In order to characterize the quality of resins, a solution of the resin must be
prepared. The quality of the solution mainly depends on the parameters:
- the quality of the solvent
- the consistency of the preparation
For printing ink applications special brands of paraffinic or naphthenic oils are showing good performance. Naphthenic oils exhibit better solubility properties than the paraffinic ones. As in view of the VOC legislation aromatic compounds must be reduced or even eliminated, low-aromatic naphthenic oils have a growing market share in the production of printing inks. In most cases, these oils have shown to be usable, provides the resin is sufficiently easily soluble. Good varnishes can be prepared from resins and
oils if the preparation method will be consistent and the number of variables will be reduced. This means that the resin must completely be dissolved in a controlled and reproducible way.
The EUROCOMMIT group recommends to use the THERMOTRONIC-system for this purpose. The new THERMOTRONIC 200 has the same features as the standard THERMOTRONIC, but is capable to prepare much more varnish in the same time.
With the THERMOTRONIC 200 one can cook 200 grams of varnish under automatic controlled conditions. All important functions like heating rate, dwell time cooling rate and stirring rate are controlled by the internal microprocessor unit. At the end of the temperature cycle a fixed end temperature can be defined by the user and an audible alarm sounds to indicate the end of the test.
In practise it may be necessary to alter the resin concentration in order to adjust the viscosity of the sample in the right range. The THERMOTRONIC 200 has a special oil inlet in the top test head for extra oil dispension during the test.
In order to measure the rheological properties of complex systems like resin solutions, it is indispensable to use a THERMOTRONIC system.
The new THERMOTRONIC 200 is the ultimate system for quality control and laboratory applications in the printing ink industry.
The THERMOTRONIC is a microprocessor-controlled varnish cooker, which makes the quality of the varnish independent of individual operator skills. Even high resin concentrations do not effect these results, due to the powerful stirring motor and the use of a magnetic stirring bar of high volume and weight. A special metal test tube with a round bottom is used in order to avoid residual material in the test tube. The filling weight of the test tube is 50 grams (1.8 oz). The
material is heated up to a temperature level of 230 °C (450 °F) by a highly effective integrated air jet heating system and remains at this temperature level for 4 minutes during which the resin is completely dissolved in the test oil.
The solution is then cooled down under controlled cooling and stirring conditions to 90 °C (194 °F). When this temperature level is reached, an audible and visible alarm is activated to indicate that the varnish is ready for use in the viscometer. The metal test tube can be removed from the THERMOTRONIC by means of a metal clamp. The varnish can cool down in the viscometer to the standard temperature level of 25 °C (77 °F).
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Manual test method
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THERMOTRONIC 200 automated test method
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Rheological characterization
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Inaccurate
Variations in apparatus and handling
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Accurate
Defined conditions during the heating/cooling/stirring process
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Quality of varnish
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Poor
Heating, cooling and stirring is not consistent
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High
Consistent heating, cooling and stirring during the total preparation time.
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Repeatability and
reproducibility
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Bad
Result is dependent on the operator
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Good
Does not require individual operator skills
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Preparation time
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Long
Long cooking time results in inaccurate viscosity measurements
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Short
Varnish cooking and measurements can be carried out within 30 minutes
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Cost efficiency
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Low
Permanent labour involvement
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High
With the THERMOTRONIC fast and reliable results are achieved automatically. The operator can run other test simultaneously.
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