Process for producing a polypropylene resin for roughening film of oil-immersed capacitor

Abstract

The application discloses a preparation method of polypropylene resin for oil-immersed capacitor roughening film. First, a catalyst, an external electron donor and an activator are uniformly mixed, and then are reacted with propylene monomers in a prepolymerization reactor to generate polypropylene prepolymer; the polypropylene prepolymer, propylene monomers and hydrogen are jointly introduced into a first loop reactor to continue polymerization reaction, to generate polymer; the polymer, propylene monomers and hydrogen are jointly introduced into a second loop reactor to continue polymerization reaction, to generate polymer powder; the polymer powder is subjected to flash evaporation to remove liquid-phase propylene, and then is sequentially subjected to degassing, steaming and drying to obtain homopolymer powder particles; the homopolymer powder particles and a compounded additive are jointly extruded and granulated to obtain the polypropylene resin for the oil-immersed capacitor roughening film. Through the application, the problems of high ash content, difficult control of isotacticity, elimination of peculiar smell in the processing, reduction of precipitates, difficulty in roughening of the film, insufficient roughening degree and low porosity are solved.

Description

I. Technical Field:

[0001] This invention belongs to the field of polypropylene production technology, and in particular relates to a method for preparing polypropylene resin for roughening films of oil-immersed capacitors with ultra-low ash content and controllable isotacticity. II. Background Technology:

[0002] Imported products are all produced using a "slurry polymerization + washing and deashing" process. However, this process involves the use of a compounded organic solvent system for washing, deashing, and removing atactic particles, resulting in a long process flow, high production costs, material and energy consumption, and potential environmental pollution. Domestically, a highly active catalyst is used in a loop-type polypropylene process to directly polymerize the polymer within the reactor, producing "low-ash, high-isotactic" polymer powder. This eliminates the need for organic solvent washing, deashing, and removing atactic particles, resulting in a shorter process flow, lower material and energy consumption, and compliance with national environmental protection policies.

[0003] Due to significant differences between the domestic and international process routes, polypropylene resin produced by traditional loop-type polypropylene processes and conventional additive systems for (with) BOPP exhibits substantial differences from imported products in ash content, isotacticity control, isotactic sequence distribution, melting, and crystallization. Downstream film production presents the following problems: firstly, noticeable odor and excessive precipitates are observed during processing; secondly, film roughening is difficult, porosity is low, and the roughening zone is not fine enough; and thirdly, both the powder ash content and the ash content of the final product are high. III. Summary of the Invention:

[0004] The technical problem this invention aims to solve is that polypropylene resin for roughening films produced by the loop-tube polypropylene process with conventional additive systems cannot reach the level of imported counterparts in key indicators such as ash content and isotactic index control, as well as downstream processing performance. This invention provides a method for preparing polypropylene resin for roughening films of oil-immersed capacitors with ultra-low ash content and controllable isotacticity. The technical solution of this invention solves the problems of high ash content, difficulty in controlling isotacticity, elimination of odors during processing, reduction of precipitates, and difficulties in film roughening, insufficient roughness, and low porosity by optimizing key parameters and selecting an additive system suitable for the characteristics of domestically produced powders. Simultaneously, it maintains the excellent electrical and comprehensive mechanical properties of the prepared film products.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for preparing polypropylene resin for roughening films in oil-immersed capacitors, the method comprising the following steps:

[0007] 1) The catalyst, external electron donor and activator are mixed evenly, and then the mixture is introduced into the prepolymer reactor together with the propylene monomer to react and generate polypropylene prepolymer.

[0008] 2) The polypropylene prepolymer obtained in step 1) is fed together with propylene monomer and hydrogen into the first loop reactor to continue the polymerization reaction and generate polymer;

[0009] 3) The polymer obtained in step 2) is fed together with propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction and generate polymer powder.

[0010] 4) The polymer powder obtained in step 3) is subjected to flash evaporation at 70-85℃ and 1.65-2.15MPa to remove the liquid phase propylene. An antistatic agent is added during the flash evaporation process. Then, the powder is subjected to degassing, steaming and drying in sequence to obtain homopolymer powder particles (the ash content of the obtained homopolymer powder particles is ≤10ppm and the isotacticity is ≤98.0%).

