Title of Invention

A PROCESS FOR SYNTHESIS OF POLYMER LATEX NANOPARTICLES BY MONOMER ATOMIZATION IN MICROEMULSION

Abstract

This invention relates to a process for synthesis of polymer Latex nanoparticles by monomer atomization in rnicroemulsion comprising, Dissolving the surfactant and initiator in deionized water, Stirring it to form micelles, Spraying the required monomer at a constant rate on the surface of the water solution with constant stirring, Controlling the temperature condition throughout the reaction, Controlling input flow rates and discharge rates for providing specific residence time, Continuing the reaction for specific time at a constant temperature, Cooling it to room temperature (for thermal initiator system) to form transparent or translucent forms of polymer latex.

Full Text

FORM 2 THE PATENTS ACT, 1970 COMPLETE SPECIFICATION SECTION 10 TITLE "A Process for Synthesis of Polymer Latex Nanoparticles by Monomer Atomization in Microemulsion." APPLICANT North Maharashtra University Umavi Nagar, Jalgaon-425001. The following specification particularly describes the invention and the manner in which it is to be performed. -2- "A Process for Synthesis of Polymer Latex Nanoparticles by Monomer Atomization in Microemulsion." Field of Invention This invention relates to a process for synthesis of polymer latex nanoparticles with controlled particle size between 10 to 100 nm by monomer atomization in microemulsion. Background of Invention In recent years a huge amount of polymer latexes such as polyacrylamide, butadiene-styrene copolymers, poly (vinyl chloride), poly (vinyl acetate), acrylate ester copolymers and a wide range of derivatives are produced. These latexes are widely used in the field of paints, coatings, binders in textile & papers, additives, adhesives, pharmaceuticals, modifiers and biomedical sectors, and even as size calibration standards for fundamental research. The most popular technique for production of latex polymer is microemulsion. Microemulsion polymerization is a unique process producing thermodynamically stable and transparent or translucent dispersion containing water, oil, initiator and surfactant with or without -3- 3-surfactant. This process yields stable polymer latex particles with ^article size in the range of 10 to 100 nm. The benefits of this process are 1. large internal interfacial area, 2. thermodynamic stability, 3. optical transparency, 4. small domain length scales and 5. variation of structures, resulting in unique microenvironments. Microemulsion may be in the form of water-in-oil or oil-in-water. When the water phase can be dispersed in a continuous oil phase, such system is called water-in-oil (w/o) microemulsion; when an oil is dispersed in a continuous aqueous phase, the system is referred as an oil-in-water (o/w) microemulsion. The formed type of microemulsion depends on the chemical nature of the surfactant and the ratio between the oil and aqueous phases. A lot of research is being carried out in the field of microemulsion techniques. US Patent No. 7,122,608 describes a VDF polymerization process, optionally modified with small amounts of one or more fluoro-containing comonomers, carried out in the presence of a microemulsion comprising a (per) fluoropolyether having neutral end groups, average molecular weight between 400 and 3000, and a surfactant based on perfluoropolyethers with carboxylic end groups. Similarly, US Patent 7,098,280 describes a controlled polymerization process, in which the aqueous polymerization medium comprises at least one monomer, a -4- polymerization control agent, and an emulsifier, prepared in-situ within the aqueous polymerization medium. The polymerization of the said monomer is initiated within the aqueous polymerization medium. US Patent 6,469,094, discloses a polymerization process for latex preparation that includes heating of a mixture of at least one free radical polymerizable monomer compound, a free radical initiator compound and a stable free radical compound to form a latomer mixture with about 1 to 8 percent conversion of the monomer compound to an oligomeric compound, dispersing the resulting latomer mixture in water with high shear to form a miniemulsion; and a second heating of the miniemulsion, wherein there results a high stability polymer particle latex. US Patent 5,908,907 describes an aqueous emulsion of (co) polymer made from monomer containing isocyanate group and olefinic double bond. In prior arts polymer latex particles were synthesized either by emulsion or conventional microemulsion processes (such as seeded microemulsion, microemulsion in winsor I- like systems, microemulsion polymerization with drop wise addition of monomer and microemulsion polymerization via hollow-fiber feeding). All these processes contain higher surfactant and consume long reaction time to produce polymer nanoparticles. It is also difficult to get stable, highly dispersed polymer -5-latex with uniform particle size distribution. So it is necessary to develop such a process which will provide higher stability with uniform particle size distribution in spite of low surfactant concentration and consume less reaction time. In spite of the wide use, microemulsion polymerization holds many drawbacks. This technique usually requires very large amount of surfactant, and it is used rarely for controlled polymerization because the amount of surfactant often equal or exceeds to the amount