A propylene polymerization method for narrowing powder particle size distribution

Abstract

The present invention belongs to the technical field of olefin polymerization, and in particular relates to a propylene polymerization method for narrowing the particle size distribution of a powder, comprising: (1) reacting a propylene polymerization catalyst with a nucleating agent monomer to obtain a prepolymerization catalyst containing a polymer nucleating agent; and (2) adding the prepolymerization catalyst containing the polymer nucleating agent, the cocatalyst, and the optional external electron donor to a polymerization reactor already injected with propylene monomer, without pre-contacting the prepolymerization catalyst with a cocatalyst and an optional external electron donor before adding the prepolymerization catalyst containing the polymer nucleating agent to a polymerization reactor already injected with propylene monomer, so as to polymerize the propylene monomer or propylene with one or more other olefins. The present invention omits the pre-contact step of the prepolymerization catalyst with the cocatalyst (and the optional external electron donor) during the polymerization process, and can narrow the particle size distribution of the resulting polypropylene product.

Description

Technical Field

[0001] The invention belongs to the technical field of olefin polymerization, and in particular relates to a propylene polymerization method for narrowing powder particle size distribution. Background Art

[0002] Polypropylene is a semi-crystalline polymer with a high degree of crystallinity. Its thermal, mechanical, and optical properties are closely related to its crystallization properties. Nucleating agents are commonly used to modify the crystallization behavior of polypropylene to achieve higher crystallization temperatures, higher rigidity, and higher transparency. Inorganic salts, organic acid salts, sorbitol acetals, aromatic amides, and other compounds can all be used as polypropylene nucleating agents. The traditional method currently in common use is to blend the nucleating agent with the polyolefin after reaction. For example:

[0003] Borealis' patent application WO9924478A1 discloses a method for adjusting the crystallization properties of polypropylene using a polymer nucleating agent. This patent involves polymerizing propylene with a Ziegler-Natta catalyst (prepolymerization) prior to propylene polymerization to produce a catalyst containing a polymer nucleating agent. This catalyst is then used to polymerize propylene to produce polypropylene containing the polymer nucleating agent. However, this patent application does not examine the effects of prepolymerization conditions and other factors on the morphology of the catalyst particles containing the polymer nucleating agent, nor the effect of the catalyst on the morphology of the polypropylene particles. It only examines whether the catalyst imparts a higher modulus and impact strength to the resulting polypropylene.

[0004] In addition, premixing a prepolymerization catalyst containing a polymer nucleating agent with an alkyl aluminum compound and an external electron donor prior to the main polymerization is a common polymerization process in the art. This process operation is generally referred to as precontacting, preactivating, or precomplexing. Precontacting is typically performed in the absence of polymerization monomer or in the presence of only a trace amount of polymerization monomer. It is well known in the industry that bulk propylene slurry loop processes typically include precontacting and prepolymerization.

[0005] According to patent application EP0279153B1 from Fina, a magnesium chloride-supported Ziegler catalyst is first prepolymerized to obtain a prepolymerized catalyst with a prepolymerization ratio of 2-4. Before entering the polymerization reaction zone, the prepolymerized catalyst is contacted with a cocatalyst or a mixture of a cocatalyst and an electron donor. This catalyst is then used for the main polymerization. In this process, pre-contacting the prepolymerized catalyst with an alkyl aluminum compound and an external electron donor prior to the main polymerization stage significantly improves the activity and catalytic efficiency of the main polymerization stage.

[0006] Montell's patent application EP0541760A1 discloses that pre-contact and pre-polymerization processes are used in the gas-phase propylene polymerization process to improve the stereoregularity of the product.

[0007] According to the patent application document EP0823919B1 of Borealis, it is disclosed that if the mixture of the alkyl aluminum compound and the external electron donor used in the polymerization process after pre-contact is divided into two parts and added to the pre-contact stage and the main polymerization stage respectively, the polymerization activity and particle morphology can be improved.

[0008] Many research papers believe that pre-contact has an impact on the kinetics and product properties of propylene polymerization. However, the conclusions drawn from the various studies are inconsistent. For example, Yu Luqiang et al. (Petrochemical Engineering, 2003, (05), 25-28) found that the pre-contact process can improve the activity of the catalyst; Tan Yang et al. (Petrochemical Engineering, 2007, (08), 780-783) found that the pre-contact process had the same effect on SiO2 / MgCl2 dual-loaded catalysts, that is, it improved the activity of the catalyst; Ning Tan et al. (J.Appl.Polym.Sci.2015, 132(15), 41816) also made similar findings. However, Zhang Tianyi et al. (Petrochemical Engineering, 2016, 45(12), 1468-1474) found that pre-contact had the effect of reducing the activity of DQC catalysts.

