A high melt index impact copolymer polypropylene material, its preparation method and application

Abstract

The application discloses a kind of high melt index impact copolymer polypropylene material and its preparation method and application, belong to polyolefin production technical field.The first reactor can also be prepared with higher melt index polypropylene at lower hydrogen concentration by selecting compound external electron donor system, and the second reactor is prepared with higher ethylene and rubber content polypropylene material at lower ethylene concentration by selecting BCM series main catalyst and compound external electron donor to occur synergistic effect;The application also provides high melt index impact copolymer polypropylene material prepared by the preparation method, the material has higher melt index, while can keep higher impact strength and flexural modulus, and has stronger comprehensive performance, has greater competitiveness in market.

Description

Technical Field

[0001] This invention relates to the field of polyolefin production technology, specifically to a high melt index impact-resistant copolymer polypropylene material, its preparation method, and its application. Background Technology

[0002] Polypropylene resin, as one of the fastest-growing varieties of commonly used synthetic resins worldwide, boasts advantages such as low relative density, ease of processing, excellent mechanical properties and chemical resistance, and low price, leading to its significant development in the last decade or so. The melt flow and processing properties of polypropylene determine its final applications. Among these, impact-resistant copolymer polypropylene has a wide range of applications. Impact-resistant copolymer polypropylene generally refers to a blend obtained by polymerizing olefins in a reactor, using homopolymer polypropylene as the matrix material and a rubber phase containing ethylene, propylene, or ethylene, butene, and other α-olefins as the dispersed phase. Impact-resistant copolymer polypropylene can improve the toughness of homopolymer polypropylene, and this improvement is primarily due to the rubber phase; the degree of improvement is related to the content of the rubber phase. To meet the application requirements of soft materials, researchers have been continuously studying high-performance impact-resistant copolymer polypropylene in recent years.

[0003] In existing processes, impact-resistant copolymer polypropylene is mainly produced by setting up two reactors. The first reactor produces homopolymer polypropylene, and the second reactor produces ethylene propylene rubber, ultimately yielding the target product. This method can produce various grades of impact-resistant copolymer polypropylene with different melt indices. However, when the melt index of impact-resistant polypropylene increases, its impact strength decreases significantly. In order to obtain copolymer products with high melt index and high impact resistance, a large amount of hydrogen and ethylene needs to be added to the reactor during production, making it difficult to control the polymerization reaction pressure, thus limiting the production of this type of product.

[0004] To address the shortcomings in the production process of the aforementioned impact-resistant copolymer polypropylene materials, developing a production method for impact-resistant copolymer polypropylene materials that can comprehensively improve the melt flow rate (MFR), rigidity, and toughness of polypropylene materials is currently a key research focus in the field of polyolefin production technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high MFR impact-resistant copolymer polypropylene material, its preparation method and application, wherein the high MFR impact-resistant copolymer polypropylene material has a high MFR while maintaining good impact strength and flexural modulus.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a high MFR impact-resistant copolymer polypropylene material, wherein the copolymer polypropylene material has an MFR ≥ 30 g / 10 min, an impact strength ≥ 50 kJ / ㎡, and a flexural modulus ≥ 800 MPaG under the conditions of 230°C and 2.16 kg.

[0008] Secondly, the present invention provides a method for preparing a high MFR impact-resistant copolymer polypropylene material, the method comprising the following steps:

[0009] S1. In a gas-phase polypropylene polymerization apparatus, a main catalyst, a co-catalyst, and a composite external electron donor are added to a first gas-phase reactor, and propylene and hydrogen are introduced into the first gas-phase reactor to carry out a first polymerization reaction, yielding a first reaction product; subsequently, the first reaction product is added to a second gas-phase reactor, and ethylene and hydrogen are introduced into the second gas-phase reactor to carry out a second polymerization reaction, producing a polypropylene copolymer; the main catalyst is a BCM series catalyst; the molar ratio of hydrogen to propylene in the first reactor is hydrogen:propylene = 18-24:100, and the molar ratio of hydrogen to ethylene in the second reactor is hydrogen:ethylene = 9-14:100;

[0010] S2. After drying the polypropylene copolymer obtained in step S1, add additives to it and mix them evenly. After extruding and granulating the resulting mixture, the high melt index impact-resistant copolymer polypropylene material is obtained.

