Inert separator beads for use in the regeneration of mixed bed-ion exchange resins

Claim 2

Separator beads for separating anion exchange resin beads from cation exchange resin beads during regeneration of mixed-bed ion exchange resins, which separator beads are free from ion exchange functionality and comprise copolymer of from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality, and from 1 to 6 weight percent polyvinyl crosslinking monomer, the percentages being based upon the total weight of the copolymer.

Claim 3

Separator beads according to Claim 1 wherein the hydrophilic monomer comprises acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, vinyl-pyrolidone and/or hydroxyalkyl acrylamide where the alkyl group has from 2 to 6 carbon atoms, and/or the methacrylamides corresponding to these acrylamides, preferably methacrylamide.

Claim 4

Separator beads according to Claim 1 or 2 wherein the polyvinyl crosslinking monomer comprises divinylbenzene, trivinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane, trimethacrylate and/or divinylnaphthalene, preferably divinylbenzene.

Claim 5

Separator beads according to any preceding claim having a wet density between 1.15 and 1.17 g/cm 3 ,

Claim 6

Separator beads according to any preceding claim having an average particle diameter of 150 µm to 1 mm, preferably 400 to 800 µm.

Claim 7

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality and from 1 to 6 weight percent polyvinyl crosslinking monomer, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium containing dissolved salt to reduce the solubility of the hydrophilic monomer in the aqueous medium, and (c) isolating the beads which result from the suspension polymerization step.

Claim 8

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality and from 1 to 6 weight percent polyvinyl crosslinking monomer, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium containing dissolved salt to reduce the solubility of the hydrophilic monomer in the aqueous medium, and (c) isolating the beads which result from the suspension polymerization step.

Claim 9

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising 20 to 75 weight percent methyl methacrylate, 0.5 to 1 weight percent of polyvinyl crosslinking monomer, the balance of the monomer being styrene, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium to form polymer seed beads, (c) isolating the polymer seed beads, (d) suspending the polymer seed beads in an aqueous suspension medium containing dissolved salt, (e) conducting a seed polymerization by adding to the aqueous suspension medium containing the dissolved salt an emulsified monomer mixture of 70 to 90 weight percent methyl methacrylate, 3 to 10 weight percent hydrophilic monomer containing amide functionality, 2 to 6 weight percent crosslinking monomer, all said percentages based on the total weight of the monomer, water, and polymerization inhibitor soluble in the aqueous phase, with heating, until the beads grow to the desired size, and (f) isolating the beads of the desired size.

Claim 10

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising 20 to 75 weight percent methyl methacrylate, 0.5 to 1 weight percent of polyvinyl crosslinking monomer, the balance of the monomer being styrene, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium to form polymer seed beads, (c) isolating the polymer seed beads, (d) suspending the polymer seed beads in an aqueous suspension medium containing dissolved salt, (e) conducting a seed polymerization by adding to the aqueous suspension medium containing the dissolved salt an emulsified monomer mixture of 70 to 90 weight percent methyl methacrylate, 3 to 10 weight percent hydrophilic monomer containing amide functionality, 2 to 6 weight percent crosslinking monomer, all said percentages based on the total weight of the monomer, water, and polymerization inhibitor soluble in the aqueous phase, with heating, until the beads grow to the desired size, and (f) isolating the beads of the desired size.

Claim 11

A process according to Claim 7 wherein the weight ratio of monomer to seed beads during step (e) is from 1:1 to 8:1, preferably 2:1 to about 5:1, more preferably 3.5:1 to about 4.5:1.

Claim 12

A process according to Claim 7 or 8 wherein the beads from step (b) are from 150 to 500 µm in average diameter, and the desired size of the beads in step (e) is from 400 to 800µm in average diameter.

Claim 13

A process as claimed in any of Claims 7 to 9 as applied to the preparation of beads as claimed in any of Claims 2 to 8.

Claim 14

Beads as claimed in any of Claims 1 to 6 in admixture with anion and cation exchange resin beads wherein the separator beads have an hydraulic density between that of the cation and that of the anion exchange resin beads.

Claim 15

The admixture of Claim 11 containing 10 to 15 volume percent of the inert separator beads based on total bead volume.

Claim 16

A mixed bed ion exchange process wherein beads as claimed in any of Claims 1 to 6 are used to separate the cation exchange resin beads from the anion exchange resin beads during regeneration thereof.

Claim 17

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality and from 1 to 6 weight percent polyvinyl crosslinking monomer, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium containing dissolved salt to reduce the solubility of the hydrophilic monomer in the aqueous medium, and (c) isolating the beads which result from the suspension polymerization step.

