Ash content detection method for low-ash-content polyolefin material

Abstract

The invention provides a method for detecting the ash content of a low-ash-content polyolefin material, which comprises the following steps: A) pretreating a polyolefin sample with the ash content of less than or equal to 50ppm to obtain pretreated polyolefin powder; b) mixing the pretreated polyolefin powder with a digestion solution, and performing digestion under microwave and pressurization conditions to obtain a digestion product; the digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature ranges from 100 DEG C to 300 DEG C, and the digestion pressure ranges from 0.1 MPa to 10.0 MPa; and C) detecting the digestion product by adopting ICP-MS (Inductively Coupled Plasma Mass Spectrometry) to obtain the ash composition and content. According to the method, the ash content of the polyolefin material with the ultralow ash content lower than 10 ppm can be detected, compared with a direct calcination method, the ash content error can be controlled within 10%, and the accuracy of ash content detection is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to an ash content detection method for low-ash polyolefin materials. Background Art

[0002] At present, low-ash polyolefin materials are widely used in medical devices, food, electrical appliances, transportation and other industries due to their excellent mechanical strength and processing properties, and will have a broader application prospect in the future. At present, the domestic demand for ultra-low ash polypropylene for capacitors is increasing year by year. Since the ash content of low-ash polyolefin materials is generally lower than 50ppm, external factors greatly interfere with the final ash test results, which puts higher requirements on the ash content detection. Therefore, how to improve the accuracy and repeatability of the determination of low-ash polyolefin materials will provide guidance for improving the polymerization process and accelerating the production of low-ash polyolefin materials.

[0003] It can be seen that it is of great significance to develop an easy-to-operate ash content detection method for low-ash polyolefin materials. Summary of the invention

[0004] The purpose of the present invention is to provide an ash content detection method for low-ash polyolefin materials. The method of the present invention has high accuracy, small external interference, and greatly shortens the detection time.

[0005] The present invention provides an ash content detection method for a low-ash polyolefin material, comprising the following steps:

[0006] A) pre-treating a polyolefin sample having an ash content of ≤50 ppm to obtain a pre-treated polyolefin powder;

[0007] B) mixing the pretreated polyolefin powder with a digestion solution, and digesting the mixture under microwave and pressure conditions to obtain a digestion product;

[0008] The digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature is 100-300°C, and the digestion pressure is 0.1-10.0MPa;

[0009] C) using ICP-MS to detect the digestion product to obtain the ash composition and content.

[0010] Preferably, the pretreatment includes drying, the drying temperature is 70-80° C., and the drying time is 0.5-2 hours.

[0011] Preferably, the ratio of the mass of the pretreated polyolefin powder to the volume of the digestion solution is 0.1 g: (1-10) mL.

[0012] Preferably, the pretreated polyolefin powder is mixed with the digestion liquid in a digestion tube, the digestion tube is placed on a digestion bracket, the digestion bracket is placed in a digestion tank, a load liquid is added to the digestion tank, and digestion is performed under microwave and pressurized conditions to obtain a digestion product.

[0013] Preferably, the loading liquid comprises nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid or dilute perchloric acid.

[0014] Preferably, the power of the microwave is 300-2100 W, and the digestion time is 0.1-2 hours.

[0015] Preferably, the digestion is carried out according to the following heating program:

[0016] Stage 1: Raise the temperature from room temperature to 110-130°C within 3-8 minutes, and keep warm for 5-15 minutes;

[0017] Stage 2: Raise the temperature to 150-170°C within 3-8 minutes and keep warm for 5-15 minutes;

[0018] Stage 3: Raise the temperature to 190-250°C within 3-8 minutes and keep warm for 25-40 minutes.

[0019] Preferably, the digestion product is mixed with water to be used as a test solution for ICP-MS detection.

[0020] Preferably, in ICP-MS detection, the mass concentration of the test solution is 0.01 to 10.0 ppm.

[0021] Preferably, in ICP-MS detection, the sample amount of the test solution is 0.1 to 1.0 g.

