REVERSE-PHASE POLYMERISATION PROCESS INCORPORATING A MICROFLUIDIC DEVICE

Abstract

Disclosed herein is a polymerization process involving the steps of generating monomer micro-volumes in a microfluidic device, feeding the monomer micro-volumes through the at least one first microfluidic channel towards a monomer feed point at which the monomer micro-volumes enter into or onto a volume of a non-aqueous liquid and form aqueous monomer droplets, allowing the aqueous monomer droplets to flow towards a polymer bead discharge point, initiating polymerisation of the aqueous monomer droplets to form polymerising beads, removing a suspension of the polymer beads in the non-aqueous liquid from the vessel at the polymer bead discharge point, and recovering water soluble or water swellable polymer beads from the suspension. The present disclosure also includes an apparatus for performing the polymerization process and water soluble or water swellable polymer beads obtained by the polymerization process.

Claims

1. A reverse-phase suspension polymerisation process for the manufacture of polymer beads comprising forming aqueous monomer droplets of an aqueous solution comprising water-soluble ethylenically unsaturated monomer or monomer blend and polymerising the monomer or monomer blend, to form polymer beads while suspended in a non-aqueous liquid, and recovering polymer beads, the process comprising: providing in a vessel a volume of non-aqueous liquid wherein the volume of non-aqueous liquid extends between at least one polymer bead discharge point and at least one monomer feed point, generating monomer micro-volumes in at least one microfluidic device, said monomer micro-volumes being separated by non-aqueous liquid in at least one first microfluidic channel, feeding the monomer micro-volumes through the at least one first microfluidic channel towards the at least one monomer feed point at which the monomer micro-volumes enter into or onto the volume of non-aqueous liquid and form aqueous monomer droplets, allowing the aqueous monomer droplets to flow towards the polymer bead discharge point, initiating polymerisation of the aqueous monomer droplets to form polymerising beads, wherein the polymerising beads have formed polymer beads when they reach the polymer bead discharge point, removing a suspension of the polymer beads in non-aqueous liquid from the vessel at the polymer bead discharge point, and recovering water soluble or water swellable polymer beads from the suspension, wherein: the at least one microfluidic device (5) comprises at least one second microfluidic channel conveying non-aqueous liquid; at least one third microfluidic channel conveying the aqueous solution comprising water soluble ethylenically unsaturated monomer or monomer blend; and at least one intersection between the at least one third microfluidic channel and the at least one second microfluidic channel; the at least one first microfluidic channel is in communication with the at least one intersection, and the monomer micro volumes are formed at the at least one intersection before being fed through the at least one first microfluidic channel towards the monomer feed point.

2. The process according to claim 1, wherein the polymer beads removed from the vessel at the polymer bead discharge point are subjected to a post polymerisation stage.

3. The process according to claim 1, wherein the monomer micro-volumes are obtained in the microfluidic device employing at least one of the techniques selected from the group consisting of hydrodynamic flow focusing, coaxial shear flow, crossflow shear in cross junction, co-flow junction and T-junction microchannel geometries.

4. The process according to claim 1, wherein the at least one second and at least one third microfluidic channels each intersect the first microfluidic channel are substantially non-right angles.

5. The process according to claim 1, wherein the at least one second and at least one third microfluidic channels each intersect the first microfluidic channel are substantially at right angles.

6. The process according to claim 1, wherein the diameter of the at least one first microfluidic channel is between 30 m and 3500 m.

7. The process according to claim 1, wherein the diameter of the at least one second microfluidic channel and the diameter of the at least one third microfluidic channel are each independently selected from diameters in the range of from 10 m to 5000 m.

8. The process according to claim 1, wherein the monomer micro-volumes are formed by delivering a flow of the aqueous solution comprising water-soluble ethylenically unsaturated monomer or monomer blend from the at least one third microfluidic channel into the at least one intersection.

9. The process according to claim 1, wherein the process is conducted in two or more vessels in parallel.

10. The process according to claim 1, wherein the aqueous monomer or monomer blend and/or the non-aqueous liquid contains a polymerisation initiator.

