Impact-resistant co-polypropylene material with high melt index as well as preparation method and application of impact-resistant co-polypropylene material

Abstract

The invention discloses a high-melt-index anti-impact co-polypropylene material as well as a preparation method and application thereof, and belongs to the technical field of polyolefin production. According to the invention, polypropylene with a high melt index can be prepared in the first reactor at a low hydrogen concentration by selecting a compound external electron donor system, and the main catalyst of the BCM series and the compound external electron donor generate a synergistic effect, so that the polypropylene with a high melt index can be prepared in the second reactor at a low ethylene concentration. The polypropylene material with high ethylene and rubber content is prepared; the invention also provides the high-melt-index impact-resistant co-polypropylene material prepared by the preparation method, and the material has high melt index, can maintain high impact strength and flexural modulus, has strong comprehensive performance, and has great competitiveness in the market.

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin production, and in particular to a high melt index impact-resistant copolymer polypropylene material and a preparation method and application thereof. Background Art

[0002] As one of the most rapidly growing varieties of general-purpose synthetic resins in the world, polypropylene resin has the advantages of low relative density, easy processing, excellent mechanical properties and chemical resistance, and low price. It has achieved great development in the past decade. The melt flow and processing properties of polypropylene determine its final use. Among them, impact-resistant copolymer polypropylene is widely used. Impact-resistant copolymer polypropylene generally refers to a blend obtained by polymerization of olefins in a reactor, with homopolymer polypropylene as the matrix material and a rubber phase containing ethylene, propylene or ethylene, butene and other α-olefin copolymers as the dispersed phase. Impact-resistant copolymer polypropylene can improve the toughness of homopolymer polypropylene, and the improvement of its toughness is mainly due to the rubber phase, and the degree of improvement is related to the content of the rubber phase. In order to meet the application needs of soft materials, in recent years, researchers have been continuously studying high-performance impact-resistant copolymer polypropylene.

[0003] In the existing process, impact-resistant copolymer polypropylene is mainly produced by setting up two reactors, wherein the first reactor produces homopolymer polypropylene and the second reactor produces ethylene-propylene rubber, and finally the target product is obtained; this scheme can produce various melt index impact-resistant copolymer polypropylene grades, however, when the melt index of impact-resistant polypropylene increases, its impact strength will be greatly reduced. In order to obtain high melt index and high impact copolymer products, a large amount of hydrogen and ethylene need to be added to the reactor during production, which makes it difficult to control the polymerization reaction pressure, thus limiting the production of such products.

[0004] In view of the defects existing in the production process of the above-mentioned impact-resistant copolymer polypropylene material, developing a production method for the impact-resistant copolymer polypropylene material that can comprehensively improve the melt index (MFR), rigidity and toughness of the polypropylene material is the current research focus in the field of polyolefin production technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a high MFR impact-resistant copolymer polypropylene material and a preparation method and application thereof. The high MFR impact-resistant copolymer polypropylene material has a higher MFR while maintaining good impact strength and flexural modulus.

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

[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 / m2, and a flexural modulus ≥ 800 MpaG under the conditions of 230° C. and 2.16 kg.

[0008] In a second aspect, the present invention provides a method for preparing a high MFR impact copolymer polypropylene material, the method comprising the following steps:

[0009] S1. In a gas phase polypropylene polymerization device, 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 for a first polymerization reaction to obtain a first reaction product; then the first reaction product is added to a second gas phase reactor, and ethylene and hydrogen are introduced into the second gas phase reactor for a second polymerization reaction to obtain 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, drying the polypropylene copolymer obtained in step S1, adding additives thereto and mixing them evenly, and extruding and granulating the obtained mixture to obtain the high melt index impact-resistant copolymer polypropylene material.

[0011] In the first gas phase reactor of the present invention, only propylene monomer participates in the polymerization reaction, which provides rigidity for the product structure; in the second gas phase reactor, ethylene propylene copolymer is produced, which provides toughness for the product structure; by adopting the above method, the present invention can produce an impact-resistant copolymer polypropylene material with a high MFR while maintaining high impact strength and bending modulus; the above method overcomes the problem that the impact strength of the current impact-resistant copolymer polypropylene material is greatly reduced due to the increase of MFR during the preparation process, so a large amount of hydrogen and ethylene are added during production, making it difficult to control the pressure of the polymerization reaction, limiting the production of such products, and the like.

