Method for determining content of n-hexane extract in polyethylene

Abstract

The invention provides a method for determining the content of an n-hexane extract in polyethylene, and relates to the technical field of polyethylene component detection. The determination method comprises the following steps: preparing polyethylene particles into a film sample; recording the mass of the extraction sleeve, weighing the thin film, adding the thin film into the sleeve, and recording the total weight; and assembling the test equipment, adding normal hexane, extracting, drying to obtain the mass of the film, and calculating to obtain the content of the normal hexane extract in the polyethylene. According to the method, the defects in the prior art are overcome, the content of the n-hexane in the polyethylene can be measured by using less n-hexane, the test purpose is achieved, the cost is low, meanwhile, the harmfulness is small, and the whole operation process has higher simplicity and convenience.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene component detection, and in particular to a method for determining the content of n-hexane extract in polyethylene. Background Art

[0002] Polyethylene is an important thermoplastic material with excellent light transmittance and processability, and is widely used in packaging, containers, and other fields. The content of n-hexane extracts in polyethylene is a key criterion for measuring the performance of polyethylene resins. Some polyethylene is used in food and other fields. Excessive n-hexane extracts can precipitate and enter the human body, posing a health hazard. Excessive n-hexane extracts can also reduce the material's mechanical strength and other properties. Therefore, determining the content of n-hexane extracts in polyethylene is necessary to improve polyethylene materials.

[0003] The existing method for determining the n-hexane extract content in polyethylene is based on ASTM D5227-13: 1000 mL of n-hexane is added to a resin kettle, which is then placed in a water bath. A cut film sample is then added to the n-hexane, connected to a condenser, and extraction is started for 2 hours. After 2 hours, the film sample is removed and placed in a beaker, being careful not to leave any film behind. The sample is then dried in a vacuum oven for 2 hours. The dried mass is then weighed and the difference is calculated to determine the n-hexane extract content. However, this method requires 1000 mL of n-hexane at a time during actual experiments, which is both environmentally and economically unsuitable. Furthermore, the container used during the experiment is large, making sample removal difficult and inconvenient for widespread use. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for determining the content of n-hexane extract in polyethylene. The n-hexane content in polyethylene can be determined using less n-hexane, thereby achieving the testing purpose. The method has low cost and little harm, and the entire operation process is highly simple.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A method for determining the content of n-hexane extract in polyethylene, comprising the following steps:

[0007] (1) using a hot pressing tablet press to press polyethylene granules into a film and cutting the film to obtain a polyethylene film for later use;

[0008] (2) Prepare a Soxhlet extraction tube and weigh it as m0. Then add the polyethylene film into the Soxhlet extraction tube and weigh it as m1. The mass of the polyethylene film is recorded as m2.

[0009] (3) Add 200 mL of n-hexane to a 500 mL fat flask, place it in a water bath, and use the above-mentioned Soxhlet extraction sleeve equipped with polyethylene film to assemble a Soxhlet extractor and a condenser for extraction. Then remove the Soxhlet extraction sleeve, vacuum dry it, and weigh it, which is recorded as m3;

[0010] (4) Calculate the n-hexane extract content = (m1-m3) / m2×100%.

[0011] Preferably, the pressing temperature of the hot pressing tablet press in step (1) is 180°C-200°C.

[0012] Further preferably, the pressing temperature of the hot pressing tablet press in step (1) is 190°C.

[0013] Preferably, the thickness of the polyethylene film in step (1) is less than 20 μm.

[0014] Preferably, the water bath temperature of the water bath in step (3) is 84±5°C.

[0015] Further preferably, the water bath temperature of the water bath in step (3) is 84±0.5°C.

[0016] Preferably, the extraction time in step (3) is 5-36 hours.

[0017] Further preferably, the extraction time in step (3) is 10-14 hours.

[0018] Preferably, the vacuum drying temperature in step (3) is 30-80° C., and the drying time is 2-36 hours.

[0019] Further preferably, the vacuum drying temperature in step (3) is 50° C. and the drying time is 10-14 h.

