A quantitative detection method for PVC content in PVC-ABS alloy plastic

Abstract

The present invention provides a quantitative detection method for PVC content in PVC-ABS alloy plastic, comprising the following steps: (1) crushing a PVC-ABS alloy plastic sample, then ultrasonically extracting the crushed sample, then centrifuging, collecting the centrifugal supernatant and drying it to obtain the resin part in the sample as the sample to be tested; calculating the content Pr of the resin part in the PVC-ABS alloy plastic; (2) mixing an internal standard substance, the sample to be tested and a deuterated reagent, and performing a nuclear magnetic resonance hydrogen spectrum test; (3) performing area integration on the nuclear magnetic resonance hydrogen spectrum signal peaks of the target PVC and the internal standard substance, and calculating the content Pa of the target PVC in the sample to be tested according to a formula; (4) multiplying Pr by Pa, and the product obtained is the content of PVC in the PVC-ABS alloy plastic. The detection method provided by the present invention is used to detect the PVC content in the PVC-ABS alloy plastic, and the detection result has high accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of polyvinyl chloride detection, and relates to a quantitative detection method for PVC content in PVC-ABS alloy plastic. Background Art

[0002] PVC (polyvinyl chloride)-ABS (acrylonitrile-butadiene-styrene copolymer) alloy plastic is a special engineering plastic that combines the chemical resistance of PVC with the mechanical strength and processing properties of ABS. This material is usually used to manufacture automotive parts, electronic and electrical housings, building materials, etc.

[0003] The alloying of PVC and ABS is achieved by physical blending or chemical grafting copolymerization. The performance of PVC-ABS alloy plastics can be further optimized by adding additives such as toughening agents, fillers, stabilizers, lubricants, etc. Due to its excellent chemical resistance, mechanical strength and processing properties, PVC-ABS alloy plastics are widely used in many fields. For example, in the automotive industry, it can be used to manufacture components such as dashboards, door panels, and bumpers; in the field of electronic products, it can be used to manufacture structural parts such as housings and bases. In short, PVC-ABS alloy plastics, as a high-performance engineering plastic, have been widely used in various fields with the support of existing technologies. At present, the existing methods for detecting the PVC content in mixed plastics are generally to test the content of chlorine in the sample, or to convert the intensity of the C-Cl peak of the sample using an infrared spectrometer. The above detection methods have large errors and complex operations.

[0004] Therefore, in the art, it is desired to develop a method for detecting the PVC content in PVC-ABS alloy plastics, by which the PVC content can be detected more accurately. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a quantitative detection method for the PVC content in PVC-ABS alloy plastics. Specifically, PVC-ABS alloy plastics generally contain additives and fillers, etc. It is difficult to separate the polymer from the alloy plastic, and the PVC content therein is difficult to accurately and quantitatively determine. The detection method provided by the present invention can solve the above problems.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for quantitatively detecting the PVC content in a PVC-ABS alloy plastic, the method comprising the following steps:

[0008] (1) The PVC-ABS alloy plastic sample is crushed, and then the crushed sample is mixed with an extraction solvent, ultrasonically extracted, and then centrifuged. The upper layer of the centrifuged liquid is collected and dried to obtain the resin part of the sample as the sample to be tested; the content of the resin part in the PVC-ABS alloy plastic is calculated according to the following formula: ;

[0009] Wherein, M0: the weight of the sample after crushing, g;

[0010] M1: mass of the resin part in the sample, g;

[0011] Pr: The content of resin in PVC-ABS alloy plastic, %;

[0012] (2) mixing the internal standard, the sample to be tested obtained in step (1) and the deuterated reagent to obtain a test solution, and performing a nuclear magnetic resonance hydrogen spectrum test on the test solution;

[0013] (3) Perform area integration on the nuclear magnetic resonance hydrogen spectrum signal peaks of the target PVC and the internal standard, and then calculate the content of the target PVC in the sample to be tested according to the following formula: ;

[0014] Wherein, Ia: characteristic peak area of ​​the target;

[0015] Is: characteristic peak area of ​​internal standard;

[0016] Na: the proton number of the characteristic peak of the target;

[0017] Ns: the number of protons of the characteristic peak of the internal standard;

[0018] Ma: molar mass of the target compound, g / mol;

[0019] Ms: molar mass of internal standard, g / mol;

[0020] Ws: weight of internal standard, mg;

[0021] Wa: the weight of the sample to be tested in step (2), mg;

[0022] Pa: PVC content in the sample to be tested, %;

[0023] Ps: purity of internal standard, %;

[0024] (4) Multiply the Pr obtained in step (1) by the Pa obtained in step (3), and the product obtained is the PVC content in the PVC-ABS alloy plastic.

