Polypropylene dissolving agent and use thereof

Abstract

The application provides a polypropylene dissolving agent and application thereof, and belongs to the technical field of olefin dissolving agents.The polypropylene dissolving agent comprises the following raw materials in mass fractions: dicyanamide salt ionic liquid 10-25 parts, betaine salt 5-15 parts, tetrafluoroborate salt ionic liquid 5-15 parts, ethyl sulfate salt ionic liquid 5-15 parts, acetate salt ionic liquid 10-20 parts, long carbon chain anion ionic liquid 10-40 parts, dispersant 2-18 parts and auxiliary agent 2-20 parts.Under the condition of 180-280 DEG C, the mass fraction of the polypropylene dissolving agent of the application to polypropylene with a molecular weight of 500-1000 million can reach more than 15%, and the wet processing of the ultra-high molecular weight polypropylene into a film can be realized, and the polypropylene diaphragm or polypropylene fiber obtained by processing has the characteristics of high temperature resistance, high strength (including tensile and puncture strength), high porosity, high air permeability and the like.

Description

Technical Field

[0001] This invention relates to the field of olefin solvent technology, and more particularly to a polypropylene solvent and its application. Background Technology

[0002] Existing wet-process lithium-ion battery separators use polyethylene resin as raw material and are produced into thick films through co-extrusion technology, first longitudinally stretched (MD) and then transversely stretched (TD). The pore uniformity of these films is relatively poor compared to wet-process polyethylene separators. Dry-process PP separators, on the other hand, have lower porosity (30-40%) and more uniform pore size distribution, making them suitable for applications where electrolyte permeability requirements are not high. Wet-process separators, with their high porosity and mechanical strength, meet the high energy density requirements of ternary lithium-ion batteries and dominate the high-end market. To date, there are no reports of using a suitable solvent to dissolve PP and then melt it for wet processing to produce PP separators and PP fibers.

[0003] Therefore, it is of great value to provide a polypropylene solvent that has good solubility in PP and can improve the strength and porosity of polypropylene membranes or fibers. Summary of the Invention

[0004] The purpose of this invention is to provide a polypropylene solvent and its application, addressing the shortcomings of existing technologies.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a polypropylene solvent, which comprises the following raw materials in parts by weight:

[0007] 10-25 parts of dinitrileamine salt ionic liquid, 5-15 parts of betaine salt, 5-15 parts of tetrafluoroborate ionic liquid, 5-15 parts of ethyl sulfate salt ionic liquid, 10-20 parts of acetate ionic liquid, 10-40 parts of long-chain anionic ionic liquid, 2-18 parts of dispersant, and 2-20 parts of additives.

[0008] Preferably, the dinitrile ionic liquid comprises one or more of 1-butyl-3-methylimidazolium dinitrile, 1-ethyl-3-methylimidazolium dinitrile, 1-hexyl-3-methylimidazolium dinitrile, N-ethylimidazolium dinitrile, and 1,2-dimethylimidazolium dinitrile.

[0009] Preferably, the betaine salt comprises betaine citrate and / or betaine salicylate.

[0010] Preferably, the tetrafluoroborate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, N-ethylimidazolium tetrafluoroborate, and 1,2-dimethylimidazolium tetrafluoroborate.

[0011] Preferably, the ethyl sulfate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium sulfate, 1-ethyl-3-methylimidazolium sulfate, 1-octyl-3-methylimidazolium sulfate, 1-hexyl-3-methylimidazolium sulfate, N-ethylimidazolium sulfate, and 1,2-dimethylimidazolium sulfate.

[0012] Preferably, the acetate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, N-ethylimidazolium acetate, and 1,2-dimethylimidazolium acetate.

[0013] Preferably, the dispersant comprises one or more of sodium polyacrylate, sodium polycarboxylate, stearyl mustardamide, erucamide, sodium methylene bis(naphthalene) sulfonate, sodium methylene bis(naphthalene) sulfonate, sodium lignin sulfonate, sodium polyphosphate, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, oleamide, and polyethylene oxide.

