Special color master batch for lithium battery diaphragm and preparation method and application thereof

Abstract

The application belongs to the field of high polymer materials, and particularly relates to a color master batch special for lithium battery diaphragm, a preparation method and application thereof. The color master batch provided by the application includes the following components in parts by weight: 55-85 parts of polymer base material, 4-14 parts of mixed colorant, 3-7 parts of antioxidant, and 4.5-12 parts of modified nano filler; the mixed colorant includes the following components: pigment and processing aid, the processing aid is one or more of N,N'-ethylene bis-stearamide, polyethylene wax and coupling agent; and the modified nano filler is a nano filler treated by a surfactant. The application optimizes the component composition of the color master batch, especially modifies the nano filler contained therein to ensure good dispersibility, so as to ensure that the film forming raw material added with the color master batch forms a uniform pore effect in the stretching film forming process.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a special color masterbatch for lithium battery separators, its preparation method and application. Background Technology

[0002] Benefiting from the rapid development of the global new energy industry, the lithium-ion battery market has continued to expand. As one of the important materials for lithium-ion batteries, the lithium battery separator determines the performance of lithium-ion batteries and is a key link in its industrial chain. With the continuous improvement of lithium battery separator production technology, it will effectively promote the high-quality development of the industry in the future.

[0003] The separator in lithium-ion batteries is a key factor affecting their electrochemical performance. Factors influencing this include material selection, equipment status, environmental control, and on-site management, with material selection being particularly crucial. Since a battery cell primarily consists of a positive electrode, a negative electrode, an electrolyte, and a separator, the separator is the main substrate separating the positive and negative electrodes. Its primary function is to provide conductivity for ions and insulation for electrons. Ion conductivity directly impacts the battery's electrochemical performance. The quality of the separator directly affects battery performance, including not only electrical performance but also processing performance, such as short circuits and low voltage. Ion conductivity is inextricably linked to the separator because it contains numerous tiny, interconnected pores. Ions in the electrolyte can freely move through these pores. When the battery is overcharged and discharged, the internal temperature rises. At a certain temperature, the separator's micropores self-close, limiting further current increases and preventing further temperature rise and internal short circuits.

[0004] With the increasing demand for personalized products, there are no color masterbatches specifically designed for lithium batteries. However, when using ordinary color masterbatches to produce lithium battery separators, the stretching process can cause uneven pore size in the film, resulting in unstable product quality and further affecting the electrochemical performance of the batteries, including cycle life and rate performance. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a special color masterbatch for lithium battery separators, its preparation method and application. The color masterbatch provided by the present invention will not have an adverse effect on the stretching and forming of lithium battery separators, and the film pores are uniform.

[0006] This invention provides a color masterbatch for lithium battery separators, comprising the following components by weight:

[0007]

[0008] The components of the mixed colorant include: pigments and processing aids, wherein the processing aids are one or more of N,N'-ethylene bis-stearamide, polyethylene wax, and coupling agents;

[0009] The modified nanofiller is a nanofiller treated with surfactant.

[0010] Preferably, the polymer base material is polyethylene.

[0011] Preferably, the pigment is one or more of titanium dioxide, carbon black, ultramarine, phthalocyanine blue, phthalocyanine green, pigment red 122, and permanent violet.

[0012] Preferably, the mass ratio of the pigment to the processing aid is 1:(0.2 to 0.8).

[0013] Preferably, the nanofiller is nano-silica and / or alumina micro powder.

[0014] Preferably, the mass ratio of the nano-silica to the alumina micro powder is (1-10):95.

[0015] Preferably, the surfactant is a silane coupling agent.

[0016] Preferably, the mass ratio of the nanofiller to the surfactant is 100:(0.13-2).

[0017] This invention provides a method for preparing the lithium battery separator-specific masterbatch described in the above technical solution, comprising the following steps:

[0018] Polymer base material, mixed colorant, antioxidant and modified nanofiller are melt-blended and then extruded and granulated to obtain a special color masterbatch for lithium battery separator.

[0019] This invention provides a lithium battery separator, the composition of which includes the lithium battery separator-specific masterbatch described in the above technical solution.

