Application of a polyethylene catalyst in the preparation of a lithium battery separator

Abstract

The present invention discloses an application of a polyethylene catalyst in the preparation of a lithium battery separator. The bulk density of the polyethylene resin is ≥ 0.36 g / cm 3 , and it has a spherical or quasi-spherical structure. The catalyst of the present invention improves the microstructure of the polyethylene resin, and the polyethylene resin is suitable for being used as a lithium battery separator material, and the obtained lithium battery separator has good comprehensive properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene catalyst preparation, and particularly relates to the application of a polyethylene catalyst in the preparation of a lithium battery separator. Background Art

[0002] The emergence of metallocene and non-metallocene catalysts has brought revolutionary changes to the polyethylene industry. However, the Ziegler-Natta catalyst system still dominates in the industrial production of polyethylene. Its research focus is no longer on the polymerization activity of the catalyst, but on aspects such as the particle morphology and particle size distribution of the catalyst, the hydrogen response sensitivity of the catalyst, and the copolymerization performance. In the existing slurry polymerization process of ethylene, the catalytic activity of the catalyst is already much higher than the range that can be controlled by the device requirements. Therefore, it is necessary to reduce the catalytic activity to meet the device requirements. With the demand for high-end polyethylene products, it is very important to control the particle size and particle size distribution of the produced ethylene polymer. In the process of ethylene polymerization, especially in the slurry polymerization of ethylene, it is very easy to produce finer polymer particles. These fine powders are prone to generate static electricity and sometimes agglomerate, causing blockages in equipment pipelines. The key to controlling the particle size and particle size distribution of the polymer is to control the particle size and particle size distribution of the catalyst.

[0003] In addition to particle size control, the hydrogen response sensitivity and copolymerization performance of the catalyst are also very important for the preparation of high-end polyethylene. A high hydrogen response sensitivity can obtain polyethylene with the same melt index while reducing the amount of hydrogen used, thereby improving production efficiency and reducing production costs. Good copolymerization performance can not only reduce production costs, but the key is to change the properties of polyethylene by increasing the content of comonomers.

[0004] After more than twenty years, the Z-N catalyst has made great progress. Mitsui Chemicals (CN1140722A) was the first example to use an internal electron donor in an ethylene polymerization catalyst. This patent used an organosilane without active hydrogen as the electron donor and added it to the reaction of magnesium chloride and titanium tetrachloride, and a higher carbon alcohol that formed an alcohol solution with magnesium chloride, such as isooctyl alcohol. The catalyst obtained by this method has very high catalytic activity, and the particles of polyethylene have also been greatly improved compared with before. Its bulk density can reach 0.35 g / cm 3 or more. The fine powder ( 100 μm) also reached 0.6 - 1.5%. This amount is still relatively large.

[0005] CN1683420A reported a catalyst component. After dissolving magnesium halide in a system containing organic epoxide and organic phosphorus compound, it was loaded on a silica carrier, and then reacted with titanium tetrachloride to form a catalyst. This catalyst is suitable for the slurry polymerization process of ethylene. The obtained polymer has uniform particle size, narrow particle size distribution, and the catalyst has high catalytic activity and good hydrogen response sensitivity. The disadvantage is that the bulk density is only 0.33 g / cm 3 or so. The fine powder ( 200 mesh) also reached 0.7%. This amount is still relatively large. It can be seen from its particle size distribution table that the particle size distribution is still relatively wide,

[0006] CN102432726 used magnesium dichloride as a carrier, dissolved it in a mixed solution of toluene, epichlorohydrin, tributyl phosphate and ethanol, and treated it with diethylaluminum monochloride and titanium tetrachloride respectively to obtain a solid catalyst. Using this catalyst, chlorinated polyethylene was produced on the industrial device of Mitsui CX process. The maximum bulk density of the obtained polyethylene is only 0.4 g / cm 3 , and the particle size distribution is relatively wide. The proportion of 180 μm accounts for 25 - 38%, and the proportion of 106 μm accounts for 42 - 58%. The fine powder ( 75 μm) is more, and the proportion reaches 8 - 14%.

[0007] CN107840914B used commercial ethoxymagnesium as a carrier, dispersed the carrier ethoxymagnesium in a straight-chain alkane with organic solvents C6 - C13, and added a composition of an alcohol ether compound without active hydrogen and a phthalic acid diester compound as an electron donor during the catalyst preparation process. At 80°C, titanium tetrachloride was added for reaction to obtain a catalyst. Although its catalytic activity can reach 2×10 4 gPE / g.cat. However, the maximum bulk density of the obtained polyethylene is only 0.34 g / cm 3 . Its practicability is not strong.

[0008] The above patents only focus on catalytic activity and polymer particle size, and do not mention the microstructure of the prepared polyethylene particles. As high-end polyethylene for lithium battery separator materials, the polyethylene microstructure is crucial. Summary of the Invention

[0009] The present invention provides an application of a polyethylene resin in the preparation of a lithium battery separator (such as a lithium battery separator material);

[0010] The polyethylene resin has any one or two or more of the following parameters:

[0011] (1) The average particle size is 100 μm or more and 300 less than m, for example, 110 to 200 m;

[0012] (2) The pore diameter is 0.3 to 0.8 m, for example, 0.42 to 0.6 m;

[0013] (3) The pore volume is 0.8 to 1.5 cm 3 / g, for example, 0.85 to 1.2 cm 3 / g;

[0014] (4) The total pore area is 5.0 to 10.0 m 2 / g, for example, 7.0 to 9.0 m 2 / g;

[0015] (5) The porosity is 40 to 60%, for example, 42 to 55%;

[0016] (6) The particle size distribution (D 90 -D 10 ) / D 50 <0.7, for example, 0.6 < (D 90 -D 10 ) / D 50 <0.7;

[0017] Alternatively, the polyethylene resin is obtained by polymerizing ethylene in a catalyst system, and the catalyst system includes a main catalyst;

[0018] By weight percentage, the main catalyst contains 20 - 30 wt% of magnesium, 1 - 10 wt% of titanium, 5 - 20 wt% of an internal electron donor compound, and 40 - 70 wt% of a halogen atom; or, the main catalyst is obtained by the contact reaction of a dialkoxymagnesium carrier, a titanium halide compound, and an internal electron donor compound.

