A method for reducing polypropylene ash content and the application of imidazolium ionic liquids

Abstract

This invention belongs to the field of polyolefins, and particularly relates to a method for reducing the ash content of polypropylene and the application of imidazolium ionic liquids. The method provided by this invention includes the following steps: mixing imidazolium ionic liquid with crude polypropylene, filtering, and washing to obtain low-ash polypropylene; the imidazolium ionic liquid has the structure of formula (I); in formula (I), R... ‑ The ash is derived from one or more of chloride, bromide, iodide, hydroxide, acetate, thiocyanate, nitrate, methanesulfonate, tetrafluoroborate, and hexafluorophosphate ions. This invention uses an imidazolium ionic liquid with a specific chemical structure as an ash removal agent for polypropylene. This imidazolium ionic liquid can interact with the metallic ash in polypropylene, thereby significantly reducing the ash content in the washed polypropylene product.

Description

Technical Field

[0001] This invention belongs to the field of polyolefins, and particularly relates to a method for reducing the ash content of polypropylene and the application of imidazolium ionic liquids. Background Technology

[0002] Polyolefins are polymers obtained by polymerizing olefin monomers. They possess high mechanical properties, strong heat resistance, strong corrosion resistance, good insulation properties, and ease of processing. The polymerization of olefins is usually carried out under the action of a catalyst. After the polymerization reaction is complete, the catalyst inevitably remains inside the polyolefin, becoming metallic ash (Mg). 2+ Al 3 + and Ti 4+ The main source of ash is metal ash. This metal ash not only promotes the oxidative degradation of polyolefins themselves, but also accelerates the decomposition of antioxidants added to polyolefin materials, leading to a further shortening of the service life of polyolefin materials. Furthermore, residual ash reduces the mechanical properties and light transmittance of polyolefin materials, thus limiting their application range.

[0003] To reduce the metal ash content in polyolefins, scientists have made various attempts, such as selecting catalytic systems with higher catalytic activity, using different solvents for elution and removal, and using adsorbents to adsorb the polypropylene material in its dissolved or molten state. However, these methods often have drawbacks such as low efficiency, high requirements for operating temperature, and poor applicability. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for reducing the ash content of polypropylene and the application of imidazolium ionic liquid. The method provided by this invention can effectively remove ash from polypropylene and has the advantages of mild conditions, simple steps, and high efficiency.

[0005] This invention provides a method for reducing the ash content of polypropylene, comprising the following steps:

[0006] The imidazolium ionic liquid was mixed with crude polypropylene, filtered, and washed to obtain low-ash polypropylene.

[0007] The imidazolium ionic liquid has the structure of formula (I):

[0008]

[0009] In equation (I), R - It is derived from one or more of chloride ions, bromide ions, iodide ions, hydroxide ions, acetate ions, thiocyanate ions, nitrate ions, methanesulfonate ions, tetrafluoroborate ions, and hexafluorophosphate ions.

[0010] Preferably, the mass ratio of the imidazolium ionic liquid to crude polypropylene is (0.5-20):1.

[0011] Preferably, the mixing temperature is 25–150°C; and the mixing time is 0.5–5 h.

[0012] Preferably, the washing method involves sequentially performing several water washes and several organic solvent washes.

[0013] Preferably, the organic solvent used for the organic solvent washing is one or more of alcohols, dichloromethane, and chloroform with 1 to 3 carbon atoms.

[0014] Preferably, the ratio of water used in a single water washing cycle to the mass of low-ash polypropylene is (1-10):1; the ratio of organic solvent used in a single organic solvent washing cycle to the mass of low-ash polypropylene is (1-10):1.

[0015] Preferably, the washing temperature is 25–80°C; the total number of washing cycles is 2–10; and the duration of each washing cycle is 0.5–3 hours.

[0016] Preferably, the method further includes filtering and drying the washed product.

[0017] Preferably, the ash content of the crude polypropylene is 30 to 500 ppm.

