Definition
A printing ink mixer is a type of laboratory equipment used to evenly mix printing inks and their associated additives. It promotes the full dispersion of pigments, resins, solvents and other components in the ink through mechanical action to achieve stable rheological state and color consistency, providing a basis for subsequent printability testing and quality control.
Principle
The working principle of a printing ink mixer is based on a shear vs. convection mixing mechanism. The equipment is usually driven by a motor to drive the stirring shaft to rotate the stirring blades of a specific shape. The blades generate shear force when they move in the ink, breaking the pigment aggregates; At the same time, convection is formed to circulate and exchange materials in various areas of the container. This process follows the laws of fluid mechanics, and the mixing efficiency is related to factors such as stirring speed, blade design, and vessel geometry. For non-Newtonian fluid inks, the mixing behavior can be roughly described by the power law model: τ = Kγ^n, where τ is the shear stress, K is the consistency coefficient, γ is the shear rate, and n is the flow index. The mixer provides sufficient shear rate γ to achieve a uniform state of ink under continuous shear.
Measurement method
Evaluating the stirring effect is usually done using a combination of physical and chemical methods. Physical methods include observing the consistency of ink surface gloss and color, or using a viscometer to measure viscosity values with multi-point sampling before and after agitation, and viscosity change analysis according to standards such as ASTM D4040 or GB/T 13217. Chemical methods can be used to measure the dispersion by centrifugation after sampling, which detects the proportion of sediments to assess dispersion. Some laboratories combine fineness scrapers to measure the fineness of pigment particles according to standards such as ISO 1524 to indirectly judge the adequacy of agitation. These tests are performed under specified environmental conditions to ensure comparable results.
Influencing factors
The mixing effect is affected by multiple factors. In terms of equipment parameters, the stirring speed directly affects the shear force, insufficient speed may lead to uneven mixing, and too high may introduce too many bubbles or lead to an increase in temperature. The shape and size of the blades need to match the container and ink volume, and common blade types include paddle type, anchor type, etc., and their design affects the flow field distribution. In terms of material characteristics, the initial viscosity, thixotropy, and solids content of the ink determine the required stirring energy. Operating conditions such as mixing time and charging volume (usually recommended 50% to 75% of container capacity) should also be specified. Ambient temperature can alter the rheological properties of the ink, which in turn affects the mixing process.
Application:
Printing ink mixers are widely used in quality control, R&D and production in the printing industry. In the laboratory, it is used for the development and testing of new ink formulations to ensure that the components are evenly dispersed. In the printing shop, it can be used for batch ink mixing before use, or for reprocessing recycled ink. In addition, this equipment is also a basic tool in the study of ink performance in packaging materials, textile printing and other related fields. Its use helps reduce problems such as color difference and plate blockage during the printing process, and improves the stability of printing quality.
Selection
The actual needs should be comprehensively considered when selecting. First, choose a model with a suitable capacity range according to the sample volume, and the capacity of common laboratory models varies from 0.1 to 5 liters. secondly, pay attention to the speed regulation range and torque output to adapt to different viscosity inks; For high-viscosity inks, choose a model with sufficient torque. The equipment material should be resistant to solvent corrosion, usually with stainless steel or special coatings on contact parts. In terms of safety, it needs to have overload protection, fastening devices, etc. In addition, operating noise, ease of cleaning, compliance with relevant safety standards (e.g. CE, IEC standards) are also reference factors. It is recommended to conduct actual testing according to the commonly used ink types, observe the mixing efficiency and temperature rise, and make a suitable choice.