RU2782892C1 - Reversible indicator (options) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a reversible indicator characterized by the fact that it is manufactured by continuous stirring under normal conditions until the formation of a sorbent having a uniform color, followed by its drying at a temperature of 95-105°C for 23-25 hours, 85-90, wt. %, natural-sodium bentonite clay with a content of at least 80% montmorillonite with a dispersion of no more than 7.5 mm, pre-saturated with moisture up to 50-60% of its maximum moisture capacity at a relative humidity of at least 80%, and 10-15 wt. % of indicator solution, which is pre-prepared by sequential mixing under normal conditions of 19.0-20.0 wt. % 6-aqueous cobalt chloride, 0.7-1 wt. % ammonium chloride, 1,7-2,2 wt. % copper sulfate and 78.6-76.8 wt. % distilled water, brought to a boil, boiled for 50-70 seconds and cooled under normal conditions to a temperature of no more than 30°C. The invention also relates to a reversible indicator characterized by the fact that it is manufactured by applying medium or slow filtration to filter laboratory paper for quantitative analyses with a mass fraction of ash up to 0.03%, a filtering capacity of no more than 100 s and a wet pressure resistance of at least 6 kPa, preferably medium filtration for quantitative analyses with a mass fraction ash up to 0.01%, filtration capacity of no more than 45 s and resistance to pressure in the wet state of at least 6 kPa, pre-aged for at least 300 s at a relative humidity of at least 80%, with a time gap of no more than 30 s of 0.02-0.05 ml of the indicator solution, which is pre-prepared by sequential mixing under normal conditions of 19.0-20.0 wt. % 6-aqueous cobalt chloride, 0.7-1 wt. % ammonium chloride, 1,7-2,2 wt. % of copper sulfate and 78.6-76.8 wt. % distilled water, brought to a boil, boiled for 50-70 seconds and cooled under normal conditions to a temperature of no more than 30°C.

EFFECT: expansion of the range of reversible indicators.

2 cl, 22 ex, 3 dwg

Description

The invention relates to the development of preservation means, namely the creation of reversible indicators that are designed to control the level of air humidity inside the sealed volume and (or) the need to replace the main moisture absorber (re-preservation of the product).

In various fields of industry, technology and agriculture, various moisture absorbers and, accordingly, indicators are used to reduce air humidity, dehydrate, remove condensate and combat dampness inside packages, freight containers, rooms and other volumes. An analysis of the existing state of the art in this area showed that the latter are most appropriately classified into two groups: indicators for controlling the level of relative humidity (RH) and indicators for the need to replace a moisture absorber (re-preservation) (WAP).

KUV indicators are made in the form of cards made from a substrate (paper, preferably hydrophilic blotting, natural fabric, non-woven material, or combinations thereof) capable of absorbing moisture, with one or more indicators (markers) of moisture from a hygroscopic salt, a pH indicator applied to it. etc. They are divided into two types: reversible and irreversible.

The first type of KUV indicators change color reversibly when exposed to an ambient atmosphere with a certain level of relative humidity and, accordingly, are regenerated [MIL-I-8835A, patents EP 1705484 A1, EP 2085132 A1, JP 5014869 B2, EP 1293773 B1, US 4098120 A, US 2627505 A and others]. The main disadvantage of these indicators is that they “signal” the level of relative humidity directly at the moment of control (for example, when the package is opened) and will not indicate its higher value recorded earlier. However, the reversibility of EQU indicators depends on the substrates and markers used in them, and can be maintained without changing directly when the relative humidity decreases below a specified level, for a certain time, or to a certain level of relative humidity.

The second type of KUV indicators, regardless of the moment of control, indicate the achievement or excess of the relative humidity of the surrounding atmosphere of the corresponding limit value, including if subsequently the relative humidity fell below this limit value [Patents US 2214354 A, US 2249867 A, WO 2009015873 A2, US 4098120 A, EP 2463650 A1, Report No. BDX-613-1150 (Rev.) ((Maximum Humidity Indicators (Bendix Corporation, Kansas City, Mo., October 1974) et al.]. salt (for example, lithium chloride [TU 95.1926-89], calcium chloride [GOST 450-77], etc.), which has a high rate of moisture absorption at a low partial pressure of water vapor (less than 1 Pa). However, adsorbing water, such salts are converted into stable hydrates, which dissolve in their water of crystallization with the formation of a solution.In this regard, the indicators of the ECF are not regenerated (single use), which is their main drawback.