[0025] In the detection method provided by the present invention, the PVC-ABS alloy plastic is first pre-treated to separate the resin part therein, and then the nuclear magnetic resonance spectrum quantitative technology is adopted to quantitatively analyze the PVC chain segment of the resin part through nuclear magnetic resonance hydrogen spectrum test to obtain the PVC content in the resin part, thereby quantitatively detecting the PVC content in the PVC-ABS alloy plastic. The detection method is simple to operate, has a fast detection speed, a short analysis time, and a high accuracy of the detection result.

[0026] Preferably, the source of the PVC-ABS alloy plastic sample in step (1) includes a motor housing. Conventional motor housing plastics are generally composed of two or more copolymers and contain additives and fillers, which are difficult to separate and difficult to detect the polymer content. The method provided by the present invention can detect the PVC content.

[0027] Preferably, the pulverization in step (1) is to place the PVC-ABS alloy plastic sample in liquid nitrogen for low-temperature brittle fracture and then pulverize it using a sample crusher.

[0028] Preferably, the crushing step also includes a shredding step before the pulverization.

[0029] Preferably, the weighing amount of the crushed sample in step (1) is 2-5 g, for example, 2 g, 2.5 g, 3 g, 3.5 g, 4 g, 4.5 g, 5 g, etc.

[0030] Preferably, the extraction solvent in step (1) comprises chloroform or tetrahydrofuran.

[0031] Preferably, the ultrasonic extraction time in step (1) is 1-2 h, such as 1 h, 1.5 h, 2 h, etc.

[0032] Preferably, the centrifugal speed in step (1) is 8000-12000 r / min, for example, 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, 12000 r / min, etc.

[0033] Preferably, the steps of preparing the sample to be tested in step (1) specifically include:

[0034] (a) The PVC-ABS alloy plastic sample is crushed, and then the crushed sample is mixed with an extraction solvent and ultrasonically extracted until the sample is completely dissolved;

[0035] (b) The dissolved sample is placed in a centrifuge tube and centrifuged to collect the supernatant liquid. An extraction solvent is then added to the precipitate in the centrifuge tube, ultrasonic extraction is performed, centrifugation is performed, and the supernatant liquid is collected. The above steps (i.e., the steps of adding the extraction solvent to the precipitate in the centrifuge tube, ultrasonic extraction, centrifugation, and collecting the supernatant liquid) are repeated at least 5 times. All the collected supernatant liquids are dried to obtain the resin portion of the sample as the sample to be tested.

[0036] Further preferably, the step of preparing the sample to be tested in step (1) specifically includes:

[0037] (a) Crush the PVC-ABS alloy plastic sample, then mix 2-5 g (e.g., 2 g, 2.5 g, 3 g, 3.5 g, 4 g, 4.5 g, 5 g, etc.) of the crushed sample with 15-25 mL (e.g., 15 mL, 16 mL, 18 mL, 20 mL, 23 mL, 25 mL, etc.) of the extraction solvent, and perform ultrasonic extraction for 1-2 h (e.g., 1 h, 1.5 h, 2 h, etc.) until the sample is completely dissolved;

[0038] (b) placing the dissolved sample into a centrifuge tube, centrifuging at 8000-12000 r / min (e.g., 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, 12000 r / min, etc.) for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, etc.), collecting the supernatant from the centrifuge, adding the extraction solvent to the precipitate in the centrifuge tube, performing ultrasonic extraction for 1-2 h (e.g., 1 h, 1.5 h, 2 h, etc.), centrifuging at 8000-12000 r / min (e.g., 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, 12000 r / min, etc.) for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, etc.), min, etc.), collecting the centrifugal supernatant, repeating the above steps (i.e., adding the extraction solvent to the precipitate in the centrifuge tube, ultrasonically extracting for 1-2 h (e.g., 1 h, 1.5 h, 2 h, etc.), centrifuging at 8000-12000 r / min (e.g., 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, 12000 r / min, etc.) for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, etc.), collecting the centrifugal supernatant) for at least 5 times (e.g., 5 times, 6 times, 7 times, 8 times, etc.), drying all the collected centrifugal supernatants to obtain the resin portion in the sample as the sample to be tested.