of monomer present. Also, there is the problem of slow initiation or long reaction time. These emulsion polymerization processes produce polymers with high weight average molecular weights and low number average molecular weights resulting in broad polydispersities or low molecular weight and low conversion. Further, these processes are prone to generating excessive quantities of heat since the polymerization reaction is exothermic. As the viscosity of the reaction medium increases, dissipation of heat becomes more difficult. Compare to the prior art, there is need for developing a technique for polymerization of latex, wherein, the method could produce stable emulsions without hydrophobes or special equipment, utilize -6-conventional surfactants, effect rapid initiation and propagation and achieve complete conversion within a reasonable period of time. Thus, there remains a need for economical polymerization process for the preparation of polymeric latex having desirable physical properties, for example, hardness, low gel content, clarity, high gloss durability while avoiding the problems of gel formation, heat generation, multi-stage reaction systems, purification. Time consuming drop wise addition of monomer in semibatch microemulsion process is shorted out by this newly developed spray process with less time to get highly dispersed polymer latex having particle size in the range of 10-100 nm and also higher percentage of surfactant reduced by increasing wt% of initiator with respect to monomer. The present invention is therefore an attempt to remove the problems existing in the prior art and to develop an efficient process for production of latex. In the present invention, the monomer is sprayed in the form of mist or stream on the flat water surface, where the maximum concentration of micelles [above the* Critical Micelle Concentration' (CMC)] are present under controlled temperature. These atomized mist or stream gets reacted within micelles, and hence the growth of the polymer nanoparticles is initiated at a number of sites in semi batch mode. In this -7-way, coagulation of two or more polymer nanoparticles is inhibited and product is retained in nano form. Objects of Invention The main object of this invention is to develop a rapid and stable process for production of highly dispersed polymer latex nanoparticles having sizes smaller than 100 nm. Other object is to develop a process wherein rigid control of particle size, without agglomeration, by uniform particles size distribution of polymer nanoparticles with increasing initiator percentage in the latex is achieved. Another object is to develop a process using less amount of surfactant and consuming less time and electricity. Yet another object is to develop a process for the preparation of polymeric particulate material with improved reliability and yield. Further object is also to develop a process for the preparation of polymeric particulate material wherein conversion of monomers to polymers that provide high stable lattices and have improved control over the resulting latex particle size and latex particle size distribution properties is obtained. -8-Other object is also to develop a simple, fast and improved process for the preparation of highly dispersed polymer latex particles through reaction in atomized mode in micelles. Statement of Invention This invention relates to a process for synthesis of polymer Latex nanoparticles by monomer atomization in microemulsion comprising, Dissolving the surfactant and initiator in deionized water, Stirring it to form micelles, Spraying the required monomer at a constant rate on the surface of the water solution with constant stirring, Controlling the temperature condition throughout the reaction, Controlling input flow rates and discharge rates for providing specific residence time, Continuing the reaction for specific time at a constant temperature, Cooling it to room temperature (for thermal initiator system) to form transparent or translucent forms of polymer latex. Brief description of accompanying drawing Fig. 1 relates to a design of Reactor particularly to a Reaction Vessel which consists of agitator (18), atomizer (1), energy regulator (4), pressure gauge (12), vent valve (10), PID type of controller (7), distillation column (8), baffles (14), jacket (15), thermocouple (19), safety attachment-rupture disc (11), clamp (6), butterfly valve (20) and sight -9- glass (13) for visual observation of progress of reaction for intimate contacting of monomer and surfactant Fig. 2 relates to TEM analysis of nano PS showing the actual size of nanoparticles of PS with the particle size varying between 10 to 100 nm. Detailed description of the invention This invention is generally directed to develop a rapid and stable process for production of dispersed polymer latex nanoparticles having sizes smaller then 100 nm with rigid control of particle size, without agglomeration, and uniform particle size distribution of the polymer nanoparticles with increasing initiator percentage in the latex, using lesser amount of surfactant and consuming less time. Methods to produce and synthesize such latex in high volume, with a low-cost and reproducible quality are also outlined. To meet the above objects and to overcome the problems existing in the prior art, the present invention provides a simple, economic and rapid process for production of dispersed polymer latex nanoparticles