Talking about HPMC

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Talking about HPMC


1. What is the main purpose of HPMC?

——A: Hydroxypropyl methylcellulose is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries. HPMC can be divided into: building grade, food grade ,Daily chemical grade and medicine grade according to usage.

2. There are several types of hydroxypropyl methylcellulose (HPMC), what is the difference between their uses?

——Answer: Hydroxypropyl methylcellulose can be divided into instant type and hot melt type, instant type products, disperse quickly in cold water and disappear in water, at this time the liquid has no viscosity, because HPMC is only dispersed in water, there is no real Of dissolution. After about 2 minutes, the viscosity of the liquid gradually increased, forming a transparent viscous colloid. The hot-melt type product, in the presence of cold water, can disperse quickly in hot water and disappear in hot water. When the temperature drops to a certain temperature, the viscosity slowly appears until a transparent viscous colloid is formed. The hot melt type can only be used in putty powder and mortar. In liquid glue and paint, there will be clumping phenomenon, which cannot be used. Instant type, a wider range of applications, can be used in putty powder and mortar, as well as in liquid glue and paint, there is no contraindication.

3. What are the dissolution methods of hydroxypropyl methyl cellulose (HPMC)?

——Answer: Hot water dissolution method: Since HPMC does not dissolve in hot water, the initial HPMC can be evenly dispersed in hot water, and then quickly dissolved when cooled. Two typical methods are described as follows:

1) Put the required amount of hot water in the container and heat to about 70℃. Hydroxypropyl methylcellulose was gradually added with slow stirring, and HPMC began to float on the surface of water, and then a slurry was gradually formed, and the slurry was cooled with stirring.

2). Add the required amount of 1/3 or 2/3 water to the container, and heat to 70 ℃, according to 1), disperse HPMC to prepare hot water slurry; then add the remaining amount of cold water to hot water In the slurry, the mixture was cooled after stirring. A

Powder mixing method: Mix HPMC powder with a large amount of other powdered materials, mix it thoroughly with a blender, and then add water to dissolve, then HPMC can be dissolved at this time, without clumping and agglomeration, because each small corner has only a little HPMC The powder will dissolve immediately in water. ——Putty powder and mortar production enterprises use this method. [Hydroxypropyl methylcellulose (HPMC) is used as a thickener and water retention agent in putty powder mortar. ]

4. How to determine the quality of HPMC simply and intuitively?

——Answer: (1) Whiteness: Although whiteness cannot determine whether HPMC is easy to use, and if a whitening agent is added in the production process, it will affect its quality. However, most good products have good whiteness.

(2) Fineness: The fineness of HPMC is generally 80 mesh and 100 mesh, and 120 mesh is less. HPMC produced in Hebei is mostly 80 mesh. The finer the fineness, the better.

(3) Transmittance: Put hydroxypropyl methylcellulose (HPMC) in water to form a transparent colloid. Look at the light transmittance. The greater the light transmittance, the better, indicating that there are fewer insolubles in it. . The permeability of vertical reactors is generally good, and that of horizontal reactors is worse, but it cannot be said that the quality of vertical reactors is better than that of horizontal reactors. There are many factors that determine the quality of products.

(4) Specific gravity: The larger the specific gravity, the heavier the better. The specific gravity is generally because the content of hydroxypropyl is high and the content of hydroxypropyl is high, so the water retention is better. A

5. The amount of hydroxypropyl methyl cellulose (HPMC) in putty powder?

——Answer: The amount of HPMC used in practical applications depends on the climatic environment, temperature, local grey calcium quality, formula of putty powder and “quality required by customers”.

6. What is the appropriate viscosity of HPMC? A

——Answer: Putty powder is usually 100,000 yuan. The higher the requirement in the mortar, the better it is 150,000. Moreover, the most important role of HPMC is to retain water, followed by thickening. In putty powder, as long as the water retention is good, the viscosity is lower (70,000 to 80,000), of course, the viscosity is higher, the relative water retention is better, when the viscosity exceeds 100,000, the effect of viscosity on the water retention is Not big.

