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

Abstract

The present application relates to a kind of low-melt high-impact polypropylene special material and its production process.It mainly solves the problems of poor low-temperature impact resistance, low flexural modulus and fast catalyst activity decay of existing process polymers.The process includes: step A: prepolymerization reaction: catalyst and propylene are pre-polymerized to generate pre-polymerization product under prepolymerization reaction conditions;Step B: homopolymerization: under the action of catalyst, the pre-polymerization product is subjected to homopolymerization in a multi-zone circulating reactor, and under the 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 an impact copolymer powder;Step D: blending, extruding and granulating: the target product is obtained.The low-melt high-impact polypropylene special material prepared by the process has excellent low-temperature impact resistance, high strength and good processing performance.

Description

Technical Field

[0001] This invention relates to a polypropylene material, specifically to a low-melting-point, high-impact polypropylene special material and its production process. Background Technology

[0002] Low-melt-point, high-impact polypropylene is a blend of ethylene-propylene rubber components and a homopolymer matrix, produced using two reaction systems in series. The homopolymer matrix is ​​produced in the first reactor, while the base powder is copolymerized with propylene and ethylene in the second reactor using residual catalyst activity to obtain the impact copolymer powder. The Spherizone polypropylene process is a new process developed based on Basell's Spheripol II loop reactor technology. Using Spherizone technology, it achieves the production of polymers with uniform properties in a single reactor, with a melt index ranging from 0.1 to 2000 g / 10 min and a rubber content of up to 40%. However, in industrial production, this process still suffers from problems such as poor low-temperature impact resistance, low flexural modulus, and rapid catalyst activity decay. Therefore, developing a production process for low-melt-point, high-impact polypropylene materials suitable for large-scale production is crucial. Summary of the Invention

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

[0004] The present invention solves its problem through the following technical solution: a production process for a low-melting-point, high-impact polypropylene special material, comprising the following steps:

[0005] Includes the following steps:

[0006] Step A: Prepolymerization reaction

[0007] The catalyst and propylene are prepolymerized in a prepolymerization reactor to generate a prepolymerized product under prepolymerization reaction conditions.

[0008] Step B: Homopolymerization

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

[0010] Step C: Gas-phase copolymerization reaction

[0011] The polymer base powder enters the gas phase reactor, where it reacts further 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 is blended, melted, and granulated with a compound antioxidant in an extrusion granulator to obtain the target product.

[0014] In steps A and B, 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; and the external electron donor is Donor C.

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

[0016] Preferably, the catalyst for the prepolymerization reaction needs to be prepared under nitrogen protection, mixed with oil and pre-contacted at 15°C before entering the prepolymerization reactor, and then prepolymerized with propylene that has entered through an online mixer; the oil is a mixture of white oil and petrolatum in a volume ratio of 2:1.

[0017] Preferably, the prepolymerization reaction process conditions are as follows: prepolymerization is carried out in a propylene liquid phase bulk environment, in a small loop at a temperature of 20℃~25℃ and a pressure of 2.8Mpa~3.4Mpa, with a residence time of 10~20 minutes.

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

[0019] The multi-zone circulating reactor uses the spherizone process.

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

[0021] Preferably, the compound antioxidant in step D is composed of IRGANOX1010 additive, IRGANOS168 additive, calcium stearate and α nucleating agent, in a mass ratio of 10:20:20:1.

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

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

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

[0025] The target product granules generated by this invention are used to manufacture battery casings, turnover boxes, children's vehicles and toys, etc.

[0026] This invention determines the microstructure of low-melting-point, high-impact copolymer special materials and clarifies the relationship between product structure and performance. It develops an additive formulation system for these materials, conducts industrial-scale pilot production and optimizes process parameters, ultimately achieving mass production of the low-melting-point, high-impact copolymer special materials.

[0027] This product is produced using the Spherizone process, a multi-zone circulating reactor employing risers, enabling multi-zone circulating polymerization within the reactor. Inside the reactor, the catalyst undergoes a gas-phase reaction with propylene (ethylene), and the reactants circulate multiple times between two reaction zones, effectively combining the functions of multiple gas-phase and loop reactors found in other processes. This results in a high-strength, high-impact polypropylene product with excellent uniformity. This invention utilizes a low-melting-point, high-impact polypropylene special material, designed with a specific basic resin molecular structure. It optimizes the catalyst system, selecting those with good hydrogen sensitivity and moderate late-stage activity to improve the matching between the main catalyst and the external electron donor. The polymerization process is designed by investigating the effects of key parameters such as polymerization temperature, pressure, ethylene content, ethylene / ethylene+propylene ratio, hydrogen / ethylene ratio, and aluminum / silicon ratio on product performance. Furthermore, the composite additive formulation determined by the types and amounts of additives used in this invention improves the product's bending and impact resistance.

