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Discussion on Hydroxypropyl Methyl Cellulose HPMC

Views: 0     Author: Kimacell     Publish Time: 2022-09-22      Origin: Site

Discussion on Hydroxypropyl Methyl Cellulose HPMC

1. What is the main purpose of hydroxypropyl methylcellulose (HPMC)?

——A: HPMC is widely used in building materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries. HPMC can be divided into: construction grade, food grade and pharmaceutical grade according to the purpose. At present, most of the domestic products are construction grade. In the construction grade, the amount of putty powder is very large, about 90% is used for putty powder, and the rest is used for cement mortar and glue.

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

——Answer: HPMC can be divided into instant type and hot-melt type. Instant-type products disperse quickly in cold water and disappear into the water. At this time, the liquid has no viscosity, because HPMC is only dispersed in water and has no real dissolution. After about 2 minutes, the viscosity of the liquid gradually increased, forming a transparent viscous colloid. Hot-dissolving products, when encountering cold water, can be quickly dispersed 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, clumping phenomenon will occur and cannot be used. The instant type has a wider range of applications. It can be used in putty powder and mortar, as well as in liquid glue and paint, without any contraindications.

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

——Answer: Hot water dissolution method: Since HPMC is not dissolved in hot water, HPMC can be uniformly dispersed in hot water at the initial stage, and then rapidly dissolved when cooled. Two typical methods are described as follows:

1) Put the required amount of hot water in the container and heat it to about 70°C. The hydroxypropyl methylcellulose was gradually added with slow stirring, initially the HPMC floated on the surface of the water, and then gradually formed a slurry, which was cooled with stirring.

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

Powder mixing method: Mix HPMC powder with a large amount of other powdery substances, mix thoroughly with a mixer, and then add water to dissolve, then HPMC can be dissolved at this time without clumping together, because there is only a little HPMC in every tiny little corner. The powder will dissolve immediately in contact with water. ——This method is used by putty powder and mortar manufacturers. [Hydroxypropyl methylcellulose (HPMC) is used as thickener and water-retaining agent in putty powder mortar. ]

4. How to judge the quality of hydroxypropyl methylcellulose (HPMC) simply and intuitively?

——Answer: (1) Whiteness: Although whiteness cannot determine whether HPMC is easy to use, and if a brightener is added in the production process, it will affect its quality. However, most of the good products have good whiteness. (2) Fineness: The fineness of HPMC is generally 80 mesh and 100 mesh, and 120 mesh is less. Most of the HPMC produced in Hebei is 80 mesh. The finer the fineness, the better. (3) Transmittance: Put hydroxypropyl methylcellulose (HPMC) in water to form a transparent colloid, and check its transmittance. The higher the transmittance, the better, indicating that there are less insoluble substances in it . The permeability of the vertical reactor is generally good, and the horizontal reactor is worse, but it cannot be said that the quality of the vertical reactor is better than that of the horizontal reactor, and there are many factors that determine the product quality. (4) Specific gravity: the larger the specific gravity, the heavier the better. The specific gravity is large, generally because the hydroxypropyl content in it is high, and the hydroxypropyl content is high, the water retention is better.

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

——Answer: The amount of HPMC used in practical applications varies depending on the climate, temperature, local ash calcium quality, the formula of putty powder and the "quality required by customers". Generally speaking, it is between 4 kg and 5 kg. For example, most of the putty powder in Beijing is 5 kg; most of the putty powder in Guizhou is 5 kg in summer and 4.5 kg in winter;

6. What is the appropriate viscosity of hydroxypropyl methylcellulose (HPMC)?

——Answer: Putty powder is generally 100,000 yuan, and the mortar is more demanding, and it is easy to use at 150,000 yuan. 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 and the viscosity is lower (70,000-80,000), it is also possible. Of course, the viscosity is higher, and the relative water retention is better. When the viscosity exceeds 100,000, the effect of viscosity on water retention is Not much.

7. What are the main technical indicators of hydroxypropyl methylcellulose (HPMC)?

——Answer: Hydroxypropyl content and viscosity, most users care about these two indicators. The higher the hydroxypropyl content, the better the water retention. High viscosity, water retention, relatively (rather than absolute) better, and high viscosity, better use in cement mortar.

8. What are the main raw materials of hydroxypropyl methylcellulose (HPMC)?

—— A: The main raw materials of hydroxypropyl methylcellulose (HPMC): refined cotton, methyl chloride, propylene oxide, other raw materials include flake alkali, acid, toluene, isopropanol, etc.

9. What is the main role of HPMC in the application of putty powder, and is there any chemistry?

——Answer: HPMC has three functions of thickening, water retention and construction in putty powder. Thickening: Cellulose can be thickened to suspend, keep the solution uniform and consistent, and resist sagging. Water retention: Make the putty powder dry slowly, and assist the reaction of ash calcium under the action of water. Construction: Cellulose has a lubricating effect, which can make the putty powder have good workability. HPMC does not participate in any chemical reaction and only plays an auxiliary role. Adding water to the putty powder and putting it on the wall is a chemical reaction. Because of the formation of new substances, take the putty powder on the wall off the wall, grind it into powder, and use it again. It will not work, because new substances (calcium carbonate) have been formed. ) up. The main components of ash 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 Ash calcium in water and air Under the action of CO2, calcium carbonate is generated, while HPMC only retains water and assists the better reaction of ash calcium, and does not participate in any reaction itself.

