Cellulose products are all derived from natural cotton pulp or wood pulp, which are obtained through etherification. Different cellulose products use different etherification agents. Hydroxypropyl methylcellulose HPMC uses other types of etherification agents (chloromethane and propylene oxide), and hydroxyethyl cellulose HEC uses etherification agents. ethylene oxide.
In real stone paint and latex paint, hydroxyethyl cellulose can be used as a thickener. Because of its large amount of aggregate, large specific gravity and precipitation, real stone paint needs to be added with a thickener to increase its viscosity to meet the viscosity required during construction and spraying, and to improve its storage stability and achieve a certain strength.
In order to achieve good strength, good water resistance and weather resistance of real stone paint, the selection of raw materials and the design of formula are very important. Under normal circumstances, the amount of emulsion of high-quality real stone paint will be relatively high.
For example, in one ton of real stone paint, there may be 300kg of pure acrylic emulsion and 650kg of natural colored stone sand. When the solid content of the emulsion is 50%, the volume of 300kg of emulsion after drying is about 150 liters, and the volume of 650kg of sand is about 228 liters. That is to say, at this time, the PVC (pigment volume concentration) of the real stone paint is 60%. Because the particles of the colored sand are large and irregular in shape, under the condition of a certain particle size distribution, the dried real stone paint may be at the CPVC (critical level). Pigment volume concentration).
As far as the thickener is concerned, if the cellulose of the appropriate viscosity is selected, the real stone paint can form a relatively complete and dense paint film to meet the three performance requirements of the real stone paint. If the content of real stone paint emulsion is low, it is recommended to use cellulose with a higher viscosity as a thickener (such as 100,000 viscosity), especially after the price of cellulose increases, which can reduce the amount of cellulose used, and also allow real stone to be used. The paint performance is better. Some economical real stone paint manufacturers replace hydroxyethyl cellulose with hydroxypropyl methyl cellulose due to factors such as cost.
Compared with the two kinds of cellulose, hydroxyethyl cellulose has better water retention, which will not lose water retention due to gel at high temperature, and has certain mildew resistance. For performance reasons, it is recommended to use hydroxyethyl cellulose with a viscosity of 100,000 as a thickener for real stone paint.