Impact-resistant polypropylene and preparation method thereof

Abstract

The invention belongs to the field of propylene polymerization, and discloses anti-impact polypropylene and a preparation method thereof, the preparation method comprises the following steps: (1) in the presence of a catalyst system, propylene and optional first alpha-olefin are subjected to a pre-polymerization reaction; wherein the catalyst system comprises a main catalyst, a co-catalyst and a first external electron donor; (2) contacting the material subjected to the pre-polymerization reaction in the step (1), propylene, hydrogen and optional first alpha-olefin, and carrying out polymerization reaction to obtain a matrix polymer; and (3) in the presence of a matrix polymer and a second external electron donor, contacting propylene, second alpha-olefin and hydrogen, and carrying out polymerization reaction to obtain the anti-impact polypropylene, and the second external electron donor is an organosilane compound containing nitrogen atoms. According to the invention, the contents of a rubber phase and a comonomer can be obviously increased, and the problems of incapability of full-load operation, poor operation stability and the like of the existing device for producing high-impact polypropylene are solved.

Description

Technical Field

[0001] This invention relates to the field of propylene polymerization technology, and more specifically, to an impact-resistant polypropylene and its preparation method. Background Technology

[0002] The reactive preparation of impact-resistant polypropylene (PP) toughens the polypropylene material by uniformly distributing the resulting rubber phase within the matrix. The effectiveness of this toughening is primarily influenced by factors such as the type, dispersion degree, size, content, monomer content, and molecular weight of the rubber phase. Impact-resistant PP combines the rigidity of homopolymer PP with the impact resistance of rubber, exhibiting an excellent balance of rigidity and toughness. It is widely used in the automotive, home appliance, and injection molded container industries. Particularly in the automotive sector, high-rubber-content, high-impact impact-resistant PP is the mainstream product in demand.

[0003] Currently, the industry mainly uses a multi-stage reactor series to prepare high-flow, high-impact polypropylene. Typically, the matrix component of propylene homopolymer or random copolymer is prepared in the first-stage reactor, the rubber phase component is prepared in the second-stage reactor, and even another rubber phase component is prepared in the third-stage reactor, ultimately achieving effective blending of multiple components.

[0004] The main structural characteristic of high-impact polypropylene is its high rubber phase content, typically exceeding 25 wt%, which presents significant challenges in its production. This is primarily because polypropylene catalysts are "degrading" catalysts, meaning the polymerization rate gradually decreases with increasing reaction time. When producing high-impact polypropylene using a multi-stage reactor series configuration, methods such as increasing reaction pressure and extending residence time in the second or third stage reactor are needed to produce a larger amount of rubber phase. However, due to limitations in catalyst characteristics and production process conditions, simply altering the operating conditions of the second or third stage reactor is insufficient to achieve high rubber phase production. Typically, it is necessary to reduce the production load of the first stage reactor to increase the load ratio of the second or third stage reactor, thereby obtaining the high rubber phase product. However, this method leads to a lower overall plant production load, impacting plant efficiency.

[0005] CN102532380A and CN103360527A mention an asymmetric external electron donor technology to prepare impact-resistant polypropylene. Using silane-based or ether-based external electron donors, the impact performance of the product is not ideal, indicating that the rubber phase content is insufficient and cannot meet the requirements of high-impact polypropylene. Summary of the Invention

[0006] The purpose of this invention is to provide an impact-resistant polypropylene and its preparation method. This method can significantly increase the content of rubber phase and comonomer, and solve the problems of existing equipment being unable to operate at full load and having poor operational stability when producing high-impact polypropylene. At the same time, the polypropylene prepared by this method has good rigidity and toughness balance.

[0007] To achieve the above objectives, one aspect of the present invention provides a method for preparing impact-resistant polypropylene, the method comprising:

[0008] (1) In the presence of a catalyst system, propylene and optionally a first α-olefin are subjected to a prepolymerization reaction; wherein the catalyst system comprises: a main catalyst, a co-catalyst and a first external electron donor;

[0009] (2) The prepolymerized material from step (1), propylene, hydrogen and optional first α-olefin are brought into contact and polymerized to obtain the matrix polymer.

[0010] (3) In the presence of the matrix polymer and the second external electron donor, propylene, the second α-olefin and hydrogen are contacted and polymerized to obtain the impact-resistant polypropylene;

[0011] The second external electron donor is an organosilanes containing nitrogen atoms.

[0012] Another aspect of the present invention provides impact-resistant polypropylene prepared by the above-described preparation method.