[0009] Most of the above prior art studies believe that the pre-contact step is beneficial or even necessary for propylene polymerization, but this conclusion is not always true.

[0010] In view of this, whether the pre-contact step will have other effects on the propylene polymerization reaction is a direction worth studying. Summary of the Invention

[0011] The present invention aims to address the deficiencies of the prior art and provide a propylene polymerization method for improving the morphology of polypropylene particles. By omitting the pre-contact step of the catalyst components used in the propylene polymerization process without pre-polymerization, the particle size distribution of the resulting polypropylene powder can be narrowed. Compared with propylene polymerization processes in which the catalyst components need to be pre-contacted, the particle morphology of the polymer product powder is significantly improved.

[0012] In order to achieve the above object, the present invention provides the following technical solutions:

[0013] A propylene polymerization method for narrowing powder particle size distribution comprises the following steps:

[0014] (1) contacting a propylene polymerization catalyst with a nucleating agent monomer and reacting the monomers to obtain a prepolymerization catalyst containing a polymer nucleating agent;

[0015] (2) injecting propylene monomer into a polymerization reactor, without pre-contacting the pre-catalyst containing a polymer nucleating agent obtained in step (1) with a co-catalyst and an optional external electron donor before adding the pre-catalyst containing a polymer nucleating agent, the co-catalyst and the optional external electron donor into the polymerization reactor (e.g., through respective feed lines);

[0016] In the reaction system after the addition, in the presence of the pre-polymerization catalyst containing a polymer nucleating agent, a co-catalyst, and an optional external electron donor, propylene monomer or propylene and one or more other olefins are polymerized to produce polypropylene; wherein the polymerization temperature is 50 to 120° C. (for example, 55° C., 60° C., 70° C., 80° C., 90° C., 100° C., 110° C.), and the polymerization pressure is 0.1 to 5 MPa (for example, 0.2 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa);

[0017] The propylene polymerization catalyst is a Ziegler-Natta catalyst or a metallocene catalyst;

[0018] The co-catalyst is a hydrocarbyl aluminum compound, for example, one or more selected from trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum and trihexylaluminum;

[0019] The external electron donor is an organosilicon compound, for example, 3 m R 4 n Si(OR 5 ) 4-m-n The organosilicon compound shown in the formula: R 3 、R 4 are independently selected from C1-C12 linear, branched or cyclic aliphatic groups, or C3-C12 nitrogen-containing linear, branched or cyclic organic groups; R 5 A C1-C4 linear or branched aliphatic group; m and n are both natural numbers, and their values ​​satisfy 0≤(m+n)≤2;

[0020] The other olefins are ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene or 1-octene.

[0021] According to the propylene polymerization method provided by the present invention, in some embodiments, the amount of the pre-polymerization catalyst containing a polymer nucleating agent added in the obtained polypropylene is in the range of 1 to 500 ppm (for example, 2 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 450 ppm).

[0022] In step (1), for example, the nucleating agent monomer can be added to the system for reaction in steps; the total reaction time of each step is 1-72 hours (for example, 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 50 hours, 60 hours, 70 hours). For example, the nucleating agent monomer can be added in two steps: the propylene polymerization catalyst is contacted with a portion of the nucleating agent monomer for reaction, and the reaction time is 0.5-48 hours (for example, 1 hour, 4 hours, 6 hours, 8 hours, 12 hours, 18 hours, 24 hours, 28 hours, 30 hours, 32 hours, 40 hours); and then the remaining portion of the nucleating agent monomer is added to the system and the reaction is continued for 0.5-48 hours (for example, 1 hour, 4 hours, 6 hours, 8 hours, 12 hours, 18 hours, 24 hours, 28 hours, 30 hours, 32 hours, 40 hours). For example, when the nucleating agent monomer is added in two steps, the molar ratio of the nucleating agent monomer added in the first step to the nucleating agent monomer added in the second step is 1:1.

[0023] Herein, the pre-polymerization catalyst containing a polymer nucleating agent, the co-catalyst and the optional external electron donor are added to the polymerization reactor separately, which can be understood as: when no external electron donor is used, the pre-polymerization catalyst containing a polymer nucleating agent and the co-catalyst are added to the polymerization reactor separately through their respective feed lines; or, when an external electron donor is used, the mixture of the co-catalyst and the external electron donor and the pre-polymerization catalyst containing a polymer nucleating agent can be added to the polymerization reactor separately through their respective feed lines.

[0024] In the present invention, the polymer nucleating agent refers to a polymer obtained by polymerizing a nucleating agent monomer with a propylene polymerization catalyst. In step (1), the polymer nucleating agent contained in the prepolymerization catalyst is converted from the nucleating agent monomer through a polymerization reaction, and it is assumed that there is no mass loss during the conversion process. Therefore, under the premise of ensuring a conversion rate greater than 95%, the amount of nucleating agent monomer added can be determined according to the corresponding ratio calculated through theoretical calculation.

