Preparation method and application of polypropylene for electrical membrane

Abstract

The invention relates to the technical field of polypropylene, and particularly discloses a preparation method and application of polypropylene for an electrical membrane, and the preparation method comprises the following steps: carrying out polymerization reaction in a full-mixing Unipol gas phase fluidized reactor to prepare polypropylene powder; the method specifically comprises the following steps: in the presence of a Z-N catalyst, a cocatalyst and an external electron donor, adding propylene, and carrying out a polymerization reaction to obtain the polypropylene for the electrical membrane, according to the invention, a Unipol gas phase method polymerization process is used, a technology of directly polymerizing and producing the polypropylene for the electrical membrane in a reactor is adopted, key parameters of reaction are controlled, and the high-purity PP resin is directly produced in the gas phase method reactor so as to achieve the purpose that the product is free from washing, and the polypropylene for the electrical membrane with excellent performance is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene, and specifically discloses a preparation method of polypropylene for electrical membrane and application thereof. Background Art

[0002] Polypropylene is a thermoplastic resin with excellent performance, known for its light weight, cleanliness, high rigidity and high transparency. It has good mechanical properties, chemical resistance, heat resistance, electrical insulation, etc. It can also be used to manufacture electrical films with small thickness and high physical and mechanical properties. It is widely used in the capacitor and lithium battery separator manufacturing industry.

[0003] Ultra-clean polypropylene for electrical membranes is a key material for the development of my country's power industry. my country has been using imported raw materials for many years. The main technical difficulty of electrical membrane polypropylene resin is low ash content. At present, there are two technical routes for producing ultra-low ash polypropylene. One is that foreign petrochemical manufacturers generally use second-generation catalyst technology and polypropylene process with special washing process to produce electrical membrane resin. The ash content is 10-20 mg / kg and the isotacticity is 96-98%. However, this process is time-consuming, energy-consuming, costly and polluting. With the advancement of catalyst technology, it has been gradually eliminated; the second is that domestic petrochemical enterprises use existing ring tube polypropylene process technology to develop ultra-high activity catalysts to produce ultra-low ash polypropylene in one step in the reactor. The ash content is less than 30 mg / kg, which has low requirements for propylene quality and has industrial prospects.

[0004] In the prior art, the invention patent with publication number CN101896511A discloses a method for manufacturing bimodal polypropylene with low ash content. The method disclosed in the invention patent still requires a prepolymerization step and relies on at least 2 reactors, and the ash content is >30mg / kg, which cannot meet the application of high-end capacitor membranes. In the invention patent with publication number CN201911264474.6, a high-purity polypropylene polymerization method is proposed. In the scheme, polypropylene powder prepared using a high-activity ZN catalyst is subjected to two-stage flash deashing at high temperature and low pressure to reduce the ash content. However, the preparation method requires multiple reactor steps such as prepolymerization, two liquid phase polymerization reactions, and two gas phase polymerization reactions. In the invention patents with publication numbers CN202110952214.9 and CN202211396382.5, ash and oil-based organic matter in polypropylene powder are removed by supercritical CO2 or high-efficiency solvents. This method has high requirements for solvents, and once the ash content in the polypropylene powder is too high during polymerization, the ash content in the washed polypropylene powder is also likely to exceed the standard. In the invention patent with publication number CN102574939B, a catalyst component for olefin polymerization is disclosed, which uses glycol ester type and diether type internal electron donors. A preparation method of the catalyst component is also disclosed, including a catalyst of the catalyst component and an olefin polymerization method using the catalyst, which is used to prepare a low-ash polypropylene product. However, this ultra-high activity catalyst is still used in liquid phase processes such as the annular tube polypropylene process, and has not been applied in the Unipol gas phase polypropylene process. In the invention patent with publication number 202211069952.X, an ultra-clean polypropylene resin and a preparation method thereof are disclosed. However, the process disclosed therein is implemented in a liquid phase bulk method, with a washing section.

