Method for reducing ash content of polypropylene

Abstract

The invention relates to the field of chemical engineering, in particular to a method for reducing ash content of polypropylene. According to the method, the quaternary ammonium ionic liquid and the washing liquid are mixed to obtain the mixed liquid, the mixed liquid is used for carrying out washing and de-ashing reaction on the polypropylene, and then the washing liquid is used for washing and drying, so that the ultra-low ash content polypropylene is obtained. In the treatment process, the selected ionic liquid can efficiently complex metal components in polypropylene in the system, and the ash removal rate is increased. In addition, the method disclosed by the invention is simple to operate, mild in reaction condition and convenient for large-scale application.

Description

TECHNICAL FIELD

[0001] The present application relates to the chemical industry, in particular to a method for reducing the ash content of polypropylene. BACKGROUND

[0002] Polypropylene (PP) as a kind of thermoplastic synthetic resin, with its outstanding performance, in the automotive manufacturing, household appliances, electronics industry, agriculture, building packaging materials and furniture building materials and other fields have been widely used. With the rapid rise of the domestic economy, the polypropylene industry has also ushered in significant development. However, the current domestic polypropylene industry is gradually moving towards the stage of overcapacity, market competition is increasingly fierce, which will undoubtedly further compress the profit space of general-purpose polypropylene products.

[0003] In the polymerization process of polypropylene, the catalyst will inevitably remain inside the polymer, forming metal ash. These metal ash not only reduces the mechanical properties and light transmittance of polyolefin materials, thereby limiting the application range of polypropylene, but also accelerates its aging process. Therefore, it is particularly important to develop low-ash polypropylene. SUMMARY

[0004] Therefore, the present application provides a method for reducing the ash content of polypropylene. The method of the present application can efficiently remove the ash content in polypropylene.

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

[0006] S1, mixing quaternary ammonium ionic liquid with washing liquid to obtain a mixed solution;

[0007] S2, mixing the mixed solution obtained in step S1 with polypropylene and then performing solid-liquid separation to obtain a solid;

[0008] S3, washing the solid obtained in step S2 with a flushing liquid and then drying to obtain low-ash polypropylene;

[0009] The quaternary ammonium ionic liquid has a structure represented by formula (I): R4NX - Formula (I); wherein 4 R is independently selected from H or hydrocarbon group, and at least 3 R is a hydrocarbon group; X - is at least one selected from fluoride ion, chloride ion, bromide ion, iodide ion, borate ion, dihydrogen phosphate ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethane sulfonate ion, tetrafluoroborate ion and hexafluorophosphate ion.

[0010] Preferably, the hydrocarbon group is at least one of alkyl and aryl.

[0011] Preferably, the hydrocarbon group is at least one of ethyl, butyl, hexyl, octyl, phenyl, naphthyl, phenanthryl.

[0012] Preferably, the quaternary ammonium ionic liquid is at least one of triethylammonium hydrochloride ionic liquid, tetramethylammonium bromide ionic liquid, N, N-diethylmethylammonium trifluoromethane sulfonate ionic liquid, triethylamine nitrate ionic liquid, tributylammonium tetrafluoroborate ionic liquid, tetramethylammonium dihydrogen phosphate ionic liquid.

[0013] Preferably, the washing liquid is at least one of alkane solvent, alcohol solvent, ester solvent, ketone solvent.

[0014] Preferably, the alkane solvent is at least one of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol and hexanol; the ester solvent is at least one of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate; the ketone solvent is at least one of acetone, 3-pentanone, butanone and 2-pentanone.

[0015] Preferably, the volume ratio of the quaternary ammonium ionic liquid to the washing liquid is 1: (1-20).

[0016] The mass ratio of the quaternary ammonium ionic liquid in the mixed solution to the polypropylene is (1-10): 1.

[0017] Preferably, in step S2, the reaction temperature is 30-150℃, and the reaction time is 0.1-10h.

[0018] Preferably, the flushing liquid is at least one of alkane solvent and alcohol solvent.

[0019] Preferably, the alkane solvent is at least one of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol and hexanol.

[0020] Preferably, the mass ratio of the flushing liquid to the polypropylene in step S2 is (1-15): 1.

[0021] Preferably, in step S2, the ash content of the polypropylene is 50-500ppm.

[0022] The washing frequency is 1-5 times.

[0023] The drying temperature is 50-110℃.

