Thickeners for latex paints must have good compatibility with latex polymer compounds, otherwise there will be a small amount of texture in the coating film, and irreversible particle aggregation will occur, resulting in a decrease in viscosity and coarser particle size. Thickeners will change the charge of the emulsion. For example, cationic thickeners will have an irreversible effect on anionic emulsifiers and cause demulsification. An ideal latex paint thickener must have the following properties:

1. Low dosage and good viscosity

2. Good storage stability, will not reduce the viscosity due to the action of enzymes, and will not reduce the viscosity due to changes in temperature and pH value

3. Good water retention, no obvious air bubbles

4. No side effects on paint film properties such as scrub resistance, gloss, hiding power and water resistance

5. No flocculation of pigments

The thickening technology of latex paint is an important measure to improve the quality of latex and reduce costs. Hydroxyethyl cellulose is an ideal thickener, which has multifunctional effects on the thickening, stabilization and rheological adjustment of latex paint.

In the production process of latex paint, hydroxyethyl cellulose (HEC) is used as a dispersant, thickener and pigment suspending agent to stabilize the viscosity of the product, reduce agglomeration, make the paint film smooth and smooth, and make the latex paint more durable. Good rheology, can withstand high shear strength, and can provide good leveling, scratch resistance and pigment uniformity. At the same time, HEC has excellent workability, and the latex paint thickened with HEC has pseudoplasticity, so brushing, rolling, filling, spraying and other construction methods have the advantages of labor saving, not easy to clear, sag, and less splashing. HEC has excellent color development. It has excellent miscibility for most colorants and binders, which makes the latex paint have excellent color consistency and stability. Versatility for application in formulations, it is a non-ionic ether. Therefore, it can be used in a wide pH range (2~12), and can be mixed with components in general latex paint such as reactive pigments, additives, soluble salts or electrolytes.

No adverse effect on the coating film, because the HEC aqueous solution has obvious water surface tension characteristics, it is not easy to foam during production and construction, and the tendency of volcanic holes and pinholes is less.

Good storage stability. During long-term storage, the dispersibility and suspension of the pigment can be maintained, and there is no problem of floating color and blooming. There is little water layer on the surface of the paint, and when the storage temperature changes greatly. Its viscosity is still relatively stable.

HEC can increase the PVC value (pigment volume concentration) solid composition up to 50-60%. In addition, the surface coating thickener of water-based paint can also use HEC.

At present, the thickeners used in domestic medium and high-grade latex paints are imported HEC and acrylic polymer (including polyacrylate, homopolymer or copolymer emulsion thickeners of acrylic acid and methacrylic acid) thickeners.

Hydroxyethyl cellulose can be used for

1. As a dispersant or protective glue

Generally, HEC with a viscosity of 10-30mPaS is used. The HEC that can be used up to 300mPa·S will have a better dispersion effect if it is used in combination with anionic or cationic surfactants. The reference dosage is generally 0.05% of the monomer mass.

2. As a thickener

Use 15000mPa. The reference dosage of high-viscosity HEC above s is 0.5-1% of the total mass of latex paint, and the PVC value can reach about 60%. Use HEC of about 20Pa,s in latex paint, and the performance of latex paint is the best. The cost of simply using HEC above 30O00Pa.s is lower. However, the leveling properties of latex paint are not good. From the perspective of quality requirements and cost reduction, it is better to use medium and high viscosity HEC together.

3. The mixing method in latex paint

Surface-treated HEC can be added in dry powder or paste form. The dry powder is added directly to the pigment grind. The pH at the feed point should be 7 or lower. Alkaline components such as Yanbian dispersant can be added after HEC is wetted and fully dispersed. Slurries made with HEC should be blended into the slurry before the HEC has had sufficient time to hydrate and allow to thicken to an unusable condition. It is also possible to prepare HEC pulp with ethylene glycol coalescing agents.

4. Anti-mold of latex paint

Water-soluble HEC will biodegrade when in contact with molds that have special effects on cellulose and its derivatives. It is not enough to add preservatives to the paint alone, all components must be enzyme-free. The production vehicle of latex paint must be kept clean, and all equipment must be regularly sterilized with steam 0.5% formalin or O.1% mercury solution