RU2050028C1 - Process of detection of corrosion inhibitors based on amines in air - Google Patents

Abstract

FIELD: analytical chemistry. SUBSTANCE: process involves preparation of indicator tape composed of color reagent and polymer matrix, exposure of tape in air atmosphere containing corrosion inhibitors based on amines and photometric measurements within region 450-510 nm. For preparation of indicator tape there is used polymer with vitrification temperature below temperature at which detection is carried out and anhydrid-bis- indandion-1.3 as color reagent. Indicator tape is prepared by addition to starting polymer of solution of color reagent in carbon tetrachloride in the amount of 0.05-2.0% in terms of dry indicator material. Then carbon tetrachloride is removed by drying and film 20-500 μm thick is formed. Analysis of content of corrosion inhibitor is conducted in compliance with calibration graph obtained in advance by way of exposure of samples of same film in air with known content of corrosion inhibitor at same temperature at which analysis is performed. EFFECT: enhanced authenticity of process of detection. 4 tbl

Description

 The invention relates to analytical chemistry and can be used to detect as well as control the content of corrosion inhibitors in the air, which are mono- and disubstituted amines.

 A known method of controlling the concentration of a corrosion inhibitor (MSDA-1) in the air of a production building. The method consists in pumping air through absorbers, followed by isolation and photometric analysis in the presence of methyl orange [1] The disadvantage of this method is the long analysis time, unsuitability for the detection of corrosion inhibitors containing azomethine groups, as well as representing amines, which are weak bases.

 There is also a method for the determination of primary and secondary amines, based on their interaction with anhydro-bis-indanedione-1,3 [2] The disadvantage of this method is that the determination is carried out in a solution of acetic acid or in diethyl ether, and the amines are determined in the form of an aqueous solution appropriate hydrochloride.

 The closest to the results achieved is the use of a gas dosimeter for determination of amines, containing 1.2 naphthoquinone-4-sulfonic acid as a reagent [3] However, the described film gas dosimeter is rather complicated to produce a multilayer material, it is obvious that special equipment is required for its production . In addition, to determine each class of amines, certain compositions of buffer solutions are required, which would lead to the need to use several different dosimeters when detecting vapor of corrosion inhibitors.

 The objective of the invention is to simplify the method of determining corrosion inhibitors. To do this, the determination is carried out using a polymer-based indicator tape containing anhydro-bis-indandion-1,3. For the manufacture of the tape, a polymer is used whose glass transition temperature is lower than the temperature at which the determination is made. The concentration of anhydro-bis-indanedione-1,3 is 0.05-2.00 wt. it is introduced into the starting polymer in the form of a solution in carbon tetrachloride, which is then removed by drying. The indicator tape is formed in the form of a film with a thickness of 20-500 μm, the color change of the indicator tape after exposure in air containing a detectable corrosion inhibitor is recorded by photometry in the region of 450-510 nm. The determination of the content of the corrosion inhibitor in the air is carried out according to the calibration graph obtained previously by exposing the same film in air with a known content of the inhibitor at the same temperature at which the determination is made.

The method achieves the following technical results:
-anhydro-bis-indandion-1,3 forms intensely colored compounds with primary and secondary amines;
carrying out the reaction in the volume of the polymer matrix slows down the destruction of the resulting colored compound;
the use of a polymer in a highly elastic state provides the necessary for determining the diffusion rate of the corrosion inhibitor in the polymer volume;
the use of anhydro-bis-indanedione-1.3 at a concentration of 0.05-2.0 wt. sufficient to detect low reactive aliphatic amines with long hydrocarbon substituents in low concentrations, while at the same time it allows photometric determination of the most reactive amines at high concentrations.

For the experimental verification of the method, the following was used: high-density polyethylene, low density HDPE (GOST 16337-77), polypropylene PP (TU 6-05-1105-78), synthetic rubber SKI-3 (GOST 7738-79E), carbon tetrachloride (GOST 20288- 74), anhydro-bis-indandion-1,3 (TK 6-09-10-1312-78), dicyclohexylamine (TU 6-09-11-603-75). Also used corrosion inhibitors VNX-L-49 (TU 602-7-186-85); IFKHANGAZ-1 (TU 6-05-1944-83) and MSDA-1 (TU 6-02-832-74), which are respectively benzylidene cyclohexylamine; a mixture containing 68-72 wt. dialkylaminopropionitrile, 18-22 wt. dialkylamines, where alkylheptyl, octyl or nonyl and 10 wt. solvent and a salt of dicyclohexylamine and synthetic fatty acids of the general formula O _n H _{2n + 1} COOH, where 10 <n <13. The optical density of the colored compound in the indicator tape was determined using an FOU-UHL-4.2 photometer. To find the absorption band at which the optical density of the compound is determined, the absorption spectra of the indicator strips were taken before and after exposure. The following are examples of the implementation of the method.

