APPARATUS FOR THE PRODUCTION OF PARTICLES BY MEMBRANE EMULSIFICATION

Abstract

An apparatus for producing polymer particles by membrane emulsification, comprising a tank (2) and a plurality of tubes (3), each tube comprising a membrane section (26) mounted within a first tank chamber (14a) of the tank (2), the first tank chamber (14a) being configured to connect to a source of a dispersed phase liquid, each tube comprising an inlet (22) configured to connect to a source of a continuous phase, and each membrane section (26) comprising a plurality of pores (28) extending through a wall (16) of the membrane section (26).Each tube (3) comprises an outer tube section (27) extending through a tank housing (11) surrounding the first tank chamber, wherein the plurality of pores or perforations is limited to the membrane section (26) mounted within the first tank chamber (14a) of the tank (2), and wherein the outer tube section (27) of each tube (3) is configured for connection to an emulsion processing unit (30). A membrane tube and a method for preparing biopolymer particles by membrane emulsification are also described.

Description

APPARATUS FOR PARTICLE PRODUCTION BY MEMBRANE EMULSIFICATIONFIELD OF THE INVENTION

[0001] The present invention relates to an apparatus for the production of (bio)polymer particles by membrane emulsification, a membrane tube for the production of (bio)polymer particles by membrane emulsification, use of such a membrane tube for reducing coalescence of emulsion droplets in a membrane emulsification method for preparing biopolymer particles, and methods of preparing biopolymer particles using the apparatus described.BACKGROUND

[0002] The production of polymer particles by membrane emulsification is well-known and comprises the flow of a dispersed phase through pores of a membrane into a continuous phase immiscible with the dispersed phase. Droplets are formed at the pore outlet and are carried away with the continuous phase and then converted to solid particles via phase inversion, polymerization, precipitation or other similar methods. Further processing might include extraction, and optionally washing or drying, of the polymer particles.

[0003] In many applications, it is desirable to have polymer particles of a very small size, for instance as small as 1 pm. It is also desirable in many applications to have particles of a controlled size within a given range and to avoid a large variation in the size distribution of the particles. In conventional membrane emulsification systems, a major challenge is to minimize the coalescence of droplets within the emulsion which leads to undesirable aggregation to form larger droplets that lead to larger particles. Coalescence can be reduced having large spacings between pores of the membrane such that the droplets within the emulsion are spread apart by large distances, in other words the emulsion has a low density of droplets of the dispersed phase. This however reduces yield, and requires larger amounts of the continuous phase, thus leading to higher manufacturing costs.

[0004] The coalescence of droplets within the emulsification occurs in particular in zones of local turbulence in the fluid flow system of the emulsion downstream of the membrane. Such localized turbulences occur in particular at junctions, couplings and other obstacles disturbing the flow of the emulsion.

[0005] In the field of production of polymer particles by membrane emulsification, it is known to use tubular membrane structures separating the dispersed phase from the continuous phase. In US 20120175798, a tubular membrane is inserted within a tank containing the continuous phase. The dispersed phase is pumped into the tubular membrane to form dropletson the outlet of the pores on the external radial surface of the tubular membrane. A certain cross-flow of the continuous phase (which is an antisolvent) around the tube, shears the droplets and the emulsion is extracted through an outlet of the tank. The droplets within the emulsion may easily coalesce within the tank and especially when converging to the outlet of the tank and at the coupling of the tank outlet to conduits feeding the emulsion to a processing unit for extracting the particles.

[0006] Some of the inconveniences related to producing the emulsion within a tank as described above, may be overcome by injecting the dispersed phase into a container surrounding the tubular membrane and supplying the continuous phase on the inside of the tubular membrane such that the particles are formed inside the tubular membrane, as described in US 20200368699. This conventional apparatus nevertheless still has drawbacks, in particular the coupling at the outlet of the apparatus has features that create localized turbulence and may lead to coalescence of particles at the outlet. Moreover, the inside of the membrane canal is provided with a cylinder giving a very small spacing between the membrane and the cylinder for flow of the emulsion, rendering the control of fluid flow at various positions within the canal subject to manufacturing tolerances as well as increasing the cost of the apparatus. A further alternative is decoupling the formation of the emulsion from that of the particles, as described in US 20230128373A1. Here an emulsion is first formed via membrane emulsification with droplets containing the biopolymer dissolved into an appropriate solvent. Once formed, the emulsion is placed in contact with an antisolvent, which leads to the precipitation of the solid biopolymer particles.

[0007] Pumping the dispersed phase, which must be at a higher pressure than the continuous phase, into a tube interior also requires that the tube has a certain structural strength to prevent buckling which leads to increasing the wall thickness in conventional systems. The increased wall thickness then poses a problem for the production of very small pores which are typically formed by laser drilling.SUMMARY OF THE INVENTION

[0008] In view of the foregoing, it is an object of this invention to provide an apparatus and a membrane tube for the production of (bio)polymer particles by membrane emulsification that is able to produce particles of a very small size in a well-controlled manner, in particular with a narrow size distribution. It is advantageous to provide an apparatus and a membrane tube for the production of (bio)polymer droplets / particles by membrane emulsification that is economical to produce and to operate.

[0009] It is advantageous to provide an apparatus and a membrane tube for the production of (bio)polymer droplets / particles by membrane emulsification that allows to produce an emulsification with a high density of droplets in the emulsification.

[0010] It is advantageous to provide an apparatus and a membrane tube for the production of (bio)polymer droplets / particles by membrane emulsification that is reliable and easy to maintain.

[0011] Objects of the invention have been achieved by providing the apparatus according to claim 1 , and the membrane tube according to claim 20. In addition to the apparatus according to claim 1 and the membrane according to claim 20, objects of the invention have been achieved by the method for preparing biopolymer particles according to claim 27, and the membrane tube for use according to claim 34. Dependent claims recite various advantageous features of the invention. Features described herein in the context of the apparatus and the membrane tube, are applicable to the method and use and vice versa.

[0012] It will be appreciated that features of the dependent claims may be combined with each other and with features of the independent claims in combinations other than those explicitly set out in the claims. Furthermore, the approaches described herein are not restricted to specific embodiments such as those set out below, but include and contemplate any combinations of features presented herein.

[0013] The foregoing and other objects, features, and advantages of the present disclosure will appear more fully hereinafter from a consideration of the detailed description that follows along with the accompanying drawings. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the disclosure.BRIEF DESCRIPTION OF THE FIGURES

[0014] Figure 1a is a schematic top view of an apparatus for the production of polymer particles by membrane emulsification according to an embodiment of the invention.

[0015] Figure 1b is a cross-sectional view through line Ib-lb of Figure 1a but without showing the downstream connection of the external tube sections 27 to an emulsion processing unit.

[0016] Figure 1c is a cross-sectional view through line Ib-lb of Figure 1a including the direct connection of the external tube sections 27 to an emulsion processing unit 30.

[0017] Figure 1d is a cross-sectional view through line Ib-lb of Figure 1a including the directconnection of the external tube sections 27 to an emulsion processing unit 30, and with break lines 31 on each of the external tube sections 20 to show that these sections extend beyond that shown in this schematic drawing.

