HPMC no revestimento: Como é que funciona?

in this artical, we mainly talk about the application of HPMC in the coating and how does it work.

Hydroxypropyl methyl cellulose (HPMC) belongs to the group of cellulose ethers in which hydroxyl groups have been substituted with one or more of the three hydroxyl groups present in the cellulose ring. HPMC is hydrophilic (water-soluble), a biodegradable, and biocompatible polymer having a wide range of applications in constructions, dyes and paints, adesivos, coatings, agriculture, and textiles. HPMC is also soluble in polar organic solvents, making it possible to use both aqueous and nonaqueous solvents. It has unique solubility properties with solubility in both hot and cold organic solvents. HPMC possesses increased organo-solubility and thermo-plasticity compared to other methylcellulose counterparts. It forms a gel upon heating with a gelation temperature of 75℃–90℃.(From: sciencedirect)

As the performance of hydroxypropyl methyl cellulose (HPMC) is similar to other water-soluble ethers, it can be used as a film-forming agent, thickener, emulsifier, and stabilizer for latex coatings and water-soluble resin coatings so that the coating film has good abrasion resistance, leveling, and adhesion, thereby improving its surface tension, stability to acids and alkali and compatibility with metallic pigments. Because HPMC has a higher gel point than MC, it has stronger resistance to bacterial erosion than other cellulose ethers. HPMC in the coating can be used as a thickener for water emulsion paints. HPMC also has good viscosity storage stability and dispersibility, so it is particularly suitable as a dispersant in emulsified coatings.

Examples of HPMC in the coatings industry are as follows:

The coatings prepared by hydroxypropyl methyl cellulose (HPMC) with various viscosities have good abrasion resistance, high-temperature resistance, anti-bacterial degradation, washing resistance, and acid-base stability; HPMC in the coating can also be used as a thickener for paint removers containing methanol, ethanol, propanol, isopropanol, ethylene glycol, acetone, methyl ethyl ketone or diketone alcohol; The emulsified paint prepared by HPMC has excellent wet abrasiveness; HPMC in the coating is better than HEC, MHEC, and CMC as coating thickeners.

HPMC in the coating with a high degree of substitution (DS is 1.76~2.15) has better anti-bacterial corrosion resistance than the low degree of substitution. It has stable viscosity when used in polyvinyl acetate thickener. Other cellulose ethers reduce the viscosity of the coating due to chain degradation during storage.

Paint remover can be formulated with water-soluble HPMC (28%~132% of methoxyl and 7%~12% of hydroxypropyl), dichloromethane toluene, paraffin, ethanol, methanol, and applied to a vertical surface with the required viscosity and volatility.

This paint remover can remove most conventional spray paints, varnishes, enamels, and certain epoxy esters, epoxy amides, catalyzed epoxy amides, acrylic esters, etc. Many paints can peel off within a few seconds, and some paints take 10-15 minutes or more. This paint remover is particularly suitable for wood surfaces.

The water emulsion paint can be composed of 100 component inorganic or organic pigments, 0.5-20 component of water-soluble alkyl cellulose or hydroxyalkyl cellulose, and 0.0-5 component of polyoxyethylene ether or ether ester. For example, 1.5 component of HPMC, 0.05 component of polyethylene glycol alkyl phenyl ether, 99.7 component of titanium dioxide, and 0.3 component of carbon black are mixed to obtain the colorant. Then stir the mixture with 10 of 50% solids polyvinyl acetate to get a coating and apply it on thick paper with a brush to form a dry film without any differences.

MelaColl™ HPMC in  the Coating Industry

Our MelaColl™ HPMC products provide the following features for coating applications:

• Melhore a retenção de água, a resistência à flacidez, a resistência a fissuras e o efeito de espessamento.
• Enhance the adhesion of putty to various substrates
• Improve the consistency and stability of putty
• Provides putty with good workability
• Improves open time
• Improves hydrophobicity

For more information or a sample, please do not hesitate to CONTACTE-NOS.