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

- Answer: In layman's terms, non-ions are substances that do not ionize in water. Ionization refers to the process by which an electrolyte is dissociated into free-moving charged ions in a specific solvent (such as water, alcohol). For example, sodium chloride (NaCl), the salt eaten every day, dissolves in water and ionizes to produce freely moving sodium ions (Na+) that are positively charged and chloride ions (Cl) that are negatively charged. That is, when HPMC is placed in water, it does not dissociate into charged ions, but exists in the form of molecules.

11. What is the gel temperature of hydroxypropyl methylcellulose related to?

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 drop of putty powder have anything to do with HPMC?

——Answer: The powder drop of putty powder is mainly related to the quality of ash calcium, and has little to do with HPMC. The low calcium content of ash calcium and the inappropriate ratio of CaO and Ca(OH)2 in ash calcium will cause powder drop. If it has something to do with HPMC, then the poor water retention of HPMC will also cause powder drop. For the 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?

——Answer: The cold water instant type of HPMC is surface-treated with glyoxal, and it is quickly dispersed in cold water, but it is not really dissolved. When the viscosity rises, it is dissolved. The hot melt type is not surface treated with glyoxal. If the amount of glyoxal is large, the dispersion will be fast, but the viscosity will increase slowly, and the opposite will be when the amount of glyoxal is small.

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

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

15. How to choose a suitable hydroxypropyl methylcellulose (HPMC) for different purposes?

——Answer: The application of putty powder: the requirements are low, the viscosity is 100,000, it is enough, the important thing is to keep the water well. Application of mortar: high requirements, high viscosity, 150,000 is better. Application of glue: need instant product, 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 is the reason for the bubbles in putty powder?

——Answer: HPMC has three functions of thickening, water retention and construction in putty powder. Not involved in any reaction. The reasons for the bubbles: 1. Too much water is placed. 2. The bottom layer is not dry, just scrape another layer on top, and it is easy to foam.

18. What is the formula of putty powder for interior and exterior walls?

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

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?

A: MC is methyl cellulose, which is made by treating refined cotton with alkali, using chlorinated methane as an etherifying agent, and making cellulose ether through a series of reactions. Generally, the degree of substitution is 1.6~2.0, and the solubility is also different with different degrees of substitution. Belongs to non-ionic cellulose ether.

(1) The water retention of methyl cellulose depends on its addition amount, viscosity, particle fineness and dissolution rate. Generally, if the amount of addition 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 influence on the water retention rate, and the level of viscosity is not proportional to the level of water retention rate. The dissolution rate mainly depends on the degree of surface modification of the cellulose particles and the fineness of the particles. Among the above cellulose ethers, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention rates.

(2) Methylcellulose is soluble in cold water, but difficult to dissolve in hot water, and its aqueous solution is very stable in the range of pH=3~12. It has good compatibility with starch, guar gum, etc. and many surfactants. When the temperature reaches the gelation temperature, the phenomenon of 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 mortar temperature exceeds 40 °C, the water retention of methyl cellulose will be significantly worse, which will seriously affect the workability of the mortar.

(4) Methyl cellulose has a significant effect on the workability and adhesion of mortar. "Adhesion" here refers to the adhesion felt between the worker's applicator 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, and the force required by the workers in the use process is also large, and the construction of the mortar is poor. Methylcellulose adhesion is at a moderate level in cellulose ether products.

HPMC is hydroxypropyl methyl cellulose, which is a non-ionic cellulose mixed ether prepared by a series of reactions after alkali treatment of refined cotton, using propylene oxide and methyl chloride as etherifying agents. The degree of substitution is generally 1.2 to 2.0. Its properties vary depending on the proportion of methoxyl content and hydroxypropyl content.

(1) Hydroxypropyl methylcellulose is easily soluble in cold water, but it will encounter difficulties in dissolving in hot water. But its gelation temperature in hot water is significantly higher than that of methyl cellulose. The dissolution in cold water is also greatly improved compared with methyl cellulose.

(2) Hydroxypropyl methylcellulose is stable to acid and alkali, 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 speed up its dissolution and increase the viscosity. Hydroxypropyl methylcellulose is stable to common salts, but when the concentration of the salt solution is high, the viscosity of the hydroxypropyl methylcellulose solution tends to increase.

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

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

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

20. What should be paid attention to in practical application of the relationship between viscosity and temperature of HPMC?

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

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

Medium viscosity: 75000-100000 Mainly used for putty

Reason: good water retention

High viscosity: 150000-200000 Mainly used for polystyrene particle thermal insulation mortar glue powder and vitrified microbead thermal insulation mortar.

Reason: high viscosity, the mortar is not easy to fall, sag, and improve the construction.

But in general, the higher the viscosity, the better the water retention. Therefore, many dry mortar factories 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. .