[0039] Preferably, the internal standard in step (2) includes trimethoxybenzene or dimethyl sulfone.

[0040] Preferably, in step (2), the weighing amount of the internal standard is 5-20 mg, for example, 5 mg, 6 mg, 8 mg, 10 mg, 12 mg, 14 mg, 16 mg, 18 mg, 20 mg, etc.

[0041] Preferably, in step (2), the weight of the sample to be tested is 50-200 mg, for example, 50 mg, 60 mg, 80 mg, 100 mg, 120 mg, 140 mg, 160 mg, 180 mg, 200 mg, etc.

[0042] Preferably, the deuterated reagent in step (2) includes deuterated chloroform or deuterated tetrahydrofuran.

[0043] Preferably, in step (2), a nuclear magnetic resonance spectrometer is used to perform a nuclear magnetic resonance hydrogen spectrum test, and the test parameters of the nuclear magnetic resonance spectrometer are set as follows: a zg30 pulse sequence is used, the spectrum width is 20-30 ppm (for example, 20 ppm, 22 ppm, 24 ppm, 26 ppm, 28 ppm, 30 ppm, etc.), the center point is 1-10 ppm (for example, 1 ppm, 3 ppm, 5 ppm, 8 ppm, 10 ppm, etc.), the resonance frequency is 400-600 Hz (for example, 400 HZ, 420 HZ, 440 HZ, 460 HZ, 480 HZ, 500 HZ, 520 HZ, 540 HZ, 560 HZ, 580 HZ, 600 HZ, etc.), and the excitation power is 20-50 W (for example, 20 W, 22 W, 24 W, 26 W, 28 W, 30 W, 32 W, 34 W, 36 The power consumption is 10 W, 38 W, 40 W, 42 W, 44 W, 46 W, 48 W, 50 W, etc.), the sampling times is 16 to 64 times (for example, 16 times, 24 times, 32 times, 40 times, 48 ​​times, 56 times, 64 times, etc.), the acquisition time is 1 to 20 s (for example, 1 s, 3 s, 5 s, 8 s, 10 s, 13 s, 15 s, 18 s, 20 s, etc.), and the relaxation time is 10 to 30 s (for example, 10 s, 12 s, 14 s, 15 s, 16 s, 18 s, 20 s, 22 s, 24 s, 25 s, 26 s, 28 s, 30 s, etc.).

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] In the detection method provided by the present invention, the PVC-ABS alloy plastic is first pre-treated to separate the resin part therein, and then the nuclear magnetic resonance spectrum quantitative technology is adopted to quantitatively analyze the PVC chain segment of the resin part through nuclear magnetic resonance hydrogen spectrum test to obtain the PVC content in the resin part, thereby quantitatively detecting the PVC content in the PVC-ABS alloy plastic. The detection method is simple to operate, has a fast detection speed, a short analysis time, and a high accuracy of the detection result. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of the sample to be tested in Example 1. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] In this embodiment, a quantitative detection method for PVC content in PVC-ABS alloy plastic is provided, and the quantitative detection method comprises the following steps:

[0050] (1) Cut the motor housing into pieces with scissors, place it in liquid nitrogen for low-temperature brittle fracture, and then crush it with a sample crusher;

[0051] Weigh 3.00 g of the crushed sample into a glass, add 20 mL of tetrahydrofuran, and perform ultrasonic extraction for 1 h until the sample is completely dissolved;

[0052] The dissolved sample was placed in a 10 mL centrifuge tube, centrifuged at 10,000 r / min for 20 min, the supernatant was collected, tetrahydrofuran was added to the precipitate in the centrifuge tube, ultrasonic extraction was performed for 1 h, the supernatant was collected at 10,000 r / min for 20 min, and the above steps were repeated 5 times; all the collected supernatant was dried, poured into a glass dish and dried, and the resin part (2.87 g) in the sample was obtained as the sample to be tested;

[0053] According to the following formula, the content of the resin part in the PVC-ABS alloy plastic is 95.7%: ;

[0054] Wherein, M0: the weight of the sample after crushing, g;

[0055] M1: mass of the resin part in the sample, g;

[0056] Pr: The content of resin in PVC-ABS alloy plastic, %.