[0025] The precursor catalyst containing a polymer nucleating agent, for example, comprises a polymer nucleating agent component and a propylene polymerization catalyst before modification. According to the propylene polymerization method provided by the present invention, in some embodiments, in the precursor catalyst containing a polymer nucleating agent in step (1), the mass ratio of the polymer nucleating agent to the propylene polymerization catalyst before modification is 0.1 to 10:1 (for example, 0.15:1, 0.2:1, 0.4:1, 0.8:1, 1:1, 2:1, 4:1, 6:1, 8:1), preferably 0.1 to 5:1, more preferably 0.5 to 5:1.

[0026] Typically, if the procatalyst containing a polymer nucleating agent is obtained by selectively reacting a Ziegler-Natta catalyst with a nucleating agent monomer, the mass ratio of the polymer nucleating agent to the procatalyst in the Ziegler-Natta catalyst before modification can also be limited to 0.1 to 10:1 (for example, 0.15:1, 0.2:1, 0.4:1, 0.8:1, 1:1, 2:1, 4:1, 6:1, 8:1).

[0027] In some embodiments, the nucleating agent monomer is a compound represented by Formula I:

[0028]

[0029] Where R 1 and R 2 Together with the carbon atoms to which they are attached, they form an optionally substituted saturated or unsaturated or aromatic ring or condensed ring system, wherein the ring or condensed ring portion contains 4 to 20 carbon atoms, preferably a 5 to 12-membered saturated or unsaturated or aromatic ring or condensed ring system, or R 1 and R 2 are each independently an alkyl group containing 1 to 4 carbon atoms, or R 1 and R 2 Each is independently a silicon-substituted alkyl group containing 0 to 4 carbon atoms.

[0030] In some embodiments, the nucleating agent monomer is selected from one or more of vinylcycloalkanes, 3-methyl-1-butene, 3-ethyl-1-hexene, styrene, p-methylstyrene, and allyltrimethylsilane. The vinylcycloalkanes are preferably selected from vinylcyclohexane, vinylcyclopentane, vinyl-2-methylcyclohexane, or vinylnorbornane.

[0031] In some embodiments, the nucleating agent monomer is selected from one or more of vinylcyclohexane, vinylcyclopentane, styrene, and allyltrimethylsilane.

[0032] In some embodiments, the Ziegler-Natta catalyst comprises a procatalyst, a cocatalyst i, and an optional external electron donor; wherein:

[0033] The procatalyst comprises magnesium, titanium, chlorine, and an internal electron donor;

[0034] The internal electron donor is selected from one or more of benzoate compounds, phthalate compounds, 1,3-diether compounds, succinate compounds, maleate compounds, malonate compounds, 1,3-diol ester compounds, 2,4-diol ester compounds, o-diphenol ester compounds, 1,8-naphthalene diphenol ester compounds, cycloalkyl o-dicarboxylic acid ester compounds and amide ester compounds; the internal electron donor can be, for example, but not limited to, ethyl benzoate, ethyl p-ethoxybenzoate, di-n-butyl phthalate, diisobutyl phthalate, 2,2-diisopropyl phthalate, 1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, 2-ethyl-2-butyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 9,9-bis(methoxymethyl)fluorene, diethyl 2,3-diisopropylsuccinate, di-n-butyl 2,3-diisopropylsuccinate, diisobutyl 2,3-diisopropylsuccinate, di(2-ethylhexyl)citraconate, dimethyl benzylmalonate, diethyl benzylmalonate, 2,4-pentanediol Dibenzoate, 1,3-propylene glycol dibenzoate, 3-methyl-2,4-pentanediol dibenzoate, 3-methyl-5-tert-butyl-1,2-benzenediol dibenzoate, 4-tert-butyl-1,2-benzenediol dibenzoate, 3,6-dimethyl-1,2-benzenediol dibenzoate, 1,8-naphthalene dibenzoate, 2,4-pentanediol di(4-methylbenzoate), 1,3-propylene glycol di(4-methylbenzoate), 3-methyl-2,4-pentanediol di(4-methylbenzoate), 3-methyl-5-tert-butyl-1,2-benzenediol di(4-methylbenzoate) one or more of 1,2-dimethylbenzene, 1,8-naphthalene diol di(4-methylbenzoate), 1,2-diisobutyl cyclohexanediol, 1,2,3,6-tetrahydrophthalic acid diethyl ester, N-(3-benzylcarboxy-1-methylbutyl)benzamide, N-[2-benzylcarboxy-4-tert-butyl-6-methylphenyl]benzamide, and N-[3-(4-butylbenzylcarboxy)-2,2-dimethylpropyl]-4-butylbenzamide.