Example 1. To 2 g of LDPE powder was added 36.3 ml of a solution of bindone in carbon tetrachloride containing 2.0 mg of bindon (0.0034 wt.). The resulting mass was placed in a flask of a rotary evaporator and with constant stirring, the solvent was removed. A display material was pressed at a temperature of 125 ± 3 ° ^C and a pressure of 5 MPa. Rectangular samples 8 × 20 mm in size were cut from the obtained film with a thickness of 110 μm and placed in glass vessels with a volume of 21 l. A preliminary inhibitor of the MSDA-1 corrosion inhibitor in quantities of 78.5 was introduced into the vessels with a microsyringe of the Gazochrome chromatograph in the form of a water-alcohol solution; 157; 314; 471 and 785 mcg. After 2 hours of exposure, the samples were removed and the optical density was determined by photometry at 495 nm. Then six of the same samples were placed in glass vessels of the same volume, containing 200 μg of the corrosion inhibitor MSDA-1 in each. The exposure time of the samples was also 2 hours. After the end of the exposure, the samples were photometric; the obtained values of optical density and the corresponding values of the concentrations of the corrosion inhibitor, determined using a graded graph, are given in table 1.

где n число измерений,
n 6;
Δ С_i отклонение измерения от среднего арифметического,

, Δ С_i= C_i

. Случайную составляющую погрешности вычисляли по формуле:
S

В данном примере S 0,66 мг/м³; S

2,90%
П р и м е р 2. К 3 г порошка ПП добавили 27,7 мл раствора биндона в четырерххлористом углероде, содержащем 1,5 мг биндона (0,0034 мас.). Полученную массу поместили в колбу роторного испарителя и при постоянном перемешивании растворитель удалили. Индикаторный материал прессовали при температуре 185±3^оС и давлении 3 МПа. Из полученной пленки толщиной 500 мкм вырезали прямоугольные образцы размером 8х20 мм и поместили в стеклянные сосуды объемом 21 л. В сосуд предварительно микрошприцем хроматографа "Газохром" ввели дициклогексиламин в количествах 38,0; 76,0; 152; 304,1 и 456,1 мкг. После 30 мин экспозиции образцы извлекали и фотометрированием при 495 мм определяли оптическую плотность. Затем шесть таких же образцов помещали в стеклянные сосуды того же объема, содержащие по 50 мкг дициклогексиламина. Время экспозиции образцов составляло также 30 мин. После окончания экспозиции образцы фотометрировали; полученные значения оптической плотности и соответствующие им значения концентраций дициклогексиламина, определенные с использованием градуировочного графика, приведены в табл.2.The random component error was calculated by calculating the mean square deviation according to the formula
S

where n is the number of measurements
n 6;
Δ With _{i the} deviation of the measurement from the arithmetic mean,

, Δ С _i = C _i

. The random component of the error was calculated by the formula:
S

In this example, S 0.66 mg / m ³ ; S

2.90%
PRI me R 2. To 3 g of PP powder was added 27.7 ml of a solution of bindone in carbon tetrachloride containing 1.5 mg of bindon (0.0034 wt.). The resulting mass was placed in a flask of a rotary evaporator and with constant stirring, the solvent was removed. A display material was pressed at 185 ± 3 ° ^C and a pressure of 3 MPa. Rectangular samples 8 × 20 mm in size were cut from the obtained film with a thickness of 500 μm and placed in glass vessels with a volume of 21 l. Dicyclohexylamine in amounts of 38.0 was introduced into the vessel beforehand with the microsyringe of the Gasochrome chromatograph; 76.0; 152; 304.1 and 456.1 mcg. After 30 minutes of exposure, the samples were removed and the optical density was determined by photometry at 495 mm. Then six of the same samples were placed in glass vessels of the same volume containing 50 μg of dicyclohexylamine. The exposure time of the samples was also 30 min. After the exposure, the samples were photometric; the obtained values of optical density and the corresponding values of the concentrations of dicyclohexylamine, determined using the calibration curve, are given in table 2.

 The random component error and the standard deviation were calculated in the same way as in example 1.