[0018] Figures 2a to 2d are schematic representations of a membrane section of a tubular membrane suitable for an apparatus for the production of polymer particles by membrane emulsification according to embodiments of the invention.DETAILED DESCRIPTION

[0019] While various exemplary embodiments are described or suggested herein, other exemplary embodiments utilizing a variety of methods and materials similar or equivalent to those described or suggested herein are encompassed by the general inventive concepts. Those aspects and features of embodiments which are implemented conventionally may not be discussed or described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and methods described herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features.

[0020] As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0021] In this specification, unless otherwise stated, the term "about" modifying the quantity of a component refers to variation in the numerical quantity that can occur, for example, through typical measuring and handling procedures used for making concentrates, mixtures or solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the materials employed, or to carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term "about", the claims include equivalents to the quantities.

[0022] The ranges provided herein provide exemplary amounts of each of the components. Each of these ranges may be taken alone or combined with one or more other component ranges. As used herein, the term “at least” includes the end value of the range that is specified. For example, “at least 10 cm” includes the value 10 cm.

[0023] As used herein, wt% means “weight percentage” as the basis for calculating a percentage. Unless indicated otherwise, all % values are calculated on a weight basis, and are provided with reference to the total weight of the product in which the substance is present. For example, % water in the solvent of the dispersed phase refers to the wt% water based onthe total weight of the solvent. Similarly, % biopolymer in the dispersed phase refers to wt% biopolymer based on the total weight of the dispersed phase.

[0024] As used herein, “substantially free” means no more than trace amounts, i.e. the amount of the substance(s) concerned is negligible. In various embodiments, “substantially free” means no more than 1000 ppm, preferably no more than 100 ppm, more preferably no more than 10 ppm, even more preferably no more than 1 ppm of the substance(s) concerned.

[0025] The general inventive concept is centred on providing an apparatus for (bio)polymer particle production by membrane emulsification, a membrane tube for (bio) polymer particle production by membrane emulsification, and a method for preparing biopolymer particles by membrane emulsification, where the resulting particles are of a controlled size and have minimal size distribution whilst being produced without compromising yield or requiring large amounts of the continuous phase. As noted above, this is desirable in many applications but is a challenge with conventional membrane emulsification systems due to problems which include coalescence of droplets within the emulsion leading to undesirable aggregation of droplets and the formation of larger particles.

[0026] Typically, a tubular membrane is a short tube, with pores along its full length, and whose length is entirely contained within a tank section of a membrane emulsification apparatus. As such, the flow from the membrane tube is transported into an outlet chamber to be conveyed to the next step. In other words, the set-up is discontinuous. Without being bound by theory, the inventors of the present invention identified that this discontinuity may be responsible for creating conditions for coalescence of the emulsion droplets which, ultimately, leads to aggregation and large polymer particles. This issue is addressed in the present invention by providing a continuous tube to the emulsion processing unit, namely by each tube having an external section configured for direct connection to the emulsion processing unit, and confining the pores / perforations in each tube to the section mounted within the chamber connected to the source of dispersed and continuous phases.

[0027] Thus, disclosed herein is an apparatus for polymer particle production by membrane emulsification comprising a tank and a plurality of membrane tubes, each membrane tube comprising a membrane section mounted within a first tank chamber of the tank, the first tank chamber configured to be connected to a source of a dispersed phase liquid, each membrane tube comprising an inlet configured to be connected to a source of a continuous phase, each membrane section comprising a plurality of pores extending through a wall of the membrane section. Each membrane tube comprises an external tube section extending through a casing of the tank surrounding the first tank chamber.

[0028] Also disclosed herein is an apparatus for polymer particle production by membrane emulsification comprising a tank and a plurality of tubes, each tube comprising a membrane section mounted within a first tank chamber of the tank, the first tank chamber configured to be connected to a source of a dispersed phase liquid, each tube comprising an inlet configured to be connected to a source of a continuous phase, each membrane section comprising a plurality of pores or perforations extending through a wall of the membrane section, each tube comprising an external tube section extending through a casing of the tank surrounding the first tank chamber, wherein the plurality of pores or perforations are confined to the membrane section mounted within the first tank chamber of the tank, and wherein the external tube section of each tube is configured for connection to an emulsion processing unit.

[0029] By the term “connection” is meant direct connection such that the external tube section of each tube is directly connected to the emulsion processing unit, thereby ensuring continuous, uninterrupted delivery of the emulsion for downstream processing. As noted above, this is advantageous for the present invention along with the confinement of the pores or perforations to a discrete portion of the tube, namely the membrane section mounted within the first tank chamber of the tank, i.e. the chamber where the tube receives dispersed phase and continuous phase in order for membrane emulsification to take place. Such control of both the location of the pores / perforations and continuity of the tubes enables the production of polymer particles having a controlled size and / or size distribution.

[0030] The terms “pore” and “perforation” are used interchangeably herein. In an advantageous embodiment, the pores are arranged in a plurality of pore groups, the pore groups separated from adjacent pore groups by an axial spacing (Sg) that is greater than an axial spacing between adjacent pores of a same pore group. In an advantageous embodiment, the pore groups comprise one to five rows or columns of pores. In an advantageous embodiment, adjacent said rows or columns of pores are spaced apart by a distance in a range of about 2 to about 10 mm, preferably about 2 to about 5 mm.

[0031] In an advantageous embodiment, the pore groups are arranged: in columns extending substantially in an axial direction, or in rows extending substantially orthogonally to the axial direction surrounding an axis of the tube, or at an oblique angle p with respect to the axial and radial directions of the tube, the angle being in a range of about 10 degrees to about 80 degrees with respect to the axial direction of the tube (10° < / 3 < 80°), preferably in a range of about 30 degrees to about 60 degrees (30° < / 3 < 60°).

[0032] In an advantageous embodiment, the membrane section of each tube, at least where the pore groups are positioned, comprises or consists of a fluoropolymer material. In an advantageous embodiment, the membrane section of each tube, at least where the pore groups are positioned, have a thickness in a range of about 100pm to about 1000pm, preferably wherein each tube consists of a fluoropolymer material and has a thickness in a range of about 100pm to about 1000pm.

[0033] In an advantageous embodiment, the tube comprises a ring shape reinforcement provided by a greater wall thickness or an additional ring structure or reinforcement layer in areas of the tube where the pore groups are not positioned. In an advantageous embodiment, the tubular reinforcement is positioned in an axial space between pore groups.

[0034] In an advantageous embodiment, the pores have a diameter on an inner side of the membrane tube in a range of about 1 pm to about 10 pm. In an advantageous embodiment, the pores have a cross-sectional surface area on an inner side of the tube that is smaller than a cross-sectional surface area of the pore on an outer side of the tube.

[0035] In an advantageous embodiment, the tank comprises a second tank chamber separated from the first tank chamber by a separating wall, and inlet ends of the tubes are formed at the separating wall for fluid connection with the second tank chamber. In an advantageous embodiment, the second tank chamber comprises an inlet configured for connection to a source of a continuous phase liquid.

[0036] In an advantageous embodiment, the plurality of tubes is greater than four, preferably greater than five. In an advantageous embodiment, a diameter of the tube on the inner side is within a range of about 5 to about 20 mm, preferably about 8 to about 10 mm.

[0037] In an advantageous embodiment, each tube comprises a tube wall extending the whole length of the membrane section and over a portion or all of the external tube section extending out of the outer casing, preferably wherein the tube wall extends the whole length of the membrane tube and all of the external tube section. In an advantageous embodiment, the external tube section of each tube is exposed. By the term “exposed” is meant that the external tube section of each tube is not mounted within a chamber.

