Method for determining content of p-tert-butyl benzoic acid in PVC heat stabilizer

Abstract

The application discloses a method for determining the content of p-t-butylbenzoic acid in PVC heat stabilizer, which comprises the following steps: S1, mixing the stabilizer sample with hydrochloric acid and adding petroleum ether to obtain a first product with obvious stratification; S2, sucking the upper oil agent of the first product out with a dropper, storing it for later testing, filtering the petroleum ether layer and the precipitated part of the first product, washing the precipitated part after filtration with petroleum ether, drying, obtaining a second product, weighing and recording the mass; S3, filtering the upper oil agent sucked out with the dropper with an organic filter membrane to obtain free p-t-butylbenzoic acid, determining the content of the free p-t-butylbenzoic acid through a GC-MS instrument, and the content of the p-t-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of the p-t-butylbenzoic acid in the precipitated part and the content of the free p-t-butylbenzoic acid. The application can effectively detect the content of the p-t-butylbenzoic acid in the heat stabilizer, so that the formula can be better adjusted and the performance of the stabilizer can be improved.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, specifically to a method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers. Background Technology

[0002] Polyvinyl chloride (PVC) is one of the five major general-purpose plastics. Its inherent thermal stability is relatively poor, and its products tend to darken in color and degrade in performance during processing and molding, thus limiting its application and development. Therefore, appropriate heat stabilizers must be added during processing. Currently, widely used PVC heat stabilizers include lead salts, organotin compounds, metal soaps, and rare earth compounds.

[0003] Metal soap stabilizers, with their advantages of good lubricity, low volatility, and ease of use, are seeing their usage increase year by year. Metal soaps generally refer to organometallic acid salts other than sodium and potassium. Their thermal stability is usually related to the ratio of each component. When added to PVC, they can replace unstable chloride ions and neutralize and absorb HCl. The chlorination products after the reaction do not accelerate resin degradation, thus exhibiting excellent long-term thermal stability.

[0004] Therefore, the content of metals and organic acids in stabilizers is crucial to their performance. While existing patents describe methods for detecting the content of metals such as barium and zinc in stabilizers, methods for testing the content of organic acids are rarely proposed. Furthermore, existing conventional methods suffer from problems such as complex sample preparation and significant discrepancies in quantitative results. Therefore, finding a simpler, faster, more convenient, and more effective method for detecting the content of certain organic acids in heat stabilizers is an urgent problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to propose a method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers, aiming to solve the problems of complex sample preparation, large differences in quantitative results, and complicated operation in existing methods for testing organic acid content.

[0006] To achieve the above objectives, this invention proposes a method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers, comprising the following steps:

[0007] S1. Mix the stabilizer sample with hydrochloric acid, add petroleum ether, and obtain the first product with obvious stratification.

[0008] S2. The upper oil layer of the first product is extracted with a dropper and stored for later testing. The petroleum ether layer and the precipitate of the first product are filtered, and the filtered precipitate is washed with petroleum ether, dried, and the second product is obtained. The weight of the second product is weighed and recorded.

[0009] S3. Filter the upper layer of oil drawn out by the dropper with an organic filter membrane to obtain an oil sample. Measure the content of free p-tert-butylbenzoic acid in the oil sample using a gas chromatography-mass spectrometry (GC-MS) instrument. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid.

[0010] Optionally, the determination of free p-tert-butylbenzoic acid content using the gas chromatography-mass spectrometry (GC-MS) instrument includes the following steps:

[0011] S31. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution;

[0012] S32. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations;

[0013] S33. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6;

[0014] S34. Use a gas chromatography-mass spectrometry (GC-MS) instrument to determine the chromatographic peak areas of the standards and samples. Plot a standard curve with the concentrations of standards 1-5 on the x-axis and the chromatographic peak areas determined by the GC-MS instrument on the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6.

[0015] Optionally, in step S31, the organic solvent is at least one of dichloromethane, petroleum ether, and methanol.

[0016] Optionally, in step S33, the oil sample is taken in a mass of 0.01 to 0.1 g and dispersed in 10 to 20 g of organic solvent.

[0017] Optionally, in step S1, the hydrochloric acid is concentrated hydrochloric acid, and the mass fraction of the hydrochloric acid is 36% to 38%.

[0018] Optionally, in step S1, the mass ratio of the stabilizer sample to hydrochloric acid is 5-10:3-7.

[0019] Optionally, in step S2, slow-speed filter paper is used for filtration, and the drying temperature is 50-90°C.

[0020] Optionally, in step S2, the drying time is 2 to 4 hours.

[0021] Optionally, in step S3, the washing is performed 1 to 5 times.

