Celluloid nitrocotton stability quantitative determination method based on conductivity analysis

Abstract

The invention provides a celluloid nitrocotton stability quantitative determination method based on conductivity analysis, and the method comprises the following steps: determining the conductivity of standard nitrogen oxide gas dissolved in an aqueous solution by adopting a conductivity meter through a standard gas simulation mode according to the criterion of Beckmann-Lockg method 2mL / g; taking the numerical value as a stability index critical value of the celluloid nitrocotton; the method comprises the following steps: absorbing nitrocotton with the same mass by using ultrapure water, heating at 132 DEG C for 2 hours, releasing nitrogen oxide gas, recording the change value of the conductivity in the solution along with time in real time by using an oxidation stability tester, obtaining the change value of the conductivity after 2 hours, and determining the content of nitrogen oxide according to the comparison between the conductivity value and a critical value. And judging whether the stability of the celluloid nitrocotton sample is qualified or not. The method provided by the invention can solve the technical problem that accurate quantitative judgment is difficult to realize due to large sample quantity, high safety risk, tedious operation process and large color change error of test paper observed by human eyes in the traditional method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of physical and chemical analysis and detection, and relates to nitrocellulose, in particular to a quantitative determination method for the stability of collodion nitrocellulose based on conductivity analysis. BACKGROUND

[0002] Nitrocellulose, also known as cellulose nitrate, is an important industrial raw material. Collodion is a plastic material made of nitrocellulose as the main component and adding additives such as camphor. It is the final product, usually hard sheet, rod, etc. Nitrocellulose is the core material of collodion, accounting for about 70wt%, and there is no collodion without nitrocellulose. Collodion with nitrocellulose is widely used in manufacturing table tennis, glasses, toothbrush handles, piano keys, educational supplies, X-ray film, etc. It has the characteristics of easy molding, aging resistance, good strength and flexibility, and high transparency.

[0003] There are many quality indicators for collodion nitrocellulose, including nitrogen content, viscosity, solubility, whiteness, light transmittance, stability, light transmittance, flash point, acidity, ash content, etc. Since nitrocellulose is a dangerous chemical, its stability is an important test index in quality inspection. The stability test method specified in "WJ / T 9015-1993 Collodion Nitrocellulose" is 80℃ heat resistance test (Abel method) and 132℃ heat resistance test (Bekman-Runk method). These two methods play an important role in daily inspection, but they also have certain limitations. The Abel method is to put a quantitative sample into a special test tube and heat it at 80℃ to decompose. The heating time for the released gas to make the iodized potassium starch test paper appear yellow-brown at the dry-wet boundary is measured. The Abel method has the problems of large eye observation error and color change result judgment depending on experience. The Bekman-Runk method puts the sample in a special test tube and heats it at 132℃. The released nitrogen oxide gas is absorbed by water, titrated with sodium hydroxide solution and calculated. The Bekman-Runk method has the problems of multiple chemical titration operation steps and complexity. Therefore, it is necessary to improve the stability test method of collodion nitrocellulose. If a new method based on a new technical principle can detect the amount of decomposition gas product of nitrocellulose under heating conditions, and the sample amount is small, real-time monitoring can be achieved, and a quantitative criterion can be given, it will be an important supplement to the stability test method of collodion nitrocellulose.

[0004] The experimental method for the chemical stability of the celluloid nitrocellulose specified in "WJ / T 9015-1993 celluloid nitrocellulose" is that 2g of the sample is weighed, heated at 132 DEG C for 2h, and then the oxidized nitrogen decomposed in the heating is washed into a conical flask with water, and the oxidized nitrogen is determined by the iodine quantity method, and the product qualified criterion is 2mL / g. Generally, since the unqualified sample in stability has a large safety hazard, the unqualified product is directly destroyed, and therefore the unqualified sample, especially the extreme sample with the stability index of 2mL / g, cannot be obtained, and therefore an indirect simulation method is needed to establish the corresponding relationship between the criterion of the new method and the Beckmann-Junk method, so as to provide data basis for the criterion of the new method.

[0005] In summary, the traditional celluloid nitrocellulose stability detection method of the Abell method has the problems of large observation error of the test paper discoloration by the human eye, and the end point judgment depends on experience, and the Beckmann-Junk method has the problems of full process dependence on manual operation and complicated operation steps, and the like. In order to make up for the deficiencies of the existing stability detection method, it is urgent to provide a detection method with less sample amount, simple operation, real-time dynamic monitoring, and quantitative criterion, so as to provide a new evaluation method for the celluloid nitrocellulose stability detection. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a celluloid nitrocellulose stability quantitative determination method based on conductivity analysis, so as to solve the technical problem that the traditional method is difficult to realize accurate quantitative determination.

