Currently, most of the domestically produced ones are construction grade. Among the construction grade, putty powder is used in large quantities, about 90% is used to make putty powder, and the rest is used to make cement mortar.
1.Why does Hydroxypropyl Methylcellulose (HPMC) have an odor?
HPMC produced by the solvent method uses toluene and isopropanol as solvents. If it is not washed well enough, there will be some residual smell.
2.What are the dissolution methods of hydroxypropyl methylcellulose (HPMC)?
Hot water dissolution method: Since HPMC does not dissolve in hot water, HPMC can be evenly dispersed in hot water at the beginning, 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℃. Add hydroxypropyl methylcellulose gradually under slow stirring. HPMC will float on the surface of the water at first, and then gradually form a slurry. Cool the slurry under stirring.
2) Add 1/3 or 2/3 of the required amount of water to the container and heat it to 70℃. Disperse HPMC according to method 1) to prepare hot water slurry; then add the remaining amount of cold water to the hot water slurry, stir and cool the mixture. Powder mixing method: Mix HPMC powder with a large amount of other powdered ingredients with a mixer, then add water to dissolve. At this time, HPMC can be dissolved without agglomeration, because there is only a little HPMC powder in each tiny corner, which will dissolve immediately when it encounters water. --Putty powder and mortar manufacturers use this method. [Hydroxypropyl methylcellulose (HPMC) is used as a thickener and water-retaining agent in putty mortar.
3.How to simply and intuitively judge the quality of hydroxypropyl methylcellulose (HPMC)?
(1) Whiteness: 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 good products have good whiteness.
(2) Fineness: The fineness of HPMC is generally 80 mesh and 100 mesh, and 120 mesh is less common. Most HPMC produced in Hebei is 80 mesh. The finer the fineness, the better it is generally.
(3) Transparency: Put hydroxypropyl methylcellulose (HPMC) in water to form a transparent colloid, and then look at its transmittance. The higher the transmittance, the better, indicating that there are fewer insoluble substances in it. The transmittance of vertical reactors is generally good, while that of horizontal reactors is worse, but this does not mean that the quality of vertical reactor production is better than that of horizontal reactor production. There are many factors that determine product quality.
(4) Specific gravity: The larger the specific gravity, the heavier it is. The higher the specific gravity, the better it is. The higher the specific gravity, the higher the weight.
4.What is the difference between the cold water soluble type and the hot water soluble type of hydroxypropyl methylcellulose in the production process?
HPMC's fast dispersible type is treated with glyoxal on the surface. It disperses quickly in cold water, but it is not truly dissolved. It is dissolved only when the viscosity increases. The instant type is not treated with glyoxal on the surface. If the amount of glyoxal is large, it will disperse quickly, but the viscosity will increase slowly. If the amount is small, the opposite is true.
5.What is the main role of HPMC in putty powder? Does it cause any chemical reaction?
HPMC plays three roles in putty powder: thickening, water retention and construction.
Thickening: Cellulose can thicken and suspend the solution, keep it uniform and consistent, and resist sagging.
Water retention: Make the putty powder dry slower and assist the lime calcium to react under the action of water.
Construction: Cellulose has a lubricating effect, which can make the putty powder have good construction properties.
Adding water to putty powder on the wall is a chemical reaction, because new substances are generated. If the putty powder on the wall is taken off the wall and ground into powder, it will not work again, because new substances (calcium carbonate) have been formed.
The main components of lime 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. Under the action of water and CO2 in the air, lime calcium generates calcium carbonate, while HPMC only retains water and assists lime calcium to react better, and it does not participate in any reaction itself.
6.What is the difference between the cold water soluble type and the hot water soluble type of hydroxypropyl methylcellulose in the production process?
HPMC's fast dispersible type is treated with glyoxal on the surface. It disperses quickly in cold water, but it is not truly dissolved. It is dissolved only when the viscosity increases.
7.HPMC is a non-ionic cellulose ether, so what does it mean to be non-ionic?
In layman's terms, non-ionic substances are substances that do not ionize in water. Ionization refers to the process in which electrolytes are dissociated into freely moving charged ions in a specific solvent (such as water, alcohol). For example, the salt we eat every day, sodium chloride (NaCl), is ionized after being dissolved in water to produce freely moving sodium ions (Na+) with positive charge and chloride ions (Cl) with negative charge. In other words, when HPMC is placed in water, it will not dissociate into charged ions, but exist in the form of molecules.