[0038] In an advantageous embodiment, the apparatus further comprises the emulsion processing unit, wherein the emulsion processing unit is connected to the external tube section of each tube. The means of connection is not limited and would be any suitable mechanical connecting means available in the art. For example, the apparatus may comprise the emulsionprocessing unit, wherein the emulsion processing unit is connected to the external tube section of each tube, the external tube section of each tube being exposed.

[0039] Also provided by the present invention is a membrane tube for polymer particle production by membrane emulsification, wherein the tube comprises an inlet configured to be connected to a source of a continuous phase, a membrane section comprising a plurality of pores or perforations extending through a wall of the membrane section, a non-membrane section, and an outlet configured for connection to an emulsion processing unit, wherein the pores or perforations are confined to the membrane section and arranged in a plurality of pore or perforation groups, wherein the tube wall extends along the length of the membrane section and non-membrane section so that the tube is continuous, and wherein at least the membrane section comprises or consists of a fluoropolymer material. As the skilled person will understand, the advantageous embodiments defined above in the context of the apparatus are also applicable in the context of the membrane tube. For example, the membrane section, plurality of pores, emulsion processing unit, and fluoropolymer material. By the term ‘nonmembrane section’ is meant the section of the tube which does not have pore or perforation groups; this corresponds to the external tube section in the context of the apparatus.

[0040] In addition to the above-defined advantageous embodiments, the length ratio of the membrane section to the non-membrane section may be defined. In an advantageous embodiment, said length ratio is about 1 :1 to about 1 :5, i.e. the non-membrane section may be up to five times longer than the membrane section. This is shown by a break line 31 in Figure 1d. Such embodiment also applies to the apparatus in that the length ratio of the membrane section to the external tube section may be about 1 :1 to about 1 :5.

[0041] Also provided by the present invention is a method for preparing biopolymer particles. The method comprises (a) a membrane emulsification of a dispersed phase into a continuous phase, wherein the dispersed phase comprises the biopolymer in a solvent, and wherein the dispersed phase and the continuous phase are provided to an apparatus comprising a tank and a plurality of tubes, each tube comprising a membrane section mounted within a first tank chamber of the tank, the first tank chamber being connected to a source of the dispersed phase, each tube further comprising an inlet connected to a source of the continuous phase, each membrane section comprising a plurality of pores or perforations extending through a wall of the membrane section, wherein each tube comprises an external tube section extending through a casing of the tank surrounding the first tank chamber, and wherein passing the dispersed phase through the membrane section of each tube forms an emulsion of the biopolymer in the continuous phase.

[0042] In the same manner as noted above for the membrane tube, the advantageous embodiments defined above in the context of the apparatus are also applicable in the context of the method. Similarly, the advantageous embodiments defined above in the context of the membrane tube are also applicable in the context of the method. In a particularly advantageous embodiment, the membrane section of each tube comprises or consists of a fluoropolymer material, preferably wherein each tube consists of a fluoropolymer material.

[0043] All aspects of the present disclosure concern polymer particles and preferably biopolymer particles. By the term “biopolymer” is meant a polymer produced by living organisms. In other words, a polymeric biomolecule. There are three main classes of biopolymers, classified according to the monomeric units used and the structure of the biopolymer formed: polynucleotides (RNA and DNA), which are polymers composed of 13 or more nucleotide monomers; polypeptides, which are polymers of amino acids; and polysaccharides, which are typically polymeric carbohydrate structures. Other examples of biopolymers include rubber, suberin, melanin, chitin and lignin.

[0044] The biopolymer may be selected from the group consisting of polynucleotides, polypeptides and polysaccharides. Preferably, the biopolymer is selected from the group consisting of polypeptides and polysaccharides. More preferably, the biopolymer is a polysaccharide, for example, starch, cellulose, chitin, chitosan or glycogen. Even more preferably the biopolymer is starch or cellulose. Most preferably the biopolymer is cellulose. Cellulose is a linear polymer made up of p-D-glucopyranose units covalently linked with 1^4 glycosidic bonds. Cellulose may be obtained from many different sources and the present disclosure is not necessarily limited as to the origin, form, or other characteristics of the cellulose. Cellulose is typically obtained from plant sources, for example from virgin or recycled wood pulp. Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Cellulose may be obtained from virgin sources or advantageously from recycled sources.

[0045] The term “particle” refers to a discrete solid entity with defined size and shape. The size of the biopolymer particles of the present disclosure is not limited, and the skilled person will be able to select sizes according to a desired application. The size of the particles may be readily identified by a person skilled in the art, for example, using an optical microscope image and image analysis software with a suitable detection algorithm (e.g. Imaged using an edge detection algorithm), laser diffraction with commercially available equipment such as Mastersizer from Malvern Panalytical (e.g. Mastersizer 3000), with an appropriately sized sieve, or by using a caliper.

[0046] In various embodiments of the present disclosure, the biopolymer particles are approximately spherical. Approximately spherical biopolymer particles may be advantageous in certain applications, for example in biocatalysis, where such a shape can facilitate industrial processing and recovery processes such as filtration.

[0047] As recited herein, “diameter” takes its usual meaning. Thus, the skilled person will understand that the diameter of an approximately spherical particle as recited herein will be approximately the same when measured in any direction through the centre of said particle. In some embodiments, the particles may have a diameter of at least about 1 pm. In some embodiments, the particles may have a diameter of at least about 10 pm. In some embodiments, the particles may have a diameter of at least about 25 pm. In some embodiments, the particles may have a diameter of at least about 50 pm. In some embodiments, the particles may have a diameter of at least about 100 pm.

[0048] In some embodiments, the particles may have a diameter of less than about 5 mm. In some embodiments, the particles may have a diameter of less than about 4 mm. In some embodiments, the particles may have a diameter of less than about 3 mm. In some embodiments, the particles may have a diameter of less than about 2 mm. In some embodiments, the particles may have a diameter of less than about 1 mm.

[0049] Solvents for use in the preparation of biopolymer particles by membrane emulsification, are known and ionic liquids are commonly favoured as they are able to solubilise recalcitrant biopolymers. Ionic liquids are salts that are in liquid form at a temperature between ambient temperature and 100°C, for example imidazolium based ionic liquids such as 1-ethyl-3-methylimidazolium acetate (EmimOAc), 1-butyl-3-methylimidazolium chloride (BmimOAc) or the like. Moreover, ionic liquids are essentially non-volatile (avoiding fugitive emissions) and are considered to have environmental benefits over other solvents. Ionic liquids can, for example, be readily recycled by distillation to remove the anti-solvent. Ionic liquids are typically not used in pure form, however. An amount of a co-solvent is often added to the ionic liquid when dissolving biopolymers such as cellulose. The use of a cosolvent may assist in dissolution of the biopolymer, and may reduce the amount of costly ionic liquid required. In methods for forming biopolymer particles, the inclusion of a co-solvent may also improve the efficiency and yield of the process by modifying the viscosity of the dispersed phase, which may in turn reduce the amount of deformation exhibited by the particles.