11. The process according to claim 1, wherein the suspension of the polymer beads in the non-aqueous liquid removed at the polymer bead discharge point has a concentration of at least 10% polymer beads on total weight of suspension.

12. The process according to claim 1, wherein the aqueous polymer beads are produced at a rate of at least 15 kg/hour, preferably at a rate of at least 20 kg/h.

13. The process according to claim 1, wherein an amphipathic stabiliser is included in the non-aqueous liquid.

14. The process according to claim 1, wherein the water-soluble ethylenically unsaturated monomer or monomer blend comprises at least one monomer selected from the group consisting of acrylamide, methacrylamide, N-vinyl pyrrolidone, 2-hydroxy ethyl acrylate, acrylic acid (or salts thereof), methacrylic acid (or salts thereof), itaconic acid (or salts thereof), maleic acid (or salts thereof), 2-acrylamido-2-propane sulphonic acid (or salts thereof), vinyl sulphonic acid (or salts thereof), allyl sulphonic acid (or salts thereof), dimethyl amino ethyl acrylate (or acid salts or quaternary ammonium salts thereof), dimethyl amino ethyl methacrylate (or acid salts or quaternary ammonium salts thereof), dimethyl amino propyl acrylamide (or acid salts or quaternary ammonium salts thereof), dimethyl amino propyl methacrylamide (or acid salts or quaternary ammonium salts thereof), vinyl formamide and combinations of any of the above.

15. The process according to claim 14, wherein at least one monomer has been prepared by a chemically catalysed process, a biologically catalysed process or a biological process.

16. The process according to claim 14, wherein the acrylamide has been prepared by a biological catalysed process or a biological process.

17. The process according to claim 1, wherein the so formed polymer beads are ground to produce a polymer powder.

18. The process according to claim 1, wherein the process is performed in a continuous mode.

19. An apparatus suitable for a reverse-phase suspension polymerisation process for the manufacture of polymer beads from an aqueous solution comprising water-soluble ethylenically unsaturated monomer or monomer blend, the apparatus comprising: a vessel comprising a monomer feed point and a polymer bead discharge point, which vessel is suitable for containing a volume of non-aqueous liquid between the monomer feed point and the polymer bead discharge point, at least one microfluidic device suitable for generating monomer micro-volumes, said monomer micro volumes being separated by non-aqueous liquid in at least one first microfluidic channel, a feeder for feeding the monomer micro-volumes through the at least one first microfluidic channel towards the at least one monomer feed point, a droplet feeder for enabling the monomer micro-volumes to enter into or onto the volume of nonaqueous liquid and forming aqueous monomer droplets, a droplet discharge line for allowing the aqueous monomer droplets to flow towards the polymer bead discharge point, an initiator for initiating polymerisation of the aqueous monomer droplets such that they form polymerising beads which have formed polymer beads when they reached the polymer bead discharge point, a suspension remover for removing a suspension of aqueous polymer beads in non-aqueous liquid at polymer bead discharge point, and a polymer bead recoverer for recovering water-soluble or water swellable polymer beads from the suspension, wherein: the at least one microfluidic device comprises at least one second microfluidic channel suitable for conveying non-aqueous liquid; at least one third microfluidic channel suitable for conveying the aqueous solution comprising water soluble ethylenically unsaturated monomer or monomer blend; and at least one intersection between the at least one third microfluidic channel and the at least one second microfluidic channel; the at least one first microfluidic channel is in communication with the at least one intersection, and a micro-volume former is provided for forming the monomer micro-volumes at the at least one intersection before being fed through the at least one first microfluidic channel towards the monomer feed point.

20. Water soluble or water swellable polymer beads obtainable by the process of claim 1.

Description

[0174] FIG. 1 shows one type of apparatus, consisting of a cylindrical vessel (1) containing two concentric walls and a microfluidic device (5) for producing monomer droplets.