[0019] According to an embodiment of the present invention, the pore diameter, pore volume, total pore area, and porosity are obtained by mercury intrusion porosimetry.

[0020] According to an embodiment of the present invention, the polyethylene resin is spherical or quasi-spherical.

[0021] According to an embodiment of the present invention, the bulk density of the polyethylene resin is ≥ 0.36 g / cm 3 , preferably ≥ 0.39 g / cm 3 , for example, 0.36 to 0.55 g / cm 3 , exemplarily 0.40 g / cm 3 , 0.45 g / cm 3 , 0.50 g / cm 3 , 0.51 g / cm3 、0.53 g / cm 3 。

[0022] According to an embodiment of the present invention, the particle size of the main catalyst is 3.0 to 10.0 m, such as 3.5 to 6.0 m; and / or, the catalyst is spherical or quasi-spherical.

[0023] According to an embodiment of the present invention, the internal electron donor compound may be selected from alkoxysilane compounds having the structure shown in Formula I,

[0024] R’ n Si(OR’’) 4n’ Formula I

[0025] wherein, R’ and R’’ are the same or different and are independently selected from C 1~12 hydrocarbon groups;

[0026] n and n’ are the same or different and are independently selected from natural numbers from 1 to 3, such as selected from 1, 2 or 3;

[0027] For example, the hydrocarbon groups include alkyl, cycloalkyl, alkenyl, phenyl, alkoxy, haloalkyl, halocycloalkyl, haloalkenyl, halophenyl, haloalkoxy.

[0028] According to an embodiment of the present invention, the particle size of the dialkoxymagnesium carrier is 2.0 to 10.0 m, and / or, is spherical or quasi-spherical;

[0029] Alternatively, the dialkoxymagnesium carrier is prepared by the following method: in the presence of an initiator, magnesium and alcohol are reacted at a temperature T, 30°C ≤ T < 80°C.

[0030] According to an embodiment of the present invention, the catalyst system further includes a co-catalyst, which is an organometallic compound, preferably an organoaluminum compound R’’’ 3-m A1X m , where X is a halogen, and R’’’ is a C 1~12 alkyl group (such as a C 1~6 alkyl group, exemplarily methyl, ethyl, propyl, isopropyl, butyl, isobutyl), and m is an integer from 0 to 2.

[0031] According to an embodiment of the present invention, the molar ratio of aluminum in the co-catalyst to titanium in the active component of the main catalyst is 10 to 300, preferably 10 to 150, more preferably 30 to 100.

[0032] In some embodiments, the R’’’ is ethyl and m = 0, that is, the co-catalyst is triethylaluminum.

[0033] According to an embodiment of the present invention, the temperature of the polymerization reaction is 30-90 °C, preferably 40-80 °C; and / or, the pressure of the polymerization reaction is 0.1-1.0 MPa, preferably 0.2-0.8 MPa.

[0034] The present invention also provides an application of a dialkoxymagnesium carrier or a catalyst system in the preparation of a polyethylene resin or a lithium battery separator, and the dialkoxymagnesium carrier, the catalyst system and the polyethylene resin have the definitions as shown above.

[0035] The present invention also provides a lithium battery separator prepared from the above polyethylene resin.

[0036] Beneficial effects

[0037] The catalyst of the present invention improves the microstructure of the polyethylene resin, and the polyethylene resin is suitable for being used as a lithium battery separator material, and the obtained lithium battery separator has good comprehensive performance.

[0038] Term definition and description

[0039] The quasi-spherical structure is a three-dimensional granular structure with a spherical structure as the main body, but there are irregular concave and convex structures on the surface, resulting in a slight difference from the spherical shape. This is a conventional statement in the art. Preferably, it is a three-dimensional particle structure with a diameter ratio of 1: (0.7-1.5): (0.7-1.5) in the longitudinal, horizontal, and vertical directions; or judged by sphericity, the sphericity is equal to the ratio of the surface area of a sphere with the same volume as the object to the surface area of the object. The closer the morphology of the particle is to a sphere, the closer its sphericity is to 1; for example, 0.5 < sphericity < 1 is considered a quasi-spherical structure, preferably 0.6 ≤ sphericity < 1, 0.7 ≤ sphericity < 1, 0.8 ≤ sphericity < 1, 0.9 ≤ sphericity < 1. Description of the drawings

[0040] Figure 1 It is the electron microscope image of the carrier in Catalyst Example 1;

[0041] Figure 2 It is the electron microscope image of the catalyst obtained in Catalyst Example 1;

[0042] Figure 3 It is the electron microscope image of the polyethylene resin prepared in Catalyst Example 13;

[0043] Figure 4 It is the electron microscope image of the polyethylene resin prepared in Catalyst Example 14. Detailed implementation manners

[0044] [Dialkoxymagnesium carrier and its preparation method]

[0045] The above-mentioned dialkoxymagnesium carrier has a particle size of 2.0-10.0 m (such as 2.5 m, 2.82 m, 3.0 m, 3.2 m, 3.5 m, 4.0 m, 4.5 m, 5.0 m, 5.2 m, 5.5 m, 6.0 m, 6.5 m, 7.0 m, 8.0 m, 9.0 m), being spherical or quasi-spherical.

[0046] According to an embodiment of the present invention, the method for preparing the dialkoxymagnesium carrier comprises: reacting magnesium and an alcohol in the presence of an initiator at a temperature T, where 30°C ≤ T ≤ 60°C, to obtain the dialkoxymagnesium carrier.