[0005] In the existing disclosures, the process technology for preparing ultra-low ash polypropylene is still concentrated in three aspects: (1) the second-generation polypropylene process with a deashing section; (2) the liquid bulk method, which has good operability in ultra-high activity catalysts. China has taken the lead in developing a breakthrough in the one-step preparation of ultra-low ash polypropylene using ultra-high activity catalysts in the liquid bulk method, without the need for a deashing section; (3) the liquid bulk method based on high activity catalysts with a washing section.

[0006] In summary, the production capacity of Unipol gas-phase polypropylene process has increased rapidly in recent years, but there is no industrial experience in producing ultra-low ash polypropylene resin by Unipol gas-phase polypropylene process at home and abroad. The present invention explores the application of ultra-high activity catalyst in Unipol gas-phase process reactor to prepare low-ash polypropylene in one step, thereby reducing the ash content of Al, Ti, Cl and other ash from the source to achieve the purpose of product washing-free; the prepared product has application prospects in electrical membranes and lithium battery separators. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing polypropylene for electrical membrane and its application, so as to solve the problems raised in the prior art.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a method for preparing polypropylene for electrical membrane, comprising the following steps: S1: preparing polypropylene powder by polymerization reaction in a fully mixed Unipol gas-phase fluidized reactor; specifically comprising the following steps: adding propylene in the presence of a ZN catalyst, a co-catalyst and an external electron donor, carrying out a polymerization reaction, and obtaining polypropylene for electrical membrane.

[0009] More optimally, the feed rate of the ZN catalyst is 1-2 kg / h; the co-catalyst is triethylaluminum, and the feed rate is 1-5 kg / h; the external electron donor is D9700, and the feed rate is 0.5-1.5 kg / h; and the feed rate of propylene is 30,000-50,000 kg / h.

[0010] More preferably, the ZN catalyst is an ultra-high activity ZN catalyst that can be purchased from the market. C602; the catalyst has a titanium content of 4.2wt%, a solid content of 26wt%, a catalyst activity of 54 to 62kgPP / g Cat, and a bulk density of 0.39g×cc -1 .

[0011] More optimally, during the polymerization reaction, the polymerization temperature is 65-75°C, the polymerization pressure is 3-3.5 MPa, and the hydrogen flow rate is 1-2 kg / h.

[0012] More optimally, the use of the polypropylene for electrical membrane prepared by the above-mentioned preparation method of polypropylene for electrical membrane is as follows: additives are added to the polypropylene for electrical membrane, melt extruded and granulated by a twin-screw extruder, extruded, cast, longitudinally stretched, transversely stretched, trimmed, corona treated, rolled, aged, and slit to make an electrical membrane; the preparation of the additive comprises the following steps: step 1: taking PVA, water, and DMSO, stirring evenly, adding urea and 2-amino-4-hydroxybenzoic acid, stirring evenly, reacting at 90-95°C for 3-5h, removing the solvent, and obtaining a modified PVA;

[0013] Step 2: add anhydrous magnesium sulfate and aluminum sulfate 18hydrate into water, stir evenly, and record as substance A; add sodium hydroxide and anhydrous sodium carbonate into water, stir evenly, and record as substance B; add modified PVA into water and DMSO, stir evenly, heat to 70-75°C, keep stirring, add substance A and substance B, stir for 2-3h, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0014] Step 3: Take the intercalated modified hydrotalcite and add it to water and DMSO, stir evenly, control the temperature at 30-40°C, add β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride, stir the reaction for 15-20 hours, remove the solvent, and obtain the additive.

[0015] More optimally, the additive is added in an amount of 0.2-0.4% of the mass of the polypropylene for the electrical membrane.

[0016] More optimally, the modified PVA includes the following raw materials, by weight: 10-15 parts of PVA, 80-100 parts of water, 30-60 parts of DMSO, 20-30 parts of urea, 30-40 parts of 2-amino 4-hydroxybenzoic acid; the substance A includes the following raw materials, by weight: 8-12 parts of anhydrous magnesium sulfate, 12-15 parts of aluminum sulfate 18hydrate, 50-80 parts of water; the substance B includes the following raw materials, by weight: The amount of the ingredients is as follows: 2 to 4 parts of sodium hydroxide, 7 to 10 parts of anhydrous sodium carbonate, and 50 to 80 parts of water; the intercalated modified hydrotalcite includes the following raw materials, which are calculated by mass: 15 to 20 parts of modified PVA; the additive includes the following raw materials, which are calculated by mass: 10 to 15 parts of intercalated modified hydrotalcite, 100 to 120 parts of water, 20 to 30 parts of DMSO, and 1 to 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride.