[0011] 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film (the obtained polypropylene resin has an ash content of ≤15ppm and an isotacticity of ≤97.5%).

[0012] According to the above-mentioned preparation method of polypropylene resin for roughening membrane of oil-immersed capacitor, the catalyst activity in step 1) is ≥150kgPP / gcat, the catalyst is HA-R catalyst (belonging to ZN titanium-based catalyst); the external electron donor is cyclohexylmethyldimethoxysilane; and the activator is triethylaluminum.

[0013] According to the above-described method for preparing polypropylene resin for roughening membranes of oil-immersed capacitors, in step 1), the flow rate of the catalyst is 0.8–1.2 kg / h, the flow rate of the propylene monomer is 1200–1800 kg / h, the amount of external electron donor added is 0.004–0.04 kg external electron donor / ton of propylene monomer, and the amount of activator added is 0.02–0.08 kg activator / ton of propylene monomer.

[0014] According to the above-described method for preparing polypropylene resin for roughening membrane of oil-immersed capacitor, during the reaction described in step 1), the reaction temperature is controlled at 15-25℃, the pressure at 3.3-4.0MPa, and the residence time at 5-10min.

[0015] According to the above-described method for preparing polypropylene resin for roughening membrane of oil-immersed capacitor, in step 2), the flow rate of propylene monomer entering the first loop reactor is 14.0 to 16.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 to 1150 ppm.

[0016] (The flow rate of the polypropylene prepolymer entering the first loop reactor is the same as the flow rate of the propylene monomer entering the prepolymer reactor, i.e., 1200-1800 kg / h).

[0017] According to the above-described method for preparing polypropylene resin for roughening membrane of oil-immersed capacitor, during the polymerization reaction in step 2), the reaction temperature is controlled at 68-74℃, the pressure at 3.3-4.0MPa, and the residence time at 50-90min.

[0018] According to the above-described method for preparing polypropylene resin for roughening membrane of oil-immersed capacitor, in step 3), the flow rate of propylene monomer entering the second loop reactor is 7.0 to 9.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1050 to 1150 ppm.

[0019] (The flow rate of the polymer entering the second loop reactor is the same as the flow rate of the propylene monomer entering the first loop reactor, i.e., 14.0 to 16.0 t / h).

[0020] According to the above-described method for preparing polypropylene resin for roughening membrane of oil-immersed capacitor, during the polymerization reaction in step 3), the reaction temperature is controlled at 68-74℃, the pressure at 3.3-4.0MPa, and the residence time at 30-60min.

[0021] According to the above-described method for preparing polypropylene resin for roughening film of oil-immersed capacitor, the antistatic agent in step 4) is amine ethoxide; the amount of antistatic agent added is 0.4-0.8 kg / h.

[0022] According to the above-mentioned preparation method of polypropylene resin for roughening film of oil-immersed capacitor, the mass concentration of the compounding agent in step 5) in the polymer powder particles is 1500-3500 ppm, that is, 1.5-3.5 kg of compounding agent is added to each ton of homopolymer polymer powder particles.

[0023] The compound adjuvant is at least two of the following: tetraphenol antioxidants, phosphite antioxidants, triphenol antioxidants, and acid absorbents;

[0024] The tetraphenolic antioxidant is antioxidant 1010, the phosphite antioxidant is antioxidant 168 or antioxidant 626 (preferably antioxidant 168), the triphenolic antioxidant is antioxidant 330 or antioxidant CA (preferably antioxidant 330), and the acid absorbent is calcium stearate, hydrotalcite, or zinc oxide (preferably calcium stearate).

[0025] The positive and beneficial effects of this invention are:

[0026] 1. This invention utilizes an ultra-highly active titanium-based catalyst supported on magnesium dichloride in a loop-type polypropylene process. By optimizing key process parameters such as Al / PR, Al / Si, residence time, and loading ratio, a polymer powder with ultra-low ash content (≤10ppm) and high isotacticity (≤98.0%) is obtained. Based on this, an additive system adapted to the characteristics of the domestically produced powder is designed. Through melt extrusion granulation, a domestically produced polypropylene resin for capacitor roughening films that meets the requirements (ash content ≤15ppm, isotacticity ≤97.5%, excellent downstream processing performance) is obtained.

[0027] 2. The oil-immersed capacitor made using the product prepared in Example 1 of this invention was successfully connected to the grid and operated well, according to experimental testing.