[0020] Compared with existing technologies, this invention provides a color masterbatch specifically for lithium battery separators, its preparation method, and its application. By weight, the color masterbatch provided by this invention comprises the following components: 55-85 parts polymer base, 4-14 parts mixed colorant, 3-7 parts antioxidant, and 4.5-12 parts modified nanofiller; the mixed colorant comprises pigments and processing aids, wherein the processing aids are one or more of N,N'-ethylene bis-stearamide, polyethylene wax, and coupling agents; the modified nanofiller is a nanofiller treated with a surfactant. This invention optimizes the composition of the color masterbatch, especially by modifying the nanofiller it contains, ensuring good dispersibility and thus ensuring that the film-forming raw material with this color masterbatch forms a uniform porosity during the stretching and film-forming process. Detailed Implementation

[0021] 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.

[0022] This invention provides a color masterbatch for lithium battery separators, comprising the following components by weight:

[0023]

[0024] In the color masterbatch provided by the present invention, the polymer base material is preferably polyethylene; the number average molecular weight of the polyethylene is preferably 50,000 to 200,000, specifically 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, 170,000, 180,000, 190,000 or 200,000.

[0025] In the color masterbatch provided by the present invention, the content of the polymer base material can specifically be 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 71.5 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, or 85 parts by weight.

[0026] In the masterbatch provided by the present invention, the components of the mixed colorant include: pigment and processing aid; wherein, the processing aid is one or more of N,N'-ethylene bis-stearamide, polyethylene wax and coupling agent, preferably N,N'-ethylene bis-stearamide and coupling agent; the mass ratio of N,N'-ethylene bis-stearamide and coupling agent is preferably (0.4-5):(0.8-1.7), specifically 5:0.8, 4.2:1.2, 5:1.2, 3.8:1.1; the coupling agent is preferably a titanate coupling agent, preferably GDX-401.

[0027] In the masterbatch provided by the present invention, the pigment in the mixed colorant is preferably one or more selected from titanium dioxide, carbon black, ultramarine, phthalocyanine blue, phthalocyanine green, pigment red 122, and permanent violet. In one embodiment of the present invention, the pigment is titanium dioxide, carbon black, ultramarine, phthalocyanine blue, and phthalocyanine green, and the mass ratio of titanium dioxide, carbon black, ultramarine, phthalocyanine blue, and phthalocyanine green is preferably 8:(0.05~0.5):(0.5~1.5):(0.1~1):(2~8), more preferably 8:(0.1~0.3):(0.6~1):(0.3~0.7):(3~6), and most preferably 8:0.2:0.8:0.5:4. In one embodiment of the present invention, the pigment is titanium dioxide and ultramarine, and the mass ratio of titanium dioxide and ultramarine is preferably 10:(0.5~1.5), more preferably 10:(0.6~1), and most preferably 10:0.8. In one embodiment of the present invention, the pigment is titanium dioxide and phthalocyanine green, and the mass ratio of titanium dioxide to phthalocyanine green is preferably 1.2:(10-20), more preferably 1.2:(12-16), and most preferably 1.2:14. In another embodiment of the present invention, the pigment is titanium dioxide and phthalocyanine blue, and the mass ratio of titanium dioxide to phthalocyanine blue is preferably 1.2:(5-15), more preferably 1.2:(8-12), and most preferably 1.2:10.

[0028] In the masterbatch provided by the present invention, the mass ratio of the pigment to the processing aid in the mixed colorant is preferably 1:(0.2-0.8), specifically 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.43, 1:0.44, 1:0.45, 1:0.46, 1:0.47, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75 or 1:0.8.

[0029] In the color masterbatch provided by the present invention, the particle size of the mixed colorant is preferably ≤2μm, more preferably ≤1.5μm, and most preferably ≤1.3μm.

[0030] In the color masterbatch provided by the present invention, the content of the mixed colorant can specifically be 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, 10.5 parts by weight, 11 parts by weight, 11.5 parts by weight, 12 parts by weight, 12.5 parts by weight, 13 parts by weight, 13.5 parts by weight, or 14 parts by weight.

[0031] In the color masterbatch provided by the present invention, the antioxidant is preferably one or more of hindered phenolic antioxidants, phosphite antioxidants and thio-antioxidants, more preferably one or more of antioxidant 1010, antioxidant 168 and antioxidant DSTDP; the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant DSTDP is preferably 1:(1~5):(0.5~1), more preferably 1:2:0.7.

[0032] In the color masterbatch provided by the present invention, the content of the antioxidant can specifically be 3 parts by weight, 3.2 parts by weight, 3.5 parts by weight, 3.7 parts by weight, 4 parts by weight, 4.2 parts by weight, 4.5 parts by weight, 4.7 parts by weight, 5 parts by weight, 5.2 parts by weight, 5.5 parts by weight, 5.7 parts by weight, 6 parts by weight, 6.2 parts by weight, 6.5 parts by weight, 6.7 parts by weight, or 7 parts by weight.

