Ink Viscosity for flexographic printing

What is flexographic printing?

Flexography is a commonly used form of printing process which utilizes a flexible relief plate. It can be used for printing on almost any type of substrate, including plastic, metallic films, cellophane, and paper.

This printing is usually utilised by the food industry on the non-porous substrates required for various types of food packaging; (it is also well suited for printing large areas of solid colour).

The basic principle of each printing technique is the same. To deliver the ink skilfully onto the substrate while ensuring the correct properties according to the process requirements.

The printing market is facing a rapid growth driven primarily by packaging and labels, as online delivery is more and more used.

Crucial ink viscosity

In the pressroom, ink viscosity is critical.

Measuring viscosity is extremely important because knowing the speed and fluidity of the ink helps you know how the ink will perform on the press. But also how fast the press will operate when using a particular ink.

In virtually all printing applications, correct ink viscosity is key to a good ink quality. Ink viscosity characterizes many aspects of how the ink will transfer to its substrate. Its properties can have several effects on absorption, colour strength and drying.

Highly viscous inks create stickiness and make it difficult to transfer the image to the substrate, while low viscosity makes the ink more mobile and harder to control, resulting in loss of sharpness and a dirty print.

The strong link between temperature and viscosity means that temperature variations have a significant impact on ink quality. It is therefore important to measure both simultaneously if they evolve together. 

Real-time in-line viscosity control and monitoring in the printing process is essential to improve performance and reduce costs in flexographic printing process.

Sofraser’s expertise on ink viscosity

The installation of a MIVI on tank or a SOFINK on-line viscometer, either on tank, either on the circulation loop, allows you a precise and continuous follow-up of the ink viscosity, to always have the best possible batch.

MIVI Viscometer

Sofraser’s allows you close monitoring of the ink’s viscosity and temperature in real time and ensures quality in the printing process.

As it is maintenance-free, the sensor doesn’t not to be clean. Its sensitivity in low and high viscosities is also an advantage in this application.

SOFINK Viscometer

The implementation of a SOFRASER viscometer on your process also allows an overall ink consumption saving of 5%, generating a fast ROI (return on investment).

Using an in-line viscosity sensor to measure and control ink viscosity ensures consistency, consistency and uniformity of ink deposition. All while maximizing printing speed.

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Viscosity of adhesives & sealants

The adhesives & sealants industry

The industry for adhesives and sealants is challenged by the limited raw materials and the negative impact of synthetic compounds on human health and the environment, which an answer is already brought up about: a new generation of adhesives and sealants are now water based, making them less toxic and more environmentally friendly.

Furthermore those products are widely used to assemble, protect and seal systems in construction, manufacture and perform maintenance. They are key components for a lot of projects, therefore their impact is great in the industry itself.

The main raw materials used in the manufacturing of adhesives still come from crude oil and petrochemicals, product whose prices are extremely volatiles and higher than ever.

To ensure a consistent, high-quality and defect-free application of adhesives and sealants, viscosity changes throughout the process flow have to be monitored in real time. Taking measurements from a baseline rather than simply measuring absolute values, and adjusting viscosity by adjusting mix components and temperature compensation helps keeping the process within its specified limits.

Most adhesives are non-Newtonians and viscosity control is prioritized at the end-point, although viscometers can monitor its entirety.

By continuously monitoring viscosity online, preparation and delivery can be controlled more efficiently. Thus significantly improving the flow properties of the final product.

Sofraser’s viscometers

To monitor viscosity throughout the process, the best solution is to install a Sofraser viscometer. More precisely a MIVI sensor with a 9720 multi-product HMI processor, because often, several sealants are produced in the same tank.

mivi sensor viscometer

Compatible across a wide viscosity range, the MIVI can measure from thick pastes to light fluids. Requiring no special preparation, MIVI can be used directly in your process lines. Its ease of use and configuration will allow your operators to use it quickly, easily and with optimal efficiency.

Thanks to their vibrating needle, Sofraser viscometers have a self-cleaning effect, resulting in an almost maintenance free viscosity instrumentation.

Resulting in peak production, the sensor delivers 24/7 instant measurement and is compatible easy to install.

Inventor of the vibrating type technology and with more than 50 years of expertise, Sofraser viscometers are the most reliable process viscometers on the market.

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Viscosity in starch glue manufacturing

Usage of starch glue

Starch glue is principally used for bonding paper products. Most corrugated boxboard for making cartons is bonded with starch based adhesives; starch adhesives are readily available, low in cost, and easy to apply from water dispersion.

Since these adhesives cure to a thermosetting structure, they have excellent heat resistance. Other significant advantages are their very slow curing rate allowing ample assembly time and that they are non-toxic and biodegradable.

The control of the adhesives viscosity at the end of the preparation and during application is critical.

Paper application

Challenges faced by the industry

For the production of corrugated cardboard, glue application systems must allow a perfect centring of the adhesive deposited on top of the groove and fit accurately the quantities of adhesives necessary and sufficient for each type of board manufactured.

Furthermore the viscosity of the adhesive is critical. When the viscosity is too low, this results in imperfections and can cause projections and/or burrs.

In addition, the rheological behaviour of the starch glues is complex. It is mainly pseudo plastic and thixotropic and the non-Newtonian behaviour can be quantitatively significantly different between the two products. This requires to master the conditions of viscosity measurement.

