When producing putty powder dry mortar, the viscosity selection of hydroxypropyl methylcellulose (HPMC) is crucial because it directly affects the performance and construction effect of the product.

1. Basic properties of HPMC
HPMC is an important additive in putty powder and dry mortar, with good water retention, thickening and stability. The viscosity of HPMC depends on its molecular weight and degree of substitution, and the viscosity unit is usually mPa.s (millipascal seconds).

2. The importance of viscosity selection
Water retention: HPMC with high viscosity usually has better water retention, which can effectively prevent water from evaporating too quickly during the drying process, ensuring that putty powder and dry mortar have good workability and applicability during construction.
Thickening: HPMC with higher viscosity can provide better thickening effect, increase the viscosity of the mixture, prevent sagging, and improve the adhesion of vertical surfaces.
Fluidity and construction: Appropriate viscosity helps the mixture to be evenly dispersed and have good fluidity, ensuring easy application and leveling during construction.

3. Specific considerations for viscosity selection
Construction environment: In high temperature and low humidity environments, it is recommended to select HPMC with higher viscosity to ensure good water retention; in low temperature and high humidity environments, HPMC with lower viscosity can be selected to ensure the fluidity and operability of the mixture.
Substrate type: Different substrates have different requirements for putty powder and dry mortar. For substrates with strong water absorption, such as brick walls and cement walls, it is recommended to select HPMC with high viscosity to improve water retention; for substrates with weak water absorption, such as gypsum boards and concrete walls, HPMC with medium viscosity can be selected.
Construction thickness: When thick layers are applied, high viscosity HPMC can prevent cracks and shrinkage during drying; when thin layers are applied, medium and low viscosity HPMC can improve construction efficiency and surface flatness.
Construction process: Manual application and machine spraying have different requirements for HPMC viscosity. When applied manually, moderate viscosity can improve operability; when sprayed by machine, HPMC with lower viscosity can ensure the smooth operation of the spraying equipment.

4. Specific suggestions for viscosity selection
Interior wall putty powder: HPMC with a viscosity of 20,000-60,000 mPa.s is usually selected. This type of putty powder requires good water retention and thickening properties to improve workability and surface quality.
Exterior wall putty powder: HPMC with a viscosity of 100,000-200,000 mPa.s is usually selected. Exterior wall putty powder requires higher water retention and crack resistance to cope with changes in the external environment.
Dry mortar: HPMC with different viscosities is selected according to specific uses. Generally speaking, tile adhesives, leveling mortars, etc. require HPMC with a higher viscosity (75,000-150,000 mPa.s), while dry mortars used for thin layer coating can choose HPMC with a medium or low viscosity (20,000-60,000 mPa.s).

5. Experimental verification of viscosity selection
In actual production, it is necessary to verify the influence of HPMC with different viscosities on the performance of putty powder and dry mortar through experiments. The most suitable HPMC viscosity can be found by adjusting the viscosity and dosage of HPMC, testing the water retention, anti-sagging, workability and strength of the mixture after hardening.

The selection of HPMC viscosity needs to comprehensively consider factors such as water retention, thickening, workability and substrate type. Through scientific experiments and reasonable selection, the product performance and construction effect of putty powder and dry mortar can be improved. For different application scenarios and construction conditions, it is very important to choose HPMC with appropriate viscosity to ensure product stability and user satisfaction.