[0013] The technical solution of the present invention has the following beneficial effects: the present invention can significantly increase the content of rubber phase and comonomer, and solve the problems of existing equipment being unable to operate at full load and having poor operational stability when producing high-impact polypropylene. At the same time, the polypropylene prepared by this method has good rigidity and toughness balance.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0015] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0016] One aspect of the present invention provides a method for preparing impact-resistant polypropylene, the method comprising:

[0017] (1) In the presence of a catalyst system, propylene and optionally a first α-olefin are subjected to a prepolymerization reaction; wherein the catalyst system comprises: a main catalyst, a co-catalyst and a first external electron donor;

[0018] (2) The prepolymerized material from step (1), propylene, hydrogen and optional first α-olefin are brought into contact and polymerized to obtain the matrix polymer.

[0019] (3) In the presence of the matrix polymer and the second external electron donor, propylene, the second α-olefin and hydrogen are contacted and polymerized to obtain the impact-resistant polypropylene;

[0020] The second external electron donor is an organosilanes containing nitrogen atoms.

[0021] According to the present invention, preferably, the first external electron donor is at least one of the compounds shown in formula (1);

[0022] (R1O)(R2O)SiR 3 R 4 Equation (1);

[0023] In formula (1), R1 and R2 are each independently a hydrocarbon group having 1-10 carbon atoms, preferably a hydrocarbon group having 2-8 carbon atoms, and more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl or methylcyclohexyl; R1 and R2 may be the same or different, preferably the same;

[0024] R 3 and R 4 Each is independently a hydrocarbon group having 1-16 carbon atoms or a C1-16 hydrocarbon group in which one carbon atom is replaced by a heteroatom; the heteroatom is N, P or S; preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl, methylcyclohexyl, octyl, nonyl, decyl, phenyl, methylphenyl or benzyl; the R 3 and R 4 For the same or different.

[0025] According to the present invention, preferably, the second external electron donor is at least one of the compounds shown in formula (2);

[0026] (RO) n Si(NR 1 R 2 ) m Equation (2);

[0027] In formula (2), R is a hydrocarbon group having 1-10 carbon atoms, preferably a hydrocarbon group having 2-8 carbon atoms, and more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl or methylcyclohexyl; n Rs may be the same or different, preferably the same;

[0028] R 1 R is a hydrocarbon group or hydrogen atom with 1-12 carbon atoms. 2 It is a hydrocarbon group having 1-12 carbon atoms or a C1-12 hydrocarbon group in which one carbon atom is replaced by a heteroatom; said heteroatom is N, P or S; R 1 and R 2 For the same or different, or R 1 and R 2 They can be connected to N to form a ring structure. R 1 and R 2 Each of the following can be independently methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl, methylcyclohexyl, octyl, nonyl, decyl, phenyl, methylphenyl or benzyl;

[0029] n+m=4, where n is 1, 2 or 3, with 2 or 3 being preferred.

[0030] According to the present invention, preferably, the second external electron donor is at least one of dimethylaminotriethoxysilane, diethylaminotriethoxysilane, dimethylaminotrimethoxysilane, diethylaminotrimethoxysilane, diethylaminotri-n-propoxysilane, di-n-propylaminotriethoxysilane, methyl-n-propylaminotriethoxysilane, methylethylaminotriethoxysilane, ethyl-n-propylaminotriethoxysilane, tert-butylaminotriethoxysilane, ethyl isopropylaminotriethoxysilane, bis(cyclohexylamino)dimethoxysilane, bis(cyclohexylamino)diethoxysilane, bis(cyclopentylamino)dimethoxysilane, bis(cyclopentylamino)diethoxysilane, bis(dimethylamino)diethoxysilane, bis(diethylamino)diethoxysilane, bis(diethylamino)dimethoxysilane, and bis(dimethylamino)dimethoxysilane.

[0031] According to the present invention, preferably, the Lewis basicity of the second external electron donor is weaker than that of the first external electron donor;

[0032] Preferably, the HOMO value of the second external electron donor is at least 0.2 eV higher than the HOMO value of the first external electron donor.

[0033] The orbital with the highest energy level where an electron donor has occupied an electron is called the highest occupied orbital (HOMO), and the orbital with the lowest energy level where an electron donor has not occupied an electron is called the lowest unoccupied orbital (LUMO). HOMO and LUMO are collectively referred to as frontier orbitals. HOMO orbitals have a relatively loose bond to their electrons and exhibit electron-donating properties; therefore, the higher the HOMO value, the stronger the electron-donating ability and the stronger the basicity.

