CS230310B1 - Method of determination of shade and purity in water unsoluble organic ccolouring agents - Google Patents

Description

The invention solves the problem of determining the color shade and the purity (brightness) of water-insoluble organic dyes that can be supplied as a powder, aqueous paste or aqueous suspension for determination.

By color shade is meant the difference in color perception of the observed organic dye and the standard type of dye. By the purity (brightness or turbidity) of the dye is meant the difference in perception of the color purity of the dye of interest and the standard type of dye.

The shade and purity of organic dyes are determined by subjective method. The first method consists in subjective comparison of the color shade and purity of the coating (or coloring) of the dye and the standard dye type. The objective evaluation consists in finding the color coordinates by measuring the remission spectrum of the paint film or the color. An accurate spectrophotometer is required for this. Neither the subjective nor the objective method can say anything about the other properties of the dyes, eventually about the causes of color change and purity. Only dried pigments can be evaluated by both methods.

SUMMARY OF THE INVENTION The present invention provides a novel method for determining the color shade and purity of water-insoluble organic dyes based on comparing the experimentally determined particle size distribution of the organic dye with the experimentally determined particle size distribution of the standard types of dye, i.e. dyes whose color shade has been selected as comparative and dyes whose color shade has been previously determined by the subjective method determined by the centrifugal method.

The particle size distribution of the dye is determined in an aqueous suspension containing the dispersant by the centrifugal method described in the literature. To ensure reproducibility of the results and hence reproducibility of color and purity determination, experimental work should be carried out at a constant and uniform temperature. The effect of imperfect suspension and temperature is the determination of agglomerates formed secondary to the preparation of the dye suspension. Therefore, the preparation of the corresponding dye suspension plays an important role in the implementation of the process of the invention.

Advantageously, the preparation of the suspension according to the author's certificate No. 217 250 can be used. The suspension then contains only those primary particles and particle aggregates containing the original dye. However, the suspension contains a relatively large amount of surfactants, which must be taken into account when evaluating the results of the centrifugal analysis. The experimental results of the centrifugal method are evaluated graphically, plotting experimentally determined percentages of particles smaller than the selected size of V 1 to V _n in log-normal distribution plots and joining the plotted points with a line or a polyline (linearization of the composite curve). The point-to-point connection is a new feature and expresses the fact that not all of the above-described centrifugation analysis of experimentally determined values in the size range from 0.03 μτη to 2 to 5 μαη can be used to determine the particle size distribution of water-insoluble organic dyes. The dye distributions are relatively very narrow, since the isolation of fine polydisperse dyes from an aqueous medium containing virtually always a small amount of salts results in rapid preferential aggregation of the smallest particles up to approximately 1 μΐη. When determining the content of particles smaller than 1 to 2 μιη, the determination error should be taken into account due to the high content of surfactants in the suspension.

Comparison of the particle size distribution of the dye whose hue and purity are determined with the particle size distribution of the standard dye type is realized as a comparison of the slope of one or two or three cumulative straight lines of the respective dyes with the one to three cumulative straight lines . Conformity of the directives of the respective dyes and of the standard type implies concordance of color shades and purity (comparison of harvatives).

Influence of color shade by modification, environment, crystal shape, particle size (mean particle size is also discussed in the literature) The effect of particle size distribution determined by electron microscopy (commutative relative frequency determination) on shade purity is also discussed. Partial effects of these effects are not challenged by correlating particle size distribution and color shade, and purity. Particles of any shape are evaluated in the centrifugal method as spherical and their different shape and surface properties are reflected in the particle size determination.

The advantage of the novel process is that the color shade and purity need not be supplied dry _{with the} product to evaluate color shade and purity, but it is also possible to use a dye suspension in an aqueous paste or waterworks. Another advantage over other methods is that in addition to the actual determination of the color shade and purity, information on other properties of the colorant, possibly on the causes of color shade and purity changes, is obtained. Another advantage lies in the fact that the process can be carried out using a low-cost device such as a Jenetzki T 23 centrifuge and a colorimeter.

Ohr. 1 shows the cumulative (straight line in the logarithmic normal .grafu .rozdělení obtained in evaluating the results centrifugaoního determining particle sizes of less than a selected size of VI to V _n of phthalocyanine pigments of different hues and .čistoty; these colors were determined by the subjective method.

The particles were separated by centrifugation from an aqueous suspension containing a cationic dispersant based on a mlkylaminopolyethylene glycol commercially available from Berol Visco. The yield of analyzed segments was approximately the same.

The line 1 represents tthalocyanine pigments whose shade is according to the subjective evaluation method (SMHj yellow and bright (distribution of the standard type of yellow bright shade). The same angle line also presents the anthraquin pigments of constitution

as rated yellow and clear; broken line 2 represents phthalocyanine pigments whose shade according to SMH is yellow and turbid (standard type distribution of yellow and turbid); line 3 represents a standard type of phthalocyanine pigment whose shade is SMH rated as red, but also a basic standard type of the above red amtrachinone pigment (shade 0, brightness D); Angled line 4 represents the basic standard type of the β-imodification of the phthalocyanine pigment (shade 0, brightness - sludge 0;

Giant. 2. Influence of temperature on results of centrifugation determination of percentage of particles - smaller limit 2 mn (for illustration - connected by lines) - smaller than 1 μια - smaller than 0,5 μΐη - smaller than. 0.2 yim.

Experimental example of the centrifugal method: 0.1 g of powder or 1.2 g of 50% aqueous phthalocyanine pigment paste was mixed in a weighing bar with 1 g of an alkylaminopolyglycal cationic dispersant and the resulting dough was further mixed into water. Volume of .suspension and

was adjusted to 250 ml with distilled water. The suspension was prepared and centrifuged at 22.4 ° C. Centrifugation was performed on a Janezki T 23 centrifuge. After centrifugation of the particles of the selected size V, 1 ml of suspension at depth a was collected from the cuvettes

cm @ 2, dissolved in concentrated sulfuric acid (50 ml volumetric flask) and the concentration of the resulting solution was determined colorimetrically. From the concentration found, the percentage of particles smaller than the size V was calculated. Assay values for the different V sizes were plotted on a log-normal distribution plot.

Claims (1)

Method for determining the color shade and purity of water-insoluble organic dyes from a comparison of dyes and standard types of said dyes, characterized in that the determination of color shade and purity is carried out as a comparison of the particle size distribution of the dye and the particle size distribution .