[0033] In the color masterbatch provided by the present invention, the modified nanofiller is a nanofiller treated with surfactant. The nanofiller is preferably nano-silica and / or alumina micropowder; the mass ratio of nano-silica to alumina micropowder is preferably (1-10):95, specifically 1:95, 2:95, 3:95, 4:95, 5:95, 6:95, 7:95, 8:95, 9:95, or 10:95; the surfactant is preferably a silane coupling agent, more preferably vinyltrimethoxysilane; the mass ratio of nanofiller to surfactant is preferably 100:(0.13-2), specifically 100:0.13, 100:0.14, 100:0.15, 100:0.17, 100:0.2, 100:0.25, 100:0.3, 100:0.35, 100:0.4, 100:0.45, 100:0.5, etc. The ratios are 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1, 100:1.2, 100:1.5, 100:1.7, or 100:2; the preferred processing temperature is 100–150°C, specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C; the preferred processing time is 2–20 min, specifically 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min.

[0034] In the color masterbatch provided by the present invention, the content of the modified nanofiller can specifically be 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, 10.5 parts by weight, 11 parts by weight, 11.5 parts by weight, or 12 parts by weight.

[0035] This invention also provides a method for preparing the lithium battery separator-specific masterbatch described in the above technical solution, comprising the following steps:

[0036] Polymer base material, mixed colorant, antioxidant and modified nanofiller are melt-blended and then extruded and granulated to obtain a special color masterbatch for lithium battery separator.

[0037] In the preparation method provided by the present invention, the mixed colorant is preferably prepared according to the following steps:

[0038] Pigments and processing aids are mixed and refined to obtain a mixed colorant.

[0039] In the preparation method provided by the present invention, the modified nanofiller is preferably prepared according to the following steps:

[0040] Modified nanofillers are obtained by heating and mixing nanofillers and surfactants.

[0041] In the above-mentioned modified nanofiller preparation steps provided by the present invention, the nanofiller is preferably dehumidified before heating and mixing; the dehumidification method is preferably heating and stirring dehumidification; the dehumidification temperature is preferably 95-105℃, specifically 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃ or 105℃; the stirring speed for dehumidification is preferably 350-450 rpm, specifically 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm or 450 rpm.

[0042] In the above-mentioned modified nanofiller preparation steps provided by the present invention, the heating and mixing temperature is preferably 100-150℃, specifically 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃; the heating and mixing time is preferably 2-20min, specifically 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20min.

[0043] In the preparation method provided by this invention, the polymer base, mixed colorant, antioxidant, and modified nanofiller are preferably first kneaded before being melt-mixed, and then the mixture obtained by kneading is melt-blended. The kneading equipment is preferably a Banbury mixer; the kneading temperature is preferably 90–95°C, specifically 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C; the kneading time is preferably 25–37 min, specifically 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, or 37 min.

[0044] In the preparation method provided by the present invention, the melt blending temperature is preferably 170-200℃, specifically 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃; the melt blending is carried out in an extruder; the speed of the extruder is preferably 280-300 rpm, specifically 280 rpm, 285 rpm, 290 rpm, 295 rpm or 300 rpm.

[0045] In the preparation method provided by the present invention, the granulation method is preferably water ring hot cutting; the rotation speed of the water ring hot cutting is preferably 300-350 rpm, specifically 300 rpm, 305 rpm, 310 rpm, 315 rpm, 320 rpm, 325 rpm, 330 rpm, 335 rpm, 340 rpm, 345 rpm or 350 rpm.

[0046] In the preparation method provided by the present invention, it is preferable to further dehydrate the obtained color masterbatch.

[0047] The present invention also provides a lithium battery separator, the components of which include polymer materials and the lithium battery separator-specific color masterbatch described in the above technical solution; wherein, the polymer materials include, but are not limited to, polyethylene; the mass ratio of the polymer materials to the lithium battery separator-specific color masterbatch is preferably 100:(1-10), specifically 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10.

[0048] In the lithium battery separator provided by the present invention, the lithium battery separator is obtained by stretching, and the more specific preparation process preferably includes:

[0049] The polymer material is melt-plasticized with a special color masterbatch for lithium battery separators and then cast into a film, which is then stretched to obtain a lithium battery separator. The stretching ratio is preferably 1:(2-8), specifically 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, or 1:8. The stretching process preferably includes sequential cold stretching and hot stretching. The traction speed for cold stretching is preferably 10-50 m / min, specifically 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, or 50 m / min. The preferred temperature for hot stretching is 80–130°C, specifically 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, or 130°C; the preferred stretching speed is 20–60 m / min, specifically 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, 55 m / min, or 60 m / min.

