Special Grades
KURARAY R-POLYMER
  1. Introduction

    KURARAY R-polymer is water-soluble polymer, which has peculiar functional groups, i.e., silanol groups, in their molecular structures. The silanol groups are reactive with inorganic substances such as silica or alumina. R-polymer can be easily cross-linked by changing PH of their aqueous solutions or by mixing with inorganic substances and can form water resistant films.
    R-polymer is mainly used as a binder for inorganic substances and as surface coating agent for organic materials containing inorganic substances such as paper.


  2. Grades and specifications

    GRADES AND SPECIFICATIONS
    Grades R-1130 R-2105 R-3109
    Appearance pale yellow granular powder
    Solubility water soluble water soluble water soluble
    Volatiles(% max) 5.0 5.0 5.0
    Viscosity(cps)*1 20-30 4.5-6 9-12
    Remarks
    *1)Viscosity in cps of 4% aqueous solution at 20 is determined by Brookfield Viscometer.

    The conventional R-polymer, such as R-1130, has some difficulties in its usage for paper coating since they have comparatively higher viscosity. KURARAY R-polymer R-3109 is newly developed improving such difficulties by adjusting their viscosity and it is easy to use them in the actual operation of the paper coating.


  3. Characteristics of R-polymer

    Reactivity with inorganic substances
    R-polymer has high reactivity with a variety of inorganic substances and forms water resistant films. In particular, adhesion to glass or alumina is remarkable and the film made from the mixture of R-polymer and colloidal silica is superior in transparency and water-resistance.

  4. Applications of R-polymer

    R-polymer are applied mainly for the paper industry and as binder of inorganic materials such as:
    *under coating agent for release paper
    *pigment binder for ink-jet printing paper
    *internal bond for glass fiber paper
    *binder for filler containing agricultural chemicals
    *primer for calcium silicate board
    *surface sizing agent for paper containing large amount of filler


    1. Under coating agent for release paper
      In case of release paper application, PVA is generally used for under coating of silicon used as releasing agent. PVA offers a good barrier property since its superior adhesion to paper, film-forming ability and organic solvent resistance.
      As mentioned above, R-polymer is easily cross linked by aluminium ion. The R-polymer solution, which is coated in size-press process onto paper surface, reacts on paper surface with aluminium ion contained in paper and remains on the surface because the viscosity of the solution is increased extremely. Then the solution gets gelling and forms a film on the surface, which has excellent resistance against oil and organic solvent. In these points, R-polymer offers more outstanding performance than PVA.


    2. Pigment binder for ink-jet printing paper
      In general, porous silica powder is used for ink-jet paper application because of its high absorption capability of ink-jet ink and PVA is used as binder.
      A better absorption of ink, namely better print-ability is heavily related to the amount of pore of such silica. In this sense, logically, the smaller amount of binder gives better absorption of ink, since the binder trends to cover the pore. Because of better adhesion to silica, R-polymer offers good performance with smaller amount than PVA.


    3. Internal bond for glass fiber paper
      In glass fiber paper manufacturing, fine powder type of PVA is used as internal bond as it has good adhesion to glass. R-polymer offers better performance because of excellent adhesion to glass.


    4. Binder for filler containing agricultural chemicals
      In order to granulate filler containing agricultural chemicals, PVA is widely used as binder for such filler. In case of PVA, the granule is easily broken by water such as rain. This is suitable for quick effect type.
      However, for slow effect type, R-polymer is recommendable because of its moderate solubility.


    5. Primer for calcium silicate board
      Polyacrylester emulsion is generally used as an aqueous primer for calcium silicate board to strengthen the surface and, to some extent, it can offer water barrier property. In this application, R-polymer gives excellent surface strength and water barrier property.


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