[0034] In this invention, the HOMO value of the external electron donor is calculated by the Fukui function method, referring to (Yang Guang. Effect of silane external electron donors on propylene polymerization catalyzed by Ziegler-Natta catalyst [J]. Petrochemical Technology, 2013, 42(2):6) and (Chattaraj P K. Chemical Reactivity and Selectivity: Local HSAB Principle versus Frontier Orbital Theory [J]. Journal of Physical Chemistry A, 2001, 105(2):511-513).

[0035] This invention provides exemplary HOMO values ​​for common external electron donors in the art, as shown in Table 1. Due to differences in calculation software or parameter selection, values ​​for the same compound may vary in different literature sources. The basicity of other external electron donors can be determined by calculating their HOMO values.

[0036] Table 1

[0037] External electron donor HOMO / eV Diethylaminotriethoxysilane DEATES -4.866 tert-butylaminotriethoxysilane (TBATES) -5.180 bis(dimethylamino)diethoxysilane DDMADES -4.654 Dicyclopentyldimethoxysilane DCPDMS -5.852 Dicyclohexyldimethoxysilane DCHDMS -5.497 Cyclohexylmethyldimethoxysilane (CHMMS) -5.832 Diisopropyldimethoxysilane DIPDMS -5.848 Diisobutyldimethoxysilane DIBDMS -5.851 Tetraethylsilane TEOS -6.223

[0038] According to the present invention, preferably, the mass ratio w of the first external electron donor to the second external electron donor is 1:99-95:5, and more preferably 5:95-60:40;

[0039] Preferably, the mass ratio w of the first external electron donor and the second external electron donor is negatively correlated with the absolute value F of the HOMO difference between the first external electron donor and the second external electron donor, satisfying the formula: F*w = 0.002-100, preferably 0.01-50, and most preferably 0.01-10.

[0040] According to the present invention, preferably, the main catalyst is a Ziegler-Natta catalyst;

[0041] The Ziegler-Natta catalyst is spherical or near-spherical, and the ratio of the average major axis to the average minor axis of the Ziegler-Natta catalyst is ≤2, preferably ≤1.6, and most preferably ≤1.4.

[0042] Preferably, the average particle diameter D50 of the Ziegler-Natta catalyst is 30-100 μm, more preferably 30-80 μm;

[0043] Preferably, the specific surface area of ​​the Ziegler-Natta catalyst is 100-500 m². 2 / g, preferably 200-400m 2 / g, with a porosity of 0.1-1.0ml / g, preferably 0.2-0.7ml / g.

[0044] In this invention, the particle size of the Ziegler-Natta catalyst is preferably 10-200 μm.

[0045] In this invention, the sphericity of the main catalyst particles is assessed by the ratio of their average major axis (LA) to their average minor axis (SA) as projected under a microscope. The average particle diameter and particle size distribution of the main catalyst can be measured using a Master Sizer 2000 laser particle size analyzer (manufactured by Malvern Instruments Ltd.). The specific surface area and porosity of the catalyst particles are determined using the method described in GB / T19587-2017.

[0046] In this invention, the Ziegler-Natta catalyst comprises magnesium, halogens, and an internal electron donor, the main components of which are known to those skilled in the art. Specific examples of such components are disclosed in Chinese patent documents CN1215061A, CN1097596C, CN1097597C, CN1036011C, CN1137155C, and CN1169845C, the entire contents of which are incorporated herein by reference. The internal electron donor is selected from at least one of esters, ethers, succinates, 1,3-ol esters, and sulfonamides. The specific structure of such internal electron donors is well known to those skilled in the art, and is specifically embodied in Chinese patent documents CN112175118B, CN116023560A, CN116003916A, CN105566533B, CN1948352A, CN101486776A and CN113621098B, but is not limited to this.

[0047] According to the present invention, preferably, the co-catalyst is an alkylaluminum compound, more preferably a trialkylaluminum compound, and more preferably at least one selected from triethylaluminum, triisobutylaluminum, tri-n-butylaluminum and trihexylaluminum.

[0048] In this invention, in step (1), the main catalyst (Ziegler-Natta catalyst), the first external electron donor, and the co-catalyst can be directly added to the reactor, or they can be added to the reactor after pre-complexation, which is common in the industry. Preferably, pre-complexation is performed. The reactor type and operating conditions for pre-complexation are well known to those skilled in the art.