[0175] An aqueous monomer solution is fed along a third microfluidic channel (7) and a non-aqueous liquid is fed along two second microfluidic channels (8) and the three microfluidic channels connect at an intersection (9). The intersection (9) is a T-junction in which the flow of the non-aqueous liquid from the two second microfluidic channels (8) is 90 to the flow of the third microfluidic channel (7). Micro-volumes of the monomer are formed in the intersection and travel along a first microfluidic channel (6), each monomer micro-volume separated by non-aqueous liquid. The monomer micro-volumes exit the first microfluidic channel (6) and form droplets which enter the volume of non-aqueous liquid (2) at the monomer feed point (4) and are initiated and irradiated using the UV source and descend as polymerising beads through a volume of non-aqueous liquid between the concentric walls of the vessel. The suspension of polymer beads is removed through the polymer discharge point (3) situated at the base of the vessel.

[0176] FIG. 2 shows another type of apparatus and differs from the apparatus of FIG. 1 in that the vessel (1) has a rectangular horizontal cross-section. In addition the intersection consists of a Y arrangements in which only one microfluidic channel carrying the non-aqueous liquid and with the microfluidic channel carrying the monomer solution meet.

[0177] FIG. 3 is a photographic illustration of the laboratory microfluidic device showing the two second microfluidic channels carrying the Exxsol D40 non-aqueous liquid entering the intersection at 90 to the third microfluidic channel carrying the cationic monomer mixture.

[0178] The examples which follow are only intended as an illustration of the invention and do not limit the claims.

EXAMPLES

Example 1

[0179] Monodisperse monomer droplets are produced by employing a microfluidic device test rig shown in FIG. 2. Non-aqueous liquid, Exxsol D40, and an amphipathic stabiliser is fed through two microfluidic channels to an intersection and an aqueous liquid containing monomer intended to form an aqueous phase, is fed along a microfluidic channel to the intersection and in which the aqueous liquid enters the intersection at right angles to the Exxsol D 40. Micro-volumes of the aqueous liquid containing the monomer are formed in the intersection and flow from the intersection along a further microfluidic channel. The micro-volumes of the aqueous liquid passed from the microfluidic channel into a volume of Exxsol D 40 and formed aqueous droplets within a volume of Exxsol D 40.

[0180] The microfluidic channels each have an internal diameter of 1000 m and constructed from polytetrafluoroethylene (PTFE). The microfluidic device is also equipped with syringe pumps and a camera to observe the formation of the micro-volumes and subsequently formed droplets.

[0181] Three different aqueous liquids were used to produce monodisperse aqueous droplets as follows:

Aqueous liquid 1: water;
Aqueous liquid 2: 50% by weight aqueous solution of propionamide;
Aqueous liquid 3: Cationic Mixture (75% by weight aqueous mixture including water-soluble cationic monomer).

[0182] The aqueous mixture contained components shown in Table 1:

TABLE-US-00001 TABLE 1 Component Mass (g) Propionamide 33.60 Dimethyl amino ethyl acrylate methylchloride quaternary salt 63.88 Adipic acid 2.10 Trilon C (sequesterant available from BASF) 0.06 Water 0.36

[0183] The non-aqueous phase consisted of Exxsol D40 containing 0.19% by weight of an amphipathic stabiliser.

[0184] Different dispersions containing different ratios of aqueous phase to non-aqueous phase were prepared for each aqueous liquid. The results illustrating the different ratios of aqueous dispersed phase to non-aqueous continuous phase are shown in Tables 2 to 4.

TABLE-US-00002 TABLE 2 Water Mass ratio volume ratio Max. throughput of continuous:dispersed continuous:dispersed dispersed phase [g/min] 60:40 65.2:34.8 3.5 50:50 55.6:44.4 4.4 30:70 34.9:65.1 5.2

TABLE-US-00003 TABLE 3 Propionamide Mass ratio volume ratio Max. throughput of continuous:dispersed continuous:dispersed dispersed phase [g/min] 60:40 65.6:34.4 2.1 50:50 55.9:44.1 2.6 40:60 45.9:54.1 3.2

TABLE-US-00004 TABLE 4 Cationic Mixture Mass ratio volume ratio Max. throughput of continuous:dispersed continuous:dispersed dispersed phase [g/min] 60:40 65.6:34.4 2.1 50:50 56.0:44.0 Not stable 40:60 45.9:54.1 Not stable

[0185] The results demonstrate that the microfluidic device is useful for the generation of aqueous monomer dispersions of monodisperse droplet size distributions in a non-aqueous liquid.