[0012] The inventors have found through a large number of experiments that by selecting a suitable catalyst system, a polypropylene material with good comprehensive performance can be prepared; in the process of preparing the polypropylene material, a composite external electron donor is introduced, and the composite external electron donor as a modifier has a higher hydrogen adjustment sensitivity than the ordinary modifier, so that the reactor can also make the product reach a higher MFR at a lower hydrogen concentration, and the deep cooling unit of the auxiliary device is used for pressure control, and finally a homopolymer polypropylene powder with a higher MFR can be prepared in the first reactor. In addition, in the current production process for preparing copolymerized polypropylene, a large amount of ethylene needs to be added to the second reactor to keep the molar ratio of hydrogen to ethylene in a higher range, so that the polypropylene can reach the expected ethylene-propylene rubber content, and ethylene and hydrogen are both non-condensable gases. When the ethylene content in the reactor increases, it will cause the reactor pressure control difficulty to increase; in order to solve the pressure control problem of the second reactor, the present invention adopts a BCM series main catalyst with large size, slow activity decay and high ethylene reactivity rate, and the catalyst can synergize with the composite external electron donor to further improve the ethylene polymerization reactivity rate in the second reactor, so that the second reactor can prepare a polypropylene material with high ethylene and rubber content at a lower ethylene concentration.

[0013] The inventors also found that the molar ratio of hydrogen to propylene in the first reactor has a great influence on the performance of the polypropylene finally prepared; hydrogen is a non-condensable gas, and a large amount of addition will cause the dew point of the circulating gas component of the first reactor system to decrease, so it is necessary to control its addition amount. By controlling the molar ratio of hydrogen to propylene in the first reactor within the above range, the MFR of the polypropylene can reach the expected value.

[0014] The inventors also found that the molar ratio of hydrogen to ethylene in the second reactor also affects the properties of the final 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 copolymer polypropylene material of the present invention, the limitation of the above parameters is very important, and each link is closely linked and directly affects the various properties of the final polypropylene.

[0016] As a preferred embodiment of the method for preparing high MFR impact 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] As a preferred embodiment of the method for preparing a high MFR impact-resistant copolymer polypropylene material of the present invention, in step S1, the co-catalyst comprises at least one of triethylaluminum and triisobutylaluminum, the composite external electron donor comprises diisobutyldimethoxysilane, diisopropyldimethoxysilane and a composite BT catalyst, and the composite BT catalyst comprises dicyclopentyldimethoxysilane and diisobutyldimethoxysilane.

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

[0019] As a more preferred embodiment of the method for preparing the high MFR impact-resistant copolymer polypropylene material of the present invention, the co-catalyst is triethyl aluminum, and the composite external electron donor is a composite BT; in the first reactor, the role of the BCM series main catalyst is to initiate the propylene polymerization reaction, the role of triethyl aluminum is to activate the main catalyst to form an active center, and the role of the composite external electron donor is to improve the hydrogen adjustment sensitivity of the main catalyst, reduce the hydrogen concentration required by the reactor, and better control the reactor pressure.

[0020] As a preferred embodiment of the method for preparing a high MFR impact-resistant copolymer polypropylene material of the present invention, 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; the inventors have found through a large number of experiments that when the ratio of each catalyst is 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 of the present invention needs to be pretreated before entering the reactor, and the pretreatment steps are: adding propylene monomer, main catalyst, co-catalyst and modifier silane into the catalyst pretreatment tank, and reacting at 15°C and 60kPa; the pretreatment is a polymerization reaction with lower activity, which can form a thin polypropylene film around the catalyst, so that the catalyst can maintain a good shape when entering the reactor to undergo a more active reaction, thereby reducing the generation of fine powder.