APW indicators are made from a sorbent (silica gels, clays, molecular sieves, activated carbons, etc., or combinations thereof) treated (impregnated) with one (usually salt) or several substances (for example, salt and a pH indicator) that have a different color in an anhydrous state and in combination with water (for example, in a hydrated state), for example, cobalt chloride, zinc chloride, etc. They, as well as indicators of ECF, are divided into two types: reversible (regenerated) [Patents US 2580737 A, US 2526938 A, US 2460065 A, US 2460071 A, EP 0268493 A2, WO 2001009601 A1, US 6559096 B1, US 4036360 A, US 2627505 A, EP 1705484 A1, JP 5014869 B2, and other irreversible WO 2001009601 A1, US 6559096 B1, US 4036360 A and others].

The closest technical result achieved and having a purpose coinciding with the purpose of the invention (prototype) is silica gel indicator [GOST 8984-75] - dry grains of finely porous silica gel impregnated with solutions of cobalt salts. It is used (in accordance with GOST 8984-75) to control the relative humidity of the environment in a closed volume by changing its color during the production, transportation and storage of materials, mechanisms and parts.

In accordance with paragraph 1.2 of GOST 8984-75, the change in the color of the indicator silica gel (from blue, light blue, cyan or light blue to lilac or pink) depends on the relative humidity of the environment (from 20% to 50%). In this regard, it should be attributed to the reversible indicators of EQL.

It should be noted that the main methodological tools for assessing the properties and characteristics of indicator silica gel are the analysis methods described in paragraph 3 of GOST 8984-75, however, they take into account its moisture capacity during static absorption of moisture from the environment. Table 1 of GOST 8984-75 (physico-chemical indicators of indicator silica gel) indicates the moisture capacity of indicator silica gel for different relative humidity with dynamic moisture absorption (in accordance with clause 3.4 of GOST 8984-75).

To determine the moisture capacity during static moisture absorption, the indicator silica gel samples were packed (50 ± 1) g each in suitable bags made of cotton fabric (long-staple cotton paper was placed inside the bags to prevent dusting). If necessary (in accordance with the test conditions), packaged fractions of indicator silica gel in bags were dried (regenerated) at a temperature of (120±5)°C in an oven for (24±1) hours. The indicator silica gel fractions in the bags were weighed to the fourth decimal place and placed in a climatic chamber, in which the humidity and temperature were previously set in accordance with the test conditions, so that the distance between the bags was at least 0.1 m, the distance between samples and walls of the chamber - not less than 0.2 m, the distance from the lower edge of the samples to the bottom of the chamber - not less than 0.2 m. Weighing the bags and determining the color of the silica gel indicator were carried out after 0.1 hours. Calculation of moisture capacity at static absorption of moisture was carried out in accordance with clause 3.4 of GOST 8984-75. The determination of the maximum moisture capacity was considered complete when the discrepancies between the calculation results between two successive weighings did not exceed 0.2%.

The tests carried out, the generalized and systematized results of which according to Examples No. 1-16 are presented in the table in Fig. 1 showed that the color change of the indicator silica gel according to GOST 8984-75 does not have a direct dependence on the relative humidity of the environment, but depends on the moisture content (moisture capacity) in it: blue or light blue - at 0-2.0 wt. %, blue or light blue - at 2.9-5.5 wt.%, violet or light purple - at 5.8-7.8 wt.%, pink or light pink - at 8.0-20 ,1 wt.% In this case, the moisture capacity depends on the relative humidity, ambient temperature and exposure time.

Thus, silica gel-indicator according to GOST 8984-75 is most expediently referred to as reversible indicators of the APV. In addition, GOST 9.014-78 states that it is used as a moisture indicator, the pink color of which indicates “the need for re-preservation of products” (replacement of the main moisture absorber - finely porous technical silica gel according to GOST 3956-76).

