DESC:FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
[See Section 10 and rule 13]

PROCESS FOR REMOVING NON-FLUORINATED SURFACTANTS FROM FLUOROPOLYMERS

GUJARAT FLUOROCHEMICALS LIMITED an Indian Company of INOX Towers, Plot No. 17, Sector 16-A, Noida, Uttar Pradesh 201301, India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION:
The invention relates to a process for removing non-fluorinated surfactants from fluoropolymers.

BACKGROUND OF THE INVENTION:
Typically, surfactants are used during the preparation of fluoropolymers primarily to control the dispersion and stability of the polymer particles in the reaction medium. Since fluoropolymers tend to have low solubility and high viscosity, surfactants help in overcoming these challenges and achieving a uniform dispersion of the polymer particles.

Some of the roles played by the surfactants during the process of preparing fluoropolymers include:
Dispersion: Fluoropolymers are usually produced via emulsion polymerization, where the monomers are dispersed in an aqueous medium. Surfactants are employed to stabilize the monomer droplets and prevent their coalescence. They form a protective layer around the monomer droplets, reducing interfacial tension and facilitating the formation of stable emulsions.
Particle Size Control: Surfactants aid in controlling the particle size of the fluoropolymers during the polymerization process. By adjusting the surfactants concentration, the kinetics of polymerization can be regulated, leading to the desired particle size distribution. This control is crucial as it influences the properties of the resulting fluoropolymers, such as its mechanical strength and thermal stability.
Polymerization Control: Surfactants also affect the polymerization rate and the molecular weight distribution of the fluoropolymers. They can act as stabilizers, controlling the growth of the polymer chains and preventing excessive particle coagulation. By choosing the appropriate surfactants type and concentration, it is possible to achieve the desired polymerization kinetics and control the resulting polymer properties.
Stability: Surfactants provide stability to the fluoropolymers emulsion by preventing particle aggregation, settling, or flocculation. They inhibit the formation of large polymer aggregates, ensuring a uniform dispersion of the particles throughout the reaction medium. This stability is essential for obtaining consistent product quality and ease of handling during subsequent processing steps.

It's worth noting that the selection of surfactants for fluoropolymers preparation is crucial and depends on factors such as the type of fluoropolymers being produced, the desired properties of the final product, and the specific conditions of the polymerization process. Different surfactants types, including ionic or nonionic surfactants, may be employed to optimize the polymerization process and achieve the desired performance characteristics in the fluoropolymers.

Surfactants with fluoromolecules are often used in the process of preparing fluoropolymers. However, the use of such fluoro-surfactants comes with known disadvantages. In some instances, non-fluorinated surfactants are also used during the process of preparing fluoropolymers.

It has however been observed that even when non-fluorinated surfactants are used during the process for preparing fluoropolymers, one or more of the following disadvantages are encountered:
Discoloration: The fluoropolymers particles thus formed undergo discoloration, especially turn into black or brown during subsequent processing, including for example, high-temperature drying. The discoloration leads to reduction of the reduction in aesthetic value of the product.
Degradation in performance: Presence of non-fluorinated surfactants in the fluoropolymers particles thus formed leads to adversely affecting one or more properties of the fluoropolymers particles thus formed which include mechanical strength, thermal stability, chemical resistance, etc.

The most commonly followed technique for removing the non-fluorinated surfactants from the fluoropolymers particles includes treating the fluoropolymers particles with solution containing specific metal salts. However, use of such metal salts for removal of the non-fluorinated surfactants has its own disadvantages. For instance, use metal salts for removal of the non-fluorinated surfactants from the fluoropolymers particles changes the electrical properties of the fluoropolymers particles, which is un-desirable. Also, the metal salts act as un-desired impurities which gets incorporated in the fluoropolymers particles and their removal is highly difficult.

Thus, there is a need to provide a process that can effectively remove non-fluorinated surfactants that are used during the process for preparing fluoropolymers and which form part of the fluoropolymers particles thus formed.

STATEMENT OF THE INVENTION:
This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention, and nor is it intended for determining the scope of the invention.

