Views:48 Author:Site Editor Publish Time: 2021-04-07 Origin:Site
Hydroxypropyl methyl cellulose is in recent years production, dosage are rapidly increasing cellulose varieties.It is made of refined cotton after alkali treatment, with propylene oxide and chloroform as etherifying agent, through a series of reactions and made of non-ionic cellulose mixed ether.The degree of substitution is generally 1.2~2.0.Its properties by the content of methoxy and hydroxypropyl content of the proportion of different, and have a difference.
(1) Hydroxypropyl methyl cellulose is easily soluble in cold water, hot water will encounter difficulties.However, its gelation temperature in hot water is significantly higher than that of methylcellulose.Dissolution in cold water, compared with methyl cellulose also has a great improvement.
(2) the viscosity of hydroxypropyl methyl cellulose is related to the size of its molecular weight, and the higher molecular weight is the higher viscosity.Temperature also affects its viscosity. As the temperature increases, the viscosity decreases.But the effect of its high viscosity temperature is lower than that of methylcellulose.The solution is stable when stored at room temperature.
(3) Hydroxypropyl methyl cellulose water retention depends on the amount of its addition, viscosity, etc., the same amount of water retention rate is higher than that of methyl cellulose.
(4) Hydroxypropyl methyl cellulose is stable to acid and alkali, and its aqueous solution is very stable in the pH range of 2~12.Caustic soda and lime water do not have much effect on their properties, but the alkali can accelerate the dissolution rate and improve the viscosity pin.Hydroxypropyl methyl cellulose has stability to general salts, but when the concentration of salt solution is high, the viscosity of Hydroxypropyl methyl cellulose solution has a tendency to increase.
(5) Hydroxypropyl methyl cellulose can be mixed with water-soluble polymer compounds to become a uniform, higher viscosity solution.Such as polyvinyl alcohol, starch ether, vegetable gum and so on.
(6) Hydroxypropyl methyl cellulose has better enzyme resistance than methyl cellulose, and the possibility of solution enzyme degradation is lower than that of methyl cellulose.The adhesion of hydroxypropyl methyl cellulose to mortar construction is higher than that of methyl cellulose.
Hydroxyethyl cellulose (HEC)
By the refined cotton after alkali treatment, in the presence of acetone, with ethylene oxide as etherifying agent for reaction and made.The degree of substitution is generally 1.5~2.0.It has strong hydrophilicity and is easy to absorb moisture.
(1) Hydroxyethyl cellulose is soluble in cold water, and it is difficult to dissolve in hot water.The solution is stable at high temperature and does not have gel properties.It can be used for a long time at high temperature in mortar, but its water retention is lower than that of methyl cellulose.
(2) Hydroxyethyl cellulose on the general acid and base have stability, the base can accelerate its dissolution, and slightly improve the viscosity, its dispersion in water than methyl cellulose and hydroxypropyl methyl cellulose slightly worse.
(3) Hydroxyethyl cellulose has a good anti-hanging performance for mortar, but a longer retarding time for cement.
(4) some of the domestic production of hydroxyethyl cellulose, due to water content, high ash and its performance is significantly lower than that of methyl cellulose.