Selection and application of cooking-resistant plastic ink pigments (2)

Experimental results and discussion

1. The effect of dry baking on the properties of inks and pigments

1) Discoloration of ink after dry-drying 1 Evaluation of standard inks and pigments The heat-resistance evaluation uses 5 levels: 5 levels, the same as the standard color pattern; 4 levels, slight discoloration; 3 levels, lighter discoloration; 2 levels, Discoloration is heavier; Grade 1, severely discolored.
2Experimental methods and results The three thin film specimens and the pigment were placed in a constant temperature oven at the same time. After baking at a predetermined time, two specimens were taken out. After cooling, they could be touched by hand and were not sticky, and they could be compared with standard samples. . Table 1 lists the discoloration of inks and pigments after dry baking under different conditions.
2) Analysis of the results When the heating temperature is below 135°C, the temperature has little effect on the discoloration of the film ink. The discoloration of the golden light C ink is slightly more serious than the other three inks. When the heating temperature is higher than 135°C, discoloration of the ink increases. Taken together, the heat resistance of Everlast Red 2B ink is slightly better than that of Everfix Red F4R and Lisol Red BK. Simply from the heat resistance of the pigments, the Everlasting Red F4R is better than the Lisol Red BK, and the Lisol Red BK is slightly better than the Everlast Red 2B.
2. Effect of boiled on ink properties 1) Discoloration of ink after boiled 1 Evaluation criteria and conditions Heat resistance of boiled water The evaluation criteria and sampling methods are the same as those of dry baking. In the experiment, distilled water was used for boiling experiment. The boiling temperature is 100°C and 120 to 121°C, respectively.
2 Experimental results After boiled at 100°C, there is almost no change in the color of Yongzhuhong 2B after boiled; the other 3 pigment inks fade more seriously, and the water color appears orange-yellow; the order of discoloration is golden light red C/PET film> permanent Red F4R/PET Film > Lisol Red BK/PET Film. Table 2 shows the discoloration of the samples under different boiling conditions.

2) Analysis of results After boiled in distilled water at 100°C, the effect of Everlast Red 2B is best, and other inks are slightly discolored. After boiled at 121 °C, the golden red C ink is severely discolored, so it is possible to eliminate the possibility of golden red C as a colorant resistant to cooking ink. Everlasting Red 2B's high temperature cooking performance is slightly better than the other two inks. After BOPA film cooking, there is a phenomenon of yellowing, and the discoloration of the ink on the film is worse than that of the PET film. This shows that the discoloration of the substrate can also affect the hiding effect of the colorant.

After boiling and dry baking experiments, the possibility of using golden red C pigment as a colorant for plastics resistant to cooking ink has been substantially eliminated. Therefore, in the following ink performance testing experiments, the relevant properties of the Golden Red C ink are no longer tested.

3. Determination of ink properties 1) Ink adhesion fastness test 1 The reference standard is GB/T 13217.7-91 GB/T 13217.1-91, which detects the conditions at a temperature of 25±1°C and a humidity of 65%±5%. Proceed.

2 Test results and analysis The BOPA film was subjected to ion bombardment treatment with a vacuum coating machine for 3 minutes to increase the surface tension of the film. After the comparison experiment with the PET film (see Table 3), the following conclusions can be drawn:
a. The printing materials are different, and the adhesion fastness to the ink is different. Lisolol Baohong BK ink is the most affected by the material, and the fastness of 3 materials such as Everlast Red 2B is relatively close, and the attachment fastness is less affected by the material.
b. The fastness of permanent red 2B is better, and the permanent red F4R is the worst.
c. After the ion-treated film material, the attachment fastness to various inks has been significantly improved.
2) Determination of Ink Luster 1 Reference Standard: GB/T 13217.2-91. The test was performed at a temperature of 25±1°C and a humidity of 65%±5%.
2 Test results and analysis The experimental results show that the order of the glossiness of the three inks is: Yongkanghong 2B> Yongguhong F4R> Lithol Baohong BK. It can also be seen from the table that the glossiness of the ink is not related to the printing material. Some deviations in the data in the table are relatively large. The main reason may be that the ink on the film is not uniform, resulting in different reflectivity to light.

