl or (un) substituted or substituted aryl.

In another aspect, the present invention provides sulphur functionalized polyurea of Formula (II);

polyurea funtionalized and crosslinked with thioureas

Formula II

In another aspect, the present invention provides an efficient and low cost process for preparation of sulphur containing polyurea, wherein, sulphur moiety is covalently linked onto the polyurea framework that allows the construction of insoluble and stable polymeric supports which can be used as aids to remove or scavenge metallic species from solvent streams and other reservoirs.

The polyurea is prepared by interfacial polymerization of a polyisocyanate with an amine molecule containing a thiol group or with thiourea or substituted thioureas, which is accomplished by creating oil- water interphase.

The process includes, dispersing polyisocyanates dissolved in an organic solvent and adding the same at a steady rate into an aqueous media consisting of emulsifiers, surfactants, water-soluble amino thiol to initiate interfacial polymerisation followed by shearing and stirring to obtain solid polyurea covalently linked by sulphur atoms which is filtered, washed and dried. The process is carried at ambient or room temperature and to accelerate the process, optionally a catalyst is added to the aqueous medium or the temperature of the mixture is raised to about 60°C during stirring to obtain the product.

In yet another aspect, the present invention provides the use of sulphur functionalized polyurea of formula (I) and formula (II) for removal of metal residue from solvent streams and other reservoirs by metal scavenging process.

Detailed description of invention:

The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

Polyurea, an elastomer, obtained by the chemical reaction (polyaddition) between a di-isocyanate (NCO-R-NCO) and an amine or polyamine ( H2-R- H2), have excellent adhering properties, has good thermal and chemical stability. Polyurea and functionalized polyurea or polyurea in combination with other polymer are known in the art and are disclosed in US4285720, US4048106, US5225118, US20110077375 and US2013079485 that find application in coatings, as sealants, in casting, in the form of microcapsules for chronic wound dressings etc.

In view of the shortcomings in use of inorganic polymers as metal scavengers and the advantages in the use of polyurea having excellent binding properties, the present inventors have worked around in developing functionalized polyurea that can aid in removal of undesired metal residues more effectively. The functionalized polyurea developed in the instant invention not only hold on to the metals effectively but also provide easy recovery through simple combustion processes, which is not feasible with the use of inorganic polymers. In an embodiment, the present invention provides sulphur functionalized polyurea of Formula (I) composed of polyisocyanate and amino thiol useful as metal scavengers;

Formula (I):

(I)

wherein, A is selected from mono, di or poly (un) substituted or substituted aromatic or aliphatic hydrocarbons;

R is selected independently from (un) substituted or substituted alkyl, (un) substituted or substituted aryl; carboxyl, ester or ether;

B is selected from linear or branched chain comprising of (un) substituted or substituted alkyl, (un) substituted or substituted alkenyl, (un) substituted or substituted alkynyl, (un) substituted or substituted aryl, (un) substituted or substituted heteroaryl, wherein the linear or branched chain may be interspersed with oxygen or nitrogen;

Z is selected independently from hydrogen, (un) substituted or substituted alkyl or (un) substituted or substituted aryl.

In another embodiment, the polyurea is bonded to thiourea or substituted thioureas as depicted in formula (II).

Formula (II):

polyurea funtionalized and crosslinked with thioureas

wherein, A is selected from mono, di or poly (un) substituted or substituted aromatic or aliphatic hydrocarbons; In yet another embodiment, the polyurea is bonded to the thiol having monosubstituted sulphide.

The polyurea is prepared using interfacial polymerization techniques that requires dispersion of the oil or organic phase into a continuous aqueous phase to form an emulsion which is stabilized by a suitable emulsifier or surfactant.

Accordingly, the process for preparation of polymeric composition consisting of sulphur containing polyurea of Formula I and Formula II, wherein, said sulphur moiety is covalently linked onto the polyurea framework comprises dispersing polyisocyanates dissolved in an organic solvent and adding the same at a steady rate into an aqueous media consisting of emulsifier or surfactants, water-soluble amino thiols/ or water soluble thiols or thioureas or substituted thiourea to initiate interfacial polymerisation followed by shearing and stirring to obtain solid polyurea covalently linked by sulphur atoms which is filtered, washed and dried.

The process is carried out at ambient or room temperature and to accelerate the process, optionally a catalyst is added to the aqueous medium or the temperature of the mixture is raised to about 60°C during stirring to obtain the product.

The process can also be carried out without using a two phase mixture comprising of stabilizers and by directly mixing the polyisocyanate with thiourea.

