Description:FIELD OF THE INVENTION
[0001] The present disclosure relates to a surfactant free fluorinated polyacrylate emulsion. The present disclosure also relates to a method of preparation of surfactant free fluorinated polyacrylate emulsion.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Aqueous based emulsions are preferred as they don’t lead to generation of volatile organic content (VOC) in the environment. Emulsion polymerizations of fluoroacrylate monomersin water are typically difficult as fluorous segments are very hydrophobic and high density leads to poor transport of these monomers to the micelle through water phase.
[0004] The conventional processes of manufacture of aqueous phase fluoropolymers (Perfluoroacrylate copolymers) emulsions uses fluorocarbon surfactants such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). However, since 2015, PFOA and PFOS have been forbidden in many countries due to their long-term environmental impact. Therefore, efforts were made to replace fluorocarbon surfactants of PFOA- and PFOS with various organic based surfactants such as Triton X-405, sodium dodecyl sulfate.
[0005] However, still the conventional emulsion polymerization exhibited the following limitations such as the large usage of small molecular surfactants that pollute the environment and limited materials properties of finished product such as freeze stability, mechanical stability, wet and dry rubbing resistance, and corrosion issues.
[0006] In order to avoid these disadvantages, the present disclosure employed alkali soluble resin (ASR) as emulsifier to prepare fluoro-acrylate copolymers by aqueous phase emulsion polymerization.

OBJECTS OF THE INVENTION
[0007] An objective of the present invention is to provide a surfactant-free fluorinated aqueous polyacrylate emulsion.
[0008] Another objective of the present invention is to provide a method of preparation of surfactant-free aqueous fluorinated polyacrylate emulsion.
[0009] Another objective of the present invention is to provide a method for regulating viscosity and hydrophobicity of surfactant-free aqueous fluorinated polyacrylate emulsion for coating application.

BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 showed ASR based surfactant free fluorinated polyacrylate emulsion.
[0011] Figure 2 showed freeze thaw stability of the synthesized surfactant free fluorous based core-shell emulsion copolymer.
[0012] Figure 3 showed water contact angle (WCA) of the synthesized fluorous based emulsion copolymer with core-shell structure (a) EA-1, (a) EF-6, (b) EF-8, and (c) EF-7.
[0013] Figure 4 showed HRTEM images showing core-shell structure of the synthesized surfactant free fluorous based emulsion copolymer.

SUMMARY OF THE INVENTION
[0014] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0015] The present disclosure discloses a surfactant-free aqueous fluorinated polyacrylate emulsion comprising: 4 to 20 % w/w of an alkali soluble resins (ASRs) of the total weight of the emulsion; 5 to 30 % w/w of a fluorinated acrylates of the total weight of the emulsion; 5 to 30 % w/w of an acrylate derivative of the total weight of the emulsion, 0.2 to 1.2 % w/w of sodium meta sulphite of the total weight of the emulsion; 0.2 to 1.2 % w/w of tert-butyl hydrogen peroxide of the total weight of the emulsion; and 30 to 80 % w/w of water of the total weight of the emulsion.
[0016] The present disclosure discloses a method of preparation of a surfactant free fluorinated polyacrylate emulsion comprising: a) stirring 4 to 20 % w/w of an alkali soluble resins (ASRs) in 30 to 80 % w/w of water under condition to obtain a mixture; b) adding 0.5 to 1.5 % w/w of ammonia solution dropwise in the mixture with stirring till the complete dissolution of ASR to obtain a ASR solution; c) adding 5 to 30 % w/w of a fluorinated acrylates and 5 to 30% w/w of an acrylate derivative to the ASR solution dropwise to form a pre-emulsion; d) homogenizing the pre-emulsion under condition to form a miniemulsion; and e) processing the miniemulsion to form a surfactant free fluorinated polyacrylate emulsion.
[0017] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

DETAILED DESCRIPTION OF THE INVENTION
[0018] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0019] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0020] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0021] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0022] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.
[0023] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0024] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0025] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0026] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0027] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0028] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0029] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0030] The fluorinated polymers possess unique properties and wide range of applications. Small fluorine atoms having low polarizibility are devoid of “London Dispersion Forces,” which leads to low inter-molecular forces of attraction and hence, have excellent resistance to oil, water, and organic solvents. Fluoropolymers also have application in self-cleaning paints and coatings due to their low surface energy.