[0007] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0008] A celluloid nitrocellulose stability quantitative determination method based on conductivity analysis, according to the criterion of 2mL / g of the Beckmann-Junk method, the conductivity of the standard nitrogen oxide gas dissolved in the aqueous solution is determined by the conductivity meter in the form of standard gas simulation, and the value is used as the stability index critical value of the celluloid nitrocellulose; the same mass of nitrocellulose is heated at 132 DEG C for 2h, and the nitrogen oxide gas released in the heating is absorbed by the ultrapure water, and the change value of the conductivity of the solution with time is recorded in real time by the oxidation stability tester, and the change value of the conductivity after 2h is obtained, and according to the comparison between the conductivity value and the critical value, the determination of whether the celluloid nitrocellulose sample is qualified or not is performed.

[0009] Compared with the prior art, the present application has the following technical effects:

[0010] (I) This invention provides a novel principle-based stability detection technology based on the absorption of decomposition gas products from celluloid nitrocellulose by ultrapure water under heating conditions, and the monitoring of changes in the conductivity of the aqueous solution. This method solves the technical problems of traditional methods, which suffer from high safety risks due to large sample volumes, cumbersome operation procedures, and large errors in visual observation of test paper color changes, making accurate quantitative determination difficult.

[0011] (II) This invention first uses a well-sealed, airtight injection needle to draw a certain amount of nitrogen oxide standard gas and inject it into ultrapure water. The conductivity of the solution is then measured using a conventional conductivity meter to obtain the critical value for the conductivity of celluloid nitrocellulose. Using a commercially available oxidation stability tester, an equal amount of celluloid nitrocellulose is weighed and heated at 132°C for 2 hours. The decomposed nitrogen oxide gas is absorbed by the ultrapure water. The change in the conductivity of the aqueous solution is measured and recorded in real time. The change in conductivity is compared with the critical value to evaluate the stability of the celluloid nitrocellulose product.

[0012] (III) The experimental process of this invention is highly automated and easy to operate, and can provide critical values ​​for stability. It solves the problems of cumbersome operation and reliance on human experience in traditional methods, and can provide a new technical means for the quantitative analysis of the stability of celluloid nitrocellulose samples. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the experimental method of the present invention.

[0014] Figure 2 Graph of conductivity test of standard gas solution

[0015] Figure 3 The graph shows the change in conductivity of a 500mg celluloid nitrocellulose sample over time after heating at 132℃ for 2 hours.

[0016] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, all materials and devices used in this invention are those known in the art.

[0018] The principle of this invention is as follows:

[0019] During the thermal decomposition of celluloid nitrocellulose, small-molecule nitrogen oxide gaseous products are released. These gaseous products are purged into a water-containing measuring cup using a carrier gas, causing a change in the conductivity of the aqueous solution, thus quantifying the amount of nitrogen oxide gas generated. Based on the Beckman-Junker criterion, the critical value for the conductivity method is obtained through standard gas simulation. Therefore, by measuring the change in conductivity of celluloid nitrocellulose, the stability of the celluloid nitrocellulose can be determined.

[0020] The experimental method principle diagram is as follows: Figure 1 As shown, by comparing with standard methods, a pass criterion for the chemical stability of celluloid nitrocellulose was obtained through conductivity determination. The experimental apparatus used in the conductivity method was a commercially available conductivity meter. After obtaining the conductivity critical value, an equal amount of celluloid nitrocellulose was weighed using a commercially available oxidation stability tester and heated at 132℃ for 2 hours. The decomposed nitrogen oxide gas was absorbed by ultrapure water, and the change in the conductivity of the aqueous solution was measured in real time. After 2 hours, if the conductivity value was less than the critical value, the nitrocellulose sample was considered to be stable; otherwise, it was considered unqualified. This method can be used to evaluate the stability of celluloid nitrocellulose.

[0021] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0022] Example:

[0023] This embodiment provides a method for quantitatively determining the stability of celluloid nitrocellulose based on conductivity analysis, characterized by the following steps:

[0024] Step 1: Based on the Beckman-Junker stability index of 2 mL / g for celluloid nitrocellulose, and the sample mass of 500 mg calculated by the conductivity method, the volume of nitrogen oxide gas is 1 mL. Nitrogen oxide standard gas is extracted using an airtight microsyringe and injected into a 50 mL stoppered conical flask containing 25 mL of ultrapure water. The stopper is then quickly closed and the flask is shaken well.

[0025] In this embodiment, the airtight microsyringe is 1000uL, manufactured by Shanghai Bolige Industry & Trade Co., Ltd.

[0026] In this embodiment, the nitric oxide standard gas used is nitric oxide standard gas with a concentration of 28.90 μmol / mol, standard substance number: GSB 07-1406-2019, Dalian Date Gas Co., Ltd.

[0027] Step 2: After the standard nitric oxide gas has dissolved and been absorbed, the conductivity of the solution in the conical flask is measured using a conductivity meter. Before use, the electrode is rinsed twice with deionized water at a concentration of 0.5 μS / cm. The test is repeated multiple times at 25°C. This conductivity value is the critical value for the stability of celluloid nitrocellulose.

[0028] In this embodiment, the conductivity meter used is a DDS-307 conductivity meter, manufactured by Shanghai Instrument & Electronics Scientific Instruments Co., Ltd.