7. What are the main technical indicators of HPMC?

——Answer: The content and viscosity of hydroxypropyl, most users care about these two indicators. If the content of hydroxypropyl is high, the water retention is generally better. Viscosity is high, water retention, relatively (not absolute) is better, and viscosity is higher, it is better used in cement mortar. A

8. What are the main raw materials of HPMC?

—— A: The main raw materials of hydroxypropyl methyl cellulose (HPMC): refined cotton, methyl chloride, propylene oxide, and other raw materials, such as caustic soda, acid, toluene, isopropyl alcohol, etc.

9. What is the main role of HPMC in putty powder? Is it chemical?

——Answer: HPMC plays the role of thickening, water retention and construction in the putty powder. Thickening: Cellulose can thicken to suspend and keep the solution evenly up and down, and resist sagging. Water retention: Make the putty powder dry slower, and help the gray calcium react under the action of water. Construction: cellulose has a lubricating effect, which can make the putty powder have good construction. HPMC does not participate in any chemical reaction, only plays an auxiliary role. Adding water to the putty powder and putting it on the wall is a chemical reaction. Because new substances are generated, remove the putty powder from the wall and grind it into a powder and reuse it. It will not work because new substances (calcium carbonate have been formed ). The main components of gray calcium powder are: a mixture of Ca(OH)2, CaO and a small amount of CaCO3, CaO+H2O=Ca(OH)2-Ca(OH)2+CO2=CaCO3↓+H2O gray calcium in water and air Under the action of CO2, calcium carbonate is produced, and HPMC only retains water, and assists in the better reaction of gray calcium, which itself does not participate in any reaction.

10. HPMC is a non-ionic cellulose ether, so what is non-ionic?

-Answer: In layman’s terms, non-ions are substances that are not ionized in water. Ionization refers to the process in which an electrolyte is dissociated into charged ions that can move freely in a specific solvent (such as water or alcohol). For example, sodium chloride (NaCl), a salt eaten every day, is dissolved in water and ionized to produce freely moving sodium ions (Na+) with positive charge and chloride ions (Cl) with negative charge. In other words, HPMC does not dissociate into charged ions in water, but exists in the form of molecules. A

11. What is the gel temperature of hydroxypropyl methylcellulose? A

——Answer: The gel temperature of HPMC is related to its methoxyl content. The lower the methoxyl content ↓, the higher the gel temperature ↑.

12. Is there any relationship between the putty powder and HPMC?

——Answer: The powder loss of putty powder is mainly related to the quality of gray calcium and not much to HPMC. The low calcium content of gray calcium and the inappropriate ratio of CaO and Ca(OH)2 in gray calcium will cause powder loss. If it has something to do with HPMC, it may cause powder loss if HPMC has poor water retention. For specific reasons, please refer to question 9.

13. What is the difference between the cold water instant type and hot melt type of hydroxypropyl methyl cellulose in the production process?

——Answer: HPMC’s cold water instant type is surface-treated with glyoxal and quickly dispersed in cold water, but it is not really dissolved. The viscosity is up, and it is dissolved. The hot-melt type does not undergo surface treatment with glyoxal. A large amount of glyoxal will disperse quickly, but the viscosity will come up slowly, and a small amount will be the opposite.

14. What is the smell of hydroxypropyl methylcellulose (HPMC)?

——Answer: The HPMC produced by the solvent method uses toluene and isopropyl alcohol as solvents. If the washing is not very good, there will be some residual taste.

15. For different uses, how to choose the appropriate hydroxypropyl methyl cellulose (HPMC)?

——Answer: The application of putty powder: the requirement is lower, the viscosity is 100,000, it is enough, the important thing is that the water retention is better. Application of mortar: higher requirements, high viscosity, 150,000 is better. Application of glue: need instant products, high viscosity.

16. What is the alias of hydroxypropyl methylcellulose?

——Answer: Hydroxypropyl Methyl Cellulose, English: Hydroxypropyl Methyl Cellulose Abbreviation: HPMC or MHPC Alias: Hypromellose; Cellulose hydroxypropyl methyl ether; Hypromellose, Cellulose, 2-hydroxypropylmethyl Cellulose ether. Cellulose hydroxypropyl methyl ether Hyprolose.