[0011] In the first gas-phase reactor of this invention, only propylene monomer participates in the polymerization reaction, providing rigidity to the product structure. In the second gas-phase reactor, ethylene-propylene copolymer is produced, providing toughness to the product structure. By adopting the above method, this invention can produce impact-resistant copolymer polypropylene materials with high MFR while maintaining high impact strength and flexural modulus. The above method overcomes the problems of current impact-resistant copolymer polypropylene materials where the impact strength is greatly reduced due to the increase of MFR during preparation, thus requiring the addition of large amounts of hydrogen and ethylene during production, making it difficult to control the pressure of the polymerization reaction and limiting the production of such products.

[0012] Through extensive experimentation, the inventors discovered that by selecting a suitable catalyst system, polypropylene materials with good overall performance can be prepared. In the process of preparing polypropylene materials, a composite external electron donor is introduced. Compared with ordinary modifiers, this composite external electron donor has higher hydrogen sensitivity, allowing the reactor to achieve a high molecular weight ratio (MFR) even at lower hydrogen concentrations. Simultaneously, the cryogenic unit of the device is used for pressure control, ultimately producing homopolymer polypropylene powder with a high MFR in the first reactor. Furthermore, in current production processes for copolymer polypropylene, a large amount of ethylene needs to be added to the second reactor to maintain a high molar ratio of hydrogen to ethylene to achieve the desired ethylene-propylene rubber content. However, ethylene and hydrogen are both non-condensable gases, and an increase in the ethylene content in the reactor leads to greater difficulty in controlling the reactor pressure. To solve the pressure control problem in the second reactor, this invention uses the BCM series main catalyst, which is large in size, has slow activity decay, and a high ethylene polymerization rate. This catalyst can synergistically interact with the composite external electron donor to further improve the ethylene polymerization rate in the second reactor, enabling the second reactor to produce polypropylene materials with high ethylene and rubber content at lower ethylene concentrations.

[0013] The inventors also discovered that the molar ratio of hydrogen to propylene in the first reactor has a significant impact on the performance of the final polypropylene produced. Hydrogen is a non-condensable gas, and adding a large amount will cause the dew point of the circulating gas components in the first reactor system to decrease. Therefore, it is necessary to control the amount added. By controlling the molar ratio of hydrogen to propylene in the first reactor within the above-mentioned range, the MFR of polypropylene can reach the expected value.

[0014] The inventors also discovered that the molar ratio of hydrogen to ethylene in the second reactor also affects the final performance of the polypropylene; when the molar ratio of hydrogen to ethylene in the second reactor is within the above range, the ethylene propylene rubber content in the polypropylene can reach the expected value.

[0015] In the preparation process of the high MFR impact-resistant copolymer polypropylene material of the present invention, the limitation of the above parameters is very important. Each link is interconnected and directly affects the various properties of the final polypropylene.

[0016] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, in step S1, the BCM series catalyst includes BCM100 series catalyst and BCM200 series catalyst, and the main component is titanium tetrachloride.

[0017] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, in step S1, the co-catalyst includes at least one of triethylaluminum and triisobutylaluminum, and the compound external electron donor includes diisobutyldimethoxysilane, diisopropyldimethoxysilane and a compound BT catalyst, wherein the compound BT catalyst includes dicyclopentyldimethoxysilane and diisobutyldimethoxysilane.

[0018] It should be noted that the dicyclopentyldimethoxysilane and diisobutyldimethoxysilane in the compound BT catalyst can be mixed in any mass ratio.

[0019] In a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the co-catalyst is triethylaluminum, and the compounded external electron donor is compounded BT; in the first reactor, the role of the BCM series main catalyst is to initiate the propylene polymerization reaction, the role of triethylaluminum is to activate the main catalyst to form active centers, and the role of the compounded external electron donor is to improve the hydrogen regulation sensitivity of the main catalyst, reduce the hydrogen concentration required by the reactor, and enable better control of the reactor pressure.

[0020] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, in step S1, the molar ratio of the main catalyst and the co-catalyst is 4:1, and the molar ratio of the compounded external electron donor to the co-catalyst is 6:1. The inventors have found through a large number of experiments that when the proportions of each catalyst are within the above range, a polypropylene product with better comprehensive performance can be prepared.