The polyisocyanates used in the process are selected from both aromatic and aliphatic mono, di and poly functional isocyanates. Several such substances include but are not limited to polymethylene polyphenylene isocyanate (PMPPI), 1-chloro- 2,4-phenylene di-isocyanate, m-phenylene di-iodocyanate, p-phenylene di- isocyanate and their hydrogenated forms, 4,4' -methylene bis (phenyl isocyanate), 2,4 and 2,6 tolylene di-isocyanate in varying isomeric mixtures or enriched forms, 3,3'-dimethyl-4,4'biphenylene di-isocyanate, 4,4'methyene bis (2-methyl phenyl isocyanate), 3,3'-dimethoxy-4,4'-biphenylene di-isocyanate, 2,2',5,5'tetramethyl- 4,4'-biphenylenedi-isocyanate, 1,6-hexam ethylene di-isocyanate, isophorone di- isocyanate, tetramethylene di-isocyanate and 1,5-naphthylene di-isocyanate.

The stabilizers are selected from the group of alkyl and aryl polyether glycol ethers and esters, sulfates, sulfonates, phosphates, quaternary ammonium salts, amines, amides, silicones, silicates, glycerides and other condensates of alkyl, aryl, propylene oxide and anionic derivatives thereof such as the corresponding ether sulfates, carboxylates and phosphate esters; condensates of ethylene oxide of varying alkanols differing in carbon chain length and molar proportions; polyvinyl alcohols; alkyl and aryl ammonium salts with colloidal stabilizing properties; a variety of sorbitan esters condensed with a range of molar proportions of ethylene oxide; polyelectrolyte polymers such as lignosulfonates.

The water soluble amine containing sulphur functionality/ or water soluble thiols is selected in its racemic or chiral form from the group of alkyl or aryl sulphide such as methionine, cysteine, thiophenol, 1,2-benzenedithiol, cysteamine, butanethiol, benzylmercaptan, ethanethiol, 1,2-ethanedithiol, Glutathione, Homocysteine, 2- mercaptoethanol, 2-mercaptopyridine, methanethiol, 1,2, propanedithiol, 1,3- propanedithiol, thioglycolic acid, thiosalicylic acid, pyrithione, 2- (methylthio)ethanamine, substituted aminobenzene thiols and the like.

In another embodiment the above mentioned thiol amines can be replaced with thiourea or substituted thiourea. A requisite amount of thiourea or substituted thiourea is added to the aqueous solution depending on the amount of sulphur functionality required to be covalently bonded into the polyurea framework. This can also be done without the need for a two phase solvent system and stabilizers and the isocyanates can be mixed directly with thiourea or substituted thiourea in a suitable organic solvent or neat along with any trialkyl amine bases. In some examples this is done without the use of any organic amine bases. The solvent used in the process is selected from polar or non-polar, protic or aprotic solvents such as alcohols, ethers, halogenated hydrocarbons, ketones, acetonitrile, hydrocarbons and the like.

In the process, suitable polyisocyanate dissolved in an organic solvent is dispersed into the aqueous layer consisting of emulsifiers, stabilizers and water-soluble amino thiol /or thiourea. After dispersing the organic solution containing the suitable polyisocyanate in the aqueous medium, interfacial polymerization is initiated. Under these conditions, isocyanate functionality at the oil-water interface readily reacts with the more nucleophilic amine functionality to instantly form a urea bond which holds the framework carrying a sulphur atom at one end. Depending on the loading required of such sulphur atoms, the ratio of the amino thiol or the thiourea added to the aqueous layer is varied proportionately. After and during initial reaction at the interface with the molecules carrying both sulphur and amine functional groups, the remaining isocyanate groups are hydrolyzed to free amines via their reaction with any water molecule as depicted in Scheme 1 to subsequently form urea and cross link to form a polyurea matrix. The process is carried out for a few hours to a day depending on the conditions being used. The resulting solid polyurea is separated by a simple filtration process and washed with water and organic solvents to remove any of the emulsifiers, surfactants or organic solvent that may be trapped within the polymeric matrix and dried in air, under vacuum or an oven at temperatures up to 60°C.

