Hydroxypropyl methylcellulose HPMC is generally used in the production of interior and exterior wall putty powder with a viscosity of 100,000 cellulose, in dry powder mortar, diatom mud and other building material products, cellulose with a viscosity of 200,000 is commonly used, and in self-leveling and other special mortars, cellulose with a viscosity of 400 is commonly used. Viscosity cellulose, this product has good water retention effect, good thickening effect and stable quality. HPMC is widely used in the building materials industry and is used in a large amount. Cellulose can be used as a retarder, water retention agent, thickener and binder. Cellulose ether plays an important role in ordinary dry-mixed mortar, external wall insulation mortar, self-leveling mortar, dry powder plastering adhesive, tile bonding mortar, putty powder, interior and exterior wall putty, waterproof mortar, thin-layer joints, etc. , they have an important influence on the water retention, water demand, firmness, retardation and workability of the stucco system.

Commonly used cellulose ethers include HEC, HPMC, CMC, PAC, MHEC, etc. Nonionic water-soluble cellulose ether has cohesiveness, dispersion stability and water retention capacity, and is a useful additive for building materials. HPMC, MC or EHEC are used in most cement-based or gypsum-based constructions, such as masonry mortar, cement mortar, cement coating, gypsum, cementitious mixture and milky putty, etc., which can enhance the dispersion of cement or sand and greatly improve the Adhesion, which is very important for plaster, tile cement and putty. HEC is used in cement, not only as a retarder, but also as a water-retaining agent, and HEHPC is also used in this regard. MC or HEC are often used together with CMC as a solid part of the wallpaper. Medium-viscosity or high-viscosity cellulose ethers are commonly used in wallpaper glued building materials.

Properties of hydroxypropyl methylcellulose

Hydroxypropyl methylcellulose HPMC products combine many physical and chemical properties to become a unique product with multiple uses. The various properties are as follows:

(1) Water retention: It can hold water on porous surfaces such as wall cement boards and bricks.

(2) Film formation: It can form a transparent, tough and soft film with excellent oil resistance.

(3) Organic solubility: The product is soluble in some organic solvents, such as ethanol/water, propanol/water, dichloroethane, and a solvent system composed of two organic solvents.

(4) Thermal gelation: When the aqueous solution of the product is heated, it will form a gel, and the formed gel will become a solution again after cooling.

(5) Surface activity: Provide surface activity in the solution to achieve the required emulsification and protective colloid, as well as phase stabilization.

(6) Suspension: hydroxypropyl methylcellulose can prevent solid particles from settling, thus inhibiting the formation of precipitates.

(7) Protective colloid: it can prevent droplets and particles from coalescing or coagulating.

(8) Adhesiveness: Used as an adhesive for pigments, tobacco products, and paper products, it has excellent performance.

(9) Water solubility: The product can be dissolved in water in different quantities, and its maximum concentration is only limited by viscosity.

(10) Non-ionic inertness: The product is a non-ionic cellulose ether, which does not combine with metal salts or other ions to form insoluble precipitates.

(11) Acid-base stability: suitable for use within the range of PH3.0-11.0.

(12) Tasteless and odorless, not affected by metabolism; used as food and drug additives, they will not be metabolized in food and will not provide calories.

Common and simple ways to identify quality

1. Pure HPMC is visually fluffy and has a low bulk density, ranging from 0.3-0.4g/ml; adulterated HPMC has better fluidity and feels heavier, which is obviously different from the genuine product in appearance.

2. Pure HPMC has good whiteness, which means that the raw materials used in production are pure, and the reaction is more thorough without impurities. Compared with related foreign cellulose ether products, it can be seen that the whiteness of a good cellulose ether product is always better than that of domestic second-tier brand products.

3. Pure HPMC aqueous solution is clear, high light transmittance, water retention rate ≥ 97%; adulterated HPMC aqueous solution is turbid, and the water retention rate is difficult to meet the requirements. The light transmittance of the aqueous solution is good, which indicates that the product contains less insoluble substances and has a high content of active ingredients.

4. Pure HPMC should not smell ammonia, starch and alcohol; adulterated HPMC can often smell all kinds of smells, even if it is odorless, it will feel heavy.

5. Pure HPMC powder is fibrous under a microscope or magnifying glass; adulterated HPMC can be observed as granular solids or crystals under a microscope or magnifying glass.

6. The simple test method for the ash content of cellulose ether is to weigh one to two grams of cellulose ether, light it with a lighter, and weigh the ash residue left after the cellulose ether is burned. When the ash residue/cellulose ether ≥ 5%, the fiber The quality of plain ether is basically unqualified. (Sometimes there are errors in this method. One is that the manufacturer has added a designated product suitable for a specific customer after leaving the factory; the other is that the agent or manufacturer added flammable substances with low ash content when adulterating )

7. Some manufacturers compound a small amount of CMC into hydroxypropyl methyl cellulose ether, and when the CMC aqueous solution meets tin, silver, aluminum, lead, iron, copper and some heavy metals, a precipitation reaction will occur; the CMC aqueous solution and calcium When , magnesium, and salt coexist, no precipitation will occur, but the viscosity of the CMC aqueous solution will be reduced.

8. If conditions permit, directly test the viscosity of the aqueous solution of cellulose ether and compare the water retention rate of low-volume cellulose ether mortar.