Study on thickening of water-based inorganic zinc-rich coatings (4)

2.3 Thickening effect of cellulose thickeners on water-based inorganic zinc-rich coatings
Cellulose thickeners are the most commonly used type of thickeners in interior wall coatings. The main varieties of cellulose thickeners are hydroxyethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, and the most widely used is hydroxyethyl cellulose.
high-speed stirring will be a certain amount of hydroxyethyl cellulose slowly added to the ionized water, until the solution is completely transparent clarification, the concentration of 2% to 3% hydroxyethyl cellulose thickener, and then in high-speed stirring using different additions in accordance with this article 1 .2 Method prepares the base part of 50 g water-based inorganic zinc-rich coating, tests the results of the change in the viscosity of the base material as shown in Figure 5;hydroxyethyl cellulose is a non-ion cellulose derivative, its solution viscosity in the pH range of 2 to 12 changes very little, in addition, due to its own non-ion type, can coexist with a wide range of other water-soluble polymers, with inorganic silicate compatible very good, so it can also be directly added to the water-based inorganic zinc-rich coating substations without the need to add organic emulsion. Cellulose forms hydrogen bonds within or between molecules, and can also improve viscosity through water cooperation and winding of molecular chains, thus giving water-based inorganic zinc-rich coatings excellent anti-sinking.
2.4 The thickening effect of gas-phase silica on water-based inorganic zinc-rich coatings
Gas-phase silica has small particle size, larger surface area, high surf activity and high purity characteristics, the surface has a lot of highly active silicon hydroxyl, surface hydroxyl and liquid system micro-interaction can thicken the system. Three types of silica, HL-200, T-200 and ST-30-C, were selected for experiments, of which T-200 was an alternative to the imported HL-200. Experiments found that the system with ST-30-C thickening is relatively cloudy, placed in the 50 oC oven 2 d is layered, with HL-200 and T-200 thickening system to clarify, placed in the 50 oC oven 1 d will not appear layering and gel phenomenon. Compared with the T-200, the HL-200 is more hydrolysive and has better wetting in the addition process, so the experiment is mainly conducted with HL-200. The effect of HL-200 on the viscosity of the substit span and the rate of zinc powder seation in the coating is shown in Figure 6.as can be known from Figure 6, HL-200 gas phase silica can very well improve the viscosity of water-based inorganic zinc-rich base ingredients, adding 1.5% content, the viscosity of the base material can be doubled to 18.4 mPa. When the addition of gas-phase silica continued to increase to 1.75% to 2% (mass fraction, the same after), the viscosity mutated point and rose sharply. Before the mutation of the viscosity of the base material, the anti-sinking resistance of the preparation coating was still poor, and the samples of the added amount of 1 h were placed with a very obvious zinc powder subsidence phenomenon, and the subsidence rate was higher than 45%. Experiments also found that when the HL-200 gas phase silicon dioxide addition of more than 5%, the base material quickly occurred gel. The system stability and viscosity changes of different additions are shown in Table 4.by Table 4, it can be known that the HL-200 gas phase silicon dioxide addition amount of less than 2% of the system has a good stability, and water-based inorganic zinc-rich coating substation has a significant thickening effect..