[0035] In some embodiments, the cocatalyst i is a hydrocarbyl aluminum compound, preferably one or more selected from trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum and trihexylaluminum.

[0036] In some embodiments, the external electron donor is of the formula R3 m R 4 n Si(OR 5 ) 4-m-n The organosilicon compound shown in the formula: R 3 、R 4 are independently selected from C1-C12 linear, branched or cyclic aliphatic groups, or C3-C12 nitrogen-containing linear, branched or cyclic organic groups; R 5 Selected from C1-C4 straight chain or branched aliphatic groups; m and n are both natural numbers, and the values ​​satisfy 0≤(m+n)≤2; the external electron donor can be, for example, but not limited to, dimethyldimethoxysilane, diphenyldimethoxysilane, methylcyclopentyldimethoxysilane, methylcyclohexyldimethoxysilane, methyl(3,3,3-trifluoropropyl)dimethoxysilane, dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, di-n-propyldimethoxysilane, di-n-butyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, isopropylisopentyldimethoxysilane, methylcyclopentyldiethoxysilane, methylcyclohexyldiethoxysilane, methyl(3,3,3-trifluoropropyl)diethoxysilane, dicyclopentyldiethoxysilane, dicyclohexyldiethoxysilane, di One or more of n-propyldiethoxysilane, di-n-butyldiethoxysilane, diisopropyldiethoxysilane, diisobutyldiethoxysilane, isopropylisopentyldiethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, isopentyltrimethoxysilane, cyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, allyltrimethoxysilane, vinyltrimethoxysilane, diethylaminotrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane, isobutyltriethoxysilane, isopentyltriethoxysilane, cyclopentyltriethoxysilane, cyclohexyltriethoxysilane, allyltriethoxysilane, vinyltriethoxysilane, diethylaminotriethoxysilane, tetramethoxysilane and tetraethoxysilane.

[0037] In some embodiments, the metallocene catalyst comprises a support, a metallocene coordination compound, and a co-catalyst ii; wherein:

[0038] The carrier is selected from granular silica or layered silicate;

[0039] The metallocene coordination compound is selected from bridged C2-symmetrical compounds containing a Group IV metal and an indenyl group, preferably selected from one or more of rac-dimethylsilyl-bis(2-methyl-4-phenylindenyl)zirconium dichloride, rac-dimethylsilyl-bis(2-methyl-4,5-benzylindenyl)zirconium dichloride, rac-dimethylsilyl-bis(2-methyl-4-carbazolylindenyl)zirconium dichloride, and rac-dimethylsilyl-bis[2-methyl-4-(3,5-di-tert-butylphenyl)-7-methoxyindenyl]zirconium dichloride;

[0040] The co-catalyst ii is selected from methylaluminoxane or modified methylaluminoxane.

[0041] Typically, if the precursor catalyst containing a polymer nucleating agent is obtained by modifying a Ziegler-Natta catalyst and a nucleating agent monomer, then in the propylene polymerization system, the dosage ratio of the precursor catalyst containing a polymer nucleating agent, the cocatalyst, and the optional external electron donor is calculated based on the molar ratio of the aluminum contained in the cocatalyst to the titanium contained in the precursor catalyst containing the polymer nucleating agent, and the aluminum-titanium molar ratio is 1:1 to 300:1 (for example, 2:1, 10:1, 50:1, 100:1, 120:1, 155:1, 160:1). :1, 170:1, 180:1, 200:1, 220:1, 240:1, 260:1, 280:1, 290:1), more preferably 150:1-300:1; the aluminum-silicon molar ratio, calculated based on the molar ratio of the aluminum contained in the co-catalyst to the silicon contained in the external electron donor, is 1:1-20:1 (for example, 2:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1), more preferably 3:1-6:1.

[0042] As is well known in the art, propylene polymerization generally involves a prepolymerization and main polymerization process. Prepolymerization refers to a propylene polymerization reaction conducted at a lower pressure and / or lower temperature prior to the main polymerization. The main polymerization is characterized by a reaction temperature of no less than 50°C and a pressure of no less than 1 MPa. During the main polymerization stage, propylene is present in significant excess relative to the added catalyst. For example, the polymer / catalyst (weight ratio) in the powder particles during the main polymerization stage is no less than 1000 / 1.

[0043] The propylene polymerization method of the present invention does not include a prepolymerization step, and the prepolymerization catalyst containing the polymer nucleating agent directly enters the main polymerization stage to carry out propylene polymerization reaction to prepare a polypropylene product.

[0044] In the present invention, the propylene polymerization catalyst containing a (polymer) nucleating agent is synonymous with the prepolymerization catalyst containing a polymer nucleating agent.

