A rapid detection method of neutral defatting agent

Abstract

The application discloses a rapid detection method of neutral defatting agent, acid solution is quantitatively added in a certain volume of defatting liquid, the higher the defatting agent concentration is, the more acid is consumed, that is, the higher the pH value is, and vice versa, then the measured pH value is nonlinearly polynomially fitted with the defatting agent concentration to obtain a relationship function of both, and then the defatting agent concentration in the defatting liquid on site is calculated by using the relationship function; the application adopts common laboratory equipment and vessels such as a pH meter, an adjustable pipette and a volumetric flask, does not need to use special equipment and devices, is low in cost and simple in operation; the operation process of the application is short, the requirement for the operation experience of personnel is not high, the application is easy to master, the defatting liquid concentration adjustment time is effectively shortened, the work efficiency is improved, and the problem of low accuracy of the neutral defatting agent concentration determined by the weight method and the titration method is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analysis and detection, in particular to a rapid detection method of neutral degreasing agent. BACKGROUND

[0002] In some high-quality metal materials such as the degreasing process of precision copper strip, in order to remove the surface oil, the surface is usually cleaned with a suitable concentration of degreasing agent. In order to avoid the corrosion of the metal surface caused by the acidic or alkaline environment, it is required that the pH value of the degreasing agent used should be kept neutral. Such degreasing agent is usually composed of various surfactants, penetrants and corrosion inhibitors, and the working pH value is about 7-8. It has been widely used in the production process of copper and copper alloy strip. During the use of the degreasing agent, the effective components will be continuously lost in the production process, so it is necessary to supplement the original liquid to the degreasing tank to ensure that the concentration of the degreasing liquid in the degreasing tank is within a reasonable preset range, otherwise it will directly affect the degreasing effect and the surface quality.

[0003] The commonly used methods for detecting the concentration of degreasing agent include drying and weighing method and titration method, but both of them have great limitations. The drying and weighing method has a long detection period, and because the degreasing liquid will be mixed with many interfering factors such as oil, ash and metal ions during use, the detection result is often higher and the accuracy is lower. The titration method generally uses hydrochloric acid or sulfuric acid standard solution to titrate the alkaline components in the degreasing liquid, and is mainly applied to alkaline degreasing agents. For neutral degreasing agents, because the acidity and alkalinity are neutral, the volume of the acid and alkali standard solution consumed by the titration method is very small, resulting in a large detection error. The titration method also requires the operator to have certain literacy and operation experience. Guo Qiang et al. disclosed an industrial online automatic titration system and method for detecting the concentration of degreasing agent, Wei Fei et al. disclosed an online detection and control device for the concentration of degreasing agent, and Guo Tingyi disclosed a titration device for detecting the concentration of degreasing agent. The basic principles of the above-mentioned methods are titration method, which is suitable for alkaline degreasing agents, and the detection accuracy for neutral degreasing agents is poor, and special equipment must be used, so the universal applicability is not strong.

[0004] In view of the above reasons, a rapid detection method of neutral degreasing agent is developed. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, provide a rapid detection method of neutral degreasing agent, which has a short operation process, requires no high operation experience, is easy to master, and can be completed in 2-3 minutes after the work curve fitting is completed, effectively shortens the degreasing liquid concentration adjustment time, improves the work efficiency, and the work curve and the relationship function can be used for 1-2 months. The method also has good precision and accuracy, and solves the problem of low accuracy of weight method and titration method in detecting the concentration of neutral degreasing agent.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a rapid detection method for neutral degreasing agents, wherein an acid solution is quantitatively added to a certain volume of degreasing liquid. The higher the concentration of the degreasing agent, the more acid is consumed in the reaction, i.e., the higher the pH value, and vice versa. Then, the measured pH value and the degreasing agent concentration are fitted with a nonlinear polynomial to obtain the relationship function between the two, and then the concentration of the degreasing agent in the degreasing liquid on site is calculated using the relationship function.

[0007] Furthermore, the specific steps of the rapid detection method are as follows:

[0008] Step 1. Preparation of working curve solution: In eight 100mL volumetric flasks, use an adjustable pipette to pipette 0.50mL, 1.00mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL, 3.50mL, and 4.00mL of degreasing agent stock solution, respectively, and dilute with water to the mark. Mix well. The concentrations of this working curve solution are 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, and 4.00%, respectively.

[0009] Step 2. Nonlinear Fitting of the Working Curve: Add acid solution to each of the eight volumetric flasks using an adjustable pipette, with a volume ranging from 1.00 mL to 10.00 mL. Mix well and measure the pH value of the liquid in each of the eight volumetric flasks using a pH meter. Plot the pH value on the x-axis and the concentration on the y-axis, and perform 3rd to 6th order nonlinear polynomial fitting using Excel to obtain the working curve and the relationship function between the two. The fitted working curve and relationship function are obtained when the acid solution concentration does not change significantly.

