After alkali treatment of refined cotton, cellulose ether is prepared through a series of reactions with methyl chloride as etherifying agent. Generally, the degree of substitution is 1.6~2.0, and the solubility varies with the degree of substitution. It belongs to non-ionic cellulose ether.
1. Methylcellulose is soluble in cold water, but it is difficult to dissolve in hot water. Its aqueous solution is very stable in the range of pH=3-12. It has good compatibility with starch, guar gum and many surfactants. When the temperature reaches the gel temperature, gel phenomenon will occur.
2. The water retention of methyl cellulose depends on its addition, viscosity, particle size and dissolution rate. Generally, the water retention rate is high if the addition amount is large, the fineness is small, and the viscosity is large. The addition amount has the greatest impact on the water retention rate, and the viscosity is not directly proportional to the water retention rate. The dissolution rate mainly depends on the degree of surface modification and particle fineness of cellulose particles. Among the above cellulose ethers, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention.
3. The change of temperature will seriously affect the water retention of methyl cellulose. Generally, the higher the temperature, the worse the water retention. If the temperature of the mortar exceeds 40 ℃, the water retention of methyl cellulose will obviously deteriorate, seriously affecting the workability of the mortar.
4. Methylcellulose has obvious influence on the workability and adhesion of mortar. The "adhesion" here refers to the adhesive force felt by the workers between the tool and the wall substrate, that is, the shear resistance of the mortar. The adhesive property is large, the shear resistance of mortar is large, the strength required by workers in the process of use is also large, and the workability of mortar is poor. In cellulose ether products, the adhesion of methyl cellulose is at a medium level.