[0050] Typical co-solvents employed in combination with ionic liquids are dipolar aprotic solvents, such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and the like.However, such solvents are not generally considered to be environmentally friendly, and the use thereof may therefore have a negative impact on the overall environmental benefits of ‘green’ processes that use ionic liquids. Notably, DMSO is listed in Annex II of Regulation (EC) No. 1223 / 2009 on Cosmetic Products (available at https: / / echa.europa.eu / cosmetics- prohibited-substances), and DMF is associated with toxic effects. Such co-solvents therefore cannot be used in processes for the preparation of biopolymer particles for use in cosmetic and personal care as well as other applications. The use of dipolar aprotic solvents may also complicate the recycling of the ionic liquid and increase costs. For example, some degree of distillation of DMSO is to be expected during recycling and the presence of aprotic solvent has been reported to reduce the thermal stability of 1-ethyl-3-methylimidazolium acetate (EmimOAc) [see Williams et al., Thermochimica Acta (2018), 669 126-139, for example],

[0051] Turning now to the anti-solvents that may be used when preparing biopolymer particles, organic solvents such as ethanol are typical. Again, however, these substances may reduce the overall environmental benefits of the process, may be associated with safety concerns, and may complicate and increase the cost of recycling of ionic liquids. Thus, in various embodiments, an aqueous solvent and an aqueous anti-solvent may be used. The use of an aqueous solvent and anti-solvent may obviate the use of reagents associated with environmental and safety concerns and may also simplify and reduce the cost of solvent recycling. In particular, use of such solvents and anti-solvents may increase the stability of ionic liquids against temperature-based degradation [Williams et al., Thermochimica Acta (2018), 669: 126-139], which may allow an increased number of recycling cycles to be performed, for example. Finally, the inclusion of water in the dispersed phase may increase the likelihood of bead sphericity.

[0052] Accordingly, in various embodiments, the dispersed phase from which the biopolymer particles may be prepared comprises a solvent in which the biopolymer is dispersed or dissolved, which solvent comprises water. By the term “solvent” is therefore meant any substance (e.g. liquid) which disperses or dissolves the biopolymer. The term “solvent” also includes solvent mixtures.

[0053] The solvent of the dispersed phase may comprise water and may comprise an ionic liquid, an organic solvent, an inorganic nonaqueous solvent, or a combination thereof. In various embodiments of the present disclosure, the solvent for the dispersed phase comprises water and at least one of an ionic liquid, an organic solvent, an inorganic nonaqueous solvent, or a combination thereof. In various embodiments of the present disclosure, the solvent for the dispersed phase comprises water and one or more ionic liquid(s).

[0054] Non-limiting examples of solvents for the dispersed phase other than water include methanol, ethanol, ammonia, acetone, acetic acid, n-propanol, n-butanol, isopropyl alcohol, ethyl acetate, dimethyl sulfoxide, sulfuryl chloride, phosphoryl chloride, carbon disulfide, morpholine, N-methylmorpholine, NaOH without and with association of urea and thiourea, bromine pentafluoride, hydrogen fluoride, sulfuryl chloride fluoride, acetonitrile, dimethylformamide, hydrocarbon oils and blends thereof, toluene, chloroform, carbon tetrachloride, benzene, hexane, pentane, cyclopentane, cyclohexane, 1 ,4-dioxane, dichloromethane, nitromethane, propylene carbonate, formic acid, tetrahydrofuran, diethyl ether, phosphoric acid, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-methoxymethyl-3-methylimidazolium bromide, N-ethylpyridinium chloride, N- methylmorpholine-N-oxide, 1 -methylimidazole, N,N-dimethylformamide, N,N'- dimethylimidazolidin-2-one, N,N-dimethylacetamide, sulfolane, y-valerolactone, y- butyrolactone, N,N,N',N'-tetramethylurea, N-methylpyrrolidinone, and methylene chloride. The skilled person will readily recognise which of the exemplary solvents are ionic liquids, organic solvents, and / or inorganic non-aqueous solvents.

[0055] As will be understood by the skilled person in the art, the dispersed phase will depend on the biopolymer being used. The identification of suitable solvents for the dispersed phase of the present disclosure is specifically within the common general knowledge of the skilled person.

[0056] In various embodiments, the solvent for the dispersed phase comprises water and an ionic liquid. The ionic liquid may be selected from 1-ethyl-3-methylimidazolium acetate (EmimOAc), 1-butyl-3-methylimidazolium chloride (BmimOAc), and a combination thereof. In some embodiments, the solvent for the dispersed phase comprises water and one or more organic solvents. In other embodiments, the solvent for the dispersed phase is substantially free of organic solvents. The term “substantially free” is defined above. The skilled person will understand that when the solvent of the dispersed phase consists of water and an ionic liquid, the total wt% of water and ionic liquid in the dispersed phase solvent will total 100 wt%. If water is present, for example, in an amount of at least 0.5 wt%, an ionic liquid may be present in an amount of at least 99.5 wt%, with the proviso that the total of water and ionic liquid is 100 wt%. In other words, the ionic liquid may be present as the remainder of the solvent. Preferably, the solvent used for the dispersed phase is environmentally friendly. By the term “environmentally friendly” is meant not harmful to the environment such that the solvent can be disposed of without the need for specialist equipment or process(es), i.e. non-toxic. It is known in the art that polysaccharides have limited dissolution in most of the common solvents.It is also known in the art that those solvents which do dissolve polysaccharides are often toxic and / or highly selective. When the biopolymer is a polysaccharide such as cellulose, starch, chitin, glycogen, and / or chitosan, the solvent for the dispersed phase may therefore comprise an ionic liquid in addition to water. The dissolution of cellulose with the ionic liquid 1 -butyl-3- methylimidazolium chloride is, for example, discussed in Richard et al., J. Am. Chem. Soc. 2002, 124, 4974-4975. Verma et al., Sustainable Chemistry and Pharmacy 13 (2019), 100162 similarly discusses the solubility of cellulose in ionic liquids and ionic liquids with co-solvents. Each of these disclosures is incorporated herein by reference.

[0057] The concentration of biopolymer in the dispersed phase is not limited and may be any concentration suitable for the methods discussed herein. In various embodiments, the biopolymer is present in the dispersed phase in an amount from about 0.1 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 0.5 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 1 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 1.5 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 2 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 2.5 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 3 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 3.5 wt% to about 15 wt%. In various embodiments the biopolymer is present in the dispersed phase in an amount from about 4 wt% to about 15 wt%.

[0058] The dispersed phase may further include optional components. These optional components include, but are not limited to, surfactants, porogens, active ingredients, pockets of air, double emulsions, pigments, and dyes. The level of any of the optional components is not significant in the present disclosure. In various embodiments, the dispersed phase includes a co-solvent.

[0059] The surfactant may be any suitable surfactant known in the art, for example, any ionic or non-ionic surfactant. Ionic surfactants may include sulfates, sulfonates, phosphates and carboxylates such as alkyl sulfates, ammonium lauryl sulfates, sodium lauryl sulfates, alkyl ether sulfates, sodium laureth sulfate and sodium myreth sulfate, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, perfluorobutanesulfonate, alkyl benzene sulfonates, alkyl aryl ether phosphates, alkyl ether phosphates, and alkyl carboxylates. Non-ionic surfactants may include polyethers, polyoxyalkylene derivatives of hexitol, partial long-chainfatty acid esters such as sorbitan oleates, ethylene oxide derivatives of long-chain alcohols, ethoxylated vegetable oil, polydimethylsilxoxanes, and ethylene oxide / propylene oxide copolymers.

