The role of hydroxypropyl methylcellulose in putty
From thickening, water retention and construction of three functions.
Thickening: Cellulose can be thickened to suspend, keep the solution uniform and consistent, and resist sagging. Water retention: Make the putty powder dry slowly, and assist the reaction of ash calcium under the action of water. Construction: Cellulose has a lubricating effect, which can make the putty powder have good workability. Hydroxypropyl methylcellulose does not participate in any chemical reaction and only plays an auxiliary role. Putty powder is added with water to batch the wall, which is a chemical reaction, because there is the formation of a new substance calcium carbonate. The main components of ash calcium powder are: a mixture of calcium hydroxide Ca(OH)2, calcium oxide CaO and a small amount of calcium carbonate CaCO3. Ash calcium forms calcium carbonate under the action of CO2 in water and air, while hydroxypropyl methyl Cellulose just retains water and assists the better reaction of ash calcium, which itself does not participate in any reaction.
We first analyze the reasons for the powder drop of the putty from the raw materials of the putty: ash calcium powder, hydroxypropyl methylcellulose, heavy calcium powder, water ash calcium powder
1. In actual production, in order to speed up the decomposition, the calcination temperature is often increased to 1000-1100 °C. Due to the large size of limestone raw materials or the uneven temperature distribution in the kiln during calcination, lime often contains underfired lime and overfired lime. The calcium carbonate in the underfire lime is not completely decomposed, and it lacks cohesive force during use, which cannot provide sufficient cohesive strength to the putty, resulting in powder removal caused by insufficient hardness and strength of the putty.
2. The higher the content of calcium hydroxide in the ash calcium powder, the better the hardness of the putty produced. On the contrary, the lower the content of calcium hydroxide in the ash calcium powder, the worse the hardness of the putty at the production place, resulting in the problem of powder removal and powder removal.
3. The ash calcium powder is mixed with a large amount of heavy calcium powder, which causes the content of the ash calcium powder to be too low to provide sufficient hardness and strength to the putty, causing the putty to drop powder. The main function of putty powder is to retain water, provide sufficient water for the hardening of ash calcium powder, and ensure sufficient hardening effect. If there is a problem with the quality of hydroxypropyl methylcellulose or the effective content is low, sufficient moisture cannot be provided, which will cause the hardening to be insufficient and cause the putty to drop powder.
It can be found from the above that the quality of hydroxypropyl methylcellulose is very poor and cannot achieve a certain effect, and the putty powder will fall off. The main reason is gray beggar heavy calcium.
Post time: Sep-22-2022