[0047] According to an embodiment of the present invention, there is no particular limitation on the shape and particle size of magnesium. For example, magnesium powder is selected, and the particle size is 50 - 200 m.

[0048] According to an embodiment of the present invention, the alcohol is selected from aliphatic alcohols represented by the general formula R-OH, where R represents a C 1-6 alkyl; for example, the alcohol is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, neopentanol, cyclopentanol, and cyclohexanol. In an exemplary embodiment, it is ethanol.

[0049] According to an embodiment of the present invention, the weight ratio of the alcohol to magnesium is (8 - 30):1, preferably (10 - 20):1. When less than 8:1, the viscosity of the slurry increases rapidly; while when more than 30:1, the bulk density of the dialkoxymagnesium carrier decreases. In addition, the ratio of the alcohol to magnesium powder also affects the particle size of the carrier. The lower the ratio, the smaller the particle size.

[0050] According to an embodiment of the present invention, the initiator is selected from N-chlorosuccinimide, N-bromosuccinimide, or I2.

[0051] According to an embodiment of the present invention, the weight ratio of the initiator to magnesium is (0.005 - 0.3):1. When less than 0.005:1, the reaction rate becomes too slow; while when more than 0.3:1, the size of the generated particles becomes uneven, and there are too many fine particles sticking together.

[0052] The inventors found that the reaction temperature has a great influence on the particle size of the dialkoxymagnesium carrier. The lower the temperature, the smaller the particle size. The temperature T is preferably 40-60 °C.

[0053] According to an embodiment of the present invention, the reaction time is 3-12 hours, preferably 4-8 hours. The inventors found that increasing the temperature will cause the particles to become larger or uneven, so the present invention does not require increasing the temperature for aging. The carrier particles are aged through a certain reaction time (i.e., the aging time).

[0054] According to an embodiment of the present invention, the reaction is carried out under stirring. For example, the stirring rate is 200-1500 rpm, preferably 300-1200 rpm. When the stirring rate exceeds the above range, problems of irregular particle distribution will occur.

[0055] According to an embodiment of the present invention, the reaction is carried out in an inert environment, for example, in a nitrogen atmosphere.

[0056] According to an embodiment of the present invention, the method for preparing the dialkoxymagnesium carrier includes:

[0057] In an inert environment, an alcohol and an initiator are stirred and mixed, heated to temperature T, and after the initiator is dissolved, magnesium powder is added for reaction to obtain the dialkoxymagnesium carrier.

[0058] [Main catalyst and its preparation method]

[0059] The main catalyst described above contains the above-mentioned dialkoxymagnesium carrier or is obtained by contacting and reacting the dialkoxymagnesium carrier, a titanium halide compound, and an internal electron donor compound.

[0060] According to an embodiment of the present invention, the particle size of the main catalyst is 3.0-10.0 m, such as 3.5 m, 4.0 m, 4.3 m 4.5 m, 4.6 m, 4.8 m, 5.0 m, 5.2 m, 5.5 m, 6.0 m, 6.5 m, 7.0 m, 8.0 m, 9.0 m; and / or, the main catalyst is spherical or quasi-spherical.

[0061] According to an embodiment of the present invention, by weight percentage, the main catalyst contains 20 - 30% by weight of magnesium, 1 - 10% by weight of titanium, 5 - 20% by weight of an internal electron donor compound, and 40 - 70% by weight of halogen atoms.

[0062] According to an embodiment of the present invention, the preparation method of the main catalyst includes contacting and reacting the dialkoxymagnesium carrier, titanium halide, and internal electron donor compound;

[0063] Preferably, the preparation method includes:

[0064] (S1) First, react the dialkoxymagnesium carrier and titanium halide in an organic solvent to generate an alkoxy group of halogen - based substituted dialkoxymagnesium;

[0065] (S2) After step (S1) is completed, add the internal electron donor compound to the system, raise the temperature for reaction, and obtain the catalyst.

[0066] According to an embodiment of the present invention, the titanium halide can be selected from titanium halides known in the art, such as titanium tetrachloride.

[0067] According to an embodiment of the present invention, relative to 1 mol of dialkoxymagnesium, the dosage of the titanium halide is 0.1 - 10 mol, such as 0.3 - 8 mol or 0.5 - 5 mol.

[0068] According to an embodiment of the present invention, the organic solvent can be selected from (saturated) aliphatic hydrocarbons or aromatic hydrocarbons of C 6-12 preferably saturated aliphatic hydrocarbons or aromatic hydrocarbons of C 7-10 and is, for example, selected from one or more of octane, nonane, decane, toluene, and xylene.

[0069] According to an embodiment of the present invention, the internal electron donor compound can preferably be an alkoxysilane compound having the structure shown in formula I,

[0070] R’ n Si(OR’’) 4n’ Formula I

[0071] wherein, R’ and R’’ are the same or different and are independently selected from hydrocarbon groups of C 1~12 ;

[0072] n and n’ are the same or different and are independently selected from natural numbers from 1 to 3, such as selected from 1, 2, or 3;

[0073] For example, the hydrocarbon group includes alkyl, cycloalkyl, alkenyl, phenyl, alkoxy, haloalkyl, halocycloalkyl, haloalkenyl, halophenyl, haloalkoxy;

[0074] In some embodiments, R' and R'' are the same or different and are independently selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, vinyl, γ-chloropropyl, methoxy, and ethoxy.

[0075] Exemplarily, the internal electron donor compound is selected from dimethyldimethoxysilane, dipropyldimethoxysilane, diisopropyldimethoxysilane, isobutyldimethoxysilane, dibutyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylisopropyldimethoxysilane, cyclopentylisobutyldimethoxysilane, cyclopentylisopropyldimethoxysilane, cyclopentylbutyldimethoxysilane, cyclopentylpropyldimethoxysilane, dicyclopentyldimethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrioxysilane, dimethyldiethoxysilane, dipropyldiethoxysilane, diisopropyldiethoxysilane, isobutyldiethoxysilane, dibutyldiethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexylisopropyldiethoxysilane, cyclopentylisobutyldiethoxysilane, cyclopentylisopropyldiethoxysilane, cyclopentylbutyldiethoxysilane, cyclopentylpropyldiethoxysilane, dicyclopentyldiethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, methyltriethoxysilane, butyltriethylsilane, isobutyltriethoxysilane, γ-chloropropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, and tetraethoxysilane, or more than one of them.