[0014] Preferably, the additives comprise one or more of the following: isooctyl alcohol polyoxyethylene ether phosphate, lauryl ether phosphate, sorbitan monooleate polyoxyethylene ether, polyoxyethylene sorbitan anhydride monolaurate, trimethylolpropane trimethacrylate, acetylsic acid tributyl ester, polyethylene glycol 6000 distearate, glyceryl tri(ethylhexanoate), cetearyl phosphate, trimethylolpropane tri(3-mercaptopropionic acid), trimethylolpropane octadecenoate, calcium stearate, dioctyl phthalate, dibutyl phthalate, diisononyl cyclohexane 1,2-dicarboxylate, diisononyl phthalate, dimethyl phthalate, isodioctyl sebacate, di(2-ethylhexyl) adipate, castor oil polyoxyethylene ether, cashew phenol polyoxyethylene ether, and trioctyl trimellitate.

[0015] The present invention also provides the application of the polypropylene solvent in the preparation of polypropylene membranes or polypropylene fibers.

[0016] In this invention, polypropylene powder is dissolved in a polypropylene solvent, and the solution is extruded and plasticized before being cast into sheets or spun into polypropylene membranes or polypropylene fibers.

[0017] The beneficial effects of this invention are:

[0018] 1) Under conditions of 180–280°C, the polypropylene solvent of the present invention can dissolve polypropylene with a molecular weight of 500,000 to 10,000,000 by a mass fraction of more than 15%, and a twin-screw extruder can effectively extrude the polypropylene. The polypropylene solvent of the present invention can realize the wet processing of ultra-high molecular weight polypropylene into film (molecular weight of 500,000 to 10,000,000). The polypropylene diaphragm or polypropylene fiber obtained by the process has the characteristics of high temperature resistance, high strength (including tensile and puncture strength), high porosity / high air permeability, etc.

[0019] 2) After dissolving PP powder, cast sheets or spin fibers are produced. The cast sheets or PP fibers are then washed with ethanol / dichloromethane / tetrachloroethylene / ionic liquid extractant to remove the ionic liquid, thus preparing polypropylene membranes or polypropylene fibers. The washed ionic liquid is then concentrated and purified to effectively recover the ionic liquid and achieve recycling of the ionic liquid. Attached Figure Description

[0020] Figure 1 Image showing the complete dissolution of polypropylene powder in Application Example 1;

[0021] Figure 2 Image showing the complete dissolution of polypropylene powder in Application Example 2;

[0022] Figure 3 Image showing the complete dissolution of polypropylene powder in Application Example 3;

[0023] Figure 4 Image showing the complete dissolution of polypropylene powder in Application Example 4;

[0024] Figure 5 Image showing the complete dissolution of polypropylene powder in Application Example 5;

[0025] Figure 6 The image shows the finished diaphragm after the polypropylene powder in Application Example 2 was dissolved, stretched, extracted, and dried.

[0026] Figure 7 This is an image showing the polypropylene powder from Application Example 5 being melted and stretched into pre-oriented fibers. Detailed Implementation

[0027] This invention provides a polypropylene solvent, which comprises the following raw materials in parts by weight:

[0028] 10-25 parts of dinitrileamine salt ionic liquid, 5-15 parts of betaine salt, 5-15 parts of tetrafluoroborate ionic liquid, 5-15 parts of ethyl sulfate salt ionic liquid, 10-20 parts of acetate ionic liquid, 10-40 parts of long-chain anionic ionic liquid, 2-18 parts of dispersant, and 2-20 parts of additives.

[0029] In the polypropylene solvent of the present invention, the preferred mass fraction of the dinitrileamine salt ionic liquid is 13-21 parts, more preferably 15-20 parts, and even more preferably 17-18 parts; the preferred mass fraction of the betaine salt is 7-12 parts, more preferably 8-10 parts, and even more preferably 9 parts; the preferred mass fraction of the tetrafluoroborate ionic liquid is 7-12 parts, more preferably 8-10 parts, and even more preferably 9 parts; the preferred mass fraction of the ethyl sulfate salt ionic liquid is 7-12 parts, more preferably 8-10 parts, and even more preferably 9 parts; the preferred mass fraction of the acetate ionic liquid is 12-18 parts, more preferably 14-16 parts, and even more preferably 15 parts; the preferred mass fraction of the long-chain anionic ionic liquid is 20-30 parts, and even more preferably 25 parts; the preferred mass fraction of the dispersant is 5-12 parts, more preferably 8-10 parts; and the preferred mass fraction of the additive is 4-15 parts, and even more preferably 6-10 parts.