[0010] Step 3. Sample determination: Add the degreasing solution sample to a 100mL volumetric flask to the mark, add the same volume and type of acid solution as used for fitting the working curve, mix well, and measure its pH value with a pH meter.

[0011] Step 4. Calculation of results: Substitute the measured pH value into the pre-fitted relationship function, and use EXCEL or other calculation tools to quickly calculate the concentration of degreasing agent in the sample;

[0012] Step 5. Daily quality monitoring: Prepare test solutions of known concentrations using the degreasing agent stock solution weekly, and measure according to Steps 3 and 4. Determine whether to recreate the working curve based on the deviation of the test results from the known results. The deviation should not exceed 0.15%.

[0013] Furthermore, the acid solution in step two is either hydrochloric acid or sulfuric acid, and the hydrogen ion concentration of the acid solution is 0.05-0.20 mol / L.

[0014] Further, the pH meter has the precision of 0.01 and has the automatic temperature compensation function.

[0015] Further, the order of the non-linear polynomial fitting in the step two is determined by the residual sum of squares of the working curve, that is, the smaller the calculated residual sum of squares of the working curve is, the better the fitting effect is.

[0016] Further, the concentration and volume of the acid solution in the step three are determined by the preset curve midpoint method, that is, taking the concentration as the vertical axis, taking the end point of the working concentration range of the degreasing agent as the vertical axis midpoint, taking the pH as the horizontal axis, taking the pH=4 as the horizontal axis midpoint, adjusting the pH value of the degreasing agent with the vertical axis midpoint concentration to the vicinity of 4, and determining the concentration and volume of the added acid solution by the amount of the consumed acid.

[0017] The beneficial effects of the present application are: compared with the prior art, the present application adopts the pH meter, the adjustable pipette, the volumetric flask and other commonly used laboratory equipment and vessels, does not need to use special equipment and devices, has low cost and simple operation; the operation process of the present application is short, the personnel operation experience requirement is not high, is easy to master, after the working curve fitting is completed in advance, the determination of each sample can be completed in 2-3 minutes, the degreasing agent concentration adjustment time is effectively shortened, the working efficiency is improved, the working curve and the relationship function can be used for 1-2 months, the present application also has good precision and correctness, solves the problem of low accuracy of the neutral degreasing agent concentration determined by the gravimetric method and the titration method; the part not detailed in the present application is the commonly used technology. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present application will be further described below in combination with the drawings:

[0019] Figure 1 is the working curve and the relationship function diagram. DETAILED DESCRIPTION

[0020] The present application will be further described below in combination with the embodiments and the specific implementation manners:

[0021] Embodiment 1

[0022] A process of analyzing the concentration of the neutral degreasing agent for a copper strip production:

[0023] 1. Preparation of the working curve solution: in 8 100mL volumetric flasks, 0.50mL, 1.00mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL, 3.50mL and 4.00mL of the degreasing agent stock solution are respectively taken by the adjustable pipette, and diluted to the scale with water and mixed, and the concentrations of the working curve solutions are respectively 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50% and 4.00%;

[0024] 2. Nonlinear fitting of working curve: 3.00 mL of 0.10 mol / L hydrochloric acid solution was added into each of the above eight volumetric flasks using a adjustable pipette, and the pH values of the solutions in the eight volumetric flasks were measured on a pH meter. The results are shown in Table 1.

[0025] Table 1 pH values of working curve solutions after adding acid

[0026]

[0027] The working curve and the relationship function between the two were obtained by using Excel to perform 3rd-6th order nonlinear polynomial fitting with the pH value as the abscissa and the concentration as the ordinate. Figure 1 ;

[0028] The residual sum of squares of the 3rd-6th order fitting was calculated, and the residual sum of squares of the 4th order fitting was the smallest, i.e. 0.0050%, and the 4th order fitting function was obtained as follows: y = -0.0369x 4 + 0.8721x 3 - 6.7989x 2 + 22.655x - 26.404.

[0029] 3. Determination of sample: the sample of degreasing solution to be determined was added into a 100 mL volumetric flask to the calibration line, 3.00 mL of 0.10 mol / L hydrochloric acid solution was added, and the pH value was measured to be 4.05.

[0030] 4. Calculation of results: the relationship function y = -0.0369x 4 + 0.8721x 3 - 6.7989x 2 + 22.655x - 26.404 was edited as a formula in EXCEL software, and the measured pH value 4.08 was input into the edited formula, and the concentration of the degreasing solution was automatically calculated to be 1.85%.

[0031] 5. Interference analysis

[0032] In addition to the degreasing agent, the degreasing solution generally contains lubricating oil, ash and metal ions; the content of ash and metal ions is relatively low, and the amount of consumed hydrochloric acid can be ignored, so the interference of ash and metal ions can be ignored. The lubricating oil is cleaned from the metal surface after long-term work of the degreasing solution, and the content can reach 2%-3%.

