1. What is the main use of hydroxypropyl methylcellulose?
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 industrial grade, food grade and pharmaceutical grade according to its use.
2. There are several types of hydroxypropyl methylcellulose. What are the differences between them?
HPMC can be divided into instant type (brand suffix “S”) and hot-soluble type. Instant type products disperse quickly in cold water and disappear in the water. At this time, the liquid has no viscosity because HPMC is only dispersed in water and has no real solution. After about (stirring) 2 minutes, the viscosity of the liquid slowly increases and a transparent viscous colloid is formed. Hot-soluble products, in cold water, can quickly disperse in hot water and disappear in hot water. When the temperature drops to a certain temperature (according to the gel temperature of the product), the viscosity slowly appears until a transparent and viscous colloid is formed.
3. What are the hydroxypropyl methylcellulose solution methods?
1. All models can be added to the material by dry mixing;
2. It needs to be added directly to the normal temperature aqueous solution. It is best to use cold water dispersion type. After addition, it usually reaches thickening within 10-90 minutes (stir, stir, stir)
3. For ordinary models, stir and disperse with hot water first, then add cold water to dissolve after stirring and cooling.
4. If agglomeration or wrapping occurs during dissolution, it is because the stirring is insufficient or the ordinary model is directly added to cold water. At this point, stir quickly.
5. If bubbles are generated during dissolution, they can be left for 2-12 hours (the specific time depends on the consistency of the solution) or removed by vacuum extraction, pressurization, etc., and an appropriate amount of defoaming agent can also be added.
4. How to judge the quality of hydroxypropyl methylcellulose simply and intuitively?
1. Whiteness. Although whiteness cannot judge whether HPMC is good or not, and adding whitening agents during the production process will affect its quality, most good products have good whiteness.
2. Fineness: HPMC fineness is generally 80 mesh and 100 mesh, below 120, the finer the better.
3. Light transmittance: HPMC forms a transparent colloid in water. Look at the light transmittance. The larger the light transmittance, the better the permeability, which means there are less insoluble substances in it. The vertical reactor is generally good, and the horizontal reactor will emit some. But it cannot be said that the production quality of vertical kettles is better than that of horizontal kettles. There are many factors that determine product quality.
4. Specific gravity: The greater the specific gravity, the heavier the better. The greater the specific gravity, the higher the hydroxypropyl content is. Generally, the higher the hydroxypropyl content, the better the water retention.
5. How much hydroxypropyl methylcellulose is used in putty powder?
The amount of HPMC used in actual applications varies from place to place, generally speaking, it is between 4-5 kg, depending on the climate environment, temperature, local calcium ash quality, putty powder formula and customer quality requirements.
6. What is the viscosity of hydroxypropyl methylcellulose?
Putty powder generally costs RMB 100,000, while mortar has higher requirements. It costs RMB 150,000 to be easy to use. Moreover, the more important function of HPMC is to retain water, followed by thickening. In putty powder, as long as the water retention is good and the viscosity is low (7-8), it is also possible. Of course, the greater the viscosity, the better the relative water retention. When the viscosity is above 100,000, the viscosity has little effect on the water retention.
7. What are the main technical indicators of hydroxypropyl methylcellulose?
Hydroxypropyl content
Methyl content
viscosity
Ash
dry weight loss
8. What are the main raw materials of hydroxypropyl methylcellulose?
The main raw materials of HPMC: refined cotton, methyl chloride, propylene oxide, other raw materials, caustic soda, and acid toluene.
9. The application and main function of hydroxypropyl methylcellulose in putty powder, is it chemical?
In putty powder, it plays three major functions: thickening, water retention and construction. Thickening can thicken cellulose and play a suspending role, keeping the solution uniform up and down and preventing sagging. Water retention: Make the putty powder dry more slowly and assist the gray calcium to react under the action of water. Workability: Cellulose has a lubricating effect, which makes the putty powder have good workability. HPMC does not participate in any chemical reactions and only plays a supporting role.
