Low-melting high-impact polypropylene special material and production process thereof

Abstract

The invention relates to a low-melting high-impact polypropylene special material and a production process thereof. The problems of poor normal and low temperature impact resistance, low flexural modulus and fast catalyst activity attenuation of polymers in the prior art are mainly solved. The process comprises the following steps: step A, prepolymerization reaction: prepolymerizing a catalyst and propylene to generate a prepolymerization product under prepolymerization reaction conditions; step B, homopolymerization reaction: under the action of a catalyst, the prepolymerization product is subjected to homopolymerization reaction in a multi-zone circulation reactor, and polymer basic powder is obtained under polymerization process conditions; step C, gas phase copolymerization reaction: the polymer basic powder enters a gas phase reactor, and further reacts with propylene and ethylene by utilizing the residual activity of a catalyst to generate impact-resistant copolymer powder; and D, blending, extruding and granulating to obtain a target product. The low-melting high-impact polypropylene special material prepared by the process has excellent normal and low temperature impact resistance, high strength and good processability.

Description

Technical Field

[0001] The invention relates to a polypropylene material, in particular to a special low-melting high-impact polypropylene material and a production process thereof. Background Art

[0002] Low-melting high-impact polypropylene is a blend of ethylene-propylene rubber components and homopolymer matrix. It is produced by connecting two reaction systems in series. The homopolymer matrix is ​​produced in the first reactor, and the base powder is copolymerized with propylene and ethylene in the second reactor using the residual activity of the catalyst to obtain an impact copolymer powder. The spherizone polypropylene process is a new process developed on the basis of BASELL's Spheripol II generation loop tube technology. The spherizone process technology is used to produce polymers with uniform performance in one reactor. The product melt index ranges from 0.1 to 2000 g / 10min, and the rubber content can reach up to 40%. However, in the process of industrial production, this process still has the following problems: poor impact resistance of the polymer at normal low temperatures, low bending modulus, and rapid decay of catalyst activity. Therefore, it is very important to develop a production process for low-melting high-impact polypropylene special materials suitable for large-scale production. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the problems of poor low temperature impact resistance, low bending modulus and rapid catalyst activity decay of existing process polymers in the background technology, and to provide a low-melting high-impact polypropylene special material and a production process thereof. The low-melting high-impact polypropylene special material prepared by the production process has excellent low temperature impact resistance, high strength and good processing performance.

[0004] The present invention solves the problem through the following technical solution: A production process of a low-melting high-impact polypropylene special material comprises the following steps:

[0005] The following steps are involved:

[0006] Step A: Prepolymerization

[0007] Prepolymerizing the catalyst and propylene in a prepolymerization reactor to generate a prepolymer product under prepolymerization reaction conditions;

[0008] Step B: Homopolymerization

[0009] Under the action of the catalyst, the prepolymer product undergoes homopolymerization in a multi-zone circulation reactor, and under polymerization process conditions, a polymer base powder is obtained;

[0010] Step C: Gas Phase Copolymerization

[0011] The polymer base powder enters the gas phase reactor and further reacts with propylene and ethylene using the residual activity of the catalyst to generate impact copolymer powder;

[0012] Step D: Blending, extrusion and granulation

[0013] The generated impact copolymer powder and the compound antioxidant are blended, melted and granulated in an extrusion granulator to obtain the target product;

[0014] The catalyst in step A and step B is composed of a main catalyst, a co-catalyst and an external electron donor; the main catalyst is ZN118; the co-catalyst is triethylaluminum; and the external electron donor is DonorC.

[0015] Preferably, the ratio of the co-catalyst to the main catalyst is 2-6:1; the ratio of the co-catalyst to the external electron donor is 3-9:1.

[0016] Preferably, the catalyst for the prepolymerization reaction needs to be mixed with oil and fat under nitrogen protection conditions, and then enter the prepolymerization reactor after pre-contact at 15°C, and undergo prepolymerization reaction with propylene entering through an online mixer; the oil component is a mixture of white oil and vaseline in a volume ratio of 2:1.

