This standard is equivalent to the use of ISO 787/16-1986 "General testing methods for pigments and extender pigments - Part 16: Determination of the relative tinting strength of color pigments (can be equivalent coloring value) and the color - the visual comparison method.

1 Topic Instinct and Scope of Application This standard specifies a general test method for determining the relative tinting strength and lightening color of two identical coloring pigments by visual comparison. When this general method is not applicable to a particular product, a special method should be specified to determine the color and relative tinting strength of the pigment.

2 Principle The dispersions of the test sample and the standard sample are prepared by an automatic grinding machine under certain conditions. The two dispersions and the color paste are mixed with a certain proportion of white pigment paste to make up the two washed-out colors. The pastes were compared for tinting strength and tinting. The main factors influencing the coloring power of pigments are as follows: the force exerted on the automatic grinding machine; the selection of the optimum grinding concentration of the dispersion; the optimum number of rotations of the dispersion; the proportion of dilution; the strict control of weighing and operation.

3 Materials 3.1 Lacquer The following two paint bases are recommended: 3.1.1 Alkyd resin: a mixture based on 63% (m/m) linseed oil and 23% (m/m) phthalic anhydride, acid The maximum value is 15mgKOH/g; the viscosity (no solution) is 7~10Pa·s; the hydroxyl value is about 40mgKOH/g). 3.1.2 urethane modified linseed oil; linseed oil content of about 80%; acid value of zero; free isocyanate zero; free hydroxyl 0.8% ~ 1.2%; viscosity (20 °C) 15 ~ 18Pa · s. 3.2 White pigment paste 3.2.1 The alkyd resin-based white pulp should have the following composition: 40 parts by mass of R-type titanium dioxide; 56 parts by mass of alkyd resin; 4 parts by mass of calcium stearate. The above components were uniformly mixed with a knife, and then ground on a three-roll mill until the fineness of the fineness test plate was less than 15 μm, and stored in an airtight container, preferably a hose with a screw cap.

3.2.2 White liquor based on urethane-modified linseed oil should have the following composition: 40 parts by mass of R-type titanium dioxide; 50 parts by mass of carbamate-modified linseed oil; 7 Parts by mass of calcium stearate; 3 parts by mass of synthetic silica. The above components are uniformly mixed with a knife, and then ground on a three-roll mill until the fineness of the fineness test plate is less than 15 μm, and stored in an airtight container, preferably a hose with a screw cap. The above two kinds of white pulp may be optionally selected according to need. 4 Automatic grinding machine (the diameter of the frosted glass plate is 180~250mm, the force applied on the grinding machine is about 1KN, the rotating speed is 70~120r/min); The adjusting knife (steel, tapered blade body, about 140~150mm, the widest At about 20~25mm, the narrowest point is not less than 12.5mm); Glass plate (colorless and transparent, size is about 150mm x 150mm); Wet film preparation device (gap 50~100um). 5 Sampling Select the representative sample of the test pigment according to the provisions of GB9285. 6 Determination Procedure 6.1 Establishment of Optimum Grinding Conditions for Pigment Dispersions 6.1.1 Grinding Concentration of Pigment Dispersions The appropriate mass ratio of the pigment and paint base depends not only on the oil absorption of the pigment but also on the viscosity of the mixture during the grinding operation. In order to achieve the appropriate concentration of low paint, medium paint, high paint demand pigments, in order to give about 2ml of mixture for each case, the following three groups are recommended: a. 3.0g pigment and 1.5g of paint base; b. 1.0g of pigment and 1.5g of paint base; c. 0.5g of paint and 1.5g of paint base; Note: If the selected mixture is found to be too thick or too thin on the grinder, Another ratio should be used.

6.1.2 Grinding rotation number of pigment dispersion Weigh 1.5g lacquer base and the appropriate amount of pigment above, add 1KN force to the grinding machine for grinding, 50 cycles per pass, total grinding 200 rotations, taking out approximately 1/4 of the total volume The slurry was stored in a suitable container, and grinding was continued until 300 and 400 rotations, respectively, and the same small fraction as above was removed. Also stored in a suitable container, set aside for use. On the lower plate of the grinder, 3±0.01 g of the white pigment paste and 200 g of the pigmented pigment paste have been ground in an amount of about 0.12 g of the coloring pigment. The two color pastes were mixed under no grinding effect, and then minimum force was applied. Each pass was polished 25 times for a total of 4 times, and the collected slurry was left to stand. The same operation was repeated by weighing the same amount of paste colored at 300 revolutions and 400 revolutions and 3±0.01 g of white pulp. The prepared dilute color pastes are sequentially arranged on a colorless glass plate, uniformly pulled down by a wet film preparation device, and the intensity of each colorant is immediately visually compared to evaluate the color paste showing the maximum color intensity, and the record is recorded. The most reasonable number of grinding revolutions for the paste is the optimum number of grinding revolutions for the test. Note: The pigmented pigment paste containing 0.12 g of coloring pigment has a dip ratio of 1:10 when mixed with 3.0 g of the white pigment paste. In order to produce a strong dip color suitable for evaluating the intensity and hue of the dilute paste, the ratio should be corrected to 1:5 or 1:20 (for weak or strong pigments, respectively).

6.2 Preparation of Pigment Dispersions Pigment standard and sample dispersions were prepared according to the conditions established in 7.1. 6.3 Preparation of Diluted Paste Weigh 3±0.01g of white pulp, according to the amount of standard dip ratio of the selected dilution of the pigment, under the application of the minimum force grinding, grinding 25 times per pass, grinding a total of 4 times, the collection of dilute Color paste is ready for use. Dilute the sample with the same method. 6.4 Comparison of color wash and determination of relative tinting strength Two blank pastes prepared in 7.3 were arranged on a colorless glass plate, and they were pulled down by a wet film preparation device to form two widths of not less than 25 mm and the length of the contact sides. Uniform-thickness opaque strips of not less than 40 mm were rubbed on each strip with one finger, comparing the difference in surface shade depth of the rubbed and unerased surfaces, and recording was made if the results were significantly different. Continue to test the unshaven surface and immediately compare the tinted strength and hue of the two in a scattered glass or artificial sunlight through a glass plate.

If the color intensities are the same and the hue is the same, the diluting colors are the same, and the relative tinting strength of the test sample is 100%. However, if the color intensity is equal and the hue is different, then the difference in lightening color is in its nature. If the color intensity is different, the amount of dispersion of the sample to be tested should be estimated. After weighing, another dilute paste is prepared according to 7.3, and the standard sample is unchanged, and then the comparison is performed until the color strength is equal. Note: The lacquer base of the white paste should be consistent with that of the pigment dispersion paint base so as to avoid flocculation. 7 Calculate the relative tinting strength X (%) of the test sample according to the formula (1): X = standard sample b × 100 / a (1) where: a - the quality of the sample with the same tint strength as the standard, g b - the mass of the standard sample, g.