However, the tests carried out as part of the research work according to the previously mentioned test methodology, the generalized and systematized results of which, according to Examples No. 1-22, are presented in the table in Fig. 1 showed the following:

- the maximum moisture capacity of silica gel-indicator according to GOST 8984-75 at levels of relative humidity of the environment of 50-100%, at which it changes its color to pink or pale pink, on average 1.9 times less than that of silica gel according to GOST 3956-76;

- the value of the moisture capacity of the indicator silica gel according to GOST 8984-75, at which it changes its color to pink or pale pink, is 8.0 wt.%, which is on average 3.5 times less than the maximum moisture capacity of silica gel according to GOST 3956-76 at ambient relative humidity levels of 50-100%;

- when environmental conditions change, namely, a decrease in relative humidity to 20-60% and an increase in temperature over 35 ° C, the silica gel-indicator saturated with moisture according to GOST 8984-75 releases moisture into the environment, changing its moisture capacity and, accordingly, color ( Examples No. 15, 16 in the table in Fig. 1).

Thus, the use of silica gel-indicator according to GOST 8984-75 as a reversible indicator of the AWP causes the following disadvantages when protecting products using static air drying (for example, according to the variant of temporary anti-corrosion protection VZ-10 in accordance with GOST 9.014-78):

1) premature replacement (re-preservation) of the main moisture absorber, in particular, silica gel according to GOST 3956-76 (with pink or light pink color of indicator silica gel according to GOST 8984-75, the moisture capacity margin of silica gel according to GOST 3956-76 is at least 48%) , which leads to a decrease in the time of effective use of the main sorbent and (or) increases its required (required) amount;

2) erroneous control of the need to replace the main moisture absorber due to the insufficient ability of silica gel-indicator according to GOST 8984-75 to retain water in its volume, in particular, when environmental conditions change (relative humidity decreases to 20-60% and temperature rises more than 35 °C).

In addition, given the disadvantages of silica gel according to GOST 3956-76, described in the patent for a regenerated desiccant based on bentonite clay (options) [Patent RU 2744661 C1], indicator silica gel according to GOST 8984-75 has poor resistance to repeated frosts and low moisture absorption capacity. at an ambient temperature of less than 0-1°C, when the water in the pores of silica gels turns into ice.

The objective of the present invention is to eliminate these shortcomings of the prototype by creating a reversible VPV indicator, which is regenerated only when exposed to a temperature (drying) of at least 95 ° C, and creating a reversible EQL indicator that changes color from blue (light blue) to pink (light pink) when exposed to an ambient atmosphere with a relative humidity level of 48-50% (when the relative humidity of the environment is less than 50-55% [GOST 9.014-78]): the rate of atmospheric corrosion, which has the main effect on the change in the technical condition of products and (or) the destruction of metallic materials , is insignificant; the rate of biocorrosion and the development of biodamages are insignificant, because the main strains of mold fungi do not "live an active life", do not spore, but do not die) and retaining it to a level of relative humidity of the environment of at least 30% at a temperature of no more 35°C or until regeneration at temperatures above 35°C (drying).

The essence of the invention lies in the development of methods for obtaining and compositions of a reversible VPV indicator based on natural sodium bentonite clay and a reversible KUV indicator based on laboratory filter paper, the indicator properties of which are provided by a complex solution based on cobalt chloride, ammonium chloride and copper sulphate.

When solving the problem of developing the optimal composition and method for obtaining a reversible WPV indicator, a technical result was achieved, which consists in providing resistance to repeated frosts without loss of properties, the ability to sorb from the environment, bind and retain water molecules until regeneration under certain conditions, and also an increase in moisture capacity, on which the change in indicator color depends.

The specified technical result is achieved by the fact that as a sorbent for a reversible indicator of the WAP, granules with a size of not more than 7.5 mm of natural sodium bentonite clay with a content of at least 80% of montmorillonite are used [Patent RU 2744661 C1]. The required granules are obtained by grinding (crushing) and separating the specified mineral raw materials by any known method. The resulting sorbent is saturated with moisture up to 50-60% of its maximum moisture capacity (36.1-48.9 wt.%) at a relative ambient humidity of at least 80%, processed (impregnated) under normal conditions and continuous mixing until the formation of a sorbent having a homogeneous color, indicator solution in a percentage ratio (by weight), respectively, 85-90% to 10-15%, and dried at a temperature of 95-105°C for (24±1) hours.