[0045] In the present invention, pre-contacting refers to pre-contacting or mixing the pre-polymerization catalyst containing a polymer nucleating agent with a co-catalyst or a mixture of a co-catalyst and an external electron donor before contacting the propylene monomer. The contact time is generally 5-60 minutes. However, this pre-contacting step is omitted in the propylene polymerization step of the present invention.

[0046] The inventors have discovered that, in the polymerization reaction system of the present invention, no prepolymerization step is performed, and the prepolymerization catalyst containing a polymer nucleating agent directly enters the main polymerization stage. Omitting the pre-contact step with the co-catalyst and the optional external electron donor can significantly improve the morphology of the polypropylene particles in the reaction system and narrow the size distribution of the polypropylene particles.

[0047] After a prepolymerization catalyst containing a polymer nucleating agent is prepared, a cocatalyst and an optional external electron donor need to be added to activate it during the main polymerization stage of propylene polymerization. However, if the prepolymerization catalyst containing a polymer nucleating agent is pre-contacted with a cocatalyst or a mixture of a cocatalyst and an external electron donor before contacting propylene monomer, the prepolymerization catalyst will be activated prematurely, which will cause excessively high initial polymerization kinetics, increased powder particle breakage, a widened powder particle size distribution, and even an increase in fine powder content in severe cases. The present inventors have discovered that by separately introducing the prepolymerization catalyst containing a polymer nucleating agent and the cocatalyst and / or external electron donor into the main polymerization reactor before entering the polymerization system (i.e., without contacting each other before entering the main polymerization reactor), a polypropylene product with a narrow particle size distribution can be obtained after the polymerization reaction, and the product has excellent mechanical and optical properties. DETAILED DESCRIPTION

[0048] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0049] <Source of raw materials>

[0050] In each of the Examples and Comparative Examples, the procatalyst contained in the propylene polymerization catalyst used in the reaction with the nucleating agent monomer was a commercial SUG slurry catalyst (with a titanium content of 7.25 mg / mL and a solid catalyst component content of approximately 0.26 g / mL as measured by ICP-AES) and a SAL dry powder catalyst (with a titanium content of 2.78 wt% as measured by ICP-AES) purchased from Lihe Technology Development Co., Ltd.

[0051] In the present invention, the improvement of the particle morphology of the product refers to that the particle size distribution of the particles becomes narrower, that is, the parameter used to measure the particle size distribution becomes smaller.

[0052] In the present invention, there are two parameters to measure the particle size distribution, namely D1 and D2:

[0053] D1=(d90-d10) / d50

[0054] In the above formula, d10, d50, and d90 are the particle sizes corresponding to the 10%, 50%, and 90% values ​​of the vertical coordinate of the integral curve obtained by normalizing and integrating the area under the curve of the particle size distribution curve.

[0055] D2=dv / dn

[0056] Where dv is the volume-weighted average of all particles, and dn is the number-weighted average of all particles.

[0057] <Test Method>

[0058] The particle size distribution of polypropylene powder is measured using a Microtrac S3500 laser particle size analyzer, which can directly obtain the parameters d10, d50, d90, dv, and dn mentioned above.

[0059] Example 1

[0060] The preparation process of the prepolymerization catalyst containing a polymer nucleating agent comprises the following steps:

[0061] 1 mL of the shaken SUG slurry catalyst was dispersed in 5 mL of mineral oil, and the prepared triisobutylaluminum n-hexane solution was slowly injected according to the aluminum-titanium molar ratio of 1.5, followed by slowly adding 0.5 g of vinylcyclohexane (VCH) and carrying out the prepolymerization reaction at normal pressure and room temperature for 24 hours; then, 0.5 g of vinylcyclohexane was added and the reaction was continued for 24 hours to obtain a prepolymerization catalyst slurry containing a polymer nucleating agent.

[0062] The above obtained prepolymer catalyst containing polymer nucleating agent is used in propylene polymerization system:

[0063] 1 L of liquid propylene was added to a 2 L stainless steel reactor, 0.1 MPa of hydrogen was introduced, and the temperature was raised to 70°C; a freshly prepared triethylaluminum / dicyclopentyldimethoxysilane mixed solution was added to the stainless steel reactor;

[0064] Subsequently, 0.1 mL of the shaken prepolymerization catalyst slurry containing the polymer nucleating agent was mixed with 10 mL of freshly purified n-hexane and transferred to a feed tank for use; the prepolymerization catalyst slurry containing the polymer nucleating agent prepared in the feed tank was then injected into a stainless steel reactor with high-pressure hexane to initiate the polymerization reaction, which lasted for 30 minutes; wherein,

[0065] The ratio of the triethylaluminum / dicyclopentyldimethoxysilane mixed solution to the pre-polymerization catalyst containing a polymer nucleating agent is calculated based on a molar ratio of aluminum contained in triethylaluminum to titanium contained in the pre-polymerization catalyst containing a polymer nucleating agent of 200:1, and a molar ratio of aluminum to silicon in triethylaluminum / dicyclopentyldimethoxysilane of 5:1.