[0020] The present invention provides a method for determining the content of n-hexane extract in polyethylene, which has the following advantages over the prior art:

[0021] The testing method of the present invention only requires 200 ml of n-hexane for each test, and the n-hexane can be reused, thereby reducing the amount of n-hexane used, reducing experimental hazards, and lowering costs. At the same time, during the test, only the extraction sleeve needs to be taken out for weighing, and there is no need to take out the film sample separately, thereby reducing the difficulty of taking out the film sample and the loss of the film sample caused by human factors, and ensuring the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram of the overall experimental setup in Example 1 of the present invention;

[0023] Figure 2This is an enlarged view of the experimental extraction part in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are 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 making creative efforts are within the scope of protection of the present invention.

[0025] Example 1:

[0026] Measurement of n-hexane extractable content in polyethylene:

[0027] PE-1 pellets (Satellite FS7000) were used as the test sample. 3.0482 g of PE-1 pellets were weighed and compressed using a Hal Technology HTYP-20 laboratory tablet press at 190°C. The portion with a thickness of less than 20 μm was cut into small pieces to obtain film samples for later use.

[0028] The mass of the empty extraction sleeve was weighed as m0 = 47.8071 g. After adding the film sample into the extraction sleeve, the total mass was weighed as m1 = 49.8250 g. The mass of the film sample was recorded as m2 = 2.0179 g.

[0029] Add 200 ml of n-hexane to a 500 ml fat flask, place in a constant temperature water bath at 84°C, assemble the Soxhlet extractor and condenser, and begin the experiment. Extract for 12 hours. After 12 hours, remove the extraction cannula and dry in a vacuum oven at 50°C for 12 hours. Weigh m³ = 49.7948 g.

[0030] Calculate the content of n-hexane extract =

[0031] (m1-m3) / m2×100%=(49.8250-49.7948) / 2.0179×100%=1.50%

[0032] Example 2:

[0033] Measurement of n-hexane extractable content in polyethylene:

[0034] The specific method is the same as that of Example 1, except that Example 2 uses PE-2 (Iran Torch 7000F) for measurement;

[0035] The mass of the empty extraction sleeve is weighed as m0 = 47.8066 g. After adding the film sample into the extraction sleeve, the total mass is weighed as m1 = 49.8153 g. The mass of the film sample is recorded as m2 = 2.0087 g.

[0036] After drying, the mass of the extraction sleeve was weighed to be m3 = 49.7884 g.

[0037] Calculate the content of n-hexane extract =

[0038] (m1-m3) / m2×100%=(49.8153-49.7884) / 2.0179×100%=1.33%

[0039] Example 3:

[0040] Measurement of n-hexane extractable content in polyethylene:

[0041] The specific method is the same as that of Example 1, except that PE-3 (Secco 5301) is used for measurement in Example 3;

[0042] The mass of the empty extraction sleeve was weighed to be m0 = 47.8073 g. After adding the film sample into the extraction sleeve, its total mass was weighed to be m1 = 49.8251 g. The mass of the film sample was recorded as m2 = 2.0178 g.

[0043] After drying, the mass of the extraction sleeve was weighed to be m3 = 49.8073 g.

[0044] Calculate the content of n-hexane extract =

[0045] (m1-m3) / m2×100%=(49.8251-49.8073) / 2.0178×100%=0.88%.

[0046] Example 4:

[0047] Measurement of n-hexane extractable content in polyethylene:

[0048] The specific method is the same as that of Example 1, except that PE-4 (Daqing 6097) is used for measurement in Example 4;

[0049] The empty extraction sleeve was weighed to m0 = 47.8068 g. After adding the film sample to the extraction sleeve, the total mass was weighed to m1 = 49.8289 g. The sample mass was recorded as m2 = 2.0221 g. After drying, the extraction sleeve was weighed to m3 = 49.8085 g.

[0050] Calculate the content of n-hexane extract =

[0051] (m1-m3) / m2×100%=(49.8289-49.8085) / 2.0221×100%=1.01%.