[0022] Optionally, in step S4, the test conditions for the gas chromatography-mass spectrometry (GC-MS) to determine the standard and sample are as follows:

[0023] Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm;

[0024] Detector: Flame ionization detector;

[0025] Testing chamber temperature: 300℃;

[0026] Vaporization chamber temperature: 300℃;

[0027] Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min;

[0028] Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0 mL / min;

[0029] Fuel gas: Hydrogen, purity ≥ 99.999%, flow rate 30 mL / min;

[0030] Combustion aid: Air, flow rate 400 mL / min.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) In the technical solution provided by the present invention, the total content of p-tert-butylbenzoic acid in the stabilizer can be determined by simple processing. The amount of organic solvent used in this process is small, which saves resources. The operation method is convenient and fast, and it is easy to achieve batch processing. The reaction process has a low temperature and high safety.

[0033] (2) The sample pretreatment process is simple, requiring only simple mixing of reactants. The filtration process is quick and efficient. After adding solvent, the target substance in the oil can be quickly transferred without much manpower or material resources. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is the infrared spectrum of the precipitate produced in Example 1 of the present invention;

[0036] Figure 2 This is a gas chromatogram of p-tert-butylbenzoic acid in Example 1 of the present invention.

[0037] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Given the limited existing methods for detecting the content of components in heat stabilizers, and the fact that conventional single testing methods such as HPLC, IC, and GCMS suffer from problems such as complex sample preparation and large discrepancies in quantitative results, this invention proposes a method for determining the content of some organic acids and metals in PVC heat stabilizers. This method aims to better adjust the formulation and improve the performance of the stabilizer, while also providing a new analytical approach for the detection of other components in heat stabilizers.

[0040] This invention proposes a method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers, comprising the following steps:

[0041] S1. Mix the stabilizer sample with hydrochloric acid, add petroleum ether, and obtain the first product with obvious stratification.

[0042] In this step, the hydrochloric acid is concentrated hydrochloric acid with a mass fraction of 36% to 38%, and the mass ratio of the stabilizer sample to hydrochloric acid is 5 to 10: 3 to 7. By adding appropriate amounts of hydrochloric acid and petroleum ether, the reaction is made sufficient, and the product can be clearly separated into layers.

[0043] S2. The upper oil layer of the first product is extracted with a dropper and stored for later testing. The petroleum ether layer and the precipitate of the first product are filtered, and the filtered precipitate is washed with petroleum ether, dried, and the second product is obtained. The weight of the second product is weighed and recorded.

[0044] In this step, the petroleum ether layer and the precipitate are filtered using slow-speed filter paper. After filtration, the product is placed in an oven for drying at a temperature of 50–90°C for 2–4 hours.

[0045] S3. Filter the upper layer of oil extracted by the dropper with an organic filter membrane to obtain an oil sample. Measure the content of free p-tert-butylbenzoic acid in the oil sample using a gas chromatography-mass spectrometry (GC-MS) instrument. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid.

[0046] In this step, the test conditions for measuring the standard and sample using the gas chromatography-mass spectrometry (GC-MS) are as follows:

[0047] Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm; Detector: Flame ionization detector; Detector temperature: 300℃; Vaporization chamber temperature: 300℃; Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min; Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0mL / min; Fuel gas: Hydrogen, purity ≥99.999%, flow rate 30mL / min; Combustion oxidizer: Air, flow rate 400mL / min.

[0048] The technical solution provided by this invention features a simple sample pretreatment process. It only requires simple mixing of reactants to obtain products with different layers, followed by weighing and further processing to obtain the p-tert-butylbenzoic acid content. The determination process uses a small amount of organic solvent, saving resources. The operation method is convenient and fast, and it is easy to achieve batch processing. The filtration process is short and efficient. After adding solvent, the target substance in the oil can be quickly transferred without much manpower or material resources. Furthermore, the reaction process has a low temperature and high safety.

[0049] Specifically, the determination of free p-tert-butylbenzoic acid using the gas chromatography-mass spectrometry (GC-MS) instrument includes the following steps:

[0050] S31. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution;

[0051] S32. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations;

[0052] S33. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6;

[0053] S34. Use a gas chromatography-mass spectrometry (GC-MS) instrument to determine the chromatographic peak areas of the standards and samples. Plot a standard curve with the concentrations of standards 1-5 on the x-axis and the chromatographic peak areas determined by the GC-MS instrument on the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6.