Patent-pending reversible APB indicator provides:

- control of the indication of the replacement of the main moisture absorber by changing its color, which depends on its moisture capacity as follows: light blue - at 0-3.2 wt.%, blue or light blue - at 4.8-10.6 wt. %, light purple - at 11.4-23.3 wt.%, light pink - at 26.9-70.7 wt.%;

- sorption of water molecules from the environment, their binding and retention until regeneration at a temperature not lower than 95°C;

- preservation of its indicator properties during repeated frosts.

The indicator solution is prepared by mixing the following substances under normal conditions: 6-water cobalt chloride [GOST 4525-77] - 19.0-20.0 wt.%, ammonium chloride [GOST 3773-72] - 0.7-1 wt. %, copper sulfate [GOST 19347-2014] - 1.7-2.2 wt.%, distilled water [GOST R 58144-2018] - the rest. The resulting solution is brought to a boil, boiled for (60 ± 10) s and cooled under normal conditions to a temperature not exceeding 30°C.

One of the essential distinguishing features of the reversible WAP indicator is the use of granules no larger than 7.5 mm in size of natural sodium bentonite clay with a content of at least 80% montmorillonite as a sorbent. The use of another sorbent, as well as the use of bentonite clay, which has a dispersity, mineral composition and (or) composition of exchangeable cations different from the claimed one, leads to a change in the moisture capacity of the reversible WAP indicator, on which, accordingly, the change in its color also depends (Examples No. 1- 22 in the table in Fig. 2), as well as to a change in temperature and (or) other conditions for its reversibility and (or) regeneration (Examples No. 1-19 in the table in Fig. 2).

In other words, the reversible WAP indicator based on said bentonite clay only changes color when its moisture capacity increases, despite the fact that existing indicators based on cobalt salts reversibly change their color depending on the level of relative humidity of the environment. At the same time, a decrease in the moisture capacity of the patented WAP indicator, which causes its regeneration and, accordingly, “restoration” of color, is possible only by drying at a temperature of 95-105°C.

The second significant distinguishing feature is the qualitative and quantitative composition of the indicator solution used for processing (impregnation) of the sorbent (for the SPV indicator) or the substrate (for the EQL indicator). The use of other components in the indicator solution, as well as the use of their other ratio, leads to a change in the color of the indicator treated (impregnated) with this solution, depending on its moisture capacity (for the indicator of the SPV according to Examples No. 1, 2, 6, 8, 9, 11, 13, 15, presented in the table in Fig. 3) or the relative humidity of the environment (for the EQL indicator according to Examples No. 3-5, 7, 10, 12, 14, 16, presented in the table in Fig. 3).

As an explanation, it should be noted that when exposed to a humid environment, the change in the color of the indicators occurs as a result of moisture sorption by the indicator substrate (for the SPV indicator - bentonite clay, for the KUV indicator - filter laboratory paper) and the interaction of water molecules with anhydrous indicator salts in it. Therefore, a change in the specified composition of the indicator solution leads to a change in the amount of water and, accordingly, the partial pressure of its vapor required to reverse the color of the salts used in this solution.

The third significant distinguishing feature is the procedure for preparing the indicator solution. Using a different order of preparation, in particular, boiling the solution for more or less than (60 ± 10) s and (or) cooling it under other conditions, leads to a change in the composition of the indicator solution, which ultimately leads to excellent moisture capacity values (for the WAT indicator ) or relative humidity of the environment (for the KUV indicator), which determine, respectively, the change in color of the indicator treated (impregnated) with this solution.

