Patent ID: 11939446
Assignee: NOURYON CHEMICALS INTERNATIONAL B.V.
Field: Chemical engineering (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 18:
19. A process for the manufacture of thermally expandable thermoplastic microspheres, the process comprising:
providing a mixture of monomeric materials suitable for polymerisation to form a thermoplastic polymer and at least one blowing agent,
providing a colloidal silica that is surface-modified with at least hydrophobic organosilane groups;
contacting the mixture of one or more monomers and at least one blowing agent with the surface-modified colloidal silica and forming an o/w emulsion comprising droplets of the mixture of one or more monomers and the at least one blowing agent in an aqueous phase; and
polymerising the one or more monomers in the droplets to form an aqueous slurry and/or wet cake of thermally expandable thermoplastic microspheres,
wherein the colloidal silica is modified with the hydrophobic organosilane groups that are alkylsilyl groups, vinylsilyl groups, and/or phenylsilyl groups, and is further surface-modified with hydrophilic organosilane groups; and
wherein the colloidal silica that is surface-modified with at least hydrophobic organosilane groups has a degree of surface modification (DM) of up to 190%, wherein 190% means an amount of 4.5 μmol hydrophobic organosilane groups per m2 of the colloidal silica, and
wherein DM is calculated according to the equation:, D
   ⁢
   M
  
  =
  
   
    N
    sil
   
   ⁢
   
    W
    CS
   
   ×
   
    C
    CS
   
   ×
   
    SA
    CS
   
  
 

in which;
DM is the Degree of Surface Modification in units of μmol m−2;
Nsil is the quantity of organosilane added to colloidal silica in units of μmol;
WCS is the weight of colloidal silica before it is surface modified in units of g (grams);
CCS is the percentage by weight of silica in the colloidal silica before it is surface-modified; and
SACS is the surface area of the silica in the colloidal silica before it is surface modified, the surface area being calculated by Sears Titration, in units of m2 g−1; and
wherein a proportion of the degree of surface modification of hydrophobic organosilane groups/hydrophilic organosilane groups is 50%/50%.