[0021] It should be noted that the BCM series main catalyst described in this invention needs to be pretreated before entering the reactor. The pretreatment steps are as follows: adding propylene monomer, main catalyst, co-catalyst and modifier silane into the catalyst pretreatment tank, and reacting under the conditions of 15°C and 60 kPa; the pretreatment is a low-activity polymerization reaction, which can form a thin polypropylene film around the catalyst, so that the catalyst can maintain a good morphology when it enters the reactor and undergoes a more active reaction, reducing the generation of fine powder.

[0022] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, in step S1, the temperature in the first gas phase reactor is 58-65℃ and the pressure is 2.2-2.45 MPaG, and the temperature in the second gas phase reactor is 50-65℃ and the pressure is 2.2-2.45 MPaG. The inventors have found through a large number of experiments that when the temperature and pressure in the reactor are within the above range, the polypropylene material prepared can have better comprehensive performance.

[0023] It should be noted that, in order to better control the pressure in the reactor, a cooler is used to condense the first gaseous component into a liquid phase to control the system pressure.

[0024] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the drying process in step S2 is as follows: the polypropylene copolymer is devolatile in a biaxial heater, and then nitrogen vapor is added to the deactivation chamber to deactivate the residual catalyst.

[0025] The above method is used to dry the polypropylene copolymer and remove volatiles, which can reduce the concentration of volatiles in the polypropylene copolymer powder from 2000 ppm to below 500 ppm. The deactivation treatment further reduces the concentration of volatiles in the polypropylene copolymer powder to below 200 ppm, which greatly improves the quality of the final polypropylene material.

[0026] As a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the temperature during the drying process to remove volatiles is 90-105°C and the pressure is 10-12 kPa.

[0027] In a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the mass ratio of water vapor to nitrogen vapor in the nitrogen vapor during the deactivation treatment of the drying process is water vapor: nitrogen vapor = 1:0.00224.

[0028] As a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the temperature in the deactivation chamber during the deactivation treatment of the drying process is 120-125℃ and the pressure is 10-12kPa.

[0029] In a preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the additives in step S2 include antioxidants and acid absorbers. The addition of the additives can stabilize the structure of the final polypropylene, facilitate long-term storage, and further improve the rigidity and toughness of the polypropylene.

[0030] In a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the antioxidant includes antioxidant 1010 and antioxidant 168. The introduction of the antioxidant can improve the heat aging resistance of the product during processing and use.

[0031] In the most preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the concentration of the antioxidant is 1800-2000 ppm.

[0032] In a more preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the acid absorbent comprises calcium stearate and hydrotalcite.

[0033] In the most preferred embodiment of the preparation method of the high MFR impact-resistant copolymer polypropylene material of the present invention, the concentration of calcium stearate is 400-600 ppm and the concentration of hydrotalcite is 2000-2500 ppm.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention establishes a high MFR impact-resistant copolymer polypropylene material, its preparation method and application. By selecting a compound external electron donor system, the first reactor can also prepare polypropylene with a high MFR at a low hydrogen concentration. By selecting a BCM series main catalyst and the compound external electron donor system to achieve synergistic effect, the second reactor can prepare polypropylene material with a high ethylene and rubber content at a low ethylene concentration. The present invention also provides a high MFR impact-resistant copolymer polypropylene material prepared by the above preparation method. This material has a high MFR, while maintaining high impact strength and flexural modulus, and has strong comprehensive performance, making it highly competitive in the market. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of the high melt flow index impact-resistant copolymer polypropylene material described in this invention. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to explain the content of this invention in detail, not to limit it. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and equipment designed for implementation of this invention are all commonly used reagents and equipment.

