Printing and printing inks resistance to acid

1 Scope

This standard specifies the method for evaluating the acid resistance of printing.
This standard applies to all printing process substrates such as paper, cardboard, plastics and metals (metal foils and metal plates).

2 Reference standards

The provisions included in the following standards form the provisions of this standard by reference in this standard. When the standard is published, the versions shown are valid. All standards will be revised, and all parties using this standard shall explore and use the possibility of the latest edition of the following standards.
ISO 105-A03:1993 Textiles - Quick Tests for Color - Part A03: Grey Scales for Evaluation of Colors.

3 Definitions

This standard uses the following definitions:
3.1 Acid resistance of printed matter: The ability of a printed material to withstand a specific concentration of a particular acid within a specified period of time.
Note 1: The printed matter has no significant change in the specific acid under the experimental conditions, and it can be judged that the print has acid resistance to the acid.

4 Principle

The print is pressed between two filter papers previously wetted with a specific acid solution.
Acid resistance evaluation was performed by the degree of color change of the printed matter and the degree of color impregnation of the filter paper.
Note 2: The type, concentration and time of the acid used are not fixed because the acid resistance is affected by the ink, the substrate itself, and the interaction between the ink and the substrate.

5 Instruments and Reagents

5.1 Quantitative filter paper for white experiments: chemical analysis grade, surface smooth, soft, filter paper size 60mm × 90mm.
5.2 Reference prints and test prints.
5.3 Test acid.
5.4 Glass plate: 60mm x 90mm.
5.5 Grey ruler for color evaluation (see ISO 105-A03).
5.6 distilled water.
5.7 1kg weight.
5.8 oven: temperature control range (50 ± 2) °C.

6 test conditions

Tests should be conducted at standard temperatures.
Note 4: According to the general laboratory operating conditions, the test temperature can be set to 20 °C, 23 °C, or 27 °C, according to the print environment temperature selected.

7 test procedures

The two test filters were completely immersed in the test acid solution, and then the acid solution on the surface of the filter paper was removed until there was no acid droplets. Place one of the filter papers on the glass plate, place a 20mm x 50mm test print on top of the filter paper, cover the test print with the second filter paper, and use the other glass plate on the top layer. Place the prepared glass test panel in a sealed package or container and place a 1 kg weight on the glass panel.
Test samples were taken out after permeation for a specified time (see Table A1) and rinsed with distilled water until the pH of the rinse solution became neutral. The test sample was placed in an oven at (50 ± 2) °C for 30 minutes.
The filter paper naturally dries in the air and cannot be rinsed with water before testing.
8 Evaluation Compare the dried test sample with the reference sample and test the filter paper. Evaluate the test results according to the following terms:
1) The appearance of the test prints changed significantly and there was no acid resistance.
2) There is no obvious change in the appearance of the test prints, but the filter paper is soaked and needs to be evaluated according to the degree. If the degree of impregnation reaches level 4 of the grey scale (see ISO 105-A03), the print can be determined to decolorize.

9 test report test report should include the following content;
a) the applied standard;
b) Test acid;
c) Test acid concentration;
d) room temperature and the temperature of the test solution;
e) the time of soaking;
f) Test whether the color of the printed sample has changed. If the color changes, record the degree of change. The color change caused by the substrate should be clearly marked.
g) whether the filter paper in contact with the test print is impregnated with dye;
h) Clearly record changes in the printed product throughout the test.
Note 5: According to this standard, some prints do not have acid resistance. Although many prints have been impregnated on filter paper, the printed matter can be satisfactorily used in practical applications. The degree of immersion was evaluated by comparison with a grey scale.

Appendix A (Appendix of Tips)

Recommended Acid Solutions Table A1 is an acid commonly used to test acid resistance of printed products and its concentration and immersion time.

acid

Lactate

Citric acid

acetic acid

hydrochloric acid

sulfuric acid

1)

2)

1)

2)

1)

2)

1)

2)

1)

2)

concentration

10

5

5

1

5

1

5

1

5

1

Soaking time

1h

24h

1h

24h

30min

24h

10min

24h

10min

24h

The substitute for the acid

Cheese and its products

Lemon juice

Product PH<2

Note 6: These recommended acids, concentrations, and soak times apply only when no other acids and conditions of use are involved.

Source: 21st Century Fine Chemicals Network