[0049] According to the present invention, preferably, in step (1), the mass ratio of the co-catalyst to the first external electron donor is (0.5-100):1, more preferably (1-50):1;

[0050] The mass ratio of the co-catalyst to the main catalyst is (0.25-50):1, preferably (2-20):1.

[0051] According to the present invention, preferably, the mass ratio of the co-catalyst in step (1) to the sum of the amounts of propylene and optionally the first α-olefin in step (2) is (1 × 10⁻⁶). -5 -1×10 -3 :1, preferably (5×10 -5 -5×10 -3 ):1;

[0052] In step (2), the volume concentration of hydrogen is 100-100000 ppmv, preferably 1000-50000 ppmv, based on the total gaseous volume of propylene, hydrogen and optional first α-olefin.

[0053] In this invention, in step (2), hydrogen is used as a molecular weight regulator for component a.

[0054] According to the present invention, preferably, in step (2): the first α-olefin is ethylene and / or an α-olefin having 4-10 carbon atoms, preferably at least one of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylisopentene, 1-octene and 1-decene;

[0055] Based on the total weight of the propylene and the first α-olefin, the amount of the first α-olefin is 0-5 wt%, preferably 0-2 wt%, and the amount of the propylene is 95-100 wt%, preferably 98-100 wt%.

[0056] According to the present invention, preferably, in step (2): the reaction temperature of the polymerization reaction is 30-150℃, preferably 50-100℃; the reaction pressure is 1-8MPa, preferably 1.2-5.5MPa; and the reaction residence time is 10-180min, preferably 20-120min.

[0057] The number of reactors used may be one or more.

[0058] In this invention, when there are multiple reactors, all reactors may undergo homopolymerization, or all reactors may undergo random copolymerization, or some reactors may undergo homopolymerization and some reactors may undergo random copolymerization.

[0059] In this invention, the reaction states in step (2) include bulk polymerization, gas-phase polymerization, slurry polymerization, multiphase polymerization, and solution polymerization. The reactor types can include ring reactors, gas-phase fluidized bed reactors, horizontal stirred reactors, vertical stirred reactors, and multi-zone reactors.

[0060] In this invention, the polymer obtained in step (2) can be directly transported to the reactor in step (3), or the polymer in step (2) can be first subjected to gas-solid separation, and then the separated polymer can be transported to the reactor in step (3). The latter is preferred.

[0061] According to the present invention, preferably, in step (3), the volume concentration of hydrogen is 2-30000 ppmv, more preferably 10-10000 ppmv, based on the total gas phase volume of propylene, hydrogen and the second α-olefin.

[0062] In this invention, hydrogen is used as a molecular weight regulator for component b in step (3).

[0063] According to the present invention, preferably, in step (3), the second α-olefin is ethylene and / or an α-olefin having 4-10 carbon atoms, preferably at least one of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylisopentene, 1-octene and 1-decene;

[0064] The mass ratio of the second α-olefin to propylene is 5:95-60:40, preferably 10:90-50:50.

[0065] According to the present invention, preferably, in step (3): the reaction temperature of the polymerization reaction is 30-150℃, preferably 50-100℃; the reaction pressure is 0.5-4.0MPa, preferably 1.0-3.0MPa; and the reaction residence time is 10-180min, preferably 20-90min.

[0066] The number of reactors used may be one or more.

[0067] In this invention, the reaction state in step (3) includes gas-phase polymerization, multiphase polymerization, etc. The reactor types include gas-phase fluidized bed reactors, horizontal stirred reactors, vertical stirred reactors, etc.

[0068] According to the present invention, preferably, the preparation method further includes step (4): pre-treating the polymer powder obtained by the polymerization reaction in step (3), and then melt-blending, extruding and granulating the pre-treated polymer powder with an additive to obtain the impact-resistant polypropylene;

[0069] The pretreatment preferably includes steam deactivation and drying;

[0070] Preferably, the mass concentration of the additive is 500-10000 ppmw, more preferably 500-5000 ppmw, based on the total weight of the pretreated polymer powder and the additive.

[0071] In this invention, the additives are conventional additives in the art, such as at least one of antioxidants, deacidifying agents, nucleating agents and dyeing agents.

[0072] Another aspect of the present invention provides impact-resistant polypropylene prepared by the above-described preparation method.