Accordingly, the present invention provides a process for non-fluorinated surfactants from fluoropolymers particles. The process involves subjecting the fluoropolymers particles containing non-fluorinated surfactants to at least one stage of washing with one or more washing solvent wherein the washing solvent comprises an alcohol optionally along with water.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof. It is appreciated that the embodiments of the invention are not to be considered limiting of the scope of the invention.

Detailed Description of the Invention:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such processor method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

As used herein, and unless the context dictates otherwise, the terms "coupled to", “connected to”, “operably connected to”, “operatively connected to” are intended to include both direct connection / coupling (in which two elements that are coupled / connected to each other contact each other) and indirect coupling / connection (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Similarly, the terms “connected to” and “connected with” are used synonymously.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The methods, devices, and examples provided herein are illustrative only and not intended to be limiting.

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.

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 of all Markush groups used in the appended claims. Embodiments of the present invention will be described below in detail.

Accordingly, the present invention provides a process for non-fluorinated surfactants from fluoropolymers particles. The process involves subjecting the fluoropolymers particles containing non-fluorinated surfactants to at least one stage of washing with one or more washing solvent.

In an embodiment of the invention, the washing solvent comprises at least one organic solvent optionally along with water.

In another embodiment of the invention, the at least one organic solvent comprises an alcohol optionally along with water.

In another embodiment of the invention, the at least one organic solvent is selected from a group comprising, but is not limited to, an alcohol, an ether or glycol ether, and a combination thereof.

In still another embodiment of the invention, the alcohol is selected from, but is not limited to, a group comprising methanol, ethanol, isopropyl alcohol, butanol, glycol, and combinations thereof.

In yet another embodiment of the invention, the ether or glycol ether is selected from, but is not limited to, a group comprising Ethylene glycol monomethyl ether (2-methoxyethanol, CH3OCH2CH2OH), Ethylene glycol monoethyl ether (2-ethoxyethanol, CH3CH2OCH2CH2OH), Ethylene glycol monopropyl ether (2-propoxyethanol, CH3CH2CH2OCH2CH2OH), Ethylene glycol monoisopropyl ether (2-isopropoxyethanol, (CH3)2CHOCH2CH2OH), Ethylene glycol monobutyl ether (2-butoxyethanol, CH3CH2CH2CH2OCH2CH2OH), Ethylene glycol monophenyl ether (2-phenoxyethanol, C6H5OCH2CH2OH), Ethylene glycol monobenzyl ether (2-benzyloxyethanol, C6H5CH2OCH2CH2OH), Propylene glycol methyl ether, (1-methoxy-2-propanol, CH3OCH2CH(OH)CH3), Diethylene glycol monomethyl ether (2-(2- methoxyethoxy)ethanol, methyl carbitol, CH3OCH2CH2OCH2CH2OH), Diethylene glycol monoethyl ether (2-(2-ethoxyethoxy)ethanol, carbitolcellosolve, CH3CH2OCH2CH2OCH2CH2OH), Diethylene glycol mono-n-butyl ether (2-(2- butoxyethoxy)ethanol, butyl carbitol, CH3CH2CH2CH2OCH2CH2OCH2CH2OH), Dipropyleneglycol methyl ether, and mixtures thereof.

In still another embodiment of the invention, the alcohol is selected from a group comprising methanol, ethanol, isopropyl alcohol, and butanol, optionally along with water.

In a further embodiment of the invention, the washing is performed at ambient temperature to a temperature which is less than boiling point of the washing solvent.

In a furthermore embodiment of the invention, the washing is performed at ambient temperature.

In an embodiment of the invention, the washing is performed in a plurality of stages including a first stage washing and at least one further stage of washing.

In another embodiment of the invention, the first stage washing is performed with a first stage washing solvent and the second stage washing is performed with a second stage washing solvent, wherein the first stage washing solvent is same as that of the second stage washing solvent.

In yet another embodiment of the invention, the first stage washing is performed with a first stage washing solvent and the second stage washing is performed with a second stage washing solvent, wherein the first stage washing solvent is different as that of the second stage washing solvent.

