How to add hydroxyethyl cellulose to coatings
Hydroxyethylcellulose (HEC) has many functions, including: thickening, suspension, adhesion, emulsification, film formation, stabilization, dispersion, water retention, and formation of protective colloids.
It is easily soluble in hot or cold water, can be formulated into a wide range of viscosity solutions, and has excellent resistance to dissolved electrolytes.
method （one)
Add directly when grinding the pigment:
1. Add appropriate purified water to the vat equipped with high-resistance agitator. (Generally, ethylene glycol, wetting agent and film-forming agent are added in this step).
2. Start stirring constantly at low speed and slowly sieve hydroxyethyl cellulose into the solution.
3. Continue stirring until all particles are wet.
4. Then add antifungal agent, alkaline additives, such as pigment dispersion aid, ammonia.
5. Stir until all the hydroxyethyl cellulose is completely dissolved (the viscosity of the solution is significantly increased) before adding the other components in the formula and grind until the paint is formed.
Method （2)
Equipped with mother liquor standby:
This method is first equipped with a higher concentration of mother liquor, and then added to the latex paint. The advantage of this method is that it has greater flexibility and can be directly added to the finished paint, but it must be stored properly.
The steps are similar to steps 1 to 4 in method (1), except that there is no need to use a high shear mixer, and only a stirrer with sufficient power to keep the hydroxyethyl cellulose uniformly dispersed in the solution can be used. Continue stirring until completely dissolved into a viscous solution.
It should be noted that the antifungal must be added to the mother liquor as soon as possible.
Method (3)
Prepared for porridge use:
Since organic solvents are poor solvents for hydroxyethyl cellulose, these organic solvents can be used to prepare porridge.
The most commonly used organic solvents are organic liquids in paint formulations such as ethylene glycol, propylene glycol, and film formers (such as hexanediol or diethylene glycol butyl acetate).
Ice water is also a poor solvent, so ice water is often used with organic liquids to prepare porridge.
Porridge-like hydroxyethyl cellulose can be directly added to the paint. The hydroxyethylcellulose was fully swollen in the form of porridge. When added to the paint, it dissolves immediately and acts as a thickener. After the addition, it is necessary to continue stirring until the hydroxyethyl cellulose is completely dissolved and uniform.
Generally, porridge is made by mixing six parts of organic solvent or ice water with one part of hydroxyethyl cellulose. After about 5-30 minutes, the hydroxyethyl cellulose is hydrolyzed and obviously swells. Generally, the temperature of water is too high in summer, so it should not be used for congee.
Matters needing attention in hydroxyethyl cellulose mother liquor:
Hydroxyethylcellulose is generally treated as a powder or granule. As long as the following points are noted, it is easy to handle and dissolve it in water.
1. Before and after adding hydroxyethyl cellulose, you must keep stirring until the solution is completely transparent and clear.
2. It must be sifted into the mixing tank slowly. Do not add the hydroxyethyl cellulose which has been formed into a block or a ball directly into the mixing tank.
3. Water temperature and pH value in water have a clear relationship with the dissolution of hydroxyethylcellulose, so special attention must be paid.
4. Never add some alkaline substances to the mixture before the hydroxyethyl cellulose powder is wetted with water. Increasing the pH after soaking will help dissolve.
5. To the extent possible, add an antifungal agent early.
6. When using high viscosity type hydroxyethyl cellulose, the concentration of the mother liquor should not be higher than 2.5-3% (by weight), otherwise the mother liquor is difficult to handle.
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