1. What is the main application of hydroxypropyl methylcellulose (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 pharmaceutical grade according to the purpose. At present, most of the domestic products are 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 methylcellulose (HPMC), and what are the differences in their uses?
HPMC can be divided into instant type and hot-dissolution type. The instant type product disperses quickly in cold water and disappears into the water. At this time, the liquid has no viscosity because HPMC is only dispersed in water without real dissolution. About 2 minutes, the viscosity of the liquid gradually increases, forming a transparent viscous colloid. Hot-melt products, when met with cold water, can disperse quickly in hot water and disappear in hot water. When the temperature drops to a certain temperature, the viscosity will slowly appear until it forms a transparent viscous colloid. The hot-melt type can only be used in putty powder and mortar. In liquid glue and paint, there will be grouping phenomenon 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 liquid glue and paint, without any contraindications.
3. 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 initial stage, and then quickly dissolves when cooled. Two typical methods are described as follows:
1) Put the required amount of hot water into the container and heat it to about 70°C. The hydroxypropyl methylcellulose was gradually added under slow stirring, initially the HPMC floated on the surface of the water, and then gradually formed a slurry, which was cooled under stirring.
2), add 1/3 or 2/3 of the required amount of water into the container, and heat it to 70°C, disperse HPMC according to the method of 1), and prepare hot water slurry; then add the remaining amount of cold water to hot water 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 there is only a little HPMC in every tiny corner Powder, will dissolve immediately when in contact with water. ——Putty powder and mortar manufacturers are using this method. [Hydroxypropyl methylcellulose (HPMC) is used as a thickener and water retention agent in putty powder mortar. ]
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 whitening agents are added during the production process, it will affect its quality. However, most of the good products have good whiteness.
(2) Fineness: The fineness of HPMC generally has 80 mesh and 100 mesh, and 120 mesh is less. Most HPMC produced in Hebei is 80 mesh. The finer the fineness, generally speaking, the better.
(3) Light transmittance: put hydroxypropyl methylcellulose (HPMC) into water to form a transparent colloid, and look at its light transmittance. The greater the light transmittance, the better, indicating that there are less insolubles in it. . The permeability of vertical reactors is generally good, and that of horizontal reactors is worse, but it does not mean that the quality of vertical reactors is better than that of horizontal reactors, and product quality is determined by many factors.
(4) Specific gravity: The larger the specific gravity, the heavier the better. The specificity is large, generally because the content of hydroxypropyl group in it is high, and the content of hydroxypropyl group is high, the water retention is better.