[0017] Preferably, the prepolymerization reaction process conditions are: the prepolymerization is carried out in a bulk propylene liquid phase environment, at a temperature of 20° C. to 25° C. and a pressure of 2.8 MPa to 3.4 MPa in a small loop tube, and the residence time is 10 to 20 minutes.

[0018] Preferably, the polymerization process conditions of the homopolymerization reaction in step B are: temperature 69°C to 73°C, pressure 2.7MPa to 3.0MPa, residence time 65-70 minutes; the ratio of the co-catalyst to the main catalyst is 2-6:1, and the ratio of the co-catalyst to the external electron donor is 3-9:1; the amount of Atmer163 added to the main reactor discharge is 1-3kg / h; hydrogen is added to the multi-zone circulation reactor to adjust the molecular weight to ensure that the melt index of the homopolymerized polypropylene powder generated in the reactor is 4.0 to 6.0g / 10min;

[0019] The multi-zone circulating reactor is a spherizone process.

[0020] Preferably, in step C, the pressure of the gas phase reactor is 0.9-1.2 MPa, the mass ratio of the comonomer ethylene content is 8-9.5%, the ethylene / ethylene+propylene ratio is 0.33-0.39%, the hydrogen / ethylene*1000 is 2-6, the circulating gas inlet temperature of the gas phase reactor is 52-55°C, and the amount of Atmer163 added is 1.6-2.3 kg / h.

[0021] Preferably, the compounded antioxidant in step D is compounded with IRGANOX1010 additive, IRGAFOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:1;

[0022] Preferably, the α-nucleating agent is an organic phosphate compound.

[0023] Preferably, the target product pellets generated in step D have a melt index of 2.0 to 4.0 g / 10 min; and the amount of the compounded antioxidant added to the impact-resistant copolymer powder is 1500 ppm to 2000 ppm.

[0024] The present invention also provides a special material for low-melting and high-impact polypropylene, which is prepared by the above method.

[0025] The target product granules produced by the invention are used for preparing battery shells, turnover boxes, baby carriage toys and the like.

[0026] The present invention determines the microstructure of low-melting high-impact copolymer special materials, clarifies the relationship between product structure and performance, develops a low-melting high-impact special material auxiliary formulation system, conducts industrial trial production and optimization of process parameters, and completes the batch production of low-melting high-impact copolymer special materials.

[0027] This product is produced by the Spherizone process. The polymerization reactor of this process is a multi-zone circulation reactor using a riser, and multi-zone circulation polymerization can be achieved in the polymerization reactor. In the reactor, the catalyst reacts with propylene (ethylene) in the gas phase, and the reaction materials are circulated in two reaction zones for many times, which has the effect of multiple gas phase and loop reactors in other processes, so that the high-rigidity and toughness products produced have good uniformity. The special material for low-melting and high-impact polypropylene of the present invention designs the molecular structure of the basic resin; the catalyst system with good hydrogen adjustment sensitivity and moderate late activity is preferably selected to improve the matching of the main catalyst and the external electron donor; the polymerization process is set by investigating the influence of key parameters such as polymerization temperature, pressure, ethylene content, ethylene / ethylene+propylene, hydrogen / ethylene, aluminum / silicon on product performance; the composite auxiliary agent formula determined by the type of auxiliary agent and the amount of addition of the present invention improves the bending and impact properties of the product.

[0028] Compared with the above background technology, the present invention has the following beneficial effects:

[0029] The product prepared by the production process of the special material for low-melting high-impact polypropylene of the present invention adopts the Spherizone process. The polymerization reactor of this process is a multi-zone circulation reactor using a riser, and multi-zone circulation polymerization can be realized in the polymerization reactor. In the reactor, the catalyst reacts with propylene (ethylene) in gas phase, and the reaction materials are circulated in two reaction areas for many times, which has the functions of multiple gas phase and loop reactors in other processes, so that the high-rigidity and toughness products produced have good uniformity. The present invention preferably uses a catalyst system with good hydrogen adjustment sensitivity and moderate late activity, improves the matching of the main catalyst and the external electron donor; improves the polymerization process through the influence of key parameters such as polymerization temperature, pressure, ethylene content, ethylene / ethylene+propylene, hydrogen / ethylene, aluminum / silicon on product performance; the composite auxiliary agent formula determined by the type of auxiliary agent and the amount of addition used in the present invention improves the bending and impact properties of the product.