[0031] Perfluoroacrylates are particularly appealing due to their facile polymerization and good reactivity with different monomers under radical copolymerization. Further, due to the low crystallinity and good solubility of perfluoroacrylate copolymers, they can be readily processed in addition to their advantages of fluorous segments with unique characteristics such as low surface energy, low friction coefficient and conventional solvent compatibility; due to these advantages, the resulting coatings play an essential role in microelectronics, antifogging, and antifouling applications and even have promising medical applications.
[0032] Polymeric emulsion with core-shell morphology has several advantages over conventional polymer lattices. For example, they have better film formation properties. These core-shell fluorinated copolymers are conventionally prepared by semi continuous or seeded emulsion polymerization using fluorinated surfactant. Preparation of fluorinated polymers using alkali soluble resin (ASR) as an emulsifier with core-shell structure has several advantageous compared to conventional surfactants. The ASR based emulsion provides fine particles size and better film formation properties. Moreover, fluorous based polymer in aqueous emulsion leads to reduction in volatile organic content (VOC) in the environment.
[0033] An embodiment of the present disclosure discloses a surfactant free fluorinated polyacrylate emulsion comprising 4 to 20 % w/w, preferably 8 to 16 % w/w of an alkali soluble resins (ASRs) of the total weight of the emulsion; 5 to 30% w/w, preferably 10 to 25 % w/w of a fluorinated acrylates of the total weight of the emulsion; and 5 to 30% w/w, preferably 10 to 25 %w/w of an acrylate derivative of the total weight of the emulsion, 0.2 to 1.2 % w/w of sodium meta sulphite of the total weight of the emulsion; 0.2 to 1.2 % w/w of tert-butyl hydrogen peroxide of the total weight of the emulsion; and 30 to 80 % w/w, preferably 40 to 70 % w/w of water of the total weight of the emulsion.
[0034] In an embodiment of the present disclosure discloses that the fluorinated acrylates is selected from a group consisting of fluorinated esters of acrylic acid, methacrylic acid 2-Fluoroacrylic acid such as 2,2,2-Trifluoroethyl acrylate, 2,2,2-Trifluoroethyl methacrylate (TFMA), Methyl 2-fluoroacrylate, 2,2,2-Trifluoroethyl α-fluoroacrylate, 2,2,3,3-Tetrafluoropropyl acrylate, 2,2,3,3,3-Pentafluoropropyl methacrylate, 2,2,3,3,4,4,4-Heptafluoro butyl acrylate (HFBA), 2,2,3,3,4,4,4-Heptafluorobutyl methacrylate, 2,2,3,4,4,4-Hexafluorobutyl methacrylate, 1H,1H,5H-Octafluoropentyl methacrylate, 1H,1H,2H,2H-Nonafluorohexyl methacrylate, Hexafluoro-iso-propyl methacrylate, Pentafluorophenyl acrylate, Pentafluorophenyl methacrylate, Pentafluorobenzyl methacrylate (Scheme 1) and combination thereof. Preferably, the fluorinated acrylates are 2,2,2-Trifluoroethyl acrylate, 2,2,2-Trifluoroethyl methacrylate (TFMA), 2,2,3,3,3-Pentafluoropropyl methacrylate, 2,2,3,3,4,4,4-Heptafluoro butyl acrylate (HFBA), 2,2,3,3,4,4,4-Heptafluorobutyl methacrylate, 2,2,3,4,4,4-Hexafluorobutyl methacrylate.

Scheme 1. Details of fluorinated acrylate moieties
[0035] In an embodiment of the present disclosure discloses that the acrylate derivative is selected from a group consisting of esters of acrylic acid and methacrylic acid such as methyl acrylate, methyl methacrylate (MMA), ethyl acrylate, ethyl methacrylate, butyl acrylate (BA), butyl methacrylate, iso-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, 2-hydroxy methacrylate, 2-ethyl hexyl acrylate, benzyl acrylate, Poly(ethylene glycol) methyl ether acrylate, 2-norbornyl acrylate, furfuryl methacrylate (Scheme 2) and combination thereof. Preferably, the acrylate derivativesare methyl acrylate, methyl methacrylate (MMA), ethyl acrylate, ethyl methacrylate, butyl acrylate (BA) and butyl methacrylate.