[0022] The invention provides an ash detection method for a low-ash polyolefin material, comprising the following steps: A) pre-treating a polyolefin sample with an ash content of ≤50ppm to obtain a pre-treated polyolefin powder; B) mixing the pre-treated polyolefin powder with a digestion solution, and digesting the mixture under microwave and pressurization conditions to obtain a digestion product; the digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature is 100-300°C, and the digestion pressure is 0.1-10.0MPa; C) using ICP-MS to detect the digestion product to obtain ash composition and content. The present invention establishes a comprehensive three-dimensional detection method for ash distribution, composition and content of ultra-low ash polyolefin resin, which can realize ash detection of polyolefin materials with ultra-low ash content below 10ppm, and compared with the direct calcination method, the ash error can be controlled within 10%, which significantly improves the accuracy of ash detection, especially the ash distribution can be clearly detected, improves the detection sensitivity and accuracy of samples, and has faster pre-processing speed, no ash loss, little external interference, high degree of automation, and greatly shortens the detection time. DETAILED DESCRIPTION

[0023] The present invention provides an ash content detection method for a low-ash polyolefin material, comprising the following steps:

[0024] A) pre-treating a polyolefin sample having an ash content of ≤50 ppm to obtain a pre-treated polyolefin powder;

[0025] B) mixing the pretreated polyolefin powder with a digestion solution, and digesting the mixture under microwave and pressure conditions to obtain a digestion product;

[0026] The digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature is 100-300°C, and the digestion pressure is 0.1-10.0MPa;

[0027] C) using ICP-MS to detect the digestion product to obtain the ash composition and content.

[0028] The present invention firstly pretreats the polyolefin sample to obtain pretreated polyolefin powder.

[0029] In the present invention, the polyolefin sample is a low-ash polyolefin material, and the ash content in the low-ash polyolefin material is preferably ≤10 ppm.

[0030] In the present invention, the sample processing can ensure that no other impurities are introduced, and the authenticity and reliability of the data are ensured. The detection cycle is short, less reagents are used, and less pollution is caused. The pretreatment includes drying, and the drying temperature is preferably 70 to 80°C, more preferably 75 to 78°C; the drying time is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours.

[0031] In the present invention, when the polyolefin material is in other forms other than powder, such as pellets, films, etc., the pretreatment further comprises a crushing step, wherein the polyolefin material is crushed and then dried to obtain pretreated polyolefin powder.

[0032] After obtaining the pretreated polyolefin powder, the present invention mixes the pretreated polyolefin powder with a digestion solution and puts it into a microwave digestion tube, wherein the digestion tube is placed on a digestion support, the digestion support is placed in a digestion tank, a load liquid is added inside the digestion tank, and then the digestion tank with the digestion tube is placed in a microwave digestion instrument to perform microwave digestion to obtain a digestion product.

[0033] In the present invention, the digestion solution is preferably one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the ratio of the mass of the pretreated polyolefin powder to the volume of the digestion solution is preferably 0.1g:(1-10)mL, more preferably 0.1g:(2-8)mL, such as 0.1g:1mL, 0.1g:2mL, 0.1g:3mL, 0.1g:4mL, 0.1g:5mL, 0.1g:6mL, 0.1g:7mL, 0.1g:8mL, 0.1g:9mL, 0.1g:10mL, preferably a range value with any of the above values ​​as the upper or lower limit.

[0034] In the present invention, the digestion tube is made of quartz material and is placed on a digestion bracket, the digestion bracket is placed in a digestion tank filled with a load liquid, and the digestion tank is placed in a microwave digestion instrument. The digestion tube is easy to install and clean, and the digestion liquid is easy to transfer, and this process reduces the risk of metal ion contamination.

[0035] In the present invention, the loading liquid preferably includes nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid or dilute perchloric acid. The present invention preferably mixes the nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid or dilute perchloric acid with water as the loading liquid. The loading liquid can ensure uniform temperature during the digestion process.

[0036] In the present invention, the microwave digestion is carried out under pressurized conditions, and the pressurized pressure is preferably 0.1-10.0 MPa, more preferably 1-8 MPa, such as 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit; the power of the microwave is preferably 300-2100 W, more preferably 500-1500 W, such as 300 W, 500 W, 800 W, 1000 W, 1500 W, 2000 W, 2100 W, preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit.

[0037] In the present invention, the temperature of the microwave digestion is preferably 100 to 300° C., more preferably 100 to 250° C., the time of the microwave digestion is preferably 0.1 to 2 hours, more preferably 0.5 to 1.5 hours, and preferably, the microwave digestion is performed according to the following heating program:

[0038] Stage 1: Raise the temperature from room temperature to 110-130°C within 3-8 minutes, and keep warm for 5-15 minutes;

[0039] Stage 2: Raise the temperature to 150-170°C within 3-8 minutes and keep warm for 5-15 minutes;

[0040] Stage 3: Raise the temperature to 190-250°C within 3-8 minutes and keep warm for 25-40 minutes;

[0041] More preferably, the microwave digestion is performed according to the following heating program:

[0042] Stage 1: Raise the temperature from room temperature to 120-125°C within 5-6 minutes, and keep warm for 10-12 minutes;

[0043] Stage 2: Raise the temperature to 160-165°C within 5-6 minutes and keep warm for 10-12 minutes;

[0044] Stage 3: Raise the temperature to 200-220°C within 5-6 minutes and keep warm for 30-35 minutes.