3) Determination of ink fineness 1 Reference standard: GB/T 13217.2-91. The test was carried out at a temperature of 25±1°C and a humidity of 65%±5%.
2 Test Results and Analysis Take 3 samples of each ink. The measurement of fineness is: the average value of the fineness of Litholol BK ink is 4μm, and the average value of the fineness of Everlasting red F4R ink is 2μm. The average value of the fineness of the red 2B ink is 5 μm, and the average value of the fineness of the golden red C ink is 21 μm.
The results showed that the average fineness of Everfix Red F4R ink and Lithol Baohong BK ink is similar, and the particles of Jinguanghong C ink are relatively hard. In the process of ink preparation, the grinding time should be prolonged.

4) Measurement of ink flow 1 Reference standard: GB/T14624.3-93, measured at a temperature of 25±1°C and a humidity of 65%±5%.
2 Experimental results and analysis The ink flow was measured by transverse measurement and longitudinal measurement. The average diameters of the three inks were measured. The measurement results are: Lithol Baohong BK is 62mm, Yongguhong F4R is 58mm, and the permanent red 2B is 62.5mm.
The experimental results show that the three inks have little difference in fluidity. The flow of Everhold Red 2B ink and Lithol Baohong BK ink is almost the same, slightly better than Everfix Red F4R ink.

5) Ink initial measurement 1 Reference standard: GB/T 13217.5-91, test at a temperature of 25 ± 1 °C, humidity 65% ​​± 5%.
2 Experimental results and analysis The average value of the initial dry length of the three inks was Lisuobaohong BK 55.5mm, Everlasting red F4R 41.5mm, and Everlasting red 2B 50.5mm.
The initial dryness of Lisol's Baohong BK ink is much better than that of the other two inks. The permanent dryness of Everlasting red F4R is the worst.

6) Ink resistance test 1 Reference standards: GB/T13217.8-91, GB/T13217.1-91, test temperature 50±1°C.
2 Test results and analysis The anti-blocking properties of the three inks were in the order of Everfix Red 2B (90)> Permanent Red F4R (40)> Lisol Red BK (15).
The experimental results show that the anti-blocking property of Yongguhong 2B is best.

7) Ink drying speed test The natural drying speed of the ink was tested under the conditions of a temperature of 19°C and a humidity of 68%, as shown in Table 4.
The test method is to press the coated paper on the ink layer of the film and immediately lift it. There is no ink on the coated paper to dry the ink. In actual production, the printing speed can be adjusted according to the drying characteristics of the ink and the productivity can be improved. The drying speeds of the four inks are slightly different due to the different substrates. Among them, the golden red C ink has a relatively slow drying speed.

in conclusion

Comprehensive performance characteristics of several inks, in the selection of red cooking ink resistance, if the product needs to be subjected to a higher temperature treatment (above 100 °C), should try to use permanent red 2B pigment as a coloring agent; if the initial dryness of the ink And the requirement of adhesion strength is high, and the processing temperature is around 100°C. Litholone BK pigment can be considered as the colorant of the ink; due to the poor fastness of the permanent red F4R pigment ink, it can be used in some pairs. Printing quality and temperature conditions require less application in packaging printing (in the absence of the first two pigments); gold-red C pigments are generally not used as colorants for cooking-resistant inks.

In addition, when preparing experimental inks, it should be noted that Jinguanghong C ink is relatively dilute. After being placed for a period of time, serious stratification will occur. Therefore, the proportion of solvents may be appropriately reduced during the preparation. Jinguanghong C pigments have large particles and the grinding time should be lengthened. Everlasting Red 2B ink is very viscous, adding a solvent when used, the situation will change; or in the preparation of permanent red 2B ink, increase the proportion of solvent.

Source: 21st Century Fine Chemicals Network