Example 1
Into a 2 liter glass reactor equipped with an overhead mechanical stirrer and a heating mantle is added 100 g of IRIODIN® 100 Silver Pearl pigment (available from E. Merck KGaA, Darmstadt) 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, 100 g of polyamide resin, such as nylon 6,6, is dissolved in N-methyl-2-pyrrolidone (NMP) with vigorous agitation. To this mixture is added 10 g of the epoxide functionalized IRIODIN® 100 Silver Pearl pigment from above and the reaction mixture with continuous agitation is increased to 150° C. for 2 hours to facilitate the curing reaction of the amino functional groups of the polyamide resin with the pendent glycidyloxypropyl (epoxide) group coating the surface of IRIODIN® 100 Silver Pearl pigment. After the polyamide resin has cured and coated the suspended IRIODIN® 100 Silver Pearl pigment the solvent is removed by filtering the particles using vacuum filtration and the material is thoroughly dried in a vacuum oven for 24 hours. Then a portion of this mixture is mixed with non-pigment-pendant polyamide in the Haake reaction with PDMS to form the particles.
Using 2.5 g of IRIODIN® 100 Silver Pearl pigment-pendent crosslinked by polyamide resin onto the pigment surface and 27.5 g of nylon 6,6 is melt mixed with 150 g of polydimethylsiloxane (PDMS) of 60,000 specific viscosity by hot melt emulsification in a Haake mixer fitted with a 300 ml mixing vessel. The mixer is heated to 230° C. and mixed at 200 rpm for 20 minutes. Then, the mixture is discharged from the Haake onto a cold surface to provide rapid quench cooling. The resultant mixture is then filtered through a 90 mm WHATMAN® #1 paper filter (available from SigmaAldrich) to separate the PP-polyamide particles from the carrier fluid. The PP-polyamide particles are washed three times with 1000 mL of ethyl acetate. The PP-polyamide particles are then allowed to air dry overnight in an aluminum pan in a fume hood. Optionally, the dried PP-polyamide 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 50 μm with a span of about 0.85.