17. The application of HPMC in putty powder, what causes bubbles in putty powder?

——Answer: HPMC plays the role of thickening, water retention and construction in the putty powder. Not involved in any response. Reasons for bubbles: 1. Too much water. 2. If the bottom layer is not dry, just scrape another layer on it, and it is easy to foam.

18. Formula of putty powder for internal and external walls?

——Answer: Interior wall putty powder: heavy calcium 800KG gray calcium 150KG (starch ether, pure green, Peng Runtu, citric acid, polyacrylamide, etc. can be added as appropriate)

External 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 methylcellulose, which is made of cellulose ether after a series of reactions by using purified methane as an etherifying agent after alkali treatment. The general substitution degree is 1.6~2.0, and the solubility is also different according to the substitution degree. Belongs to non-ionic cellulose ether. A

(1) The water retention of methyl cellulose depends on its added amount, viscosity, particle fineness and dissolution rate. Generally, the added amount is large, the fineness is small, and the viscosity is large, the water retention rate is high. Among them, the amount of addition has the greatest effect on the water retention rate, and the viscosity is not proportional to the water retention rate. The dissolution rate mainly depends on the surface modification degree and particle fineness of cellulose particles. Among the above cellulose ethers, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention. A

(2) Methyl cellulose is soluble in cold water. Difficulties in dissolving hot water will be encountered. Its 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, a gel phenomenon occurs.

(3) Changes in 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°C, the water retention of methyl cellulose will be significantly deteriorated, seriously affecting the workability of the mortar. A

(4) Methyl cellulose has a significant impact on the construction and adhesion of mortar. “Adhesion” here 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 worker needs a large force during use, and the workability of the mortar is poor. In cellulose ether products, the adhesion of methyl cellulose is at a medium level.

HPMC is hydroxypropyl methylcellulose, which is a non-ionic cellulose mixed ether produced by a series of reactions using purified cotton after being alkalized, using propylene oxide and methyl chloride as etherifying agents. The degree of substitution is generally 1.2 to 2.0. Its properties are affected by the different proportions of methoxy content and hydroxypropyl content. A

(1) Hydroxypropyl methylcellulose is easy to dissolve in cold water, and it will be difficult to dissolve in hot water. But its gelation temperature in hot water is significantly higher than methyl cellulose. The solubility in cold water is also greatly improved compared to methyl cellulose. A

(2) Hydroxypropyl methyl cellulose is stable to acids and alkalis, and its aqueous solution is very stable in the range of pH=2~12. Caustic soda and lime water have little effect on its performance, but alkali can accelerate its dissolution rate and improve viscosity. Hydroxypropyl methylcellulose is stable to general salts, but when the salt solution concentration is high, the viscosity of the hydroxypropylmethyl cellulose solution tends to increase.

(3) Hydroxypropyl methylcellulose can be mixed with water-soluble polymer compounds to form a uniform and higher viscosity solution. Such as polyvinyl alcohol, starch ether, vegetable gum, etc. A

(4) The adhesion of hydroxypropyl methyl cellulose to mortar construction is higher than that of methyl cellulose.

(5) Hydroxypropyl methylcellulose has better enzyme resistance than methylcellulose, and the possibility of solution enzyme degradation is lower than that of methylcellulose.

20. What is the relationship between HPMC viscosity and temperature?

——Answer: The viscosity of HPMC is inversely proportional to the temperature, that is, the viscosity increases as the temperature decreases. What we usually say about the viscosity of a product refers to the test result of its 2% aqueous solution at a temperature of 20 degrees Celsius. A

In practical applications, in areas with large temperature differences between summer and winter, it should be noted that it is recommended to use a relatively low viscosity in winter, which is more conducive to construction. Otherwise, when the temperature is low, the viscosity of cellulose will increase, when the batch is scraped, the feel will be heavy.

Medium viscosity: 75000-100000 is mainly used for putty

Reason: good water retention

High viscosity: 150000-200000 is mainly used for polystyrene particle insulation mortar powder and vitrified microsphere insulation mortar.

Reasons: The viscosity is high, the mortar is not easy to fall, sag, and the construction is improved.

But generally speaking, the higher the viscosity, the better the water retention, so many dry powder mortar plants consider the cost and use medium viscosity cellulose (75000-100000) instead of medium and low viscosity cellulose (20000-40000) to reduce the amount of addition .