[0037] Example 1

[0038] This embodiment provides a method for preparing K9930 polypropylene, the method comprising the following steps:

[0039] S1. Propylene monomer, main catalyst, co-catalyst, and modifier silane are added to the catalyst pretreatment tank, and the reaction is carried out at 15°C and 60 kPa. Subsequently, in the gas-phase polypropylene polymerization apparatus, the main catalyst BCM (mainly composed of titanium tetrachloride), the co-catalyst triethylaluminum, and the composite external electron donor BT are added to the first gas-phase reactor, and propylene and hydrogen are introduced into the first gas-phase reactor to carry out the first polymerization reaction, obtaining the first reaction product. The molar ratio of the main catalyst to the co-catalyst is 4:1, the molar ratio of the composite external electron donor to the co-catalyst is 6:1, the molar ratio of hydrogen to propylene is hydrogen:propylene = 18:100, the reaction temperature is 58°C, and the pressure is 2.2 MPaG. Subsequently, the first reaction product is added to the second gas-phase reactor, and ethylene and hydrogen are introduced into the second gas-phase reactor to carry out the second polymerization reaction, obtaining the polypropylene copolymer. The molar ratio of hydrogen to ethylene is hydrogen:ethylene = 9:100, the reaction temperature is 50°C, and the pressure is 2.2 MPaG.

[0040] S2. The polypropylene copolymer obtained in step S1 is devolatile in a biaxial heater at a temperature of 100°C and a pressure of 10 kPa. Then, nitrogen vapor is added to the deactivation chamber to deactivate the residual catalyst at a temperature of 120°C and a pressure of 10 kPa. The mass ratio of water vapor to nitrogen vapor is water vapor: nitrogen vapor = 1:0.00224. 2000 ppm of a mixture of antioxidant 1010 and antioxidant 168, 500 ppm of calcium stearate, and 2000 ppm of hydrotalcite are added to the dried polypropylene copolymer. The resulting mixture is placed in a twin-screw extruder and melt-blended and extruded to granulate, thus obtaining the high melt index impact-resistant copolymer polypropylene material.

[0041] Example 2

[0042] The only difference between this embodiment and Embodiment 1 is that in step S1, the reaction temperature in the first reactor is 65°C and the pressure is 2.45 MPaG; the remaining steps are the same as in Embodiment 1.

[0043] Example 3

[0044] The only difference between this embodiment and Embodiment 1 is that in step S1, the molar ratio of hydrogen to propylene in the first reactor is hydrogen:propylene = 24:100; the remaining steps are the same as in Embodiment 1.

[0045] Example 4

[0046] The only difference between this embodiment and Embodiment 1 is that in step S1, the reaction temperature in the second reactor is 65°C and the pressure is 2.45 MPaG; the remaining steps are the same as in Embodiment 1.

[0047] Example 5

[0048] The only difference between this embodiment and Embodiment 1 is that in step S1, the molar ratio of hydrogen to ethylene is hydrogen:ethylene = 14:100; the remaining steps are the same as in Embodiment 1.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that in step S1, the reaction temperature in the first reactor is 75°C and the pressure is 3 MPaG; the remaining steps are the same as in Example 1.

[0051] Comparative Example 2

[0052] The only difference between this comparative example and Example 1 is that in step S1, the reaction temperature in the first reactor is 50°C and the pressure is 1 MPaG; the remaining steps are the same as in Example 1.

[0053] Comparative Example 3

[0054] The only difference between this comparative example and Example 1 is that in step S1, the reaction temperature in the second reactor is 40°C and the pressure is 1 MPaG; the remaining steps are the same as in Example 1.

[0055] Comparative Example 4

[0056] The only difference between this comparative example and Example 1 is that in step S1, the reaction temperature in the first reactor is 80°C and the pressure is 3 MPaG; the remaining steps are the same as in Example 1.

[0057] Comparative Example 5

[0058] The only difference between this comparative example and Example 1 is that in step S1, the molar ratio of hydrogen to propylene in the first reactor is hydrogen:propylene = 40:100; the remaining steps are the same as in Example 1.

[0059] Comparative Example 6

[0060] The only difference between this comparative example and Example 1 is that in step S1, the molar ratio of hydrogen to ethylene is hydrogen:ethylene = 30:100; the remaining steps are the same as in Example 1.

