Definition
Paint dispersion mixer is a kind of laboratory or production equipment used in the field of coatings, inks and related chemicals, its main function is to evenly disperse solid particles such as pigments and fillers in the liquid base through mechanical action, and promote the full mixing of various components to form a stable and uniform dispersion system. This equipment plays a fundamental role in the process of coating research and development, quality control and small-batch preparation.
Principle
Paint dispersion mixers work based on the principles of fluid mechanics and shear dispersion. The equipment usually consists of a motor, a drive shaft and a mixing blade (such as a zigzag impeller). The motor drives the impeller to rotate at high speed in the container, and the edge of the impeller generates a high linear velocity, which causes the material to be subjected to strong shear and impact. At the same time, the vortex formed by the rotation of the impeller sucks the material from the bottom of the container and circulates along the axial and radial directions to achieve the combination of macroscopic mixing and microscopic dispersion. The dispersion process can be described as the solid aggregate being broken up under shear forces, then wetted by the liquid and stably distributed in the system. For high-viscosity systems, equipment is often equipped with liftable brackets to accommodate different process requirements.
Measurement and evaluation methods
The evaluation of dispersion effects requires a combination of multiple indicators. Fineness is usually measured using a scraper fineness meter according to GB/T 1724 or ASTM D1210 standards, reflecting the maximum particle size in micron-level readings. Viscosity measurement can be done using a rotational viscometer, referring to the GB/T 9269 or ASTM D2196 method. Stability can be quantified by observing post-storage sedimentation or by using a centrifugal sedimentation meter. Colorimeter and gloss meter can be used separately for color difference and gloss, referring to ISO 7724 and ASTM D523 standards. In addition, the dispersion process can monitor the power consumption curve, and the power tends to stabilize and often indicates that the dispersion stage is completed.
Influencing factors
The dispersion effect is affected by multiple factors. Impeller design is a key factor, and the serrated impeller can provide strong shear force and is suitable for initial crushing. The paddle impeller is more conducive to mixing. The ratio of impeller diameter to vessel diameter affects the flow field morphology and circulation efficiency. The rotation speed directly affects the shear rate, which needs to be adjusted according to the viscosity of the material and the target particle size. The dispersion temperature may affect the rheological properties of the material and the efficiency of the dispersant. Dispersion time needs to be balanced with energy consumption, which can lead to overheating or excessive shearing. Material characteristics such as pigment specific gravity, wettability, and the type and dosage of dispersant in the formula had significant effects on the dispersion process.
Applications
Paint dispersion mixers are widely used in fields where liquid-solid mixing and dispersion are required. In the coating industry, it is used for R&D and testing of architectural coatings, industrial coatings, wood paints, etc. In ink manufacturing, it is used for pigment paste preparation and mixing of connectors. It is also commonly used in the production of adhesives and sealants for filler dispersion. In addition, it is also used in laboratory research in the fields of cosmetics, food coloring and certain electronic material pastes. The equipment is suitable for a wide range of fluid systems from low to medium to high viscosity.
Key points of selection
The selection should comprehensively consider the process requirements and material characteristics. First, the motor power and torque output capacity should be determined according to the viscosity range and processing volume of commonly used samples. The speed range should cover the needs from low-speed mixing to high-speed dispersion, and stepless speed regulation provides more flexible operation. The lifting mechanism stroke should be adapted to the height of the commonly used container and ensure smooth operation. The material of the mixing shaft and impeller should have sufficient mechanical strength and corrosion resistance, such as stainless steel. Equipment safety needs to pay attention to overload protection and electrical protection level. In addition, operational noise, ease of maintenance and compliance with relevant safety standards are also important considerations.