Method for reducing ash content of polypropylene

Abstract

The invention provides a method for reducing ash content of polypropylene, which comprises the following steps: mixing a pyridine ionic liquid with a structure shown as a formula I with a polypropylene washing liquid, adding polypropylene powder to be treated, reacting under a stirring condition, and filtering to obtain a mixed washing liquid; and mixing the mixed washing liquid and the polypropylene washing liquid, washing, filtering and drying to obtain the low-ash polypropylene powder. By adopting the pyridine ionic liquid with the structure shown in the formula I, the ash in the polypropylene powder can be complexed, and the removal rate of the ash is high; the method is simple to operate and mild in reaction condition. The removal rate of ash in the polypropylene powder treated by the method is more than 90%, and the ash content is 1.6-6.6 ppm. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin post-processing, and in particular relates to a method for reducing the ash content of polypropylene. Background Art

[0002] Polypropylene (PP) is a thermoplastic synthetic resin with excellent performance, widely used in the automotive industry, household appliances, electronics, agriculture, construction packaging, building materials and furniture. With the rapid development of the domestic economy, the polypropylene industry has also made significant progress. However, the domestic polypropylene industry is about to enter a stage of absolute oversupply, and fierce market competition will inevitably further reduce the profits of general-purpose polypropylene products. After polypropylene polymerization is completed, the catalyst will remain within the polyolefin as metallic ash. This metallic ash not only reduces the mechanical properties and light transmittance of the polyolefin material, thereby reducing its application areas, but also accelerates the aging of the polypropylene. Therefore, there is a need to produce low-ash polypropylene.

[0003] Low-ash polypropylene (PP) boasts excellent electrical properties and easy processing, making it suitable for use in the electrical industry and enhancing its added value. Low-ash PP exhibits extremely low high-frequency losses, high dielectric strength, high insulation resistance, and a small negative temperature coefficient. These excellent properties broaden the application of PP in the electrical industry. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for reducing the ash content of polypropylene, which adopts a specific ionic liquid, has a high efficient complexing ability, and a high ash removal rate.

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

[0006] The pyridine ionic liquid having the structure of formula I is mixed with a polypropylene washing liquid, and the polypropylene powder to be treated is added, reacted under stirring conditions, and filtered to obtain a mixed washing liquid;

[0007]

[0008] The R1 is selected from one or more of ethyl, butyl, hexyl, octyl, decyl, dodecyl and hexadecyl; the R2 - One or more selected from chloride ion, bromide ion, iodide ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethanesulfonate ion, acetate ion, tetrafluoroborate ion and hexafluorophosphate ion; wherein R3 is selected from methyl or hydrogen;

[0009] The mixed washing liquid and the polypropylene flushing liquid are mixed, flushed, filtered, and dried to obtain low-ash polypropylene powder.

[0010] Preferably, the volume ratio of the pyridine ionic liquid to the polypropylene washing liquid is 1:(1-10);

[0011] The mass ratio of the pyridine ionic liquid to the polypropylene powder to be treated is (1-8):1.

[0012] Preferably, the pyridinium ionic liquid having the structure of formula I is selected from one or more of N-ethylpyridinium chloride ionic liquid, N-ethylpyridinium tetrafluoroborate ionic liquid, N-butylpyridinium bromide ionic liquid, 3-methyl-N-butylpyridinium bromide ionic liquid, N-dodecylpyridinium bromide ionic liquid and N-hexylpyridinium trifluoromethanesulfonate ionic liquid.

[0013] Preferably, the reaction temperature is 30-150° C., and the reaction time is 0.5-10 h.

[0014] Preferably, the mass ratio of the polypropylene flushing liquid to the polypropylene powder is (1-15):1.

[0015] Preferably, the flushing is performed 1 to 5 times.

[0016] Preferably, the drying temperature is 50-120°C.

[0017] Preferably, the polypropylene washing liquid is selected from one or more of alkane solvents, alcohol solvents, ester solvents, and ketone solvents;

[0018] The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol; the ester solvent is selected from one or more of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate; the ketone solvent is selected from one or more of acetone, 3-pentanone, butanone and 2-pentanone.