[0024] The application provides a post-treatment method of polypropylene, which comprises the following steps: mixing a quaternary ammonium ionic liquid with a washing liquid to obtain a mixed liquid, washing and desalting the polypropylene by using the mixed liquid, then washing by using a flushing liquid, and drying to obtain ultra-low ash polypropylene.

[0025] The test results show that the ash removal rate of the polypropylene can reach more than 96% by using the method, the ash in the polypropylene can be efficiently removed, and low-ash polypropylene can be obtained. DETAILED DESCRIPTION

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0027] In the technical features described in an open manner herein, both a closed technical solution consisting of listed features and an open technical solution containing listed features are included.

[0028] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] In the present text, in relation to numerical intervals, unless otherwise specified, the numerical intervals are considered to be continuous and include the minimum and maximum values of the range and every value between such minimum and maximum values. Further, when ranges are referred to as integers, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood as including any and all sub-ranges subsumed therein.

[0030] In the present text, in relation to units of data ranges, if only the right end point is followed by a unit, it means that the units of the left end point and the right end point are the same. For example, 30~150℃ means that the units of the left end point "30" and the right end point "150" are both ℃.

[0031] The application provides a method for reducing the ash content of polypropylene, comprising the following steps:

[0032] S1, mixing a quaternary ammonium ionic liquid with a washing liquid to obtain a mixed liquid;

[0033] S2, mixing and reacting the mixed liquid obtained in step S1 with polypropylene, then solid-liquid separation to obtain a solid;

[0034] S3, washing the solid obtained in step S2 with a washing liquid, and then drying to obtain low-ash polypropylene;

[0035] The quaternary ammonium ionic liquid has a structure shown in formula (I): R4NX - Formula (I); wherein, 4 R are independently selected from H or a hydrocarbon group, and at least 3 R are hydrocarbon groups; X - at least one selected from fluoride ion, chloride ion, bromide ion, iodide ion, borate ion, dihydrogen phosphate ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethanesulfonate ion, tetrafluoroborate ion and hexafluorophosphate ion.

[0036] With regard to step S1 :

[0037] S1, mixing the quaternary ammonium ionic liquid with a washing liquid to obtain a mixed liquid.

[0038] In the present application, the quaternary ammonium ionic liquid has a structure shown in formula (I): R4NX - Formula (I).

[0039] wherein:

[0040] 4 R are independently selected from H or a hydrocarbon group, and at least 3 R are hydrocarbon groups. The "4 R are independently selected from H or a hydrocarbon group" means that each of the 4 R is independently selected from H or a hydrocarbon group, and each R is independent of each other, and each R can be the same or different. In the present application, the hydrocarbon group is preferably at least one of an alkyl group and an aryl group, and more preferably at least one of an ethyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, a naphthyl group and a phenanthryl group. In one embodiment of the present application, among the 4 R, one is H and the other three are ethyl groups. In another embodiment of the present application, the 4 R are methyl groups. In another embodiment of the present application, among the 4 R, one is H, one is a methyl group and the other two are ethyl groups. In another embodiment of the present application, among the 4 R, one is H and the other three are butyl groups.

[0041] X - is at least one selected from fluoride ion (F - ), chloride ion (Cl - ), bromide ion (Br - ), iodide ion (I - ), borate ion (BO2 - ), dihydrogen phosphate ion (H2PO4 - ), acetate ion (CH3COO - ), nitrate ion (NO3 - ), hydroxide ion (OH - ), methanesulfonate ion (CH3SO3 -), thiocyanate ion (SCN - ), trifluoromethane sulfonate ion (CF3SO3 - ), tetrafluoroborate ion (BF4 - ) and hexafluorophosphate ion (PF6 - ) ; preferably at least one of chloride ion (Cl - ), bromide ion (Br - ), dihydrogen phosphate ion (H2PO4 - ), nitrate ion (NO3 - ), trifluoromethane sulfonate ion (CF3SO3 - ), tetrafluoroborate ion (BF4 - ).

[0042] In the present application, more preferably, the quaternary ammonium ionic liquid is at least one of triethylammonium hydrochloride ionic liquid, tetramethylammonium bromide ionic liquid, N, N-diethylmethylammonium trifluoromethane sulfonate ionic liquid, triethylamine nitrate ionic liquid, tributylammonium tetrafluoroborate ionic liquid and tetramethylammonium dihydrogen phosphate ionic liquid.

