CS259321B1 - A method for determining the content of higher carboxylic acids on micronized limestone - Google Patents

Abstract

The solution concerns the determination of the content of higher carboxylic acids on micro-ground limestone. The time of absorption of a drop of an aqueous solution containing 10 to 90% by volume of a water-miscible solvent into the surface of a powdered filler shaped into a spherical depression under a pressure of 10 Pa to 10 MPa is measured and compared with calibration values.

Description

The invention relates to a method for determining the content of higher carboxylic acids and their derivatives in micro-ground limestone.

Surface-treated micro-ground limestones are used as fillers for organic polymers. One of the methods of treating micro-ground limestone is treatment with higher carboxylic acids or their derivatives, mostly esters or salts.

The method and quality of surface treatment is an important feature determining the resulting properties of the filled polymer.

Numerous chemical or physicochemical methods have been described for determining the content of higher carboxylic acids, such as alkalimetric titration of higher carboxylic acids after dissolving limestone in hydrochloric acid and subsequent extraction of the higher carboxylic acid with chloroform, or chromatographic analysis also after dissolving limestone in hydrochloric acid and after extraction with chloroform. These methods are accurate, but are always instrument- and time-consuming. On the other hand, for example, determination of the oil number or the method for checking the hydrophobicity of powder fillers according to AO 211 968 provide only a very rough basic orientation of a rather qualitative nature.

The subject of the invention is a method for determining the content of higher carboxylic acids with C ₁₀ to C ₄₀ on micro-ground limestone, in which a drop of an aqueous solution containing 10 to 90% by volume of a water-miscible solvent is applied to a sample of powdered filler, treated with a pressure of 10 Pa to 10 MPa into the shape of a spherical depression, the time of its absorption into the surface of the filler is measured and compared with calibration values.

To assess the amount of higher carboxylic acids with 10 to 40 carbon atoms, including their derivatives, on micro-ground limestone, it is possible to measure the rate of absorption of a reagent, which is a mixture of a suitable solvent with water. The time it takes for a drop to absorb depends on the amount of higher carboxylic acid or its derivative on the limestone. Under defined test conditions, the absorption time of a drop of reagent in a sample is compared with standards with a known content of the determined substance, and the desired content is evaluated by interpolation or using a graph.

The rate of agent absorption in micro-ground limestone is determined mainly by capillary forces and surface tension. The layer of higher carboxylic acid or its derivative prevents absorption, which occurs only after its disruption or dissolution. This results in a differentiation of the absorption time depending on the amount of higher carboxylic acid or its derivative on the limestone surface.

Leaching is also affected by the quality and processing method of the limestone itself. Therefore, for a certain type of limestone, it is necessary to prepare appropriate comparison standards with a known content of the specified substance.

By choosing the reagent and its concentration composition, the rate of absorption can be significantly influenced so that the measured times are optimal in terms of the accuracy of the method. According to the invention, for example, for limestone with a particle size of 2 microns with a stearin coating, an ethanol solution with a concentration of 50, 60, or 80% by volume depending on the stearin content can be used. It is appropriate to add 0.5% by weight of a dye, e.g. sodium alizarin sulfonate, to the reagent, which allows for a more accurate determination of the moment of absorption of the reagent.

Compliance with the test conditions is a prerequisite for achieving correct results.

The surface of the limestone must be prepared in a defined manner. A suitable procedure that allows for productive execution of parallel tests is the use of, for example, a device consisting of a metal plate with several depressions of 16 mm diameter and 8 mm depth, with a guide rail with holes of the same diameter fixed concentrically above the depressions in the plate, a cylindrical body of 15 mm diameter, 30 mm high, with a hemispherical protrusion of 5 mm diameter at its base and a load body of 150 g. 1 g of sample weighed to an accuracy of + 0.1 g is poured into the depression, the surface is leveled, the cylindrical body is carefully placed on the surface of the sample and loaded with the load body for 15 s. The body is removed, 1 drop of reagent is pipetted into the depression and the time taken for the drop to be absorbed is measured. The concentration of the organic solvent in the reagent is chosen for a certain range of deposition on micro-ground limestone in order to achieve sensitive resolution of the deposition content and an adequate limit of the achieved time within a few tens of seconds, maximum up to 90 seconds.

Methanol, ethanol, propanol, isopropanol, acetone, etc. can be used as water-miscible solvents.

The invention will be illustrated by the following examples. The % in the examples are by weight unless otherwise stated.

Example 1

Calcium carbonate characterized by an average particle size of 2 microns and a 94% fraction of particles smaller than 10 microns was impregnated to varying degrees with stearin in chloroform solution. The dried filler was prepared for testing as described above.

An aqueous solution containing 60% by volume ethanol was used as the reagent. The results are summarized in Table 1.

Table

Stearin content Soaking time Average (%) (s) (s)

0 3.8 4.3 4.7 4.3 0.1 5.4 5.3 5.4 5.4 0.2 8.4 8.5 8.5 8.5 0.3 16.2 18.2 17.3 17 0.4 36.2 38.5 30.0 35 0.5 92.3 93.2 75.2 87 0.6 over 3 minutes

Example 2

The procedure was as in Example 1, except that an aqueous solution with 80% by volume ethanol was used as the reagent. The results are shown in Table 2.

Stearin content (%) Soaking time (s) Average (s) 0 3.2 4.0 3.5 3.6 0.1 5.4 5.2 5.5 5.4 0.2 7.5 7.0 6.8 7.1 0.3 9.2 9.7 8.5 9.1 0.4 12.0 12.0 11.2 12 0.5 14.8 16.0 14.6 15 0.6 24.1 22.5 21.3 23 0.7 39.6 41.0 42.0 41 0.8 64.5 54.8 65.2 61 0.9 over 2 minutes

Example3

Micro-ground limestone of Czechoslovak origin was impregnated with stearin. An aqueous solution containing 50% by volume ethanol was used as the reagent. The results are shown in Table 3.

Claims (1)

Method for determining the content of higher carboxylic acids with ΟΟ θ up to micronized limestone, characterized in that a drop of an aqueous solution containing 10 to 90% by volume of a water-miscible solvent is applied to a spherical depression-shaped powder filler sample. the time of its absorption into the filler surface is measured and compared with the calibration values.