La aplicación de HPMC en la masilla en polvo

Putty is a coating material that is often used for base surface treatment when painting interior and exterior walls. The main function is to fill in the defects of the base wall and to micro-level the base surface. For better work results, we recommend using HPMC in putty powder.

What is Hydroxypropyl Methyl Cellulose (HPMC)?

Hydroxypropyl Methyl Cellulose (HPMC) is a non-ionic cellulose ether. It is an odorless and tasteless white powder. It is made from purified cotton or wood pulp through a series of etherification reactions.

Properties of HPMC

Hydroxypropyl Methyl Cellulose (HPMC) has thermal gelation property. Its aqueous solution will precipitate and gel and then dissolve again after cooling. The gelation temperatures vary according to different specifications. Its solubility also varies with the viscosity, and the lower the viscosity is, the higher the solubility will be. Essentially, HPMC is methyl cellulose modified by epoxy methane, so it has similar characteristics to methyl cellulose that soluble in cold water but insoluble in hot water. The solution doesn’t contain an ionic charge, so it will not react with metal salts or ionic compounds.

Hydroxypropyl Methyl Cellulose (HPMC) has good dispersibility, emulsification, thickening, adhesiveness, water-retention, and glue-retention, so it is widely used in pharmaceuticals, petrochemicals, construction, ceramics, textiles, food, household chemicals, synthetic resins, coatings, and electronic products, etc.

Applications of HPMC in Putty Powder

According to the application, Hydroxypropyl Methyl Cellulose (HPMC) can be divided into construction grade, food-grade, and medical grade. In construction, HPMC is mainly used in putty powder, accounting for 90% of the total.

HPMC in putty powder are mainly used as thickeners, water-retentioner, and lubricants.

• Espesante: Using HPMC in putty powder can thicken putty powder to enhance its suspension ability, anti-sagging ability as well as keep the solution uniform.
• Water–retentioner: Using HPMC in putty powder can keep it in a moist state and make the auxiliary ash calcium react to underwater action.
• Lubricant: Hydroxypropyl Methyl Cellulose has a lubricating effect. Using HPMC in putty powder can make the putty powder have good workability and keep it smooth during the construction process, saving manpower.

Hydroxypropyl Methyl Cellulose (HPMC) does not participate in any chemical reactions except as an auxiliary molecule. The process of adding water to putty powder is placed on the wall as a chemical reaction. In the process, a new substance (calcium carbonate) is formed.

The main components of ash calcium powder are: Ca(OH)₂, a mixture of CaO, and a small amount of CaCO₃. The reaction equation is as follows:

CaO+H₂O=Ca(OH)₂ —Ca(OH)₂+CO₂=CaCO₃↓+H₂O

In this process, gray calcium will be transformed into calcium carbonate under the action of CO₂ and water, while HPMC is only working as a water-retentioner to assist the reaction under the better condition without participating in the reaction.

El fórmula de la masilla can be different according to different specifications. Therefore, the viscosity and the dosage of Hydroxypropyl Methyl Cellulose (HPMC) are also different. In practical applications, it is recommended to use HPMC products with lower viscosity in winter, which is more conducive to construction. Otherwise, when the temperature is low, the viscosity will increase, which may cause trouble for further applications.

At the same time, the corresponding preparations should be done before construction. The underlying surface should remain firm and level. Dry and clean in advance to ensure that the surface of the base is free of grease, batik and other loose substances. Construction workers should also do safety protection work before construction to avoid contamination of window sills, door and window glass and other completed sub-projects during the construction process.