The polyurea matrix is also permeable to the extent that would permit the flow of a continuous phase, enable interaction with the urea, aromatic and sulphur functional groups that would bind and hold any metal species that may be present. Depending on the amount of sulphur required to be bound to the polyurea support one could alter and vary the concentration of the amino thiol or the thiourea or substituted thiourea in the aqueous. The ratio can be adjusted accordingly with the weight of the sulphide or the thiourea with respect to the di and/or polyisocyanate being used to achieve the desirable level of sulfur loading. Polyurea is prepared by the condensation of at least one polyisocyanate such as polyphenyleneisocyanate (PMPPI) with or without tolylene diisocyanate (TDI). These isocyanates are cross linked by amines to form the polymeric chains by interfacial polymerization. The particle size of the oil droplets in the emulsion is dependent on the shearing speed and size of the impeller blade use during dispersion and the type and extent of the emulsifiers or surfactants being used. The process is illustrated in Scheme 1 below:

Scheme 1:

Catalyst for accelerating the process is selected from tertiary amine such as trialkyl amine viz. triethylamine; dimethyl aminopyridine (DMAP), 1,4- diazabicyclo[2.2.2]octane (DABCO) and the like. The proportion of the catalyst can be adjusted with respect to the quantity of polyisocyanate being dispersed depending on how the reaction needs to be accelerated.

When tertiary amine is used as catalyst for formation of polyurea framework, nucleophilic attack on the carbon atom of the isocyanate results in a highly reactive charged intermediate as depicted in Scheme 2 which facilitates the attack by another nucleophilic species such as primary or secondary amine to obtain urea or alternatively allow a water molecule to react giving carbamic acid and subsequent amine which proceeds to finally form urea. In the event of such an amine not having an isocyanate group within its vicinity or reach to permit the urea bond forming reaction, it will remain within the core or shell as an amine. In some cases, such free amine groups are capped at a later stage with suitable groups known in the art. In the current application cross linking could be achieved directly by reaction with the thiourea with isocyanates groups in the vicinity along the oil-water interface and allow for the covalent bond formation along with growth of the polymer framework

(Scheme 3).

Scheme 2:

The interfacial polymerization results in fine particles that are cross linked and as a consequence is insoluble in all common organic and aqueous solvents.

Scheme 3:

A = oil droplet containing isocyanates dissolved in an organic solvent and dispersed in water that contain thiourea

The process of present invention is depicted below in Scheme 4 and Scheme 5

below:

Scheme 4:

wherein, A is selected from mono, di or poly (un) substituted or substituted aromatic or aliphatic hydrocarbons; B is any structure that contains an amine along with a thiol or sulphide. R is selected independently from (un) substituted or substituted alkyl, (un) substituted or substituted aryl; carboxyl, ester or ether;

B is selected from linear or branched chain comprising of (un) substituted or substituted alkyl, (un) substituted or substituted alkenyl, (un) substituted or substituted alkynyl, (un) substituted or substituted aryl, (un) substituted or substituted heteroaryl, wherein the linear or branched chain may be interspersed with oxygen or nitrogen;

Z is selected independently from hydrogen, (un) substituted or substituted alkyl or (un) substituted or substituted aryl.

Scheme 5:

wherein, A is selected from mono, di or poly (un) substituted or substituted aromatic or aliphatic hydrocarbons.

The formation of polyurea with thiourea units in-between can be made by using the following methods.

(i) Addition of aqueous solution of aminothiol and/or a thiourea or substituted thiourea and surfactants or stabilizer to the solution of PMPPI with or without tolylene diisocyanate (TDI in any organic solvent.

(ii) Addition of neat PPMPI to the solution of aminothiol and/or a thiourea or substituted thiourea in aromatic organic bases such as pyridine or substitutes pyridines such as 2-chloropyridine. Addition of neat PPMPI to the solution of aminothiol and/or a thiourea or substituted thiourea in tertiary organic bases such as trialkyl amine bases.

Addition of aminothiol and/or a thiourea or substituted thiourea portion wise to the solution of PMPPI with or without tolylene diisocyanate (TDI in organic solvent.

In another embodiment, the present invention discloses an efficient, low cost process to covalently link amines having thiol moiety onto the polyurea framework that allows the construction of insoluble and stable polymeric supports which can be used as aids to remove or scavenge metallic species through strong chelation.

In another embodiment, the polymer matrix would comprise of both urea and carbamate type linkages. This is achieved when a suitable di- or polyisocyanate is subjected to interfacial polymerization in the presence of hydroxy thiols (Figure II). Here, two path ways occur wherein at the oil water interface, the isocyanate group is hydrolysed to an amine via carbamic acid and the resulting amine reacts with another isocyanate in its vicinity to form a urea bond and this process repeats to allow further cross linking. The other process is wherein the hydroxyl thiol in the water layer reacts at the interface with an isocyanate group to give a carbamate. By adjusting the stoichiometry of the di and/or polyisocyanate with that of the hydroxy thiol, one can allow for efficient crosslinking to obtain an insoluble polyurea matrix that has sulfur functionality attached as carbamates.