Scheme 2. Details of Conventional acrylate moieties
[0036] In an embodiment of the present disclosure discloses that the alkali soluble resins (ASRs) comprising: hydrophobic co-monomer is selected from a group consisting of a styrene, an alpha-methyl styrene and combination thereof; and hydrophilic co-monomer is selected from an acrylic acid derivative, preferably acrylic acid, wherein the amount of the hydrophobic co-monomer is 60 to 80 % w/w and hydrophilic co-monomer is 20 to 40 % w/w.
[0037] In an embodiment of the present disclosure discloses that the acrylic acid derivative is selected from a group consisting of acrylic acid, dimer rich acrylic acid, methacrylic acid, dimer rich methacrylic acid, crotonic acid, maleic anhydride, fumaric acids, maleic acid, itaconic acid, 4-vinylbenzoic acid and combination thereof.
[0038] In an embodiment of the present disclosure discloses that the alkali soluble resins (ASRs) is prepared by the steps comprises: mixing of 60 to 80 % w/w of hydrophobic co-monomer selected from a group consisting of astyrene, alpha-methyl styrene and combination thereof and 20 to 40 % w/w of hydrophilic co-monomer selected from an acrylic acid derivative, preferably acrylic acid, to obtain a reaction mixture; heating the reaction mixture at a temperature in the range of 250-270 °C for a period in the range of 40-50 min to obtain the alkali soluble resins (ASRs). The preferred condition includes temperature at 260 °C for a time period of 45 min for heating the reaction mixture.
[0039] An embodiment of the present disclosure discloses a method of preparation of a surfactant free fluorinated polyacrylate emulsion comprising: a) stirring 4 to 20 % w/w, preferably 8 to 16 % w/w of an alkali soluble resins (ASRs) in 30 to 80 % w/w, preferably 40 to 70 % w/w of water under heating condition to obtain a mixture; b) adding 0.5 to 1.5 % w/w of ammonia solution dropwise in the mixture with stirring till the complete dissolution of ASR to obtain a ASR solution; c) adding 5 to 30 % w/w, preferably 10 to 25 % w/w w/w of a fluorinated acrylates and 5 to 30 % w/w, preferably 10 to 25 % w/w of an acrylate derivative to the ASR solution dropwise to form a pre-emulsion; d) homogenizing the pre-emulsion under ambient condition to form a miniemulsion; and e) processing the miniemulsion to form a surfactant free fluorinated polyacrylate emulsion.
[0040] In an embodiment of the present disclosure discloses that the condition in step a) includes temperature in the range of 50-60 °C under nitrogen atmosphere. Preferred temperature is 55 °C.
[0041] In an embodiment of the present disclosure discloses that the pre-emulsion is ultrasonicated for a period in the range of 5 to 10 min.
[0042] In an embodiment of the present disclosure discloses that the processing step e) comprises: taking the miniemulsion in a four necked glass reactor and purging nitrogen for a period of 20-40 min followed by heating in an oil bath at a temperature in the range of 50-60 °C to obtain a heated miniemulsion; and adding 0.2 to1.2 % w/w of sodium meta bisulphite and 0.2 to 1.2 % w/w of tert-butyl hydrogen peroxide simultaneously and dropwise to the heated miniemulsion and maintaining the temperature of reaction mixture in the range of 50-60 °C for a period in the range of 1 to 3 hrs followed by addition of 0.03 to 0.15 % w/w of TBHP at a temperature in the range of 50-55 °C to minimize the residual monomer and formation of a surfactant free fluorinated polyacrylate emulsion.
[0043] In an embodiment of the present disclosure discloses that the emulsion has the water contact angle which is varied in the range of 100 to 116° by varying the polyfluoroacrylates with side chain pendent fluorinated group [(CF2)n].
[0044] Alkali soluble resins (ASRs) are widely used as stabilizer for production of waterborne dispersed polymers having applications in coatings and ink industry as pigment dispersants, emulsifiers, and overprint varnishes (OPV) for gloss improvement applications. However, the fluorinated monomers have never been polymerized using ASR.
[0045] Fluorinated polymers are widely used in composite materials, films, and coatings for advanced applications, such as aerospace, marine and electronics, due to their high resistance to harsh weather conditions and excellent inertness to a wide range of chemical environments. The presence of fluorous units into polymers is of great interest because they endow the polymer with excellent thermal stability, good physical and chemical properties, and hydrophobicity.
