Method of preparing small particles of polypropylene

DETAILED DESCRIPTION What I claim and desire to protect by Letters Patent is: 1.
A method of preparing a dispersion of polypropylene in the form of discrete substantially spherical particles of about 1 to 100 microns in diameter which comprises preparing a homogeneous solution of about 10 to 25% concentration by weight of polypropylene at an elevated temperature in a normally liquid organic material which is a solvent for polypropylene at a temperature of at least 120.
degree.
C.
and which has a solubility parameter of about 6.
6 to 10.
3 (Cal/cc).
sup.
1/2, a dipole moment of about 0 to 1.
7 Debye units and a hydrogen bonding parameter of about 0 to 18.
7 cm.
.
sup.
-.
sup.
1, thereafter cooling said solution to room temperature under quiescent conditions to precipitate the polypropylene, subjecting the precipitated polymer to high shear conditions and recovering a dispersion of particles in the organic liquid.
2.
The method of claim 1 where the normally liquid organic material is selected from the class consisting of paraffin hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, cycloaliphatic hydrocarbons, and aliphatic alcohols.
3.
The method of claim 2 including the additional step of incorporating a coloring material into the polymer solution in an amount up to about 50% by weight of the polymer prior to quiescently cooling the solution.
4.
A method of preparing discrete, substantially spherical particles of polypropylene about 1 to 100 microns in diameter which method comprises preparing a dispersion of polypropylene according to the method of claim 1 and thereafter removing the resultant particles from the liquid organic material, washing with a polar organic liquid and drying.
5.
The method of claim 4 including the additional step of incorporating a coloring material into the polymer solution in an amount up to about 50% by weight of the polymer prior to quiescently cooling the solution.




Description:
This invention relates to the preparation of small, spherical particles of polypropylene