Production of Superabsorbent Polymers on a Continuous Belt Reactor

{
  "publication_number": "US2009312184A1",
  "country": "US",
  "kind": "A1",
  "title": "Production of Superabsorbent Polymers on a Continuous Belt Reactor",
  "abstract": "The invention relates to the production of superabsorbent polymers on a continuous belt reactor, wherein the continuous belt rests at least partly upon at least one support belt and the at least one continuous support belt is a metallic belt with a basis weight of at least 1 kg/m 2.",
  "claims": [
    "1. A process for production of superabsorbent polymers on a continuous belt reactor, comprising i) a continuous polymerization belt and ii) at least one continuous support belt, wherein the continuous polymerization belt i) rests at least partly upon an upper surface of the at least one continuous support belt ii) and the at least one continuous support belt ii) is a metallic belt with a basis weight of at least 1 kg/m 2.",
    "2. The process according to claim 1 wherein the at least one continuous support belt ii) has meshes with a mesh size of at least 6 mm.",
    "3. The process according to claim 1 wherein the at least one continuous support belt ii) has a thickness of at least 4 mm.",
    "4. The process according to claim 1 wherein the at least one continuous support belt ii) is a flat wire belt.",
    "5. The process according to claim 1 wherein the at least one continuous support belt ii) is a flat wire belt with a strip thickness of less than 2 mm.",
    "6. The process according to claim 1 wherein the at least one continuous support belt ii) slides at least partly on a fixed surface.",
    "7. The process according to claim 6 wherein less than 20% of a width of the at least one continuous support belt ii) slides on the fixed surface.",
    "8. The process according to claim 7 wherein the fixed surface is at least one slide bar.",
    "9. The process according to claim 8 wherein an upper surface of the slide bar is at least partly coated with a material having a friction coefficient of less than 0.5.",
    "10. The process according to claim 9 wherein the coating material is polytetrafluoroethylene.",
    "11. The process according to claim 1 wherein the continuous polymerization belt i) comprises a carcass and a cover.",
    "12. The process according to claim 1 wherein the continuous polymerization belt i) rests upon at least two continuous support belts ii).",
    "13. The process according to claim 1 wherein lateral edges of the continuous polymerization belt i) are curved upwardly from a horizontal plane by at least one fixed support means.",
    "14. The process according to claim 1 wherein a first section of the continuous polymerization belt i) forms a trough.",
    "15. The process according to claim 1 wherein the at least one continuous support belt ii) is stiffed in transverse direction.",
    "16. The process according to claim 1 wherein the at least one continuous support belt ii) forms at an end in downward direction a barrier for liquids.",
    "17. The process according to claim 1 wherein a monomer that is processed on the continuous belt reactor is at least 50 wt. % acrylic acid and/or a salt thereof."
  ],
  "description_excerpt": "The present invention relates to a process for production of superabsorbent polymers on a continuous belt reactor, wherein a continuous polymerization belt rests at least partly upon the upper surface of at least one continuous support belt.\n\nSuperabsorbent polymers are in particular polymers of (co)polymerized hydrophilic monomers, graft (co)polymers of one or more hydrophilic monomers on a suitable grafting base, crosslinked ethers of cellulose or of starch, crosslinked carboxymethyl-cellulose, partially crosslinked polyalkylene oxide or natural products swellable in aqueous fluids, such as guar derivatives for example. Such polymers are used as products capable of absorbing aqueous solutions to produce diapers, tampons, sanitary napkins and other hygiene articles, but also as water-retaining agents in market gardening.\n\nSuperabsorbent polymers typically have a Centrifuge Retention Capacity in the range from 25 to 60 g/g, preferably of at least 30 g/g, more preferably of at least 32 g/g, even more preferably of at least 34 g/g and most preferably of at least 35 g/g. Centrifuge Retention Capacity (CRC) is determined by EDANA (European Disposables and Non-wovens Association) recommended test method No. WSP 241.2-05 “Centrifuge retention capacity”.\n\nTo improve their performance characteristics, for example permeability, superabsorbent polymeric particles are generally postcrosslinked. This postcrosslinking can be carried out in the aqueous gel phase. Preferably, however, dried, ground and screened particles of the base polymer are surface coated with a postcrosslinker, dried and thermally postcrosslinked.",
  "cpc": [
    "B01J 19/22",
    "B65G 15/60",
    "C08F 2/01"
  ],
  "ipc": [
    "B01J 20/26"
  ],
  "assignees": [
    "BASF SE"
  ],
  "inventors": [
    "Matthias Weismantel",
    "Rüdiger Funk",
    "Leigh R. Blair",
    "Kevin D. Heitzhaus",
    "Bruce Storey"
  ],
  "filing_date": "2008-01-10",
  "publication_date": "2009-12-17",
  "priority_date": "2007-01-16",
  "application_number": "US-52210908-A",
  "family_id": "39148275",
  "cited_by_count": 7,
  "citations": [
    "US3794155A",
    "US4389357A",
    "US4857610A",
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    "US5004761A",
    "EP0955086A2",
    "US6241928B1",
    "DE19928896A1",
    "US6710141B1",
    "US6530469B2",
    "US20060167198A1"
  ]
}