Polyolefin catalyst prepolymerization method, polyolefin catalyst composition and application thereof

Abstract

The invention relates to the field of polyolefin, and discloses a polyolefin catalyst prepolymerization method, a polyolefin catalyst composition and application of the polyolefin catalyst composition. The method comprises the following steps: (1) in a first prepolymerization reactor, mixing a polymeric monomer a with a first prepolymerization catalyst component to carry out a first prepolymerization reaction; (2) continuously conveying a product obtained in the step (1) into a second prepolymerization reactor, and contacting the product with a second prepolymerization catalyst component and a polymerization monomer b to carry out a second prepolymerization reaction; wherein the prepolymerization multiplying power REP1 in the first prepolymerization reactor is less than or equal to 35 times under the condition of the first prepolymerization reaction. According to the method disclosed by the invention, the melting temperature, crystallization temperature and long-period thickness of the polymer and the flexural modulus of the polymer can be remarkably improved, a nucleating agent does not need to be added in the subsequent processing process, and meanwhile, the obtained polymer is more stable in performance parameter and more stable in quality.

Description

Technical Field

[0001] The invention relates to the field of polyolefins, and in particular to a method for prepolymerization of a polyolefin catalyst, a polyolefin catalyst composition and applications thereof. Background Art

[0002] In order to solve or improve the problems of existing polyolefin catalysts and their polymers being easy to break and agglomerate, the process control means of catalyst prepolymerization has been widely used. For example, some Hypol polypropylene processes and Horizone gas phase polypropylene processes use intermittent prepolymerization, and the slurry after prepolymerization is continuously passed into the main reactor. The Spheripol polypropylene process and ST polypropylene process use continuous methods for prepolymerization. Compared with intermittent prepolymerization, continuous prepolymerization can simplify the operating steps, avoid the possibility of unstable quality between batches caused by intermittent prepolymerization, and achieve stable production of the device. The prepolymerization stage is also often used for functional modification of polymers, such as the preparation of in-situ nucleated polymers, in-situ antioxidant polymers, and branched polymers.

[0003] Methods for preparing polymers with self-nucleating effect through polymerization process include: preparation of polyolefin catalysts with nucleating effect, pretreatment of polyolefin catalysts for nucleation modification, addition of nucleating agents during polymerization process, etc. CN114773506A discloses adding α-nucleating agent polymers during catalyst preparation process for preparing self-nucleating polypropylene products. CN1106409C and WO0068315A1 disclose two methods for preparing polypropylene with nucleating effect through polymerization process, one of which is to pretreat vinyl compounds with Ziegler-Natta catalysts to obtain pretreated catalysts with nucleating effect, and then send the pretreated catalysts to a reactor for polymerization to obtain self-nucleating polypropylene; the other is to introduce polymers of vinyl compounds into the polymerization process to prepare self-nucleating polypropylene.

[0004] Whether it is through the method of catalyst preparation or catalyst pretreatment, it is an intermittent batch operation, and the instability of catalyst quality between each batch will have a great impact on the final polymer performance. Although adding the finished nucleating agent in the continuous reaction process solves the problem of unstable batch quality, it also brings about the problems of poor dispersion of the nucleating agent and poor nucleation effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a method for prepolymerization of a polyolefin catalyst and a polyolefin catalyst composition and application thereof.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for prepolymerization of a polyolefin catalyst, wherein the method comprises:

[0007] (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction;

[0008] (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerization monomer b to carry out a second prepolymerization reaction;

[0009] Wherein, the conditions of the first prepolymerization reaction are such that the prepolymerization ratio REP1 in the first prepolymerization reactor is ≤35 times.

[0010] A second aspect of the present invention provides a polyolefin catalyst composition, which is prepared by the above method.

[0011] The third aspect of the present invention provides use of the above-mentioned polyolefin catalyst composition in the preparation of polyolefin.

[0012] A fourth aspect of the present invention provides a method for preparing polyolefins, the method further comprising: mixing the above-mentioned polyolefin catalyst composition with a polymerization monomer c for polymerization.

[0013] Through the above technical scheme, the method of the present invention can significantly improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer under the condition of lower raw material dosage, and no nucleating agent needs to be added in the subsequent processing process. At the same time, compared with the method of intermittent pretreatment of the catalyst and the polymerization monomer a, the polymer obtained by the method of the present invention has more stable performance parameters and more stable quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the polymerization reaction of Example 1.