[0076] According to an embodiment of the present invention, the amount of the internal electron donor compound is 0.05 - 1.0 mol, for example, 0.1 - 0.5 mol, relative to 1 mol of magnesium. When the amount of the internal electron donor compound exceeds this preferred range, there may be a problem that the polymerization activity of the generated catalyst decreases.

[0077] According to an embodiment of the present invention, in step (S1), first, the dialkoxymagnesium carrier and an organic solvent are mixed and stirred, cooled to -20 - 10°C, titanium halide is added thereto, and then the temperature is raised to 60 - 80°C;

[0078] Preferably, the titanium halide is added in a dropwise manner, for example, the addition is completed within 30 minutes to 2 hours;

[0079] Preferably, the temperature increase is a programmed temperature increase, and the temperature is increased to 60 - 80°C in 1.0 - 2.0 hours by programmed temperature increase.

[0080] The dialkoxymagnesium carrier reacts with the titanium halide at low temperature in a state suspended in an organic solvent. Outside these reaction temperature ranges, there may be a problem of a large amount of fine particles and agglomerated particles being generated, which is due to the destruction of the carrier particle shape.

[0081] According to an embodiment of the present invention, the temperature when the internal electron donor compound is added to the system in step (S2) is 60 - 80 °C.

[0082] According to an embodiment of the present invention, the temperature is raised to 100 - 120 °C in step (S2), and the reaction is carried out for 1 - 3 h.

[0083] According to an embodiment of the present invention, the preparation method further includes post-treatment. After the reaction in step (2) ends, the solid catalyst is hot-filtered out, washed with n-decane and n-hexane respectively until the filtrate is basically colorless, and a solid is obtained after drying.

[0084] [Catalyst system]

[0085] The catalyst system described above includes:

[0086] a) The main catalyst described above;

[0087] b) A cocatalyst, which is an organometallic compound, preferably an organoaluminum compound R''' 3-m A1X m , where X is a halogen, and R''' is C 1~12 alkyl (such as C 1~6 alkyl, exemplified by methyl, ethyl, propyl, isopropyl, butyl, isobutyl), and m is an integer from 0 to 2.

[0088] According to an embodiment of the present invention, the molar ratio of aluminum in the cocatalyst to titanium in the active component of the main catalyst is 10 - 300, preferably 10 - 150, more preferably 30 - 100.

[0089] In some embodiments, the R''' is ethyl and m = 0, that is, the cocatalyst is triethylaluminum.

[0090] [Polyethylene resin and its preparation method]

[0091] The preparation method of the polyethylene resin described above includes the following steps:

[0092] In an inert environment, a solvent (such as hexane), a cocatalyst, and a main catalyst are mixed in a reaction kettle, and the temperature is raised to 40-60 °C (such as 45-55 °C). Ethylene is introduced into the reaction kettle until the kettle pressure reaches 0.1-1.0 MPa (preferably 0.2-0.8 MPa). Then, the temperature is further raised to 70-90 °C (such as 75-85 °C), and the kettle pressure is kept constant while continuously introducing hydrogen. The mass ratio of ethylene to hydrogen is controlled to be (4000-7000):1 (such as (5000-6000):1). The polymerization reaction is carried out for 1-6 h (such as 2-5 h). After cooling to room temperature and discharging and drying, polyethylene resin is obtained.

[0093] According to the embodiments of the present invention, the polyethylene resin has any one or more than two of the following parameters, and preferably has the parameters shown in (1)-(6) simultaneously:

[0094] (1) The average particle size (D 50 ) is above 100 μm and below 300 μm, such as 110-200 μm, and exemplarily 115 μm, 116 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm;

[0095] (2) The pore diameter is 0.3-0.8 μm, such as 0.42-0.6 μm, and exemplarily 0.45 μm, 0.46 μm, 0.47 μm, 0.48 μm, 0.49 μm, 0.50 μm, 0.55 μm;

[0096] (3) The pore volume is 0.8-1.5 cm 3 / g, such as 0.85-1.2 cm 3 / g, and exemplarily 0.9 cm 3 / g, 0.92 cm 3 / g, 0.94 cm 3 / g, 0.96 cm 3 / g, 0.99 cm 3 / g, 1.0 cm 3 / g, 1.1 cm 3 / g;

[0097] (4) Total pore area is 5.0 - 10.0 m 2 / g, such as 7.0 - 9.5 m 2 / g, exemplarily 7.5 m 2 / g, 8.0 m 2 / g, 8.1 m 2 / g, 8.2 m 2 / g, 8.3 m 2 / g, 8.4 m 2 / g, 8.5 m 2 / g, 8.6 m 2 / g, 8.7 m 2 / g, 8.8 m 2 / g, 8.9 m 2 / g, 9.0 m 2 / g, 9.1 m 2 / g, 9.3 m 2 / g, 9.5 m 2 / g;

[0098] (5) Porosity is 40 - 60%, such as 42 - 55%, exemplarily 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%;

[0099] (6) Particle size distribution (D 90 - D 10 ) / D 50 < 0.7, such as 0.6 < (D 90 - D 10 ) / D 50 < 0.7, exemplarily 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69;

[0100] (7) The bulk density of the polyethylene resin ≥ 0.36 g / cm 3 , preferably ≥ 0.39 g / cm 3 , such as 0.36 - 0.55 g / cm 3 , exemplarily 0.40 g / cm 3 , 0.45 g / cm 3 , 0.50 g / cm 3 , 0.51 g / cm 3 , 0.53 g / cm 3 ;

[0101] (8) Melt index (21.6 kg): 0.2 to 2.0 g / 10 min, such as 0.3 to 1.0 g / 10 min, and exemplary values are 0.33 g / 10 min, 0.35 g / 10 min, 0.39 g / 10 min, 0.40 g / 10 min, 0.41 g / 10 min, 0.45 g / 10 min, 0.50 g / 10 min, 0.60 g / 10 min, 0.70 g / 10 min, 0.80 g / 10 min, 0.90 g / 10 min.

