CN110551242B - Impact-resistant co-polypropylene and preparation method thereof - Google Patents
Impact-resistant co-polypropylene and preparation method thereof Download PDFInfo
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Abstract
The invention provides impact-resistant co-polypropylene and a preparation method thereof. The preparation method of the impact copolymer polypropylene comprises the following steps: adding a main catalyst, a cocatalyst and a modifier into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product; and collecting the solid phase part of the first reaction product, adding the solid phase part into a second gas phase reactor, introducing ethylene, propylene and hydrogen into the second gas phase reactor to carry out a second polymerization reaction, and collecting the solid phase part in the second reaction product to prepare the impact-resistant co-polypropylene, wherein the activity of the main catalyst is 10000-20000 g/g. The preparation method can ensure the long-period stable production of the impact-resistant co-polypropylene, and ensures that the impact strength of the impact-resistant co-polypropylene simple-supported beam is more than or equal to 45kJ/m2The melt index is 14-19 g/10min, the odor grade is less than or equal to 3, and the high-impact middle-melt-index low-odor impact-resistant co-polypropylene is prepared.
Description
Technical Field
The invention relates to a high polymer material processing technology, in particular to impact-resistant co-polypropylene and a preparation method thereof, and especially relates to high-impact-resistant middle-melting-index low-odor impact-resistant co-polypropylene and a preparation process thereof.
Background
Polypropylene (PP) is a thermoplastic synthetic resin with excellent performance, has the advantages of low density, no toxicity, easy processing, high strength, good chemical stability and electrical insulation and the like, and is the product with the best heat resistance in general resins. However, the impact resistance is poor due to the high regularity of the molecular structure and the high glass transition temperature. In order to expand the application range of polypropylene, a second monomer is usually introduced into the basic structure of the polypropylene molecular chain for copolymerization and modification, wherein ethylene is the most commonly used second monomer, and the obtained impact-resistant copolymerized polypropylene (IPC) has further improved impact resistance compared with polypropylene (the name of the impact-resistant copolymerized polypropylene also comes from the fact). In particular to high-impact middle-melting-index low-odor impact-resistant co-polypropylene (namely impact strength of a simply supported beam is more than or equal to 45 kJ/m)2And the impact-resistant copolymerized polypropylene with the melt index of 10g/10 min-20 g/10min and the odor grade of less than or equal to 3), and because the high-impact-resistant medium-melt-index low-odor impact-resistant copolymerized polypropylene has outstanding comprehensive performance, the high-impact-resistant medium-melt-index low-odor impact-resistant copolymerized polypropylene can continuously replace the original metal material and high polymer material in the aspects of household appliances, automobile parts and the like.
At present, the method for producing the impact-resistant copolymerized polypropylene mainly comprises a liquid-gas four-kettle series connection method, a liquid-phase bulk method and the like. The liquid-gas four-kettle series method adopts two liquid phase kettles and two gas phase kettles which are connected in series, wherein the first two liquid phase kettles are used for liquid phase bulk polymerization, and the second two gas phase kettles are used for gas phase bulk polymerization. The liquid-gas four-kettle series connection method is easy to control the proportion of ethylene and propylene when producing the block copolymer, but the method has relatively complex process; the liquid phase bulk method adopts the series connection of a liquid phase reactor and a gas phase reactor, and the product has low impact strength and poor fluidity.
In addition, gas phase polymerization two-step processes, using special synthesis processes and reactors, and using Ziegler-Natta catalyst systems (Z-N catalyst systems) or using modified Z-N catalyst systems, have also been reported. In the first step, propylene monomer is polymerized, and when most of the propylene monomer is consumed, a certain amount of ethylene monomer is added into the reaction kettle to carry out copolymerization. The process method has the advantages of quick polymerization reaction start, short reaction time and the like, but the high-impact middle-melting-index low-odor impact-resistant copolymerized polypropylene material is difficult to obtain. In addition, the method is easy to generate block materials, and the discharge line and the conveying rotary valve of the reaction kettle are easy to block, so that the production of the impact-resistant co-polypropylene is difficult to maintain long-period stable operation.