[0045] After the sample is completely digested, the digestion product is transferred out and mixed with ultrapure water to serve as a test solution.

[0046] In the present invention, the mass concentration of the test solution is preferably 0.01 to 10.0 ppm, more preferably 0.1 to 5 ppm.

[0047] The present invention uses an ICP-MS (inductively coupled plasma mass spectrometry) method to detect the sample solution to obtain the ash composition and content. ICP-MS converts the sample into an aerosol and introduces it into a high-temperature plasma for atomization and ionization, and uses a mass spectrometer to separate and detect ions of different masses, thereby realizing the analysis and quantification of elements in the sample. The ICP can be used to quickly determine the content of each metal element in the solution, and the mass of the metal oxide is further calculated by determining the content of the metal element, and the ash content of the olefin resin is expressed as the sum of the main metal oxides.

[0048] In the present invention, firstly, a standard solution is prepared, and standard curves of aluminum, magnesium, titanium, calcium and iron are established according to a gradient of 0.5 mg / L, 1.0 mg / L, 3 mg / L, 5 mg / L and 10 mg / L. The volumetric flask and pipette for establishing the standard curve are cleaned and soaked in high-grade pure nitric acid before use to avoid introducing interference.

[0049] In the present invention, the method for establishing a standard curve is a conventional method in the art, and the present invention will not be repeated here.

[0050] The present invention injects the test solution into an inductively coupled plasma mass spectrometer for detection, and the sample amount of the test sample is preferably 0.1-1.0 g, more preferably 0.1-0.5 g, such as 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g, 0.9 g, 1.0 g, preferably a range value with any of the above values ​​as the upper or lower limit.

[0051] The invention provides an ash detection method for a low-ash polyolefin material, comprising the following steps: A) pre-treating a polyolefin sample with an ash content of less than 10 ppm to obtain a pre-treated polyolefin powder; B) mixing the pre-treated polyolefin powder with a digestion solution, and digesting the mixture under microwave and pressurization conditions to obtain a digestion product; the digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature is 100-300 DEG C, and the digestion pressure is 0.1-10.0 MPa; C) using ICP-MS to detect the digestion product to obtain ash composition and content. The present invention establishes a comprehensive three-dimensional detection method for ash distribution, composition and content of ultra-low ash polyolefin resin, which can realize ash detection of polyolefin materials with ultra-low ash content below 10ppm, and compared with the direct calcination method, the ash error can be controlled within 10%, which significantly improves the accuracy of ash detection, especially the ash distribution can be clearly detected, improves the detection sensitivity and accuracy of samples, and has faster pre-processing speed, no ash loss, little external interference, high degree of automation, and greatly shortens the detection time.

[0052] In order to further illustrate the present invention, an ash detection method for a low-ash polyolefin material provided by the present invention is described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0053] The ash content of the embodiments and comparative examples was calculated according to the following method:

[0054] Ash calculation:

[0055] Calculation of the content of the metal element to be measured

[0056] Calculate according to the following formula:

[0057]

[0058] Where:

[0059] C: concentration of element in parts per million of test solution (mg / kg);

[0060] C0: The concentration of the element in the test solution, in milligrams per liter (mg / L), which is obtained by the ICP instrument test;

[0061] f: dilution factor;

[0062] V0: The volume of the sample after digestion, in milliliters (mL);

[0063] m0: The mass of the sample taken when analyzing the sample, in grams (g).

[0064] Ash content (ASH) calculation

[0065] The ash content of polypropylene resin (ASH) is the sum of the measured metal element oxides. The calculation formula for the ash content of the oxide of element A in polypropylene resin is as follows:

[0066]

[0067] Where:

[0068] C: concentration of element in parts per million of test solution (mg / kg);

[0069] x: the amount of element A in its oxide;

[0070] M A : Relative molecular mass of element A;

[0071] M AxOy : Relative molecular mass of element A oxide.

[0072] Example 1

[0073] 1. Sample pretreatment: Take a polypropylene powder sample (ash content 10ppm) and dry it at 75℃ for 1.0h, then cool it to room temperature for later use.