having sizes smaller then 100 nm with rigid control of particle size, without agglomeration, by uniform particle size distribution of the polymer nanoparticles with increasing initiator percentage in the latex, using -10- lesser amount of surfactant and consuming less time as described herein, According to figure 1, monomer is sprayed through the nozzles of atomizers by reciprocating compressor (1) at controlled pressure and flow rate. A stream of monomer is sprayed over entire surface of the clear solution (2) where a unique environment of the microemulsion proceeds. An agitator (18) rotating at a speed between 200-250 rpm to disperse the monomer stream in the entire water solution in presence of surfactant micelle. The dimensions of latex reactor are as given in Fig. 1. The temperature of reaction mixture was regulated through PID type of controller (7) electrical heating of coils maintained in jacket (15) of reactor through set point comparison with that indicated by thermocouple (19). The baffles (14) are maintained at the top of reactor to bounce back the monomer stream from outgoing air. The exhaust is then lead through distillation column (8) for recovery of monomer. A butterfly valve (20) located at dish bottom of the reactor discharges the reaction mixture. The process is monitored through control of orifice size, reciprocating compressor pressure, speed, reaction temperature, distance between atomizer and reaction zone, etc. -11- EXAMPLE 1 In a flat one-litre stainless steel reactor 8 gm of sodium dodecyl sulfate (SDS) surfactant with 1 gm of n-pentanol cosurfactant were dissolved in 180 gm of deionized water. The mixture was stirred with magnetic stirrer at about 200 rpm with constant temperature at 75°C resulting in a clear solution. Two gm of ammonium persulfate (APS) thermal initiator was dissolved in 20 gm water and added in the reactor for formation of free radicals and the reactor was sealed. 100 gm of stabilizer free styrene monomer was sprayed by using atomizer in the form of fine mist into the reactor at a constant rate of 0.2 gm per second. The temperature was maintained at 75°C through out the reaction. After the complete addition of monomer, the reaction was continued for one hr and polymerization reaction was stopped by cooling the mixture to room temperature. A transparent or translucent dispersion was formed to indicate the microemulsion. The synthesized polystyrene latex nanoparticles characterized by TEM (Transmission Electron Microscopy), indicated the particle size varying from 10 to 100 nm. Polymer solid content was about 42-45% by weight. EXAMPLE 2 In a flat one litre stainless steel reactor 4 gm of sodium dodecyl sulfate (SDS) surfactant with 0.5 gm of n-pentanol cosurfactant were dissolved -12-in 130 gm of deionized water. The mixture was stirred with magnetic stirrer at about 200 rpm with constant temperature at 35°C resulting in a clear solution. 0.9 gm of ascorbic acid in combination with 0.6 gm of hydrogen peroxide redox initiator was dissolved in 20 gm water and added in the reactor for formation of free radicals and the reactor was sealed. 50 gm of stabilizer free methyl methacrylate (MMA) monomer was sprayed by using atomizer in the form of fine mist into the reactor at a constant rate of 0.12 gm per second. The temperature was maintained at 35°C through out the reaction. After the complete addition of monomer, the reaction was continued for one hr to complete polymerization reaction. A transparent or translucent dispersion was formed to indicate the microemulsion. The synthesized polystyrene latex nanoparticles characterized by TEM (Transmission Electron Microscopy), indicated the particle size varying from 10 to 100 nm. Polymer solid content was about 30-32% by weight. EXAMPLE 3-8 The different variables governing degree of atomization and intimacy of reactants contact were established for all these examples. The illustration of effects of these variables have been provided for synthesis of poly (methyl methacrylate) latex particles in example 3 to 8 -13- EXAMPLE 3 The nozzle orifice diameter was varied from 0.03 to 0.07 cm. It was seen that, smaller the orifice, better was the degree of atomization. However, smaller orifice must have good spreading pattern for permitting larger distribution of atomized droplets over reaction surface. EXAMPLE 4 The rate of atomization was increased from 0.12 gram per second to 0.4 gram per second. Increase in rate of atomization increased reaction speed, thus enhancing formation of larger particles which broader the particle size distribution (PSD) of polymer nanoparticles. Decrease in addition rate causing insufficient supply of monomer in the reaction mixture that reduces the free radical concentration either by combination, termination or disproportionation. EXAMPLE 5 The distance between reaction zone and atomizer orifice was varied from 15 cm to 30 cm by changing the length of spray gun from the water surface layer. Larger the distance, better the distribution of atomized droplets over reaction zone permitting minimum bounce back loss. At the same time with increase in distance some atomized droplets missed the reaction surface, thus it increases in overspray and fallout losses. -14-EXAMPLE 6 Polymerization reaction may be initiated by two ways, either by thermal initiator or by redox initiator. Redox system was more advantageous because of lower decomposition temperature (at room