novomatics HEMOTRONIC III, Руководство по эксплуатации

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CHEMOTRONIC III
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3. Testing printing ink resins
Statistically, specifications of raw materials can at best be only as consistent as the
test procedures used to determine them. Test procedures should be based on
scientifically
approved principles, which means accurate test equipment for controlled test condi-
tions such as heating and cooling temperature profiles, top temperature dwell time,
agitation speed, turbidity determination, etc.
Moreover the test oil in which the resin is dissolved must have analytical quality.
3.1. Cloud point or mineral oil tolerance (MOT)
Some product specifications have been based on the MOT-value (mineral oil toler-
ance) in the past. The MOT-value is calculated from the ratio in weight when a hard
resin dissolved in a mixture of mineral distillates is titrated with mineral distillate
until the solution becomes cloudy. This method is relatively inaccurate and depends
strongly on the temperature of the solution way of stirring, observation of
precipitation and the experience of the person performing this test.
3.2. Automatic cloud point test method
The cloud point temperature is a characteristic value resins for printing inks.
Deviations in cloud point can lead to sedimentation in the varnish, differences in
drying speed, loss of gloss and tack stability.
The cloud point is the temperature at which a resin begins to precipitate in the
liquid phase. The automatic cloud point test method introduced here, has been
approved by a great number of resin manufacturers world-wide as a standard
method for production setting and quality control of resins for printing inks.