[0060] The temperature of the dispersed phase is not limited. By the expression “temperature of the dispersed phase” or “the dispersed phase is at a temperature of’, or the like, is meant the temperature of the dispersed phase prior to membrane emulsification (e.g. when it is placed in the apparatus for such emulsification), and / or the temperature of the apparatus during emulsification of the dispersed phase. The emulsification means may be heated so that the dispersed phase remains at an elevated temperature in situ.

[0061] In some embodiments, the dispersed phase is at ambient or room temperature, namely between about 20 and about 25°C. In various embodiments the dispersed phase is heated above ambient temperature. The dispersed phase may be heated using any suitable means. The dispersed phase is preferably heated in situ such that there is no temperature loss prior to membrane emulsification, for example by heating a vessel containing the dispersed phase and / or the emulsification means. Suitable heating apparatus may comprise a heating element, for example a Peltier element, as well as a means of regulating the temperature, such as a thermocouple and controller.

[0062] Thus, in various embodiments, the temperature of the dispersed phase is from about 5°C to less than about 100°C, from about 10°C to less than about 100°C, from about 15°C to less than about 100°C, from about 20°C to less than about 100°C, from about 25°C to less than about 100°C, or from about 30°C to less than about 100°C. The maximum temperature will be set by the point at which the evaporation of water from the dispersed phase becomes prohibitive and / or decomposition of the ionic liquid begins to occur. This will readily be determined by the person skilled in the art.

[0063] In an advantageous embodiment, the external tube section of each tube is connected to an emulsion processing unit, and the method further comprises a phase inversion with an anti-solvent to form particles of the biopolymer in said unit. The anti-solvent may comprise water, i.e. it may be aqueous. In various embodiments, the anti-solvent may comprise water and an organic solvent such as an alcohol or acetone, or any other organic solvent known in the art. Suitable alcohols include ethanol and / or methanol. Preferably, the anti-solvent is environmentally friendly. More preferably, the solvent and anti-solvent are both environmentally friendly. Thus, in various embodiments, the anti-solvent is substantially free of organic solvents. In various embodiments, the anti-solvent is or consists of water.

[0064] In various embodiments, the anti-solvent further comprises an ionic liquid. In some embodiments, the anti-solvent may comprise water and an ionic liquid before phase inversion or extrusion of the dispersed phase. In other embodiments, the ionic liquid may be introduced into the anti-solvent during the phase inversion or extrusion. In some embodiments where the dispersed phase comprises an ionic liquid, the ionic liquid may be introduced into the antisolvent from the dispersed phase during the phase inversion or extrusion process.

[0065] In various embodiments, the concentration of ionic liquid in the anti-solvent is up to about 50 wt% - the term “up to” being understood to mean greater than zero. In various embodiments the concentration of ionic liquid in the anti-solvent is up to about 40 wt%. In various embodiments the concentration of ionic liquid in the anti-solvent is up to about 30 wt%. In various embodiments the concentration of ionic liquid in the anti-solvent is up to about 20 wt%. In various embodiments the concentration of ionic liquid in the anti-solvent is up to about 10 wt%.

[0066] Where the anti-solvent comprises water and an ionic liquid, the ionic liquid may be 1- ethyl-3-methylimidazolium acetate (EmimOAc), 1-butyl-3-methylimidazolium chloride (BmimOAc), or mixtures thereof. In various embodiments, the ionic liquid is 1-ethyl-3- methylimidazolium acetate (EmimOAc).

[0067] The temperature of the anti-solvent is not limited. In various embodiments, the temperature of the anti-solvent is from about 5°C to about 80°C. In various embodiments, the temperature of the anti-solvent is from about 10°C to about 70°C. In various embodiments the temperature of the anti-solvent is from about 15°C to about 60°C.

[0068] In the membrane emulsification process discussed herein, the temperature of the antisolvent may be ambient such that phase inversion is carried out at ambient temperature, namely between about 20 and about 25°C. In such embodiments, the anti-solvent has a temperature between about 20 and about 25°C. Alternatively and preferably, the anti-solvent is cooled to a temperature below ambient temperature, namely below about 20°C. For example, the anti-solvent may be cooled to a temperature T2, for the phase inversion (b), T2 being less than Tdisp. Preferably T2 is substantially equal to T1, more preferably T2 is equal to T1 , where T1 is defined above.

[0069] In various embodiments of the present disclosure, phase inversion is carried out under shear; the skilled person will be aware of suitable shear conditions for phase inversion. Shear may, for example, be achieved through the use of a stirred vessel (e.g. a mechanically stirred vessel) or a settling vessel (e.g. a gravity settling vessel). The term “shear” is used herein torefer to an external force acting on an object or surface parallel to the slope or plane in which it lies, the stress tending to produce strain.

[0070] In various embodiments, phase inversion comprises a filtration process. The filtration process is not limited and may involve mechanical or any other type of filtration (e.g. using equipment known in the art such as a hydrocyclone). A filtration process may also be encompassed by the phase inversion being carried out under shear as described above. In various embodiments, a filtration medium (e.g. filter) may be used to filter the emulsion through the anti-solvent and thereby collect the biopolymer particles. In such embodiments, the emulsion may gravity settle (shear) through the anti-solvent and into the filter, whilst the continuous phase passes through the filter (the filtrate). The frozen droplets may then be collected in the filter as the filter cake.

[0071] If not collected as part of phase inversion (e.g. via filtration or otherwise), the biopolymer particles may be separated from the anti-solvent / continuous phase mixture or the anti-solvent / continuous phase mixture may be removed from the particles. The method of removal is not limited. In various embodiments, however, the method of removal depends on whether the method is being operated in batch or continuous mode.

[0072] In various embodiments, phase inversion is followed by or involves removal of the biopolymer particles as described above. Phase inversion may be followed by decanting and then biopolymer particle removal from the mixture and / or phase inversion may involve mechanical filtration of the wetted particles from the anti-solvent / continuous phase / particle mixture.

[0073] Alternatively, the biopolymer particles may be removed from the continuous phase before phase inversion. In such embodiments, wetted frozen droplets may be removed from the sol (e.g. using filtration) and then phase inversion carried out to precipitate the biopolymer and form particles thereof.

[0074] In another aspect the present invention provides the membrane tube as defined hereinabove for use in reducing coalescence of emulsion droplets in a membrane emulsification method for preparing biopolymer particles. The membrane emulsification method may be the method as defined hereinabove. The reduction in coalescence of emulsion droplets may be quantified by measuring the droplet size distribution using an optical measurement device, based on dynamic light scattering methodology. The dispersion of the droplets passes through a laser beam that illuminates the droplets, and a series of detectors measure the light scattered for the red and blue lightwavelengths. The droplet size distributionof the droplets, in volume and number, gives the D10, D50 and D90 measurements that allows to fully characterize the dispersion. The reduction in coalescence is advantageously relative to the membrane emulsification method using an apparatus for polymer particle production by membrane emulsification comprising a tank and a plurality of tubes, where each tube is not the membrane tube as defined herein, and where each tube is not connected to an emulsion processing unit.

[0075] Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations.

[0076] Figures 1 a, 1 b, 1 c and 1 d illustrate a polymer particle production apparatus 1 according to embodiments of the invention comprises a tank 2 and a plurality of tubes 3.

[0077] The tank 2 comprises a casing 11 forming a first tank chamber 14a comprising a dispersed phase inlet 8 configured to be connected to an upstream supply of a dispersed phase liquid medium pumped or otherwise delivered into the first tank chamber 14a. The dispersed phase may be as defined hereinabove.