[0073] According to the present invention, preferably, the impact-resistant polypropylene comprises: component a and component b;

[0074] Component a is a propylene homopolymer and / or a random copolymer of propylene and a first α-olefin, preferably a propylene homopolymer; the melt mass flow rate (MFR) of component a at 230°C and 2.16 kg load is ≤100 g / 10 min, preferably 20-100 g / 10 min;

[0075] Component b is a copolymer of propylene in the rubber phase and a second α-olefin. The copolymer comprises 15-60 wt%, preferably 25-50 wt%, of the second α-olefin by total weight. The second α-olefin is preferably ethylene and / or a C4-C10 α-olefin.

[0076] In this invention, when component a contains a random copolymer of propylene and a first α-olefin, the comonomer is the first α-olefin, and the content of the comonomer in the random copolymer is 0.3-4.0 wt%, preferably 0.3-2.0 wt%, based on the total weight of the random copolymer of propylene and the first α-olefin.

[0077] According to the present invention, preferably, based on the total weight of the components a and b, the content of component a is 50-90 wt%, more preferably 60-80 wt%, and the content of component b is 10-50 wt%, more preferably 20-40 wt%.

[0078] According to the present invention, preferably, the melt mass flow rate (MFR) of the impact-resistant polypropylene at 230°C and 2.16 kg load is ≤60 g / 10 min, and more preferably 5-50 g / 10 min.

[0079] The present invention will be described in detail below through embodiments.

[0080] In the following embodiments and comparative examples:

[0081] The method for detecting hydrogen was online chromatography, using an ABB TGC-2000 online chromatograph.

[0082] Step (3) The composition analysis of hydrogen, ethylene and propylene in the ethylene / propylene copolymerization reaction was performed using an ABB TGC-2000 online chromatograph;

[0083] The ethylene content, rubber phase content, and ethylene content in the rubber of the final impact-resistant polypropylene were determined using a ThermoNicolet 200 infrared analyzer.

[0084] Melt mass flow rate (MFR): determined according to GB / T 3682.1-2018 at 230℃ and 2.16kg load;

[0085] Flexural modulus: Measured according to GB / T9341-2008 for injection molded samples;

[0086] Notched impact strength (Izod) of simply supported beams: measured at 23℃ for injection-molded samples according to GB / T 1043.1-2008;

[0087] Specific surface area and porosity of catalyst particles: determined by the method described in GB / T 19587-2017;

[0088] Catalyst sphericity: The sphericity of catalyst particles is assessed by the ratio of their average major axis (LA) to their average minor axis (SA) as projected under a microscope.

[0089] Average particle diameter of catalyst: measured using a Master Sizer 2000 laser particle size analyzer (manufactured by Malvern Instruments Ltd).

[0090] Example 1

[0091] The experiment was conducted on a 25 kg / h loop polypropylene pilot plant, which includes a pre-complexing reactor, a pre-polymerization reactor, a loop reactor, and a gas-phase reactor.

[0092] (1) Pre-complexation reaction and pre-polymerization reaction

[0093] The main catalyst (DQC-401 catalyst, Beijing Aoda Company, Sinopec Catalyst Branch) flow rate was 1.0 g / h, the co-catalyst (triethylaluminum, TEA) flow rate was 7.0 g / h, and the first external electron donor ED1 (diisopropyldimethoxysilane, DIPDMS) flow rate was 0.25 g / h. The pre-complexation reaction was carried out in a pre-complexation reactor at 10 °C for 8 min. The main catalyst had an LA / SA ratio of 1.15, an average particle diameter (D50) of 38 μm, and a specific surface area of ​​305 m². 2 / g, porosity 0.37ml / g.

[0094] The pre-complexed catalyst system was continuously added to a continuous stirred tank prepolymerization reactor, and the prepolymerization reaction was carried out in a propylene liquid phase bulk environment. The amount of propylene used was such that the weight ratio of the main catalyst (DQC401 catalyst) to propylene (12 kg / h) was 8.33 × 10⁻⁶. -5 1. The temperature is 16℃, the pressure is 4.0MPa, and the reaction residence time is about 12min.

[0095] (2) Homopolymerization of propylene

[0096] The prepolymerized material was continuously fed into a loop reactor (R1). Propylene (30 kg / h) and hydrogen (5 g / h) were mixed and then fed into the loop reactor. Online chromatographic analysis showed that the hydrogen concentration was 3500 ppmv. The polymerization temperature was 70℃, the reaction pressure was 4.0 MPa, the slurry density in the reactor was 520 ± 5 kg / m³, and the reaction residence time was approximately 1.5 h. The product from the loop reactor was discharged into a high-pressure flash tank. The MFR(a) of the polymer (component a) after gas-solid separation was 30 g / 10 min.