Therefore, it is particularly desired to develop an industrial production method of high impact-resistant, medium melt-index, low odor impact-resistant copolymerized polypropylene, which can realize stable production over a long period of time and ensure stable product quality.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method of impact-resistant copolymerized polypropylene, which can realize long-period stable production of the impact-resistant copolymerized polypropylene and can obtain the impact-resistant copolymerized polypropylene with high impact resistance, medium melting index and low odor.
The impact-resistant copolymerized polypropylene prepared by the preparation method has the characteristics of high impact strength, proper melt index and low odor.
In order to achieve the above object, the present invention provides, in a first aspect, a method for preparing an impact co-polypropylene, comprising:
adding a main catalyst, a cocatalyst and a modifier into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product;
collecting the solid phase part in the first reaction product, adding the solid phase part into a second gas phase reactor, introducing ethylene, propylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction, collecting the solid phase part in the second reaction product to prepare the impact-resistant co-polypropylene,
wherein the activity of the main catalyst is 10000-20000 g/g.
According to the technical scheme of the invention, the preparation method of the impact-resistant copolymerized polypropylene belongs to an Innovene gas-phase polymerization method. Specifically, the first polymerization reaction is actually a process in which a polypropylene monomer firstly generates an isotactic polypropylene homopolymer through homopolymerization, and by adjusting the reaction conditions of the first polymerization reaction, an ultra-high melt index polypropylene homopolymer with a relatively large molecular weight can be obtained, and the Melt Index (MI) of the ultra-high melt index polypropylene homopolymer can generally reach 110-140 g/10 min. In addition, the first reaction product includes solid phase portions such as a main catalyst, a cocatalyst and a modifier, and gas phase portions such as unreacted propylene and hydrogen. And collecting the solid phase part in the first reaction product, and continuously carrying out second polymerization reaction with propylene, ethylene and hydrogen, wherein in the process, ethylene monomers and propylene monomers carry out copolymerization reaction to generate ethylene-propylene copolymers in the particle pores of the polypropylene homopolymer, thereby finally obtaining the impact copolymer polypropylene. And, by controlling the reaction conditions of the second polymerization reaction, the weight average molecular weight (M) of the impact-resistant copolymerized polypropylene can be adjustedw) And molecular weight distribution index (M)w/Mn) And the melt index and the like, wherein the weight average molecular weight of the final impact-resistant copolymerized polypropylene product can reach 380,000-600,000, and the number average molecular weight (M)n) Can reach 50,000-58,000, and the molecular weight distribution index is 6-10; the melt index is 14-18 g/10 min; the odor grade is less than or equal to 3, so that the high-impact middle-melting-index low-odor impact-resistant co-polypropylene product is obtained.
The inventor of the present invention has found through research and analysis that, in the above process for preparing impact-resistant co-polypropylene, if other catalysts with higher activity are used as main catalysts, for example, catalysts with activity greater than or equal to 35000g/g, a large amount of lump materials are generated in the second gas phase reactor, which may result in undesirable phenomena such as blockage of rotary valves or feed lines. The reason may be that these conventional catalysts have high activity, resulting in faster copolymerization reaction and generation of lumps when highly active ethylene monomer is added. The selection of a catalyst with lower activity, for example, a catalyst with activity less than 10000g/g, is likely to cause the reaction to proceed very slowly, which not only affects the reaction efficiency, but also affects the comprehensive performance of the product. In view of the above, the catalyst with the activity of 10000-20000 g/g is used as the main catalyst, so that the adverse phenomena of stirrer fracture, rotary valve or material conveying pipeline blockage, device shutdown and the like caused by a large amount of lump materials generated by other catalysts with higher activity are avoided, and the problems of the production efficiency and the comprehensive performance of products influenced by low-activity catalysts are avoided, so that the long-period stable production of the impact-resistant co-polypropylene is ensured while the high-impact-resistant middle-melting-index low-odor impact-resistant co-polypropylene is obtained.
