Frequently Asked Questions About Hydroxypropyl Methyl Cellulose

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

——Answer: Hydroxypropyl methylcellulose is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries. Hydroxypropyl methylcellulose can be divided into construction grade, food grade and pharmaceutical grade according to its application. At present, most of the domestic products are construction grade. In construction grade, putty powder is used in a large amount, 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 are the differences in their uses?

——Answer: HPMC can be divided into instant type and hot-dissolution 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 without real dissolution. About 2 minutes, the viscosity of the liquid gradually increases, forming a transparent viscous colloid. Hot-melt products, when met with cold water, can disperse quickly in hot water and disappear in hot water. When the temperature drops to a certain temperature, the viscosity will slowly appear until it forms a transparent viscous colloid. The hot-melt type can only be used in putty powder and mortar. In liquid glue and paint, there will be grouping phenomenon 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 liquid glue and paint, without any contraindications.

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

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

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

2), add 1/3 or 2/3 of the required amount of water into the container, and heat it to 70°C, disperse HPMC according to the method of 1), and prepare hot water slurry; then add the remaining amount of cold water to hot water 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 agglomeration, because there is only a little HPMC in every tiny corner Powder, will dissolve immediately when in contact with water. ——Putty powder and mortar manufacturers are using this method. [Hydroxypropyl methylcellulose (HPMC) is used as a thickener and water retention 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 whitening agents are added during the production process, it will affect its quality. However, most of the good products have good whiteness. (2) Fineness: The fineness of HPMC generally has 80 mesh and 100 mesh, and 120 mesh is less. Most HPMC produced in Hebei is 80 mesh. The finer the fineness, generally speaking, the better. (3) Light transmittance: put hydroxypropyl methylcellulose (HPMC) into water to form a transparent colloid, and look at its light transmittance. The greater the light transmittance, the better, indicating that there are less insolubles in it. . The permeability of vertical reactors is generally good, and that of horizontal reactors is worse, but it does not mean that the quality of vertical reactors is better than that of horizontal reactors, and product quality is determined by many factors. (4) Specific gravity: The larger the specific gravity, the heavier the better. The specificity is large, generally because the content of hydroxypropyl group in it is high, and the content of hydroxypropyl group is high, the water retention is better.

5. What is the amount of hydroxypropyl methylcellulose (HPMC) in the putty powder?

——Answer: The amount of HPMC used in practical applications varies depending on the climate, temperature, quality of local ash calcium, formula of putty powder and "quality required by customers". Generally speaking, 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; the amount of putty in Yunnan is relatively small, generally 3 kg to 4 kg, etc.

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

——Answer: Generally, 100,000 yuan is enough for putty powder, and the requirements for mortar are higher, and 150,000 yuan is required for easy use. Moreover, the most important function of HPMC is water retention, followed by thickening. In the putty powder, as long as the water retention is good and the viscosity is low (70,000-80,000), it is also possible. Of course, the higher the viscosity, the better the relative water retention. When the viscosity exceeds 100,000, the viscosity will affect the water retention. Not much anymore.

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

——Answer: Hydroxypropyl content and viscosity, most users are concerned about these two indicators. Those with high hydroxypropyl content generally have better water retention. The one with high viscosity has better water retention, relatively (not absolutely), and the one with high viscosity is better used in cement mortar.

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

—— Answer: The main raw materials of hydroxypropyl methylcellulose (HPMC): refined cotton, methyl chloride, propylene oxide, and other raw materials, caustic soda, acid, toluene, isopropanol, etc.

9. What is the main function of the application of HPMC in putty powder, and does it happen chemically?

——Answer: In the putty powder, HPMC plays three roles of thickening, water retention and construction. Thickening: Cellulose can be thickened to suspend and keep the solution uniform up and down, and resist sagging. Water retention: make the putty powder dry slowly, and assist the ash calcium to 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 reactions, but 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 formed. If you remove the putty powder on the wall from the wall, grind it into powder, and use it again, it will not work because new substances (calcium carbonate) have been formed. ) too. 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 is in water and air Under the action of CO2, calcium carbonate is generated, while HPMC only retains water, assisting the better reaction of ash calcium, and does not participate in any reaction itself.