[0046] Conventionally, fluoropolymers are being prepared by using fluorinated surfactants. There are serious concerns regarding the toxicity and adverse effects of fluorinated surfactants on humans and the environment. Preparation of surfactant free fluoro polyacryaltes will be great interest for development of eco-friendly hydrophobic coatings.
[0047] An aspect of the present investigation deals with copolymerization of fluorinated acrylates such as Heptafluoro butyl acrylate (HFBA), Trifluoromethacrylate (TFMA) and conventional acrylates like butyl acrylate (BA), methyl methacrylate (MMA) using surfactant-free alkali soluble polymerizable resins. Dimer rich and dimer free acrylic acid feed stocks are used for the preparation of ASR. The resultant fluorous based copolymer emulsions have core-shell structure which was confirmed from the High Resolution-Transmission Electron Microscope (HR-TEM).
[0048] An aspect of the present studies is to provide water borne hydrophobic fluorous based emulsion polymers with core-shell structure and method of preparation thereof.
[0049] An aspect of the present studies deals with regulating the hydrophobicity and viscosity of the emulsions by varying the chain length of the fluorous segment of fluoro-acrylate, and ASR composition, respectively.
[0050] Hydrophobicity also depends upon the fluorous chain length and structure of side chain of polyfluoroacrylates. Increasing the fluorous chain length leads to higher hydrophobicity. Polyfluoroacrylates with short pendent fluorinated group [(CF2)n where n≤6] show poor hydrophobicity due to disordered arrangement arising from molecular mobility. [Macromolecules 2005, 38, 13, 5699–5705] The hydrophobicity offluoroacrylate copolymers in this study has been varied using fluoroacrylate monomers with different fluorous chain lengths viz. 2,2,2-Trifluoroethyl methacrylate (TFMA), with n = 1 and 2,2,3,3,4,4,4-Heptafluoro butyl acrylate (HFBA) with n = 3.
[0051] Two grades of ASR, based on (a) dimer free (glacial) acrylic acid and (b) dimer rich acrylic acids, are used to obtain viscosity range of 10 to 500 cP by varying the solid content from 40 to 50%. Lower viscosity was observed in case of dimer rich acrylic acid ASR based emulsions whereas higher viscosity for the dimer free (glacial) acrylic acid ASR based emulsion. It could be due to chain transfer effect of dimer of acrylic acid leads to control molecular weight ASR as compared to dimer free (glacial) acrylic acid one.
Solid Content and Gravimetric Conversion
[0052] The emulsion polymer was dried to a constant mass at a temperature of 130°C (according to ISO 1625) and the solids content is then expressed as the percentage ratio of the dry matter to the total mass of the sample.
Theoretical solid content % = Total introduced solid × 100 / Total weight
Actual solid content % = Weight of the sample after drying × 100 / Weight of the sample before drying
Gravimetric Conversion = Actual solid content % / theoretical solid content
Coagulum Content
[0053] The prepared emulsion was filtered through nylon cloth (400 mesh). The filterable solids were dried. The coagulum content was then calculated according to
Coagulation% = Mf / (solid% × Ms + Mf)
where, Mf and Ms are the weights of dried filterable solids and weight of emulsion after filtration, respectively.

ADVANTAGES OF PRESENT INVENTION
[0054] The ASR based core-shell emulsion enhances the gloss properties, corrosion resistance, adhesion towards metals, and low and high temperature stability. Further, the ASR core-shell emulsion allows to control the viscosity according to desired applications.
Silent features of the present invention
[0055] Eco-friendly process: No organic solvent used - Water borne emulsion, no fluorinated surfactant used.
[0056] Low particle size in the range of 100-200 nm.
[0057] Highly stable emulsion – Emulsions are stable at very low and high temperature.
[0058] Stable hydrophobic coatings on polar surface achieved due to core-shell structure.
[0059] Tuneable Viscosity.
[0060] Multipurpose Coatings using spray, spin or dip –casting.
[0061] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES
[0062] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Synthesis of alkali soluble resins (ASRs)
[0063] General Methodology: All synthesis was conducted in an inert atmosphere. The ASR reactions were carried out in high temperature high pressure Parr Reactor (Model Parr 4533) by bulk polymerization.
[0064] ASR-1: The reactor was charged with 50 g of styrene, 50 g of alpha-methyl styrene and 50 g of glacial acrylic acid. The reaction was performed at 260°C for 45 min.