In the present invention, the activity of the main catalyst means the amount of product produced per 1g of the main catalyst. The activity of the main catalyst is 10000 g/g-20000 g/g, namely 10000 g-20000 g of high impact-resistant middle melting-referred to as low-odor impact-resistant co-polypropylene can be produced per 1g of the main catalyst.
Specifically, the first polymerization reaction and the second polymerization reaction are respectively completed in two gas phase reactors. It is to be noted that in the description of the present invention, the terms "first gas phase reactor" and "second gas phase reactor" are used only for convenience in describing the different reaction apparatuses, and are not to be understood as indicating or implying relative importance.
It is understood that the first gas phase reactor is connected in series with the second gas phase reactor. The present invention is not limited to the first gas phase reactor and the second gas phase reactor, and a gas phase reactor conventional in the art, such as a horizontal gas phase stirred plug flow reactor, may be used.
The present invention is not particularly limited with respect to the specific manner of collecting the solid phase portion of the first reaction product, and the gas phase and the solid phase of the first reaction product may be separated by a conventional manner in the art. For example, the first reaction product may be fed to a powder delivery system capable of isolating the gas phase portion in the first gas phase reactor and delivering the separated solid phase portion to the second gas phase reactor.
In the present invention, a prepolymerized catalyst, which is obtained by prepolymerizing a titanium-based catalyst containing magnesium with a propylene monomer, can be used as the main catalyst. The magnesium-containing titanium catalyst can be a conventional supported titanium catalyst for polypropylene gas phase polymerization, such as a domestic SPG and imported CDi catalyst using magnesium chloride as a carrier.
Further, in the prepolymerized catalyst, the titanium content may be 0.8 to 3.5% by mass and the magnesium content may be 8 to 20% by mass.
In the specific implementation process of the invention, the used prepolymerized catalyst can be a relatively economic domestic supported titanium catalyst, for example, a Y180 prepolymerized catalyst which is ordered from Riqiu City and science and technology development Co., Ltd, and a titanium catalyst (taking magnesium chloride as a carrier) with the activity of over 35000g/g is prepolymerized with a propylene monomer by a manufacturer, so that the outer surface of the titanium catalyst particle is coated with a layer of polypropylene, and the activity of the obtained Y180 prepolymerized catalyst is about 16000 g/g.
The cocatalyst is used for improving the activity, selectivity, antitoxic property or stability of the main catalyst. In the present invention, the cocatalyst used may be an alkyl aluminum, specifically Triethylaluminum (TEAL), and its molecular formula is (C)2H5)3Al。
The proportion of the aluminum element in the cocatalyst and the magnesium element in the main catalyst is reasonably controlled, so that the main catalyst has good activity and stability, and the reactivity ratio of the ethylene monomer and the propylene monomer in the second polymerization reaction process is influenced by the stable residual activity of the catalyst. In the specific implementation process of the invention, the molar ratio of aluminum in the cocatalyst to magnesium in the prepolymerized catalyst is (2-10): 1, further (2-8): 1, generally controlling the following steps: 1, such as (5-7): 1.
in the present invention, the modifier used may be selected from modifiers (external electron donors) commonly used in the gas phase polymerization of propylene. Specifically, the modifier used may be at least one selected from diisobutyldimethoxysilane (DIBDMS, Donor B), diisopropyldimethoxysilane (DIPDMS, Donor P) and n-Propyltriethoxysilane (n-Propyltriethoxysilane), and the molar ratio between aluminum in the cocatalyst and silicon in the modifier is generally controlled to be (1 to 10): 1.
in the specific implementation process of the invention, n-propyltriethoxysilane is selected as a modifier, and the molar ratio of aluminum in the cocatalyst to silicon in the n-propyltriethoxysilane is generally controlled to be (1-8): 1, typically (2-7): 1, such as (5-7): 1, ultimately resulting in a resulting impact co-polypropylene having higher impact strength and higher melt index.
