Firstly, the cellulose raw material wood pulp/refined cotton is crushed, then alkalized and pulped under the action of caustic soda. Add olefin oxide (such as ethylene oxide or propylene oxide) and methyl chloride for etherification. Finally, water washing and purification are carried out to finally obtain a white methylcellulose powder. This powder, especially its aqueous solution, has interesting physical properties. The cellulose ether used in the construction industry is methyl hydroxyethyl cellulose ether or methyl hydroxypropyl cellulose (referred to as MHEC or MHPC, or a more simplified name MC). This product plays a very important role in the field of dry powder mortar. important role.
What is the water retention of methyl cellulose ether (MC)?
Answer: The level of water retention is one of the important indicators to measure the quality of methyl cellulose ether, especially in the thin layer construction of cement-based and gypsum-based mortar. Enhanced water retention can effectively prevent the phenomenon of strength loss and cracking caused by excessive drying and insufficient hydration. The excellent water retention of methyl cellulose ether under high temperature conditions is one of the important indicators to distinguish the performance of methyl cellulose ether. Under normal circumstances, the water retention of most common methyl cellulose ethers decreases with the increase of temperature. When the temperature rises to 40°C, the water retention of common methyl cellulose ethers is greatly reduced, which is very important in hot and dry areas. And the thin-layer construction on the sunny side in summer will have a serious impact. However, making up for the lack of water retention through high dosage will cause high viscosity of the material due to high dosage, which will cause inconvenience to construction.
Water retention is very important to optimize the hardening process of mineral gelling systems. Under the action of cellulose ether, the moisture is gradually released to the base layer or the air over a prolonged period of time, thus ensuring that the cementitious material (cement or gypsum) has a long enough time to interact with water and gradually harden.
What is the role of methyl cellulose ether in dry powder mortar?
Methyl hydroxyethyl cellulose ether (MHEC) and methyl hydroxypropyl cellulose ether (HPMC) are collectively referred to as methyl cellulose ether.
In the field of dry powder mortar, methyl cellulose ether is an important modified material for dry powder mortar such as plastering mortar, plastering gypsum, tile adhesive, putty, self-leveling material, spray mortar, wallpaper glue and caulking material. In various dry powder mortars, methyl cellulose ether mainly plays the role of water retention and thickening.