[0050] The technical solution provided by this invention optimizes the composition of the color masterbatch, especially by modifying the nanofillers it contains, to ensure good dispersibility. This ensures that the film-forming raw material with the added color masterbatch forms a uniform porosity during the stretching and film-forming process. The color masterbatch provided by this invention is low in cost, has excellent processability, and offers good economic benefits.

[0051] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0052] Example 1

[0053] 1) Pour 5 parts by weight of nano-silica (particle size 0.5-10nm) and 95 parts by weight of alumina micro powder (particle size 0.3-0.8nm, 5N grade) into a 200-liter high-speed mixer. First, start low-speed mixing for 2 minutes, then switch to high-speed mixing (400 rpm). Heat and stir the material at 95°C in the high-speed mixer for a period of time to remove moisture. Then continue heating until the material temperature reaches 115°C. Add 0.13 parts by weight of silane coupling agent (vinyltrimethoxysilane, XL-10 coupling agent, Wacker Chemie) and mix at high speed for 6 minutes to obtain modified nanofiller for later use.

[0054] 2) Add 8 parts by weight of titanium dioxide, 0.2 parts by weight of carbon black, 0.8 parts by weight of ultramarine, 0.5 parts by weight of phthalocyanine blue, 4 parts by weight of phthalocyanine green, 5 parts by weight of N,N'-ethylene bis-stearamide, and 0.8 parts by weight of titanate coupling agent (GDX-401, Kramar) to a high-speed mixer and mix evenly. Then grind the mixture to <1.3μm using a three-roll mill to obtain a mixed colorant for later use.

[0055] 3) Add 4.5 parts by weight of modified nanofiller, 4 parts by weight of mixed colorant, 85 parts by weight of polyethylene (number average molecular weight 150,000), and 6.5 parts by weight of antioxidant (antioxidant 1010, antioxidant 168, and antioxidant DSTDP in a mass ratio of 1:2:0.7) to a mixer and mix for 28 minutes. The temperature of the mixer is set to 92℃.

[0056] 4) Pour the mixture obtained in 3) into a double cone forced feeder and extrude it through a twin screw extruder. Set the extruder speed to 280 rpm and the temperature of each zone of the extruder to 180℃. The extruded material is then subjected to water ring hot cutting (320 rpm) and dehydration to obtain color masterbatch.

[0057] 5) Add 5 parts by weight of the prepared color masterbatch to 100 parts by weight of ultra-high molecular weight polyethylene (number average molecular weight 1 million to 1.5 million) to form a film. The specific film-forming process includes:

[0058] 5.1) Feeding: Mix the color masterbatch and ultra-high molecular weight polyethylene at low speed until uniform, and then convey them to the extrusion system;

[0059] 5.2) Casting: The pretreated raw material is melted and plasticized in the extrusion system and then extruded from the die to form a molten membrane. After casting, the melt forms a base film with a specific crystalline structure.

[0060] 5.3) Stretching: The base film was cold-stretched (traction speed 30 min / min) and hot-stretched (temperature 110℃, traction speed 40 min / min) to form a nanoporous membrane with a stretching ratio of 1:5.

[0061] 5.4) Slitting: Cut the nanoporous membrane into finished membranes according to the customer's specifications.

[0062] The pigment dispersion grade was tested according to GB / T18251-2000, and the result was: the pigment dispersion grade was 2.0; after stretching, the diaphragm was observed to have uniform pores under an electron microscope.

[0063] Example 2

[0064] 1) Pour 5 parts by weight of nano-silica (particle size 0.5-10nm) and 95 parts by weight of alumina micro powder (particle size 0.3-0.8nm, 5N grade) into a 200-liter high-speed mixer. First, start low-speed mixing for 2.5 minutes, then switch to high-speed mixing (410 rpm). Heat and stir the material at 98°C in the high-speed mixer for a period of time to remove moisture. Then continue heating until the material temperature reaches 115°C. Add 0.14 parts by weight of silane coupling agent (vinyltrimethoxysilane, XL-10 coupling agent, Wacker Chemie) and mix at high speed for 6 minutes to obtain modified nanofiller for later use.