[0018] This invention also provides an application of imidazolium ionic liquid in reducing the ash content of polypropylene, wherein the imidazolium ionic liquid has the structure of formula (I):

[0019]

[0020] In equation (I), R - It is derived from one or more of chloride ions, bromide ions, iodide ions, hydroxide ions, acetate ions, thiocyanate ions, nitrate ions, methanesulfonate ions, tetrafluoroborate ions, and hexafluorophosphate ions.

[0021] Compared with existing technologies, this invention provides a method for reducing the ash content of polypropylene and the application of imidazolium ionic liquids. The method provided by this invention includes the following steps: mixing imidazolium ionic liquid with crude polypropylene, filtering, and washing to obtain low-ash polypropylene; the imidazolium ionic liquid has the structure of formula (I); in formula (I), R... -The ash is derived from one or more of chloride, bromide, iodide, hydroxide, acetate, thiocyanate, nitrate, methanesulfonate, tetrafluoroborate, and hexafluorophosphate ions. This invention uses an imidazolium ionic liquid with a specific chemical structure as an ash removal agent for polypropylene. This imidazolium ionic liquid can interact with the metallic ash in polypropylene, thereby significantly reducing the ash content in the washed polypropylene product. Experimental results show that after deashing polypropylene using the method provided by this invention, the ash content of the product is below 10 ppm. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0023] This invention provides a method for reducing the ash content of polypropylene, comprising the following steps:

[0024] The imidazolium ionic liquid was mixed with crude polypropylene, filtered, and washed to obtain low-ash polypropylene.

[0025] The imidazolium ionic liquid has the structure of formula (I):

[0026]

[0027] In equation (I), R - It is derived from one or more of chloride ions, bromide ions, iodide ions, hydroxide ions, acetate ions, thiocyanate ions, nitrate ions, methanesulfonate ions, tetrafluoroborate ions, and hexafluorophosphate ions.

[0028] In the method provided by the present invention, the ash content of the crude polypropylene is preferably 30 to 500 ppm, specifically 30 ppm, 50 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 150 ppm, 200 ppm, 230 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 410 ppm, 450 ppm or 500 ppm.

[0029] In the method provided by this invention, the mass ratio of the imidazolium ionic liquid to crude polypropylene is preferably (0.5-20):1, specifically 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1.

[0030] In the method provided by the present invention, the mixing temperature is preferably 25-150℃, specifically 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, or 150℃; the mixing time is preferably 0.5-5h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h.

[0031] In the method provided by this invention, the washing process preferably involves sequentially performing several water washes and several organic solvent washes. The organic solvent used for the organic solvent washes is preferably one or more of an alcohol with 1-3 carbon atoms, dichloromethane, and chloroform, specifically one or more of methanol, ethanol, and propanol. The ratio of water volume per water wash to the mass of low-ash polypropylene is preferably (1-10):1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. The ratio of organic solvent volume per organic solvent wash to the mass of low-ash polypropylene is (1-10):1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, or 7:1. The washing ratio is 8:1, 9:1, or 10:1; the washing temperature is preferably 25-80℃, specifically 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃; the total number of washing cycles is preferably 2-10, specifically 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the number of water washing and organic solvent washing cycles is preferably 1-5, specifically 1, 2, 3, 4, or 5; the duration of each washing cycle is preferably 0.5-3 hours, specifically 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0032] The method provided by the present invention preferably further includes filtering and drying the washed product. Wherein, if multiple washings are performed, it is preferable to filter after each washing.

[0033] In the method provided by the present invention, the ash content of the obtained low-ash polypropylene is preferably less than 10 ppm; the content of magnesium, aluminum and titanium in the low-ash polypropylene is preferably 1 to 3 ppm independently.

[0034] In the method provided by this invention, the final low-ash polypropylene product can be dried and digested, and then the content of different elements can be determined using an inductively coupled plasma spectrometer.

[0035] The method provided by this invention uses an imidazolium ionic liquid with a specific chemical structure as an ash removal agent for polypropylene. This imidazolium ionic liquid can interact with the metallic ash in polypropylene, thereby significantly reducing the ash content in the washed polypropylene product. More specifically, the method provided by this invention has the following technical advantages:

[0036] 1) High safety: Ionic liquids have almost no volatility and low toxicity, which greatly reduces the fire hazard and harm to the human body during the deashing process.