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

[0029] The product prepared by the low-melting-point, high-impact polypropylene special material production process of this invention adopts the Spherizone process. This process utilizes a multi-zone circulating reactor with risers, enabling multi-zone circulating polymerization within the reactor. Inside the reactor, the catalyst undergoes a gas-phase reaction with propylene (ethylene), and the reactants circulate multiple times between two reaction zones, effectively functioning as multiple gas-phase and loop reactors in other processes. This results in a high-strength, high-toughness product with excellent uniformity. This invention preferentially uses a catalyst system with good hydrogen sensitivity and moderate late-stage activity, improving the matching between the main catalyst and the external electron donor. The polymerization process is improved by studying the influence of key parameters such as polymerization temperature, pressure, ethylene content, ethylene / ethylene+propylene ratio, hydrogen / ethylene ratio, and aluminum / silicon ratio on product performance. The composite additive formulation used in this invention, determined by the types and amounts of additives, improves the product's bending and impact properties.

[0030] After the catalyst and various monomers enter the reactor, they circulate between two reaction zones. The multi-zone circulating reactor allows polymer particles to continuously circulate between the two reaction zones of a single reactor, with each cycle being much shorter than the average residence time of the polymer particles within the reactor. This invention, through comparative analysis of process parameters such as catalyst type and activity, the amount of Atmer163 added, the amount of ethylene comonomer added, the (ethylene / ethylene+propylene) and (hydrogen / ethylene) ratios, and reactor temperature, pressure, and material level, determines the production of a low-melting-point, high-impact copolymer product with excellent low-temperature impact resistance, high strength, and good processability.

[0031] 1. This invention uses the ZN118 series catalyst, which has higher activity and longer durability. After use, the product's room temperature impact strength reaches a maximum of 59 kJ / m. 2 .

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

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

[0034] 4. Breaking the notion that higher ethylene content equates to greater impact strength, this product precisely controls ethylene content, effectively suppressing the generation of ineffective EEE and PEE segments. It also reduces hydrogen carryover from the gas-phase reactor, improving the rubber phase content and compatibility and continuity with the polypropylene matrix. The product's room-temperature impact strength remains stable at 50 kJ / m². 2 above.

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

[0036] The present invention will be further described below with reference to specific embodiments:

[0037] The production process of the low-melting-point, high-impact polypropylene special material of this invention includes the following steps:

[0038] Step A: Prepolymerization reaction

[0039] Prepolymerization is carried out in a propylene liquid phase bulk environment. The catalyst and propylene are prepolymerized in a prepolymerization reactor at a temperature of 20℃~25℃ and a pressure of 2.8Mpa~3.4Mpa in a small loop tube for a residence time of 10~20 minutes. Prepolymerized products are 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, and the external electron donor is DonorC; 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.

[0041] The catalyst for the prepolymerization reaction needs to be prepared under nitrogen protection, mixed with oil and pre-contacted at 15°C before entering the prepolymerization reactor, where it undergoes a prepolymerization reaction with propylene that has entered through an online mixer; the oil is a mixture of white oil and petrolatum at a volume ratio of 2:1.

[0042] Step B: Homopolymerization

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

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

[0045] Step C: Gas-phase copolymerization reaction

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

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

[0048] Step D: Blending, extrusion, and granulation

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

[0050] The compound antioxidant is composed of IRGANOX1010 additive, IRGANOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:1.

[0051] The target product granules generated by this invention have a melt index of 2.0 to 4.0 g / 10 min and are used to prepare battery casings, turnover boxes, children's vehicles and toys, etc.

[0052] The following example, using the production process of the low-melting-point, high-impact polypropylene special material of this invention developed and applied at Daqing Petrochemical Company, illustrates its preparation method in detail.