[0066] After the reaction was completed, the materials in the reactor were discharged into a receiving tank to obtain a polypropylene product. The mass content of the prepolymerization catalyst containing a polymer nucleating agent in the obtained polypropylene was about 108 ppm. The test results are shown in Table 1.

[0067] Comparative Example 1

[0068] The preparation process of the prepolymerization catalyst containing a polymer nucleating agent is as described in Example 1.

[0069] The above obtained prepolymer catalyst containing polymer nucleating agent is used in propylene polymerization system:

[0070] Add 1 L of liquid propylene into a 2 L stainless steel reactor, introduce 0.1 MPa of hydrogen, and heat to 70 °C;

[0071] 0.1 mL of a well-shaken pre-polymerization catalyst slurry containing a polymer nucleating agent was pre-contacted with a freshly prepared triethylaluminum / dicyclopentyldimethoxysilane mixed solution in a pre-contact feeding tank for 5 minutes; then, the pre-polymerization catalyst slurry containing a polymer nucleating agent and triethylaluminum / dicyclopentyldimethoxysilane obtained after the pre-contact treatment was injected into the stainless steel reactor using high-pressure hexane to initiate a polymerization reaction, which lasted for 30 minutes; wherein,

[0072] The ratio of the triethylaluminum / dicyclopentyldimethoxysilane mixed solution to the pre-polymerization catalyst containing a polymer nucleating agent is calculated based on a molar ratio of aluminum contained in triethylaluminum to titanium contained in the pre-polymerization catalyst containing a polymer nucleating agent of 200:1, and a molar ratio of aluminum to silicon in triethylaluminum / dicyclopentyldimethoxysilane of 5:1.

[0073] After the reaction was completed, the materials in the reactor were discharged into a receiving tank to obtain a polypropylene product. The mass content of the prepolymerization catalyst containing the polymer nucleating agent in the obtained polypropylene was about 87 pm. The test results are shown in Table 1.

[0074] Example 2

[0075] The preparation process of the prepolymerization catalyst containing a polymer nucleating agent comprises the following steps:

[0076] 0.24 g of SAL dry powder catalyst was dispersed in 6 mL of mineral oil, and a prepared n-hexane solution of triisobutylaluminum was slowly injected according to an aluminum-titanium molar ratio of 1.5. Subsequently, 0.5 g of vinylcyclohexane (VCH) was slowly added, and a prepolymerization reaction was carried out at normal pressure and room temperature for 24 hours; then, 0.5 g of vinylcyclohexane was added and the reaction was continued for 48 hours to obtain a prepolymerization catalyst slurry containing a polymer nucleating agent.

[0077] The above obtained prepolymer catalyst containing polymer nucleating agent is used in propylene polymerization system:

[0078] 2 L of liquid propylene was added to a 5 L stainless steel reactor, 0.1 MPa of hydrogen was introduced, and the temperature was raised to 70°C; a freshly prepared triethylaluminum / dicyclopentyldimethoxysilane mixed solution was added to the stainless steel reactor;

[0079] Subsequently, 0.2 mL of the shaken prepolymerization catalyst slurry containing the polymer nucleating agent was mixed with 10 mL of freshly purified n-hexane and transferred to a feed tank for use; the prepolymerization catalyst slurry containing the polymer nucleating agent prepared in the feed tank was then injected into a stainless steel reactor with high-pressure hexane to initiate the polymerization reaction, which lasted for 60 minutes; wherein,

[0080] The ratio of the triethylaluminum / dicyclopentyldimethoxysilane mixed solution to the pre-polymerization catalyst containing a polymer nucleating agent is calculated based on a molar ratio of aluminum contained in triethylaluminum to titanium contained in the pre-polymerization catalyst containing a polymer nucleating agent of 200:1, and a molar ratio of aluminum to silicon in triethylaluminum / dicyclopentyldimethoxysilane of 5:1.

[0081] After the reaction was completed, the materials in the reactor were discharged into a receiving tank to obtain a polypropylene product. The mass content of the prepolymerization catalyst containing the polymer nucleating agent in the obtained polypropylene was about 165 pm. The test results are shown in Table 1.

