Polyurethane thickener, abbreviated as HEUR, is a hydrophobic group-modified ethoxylated polyurethane water-soluble polymer, which is a non-ionic conjoined thickener.
HEUR is composed of hydrophobic group, hydrophilic chain and polyurethane group. The hydrophobic group plays the role of linkage and is the determining factor of thickening, usually oil group, octadecyl, dodecylphenyl, nonylphenol group, etc. The hydrophilic chain provides chemical stability and viscosity stability, commonly used are polyethers, such as polyoxyethylene and its derivatives. HEUR molecular chain is extended by polyurethane groups, and the polyurethane groups used are IPDI, TDI and HMDI.
For example, the absorption value of the medium pigment carbon black (Special 4) DBP is 110, and the addition amount of the effective solids of the dispersant should be 22%. If the solid content of the dispersant is 50%, 44% of the amount of carbon black should be added according to the form of supply.
The solid content of organic pigments and general dispersants should be 25%-50% of the BET value ptfe pe wax (specific surface area) of the pigment.
For example, GGL yellow, BET is 44m²/g, and the solid content of dispersant should be 22%. If the solid content of the dispersant is 40%, the added amount of the supply form should be 55% of GGL yellow.
The company’s experience is very valuable and can save a lot of experimental time, but the final accurate formula should be determined through experiments.
Adding order of dispersant
To make the dispersant work better, the dispersant should have the greatest chance of contact with the pigment surface. Therefore, the resin content should not be too much, and it is generally controlled at about 10% of the grinding formula, so as not to allow the resin to occupy more surface of the pigment. A large amount of resin is not conducive to the viscosity of the grinding paste, so it is better to use less.
Also pay attention to the order of addition: first add the dispersant to the solvent, add the pigment while stirring, stir for 5-10 minutes after the addition, and finally add the resin polymer solution, stir and disperse evenly, and then grind to below 5pm . It is required to use less resin and pay attention to the order of addition. The purpose is to create conditions for the anchor group of the dispersant to be adsorbed on the surface of the pigment.
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