HPMC hydroxypropyl methylcellulose 20 questions (2)
11. What is the gel temperature of hydroxypropyl methylcellulose?
A: The gel temperature of HPMC is related to its methoxy content. The lower the methoxy content, the higher the gel temperature.
12. Does the powder of putty powder have any relationship with HPMC?
A: The powder of putty powder is mainly related to the quality of gray calcium. And has little to do with HPMC.And the low calcium content of gray calcium .And the inappropriate ratio of CaO and Ca(OH)2 in gray calcium can cause powder loss.
If it is related to HPMC, then HPMC’s poor water retention will also cause powder loss. For specific reasons, please refer to Question 9.
13. What is the difference between the cold water instant type and the hot soluble type of hydroxypropyl methylcellulose in the production process?
A: HPMC’s cold water instant type is treated with glyoxal surface and quickly dispersed in cold water, but it is not really dissolved. Viscosity comes up and it dissolves.
The hot soluble form is not surface treated with glyoxal. When the amount of glyoxal is large, the dispersion is fast, but the viscosity is slow. And the amount is small.
14. What is the smell of hydroxypropyl methylcellulose (HPMC)?
Answer: The HPMC produced by the solvent method uses toluene and isopropanol as solvents. If the washing is not very good, there will be some residual taste.
15. How to choose the right hydroxypropyl methylcellulose (HPMC) for different purposes?
Answer: The application of putty powder: the requirement is lower, the viscosity is 100,000. it is ok, the important thing is to keep the water better.
Application of mortar: high requirements, high viscosity, 150,000 is better.
Glue application: Need instant type product, high viscosity.
16. What is the alias of hydroxypropyl methylcellulose?
A: Hydroxypropyl methylcellulose, English: Hydroxypropyl Methyl Cellulose Abbreviation: HPMC or MHPC Alias: Hypromellose; So Cellulose hydroxypropyl methyl ether; Hypromellose, Cellulose, 2-hydroxypropyl methyl Cellulose ether. Cellulose hydroxypropyl Methyl ether Hyprolose.
17. The application of HPMC in putty powder, what is the cause of foam in putty powder?
A: HPMC plays the role of thickening, water retention and construction in the putty powder. Do not participate in any reaction.
The reason for the bubble: 1, the water is too much. 2, the bottom layer is not dry, just scrape a layer on the top, it is also easy to foam.
18.the inner and outer wall putty powder formula?
Answer: Interior wall putty powder: Heavy calcium 800KG Gray calcium 150KG (Starch ether, pure green, Peng Run soil, citric acid, polyacrylamide, etc. So can be added as appropriate)
Exterior wall putty powder: cement 350KG heavy calcium 500KG quartz sand 150KG latex powder 8-12KG cellulose ether 3KG starch ether 0.5KG wood fiber 2KG
19. What is the difference between HPMC and MC?
Answer: MC is methyl cellulose. After the refined cotton is treated with alkali, methyl chloride is used as an etherifying agent. After a series of reactions, cellulose ether is prepared.
The degree of substitution is generally 1.6 to 2.0, and the degree of substitution differs depending on the solubility. It belongs to nonionic cellulose ether.
(1) The water retention of methyl cellulose depends on the amount of addition, viscosity, particle fineness and dissolution rate. Generally, the amount of addition is large, the fineness is small, and the viscosity is large, and the water retention rate is high.
The addition amount has the greatest influence on the water retention rate.So the viscosity level is not proportional to the water retention rate.
The rate of dissolution depends mainly on the degree of surface modification of the cellulose particles and the fineness of the particles. Among the above cellulose ethers, methylcellulose and hydroxypropylmethylcellulose have a high water retention rate.
(2) Methylcellulose is soluble in cold water, and it is difficult to dissolve in hot water. The aqueous solution is very stable in the range of pH=3~12.
It has good compatibility with starch, guar gum and many other surfactants. When the temperature reaches the gelation temperature, gelation occurs.
(3) The change of temperature will seriously affect the water retention rate of methyl cellulose. Generally, the higher the temperature, the worse the water retention.
If the temperature of the mortar exceeds 40 ° C, the water retention of methyl cellulose will be significantly deteriorate, which seriously affects the construction of the mortar.
(4) Methylcellulose has a significant effect on the workability and adhesion of the mortar. “Adhesiveness” herein refers to the adhesive force felt between the worker’s application tool and the wall substrate, that is, the shear resistance of the mortar.
The adhesion is large, the shear resistance of the mortar is large, the force require by the worker during use is also large, and the workability of the mortar is poor.
Methylcellulose adhesion is intermediate in cellulose ether products. So HPMC is hydroxypropyl methylcellulose, which is alkalized from refined cotton and uses propylene oxide and methyl chloride as etherifying agents.
So A nonionic cellulose mixed ether produced by a series of reactions. The degree of substitution is generally 1.2 to 2.0. Its nature is different depending on the ratio of methoxyl content and hydroxypropyl content.
(1) Hydroxypropyl methylcellulose is easily soluble in cold water, and it may be difficult to dissolve in hot water. However, its gelation temperature in hot water is significantly higher than that of methyl cellulose. The dissolution in cold water is also much better than methyl cellulose.
(2) The viscosity of hydroxypropylmethylcellulose is related to the molecular weight thereof, and the viscosity is high when the molecular weight is large.
The temperature also affects its viscosity, the temperature rises, and the viscosity decreases. However, the effect of high viscosity is lower than that of methyl cellulose. Its solution is stable at room temperature.
(3) Hydroxypropyl methylcellulose is stable to acids and bases, and its aqueous solution is very stable in the range of pH=2~12. Caustic soda and lime water do not have much effect on their properties, but alkali accelerates their dissolution rate and increases viscosity.
Hydroxypropyl methylcellulose has stability to general salts, but when the concentration of the salt solution is high. the viscosity of the hydroxypropylmethylcellulose solution tends to increase.
(4) The water retention of hydroxypropylmethylcellulose depends on the amount of addition, viscosity, etc. And the water retention rate under the same amount is higher than that of methylcellulose.
(5) Hydroxypropyl methylcellulose can be mixed with a water-soluble polymer compound to form a uniform, higher viscosity solution. Such as polyvinyl alcohol, starch ether, vegetable gum and the like.
(6) Hydroxypropyl methylcellulose has higher adhesion to mortar than methyl cellulose.
(7) Hydroxypropyl methylcellulose has better enzymatic resistance than methylcellulose. And its solution is less likely to be enzymatically degraded than methylcellulose.
20. HPMC viscosity and temperature relationship, what should be paid attention to in practical applications?
A: The viscosity of HPMC is inversely proportional to temperature.That is, the viscosity increases with decreasing temperature. The viscosity of a product we usually refer to is the result of a 2% aqueous solution at a temperature of 20 degrees Celsius.
In practical applications, in areas with large temperature differences between summer and winter. it should be note that it is recommended to use a relatively low viscosity during the winter, which is more conducive to construction.
Otherwise, when the temperature is low, the viscosity of cellulose will increase, and when it is scrape, the hand feel will be heavy.
Medium viscosity: 75000-100000 Mainly used for putty Reason: good water retention
High viscosity: 150000-200000 Mainly used for polystyrene granule insulation mortar rubber powder and vitrified microbead insulation mortar. Reason: high viscosity, mortar is not easy to fall, sag, improve construction.
However, in general, the higher the viscosity, the better the water retention. So many dry mortar plants consider the cost, and replace the medium and low viscosity cellulose (20000-40000) with medium viscosity cellulose (75000-100000) to reduce the amount of addition.
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