Application knowledge of hydroxypropyl methylcellulose in putty powder

Application knowledge of hydroxypropyl methylcellulose in putty powder

 

The amount of HPMC used in practical applications varies depending on the climate, temperature, quality of local ash calcium powder, formula of putty powder and “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; the amount of putty in Yunnan is relatively small, generally 3 kg to 4 kg, etc.

 

What is the appropriate viscosity of hydroxypropyl methylcellulose (HPMC) for the production of putty powder?

 

Putty powder is generally 100,000 yuan, and the requirements for mortar are higher, and 150,000 yuan is required for easy use. Moreover, the most important function of HPMC is water retention, followed by thickening. In the putty powder, as long as the water retention is good and the viscosity is low (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 viscosity will affect the water retention. Not much anymore.

 

What is the main function of the application of HPMC in putty powder?

 

In the putty powder, HPMC plays three roles of thickening, water retention and construction.

 

Thickening: Cellulose can be thickened to suspend and keep the solution uniform up and down, and resist sagging.

 

Water retention: make the putty powder dry slowly, and assist the ash calcium to react under the action of water.

 

Construction: Cellulose has a lubricating effect, which can make the putty powder have good construction.

 

HPMC does not participate in any chemical reactions, but only plays an auxiliary role. Adding water to the putty powder and putting it on the wall is a chemical reaction, because new substances are formed. If you remove the putty powder on the wall from the wall, grind it into powder, and use it again, it will not work because new substances (calcium carbonate) have been formed. ) too. 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 The role of ash calcium in CO2 in water and air Under this condition, calcium carbonate is generated, while HPMC only retains water, assisting the better reaction of ash calcium, and does not participate in any reaction itself.