[0102] [Lithium battery separator and its preparation]

[0103] The aforementioned lithium battery separator is prepared from the above polyethylene resin.

[0104] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0105] Unless otherwise specified, the raw materials and reagents used in the following embodiments are commercially available products, or can be prepared by known methods.

[0106] Polymer property determination

[0107] Melt flow index (MI): According to the ASTM-D1238 standard method, the measurement temperature is 190 °C, and the measurement loads are 5.0 kg and 21.6 kg.

[0108] Determination of polymer density: It is determined according to the standard test method for determining the density of plastics by the density gradient method (ASTM1505-03).

[0109] The apparent density is measured by the ASTM-D-1895 method.

[0110] Screening is measured by the GB / T19077-2016 method.

[0111] The particle size of polyethylene is measured by a laser particle analyzer (Mastersizer X, Malvern), where the D10, D50, and D90 distributions refer to the sizes of the particles at the respective percentages of 10, 50, and 90. D50 is defined as the average particle distribution, and the particle size distribution is defined as (D90 - D10) / D50.

[0112] The weight average molecular weight and molecular weight distribution of the polymer are obtained by high-temperature GPC-IR testing.

[0113] Description of the performance detection method of the lithium battery separator

[0114] The ash content is tested in accordance with GB / T9345.5-2010;

[0115] The diaphragm thickness is tested in accordance with GB / T6672-2001;

[0116] The air permeability is tested in accordance with GB / T458-2008;

[0117] The porosity and surface density are tested in accordance with GB / T24218.1-2009;

[0118] The tensile strength is tested in accordance with GB / T1040.3-2006;

[0119] The puncture strength is tested in accordance with GB / T23318-2009;

[0120] The needle punching strength is tested in accordance with GB / T 10004-2008;

[0121] The MD elongation and TD elongation are tested in accordance with ASTM D882-2018;

[0122] The minimum pore diameter, average pore diameter, and maximum pore diameter: are tested in accordance with GB / T 38949-2020;

[0123] The shrinkage rate MD, MD: is tested in accordance with GB / T13395-2008.

[0124] In the specific implementation manner of the present application, the particle size of the magnesium powder used in the preparation of the carrier is 50-200 m.

[0125] Catalyst Example 1

[0126] Preparation of the active Mg(OEt)2 carrier: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) are successively added to a 500 ml reaction kettle replaced with nitrogen. The stirring speed is 1000 rpm. After heating to 40 °C, stirring is carried out for 5 min to fully dissolve NCS. 6 g of magnesium powder is added thereto, and the reaction is carried out for 8 hours until the reaction solution becomes grayish-white and no hydrogen is generated. After filtration, the obtained solid is washed with n-hexane and then dried to obtain a white carrier, namely the active Mg(OEt)2 carrier. The electron microscope shows that the particle size of the carrier is 4.5 μm, and it is of a certain shape (see Figure 1 )

[0127] Add 7.5 g of activated Mg(OEt)₂ support and 200 mL of toluene (dried over 4A molecular sieve) successively into a 500 mL reactor purged with nitrogen. Stir at 300 rpm. First, cool down to -10 °C, then add 15 mL of titanium tetrachloride dropwise. After the addition is complete, increase the temperature program - matically to 70 °C. At this temperature, add 2 mL of γ - chloropropyltriethoxysilane electron donor, and continue to heat up to 110 °C and react for 120 minutes to obtain a solid catalyst. After the reaction, filter out the solid catalyst hot. Wash it 4 times with n - decane and n - hexane respectively, 200 mL each time, until the filtrate is basically colorless, and then dry to obtain a solid. The titanium content of the catalyst thus obtained is 7.5 wt%. The electron microscope shows that the particle size of the catalyst is 4.5 μm and it is spherical - like (see Figure 2 ).

[0128] Catalyst Example 2

[0129] The preparation of the activated Mg(OEt)₂ support is the same as that in Catalyst Example 1.

[0130] Add 7.5 g of activated Mg(OEt)₂ support and 200 mL of toluene (dried over 4A molecular sieve) successively into a 500 mL reactor purged with nitrogen. Stir at 300 rpm. First, cool down to -10 °C, then add 15 mL of titanium tetrachloride dropwise. After the addition is complete, increase the temperature program - matically to 70 °C. At this temperature, add 2 mL of γ - chloropropyltrimethoxysilane electron donor, and continue to heat up to 110 °C and react for 120 minutes to obtain a solid catalyst. After the reaction, filter out the solid catalyst hot. Wash it 4 times with n - decane and n - hexane respectively, 200 mL each time, until the filtrate is basically colorless, and then dry to obtain a solid. The titanium content of the catalyst thus obtained is 5.5 wt%. The electron microscope shows that the particle size of the catalyst is 4.5 μm and it is spherical - like.

[0131] Catalyst Example 3

[0132] The preparation of the activated Mg(OEt)₂ support is the same as that in Catalyst Example 1.

[0133] 7.5 g of active Mg(OEt)2 support and 200 mL of toluene (dried over 4A molecular sieve) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 300 rpm. First, the temperature was lowered to -10 °C, and 15 mL of titanium tetrachloride was added dropwise thereto. After the addition was completed, the temperature was programmed to rise to 70 °C. At this temperature, 2 mL of a donor mixture of γ-chloropropyltrimethoxysilane and γ-chloropropyltriethoxysilane (3:7) was added, and the temperature was further raised to 110 °C and reacted for 120 minutes to obtain a solid catalyst. After the reaction, the solid catalyst was filtered out hot. It was washed 4 times with n-decane and n-hexane respectively, 200 mL each time, until the filtrate was basically colorless, and then dried to obtain a solid. The titanium content of the catalyst thus obtained was 6.2 wt%. The electron microscope showed that the particle size of the catalyst was 4.6 μm and it was spherical-like.

