CN115702268A - Sulfonated Polystyrene Nonwovens - Google Patents

Abstract

Sulfonated polystyrene fibers having an average diameter from 450nm to 2000nm and a capacity from 0.05meq/g to 2.0 meq/g.

Description

Sulfonated Polystyrene Nonwovens

Background technique

The present invention generally relates to sulfonated polystyrene nonwovens and methods of making the same.

The functionalization of polystyrene fibers by sulfonation is known. For example, Nitanan Todsapon, Tropical Journal of Pharmaceutical Research, 2014, 13(2), 191-197 discloses sulfonation of polystyrene fibers for use in controlled release drug delivery. However, this reference does not disclose sulfonated fibers that can be used to form nonwoven fabric mats for metal ion removal.

Contents of the invention

The present invention relates to a sulfonated polystyrene nonwoven having an average diameter of from 450 nm to 2000 nm and a capacity of from 0.05 meq/g to 2.0 meq/g.

Detailed ways

All percentages are by weight (wt %) and all temperatures are in °C unless otherwise indicated. Means are arithmetic means unless otherwise indicated. All manipulations were performed at room temperature (from 18°C to 25°C) unless otherwise stated. Capacity was measured by first exchanging the acidic sites with 4.0M aqueous _NaNO3 and then titrating the resulting acidified solution with 0.1M NaOH using a Mettler Toledo T90 automatic titrator, or calculated by mass balance of the sulfonation reaction.

Preferably, the polystyrene used to make the fibers is high heat crystalline polystyrene, preferably high heat crystalline polystyrene acceptable in pharmaceutical processing.

Preferably, the average diameter of the fibers is at least 480 nm, preferably at least 500 nm, preferably at least 520 nm; preferably not greater than 1750 nm, preferably not greater than 1500 nm, preferably not greater than 1200 nm, preferably not greater than 1000 nm, preferably not greater than 800 nm, preferably not greater than 750 nm, preferably Not greater than 700nm.

Preferably, the fibers are produced by hybrid membrane technology (HMT). This technique is eg described in US7618579. Preferably, the fibers are made from a solution of polystyrene in an aprotic solvent. Preferred solvents are those capable of dissolving polystyrene at room temperature, and include, for example, N,N-dimethylformamide (DMF), dimethylacetamide, methyl ethyl ketone, dichloromethane, and toluene. Preferably, the solution is processed by electroblowing under conditions that can be adjusted by known techniques to alter the fiber properties to produce a nonwoven fibrous mat. Preferably, the concentration of polystyrene in the solvent is from 15 to 30 wt%, preferably 18 to 27 wt%. Preferably, the solution is processed on a single or multi-hole electroblowing unit. Preferably, the fibers are spun onto rotating drums.

Preferably, the fibers are treated with a crosslinking agent capable of crosslinking polystyrene prior to sulfonation. Preferred crosslinkers are aldehydes and dialdehydes, preferably formaldehyde/sulfuric acid or glutaraldehyde/sulfuric acid, preferably formaldehyde/sulfuric acid. Preferably at least 90 wt%, preferably at least 94 wt%, preferably at least 96 wt%, preferably at least 98 wt% of the polystyrene molecules contain crosslinks. The wt% of cross-linked polystyrene molecules can be determined by immersing the fibers in methylene chloride and weighing the soluble material, which is the cross-linked polystyrene molecules. Preferably, the fibers are treated with the crosslinking agent at a temperature of from 20°C to 110°C, preferably at least 45°C, preferably at least 55°C; preferably not greater than 100°C, preferably not greater than 95°C. Both time and temperature can be adjusted to produce the desired degree of crosslinking, however typical times preferably range from 30 minutes to 6 hours, preferably 1 to 4 hours. Preferably, the treatment with the crosslinking agent is carried out without catalyst under the conditions given above. If a catalyst (eg _Ag2SO4 ) _is used, the time at a given temperature will be much shorter and can be adjusted to provide the desired characteristics.

Preferably, the fibers resulting from treatment with a crosslinking agent are sulphonated by contacting them with a sulphonating agent, preferably at least 80% by weight (the remainder being at least 95% water), preferably at least 90% by weight, preferably at least 94% by weight. %. Sulfonating agents are reagents capable of sulfonating aromatic rings. Preferred sulfonating agents include sulfuric acid, chlorosulfonic acid and oleum; sulfuric acid is preferred. Preferably, sulfonation is carried out at a temperature of from 30°C to 160°C, preferably at least 50°C, preferably at least 70°C: preferably not more than 120°C, preferably not more than 110°C. Both time and temperature can be adjusted to produce the desired capacity, however typical times preferably range from 30 minutes to 6 hours, preferably 1 to 4 hours. Preferably, the fibers are contacted with concentrated sulfuric acid for a time sufficient to produce sulfonated polystyrene fibers having a capacity of from 0.4 meq/g to 2.0 meq/g, or any desired range subsumed therein. Preferably, the sulfonation is carried out without catalyst under the conditions given above. If a catalyst is used (eg _Ag2SO4 , acetic anhydride, trifluoroacetic anhydride), the _time at a given temperature will be much shorter and can be adjusted to provide the desired characteristics.

Preferably, the capacity of the sulfonated nonwoven is at least 0.2 meq/g, preferably at least 0.4 meq/g, preferably at least 0.45 meq/g, preferably at least 0.50 meq/g, preferably at least 0.55 meq/g, preferably at least 0.60 meq/g g, preferably at least 0.65meq/g; preferably not more than 1.8meq/g, preferably not more than 1.6meq/g, preferably not more than 1.5meq/g, preferably not more than 1.4meq/g, preferably not more than 1.3meq/g, preferably Not more than 1.2 meq/g, preferably not more than 1.1 meq/g.

example

In these instances, numbers followed by "C" (eg, 30C) are understood to be temperatures in °C.