[0054] This embodiment provides the implementation steps of a specific measurement method:

[0055] (1) Sample processing

[0056] 4.95 g of stabilizer sample and 3.45 g of hydrochloric acid were placed in a beaker, and petroleum ether was added to cause the product to separate into distinct layers. The upper oil layer was aspirated with a dropper and stored. After filtering the petroleum ether layer and the precipitate using slow-speed filter paper, the product was washed three times with petroleum ether to remove the oil adhering to the precipitate surface. The product was dried in a 60 °C oven for 2 hours. After drying, the product was weighed and the mass was recorded. The upper oil layer was filtered through a 0.22 μm organic filter membrane and then used for gas chromatography-mass spectrometry (GC-MS) to determine the free p-tert-butylbenzoic acid content.

[0057] (2) External standard method for quantification

[0058] Disperse the standard p-tert-butylbenzoic acid reagent in dichloromethane solvent, and denote this as the diluent. Prepare five standard working solutions of different concentrations from the diluent, numbered 1, 2, 3, 4, and 5, with mass fractions of 0.1%, 0.125%, 0.167%, 0.25%, and 0.5%, respectively. Plot the standard working curve y = ax + b with concentration as the x-axis and peak area as the y-axis.

[0059] The separated oil sample was dispersed in dichloromethane solvent, numbered 6, and its content was recorded as C0. The peak area obtained after chromatographic analysis of the sample was substituted into the working curve to calculate the concentration C of p-tert-butylbenzoic acid in the test solution.

[0060] Calculate the content (%) of p-tert-butylbenzoic acid in the upper layer oil using the following formula (1):

[0061]

[0062] In the formula:

[0063] C: Content of p-tert-butylbenzoic acid in the test solution, %;

[0064] C0: Oil content in the sample, %;

[0065] W 上 The content of p-tert-butylbenzoic acid in the upper layer oil, %.

[0066] The final test result of this test method is the average of three parallel determinations, and the relative standard deviation of the parallel determination results is less than 10%.

[0067] (3) Calculation of the content of p-tert-butylbenzoic acid in the sample

[0068] The content (%) of p-tert-butylbenzoic acid in the precipitate can be calculated using formula (2) by recording the mass during the weighing of the precipitate:

[0069]

[0070] In the formula:

[0071] m: Mass recorded during sedimentation, in grams;

[0072] M: Mass of the stabilizer sample, g;

[0073] W 下 : Amount of p-tert-butylbenzoic acid precipitate, %.

[0074] The total content of p-tert-butylbenzoic acid in the stabilizer sample is the sum of the content in the precipitate and the content in the oil phase.

[0075] Calculate the total content (%) of p-tert-butylbenzoic acid in the stabilizer sample according to formula (3):

[0076] W 总 =W 上 +W 下 (3)

[0077] In the formula:

[0078] W 上 : Content of p-tert-butylbenzoic acid in the upper layer oil, %;

[0079] W 下 : Amount of p-tert-butylbenzoic acid precipitate, %.

[0080] W 总 : Total content of p-tert-butylbenzoic acid in the stabilizer sample, %.

[0081] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0082] Example 1: Method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers

[0083] (1) Sample processing

[0084] 4.993 g of stabilizer sample and 3.49 g of concentrated hydrochloric acid were placed in a beaker, and a small amount of petroleum ether was added to cause the product to separate into distinct layers. The upper oil layer was aspirated with a dropper for analysis using gas chromatography-mass spectrometry (GC-MS). After filtering the petroleum ether layer and the precipitate using slow-speed filter paper, the product was washed three times with petroleum ether to remove the oil adhering to the precipitate surface. The filtered product was dried in an oven at 80 °C for 2 hours. After drying, the product was weighed and the mass was recorded. The upper oil layer was filtered through a 0.22 μm organic filter membrane, and the free p-tert-butylbenzoic acid was quantitatively tested. The test results are shown in Table 1 below.

[0085] Table 1. Record of the mass of two precipitates generated during the reaction of the stabilizer sample with hydrochloric acid.

[0086] sample weight / g 36% hydrochloric acid / g Precipitate weighing / g Precipitation content / % stabilizer 4.993 3.49 0.328 6.57

[0087] (2) External standard method for quantification

[0088] A small amount of the upper layer of oil was dissolved in dichloromethane solvent and labeled as the diluent. Five standard working solutions of different concentrations were prepared from the diluent, numbered 1, 2, 3, 4, and 5, with mass fractions of 0.105%, 0.129%, 0.163%, 0.246%, and 0.491%, respectively. A standard working curve y = ax + b was plotted with concentration on the x-axis and peak area on the y-axis. The separated oil sample was dispersed in dichloromethane solvent and labeled as 6, with a content denoted as C0. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the oil sample, yielding... Figure 2 After substituting the peak areas obtained from the chromatographic analysis of the sample into the working curve, the concentration C of p-tert-butylbenzoic acid in the test solution was calculated. The calculation table of p-tert-butylbenzoic acid content in the upper oil layer of the stabilizer sample is as follows.

