Today we will focus on how to add specific types of thickeners.
The types of commonly used thickeners are mainly inorganic, cellulose, acrylic, and polyurethane.
Inorganic
Inorganic materials are mainly bentonite, fumed silicon, etc., which are generally added to the slurry for grinding, because it is difficult to completely disperse them due to the conventional paint mixing strength.
There is also a small part that will be pre-dispersed and prepared into a gel for use.
They can be added to paints by grinding to make a certain amount of pre-gel. There are also some that are easy to disperse and can be made into gel by high-speed stirring. During the preparation process, the use of warm water can promote this process.
Cellulose
The most commonly used cellulosic product is hydroxyethyl cellulose (HEC). Poor flow and leveling, insufficient water resistance, anti-mold and other properties, it is rarely used in industrial paints.
When applied, it can be added directly or dissolved in water in advance.
Before adding, attention should be paid to adjusting the pH of the system to alkaline conditions, which is conducive to its rapid development.
Acrylic
Acrylic thickeners have certain applications in industrial paints. It is mainly used in relatively conventional coatings such as single component and high pigment-to-base ratio, such as steel structures and protective primers.
In topcoat (especially clear topcoat), two-component, baking varnish, high-gloss paint and other systems, it has some defects and cannot be fully competent.
The thickening principle of the acrylic thickener is: the carboxyl group on the polymer chain is converted into an ionized carboxylate under alkaline conditions, and the thickening effect is achieved through electrostatic repulsion.
Therefore, the pH of the system should be adjusted to alkaline before use, and the pH should also be maintained at >7 during subsequent storage.
It can be added directly or diluted with water.
It can be pre-dissolved for use in some systems that require relatively high viscosity stability. Namely: firstly dilute the acrylic thickener with water, and then add the pH adjuster while stirring. At this time, the solution thickens obviously, from milky white to transparent paste, and it can be left to stand for later use.
Using this method sacrifices the thickening efficiency, but it can fully expand the thickener in the early stage, which is conducive to the stability of the viscosity after the paint is made.
In the formulation and production process of H1260 water-based one-component silver powder paint, the thickener is used in this way.
Polyurethane
Polyurethane thickeners are widely used in industrial coatings with excellent performance and are suitable for use in various systems.
In application, there is no requirement on the pH of the system, it can be added directly or after dilution, either with water or solvent. Some thickeners have poor hydrophilicity and cannot be diluted with water, but can only be diluted with solvents.
emulsion system
Emulsion systems (including acrylic emulsions and hydroxypropyl emulsions) do not contain solvents and are relatively easy to thicken. It is best to add them after dilution. When diluting, according to the thickening efficiency of the thickener, dilute a certain ratio.
If the thickening efficiency is low, the dilution ratio should be lower or not diluted; if the thickening efficiency is high, the dilution ratio should be higher.
For example, SV-1540 water-based polyurethane associative thickener has a high thickening efficiency. When used in an emulsion system, it is generally diluted 10 times or 20 times (10% or 5%) for use.
Hydroxypropyl Dispersion
Hydroxypropyl dispersion resin itself contains a certain amount of solvent, and it is not easy to thicken during the paint making process. Therefore, polyurethane is generally added in a lower dilution ratio or added without dilution in this type of system.
It is worth noting that due to the influence of a large amount of solvents, the thickening effect of many polyurethane thickeners in this type of system is not obvious, and a suitable thickener needs to be selected in a targeted manner. Here, I would like to recommend a SV-1140 water-based polyurethane associative thickener, which has a very high thickening efficiency and has excellent performance in high-solvent systems.
Post time: Apr-25-2024