In the present invention, the amount of hydrogen introduced can be used to adjust the melt index (otherwise known as melt flow rate) of the impact co-polypropylene product. Therefore, the whole process can be controlled by adjusting the adding amount of the hydrogen. Specifically, in the process of the first polymerization reaction, the molar ratio of hydrogen to propylene can be controlled to be (5-10): 1, such as (5-9): 1, further (6-9): 1.
in the process of the second polymerization reaction, the molar ratio of hydrogen to ethylene to propylene is controlled to be (0.5-3): (20-50): 1. specifically, the molar ratio of hydrogen to propylene is usually controlled to be (0.8-2.8): 1, further (1.0-2.7): 1, further (1.0 to 2.5): 1.
the rigidity and toughness of the impact copolymer polypropylene can be controlled by further adjusting the ratio of ethylene to propylene, and the molar ratio of ethylene to propylene can be controlled to be (24-45): 1, further (30-40): 1, so that the impact-resistant copolymerized polypropylene product has good rigidity and toughness.
It is understood that the reaction rate and the properties of the final product can be influenced by reasonably controlling the conditions of reaction temperature, pressure and the like. In the present invention, it is also possible to adjust the length of the reaction time by controlling the level of the powder, that is, to control the reaction time of the first polymerization reaction and the second polymerization reaction by controlling the level of the powder.
In the specific implementation process of the invention, the temperature of the first polymerization reaction can be controlled to be 60-70 ℃, the absolute pressure is 2.0-2.3 MPa, and the material level of the powder is optimally 68-73%, so that the homopolymerized polypropylene powder can be regarded as the completion of the first polymerization reaction after the homopolymerized polypropylene powder maintains the retention time of about 1 h. The temperature of the second polymerization reaction can be controlled to be 65-73 ℃, the absolute pressure is 2.0-2.3 MPa, and the material level of the powder is 68-73%, so that the polypropylene copolymer powder can be maintained for about 1 hour of residence time, and the second polymerization reaction can be considered to be completed.
Furthermore, the temperature and the powder material level in the second polymerization reaction process can be respectively not lower than those in the first polymerization reaction, so that more macromolecular polypropylene chains can be generated in the second polymerization reaction process, and the impact resistance of the product is improved.
The invention is not particularly limited as to how the solid portion of the second reaction product is made into the impact co-polypropylene, and can be accomplished by means of conventional techniques in the art. In the specific implementation process of the invention, the preparation method further comprises the steps of devolatilizing, inactivating and granulating the second reaction product to obtain the impact-resistant co-polypropylene. Wherein devolatilization refers to the removal of low molecular weight hydrocarbon components from the polymer system; deactivation refers to deactivation of the procatalyst; the granulation can be carried out by a conventional apparatus such as an extruder.
Another aspect of the present invention is to provide an impact co-polypropylene, which is prepared by the above-mentioned preparation method.
According to the preparation method provided by the invention, through two times of polymerization reaction, the impact-resistant copolymerized polypropylene powder finally prepared accounts for 75-90% of particles with the particle size larger than 800 microns, the mass content of ethylene is 12.5-22%, the weight-average molecular weight reaches 380,000-600,000, and the molecular weight distribution index is 6-10. Therefore, the impact-resistant co-polypropylene has very outstanding comprehensive performance, and the impact strength of a simply supported beam is more than or equal to 45kJ/m2Tensile yield stress of not less than 17.5MPa, flexural modulus of not less than 820MPa, melt index of 14-19 g/10min, odor and the likeThe grade is less than or equal to 3, so that the material can be well used for replacing the original metal materials and high polymer materials in automobile parts, household appliances and the like, for example, the material can be used as the processing raw material of automobile interior parts.
