Focus on Cellulose ethers

Hydroxypropyl methylcellulose (HPMC) knowledge?

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

HPMC is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, tobacco and other industries.

HPMC can be divided into construction grade, food grade and medical grade according to its purpose.

At present, most domestic products are of 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 methyl cellulose (HPMC). What is the difference between their uses?

HPMC can be divided into instant type and hot melt type.

The instant product disperses quickly in cold water and disappears in the water. At this time, the liquid has no viscosity, because HPMC is only dispersed in water and does not really dissolve. About 2 minutes, the viscosity of the liquid gradually increased, forming a transparent viscous colloid.

Instant type, a wider range of applications, can be used in putty powder and mortar, as well as in liquid glue and paint.

The hot-melt product, when it meets cold water, it 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.

Hot melt type can only be used in putty powder and mortar.

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

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 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. Gradually add hydroxypropyl methylcellulose with slow stirring, start HPMC floating on the surface of the water, and then gradually form a slurry, and cool the slurry 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 above method, disperse HPMC to prepare a hot water slurry; then add the remaining amount of cold water to the hot water slurry. In the slurry, cool the mixture after stirring.

Powder mixing method: Mix HPMC powder with a large amount of other powdery ingredients with a mixer, 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 bit of HPMC The powder will dissolve immediately when it meets water.

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

(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, 120 mesh is less, the finer the fineness, generally the better.

(3) Transmittance: After putting HPMC in water to form a transparent colloid, look at its transmittance. The greater the transmittance, the better, indicating that there are less insolubles inside.

(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. What are the main technical indicators of hydroxypropyl methyl cellulose (HPMC)?

Hydroxypropyl content and viscosity, most of which are concerned about these two indicators. The water retention is generally better for those with high hydroxypropyl content. High viscosity, water retention, relative (rather than absolute) is better, and high viscosity, better used in cement mortar.

6. What are the main raw materials of hydroxypropyl methyl cellulose (HPMC)?

The main raw materials of HPMC: refined cotton, methyl chloride, propylene oxide, etc.

7. What is the main function of the application of hydroxypropyl methyl cellulose (HPMC) in putty powder? Is there a chemical reaction?

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 and up and down, and anti-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.

8. What is the odor of hydroxypropyl methyl cellulose (HPMC)?

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.

9. How to choose the right hydroxypropyl methylcellulose (HPMC) for different purposes?

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 is better.

Glue application: instant products are required, with high viscosity.

10. The application of hydroxypropyl methyl cellulose (HPMC) in putty powder, what causes the putty powder to produce bubbles?

In the putty powder, HPMC plays three roles of thickening, water retention and construction. Do not participate in any reaction.

Reasons for bubbles:

1. Put too much water.

2. If the bottom layer is not dry, just scrape another layer on the top, it will also be easy to foam.

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Post time: Oct-22-2021
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