[0017] More optimally, the Mn of the PVA is 3000-5000.

[0018] More optimally, the preparation of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride comprises the following steps: taking β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate methyl ester and ethanol, stirring evenly, adding sodium hydroxide solution dropwise under nitrogen protection, reacting at 65-70°C for 5-6 hours, adjusting the pH value to 3-4, filtering, washing, and drying to obtain an intermediate; taking the intermediate and chloroform, stirring evenly, adding dichlorothionyl under nitrogen protection, reacting at 50-60°C for 5-6 hours, removing the solvent, and obtaining β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride.

[0019] More optimally, the intermediate includes the following raw materials, calculated by mass: 30 to 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) methyl propionate, 50 to 80 parts of ethanol, and 55 to 65 parts of 30% (m / m) sodium hydroxide solution; the β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride includes the following raw materials, calculated by mass: 5 to 8 parts of the intermediate, 50 to 80 parts of chloroform, and 4 to 6 parts of dichlorothionyl.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) Researching an efficient catalyst system for producing polypropylene for electrical membranes, using an efficient ZN catalyst, a silicon-containing compound and an alkyl aluminum, and performing efficient synergistic polymerization to improve the catalytic activity, thereby reducing the ash content of Al, Ti, Cl and the like from the source, and producing polypropylene with a low ash content; using the Unipol gas phase polymerization process, researching and developing a technology for producing polypropylene for electrical membranes by direct polymerization in a reactor, controlling the key reaction parameters, and directly producing high-purity PP resin in a gas phase reactor to achieve the purpose of eliminating the need for washing the product, thereby producing polypropylene for electrical membranes with excellent performance;

[0021] (2) The present invention also prepares an additive, which is first modified with PVA and then intercalated into hydrotalcite; the hydrotalcite containing the intercalated structure is itself an acid absorbent; 2-amino-4-hydroxybenzoic acid is an aromatic compound, which can introduce deep traps in the polymer matrix, restrict the carrier migration characteristics, and thus achieve dielectric performance enhancement; and the hydroxyl groups in PVA are further grafted with β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride that can capture free radicals to obtain the additive; wherein the Mn of PVA should be controlled to be 3000-5000. If the molecular weight is too large, it will hinder the crystallization process of the polypropylene material, resulting in a decrease in crystallinity, affecting the orientation and regularity of the molecular chain, and manifesting as a deterioration in mechanical properties; similarly, the amount of the additive added should not be too much, otherwise the performance will be reduced due to compatibility. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The following parts are by mass unless otherwise specified;

[0024] Example 1: Polypropylene powder is prepared by polymerization reaction in a fully mixed Unipol gas-phase fluidized reactor; specifically comprising the following steps: in the presence of ZN catalyst, co-catalyst triethylaluminum, and external electron donor D9700, the polymerization temperature is controlled to 69.5°C, the polymerization pressure is 3.38MPa, and the hydrogen flow rate is 1kg / h, propylene is added, and polypropylene for electrical membrane is prepared by polymerization reaction; the ZN catalyst feed rate is 1.6kg / h, the triethylaluminum feed rate is 2kg / h, the D9700 feed rate is 0.68kg / h, and the propylene feed rate is 40000kg / h.

[0025] Example 2: Polypropylene powder is prepared by polymerization reaction in a fully mixed Unipol gas-phase fluidized reactor; specifically comprising the following steps: in the presence of ZN catalyst, co-catalyst triethylaluminum, and external electron donor D9700, the polymerization temperature is controlled to 68.5°C, the polymerization pressure is 3.42MPa, the hydrogen flow rate is 1kg / h, propylene is added, and polypropylene for electrical membrane is prepared by polymerization reaction; the feed rate of ZN catalyst is 1.5kg / h, triethylaluminum is 4kg / h, D9700 is 1.36kg / h, and the feed rate of propylene is 50000kg / h.