temperature) and temperature control was easier. The more important thing was that redox initiation system can generate more radicals than thermal initiation system, resulting smaller particle size. EXAMPLE 7 The monomer to water ratio was increased from 1:2 to 1:7 at fixed percentage of surfactant. There was a decrease in micelle concentration which increased the particle size of the polymer nanoparticles in the polymer latex. EXAMPLE 8 The weight percentage of initiator was increased from 0.5%wt to 4%wt of monomer. There was an increase in the free radical concentration at the reaction zone, thereby enhancing formation of short polymer, chain resulting in decreased particle size of the polymer nanoparticles in the polymer latex. -15-The present invention is advantageously provides several area of applications, such as, paint, drug delivery, textiles, surface modification in rubbers, elastomers and thermoplastics. Vinyl aromatic (e. g. polystyrene) nanoparticles have been prepared for uses as a reference standard in the calibration of various instruments, in medical research and in medical diagnostic tests. Particularly, the present invention relates to a simple, fast and improved process for the preparation of highly dispersed polymer latex particles through reaction in atomized mode in micelles. In one form of the invention, the surfactant may be selected from the group of Dodecyl benzene sulfonate, Sodium dodecyl sulfate, In one form of the invention, the initiator may be selected from the group of ammonium persulfate (APS), potassium persulfate (KPS), ascorbic acid in combination with hydrogen peroxide. In one more form of the invention, the cosurfactant may be selected from the group of 1-Butanol, n-Pentanol, n-Hexanol In one more form of the invention, the monomers may be selected from the group of styrene, methyl methacrylate, vinyl acetate, ethyl methacrylate, butylacrylate, acrylonitrile and mixture of Styrene-methyl methacrylate, Styrene-Butyl Acrylate, Styrene-Arylonitrile etc. -16-In one more form of the present invention, the process for the preparation of highly dispersed polymer latex nanoparticles may include design of reactors for intimate contact of monomer and initiator within the micelles. In another form of the present invention, the process for the preparation of highly dispersed nanoparticles through establishment of these variables governing the particle size at nano scale. In yet another form of the present invention, the process for the preparation of highly dispersed polymer latex particles may include methods for synthesis of nano polymer particles of polystyrene, poly (methyl methacrylate), poly (vinyl acetate), poly (ethyl methacrylate), poly (butylacrylate), Poly (acrylonitrile). In one more form of the present invention, the process for the preparation of highly dispersed nanoparticles may include methods for synthesis of copolymer latex particles of Styrene- Methyl methacrylate, Styrene-Butyl Acrylate, and Styrene- Arylonitrile etc. Particularly, the present invention relates to a simple, rapid and stable process for production of highly dispersed polymer latex nanoparticles having sizes smaller then 100 nm with rigid control of particle size, without agglomeration, by uniform particle size distribution of the -17-polymer nanoparticles with increasing initiator percentage in the latex, using lesser amount of surfactant and consuming less time as well as methods to produce and synthesize such latex in high volume, with a low-cost and reproducible quality. -18- we Claim 1. A process for synthesis of polymer latex nanoparticles by monomer atomization in microemulsion comprising: - a. Dissolving the surfactant and initiator in deionized water b. Stirring it to form micelles c. Spraying the required monomer at a constant rate on the surface of the water solution with constant stirring d. Controlling the temperature condition throughout the reaction e. Controlling input flow rates and discharge rates for providing specific residence time f. Continuing the reaction for specific time at a constant temperature g. Cooling it to room temperature (for thermal initiator system) to form transparent or translucent forms of polymer latex. 2. A process for synthesis of polymer Latex nanoparticles as claimed in claim 1, wherein surfactant is selected from the group consisting of Dodecyl benzene sulfonate, Sodium dodecyl sulfate. 3. A process for synthesis of polymer Latex nanoparticles as claimed in claim 1, wherein initiator is selected from the group consisting of ammonium persulfate (APS), potassium persulfate (KPS), and ascorbic acid in combination with hydrogen peroxide. -19- 4. A process for synthesis of polymer Latex nanopartides as claimed in claim 1, wherein the cosurfactant is selected from the group consisting of 1-Butanol, n-Pentanol, n-He^anol etc. 5. A process for synthesis of polymer Latex rianoparticles as claimed in claim 1, wherein the monomer is selected from the group consisting of styrene, methyl methacrylate, vinyl acetate, ethyl methacrylate, butylacrylate, acrylonitrile #nd mixture of Styrene-methyl methacrylate, Styrene-Butyl Acrylate, Styrene-Arylonitrile etc. 6. A process for synthesis oi polymer Latex nanopartides as claimed in claim 1, wherein the reaction temperature is from about 30° to about 75°C. 7. A process for synthesis of polymer katex nanopartides by monomer atomization in microemulsion as described and illustrated herein.