[0015] Description of Reference Numerals

[0016] 01, first prepolymerization reactor; 02, second prepolymerization reactor; 03, main reactor; 101, catalyst composition; 102, first material flow containing polymerization monomer a; 103, first prepolymerization reactor refrigerant inlet; 104, first prepolymerization reactor refrigerant outlet; 201, first prepolymerization catalyst slurry; 202, second material flow containing polymerization monomer b; 203, second prepolymerization reactor refrigerant inlet; 204, second prepolymerization reactor refrigerant outlet; 301, second prepolymerization catalyst slurry; 302, main reactor outlet. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] A first aspect of the present invention provides a method for prepolymerization of a polyolefin catalyst, wherein the method comprises:

[0019] (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction;

[0020] (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerization monomer b to carry out a second prepolymerization reaction;

[0021] Wherein, the conditions of the first prepolymerization reaction are such that the prepolymerization ratio REP1 in the first prepolymerization reactor is ≤35 times, and can be 1 times, 5 times, 10 times, 20 times, 30 times, 35 times or a range formed by any two of the above values ​​and a value within the range.

[0022] In the present invention, the polymerized monomer a and the polymerized monomer b may be the same or different, and are preferably different.

[0023] In the present invention, the terms "prepolymerization" and "prepolymerization" used refer to a polymerization reaction carried out to achieve a lower reaction rate and monomer conversion rate than the reaction rate and monomer conversion rate under normal polymerization conditions. "Prepolymerization ratio" refers to the ratio of the mass of the polymer produced in the prepolymerization reactor to the mass of the main catalyst. The prepolymerization ratio in the first prepolymerization reaction is expressed by the formula: the mass of the polymer produced in the first prepolymerization / the mass of the main catalyst; the prepolymerization ratio in the second prepolymerization reaction is expressed by the formula: the mass of the polymer produced in the second prepolymerization / the mass of the main catalyst. "Time" refers to the average residence time of the polyolefin catalyst in the prepolymerization reactor, which is expressed by the formula: reactor volume / volume flow rate of the medium entering the reactor.

[0024] In the present invention, in order to maintain a high melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer and reduce the amount of raw materials used, the prepolymerization ratio REP1 in the first prepolymerization reactor is ≤20 times, preferably ≤15 times.

[0025] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the conditions of the second prepolymerization reaction are such that the prepolymerization ratio REP2 in the second prepolymerization reactor is 1-1000 times, which can be 1 times, 5 times, 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, 100 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, 550 times, 600 times, 650 times, 700 times, 750 times, 800 times, 850 times, 900 times, 950 times, 1000 times, preferably 5-800 times, more preferably 10-500 times or the range formed by any two of the above values ​​and the value within the range.

[0026] In the present invention, in order to further increase the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, REP1≤REP2; preferably, REP1 / REP2≤0.5, more preferably REP1 / REP2≤0.2.

[0027] In the present invention, in order to further increase the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, 1 times ≤ REP1+REP2 ≤ 1000 times, more preferably 10 times ≤ REP1+REP2 ≤ 1000 times, and further preferably 50 times ≤ REP1+REP2 ≤ 800 times.

[0028] In the present invention, the second prepolymerization reaction is directly carried out after the first prepolymerization reaction is completed. Preferably, the method does not include cooling and / or drying operations between step (1) and step (2).

[0029] In the present invention, in order to make the first prepolymerization ratio and the second prepolymerization ratio within the above range, in actual operation, the conditions of the first prepolymerization reaction preferably include: temperature of -20-90°C, preferably 10-70°C; time of 1-36h, preferably 3-20h; pressure of 0.1-10MPaG, preferably 0.5-5MPaG. The conditions of the second prepolymerization reaction preferably include: temperature of -30-100°C, preferably -10-70°C; pressure of 0.1-10MPaG, preferably 0.5-5MPaG; time ≤2h, preferably 1-90min.

[0030] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the structural formula of the polymerized monomer a is CH2=CR1R2, wherein R1 and R2 are independently hydrogen, substituted or unsubstituted chain carbon-containing groups, substituted or unsubstituted cyclic carbon-containing groups, substituted or unsubstituted aromatic ring groups or substituted or unsubstituted condensed ring groups; preferably, when R1 is hydrogen, R2 is different from R1. More preferably, the chain carbon-containing group contains 4-20 carbon atoms; the aromatic ring group or condensed ring group contains 6-20 carbon atoms, preferably 6-16 carbon atoms; the cyclic carbon-containing group contains 3-12 carbon atoms.

[0031] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the polymerized monomer a is at least one of vinyl compounds containing cyclic alkyl, aromatic or branched alkyl groups; preferably, the polymerized monomer a is selected from at least one of vinyl cyclohexane, styrene, vinyl cyclopentane, vinyl-2-methylcyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene and 4-methyl-1-pentene.

[0032] In the present invention, the first prepolymerization reaction system also includes an inert solvent, which does not participate in the polymerization reaction, and is selected from at least one of oils and fats and hydrocarbon compounds; preferably, the carbon number of the oils and fats is 8-40; more preferably, the carbon number of the hydrocarbon compound is 2-16, and more preferably 3-10; further preferably, the hydrocarbon compound is selected from at least one of propane, n-butane, isobutane, n-pentane, isopentane, n-hexane and cyclohexane.