Fiber preparation:

Polystyrene (PS) solutions were prepared using PS 685D grade polystyrene obtained from Aldrich. The solvent is dimethylformamide (DMF). Solutions with concentrations ranging from 21 to 25% by weight were detected. The sample solution was spun on a single hole electroblowing unit. The fibers were spun onto a rotating drum and the sample nonwoven was collected from the drum after the run. A typical sample was prepared from a 21 wt% solution with 0.1 wt% salt added on a solution basis. Typical basis weights vary from 60 to 100 gsm. The typical distance between the spin pack and the drum collector is 33 cm. Typical applied voltage is 100kV. Typical spinning chamber temperature is 30C. Typical sample mean flow pour is 1 micron.

Treatment with sulfuric acid and formalin

Nanofibrous membranes (average fiber diameter 1700 nm) were immersed in a bath containing a mixture of reagent grade concentrated sulfuric acid and formalin (37 wt% formaldehyde) (typically 90:10 sulfuric acid:formalin (V/V)) . Typically the bath is heated to 7OC for 3h with gentle shaking at 60-120rpm on an orbital shaker. Next, the bath was cooled to <50C, the reaction fluid was decanted, and the membrane was slowly hydrated with 50% sulfuric acid and gradually diluted to pure DI water.

Sulfonated

The sulfuric acid/formalin treated nanofibrous membrane was immersed in concentrated sulfuric acid (typically 96%) and then heated to 90C for 0 to 8 h while shaking on a rail. Next, the bath was cooled to <50C, the reaction fluid was decanted, and the membrane was slowly hydrated with 50% sulfuric acid and then gradually diluted to pure DI water.

1. Conditions for sulfuric acid/formalin treatment in top chamber, conditions for sulfonation in bottom chamber.

2. The results for the last two rows are obtained from fiber mats that have been compressed, which typically significantly degrades the properties measured here. However, the achievement of acceptable properties indicated that a felt with a capacity of 0.49 or even lower was acceptable.

Metal residues were washed from the following PS membranes and AmberTec ^™ UP1400 ion exchange resin:

47mm disc nonwoven PS membrane (average fiber diameter: 1718nm, capacity: 0.67meq/g), UP1400 resin (strongly acidic cation exchange) (d=4em, h=6cm)

Reagent: Low metal level HCl

Volumetric flow rate: 6.9 ml/min for the membrane and 5 ml/min for the ion exchange resin.

The metal content of the nonwoven PS film decreased to 9.76 ppb in 210 minutes, at which time the resin still had a metal content of 20.26 ppb.

After the HCl wash, the medium was further rinsed with DI water to at least pH >5.

Metals were removed from spiked solvents with PS membranes and ion exchange resins.

Propylene glycol methyl ether acetate (PGMEA) doped with 100 ppb each of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, K, Na, Sn, Ti and Zn was passed through a UP1400 resin filled 4cm x 6cm (D x h) column and 47mm PS disc washed with HCl and DI water as described above. Volumetric flow rate: 6.9 ml/min for the membrane and 5 ml/min for the ion exchange resin. The residence time in the resin bed was 15 min and in the PS membrane disc was 3.5 seconds. The total metals content in the initial resin bed effluent was 512.7 ppb and the total metals in the membrane disc effluent was 823.4 ppb. The membrane discs removed 96% of the initial metal at a first residence time of 3.5 seconds, while the ion exchange membrane removed 94% of the initial metal at a first residence time of 15 min.

Claims (10)

Claims 1. A sulfonated polystyrene nonwoven comprising fibers having an average diameter of from 450 nm to 2000 nm and a capacity of from 0.05 meq/g to 2.0 meq/g. 2. The nonwoven according to claim 1, which has a capacity of from 0.4 to 1.5 meq/g. 3. The nonwoven of claim 2, wherein the fibers have an average diameter of from 450 nm to 1750 nm. 4. The nonwoven of claim 3, wherein at least 90% by weight of the polystyrene molecules contain crosslinks. 5. A method for producing a sulfonated polystyrene nonwoven; said method comprising the steps of: a) providing polystyrene nonwoven fibers having an average diameter from 450nm to 2000nm; b) contacting said polystyrene fibers with a crosslinking agent at a temperature from 30°C to 150°C; and c) contacting the product of step b) with at least 90% by weight of sulfuric acid at a temperature from 30°C to 150°C. 6. The method of claim 5, wherein the fibers have an average diameter of from 450 nm to 1750 nm. 7. The method of claim 6, wherein step c) is performed for a time sufficient to produce sulfonated polystyrene fibers having a capacity of from 0.4 meq/g to 2.0 meq/g. 8. The method of claim 7, wherein the crosslinking agent is sulfuric acid and an aldehyde or dialdehyde, and wherein step b) is carried out for a time sufficient to produce sulfonated polystyrene fibers, wherein at least 90% by weight of the The fibers contain crosslinks. 9. The method of claim 8, wherein step c) is performed for a time sufficient to produce sulfonated polystyrene fibers having a capacity of from 0.4 meq/g to 1.5 meq/g. 10. A method for removing metals from a liquid, the method comprising contacting the liquid with a polystyrene nonwoven comprising an average diameter of from 450 nm to 2000 nm and a Fibers with a capacity of 0.05 meq/g to 2.0 meq/g.