[0053] Example 1

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

[0055] S1. Using the production process of the low-melting-point high-impact polypropylene special material of the present invention, qualified low-melting-point impact-resistant polypropylene powder is prepared:

[0056] Step A: Prepolymerization reaction

[0057] Prepolymerization is carried out in a propylene liquid phase bulk environment. The catalyst and propylene are prepolymerized in a prepolymerization reactor at a temperature of 20℃~22℃ and a pressure of 2.8Mpa~3.2Mpa in a small loop tube for a residence time of 15 minutes. Prepolymerized products are 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, and the external electron donor is DonorC; the ratio of the co-catalyst to the main catalyst is 4:1; and the ratio of the co-catalyst to the external electron donor is 7:1.

[0059] The catalyst for the prepolymerization reaction needs to be prepared under nitrogen protection, mixed with oil and pre-contacted at 15°C before entering the prepolymerization reactor, where it undergoes a prepolymerization reaction with propylene that has entered through an online mixer; the oil is a mixture of white oil and petrolatum at a volume ratio of 2:1.

[0060] Step B: Homopolymerization

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

[0062] The polymerization process conditions for homopolymerization are as follows: temperature 69℃~72℃, 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 amount of Atmer163 added to the main reactor is 2kg / h; hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt index of the homopolymer polypropylene powder generated in the reactor is 6.0g / 10min.

[0063] Step C: Gas-phase copolymerization reaction

[0064] The polymer base powder obtained from the homopolymerization reaction is fed into a gas-phase reactor, where it is further reacted with propylene and ethylene using the residual activity of the catalyst to generate an impact copolymer; thus, qualified low-melting-point impact-resistant polypropylene powder is obtained.

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

[0066] S2. The additive formulation system for low-melt impact-resistant polypropylene was determined through extrusion experiments and data testing.

[0067] Test materials: qualified low-melting-point impact-resistant polypropylene powder and compounded antioxidants.

[0068] The compound antioxidant is composed of IRGANOX1010 additive, IRGANOS168 additive, calcium stearate and α nucleating agent in a mass ratio of 10:20:20:1; the α nucleating agent is nucleating agent JHC671, manufactured by Beijing Jihaichuan Technology Development Co., Ltd.

[0069] Sample A0, with a compounding agent dosage of 1500 ppm;

[0070] Sample A1, compounding agent 1800 ppm;

[0071] Sample A2, compounding agent 2000ppm.

[0072] In the pilot laboratory, impact-resistant polypropylene powder and compound antioxidants were mixed in a high-speed mixer according to the specified formula. The samples were then extruded and granulated using a twin-screw extruder to select a suitable compound antioxidant system. The extruder parameters, from the feed port to the die head, were as follows: temperature at each section: 180℃, 210℃, 210℃, 210℃, 210℃, 200℃; main extruder speed: 230 rpm; melt pressure: 1.2 MPa; melt temperature: 215℃.

[0073] Resin was used to create injection-molded test specimens. The specimens were injection molded using a twin-screw injection molding machine at the following temperatures: 200℃, 230℃, 230℃, 230℃, and 210℃. Mechanical properties and microstructure characterization of the test specimens were performed according to national standards. The test data are shown in Table 1 below.

[0074] Table 1

[0075]

[0076] The above formula test data shows that the flexural modulus and tensile strength of the A2 formula system are better than those of the A0 and A1 formula systems, and the impact strength at room temperature and low temperature is comparable. Therefore, the A2 additive system is the preferred choice for this invention.

[0077] Example 2

[0078] The Spherizone process polypropylene unit at Daqing Petrochemical Company uses 99.8% pure liquid propylene as the main feedstock and employs the more active and durable ZN118 catalyst with a specific surface area of ​​160.8928 m². 2 / g, with an activity of 7000g PP / g.cat, the ethylene content of the comonomer was strictly controlled at 8.6% (mass ratio), and the ethylene / ethylene+propylene ratio was 0.35%, ensuring the propylene concentration in the gas phase reactor. The impact-resistant copolymer powder prepared using the formulation and process of Example 1 was used as the base resin. This resin was mixed with a compound antioxidant (the compounding ratio was the same as the A2 formulation system in Example 1), melted, and extruded into granules in an extrusion granulator to produce low-melting-point impact-resistant polypropylene granules with a narrow molecular weight distribution and a melt index of 2.0–3.0 g / 10 min. The finished granules, as shown in the factory certificate below, achieve a good balance between rigidity and toughness, exhibiting excellent performance. The finished granule test data are shown in Table 2 below:

[0079] Table 2

[0080]

[0081] Example 3

[0082] To further improve the basic physical properties of the finished pellets from Example 2, the process parameters were adjusted as follows:

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

[0084] 2) Reduce the Atmer163 addition amount 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 was significantly 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 in the gas phase reactor (from 56°C to 54°C), remove heat in time to prevent material from sticking and clumping, and ensure the smooth progress of the reaction.