[0030] After the catalyst and various monomers enter the reactor, they circulate between the two reaction zones. The multi-zone circulation reactor allows polymer particles to circulate continuously in the two reaction zones of a reactor, and each cycle period is much shorter than the average residence time of the polymer particles in the reactor. The present invention compares and determines the process parameters such as the type and activity of the catalyst, the amount of Atmer163 added, the amount of comonomer ethylene added, (ethylene / ethylene+propylene), (hydrogen / ethylene) ratio, and the temperature, pressure, material level, etc. of the reactor, so that the low-melting and high-impact copolymer special material product produced has excellent normal low temperature impact resistance, high strength, and good processing performance.

[0031] 1. The present invention adopts ZN118 series catalysts with higher activity and longer durability. After use, the product has a room temperature impact strength of up to 59kJ / m 2 .

[0032] 2. Break the inherent production ideas, significantly adjust the process parameters to match the high-efficiency catalytic system, ensure the lasting release of catalyst activity in the gas phase reactor, and increase the yield by 50%.

[0033] 3. Significantly reduce the discharge of the main reactor and the amount of Atmer163 added to the gas phase reactor to ensure that the catalyst activity is shifted as far back as possible.

[0034] 4. It breaks the concept that the higher the ethylene content, the greater the impact strength of the product. It accurately controls the ethylene content of the product, effectively inhibits the generation of EEE and PEE invalid segments, and also reduces the amount of hydrogen introduced into the gas phase reactor, thereby increasing the rubber phase content of the product and its compatibility and continuity with the polypropylene matrix. The room temperature impact strength of the product is stabilized at 50kJ / m 2 above.

[0035] 5. The product additive system determined by the present invention increases the flexural modulus of the product from 817MPa to 1212MPa, achieving a good balance of rigidity and toughness. Specific implementation method:

[0036] The present invention will be further described below in conjunction with specific embodiments:

[0037] The production process of the low-melting high-impact polypropylene special material of the present invention comprises the following steps:

[0038] Step A: Prepolymerization

[0039] The prepolymerization is carried out in a propylene liquid phase bulk environment, the catalyst and propylene are prepolymerized in a prepolymerization reactor, the prepolymerization is carried out in a small loop at a temperature of 20°C to 25°C and a pressure of 2.8Mpa to 3.4Mpa, the residence time is 10 to 20 minutes, and a prepolymerization product is generated under the prepolymerization reaction conditions;

[0040] The catalyst is composed of a main catalyst, a co-catalyst and an external electron donor; the main catalyst is ZN118, the co-catalyst is triethylaluminum; the external electron donor is DonorC; the ratio of the co-catalyst to the main catalyst is 2-6:1; the ratio of the co-catalyst to the external electron donor is 3-9:1.

[0041] The catalyst for the prepolymerization reaction needs to be mixed with oil and fat under nitrogen protection conditions, and then enter the prepolymerization reactor after pre-contact at 15°C to undergo prepolymerization reaction with propylene entering through an online mixer; the oil component is a mixture of white oil and vaseline in a volume ratio of 2:1.

[0042] Step B: Homopolymerization

[0043] Under the action of the catalyst, the prepolymer product undergoes homopolymerization in a multi-zone circulation reactor (spherizone process) to obtain a polymer base powder under polymerization process conditions; the catalyst for the homopolymerization reaction is the same as that for the prepolymerization reaction.

[0044] The polymerization process conditions of the homopolymerization reaction are: temperature 69°C to 73°C, pressure 2.7MPa to 3.0MPa, residence time 65 to 70 minutes; the ratio of co-catalyst to main catalyst is 2 to 6:1, and the ratio of co-catalyst to external electron donor is 3 to 9:1; the amount of Atmer163 added to the main reactor discharge is 1-3kg / h; hydrogen is added to the multi-zone circulation reactor to adjust the molecular weight to ensure that the melt index of the homopolymerized polypropylene powder generated in the reactor is 4.0 to 6.0g / 10min.