[0033] In the present invention, the first prepolymerization reactor can be in various forms, such as a kettle reactor, a tubular reactor, or even a pipeline reactor. Any container that meets the above operating conditions can be defined as the first prepolymerization reactor, preferably a tubular reactor or a pipeline reactor.

[0034] In the present invention, the first prepolymerization reaction can even be carried out in a continuous pre-complexing reactor. Pre-complexing reactors are well known to those skilled in the art.

[0035] In the present invention, each of the catalyst components may be added to the first prepolymerization reactor separately, or may be added to the first prepolymerization reactor after being mixed.

[0036] In the present invention, the polymerizable monomer a can be added to the first prepolymerization reactor alone, or the polymerizable monomer can be added to the first prepolymerization reactor after being mixed and contacted with the above-mentioned catalyst components in a pipeline. Preferably, the polymerizable monomer a is added to the first prepolymerization reactor after being mixed and contacted with the above-mentioned catalyst components in a pipeline.

[0037] In the present invention, the first prepolymerization reaction system has a kinematic viscosity of 1-500 mm at 40°C. 2 / s, preferably 10-300mm 2 / s. The measurement method for kinematic viscosity of liquid system is GB / T 10247-2008.

[0038] In the present invention, the second prepolymerization reaction system further comprises an inert solvent, which has been described above and will not be described in detail here.

[0039] In the present invention, in order to adjust the molecular weight, the first prepolymerization reactor and the second prepolymerization reactor may further contain hydrogen.

[0040] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the first prepolymerization catalyst component includes a main catalyst, an optional first impurity remover and an optional first external electron donor; more preferably, the weight ratio of the polymerization monomer a to the main catalyst is 1:0.01-0.5, and can be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5 or the range formed by any two of the above values ​​and the value within the range.

[0041] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the weight ratio of the polymerized monomer a to the first impurity remover is 1:0.01-1, and can be 1:0.01, 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 or the range formed by any two of the above values ​​and the value within the range.

[0042] In the present invention, in order to further increase the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the weight ratio of the polymerized monomer a and the first external electron body is 1:0.001-0.1, and can be 1:0.001, 1:0.005, 1:0.01, 1:0.05, 1:0.1 or the range formed by any two of the above values ​​and the value within the range.

[0043] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the weight ratio of the polymerized monomer a to the polymerized monomer b is 1:10. 2 -10 4 , can be 1:(1×10 2 )、1:(2×10 2 )、1:(4×10 2 )、1:(6×10 2 )、1:(8×10 2 )、1:(1×10 3 )、1:(2×10 3 )、1:(4×10 3 )、1:(6×10 3 )、1:(8×10 3 )、1:(1×10 4 ) or the range formed by any two of the above values ​​and the values ​​within the range.

[0044] Preferably, relative to the first prepolymerization reactor with a volume of 3L, the flow rate of the polymerization monomer a is 0.2-5g / hr; preferably, relative to the second prepolymerization reactor with a volume of 5L, the flow rate of the polymerization monomer b is 5-30kg / hr.

[0045] In the present invention, in actual operation, the polymerizable monomer a, the main catalyst, the first impurity remover and the first external electron donor are input in the form of a solution, wherein the concentration of the main catalyst in the main catalyst solution is 0.01-0.5 g / mL, the concentration of the first impurity remover in the first impurity remover solution is 5-15wt%, and the concentration of the external electron donor in the first external electron donor solution is 5-15 g / mL. The solvent is an inert solvent. Preferably, the first impurity remover and the first external electron donor are delivered in the form of pure components.

[0046] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the main catalyst is selected from at least one of a Ziegler-Natta catalyst, a chromium-based catalyst, a vanadium-based catalyst and a metallocene catalyst, and is more preferably a Ziegler-Natta catalyst and / or a metallocene catalyst.

[0047] In the present invention, in order to further increase the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the second prepolymerized catalyst component includes a second impurity-removing agent and a second external electron donor. Preferably, based on the total weight of the first impurity remover and the second impurity remover, the amount of the first impurity remover is 1-99 weight%, which can be 1 weight%, 5 weight%, 10 weight%, 20 weight%, 30 weight%, 40 weight%, 50 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight%, 99 weight% or the range formed by any two of the above values ​​and the value within the range, more preferably 5-90 weight%. Further preferably, based on the total weight of the first external electron donor and the second external electron donor, the amount of the first external electron donor is 1-100 weight%, which can be 1 weight%, 5 weight%, 10 weight%, 20 weight%, 30 weight%, 40 weight%, 50 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight%, 100 weight% or the range formed by any two of the above values ​​and the value within the range, more preferably 5-90 weight%.

