This article is about HPMC questions in Landcel.
Industrial-grade hydroxypropyl methyl cellulose used in mortar is distinguished by viscosity. Generally, the following types are commonly used
Low viscosity: 400 is mainly used for self-leveling mortar. Reason: low viscosity, good leveling, high mortar density.
Medium and low viscosity: 20000-40000 Medium viscosity: 75000-100000
High viscosity: 150000-200000 mainly used for mortar Reason: high viscosity, the mortar is not easy to fall off, sag, and improve workalibity.
1. What is the main application of HPMC?
——Answer: HPMC is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries. At present, most Cellulose Ethers is 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. What are the types of HPMC and what are the differences?
——Answer: HPMC can be divided into instant type and hot-melt type. The instant type products are quickly dispersed in cold water and disappear in the water. At this time, the liquid has no viscosity, because Cellulose Ethers is only dispersed in water without real dissolution. About 2 minutes, the viscosity of the liquid gradually increased, forming a transparent viscous colloid.
Hot-melt products, when they come together in cold water, they can quickly disperse 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. Hot-melt type can only be used in putty powder and mortar. In liquid glue and paint, clumping occurs 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. There is no contraindication.
3. What are the dissolution methods of HPMC ?
——Answer: Hot water dissolution method: Since HPMC does not dissolve in hot water, HPMC can be uniformly dispersed in hot water at the initial stage, and then quickly dissolve during cooling.
Two typical methods are described as follows:
1), put in a container Fill in the required amount of hot water and heat to about 70°C. Gradually add hydroxypropyl methyl cellulose under slow stirring, start HPMC floating on the surface of water, and then gradually form a slurry, and cool the slurry under 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 to prepare hot water slurry; then add the remaining amount of cold water to hot water In the slurry, cool the mixture after stirring.
Powder mixing method: mix HPMC powder with a large amount of other powdery materials, mix thoroughly with a blender, and then add water to dissolve, then HPMC can be dissolved at this time without clumping, because each tiny corner, there is only a little HPMC The powder will dissolve immediately when it meets water. ——Putty powder and mortar manufacturers use this method. [ Hydroxypropyl methylcellulose (HPMC) is used as a thickener and water-retaining agent in putty powder mortar. ] Organic solvent is the wet method: pre-disperse or moisten HPMC with an organic solvent, such as ethanol, ethylene glycol or oil, and then add water to dissolve, then HPMC can also be dissolved smoothly.
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 good products have good whiteness. (2) Fineness: The fineness of HPMC is generally 80 mesh and 100 mesh, 120 mesh is less, and most HPMC produced in Hebei is 80 mesh. The finer the fineness, the better in general. (3) Transmittance: Put hydroxypropyl methylcellulose (HPMC) in water to form a transparent colloid, and look at its transmittance. The greater the transmittance, the better, indicating that there are fewer insolubles inside. . The permeability of vertical reactors is generally good, while that of horizontal reactors is worse. (4) Proportion: The greater the proportion, the heavier the better. The high specificity is generally due to the high hydroxypropyl content in it, and the higher the hydroxypropyl content, the better the water retention.
5. How much is hydroxypropyl methyl cellulose (HPMC) in putty powder?
——Answer: The amount of HPMC used in actual applications varies depending on the climate, temperature, local ash calcium quality, formula of putty powder and “quality required by customers”. Generally speaking, it is between 4 kg and 5 kg. For example, Beijing putty powder is mostly 5 kg; Guizhou is mostly 5 kg in summer and 4.5 kg in winter; Yunnan is relatively small, usually 3 kg-4 kg and so on.
6. What is the proper viscosity of hydroxypropyl methylcellulose (HPMC)?
——Answer: Generally 100000cps is enough for putty powder, and the requirement for mortar is higher, and 100000-200000cps is better. Moreover, the most important role of HPMC is water retention, followed by thickening. In putty powder, as long as the water retention is good, the viscosity is lower (30,000-80,000), it is also possible, of course, the viscosity is higher, the relative water retention is better.
7. What are the main raw materials of hydroxypropyl methyl cellulose (HPMC)?
—— A: The main raw materials of hydroxypropyl methylcellulose (HPMC): refined cotton, methyl chloride, and propylene oxide.
8. What is the main function of the application of HPMC in putty powder? Does chemistry occur?
——Answer: HPMC plays three roles of thickening, water retention and construction in the putty powder. Thickening: Cellulose can be thickened to suspend, keep the solution uniform, and resist sagging. Water retention: make the putty powder dry slowly, and assist the gray calcium to react 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, only plays a supporting role.
Putty powder is added with water and applied to the wall. It is a chemical reaction. Because of the formation of new substances, the putty powder on the wall is removed from the wall and ground into powder. Then it will not work, because a new substance (calcium carbonate) ) Again. 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 formed, while HPMC only retains water and assists the better reaction of gray calcium. It does not participate in any reaction.
9. What is the gel temperature of hydroxypropyl methylcellulose related to?
——Answer: The gel temperature of HPMC is related to its methoxy group content. The lower the methoxy group content, the higher the gel temperature ↑ .
10. Is there any relationship between the drop of putty powder and HPMC?
——Answer: The drop of putty powder is mainly related to the quality of ash calcium, but not to HPMC. Low calcium content of gray calcium and inappropriate ratio of CaO and Ca(OH)2 in gray calcium will cause powder loss. If it has something to do with HPMC, then the poor water retention of HPMC will also cause powder drop. For specific reasons, please refer to question 9.
11. What is the difference between the cold water instant type and the hot melt type of hydroxypropyl methylcellulose in the production process?
——Answer: The cold water quick-dissolving 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 has no surface treatment of glyoxal. If the amount of glyoxal is large, the dispersion will be faster, but the viscosity will rise slowly, and if the amount is small, the opposite is true.
12. What is the odor of hydroxypropyl methylcellulose (HPMC)?
——Answer: The HPMC produced by the solvent method uses toluene and isopropanol as the solvent. If it is not washed well, it will have some residual smell.
13. 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 enough, the important thing is to keep the water better. Application of mortar: high requirements, high viscosity, 150,000-200,000 is better. Glue application: instant products are required, with high viscosity.
14. The application of HPMC in putty powder, why the putty powder produces bubbles?
——Answer: HPMC plays three roles in the putty powder: thickening, water retention and construction. Do not participate in any reaction. Reasons for bubbles: 1. Too much water was put in. 2. If the bottom layer is not dry, just scrape another layer on it, which will also cause bubbles.
15. What should be paid attention to in the actual application of the relationship between the viscosity of HPMC and temperature?
——Answer: The viscosity of HPMC is inversely proportional to temperature, that is, the viscosity increases as the temperature decreases. We usually say that the viscosity of a product refers to the result of testing its 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 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 the cellulose will increase, and the hand will feel heavy when scraped.
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