Roll coating leveling tester and test method

1 Foreword
spraying, brush coating, roller coating, curtain coating, etc. are different construction methods of paint, roller coating can be divided into the same-way roller coating, reverse roller coating, small area roller coating, large area roller coating. As we all know, with different coating methods, different construction process conditions, the paint formed by the wet film surface state is different, drying process, leveling and the causes of various ills of coating film also vary. In this paper, the tester and test method of coating leveling in the process of coating of Makou iron sheet rollers are discussed
the
. The method of determining paint leveling is the national standard GB 1750-79, and this method is not suitable for determining the leveling of iron sheet coatings in Makou. Because the GB1750-79 uses brushing and spraying, while the iron sheet of the horse mouth is applied by rollers. Brush marks formed by brush coating are basically parallel convex dents, spraying to form points marks, the two coating methods formed by the marks are relatively uniform, marks and marks are very similar, the thickness of the formation of the coating film is more than 25 m, and the roll coating formed like bark, different length, depth is different, much more complex than the above two marks, and coating thickness of 8 to 12 m, much thinner than 25 m.
is
relationship (in the class, a0 is the initial amplitude; at is the amplitude of time t; h is the average thickness of the coating, r is the surface pressure of the coating, η is the viscosity of the coating, and the thickness of the coating and the wavelength of the flow level process has a great impact, the thickness is 3 square, the wavelength is 4 square, if the other parameters remain unchanged, the thickness of the coating is doubled, the flow level time is reduced by 1/8, and the thickness is halved and the flow level time is increased by 8 times. When the wavelength is increased by 1x, the leveling time is increased by 16 times, and the wavelength is halved and the flow level time is reduced by 16x. According to the relationship t obtained from the sub-analysis, the η. L/r (where t is leveling time; L is the brush mark shape) as you know, the leveling time is closely related to the brush mark. The thickness of the coating film formed by the roller coating is only half of the brush coating and spraying, and the traces are completely different, so the coating leveling measured by GB 1750-79 method can not explain its leveling in the production application at all, in order to make the measurement results consistent with the actual application, we designed the roll coating leveling tester, established a roll coating leveling test method.
2 Roll coating leveling tester
for roller coating, leveling is very important, leveling is not good paint, the formation of uneven coating thickness, poor cover force, consumption, high cost, roller painted pattern color depth, light and dark phase, high yield, after processing also has adverse effects. Since GB 1750-79 can not be used to assess the leveling of roller coating, in order to find a better test leveling method, we go deep into the first line of iron production, carefully observe and study the state of coating during large-scale production and coating film formation principles and characteristics, design and manufacture of a simple, practical leveling tester (see Figure 1), can form thickness and form and production of the actual same coating film.
1 - Rubber roller; 2 - coating rod; 3 - handle; 4 - test plate fixed surface; 5 - rail
Figure 1 roll coating leveling tester
3 roll coating leveling test method
3. 1 test equipment, materials
roll leveling tester; MIKROTEST thicknessometer; thermostat oven (0 to 250 degrees C); oven fixed clock (0 to 60 min); coat - 4 cups; stopwatch; thermometer (0 to 100 degrees C); paint to be measured (200 ml); 120 mm ×180 mm ×0. 2 mm.
3. 2 Test method
the viscosity of the coating under test is determined according to GB 1723-79 Paint Viscosity Determination. Place the clean horse mouth iron sheet on the roller level tester fixed, put a certain amount of paint to be tested near the end of the horse mouth iron sheet near the roller, shake the hand wheel at a constant speed, form thickness and roller mark form on the iron sheet and the production of the actual similar coating film. Remove the iron flakes, place them in the oven, place them in a oven that has been adjusted for temperature, set the clock, and remove the iron sheets and cool them when the clock rings. The thickness of the coating film is determined by a thickness meter. Under sufficient light source, observe the flatness of the coating film from different angles.
3. 3 Coating leveling evaluation
the thickness of the coating film is evaluated 8 to 15 m. The surface roller marks of the coating film are obvious, and the form of the just roll is the same, like bark, the bottom is serious, the hand feels uneven, then the level is poor;, the feel is basically smooth, then the level is not qualified, the coating film surface roller marks are less, short, shallow, slightly exposed, the feel is smooth, then the level is qualified, the coating film surface is basically no roller marks, no exposed bottom, the hand feel smooth, then the flow level is good.
the test method of the 4-roll coating leveling tester and the test method
4. 1 Adaptability
A white paint with poor leveling proved by actual production was selected, and its leveling was determined according to the GB 1750-79 method and the method described in this paper, respectively, as shown in Table 1.Table
1 White polyester magnetic paint leveling test
brushing and spraying on the viscosity of the paint is limited, in order to ensure that brushing and spraying smoothly, the viscosity of the paint must be in a lower range, while roller coating is not limited, as long as the paint level is good, high viscosity does not matter. In practice, the test conditions of the national standard GB 1750-79 are limited. According to GB 1750-79 test requirements of the preparation of the coating is difficult to get less than 12 m coating film, and in practice, the thickness of the general roller coating film 6 to 18 m, to 10 to 12 m for the most common. However, the thickness of the coating formed by the coating required by the GB1750-79 test exceeds this practical range (see Table 1), which is 24 m and 30 m, respectively. In this condition, the leveling of the coating is of course good, because the flattening time of the coating film is inversely inversely related to the thickness of 3 squares. In other words, the leveling qualified film thickness that can be determined by GB 1750-79 is not allowed in the actual roller coating. The same coating according to GB 1750-79 determination, due to its test requirements of the paint viscosity is low, coating thick, so leveling qualified, and with the method described in this paper, the conclusion may be different; This tester determines that the film thickness range of the coating film is 5 to 30 m, which is more suitable for evaluating the leveling of the roll coating.
4. 2 Accuracy
To verify the accuracy of this tester, different testers determined the leveling of the coating according to the method in this paper, the results of which can be found in Table 2.
to test the leveling of good paint with this method to the production line test machine, observe the flatness of the coating in practical application, test whether the laboratory test results and the actual situation of production is consistent. During the test machine, the flatness of the coating was evaluated by adjusting the viscosity of the coating and the thickness of the coating film, and the results were found in Table 3.
3 White acrylic coating leveling test
Note: (1) The viscosity of the production test machine is different from that of the laboratory test due to different ambient temperatures.
(2) dry film thickness is different, and the production test machine difference is large, because the production test machine is complex, it is not possible to control the thickness in 1 to 2 m, the same iron plate film thickness difference of 5 m is a normal phenomenon.
(3) production test machine leveling is better than the laboratory, because the production line oven temperature has a gradient, conducive to leveling, and the laboratory oven is constant temperature. The results of the laboratory are consistent with the production.
can be seen from Tables 2 and 3, the leveling repeatability of the coatings tested with the testers and methods described in this paper is good, in line with the actual situation of production.
5 Conclusion
(1) Roll coating leveling tester can form a thickness and geometric form and the actual production situation is very similar to the coating film, the impact of leveling factors are basically the same, drying process, the micro-movement inside the coating film is about the same, the final formation of the coating surface condition is very similar to the actual production. This tester and method is very suitable for evaluating the leveling of roller coating.
(2) roll coating leveling tester and test method repetition is good, high accuracy, can correctly evaluate the roll coating leveling.