[0065] 2) Add 10 parts by weight of titanium dioxide, 0.8 parts by weight of ultramarine, 4.2 parts by weight of N,N'-ethylene bis-stearamide, and 1.2 parts by weight of titanate coupling agent (GDX-401, Kramar) to a high-speed mixer and mix evenly. Then grind the mixture to <1.3μm using a three-roll mill to obtain a mixed colorant for later use.

[0066] 3) Add 5 parts by weight of modified nanofiller, 5 parts by weight of mixed colorant, 83 parts by weight of polyethylene (number average molecular weight 150,000), and 7 parts by weight of antioxidant (antioxidant 1010, antioxidant 168, and antioxidant DSTDP in a mass ratio of 1:2:0.7) to a mixer and mix for 25 minutes. The temperature of the mixer is set to 90℃.

[0067] 4) Pour the mixture obtained in 3) into a double cone forced feeder and extrude it through a twin screw extruder. Set the extruder speed to 280 rpm and the temperature of each zone of the extruder to 185℃. The extruded material is then subjected to water ring heat cutting (320 rpm) and dehydration to obtain color masterbatch.

[0068] 5) Add 5 parts by weight of the prepared color masterbatch to 100 parts by weight of ultra-high molecular weight polyethylene (number average molecular weight 1 million to 1.5 million) and prepare a film according to the method of Example 1.

[0069] The pigment dispersion grade was tested according to GB / T18251-2000, and the result was: the pigment dispersion grade was 1.8; after stretching, the diaphragm was observed to have uniform pores under an electron microscope.

[0070] Example 3

[0071] 1) Pour 5 parts by weight of nano-silica (particle size 0.5-10nm) and 95 parts by weight of alumina micro powder (particle size 0.3-0.8nm, 5N grade) into a 200-liter high-speed mixer. First, start low-speed mixing for 2.5 minutes, then switch to high-speed mixing (420 rpm). Heat and stir the material at 105°C in the high-speed mixer for a period of time to remove moisture. Then continue heating until the material temperature reaches 120°C. Add 1.7 parts by weight of silane coupling agent (vinyltrimethoxysilane, XL-10 coupling agent, Wacker Chemie) and mix at high speed for 10 minutes to obtain the modified nanofiller for later use.

[0072] 2) Add 1.2 parts by weight of titanium dioxide, 14 parts by weight of phthalocyanine green, 5 parts by weight of N,N'-ethylene bis-stearamide, and 1.2 parts by weight of titanate coupling agent (GDX-401, Kramar) to a high-speed mixer and mix evenly. Then grind the mixture to <1.3μm using a three-roll mill to obtain a mixed colorant for later use.

[0073] 3) Add 12 parts by weight of modified nanofiller, 11 parts by weight of mixed colorant, 71.5 parts by weight of polyethylene (number average molecular weight 150,000), and 5.5 parts by weight of antioxidant (antioxidant 1010, antioxidant 168, and antioxidant DSTDP in a mass ratio of 1:2:0.7) to a mixer and mix for 30 minutes. The temperature of the mixer is set to 95°C.

[0074] 4) Pour the mixture obtained in 3) into a double cone forced feeder and extrude it through a twin screw extruder. Set the extruder speed to 280 rpm and the temperature of each zone of the extruder to 185℃. The extruded material is then subjected to water ring heat cutting (320 rpm) and dehydration to obtain color masterbatch.

[0075] 5) Add 5 parts by weight of the prepared masterbatch to 100 parts by weight of ultra-high molecular weight polyethylene (number average molecular weight 1 million to 1.5 million), and prepare a membrane according to the method in Example 1. Stretch the membrane to form a lithium battery separator; the pigment dispersion grade was tested and found to be 1.9; after stretching, the separator was observed to have uniform pores under an electron microscope.

[0076] Example 4

[0077] 1) Pour 5 parts by weight of nano-silica (particle size 0.5-10nm) and 95 parts by weight of alumina micro powder (particle size 0.3-0.8nm, 5N grade) into a 200-liter high-speed mixer. First, start low-speed mixing for 2.5 minutes, then switch to high-speed mixing (420 rpm). Heat and stir the material at 105°C in the high-speed mixer for a period of time to remove moisture. Then continue heating until the material temperature reaches 120°C. Add 1.7 parts of silane coupling agent (vinyltrimethoxysilane, XL-10 coupling agent, Wacker Chemie) and mix at high speed for 10 minutes to obtain modified nanofiller for later use.

