EFFECT OF SURFACTANTS ON THE PARTICLE SIZES OF RED 170 POLYUREA MICROCAPSULES

Red #170 (pigment) polyurea microcapsules have been successfully prepa red at our laboratory. Both core and shell of these microcapsules are demonstrated to be red #170 pigment and Polyurea, respectively, by inf rared (IR) spectra. The number-average particle sizes of these microca psules are seen to decrease with increasing concentration and the ethy lene oxide chain length of nonylphenylpolyoxyethylene ether (NP(n); n = 6, 8, 10, 12, 16) as an emulsifier in the water phase used for makin g microcapsules. Experimental results indicate that the average partic le sizes of red #170 polyurea microcapsules are smaller for the system with NP16 than for the system with NP4 (in the oil phase) and/or NP16 (in the water phase) and that, in the presence of NP(n), these partic le sizes are seen to be slightly smaller for use of methylcellulose th an for use of sodium carboxymethylcellulose as a protective colloid. I t is also interesting to note that the released amounts of red #170 pi gment from polyurea microcapsules in di-n -butylphthalate solvent is l ower for a system with NP16 than for a system with methylcellulose, as a result of good emulsification leading to decrease the interaction b etween toluene diisocyanate and water molecules. This may further caus e more crosslinkage to take place at the urea groups, resulting in a d ecrease in the porosity of the capsules. (C) 1994 John Wiley & Sons, I nc.