By way of example, the fluoropolymers particles are immersed in the washing solvent and agitated to facilitate the removal of surfactants. This can be achieved through stirring, ultrasonic bath, or other mechanical means. The duration and intensity of the washing process depend on factors such as the type and concentration of the surfactants, the particle size, and the desired level of surfactants removal.

After the washing process, the fluoropolymers particles are separated from the washing medium again to remove any residual surfactants. Filtration or centrifugation or any other separation process can be employed once more to isolate the cleaned fluoropolymers particles from the washing solvent.

The fluoropolymers particles thus separated may be dried. The drying can be done through evaporation or by using techniques such as vacuum drying or air drying.

In an embodiment of the invention, the present invention provides fluoropolymers particles having improved colour: The solvent washing technique effectively removes non-fluorinated surfactants from fluoropolymers, resulting in a significant improvement in colour. The issue of black or brown coloration caused by surfactants charring during high-temperature drying is addressed, leading to enhanced aesthetics and market appeal of the fluoropolymers.

In an embodiment of the invention, the present invention provides fluoropolymers particles having enhanced performance: By eliminating the presence of non-fluorinated surfactants, the solvent washing technique improves the performance of the fluoropolymers. Surfactants residues can negatively impact various properties of the material, such as mechanical strength, thermal stability, and chemical resistance. The invention overcomes these limitations, allowing the fluoropolymers to exhibit its desired functional characteristics to a greater extent.

In an embodiment of the invention, the solvent washing method is simple and cost effective. The solvent washing technique offers a simple and cost-effective solution for surfactants removal from fluoropolymers. The process can be conducted at ambient temperature, eliminating the need for expensive equipment or complex procedures. It provides an efficient alternative to other methods that may involve extensive purification steps or specialized technologies.

In an embodiment of the invention, the proposed technique is scalable and can be easily integrated into existing fluoropolymers manufacturing processes. It can be applied to large-scale production without significant modifications, making it suitable for industrial implementation.

In an embodiment of the invention, the solvent washing technique reduces the reliance on non-fluorinated surfactants in fluoropolymers production, which may have environmental implications. By removing these surfactants, the invention contributes to the development of more sustainable and environmentally friendly manufacturing practices.

In an embodiment of the invention, the invention provides a solvent based washing technique instead of metal salts, the disclosed technique provides a solution that effectively removes non-fluorinated surfactants from fluoropolymers without introducing undesirable contaminants or interfering with the material's desired properties. Thus, the invention offers a promising approach to mitigate the limitations associated with metal salt-based surfactants removal methods and enables the fluoropolymers to retain its intended performance characteristics in various applications, including those requiring specific electrical properties.

The invention disclosed herein relates to a novel technique for the removal of non-fluorinated surfactants from fluoropolymers materials using solvent washing.

In an embodiment of the invention, the fluoropolymers particles thus produced have better mechanical strength, better thermal stability, and better chemical resistance. Thus, the fluoropolymers particles can manifest its desired functional characteristics to a greater extent, expanding its potential applications across various industries.

To better understand the working of the invention, reference is drawn to the following examples.

Example 1: Removal of Alkydiphenyloxide Disulfonate surfactants from polytetrafluoroethylene (PTFE) Powder.

100 liters of 14% w/v PTFE latex having 0.024 % (2400 ppm) of Alkydiphenyloxide Disulfonate surfactants coagulated with ammonium carbonate, stir for 10-35 minutes @ 160 rpm at 25-35 °C, collect the 14 kg PTFE powder by filtration. Add 2 vol of Solvent as mentioned in Table 1 to filtered PTFE powder, stir for 30-45 minutes @ 160 rpm at 25-35 °C, filter the PTFE powder, again 2.0 vol of solvent added to filtered power, stirred for 20-30 °C at 25-35 °C, filter the PTFE powder. This process repeats for 6-7 times. Thereafter, the Surfactants particles were removed from the fluoropolymers powder by filtration and was subjected to oven drying. The temperature for oven drying was 210-230 °C and the time period for oven drying was 10-14 hours. Thereafter, the fluoropolymers particles were analyzed to determine the residual amount of Alkydiphenyloxide Disulfonate surfactants which was summarized in Table 1.

