1. The polyvinyl alcohol powder is completely dissolved in deionized water and filtered. (Optional PVA-1788 2488, etc.)
2. Put the polyvinyl alcohol glue into the stainless steel reaction vessel (the enamel reactor can also be used, but the heat transfer effect of the enamel kettle is not as good as that of the stainless steel reactor), then add the emulsifier OP-10, and start the mixer to mix it evenly.
3. Add 15% of the total amount of polyvinyl acetate monomer (ie 6.9) and 40% of the potassium persulfate formulation (ie 0.036) to the stainless steel reactor, continue stirring, and start to heat up. When the temperature rises to 60-65 ° C, the heating is stopped. It should be noted that the initiator potassium persulfate should be firstly mixed with pure water to form an aqueous solution of 8% to 10%, which is added in multiple times.
4. Under the action of the initiator, although the heating is stopped, the temperature rises by itself. When the temperature is above 65 ° C, the reflux device of the reactor begins to reflux. When the temperature rises above 80 ° C, the reflux gradually decreases. At this time, the dropping of the polyvinyl acetate monomer was carried out from the dropping tank of the reaction vessel, and the dropping rate was controlled to be about 10% of the total amount per hour (that is, about 4.6). During the reaction, pay close attention to the reaction temperature, and add cooling water to the reactor jacket to control the reaction temperature, not higher than 80 °C.
5. While adding vinyl acetate monomer, the initiator is also added, and the amount added per hour is about 4.5% of the formula amount.
6. Vinyl acetate and initiator should be controlled to be added around 8h. Due to the action of the initiator, the reaction is strong. After the monomer is added, the reaction temperature will rise by itself. When it rises to about 93 °C, it is kept for 30 minutes. The polymerization is almost complete.
7. Turn on the cooling water to lower the temperature in the stainless steel reactor. When it drops below 50 °C, add sodium bicarbonate solution (10% concentration should be dissolved in advance) and dibutyl phthalate. Adjust the pH to 6~7. until.
8. The mixer of the stainless steel reaction kettle can not be stopped at all times. When it is cooled to room temperature, the finished white latex is obtained, and the stirring, discharging and packaging are stopped.
9. When the viscosity of the white latex product is too large and the water resistance is poor, the amount of polyvinyl alcohol in the formulation can be appropriately reduced.
10. If the stability of the white latex emulsion is poor, the amount of some initiators in the formulation may be appropriately reduced. When too little, the amount of the initiator may not be caused, resulting in difficulty in polymerization of the monomer.
11. The amount of dibutyl phthalate should not be too much, not more than 10% of the monomer, otherwise the adhesiveness of the white latex finished product will decrease and the cost will increase. Its main role is to increase the toughness of the emulsion and reduce the film formation temperature of the emulsion.
12. If the white latex product has more foam, add an appropriate amount of defoamer.
13. The amount of initiator potassium persulfate and the addition time should be mastered. When the reflux starts, if the reflux rate is large, it indicates that the initiator has no effect. If there is too much monomer, the monomer should be stopped. The initiator is added to the monomer when the reflux is normal.
14. The white latex produced by the above white latex formulation and preparation method is a white uniform emulsion liquid having a solid content of about 50% and a pH of about 5.
In addition, the white latex product can also be added with 801 glue and anatase titanium dioxide to produce modified white latex.
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