The sulphur atom react with the isocyanate functionality as depicted in Scheme 4 which is capable of metal chelation and binding.

The sulphur functionalized polyurea of formula (I) where the urea bonds are formed by reaction of a polyisocyanate with an amine molecule containing a thiol functionality.

In yet another embodiment, the polymer is the product of self -condensation and/or cross linking of urea-formaldehyde resins or prepolymers with amino thiols.

In another embodiment, the polymeric composition comprising sulphur functionalized polyurea of Formula (I) and Formula (II) is used to remove metals by metal scavenging process. One process involves dissolving material contaminated with metal residue in a suitable solvent to which is added sulphur functionalized polyurea of the instant invention and stirred for a suitable time to allow for the metal scavenging process. This process can is carried out at an elevated temperature to accelerate the process. After stirring for suitable time, the polyurea is collected using any suitable filter aid. The extent of metal removed is quantified using analytical methods for measuring the content of metal in parts-per- million (ppm) or parts-per-billion (ppb).

In another application, the sulphur functionalized polyurea is packed in cartridges of varying length and width and used as filter aids through which a mobile phase carrying the metal residues is allowed to pass. Elution through the chelating mobile phase ensures interaction with the sulphur functionality and binding of the metal within the polymeric matrices.

In another embodiment, the present invention discloses a method to remove undesired metal residues from solvent streams and other reservoirs comprising reacting the metal residue with use of polymeric composition comprising sulphur functionalized polyurea of Formula (I) and Formula (II) by the process for scavenging mentioned above.

It will be appreciated that the scope of the polyurea scavenger would not be limited to any particular metal or the form and composition in which it may exist as a complex or salt, its source, stream or reservoir but can be used in general when metal contamination needs to be reduced or eliminated.

In yet another embodiment, the process of the present invention can be adopted for attaching a variety of amines with sulphur moiety or thioureas onto the polyurea framework. This allows the construction of insoluble and stable polymeric supports that can be used as aids to remove or scavenge metallic species through strong chelation with the sulphur atoms which is also further assisted by urea and aromatic functionality as is known in the art to coordinate with metals through electrostatic interactions. The process for preparation of sulphur functionalized polyurea is efficient as compared to the processes known in the art where the framework comprises primarily of a hydrocarbon structure such as polystyrene or polypropylene. Another advantage is to lend itself to combustion unlike inorganic polymers where modified and functionalized silica form the core of the insoluble matrix. Extracting the metals bound to such silica based systems require further chemical treatments as combustion techniques would not be applicable. The polymer composition of the present invention, not only holds on to the metals effectively but also provides easy recovery through simple combustion processes where the support is burnt under oxygen leaving only the metal residues behind in a crucible. The invention is illustrated by examples but is not limited to the use for any specific reaction as one well versed in the art would be able to extend this method to any sulphur containing molecule that has a functional group such as an amine, thiourea, thiol or alcohol that is capable of reaction with an isocyanate to form a covalent bond.

Material:

Sodium lignin sulfonate, sodium dodecyl sulphate, Poly vinyl alcohol and Poly (ethylene glycol-ran-propylene-glycol) mono butyl ether were bought respectively from TCI chemicals, Loba chemicals and Sigma-Aldrich.

Example 1: Preparation of polyurea with PMPPI and methionine (D, L and racemic forms)

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane. The solution was added at a steady rate to an aqueous solution comprising of water (100 ml), sodium lignin sulfonate (0.8 g), poly vinyl alcohol (0.4 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.2 g) and methionine (5 g) while shearing the mixture using impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 30 hours during which time a solid separated out and was filtered, washed with water, acetone and dichloromethane and dried.

Example 2:

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane. This solution was added at a steady rate to an aqueous solution comprising of water (100 ml), sodium lignin sulfonate (0.8 g), poly vinyl alcohol (0.4 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.2 g), triethylamine (1 g) and methionine (5 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 3

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane. This solution was added at a steady rate to an aqueous solution comprising of water (100 ml), sodium lignin sulfonate (0.8 g), poly vinyl alcohol (0.4 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.2 g) and methionine (5 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred at 50° C for 12 hours during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 4: Preparation of polyurea with PMPPI and cysteine (chiral and racemic form)

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane. This solution was added at a steady rate to an aqueous solution comprising of water (100 ml), sodium lignin sulfonate (0.8 g), poly vinyl alcohol (0.4 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.2 g) triethyl amine (1 g) and cysteine (5 g) while shearing the mixture using impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 24 hours during which time a solid separated out. The solid was filtered, washed with water, acetone and dichloromethane and dried.

