Hydroxy ethyl Cellulose - HEC

Grades

  • HEC 30000
  • HEC 100000
  • HEC 150000

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Hydroxyethyl cellulose is a non-ionic polymer. Aqueous solution of HEC are pseudoplastic. Newtonian rheology is approached by very dilute solutions as well as by lower molecular weight products.
A large part of the hydroxyethylcellulose production goes to the paint industry. It is used in paints in a range from latex paints containing small amounts as a stabilizer and thickener to paints consisting entirely of pigments, extenders, hydroxyethylcellulose and water.
The use of hydroxyethylcellulose in paints containing an alkyd modified acrylic and in manufacturing of alkyd emulsions are example of use of this ether in paints for exterior use.
Water solutions of hydroxyethylcellulose exhibit pseudoplastic flow that produces superior flow and leveling in latex paints. The ether also gives very good brushability (low viscosity at high rates of shear) to a paint. Because only small amount of hydroxyethylcellulose are required to give a desired viscosity, it has no effect on the washability of ordinary latex paints. 
As painting habits differ widely between countries, so does the use of hydroxyethylcellulose.
*HEC is modified with Glycidyltrimethylammonium chloride to give cationic cellulose ether.

Low hydroxyethyl substitution (MS=0.05-0.5) yield products that are soluble only in aqueous alkali. Higher substitution (MS>1.5) produce water soluble HEC. The bulk of commercial HEC falls into later category. The water soluble HEC is widely used because of its broad compatibility of cations. A lack of solution gel or precipitation point in water upto boiling point. The MS of Commercial HEC varies from about 1.8-3.5.
Cellulose ethers are subject to enzymatic degradation by cellulose enzymes, but by adjusting the conditions of ethoxylation, it is possible to obtain HEC with more uniform conditions of hydroxyethyl substituents resulting in substantially improved enzyme resistance.

This cellulose ether is soluble in hot and cold water but insoluble in hydrocarbon solvents. HEC swells or becomes partly to mostly soluble in select polar solvents, usually those that are miscible with water. Because HEC is non-ionic, it can be dissolved in many salt solution that do not dissolve other water soluble polymers. It is soluble in most 10% salt solutions and in many 50% (or saturated) salt solutions such as sodium chloride, aluminium nitrate.

However as with most water soluble thickeners the particles have tendency to agglomerate, or lump, when first wetted with water. This is especially evident when HEC is added to water with poor agitation. Manufacturers have eliminated the problem of lumping and slow dissolving by surface treating the particle, most commonly with glyoxal. When added to water particles completely disperse. After initial induction period, commonly term delayed hydration time, the dispersed particles begin to dissolve, producing smooth, lump-free solutions. The delayed hydration time can be increased or decrease by lowering or raising, respectively the pH. Most manufacturers around the globe supply dispersible grades.

Commercially HEC is available in wide range of viscosity grades, ranging from greater than 500 mPa.s (=cP) at 1% solids to less than 100 mPa.s (=cP) at 5% total solids. As a rule, the lower substitution grade are more salt tolerant.



Cellulose Ether
( HEC, HPMC, MHEC, MC)

2% Aqueous Solution NDJ-1

2% Aqueous Solution Brookfield

60000

30000

75000

35000

100000

45000

100000

45000

150000

55000

200000

65000

Viscosity change little between 2.0-12.0, but are affected by acid hydrolysis or alkaline oxidation under pH and temperature extremes.
Temperature

Viscosity of HEC solutions change reversibly with temperatures, increasing when cooled and decreasing when warm.

HEC is generally is compatible with other water soluble cellulose ethers to give clear homogenous solution. When mixed with anionic polymer such as CMC, however, interaction between 2 polymers may result in synergistic behavior, ie, viscosity is higher than predicted and calculated. HEC has excellent compatibility with natural gums.