The viscosity of HPMC is inversely proportional to temperature, meaning that viscosity increases as temperature decreases. When we refer to the viscosity of a certain product, it generally refers to the measurement result of its 2% water solution at 20 degrees Celsius. In practical applications, in regions with large temperature differences between summer and winter, it is advisable to use relatively lower viscosity during winter for better construction. Otherwise, at low temperatures, the viscosity of the cellulose increases, resulting in a heavier feel during application. Medium viscosity: 75,000-100,000 (mainly used for putty) Reason: Good water retention. High viscosity: 150,000-200,000 (mainly used for polystyrene particle insulation mortar powder and foamed glass bead insulation mortar) Reason: High viscosity, reduces mortar dusting and sagging, improves construction. However, in general, higher viscosity provides better water retention. Therefore, many dry mortar manufacturers consider using medium-viscosity cellulose (75,000-100,000) instead of low-viscosity cellulose (20,000-40,000) to reduce the dosage and costs.

MC stands for methyl cellulose, which is a cellulose ether made from purified cotton through alkali treatment using chloromethane as the etherification agent, followed by a series of reactions. The degree of substitution is generally 1.6-2.0, and different degrees of substitution result in different solubilities. It belongs to non-ionic cellulose ethers. 1. Methyl cellulose's water retention depends on the amount added, viscosity, particle size, and dissolution rate. Generally, a higher amount, smaller particle size, and higher viscosity result in better water retention. Among these cellulose ethers, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention. 2. Methyl cellulose is soluble in cold water but has difficulty dissolving in hot water. Its aqueous solution is stable within the pH range of 3-12. It has good compatibility with starch, guar gum, and many surfactants. Gelation occurs when the temperature reaches the gelation temperature. 3. Temperature variation significantly affects the water retention of methyl cellulose. Generally, higher temperatures result in poorer water retention. If the temperature of the mortar exceeds 40°C, the water retention of methyl cellulose decreases significantly, which adversely affects the workability of the mortar. 4. Methyl cellulose has a noticeable impact on the workability and adhesion of mortar. "Adhesion" refers to the adhesion force between the worker's application tool and the wall substrate, i.e., the shear resistance of the mortar. A higher adhesion leads to higher shear resistance, requiring more force from the worker during application and resulting in poorer workability. Among cellulose ether products, methyl cellulose has a moderate level of adhesion. HPMC stands for Hydroxypropyl Methyl Cellulose. It is a non-ionic cellulose ether derived from refined cotton through alkalization, using epichlorohydrin and chloromethane as etherification agents in a series of reactions. The degree of substitution is generally between 1.2 and 2.0. Its properties vary with the ratio of methoxy content to hydroxypropyl content. (1) Hydroxypropyl Methyl Cellulose is soluble in cold water, but it can be difficult to dissolve in hot water. However, its gelation temperature in hot water is significantly higher than that of methyl cellulose. Its solubility in cold water is greatly improved compared to methyl cellulose. (2) The viscosity of Hydroxypropyl Methyl Cellulose depends on its molecular weight, with higher molecular weight leading to higher viscosity. Temperature also affects its viscosity, with viscosity decreasing as temperature rises. However, its viscosity is less affected by temperature compared to methyl cellulose. Its solution is stable when stored at room temperature. (3) Hydroxypropyl Methyl Cellulose exhibits stability in acids and alkalis, and its aqueous solution is highly stable within the pH range of 2 to 12. It is minimally affected by sodium hydroxide and lime water, although alkalis can accelerate its dissolution and slightly increase its viscosity. It demonstrates stability in general salts, but at higher salt concentrations, the viscosity of Hydroxypropyl Methyl Cellulose solution tends to increase. (4) The water retention capacity of Hydroxypropyl Methyl Cellulose depends on factors such as the dosage and viscosity, and at the same dosage, its water retention rate is higher than that of methyl cellulose. (5) Hydroxypropyl Methyl Cellulose can be mixed with water-soluble high molecular weight compounds to form homogeneous solutions with higher viscosity. Examples include polyvinyl alcohol, starch ethers, and plant gums. (6) Hydroxypropyl Methyl Cellulose exhibits higher adhesion in mortar construction compared to methyl cellulose. (7) Hydroxypropyl Methyl Cellulose has better resistance to enzymatic degradation compared to methyl cellulose, and its solution is less likely to undergo enzymatic degradation.

