Views: 4 Author: Site Editor Publish Time: 2022-01-22 Origin: Site
HEC is short for hydroxyethyl Cellulose. Hydroxyethyl cellulose HEC is a white or pale yellow, tasteless, non-toxic, fibrous or powdery solid prepared by the etherification of alkaline cellulose and ethylene oxide (or chloroethanol). It is a non-ionic soluble cellulose ether. As a non-ionic surfactant, in addition to thickening, suspension, bonding, floating, film forming, dispersing, water retention and protection.
1, HEC can be dissolved in hot or cold water, high temperature or boiling does not precipitate, so that it has a wide range of solubility and viscosity properties, and non-thermal gel;
2, its non-ionic can coexist with a wide range of other water-soluble polymers, surfactants, salts, is an excellent colloidal thickener containing high concentration of electrolyte solution;
3, water retention capacity is twice higher than methyl cellulose, with good flow adjustability,
4. HEC has the worst dispersion ability compared with the recognized methyl cellulose and hydroxypropyl methyl cellulose, but the strongest colloid protection ability.
Therefore, hydroxyethyl cellulose is widely used in petroleum exploitation, coating, construction, medicine and food, textile, paper making and polymer polymerization reaction and other fields.
Main properties of HEC for latex paint
Hydroxyethyl cellulose (HEC) is an ideal thickener for coatings and cosmetics. In practical application, the combination of its thickening with suspension, safety, dispersity and water retention will produce ideal results.
Pseudoplasticity is the property that the viscosity of solution decreases with the increase of rotational speed. HEC containing latex paint is easy to apply with a brush or roller and can increase the smoothness of the surface, which can also increase work efficiency; Hec-containing shampoos are fluid and sticky, easily diluted and easily dispersed.
3. Salt resistance
HEC is stable in highly concentrated saline solutions and does not decompose into ionic states. Used in electroplating, can make the plating surface more complete, more bright. More noteworthy is the application of borate, silicate and carbonate latex paint, still has a very good viscosity.
The membrane formation properties of HEC can be used in many industries. In papermaking operations, coated with HEC glazing agent, can prevent grease penetration, and can be used to prepare other aspects of papermaking solution; HEC increases the elasticity of the fibers during the weaving process and thus reduces mechanical damage to them. HEC acts as a temporary protective film during sizing and dyeing of the fabric and can be washed away from the fabric with water when its protection is not needed.
4. Water retention
HEC helps to keep the moisture of the system in an ideal state. Because a small amount of HEC in aqueous solution can achieve a better water retention effect, so that the system reduces the demand for water in the preparation. Without water retention and adhesion, cement mortar will reduce its strength and adhesion, and clay will also reduce plasticity under certain pressure.
Application method of hydroxyethyl cellulose HEC in latex paint
1. Add directly when grinding pigment: this method is the simplest, and the time used is short. The detailed steps are as follows:
(1) Add appropriate purified water into the VAT of the high cutting agitator (generally, ethylene glycol, wetting agent and film forming agent are added at this time)
(2) Start stirring at low speed and slowly add hydroxyethyl cellulose
(3) Continue to stir until all particles are soaked
(4) add mildew inhibitor, PH regulator, etc
(5) Stir until all hydroxyethyl cellulose is completely dissolved (the viscosity of the solution is significantly increased) before adding other components in the formula, and grind until it becomes paint.
2 equipped with mother liquid waiting: this method is first equipped with a higher concentration of mother liquid, and then add latex paint, the advantage of this method is greater flexibility, can be directly added to paint finished products, but must be appropriate storage. Steps and methods are similar to steps (1) - (4) in Method 1, except that a high cutting agitator is not required and only some agitator with sufficient power to keep the hydroxyethyl fibers evenly dispersed in the solution is sufficient. Continue stirring until it completely dissolves into a thick solution. Note that the mildew inhibitor must be added to the mother liquor as soon as possible.
3. Porridge like phenology: Since organic solvents are bad solvents for hydroxyethyl cellulose, these organic solvents can be equipped with porridge. The most commonly used organic solvents such as ethylene glycol, propylene glycol, and film forming agents (such as hexadecanol or diethylene glycol butyl acetate), ice water is also a poor solvent, so ice water is often used with organic liquids in porridge.
Gruel - like hydroxyethyl cellulose can be directly added to the paint. Hydroxyethyl cellulose has been saturated in porridge form. After adding lacquer, dissolve immediately and have thickening effect. After adding, continue to stir until hydroxyethyl cellulose completely dissolved and uniform. A typical 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 hydrolyzes and visibly rises. In summer, the humidity of water is too high to be used for porridge.
4. Matters needing attention when equipping hydroxyethyl cellulose mother liquor
Since hydroxyethyl cellulose is a treated granular powder, it is easy to handle and dissolve in water with the following precautions.
4.1 Before and after adding hydroxyethyl cellulose, must be stirred continuously until the solution is completely transparent and clear.
4.2. Sieve the hydroxyethyl cellulose into the mixing tank slowly. Do not add it into the mixing tank in large quantities or directly into the bulk or spherical hydroxyethyl cellulose.
4.3 water temperature and pH value of water have obvious relation to the dissolution of hydroxyethyl cellulose, so special attention should be paid to it.
4.4 Do not add some basic substance to the mixture before the hydroxyethyl cellulose powder is soaked with water. Raising the pH after soaking helps dissolve.
4.5 As far as possible, early addition of mildew inhibitor.
4.6 When using high viscosity hydroxyethyl cellulose, the concentration of mother liquor should not be higher than 2.5-3% (by weight), otherwise the mother liquor is difficult to operate.
Factors affecting the viscosity of latex paint
1 The more residual air bubbles in the paint, the higher the viscosity.
2 Is the amount of activator and water in the paint formula consistent?
3 in the synthesis of latex, residual catalyst oxide content of the amount.
4. The dosage of other natural thickeners in the paint formula and the dosage ratio with HEC hydroxyethyl cellulose.)
5 in the process of making paint, the order of steps to add thickener is appropriate.
6 Due to excessive agitation and excessive humidity during dispersion.
7 Microbial erosion of thickener.