[0078] The tank 2 may optionally have a dispersed phase outlet 9, which is useful in particular for maintenance operations, for instance for flow through to clean the first tank chamber.

[0079] Each tube has a membrane section 26 that is mounted within the tank chamber 14, and an external section 27 extending from the membrane section through the tank casing 11 to the outside of the first tank chamber 14a, configured for downstream and direct connection to an emulsion processing unit or station (30). The emulsion processing unit or station (30) is shown in each of Figures 1c and 1d. The emulsion processing unit or station may contain a tank into which the external tube section feeds the emulsion, the tank containing an antisolvent that forms solid polymer particles from the droplets in the emulsion. The antisolvent and use thereof to prepare polymer particles from the droplets is described hereinabove.

[0080] In the illustrated embodiment, each tube 3 comprises an inlet 22 positioned within the casing 11 of the tank 2. The inlets 22 are fluidly connected to an upstream source of a continuous phase liquid. The continuous phase may be as defined hereinabove. The first module chamber 14a is separated from the second module chamber 14b by separating wall 13.

[0081] In a variant, it may be noted that the inlets of each tube 3 may be positioned outside of the module casing 11 , at an upstream position, the tubes 3 extending through one end of the casing 11 into the tank chamber and then out through the other end of the casing to theemulsion processing unit or station. In other words, the tubes may extend each completely through the casing enclosing a single tank chamber in which the dispersed phase liquid is contained.

[0082] In the illustrated embodiment, the module comprises a first chamber 14a and a second chamber 14b separated by the separating wall 13, the separating wall comprising inlet holes connected to an inlet end of the tube and forming the inlets 22 of the tubes 3. In this embodiment, as illustrated, the continuous phase is supplied from an upstream source of continuous phase liquid connected to an inlet 10 of the second chamber 14b for flow into each of the tubes.

[0083] The membrane section 26 of each tube 3 comprises a tube wall 16 having an inner side 18 and an outer side 20, with a plurality of pores or perforations 28 extending through the tube wall 16. The pores 28 may have a constant cross-sectional area, but in a preferred embodiment the pores have a larger cross-sectional area on an outer side 20 surrounded by the dispersed phase liquid than on an inner side 18 in contact with the continuous phase liquid flow. The dispersed phase liquid in the first module chamber 14a may be supplied at a higher pressure than the continuous phase liquid within the membrane tube 3 such that the dispersed phase flows through the membrane pores 28 from the outer side 20 to the inner side 18 where the flow of the continuous phase liquid shears the dispersed phase to form an emulsion upstream of the pores. The emulsion then flows into the external tube section 27 of the tubes 3 and directly into the emulsion processing unit 30. Because the emulsion is generated within the tubes and the tubes extend out of the first chamber 14a that contains the dispersed phase, directly into an emulsion processing unit 30, local turbulences are avoided by the absence of couplings and other restrictions or obstacles in the path of the emulsion exiting the tank. This is particularly advantageous when coupled with the confinement of the pores 28 to the membrane section of each tube 3 in the first tank chamber 14a.

[0084] Each of the tubes 3 is therefore configured for connection to a downstream emulsion processing unit and thereby configured to extract the polymer droplets / particles before they have the chance to coalesce and aggregate into larger droplets / particles. The emulsion processing unit may perform phase inversion with an anti-solvent to convert the droplets into polymer particles, followed by further processing, e.g. extraction drying etc.

[0085] The membrane section 26 of each of the tubes 3 may advantageously comprise or consist of a fluoropolymer material, and optionally with the thickness in a range of about 100 to about 1000 pm. The use of a fluoropolymer material (for instance EPF, PFE, PVDF, PTFE) advantageously has hydrophobic properties that obviates the need for further surfacetreatment or special coatings on the membrane wall for the optimal generation of small droplets from the dispersed phase passing through the pores 28.

[0086] In an advantageous embodiment, the pores 28 may be formed by laser drilling and have a minimum diameter on the inner side 18 in a range of about 1 pm to about 10 pm thus allowing the formation of very small emulsion droplets, typically of less than about 15 pm diameter and preferably of less than about 10 pm diameter. The membrane pores 28 may, in variants, be made by other manufacturing techniques per se known, such as by water jet perforation, etching, and other known subtractive manufacturing techniques. In advantageous embodiments, however, the membrane pores 28 may be formed by laser drilling, the tube consisting of a fluoropolymer material. Membrane tubes may be made by extrusion or as a flat membrane that is folded and joined at a longitudinal seam by welding or bonding. In the latter variant, the pores 28 may be formed on the flat membrane sheet before folding into a tube.

[0087] According to an advantageous aspect of the invention, the pores 28 are not evenly distributed around the entire perimeter of the tube along the membrane section, but instead arranged in a plurality of pore groups 29 configured to preserve structural strength of the tubular shape of the tubular membrane. In effect, in conventional solutions where the pores are substantially evenly distributed on the surface of the membrane, the pores lead to a weakening of the structural integrity of the tube that could lead to buckling due to the higher pressure of the dispersed phase liquid compared to the continuous phase liquid within the tube. This problem would not be present in tubes that have the dispersed phase flowing within the tube since the wall of the tube would act in traction, whereas in a solution where the emulsion is formed within the tube, pressure on the outer side of the tube means that the walls act in compression and can buckle with excessive pressure. Thus, according to this aspect of the invention, where the pores are arranged in groups separated by spaces, these are configured to maintain the resistance against compression of the tube wall.

[0088] Embodiments of various groupings of pores according to the invention are illustrated in Figures 2a to 2d. In the embodiment of Figure 2a, the pores 28 are arranged longitudinally in one or two substantially axially aligned columns of pores forming a pore group 29. Adjacent pores within a pore group are spaced apart by a pore spacing Sp. There may be a plurality of columns however there are preferably one, two or maximum three columns per pore group 29. A plurality of pore groups is preferably provided spaced around the axis of the tube, for instance at 90 degrees from each other such that four pore groups are positioned spaced around the tube axis at a given height along the tube. Depending on the length of the membrane section 26, the pore groups 29 may be arranged at different heights along the tube,adjacent pore groups being spaced apart by an axial pore group spacing Sg. The tubular wall thus forms a continuous ring in the spacing Sg that ensures greater strength against compressive buckling.

[0089] It may be noted that the fluoropolymer membrane wall may have a greater thickness in the tubular uninterrupted sections or the tubular sections without pores, or may be provided with a support structure on the outer side of the membrane tubes in the axial spacing between pore groups so as to provide the resistance against compressive buckling. Preferably the additional thickness or the additional support ring structures are provided on the outer side of the membrane tubes so that the inner side of the tube remains smooth with a substantially continuous diameter. The smooth inner surface avoids turbulent flow due to obstacles in the flow path.

[0090] In the embodiment illustrated in Figure 2b, the pore groups are arranged in one, two, three or more rows, preferably no more than three rows, substantially orthogonal to the axis of the tube. The rows separated by an axial pore group spacing Sg that is one to five times preferably one to three times greater than the axial width Sp of the pore group. Here also, within the axial spacing between pore groups, ring reinforced thickness or added structure may be provided to the outer side of the membrane to provide resistance against compressive buckling.