Table 1
Solvent Before washing Amount of Residual Alkydiphenyloxide Disulfonate surfactants contained by the PTFE After washing Amount of Residual Alkydiphenyloxide Disulfonate surfactants contained by the PTFE. Powder Color after OD @ 220 degree
Methanol 2400 ppm 240 ppm Off White powder
Ethanol 2400 ppm 300 ppm Off White powder
Isopropyl alcohol 2400 ppm 65 ppm White powder
Butanol 2400 ppm 250 ppm Off White powder
Genagen NBP (Normal Name) 2400 ppm 1000 ppm Brown
Di propylene glycol DME 2400 ppm 900 ppm Brown
Monoethylene Glycol 2400 ppm 1000 ppm Brown
Polyethylene Glycol-200 2400 ppm 800 ppm Brown
Monoethylene glycol mono ethyl ether 2400 ppm 1150 ppm Dark Brown
Di ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
Tri ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
mono ethylene glycol mono methyl ether 2400 ppm 600 ppm Brown
Ethylene Carbonate 2400 ppm 1300 ppm Dark Brown
Isopropyl alcohol + water (60:40) 2400 ppm 100 ppm White powder
Methanol + water (60:40) 2400 ppm 240 ppm Off White powder
Ethanol + water (60:40) 2400 ppm 300 ppm Off White powder
Butanol + water (60:40) 2400 ppm 200 ppm Off White powder

Thus, it can be seen that whenever the solvent is one of methanol, ethanol, isopropyl alcohol, and butanol, either alone or in combination with water, the residual amount of Alkydiphenyloxide Disulfonate surfactants is substantially low, as evidenced by the color of the particles after oven drying at 220o C.

Example 2: Removal of sodium Alkylbenzene sulfonate surfactants from polytetrafluoroethylene (PTFE) Powder.

100 liters of 14% w/v PTFE latex having 0.024 % (2400 ppm) of sodium Alkylbenzene sulfonate surfactants coagulated with ammonium carbonate, stir for 10-35 minutes @ 160 rpm at 25-35 °C, collect the 14 kg PTFE powder by filtration. Add 2 vol of Solvents as mentioned in Table 2 to filtered PTFE powder, stir for 30-45 minutes @ 160 rpm at 25-35 °C, filter the PTFE powder, again 2.0 vol of solvent added to filtered power, stirred for 20-30 °C at 25-35 °C, filter the PTFE powder. This process repeats for 6-7 times. Thereafter, the Surfactants particles were removed from the fluoropolymers powder by filtration and was subjected to oven drying. The temperature for oven drying was 210-230 °C and the time period for oven drying was 10-14 hours. Thereafter, the fluoropolymers particles were analyzed to determine the residual amount of sodium Alkylbenzene sulfonate surfactants which was summarized in Table 2.

Table 2
Solvent Before washing Amount of Residual sodium Alkylbenzene sulfonate surfactants contained by the PTFE After washing Amount of Residual sodium Alkylbenzene sulfonate surfactants contained by the PTFE. Powder Color after OD @ 220 degree
Methanol 2400 ppm 350 ppm Off White powder
Ethanol 2400 ppm 300 ppm Off White powder
Isopropyl alcohol 2400 ppm 80 ppm White powder
Butanol 2400 ppm 200 ppm Off White powder
Genagen NBP 2400 ppm 800 ppm Brown
Di propylene glycol DME 2400 ppm 900 ppm Brown
Monoethylene Glycol 2400 ppm 850 ppm Brown
Polyethylene Glycol-200 2400 ppm 800 ppm Brown
Monoethylene glycol mono ethyl ether 2400 ppm 1150 ppm Dark Brown
Di ethylene glycol mono ethyl ether 2400 ppm 1000 ppm Brown
Tri ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
mono ethylene glycol mono methyl ether 2400 ppm 500 ppm Brown
Ethylene Carbonate 2400 ppm 1300 ppm Dark Brown
Isopropyl alcohol + water (60:40) 2400 ppm 100 ppm White powder
Methanol + water (60:40) 2400 ppm 350 ppm Off White powder
Ethanol + water (60:40) 2400 ppm 300 ppm Off White powder
Butanol + water (60:40) 2400 ppm 200 ppm Off White powder