[0037] 2) Wide applicability: This deashing method has low requirements for raw materials and can remove ash from different raw materials under various conditions.

[0038] 3) High deashing efficiency: This technology is carried out under solvent-free conditions, which allows the ionic liquid to fully contact the raw materials, reducing the use of chemical reagents and the generation of pollutants.

[0039] 4) Good economic efficiency: The ionic liquids used in the deashing process and the organic reagents used in the washing process can be recycled and purified, thus reducing the cost of practical application.

[0040] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0041] Example 1

[0042] 1-Butyl-3-methylimidazolium chloride was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0043]

[0044] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium chloride (500g) and polypropylene (100g, ash content 120ppm) are mixed at 130℃ and stirred for 2.5h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (400g), washed at 50℃ for 1h, filtered, and washed once more. Then, methanol (200g) is used to wash twice in the same way. After filtration and drying, the low-ash polypropylene product is obtained.

[0045] Example 2

[0046] The ash removal of polypropylene by applying 1-butyl-3-methylimidazolium bromide has the following structural formula:

[0047]

[0048] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium bromide (500g) and polypropylene (90g, ash content 150ppm) are mixed at 60℃ and stirred for 3h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (400g), washed at 25℃ for 2h, filtered, and washed once more with water. Then, it is washed twice with ethanol (300g) using the same method, filtered, and dried to obtain a low-ash polypropylene product.

[0049] Example 3

[0050] 1-Butyl-3-methylimidazolium iodide was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0051]

[0052] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium iodide (500g) and polypropylene (80g, ash content 110ppm) are mixed at 90℃ and stirred for 2.5h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (200g), washed at 40℃ for 1.5h, filtered, and washed once more. Then, it is washed twice with dichloromethane (400g) using the same method, filtered, and dried to obtain a low-ash polypropylene product.

[0053] Example 4

[0054] The ash removal of polypropylene by 3-butyl-1-methyl-1H-imidazolium-3-hydroxide is described in the following structural formula:

[0055]

[0056] The specific ash removal process is as follows: First, 600g of 3-butyl-1-methyl-1H-imidazolium-3-hydroxide and 100g of polypropylene (ash content of 230ppm) are mixed at 100℃ and stirred for 3h. Then, the mixture is filtered to obtain a crude polypropylene product with low ash content. Next, the obtained solid is added to deionized water (300g), washed at 50℃ for 1h, filtered, and washed once more with water. Then, the mixture is washed twice with ethanol (300g) using the same method, filtered, and dried to obtain the polypropylene product with low ash content.

[0057] Example 5

[0058] The ash removal of polypropylene by applying 1-butyl-3-methylimidazolium acetate has the following structural formula:

[0059]

[0060] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium acetate (500g) and polypropylene (50g, ash content 410ppm) are mixed at 110℃ and stirred for 2h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (200g), washed at 60℃ for 0.5h, filtered, and washed once more. Then, it is washed twice with dichloromethane (100g) using the same method, filtered, and dried to obtain a low-ash polypropylene product.

[0061] Example 6

[0062] 1-Butyl-3-methylimidazolium thiocyanate was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0063]

[0064] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium thiocyanate (500g) and polypropylene (25g, ash content 350ppm) are mixed at 150℃ and stirred for 0.5h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (200g), washed at 40℃ for 1.5h, filtered, and washed once more with water. Then, ethanol (200g) is used to wash twice in the same way. After filtration and drying, a low-ash polypropylene product is obtained.

[0065] Example 7

[0066] 1-Butyl-3-methylimidazolium nitrate was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0067]

[0068] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium nitrate (500g) and polypropylene (40g, ash content 130ppm) are mixed at 50℃ and stirred for 3h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (300g), washed at 50℃ for 1h, filtered, and the water washing is repeated once. Then, ethanol (200g) is used to wash twice in the same way. After filtration and drying, a low-ash polypropylene product is obtained.