10. Hydroxypropyl methylcellulose is a non-ionic cellulose ether, so what is a non-ionic type?
Generally speaking, inert substances do not participate in chemical reactions.
CMC (carboxymethylcellulose) is a cationic cellulose and will turn into tofu dregs when exposed to calcium ash.
11. What is the gel temperature of hydroxypropyl methylcellulose related to?
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 putty powder and hydroxypropyl methylcellulose?
This is important! HPMC has poor water retention and will cause powdering.
13. What is the difference in the production process between cold water solution and hot water solution of hydroxypropyl methylcellulose?
HPMC cold water-soluble type is quickly dispersed in cold water after surface treatment with glyoxal, but it does not actually dissolve. The viscosity rises, that is, it dissolves. The hot melt type is not surface treated with glyoxal. Glyoxal is large in size and disperses quickly, but has a slow viscosity and small volume, and vice versa.
14. What is the smell of hydroxypropyl methylcellulose?
HPMC produced by the solvent method is made with toluene and isopropyl alcohol as solvents. If not washed well, there will be some residual smell. (Neutralization and recycling is a key process for odor)
15. How to choose the appropriate hydroxypropyl methylcellulose for different uses?
Putty powder: high water retention requirements and good construction convenience (recommended brand: 7010N)
Ordinary cement-based mortar: high water retention, high temperature resistance, instantaneous viscosity (recommended grade: HPK100M)
Construction adhesive application: instant product, high viscosity. (Recommended brand: HPK200MS)
Gypsum mortar: high water retention, medium-low viscosity, instantaneous viscosity (recommended grade: HPK600M)
16. What is the other name of hydroxypropyl methylcellulose?
HPMC or MHPC is also known as hydroxypropyl methylcellulose and hydroxypropyl methylcellulose ether.
17. Application of hydroxypropyl methylcellulose in putty powder. What causes putty powder to foam?
HPMC plays three major roles in putty powder: thickening, water retention and construction. The reasons for bubbles are:
1. Add too much water.
2. If the bottom is not dry, scraping another layer on top will cause blisters easily.
18. What is the difference between hydroxypropyl methylcellulose and MC:
MC, methyl cellulose, is made from refined cotton after alkali treatment, using methane chloride as the etherifying agent, and a series of reactions to produce cellulose ether. The general degree of substitution is 1.6-2.0, and the solubility of different degrees of substitution is also different. It is a non-ionic cellulose ether.
(1) The water retention of methylcellulose depends on its addition amount, viscosity, particle fineness and dissolution rate. Generally speaking, the addition amount is large, the fineness is small, the viscosity is high, and the water retention rate is high. The addition amount has a great influence on the water retention rate, and the viscosity has nothing to do with the water retention rate. The dissolution rate mainly depends on the surface modification degree and particle fineness of the cellulose particles. Among the above cellulose ethers, methylcellulose and hydroxypropylmethylcellulose have higher water retention rates.
(2) Methyl cellulose can be dissolved in cold water, but will encounter difficulty in dissolving in hot water. Its aqueous solution is very stable in the range of pH=3-12, and has good compatibility with starch and many surfactants. When the temperature reaches the gel When the gelation temperature increases, gelation will occur.
(3) Temperature changes will seriously affect the water retention rate of methylcellulose. Generally, the higher the temperature, the worse the water retention rate. If the mortar temperature exceeds 40 degrees, the water retention of methylcellulose will significantly deteriorate, seriously affecting the construction of the mortar.
(4) Methylcellulose has a significant impact on the construction and adhesion of mortar. The adhesion here refers to the adhesion felt between the worker’s application tool and the wall base material, that is, the shear resistance of the mortar. The adhesiveness is high, the shear resistance of the mortar is high, and the force required by workers during use is also high, so the construction performance of the mortar is poor.
Post time: Jan-31-2024