The Generation of HPMC
Hydroxypropyl methyl cellulose（HPMC）is selected from highly pure cotton cellulose as raw material, treated with lye at 35-40 ° C for half an hour, pressed, The cellulose was pulverized and appropriately aged at 35 ° C so that the average degree of polymerization of the obtained alkali fibers was within a desired range.
The alkali fiber was charged into an etherification kettle, and propylene oxide and methyl chloride were sequentially added thereto, and etherified at 50 to 80 ° C for 5 hours, and the maximum pressure was about 1.8 MPa. Then, an appropriate amount of hydrochloric acid and oxalic acid are added to the hot water at 90 ° C to wash the material, and the volume is expanded, and then dehydrated by a centrifuge, and finally washed repeatedly until neutral.
1.Effect of Hydroxypropyl Methyl Cellulose on Water-Retention Performance of Dry-mixed Masonry Mortar:
HPMC has sufficient time in the mortar to promote continuous hydration of the cement and improve the adhesion of the mortar to the substrate.
2.Effect of particle size and mixing time of HPMC ether on water retention rate:
The water retention capacity of the mortar is largely controlled by the dissolution time. The finer cellulose dissolves faster and the water retention performance is faster.
For mechanized construction, due to time constraints, the choice of cellulose must be finer powder.
3.Effect of etherification degree and temperature of HPMC ether on water retention:
The solubility and temperature of hydroxypropyl methyl cellulose in water depend on the degree of etherification, the outside temperature rises, and the water retention decreases.
The higher the degree of etherification, the better the water retention of cellulose ether.
4.Effect of HPMC on Mortar Consistency and Sliding Resistance:
The consistency and slip resistance of the mortar is a very important indicator. For thick layer construction and tile adhesives, proper consistency and slip resistance are required.
Consistency test method (determined according to JG/J70-2009 standard)
The consistency and anti-slip property are mainly achieved by the viscosity and particle size of Hydroxypropyl Methyl Cellulose. As the viscosity and dosage increase, the consistency of the mortar increases. The finer the particle size, the more the initial consistency of the fresh mortar increases.
Effect of HPMC on the amount of air in the mortar:
- In the mortar, due to the addition of HPMC, a certain amount of tiny, uniform and stable bubbles are introduced into the fresh mortar. Due to the ball effect, the mortar has good workability, reducing the shrinkage of the mortar and the turtle. Crack and increase the yield of mortar. Cellulose has a venting function. When adding cellulose, consider the amount of blending, viscosity (the viscosity is too high will affect the workability), and the venting property, and select cellulose suitable for different mortars.
- Compared with the traditional mortar mixed on site, the biggest difference between the machine spray mortar is the introduction of a series of additives such as HPMC which can optimize the performance of the mortar, so that the new mixed mortar has good workability. It has high water retention rate and good working performance after long distance and large height pumping. The biggest advantage is that the construction efficiency is high, and the quality of the mortar after molding is good. Because the mortar has a large initial speed during spraying, it can have a relatively strong gripping effect with the substrate, which can effectively reduce the phenomenon of hollow drum cracking.
The alkali fiber was charged into an etherification kettle, and propylene oxide and methyl chloride were sequentially added thereto, and etherified at 50 to 80 ° C for 5 hours, and the maximum pressure was about 1.8 MPa. Then, an appropriate amount of hydrochloric acid and oxalic acid are added to the hot water at 90 ° C to wash the material, and the volume is expanded, and then dehydrated by a centrifuge, and finally washed repeatedly until neutral.