And the impact-resistant co-polypropylene has wider molecular weight distribution, and is further favorable for being processed into automobile parts or functional parts of household appliances due to good processing performance.
The preparation method of the impact-resistant copolymerized polypropylene provided by the invention utilizes two serially connected gas-phase reactors to prepare the impact-resistant copolymerized polypropylene and adopts the main catalyst with low activity, thereby solving the problems of blockage of a rotary valve or a material conveying pipeline, shutdown of a device and the like caused by a large amount of lump materials generated by the existing high-activity catalyst in the gas-phase reaction process, and realizing the long-period stable production of the impact-resistant copolymerized polypropylene.
In addition, the impact-resistant co-polypropylene prepared by the preparation method has the impact strength of a simply supported beam of more than or equal to 45kJ/m2The tensile yield stress is more than or equal to 17.5MPa, the flexural modulus is more than or equal to 820MPa, the melt index is 14-19 g/10min, and the odor grade is less than or equal to 3, so that the high-impact-resistance middle-melting-index low-odor impact-resistance co-polypropylene is obtained, the particle size of the high-impact-resistance middle-melting-index low-odor impact-resistance co-polypropylene is 75-90% of 800 mu m, the mass content of ethylene is 12.5-22%, the weight average molecular weight is 380,000-600,000, and the molecular weight distribution index is 6-10, so that the impact-resistance co-polypropylene has very outstanding comprehensive performance and can be widely used for preparing automobile parts and functional parts of household appliances.
Meanwhile, the whole preparation process is simple, the selection of a modifier and the proportioning of a catalyst can be optimized, and the process conditions such as reaction temperature, pressure, raw material ratio and the like can be flexibly set, so that the whole process production process is controllable. Therefore, the preparation method is suitable for large-scale popularization and application.
The impact-resistant co-polypropylene provided by the invention has very outstanding comprehensive performance, and the impact strength of a simply supported beam is more than or equal to 45kJ/m2Tensile yield stress of not less than 17.5MPa, flexural modulus of not less than 820MPa, melt index of 14-19 g/10min, odor and the likeThe grade is less than or equal to 3, so the polypropylene copolymer has the advantages of high ethylene content (12.5-22%), wide molecular weight distribution (6-10), large weight average molecular weight (380,000-600,000) and moderate particle size (75-90% of the particle size larger than 800 mu m), and has good toughness and processability.
Particularly, the impact-resistant co-polypropylene has the odor grade of less than or equal to 3, meets the requirements of the automotive interior part odor experimental standard PV3900 and the new national standard passenger in-vehicle air quality evaluation guideline, has the characteristic of environmental protection, and can be used as a processing raw material of the automotive interior part.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The main catalysts used in the following examples are all prepolymerized catalysts, which were purchased from Rituer City & lt & gt and science and technology development Co., Ltd, and have a product type of Y180 and an activity of 16000g/g or so.
In the following examples, the melt index is determined by reference to the GB/T3682.1-2018 determination of melt Mass Flow Rate (MFR) and melt volume flow Rate (MVR) of thermoplastics; the tensile yield stress is carried out according to the standard GB/T1040.1-2006 determination of the tensile property of plastics; the flexural modulus is determined according to the standard of GB/T9341-2008 determination of the flexural property of plastics; the impact strength of the simply supported beam is determined according to the standard of GB/T1043.1-2008 determination of the impact performance of the plastic simply supported beam; the molecular weight and molecular weight distribution were determined according to ASTM D6474-2012 test method for determining polyolefin molecular weight distribution and molecular weight average by high temperature gel permeation chromatography; the odor grade test is carried out according to the automotive interior part odor test standard PV 3900; the particle size is measured according to the sieve method.