Sofraser’s solution for starch glue viscosity control 

Thanks to its flexibility, the installation of a MIVI sensor on the production line or in storage tank or on starch glue kitchen provides continuous and stable viscosity values during the laying of the adhesive. The MIVI viscometer and associated electronics guarantee zero default in viscosity deposit. This sensor is repeatable and reliable for permanent efficiency.

It is an easy to use and to install solution with a wide variety of mountings and positions available. The plus? No maintenance required.

MIVI viscometer

Coating process and its viscosity for Lithium batteries

The use of lithium batteries

Lithium batteries are safe and reliable and have a wide range of applications including powering electric vehicles. The battery manufacturing process needs to be controlled and optimized in order to guarantee the quality and reliability of the product. Among the global manufacturing process, there is the electrode manufacturing step that includes a coating process. The viscosity of the components and the slurry during the coating process is particularly important. It influences the final quality, efficiency and consistency of the electrode.

A necessary control of viscosity

The viscosity of the polymer binder solution affects the performance of the coating and the ease with which powders are dispersed, as well as the power required for mixing and the speed of application for a uniform coating.

Lithium battery
EV (electric vehicle) Li-Ion battery concept. Close up view. 3d rendering.

Density and viscosity control to optimize batch processes ensures consistency, quality and significant cost savings on materials. Control and traceability of the continuous mixing process can be improved through on-line monitoring and density and viscosity measurements. Automation, supported by on-line integration enables the optimization of all processes on production lines. Battery manufacturing is also speed up to meet growing demand.

A high viscosity of the battery suspension decreases the sedimentation speed at rest and delivers a thicker electrode film at the end of the coating step/phase. But too high viscosity may also make the coating process more difficult to control, which can lead to irregular coating and variable layer density. It resultes in variable ion transfer rates and thus unpredictable battery life (and unpredictable charging cycle time).

Finding the perfect viscosity can be tricky and difficult. The solution is to monitor and controll within the appropriate ranges according to the requirements of the process. With the control of viscosity, batteries and their components are safer and more durable.

The use of viscosimeters

Viscometers are an essential part of the solution for reliable batteries.
Electrodes density has an effect on cycle performance and irreversible loss of capacity in lithium-ion batteries.

The rheological behavior of the slurry is a highly complex and one. Even within the non-Newtonian fluids, finding the right balance for an easy to apply products can be very difficult.

MIVI process viscometers provides a high sensitivity viscosity measure that will detect the smallest changes in slurry composition. When combined with the density feature it adds the indirect monitoring of the concentration. Thanks to its instantaneous and continuous measure, combined with the outputs that deliver the measures to the end-user DCS. Sofraser viscometers are a great solution for automated process control, as they are maintenance free and highly reliable.

Similar processes are also valid for solid-state batteries. They are an interesting furure alternative that are a great way to support the growing demand for electric batteries.

Lithium batteries
Lithium batteries

Electric board coating process

Viscosity measurement in electronic board coating process

Dosing the solvent of a coating solution into electronic boards requires precise adjustment. In order to obtain uniform application of the coating; reflected by a constant viscosity. An inhomogeneous coating, either too thick or too thin, can be the source of serious problems. A company’s reputation is at stake if too many customer complaints are related to the poor quality of the finished product. Consequently, costs increase due to inefficient production and raw material losses.

In this way, the installation of a MIVI process viscometer in the circulation loop of the coating process allows the right amount of solvent to be injected into the base resin at the right time during the entire production process.

The MIVI viscometer works continuously, instantly detecting and correcting any viscosity variation.

Use of the MIVI viscometer
Viscosity measurement in electronic board coating process

The printed circuit boards are immersed in a resin-based coating that solidifies at room temperature. The uniformity of the coating reaches 100% quality thanks to the inline viscosity measurement; which also allows a reduction of resin and solvent consumption. Our MIVI inline viscometer allows the achievement of a constant coating viscosity. It increases process repeatability, coating homogeneity and uniformity, and generates material and time savings.

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On-line viscosity measurement in ink deposition on special films

On-line viscosity measurement is the most reliable way to monitor the uniformity and quality of ink deposit on papers; films and specialty substrates. If the process does not allow for consistent ink viscosity, poor batches will be produced. Resulting not only in increased manufacturing costs but also in quality and corporate reputation problems.

The installation of a MIVI on-line viscometer in the ink tank allows a precise and continuous follow-up of the ink viscosity. MIVI adjusts the viscosity of the ink; if necessary according to various parameters such as temperature, flow rate, the need for pigments; solvent addition, chemical reactions and other characteristics related to the production in question.

On-line viscosity measurement in ink deposition on special films
Application of viscosity in printing

The MIVI viscometer ensures permanent operation without time drift and is particle tolerant. It is not necessary to clean the sensor separately from the process. Its sensitivity in low and high viscosities is also an advantage in this application.

As a general rule, the implementation of a MIVI viscometer on press allows an overall ink consumption saving of 5%, generating a return on investment of about one year. The use of an in-line MIVI viscometer ensures the consistency, homogeneity and uniformity of the ink deposit by maximizing the printing speed. MIVI improves print quality, ensuring, among other things, color continuity.

Discover the detailed sheet in English on the use of the MIVI viscometer in printing and coating processes.

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