hydroxypropyl methylcellulose HPMC in Plastering MortarFebruary 2nd 2023
Cellulose products are all derived from natural cotton pulp or wood pulp, and are made through etherification. Different cellulose products use different etherifying agents. The etherifying agent used in hydroxyethyl cellulose (HEC) is ethylene oxide, and hydroxypropyl methylcellulose (HPMC) uses other types of etherifying agents. (Methyl chloride and propylene oxide). In real stone paint and latex paint, hydroxyethyl cellulose can be used as a thickener. Real stone paint is easy to precipitate because of its large amount of aggregates and high specificity. Thickeners need to be added to increase its viscosity to meet the viscosity required during construction spraying, improve its storage stability, and achieve a certain strength. For real stone paint to achieve good strength, good water resistance and weather resistance, the selection of raw materials and the design of formulations are very important. Under normal circumstances, the amount of emulsion for high-quality real stone paint is 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 colored sand has large particles and irregular shapes. Under certain particle size distribution conditions, the dried real stone paint may be in CPVC (critical Pigment volume concentration). As far as the thickener is concerned, if the cellulose of appropriate viscosity is selected, the real stone paint can form a relatively complete and dense paint film to meet the three major performance requirements of the real stone paint. If the content of real stone paint emulsion is low, it is recommended to use higher viscosity cellulose as a thickener (such as 100,000 viscosity), especially after the price of cellulose rises, so that the amount of cellulose used can be reduced and the real stone The performance of the paint is more excellent. Some economical real stone paint manufacturers use hydroxypropyl methylcellulose instead of hydroxyethyl cellulose due to cost and other factors. Compared with the two celluloses, hydroxyethyl cellulose has better water retention, will not lose water retention due to gel under high temperature, and has a certain degree of mildew resistance. For performance considerations, it is recommended to use 100,000-viscosity hydroxyethyl cellulose as a thickener for real stone paint.