Thus, it can be seen that whenever the solvent is one of methanol, ethanol, isopropyl alcohol, and butanol, either alone or in combination with water, the residual amount of Alkylbenzene sulfonate surfactants is substantially low, as evidenced by the color of the particles after oven drying at 220o C.

Example 3: Removal of Lauryl Imino Diacetic Acid (LIDA) from polytetrafluoroethylene (PTFE) Powder.

100 liters of 14% w/v PTFE latex having 0.024 % (2400 ppm) of Lauryl Imino Diacetic Acid (LIDA) surfactants coagulated with ammonium carbonate, stir for 10-35 minutes @ 160 rpm at 25-35 °C, collect the 14 kg PTFE powder by filtration. Add 2 vol of Solvents as provided in Table 3 to filtered PTFE powder, stir for 30-45 minutes @ 160 rpm at 25-35 °C, filter the PTFE powder, again 2.0 vol of solvent added to filtered power, stirred for 20-30 °C at 25-35 °C, filter the PTFE powder. This process repeats for 6-7 times. Thereafter, the Surfactants particles were removed from the fluoropolymers powder by filtration and was subjected to oven drying. The temperature for oven drying was 210-230 °C and the time period for oven drying was 10-14 hours. Thereafter, the fluoropolymers particles were analyzed to determine the residual amount of Lauryl Imino Diacetic Acid surfactants which was summarized in Table 3.

Table 3:

Solvent Before washing Amount of Residual Lauryl Imino Diacetic Acid contained by the PTFE After washing Amount of Residual Lauryl Imino Diacetic Acid contained by the PTFE. Powder Color after OD @ 220 degree
Methanol 2400 ppm 300 ppm Off White powder
Ethanol 2400 ppm 350 ppm Off White powder
Isopropyl alcohol 2400 ppm 110 ppm White powder
Butanol 2400 ppm 150 ppm White powder
Genagen NBP 2400 ppm 950 ppm Brown
Di propylene glycol DME 2400 ppm 950 ppm Brown
Monoethylene Glycol 2400 ppm 1100 ppm Brown
Polyethylene Glycol-200 2400 ppm 700 ppm Brown
Monoethylene glycol mono ethyl ether 2400 ppm 1200 ppm Dark Brown
Di ethylene glycol mono ethyl ether 2400 ppm 1050 ppm Brown
Tri ethylene glycol mono ethyl ether 2400 ppm 1200 ppm Dark Brown
mono ethylene glycol mono methyl ether 2400 ppm 600 ppm Brown
Ethylene Carbonate 2400 ppm 900 ppm Brown
Isopropyl alcohol + water (60:40) 2400 ppm 150 ppm White powder
Methanol + water (60:40) 2400 ppm 350 ppm Off White powder
Ethanol + water (60:40) 2400 ppm 300 ppm Off White powder
Butanol + water (60:40) 2400 ppm 250 ppm Off White powder

Thus, it can be seen that whenever the solvent is one of methanol, ethanol, isopropyl alcohol, and butanol, either alone or in combination with water, the residual amount of Lauryl Imino Diacetic Acid surfactants is substantially low, as evidenced by the color of the particles after oven drying at 220o C.

Example 4: Removal of ammonium Lauryl sulphate (ALS) from polytetrafluoroethylene (PTFE) Powder.