[0045] Step C: Gas Phase Copolymerization

[0046] The base powder enters the gas phase reactor and further reacts with propylene and ethylene using the residual activity of the catalyst to generate impact copolymer powder;

[0047] The gas phase reactor has a pressure of 0.9-1.2 MPa, a comonomer ethylene content of 8-9.5% (mass ratio), an ethylene / ethylene+propylene ratio of 0.33-0.39%, a hydrogen / ethylene*1000 ratio of 2-6, a gas phase reactor circulating gas inlet temperature of 52-55°C, and an Atmer163 addition amount of 1.6-2.3 kg / h.

[0048] Step D: Blending, extrusion and granulation

[0049] The obtained impact-resistant copolymer powder is mixed with the compound antioxidant, and melt-extruded and granulated to obtain the target product. The target product granules have a melt index of 2.0 to 4.0 g / 10 min.

[0050] The compound antioxidant is compounded by IRGANOX1010 additive, IRGAFOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:1.

[0051] The target product pellets produced by the invention have a melting index of 2.0-4.0 g / 10 min and are used for preparing battery shells, turnover boxes, baby carriage toys and the like.

[0052] The following takes the production process of the low-melting high-impact polypropylene special material of the present invention developed and applied in Daqing Refining and Chemical Company as an example to specifically illustrate its preparation method.

[0053] Example 1

[0054] A production process for a low-melting high-impact polypropylene special material comprises the following steps:

[0055] S1. Prepare low-melting high-impact polypropylene qualified powder by the production process of the special low-melting high-impact polypropylene material of the present invention:

[0056] Step A: Prepolymerization

[0057] The prepolymerization is carried out in a propylene liquid phase bulk environment, the catalyst and propylene are prepolymerized in a prepolymerization reactor, the prepolymerization is carried out in a small loop at a temperature of 20° C. to 22° C. and a pressure of 2.8 Mpa to 3.2 Mpa, the residence time is 15 minutes, and a prepolymerization product is generated under the prepolymerization reaction conditions;

[0058] The catalyst is composed of a main catalyst, a co-catalyst and an external electron donor; the main catalyst is ZN118, the co-catalyst is triethylaluminum; the external electron donor is DonorC; the ratio of the co-catalyst to the main catalyst is 4:1; the ratio of the co-catalyst to the external electron donor is 7:1.

[0059] The catalyst for the prepolymerization reaction needs to be mixed with oil and fat under nitrogen protection conditions, and then enter the prepolymerization reactor after pre-contact at 15°C to undergo prepolymerization reaction with propylene entering through an online mixer; the oil component is a mixture of white oil and vaseline in a volume ratio of 2:1.

[0060] Step B: Homopolymerization

[0061] Under the action of the catalyst, the prepolymer product undergoes homopolymerization in a multi-zone circulation reactor (spherizone process) to obtain a polymer base powder under polymerization process conditions; the catalyst for the homopolymerization reaction is the same as that for the prepolymerization reaction.

[0062] The polymerization process conditions of the homopolymerization reaction are: temperature 69°C ~ 72°C, pressure 2.7MPa ~ 3.0MPa, residence time 70 minutes; the ratio of co-catalyst to main catalyst is 4:1, and the ratio of co-catalyst to external electron donor is 7:1; the addition amount of Atmer163 to the discharge of the main reactor is 2kg / h; hydrogen is added to the multi-zone circulation reactor to adjust the molecular weight to ensure that the melt index of the homopolymerized polypropylene powder generated in the reactor is 6.0g / 10min.

[0063] Step C: Gas Phase Copolymerization

[0064] The polymer base powder obtained by the homopolymerization reaction enters the gas phase reactor, and further reacts with propylene and ethylene using the residual activity of the catalyst to generate an impact copolymer; thus obtaining a low-melting impact polypropylene qualified product powder.

[0065] The gas phase reactor pressure is 1.2 MPa, the comonomer ethylene content is 8.6% (mass ratio), the ethylene / ethylene+propylene ratio is 0.35%, the hydrogen / ethylene*1000 is 6, the gas phase reactor circulating gas inlet temperature is 56°C, and the Atmer163 addition amount is 2.1 kg / h.

[0066] S2. Determine the additive formula system of low-melting impact-resistant polypropylene through formula extrusion experiments and data testing.