10. HPMC is a 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 in which an electrolyte is dissociated into charged ions that can move freely in a specific solvent (such as water, alcohol). For example, sodium chloride (NaCl), the salt we eat every day, dissolves in water and ionizes to produce freely movable sodium ions (Na+) that are positively charged and chloride ions (Cl) that are negatively charged. That is to say, when HPMC is placed in water, it will not dissociate into charged ions, but exist in the form of molecules.

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

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

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

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

——Answer: The cold water instant type of HPMC is surface-treated with glyoxal. It disperses quickly in cold water, but it does not really dissolve. It only dissolves when the viscosity increases. Hot melt types are not surface treated with glyoxal. If the amount of glyoxal is large, the dispersion will be fast, but the viscosity will increase slowly, and if the amount is small, the opposite will be true.

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 smell.

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

——Answer: The application of putty powder: the requirements are relatively low, and the viscosity is 100,000, which is enough. The important thing is to keep water well. Application of mortar: higher requirements, high viscosity, 150,000 is better. Application of glue: instant products with high viscosity are required.

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 the putty powder?

——Answer: In the putty powder, HPMC plays three roles of thickening, water retention and construction. Do not participate in any reactions. Reasons for bubbles: 1. Put too much water. 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: Putty powder for interior walls: heavy calcium 800KG gray calcium 150KG (starch ether, pure green, pentagentite, 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?

——Answer: MC is methyl cellulose, which is made of cellulose ether by treating refined cotton with alkali, using methane chloride as etherification agent, and going 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. It 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 addition 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 impact on the water retention rate, and the level of viscosity is not directly proportional to the level of water retention rate. The dissolution rate mainly depends on the degree of surface modification of cellulose particles and particle fineness. Among the above cellulose ethers, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention rates.

(2) Methylcellulose is soluble in cold water, and it will be difficult to dissolve in hot water. 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, gelation occurs.

(3) Changes in 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 reduced, seriously affecting the construction of the mortar.

(4) Methyl cellulose has a significant effect on the construction and adhesion of mortar. The "adhesion" here refers to the adhesive force felt between the worker's applicator tool and the wall substrate, that is, the shear resistance of the mortar. The adhesiveness is high, the shear resistance of the mortar is large, and the strength required by the workers in the process of use is also large, and the construction performance of the mortar is poor. Methyl cellulose adhesion is at a moderate level in cellulose ether products.

HPMC is hydroxypropyl methylcellulose, which is a non-ionic cellulose mixed ether made from refined cotton after alkalization, using propylene oxide and methyl chloride as etherification agents, and through a series of reactions. The degree of substitution is generally 1.2~2.0. Its properties are different due to the different ratios of methoxyl content and hydroxypropyl content.

(1) Hydroxypropyl methylcellulose is easily soluble in cold water, and 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 solubility 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 its viscosity. Hydroxypropyl methylcellulose is stable to common salts, but when the concentration of salt solution is high, the viscosity of hydroxypropyl methylcellulose 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.

(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 is less likely to be degraded by enzymes than methylcellulose.

20. What should be paid attention to in the actual application of the relationship between the viscosity and temperature of hydroxypropyl methylcellulose?

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

In practical applications, it should be noted that in areas with large temperature differences between summer and winter, 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 the cellulose will increase, and the hand feel will be heavy when scraping.

Medium viscosity: 75000-100000 mainly used for putty

Reason: good water retention

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

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

But generally speaking, the higher the viscosity, the better the water retention. Therefore, considering the cost, many dry powder mortar factories replace medium and low viscosity cellulose (20000-40000) with medium-viscosity cellulose (20000-40000) to reduce the amount of addition.