[0048] In the present invention, the first impurity remover and the second impurity remover are Group IIIA metal compounds, preferably aluminum compounds, and the aluminum compound can be appropriately selected from alkyl aluminum, alkyl aluminum halide, alkoxy aluminum, alkyl alkoxy aluminum or alkoxy aluminum halide compounds, more preferably trialkyl aluminum, most preferably at least one of triethyl aluminum, triisobutyl aluminum and tri-n-butyl aluminum. The first impurity remover and the second impurity remover are the same or different.

[0049] In the present invention, when the first prepolymerization catalyst component is a Ziegler-Natta type catalyst component, the catalyst component comprises: (1) a main catalyst (Ziegler-Natta type catalyst): a support-type solid catalyst containing an internal electron donor and an active component titanium; (2) an optional first impurity remover (which simultaneously performs the functions of co-catalysis and impurity removal), wherein the first impurity remover is a Group IIIA metal compound, preferably an aluminum compound, and the aluminum compound can be appropriately selected from alkyl aluminum, alkyl aluminum halide, alkyl alkoxy aluminum, alkyl alkoxy aluminum or alkoxy aluminum halide compounds, more preferably trialkyl aluminum; (3) an optional first external electron donor.

[0050] In the present invention, the first external electron donor and the second external electron donor are organic silicon compounds, which are at least one of compounds of the general formula (R3)aSi(OR4)b, wherein a and b are independently selected from any integer of 0-4, and a+b=4.

[0051] Wherein R3 is selected from C1-C6 straight chain carbon-containing groups, C1-C6 branched chain carbon-containing groups, C3-C8 cyclic carbon-containing groups, C5-C 12aryl or heteroaryl. When there are non-carbon atoms, R3 is preferably a C1-C6 straight chain alkyl, C1-C6 branched chain alkyl, C3-C8 cycloalkyl, C5-C12 heteroaryl substituted with F, Cl or Br atoms, or a C1-C6 straight chain group, C1-C6 branched chain group, C3-C8 cycloalkyl group containing atoms such as B, N, P or O, and the heteroatoms such as B, N, P or O can be directly connected to the Si atom. When a≥2, multiple R3s can be different and independently selected from any one of the above groups. R4 is a C1-C6 straight chain or branched chain alkyl, and when b≥2, multiple R4s can be different and independently selected from any one of the above groups. Specifically, the external electron donor includes but is not limited to methyl-cyclopentyl-dimethoxysilane, ethyl-cyclopentyl-dimethoxysilane, n-propyl-cyclopentyl-dimethoxysilane, bis(2-methylbutyl)-dimethoxysilane, bis(3-methylbutyl)-dimethoxysilane, 2-methylbutyl-3-methylbutyl-dimethoxysilane, bis(2,2-dimethyl-propyl)-dimethoxysilane, 2-methylbutyl-2,2-dimethyl-propyl-dimethoxysilane, 3-methylbutyl-2,2-dimethyl- Propyl-dimethoxysilane dimethyldimethoxysilane, dimethyldiethoxysilane, diisobutyldimethoxysilane, methylcyclohexyldimethoxysilane, methylisobutyldimethoxysilane, dicyclohexyldimethoxysilane, methyl-isopropyldimethoxysilane, isopropyl-cyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, methyl-isopropyldimethoxysilane, isopropyl-cyclopentyldimethoxysilane, dicyclopentyldimethoxysilane, isopropyl-isobutyldimethoxysilane, diisopropyldimethoxysilane, etc. Preferably, at least one of dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, methylcyclohexyldimethoxysilane, diisopropyldimethoxysilane, diethylaminomethyltriethoxysilane, diethylaminotriethoxysilane, diisobutyldimethoxysilane and tetramethoxysilane is selected. The first external electron donor and the second external electron donor are the same or different. When they are different, the second external electron donor is preferably an external electron donor that can further increase the isotactic index of the polymer. The degree of influence of different external electron donors on the isotactic index of the polymer is well known to those skilled in the art.

[0052] In the present invention, when the catalyst component is a metallocene catalyst component, the metallocene catalyst component comprises: (1) a main catalyst (main catalyst in a metallocene catalyst): a metallocene catalyst b formed by loading or self-loading a metallocene compound; (2) a main catalyst (co-catalyst in a metallocene catalyst): any compound capable of converting a metallocene catalyst precursor into an active polymerization catalyst, and preferably comprising at least one of an alkylaluminoxane compound (alumoxane), an organic boron, an ionic compound and a borate; (3) an optional first impurity remover, wherein the first impurity remover is a Group IIIA metal compound, preferably an aluminum compound, and the aluminum compound can be suitably selected from alkylaluminum, alkylaluminum halide, alkoxyaluminum, alkylalkoxyaluminum or alkoxyaluminum halide compounds, more preferably trialkylaluminum. The specific preparation method of the metallocene catalyst can be found in CN105622796B.