[0033] To investigate the interference of lubricating oil, three pre-prepared degreasing liquids with concentrations of 1.00%, 2.00% and 3.00% were transferred into 100 mL volumetric flasks, respectively, and diluted to the mark. Then, 3 mL of lubricating oil was added to each flask, and the mixture was shaken thoroughly. The concentration of the degreasing liquid was determined according to the method, and the results were compared with those of the samples without lubricating oil. The results in Table 2 show that the influence of lubricating oil in the degreasing liquid on the detection results can be ignored.

[0034] Table 2: Interference test of lubricating oil addition

[0035]

[0036] 6. Repetitive test

[0037] Three samples of degreasing liquid were taken at different times in the production site, and the concentration was determined 6 times under repetitive conditions according to the method. The relative standard deviation (RSD) was between 0.85% and 1.17%, indicating that the method had good precision. The determination results are shown in Table 3.

[0038] Table 3: Repetitive test

[0039]

[0040] 7. Spiking recovery test

[0041] Three samples of degreasing liquid that had been previously tested were taken in three 100 mL volumetric flasks, and 1.00 mL of degreasing agent stock solution was added to each flask. The concentration was determined according to the method, and the spiking recovery rate was calculated to evaluate the accuracy of the method. The test results in Table 4 show that the spiking recovery rate was between 98.52% and 103.34%, indicating that the method had high accuracy and could meet the use requirements.

[0042] Table 4: Spiking recovery test

[0043]

[0044] The method of the present application is used to determine the concentration of neutral degreasing agent, and the method has good accuracy and precision, the spiking recovery rate meets the requirements, the determination results are accurate and reliable, the instrument and equipment used in the method are low in cost, easy to operate and easy to master, can effectively guide the use of degreasing liquid in the production process, and improve the degreasing efficiency of metal surface. The concentration adjustment time of the degreasing liquid can be effectively shortened, and the work efficiency can be improved.

Claims

1. A rapid detection method for a neutral degreasing agent, characterized in that: A certain amount of acid solution is added to a certain volume of degreasing liquid. The higher the concentration of degreasing agent, the more acid is consumed in the reaction, i.e., the higher the pH value, and vice versa. Then, the measured pH value and the concentration of degreasing agent are fitted with a nonlinear polynomial to obtain the relationship function between the two. Then, the concentration of degreasing agent in the degreasing liquid on site is calculated using this relationship function. The specific steps of the rapid detection method are as follows: Step 1. Preparation of the working curve solution: In eight 100mL volumetric flasks, use an adjustable pipette to pipette 0.50mL, 1.00mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL, 3.50mL, and 4.00mL of degreasing agent stock solution, respectively, and dilute with water to the mark. Mix well. The concentrations of this working curve solution are 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, and 4.00%, respectively; Step 2. Nonlinear fitting of the working curve: Use an adjustable pipette to... Add acid solution to each of the above 8 volumetric flasks, with a volume ranging from 1.00 mL to 10.00 mL. Mix well and measure the pH value of the liquid in each of the 8 volumetric flasks using a pH meter. Plot the pH value on the x-axis and the concentration on the y-axis, and use Excel to perform a 3rd to 6th order nonlinear polynomial fitting to obtain the working curve and the relationship function between the two. The working curve and relationship function are fitted when the acid solution concentration does not change significantly. Step 3. Sample determination: Add the degreasing liquid sample to a 100 mL volumetric flask to the mark, add the same volume and type of acid solution as when fitting the working curve, mix well, and measure its pH value using a pH meter. Step 4. Calculation of Results: Substitute the measured pH value into the pre-fitted relational function, and use EXCEL or other calculation tools to quickly calculate the concentration of degreasing agent in the sample; Step 5. Daily Quality Monitoring: Prepare test solutions of known concentrations using the degreasing agent stock solution weekly, and measure according to Step 3 and Step 4. Determine whether to recreate the working curve based on the degree of deviation between the measured results and the known results, with the deviation not exceeding 0.15%.

2. The rapid detection method for a neutral degreasing agent according to claim 1, characterized in that: The acid solution in step two is either hydrochloric acid or sulfuric acid, and the hydrogen ion concentration of the acid solution is 0.05-0.20 mol / L.

3. The rapid detection method for a neutral degreasing agent according to claim 1, characterized in that: The pH meter has an accuracy of 0.01 and features automatic temperature compensation.

4. The rapid detection method for a neutral degreasing agent according to claim 1, characterized in that: The order of the nonlinear polynomial fitting in step two is determined by the sum of squared residuals of the working curve; that is, the smaller the sum of squared residuals of the working curve, the better the fitting effect.

5. The rapid detection method for a neutral degreasing agent according to claim 1, characterized in that: The concentration and volume of the acid solution in step three are determined by the midpoint method of a preset curve. That is, the midpoint of the working concentration range of the degreasing agent is set as the vertical axis with concentration as the vertical axis and pH is set as the horizontal axis with pH=4 as the horizontal axis midpoint. The pH value of the degreasing solution with concentration as the vertical axis midpoint is adjusted to around 4, and the concentration and volume of the acid solution added are determined by the amount of acid consumed.

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