[0091] It may be noted that although the columns in the embodiment of Figure 2a and the rows in the embodiment of Figure 2b show pores in the different rows that are aligned with adjacent pores in the axial direction A, they may be offset in order to increase the axial distance between the pores on the same axial direction A which corresponds to the direction of flow of the continuous phase. Thus, a greater separation between particles that are formed at the outlet of the pores, which are found on the inlet inner side of the tube, reduces the likelihood of interaction between particles that could lead to coalescence.

[0092] In another embodiment, the pore groups may be provided in rows / columns at an oblique angle jB that has both a circumferential component and an axial component. In such case the reinforcement thickness, or additional support ring, may also have an oblique angle. If the spacing Sg between the pore groups is such that there is no overlap in the axial direction A such that there is an axial spacing between the pore groups, the reinforcement or support ring may have a simple ring shape as in the above-mentioned variants.

[0093] It may be noted in the embodiments of Figures 2b and 2c that the pore groups may either completely surround the circumference of the tube or may extend only over an arcsection of the tube of less than 180 degrees, such that for instance two to four groups separated by an arc section gap may be provided around the tube axis.

[0094] In the embodiment of Figure 2d, the pore groups 29 may include a combination of the pore groups 29 arranged longitudinally similar to the embodiment of Figure 2a and of the pore groups 29 arranged in rows similar to the embodiment of Figure 2b.

[0095] The material of the external tube section 27 that extends out of the outer casing of the module as well as portions of the membrane tube section 26 which do not comprise the pore groups 29, may be made of different materials or with different layers of materials of different compositions or different thicknesses, provided that the sections of the membrane comprising the pores has a thin wall of thickness less than about 1000pm, and that the inner side of the membrane tube has a substantially smooth surface configured to avoid local turbulences.

[0096] The low thickness of the membrane wall where the pore groups are arranged is intended to enable production of very small diameter pores, for instance in a range of about 1 to about 10 pm, with laser drilling or other perse known perforation techniques.

[0097] One of the applications for the production of polymer particles is for instance the production of biopolymer particles as described for instance in WO 2023052744. Other polymer particles may however also be generated benefitting from the advantageous aspects of the present invention.

[0098] The invention will be described further in the following numbered clauses:1. An apparatus for polymer particle production by membrane emulsification comprising a tank (2) and a plurality of membrane tubes (3), each membrane tube comprising a membrane section (26) mounted within a first tank chamber (14a) of the tank (2), the first tank chamber (14a) configured to be connected to a source of a dispersed phase liquid, each membrane tube comprising an inlet (22) configured to be connected to a source of a continuous phase, each membrane section (26) comprising a plurality of pores (28) extending through a wall (16) of the membrane section (26), characterized in that each membrane tube (3) comprises an external tube section (27) extending through a casing (11) of the tank surrounding the first tank chamber.2. The apparatus according to the preceding clause wherein the pores (28) include pores arranged in a plurality of pore groups (29), the pore groups separated from adjacent pore groups by an axial spacing (Sg) that is greater than an axial spacing between adjacent pores of a same pore group.3. The apparatus according to the preceding clause wherein the pore groups comprise one to five rows or columns of pores.4. The apparatus according to the preceding clause wherein adjacent said rows or columns of pores are spaced apart by a distance in a range of 2 to 10 mm, preferably 2 to 5 mm.5. The apparatus according either of the two directly preceding clauses wherein the pore groups are arranged:- in columns extending substantially in an axial direction, or- in rows extending substantially orthogonally to the axial direction surrounding an axis of the membrane tube, or- at an oblique angle p with respect to the axial and radial directions of the membrane tube, the angle being in a range of 10 degrees to 80 degrees with respect to the axial direction of the membrane tube degrees (10° < / 3 < 80°), preferably in a range of 30 degrees to 60 degrees (30° < / 3 < 60°).6. The apparatus according to any of the four directly preceding clauses wherein the membrane sections of the membrane tube, at least where the pore groups are positioned, comprises or consists of a fluoropolymer membrane having a thickness in a range of 100pm to 1000pm.7. The apparatus according to any of the five directly preceding clauses wherein the membrane tube comprises a ring shape reinforcement provided by a greater wall thickness or an additional ring structure or reinforcement layer in areas of the membrane tube where the pore groups are not positioned.8. The apparatus according to the preceding clause wherein the tubular reinforcement is positioned in an axial space between pore groups.9. The apparatus according to any preceding clause wherein the pores have a diameter on an inner side (18) of the membrane tube in a range of 1 pm to 10 pm.10. The apparatus according to any preceding clause wherein the pores have a cross- sectional surface area on an inner side of the membrane tube that is smaller than a cross- sectional surface area of the pore on an outer side of the membrane tube.11. The apparatus according to any preceding clause wherein the tank (2) comprises a second tank chamber (14b) separated from the first tank chamber by a separating wall (13), inlet ends of the membrane tubes formed at the separating wall (13) for fluid connection with the second tank chamber.12. The apparatus according to any preceding clause wherein the second tank chamber comprises an inlet configured for connection to a source of a continuous phase liquid.13. The apparatus according to any preceding clause wherein the plurality of membrane tubes is greater than four, preferably greater than five.14. The apparatus according to any preceding clause wherein a diameter of the membrane tube on the inner side is within a range of 5 to 20 mm, preferably 8 to 10 mm.15. The apparatus according to any preceding clause wherein the membrane tube comprises a membrane tube wall extending the whole length of the membrane sections (26) and over a portion or all of the external tube section (27) extending out of the outer casing (11).List of referencesPolymer bead production apparatus 1Main tank 2Dispersed phase inlet 8Dispersed phase outlet 9Continuous phase inlet 10Casing 11Tank walls 12Separating wall 13Tank chamber 14Tank first chamber 14aTank second chamber 14bTube 3Tube wall 16Inner side 18Outer side 20Inlet 22Outlet 24Membrane tube sections 26Pores 28Inner side 30Outer side 32Pore groups 29External tube section 27Emulsion processing unit 30Break line 31Continuous phase liquid 4Dispersed phase liquid 5Emulsion 6Polymer beadsPore diameterInner side diameter DiOuter side diameter DoMembrane wall thickness WtSpacing between adjacent pores of a group SpSpacing between adjacent pore groups SgAngle of pore group relative to the axial direction / 3Angle between pore groups arranged around tube axis a

Claims

CLAIMS1. An apparatus for polymer particle production by membrane emulsification comprising a tank (2) and a plurality of tubes (3), each tube comprising a membrane section (26) mounted within a first tank chamber (14a) of the tank (2), the first tank chamber (14a) configured to be connected to a source of a dispersed phase liquid, each tube comprising an inlet (22) configured to be connected to a source of a continuous phase, each membrane section (26) comprising a plurality of pores or perforations (28) extending through a wall (16) of the membrane section (26), each tube (3) comprising an external tube section (27) extending through a casing (11) of the tank surrounding the first tank chamber, wherein the plurality of pores or perforations are confined to the membrane section (26) mounted within the first tank chamber (14a) of the tank (2), and wherein the external tube section (27) of each tube (3) is configured for connection to an emulsion processing unit (30).

2. The apparatus according claim 1 wherein the pores or perforations (28) are arranged in a plurality of pore or perforation groups (29), the pore or perforation groups being separated from adjacent pore or perforation groups by an axial spacing (Sg) that is greater than an axial spacing between adjacent pores or perforations of a same pore or perforation group.

3. The apparatus according to claim 2 wherein the pore or perforation groups comprise one to five rows or columns of pores or perforations.

