Preparation method of polypropylene resin for oil-immersed capacitor coarsening film

Abstract

The invention discloses a preparation method of polypropylene resin for an oil-immersed capacitor coarsening film. The preparation method comprises the following steps: firstly, uniformly mixing a catalyst, an external electron donor and an activating agent, and then enabling the mixture and a propylene monomer to enter a prepolymerization reactor for reaction to generate a polypropylene prepolymer; the polypropylene prepolymer, a propylene monomer and hydrogen jointly enter a first loop reactor for continuous polymerization reaction to generate a polymer; enabling the polymer, a propylene monomer and hydrogen to enter a second loop reactor together for continuous polymerization reaction to generate polymer powder; performing flash evaporation on the polymer powder to remove liquid-phase propylene, and then sequentially performing degassing, steaming and drying to obtain homopolymer powder particles; and co-extruding and granulating the homopolymer powder particles and a compound auxiliary agent to obtain the polypropylene resin for the oil-immersed capacitor coarsening film. Through the method, the problems that the ash content is high, the isotacticity is not easy to control, peculiar smell in the processing process is eliminated, precipitates are reduced, and the problems that the film is difficult to coarsen, the coarsening degree is not enough and the porosity is low are solved.

Description

1. Technical field:

[0001] The invention belongs to the technical field of polypropylene production, and in particular relates to a method for preparing a polypropylene resin for an oil-immersed capacitor roughening film with ultra-low ash content and controllable isotacticity. 2. Background technology:

[0002] Imported products are all produced using the "slurry polymerization + washing and deashing" process route, but because this process route uses a composite organic solvent system for washing, deashing and removing irregulars, the process is long, the production cost and material and energy consumption are high, and it is easy to cause environmental pollution. Domestically, high-activity catalysts are used in the ring tube polypropylene process device to directly polymerize in the reactor to generate "low ash, high regularity" polymer powder, without the need to use organic solvents for washing, deashing and removing irregulars. The process is short, the material and energy consumption is low, and it is in line with national environmental protection policies.

[0003] Due to the large differences between the two process routes abroad and at home, the polypropylene resin produced by the traditional annular tube polypropylene process device and the conventional additive system for (additional) BOPP has large differences in ash content, isotacticity control and isotactic sequence distribution, as well as melting and crystallization compared with imported products. There are the following problems in the downstream film-making process: first, there is a more obvious odor and more precipitates during the processing; second, the film is difficult to coarsen during processing, the porosity is low, and the coarsening circle is not fine enough; third, the ash content of the powder and the ash content of the final product are high. 3. Summary of the invention:

[0004] The technical problem to be solved by the present invention is: for the polypropylene resin for roughening film produced by the ring tube polypropylene process + conventional auxiliary agent system, the key indicators such as ash content, isotactic index control and downstream processing performance cannot reach the level of similar imported products. The present invention provides a method for preparing polypropylene resin for roughening film of oil-immersed capacitor with ultra-low ash content and controllable isotacticity. The technical solution of the present invention solves the problems of high ash content and difficult control of isotacticity, eliminates odor during processing, reduces precipitates, solves the problems of difficult film roughening, insufficient roughening degree and low porosity by optimizing and adjusting key parameters and selecting an auxiliary agent system adapted to the characteristics of domestic powders; at the same time, the prepared film products are kept to have excellent electrical properties and comprehensive mechanical properties.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is:

[0006] The present invention provides a method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor, the preparation method comprising the following steps:

[0007] 1) mixing the catalyst, the external electron donor and the activator uniformly, and then introducing the mixed catalyst into a prepolymerization reactor together with the propylene monomer to react and generate a polypropylene prepolymer;

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

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

[0010] 4) flashing the polymer powder obtained in step 3) at 70-85° C. and 1.65-2.15 MPa to remove liquid propylene, adding an antistatic agent during the flashing process, and then degassing, steaming, and drying in sequence to obtain homopolymer powder particles (the ash content of the obtained homopolymer powder particles is ≤10 ppm and the isotacticity is ≤98.0%);

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

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

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

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

[0015] According to the above-mentioned method for preparing polypropylene resin for roughening film of oil-immersed capacitor, in step 2), the flow rate of propylene monomer entering the first loop reactor is 14.0-16.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050-1150 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 prepolymerization reactor, i.e. 1200-1800 Kg / h).