Example 1
This example provides a method for preparing an impact-resistant co-polypropylene, comprising the following steps:
1. first polymerization reaction
Adding a prepolymerization catalyst, a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg between the aluminum in the triethyl aluminum and the magnesium in the prepolymerized catalyst is 7: 1, the molar ratio Al/Si between the aluminium in the triethylaluminium and the silicon in the modifier silane is 7: 1, molar ratio of hydrogen to propylene of 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 113g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is 2: 1, the molar ratio of ethylene to propylene being 40: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, deactivating the devolatilized second reaction product to deactivate the prepolymerized catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene blocks, the adhesive and the fine powder are less, and the production is stable.
The impact-resistant co-polypropylene prepared in this example was tested to have a melt index (2.16kg, 230 ℃) of 15g/10min, a tensile yield stress of 17.5MPa, a flexural modulus of 821MPa, and a simple beam impact strength (23 ℃) of 61kJ/m2The weight average molecular weight is 453,682, the molecular weight distribution index is 7.9, the odor grade is 3.0, and the ethylene mass content is 14.4%; and the impact copolymerized polypropylene powder has particle size greater than 800 microns accounting for 85.4%, see Table 1 for specific results.
Example 2
This example provides a method for preparing an impact-resistant co-polypropylene, comprising the following steps:
1. first polymerization reaction
Adding a prepolymerization catalyst, a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg between the aluminum in the triethyl aluminum and the magnesium in the prepolymerized catalyst is 7: 1, the molar ratio Al/Si between the aluminum in the triethyl aluminum and the silicon in the modifier is 7: 1, molar ratio of hydrogen to propylene of 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 114g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is 2: 1, the molar ratio of ethylene to propylene being 35: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, deactivating the devolatilized second reaction product to deactivate the prepolymerized catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene blocks, the adhesive and the fine powder are less, and the production is stable.
The impact-resistant polypropylene copolymer prepared in the example was tested to have a melt index (2.16kg, 230 ℃) of 15g/10min, a tensile yield stress of 18.6MPa, a flexural modulus of 905MPa, and a simple beam impact strength (23 ℃) of 52kJ/m2The weight average molecular weight is 422,043, the molecular weight distribution index is 6.8, the odor grade is 3.0, and the ethylene mass content is 13.3%; and the impact copolymerized polypropylene powder has particle size greater than 800 microns accounting for 85.1%, and the specific results are shown in Table 1.
Example 3
This example provides a method for preparing an impact-resistant co-polypropylene, comprising the following steps:
1. first polymerization reaction
Adding a prepolymerization catalyst, a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg between the aluminum in the triethyl aluminum and the magnesium in the prepolymerized catalyst is 7: 1, the molar ratio Al/Si between the aluminum in the triethyl aluminum and the silicon in the modifier is 7: 1; the molar ratio of hydrogen to propylene was 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 115g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is 2: 1, the molar ratio of ethylene to propylene being 32: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, deactivating the devolatilized second reaction product to deactivate the prepolymerized catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene blocks, the adhesive and the fine powder are less, and the production is stable.
The impact-resistant co-polypropylene prepared in the example was tested to have a melt index (2.16kg, 230 ℃) of 15g/10min, a tensile yield stress of 19.8MPa, a flexural modulus of 948MPa, and a simple beam impactThe impact strength (23 ℃) was 49kJ/m2The weight average molecular weight is 391,733, the molecular weight distribution index is 6.5, the odor grade is 2.9, and the ethylene mass content is 12.9%; and the impact copolymerized polypropylene powder has particle size greater than 800 microns accounting for 85.6%, see Table 1 for specific results.
Example 4
This example provides a method for preparing an impact-resistant co-polypropylene, comprising the following steps:
1. first polymerization reaction
Adding a prepolymerization catalyst, a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg between the aluminum in the triethyl aluminum and the magnesium in the prepolymerized catalyst is 7: 1, the molar ratio Al/Si between the aluminum in the triethyl aluminum and the silicon in the modifier is 7: 1, molar ratio of hydrogen to propylene of 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 114g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is controlled to be 2: 1, the molar ratio of ethylene to propylene being 30: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, deactivating the devolatilized second reaction product to deactivate the prepolymerized catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene blocks, the adhesive and the fine powder are less, and the production is stable.