[0089] Table 2. Calculation of p-tert-butylbenzoic acid content in the upper layer oil of stabilizer samples.

[0090]

[0091] (3) Calculation of the content of p-tert-butylbenzoic acid in the sample

[0092] The total content of p-tert-butylbenzoic acid in the stabilizer sample is calculated according to formula (3) as the sum of the content in the precipitate and the content in the oil phase. The content of each component is recorded in Table 3 below.

[0093] Table 3. Record of p-tert-butylbenzoic acid content in precipitate and oil phase

[0094]

[0095]

[0096] Based on the test results, it can be seen that the measured value of p-tert-butylbenzoic acid content in PVC heat stabilizer is very close to the actual value, and this method can be used for determination.

[0097] In summary, the method for determining the content of p-tert-butylbenzoic acid in PVC heat stabilizers proposed in this invention can effectively detect the content of p-tert-butylbenzoic acid in stabilizer samples, and the determination results are accurate with small errors. The method is also simple to operate and easy to process in batches.

[0098] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for determining the content of p-tert-butylbenzoic acid in a PVC heat stabilizer, characterized in that, Includes the following steps: S1. Weigh a certain amount of stabilizer sample, mix the stabilizer sample with hydrochloric acid, add petroleum ether, and obtain the first product with obvious layering. S2. The petroleum ether layer of the first product is aspirated with a dropper and stored for later testing. The remaining petroleum ether layer and precipitate of the first product are filtered, and the filtered precipitate is washed with petroleum ether, dried, and the second product is obtained. The weight of the second product is weighed and recorded. S3. Filter the upper layer of oil drawn out by the dropper with an organic filter membrane to obtain an oil sample. Measure the content of free p-tert-butylbenzoic acid in the oil sample by gas chromatography-mass spectrometry. The content of p-tert-butylbenzoic acid in the PVC heat stabilizer is the sum of the content of p-tert-butylbenzoic acid in the precipitate and the content of free p-tert-butylbenzoic acid. The determination of free p-tert-butylbenzoic acid using gas chromatography-mass spectrometry (GC-MS) includes the following steps: S31. Dissolve the standard p-tert-butylbenzoic acid reagent in an organic solvent to obtain a diluted solution; S32. Disperse the diluted solution in organic solvents of different masses to obtain standard samples 1, 2, 3, 4, and 5 of different concentrations; S33. Weigh and record the weight of the oil sample, disperse it in a certain amount of organic solvent, and record it as sample 6; S34. Use a gas chromatography-mass spectrometry (GC-MS) instrument to determine the chromatographic peak area of ​​the standard and the sample. Plot a standard curve with the concentration of standards 1-5 as the x-axis and the chromatographic peak area determined by the GC-MS instrument as the y-axis. Then, obtain the content of free p-tert-butylbenzoic acid by using the standard curve and the peak area of ​​sample 6. The content of p-tert-butylbenzoic acid in the precipitate is calculated by the following formula: ； In the formula: m: Mass recorded during sedimentation, in grams; M: Mass of the stabilizer sample, g; W 下 : Amount of p-tert-butylbenzoic acid precipitate, %.

2. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S31, the organic solvent is at least one of dichloromethane, petroleum ether, and methanol.

3. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S33, the oil sample is taken in a mass of 0.01~0.1 g and dispersed in 10~20 g of organic solvent.

4. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S1, the hydrochloric acid is concentrated hydrochloric acid, and the mass fraction of the hydrochloric acid is 36%~38%.

5. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S1, the mass ratio of the stabilizer sample to hydrochloric acid is 5~10:3~7.

6. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S2, slow-speed filter paper is used for filtration, and the drying temperature is 50~90℃.

7. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S2, the drying time is 2 to 4 hours.

8. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S3, the washing is performed 1 to 5 times.

9. The method for determining the content of p-tert-butylbenzoic acid in the PVC heat stabilizer as described in claim 1, characterized in that, In step S4, the test conditions for the gas chromatography-mass spectrometry (GC-MS) instrument to determine the standard and sample are as follows: Chromatographic column: (5% phenyl)-methylpolysiloxane capillary column, 30m × 0.53mm × 1.0μm; Detector: Flame ionization detector; Testing chamber temperature: 300℃; Vaporization chamber temperature: 300℃; Temperature program: Initial column temperature 230℃, hold for 2 min, then increase to 300℃ at a rate of 10℃ / min; Carrier gas: Nitrogen, purity ≥99.999%, flow rate 1.0 mL / min; Fuel gas: Hydrogen, purity ≥ 99.999%, flow rate 30 mL / min; Combustion aid: Air, flow rate 400 mL / min.

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