[0057] (2) Using trimethoxybenzene as the internal standard, weigh 102.30 mg of the sample to be tested and 14.82 mg of trimethoxybenzene using a 1 / 10,000 balance and place them in a 1.5 mL centrifuge tube. Then add 0.5 mL of deuterated chloroform, mix well and transfer to a 5 mm NMR tube. Place the NMR tube containing the test solution in the automatic sampler of the NMR spectrometer for NMR hydrogen spectrum testing. The test parameters are: using the zg30 pulse sequence, the spectrum width is 20 ppm, the center point is 6 ppm, the resonance frequency is 400.15 Hz, the excitation power is 24.48 W, the number of samples is 32, the acquisition time is 5 s, and the relaxation time is 20 s.

[0058] (3) After obtaining the spectrum, the area of ​​the target PVC and internal standard H NMR spectrum signal peaks is integrated, and then the content of the target PVC in the sample to be tested is calculated according to the following formula: ;

[0059] Wherein, Ia: characteristic peak area of ​​the target;

[0060] Is: characteristic peak area of ​​internal standard;

[0061] Na: the proton number of the characteristic peak of the target;

[0062] Ns: the number of protons of the characteristic peak of the internal standard;

[0063] Ma: molar mass of the target compound, g / mol;

[0064] Ms: molar mass of internal standard, g / mol;

[0065] Ws: weight of internal standard, mg;

[0066] Wa: the weight of the sample to be tested in step (2), mg;

[0067] Pa: PVC content in the sample to be tested, %;

[0068] Ps: purity of internal standard, %.

[0069] The values ​​of the parameters in the above formula are shown in Table 1:

[0070] Table 1

[0071]

[0072] (4) Multiply the Pr obtained in step (1) by the Pa obtained in step (3), and the product obtained is the PVC content in the PVC-ABS alloy plastic.

[0073] The nuclear magnetic resonance hydrogen spectrum of the sample to be tested in this embodiment is as follows Figure 1 As shown, 3.8~4.7 ppm is the signal peak of the PVC molecular chain segment.

[0074] Example 2

[0075] The only difference between this example and Example 1 is that the extraction solvent tetrahydrofuran in step (1) is replaced by an equal volume of chloroform (i.e., all tetrahydrofuran-related portions in step (1) are replaced by chloroform).

[0076] Example 3

[0077] The difference between this embodiment and embodiment 1 is that the test parameters in step (2) are different, specifically as follows: a zg30 pulse sequence is used, the spectrum width is 30 ppm, the center point is 5 ppm, the resonance frequency is 400.15 Hz, the excitation power is 24.48 W, the number of sampling times is 64, the acquisition time is 10 s, and the relaxation time is 30 s.

[0078] Comparative Example 1

[0079] In this comparative example, 100 mg of the motor housing sample and 20 mg of the internal standard trimethoxybenzene were directly weighed and placed in a 1.5 mL centrifuge tube, and then 0.5 mL of deuterated chloroform was added. After mixing evenly, the mixture was transferred to a 5 mm nuclear magnetic resonance tube; the nuclear magnetic resonance tube containing the test solution was placed in the automatic sampler of the nuclear magnetic resonance spectrometer for nuclear magnetic resonance hydrogen spectrum testing, and the test parameters were consistent with those in Example 1.

[0080] Comparative Example 2

[0081] A 20 mg motor housing sample was taken for thermogravimetric analysis, and the PVC content was calculated based on the decomposition content of hydrogen chloride in the PVC segment at 250°C. The specific test conditions are as follows: an alumina crucible (100 μL) was used; the sample purge gas was nitrogen, with a flow rate of 50 mL / min; the heating program was the initial temperature: 40°C for 2 min, and then heated to 750°C at 10°C / min; the sample purge gas was switched to oxygen, with a flow rate of 50 mL / min; the temperature was raised to 850°C at 10°C / min and kept constant for 1 min.

[0082] The test results of the embodiments and comparative examples are shown in Table 2.

[0083] Table 2

[0084]

[0085] As can be seen from Table 2, the test results of Examples 1, 2, and 3 have a small error with the standard amount test of PVC, while the test results of Comparative Examples 1 and 2 have a large error with the standard amount test of PVC. This is because Comparative Example 1 directly uses the original sample for nuclear magnetic resonance spectroscopy test, the solubility of the sample is poor, and no fine pre-treatment extraction is performed, resulting in the PVC in the sample not being completely dissolved in the deuterated reagent, so that the quantitatively detected PVC content is low; while in Comparative Example 2, a thermogravimetric analyzer is used to test the original motor housing, and the degradation at 250°C is used to convert the PVC content, but a conventional motor housing is generally made of two or more polymers and additives, and some of the remaining polymer molecular segments and additives will degrade at 250°C, so the PVC content tested will be too large.