The impact-resistant co-polypropylene prepared in this example was tested to have a melt index (2.16kg, 230 ℃) of 15g/10min, a tensile yield stress of 21.3MPa, a flexural modulus of 978MPa, and a simple beam impact strength (23 ℃) of 45kJ/m2The weight average molecular weight is 383,928, the molecular weight distribution index is 6.0, the odor grade is 2.9, and the ethylene mass content is 12.7%; and the impact copolymerized polypropylene powder has particle size greater than 800 microns accounting for 85.5%, see Table 1 for specific results.
Example 5
This example provides a method for preparing an impact-resistant co-polypropylene, comprising the following steps:
1. first polymerization reaction
Adding a prepolymerization catalyst, a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg of aluminum in the triethyl aluminum to magnesium in the prepolymerized catalyst is 7: 1, the molar ratio of aluminum in triethyl aluminum to silicon in modifier silane, Al/Si, is 7: 1, molar ratio of hydrogen to propylene of 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 112g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is 2: 1, the molar ratio of ethylene to propylene being 38: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, deactivating the devolatilized second reaction product to deactivate the prepolymerized catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene blocks, the adhesive and the fine powder are less, and the production is stable.
The impact-resistant co-polypropylene prepared in this example was tested to have a melt index (2.16kg, 230 ℃) of 15g/10min, a tensile yield stress of 18.1MPa, a flexural modulus of 875MPa, and a simple beam impact strength (23 ℃) of 58kJ/m2The weight average molecular weight is 432,986, the molecular weight distribution index is 7.2, the odor grade is 3.0, and the ethylene mass content is 13.6%; and the impact copolymerized polypropylene powder has particle size greater than 800 microns accounting for 85.8%, see Table 1 for specific results.
TABLE 1 results of measurements of the properties of the first reaction product and of the impact-resistant copolymerized polypropylene in the examples
As shown in Table 1, the preparation method provided by the invention can be used for preparing the high-impact-resistance middle-melting-index low-odor impact-resistance co-polypropylene, and has the advantages of high ethylene content, wide molecular weight distribution, large weight average molecular weight and moderate particle size, so that the high-impact-resistance middle-melting-index low-odor impact-resistance co-polypropylene has the characteristics of low odor, wide molecular weight distribution, high melting temperature, high impact strength, excellent injection molding processability and the like.
Comparative example 1
The comparative example provides a preparation method of impact-resistant co-polypropylene, which comprises the following steps:
1. first polymerization reaction
Adding a catalyst P100 (purchased from an Enlish group), a cocatalyst triethyl aluminum and a modifier n-propyl triethoxysilane into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product.
Wherein the molar ratio Al/Mg of aluminum in the triethyl aluminum to magnesium in the P100 catalyst is 4: 1, the molar ratio of aluminum in triethyl aluminum to silicon in modifier silane, Al/Si, is 6: 1, molar ratio of hydrogen to propylene of 9: 1;
the temperature of the first polymerization reaction was 64 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
2. Separating the first reaction product
The first reaction product in the first gas phase reactor is sent to a powder conveying system, so that the gas phase part in the first reaction product is separated to obtain the solid phase part in the first reaction product.
The solid fraction was tested and had a melt index (2.16kg, 230 ℃) of 113g/10min, see in particular Table 1.
3. Second polymerization reaction
And adding the solid phase part in the first reaction product into a second gas phase reactor which is connected with the first gas phase reactor in series, and introducing propylene, ethylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction to obtain a second reaction product.
Wherein the molar ratio of hydrogen to propylene is 2: 1, the molar ratio of ethylene to propylene is 18: 1;
the temperature of the second polymerization reaction was 66 ℃, the absolute pressure was 2.2MPa, and the powder level was 70%.