[0065] ASR-2: The reactor was charged with 50 g of styrene, 50 g of alpha-methyl styrene and 50 g of dimer rich acrylic acid (10% dimer content in acrylic acid). The reaction was performed by bulk polymerization at 260°C for 45 min.
Table 1: Details of synthesized ASRs
Samples Monomers for ASR Non-VOC Yield (%) Mn PDI Acid content
ASR-1 Sty (33.33%)
AMS(33.33%)
GAA(33.33%) 98% >95 18,400 2.51 250
ASR-2 Sty (33.33%)
AMS (33.33%)
DAA (33.33%)
98% >95 8,800 2.06 241

Synthesis of fluorous based emulsion copolymer with core-shell structure using dimer-free and dimer-rich alkali-soluble resins (ASRs)
[0066] General Methodology: In a 100 mL round bottom flask equipped with a condenser, 3.73 g of respective ASR was vigorously stirred in requisite quantity of water at 50-60°C under a nitrogen atmosphere. Subsequently, 1.52 g of ammonia solution was added dropwise and stirred till the complete dissolution of the ASR solution. Then, a monomer system containing 4.33 g of Methyl methacrylate (MMA) or 2,2,2-Trifluoroethyl methacrylate (TFMA) or 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) and 4.33 g of butyl acrylate (BA) (4.33 g) were added dropwise to the aqueous phase with stirring to form a pre-emulsion. This pre-emulsion was then ultrasonicated for 5 to 10 min. At this point, the organic phase disperses completely in the aqueous phase forming a miniemulsion. This resultant miniemulsion was transferred to a four necked glass reactor. The reactor was deoxygenated by purging nitrogen for 30 min, and then, it was placed in the oil bath preheated at reaction temperature (50-60°C). At this stage, 10% solution of sodium meta bisulphite (0.100 g) and tert-Butyl hydrogen peroxide (0.100 g) (initiator system) were injected simultaneously and dropwise. After addition of initiators, the reaction mixture was held for 2 hours at the same temperature. Further, 0.02 g of TBHP was added post-polymerization at 50-55°C to minimize the residual monomers (Figure 1).
Example 1: Comparative Example
[0067] EA-1. The composition for the preparation of EF-1 was neutralized ASR-2 and monomer system, Methyl methacrylate (MMA) and butyl acrylate (BA). Theoretical solid content is 40%.
Example 2: Present invention
[0068] EF-1. The composition for the preparation of EF-1 was neutralized ASR-1 and monomer system 2,2,2-Trifluoroethyl methacrylate (TFMA) and of butyl acrylate (BA). Theoretical solid content is 40%.
Example 3
[0069] EF-2. The composition for the preparation of EF-2 was neutralized ASR-2 and the monomer system 2,2,2-Trifluoroethyl methacrylate (TFMA) and butyl acrylate (BA). Theoretical solid content is 40%.
Example 4
[0070] EF-3. The composition for the preparation of EF-3 was neutralized ASR-1 and monomer system 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) and butyl acrylate (BA). Theoretical solid content is 40%.
Example 5
[0071] EF-4. The composition for the preparation of EF-4 was neutralized ASR-2 and monomer system 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) and butyl acrylate (BA). Theoretical solid content is 40%.
Example 6
[0072] EF-5. The composition for the preparation of EF-5 was neutralized ASR-1 and monomer system 2,2,2-Trifluoroethyl methacrylate (TFMA) and of butyl acrylate (BA). Theoretical solid content is 50%
Example 7
[0073] EF-6. The composition for the preparation of EF-6 was neutralized ASR-2 and monomer system 2,2,2-Trifluoroethyl methacrylate (TFMA) and of butyl acrylate (BA). Theoretical solid content is 50%.
Example 8
[0074] EF-7. The composition for the preparation of EF-7 was neutralized ASR-1 and monomer system 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) and of butyl acrylate (BA). Theoretical solid content is 50%.
Example 9
[0075] EF-8. The composition for the preparation of EF-8 was neutralized ASR-2 and monomer system 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) and of butyl acrylate (BA). Theoretical solid content is 50%.
[0076] The acrylate and fluoro acrylate are taken in 1:1 ratio as mentioned in the examples. The water is added to achieve solid content of 40 % or 50 % as mentioned in the examples.