[0026] Example 3: Add 0.3% of the weight of the additive to the polypropylene for electrical membrane prepared in Example 2, melt extrude at 225°C using a twin-screw extruder, granulate, and use a flat film method to extrude, cast, longitudinally stretch, transversely stretch, trim, corona treat, wind, age, and slit to prepare an electrical membrane with a thickness of 5.8 μm;

[0027] The preparation of the additive comprises the following steps: Step 1: weigh 14 parts of PVA with an Mn of 3400, 80 parts of water, and 40 parts of DMSO, heat to 90°C and stir evenly, add 25 parts of urea, heat to 95°C, add 35 parts of 2-amino-4-hydroxybenzoic acid, stir evenly, react at 95°C for 5h, remove the solvent, and obtain modified PVA;

[0028] Take 10 parts of anhydrous magnesium sulfate and 13 parts of aluminum sulfate 18hydrate, add them to 60 parts of water, stir evenly, and record it as substance A; take 3 parts of sodium hydroxide and 8 parts of anhydrous sodium carbonate, add them to 60 parts of water, stir evenly, and record it as substance B; take 18 parts of modified PVA, add them to 100 parts of water and 20 parts of DMSO, and stir evenly; heat to 75°C, keep stirring, add substance A and substance B, stir for 3 hours, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0029] Step 2: Take 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and 80 parts of ethanol, stir evenly, add 60 parts of 30% (m / m) sodium hydroxide solution dropwise under nitrogen protection, react at 70°C for 6 hours, adjust the pH value to 3, filter, wash, and dry to obtain an intermediate; take 6 parts of the intermediate and 60 parts of chloroform, stir evenly, add 5 parts of dichlorothionyl under nitrogen protection, react at 60°C for 6 hours, remove the solvent, and obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride;

[0030] Step 3: Take 12 parts of intercalated modified hydrotalcite and add them to 120 parts of water and 25 parts of DMSO, stir evenly, control the temperature at 35°C, add 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, stir the reaction for 18 hours, remove the solvent, and obtain the additive.

[0031] Comparative Example 1 (PVA with a Mn of 9200 was selected, and the remaining steps were consistent with those of Example 3): The preparation of the additive comprises the following steps: Step 1: Weigh 14 parts of PVA with a Mn of 9200, 80 parts of water, and 40 parts of DMSO, heat to 90°C and stir evenly, add 25 parts of urea, heat to 95°C, add 35 parts of 2-amino-4-hydroxybenzoic acid, stir evenly, react at 95°C for 5h, remove the solvent, and obtain modified PVA;

[0032] Take 10 parts of anhydrous magnesium sulfate and 13 parts of aluminum sulfate 18hydrate, add them to 60 parts of water, stir evenly, and record it as substance A; take 3 parts of sodium hydroxide and 8 parts of anhydrous sodium carbonate, add them to 60 parts of water, stir evenly, and record it as substance B; take 18 parts of modified PVA, add them to 100 parts of water and 20 parts of DMSO, and stir evenly; heat to 75°C, keep stirring, add substance A and substance B, stir for 3 hours, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0033] Step 2: Take 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and 80 parts of ethanol, stir evenly, add 60 parts of 30% (m / m) sodium hydroxide solution dropwise under nitrogen protection, react at 70°C for 6 hours, adjust the pH value to 3, filter, wash, and dry to obtain an intermediate; take 6 parts of the intermediate and 60 parts of chloroform, stir evenly, add 5 parts of dichlorothionyl under nitrogen protection, react at 60°C for 6 hours, remove the solvent, and obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride;

[0034] Step 3: Take 12 parts of intercalated modified hydrotalcite and add them to 120 parts of water and 25 parts of DMSO, stir evenly, control the temperature at 35°C, add 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, stir the reaction for 18 hours, remove the solvent, and obtain the additive.