[0019] Preferably, the polypropylene flushing liquid is selected from alkane solvents and / or alcohol solvents;

[0020] The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane;

[0021] The alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol.

[0022] Preferably, the ash content of the low-ash polypropylene powder is 1.6 to 6.6 ppm.

[0023] The present invention provides a method for reducing the ash content of polypropylene, comprising the following steps: mixing a pyridine ionic liquid having the structure of Formula I with a polypropylene washing liquid, adding the mixture to the polypropylene powder to be treated, reacting under stirring, and filtering to obtain a mixed washing liquid; and mixing the mixed washing liquid with a polypropylene rinse liquid, rinsing, filtering, and drying to obtain a low-ash polypropylene powder. The pyridine ionic liquid having the structure of Formula I used in the present invention can complex the ash in the polypropylene powder, resulting in a high ash removal rate. The method is simple to operate and operates under mild reaction conditions. Experimental results demonstrate that the ash removal rate of the polypropylene powder treated by this method exceeds 90%, with an ash content of 1.6 to 6.6 ppm. DETAILED DESCRIPTION

[0024] The present invention provides a method for reducing the ash content of polypropylene, comprising the following steps:

[0025] The pyridine ionic liquid having the structure of formula I is mixed with a polypropylene washing liquid, and the polypropylene powder to be treated is added, reacted under stirring conditions, and filtered to obtain a mixed washing liquid;

[0026]

[0027] The R1 is selected from one or more of ethyl, butyl, hexyl, octyl, decyl, dodecyl and hexadecyl; the R2 - One or more selected from chloride ion, bromide ion, iodide ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethanesulfonate ion, acetate ion, tetrafluoroborate ion and hexafluorophosphate ion; wherein R3 is selected from methyl or hydrogen;

[0028] The mixed washing liquid and the polypropylene flushing liquid are mixed, flushed, filtered, and dried to obtain low-ash polypropylene powder.

[0029] The method provided by the present invention has the advantages of simple operation, mild reaction conditions, high deashing efficiency, etc.

[0030] In the present invention, the pyridine ionic liquid having the structure of formula I is known to be stable, easy to store, and easy to react with metal elements, and has a good ash removal effect; it is highly safe, the ionic liquid is not easy to volatilize, and has low toxicity.

[0031]

[0032] The R1 is selected from one or more of ethyl, butyl, hexyl, octyl, decyl, dodecyl and hexadecyl; the R2 -One or more selected from chloride ion, bromide ion, iodide ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethanesulfonate ion, acetate ion, tetrafluoroborate ion and hexafluorophosphate ion; and R3 is selected from methyl or hydrogen.

[0033] In a specific embodiment, the pyridine ionic liquid is selected from any one of Formulas 101 to 106;

[0034]

[0035] In the present invention, the volume ratio of the pyridine ionic liquid to the polypropylene washing liquid is 1:(1-8), specifically 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8.

[0036] The polypropylene washing liquid of the present invention is selected from one or more of alkane solvents, alcohol solvents, ester solvents and ketone solvents;

[0037] The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol; the ester solvent is selected from one or more of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate; the ketone solvent is selected from one or more of acetone, 3-pentanone, butanone and 2-pentanone.

[0038] The ash content of the polypropylene powder to be treated is 50 to 500 ppm. In the present invention, the mass ratio of the pyridine ionic liquid to the polypropylene powder to be treated is (1 to 8):1, specifically 5:1, 4:1, 3:1, 2:1, or 1:1.

[0039] In the present invention, the washing temperature is 30-150°C, preferably 30-120°C, specifically 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C; the washing time is 0.5-10h, preferably 1-8h; specifically 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h.

[0040] The polypropylene flushing liquid of the present invention is selected from alkane solvents and / or alcohol solvents;

[0041] The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane;

[0042] The alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol.

[0043] In the present invention, the mass ratio of the polypropylene flushing liquid to the polypropylene powder is (1-15):1, preferably (1-10):1; specifically, it can be 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, or 1:1.

[0044] The number of flushing in the present invention is 1 to 5 times, preferably 2 to 4 times; specifically, it can be 2 times, 3 times or 4 times.

