redispersible latex powder RDP for tile adhesivesDecember 7th 2023
1. There are several types of hydroxypropyl methylcellulose, and what is the difference between their uses?
Hydroxypropyl methylcellulose 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 to form a transparent viscous colloid. The hot-dissolving product forms agglomerates in cold water, disperses rapidly in hot water, and disappears 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.
2. What is the main purpose of hydroxypropyl methylcellulose?
Hydroxypropyl methylcellulose 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 to make putty powder, and the rest is used for cement mortar and glue.
3. What are the dissolving methods of hydroxypropyl methylcellulose?
Hot water dissolving method: Since hydroxypropyl methylcellulose is not dissolved in hot water, HPMC can be uniformly dispersed in hot water at the initial stage, and then rapidly dissolved during cooling. 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 the required amount of 1/3 or 2/3 of the water in the container, and heat 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 In an aqueous 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 every tiny little corner, only a little HPMC The powder will dissolve immediately in contact with water.
4. How to judge the quality of hydroxypropyl methylcellulose 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, the better in general.
(3) Transmittance: Put hydroxypropyl methylcellulose in water to form a transparent colloid, and look at its transmittance. The greater 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 in putty powder?
The amount of hydroxypropyl methylcellulose used in practical applications varies depending on the climate environment, 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?
Putty powder is generally 100,000 yuan, and the requirements for mortar are higher, and it is easy to use 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 higher the viscosity, the better the relative water retention. 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?
Hydroxypropyl content and viscosity, most users are concerned about these two indicators. The higher the hydroxypropyl content, the better the water retention. The viscosity is high, the water retention is relatively (rather than absolute), and the viscosity is high, and it is better used in cement mortar.
8. What are the main raw materials of hydroxypropyl methylcellulose?
The main raw materials of hydroxypropyl methyl cellulose: 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?
In the putty powder, hydroxypropyl methylcellulose plays three functions: thickening, water retention and construction. 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 a non-ionic cellulose ether, so what is leek ion?
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 (eg, water, alcohol). For example, sodium chloride (NaCI), the salt eaten every day, dissolves in water and ionizes to produce freely mobile sodium ions (Na+) that are positively charged and chloride ions (CI) 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.