Granulation and Granularity Control of Electrostatic Copying Powder Preparation by Suspension Polymerization (Part 2)

2.2 Experimental study of liquid-liquid dispersion conditions

The liquid-liquid dispersion control factors that affect the final particle size of the powder are: (1) the homogenizer agitation speed and time, (2) the reactor agitation speed, (3) the dispersant type and concentration, and (4) the water-oil ratio.

The method for studying the liquid-liquid dispersion system is mainly to determine the size and distribution of the droplet diameter of dispersed phase [8]: direct photography method, light transmission method, light scattering method, laser Doppler method, Coulter counter method ,Interfacial reaction method,Capillary method,Sound wave method,radiation scintillation detection method, etc. In this experiment, direct photographic method was used to observe and measure the diameter of dispersed phase to prevent disperse phase aggregation, and a drop of 0.3% PVA solution was preliminarily placed on the slide [9].

2.2.1 Tests on Homogenizer Stirring Conditions

Test conditions: According to the basic formula (Table 1), the monomer phase and the water phase are arranged and mixed, and the homogenizer is started to stir. The number of dispersed phases is measured by the droplet diameter test. The diameter of 200 droplets is tested under a microscope and the average value is taken. [9]

(1) Homogenizer stirring time test

In the homogenizer stirring 2min5min10min20min when the sampling observation photographed, the results obtained in Table 2 can be seen that the dispersed phase droplets gradually uniform with time, and the stirring average initial droplet diameter changes quickly, after 10min change slowly, 15min basically reached stable

Test to determine the stirring time 20min so that the degree of dispersion is fully stable

(2) Homogenizer stirring speed test

Prepare the sample according to Table 1, and stir at the homogenizer stirring speed 2000r/min 5000r/min 7000r/min for 15min, sample and observe and measure the dispersed phase droplet diameter (sample 578 in Table 2), you can see the stirring speed increased, The input energy density increases, the dispersed phase drop decreases. 5000 r/min (8.9 m/s) is selected in this paper.

2.2.2 experimental conditions of reactor stirring speed conditions

During the test, disperse phase and dispersion medium were prepared according to the basic composition shown in Table 1. The mixture was placed in the reactor and stirred for 15 minutes. Samples were taken and observed. The stirring speed was 400r/min.600r/min.700r/min.800r/min.1000r/min. Figure 2 In this experiment, the purpose of the reactor stirring is to maintain the dispersion system has been formed and the transfer of heat, stirring speed is too high, resulting in high energy consumption; stirring speed is too low, the monomer droplets in the reaction process to gather and get Larger particle size of the toner [7] See [7] According to the experimental results, determine the stirring speed 800r/min (2.6m/s)