Example 5: Preparation of polyurea with TDI and thiourea

Toluene diisocyanate (TDI) (10 g) was dissolved in 15 ml of dichloroethane. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g) and thiourea (4.6 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 6:

Toluene diisocyanate (TDI) (10 g) was dissolved in 15 ml of dichloroethane. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g) and thiourea (10 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 7: Preparation of polyurea with PMPPI and thiourea

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g) and thiourea (10 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 8:

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane/ ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g), pyridine (0.47 g) and thiourea (4.6 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried. Example 9:

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g), DABCO (l,4-diazabicyclo[2.2.2]octane; 0.67 g) and thiourea (4.6 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 10:

Polymethylene polyphenylene isocyanate (PMPPI) (10 g) was dissolved in 15 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (0.1 g), DMAP (4-dimethyl amino pyridine ;0.73 g) and thiourea (4.6 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 11:

Polymethylene polyphenylene isocyanate (PMPPI) (500 g) was dissolved in 750 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (2000 ml), sodium lignin sulfonate (16 g), poly vinyl alcohol (8 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (4 g), DMAP (36.9 g) and thiourea (230 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried. Example 12:

Polymethylene polyphenylene isocyanate (PMPPI) (100 g) was dissolved in 150 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (500 ml), sodium lignin sulfonate (4 g), poly vinyl alcohol (2 g), poly (ethylene glycol-ran-propylene-glycol) mono butyl ether (1 g), DMAP (7.38 g) and thiourea (46 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at ambient temperature during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 13: Preparation of polyurea with a mixture of TDI & PMPPI and thiourea

Toluene diisocyanate (TDI) (5 g) and Polymethylene polyphenylene isocyanate (PMPPI) (5 g) was dissolved in 15 ml of dichloroethane/ethyl acetate. This solution was added at a steady rate to an aqueous solution comprising of water (50 ml), sodium lignin sulfonate (0.4 g), poly vinyl alcohol (0.2 g), poly (ethylene glycol- ran-propylene-glycol) mono butyl ether (0.1 g) and thiourea (4.6 g) while shearing the mixture using an impeller blade fitted to an overhead stirrer for a period of 3 hours. The mixture was stirred for 16 hours at 50°C during which time a solid separated out, filtered, washed with water, acetone and dichloromethane and dried.

Example 14: Preparation of polyurea with PMPPI and thiourea without two phase system

Thiourea (23 g) was added to 250 ml of N-methyl -2-pyrrolidine ( MP) and stirred for 5 minutes with impeller blade fitted to an overhead stirrer. PMPPI (50 g) added to the above solution in steady rate at 5°C for about 30 minutes. The resulting mixture was stirred for additional 12 hours at ambient temperature during which time a solid separated out, filtered, washed with dichloromethane followed with water. Example 15:

Thiourea (4.6 g) was added to 50 ml of pyridine and stirred for 5 minutes with impeller blade fitted to an overhead stirrer. PMPPI (10 g) added to the above solution in steady rate at 5°C for about 10 minutes. The resulting mixture was stirred for additional 12 hours at ambient temperature during which time a solid separated out, filtered, washed with dichloromethane followed with water.

Example 16:

PMPPI (10 g) dissolved in 15 ml of ethylene dichloride (EDC) and stirred for 5 minutes with impeller blade fitted to an overhead stirrer. Thiourea (4.6 g) added to the above solution portion wise over 5 minutes. The resulting mixture was stirred for additional 12 hours at ambient temperature during which time a solid separated out, filtered, washed with dichloromethane followed with water.

Example 17: Preparation of polyurea with Wannate and thiourea

Wannate (1085g) was dissolved in 2500ml ethylene dichloride. This solution was added drop wise to an aqueous solution comprising of water (3550 ml), sodium dodecyl sulfate (25 g, 0.086 moles) and thiourea(500 g, 6.56 moles). The mixture was stirred for 24 hours at 45°C. the mixture was diluted with methanol (2500ml) and the obtained solid was collected by filtration. Yield: 1.55 kg of the off white solid was isolated.