In the production of building materials, especially dry powder mortar, cellulose ether plays an important role, especially in the production of special mortar (modified mortar), it is an important component. The important role of water-soluble cellulose ether in mortar is mainly its excellent water retention capacity. The water retention effect of cellulose ether depends on the water absorption of the base layer, the composition of the mortar, the thickness of the mortar layer, the water demand of the mortar, and the setting time of the setting material.

Many masonry and plastering mortars do not hold water well, and the water and slurry will separate after a few minutes of standing. Water retention is an important performance of methyl cellulose ether, and it is also a performance that many domestic dry-mix mortar manufacturers, especially those in southern regions with high temperatures, pay attention to. Factors that affect the water retention effect of dry powder mortar include the amount of addition, viscosity, fineness of particles, and the temperature of the use environment.

The water retention of cellulose ether itself comes from the solubility and dehydration of cellulose ether itself. As we all know, although the cellulose molecular chain contains a large number of highly hydratable OH groups, it is not soluble in water, because the cellulose structure has a high degree of crystallinity. The hydration ability of hydroxyl groups alone is not enough to cover the strong hydrogen bonds and van der Waals forces between molecules. Therefore, it only swells but does not dissolve in water. When a substituent is introduced into the molecular chain, not only the substituent destroys the hydrogen chain, but also the interchain hydrogen bond is destroyed due to the wedging of the substituent between adjacent chains. The larger the substituent, the greater the distance between the molecules. The greater the distance. The greater the effect of destroying hydrogen bonds, the cellulose ether becomes water-soluble after the cellulose lattice expands and the solution enters, forming a high-viscosity solution. When the temperature rises, the hydration of the polymer weakens, and the water between the chains is driven out. When the dehydration effect is sufficient, the molecules begin to aggregate, forming a three-dimensional network structure gel and folded out.

Generally speaking, the higher the viscosity, the better the water retention effect. However, the higher the viscosity and the higher the molecular weight, the corresponding decrease in its solubility will have a negative impact on the strength and construction performance of the mortar. The higher the viscosity, the more obvious the thickening effect on the mortar, but it is not directly proportional. The higher the viscosity, the more viscous the wet mortar will be, that is, during construction, it is manifested as sticking to the scraper and high adhesion to the substrate. But it is not helpful to increase the structural strength of the wet mortar itself. During construction, the anti-sag performance is not obvious. On the contrary, some medium and low viscosity but modified methyl cellulose ethers have excellent performance in improving the structural strength of wet mortar.