[0043] In the present application, the washing liquid is preferably at least one of alkane solvent, alcohol solvent, ester solvent and ketone solvent. The alkane solvent is preferably at least one of n-butane, iso-pentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane. The alcohol solvent is preferably at least one of methanol, ethanol, propanol, isopropanol, butanol and hexanol. The ester solvent is preferably at least one of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate. The ketone solvent is preferably at least one of acetone, 3-pentanone, butanone and 2-pentanone.

[0044] In the present application, the volume ratio of the quaternary ammonium ionic liquid to the washing liquid is preferably 1: (1-20), and more preferably 1: (1-8).

[0045] In the present application, the mixing of the quaternary ammonium ionic liquid and the washing liquid is not particularly limited, and the two can be mixed according to the conventional mixing method in the art.

[0046] With regard to step S2 :

[0047] S2, mixing the mixed liquid obtained in step S1 with polypropylene and then performing solid-liquid separation to obtain a solid.

[0048] In the present application, the polypropylene is preferably polypropylene powder. In the present application, the ash content of the polypropylene is preferably 50-500 ppm, more preferably 80-400 ppm, and specifically can be 80 ppm, 100 ppm, 120 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, or 400 ppm.

[0049] In the present application, the mass ratio of the quaternary ammonium ionic liquid in the mixed solution to the polypropylene is preferably (1-10):1, and specifically can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, and more preferably (1-5):1.

[0050] In the present application, the temperature of the reaction is preferably 30-150℃, and specifically can be 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃, and more preferably 30-120℃. The time of the reaction is preferably 0.1-10h, and specifically can be 0.1h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, and more preferably 1-8h. In the present application, the reaction is preferably accompanied by stirring. The polypropylene is washed by the above mixing reaction, and then solid-liquid separation is performed. In the present application, the mode of the solid-liquid separation is preferably centrifugal separation. After centrifugal separation, the washing waste liquid is discharged, and a solid substance is obtained.

[0051] With regard to step S3 :

[0052] S3, washing the solid substance obtained in step S2 with a flushing liquid, and then drying to obtain low-ash polypropylene.

[0053] In the present application, the flushing liquid is preferably at least one of an alkane solvent and an alcohol solvent. The alkane solvent is preferably at least one of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane, and n-dodecane. The alcohol solvent is preferably at least one of methanol, ethanol, propanol, isopropanol, butanol, and hexanol.

[0054] In the present application, the mass ratio of the flushing liquid to the polypropylene in step S2 is preferably (1-15):1, and specifically can be 1:1, 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, and more preferably (1-10):1.

[0055] In the present application, the washing comprises mixing the flushing liquid with the solid obtained in step S2, and then performing solid-liquid separation. Preferably, the solid-liquid separation is performed by centrifugal separation. In the present application, the number of washing is preferably 1-5 times, and can be 1 time, 2 times, 3 times, 4 times or 5 times.

[0056] In the present application, after washing, drying is performed. The drying temperature is preferably 50-110℃, and can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃ or 110℃, and is more preferably 50-100℃. After the above treatment, the de-ashed polypropylene is obtained, which is ultra-low-ash polypropylene.

[0057] Low-ash polypropylene has great application potential in the electrical field due to its excellent electrical properties and easy processing characteristics, and can effectively improve the added value of polypropylene. Such materials have extremely low high-frequency loss, high dielectric strength, excellent insulation resistance and stable positive temperature coefficient. These excellent properties greatly expand the application scenarios of polypropylene in the electrical field. However, the polypropylene products prepared by the existing technology have high metal ash, which reduces the performance of polypropylene and limits its application. In view of this, the present application provides a post-treatment method of polypropylene. First, a quaternary ammonium ionic liquid is mixed with a washing liquid to obtain a mixed liquid, and then the mixed liquid is used for washing and de-ashing reaction of polypropylene. Then, a flushing liquid is used for washing and drying, so as to obtain ultra-low-ash polypropylene. During the treatment process, the selected ionic liquid can efficiently complex the metal in the polypropylene in the system of the present application, thereby improving the ash removal rate. In addition, the method of the present application is simple in operation, mild in reaction conditions, and convenient for large-scale application.

[0058] The test results show that the method of the present application can make the ash removal rate of polypropylene reach more than 96%, and can efficiently remove the ash in polypropylene to obtain low-ash polypropylene.

[0059] In order to further understand the present application, the preferred embodiments of the present application are described below in combination with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations on the claims of the present application.