Table 2: Details pertaining to the synthesized emulsion copolymers.
Parameter EA-1 EF-1 EF-2 EF-3 EF-4 EF-5 EF-6 EF-7 EF-8
Monomers MMA-BA TFMA-BA TFMA-BA HFBA-BA HFBA-BA TFMA-BA TFMA-BA HFBA-BA HFBA-BA
ASR Grade ASR-2 ASR-1 ASR-2 ASR-1 ASR-2 ASR-1 ASR-2 ASR-1 ASR-2
Theoretical Solid content (%) 40 40 40 40 40 50 50 50 50
Obtained solid content (%) 38.2 34.8 35.1 32.6 32.8 46.0 46.1 44.6 45.1
Gravimetric Conversion (%) 95.5 87.0 87.8 81.5 82.0 92.0 92.2 89.2 90.2
Coagulum content (%) ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5 ≥ 0.5
pH 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5 7.5-8.5

Stability of the ASR Emulsion
[0077] The fluorous-based ASR copolymer emulsion was subjected to different conditions such as storage at room temperature, high temperature (60 °C) and low temperature (0 °C) for one month, and dilution with distilled water, and then observed whether there was a phenomenon of stratification, precipitation, flocculation, and so on, to evaluate its storage stability, chemical stability, and dilution stability. The stability testing of emulsion at 60 °C is referred to as hot-box stability and at 0 °C for one month is called freeze-thaw stability (Figure 2).
Table 4: Stability studies of the synthesized fluorous based core-shell emulsion copolymer
Parameter EF-1 EF-2 EF-3 EF-4 EF-5 EF-6 EF-7 EF-8
Freeze Thaw stability Stable Stable Stable
Stable Stable Stable Stable Stable
Hot-box stability Stable Stable Stable
Stable Stable Stable Stable Stable
Dilution Stability Stable Stable Stable
Stable Stable Stable Stable Stable

Surface properties: Water contact Angle (WCA)
[0078] The surface properties like hydrophobicity of films of fluorous-based emulsion copolymer with core-shell structure were studied by water contact angle measurements. Thin films of the polymers were prepared by spray-coating onto glass slides on which water drops were deposited using a sessile water syringe. Before testing, the polymer film was annealed at 120 °C for 24 h. Contact angle measurements were carried out on a Contact Angle Meter DMe 211 using the sessile water drop method at ambient temperature. Water was used as a probe liquid in a 0.6 μL volume from a 0.305 mm width needle, and the average WCA (θH2O) value was determined from five different samples of the same polymer (Figure 3).
Surface energies
[0079] The surface energies of the of fluorous based emulsion copolymers were calculated from the equation, 1 + cos θ = 2(γS + γL)1/2 exp[−β(γS−γL)]2 [where β is a constant with a value of 0.0001247 (m2 mj−1)2 and θ, γS, and γL are the contact angle, surface energy of the solid, and surface energy of the tested liquid, respectively.
Rheology studies
[0080] The ASR emulsion polymer was studied for rheological properties. The rheological test measurements were carried out under atmospheric conditions using Anton Parr Rheometer (MCR302) with SN81948116-81948215; FW4.42; slot (8,-1); adj (9,0)d, measuring system: CP25-1-SN5270; [d= 0.05 mm], Peltier temperature control. The viscosity was performed using cylindrical cone SN81936601; FW4.42; slot (7,-1); adj (9,0)d, measuring system: CC27-SN20708; [d = 0.05 mm], with Peltier temperature control.
Table 3: Properties of synthesized emulsion copolymers
Parameter EA-1 EF-1 EF-2 EF-3 EF-4 EF-5 EF-6 EF-7 EF-8
Viscosity (cP) 15 49 8 51 17 78 44 450-500 260-285
WCA (o) 83 100 100 114 115 101 101 116 114
Surface energy
(mN/m) 29.3 23.5 23.5 18.7 18.3 23.2 23.2 18.0 18.7
Note: Surface energy was calculated from the WCA.
[0081] The resultant fluorous based copolymer emulsions have core-shell structure which was confirmed from the High Resolution-Transmission Electron Microscope (HR-TEM) as shown in Figure 4.