[0045] In the present invention, the drying temperature is 50-120°C, preferably 50-100°C; specifically, it can be 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C.

[0046] The ash content of the low-ash polypropylene powder prepared by the method provided by the invention is 1.6-6.6 ppm.

[0047] In the method provided by the present invention, the washed polypropylene is digested by using a microwave digester, and then the contents of different elements therein are determined by using an inductively coupled plasma instrument.

[0048] In order to further illustrate the present invention, a method for reducing the ash content of polypropylene provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] N-ethylpyridinium chloride ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0051]

[0052] N-ethylpyridinium chloride ionic liquid (500 ml) was mixed with n-hexane (4000 ml). Polypropylene powder (100 g) with an ash content of 400 ppm was then added. The mixture was stirred at 100°C for 8 hours, filtered, and the mixed washings were discharged. Ethanol (1000 g) was added, and the mixture was rinsed and filtered four times. The mixture was then dried in an 80°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0053] Example 2

[0054] N-ethylpyridinium tetrafluoroborate ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0055]

[0056] N-ethylpyridinium tetrafluoroborate ionic liquid (500 ml) was mixed with isopropyl alcohol (2500 ml). Polypropylene powder (200 g) with an ash content of 200 ppm was then added. The mixture was stirred at 80°C for 4 hours, filtered, and the mixed washing liquid was discharged. n-Butane (1000 g) was added, and the mixture was rinsed and filtered three times. The mixture was then dried in an 80°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0057] Example 3

[0058] N-butylpyridinium bromide ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0059]

[0060] Mix N-butylpyridinium bromide ionic liquid (200 ml) with ethyl acetate (1400 ml), then add 100 g of polypropylene powder with an ash content of 100 ppm. Stir and react at 120°C for 2 hours, filter, and discard the mixed washings. Add n-hexane (500 g), rinse, filter, and repeat this process twice. Then, dry in a 50°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0061] Example 4

[0062] 3-Methyl-N-butylpyridinium bromide ionic liquid is used for removing ash from polypropylene, and its structural formula is as follows:

[0063]

[0064] Mix 3-methyl-N-butylpyridinium bromide ionic liquid (300 ml) with butanone (900 ml), then add 100 g of polypropylene powder with an ash content of 80 ppm. Stir and react at 70°C for 6 hours, filter, and discard the mixed washings. Add n-decane (700 g), rinse, filter, and repeat this process three times. Then, dry in a 90°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0065] Example 5

[0066] N-dodecylpyridinium bromide ionic liquid is used to remove ash from polypropylene, and its structural formula is as follows:

[0067]

[0068] N-dodecylpyridinium bromide ionic liquid (300 ml) was mixed with n-hexane (600 ml). Polypropylene powder (300 g) with an ash content of 100 ppm was then added. The mixture was stirred at 100°C for 3 hours, filtered, and the mixed washings were discharged. N-butanol (900 g) was added, and the mixture was rinsed and filtered three times. The mixture was then dried in a 100°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0069] Example 6

[0070] N-hexylpyridinium trifluoromethanesulfonate ionic liquid is used to remove ash from polypropylene, and its structural formula is as follows:

[0071]

[0072] N-hexylpyridinium trifluoromethanesulfonate ionic liquid (400 ml) was mixed with methyl formate (2400 ml). Polypropylene powder (100 g) with an ash content of 300 ppm was then added. The mixture was stirred at 50°C for 7 hours, filtered, and the mixed washings were discharged. N-pentane (3200 g) was added, and the mixture was rinsed and filtered four times. The mixture was then dried in a 60°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0073] Comparative Example 1

[0074] Deionized water (500 ml) and n-hexane (4000 ml) were mixed, followed by the addition of 100 g of polypropylene powder with an ash content of 400 ppm. The mixture was stirred at 100°C for 8 hours, filtered, and the mixed washings were discharged. Ethanol (1000 g) was added, and the mixture was rinsed and filtered four times. The mixture was then dried in an 80°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0075] Comparative Example 2

[0076] 1-Butyl-3-methylimidazolium tetrafluoroborate ionic liquid is used to remove ash from polypropylene, and its structural formula is as follows:

[0077]

[0078] 1-Butyl-3-methylimidazolium tetrafluoroborate ionic liquid (500 ml) was mixed with n-hexane (4000 ml). Polypropylene powder (100 g) with an ash content of 400 ppm was then added. The mixture was stirred at 100°C for 8 hours, filtered, and the mixed washings were discharged. Ethanol (1000 g) was added, and the mixture was rinsed and filtered four times. The mixture was then dried in an 80°C oven to obtain ultra-low ash polypropylene powder. The content of various elements in the powder was determined using an inductively coupled plasma analyzer.

