Main application :
nano environmental protection coatings, automotive topcoats, special anti-corrosion coatings, metal coatings, thermal insulation coatings, coated paper, wallpaper, antibacterial ceramics, marine coatings, special ink, aerospace, rubber, plastic, paper, ink, chemical fiber, cosmetics, pharmaceutical grade, pigment grade, ceramic grade, enamel, etc.
Cellulose ether and its derivatives
According to reports! 7, hydroxyethyl cellulose (HEC) was first industrialized by Union Car-bide in 1932, and has a history of more than 70 years.
At present, the thickeners of cellulose ether and its derivatives mainly include hydroxyethyl cellulose (HEC), methyl hydroxyethyl cellulose (MHEC), ethyl hydroxyethyl cellulose (EHEC), and methyl hydroxypropyl cellulose. Base cellulose (MH PC), methyl cellulose (MC) and xanthan gum, etc., these are all ethylene acrylic acid dispersion non-ionic thickeners, at the same time belong to the non-associative water phase thickener, the relative molecular mass is generally 5×10* ~8×10%. Among them, the most commonly used in latex paint is HEC, and its structure is shown in Figure 19-3, such as Natr osol 250 from A qualon and Cellu size QP from Union Carbide. MHEC, EHEC, and MH-PC have a certain degree of hydrophobicity, and are slightly better than HEC in terms of ICI viscosity, splash resistance and flow level. In addition, polyanionic cellulose (PAC) has also begun to be used in coatings.
The thickening mechanism of this kind of thickener is due to the high hydration of hydrogen bonds and the entanglement between macromolecules. When it is added to the latex paint, it can immediately absorb a large amount of water, which greatly expands its volume. At the same time, the high molecular weight thickeners are entangled with each other, so that the viscosity of the latex paint is significantly increased and the thickening effect is produced.
The characteristics of this type of thickener are: water phase thickening, good compatibility with the components in latex paint, good low-shear thickening effect, large tolerance to pH changes, good water retention, and high thixotropy. Due to the high low-shear viscosity and high thixotropy, it has good sag resistance but poor leveling and has an impact on the gloss of the coating film. Because the molecular weight is large, the molecular chain is more flexible, and the viscosity is low at high shear rates, the paint roller coating has poor splash resistance. The viscosity is low at high shear rates, resulting in poor film fullness. The glycoside bond is easily eroded and degraded by bacteria, which reduces the viscosity of the coating and even deteriorates. Therefore, when using it, a certain preservative must be added to the system.
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