4. The apparatus according to claim 3 wherein adjacent said rows or columns of pores or perforations are spaced apart by a distance in a range of about 2 to about 10 mm, preferably in a range of about 2 to about 5 mm.

5. The apparatus according to claim 3 or claim 4 wherein the pore or perforation groups are arranged:- in columns extending substantially in an axial direction, or- in rows extending substantially orthogonally to the axial direction surrounding an axis of the tube, or- at an oblique angle p with respect to the axial and radial directions of the tube, the angle being in a range of 10 degrees to 80 degrees with respect to the axial direction of the tube (10° < / 3 < 80°), preferably in a range of 30 degrees to 60 degrees (30° << 60°).

6. The apparatus according to any of claims 2 to 5 wherein the membrane section of each tube, at least where the pore or perforation groups are positioned, comprises or consists of a fluoropolymer material, preferably wherein each tube (3) consists of a fluoropolymer material.

7. The apparatus according to claim 6, wherein the membrane section of each tube, at least where the pore or perforation groups are positioned, have a thickness in a range of about 100pm to about 1000pm, preferably wherein each tube (3) consists of a fluoropolymer material and has a thickness in a range of about 100pm to about 1000pm.

8. The apparatus according to any of claims 2 to 7 wherein the tube comprises a ring shape reinforcement provided by a greater wall thickness or an additional ring structure or reinforcement layer in areas of the tube where the pore or perforation groups are not positioned.

9. The apparatus according to claim 8 wherein the tubular reinforcement is positioned in an axial space between pore or perforation groups.

10. The apparatus according to any preceding claim wherein the pores or perforations have a diameter on an inner side (18) of the tube in a range of about 1 pm to about 10 pm.

11. The apparatus according to any preceding claim wherein the pores or perforations have a cross-sectional surface area on an inner side of the tube that is smaller than a cross-sectional surface area of the pore or perforation on an outer side of the tube.

12. The apparatus according to any preceding claim wherein the tank (2) comprises a second tank chamber (14b) separated from the first tank chamber by a separating wall (13), and inlet ends of the tubes are formed at the separating wall (13) for fluid connection with the second tank chamber.

13. The apparatus according to any preceding claim wherein the second tank chamber comprises an inlet configured for connection to a source of a continuous phase liquid.

14. The apparatus according to any preceding claim wherein the plurality of tubes is greater than four, preferably greater than five.

15. The apparatus according to any preceding claim wherein a diameter of the tube on the inner side is within a range of about 5 to about 20 mm, preferably about 8 to about 10 mm.

16. The apparatus according to any preceding claim wherein each tube comprises a tube wall extending the whole length of the membrane section (26) and over a portion or all of the external tube section (27) extending out of the outer casing (11), preferably wherein the tube wall extends the whole length of the membrane section (26) and all of the external tube section (27).

17. The apparatus according to any preceding claim wherein the external tube section (27) of each tube (3) is exposed.

18. The apparatus according to any preceding claim further comprising the emulsion processing unit (30), wherein the emulsion processing unit is connected to the external tube section of each tube (3).

19. The apparatus according to claim 18 wherein the tube wall of each tube (3) extends along the length of the external tube section (27) to the emulsion processing unit (30).

20. A membrane tube (3) for polymer particle production by membrane emulsification, wherein the tube comprises an inlet (22) configured to be connected to a source of a continuous phase, a membrane section (26) comprising a plurality of pores or perforations (28) extending through a wall (16) of the membrane section (26), a nonmembrane section (27), and an outlet configured for connection to an emulsion processing unit (30), wherein the pores or perforations (28) are confined to the membrane section (26) and arranged in a plurality of pore or perforation groups (29), wherein the tube wall extends along the length of the membrane section (26) and nonmembrane section (27) so that the tube is continuous, and wherein at least the membrane section (26) comprises or consists of a fluoropolymer material.

21. The membrane tube according to claim 20, wherein the tube consists of a fluoropolymer material.

22. The membrane tube according to claim 20 or claim 21 , wherein the length ratio of the membrane section (26) to the non-membrane section (27) is about 1 :1 to about 1 :5.

23. The membrane tube according to any of claims 20 to 22, wherein the pore or perforation groups are separated from adjacent pore or perforation groups by an axial spacing (Sg) that is greater than an axial spacing between adjacent pores or perforations of a same pore or perforation group.

24. The membrane tube according to any of claims 20 to 23, wherein the membrane section (26), at least where the pore or perforation groups are positioned, has a thickness in a range of about 100pm to about 1000pm, preferably wherein the tube (3) consists of a fluoropolymer material and has a thickness in a range of about 100pm to about 1000pm.

25. The membrane tube according to any of claims 20 to 24 wherein the pore or perforation groups are arranged:- in columns extending substantially in an axial direction, or- in rows extending substantially orthogonally to the axial direction surrounding an axis of the tube, or- at an oblique angle p with respect to the axial and radial directions of the tube, the angle being in a range of 10 degrees to 80 degrees with respect to the axial direction of the tube (10° < / 3 < 80°), preferably in a range of 30 degrees to 60 degrees (30° << 60°).

26. The membrane tube according to any of claims 20 to 25 wherein the tube comprises a ring shape reinforcement provided by a greater wall thickness or an additional ring structure or reinforcement layer in areas of the tube where the pore or perforation groups are not positioned, preferably wherein the tubular reinforcement is positioned in an axial space between pore or perforation groups.

27. A method for preparing biopolymer particles comprising: a. a membrane emulsification of a dispersed phase into a continuous phase, wherein the dispersed phase comprises the biopolymer in a solvent, and wherein the dispersed phase and the continuous phase are provided to an apparatus comprising a tank (2) and plurality of tubes (3), each tube comprising a membrane section (26) mounted within a first tank chamber (14a) of the tank (2), the first tank chamber (14a) being connected to a source of the dispersed phase, each tube further comprising an inlet (22) connected to a source of the continuous phase, each membrane section (26) comprising a plurality of pores or perforations (28) extending through a wall (16) of the membrane section (26),wherein each tube (3) comprises an external tube section (27) extending through a casing (11) of the tank surrounding the first tank chamber, and wherein passing the dispersed phase through the membrane section (26) of each tube forms an emulsion of the biopolymer in the continuous phase.

28. The method according to claim 27, wherein the membrane section (26) of each tube comprises or consists of a fluoropolymer material, preferably wherein each tube (3) consists of a fluoropolymer material.

29. The method according to claim 27 or claim 28, wherein the external tube section of each tube (3) is connected to an emulsion processing unit (30), and the method further comprises: b. a phase inversion with an anti-solvent to form particles of the biopolymer in said unit (30).

30. The method according to any of claims 27 to 29, wherein each tube (3) is continuous, and the plurality of pores or perforations are confined to the membrane section (26) mounted within the first tank chamber (14a) of the tank (2).31 . The method according any of claims 27 to 30, wherein the solvent of the dispersed phase comprises water and / or wherein the anti-solvent comprises water.

32. The method according to any of claims 27 to 31 , wherein the biopolymer is a polysaccharide, preferably wherein the biopolymer is cellulose.

33. The method according to any of claims 27 to 32, wherein the solvent of the dispersed phase comprises an ionic liquid, and / or wherein the anti-solvent further comprises an ionic liquid.

34. The membrane tube according to any of claims 20 to 26 for use in reducing coalescence of emulsion droplets in a membrane emulsification method for preparing biopolymer particles.