[0082] Comparative Example 2

[0083] The preparation process of the polypropylene precursor catalyst containing a polymer nucleating agent is as follows:

[0084] The above obtained prepolymer catalyst containing polymer nucleating agent is used in propylene polymerization system:

[0085] 2 L of liquid propylene was added to a 5 L stainless steel reactor, 0.1 MPa of hydrogen was introduced, and the temperature was raised to 70 °C;

[0086] 0.2 mL of the shaken pre-polymerization catalyst slurry containing the polymer nucleating agent was pre-contacted with a freshly prepared triethylaluminum / dicyclopentyldimethoxysilane mixed solution in a pre-contact feeding tank for 5 minutes; then, the slurry of the pre-polymerization catalyst containing the polymer nucleating agent and triethylaluminum / dicyclopentyldimethoxysilane obtained after the pre-contact treatment was injected into a stainless steel reactor with high-pressure hexane to initiate the polymerization reaction, and the reaction lasted for 60 minutes; wherein,

[0087] The ratio of the triethylaluminum / dicyclopentyldimethoxysilane mixed solution to the pre-polymerization catalyst containing a polymer nucleating agent is calculated based on a molar ratio of aluminum contained in triethylaluminum to titanium contained in the pre-polymerization catalyst containing a polymer nucleating agent of 200:1, and a molar ratio of aluminum to silicon in triethylaluminum / dicyclopentyldimethoxysilane of 5:1.

[0088] After the reaction was completed, the materials in the reactor were discharged into a receiving tank to obtain a polypropylene product. The mass content of the prepolymerization catalyst containing the polymer nucleating agent in the obtained polypropylene was about 154 pm. The test results are shown in Table 1.

[0089] Table 1

[0090]

[0091] From the test results shown in Table 1, it can be seen that compared with Comparative Examples 1-2, the particle size distribution parameters D1 and D2 of the polypropylene powder obtained in Examples 1-2 are significantly reduced; this shows that if the pre-contact step is omitted in the propylene polymerization process, the particle size distribution of the obtained polypropylene is narrowed, which can effectively improve the morphology of the polypropylene particles and reduce the product subdivision content.

[0092] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A propylene polymerization method for narrowing the powder particle size distribution, characterized in that: The steps include: (1) contacting a propylene polymerization catalyst with a nucleating agent monomer and reacting the monomers to obtain a prepolymerization catalyst containing a polymer nucleating agent; (2) injecting propylene monomer or propylene and one or more other olefins into a polymerization reactor, the pre-polymerization catalyst containing a polymer nucleating agent obtained in step (1) is not pre-contacted with a co-catalyst and an optional external electron donor before being added to the propylene polymerization system, and the pre-polymerization catalyst containing a polymer nucleating agent, the co-catalyst and the optional external electron donor are added to the polymerization reactor separately; In the reaction system after the addition, in the presence of the prepolymerization catalyst containing a polymer nucleating agent, a cocatalyst, and an optional external electron donor, propylene monomer or propylene and one or more other olefins are polymerized to produce polypropylene; wherein the polymerization temperature is 50 to 120° C. and the polymerization pressure is 0.1 to 5 MPa; The propylene polymerization catalyst is a Ziegler-Natta catalyst or a metallocene catalyst; The co-catalyst is a hydrocarbyl aluminum compound, and the external electron donor is an organosilicon compound; The other olefins are ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene or 1-octene; The nucleating agent monomer is a compound represented by the general formula I: Where R 1 and R 2 Together with the carbon atoms to which they are attached, they form an optionally substituted saturated or unsaturated or aromatic ring or fused ring system, wherein the ring or fused ring portion contains 4 to 20 carbon atoms, or R 1 and R 2 are each independently an alkyl group containing 1 to 4 carbon atoms; and / or, The nucleating agent monomer is allyltrimethylsilane.

2. The propylene polymerization method according to claim 1, wherein The amount of the prepolymerization catalyst containing the polymer nucleating agent added to the obtained polypropylene is in the range of 1 to 500 ppm by mass.

3. The propylene polymerization method according to claim 1, wherein In the pre-polymerization catalyst containing a polymer nucleating agent in step (1), the mass ratio of the polymer nucleating agent to the propylene polymerization catalyst before modification is 0.1 to 10:

1.

4. The propylene polymerization method according to claim 3, wherein In the pre-polymerization catalyst containing a polymer nucleating agent in step (1), the mass ratio of the polymer nucleating agent to the propylene polymerization catalyst before modification is 0.1 to 5:

1.

5. The propylene polymerization method according to claim 3, wherein In the pre-polymerization catalyst containing a polymer nucleating agent in step (1), the mass ratio of the polymer nucleating agent to the propylene polymerization catalyst before modification is 0.5 to 5:

1.