In this example, S 0.18 mg / m ³ ; S 3.01%
PRI me R 3. 1.5 g SKI-3 was placed in 100 ml of a suspension of bindone in carbon tetrachloride containing 30.6 mg of bindon. The resulting mass was heated to the boiling point of the solvent and boiled until the rubber was completely dissolved, then films with a thickness of 20 μm were obtained from it by irrigation. Rectangular samples 8x20 mm in size were cut from the film and placed in a 21-liter vessel containing 59.2; 118.4; 236.8; 355.3; 473.3 and 710.6 mcg. After 2 hours of exposure, the samples were removed and the optical density was determined by photometry at 495 nm. Then six of the same samples were placed in six glass vessels containing 500 μg of inhibitor. After the end of the exposure, the samples were photometric, the obtained values of optical density and the corresponding values of the concentrations of the corrosion inhibitor IFKHANGAZ-1, determined using the calibration curve, are shown in Table 3.

 The random component of the error and the standard deviation were calculated in the same way as in example 1.

1,38%
П р и м е р 4. К 2 г порошка ПЭВД добавили 73,8 мл раствора биндона в четыреххлористом углероде, содержащем 4,0 мг биндона (0,0034 мас.). Полученную массу поместили в колбу роторного испарителя и при постоянном перемешивании растворитель удалили. Индикаторный материал прессовали при температуре 130±3^оС и давлении 5 МПа. Из полученной пленки толщиной 80 мкм вырезали прямоугольные образцы размером 8х20 мм и поместили в стеклянные сосуды объемом 21 л, в которые предварительно был введен ингибитор коррозии ВНХ-Л-49 в количествах 39,0; 78,1; 156,2; 234,4; 312,4; 468,8 мкг. После 1 ч экспозиции образцы извлекали и фотометрированием при 495 нм определяли оптическую плотность. Затем шесть таких же образцов помещали в стеклянные сосуды того же объема, содержащие по 100 мкг ингибитора коррозии ВНХ-Л-49 в каждом. Время экспозиции образцов составляло также 1 ч. После окончания экспозиции образцы фотометрировали; полученные значения оптической плотности и соответствующие им значения концентраций ингибитора коррозии, определенные с использованием градуировочного графика, приведены в табл.4.In this example: S 0.81 mg / m ³ ; S

1.38%
PRI me R 4. To 2 g of LDPE powder was added 73.8 ml of a solution of bindon in carbon tetrachloride containing 4.0 mg of bindon (0.0034 wt.). The resulting mass was placed in a flask of a rotary evaporator and with constant stirring, the solvent was removed. A display material was pressed at 130 ± 3 ° ^C and a pressure of 5 MPa. Rectangular samples 8x20 mm in size were cut out of the obtained film with a thickness of 80 μm and placed in glass vessels with a volume of 21 l, into which the corrosion inhibitor BHX-L-49 was previously introduced in amounts of 39.0; 78.1; 156.2; 234.4; 312.4; 468.8 mcg. After 1 h of exposure, the samples were removed and the optical density was determined by photometry at 495 nm. Then six of the same samples were placed in glass vessels of the same volume, containing 100 μg of the corrosion inhibitor BX-L-49 in each. The exposure time of the samples was also 1 hour. After the end of the exposure, the samples were photometric; the obtained values of optical density and the corresponding values of the concentrations of the corrosion inhibitor, determined using the calibration curve, are given in table 4.

 The random component of the error and the standard deviation were calculated in the same way as in example 1.

1,38%In this example: S 0.168 mg / m ³ ; S

1.38%

Claims (1)

 A METHOD FOR DETERMINING CORROSION INHIBITORS BASED ON AMINS IN AIR, consisting in preparing a polymer-based indicator tape containing a color reagent, exposing the indicator tape in an air environment containing a detectable amine, detecting a color change of the indicator tape and determining the color of the amine content air, characterized in that for the preparation of the indicator tape polymer powder with a glass transition temperature below the temperature at which the determination is made, mix with a solution of anhydro-bis-indanedione-1,6 color reagent in carbon tetrachloride to a color reagent content in the polymer of 0.05 2.00% by weight of the dry indicator tape, carbon tetrachloride is removed by drying, the indicator tape is formed into a film thickness of 20 500 μm, registration the color change of the indicator tape after exposure is carried out by photometry in the region of 450 510 nm, the content of inhibitors in the air is determined according to a calibration graph obtained previously by exposing samples of the same film in air an ear with a known content of a detectable inhibitor at the same temperature at which the determination is made.

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