Wax is a complex mixture of organic compounds. Different kinds of waxes have different compositions and properties. They are classified according to their sources, mainly including natural waxes and synthetic waxes. The former comes from natural existence, and there are mainly three kinds: animal wax, plant wax and mineral wax; The latter comes from synthetic preparation, which is actually a compound with fixed chemical and physical properties, such as polyethylene wax, polypropylene wax and so on. Blended wax is the most widely used in various industries in China, and its performance is significantly improved compared with ordinary wax. However, with industrial development and technological progress, blended wax is no longer applicable in many fields, and modified wax came into being.
Modified wax is a product obtained by chemical modification of non-polar wax. It does not belong to natural wax or synthetic wax, but between them. After the groups – Oh, – COOH, – coor, – CONH, – coch3, etc. are introduced, they act, resulting in the change of its surface properties. Not only the solubility and lubricity are improved, but also the emulsification and dispersion are improved, which greatly expands its application field.
The formation of emulsified wax is mainly due to the reduction of surface tension between wax and water under the action of emulsifier, and then stirring, or adopting similar methods to disperse the wax in water until it is uniform to form a stable lotion. It is generally believed that there are two types of lotion, namely, w/o type and o/w type . Its composition largely determines its specific type. The research shows that the critical oil phase volume fraction is 25.98% and 74.02% respectively. If it is less than 25.98%, only O / W type is formed; Similarly, other types are also determined. If it is greater than 74.02%, only w / O type is formed; Between the two, the two types coexist. O / W type is more common in practical application .
Emulsification method is the key in the production and preparation process of emulsified wax. To prepare a stable wax lotion with translucent or white viscous appearance, pH value of about neutral, and storage for a period of time without delamination and wax floating, the most important thing is how to select emulsifier. Generally, according to the HLB value, specifically, the promotion effect of hydrophilic part and lipophilic part on the improvement of surfactant molecular properties is usually measured by this physical quantity. The matching degree of HLB value between emulsifier and wax lotion is directly proportional to the emulsifying performance, that is, the one with high matching degree can be used as the best emulsifier. In practical application, a single emulsifier can not meet the emulsification requirements. For HLB value, if one is too large and the other is too small, the two can be mixed and compounded according to additivity, and the emulsification effect will be better.
The preparation methods of emulsified wax are constantly developing and improving. The following methods can be adopted: primary soap method, liquid addition method in turn, agent in water method, agent in oil method and phase inversion emulsification method [6]. In the preparation process, the phase inversion emulsification method is usually used to prepare w/o lotion first, and then generate o/w type lotion by phase inversion. The general steps are as follows: under the heating condition, melt the main components (wax, emulsifier and additives), add a small amount of hot water, mix and form w/o lotion under the action of external force, and then add the remaining hot water as soon as possible to emulsify uniformly under the action of emulsifying equipment such as high-speed disperser, O/w type lotion is formed, and emulsified wax is obtained after cooling.
Emulsified wax is non-toxic and non corrosive, and has good compatibility with aqueous solution or emulsion. It is convenient, fast and safe in production, preparation and use. Its price is also relatively low, so it is more widely used. However, emulsified wax is not easy to store, which is affected by the nature of the wax itself, but also related to the type of emulsifier in the emulsification reaction, the mass fraction of wax, emulsification temperature, etc. the stability will decline after long-term storage, which will have a great impact on its service performance.