100 liters of 14% w/v PTFE latex having 0.024 % (2400 ppm) of ammonium Lauryl sulphate (ALS) surfactants coagulated with ammonium carbonate, stir for 10-35 minutes @ 160 rpm at 25-35 °C, collect the 14 kg PTFE powder by filtration. Add 2 vol of Solvents as provided in Table 4 to filtered PTFE powder, stir for 30-45 minutes @ 160 rpm at 25-35 °C, filter the PTFE powder, again 2.0 vol of solvent added to filtered power, stirred for 20-30 °C at 25-35 °C, filter the PTFE powder. This process repeats for 6-7 times. Thereafter, the Surfactants particles were removed from the fluoropolymers powder by filtration and was subjected to oven drying. The temperature for oven drying was 210-230 °C and the time period for oven drying was 10-14 hours. Thereafter, the fluoropolymers particles were analyzed to determine the residual amount of ammonium Lauryl sulphate surfactants which was summarized in Table 4.

Table 4:
Solvent Before washing Amount of Residual ammonium Lauryl sulphate contained by the PTFE After washing Amount of Residual ammonium Lauryl sulphate contained by the PTFE. Powder Color after OD @ 220 degree
Methanol 2400 ppm 250 ppm Off White powder
Ethanol 2400 ppm 250 ppm Off White powder
Isopropyl alcohol 2400 ppm 100 ppm White powder
Butanol 2400 ppm 300 ppm Off White Powder
Genagen NBP 2400 ppm 1100 ppm Brown
Di propylene glycol DME 2400 ppm 800 ppm Brown
Monoethylene Glycol 2400 ppm 1100 ppm Brown
Polyethylene Glycol-200 2400 ppm 950 ppm Brown
Monoethylene glycol mono ethyl ether 2400 ppm 1150 ppm Brown
Di ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
Tri ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
mono ethylene glycol mono methyl ether 2400 ppm 500 ppm Brown
Ethylene Carbonate 2400 ppm 1200 ppm Brown
Isopropyl alcohol + water (60:40) 2400 ppm 150 ppm White powder
Methanol + water (60:40) 2400 ppm 200 ppm Off White powder
Ethanol + water (60:40) 2400 ppm 150 ppm White powder
Butanol + water (60:40) 2400 ppm 200 ppm Off White

Thus, it can be seen that whenever the solvent is one of methanol, ethanol, isopropyl alcohol, and butanol, either alone or in combination with water, the residual amount of ammonium Lauryl sulphate surfactants is substantially low, as evidenced by the color of the particles after oven drying at 220o C.

Example 5: Removal of Sodium Lauryl sulphate from polytetrafluoroethylene (PTFE) Powder.

100 liters of 14% w/v PTFE latex having 0.024 % (2400 ppm) of Sodium Lauryl sulphate (SLS) surfactants coagulated with ammonium carbonate, stir for 10-35 minutes @ 160 rpm at 25-35 °C, collect the 14 kg PTFE powder by filtration. Add 2 vol of Solvents as provided in Table 5 to filtered PTFE powder, stir for 30-45 minutes @ 160 rpm at 25-35 °C, filter the PTFE powder, again 2.0 vol of solvent added to filtered power, stirred for 20-30 °C at 25-35 °C, filter the PTFE powder. This process repeats for 6-7 times. Thereafter, the Surfactants particles were removed from the fluoropolymers powder by filtration and was subjected to oven drying. The temperature for oven drying was 210-230 °C and the time period for oven drying was 10-14 hours. Thereafter, the fluoropolymers particles were analyzed to determine the residual amount of Sodium Lauryl sulphate (SLS) surfactants which was summarized in Table 5.