[0053] In the present invention, the second prepolymerization reactor can be in various forms, such as a kettle reactor, a tubular reactor, or even a pipeline reactor. Any container that meets the above operating conditions can be defined as the first prepolymerization reactor, preferably a tubular reactor or a pipeline reactor.

[0054] In the present invention, the polymerizable monomer b can be added to the second prepolymerization reactor alone, or the polymerizable monomer b can be added to the second prepolymerization reactor after being mixed and contacted with the product obtained in the above step (1) in a pipeline. Preferably, the polymerizable monomer b is added to the second prepolymerization reactor after being mixed and contacted with the product obtained in the above step (1) in a pipeline.

[0055] In the present invention, in order to further improve the melting temperature, crystallization temperature and long-period thickness of the polymer and the bending modulus of the polymer, the polymerized monomer b is selected from olefin compounds and / or aromatic hydrocarbon compounds; preferably, the polymerized monomer b contains a carbon-carbon double bond and / or a carbon-carbon triple bond; more preferably, the number of carbon atoms in the polymerized monomer b is 2-16; further preferably, the polymerized monomer b is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefin, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane.

[0056] Preferably, the polymerized monomer b and the polymerized monomer a may be the same or different, preferably different.

[0057] According to the present invention, the method comprises:

[0058] (1) in a first prepolymerization reactor, a polymerizable monomer a is mixed with a primary catalyst, a first impurity-removing agent and an optional first external electron donor to conduct a first prepolymerization reaction;

[0059] (2) The product obtained in step (1) is continuously transported to a second prepolymerization reactor, and is contacted with a polymerizable monomer b, a second impurity-removing agent and an optional second external electron donor to carry out a second prepolymerization reaction.

[0060] A second aspect of the present invention provides a polyolefin catalyst composition, which is prepared by the above method.

[0061] The third aspect of the present invention provides use of the above-mentioned polyolefin catalyst composition in the preparation of polyolefin.

[0062] A fourth aspect of the present invention provides a method for preparing polyolefins, the method further comprising: mixing the above-mentioned polyolefin catalyst composition with a polymerization monomer c for polymerization.

[0063] Preferably, the polymerization conditions include: temperature of 20-100°C, preferably 40-91°C; pressure of 0.1-10MPaG, preferably 1-5MPaG, time ≤4h, preferably 1-3h; preferably, the polymerizable monomer b is selected from olefin compounds and / or aromatic compounds; more preferably, the polymerizable monomer b contains a carbon-carbon double bond and / or a carbon-carbon triple bond; more preferably, the number of carbon atoms in the polymerizable monomer b is 2-16; further preferably, the polymerizable monomer c is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefin, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane.

[0064] In the present invention, the polymerizable monomer c and the polymerizable monomer b may be the same or different, and are preferably the same.

[0065] In the present invention, the weight ratio of the total weight of the polymerized monomers b and c to the weight of the polymerized monomer a in step (2) is 10 3 -10 5 :1, which can be (1×10 3 ):1,(2×10 3 ):1,(4×10 3 ):1,(6×10 3 ):1,(8×10 3 ):1,(1×10 4 ):1,(2×10 4 ):1,(4×10 4 ):1,(6×10 4 ):1,1:(8×10 4 ):1,(1×10 5):1 or the range formed by any two of the above values ​​and the values ​​within the range.

[0066] In the present invention, the polyolefin catalyst composition flows out from the second prepolymerization reactor and is continuously transported to the main reactor.

[0067] In the present invention, the main reactor is in the form of one or more reactors in various forms such as fluidized bed reactor, tubular reactor, kettle reactor, multiphase multi-zone reactor, etc., and the reaction phase in the reactor is various phases such as gas-solid phase, solid-liquid phase, solid-liquid-gas phase, solution phase, etc.

[0068] According to the present invention, the polyolefin includes polypropylene (homopolymer, random copolymer, block copolymer and / or impact copolymer, etc.), polyethylene (homopolymer, random copolymer, ethylene-propylene rubber, linear low-density polyethylene, high-density polyethylene and / or plastomer, etc.), and other C4-C 16 Polyolefins include polybutene, poly(butene-hexene), poly(ethylene-butene), poly(ethylene-hexene) and the like.

[0069] In the present invention, the main reactor also includes hydrogen, and the concentration of the hydrogen is 1000-3000 ppmv.

[0070] The present invention will be described in detail by way of examples. In the following examples, the first prepolymerization ratio = the mass of the polymer produced by the first prepolymerization / the mass of the main catalyst, wherein the mass of the main catalyst in the sampling tank is calculated by weighing the sample using an online fixed volume sampling tank and calculating the mass of the main catalyst in the sampling tank.

[0071] The second prepolymerization ratio = the mass of the polymer generated by the second prepolymerization / the mass of the main catalyst, wherein the mass of the main catalyst in the sampling tank is calculated by sampling and weighing using an online fixed volume sampling tank, and the mass of the main catalyst in the sampling tank is calculated and obtained by calculation and analysis.