4. Devolatilizing, inactivating and granulating
Devolatilizing the second reaction product to remove low molecular weight components from the second reaction product; subsequently, the devolatilized second reaction product is subjected to a deactivation treatment to deactivate the polymerization catalyst; and finally, granulating by adopting an extruder to obtain the impact-resistant co-polypropylene.
In addition, in the preparation process of the impact-resistant co-polypropylene, the polypropylene block material and the adhesive material are few, the fine powder is more, and the tube pass blockage of the heat exchanger is easy to cause.
The impact-resistant copolymerized polypropylene prepared in the comparative example was examined to find that it had a melt index (2.16kg, 230 ℃ C.) of 14g/10min, a tensile yield stress of 23.1MPa, a flexural modulus of 1190MPa, and a simple beam impact strength (23 ℃ C.) of 23kJ/m2The weight average molecular weight is 242,986, the molecular weight distribution index is 4.2, the odor grade is 3.5, and the ethylene mass content is 7.1%; and the particle diameter of the impact copolymerization polypropylene powder is larger than 800 mu m and accounts for 37.6 percent, the specific results are shown in Table 1, so that the high-impact middle-melting low-odor impact copolymerization polypropylene is not obtained, and the weight average molecular weight, the molecular weight distribution index, the ethylene content and the proportion of the particle diameter larger than 800 mu m are all smaller than the products in the above examples.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A method for preparing impact copolymer polypropylene, which is characterized by comprising the following steps:
adding a main catalyst, a cocatalyst and a modifier into a first gas phase reactor, and introducing propylene and hydrogen into the first gas phase reactor to perform a first polymerization reaction to obtain a first reaction product;
collecting the solid phase part in the first reaction product, adding the solid phase part into a second gas phase reactor, introducing ethylene, propylene and hydrogen into the second gas phase reactor to carry out second polymerization reaction, collecting the solid phase part in the second reaction product to prepare the impact-resistant co-polypropylene,
wherein the activity of the main catalyst is 10000-20000 g/g;
in the process of the first polymerization reaction, controlling the molar ratio of hydrogen to propylene to be (5-10): 1, the material level of the powder is 68-73%;
in the process of the second polymerization reaction, the molar ratio of hydrogen to ethylene to propylene is controlled to be (0.5-3): (20-50): 1;
the main catalyst is a prepolymerization catalyst, and the prepolymerization catalyst is obtained by prepolymerization of a magnesium-containing titanium catalyst and a propylene monomer;
the modifier is an alkoxy silane compound.
2. The preparation method according to claim 1, wherein the cocatalyst is an aluminum alkyl, and the molar ratio of aluminum in the cocatalyst to magnesium in the prepolymerized catalyst is (2-10): 1.
3. the preparation method according to claim 2, wherein the molar ratio of the aluminum in the cocatalyst to the silicon in the modifier is (1-10): 1.
4. the production method according to any one of claims 1 to 3, wherein the temperature of the first polymerization reaction is controlled to 60 to 70 ℃ and the absolute pressure is controlled to 2.0 to 2.3 MPa.
5. The process according to any one of claims 1 to 3, wherein the temperature of the second polymerization reaction is controlled to 65 to 73 ℃ and the absolute pressure is controlled to 2.0 to 2.3MPa, and the powder level is controlled to 68 to 73%.
6. The process according to claim 4, wherein the temperature of the second polymerization reaction is controlled to 65 to 73 ℃, the absolute pressure is 2.0 to 2.3MPa, and the powder level is controlled to 68 to 73%.
7. The method of claim 1, further comprising: and carrying out devolatilization, inactivation and granulation on the solid phase part in the collected second reaction product to prepare the impact-resistant co-polypropylene.
8. An impact-resistant polypropylene copolymer, characterized by being produced by the production process according to any one of claims 1 to 7.
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