[0069] Example 8

[0070] 1-Butyl-3-methylimidazolium methanesulfonate was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0071]

[0072] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium methanesulfonate (500g) and polypropylene (70g, ash content 110ppm) are mixed at 80℃ and stirred for 2.5h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (400g), washed at 25℃ for 2h, filtered, and washed once more. Then, methanol (200g) is used to wash twice in the same way. After filtration and drying, a low-ash polypropylene product is obtained.

[0073] Example 9

[0074] 1-Butyl-3-methylimidazolium tetrafluoroborate was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0075]

[0076] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium tetrafluoroborate (500g) and polypropylene (60g, ash content 200ppm) are mixed at 100℃ and stirred for 2h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (400g), washed at 60℃ for 1h, filtered, and the water washing is repeated once. Then, methanol (200g) is used to wash twice using the same method. After filtration and drying, a low-ash polypropylene product is obtained.

[0077] Example 10

[0078] 1-Butyl-3-methylimidazolium hexafluorophosphate was applied to the ash removal of polypropylene, and its structural formula is as follows:

[0079]

[0080] The specific ash removal process is as follows: First, 1-butyl-3-methylimidazolium hexafluorophosphate (500g) and polypropylene (100g, ash content 120ppm) are mixed at 120℃ and stirred for 1.5h. Then, the mixture is filtered to obtain a low-ash polypropylene crude product. Next, the obtained solid is added to deionized water (500g), washed at 50℃ for 0.5h, filtered, and washed once more with water. Then, ethanol (300g) is used to wash twice in the same way. After filtration and drying, a low-ash polypropylene product is obtained.

[0081] Comparative Example 1

[0082] 100g of polypropylene (100g, ash content 120ppm) was added to deionized water (400g), washed at 50℃ for 1h, filtered, and washed once with water. Then, methanol (200g) was used to wash twice in the same way. After filtration and drying, the control product was obtained.

[0083] Effect evaluation

[0084] The ash content and metal element content of the products obtained in Examples 1-10 and Comparative Example 1 were determined, and the test data are as follows:

[0085]

[0086] The data in the table above demonstrates that the imidazolium ionic liquid used in this invention has excellent ash removal effects on polypropylene materials containing high ash content.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of reducing the ash content of polypropylene, characterized in that, Includes the following steps: The imidazolium ionic liquid was mixed with crude polypropylene, filtered, and washed to obtain low-ash polypropylene. The imidazolium ionic liquid has the structure of formula (I): Formula (I); In formula (I), R - one or more of chloride, bromide, iodide, hydroxide, acetate, thiocyanate, nitrate, methanesulfonate, tetrafluoroborate, and hexafluorophosphate. The mass ratio of the imidazolium ionic liquid to crude polypropylene is (0.5~20):

1.

2. The method of claim 1, wherein, The mixing temperature is 25~150℃; the mixing time is 0.5~5h.

3. The method of claim 1, wherein, The washing method involves sequentially performing several water washes and several organic solvent washes.

4. The method of claim 3, wherein, The organic solvent used for washing is one or more of alcohols, dichloromethane, and chloroform, which have 1 to 3 carbon atoms.

5. The method of claim 3, wherein, The ratio of water usage per wash to the mass of low-ash polypropylene is (1~10):1; the ratio of organic solvent usage per wash to the mass of low-ash polypropylene is (1~10):

1.

6. The method of claim 3, wherein, The washing temperature is 25~80℃; the total number of washing cycles is 2~10; and the duration of each washing cycle is 0.5~3 hours.

7. The method according to claim 1, characterized in that, Also includes: The washed product is then filtered and dried.

8. The method according to any one of claims 1 to 7, characterized in that, The ash content of the crude polypropylene is 30~500ppm.

9. Application of imidazolium ionic liquid in reducing polypropylene ash content, wherein the imidazolium ionic liquid has the structure of formula (I): Equation (I); In formula (I), R - one or more of chloride, bromide, iodide, hydroxide, acetate, thiocyanate, nitrate, methanesulfonate, tetrafluoroborate, and hexafluorophosphate.

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