[0079] Table 1 Test results of ash content of polypropylene powder obtained in Examples and Comparative Examples

[0080]

[0081] As can be seen from the above table, the present invention uses the pyridine ionic liquid having the structure of Formula I to effectively remove ash from polypropylene, and has a highly efficient deashing effect.

[0082] As can be seen from the above examples, the present invention provides a method for reducing the ash content of polypropylene, comprising the following steps: mixing a pyridine-based ionic liquid having the structure of Formula I with a polypropylene washing liquid, adding the mixture to the polypropylene powder to be treated, reacting under stirring, and filtering to obtain a mixed washing liquid; and mixing the mixed washing liquid with a polypropylene rinse liquid, rinsing, filtering, and drying to obtain a low-ash polypropylene powder. The pyridine-based ionic liquid having the structure of Formula I employed in the present invention is capable of complexing the ash in the polypropylene powder, resulting in a high ash removal rate. The method is simple to operate and operates under mild reaction conditions. Experimental results demonstrate that the ash removal rate of the polypropylene powder treated by this method exceeds 90%, with an ash content of 1.6 to 6.6 ppm.

[0083] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for reducing the ash content of polypropylene, comprising the following steps: The pyridine ionic liquid having the structure of formula I is mixed with a polypropylene washing liquid, and the polypropylene powder to be treated is added, reacted under stirring conditions, and filtered to obtain a mixed washing liquid; The R1 is selected from one or more of ethyl, butyl, hexyl, octyl, decyl, dodecyl and hexadecyl; the R2 - One or more selected from chloride ion, bromide ion, iodide ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethanesulfonate ion, acetate ion, tetrafluoroborate ion and hexafluorophosphate ion; wherein R3 is selected from methyl or hydrogen; The mixed washing liquid and the polypropylene flushing liquid are mixed, flushed, filtered, and dried to obtain low-ash polypropylene powder.

2. The method according to claim 1, characterized in that The volume ratio of the pyridine ionic liquid to the polypropylene washing liquid is 1:(1-10); The mass ratio of the pyridine ionic liquid to the polypropylene powder to be treated is (1-8):

1.

3. The method according to claim 1, characterized in that The pyridinium ionic liquid having the structure of formula I is selected from one or more of N-ethylpyridinium chloride ionic liquid, N-ethylpyridinium tetrafluoroborate ionic liquid, N-butylpyridinium bromide ionic liquid, 3-methyl-N-butylpyridinium bromide ionic liquid, N-dodecylpyridinium bromide ionic liquid and N-hexylpyridinium trifluoromethanesulfonate ionic liquid.

4. The method according to claim 1, wherein The reaction temperature is 30-150° C. and the reaction time is 0.5-10 h.

5. The method according to claim 1, wherein The mass ratio of the polypropylene flushing liquid to the polypropylene powder to be treated is (1-15):

1.

6. The method according to claim 1, characterized in that The number of flushing is 1 to 5 times.

7. The method according to claim 1, characterized in that The drying temperature is 50-120°C.

8. The method according to claim 1, characterized in that The polypropylene washing liquid is selected from one or more of alkane solvents, alcohol solvents, ester solvents, and ketone solvents; The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol; the ester solvent is selected from one or more of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate; the ketone solvent is selected from one or more of acetone, 3-pentanone, butanone and 2-pentanone.

9. The method according to claim 1, characterized in that The polypropylene flushing liquid is selected from alkane solvents and / or alcohol solvents; The alkane solvent is selected from one or more of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; The alcohol organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, butanol and hexanol.

10. The method according to claim 1, characterized in that The ash content of the low-ash polypropylene powder is 1.6 to 6.6 ppm.

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