[0082] The core-shell emulsions were coated on glass surface to achieve hydrophobic coating with water contact angle, WCA > 106o, which is higher than reported WCA = 93o for homopolymer of 4,4,4,3,3,2,2-Heptafluoro butyl acrylate (HFBA) prepared using conventional non-fluoro surfactants (SDS and Triton-X). (Ref.: Journal of Colloid and Interface Science 408 (2013) 66-74). This property renders application in hydrophobic coatings.
[0083] The core-shell emulsions when coated on the glass surface leads to rearrangement of molecular structure in a way that the polar carboxylate groups of the ASR interact with hydrophilic glass surface leading to stable coating formation and the fluoroalkyl moieties are exposed outward. The lower surface energy of the coated film was achieved due to presence of the fluoroalkyl moieties at the surface.The control experiment without fluorine moiety (EA-1) in the core-shell structure exhibited WCA = 83o, hence, not exhibiting hydrophobic surface property.
[0084] Hydrophobicity also depends upon the fluorous chain length and structure of side chain of polyfluoroacrylates. On increasing of fluorous chain length, higher hydrophobicity is achieved. Polyfluoroacrylates with short pendent fluorinated group [(CF2)n where n≤6] show poor hydrophobicity due to disordered arrangement arising from molecular mobility. [Macromolecules 2005, 38, 13, 5699–5705]. In our case, EF-3, EF-4, EF-7 and EF-8 with fluorinated chain of medium length (n = 3) exhibited higher WCA of 114-116 ocompared to EF-1, EF-2, EF-5 and EF-6 with short fluorinated chain (n = 1) which showed WCA = 100-101o.
[0085] Complete homopolymer of short chain fluorinated group also have lesser hydrophobicity. For example, homopolymer of heptafluorobutylacrylate (n = 3) is reported to exhibit WCA = 93o. [Macromolecules 2005, 38, 13, 5699–5705]In our study, the surfactant free ASR based core-shell emulsions with combination of fluorinated and other acylates copolymer exhibited water contact angle (WCA)> 100o on glass coated surface, even for (CF2)n with n = 1. The observed highly hydrophobic nature in our study arises out of the core-shell structure of the particles. When these ASR based core-shell emulsions are coated on hydrophilic glass surface, there is re-organization of polar ionic carboxylate functionalities of the core-shell emulsion towards the hydrophilic glass surface and outward movement of the perfluoroalkyl chains from the glass surface. The exposure of the perfluoroalkyl on the surface renders high hydrophobicity.
[0086] Two grades of ASR based on (a) dimer free (glacial) acrylic acid and (b) dimer rich acrylic acids are used to obtain viscosity range of 10 to 500 cP byvarying the solid content from 40 to 50%. Lower viscosity was observed inthe case of dimer rich ASR based emulsions whereas higher viscosity for the dimer free (glacial) acrylic acid ASR based emulsion. It could be due to chain transfer effect of dimer of acrylic acid leads to control molecular weight ASR as compared to dimer free (glacial) acrylic acid one.
[0087] A skilled artisan will appreciate that the quantity and type of each ingredient can be used in different combinations or singly. All such variations and combinations would be falling within the scope of present disclosure.
[0088] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.
, Claims:1. A surfactant free fluorinated polyacrylate emulsion comprising:
4 to 20 % w/w of an alkali soluble resins (ASRs) of the total weight of the emulsion;
5 to 30% w/w of a fluorinated acrylates of the total weight of the emulsion;
5 to 30% w/w of an acrylate derivative of the total weight of the emulsion.
0.2 to 1.2 % w/w of sodium meta sulphite of the total weight of the emulsion;
0.2 to 1.2 % w/w of tert-butyl hydrogen peroxide of the total weight of the emulsion; and
30 to 80 % w/w of water of the total weight of the emulsion.
2. The emulsion as claimed in claim 1, wherein the fluorinated acrylates is selected from a group consisting of fluorinated esters of acrylic acid, methacrylic acid 2-Fluoroacrylic acid such as 2,2,2-Trifluoroethyl acrylate, 2,2,2-Trifluoroethyl methacrylate (TFMA), Methyl 2-Fluoroacrylate, 2,2,2-trifluoroethyl α-fluoroacrylate, 2,2,3,3-Tetrafluoropropyl acrylate, 2,2,3,3,3-Pentafluoropropyl methacrylate, 2,2,3,3,4,4,4-Heptafluoro butyl acrylate (HFBA), 2,2,3,3,4,4,4-Heptafluorobutyl methacrylate, 2,2,3,4,4,4-Hexafluorobutyl methacrylate, 1H,1H,5H-Octafluoropentyl methacrylate, 1H,1H,2H,2H-Nonafluorohexyl methacrylate, Hexafluoro-iso-propyl methacrylate, Pentafluorophenyl acrylate, Pentafluorophenyl methacrylate, Pentafluorobenzyl methacrylate and combination thereof.
