The cellulose ether is obtained from pure cotton fiber through alkali treatment, methyl chloride as etherification agent, and methyl cellulose MC is obtained through a series of reactions. The general degree of substitution is 1.6~2.0, and the solubility of the degree of substitution varies.
1. The water content of Methylcellulose Hv depends on the addition amount, viscosity, particle size and solubility. The addition of water is large, the fineness is small, the viscosity is large, and the water retention performance is good. In the water retention test, the addition amount had the greatest influence on the water retention, while the viscosity had no direct relationship with the water retention. The water content of methyl cellulose ether and hydroxypropyl Methylcellulose Hv were both higher.
2. Methylcellulose Hv is soluble in cold water but not easy to dissolve in hot water, and its aqueous solution has good stability in the range of pH=3~12. It has good compatibility and can be compatible with surfactants such as starch and fatty acid glue. When the gelation temperature reaches a certain level, the phenomenon of gelation occurs.
3. The change of temperature will seriously affect the ability of methyl cellulose to store water. When the temperature is above 40 ℃, the water-retention performance of methyl cellulose decreases significantly, which has a great impact on the structural properties of the mortar.
Hydroxypropyl methyl cellulose HPMC prepares a non-ionic mixed ether through a series of reactions under alkaline conditions, using propylene oxide and methyl chloride as etherifying agents. Generally, the degree of substitution is usually between 1.2 and 2.0, and the ratio of methoxyl content to hydroxypropyl content is different, and its properties are also different.
1. Hydroxypropyl methylcellulose is easily soluble in cold water, but difficult to dissolve in hot water.
2. Hydroxypropyl methylcellulose is stable to acid and alkali, and its aqueous solution is very stable between pH=2~12. Sodium salt and lime water also have little effect on its performance, but can speed up its dissolution. For general salts, hydroxypropyl methylcellulose is stable, but when the concentration of the salt solution is higher, the viscosity of the hydroxypropyl methylcellulose solution is higher.
3. Hydroxypropyl methylcellulose has better resistance to enzymes, and its enzymatic degradation ability in solution is lower than that of methylcellulose.