[0035] Comparative Example 2 (the intercalation modified hydrotalcite and β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride are not compounded, and the remaining method steps are consistent with Example 3): The preparation of the additive comprises the following steps: Step 1: Weigh 14 parts of PVA, 80 parts of water, and 40 parts of DMSO, heat to 90°C and stir evenly, add 25 parts of urea, heat to 95°C, add 35 parts of 2-amino-4-hydroxybenzoic acid, stir evenly, react at 95°C for 5h, remove the solvent, and obtain modified PVA;

[0036] Take 10 parts of anhydrous magnesium sulfate and 13 parts of aluminum sulfate 18hydrate, add them to 60 parts of water, stir evenly, and record it as substance A; take 3 parts of sodium hydroxide and 8 parts of anhydrous sodium carbonate, add them to 60 parts of water, stir evenly, and record it as substance B; take 18 parts of modified PVA, add them to 100 parts of water and 20 parts of DMSO, and stir evenly; heat to 75°C, keep stirring, add substance A and substance B, stir for 3 hours, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0037] Step 2: Take 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and 80 parts of ethanol, stir evenly, add 60 parts of 30% (m / m) sodium hydroxide solution dropwise under nitrogen protection, react at 70°C for 6 hours, adjust the pH value to 3, filter, wash, and dry to obtain an intermediate; take 6 parts of the intermediate and 60 parts of chloroform, stir evenly, add 5 parts of dichlorothionyl under nitrogen protection, react at 60°C for 6 hours, remove the solvent, and obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride;

[0038] Step 3: Take 12 parts of intercalated modified hydrotalcite and 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, stir evenly to obtain an additive.

[0039] Comparative Example 3 (increasing the amount of additive used, and the remaining method steps are consistent with Example 3): Add 0.8% of the weight of the additive to the polypropylene for electrical membrane prepared in Example 1, melt extrude at 225°C using a twin-screw extruder, granulate, and use a flat film method to extrude, cast, longitudinally stretch, transversely stretch, trim, corona treat, wind, age, and slit to prepare an electrical membrane with a thickness of 5.8 microns; the preparation of the additive includes the following steps: Step 1: weigh 14 parts of PVA, 80 parts of water, and 40 parts of DMSO, heat to 90°C and stir evenly, add 25 parts of urea, heat to 95°C, add 35 parts of 2-amino 4-hydroxybenzoic acid, stir evenly, react at 95°C for 5h, remove the solvent, and obtain modified PVA;

[0040] Take 10 parts of anhydrous magnesium sulfate and 13 parts of aluminum sulfate 18hydrate, add them to 60 parts of water, stir evenly, and record it as substance A; take 3 parts of sodium hydroxide and 8 parts of anhydrous sodium carbonate, add them to 60 parts of water, stir evenly, and record it as substance B; take 18 parts of modified PVA, add them to 100 parts of water and 20 parts of DMSO, and stir evenly; heat to 75°C, keep stirring, add substance A and substance B, stir for 3 hours, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0041] Step 2: Take 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and 80 parts of ethanol, stir evenly, add 60 parts of 30% (m / m) sodium hydroxide solution dropwise under nitrogen protection, react at 70°C for 6 hours, adjust the pH value to 3, filter, wash, and dry to obtain an intermediate; take 6 parts of the intermediate and 60 parts of chloroform, stir evenly, add 5 parts of dichlorothionyl under nitrogen protection, react at 60°C for 6 hours, remove the solvent, and obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride;

[0042] Step 3: Take 12 parts of intercalated modified hydrotalcite and add them to 120 parts of water and 25 parts of DMSO, stir evenly, control the temperature at 35°C, add 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, stir the reaction for 18 hours, remove the solvent, and obtain the additive.

[0043] Comparative Example 4 (reducing the amount of additives used, and the remaining method steps are consistent with Example 3): Add 0.1% of the weight of the additive to the polypropylene for electrical membrane prepared in Example 1, melt extrude at 225° C. using a twin-screw extruder, granulate, and use a flat film method to extrude, cast, longitudinally stretch, transversely stretch, trim, corona treat, wind, age, and slit to prepare an electrical membrane with a thickness of 5.8 μm;

[0044] The preparation of the additive comprises the following steps: Step 1: weigh 14 parts of PVA, 80 parts of water, and 40 parts of DMSO, heat to 90° C. and stir evenly, add 25 parts of urea, heat to 95° C., add 35 parts of 2-amino-4-hydroxybenzoic acid, stir evenly, react at 95° C. for 5 hours, remove the solvent, and obtain modified PVA;