3. The emulsion as claimed in claim 1, wherein the acrylate derivative is selected from a group consisting of esters of acrylic acid and methacrylic acid such as Methyl acrylate, methyl methacrylate (MMA), ethyl acrylate, ethyl methacrylate, butyl acrylate (BA), butyl methacrylate, iso-butyl acrylate,tert-butyl methacrylate, cyclohexyl acrylate, 2-hydroxy methacrylate, 2-ethyl hexyl acrylate, Benzyl acrylate, Poly(ethylene glycol) methyl ether acrylate, 2-norbornyl acrylate, furfuryl methacrylateand combination thereof.
4. The emulsion as claimed in claim 1, wherein the alkali soluble resins (ASRs) comprising:
hydrophobic co-monomer is selected from a group consisting ofa styrene,an alpha-methyl styreneand combination thereof; and
hydrophilic co-monomer is selected froman acrylic acid derivative,
wherein the amount of hydrophobic co-monomer is 60 to 80 % w/w andhydrophilicco-monomer is 20 to 40 % w/w.
5. The emulsion as claimed in claim 4, wherein the acrylic acid derivative is selected from a group consisting of acrylic acid, dimer rich acrylic acid, methacrylic acid, dimer rich methacrylic acid, crotonic acid, maleic anhydride, fumaric acids, maleic acid, itaconic acid, 4-vinylbenzoic acid and combination thereof.
6. The emulsion as claimed in claim 4, wherein the alkali soluble resins (ASRs) are prepared by the steps comprises:
mixing of 60 to 80 % w/w of hydrophobic co-monomer is selected from a group consisting of a styrene, an alpha-methyl styrene and combination thereof and 20 to 40 % w/w hydrophilic co-monomer is selected from an acrylic acid derivativeto obtain a reaction mixture;
heating the reaction mixture at a temperature in the range of 250-270 °C for a period in the range of 40-50 min to obtain the alkali soluble resins (ASRs).
7. A method of preparation of a surfactant free fluorinated polyacrylate emulsion comprising:
a) stirring 4 to 20 % w/w of an alkali soluble resins (ASRs) in 30 to 80 % w/w of water under condition to obtain a mixture;
b) adding 0.5 to 1.5 % w/w of ammonia solution dropwise in the mixture with stirring till the complete dissolution of ASR to obtain an ASR solution;
c) adding 5 to 30 % w/w of a fluorinated acrylates and 5 to 30 % w/w of an acrylate derivative to the ASR solution dropwise to form a pre-emulsion;
d) homogenizing the pre-emulsion under condition to form a miniemulsion; and
e) processing the miniemulsion to form a surfactant free fluorinated polyacrylate emulsion.
8. The method as claimed in claim 1, wherein the condition in step a) includes temperature in the range of 50-60 °C under nitrogen atmosphere.
9. The method as claimed in claim 1, wherein the pre-emulsion is ultrasonicated for a period in the range of 5 to 10 min.
10. The method as claimed in claim 1, wherein the processing step e) comprises:
taking the miniemulsion in a four necked glass reactor and purging nitrogen for a period of 20-40 min followed by heating in an oil bath at a temperature in the range of 50-60 °C to obtain a heated miniemulsion; and
adding 0.2 to 1.2 % w/w of sodium meta bisulphite and 0.2 to 1.2 % w/w of tert-butyl hydrogen peroxide simultaneously and dropwise to the heated miniemulsion and maintaining the temperature of reaction mixture in the range of 50-60 °C for a period in the range of 1 to 3 hrs followed by addition of 0.03 to 0.15% w/w of TBHP at a temperature in the range of 50-55 °C to minimize the residual monomer and formation of a surfactant free fluorinated polyacrylate emulsion.
11. The method as claimed in claim 10, wherein the emulsion has the water contact angle which is varied in the range of 100 to 116° by varying the polyfluoroacrylates with side chain pendent fluorinated group [(CF2)n].