Method for producing low bulk density, free-flowing polymer powders

Claim 2

The method according to claim 2 wherein the alcohol is n-propanol.

Claim 3

The method according to claim 2 wherein the medium contains from about 2 to about 20 volume percent of the aliphatic alcohol.

Claim 4

The method according to claim 1 wherein the wetting agent is a polyoxyethylene agent.

Claim 5

The method according to claim 5 wherein the polyoxyethylene agent is an alkyl phenoxypolyoxyethylene ethanol.

Claim 6

The method according to claim 5 wherein the medium contains from about 0.2 to about 0.5 volume percent of the polyoxyethylene agent.

Claim 7

The method according to claim 1 wherein the polymer is an olefin polymer.

Claim 8

The method according to claim 8 wherein the olefin polymer is polyethylene.

Claim 9

The method according to claim 1 comprising the steps of (1) dispersing a finely divided powder of polyethylene in an aqueous medium in proportions such that the medium-to-powder ratio is from about 5:1 to 100:1 by weight, said aqueous medium containing about 2 to about 20 volume percent based on the medium of n-propanol, (2) heating the resulting dispersion to a temperature ranging from about 5* to 2* C. below the Vicat softening point of the polyethylene for at least two minutes while subjecting the dispersion to agitation at a rate only sufficient so that the particles of said powder do not agglomerate and (3) cooling the dispersion under continued agitation until the resulting heat softened particles of said powder harden.

Claim 10

A method according to claim 1 for preparing low bulk density, free-flowing powders of a normally solid, water-insoluble, thermoplastic organic polymer selected from the group consisting of the homopolymers and copolymers of the following monomers; Alpha -olefins, monovinylidene aromatic compounds, alkyl acrylates and derivatives thereof, and vinyl acetate, said method comprising the steps of (1) dispersing a finely divided powder of the normally solid, water-insoluble, thermoplastic organic polymer in a nonsolvent liquid dispersing medium in proportions such that a stirrable slurry results, said dispersing medium containing from about 0.1 to about 100 volume percent based on the volume of the medium of a nonionic wetting agent which is a nonsolvent for the polymer, said agent selected from the group consisting of aliphatic monohydric alcohols, dihydric alcohols, trihydric alcohols, polyhydric alcohols and polyoxyalkylene, the remaining portion of the medium being water, with the proviso that when the wetting agent is a polyoxyalkylene the medium contains from about 0.1 to about 1 volume percent of the wetting agent; (2) heating the resulting dispersion to a temperature ranging from about 10* C. below the Vicat softening point to about the Vicat softening point of the polymer until the particles of said polymer are heat-softened while subjecting the dispersion to agitation at a rate only sufficient so that the particles of said powder do not agglomerate into large masses; and (3) cooling the dispersion under continued agitation until the resulting heat-softened particles of powder harden.

Claim 11

The method according to claim 11 wherein the thermoplastic organic polymer is selected from the group consisting of homopolymers and copolymers of Alpha -olefins and the wetting agent is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, glycerol, sorbitol, mannitol, ethylene glycol polyether, ethylene nonyl phenol polyEther, alkyl phenoxypolyoxyethylene ethanol, and propylene glycol fatty acid ester.