[0022] As a preferred embodiment of the method for preparing a high MFR impact copolymer polypropylene material of the present invention, in step S1, the temperature in the first gas phase reactor is 58-65°C, and the pressure is 2.2-2.45MpaG, and the temperature in the second gas phase reactor is 50-65°C, and the pressure is 2.2-2.45MpaG; 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 comprehensive performance of the prepared polypropylene material can be better.

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

[0024] As a preferred embodiment of the method for preparing high MFR impact copolymer polypropylene material of the present invention, in step S2, the drying process is: removing volatiles from the polypropylene copolymer in a biaxial heater, and then adding nitrogen vapor to a deactivation chamber to deactivate the residual catalyst.

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

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

[0027] As a more preferred embodiment of the method for preparing high MFR impact copolymer polypropylene material of the present invention, the mass ratio of water vapor and nitrogen vapor in the nitrogen vapor during the inactivation treatment in the drying process is water vapor: nitrogen vapor = 1:0.00224.

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

[0029] As a preferred embodiment of the method for preparing the high MFR impact-resistant copolymer polypropylene material of the present invention, in step S2, the additives 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] As a more preferred embodiment of the method for preparing the high MFR impact-resistant copolymer polypropylene material of the present invention, the antioxidant comprises antioxidant 1010 and antioxidant 168. The introduction of the antioxidant can improve the heat aging resistance of the product during processing and use.

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

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

[0033] As the most preferred embodiment of the method for preparing the high MFR impact-resistant copolymer polypropylene material of the present invention, the concentration of the calcium stearate is 400-600 ppm, and the concentration of the 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 and a preparation method and application thereof; by selecting a composite external electron donor system, the first reactor can also prepare polypropylene with a higher MFR at a lower hydrogen concentration; the BCM series main catalyst is selected to have a synergistic effect with the composite external electron donor, so that the second reactor can prepare a polypropylene material with a higher ethylene and rubber content at a lower ethylene concentration; the present invention also provides a high MFR impact-resistant copolymer polypropylene material prepared by the preparation method, the material has a higher MFR, can maintain a higher impact strength and bending modulus, has a stronger comprehensive performance, and has greater competitiveness in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention provides a flow chart for preparing the high melt index impact copolymer polypropylene material. DETAILED DESCRIPTION

[0036] In order to better reflect the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, its purpose is to explain the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and equipment designed for the implementation of the present invention are all commonly used common reagents and equipment unless otherwise specified.

[0037] Example 1

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

[0039] S1, add propylene monomer, main catalyst, co-catalyst and modifier silane into the catalyst pretreatment tank, and react under the conditions of 15°C and 60kPa; then in the gas phase polypropylene polymerization device, add the main catalyst BCM whose main components are titanium tetrachloride, co-catalyst triethylaluminum and composite external electron donor BT into the first gas phase reactor, and introduce propylene and hydrogen into the first gas phase reactor for a first polymerization reaction to obtain a first reaction product, wherein 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 2.2MpaG; then add the first reaction product into the second gas phase reactor, and introduce ethylene and hydrogen into the second gas phase reactor for a second polymerization reaction to obtain a polypropylene copolymer; the molar ratio of hydrogen to ethylene is hydrogen:ethylene=9:100, the reaction temperature is 50°C, and the pressure is 2.2MpaG;

[0040] S2. The polypropylene copolymer obtained in step S1 is devolatiled in a biaxial heater, the temperature in the biaxial heater is 100° C., and the pressure is 10 kPa. Subsequently, nitrogen vapor is added to a deactivation chamber to deactivate the residual catalyst. The temperature in the deactivation chamber is 120° C., the pressure is 10 kPa, and 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, and the obtained mixture is placed in a twin-screw extruder for melt blending and extrusion granulation to obtain 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 consistent with 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 consistent with 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 consistent with 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 consistent with embodiment 1.

[0049] Comparative Example 1

[0050] The 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 consistent with Example 1.

[0051] Comparative Example 2

[0052] The 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 consistent with Example 1.

[0053] Comparative Example 3

[0054] The 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 consistent with Example 1.

[0055] Comparative Example 4

[0056] The 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 consistent with 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 consistent with Example 1.