[0028] 3. The product prepared by this invention was tested and found to have an isotacticity of 97.4% (testing unit: Ningbo Customs Technology Center) and an ash content of 13 ppm (testing unit: Zhonglan Chenguang Chengdu Testing Technology Co., Ltd.). IV. Detailed Implementation Methods:

[0029] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0030] The catalyst used in the following examples is an HA-R catalyst (belonging to the ZN titanium-based catalyst), with an activity ≥150 kgPP / gcat; the external electron donor is cyclohexylmethyldimethoxysilane; and the activator is triethylaluminum.

[0031] Comparative Example 1:

[0032] A method for preparing polypropylene resin for roughening film of oil-immersed capacitors, the detailed steps of which are as follows:

[0033] 1) Mix the catalyst, external electron donor and activator evenly, and then introduce them together with propylene monomer into the prepolymer reactor for reaction. Control the reaction temperature at 23℃, the pressure at 3.4MPa and the residence time at 5min to generate polypropylene prepolymer.

[0034] The catalyst addition amount is 1.2 kg / h, the fresh propylene monomer flow rate is 1800 kg / h, the external electron donor addition amount is 0.04 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.08 kg activator / ton of propylene monomer.

[0035] 2) The polypropylene prepolymer obtained in step 1) is introduced into the first loop reactor along with fresh propylene monomer and hydrogen to continue the polymerization reaction. The reaction temperature is controlled at 70℃, the pressure at 3.4MPa and the residence time at 70min to generate polymer.

[0036] The flow rate of fresh propylene monomer entering the first loop reactor is 14.5 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1150 ppm.

[0037] 3) The polymer obtained in step 2) is fed together with fresh propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction. The reaction temperature is controlled at 70°C, the pressure at 3.4 MPa and the residence time at 30 min to generate polymer powder.

[0038] The flow rate of fresh propylene monomer entering the second loop reactor is 8.5 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1150 ppm;

[0039] 4) The polymer powder obtained in step 3) is subjected to flash evaporation to remove the liquid phase propylene at 72-78℃ and 1.7-1.9MPa. During the flash evaporation process, an antistatic agent, amine ethoxide, is added at a rate of 0.8 kg / h. Then, the mixture is subjected to degassing, steaming, and drying to obtain homopolymer powder particles.

[0040] 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film (the ash content, isotacticity and other properties of the obtained polypropylene resin are detailed in Table 1).

[0041] The mass concentration of the compounded additive in the polymer powder particles is 3500 ppm; the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 1750 ppm, phosphite antioxidant (antioxidant 168) 1650 ppm, acid absorbent (calcium stearate) 100 ppm; the total added concentration is 3500 ppm.

[0042] Comparative Example 2:

[0043] A method for preparing polypropylene resin for roughening film of oil-immersed capacitor is basically the same as that of Comparative Example 1, except that:

[0044] In step 1): the reaction temperature is controlled at 22℃, the pressure at 3.5MPa, and the residence time at 6min;

[0045] The catalyst addition amount is 1.1 kg / h, the fresh propylene monomer flow rate is 1700 kg / h, the external electron donor addition amount is 0.025 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.07 kg activator / ton of propylene monomer.

[0046] In step 2): the reaction temperature is controlled at 72℃, the pressure at 3.5MPa, and the residence time at 65min;

[0047] The flow rate of fresh propylene monomer entering the first loop reactor is 15.5 t / h;

[0048] In step 3): the reaction temperature is controlled at 70℃, the pressure at 3.5MPa, and the residence time at 35min;

[0049] The flow rate of fresh propylene monomer into the second loop reactor is 7.5 t / h; the load ratio of the first and second loop reactors is 65%:35%.

[0050] In step 5): the mass concentration of the compounded additive in the polymer powder particles is 3000 ppm; wherein the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 1500 ppm, phosphite antioxidant (antioxidant 168) 1450 ppm, acid absorbent (calcium stearate) 50 ppm; the total added concentration is 3000 ppm.