[0074] 2. Sample digestion: Accurately weigh 0.5g (accurate to 0.0001g) of sample into a 30mL microwave digestion tube, add about 10mL of high-grade pure nitric acid, place the digestion tube in the digestion tube holder, and place it in a digestion tank containing 150mL of loading liquid (mixed with 5mL of high-grade pure nitric acid and 150mL of ultrapure water). The digestion tank is transferred to the microwave digestion instrument (the exposure time in the environment should be minimized during this process). The microwave digestion instrument program setting: pre-pressurization 5.0MPa, heating program: stage 1: 5min heating to 120℃, keep warm for 10min, stage 2: 5min heating to 160℃, keep warm for 5min, stage 3: 5min heating to 200℃, keep warm for 30min. After the sample is completely digested, cool it and transfer it to a 125mL PP ultra-clean bottle. When transferring, quickly add 20 mL of ultrapure water, mix the liquid evenly, transfer it out at one time, and weigh it to 100 g with ultrapure water as the sample test solution. The parallel sample and process blank operation procedures are the same.

[0075] 3. ICP test: Use standard solution to establish standard curves for aluminum, magnesium, titanium, calcium, and iron according to the gradient of concentrations of 0.5 mg / L, 1.0 mg / L, 3 mg / L, 5 mg / L, and 10 mg / L. The volumetric flask and pipette used to establish the standard curve must be cleaned and soaked in high-grade pure nitric acid before use to avoid interference. First, draw the standard curve according to the concentration gradient of the standard curve, and then take 10g of the test solution and measure it on the machine to obtain the main element content of the sample.

[0076] 4. Ash calculation: The results obtained by calculating each element and ash content are shown in Table 1.

[0077] Example 2

[0078] 1. Sample pretreatment: Take some polypropylene pellets (ash content 15 ppm) with uniform particle size for later use.

[0079] 2. Sample digestion: Accurately weigh 0.2g (accurate to 0.0001g) of sample into a 30mL microwave digestion tube, add about 10mL of aqua regia, place the digestion tube in the digestion tube holder, and place it in a digestion tank containing 150mL of loading liquid (mixed with 5mL of high-grade pure nitric acid and 150mL of ultrapure water). The digestion tank is transferred to the microwave digestion instrument (the exposure time in the environment should be minimized during this process). The microwave digestion instrument program setting: pre-pressurization 5.0MPa, heating program: stage 1: 5min heating to 120℃, keep warm for 10min, stage 2: 5min heating to 160℃, keep warm for 5min, stage 3: 5min heating to 200℃, keep warm for 30min. After the sample is completely digested, cool it and transfer it to a 125mL PP ultra-clean bottle. When transferring, quickly add 20 mL of ultrapure water, mix the liquid evenly, transfer it out at one time, and weigh it to 100 g with ultrapure water as the sample test solution. The parallel sample and process blank operation procedures are the same.

[0080] 3. ICP test: Use standard solution to establish standard curves for aluminum, magnesium, titanium, calcium, and iron according to the gradient of concentrations of 0.5 mg / L, 1.0 mg / L, 3 mg / L, 5 mg / L, and 10 mg / L. The volumetric flask and pipette used to establish the standard curve must be cleaned and soaked in high-grade pure nitric acid before use to avoid interference. First, draw the standard curve according to the concentration gradient of the standard curve, and then take 10g of the test solution for testing to obtain the main element content of the sample.

[0081] 4. Ash calculation: The results obtained by calculating each element and ash content are shown in Table 1.

[0082] Example 3

[0083] 1. Sample pretreatment: Take flaky polypropylene pellets (ash content 30ppm) and crush them using a clean crusher.

[0084] 2. Sample digestion: Accurately weigh 0.2g (accurate to 0.0001g) of sample into a 30mL microwave digestion tube, add about 8mL concentrated nitric acid and 2mL hydrogen peroxide, place the digestion tube in the digestion tube holder, and place it in a digestion tank containing 150mL of loading liquid (mixed with 5mL of high-grade pure nitric acid and 150mL of ultrapure water), transfer the digestion tank into the microwave digestion instrument (the exposure time in the environment should be minimized during this process), wait for the sample to be completely digested, and transfer it to a 125mL PP ultra-clean bottle after cooling. When transferring, quickly add 20mL of ultrapure water, mix the liquid evenly, transfer it out at one time, and weigh it to 100g with ultrapure water as the sample test solution. The parallel sample and process blank operation procedures are the same.