[0059] Comparative Example 6

[0060] The 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 consistent with Example 1.

[0061] Effect example

[0062] The polypropylene powders prepared by the methods described in Examples 1-5 and Comparative Examples 1-6 were subjected to various performance tests. 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] It can be seen from Table 1-3 that, by adjusting the preparation parameters in Examples 1-5 of the present invention, the copolymerized polypropylene material described in Examples 1-5 has MFR>28g / 10min at 230°C and 2.16kg, and the impact strength (23°C) is ≥50kJ / ㎡, and while ensuring high impact strength, the flexural modulus is maintained at ≥800MPaG, so that the MFR, rigidity and toughness of the copolymerized polypropylene material can be comprehensively improved, and the comprehensive performance of the product has greater competitiveness in the market; while in Comparative Examples 1-6, since the parameters in the preparation process are not within the range provided by the present invention, the various properties of the final product are not as good as those of Examples 1-5.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A high melt index impact copolymer polypropylene material, characterized in that: The copolymerized polypropylene material has a melt index of ≥30 g / 10 min, an impact strength of ≥50 kJ / m2, and a bending modulus of ≥800 MpaG under the conditions of 230° C. and 2.16 kg.

2. The method for preparing the high melt index impact copolymer polypropylene material according to claim 1, characterized in that: The method comprises the following steps: S1. In a gas phase polypropylene polymerization device, 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 for a first polymerization reaction to obtain a first reaction product; then the first reaction product is added to a second gas phase reactor, and ethylene and hydrogen are introduced into the second gas phase reactor for a second polymerization reaction to obtain 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, drying the polypropylene copolymer obtained in step S1, adding additives thereto and mixing them evenly, and extruding and granulating the obtained mixture to obtain the high melt index impact-resistant copolymer polypropylene material.

3. The method for preparing the high melt index impact copolymer polypropylene material according to claim 2, characterized in that: In the step S1, the BCM series catalyst includes a BCM100 series catalyst and a BCM200 series catalyst, and the main component is titanium tetrachloride; the co-catalyst includes at least one of triethylaluminum and triisobutylaluminum; the composite external electron donor includes diisobutyldimethoxysilane, diisopropyldimethoxysilane and a composite BT catalyst, and the composite BT catalyst includes dicyclopentyldimethoxysilane and diisobutyldimethoxysilane.

4. The method for preparing the high melt index impact copolymer polypropylene material according to claim 3, characterized in that: The co-catalyst is triethylaluminum, and the composite external electron donor is a composite BT catalyst.

5. The method for preparing the high melt index impact copolymer polypropylene material according to claim 2, characterized in that: In the 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.

6. The method for preparing the high melt index impact copolymer polypropylene material according to claim 2, characterized in that: In step S1, the temperature in the first gas phase reactor is 58-65°C and the pressure is 2.2-2.45MpaG, and the temperature in the second gas phase reactor is 50-65°C and the pressure is 2.2-2.45MpaG.

7. The method for preparing the high melt index impact copolymer polypropylene material according to claim 2, characterized in that: In step S2, the drying process is: removing the volatile matter from the polypropylene copolymer in a biaxial heater, and then adding nitrogen vapor to a deactivation chamber to deactivate the residual catalyst; Preferably, the temperature during the removal of volatiles is 90-105°C and the pressure is 10-12 kPa; the temperature in the deactivation chamber during the deactivation treatment is 120-125°C and the pressure is 10-12 kPa, and the mass ratio of water vapor in the nitrogen vapor to nitrogen vapor is water vapor: nitrogen vapor = 1:0.00224.

8. The method for preparing the high melt index impact copolymer polypropylene material according to claim 2, characterized in that: In the step S2, the additives include antioxidants and acid absorbers.

9. The method for preparing the high melt index impact copolymer polypropylene material according to claim 8, characterized in that: In the step S2, the antioxidant comprises antioxidant 1010 and antioxidant 168, and the acid absorbent comprises calcium stearate and hydrotalcite.

10. The method for preparing the high melt index impact copolymer polypropylene material according to claim 9, characterized in that: In the 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.

Images