| Physical blowing microcapsules, because of their expandable property, have been used in the three-dimensional pigment printing, and their applications have been extending widely into other special fields since recent years. There are good prospects of market for the physical blowing microcapsules. But there is not any factory which could manufacture the microcapsule in industry scale in our country. Under this circumstance SHENZHEN HAOLI chemical Co., Ltd. entrusted us with the research for preparing microcapsules.This paper dealt with the preparation of the physical blowing microcapsule and its application in the three-dimensional pigment printing. Physical blowing microcapsules were prepared by means of In-situ polymerization method. Relationship between the microencapsulation process and blowing performance of the product prepared was investigated accordingly.In the meanwhile, the acid values of the polycondensates which were intended to be the dispersants obtained under different reaction conditions were measured by titrimetric method, the relationship between acid value and dispersion performance was studied; The particle size and size distributions of the physical blowing microcapsules were analyzed by UV-M image analysis system; the surface morphology of the microcapsules was observed by optical microscope, SEM and scan probe microscope; DSC thermo-analysis was carried out by Pyrisl DSC for the physical blowing microcapsules prepared with different conditions; The blowing performance of the physical blowing microcapsule was observed by WRX-IS thermo-optical analysis; the relationships between microcapsule structure and blowing performance were obtained.From the results the following conclusions could be drown:1. Factors affecting the acid value of polycondensate from strong to weak were the temperature, time, vacuum supply and the quantity of p-toluene sulfonic acid; the acid value of polycondensate decreased as the reaction temperature was raised; at 120℃, the acid value of polycondensate decreased very slowly as the reaction time prolonged, while at 160℃, the acid value of polycondensate decreased fast and finally the system came to gelation; it seemed to us that the catalytic effect of the p-toluene sulfonic acid was rather negative than positive at 160℃ ; while at 120℃ and 140℃ the p-toluene sulfonic showed hardly any catalytic effect; Vacuum supply promoted the polycondensation obviously and the acid value of polycondensate fell quick down under a vacuum supply.2. Polycondensate with an acid value of 75.7 mgKOH/g performed an outstanding emulsifying performance, even better than that of PVP K-17. The range of acid values of polycondensates suitable for dispersants in preparing physical blowing microcapsule should be 75 to 104 mgKOH/g.3. As necessary powdered dispersants for preparing the physical blowing microcapsule the colloidal silica was much better than the magnesium hydrate; both the PVP K-17 and the polycondensate with an acid value of 75.7mgKOH/g could be used as the necessary water-soluble polymeric dispersants in preparingphysical blowing microcapsule; the K-values of PVP possessed evident effect on the particle size and size distribution of physical blowing microcapsules, the particle size distribution of microcapsules prepared with PVP K-17 appeared narrower, the physical blowing microcapsules prepared with both polycondensate of 75.7 mgKOH/g and PVP K-17 as dispersants showed clearly a single-cored spherical shape.4. Regardless of the continuous or batch mixer, the particle size of microcapsule became smaller as the homogenization speed was raised, the particle size distribution of microcapsules became sharper as the homogenization times increased or the homogenization time prolonged. The continuous mixer was preferred in preparing the physical blowing microcapsule considering the volatility of the oil phase. The common salt was beneficial to ensure the uniformity of microcapsules. A water-soluble polymeriza...
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