[0045] Take 10 parts of anhydrous magnesium sulfate and 13 parts of aluminum sulfate 18hydrate, add them to 60 parts of water, stir evenly, and record it as substance A; take 3 parts of sodium hydroxide and 8 parts of anhydrous sodium carbonate, add them to 60 parts of water, stir evenly, and record it as substance B; take 18 parts of modified PVA, add them to 100 parts of water and 20 parts of DMSO, and stir evenly; heat to 75°C, keep stirring, add substance A and substance B, stir for 3 hours, filter, wash, and dry to obtain intercalated modified hydrotalcite;

[0046] Step 2: Take 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and 80 parts of ethanol, stir evenly, add 60 parts of 30% (m / m) sodium hydroxide solution dropwise under nitrogen protection, react at 70°C for 6 hours, adjust the pH value to 3, filter, wash, and dry to obtain an intermediate; take 6 parts of the intermediate and 60 parts of chloroform, stir evenly, add 5 parts of dichlorothionyl under nitrogen protection, react at 60°C for 6 hours, remove the solvent, and obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride;

[0047] Step 3: Take 12 parts of intercalated modified hydrotalcite and add them to 120 parts of water and 25 parts of DMSO, stir evenly, control the temperature at 35°C, add 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, stir the reaction for 18 hours, remove the solvent, and obtain the additive.

[0048] In the above examples, the test methods used are conventional methods unless otherwise specified; the raw materials used are commercially available unless otherwise specified, and the sources of the raw materials are as follows: ethanol (CAS: 64-17-5); chloroform (CAS: 67-66-3); triethylaluminum (CAS: 97-93-8); PVA (PVOH28K: Mn9200; PVOH5K: Mn3400, Shanghai Zhenzhun Biotechnology Co., Ltd.); DMSO (CAS: 67-68-5); urea (CAS: 57-13-6); 2-amino 4-hydroxybenzoic acid (S97309, Shanghai Yuanye); anhydrous magnesium sulfate (S24253, Shanghai Yuanye); aluminum sulfate 18hydrate (S30352, Shanghai Yuanye); sodium hydroxide (CAS: 1310-73-2); anhydrous sodium carbonate (S24152, Shanghai Yuanye); β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (CAS: 6386-38-5); dithionyl chloride (CAS: 7719-09-7).

[0049] Experiment: (1) Take the polypropylene for electrical membrane prepared in Examples 1-2, and its basic properties are shown in Table 1;

[0050] Table 1:

[0051]

[0052] (2) The electrical films prepared in Example 3 and Comparative Examples 1 to 4 were tested for mechanical properties with reference to GB / T13542.2-2009; the thermal oxidation resistance was evaluated by observing the change in the melt index after multiple extrusion processes, and the number of extrusions was 5; see Table 2 for details;

[0053] Table 2:

[0054]

[0055]

[0056] In comparative example 1, PVA with an Mn of 9200 is selected as the additive, which has a large molecular weight and affects the molecular chain of the polypropylene matrix, resulting in poor mechanical properties; in comparative example 2, the intercalated modified hydrotalcite and β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride are not compounded, and the performance is not as good as that of the embodiment; in comparative example 3, the amount of additive used is increased, and the performance is poor due to compatibility problems; in comparative example 4, the amount of additive used is reduced, and the performance decreases, which shows that the amount of addition needs to be strictly controlled; in summary, the polypropylene powder prepared by the present invention has low ash content, and after adding the additive, the mechanical properties and thermal oxidation resistance are good.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing polypropylene for electrical membrane, characterized in that: The following steps are involved: S1: preparing polypropylene powder by polymerization reaction in a fully mixed Unipol gas phase fluidized reactor; The method specifically comprises the following steps: adding propylene in the presence of a ZN catalyst, a co-catalyst and an external electron donor to carry out a polymerization reaction to obtain polypropylene for electrical membranes.

2. The method for preparing polypropylene for electrical membrane according to claim 1, characterized in that: The feed amount of the ZN catalyst is 1-2 kg / h; the co-catalyst is triethylaluminum, and the feed amount is 1-5 kg / h; the feed amount of the external electron donor is 0.5-1.5 kg / h; and the feed amount of propylene is 30000-50000 kg / h.

