Method for detecting ash content of ultralow-ash-content polyolefin film

Abstract

The invention discloses a method for detecting the ash content of an ultralow-ash-content polyolefin film, and relates to the technical field of material detection. The method comprises the following steps: S1, detecting the ash content distribution of the ultra-low ash content film by using a time-of-flight secondary ion mass spectrometer; S2, digesting the polyolefin film in a polytetrafluoroethylene digestion tube; and S3, detecting the solution to be detected by using an inductively coupled plasma mass spectrometer and an inductively coupled plasma emission spectrometer. According to the invention, through the detection methods of S1-S3, the ash content detection accuracy is significantly improved, especially the distribution condition of the ash content can be clearly detected, the detection sensitivity and accuracy are improved, the pretreatment speed is higher, the ash content is free of any loss, the external interference is small, the automation degree is high, and the detection time is greatly shortened.

Description

Technical Field

[0001] The invention relates to the technical field of material detection, in particular to a method for detecting the ash content of an ultra-low ash polyolefin film. Background Art

[0002] The ash content of polyolefin products is mainly caused by the introduction of catalysts, electron donors, activators, additives and system impurities during the processing. Polyolefin materials with high ash content will not only increase production costs, but also seriously affect the plastic processing technology and have a great impact on their physical and chemical properties. At the same time, as the application scope of polyolefin materials continues to expand, low-ash high-purity polyolefin materials have broad application prospects in the electronics, medical, and food industries. For example, the ash mass fraction of PP materials used in capacitor films is required to not exceed 0.0050%, and preferably below 0.0030%. Therefore, it is of great significance to accurately measure the ash content in ultra-low ash polyolefin films;

[0003] The commonly used detection method at present is the weight method. According to the relevant provisions of the national standard GB / T9345.1-2008, the polyolefin film is heated and carbonized at a certain temperature and atmosphere, and then placed in a muffle furnace to burn to constant weight, and then weighed to obtain the ash mass. The advantage of this method is low analysis cost and relatively cheap consumables. The disadvantage is that it takes a long time, consumes a large amount of samples, and generates a lot of dust to pollute the environment. In addition, this method has large test errors and poor reproducibility.

[0004] Another typical direct measurement method is X-ray fluorescence spectrometry (XRF). In this method, the sample is injection molded into a disc of a certain specification, and the metal element content is determined by XRF, and the total ash content is calculated. The main advantages of this method are improved accuracy and reproducibility, less time consumption, and reduced environmental pollution. However, the disadvantage of this method is that the sample thickness and surface smoothness have a great influence on the analysis results, resulting in cumbersome sample processing.

[0005] Based on the above two detection methods, the existing detection methods for ultra-low ash polyolefin films mainly have the disadvantages of low detection accuracy, long test time, large environmental pollution, cumbersome sample preparation, large external interference, large sample volume and inability to obtain ash distribution;

[0006] In view of the above problems, the inventors proposed a method for detecting the ash content of ultra-low ash polyolefin films to solve the above problems. Summary of the invention

[0007] In order to solve the above problems, the object of the present invention is to provide a method for detecting the ash content of ultra-low ash polyolefin film.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for detecting the ash content of ultra-low ash polyolefin film, comprising the following steps:

[0009] S1. Use time-of-flight secondary ion mass spectrometry to detect the ash distribution of ultra-low ash films, with sample size <1×1cm, surface detection depth <2nm, and depth analysis depth 1-3μm to calculate the surface and three-dimensional ash composition of polyolefin films;

[0010] S2, take a polyolefin film in a polytetrafluoroethylene digestion tube, the mass is 0.1000-0.5000g, then add an acidic digestion solution, the mass ratio of the digestion solution to the film is 1:50-80, place it in a microwave digestion instrument for digestion, the digestion temperature is 120-220°C, the microwave power is 800-1200W, the time is 30-90min, and a digestion solution is obtained, the acid is driven out until it is nearly dry, and the volume is fixed with deionized water to obtain 20-40mL of ash solution;

[0011] S3. The solution to be tested is tested using an inductively coupled plasma mass spectrometer and an inductively coupled plasma emission spectrometer, and the composition and content of ash in the polyolefin film are obtained by calculation.

[0012] Preferably, the ultra-low ash polyolefin film includes any one of biaxially oriented polypropylene, polyethylene, polyethylene terephthalate and polycarbonate.

[0013] Preferably, the acidic digestion solution is composed of concentrated nitric acid, concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4-6:1-4:0.1-0.3.

[0014] Preferably, the digestion program includes a temperature ramp time of 8 to 15 minutes, a microwave power ramp time of 8 to 15 minutes, and a target temperature constant time of 20 to 60 minutes.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] In the present invention, the detection method of S1-S3 significantly improves the accuracy of ash detection, especially the distribution of ash can be clearly detected, the detection sensitivity and accuracy of samples are improved, and the pre-processing speed is faster, there is no loss of ash, external interference is small, the degree of automation is high, and the detection time is greatly shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a schematic diagram of the TOF-SIMS detection principle of the present invention.