[0097] (3) Ethylene / propylene copolymerization

[0098] After gas-solid separation, the polymer (component a), carrying some propylene and hydrogen, enters the gas-phase fluidized bed reactor (R2). No hydrogen is added separately to the gas-phase fluidized bed; ethylene and propylene are continuously introduced. Online chromatographic analysis shows that the ethylene / (propylene + ethylene) ratio in the reactor is 0.41 (volume ratio), and the hydrogen volume concentration in the reactor is 500-650 ppmv. The flow rate of the second external electron donor, ED2 (diethylaminotriethoxysilane, DEATES), is 1.0 g / h. The gas-phase reactor level is controlled at 80%, the reactor pressure is 1.15 MPa, the reaction temperature is 70℃, and the residence time is approximately 30 min.

[0099] The polymer powder obtained from the polymerization reaction in step (3) was deactivated by steam and dried. Then, the deactivated and dried polymer powder was melt-blended, extruded, and granulated with additives to obtain the impact-resistant polypropylene. The additives, based on the total weight of the deactivated and dried polymer powder and additives, include: 1000 ppmw of antioxidant 1010, 500 ppmw of antioxidant 168, and 500 ppm of calcium stearate. The melt blending, extrusion, and granulation operations were carried out on a GLS-30B plastic granulator from Suzhou Gongle Rubber & Plastic Machinery Co., Ltd. The screw extruder speed was 350 rpm, and the temperatures of the first to sixth stages were 210℃, 205℃, 205℃, 200℃, 215℃, and 215℃, respectively.

[0100] Following the above testing method, the impact-resistant polypropylene granules were prepared into samples, and then analyzed for MFR, mechanical properties, etc.

[0101] Some experimental parameters and the performance test results of the obtained granules are shown in Table 2.

[0102] Example 2

[0103] This embodiment prepares impact-resistant polypropylene according to the method of Example 1, except that in step (3), tert-butylaminotriethoxysilane (TBATES) is used instead of diethylaminotriethoxysilane (DEATES).

[0104] Example 3

[0105] This embodiment prepares impact-resistant polypropylene according to the method of Example 1, except that in step (3), dicyclohexyldiethylaminosilane (DDMADES) is used instead of diethylaminotriethoxysilane (DEATES).

[0106] Example 4

[0107] This embodiment prepares impact-resistant polypropylene according to the method of Example 1, except that the flow rate of the first external electron donor (diisopropyl dimethoxysilane DIPDMS) in step (1) is 0.1 g / h.

[0108] Example 5

[0109] This embodiment prepares impact-resistant polypropylene according to the method of Example 1, except that the main catalyst in step (1) is DQC-602, which was purchased from Beijing Aoda Company of Sinopec Catalyst Branch. The main catalyst has an LA / SA ratio of 1.22, an average particle diameter (D50) of 56 μm, a specific surface area of ​​289 m2 / g, and a porosity of 0.40 ml / g.

[0110] Example 6

[0111] This embodiment prepares impact-resistant polypropylene according to the method of Example 1, except that in step (2), the hydrogen flow rate is 8 g / h and the hydrogen concentration is 5600 ppmv according to online chromatography. In step (3), the hydrogen volume concentration in the gas-phase fluidized bed reactor is 800-1000 ppmv.

[0112] Comparative Example 1

[0113] This comparative example prepared impact-resistant polypropylene according to the method of Example 1, except that diethylaminotriethoxysilane (DEATES) was not added in step (3).

[0114] Comparative Example 2

[0115] This comparative example prepares impact-resistant polypropylene according to the method of Comparative Example 1, except that in step (2), the hydrogen flow rate is 8 g / h and the hydrogen concentration is 5600 ppmv according to online chromatography. In step (3), the hydrogen volume concentration in the gas-phase fluidized bed reactor is 800-1000 ppmv.

[0116] As shown in Table 2, the embodiments of this invention employ a combination of two different external electron donors and catalysts, enabling the production of polymers with high ethylene and high rubber content in a loop reactor at normal density while simultaneously achieving a low reaction pressure in the gas-phase reactor. This means that this invention does not require reducing the load on the loop reactor to prepare high-rubber phase products. The polymer obtained by this invention maintains good rigidity (flexural modulus) while significantly improving the polymer's impact resistance, exhibiting a good balance between rigidity and toughness.