3. The method for preparing polypropylene for electrical membrane according to claim 1, characterized in that: During the polymerization reaction, the polymerization temperature is 65-75° C., the polymerization pressure is 3-3.5 MPa, and the hydrogen flow rate is 1-2 kg / h.

4. Use of the polypropylene for electrical membrane prepared by the method for preparing polypropylene for electrical membrane according to any one of claims 1 to 3, characterized in that: Adding additives to polypropylene for electrical membrane, using a twin-screw extruder to melt extrude, granulate, extrude, cast, longitudinally stretch, transversely stretch, trim, corona treat, roll, age, and slit to make electrical membrane; Preparation of the additives The method comprises the following steps: Step 1: taking PVA, water and DMSO, stirring evenly, adding urea and 2-amino-4-hydroxybenzoic acid, stirring evenly, reacting at 90-95° C. for 3-5 hours, removing the solvent, and obtaining modified PVA; Step 2: add anhydrous magnesium sulfate and aluminum sulfate 18hydrate into water, stir evenly, and record as substance A; add sodium hydroxide and anhydrous sodium carbonate into water, stir evenly, and record as substance B; add modified PVA into water and DMSO, stir evenly, heat to 70-75°C, keep stirring, add substance A and substance B, stir for 2-3h, filter, wash, and dry to obtain intercalated modified hydrotalcite; Step 3: Take the intercalated modified hydrotalcite and add it to water and DMSO, stir evenly, control the temperature at 30-40°C, add β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride, stir the reaction for 15-20 hours, remove the solvent, and obtain the additive.

5. The use of polypropylene for electrical membrane according to claim 4, characterized in that: The additive is added in an amount of 0.2-0.4% of the mass of the polypropylene for electrical membrane.

6. The use of polypropylene for electrical membrane according to claim 4, characterized in that: The modified PVA includes the following raw materials, calculated by weight: 10 to 15 parts of PVA, 80 to 100 parts of water, 30 to 60 parts of DMSO, 20 to 30 parts of urea, and 30 to 40 parts of 2-amino 4-hydroxybenzoic acid; the substance A includes the following raw materials, calculated by weight: 8 to 12 parts of anhydrous magnesium sulfate, 12 to 15 parts of aluminum sulfate 18hydrate, and 50 to 80 parts of water; the substance B includes the following raw materials, calculated by weight: The invention discloses a novel intercalation modified hydrotalcite comprising the following raw materials, calculated by weight: 2 to 4 parts of sodium hydroxide, 7 to 10 parts of anhydrous sodium carbonate, and 50 to 80 parts of water; the intercalation modified hydrotalcite comprises the following raw materials, calculated by weight: 15 to 20 parts of modified PVA; the additive comprises the following raw materials, calculated by weight: 10 to 15 parts of intercalation modified hydrotalcite, 100 to 120 parts of water, 20 to 30 parts of DMSO, and 1 to 2 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride.

7. The use of polypropylene for electrical membrane according to claim 4, characterized in that: The Mn of the PVA is 3000-5000.

8. The use of polypropylene for electrical membrane according to claim 4, characterized in that: The preparation of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride comprises the following steps: taking β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate methyl ester and ethanol, stirring evenly, dropping sodium hydroxide solution under nitrogen protection, reacting at 65-70° C. for 5-6 hours, adjusting the pH value to 3-4, filtering, washing, and drying to obtain an intermediate; taking the intermediate and chloroform, stirring evenly, dropping thionyl chloride under nitrogen protection, reacting at 50-60° C. for 5-6 hours, and removing the solvent to obtain β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride.

9. The use of polypropylene for electrical membrane according to claim 7, characterized in that: The intermediate comprises the following raw materials, calculated by mass: 30 to 35 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl) methyl propionate, 50 to 80 parts of ethanol, and 55 to 65 parts of 30% (m / m) sodium hydroxide solution; the β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride comprises the following raw materials, calculated by mass: 5 to 8 parts of the intermediate, 50 to 80 parts of chloroform, and 4 to 6 parts of dichlorothionyl.

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