In the latex paint manufacturing process, some problems sometimes occur. Technicians need to analyze the reason and solve it as soon as possible so that the production is less or not affected, and at the same time, measures should be taken to prevent similar problems from happening.
Viscosity deviates from control range
In production, the viscosity of latex paint often deviates from the control range. There are four reasons for this.
① Changes in the properties of raw materials. For example, the fineness of pigments and fillers changes, the fineness becomes finer, the viscosity increases, the fineness becomes thicker, and the viscosity decreases. For example, the thickening efficiency of the thickener or the wetting and dispersing efficiency of the wetting and dispersing agent change. This also happens when the mixture is not stirred well before weighing.
② Changes in the measurement of raw materials, such as overcounting or undercounting of certain raw materials.
③ Not all the ingredients are added when adding, especially for those raw materials that are small and very sticky, because they stick to the container wall and cannot be added completely.
④ Changes in pH may also lead to changes in viscosity.
Solution: If the viscosity is too high, add water to reduce the viscosity, and if the viscosity is too low, add a thickener to increase the viscosity. If it is a pH problem, adjust the pH. From a long-term perspective, after analyzing the reasons, we will solve them in a targeted manner. Pay attention to the stability of raw materials, such as strengthening the control of raw materials, fully stirring the liquid raw materials evenly before weighing, etc. Improve metering accuracy. For those raw materials that are very viscous when used in small quantities, some of the water in the formula can be used to wash away the raw materials stuck to the container wall and add them.
Decrease in viscosity during storage
There are several reasons for the decrease in viscosity during storage.
①The cellulose thickener is degraded by microorganisms or enzymes. The solution is to increase the anti-corrosion
dosage, or choose a more effective preservative to protect the cellulose thickener from microbial or enzymatic degradation. For latex paints whose viscosity has been reduced, add preservatives to sterilize and add thickeners.
②The decrease of pH value leads to the decrease of the thickening effect of the alkali swelling thickener, so stable
pH regulator.
When color matching, add color paste to reduce the viscosity
When color matching, adding color paste will cause the viscosity to drop, especially when matching with dark latex paint, the viscosity may drop even more. The reason is that the color paste contains more glycol solvents and surfactants. The addition of them will affect the thickening effect of the thickener, and the effect on the associative thickener is greater. The solution is to add a non-associative thickener. If possible, the viscosity of the latex paint or base material to be matched can also be increased in advance.