[0072] The polymerization activity is obtained by calculating the mass ratio of olefin polymer to polyolefin catalyst per unit time;

[0073] Flexural modulus: The prepared polymer was granulated by screw and injection molded to obtain a specimen, which was measured in accordance with GB / T9341-2008;

[0074] Long-period thickness calculation: The injection molded splines were tested using a Nanostar small-angle X-ray scatterer from Bruker, Germany. The instrument tube voltage was 45 kV, the tube current was 0.65 mA, and the Cu K ray (wavelength 0.1542 nm) was used. The resolution of the two-dimensional surface detector was 2048 × 2048, and the pixel size was 68 m × 68 m. The distance from the injection molded spline to the detector was 104.65 cm. The test time for a single spline was 30 minutes. The obtained two-dimensional scattering pattern was normalized and back-ground corrected. Subsequently, the one-dimensional Iq (I is the scattering intensity, q is the scattering vector) scattering curve was obtained by integration, and the fan integration angle was 0-180°. Long-period thickness d T According to the Bragg formula based on one-dimensional scattering curve Calculate, where q amx is the q value at the maximum scattering intensity I of the one-dimensional scattering curve;

[0075] Melting temperature and crystallization temperature: measured by differential scanning calorimetry according to GB / T 19466.3-2004; Example 1

[0076] Propylene polymerization Figure 1 Process:

[0077] The propylene polymerization reaction is carried out in a bulk propylene polymerization device, which mainly includes a first prepolymerization reactor (3L), a second prepolymerization reactor (5L) and a loop reactor (75L).

[0078] (1) First Prepolymerization Reaction

[0079] The main catalyst (Ziegler-Natta catalyst, HR, produced by Sinopec Oda Catalyst Branch, catalyst oil slurry 0.1g / mL) flow rate is 4mL / hr, the triethylaluminum hexane solution (10wt%) flow rate is 10g / hr, and the external electron donor (cyclohexylmethyldimethoxysilane, C-donor) hexane solution (10wt%) flow rate is 1g / hr to form a catalyst composition, which is continuously injected into the first prepolymerization reactor 01.

[0080] The liquid phase feed stream 102 composed of 4-methyl-1-pentene hexane solution (1wt%) has a flow rate of 0.2kg / hr and is continuously injected into the first prepolymerization reactor 01; the prepolymerization temperature of the first prepolymerization reactor 01 is 55°C, the operating pressure is 4MPaG, the residence time is about 9.1h, and the first prepolymerization ratio is about 3 times.

[0081] (2) Second Prepolymerization

[0082] The first prepolymerization catalyst slurry 201, 0.21kg / hr, is mixed with the liquid propylene stream 202 with a flow rate of 15kg / hr and then injected into the second prepolymerization reactor 02; the flow rate of triethylaluminum hexane solution (10wt%) is 90g / hr, and the flow rate of external electron donor (C-donor) hexane solution (10wt%) is 10g / hr; the prepolymerization temperature of the second prepolymerization reactor 02 is 18°C, the operating pressure is 4MPaG, the residence time is about 10min, and the second prepolymerization ratio is about 100 times.

[0083] (3) Polymerization reaction in the main reactor

[0084] The second prepolymerization catalyst slurry 301 was continuously injected into the main reactor 03 at a flow rate of about 15.3 kg / h. The polymerization temperature was 70° C., the reaction pressure was 4 MPaG, the total propylene feed (including liquid propylene feed stream 202) in the reactor was 30 kg / h, and hydrogen was fed into the main reactor with the propylene feed. The hydrogen concentration in the reactor was about 2000 ppmv. The obtained polymer is shown in Table 1.

[0085] Example 2

[0086] The method of Example 1 was followed, except that 4-methyl-1-pentene was replaced with vinylcyclohexane. The first prepolymerization ratio was about 3 times, and the second prepolymerization ratio was about 100 times. The obtained polymer is shown in Table 1.

[0087] Example 3

[0088] The method of Example 1 was followed, except that the flow rate of the 4-methyl-1-pentene hexane solution in step (1) was 0.4 kg / hr, and the residence time was about 4.7 h. The first prepolymerization ratio was about 1.5 times, and the second prepolymerization ratio was about 100 times. The obtained polymer is shown in Table 1.

[0089] Example 4

[0090] The method of Example 1 is different in that the first prepolymerization reaction in step (1) is as follows:

[0091] The main catalyst (metallocene catalyst, prepared according to Example 1 of CN105622796B, catalyst grease slurry 0.25g / mL) flow rate is 4mL / hr, and the triethylaluminum hexane solution (10wt%) flow rate is 5g / hr to form a catalyst composition, which is continuously injected into the first prepolymerization reactor 01.