[0029] In this embodiment, typical test results are as follows: Figure 2As shown in the figure, the measurement was repeated 6 times, and the experimental results are shown in Table 1.

[0030] Table 1 Results of conductivity measurement of standard gas solutions

[0031] Item Conductivity value First test 10.81 Second test 10.81 Third test 10.80 Fourth test 10.81 Fifth test 10.79 Sixth test 10.82 Average value 10.81

[0032] Step 3: Use an oxidation stability tester to record the change in conductivity of celluloid nitrocellulose after the gaseous products dissolve in water under heating conditions over time; ensure that all pipelines of the oxidation stability tester are clean and dry before measurement.

[0033] In this embodiment, the oxidation stability tester used is the Model 892 oxidation stability tester, manufactured by Metrohm, Switzerland.

[0034] Step 4: The celluloid nitrocellulose sample needs to be dried before weighing to ensure that the moisture content of the sample before heating does not exceed 1.0 wt% to avoid the influence of moisture on conductivity; accurately weigh the sample and spread it evenly at the bottom of the reaction tube.

[0035] Step 5: Fill the measuring cup with 25 mL of ultrapure water, connect it to the oxidation stability tester, and set the gas flow rate, temperature to 132℃, and time to 2 hours. First, turn on the gas flow rate, and after checking that the oxidation stability tester and pipeline are properly sealed, turn on the heating.

[0036] Step 6: Once the conditions of the oxidation stability tester reach the set parameters such as gas flow rate and temperature, press the start button on the oxidation stability tester and immediately place the reaction tube containing the sample onto the heating module. The oxidation stability tester will then begin operation.

[0037] Step 7: During the test, the oxidation stability tester records the change curve of conductivity with heating time in real time. After heating at 132℃ for 2 hours, the change value of conductivity is observed. If the conductivity value is less than the critical value after 2 hours, the stability of the nitrocellulose sample is considered to be qualified; otherwise, it is considered unqualified.

[0038] In this embodiment, the conductivity of a batch of celluloid nitrocellulose (NC) samples was obtained as a function of time after heating at 132°C for 2 hours. Figure 3 As shown, by Figure 3 It can be seen that the conductivity of the sample increases continuously with the extension of heating time. After heating for 2 hours, the conductivity of the sample changes by 2.53 μS / cm, which is less than the critical value of 10.81 μS / cm, indicating that the stability of the sample is qualified.

Claims

1. A method for quantitatively determining the stability of nitrocellulose based on conductivity analysis, characterized by, The method is based on the Beckman-Junk method 2mL / g criterion, through the standard gas simulation mode, using conductivity meter to determine the conductivity of standard nitrogen oxide gas dissolved in aqueous solution, which is used as the critical value of the stability index of celluloid nitrocellulose; the same mass of nitrocellulose is heated in ultrapure water at 132℃ for 2h, and the nitrogen oxide gas released by decomposition is absorbed, and the change value of conductivity of the solution with time is recorded in real time by using the oxidation stability tester, and the change value of conductivity after 2h is obtained, and the comparison of the conductivity value and the critical value is carried out to determine whether the stability of the celluloid nitrocellulose sample is qualified or not.

2. The method for quantitatively determining the stability of nitrocellulose celluloid based on conductivity analysis according to claim 1, wherein The method comprises the following steps: Step one, according to the stability qualified index 2mL / g of celluloid nitrocellulose in the Beckman-Junk method, the volume of nitrogen oxide gas is converted according to the sample mass of the conductivity method, and the nitrogen oxide standard gas is extracted by using airtight micro-sampler and injected into a 50mL conical flask with a stopper containing 25mL ultrapure water, and the stopper is quickly covered and shaken uniformly; Step two, the conductivity of the solution in the conical flask is measured by using a conductivity meter, and the electrodes are washed twice with 0.5μS / cm deionized water before use, and repeated testing is carried out at 25℃, and the conductivity value is the critical value of the stability of celluloid nitrocellulose; Step three, the change value of conductivity of celluloid nitrocellulose with time after the gaseous product is dissolved in water under heating condition is recorded by using the oxidation stability tester; Step four, the celluloid nitrocellulose sample needs to be dried before weighing to ensure that the moisture content of the sample before heating should not exceed 1.0wt%; accurately weigh the sample and evenly spread it on the bottom of the reaction tube; Step five, 25mL ultrapure water is loaded into the measuring cup, the oxidation stability tester is connected, the gas flow, temperature 132℃ and time 2h of the oxidation stability tester are set; first open the gas flow, check that the oxidation stability tester and pipeline are in good sealing condition, and then open the heating; Step six, after the oxidation stability tester reaches the set gas flow, temperature and other parameters, press the start button on the oxidation stability tester, immediately place the sample-loaded reaction tube on the heating module, and the oxidation stability tester starts to run; Step seven, during the test, the oxidation stability tester records the change curve of conductivity with heating time in real time, heats at 132℃ for 2h, and observes the change value of conductivity, and when the conductivity value is less than the critical value after 2h, it is considered that the stability of the nitrocellulose sample is qualified, otherwise it is considered unqualified.

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