6. The propylene polymerization method according to claim 1, wherein In the general formula I, R 1 and R 2 Together with the carbon atoms to which they are attached, they form an optionally substituted saturated or unsaturated or aromatic ring or condensed ring system, wherein the ring or condensed ring portion is a 5- to 12-membered saturated or unsaturated or aromatic ring or condensed ring system, or R 1 and R 2 Each is independently an alkyl group containing 1 to 4 carbon atoms.

7. The propylene polymerization method according to claim 1, wherein The nucleating agent monomer is selected from one or more of vinyl cycloalkanes, 3-methyl-1-butene, 3-ethyl-1-hexene, styrene, p-methylstyrene and allyltrimethylsilane; The vinylcycloalkane is selected from vinylcyclohexane, vinylcyclopentane, vinyl-2-methylcyclohexane or vinylnorbornane.

8. The propylene polymerization method according to claim 7, wherein The nucleating agent monomer is selected from one or more of vinylcyclohexane, vinylcyclopentane, styrene and allyltrimethylsilane.

9. The propylene polymerization method according to claim 1, wherein The Ziegler-Natta catalyst comprises a procatalyst, a cocatalyst i and an optional external electron donor; The procatalyst comprises magnesium, titanium, chlorine, and an internal electron donor; The internal electron donor is selected from one or more of benzoate compounds, phthalate compounds, 1,3-diether compounds, succinate compounds, maleate compounds, malonate compounds, 1,3-diol ester compounds, 2,4-diol ester compounds, o-diphenol ester compounds, 1,8-naphthalene diphenol ester compounds, cycloalkyl o-dicarboxylic acid ester compounds and amide ester compounds; The co-catalyst i is a hydrocarbyl aluminum compound.

10. The propylene polymerization method according to claim 9, characterized in that The co-catalyst i is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum and trihexylaluminum.

11. The propylene polymerization method according to claim 1, wherein The external electron donor is of the general formula R 3 m R 4 n Si(OR 5 ) 4-m-n The organosilicon compound shown in the formula: R 3 、R 4 are independently selected from C1-C12 linear, branched or cyclic aliphatic groups, or C3-C12 nitrogen-containing linear, branched or cyclic organic groups; R 5 Selected from C1-C4 straight-chain or branched aliphatic groups; m and n are natural numbers, and the values ​​satisfy 0≤(m+n)≤2.

12. The propylene polymerization method according to claim 11, characterized in that The external electron donor is selected from dimethyldimethoxysilane, diphenyldimethoxysilane, methylcyclopentyldimethoxysilane, methylcyclohexyldimethoxysilane, methyl(3,3,3-trifluoropropyl)dimethoxysilane, dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, di-n-propyldimethoxysilane, di-n-butyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, isopropylisopentyldimethoxysilane, methylcyclopentyldiethoxysilane, methylcyclohexyldiethoxysilane, methyl(3,3,3-trifluoropropyl)diethoxysilane, dicyclopentyldiethoxysilane, dicyclohexyldiethoxysilane, di-n-propyldiethoxysilane, di-n-butyldiethoxysilane, diisopropyl ... One or more of trimethoxysilane, trimethoxysilane, isopropyltrimethoxysilane, triethoxysilane, ethyltrimethoxysilane, trimethoxysilane, n-propyltrimethoxysilane, trimethoxysilane, isobutyltrimethoxysilane, isopentyltrimethoxysilane, cyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, allyltrimethoxysilane, vinyltrimethoxysilane, diethylaminotrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, triethoxysilane, n-propyltriethoxysilane, triethoxysilane, isobutyltriethoxysilane, isopentyltriethoxysilane, cyclopentyltriethoxysilane, cyclohexyltriethoxysilane, allyltriethoxysilane, vinyltriethoxysilane, diethylaminotriethoxysilane, tetramethoxysilane and tetraethoxysilane.

13. The propylene polymerization method according to claim 1, wherein The metallocene catalyst comprises a carrier, a metallocene coordination compound and a co-catalyst ii.

14. The propylene polymerization method according to claim 13, characterized in that In the metallocene catalyst, the carrier is selected from granular silica or layered silicate; The metallocene coordination compound is selected from bridged C2-symmetric compounds containing a Group IV metal and an indenyl group; The co-catalyst ii is selected from methylaluminoxane or modified methylaluminoxane.

15. The propylene polymerization method according to claim 14, characterized in that In the metallocene catalyst, the metallocene coordination compound is selected from one or more of rac-dimethylsilyl-bis(2-methyl-4-phenylindenyl)zirconium dichloride, rac-dimethylsilyl-bis(2-methyl-4,5-benzylindenyl)zirconium dichloride, rac-dimethylsilyl-bis(2-methyl-4-carbazolylindenyl)zirconium dichloride and rac-dimethylsilyl-bis[2-methyl-4-(3,5-di-tert-butylphenyl)-7-methoxyindenyl]zirconium dichloride.

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