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

[0018] According to the above-mentioned method for preparing polypropylene resin for roughening film of oil-immersed capacitor, in step 3), the flow rate of propylene monomer entering the second loop reactor is 7.0-9.0 t / h; the molar concentration of the hydrogen added in the propylene monomer entering the second reactor is 1050-1150 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. 14.0-16.0 t / h).

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

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

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

[0023] The compounding auxiliary agent is at least two of a tetraphenol antioxidant, a phosphite antioxidant, a triphenol antioxidant and an acid absorbent;

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

[0025] The positive beneficial effects of the present invention are:

[0026] 1. The present invention uses an ultra-high active titanium catalyst with magnesium dichloride as a carrier, and optimizes key process parameters such as Al / PR, Al / Si, residence time and load ratio on a loop-pipe polypropylene process device to obtain a polymer powder with ultra-low ash content (≤10ppm) and high isotacticity ≤98.0%). On this basis, an additive system adapted to the characteristics of domestic powder is designed, and a domestic polypropylene resin for capacitor roughening film that meets the requirements (ash content ≤15ppm, isotacticity ≤97.5%, and excellent downstream processing performance) is obtained through melt extrusion granulation.

[0027] 2. The oil-immersed capacitor made of the product prepared in Example 1 of the present invention can be smoothly connected to the grid and operates well after experimental testing.

[0028] 3. The product prepared by the present invention was tested, and the isotacticity was 97.4% (testing unit: Ningbo Customs Technology Center), and the ash content was 13 ppm (testing unit: China Bluestar Chengdu Testing Technology Co., Ltd.). 4. Specific implementation methods:

[0029] The present invention is further described below in conjunction with embodiments, but the protection scope of the technical solution of the present invention is not limited thereto.

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

[0031] Comparative Example 1:

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

[0033] 1) The catalyst, the external electron donor and the activator are mixed evenly, and after mixing, they are put into a prepolymerization reactor together with the propylene monomer for reaction, and the reaction temperature is controlled to be 23° C., the pressure is 3.4 MPa, and the residence time is 5 min to generate a polypropylene prepolymer;

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

[0035] 2) the polypropylene prepolymer obtained in step 1) is introduced into a first loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 70 min to generate a 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 into a second loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 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 the hydrogen added in the propylene monomer entering the second reactor is 1150 ppm;

[0039] 4) flash distilling the polymer powder obtained in step 3) at 72-78° C. and 1.7-1.9 MPa to remove liquid propylene, and adding antistatic agent ethoxylated amine during the flash distillation process, with the amount of antistatic agent added being 0.8 kg / h, and then degassing, steaming and drying in sequence to obtain homopolymer powder particles;

[0040] 5) The homopolymer powder particles obtained in step 4) and the compounding auxiliary agent are fed into a twin-screw extruder for extrusion granulation to obtain a polypropylene resin for a roughening film of an oil-immersed capacitor (the ash content, isotacticity and other properties of the obtained polypropylene resin are shown in Table 1);

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

[0042] Comparative Example 2:

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

[0044] In step 1), the reaction temperature was controlled to be 22°C, the pressure to be 3.5 MPa, and the residence time to be 6 min;

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

[0046] In step 2), the reaction temperature was controlled to be 72°C, the pressure to be 3.5 MPa, and the residence time to be 65 min;

[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 to be 70°C, the pressure is 3.5 MPa, and the residence time is 35 min;

[0049] The flow rate of fresh propylene monomer entering 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 auxiliary agent in the polymer powder particles is 3000ppm; wherein the compounded auxiliary agent adopts: tetraphenol antioxidant + phosphite antioxidant + acid absorber (calcium stearate) system; the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 1500ppm, phosphite antioxidant (antioxidant 168) 1450ppm, acid absorber (calcium stearate) 50ppm; the total added concentration is 3000ppm.

[0051] Comparative Example 3:

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

[0053] In step 1), the reaction temperature is controlled to be 20°C, the pressure is 3.5MPa, and the residence time is 7min;

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

[0055] In step 2), the reaction temperature was controlled to be 72°C, the pressure to be 3.5 MPa, and the residence time to be 65 min;

[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 to be 70°C, the pressure is 3.5 MPa, and the residence time is 35 min;

[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 auxiliary agent in the polymer powder particles is 2500ppm; wherein the compounded auxiliary agent adopts: tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate) system; the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 850ppm, phosphite antioxidant (antioxidant 168) 750ppm, triphenol antioxidant (antioxidant 330) 850ppm, acid absorbent (calcium stearate) 50ppm; the total added concentration is 2500ppm.