1. Interior wall putty powder: Heavy calcium carbonate 800KG, light calcium carbonate 150KG (Starch ether, pure Qing, Peng run soil, citric acid, polyacrylamide, etc., can be added as appropriate). 2. Exterior wall putty powder: Cement 350KG, heavy calcium carbonate 500KG, quartz sand 150KG, latex powder 8-12KG, cellulose ether 3KG, starch ether 0.5KG, wood fiber 2KG.

HPMC has three functions in putty powder: thickening, water retention, and facilitating construction. It does not participate in any reaction. The formation of bubbles in putty powder can be caused by two reasons: (1) Excessive water content. (2) Applying another layer on top before the bottom layer has dried, which can also lead to the formation of bubbles.

Hydroxypropyl Methyl Cellulose, in English: Hydroxypropyl Methyl Cellulose, also known as HPMC or MHPC. Other names: Hydroxypropyl Methyl Cellulose; Cellulose Hydroxypropyl Methyl Ether; Hypromellose; Cellulose, 2-hydroxypropylmethyl Cellulose ether; Cellulose hydroxypropyl methyl ether; Hyprolose.

For putty applications, a lower viscosity of 100,000 is sufficient, and good water retention is important. For mortar applications, higher viscosity of 150,000 is preferred. For adhesive applications, a high-viscosity, quick-dissolving product is required.

HPMC produced using solvent methods uses solvents such as toluene and isopropanol. If the washing process is not thorough, there may be some residual odor.

The cold-water soluble type of HPMC is surface-treated with formaldehyde, allowing it to disperse rapidly in cold water but not truly dissolve. It only dissolves when the viscosity increases. The thermal soluble type does not undergo surface treatment with formaldehyde. A higher dosage of formaldehyde results in faster dispersion but slower viscosity increase, while a lower dosage has the opposite effect.

The powder loss in putty is mainly related to the quality of the lime powder and has little to do with HPMC. Low calcium content in lime powder and an improper ratio of CaO and Ca(OH)2 in lime powder can both cause powder loss. If there is a slight relationship with HPMC, it would be that poor water retention of HPMC can also contribute to powder loss.

The gelation temperature of HPMC is related to its methoxy content. The lower the methoxy content, the higher the gelation temperature.

In simple terms, "non-ionic" refers to a substance that does not ionize in water. Ionization refers to the process in which electrolytes dissolve in specific solvents (such as water or alcohol) and dissociate into freely moving charged ions. For example, table salt we consume daily—sodium chloride (NaCl)—when dissolved in water, ionizes and produces freely moving sodium ions with a positive charge and chloride ions with a negative charge. In other words, when HPMC is placed in water, it does not dissociate into charged ions but exists in molecular form.

In the application of HPMC in putty powder, it plays three roles: thickening, water retention, and facilitating construction. Thickening: Cellulose can thicken the mixture, maintain uniform suspension, and prevent sagging. Water retention: It slows down the drying process of putty powder and assists in the reaction of lime and calcium in water. Construction: Cellulose acts as a lubricant, improving the workability of the putty powder. HPMC does not participate in any chemical reactions; it only serves as an auxiliary agent. When putty powder is mixed with water and applied to the wall, a chemical reaction occurs because new substances are formed. However, if the putty powder is scraped off the wall, ground into powder, and reused, it is not suitable because a new substance (calcium carbonate) has already formed. The main components of lime and calcium powder are Ca(OH)2, CaO, and a small amount of CaCO3. The reaction can be represented as: CaO + H2O = Ca(OH)2 — Ca(OH)2 + CO2 = CaCO3 ↓ + H2O. Under the action of water and carbon dioxide in the air, lime and calcium carbonate are formed. HPMC only assists in water retention and the better reaction of lime and calcium; it does not participate in any reactions itself.