[0060] Example 1

[0061] The triethylammonium hydrochloride ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0062] .

[0063] The treatment process is as follows:

[0064] S1, mix triethylammonium hydrochloride ionic liquid (500mL) with n-hexane (4000mL) to obtain a mixed liquid.

[0065] S2, add polypropylene powder (100 g) with ash content of 400 ppm to the mixture obtained in step S1, stir and react at 100°C for 8 h, centrifugal filtration, and discharge the mixed washing liquid to obtain solid substance.

[0066] S3, re-add ethanol (1000 g) to the solid substance for flushing, centrifugal filtration, repeat the operation 4 times, and then dry in an oven at 80°C to obtain polypropylene powder with ultra-low ash content.

[0067] Example 2

[0068] The tetramethylammonium bromide ionic liquid is used for polypropylene ash removal, and the structural formula is as follows:

[0069] .

[0070] The treatment process is as follows:

[0071] S1, mix tetramethylammonium bromide ionic liquid (500 mL) with isopropyl alcohol (2500 mL) to obtain a mixture.

[0072] S2, add polypropylene powder (200 g) with ash content of 300 ppm to the mixture obtained in step S1, stir and react at 80°C for 4 h, centrifugal filtration, and discharge the mixed washing liquid to obtain solid substance.

[0073] S3, re-add n-butane (1000 g) to the solid substance for flushing, centrifugal filtration, repeat the operation 3 times, and then dry in an oven at 80°C to obtain polypropylene powder with ultra-low ash content.

[0074] Example 3

[0075] The N,N-diethylmethylammonium trifluoromethanesulfonate ionic liquid is used for polypropylene ash removal, and the structural formula is as follows:

[0076] .

[0077] The treatment process is as follows:

[0078] S1, mix N,N-diethylmethylammonium trifluoromethanesulfonate ionic liquid (200 mL) with ethyl acetate (1400 mL) to obtain a mixture.

[0079] S2, add polypropylene powder (100 g) with ash content of 300 ppm to the mixture obtained in step S1, stir and react at 120°C for 2 h, centrifugal filtration, and discharge the mixed washing liquid to obtain solid substance.

[0080] S3, re-add n-decane (700g) to the solid to rinse, centrifugal filtration, repeat this operation 3 times, and then put in a 90°C oven to dry, to obtain the ultra-low ash polypropylene powder.

[0081] Example 4

[0082] The triethylamine nitrate ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0083] .

[0084] The treatment process is as follows:

[0085] S1, mix the triethylamine nitrate ionic liquid (300mL) with butanone (900mL) to obtain a mixed solution.

[0086] S2, add the polypropylene powder (100g) with ash content of 200ppm to the mixed solution obtained in step S1, stir and react at 70°C for 6h, centrifugal filtration, and discharge the mixed washing liquid to obtain the solid.

[0087] S3, re-add n-decane (700g) to the solid to rinse, centrifugal filtration, repeat this operation 3 times, and then put in a 90°C oven to dry, to obtain the ultra-low ash polypropylene powder.

[0088] Example 5

[0089] The tributylammonium tetrafluoroborate ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0090] .

[0091] The treatment process is as follows:

[0092] S1, mix the tributylammonium tetrafluoroborate ionic liquid (300mL) with n-hexane (600mL) to obtain a mixed solution.

[0093] S2, add the polypropylene powder (300g) with ash content of 200ppm to the mixed solution obtained in step S1, stir and react at 100°C for 3h, centrifugal filtration, and discharge the mixed washing liquid to obtain the solid.

[0094] S3, re-add n-butanol (900g) to the solid to rinse, centrifugal filtration, repeat this operation 3 times, and then put in a 100°C oven to dry, to obtain the ultra-low ash polypropylene powder.

[0095] Example 6

[0096] The tetramethylammonium dihydrogen phosphate ionic liquid is used for polypropylene ash removal, and its structural formula is as follows:

[0097] .

[0098] The process is as follows:

[0099] S1, tetramethylammonium phosphate dihydride ionic liquid (400 mL) is mixed with methyl formate (2400 mL) to obtain a mixed solution.

[0100] S2, polypropylene powder (100 g) with ash content of 80 ppm is added to the mixed solution obtained in step S1, and stirred at 50℃ for 7 h, centrifuged and filtered, and the mixed washing liquid is discharged to obtain a solid.

[0101] S3, the solid is washed with n-pentane (3200 g) again, centrifuged and filtered, and the operation is repeated 4 times, and then dried in a 60℃ oven to obtain an ultra-low-ash polypropylene powder.