[0030] In this invention, the dinitrile amine salt ionic liquid preferably comprises one or more of 1-butyl-3-methylimidazolium dinitrile amine salt, 1-ethyl-3-methylimidazolium dinitrile amine salt, 1-hexyl-3-methylimidazolium dinitrile amine salt, N-ethylimidazolium dinitrile amine salt and 1,2-dimethylimidazolium dinitrile amine salt.

[0031] In this invention, the betaine salt preferably comprises betaine citrate and / or betaine salicylate.

[0032] In this invention, the tetrafluoroborate ionic liquid preferably comprises one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, N-ethylimidazolium tetrafluoroborate, and 1,2-dimethylimidazolium tetrafluoroborate.

[0033] In this invention, the ethyl sulfate ionic liquid preferably comprises one or more of 1-butyl-3-methylimidazolium sulfate, 1-ethyl-3-methylimidazolium sulfate, 1-octyl-3-methylimidazolium sulfate, 1-hexyl-3-methylimidazolium sulfate, N-ethylimidazolium sulfate, and 1,2-dimethylimidazolium sulfate.

[0034] In this invention, the acetate ionic liquid preferably comprises one or more of 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, N-ethylimidazolium acetate, and 1,2-dimethylimidazolium acetate.

[0035] In this invention, the long-chain anionic liquid preferably contains one or more of the following: dodecyl sulfonate, dodecylbenzene sulfonate, dodecanoate, tetradecanoate, hexadecanoate, octadecanoate, octadecenoate, hexadecenoate, 12-hydroxyl, cis-9-octadecadienoate, cis,cis-9,12-octadecadienoate, docosahexaenoic acid, and docosahexaene. The corresponding cation is preferably 1-butyl-3-methylimidazolium.

[0036] In this invention, the dispersant preferably comprises one or more of sodium polyacrylate, sodium polycarboxylate, stearyl mustardamide, erucamide, sodium methylene bis(naphthalene) sulfonate, sodium methylene bis(naphthalene) sulfonate, sodium lignin sulfonate, sodium polyphosphate, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, oleamide, and polyethylene oxide.

[0037] In this invention, the additives preferably comprise one or more of the following: isooctyl alcohol polyoxyethylene ether phosphate, lauryl ether phosphate, sorbitan monooleate polyoxyethylene ether, polyoxyethylene sorbitan anhydride monolaurate, trimethylolpropane trimethacrylate, acetylsic acid tributyl ester, polyethylene glycol 6000 distearate, glyceryl tri(ethylhexanoate), cetearyl phosphate, trimethylolpropane tri(3-mercaptopropionic acid), trimethylolpropane octadecenoate, calcium stearate, dioctyl phthalate, dibutyl phthalate, diisononyl cyclohexane 1,2-dicarboxylate, diisononyl phthalate, dimethyl phthalate, isodioctyl sebacate, di(2-ethylhexyl) adipate, castor oil polyoxyethylene ether, cashew phenol polyoxyethylene ether, and trioctyl trimellitate.

[0038] The present invention also provides the application of the polypropylene solvent in the preparation of polypropylene membranes or polypropylene fibers, wherein polypropylene powder is dissolved in the polypropylene solvent, and the solution is extruded and plasticized before being cast or spun to obtain polypropylene membranes or polypropylene fibers.

[0039] In this invention, polypropylene powder is dissolved in a solution obtained by a polypropylene solvent. The mass fraction of the polypropylene powder is preferably 15-35%, and the molecular weight of the polypropylene is preferably 500,000-10,000,000. When the molecular weight of the polypropylene is 1,000,000-3,000,000, the mass fraction of the polypropylene powder in the solution is preferably 20-35%, more preferably 25-30%. When the molecular weight of the polypropylene is 3,000,000-5,000,000, the mass fraction of the polypropylene powder in the solution is preferably 15-22%, more preferably 18-20%. When the molecular weight of the polypropylene is 8,000,000-10,000,000, the mass fraction of the polypropylene powder in the solution is preferably 15-20%, more preferably 16-18%. The polypropylene is preferably isotactic polypropylene, syndiotactic polypropylene, or atactic polypropylene.