Claim 18

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality and from 1 to 6 weight percent polyvinyl crosslinking monomer, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium containing dissolved salt to reduce the solubility of the hydrophilic monomer in the aqueous medium, and (c) isolating the beads which result from the suspension polymerization step.

Claim 19

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising 20 to 75 weight percent methyl methacrylate, 0.5 to 1 weight percent of polyvinyl crosslinking monomer, the balance of the monomer being styrene, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium to form polymer seed beads, (c) isolating the polymer seed beads, (d) suspending the polymer seed beads in an aqueous suspension medium containing dissolved salt, (e) conducting a seed polymerization by adding to the aqueous suspension medium containing the dissolved salt an emulsified monomer mixture of 70 to 90 weight percent methyl methacrylate, 3 to 10 weight percent hydrophilic monomer containing amide functionality, 2 to 6 weight percent crosslinking monomer, all said percentages based on the total weight of the monomer, water, and polymerization inhibitor soluble in the aqueous phase, with heating, until the beads grow to the desired size, and (f) isolating the beads of the desired size.

Claim 20

A process for preparing inert separator beads which comprises the steps, performed in the following order, of (a) preparing a monomer mixture comprising 20 to 75 weight percent methyl methacrylate, 0.5 to 1 weight percent of polyvinyl crosslinking monomer, the balance of the monomer being styrene, (b) suspension polymerizing the monomer mixture in an aqueous suspension medium to form polymer seed beads, (c) isolating the polymer seed beads, (d) suspending the polymer seed beads in an aqueous suspension medium containing dissolved salt, (e) conducting a seed polymerization by adding to the aqueous suspension medium containing the dissolved salt an emulsified monomer mixture of 70 to 90 weight percent methyl methacrylate, 3 to 10 weight percent hydrophilic monomer containing amide functionality, 2 to 6 weight percent crosslinking monomer, all said percentages based on the total weight of the monomer, water, and polymerization inhibitor soluble in the aqueous phase, with heating, until the beads grow to the desired size, and (f) isolating the beads of the desired size.

Claim 21

A process according to Claim 2 wherein the weight ratio of monomer to seed beads during step (e) is from 1:1 to 8:1, preferably 2:1 to about 5:1, more preferably 3.5:1 to about 4.5:1.

Claim 22

A process according to Claim 2 or 3 wherein the beads from step (b) are from 150 to 500 µm in average diameter, and the desired size of the beads in step (e) is from 400 to 800µm in average diameter.

Claim 23

A mixture of anion exchange resin beads, cation exchange resin beads and separator beads which separator beads are free from ion exchange functionality and comprise copolymer of from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality, and from 1 to 6 weight percent polyvinyl crosslinking monomer, the percentages being based upon the total weight of the copolymer, and have an hydraulic density between that of the cation and that of the anion exchange resin beads.

Claim 24

A mixture of anion exchange resin beads, cation exchange resin beads and separator beads which separator beads are free from ion exchange functionality and comprise copolymer of from 60 to 90 weight percent methyl methacrylate, from 5 to 15 weight percent styrene, from 2 to 10 weight percent hydrophilic monomer containing amide functionality, and from 1 to 6 weight percent polyvinyl crosslinking monomer, the percentages being based upon the total weight of the copolymer, and have an hydraulic density between that of the cation and that of the anion exchange resin beads.

Claim 25

A process or a mixture according to any preceding claim wherein the hydrophilic monomer comprises acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, vinyl-pyrolidone and/or hydroxyalkyl acrylamide where the alkyl group has from 2 to 6 carbon atoms, and/or the methacrylamides corresponding to these acrylamides, preferably methacrylamide.

Claim 26

A process or a mixture according to any preceding claim wherein the polyvinyl crosslinking monomer comprises divinylbenzene, trivinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane, trimethacrylate and/or divinylnaphthalene, preferably divinylbenzene.

Claim 27

A process or a mixture according to any preceding claim wherein the separator beads have a wet density between 1.15 and 1.17 g/cm 3 .

Claim 28

A process or a mixture according to any preceding claim wherein the separator beads have an average particle diameter of 150 µm to 1 mm, preferably 400 to 800 µm.

Claim 29

A mixture according to any of Claims 5 to 9 containing 10 to 15 volume percent of the inert separator beads based on total bead volume.

Claim 30

A mixed bed ion exchange process wherein beads as defined in any of Claims 5 to 9 or as produced by a process according to any of Claims 1 to 9 are used to separate the cation exchange resin beads from the anion exchange resin beads during regeneration thereof.