Hydroxyethyl cellulose (HEC) is a white or light yellow, odorless, non-toxic fibrous or powdery solid, made of raw cotton linters or refined pulp soaked in 30% liquid alkali, taken out and pressed after half an hour, Squeeze until the ratio of alkaline water reaches 1:2.8, then crush. It is prepared by etherification reaction and belongs to non-ionic soluble cellulose ethers. Hydroxyethyl cellulose is an important thickener in latex paint. Let’s focus on how to use hydroxyethyl cellulose HEC in latex paint and the precautions.
1. Equipped with mother liquor for use: first use hydroxyethyl cellulose HEC to prepare a mother liquor with a higher concentration, and then add it to the product. The advantage of this method is that it has greater flexibility and can be directly added to the finished product, but it must be properly stored. The steps of this method are similar to most of the steps in method 2; the difference is that there is no need for a high-shear agitator, and only some agitators with sufficient power to keep the hydroxyethyl cellulose uniformly dispersed in the solution can be continued without stopping Stir until completely dissolved into a viscous solution. However, it must be noted that the fungicide must be added to the mother liquor as soon as possible.
2. Add directly during production: this method is the simplest and takes the shortest time. Add clean water to a large bucket equipped with a high shear mixer. Start to stir continuously at low speed and slowly sieve the hydroxyethyl cellulose into the solution evenly. Continue to stir until all particles are soaked. Then add preservatives and various additives. Such as pigments, dispersing aids, ammonia water, etc. Stir until all the hydroxyethyl cellulose HEC is completely dissolved (the viscosity of the solution increases obviously) and then add other components in the formula for reaction.
Precautions;
(1) When using high-viscosity hydroxyethyl cellulose HEC, the concentration of the mother liquor should not be higher than 2.5-3% (by weight), otherwise the mother liquor will be difficult to handle.
(2) Before and after adding hydroxyethyl cellulose HEC, it must be stirred continuously until the solution is completely transparent and clear.
(3) As much as possible, add antifungal agent in advance.
(4) Water temperature and pH value of water have obvious relationship to the dissolution of hydroxyethyl cellulose, so special attention should be paid.
(5) Do not add some alkaline substances to the mixture before the hydroxyethyl cellulose powder is soaked with water. Raising the pH after soaking will help dissolve.
(6) It must be slowly sifted into the mixing tank, and do not add large quantities or directly add the hydroxyethyl cellulose that has formed lumps and balls into the mixing tank.
Important factors affecting the viscosity of latex paint:
1 Corrosion of thickener by microorganisms.
2 In the paint making process, whether the sequence of adding thickener is correct.
3 Whether the amount of surface activator and the amount of water in the paint formula are appropriate.
4 The ratio of the amount of other natural thickeners to the amount of hydroxyethyl cellulose in the paint formulation.
5 When the latex is formed, the content of residual catalysts and other oxides.
6 The temperature is too high during dispersion due to excessive stirring.
7 The more air bubbles remain in the paint, the higher the viscosity.
The viscosity of hydroxyethyl cellulose HEC changes slightly in the pH range of 2-12, but the viscosity decreases beyond this range. It has the properties of thickening, suspending, binding, emulsifying, dispersing, maintaining moisture and protecting colloid. Solutions in different viscosity ranges can be prepared. Unstable under normal temperature and pressure, avoid humidity, heat, and high temperature, and has exceptionally good salt solubility to dielectrics, and its aqueous solution is allowed to contain high concentrations of salts and remains stable.
Post time: Feb-14-2023