[0061] Comparative Example 4:

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

[0063] In step 1), the reaction temperature is controlled to be 20°C, the pressure is 3.5MPa, and the residence time is 8min;

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

[0065] In step 2), the reaction temperature is controlled to be 70°C, the pressure is 3.5 MPa, and the residence time is 67 min;

[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 was controlled to be 70°C, the pressure to be 3.5 MPa, and the residence time to be 33 min;

[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 auxiliary agent in the polymer powder particles is 1900ppm; wherein the compounded auxiliary agent adopts: tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate) system; the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 650ppm, phosphite antioxidant (antioxidant 168) 550ppm, triphenol antioxidant (antioxidant 330) 650ppm, acid absorbent (calcium stearate) 50ppm; the total added concentration is 1900ppm.

[0071] Comparative Example 5:

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

[0073] In step 1), the reaction temperature was controlled to be 18°C, the pressure was 3.4 MPa, and the residence time was 9 min;

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

[0075] In step 2), the reaction temperature was controlled to be 70°C, the pressure to be 3.4 MPa, and the residence time to be 67 min;

[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 was controlled to be 70°C, the pressure to be 3.4 MPa, and the residence time to be 33 min;

[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 auxiliary agent in the polymer powder particles is 1500ppm; the compounded auxiliary agent adopts: tetraphenol antioxidant + phosphite antioxidant + triphenol antioxidant + acid absorbent (calcium stearate) system; the added concentrations are: tetraphenol antioxidant (antioxidant 1010) 1000ppm, phosphite antioxidant (antioxidant 168) 250ppm, triphenol antioxidant (antioxidant 330) 200ppm, acid absorbent (calcium stearate) 50ppm; the total added concentration is 1500ppm.

[0081] Embodiment 1:

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

[0083] 1) The catalyst, the external electron donor and the activator are mixed uniformly, and after mixing, they are put into a prepolymerization reactor together with the propylene monomer for reaction, and the reaction temperature is controlled to be 18° C., the pressure is 3.4 MPa, and the residence time is 10 min to generate a polypropylene prepolymer;

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

[0085] 2) the polypropylene prepolymer obtained in step 1) is introduced into a first loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 67 min to generate a 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 into a second loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 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 the 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) flashing the polymer powder obtained in step 3) at 72-78° C. and 1.7-1.9 MPa to remove liquid propylene, adding an antistatic agent, ethoxylated amine, during the flashing process, with the amount of the antistatic agent added being 0.4 kg / h, and then degassing, steaming, and drying in sequence to obtain homopolymer powder particles;

[0090] 5) The homopolymer powder particles obtained in step 4) and the compounding auxiliary agent are fed into a twin-screw extruder for extrusion granulation to obtain a polypropylene resin for a roughening film of an oil-immersed capacitor (the ash content, isotacticity and other properties of the obtained polypropylene resin are shown in Table 1);

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

[0092] Embodiment 2:

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

[0094] 1) The catalyst, the external electron donor and the activator are mixed uniformly, and after mixing, they are put into a prepolymerization reactor together with the propylene monomer for reaction, and the reaction temperature is controlled to be 18° C., the pressure is 3.4 MPa, and the residence time is 10 min to generate a polypropylene prepolymer;

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

[0096] 2) the polypropylene prepolymer obtained in step 1) is introduced into a first loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 67 min to generate a 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 into a second loop reactor together with fresh propylene monomer and hydrogen to continue polymerization reaction, the reaction temperature is controlled to be 70° C., the pressure is 3.4 MPa, and the residence time is 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 the 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) flashing the polymer powder obtained in step 3) at 72-78° C. and 1.7-1.9 MPa to remove liquid propylene, adding an antistatic agent, ethoxylated amine, during the flashing process, with the amount of the antistatic agent added being 0.4 kg / h, and then degassing, steaming, and drying in sequence to obtain homopolymer powder particles;

[0101] 5) The homopolymer powder particles obtained in step 4) and the compounding auxiliary agent are fed into a twin-screw extruder for extrusion granulation to obtain a polypropylene resin for a roughening film of an oil-immersed capacitor (the ash content, isotacticity and other properties of the obtained polypropylene resin are shown in Table 1);

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

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

[0104]

[0105] As can be seen from the data in Table 1, the polypropylene resins prepared by Examples 1-2 and Comparative Examples 1-5 of the present invention have better performance in terms of ash content, isotacticity control, etc., and are relatively excellent in processability during film making, and all film indexes meet the requirements. Although all indexes of Comparative Example 5 (whether resin index or film index and processability) are excellent, when the durability test (generally not less than 500-1000h) is made into an oil-immersed capacitor, Comparative Example 1-5 does not pass at all. Compared with Example 1, Example 2 also passed the 1000h durability test, but after the experiment, the breakdown voltage of the capacitor dropped more than that of Example 1 (also reached the national standard).