[0040] The polypropylene separator prepared by this invention has a uniform pore size (±5% size deviation), making it suitable for power batteries. The detection of one or more residues of the solvent described in this invention on the polypropylene separator proves that the solvent of this invention can be used to produce and process polypropylene separators. The polypropylene separator produced by the solvent of this invention has a puncture strength of 200–1000 gf and a transverse tensile strength of 1000–9000 kgf / cm². 2 Longitudinal tensile strength is 100–9000 kgf / cm² 2 The air permeability (100mL) is 30-500s, and the porosity is 20-95%.

[0041] The polypropylene fibers prepared by this invention have high strength and are suitable for fiber weaving and textile processing. The detection of one or more substances of the solvent described in this invention on the polypropylene fibers proves that the solvent of this invention can be used to produce and process polypropylene fibers. The polypropylene fibers produced by the solvent of this invention have a fineness of 20–1500D and a strength of 20–100 cN.

[0042] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] The polypropylene solvent in this embodiment is composed of the following raw materials in parts by weight: 18 parts of 1-butyl-3-methylimidazolium dinitrile amine salt, 10 parts of betaine citrate, 10 parts of 1-butyl-3-methylimidazolium tetrafluoroborate, 10 parts of 1-butyl-3-methylimidazolium ethyl sulfate salt, 15 parts of 1-butyl-3-methylimidazolium acetate, 25 parts of 1-butyl-3-methylimidazolium dodecyl sulfonate, 8 parts of sodium methylene bisnaphthalene sulfonate, 3 parts of dioctyl sebacate, and 3 parts of isooctanol polyoxyethylene ether phosphate.

[0045] Example 2

[0046] The polypropylene solvent in this embodiment is composed of the following raw materials in parts by weight: 15 parts of 1-ethyl-3-methylimidazolium dinitrile, 12 parts of betaine citrate, 6 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate, 8 parts of 1-ethyl-3-methylimidazolium sulfate ethyl ester salt, 18 parts of 1-ethyl-3-methylimidazolium acetate, 20 parts of 1-butyl-3-methylimidazolium dodecyl sulfonate, 4 parts of sodium lignosulfonate, 5 parts of dioctyl phthalate, and 5 parts of trimethylolpropane trimethacrylate.

[0047] Example 3

[0048] The polypropylene solvent in this embodiment is composed of the following raw materials in parts by weight: 22 parts of 1-hexyl-3-methylimidazolium dinitrile, 8 parts of betaine salicylate, 15 parts of 1-hexyl-3-methylimidazolium tetrafluoroborate, 12 parts of 1-hexyl-3-methylimidazolium sulfate ethyl ester, 12 parts of 1-hexyl-3-methylimidazolium acetate, 30 parts of 1-butyl-3-methylimidazolium dodecylbenzene sulfonate, 12 parts of polyethylene oxide (molecular weight 120,000), 2 parts of trimethylolpropane octadecenoate, and 3 parts of dioctyl phthalate.

[0049] Example 4

[0050] The polypropylene solvent in this embodiment is composed of the following raw materials in parts by weight: 15 parts of N-ethylimidazolium dinitrile amine salt, 9 parts of betaine citrate, 13 parts of 1,2-dimethylimidazolium tetrafluoroborate, 14 parts of 1-octyl-3-methylimidazolium sulfate ethyl ester salt, 10 parts of N-ethylimidazolium acetate, 25 parts of 1-butyl-3-methylimidazolium hexadecanoate, 10 parts of 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 6 parts of trimethylolpropane tris(3-mercaptopropionic acid) ester, and 4 parts of acetylsicitrin tributyl citrate.

[0051] Example 5

[0052] The polypropylene solvent in this embodiment is composed of the following raw materials in parts by weight: 17 parts of 1,2-dimethylimidazolium dinitrile amine salt, 4 parts of betaine citrate, 4 parts of betaine salicylate, 10 parts of 1-octyl-3-methylimidazolium tetrafluoroborate, 10 parts of 1,2-dimethylimidazolium sulfate ethyl ester salt, 18 parts of 1,2-dimethylimidazolium acetate, 23 parts of 1-butyl-3-methylimidazolium tetradecanoate, 17 parts of erucamide, 3 parts of di(2-ethylhexyl) adipic acid, and 7 parts of hexadecanoic acid phosphate.