Table 5:
Solvent Before washing Amount of Residual Sodium Lauryl sulphate contained by the PTFE After washing Amount of Residual Sodium Lauryl sulphate contained by the PTFE. Powder Color after OD @ 220 degree
Methanol 2400 ppm 300 ppm Off White powder
Ethanol 2400 ppm 400 ppm Off White powder
Isopropyl alcohol 2400 ppm 150 ppm White powder
Butanol 2400 ppm 400 ppm Off White powder
Genagen NBP 2400 ppm 1000 ppm Brown
Di propylene glycol DME 2400 ppm 950 ppm Brown
Monoethylene Glycol 2400 ppm 1000 ppm Brown
Polyethylene Glycol-200 2400 ppm 750 ppm Brown
Monoethylene glycol mono ethyl ether 2400 ppm 950 ppm Brown
Di ethylene glycol mono ethyl ether 2400 ppm 1200 ppm Dark Brown
Tri ethylene glycol mono ethyl ether 2400 ppm 1100 ppm Brown
mono ethylene glycol mono methyl ether 2400 ppm 400 ppm Off White
Ethylene Carbonate 2400 ppm 1300 ppm Dark Brown
Isopropyl alcohol + water (60:40) 2400 ppm 100 ppm White powder
Methanol + water (60:40) 2400 ppm 250 ppm Off White powder
Ethanol + water (60:40) 2400 ppm 300 ppm Off White powder
Butanol + water (60:40) 2400 ppm 250 ppm Off White powder

Thus, it can be seen that whenever the solvent is one of methanol, ethanol, isopropyl alcohol, and butanol, either alone or in combination with water, the residual amount of Sodium Lauryl sulphate surfactants is substantially low, as evidenced by the color of the particles after oven drying at 220o C.

It may be noted that the residual amount of the surfactants Alkydiphenyloxide Disulfonate in Example 1, Sodium Alkylbenzene Sulfonate in Example 2, Lauryl Imino Diacetic Acid in Example 3, Ammonium Lauryl Sulphate in Example 4, and Sodium Lauryl Sulphate in Example 5, were determined using HPLC chromatographic technique with the following conditions:

HPLC chromatographic condition:
Column: Zorbex Eclips C18, 4.6X 250
Flow: 1.0 ml/minutes
Detector: UV, wavelength 254 nm
Column Oven temperature: 35 C
Injection Volume: 10 µl
Run time: 15 minutes
Mobile phase:
Isocratic method:
Mobile phase A: 90 ml water and 10 methanol + 0.192 g ammonium acetate PH maintain through formic acid 3.5-4.5
Mobile phase B: 100 % methanol
Diluent: methanol + water ratio: 60:40
Time Mobile phase A Mobile phase b
0 20 80
1 20 80
15 20 80
18 20 80
20 20 80

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced.
,CLAIMS:WE CLAIM:

1. A process for removing non-fluorinated surfactants from fluoropolymers particles, the process comprising subjecting the fluoropolymers particles containing non-fluorinated surfactants to at least one stage of washing with one or more washing solvent.

2. The process as claimed in claim 1, wherein the washing solvent comprises at least one organic solvent optionally along with water.

3. The process as claimed in claim 2, wherein the at least one organic solvent comprises an alcohol optionally along with water.

4. The process as claimed in claim 3, wherein the alcohol is selected from a group comprising methanol, ethanol, isopropyl alcohol, butanol, optionally along with water.

5. The process as claimed in claim 1, wherein the washing is performed at ambient temperature to a temperature which is less than boiling point of the washing solvent.

6. The process as claimed in claim 1, wherein the washing is performed in a plurality of stages including a first stage washing and at least one further stage of washing.

7. The process as claimed in claim 1, wherein at least one of:
the first stage washing is performed with a first stage washing solvent and the second stage washing is performed with a second stage washing solvent, wherein the first stage washing solvent is same as that of the second stage washing solvent.
the first stage washing is performed with a first stage washing solvent and the second stage washing is performed with a second stage washing solvent, wherein the first stage washing solvent is different as that of the second stage washing solvent.

8. The process as claimed in claim 1, wherein the fluoropolymers particles are immersed in the washing solvent and agitated to facilitate the removal of surfactants, wherein agitation comprises at least one of stirring, ultrasonic bath, or a mechanical means.

9. The process as claimed in claim 1, wherein a duration and intensity of the washing process depend on factors selected from a type of surfactants, a concentration of the surfactants, a particle size of the fluoropolymers particles, and a desired level of surfactants removal.

10. The process as claimed in claim 1, wherein after the washing process, the fluoropolymers particles are separated from the washing medium again to remove any residual surfactants, wherein separation comprises filtration or centrifugation.