Melt emulsion extrusion methods for producing thermoplastic polymer particles

1. A method comprising:

providing a mixture comprising an emulsion stabilizer, a thermoplastic polymer, and a carrier fluid that is immiscible with the thermoplastic polymer at a temperature greater than a melting point or softening temperature of the thermoplastic polymer;

shearing the mixture in an extruder at the temperature greater than the melting point or softening temperature of the thermoplastic polymer and at a shear rate sufficiently high to disperse the thermoplastic polymer in the carrier fluid as molten thermoplastic polymer droplets to form an emulsion with the emulsion stabilizer between the thermoplastic polymer and the carrier fluid;

wherein the emulsion stabilizer comprises nanoparticles having a D50 of 1 nm to 500 nm and the nanoparticles comprise a plurality of metal oxide nanoparticles, carbon black, or any combination thereof;

cooling the emulsion to below the melting point or softening temperature of the thermoplastic polymer to form solidified particles in the presence of the nanoparticles, the solidified particles having a circularity of 0.90 or greater and comprising the thermoplastic polymer and the nanoparticles forming a coating upon an outer surface of the solidified particles;

wherein cooling the emulsion to form the solidified particles takes place in the extruder and/or after the emulsion exits the extruder; and

separating the solidified particles from the carrier fluid.

2. The method of claim 1 , wherein at least some of the nanoparticles are embedded in an outer surface of the solidified particles.

3. The method of claim 1 , wherein at least some of the solidified particles have a void therein, the void having the nanoparticles at a void/thermoplastic polymer interface.

4. The method of claim 3 , wherein the nanoparticles are embedded in the void/thermoplastic polymer interface.

5. The method of claim 3 , wherein the void contains the carrier fluid.

6. The method of claim 1 , wherein the nanoparticles comprise silica nanoparticles.

7. The method of claim 1 , wherein the solidified particles further comprise elongated structures on the outer surface of the solidified particles, wherein the elongated structures comprise the thermoplastic polymer.

8. The method of claim 1 , wherein the emulsion stabilizer is present in the mixture at 0.01 wt % to 10 wt % by weight of the thermoplastic polymer.

9. The method of claim 1 , wherein the thermoplastic polymer is present the mixture at 5 wt % to 60 wt % of the mixture.

10. The method of claim 1 , wherein the thermoplastic polymer is selected from the group consisting of polyamides, polyurethanes, polyethylenes, polypropylenes, polyacetals, polycarbonates, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polyhexamethylene terephthalate, polystyrenes, polyvinyl chlorides, polytetrafluoroethenes, polyesters, polylactic acid, polyethers, polyether sulfones, polyetherether ketones, polyacrylates, polymethacrylates, polyimides, acrylonitrile butadiene styrene (ABS), polyphenylene sulfides, vinyl polymers, polyarylene ethers, polyarylene sulfides, polysulfones, polyether ketones, polyamide-imides, polyetherimides, polyetheresters, copolymers comprising a polyether block and a polyamide block, grafted or ungrafted thermoplastic polyolefins, functionalized or nonfunctionalized ethylene/vinyl monomer polymers, functionalized or nonfunctionalized ethylene/alkyl (meth)acrylates, functionalized or nonfunctionalized (meth)acrylic acid polymers, functionalized or nonfunctionalized ethylene/vinyl monomer/alkyl (meth)acrylate terpolymers, ethylene/vinyl monomer/carbonyl terpolymers, ethylene/alkyl (meth)acrylate/carbonyl terpolymers, methylmethacrylate-butadiene-styrene (MBS)-type core-shell polymers, polystyrene-block-polybutadiene-block-poly (methyl methacrylate) (SBM) block terpolymers, chlorinated or chlorosulphonated polyethylenes, polyvinylidene fluoride (PVDF), phenolic resins, poly(ethylene/vinyl acetate)s, polybutadienes, polyisoprenes, styrenic block copolymers, polyacrylonitriles, silicones, and any combination thereof.

11. The method of claim 1 , wherein the melting point or softening temperature of the thermoplastic polymer is 50° C. to 450° C.

12. The method of claim 1 , wherein the temperature above the melting point or softening temperature of the thermoplastic polymer is about 1° C. to about 50° C. greater than the melting point or softening temperature of the thermoplastic polymer.

13. The method of claim 1 , wherein the carrier fluid is selected from the group consisting of silicone oil, fluorinated silicone oils, perfluorinated silicone oils, polyethylene glycols, alkyl-terminal polyethylene glycol, paraffins, liquid petroleum jelly, vison oils, turtle oils, soya bean oils, perhydrosqualene, sweet almond oils, calophyllum oils, palm oils, parleam oils, grapeseed oils, sesame oils, maize oils, rapeseed oils, sunflower oils, cottonseed oils, apricot oils, castor oils, avocado oils, jojoba oils, olive oils, cereal germ oils, esters of lanolic acid, esters of oleic acid, esters of lauric acid, esters of stearic acid, fatty esters, higher fatty acids, fatty alcohols, polysiloxanes modified with fatty acids, polysiloxanes modified with fatty alcohols, polysiloxanes modified with polyoxy alkylenes, and any combination thereof.

14. The method of claim 1 , wherein cooling is at a rate of about 10° C./hour to about 100° C./second.

15. The method of claim 1 , wherein the extruder is selected from the group consisting of a single screw extruder, a twin-screw extruder, and an extruder that includes more than two co-rotating or counter-rotating screws.

16. The method of claim 1 , wherein the extruder has two or more zones at different temperatures.

17. The method of claim 1 , wherein the solidified particles have a D10 of about 0.5 μm to about 125 μm, a D50 of about 1 μm to about 200 μm, and a D90 of about 70 μm to about 300 μm, wherein D10<D50<D90.

18. The method of claim 1 , wherein the solidified particles have a diameter span of about 0.2 to about 10.

19. A method comprising:

adding an emulsion stabilizer comprising nanoparticles having a D50 of 1 nm to 500 nm, a thermoplastic polymer, and a carrier fluid, in any order, to an extruder to produce a mixture;

wherein the carrier fluid is immiscible with the thermoplastic polymer at a temperature greater than a melting point or softening temperature of the thermoplastic polymer, and the emulsion stabilizer is not an internal additive of the thermoplastic polymer; and

wherein the nanoparticles comprise a plurality of metal oxide nanoparticles, carbon black, or any combination thereof;

shearing the mixture in the extruder at about 1° C. to about 50° C. greater than the melting point or softening temperature of the thermoplastic polymer and at a shear rate sufficiently high to form an emulsion comprising molten thermoplastic polymer droplets dispersed in the carrier fluid with the emulsion stabilizer at an interface between the molten thermoplastic polymer droplets and the carrier fluid;

cooling the emulsion to below the melting point or softening temperature of the thermoplastic polymer at a rate of about 10° C./hour to about 100° C./second to form solidified particles in the presence of the nanoparticles, the solidified particles having a circularity of 0.90 or greater and comprising the thermoplastic polymer and the nanoparticles forming a coating upon an outer surface of the solidified particles;

wherein cooling the emulsion to form the solidified particles takes place in the extruder and/or after the emulsion exits the extruder; and

separating the solidified particles from the carrier fluid.