[0117] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0118]

Claims

1. A method for preparing impact-resistant polypropylene, characterized in that, The preparation method includes: (1) In the presence of a catalyst system, propylene and optionally a first α-olefin are subjected to a prepolymerization reaction; wherein the catalyst system comprises: a main catalyst, a co-catalyst and a first external electron donor; (2) The prepolymerized material from step (1), propylene, hydrogen and optional first α-olefin are brought into contact and polymerized to obtain the matrix polymer. (3) In the presence of the matrix polymer and the second external electron donor, propylene, the second α-olefin and hydrogen are contacted and polymerized to obtain the impact-resistant polypropylene; The second external electron donor is an organosilanes containing nitrogen atoms.

2. The preparation method according to claim 1, wherein, The first external electron donor is at least one of the compounds shown in formula (1); (R1O)(R2O)SiR 3 R 4 Equation (1); In formula (1), R1 and R2 are each independently a hydrocarbon group having 1-10 carbon atoms, preferably a hydrocarbon group having 2-8 carbon atoms, and more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl or methylcyclohexyl; R1 and R2 may be the same or different, preferably the same; R 3 and R 4 Each is independently a hydrocarbon group having 1-16 carbon atoms or a C1-16 hydrocarbon group in which one carbon atom is replaced by a heteroatom; the heteroatom is N, P or S; preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl, methylcyclohexyl, octyl, nonyl, decyl, phenyl, methylphenyl or benzyl; the R 3 and R 4 For the same or different.

3. The preparation method according to claim 1, wherein, The second external electron donor is at least one of the compounds shown in formula (2); (RO) n Si(NR 1 R 2 ) m Formula (2); In formula (2), R is a hydrocarbon group having 1-10 carbon atoms, preferably a hydrocarbon group having 2-8 carbon atoms, and more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl or methylcyclohexyl; n Rs may be the same or different, preferably the same; R 1 R is a hydrocarbon group or hydrogen atom with 1-12 carbon atoms. 2 It is a hydrocarbon group having 1-12 carbon atoms or a C1-12 hydrocarbon group in which one carbon atom is replaced by a heteroatom; said heteroatom is N, P or S; R 1 and R 2 For the same or different, or R 1 and R 2 They can be connected to form a ring structure with N; R 1 and R 2 Each of the following can be independently methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, isopentyl, cyclopentyl, n-hexyl, cyclohexyl, methylcyclopentyl, methylcyclohexyl, octyl, nonyl, decyl, phenyl, methylphenyl or benzyl; n+m=4, where n is 1, 2 or 3, with 2 or 3 being preferred.

4. The preparation method according to claim 1, wherein, The second external electron donor is at least one of dimethylaminotriethoxysilane, diethylaminotriethoxysilane, dimethylaminotrimethoxysilane, diethylaminotrimethoxysilane, diethylaminotri-n-propoxysilane, di-n-propylaminotriethoxysilane, methyl-n-propylaminotriethoxysilane, methylethylaminotriethoxysilane, ethyl-n-propylaminotriethoxysilane, tert-butylaminotriethoxysilane, ethyl isopropylaminotriethoxysilane, bis(cyclohexylamino)dimethoxysilane, bis(cyclohexylamino)diethoxysilane, bis(cyclopentylamino)dimethoxysilane, bis(cyclopentylamino)diethoxysilane, bis(dimethylamino)diethoxysilane, bis(diethylamino)diethoxysilane, bis(diethylamino)dimethoxysilane, and bis(dimethylamino)dimethoxysilane.

5. The preparation method according to claim 1, wherein, The Lewis basicity of the second external electron donor is weaker than that of the first external electron donor; Preferably, the HOMO value of the second external electron donor is at least 0.2 eV higher than the HOMO value of the first external electron donor.

6. The preparation method according to claim 1, wherein, The mass ratio w of the first external electron donor to the second external electron donor is 1:99-95:5, preferably 5:95-60:40; Preferably, the mass ratio w of the first external electron donor and the second external electron donor is negatively correlated with the absolute value F of the HOMO difference between the first external electron donor and the second external electron donor, satisfying the formula: F*w = 0.002-100, preferably 0.01-50, and most preferably 0.01-10.

7. The preparation method according to claim 1, wherein, The main catalyst is a Ziegler-Natta catalyst; The Ziegler-Natta catalyst is spherical or near-spherical, and the ratio of the average major axis to the average minor axis of the Ziegler-Natta catalyst is ≤2, preferably ≤1.6, and most preferably ≤1.

