In the ready-mixed mortar, the amount of cellulose ether added is very low, but it can significantly improve the performance of the wet mortar and is a major additive that affects the construction performance of the mortar. Reasonable selection of cellulose ethers of different varieties, different viscosities, different particle sizes, different degrees of viscosity and added amount will have a positive effect on the improvement of the performance of dry mortar. Currently, many masonry and plastering mortars have poor water retention properties, and water slurry separation occurs after a few minutes of standing still.
Water retention is an important performance of cellulose ether, and it is also a performance that many domestic dry mortar manufacturers, especially those in areas with higher temperatures in the south, pay attention to. The factors that affect the water retention effect of dry mortar include the amount of MC added, the viscosity of MC, the fineness of particles and the temperature of the environment in which it is used.
Cellulose ether is a synthetic high molecular polymer prepared by chemical modification of natural cellulose. Cellulose ether is a derivative of natural cellulose. The production of cellulose ether is different from synthetic polymers. Its most basic material is cellulose, a natural polymer compound. Due to the special structure of natural cellulose, cellulose itself has no ability to react with etherifying agents. But after the swelling agent is treated, the strong hydrogen bonds between the molecular chains and within the chain are destroyed, and the active release of the hydroxyl group becomes alkali cellulose with reactive ability. After the etherification agent reacts, the -OH group is converted into -OR group. Obtain cellulose ether.
The properties of cellulose ether depend on the type, quantity and distribution of substituents. The classification of cellulose ethers is also based on the types of substituents, the degree of etherification, solubility and related applications. According to the type of substituents on the molecular chain, it can be divided into monoethers and mixed ethers. The MC we usually use is monoether, and HPMC is mixed ether. Methyl cellulose ether MC is the product after the hydroxyl group on the natural cellulose glucose unit is replaced by a methoxy group. The structural formula is [CO H7O2(OH)3-h(OCH3)h]x, hydroxypropyl methylcellulose ether HPMC It is a product obtained by replacing part of the hydroxyl group on the unit with methoxy and the other part with hydroxypropyl group. The structural formula is [C6H7O2(OH)3-mn(OCH3)m[OCH2CH(OH)CH3] n]x. Hydroxyethyl methyl cellulose ether HEMC, these are the main varieties widely used and sold on the market.
In terms of solubility, it can be divided into ionic and non-ionic. Water-soluble non-ionic cellulose ethers are mainly composed of two series of alkyl ethers and hydroxyalkyl ethers. Ionic CMC is mainly used in synthetic detergent textile printing and dyeing food and petroleum exploitation. Non-ionic MC, HPMC, HEMC, etc. are mainly used in building materials, latex coatings, medicine, daily chemistry, etc. Used as a thickener, water-retaining agent, stabilizer, dispersant, and film-forming agent.