[0053] Application Example 1

[0054] At 200°C, isotactic polypropylene powder with a molecular weight of 1.5 million (average particle size 150 μm) was dissolved in the polypropylene solvent of Example 1, with a polypropylene mass fraction of 30% in the solution. The solution was then subjected to extrusion plasticizing (extrusion temperature 230°C), casting cooling (5°C), biaxial stretching (transverse stretching temperature 70°C, longitudinal stretching temperature 130°C), extraction (30°C), drying (70°C), stretching, edge trimming and thickness measurement, post-treatment, and winding to obtain a polypropylene diaphragm. The performance test results of the polypropylene diaphragm are shown in Table 1.

[0055] Table 1. Performance of polypropylene membranes prepared from polypropylene with a molecular weight of 1.5 million.

[0056]

[0057] The image shows the complete dissolution of polypropylene powder in Application Example 1. Figure 1 As shown.

[0058] Application Example 2

[0059] At 210°C, isotactic polypropylene powder with a molecular weight of 3 million (average particle size 150 μm) was dissolved in the polypropylene solvent of Example 2, with a polypropylene mass fraction of 20% in the solution. The solution was then subjected to extrusion plasticizing (extrusion temperature 250°C), casting cooling (10°C), biaxial stretching (transverse stretching temperature 90°C, longitudinal stretching temperature 140°C), extraction (30°C), drying (70°C), stretching, edge trimming and thickness measurement, post-treatment, and winding to obtain a polypropylene diaphragm. The performance test results of the polypropylene diaphragm are shown in Table 2.

[0060] Table 2. Performance of polypropylene membranes prepared from polypropylene with a molecular weight of 3 million.

[0061]

[0062] The image shows the complete dissolution of polypropylene powder in Application Example 2. Figure 2 As shown.

[0063] Application Example 3

[0064] At 250°C, isotactic polypropylene powder with a molecular weight of 10 million (average particle size 150 μm) was dissolved in the polypropylene solvent of Example 3, with a polypropylene mass fraction of 15% in the solution. The solution was then subjected to extrusion plasticizing (extrusion temperature 250°C), casting cooling (5°C), biaxial stretching (transverse stretching temperature 100°C, longitudinal stretching temperature 150°C), extraction (30°C), drying (70°C), stretching, edge trimming and thickness measurement, post-treatment, and winding to obtain a polypropylene diaphragm. The performance test results of the polypropylene diaphragm are shown in Table 3.

[0065] Table 3. Performance of polypropylene membranes prepared from polypropylene with a molecular weight of 10 million.

[0066]

[0067] The image shows the complete dissolution of the polypropylene powder in Application Example 3. Figure 3 As shown.

[0068] Application Example 4

[0069] At 230°C, atactic polypropylene powder with a molecular weight of 3 million was dissolved in the polypropylene solvent of Example 4, and the mass fraction of polypropylene in the solution was 22%. The solution was then subjected to extrusion (230°C), cooling (20°C), equilibration, primary stretching (35°C), extraction (30°C), drying (70°C), edge trimming and thickness measurement (stretching temperature 140°C), post-treatment, and winding to obtain polypropylene fibers. The performance test results of the polypropylene fibers are shown in Table 4.

[0070] Table 4. Properties of polypropylene fibers prepared from polypropylene with a molecular weight of 3 million.

[0071]

[0072] The image shows the complete dissolution of polypropylene powder in Application Example 4. Figure 4 As shown.

[0073] Application Example 5

[0074] At 270°C, syndiotactic polypropylene powder with a molecular weight of 10 million was dissolved in the polypropylene solvent of Example 5, with a polypropylene mass fraction of 15% in the solution. The solution was then subjected to extrusion (270°C), cooling (20°C), equilibration, primary stretching (35°C), extraction (30°C), drying (70°C), edge trimming and thickness measurement (stretching temperature 140°C), post-treatment, and winding to obtain polypropylene fibers. The performance test results of the polypropylene fibers are shown in Table 5.

[0075] Table 5. Properties of polypropylene fibers prepared from polypropylene with a molecular weight of 10 million.

[0076]

[0077] The image shows the complete dissolution of the polypropylene powder in Application Example 5. Figure 5 As shown.