[0067] Test materials: qualified low-melting impact polypropylene powder, compound antioxidant.

[0068] The compound antioxidant is compounded by IRGANOX1010 additive, IRGAFOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:1; the α nucleating agent is nucleating agent JHC671, and the manufacturer is Beijing Jihaichuan Technology Development Co., Ltd.

[0069] Sample A0, compounding agent addition amount 1500ppm;

[0070] Sample A1, compounding agent 1800ppm;

[0071] Sample A2, compounding agent 2000ppm.

[0072] In the pilot laboratory, impact-resistant polypropylene powder and compound antioxidant were mixed in a high-speed mixer according to the prescribed formula, and the sample was extruded and granulated through a twin-screw extruder to select a suitable compound antioxidant system. The extruder parameters were as follows: temperatures of each section from the feed port to the die: 180°C, 210°C, 210°C, 210°C, 210°C, 210°C, 200°C, main engine speed 230rpm, melt pressure 1.2Mpa, and melt temperature 215°C.

[0073] The resin was injected into the test strips, and the test strips were injected into the test strips using a twin-screw injection molding machine. The injection temperatures were set at 200°C, 230°C, 230°C, 230°C, and 210°C. The mechanical properties and microstructure characterization of the test strips were performed in accordance with national standards. The test data are shown in Table 1 below:

[0074] Table 1

[0075]

[0076] It can be seen from the above formula test data that the flexural modulus and tensile strength values ​​of the A2 formula system material are better than those of the A0 and A1 formula systems, and the normal and low temperature impact strength values ​​are equivalent, so A2 is preferably selected as the auxiliary agent system of the present invention.

[0077] Example 2

[0078] In the spherizone process polypropylene unit of Daqing Refining and Chemical Company, liquid propylene with a purity of 99.8% is used as the main raw material, and the ZN118 catalyst with higher activity and longer lasting performance is adopted, with a specific surface area of ​​160.8928m 2 / g, activity is 7000g PP / g.cat, the ethylene content of the comonomer is strictly controlled to be 8.6% (mass ratio), and the ethylene / ethylene+propylene ratio is 0.35%, which ensures the propylene concentration in the gas phase reactor. The impact-resistant copolymer powder prepared by the formula and process of Example 1 is used as the base resin and is mixed, melted, and extruded and granulated with a compounded antioxidant (the compounding ratio of the two is the same as the ratio of the A2 formula system in Example 1) in an extrusion granulator to produce low-melting impact-resistant polypropylene particles with a narrow molecular weight distribution and a melt index of 2.0 to 3.0 g / 10min. It can be seen from the factory acceptance list in the table below that the finished pellets achieve a good balance of rigidity and toughness and excellent performance. The test data of the finished pellets are shown in Table 2 below:

[0079] Table 2

[0080]

[0081] Example 3

[0082] In order to further improve the basic physical properties of the finished pellets in Example 2, the process parameters were adjusted as follows:

[0083] 1) Increase the T / D (ratio of co-catalyst to external electron donor) aluminum-silicon ratio to 9, reduce rigidity and increase toughness.

[0084] 2) Reduce the amount of Atmer163 added to 1.9 kg / h to ensure the residual activity of the catalyst in the gas phase reactor and provide kinetic energy for the generation of the rubber phase.

[0085] 3) The hydrogen / ethylene ratio is greatly reduced (from 6 to 2), ensuring the formation and stability of the rubber phase.

[0086] 4) Significantly reduce the inlet temperature of the circulating gas of the gas phase reactor (from 56 to 54°C), remove heat in time to prevent materials from sticking and agglomerating, and ensure smooth reaction.

[0087] 5) Through the above process adjustment, the product particles have good appearance and no transparent particles, and excellent comprehensive mechanical properties. The test data is shown in Table 3 below:

[0088] Table 3

[0089]

[0090]

[0091] It can be seen from Table 3 that by further optimizing the production process parameters, the product's room and low temperature impact strength, flexural modulus and tensile strength are further improved.