[0106] The oil-immersed capacitor made of the product prepared in Example 1 of the present invention can be smoothly connected to the grid and has a good operating condition after experimental testing.

Claims

1. A method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor, characterized in that: The preparation method comprises the following steps: 1) mixing the catalyst, the external electron donor and the activator uniformly, and then introducing the mixed catalyst into a prepolymerization reactor together with the propylene monomer to react and generate a polypropylene prepolymer; 2) the polypropylene prepolymer obtained in step 1) is fed into a first loop reactor together with propylene monomer and hydrogen to continue polymerization reaction to generate a polymer; 3) the polymer obtained in step 2) is fed into a second loop reactor together with propylene monomer and hydrogen to continue polymerization reaction to generate polymer powder; 4) flashing the polymer powder obtained in step 3) at 70-85° C. and 1.65-2.15 MPa to remove liquid propylene, adding an antistatic agent during the flashing process, and then degassing, steaming, and drying in sequence to obtain homopolymer powder particles; 5) The homopolymer powder particles obtained in step 4) and the compounding auxiliary agent are fed into a twin-screw extruder for extrusion granulation to obtain a polypropylene resin for a roughening film of an oil-immersed capacitor.

2. The method for preparing the polypropylene resin for roughening film of oil-immersed capacitor according to claim 1, characterized in that: The activity of the catalyst in step 1) is ≥150kgPP / gcat, the catalyst is HA-R catalyst; the external electron donor is cyclohexylmethyldimethoxysilane; and the activator is triethylaluminum.

3. The method for preparing the polypropylene resin for roughening film of oil-immersed capacitor according to claim 1, characterized in that: 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 the external electron donor added is 0.004-0.04 Kg external electron donor / ton of propylene monomer, and the amount of the activator added is 0.02-0.08 Kg activator / ton of propylene monomer.

4. The method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor according to claim 1, characterized in that: During the reaction in step 1), the reaction temperature is controlled to be 15-25° C., the pressure is controlled to be 3.3-4.0 MPa, and the residence time is controlled to be 5-10 min.

5. The method for preparing the polypropylene resin for roughening film of oil-immersed capacitor according to claim 1, characterized in that: In step 2), the flow rate of propylene monomer entering the first loop reactor is 14.0-16.0 t / h; the molar concentration of hydrogen added in the propylene monomer entering the first loop reactor is 1050-1150 ppm.

6. The method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor according to claim 1, characterized in that: During the polymerization reaction in step 2), the reaction temperature is controlled to be 68-74° C., the pressure is controlled to be 3.3-4.0 MPa, and the residence time is controlled to be 50-90 min.

7. The method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor according to claim 1, characterized in that: In step 3), the flow rate of propylene monomer entering the second loop reactor is 7.0-9.0 t / h; the molar concentration of the hydrogen added in the propylene monomer entering the second reactor is 1050-1150 ppm.

8. The method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor according to claim 1, characterized in that: During the polymerization reaction in step 3), the reaction temperature is controlled to be 68-74° C., the pressure is controlled to be 3.3-4.0 MPa, and the residence time is controlled to be 30-60 min.

9. The method for preparing a polypropylene resin for a roughening film of an oil-immersed capacitor according to claim 1, characterized in that: Step 4) The antistatic agent is ethoxylated amine; the amount of the antistatic agent added is 0.4 to 0.8 kg / h.

10. The method for preparing the polypropylene resin for roughening film of oil-immersed capacitor according to claim 1, characterized in that: The mass concentration of the compounding auxiliary agent in the polymer powder particles in step 5) is 1500-3500 ppm, that is, 1.5-3.5 kg of compounding auxiliary agent is added to each ton of homopolymer powder particles; The compounding auxiliary agent is at least two of a tetraphenol antioxidant, a phosphite antioxidant, a triphenol antioxidant and an acid absorbent; The tetraphenol antioxidant is antioxidant 1010, the phosphite antioxidant is antioxidant 168 or antioxidant 626, the triphenol antioxidant is antioxidant 330 or antioxidant CA, and the acid absorbent is calcium stearate, hydrotalcite or zinc oxide.

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