[0087] 5) Through the above process adjustments, the product particles have a good appearance with no transparent particles, and excellent overall mechanical properties. Test data is shown in Table 3 below:

[0088] Table 3

[0089]

[0090]

[0091] As can be seen from Table 3, by further optimizing the production process parameters, the product's low-temperature impact strength, flexural modulus, and tensile strength have been further improved.

[0092] The product described in this invention has undergone multiple industrial production processes. By increasing the aluminum-silicon ratio (to 9), reducing the Atmer163 addition to the gas-phase reactor (to 1.9 kg / h), significantly reducing the hydrogen / ethylene ratio (to 2), and lowering the inlet temperature of the circulating gas in the gas-phase reactor (to 54°C), the ethylene / ethylene+propylene ratio was determined (set to 0.35%). Through comprehensive control of the above key process parameters, the basic physical properties of the product, including impact strength at room temperature and low temperature, flexural modulus, and tensile yield strength, have been gradually improved. The product is widely used in automotive parts, turnover boxes, children's vehicles and toys, sheet metal, and power pipes.

[0093] Unless otherwise stated, all raw materials and components used in the above embodiments are commercially available.

[0094] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Therefore, the content of the present invention is not limited to the embodiments listed, and any equivalent modifications made to the technical solutions of the present invention by those skilled in the art through reading the present invention specification are covered by the claims of the present invention.

Claims

1. A production process for a low-melting-point, high-impact polypropylene special material, characterized in that, Includes the following steps: Step A: Prepolymerization reaction The catalyst and propylene are prepolymerized in a prepolymerization reactor to generate a prepolymerized product under prepolymerization reaction conditions. Step B: Homopolymerization Under the action of a catalyst, the prepolymer product undergoes homopolymerization in a multi-zone circulating reactor, and under the polymerization process conditions, a polymer base powder is obtained. Step C: Gas-phase copolymerization reaction The polymer base powder enters the gas phase reactor, where it reacts further 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 is blended, melted, and granulated with a compound antioxidant in an extrusion granulator to obtain the target product. The catalyst in steps A and 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. The polymerization conditions for the homopolymerization reaction in step B are as follows: temperature 69℃~73℃, pressure 2.7MPa~3.0MPa, residence time 65-70 minutes; the ratio of co-catalyst to main catalyst is 2~6:1, and the ratio of co-catalyst to external electron donor is 3~9:1; the amount of Atmer163 added to the main reactor is 1-3kg / h; hydrogen is added to the multi-zone circulating reactor to adjust the molecular weight, ensuring that the melt index of the homopolymer polypropylene powder generated in the reactor is 4.0~6.0g / 10min. In step C, the pressure of the gas phase reactor is 0.9–1.2 MPa, the mass content of the comonomer ethylene is 8–9.5%, the ethylene / (ethylene + propylene) ratio is 0.33–0.39%, the (hydrogen / ethylene)*1000 is 2–6, the inlet temperature of the circulating gas in the gas phase reactor is 52–55°C, and the Atmer163 addition rate is 1.6–2.3 kg / h. The antioxidant compounded in step D is composed of IRGANOX1010 additive, IRGANOS168 additive, calcium stearate and α nucleating agent, in a mass ratio of 10:20:20:

1.

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

3. The production process of low-melting-point high-impact polypropylene special material according to claim 1, characterized in that, The multi-zone circulating reactor is a spherizone process unit.

4. The production process of low-melting-point high-impact polypropylene special material according to claim 1, characterized in that, The α-nucleating agent is an organophosphate nucleating agent.

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

6. A special low-melting-point, high-impact polypropylene material, characterized in that, The low-melting-point, high-impact polypropylene special material is prepared using the production process described in any one of claims 1-5.

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