[0092] The product of the present invention has undergone multiple industrial productions, and by increasing the aluminum-silicon ratio (to 9), reducing the amount of Atmer163 added to the gas phase reactor (to 1.9 kg / h), significantly reducing the hydrogen / ethylene value (to 2) and the inlet temperature of the gas phase reactor circulating gas (to 54°C), determining the ethylene / ethylene+propylene ratio (to 0.35%), and comprehensively regulating the above key process parameters, the basic physical property values ​​of the product's normal and low temperature impact strength, bending modulus, and tensile yield strength are gradually improved. The product is widely used in the fields of auto parts, turnover boxes, baby carriage toys, plates, and power pipes.

[0093] The raw materials and components used in the above examples are commercially available unless otherwise specified.

[0094] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Therefore, the content of the present invention is not limited to the examples listed, and any equivalent changes taken by ordinary technicians in the field of the present invention by reading the specification of the present invention to the technical solution of the present invention are all covered by the claims of the present invention.

Claims

1. A production process for low-melting high-impact polypropylene special material, characterized in that: The following steps are involved: Step A: Prepolymerization Prepolymerizing the catalyst and propylene in a prepolymerization reactor to generate a prepolymer product under prepolymerization reaction conditions; Step B: Homopolymerization Under the action of the catalyst, the prepolymer product undergoes homopolymerization in a multi-zone circulation reactor, and under polymerization process conditions, a polymer base powder is obtained; Step C: Gas Phase Copolymerization The polymer base powder enters the gas phase reactor and further reacts with propylene and ethylene using the residual activity of the catalyst to generate impact copolymer powder; Step D: Blending, extrusion and granulation The generated impact copolymer powder and the compound antioxidant are blended, melted and granulated in an extrusion granulator to obtain the target product; The catalyst in step A and step B is composed of a main catalyst, a co-catalyst and an external electron donor; the main catalyst is ZN118; the co-catalyst is triethylaluminum; and the external electron donor is DonorC.

2. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: The ratio of the co-catalyst to the main catalyst is 2-6:1; the ratio of the co-catalyst to the electron donor is 3-9:

1.

3. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: The prepolymerization reaction process conditions are as follows: the prepolymerization is carried out in a bulk propylene liquid phase environment, at a temperature of 20° C. to 25° C. and a pressure of 2.8 MPa to 3.4 MPa in a small loop tube, with a residence time of 10 to 20 minutes.

4. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: The polymerization process conditions of the homopolymerization reaction in step B are: temperature 69° C. to 73° C., pressure 2.7 MPa to 3.0 MPa, residence time 65-70 minutes; the ratio of the co-catalyst to the main catalyst is 2-6:1, and the ratio of the co-catalyst to the external electron donor is 3-9:1; the amount of Atmer163 added to the discharge of the main reactor is 1-3 kg / h; hydrogen is added to the multi-zone circulation reactor to adjust the molecular weight to ensure that the melt index of the homopolymerized polypropylene powder generated in the reactor is 4.0 to 6.0 g / 10 min.

5. The production process of low-melting high-impact polypropylene special material according to claim 4, characterized in that: The multi-zone circulating reactor is a spherizone process.

6. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: In the step C, the pressure of the gas phase reactor is 0.9-1.2 MPa, the mass ratio of the ethylene content of the comonomer is 8-9.5%, the ethylene / ethylene+propylene ratio is 0.33-0.39%, the hydrogen / ethylene*1000 is 2-6, the circulating gas inlet temperature of the gas phase reactor is 52-55°C, and the addition amount of Atmer163 is 1.6-2.3 kg / h.

7. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: The compounded antioxidant in step D is compounded by IRGANOX1010 additive, IRGAFOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:

1.

8. The production process of low-melting high-impact polypropylene special material according to claim 7, characterized in that: The α nucleating agent is an organic phosphate nucleating agent.

9. The production process of low-melting high-impact polypropylene special material according to claim 1, characterized in that: The target product pellets generated in step D have a melt index of 2.0 to 4.0 g / 10 min; the amount of the compounded antioxidant added to the impact-resistant copolymer powder is 1500 ppm to 2000 ppm.

10. A low-melting high-impact polypropylene special material, characterized in that: The low-melting high-impact polypropylene special material is prepared by the method described in any one of the above claims.

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