Chromatography medium

1. A process for preparing a functionalised polymeric chromatography medium, which process comprises

(I) providing a stack of two or more non-woven sheets stacked one on top of the other, each said sheet consisting essentially of one or more polymer nanofibres,

(II) simultaneously heating and pressing the stack of sheets to fuse points of contact between the nanofibres of adjacent sheets to form a pressed and heated product, and

(III) contacting the pressed and heated product of step (II) in a batchwise fashion in a plurality of batches with a respective batch reagent associated with each batch of the plurality of batches, said respective batch reagent being same or different in the plurality of batches, to cause the respective batch reagent to be partially retained within the polymer nanofibers and generate the functionalized polymeric chromatography medium,

wherein a pressure of between 1 kPa to 500 kPa is applied to the stack of sheets in step (II) and wherein the stack of sheets is heated at a temperature between 190° and 220° in step (II), and

wherein the pressed and heated product is treated to deprotect or activate any functional groups on the one or more polymer nanofibers prior to the step of contacting with the respective batch reagent.

2. The process according to claim 1 , wherein between two and thirty said sheets are stacked one on top of the other in step (I); or wherein between five and twenty five said sheets are stacked one on top of the other in step (I).

3. The process according to claim 1 , wherein each non woven sheet consists of a single polymer nanofibre, or comprises 2, 3, 4, 5, 6, 7, 8, 9 or 10 polymer nanofibres.

4. The process according to claim 1 , wherein the polymer is selected from the group consisting of cellulose, cellulose acetate, polysulfones, polyamides, polyacrylic acid, polymethacrylic acid, polyacrylonitrile, polystyrene, polyethylene oxide, and mixtures thereof.

5. The process according to claim 1 , wherein the said nanofibres are cellulose acetate nanofibres, and the pressed and heated product is treated between steps (II) and (III) to convert the cellulose acetate to cellulose.

6. The process according to claim 1 , wherein the stack of sheets is heated at a temperature between 200° and 220° C. in step (II).

7. The process according to claim 1 , each step of contacting with the respective batch reagent in a respective batch of the plurality of batches comprising (a) contacting with the respective batch reagent, (b) isolating the product of step (a) from the reagent, (c) treating the product of step (b) with aqueous alkali, and (d) washing the product of step (c) with water.

8. The process according to claim 1 , wherein the plurality of batches comprises between two and four batches.

9. The process according to claim 1 , step (III) comprising placing the pressed and heated product of step (II) in a holder, and (IV) causing the respective batch reagent to flow through the holder so that the respective batch reagent flows in contact with the pressed and heated product of step (II) which functionalises the product of step (II) as a chromatography medium.

10. The process according to claim 9 , wherein step (IV) comprises

causing the respective batch reagent to flow through the holder under pressure; and/or

causing the respective batch reagent to flow through the holder using a pump; and/or

causing the respective batch reagent to flow through the holder in a cyclical manner; and/or

causing the respective batch reagent to flow through the holder for a period of time from 1 to 20 minutes.

11. The process according to claim 1 , wherein the respective batch reagent functionalises the pressed and heated product so that the resultant functionalised chromatography medium is suitable for use in a chromatography method chosen from the group consisting of ion exchange, affinity capture, hydrophobic interaction and mixed mode methods.

12. The process according to claim 1 , wherein one or more polymer nanofibers comprise hydroxyl, amino, or carboxy groups, and wherein the respective batch reagent functionalises the hydroxyl, amino or carboxylic acid groups.

13. The process according to claim 1 , wherein

between five and twenty five said sheets are stacked one on top of the other in step (I), each sheet comprising 1, 2 or 3 polymer nanofibres, and each sheet having a thickness of from 5 to 40 μm, and/or

in step (II) a temperature below the melting point of the polymer at between 190° and 220° and a pressure of from 1 kPa to 500 kPa are applied for 1 to 120 minutes so as to obtain a pressed and heated product having an average density of 250 to 750 kg/m 3 and a thickness of 0.05 to 10 mm.

14. The process according to claim 1 , wherein

between five and twenty said sheets are stacked one on top of the other in step (I), each sheet consisting of a single polymer nanofibre, and each sheet having a thickness of from 5 to 120 μm and an area density of from 1 to 40 g/m 2 , and/or

in step (II) a temperature below the melting point of the polymer and a pressure of from 1 to 500 kPa are applied for 1 to 30 minutes so as to obtain a pressed and heated product having an average density of 200 to 1000 kg/m 3 and a thickness of 0.05 to 10 mm.