[0051] Comparative Example 3:

[0052] A method for preparing polypropylene resin for roughening film of oil-immersed capacitor is basically the same as that of Comparative Example 1, except that:

[0053] In step 1): the reaction temperature is controlled at 20℃, the pressure at 3.5MPa, and the residence time at 7min;

[0054] The catalyst addition amount is 1.1 kg / h, the fresh propylene monomer flow rate is 1600 kg / h, the external electron donor addition amount is 0.015 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.05 kg activator / ton of propylene monomer.

[0055] In step 2): the reaction temperature is controlled at 72℃, the pressure at 3.5MPa, and the residence time at 65min;

[0056] The flow rate of fresh propylene monomer entering the first loop reactor is 15.5 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1100 ppm.

[0057] In step 3): the reaction temperature is controlled at 70℃, the pressure at 3.5MPa, and the residence time at 35min;

[0058] The flow rate of fresh propylene monomer entering the second loop reactor is 7.5 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second loop reactor is 1100 ppm; the load ratio of the first and second loop reactors is 65%:35%;

[0059] In step 4): the amount of antistatic agent added is 0.7 kg / h;

[0060] In step 5): the mass concentration of the compounded additive in the polymer powder particles is 2500 ppm; wherein the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 850 ppm, phosphite antioxidant (antioxidant 168) 750 ppm, triphenol antioxidant (antioxidant 330) 850 ppm, and acid absorbent (calcium stearate) 50 ppm; the total added concentration is 2500 ppm.

[0061] Comparative Example 4:

[0062] A method for preparing polypropylene resin for roughening film of oil-immersed capacitor is basically the same as that of Comparative Example 1, except that:

[0063] In step 1): the reaction temperature is controlled at 20℃, the pressure at 3.5MPa, and the residence time at 8min;

[0064] The catalyst addition amount is 1.0 kg / h, the fresh propylene monomer flow rate is 1500 kg / h, the external electron donor addition amount is 0.008 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.03 kg activator / ton of propylene monomer.

[0065] In step 2): the reaction temperature is controlled at 70℃, the pressure at 3.5MPa, and the residence time at 67min;

[0066] The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm.

[0067] In step 3): the reaction temperature is controlled at 70℃, the pressure at 3.5MPa, and the residence time at 33min;

[0068] The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second loop reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%;

[0069] In step 4): the amount of antistatic agent added is 0.6 kg / h;

[0070] In step 5): the mass concentration of the compounded additive in the polymer powder particles is 1900 ppm; wherein the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 650 ppm, phosphite antioxidant (antioxidant 168) 550 ppm, triphenol antioxidant (antioxidant 330) 650 ppm, and acid absorbent (calcium stearate) 50 ppm; the total added concentration is 1900 ppm.

[0071] Comparative Example 5:

[0072] A method for preparing polypropylene resin for roughening film of oil-immersed capacitor is basically the same as that of Comparative Example 1, except that:

[0073] In step 1): the reaction temperature is controlled at 18℃, the pressure at 3.4MPa, and the residence time at 9min;

[0074] The catalyst addition amount is 0.9 kg / h, the fresh propylene monomer flow rate is 1350 kg / h, the external electron donor addition amount is 0.004 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.02 kg activator / ton of propylene monomer.

[0075] In step 2): the reaction temperature is controlled at 70℃, the pressure at 3.4MPa, and the residence time at 67min;

[0076] The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm.

[0077] In step 3): the reaction temperature is controlled at 70℃, the pressure at 3.4MPa, and the residence time at 33min;

[0078] The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second loop reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%;

[0079] In step 4): the amount of antistatic agent added is 0.4 kg / h;

[0080] In step 5): the mass concentration of the compounded additive in the polymer powder particles is 1500 ppm; wherein the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 1000 ppm, phosphite antioxidant (antioxidant 168) 250 ppm, triphenol antioxidant (antioxidant 330) 200 ppm, acid absorbent (calcium stearate) 50 ppm; the total added concentration is 1500 ppm.

[0081] Example 1:

[0082] The preparation method of polypropylene resin for roughening film of oil-immersed capacitor of the present invention includes the following detailed steps:

[0083] 1) Mix the catalyst, external electron donor and activator evenly, and then introduce them together with propylene monomer into the prepolymer reactor for reaction. Control the reaction temperature at 18℃, the pressure at 3.4MPa and the residence time at 10min to generate polypropylene prepolymer.

[0084] The catalyst addition amount is 0.8 kg / h, the fresh propylene monomer flow rate is 1200 kg / h, the external electron donor addition amount is 0.004 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.02 kg activator / ton of propylene monomer.