Documents:

566-MUM-2009-ABSTRACT(23-7-2012).pdf

566-mum-2009-abstract.doc

566-mum-2009-abstract.pdf

566-MUM-2009-CLAIMS(AMENDED)-(23-7-2012).pdf

566-mum-2009-claims.doc

566-mum-2009-claims.pdf

566-mum-2009-correspondance.pdf

566-MUM-2009-CORRESPONDENCE(06-07-2009).pdf

566-MUM-2009-CORRESPONDENCE(16-3-2009).pdf

566-MUM-2009-CORRESPONDENCE(8-10-2009).pdf

566-mum-2009-description (complete).doc

566-mum-2009-description (complete).pdf

566-mum-2009-drawing.pdf

566-MUM-2009-FORM 1(06-07-2009).pdf

566-MUM-2009-FORM 1(16-3-2009).pdf

566-mum-2009-form 1.pdf

566-MUM-2009-FORM 18 (8-10-2009).pdf

566-MUM-2009-FORM 18(9-10-2009).pdf

566-mum-2009-form 2 (title page).pdf

566-mum-2009-form 2.doc

566-mum-2009-form 2.pdf

566-MUM-2009-FORM 26(23-7-2012).pdf

566-MUM-2009-FORM 3(23-7-2012).pdf

566-MUM-2009-POWER OF ATTORNEY(06-07-2009).pdf

566-MUM-2009-RECEIPT(8-10-2009).pdf

566-MUM-2009-REPLY TO EXAMINATION REPORT(23-7-2012).pdf

566-MUM-2009-SPECIFICATION(AMENDED)-(23-7-2012).pdf

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