Title of Invention

"A PROCESS FOR THE PREPARATION OF NOVEL POLYESTERAMIDE MEMBRANES"

Abstract

A process for preparation of novel polyesteramide membranes: This invention provides a process for the preparation of phthalein based polyesteramide membranes. More particularly it provides asymmetric polyester and polyesteramide based thin-film-composite membranes synthesized by reacting a phthalein containing diol with/without diamine in aqueous phase in presence of a phase transfer catalyst, followed by reacting polyacyl halide in organic phase by interfacial reaction. The resultant membrane composite may be used in separation processes such as nanofiltration or ultrafiltration.

Full Text

This invention relates to a process for the preparation of novel polyesteramide membranes. This invention particularly relates to a process for the preparation of phenolphthalein based polyesteramide membranes. More particularly it relates to novel asymmetric polyester and polyesteramide based thin-film-composite membranes synthesized by reacting a phthalein containing diol with/without diamine in aqueous phase with polyacyl halide in organic phase by interfacial reaction. The resultant membrane composite may be used in separation processes such as nanofiltration or ultrafiltration. In the prior art, thin film composite membranes have been prepared from a variety of materials. These films are formed on a porous backing material. The membranes are generally prepared by the process mentioned in US Patent 4,277,344 (J. E. Cadotte) as suitable for reverse osmosis. The process involves coating an aqueous solution of diamine on a porous support membrane and removing the excess solution. It is then coated with an organic solution of polyacyl halide. The interfacial polymerization condensation product is formed within and/or on a porous support. Kim et. al. (1997) described a polyester based thin film composite (TFC) membrane wherein the polysulphone (PSF) support is cor.ted with either an aromatic polyester or a copolymer of an aromatic polyester and an aromatic polyamide. Aromatic polyester based membranes were formed by the interfacial reaction between 4,4'-dihydroxybiphenyl and trimesoyl chloride (TMC). Coploymer membranes were made by the interfacial reaction of an aqueous solution containing both 4,4-dihydroxybiphenyl and m-phenylene diamine with TMC in n-hexane. These membranes exhibited NaCl rejection of 96.5% at 0.34 MPa using a 5000 ppm synthetic brine solution. Ultrafiltration membranes are not able to discriminate efficiently between salt and low molecular weight organic molecules such as sucrose, whereas reverse-osmosis membranes reject both sucrose and salt. It is desirable to have membranes with low monovalent salt rejection combined with higher rejections for organic solutes (mol. wt.> 300 gmol"1) and multivalent ions. These nanofiltration membranes can be useful for treatment of water and hazardous wastes, separation processes in food, beverage, pulp and paper industries, and recovery of organic and inorganic material from chemical processes. The membrane should be resistant to microbial and chemical attack. Reported polyamide membranes contain -MH groups which show susceptibility to chlorine attack. Membranes are required in which separation and mechanical characteristics should not change after a long term operation. Another important feature is that a membrane should possess high flux. The main object of the present invention is to provide a process for preparation of novel polyesteramide membranes. The present invention relates to high flux semipermeable nanofiltration membrane based on polyester or polyesteramide coatings with cut-off of higher molecular weight species (>300 gmor1) and suitable for separation of divalent salts from monovalent salts. Accordingly the present invention provides a process for preparation of novel polyesteramide membranes which comprises preparing an aqueous solution of a phthaline having diol group of general formula I as shown in figure of the drawing accompanying this specification, wherein R^ R2 = H, CH3 , C2H5, C6H5) with or without a diamine having formula II of the drawing accompanying this specification , dipping an organic support selected from the group comprising polysulfone , polyphenylene ether , polyvinylidine fluoride or polyethersulphone in the above solution in presence of a phase transfer catalyst and 2.0 to 2.5 moles of alkali hydroxide such as herein described wherein the ratio of the catalyst is in the range of 0.01 to 0.03 mole with respect to phthalein , for a period of 3 minutes to get a thin membrane , draining the excess solution , followed by dipping the obtained membrane for a period ranging between 1 to 3 minutes in a solution of polyacyl halide having formula III, wherein solvent used for preparing the said solution of polyacyl halide is non-polar solvent selected from hexane or petroleum ether, at a temperature range 25° to 35° C and drying the membrane at a temperature ranging between 50° to 70°C for 5 to 10 minutes, to obtain the novel polyesteramide membrane. In one of the embodiments of the present invention the phthalein containing diol may be phenolphthalein or phenolphthalein substituted with alkyl such as CHa or C2H5 or aryl substituent such as C6H5. In another embodiment the diamine may be p-phenylenediamine, m-phenylenediamine or o-phenylenediamine. In yet another embodiment the polyacyl halide may be terephthaloyl chloride, isophthaloyl chloride or trimesoyl chloride. In still another embodiment the solvent used for preparing the solution of polyacyl halide may be non-polar solvents such as n-hexane or petroleum ether. In still another embodiment the support used may be based on polysulfone, polyphenylene ether, polyvinylidine fluoride or polyethersulphone. In still another embodiment drying of the membrane may be carried out at a temperature ranging between 50 to 70°C for 5 to 10 minutes to obtain the product. In still another embodiment aqueous solution of phenolphthalein may be prepared in the presence of alkali such as NaOH or KOH and phase transfer catalyst such as tetrabutylammonium bromide or benzyl triethylammonium chloride. The membranes can be used for separation of monovalent ions from divalent ions and higher organics (>300 gmol"1). Compared to previously known polyamide membranes, the polyesteramides and polyester based membranes of this invention are more resistant to oxidative degradation. Also the use of diols with bulky cardo groups as shown in figure I gives membranes with high flux. The process of the present invention is described hereinbelow with reference to examples which are illustrative only and should not be construed to limit the scope of the present invention in any manner. Example 1 A thin film composite membrane was prepared by contacting a porous polysulfone membrane (water permeability of 30-40 1pm , 70-80 % Bovine Serum Albumin (BSA) rejection at 0.7 kg/cm2) with an aqueous solution containing 2% w/w of phenolphthalein, sodium hydroxide (2.2 moles with respect to phenolphthalein), and tetrabutylammonium bromide (0.025 mole with respect to phenolphthalein) for 3 minutes followed by draining off excess solution. The film was then contacted with an organic phase consisting of 0.15% (w/v) trimesoyl chloride in petroleum ether for 1 minute . Following this, the membrane was washed with saturated sodium bicarbonate solution to remove excess acid and washed with water. Thereafter the membrane was heated at 50° C for 5 minutes. Example 2 The membrane thus prepared in Example I was placed in a membrane testing cell and tested with a solution containing sodium chloride (2000 ppm) and sucrose (5% w/v) with the thin film on the supporting membrane facing the flow. The feed flow rate was 1 litre/ minute and feed pressure was 400 psi. Temperature was maintained at room temperature. The flux in gallons/ft2/day(gfd) and % rejection were determined as shown below: Table 1 (Table Removed) Example 3 A thin film composite nanofiltration membrane was prepared by contacting polysulfone support with an 2% w/w aqueous solution containing phenolphthalein and m-phenylenediamine in the molar ratio 7:3, sodium hydroxide (2.2 moles with respect to phenolphthalein), and tetrabutylammonium bromide (0.025 mole with respect to phenolphthalein) for 3 minutes. Excess solution was drained off. The film was then brought into contact with an organic solution of 0.15% (w/v) trimesoyl chloride in petroleum ether for 1 minute. The membrane was washed with sodium