The fourth essential distinguishing feature is the method of obtaining the PVL indicator. The use of a different order of obtaining leads to a change in the values of the moisture content of the APW indicator, causing, accordingly, a change in its color, in particular:

- treatment (impregnation) with an indicator solution of bentonite clay saturated with moisture less than 50% of its maximum moisture capacity (less than 36.1 wt.%) leads to chemical interaction of salts contained in the indicator solution with an unacceptably large amount of mineral components of bentonite clay;

- treatment (impregnation) with an indicator solution of bentonite clay saturated with moisture of more than 60% of its maximum moisture capacity (more than 48.9 wt.%) leads to insufficient "activation" of bentonite clay;

- the lack of mixing of the components before the formation of a sorbent having a uniform color leads to uneven "activation" of bentonite clay;

- drying of the prepared WAP indicator (bentonite clay saturated with moisture up to 50-60% of its maximum moisture capacity and treated (impregnated) with an indicator solution) at a temperature of less than 95 ° C does not reduce its moisture capacity to "working" (initial) values (less than 1, 8 wt%);

- drying of the prepared indicator APW at a temperature of more than 105°C leads to a decrease in the amount of "activated" indicator solution of bentonite clay.

The fifth significant distinguishing feature is the percentage of bentonite clay and the prepared indicator solution used in the preparation of the indicator. The use of more than 15 wt.%, the prepared indicator solution leads to a decrease in the moisture capacity of the reversible indicator of the SPV, on which, accordingly, the change in its color also depends (Examples No. 18, 19 in the table in Fig. 2). The use of less than 10 wt.%, the prepared indicator solution in the preparation of the indicator SPV causes a slight change in color when saturated with moisture (Examples No. 1, 2 in the table in Fig. 2).

When solving the problem of developing a composition and a method for obtaining a reversible indicator of EQS, a technical result was achieved, which consists in the fact that control is provided for an increase in the level of relative humidity of the environment of more than 48-50% by changing the color from blue (light blue) to pink (light blue). pink), the reversibility (color restoration) of which occurs at an ambient relative humidity level of less than 27% and a temperature of less than 75 ° C or at an ambient relative humidity level of less than 48% and a temperature of at least 75 ° C, as well as resistance to repeated frosts without property loss.

The specified technical result is achieved by the fact that filtering laboratory paper [GOST 12026-76] of medium or slow filtration for quantitative analyzes with an ash mass fraction of up to 0.03%, a filtering capacity of not more than 100 s and bursting resistance during wet state not less than 6 kPa (FS-I, FS-II, FM-I or FM-II), preferably medium filtration for quantitative analysis with an ash mass fraction of up to 0.01%, a filtering capacity of not more than 45 s and bursting resistance in wet state not less than 6 kPa (FS-I). 0.02-0.05 ml (one drop) of an indicator solution, previously prepared in the manner indicated earlier.

Before being used for its intended purpose, the reversible KUV indicator obtained by this method is preliminarily dried (regenerated) at a temperature of at least 75°C, preferably at a temperature of 75-150°C, until it takes on (restores) a blue (light blue) color. It is allowed to store the regenerated (restored) KUV indicator at a relative ambient humidity of not more than 25% (for example, in a desiccator with a moisture absorber).

The patent-pending reversible EQUV indicator provides monitoring of an increase in the level of relative humidity of the environment of more than 48-50%, reversibility (color restoration) at an ambient relative humidity level of less than 27% and a temperature of less than 75 ° C or an ambient relative humidity level of less than 48% and temperature not less than 75°C, preferably at a temperature of 75-150°C (regeneration), as well as resistance to repeated frosts without loss of properties.

One of the essential distinguishing features of the reversible indicator is the use of filter paper of medium or slow filtration as a substrate for quantitative analysis with an ash mass fraction of up to 0.03%, a filtering capacity of not more than 100 s, and a bursting resistance in the wet state of at least 6 kPa ( FS-I, FS-I, FM-I or FM-P). The use of laboratory filter papers with a wet burst strength of less than 6 kPa, such as very fast or fast filtering laboratory papers, will cause the ECF indicator to change color from blue (light blue) to pink (light pink) at ambient relative humidity levels. environment 35-43%, as well as to restore color (reversibility) at a level of relative humidity of the environment less than 27% and a temperature of not more than 30°C or at a level of relative humidity of the environment of less than 48% and a temperature of more than 30°C. The use of laboratory filter paper with an ash mass fraction of more than 0.03%, such as filter paper for qualitative analysis, causes the ECF indicator to change color from blue (light blue) to pink (light pink) at an ambient relative humidity level of 62 -68% (depending on filtration capacity and bursting resistance when wet) and color recovery (reversibility) at an ambient relative humidity of at least 53% and a temperature of less than 75°C or an ambient relative humidity of less than 62 % and temperature not less than 75°С.