4. Preferably, the average particle diameter D50 of the Ziegler-Natta catalyst is 30-100 μm, more preferably 30-80 μm; Preferably, the specific surface area of ​​the Ziegler-Natta catalyst is 100-500 m². 2 / g, preferably 200-400m 2 / g, with a porosity of 0.1-1.0ml / g, preferably 0.2-0.7ml / g.

8. The preparation method according to claim 1, wherein, The co-catalyst is an alkylaluminum compound, preferably a trialkylaluminum compound, and more preferably at least one selected from triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, and trihexylaluminum.

9. The preparation method according to claim 1, wherein, In step (1), the mass ratio of the co-catalyst to the first external electron donor is (0.5-100):1, preferably (1-50):1; The mass ratio of the co-catalyst to the main catalyst is (0.25-50):1, preferably (2-20):

1.

10. The preparation method according to claim 1, wherein, The mass ratio of the co-catalyst in step (1) to the sum of the amounts of propylene and optional first α-olefin in step (2) is (1 × 10⁻⁶). -5 -1×10 -3 :1, preferably (5×10 -5 -5×10 -3 ):1; In step (2), the volume concentration of hydrogen is 100-100000 ppmv, preferably 1000-50000 ppmv, based on the total gaseous volume of propylene, hydrogen and optional first α-olefin.

11. The preparation method according to claim 1, wherein, In step (2): the first α-olefin is ethylene and / or an α-olefin having 4-10 carbon atoms, preferably at least one of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylisopentene, 1-octene and 1-decene; Based on the total weight of the propylene and the first α-olefin, the amount of the first α-olefin is 0-5 wt%, preferably 0-2 wt%, and the amount of the propylene is 95-100 wt%, preferably 98-100 wt%.

12. The preparation method according to claim 1, wherein, In step (2): the reaction temperature of the polymerization reaction is 30-150℃, preferably 50-100℃; the reaction pressure is 1-8MPa, preferably 1.2-5.5MPa; the reaction residence time is 10-180min, preferably 20-120min; The number of reactors used may be one or more.

13. The preparation method according to claim 1, wherein, In step (3), the volume concentration of hydrogen is 2-30000 ppmv, preferably 10-10000 ppmv, based on the total gaseous volume of propylene, hydrogen and the second α-olefin.

14. The preparation method according to claim 1, wherein, In step (3), the second α-olefin is ethylene and / or an α-olefin having 4-10 carbon atoms, preferably at least one of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methylisopentene, 1-octene and 1-decene; The mass ratio of the second α-olefin to propylene is 5:95-60:40, preferably 10:90-50:

50.

15. The preparation method according to claim 1, wherein, In step (3): the reaction temperature of the polymerization reaction is 30-150℃, preferably 50-100℃; the reaction pressure is 0.5-4.0MPa, preferably 1.0-3.0MPa; the reaction residence time is 10-180min, preferably 20-90min; The number of reactors used may be one or more.

16. The preparation method according to claim 1, wherein, The preparation method further includes step (4): pre-treating the polymer powder obtained by the polymerization reaction in step (3), and then melt-blending, extruding and granulating the pre-treated polymer powder with the additives to obtain the impact-resistant polypropylene; The pretreatment preferably includes steam deactivation and drying; Preferably, the mass concentration of the additive is 500-10000 ppmw, more preferably 500-5000 ppmw, based on the total weight of the pretreated polymer powder and the additive.

17. Impact-resistant polypropylene prepared by the preparation method according to any one of claims 1-16.

18. The impact-resistant polypropylene according to claim 17, wherein, The impact-resistant polypropylene comprises: component a and component b; Component a is a propylene homopolymer and / or a random copolymer of propylene and a first α-olefin; the melt mass flow rate (MFR) of component a at 230°C and 2.16 kg load is ≤100 g / 10 min, preferably 20-100 g / 10 min; Component b is a copolymer of propylene in the rubber phase and a second α-olefin. The copolymer comprises 15-60 wt%, preferably 25-50 wt%, of the second α-olefin by total weight. The second α-olefin is preferably ethylene and / or a C4-C10 α-olefin.

19. The impact-resistant polypropylene according to claim 17, wherein, Based on the total weight of components a and b, the content of component a is 50-90 wt%, preferably 60-80 wt%, and the content of component b is 10-50 wt%, preferably 20-40 wt%.

20. The impact-resistant polypropylene according to claim 17, wherein, The impact-resistant polypropylene has a melt mass flow rate (MFR) of ≤60g / 10min at 230℃ and 2.16kg load, preferably 5-50g / 10min.

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