Technical Guidelines for Hydroxypropyl Methylcellulose (HPMC)

What is the main use of hydroxypropyl methyl cellulose (HPMC)?

Hydroxypropyl methyl cellulose (HPMC) finds extensive application across various industries, including building materials, coatings, synthetic resins, ceramics, medicine, food, textiles, agriculture, cosmetics, and tobacco. HPMC is categorized into construction grade, food grade, and pharmaceutical grade. In the construction industry, HPMC is predominantly used for putty powder, with about 90% utilized for this purpose, while the remaining is applied in cement mortar and glue.

Hydroxypropyl methyl cellulose (HPMC) types and their uses

HPMC is classified into instant type and hot dissolve type. Instant products quickly disperse in cold water, forming an initial liquid with no viscosity. Over time, the viscosity increases, creating a transparent gel. Hot soluble products disperse in hot water and form a viscous colloid as the temperature decreases. The instant type is versatile, suitable for putty powder, mortar, liquid glue, and paint. In contrast, the hot soluble type is mainly used in putty powder and mortar.

Methods to dissolve hydroxypropyl methyl cellulose (HPMC)

There are several ways to dissolve HPMC:

• Hot water solution method: HPMC is not soluble in hot water, but it can be dispersed and later dissolved upon cooling. One method involves heating water to around 70℃, adding HPMC, forming a slurry, and then allowing it to cool while stirring. Another approach is to prepare a hot water slurry followed by adding cold water to cool and dissolve the mixture.
• Powder mixing method: Mix HPMC powder with other powder ingredients, then add water to dissolve it. This method prevents sticking and ensures immediate dissolution, often used in putty powder and mortar production.

How to evaluate the quality of hydroxypropyl methyl cellulose (HPMC)?

The quality of HPMC can be judged based on the following criteria:

• Whiteness: While not a definitive measure of quality, a whiter product usually indicates higher quality.
• Fineness: Finer HPMC (e.g., 100 mesh) is generally better.
• Transmittance: Transparent colloid formation in water is a sign of good quality.
• Proportion: Higher hydroxypropyl content results in better water retention.

How much HPMC is used in putty powder?

The amount of HPMC in putty powder typically ranges from 4kg to 5kg, depending on environmental factors and customer requirements. For example, 5kg is common in Beijing, while Guizhou uses 5kg in summer and 4.5kg in winter. Yunnan generally uses between 3kg and 4kg.

Is high viscosity of hydroxypropyl methyl cellulose (HPMC) necessary?

For putty powder, a viscosity of around 100,000 is often sufficient, while higher viscosities (150,000) are preferred for mortar. The primary function of HPMC is water retention, followed by thickening. As long as water retention is adequate, moderate viscosity levels are acceptable.

Main technical indicators of hydroxypropyl methyl cellulose (HPMC)

The key technical indicators for HPMC are hydroxypropyl content and viscosity. Higher hydroxypropyl content and viscosity generally improve water retention and are preferable for use in cement mortar.

Raw materials of hydroxypropyl methyl cellulose (HPMC)

HPMC is made from refined cotton, chloromethane, propylene oxide, and other materials such as alkali, acid, toluene, and isopropyl alcohol.

Role of HPMC in putty powder applications

In putty powder, HPMC serves three main functions: thickening, water retention, and aiding construction. It does not participate in chemical reactions but helps maintain uniformity, lubrication during application, and slow drying.

Understanding non-ionic cellulose ethers

Non-ionic substances, such as HPMC, do not ionize in water. They exist as molecules, unlike electrolytes that dissociate into charged ions in solvents like water or alcohol.

Factors affecting the gel temperature of hydroxypropyl methyl cellulose

The gel temperature of HPMC is influenced by its methoxy content: lower methoxy content results in a higher gel temperature.

Is the powder loss of putty powder related to HPMC?

The powder loss is primarily connected to the quality of hydrated lime and has little to do with HPMC. Poor water retention by HPMC might contribute to powder loss, but the main factors are lime quality and the CaO to Ca(OH)2 ratio.

Difference between cold water instant and hot soluble HPMC

Cold water instant HPMC is surface-treated with glyoxal, enabling quick dispersion but slow viscosity development. Hot soluble HPMC is not surface-treated, resulting in opposite characteristics.

Reason for the odor in Hydroxypropyl Methylcellulose (HPMC)

HPMC produced via solvent methods may have residual odors if solvents like toluene and isopropanol are not thoroughly washed out.

Selecting the appropriate Hydroxypropyl Methylcellulose (HPMC) for different purposes

For putty powder, a viscosity of 100,000 is usually sufficient with good water retention. Mortar applications require higher viscosity, around 150,000. Adhesives need quick-dissolving, high-viscosity products.

Alternative names for Hydroxypropyl Methylcellulose

HPMC is also known as MHPC, hydroxypropyl methyl cellulose, hydroxypropyl methylcellulose ether, hypromellose, cellulose 2-hydroxypropylmethyl, and cellulose hydroxypropyl methyl ether.

Application of HPMC in putty powder and reasons for bubble formation

HPMC provides thickening, water retention, and construction aid in putty powder. Bubbles form due to excessive water content or applying a second coat before the first layer dries.

Formulas for interior and exterior wall putty powder

Interior wall putty powder consists of:

• 800KG heavy calcium
• 150KG hydrated lime

Exterior wall putty powder includes:

• 350KG cement
• 500KG heavy calcium
• 150KG quartz sand
• 8-12KG latex powder
• 3KG cellulose ether
• 0.5KG starch ether
• 2KG wood fiber

Difference between HPMC and MC

Methyl Cellulose (MC) and HPMC differ in their production processes and properties. MC is derived from alkali-treated refined cotton and etherified with methyl chloride. HPMC is treated with epichlorohydrin and chloromethane. Both have varying degrees of substitution affecting their solubility and usability.

Considering HPMC viscosity and temperature in practical applications

HPMC viscosity decreases as temperature increases. For optimal performance in varying temperatures, it's advisable to adjust the viscosity of HPMC used. Medium viscosity HPMC (75,000-100,000) is suited for putty, whereas high viscosity (150,000-200,000) is ideal for insulation mortar. More information can be found at more details.