The second significant distinguishing feature is the qualitative and quantitative composition of the indicator solution, as well as the procedure for its preparation, described earlier.

The third essential distinguishing feature is the method of obtaining the EQL indicator. The use of a different order of preparation, in particular, the application of an indicator solution to laboratory filter paper previously conditioned for less than 300 s at a relative ambient humidity of at least 80% or pre-aged for at least 300 s at a relative ambient humidity of less than 80%, with a time gap of no more than 30 s, as well as an increase in this gap of more than 30 s, leads to a change in the color of the EQL indicator from blue (light blue) to pink (light pink) at a relative humidity level of 28-36% due to insufficient moisture content of the laboratory filter paper on which the indicator solution is applied.

Evaluation of the properties of the APW indicators and the prototype was carried out according to the previously mentioned method, except that the drying (regeneration) of the APW indicators was carried out at a temperature of 95-105°C in an oven for (24±1) hours. The generalized and systematized test results are presented in the tables in Fig. 1 (Examples No. 1-16), Fig. 2 and FIG. 3 (Examples #1, 2, 6, 8, 9, 11, 13, 15).

In order to study the properties of ECF indicators, the samples obtained by the above method were placed in a climatic chamber, in which the humidity and temperature were previously set in accordance with the test conditions, so that the distance between the samples was at least 0.1 m, the distance between the samples and walls of the chamber - not less than 0.2 m, the distance from the lower edge of the samples to the bottom of the chamber - not less than 0.2 m. The generalized and systematized test results are presented in the table in Fig. 3 (Examples #3-5, 7, 10, 12, 14, 16).

From the data shown in the tables in Fig. 1, Fig. 2 and FIG. 3, it can be seen that the indicators of the SPV and EQU obtained according to the claimed invention, have indicators that exceed the corresponding values of the prototype. The conducted patent research did not reveal technical solutions that became publicly available in the world before the priority date of the claimed invention and are characterized by the claimed set of features, therefore, it can be assumed that the specified technical solution meets the condition of patentability "novelty".

The claimed invention is simple to implement, uses available components and standard technological equipment to obtain it, has been tested in pilot conditions, which corresponds to the condition of patentability "industrial applicability".

Claims (2)

1. A reversible indicator, characterized in that it is produced by continuous stirring under normal conditions until the formation of a sorbent having a uniform color, followed by drying at a temperature of 95-105 ° C for 23-25 hours, 85-90 wt.% natural - sodium bentonite clay with a content of at least 80% montmorillonite with a dispersion of not more than 7.5 mm, pre-saturated with moisture up to 50-60% of its maximum moisture capacity at a relative ambient humidity of at least 80%, and 10-15 wt.% indicator solution, which is preliminarily prepared by sequential mixing under normal conditions of 19.0-20.0 wt.% 6-water cobalt chloride, 0.7-1 wt.% ammonium chloride, 1.7-2.2 wt.% copper sulphate and 78, 6-76.8 wt.% distilled water, bringing to a boil, boiling for 50-70 s and cooling under normal conditions to a temperature of not more than 30°C. 2. A reversible indicator, characterized in that it is made by applying medium or slow filtration laboratory filter paper for quantitative analysis with an ash mass fraction of up to 0.03%, a filtering capacity of not more than 100 s, and a bursting resistance in the wet state of at least 6 kPa , preferably medium filtration for quantitative analysis with an ash mass fraction of up to 0.01%, a filtering capacity of not more than 45 s and a bursting resistance in the wet state of at least 6 kPa, previously aged for at least 300 s at a relative ambient humidity of at least 80 %, with a time gap of not more than 30 s 0.02-0.05 ml of an indicator solution, which is preliminarily prepared by sequential mixing under normal conditions 19.0-20.0 wt.% 6-water cobalt chloride, 0.7-1 wt.% ammonium chloride, 1.7-2.2 wt.% copper sulphate and 78.6-76.8 wt.% distilled water, bringing to a boil, boiling for 50-70 s and cooling under normal conditions up to a temperature not exceeding 30°C.

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