[0092] The liquid phase stream 102 composed of 4-methyl-1-pentene hexane solution (1wt%) has a flow rate of 0.2kg / hr and is continuously injected into the first prepolymerization reactor 01; the prepolymerization temperature of the first prepolymerization reactor 01 is 55°C, the operating pressure is 4MPaG, and the residence time is about 9.1h. The first prepolymerization ratio is about 1.5 times, and the second prepolymerization ratio is about 45 times. The obtained polymer is shown in Table 1.

[0093] Example 5

[0094] The method of Example 3 is followed, except that the first prepolymerization temperature is controlled to be -5°C, at which time the first prepolymerization ratio is ≤ 0.5 times; and the second prepolymerization temperature is controlled to be -5°C, at which time the second prepolymerization ratio is about 8 times. The obtained polymer is shown in Table 1.

[0095] Example 6

[0096] The method of Example 1 was followed, except that the external electron donor was changed to dicyclopentyldimethoxysilane (D-donor). The obtained polymer is shown in Table 1.

[0097] Example 7

[0098] The method of Example 1 was followed, except that 4-methyl-1-pentene was adjusted to be a pure solvent feed with a flow rate of 0.1 kg / hr. At this time, the first prepolymerization residence time was about 18.2 h, and the first prepolymerization ratio was about 35 times. The obtained polymer is shown in Table 1.

[0099] Comparative Example 1

[0100] The method of Example 1 is different in that the first prepolymerization reactor is eliminated, and the material originally entering the first prepolymerization reactor is mixed with the liquid propylene feed stream 202 and then injected into the second prepolymerization reactor 02. The obtained polymer is shown in Table 1.

[0101] Comparative Example 2

[0102] The method of Example 4 is different in that the first prepolymerization reactor is eliminated, and the material originally entering the first prepolymerization reactor is mixed with the liquid propylene stream 202 and then injected into the second prepolymerization reactor 02. The obtained polymer is shown in Table 1.

[0103] Comparative Example 3

[0104] (1) Catalyst treatment

[0105] The main catalyst (Ziegler-Natta catalyst, HR, produced by Sinopec Aoda Catalyst Branch) has a mass of 100 g, triethylaluminum hexane solution (10 wt%) is 2500 g, external electron donor (C-donor) hexane solution (10 wt%) is 250 g, and 4-methyl-1-pentene is 500 g. They are stirred and blended in a 10 L stainless steel container at 55 ° C for 9 hours, and the first prepolymerization ratio is about 4 times. Then the solid catalyst particles are obtained by cooling and drying.

[0106] (2) Prepolymerization

[0107] The solid catalyst particles obtained above were formulated into 0.3g / mL oil slurry with a flow rate of 8mL / hr, triethylaluminum hexane solution (10wt%) with a flow rate of 90g / hr, and an external electron donor (C-donor) hexane solution (10wt%) with a flow rate of 10g / hr, and after blending with a liquid propylene stream 202 with a flow rate of 15kg / hr, they entered the second prepolymerization reactor 02 described in Example 1. The prepolymerization temperature was 18°C, the operating pressure was 4MPaG, the residence time was about 10min, and the second prepolymerization ratio was about 100 times.

[0108] (3) Polymerization reaction in the main reactor

[0109] Same as Example 1. The obtained polymer is as shown in Comparative Example 3-1 in Table 1.

[0110] (4) Repeat steps (1) to (3) twice to obtain polymers as shown in Comparative Example 3-2 and Comparative Example 3-3 in Table 1.

[0111] Table 1

[0112]

[0113] It can be seen from the above results that compared with directly injecting the polymerized monomer a and the polymerized monomer b into a prepolymerization reactor, the two-step continuous prepolymerization method of the present invention can significantly increase the melting temperature (Tm), crystallization temperature (Tc) and long period thickness (d T ) and the bending modulus of the polymer. At the same time, compared with the method of intermittent pretreatment of the catalyst and the polymer monomer a, the polymer performance parameters obtained by this method are more stable, and although Example 7 can also effectively improve the melting temperature (Tm), crystallization temperature (Tc) and long period thickness (d T ) and the flexural modulus of the polymer, but more polymerization monomer a is required, the cost will increase, and the melting temperature (Tm), crystallization temperature (Tc) and long period thickness (d T ) and the flexural modulus of the polymer are not increased very much.

[0114] It can be seen that the method for continuous prepolymerization of polyolefin catalysts can prepare catalyst prepolymers with efficient self-nucleating effect. At the same time, the present invention can improve the quality stability of self-nucleating polymer products.

[0115] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for prepolymerization of polyolefin catalysts, characterized in that: The method comprises: (1) in a first prepolymerization reactor, mixing a polymerizable monomer a with a first prepolymerization catalyst component to conduct a first prepolymerization reaction; (2) continuously conveying the product obtained in step (1) to a second prepolymerization reactor, contacting it with a second prepolymerization catalyst component and a polymerization monomer b to carry out a second prepolymerization reaction; Wherein, the conditions of the first prepolymerization reaction are such that the prepolymerization ratio REP1 in the first prepolymerization reactor is ≤35 times.