[0078] This invention provides a polypropylene solvent that, at 180–280°C, dissolves polypropylene with a molecular weight of 500,000 to 10,000,000 by a mass fraction of over 15%, enabling effective extrusion using a twin-screw extruder. The polypropylene solvent of this invention enables wet processing of ultra-high molecular weight polypropylene into film sheets (molecular weight 500,000 to 10,000,000). The resulting polypropylene diaphragms or fibers exhibit high temperature resistance, high strength (including tensile and puncture strength), and high porosity / high air permeability.

[0079] 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 polypropylene solvent, characterized in that, The polypropylene solvent is composed of the following raw materials in parts by weight: 10-25 parts of dinitrileamine salt ionic liquid, 5-15 parts of betaine salt, 5-15 parts of tetrafluoroborate ionic liquid, 5-15 parts of ethyl sulfate salt ionic liquid, 10-20 parts of acetate ionic liquid, 10-40 parts of long carbon chain anionic ionic liquid, 2-18 parts of dispersant, and 2-20 parts of additives. The dispersant comprises one or more of the following: sodium polycarboxylate, stearyl mustardamide, erucamide, sodium methylene bis(naphthalene) sulfonate, sodium methylene bis(naphthalene) sulfonate, sodium lignin sulfonate, sodium polyphosphate, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, oleamide, and polyethylene oxide; The betaine salt comprises betaine citrate and / or betaine salicylate; In the long-chain anionic liquid, the long-chain anion is one or more of the following: dodecyl sulfonate, dodecylbenzene sulfonate, dodecanoate, tetradecanoate, hexadecanoate, octadecanoate, octadecenoate, hexadecenoate, cis-9-octadecadienoate, and cis,cis-9,12-octadecadienoate, and the corresponding cation is 1-butyl-3-methylimidazolium. The adjuvants comprise one or more of the following: isooctyl alcohol polyoxyethylene ether phosphate, lauryl ether phosphate, sorbitan monooleate polyoxyethylene ether, polyoxyethylene sorbitan anhydride monolaurate, trimethylolpropane trimethacrylate, acetylsic acid tributyl ester, polyethylene glycol 6000 distearate, glyceryl tri(ethylhexanoate), cetearyl phosphate, trimethylolpropane tri(3-mercaptopropionic acid), trimethylolpropane octadecenoate, calcium stearate, dioctyl phthalate, dibutyl phthalate, diisononyl cyclohexane 1,2-dicarboxylate, diisononyl phthalate, dimethyl phthalate, isodioctyl sebacate, di(2-ethylhexyl) adipate, castor oil polyoxyethylene ether, cashew phenol polyoxyethylene ether, and trioctyl trimellitate.

2. The polypropylene solvent according to claim 1, characterized in that, The dinitrile amine salt ionic liquid comprises one or more of 1-butyl-3-methylimidazolium dinitrile amine salt, 1-ethyl-3-methylimidazolium dinitrile amine salt, 1-hexyl-3-methylimidazolium dinitrile amine salt, N-ethylimidazolium dinitrile amine salt, and 1,2-dimethylimidazolium dinitrile amine salt.

3. The polypropylene solvent according to claim 2, characterized in that, The tetrafluoroborate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-decyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, N-ethylimidazolium tetrafluoroborate, and 1,2-dimethylimidazolium tetrafluoroborate.

4. The polypropylene solvent according to claim 3, characterized in that, The ethyl sulfate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium sulfate, 1-ethyl-3-methylimidazolium sulfate, 1-octyl-3-methylimidazolium sulfate, 1-hexyl-3-methylimidazolium sulfate, N-ethylimidazolium sulfate, and 1,2-dimethylimidazolium sulfate.

5. The polypropylene solvent according to claim 4, characterized in that, The acetate ionic liquid comprises one or more of 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, N-ethylimidazolium acetate, and 1,2-dimethylimidazolium acetate.

6. The use of the polypropylene solvent according to any one of claims 1 to 5 in the preparation of polypropylene membranes or polypropylene fibers.

7. The application according to claim 6, characterized in that, Polypropylene powder is dissolved in a polypropylene solvent, and the solution is extruded and plasticized before being cast into sheets or spun into polypropylene membranes or polypropylene fibers.

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