[0134] Catalyst Example 4

[0135] Same as Catalyst Example 1, except that the titanium dropping temperature was changed to -20 °C. The titanium content of the catalyst thus obtained was 5.8 wt%. The electron microscope showed that the particle size of the catalyst was 4.6 μm.

[0136] Catalyst Example 5

[0137] Same as Catalyst Example 1, except that the amount of titanium tetrachloride used was changed to 35 mL. The titanium content of the catalyst thus obtained was 8.6 wt%. The electron microscope showed that the particle size of the catalyst was 4.8 μm.

[0138] Catalyst Example 6

[0139] Same as Catalyst Example 1, except that the stirring speed was increased to 1000 rpm. The titanium content of the catalyst thus obtained was 4.8 wt%. The electron microscope showed that the particle size of the catalyst was 4.3 μm.

[0140] Catalyst Example 7

[0141] Preparation of active Mg(OEt)2 support: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1200 rpm. After heating to 40 °C, it was stirred for 5 min to fully dissolve NCS. 6 g of magnesium powder was added thereto, and the reaction was carried out for 8 hours until the reaction solution became grayish white and no hydrogen was generated. After filtration, the obtained solid was washed with n-hexane and then dried to obtain a white support. The electron microscope showed that the particle size of the support was 3.5 μm and it was spherical-like.

[0142] Others were the same as Catalyst Example 1.

[0143] The titanium content of the catalyst thus obtained was 8.0 wt%. The electron microscope showed that the particle size of the catalyst was 3.5 μm.

[0144] Catalyst Example 8

[0145] Preparation of active Mg(OEt)₂ support: 200 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1000 rpm. After heating to 40 °C, stirring was carried out for 5 min to fully dissolve NCS. Then 6 g of magnesium powder was added, and the reaction was carried out for 8 hours until the reaction solution became grayish-white and no hydrogen was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. Electron microscopy showed that the particle size of the support was 5.0 μm and it was spherical-like.

[0146] Others were the same as Catalyst Example 1.

[0147] The titanium content of the catalyst obtained thus was 7.6 wt%. Electron microscopy showed that the particle size of the catalyst was 5.0 μm.

[0148] Catalyst Example 9

[0149] Preparation of active Mg(OEt)₂ support: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1200 rpm. After heating to 50 °C, stirring was carried out for 5 min to fully dissolve NCS. Then 6 g of magnesium powder was added, and the reaction was carried out for 8 hours until the reaction solution became grayish-white and no hydrogen was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. Electron microscopy showed that the particle size of the support was 4.0 μm and it was spherical-like.

[0150] Others were the same as Catalyst Example 1.

[0151] The titanium content of the catalyst obtained thus was 6.1 wt%. Electron microscopy showed that the particle size of the catalyst was 4.0 μm.

[0152] Catalyst Example 10

[0153] Preparation of active Mg(OEt)₂ support: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1200 rpm. After heating to 60 °C, stirring was carried out for 5 min to fully dissolve NCS. Then 6 g of magnesium powder was added, and the reaction was carried out for 8 hours until the reaction solution became grayish-white and no hydrogen was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. Electron microscopy showed that the particle size of the support was 6.5 μm and it was spherical-like.

[0154] Others were the same as Catalyst Example 1.

[0155] The titanium content of the resulting catalyst is 5.2 wt %. The particle size of the catalyst by electron microscopy is 6.5 μm.

[0156] Catalyst Example 11

[0157] Preparation of the active Mg(OEt)2 support: 100 mL of anhydrous ethanol and 0.03 g of I2 were successively added to a 500 ml reaction kettle purged with nitrogen. The stirring speed was 1200 rpm. After heating to 50 °C, stirring was carried out for 5 min to fully dissolve I2. Then 6 g of magnesium powder was added thereto, and the reaction was carried out for 8 hours until the reaction solution became grayish white and no hydrogen gas was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. The particle size of the support by electron microscopy was 5.0 μm and it was spherical-like.

[0158] Others are the same as Catalyst Example 1.

[0159] The titanium content of the resulting catalyst is 5.4 wt %. Electron microscopy shows that the particle size of the catalyst is 5.0 μm.

[0160] Catalyst Example 12

[0161] Preparation of the active Mg(OEt)2 support: 100 mL of anhydrous ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 ml reaction kettle purged with nitrogen. The stirring speed was 1000 rpm. After heating to 40 °C, stirring was carried out for 5 min to fully dissolve NCS. Then 6 g of magnesium powder was added thereto, and the reaction was carried out for 4 hours until the reaction solution became grayish white and no hydrogen gas was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. The particle size of the support by electron microscopy was 5.2 μm and it was spherical-like.

[0162] Others are the same as Catalyst Example 1.

[0163] The titanium content of the resulting catalyst is 5.3 wt %. Electron microscopy shows that the particle size of the catalyst is 5.2 μm.

[0164] Catalyst Example 13

[0165] Preparation of the active Mg(OEt)2 support: 100 mL of anhydrous ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 ml reaction kettle purged with nitrogen and soaked overnight. The next day, 6 g of magnesium powder was added thereto, the stirring speed was 1000 rpm, the reaction temperature was 50 °C, and the reaction was carried out for 6 hours until the reaction solution became grayish white and no hydrogen gas was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. The particle size of the support by electron microscopy was 3.20 μm and it was spherical-like.