The main raw materials for Hydroxypropyl Methylcellulose (HPMC) include refined cotton, chloromethane, epichlorohydrin, and other materials such as soda ash, acid, toluene, isopropanol, etc.

The two main indicators most users are concerned about are the content of hydroxypropyl and viscosity. Higher hydroxypropyl content generally indicates better water retention. A higher viscosity also provides relatively better water retention (not absolute), and HPMC with higher viscosity is more suitable for cement mortar.

For putty powder, a viscosity of around 100,000 is generally sufficient, while mortar requires a higher viscosity, around 150,000, to be effective. Moreover, the most important function of HPMC is water retention, followed by thickening. In putty powder, as long as it has good water retention and a lower viscosity (70,000-80,000), it can still be used. Of course, a higher viscosity provides relatively better water retention. However, when the viscosity exceeds 100,000, the impact of viscosity on water retention becomes less significant.

The dosage of HPMC in actual application varies depending on factors such as climate, temperature, local lime and calcium quality, putty powder formulation, and the desired quality specified by the customer. Generally, it ranges between 4 kg to 5 kg. For example, in Beijing, most putty powders use around 5 kg; in Guizhou, it is mostly 5 kg in summer and 4.5 kg in winter; in Yunnan, the dosage is smaller, usually around 3 kg to 4 kg, and so on.

1. Whiteness: Although whiteness alone does not determine the usefulness of HPMC, higher-quality products usually have better whiteness. 2. Fineness: HPMC is typically available in 80 and 100 mesh sizes, with fewer options in 120 mesh. Finer particles generally indicate better quality. 3. Transmittance: When HPMC is dissolved in water and forms a transparent colloidal solution, higher transmittance indicates fewer insoluble impurities. 4. Specific gravity: Higher specific gravity is generally better. A higher specific gravity is often due to a higher content of hydroxypropyl, which results in better water retention.

1. Hot water dissolution method: HPMC does not dissolve in hot water, but it can disperse evenly in hot water initially and then rapidly dissolve upon cooling. There are two typical methods described as follows: (1) Place the required amount of hot water in a container and heat it to approximately 70°C. Gradually add HPMC while stirring slowly. Initially, HPMC will float on the water's surface and gradually form a slurry, which cools down under stirring. (2) Add 1/3 or 2/3 of the required amount of water to a container and heat it to 70°C. Disperse HPMC according to method (1) to prepare a hot water slurry. Then, add the remaining cold water to the hot water slurry and cool the mixture after stirring. 2. Powder mixing method: Mix HPMC powder with a large amount of other powdered substances using a blender. Afterward, add water for dissolution. In this case, HPMC can dissolve without clumping because each tiny corner of the powder contains only a small amount of HPMC, which dissolves immediately upon contact with water. This method is commonly used in putty powder and mortar production.

HPMC can be divided into two types: instant soluble and heat soluble. Instant soluble HPMC quickly disperses in cold water, disappearing in the water. At this stage, the liquid does not have viscosity because HPMC is only dispersed in the water and not completely dissolved. After about 2 minutes, the viscosity of the liquid gradually increases, forming a transparent and viscous colloidal solution. Heat soluble HPMC tends to agglomerate in cold water but can rapidly disperse in hot water, disappearing in it. As the temperature decreases to a certain point, viscosity slowly appears until a transparent and viscous colloidal solution is formed. Heat soluble HPMC can only be used in putty powder and mortar, as it tends to agglomerate in liquid adhesives and coatings and cannot be used effectively. Instant soluble HPMC has a wider range of applications and can be used in putty powder, mortar, liquid adhesives, and coatings without any restrictions.

HPMC is widely used in industries such as construction materials, coatings, synthetic resins, ceramics, pharmaceuticals, food, textiles, agriculture, cosmetics, and tobacco. HPMC can be classified into architectural grade, food grade, and pharmaceutical grade based on its application. Currently, most domestically produced HPMC falls under the architectural grade category. In the architectural grade, a large amount of HPMC is used in putty powder, accounting for approximately 90% of its usage, while the rest is used in cement mortar and adhesives.