[0085] 2) The polypropylene prepolymer obtained in step 1) is introduced into the first loop reactor along with fresh propylene monomer and hydrogen to continue the polymerization reaction. The reaction temperature is controlled at 70℃, the pressure at 3.4MPa and the residence time at 67min to generate polymer.

[0086] The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm.

[0087] 3) The polymer obtained in step 2) is fed together with fresh propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction. The reaction temperature is controlled at 70°C, the pressure at 3.4 MPa and the residence time at 33 min to generate polymer powder.

[0088] The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%;

[0089] 4) The polymer powder obtained in step 3) is subjected to flash evaporation to remove the liquid phase propylene at 72-78℃ and 1.7-1.9MPa. During the flash evaporation process, the antistatic agent amine ethoxide is added at a rate of 0.4 kg / h. Then, the mixture is subjected to degassing, steaming, and drying to obtain homopolymer powder particles.

[0090] 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film (the ash content, isotacticity and other properties of the obtained polypropylene resin are detailed in Table 1).

[0091] The mass concentration of the compounded additive in the polymer powder particles is 1500 ppm; wherein the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 570 ppm, phosphite antioxidant (antioxidant 168) 500 ppm, triphenol antioxidant (antioxidant 330) 400 ppm, and acid absorbent (calcium stearate) 30 ppm; the total added concentration is 1500 ppm.

[0092] Example 2:

[0093] The preparation method of polypropylene resin for roughening film of oil-immersed capacitor of the present invention includes the following detailed steps:

[0094] 1) Mix the catalyst, external electron donor and activator evenly, and then introduce them together with propylene monomer into the prepolymer reactor for reaction. Control the reaction temperature at 18℃, the pressure at 3.4MPa and the residence time at 10min to generate polypropylene prepolymer.

[0095] The catalyst addition amount is 0.8 kg / h, the fresh propylene monomer flow rate is 1200 kg / h, the external electron donor addition amount is 0.004 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.02 kg activator / ton of propylene monomer.

[0096] 2) The polypropylene prepolymer obtained in step 1) is introduced into the first loop reactor along with fresh propylene monomer and hydrogen to continue the polymerization reaction. The reaction temperature is controlled at 70℃, the pressure at 3.4MPa and the residence time at 67min to generate polymer.

[0097] The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm.

[0098] 3) The polymer obtained in step 2) is fed together with fresh propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction. The reaction temperature is controlled at 70°C, the pressure at 3.4 MPa and the residence time at 33 min to generate polymer powder.

[0099] The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%;

[0100] 4) The polymer powder obtained in step 3) is subjected to flash evaporation to remove the liquid phase propylene at 72-78℃ and 1.7-1.9MPa. During the flash evaporation process, the antistatic agent amine ethoxide is added at a rate of 0.4 kg / h. Then, the mixture is subjected to degassing, steaming, and drying to obtain homopolymer powder particles.

[0101] 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film (the ash content, isotacticity and other properties of the obtained polypropylene resin are detailed in Table 1).

[0102] The mass concentration of the compounded additive in the polymer powder particles is 1500 ppm; the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate); the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 750 ppm, phosphite antioxidant (antioxidant 168) 360 ppm, triphenol antioxidant (antioxidant 330) 360 ppm, and acid absorbent (calcium stearate) 30 ppm; the total added concentration is 1500 ppm.

[0103] Table 1. Performance and applications of the products prepared in Comparative Examples 1-5 and Examples 1-2 of the present invention.

[0104]

[0105] As shown in Table 1, the polypropylene resins prepared in Examples 1-2 and Comparative Examples 1-5 of this invention exhibited better performance in terms of ash content and isotacticity control, and also demonstrated excellent processability during film formation. All film indicators met the requirements. Although Comparative Example 5 showed excellent performance in all aspects (resin, film, and processing properties), it failed the durability test (generally not less than 500-1000 hours) after being manufactured into an oil-immersed capacitor. Compared to Example 1, Example 2 also passed the 1000-hour durability test, but the breakdown voltage of the capacitor decreased significantly after the experiment (also meeting national standards).

[0106] The oil-immersed capacitor made using the product prepared in Example 1 of this invention was successfully connected to the grid and operated well, according to experimental testing.

