| 摘要 |
PURPOSE:To obtain the powder improved in blocking resistance by mixing an aq. emulsion of charged synthetic resin particles with a dispersion of oppositely charged fine inorg. particles at a ratio satisfying a given formula, and then spray-drying the resulting mixture. CONSTITUTION:An aq. emulsion of a synthetic resin, such as polyvinyl acetate, having positively or negatively charged surfaces of the particles thereof having an average particle size of 0.01 to 50mum is prepd. by emulsion polymn. or the like. On the other hand, a dispersion of fine inorg. particles, such as silica, having an opposite charge to that of the emulsion particles and an average particle size of at most 1/2 of that of the emulsion particles is prepd. by dispersing the inorg. particles in a solvent such as water. The aq. emulsion of the synthetic resin is mixed with the dispersion of the inorg. particles at a ratio satisfying the formula (wherein (a) is the average particle size of the emulsion particles; (b) is the average particle size of the inorg. particles; and R is the number of the inorg. particles/the number of the emulsion particles) to prepare an emulsion. This emulsion is spray-dried in hot air to obtain a blocking- resistant synthetic resin emulsion powder having the emulsion particles uniformly covered with the inorg. particles and having a glass transition point of at most 20 deg.C. |