[0019] Figure 2 This is a diagram of the surface and three-dimensional ash composition of a domestically produced commercial BOPP film according to Example 1 of the present invention.

[0020] Figure 3 This is a diagram of the surface and three-dimensional ash composition of the domestically produced commercial PE film according to Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1: Figure 1 and Figure 2 As shown, the present invention provides a method for detecting the ash content of ultra-low ash polyolefin film, comprising the following steps:

[0023] S1. Take a domestically produced commercial biaxially oriented polypropylene (BOPP) film with a size of 0.5×0.5 cm and a thickness of 5.5 μm. Use a secondary ion mass spectrometer (TOF-SIMS) to detect the ash distribution of the film. The detection depth is 1 nm, and the ash composition of the surface layer of the film is obtained. When the detection depth is increased to 1 μm, the three-dimensional distribution of the ash content of the film is calculated. The results are as follows: Figure 2 As shown;

[0024] S2, take 0.1000g of the above-mentioned biaxially oriented polypropylene (BOPP) film into a polytetrafluoroethylene digestion tube, add acidic digestion solution, HNO3 / H2O2 / H2SO4=5:2:0, place it in a microwave digestion instrument for digestion, microwave power 800W, ramp time 15min, temperature 200°C, ramp time 15min, target constant temperature time 35min, after digestion is completed, drive out acid until nearly dry, use deionized water to make up to 30mL, and obtain ash solution;

[0025] S3. The ash solution was tested by inductively coupled plasma mass spectrometry (ICP-MS), and the composition and content of ash in the film sample were obtained by calculation. The results are shown in Table 1.

[0026]

[0027] Table 1 Ash composition and content of domestic commercial BOPP

[0028] Embodiment 2: Figure 1 and Figure 3 As shown, the present invention provides a method for detecting the ash content of ultra-low ash polyolefin film, comprising the following steps:

[0029] S1. Take a domestic commercial polyethylene (PE) film with a size of 1×1 cm and a thickness of 10 μm. Use secondary ion mass spectrometry (TOF-SIMS) to detect the ash distribution of the film. The detection depth is 1 nm to obtain the ash composition of the surface layer of the film. The detection depth is increased to 5 μm, and the three-dimensional distribution of the ash content of the film is calculated. The results are as follows: Figure 3 As shown;

[0030] S2, take 0.2000g polyethylene (PE) film into a polytetrafluoroethylene digestion tube, add acidic digestion solution, HNO3 / H2O2 / H2SO4=4:1:0.1, place it in a microwave digestion instrument for digestion, microwave power 1200W, ramp time 10min, temperature 150℃, ramp time 10min, target constant temperature time 30min, after digestion is completed, drive acid to nearly dry, use deionized water to make up to 40mL, and obtain ash solution;

[0031] S3. The ash solution was tested using an inductively coupled plasma atomic emission spectrometer (ICP-AES), and the composition and content of the ash in the film sample were obtained by calculation. The results are shown in Table 2.

[0032]

[0033] Table 2 Ash composition and content of domestic commercial PE films

[0034] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for detecting the ash content of ultra-low ash polyolefin film, characterized in that: The following steps are involved: S1. Use time-of-flight secondary ion mass spectrometry to detect the ash distribution of ultra-low ash films, with sample size <1×1cm, surface detection depth <2nm, and depth analysis depth 1-3μm to calculate the surface and three-dimensional ash composition of polyolefin films; S2, take a polyolefin film in a polytetrafluoroethylene digestion tube, the mass is 0.1000-0.5000g, then add an acidic digestion solution, the mass ratio of the digestion solution to the film is 1:50-80, place it in a microwave digestion instrument for digestion, the digestion temperature is 120-220°C, the microwave power is 800-1200W, the time is 30-90min, and a digestion solution is obtained, the acid is driven out until it is nearly dry, and the volume is fixed with deionized water to obtain 20-40mL of ash solution; S3. The solution to be tested is tested using an inductively coupled plasma mass spectrometer and an inductively coupled plasma emission spectrometer, and the composition and content of ash in the polyolefin film are obtained by calculation.

2. A method for detecting the ash content of ultra-low ash polyolefin film according to claim 1, characterized in that: The ultra-low ash polyolefin film includes any one of biaxially oriented polypropylene, polyethylene, polyethylene terephthalate and polycarbonate.

3. A method for detecting the ash content of ultra-low ash polyolefin film according to claim 1, characterized in that: The acidic digestion solution is composed of concentrated nitric acid, concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4-6:1-4:0.1-0.

3.

4. A method for detecting the ash content of ultra-low ash polyolefin film according to claim 1, characterized in that: The digestion procedure includes a temperature ramp-up time of 8 to 15 minutes, a microwave power ramp-up time of 8 to 15 minutes, and a target temperature constant temperature time of 20 to 60 minutes.

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