Water Retention Mechanism of HPMC in Cement Mortar
1. What is the main purpose of hydroxypropyl methylcellulose (HPMC)?
——A: 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: 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 for putty powder, and the rest is used for cement mortar and glue.
2. There are several types of hydroxypropyl methylcellulose (HPMC), and what is the difference in their uses?
——Answer: HPMC 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, forming a transparent viscous colloid. Hot-dissolving products, when encountering cold water, can be quickly dispersed 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. 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.
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3. What are the dissolving methods of hydroxypropyl methylcellulose HPMC?
Answer: Hot water dissolution method: Since HPMC is not dissolved in hot water, HPMC can be uniformly dispersed in hot water at the initial stage, and then rapidly dissolved when cooled. Two typical methods are described as follows:
1), add 1/3 or 2/3 of the required amount of water in the container, and heat it 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 water In the 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 clumping together, because every tiny little corner has only a little HPMC The powder will dissolve immediately in contact with water. ——This method is used by putty powder and mortar manufacturers. [Hydroxypropyl methylcellulose (HPMC) is used as thickener and water-retaining agent in putty powder mortar.
2), put the required amount of hot water in the container, and heat it to about 70 ℃. 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.