[0052] Comparative Example 1:

[0053] PE-1 pellets were tested using the ASTM D5227-13 test method:

[0054] Weigh 3.1059g of PE-1 pellets and compress them using a Hal Technology HTYP-20 laboratory tablet press. A film sample with a thickness of less than 0.1mm was obtained, weighing m0 = 2.4957g. The sample was placed in a 1500ml flask, followed by 1000ml of n-hexane and placed in a 50°C waterbath. After installing a condenser, extract the sample for 2 hours. After 2 hours, remove the film, place it in a beaker, and dry it in a vacuum oven at 80°C for 2 hours. The film mass was then measured at m1 = 2.4588g.

[0055] Calculated n-hexane extract content = (m0-m1) / m0 = 1.48%.

[0056] Comparative Example 2:

[0057] The steps are the same as those in Comparative Example 1, except that Comparative Example 2 uses PE-2 for testing, and the film mass is weighed to be m0 = 2.4874 g. After drying, the film mass is taken out and weighed to be m1 = 2.4556 g.

[0058] Calculated n-hexane extract content = (m0-m1) / m0 = 1.28%.

[0059] Comparative Example 3:

[0060] The steps are the same as those in Comparative Example 1, except that Comparative Example 3 uses PE-3 for testing, and the film mass is weighed to be m0 = 2.5176 g. After drying, the film mass is taken out and weighed to be m1 = 2.4948 g.

[0061] Calculated n-hexane extract content = (m0-m1) / m0 = 0.91%.

[0062] Comparative Example 4:

[0063] The steps are the same as those in Comparative Example 1, except that Comparative Example 4 uses PE-4 for testing, and the film mass is weighed to be m0 = 2.4981 g. After drying, the film mass is taken out and weighed to be m1 = 2.4731 g.

[0064] Calculate the n-hexane extract content = (m0-m1) / m0 = 1.00%.

[0065] The specific test process data and results of the above examples and comparative examples are shown in the following table:

[0066]

[0067]

[0068] That is, the method of Examples 1-4 can accurately determine the content of n-hexane extract in polyethylene using less n-hexane.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for determining the content of n-hexane extract in polyethylene, characterized in that: The determination method comprises the following steps: (1) using a hot pressing tablet press to press polyethylene granules into a film and cutting the film to obtain a polyethylene film for later use; (2) Prepare a Soxhlet extraction tube and weigh it as m0. Then add the polyethylene film into the Soxhlet extraction tube and weigh it as m1. The mass of the polyethylene film is recorded as m2. (3) Add 200 mL of n-hexane to a 500 mL fat flask, place it in a water bath, and use the above-mentioned Soxhlet extraction sleeve equipped with polyethylene film to assemble a Soxhlet extractor and a condenser for extraction. Then remove the Soxhlet extraction sleeve, vacuum dry it, and weigh it, which is recorded as m3; (4) Calculate the n-hexane extract content = (m1-m3) / m2×100%.

2. The assay method according to claim 1, wherein: The temperature of the hot pressing tablet press in step (1) is 180°C-200°C.

3. The measuring method according to claim 1, wherein: The pressing temperature of the hot pressing tablet press in step (1) is 190°C.

4. The measuring method according to claim 1, wherein: The thickness of the polyethylene film in step (1) is less than 20 μm.

5. The measuring method according to claim 1, wherein: The water bath temperature of the water bath in step (3) is 84±5°C.

6. The measuring method according to claim 1, wherein: The water bath temperature of the water bath in step (3) is 84±0.5°C.

7. The assay method according to claim 1, wherein: The extraction time in step (3) is 5-36 hours.

8. The assay method according to claim 1, wherein: The extraction time in step (3) is 10-14 hours.

9. The measuring method according to claim 1, wherein: The vacuum drying temperature in step (3) is 30-80° C., and the drying time is 2-36 hours.

10. The determination method according to claim 1, wherein: The vacuum drying temperature in step (3) is 50° C. and the drying time is 10-14 h.

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