bicarbonate solution. The membrane was then heated at 50° C for 5 minutes. The membrane was tested for flux (gfd), and sucrose, sodium chloride rejection (%) were determined in a manner similar to that set forth in Example 2. Table 2 (Table Removed) Example 4 A thin film composite nanofiltration membrane was prepared by contacting polysulfone membrane with an 2% w/w aqueous solution containing phenolphthalein and m-phenylenediamine in the molar ratio 1:1, sodium hydroxide (2.2 moles with respect to phenolphthalein), and tetrabutylammonium bromide (0.025 mole with respect to phenolphthalein) for 3 minutes. Excess solution was drained off. The film was then brought into contact with an organic solution of 0.15% (w/v) trimesoyl chloride in petroleum ether for 1 minute. The membrane was washed with sodium bicarbonate solution and washed with water. The membrane was then heated at 50° C for 5 minutes. The membrane was tested for flux (gfd) and (%) rejection of sodium chloride and sucrose were determined in a manner similar to that set forth in Example 2. Table 3 (Table Removed) Example 5 Phenolphthalein based membranes based on reaction of phenolphthalein (Phe) with trimesoyl chloride (TMC) as in example 1, Phenolphthalein (Phe) and m-phenylenediamine (MPDA) (7:3) with trimesoyl chloride (TMC) as in example 3, and phenolphthalein (Phe) and m-phenylenediamine (MPDA) (1:1) with trimesoyl chloride (TMC) as in example 4 were tested for NaCl, Na2SO4and CaCl2 rejection (%). Membranes were tested with NaCl, Na2SO4, and CaCl2 solutions (5000 ppm) each and flux (gfd) was determined. The flow rate was 1 litre/minute and feed pressure was 400 psi. The results are shown below. Table 4 (Table Removed) We Claim: 1. A process for preparation of novel polyesteramide membranes which comprises preparing an aqueous solution of a phthaline having diol group of general formula as shown in figure 1 of the drawing accompanying this specification, wherein R1, R2 = H, CH3 , C2H5, C6H5, with or without a diamine having formula as shown in figure 2 of the drawing accompanying this specification , dipping an organic support selected from the group comprising polysulfone , polyphenylene ether , polyvinylidine fluoride or polyethersulphone in the above solution in presence of a phase transfer catalyst and 2.0 to 2.5 moles of alkali hydroxide such as herein described wherein the ratio of the catalyst is in the range of 0.01 to 0.03 mole with respect to phthalein , for a period of 3 minutes to get a thin membrane , draining the excess solution , followed by dipping the obtained membrane for a period ranging between 1 to 3 minutes solution of polyacyl halide having formula as shown in figure 3 , wherein solvent used for preparing the said solution of polyacyl halide is non-polar solvent selected from hexane or petroleum ether, at a temperature range 25° to 35° C and drying the membrane at a temperature ranging between 50° to 70°C for 5 to 10 minutes, to obtain the novel polyesteramide membrane. 2. A process as claimed in claim 1 wherein the phthalein having diol group is selected from phenolphthalein or phenolphthalein substituted with alkyl selected from CH3 or C2H5 or aryl substituent selected from C6H5 3. A process as claimed in claims 1 to 2 wherein the diamine is selected from p - phenylenediamine, m - phenylenediamine or o- phenylenediamine. 4. A process as claimed in claims 1 to 3 wherein the polyacyl halide used is selected from isophthaloyl chloride, terephthaloyl chloride or trimesoyl chloride. 5. A process as claimed in claims 1 to 5 wherein phase transfer catalyst used is selected from tetrabutylammoniumbromide or benzyl triethylammonium chloride. 6. A process as claimed in claims 1 to 6 wherein the alkali hydroxide used is selected from NaOH or KOH. 7. A process for the preparation of novel polyesteramide membranes as substantially described hereinbefore with reference to examples contained hereinbefore and drawing accompanying this specification.

Documents:

88-del-2000-abstract.pdf

88-del-2000-claims.pdf

88-del-2000-correspondence-others.pdf

88-del-2000-correspondence-po.pdf

88-del-2000-description (complete).pdf

88-del-2000-drawings.pdf

88-del-2000-form-1.pdf

88-del-2000-form-19.pdf

88-del-2000-form-2.pdf

88-del-2000-form-3.pdf