Process for the preparation of polymer particles

{
  "publication_number": "US6160027A",
  "country": "US",
  "kind": "A",
  "title": "Process for the preparation of polymer particles",
  "abstract": "PCT No. PCT/EP97/03608 Sec. 371 Date Dec. 30, 1998 Sec. 102(e) Date Dec. 30, 1998 PCT Filed Jul. 3, 1997 PCT Pub. No. WO98/01489 PCT Pub. Date Jan. 15, 1998It is desirable to reduce the amount of volatile organic blowing agent in expandable polystyrene. This may be accomplished by partially polymerizing a mass of styrene and incorporating therein water together with an emulsifier. The partially polymerized mass is then polymerized to a high conversion using conventional suspension techniques. The polymer beads containing water which acts as a blowing agent are recovered.",
  "claims": [
    "1. Process for the preparation of polymer particles containing a vinylarene polymer by suspension polymerization, which process comprises: a) pre-polymerising vinylarene monomers to a conversion degree of 20 to 70%, based on the vinylarene monomer, to yield a pre-polymerised mass, which pre-polymerised mass further contains water emulsified therein and an emulsifier, which pre-polymerisation is carried out with water already present or before water is added; b) suspending the pre-polymerised mass in an aqueous medium to yield suspended droplets; and c) polymerising the vinylarene monomer in the suspended droplets to complete monomer conversion to yield suspended polymer particles.",
    "2. Process according to claim 1, in which the polymer particles obtained are separated from the aqueous mixture and expanded to yield pre-expanded particles.",
    "3. Process according to claim 1, in which the water, an emulsifier and the vinylarene monomer are stirred to create an emulsion which is subsequently subjected to pre-polymerization to the desired conversion degree to yield the pre-polymerized mass.",
    "4. Process according to claim 1, in which the vinylarene monomer is first subjected to prepolymerisation in the presence of emulsifier, and, subsequently, water is added to the pre-polymerised vinylarene mixture and water is emulsified.",
    "5. Process according to claim 1, in which the emulsifier is selected from bisalkylsulphosuccinates, sorbitol-C 8-20 -carboxylates and C 8-20 -alkylxylene sulphonates.",
    "6. Process according to claim 1, in which the amount of emulsifier ranges from 0.01 to 5% wt, baseded on the amount of vinylarene monomer.",
    "7. Process according to claim 1, in which the amount of water to be used in step a) ranges from 1 to 20% wt, based on the weight of water and vinylarene monomer.",
    "8. Process according to claim 1, in which the pre-polymerisation step a) and the polymerisation step c) are conducted by free-radical polymerization.",
    "9. Process according to claim 1, in which polar polymers are incorporated in the pre-polymerised mass.",
    "10. Process according to claim 1, in which cross-linking agent is present during polymerisation."
  ],
  "description_excerpt": "The present invention relates to a process for the preparation of polymer particles containing a polymer of a vinylarene monomer and a physical foaming agent, and to such polymer particles.\n\nParticles that contain such a polymer and foaming agent are generally known as expandable polymer particles. A well-known type of expandable polymer particles is expandable polystyrene. Expandable polystyrene is produced on a commercial scale by suspension polymerization. The foaming agent is usually a low-boiling hydrocarbon, such as a C 3 -C 8 hydrocarbon, in particular pentane isomers. The expandable polystyrene is used for making foamed articles that are produced by expanding the polystyrene particles. In the expansion process the hydrocarbon foaming agent is released and may be emitted into the environment. Such emissions are regarded undesirable and ways are sought to avoid such emissions. One way is to recover or burn the emitted hydrocarbon. Another way is to reduce the amount of hydrocarbon foaming agent in the expandable polymer particles.\n\nIn U.S. Pat. No. 5,096,931 expandable polystyrene is described which contains polystyrene, a small amount of a polar polymer, some water and a reduced amount of hydrocarbon foaming agent. Although the content of hydrocarbon foaming agent has been reduced such agent must still be present to achieve satisfactory expansion.\n\nGB-A-1,106,143 discloses a process for preparing water-expandable polystyrene particles by mixing by vigorous mechanical agitation styrene monomer, water and an emulsifier with a free-radical initiator to obtain an emulsion containing small droplets of water.",
  "cpc": [
    "C08J 9/20",
    "C08F 12/04",
    "C08J 2325/08"
  ],
  "ipc": [
    "C08F 12/00",
    "C08F 12/04",
    "C08F 2/18",
    "C08J 9/12",
    "C08J 9/20"
  ],
  "assignees": [
    "Nova Chemicals International SA"
  ],
  "inventors": [
    "Jeroen Joost Crevecoeur",
    "Eric Wilhelmus Johannes Frederik Neijman",
    "Laurentius Nicolaas Ida Hubertus Nelissen",
    "Johannes Maria Zijderveld"
  ],
  "filing_date": "1997-07-03",
  "publication_date": "2000-12-12",
  "grant_date": "2000-12-12",
  "priority_date": "1996-07-04",
  "application_number": "US-21425898-A",
  "family_id": "8224157",
  "cited_by_count": 79,
  "citations": [
    "GB1106143A",
    "US5096931A"
  ]
}