[0166] 7.5 g of activated Mg(OEt)2 support and 300 mL of toluene (dried with 4A molecular sieve) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1000 rpm. First, the temperature was lowered to -10 °C, and 20 mL of titanium tetrachloride was added dropwise thereto. After the addition was completed, the temperature was programmed to rise to 70 °C. At this temperature, 2 mL of γ-chloropropyltriethoxysilane electron donor was added, and the temperature was further raised to 110 °C and reacted for 120 minutes to obtain a solid catalyst. After the reaction, the solid catalyst was filtered out by hot filtration. It was washed 4 times with n-decane and n-hexane, 200 mL each time, until the filtrate was basically colorless, and the solid was obtained after drying. The titanium content of the catalyst thus obtained (denoted as catalyst 13) was 6.9 wt%. The electron microscope showed that the particle size of the support was 3.35 μm and it was spherical-like.

[0167] Catalyst Example 14

[0168] Preparation of activated Mg(OEt)2 support: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reactor purged with nitrogen, and soaked overnight. The next day, 6 g of magnesium powder was added thereto, the stirring speed was 1000 rpm, the reaction temperature was 45 °C, and the reaction was carried out for 6 hours until the reaction solution became grayish white and no hydrogen was generated. After filtration, the obtained solid was washed with n-hexane and then dried to obtain a white support. The electron microscope showed that the particle size of the support was 2.82 μm and it was spherical-like.

[0169] 7.5 g of activated Mg(OEt)2 support and 300 mL of toluene (dried with 4A molecular sieve) were successively added to a 500 mL reactor purged with nitrogen. The stirring speed was 1000 rpm. First, the temperature was lowered to -10 °C, and 20 mL of titanium tetrachloride was added dropwise thereto. After the addition was completed, the temperature was programmed to rise to 70 °C. At this temperature, 2 mL of γ-chloropropyltriethoxysilane electron donor was added, and the temperature was further raised to 110 °C and reacted for 120 minutes to obtain a solid catalyst. After the reaction, the solid catalyst was filtered out by hot filtration. It was washed 4 times with n-decane and n-hexane, 200 mL each time, until the filtrate was basically colorless, and the solid was obtained after drying. The titanium content of the catalyst thus obtained (denoted as catalyst 14) was 7.2 wt%. The electron microscope showed that the particle size of the support was 2.95 μm and it was spherical-like.

[0170] Comparative Catalyst Example 1

[0171] Preparation of the support: 100 mL of absolute ethanol and 0.045 g of N-chlorosuccinimide (NCS) were successively added to a 500 mL reaction kettle purged with nitrogen. The stirring speed was 1000 rpm. After heating to 80 °C, stirring was carried out for 5 min to fully dissolve NCS. Then 6 g of magnesium powder was added thereto, and the reaction was carried out for 8 hours until the reaction solution became grayish white and no hydrogen gas was generated. After filtration, the obtained solid was washed with n-hexane and dried to obtain a white support. Electron microscopy showed that the particle size of the support was 10.5 μm and it was irregular in shape.

[0172] Others were the same as in Catalyst Example 1.

[0173] The titanium content of the thus obtained catalyst (denoted as Comparative Catalyst 1) was 7.2 wt%. Electron microscopy showed that the particle size of the catalyst was 10.5 μm.

[0174] Preparation of lithium battery separator material

[0175] In a 500 L stainless steel autoclave, after purging with nitrogen, 350 L of dehydrated hexane, a hexane solution of triethylaluminum (cocatalyst) (with the molar ratio of Al in triethylaluminum to Ti in the active component of the catalyst being 30:1), and 2.5 g of the catalyst (Catalysts 13, 14, Comparative Catalyst 1) were successively added. The stirring speed was 500 rpm. The temperature was raised to 50 °C, and then ethylene was introduced until the autoclave pressure reached 0.8 MPa (gauge pressure). At 85 °C and maintaining the autoclave pressure at 0.8 MPa, hydrogen was continuously introduced, and the mass ratio of ethylene / hydrogen was controlled at 6000:1. After the polymerization reaction for 2 hours, the temperature was lowered to room temperature, and the product was discharged and dried to obtain polyethylene samples A - C. The polymerization results are shown in Table 1 and Table 2. Figure 3 and Figure 4 .

[0176] It can be seen from the data in Table 1 that the catalyst of the present invention can not only prepare high-density polyethylene but also prepare special materials for lithium battery separators, and the particle size meets the requirements of lithium battery separator materials. Figure 3 and Figure 4 It is shown that the lithium battery separator materials prepared from Catalysts 13 and 14 are spherical-like and have a porous structure. Table 2 also proves the existence of the porous structure. This structure is very beneficial to the penetration of solvents and is conducive to rapid dissolution.

[0177] Table 1

[0178]

[0179] Table 2

[0180]

[0181] Preparation of lithium ion battery separator

[0182] The steps for preparing a lithium ion battery separator from polyethylene are as follows:

[0183] Step 1, batching and stirring: Polyethylene samples A, B, and C are respectively dissolved in paraffin oil, and antioxidant 1010 with a mass concentration of 0.1% is added to form a semi-dilute solution. Then, it is placed in a stirring device for stirring, and the rotation speed of the stirring device is adjusted to 200 rpm.

[0184] Step 2, heating and extrusion: The stirred mixed raw materials are taken out, and a twin-screw extruder is used to continuously extrude the mixed raw materials, and the raw materials are maintained at 200 °C inside the twin-screw extruder. The extruded mixed raw materials form a sheet.

[0185] Step 3, cooling and forming: A cooling and forming machine is used to cool the mixed raw materials that have formed into a sheet, and while cooling, a waterproof layer is adhered to the surface of the sheet.

[0186] Step 4, stretching and forming: The sheet is subjected to a stretching operation through a biaxial stretching device, and while stretching, a heat-resistant layer is adhered to the outside of the waterproof layer; an adhesive layer containing a high-strength glue is adhered to the outside of the waterproof layer through an extrusion device.