2. The method according to claim 1, wherein: The prepolymerization ratio REP1 in the first prepolymerization reactor is ≤20 times, preferably ≤15 times; and / or, the conditions of the second prepolymerization reaction are such that the prepolymerization ratio REP2 in the second prepolymerization reactor is 1-1000 times, preferably 5-800 times, more preferably 10-500 times; And / or, the method does not include cooling and / or drying operations between step (1) and step (2); Preferably, REP1≤REP2; Preferably, REP1 / REP2≤0.5, more preferably REP1 / REP2≤0.2; Preferably, 1 times ≤ REP1+REP2 ≤ 1000 times, more preferably 10 times ≤ REP1+REP2 ≤ 1000 times, further preferably 50 times ≤ REP1+REP2 ≤ 800 times.

3. The method according to claim 1 or 2, wherein: The structural formula of the polymerizable monomer a is CH2=CR1R2, wherein R1 and R2 are independently hydrogen, a substituted or unsubstituted chain carbon-containing group, a substituted or unsubstituted cyclic carbon-containing group, a substituted or unsubstituted aromatic ring group or a substituted or unsubstituted condensed ring group; Preferably, R1 is hydrogen, and R2 is different from R1; Preferably, the chain carbon-containing group contains 4-20 carbon atoms; Preferably, the cyclic carbon-containing group contains 3-12 carbon atoms; Preferably, the aromatic ring group or condensed ring group contains 6-20 carbon atoms, preferably 6-16 carbon atoms; Preferably, the polymerizable monomer a is at least one of vinyl compounds containing a cyclic alkyl group, an aryl group or a branched alkyl group; Preferably, the polymerizable monomer a is at least one selected from vinylcyclohexane, styrene, vinylcyclopentane, vinyl-2-methylcyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene and 4-methyl-1-pentene.

4. The method according to claim 1 or 2, wherein: The first prepolymerized catalyst component comprises a main catalyst, an optional first impurity remover and an optional first external electron donor; Preferably, the weight ratio of the polymerizable monomer a, the main catalyst and the first impurity remover is 1:0.01-0.5:0.01-1; Preferably, the weight ratio of the polymerizable monomer a to the first external electron donor is 1:0.001-0.1; More preferably, the weight ratio of the polymerizable monomer a to the polymerizable monomer b is 1:

10. 2 -10 4 ; Preferably, relative to the first prepolymerization reactor with a volume of 3L, the flow rate of the polymerization monomer a is 0.2-5g / hr; Further preferably, relative to the second prepolymerization reactor with a volume of 5L, the flow rate of the polymerization monomer b is 5-30kg / hr; Preferably, the main catalyst is selected from at least one of a Ziegler-Natta catalyst, a chromium-based catalyst, a vanadium-based catalyst and a metallocene catalyst, more preferably a Ziegler-Natta catalyst and / or a metallocene catalyst; More preferably, the second prepolymerized catalyst component comprises a second impurity remover and optionally a second external electron donor; Preferably, based on the total weight of the first impurity remover and the second impurity remover, the amount of the first impurity remover is 1-99% by weight, more preferably 5-90% by weight; Further preferably, based on the total weight of the first external electron donor and the second external electron donor, the amount of the first external electron donor is 1-100 wt %, more preferably 5-90 wt %.

5. The method according to claim 1 or 2, wherein: The polymerizable monomer b contains a carbon-carbon double bond and / or a carbon-carbon triple bond; More preferably, the number of carbon atoms in the polymerizable monomer b is 2-16; More preferably, the polymerizable monomer b is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane; Preferably, the polymerized monomer b is different from the polymerized monomer a.

6. A polyolefin catalyst composition, characterized in that: The composition is prepared by the method described in any one of 1-5.

7. Use of the polyolefin catalyst composition according to claim 6 in the preparation of polyolefins.

8. A method for preparing polyolefin, characterized in that: The method further comprises: mixing the polyolefin catalyst composition according to claim 6 with a polymerization monomer c for polymerization.

9. The method according to claim 8, wherein: The polymerization conditions include: temperature of 20-100°C, preferably 40-91°C; pressure of 0.1-10MPaG, preferably 1-5MPaG, time ≤4h, preferably 1-3h; And / or, the weight ratio of the total weight of the polymerized monomers b and c to the weight of the polymerized monomer a in step (2) is 10 3 -10 5 :1; And / or, the polymerizable monomer c contains a carbon-carbon double bond and / or a carbon-carbon triple bond; More preferably, the number of carbon atoms in the polymerizable monomer c is 2-16; More preferably, the polymerizable monomer c is selected from ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 One of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane; More preferably, the polymerized monomer b and the polymerized monomer c are the same or different.

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