[0086] In summary, the detection method provided by the present invention is used to detect the PVC content in PVC-ABS alloy plastic, the detection result is highly accurate, and the detection method is simple to operate, the detection speed is fast, and the analysis time is short.

[0087] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the quantitative detection method of PVC content in PVC-ABS alloy plastic of the present invention, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A quantitative detection method for PVC content in PVC-ABS alloy plastic, characterized in that: The quantitative detection method comprises the following steps: (1) The PVC-ABS alloy plastic sample is crushed, and then the crushed sample is mixed with an extraction solvent, ultrasonically extracted, and then centrifuged. The upper layer of the centrifuged liquid is collected and dried to obtain the resin part of the sample as the sample to be tested; the content of the resin part in the PVC-ABS alloy plastic is calculated according to the following formula: ; Wherein, M0: the weight of the sample after crushing; M1: the mass of the resin part in the sample; Pr: The content of resin in PVC-ABS alloy plastic, %; (2) mixing the internal standard, the sample to be tested obtained in step (1) and the deuterated reagent to obtain a test solution, and performing a nuclear magnetic resonance hydrogen spectrum test on the test solution; (3) Perform area integration on the nuclear magnetic resonance hydrogen spectrum signal peaks of the target PVC and the internal standard, and then calculate the content of the target PVC in the sample to be tested according to the following formula: ; Wherein, Ia: characteristic peak area of ​​the target; Is: characteristic peak area of ​​internal standard; Na: the proton number of the characteristic peak of the target; Ns: the number of protons of the characteristic peak of the internal standard; Ma: molar mass of the target compound, g / mol; Ms: molar mass of internal standard, g / mol; Ws: sample weight of internal standard; Wa: the weight of the sample to be tested in step (2); Pa: PVC content in the sample to be tested, %; Ps: purity of internal standard, %; (4) Multiplying Pr obtained in step (1) by Pa obtained in step (3), and the product obtained is the content of PVC in the PVC-ABS alloy plastic; The extraction solvent in step (1) includes chloroform or tetrahydrofuran; The internal standard in step (2) includes trimethoxybenzene or dimethyl sulfone; The deuterated reagent in step (2) includes deuterated chloroform or deuterated tetrahydrofuran.

2. The quantitative detection method according to claim 1, characterized in that: The source of the PVC-ABS alloy plastic sample in step (1) includes a motor housing.

3. The quantitative detection method according to claim 1, characterized in that: The pulverization in step (1) is to place the PVC-ABS alloy plastic sample in liquid nitrogen to break it and then pulverize it with a sample crusher; The method also includes a shearing step before the pulverization.

4. The quantitative detection method according to claim 1, characterized in that: The sample weight after crushing in step (1) is 2-5 g.

5. The quantitative detection method according to claim 1, characterized in that: The ultrasonic extraction time in step (1) is 1-2 h; The centrifugal speed in step (1) is 8000-12000 r / min.

6. The quantitative detection method according to claim 1, characterized in that: The steps of preparing the sample to be tested in step (1) specifically include: (a) The PVC-ABS alloy plastic sample is crushed, and then the crushed sample is mixed with an extraction solvent and ultrasonically extracted until the sample is completely dissolved; (b) The dissolved sample is placed in a centrifuge tube and centrifuged to collect the supernatant. An extraction solvent is then added to the precipitate in the centrifuge tube, ultrasonic extraction is performed, and centrifugation is performed to collect the supernatant. The above steps are repeated at least 5 times. All the collected supernatant is dried to obtain the resin portion of the sample as the sample to be tested.

7. The quantitative detection method according to claim 1, characterized in that: In step (2), the weighing amount of the internal standard is 5-20 mg, and the weighing amount of the sample to be tested is 50-200 mg.

8. The quantitative detection method according to claim 1, characterized in that: In step (2), a nuclear magnetic resonance hydrogen spectrum test is performed using a nuclear magnetic resonance spectrometer, and the test parameters of the nuclear magnetic resonance spectrometer are set as follows: a zg30 pulse sequence is used, the spectrum width is 20-30 ppm, the center point is 1-10 ppm, the resonance frequency is 400-600 Hz, the excitation power is 20-50 W, the sampling number is 16-64 times, the acquisition time is 1-20 s, and the relaxation time is 10-30 s.

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