[0085] 3. ICP test: Use standard solution to establish standard curves for aluminum, magnesium, titanium, calcium, and iron according to the gradient of concentrations of 0.5 mg / L, 1.0 mg / L, 3 mg / L, 5 mg / L, and 10 mg / L. The volumetric flask and pipette used to establish the standard curve must be cleaned and soaked in high-grade pure nitric acid before use to avoid interference. First, draw the standard curve according to the concentration gradient of the standard curve, and then take 10g of the test solution for testing to obtain the main element content of the sample.

[0086] 4. Ash calculation: The results obtained by calculating each element and ash content are shown in Table 1.

[0087] Comparative Example 1

[0088] The detection was carried out according to the method of Example 1, except that no pre-pressurization was performed during the microwave digestion process in Comparative Example 1. The results obtained by calculating the elements and ash content are shown in Table 1.

[0089] Comparative Example 2

[0090] The detection was carried out according to the method of Example 1, except that the temperature was raised to 180° C. in stage 3 of the microwave digestion process in Comparative Example 2. The results obtained by calculating the elements and ash content are shown in Table 1.

[0091] Comparative Example 3

[0092] The detection was carried out according to the method of Example 1, except that the holding time in stage 3 of the temperature rise during the microwave digestion process in Comparative Example 2 was 20 minutes. The results obtained by calculating the elements and ash content are shown in Table 1.

[0093] Table 1 Polypropylene ash composition obtained by testing in the examples and comparative examples

[0094]

[0095]

[0096] It can be seen from the above embodiments that the method of the present invention significantly improves the accuracy of ash content detection, especially can clearly detect the distribution of ash content, improves the detection sensitivity and accuracy of samples, and has a faster pre-processing speed, no loss of ash content, little external interference, a high degree of automation, and greatly shortens the detection time.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting ash content of a low-ash polyolefin material, comprising the following steps: A) pre-treating a polyolefin sample having an ash content of ≤50 ppm to obtain a pre-treated polyolefin powder; B) mixing the pretreated polyolefin powder with a digestion solution, and digesting the mixture under microwave and pressure conditions to obtain a digestion product; The digestion solution is one or more of hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid, dilute perchloric acid, nitric acid, hot concentrated perchloric acid, concentrated sulfuric acid and hydrogen peroxide; the digestion temperature is 100-300°C, and the digestion pressure is 0.1-10.0MPa; C) using ICP-MS to detect the digestion product to obtain the ash composition and content.

2. The ash content detection method of polyolefin material according to claim 1, characterized in that: The pretreatment includes drying, the drying temperature is 70-80° C., and the drying time is 0.5-2 hours.

3. The ash content detection method of polyolefin material according to claim 1, characterized in that: The ratio of the mass of the pretreated polyolefin powder to the volume of the digestion solution is 0.1 g: (1-10) mL.

4. The ash content detection method of polyolefin material according to claim 1, characterized in that: The pretreated polyolefin powder is mixed with the digestion liquid in a digestion tube, the digestion tube is placed on a digestion bracket, the digestion bracket is placed in a digestion tank, the digestion tank is filled with a load liquid, and digestion is performed under microwave and pressurized conditions to obtain a digestion product.

5. The ash content detection method of polyolefin material according to claim 4, characterized in that: The loading liquid includes nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, dilute sulfuric acid or dilute perchloric acid.

6. The ash content detection method of polyolefin material according to claim 1, characterized in that: The power of the microwave is 300-2100W, and the digestion time is 0.1-2 hours.

7. The ash content detection method of polyolefin material according to claim 1, characterized in that: The digestion is carried out according to the following heating program: Stage 1: Raise the temperature from room temperature to 110-130°C within 3-8 minutes, and keep warm for 5-15 minutes; Stage 2: Raise the temperature to 150-170°C within 3-8 minutes and keep warm for 5-15 minutes; Stage 3: Raise the temperature to 190-250°C within 3-8 minutes and keep warm for 25-40 minutes.

8. The ash content detection method of polyolefin material according to claim 1, characterized in that: The digestion product was mixed with water to obtain a test solution for ICP-MS detection.

9. The ash content detection method of polyolefin material according to claim 8, characterized in that: In ICP-MS detection, the mass concentration of the test solution is 0.01 to 10.0 ppm.

10. The ash content detection method of polyolefin material according to claim 8, characterized in that: In ICP-MS detection, the sample solution is added in an amount of 0.1 to 1.0 g.

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