[0187] Step 5, slitting and packaging: Through a micro-drilling device, through grooves are opened inside the waterproof layer, heat-resistant layer, and adhesive layer, and anti-wrinkle particles are arranged inside the through grooves. After the battery separator is segmented and cut by a slitter, the finished product is then placed in a packing box for centralized packaging.

[0188] The prepared battery separator is tested, and the specific test results are shown in Table 3, where the existing comparative product is a polyolefin lithium battery separator numbered GU4116 produced by Celanese Corporation.

[0189] Table 3

[0190]

[0191] It can be found from the data in Table 3 that the lithium battery separator of the present invention has good comprehensive performance.

[0192] Above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Use of polyethylene resin in the preparation of lithium battery separators, characterized in that, The polyethylene resin is spherical or quasi-spherical and has the following parameters: (1) The average particle size is 100 m or more and 200 m or less; (2) The pore diameter is 0.3 to 0.6 m; (3) Pore volume: 0.85 - 1.2 cm 3 / g; (4)Total pore area: 7.0 - 10.0 m 2 / g; (5) Porosity: 40-60%; (6) Particle size distribution 0.6 < (D 90 - D 10 ) / D 50 < 0.7; (7) Bulk density ≥ 0.36 g / cm 3 ; The polyethylene resin is obtained by polymerizing ethylene in a catalyst system, and the catalyst system includes a main catalyst, which is obtained by the contact reaction of a dialkoxymagnesium carrier, a titanium halide compound, and an internal electron donor compound; The internal electron donor compound is selected from alkoxysilane compounds having the structure shown in Formula I, R’ n Si(OR’’) 4n’ Formula I wherein R' and R'' are the same or different and are each independently selected from C 1~12 hydrocarbyl groups; n and n' are the same or different and are independently selected from natural numbers of 1-3; The hydrocarbon group includes alkyl, cycloalkyl, alkenyl, phenyl, alkoxyl, haloalkyl, halocycloalkyl, haloalkenyl, halophenyl, and haloalkoxyl; The dialkoxymagnesium carrier is prepared by the following method: in the presence of an initiator, magnesium and an alcohol are stirred and reacted at a temperature T, where 30°C ≤ T ≤ 40°C, and no temperature increase is required for ripening during the reaction process to obtain the dialkoxymagnesium carrier; The alcohol is selected from aliphatic alcohols represented by the general formula R-OH, where R represents a C 1-6 alkyl group; The weight ratio of the alcohol to magnesium is (8-30):1; The stirring rate is 600-1500 rpm; The particle size of the dialkoxymagnesium carrier is 2.0 to 10.0 m, and the dialkoxymagnesium carrier is spherical or quasi-spherical; The initiator is selected from N-chlorosuccinimide, N-bromosuccinimide, or I2.

2. The application according to claim 1, wherein The bulk density of the polyethylene resin ≥ 0.40 g / cm 3 .

3. The application according to claim 1, wherein By weight percentage, the main catalyst contains 20-30 wt% of magnesium, 1-10 wt% of titanium, 5-20 wt% of the internal electron donor compound, and 40-70 wt% of halogen atoms.

4. The application according to claim 1, characterized in that, The particle size of the main catalyst is 3.0 to 10.0 m; and / or, the catalyst is spherical or quasi-spherical.

5. The application according to claim 1, wherein The bulk density of the polyethylene resin is 0.36 to 0.55 g / cm 3 .

6. The application according to claim 3, characterized in that, The catalyst system further includes a cocatalyst R''' 3- m A1X m , where X is a halogen, R''' is a C 1~12 alkyl group, and m is an integer from 0 to 2.

7. The application according to claim 6, wherein The molar ratio of aluminum in the cocatalyst to titanium in the active component of the main catalyst is 10-300.

8. The application according to claim 3, characterized in that, The temperature of the polymerization reaction is 30-90°C, and / or the pressure of the polymerization reaction is 0.1-1.0 MPa.

9. A lithium battery separator, characterized in that, The lithium battery separator is prepared from the polyethylene resin; The polyethylene resin is spherical or quasi-spherical and has the following parameters: (1) The average particle size is 100 m or more and 200 m or less; (2) The pore diameter is 0.3 to 0.6 m; (3) Pore volume: 0.85~1.2 cm 3 / g; (4)Total pore area: 7.0 - 10.0 m 2 / g; (5) Porosity: 40-60%; (6) Particle size distribution 0.6 < (D 90 - D 10 ) / D 50 < 0.7; (7) Bulk density ≥ 0.36 g / cm 3 ; The polyethylene resin is obtained by polymerizing ethylene in a catalyst system, and the catalyst system includes a main catalyst, which is obtained by the contact reaction of a dialkoxymagnesium carrier, a titanium halide compound, and an internal electron donor compound; The internal electron donor compound is selected from alkoxysilane compounds having the structure shown in Formula I, R’ n Si(OR’’) 4n’ Formula I Wherein, R' and R'' are the same or different and are each independently selected from C 1~12 hydrocarbyl groups; n and n' are the same or different and are independently selected from natural numbers of 1-3; The hydrocarbon group includes alkyl, cycloalkyl, alkenyl, phenyl, alkoxyl, haloalkyl, halocycloalkyl, haloalkenyl, halophenyl, and haloalkoxyl; The dialkoxymagnesium carrier is prepared by the following method: in the presence of an initiator, magnesium and an alcohol are stirred and reacted at a temperature T, where 30°C ≤ T ≤ 40°C, and no temperature increase is required for ripening during the reaction process to obtain the dialkoxymagnesium carrier; The alcohol is selected from fatty alcohols represented by the general formula R-OH, where R represents a C 1-6 alkyl group; The weight ratio of the alcohol to magnesium is (8-30):1; The stirring rate is 600-1500 rpm; The particle size of the dialkoxymagnesium carrier is 2.0 to 10.0 m, and the dialkoxymagnesium carrier is spherical or quasi-spherical; The initiator is selected from N-chlorosuccinimide, N-bromosuccinimide, or I2.

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