[0078] 2) Add 1.2 parts by weight of titanium dioxide, 10 parts by weight of phthalocyanine blue, 3.8 parts by weight of N,N'-ethylene bis-stearamide, and 1.1 parts by weight of titanate coupling agent (GDX-401, Kramar) to a high-speed mixer and mix evenly. Then grind the mixture to <1.3μm using a three-roll mill to obtain a mixed colorant for later use.

[0079] 3) Add 12 parts by weight of modified nanofiller, 9 parts by weight of mixed colorant, 75 parts by weight of polyethylene (number average molecular weight 150,000), and 4 parts by weight of antioxidant (antioxidant 1010, antioxidant 168, and antioxidant DSTDP in a mass ratio of 1:2:0.7) to a mixer and mix for 30 minutes. The temperature of the mixer is set to 95°C.

[0080] 4) Pour the mixture obtained in 3) into a double cone forced feeder and extrude it through a twin screw extruder. Set the extruder speed to 280 rpm and the temperature of each zone of the extruder to 185℃. The extruded material is then subjected to water ring heat cutting (320 rpm) and dehydration to obtain color masterbatch.

[0081] 5) Add 5 parts by weight of the prepared color masterbatch to 100 parts by weight of ultra-high molecular weight polyethylene (number average molecular weight 1 million to 1.5 million) and prepare a film according to the method of Example 1.

[0082] The pigment dispersion grade was tested according to GB / T18251-2000, and the result was: the pigment dispersion grade was 1.9; after stretching, the diaphragm was observed to have uniform pores under an electron microscope.

[0083] Comparative Example 1

[0084] 1) Add 0.55 parts by weight of nano-silica (particle size 0.5-10 nm), 9.5 parts by weight of alumina micro powder (particle size 0.3-0.8 nm, 5N grade), and 0.3 parts by weight of silane coupling agent (vinyltrimethoxysilane, XL-10 coupling agent, Wacker Chemie).

[0085] 2) Mix 1.1 parts by weight of titanium dioxide, 6 parts by weight of phthalocyanine blue,

[0086] 3) 78.55 parts by weight of polyethylene (number average molecular weight 150,000) and 4 parts by weight of antioxidants (antioxidant 1010, antioxidant 168, and antioxidant DSTDP in a mass ratio of 1:2:0.7) were added to a mixer and mixed for 30 minutes. The temperature of the mixer was set to 95°C.

[0087] 4) Pour the mixture obtained in 3) into a double cone forced feeder and extrude it through a twin screw extruder. Set the extruder speed to 280 rpm and the temperature of each zone of the extruder to 185℃. The extruded material is then subjected to water ring heat cutting (320 rpm) and dehydration to obtain color masterbatch.

[0088] 5) Add 5 parts by weight of the prepared color masterbatch to 100 parts by weight of ultra-high molecular weight polyethylene (number average molecular weight 1 million to 1.5 million) and prepare a film according to the method of Example 1.

[0089] According to GB / T18251-2000, the dispersion grade of the pigment was tested and the result was: the pigment dispersion grade was 4.5; after stretching, the diaphragm was observed to have uneven pore size under an electron microscope.

[0090] 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 masterbatch for lithium battery separator, comprising the following components in parts by weight: The ingredients of the mixed colorant include: pigments and processing aids, the processing aids being one or more of N,N'-ethylene bis stearamide, polyethylene wax and coupling agent; the modified nano-filler is a nano-filler treated with a surfactant; the nano-filler is nano-silica and alumina powder, the mass ratio of the nano-silica to the alumina powder being (1-10):95; the surfactant is a silane coupling agent; the mass ratio of the nano-filler to the surfactant is 100:(0.13-2).

2. The masterbatch for lithium battery separator specialty according to claim 1, characterized in that, the polymer base is polyethylene.

3. The masterbatch for lithium battery separator specialty as claimed in claim 1, wherein, the pigments are one or more of titanium dioxide, carbon black, ultramarine, phthalocyanine blue, phthalocyanine green, pigment red 122 and permanent violet.

4. The masterbatch for lithium battery separator specialty according to claim 1, characterized in that, the mass ratio of the pigments to the processing aids is 1:(0.2-0.8). 5.A method for preparing the masterbatch for lithium battery separator according to any one of claims 1-4, comprising the following steps: melt blending the polymer base, the mixed colorants, the antioxidant and the modified nano-filler, and then extruding and granulating to obtain the masterbatch for lithium battery separator. 6.A lithium battery separator, comprising a polymer material and the masterbatch for lithium battery separator according to claim 5; the polymer material is polyethylene; the mass ratio of the polymer material to the masterbatch for lithium battery separator is 100:(1-10).

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