Which Cellulose Ether Is Best for Coating Industry?
Cellulose ethers are polymers derived from cellulose. As the most abundant polymer in nature, cellulose ethers are specifically divided into the below types: hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (MHEC), methyl cellulose (MC), hydroxypropyl cellulose ( HMC), hydroxyethyl cellulose (HEC), ethyl cellulose (EC) and carboxymethyl cellulose (CMC). HPMC, MHEC, MC, HEC and CMC are all water-soluble cellulose ether, but EC is a kind of solvent-based cellulose ether.
Cellulose ethers play a key role in coating formulations, for which our coating engineers have been deeply researched on cellulose ether. Here we would like to analyze on the below question: which cellulose ether is more suitable for coating industry?
When the temperature up to 60-70℃, the aqueous solution of hydroxypropyl methyl cellulose (HPMC) will become gel. The temperature is usually 50℃ or 60℃ when we doing storage stability experiments, so a jelly-like appearance will appear when cellulose ether is doped with methyl or HPMA. In addition, hydroxypropyl methyl cellulose (HPMC) and hydroxyethyl methyl cellulose (HEMC) contain higher methyl groups, so there will be more air bubbles produced when paints and coatings doped with HPMC or HEMC. Besides, the problem of delamination caused by hydroxypropyl methyl cellulose (HPMC) and hydroxyethyl methyl cellulose (HEMC) still can’t be solved.
Carboxymethyl cellulose (CMC) is an anionic cellulose ether. There are a wide verity of raw materials for coatings, and natural fillers contains high-valent ions or metal ions. Therefore, precipitation or flocculation will appear if the cellulose ether is doped with CMC.
Hydroxyethyl cellulose (HEC) has good water retention and thickening properties as well as good adaptability to temperature changes. In addition, hydroxyethyl cellulose (HEC) has a higher molar substitution degree. So, using HEC for paints and coatings, delamination will be not a problem anymore and the effect can last longer time.
In conclusion, hydroxyethyl cellulose (HEC) is best for coatings industry.