Example 4
Into a 2 liter glass reactor equipped with an overhead mechanical stirrer and a heating mantle is added 100 g of Reflex® Glitter Blue pigment, product code R-781E (available from Creation of Quality Value Company Ltd.) suspended in 900 mL of deionized water and heated to 40° C. with vigorous stirring. The suspension is adjusted to pH of 3.3 using 2.5% hydrochloric acid and the temperature is raised to 75° C.
Subsequently, 3.0 g of (3-glycidyloxypropyl)trimethoxysilane (available from Millipore Sigma) is added over the course of 10 minutes and the pH is kept constant using the 2.5% hydrochloric acid solution. At the end of the addition, stirring is continued at 75° C. for 2 hours during which the silane hydrolyzes and the resulting silanols associate with the inorganic pigment surface.
Subsequently, the system is adjusted to a pH of 8.0 while maintaining the reaction temperature of 75° C. using 2.5% sodium hydroxide solution very slowly over the course of 1 hour during which time the condensation reaction occurs and the resulting siloxane bonds to the pigment surface leaving the unreacted epoxy end group free for subsequent functionalization. Stirring is continued at 75° C. for an additional 1 hour to complete the reaction and the pH falls to 7.0. The product is filtered off using vacuum filtration, washed with deionized water and dried at 140° C. for approximately 16 hours.
Subsequently, 50 g of polyamide resin such as nylon 6,6 is melt mixed with 10 g of the above epoxide surface functionalized mica pigment Reflex® Glitter Blue R-871E melt mixed in the Haake mixer at 150° C. to 200° C. for 20 to 30 minutes to facilitate the crosslinking reaction of the epoxide with the amino group of the polyamide resin. The resulting pigment-pendent polyamide resin concentrate is discharged from the Haake mixer, cooled and grounded into a fine powder for subsequent incorporation into pigmented polyamide micron particles.
Using 30 g of REFLEX® Glitter Blue R-871E pigment-pendent crosslinked polyamide resin onto the pigment surface and 570 g of nylon 6,6 is melt mixed with 2000 g of polydimethylsiloxane (PDMS) of 10,000 specific viscosity by hot melt emulsification in a 25 mm twin-screw extruder (Werner & Pfleiderer ZSK-25). The polymer pellets are added to the extruder first, brought to the temperature of 230° C. and rpm of 900, and then preheated carrier fluid having AEROSIL® R812S silica nanoparticles (1.1 wt % relative to PP-polyamide) dispersed therein is added to the molten polymer in the extruder.
Then the mixture is discharged into a container and allowed to cool to room temperature over several hours. The resultant mixture is then filtered through a 90 mm WHATMAN® #1 paper filter (available from SigmaAldrich) to separate the PP-polyamides particles from the carrier fluid. The particles are washed three times with 2000 mL of ethyl acetate. The particles are then allowed to dry overnight in vacuum oven at ambient temperature. Optionally, the dried particles can be screened through a 150-μm sieve. The PP-polyamide particles are then characterized for size with a Malvern MASTERSIZER™ 3000 and morphology with SEM micrographs. The D50 (μm) is predicted to be around 65 μm with a span of about 1.10.