[0102] Comparative Example 1

[0103] According to Example 1, except that triethylammonium hydrochloride ionic liquid is replaced by deionized water.

[0104] Comparative Example 2

[0105] According to Example 1, except that triethylammonium hydrochloride ionic liquid is replaced by another quaternary ammonium ionic liquid, triethylammonium formate.

[0106] Comparative Example 3

[0107] According to Example 1, except that no ethanol is added in step S3.

[0108] Effect test :

[0109] The polypropylene powders obtained in each of the examples and comparative examples are digested by a microwave digestion instrument, and then the content of different elements in the polypropylene powders is determined by an inductively coupled plasma instrument. The results are shown in Table 1.

[0110] Table 1: Test results of each example and comparative example

[0111]

[0112] As can be seen from the test results in the above table, the ash removal rate of Examples 1-6 of the present application is more than 96%, which can efficiently remove the ash in the polypropylene to obtain low-ash polypropylene.

[0113] The principles and implementations of the present application are described herein with specific examples, and the above descriptions of the examples are only used to help understand the method of the present application and its core ideas, including the best mode, and also enable any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. The scope of patent protection of the present application is defined by the claims, and can include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal expressions of the claims, or if they include equivalent structural elements that are not substantially different from the literal expressions of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method of reducing the ash content of polypropylene, characterized in that, The method comprises the following steps: S1, mixing quaternary ammonium ionic liquid with washing liquid to obtain a mixed liquid; S2, mixing the mixed liquid obtained in step S1 with polypropylene for reaction, then performing solid-liquid separation to obtain solid matter; S3, washing the solid matter obtained in step S2 with flushing liquid, then drying to obtain low-ash polypropylene; The quaternary ammonium ionic liquid has a structure shown in formula (I): R4NX - Formula (I); wherein, 4 R's are independently selected from H or a hydrocarbon group, and at least 3 R's are hydrocarbon groups; X - at least one selected from fluoride ion, chloride ion, bromide ion, iodide ion, borate ion, dihydrogen phosphate ion, acetate ion, nitrate ion, hydroxide ion, methanesulfonate ion, thiocyanate ion, trifluoromethane sulfonate ion, tetrafluoroborate ion, and hexafluorophosphate ion.

2. The method of claim 1, wherein, The hydrocarbon group is at least one of alkyl and aryl.

3. The method according to claim 1 or 2, characterized in that, The hydrocarbon group is at least one of ethyl, butyl, hexyl, octyl, phenyl, naphthyl and phenanthryl.

4. The method of claim 1, wherein, The quaternary ammonium ionic liquid is at least one of triethylammonium hydrochloride ionic liquid, tetramethylammonium bromide ionic liquid, N, N-diethylmethylammonium trifluoromethanesulfonate ionic liquid, triethylamine nitrate ionic liquid, tributylammonium tetrafluoroborate ionic liquid and tetramethylammonium dihydrogen phosphate ionic liquid.

5. The method of claim 1, wherein, The washing liquid is at least one of alkane solvent, alcohol solvent, ester solvent and ketone solvent; The alkane solvent is at least one of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; the alcohol solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol and hexanol; the ester solvent is at least one of ethyl acetate, isopropyl acetate, methyl propionate, methyl formate, isobutyl formate and dimethyl carbonate; and the ketone solvent is at least one of acetone, 3-pentanone, butanone and 2-pentanone.

6. The method of claim 1, wherein, The volume ratio of the quaternary ammonium ionic liquid to the washing liquid is 1:(1-20); The mass ratio of the quaternary ammonium ionic liquid in the mixed liquid to the polypropylene is (1-10):

1.

7. The method of claim 1, wherein, In step S2, the reaction temperature is 30-150℃ and the reaction time is 0.1-10h.

8. The method of claim 1, wherein, The flushing liquid is at least one of alkane solvent and alcohol solvent; The alkane solvent is at least one of n-butane, isopentane, n-pentane, n-hexane, n-heptane, n-decane and n-dodecane; and the alcohol solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol and hexanol.

9. The method of claim 1, wherein, The mass ratio of the flushing liquid to the polypropylene in step S2 is (1-15):

1.

10. The method of claim 1, wherein, The ash content of the polypropylene in step S2 is 50-500ppm; The washing is performed for 1-5 times; The drying temperature is 50-110℃.

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