Claims

1. A method for preparing polypropylene resin for roughening films in oil-immersed capacitors, characterized in that, The preparation method includes the following steps: 1) Mix the catalyst, external electron donor and activator evenly, and then introduce them together with propylene monomer into the prepolymer reactor for reaction. Control the reaction temperature at 18℃, the pressure at 3.4MPa and the residence time at 10min to generate polypropylene prepolymer. The catalyst addition amount is 0.8 kg / h, the fresh propylene monomer flow rate is 1200 kg / h, the external electron donor addition amount is 0.004 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.02 kg activator / ton of propylene monomer. 2) The polypropylene prepolymer obtained in step 1) is introduced into the first loop reactor along with fresh propylene monomer and hydrogen to continue the polymerization reaction. The reaction temperature is controlled at 70℃, the pressure at 3.4MPa and the residence time at 67min to generate polymer. The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm. 3) The polymer obtained in step 2) is fed together with fresh propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction. The reaction temperature is controlled at 70°C, the pressure at 3.4 MPa and the residence time at 33 min to generate polymer powder. The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%. 4) The polymer powder obtained in step 3) is subjected to flash evaporation at 72-78℃ and 1.7-1.9MPa to remove the liquid phase propylene. During the flash evaporation process, an antistatic agent, amine ethoxide, is added at a rate of 0.4 kg / h. Then, the mixture is subjected to degassing, steaming, and drying to obtain homopolymer powder particles. 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film. The mass concentration of the compounded additive in the polymer powder particles is 1500 ppm; the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent, namely calcium stearate; the added concentrations are as follows: tetraphenol antioxidant 1010 570 ppm, phosphite antioxidant 168 500 ppm, triphenol antioxidant 330 400 ppm, and acid absorbent, namely calcium stearate 30 ppm; the total added concentration is 1500 ppm.

2. A method for producing a polypropylene resin for oil-immersed capacitor roughing film, characterized by comprising: The preparation method includes the following steps: 1) Mix the catalyst, external electron donor and activator evenly, and then introduce them together with propylene monomer into the prepolymer reactor for reaction. Control the reaction temperature at 18℃, the pressure at 3.4MPa and the residence time at 10min to generate polypropylene prepolymer. The catalyst addition amount is 0.8 kg / h, the fresh propylene monomer flow rate is 1200 kg / h, the external electron donor addition amount is 0.004 kg external electron donor / ton of propylene monomer, and the activator addition amount is 0.02 kg activator / ton of propylene monomer. 2) The polypropylene prepolymer obtained in step 1) is introduced into the first loop reactor along with fresh propylene monomer and hydrogen to continue the polymerization reaction. The reaction temperature is controlled at 70℃, the pressure at 3.4MPa and the residence time at 67min to generate polymer. The flow rate of fresh propylene monomer entering the first loop reactor is 15.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050 ppm. 3) The polymer obtained in step 2) is fed together with fresh propylene monomer and hydrogen into the second loop reactor to continue the polymerization reaction. The reaction temperature is controlled at 70°C, the pressure at 3.4 MPa and the residence time at 33 min to generate polymer powder. The flow rate of fresh propylene monomer entering the second loop reactor is 8.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the second reactor is 1050 ppm; the load ratio of the first and second loop reactors is 67%:33%. 4) The polymer powder obtained in step 3) is subjected to flash evaporation at 72-78℃ and 1.7-1.9MPa to remove the liquid phase propylene. During the flash evaporation process, an antistatic agent, amine ethoxide, is added at a rate of 0.4 kg / h. Then, the mixture is subjected to degassing, steaming, and drying to obtain homopolymer powder particles. 5) The homopolymer powder particles obtained in step 4) are fed together with the compounded additives into a twin-screw extruder for extrusion granulation to obtain polypropylene resin for oil-immersed capacitor roughening film. The mass concentration of the compounded additive in the polymer powder particles is 1500 ppm; the compounded additive adopts a system of tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent, namely calcium stearate; the added concentrations are: tetraphenol antioxidant 1010 750 ppm, phosphite antioxidant 168 360 ppm, triphenol antioxidant 330 360 ppm, and acid absorbent, namely calcium stearate, 30 ppm; the total added concentration is 1500 ppm.

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