[0061] Example of effect

[0062] Various performance tests were conducted on the polypropylene powders prepared by the methods described in Examples 1-5 and Comparative Examples 1-6. Table 1 shows the performance test results of different batches of Example 1, and Tables 2 and 3 show the performance test results of Examples 2-5 and Comparative Examples 1-6.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067] Table 3

[0068]

[0069]

[0070] As can be seen from Tables 1-3, by adjusting the preparation parameters, the copolymer polypropylene materials described in Examples 1-5 of the present invention have an MFR > 28 g / 10 min and an impact strength (23℃) ≥ 50 kJ / ㎡ under the conditions of 230℃ and 2.16 kg. While ensuring high impact strength, they can also maintain a flexural modulus ≥ 800 MPaG. This can comprehensively improve the MFR, rigidity, and toughness of the copolymer polypropylene materials, and the overall performance of the products is highly competitive in the market. In contrast, the parameters in the preparation process of Comparative Examples 1-6 are not within the range provided by the present invention, and the final performance of the products is not as good as that of Examples 1-5.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high melt flow index impact-resistant copolymer polypropylene material, characterized in that, The copolymer polypropylene material has a melt flow index ≥30g / 10min, impact strength ≥50kJ / m², and flexural modulus ≥800MPaG under conditions of 230℃ and 2.16kg. The preparation method of the high melt flow index impact-resistant copolymer polypropylene material includes the following steps: S1. In a gas-phase polypropylene polymerization apparatus, a main catalyst, a co-catalyst, and a composite external electron donor are added to a first gas-phase reactor, and propylene and hydrogen are introduced into the first gas-phase reactor to carry out a first polymerization reaction, yielding a first reaction product; subsequently, the first reaction product is added to a second gas-phase reactor, and ethylene and hydrogen are introduced into the second gas-phase reactor to carry out a second polymerization reaction, producing a polypropylene copolymer; the main catalyst is a BCM series catalyst; the molar ratio of hydrogen to propylene in the first reactor is hydrogen:propylene = 18-24:100, and the molar ratio of hydrogen to ethylene in the second gas-phase reactor is hydrogen:ethylene = 9-14:100; S2. After drying the polypropylene copolymer obtained in step S1, add additives to it and mix them evenly. After extruding and granulating the resulting mixture, the high melt index impact-resistant copolymer polypropylene material is obtained.

2. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 1, characterized in that, In step S1, the BCM series catalyst includes BCM100 series catalyst and BCM200 series catalyst, the main component of which is titanium tetrachloride; the co-catalyst includes at least one of triethylaluminum and triisobutylaluminum; the composite external electron donor includes diisobutyldimethoxysilane, diisopropyldimethoxysilane and composite BT catalyst, wherein the composite BT catalyst includes dicyclopentyldimethoxysilane and diisobutyldimethoxysilane.

3. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 2, characterized in that, The co-catalyst is triethylaluminum, and the composite external electron donor is a composite BT catalyst.

4. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 1, characterized in that, In step S1, the molar ratio of the main catalyst to the co-catalyst is 4:1, and the molar ratio of the composite external electron donor to the co-catalyst is 6:

1.

5. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 1, characterized in that, In step S1, the temperature in the first gas phase reactor is 58-65℃ and the pressure is 2.2-2.45 MPaG, and the temperature in the second gas phase reactor is 50-65℃ and the pressure is 2.2-2.45 MPaG.

6. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 1, characterized in that, In step S2, the drying process is as follows: the polypropylene copolymer is devolatile in a biaxial heater, and then nitrogen vapor is added to the deactivation chamber to deactivate the residual catalyst. The temperature for removing volatiles is 90-105℃ and the pressure is 10-12kPa; the temperature in the deactivation chamber during the deactivation treatment is 120-125℃ and the pressure is 10-12kPa, and the mass ratio of water vapor to nitrogen vapor in the nitrogen vapor is water vapor: nitrogen vapor = 1:0.00224.

7. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 1, characterized in that, In step S2, the additives include antioxidants and acid absorbers.

8. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 7, characterized in that, In step S2, the antioxidant includes antioxidant 1010 and antioxidant 168, and the acid absorber includes calcium stearate and hydrotalcite.

9. The high melt flow index impact-resistant copolymer polypropylene material as described in claim 8, characterized in that, In step S2, the concentration of the antioxidant is 1800-2000 ppm, the concentration of the calcium stearate is 400-600 ppm, and the concentration of the hydrotalcite is 2000-2500 ppm.

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